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Biomedical subjects

C Pasquier

Publications and source records attributed to C Pasquier.

At least 91 records · Page 5Linked to original sources
PubMed1988

Superoxide anion production in glass-adherent polymorphonuclear leukocytes and its relationship to calcium movement.

The production of superoxide anion (O2-.) was measured in relation to 45Ca movement in glass-adherent polymorphonuclear leukocytes (PMNs), and the results were compared with those obtained by ourselves and others on PMNs in suspension. In adherent PMNs, O2-. production stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) was of rapid onset and short duration; this was also true of PMNs in suspension. However, O2-. production was insensitive to the concentration of extracellular calcium. Both in adherent and non-adherent PMNs, O2-. production stimulated with phorbol myristate acetate (PMA) had a latency time and was of long duration. In adherent PMNs, pretreatment with PMA potentiated the FMLP-induced O2-. production by lengthening its duration without changing its initial rate. In adherent PMNs (10(-10)-10(-7) M) FMLP induced a fast but transient dose-dependent increase in 45Ca within 1 min, whereas PMA only released 45Ca about 5 min after its addition to the cell culture medium. Pretreatment of PMNs with 10 or 100 ng/ml PMA for 3 min before stimulation by 10(-7) M FMLP reduced the 45Ca efflux observed with FMLP alone. We conclude that O2-. production by adherent PMNs cannot simply be related to Ca2+ movement. In comparison with non-adherent cells, adherence seemed to interfere with the characteristics of both calcium and O2-. generation, probably by modifying the cytoskeleton.

Calcium↗
PubMed1988

In vivo 31P nuclear magnetic resonance (NMR) study of cerebral metabolism during histotoxic hypoxia in mice.

The alterations of cerebral energetic metabolism and intracellular brain pH that occur during histotoxic hypoxia were estimated in mice by in vivo 31P nuclear magnetic resonance (NMR) spectrometry. The brain spectra obtained by means of chronically implanted surface coils connected to a special designed probe were recorded sequentially and continuously before, during, and after histotoxic hypoxia induced by an injection of potassium cyanide. The levels of PCr, ATP, inorganic phosphate, and intracellular pH estimated from the records of the 31P cerebral spectra and the cerebral cortical activity allow noninvasive monitoring of both the energetic metabolism and the functional state of the brain in unanesthetized animals. The time courses of these different parameters are largely the same as those obtained previously by invasive methods, however, the simultaneous and continuous monitoring performed in this study exhibits several unexpected dissociations between, respectively, onset of coma, decrease in PCr level and intracellular pHi, and recovery of normal levels of PCr and intracellular pH. These dissociations indicate that tissue acidosis plays a minor role in the changes in PCr levels, compared with ATP, and they confirm that the thresholds of oxidative metabolism required for functional tissue activity and a normal rate of ATP are clearly different.

Animals↗
PubMed1988

Deferoxamine reduces neutrophil-mediated free radical production during cardiopulmonary bypass in man.

We assessed the effects of the iron chelator deferoxamine in 24 adult patients (12 controls, 12 treated) undergoing cardiopulmonary bypass for various cardiac operations. Deferoxamine was given both intravenously (30 mg/kg of body weight, starting 30 minutes before and ending 30 minutes after bypass) and as an additive to the cardioplegic solution (250 mg/L). Right atrial blood samples were taken before, during, and after bypass, and isolated polymorphonuclear neutrophils were evaluated for their capacity to generate superoxide radicals after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FLMP, 10(-7) mol) and phorbol myristate acetate (100 ng/ml). At the same sampling times, measurement of the plasma levels of 6-keto-prostaglandin F1 alpha, the stable derivative of prostacyclin, was used as an index of membrane phospholipid breakdown. The two groups were not significantly different with regard to age, duration of bypass, and quantitative changes in polymorphonuclear neutrophil counts during the operation. Before bypass, the superoxide production of FMLP-stimulated polymorphonuclear neutrophils was comparable in the two groups. Conversely, after bypass, polymorphonuclear neutrophils harvested from deferoxamine-treated patients produced significantly fewer superoxide radicals than those of control patients (1.9 +/- 0.3 versus 3.7 +/- 0.2 nmol/10(6) polymorphonuclear neutrophils per minute, p less than 0.05). Stimulation of polymorphonuclear neutrophils by phorbol myristate acetate yielded similar changes, as the postbypass superoxide production was 12.6 +/- 2.5 nmol/10(6)/min in control patients and 7.1 +/- 0.9 nmol/10(6)/min in those receiving deferoxamine (p less than 0.05). In contrast, plasma levels of 6-keto-prostaglandin F1 alpha were not significantly different between the two groups. We conclude that deferoxamine-exposed polymorphonuclear neutrophils have a decreased oxidative responsiveness, compatible with the fact that they may have been less "primed" by secretagogues released during bypass, as compared with cells of untreated patients. Our results are consistent with the hypothesis that deferoxamine, by inhibiting iron-catalyzed free radical production, may limit the free radical-mediated amplification of the inflammatory response to bypass and as such could be effective in reducing the harmful effects of extracorporeal circulation.

Cardiopulmonary Bypass↗
PubMed1988

Ca2+ measurement with ion selective electrodes. The French coordinated evaluation of seven analyzers, for a better clinical relevance and acceptance.

The measurement of ionized calcium has evolved in the last decade, and can now be easily performed by clinical laboratories using direct potentiometric analyzers available from a number of manufacturers. An original protocol for a comparison of the analyzers was used through a parallel multicenter evaluation in France. Using newly developed aqueous buffered solutions, this study focused not only on the analytical performance and operational handling of analyzers, but also on possible interferences in biological samples and the clinical relevance of the measurement with respect to the techniques of sample collection. All the instruments exhibited good precision and linearity, and were easy to handle and robust for daily use. However, not all the models gave identical results on the same patient's specimen. The utility of some Ca2+ analyzers has been further enhanced by the ability to "correct" the results to pH 7.40, although care must be taken in the interpretation of these results. While there are a number of clear-cut situations in which Ca2+ measurement is more relevant than total calcium, it seems that chemical activity of Ca2+ in blood may sometimes be considered with great caution under pathological conditions. The role of Ca2+ measurement in routine will be discussed in relation to the potential benefits of the instruments in laboratories.

Autoanalysis↗
PubMed1988

[Influence of gamma irradiation on the chemiluminescence of alveolar macrophages in guinea pigs at rest or activated].

The capacity of Guinea Pig alveolar macrophages to produce oxygenated free radicals after in vitro gamma irradiation was studied. We observed an increase of resting cell chemiluminescence with 3 Gy, then an important decrease from 3 Gy to 30 Gy. Chemiluminescence of zymosan activated macrophages was reduced at 10 Gy and 30 Gy, while activation by IgG anti-MHC antigens was not affected by the same radiation doses. These results could be of great interest for the study pulmonary defense mechanisms after irradiation.

Animals↗
PubMed1986

Cytoplasmic pH Regulation in Acer pseudoplatanus Cells: I. A P NMR Description of Acid-Load Effects.

Modifications of cytoplasmic pH in Acer pseudoplatanus L. cells cultivated in suspension have been induced by acid-loads and studied by using (31)P nuclear magnetic resonance spectroscopy. The initial drop of cytoplasmic pH, observed in the first minutes of exposure to weak lipophilic acids, was followed by a slow recovery to reach a plateau phase with a pH value lower than the initial one. Conversely, removal of the acid led to a sharp increase of cytoplasmic pH with in most cases an overshoot toward more alkaline values than the initial one and a subsequent decrease to more acidic values. This shows that A. pseudoplatanus cells powerfully regulate their cytoplasmic pH both on the acid side of their normal pH, during the acid-load, and on the alkaline side, after removal of acid. Similar results were obtained with different types of acid-loads, i.e. treatments with propionic or benzoic acid or bubbling with CO(2)-enriched air. This indicates that the occurrence of pH regulation does not depend upon the method used to acid-load the cells. The time courses of cytoplasmic pH observed for A. pseudoplatanus and also Catharanthus roseus cells are similar to those recorded for animal cells but different from those described for other plant materials for which no recovery phase was observed. This can be explained by different balances between the initial rate of proton influx brought in by the acids, and the capacity of proton consumption by the regulatory mechanisms. The existence of the recovery phase offers a unique possibility to study the regulation of the cytoplasmic pH of plant cells, as it has been done in animal systems.

Journal Article↗
PubMed1986

Cytoplasmic pH Regulation in Acer pseudoplatanus Cells: II. Possible Mechanisms Involved in pH Regulation during Acid-Load.

Qualitative and quantitative aspects of the mechanisms involved in the regulation of cytoplasmic pH during an acid-load have been studied in Acer pseudoplatanus cells. Two main processes, with about the same relative importance, account for the removal of H(+) from the cytoplasm, namely a ;metabolic consumption' of protons and the excretion of protons or proton-equivalents out of the cells. The metabolic component corresponds to a change in the equilibrium between malate synthesis and degradation leading to a 30% decrease of the malate content of the cells during the period of cytoplasmic pH regulation. Various conditions which severely inhibit the activity of the plasmalemma proton pump ATPase reduce, at most by 50%, the excretion of H(+). This suggests that, besides the plasmalemma proton-pump, other systems are involved in the excretion of proton-equivalents. Indirect information on qualitative and quantitative features of these systems is described, which suggests the involvement of Na(+) and HCO(3) (-) exchanges in the regulation of cytoplasmic pH of acid-loaded cells.

Journal Article↗
PubMed1985

Spectroscopic interference of hemoglobin with neutrophil cytochrome b-245 and its elimination by carbon monoxide.

A cytochrome b, designated as cytochrome b-245, exists in neutrophils and is probably involved in their stimulated oxidative burst. As a rule, its concentration is spectroscopically measured by the height of its alpha-peak at 558-559 nm (dithionite-reduced minus oxidized). Hemoglobin (Hb), which usually contaminates neutrophils isolated from blood, interferes with the spectroscopic measurement of the cytochrome. Hb contamination from less than 0.4 red blood cells per 100 neutrophils leads to over-estimation of the cytochrome by approximately 50%. This interference can be overcome by bubbling CO through neutrophil homogenates heavily contaminated by Hb, prior to the conventional spectroscopic procedure. The cytochrome B-245 concentration obtained in neutrophils by CO bubbling is 7.2 +/- 1.28 pmoles per 10(6) polymorphonuclear neutrophils.

Carbon Monoxide↗
PubMed1985

Cytochrome b-245 in human alveolar macrophages.

To kill microorganisms, phagocytes exhibit an oxidative burst with, in particular, a NADPH-dependent, superoxide-generating system that consists, in polymorphonuclear leukocytes (PMN), of a flavin enzyme and cytochrome b-245 (cyt b-245). We investigated the existence of this cytochrome in human alveolar macrophages (AM) because its presence would support its wide-spread occurrence in phagocytes and would raise the possibility of similarities in the oxygen-dependent killing mechanisms in AM and PMN. Moreover, we compared the amount of cyt b-245 in AM from patients with lung disorders with that from healthy subjects, by a differential spectroscopic measurement of its 558 to 559 nm characteristic band. This spectrum showed that cyt b-245 was present in AM. In AM of healthy subjects, the amount was similar to that found in PMN of blood. In AM of patients with miscellaneous lung diseases and in Am of infected lungs, the data were not modified.

Cytochrome b Group↗
PubMed1984

Luminol assay for microdetermination of superoxide dismutase activity: its application to human fetal blood.

A microtechnique for determining the superoxide dismutase activity in erythrocytes is described. This technique involves the inhibition of luminol-enhanced chemiluminescence of superoxide anion generated by xanthine-xanthine oxidase. Measurements required a steady-state chemiluminescence whether superoxide dismutase was present or absent; the level of luminescence was correlated to enzyme activity. Superoxide dismutase activity measured by this technique was 836 +/- 112 micrograms/g of hemoglobin for whole blood and 834 +/- 109 micrograms/g of hemoglobin for erythrocytes. When the reference technique was applied to larger amounts of blood, the results were 862 +/- 58 and 858 +/- 116 micrograms/g of hemoglobin for whole blood and washed erythrocytes, respectively. The enzymatic activity of superoxide dismutase from fetal blood (obtained by venipuncture in utero and of 19-26 weeks gestational age) was similar to that of adult blood, when measured by the new technique.

Adult↗
PubMed1984

Manganese-containing superoxide-dismutase deficiency in polymorphonuclear leukocytes of adults with rheumatoid arthritis.

Superoxide dismutase (SOD) is known to regulate the level of superoxide radicals inside cells. The purpose of this work was to investigate the role of SOD activity in tissue damage produced by superoxide radicals. SOD was measured in polymorphonuclear cells of patients with rheumatoid arthritis and controls. The distinct SOD activities, including manganese-containing and copper-zinc-containing enzymes, were evaluated in cytoplasma and mitochondria of human granulocytes. Except for the comparison between total SOD and cytoplasmic copper-zinc SOD, no correlation was found among the different SOD levels. Moreover, a significant decrease was observed only for cytoplasmic manganese-containing enzyme in granulocytes of adults with rheumatoid arthritis. These data confirm the necessity of evaluation of various SOD classes and suggest the interest of biochemical tests in granulocytes for early diagnosis and better comprehension of tissue damage due to inflammation.

Adult↗
PubMed1983

Pituitary-adrenal axis activity in rats after whole-body irradiation. Comparison with plasma cortisol evolution in four cases of human protracted whole-body irradiation.

Plasma ACTH and adrenal and plasma corticosterone levels were studied in rats during 30 days after LD50 irradiation. Plasma cortisol levels were studied in man after protracted whole-body irradiation. In both cases, a period of great instability of adrenal function was associated with bad clinical conditions. Then, a period of adrenal dysfunctioning, reversible with time, occurred in rats and in one patient.

Adrenal Glands↗
PubMed1983

[Role of membrane sialic acid of human granulocytes in the stimulation of NADPH,H+ oxidase activity].

The treatment of human polymorphonuclear cells by neuraminidase "type-X" removes about 15% of cell sialic acid without modifications of NADPH oxidase activity of granulocytes before and after stimulation by opsonized zymosan. A mild periodate treatment oxidizes only the poly-hydroxilic chain of sialic acid with formation of aldehyde groups. This treatment increases cellular NADPH oxidase activity and also largely prevents the stimulation of polymorphonuclear cells by opsonized zymosan.

Cell Membrane↗