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Biomedical subjects

J Arnaud

Publications and source records attributed to J Arnaud.

At least 145 records · Page 8Linked to original sources
PubMed1985

Haematology and erythrocyte metabolism in man at high altitude: an Aymara-Quechua comparison.

In the course of haematological and biological investigations among Aymara and Quechua populations in Bolivia, an anthropological study of the erythrocytary respiratory function was carried out on the two groups at two altitudes: 3,600 m and 450 m. A difference in the intensity of the biological variations of the two populations is observed at high altitude. In the Quechuas, as in any lowland native, the adaptative phenomena are totally and quickly reversible. In the Aymaras, we detected the existence of more marked haematological and biochemical characters: moderate polycythemia, hyperhaemoglobinemia, microcytosis, metabolical hyperactivity with accumulation of 2-3 di-phosphoglycerate and ATP, and methaemoglobinemia with a drop in the activity of the methaemoglobin reductases. The Aymaras preserve some of those characters (methaemoglobinemia excepted) when they settle in lowlands.

Acclimatization↗
PubMed1985

Recombination between HLA-A and C and between HLA-B and complement locus C4 in the same individual.

In a French family with 2 parents and 5 children a crossing over was found in the HLA region on both of the parental haplotypes of one of the children. The following markers were studied: HLA-A, B, C,DR, DQ(MB), DP(SB), complement allotypes C4 and Bf and glyoxalase I polymorphism. In the third child, the paternal haplotype had a recombination between HLA-A and HLA-C and the maternal haplotype a recombination between HLA-B and complement locus C4. Mixed lymphocyte cultures confirmed the serological findings and non-HLA markers (blood groups and immunoglobulin allotypes) showed no evidence of extrapaternity. The family also demonstrates a probable duplication of the C4B1 gene in one of the paternal haplotypes.

Complement C4↗
PubMed1985

[Trace elements (zinc, copper, manganese) in alcoholic cirrhosis: effect of chronic alcoholism].

The authors studied the influence of alcohol intake and liver disease in the disturbances of trace elements detected in patients with alcoholic cirrhosis. A determination of zinc, copper and manganese was carried out in the serum, the 24 h urine and a liver sample in 15 patients with alcoholic cirrhosis, 11 chronic alcoholics and 17 control subjects. In the serum of cirrhotic patients, zinc was significantly decreased, copper and manganese significantly increased. In the liver, zinc was decreased and copper increased, but the difference did not read significantly. The elimination of zinc in urine was increased and that of manganese decreased. In the chronic alcoholic patients only the serum zinc was decreased. Chronic alcoholism seemed to be therefore one of the factors responsible for low serum zinc in patients with alcoholic liver disease.

Adult↗
PubMed1984

Human red cell glycolysis in high altitude chronic hypoxia.

We have found that glycolysis in human red blood cells under the hypoxic conditions found at high altitudes is connected with changes in enzyme activities and levels of various metabolic intermediates. The sensitivity of the four kinases to hypoxia results in 1) glycolytic hyperactivity leading to a higher intracellular energy state, and 2) accumulation of 2-3 DPG, whose role in the adaptation of red blood cell respiration to high altitude has been shown by previous research. PEP, 3PG , and G6P appear to be the main regulating intermediates in glycolysis in this system. The reason for the very large increase in G1- 6DP is still not clear.

2,3-Diphosphoglycerate↗
PubMed1984

Cytochemical detection of phosphatase and arylsulphatase activities in the midgut of Centropages typicus (Copepod, Calanoid).

Ultrastructural study of the midgut of Calanoid Copepods revealed the presence of several cell types in all species. In a previous report we described and assigned a function to each of these cell types. In order to affirm the validity of those assignments we undertook an investigation of enzymatic activity especially of phosphatase and arylsulphatase. By cytochemical methods, alkaline phosphatase activity was detected in R-, R'-D- and B-cells, with labelling being observed on the apical plasmic membrane level in all four, and in B-cells on the pinocytotic vesicle membranes. Acid phosphatase and aryl-sulphatase activities were only detectable in B-cells; the most frequently labelled structures were located in the vacuolar system, dictyosomes and Golgi vesicles, although Golgi structures occasionally reacted to acid phosphatase. Nome of the dense bodies observed in B-cells reacted to arylsulphatase. Similarly they were unevenly labelled during acid phosphatase tests. Hence it may be assumed that dense bodies are not involved in hydrolases. It is possible that these enzymes originated from vesicles generated by the Golgi saccules surrounding and joined to the vacuoles, thus bypassing the lysosome I stage.

Animals↗
PubMed1983

On the similarity of triacylglycerol and acylcholesterol lipases in rat brain.

Previously, we described a similar stimulating effect of adrenocorticotrophic hormone (ACTH) and ACTH-related synthetic peptides on triacylglycerol (TAGL) and acylcholesterol (ACL) lipase activities of rat brain. In present study, TAGL and ACL activities from rat brain were further investigated and compared through the use of tri-[3H]oleoylglycerol and [14C]oleoylcholesterol, respectively, as the substrates. A number of specific properties proved to be similar for both activities: (a) comparable rates of activity decay were observed upon heat treatment, (b) similar reaction kinetics as determined at different substrate concentrations with and without ACTH (10(-4) M), (c) both activities showed a common susceptibility to the presence of sodium taurocholate (5 mM) or trace amounts (5 microliter/ml) of organic solvent in the assay medium, (d) the distributions of the two activities in various brain regions were comparable. Taken together, these data, along with the similar activability by ACTH, suggest a common structural basis for TAGL and ACL activities in rat brain.

Adrenocorticotropic Hormone↗
PubMed1983

Characterization of a diester lipase activity in human erythrocytes.

A diester lipase activity is described in human red blood cells (RBC). Diester lipase activity acts as a membrane-bound enzyme and is assayed using intact RBC as the enzyme source. An emulsion of di-[3H]-oleoylglycerol (0.6 mM) serves as the substrate. The optimum pH for the reaction is 7.8 at 37 degrees C. Lipolytic rates are monitored by quantitation of the amount of [3H]-oleic acid released during 20 min of incubation after a two-step purification procedure. [3H]-oleic acid is first extracted from the incubation mixture by means of a liquid-liquid partition system and further isolated by thin-layer chromatography. Suspensions of purified RBC obtained from 36 healthy adult subjects had a diester lipase activity of 196 +/- (SD) 45 mU/10(12) RBC, with no difference between men and women.

Adult↗
PubMed1983

The effect of high altitude on the glycolytic activity of erythrocytes in natives of the Andean Altiplano.

Glucose consumption by anaerobic glycolysis and the pentose pathway were studied in two Aymara populations living at different altitudes (3 600 m and 450 m). The measurements were made both with and without methylene blue. We observed a Pasteur effect for both pathways which may explain the increase in 2-3 DPG and ATP levels found in blood samples from people living at high altitudes. The results in the presence of methylene blue showed a reduced activity of the methaemoglobin reductase system in the high altitude group which may be partly responsible for their increased levels of methaemoglobin.

Adult↗
PubMed1982

[Oogenesis in Centropages typicus (Copepoda, Calanoida)].

We carried out a complete study of oogenesis in Centropages typicus using structural, ultrastructural and cytochemical data. The usual stages of oogenesis, i.e. germinative phase, premeiosis, primary and secondary vitellogenesis, were found. The latter two stages were the most typical. Primary vitellogenesis consisted of endogenous yolk accumulations; these substances, probably of lipoprotein or lipoglycoprotein nature, were produced at the granular endoplasmic reticulum level and then stocked in the reticulum cavities. During secondary vitellogenesis, endogenous yolk production continued, but we mainly observed the development of exogenous yolk accumulation (lipid droplets and protein globules) in the ooplasm. These accumulations resulted from the fusion of very numerous pinocytotic vesicles arising from the oolemma and containing substances probably brought to the oocytes by the hemolymph. The effect of various proteases on the vitellus globules caused a more or less marked digestion of their contents, tending to prove their protein nature. The end of vitellogenesis was marked by the appearance of vacuolar formations with dense lamellae which could correspond to cortical granules.

Animals↗
PubMed1981

Does the neurotropic action of adrenocorticotrophic hormone involve a lipolytic step?

The stimulatory effect of adrenocorticotrophic hormone (ACTH)-related synthetic peptides on the hydrolysis of emulsified trioleoylglycerol by a rat brain lipase was studied. The ACTH effect was related to the net positive charge associated with the basic amino acid residues at position 15-18 in the ACTH sequence, as well as to the presence of the NH2-terminal amino acid residues at position 1-2. The ACTH effect on lipolysis was markedly reduced when lipids were partially removed from the enzyme preparation by extraction with chloroform/acetone. Full restoration of the stimulatory effect was obtained upon addition of phosphatidylcholine (2 mg/ml) to the lipolytic medium. Striking similarities between the structure-activity pattern for the stimulatory effect of ACTH on brain lipase and that described for the receptor-mediated actions of ACTH on adrenal and fat cells suggest that the ACTH effect might involve recognition of a binding site associated with the brain enzyme. Complete log concentration response curves obtained with four ACTH analogs may also be regarded as simulating hormone-receptor interaction. These findings are discussed in relation to the possibility that ACTH may have a neurohormonal role via lipase-catalyzed changes in the lipid matrix of membranes.

Adrenocorticotropic Hormone↗
PubMed1981

Enhanced activity of brain lipase in the presence of adrenocorticotrophic hormone. Comparison with a colipase effect.

The characteristics of the pH-dependent stimulatory influence of adrenocorticotrophic hormone (ACTH) on lipolysis (Arnaud, J., Nobili, O. and Boyer, J. (1980) Biochim, Biophys. Acta 617, 524-528) were investigated further. ACTH enhanced 7-30 times the rates of hydrolysis of emulsified trioleoylglycerol by a rat brain lipase, when added to the medium both before and after the enzyme. When lipase activity was inhibited by sodium taurocholate, ACTH fully reversed the inhibition at bile salt concentration up to 2 mM. The reactivation process followed a sharp S-shaped pattern, leveling off at about 10(-4) M ACTH. With and without bile salt, the stimulatory effect of ACTH culminated at pH 5.75, and was dependent on the presence of trace amount of a water-insoluble solvent in the substrate emulsion. Taken together, the results suggest that ACTH acts at the lipid-water interface in facilitating the enzyme-substrate interaction. The relevance of the hormonal influence to a colipase-like effect is discussed.

Adrenocorticotropic Hormone↗
PubMed1981

Human erythrocyte monoester lipase: characterization and radiochemical assay of the cell-bound enzyme in normal subjects.

A monoester lipase (MEL) activity (EC 3.1.1.3) is described in human red blood cells (RBC). The lipase acts as a cell-bound enzyme and is able to exert its catalytic activity in vitro toward an exogenously added emulsified substrate. The enzyme activity, which appears to be confined to the cell membrane, is inhibited by Triton X-100. The MEL activity of human RBC is assayed using intact RBC as the enzyme source, with an emulsion of ethyl [3H]oleate (2 mM) as the substrate. The optimum pH for the reaction is 7.8 at 37 C. Lipolytic rates are monitored by quantitation of the amount of [3H]oleic acid released during 20 min of incubation after extraction by means of a liquid-liquid partition system. Suspensions of purified RBC obtained from 161 healthy adult subjects had a MEL activity of 1022 +/- 134 microunits/10(12) RBC (mean +/- SD), with a normal range (+/- 2 SD) between 754-1290 microunits. The individual activity values varied from 733-1490 microunits. The median of the 161 subjects was 1010 microunits/10(12) RB. There was no significant difference between the mean activities of RBC samples from men and women. MEL activity in RBC from the cord blood of 16 normal infants was found to be 43% higher than that in adults, with an average activity of 1458 +/- 174 microunits (mean +/- SD).

Adult↗
PubMed1980

In vitro effect of adrenocorticotrophic hormone on the pH profile of tri- and diester lipase activities from rat brain.

The influence of adrenocorticotrophic hormone (ACTH) on the hydrolysis of tri- and dioleoylglycerol by a cerebral lipase was studied using a synaptosomal preparation from rat brain as source of enzyme. When ACTH was added to the lipolytic medium, it caused a marked shift of the optimum pH values of catalysis towards alkaline values. In the pH range 5.8-6.5, these shifts resulted in reaction rates 5- to 20-fold higher, depending on the experimental conditions, than those measured without hormone. The ACTH effect was dependent on the NH2-terminal sequence extending through the amino acid residues 15-18. The results suggest that the hormonal influence is specific and mediated through a colipase-like effect.

Adrenocorticotropic Hormone↗