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Biomedical subjects

M Jacobs

Publications and source records attributed to M Jacobs.

At least 253 records · Page 14Linked to original sources
PubMed1981

Toxicological effects of sodium selenite in Sprague-Dawley rats.

Acute and chronic effects of Se as sodium selenite given as a supplement in the drinking water of Sprague-Dawley rats for 35 d, 1 yr, and 2 yr are compared. For the 35-d study the experimental groups were untreated controls and rats supplemented with 1, 4, 8, 16, and 64 ppm Se. Survival was 100% in the control and 1 and 4 ppm groups, decreased in the 8 and 16 ppm groups, and was zero in the 64 ppm group. Body weights increased and were equivalent in the control and 1 and 4 ppm groups and substantially decreased in the 16 and 64 ppm groups., Serum alkaline phosphatase and glutamic-oxaloacetic transaminase (SGOT) increased with 16 ppm Se and higher supplements. Se toxicity was apparent in microscopic pathology showing liver congestion, fatty degeneration of parenchymal cells, and necrosis. In the chronic studies untreated controls are compared with rate receiving 4 ppm Se in the drinking water. In general, the weight gains throughout were equivalent for both groups. The 1-yr survival in each was above 90% and the 2-yr survival above 50%. With increased age there was a slight reduction in hemoglobin and white blood cells. The latter effect was greater in Se-treated then in control rats. Several serum components were equivalent in both groups, including alkaline and acid phosphatase, SGOT, protein, glucose, and sialic acid. Liver glutathione peroxidase was half and Se levels in the Se-treated rats were twice those in the controls. Data are presented for male rats in the chronic study with occasional reference to data on females. The parameters measured in the chronic study are highly dependent on the age of the rat when Se-supplemented drinking water is initiated.

Age Factors↗
PubMed1981

Toxicological effects of sodium selenite in Swiss mice.

Se as sodium selenite was administered by gavage (three consecutive times) and as drinking water supplements for 46 d to male and female Swiss mice. With respect to survival in 7-wk-old mice, Se was less toxic in males than in females when gavaged. Drinking water supplements of 1-64 ppm Se resulted in 1 male and 1 female death in mice first given Se at 7 wk of age. Se supplements to the drinking water of adult (18-wk-old) mice was less toxic in females. All young (7-wk-old) and adult (18-wk-old) mice provided 1-16 ppm Se in the drinking water survived the 46-d treatment, but in adult mice 64 ppm Se significantly reduced survival. Only 64 ppm Se supplements caused a sharp reduction in body weight in young and adult mice of both sexes. Supplements of 1-8 ppm Se in all mice elicited growth responses similar to those of untreated controls. Occasional liver and kidney congestion, liver necrosis, parenchymal cell degeneration, and bile duct proliferation were observed in control and treatment groups. Serum alkaline phosphatase and glutamic-oxaloacetic transaminase (SGOT) increased with 32 ppm Se and higher supplements. Survival, growth, serum enzymes, and pathology were normal in untreated controls and in mice of growth ages and sexes give 1, 4, and 8 ppm Se supplements. A chronic toxicity study was conducted in female Swiss mice given 1, 4, and 8 ppm Se supplements for 50 wk. The survival of Se-treated groups was more than 90% and that of controls was only 72% after 50 wk. All mice gained weight, but the group treated with 8 ppm Se gained half as much as other groups. Both liver Se and glutathione peroxidase activity increased in Se-treated mice compared to controls at 25 and 50 wk. A reduced white blood cell count and increased alkaline phosphatase and SGOT suggested a mild toxic effect of the 8 ppm Se supplement in the chronic study.

Alkaline Phosphatase↗
PubMed1981

Health and housing: a historical examination of alternative perspectives.

The deleterious effect of low-quality housing and related environmental factors on the physical and mental health of its residents is a widely accepted phenomenon. Yet low-quality housing continues to exist, partly because of the nature of housing as a commodity in a capitalist system. This paper defines three political-analytic perspectives within which the housing-health relationship can be seen: individualistic, reformist, and dialectical-materialist. These approaches incorporate perspectives on the nature of the relationship as well as strategic implications arising from them. In this context, the housing-health relationship is examined in fact and interpretation from the 1840s to the present. All three perspectives are illustrated by various popular analyses of changes in urban form and housing as well as the housing-health relationship. The dependence of housing quality on the mode of production is shown, demonstrating the weaknesses of the individualistic and reformist perspectives, which assume housing quality to be independent of the mode of production. The different strategic implications of the three perspectives are illustrated in the conclusion in a discussion of the case of lead paint poisoning.

Environmental Health↗
PubMed1981

Uniform admissions system for a medical laboratory sciences program.

A system for selection of medical technology students has been developed that features numerical ranking of applicants according to a uniform point system. Each applicant is quantitatively evaluated on achievement of academic and non-academic criteria identified as predictors of success in the student program and in clinical practice. This admissions system has been statistically evaluated by comparing admissions data for 59 graduates with subsequent measures of success during the program and in their first professional employment. The academic and non-academic predictors used in this system describe separate sets of applicant characteristics and appear to be effective as predictors of success. Academic and non-academic predictors are found to function independently of each other as predictors of success in the academic aspects of the program and in the clinical, non-cognitive aspects of both the student program and subsequent professional practice, respectively.

Educational Measurement↗
PubMed1980

Vanadate inhibition of auxin-enhanced H secretion and elongation in pea epicotyls and oat coleoptiles.

In experiments carried out to investigate the acid secretion theory of auxin action, we utilized sodium orthovanadate, an agent found to be a selective inhibitor of a plasma membrane-associated H(+)-pumping ATPase in Neurospora [Bowman, B. J. & Slayman, C. W. (1979) J. Biol. Chem. 245, 2928-2934]. At 1 mM, vanadate inhibited auxin-enhanced medium acidification by pea epicotyl segments within 5 min, whether added 0.5 or 2.5 hr after auxin. Inhibition of acidification was total after 10-15 min but could be reversed within 10 min after vanadate removal. When given as a 40-min pretreatment, vanadate completely prevented any auxin-enhanced acidification. Vanadate inhibition of medium acidification by oat coleoptile segments was also total and reversible, but both inhibition and reversal occurred after longer lag times than in pea. Inhibitory effects of vanadate on elongation in pea and oat tissue closely paralleled its effects on acidification, and the inhibitory effect of vanadate on elongation could be reversed by an acidic buffer. Vanadate did not inhibit respiration or protein synthesis in pea epicotyl segments, although it strongly inhibited L-[(14)C]leucine uptake. These results indicate the importance of cell wall acidification for short- and long-term auxin-enhanced growth and suggest the participation in wall acidification of a plasma membrane-associated ATPase acting as an H(+) pump.

Journal Article↗
PubMed1979

Tubulin-associated nucleoside diphosphokinase.

Microtubule protein, prepared by cycles of polymerisation and dissociation, contained a nucleoside diphosphokinase (NDP kinase) activity (EC 2.7.4.6). This activity was not intrinsic to the tubulin dimer or the so-called microtubule-associated proteins. The NDP kinase had the following properties. (1) The enzyme existed in a low-molecular-weight form and in association with the complex of microtubule-associated proteins and tubulin (i.e. multimeric tubulin). (2) The low-molecular-weight species was also formed by dissociation of multimeric tubulin by salt or by removal of microtubule-associated proteins on phosphocellulose. (3) GDP bound to the exchangeable site of multimeric tubulin and also GDP derived from the E site of the tubulin dimer was a substrate for the NDP kinase. (4) The NDP kinase showed a 7-fold increase in activity during ATP-dependent microtubule assembly. On the basis of these properties, it is proposed that microtubule protein contains an NDP kinase specifically associated with tubulin and its functions.

Adenosine Triphosphate↗