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C Richaud

Publications and source records attributed to C Richaud.

At least 73 records · Page 4Linked to original sources

[Urological aspect of vesico-intestinal fistulas. Apropos of 14 cases].

This series of 14 cases of vesico-intestinal fistulae, together with a review of the literature, led to a certain number of remarks: From an aetiological standpoint, in addition to classical concepts with the predominance of diverticulosis of the colon accounting for 46% of cases, followed by carcinoma of the colon (14%) and Crohn's disease, we feel it to be of interest to stress the possible urinary origin of vesico intestinal fistulae (4 of our cases, and 4.5% of the total number collectedin the literature). From a diagnostic standpoint, we would emphasise that these fistulae present almost solely with urinary symptoms and signs and stress the clinical importance of what is now known, since J. Cibert, as "pre-fistulous cystitis" preceding the development of pathognomic signs--faecaluria and pneumatria. Radiological opacification of the colon and rectum is essential in patients with a syndrome of chronic urinary infection unexplained by a urological cause. From a therapeutic standpoint, the surgical treatment of vesico-intestinal fistulae is associated with a high operative mortality (2 deaths amongst our 14 patients) and which, independently of the aetiological factor (predominance of carcinomas) is explained above all by the septic nature of the lesions.

Adult↗

Role of lysyl-tRNA in the regulation of lysine biosynthesis in Escherichia coli K12.

A mutant of lysyl-tRNA synthetase has been isolated in Escherichia coli K12. With this strain the Kmapp for lysine is 25 fold higher than with the parental strain. The percentage of charged tRNAlys in vivo is only 7 per cent (as against 65 per cent with HFR H). Under these conditions no derepression of synthesis is observed for three lysine biosynthetic enzymes (AK III, ASA-dehydrogenase, DAP-decarboxylase) ; a partial derepression is obtained in the case of the dhdp-reductase. Thus lysyl-tRNA does not act as the only corepressor molecule in the lysine regulon.

Amino Acyl-tRNA Synthetases↗

Regulation of lysine biosynthesis in Escherichia coli K12.

A general survey of the regulation in lysine biosynthesis in Escherichia coli K12 is presented. No polygenic operon exists for the genes that code for enzymes of the lysine biosynthetic pathway. Lysyl-tRNA is not directly involved as a co-repressor in the pathway. Different regulation mechanisms must exist for the different enzymes. In the case of the last enzyme, diaminopimelate decarboxylase, its synthesis is induced in vivo by the lysine-sensitive aspartokinase under its non-inhibited allosteric conformation.

Adenosine Triphosphate↗

Protease II from Escherichia coli. Purification and characterization.

We have previously demonstrated the existence of two types of endopeptidase in Escherichia coli. A purification procedure is described for one of these, designated protease II. It has been purified about 13,500-fold with a recovery of 24%. The isolated enzyme appears homogeneous by electrophoresis and gel filtration. Its molecular weight is estimated by three different methods to be about 58,000. Its optimal pH is around 8. Protease II activity is unaffected by chelating agents and sulfhydryl reagents. Amidase and proteolytic activities are stimulated by calcium ion, which decreases the enzyme stability. Like pancreatic trypsin, this endopeptidase catalyses the hydrolysis of alpha-amino-substituted lysine and arginine esters. It appears distinct from the previously isolated protease I, which is a chymotrypsin-like enzyme. The apparent Michaelis constant for hydrolysis of N-benzoyl-L-arginine ethyl ester is 4.7 X 10(-4) M. The esterase activity is inhibited by diisopryopylphosphorofluoridate (Ki(app) equals 2.7 X 10(-3) M) and tosyl lysine chloromethyl ketone (Ki(app) equals 1.8 X 10(-5) M), indicating that serine and histidine residues may be present in the active site. However, protease II is insensitive to phenylmethanesulfonyl fluoride and several natural trypsin inhibitors. Its amidase and esterase activities are competitively inhibited by free arginine and aromatic amidines. The proteolytic activity measured on axocasein is very low. In contrast to trypsin, protease II is without effect on native beta-galactosidase. It easily degrades aspartokinase I and III. Nevertheless both enzymes are resistant to proteolysis in the presence of their respective allosteric effectors. These results provide further evidence that such differences in protease susceptibility can be related to the conformational state of the substrate. The possible implication of structural changes in the mechanism of preferential proteolysis in vivo, is discussed.

Binding, Competitive↗