Collagenolysis by human gingival fibroblast cell lines.

Human gingival fibroblast cell lines were initiated in flask cultures from four periodontal patients with the diagnoses of periodontitis (two patients), fibromatosis, and Dilantin hyperplasia. The collagenolytic propensity of these fibroblasts cultivated on collagen-coated cover slips and the inhibitory effect of serum were evaluated by direct microscopic observations.


Diurnal variation in epithelial cell population kinetics of young mouse tongue.

The purpose of this study was to determine if there was a  diurnal variation in the DNA synthesis pattern of epithelial basal cells in the dorsum of the mouse tongue between infancy and preadult ages. The pattern of DNA synthesis in the basal cells of mouse tongue in 24-hour periods for different age groups was studied by isotope labeling and radioautography. A strong diurnal variation was found in the pattern of DNA synthesis with the degree of variation dependent on the age of the experimental groups.


The turnover of collagen in the dental pulp of rat incisors.

The turnover of collagen in the dental pulp was studied using H3-proline and microchemical techniques. The incorporation of label into the whole tissue was very high, with most of the label being incorporated into the noncollagenous substances. The rate of disappearance of label from collagen approximated the disappearance of label from noncollagenous components, suggesting that the whole pulp was undergoing rapid remodeling. There seems to be more than one metabolic pool of collagen.


A training model for alternative teaching methods for a school of dentistry.

In the summer of 1974 the University of Louisville contracted with an educational consulting team to develop a training program to build alternative teaching methods for the school's educational program. A four-stage model consonant with the goals and objectives of the administration, the faculty, and the consultants was established. The uniqueness of the model was its personalization to individual faculty members' needs and educational interests. While other intervention processes which address the cognitive aspects of education have been developed, this model focused upon the real day-to-day problems faced by faculty. The model addressed itself to people rather than to theory and dealt with interpersonal behavior, communication skills, and classroom dynamics in education. This paper described the four phases of the training model developed for the University of Louisville and discusses the results of using the model.


An evaluation system for preclinical and clinical endodontics.

One of the most difficult tasks, facing the dental educator is the evaluation of students' preclinical and clinical performance. This article describes the development of an evaluation system that eliminates some of the problems associated with the assessment of psychomotor skills including rater subjectivity and the validity of evaluation instruments. The evaluation system discussed is currently being used by the Department of Endodontics at the Louisiana State University School of Dentistry for both preclinical and clinical endodontics. The article focuses on the development of the system, use of the clinical rating scale, and an assessment of the system's effectiveness.


Dental practice management game: a new tool for teaching practice management.

This paper describes the structure of a dental practice management game. The game covers a wide spectrum of management decisions in setting up and in running a dental practice. The decisions considered include practice location, the form of practice, staffing mix, salaries, and the purchasing or leasing of equipment. The game also covers major daily, monthly, and yearly decisions including forecasting patient load, economic analysis, and scheduling of patients, workers, and operatories. The paper also discusses the cost and time required to run the game. Many sample printouts are included.


Dental student attrition.

In summary, the attrition rate for the recent dental school freshman classes has been reduced to 3 1/2 %. The national freshman enrollment of US dental schools can be expected to have approximately a 7% attrition rate by the time of graduation. The reasons for student withdrawal are evenly divided between personal and academic problems. The academic problems are experienced with slightly more frequency in nonclinical courses than in technique courses, both areas of difficulty being predicted significantly by DAT scores. Finally, the attrition rate for women is higher than for men, which has been true to a significant degree in the first-year classes during the past two years, as well as for all four years of dental school. However, no specific reason has been identified for this difference.


Factors influencing the choice of practice location for recent dental graduates.

A survey of factors that influenced the selection of practice location was carried out among 1971 dental school graduates. The decision process involved in this selection is a complex phenomenon that involves many personal and community value judgments. The two most important stated reasons appear to be geographic preference and recreational and cultural advantages. As in previous surveys of this type, the place of rearing seems to exert a strong influence, although less than 25% of the respondents indicated this in their three choices of most influential factors. In point of fact, however, 47% of the respondents did locate their practice near their place of rearing. This is further reinforced by the place of rearing of their spouses, if they were married. The respondent's father's occupation had some influence, but this was less significant than the other factors. Choice of specialty in all areas except dental public health, oral pathology, and orthodontics strongly influenced the respondent toward an urban practice. More rural dentists, as one would expect, were self-employed and without a partner.


A survey of 4,793 oral lesions with emphasis on neoplasia and premalignancy.

A survey was taken of a selected group of 4,793 oral lesions submitted to the oral pathology biopsy service between 1950 and 1970. About two thirds of all the specimens examined microscopically were classified as inflammatory, infectious, or reactive hyperplasia. Of the 12.6% of the sample classified as neoplasms, one of every five was malignant. Three of every four of the malignant neoplasms were microscopically diagnosed as squamous cell carcinomas. Benign neoplasms were most common in ages 40 to 60, whereas premalignancies and malignancies were most commonly discovered in the slightly older age group of 50 to 70. Although malignant neoplasms were found more often in men than women, there was a striking increase in the incidence of malignancies in women in the second ten-year period of the study. There were unexplainably few malignant neoplasms found in blacks. Patients should be taught to recognize the early signs of oral premalignancy and malignancy through the use of a simple method of self-examination at home. They should be discouraged from the frequent use of tobacco and alcohol, which have long been known to be predisposing factors in the production of oral squamous cell carcinomas.


Cold sterilization of gutta-percha cones with formocresol vapors.

Cold sterilization of gutta-percha cones was accomplished by exposing them to formocresol vapors for 16 hours. The data obtained from this in vitro study indicate that gaseous sterilization with formocresol vapors is effective against a variety of gram-positive, gram-negative, and spore-forming microorganisms.


Surface properties of dental amalgam: roughness produced by setting reaction.

During the setting of dental amalgam, silver-mercury (gamma1) and tin mercury (gamma2) intermetallic compounds (phases) are formed. Since these compounds have distinct crystalline forms, they may be discerned on the surface of a setting sample. Visual identification of these phases on polished and etched samples is often difficult and, hence, surface morphology studies have an advantage in following the stages of the setting reaction. The purpose of this investigation was to use high-resolution light microscopy to follow the course of the setting reaction. Amalgam specimens were triturated and condensed against glass plates under pressure. The sample surfaces were then photographed under a high-resolution metallographic microscope using oblique illumination. The roughness of four samples for each alloy type was determined with a surface profile analyzer at times between ten minutes and 23 hours after trituration. An electron microprobe was used to identify the gamma1 and gamma2 phases. The gamma1 phase had a polyhedramorphology, and the gamma2 crystals formed intermeshed smooth areas. During the setting reaction, the average times for the roughness to reach 95% of the final value were 189, 227, 96, 65, and 116 minutes after trituration for the various amalgam types studied. All alloys tested required polishing several hours after trituration.


Wetting of amalgam alloys by mercury.

The degree of wetting of amalgam alloy by mercury during trituration is an important variable in determining reaction rates and the degree of amalgamation. The purpose of this study was to measure the contact angle made by mercury on various phases present in amalgam alloy in air and on commercial alloys. During amalgamation, mercury is in contact with the oxides present on the amalgam alloy as well as the metallic amalgam phase. To measure the degree of wetting of the metallic phases, silver, tin, and copper were melted in such proportions as to give specimens of silver, tin, the alpha, beta, and gamma silver-tin phases, the eutectic in the silver-copper system. These were cast in the form of cylinders, sectioned, and the surfaces prepared by sandblasting. Oxide specimens of AgO, Ag2O, SnO, and SnO2 were prepared by compaction in a mold. Four commercial amalgam alloys also were tested. Mercury drops were then placed on the surfaces and the contact angles measured at different time intervals. The initial contact angles of mercury on the alpha, beta, gamma, and eutectic phases were found to be 90degrees, 112 degrees, 145 degrees, and 138 degrees, respectively. Mercury reacted with silver and tin, resulting in a change of contact angle with time. Contact angles measured on the commerical alloys were also high, on the order of 145 degrees. The gamma phase had contact angles closest to those of commercial alloys. Surface oxide phases are most likely responsible for this poor wettablility by mercury.


The efficacy of the laryngeal reflex in conscious sedation.

The Jorgensen technique and nitrous oxide-oxygen sedation were evaluated for the risk of aspiration. Volunteers and patients were studied in the supine, semisupine, and Trendelenburg positions. Aspiration occurred in a single patient under the Jorgensen technique and could be related to the presence of a narcotic in the mixture. The incidence of tracheal soiling was lower than that with other intravenous techniques and could be attributed to the use of the semisupine position or the baseline concept of narcotic dosage in the Jorgensen technique. In the nitrous oxide-oxygen sedation technique, aspiration was not noted. The study suggests that use of a narcotic in an intravenous sedative technique increases the hazard of aspiration.


Gastroscopic removal of a partial denture.

This report of an ingested dental prosthesis is submitted to emphasize the need for incorporation of radiopaque material in dental appliances and also to report the safety and efficacy of fiberoptic endoscopy in the nonsurgical treatment of accidental ingestions.


Clinical examination of the head and neck.

In the head and neck examination portion of the ADA health screening program approximately 6% of the examinees were found to have at least one abnormality. Three patients had lesions that were highly suspected of being malignant. Most of the examinees were unaware of their condition, but a small percentage were aware and had chosen to have no diagnostic or curative procedures initiated. Three patients had manifestations of systemic disease of which they were unaware. A method of doing a head and neck examination was demonstrated to the dentists, and the finding of 6% of the dentists with some abnormality indicates the significance of the head and neck examination.


A new intra-oral screw jack.

A new pattern of screwjack for assessing the vertical dimension for occlusion utilizing an edentulous patient's proprioceptive sensation is described. It provides a greater range of movement than other, giving infinitely variable heights between 9 and 21 mm. The elements being captive, it cannot come to pieces in use. Laboratory experiments were contrived to define the magnitude of reading errors and the play in the screw threads. It was found that, only in instances where a graduation related closely to the datum mark, did errors of interpretation arise. These were found to exceed the height set for test purposes by 0-1 mm consistently. An error of this order is of no practical significance clinically and is no impediment to such an application of the device. Mean play in the new pattern jacks was 0-01 mm compared to 0-05 mm in the Timmer versions. In a clinical experiment the performance of the screw was compared to that of Timmer. Statistical evidence was found which suggested a functional difference between the two, the new pattern being significantly more accurate.


A comparative study of three different approaches to the comfortable zone.

By means of a screw jack device, applied to thirteen edentulous subjects, the comfortable zone was approached in three different ways, by the central, the internal and the external approaches. Correspondingly, the zonal borders behaved differently. Applying the central approach it was found that the initial height of the screw jack had a lingering effect upon subsequent adjustments of the screw. Moreover, lower border data collected by the external approach distinguished themselves from other zonal border data by showing a significantly lower susceptibility to successive adjustments. The study suggests that muscle activity is a factor on which the perceptual mechanism relies, when a zonal border is assessed subjectively by a patient.


Aspects of functional improvement after treatment of a pain dysfunction patient.

First results of an investigation of several aspects of the function of the chewing apparatus by means of optical-electric movement scanning, EMG and occlusal sound registration on one time base, are presented. Observations made on a patient with pain-dysfunction syndrome before and after treatment has been compared with observations made on a healthy subject. It has been suggested that the method used, may be of value for objective evaluation of functional improvement and analyses of several aspects of the physiology of the chewing apparatus.


Colorimetric determination of the masticatory performance.

A description is given of a colorimetric method to measure the masticatory function. It is based on the release of dye when chewing raw carrots. Information is given about the reproducibility of the method. The procedure takes 30 min for eight tests on one subject and can be carried out with standard laboratory equipment.


Dimension discrimination at two different degrees of mouth opening and the effect of anaesthesia applied to the periodontal ligaments.

The dimension discrimination ability of twenty-five young persons was tested at two different degrees of mouth opening. One reference stick of 10-0 mm and another of 45-0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments. Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10-0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45-0 mm stick incorrect assessments were distributed evenly between dimensions higher or lower than the reference stick.


Tooth tapping ability of young and elderly males and females.

The ability to perform high frequency tooth tapping movements was studied in young dentulous, elderly dentulous and elderly edentulous subjects of both sexes as a possible test of the overall efficiency of the masticatory motor apparatus and related structures. Tapping frequency was measured during a test period of 90s by counting the number of taps per 5 s intervals. It was found that observed values of tapping frequency could be fitted to an exponential equation with a high degree of fit for 90% of the young subjects and for 60% of the elderly subjects. The values of the remaining elderly subjects were best fitted to straight lines. The elderly subjects could thus be regarded as belonging to two different populations which were differently affected by advanced age and loss of teeth regarding their tooth tapping ability. Young dentulous subjects had the highest starting frequency (6-1 Hz) followed by elderly dentulous (5-5 Hz) and elderly edentulous subjects (4-9 Hz). The lower limits were 4-6 Hz for young dentulous subjects, 4-1 Hz for elderly dentulous and 3-7 Hz for elderly edentulous subjects. The average group means pointed all in the same direction that increased age and loss of teeth change the functional ability by deteriorating it.


The performance of ultraviolet lights used to polymerize fissure sealants.

The performances of ultraviolet (uv) lights used to initiate polymerization in fissure sealant systems were studied with a view to establishing recommendations for improving clinical results. The relationship between the setting time of an uv polymerized sealant (Nuva-seal) and the intensity of radiation applied was first established. This was compared with the intensity and distribution of radiation from seven Nuva-lites and one Quartzlite. It was found that some of the Nuva-lites did not produce an average intensity of uv radiation sufficient to completely polymerize Nuva-seal within the manufacturer's recommended exposure times. It is suggested that this may be a factor contributing to the large variation in sealant retention found in the different clinical trials with Nuva-seal. Finally, a number of recommendations are made to ensure that sufficient uv radiation is applied to all sealant surfaces when the Nuva-seal system is used.


Musculo-articular disorders of the stomatognathic system in school children examined according to clinical criteria.

The present investigations were undertaken for establishing the frequency of musculo-articular disorders of the stomatognathic system in healthy children as well as determining their features and degree. The study covered 500 children from Warsaw's primary schools--250 children aged 6-8 years and 250 aged 13-15 years. An incidence of disorder of 56-4 and 67-6% was found in the groups of younger and older children, respectively; their number and severity being significantly higher among the latter. The chi-square test showed no relation between the disorders of the temporomandibular joint and malocclusion or the premature loss of teeth in the group of younger children; in the older group the correlation was significant but of very low degree. The suggestion is made that the correlation between musculo-articular disorders, malocclusions and loss of teeth, is probably determined by the length of time during which the dysfunction is exerting its effect.


Small segmental and unitooth ostectomies to correct dentoalveolar deformities.

The experiences gained in the use of small-segment and unitooth ostectomies completed in a two-stage technique are presented. In the adult patient, this procedure has become reliable to improve both form and function and to give a stable, predictable result.


The early results of treatment of the obese by a diet regimen enforced by maxillomandibular fixation.

The early results of a technique of dieting enforced by maxillomandibular fixation for the treatment of the obese patient are reported. The results showed that some grossly obese patients can lose a considerable amount of weight with the technique. The maxillomandibular fixation was applied by metal cap splints and, clinically, they had no detrimental effect on the dental tissues.


Microspectrophotometric determination of DNA in oral lesions.

The DNA content of the epithelial basal cells of oral lesions was determined by Feulgen microspectrophotometry. The DNA histograms of the radicular cysts showed a definite peak in the diploid range and a slight deviation to the right. The keratocysts also showed a well-defined modal peak in the diploid range; however, another cell population defined a peak in the tetraploid range. In leukoplakias of the oral cavity, two different profiles of DNA distribution were found. Where both the clinical and microscopic traits defined a nondysplastic lesion, the histogram showed a diploid peak and a percentage of cells in diploid-tetraploid range. For the more active lesion, a shift of the mode towards higher values was evident. The microspectrophotometric studies of oral epidermoid carcinomas showed a broad distribution towards the right and ill-defined modal values.


Late effects of condylar irradiation in a child: review of the literature and report of case.

An unusual case in which hypertrophy of the mandibular condyle and hypoplasia of the maxilla and zygoma were observed in an 8-year-old child who had been irradiated at age 2 for malignant disease has been presented. Pertinent literature on the effect of irradiation of epiphyseal centers of growing bone has been reviewed. Consideration has been given to the possible mechanisms operative in producing the aberrations observed in this case, but the precise etiology remains obscure.


Possible relationship of primary hyperparathyroidism and fibrous dysplasia: report of case.

This report has considered the possibility that the described patient had a maxillary and possibly a mandibular fibrous dysplasia concomitant with a parathyroid abnormality. It has attempted to arouse the diagnostician's suspicion of possible interrelations of fibrous dysplasia and endocrine abnormalities, and to strengthen the hypothesis of others that association of fibrous dysplasia and hyperparathyroidism is not coincidental. Clinical, radiographic, and laboratory examinations more than a year postoperatively further substantiate our hypothesis that the patient had a facial fibrous dysplasia concomitant with primary hyperparathyroidism. The maxilla and mandible continued to enlarge clinically. Systemic manifestations of hyperparathyroidism had resolved. Calcium phosphorus, and parathyroid hormone levels returned to normal limits. Radiographically, there had been remodeling and recalcification of all involved bones except the maxilla and mandible which continued to expand. A possible explanation is that the maxillofacial lesions represent the polyostotic fibrous dysplasia component of the Albright syndrome. The endocrine abnormality could be manifested by the hyperparathyroidism. The third component of Albright syndrome, café au lait lesions, has not been identified. The potential interrelation of fibrous dysplasia with endocrine abnormalities is obviously important from a diagnostic and therapeutic standpoint. If there is more than a coincidental relationship-hereditary, hormonal, neurological, developmental, or any as-yet-unknown factor-only further research and studies will confirm or disprove it.


Plasmacytoma of the maxilla: report of case.

A case report of plasma cell tumor of the maxilla has been reported. In addition, the characteristics of both the solitary lesion and multiple myeloma are presented to compare and contrast the two lesions. We realize that the follow-up period to date has not been sufficient to justify the final diagnosis of solitary plasma cell tumor, even though laboratory data thus far have not indicated dissemination. The patient's condition may or may not progress into the disseminated stage, but this will be determined by time.


Neurofibrosarcoma of the mandible.

A case has been reported to illustrate the apparent transition of a neurofibroma into a neurofibrosarcoma. Biopsy of the inferior alveolar nerve, proximal to the lesion, was used to determine the extent of tumor extension. En block excision of the tumor was performed. The patient has been without evidence of recurrence for approximatley 3 1/2 years. Bone graft reconstruction has been completed and full function has been restored to the mandible.


Primary intraoral sarcoidosis.

A case of sarcoidosis manifesting primarily in the oral cavity has been documented and clinicopathological findings are discussed. The diagnosis of sarcoidosis can nearly always be established by an assessment of the clinical picture in combination with the histologic features of an adequate biopsy specimen. The Kveim test is a useful tool in clinical diagnosis, but is not always positive in patients with sarcoidosis. The clinician should also be aware that false positives can occur. Scalene node biopsy can also be a useful diagnostic adjunct. The current case emphasizes that biopsy of an intraoral lesion, scalene node biopsy, and Kveim testing are useful in establishing a diagnosis of sarcoidosis.


A simple metal bone implant for postsurgical radiographic evaluation.

A simplified method of implanting metal markers in bone enables the surgeon to make more accurate postsurgical radiographic assessments of changes in facial bones.


Periodontal osseous defects associated with vitally submerged roots.

1. Vital roots associated with periodontal osseous defects can be clinically submerged beneath a soft tissue flap. 2. Connective tissue fibers filled the submerged osseous defects and were oriented parallel to the root surfaces in the majority of cases. 3. New cementum lined the root surface at the base of two successfully submerged defects, but was not apparent on the dentin amputation sites of any submerged roots. 4. Eight of the nine clinically submerged defects exhibited positive radiographic changes. The six control defects showed no positive radiographic changes. 5. All successfully submerged defects showed histologic evidence of new bone formation. New bone formation was not apparent in any of the control defects or nonsubmerged defects. 6. Either no epithelium or only a narrow band of epithelium was associated with the successfully submerged roots. A connective tissue inflammatory infiltrate was not present within the submerged defects. 7. The defects of all control teeth and nonsubmerged experimental roots contained epithelial downgrowth accompanied by a chronic inflammatory response in the connective tissue. 8. Pulpal tissues associated with submerged roots appeared vital without significant degenerative or inflammatory changes. Pulpal tissue was continuous with overlying connective tissue.


Human clinical and histologic repair responses following the use of citric acid in periodontal therapy.

Seven blocks containing one tooth each were obtained from two patients undergoing treatment for periodontitis. Sixteen weeks prior to block removal, these sites were treated by periodontal flap surgery. In six teeth a citric acid solution (pH = 1) was applied for 2 minutes to the planed root surfaces. The seventh tooth received identical periodontal therapy except that saline was applied to the planed root for 2 minutes. At the end of the experimental period, the blocks were removed and prepared for histologic study. In five out of six citric acid treated specimens, no evidence was observed suggesting that citric acid applications either initiated or accelerated cementogenesis or functional connective tissue attachment at root surfaces previously exposed to periodontal pockets. In one specimen, repair cementum was seen crestally to the alveolar margin. This cementum was deposited on the surface of acellular cementum. Unfortunately, however, the specimen does not allow us to date the deposition of the repair cementum. It thus remains questionable whether this cemental deposition is indeed a repair response to the specific treatment performed.


Effect of soluble extracts from periodontal dressings on human granulocytic leukocytes in vitro.

Purified populations of human polymorphonuclear granulocytic leukocytes were exposed in vitro to solubilized material(s) extracted from two commerical periodontal dressings. The composiitonof one dressing contained eugenol while that of the other lacked it. Extracts were prepared by placing each mixed dressing in isotonic saline for 18 to 24 hours. Granulocytic leukocytes received serial dilutions of each extract and were then evaluated at 15 minutes and at 3 hours of culture for changes in viability and elaboration of cyto-plasmic and lysosomal enzymes. High concentrations of extract from each dressing were toxic to the cultured granulocytes. Measurements for cell viability and release of cytoplasmic enzyme revealed that the toxic potential in the eugenol-free dressing was greater. With cell damage, extracellular release of the lysosomal enzymes was found to occur. Serially increased dilutions of either extract to nontoxic concentrations failed to selectively release lysosomal enzymes.


Migratory stomatitis: a case report.

This case report discusses a 42-year-old male patient who presented with migratory stomatitis located on the labial  and buccal mucosa and the lateral tongue border. The lesions were circumscribed, flat, smooth, and red in color with a slightly raised white border varying in size from 3 mm to over 1 cm. Duration was between 7 and 14 days and healing transpired without scarring. Follow-up continued for approximately 1 year and at each visit several lesions were seen. The possibility of stress and heredity as positive factors was considered, but with so few reported cases conclusions would be purely speculative. The absence of dermatologic pathology does not aid in establishing a relationship with psoriasis, however there is a microscopic similarity. An almost total lack of clinical symptoms may contribute to this sparse documentation, therefore dental practitioners should be articularly observant when examining oral soft tissues. Further recognition and investigation is necessary before a cause can be discovered.


Protracted gingival pain associated with free nerve endings-report of a case.

This report describes a localized painful gingiva in the region of the incisive papilla of 5 years duration in a 68-year-old Caucasian woman. Clinical examination revealed no recognizable lesion. The histological observations showed a relatively large number of free nerve endings within the epithelium and the lamina propria. Excision of the painful area relieved the symptoms.


[Pseudo-sarcomatous osteomyilitis in the child (author's transl)].

The authors report three unusual cases of paediatric osteomyelitis resembling a lytic or mixed osteosarcoma. The severity of the radiological lesions is such that only a diagnostic approach is possible before surgical biopsy. Under the effects of treatment, osteolysis resolved in two cases by bone eburnation in two cases and pandiaphyseal sequestration in one case. These three cases were collected in less than a year. Thus osteomyelitis is currently adding new diagnostic traps in bone pathology in children.


Differences in social perceptions between male and female first-year dental students.

Male and female first-year dental students generally possess the same attitudes and the same perceptions about themselves, dentists they observe, and about their ideals for dentists and patients. The null-hypothesis, that is, assuming no difference between the two groups on the basis of these data, is accepted. In general, one must assume that those women who choose dentistry as a career are not significantly different from their men counterparts, although indirect evidence shows a possible exception of a more compassionate identification with the patient by female students. The findings suggest that it would not be appropriate or accurate to either admit or exclude male or female students based on what may well be "sexist" assumptions regarding women's perceptions of themselves as dentists or their perception of their relationships to patients. The findings should be generalized very cautiously beyond the UCLA School of Dentistry. However, at the time this study was conducted, this dental school had both the largest number of female students and the highest percentage of female students in the United States. The study is limited to perceptual differences of freshmen and does not attempt to deal with issues such as productivity or longevity of professional involvement. These issues may have some bearing on the formation of attitudes toward women entering the profession, but additional longitudinal studies following the careers of the current cohort of female dental students will be necessary to allay criticisms of women in dentistry.


A survey of dental care programs offered by "qualified" HMOS.

None of the federally qualified HMOs had a fully prepaid comprehensive dental care program. Less than a third of the plans went beyond the then mandated benefits of the Act, and those that did, only provided the benefits on a fee-for-service basis. The more established plans, with enrollments exceeding 15,000 members, offered a full spectrum of services, and have acceptable levels of utilization. There appears to be a relation between size and services offered and overall utilization of the dental services. The general direction HMOs are taking with regard to the scope of services provided is hard to predict because more than two thirds of the HMOs studied were "transitional" HMOs. The more mature plans appeared to be leaning toward fully comprehensive services; however, only the "basic" dental services then mandated by the Act were covered by prepayment. It is difficult to predict how the nearly 200 HMOs now being planned and developed will integrate dental care into their programs, especially when dental care services are no longer required as a "basic health service". Based upon the cautious approaches used by the HMOs now in operation, it appears safe to assume that comprehensive dental care programs will not be offered by HMOs until they are forced to do so by competing health insurance carriers or a dental program provides them with a competitive edge.


Chromosome studies of the transplantable Shay chloroleukemia in rats.

Chromosomes obtained from tumors in male Long-Evans rats with transplantable Shay chloroleukemia were counted and analyzed with Giemsa staining and quinacrine fluorescence. Several consistent abnormalities were noted in the 43 cells in metaphase. An interstitial deletion of the distal portion of chromosome No 2 was noted in all cells. Trisomy for No 2 was found in 27 of 43 metaphases; the third No 2 had a terminal deletion, resulting in a chromosome shorter than the other deleted No 2. All cells were missing a No 11 chromosome. Most cells contained a large acrocentric chromosome that appeared to be a No 10 with a terminal addition (10q+). Several markers were also consistently noted. These chromosome abnormalities were compared to previous cytogenic analyses on the transplantable Shay chloroleukemia, in which new fluorescent banding techniques were not utilized. Since all the studies ultimately derived from the original Shay chloroleukemia, karyotypic differences and changes could be viewed over an extended period of time. This study corroborated previous reports on the specificity of involvement of chromosome No 2 in chemically induced tumors and supported the idea that chromosome No 2 may be important in oncogenesis in the rat and in the host response to different etiologic agents.


Lead-contaminated health food. Association with lead poisoning and leukemia.

A doctor prescribed a dietary supplement prepared from powdered animal bone for a young woman with dysmenorrhea. Severe lead poisoning developed while she was taking the powder, which was shown to be contaminated with lead. The diagnosis eluded more than 20 physicians and was finally made by the patient herself. The Food and Drug Administration, informed of the contamination, declined to take action, stating that a food supplement is neither a food nor a drug and, besides, there are no maximal limits for heavy-metal contamination of foods and drugs.


[Induction and maintenance treatment of acute myelogenous leukemia in adults by sequential use of combination chemotherapy (author's transl)].

The therapeutic regimens for acute myelogenous leukemia in 2 different periods of time will be described with comparison of their results. A. 28 adults were treated with cytosine arabinoside and 6-thioguanine only. Thereby, 28% complete and 16% partial remissions were achieved. The mean duration of the complete remissions was 23 weeks. The mean survival time of the patients with complete remission amounted to 53 weeks B. 46% complete and 12% partial remissions were obtained in 37 patients treated with cytosine arabinoside and 6-thioguanine doubling the dosage of the above mentioned regimen followed by 3 cycles of TRAP (and COAP). Using a maintenance therapy with modified TRAP, COAP, and POMP cycles the complete remissions lasted 47 weeks at an average. The mean survival time of patients with complete remission was 87 weeks after start of treatment.


[Septicaemia in leukaemia (author's transl)].

From 244 patients with leukaemia 34 (13,9%) suffered from septicaemia. Although all forms of leukaemia had been concerned, lymphocytic leukaemias (acute and chronic) predominated. Besides other factors, the most important one is the cellular and humoral immuno-deficiency state in this disease. Gram-negative bacteria occur most frequently, followed by staphylococci, streptococci and fungi. The site of origin of infection is rarely known, presumably in most cases the skin, intestinal and genital mucous membranes and the lungs. The clinical picture of septicaemia in leukaemia is not a typical septicaemic one, as the symptoms of the underlying disease predominate. Diagnosis therefore is only based on blood cultures. As therapy is necessary previous to the knowledge of the bacteriological result, it may be initiated by the application of gentamycin (or, in case of resistance, amikacin) combined with ampicillin or chloramphenicol, corrected later in accordance with the antibiogram. High doses of corticosteroids are used specially in shock states. The prevention of septicaemic complications in leukaemia is most important with regard to better results in cytostatic therapy of leukaemias.


Aggressive juvenile fibromatosis involving the mandible: surgical excision with immediate reconstruction.

Aggressive juvenile fibromatosis involving the facial bones is rare, difficult to diagnose clinically, histologically confusing, and requires aggressive surgical treatment. Only four cases involving the mandible have been previously reported. A review of the literature is presented here in conjunction with a case report of this rare tumor.


Aseptic osteomyelitis and necrosis of the mandibular condylar head after intracapsular fracture.

Aseptic osteomyelitis and necrosis of the mandibular condylar head is a rare complication which may occur several months after an untreated intracapsular fracture. Clinical symptoms are pain in the temporomandibular joint on the affected side and limitation of opening of the mouth. Radiographically, the condylar head is characteristically eroded and irregular. Treatment consists of surgical removal of the necrotic condylar head and débridement of the area, which are performed via a preauricular approach.


The human accessory parotid gland: its incidence, nature, and significance.

Observations on ninety-six dissections of human parotid glands have been presented, with the incidence, size, location, and histologic features of accessory parotid glands noted. Twenty-one per cent of the dissections revealed clearly detached accessory glands at variable distances from the main gland. There were no appreciable histopathologic differences between the accessory gland and the main gland in the same facial half. Aging changes, such as decreased glandular elements, increased fat, and increased fibrous connective tissue, were not more extensive in the accessory gland than in the main gland. Because of the histologic similarity, pathoses of the main gland could also involve the accessory parotid gland. Failure to remove a distantly separated accessory gland during parotidectomy could be a cause of tumor recurrence. X-ray films and sialograms were examined for visualization of accessory parotid glands and their ducts. Whereas routine diagnostic x-ray films were limited in their usefulness, sialograms provided visualization of accessory glands for diagnostic purposes.


Congenital epulis of the newborn.

Reported is a case of congenital epulis of the newborn occurring in the mandible and the maxilla. The masses were of such size as to cause respiratory and nursing difficulties. The theories of pathogenesis, the surgical treatment, the histologic appearance, and a 5-year follow-up are described. As with previous cases reported, there has been no recurrence.


Osteochondroma of the coronoid process of the mandible.

A case of osteochondroma of the coronoid process is presented. The proper diagnosis of ill-defined symptoms in the temporomandibular joint requires conformity between clinical manifestations and radiologic findings. The importance of a thorough radiologic examination is stressed for the correct diagnosis of these rare, insidious, slow-growing tumors. A short review of the literature is presented, and the treatment and surgical approach to these tumors are discussed.


Cat scratch disease. Report of a case.

Members of the health care professions who examine the head and neck regions should be familiar with cat scratch disease and consider it in a differential diagnosis. This article summarizes the history, literature, diagnosis, and treatment of cat scratch disease.


Severe enamel hypoplasia in a case of intestinal lymphangiectasia: a rare protein-losing enteropathy.

A unique case of enamel hypoplasia is presented. This appears to be the first case to be published in connection with the rare protein-losing enteropathy, intestinal lymphangiectasia. It seems likely that if the treatment of systemic disease is delayed, disruption of normal tooth formation is inevitable.


Influence of obesity and hypertension on the severity of periodontitis in rats.

The purpose of this investigation was to evaluate the extent to which obesity and/or hypertension may modify the response of rats' periodontium to chronic gingival irritation. Forty-four normal, spontaneously hypertensive, obese, and obese-hypertensive rats were used. Histopathologic evaluation of the periodontal structure showed both hyperplasia and hypertrophy of the walls of blood vessels supplying the periodontium in the hypertensive and obese-hypertensive animals. The results also indicated that obesity significantly contributed to e severity of periodontal disease. Hypertension alone was not a significant factor. The obese-hypertensive rats showed the most severe periodontal response to local irritation.


Necrotizing sialometaplasia of the mandible.

A brief review of the literature on necrotizing sialometaplasia has been presented. A patient with necrotizing sialometaplasia of the retromolar pad is reported. This is the first such lesion to be described in an oral site other than the palate. Clinical, histologic, and etiologic aspects of the lesion have veen discussed.


Parosteal osteosarcoma of the maxilla.

Parosteal osteosarcoma is a low-grade form of osteosarcoma that rarely affects the jaws. A case involving the maxilla of a 25-year-old man is presented, and four previously reported cases are reviewed.


Chondroma of the tongue.

A case of lingual chondroma is presented, along with the pertinent light and electron microscopy findings. The literature on lingual chondromas has been reviewed, and the pertinent clinical features are discussed and compared with those of other hard lingual tumors, the osteoma and osteochondroma.


Radicular (type 1) dentin dysplasia.

Radicular dentin dysplasia is a peculiar anomaly in which abnormal dentin resembling the plici-dentin found in certain fish and reptiles obliterates the pulp chamber. The almost complete absence of roots leads to the early loss of teeth and predisposes to paradontal infection and the formation of cysts.


Isolation of anaerobic bacteria from the root canal systems of necrotic teeth by the use of a transport solution.

The purpose of this study was to develop a clinically practical technique for isolating predominant anaerobic microorganisms from the root canal systems of intact necrotic teeth. Fifty-five consecutive teeth, all of which were necrotic, were sampled for this study. The technique developed involved a transport solution into which each sample was placed. At least one anaerobic bacterium was isolated from each case, with as many as four anaerobic bacteria being isolated from one case. Over half of the total number of organisms isolated were anaerobes, and almost half of these organisms were gram-negative. Whereas this technique has enabled the author to isolate and identify the same spectrum of predominant anaerobic bacteria as has been reported recently by others using the rigid VPI technique, the author suggests that the technique described here be utilized when the VPI technique cannot be performed.


Is gingival infection likely to act as a focus? The epithelial barrier.

Of the infectious lesions in and around the mouth, gingival infection in more advanced stages of periodontal disease seems to be the most likely candidate for acting as a focus of infection. However, there is little evidence to indicate that more than a transient bacteremia may occur from this source in cases of local injury, because of the nature of the epithelial barrier. Established oral foci should, nevertheless, be treated irrespective of their relation to extraoral or systemic damage, and in an effort to protect from bacteremia, precautionary measures should be taken prior to manipulations in this area.


Densitometric analysis of experimentally produced periapical radiolucencies.

Artificial periapical lesions were created in a mounted dried human mandible. These lesions were radiographed by means of a reproducible projection technique. A penetrometer was projected on the same radiographs as the dental and bony structures. The developing process was standardized. The radiographs were evaluated by means of densitometric analysis. The densitometer readings of the dental and bony structures on the radiographs were converted to a millimeters-of-aluminum-equivalents scale by means of the densitometer readings of the penetrometer images on the same radiographs. The measurements on the radiographs were presented in graphs and isodensitometric images. Areas where bone was removed could be reproducibly distinguished by densitometric analysis from areas where no bone was removed. For this purpose, the densitometric analysis of periapical radiographs proved to very useful, whereas the interpretations of the same radiographs by ten dentists differed greatly.


A nonlinear model for predicting radiographic contrast.

A computerized model has been developed which permits ideal maximum radiographic contrast, associated with clinically meaningful changes in x-ray attenuation for any combination of tissues, to be predicted from the spectral energy of the primary beam and the characteristics of the film. Results suggest that these factors influence available contrast in ways which depend on the specific diagnostic task to be accomplished. Hence, it appears that no single technique is optimal for all tissue configurations. Although contrast computed in this way does not take into account other factors of diagnostic interest, such as image resolution and context-dependent cues to lesion identity, it is an independent factor which can profoundly influence the detectability of specific changes in tissue attenuation and, as such, it may be considered a reasonable basis for predicting diagnostic performance.


The pathogenesis of hyperuricemia in glycogen storage disease, type I.

After the infusion of fructose, 0.25 g/kg body weight, blood uric acid levels were significantly increased above the mean basal value in five patients with glycogen storage disease (GSD), type I (P less than 0.02-P less than 0.05). The mean fasting blood inorganic phosphate (Pi) level in the patients was 3.9 +/- 0.3 mg/100 ml and was significantly lower than the mean Pi value of 4.8 +/- 0.3 mg/100 ml of the control subjects (P less than 0.05). Blood Pi levels were significantly lower in the patients than in the control subjects at varying times after the administration of fructose (P less than 0.005-P less than 0.05). Uric acid excretion did not increase significantly in the patients after fructose was given. In contrast to normal children, the mean peak blood uric level in the patients increased significantly after the administration of glucagon (P less than 0.001). In both patients (P less than 0.005) and control subjects (P less than 0.05), mean blood Pi concentrations decreased significantly after the administration of glucagon; however, the blood Pi concentrations in the patients were significantly lower than in the control subjects. Uric acid excretion increased after glucagon administration in both patients and control subjects, but the differences in uric acid excretion between the two groups were not significant. The data in our patients after fructose and glucagon administration suggest that hyperuricemia in GSD results from enhanced nucleotide catabolism. The concentrations of hepatic Pi and ATP may be low in patients with GSD; hepatic Pi and ATP content would therefore be further diminished by the administration of fructose and glucagon. By a mechanism similar to that of fructose-induced hyperuricemia, diminished hepatic Pi and ATP content might increase the breakdown of adenine nucleotides with resultant hyperuricemia.


Lactate production in McArdle's disease.

A case of McArdle's disease in a man is described in detail and a less complete study of his family is reported. This patient showed the classical features of McArdle's disease and the diagnosis was confirmed by muscle biopsy. Unlike other reported cases of this disorder, this case showed a normal rise in blood lactate levels on ischaemic exercise. This apparently paradoxical finding is discussed. It is suggested that a normal rise in the level of blood lactate on ischaemic exercise should not exclude myophosphorylase deficiency.


Acute leukaemia during azathioprine therapy.

Various tumours, in particular lymphomas, have been reported in association with azathioprine treatment, both after renal transplantation and in other conditions. A case is reported here of acute myeloid leukaemia associated with azathioprine therapy for rheumatoid arthritis, and this is now the third case reported in the world literature of leukaemia arising during azathioprine therapy for a non-malignant condition.


Unified picture of mechanisms of catalysis by carboxypeptidase A.

We have reported evidence that an anhydride intermediate is not involved in the hydrolysis of typical peptide substrates by carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.12.2), and we describe further evidence here. Recently an anhydride intermediate has been detected in the hydrolysis of an ester substrate by this enzyme. Other evidence also suggests that esters and peptides may not be cleaved by the same type of mechanism. A possible explanation is that the substrate carbonyl and a water molecule are always aligned between glutamate-270 and the zinc atom of the enzyme, but not always in the same sequence. With peptides the carbonyl is coordinated to zinc, and the water is delivered by glutamate acting as a general base. Esters are weaker ligands, and in some cases the ester carbonyl may not displace water from zinc. This would lead to a nucleophilic mechanism, with glutamate-270 forming an anhydride while zinc-aquo serves as a Brönsted acid. This picture is consistent with other evidence on ester cleavage, and resolves the otherwise baffling discrepant data on peptide as compared to ester substrates.


Molecular description of dioxygen bonding in hemoglobin.

From ab initio quality calculations on model systems, we conclude that in unliganded Fe-porphyrin the FE lies in the plane for both the high-spin (q) and intermediate-spin (t) states. Thus, the high-spin d6 Fe is not too big to fit into the porphyrin plane (as often suggested). We find the q state lower for a porphyrin hole radius greater than 1.94 A and the t state lower for smaller sizes. For the five-coordinate complex including an axial nitrogenous ligand [a model for myoglobin (Mb) and hemoglobin  (Hb)], we find the ground state to be q with the Fe 0.3 A out of the plane (recent x-ray data on deoxy Mb suggests about 0.4 A). The origin of this out-of-plane displacement is the nonbonded repulsions between the axial ligand and porphyrin nitrogen orbitals. Pushing the Fe of the five-coordinate complex into the plane does not lead to a stable low-spin state (as usually suggested), the q and t states being the low-lying states. Bonding the O2 to form the six-coordinate complex stabilizes the t form of the Mb model, leading to a singlet state of MbO2 with Fe in the plane. (It has often been suggested that the Fe of MbO2 and HbO2 is low-spin Fe2+; however, we find this not to be the case.) The bonding in the MbO2 model confirms the ozone model of the bonding, leading to a structure consistent with the Pauling model (our calculated FeOO bond angle is 119 degrees). The total charge transfer to the O2 is 0.10 electron, in disagreement with the Weiss model. Molecular orbital calculations (Hartree-Fock) incorrectly lead to septet ground state (S = 3) for the MbO2 model. The implications for the cooperative O2 binding in hemoglobin and protein modifications of the energetics of the active site are considered. Use of our calculated force constants for displacement of Fe perpendicular to the heme plane suggests that the movement of the Fe upon a change in the quaternary structure from the T to the R form is only about 0.04 A toward the heme plane.


Model of protein folding: incorporation of a one-dimensional short-range (Ising) model into a three-dimensional model.

In this paper, we have incorporated a one-dimensional short-range model into a three-dimensional model for protein folding. It has been applied, by extending the concept of the three-step mechanism for protein folding proposed in our previous paper, to simulate the folding of bovine pancreatic trypsin inhibitor, using a Monte Carlo procedure in all three steps, A, B, and C. The statistical mechanical ensemble treatment of the short-range model serves as a constraint on the Monte Carlo procedure, in which conformational transitions are introduced. The preliminary results of 10 independent Monte Carlo trials indicate that, while folding is achieved, improvements are required in order to account for the correct three-dimensional structure of a globular protein.


Nonidentifiability in stochastic models of illness and death.

The interpretation of animal survival experiments in which disease incidence is determined at death or following sacrifice is shown to involve certain ambiguities. In particular, quantities of interest such as the expected duration of life for an animal contracting a specific disease at a specific age are found to be nonidentifiable. An example is constructed in which two populations of animals will appear similar to the experimenter but in which animals contracting a particular disease in one population may have double the life expectancy of similarly afflicted animals in the other population.


Age incidence curves for cancer.

Age incidence curves for carcinomas tend to be linear on doubly logarithmic graphs. This fact has been used to support the somatic mutation hypothesis. It is shown that this should also be expected on the epigenetic hypothesis when the reversible cellular changes are programmed to occur randomly. Such changes could be programmed differently to obtain the age incidence curves observed for other cancers, e.g., leukemias and sarcomas.


Association of a protein structure of probable membrane derivation with HeLa cell mitochondrial DNA near its origin of replication.

Almost all (about 95%) of the mitochondrial DNA molecules released by Triton X-100 lysis of HeLa cell mitochondria in the presence of 0.15 M salt are associated with a single protein-containing structure varying in appearance between a 10-20 nm knob and a 100-500 nm membrane-like patch. Analysis by high resolution electron microscopy and by polyacrylamide gel electrophoresis after cleavage of mitochondrial DNA with the endonucleases EcoRI, HindIII, and Hpa II has shown that the protein structure is attached to the DNA in the region of the D-loop, and probably near the origin of mitochondrial DNA replication. The data strongly suggest that HeLa cell mitochondrial DNA is attached in vivo to the inner mitochondrial membrane at or near the origin of replication, and that a membrane fragment of variable size remains associated with the DNA during the isolation. After sodium dodecyl sulfate extraction of mitochondrial DNA, a small 5-10 nm protein is found at the same site on a fraction of the mitochondrial DNA molecules.


Rat liver preproalbumin: in vitro synthesis and partial amino acid sequence.

Rat liver poly(A)-containing RNA greatly stimulated incorporation of radioactive amino acids into protein when added to a wheat germ in vitro translation system. Approximately 7% of the labeled synthetic product was precipitated following indirect immunoprecipitation with antisera to rat serum albumin. Analysis of this material, and of the cyanogen bromide fragments derived from it, by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed that it contained an NH2-terminal extension of about 2500 daltons when compared to rat serum albumin. Automated sequence determination of purified cell-free product labeled with various radioactive amino acids revealed the presence of 18 additional amino acids NH2-terminal to the sequence of rat proalbumin. The partial sequence of this extension was found to be: Met-X-X-X-X-Phe-Leu-Leu-Leu-Leu-Phe-X-X-X-X-X-Phe-X-proalbumin. On the basis of this evidence, the immunoprecipitable cell-free product was designated preproalbumin.


Relative conformational rigidity in oxytocin and (1-penicillamine)-oxytocin: a proposal for the relationship of conformational flexibility to peptide hormone agonism and antagonism.

A comparative study of the proton and carbon-13 nuclear magnetic resonance spectral parameters of the peptide hormone oxytocin and of its competitive inhibitor [1-L-penicillamine]oxytocin has been made, and the results analyzed in terms of comparative conformational and dynamic properties. The results indicate that oxytocin has a flexible conformation, while [1-L-penicillamine]oxytocin has a more restricted conformation. The results provide a framework for understanding the mechanism of peptide hormone agonism and antagonism for these compounds, and an approach for understanding some features of the interaction of the hormone and related compounds with their receptor.


Dissociation and reassociation of immobilized porphobilinogen synthase: use of immobilized subunits for enzyme isolation.

The dissociation and association of an immobilized preparation of the octameric enzyme porphobilinogen synthase [5-aminolevulinate hydro-lyase (adding 5-aminolevulinate and cyclizing), EC 4.2.1.24] is described. On treatment of the immobilized preparation with 4 M urea, four subunits per octamer are removed which can be reassociated into a soluble octameric enzyme. The tetrameric bound residual protein can also be reassembled into an octameric structure, with the same initial enzyme activity, by exposing the residual bound protein to a soluble pure enzyme preparation or to a crude liver extract in the presence of urea. The dissociation of the reconstituted bound enzyme releases subunits that again can be reassembled into a soluble octameric pure protein even when the crude liver preparation is used as the donor of the subunits. Thus, a pure enzyme can be isolated in a reassociation-dissociation cycle. The use of immobilized preparations of oligomeric proteins is considered for intra- and interspecies hybridization studies and for the ready preparation of purified enzyme preparations from different species and is suggested as a model for study of the formation of an oligomeric enzyme in the presence of other polypeptides.


Evidence that dephosphorylation inactivates glucocorticoid receptors.

Highly purified alkaline phosphatase [orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] from calf intestine inactivates the glucocorticoid-binding capacity of soluble preparations from mouse fibroblasts (L cells) and rat liver. The unbound receptor is sensitive to inactivation whereas the steroid-bound receptor is unaffected. The ability of the enzyme preparation to inactivate the receptor, like its ability to dephosphorylate p-nitrophenyl phosphate, is dependent on zinc and inhibited by arsenate. Both the dephosphorylating and receptor inactivating activities coelute during DEAE-cellulose purification of the enzyme. There is no detectable proteolytic activity in the purified alkaline phosphatase preparation. In a mixed system containing both glucocorticoid and estrogen receptors, the glucocorticoid receptor is selectively inactivated. Although these observations do not prove that the receptor molecule itself is the substrate, they are consistent with the proposal that the glucocorticoid receptor can be inactivated by dephosphorylation and that only the phosphorylated form of the molecule is capable of binding steroid. A phosphorylation-dephosphorylation mechanism may be responsible for determining the level of active receptor in the cell.


In vitro biosynthesis of beta-endorphin in pituitary glands.

beta-Endorphin is a 31 amino acid polypeptide isolated from the pituitary gland of different species of animals. It has strong morphine-like activity. It is formed of amino acid residues 61-91 of beta-lipotropin. Speculation has arisen whether it is biosynthesized in situ or transformed after secretion of beta-lipotropin. The present in vitro studies show that it is found as beta-endorphin in bovine pituitary slices incubated with radioactive amino acid precursor [35S]methionine. Chemical characterization and microsequencing of the newly biosynthesized material proves its identity with isolated unlabeled beta-endorphin and shows that it has a methionine residue at its fifth position, as expected.


Heterogeneous nuclear RNA secondary structure: oligo (U) sequences base-paired with poly (A) and their possible role as binding sites for heterogeneous nuclear RNA-specific proteins.

HeLa cell heterogeneous nuclear RNA derived from high-molecular-weight nuclear ribonucleoprotein (RNP) particles contains oligo(U) sequences of 15-50 nucleotides base-paired with poly(A). These duplexes are resistant to pancreatic RNase at 0.5 M NaCl in native RNP, remain so after chemical deproteinization of the RNP digests, and then copurify with poly(A) on oligo(dT)-cellulose chromatography. Oligo(dT)-cellulose binding capacity of the oligo(U)-poly(A) duplexes is abolished by prior titration of the nonduplex poly(A) regions with excess poly(U). The oligo(dT)-purified fraction is 97.5 mole % A + U and the [3H]uridine-labeled component is resistant to redigestion by pancreatic RNase at 0.5 M NaCl but not at 0.01 M NaCl. After thermal denaturation, the [3H]uridine-labeled chains become RNase-sensitive at 0.5 M NaCl. Electrophoresis of [3H]adenosine- or [3H]uridine-labeled material in polyacrylamide gels containing 99% formamide confirms that the oligo(U) sequences are not covalently linked to poly(A). Controls establish that the A-U duplexes are not formed artifactually during isolation of heterogeneous nuclear RNP or subsequent fractionation. The oligo(U)-poly(A) duplexes appear to be associated with protein in native heterogeneous nuclear RNP, as reflected by the differential pancreatic RNase sensitivity of the duplexed oligo(U) in RNP (resistant) and RNA (sensitive), measured at physiological ionic strength.


Collagen degradation in rat skin but not in intestine during rapid growth: effect on collagen types I and III from skin.

Metabolic degradation of prelabeled collagen in whole body skin and whole intestine was compared to that of types I and III collagens from skin in young, rapidly growing rats. Pregnant rats were given [3H]proline during the last week of gestation; and after birth, littermates were compared. Between the second and sixth weeks of age, there was a 43% loss of radioactivity from dermal collagen but no significant loss of radioactivity from intestinal collagen. Pepsin treatment solubilized 90% of the dermal collagen but only 12% of intestinal collagen. Skin from 2- and 6-week-old rats yielded the same proportions of type I and type III collagens (type I, 82%; type III, 18%). The relative losses of total radioactivity from types I and III were similar to each other (50 and 44%, respectively) and to the loss from whole skin. Because types I and III collagens are known to be present in both skin and intestine, the marked degradation of both collagen types in skin but not in the intestine may be related to the amount and kind of intermolecular crosslinks present.


Invariance and heterogeneity in the major structural and regulatory proteins of chick muscle cells revealed by two-dimensional gel electrophoresis.

A two-dimensional gel electrophoresis system is used to investigate some of the properties of desmin, the major subunit of the 100-A filaments from chick muscle cells, and to compare these properties to those of the other major contractile and regulatory proteins of muscle. Desmin from embryonic and adult smooth, skeletal, and cardiac muscle cells is resolved into two isoelectric variants, alpha and beta, which possess slightly different electrophoretic mobilities in sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Both the alpha and the beta variants from all six preparations appear to be identical in isoelectric point and apparent molecular weight. The alpha and beta desmin are present in approximately equal amounts in all three types of muscle, suggesting that both isoelectric variants of desmin serve as the structural subunits of the 100-A filaments in chick muscle cells. Tropomyosin also can be resolved into two subunits, alpha and beta, in all three types of muscle. However, in each type of muscle both subunits differ from their counterparts in the other types of muscle, either by molecular weight or by isoelectric point. These results indicate that, with regard to apparent isoelectric point and molecular weight, desmin, a major muscle structural protein, is invariant, while tropomyosin, a major muscle regulatory protein, exhibits heterogeneity in the three types of muscle.


Selective scattering spectra as an approach to internal structure of granal and agranal chloroplasts.

Selective scattering spectra of granal and agranal chloroplasts were measured in the red spectral region and compared with calculations based on the Mie theory. The spectra were influenced considerably by the intactness and ultrastructural pattern of the chloroplasts. It was demonstrated that the spectra consist of two components: one attributable to grana and the other, to single lamellae. The dependence of the selective scattering spectra on the ultrastructural characteristics offers a convenient method for monitoring the quality of chloroplast preparations by a procedure much faster than electron microscopy.


Secondary structural complementarity between DNA and proteins.

A model for the complex between double-stranded DNA and a beta-ribbon (a two-stranded antiparallel beta-sheet) of proteins is proposed as one of the possible modes of structural recognition between DNA and proteins. In this model, the contact occurs on the narrow groove of DNA, and the symmetry elements as well as the repeat distances of DNA and the beta-ribbon coincide, thus providing favorable complementary contacts.


Relationship between interferon production and interferon messenger RNA synthesis in human fibroblasts.

Poly(A) containing mRNA prepared from poly(rI)-poly(rC)-induced human fibroblasts stimulated [14C]leucine incorporation into protein in wheat germ cell-free extracts. For the translation of interferon mRNA into a biologically active product, the presence of spermine was essential. The protein synthesized in vitro fulfilled the criteria for human interferon--namely, its antiviral activity was species specific, and its activity was completely neutralized by antiserum to human fibroblast interferon. The amount of interferon synthesized in human fibroblasts induced by poly(rI)-poly(rC) (normal induction) and poly(rI)-poly(rC) in the presence of cycloheximide (superinduction) was compared to the amount of translatable interferon mRNA both in the wheat germ cell-free system and the Xenopus oöcyte system. Although the production of interferon after the termination of transcription by actinomycin D was markedly increased in superinduced cells, the measurable amount of interferon mRNA as assayed in the oöcyte system was only slightly higher in superinduced cells than in cells induced with poly(rI)-poly(rC) alone. When compared in the wheat germ cell-free system, however, the translational product of mRNA preparation from cells induced with poly(rI)-poly(rC) alone was inactive while that from superinduced cells was active.


Unexpected additional mode of energization of amino-acid transport into Ehrlich cells.

Ehrlich cells treated with dinitrophenol and iodoacetate rapidly recover their 30-sec uptake of 2-(methyl-amino)-isobutyrate on treatment with 0.1 mM phenazine methosulfate + 20 mM sodium ascorbate before they begin to recover from the severely depressed ATP levels and alkali-ion gradients. Addition of 10 mM pyruvate also restores uptake of methylaminoisobutyrate before the alkali-ion gradients rise. This restoration is prevented by rotenone, but rotenone does not handicap restoration by phenazine methosulfate/ascorbate. Na+-independent uptake of 2-aminonorbornane-2-carboxylate by Ehrlich cells is affected the same way. Quinacrine almost completely suppresses uptake of methylaminoisobutyrate within the 30-sec uptake test, even when ATP levels are sustained by pyruvate and alkali-ion gradients are not depressed. Ouabain prevents restoration of both Na+-dependent and Na+-independent amino-acid transport by phenazine methosulfate/ascorbate or pyruvate. We interpret these results to indicate that amino-acid transport can be energized not only by known means, but also by reducing equivalents, which presumably reach the plasma membrane in the form of NADH from the mitochondria when the source of energy is pyruvate. In support of this hypothesis, the distribution of methylaminoisobutyrate between plasma membrane vesicles and their supporting media was influenced in the predictable way by NADH, quinacrine, and an uncoupling agent, proceeding on the assumption that more of the vesicles had the everted rather than the natural orientation.


Molecular properties of the nerve growth factor secreted by L cells.

The molecular size and stability of the nerve growth factor (NGF) secreted in culture by L cells have been studied by sedimentation and gel filtration chromatography. Results indicate that L cell NGF has a molecular weight of 160,000. It contains as part of its structure a protein component that is biologically, immunologically, and electrophoretically indistinguishable from the biologically active factor purified from mouse submandibular glands. However, unlike pure gland NGF, L cell NGF is highly stable in solution, and this finding indicates that L cell NGF is a form of the factor different from that previously described.


Characterization of the integration protein of bacteriophage lambda as a site-specific DNA-binding protein.

The Int protein specified by bacteriophage lambda is required for the recombination event that integrates the viral DNA into the host genome at its specific attachment site. Using a DNA-binding assay, we have partially purified the Int protein and studied some of the features of its binding specificity and regulation. The DNA-binding activity is attributed to Int protein because the activity is eliminated by a nonsense mutation or a deletion in the int gene, and is rendered thermolabile by temperature-sensitive mutations in the int gene. The DNA-binding activity is specific for DNA carrying an appropriate attachment site, suggesting that Int protein directs the sequence-specific recognition essential for integrative recombination. The specific DNA-binding activity is also missing after infection by phage carrying mutations in the cII and cIII regulatory genes of lambda. This finding corroborates the conclusion from other types of experiments that regulation of the int and cI genes by cII/cIII provides for coordinate regulation of both major events of the lysogenic response, establishment of repression and insertion of viral DNA.


Role of sialic acid in survival of erythrocytes in the circulation: interaction of neuraminidase-treated and untreated erythrocytes with spleen and liver at the cellular level.

Sialidase (neuraminidase; acylneuraminyl hydrolase; EC 3.2.1.18)-treated erythrocytes obtained from different species are susceptible to rapid elimination from the circulation and are sequestered in the liver and spleen. The present studies were concerned with the mechanism of this clearance and how it may relate to the normal physiological process of removing senescent erythrocytes from the circulation. The results obtained indicate a preferential recognition of sialidase-treated as compared to normal erythrocytes by mono-nuclear spleen cells and Kupffer cells of the liver. This recognition manifests itself in both autologous and homologous systems by adhesion of the complementary cells in the form of rosettes, and as such could explain the removal of enzyme-treated erythrocytes from the circulation with their accumulation in liver and spleen. This phenomenon may represent a normal physiological mechanism for removal of senescent erythrocytes containing decreased sialic acid.


Partial amino acid sequence of two major component polypeptides of hepatitis B surface antigen.

Determination of the amino acid sequence of the immunogenic polypeptides of hepatitis B surface antigen may not only permit molecular localization of the distinct determinants a, d, and y but may also lead to the synthesis of a hapten useful in prophylactic immunization against hepatitis B virus infection. For this purpose, purified monotypic hepatitis B surface antigen of adw subtype was resolved into equal amounts of two major polypeptides (22,000 and 28,000 daltons) and up to six other minor polypeptides by polyacrylamide gel electrophoresis. With the periodate staining reaction, only the 28,000-dalton polypeptide stained as a glycoprotein. Guinea pigs immunized with the 22,000-dalton polypeptide produced potent antisera against determinants a and d, but the 28,000-dalton glycoprotein did not induce a response. Both polypeptides isolated by preparative polyacrylamide gel electrophoresis showed amino acid composition identical with that of the intact antigen. For both polypeptides, hydrazinolysis gave Ile as the carboxyterminus, and carboxypeptidase A digestion gave the same terminal sequence, Val-Tyr-Ile. Both peptides also yielded an identical sequence of amino acids in nine steps of Edman degradation--Met-Glu-Asn-Ile-Thr-Ser(Cys)-Gly-Phe-Leu. Our data suggest that hepatitis B surface antigen contains a single major immunogenic 22,000-dalton polypeptide component, part of which is modified by the addition of carbohydrate to give rise to the glycopeptide of apparent molecular weight 28,000.


Transmembrane movement of cholesterol in human erythrocytes.

We studied the exchange of cholesterol between radioactively labeled plasma and human erythrocytes. Results from experiments in which [3H]cholesterol and [14C]-cholesterol were exchanged sequentially into the cells and back out into unlabeled plasma, showed that transmembrane movement of cholesterol occurred with a half-time that was either less than 50 min or greater than 10 days. To obtain further information about the transmembrane movement of cholesterol, we used a technique [Jacobson, B. S. & Branton, D. (1977) Science 195, 302-304] for exposure of the cytoplasmic surface of erythrocyte membranes. This method involved the ionic attachment of erythrocytes to derivatized glass beads followed by disruption of the cells, leaving the beads covered by membrane with the cytoplasmic surface exposed [3H]Cholesterol was exchanged into intact erythrocytes which then were attached to beads. The beads with attached membrane were incubated with phospholipid-cholesterol vesicles and the exchange of cholesterol between the membrane cytoplasmic surface and vesicles was studied. We found that [3H]cholesterol was present at the cytoplasmic surface, indicating that transmembrane movement of cholesterol had occurred within the 2.5 hr required to complete the experiment. This result suggests that the more rapid rate of transmembrane cholesterol movement, inferred from the experiments described above, is the one that applies.


Different rate-limiting steps in excision repair of ultraviolet- and N-acetoxy-2-acetylaminofluorene-damaged DNA in normal human fibroblasts.

In normal human cells the amount of excision of ultraviolet damage to DNA saturates at high doses. In these cells some chemicals mimic ultraviolet damage as far as their biological and repair characteristics are concerned. One of these chemicals is N-acetoxy-2-acetylaminofluorene. We determined whether the limited repair capacity for ultraviolet damage was affected by treatment with N-acetoxy-2-acetylaminofluorene. To measure repair we determined unscheduled DNA synthesis and the number of sites sensitive to an ultraviolet endonuclease in an assay using an extract of Micrococcus luteus. The nuclease does not act on DNA treated with the chemical. The amount of unscheduled DNA synthesis due to a combined chemical and ultraviolet treatment was the sum of those observed from the separate treatments, even at saturation doses. The combined treatment did not affect the removal of nuclease-sensitive sites. We conclude that there are different rate-limiting steps in excision repair of the ultraviolet and the chemical damage and suggest a model involving a complex of enzymes to explain the data.


Differences in removal of acetylaminofluorene and pyrimidine dimers from the DNA of cultured mammalian cells.

The rate and extent of disappearance of two DNA lesions (pyrimidine dimers and covalently bound acetylaminofluorene), both thought to be removed by the so-called wide-patch (approximately 100 nucleotides) repair process, were studied in a variety of cultured mammalian cells. With the exception of mouse cells, dimers were removed more rapidly and extensively than covalently bound acetylaminofluorene. In human cells, for example, about 50% of the dimers were excised from DNA in 1 hr while only 25-50% of the chemically induced lesions were excised from DNA after 48 hr. Surprisingly mouse cells, which remove few dimers, were about as competent as control human fibroblasts at removing acetylaminofluorene lesions; however, xeroderma pigmentosum cells (group D) removed fewer N-acetoxy-2-acetylaminofluorene-induced lesions than control human cells. Our data raise the possibility of separate repair processes for these two types of lesions and suggest that their expression may be under similar genetic control in human cells.


Adenylate cyclase from synchronized neuroblastoma cells: responsiveness to prostaglandin E1, adenosine, and dopamine during the cell cycle.

Neuroblastoma cells were synchronized by a combined isoleucine plus glutamine starvation. Adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] was measured under basal conditions and in the presence of dopamine, adenosine and prostaglandin (PG) E1. A clear dissociation occurred between the respective evolution patterns of basal and agonist-stimulated adenylate cyclase activities. The magnitudes of the enzyme response to PGE1, adenosine, and dopamine also exhibited different evolution patterns during the cell cycle. Evolution of adenylate cyclase responsiveness to PGE1 during the cell cycle exhibited striking similarities with the intracellular 3':5'-cyclic AMP changes observed elsewhere. Use of theophylline and fluphenazine as specific inhibitors of adenosine and dopamine, respectively, made it possible to demonstrate that adenosine, dopamine, and PGE1 stimulated adenylate cyclase through independent receptor sites. Furthermore, whatever the stage of the cell cycle, responses to these three agonists were not additive, indicating that the receptors of adenosine, dopamine, and PGE1 control the same adenylate cyclase moieties. The data suggest that adenylate cyclase cell content and enzyme responsiveness to specific agonists can be independently controlled.


Magnesium and calcium effects on uptake of hexoses and uridine by chick embryo fibroblasts.

Cultures of chick embryo fibroblasts were incubated for varying periods in media containing different concentrations of Ca2+ and Mg2+-Mg2+ deprivation produced a gradual decrease in the Vmax of the glucose transport system for the D-glucose analogues 3-O-[3H]methyl-D-glucose and 2-deoxy-D-[3H]glucose and a parallel decrease in the rate of production of lactate from glucose in the medium. It greatly reduced the rates of [3H]uridine uptake and incorporation by decreasing the Vmax of the uridine transport system. Addition of Mg2+ to Mg2+-deprived cultures rapidly increased the rate of [3H]uridine uptake without requiring protein synthesis and increased the rate of 2-deoxy-D-[3H]glucose uptake without requiring RNA synthesis. These effects of changes in Mg2+ concentration qualitatively reproduce the effects of such variables as cell density and serum and insulin concentrations. Ca2+ deprivation resulted in similar, though much smaller, changes in the activities of the two transport systems, but also greatly increased the "leakiness" of the cells to the nontransported hexose L-[3H]glucose.


Higher-order structure of human mitotic chromosomes.

From observations on the partial disintegration of isolated human metaphase chromosomes we propose that human metaphase chromatids have a rather simple organization based on the folding and coiling of a long, regular, hollow cylindrical structure with a diameter of about 4000 A. This cylindrical structure, the unit fiber, is postulated to be a super-solenoid formed by the coiling of a 300 A solenoid, itself composed by coiling the basic string of nucleosomes. The structure of a human chromatid would thus be a hierarchy of helices, the contraction ratio of each coil, in ascending order of size, being approximately 7, 6, 40, and 5. This model appears to explain the estimated mass/unit length and accounts for many of the known features of human mitotic chromatids.


Two-dimensional analysis of flagellar proteins from wild-type and paralyzed mutants of Chlamydomonas reinhardtii.

Flagellar polypeptides of Chlamydomonas reinhardtii were analyzed in two-dimensions by isoelectric focusing and electrophoresis in the presence of sodium dodecyl sulfate. In addition to flagellar tubulin, over 130 polypeptides were resolved and 100 of these were identified as axonemal components in wild-type organisms. Flagella of two nonconditional paralyzed mutants, pf 14 and pf 1, were also analyzed and, at the same time, electron microscopic studies were carried out. pf 14 flagella, which completely lack radial spokes and associated spokeheads, are missing 12 polypeptides. Six of these polypeptides are also missing from pf 1 flagella in which spokes are clearly present but spoke heads appear to be absent.


Absence of a measurable G2 phase in two Chinese hamster cell lines.

Evidence is presented that demonstrates the absence of a measurable G2 phase in the cell cycles of two sublines of the Chinese hamster lung fibroblast V79. One of the sublines, in addition, lacks a detectable G1 phase, thereby possessing a cell cycle comprised of simply two phases, DNA synthesis (S) and mitosis (M).


Extension of the lifespan of cultured normal human diploid cells by vitamin E: a reevaluation.

Previously we reported [Packer, L. & Smith, J.R. (1974) Proc. Natl. Acad. Sci. USA 71, 4763-4767] that the lifespan of WI-38 human diploid fibroblasts in vitro was significantly increased by continuously growing the cell cultures in the presence of vitamin E(dl-alpha-tocopherol), but in 19 subsequent subcultivation series we were unable to reproduce these findings. While vitamin E is incorporated into the cells and is able to act effectively as an antioxidant, apparantly is intracellular antioxidant properties alone do not routinely result in an increase of cell lifespan. A synergism between vitamin E and some component(s) in the first of two lots of serum used in the original experiments seems the most likely explanation for our earlier findings.


Extinction of hemoglobin inducibility in Friend erythroleukemia cells by fusion with cytoplasm of enucleated mouse neuroblastoma or fibroblast cells.

Friend mouse erythroleukemia cells (T3c1-2 and its subline 5000) can be induced to synthesize hemoglobin after treatment with 1.5% (vol/vol) dimethylsulfoxide. When these cells are fused with nonerythroid cells (namely, mouse neuroblastoma or L cells) hemoglobin induction is extinguished. In order to determine if the nucleus of the nonerythroid cell is necessary for this extinction, fusions were performed between mouse erythroleukemia cells and enucleated neuroblastoma or L cells. Hemoglobin induction was reduced or eliminated in clones of these hybrids even after 6 months of continuous culture. These results suggest that the cytoplasm of nonerythroid cells contains factor(s) that extinguish hemoglobin inducibility in erythroleukemic cells and that this new phenotype can be inherited.


The cost of evolution and the imprecision of adaptation.

Comparisons of six hypothetical cases suggest that Haldane overstimated the cost of natural selection by allele substitution. The cost is reduced if recessive alleles are advantageous, if substitutions are large and few, if selection is strong and substitutions are rapid, if substitutions are serial, and if substitutions in small demes are followed by deme-group substitutions. But costs are still so heavy that the adaptations of complex organisms in complex and changing environments are never completed. The rule probably is that most species most of the time are not fully adapted to their environments, but are just a little better than their competitors for the time being.


Effect of polyploidy on phosphoglucose isomerase diversity in Festuca microstachys.

Studies of the inheritance of electrophoretic banding patterns in Festuca microstachys support the hypothesis that three closely related loci, one located in each of the three ancestral genomes, code the multiple phosphoglucose isomerase (glucosephosphate isomerase; D-glucose-6-phosphate ketol-isomerase, EC 5.3.1.9) variants found in this hexaploid species. The close relationship among the three loci is indicated by the observation that hybrid enzymes of intercistronic origin form when the loci in different genomes carry alleles coding homodimers with unlike migration rates. Homozygous individuals fixed for different alleles in different genomes produce hybrid enzymes and, when self-fertilized, they breed true for isozyme patterns normally found only in the heterozygotes of diploid species. Biochemical diversity due to this "fixed heterozygosity" is high in F. microstachys; although this species is more than 99% self-fertilized the proportion of individuals with at least one heterodimer exceeded 61% in all of the 16 natural populations studied and it exceeded 92% in 11 of the populations. This great biochemical diversity may contribute to the ability of F. microstachys to survive in the wide range of habitats in which it is found over western North America.


Structural heterogeneity of C2 Complement protein and its genetic variants in man: a new polymorphism of the HLA region.

A zymogram method, following thin-layer isoelectric focusing in a polyacrylamide gel, allows resolution of the lytic activity of serum C2 complement protein in a spectrum of molecular forms. This spectrum is characteristic in each of the species studied (man, rhesus monkey, guinea pig, and hamster). Moreover, two different alternative patterns are observed in man: each of the six major lytic bands characteristic of the most common pattern (herein designated C2(1) is duplicated in the least common pattern (C2(2-1), with an additional band displaced cathodally by not more than 0.04 pH unit. Distribution of phenotypes C2(1) and C2(2-1) in a Caucasion population is in agreement with the hypothesis that they are controlled by two alleles, C2(1) and C2(2), with frequencies 0.96 and 0.04 +/- 0.01. Segregation studies show that the two alleles are codominant and identify a locus in the HLA region. No recombinants with HLA-B were detected among 27 informative meioses, generating a cumulative lod score of 6.321 at equals 0. These findings suggest that the individuals with the C2-deficient trait might be interpreted as homozygotes for a third and rarest amorph C2 degrees of the same locus.


Increased resistance of cystic fibrosis fibroblasts to ouabain toxicity.

Diploid skin fibroblasts derived from several unrelated patients with cystic fibrosis (CF) were tested for resistance to the cytotoxic effects of ouabain in comparison with cells from normal individuals. Cells from CF and normal individuals were plated at low density and exposed to ouabain at different concentrations for 24 hr. Dose-response curves showed that CF cells survived significantly better than did normal cells at all ouabain concentrations from 0.1 nM to 1 micronM in potassium-deficient medium. In medium containing the usual amount of potassium (6.25 mM), survival of the CF cells exposed to ouabain was decreased to that of the normal cells. If the glucose concentration of the potassium-deficient medium was decreased to 10% of the usual amount, the resistance of the CF cells to ouabain disappeared and their survival was identical to that of the normal cells. These findings may be useful in understanding the biochemical basis of CG and its clinical manifestations.


Activation of the alternative complement pathway due to resistance of zymosan-bound amplification convertase to endogenous regulatory mechanisms.

The surface of zymosan (Zy), by affording a protected microenvironment for C3b and the amplification convertase stabilized by properdin, P,C3b,Bb, shifts the alternative complement pathway from slow fluid phase turnover to the amplification phase of its expression. This mode of activation is in contradistinction to that of the classical pathway, which follows conversion of a proenzyme, Cl, to its active form, C1. Under conditions in which the control proteins, C3b inactivator (C3bINA) and beta1H, completely, inactivated C3b on the sheep erythrocyte intermediate, EAC4b,3b, the activity of C3b bound to Zy,ZyC3b, was diminished by only one-third. Further, when ZyC3b was converted to ZyC3b,Bb,P there was an additional point of deregulation in that the convertase was resistant to beta1H-mediated decay-dissociation while P,C3b,Bb on the sheep erythrocyte exhibited the usual susceptibility to beta1H. That Zy alone could indeed promote rapid C3 cleavage by the alternative pathway through assembly and protection of the amplification convertase on its surface was demonstrated with a mixture of alternative pathway proteins, C3,B,D,P, C3bINA, and beta1H, that had each been purified to homogeneity. Interaction of these proteins at one-tenth their relative serum concentrations with Zy permitted low-grade inactivation of C3 and B to advance to the level of amplification after a 15 min lag period. Because the reaction of the purified proteins proceeded spontaneously when either regulatory protein was deleted, the effect of Zy was attributed to deregulation rather than to conversion of one of the proteins to a specific initiating state. The alternative pathway, through the normal presence of D, interacts with a microbial surface, such as Zy, to amplify deposition of C3b by circumvention of endogenous regulatory mechanisms, thereby augmenting host defense.


Host specificity of a serum marker for hepatitis B: evidence that "e antigen" has the properties of an immunoglobulin.

A family of antigens, referred to collectively as e antigen (eAg), has been detected in sera of some individuals with liver disease who test positive for hepatitis B surface antigen. Studies on eAg partially purified by affinity chromatography on insolubilized antibodies to eAg revealed the following: (i) eAg has the physicochemical and immunologic properties of an immunoglobulin, predominantly of the IgG4 subclass, and (ii) specific antigenic sites, designated as e determinants, differentiate eAg from other immunoglobulins. We suggest that these determinants represent idiotypic determinants on antibodies that are formed in response to hepatitis B virus infection and that block the host's immune surveillance mechanisms by which virus proliferation is stopped.


Cell-free synthesis of the fourth component of guinea pig complement (C4): identification of a precursor of serum C4 (pro-C4).

Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which is then converted to C4, a three-chain (molecular weights 95,000, 78,000 and 31,000) structure linked by interchain disulfide bridges. Pro-C4 was also detected intracellularly in short-term tissue cultures of guinea pig liver. C4 was found in the medium harvested from these cultures.


Radioimmunoassay of creatine kinase-B isoenzyme in human sera: results in patients with acute myocardial infarction.

A radioimmunoassay was developed to measure serum levels of the B isoenzyme of creatine kinase(ATP: creatine N-phosphotransferase, EC 2.7.3.2) (CPK) in order to evaluate the time course and frequency of MB isoenzyme elevation in patients with acute myocardial infarction. The method can identify as little as 0.2 ng of the B portion of the CPK-MB isoenzyme, does not significantly crossreact with CPK-MM isoenzyme, and is not affected by storage of serum at --20 degrees CPK isoenzyme containing B subunits was detected in 48 out of 51 sera from normal adults; serum levels in these individuals ranged between 1.2 and 12.5 ng/ml [mean +/- SEM was 2.7 +/- 0.30 ng/ml]. The mean serum level of CPK-B isoenzyme in a pool of sera obtained from 100 normal subjects was 2.9 +/- 0.35 ng/ml; two patients with rhabdomyolysis that were studied had serum CPK-B isoenzyme levels of 2.5 and 3.5 ng/ml, respectively. In contrast, serum levels of the CPK-B isoenzyme were markedly elevated in sera from 18 patients with acute myocardial infarcts when obtained within 12 hr after hospital admission; the mean +/- SEM concentration was 56 +/- 7.8 ng/ml. We performed serial determinations on 14 patients with acute myocardial infarcts and demonstrated that maximal serum CPK-B levels occurred within the first 12 hr after admission and were lower thereafter. The serum concentration of B-containing CPK isoenzyme in 19 additional patients admitted with chest pain but without acute myocardial infarction was 3.4 +/- 0.50 ng/ml. Thus, radioimmunoassay measurement of CPK-B isoenzyme appears to be a useful and sensitive test for the detection of acute myocardial infarcts in patients.


5'-deoxypyridoxal as a potential anti-sickling agent.

5'-Deoxypyridoxal, which reacts specifically with the terminal amino groups of the alpha chains of hemoglobin, increases the oxygen affinity of hemoglobin solutions as well as of dilute suspensions of normal and sickle red cells and whole blood. As a result, the proportion of deoxyhemoglobin (which is responsible for sickling) is decreased at venous oxygen tensions and this is reflected by a sharply reduced sickle cell count in this range of oxygen pressures.


Effect of regenerated endothelium on lipid accumulation in the arterial wall.

We tested the hypothesis that loss of endothelium results in increased transport of lipoprotein into the arterial wall, favors accumulation of lipid, and thus predisposes to atherosclerosis. In rabbits initially fed a diet low in lipid, the aortas were de-endothlialized with an intraarterial balloon catheter; 28 days later, the animals were divided into two groups. Group I animals were continued on a diet low in lipid and sacrificed at 8, 11, 13, and 15 weeks after de-endothelialization. Group II animals were fed the same diet supplemented with 0.5% cholesterol and sacrificed at comparable intervals. Aortas of group I animals revealed proliferative fibromuscular intimal thickening in both de-endothelialized and re-endothelialized areas, with little or no fatty change in the intima. In contrast, aortas of group II animals revealed slight to marked fatty change in the intima, characterized by accumulation of oil red O-positive material with anisotropic lipid inclusions. The greatest quantity of lipid was present in intimal thickening beneath regenerated endothelium, and not in adjacent intimal thickening lacking an endothelial lining. These results do not support the hypothesis that the absence of endothelium favors accumulation of lipid and predisposes to atherosclerosis. The experiments indicate that lipid accumulates preferentially in areas of intimal thickening covered by regenerated endothelium.