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Biomedical subjects

F Stirpe

Publications and source records attributed to F Stirpe.

At least 181 records · Page 10Linked to original sources
PubMed1971

Effect of alpha-amanitin on ribonucleic acid polymerase II of rat brain nuclei and on retention of avoidance conditioning.

1. alpha-Amanitin inhibits in vitro the activity of RNA polymerase II of rat brain nuclei. 2. The toxin does not pass the blood-brain barrier, but when injected intracerebrally is highly toxic for rats, and causes inhibition of RNA polymerase II of isolated brain nuclei. 3. Intracerebral injection of alpha-amanitin 6h before training to a passive avoidance task is followed by impaired performance of rats on retesting after 7 days, without affecting performance on retesting immediately after training.

Animals↗
PubMed1970

Inhibition by alpha-amanitin of ribonucleic acid polymerase solubilized from rat liver nuclei.

1. alpha-Amanitin inhibits in vitro the RNA polymerase solubilized from isolated rat liver nuclei. 2. In contrast with previous observations with whole nuclei, the inhibition occurs approximately to the same extent in the presence and in the absence of ammonium sulphate. 3. Evidence is presented that the toxin acts by interacting with the enzyme itself and not with DNA or other components.

Animals↗
PubMed1970

The regulation of xanthine oxidase. Inhibition by reduced nicotinamide-adenine dinucleotide of rat liver xanthine oxidase type D and of chick liver xanthine dehydrogenase.

1. Rat liver xanthine oxidase type D (NAD(+)-dependent) and chick liver xanthine oxidase are inhibited by NADH, which competes with NAD(+). 2. The addition of a NADH-reoxidizing system in the assay of these enzyme activities is proposed. 3. Rat liver xanthine oxidase type O (oxygen-dependent) is not affected by NADH.

Animals↗
PubMed1969

The effects of copper and other ions on the ribonucleic acid polymerase activity of isolated rat liver nuclei.

1. The effects of various ions on the Mg(2+)- and Mn(2+)/ammonium sulphate-activated RNA polymerase activities of isolated liver nuclei were studied. 2. The Mg(2+)-activated RNA polymerase reaction was inhibited by more than 60% by Cd(2+), SeO(3) (2-), Be(2+), Cu(2+), Co(2+), Ca(2+) and La(3+), all at 1mm concentrations. 3. The Mn(2+)/ammonium sulphate-activated RNA polymerase reaction was strongly inhibited by Hg(2+), Cd(2+), Cu(2+) and Ag(+). The effect of Hg(2+), Cd(2+) and Ag(+) was relieved by cysteine or mercaptoethanol. 4. Inhibition by Cu(2+) was not affected by addition of DNA, and was relieved only partially by EDTA or histidine. 5. No changes of RNA polymerase activities were observed in nuclei isolated from the liver of rats treated with copper albuminate.

Animals↗
PubMed1969

Experimental conditions affecting ribonucleic acid polymerase in isolated rat liver nuclei. Effect of nucleoside triphosphate concentration, temperature, ammonium sulphate and heparin.

1. The conditions affecting the activity of RNA polymerase in isolated rat liver nuclei were studied with Mg(2+) or Mn(2+) as activating ions. 2. The enzyme assayed with Mg(2+) and at low ionic strength is saturated by a lower concentration of nucleotide substrates than if assayed with Mn(2+) at low ionic strength or with either ion at high ionic strength. 3. At low and at high ionic strength the incorporation of AMP is affected in a similar way by variations in the temperature of incubation. Preincubation at 37 degrees impairs the AMP incorporation. 4. Heparin stimulates the RNA polymerase activity in the presence of Mn(2+). 5. Both ammonium sulphate and heparin ;restart' the reaction if added after 15min., the effect being more marked with ammonium sulphate than with heparin, and also more marked in the presence of Mn(2+) than of Mg(2+). 6. alpha-Amanitin abolishes the effect of ammonium sulphate and of heparin.

Adenine Nucleotides↗
PubMed1969

The regulation of L-asparaginase activity in rats and mice. Effects of normal and malignant growth, of sex and of dietary changes.

1. The activity of l-asparaginase was very low in the liver of newborn rats and mice, and increased within a few days of birth. 2. In rats, but not in mice, the enzyme activity was higher in females than in males, was enhanced by administration of oestradiol, and was decreased by gonadectomy. 3. The enzyme activity decreased in mice starved or fed on a low-protein diet; in rats it was enhanced by starvation, by feeding them on a high-protein diet, or by administration of l-asparagine. 4. The asparaginase activity was decreased in regenerating liver, and was almost absent in the Morris hepatoma 5123.

Age Factors↗
PubMed1968

Activity of nicotinamide-adenine dinucleotide pyrophosphorylase in liver nuclei. Effects of partial hepatectomy, hepatotoxins and dietary changes.

1. The activity of NAD pyrophosphorylase is lower in nuclei isolated from regenerating rat liver than in normal nuclei, and this is due to leakage of the enzyme from the nuclei during the isolation. 2. The NAD pyrophosphorylase activity is lower in liver nuclei from newborn rats, and from rats on a protein-free diet, but no leakage occurs in these cases. 3. Poisoning with alpha-amanitin brings about a transient enhancement of NAD pyrophosphorylase activity in mouse liver nuclei. 4. No changes of enzyme activity were observed after 72hr. starvation, administration of actinomycin D or infection with MHV3 virus.

Animals↗