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M V Chari

Publications and source records attributed to M V Chari.

16 recordsLinked to original sources
PubMed1992

Triglyceride metabolism in 3T3-L1 cells. An in vivo 13C NMR study.

13C nuclear magnetic resonance spectroscopy has been used to study triglyceride metabolism in 3T3-L1 cells incubated with [1-13/14C] acetate, myristate, palmitate, stearate, or oleate. Labeled cells embedded in agarose filaments were perfused in a specially fitted NMR tube within the spectrometer magnet. Incubation of 3T3-L1 cells with a specific fatty acid enriched the cellular triglycerides with that fatty acid; the NMR signal observed in the carbonyl region of the cell spectrum was due in large part to that fatty acid. NMR data demonstrated that cellular enzymes preferentially esterified saturated fatty acids at the glyceride sn-1,3 position and unsaturated fatty acids at the sn-2 position. cellular triglyceride hydrolysis by hormone-sensitive lipase was monitored by measuring the decrease in the integrated intensities of resonances arising from fatty acyl carbonyls esterified at glycerol carbons sn-1,3 and sn-2. Under basal conditions, the time courses were first-order, and the average rates were 0.14% of signal/min at both carbonyl positions. Under isoproterenol stimulated conditions, these rates were still first-order and increased 6.4-fold at the sn-1,3 position and 2.4-fold at the sn-2 position. The observation that the hydrolysis time courses were first-order suggested that only a small amount of cellular triglyceride was available to hormone-sensitive lipase, supporting the view that lipolytic enzymes operate at lipid surfaces where only small amounts of neutral lipid may be soluble. Attempts to correlate the measured rates with the rates of hydrolysis at the sn-1,3 and sn-2 positions were hindered by the fact that the chemical shifts of the carbonyl carbons of the diglyceride hydrolysis product did not overlie those of the triglyceride. Analysis of hydrolysis kinetics revealed that hormone-sensitive lipase exhibited little preference for a particular esterified fatty acid under basal conditions; however, under stimulated conditions, the enzyme exhibited a preference for certain triglyceride species.

3T3 Cells↗
PubMed1991

NMR studies of beta-oxidation and short-chain fatty acid metabolism during recovery of reperfused hearts.

The effects of beta-oxidation on the contractile recovery and metabolic activity of postischemic (10 min) rabbit hearts were examined during reperfusion with the short-chain fatty acid butyrate. Hearts received either 13C-enriched butyrate or acetate to evaluate metabolic targeting with 13C nuclear magnetic resonance (NMR) spectroscopy. Acetate and butyrate supported similar contractility (rate of pressure development, dP/dt) and 31P-NMR-detected, high-energy phosphate (HEP) levels during normal perfusion. In postischemic hearts, butyrate sustained a greater percentage of preischemic dP/dt (83 +/- 4%) than did acetate reperfusion (44 +/- 6%, P less than 0.05) with no differences in HEP. The efficiency of oxygen consumption per unit of work was greater in hearts reperfused with butyrate (2.8 +/- 0.2 microM.g-1.mmHg-1) vs. acetate (3.4 +/- 0.1). Inhibition of butyrate oxidation with 4-bromocrotonic acid (4-BCA) during normal perfusion severely reduced dP/dt and HEP. Acetate supported normal dP/dt and HEP levels during perfusion with 4-BCA and butyrate, but contractile recovery during reperfusion with acetate, 4-BCA, and butyrate (46 +/- 6%) was similar to that with acetate alone. With acetate and butyrate combined at reperfusion, acetate accounted for 56% of substrate entering oxidative metabolism at acetyl CoA and delayed contractile recovery (57 +/- 5% at midpoint and 80 +/- 6% at end). Thus improved respiratory efficiency of contraction in reperfused hearts was related to the activity of beta-oxidation.

Acetates↗
PubMed1987

Isolation and characterization of the two major apoproteins in human lipoprotein [a].

Human Lp[a] was isolated in preparative amounts from two donors; the native lipoprotein and its constituent apoproteins, apo[a] and apoB, were characterized extensively. Based on differences in apparent molecular weight, four different isoforms of apo[a], a1-a4, were observed between the two donors. The number and relative distribution of these isoforms varied between donors but were constant for each donor. Each apo[a] isoform was shown to be derived from a discrete apo[a]-B100 disulfide-linked complex present before reduction. Complete delipidation of Lp[a] was followed by solubilization, reduction, and carboxamidomethylation of the constituent apoproteins. These apoproteins were then separated by immunoaffinity chromatography using anti-apo[a]- or anti-apoB-Sepharose; their purity and structural integrity were demonstrated by Western blot analysis. ApoB isolated by this procedure was essentially identical to apoB from autologous LDL with respect to molecular weight, secondary structure, amino acid composition, and sialic acid content. However, apo[a] differed from apoB in that it exhibited: a much less alpha-helical, less beta, but much more disordered structure; a lower proportion of aspartate, isoleucine, leucine, phenylalanine, and lysine, but a higher proportion of proline, glycine, and threonine; and a much higher content of sialic acid. These results indicate that apo[a] is not a superglycosylated form of apoB but is distinctly different in its composition and structure.

Amino Acids↗
PubMed1986

Motion and surface accessibility of spin-labeled lipids in a model lipoprotein containing cholesteryl oleate, dimyristoylphosphatidylcholine, and apolipoprotein E.

A series of spin-labeled phosphatidylcholines (PCs) and cholesteryl esters (CEs) bearing the paramagnetic 2,2-dimethyloxazolidinyl-1-oxy (doxyl) group at fatty acyl carbon C5', C12', or C16' were used to study acyl chain motions in the polar surface shell and hydrophobic core domains of microemulsion (ME) particles containing cholesteryl oleate and dimyristoylphosphatidylcholine (DMPC), and of particles with apolipoprotein E (apoE) bound to their surfaces. Electron paramagnetic resonance data obtained with the doxyl-labeled PCs indicated a gradient of motion in the ME surface monolayer similar to that observed with the same probes in a bilayer. The 5- and 12-doxyl-CEs clearly demonstrated a higher degree of order for the cholesteryl ester rich core than the corresponding doxyl-PCs showed for the phospholipid-rich surface over the entire range 10-60 degrees C. The temperature dependencies of spectra of the 16-doxyl-CE in the core and PC in the surface of the ME were almost identical, suggesting that there was no sharp boundary between core and surface domains. None of the probes detected either the surface phospholipid transition (31 degrees C) or the cholesteryl ester core transition (46 degrees C) measured previously by differential scanning calorimetry and 13C nuclear magnetic resonance. Binding of apoE to spin-labeled DMPC vesicles increased the order of the 5'-position of the sn-2 acyl chain over the range 15-33 degrees C; the thermal transition was broadened and its midpoint elevated. The effect of protein binding was not as striking for the ME particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Excretion of cholate glucuronide.

[3-3H]Cholic acid glucuronide [7 alpha,12 alpha-dihydroxy-3 alpha-O-(beta-D-glucopyranosyluronate)-5 beta- cholan-24-oate] was synthesized and administered to rats prepared with either an external biliary fistula or a ligated bile duct. When bile fistula animals were given either microgram or milligram amounts of the glucuronide, biliary secretion of label was rapid and efficient: greater than 90% of the administered label was secreted within 60 min and total recovery of label in bile was 98.6 +/- 1.2%. Studies in which [14C]taurocholate was included in the dose indicated that this bile acid was secreted into bile significantly more rapidly than was the glucuronide. In animals with ligated bile ducts, urinary excretion was the major route of elimination: after 20 hr, 83.4 +/- 9.3% of the administered dose had been excreted in urine. Urinary excretion of cholate glucuronide was significantly more rapid than that of taurocholate. Gas-liquid chromatographic analysis of the methyl ester acetate derivatives of labeled compounds isolated from bile and urine by chromatography established that the bulk (greater than 70%) of the administered material was secreted in bile or excreted in urine as the intact cholate glucuronide. From these results, we conclude that the glucuronidation of cholic acid produces a derivative which is rapidly and effectively cleared from the circulation and excreted.

Animals↗
PubMed1984

Lithocholate glucuronide is a cholestatic agent.

Lithocholic acid and its taurine, glycine, and sulfate derivatives are potent cholestatic agents. Lithocholate glucuronide is present in the plasma and urine of patients with cholestatic syndromes, but little is known of its metabolism, excretion, and cholestatic potential. [3 beta-3H]lithocholate 3-O-beta-D-glucuronide was synthesized, and chemical and radiochemical purity were established. The aqueous solubility of lithocholate glucuronide was determined and found to be greater than that of lithocholic acid or several of its derivatives. In the range of concentrations examined, calcium ions precipitated lithocholate glucuronide stoichiometrically. The material was administered to rats prepared with an external biliary fistula. When 17-25 micrograms quantities were administered, 89.1 +/- 4.5% (mean +/- SEM) of the radiolabel was secreted in bile within the first 20 h after administration, the major fraction being secreted in less than 20 min. Four-fifths of the radiolabeled material in bile was the administered unaltered parent compound, while a minor fraction consisted of a more polar derivative(s). We showed that increasing biliary concentrations of more polar derivatives were observed with milligram doses of [3H]lithocholate glucuronide, and with time after the administration of these loading doses. Milligram doses of [3H]lithocholate glucuronide resulted in partial or complete cholestasis. When induced cholestasis was partial, secretion in bile remained the primary excretory route (82.5-105.6% recovery in bile), while, when complete cholestasis was induced, wide tissue distribution of radiolabel was observed. Cholestasis developed rapidly during infusion of [3H]lithocholate glucuronide. Bile flow was diminished within 10-20 min of the start of an infusion of 0.05 mumol, 100 g-1 body weight, minute-1, administered concomitantly with an equimolar infusion of taurocholate. The results establish that lithocholate glucuronide exerts cholestatic effects comparable to those exerted by unconjugated lithocholic acid.

Animals↗
PubMed1971

Evaluation of the Dirofilaria immitis filarial skin test antigen in the diagnosis of filariasis.

Conflicting opinions on the value of a skin test in the diagnosis of human filariasis emphasized the need for a careful examination of this procedure. The evaluation was made by asking workers in different countries to use an antigen prepared from Dirofilaria immitis in groups of people who could be examined for parasitic infection.In one non-endemic area, repeated tests over a 1-year period did not lead to sensitization, but the reactions of individuals varied from test to test. In endemic areas of filariasis, exposure to infective bites seemed to influence the pattern of skin reactions to a greater degree than did the development of overt infection with Wuchereria bancrofti. No particular size of reaction could be considered indicative of filarial infection.THE VALUE OF THE SKIN TEST WITH THIS ANTIGEN SEEMS LIMITED TO TWO SITUATIONS: (1) a large reaction may help to confirm a clinical diagnosis of filariasis when parasites cannot be found, and (2) the frequency distribution of skin reaction sizes in local populations may help, where blood surveys are impossible, to indicate areas in which some filarial infection is being transmitted.Results of skin test surveys should be expressed as frequency distributions of reaction sizes and negative/positive classification should be avoided.

Adolescent↗
PubMedDate not supplied

MR of intracranial epidermoid tumors: correlation of in vivo imaging with in vitro 13C spectroscopy.

We analyzed the MR findings of five patients with benign intracranial epithelial tumors, commonly called epidermoids. The neoplasms were categorized into two groups on the basis of T1-weighted MR signal intensity (relative to brain): high-signal-intensity masses (short T1) and low-signal-intensity masses (long T1). Surgical specimens were obtained and analyzed by means of 13C MR spectroscopy. Epidermoids with short T1 values (white epidermoids) had a high lipid content comprising mixed triglycerides containing unsaturated fatty acid residues. Epidermoids with long T1 values (black epidermoids) exhibited a much reduced lipid content with no triglycerides or fatty acids. There was evidence of trace amounts of cholesterol in the black epidermoids. Our data indicate that epidermoids are a heterogeneous group of neoplasms that behave differently with T1-weighted MR imaging and 13C MR spectroscopy. The combination of MR imaging and spectroscopy holds the potential of further elucidating the nature of epidermoids as well as of other forms of neoplasms.

Brain↗