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R Rosset

Publications and source records attributed to R Rosset.

At least 37 records · Page 2Linked to original sources
PubMed1982

Nucleolar organizer structure and activity in a nucleolus without fibrillar centres: the nucleolus in an established Drosophila cell line.

Classical electron-microscopic techniques (enzymic digestion, EDTA regressive staining) allied with autoradiographic studies after [3H]uridine incorporation or after RNA synthesis initiated by an exogeneous RNA polymerase in the presence of tritiated GTP, enabled us to describe the fine structure and activity of the nucleolus in an established Drosophila cell line. This nucleolus is composed of a large central multilobed core containing proteins, RNA molecules and a DNA-containing component. This core is surrounded by and connected to large clumps of dense fibrillar nucleolus-associated chromatin, which are intermingled with fibrillogranular ramifications extending from the core towards the nuclear envelope. These ramifications are covered by granules of ribosomal ribonucleoprotein. As shown by EDTA regressive staining the nucleolar core contains a ribonucleoprotein network, which unravels and ramifies within a fibrous matrix. RNA synthesis takes place at the level of this network in the internal part of the core. The molecules synthesized are associated with proteins and are exported out of the core in the form of granules. Although it is composed of the same constituents as other nucleoli, the nucleolus of Drosophila cells seems to be less organized, in that it never displays fibrillar centres, which have been referred to as the nucleolar counterparts of the nucleolus-organizers in a wide variety of organisms.

Animals↗
PubMed1979

Assembly of ribosomal subunits affected in a ribosomal mutant of E. coli having an altered L22 protein.

In this article we describe some in vivo properties of a coldsensitive ribosomal mutant from Escherichia coli. The mutation affects the rplV gene which is the structural gene of ribosomal protein L22. Our work shows that at 22 degrees C, the biosynthesis of both ribosomal subunits and the maturation processing of 15S and 23S ribosomal RNA are impaired. Integration of our results in a general model of in vivo ribosomal assembly in E. coli is presented.

Cold Temperature↗
PubMed1978

Characterization of an Escherichia coli K12 mutant that is sensitive to chlorate when grown aerobically.

Escherichia coli can normally grow aerobically in the presence of chlorate; however, mutants can be isolated that can no longer grow under these conditions. We present here the biochemical characterization of one such mutant and show that the primary genetic lesion occurs in the ubiquinone-8-biosynthetic pathway. As a consequence of this, under aerobic growth conditions the mutant is apparently unable to synthesize formate dehydrogenase, but can synthesize a Benzyl Viologen-dependent nitrate reductase activity. The nature of this activity is discussed.

Acridines↗
PubMed1978

Turbidimetric and potentiometric studies of ribosomal subunits from an erythromycin resistant mutant of Escherichia coli.

Turbidimetric and potentiometric techniques were applied to the analysis of an EryR mutant. Results show that in the mutant, the 30S subunits are drastically altered, as indicated by a higher Mg2+ requirement for subunit association and by an important difference in the titratable groups. Replacement of parental 50S by mutant 50S subunits does not decrease the association capacity with 30S parental subunits, but a structural difference is detected in the mutant 50S with potentiometric measurements. The mutation results in decreased ribosomal in vitro activities at 22 degrees C including lowered polyphenylalanine synthesis, drastic altered initiation step and the loss of erythromycin binding to the ribosomes. The results extend previous observation of a gene eryC part in the maturation of both subunits.

Drug Resistance, Microbial↗
PubMed1978

[Preservation of meats in a controlled atmosphere].

Commercializing meat sets problems more particularly connected with its organoleptic and microbiological qualities. As these qualities, resulting from biochemical and microbial effects, develop during the storage, the conditioning must precisely help their controlling. After examining their factors, the Author analyses the processes of conditioning which he classifies in three categories according to the techniques used and the desired finality (need to store at -1 degree C + 3 degrees C). 1. Conditioning under a steam-proof and gas pervious (O2-CO2) film. Composition of the internal atmosphere permanently close to that of the normal atmosphere. No change in the bright red colouring at the surface (oxymyoglobin). Microbial growth slowed down by refrigeration. Limited storage (a few days). Comminuted meat trade. 2. Conditioning under a totally steam--and gas--proof film. Internal atmospheric air under reduced volume and pressure ("vacuum-packed" meats). Internal changes during the storage: reduced rate O2; increased rate CO2 (cellular and microbial respirations). Surface becoming darker (absence of oxymyoglobin). Growth of the germs arrested (pathogenic and spoilage). However development of microaerophilic and acidophilic germs (in particular the lactic B.). Storage possibly extended to 8 weeks. Re-apparition of the red colour after oxygenation (opened package). Wholesale meat trade. 3. Conditioning under a film with properties close to that of (2 degrees). Initial constitution of an internal "artificial" atmosphere increased in O2 and CO2 (gas injection). No change in the bright red colouring (oxymyoglobin). Growth of the germs arrested (pathogenic and spoilage). Selection of an acidophilic aerobic flora including lactic B. and microbacterium. Storage until 12-15 days. Comminuted meat trade.

Carbon Dioxide↗
PubMed1977

Properties of ribosomes from erythromycin resistant mutants of Escherichia coli.

We have studied the in vitro properties of ribosomes from several mutants resistant to erythromycin. Mutations in three different genes may confer resistance to erythromycin. Two of them are structural genes for proteins L4 and L22 of the large subunit. The third mutation (in eryC gene) seems to affect mainly the small subunit. The mechanism of action of the antibiotic may involve both subunits.

Drug Resistance, Microbial↗
PubMed1977

Linkage of 5S RNA and 16S+23S RNA genes on the E. coli chromosome.

Episomes carrying limited regions of the chromosome where 5S RNA genes have previously been located are described. The DNA purified from each of these episomes contains one gene per molecule for each of the three ribosomal RNA species as shown by hybridization experiments.

Chromosomes, Bacterial↗
PubMed1976

[High-performance liquid chromatography of penimocycline (author's transl)].

Penimocycline is an antibiotic obtained by Mannich reaction between tetracycline and ampicilline. Separation of penimocycline from tetracyclines and other impurities has been studied by high-performance liquid chromatography. The most effective method is liquid-liquid partition on a Micropak CH column (non-polar hydrocarbon bonded on porous silica microparticles) and gradient elution with water-methanol, 0.02 M phosphate buffer (pH 7.6) and 1 mM EDTA. Some results on hydrolysis of penimocycline are given.

Ampicillin↗
PubMed1975

Studies on the recovery of aflatoxin b1 injected into frozen beef at different intervals of storage.

Beef stored at --18 degrees C for 20,25,32,153, and 183 days showed a diminution in the recovery of injected aflatoxin B1. An unusual passing of aflatoxin in ether and hexane fractions of silica gel column was noted. Ether fraction contained aflatoxin B1-like substance from stored beef samples. Probable occlusion of aflaton B1 to meat constituents due to physico-chemical changes associated with muscle during storage was discussed.

Aflatoxins↗
PubMed1974

Abnormal maturation of precursor 16S RNA in a ribosomal assembly defective mutant of E. coli.

The precursor and mature 16S ribosomal RNAs from a novel thermosensitive ribosomal assembly defective mutant of E. coli, in which genetic evidence suggests that the ribosomal protein S4 is altered, have been isolated and characterised by finger-printing methods. The precursor 16S RNA, which is accumulated at 42 degrees , appears to be identical with that present in wild-type strains, and with that previously described by other workers. However, the mature 16S RNA, which is contained in apparently normal functional 30S ribosomal particles synthesised at the growth-permissive temperature of 30 degrees , is incompletely trimmed and has either one or two additional nucleotides at its 5'-terminus. This might be due either to an accumulation of two late intermediates in the maturation process, or to mis-trimming of the RNA. Both possibilities suggest that the change in the protein S4 is not only responsible for the thermosensitive character of ribosomal assembly in this mutant, but also causes an alteration in the trimming site, affecting its recognition by the enzyme involved in the maturation.

Base Sequence↗
PubMed1973

Ribosomal assembly influenced by growth in the presence of streptomycin.

Translational leakiness (i.e., nonspecific suppression) of nonsense mutants of bacteriophage T4 is increased in cells of certain streptomycin-resistant strains previously grown in the presence of streptomycin. Concomitantly, ribosomes extracted from these streptomycin-grown cells possess a high level of misreading. Increased suppression ability as well as ribosomes that highly misread accumulate with kinetics expected for a constant differential rate of synthesis of a new product induced by drug action. The misreading ribosomes do not contain appreciable amounts of streptomycin and the misreading property is lost by exposure to high salt concentrations. It is suggested that streptomycin (or dihydrostreptomycin, or paromomycin) induces a reversible modification in 30S subunit assembly without physically participating in the modified structure. The extent of this modification appears dependent upon the strA allele.

Bacterial Proteins↗