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G S Getz

Publications and source records attributed to G S Getz.

At least 127 records · Page 7Linked to original sources
PubMed1973

Changes in kidney medullary phospholipid metabolism in the potassium-deficient rat. I.

Renal medullary phospholipids (PLs) increase rapidly in rats placed on a low potassium (K) diet. There is a unique pattern of morphologic change in renal medullary cells which parallels this biochemical alteration. Highly membranous multivesicular bodies (MVBs) appear in all cell types of the kidney medulla, and the number and size of these MVBs increase with further K depletion. Medullary PL levels are doubled in rats after 11 days on the low K diet and continued increase occurs with longer depletion. There are no major changes in the relative proportion of different medullary PL species with this increase. The rise in PL levels is quickly reversed by the addition of K to the low K diet of depleted rats. Potassium repletion returns renal medullary PL levels to normal values with a concomitant rapid loss of MVBs from medullary cells. Tissue slices of kidney medulla from rats in various stages of K depletion have been incubated with radioactive precursors of PL. These incubation studies indicate that the in vitro ability to incorporate label into PL is increased in medulla from K-depleted animals, suggesting that increased renal medullary PL synthesis causes the PL accumulation in K deficiency.

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PubMed1973

Changes in kidney medullary phospholipid metabolism in the potassium-depleted rat. II.

In vivo studies of renal medullary phospholipid (PL) turnover in control, potassium (K)-depleted, and K-repleted rats have been performed following intravenous administration of radioactive glycerol. These studies show an identity in turnover of the PL-glycerol moiety derived from medulla of normal and depleted animals. This turnover identity supports the idea that increased PL synthesis is the cause of the PL accumulation occurring with K depletion. In K repletion, PL-glycerol turnover increases while tissue PL levels decline, indicating that accelerated PL breakdown removes the PL which had accumulated within renal medullary cells of K-depleted animals.

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PubMed1972

The metabolism of proinsulin and insulin by the liver.

The removal of bovine proinsulin by the isolated perfused rat liver has been studied and the results compared with the removal of insulin. At high concentrations of insulin (> 180 ng/ml) the removal process was saturated and the t(1/2) varied between 35 and 56 min. With low initial insulin levels the disappearance followed first-order kinetics, the mean regression coefficient being - 0.022, t(1/2) 13.8 min, and the hepatic extraction 4.0 ml/min. The results with proinsulin were in striking contrast to these findings. At both high and low concentrations the hepatic removal of proinsulin was considerably slower, averaging 10-15 times less than that of insulin. Specific immunoassay techniques and gel filtration of samples taken from perfusions to which both labeled and unlabeled proinsulin had been added did not show conversion to either insulin or the C-peptide. Bovine and rat (131)I-labeled proinsulins were degraded more slowly than bovine insulin-(131)I by bovine and rat liver homogenates. Both proinsulin and insulin inhibited the degradation of insulin-(131)I, equimolar quantities of proinsulin being 2-5 times less effective than insulin. These results indicate significant differences in the capacity of the liver to remove and degrade insulin and proinsulin. The low hepatic extraction of proinsulin may account for its prolonged half-life in vivo and contribute to its relatively high plasma concentration in the fasting state. Furthermore this finding will have to be taken into account in the interpretation of changes in the proinsulin:insulin ratios in peripheral blood in a variety of metabolich situations.

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PubMed1971

Mitochondrial development in liver of foetal and newborn rats.

THE DEVELOPMENT OF THE INNER MITOCHONDRIAL MEMBRANE IN FOETAL AND NEONATAL RAT LIVER WAS STUDIED BY FOLLOWING THREE PARAMETERS: (1) the activity of several respiratory enzymes in homogenates and purified mitochondria, (2) the spectrophotometric determination of cytochrome content in the mitochondria and (3) the cardiolipin content in both homogenates and purified mitochondria. Respiratory-enzyme activities of homogenates of foetal liver were one-quarter to one-twentieth of those of homogenates of adult liver, and the enzyme specific activities in purified mitochondria from foetal liver were one-half to one-eighth of those in mitochondria from adult liver. The cardiolipin content of liver homogenates increased approximately twofold during the development period, but there was no significant change in the cardiolipin content of purified mitochondria. It is concluded that cell mitochondrial content approximately doubles in the immediate postnatal period. There was no evidence for an increase in the relative amount of cristae protein in mitochondria during this period to account for increases in mitochondrial enzyme specific activity, since cardiolipin and cytochrome concentrations remained unchanged and electron micrographs revealed no differences. The cause of the lower respiratory-enzyme specific activity in foetal liver mitochondria is unclear. Qualitative differences in respiratory units in foetal and mature animals are suggested.

Animals↗
PubMed1971

Cardiolipin content of wild type and mutant yeasts in relation to mitochondrial function and development.

The phospholipid composition of various strains of the yeast, Saccharomyces cerevisiae, and several of their derived mitochondrial mutants grown under conditions designed to induce variations in the complement of mitochondrial membranes has been examined. Wild type and petite (cytoplasmic respiratory deficient) yeasts were fractionated into various subcellular fractions, which were monitored by electron microscopy and analyzed for cytochrome oxidase (in wild type) and phospholipid composition. 90% or more of the phospholipid, cardiolipin was found in the mitochondrial membranes of wild type and petite yeast. Cardiolipin content differed markedly under various growth conditions. Stationary yeast grown in glucose had better developed mitochondria and more cardiolipin than repressed log phase yeast. Aerobic yeast contained more cardiolipin than anaerobic yeast. Respiration-deficient cytoplasmic mitochondrial mutants, both suppressive and neutral, contained less cardiolipin than corresponding wild types. A chromosomal mutant lacking respiratory function had normal cardiolipin content. Log phase cells grown in galactose and lactate, which do not readily repress the development of mitochondrial membranes, contained as much cardiolipin as stationary phase cells grown in glucose. Cytoplasmic mitochondrial mutants respond to changes in the glucose concentration of the growth medium by variations in their cardiolipin content in the same way as wild type yeast does under similar growth conditions. It is concluded that cardiolipin content of yeast is correlated with, and is a good indicator of, the state of development of mitochondrial membrane.

Carbon↗
PubMed1971

Serum lipoprotein accumulation in the livers of orotic acid-fed rats.

This study provides confirmation of previous observations that showed that rats fed a diet containing 1% orotic acid for 7 days develop a fatty liver and that there is an inhibition of the secretion of low density lipoproteins without altering general liver protein synthesis. Accumulated fat droplets (liposomes) are entrapped within rough endoplasmic reticulum vesicles. In this study, these vesicles have been shown to accumulate the apolipoproteins of low and very low density lipoproteins. Inhibition of lipoprotein secretion was demonstrated by perfusion of livers from orotic acid-fed rats with a serum-free medium. Liposomes were isolated from these rats. Partially delipidated liposomes, but not similarly treated microsomes or cell sap, were found to form a precipitation line when reacted against anti-low density lipoprotein antiserum. Detergent solubilization of the liposome followed by density gradient centrifugation resulted in a peak at d 1.025 g/ml containing both lipid and protein. Acrylamide electrophoresis in 8 m urea after total delipidation demonstrated liposomal bands which coelectrophoresed with three of four very low density lipoprotein bands; there was no band corresponding to the very low density lipoprotein band which travels furthest in acrylamide electrophoregrams. However, acrylamide electrophoresis of the apoproteins of serum high density lipoprotein from orotic acid-fed animals revealed the presence of the latter band. The results indicate that liver liposomes from orotic acid-fed rats apparently contain the low density apoprotein and probably several other very low density lipoprotein peptides.

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