Phenotype masking and streptomycin dependence.

In attempting to define the role of ribosomes in the mechanism of streptomycin dependence, a new phenomenon has been discovered. Analysis of this phenomenon-called phenotypic masking-leads to the conclusion that "streptomycin dependent" mutants are actually "drug dependent" because their dependence is equally satisfied by several drugs. These drugs, some of which are totally unrelated chemically, act on the ribosome and induce misreading in vitro and suppression in vivo.

Genetic and molecular analysis of terminal deletions of chromosome 3R of Drosophila melanogaster.

Terminal deletions of chromosome 3R are induced at a high frequency (3.2 x 10(-3)) by irradiating 45-4 Drosophila melanogaster females with a low dose of X-rays. The 45-4 line carries a white transgene inserted at 16 kb from the terminus and is homozygous for the mu-2 mutation, a gene involved in the repair of double-strand DNA breaks. Four of the 51 recovered deleted strains have lost modulo, the distalmost essential gene on chromosome 3R. Breakpoints of 22 deletions have been localised in a single hybridisation step, using pulsed-field gel electrophoresis to separate genomic DNA fragments obtained from digestion with a rare-cutter restriction enzyme. Breaks do not occur at random, but are rather clustered in three susceptible chromosomal domains. Backcross experiments resulting in transheterozygous (deleted chromosome/45-4) animals indicate that the activity of the white transgene is enhanced when the DNA break has occurred proximal to a critical position. This suggests that homologous chromosomal pairing distal to the critical position results in the definition of a more compact chromatin structure and, due to position effect, in the silencing of white.

Feasibility study of colorectal cancer screening by immunochemical faecal occult blood testing: results in a northern Italian community.

AIM: Screening by means of faecal occult blood testing (FOBT) has proved to be effective in reducing colorectal cancer incidence and mortality. We performed a pilot screening for colorectal cancer by latex immunological FOBT in two municipalities of the region Valle d'Aosta, Italy, focusing on problems and obtaining indications for the feasibility and extension of the screening programme on a regional basis. METHODS: A total of 2961 subjects aged 50-74 years were invited by mail to perform a one-day immunochemical FOBT without any dietary restrictions and with a positive threshold put at 100 ng/ml. Patients with positive tests were then invited to undergo colonoscopy and double-contrast barium enema if colonoscopy was incomplete. RESULTS: A total of 1631 subjects performed the screening test with an overall compliance of 55.1%. Seventy-two subjects had a positive FOBT. Detection rates for cancer and adenomas were 1.8 per thousand and 16.6 per thousand, respectively. Positive predictive values (PPVs) for cancer and adenomas were 4.5% and 40.3%, respectively. CONCLUSIONS: Screening had an adequate attendance rate and the majority of the indicators were satisfactory. The use of a one-day quantitative latex FOBT with no dietary restrictions, automation of the analytical procedure, and a positive threshold of 100 ng/ml has shown that a programme based on this test is feasible in both organizational and attendance terms. On the basis of this experience, the extension of the screening on a regional basis is suggested.

[Microbial growth and cold. Study of the particular case of Listeria monocytogenes]. / Croissance microbienne et froid. Etude du cas particulier de Listeria monocytogènes.

Some of micro-organisms are able to adapt themselves to hardest environmental conditions. So, about cold conditions, most of them can still grow at very low temperatures under 0 degree Celsius (nitrogen liquefied at -169 degrees C is the best way for preserving microbes). By another way some germs, qualified psychrotophic bacteria, grow quite easily between 0 degree C and +10 degrees C. Among these bacteria the author draw the attention to Listeria monocytogenes, a germ contaminating often foodstuffs and being responsible of deep diseases by eating food preserved in bad conditions (breaking off of refrigeration chain, bad use of domestic refrigerators). Recommendations are laid down to avoid these diseases, more particularly for frail consumers as immuno compromised adults.

[Preservation of meats in a controlled atmosphere]. / Conservation de la viande sous atmosphère controlée.

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.

A new ribosomal mutation which affects the two ribosomal subunits in Escherichia coli.

A new ribosomal mutant resistant to erythromycin is described. The product of the gene eryC seems to be implicated in the assembly of the two ribosomal subunits, particularly in the maturation process of the RNA 23S and 16S.

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.

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.

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.

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.

Retention of polycyclic aromatic hydrocarbons on an improved tetrachlorophthalimidopropyl silica.

An improved synthesis of a chemically bonded electron acceptor, namely tetrachlorophthalimidopropyl silica, is described. Factors governing the silane preparation and its bonding to silica have been studied, namely reaction temperature and duration, pretreatment of silica, specific area, pore diameter, washing of the bonded silica, influence of solvent drying. A ligand density of 2.7 mumol/m2 is obtained with reduced plate heights in the range 5-20 which demonstrate the absence of polymerization. The retention of six polycyclic aromatic hydrocarbons has been studied. The minimum capacity factors allow high recovery rates in non-polar media.

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.

Overproduction of the first three enzymes of pyrimidine nucleotide biosynthesis in Drosophila cells resistant to N-phosphonacetyl-L-aspartate.

Drosophila cells were treated in vitro with N-phosphonacetyl-L-aspartate (PALA) which is a specific inhibitor of aspartate transcarbamylase, the second enzyme of the pyrimidine biosynthetic pathway. By stepwise selection using increasing amounts of this inhibitor, PALA-resistant (PALAr) stable clones have been isolated. Enzymatic activities of aspartate transcarbamylase, carbamyl phosphate synthetase and dihydro-orotase, borne by the same multifunctional protein, CAD, are increased 6-12-fold in these resistant clones compared with parental cells. The aspartate transcarbamylase in PALAr cells is shown by physical, kinetic and immunological criteria to be normal. The data from immunotitration and immunoblotting experiments indicate that the increased enzyme activities result from the overproduction of CAD.

Isolation and characterization of a region of the Drosophila genome which contains a cluster of differentially expressed maternal genes (yema gene region).

We have characterized a genomic clone of Drosophila melanogaster which codes for four transcripts that are synthesized during oogenesis, remain abundant in the preblastoderm embryo, and then vanish during gastrulation. One of the transcripts varies in concentration along the anterior-posterior axis of the oocyte. This cluster of maternally acting genes (yema) maps to 98 F3-10 on chromosome arm 3 R.

Supragenic loop organization: mapping in Drosophila embryos, of scaffold-associated regions on a 800 kilobase DNA continuum cloned from the 14B-15B first chromosome region.

The supragenic loop organization of the Drosophila genome was investigated on a 800 kilobase (kb) DNA continuum from the 14B-15B first chromosome region. Nuclear scaffolds from 0-18 hr embryos were prepared with Laemmli's low-salt, detergent procedure and digested with restriction enzymes. Scaffold-associated regions (SARs) were mapped by probing Southern transfers of total, scaffold-associated and free DNA with a set of 70 recombinant phages overlapping the investigated genomic region. In all, 85 restriction fragments showed association to scaffolds. 12 of them were present in the majority of scaffolds. They bore strong SARs organizing the DNA molecule as consecutive loops with sizes ranging from 15 to 115 kb. 44 were present in only a fraction of scaffolds. They contained weak SARs subdividing the basic loops into smaller ones. 29 additional restriction fragments were present in a very small fraction of scaffolds. The position of SARs with respect to transcribed regions was investigated. Strong SARs appeared to be located on untranscribed DNA and to frame transcription units. In contrast, at least some weak SARs were shown to comap with transcribed regions or to reside within characterized transcription units. Statistical analyses established that strong and weak SARs were periodically positioned on the DNA continuum and that there was a potential contact point between scaffolds and the DNA continuum every 11 kb, or multiples thereof. Implications for SAR role(s) are discussed.