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Biomedical subjects

P Roques

Publications and source records attributed to P Roques.

At least 73 records · Page 4Linked to original sources
PubMed1989

A new type of chemically modified tRNA as a tool for the study of tRNA-aminoacyl-tRNA synthetase interaction.

tRNA(Phe) in which the adenine and cytosine rings in the aminoacyl arm and in the anticodon loop were converted to alkylating derivatives by mild treatment with methyl chlorotetrolate was used to study the tRNA(Phe)-yeast phenylalanyl-tRNA(Phe) synthetase interaction. At neutral pH, modified tRNA inhibited the enzyme competitively. At pH 9 this binding is accompanied by irreversible inactivation of the enzyme due to alkylation of the alpha subunit of the synthetase. Such a derivatization of tRNA could probably be used to investigate the interaction of other tRNAs with their cognate synthetases.

Alkylation↗
PubMed1989

Predisposing locus for Alzheimer's disease on chromosome 21.

Linkage between Alzheimer's disease and markers on the long arm of chromosome 21 was investigated in six families affected by disease of early onset. Linkage was confirmed and the disease locus shown to be centromeric to the locus D21S1/S11 on the long arm of the chromosome. It is argued that the data are consistent with the notion that all patients with Alzheimer's disease of genetic aetiology have a predisposing locus on chromosome 21.

Adult↗
PubMed1988

Reaction of nucleic acid bases with alpha-acetylenic esters. Part IV. Preparation of an alkylating derivative of tRNA(Phe) by conformation-specific chemical modification.

The reaction of yeast tRNA(Phe) with methyl chlorotetrolate, ClCH2-C identical to C-COOCH3, was studied. This reagent converts adenine and cytosine rings into derivatives in which an additional heterocycle bearing the alkylating chloromethyl group is fused to the original base; these derivatives can exist in two isomeric forms. Modified nucleosides of this type can be easily identified by reverse-phase HPLC. It was found that under native conditions, the modification of tRNA involves the anticodon loop and the 3'-end. The isomers of adenine derivatives formed in the anticodon loop were different from those formed in the 3'-end. It is suggested that the isomeric structure of the derivatives is related to the fine conformational differences between these two regions of tRNA(Phe). Methyl chlorotetrolate could thus be used as a conformational probe of single-stranded nucleic acids. Preliminary assays showed that modified tRNA(Phe) binds irreversibly to yeast phenylalanyl-tRNA synthetase.

Alkylation↗
PubMed1988

Platelet serotonin content and plasma tryptophan in peri- and postmenopausal women: variations with plasma oestrogen levels and depressive symptoms.

Platelet serotonin content was measured by high pressure liquid chromatography in 56 peri- and postmenopausal women, in order to study variations of this parameter with hormonal status and depressive mood symptoms. Clinical symptoms were assessed by a self-report depression symptom scale (CES-D of NIMH). Thirty-eight women with a score of 16 or more were considered as presenting depressive symptoms (mean score +/- SD = 28.8 +/- 10.5), while the others formed the control group (n = 18, score = 4.4 +/- 4.2). Platelet serotonin contents were significantly lower in the 'depressed' group (0.302 +/- 0.010 vs. 0.366 +/- 0.020 nmol 10(-8) platelets, means + SEM, P less than 0.001 by Mann-Whitney U-test). In 'depressed' women who had been treated for one or more depressive episodes, platelet 5-HT contents (0.283 +/- 0.023, n = 18, P less than 0.01) were significantly lower with respect to controls. In patients without previous episodes of depression, serotonin expressed in nmol 10(-8) platelets did not differ significantly from controls but serotonin expressed in nmol ml-1 of blood was slightly lower than control values (0.890 +/- 0.085, n = 20 vs. 1.088 +/- 0.090 nmol ml-1, n = 18, P less than 0.02). Platelet serotonin content was positively correlated to plasma oestrone and oestradiol concentrations among the control group but not in the 'depressed' group.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1987

Reactions of nucleic acid bases with alpha-acetylenic esters. Chemical modification of poly(A) and poly(C).

The reaction of chlorotetrolic (4-chloro-2-butynoic) esters with adenine and cytosine derivatives, in which a new heterocycle bearing an alkylating chloromethyl side chain is fused to the purine or pyrimidine ring, was extended to poly(A) and poly(C) used as models of nucleic acids. The derivatization proceeds under mild conditions and its extent can be controlled by the reaction time. The additional rings can exist in two isomeric forms and the nature of the isomer formed depends on steric factors in the vicinity of the reacting base. The reaction with chlorotetrolic esters discriminates between the single-stranded (reactive) and double-stranded (unreactive) forms, between the exposed an hidden adenine and cytosine bases and even between the exposed and sterically hindered fragments of the base moiety and thus allows structural investigations of these nucleic acids. The chloromethyl group of the derivatized nucleobases can be used to bind the modified polymers to other molecules.

Alkaline Phosphatase↗
PubMed1985

Platelet serotonin and blood tryptophan in spontaneously hypertensive and normotensive Wistar-Kyoto rats.

The number of platelets and their content in serotonin (5-HT) were determined in 12-week-old spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP) and in normotensive Wistar-Kyoto rats (WKY). Spontaneously hypertensive rats had 49% more platelets and a 65% higher platelet 5-HT circulating pool than SHRSP and WKY. An increased synthesis of 5-HT by enterochromaffin cells in SHR is suggested by the lower level of plasma total and albumin-bound tryptophan and by the higher free/bound tryptophan ratio found in those rats, as compared with WKY. In SHRSP, a decrease of platelet survival time was reported, associated to an increased platelet production. This would explain the absence of variation of platelet number and 5-HT content.

Animals↗