Les génotypes responsables de mucoviscidose ou d’absence bilatérale des canaux déférents ABCD

Over the last decade, the genetic basis for CBAVD has been identified by its association with CFTR gene mutations, and CBAVD is now generally considered to be a mild or incomplete form of CF. In this review, the author summarizes the main results of compilation of CFTR gene analysis conducted in French laboratories for 3,923 patients with CF and 800 males with CABVD. The degree of clinical expression can be affected by several variables, including the molecular mechanisms by which the various CFTR mutations impair or disrupt the function of the CFTR chloride channel. Phenotypic expression of CFTR mutational genotypes varies from severe, progressive pulmonary disease with pancreatic insufficiency (CF-PI), to mild pulmonary disease with pancreatic sufficiency (PS) or singleorgan forms of “CFTR-opathies”. In CF, a total of 310 different CFTR mutations accounting for 94% of 7,846 CF alleles have generated almost 500 different genotypes, comprising 2 severe mutations in 88% of cases (CF-PI), one severe mutation in trans to a mild mutation in 11% (CF-PS), and 2 mild mutations in 1% of identified genotypes. In CBAVD, 137 mutations scattered over the whole gene were identified in 60% of 1,600 CBAVD alleles during the study. Among the 150 characterized mutational CFTR genotypes, compound heterozygosity was the rule, and the most frequent CBAVD combinations were ΔF508/5T (35%), ΔF508/other mutation (30%, including ΔF508/R117H-7T: 5,6%), and 5T/other mutation (17%). No combination of two severe mutations was found in CBAVD (0%); by contrast with the CF population, 88% of genotypes identified in CBAVD comprised a severe mutation in trans to a mild mutation, and 12% consisted of 2 mild mutations. A total of 22 genotypes were shared by both CF and CBAVD. The role of the 5T allele as a splicing variant with variable, incomplete disease penetrance in CBAVD is reviewed. Other haplotype backgrounds, such as the TG12 sequence and the M470V polymorphism, may influence CFTR splicing and/or function. This study confirms the high molecular heterogeneity of CFTR mutations in CBAVD and emphasizes the importance of extensive CFTR analysis in these patients. Longterm follow-up studies of CBAVD patients are necessary in order to predict the phenotypic consequences of numerous CFTR mutational genotypes.     

Advances in endophenotyping schizophrenia

The search for the genetic architecture of schizophrenia has employed multiple, often converging strategies. One such strategy entails the use of tracing the heritability and neurobiology of endophenotypes. Endophenotypes are quantifiable traits not visible to the eye, which are thought to reflect an intermediate place on the path from genes to disorder. Endophenotype abnormalities in domains such as neurophysiology or neurocognition occur in schizophrenia patients as well as their clinically “unaffected” relatives, and reflect polymorphisms in the DNA of schizophrenia spectrum subjects which create vulnerability to developing schizophrenia. By identifying the single nucleotide polymorphisms (SNPs) associated with endophenotypes in schizophrenia, psychiatric neuroscientists can select new strong inference based molecular targets for the treatment of schizophrenia.     

Experiments on the spread of rugose mosaic and leaf roll in potato crops in 1946

A series of experiments on the spread of potato rugose mosaic (virus Y ), and leaf roll, which has been in progress on a uniform plan since 1943, was ended in 1946. Mean values for thirteen centres in England and Wales showed that in 1946 69% of the infections with virus Y and 48 % of those with leaf-roll virus reached the tubers of Majestic potatoes by the beginning of August. There was usually little subsequent increase of rugose mosaic, but a late increase of leaf roll was associated with a relatively high initial spread. Three-quarters of the virus Y and over half the leaf-roll infections occurred within five plants distance of the source. There was no close correlation between the spread of either virus and the maximum number of Myzus persicae , either apterous forms on the plants or alate forms caught on adhesive traps, but centres with high trap catches in July and August showed pronounced late season spread of leaf roll. There were marked differences at different centres in the relative spread of the two viruses. The amount of spread and the gradients from source of infection of the two viruses are compared over the period 1943–6.     

Capture and Ingestion of Paramecium by Didinium nasutum

SYNOPSIS. This study attempts to analyze how a number of specialized organelles are coordinated in a rapid but complex sequence of events during the capture and ingestion of prey by Didinium . Accidental contact between a Paramecium and the proboscis of a hungry Didinium causes instantaneous discharge of 2 kinds of extrusive organelles from the latter. The short pexicysts attach to the surface of Paramecium but do not penerate. The long toxicysts penetrate the victim, altho their proximal end s remain embedded in the proboscis of Didinium . Cytoplasmic streaming pulls the discharged toxicysts inward, and since they are firmly attached to the prey, the latter is drawn steadily into the cytostome. As the prey is being swallowed, it is compressed, and its volume is reduced by elimination of fluid. When the prey is completely inside the predator, the temporary cytostome closes, and the proboscis is reformed.     

Could the elongate yellow-orange nostrils of Anguilla bicolor McClelland, 1844 function as fishing lures?

The shortfin eel Anguilla bicolor has elongate, yellow nostrils tipped with orange that protrude forward above the mouth. They are a striking, highly visible feature and it is hypothesised that they function as lures to attract prey, analogous to the illicium and esca of anglerfishes and frogfishes and the lingual appendage of the alligator snapping turtle. Another possible function is as an intraspecific signalling device. The first hypothesis is favoured here.     

Assessment of soil calcium status in red spruce forests in the northeastern United States

Long-term changes in concentrations of available Ca in soils of redspruce forests have been documented, but remaining questions aboutthe magnitude and regional extent of these changes have precluded anassessment of the current and future status of soil Ca. To addressthis problem, soil samples were collected in 1992—93from 12 sites in New York, Vermont, New Hampshire, and Maine toprovide additional data necessary to synthesize all availableresearch results on soil Ca in red spruce forests. Sites werechosen to encompass the range of environmental conditionsexperienced by red spruce. Concentrations of exchangeableCa ranged from 2.13 to 21.6 cmol_ckg^–1 in the Oa horizon, and from 0.11 to 0.68cmol_c kg^–1 in the upper 10 cm of theB horizon. These measurements expanded the range of exchangeable Ca reported in the literature for both horizons in northeastern redspruce forests. Exchangeable Ca was the largest Ca fraction in theforest floor at most sites (92% ofacid-extractableCa), but mineral Ca was the largest fraction at the three sites that also had the highest mineral-matter concentrations. Theprimary factor causing variability in Ca concentrations among siteswas the mineralogy of parent material, but exchangeable concentrationsin the B horizon of all sites were probably reduced by acidicdeposition. Because the majority of Ca in the forest floor isin a readily leachable form, and Ca inputs to the forest floor from the mineral soil and atmospheric deposition have beendecreasing in recent decades, the previously documented decreasesin Ca concentrations in the forest floor over previous decades mayextend into the future.     

Putative odour receptors localize in cilia of olfactory receptor cells in rat and mouse: a freeze-substitution ultrastructural study

Two different polyclonal antibodies were raised to synthetic peptides corresponding to distinct putative odour receptors of rat and mouse. Both antibodies selectively labelled olfactory cilia as seen with cryofixation and immunogold ultrastructural procedures. Regions of the olfactory organ where label was detected were consistent with those found at LM levels. Immunopositive cells were rare; only up to about 0.4% of these receptor cells were labelled. Despite chemical, species, and topographic differences both antibodies behaved identically in their ultrastructural labelling patterns. For both antibodies, labelling was very specific for olfactory cilia; both bound amply to the thick proximal and the thinner and long distal parts of the cilia. Dendritic knobs showed little labelling if any. Dendritic receptor cell structures below the knobs, supporting cell structures, and respiratory cilia did not immunolabel. There were no obvious differences in morphology between labelled and unlabelled receptor cells and their cilia. Labelling could be followed up to a distance of about 15 μm from the knobs along the distal parts of the cilia. When labelled cells were observed, this signal was detectable in two, sometimes three, sections taken through these cells while being consistently absent in neighbouring cells. This pattern argues strongly for the specificity of the labelling. In conclusion, very few receptor cells labelled with the antibodies to putative odour receptors. Additionally the olfactory cilia, the cellular regions that first encounter odour molecules and that are thought to transduce the odorous signal, displayed the most intense labelling with both antibodies. Consequently, the results showed these cilia as having many copies of the putative receptors. Finally, similar patterns of subcellular labelling were displayed in two different species, despite the use of different antibodies. Thus, this study provides compelling evidence that the heptahelical putative odour receptors localize in the olfactory cilia.