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Biomedical subjects

J Berndt

Publications and source records attributed to J Berndt.

At least 37 records · Page 2Linked to original sources
PubMed1983

Participation of pterins in the control of lymphocyte stimulation and lymphoblast proliferation.

Biopterin accumulation had been demonstrated as the result of normal and, especially, of malignant hemopoietic cell proliferation (Ziegler, I. et al. Blut, 44: 231-240, and 261-270, 1982). Among 13 major intermediates of pterin metabolism and two lumazines, xanthopterin (but not dihydroxanthopterin) was found to inhibit cell proliferation (half-maximum inhibition at 1.8 X 10(-5) M) during concanavalin A-induced lymphocyte activation in pre-stimulated lymphocytes and in a lymphoid cell line grown in continuous culture (LS-2). LS-2 cells exposed to maximum inhibitor concentrations largely maintained the initial thymidine incorporation rate for about 40 hr but failed to enter logarithmic growth. Isoxanthopterin inhibition was found only in serum-free medium, since it is trapped by the alpha-acid glycoprotein present in the serum. The reduced biopterin derivatives, sepiapterin, dihydrobiopterin, and tetrahydrobiopterin, are costimulators during concanavalin A-induced lymphocyte activation. Their costimulatory effect follows an optimum curve and peaks at 1.5 to 3 X 10(-5) M. It is highest at the suboptimal and supraoptimal concanavalin A concentration. The D-erythro isomer dihydroneopterin was inactive. The results indicate that the anabolic-reduced biopterin derivatives are not simply lymphocytic products, but, in combination with the catabolites xanthopterin and isoxanthopterin, they also participate in the regulation of lymphocyte activation. Hence, they fulfill the criteria for lymphokines.

Animals↗
PubMed1982

Differential effects of environmental chemicals on liposomal bilayers. Fluorescence polarization and pesticide-lipid association studies.

The thermal dependence of the fluorescence polarization of 1,6-diphenylhexatriene was recorded upon interaction of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and some other pesticides with dipalmitoylphosphatidylcholine liposomes. Differential effects on the gel-crystalline phase were observed. Most substances decreased probe polarization; pentachlorophenol caused an increase of this parameter. The DDT-induced change of polarization was also dependent on the vesicle concentration thus indicating the influence of light scattering. The amount of DDT and pentachlorophenol residing in the lipid bilayer was determined to confirm the localization in the membrane. Correlation with the effects on probe polarization was obtained. The difference in response of the fluorescent probe to the presence of foreign molecules in the lipid bilayer may reflect different modes of interaction.

DDT↗
PubMed1982

Age-related differences in dietary regulation of lipogenic enzymes in rat liver.

The activity of lipogenic enzymes in rat liver decreases during fasting and is increased on subsequent refeeding. There are considerable age-related differences in the activities of the lipogenic enzymes on dietary manipulation. On refeeding starved animals with either a standard diet or with a high-sucrose, fat-free diet, the increase of the activities was much greater in young animals than in old ones. Old animals exhibited a hyperlipoproteinemia and the activities of their lipogenic enzymes were decreased. The present results, together with reports in the literature, make it likely that the diminished activity of lipogenesis in old animals is a function of adipositas rather than of age.

ATP Citrate (pro-S)-Lyase↗
PubMed1981

Effect of unsaturated fatty acids on the biosynthesis of glucose-repressed enzymes in yeast.

In anaerobically glucose-grown yeast isocitrate lyase (EC 4.1.3.1.), and malate dehydrogenase (EC 1.1.1.37.) are repressed by glucose. 24 h cultures still contain 0.3--0.4% glucose in the medium, which is enough to completely repress these activities. Aeration of these cells, in buffer containing acetate, initiates the formation of the three enzymes. Within 16 h, the specific activities of these enzymes increase about 140, 120 and 70-fold, respectively. Glucose-6-phosphate dehydrogenase activity was not altered. When the yeast was grown anaerobically, but with a supplement of an unsaturated fatty acid in the medium, synthesis of the three enzymes was much faster and the specific activities after 16 h of derepression were considerably higher. A relationship exists between the number of double bonds in the unsaturated fatty acid molecule and its capability to stimulate enzyme synthesis: linolenic acid is more effective than linoleic acid, which, in turn, is much more effective than oleic acid. Increasing periods of aeration with glucose of anaerobically grown cells prior to derepression results in an increasing stimulation of enzyme synthesis on subsequent derepression. Anaerobic incubation of yeast in the presence of an unsaturated fatty acid in advance to derepression also increased the velocity of enzyme formation. It is suggested that during the aeration period with glucose and during anaerobic incubation with an unsaturated fatty acid a more active protein synthesizing apparatus was formed.

Fatty Acids, Unsaturated↗
PubMed1981

In vivo effect of cholesterol feeding on the short term regulation of hepatic hydroxymethylglutaryl coenzyme A reductase during the diurnal cycle.

Light-dark-cycled rats were fed a 3% cholesterol-supplemented diet at the beginning of the dark phase. Cholesterol-fed and control animals were taken at intervals throughout the following 12 h and the microsomal and solubilized hepatic 3-hydroxy-3-methylglutaryl coenzyme A reductase was isolated. Immunotitrations of this microsomal and solubilized enzyme were performed with a monospecific antibody to 3-hydroxy-3-methylglutaryl coenzyme A reductase. In contrast to the specific activity of the enzyme, which differs extremely during the diurnal cycle, the immunotitrations obtained from cholesterol-fed and control animals, yielded in identical antisera equivalence points. On the other hand, when the enzyme was phosphorylated in vitro, the antisera equivalence points corresponded to the alterations of the specific activity. In contrast to the results published by Higgins and Rudney ((1973) Nature New Biol. 246, 60-61), our data prove that even the in vivo short term changes in enzyme activity are due to changes in the quantity of enzyme rather than to a modulation of the catalytic activity.

Animals↗
PubMed1981

Interaction of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane with liposomal phospholipids.

The influence of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and several other pesticides on the physical state of membrane phospholipids was investigated using model lipids. The thermal dependence of fluorescence intensity of the probe parinaric acid in dipalmitoylphosphatidylcholine liposomes and lipid vesicles of mixed composition were recorded. DDT was incorporated into the liposomal bilayer. The insecticide lowered the phase transition temperature and broadened the temperature range of the transition. The effects were concentration-dependent. The results may be interpreted as a sort of blurred and facilitated phase transition of bilayer lipids caused by intercalation of DDT between fatty acyl chains of membrane phospholipids.

DDT↗
PubMed1980

Effect of unsaturated fatty acids on sterol biosynthesis in yeast.

Lipid-depleted yeast, grown anaerobically, contains only very low amounts of sterols. The hydroxymethylglutaryl-CoA reductase activity, the regulatory enzyme of sterol synthesis in yeast, is also low. Aeration of such cells in a buffer containing a carbon source induces hydroxymethylglutaryl-CoA reductase activity and increases sterol synthesis. The velocity of the increase depends on the carbon source present during the aeration period. Glucose and sugars that are easily converted to glucose were found to be most effective. A supplement of unsaturated fatty acids during anaerobic growth causes a several-fold greater velocity of the enzyme induction and of sterol biosynthesis. Linolenic acid (30 microM) accelerated sterol biosynthesis about 7-fold. Activities of galactokinase and galactose-1-phosphate uridyltransferase, which are involved in the conversion of galactose to glucose, increased several-fold in the supplemented cells within 6 h of aeration, concomitantly with stimulation of sterol synthesis from galactose. It is suggested that the stimulation of enzyme induction and sterol biosynthesis in fatty acid supplemented cells is due to a completion of the protein-synthesizing apparatus during cell growth. A markedly enhanced capacity of these cells to incorporate leucine into acid-precipitable protein supports this assumption.

Acetates↗
PubMed1979

Respiratory syncytial virus infection in inbred mice.

Respiratory syncytial virus infected the nose and lungs of each of 20 strains of inbred mice, with viral titers varying 100-fold from least permissive to most permissive strains. Viral titers appeared to be under genetic control, but did not correlate with the H-2 haplotype.

Animals↗