Search PubMed⌕ Search

Biomedical subjects

G S Getz

Publications and source records attributed to G S Getz.

At least 109 records · Page 6Linked to original sources
PubMed1980

Apolipoprotein B variant derived from rat intestine.

A variant of apolipoprotein B has been observed in the lymph lipoproteins [chylomicrons, very low density lipoproteins (VLDL), and low density lipoproteins (LDL)] of rats, in the plasma VLDL of fed rats, and in the plasma VLDL and LDL of rats fed a high-fat, high-cholesterol diet. It is the sole apolipoprotein B in the chylomicrons and VLDL of lymph. It differs from the apolipoprotein B of normal plasma LDL in its immunological properties and in its apparent molecular weight from electrophoresis on 3.5% NaDodSO4/polyacrylamide gel.

Amino Acids↗
PubMed1980

Lipid interactions with human alpha-fetoprotein (AFP). A study of the role of such interactions in the ability of human AFP to suppress lymphocyte transformation.

The ability of human alpha-fetoprotein (HAFP) isolates to inhibit human lymphocyte transformation varies over 2-3 orders of magnitude. Since HAFP is known to bind fatty acids, we have examined the possible role of lipid binding in producing this variability. While certain oxygenated sterols are potent inhibitors of lymphocyte transformation, and while the kinetics of such inhibition precisely mimic those of HAFP, HAFP is, by contrast, a weak inhibitor of sterol synthesis in mitogen-stimulated human lymphocytes. Fatty acids (18:0, 18:1, 18:2, 18:3, 20:4, 22:6) and 10(-4) M have little or no effect upon lymphocyte transformation. The fatty acid content of seen HAFP isolates ranged from 2.3 to 8.0 mol fatty acid/mol HAFP and included 12:0, 14:0, 16:0 (the most abundant), 18:0, 20:4, and 22:0; no 22:6 was found. There was no correlation between the total or individual fatty acid contents of HAFPs and their ability to inhibit lymphocyte transformation. Lysooleoyl-, lysostearoyl-, and lysopalmitoyl-lecithin at 5 X 10(-5) M all inhibited lymphocyte transformation (30.1%, 52.1%, and 58.1%, respectively) and the latter was active at 6.3 X 10(-6) M. Exposure of HAFP to a 5-fold molar excess of [14C]-lysopalmitoyl lecithin resulted in significant (10%) binding to HAFP, while no significant binding of dipalmitoyl lecithin occurred under similar conditions. Analysis of lipid extracts of potent HAFP isolates by thin-layer chromatography failed to reveal the presence of phospholipids. Although HAFP can bind certain lipids, and although certain lipids inhibit lymphocyte transformation, we conclude that HAFP suppression of lymphocyte transformation cannot be attributed to the binding of hydrocortisone, prostaglandins, fatty acids, lysolecithins, or oxygenated sterol compounds.

Chemical Phenomena↗
PubMed1979

Isolation and partial characterization of high-density lipoprotein HDL1 from rat plasma by gradient centrifugation.

The lipoproteins isolated from rat plasma by flotation in the density range 1.019-1.063 g/ml were further characterized. Using rate zonal ultracentrifugation, we isolated two lipoproteins in almost equal proportions from this density range. Similar isolations may be accomplished with density gradients in a swinging-bucket rotor. On isopycnic-density-gradient ultracentrifugation one component banded at rho = 1.031 g/ml and the other at rho = 1.054 g/ml. More that 98% of the apoprotein of the lighter component was B protein, and hence this particle is LD (low-density) lipoprotein. Of the apoproteins of the rho = 1.054 g/ml particles, designated lipoprotein HDL1, over 60% was arginine-rich peptide, and the remainder was A-I, A-IV and C peptides. The molecular weight of these lipoproteins determined by agarose column chromatography was 2.36 x 10(6) for LD lipoprotein and 1.30 x 10(6) for lipoprotein HDL1. On electron microscopy the radius of LD lipoprotein was 14.0 nm and that of lipoprotein HDL1 was 10.0 nm, in contrast with molecular radii of 10.4 nm and 8.4 nm respectively determined from the gel-permeation-chromatography data. The lipid and phospholipid composition of both particles was determined. Lipoprotein HDL1 was notable for both the concentration of its esterified cholesterol, which was similar to that of LD lipoprotein, and the low triacylglycerol content, resembling that of HD lipoprotein. The possible origin of lipoprotein HDL1 is discussed.

Animals↗
PubMed1979

Cytoplasmically inherited respiratory deficiency of a mouse fibroblast line which is resistant to rutamycin.

Mouse fibroblasts resistant to the drug rutamycin were isolated and found also to be respiratory deficient. These cells produce large amounts of lactic acid, and oxygen consumption data indicate that the first complex of the electron transport chain, NADH-coenzyme Q reductase, is defective. Levels of rotenone-sensitive NADH-cytochrome c reductase and pyruvate decarboxylase of the pyruvate dehydrogenase complex are markedly depressed in the mutant cells. Other components of the electron transport chain appear to be fully functional. The mutant cells were enucleated and fused with another cell line, and the resulting cybrid demonstrated a similar pattern of respiratory deficiency as did the original mutant. These results indicate that this defect in respiration is a cytoplasmically inherited characteristic in this cell line.

Animals↗
PubMed1979

Translation in vivo and in vitro of proteins resembling apoproteins of rat plasma very low density lipoprotein.

Antibodies raised against rat plasma apoVLDL and a purified fraction of arginine-rich peptides (ARP) were labeled with Na125I and were shown to bind to polyribosomes isolated from rat liver. Antibody fractions enriched by selective affinity chromatography exhibited increased levels of binding to polysomes. Anti-apoVLDL immunoreactivity was further resolved into anti-ARP and anti apoB components, each reactive with a distinct polysome population. Binding was specific for rat polysomes, and was directed toward nascent polypeptide chains. About 2% of normal rat liver polysomes were recovered by indirect immunoprecipitation with anti-apoVLDL. Ribonucleic acid (RNA) extracted from this immunoprecipitate contained species with polyadenylate (poly[A] sequences characteristic of eukaryotic messenger RNA (mRNA). These species, purified by affinity chromatography on poly(U)-Sepharose, stimulated the in vitro synthesis of immunoprecipitable apoVLDL-like proteins by about 17-fold when compared to unfractionated rat liver mRNA. Most of the in vitro translation products precipitated by purified anti-ARP migrated identically on polyacrylamide gel electrophoresis with unlabeled purified ARP. Some implications of these findings with respect to plasma VLDL biosynthesis are discussed.

Animals↗
PubMed1979

The synthesis and metabolism of the lipoproteins implicated in atherosclerosis.

The basic concepts of lipoprotein biogenesis and metabolism have been briefly reviewed. Emphasis has been placed upon the distinctive roles of the liver and intestine in apolipoprotein synthesis and delivery, upon the complex interchange of lipids and apolipoproteins between lipoproteins which accompanies nascent lipoprotein maturation and metabolism within the vascular compartment, upon the primary role of these latter processes in the genesis of low density lipoprotein and upon remodelling of nascent lipoproteins to achieve a structure suitable for the function of the mature between the liver, intestine and peripheral tissues.

Arteriosclerosis↗
PubMed1978

CTP-phosphatidic acid cytidyltransferase from Saccharomyces cerevisiae. Partial purification, characterization, and kinetic behavior.

CTP-phosphatidic acid cytidyltransferase catalyzes the formation of CDP-diglyceride from CTP and phosphatidic acid. The enzyme was solubilized from crude mitochondrial membrane by treatment with digitonin and was further purified by chromatography on DEAE-Sephadex, quaternary aminoethyl (QAE) Sephadex, and Sepharose 6B columns. At this stage the enzyme, enriched 550-fold over crude cell homogenate, still remains associated with phospholipid and has an estimated approximate molecular weight of 400,000 on the basis of gel filtration chromatography. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the 550-fold enriched enzyme yielded two major protein bands having molecular weights of 45,000 and 19,000. The enzyme exhibits an absolute dependence on Triton X-100, a sharp Mg2+ dependence with an optimum at 20 mM, and a pH optimum of 6.5 for activity. The product of the CTP-phosphatidic acid cytidyl-transferase reaction has been isolated and identified as CDP-diglyceride, both for the crude enzyme preparation as well as for the 550-fold enriched enzyme. CTP-phosphatidic acid cytidyltransferase is capable of catalyzing the reverse reaction in the presence of pyrophosphate, utilizing CDP-diglyceride as substrate. The product of the reverse reaction was identified as CTP. Kinetic analysis of the behavior of CTP-phosphatidic acid cytidyltransferase was performed at three different stages of its purification. Initial analysis of the data yielded biphasic behavior in double reciprocal plots with respect to both substrates. Hill plots of the data indicated the presence of negative cooperativity. A detailed analysis of the kinetic behavior was performed on the enzyme purified 550-fold. The data suggest a mechanism involving two distinct cycles of catalysis, responsive to homotropic modification, with different affinities for both substrates. Further analysis of the kinetic behavior in the presence of inhibitors (dCTP and PPi) yielded a reaction order for the entrance of substrates and departure of products from the reaction cycles. The high affinity site catalyzes the reaction via a double displacement mechanism and is the predominant form at low concentrations of substrates. At high concentrations of substrates the low affinity site starts contributing significantly to the reaction velocity with an ordered single displacement mechanism. In each case CTP is the first substrate to attach and PPi is the first product released.

Cytidine Diphosphate Diglycerides↗
PubMed1978

Cytoplasmic inheritance of rutamycin resistance in mouse fibroblasts.

Mouse fibroblasts resistant to the drug rutamycin were isolated by selectively introducing BrdUrd into the mitochondrial genome of a line of mouse fibroblasts (clone 1 D) lacking a cytoplasmic thymidine kinase enzyme. The ATPase (ATP phosphohydrolase; EC 3.6.1.3) activity of mitochondria isolated from these cells was resistant to rutamycin. The rutamycin-resistant mutants were enucleated with cytochalasin B and fused with mouse A 9 cells resistant to 8-azaguanine and sensitive to rutamycin. Cytoplasmic hybrids, or cybrids, were selected as cells resistant to rutamycin and 8-azaguanine, and appeared at a high frequency. Other fusions between rutamycin-resistant nucleated cells and A 9 produced colonies at a much lower frequency. Finally, fusions between enucleated clone 1 D cells and A 9 cells produced no rutamycin-resistant colonies. These results indicate that rutamycin resistance is a cytoplasmically inherited characteristic in this cell line.

Adenosine Triphosphatases↗
PubMed1977

The effect of thyroid hormone on in vitro rat liver mitochondrial RNA synthesis.

Liver mitochondrial preparations from normal, thyroidectomized, and triiodothyronine-treated thyroidectomized rats were assayed for in vitro RNA synthetic activity. Thyroidectomized rat mitochondrial preparations incorporated UTP into RNA at 70% the rate of normal control preparations. Mitochondrial preparations from triiodothyronine-treated thyroidectomized rats incorporated UTP at rates 35%-45% greater than those of sham-injected thyroidectomized rats. These differences were statistically significant and could not be attributed to inequalities in mitochondrial sampling, dilution of labeled precursor specific activity, nucleotide substrate concentrations, or differences in ribonuclease activities.

Acriflavine↗
PubMed1977

Formation of renal medullary lysosomes during potassium depletion nephropathy.

The biochemical correlates of droplet formation in renal inner medullary cells of potassium-deficient rats were studied. An increase in the activities of five hydrolytic enzymes typical of lysosomes was associated with an increase in the number and size of droplets observed during progressive potassium depletion. Acid phosphatase activity increased 7-fold whereas beta-glucuronidase, beta-galactosidase, cathepsin, and acid DNase increased 2- to 4-fold in medullary homogenates at 25 days of depletion. Following potassium repletion the activities returned to normal at a rate dependent upon the duration of potassium depletion. The decreases in enzyme activities were associated with a concomitant rapid disappearance of the droplets from medullary cells. Protein synthesis for new droplet enzyme formation was studied by measuring the rate of [14C]leucine incorporation into protein in medullary slices. The rate increased at 1 day of depletion and reached a maximum which was 139 per cent higher than control after 7 days of depletion. In droplets isolated from medullary tissue during progressive potassium depletion the rate of protein labeling with [14C]leucine and acid phosphatase specific activity increased in parallel. When droplet proteins were separated by gel electrophoresis, acid phosphatase activity was detected in a protein band which had been labeled with [14C]leucine, thereby suggesting new enzyme protein formation. The increase in enzyme and protein synthesis and a previously demonstrated increase in phospholipid synthesis and membrane formation indicate that potassium depletion induces specific alterations in renal inner medullary cell metabolism which result in increased lysosome formation.

Acid Phosphatase↗
PubMed1975

Cytochrome synthesis in synchronous cultures of the yeast, Saccharomyces cerevisiae.

The synthesis of cytochromes aa3, b, and c has been investigated during synchronous growth in the yeast, Saccharomyces cerevisiae. These cytochromes increase in concentration continuously throughout each cell cycle, with an approximate doubling in rate during successive cycles. The rates of cytochrome formation are considerably higher in galactose-grown cultures than in cells grown in glucose. Although cytochrome aa3 increases at a continuous rate, its functional counterpart, cytochrome c oxidase, increases in stepwise fashion, with the increments occurring at the beginning of each new cell cycle. Chloramphenicol, a specific inhibitor of intramitochondrial protein synthesis, inhibits the formation of cytochrome aa3 at all stages of the cell cycle, but does not inhibit cytochrome c. Chloramphenicol exhibits a somewhat intermediate effect on cytochrome b synthesis, with transient inhibition occurring only when the drug is added prior to or during the initial part of the first cell cycle. After this time, chloramphenicol had no effect on the rate of cytochrome b synthesis. The data indicate that under our conditions of cell synchrony mitochondrial membrane formation as reflected by increments in mitochondrial cytochromes occurs by continuous accretion of new material throughout the cell cycle. Intramitochondrially synthesized polypeptide products, responsible for the formation of new cytochrome aa3, appear to be synthesized throughout the cell cycle.

Cell Division↗
PubMed1974

Tandem inverted repeats in mitochondrial DNA of petite mutants of Saccharomyces cerevisiae.

Denatured mitochondrial DNA (mtDNA) from a grande (wild-type) yeast strain and a series of derived genetically characterized cytoplasmic petite mutants was examined in the electron microscope as DNA-protein monolayers prepared under conditions that permitted little bimolecular renaturation. In the grande and some petite strains, the mtDNA remained predominantly single-stranded. However, in several petite strains, a large proportion of molecules contained double-stranded segments indicative of unimolecular renaturation due to the presence of inverted repeat sequences. The length of the double-stranded segments of strain E41 was compared to the periodicity seen on denaturation maps. A repeat spacing twice the length of the inverted repeats was observed in the denaturation map. Inverted repeat length was similar to contour length of circular mtDNA molecules in this strain. On the basis of these observations most of the mtDNA from petite strain E41 appeared to consist of polymers of tandem inverted repeats interspersed with a small single-stranded "spacer" sequence between the repeat segments. In contrast, petite strain F13 mtDNA had few or no inverted repeats and showed a regular periodicity of 0.14 mum in the denaturation map, similar in length to the 0.13-mum circles present in the isolated mtDNA.

Base Sequence↗