Demineralization and remineralization of dental enamel.

Experimentation in vitro using organic acid buffers as demineralizing media shows that caries-like lesions can be obtained which are very similar in morphology and developmental stages to early lesions formed naturally under oral conditions. The use of these chemical systems and of mechanistic models advanced to explain the unique histological features of incipient caries have yielded a good understanding of the processes involved in caries formation. The study of natural and induced factors influencing the demineralization process has been greatly facilitated by the use of bacteriological systems in which demineralization is produced by direct colonization of cariogenic microorganisms on the surfaces of extracted teeth. Comparison of results obtained with these latter systems and with chemical systems has allowed us, for example, to elucidate the mechanism by which acquired salivary pellicles and fluoride topical solutions decrease the rate of enamel demineralization. The pellicle retards transport of matter across the enamel surface, whereas the fluoride topical solutions decrease the cariogenicity of the colonizing bacteria.


Enamel crystal chemistry--where do we go from here?

This section of the meeting has been devoted to enamel crystal chemistry and its behavior during formation and demineralization. In dealing with calcified tissues of any type we are looking at a crystalline formation with the most diverse range of properties which one could choose for its purpose. The size, shape, and intercrystalline binding give mechanical strength, cutting ability, and flexibility where necessary.


Matrix--mineral relationships in enamel tissues.

A personal view of vertebrate enamels and their matrix-mineral relationships is given by first considering enamel types and speculating on the nature, distribution, formation and role of enamel protein. Not all the work consulted is mentioned in the text. The additional works are, however, included in the list of references.


Matrix-mineral relationships--a morphologist's viewpoint.

The literature on the ultrastructural morphology of the enamel matrix and its relationship to the crystals is reviewed. Two morphological entities of the matrix are discussed. One is the so-called stippled material which may be the initial cell product; the other, variously described as fibrillar, lamellar, tubular or helical, is thought by many to play a crucial role in nucleation and orientation of the crystals. A number of observations, however, suggest that the latter structures form secondarily to the crystals and that in reality they represent organic material adsorbed to the crystal surface and maintained as independent structures upon removal of the mineral. The need for additional studies is stressed including systematic studies of interactions between constituents of the organic matrix and the apatite crystals.


Differential adsorption and chemical affinities of proteins for apatitic surfaces.

Studies are reviewed which identify the interacting groups involved in protein adsorption onto hydroxyapatite. Thus, carboxyl and phosphoester groups bind to calcium sites in the adsorbent, and basic groups bind to phosphate sites. Detailed adsorption studies have been performed to quantitate some of these interactions. An adsorption model, based on the Langmuir adsorption isotherm, adequately fitted the data from experiments using selected amino acids, bovine albumin and two human salivary proteins. Adsorption parameters (affinities and maximum number of sites) were obtained for several apatitic adsorbents, with affinities increasing considerably in the series hydroxy- (HA), fluorhydroxy- (FHA) and fluorapatite (FA). A modest increase in the number of sites was also noted. The change in adsorption behavior, with increasing fluoride content, was attributed to a reduction in the surface free energy of the adsorbent, with a concomitant decrease in the interaction of the adsorbent with water, and a consequent enhancement of the adsorption bond. It is suggested that this effect may play a role in the cariostatic effect of fluoride. Unusual structural aspects of the salivary proteins are discussed in relation to their adsorption behavior, and the molecular segments responsible for binding to the adsorbent tentatively identified.


Enamel matrix and crystals--chicken and eggs?

This discussion is presented as an attempt to interrelate the matrix and mineral in terms of our existing knowledge as presented at this Symposium, and to relate it, where possible, to what is being accomplished in allied disciplines and research areas elsewhere. The present author is fully aware of the difficulties involved in this task and of his own inadequacies in attempting to perform it. As a general rule, with perhaps the morphologists being the exception to it, the matrix and crystal components have been investigated independently of each other. This, of course, is quite justifiable, as the presence of one can often interfere with the investigation of the other, and each needs to be examined initially in as pure a state as possible.


Dynamics of enamel formation in the rat incisor tooth.

Enamel formation was reviewed by morphology and radioautography in rat incisors. Labeled amino acids and sugars were used as matrix precursors whereas labeled calcium monitored mineral deposition. All ameloblasts synthesize organic material, but only cells in the zone of secretion release labeled matrix. The pattern of matrix deposition indicates that enamel rods are elaborated by Tomes' processes within cavities formed by interrod partitions. The latter are elaborated by cytoplasmic projections from adjacent ameloblasts. Initially-labeled matrix is added as a band near the cells. With time the label randomizes throughout the entire immature enamel and most of it is lost in the zone of maturation. However, a glycoprotein component attributed to remnants of Tomes' process membrane persists in mature enamel. Labeled calcium is incorporated into crystals which grow at a uniform rate throughout the entire layer of enamel in the zone of secretion and up to the middle of the zone of maturation. The ribbon-like crystals are built close to the cell membrane and elongate as the cell recedes. Crystal elongation occurs in the same location as new matrix is deposited; that is, rod crystals are related to Tomes' processes and interrod crystals, to cytoplasmic projections. The crystals grow to full size mainly by thickening and this growth presumably displaces the organic matrix.


Normal mature human enamel protein.

Pure enamel was prepared using an original microdissection technic. Protein concentration was 375 microgram per gram of enamel. Polyacrylamide gel electrophoresis showed a single fast-migrating zone containing a thin double band. Ultracentrifugation studies suggested that the proteins were of low molecular weight or of weak density. Absorption spectra showed a strong absorbance at 260nm. Amino acid analyses yielded a composition of 25% Gly, 13.5% Glu, 11% Ser, 11% Pro, 2% Cys and 2% Hyp. A glucidic content of 15% was estimated and glucose, galactose, mannose and fucose were identified. The organic matrix of enamel seemed to be constituted of two major glycoproteins probably fibrous but different from keratin.


"Proenamel leads to enamel leads to polypeptides": a concept.

Our laboratory is interested in determining the number of enamel protein gene products which characterize the ameloblast phenotype, and to what extent these proteins are degraded as a function of enamel maturation. Many investigators have reported a large number of heterogeneous proteins within the enamel matrix (Eggert, Allen and Burgess, 1973; Weidmann and Eyre, 1971). One explanation for this apparent heterogeneity may be the uncertain age of the analyzed enamel matrix; specimens may have undergone degradative processes associated with enamel maturation. To overcome this difficulty, our laboratory selected 26-day embryonic New Zealand White (NZW) rabbit incisor and molar tooth organs to isolate enamel protein(s). At this developmental stage it is possible to identify newly-secreted enamel matrix proteins.


Dental enamel matrix--isolation and partial sequence of a peptide component.

Chromatography of demineralized bovine fetal enamel matrix proteins on 'Biogel P6' was shown to yield a trailing peak which contained a single electrophoretic component. This polypeptide, further purified by chromatography on 'Biogel P4', was found to be homogeneous by disc electrophoresis and gel isoelectric focussing. Amino acid analyses indicated this component (designated: "E5') to be similar to some of the phosphopeptides previously described. Cyanogen bromide cleavage of E5 yielded three principal products whose amino acid compositions and N-terminal residues were investigated. A partial sequence for component E5 was proposed and comparison with previous bovine matrix isolates was made.


Differences between the medical and dental health care sectors.

The majority of economic research on the health care system has focused on the medical sector to the near exclusion of other components, such as the dental sector. Based on the size, scope, and costs associated with the medical sector, this is understandable. However, this health research focus has often resulted in the casual and perhaps inappropriate generalization of medical findings to the dental sector. The purpose of this paper is to identify and review some of the differences between the profession and practice of dentistry and that of medicine. Differences discussed are those that exist in the respective education systems, work forces, delivery systems, disease entities, patients' perceptions of medical and dental needs, and the financing of services demanded. Researchers and policy leaders alike are urged to weight the significance of these differences as they consider the applicability of medical sector findings to dentistry.


An analysis of the decline in dental school applicants, 1975-1978.

There has been a significant reduction over the past three years in the number of applicants to dental school. This paper, which is based on an analysis of over 30 variables contained in the American Association of Dental Schools Application Service data bases for the 1975, 1976, 1977, and 1978 entering class years, indicates that only four of these variables are related to the decline in applicants: (1) region of parents' residence, (2) grade point average, (3) college major, and (4) parents' socio-economic status. The decline in applicants from the socio-economic lower middle class documented here once again raises the possibility that access to dental education is being denied to the economically disadvantaged.


Dental school of graduation in relation to dentist location.

This is a statistical study of the 1976 location, by region and state, of the active civilian dentists of the United States in relation to the dental schools from which they graduated. The focus of the study is a master matrix table which shows state-by-state distribution of the graduates of each dental school and, conversely, where each state obtained its dentists, by individual dental school of graduation. Comparisons are made with similar data from several studies since the early 1950s, certain relationships and trends are identified, and a few projections are made to 1990. The study provides detailed information useful to organizations and individuals studying dental manpower and who are planning dental educational facilities and programs. A most important aid in such planning is information not only on the location but also on the sources of present dentist manpower.


Dental education and public policy: a research agenda.

The Work Group on the Education of the Health Professions and the Nation's Health offers the theme of discontinuity to describe why so little useful knowledge has been derived from research in this area and to suggest a more productive approach for future studies. Discontinuities are evident among the needs of patients and populations and how dentists practice and in what dentists do in practice versus the content of dental education. The Work Group recommends six areas directly applicable to dentistry in which research might alleviate these discontinuities.


Dental survey of 620 Soviet immigrants.

Six hundred twenty recently arrived Soviet immigrants were examined at the Northern Dispensary. There was a need for extensive dental treatment among these persons and much of their previous treatment did not meet currently accepted American standards.


The office anesthesia record.

The Anesthesia Record Committee of the Massachusetts Dental Society of Anesthesiology has developed a form to record vital signs and agents used in control of pain in the practice of dentistry. This anesthesia record is simple to use, provides information useful for subsequent dental-anesthetic treatment, and provides adequate written documentation to place the dentist in a legally defensible position.


"Recreational" misuse of nitrous oxide.

With the use of nitrous oxide increasing, overuse and excessive exposure to this gas are also more prevalent. Neuropathy, expressed as amnesia, aphasia or weakness, numbness, and incoordination affecting all extremities, is the common result of frequent overexposure. For optimal dental treatment, it is recommended that both patient and dentist be aware that nitrous oxide can be an exogenous toxin, damaging to neuronal structures, if used in excess.


Transposition of teeth.

Transposition is a rare dental anomaly. Two cases of transposition of canines have been presented, the causes are discussed, and modes of treatment are suggested.


Bronchogenic carcinoma metastatic to the lip and the mandible.

Two cases of metastatic bronchogenic carcinoma are reported. Possible pathways of dissemination are discussed, along with the symptoms, diagnosis, and management of these lesions.


An instrumented technique for occlusal adjustment.

A technique is suggested for adjustment of the natural dentition. It permits the dentist to identify and to remove occlusal interferences and to establish smooth, gliding, harmonious jaw movements for patients with occlusal problems.


Vitamin B6 responsive infantile convulsions and branched chain amino aciduria.

This study reports of a case with neo-natal convulsions and branched amino-aciduria in addition to tryptophanuria. These abnormalities were promptly corrected by administration of pyridoxine.


Comparative electrophoretic study of Mallory body and intermediate filament protein.

To investigate the possibility that Mallory bodies (MBs) are composed of intermediate filaments (IFs), the electrophoretic patterns of MB proteins from human liver were compared with the IF protein extracted from chicken gizzard smooth muscle and extracts of mouse liver which contained MBs. The human MB had a protein component which had a similar mobility as that of the IF protein extracted from smooth muscle. A similar protein band was found in the extracts of mouse liver which contained MBs. No protein band corresponding to actin protein was found in human MB protein. The IF-like protein was also present in control mouse liver extract. The estimated molecular weight of the IF protein was 54,000. The evidence suggests that MBs are, in part, composed of IF protein. The IF protein is a normal constituent of liver and smooth muscle.


Neuraminidase alteration of human lymphocyte reactivity to mitogens, antigens and allogenic lymphocytes.

Lymphocyte reactivity to phytohemagglutinin (PHA) was reduced significantly in whole-blood cultures initiated with nontoxic concentrations of Vibrio cholerae neuraminidase (VCN). Reduced responsiveness was not due to degradation or inactivation of PHA by this enzyme, and the reaction was dependent upon the dose and time at which this mitogen and enzyme were added to the cultures. In cultures from some subjects, VCN also inhibited reactivity to concanavalin A. In contrast, lymphocyte reactivity to mitogens from pokeweed or Staphylococcus aureus as well as to antigens or allogeneic lymphocytes was enhanced by VCN. At concentrations required to elicit these effects, VCN itself was not stimulatory.


New treatment for herpes simplex virus type 2 [ultrasound and zinc, urea, and tannic acid ointment]. Part I--Male patients.

Twenty-three male patients with herpes simplex virus type 2 blisters on the prepuce, glans penis, and penile shaft were divided into two groups. Ten patients served as controls, and thirteen patients were treated with ultrasound (1 watt/cm2 for 60 seconds) and Herpigon on three consecutive days. Results showed a negative virus culture after three days of treatment and significant reduction of recurrent infection in the treated group while the control group experienced recurrent infection within 62-80 days. This method offers a new therapeutic treatment for genital herpes simplex virus.


Studies on platelet aggregation in vivo. VII: Effect of pentoxyfylline on circulating tumor cells.

Pentoxifylline, a platelet aggregation inhibitor, increased circulation time of intravenously injected, labeled tumor cells in male mice.


Carcinoma of the lung metastatic to the gingiva: review of the literature and report of case.

A rare case of metastasis to the gingiva from carcinoma of the lung has been presented. From the review of the literature, only ten other cases have met the criteria to be considered as metastatic malignancy to the gingiva.


Metastatic malignant melanoma to the palatine tonsils: report of case.

A rare case of metastatic melanoma to the palatine tonsils was presented. The patient had no symptoms, and the metastatic oral lesion was discovered on routine examination.


Subcutaneous emphysema after Le Fort I osteotomy: report of two cases.

Two cases of subcutaneous emphysema that occurred after Le Fort I osteotomies are reported, and diagnosis and treatment are discussed.


Polyostotic fibrous dysplasia involving the maxilla and mandible: report of case.

The case presented here represents an aggressive form of polyostotic fibrous dysplasia. Because of lack of evidence to substantiate precocious puberty and abnormal pigmentation, Albright syndrome cannot be established. Because of the nature of this disease, its clinical course and prognosis are unpredictable. However, it is believed that continued growth of the lesion may necessitate additional surgery.


Actinomycosis of the tongue: report of case.

A brief review of the pathogenesis of actinomycotic infections, including cause, frequency, distribution, and symptoms has been presented. A relatively rare occurrence of actinomycosis in the tongue was reported to serve as an illustration of the diagnostic and therapeutic considerations pertinent to this disease.


Use of microcrystalline collagen for hemostasis after oral surgery in a hemophiliac.

A microcystalline collagen hemostat effected rapid hemostasis in dental extractions for a hemophilic patient with a significant level of inhibitor where preoperative transfusion of deficient factor was contraindicated. It appears that MCH can be used safely and effectively for a variety of oral procedures. In addition to its hemostatic properties, the ease with which it can be handled and its adherence make it adaptable for use in locations of limited access. In comparison with currently used materials, such as gelatin foam, it may have wider application and may be of greater benefit in achieving hemostasis in procedures in the oral cavity.


A technique for simultaneous fracture repair and augmentation of the atrophic edentulous mandible.

A technique that uses autogenous rib grafts for repair of fractures of an atrophic, edentulous mandible and augmentation of the ridge has been presented. Nine cases have been treated in this manner. We advocate this treatment to promote healing of the fractures and to provide necessary mandibular bone for future vestibuloplasty and, ultimately, restoration of function with denture construction.


Morbidity associated with extraoral open reduction of mandibular fractures.

One hundred consecutive extraoral open reductions of mandibular fractures were analyzed in an attempt to quantitate the morbidity of this technique and demonstrate possible predisposing factors. A complication rate of 13% was found in this series. Age of the patient, coexisting systemic disease, operative delay and operative and postoperative misadventures could not be correlated with morbidity. An obvious relationship was found between the area of the fracture and the presence and disposition of teeth in the fracture line, and the incidence of complications. Open reductions of the mandibular angle associated with teeth removed from the fracture line produced the greatest incidence of complications both quantitatively and qualitatively.


Observations of carbon dioxide laser and bone bur in the osteotomy of the rabbit tibia.

The tissue responses of a rabbit tibia to superpulse laser osteotomy, continuous-wave laser osteotomy, and bur osteotomy were compared. Healing of the bone occurred after use of all three modalities, but there was a delay in healing after laser osteotomy when compared with bur osteotomy. Laser osteotomy is feasible, but improvements will be needed to make such bone cutting as efficient and controllable as the rotating bur.


Changes in soft tissue profile after surgical correction of skeletal class III malocclusion.

Cephalometric analysis of the facial soft tissue profile after surgical correction of skeletal Class III malocclusion performed either in the ascending ramus or in the mandibular body in 33 patients showed a close correlation between the horizontal movements of the soft tissue landmarks and those of the underlying skeletal and dental structures. In the vertical direction, the changes were more variable. A comparison of these results with the soft tissue profile of normal persons indicated that a natural appearance could be achieved after correction of Class III malocclusion by combined surgery and orthodontic treatment.


A comparison of three methods of measuring maximal opening of the mouth.

Two extraoral techniques are compared with a direct technique for measuring maximal opening of the mouth. The extraoral techniques allow recording of the variable independent of the teeth. The accuracy and precision of the three techniques are calculated and compared statistically, and the significance of the results are discussed.


Vascular injury and penetrating facial trauma.

Three patients with gunshot wounds to facial and vascular structures were described. They demonstrate the importance of angiography in the acute care phases of treatment. In one case, angiography lead to eventual surgical management of an arteriovenous fistula. The other two cases described arterial injury that required careful surgical follow-up to detect delayed complications.


Furcation morphology relative to periodontal treatment. Furcation entrance architecture.

The furcation entrance diameter of first permanent molar teeth has been investigated in a sample of 114 maxillary and 103 mandibular teeth, and found to be smaller than the blade face width of commonly used periodontal curettes in 58% of the furcations examined. It is suggested that because of this size disparity curettes when used alone may not be suitable for root preparation in this area as part of periodontal therapy. Alternative methods of instrumentation require clinical appraisal before recommendation. The buccal furcation entrance diameters of the maxillary first molar teeth examined tended to be smaller than either the mesiopalatal or distopalatal. Similarly the buccal entrance diameter in the mandibular first molar teeth examined tended to be smaller than the linqual. The mesiodistal widths at the cementoenamel junction of both maxillary and mandibular first molar teeth were found to have very low correlation with their furcation entrance diameters. Large teeth therefore do not necessarily have large furcation entrance diameters.


Periodontal surgery for the apprehensive patient with anesthetic management. A review of 150 patients.

Full mouth periodontal surgery, while not a routine procedure, is invaluable in treating a sizable population that otherwise could not be treated. A series of 150 cases has been analyzed to determine who utilizes these procedures and why. The author feels that this is a valuable modality that will become more common.


Mitotic response in basal cells of the crevicular epithelium to gingival surgery.

A total of 18 periodontal patients participated in this study. After initial preparation, a gingivectomy was performed on the lingual surfaces of posterior teeth with pockets ranging from 3 to 5 mm in depth. Control specimens were obtained at time of gingivectomy. Subsequently, the patients were divided into three groups (Group I, II, III). Each group contained three male and three female patients. The gingivectomy site was biopsied after surgery at 7, 14, and 28 days. The mean mitotic indices of the basal cell layer of the crevicular epithelium were obtained. At 0 day, the mean mitotic index was 6.6, increased to 11.4 at 7 days, and rose to a high value of 11.6 at 14 days. It was reduced to a value of 9.7 at 28 days. From our data, it appeared that the rise in mitotic activity which followed gingival injury did not fall to preoperative levels at 30 days postsurgery.


Epithelial dysplasia of the gingiva. Report of a case.

A case of epithelial dysplasia of the mandibular gingiva is reported. The significance of this lesion and its implications are discussed.


Indicator pastes: their behavior and use.

Indicator pastes were subjected to a laboratory investigation and a clinical trail. The tests showed: 1. An increase in temperature increased the rate of flow of the pastes. 2. An increase in applied pressure increased the rate of the flow of the pastes. 3. Pastes containing a small percentage of filler were compressed to a smaller thickness than those containing a greater percentage of filler. 4. The zinc oxide-hydrogenated oil mixture demonstrated a biphasic flow pattern. Pressure Indicator Paste demonstrated a simple flow pattern. 5. Similar tests did not give identical results. However, the characteristics of flow curves for similar tests were consistent. 6. A clinical trial using eight subjects showed no marked differences between three indicator pastes but did show significant differences between the interpretations of paste patterns by four dentists. This evidence suggests that the nature of the suspension medium affects both the type of flow and the rate of flow of an indicator paste. The percentage composition of filler affects both the final film thickness and the rate of flow. Improved criteria for the interpretation of paste patterns must be developed before clinical differences in paste behavior are noted.


The relationship of canine-protected occlusion to a periodontal index.

A clinical evaluation was made on 1,000 teeth in 100 patients with Angle's Class I occlusion who were free from histories of orthodontics, removable or fixed prosthesis, occlusal equilibration, maxillary or mandibular jaw fractures, and systemic diseases. The study was made to determine if there was a relation between their patterns of disclusion and a periodontal disease index. In this study, 14% of the subjects exhibited canine protection, 16% a pattern called progressive disclusion, 46% group function, and 24% a different disclusion pattern on each side. The teeth of mouths having canine-protected occlusions had significantly lower mean periodontal disease index scores than the teeth of mouths having progressive disclusion or group function. Also, the canines and the molars in the canine-protected group exhibited lower mean periodontal disease index scores than their counterparts in the progressive disclusion or group function categories.


Bacteria and pulpal reactions under silicate cement restorations.

Silicate cement was inserted in deep unlined cavities in 70 human teeth; 35 cavities were cleaned with an antibacterial cleanser, and the other 35 cavities in the contralateral teeth were treated with water spray only. In all teeth, invasion of bacteria from the tooth surface was prevented with a surface seal. Histologic examinations after 4 weeks revealed bacterial growth on dentinal walls in 9 of the uncleaned and in 2 cleaned cavities. Only in these 11 teeth was an inflammatory reaction seen in the pulp. Under eight cavities without bacterial growth and with silicate cement placed directly on an exposed pulp, no serious injury and no inflammatory reactions were observed. It was concluded that silicate cement per se does not seriously irritate the pulp. Infection of cavity walls should be avoided, not only by removing grinding debris and antibacterial cleansing, but also by use of a liner to prevent invasion of bacteria from the surface of the tooth.


Replica technique for scanning electron microscope examination of occlusal amalgam margins.

A new replicating technique, the modified adhesion relief method, was developed to investigate the marginal integrity of the occlusal surface of amalgam restorations over a period of years. The accuracy of the replicas was confirmed by scanning electron microscope comparison with the original teeth. The tooth to be studied need not be extracted. The technique makes it possible to continue the observation of restored teeth in the oral cavity for long periods. The technique does not require special equipment and is uncomplicated.


Elastomeric impression materials: effect of bulk on accuracy.

Impression trays were fabricated providing 2, 4, and 6 mm spaces to determine the stability and accuracy of nine elastomeric impression materials on a simulated full crown preparation steel die. The interface space of 2 mm produced the most accurate impressions for all of the materials tested. All impression materials except one fell within the revised American Dental Association Specifications. The clinical-type tests, using castings on dies poured from these materials, corroborated the acceptance of those materials and techniques exhibiting the least dimensional change.


A combination obturator.

A combination of flexible and rigid extensions can be used on a prosthesis to provide stability, retention, decreased weight, and obturation of residual palatal defects. The combination extensions present a design of a maxillofacial prosthesis which takes maximum advantage of the patient's remaining anatomy.


Utilization of cadaver tissue for a scanning electron microscopic study of the insertion of the masseter muscle.

1. The generally poor state of soft tissue preservation that complicates observations by gross dissection and light microscopy posed no hindrance to scanning electron microscopic (SEM) studies of bone surface, because all of the soft tissues are chemically removed. 2. Specific and identifiable surface patterns representing locations of periosteal and fibrous muscle attachments can be readily observed in cadaver tissue with the SEM. 3. SEM observations confirmed earlier literature concerning the extent of periosteal and intraosseus attachments of the masseter muscle. The masseter muscle attached periosteally on the lateral surface of the mandible and along the inferior border. Just above the inferior border, a ridge of intraosseous attachment was noted. 4. The correlation of SEM observation of bone surface patterns with gross dissection and light microscopy demonstrated that SEM can be useful in determining the extent of muscle attachments in cadaver tissue even when the soft tissue is poorly preserved.


Computer-monitored radionuclide tracking of three-dimensional mandibular movements. Part I: theoretical approach.

A new technique for the three-dimensional recording of a person's mandibular movement is described. A small and harmless radioactive source is fixed on the patient's skin at the point of interest or sealed in a tooth cavity. Using the proper collimation, the motion of the point source is recorded via a gamma  camera and minicomputer. Long-term storage on a magnetic device offers playback, slow motion facilities, and data analysis through the use of sophisticated computer languages. Simultaneous recordings using two cameras, or postsynchronization of two different views of an experiment, enable the three-dimensional restitution of mandibular movements. Superimposition of a grid of radioactive spots spaced at measured intervals during the recording permits a straightforward calibration of the patient's motion. Multiple sources in a single experiment may be recorded to describe the displacement of several points of interest. This method, derived from nuclear medicine techniques, offers a powerful tool of general interest for the tracking of dynamic events in many fields of dentistry such as temporomandibular joint dysfunction and prosthetic restorative techniques. Further considerations on our experimental settings and results will be published in part II.


In vitro properties of epithelial cell lines established from human carcinomas and nonmalignant tissue.

A series of 16 epithelial cell lines derived from human carcinomatous and nonmalignant epithelial tissues were characterized for markers known to correlate with neoplasia in various model systems. The goal of these studies was to determine which in vitro transformation properties were relevant to human epithelial malignancy. The parameters tested were 1) colony formation in Methocel and on confluent monolayers of normal human epithelial cells and fibroblasts and 2) tumor induction in immunosuppressed mice. Cell lines derived from normal tissue and nonmalignant tissue peripheral to cancerous lesions were generally negative for these properties, whereas the carcinoma-derived lines varied in their expression (some lines being more abnormal than others). In most cases, the lines derived from metastatic lesions had more abnormal properties than did those derived from primary carcinomas.


Photoradiation in the treatment of recurrent breast carcinoma.

Photoradiation, with the use of hematoporphyrin derivative (Hpd) activated by visible light in the red region of the spectrum, was an effective treatment for controlling local and regional chest wall recurrences of breast carcinoma. With sufficient time between iv injection of the drug and local activation with red light, cutaneous and subcutaneous masses were treated effectively without undue damage to overlying and adjacent skin. This high therapeutic ratio resulted from the ability to Hpd to accumulate and/or to be retained to a higher degree in malignant tissue than in many normal tissues. This technique can be used as a primary treatment or upon tumor recurrence following conventional modalities such as surgery, chemotherapy, and radiation therapy.


Breast gross cystic disease fluid analysis. I. Isolation and radioimmunoassay for a major component protein.

Human breast gross cystic disease (GCD) fluid was analyzed by sodium dodecyl sulfate-acrylamide gel electrophoresis, and four major proteins (GCDFP-70), GCDFP-44, GCDFP-24, and GCDFP-15) were identified. By fractionation techniques, these proteins were separated from one another. The GCDFP-70 was immunologically identical to human albumin and was present in GCD fluid at approximately a 100-fold lower concentration than in plasma. The GCDFP-44 was immunologically identical to human plasma Zn-alpha2-glycoprotein; however, it was present in GCD fluid at an approximately 50-fold higher concentration than in plasma. The GCDFP-24 was the major component protein of GCD fluid. It had progesterone binding activity, and immunologically it was identical to a component of human plasma; however, antisera that identified 30 separate components of plasma failed to identify the GCDFP-24 as one of these plasma proteins. The GCDFP-24 concentration in GCD fluid was approximately 100-fold higher than the plasma analog. The GCDFP-15 component was immunologically distinct from any plasma components, as judged by Ouchterlony analysis. It was, however, immunologically identical with a component of both human milk and saliva. As revealed by radioimmunoassay, plasma levels in normal subjects were 7-85 ng/ml. In patients with metastatic breast carcinoma, markedly plasma levels (150-30,000 ng/ml) of this protein were detected. Short-term tissue cultures of breast carcinoma explants released this protein into the culture medium.


Double minutes in human carcinoma cell lines, with special reference to breast tumors.

Small DNA-containing particles called double minutes (dm) were observed in metaphases during a survey of human tumor cell lines. Detection of dm in uncultured malignant effusions, in a series of 14 breast carcinoma cell lines, and in a cervical carcinoma cell line, and a literature survey indicated that dm may be more common among human malignant cells than previously suspected. Some of the human breast carcinoma cell lines showed a high incidence of dm, which permitted a series of cytochemical studies. The dm stained identically with euchromatic regions of human chromosomes. Unlike typical chromsomes, dm contained neither C-bands nor Cd bands indicative of paracentromeric heterochromatin and centromeres, respectively. The dm were observed to cluster at the ends of chromosomes, and individual dm adhered to chromosomes. This clustering behavior allows dm to pass through cell division in the absence of centromeric regions. These results should alert tumor cytogeneticists to the possibility that their material may contain a low incidence of undetected dm.


A human breast adenocarcinoma with chromosome and isoenzyme markers similar to those of the HeLa line.

Pleural effusion was obtained from a 51-year-old black woman who had breast adenocarcinoma and had received chemotherapy and radiation therapy after a radical mastectomy. Cytogenetic and isoenzymic analyses of the cells were performed within a few hours of obtaining the sample. Similar analyses were also done with a cell line established from this effusion. The stemline chromosome number was 35, one of the lowest in human neoplasms. In addition to a marker chromosome involving 1q, which is common in human breast tumors, we found several other marker chromosomes whose G-banding patterns were similar to some of the typical HeLa markers. Genetic signature analysis of 15 isoenzyme loci revealed that 13 were identical to those of HeLa. Both HeLa and the cell line described here express glucose-6-phosphate dehydrogenase type a, yet they were derived from heterozygotic individuals (ab). Our data indicate the necessity to extensive cytogenetic and biochemical analysis before conclusions are made that cell lines are actually intercell-line contaminants.


Absence of late-replicating X-chromosome in a female patient with acute myeloid leukemia and the 8;21 translocation.

Autoradiography was used to demonstrate that the x-chromosome of the 45,X,-X,t(8;21) stemline of a female patient with acute myeloid leukemia (AML) was the active X-chromosome. This suggested that in patients housing AML with the 8;21 translocation, the loss of the inactive X-chromosome in females and of the Y in males (which is known to occur in nearly half of the patients) entails selective advantage to the stemline.


A case-control study of hair dye use and breast cancer.

A case-control study of the relationship between hair dye use and breast cancer included 129 breast cancer patients and 193 control women drawn from the records of a multiphasic screening clinic. Information was obtained by telephone interview on a number of risk factors for breast cancer and on variables pertaining to hair dye use: chronologic time, duration, frequency, type, and color. From this, quantitative measures of cumulative hair dye use at various intervals prior to breast cancer (or an equivalent for controls) were obtained. A multivariate risk factor score was used to control for confounding variables. The adjusted relative risks for breast cancer versus hair dye use were greater than unity but were not generally significant. However, integral measures of hair dye use (No. of yr times frequency per yr) were significantly related to breast cancer when confounding variables were controlled. The association between hair dye use and breast cancer was greatest among women over 50 years of age and among those at lower natural risk for breast cancer. An analysis of temporal patterns showed that breast cancer was related mainly to hair dye use 10 or more years before cancer diagnosis. Because of the retrospective nature of the hair dye data and the small sample size, these results require further validation.


Possible carcinogenic properties of a new chromogen, dicarboxydine (gamma,gamma'-3,3'-benzidine dioxydibutyric acid), tested in rats and mice.

The carcinogenic properties of gamma,gamma'-3,3'-benzidine dioxydibutyric acid [dicarboxydine (DCD)] were studied in 208 rats and 127 mice by either sc administration or by feeding of the compound for 24 months. Tumors developed in 21 of the 99 DCD-treated rats that survived to the time of the first tumor appearance. In DCD-treated rats, tumors different from those in the controls were noted in the bladder, prostate gland, uterine body, and other organs, but in single cases only. Four rats had sarcomas at the site of DCD injection. DCD had no carcinogenic effect in mice. In view of the longer times of tumor induction and multiple tumor development only in rats given sc injections of DCD, the conclusion was reached that DCD is of dubious or negative carcinogenicity.


Chemical carcinogenesis in nude mice: comparison between nude mice from homozygous matings and heterozygous matings and effect of age and carcinogen dose.

The incidence and latency periods for local tumor development after sc injection of 3-methylcholanthrene (MCA) into 30-day-old nude mice (nu/nu partially inbred on the CBA/H background) derived from homozygous matings (nu/nu times nu/nu) or heterozygous matings (nu/+ times nu/+) were comparable and did not differ with the immunologically normal controls, even when the carcinogen dosages ranged from 0.01 to 0.10 mg. Similarly, no differences in tumor incidence or latency periods between nude mice from homozygous or heterozygous matings as well as their immunologically normal controls were observed when weight-adjusted doses of MCA equivalent to 0.02 to 0.10 mg in the 30-day-old mice were administered at 120, 210, or 360 days of age. Tumor incidence was lower in nude mice and normal mice when MCA was administered at 210 and 360 days of age, especially in mice given the lower dose of MCA. The lower dosages of MCA (0.01-0.05 mg) had no detectable immunodepressive effects in normal mice. Thus the "normal" tumor incidence in nude mice after MCA administration could not be attributed to: 1) the effect of humoral thymus gland function (in the nude mice derived from heterozygous matings), 2) the immunodepressive effects of the carcinogen (the lower MCA dosages are not immunodepressive), or 3) the age of the mice at administration. These results argue against the thymus dependency of immunologic surveillance.


Glycosphingolipids of subcellular fractions from normal rat liver and Morris hepatoma 5123TC.

Neutral glycosphingolipids and gangliosides were quantified in lipid extracts from plasma membranes, mitochondria, microsomes, and nuclei isolated from normal rat liver and Morris hepatoma 5123TC. Results showed a higher content of glycosphingolipids, especially gangliosides, in hepatomas and differences in the distribution of glycosphingolipids among subcellular fractions. Differences in the glycosphingolipid composition of the hepatoma, namely, the absence of trisialogangliosides and an increase in the lower molecular weight gangliosides, reflected an altered metabolism of glycosphingolipids in this tumor. The results indicated that changes in membrane glycosphingolipids were not restricted to the cell surfaces of malignant cells, inasmuch as intracellular membrane fractions also exhibited altered glycosphingolipid profiles.


Lung carcinoma of sheep (jaagsiekte): tissue-bound precipitating antibodies.

Firmly bound IgG was examined and its activity was tested in spontaneous lung carcinoma of sheep (jaagsiekte). High levels of IgG were extracted by acid-glycine buffer (GB) at pH 2.8 from both the tumor tissue and normal lung, which were exhaustively prewashed by phosphate-buffered saline (PBS) at pH 7.4. The first acid-GB eluates of the normal or tumor tissue acted in the immunodiffusion test as precipitating antibodies against antigens of the first PBS eluate of the tumor tissue. In addition, free intracytoplasmic type A particles were observed in cell-free tumor extract.


Monitoring the therapy of human tumor xenografts in nude mice by the use of lactate dehydrogenase.

With the use of circulating human lactate dehydrogenase (LDH) as a tumor marker, growth and remission of human tumor lines SW480, HEp-2, and Clouser, implanted into female BALB/c athymic nude mice, were followed during therapy. Three types of therapy were used: X-radiation, cyclophosphamide, and diphtheria toxin. After therapy tumor sizes were measured with calipers and compared to changes in the levels of circulating human LDH. Changes in LDH levels paralleled changes in tumor size, but the enzyme fluctuations were more pronounced. Mice bearing intraperitoneally growing SW480 and HEp-2 tumors were effectively treated with diphtheria toxin, and the measurement of circulating LDH was examined as a parameter for gauging the effectiveness of chemotherapy on tumors that could not be visualized. Circulating human LDH can be used to detect intraperitoneal tumor growth and/or remission and to predict death of the animal due to the tumor.


Adenocarcinoma of the gallbladder in guinea pigs.

Adenocarcinoma of the gallbladder developed in 17 of 68 untreated and in 26 of 83 irradiated guinea pigs of inbred strains 2 and 13. The carcinomas spread widely by direct extension and through lymphatic and blood vessels to lymph nodes, mesenteries, omenta, abdominal wall, liver, lungs, bones, and spleen. Whole-body exposure to gamma or X-radiation increased both the number of tumors and metastases in male inbred guinea pigs but not in females. Significantly fewer (9 of 98) noninbred than inbred guinea pigs developed gallbladder carcinomas after irradiation. In 9 untreated noninbred guinea pigs gallbladder carcinomas were not found. Inasmuch as the effect of irradiation was not dose-dependent, an indirect systemic effect of irradiation was postulated. This is the first report on the occurrence of spontaneous gallbladder adenocarcinomas in guinea pigs.


Tissue perfusion inhomogeneity during early tumor growth in rats.

Tissue perfusion in BA 1112 sarcomas of WAG inbred Rijswijk rats was determined from in vivo measurements of capillary density, length, and erythrocyte velocity in modified Algire chamber preparations. Studies were done with the use of television techniques in situ during a period of 26 days, both in control chambers and after implantation of a 0.1-mm3 piece of tumor tissue. Perfusion in control areas void of tumor tissue. Perfusion in control areas void of tumor was approximately 8-10 ml/minute/100 g of tissue. Flow in active tumor growth regions on the outward side of the tumor edge was through undifferentiated channels and had characteristics of flow through a porous medium. Despite enhanced arterial supply, the stabilized tumor microcirculation at the inward side of the growing tumor retained its perfusion rate constant (15-18 ml/min/100 g). Perfusion in central portions of the tumor was about 2-4 ml/minute/100 g during 12 days, whereas the tumor doubled in diameter. Our findings support the concept of temporal and functional blood flow inhomogeneity in the microcirculation of spreading tumors.


Carcinogenicity of methylated derivatives of N-nitrosodiethylamine and related compounds in Sprague-Dawley rats.

Five nitrosamines, which can be considered alkyl derivatives of N-nitrosodiethylamine, were tested for carcinogenicity by administration to Sprague-Dawley rats in drinking water at approximately equimolar concentrations. N-Nitrosodi-n-propylamine was a potent carcinogen but less so than N-nitrosodiethylamine and gave the same spectrum of tumors. N-Nitrosodiisopropylamine was very much weaker than N-nitrosodiethylamine and induced only tumors of the nasal turbinates in significant incidence. At the doses given, neither N-nitrosodiisobutylamine nor N-nitrosodi-sec-butylamine was significantly carcinogenic. In contrast, the cyclic nitrosamine N-nitrosohexamethyleneimine was equally potent with N-nitrosodiethylamine and gave the same spectrum of tumors in liver, esophagus, and nasal turbinates. The results support the concept that oxidation at the alpha carbon atom of nitrosamines is a significant step in carcinogenesis.


Suppression of malignancy in human lung cancer (A549/8) times mouse fibroblast (3T3-4E) somatic cell hybrids.

Interspecies hybrid cells were formed by the fusion of two parent cells: 1) the human lung cancer (bronchioloalveolar) line A549/8, which is not contact inhibited, rapidly produces tumors in athymic nude (nu/nu) mice, and forms colonies in agarose, and 2) the mouse fibroblast line 3T3-4E, which is contact inhibited, is nontumorgenic in nuce mice, and does not form colonies in agarose. These hybrid cells were tested 40-50 generations after fusion. The presence of 20 of the 23 different human chromosomes was tested by isoenzyme analysis, and examples of expression of each isoenzyme marker were found in at least some hybrid clones. All 14 independent hybrid clones tested were nontumorigenic in nude mice. Testing of hybrid clones for their ability to form colonies in agarose revealed two distinct phenotypes: agarose (clones forming colonies at 1-4% of the plated cells) and agarose (no colonies formed/10(5) cells tested). These phenotypes were discordant with all human isoenzymes tested. Malignant human lung cancer A549/8 times non-malignant mouse 3T3-4E cell hybrids were nontumorigenic in nude mice; thus malignancy of the bronchioloalveolar lung cancer behaved as a recessive trait. This nontumorigenicity was not accounted for by an absolute loss of the human chromosomes tested, but gene dosage may play a role. In contrast, the ability to clone in agarose was expressed in some hybrids (and thus behaved as a dominant trait); at present, agarose clonability cannot be related to specific human chromosomes.


Tumor development in organ transplants obtained from carcinogen-exposed rats.

F344 rats were exposed intragastrically to two different dose levels of N-nitrosoheptamethyleneimine (NHMI) resulting in a cumulative dose of either 225 or 450 mg/kg body weight. Tumor development was followed either in situ in the NHMI-exposed animals or in tracheas and esophagi from NHMI-exposed donors after these organs were grafted to isogeneic recipients. Tumor responses in situ and in organ grafts were compared. The results showed that the process of carcinogenesis is not disrupted by the transplantation procedure. The carcinogen dose-response relationship observed in situ was also seen in the transplanted organs. At the high carcinogen dose, the tumor incidence was 100% in situ and transplanted esophagi and 20% in tracheas in situ compared to 25% in tracheal transplants. At the low dose, the tumor incidence was 36% in the esophagi in situ compared to 100% in transplanted esophagi, which suggests a greater sensitivity of the transplant system to detect the carcinogenicity of NHMI. The proportion of carcinomas to papillomas was markedly higher in transplanted esophagi. The tracheal tumor response at both NHMI dose levels showed the same trend but was too low to allow any firm conclusions.


In vivo antitumor activity of various forms of delayed-type hypersensitivity in mice.

Relationships among various forms of delayed-type hypersensitivity (DTH) and nonspecific resistance to Lewis lung tumor were studied in syngeneic and semisyngeneic mice. Only the tuberculin type of DTH obviated a virulent inoculum of 10(6) tumor cells. The Jones-Mote type of DTH, even modified by cyclophosphamide pretreatment, produced a significant local inflammatory reaction which was unable to destroy tumor cells. The antitumor effect of the tuberculin type was observed in BCG-or in Corynbacterium parvum-immune mice and also in sheep red blood cell-immunized mice, but only after the modulating effect of BCG. The antitumor activity of the DTH reaction was anatomically restricted and time related, and it required local persistence of specific antigen. A minimal number of bacteria, 1 times 10(6) living or heat-killed BCG organisms, were equally able to eradicate 10(5) tumor cells in BCG-immune mice. Biphasic effects on tumor growth were observed when systemic specific inflammatory reactions were elicited in BCG-immune mice. However, tumor-specific immunity was never observed, inasmuch as BCG-immune mice surviving injection of a mixture of BCG and tumor cells did not resist a second tumor cell challenge.


A radioimmunometric antibody-binding assay for evaluation of xenoantisera to melanoma-associated antigens.

A radioimmunometric antibody-binding assay was developed with the use of 125I-labeled protein A of Staphylococcus aureus (SpA) for the evaluation of xenoantisera to human melanoma-associated antigens. Antisera were produced in New Zealand male albino rabbits by the injection of cultured human melanoma cells or soluble, partially purified melanoma-associated antigens isolated from these cells. Xenoantisera were rendered operationally specific for melanoma-associated antigens by absorption with human red cells and cultured lymphoblasts. The methodologic parameters and the quantitative relationships among xenoantisera, cultured melanoma target cells, and 125I-labeled SpA and their effect on the measurement of xenoantibody binding were critically evaluated. Data indicated the usefulness of the radioimmunometric assay in monitoring the efficacy of absorption and in characterizing the specificity of xenoantisera to melanoma-associated antigens. The radioimmunometric binding assay when modified and used as a binding inhibition assay was effective in the assessment of the serologic activity of soluble melanoma-associated antigens and thus may be used to monitor the progress of antigen purification.


Impact of long-term filter cigarette usage on lung and larynx cancer risk: a case-control study.

A case-control study was conducted among 1.034 white male and female hospital patients with histologically proved lung cancer (Kreyberg type l) or larynx cancer. After adjustment for duration of the smoking habit, inhalation, and butt length, relative risks of developing lung or larynx cancer were consistently lower among long-term smokers of filter cigarettes than among smokers of nonfilter cigarettes, irrespective of quantity smoked. Relative risks in all groups declined with increased years of smoking cessation. The observed risk reduction among current smokers of filter cigarettes was consistent with that expected, considering that these persons had smoked the older high-tar nonfilter cigarettes for a large proportion of their lives.


Effect of age on incidence of breast cancer in females.

Incidence and mortality data on breast cancer in females from various Occidental (Western) and Japanese populations were analyzed. After adjustment for birth cohort and year of event, the age curves from all the Western populations were very similar in shape. The age curve for Osaka incidence was very similar in shape to the Western incidence curves. The Osaka curve continued to increase after menopause; the postmenopausal decrease in rates in individual cross sections was the result of a strong cohort effect. The premenopausal mortality curve for Japan was very similar in shape to the Western curves; however, the postmenopausal Japanese mortality curve had a smaller slope at each point.


Tritiated thymidine labeling index and response in human breast cancer.

Tumor cell uptake of tritiated thymidine, expressed as the labeling index (Ll), was determined prior to treatment of 25 patients with disseminated breast carcinoma. All patients subsequently received combination chemotherapy with adriamycin, cyclophosphamide, and an antimetabolite (usually 5-fluorouracil), with or without vincristine. The Ll was significantly higher in responders to chemotherapy than in nonresponders (mean, 15 vs. 7.1; P less than 0.01). Other pretreatment variables examined did not show a significant association with likelihood of response. Measurements of the tumor cell Ll in patients with accessible tumor may be of benefit in selection of treatment; 0 of 9 patients with an Ll less than 9 had a response in our series in contrast to 11 of 16 patients with an Ll greater than 9 who had a response (P = 0.001).


Accretion of biopsy specimens of vaginal adenosis from patients exposed in utero to diethylstilbestrol, when transplanted to athymic nude mice.

Vaginal adenosis biopsy specimens from 10 patients exposed in utero to diethylstilbestrol were transplanted for 30 days into athymic (nude) mice. Almost all grafts were recovered, and they had morphologic features closely resembling those of the original biopsy specimens, i.e., cystic, complex, and simple occult glands covered mainly with an endocervical type of epithelium showing extensive squamous metaplasia. Autoradiographic analysis of these grafts after pulse administration of [3H]thymidine into the mice revealed extensive labeling of epithelial cells. These results imply that female athymic (nude) mice are compatible hosts for accretion of the human adenosis.


Hematopoietic stem cells in Friend murine leukemia virus-infected mice undergoing chemotherapy: remission and relapse of erythropoietin-independent erythropoiesis induced by hydroxyurea.

Hydroxyurea (HU), given ip four times, each time at 500 mg/kg in 6-hour intervals, was used to treat DBA/2 mice with Friend murine leukemia virus-induced polycythemia (F-MuLV-P). In these mice a new cell type, found after virus infection, gave rise to erythropoietic colonies in vitro without addition of erythropoietin (Ep) and completely replaced Ep-dependent normal erythropoietic colonies in vitro. The colony-forming units in the spleen (CFUs), the colony-forming units in culture (CFUc), and the erythropoietic colony-forming units (CFUE) were studied. Two days after treatment, CFUs were reduced to about 20% in controls and F-MuLV-P-infected animals, and CFUc were reduced to 6-11% in controls and F-MuLV-P-infected animals. CFUE were not detectable. At day 4 after the first HU dose, when CFUs has regenerated to about normal levels, a sharp rise in Ep-dependent CFUE was seen in the marrow; this rise was not present before HU treatment. The subsequent fall at day 7 coincided with a regeneration of CFUE in the spleen, but in the spleen these CFUE were all Ep-independent. Possibly, the normal Ep-dependent CFUE during regeneration in the marrow might have derived from previously resting CFUs that were not killed by HU. The subsequent conversion to Ep independency could have been due to reinfection by F-MuLV-P persisting in the animal.


Some prognostic and epidemiologic factors in canine osteosarcoma.

Naturally occurring skeletal osteosarcomas in a series of 144 untreated dogs were found especially to involve the ends of the long bones of the forelimbs and affected predominantly older male dogs of giant and large breeds. Most tumors were large and partially necrotic and had extended into soft tissues. Of 12 host and tumor characteristics tested in the first part of the study, tumor diameter and volume were significantly associated with the presence of pulmonary metastases at autopsy. The second part of the study revealed that extension of the tumor into the soft tissues and localization of the tumor in the hind legs were associated with a poor prognosis, whereas the fibrosarcomatous type of tumor was associated, as in man, with a favorable prognosis. An association between the 12 characteristics tested was found in 11 of 78 combinations at the 5% level and in 5 combinations at the 1% level. Affected giant dogs were generally younger than affected small and medium-sized dogs. Especially in giant dogs, the osteosarcomas involved the long bones and were of relatively large diameters. The sarcomas in female dogs were larger in volume than those in males. Pure osteoblastic osteosarcomas were generally smaller than combined (chondroblastic and fibroblastic) osteosarcomas. Peritumorous lymphocytes and plasma cells were present in 50% of the dogs, especially in small and young dogs. When compared with a reference population, great Danes, rottweilers, German shepherds, and boxers were found to be overrepresented in the osteosarcoma group.


Karyotypic evolution associated with loss of tumorigenicity.

A reproducible association between loss of tumorigenicity and specific karyotypic changes was described in cell culture lines SLU-5 and DMS-402 established from mouse plasmacytoma MOPC-21 carried in BALB/c mice. The defect in chromosome no. 15, which has been specifically associated with mouse myelomas, was neither corrected nor eliminated in the karyotypic evolution that occurred simultaneously and progressively with the grandual loss of oncogenicity.


Antiviral effect of N-phenylacetoaminomethylene-DL-p-nitrophenylalanine (A-101) on murine leukemia viruses.

N-Phenylacetoaminomethylene-DL-p-nitrophenylalanine (A-101), when administered ip to male DDY mice infected with Friend leukemia virus, significantly inhibited virus-induced splenomegaly, reduced viable virus titers in spleen and plasma, and significantly prolonged survival time. A-101 also inhibited multiplication of the Friend and Moloney viruses in tissue culture systems.


Carcinogenesis bioassay of technical-grade piperonyl butoxide in F344 rats.

The insecticide synergist piperonyl butoxide--alpha-[2-(2-butoxyethoxy)ethoxy]-4,5-methylenedioxy-2-propyltoluene--was tested for carcinogenicity in inbred F344 rats in a 2-year study employing doses of 10,000 and 5,000 ppm of the compound administered continuously in the feed. Although a statistically significant dose-related increase in the incidence of lymphoreticular neoplasia was associated with administration of the compound to females, the incidence of that class of neoplasm was higher in control males than in treated males. The finding of statistical significance in one sex is not considered by itself to constitute sufficient evidence of a biologic effect to justify an indictment of carcinogenic action. However, inasmuch as the chief use of this substance is to alter the in vivo metabolism of other chemicals, its possible role as a cocarcinogen should be carefully considered in any risk-benefit evaluation aimed at setting policies regarding its uses.


Correlation between concanavalin A agglutinability and cytotoxic sensitivity to antiserum against tumor-associated antigen in rat fibrosarcoma cells.

An ip transplantation of 3-methylcholanthrene-induced, transplanted fibrosarcoma KMT-17 cells (1 X 10(8)) grew rapidly and killed syngeneic WKA rats in 3-4 days. Agglutinability induced by concanavalin A (Con A) and antigenic expression of KMT-17 cells were investigated in relation to days after ip transplantation. Agglutinability was highest in 1-day-old cells and lowest in 3-day-old cells. The agglutinability of 3-day-old cells increased again when these cells were transplanted into normal rats. The cytotoxic sensitivity of tumor cells to antiserum against tumor-associated surface antigen (TASA) changed simultaneously with the degree of Con A agglutinability. This phenomenon disappeared after artificial infection of tumor cells with Friend murine leukemia virus. The result of the quantitative absorption test at 4 degrees C overnight was that 1- and 3-day-old cells did not differ in their absorbing capacities to anti-TASA sera. However, when the absorption test was done at 37 degrees C for 60 minutes, 1-day-old cells had approximately 16 times more absorbing capacity than 3-day-old cells. However, the cytotoxic sensitivity to antiserum against histocompatibility antigen did not change, regardless of the number of days after ip transplantation. Analysis based on the quantitative absorption test revealed no difference in antibody-absorbing capacities between 1- and 3-day-old cells at both 4 degrees C and 37 degrees C. The relationship between Con A agglutinability and cytotoxic sensitivity to anti-TASA serum is discussed from the viewpoint of "lateral receptor mobility" on the cell surface.


Neoplasms in Tasmanian devils (Sarcophilus harrisii).

Pathologic studies were made on 18 Tasmanian devils that were necropsied at the San Diego Zoo. Spontaneous neoplasms and/or preneoplastic hyperplasia were the most frequently occurring diseases. Abnormal proliferative lesions were present in 9 animals; 6 of these had two or more concomitant proliferative diseases. Renal disease was observed in 7 animals.


Differential response of malignant BALB/c mammary epithelial cells to the multiplication-stimulating activity of insulin.

Investigations were done to distinguish normal from malignant BALB/c mammary epithelial cells by growth differences. In a high concentration (15%) of serum, normal epithelial cells (from mice at midterm of first pregnancy) and malignant BALB/c mammary epithelial cells in primary culture divided at the same rate (doubling time = 24 hr) and exhibited an extremely short longevity (three doublings). Insulin did not affect growth rate or longevity. Growth rate of normal and malignant cellss was serum-dependent. At serum concentrations limiting for normal cell multiplication, malignant cells showed no proliferative advantage. Insulin complemented but did not replace limiting serum for multiplication of both normal and malignant cells. When allowed to become confluent before three doublings, normal and malignant cell exhibited a contact-mediated (or density-mediated) growth inhibition. Both normal and malignant cells were arrested in the G1 phase of the cell cycle at the same density. Near physiologic doses of insulin stimulated DNA synthesis and mitosis in malignant cells but not in normal cells. Approximately 6% of malignant cells were stimulated to divide in the presence of insulin. Maximum DNA synthesis occurred at 24 hours and maximum mitotic activity at 30 hours after addition of insulin. The data suggested that malignant mammary epithelial cells are more sensitive to insulin as an overgrowth-stimulating factor than are normal cells.


Changes in the transplantability of a virus-induced murine leukemia tumor.

The subcutaneous growth potential of a Friend virus-induced murine leukemia cell line (FBL-3) passaged in the ascites form was found to change, depending on the interval of time spent in the peritoneal cavity. Injection sc of the original stock of FBL-3 (growth continuously in vitro) into C57BL/10 mice produced transient tumors uniformly rejected by days 20-40. The tumor cells passaged in the ascites form for 7 days behaved like the in vitro-grown cells, whereas ascites cells harvested at 14 days produced progressive lethal subcutaneous tumors in 50-70% of the recipients. The change in subcutaneous growth was reversible simply by alteration of the ascites passage schedule. Day 7 ascites cells (regressors) were converted to progressors by ip passage for 14 days, and day 14 ascites cells (progressors) were converted to regressors by ip passage for 7 days. The difference in growth potential between day 7 and day 14 ascites cells was not due to effects of nonneoplastic host cells accompanying the tumor cells in the ascites population, because neither dilution of nonneoplastic cells by in vitro culture nor selective killing of H-2a/b host cells by anti-H-2 serum and complement altered the subcutaneous growth behavior or either day 7 or day 14 ascites cells. These results indicated that the change in the growth potential of FBL-3 occurred at the level of the tumor cells. However, no quantitative differences were observed in the expression of serologically detectable tumor-associated antigens by these two populations. Possible mechanisms for this change in transplantability were considered.


Behavior of cervical epithelium during carcinogenesis: autoradiography of tritiated cytidine in the C57BL mouse.

The autoradiographic patterns of the cervical epithelia of 39 virgin C57BL mice after in vivo injection of [3H]cytidine was investigated. Of the 22 animals painted with benzo[a]pyrene for 5 months, 8 developed intraepithelial atypias and 2 had invasive carcinoma. The mean number of silver grains in individual cells increased from histologically normal cervical epithelium through atypical epithelium to invasive carcinoma. It is apparent that the autoradiographic patterns in normal, atypical, and invasive carcinoma cells reflected quantitative differences in cytidine incorporation. These differences may denote increased demand for RNA precursors in the cervical epithelium during carcinogenesis.


Karyotype and tumorigenicity of 1-methylguanine-transformed Chinese hamster cells.

Chinese hamster embryo cells transformed with the tRNA catabolite 1-methylguanine were characterized by Giemsa-banded karyotyping and by their tumorigenic potency in athymic nude mice. All seven 1-methylguanine-transformed cell lines were hyperdiploid with a modal chromosome number of 23. Three of these lines had an additional marker chromosome derived from the long (q) arm of chromosome no. 4, and they had alterations of chromosome no. 5 as well. Two of these three cell lines were tumorigenic. Nonrandom chromosome changes were observed in the other four 1-methylguanine-transformed cell lines, which included the addition of all or a portion of chromosome no. 6. One of these cell lines was also tumorigenic in nude mice, Specific cytogenetic changes were observed in most 1-methylguanine-transformed populations in contrast to the karyotypic heterogeneity of a benzo[a]pyrene-transformed cell line.


Selective activation of human beta-but not gamma-globin gene in human fibroblast x mouse erythroleukaemia cell hybrids.

The human alpha- and beta-globin genes have been activated in MEL X human fibroblast cell hybrids. However, even though the human gamma- and beta-globin genes are closely linked and were shown in these hybrid clones to be present in approximately equal numbers, no human gamma-globin mRNA was produced. Thus, the human beta- and gamma-globin genes in these cells are differentially regulated apparently by a positive regulatory factor(s) specific for individual globin genes.


Findings in computerized axial tomography after intrathecal methotrexate and radiation.

Medulloblastoma and acute lymphocytic leukemia patients treated by intrathecal methotrexate and radiation were investigated by means of computerized axial tomography. More than 50% of them turned out to have acquired encephalopathy. Only gross morphologic brain defects, as visualized by computerized tomography, caused manifest clinical signs of brain dysfunction, such as epilepsy, mental retardation, paresis, and apallic syndrome. Mild morphologic changes were found even in asymptomatic children. The preferred site of defects in brain substance was the paraventricular white matter.


Sex information and attitudes in young people.

A questionnaire survey was conducted in the Wellington area among 696 senior secondary school pupils. The first part of the questionnaire studied aspects of sexual knowledge and the sources of information. The general level of knowledge was good at an elementary level but less than adequate when more detailed knowledge was considered. The role of peers, parents and schools was complementary. In the second part of the questionnaire a standard attitude test was administered. A majority of young people in this survey supported a standard of permissiveness with affection and did not support a double standard giving greater rights to males. Boys were more permissive than girls.


Abortion: some observations on the contraceptive practice of women referred for psychiatric assessment in Dunedin.

Factors associated with the contraceptive practice of 31 women referred for psychiatric assessment prior to therapeutic termination of pregnancy are analysed. Poor contraceptive practice is a significant contributing factor to the increasing rate of unwanted pregnancy and abortion. More research at a psychological level into this important sociological phenomenon is needed.


A comparative anthropometric study of Cook Islands and Australian preschool children.

An anthropometric study was conducted on a sample of preschool children from Mangaia, Cook Islands, and a comparison made with similar measurements made on Caucasian children aged two and four years. At two years there were no differences in height, weight, or fatness as measured by skinfold thicknesses between the populations. By four years, the Mangaian children were shorter, lighter and fatter. It is proposed that this disparity in somatic growth is a result of subtle nutritional deficits in the Mangaian children.


Eosinophilic meningitis in Tahiti: clinical study of 54 patients.

Eosinophilic meningitis is due to infestation of the nervous system by the larvae of Angiostrongylus cantonensis. The infection is from infected prawns and slugs. In a study of 54 patients from Tahiti the leading symptoms were headaches, neck stiffness, limb pains and sometimes a facial palsy. The diagnosis is made by examination of the CSF when the leucocytes are usually over 100/mm3 and over half are eosinophilic cells. The blood eosinophil count is often raised, above 400/mm3. The disease is self-limiting and there is no known specific treatment.


Pre-anaesthetic administration of dantrolene sodium to a patient at risk from malignant hyperthermia: case report.

The pre-anaesthetic administration of dantrolene sodium to individuals at risk from malignant hyperthermia has not yet found an accepted place in human anaesthetic practice, although the effectiveness of dantrolene sodium as a prophylactic drug has been clearly shown in animal studies. In the patient described in this report, no conclusion is drawn about the effectiveness of dantrolene sodium, but attention is drawn to a brief episode of vomiting and diarrhoea some two hours after ingestion of the drug. Modification of the dosage scheme may be advisable.


Odontogenic myxoma. Surgical management and an ultrastructural study.

Odontogenic myxoma is a tumor of primitive mesenchyme, probably derived from the dental apparatus. Surgical management of this benign but locally aggressive tumor is either by curettage or en bloc resection. Two cases of odontogenic myxoma of the mandible are reported. In one case, en bloc resection. Two cases of odontogenic myxoma of the mandible are reported. In one case, en block resection with immediate reconstruction was undertaken. In the second case, the neoplasm was thoroughly curetted. The first case was studied by electron microscopy. Six ultrastructural studies of seven odontogenic myxomas have been previously reported. The ultrastructural features of odontogenic epithelium that may be present in myxomas of the jaws have been examined by electron microscopy once before. Our observations are in agreement with those of other workers who suggest that the connective tissue cell is the proliferating component of the tumor and is very similar to a fibroblast but has enough ultrastructural and functional features to deserve the term myxoblast. The majority of the tumor cells are metabolically active and secretory and there is adequate evidence that the tumor matrix consists of large amounts of mucopolysaccharides. It is reasonable, therefore, to conclude that myxoblasts secrete the mucoid matrix that is so characteristic of odontogenic myxomas. Unlike normal or neoplastic fibroblasts, the myxoblasts are not engaged in abundant synthesis of banded collagen throughout the entire lesion.


Malignant hyperthermia. Report of two cases.

A dentist using local or general anesthetics must be cognizant of the possibility of malignant hyperthermia presenting as a catastrophic emergency. The purpose of this article is to describe the syndrome of malignant hyperthermia, to emphasize its early clinical symptoms, and to outline definitive treatment. Two cases of malignant hyperthermia in pediatric dental patients illustrate the clinical and laboratory features and the appropriate therapy.


Cervical sympathetic block following intraoral local anesthesia.

The sympathetic block of the nerves supplying the head, neck, and arm (Horner's syndrome) resulted from a misdirected intraoral local anesthetic injection. The anatomy of the fascial spaces and the potential risk of infection are discussed.


Hemifacial lipodystrophy. Report of a case.

Lipodystrophy, which may be subdivided into a partial and a total form, is not a commonly reported disorder. One patient is presented in whom the lipodystrophy was not only confined to the face but even to one side. Progressive hemifacial atrophy was excluded by roentgencephalometric analysis and electromyography. It is suggested that the reported entity be considered as a separate group under the name of hemifacial lipodystrophy.


Delayed healing of mandibular fracture in idiopathic myxedema.

Lack of adequate amount of thyroid hormone may interfere with healing. A patient in whom a fracture of the mandible failed to heal in the 2 years following surgical treatment is presented. When thyroid hormone supplementation was introduced, the fracture progressed to union. The physical findings of hypothyroidism and the role of thyroid hormone in healing are discussed.


Wound healing following curettement of bifurcation abscesses of human primary molars.

Forty-five abscessed human mandibular primary molars with bifurcation radiolucency were subjected to a two-stage formocresol treatment of the pulp chamber. On the first appointment, an elliptical patch of buccal mucosa was removed. Bony defects varied from 2 mm. to more than 4 mm. in diameter. Periapical radiographs were used to record changes in bone development. Punch biopsy specimens were taken from the bifurcation area of some subjects from 2 weeks up to a year after surgical curettement. Biopsied tissue was studied by electron and light microscopy to examine wound healing of the bifurcation, revealing an early proliferation of fibroblasts with extracellular collagen fibers. Some of the fibroblasts exhibited an extensive network of rough endoplasmic reticulum, scattered free ribosomes, mitochondria, and other organelles which are normally observed in healthy fibroblasts. Histologic and clinical evaluation support the treatment tested for retention of previously abscessed primary molars.


Microscopic study of standardized gutta-percha points.

Eleven brands of gutta-percha cones were analyzed with the optical microsocpy, showing deformations in the apical thirds which would not allow the correct adaptation of them in the apical section of the root canal.


The distribution of [14C] leucine and 85Sr labeled microspheres from rat incisor root canals.

The distribution of [14C] leucine and 85Sr labeled tracer microspheres from rat incisor pulp canals was investigated in an effort to establish the potential for passage of substances from within the root canal to the systemic circulation. Following introduction of the tracer materials into the pulp canals, the radioactivity in the lungs, spleen, kidney, liver, heart, blood, skeletal muscle, adrenal glands, salivary glands, and submandibular lymph nodes was determined. At all of the time intervals studied the incorporation of [14C] leucine into the adrenal gland was significantly greater than the [14C] leucine incorporation into the other organs. High levels of 85Sr labeled microspheres were detected in the ipsilateral submandibular glands and submandibular lymph nodes and in the lungs.


The free focus concept in dental and maxillofacial radiography. The present status of the miniaturized dental x-ray machines.

"Free focus" radiography has shown promise in the examination of complex anatomy in many parts of the body, where conventional and tomographic exposures provide limited information. The approach was introduced in dentistry three decades ago and applied clinically from the time the miniaturized x-ray machines with rod anodes became available in the early 1960's. Yet it has received little attention in the international literature. Recent generations of the unique machines allow free focus surveys of the dentition in two exposures with a film quality comparable to or better than conventional periapical surveys and with a fraction of the radiation load. There is a need for evaluation of such procedures for use in dental practice. Additional applications of free focus radiography promise unusual flexibility in the use x-ray examinations in endodontics, pedodontics, periodontics, and oral surgery, which may justify further development of the miniaturized equipment for such new approaches. Specific suggestions for technical improvements are discussed.


Radiology of maxillofacial gunshot injuries.

The relative advantages and disadvantages of conventional facial radiographic techniques, facial tomography, and carotid arteriography for gunshot injury cases are discussed. The conventional series of skull, facial, or cervical spine projections forms a base line upon which the more complex procedures may be added. Five cases illustrate the radiographic principles involved in the determination of gunshot fragment localization, bone fracture, soft-tissue swelling, and maxillary sinus involvement.


[Intracerebral calcifications associated with intrathecal methotrexate therapy in acute lymphocytic leukemia (author's transl)].

A case of a child with acute lymphocytic Leukemia is reported. The roentgenograms of the skull show intracerebral "railroad-track-like" calcifications mimicking those seen in Sturge-Weber syndrome. These calcifications are described and their etiology is discussed. The frequency of such observations in cases of acute lymphocytic leukemia with CNS-treatment is increasing.


Biochemical studies of olfaction: binding specificity of radioactively labeled stimuli to an isolated olfactory preparation from rainbow trout (Salmo gairdneri).

The extent of binding of 10 radioactively labeled odorant amino acids to a sedimentable fraction (fraction P2) derived from the olfactory rosettes of the rainbow trout Salmo gairdneri corresponded closely with their reported relative stimulatory effectiveness measured electrophysiologically. L isomers were bound to a greater extent than their respective D isomers. Binding of L-alanine was strongly and irreversibly inhibited by mercurials but was not affected by sulfhydryl-blocking reagents. Binding was saturable and reversible. Scatchard analyses gave evidence of two types of binding sites for most of the amino acids studied. The Kd values of the higher-affinity binding sites were similar among the amino acids, being in the range of 10(-6) M; differences occurred in the relative numbers of sites, n. These results, coupled with those from competition experiments, lead to the postulate that a multiplicity of types of olfactory binding sites exist in the trout: site TSA, which binds L-threonine, L-serine, and L-alanine; site L, which binds L-lysine; and site AB which binds beta-alanine. Tentative assignments are: site V, which binds L-valine; site H, which binds L-histidine; and site AD, which binds D-alanine. Site AD may be a lower affinity site for L-alanine. Binding of olfactory stimulus molecules appears to be an initial discrimination step in olfaction.


Actinomycin D-deoxynucleotide interactions: binding isotherms at the benzenoid and quinoid portions of the drug.

Titrations of actinomycin D (AMD) with dG and with dG-dC were monitored by circular dichroism at 380 nm and 470 nm. These wavelengths are sensitive predominantly to nucleotide binding processes at the benzenoid and quinoid portions, respectively, of the phenoxazone ring of the drug chromophore [Auer, H.E., Pawlowski-Konopnicki, B.E., Chiao, Y.C.C. & Krugh, T.R. (1978), Biopolymers, 17, 1891-1911.]. The temperature dependence of these isotherms was analyzed by the van't Hoff equation to obtain values for the enthalpy and entropy changes. For dG these are about -11 kcal mol-1 and -20 cal mol-1 deg-1, respectively, for complex formation at both the benzenoid and quinoid sites (1 cal = 4.184 J). The enthalpy and entropy changes for complex formation with dG-dC remain unchanged at the benzenoid site, but both values are more negative at the quinoid site. These results indicate that the additional process of binding C in the intercalated AMD-(dG-dC)2 complex, with respect to the simply stacked AMD-dG2 complex, has distinctive properties at the two sites, reflecting their structural differences. The ability to resolve binding processes at the two sites by circular dichroism has permitted us to suggest assignments for the two 31P magnetic resonance lines from the phosphodiester groups observed in the AMD-(pdG-dC)2 complex.


Isolation of two interferon-induced translational inhibitors: a protein kinase and an oligo-isoadenylate synthetase.

Large-scale purification of translational inhibitors present in interferon-treated mouse L cells, but not in untreated cells, led to the isolation of two interferon-induced activities. One is a protein kinase system that is activatable by double-stranded RNA and ATP and that phosphorylates a Mr 67,000 protein and the smallest subunit of eukaryotic initiation factor-2. The purified protein kinase is a strong translational inhibitor. The second activity is an enzyme that, with double-stranded RNA, slowly polymerizes ATP into oligoadenylate with a 2'-5' phosphodiester linkage. The oligo-isoadenylate in turn activates a potent inhibitor of mRNA translation.


alpha-Lactalbumin mRNA in 4-day lactating rat mammary gland.

Rat alpha-Lactalbumin (alpha-LA) mRNA has been purified from the total RNA of 4-day lactating mammary gland by poly(U)-Sepharose chromatography and by fractionation of the poly(A)+ RNA on sucrose gradients. alpha-LA mRNA was homogeneous as judged by electrophoresis in urea/agarose gel and in 1.5% agarose gel under glyoxal-denaturation conditions, which gave a molecular weight of 210,000. The chymotryptic fingerprints of the protein synthesized with this mRNA, in a translational system derived from wheat germ, were similar to those of purified rat alpha-LA. In rat milk or lactating gland, the content of Mr 42,000 casein is 6 times greater than that of Mr 29,000 casein and 10 times greater than that of alpha-LA. However, alpha-LA mRNA (Mr 210,000) and two casein mRNas (Mr 460,000 and 390,000), coding for Mr 42,000 and 29,000 caseins, were present in equal proportions when measured with cDNA probes in the total RNA of 4- to 5-day lactating gland. Moreover, alpha-LA and total casein were synthesized in a ratio fo 1:2.5 in a wheat-germ translational system using the total RNA of the lactating gland. The results suggest post-transcription controls in the synthesis of these proteins.


Circular dichroism analysis of mononucleosome DNA conformation.

Mononucleosomes were isolated from micrococcal nuclease digests of chicken erythrocyte nuclei. The circular dichroism properties of mononucleosome preparations, differing in average DNA length and in H1 and H5 content, demonstrate that the spectrum of chromatin is due only to the complete structure of its repeating subunits. The nucleoprotein spectra are all altered relative to protein-free DNA by the emergence of a single negative band at 275 nm, similar to the band observed for psi DNA. The intensity of the psi-type band depends on the proportion of DNA condensed in a specific manner. The psi-type band is proposed to be due to the compact DNA tertiary structure; i.e., the manner in which the DNA is wound around the histone core allowing interactions between adjacent turns of the superhelix. This interpretation attributes changes and variability in nucleoprotein circular dichroism spectra under different experimental conditions to alterations in DNA tertiary structure rather than secondary structure.


Acid catalysis of the formation of the slow-folding species of RNase A: evidence that the reaction is proline isomerization.

Unfolded RNase A is known to contain an equilibrium mixture of two forms, a slow-folding form (U(1)) and a fast-folding form (U(2)). If U(1) is produced after unfolding by the slow cis-trans isomerization of proline residues about X-Pro imide bonds, then the formation of U(1) should be catalyzed by strong acids. Therefore, the rate of formation of U(1) has been measured at different HClO(4) concentrations. After rapid unfolding of the native protein in concentrated HClO(4) at 0 degrees , the slow formation of U(1) was measured by use of refolding assays. Catalysis of its formation was found at HClO(4) concentrations above 5 M. The uncatalyzed reaction follows apparent first-order kinetics but, in the acid-catalyzed range, two reactions are found. The faster reaction produces two-thirds of the slow-folding species and shows acid catalysis above 5 M HClO(4). Catalysis of the slower reaction begins at 8 M HClO(4). The faster reaction shows a 100-fold increase in rate at 10.6 M HClO(4) over the rate of the uncatalyzed reaction of 5 M. The activation enthalpy of the uncatalyzed reaction has been measured in two sets of unfolding conditions: DeltaH(double dagger) is 21.5 kcal/mol (1 kcal = 4.2 x 10(3) J) in 3.3 M HClO(4) and 21.0 kcal/mol in 5 M guanidine HCl, pH 2.5.Both acid catalysis of the formation of U(1) and its high activation enthalpy are consistent with the rate-limiting step being cis-trans isomerization either of X-Pro imide bonds or of peptide bond. The rate of the uncatalyzed reaction is in the range expected for proline isomerization and is 0.1% of that of peptide bond isomerization; thus, the simplest explanation for the formation of U(1) is proline isomerization. Earlier data, showing that the kinetic properties of the U(1) right arrow over left arrow U(2) reaction in refolding conditions differ from those of proline isomerization, can be explained if there is kinetic coupling between early steps in the folding of U(1) and its conversion to U(2).The existence of two acid-catalyzed reactions that are distinguished by the HClO(4) concentration at which catalysis begins suggests that at least two essential proline residues produce slow-folding species of RNase A by isomerization after unfolding. Because protonation of imide bonds is responsible for acid catalysis of proline isomerization, the slower reaction probably involves an imide bond with a low pK. It may be the bond connecting Lys-41 and Pro-42, because the positive charge on Lys-41 could make this bond more difficult to protonate.


Symmetry mismatch and DNA packaging in large bacteriophages.

A model is presented for the mechanism of packaging double-stranded DNA into phage heads. The model is based on, and rationalizes, the mismatch in symmetry between the heads and tails of large bacteriophages. DNA movement is postulated to be mediated by a rotating protein structure at the tail-proximal vertex of the head.


Phosphate (oxygen)-water exchange reaction catalyzed by human prostatic acid phosphatase.

Conclusive evidence is presented that an acid phosphatase catalyzes phosphate (oxygen)-water exchange. Studies conducted with human prostatic acid phosphatase by two independent methods have established that, despite earlier reports to the contrary, the enzyme catalyzes an exchange reaction between oxygen atoms of phosphate ion and of water. Kinetic data were obtained both by chemical conversion to trimethyl phosphate followed by mass spectroscopy and by a totally independent method involving 31P isotope shift nuclear magnetic resonance spectroscopy. Analysis showed that the enzyme catalyzes the exchange in a random, noncoupled process. If any coupled exchange occurs, it must represent less than 10% of the total. By mass spectral analysis, catalytic rate constants kcat = 0.14 sec-1 (4 degrees) and 1.8 sec-1 (37.5 degrees) were obtained. By 31P nuclear magnetic resonance kcat = 1.6 sec-1 (31 degrees) was obtained. The energy of activation for the exchange reaction is approximately 13kcal mol-1. The kcat value for exchange is about 10-fold greater than that observed with Escherichia coli alkaline phosphatase.


An alternative membrane transport pathway for phosphate and adenine nucleotides in mitochondria and its possible function.

This paper describes the properties and a possible biological role of a transport process across the inner membrane of rat liver mitochondria resulting in the exchange of ATP(4-) (out) for ADP(3-) (in) + 0.5 phosphate(2-) (in). This transmembrane exchange reaction, designated as the ATP-ADP-phosphate exchange, is specific for the ligands shown, electroneutral, insensitive to N-ethylmaleimide or mersalyl, inhibited by atractyloside, and appears to occur only in the direction as written. It is thus distinct from the well-known phosphate-hydroxide and phosphate-dicarboxylate exchange systems, which are inhibited by mersalyl, and from the ATP-ADP exchanger, which does not transport phosphate. During ATP hydrolysis by mitochondria, half of the phosphate formed from ATP passes from the matrix to the medium by the mersalyl-insensitive ATP-ADP-phosphate exchange and the other half by the well-known mersalyl-sensitive phosphate-hydroxide exchange. These and other considerations have led to a hypothesis for the pathway and stoichiometry of ATP-dependent reverse electron transport, characterized by a requirement of 1.33 molecules of ATP per pair of electrons reversed and by the utilization of a different membrane transport pathway for phosphate and adenine nucleotides than is taken in forward electron flow and oxidative phosphorylation. The possible occurrence of independent pathways for ATP-forming forward electron flow and ATP-consuming reverse electron flow is consonant with the fact that the opposing degradative and synthetic pathways in the central routes of cell metabolism generally have different pathways that are independently regulated.


Glucose-induced conformational change in yeast hexokinase.

The A isozyme of yeast hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) crystallized as a complex with glucose has a conformation that is dramatically different from the conformation of the B isozyme crystallized in the absence of glucose. Comparison of the high-resolution structures shows that one lobe of the molecule is rotated by 12 degrees relative to the other lobe, resulting in movements of as much as 8 A in the polypeptide backbone and closing the cleft between the lobes into which glucose is bound. The conformational change is produced by the binding of glucose (R.C. McDonald, T.A. Steitz, and D.M. Engelman, unpublished data) and is essential for catalysis [Anderson, C.M., Stenkamp, R.E., McDonald, R.C. & Steitz, T.A. (1978) J. Mol. Biol. 123, 207-219] and thus provides an example of induced fit. The surface area of the hexokinase A-glucose complex exposed to solvent is smaller than that of native hexokinase B. By using the change in exposed surface area to estimate the hydrophobic contribution to the free energy changes upon glucose binding, we find that the hydrophobic effect alone favors the active conformation of hexokinase in the presence and absence of sugar. The observed stability of the inactive conformation of the enzyme in the absence of substrates may result from a deficiency of complementary interactions within the cavity that forms when the two lobes close together.


Ovalbumin gene: evidence for a leader sequence in mRNA and DNA sequences at the exon-intron boundaries.

Selected regions of cloned EcoRI fragments of the chicken ovalbumin gene have been sequenced. The positions where the sequences coding for ovalbumin mRNA (ov-mRNA) are interrupted in the genome have been determined, and a previously unreported interruption in the DNA sequences coding for the 5' nontranslated region of the messenger has been discovered. Because directly repeated sequences are found at exon-intron boundaries, the nucleotide sequence alone cannot define unique excision-ligation points for the processing of a possible ov-mRNA precursor. However, the sequences in these boundary regions share common features; this leads to the proposal that there are, in fact, unique excision-ligation points common to all boundaries.


Protein synthesis in rabbit reticulocytes: characteristics of a ribosomal factor that reverses inhibition of protein synthesis in heme-deficient lysates.

A ribosomal salt (0.5 M KCl) wash factor (RF) that reverses inhibition of protein synthesis in heme-deficient reticulocyte lysates has been resolved from the bulk of Met-tRNAfMet-binding factor (EIF-1), Co-EIF-1, and EIF-2 (ternary complex dissociation factor, TDF). The purified RF restores protein synthesis activity of heme-deficient lysates to the level observed in the presence of hemin. No direct correlation exists between amount of EIF-1 activity and ability to reverse inhibition of protein synthesis in heme-deficient lysates. Homogeneous preparations of EIF-1 are completely inactive in reversal of protein synthesis inhibition in heme-deficient lysates. These findings suggest that RF activity is not due to EIF-1 alone but may or may not require EIF-1 as a component of a complex factor.


Visualization of an inverted terminal repetition in vaccinia virus DNA.

An inverted terminal repetition was observed in DNA molecules extracted from vaccinia virus. The repeated sequence was visualized by (i) nicking the hairpin loops present of the ends of vaccinia virus DNA, (ii) separating the strands of DNA by alkali denaturation, (iii) allowing the single strands to self-anneal, and (iv) examining the DNA with an electron microscope. Single-stranded circular molecules, each of which contained a duplex projection (3.54 +/- 0.12 micron) representing the terminal repetition, readily formed. Similar size projections were also seen in heteroduplex structures formed by crosshybridization of the separated strands of the two terminal HindIII restriction fragments. Based on contour length measurements and the electrophoretic mobility of the isolated inverted terminal repetition, a molecular weight of approximately 6.9 X 10(6), equivalent to about 10,500 nucleotide base pairs, was estimated. Evidence was obtained from DNA-RNA hybridization studies that the terminal repetition is transcribed.