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P Laurent

Publications and source records attributed to P Laurent.

At least 19 recordsLinked to original sources
PubMed1992

Mechanisms of ion and acid-base regulation at the gills of freshwater fish.

This review examines the branchial mechanisms utilized by freshwater fish to regulate internal acid-base status and presents a model to explain the underlying basis of the compensatory processes. Rainbow trout, Oncorhynchus mykiss, and brown bullhead, Ictalurus nebulosus, were examined under a variety of experimental treatments which induced respiratory and metabolic acid-base disturbances. Acid-base regulation was achieved by appropriate adjustments of Na+ and Cl- net fluxes across the gills which, in turn, were accomplished by variable contributions of three different branchial mechanisms: 1) differential changes in Na+ and Cl- diffusive effluxes, 2) changes in internal substrate (H+, HCO3-) availability, and 3) morphological adjustments to the gill epithelium. Differential diffusive efflux of Na+ over Cl- was involved only during periods of metabolic alkalosis. The importance of internal substrate availability was demonstrated using a two-substrate model. According to the model, ionic flux rates (J(in)Cl-, J(in)Na+) are determined not only by the concentration of the external ion (Na+, Cl-) but also by the concentration of the internal counterion (H+, HCO3-). This system provides for an "automatic negative feedback" to aid in the compensation of metabolic acid-base disturbances. Morphological alteration of the gill epithelia and the associated regulation of chloride cell (CC) fractional area is an essential third mechanism which is especially important during respiratory acid-base disturbances. Specifically, fish vary the availability of the CC associated Cl-/HCO3- exchange mechanism by physical covering/uncovering of CCs by adjacent pavement cells.

Acid-Base Equilibrium↗
PubMed1992

The neuroepithelial cells of the fish gill filament: indolamine-immunocytochemistry and innervation.

The neuroepithelial cells (NECs) of the fish gill filament share several morphofunctional features with the cells of the neuroepithelial bodies in the lungs of air-breathing vertebrates. In the present study, a detailed indolamine-immunocytochemical analysis of the branchial neuroepithelial cells and nerves was undertaken in non-teleost and teleost species, with particular emphasis on the latter. In the rainbow trout, Oncorhynchus mykiss, the chemical degeneration of either catecholaminergic (by 5- and 6-hydroxydopamines) or indolaminergic (by 5,6-dihydroxy-tryptamine) innervations associated with the NECs was studied using electron microscopy. In teleosts, the NECs are located primarily on the distal half of the filament. In the trout particularly, these cells are innervated mainly by non-indolaminergic nerves taking up sympathetic neurotoxins. The proximal half of the filament contains isolated NECs innervated additionally by intrinsic indolaminergic neurons. Serotonin-like immunoreactivity of the NECs is evident in the granular vesicles packed within the basal soma and processes which surround non-vascular and vascular smooth muscles in the filament. Apical processes from the neuroepithelial cells occasionally contact the water on the surface of the filament epithelium. The secretory function of the NECs is discussed with reference to the probable involvement of serotonin in the modulation of fish gill function. In addition, their connections with both central and branchial nervous systems suggest a possible chemoreceptor role.

Animals↗
PubMed1992

Evidence for a morphological component in acid-base regulation during environmental hypercapnia in the brown bullhead (Ictalurus nebulosus).

Exposure of adult brown bullheads Ictalurus nebulosus (120-450 g) to environmental hypercapnia (2% carbon dioxide in air) and subsequent recovery caused transient changes in whole body net sodium flux (JnetNa+) and net chloride flux (JnetCl-) resulting largely from changes in whole body sodium influx (JNa+in) and chloride influx (JinCl-). Scanning electron microscopy (SEM) revealed that the fractional area of chloride cells (CCs) on the interlamellar regions was reduced by 95% during environmental hypercapnia. During post-hypercapnic recovery, gill filament CC fractional area increased. The changes in JinCl- during and after environmental hypercapnia were closely associated with the changes in CC fractional area while the changes in JinNa+ did not correspond to the changes in CC fractional area. Transmission electron microscopy (TEM) supported the SEM observations of CC surface area changes and demonstrated that these changes were caused by covering/uncovering by adjacent pavement cells (PVCs). Lamellar and filament PVC microvilli density increased during hypercapnia while there was a subsequent reduction in the posthypercapnic period. These data suggest that an important mechanism of acid-base regulation during hypercapnic acidosis is modification of the chloride cell-associated Cl-/HCO3- exchange mechanism. We suggest that bullheads vary availability, and thus functional activity, of this transporter via reversible morphological alterations of the gill epithelium. The increase in density of PVC microvilli may be associated with sodium uptake and/or acidic equivalent excretion during acidosis.

Acid-Base Equilibrium↗
PubMed1991

Expression and pharmacological characterization of the human peripheral-type benzodiazepine receptor in yeast.

Recently we cloned the cDNA coding for the putative human peripheral-type benzodiazepine receptor (hPBR). This report describes the expression of this cDNA in Saccharomyces cerevisiae and the characterization of the recombinant protein. The expression was achieved by placing the receptor cDNA under the control of a galactose-regulated artificial promoter. After galactose induction, the transformed cells expressed a functional hPBR which displayed a Kd for the specific peripheral-type ligand [3H]PK11195 of 9.9 +/- 1.3 nM and a maximal binding capacity of 249,300 +/- 50,400 sites/cell. The pharmacological characterization of the recombinant receptor, determined in competitive ligand binding experiments, agrees closely with that described for the natural receptor expressed by human cells. Furthermore, the binding was stereospecific as shown by the displacement of the [3H]PK11195 binding by PK14067 (-Q1) and not by PK14068 (+Q1). Photolabeling experiments showed that transformed cells expressed a 18 kDa protein which was specifically labeled with [3H]PK14105. Altogether these results show that the cDNA transfected in yeast encodes a 18 kDa protein with the expected characteristics of the hPBR.

Affinity Labels↗
PubMed1991

Active urea transport independent of H+ and Na+ transport in frog skin epithelium.

We investigated the relationship between H+ secretion (JH), Na+ absorption (JNa), and urea transport (Ju) in skin of frogs (Rana esculenta) adapted to running tap water, NaCl (100 mM), and KCl (100 mM). In addition, cell morphological changes, particularly in the mitochondria-rich cells (MRC), were followed. NaCl adaptation stimulated an active Ju, reduced JNa and JH, and caused a decrease in the apical surface of MRC. After KCl adaptation, JNa and JH were increased and highly correlated, with a twofold increase in Ju, whereas the numerous MRC developed infoldings on their apical membranes. No correlation was found between JH and Ju. Clamping the skins in a range of +/- 50 mV or changing the external pH from 7.4 to 5.4 (at high cellular buffering power) had no effect on Ju. Depolarization of the basolateral membranes (serosal KCl-Ringer) had no effect on Ju. Ju was reversibly blocked by acidification of the cells by oxygen-free solution and sulfhydryl reagents (Hg2+, p-chloromercuribenzenesulfonic acid, and N-ethylmaleimide). Diethylstilbestrol, a proton transport blocker, had no effect on Ju. Apical addition of amiloride and derivatives (phenamil and ethylisopropyl amiloride) reversibly blocked Ju, whereas ouabain had no effect. We conclude that a cation (Na+ or H+)-dependent process is unlikely to exist in R. esculenta skin. A primary active transport in a two-step process is the simplest hypothesis to account for the energy-dependent Ju that develops in NaCl-adapted frogs.

Adenosine Triphosphatases↗
PubMed1990

Direct radioimmunoassay of rat cystatin C: increased urinary excretion of this cysteine proteases inhibitor during chromate nephropathy.

Rat cystatin C was purified to apparent homogeneity from rat urine after induction of a tubular dysfunction with sodium chromate. The two-steps purification procedure included a Carboxymethyl-papain affinity chromatography and anion exchange chromatography. The purified protein was identified as rat cystatin C by the following criteria: firstly retained on a Cm-papain affinity column, secondly an apparent molecular weight of 15 kDa and pI of 10.2. Antisera raised in rabbits against our purified rat cystatin C did not cross-react with other urinary proteins such as rat albumin and rat kallikrein, but partially cross-reacted with human cystatin C. A direct radioimmunoassay was developed and it enabled 8.32 fmol/ml of rat cystatin C to be detected. The detection range was between 0.125 and 62.5 ng/ml, with 10% intra-assay variation and 14% inter-assay variation. Physiological rat cystatin C excretion (40 +/- 18 micrograms/24 h) was found by the direct assay. In the chromate-intoxicated rat, urinary excretion increased twenty-fivefold (1017 +/- 391 micrograms/24 h) and returned to normal level one week after intoxication. This RIA will allow the study of rat cystatin C metabolism particularly during renal dysfunction.

Acute Kidney Injury↗
PubMed1990

Activation of human platelets by C5a-stimulated neutrophils: a role for cathepsin G.

Human platelets can be stimulated by recombinant human fifth component of complement (rhC5a) in the presence of human neutrophils. After challenge with N-formyl-Met-Leu-Phe or rhC5a, concentrated neutrophils release cathepsin G into the supernatant. The concentrations of cathepsin G recovered by titration of the enzymatic activity correlate with the capability of these supernatants to induce platelet stimulation as measured by serotonin release. Cathepsin G purified from neutrophil granules triggered platelet aggregation and serotonin release independent of arachidonic acid metabolites and platelet-activating factor formation. A concentration of 100 nM of cathepsin G, which was reached in the surrounding space of activated neutrophils, induced a 50% platelet stimulation. Three distinct antiproteinases were tested against cathepsin G-induced platelet activation. Z-Gly-Leu-Phe-CH2Cl, a specific inhibitor of cathepsin G enzymatic activity, proved to be nonspecific in our biological system. By contrast, alpha 1-antichymotrypsin and alpha 1-antitrypsin displayed specific activities. The physiological specific inhibitor of cathepsin G, alpha 1-antichymotrypsin, was the most potent and was used in the rhC5a-induced neutrophils-mediated platelet activation. A complete inhibition was achieved, showing that release of cathepsin G from neutrophils accounts for platelet activation. Such a chain of events involving C5a, neutrophils, cathepsin G, and platelets may be of relevance in certain inflammatory states, particularly the adult respiratory distress syndrome.

Amino Acid Sequence↗
PubMed1990

Leaching of antioxidants and vulcanization accelerators from rubber closures into drug preparations.

A thin-layer chromatographic method was used to highlight the leaching into drug preparations of several constituents of elastomeric closures. Among the 150 preparations analysed, the twenty-eight local anaesthetics presented in single-dose delivery syringe-cartridges, one Epinephrine injection in prefilled syringes, eight insulin preparations and two Prednisolone acetate suspensions in the form of small volume flasks (less than or equal to 20 ml) were contaminated by one or more of the following: 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole disulphide and 2-mercaptobenzimidazole (MBI). Prednisolone acetate suspensions also contained 2,2'-methylene-bis(4-methyl-6-alpha-methylcyclohexylphenol). No contamination was found in drug preparations presented in large volume flasks (250-1000 ml). 2-(2-Hydroxyethylthio)-benzothiazole was not present, which indicated that the rubbers had not been sterilized with ethylene oxide. Elastomeric parts of drug closures analysed in the same way contained the same compounds as those found in drugs, one case excepted, which confirms the origin of the contamination. The lowest and the highest concentrations were found in syringe-cartridges; they ranged from 8.3 to 13.8 micrograms ml-1 for MBT, from 2.9 to 9.3 micrograms ml-1 for MBTS and from 2.8 to 11.1 micrograms ml-1 for MBI. Variable results were obtained, for a same preparation, depending upon the batches analysed, which indicates that rubber formulations and/or vulcanization conditions differed. The allergenic, toxic, embryotoxic and mutagenic properties of the compounds leached are discussed.

Antioxidants↗
PubMed1990

Interactions between cigarette smoking and the natural history of idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis is characterized by an inflammation of the walls of the respiratory airspaces that proceed to fibrotic alveolar derangement. Smoking habits are associated with changes in the number and the activation state of immune and inflammatory alveolar cells. Cigarette smoke could interact with the course of this disease. To evaluate the effects of smoking on IPF, 11 smokers and 16 nonsmokers were compared. Clinical presentation, PFTs, BAL cell populations, short-term glucocorticoid responsiveness and survival were evaluated. Similar PFT results were observed in both groups. Lymphocyte cells were higher in nonsmokers than in smokers. Glucocorticoid responsiveness was mainly observed in nonsmokers. Nonsmoking status was not associated with survival advantage. We conclude that the subset of IPF characterized by an aggressive onset, a BAL fluid high lymphocyte count and a substantial PFT improvement after therapy began, occurs predominantly in the absence of cigarette smoking habits.

Bronchoalveolar Lavage Fluid↗
PubMed1990

[Effect of a sanguinarine mouthwash on children with and without upper extremity motor handicap].

A survey was done at the Center of Child Readaptation at Flavigny (Meurthe-et-Moselle) to determine the effect of a mouth rinse containing 0.03% sanguinaria extract, on the plaque accumulation and gingivitis of 30 children 8 to 17 years old. 13 children had a motricity handicap of their superior members and 17 did not. All subjects rinsed their mouths twice with 15 ml of solution each time. The mouth rinses were performed in the morning and in the evening during three weeks. The children were photographed and examined using the P1I and GI indices on days 0, 7, 14, 21 and 35. No statistical significant difference was observed at any moment between children with or without handicapped upper limbs. After 3 weeks of treatment the Plaque Index had decreased 47.3% and Gingival Index 55.6%.

Adolescent↗
PubMed1989

Kinetics of the inhibition of free and elastin-bound human pancreatic elastase by alpha 1-proteinase inhibitor and alpha 2-macroglobulin.

At pH 8.0 and 25 degrees C alpha 1-proteinase inhibitor and alpha 2-macroglobulin bind human pancreatic elastase with rate constants of 4.7.10(5) M-1.s-1 and 6.4.10(6) M-1.s-1, respectively. The corresponding delay times of elastase inhibition in plasma are 0.4 s and 0.2 s, respectively, indicating that both inhibitors may act as physiological antielastases. Elastin impairs the elastase inhibitory capacity of alpha 1-proteinase inhibitor and alpha 2-macroglobulin. In presence of human elastin, the former behaves like a slow-binding elastase inhibitor, with a rate constant of about 260 M-1.s-1. In contrast, alpha 2-macroglobulin is a fast-binding inhibitor of elastin-bound elastase, but only one of its two sites is functioning in presence of elastin.

Animals↗
PubMed1989

Effects of serum amyloid A protein on lymphocytes, HeLa, and MRC5 cells in culture.

A major human acute phase protein, the serum amyloid A protein, has been tested in vitro for its effect on lymphocyte proliferation, the formation of E-stable rosettes, as well as the growth of HeLa and MRC5 cell cultures. Serum amyloid A protein has been found to be markedly inhibitory at 30, 100, 200, and 300 micrograms/mL, and is a very potent inhibitor of in vitro biological functions.

Acute-Phase Reaction↗
PubMed1989

Occurrence and morphology of tumors induced in nude mice transplanted with chrysotile-transformed rat pleural mesothelial cells.

Rat pleural mesothelial cells treated in vitro with chrysotile fibers have been successfully transplanted into nude mice. Three cultures (1 untreated, 2 treated) were injected at passage 75; a fourth culture was obtained from a mesothelioma induced in rat by chrysotile fibers. Overall, tumors grew in each series, but the delay between cell injection and tumor formation was 22 wk with untreated cells whereas only 1 or 2 wk were needed with treated cells, and 1 wk with cells from in vivo-induced mesothelioma. Pathological study by light and electron microscopy of tumors is reported here and showed the mesothelial nature of the cells. Comparison between the ultrastructure of the injected cells and tumor cells indicated that the morphology of injected cells was retained in tumors even if the delay in tumor formation was long. These results suggest that this model is useful for investigating mesothelial cell transformation resulting from in vitro or in vivo exposure to certain carcinogens.

Animals↗
PubMed1989

Plasma catecholamines in rainbow trout (Salmo gairdneri) during hypoxia.

Plasma catecholamines (CAs) were assayed radioenzymatically in normoxic and variably hypoxic rainbow trout (Salmo gairdneri). Results were grouped according to four levels of progressively deeper hypoxemia. Only in animals where PaO2 fell below 6.7 kPa, were both adrenaline (A) and noradrenaline (NA), slightly, but significantly, increased. In contrast, substantial increases of plasma CAs occurred when PaO2 was reduced below 3.99 kPa (increment factor: A = 3.8, NA = 3.4). Comparisons between dose/response data from the literature and the present results suggest that plasma CAs might have a functional role during deep hypoxia. The regulatory role during mild hypoxia remains uncertain due to the lack of data concerning plasma CA prebranchial concentrations and of more precise dose/response relationships.

Animals↗
PubMed1988

Quantitation of elastin in human urine and rat pleural mesothelial cell matrix by a sensitive avidin-biotin ELISA for desmosine.

A specific enzyme-linked immunosorbent assay (ELISA) was developed for the determination of desmosine, a cross-linked amino acid specific to fibrous elastin. Competition between solid phase-bound desmosine-protein conjugate and free desmosine for binding to monospecific anti-desmosine antiserum constituted the underlying principle of the assay. The conjugation of desmosine to different protein carriers was carried out with the 1-ethyl-3-(dimethylamino-propyl)carbodiimide (ECDI); rabbits were immunized with desmosine-bovine serum albumin and micro-titer plates were coated with desmosine-egg albumin. An avidin-biotin peroxidase system was used to reveal anti-desmosine antibodies bound to the desmosine-protein conjugate. As both conjugates revealed new non-specific common epitopes on the carrier proteins, prior absorption of the anti-desmosine antiserum on rabbit albumin polymerized with ECDI was required to remove the antibodies directed against these neo-antigens. The absorption procedure resulted in an increased specificity and sensitivity. Values ranging from 0.07 to 4 ng of desmosine/well could be detected and this sensitivity was greater than that obtained in previous immunoassays for desmosine. In order to assess the specificity of the test, samples containing aminoacids and urine hydrolysates were included in an assay. Some cross-reactivity was observed with the desmosine precursor lysinonorleucine and the desmosine isomer isodesmosine but, in contrast the very low cross-reactivity observed with collagen hydrolysate was similar to that exhibited by albumin hydrolysate. Analysis of urine samples from 118 normal male volunteers showed, firstly, that urinary creatinine measurement was a good indicator of the amount of urine which could be safely introduced in the assay without risk of non-specific interference by other organic compounds and, secondly, that the desmosine/creatinine ratio was a reliable index for an in vivo assessment of degraded elastin excretion. The assay also allowed quantitation of elastin fiber biosynthesis in the connective tissue matrix of cultured rat pleural mesothelial cells. This ELISA for demosine is a simple technique which should be useful for further in vivo or in vitro investigations of fibrous elastin tissue metabolism.

Amino Acids↗
PubMed1988

Identification and immunocytochemical localization of two different carbonic anhydrase isoenzymes in teleostean fish erythrocytes and gill epithelia.

Carbonic anhydrase was purified from the gills (CAB) of the rainbow trout Salmo gairdneri and from erythrocytes (CAE) of the fresh water carp Cyprinus carpio. The purification of the isozymes was confirmed by SDS acrylamide gel electrophoresis. Antibodies against the purified CAB and CAE were then raised in rabbits. Specificity was verified by immunoblotting. No cross-reaction was found between them, using the immunodot technique. CAB antiserum was used to specifically localize gill CA in the trout. Immunoperoxidase labelling revealed a concentration of enzyme on the apical region of the outer layer of the gill epithelial cells. The inner layer of the epithelium was only weakly positive. Results obtained using the immuno-gold technique confirmed the immunoperoxidase labelling: there was a concentration of label in the apical regions of chloride cells. In mucous cells, only the mucous granules were labelled. In the lamellae, the label was distributed in the apical part of the pavement cells. The villi and microplicae were strongly positive. CAE antiserum stained the red blood cells. The discrepancy between histochemical localization in the gill or in the opercular skin of killifish and our present immunolocalization was discussed. It was concluded that the most typical localization of CA is on the apical surface of the lamellar epithelium lying in contact with the environment. The result suggests that one of the main roles of gill CA may be to facilitate the diffusion of CO2 from blood to water.

Animals↗