Extracts from over 100 normal human placentas have been examined for RNA-directed DNA polymerase (DNA nucleotidyltransferase, EC 2.7.7.7) activity. More than 80% of these placentas contained this enzyme activity, which banded at a density of 1.15-1.17 g/ml in sucrose. After heat treatment, this enzyme activity was shifted in density to 1.22-1.24 g/ml. The enzymatic activity was greater with (rC)n.(dG)12-18 than with (dC)n.(dG)12-18 and was not stimulated by (dG)12-18 alone. The product of the endogenous reaction, which was sensitive to RNase, had the characteristics of a small DNA associated with a large RNA by hydrogen bonding. Electron microscopic inspection of the material with a density of 1.15-1.17 g/ml revealed numerous retrovirus-like particles with central electron-dense cores and double-membraned envelopes. The enzyme may be associated with the retrovirus-lik particles noted in the trophoblast layer of some human placentas.

Female↗

PubMed1978

Plasma activity of pyruvate kinase and glutamic oxalacetic transaminase as indices of myopathy in the vitamin E deficient rat.

Weanling rats were fed vitamin E deficient diets for 6 to 15 weeks and then given vitamin E orally for 4 days. Plasma obtained 1 day after the last dose was assayed for glutamic oxalacetic transaminase (GOT) and pyruvate kinase activity (PK). Administration of vitamin E resulted in reduction in activity of both enzymes. Plasma levels of alkaline phosphatase, lactic dehydrogenase, and bilirubin were unaffected by vitamin E and there was no histological evidence of liver degeneration. The number of phagocytized muscle fibers was greatly reduced by vitamin E treatment, but a substantial number of necrotic fibers were still present. With more prolonged (8 days) treatment, plasma PK and GOT levels were reduced to levels found in plasma of vitamin E replete animals and few degenerated muscle fibers could be observed. It was concluded that resolution of the necrotizing myopathy in vitamin E deficient rats is a rapid process and that the decreased activity of PK and GOT in plasma is a sensitive indicator of the resolution process. The decrease in plasma enzyme levels is an easily quantitated and reproducible biological response to vitamin E administration. Thus, this approach provides a basis for a sensitive and accurate bioassay for vitamin E activity.

Animals↗

PubMed1978

Lithium in diabetes mellitus: a paradoxical response.

An unusual hyperglycemic effect of lithium was observed in a patient suffering from diabetes mellitus and mania. In the presence of constant insulin dosage, high serum lithium levels were correlated with high fasting bloos sugar, while lowering of the lithium level led to a lowering the fasting blood sugar. These observations are discussed in terms of the effects of lithium on glucose metabolism and with particular emphasis on the ability of lithium to increase the release of glucagon.

Bipolar Disorder↗

PubMed1977

Deuterolysis of amino acid precursors: evidence for hydrogen cyanide polymers as protein ancestors.

Deuterolysis experiments suggest that hydrogen cyanide polymers rather than aminoacetonitriles are major precursors of alpha-amino acids obtained from spark reactions and other studies on chemical evolution. These results are consistent with the hypothesis that the original heteropolypeptides on the earth were synthesized spontaneously from hydrogen cyanide and water without the intervening formation of alpha-amino acids.

Amino Acids↗

PubMed1977