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Biomedical subjects

D E Vance

Publications and source records attributed to D E Vance.

179 records · Page 10Linked to original sources
PubMed1975

Metabolism of neutral glycosphingolipids in plasma of a normal human and a patient with Fabry's disease.

[6-2H2]Glucose was used as a tracer for a comparative study on the metabolism of the neutral glycosylceramides in plasma of a control subject and a patient with Fabry's disease. The incorporation of the tracer into the glucosyl and galactosyl moieties of the glycosphingolipids was measured by gas chromatography-mass spectrometry of the tetra-0-acetyl methyl glycoside derivatives. Experiments on the precision and accuracy for measurements of [6,6-2H2]hexose in a sample demonstrated that incorporation of 0.2% or more of [6,6-2H2]glucose could be detected with a 95% confidence limit of +/-0.16%. The labeled substrate (35g) was infused into each subject with a 5-g priming dose and the remainder administered at a constant rate of 3 g/hour over a 10-hour period. During the infusion, the plasma glucose of each subject attained a concentration of about 30% [6,6-2H2]glucose which diminished rapidly after the administration of substrate was complete. A concentration of 0.8% [6,6-2H2]glucose was observed in glucosylceramide (GL-la) from plasma of both subjects between 48 and 72 hours after the infusion began. The label disappeared from this lipid at a logarithmic rate and 0.2% or less of the molecules were labeled 9 days after the experiment began. In contrast to the results with GL-la, the maximum incorporation of [6,6-2H2]hexose into lactosylceramide (galactosyl-(beta1 leads to 4)-glucosylceramide) was 2-fold higher in the Fabry patient (1.6%) than in the control (0.8%). The trihexosylceramide (galactosyl-(alpha1 leads to 4)-galactosyl-(beta1 leads to 4)-glucosylceramide, GL-3a) from plasma of the control reached a maximum of 0.4% [6,6-2H2]hexose in both the glucosyl and galactosyl moieties whereas the GL-3a from the Fabry patient was not significantly labeled. The maximal labeling of the GL-4a fraction (N-acetyl-galactosaminyl-galactosyl-galactosyl-glucosylceramide) was slightly depressed in the Fabry patient (0.4%) as compared to the control (0.7%). Turnover times for the glycosphingolipids of plasma were calculated to be from 4 to 8 days and the turnover rates were from 1 to 6 mumol/day.

Adult↗
PubMed1975

Elongation of fatty acids by microsomal fractions from the brain of the developing rat.

Elongation of fatty acids by microsomal fractions obtained from rat brain was measured by the incorporation of [2-14C]malonyl-CoA into fatty in the presence of palmitoyl-CoA or stearoyl-CoA. 2. Soluble and microsomal fractions were prepared from 21-day-old rats; density gradient centrifugation demonstrated that the stearoyl-CoA elongation system was localized in the microsomal fraction whereas fatty acid biosynthesis de novo from acetyl-CoA occurred in the soluble fraction. The residual activity de novo in the microsomal fraction was attributed to minor contamination by the soluble fraction. 3. The optimum concentration of [2-14C]malonyl-CoA for elongation of fatty acids was 25 mum for palmitoyl-CoA or stearoyl-CoA, and the corresponding optimum concentrations for the two primer acyl-CoA esters were 8.0 and 7.2 muM respectively. 4. Nadph was the preferred cofactor for fatty acid formation from palmitoyl-CoA or stearoyl-CoA, although NADH could partially replace it. 5. The stearoyl-CoA elongation system required a potassium phosphate buffer concentration of 0.075M for maximum activity; CoA (1 MUM) inhibited this elongation system by approx. 30%. 6. The fatty acids formed from malonyl-CoA and palmitoyl-CoA had a predominant chain length of C18 whereas stearoyl-CoA elongation resulted in an even distribution of fatty acids with chain lengths of C20, C22 and C24. 7. The products of stearoyl-CoA elongation were identified as primarily unesterified fatty acids. 8. The developmental pattern of fatty acid biosynthesis by rat brain microsomal preparations was studied and both the palmitoyl-CoA and stearoyl-CoA elongation systems showed large increases in activity between days 10 and 18 after birth.

Animals↗
PubMed1975

Sindbis virus inhibits phosphatidylcholine biosynthesis in BHK-21 cells.

Sindbis virus inhibits the incorporation of [methyl-3H]choline into the phospholipids of BHK-21 cells and also inhibits the activity of the enzyme that catalyzes the final reaction involved in phosphatidylcholine biosynthesis (cytidine diphosphate-choline:1,2-diacylglycerol cholinephosphotranferase; EC 2.7.8.2).

Cell Line↗
PubMed1975

Inhibition of phosphatidylethanolamine biosynthesis in baby hamster kidney-21 cells infected with Semliki Forest virus.

Semliki Forest virus inhibits phosphatidylethanolamine biosynthesis in baby hamster kidney-21 cells 6 h after infection. Viral infection reduced the incorporation of [1,2-14C]-ethanolamine into intact cells by approximately 50%. A similar reduction in the activity of the ethanolaminephosphotransferase (EC 2.7.8.1) was also observed. The apparent Km for CDPethanolamine was 60 muM for the microsomal enzymes from infected or mock-infected cells. In addition, exogenous diglyceride only stimulated by 1.5-fold the ethanolaminephosphotransferase from virus- or mock-infected cells, whereas the same diglyceride preparations stimulated the cholinephosphotransferase (EC 2.7.8.2) from baby hamster kidney cells by sixfold. Generation of endogenous diglyceride by pretreatment of the microsomes with phospholipase C (EC 3.1.4.3) stimulated the activity of the cholinephosphotransferase but not the ethanolaminephosphotranferase. Semliki Forest virus does not inhibit all microsomal enzymes, since the activities of NADH- K3Fe(CN)6 reductase and NADH dehydrogenase (EC 1.6.99.3) were not affected. The ethanolaminephosphotransferase from virus- and mock-infected cells showed similar profiles of activity as a function of temperature; this result and other studies suggest that that membranous environment of the ethanolaminephosphotransferase was not significantly modified by the virus.

Cell Line↗
PubMed1969

Concentrations of glycosyl ceramides in plasma and red cells in Fabry's disease, a glycolipid lipidosis.

Concentrations of four neutral glycosyl ceramides were determined in plasma and erythrocytes from nine hemizygous patients with Fabry's disease (a hereditary glycolipid lipidosis), from the sister of one of the patients, and from the heterozygous mother of another one. The concentration of a trihexosyl ceramide, galactosylgalactosylglucosyl ceramide, was elevated in plasma from the patients about threefold above the normal mean level, and the amount of this lipid was also increased in plasma from the two female relatives. The concentrations of glucosyl ceramide and lactosyl ceramide in plasma were slightly less than normal in the affected males, while globoside or a similar tetrahexosyl ceramide was slightly higher than normal. All but one of the Fabry patients had significantly less globoside in the red cells, as compared with the normal range, although the red cell concentration of trihexosyl ceramide was normal in all of the patients. Thus the concentration of the lipid that accumulates in the tissues in Fabry's disease is elevated in plasma but not in red cells, whereas in Gaucher's disease the accumulating lipid (glucosyl ceramide) is elevated in both plasma and red cells.

Adolescent↗
PubMed1967

Quantitative determination of the neutral glycosyl ceramides in human blood.

A method is described for the qualitative and quantitative estimation of four neutral glycosyl ceramides from human plasma and erythrocytes. Total lipids extracted from 50 ml of plasma or packed erythrocytes were separated by silicic acid chromatography into neutral lipids, a fraction of mixed glycolipids that was eluted with acetone-methanol 9:1, and phospholipids. After mild alkali-catalyzed methanolysis to remove contaminants from the crude fraction of glycolipids, individual glycosyl ceramides were isolated by preparative thin-layer chromatography. The oligosaccharide portions of these lipids were characterized by cleavage with methanolic hydrogen chloride and gas chromatography of the O-trimethylsilyl methyl glycosides. It was possible to study the composition of the carbohydrate and sphingolipid base fractions in the same gas chromatographic analysis. With mannitol as an internal standard for gas chromatographic estimation of glucose, concentrations of each of the glycosyl ceramides were determined with a precision of about 10%. Recoveries of the lipids from plasma varied with the complexity of the oligosaccharide moiety and ranged from 94% with glucosyl ceramide to 71% with globoside. Concentrations of the four glycosyl ceramides in plasma and in erythrocytes were determined for samples from young, healthy males. Amounts of glycolipid as low as 0.1 micromole can be determined conveniently by this procedure.

Adult↗
PubMedDate not supplied

Trace element content in fingernails and hair of a nonindustrialized US control population.

The concentrations of 17 elements in the nail and hair of 117 subjects from a nonindustrialized environment were determined by instrumental neutron activation analysis (INAA). A new method of statistical treatment that allows for more meaningful use of detection limit values was used to process the concentration data. Geometric means and standard errors are presented for each element, along with a summary of the effects of age, sex, and treatment on the concentration of each element. For nails, these data represent the first comprehensive study for several important elements. Correlations for each element between hair and nail were determined. With few exceptions, concentrations of nonessential trace elements were positively correlated in hair and nail, whereas concentrations of essential elements showed no correlations. The factors affecting concentrations and control levels must be considered in studying alterations in disease states.

Adolescent↗
PubMedDate not supplied

A search for longitudinal variations in trace element levels in nails of Alzheimer's disease patients.

Levels of Br, Hg, K, and Zn were determined by INAA in the nails of Alzheimer's disease (AD) patients at 6-mo intervals for up to 3 yr. These elements have been shown to be imbalanced in AD nail. Bromine showed no trends. Mercury tended to decrease in nail with increasing age of patient, and with the duration and severity of the dementia. Potassium and Zn tended to increase with these same factors. Hence, progressive changes in trace-element levels do occur in AD nail, although imbalances are detected even in the earliest sampled stages of the disease.

Age Factors↗
PubMedDate not supplied

Role of axons in membrane phospholipid synthesis in rat sympathetic neurons.

The axonal synthesis of phospholipids has been demonstrated in compartmented cultures of rat sympathetic neurons. In this model of neuron culture, metabolic events occurring in distal axons were studied independently of those occurring in cell bodies. Using radiolabeled tracers the axonal biosynthesis of the major membrane phospholipids and fatty acids but not cholesterol was detected. The capacity of axons for synthesis of phosphatidylcholine (PC), the major membrane lipid, was confirmed by the demonstration that key enzymes of PC biosynthesis were present in distal axons. A double-labeling experiment showed that at least 50% of axonal PC was synthesized locally in axons, with the remainder being made in cell bodies and transported into axons. The requirement of axonal PC synthesis for axonal elongation was investigated. When PC biosynthesis in distal axons alone was inhibited by two independent approaches (deprivation of choline or addition of the inhibitor hexadecylphosphocholine) axonal growth was markedly retarded. Our experiments demonstrated that PC synthesis in cell bodies was neither necessary nor sufficient for growth of distal axons, whereas local synthesis of PC in distal axons was required for normal axonal elongation.

Animals↗
PubMedDate not supplied

Phosphatidylethanolamine methylation and hepatoma cell growth.

Phosphatidylethanolamine is converted to phosphatidylcholine in hepatocytes via the enzyme phosphatidylethanolamine N-methyltransferase (PEMT). An isoform, PEMT2 has been cloned, expressed and localized to a mitochondria-associated membrane in rat liver. Expression of PEMT2 caused a decreased rate of cell division of cultured rat hepatoma cells. Mechanistic studies suggest that the slower growth of transfected hepatoma cells may be due to down regulation of CTP: phosphocholine cytidylyltransferase and the CDP-choline pathway for phosphatidylcholine biosynthesis. A role for PEMT2 in the regulation of hepatocyte cell division is also indicated by PEMT2 down-regulation in regenerating rat liver.

Animals↗