Aurin tricarboxylic acid inhibits platelet adhesion to collagen by binding to the 509-695 disulphide loop of von Willebrand factor and competing with glycoprotein Ib.

Aurin tricarboxylic acid (ATA) is known to inhibit ristocetin-induced platelet agglutination but not arachidonic acid-, epinephrine- or ADP-induced aggregation. Its capacity to abolish human von Willebrand factor (vWF)-platelet interactions was further investigated by measurement of platelet adhesion to collagen, platelet agglutination tests and binding studies. In flowing blood using parallel-plate perfusion chambers and human collagen, ATA inhibited platelet adhesion to completion in a dose-dependent manner only at the highest shear rate tested (2,600 s-1). It was without effect at 100 and 650 s-1. ATA completely abolished vWF-dependent platelet agglutination induced by ristocetin, botrocetin and asialo-vWF, respectively. 125I-vWF binding to ristocetin- and botrocetin-treated platelets, to heparin and to sulfatides as well as 125I-botrocetin binding to vWF was competitively inhibited by ATA. By contrast, binding of 125I-vWF to collagen was not affected. To further localize the domain of vWF interacting with ATA, experiments of inhibition of binding of selected 125I-monoclonal antibodies (MoAbs) to immobilized vWF by ATA were performed. Our data led to the conclusion that: 1) the interaction of ATA with vWF involves sequences of the A1 disulphide loop of vWF (residues 509-695) and close epitopes which interact with GPIb and 2) the inhibition of platelet adhesion by ATA occurs only at a high shear rate where vWF is known to play a key role. Thus ATA, which blocks the vWF/GPIb pathway by interfering with vWF and not with platelets, is a potential tool in preventing the early stages of thrombosis.


Biochemical and ultrastructural studies suggest that the effects of thapsigargin on human platelets are mediated by changes in intracellular calcium but not by intracellular histamine.

The involvement of intracellular histamine in thapsigargin (Tg)-induced platelet aggregation was studied. Platelet aggregation induced by 0.25 and 0.5 microM Tg was not accompanied by a rise in intracellular histamine but a significant (p < 0.01) increase in the level of intracellular histamine was observed at 1 microM Tg. Preincubation of platelets with inhibitors of histamine metabolizing enzymes had little effect on intracellular histamine levels in platelets stimulated by 0.5 microM Tg. In addition, the inhibitors of histidine decarboxylase (HDC), alpha-methyl histidine (alpha-MH) and alpha-fluoromethyl histidine (alpha-FMH) failed to inhibit Tg-induced aggregation. The intracellular histamine receptor antagonist, N,N-diethyl-2-[4-(phenylmethyl)phenoxy] ethanamine. HCl (DPPE), inhibited Tg-induced aggregation but with IC50 values dependent on the concentration of agonist used. The inhibitory effects of DPPE on Tg-induced aggregation were not reversed by the addition of histamine to saponin-permeabilized platelets suggesting non-histamine mediated effects of DPPE on Tg-induced aggregation. Tg stimulated an increase in the cytosolic free calcium concentration which was unaffected by DPPE indicating that the effects of DPPE are also not due to the inhibition of mobilization of cytosolic calcium. The ultrastructural studies suggest that the major Tg-induced changes (pseudopod formation and granule centralization) are consistent with a primary role for Tg to mobilize calcium; DPPE had very little effect on these ultrastructural changes. The results indicate that the effects of Tg on human platelets are mediated by an increase in cytosolic calcium but not by intracellular histamine.


Arachidonate transfer between platelets and lipoproteins.

Although platelets have specific bindingsites for LDL and HDL, it is doubtful whether lipoproteins modulate platelet functions via receptor-mediated processes. We investigated platelet-lipoprotein interaction during prolonged incubation with concentrations of LDL and HDL that saturate the bindingsites within a few minutes. When [3H]arachidonate-labeled human platelets were incubated for 4 h with lipoproteins, part of the 3H-radioactivity transferred to LDL and to a lesser extent to HDL. The transfer was temperature-sensitive, unaffected by modification of lysine in LDL or indomethacin treatment of the platelets, and almost irreversible. [3H]arachidonate transfer to lipoproteins could be mimicked by incubating platelets with a high concentration of fatty acid free albumin. This showed, that the loss of 3H-radioactivity reflected a decrease in endogenous arachidonate, leading to impaired aggregation, secretion and thromboxane B2 formation in platelets after stimulation with thrombin but not with arachidonate. Thus, the decrease in platelet functions seen after long incubation with HDL is caused by depletion of platelet arachidonate. Despite an even stronger arachidonate depletion by LDL, this lipoprotein initiated arachidonate metabolism and secretion independent of specific binding sites for LDL on the platelet. Surprisingly, the major part of the secretion was preserved when the formation of prostaglandin endoperoxides/thromboxane A2 was inhibited with indomethacin. These findings argue against a role for LDL and HDL receptors in the modulation of platelet functions and are more in favor of lipid exchange processes between platelets and lipoproteins.


Changes in G-actin after platelet activation in platelet rich plasma.

We have used the DNase I inhibition assay to study changes in G-actin after platelet activation in platelet-rich plasma (PRP) induced by ADP. Because of problems associated with depolymerization of F-actin after lysis of ADP-activated platelets in the presence of plasma, G-actin was measured using a lysis buffer that contained formaldehyde to prevent any depolymerization of F-actin. Different patterns of response were seen depending on the concentration of ADP used, and these were modified by avoiding aggregation by either not stirring the sample or by adding EDTA. The results show rapid conversion of G-actin to F-actin in association with shape change, and there is a further decrease in G-actin associated with irreversible platelet aggregation. Thus evidence is presented that actin polymerization occurs in two phases after ADP stimulation.


Vitamin E binds to specific binding sites and enhances prostacyclin production by cultured aortic endothelial cells.

We evaluated the effect of d-alpha-tocopherol (vitamin E) on the production of prostacyclin (PGI2) by cultured bovine aortic endothelial cells. Vitamin E at physiological doses significantly enhanced the production of PGI2 by aortic endothelial cells when added to the culture simultaneously with histamine, the Ca2+ ionophore A23187 (A23187), plasma-derived serum (PDS), or arachidonic acid. This effect was found to occur in a time- and dose-dependent manner, and the maximal enhancement was produced by 9.28 microM of vitamin E for 1 h incubations. Significantly lower amounts of lipid peroxides were measured in endothelial cells stimulated by 10% PDS with 9.28 microM of vitamin E than in those stimulated without vitamin E for over 24 h, although the stimulation during the initial 1 to 12 h period did not have a significant effect on lipid peroxide formation in cultured aortic endothelial cells. We also demonstrated that bovine aortic endothelial cells have specific binding sites for [3H]vitamin E that exhibited time- and temperature-dependent saturability. At 4 degrees C, the nonspecific binding was 8-12% of the total binding, and the specific binding reached equilibrium by 2 h. Specific binding increased with the concentration of [3H]vitamin E and became saturated at concentrations between 1.5 microM and 2.0 microM per 2.0 x 10(5) cells. Raising the unlabeled vitamin E concentration from 97.7 nM to 1,000 microM reduced the specific binding of 2.0 microM [3H]vitamin E.(ABSTRACT TRUNCATED AT 250 WORDS)


[Necessity and method of administering minerals in cattle feed].

The soil of cattle farms can differ markedly, thus making it impossible to guarantee that animals receive an adequate supply of minerals. Mineral deficits are expected first in animals grazing pastures on sand, peat and iron-rich clay soils. The quality of the rations can also differ, which underlies the necessity of mineral supplementation. Supplementation is especially necessary when fewer concentrates are given or when more single products are given. Different formulations are often needed on one farm, depending on the feed available and the needs of the animals. In general, too little attention is paid in practice to animals that are not given concentrates. There are different ways of meeting the requirements of the different groups. On the basis of a thorough investigation of farm practices and rations, it can be determined whether supplementation is necessary, and if necessary, how this can be best achieved cheaply and effectively.


[An outbreak of keratoconjunctivitis in a dairy farm].

An outbreak of infectious kerato-conjunctivitis is described in a dairy herd during the (winter)stable period. Moraxella was isolated from lacrimation fluid from three animals. The development of the infection was possibly precipitated by a vaccination with modified live IBR virus, adenovirus type 3 and parainfluenza virus type 3. Presumably, climatological-stable conditions play an important role in the clinical manifestation of the infection.


[Salmonella dublin on dairy farms in the North of the Netherlands].

During the last century many calves and cows with Salmonella dublin infections are diagnosed in the North of the Netherlands, especially in the province of Friesland. In this paper are retrospectively traced the problems by paratyphoid infections in cattle, from 1919 till now, the diagnosis of which was made at the Animal Health Service in Friesland and North-Netherlands. Over the decennia a decrease is noticed for the percentage of necropsies of calves with S. dublin infections, although some irregular peaks appear. However since 1988 an increase is observed in dairy farms with S. dublin problems, revealing high mortality in calves, abortions and sick cows.


The cost-effectiveness of chemoprophylaxis with Maloprim administered by primary health care workers in preventing death from malaria amongst rural Gambian children aged less than five years old.

In recent trials in The Gambia, mass chemoprophylaxis with Maloprim administered over several years by primary health care workers to children aged 3-59 months has reduced both mortality and morbidity without inducing impairment of natural immunity or significant development of drug resistance. Taking expenditure of both time and money, by both public authorities and village volunteers, into account, the costs and the cost effectiveness of such mass chemoprophylaxis are estimated here. The cost per child protected per season was (1990 US) $2.84; the cost per childhood death averted was $143. Both costs compare favourably with those of permethrin bed net impregnation. So in some circumstances where malaria is holoendemic, control of childhood malaria by chemoprophylaxis may be more economically efficient than provision of impregnated bed nets.


Comparison of artemisinin suppositories with intravenous artesunate and intravenous quinine in the treatment of cerebral malaria.

Seventy-nine comatose cerebral malaria patients given standard supportive treatment were randomized to receive specific antimalarial chemotherapy of intravenous quinine, intravenous artesunate, or artemisinin suppositories. Artesunate and artemisinin reduced peripheral asexual parasitaemia significantly more rapidly than quinine (90% clearance time 16 h, 18.9 h and 34.5 h respectively), but did not significantly reduce the duration of coma or mortality. The rapid lowering of peripheral parasitaemia may not ameliorate complications already present. These results demonstrate that artemisinin suppositories are as effective as artesunate and quinine given intravenously, and have economic and practical advantages for the treatment of severe malaria in areas remote from major medical centres. However, large numbers of patients will need to be studied if differences in mortality between the 3 treatment groups are to be demonstrated.


An open randomized comparison of intravenous and intramuscular artesunate in severe falciparum malaria.

An open paired randomized comparison of intramuscular and intravenous artesunate was conducted in 28 adult patients with severe falciparum malaria. The dose regimen in both groups was 2 mg/kg given immediately followed by 1 mg/kg at 12 and 24 h, and then daily until the patient could swallow. Both routes of administration were well tolerated and there was no evidence of toxicity. One patient in each treatment group died. Clinical and parasitological measures of recovery in survivors were similar in the 2 groups with mean fever clearance times of 37.3 h (standard deviation [SD] = 26.1 h) and 31.5 h (SD = 24.2 h) and mean parasite clearance times of 33.4 h (SD = 13.9 h) and 29.4 h (SD = 12.7 h) in the intravenous and intramuscular groups respectively. Artesunate is equally effective and well tolerated when given by the intravenous or intramuscular routes.


Chloroquine-resistant Plasmodium falciparum isolates from the Sudan lack two mutations in the pfmdr1 gene thought to be associated with chloroquine resistance.

Isolates of Plasmodium falciparum from 3 areas of the Sudan were recovered from cryopreservation in London and their chloroquine sensitivity was determined in vitro. Chloroquine resistance was detected in 6/6 isolates from Khartoum, 1/4 from Sennar and 3/3 from Gadarif, indicating that resistance is spreading. All the isolates were sensitive to mefloquine. Studies using blood spots on glass fibre discs and the polymerase chain reaction did not detect two mutations in the pfmdr1 gene, thought to be correlated with chloroquine-resistance, in any of the isolates studied.


The effects of multiplication and synchronicity on the vascular distribution of parasites in falciparum malaria.

The sequestration of erythrocytes containing mature forms of Plasmodium falciparum in the microvasculature of vital organs may cause large discrepancies between the peripheral blood parasite count and the total body parasite burden in falciparum malaria. Despite this, parasitaemia is widely used as an indicator of prognosis and response to treatment. A simple mathematical model describing the changes in circulating and sequestered parasite numbers during acute falciparum malaria is presented. The model uses two parameters only; the standard deviation (SD) of parasite age since merogony (schizogony) as as a measure of synchronicity, and a multiplication factor each 48 h asexual life cycle. The model predicts that during the rising phase of the infection the ratio of circulating to sequestered parasites is dependent largely on the synchronicity of infection rather than multiplication rate, and that in synchronous infections parasitaemias will show considerable fluctuation when the mean stage of parasite development is in the second half of the asexual life cycle. The model fitted well to serial parasite counts from 4 patients with acute uncomplicated falciparum malaria whose infections failed to respond to ciprofloxacin. All four infections were synchronous (SD < or = 4 h), and showed large fluctuations in parasitaemia over short periods related to synchronous sequestration and subsequent reinvasion following merogony. The parasite multiplication rate was determined mainly by the efficiency of merogony or merozoite invasion rather than clearance of circulating parasitized erythrocytes. This suggests that the spleen is relatively inactive during the rising phase of the infection. Quinine treatment did not prevent sequestration but did stop subsequent multiplication.(ABSTRACT TRUNCATED AT 250 WORDS)


Polymorphonuclear leucocyte elastase in Plasmodium falciparum malaria.

Sixty-one patients with falciparum malaria were studied prospectively to determine the plasma concentrations of the lysosomal proteinase, polymorphonuclear leucocyte elastase (PMN-elastase) and their relationship to disease severity. The patients were divided into 3 groups; severe (parasitaemia > 5%) or vital organ dysfunction (n = 23), moderate (parasitaemia 1%-5% without complications) (n = 15), and mild (parasitaemia < 1%) (n = 23). The mean plasma PMN-elastase level in 10 healthy Thai volunteers was 49.5 (SD = 21.6) ng/ml (range 33-65 ng/ml). Plasma PMN-elastase concentrations on admission were elevated (> 2 x SD above normal) in all patients with severe malaria and were above 100 ng/ml in 86.6% and 65% of the moderately severe and mild patients respectively. PMN-elastase levels during the first 3 hospital days were significantly higher in severe malaria compared with the other 2 groups (P = < 0.001-0.013). The levels decreased as the patients became afebrile and aparasitaemic. Admission plasma concentrations of PMN-elastase correlated directly with bilirubin (rs = 0.50, P < 0.001), serum glutamic oxalacetic transaminase (rs = 0.54, P0.001), parasite count (rs = 0.62, P < 0.001), blood urea nitrogen (rs = 0.54, P < 0.001) and inversely with antithrombin III activity (rs = 0.54, P < 0.001) and the platelet count (rs = 0.58, P < 0.001). Polymorphonuclear leucocyte activation may contribute to the pathogenesis of severe malaria.


Increased lymphotoxin in human malarial serum, and the ability of this cytokine to increase plasma interleukin-6 and cause hypoglycaemia in mice: implications for malarial pathology.

The origin of illness and pathology in malaria is now largely attributed to high levels of circulating tumour necrosis factor (TNF), released from cells of macrophage lineage after triggering by the products of malarial schizogony. The role of lymphocytes and their products in malarial pathology is not yet known. This paper reports the presence of a related cytokine, lymphotoxin, which is produced only by lymphocytes, in the serum of malarial patients. This is the first report of raised serum levels of lymphotoxin in a systemic disease state. When injected into mice, recombinant human lymphotoxin induced hypoglycaemia and increased serum levels of interleukin-6. These changes, which are seen in severe experimental and human malaria, were also provoked by TNF. Both of these cytokines acted synergistically with interleukin-1, which has also been reported to be raised in malaria, to produce these alterations. These observations imply that lymphotoxin, as well as TNF, may contribute to the hypoglycaemia and raised serum interleukin-6 observed in malaria. This reduces the likelihood of effectively blocking the pathology of this disease by the use of neutralizing antibody directed against just one member of this family of functionally overlapping mediators.


Demonstration by the polymerase chain reaction of mixed Plasmodium falciparum and P. vivax infections undetected by conventional microscopy.

Mixed malaria infections (Plasmodium falciparum and P. vivax) are suspected to occur at a greater frequency than is detected by conventional light microscopy. To determine this frequency we carried out a prospective 'blinded' comparison of diagnosis by conventional light microscopy and enzymatic amplification of the circumsporozoite gene extracted from dried spotted blood samples. Patients were previously healthy, active duty Thai soldiers assigned to a malaria risk area presenting with malaria. Microscopy (oil immersion objective at 1000 x magnification) involved examination of Giemsa-stained thick and thin blood films by an experienced microscopist. Whole blood samples (25 microliters) dried on filter paper were used for species-specific parasite deoxyribonucleic acid (DNA) amplification by the polymerase chain reaction (PCR) and hybridization with radiolabelled P. falciparum and P. vivax probes. Of 137 consecutive cases of malaria studied, 9% (3/32) of microscopically diagnosed P. falciparum infections and 5% (5/104) of microscopically diagnosed P. vivax infections were found to be mixed by the PCR/DNA probe systems, while 1 case was diagnosed as mixed by both microscopy and PCR. The possibility that malaria patients may have undetected mixed infections should be kept in mind because of the specific therapy required both for P. falciparum and for radical cure of P. vivax.


Aminosidine (paromomycin) in the treatment of leishmaniasis imported into the United Kingdom.

We report 11 patients with leishmaniasis from different endemic areas, treated in the UK with intravenous aminosidine alone or in combination with other drugs. Clinical and parasitological cures were achieved in all 7 patients from the Mediterranean zone who had visceral disease, with one relapse. Two of 4 patients with cutaneous or mucosal disease were cured; the other 2, from Iraq and Iran, did not respond. Toxic effects were high-tone deafness in 2 patients, one of whom had pre-existing renal impairment, and transient, mild elevation of serum creatinine in 3. Aminosidine is an effective, tolerable and relatively non-toxic alternative to existing antileishmanial drugs for the treatment of visceral leishmaniasis. Further studies will be needed to assess its place in cutaneous and mucosal disease.


Specific chemotherapy of Chagas disease: a comparison between the response in patients and experimental animals inoculated with the same strains.

Eleven strains of Trypanosoma cruzi were isolated from patients with Chagas disease in central Brazil by xenodiagnosis and inoculation into newborn mice. Biological characterization and isoenzyme analysis showed that 6 strains were type II (zymodeme 2) and 5 were type III (zymodeme 1). Patients were treated with benznidazole or benznidazole plus nifurtimox. Mice infected with each isolated strain were treated for comparison with the results obtained in the respective patient. Evaluation of cure of the patients was based on the indirect immunofluorescence test, complement fixation reaction and xenodiagnosis. For the mice, haemoculture, indirect immunofluorescence testing, xenodiagnosis and inoculation of blood into newborn mice were used. Tests were performed 3-6 months after the end of treatment. The cure rate was 66-100% in mice infected with type II strains and 0-9% in those infected with type III strains. The correlation between treatment results in patients and mice was 81.8% (9 of 11 cases). Type II strains were more susceptible to treatment, in contrast to type III strains which yielded the majority of therapeutic failures.


Direct isolation in vitro of Trypanosoma brucei from man and other animals, and its potential value for the diagnosis of gambian trypanosomiasis.

A recently described simple kit for isolating African trypanosomes in vitro (KIVI) was tested further with blood samples from man and other animals in Côte d'Ivoire and République du Congo. A high rate of success was achieved, with positive cultures being found 5-36 d after inoculation. The method was also of value in diagnosis. Parasitaemia was initially detected by the haematocrit method; in addition, the mini-anion exchange column was used for human blood and lymph fluid from patients with swollen glands was examined. The card agglutination test (CATT) was applied to the human blood samples. In Côte d'Ivoire, all 5 parasitaemic patients, who were also positive by CATT, yielded positive KIVI cultures. Of 15 animals, 2 parasitaemic and 10 apparently aparasitaemic individuals gave positive cultures. In the Congo, none of the 22 animals was parasitaemic and none gave a positive culture. Of 647 human subjects initially screened, 61, mostly with a positive CATT, were examined by KIVI; 20 gave positive cultures. Seven of these cultures originated from patients in whom no trypanosome had been seen in blood or lymph fluid, although blood from 2 parasitaemic patients failed to yield positive KIVI cultures. Some patients with CATT-negative whole blood and/or serum were positive by KIVI.


High prevalence of human skeletal muscle sarcocystosis in south-east Asia.

The prevalence of human skeletal muscle sarcocystosis in Malaysia was determined by serial examination of formalin-fixed, paraffin-embedded sections of tongue tissues obtained from consecutive, routine autopsies of subjects aged 12 years or more. Of 100 tongues examined, 21% were found to contain Sarcocystis; 66 cysts were found. The number of cysts per case varied from 1 to 13. In one case, 5 cysts were found in a single tissue section. The age range of positive cases was from 16 to 57 years (mean 37.7 years). Prevalence did not differ with regard to race, sex or occupation. The prevalence of human muscular sarcocystosis in our study was higher than that reported elsewhere. Preferential localization of Sarcocystis in tongue or head and neck and/or genuinely high prevalence in south-east Asia are possible explanations for this observation.


Cryptosporidium: different behaviour in calves of isolates of human origin.

The behaviour in calves of 3 Cryptosporidium human isolates was analysed in comparison with a bovine isolate. Twenty-four neonatal calves were infected. An isolate from a patient infected with human immunodeficiency virus (HIV) and showing mild cryptosporidiosis caused severe diarrhoea with a high production of oocysts in neonatal calves, as did a bovine isolate (group 1). Two human isolates, obtained from HIV patients with severe cryptosporidiosis, caused mild diarrhoea with low oocyst production in neonatal calves (group 2). The difference between the 2 groups in numbers of oocysts shed in calves was statistically significant (P = 0.005), as was the duration of oocyst shedding (P = 0.0004). Oocysts of group 2 isolates were less resistant to storage in 2% potassium dichromate at 4 degrees C than were oocysts of group 1. The biological and epidemiological implications are discussed.


Fibre-optic sigmoidoscopy compared with the Kato technique in diagnosis and evaluation of the intensity of Schistosoma mansoni infection.

450 patients in Riyadh, Saudi Arabia, complaining of chronic abdominal pain and, coming from different countries endemic for schistosomiasis, were examined endoscopically using fibre-optic colono- or sigmoidoscopes, and rectal biopsies were examined for Schistosoma mansoni ova. After a preliminary study showed that more than 6 biopsies did not increase the positivity rate, 6 biopsies were taken from the rectum and examined by transparency technique. 280 were positive for S. mansoni, 9 of them having in addition S. haematobium. 4 patients had polyps in the sigmoid colon and rectum. When these positive cases were examined using duplicate 50 mg Kato smears, only 160 (57.1%) were positive. There was a highly positive correlation between the intensity of infection as graded by the 2 techniques. We recommend examination of 6 rectal biopsies using fibre-optic sigmoidoscopy when available in small communities with a patchy distribution of schistosomiasis like Saudi Arabia. The method could also be used to exclude schistosomiasis in persons who have moved from rural to urban or non-endemic areas and are unlikely to be re-exposed to infection.


Cost analysis of schistosomiasis.

Cost analysis of schistosomiasis is important both in assessing the economic impact of the disease and in identifying the most cost-effective approaches to control. Economic impact has been examined both within and without the health sector, but there is a lack of measurement of the effects of disease, or the threat of disease, on patterns of production and community development. The cost-effectiveness of control approaches has been examined empirically and by using static models. Future analyses require a stronger epidemiological basis incorporating realistic demography and the temporal dynamics of reinfection, and assessment of outcomes in terms of disease rather than infection.


Detection of antibodies to secretions of Ancylostoma caninum in human eosinophilic enteritis.

To evaluate the role of canine hookworms in human eosinophilic enteritis (EE) in north-eastern Australia, we tested human sera in an enzyme-linked immunosorbent assay (ELISA) which incorporated antigens of adult Ancylostoma caninum. Sera from the following groups were examined: 10 patients with EE (unexplained recurrent abdominal pain and related symptoms, with peripheral eosinophilia) from Townsville and Brisbane; 2 persons known to be infected with A. caninum and 20 presumed unexposed healthy controls; 20 patients with other gastrointestinal diseases; 20 with other identified parasitic infections; and 20 with atopic conditions. High levels of specific immunoglobulin (Ig) G and IgE antibodies were found in patients with EE but not other gastrointestinal disease. Excretory-secretory (ES) products were more discriminating than somatic antigens in the ELISA and the IgG/ES-ELISA was the most specific; occasional cross-reactions could be explained on epidemiological or parasitological grounds. The IgM-ELISA was neither specific nor sensitive. We conclude that canine ancylostomiasis is a major cause of human EE in north-eastern Australia, and the pathogenesis is based probably on hypersensitivity to antigens secreted by the parasite.


Haemoglobin concentrations and concomitant infections of hookworm and Trichuris trichiura in Panamanian primary schoolchildren.

The blood haemoglobin concentrations and intestinal helminth infections were surveyed in 658 children aged between 6 and 12 years attending 4 primary schools in Coclé Province, Panama, in November 1987. 147 (22.3%) of the children were judged to have haemoglobin concentrations indicative of iron-deficiency anaemia. Blood haemoglobin concentrations were significantly lower in children with heavier Trichuris trichiura infections (> 5000 eggs/g) (P = 0.014), and in children with dual infections of both hookworm and T. trichiura (P = 0.005). Children with concomitant T. trichiura and hookworm infections were also significantly more likely to have blood haemoglobin levels indicative of anaemia than children who were uninfected or had single infections with either of these helminths (P < 0.005). In a longitudinal study involving 171 children selected from the original 658, blood haemoglobin concentrations were measured again in November 1988. Children who were considered to show an improvement in both hookworm and T. trichiura infections over this 12 month period showed a significantly greater increase in blood haemoglobin concentrations than children who had remained uninfected with either of these helminths throughout the study period (P < 0.05).


An outbreak of trichinosis in Lebanon.

In 1982 an outbreak of trichinosis occurred in an area of south Lebanon consisting of 4 villages, including 6440 persons. In 267 households, involving 2456 persons, typical clinical signs of Trichinella spiralis infection could be recognized among household members. Twenty-one of these households, including 193 persons, were randomly chosen for further studies. Nearly half of the household members (46%) had clinical symptoms consistent with acute trichinosis. 12 of 16 tested persons had high anti-Trichinella antibody titres (12 positive by indirect immunofluorescence (IIF) and 11 by enzyme-linked immunosorbent assay). Class-specific antibodies, IIF-immunoglobulin (Ig) G, IgM and IgA, were detected in most tested cases. Of the remaining 4 seronegative cases, 3 had a duration of clinical symptoms < or = 12 d. High peripheral eosinophilic counts (> 20%) were noted in 8 of 16 cases. In total, 15 of 16 cases were positive by one or more of these tests. The outbreak constituted one of the most extensive single outbreaks reported with a calculated > 1000 clinical cases. The cause was attributed to consumption of raw pork meat, an ingredient of kebbeh nayyeh, a favourite Lebanese dish.


Strongyloidiasis on the Thai-Cambodian border.

A series of children's deaths at a Cambodian refugee camp in Thailand prompted an investigation of children suffering from bloody diarrhoea and severe abdominal pain. Microscopical stool and blood examinations of 15 cases aged 1-7 years revealed hyperinfective strongyloidiasis as the cause of illness. Nine of 14 cases were infected wtih Strongyloides stercoralis, and 6 (42%) had concurrent infection with hookworm. Examination of 958 outpatients at the camp's daily clinic showed that mixed infections of S. stercoralis and hookworm were present in only 4.8% of the outpatients of the same age group.


Adverse reactions after community treatment of onchocerciasis with ivermectin in Guatemala.

Male and female residents on a Guatemalan coffee plantation where Onchocerca volvulus infections were hyperendemic were offered oral ivermectin (100-200 micrograms/kg) as part of a community-wide treatment programme for onchocerciasis. Forty-five persons were treated and then questioned daily for 28 d about changes in their health. Those with complaints were monitored until all signs and symptoms had resolved. Sixty-seven percent complained of some adverse event after treatment; 60% developed observable adverse reactions attributed clinically to ivermectin. No reaction was life-threatening; the most common were oedema (53%) and fever (47%). Expulsion of intestinal helminths was reported by 38%. Almost all reactions began 24-48 h after treatment; their mean duration was 5 d, despite treatment with acetaminophen and antihistamines. Three patients had oedematous changes lasting over 2 weeks. Incidence, but not severity, of reactions was related to the pretreatment density of microfilariae in skin.


Rheumatoid factor and rheumatoid factor isotypes in loiasis with and without accompanying glomerulonephritis.

We have studied the distribution of rheumatoid factor isotypes amongst patients with loiasis with and without accompanying glomerulonephritis to determine the possible role of rheumatoid factor antiglobulins in this disease. Our findings indicate an increase in both immunoglobulin (Ig) G and IgM rheumatoid factor isotypes in patients with filariasis alone as well as in patients with accompanying glomerulonephritis. No association with IgA rheumatoid factor was found. The raised IgG and IgM rheumatoid factor levels did not correlate with corresponding IgG and IgM levels.


Salivary and urinary diagnosis of human immunodeficiency viruses 1 and 2 infection in Côte d'Ivoire, using two assays.

This investigation, done at the Institut Pasteur de Cote d'Ivoire 'blind' of the previous serological findings, suggests that GACELISA, a commercial immunoglobulin G capture enzyme immunoassay for anti-human immunodeficiency virus antibody, can be successfully applied to unprocessed saliva and urine specimens. Its accuracy may be as high as that of conventional enzyme assays on serum tested under similar conditions. However, the role of GACPAT, a similar assay, as a cheap alternative screening test for urine remains in doubt unless its non-specificity can be controlled.


Complement pathway activity in serum from patients with classical dengue fever.

Complement activity in 125 cases of classical dengue fever was examined through the measurement of haemolytic activity. During the first 3 d of fever, the classical complement pathway activity (CCPA) was not altered in 109 cases. After 4 d of fever, 9 of 16 patients in the viraemic period had CCPA decreased by 45% (995 +/- 119 units/ml) and serum complement component C4 decreased by 40% (10.4 +/- 0.9 mg/dl). The alternative complement pathway activity was not affected in any case tested throughout both viraemic and convalescent stages. Both CCPA and C4 persistently decreased in 3 of these 9 patients at the convalescent stage. A decrease in serum C3 was also observed in these 3 patients only, and circulating immune complexes (CIC) levels were particularly high in these 3 patients. These results indicate that there is little evidence of complement activation on days 1-3 of viraemia but that complement activation may occur subsequently. It is concluded that both CIC and other unknown factors not related to CIC may contribute to complement activation in some cases (9/125) of classical dengue fever.


Serological evidence in sheep suggesting phlebovirus circulation in a Rift Valley fever enzootic area in Burkina Faso.

Within the Phlebovirus serogroup, Rift Valley fever (RVF) virus is endemo-enzootic in the African sahelian zone. Recently an RVF epizootic in West Africa prompted a serosurvey in the major sheep and cattle raising areas. Because of the close antigenic relationship between the phleboviruses it appeared of interest to evaluate the prevalence of the other phleboviruses also. In 1987, 482 sheep serum samples were collected in 2 different ecological zones of Burkina Faso and tested for the presence of phlebovirus antibodies. A sensitive but non-specific immunofluorescent antibody test and a specific enzyme-linked immunosorbent assay (ELISA) were used, with the following African phlebovirus antigens: Rift Valley fever (RVF), Arumowot, Gabek Forest, Gordil, Saint Floris and Odrenisrou. A total of 15.8% of the sera sampled had anti-RVF antibody in the ELISA. RVF virus appeared to be more active in drier areas such as the sahelian region, known to be an enzootic area for the disease. Antibodies to other phleboviruses were found in 11.8% of the samples, independent of RVF virus activity. It is assumed that sheep can be infected by different phleboviruses.


Septicaemic melioidosis: a review of 50 cases from Malaysia.

Fifty cases of septicaemic melioidosis were reviewed. There was a preponderance of disease among males (male:female ratio 3.2:1) and those aged over 30 years. The presenting clinical features were very varied and not pathognomonic, ranging from fever, cough and septicaemia to fulminant septicaemia and shock. Pulmonary involvement was recorded in 58% of the patients. Skin and soft tissue sepsis was seen in 24%, but many had signs and symptoms of multiorgan involvement. Associated underlying illness was identified in 76% of patients, diabetes mellitus being the commonest (38%), while 34% had more than one predisposing factor. The mortality of 65% in our series is a reflection of the less than satisfactory status of the diagnosis and therapy of septicaemic melioidosis. Only 24% of our patients received appropriate empirical antibiotic therapy. A high index of suspicion of melioidosis in endemic areas and the use of appropriate empirical antimicrobial therapy would be a step towards reducing the high mortality rate.


Does antibody to mycobacterial antigens, including lipoarabinomannan, limit dissemination in childhood tuberculosis?

Serum immunoglobulin (Ig) G responses to a variety of mycobacterial antigens were measured in children from the UK, in children with tuberculosis from Hyderabad, India and Dhaka, Bangladesh, classified according to whether the disease was disseminated or localized, and in non-tuberculous controls. Anti-lipoarabinomannan (LAM) IgG responses in UK children showed a marked trough between 6 months and 3 years coincident with the reported peak incidence of disseminated tuberculosis. Geometric mean IgG responses to sonicates of slow-growing mycobacteria (rich in LAM) in 36 children with disseminated tuberculosis were markedly lower than in 99 children with localized tuberculous lesions (for Mycobacterium scrofulaceum P < 0.01, for M. tuberculosis P < 0.01, and for M. vaccae P < 0.01). Responses to purified LAM were also lower in the disseminated tuberculosis group (P < 0.05) but there was no difference between the groups in their response to mycobacterial 65 kDa protein. Multiple regression analysis showed that the reduced response to sonicated mycobacterial antigens and to LAM in children with disseminated disease was independent of age, nutritional status, skin test reactivity, duration of previous symptoms, and city of origin. There was no evidence for sequestration of antibody to immune complexes. These findings are compatible with the hypothesis that children with low levels of antibody to sonicated mycobacterial antigen and to LAM, or those who cannot mount an antibody response, are predisposed to dissemination. A role for antibody in preventing disseminated forms of tuberculosis in childhood has implications for the development of improved vaccines and for the optimum timing of vaccination with bacille Calmette-Guérin.


Hospital admissions of Aborigines and non-Aborigines in Western Australia, 1977-1988.

Aborigines were admitted to hospital in Western Australia 2.8 times as frequently as other persons in 1977-1988. Their highest relative admission rates were in the 0-5 years age group, mostly for respiratory and gastrointestinal infections. Relative admission rates (all ages) for some categories were: infectious and parasitic, 4 to 10-fold; respiratory, 5-fold; nervous system, 4-fold; injury and poisoning, 3 to 5-fold; mental disorders, double the non-Aboriginal rate. Admissions for respiratory illnesses were consistently much higher in Aborigines of all ages. There were some significant declines in relative hospital admission rates for Aborigines over the study period.


Introduction and spread of thermophilic campylobacters in broiler flocks.

Campylobacteriosis is the most commonly reported infectious cause of human gastroenteritis in developed countries and broiler chickens are considered to be the major food-borne source of the infection. The control of the infection in man depends upon its control in broiler flocks but the epidemiology in poultry is poorly understood. Up to 50 per cent of broiler flocks may be infected and most of the birds in an infected flock carry the organisms until slaughter. Vertical transmission through the egg appears unlikely but there are many other potential sources of the infection for the chicks; direct contact with infected animals or birds has been proposed and there is also evidence for indirect transmission through drinking water or insect vectors. It is suggested that the cross-sectional studies discussed in this review should be followed by well designed case-control studies to test the aetiological hypotheses put forward.


Induction of parturition in dairy cows with dexamethasone.

Sixty Holstein cows were paired by parity and sire, and one of each pair was allocated at random to treatment or control; 17 cows were injected with 7.5 mg/100 kg dexamethasone trioxa undecanoate 14 days before the predicted date of calving, 13 cows received the same dose five days before term and 30 cows were left untreated. The treatment significantly advanced parturition and 29 of the 30 induced cows calved within 72 hours of the injection. Induction at day 14 before term was safe for calf and dam, the calves were 3.2 kg lighter than control calves and there was a high incidence of retained placenta. Treatment for this condition resulted in increased veterinary costs of 14.50 pounds per cow exclusive of dexamethasone treatment. Treatment at this stage was also associated with low pregnancy rates in the next breeding season. Calves born after induction at five days before term were not significantly lighter than calves from control cows, the problem of retained placenta was less marked and there were no subsequent effects on fertility. There were no significant effects of induction on milk yield or milk quality up to 200 days of lactation.


Appraisal of teachers in the Faculty of Veterinary Science, University of Liverpool.

In 1988, the Faculty of Veterinary Science, University of Liverpool, introduced a system of teacher appraisal, following the report of a faculty working party. The system is designed to provide information which will help the personal development of teaching skills, and also to provide the information required by the university for promoting a lecturer to senior lecturer. It incorporates opinions from students, collected formally by means of questionnaires, and from personal peers chosen by the lecturer, and a self-appraisal record which forms the basis of an annual review from the head of department. Official peers, drawn from both the veterinary faculty and the department of education and extension studies, are trained and used in pairs, to assess and report on staff eligible for promotion. The system has been evaluated by a research assistant funded by the University Funding Council.


A study of major causes and types of poisoning in Khonkaen, Thailand.

To investigate the problem of poisoning in Khonkaen Province, Thailand, a prospective data collection method was used. From 257 acute poisoning cases, the total poisoning rate was found to be 0.76/1000 hospital visits and the case fatality rate was 2.7%. Major types of poisoning found were poisonous animals (28.8%), agricultural chemicals (27.2%), misused therapeutic drugs (19.0%) and household chemicals (10.1%). Major causes of poisoning were suicide attempts (35.4%), accidents (28.4%), ignorance (26.8%) and occupational (8.6%). The most frequent age group affected was 11-30 y (58.8%). Females were found involved more than males (1.2:1). In males, the most frequent cause was unintentional poisoning; in females, it was from suicide attempts. The most frequent types among males were poisonous animals and agricultural chemicals; in females they were agricultural chemicals, misused therapeutic drugs and poisonous animals. The poisoning rate in children 0-5 was 12.1% of the total cases, and poisoning from every type of toxic substance was found. The cause in children was unintentional poisoning. The peak total poisoning time was from August to October.


The acute toxicity, primary irritancy and skin sensitizing potential of glutaric anhydride.

Glutaric anhydride (GA), an industrial chemical, was found of moderate acute peroral lethal toxicity with LD50 values (95% confidence limits) in the rat of 1.41 (0.80-2.49) g/kg (males) and 0.54 (0.36-0.79) g/kg (females), with death being due in part to gastrointestinal irritancy. Dilution with water given by gavage after peroral dosing had no effect on lethal toxicity. Acute percutaneous LD50 values (rabbit) by 24-h occlusion were 6.25 (5.34-7.33) g/kg in males and 5.66 (3.21-9.95) g/kg in females; local skin effects included erythema, edema, necrosis and ulceration. A 6-h exposure to a statically generated saturated vapor atmosphere (rat) produced no signs of toxicity or irritancy. A 4-h, but not 1-h or 3-min occluded contact with 0.5 g of moistened GA (rabbit) produced erythema, edema and necrosis. Contamination of the eye (rabbit) with 10 mg GA produced conjunctivitis (hyperemia, chemosis and discharge) which persisted 7 to 14 d, mild iritis of 2 to 14 d duration, and mild to severe corneal injury which healed within 14 d. A maximization study in guinea pigs by the method of Magnusson and Kligman showed no potential for skin sensitization with GA. The major acute hazards of GA were by swallowing, eye contact and sustained skin contact.


Carbaryl distribution in rabbit tissues and body fluids.

After single po administration of 14C-naphthylcarbamate, liquid scintillation assays evaluated the distribution of carbaryl in rabbit serum, liver, kidneys, small and large intestine, spleen, heart, muscles of the thigh and lungs and its excretion in urine and feces at 2, 4, 6 and 8 h after dosing. At 2 and 8 h radioactivity was not observed in spleen, heart, muscle and lungs, while all other tissues had increased values up to 6 h. The main excretory pathway of carbaryl was the kidneys.


The immune response of sheep to subclinical chronic exposure to the herbicide Bentazon TP.

A study of the effect of the Czechoslovakian herbicide BENTAZON TP on cells of the sheep immune system was carried out over a 3-mo period. A temporary decline in the number of T-lymphocytes in the peripheral blood was seen after 6 w of daily feeding of the herbicide. Dose-dependent statistically significant changes in the leucocyte migration index (p < 0.05) were seen at daily doses of 1/10 the LD50 (195 mg/kg body weight) and 1/20 the LD50 (97.5 mg/kg body weight) the 8th and 10th w of feeding, respectively. Significant changes of phagocytic activity and in the phagocytic index were not observed.


Characterization of rumen bacterial pyrrolizidine alkaloid biotransformation in ruminants of various species.

An in vitro assay was used to examine biotransformation of toxic Senecio jacobaea pyrrolizidine alkaloids (PA) in ovine, bovine, and caprine rumen contents. Pyrrolizidine alkaloids were analysed by high performance liquid chromatography, and the rates of the alkaloid biotransformation were determined. The microbiological "Most Probable Numbers" technique was also used, in combination with thin-layer chromatography, to estimate relative numbers of rumen PA-biotransforming bacteria in the same samples. Pyrrolizidine alkaloids were biotransformed at average rates of 2.9 micrograms/ml/h (bovine), 25.6 micrograms/ml/h (caprine), and 19.2 micrograms/ml/h (ovine). Estimates of numbers of PA-biotransforming bacteria were 1.1 x 10(7) bacteria/ml rumen contents (bovine), 2.4 x 10(7) bacteria/ml (caprine), and 3.0 x 10(7) bacteria/ml (ovine). This project is among the first to quantitate rates of PA biotransformation in rumen contents and to identify caprine and bovine, in addition to ovine, rumen PA-biotransforming activity, as well as to estimate the actual numbers of PA-biotransforming bacteria in rumen contents.


Effect of soil on aflatoxin tissue retention in chicks when added to aflatoxin-contaminated poultry rations.

The effects of silty clay loam soil on aflatoxin B1 (AFB1) absorption were investigated when added to the diets of chicks fed aflatoxin-contaminated rations. Sixty 1-d-old White Leghorn chicks were fed a control ration (< 5 ng AFB1/g), a low aflatoxin-contaminated ration (55 ng AFB1/g), a high aflatoxin-contaminated ration (4,488 ng AFB1/g), or high aflatoxin-contaminated rations (4,488 ng AFB1/g) + 25% or 50% soil. Livers in each group were pooled and analyzed for AFB1 and metabolites. The addition of soil significantly reduced the levels of AFB1 in the livers, although the reduction was less when 25% soil was fed compared with the 50% soil feeding.


Clinical studies of employees in a sheet-forming process at a paper mill.

Formaldehyde resins are used to improve the wet strength of paper. During the sheet-forming process of paper manufacture, formaldehyde fumes are liberated. Twenty-two male subjects having such exposures in a paper mill and 27 unexposed subjects were clinically evaluated to determine the effect of low level formaldehyde exposure in a tropical country. The workers were exposed to 0.03 mg formaldehyde/m3 air as an 8-h TWA. Formic acid excretion in urine was 37.2 +/- 18.9 and 20.3 +/- 4.2 ug/L among the exposed and the unexposed subjects, respectively. Significantly more respiratory problems (31.8%) were observed among the exposed subjects as compared to controls. Complaints pertaining to gastrointestinal, musculoskeletal and cardiovascular systems were also more frequent in exposed subjects. In spite of formaldehyde concentrations being well within the prescribed ACGIH limits of 1 ppm, the high rates of sickness emphasise the need for detailed studies on formaldehyde-exposed subjects in tropical countries.


Snakebites in poultry.

Eight cases of snakebite involving 5 flocks were seen in chickens, ducks and turkeys in the Avian Ambulatory Clinic of the Veterinary Teaching Hospital, Zaria, between July 1983 and August 1990. Most of the clients resided in areas with large canopies of trees and bushes. There was a large gully just behind the residential areas. Twenty-one birds were bitten; chickens constituted 85.7%, turkeys 12% and ducks 4.8% of this number. Hens incubating eggs were most vulnerable. Cocks were usually bitten when they attacked the snakes. Clinical signs were similar to those reported in other animal species. Gross lesions included congestion of visceral organs and hemorrhage in the viscera, around the bite sites and in the sc tissues. There was also im edema around bite sites. The fatality rate was 87.5%.


The biological activity of glyphosate to plants and animals: a literature review.

Glyphosate is a widely-used broad-spectrum herbicide with little to no hazard to man or the environment. Glyphosate is highly effective against 90 kinds of emerged grasses, brush and broad-leaf weeds. There is no residual soil activity, it does not leach into non-target areas, and it is non-volatile. It is practically nontoxic to mammals, birds and fish, showing no bioaccumulation in the food chain; it is biodegraded into natural products. When used correctly, glyphosate poses no threat to the environment and its inhabitants.


Plant nurseries: a reliable resource for plant identification?

Poison Centers frequently rely on the assistance of local plant nurseries to identify unknown plants involved in exposures. The reliability and accuracy of utilizing this method has never been studied; therefore, our objective was to evaluate this primary resource of plant identification. A study was done in which callers were instructed to take plant samples to a local nursery for visual identification. Once the patient was treated according to our normal protocol, the plant specimen was sent to a botanist for a second identification. The botanist provided his identification results through a blinded process. The collected data was gathered from 68 cases that completed the necessary study criteria. In 58% of the cases, plant nurseries were an unreliable source for plant identification. These incorrect identifications resulted in the "undertreatment" in 24% of the exposures.


Alterations of libido in gased Iranian men.

This investigation was done on 800 Iranian men who survived the immediate hazards and lethal phase during chemical warfare exposure. At the time of interview they had gone back to their usual lives. Men injured with chemical weapons containing mustards may have impotency and loss of or decreased libido.


Orientation selectivity of 3-month-old infants.

A modification of the visual evoked potential (VEP) technique, first employed by Braddick, Wattam-Bell and Atkinson [(1986) Nature, London, 320, 617-619] was used to estimate the orientation selectivity of 3-month-old infants. The orientation-selective VEP was recorded in response to various changes in the orientation of a square-wave grating. The magnitude (the square root of the power of the FFT) at the frequency of orientation change was assumed to represent the response to the change in grating orientation. Orientation sensitivity was then estimated by plotting the magnitude of the FFT at the frequency of orientation change as a function of the log of the orientation change in degrees. For each individual, the data were fit by nonlinear regression and threshold was defined as the largest orientation angle for which the magnitude of the FFT was zero. The results suggest that the orientation selectivity of 3-month-old infants (1.33 deg) is similar to that of adults (1.13 deg) tested with the same stimulus parameters (1 c/deg, 9 Hz). However, when adults are tested with stimulus parameters selected to optimize their VEP response (4 c/deg, 18 Hz) instead of those which optimize the infant's response, the orientation discrimination of adults improves by a factor of 2 (0.53 deg). The results obtained from adults under optimum stimulus conditions (4 c/deg, 18 Hz) approach the estimates reported in the literature for static stimuli.


Analysis of striate activity underlying the pattern onset EP of children.

The checkerboard onset Evoked Potential (EP) does not obtain its adult form before puberty. To determine the site of origin of these processes we studied the origin of the checkerboard onset EP in a group of 10 children between the ages of 6 and 16 years. Since the development of the waveform of the pattern onset EP varies with check size we also studied the dependence of these EPs on check size. The child checkerboard onset EPs described in this paper are dominated by a single source. Following an equivalent dipole source localization approach, the position, orientation and variation in strength of the equivalent dipole is estimated. The position and orientation of this dipole indicates an origin in the primary visual cortex (area 17). The variation in strength of the dipole changes from a single positive deflection, specific for children of 8 years and younger, into a negative-positive complex for the children studied between the age of 9 and 16 years. These changes in waveform must be due to changes in the activity pattern of the striate cortex.


Pattern recognition in honeybees: multidimensional scaling reveals a city-block metric.

Bees were trained to discriminate ring-patterns which varied in number of rings and in size. Transfer-tests revealed size discrimination to be largely independent of pattern type and vice versa. A multidimensional scaling procedure, using Minkowski metrics as models, was applied in order to determine the bee's "perceptual metric". The city-block metric, and not the Euclidean metric, provided the best description of the data. Apparently, the bee's perceptual system derives the overall dissimilarity of complex ring-patterns additively from the component differences. These results are discussed with regard to "holistic" and "analytic" processing modes postulated for the perception of human subjects.


Shape discrimination and the judgement of perfect symmetry: dissociation of shape from size.

We measured the accuracy with which subjects judged that a square or circle was perfectly symmetrical i.e. that aspect ratio (a/b) was exactly unity (where a and b were, respectively, the vertical and horizontal dimensions). Errors were remarkably small, ranging from 0.7 to 0.4% for the judgement of squareness and from 1.4 to < 0.1% for the judgement of circularity. Precision in judging aspect ratio was measured by requiring subjects to judge whether the aspect ratio (a/b)TEST of a test rectangle was greater or less than the aspect ratio (a/b)REF of a reference rectangle. Similar measurements were made for elliptical targets. To ensure that subjects based judgements on aspect ratio rather than a, b or (a-b), the area of each successive presentation was varied randomly. The just-discriminable percentage change of aspect ratio was as low as 1.6% at (a/b)REF = 1.0 (i.e. for a square or circular reference), and rose progressively as (a/b)REF was made progressively larger or smaller than 1.0. Aspect ratio discrimination threshold was independent of mean area over a sixteen-fold range of 0.25-4.0 deg2. For both rectangles and ellipses, the best value of aspect ratio discrimination threshold corresponded to a precision of encoding a and b of 14 sec arc or better. In further experiments, the method of constant stimuli was used to measure an aspect ratio aftereffect produced by adapting separately to rectangles of (a/b)ADAPT equal to 1.5, 1.0 and (1/1.5). Similar aftereffects were obtained whether the area of the test stimulus was fixed or varied randomly from trial to trial, and whether the test stimulus was rectangular or elliptical. The aftereffect could not be explained in terms of fatigue of neurons sensitive to linear dimension a or b. Nor could the aftereffect be explained in terms of the "contour repulsion" hypothesis, or in terms of orientation discrimination. We conclude (1) that the same neural mechanism determines aspect ratio discrimination threshold for rectangles and ellipses and (2) that this mechanism is sensitive to aspect ratio independently of linear dimensions. We propose that aspect ratio perception is determined by the balance of excitation of two pools of neurons that are selectively sensitive to different, but overlapping ranges of (a/b). One pool prefers aspect ratios > 1.0 and the others prefer aspect ratios < 1.0. We suppose that the two pools respond identically to changes in area (a * b).(ABSTRACT TRUNCATED AT 400 WORDS)


Peripheral chromatic sensitivity for flashes: a post-receptoral red-green asymmetry.

Thresholds of luminance and red-green chromatic flashes (200 msec) were measured on a yellow adapting field in the fovea and periphery (up to 12 degrees eccentricity for 1 degree flashes and 21 degrees eccentricity for 2 degrees flashes). Chromatic sensitivity (in cone contrast coordinates) is about 7 times higher than luminance sensitivity in the fovea but falls faster with eccentricity, so that luminance and chromatic sensitivities are similar at eccentricities of 20 degrees or less. At eccentricities greater than about 14 degrees, there is a clear asymmetry wherein green chromatic flashes are considerably less detectable than red ones. By measuring complete detection contours for many ratios of incremental and decremental red and green flashes, we isolated the red and green chromatic detection mechanisms, and demonstrated that the red-green asymmetry is not a property of the L- or M-cone response per se, but rather is a property of the post-receptoral, chromatic mechanisms. The peripheral luminance and chromatic mechanisms could be further separated with a suprathreshold luminance flash (a pedestal), since an intense pedestal masks coincident luminance test flashes but facilitates the chromatic flashes. The luminance pedestal approximately linearizes the chromatic detection function (the psychometric function).


Visually induced cycloversion and cyclovergence.

Binocular cyclorotatory (torsional) eye movements in response to visual patterns, which oscillated sinusoidally in the frontal plane, were recorded with scleral induction coils in human subjects. Conjugate cycloversion and disjunctive cyclovergence were directly compared by in-phase and out-of-phase oscillation of the same pattern. Stimulus motion had a frequency of 0.2 Hz and amplitudes of 2-8 deg. Both response types had a similar and low gain (about 0.2 averaged over all subjects). Cycloversion showed no time lag, while cyclovergence lagged by about 600 msec. Non-fusible patterns were effective in eliciting cycloversion, but not cyclovergence. Apart from this, the nature of the pattern (randomly distributed dots, regular rows of dots, horizontal or vertical grating, Julesz stereogram or images with a pictorial significance) had only the slightest effect on the magnitude of the responses.


Configural effects constrain Fourier models of pattern discrimination.

Many models of spatial pattern discrimination assume that judgments are based on information directly available from mechanisms tuned to limited ranges of spatial frequency and orientation. We tested the validity of this assumption for spatial frequency, orientation, and contrast information in a series of complex pattern discrimination experiments. Observers discriminated between simple gratings, between gratings masked by components that differed widely in spatial frequency and/or orientation, and between patterns that presented two cues to discrimination, one in each frequency and/or orientation band. Component cues were combined either in rigid-object correspondence (e.g. both components were rotated clockwise in one pattern and counterclockwise in the other) or in opposition (e.g. in one pattern one component was rotated clockwise, the other counterclockwise; the direction of rotation was reversed for each component in the second pattern). The results demonstrate that information from tuned pathways is not always used directly in making spatial judgments, but in some cases is combined across wide regions of the Fourier domain prior to the discrimination decision. We find two distinct patterns of combination that appear to independently signal information about texture and edges. These findings provide a potential link between low-level, spatially tuned analyzers in the visual system and higher-level pattern processing mechanisms.


Segregation of mesh-derived textures evaluated by resistance to added disorder.

In the "figure detection task" the strength of segregation for a particular texture pair was estimated by the threshold amount of added disorder that prevented segregation of a textured figure from a textured ground. Disorder was either jitter in the orientation of the texture elements, or jitter in their xy positions, or a mixture of the two. Other procedures included lowpass filtering, and a task requiring discrimination between textured figures of different shapes. Orientation cues are weakly or inconsistently used for segregating mesh textures. The low spatial harmonics are very important. A new finding is that orientation and position jitter thresholds for a set of figure/ground texture patterns are often proportional. In a mixture the one disorder can be exchanged for the other.


The influence of eccentricity on position and movement acuities as revealed by spatial scaling.

The rate of decline with increasing eccentricity of several position and movement acuities was measured using a method of spatial scaling. In this method all stimuli at each visual field location are simply magnified versions of each other. The influence of separation and eccentricity were dissociated by presenting stimuli on an iso-eccentric arc. For each task, the rate of decline in performance was quantified by the parameter E2 which represents the eccentricity at which stimulus size must double in order to maintain performance equivalent to that at the fovea. All tasks were found to obey the concept of spatial scaling in that performance at a given field location could be equated with performance at any other location simply by a change of scale. However, the rate at which performance deteriorated with eccentricity varied over an enormous range (over 100-fold) depending on the task itself. The advantage of such diverse peripheral gradients is clear; the goal is to establish the physiological mechanisms which underlie this phenomenon.


Blurring by fixational eye movements.

A complete description of the loss of contrast sensitivity at high spatial frequencies requires an estimate of the role of eye movements, which could blur fine detail. We describe a new technique to isolate their effect. Observers viewed either a 100 c/deg interference fringe, which the cone mosaic aliased to a low frequency zebra stripe, or an artificial zebra stripe. The real and artificial zebra stripes have similar spatial patterns, but differ in the temporal modulation produced by eye movements. Contrast threshold was measured as a function of duration for both stimuli flashed in the dark. The ratio of the contrast thresholds for the real and artificial zebra stripes with long durations, when eye movements could have a differential effect, is always within a factor of two or so of the ratio for 1 msec flashes, when eye movements are eliminated. These results support the view that eye movements are only a minor source of image degradation even at very high spatial frequencies, and provide no support for the view that they improve high resolution tasks.


Dynamic noise backgrounds facilitate target fading.

With strict fixation, a small uniform target of medium contrast, placed at 10 deg eccentricity, faded much faster when presented on a dynamic random noise background than on either a static random noise background or a uniform background of the same luminance. Time to first disappearance was between 10 and 16 sec when the background was dynamic, 26 sec when it was static, and 57 sec when it was uniform. Times were shortest for temporal noise frequencies of the background between 3.5 and 15 Hz. These findings are unexpected: the frequent change of pixel contrast at the edge of the target should perceptually enhance the border, make it less susceptible to local adaptation, and prevent fading. Instead, dynamic random noise facilitates, rather than suppresses fading. Three potential mechanisms are discussed: edge perturbation, jerk effect and surround induction.


Color mixing in the pigeon (Columba livia) II: A psychophysical determination in the middle, short and near-UV wavelength range.

Pigeons were trained to discriminate between spectral lights and additive mixtures in the 350-560 nm spectral range using a successive "autoshaping" discrimination procedure [introduced in Palacios, Martinoya, Bloch & Varela, Vision Research, 30, 587-596 (1990)]. Dichromatic mixtures were found in the short and near UV region, but not in the middle-wave region. Our results suggest that color vision in the pigeon involves the active participation of five different primary mechanisms, which are differentially active in the yellow- and red-sensitive retinal fields.


Red-green and yellow-blue opponent-color responses as a function of retinal eccentricity.

Using the hue cancellation technique, I measured the spectral sensitivities of red-green (r-g) and yellow-blue (y-b) opponent-color responses of two color-normal observers at 0 (fovea), 3.3, 10, 21, and 31 degrees along the horizontal meridian of the temporal retina. The stimulus size as a function of retinal eccentricity was varied according to the cortical magnification factor. I found that the net spectral sensitivity (i.e. corrected for macular pigment) of the r-g channel was approximately constant as a function of retinal eccentricity. On the other hand, the net spectral sensitivity of the y-b channel was not constant. For the y-b channel I found a constant spectral sensitivity as a function of eccentricity when no macular correction was made. This means that the y-b system changes its yellow and blue responses with eccentricity to counterbalance the effects of macular pigment.


Orientation bandwidth: the effect of spatial and temporal frequency.

The orientation bandwidths of psychophysically defined channels of human vision were estimated by two techniques for a wide range of spatial and temporal frequencies. The first technique was an adaptation paradigm, where the subjects' ability to see patterns of various orientations was measured before and after adapting to a high contrast pattern. The second technique evaluated subjects' ability to discriminate between two gratings of different orientations in relation to their ability to detect the patterns. Bandwidths were unaffected by temporal frequency at high spatial frequencies but increased with temporal frequency at low spatial frequencies. Bandwidths increased modestly with decreasing spatial frequency at low temporal frequencies but more drastically at high temporal frequencies. Both techniques gave similar results except for patterns with very low spatial and high temporal frequencies. In this region the stimulus appears "spatial-frequency doubled" which may be used as a cue for the orientation discrimination task.


Losses of flicker sensitivity during dark adaptation: effects of test size and wavelength.

The losses of flicker sensitivity that occur during dark adaptation following extinction of a bleach depend greatly on the test stimuli that are used to measure those losses. Generally, the larger the test size is for a given test wavelength, the later is the loss of flicker sensitivity; for sufficiently large tests, losses become progressively more gradual. Similarly, the shorter the test wavelength is (between about 660 and 580 nm) for a given test size, the later is the loss of flicker sensitivity; for sufficiently short test wavelengths, losses become progressively more gradual. Although the pattern of flicker sensitivity loss as a function of test size is the same both foveally and parafoveally, foveal losses occur later and/or more gradually for a given test stimulus. The results suggest that losses of flicker sensitivity occur when spectrally antagonistic response(s) to the test are no longer adequate to maintain the flicker-response to that test. The results suggest also that the adequacy of such spectral antagonism depends on the local adaptation state of the retina, which becomes increasingly more light-adapted with increasingly large test size.


Binocular measurements of chromatic adaptation.

In this paper we present asymmetric matching data that were obtained with a binocular presentation method. Our main motivation was the question whether chromatic adaptation, one of the important mechanisms that contribute to colour constancy, has evolved towards a better performance in the range of colours that are present in the natural image. For the eye adapted to a bluish illuminant for example the presence of an object with a deep yellow colour is very unlikely. So, it was expected that the colour difference between adapting light and target has an influence on the extent of chromatic adaptation. It was found that the colour shift in the observers' matches that can be attributed to chromatic adaptation indeed has a maximum. The location of the maximum, however, was unexpected, i.e. colour differences between target and adapting light that lie around 0.05 u'v'-chromaticity units. Additionally, several models for chromatic adaptation were fitted to our data. It was found that, except for the simple von Kries model, Retinex Theory and difference contrast, a number of models gave good predictions for the L-wave and M-wave fundamental systems, but that predictions for the S-wave system were less accurate.


Probability summation of acuity in the human infant.

Raw data from two studies of monocular and binocular acuity development were used to determine whether a binocular acuity advantage as a function of age is predicted by probability summation and whether these predictions accurately describe the course of binocular acuity development. Two decision rules for the combination of the outputs of right eye and left eye "channels" were evaluated, the decision-threshold rule and the integration rule. Both decision rules predicted a binocular acuity advantage for infants and children aged 0-60 months. However, both rules failed to adequately describe the normal course of monocular and binocular acuity development. No binocular acuity advantage was found prior to 6 months of age while, after 6 months of age, binocular acuity was superior to monocular acuity by 0.12 log unit (0.4 octave). The absence of binocular acuity superiority prior to 6 months of age is consistent with suggestions by other authors that the immature human visual system combines information from the two eyes nonselectively.


Vitamin A2-based visual pigments in fully terrestrial vertebrates.

As part of a broad study of the ocular and extraocular photoreceptors of reptiles, we have used high performance liquid chromatography (HPLC) to identify the retinoids present in whole eye extracts of the arboreal lizard Anolis carolinensis and the non-arboreal ruin lizard Podarcis sicula. Unexpectedly, only vitamin A2-derived chromophore was detected in Anolis, while a mixture of vitamin A1- and vitamin A2-derived chromophores was detected in Podarcis. These are the first examples of fully terrestrial vertebrates using vitamin A2-derived chromophore for visual pigment generation. Furthermore, microspectrophotometric (MSP) data for Anolis show a class of photoreceptor having a visual pigment with maximum absorbance at about 625 nm, some 40 nm further into the red than has been found in any terrestrial vertebrate examined to date.


The rod-cone shift and its effect on ganglion cells in the cat's retina.

We examined how several characteristics of cat retinal ganglion cells--receptive field size, spatial resolution, and centre-surround antagonism--change with background illumination. Spectral sensitivity was also measured to see how these changes depend on the rod-cone shift. The radius of the centre mechanism changed very little across the mesopic range. The absence of a change can be attributed to the connections rods make with cones, and to the small spatial spread of rods which connect to a cone. The highest spatial frequency to which a cell could respond dropped sharply with falling background illumination. This loss of spatial resolution is due partly to increasing receptive field size, and partly to loss of contrast gain. Centre-surround antagonism approached zero as background illumination fell. The loss of antagonism could have been due to either a change in the subtractive relationship between centre and surround, or due to a loss of surround strength relative to centre strength; the latter was shown to be the case.


Effects of sodium iodate on the electroretinogram c-wave in the cat.

The c-wave of the vitreal electroretinogram decreased in amplitude and was replaced by a slow, polarity reversed potential following an i.v. infusion of sodium iodate, as first described by Noell. Intraretinal recordings showed that the negative-going c-wave, induced by iodate (30 mg/kg), was composed of reduced slow pIII and trans-epithelial c-wave. The effects of iodate on these components may originate from direct effects on the retinal pigment epithelial cells, namely, a large decrease in the trans-epithelial resistance. Other factors could have contributed to the change in the c-wave amplitude.


Head orientation in pigeons during landing flight.

Landing flights of pigeons were video recorded or filmed, and frame-by-frame measurements were made of the angle of the head relative to the horizontal, and of the position of the perch in the visual field. The angle of the head increases above that seen in free flight, to a value which is correlated with the trajectory of approach to the perch. As a result, the perch is fixated 20-25 degrees above the beak early in landing flight. The possible significance of the behaviour is discussed in relation to specialised retinal areas and to lower-field myopia.


"Weber's law" for position: the role of spatial frequency and contrast.

We used Gabor bars to measure the effects of spatial bandwidth, spatial scale, contrast and separation on three-line spatial interval discrimination (bisection). In the first experiment, we used stimuli that were well above threshold. Our results show that at all spatial scales, spatial interval discrimination (three-line bisection) thresholds are proportional to the separation of the Gabor patches (i.e. Weber's law) when the separation exceeds approximately 2.5 times the standard deviation (sigma) of the Gaussian envelope. The optimal threshold occurs when the separation is approx. 2-2.5 sigma, and for separations larger than the optimal, bisection thresholds are equal to a more or less constant Weber fraction (delta s/s) of approx. 0.02-0.04. These results are consistent with a number of previous studies. In the second experiment, we examined the effect of contrast. Our results show an interaction between separation and stimulus visibility. Reducing the stimulus contrast has a marked effect on spatial interval thresholds at small separations (e.g. separations less than about 3 sigma), and much less effect at larger separations. Thus, the Weber's law relationship appears to depend on the visibility of the stimuli, but does not depend on the spatial frequency or bandwidth of the stimuli. These results can be predicted by an ideal observer model of spatial interval discrimination.


No aliasing at edges in normal viewing.

Although spatial aliasing by the extrafoveal retina can occur under natural viewing conditions, it does not commonly disturb our vision. One possible explanation for this is that real scenes do not have sufficient power in the high frequencies to produce aliasing. We examined whether aliasing distorted the appearance of a high contrast edge, which is a common stimulus in the environment. Observers made a two-interval forced-choice discrimination between low-pass filtered and unfiltered edges at 0, 10, 20, and 40 deg eccentricity. This discrimination could be made only when frequency components were removed below both the cone and ganglion cell Nyquist frequencies at each eccentricity. Since supra-Nyquist frequency components could not be detected in edges, they are incapable of producing aliasing.


The remarkable saccades of asymmetrical vergence.

The saccades that usually arise near the onset of asymmetrical changes in vergence, when one eye is aligned with both targets, are remarkably different from ordinary saccades: (1) the excursions of the two eyes are typically very unequal, often differing by several fold from each other; (2) mean excursion (version) is extremely variable across replicate tests with identical targets; (3) at the end of the saccades, eye orientation is usually not even briefly stable: the aligned eye immediately reverses its movement, indicating that the pulse in muscular forces is apparently not followed by a corresponding step; and (4) a second saccade in the opposite direction can immediately follow the initial saccade of asymmetrical divergence, with no sign of refractoriness. These phenomena suggest that the pulse and step components of saccadic motoneuron activity may be generated by largely independent processes; that the step component for each eye depends only on that eye's visual input; and that the pulse components generated for each eye depend on weighted averaging of visual stimuli that impinge on both eyes. This interpretation is incompatible with most current models of saccade generation, but was anticipated in its essentials by Ditchburn [(1973) Eye movements and visual perception. Oxford: Clarendon Press]. A corollary of this hypothesis is that disparity-evoked vergence changes can be viewed as the general-case output from that system which produces fully conjugate saccades as a special case.


Simple-pooling of unidirectional motion predicts speed discrimination for looming stimuli.

Looming objects comprise many 2D unidirectional motion elements changing over time. However, observers assign a single 3D speed to looming objects, not many independent unidirectional speeds to different regions of the object. These experiments examined speed discrimination for looming stimuli to illuminate the mechanisms underlying the perception of 3D motion. Speed discrimination thresholds for looming displays were comparable to those of fronto-parallel translating and rotating displays (approximately 5%), and thresholds were predicted from the simple linear combination of 2D unidirectional thresholds. These results suggest that 2D unidirectional motion and looming motion are not independent: the simple pooling of unidirectional motion units limits sensitivity to looming stimuli. These results do not support the notion that the visual system directly encodes relative motion within a distinct channel.


Visual acuity in the horse.

We assessed the ease with which horses could learn visual discriminations and measured their resolution acuity. We trained three horses to press their noses against one of two large wooden panels to receive a small food reward. Following training on a series of two-choice discrimination tasks, resolution acuity was measured. Although there was some variability between animals, the best acuity obtained was 23.3 c deg-1. Within the margin of error imposed by limited anatomical data, the obtained values are consistent with predictions based on retinal ganglion cell density estimates and posterior nodal distance/axial length ratios. They suggest that the resolution acuity of the horse is limited by ganglion cell density in the temporal portion of the narrow visual streak.


Separation discrimination with embedded targets.

Previous research has shown that separation discrimination thresholds are independent of the internal spatial scale (local spatial frequency) of the targets whose separation is being judged. The experiments reported here tested the generality of this conclusion for separation discrimination of targets that were embedded in an array of identical objects, where crowding could enhance the importance of the scale at which the individual target locations are encoded. No effect of the local spatial scale of the targets was found under these conditions.


Thyroxine induces a precocial loss of ultraviolet photosensitivity in rainbow trout (Oncorhynchus mykiss, Teleostei).

Small (< 30 g) juvenile rainbow trout (Oncorhynchus mykiss) possess retinal photoreceptor mechanisms sensitive to ultraviolet (UV), short (S), middle (M) and long (L) wavelengths. During normal development, the sensitivity peak of the UV cone mechanism (360 nm) shifts towards the S-wavelengths (to an intermediate lambda max of 390 nm) until, at approx. 60 g, individuals are no longer sensitive in the UV (only a S-wavelength peak at 430 nm remains). This shift in spectral sensitivity is associated with the loss of small accessory corner cones from the retinal photoreceptor cell mosaic. Treating small (< 30 g) rainbow trout with thyroid hormone induced a precocial loss of UV photosensitivity and an associated change in the retinal photoreceptor cell mosaic, identical to the events that occur during normal development.


Visual processing of optic acceleration.

We present data on the human sensitivity to optic acceleration, i.e. temporal modulations of the speed and direction of moving objects. Modulation thresholds are measured as a function of modulation frequency and speed for different periodical velocity vector modulation functions using a localized target. Evidence is presented that human detection of velocity vector modulations is not directly based on the acceleration signal (the temporal derivative of the velocity vector modulation). Instead, modulation detection is accurately described by a two-stage model: a low-pass temporal filter transformation of the true velocity vector modulation followed by a variance detection stage. A functional description of the first stage is a second order low-pass temporal filter having a characteristic time constant of 40 msec. In effect, the temporal low-pass filter is an integration of the velocity vector modulation within a temporal window of 100-140 msec. A non-trivial link of this low-pass filter stage to the temporal characteristics of standard motion detection mechanisms will be discussed. Velocity vector modulations are detected in the second-stage, whenever the variance of the filtered velocity vector exceeds a certain threshold variance in either the speed or direction dimension. The threshold standard deviations for this variance detection stage are estimated to be 17% for speed modulations and 9% for motion direction modulations.


Two separate neural mechanisms of brightness induction.

A particular rate of quantal absorption by photoreceptors may result in a dim or an intense percept, depending on light stimulating other parts of the retina. The brightness of an object in a natural scene, therefore, depends on the amount of light reflected from the object in comparison to light from other parts of the scene. We show this phenomenon is mediated by two separate neural mechanisms at distinct levels of the visual system. The first mechanism depends on retinal image contrast between adjacent regions. The second mechanism depends on the binocularly fused "cyclopian" representation and is influenced by more remote, noncontiguous areas of the visual field.


Temporal and spatial integration in dynamic random-dot stimuli.

Random-dot cinematograms comprising many different, spatially intermingled local motion vectors can produce a percept of global coherent motion in a single direction. Thresholds for discriminating the direction of global motion were measured under various conditions. Discrimination thresholds increased with the width of the distribution of directions in the cinematogram. Thresholds decreased as the duration of area of the cinematogram increased. Temporal integration for global direction discrimination extends over about 465 msec (9.3 frames) while the spatial integration limit is at least as large as 63 deg2 (circular aperture diameter = 9 deg). The large spatial integration area is consistent with the physiology of higher visual areas such as MT and MST.


Monochromatism determined at a long-wavelength/middle-wavelength cone-antagonistic locus.

The foveal increment threshold spectral sensitivity function for a 500 msec raised cosine stimulus without spatial edges exhibits a sharp drop or "notch" in sensitivity that coincides with the wavelength of a long-wavelength adapting field. An appropriate name for this phenomenon is the "Sloan notch", after Louise Sloan, who first observed a notch in a foveal threshold spectrum. We have examined suprathreshold discriminability on both sides of the Sloan notch produced by a 6700 td, 578 nm adapting field. In a temporal two-alternative forced-choice paradigm, a suprathreshold 650 nm low-frequency "standard" stimulus was paired with low-frequency "test" stimuli, of wavelength between 600 and 670 nm and varied intensity; the observer's task was to identify the interval containing the standard. Discriminability of the test and standard typically dropped to chance for some particular test intensity, producing "indiscriminability action spectra", up to 0.7 log units above threshold. Truncated spectra (between about 530 and 560 nm) were also obtained from observers on the middle wavelength side of the Sloan notch, for a 550 nm standard. The indiscriminability action spectra of each observer were identical, up to scaling, with the observer's threshold action spectrum. Analysis of the action spectra shows that the indiscriminable stimuli are rendered equivalent at the input to a neural pathway where L- and M-cone signals converge with opposite sign. We also investigated discriminability in the spectral region containing and immediately surrounding the Sloan notch. Suprathreshold stimuli in the spectral region near the notch produce percepts that are always discriminable from 650 and 550 nm standards (and from one another), and thus we conclude that in this spectral region, perception is mediated in part by a pathway distinct from that which signals the standards. The action spectrum of this latter pathway was estimated with a variant of the discrimination procedure, and found similar to V lambda over the spectral region 575-610 nm.


Reversal in the sequence of the Benham colours with a change in the wavelength of illumination.

A Benham disk was rotated at 7 c/sec and illuminated by monochromatic lights from the range 534-586 nm. The elicited colours of the rings were described either with a colour naming procedure or by matching with a Munsell chip. Exchanges of hues between the two extreme rings and between the two inner rings were reported around 557 and 566 nm by the colour naming procedure, thus resulting in a hue reversal in the spatial display of colours. Similar hue shifts were also reported with the matching procedure. The effect of a possible displacement in the equilibrium of colour-opponent cell population, resulting from chromatic adaptation, is discussed.


Motion thresholds of briefly visible stimuli increase asymmetrically with age.

During a pursuit eye movement made across a stationary stimulus, that stimulus is often perceived as moving slightly in the direction opposite to the eyes (Filehne illusion). The illusion is generally thought to increase in strength when the stimulus is made visible only briefly. In two experiments the illusion was indeed observed with young subjects. However, with older subjects brief stimulus presentations yielded a strong inverted Filehne illusion (the stimulus appeared to move in the same direction as the eyes). This age dependency of the Filehne illusion is caused by an increase of only the threshold for stimulus motion in the direction opposite to the eyes. No such effect happens with the threshold for stimulus motion in the same direction as the eyes. These findings can be explained if we assume that with increasing age it takes more time to properly register retinal image velocity within the perceptual system.


Orientation dependence in the recognition of familiar and novel views of three-dimensional objects.

We report four experiments that investigated the representation of novel three-dimensional (3D) objects by the human visual system. In the first experiment, canonical views were demonstrated for novel objects seen equally often from all test viewpoints. The next two experiments showed that the canonical views persisted under repeated testing, and in the presence of a variety of depth cues, including binocular stereo. The fourth experiment probed the ability of subjects to generalize recognition to unfamiliar views of objects previously seen at a limited range of attitudes. Both mono and stereo conditions yielded the same increase in the error rate with misorientation relative to the training attitude. Taken together, these results support the notion that 3D objects are represented by multiple specific views, possibly augmented by partial viewer-centered 3D information.


[The coronary sinus as a source of activated T-lymphocytes in patients after orthotopic heart transplantation].

Mononuclear cells are the component of blood responsible for allograft recognition, rejection and acceptance. Shifts in the patterns of various mononuclear cell subpopulations were often used as a diagnostic tool in detection of heart rejection. The specificity of mononuclear cell monitoring has remained a controversial point until today, because infections led to similar changes as organ rejection. In this study we investigated whether mononuclear cells taken from coronary sinus blood give more information about the immunological status of the transplanted heart than those taken from central verous blood. After endomyocardial biopsy, coronary sinus blood was sampled by catheterization under X-ray control. Blood from the right atrium was taken for control measurement. Mononuclear cells obtained by density gradient cytocentrifugation were stained with monoclonal fluorescein conjugated antibodies detecting CD4- (T helper)-, CD8- (T suppressor)-, CD25- (Interleukin-2 receptor), and the CD71- (Transferrin receptor) antigens. Endomyocardial biopsies were graded according to the Billingham scheme. In the absence of rejection, the phenotypes of mononuclear cells from the coronary sinus did not differ from those of right atrial cells. Mild rejection led to a statistically insignificant increase of CD4- CD25- and CD7-antigen bearing cells in the coronary sinus blood, whereas the CD8 positive cells remained stable as compared to mononuclear cells from the right atrium. However, patients with moderate rejection showed a significant elevation of CD4 positive cells and activated T-cells (CD15-, CD71-positive cells) in the coronary sinus as compared with cells from the right atrium. The T helper/suppressor ratio (Th/s-ratio) shifted towards the T-helper population.(ABSTRACT TRUNCATED AT 250 WORDS)


[Differential diagnosis of ascites and abscess forming hepatitis in AIDS patients with reference to the first patient with microsporidia infection in Austria].

We report on a 30 years-old female AIDS patient suffering from generalized pneumocystosis and intestinal microsporidiosis. The chest X-ray showed a right-sided pleural effusion; the lungs showed no areas of consolidation and the heart and the vessels were normal in size. Sonography revealed multiple cystic lesions of the liver measuring 1-3 cm in diameter, as well as ascites. Pneumocystis carinii was detected on cytological examination of the bronchoalveolar lavage fluid, the pleural effusion and the ascitic fluid. Intestinal microsporidiosis was diagnosed by cytological examination of the stool. Both pneumocystis carinii infection and microsporidiosis may cause hepatitis and ascites. In our patient the organ manifestations of the two infections did not overlap. Since simultaneous organ manifestations are possible the differential diagnosis is discussed. This is the first case of microsporidiosis reported in Austria.


[Lymph drainage with secondary lymphedema caused by Kaposi sarcoma].

For reasons not yet known HIV infected patients in the final state of their aids disease often tend to develop Kaposi's sarcoma. These tumours result in secondary lymphatic edema which is found on both sides of the sarcoma up to the regional lymphatic nodes, transferred by the tumour cells. Depending on the state of the edema, a lymph drainage treatment is indicated palliatively; the patients can thus be relieved. A fundamental deterioration of the prognosis is not to be expected, the more as all patients are in the final state of this not yet curable disease. Differing from treatment of other lymphatic edema, it is of special importance to the therapist--apart from the difficult and specifically psychic burden--to pay attention to a protection from infection by gloves as a precaution for each single treatment.


[Neurologic principles of edema in inactivity].

The complete immobilisation of a limb alone can lead to the formation of oedema. Whereas the oedema secondary to inactivity induced by immobilisation is completely reversible, and will only lead to tissue damage in the longterm, neglect of oedema secondary to inactivity in the presence of central and peripheral paresis (apoplectic insult, paraplegia, damage to the plexus brachialis) may entail serious consequences due to the danger of tissue fibrosis. With paresis of an extremity, the lymphovenous return is impaired by two decisive factors: increased hydrostatic pressure in the distal limb segment, and absence of the muscle pump. In flaccid paresis, where there is low muscle tone and no muscle pump action, there is also a low venous tone and the resultant hydrostatic pressure is especially high. Venous stasis in the sub- and prefascial veins leads to increased protein loss from the venous limb of the capillaries and the venules. Compensation initially occurs in the prefascial lymph outflow region (latent oedema) which becomes decompensated if overloaded (visible oedema). Fibrosis of the subcutis and trophic skin changes are the result. In spastic paresis the regional subfascial lymphatic system responds with lymphangiospasm. Where the sympathetic innervation is interrupted (e.g. brachial plexus paralysis) there is passive hyperaemia of the terminal vessels with vascular dilatation and lymphangioparalysis. Insufficiency of the vascular walls results in an accumulation of protein in the tissues, which ultimately ends in fibrosis with ankylosis and shortening of the tendons and muscles. The early administration of complex physical decongestion therapy with manual lymphatic drainage can prevent this state.


[Contribution of prelymphatic structures to lymph drainage].

Vitalmicroscopic findings confirm the existence of a "low resistance pathway" for the transinterstitial fluid movement from the pillaries to the initial lymphatics. One part of this prelymphatic system is represented by submicroscopical spaces along the connective tissue fibres between ground substance (high resistance pathway) and fibre surface. The other part is represented by a network of prelymphatic tissue channels which are open connected with the initial lymphatic system.