Contribution à la connaissance des bactéries des collections d'eau stagnantes et de leur rôle en hydrobiologie

Ohne ZusammenfassungDirecteur du Centre de Recherches Hydrobiologiques du C.N.R.S.Avec la collaboration technique de Mme L. Goldstein.     

Localization of lipoprotein unesterified cholesterol in nondenaturing gradient gels with filipin

A method is described for the staining of lipoprotein unesterified cholesterol in nondenaturing polyacrylamide gradient gels with the fluorescent polyene antibiotic, filipin. The sensitivity of the filipin stain was comparable to that of oil red O and Coomassie R250 in terms of the amount of lipoprotein applied. Filipin successfully stained discoidal complexes of apoA-I-phosphatidylcholine-cholesterol, which in turn were stained poorly with oil red O. The potential for the identification of unesterified cholesterol-enriched lipoprotein subclasses was demonstrated.     

Genetic duplication in the white-split interval of the X chromosome in Drosophila melanogaster

A detailed cytogenetic study of male-viable and lethal deficiencies affecting the w-spl interval in Drosophila melanogaster has revealed the existence of genetic duplication such that, for example, the consequences of the loss of salivary chromosome band 3C3 are essentially compensated for by the presence of band 3C5-6, and vice versa. Although each of the duplicate elements possesses rst ⁺ and vt ⁺ activity, rst and vt phenotypes appear in males when 3C3 and part, but not all, of 3C5-6 are deleted. The degree of rst and vt expression can be correlated with the amount of material lost from 3C5-6. Deletions removing the entire 3C3-6 interval are male lethal. Despite the duplicate elements, at least one EMS-induced, presumptive point mutation expressing only rst is known; two others express both rst and vt. No loci other than rst and vt occur between W and spl. Band 3C2 appears to be associated with the w locus, which probably extends into the interband space between 3C1 and 3C2. The w locus is not involved in the rst-vt duplication in the 3C3-6 region. — The cytogenetic characteristics of the 3C region—a high coefficient of crossing over, frequent induced chromosome breakage, ectopic pairing, constriction, and an extended replication period—can be correlated with the fact that in 3C a relatively long stretch of DNA, nearly 2% of the entire X chromosome, is highly compacted into but few adjacent bands. These characteristics do not necessarily represent special properties of intercalary heterochromatin; they can be interpreted as reflecting the properties of any similarly organized euchromatic region.This investigation was aided by research grants from the U. S. Public Health Service (GM 13631) to G. Lefevre, Jr. and the National Science Foundation (GB 27599) to M. M. Green.     

Endoplasmic reticulum accumulation of Kir6.2 without activation of ER stress response in islet cells from adult Sur1 knockout mice

Trafficking of pancreatic K_ATP channels to the plasma membrane critically depends on masking the endoplasmic reticulum (ER) retention signals of the SUR1 and Kir6.2 subunits upon their proper assembly into functional hetero-octamers. When expressed in the absence of the partner protein, each subunit might accumulate in the ER and trigger β-cell ER stress and oxidative stress. To test this hypothesis, Kir6.2 localisation, ER ultra-structure and ER-stress- and oxidative-stress-response gene mRNA levels were evaluated in pancreatic endocrine cells from adult wild-type (WT) and Sur1 knockout (Sur1 ^-/- ) mice. As previously reported, Kir6.2 was mainly expressed on secretory granules and at the plasma membrane of WT islet cells. In contrast, like the ER chaperone calreticulin, Kir6.2 was primarily localised in the rough endoplasmic reticulum (RER) of Sur1 ^-/- islet cells. ER retention of Kir6.2 was demonstrated (electron microscopy) by a significant increase in the length and Kir6.2 density of RER in Sur1 ^-/- vs WT islet cells. Despite Kir6.2 retention in RER, Xbp1 mRNA splicing and mRNA levels of preproinsulin and ER-stress-response genes Bip, Edem and Gadd153 were similar in WT and Sur1 ^-/- islets. However, mRNA levels of the antioxidant enzymes Sod1, Sod2, Gpx2 and catalase were significantly up-regulated in Sur1 ^-/- islets. Sequestration of Kir6.2 in RER of Sur1 ^-/- islet cells is thus associated with an increase in RER length and mild oxidative stress without activation of the classical ER stress response.     

ELISA detection of restriction site polymorphisms in the pig ryanodine receptor locus

We compare two strategies for ELISA detection of restriction site polymorphisms (EDRSP) that are suitable for high-throughput genotyping of the pig ryanodine receptor point mutation (RYR1 ^hal ). In both procedures, target DNA is amplified by PCR with one primer that is 5′ biotinylated and a second primer that is 5′ fluoresceinylated. PCR products are captured in duplicate wells on a streptavidin-coated, 96-well plate. The duplicates may be treated in two ways. In a single restriction enzyme assay, one duplicate is exposed to a restriction enzyme that cuts one allele specifically, and the second duplicate is exposed to no restriction enzyme. In a dual restriction enzyme assay, the second replicate is exposed to a second restriction enzyme that cuts the alternate allele specifically. Thereafter, the two procedures are similar; anti-fluorescein antibodies conjugated to peroxidase are allowed to bind to the fluoresceinylated ends, the plate is washed, and a substrate is converted to a colored end product. The ratio of the absorbances in the two wells is used to classify subjects by genotype. When the dual restriction enzyme assay is run, three genotype groups are easily distinguishable. When the single restriction enzyme assay is run, heterozygotes generate values that may overlap with those of the homozygotes that are not cut by the restriction enzyme. Dual restriction enzyme assays are more accurate than single restriction enzyme assays; however, single restriction enzyme assays are sufficient for identifying pigs that carry RYR1 ^hal . Received: 30 December 1997 / Accepted: 20 April 1998     

Marine mollusc predator-escape behaviour altered by near-future carbon dioxide levels

Ocean acidification poses a range of threats to marine invertebrates; however, the potential effects of rising carbon dioxide (CO₂) on marine invertebrate behaviour are largely unknown. Marine gastropod conch snails have a modified foot and operculum allowing them to leap backwards rapidly when faced with a predator, such as a venomous cone shell. Here, we show that projected near-future seawater CO₂ levels (961 µatm) impair this escape behaviour during a predator–prey interaction. Elevated-CO₂ halved the number of snails that jumped from the predator, increased their latency to jump and altered their escape trajectory. Physical ability to jump was not affected by elevated-CO₂ indicating instead that decision-making was impaired. Antipredator behaviour was fully restored by treatment with gabazine, a GABA antagonist of some invertebrate nervous systems, indicating potential interference of neurotransmitter receptor function by elevated-CO₂, as previously observed in marine fishes. Altered behaviour of marine invertebrates at projected future CO₂ levels could have potentially far-reaching implications for marine ecosystems.     

The cytogenetics of mutator gene-induced X-linked lethals in Drosophila melanogaster

A third chromosome mutator gene effectively increases the spontaneous frequency of sex-linked recessive lethals in females but not in females of Drosophila melanogaster. Approximately half the mutator-induced mutants occur as clusters of the same mutant implying a premeiotic origin. An appreciable number of the mutator-induced lethals are associated with comparatively long deficiencies of several salivary gland chromosome bands. The possible modes of mutator gene action are conjectured.