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Biomedical subjects

C M Allen

Publications and source records attributed to C M Allen.

At least 145 records · Page 8Linked to original sources
PubMed1982

Evidence that poly(ADP-ribose) polymerase is involved in the loss of NAD from cultured rat liver cells.

Rat hepatocytes cultured from 24h lose 60% of their NAD content. By using the differential response to inhibitors of the two major enzymes that catabolize NAD in mammalian cells, it is shown that poly(ADP-ribose) polymerase is responsible for the loss of NAD. The relevance of this observation to the use of cultured hepatocytes for the study of DNA repair induced by carcinogens is discussed.

Animals↗
PubMed1981

On the exponent in the "generalized" matching equation.

A power function equation between ratios of behavior and ratios of reinforcement rates has been called a generalized form of Herrnstein's (1961) matching law, even without a formal relationship having been shown between the two equations. The present work uses a functional relationship to prove that when ratios of reinforcement are not equivalent to ratios of behavior, and the transform leading to this inequality is consistent for every pair of reinforcement rates, the result is a power function relationship between response and reinforcement ratios. The label "generalized matching equation" for the power function equation is thus validated formally.

Journal Article↗
PubMed1981

Vasopressin secretion in the New Zealand genetically hypertensive rat.

A study was undertaken to evaluate the role of vasopressin in the pathogenesis of hypertension in New Zealand genetically hypertensive (NZGH) rats. During the course of development of hypertension in NZGH rats from 4 to 11 weeks of age, the 24 h urinary excretion of vasopressin did not differ from that of the New Zealand normotensive control rats (NZNR). Furthermore, at the conclusion of the study (rats 13 to 14 weeks old), the plasma vasopressin concentrations in NZGH and NZNR rats were not significantly different. Although there was no evidence for a difference in secretion of vasopressin from the neurohypophysis in the NZGH rats, there was a substantially increased pressor responsiveness to vasopressin in these rats. This was not specific since NZGH rats also had an increased pressor responsiveness to angiotensin II. The importance of increased pressor responsiveness to vasopressin in the hypertensive process in the NZGH rat requires further study.

Angiotensin II↗
PubMed1980

Lipid activation of undecaprenol kinase from Lactobacillus plantarum.

Extraction of membranes of Lactobacillus plantarum with Triton X-100/glycerol solubilized up to 80% of the undecaprenol kinase activity. Fractionation of the extract by gel chromatography separated endogenous phospholipid from the enzyme but simultaneously inactivated the enzyme. The kinase was reactivated by reconstitution with various synthetic phosphatidylcholines and purified L. plantarum phospholipids. Ditetradecanoylphosphatidylcholine and lysylphosphatidylglycerol were the best activators. Furthermore, the optimal environment for enzyme stimulation was provided by different defined molar ratios of Triton X-100/phospholipid. The ratios for the phospholipids tested ranged from 1.25 to 6.3. Similar substrate specificity and kinetic constants were observed for both the solubilized and reconstituted enzymes suggesting that no fundamental changes in the enzyme activity occurred during the delipidation-reconstitution process.

Enzyme Activation↗
PubMed1979

Hydrophobic chromatography of prenyl transferases.

Several prenyl transferases were examined with respect to their affinity for C0--C10 alkyl-Agarose columns. C10-alkyl Agarose was effective in adsorbing each of the prenyl transferases tested but only undecaprenyl pyrophosphate and octaprenyl pyrophosphate synthetases could be effectively eluted with Triton X-100.

Chromatography, Affinity↗
PubMed1979

Characterization of undecaprenol kinase from Lactobacillus plantarum.

A membrane-bound undecaprenol kinase from Lactobacillus has been identified by observing the ATP-dependent phosphorylation of [14C]undercaprenol. The product of this reaction was shown to be [14C]undecaprenyl monophosphate by comparison of its chromatographic mobilities with authentic undecaprenyl monophosphate. It was shown that 32P from [gamma-32P]ATP was incorporated into undecaprenyl monophosphate. The kinase was partially solubilized by a variety of methods utilizing Triton X-100. Both the membrane-associated and solubilized enzymes required Mg2+, Triton X-100 and dimethylsulfoxide for activity. The enzyme preferentially phosphorylated the C34, C50 AND C 55 polyprenols. Geranylgeraniol (C20) and dolichol (C100), however, were utilized only 6% and 13% as well as undecaprenol, respectively. Despite the 8-fold difference in apparent V values, the apparent Km values for dolichol and undecaprenol were both 14 microM. The apparent Km for the nucleotide cosubstrate, ATP, was 2 mM. No other nucleoside triphosphate could substitute for ATP.

Diterpenes↗
PubMed1978

Hemoglobin concentration in white, black, and Oriental children: is there a need for separate criteria in screening for anemia?

The concentration of hemoglobin in blacks was found to be 0.5 to 1.0 g/dl lower than that of income-matched whites in several large surveys. This difference could be a racial characteristic of blacks, or it might be due to a higher frequency of genetic traits such as thalassemia minor and hemoglobinopathies, or to environmental factors such as iron deficiency. To help in making this distinction, we analyzed the data from multiphasic examinations (1973 to 1975) on 1718 white, 741 black, and 315 Oriental healthy, nonindigent children between 5 and 14 years of age. In the entire population, the median hemoglobin concentration averaged 0.5 g/dl lower in blacks than in whites of both sexes (t test, P less than 0.001). The differences still averaged 0.5 g/dl (P less than 0.001) after exclusion of all those with abnormal hemoglobin by electrophoresis (Hgb S and C) and those whose mean corpuscular volume was more than 5% below the normal mean for age (to exclude iron deficiency or thalassemia minor). The data strengthen the impression that blacks normally have a concentration of hemoglobin averaging about 0.5 g/dl less than in whites. If this is the case, about 10% of normal blacks will be mistakenly designated anemic, if the same norms are applied.

Adolescent↗
PubMed1977

Pathoradiologic correlation of pulmonary candidiasis in immunosuppressed patients.

The diagnosis of pulmonary candidiasis can only be made with certainty when tissue invasion by the organism is demonstrated histologically. In order to ascertain whether characteristic radiographic patterns are seen in patients with pulmonary candidiasis, antemortem radiographic abnormalities were correlated with autopsy findings in 25 immunosuppressed patients who had histoinvasive pulmonary candidiasis. Pathological analysis enabled division of patients by route of infection into hematogenous and endobronchial groups, characterized by disseminated nodules and patchy bronchopneumonia, respectively. However, no specific radiographic patterns emerged in either patient group due to the small size of lesions and the high frequency of other pulmonary infections, edema, and hemorrhage. Since the radiographic patterns described for other opportunistic fungi do not appear to apply to this organism, a decision to institute antifungal therapy should not await evolution of radiographic changes.

Candidiasis↗