Tg (9 HSA-MYC), a homozygous lethal insertion in the mouse

Transgenic mice generated with different DNA sequences were surveyed for possible homozygous mutant phenotypes. We found an embryonic lethal mutation in the transgenic mouse strain (MT-MYC12.4) containing the human c-myc gene. Embryos homozygous for the transgene die shortly after implantation. The strain MT-MYC12.4 carries approximately 50 tandem copies of the recombinant plasmid sequence. The 3 flanking sequence has been cloned and analyzed. It contains a unique sequence that has been conserved during evolution and maps to Chromosome (Chr) 9. This mutant has been designated Tg 9 (HSA-MYC).     

Differences in the respiratory burst of human polymorphonuclear leukocytes induced by virulent and avirulent Legionella pneumophila Serogroup 1

Two strains of Legionella pneumophila of different virulence were examined for their influence on the metabolic oxidative activity of human polymorphonuclear leukocytes. The leukocytes exhibited decreased rates of oxygen consumption and diminished chemiluminescence activity following phagocytosis of a virulent strain of L. pneumophila serogroup 1. In contrast, phagocytosis of its multipassaged derivative rendered avirulent, was accompanied by increased rates of both oxygen consumption and chemiluminescence activity. Although no differences were observed in oxygen uptake induced by the virulent legionellae compared to leukocytes at rest, statistically significant differences were observed in the chemiluminescence responses. These observations were not unexpected, since the luminol-enhanced chemiluminescence assay, is more sensitive than the oxygen uptake assay. In spite of decreased metabolic activity of PMN in the presence of virulent legionellae, electron microscope studies showed higher numbers of intracellular L. pneumophila than the avirulent subtype. Thus, virulent and avirulent L. pneumophila can be differentiated on the basis of oxygen consumption and chemiluminescence assays.     

Cation transport mechanisms in Mycoplasma mycoides var. Capri cells. The nature of the link between K+ and Na+ transport

We have studied the links between the mechanisms of Na(+), K(+) and H(+) movements in glycolysing Mycoplasma mycoides var. Capri cells. In the light of the results reported in the preceding paper [Benyoucef, Rigaud & Leblanc (1982) Biochem. J.208, 529-538], we investigated certain properties of the membrane-bound ATPase of Mycoplasma cells, with special reference to its ionic requirements and sensitivity to specific inhibitors. Our findings show, first, that, although Na(+) stimulated ATPase activity, K(+) did not affect it, and, secondly, that NN'-dicyclocarboidi-imide and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD) were potent inhibitors of the basal ATPase activity, which was unaffected by vanadate and ouabain. We also investigated the movements of Na(+) and H(+) under the experimental conditions applied to the study of the K(+) uptake reported in the preceding paper, and found that when ;Na(+)-loaded cells' previously equilibrated with (22)Na(+) were diluted in a sodium-free medium, addition of glucose induced a rapid efflux of (22)Na(+). This energy-dependent efflux was independent of the presence of KCl in the medium. Studies of the changes in internal pH by 9-aminoacridine fluorescence or [(14)C]methylamine distribution indicated that the movement of Na(+) was coupled to that of protons moving in the opposite direction, a finding that supports the presence of an Na(+)/H(+) antiport. When Na(+)-loaded cells are diluted in an Na(+)-rich medium the Na(+)/H(+) antiport is still active, but cannot decrease the intracellular Na(+) concentration. Under such conditions, net (22)Na(+) extrusion is specifically dependent on the presence of K(+) in the medium. The present results and those derived from the study of K(+) accumulation (the preceding paper) can be rationalized by assuming that Mycoplasma mycoides var. Capri cells contain two transport systems for Na(+) extrusion: an Na(+)/H(+) antiport and an ATP-consuming Na(+)/K(+)-exchange system.     

Structure de la paroi de Aremoricanium rigaudae Deunff, 1955 (Acritarche,Ordovicien)

The wall of Aremoricanium rigaudaeDeunff, 1955, type-species by original designation of the genus AremoricaniumDeunff, 1955, is composed of two layers: the internal one has a circular opening while the second is the only one which develops the processes and a tubular expansion.     

Selenopeltis (Trilobita) from Brittany and its distribution in the ordovician

The distribution of the genus SelenopeltisHawle & Corda throughout the Selenopeltis Province shows the presence during the Arenig of northern and southern species «groups, and a Llandeilo migration of the latter is identified within the Median Armorican synclinorium. New material of S. macrophthalmus (Kloucek) is described from Brittany together with S. gallicus gallicus nov. sp., nov. subsp. and S. gallicus irroratus nov. sp., nov. subsp.     

Reduction of oxidized inorganic nitrogen compounds by a new strain of Thiobacillus denitrificans

Denitrification by Thiobacillus denitrificans "RT" strain was investigated using manometry and gas chromatography. 1. From nitrate, resting cells produced only nitrogen anaerobically with thiosulfate as the electron donor. The data suggest that nitrate was assimilated and dissimilated by the same nitrate reductase, assayed with benzyl-viologen as the electron donor. 2. From nitrite, whole cells produced nitric oxide, nitrous oxide and nitrogen, using thiosulfate as the electron donor; nitrogen was the final product of the reduction. Crude extract reduced nitrite to nitrogen with p-phenylene-diamine and dimethyl-p-phenylene diamine as the electron donors, and produced nitric oxide, nitrous oxide and nitrogen with tetramethyl-p-phenylene-diamine as the electron donor. Nitrite was reduced to nitric oxide and nitrous oxide by crude extract using ascorbate-phenazine methosulfate as the electron donor. 3. From nitric oxide, whole cells produced nitrous oxide and nitrogen using thiosulfate as the electron donor, nitrogen was the final reduction product. Nitric oxide was reduced to nitrous oxide by crude extract with the ascorbate-phenazine methosulfate system. 4. Whole cells reduced nitrous oxide to nitrogen with thiosulfate as the electron donor. It was not possible to detect any nitrous oxide reductase activity in crude extract. 5. A scheme was of denitrification by Thiobacillus denitrificans "RT" strain.     

30 years of repeat expansion disorders: What have we learned and what are the remaining challenges?

Tandem repeats represent one of the most abundant class of variations in human genomes, which are polymorphic by nature and become highly unstable in a length-dependent manner. The expansion of repeat length across generations is a well-established process that results in human disorders mainly affecting the central nervous system. At least 50 disorders associated with expansion loci have been described to date, with half recognized only in the last ten years, as prior methodological difficulties limited their identification. These limitations still apply to the current widely used molecular diagnostic methods (exome or gene panels) and thus result in missed diagnosis detrimental to affected individuals and their families, especially for disorders that are very rare and/or clinically not recognizable. Most of these disorders have been identified through family-driven approaches and many others likely remain to be identified. The recent development of long-read technologies provides a unique opportunity to systematically investigate the contribution of tandem repeats and repeat expansions to the genetic architecture of human disorders. In this review, we summarize the current and most recent knowledge about the genetics of repeat expansion disorders and the diversity of their pathophysiological mechanisms and outline the perspectives of developing personalized treatments in the future.

Tandem repeats represent one of the most abundant class of variations in human genomes, which are polymorphic by nature and become highly unstable in a length-dependent manner. The expansion of repeat length across generations is a well-established process that results in human disorders mainly affecting the central nervous system. At least 50 disorders associated with expansion loci have been described to date, with half recognized only in the last ten years, as prior methodological difficulties limited their identification. These limitations still apply to the current widely used molecular diagnostic methods (exome or gene panels) and thus result in missed diagnosis detrimental to affected individuals and their families, especially for disorders that are very rare and/or clinically not recognizable. Most of these disorders have been identified through family-driven approaches and many others likely remain to be identified. The recent development of long-read technologies provides a unique opportunity to systematically investigate the contribution of tandem repeats and repeat expansions to the genetic architecture of human disorders. In this review, we summarize the current and most recent knowledge about the genetics of repeat expansion disorders and the diversity of their pathophysiological mechanisms and outline the perspectives of developing personalized treatments in the future.     

From Aggregation to Dispersion: How Habitat Fragmentation Prevents the Emergence of Consensual Decision Making in a Group

In fragmented landscape, individuals have to cope with the fragmentation level in order to aggregate in the same patch and take advantage of group-living. Aggregation results from responses to environmental heterogeneities and/or positive influence of the presence of congeners. In this context, the fragmentation of resting sites highlights how individuals make a compromise between two individual preferences: (1) being aggregated with conspecifics and (2) having access to these resting sites. As in previous studies, when the carrying capacity of available resting sites is large enough to contain the entire group, a single aggregation site is collectively selected. In this study, we have uncoupled fragmentation and habitat loss: the population size and total surface of the resting sites are maintained at a constant value, an increase in fragmentation implies a decrease in the carrying capacity of each shelter. For our model organism, Blattella germanica, our experimental and theoretical approach shows that, for low fragmentation level, a single resting site is collectively selected. However, for higher level of fragmentation, individuals are randomly distributed between fragments and the total sheltered population decreases. In the latter case, social amplification process is not activated and consequently, consensual decision making cannot emerge and the distribution of individuals among sites is only driven by their individual propensity to find a site. This intimate relation between aggregation pattern and landscape patchiness described in our theoretical model is generic for several gregarious species. We expect that any group-living species showing the same structure of interactions should present the same type of dispersion-aggregation response to fragmentation regardless of their level of social complexity.