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Biomedical subjects

J R Lumb

Publications and source records attributed to J R Lumb.

15 recordsLinked to original sources
PubMed1987

Computer simulation of biological systems. Current trends.

The current status of mathematical models of biological systems is reviewed. Advances in supercomputer hardware allows more complex models to be constructed. The new generation of microcomputers are quite adequate for many computer simulations of biological systems. A theory of modeling is being developed to improve the relationship between the real biological system and the model. Deterministic models, stochastic models and applications of control theory and optimization methods are discussed. Examples given include models of molecular structure, of experimental techniques, and of biochemical reactions. It is recommended that experimental biologists consider the use of microcomputers to model the system under study as a part of their research program.

Computer Simulation↗
PubMed1987

The incidence of AIDS among blacks and Hispanics.

Compared with whites, the acquired immune deficiency syndrome (AIDS) has affected blacks and Hispanics disproportionately. The cumulative incidence (CI) for black men was 2.6, and for Hispanic men 2.5, times the rate for white men. Intravenous (IV) needle use alone does not account for this difference. Not counting IV needle-using cases, the CIs for black and Hispanic men were 1.7 times the CI for white men. Although there were fewer cases in women than men, the white-to-minority disparity was greater for women. The CIs for black and Hispanic women were 12.2 and 8.5 times, respectively, the CI for white women. Prevention programs are urgently needed and should focus on risky behavior (IV needle sharing and receptive anal intercourse), not just risk groups.

Acquired Immunodeficiency Syndrome↗
PubMed1986

AIDS statistics and the risk for minorities.

Analysis of the AIDS case data for the United States reported to the Centers for Disease Control reveals quite different risk group profiles for minorities and for whites. A much higher percentage of minority male AIDS cases are heterosexual, the ratio of bisexual to homosexual cases is two to three times higher, and IV needle use is a greater risk factor in minority populations. Among women and children with AIDS, 75% and 82% respectively are minorities. Whites at risk for AIDS tend to be concentrated in the gay community but blacks at risk for AIDS are dispersed throughout the entire community. As a result, AIDS education programs aimed a gay populations do not reach most of the minority populations at risk. AIDS prevention programs need to take this fact into account.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Effects of genetically different strains of mice on the microsomal activation of 2-aminofluorene.

Five strains of mice were examined for microsomal cytochrome P450 (Cyt P450) activity and ability of the microsomal preparation to activate 2-aminofluorene (2-AF) to its mutagenic form. Each strain was assayed under normal and induced conditions. Group A strains known to be easily induced to carcinogenesis by chemicals (C57BL/6J and BALB/cJ) showed higher levels of Cyt P450 and increased mutagenesis activity of the metabolized 2-AF than Group B strains which are known to be high spontaneous tumor producers (CE/J, A/HeJ, C3H/HeJ). Induction of the hepatic microsomes with Aroclor 1254 increased the difference between the two groups.

Animals↗
PubMed1982

A reinterpretation of phosphatase-N.

In order to determine the substrate specificity of the alkaline phosphatase (APase) which appears in murine lymphomas, two substrates were chosen. p-Nitrophenyl phosphatase (pNPP), the standard substrate, has an oxygen-phosphorus (O-P) bond. Cysteamine-S-phosphate (CASP) has a sulfur-phosphorus (S-P) bond. It has been reported that murine lymphoma APase does not cleave the S-P bond of CASP. These results were not confirmed. Under all conditions tested, the murine lymphoma APase showed consistent hydrolysis of CASP at approximately one-third the rate of hydrolysis of pNPP. Biochemical characteristics used to confirm this include pH optimum, heat inactivation, kinetics, magnesium activation, L-homoarginine inhibition, EDTA inhibition, and activity remaining during stages of partial purification. It is concluded that the murine lymphoma APase shows a preference of pNPP as a substrate but does hydrolyse CASP at a lower rate. The conflict between our laboratory and that of Neumann's may be one of interpretation rather than data. Neumann shows similar data to ours in terms of the 3-fold ratio, but considers all hydrolysis of CASP as representative of 'normal' APase. She uses a formula to calculate the amount of lymphoma APase based on the ratio 1.9 which is the ratio of hydrolysis of pNPP to that of CASP in kidney tissue. Our interpretation would be that the same isozyme is hydrolyzing the S-P bond at one-third the rate that it hydrolyzes the O-P bond.

4-Nitrophenylphosphatase↗
PubMed1979

Murine lymphoma alkaline phosphatase: a cell membrane carcinofetal enzyme.

Alkaline phosphatase (APase) has been shown to have a membrane-bound localization in the murine fetal thymus, in murine thymic lymphoma and in adult spleen. Since it was suggested from these previous experiments that the lymphoma APase might represent an embryonic function, a detailed biochemical comparison of the lymphoma APase with the fetal thymus, placenta, fetus and spleen APases was performed. The parameters investigated were pH optimum, activation, inhibition, heat inactivation, substrate ratios, Michaelis constant, and electrophoretic analysis in the presence and absence of neuraminidase with the substrates alpha-naphthyl phosphate, beta-glycerophosphate, and p-nitrophenyl phosphate. The results indicate that the lymphoma APase is very similar to the fetal thymus, placenta and spleen APases. Furthermore, these results lend support to the hypothesis that the APase activity which appears in thymic lymphoma might represent a derepressed embryonic function. Thus, the murine lymphoma APase may be termed a cell membrane carcinofetal enzyme.

Alkaline Phosphatase↗