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J Puech

Publications and source records attributed to J Puech.

10 recordsLinked to original sources
PubMed1998

Analysis of the kinetics of reversible enzyme inhibition by a general algebraic method. Application to multisite inhibition of the phosphoglycerate kinase from Trypanosoma brucei.

The action of an inhibitor on a stationary enzyme reaction is described by a simple equation, which reflects how the progressive binding of inhibitor molecules influences the existence and the productivity of the enzyme forms. This allows deduction of the structure of the enzyme system from the experimental results, using new type of plots (1/[I], 1/[I](a)v) where a = 0,1,2,... in complement to the usual graphs. A reaction scheme is thereby logically built. This method may be used without any theoretical calculation. It is valid whatever the inhibitor, when the association reactions of the substrates and the inhibitor to the enzyme are in rapid equilibrium, and with dead end inhibitors, more generally for steady state enzyme reactions. This method may be adapted to enzyme activation. An original inhibition mode is described with particular bifunctional molecules: cooperative binding of the inhibitor to the enzyme, outside the active site, by direct mutual interaction of two inhibitor molecules, and locking of the conformational changes that normally precede the release of the products.

Animals↗
PubMed1990

Calcium phosphate deposits in domes of human pancreatic adenocarcinoma (Capan-1) cell cultures.

Human pancreatic cells of the Capan-1 line form domes in culture during the stationary growth stage. The domes are thought to be a result of the transport of water and electrolytes by the Capan-1 cells. In older Capan-1 cultures, the epithelial sheets formed thickenings from several layers of cells of which the outermost ones were joined by tight type junctions. In the intracellular space, deposits of insoluble calcium salts were observed. Culture of Capan-1 cells in the presence of fibroblasts prolonged survival of the cultures with intact domes for more than 80 days. The Capan-1 cells proliferated forming multilayers and closed cavities which we called super-domes. X-ray spectrometry and electron diffraction analysis showed that the abundant deposits inside these cavities consisted of calcium phosphate in an apatite structure. The number of these deposits increased with time in culture, and they appeared to be formed at the sites of contact with an extracellular matrix consisting of cell debris. Deposits were not observed within the culture medium. Cells from domes were stained cytochemically for ATPases and alkaline phosphatases and examined by light and electron microscopy. The Capan-1 cells surrounding the domes were differentiated, polarized cells containing placental type alkaline phosphatases on their apical membranes and Ca2(+)-ATPases on their basolateral membranes. These enzymes were thought to play a role in the accumulation of phosphate and Ca2+ ions in the dome cavities, which then formed crystals in the presence of organic compounds produced by lysis of cells of the deepest layers of the super-domes. The crystals of hydroxyapatite observed in standard Capan-1 cell cultures and those cocultured with fibroblasts were assumed to be a result of transepithelial transport of Ca2+ and phosphate ions by these cells.

Adenocarcinoma↗
PubMed1986

[Physicochemical analysis of subcutaneous calcifications in a case of Thibierge-Weissenbach syndrome].

A physicochemical study of subcutaneous calcium deposits was performed in a patient with typical Thibierge-Weissenbach syndrome which had begun, ten years previously, with Raynaud's phenomenon and sclerodactylia. Calcium deposits had progressively developed, forming large plates on the arms, flanks and thighs. In the course of the disease they had become ulcerated, exuding a white, chalky material. X-ray films and xerograms demonstrated the extent of these deposits. The calcium-phosphorus balance was normal, and the other clinical and laboratory examinations were concordant with a diagnosis of Thibierge-Weissenbach syndrome (calcinosis). Only systemic corticosteroid therapy slowed down the pathological process; calcium chelating agents (diphosphonate) proved ineffective. The physicochemical study showed that the deposits consisted of carbonated apatite type B with the following formula: Ca8.0(PO4)4.1(CO3)1.2(HPO4)0.8 The mineral substance seemed to be less reactive and more stable than normal bone. This would account for the total lack of effectiveness of all treatments, notably calcium chelating agents, on the course of the deposits. Treatments usually produce bone demineralization before they influence the calcium deposits. This study provides much more detailed information than was hitherto available on calcium deposits and on carbonate ion contents in the apatite phase. The presence of carbonates increases the solubility and reactivity of calcium apatite.

Calcinosis↗
PubMed1984

[Cytology of peritoneal fluid in the diagnosis of pelvic endometriosis].

Fluid was collected from the Ponch of Douglas at laparoscopy or laparotomy in 104 women. Macrophages were always present. The Schiff's histochemical reaction was positive inside the cytoplasm in cases of pelvic endometriosis in our study. This technique allows characterization of the cell population in cases of chronic pelvic inflammation and confirmation of the diagnosis of mild endometriosis.

Ascitic Fluid↗
PubMed1978

[The relationship between palmitic acid and stearic acid on the pharyngeal secretions of the newborn (author's transl)].

The authors report on their study of the ratio of palmitic acid to stearic acid (P/S) in the pharyngeal secretions of the newborn before the sixth hour of life. Four groups of infants were studied: 78 infants used as controls who hac no respiratory distress, 36 with hyaline membrane disease, 16 with transitory respiratory distress and 5 with perinatal asphyxia. The aetiological diagnosis of the respiratory distress was based on clinical as well as radiological and biological criteria. The P/S ratio is always less than 3 with hyaline membrane disease and above 3 in asphyxias. In the control group and the group with transitory respiratory distress the ratio ranged between 1.3 and 14 which was evidence of false negative results, probably attributable to treatment with cortisone given to the mother in premature labour in a certain number of cases. Study of the P/S ratio in amniotic fluid and in the pharyngeal secretions of 27 children born by Caesarean operation embodies a contradiction in the results the newborns in whom the ratio in the amniotic fluid was greater than 3 never had respiratory distress although the ratio studied at the same time in the pharyngeal secretions was low and sometimes less than 3.

Amniotic Fluid↗