Specific induction of self-discrimination by follicle cells in Ciona intestinalis oocytes

Self-incompatibility, a mechanism that prevents self-fertilization in ascidians, is based on the ability of the oocyte vitelline coat to distinguish and accept only heterologous spermatozoa. In Ciona intestinalis self-discrimination is established during late oogenesis and is contributed or controlled by products of the overlying follicle cells. In this study we have further investigated the role of the follicle cells in the onset of self-discrimination by using in vitro maturation of ovarian oocytes deprived of the follicle cells and incubated with either autologous or heterologous follicle cells. Fertilization assays demonstrate that the action of the follicle cells is exerted even when they are detached from the vitelline coat and that only autologous follicle cells can promote the induction of self-sterility on the egg coat. Electron microscopy of the oocytes during maturation reveals that the switch from self-fertility to self-sterility is accompanied by the appearance of a thin electron-dense layer on the outer surface of the vitelline coat. We suggest that the formation of this layer is the result of the interaction between products of the follicle cells and the autologous vitelline coat.     

An acoustic telemetry study of seabream (Sparus aurata L.): first results on activity rhythm,effects of environmental variables and space utilization

The movements of seabream (Sparus aurata L) were recorded in two earthen ponds (250 m² and 400 m²) by tracking fish tagged with miniature acoustic transmitters. Five seabreams, 500 g in weight, were tracked for periods of four or five days. Fish positions were recorded continuously using an acoustic telemetry system. Each of the five tagged seabreams were tracked individually. Two fishes were released schooled with numerous other individuals, two others were released in isolation and one was grouped with three other individuals.The schooled seabreams were more active in general and, in the large school they were diurnal; isolated fishes however, were more active at night. Temperature influences significantly and progressively the fish activity. Activity decreases at night and increases during daylight. Oxygen saturation also influences swimming activity with a general positive relationship.The horizontal distribution of this species was not uniform. Its resting area was generally located around some particular landmarks such as inlet or outlet pipes in the ponds. No feverish feeding competition was observed between individuals of the same school. The feeding area was cleaned rapidly, in less than 10 minutes, without subsequent returns from the resting area to the feeding area.

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Résumé Les déplacements de la daurade (Sparus aurata L.) ont été enregistrés dans deux bassins en terre (250 m² et 400 m²) en suivant des poissons marqués avec des émetteurs acoustiques miniaturisés. Cinq daurades d'un poids individuel de 500 g furent suivies durant des périodes de 4 ou 5 jours. Les positions des poissons ont été enregistrées en continu avec un systéme de télémétrie acoustique. Chacun des cinq poissons marqués fut suivi individuellement. Deux poissons furent regroupés avec de nombreux autres individus, deux autres furent laissés seuls et le dernier fut mis avec trois autres individus.Les daurades groupées étaient en général plus actives et, en grand banc, étaient diurnes; les poissons isolés étaient toutefois plus actifs durant la nuit. La température influence significativement et progressivement l'activité des poissons. L'activité décroît durant la nuit et augmente pendant le jour. Le pourcentage de saturation en oxygéne agit aussi, de façon positive, sur l'activité de nage.La distribution horizontale de cette espéce n'est pas uniforme. Son aire de repos est généralement localisée dans quelques zones particuliéres comme les arrivées et les sorties d'eau. Aucune compétition alimentaire fébrile n'a été observée entre les individus d'un même banc. L'aire de nourrissage est rapidement nettoyée, en moins de 10 minutes, sans retours ultérieurs depuis la zone de repos jusqu' à la zone de nourrissage.

     

Sex estimation using the first cervical vertebra

The articular surfaces and vertebral foramen area of the first cervical vertebra are sexually dimorphic and can be used to sex complete or fragmentary specimens. Eight measurements were taken from the articular regions (superior and inferior) of 100 first cervical vertebrae from Terry collection specimens housed at the Smithsonian Institution. Seven regression and seven discriminant function equations were created that predict sex with 77–85% and 75–85% accuracy, respectively. In separate control tests, measurements from 100 first cervical vertebrae from Hamann-Todd collection individuals (Cleveland Museum of Natural History) and from 34 archaeological specimens were used with the Terry equations. The control samples were sexed with 60—85% accuracy. © 1995 Wiley-Liss, Inc.     

Mapping of a Gene for Long QT Syndrome to Chromosome 4q25-27

Long QT syndrome (LQTS) is a heterogeneous inherited disorder causing syncope and sudden death from ventricular arrhythmias. A first locus for this disorder was mapped to chromosome 11p15.5. However, locus heterogeneity has been demonstrated in several families, and two other loci have recently been located on chromosomes 7q35-36 and 3p21-24. We used linkage analysis to map the locus in a 65-member family in which LQTS was associated with more marked sinus bradycardia than usual, leading to sinus node dysfunction. Linkage to chromosome 11p15.5, 7q35-36, or 3p21-24 was excluded. Positive linkage was obtained for markers located on chromosome 4q25-27. A maximal LOD score of 7.05 was found for marker D4S402. The identification of a fourth locus for LQTS confirms its genetic heterogeneity. Locus 4q25-27 is associated with a peculiar phenotype within the LQTS entity.     

Propylthiouracil Tasting: Determination of Underlying Threshold Distributions using Maximum Likelihood

The ability to taste low concentrations of propylthiouracil(PROP) and related bitter compounds is heritable. The currentanalysis determines whether the distribution of PROP taste thresholdsis consistent with an additive or a dominant mode of Mendeliantransmission. To that end, the lowest concentration of PROPdetectable was determined for 1015 subjects and models of bi-or tri-modal distributions of PROP taste thresholds were tested.The model with the greatest likelihood had three distributionsand followed an additive model of PROP taste sensitivity ifthe variances associated with the distributions were assumedto be equal. However, if the taste thresholds were transformedto remove skewness, or if the variances were unequal, then three-or two-distribution models were equally likely. Resolution ofthe mode of inheritance for bitter taste perception awaits additionalfamily studies and the characterization of the molecular basisof taste perception for these bitter compounds. Chem. Senses20: 529–533, 1995.     

High frequency of-β-hexosaminidase deficiency in lymphoblastoid cell lines

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome.Four lines were deficient in total β-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical β-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease.The possible mechanisms explaining the high frequency of β-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.     

Surfactant secretion in a newborn rabbit lung slice model

We describe a slice model for the study of pulmonary surfactant secretion in newborn rabbits. Full term rabbits were delivered by cesarean section and injected intraperitoneally with [Me-3H]choline. Four hours later they were killed, the lungs were perfused to remove blood, slices (0.5 mm thick) were prepared and incubated in buffer at 37 degrees C. The composition of the lipids initially released into the medium resembled those of lung tissue rather than surfactant. Following 3 changes of medium, however, the composition of the lipids released was very similar to that of lung lavage. Phosphatidylcholine accounted for over 70% of the total while phosphatidylethanolamine and sphingomyelin accounted for only 7% and 4%, respectively. 52% of the phosphatidylcholine was disaturated. Less than 5% of the tissue lactate dehydrogenase was released into the medium. The rate of phosphatidyl[Me-3H]choline release during this period was, therefore, measured. Release of phosphatidyl[Me-3H]choline was linear with time and was temperature-dependent. Prostaglandin E2 stimulated its rate of release by 20% while indomethacin and flufenamic acid, inhibitors of prostaglandin synthesis, inhibited it by 52% and 37%, respectively. The calcium ionophore A23187 in the presence of Ca2+ stimulated release by 40% while colchicine an cytochalasin B inhibited it by 36% and 32%, respectively. These data suggest that both prostaglandins and Ca2+ are involved in surfactant release and that intact microtubular and microfilament systems may also be necessary.     

Spot position of rat liver ribosomal proteins by four different two-dimensional electrophoreses in polyacrylamide gel

Summary Separation of the proteins from rat liver 40S and 60S ribosomal subunits and polysomes was done in four different two-dimensional polyacrylamide gel electrophoresis systems. The first dimension was run at acidic or basic pH, the second dimension either with sodium dodecyl sulphate or at acidic pH in 18% acrylamide. The position of each individual protein of both subunits and polysomes was determined in each system. This identification resulted from a new method avoiding any previous purification of individual proteins. The new proposed uniform nomenclature for mammalian ribosomal proteins (McConkey et al. in press) was used for numbering the proteins in the four systems.