Search PubMed⌕ Search

Biomedical subjects

J Berndt

Publications and source records attributed to J Berndt.

At least 55 records · Page 3Linked to original sources
PubMed1978

Interaction of peripheral and central respiratory drives in cats. I. Effects of sodium cyanide as a peripheral chemoreceptor stimulus at different levels of CSF pH.

In cats anesthetized with chloralose-urethane, the central respiratory chemoreceptors were exposed to mock CSF of pH 7.02, 7.02, or 7.57. The right carotid body was simultaneously stimulated by intracarotid injections of 40, 80, or 160 microgram sodium cyanide in 200 microliter Ringer solution. The left carotid nerve and, in some animals, both vagosympathetic truncs were dissected. It could be demonstrated that the increase in ventilation produced by application of NaCN to the peripheral chemoreceptors is significantly larger at high than at low mock CSF pH (i.e. at low than at high central stimulus intensity). In vagotomized cats the responses of VT and V to NaCN similarly depend upon CSF pH; they are somewhat larger, though, than in intact animals. These results are discussed as compared with results reported by different authors.

Animals↗
PubMed1978

Mode of action of the lipid-lowering agents, clofibrate and BM 15075, on cholesterol biosynthesis in rat liver.

When rats were fed a diet containing 0.3% clofibrate or a derivative of this drug, BM 15075, serum cholesterol was lowered within 3-7 days by 26-38%. Both drugs diminished the activity of hydroxymethylglutaryl CoA reductase, the regulatory enzyme of hepatic cholesterol biosynthesis, in rat liver microsomes by about 60% under the same conditions. The decrease in the activity of the enzyme obviously is due to changes in the amount of enzyme protein. Under in vitro conditions microsomal hydroxymethylglutaryl CoA reductase was inhibited competitively by (1.35 mM) clofibric acid (sodium salt) and by BM 15075 (1 mM) with respect to its substrate. These results give evidence that these drugs can affect both, the rate of synthesis and the substrate affinity of hydroxymethylglutaryl CoA reductase.

Animals↗
PubMed1976

Activation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase in vitro.

Hydroxymethylglutaryl coenzyme A reductase, the regulatory enzyme of cholesterol biosynthesis, was activated by in-vitro incubation of mouse liver microsomes with an artificial system consisting of Na2SO3, MgCl2 and EDTA. The extent and the time course of the activation were very similar to those observed with a 105 000 x g liver supernatant. Throughout its diurnal rhythm hydroxymethylglutaryl-CoA reductase was activated about threefold, while after cholesterol feeding the extent of activation was diminished but was not abolished. The activation could be inhibited by 0.1M fluoride, indicating that a phosphatase might be involved in the activation process.

Alcohol Oxidoreductases↗
PubMed1975

Sterol biosynthesis in yeast. 3-Hydorxy-3-methylglutaryl-Coenzyme A reductase as a regulatory enzyme.

Anaerobically and aerobically grown yeast contains 3-hydroxy-3-methylglutaryl-CoA reductase, which is located in the mitochondrial fraction of the cell. Anaerobically grown yeast has a low specific activity of 3-hydroxy-3-methylglutaryl-CoA reductase and a low sterol content. Aeration of this yeast in buffer, without growth, results in an increase in the specific activity of the enzyme, which is paralleled by an increase in the sterol content. This induction has an oscillatory profile with yeast grown anaerobically for 24 h and a linear pattern with cells grown anaerobically for 72 h. With the latter type of yeast, glucose is necessary for an induction, whereas with the other yeast an induction occurs with and without glucose. By an anaerobic incubation in buffer of the yeast grown anaerobically for 24 h, the oscillatory profile can be transformed into a linear one. The extent of induction of the reductase is strictly dependent on the concentration of glucose present. Sterols increase in whole cells, but they do not increase in the mitochondrial fraction. The induction of 3-hydroxy-3-methylglutaryl-CoA reductase is strongly inhibited by cycloheximide, but is not affected by chloramphenicol. The induction of the enzyme is closely connected with the glucose metabolism of the cell; fructose, mannose, and ethanol can also induce the reductase.

Aerobiosis↗