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Biomedical subjects

F David

Publications and source records attributed to F David.

At least 73 records · Page 4Linked to original sources
PubMed1995

Tracing hepatic gluconeogenesis relative to citric acid cycle activity in vitro and in vivo. Comparisons in the use of [3-13C]lactate, [2-13C]acetate, and alpha-keto[3-13C]isocaproate.

The validity of the use of a carbon tracer for investigating liver intermediary metabolism in vivo requires that the labeling pattern of liver metabolites not be influenced by metabolism of the tracer in other tissues. To identify such specific tracer, livers from 48-h starved rats were perfused with recirculating buffer containing [3-13C]lactate, [2-13C]acetate, or alpha-keto[3-13C]isocaproate. Conscious 48-h starved rats were infused with the same tracers for 5 h. The labeling patterns of liver glutamate and extracellular glucose were assayed by gas chromatography-mass spectrometry. In vivo data were corrected for 13CO2 reincorporation into C-1 of glutamate and C-3 and C-4 of glucose, using data from control rats infused with NaH13CO3. With [3-13C]lactate the labeling pattern of liver glutamate was the same in perfused organs and in vivo. In contrast, with [2-13C]acetate and alpha-keto[3-13C]isocaproate the labeling pattern of liver glutamate in vivo was clearly influenced by the expected labeling pattern of citric acid cycle intermediates formed in non-gluconeogenic organs, presumably glutamine made in muscle. Indeed, the labeling pattern of plasma glutamine and liver glutamate were similar in experiments with [3-13C]lactate but different in experiments with [2-13C]acetate and alpha-keto[3-13C]isocaproate. Similar conclusions were drawn from the labeling patterns of glucose. Therefore, labeled lactate appears as the best tracer for studies of liver intermediary metabolism in vivo. Our data also show that a substantial fraction of alpha-ketoisocaproate metabolism occurs in peripheral tissues.

Acetates↗
PubMed1995

Metabolism of R-beta-hydroxypentanoate and of beta-ketopentanoate in conscious dogs.

R-beta-Hydroxypentanoate and beta-ketopentanoate are homologues of physiological ketone bodies R-beta-hydroxybutyrate and acetoacetate. They derive from the oxidation in liver of the R-moiety of R,S-1,3-pentanediol, a potential nutrient. This report documents the metabolism of R-beta-hydroxypentanoate and beta-ketopentanoate in conscious dogs. Whether administered by bolus or constant infusion, the two substrates are interconverted and rapidly metabolized. When beta-ketopentanoate was infused at a rate corresponding to 75% of the dog's caloric requirement, the steady-state total plasma concentration of the two substrates was only 1.3 mM. Because the substrates are precursors of propionyl-CoA, we assayed the urinary concentrations of markers of propionic acidemia. Their accumulation was minor compared with what is observed in patients suffering from propionic acidemia. We conclude that, at least during short-term experiments, R-beta-hydroxypentanoate and beta-ketopentanoate are well metabolized in the dog without apparent intolerance to a large supply of propionyl-CoA.

Acyl Coenzyme A↗
PubMed1995

Metabolism of (R,S)-1,3-butanediol acetoacetate esters, potential parenteral and enteral nutrients in conscious pigs.

The (R,S)-1,3-butanediol-acetoacetate monoesters and diester are nonionized sodium-free precursors of ketone bodies (beta-hydroxybutyrate and acetoacetate). They represent a convenient form of ketone body administration for parenteral and enteral nutrition. We have studied the metabolism of the esters in the conscious pig, an animal in which ketogenesis is congenitally impaired. Some pigs were infused for 3 h, intravenously or intragastrically, with the esters or with (R,S)-1,3-butanediol at 30% of the hourly caloric requirement. Other pigs were given intragastric boluses of esters or of (R,S)-1,3-butanediol at 15% of the daily caloric requirement. Our data show that continuous infusion of the esters at 30% of the caloric requirement leads to low concentrations of (R,S)-1,3-butanediol (0.1 mM) and total ketone bodies (0.5 mM). In pigs given intragastric boluses of esters at 15% of the daily caloric requirement, concentrations of (R,S)-1,3-butanediol and total ketone bodies peaked briefly at 2-3 and 5 mM, respectively. No deleterious side effects were observed in any group, including no hypoglycemia and no acidosis. Thus the (R,S)-1,3-butanediol acetoacetate esters appears to be well utilized as a nutrient by the pig despite its impaired ketogenesis.

3-Hydroxybutyric Acid↗
PubMed1995

Model of extreme hypoglycemia in dogs made ketotic with (R,S)-1,3-butanediol acetoacetate esters.

The rationale behind this study is that controlled starvation of poorly differentiated (anaplastic) fast-growing tumor cells, but not host cells, might be possible in vivo. The energy metabolism of anaplastic tumor cells, but not host cells, is largely dependent on carbohydrate metabolism at all times. Therefore depleting plasma of carbohydrate fuels could place these tumor cells at a significant metabolic disadvantage. Hence an animal model was developed in which all cells would be required to oxidize fatty acids, ketoacids, and/or 1,3-butanediol to satisfy their energy needs. To achieve this aim, one would need ketosis, severe hypoglycemia, and low lactatemia. Anesthetized normal dogs were infused with somatostatin and a mixture of (R,S)-1,3-butanediol monoacetoacetate and (R,S)-1,3-butanediol diacetoacetate; these latter compounds are nonionized precursors of ketoacids. They were infused at 90% of the dog's caloric requirement. After establishment of a moderate ketosis (2-3 mM) over < 100 min, a severe degree of hypoglycemia (close to 0.5 mM) without rebound and without hyperlactatemia was induced by infusing insulin and dichloroacetate. Tracer kinetic measurements showed 1) a 20% decrease in the rate of appearance of glucose, 2) 50 and 62% increases in glycerol and nonesterified fatty acid rates of appearance, reflecting stimulation of lipolysis, and 3) no change in the rate of glutamine appearance. We suggest that this model may prove useful for selectively starving those cancer cells that are unable to utilize fat-derived fuels while preserving nutrient supply to vital organs.

3-Hydroxybutyric Acid↗
PubMed1994

Reversibility of the mitochondrial isocitrate dehydrogenase reaction in the perfused rat liver. Evidence from isotopomer analysis of citric acid cycle intermediates.

The reversal of the mitochondrial isocitrate dehydrogenase reaction was investigated in rat livers perfused with [U-13C5]glutamate or [U-13C5]glutamine. The mass isotopomer distribution of citric acid cycle intermediates extracted from the livers was determined by gas chromatography-mass spectrometry. Citrate was enriched in an isotopomer containing five 13C. The formation of this isotopomer can only be explained by the reversal of the isocitrate dehydrogenase reaction. Calculation of kinetic parameters from the mass isotopomer data reveals a rapid interconversion of isocitrate and alpha-ketoglutarate. This interconversion results in an isotopic exchange between carbon 6 of citrate and mitochondrial CO2 that can affect the calculation of citric acid cycle kinetic parameters. Thus, the reversal of the isocitrate dehydrogenase reaction should be included in isotope labeling models of the citric acid cycle.

Animals↗
PubMed1994

Isolation of a heregulin-like growth factor secreted by estrogen receptor-negative MDA-MB-231 human breast cancer cells that stimulates estrogen receptor-positive cells.

A 52 kDa peptide growth factor secreted by the estrogen receptor (ER)-negative human breast cancer cell line MDA-MB-231 was purified to homogeneity. It induced transient membrane ruffling, lamellipodia formation, cell motility and proliferation exclusively of ER-positive human breast cancer cells. Partial sequencing revealed a high homology to the protein family of heregulins. However, the obtained amino acid sequences of the new factor were not completely identical to any of the members of the heregulin family. This finding together with the observation that the successful purification protocol was significantly different from that used to isolate other members of the heregulin family indicate the isolation of a novel heregulin-like proliferation factor for ER-positive human breast cancer cells.

Amino Acid Sequence↗
PubMed1994

Nonhomogeneous labeling of liver extra-mitochondrial acetyl-CoA. Implications for the probing of lipogenic acetyl-CoA via drug acetylation and for the production of acetate by the liver.

The labeling of liver extra-mitochondrial acetyl-CoA was investigated in isolated rat livers perfused with [2-(13)C]acetate, [1-(13)C]octanoate, or [1,2,3,4-(13)C4]docosanoate and with drugs that undergo acetylation (phenylaminobutyrate, paraaminobenzoate, and sulfamethoxazole; singly or in combination). The 13C enrichment of mitochondrial acetyl-CoA was probed by the enrichment of R-beta-hydroxybutyrate. The latter was not enriched from [1,2,3,4-(13)C4]docosanoate, thus excluding mitochondrial beta-oxidation of docosanoate. The 13C enrichment of extra-mitochondrial acetyl-CoA was probed by the enrichments of acetylated drugs and of free acetate. In most cases, the four probes yielded different enrichments. Thus, extra-mitochondrial acetyl-CoA appears nonhomogeneous. Competition between drugs alters the labeling of individual acetyl-CoA sub-pools. The labeling pattern of acetylated drugs suggests the existence of more than the two N-acetyltransferases identified so far by others. Our data question the possibility of probing the pool of lipogenic acetyl-CoA via drug acetylation.

4-Aminobenzoic Acid↗
PubMed1994

Determination of (13C) urea enrichment by gas chromatography/mass spectrometry and gas chromatography/isotope ratio mass spectrometry.

We present gas chromatographic/mass spectrometric and gas chromatographic/isotope ratio mass spectrometric assays of the 13C enrichment of plasma urea converted to its dimethylaminomethylene derivative. The limits of sensitivity of the two techniques are 0.2% and 0.02%, respectively. The techniques were tested in rats and humans infused with (13C)urea or (3-13C)lactate. (13C)Urea enrichment during the infusion of (3-13 C)lactate in humans was not detectable by gas chromatography/mass spectrometry but was easily measured by gas chromatography/isotope ratio mass spectrometry. These assays should be useful for clinical investigations, in which the incorporation of a (13C)gluconeogenic substrate into glucose must be corrected for the incorporation of 13CO2 derived from the oxidation of the substrate. This correction involves measuring the low-level 13C enrichment of urea.

Adult↗
PubMed1994

Assay of the concentration and 13C enrichment of acetate and acetyl-CoA by gas chromatography-mass spectrometry.

We present two techniques for determining the concentration and 13C enrichment of acetate in biological fluids. After the sample has been spiked with an internal standard of [2,2,2,2H3,1-13C]acetate, acetate is first enzymatically converted to acetyl-coenzyme A, which is chemically converted to acetylglycine. The latter is analyzed by gas chromatography-mass spectrometry, either as a methyl ester by positive chemical ionization or as a pentafluorobenzyl ester by negative chemical ionization. The mole percentage enrichment of tissue acetyl-CoA can also be assayed after conversion to acetylglycine pentafluorobenzyl ester.

Acetates↗
PubMed1994

Assay of the enantiomers of 1,2-propanediol, 1,3-butanediol, 1,3-pentanediol, and the corresponding hydroxyacids by gas chromatography-mass spectrometry.

We developed gas chromatographic-mass spectrometric assays for the enantiomers of 1,2-propanediol, 1,3-butanediol, 1,3-pentanediol, and their corresponding hydroxyacids, lactate, beta-hydroxybutyrate, and beta-hydroxypentanoate (3-hydroxyvalerate) in biological fluids. The corresponding ketoacids, acetoacetate and beta-ketopentanoate, can be assayed simultaneously by pretreating the samples with NaB2H4. The assays involve spiking the samples with deuterated internal standards, deproteinization, ether extraction, and derivatization of the carboxyl groups with (R,S)-2-butanol/HCl and of the hydroxyl groups with chiral (S)-(+)-2-phenylbutyryl chloride. Mass spectrometric analysis is conducted under ammonia positive chemical ionization. We used these assays to follow the metabolism of diol enantiomers in dogs. For (R,S)-1,3-butanediol and (R,S)-1,3-pentanediol, the uptakes from dog plasma of the R and S enantiomer of each diol were identical. In contrast, the metabolism of (S)-1,2-propanediol was faster than that of (R)-1,2-propanediol. (R)-1,2-Propanediol is formed during acetone metabolism, while (R,S)-1,3-butanediol and (R,S)-1,3-pentanediol are potential nutrients. The assays developed will allow further investigations of the metabolisms of acetone, (R)-lactate, and artificial nutrients derived from the 1,3-butanediol and 1,3-pentanediol enantiomers.

3-Hydroxybutyric Acid↗
PubMed1994

Revisited indications for bone marrow examinations in HIV-infected patients.

We reviewed the indications for and the results of bone marrow examination (BME) from HIV-infected patients as an attempt to improve its diagnostic yield. One-hundred-and-eight bone marrow specimens from 90 patients during a 3-year period were examined. A cytological, histological and microbiological study was carried out on the specimens. Forty-three evaluable examinations (40% of total) performed for cytopenia showed normo- or hypercellularity in 33 (77%). Fifty bone marrow specimens were cultured for mycobacteria with a yield of 42% when the indication was persistent fever. Positive cultures yielded Mycobacterium avium complex in 8 out of 12 patients. Twenty-seven patients had both culture and biopsy; granulomas were associated with all the positive (10/10) and with 1 out of 17 negative cultures (chi-square test: p < 0.001). A bone marrow involvement with lymphoma was found in 2 out of 6 patients with previously diagnosed lymphoma, and biopsy revealed a lymphoma in 2 patients. Morphological bone marrow examination should be associated with other techniques in order to appreciate bone marrow production. Bone marrow biopsy is useful for the investigation of persistent fever since granulomas suggestive of disseminated mycobacteria are frequent and allow a treatment to be initiated before microbiological confirmation and antibiotic susceptibility test.

Adolescent↗
PubMed1994

HLA-DRB and -DBQ typing by PCR amplification using sequence-specific primers (PCR-SSP): assessment after 1 year of routine use by three laboratories.

Using sequence-specific amplifications, a practical and fast technique for DRB and DQB typing has been developed. The primers are chosen in order to amplify groups of alleles corresponding to the same serological specificity. In a second step, precise allelic determination is obtained by studying the restriction fragment length polymorphism of the PCR products. The experience of three laboratories using this technique in the context of organ or bone marrow transplantation is reported.

Alleles↗
PubMed1994

Reduced variability in Y-chromosome-specific haplotypes for some Central African populations.

Only 7 nonrare haplotypes concerning Y-chromosome-specific TaqI fragments recognized by DNA probes p49f and p49a were encountered in 433 individuals belonging to 7 populations living in central Africa. Most of the haplotypes (77.7%) are characterized by the allelic combination A1,C0,D0,F1,I1 (haplotype IV). The degree of variability displayed by these sequences is low in the African population studied, compared with Europeans, probably because of the recent common origin of the Bantu-speaking populations studied and the common practice of male polygamy in Africa.

Africa, Central↗
PubMed1994

Prenatal diagnosis for the unstable CTG repeat sequence in myotonic dystrophy: a retrospective study in a French family.

The results of DNA analysis for the unstable CTG repeat are reported in a french family of myotonic dystrophy. This retrospective study confirms results obtained previously with a linked DNA marker, using the CTG repeat DNA sequence in the same family. The demonstrated possibility of predicting phenotype as well as genotype in prenatal diagnosis is important for such a disorder, were subjects may be severely affected.

Adult↗