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P Remy

Publications and source records attributed to P Remy.

At least 91 records · Page 5Linked to original sources
PubMed1990

Significance of dinucleoside tetraphosphate production by cultured tumor cells exposed to the presence of ethanol.

The use of 30 to 50% ethanol solutions to extract the nucleotides from HTC and A-459 cells results in dinucleoside tetraphosphate (Ap4X) levels 3-30-fold as high as those obtained by 5% classical trichloracetic acid extraction, while ATP levels are identical in both cases. The amplification factor varies with the percentage of ethanol and duration of contact between the cells and the extraction mixture. It remains constant for the HTC cells during cell growth, but exhibits a maximum for the A-459 cells towards the end of the exponential growth period. The incorporation of radioactivity in Ap4X when [alpha-32P]ATP is added to the extraction mixture suggests an Ap4X neosynthesis in the presence of ethanol. The results carried out in the presence of pyrophosphate, EDTA and zinc acetate strongly suggest that aminoacyl-tRNA synthetases could be responsible for the increase in Ap4A content with ethanol treatment. Nevertheless, the effect of ethanol is probably not the result of an activation of these enzymes, but rather, as already suggested by earlier results in our laboratory, the result of a fast inactivation of the degradation enzymes.

Adenosine Triphosphate↗
PubMed1989

[Sacro-rectopexy by a posterior intersphincteric approach with anteroposterior perineoplasty and mucosal resection. Therapeutic proposal in descending peritoneum syndrome. Apropos of 23 cases].

We report the results of a procedure aimed at correcting the disorders of rectal and perineal tone responsible for the descending perineum syndrome (DPS). The procedure, carried out by the perineal approach, combines a posterior intersphincteric sacro-rectopexy, an anterior perineoplasty via a pre-anal levator myorraphie, a posterior perineoplasty using a post anal repair technique and a mucosal resection aimed at freeing the anal canal. 22 F and 1 M, mean age 68 years, with DPS were operated on. Digitised rectography demonstrated pathological perineal descent (greater than 3 cm) in all cases and posterior rectal angulation at rest of more than 25 degrees (normal less than 10 degrees) confirming an important deterioration in perineal tone. Results after a mean follow up of 12 months (6 to 30 months) were excellent, with objective improvement in rectal bleeding, pain, mucosal prolapse and anal incontinence. In spite of an almost constant return to normal in the number of stools and their facility of evacuation improvement in the dyschesic syndrome (78% of patients) was subjectively variable. Improvement was judged to be very good in 34%, good in 33%, fair in 11%. Healing of mucosal lesions: solitary ulcer (n = 2), rectal inflammation (n = 2), ulcerated mucosal prolapse (n = 3) occurred in all cases within 1 month. Post operative rectography demonstrated a significant decrease in posterior rectal angulation and ano-coccygeal distance confirming the efficacy of the anatomical correction. No serious complications, in particular, infections, were noted under appropriate prophylactic antibiotic cover (Piperacillin) continued up to D5.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

A study of fibrinogen and fibrinolysis in 10 adults with nephrotic syndrome.

In 10 patients with nephrotic syndrome (NS), the coagulation inhibitors, the fibrinolytic system and several functions of the fibrinogen-fibrin molecule were studied. Among the coagulation inhibitors, only antithrombin III (AT III) was found decreased and correlated with serum-albumin levels. Venous occlusion test provoked a normal tissue plasminogen activator (tPA) release in all patients. The plasminogen activator inhibitor (PAI) had an increased activity in 5 out of the 10 patients. Thrombin and reptilase times were found abnormal in most patients. The thrombin time (TT) prolongation correlated with serum albumin levels and was corrected by adding purified albumin. The fibrinogen was purified from each of the 10 patients' plasma. Only 2 of them showed abnormal polymerization in purified system, suggesting dysfibrinogenaemia. Other functions (thrombin binding, tPA stimulating activity, lysis by purified plasmin) were found normal except in one of the 2 patients with dysfibrinogenaemia whose fibrinogen lysis by plasmin was delayed. It is concluded that an abnormal fibrinogen molecule is not the most frequent explanation for thrombin time prolongation in NS.

Adult↗
PubMed1988

Is Ap4A involved in DNA repair processes?

Hepatoma tissue culture (HTC) cells were incubated in the presence of the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) to study the variations in the bisnucleosides polyphosphates (Ap4X) pool size. A transient but sensitive accumulation of these compounds is observed; if 3-aminobenzamide (3AB) which is a potent inhibitor of the ADP-ribosyltransferase (ADPRT) is added after the MNNG treatment, a more pronounced and persistent accumulation of Ap4X can be seen. A moderate heat-shock (30 min at 43 degrees C) results also in a small accumulation of Ap4X but the shape of the accumulation curve is quite different and the increase of the Ap4X pool is not sensitive to the presence of 3AB. However, both MNNG treatment and hyperthermia cause a marked inhibition of protein synthesis. On the other hand, the ADPRT activity is enhanced in the presence of MNNG whereas hyperthermia has little or a slightly inhibitory effect on this activity. These results suggest that MNNG treatment triggers an Ap4X accumulation in eukaryotic cells different from that observed after heat-shock and it seems likely that these compounds are involved in the DNA excision repair system in which the ADPRT enzyme is also implicated.

Adenine Nucleotides↗
PubMed1987

Aminoacyl-tRNA synthetases catalyze AMP----ADP----ATP exchange reactions, indicating labile covalent enzyme-amino-acid intermediates.

Aminoacyl-tRNA synthetases (amino acid-tRNA ligases, EC 6.1.1.-) catalyze the aminoacylation of specific amino acids onto their cognate tRNAs with extraordinary accuracy. Recent reports, however, indicate that this class of enzymes may play other roles in cellular metabolism. Several aminoacyl-tRNA synthetases are herein shown to catalyze the AMP----ADP and ADP----ATP exchange reactions (in the absence of tRNAs) by utilizing a transfer of the gamma-phosphate of ATP to reactive AMP and ADP intermediates that are probably the mixed anhydrides of the nucleotide and the corresponding amino acid. AMP and ADP produce active intermediates with amino acids by entering the back-reaction of amino acid activation, reacting with labile covalent amino acid-enzyme intermediates. Gramicidin synthetases 1 and 2, which are known to activate certain amino acids through the formation of intermediate thiol-esters of the amino acids and the enzymes, catalyze the same set of reactions with similar characteristics. Several lines of evidence suggest that these activities are an inherent part of the enzymatic reactions catalyzed by the aminoacyl-tRNA synthetases and gramicidin synthetases and are not due to impurities of adenylate kinase, NDP kinase, or low levels of tRNAs bound to the enzymes. The covalent amino acid-enzyme adducts are likely intermediates in the aminoacylation of their cognate tRNAs. The use of gramicidin synthetases has thus helped to illuminate mechanistic details of amino acid activation catalyzed by the aminoacyl-tRNA synthetases.

Adenine Nucleotides↗
PubMed1987

Cell cycle variations of dinucleoside polyphosphates in synchronized cultures of mammalian cells.

Zajdela hepatoma culture cells (ZHC) and mouse embryo fibroblasts (Swiss 3T3) were synchronized in G1 or S phase by serum deprivation and aphidicolin treatment, respectively, to study the variations in adenylyl nucleotide (Ap4X) pool size during the progress of the cell cycle. Only minor variations, which never exceeded a factor of 2, were observed when the Ap4X concentrations were expressed on a cellular basis. The variations were found to be strictly parallel to the ATP variations. Upon release from an aphidicolin block, the minor variations of Ap4X followed DNA synthesis and preceded cytokinesis. When the nucleotide content was compared with the amount of proteins, the faint specific cell cycle changes were almost completely damped when the cells were synchronized by serum deprivation, but remained practically unchanged in the case of aphidicolin synchronization. These results suggest that the observed variations could reflect the accumulation of some nucleotides before cell division. It is not clear yet whether the variation in Ap4X concentration is significant by itself or is simply a phenomenon resulting from changes in the ATP pool.

Adenine Nucleotides↗
PubMed1986

Percutaneous transluminal angioplasty of renal transplant arterial stenoses.

Renal artery stenosis is a relatively frequent occurrence after renal transplantation. Forty-three hypertensive patients with such a stenosis underwent percutaneous transluminal angioplasty (PTA). The procedure was successful in 35 patients (81%). One month after a primary successful PTA, 74% of patients were improved. Restenosis occurred in seven patients. It was diagnosed in all seven before the fifth post-PTA month. In six patients, repeat PTA was attempted and was successful. One year after successful PTA, 67% of the patients were improved. No complication causing loss of renal parenchyma or needing surgery occurred. PTA is the procedure of choice for relief of transplant renal artery stenosis in patients with hypertension refractory to medical treatment or decline in renal function. It is effective and appears safer than surgery.

Adult↗
PubMed1986

De novo focal glomerular sclerosis in preeclampsia.

Eleven women were selected on the presence, in postpartum renal biopsies, of focal glomerulosclerosis (FGS) superimposed to glomerular lesions of typical pregnancy-induced nephropathy. Ten out of them presented with severe preeclampsia. The renal specimens were examined by light and/or electron and/or immunofluorescence microscopy. The present study gathered clinical and morphological data suggesting that FGS might develop during preeclampsia. In these renal biopsies with FGS and lesions of pregnancy-induced nephropathy a sparse detachment of podocyte was observed at a distance from the segmental lesions by electron microscopy. The latter has also been observed in experimental models of FGS in which FGS is dependent on glomerular hemodynamic alterations. We think that the mechanism of the development of FGS in these pathological pregnancies may be analogous to these experimental models of FGS with hyperfiltration.

Adolescent↗
PubMed1985

Effect of diadenosine tetraphosphate microinjection on heat shock protein synthesis in Xenopus laevis oocytes.

Bisnucleosides polyphosphates are thought to be chemical messengers signalling to the cell the onset of various stresses. Diadenosine tri- and tetraphosphates (respectively, Ap3A and Ap4A) accumulate in prokaryotic and eukaryotic cells under heat shock conditions, suggesting they could trigger the synthesis of heat shock proteins (hsps). In this study, Ap4A, Ap3A and, as a control, Ap4 (adenosine tetraphosphate) were injected into Xenopus oocytes. Whereas none of these compounds is able to trigger the synthesis of hsps in the absence of hyperthermic treatment, nuclear microinjection of Ap4A after a mild heat shock specifically enhances the synthesis of the 70-kd hsp, which is involved in the regulation and possibly the termination of the heat shock response. The microinjection of Ap4A prior to the hyperthermic treatment results in a strong inhibition of hsps synthesis (with the exception of the 70-kd hsp) suggesting that Ap4A is involved in the regulation and/or termination of the heat shock response. Ap3A and Ap4 do not induce any detectable modification of hsps expression.

Adenine Nucleotides↗
PubMed1985

Covalent modification of phenylalanyl-tRNA synthetase with phenylalanine during the amino acid activation reaction catalyzed by the enzyme.

Yeast phenylalanyl-tRNA synthetase (PRS) is shown to undergo autoaminoacylation with phenylalanine under in vitro amino acid activation conditions. Phenylalanyl adenylate enzyme complex yields a covalent phenylalanyl isopeptide exclusively with the beta subunit of the alpha 2 beta 2 enzyme. Contrary to previously reported cases of autoaminoacylation of aspartyl-tRNA synthetase and tryptophanyl-tRNA synthetase, the autoaminoacylation of PRS occurs under a specific set of conditions and results in the identification of only one labeled tryptic peptide on two types of high pressure liquid chromatography columns. The ability of PRS to undergo this covalent modification directly correlates with its ability to catalyze the synthesis of diadenosine 5',5"'-P1,P4-tetraphosphate from enzyme-bound phenylalanyl adenylate. Both reactions require the presence of low levels of zinc or cadmium and are inhibited by tRNAPhe or by low levels of low molecular weight thiols. Since diadenosine 5',5"'-P1,P4-tetraphosphate synthesis is known to be catalyzed in vivo in response to oxidation stress, it is also likely that the autoaminoacylation of phenylalanyl-tRNA synthetase may occur in vivo under a similar set of conditions. These reactions are thus not simply the result of accumulation of phenylalanyl adenylate and probably reflect conformational changes in the protein which are brought about by its interaction with zinc or cadmium.

Amino Acyl-tRNA Synthetases↗
PubMed1984

Fast kinetic study of yeast phenylalanyl-tRNA synthetase: role of tRNAPhe in the discrimination between tyrosine and phenylalanine.

An extensive study of the discrimination between phenylalanine and tyrosine by yeast phenylalanyl-tRNA synthetase was carried out in the presence of native tRNAPhe. Our results clearly show that, besides the previously reported dissociation of tyrosyl adenylate from the enzyme template [Lin, S. X., Baltzinger, M., & Remy, P. (1983) Biochemistry 22, 681-689], two more correction processes are involved in the rejection of tyrosine in the presence of tRNAPhe. A minor part of the misactivated tyrosine is indeed transferred to tRNAPhe, but the resulting misaminoacylated tRNA is very rapidly hydrolyzed (kh approximately equal to 60 s-1), as it has already been shown for other systems. However, the major part of the misactivated tyrosine is rejected as the result of a pretransfer correction consisting of the fast hydrolysis (k'h approximately equal to 20 s-1) of the enzyme-bound noncognate adenylate induced by the binding of native tRNAPhe. The transfer step itself is found to be non-specific, as the rate constant is almost the same for phenylalanine and tyrosine. This result is supported by the observation that tyrosine and phenylalanine are also transferred at the same rate to tRNAPheox-red. It is shown that the integrity of the 3'-terminal adenosine of the tRNA is critical for triggering the pretransfer hydrolysis of enzyme-bound noncognate aminoacyl adenylate. A detailed kinetic analysis is presented that shows that the observed rate constant of tRNAPhe tyrosylation and the rate of disappearance of enzyme-tyrosyl adenylate complex are in fact apparent rate constants.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acyl-tRNA Synthetases↗
PubMed1983

Translational recognition of messenger ribonucleic acid caps as a function of pH.

The degree to which cell-free translation of eukaryotic mRNA is stimulated by the presence of a 5'-terminal 7-methylguanosine-containing cap is affected by a variety of factors including ionic strength, temperature, mRNA concentration, and the type of mRNA. In this report, we show that pH also affects cap dependence. Translation of globin mRNA from which the cap had been enzymatically removed was relatively insensitive to pH compared with capped mRNA. Also, at low pH (6.6-7.2), the cap analogue m7GTP caused little inhibition of globin mRNA translation in a cell-free system whereas at higher pH the degree of inhibition increased. Finally, the overall extent to which globin mRNA translation could be inhibited at saturating concentrations of m7GTP increased with increasing pH. It is also shown that the pKa of the N-1 proton of m7GTP is affected by mono- and divalent cations. At the K+ and Mg2+ concentrations optimal for cell-free translation, the pKa is approximately 7.4. Since the pH optimum for translation is near 7.6, both keto and enolate forms of m7G are present in appreciable amounts. One interpretation for the observed change in cap dependence with pH is that only the enolate form of m7G is recognized by the cap-binding protein.

Animals↗
PubMed1983

Yeast phenylalanyl-tRNA synthetase: symmetric behavior of the enzyme during activation of phenylalanine as shown by a rapid kinetic investigation.

The adenylation of phenylalanine catalyzed by phenylalanyl-tRNA synthetase was investigated in the absence of tRNA, by rapid kinetic measurements using 6-(p-toluidinyl)naphthalene-2-sulfonate (TNS) as a nonspecific fluorescent reporter group. It is shown that each protomer of the enzyme is able to catalyze independently the adenylation of phenylalanine by ATP, as well as the reversion by pyrophosphate, at least in the absence of tRNA. The kinetic rate constants of synthesis and pyrophosphorolysis are respectively found equal to 100 +/- 20 s-1 and 150 +/- 50 s-1. The symmetric behavior of the enzyme is consistent with a symmetric binding of 2 mol of phenylalanine to the enzyme as shown by equilibrium dialysis experiments. The affinity of phenylalanyladenylate for the enzyme could be characterized by an equilibrium constant of 0.2 x 10(9) M-1.

Adenosine Monophosphate↗