PubMed Health⌕ Search

Biomedical subjects

J Vacher

Publications and source records attributed to J Vacher.

At least 37 records · Page 2Linked to original sources
PubMed1983

Identification of clones carrying an E. coli tRNAPhe gene by suppression of phenylalanyl-tRNA synthetase thermosensitive mutants.

Two libraries of cloned E. coli DNA were screened for plasmids which complemented thermosensitive phenylalanyl-tRNA synthetase mutants. Four plasmids were isolated which complemented pheS and pheT thermosensitive mutations but which do not carry pheS or pheT, the structural genes for phenylalanyl-tRNA synthetase. All these plasmids increased the intracellular tRNAPhe concentration. Three plasmids were shown to carry the structural gene for tRNAPhe which we call pheU. By restriction enzyme analysis, DNA blotting and DNA:tRNA hybridization, pheU was localised to a 280 bp fragment within a 5.6 kb PstI restriction fragment of E.coli DNA.

Amino Acyl-tRNA Synthetases↗
PubMed1980

Potential advantages of a cesium fluoride scintillator for a time-of-flight positron camera.

In order to improve the quality of positron tomographic imaging, a time-of-flight technique combined with a classical reconstruction method has been investigated. The decay time of NaI(Tl) and bismuth germanate (BGO) scintillators is too long for this application, and efficiency of the plastic scintillators is too low. Cesium fluoride appears to be a very promising detector material. This paper presents preliminary results obtained with a time-of-flight technique using CsF scintillators. The expected advantages were realized.

Cesium↗
PubMed1979

Characterization of an amber suppressor in Pneumococcus.

Partial revertant has been isolated, with resistance to aminopterin intermediate between wild type and mutant. This phenotype is the result of a mutation at a gene unlinked to the amiA locus. This suppressor mutation (su+) has no phenotypic characteristics by itself except a slow growth. 9 amiA mutants (belonging to 6 sites) are affected by su+ out of the 30 investigated mutants (i.e. 22 sites). The efficiency of suppression is site dependent. Two sites out of 14 mutants belonging to the thymidylate synthetase gene are suppressible. Thymidylate synthetase activity is partially restored by su+. Optochin mutants can also be suppressed. Thus su+ is not gene specific but site specific. Moreover when the str-41 allele conferring resistance to streptomycin is introduced by transformation, the suppression effect is restricted. All these properties are characteristic of an informational suppressor. The t-RNA extracted from the suppressor strain su+ but not the wild type restored the synthesis of coat protein coded by RNA from an amber mutant of bacteriophage f2. Attempts to detect ochre suppression activity gave negative results. It is suggested that the su+ gene is amber specific. Thus su+ can provide insight into the nature of suppressible mutations which should be point mutations. Both low efficiency and high efficiency mutants are affected by su+; this is additional evidence that both categories contain point mutations.

Alleles↗