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Biomedical subjects

L Goldstein

Publications and source records attributed to L Goldstein.

At least 307 records · Page 17Linked to original sources
PubMed1967

Ornithine-urea cycle activity in xenopus laevis: adaptation in saline.

The concentration of urea in the blood and the rate of urea excretion were markedly elevated in Xenopus maintained in hypertonic saline for 2 to 3 weeks. These changes were accompanied by a twofold increase in the activity of the ornithine-urea cycle as measured in liver slices. The activity of carbamoyl phosphate synthetase rose threefold in frogs adapted to saline. These results suggest that changes in activities of urea cycle enzymes may be important in the adaptation of aquatic organisms to environments of varying salinities.

Adaptation, Physiological↗
PubMed1967

Lungfish Neoceratodus forsteri: activities of ornithine-urea cycle and enzymes.

The level of activity of the ornithine-urea cycle is low in the liver of the permanently aquatic Australian lungfish. The rate of incorporation of (14)C-bicarbonate into urea by liver slices was only 100th of that previously observed in the estivating African lungfish Protopterus dolloi. The activities of enzymes of the ornithine-urea cycle were similarly reduced. The low activity of this cycle in Neoceratodus is consistent with its exclusively aquatic nature.

Animals↗
PubMed1967

Nuclear-cytoplasmic interaction in DNA synthesis.

In Amoeba proteus the transplantation of a nucleus engaged in DNA synthesis into a G(2)-phase (after DNA synthesis) cell results in inhibition of such synthesis. When the nucleus of a G(2) cell is transplanted into an S-phase (period of DNA synthesis) cell, such a nucleus may begin to synthesize DNA.

Amoeba↗
PubMed1967

Proteins in nucleocytoplasmic interactions. I. The fundamental characteristics of the rapidly migrating proteins and the slow turnover proteins of the Amoeba proteus nucleus.

By the transplantation of amino acid-(3)H-labeled nuclei between cells and the subsequent isolation of nuclei for quantitative assay, we have confirmed that all the nuclear proteins of Amoeba proteus are divisible into two classes that are sharply defined by their physiological behavior. About 40% of the proteins in the nucleus rapidly migrates back and forth between the nucleus and the cytoplasm. These rapidly migrating proteins (RMP) are 25-50 times more concentrated in the nucleus than in the cytoplasm, and migration into the nucleus therefore occurs against a high concentration differential. The remaining 60% of nuclear proteins has been classified as slow turnover proteins (STP) since (as reported in a following paper) virtually all of them ultimately undergo turnover. Turnover in this context means loss of label from the nucleus, by either protein breakdown or protein migration to the cytoplasm. Isolation of nuclei in the detergent Triton X-100 results in a 20% loss of nuclear proteins but conclusions about RMP and STP were not found to be significantly affected by this loss.

Amino Acids↗
PubMed1966

Urea synthesis in the lungfish: relative importance of purine and ornithine cycle pathways.

The relative importance of the purine pathway (uricolysis) and the ornithine cycle as routes for urea synthesis was assessed in isolated liver preparations from the African lungfish Protopterus dolloi. Incorporation of C(14)-labeled precursors into urea was used for comparison. Both pathways are present in the lungfish, but the ornithine cycle is quantitatively more important.

Animals↗