Growth interaction between Candida albicans and Streptococcus salivarius: in vitro and in vivo studies. Suppression of Candida albicans in the mouth by oral flora has been proposed as one of the mechanisms preventing candidal overgrowth. According to Liljemark and Gibbons (1973), Streptococcus salivarius plays a significant role in this process. The aim of this investigation was to study the growth interaction between C. albicans and S. salivarius in vitro and in vivo. An aerobic continuous-flow system was used for the in vitro study. Pure and mixed cultures of C. albicans (NCPF 3118) and S. salivarius (NCTC 8618) were inoculated into a buffered medium containing either 0.1 per cent or 0.001 per cent glucose concentrations and incubated at 37 degrees C for 55 hours. Two in vivo investigations were undertaken using inbred germfree C3H mice. In the first, mice were exposed to a mixed suspension of S. salivarius and C. albicans for 48 hours. In the second the mice were exposed to S. salivarius for 48 hours. Fourteen days later they were contaminated with C. albicans. A comparison of growth curves showed no growth inhibition between the species. The in vivo studies showed that oral lesions from candidal infestation occurred in all mice. We were therefore unable to demonstrate in vitro or in vivo suppression of C. albicans in the presence of S. salivarius.


Tooth and cusp size reduction in second molars. The present study examined the cusp reduction pattern of molars in two San-Hybrid groups, namely, the Vassekela and Barakwena. Cusp and crownbase area measurements were undertaken on enlarged photographs of maxillary molars and on camera lucida drawings of mandibular molars. The protocone values for the Barakwena were significantly larger than those of the Vassekela and were also the largest of the four maxillary molar cusps (especially in M2). The metacone was the second largest cusp in M1, the paracone the second largest cusp in M2 and M3, while the hypocone was the smallest cusp in all maxillary molars. Maxillary crownbase areas were larger in the Barakwena than in the Vassekela but these differences were not statistically significant. The protoconid, entoconid and metaconid were the largest of the mandibular molar cusps. Generally, the cusp area values in first and third molars were larger in the taller Barakwena than in the shorter Vassekela. These differences were not statistically significant. In second molars, however, an unexpected finding was that crownbase and cusp areas (except the metaconulid) were significantly larger in the Vassekela than in the Barakwena. This study indicates that second molars show more cusp size differences in the two groups than do the other two molars. This may be regarded as a conservative tendency (Korenhof, 1960) in which case it would indicate that some second molar cusps are in a less active phase of evolutionary reduction than the same cusps in first and third molars.


A survey of dental practice and equipment characteristics. The aim of this study was to determine what would be regarded as essential equipment required for setting up a dental practice and the cost thereof. This information could be useful for the newly qualified dentist. Seventy five completed questionnaires returned from a randomly selected group of practising dentists were analysed to obtain this information. Equipment costs were obtained from a dental supply house and are tabulated. Guidelines recommended for setting up a practice include determining the type of service to be rendered, selecting the equipment required for this purpose, seeking expert financial advice and commencing the practice on a conservative basis with only the essential items of equipment.


Plaque quantitation through protein measurement. This study was undertaken to establish whether the quantitation of dental plaque protein by a dye-binding method (Coomassie G-250) may be used as an index of the amount of dental plaque sampled. Ten sites were sampled in 34 children on 5 occasions at 4 month intervals. The mean protein concentration in 1391 plaque samples was 6.9 +/- 4.1 micrograms (micrograms) (mean +/- standard deviation). A three-way analysis of variance showed that the plaque protein concentration was similar at the different sampling sites in the same child (p = 0.14), but statistically significant differences were observed with respect to time of sampling (F = 36.24; p = 0.0001) and individual sampled (F = 5.69; p = 0.0001). These observations indicate that plaque bacterial counts may be expressed as units of protein concentration and this method may be useful to relate the number of viable bacteria to an estimate of the amount of plaque collected. This ratio allows standardisation for any variation in the amount of plaque collected.


Salivary flow induction by buccal permucosal pilocarpine in anesthetized beagle dogs. We tested whether permucosal delivery of pilocarpine nitrate could be used to elicit significant salivary secretion. Pilocarpine (pKa 6.6 at 37 degrees C) was applied as solutions (pHs 5.6, 6.6, 7.6; 15 mg/mL) to the buccal mucosa (2.8 cm2) of 6 anesthetized dogs. Saliva was collected continuously from cannulated submandibular and parotid ducts and blood sampled during and after drug administration. Plasma pilocarpine levels were determined by reversed-phase HPLC. Absorption rates were determined by use of data from separate zero-order intravenous infusions to the same dogs. Pilocarpine was buccally absorbed at a constant rate of 72.9 +/- 38.5 micrograms/kg/h following its application at pH 7.6. At this pH of the drug solution, the time to appearance of pilocarpine in blood plasma was 0.31 +/- 0.08 h, and the time to appearance of salivary flow was 0.86 +/- 0.32 h. A threshold dose of 32.9 +/- 7.5 micrograms/kg was required to induce secretion with the pH 7.6 drug, the steady-state submandibular flow rate was 0.14 +/- 0.11 mL/min/gland pair. Salivary flow induction was symmetrical and reached levels as high as 0.35 mL/min/submandibular gland pair without apparent tachyphylaxis. Results at pHs 5.6, 6.6, and 7.6 were consistent with the hypothesis that pilocarpine is primarily absorbed as un-ionized drug. The data indicate that transmucosal delivery of pilocarpine, avoiding "first pass" hepatic loss, may hold promise for the treatment of xerostomia.


Fluoride concentrations in plaque, whole saliva, and ductal saliva after application of home-use topical fluorides [published eerratum appears in J Dent Res 1993 Jan;72(1):87]. It is now well-accepted that the primary anti-caries activity of fluoride (F) is via topical action. The retention of F in the mouth after topical fluoride treatment is considered to be an important factor in the clinical efficacy of F. The purpose of this study was to evaluate F levels in ductal saliva, whole saliva, and pooled plaque after treatment with topical F agents intended for home use. Ten consenting adults, mean (SD) age 31.0 (8.2) years, participated in all aspects of the study. Two days before each test, subjects received a professional tooth cleaning and subsequently abstained from all oral hygiene procedures to permit plaque to accumulate, and from the use of F-containing dental products. Treatments consisted of a placebo dentifrice (PD), fluoride dentifrice (FD; 0.24% NaF), fluoride rinse (FR; 0.05% NaF), and fluoride gel (FG; 1.1% NaF). Unstimulated whole saliva and pooled plaque were sampled at multiple points over a 24-hour period. In a separate experimental series, stimulated parotid saliva was sampled over a two-hour period after treatment. Fluoride levels generally followed the same pattern in whole saliva and pooled plaque samples, with FG > FR > FD > PD. Night-time F application resulted in prolonged F retention in whole saliva but not in plaque. Fluoride levels in parotid saliva were only slightly higher after F treatment and returned to baseline levels within two h. The results of this study indicate that the method of F delivery, the F concentration of the agent, and the time of application (daytime vs. night-time) are important factors influencing F levels in the mouth.(ABSTRACT TRUNCATED AT 250 WORDS)


Composition of pooled plaque fluid from caries-free and caries-positive individuals following sucrose exposure. The composition of pooled plaque fluid from five population samples was determined before and at selected times (7, 15, 30, and 60 min) after a 10% sucrose rinse. Subjects were grouped according to caries status (caries-free, CF, DMFS = 0; caries-positive, CP, DMFS > 10). Samples were also studied from white-spot surfaces and from sound surfaces of the same mouths of two additional CP groups. Plaque fluid was isolated by centrifugation and analyzed for organic acids, inorganic ions (ion chromatography), and pH (microelectrodes). Prior to sucrose exposure, plaque fluids from the CF subgroups and from sound surfaces of the CP subjects had higher pH values than samples from CP subgroups and from white-spot surfaces, respectively; the ionic compositions were otherwise similar. Starved plaque fluids were also found to be supersaturated with respect to enamel and to a significantly greater degree in the CF samples, suggesting that CF plaque fluid may have a greater remineralization potential than CP samples. Following sucrose exposure, a rapid decrease in plaque fluid pH was observed, which corresponded primarily to lactic acid production. For all times examined, mean pH and DS(En) values were lower and lactic acid concentrations were higher in the CP samples than in the CF samples; noted differences were statistically significant at 7 min for pH and DS(En), and at 7, 15, and 30 min for lactic acid. Lower values of DS(En) suggest that plaque fluid from CP subjects had a measurably greater cariogenic potential.(ABSTRACT TRUNCATED AT 250 WORDS)


Effect of xylitol consumption on the plaque-saliva distribution of mutans streptococci and the occurrence and long-term survival of xylitol-resistant strains. Since the exposure of mutans streptococci to xylitol is known to select for xylitol-resistant (XR) natural mutants, the occurrence and long-term survival of such xylitol-resistant strains was evaluated in a cross-sectional sampling of participants of the Ylivieska xylitol study four years after the original two-year experimental period. Paraffin-stimulated whole saliva was first collected, and then plaque was collected and pooled. The salivary and dental plaque mutans streptococci were enumerated after growth on TSY20B agar. The proportion of XR strains was determined by autoradiography with 14C-xylitol. A strong and significant correlation (r = 0.645 and p = 0.005) between the number of mutans streptococci in saliva and in dental plaque was observed in non-consumers of xylitol. Such a correlation totally disappeared (r = 0.098 and p = 0.612) in xylitol-exposed consumers (habitual and former xylitol-consumers). The proportion of the salivary XR mutants (35%) in non-consumers (n = 16) was significantly lower than in the xylitol-exposed consumers (79%) (n = 27), (p = 0.0001) or in former consumers (75%) (n = 13), (p = 0.0008) or in the habitual consumers (83%) (n = 14), (p = 0.004). The proportion of XR mutants in dental plaque was, on the average, much lower than in the corresponding saliva. The proportion of XR in the plaque of xylitol non-consumers was half of that of the xylitol-exposed group, but the difference was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)


Effect of delmopinol on the cohesion of glucan-containing plaque formed by Streptococcus mutans in a flow cell system. Glucan-containing plaque was formed by Streptococcus mutans adhering to saliva-coated glass slides in flow cells thermostated at 37 degrees C. The substrate was Brain Heart Infusion broth containing 1% sucrose and 10% sterile saliva. During the build-up of the plaque, which lasted for 29 h, the plaque was subjected to three two-minute exposures to either 0.1 mol/L sodium acetate buffer, pH 6.0, or the same buffer containing 6.4 mmol/L (0.2%) of the surface-active anti-plaque substance delmopinol hydro-chloride. The glass slides carrying the plaque were weighed, and plaques subjected to delmopinol treatment weighed only seven percent of the control plaques. The glass slides were then mounted in a beaker containing buffer, subjected to ultrasonication, and re-weighed. The delmopinol-treated plaques lost 59% of their wet weight upon sonication, while the controls lost only 19%. Control plaques having the same weight as delmopinol-treated plaques were not different from the control plaques grown for 29 h with regard to reduction of plaque weight after sonication. Transmission electron micrographs (TEM) showed a plaque dominated by globular or fibrillar matrix components in controls, while the delmopinol-treated plaque showed empty or unordered matrix areas between more densely packed cells. The TEM results were confirmed by scanning electron micrographs, which showed amorphous material associated with the bacterial cells in the control but not in the delmopinol-treated plaque. In conclusion, delmopinol reduced surface-associated glucan synthesis and lowered the cohesion of the plaque, indicating that glucan-containing plaque formed during repeated rinsings with delmopinol may be easier to remove by mechanical means than a non-treated plaque of this type.


The influence of growth hormone on cell proliferation in odontogenic epithelia by bromodeoxyuridine immunocytochemistry and morphometry in the Lewis dwarf rat. For investigation of how growth hormone affects tooth development, bromodeoxyuridine immunocytochemistry and morphometry were used for the study of cell proliferation in odontogenic epithelial cell layers. The number of cells in the S phase, as revealed by this technique, and in mitosis, were counted in Bouin's-perfused and paraffin-embedded undecalcified maxillary incisor enamel organs of normal rats, in growth-hormone-deficient dwarf rats, and in dwarf rats treated with growth hormone (66 micrograms/100 g body wt) twice daily for six days. Significantly fewer labeled nuclei, unlabeled nuclei, and total nuclei of various odontogenic epithelia were found in dwarf rats, but in dwarf rats treated with growth hormone, numbers of labeled nuclei equivalent to normal were found in the internal enamel epithelium, stratum intermedium, and Hertwig root sheath. Moreover, the mitotic index for pre-ameloblasts was 1.64 in normal rats, 0.92 for dwarf rats, and 1.66 for growth-hormone-treated dwarf rats (SD, 0.10). Other parameters--such as the labeling index and the ratio of positive to negative nuclei--were similarly related to GH status. Thus, growth hormone may play a role in the proliferation of the odontogenic epithelia in the rat.


The relationship between level of mandibular pain and dysfunction and stage of temporomandibular joint internal derangement. Temporomandibular joint internal derangement (TMJ ID) is the most common intra-articular TM disorder and can progress from TMJ ID with reduction to TMJ ID without reduction. It is not known whether this anatomical progression is associated with increasing levels of mandibular dysfunction. The objective of this study was to determine whether the level of clinically detectable mandibular dysfunction was related to the stage of TMJ ID. Two clinicians examined 42 subjects prior to bilateral TMJ arthrographic evaluation. The level of mandibular dysfunction was calculated by Helkimo's Clinical Dysfunction Index (Di) and the Craniomandibular Index (CMI). Statistical analysis revealed that the level of mandibular dysfunction as determined by the Di and CMI was not related to the arthrographic presence or absence of TMJ ID. Therefore, the clinician cannot assume that the level of mandibular dysfunction is directly related to the absence or presence of TMJ ID. Epidemiologically, the CMI and Di can be used only for estimation of the degree of mandibular dysfunction, since they do not provide direct information on a specific TM disorder.


The relationship of undifferentiated mesenchymal cells to TMJ articular tissue thickness. Undifferentiated mesenchymal (UM) cells, the progenitor cells of the cartilage layer, have been assigned a significant role in TMJ articular tissue maintenance. This was based on reports of UM cell reduction with increased soft-tissue thickness for the condyle and temporal component. However, the strength of this inverse relationship was not presented and remained unclear. The purpose of the present study was to assess the strength of the correlation between UM cell presence and soft-tissue thickness in young adult TMJs at autopsy. Sagittal histological sections from the central thirds of 50 joints were evaluated with respect to articular soft-tissue thickness, histological character, and UM cell presence in the condyle and temporal component. The superior sector of the condyle and the articular eminence showed the greatest variability in soft-tissue thickness and were the only areas to show localized UM cell absence. The eminence was the only location to show an inverse relationship between soft-tissue thickness and UM cell presence, and this was consistent in both an ANOVA (p = 0.0016) and a Spearman correlation analysis. However, the strength of this correlation was only moderate (rho = -0.52), and no such relationship was observed in any other location. This study suggests that the relationship between UM cell presence and soft-tissue thickness is more complex than previously hypothesized and that the contribution of UM cells to articular tissue maintenance has been overstated, while other biological processes were overlooked.


A seven-and-a-half-year survival study of resin-bonded bridges. A clinical trial, concerning 203 resin-bonded bridges (RBBs), was performed for investigation of the influence of retainer-type and cementation materials on the survival of these restorations. The survival rates after a 7.5-year follow-up were 75% for anterior RBBs and 44% for posterior bridges. Etched metal RBBs (E-bridges) were significantly more retentive than perforated RBBs (P-bridges); the survival rates were 78% and 63%, respectively. With respect to the cementation materials, Clearfil F, in combination with E-bridges, had the best overall survival (89%, anterior and posterior). Maxillary anterior RBBs were more susceptible to failure than mandibular anterior RBBs.


Labile or surface pools of magnesium, sodium, and potassium in developing porcine enamel mineral. The present study was undertaken to assess the labile or surface pools of Mg, Na, and K ions in porcine enamel tissues at various developmental stages. The enamel samples, corresponding to the outer and the inner secretory, the early maturing, and the mature hard enamel, were dissected from the labial sides of permanent incisors of 6- to 8-month-old piglets. Each enamel sample was extracted successively with solutions of de-ionized water and 50 mmol/L Tris-4 mol/L guanidine buffer (for removal of organic matrix proteins, mainly amelogenins). The labile (free or organically bound) pools of Mg, Na, and K were assessed by the total amounts of these ionic species extracted by the water and Tris-guanidine buffer. The surface (adsorbed onto enamel mineral) pool of Mg was assessed directly by determination of the adsorption of Mg onto enamel mineral at various developmental stages. The results showed that: (i) 30-40% of the Mg in the secretory and early maturation enamel was in the surface pool (adsorbed onto the enamel mineral); (ii) 25 to 40% of the total sodium in the enamel samples was in labile forms; and (iii) most (around 70-80%) of the total potassium was readily extracted in water and appeared to originate from the enamel fluid; only marginal portions remained in the solids. The present adsorption studies also indicated that the maximum uptake of magnesium in the early maturation enamel was due mostly to an increase of the occupancy by Mg ions of adsorption sites on the crystal surfaces, which become accessible with a massive removal of enamel matrix proteins.(ABSTRACT TRUNCATED AT 250 WORDS)


Correlates of success and failure in behavior therapy for dental fear. Extreme dental fear and avoidance are universal problems, with severe adverse effects on the patient's oral health. Although behavior modification techniques were shown to be effective in the treatment of this problem, their success is by no means absolute. In the present article, the SCL-90 questionnaire was used for development of possible predictive measures for success and failure of behavior modification as a treatment for dental fear. Patients who failed in treatment through behavior modification were found to score significantly higher on the global score of Positive Symptom Distress Index (p < 0.01) and on individual subscales of somatization (p < 0.02) and psychoticism (p < 0.05) than patients who were treated successfully. The predictive value of chosen SCL-90 scales was 71%. The results suggest that use of SCL-90 may be valuable for the prediction of success and failure of behavior modification as a treatment for dental fear and avoidance.


Studies on the adhesion of glass-ionomer cements to dentin. This study investigated the bonding mechanisms of glass-ionomer cement to dentin. The approaches included mechanical determination of bond strengths, analysis of surface morphology by means of scanning electron microscopy (SEM) and confocal microscopy, and measurement of chemical changes of fracture bond sites by means of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The highest bond strengths were obtained with light-cured glass-ionomer cement. SEM and confocal images showed evidence of mechanical interlocking of cement in dentinal tubules. SIMS depth profiles confirmed the ion-exchange process between the light-cured glass-ionomer cement and the dentin surface. From corresponding XPS results, it was clear that the adhesion characteristics were significantly affected by light-curing and the chemical structure of the polymer.


Effects of cement-curing modes on dentin bonding of inlays. The aim of this in vitro study was to evaluate dentin adhesion after cementation of immediate direct "All Purpose" Hybrid (AP.H) composite inlays (Dentsply) and Cerec Dicor-MGC (Dentsply) inlays with the dentin adhesive Prisma Universal Bond 2 (Dentsply) and the dual-curing Dicor-MGC luting composite (Dentsply). In 24 extracted human molars, standard MOD cavities were prepared with one approximal margin located in enamel and the other one located in dentin. They were divided into four groups: (I) AP.H inlays, luting composite only, chemically cured; (II) AP.H inlays, luting composite, immediately-light-cured; (III) AP.H inlays, luting composite, initially chemically and delayed-light-cured (15 min); and (IV) MGC inlays, luting composite, initially chemically and delayed-light-cured (15 min). In vitro load cycles corresponding to five years of clinical stress followed. Initially and after specimens were loaded, the margins were analyzed quantitatively by SEM. The tooth/cement and cement/inlay interfaces were scored separately. The initial percentages of "continuous margin"--at both the tooth/luting composite and luting composite/inlay interfaces--were higher than 94% for all groups. At the end of the load cycles, the quality of the margins at the tooth/luting composite interface significantly decreased for all groups. The highest decrease was found for the cervical margins located in dentin, where only 37%-61% were scored as "continuous margin". The AP.H inlay/luting composite interface showed almost no change. At the MGC inlay/luting composite interface, the percentage of "continuous margin" decreased to 74%. After specimens were loaded, the percentage of "continuous margin" in dentin was lower than in enamel, despite the use of a dentin bonding agent (PUB 2).(ABSTRACT TRUNCATED AT 250 WORDS)


Influence of ketones on selected mechanical properties of resin composites. The present study investigated a concept for additional cross-linking of dental polymers, by which resistance to wear of resin composites might be increased. Bifunctional ketones were added to monomer mixtures, which were then made light-curing and loaded with filler. The monomer mixtures were varied with respect to type and ratio of monomer and ketone. For measurement of possible effects of the cross-linking agents added, four mechanical properties of the experimental resin composites were determined. Addition of the bifunctional ketone diacetyl resulted in the following increases in mechanical properties: diametral tensile strength, 11%; flexural strength, 29%; modulus of elasticity, 19%; and modulus of resilience, 50%.


Change in surface hardness of BisGMA/TEGDMA polymer due to enzymatic action. The surface microhardness of specimens made of a BisGMA/TEGDMA polymer was measured before and during treatment for 60 days with phosphate buffer or phosphate-buffered esterase solution with an activity corresponding to the mean hydrolase activity of human saliva. The hardness of the buffer-treated specimens was unchanged during the incubation period, while that of the esterase-treated specimens decreased gradually. After about five days of treatment, no further change in hardness was observed for up to 60 days. Based on the difference in the calculated hardness of the specimens as a function of the applied load during measurement, it was estimated that the mean microhardness of the outermost surface layer of the esterase-treated specimens was diminished by about 15%, compared with that of the buffer-treated specimens. From these results, it was concluded that the wear resistance of a BisGMA/TEGDMA polymer is most likely diminished by hydrolases in saliva.


Sexual advances by patients in dental practice: implications for the dental and dental hygiene curricula. The occurrence of patient initiated sexual advances toward dental health professionals has not previously been examined. Information from other health care specialties and reports from dental and dental hygiene students indicate that such advances do occur and that providers are rarely educated to deal effectively with them. Utilizing an anonymous survey of 300 Oregon dentists and 300 dental hygienists, this study sought to quantify the frequency of patient initiated sexual advances toward dental professionals and to survey practitioners as to their reactions to and methods of dealing with such advances. The information provided by the 483 (81 percent) respondents indicates that up to 44 percent of providers experience one or more patient verbal advances and up to 23 percent of providers experience one or more patient physical advances during a five year period. These advances are a significant source of concern for many dental professionals. Based upon this information, implications for the dental and dental hygiene curricula are considered.


Research directions in oral health promotion for older adults. Health education and health promotion facilitate voluntary adoption of behaviors and provide educational, organizational, economic, and environmental supports for behaviors conductive to health. Health education and health promotion are complementary and any effort to eliminate oral disease requires both activities. Federal research initiatives in oral health promotion have encouraged more biomedical and behavioral research on oral health and aging through the establishment of research centers. Other initiatives have been established to speed the generation of basic and clinical research. Recent initiatives encourage research on aging and provide opportunities for oral health promotion during the coming decade. These include Healthy People 2000, the nation's health objectives for the decade; the NIH framework for the development of a strategic plan, and the NIDR Long-Range Research Plan, Broadening the Scope.


Is dental education in step with current geriatric health promotion initiatives? As dramatic changes in U.S. society continue to stress our health care system, we must consider new strategies to meet the oral health needs of older individuals. Several recent national initiatives, including the Healthy People 2000 health objectives and the Surgeon General's Workshop on Health Promotion and Aging, provide measurable health objectives and suggestions for educational activities in the area of geriatric oral health promotion. Using these and other recent documents like "Practitioners for 2005, An Agenda for Action for U.S. Health Professional Schools," we can evaluate current educational programs in geriatric dentistry, as well plan programs and health promotional activities that meet the future needs of dental professionals and the patients they serve.


Oral health promotion for the older adult: implications for dental and dental hygiene practitioners. The role of the dental and dental hygiene practitioner in geriatric oral health promotion can be viewed in terms of three questions. What purposeful or directed steps have been taken to improve oral health promotion? How can health promotion be improved? How can education and research help the practitioner? Professional associations, educators, researchers, school curricula, instructional programs, and dental products companies have tried to improve oral health promotion. At each level, communication of information and effective use of information has been compromised. Geriatric oral health promotion can be improved by increased understanding of: (1) health promotion concepts, (2) cultural and generational issues, (3) chronic oral conditions, (4) patients' perspective, (5) promoting behavior change, (6) listening skills, (7) patients' everyday realities, (8) integrating oral health issues into other health promotion activities, (9) creating easy to understand health education materials, and (10) lobbying for third party reimbursement for oral health promotion.


Attitudes of dentists toward emerging competencies for health care practitioners. Dentists' attitudes about the importance of formal training in a variety of skills were assessed as a part of the Pew Health Professions Commission initiative to help health professional schools prepare for the future. Through a telephone survey with a 54 percent participation rate, attitudes of a national sample of practitioners were determined concerning the importance of training in 16 competencies that reflect skills, attitudes, and behaviors identified by the commission. Most respondents indicated that competency in treating and preventing disease, practicing ethically, communicating with patients, applying problem solving techniques, and continuing to learn were very important. Conversely, less than half of dentists indicated that competency in managing information, responding to cultural diversity, supporting community agencies, and working in managed care settings were very important. The opinions of graduates since 1980 about their own training in the competencies tended to mirror their ratings of importance. These results demonstrate the continuing need for dental educators to consider prevailing opinion of practicing professionals as a part of any evaluation or planning effort.


Genetic consequences of linkage between malathion resistance and an autosomal male-determining factor in house fly (Diptera: Muscidae). The pattern of inheritance of genes conferring resistance to malathion and genetic consequences of linkage between an autosomal male-determining factor and resistance genes on the second chromosome were investigated in a strain of house fly, Musca domestica L., selected for malathion resistance. The second and fifth chromosomes contribute significantly to malathion resistance. The presence of a male-determining factor linked with the resistance genes on the second chromosome resulted in a strong sexual dimorphism in malathion resistance. We also observed that the male-determining factor changed its linkage relationship from the third linkage group to the second linkage group during the selection experiments.


High levels of pyrethroid resistance in horn flies (Diptera: Muscidae) selected with cyhalothrin. Lambdacyhalothrin cattle ear tags controlled horn fly, Haematobia irritans (L.), for 14 wks or longer during 1986-1988 in Georgia, USA. In 1989 and 1990, control of < 50 horn flies per side of cow was achieved for < or = 4 wk because of high levels of pyrethroid resistance in horn flies selected with lambdacyhalothrin. The highest resistance ratios (RRs) were seen in 1989. These were 498 for lambdacyhalothrin; 92,000 for fenvalerate; and 54 for permethrin. RRs for cypermethrin as high as 8,800 were estimated in 1990 when the RR for fenvalerate was only 1,060. No cross-resistance to diazinon was detected. These high levels of pyrethroid resistance seem to have a large component of metabolic resistance. Synergistic coefficients as high as 3,600 were determined by addition of nonlethal amounts of piperonyl butoxide. Resistance development in a no-pyrethroid-use area indicates movements of > or = 3km by sufficient numbers of horn flies can significantly change the RR.


Detection of insecticide resistance in the German cockroach (Dictyoptera: Blattellidae) with glue-toxin traps. Glue that contained an insecticide was evaluated for its ability to yield useful toxicological data for German cockroaches, Blattella germanica (L.). Toxicities of three classes of insecticides were evaluated by topical applications (LD50) and exposure to insecticide-impregnated glue (LC50). Cockroaches that were resistant to topical insecticide applications were also resistant to the glue formulation. Reliability was greatest when mortality was scored 40 to 48 h after the cockroaches were placed on the glue. This method should be adaptable for insecticide resistance monitoring of German cockroaches.


Effects of cyromazine on reproduction and offspring development in Lucilia cuprina (Diptera: Calliphoridae). The effects of cyromazine on reproduction and subsequent hatch and larval developmental in Lucilia cuprina (Wiedemann) were examined by feeding the compound in water to adult flies at concentrations up to 100 ppm. Cyromazine did not interfere with oviposition or hatch; however, subsequent larval development was strongly inhibited in a concentration-dependent manner.


Vertebrate safety of Clostridium bifermentans serovar malaysia, a new larvicidal agent for vector control. The safety of bacterial cells of Clostridium bifermentans serovar malaysia, which is highly toxic to mosquito larvae, was tested on mice, guinea pigs, rabbits, and goldfish. Inoculations of at least 1 x 10(8) cells per animal by routes recommended by World Health Organization (subcutaneous, percutaneous, inhalation, force-feeding, intraperitoneal, intravenous) and tests of subacute toxicity, anaphylactic shock, persistence in heart blood, and virulence by successive passages, were performed on mice, guinea pigs, or both. Growth was monitored for 1 mo before necropsy. Ocular irritation and skin scarification were tested with rabbits. C. bifermentans serovar malaysia did not induce any mortality or abnormal reactions in mammals at a dose 1,000 times higher than the level established by W.H.O. for the demonstration of safety. Bacterial cells are not toxic to goldfish at a dose 1,000 times higher than the LD50 for the target-mosquito larvae. We conclude that C. bifermentans serovar malaysia bacterial cells are safe for laboratory mammals and goldfish.


Monitoring adult populations of the screwworm (Diptera: Calliphoridae) with feeding stations baited with liver. Populations of the screwworm, Cochliomyia hominivorax (Coquerel), were monitored by capturing adults with hand nets and rooted liver set on the ground. Adults were marked and released. During the 61-d study conducted in a tropical dry forest in the dry season (January to March 1989), 2,640 individual females and 460 individual males were recorded at the four liver-baited stations. The total number of visits by females was 5,769 and by males 510. The mean number of unmarked adults per day was 44.1 females and 7.6 males in an area of approximately 2.59 km2. The mean percentage of marked flies that were recovered was 64.3%. The mean number of feeding stations visited, times recaptured, and days in the study area by individual females was 2.1, 2.4, and 4.5, respectively. Daily visitational patterns by both sexes at the feeding stations were bimodal with peaks occurring between the hours of 0730 to 0859 and 1500 to 1629. Flies were most active when the mean temperature was 29.9 degrees C; the majority of the visits occurred when air temperatures were between 26 and 33 degrees C. Most females attracted to feeding stations were nulliparous (70.7%) and mated (69.7%). Our results suggest that observing adults at feeding stations is a reliable method of obtaining data on the behaviour and population dynamics of indigenous populations of screwworm adults in tropical habitats. Although this method was labor intensive, the amount of data gleaned from the manipulation of wild populations more than compensated for such costs.


Sublethal effects of insecticides on adult longevity and fecundity of German cockroaches (Dictyoptera: Blattellidae). The effects of sublethal concentrations of chlorpyrifos, cyfluthrin, and hydramethylnon on adult longevity and fecundity of German cockroaches, Blattella germanica (L.), were investigated. Longevity of males declined linearly with increasing doses of insecticide. An LD50 of cyfluthrin decreased male longevity by 52%, whereas an LD50 of hydramethylnon reduced male longevity by 81%. Longevity of females increased linearly with increasing sublethal doses of chlorpyrifos, whereas all doses of both cyfluthrin and hydramethylnon decreased longevity of females. Fecundity increased linearly with increasing sublethal doses of chlorpyrifos. Number of oothecae formed, oothecae hatched, and number of offspring produced in each ootheca increased with increasing sublethal concentrations of chlorpyrifos. In contrast, fecundity declined with increasing sublethal concentrations of cyfluthrin and hydramethylnon. Formation of the first ootheca occurred approximately 8 d after mating for untreated females but generally longer with sublethal concentrations of all insecticides. The period between oothecae hatch and the formation of subsequent oothecae increased with successive oothecae in all treatments.


Calf milk replacers as substitutes for milk in the larval diet of the screwworm (Diptera: Calliphoridae). The effect of calf milk replacers as substitutes for nonfat dry milk in the larval diet of the screwworm, Cochliomyia hominivorax (Coquerel), was determined in the laboratory. Pupal weight and fecundity of females were significantly greater than the control with some of the formulations tested. Larval crawl-off patterns for all diets were similar. Pupal weights were significantly affected only on day 1 of the 4-d crawl-off period. Among the formulations of calf milk replacer, Gold Label brand products showed the most promise as substitutes for the nonfat dry milk presently used in the screwworm production facility. Use of calf milk replacers would lead to a yearly savings of 39.3% in the cost of the dietary milk component. At a production level of 250 million flies weekly, this substitution would save approximately $338,000 dollars yearly.


Effects of stable flies (Diptera: Muscidae) and heat stress on weight gain and feed efficiency of feeder cattle. Cattle respond to the feeding of stable flies, Stomoxys calcitrans (L.), by bunching to protect their front legs. This bunching can increase heat stress which indirectly accounts for much of the reduction in cattle weight gains. We used fly-screened, self-contained feedlot pens which allowed regulation of fly populations feeding on cattle. The indirect fly effects (bunching and heat stress) accounted for 71.5% of the reduced weight gain. The direct effect of the biting flies and energy loss involved in fighting flies accounted for 28.5% of the reduced weight gain.


Optimization of murine keratinocyte culture for the production of graftable epidermal sheets. The aim of the present study was to optimize murine epidermal cell cultures in order to obtain graftable sheets. Newborn (1-3 days old) Balb/c mice skin were used to optimize culture media and plating cell concentration, then epidermal sheet production, and grafting. Epidermal cells were plated at various concentrations in different culture media containing low (0.1 mM) or high (greater than 1 mM) Ca2+ levels. After a 3 day culture at the 10(4) cells/cm2 plating cell concentration, the percentage of differentiated cells was more than 80% in the high Ca2+ culture medium and less than 50% with bulky cells in the low Ca2+ culture medium. Under these conditions confluence was not obtained. At the 10(5) cells/cm2 seeding inoculum, the percentage of confluence increased to 95-100% during the first 72 h of culture in both high and low Ca2+ culture media. Three-day-old culture showed stratified multilayer epidermal sheets in the high calcium medium, and monolayer epidermal sheets were present in the low calcium medium after seeding keratinocytes in fibronectin precoated flasks. Seven days after plating, post confluent cultures were composed of a high percentage of differentiated cells (90%) with an increase in shedding cells in the medium. Considering the above morphological observations, sheets obtained with 10(5) cells/cm2 in MCDB-153 (A), DME-HAM (B) or GMEM (C) media after 3 days in culture were grafted. Twenty days after grafting, histological analysis of biopsies showed an epidermal structure and organization comparable to normal murine epidermis without hair follicles. Epidermal transplants showed a complete basement membrane, hemidesmosomes, and tonofilament bundles. Sheets obtained after seven day culture in all media showed lower coverage of the wound bed. These studies point out the importance of the plating cell and Ca2+ concentrations, and the culture time for murine keratinocyte confluence and differentiation to obtain graftable epidermal sheets.


Photosensitivity in atopic dermatitis: demonstration of abnormal response to UVB. It is a well-known fact among clinicians that sunlight may exacerbate atopic dermatitis (AD), but little is known beyond that. In a preliminary study investigating this phenomenon, 19 patients with AD were selected for phototests. All of them had a normal minimal erythema dose (MED). However, 3 patients (15.7%) demonstrated abnormal cutaneous responses 24-72 h after provocation with ultraviolet light B (UVB). None of the patients had a positive response to pure ultraviolet light A (UVA) irradiation of up to 9 J/cm2. The photobiological results of this study confirm the existence of photosensitivity in AD and indicate that UVB wavelengths are responsible for it.


Organ culture of human hair follicles derived from different areas of the body. Whole human hair follicles derived from the scalp, chin, axilla, and pubis were organ cultured. The hair follicles were dissected from excised normal skin pieces and placed in 1.0 ml of incubation medium in a closed 5 ml glass tube under an atmosphere of air + 5% CO2. The tube was rolled at 15 rpm and 36 degrees C. The hair follicles from each area of the body grew linearly for about 6 days, both in serum-plus and serum-free media with or without fibroblast growth factor (FGF). The growth rates were slightly slower in serum-free media than in serum-plus media. No significant differences in the growth rates of hair follicles in organ culture were seen in different areas of the body. FGF did not affect the growth rate or the culture term of the hair follicles in vitro. This is the first report of human hair follicles derived from chin, axilla, and pubis growing well for about a week in organ culture.


Genetic polymorphisms in the fourth component of complement (C4) and in properdin factor B (BF) in Japanese patients with palmoplantar pustulosis. Genetic polymorphisms in the fourth component of complement (C4) and in properdin factor B (BF) were investigated in 49 and 32 Japanese patients with palmoplantar pustulosis (PPP), respectively. C4B2 was significantly increased in frequency, whereas no significant deviations were detected in BF compared with the controls. These results may indicate that complement polymorphisms are involved in the pathogenesis of PPP.


An epidemiological study of methicillin-resistant Staphylococcus aureus (MRSA) isolated from medical staff, inpatients, and hospital environment in one ward at our hospital. Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important causative microorganisms for nosocomial infections. Recently, the incidence of isolation of MRSA has been increasing every year in Japan and is, notably, much more frequently found in inpatients than in outpatients. Therefore, we have done epidemiological studies of MRSA isolated from medical staff, inpatients, and the hospital environment in one ward of our hospital. Thereafter, we examined the antibiotic susceptibility (ABPC, DMPPC, CET, CMZ, IPM, GM, MINO, OFLX, EM, CLDM, VCM), phage typing, and coagulase typing of these MRSA. MRSA were isolated more frequently from anterior nares of inpatients than from doctors and nurses. MRSA were isolated more frequently from the environment near carriers of MRSA. Coagulase type II and phage type N.T. (not typable) were the dominant types of MRSA in our hospital (69% and 61%). MRSA strains were resistant to most antibiotics with a few exceptions (VCM, IPM, CMZ, CET). The high isolation frequency of MRSA in our hospital seems to suggest that inpatients who are carrying MRSA spread MRSA throughout the hospital environment and that the anterior nares of inpatients are the major MRSA harbor.


Triple cancers in the urogenital area of a patient with aplastic anemia. Three epithelial neoplastic lesions, perineal Bowenoid papulosis, uterine cervical carcinoma, and bladder transitional cell carcinoma, which occurred in a mildly immunosuppressed patient who had aplastic anemia were studied for human papillomavirus (HPV) infection. In the Bowenoid papulosis, HPV type 16 DNA was identified by polymerase chain reaction (PCR) and by in situ hybridization (ISH). In contrast, in the uterine cervical carcinoma, HPV 16 was not detected, although possibly another unidentified type of HPV in the lesion was suggested by the ISH findings. In the bladder transitional cell carcinoma, neither papillomavirus genus-specific (PGS) antigen nor HPV DNA was found.


Necrolytic migratory erythema in glucagonoma syndrome. A 32-year-old female Chinese presenting with typical features of necrolytic migratory erythema due to glucagonoma syndrome is reported. The clinical, biochemical, histopathological, and electron-microscopic findings are described. Various different aspects of this rare entity are discussed.


A case of contact dermatitis due to methylprednisolone. A 46-year-old woman developed contact dermatitis on her face after application of an ointment containing 0.1% methylprednisolone and 0.35% fradiomycin. Her patch test result was positive with methylprednisolone, but not with fradiomycin. No cross-reactions were observed after conducting patch tests with 17 different topical corticosteroids including prednisolone.


Acne fulminans and 13-cis-retinoic acid. We report a case of acne fulminans occurring during treatment with 13-cis-retinoic acid for cystic acne. Continuing the treatment with 13-cis-retinoic acid without systemic steroid eventually cleared the systemic manifestations and skin lesions. We review the literature and discuss its pathogenesis.


Hereditary benign telangiectasia: two case reports. We present two cases of hereditary benign telangiectasia (HBT) in which the genetic findings are compatible with an autosomal dominant hypothesis. The lesions persisted indefinitely for many years without effect on the general health of the patients. The term hereditary benign telangiectasia distinguishes the disorder from the more serious hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber). The etiology remains unknown. The condition causes only cosmetic disability and is not associated with any other diseases.


Ultrastructural aspects of infiltrated eosinophils in bullous pemphigoid. By scanning (SEM) and transmission electron microscopy (TEM), we evaluated the infiltrated eosinophils in lesions at various stages of clinical development from patients with bullous pemphigoid (BP) and eosinophilia. Visualized by SEM, numerous inflammatory cells migrated through the cutaneous basement membrane into the cavity of newly formed blisters 12 to 24 hrs after formation. Many migrating cells attached to the reverse side of the bullous cavity, and some basal cells shed into the cavity. As the bullae developed 24 to 48 hrs after formation, the reverse surface of the bullous cavity became predominantly composed of these migrating cells and the exposed squamous cells. The migrating cells had villi, ruffles and ridge-like profiles on their surfaces, which were suggested eosinophils. By TEM in the same lesions, many morphologically activated eosinophils were seen to have passed through the basement membrane into the newly formed blisters; they exhibited spheroidal cytoplasmic granules with less dense crystalloid cores and intracellular channels. Eosinophils infiltrating in the developed bullous cavity directly adhered to basal cells and released their granule contents onto these target cells. These findings suggest that inflammatory cells, especially eosinophils, may amplify the formation of dermal-epidermal separation in BP lesions.


Effects of butylated hydroxyanisole on ornithine decarboxylase activity induced by ultraviolet-B and PUVA in mouse skin. The effects of butylated hydroxyanisole (BHA), a representative phenolic antioxidant, on the activity of ornithine decarboxylase (ODC, an indicator of tumor promotion and epidermal hyperproliferation) induced by ultraviolet-B (UVB) or PUVA in mouse skin were investigated. By topical application of BHA (55 mumol), PUVA-induced ODC activity was suppressed by about 60% at both 12 h and 24 h after treatment. In contrast, BHA failed to suppress UVB-induced ODC activity in mouse skin. These results suggest that the induction of ODC activity by UVB or PUVA is mediated by different pathways.


Ingrown toenails: an evaluation of elevating the nail bed-periosteal flap. Many procedures to correct ingrown toenails are available; however, they cannot avoid recurrence and nail deformities. We have performed a procedure which corrects ingrown toenail without reducing the width of the nail plate by elevating the nail bed-periosteal flap. Sixty patients were observed for longer than six months and exhibited excellent results. Only two cases of incurvated nails (2) required re-operation.


Serum hormone levels in men with severe acne. In order to evaluate the hormonal milieu in young men with severe acne, we measured serum estradiol (E2), total testosterone (T), free testosterone (FT), dihydrotestosterone (DHT), dehydroepiandrosterone sulfate (DHEA-S), and sex hormone binding globulin (SHBG) levels in sixteen male patients aged 20-30 years with severe acne, including twelve cases of nodular-cystic acne, and in seventeen age-matched normal controls. There were no significant differences in the serum levels of T, FT, DHT, DHEA-S, or SHBG between the patients and the controls, but serum E2 was significantly higher in the patient population. Thus, the hemodynamics of serum androgens in male patients with acne do not seem to differ significantly from that of normal controls. Elevated E2 levels might affect the inflammatory response of acne vulgaris through the release of thymic hormones, as reported in the literature.


Immunohistochemical characterization of cellular infiltrates in squamous cell carcinoma and Bowen's disease occurring in one patient. We investigated populations of the infiltrating cells in Bowen's disease (BD) and squamous cell carcinoma (SCC), both of which arose in the same patient, using the Avidin-Biotin-peroxidase complex method with eight monoclonal antibodies. T lymphocytes were most predominant among infiltrating cells; NK cells, B cells, and monocytes were rarely seen in either BD or SCC. Analysis of subsets of the infiltrating T lymphocytes revealed that the number of suppressor/cytotoxic (s/c) T cells was twice that of helper/inducer (h/i) T cells in BD, while the number of s/c T cells was lower than that of h/i T cells in SCC. The immunohistochemical results in the present case differed from those of predominant infiltration of h/i T cells and of s/c T cells in three other reports of BD and SCC. These results suggest that the population of the cellular infiltrates may be modulated by the nature of tumors and by the immuno-competent state of the hosts.


Fulminant dermatomyositis after removal of a cancer. Dermatomyositis developed suddenly in a diabetic patient with CREST syndrome after the removal of a malignant tumor. Scrupulous physical examination excluded further systemic or cutaneous involvement. We raise certain still unsolved aspects regarding the association between dermatomyositis and neoplastic disorders.


Fasting diet therapy for chronic urticaria: report of a case. We used fasting diet therapy with a 28-year-old woman with chronic urticaria who responded only to systemic administration of glucocorticosteroids. The rashes began to decrease on the third therapeutic day and completely disappeared on the 11th day. Although the eruptions relapsed three days after the termination of the therapy, they were milder than previous ones. We also discussed the possible efficacy of fasting diet therapy for chronic urticaria as reported in the literature.


Giant condyloma acuminatum in a baby boy. A giant condyloma acuminatum developed on the penis of a one and a half-year-old Japanese boy in two months. The histological features of this tumor were compatible with those of ordinary condyloma acuminatum. Although we detected the presence of human papilloma virus (HPV) type 16 by using the polymerase chain reaction system, we could not rule out the possibility that this HPV was present concurrently with other HPV types that cause condyloma acuminatum. The lesion was successfully treated with cryotherapy and topical application of 5% fluorouracil ointment under occlusion.


Restriction of cicatricial pemphigoid antigens to the lamina densa: confirmation by indirect immunoelectron microscopy. Circulating anti-basement membrane zone (BMZ) antibodies in a patient with cicatricial pemphigoid (CP) were examined using an indirect immunofluorescence test, indirect immunoperoxidase electron microscopy, and Western blot analysis. An indirect immunofluorescence test on salt-split skin revealed that the anti-BMZ antibodies reacted solely to the dermal side at the separating epidermal-dermal interface, and indirect immunoelectron microscopy on intact skin indicated localization of the corresponding antigens (CP antigens) over the lamina densa and within the lower half of the lamina lucida; there were no CP antigens beneath a melanocyte. Indirect immunoelectron microscopy on salt-split skin demonstrated that the CP antigens were partly dissociated from, but restricted to, the lamina densa. Western blot analysis showed no differences in molecular weight between the CP antigens and bullous pemphigoid (BP) antigens. CP antigens, as detected by this patient's serum, appear to be constituted of molecules quite similar to BP antigens, but with different epitopes. CP antigens may be shed from basal cells and locate in the area of anchoring filaments, where they play a role in connecting basal cells to the underlying lamina densa.


The induction of ornithine decarboxylase in human epidermis is independent of lipoxygenase and cyclo-oxygenase pathways. In vivo studies in rodents suggest that prostaglandins and/or leukotrienes are involved in the epidermal induction of ornithine decarboxylase (ODC). Recently, we have shown that, in human epidermis, prostaglandins are not involved in this process. Here we report the role of leukotrienes in epidermal ODC induction in human skin. Topical flufenamic acid (Dignodolin), vehicle, or nothing was applied under plastic occlusion to three sites on the backs of healthy volunteers. This was followed 1 h later by Sellotape stripping. After renewed application and occlusion for 8 h, biopsies were carried out for the estimation of ODC levels. There were no significant differences in the levels of ODC between the flufenamic acid treated and control sites. To confirm this finding, test sites were irradiated with 3 MED of UVB. This was immediately followed by the application of flufenamic acid, vehicle, or nothing to the three irradiated sites. After 8 h, biopsies were taken, and the levels of ODC were again similar in the flufenamic acid- and the vehicle-treated sites. The data indicate that, following Sellotape stripping or UVB irradiation, neither lipoxygenase not cyclooxygenase products contribute to the in vivo induction of ODC in human epidermis.


The comparison of sun protection factor values with different light sources. Sun protection factors (SPFs) were evaluated with three light sources (sunlight, a xenon arc solar simulator, and fluorescent lamps) in indoor and outdoor studies. Two types of light, UV-A+B and UV+Visible, were obtained from the solar simulator. The untanned backs of twenty-four healthy male volunteers were used as test sites. A broad spectrum sunscreen containing SPF 6, according to the manufacturer, was used. The sunscreen tested was applied at 2 mg/cm2. The actual SPF values were 4.8 with sunlight, 6.0 with UV-A+B, 4.9 with UV+Visible, and 11.8 with fluorescent lamps. There were no significant differences between the SPF values with sunlight and those with the solar simulator; the SPF value for fluorescent lamps was significantly higher. The SPF with UV-A+B of the solar simulator was similar to that with sunlight; the use of this light served to reduce pain on tested subjects. Therefore, UV-A+B from the solar simulator seems to be the most appropriate artificial light source for evaluating sunscreens.


Juvenile dermatomyositis: a statistical study of 114 patients with dermatomyositis. We conducted a statistical review of 114 cases of dermatomyositis (DMS) treated primarily at the Department of Dermatology at Nagoya University Hospital over 27 years from 1965 to 1991 in order to determine the primary characteristics of juvenile DMS with the following results. 1) Juvenile DMS was found slightly more often in males than females; the male-to-female ratio was 1.4:1. Therefore, unlike adult DMS with its preponderance of females, there was no clear gender predominance. 2) Muscular manifestations tended to follow the appearance of cutaneous manifestations, but the frequency of minor muscular manifestations was high over the entire course of the disease. 3) Laboratory findings showed increases in serum aldolase and serum creatinine kinase with significant frequency when compared with adult patients (p < 0.01 and p < 0.05, respectively). Elevated serum aldolase most often occurred prior to or at the time of the appearance of muscular manifestations, suggesting its usefulness in early diagnosis. The positive rates for the antinuclear antibody on HEp-2 cells and anti-DNA antibody were significantly lower in children than in adults (p < 0.001 and p < 0.05, respectively). 4) There were no cases of juvenile DMS complicated by malignant tumors, interstitial pneumonia, or pulmonary fibrosis. There were also no deaths, and the rate of "remission or improvement" was significantly higher than in adult DMS cases (p < 0.05). Adult cases which remained the same or worsened usually presented with intractable muscular manifestations. In children, however, the cutaneous manifestations were more difficult to treat.(ABSTRACT TRUNCATED AT 250 WORDS)


Electron microscopic X-ray microanalysis of metals deposited in oral mucosa. A 35-year-old woman exhibited bluish-brown discoloration of her buccal mucosa suggesting malignant melanoma. Histopathological examination revealed that the pigment was not melanin but caused by metal deposits. Electron microscopically, metallic particles were located on the lamina densa of basal laminae at mucosal epithelium, nerve fibers, and blood vessels and on the microfilaments of elastic fibers as well as in macrophages and fibroblasts. Electron microscopic point X-ray microanalysis revealed that these metallic particles were composed of Ag, Se, Fe, Co, Cu, and S. Analysis suggests that these metals were derived from dental amalgam and that the discoloration was caused by amalgam tattoo.


Eccrine hidrocystoma: two cases of Robinson and Smith types. Two cases of eccrine hidrocystoma, one of which is a "classic" Robinson type and the other a Smith type, were reported. The walls of both cysts consisted mainly of two layers of flat or low cuboidal epithelial cells with eosinophilic cytoplasm. Immunostaining for S-100 protein was negative in the cells of the cyst wall of the Robinson type and only weakly positive in the inner luminal layer of the Smith type. Electron microscopically, the Smith type showed double-layered cuboidal lining and cell membrane interdigitations as junctions of neighboring cells without any characteristics of the secretory segment of sweat glands, indicating substantial similarity to those of the intradermal portion of the eccrine sweat duct.


A case of adult T cell leukemia with bullae in the palmoplantar regions followed by a crisis. A 48-year-old Japanese female who had had chronic ATL for 4 years suddenly developed vesicles on the palms and soles. Histologically, these bullae were specific lesions of ATL. After a tendency toward improvement, a crisis appeared with increases in the following: peripheral white blood cells, atypical lymphocytes, CD25 positive cells, serum LDH, and soluble IL-2R. Palmoplantar bullae, a rather rare finding, may be indicative of a following crisis.


A case of trichoadenoma arising in the buttock. A 41-year-old Japanese man with trichoadenoma on his buttock was described. Histological examination showed numerous horn cysts and some tumor islands consisting entirely of eosinophilic epithelial cells. A review of 24 reported cases of trichoadenoma revealed that most of them developed on the facial region (14 of 24 cases, 58%); the buttock (6 of 24, 25%) was the next most common site.


The influence of talker differences on vowel identification by normal-hearing and hearing-impaired listeners. Vowel identification was tested in quiet, noise, and reverberation with 20 normal-hearing subjects and 20 hearing-impaired subjects. Stimuli were 15 English vowels spoken in a /b-t/context by six male talkers. Each talker produced five tokens of each vowel. In quiet, all stimuli were identified by two judges as the intended targets. The stimuli were degraded by reverberation or speech-spectrum noise. Vowel identification scores depended upon talker, listening condition, and subject type. The relationship between identification errors and spectral details of the vowels is discussed.


Temporal cues for consonant recognition: training, talker generalization, and use in evaluation of cochlear implants. Limited consonant phonemic information can be conveyed by the temporal characteristics of speech. In the two experiments reported here, the effects of practice and of multiple talkers on identification of temporal consonant information were evaluated. Naturally produced /aCa/disyllables were used to create "temporal-only" stimuli having instantaneous amplitudes identical to the natural speech stimuli, but flat spectra. Practice improved normal-hearing subjects' identification of temporal-only stimuli from a single talker over that reported earlier for a different group of unpracticed subjects [J. Acoust. Soc. Am. 82, 1152-1161 (1987)]. When the number of talkers was increased to six, however, performance was poorer than that observed for one talker, demonstrating that subjects had been able to learn the individual stimulus items derived from the speech of the single talker. Even after practice, subjects varied greatly in their abilities to extract temporal information related to consonant voicing and manner. Identification of consonant place was uniformly poor in the multiple-talker situation, indicating that for these stimuli consonant place is cued via spectral information. Comparison of consonant identification by users of multi-channel cochlear implants showed that the implant users' identification of temporal consonant information was largely within the range predicted from the normal data. In the instances where the implant users were performing especially well, they were identifying consonant place information at levels well beyond those predicted by the normal-subject data. Comparison of implant-user performance with the temporal-only data reported here can help determine whether the speech information available to the implant user consists of entirely temporal cues, or is augmented by spectral cues.


The time course and magnitude of perceptual acclimatization to frequency responses: evidence from monaural fitting of hearing aids. At high presentation levels, normally aided ears yield better performance for speech identification than normally unaided ears, while at low presentation levels the converse is true [S. Gatehouse, J. Acoust. Soc. Am. 86, 2103-2106 (1989)]. To explain this process further, the speech identification abilities of four subjects with bilateral symmetric sensorineural hearing impairment were investigated following provision of a single hearing aid. Results showed significant increases in the benefit from amplifying speech in the aided ear, but not in the control ear. In addition, a headphone simulation of the unaided condition for the fitted ear shows a decrease in speech identification. The benefits from providing a particular frequency spectrum do not emerge immediately, but over a time course of at least 6-12 weeks. The findings support the existence of perceptual acclimatization effects, and call into question short-term methods of hearing aid evaluation and selection by comparative speech identification tests.


Vowel perception strategies of normal-hearing subjects and patients using Nucleus multichannel and 3M/House cochlear implants. Vowel perception strategies were assessed for two "average" and one "star" single-channel 3M/House and three "average" and one "star" Nucleus 22-channel cochlear implant patients and six normal-hearing control subjects. All subjects were tested by computer with real and synthetic speech versions of [symbol: see text], presented randomly. Duration, fundamental frequency, and first, second, and third formant frequency cues to the vowels were the vowels were systematically manipulated. Results showed high accuracy for the normal-hearing subjects in all conditions but that of the first formant alone. "Average" single-channel patients classified only real speech [hVd] syllables differently from synthetic steady state syllables. The "star" single-channel patient identified the vowels at much better than chance levels, with a results pattern suggesting effective use of first formant and duration information. Both "star" and "average" Nucleus users showed similar response patterns, performing better than chance in most conditions, and identifying the vowels using duration and some frequency information from all three formants.


Effects of short-term auditory deprivation on speech production in adult cochlear implant users. Speech production parameters of three postlingually deafened adults who use cochlear implants were measured: after 24 h of auditory deprivation (which was achieved by turning the subject's speech processor off); after turning the speech processor back on; and after turning the speech processor off again. The measured parameters included vowel acoustics [F1, F2, F0, sound-pressure level (SPL), duration and H1-H2, the amplitude difference between the first two spectral harmonics, a correlate of breathiness] while reading word lists, and average airflow during the reading of passages. Changes in speech processor state (on-to-off or vice versa) were accompanied by numerous changes in speech production parameters. Many changes were in the direction of normalcy, and most were consistent with long-term speech production changes in the same subjects following activation of the processors of their cochlear implants [Perkell et al., J. Acoust. Soc. Am. 91, 2961-2978 (1992)]. Changes in mean airflow were always accompanied by H1-H2 (breathiness) changes in the same direction, probably due to underlying changes in laryngeal posture. Some parameters (different combinations of SPL, F0, H1-H2 and formants for different subjects) showed very rapid changes when turning the speech processor on or off. Parameter changes were faster and more pronounced, however, when the speech processor was turned on than when it was turned off. The picture that emerges from the present study is consistent with a dual role for auditory feedback in speech production: long-term calibration of articulatory parameters as well as feedback mechanisms with relatively short time constants.


Acoustic and perceptual effects of changes in vocal tract constrictions for vowels. The purpose of this study was to use vocal tract simulation and synthesis as means to determine the acoustic and perceptual effects of changing both the cross-sectional area and location of vocal tract constrictions for six different vowels: Area functions at and near vocal tract constrictions are considered critical to the acoustic output and are also the central point of hypotheses concerning speech targets. Area functions for the six vowels, [symbol: see text] were perturbed by changing the cross-sectional area of the constriction (Ac) and the location of the constriction (Xc). Perturbations for Ac were performed for different values of Xc, producing several series of acoustic continua for the different vowels. Acoustic simulations for the different area functions were made using a frequency domain model of the vocal tract. Each simulated vowel was then synthesized as a 1-s duration steady-state segment. The phoneme boundaries of the perturbed synthesized vowels were determined by formal perception tests. Results of the perturbation analyses showed that formants for each of the vowels were more sensitive to changes in constriction cross-sectional area than changes in constriction location. Vowel perception, however, was highly resistant to both types of changes. Results are discussed in terms of articulatory precision and constriction-related speech production strategies.


Speech changes following reimplantation from a single-channel to a multichannel cochlear implant. The speech of a postlingually deafened preadolescent was recorded and analyzed while a single-electrode cochlear implant (3M/House) was in operation, on two occasions after it failed (1 day and 18 days) and on three occasions after stimulation of a multichannel cochlear implant (Nucleus 22) (1 day, 6 months, and 1 year). Listeners judged 3M/House tokens to be the most normal until the subject had one year's experience with the Nucleus device. Spectrograms showed less aspiration, better formant definition and longer final frication and closure duration post-Nucleus stimulation (6 MO. NUCLEUS and 1 YEAR NUCLEUS) relative to the 3M/House and no auditory feedback conditions. Acoustic measurements after loss of auditory feedback (1 DAY FAIL and 18 DAYS FAIL) indicated a constriction of vowel space. Appropriately higher fundamental frequency for stressed than unstressed syllables, an expansion of vowel space and improvement in some aspects of production of voicing, manner and place of articulation were noted one year post-Nucleus stimulation. Loss of auditory feedback results are related to the literature on the effects of postlingual deafness on speech. Nucleus and 3M/House effects on speech are discussed in terms of speech production studies of single-electrode and multichannel patients.


Target detection, shape discrimination, and signal characteristics of an echolocating false killer whale (Pseudorca crassidens). This study demonstrated the ability of a false killer whale (Pseudorca crassidens) to discriminate between two targets and investigated the parameters of the whale's emitted signals for changes related to test conditions. Target detection performance comparable to the bottlenose dolphin's (Tursiops truncatus) has previously been reported for echolocating false killer whales. No other echolocation capabilities have been reported. A false killer whale, naive to conditioned echolocation tasks, was initially trained to detect a cylinder in a "go/no-go" procedure over ranges of 3 to 8 m. The transition from a detection task to a discrimination task was readily achieved by introducing a spherical comparison target. Finally, the cylinder was successfully compared to spheres of two different sizes and target strengths. Multivariate analyses were used to evaluate the parameters of emitted signals. Duncan's multiple range tests showed significant decreases (df = 185, p less than 0.05) in both source level and bandwidth in the transition from detection to discrimination. Analysis of variance revealed a significant decrease in the number of clicks over test conditions [F(5.26) = 5.23, p less than 0.0001]. These data suggest that the whale relied on cues relevant to target shape as well as target strength, that changes in source level and bandwidth were task-related, that the decrease in clicks was associated with learning experience, and that Pseudorca's ability to discriminate shapes using echolocation may be comparable to that of Tursiops truncatus.


Avoiding conflicts between the natural behavior of the animal and the demands of discrimination experiments. Auditory discrimination experiments are traditionally designed without regard for ethological or ecological concerns, yet land dwelling mammals may have specialized behavior with respect to sound sources. Auditory discriminations occur under field conditions, and there is some fit or matching of the animal's behavior to the acoustic environment. Understanding this fit requires a knowledge of specializations. Understanding the specializations may also guide the design of discrimination experiments. This paper reviews a number of auditory discrimination experiments that were designed to reveal some of the specialized behaviors. These experiments showed the following: (i) The position of a sound source is the dominant sensory dimension, over riding the quality of the sound; (ii) the effect of reinforcing a response in the presence of a sound is to strengthen the response of approaching the source. This effect is ubiquitous in discrimination tasks; (iii) sounds that are novel at the start of discrimination training more rapidly gain control of responding than sound to which the animal has been pre-exposed; (iv) novel low-intensity sounds elicit approach and exploration of the source. These behaviors rapidly adapt. These four behavioral attributes are considered in terms of their impact upon behavior in the field, and of the requirements they impose on the design of experimental discriminations.


Spectral and temporal weights in spectral-shape discrimination. The COSS analysis [B. G. Berg, J. Acoust. Soc. Am. 86, 1743-1746 (1989)] was used to estimate spectral and temporal weights of a three-component, amplitude-modulated stimulus in a spectral-shape discrimination task. In all experiments, the task of the observer was to detect an increment in the level of the center component. A spectral-temporal weight quantifies the relative influence of a spectral component on the decisions of an observer during a specified segment of the total stimulus duration. In the first two experiments, the signal was added to all three temporal segments of the center component. The ideal weights for each component should be the same across temporal segments. Spectral-temporal weights were obtained for four conditions with different stimulus durations. In general, the estimated weights for each component were not equal at different temporal segments. In the third experiment, the signal was added to only one of three segments of the center component. Ideally, weight patterns should have changed when the temporal position of the signal segment was altered. Two stimulus durations, 300 and 15 ms, were used. For the 300-ms condition, the signal was added to only the end segment, and for all three observers the weight patterns are different from that obtained in experiment 1 with the signal added to all segments. For the 15-ms conditions, altering the signal position changed the estimated weights for only one observer.


Middle-ear phenomenology: the view from the three windows. To provide a common ground for the comparison between theory and experiment, this paper presents a framework for the phenomenological description of middle-ear mechanics. The framework defines those measurements sufficient to characterize the transduction properties of the middle ear and its components. Phenomenological equations are represented in the form of an equivalent electrical circuit that can be used to deduce testable relations among measurable quantities. Two applications are then discussed. First, the classical concept of the middle-ear transformer ratio is generalized to include any effects of eardrum flexion or nonrotational ossicular motion. Middle-ear models predict that the resulting transformer ratios vary considerably with frequency. Second, the conditions under which the topology of existing circuit analogs satisfactorily approximates middle-ear mechanics are given. Most middle-ear models cannot be used to correctly predict the absolute pressures in the cochlea.


Analyzing reverse middle-ear transmission: noninvasive Gedankenexperiments. The phenomenological framework outlined in the companion paper [C. A. Shera and G. Zweig, J. Acoust. Soc. Am. 92, 1356-1370 (1992)] characterizes both forward and reverse transmission through the middle ear. This paper illustrates its use in the analysis of noninvasive measurements of middle-ear and cochlear mechanics. A cochlear scattering framework is developed for the analysis of combination-tone and other experiments in which acoustic distortion products are used to drive the middle ear "in reverse." The framework is illustrated with a simple psychophysical Gedankenexperiment analogous to the neurophysiological experiments of P. F. Fahey and J. B. Allen [J. Acoust. Soc. Am. 77, 599-612 (1985)].


An empirical bound on the compressibility of the cochlea. Effects of a possible inner-ear compressibility on middle-ear transfer functions are explored and a small upper bound on the magnitude of that compressibility established. Consequently. the traditional two-port representation of middle-ear mechanics remains valid to within a few percent. If the compressibility of the cochlea is small but finite, a simple phenomenological model of that compressibility correctly predicts hearing thresholds in the "middleless" ear at low frequencies. Experiments to establish the value of cochlear compressibility and to explore further its possible contributions to residual hearing in patients with missing or disarticulated middle-ear ossicles are suggested.


Temporal structure model of binaural masking level difference. It is shown that a simple cross-correlation model is not adequate to explain both binaural masking level difference (MLD) and spatial selective attention. The reason is that for a low-intensity signal in NoS(pi) condition the maximal activity in the binaural analyzer as a function of interaural delay in single spectral channel is independent of signal intensity. On the other hand, if detection ability is associated with the isolation of tonically firing units, MLD is simply explained as the increase in firing synchronization as a function of the signal's interaural phase difference (IPD). Quantitatively results are presented based on numerical solutions of the model.


Determination of sound speed in biological tissues based on frequency analysis of pulse response. The sound speed in biological tissues provides important diagnostic and treatment planning information. Conventional methods of sound-speed determination generally require that transducers make physical contact with specimens in order to measure thickness and travel time in the time domain. The physical contact may cause deformation and affect blood flow and the measurement of travel time in the time domain may be sensitive to waveform distortion due to tissue inhomogeneity and surface roughness. A method for determination of the sound speed is proposed in which the sound travel time in the sample and the difference in total travel time from the transducer to the rigid reflector due to the presence of the sample are estimated in the frequency domain and which does not require physical contact of ultrasonic probes to living or freshly excised tissue specimens. Ultrasonic speed measurements in silicone rubber and acrylic resin specimens verified the method validity. The standard deviation of the measurements over a 10- x 10-mm area is less than 4 m/s. Sound-speed distribution measurements of porcine muscle are in agreement with previously published results.


Application of the reverberation-limited form of the sonar equation to dolphin echolocation. The target detection range of two echolocating Atlantic Bottlenose dolphins as a function of target depth in Kaneohe Bay, Hawaii, was determined by Murchison [A. E. Murchison, Ph.D. dissertation, Univ. of Calif., Santa Cruz (1980)]. The threshold range decreased monotonically as the depth of the 6.35-cm-diam solid-steel sphere increased and approached the bottom. For the target lying on the bottom, the 50% correct detection threshold detection range was approximately 70 m. The scattering strength of the bottom in Kaneohe Bay at approximately the same location of the Murchison's experiment was recently measured using a simulated dolphin echolocation signal and a transducer tilted at the appropriate grazing angle. The bottom scattering strength along with the target strength of the 6.35-cm sphere and the dolphin threshold range were incorporated into the generalized form of the sonar equation for a reverberation-limited situation and a detection threshold of 4.0 dB was calculated. This detection threshold compared well with the 2.3 dB obtained in an experiment in which the dolphin was required to detect a target in the presence of a clutter screen.


Acoustics and perception of overtone singing. Overtone singing, a technique of Asian origin, is a special type of voice production resulting in a very pronounced, high and separate tone that can be heard over a more or less constant drone. An acoustic analysis is presented of the phenomenon and the results are described in terms of the classical theory of speech production. The overtone sound may be interpreted as the result of an interaction of closely spaced formants. For the lower overtones, these may be the first and second formant, separated from the lower harmonics by a nasal pole-zero pair, as the result of a nasalized articulation shifting from /c/ to /a/, or, as an alternative, the second formant alone, separated from the first formant by the nasal pole-zero pair, again as the result of a nasalized articulation around /c/. For overtones with a frequency higher than 800 Hz, the overtone sound can be explained as a combination of the second and third formant as the result of a careful, retroflex, and rounded articulation from /c/, via schwa /e/ to /y/ and /i/ for the highest overtones. The results indicate a firm and relatively long closure of the glottis during overtone phonation. The corresponding short open duration of the glottis introduces a glottal formant that may enhance the amplitude of the intended overtone. Perception experiments showed that listeners categorized the overtone sounds differently from normally sung vowels, which possibly has its basis in an independent perception of the small bandwidth of the resonance underlying the overtone. Their verbal judgments were in agreement with the presented phonetic-acoustic explanation.


Modeling phoneme perception. I: Categorical perception. On the basis of a number of vowel and stop-consonant discrimination experiments (AX and 2IFC fixed and roving) with natural stimuli, it is concluded that stop-consonant perception is highly categorical: there were few significant differences between the discrimination results and the phoneme identification results. Moreover, the discrimination and identification response maxima differed significantly from the other data points. Vowel perception was much less categorical: the maxima in the functions were much less significant, and there were significant differences between the various paradigms. Consonant discrimination was much less (if at all) subject to range effects than vowel discrimination. All these results point to different memory types for stop consonants and vowels, and, consequently, to a combination of two different theories of speech sound discrimination: dual-process theory (DPT) for consonants, and trace-context theory (TCT) for vowels.


Modeling phoneme perception. II: A model of stop consonant discrimination. Combining elements from two existing theories of speech sound discrimination, dual process theory (DPT) and trace context theory (TCT), a new theory, called phoneme perception theory, is proposed, consisting of a long-term phoneme memory, a context-coding memory, and a trace memory, each with its own time constants. This theory is tested by means of stop-consonant discrimination data in which interstimulus interval (ISI; values of 100, 300, and 2000 ms) is an important variable. It is shown that discrimination in which labeling plays an important part (2IFC and AX between category) benefits from increased ISI, whereas discrimination in which only sensory traces are compared (AX within category), decreases with increasing ISI. The theory is also tested on speech discrimination data from the literature in which ISI is a variable [Pisoni, J. Acoust. Soc. Am. 36, 277-282 (1964); Cowan and Morse, J. Acoust. Soc. Am. 79, 500-507 (1986)]. It is concluded that the number of parameters in trace context theory is not sufficient to account for most speech-sound discrimination data and that a few additional assumptions are needed, such as a form of sublabeling, in which subjects encode the quality of a stimulus as a member of a category, and which requires processing time.


Relations among different measures of speech reception in subjects using a cochlear implant. A comprehensive set of speech reception measures were obtained in a group of about 20 postlingually deafened adult users of the Ineraid multichannel cochlear implant. The measures included audio, visual, and audiovisual recognition of words embedded in two types of sentences (with differing degrees of difficulty) and audio-only recognition of isolated monosyllabic words, consonant identification (12 alternatives, /Ca/), and vowel identification (8 alternatives, /bVt/). For most implantees, the audiovisual gains in the sentence tests were very high. Quantitative relations among audio-only scores were assessed using power-law transformations suggested by Boothroyd and Nittrouer [J. Acoust. Soc. Am. 84, 101-114 (1988)] that can account for the benefit of sentence context (via a factor k) and the relation between word and phoneme recognition (via a factor j). Across the broad range of performance that existed among the subjects, substantial order was observed among measures of speech reception along the continuum from recognition of words in sentences, words in isolation, speech segments, and the retrieval of underlying phonetic features. Correlations exceeded 0.85 among direct and sentence-derived measures of isolated word recognition as well as among direct and word-derived measures of segmental recognition. Results from a variety of other studies involving presentation of limited auditory signals, single-channel and multichannel implants, and tactual systems revealed a similar pattern among word recognition, overall consonant identification performance, and consonantal feature recruitment. Finally, improving the reception of consonantal place cues was identified as key to producing the greatest potential gains in speech reception.


A model of the phonatory response time of stutterers and fluent speakers to frequency-modulated tones. Stutterers and fluent speakers tracked frequency-modulated tones by humming. The response time (RT) to the first corrective change in fundamental frequency in response to linear ramps of increasing and decreasing frequency was measured. The results demonstrate that RT is a function of the stimulus ramp velocity. A model of this dependency is provided which consists of parameters of threshold frequency and a fixed time delay. The estimated threshold frequency for the fluent speakers is 2.029 Hz with 95% confidence interval: (1.70 Hz, 2.35 Hz) whereas that of the stutterers is 3.937 Hz (3.28 Hz, 4.60 Hz). These threshold frequencies are significantly different (p < 0.0001). This implies that stutterers are slower to respond to changes in frequency than are fluent speakers. The fixed time delays for the two groups are not significantly different. This means that it is possible for the stutterers to respond as fast as the fluent speakers (i.e., their basic "reflexes" are the same); however, they spend more time in the detection of the change in a tracking signal. This supports the model of the stuttered event as being triggered by an instability in a multiloop speech motor control system.


Auditory filter bandwidths in binaural and monaural listening conditions. The shape and the effective bandwidth of the auditory filter at 500 Hz was examined for binaural and monaural tone-in-noise detection experiments in four normal listeners. In the binaural condition, a broadband noise with an interaural phase difference of 0 below and an interaural phase difference of pi above a certain "edge frequency" was employed to mask a 500-Hz probe tone with an interaural phase pi (denoted as No pi S pi). The threshold of the probe tone as a function of the edge frequency in this configuration and in a configuration with an inverted interaural phase of the masker (denoted as N pi oS pi) was fitted by assuming different filter shapes and optimizing their respective parameters. In an analogous monaural experiment, the spectral power density of the masker was 15 dB lower below the "edge frequency" or 15 dB lower above this frequency, respectively. Several filter characteristics with two free parameters describe the data almost equally well. Their equivalent rectangular bandwidths (ERB) show considerably more variations between filter shapes than the 10-dB bandwidth and the 90% bandwidth values (i.e., the bandwidths encompassing 90% of the integrated area above and below the center frequency). This indicates that either of these two bandwidth parameters is more appropriate for comparing auditory filter bandwidths than the ERB. For the rounded exponential filter, the 90% bandwidth averages to 147 Hz in the binaural and to 125 Hz in the monaural condition. These values are up to 12% higher if off-frequency detection is accounted for. Our general finding of auditory filter bandwidths in the binaural conditions exceeding the monaural bandwidths by approximately 20% may be caused by two factors: First, off-frequency detection may be performed in monaural, but not in binaural detections tasks and second, the random interaural mismatch in binaural noise reduction processes fluctuates slowly and thus modulates and spectrally smears the output signal of the binaural noise reduction process.


The effects of notched noise on intensity discrimination under forward masking. Zeng et al. [Hear. Res. 55, 223-230 (1991)] reported that at moderate levels there is an increase in the intensity jnd for 25-ms sinusoidal pedestals presented 100 ms after an intense narrow-band noise. They suggested that this effect is related to the finding that low spontaneous rate (SR) auditory-nerve neurons take a considerable time to recover from adaptation [E. M. Relkin and J. R. Doucet, Hear. Res. 55, 215-222 (1991)]: 100 ms after the noise, the low-SR neurons still have elevated thresholds. Therefore, the intensity of a pedestal falling between the saturation level of the high-SR neurons and the elevated threshold of the low-SR neurons will be poorly represented in neutral firing rates, and the jnd will be high. A problem with this interpretation is that subjects may listen "off frequency." Theoretically, it should always be possible to choose a frequency channel for which the pedestal level is within the dynamic range of the high-SR neurons. In the present study, the experiment of Zeng et al. was replicated but with the pedestal presented in the temporal center of a notched noise to prevent off-frequency listening. Surprisingly, the notched noise substantially decreased the jnd at mid levels, removing or severely reducing the mid-level jnd elevation. This was true for pedestal frequencies of 1 and 6 kHz. It was also found that even if the notched noise was terminated before pedestal onset the jnd elevation was reduced. This suggests that the effect of the notched noise is not due to suppression.(ABSTRACT TRUNCATED AT 250 WORDS)


Discrimination of narrow-band spectra. I: Spectral weights and pitch cues. The ability to detect changes in the spectral shape of narrow-band tonal complexes (spectral profiles) is examined. The standard consists of three tones of equal intensity; thresholds for detecting an increment in the level of the central, 1000-Hz tone are estimated. A roving-level procedure is used in order to impose a statistical limit on thresholds that can be obtained by basing discriminations on absolute intensity. Estimated thresholds are consistently below this limit, thus indicating the use of other cues. Generally, thresholds are constant for bandwidths ranging from less than a critical band to greater than several octaves. Spectral weight estimates, however, are highly dependent on bandwidth, providing evidence that the discrimination of narrow-band spectra involves different auditory processes than those used to discriminate wideband spectra. Additional data show that pitch cues are important within a restricted range of intermediate bandwidth, but not for wideband or very narrow-band spectra. A version of the EWAIF model involving off-frequency listening is proposed to account for the results.


Asymmetrical discrimination of narrow-band stimuli. A three-interval, forced-choice procedure that obtained complete psychometric functions was used to study frequency discrimination for 13-item continua of impulse-generated, narrow-band, buzz-like, steady-state sounds. For all subjects and durations, discrimination relative to the highest center frequency (1060 Hz) stimuli was better than discrimination relative to the lowest center frequency (940 Hz). This result is not in consonance with traditional reports of pure tone frequency discrimination and is not readily explained. However, additional experiments with similar stimuli replicated these findings.


Detection of temporal gaps in sinusoids by elderly subjects with and without hearing loss. Thresholds for the detection of temporal gaps in sinusoidal signals were measured as a function of frequency (100-2000 Hz) and level in 15 elderly hearing-impaired subjects and 11 elderly subjects with near-normal hearing at frequencies below 2000 Hz. The sinusoids were presented in a background noise intended to mask spectral splatter associated with the gap. In a separate experiment, auditory filter shapes and detection efficiency were estimated for the same subjects using the notched-noise method, at center frequencies of 100, 200, 400, and 800 Hz. The gap thresholds at higher signal levels were similar for the two groups of subjects at all center frequencies tested. The mean gap thresholds were slightly higher than those obtained previously from young normally hearing subjects, but this was mainly due to the results of a few subjects with large gap thresholds; the majority of the elderly subjects had gap thresholds within the normal range. Thus reduced temporal resolution does not seem to be an inevitable consequence of aging. Gap thresholds at low center frequencies tended to be positively correlated with the equivalent rectangular bandwidth (ERB) of the auditory filter, the opposite of what would be expected if the auditory filter played a role in limiting gap detection. Detection efficiency, as estimated from the notched-noise experiment, was poorer for both groups of elderly subjects than for young normal listeners, but detection efficiency was not significantly correlated with gap thresholds.


External ear transfer function modeling: a beamforming approach. In this article, a beamformer is proposed as a functional model for the spatial and temporal filtering characteristics of the external ear. The output of a beamformer is a weighted combination of the data received at an array of spatially distributed sensors. The beamformer weights and array geometry determine its spatial and temporal filtering characteristics. A procedure is described for choosing the weights to minimize the mean-squared error between the beamformer response and the measured response of the external ear. The effectiveness of the model is demonstrated by designing a beamformer of several hundred weights that duplicates and interpolates the measured external ear response of a cat over broad ranges of frequency and direction. A limited investigation of modeling performance as a function of array geometry is reported.