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Biomedical subjects

R L Clark

Publications and source records attributed to R L Clark.

At least 109 records · Page 6Linked to original sources
PubMed1982

Cancer 1980: achievements, challenges, and prospects.

This review article touches on various categories of research that have been expanded or made possible predominantly by funding through the National Cancer Program of the National Cancer Institute and the American Cancer Society. Under diagnosis, categories mentioned are biological markers, chromosome banding techniques, fluorescent-activated cell sorter identification of cell surface antigens, ultrastructural studies with electron microscopy, histochemical, radiologic, ultrasonographic, thermographic, angiographic techniques, nuclear magnetic resonance imaging, radioactively labeled compounds that attach to specific tumor cell surface receptors, and other agents that are preferentially taken up by tumor tissues. Predictive tests include human tumor stem cell assays, sister chromatid exchange assay, and hormone receptor assays. The techniques listed under therapy include hyperthermia, immunotherapy, chemotherapy, radiosensitizing compounds, and the supportive measures of hyperalimentation and other nutritional manipulations, psychological reinforcement, rehabilitative efforts, bone marrow transplants, blood component therapy, protective "germ-free" environments, and pain control. Drug delivery systems, animal and cell culture models, and prevention of carcinogenesis are also mentioned.

Antineoplastic Agents↗
PubMed1982

Studies of enzyme polymorphisms in the Kamuela population of Drosophila mercatorum. II. Evaluation of glycolytic intermediates.

A simple and effective cryogenic procedure for the extraction of glycolytic intermediates from whole Drosophila has been developed. This procedure gives consistent results when a measure (microM/liter/OD260) is adopted which corrects for differences in extraction efficiency. Using this measure and a homozygous strain of D. mercatorum, there are no significant differences among extracts for the levels of any of the 15 glycolytic intermediate or energy molecules considered. The profile of means is consistent across experimental designs and instrument types. Coefficients of variation are well below 50% for most variables. The methodology presented has the statistical power to detect a mean change of 10 to 50% using an experimental design which requires as few as 32 observations. The estimated energy charge for resting Drosophila from these studies is the expected value of 0.86.

Adenine Nucleotides↗
PubMed1982

Prenatal and postnatal development of protein carboxymethylation activity in the mouse.

The carboxymethylation of endogenous methyl-accepting proteins in intact cells of whole embryos decreased between days 9.5 and 11.5 of gestation and thereafter increased. This fluctuation was not due to a change in the level of protein carboxymethylase (PCM) which remained constant during this period. Embryonic PCM was located predominantly in the cytosol of the embryonic cells, as is the case in adult tissues. Brain PCM specific activity was the same as the rest of the body from gestational days 13.5 to 19.5, but thereafter underwent a two- to threefold increase so that by the end of weaning (about 30 days), it had reached the high adult level. This time course suggests that increasing PCM may be part of the brain maturation process occurring during the neonatal period.

Age Factors↗
PubMed1982

Individual mobility, population growth and labor force participation.

Trends in labor force participation rates and the age of retirement are shown to be important of upward mobility. Reductions in age specific participation rates increase the speed of movement through the employment hierarchy. In conjunction with economic development, the falling labor force participation of older men acts to offset the adverse effects of slowing population growth on promotional prospects. These conclusions are reached by extending a model of employment status developed by Keyfitz to limit employment competition to only those actually in labor force.

Adult↗
PubMed1981

Selective inhibition of human leukocyte elastase and bovine alpha-chymotrypsin by novel heterocycles.

A number of N-arylbenzisothiazolinone 1,1-dioxides have been synthesized and examined for inhibitory activity against human leukocyte and porcine pancreatic elastase (EC 3.4.21.11), bovine alpha-chymotrypsin (EC 2.4.21.1), human leukocyte cathepsin G (EC 3.4.21.20), and bovine trypsin (EC 3.4.21.4). They are potent, selective, competitive inhibitors of human leukocyte elastase and chymotrypsin. The inhibitory capacity of these compounds is directly related to the electron-withdrawing capability of the aryl substituents. When sufficiently activated, the amide bond in the heterocyclic ring can be cleaved by the enzyme, resulting in inhibition which is highly specific. The most potent inhibitor of hummotrypsin. The inhibitory capacity of these compounds is directly related to the electron-withdrawing capability of the aryl substituents. When sufficiently activated, the amide bond in the heterocyclic ring can be cleaved by the enzyme, resulting in inhibition which is highly specific. The most potent inhibitor of human leukocyte elastase, the 2,4-dinitrophenyl derivative, has a Ki of 2.16 microM with elastase and 0.77 microM with chymotrypsin. This study demonstrates that it is possible to design specificity into non-peptide, low molecular weight serine protease inhibitors, which may have considerable pharmacologic potential.

Animals↗
PubMed1981

Bladder base impressions in women: "female prostate".

Bladder base impressions due to prostate hypertrophy are a common urographic finding in older males. A similar appearance may be occasionally seen in females and presents a more difficult diagnostic problem. Sixteen such cases of bladder base defects in females at two institutions were identified. The impressions were caused by symphysis pubis asymmetry, postoperative change, urethral diverticulum, levator ani impression, or "urethral syndrome." Vaginal fibromyoma, ectopic ureterocele, and intramural bladder neoplasm can also cause this defect, although no such cases were found in this series.

Female↗
PubMed1980

Insulin stimulates synthesis of soluble proteins in isolated rat hepatocytes.

The incorporation of [3H]leucine into soluble cellular protein was measured in isolated hepatocytes at extracellular leucine concentrations ranging from 0.15 to 20.0 mM. Insulin caused a 12--15% stimulation of [3H]leucine incorporation in the presence of high extracellular leucine concentrations. It is concluded that insulin causes a small but significant increase in the rate of hepatic protein synthesis.

Animals↗
PubMed1980

Novel morphogenesis in Ax-3, a mutant strain of the cellular slime mould Dictyostelium discoideum.

The cellular slime mould Dictyostelium discoideum constructs a succession of characteristic structures (grexes) in the multicellular phase of its life cycle. Compared with the wild-type strain, NC-4, grexes of a mutant strain, Ax-3, exhibited a profound prolongation of the early mound stage of development and a premature and exaggerated tendency to construct short, broad and bulbous forms. The aberrant Ax-3 phenotype was partially corrected by increasing the temperature of development, decreasing the plating density, perfusing with fresh air, or by introducing 0.1 nm-formycin B or 3-deazaadenosine into the agar. Mixtures of NC-4 and Ax-3 formed hybrid grexes which often became transformed into toruses by spiral centrifugal movement of the cells. Under other conditions, hybrid mounds developed into binary grex structures, cylindrical columns on top of hemispherical mounds, each component of which completed the morphogenetic sequence independently. The narrow upper structure appeared to be composed primarily of NC-4 cells. These novel patterns of morphogenesis support our hypothesis that the shape of the organism is controlled by the specification of the circumference of loops of cells within the grex.

Culture Media↗
PubMed1980

Mandatory retirement and labor-force participation of respondents in the Retirement History Study.

The Age Discrimination in Employment Act (ADEA) was amended in 1978 to prohibit mandatory retirement before age 70 in most occupations. The impact of this legislation on the probability of older persons remaining in the labor force is the primary concern of this article. Specifically, questions concerning which older workers are affected by mandatory-retirement provisions and the extent to which they are forced to retire and leave the labor force are examined. Tabular analysis of data from the Retirement History Study on persons aged 62-63 in 1969 shows significant variation in mandatory-retirement coverage between the public and private sectors and across industries, occupations, and demographic groups. Until age 65, the labor-force participation rate of those facing compulsory retirement is higher than or equal to that of those not covered but it drops significantly below the noncovered rate after 65. Logit analysis of the labor-force participation of persons before and after age 65 indicates that mandatory retirement at that age reduces the probability of retirement by approximately 16.7 percentage points for white men wage earners. This results in a decline in the labor-force participation rate of all men aged 66-67 of approximately 4 percentage points.

Age Factors↗
PubMed1980

The relation of experimental arthritis to the distribution of streptococcal cell wall fragments.

The intraperitoneal injection of peptidoglycan-carbohydrate fragments from Group A streptococci produces a chronic, polyarticular, erosive synovitis in rats. The cell wall material accumulates rapidly in the liver, spleen, and lymph nodes, where it causes little injury. At the same time, selective localization and persistence of the material in the synovial and periarticular tissues occurs. Its presence in the joint is associated with acute and recurrent inflammation with focal synotivitis, pannus formation, joint destruction, and ankylosis. Cell wall fragments become localized in the synovial and periarticular tissues at a time when there are leukocytes in the bloodstream, which appear to contain the material. During this early phase vascular lesions appear in the synovium and in periarticular tissues with collections of fibrin, neutrophils, macrophages, and cell wall fragments near the venules and capillaries. Recurrent episodes of inflammation and joint injury, associated with persistent cell wall antigen within macrophages, were observed over a period of 90 days.

Animals↗
PubMed1980

Cell-mediated immune response during experimental arthritis induced in rats with streptococcal cell walls.

Chronic, remittent, erosive arthritis was produced in rats by a single intraperitoneal injection of an aqueous suspension of cell wall fragments isolated from group A streptococci. Arthritis could be induced in rats which had been immunologically compromised by neonatal thymectomy. Delayed hypersensitivity to cell wall peptidoglycan could not be elicited in these rats, although progressive joint disease was obvious by clinical and radiological measurements. A delayed skin test was elicited with peptidoglycan in non-thymectomized rats at 6 to 14 days after injection of low doses of cell wall fragments. Between 2 to 4 weeks after cell wall injection the skin test could not be elicited and these rats could not be sensitized again with peptidoglycan. After a high dose of cell wall the skin test could not be elicited at any time. These non-thymectomized rats which had been injected with cell walls remained hyporesponsive to peptidoglycan for at least 3 months. Lymphocytes from non-thymectomized cell wall-injected rats also showed a non-specific depression of lymphocyte response to phytohaemagglutinin in vitro, but this function was recovered between 2 to 4 weeks after cell wall injection. We conclude that cell-mediated immunity against bacterial cell wall antigens is not a pathogenetic factor in this experimental model of arthritis.

Animals↗
PubMed1980

Allocation of time and resources by married couples approaching retirement.

The work and retirement decisions of husbands and wives are likely to be made jointly as they allocate their available resources. This article models the allocation of family wealth and family members' time over the lifetime of the unit. The first section reports simulation results that illustrate the relationship between the value of members' time in both market work and the production of home services. The model is then tested by means of the Retirement History Study for 1969-73. The estimation is conducted by employing a simultaneous logit model of labor-force participation by the husband and wife. Principal findings are: (1) Individuals respond positively to increases in their own wage rate but tend to reduce labor-force participation as the wage rate of their spouse increases, (2) the health of the husband is an important determinant of his labor-force participation, and (3) the probability that a person will be in the labor force is raised if the spouse is employed.

Aged↗