Endocytosis-mediated downregulation of LIN-12/Notch upon Ras activation in Caenorhabditis elegans

The coordination of signals from different pathways is important for cell fate specification during animal development. Here, we define a novel mode of crosstalk between the epidermal growth factor receptor/Ras/mitogen-activated protein kinase cascade and the LIN-12/Notch pathway during Caenorhabditis elegans vulval development. Six vulval precursor cells (VPCs) are initially equivalent but adopt different fates as a result of an inductive signal mediated by the Ras pathway and a lateral signal mediated by the LIN-12/Notch pathway. One consequence of activating Ras is a reduction of LIN-12 protein in P6.p (ref. 2), the VPC believed to be the source of the lateral signal. Here we identify a 'downregulation targeting signal' (DTS) in the LIN-12 intracellular domain, which encompasses a di-leucine-containing endocytic sorting motif. The DTS seems to be required for internalization of LIN-12, and on Ras activation it might mediate altered endocytic routing of LIN-12, leading to downregulation. We also show that if LIN-12 is stabilized in P6.p, lateral signalling is compromised, indicating that LIN-12 downregulation is important in the appropriate specification of cell fates in vivo.     

Nucleolar localization of succinic dehydrogenase in human malignant cells with MTT

Résumé Les auteurs complètent leurs recherches sur la localisation cytochimique de l'activité de la déshydrogénase succinique dans les nucléoles en utilisant un troisième sel de tetrozolium, MTT d'une importance particulière.     

Role of sialic acid in the maintenance of cell surface rigidity.

Removal of the cell surface sialic acid with neuraminidase brings about cell deformation in amoeba. The membranes of these deformed cells are eventually ruptured leading to the liberation of the cell mass.     

Interaction of mammalian hemoglobins with dehydroascorbic acid

Summary Reactive sulfhydryl groups of major hemoglobins from guinea-pig, rat and cat reduced dehydroascorbic acid to ascorbic acid leading to formation of intrachain disulfide bonds. Hybridization experiments indicated that the reduction was carried out by thea chain of cat hemoglobin.This work was supported in part by UGC and a DST grant HCS/DST/258/76.     

Role of ‘adreno-ephedrine’ in the induction of persistent vaginal cornification

Zusammenfassung Adreno-Ephedrin bewirkte bei Ratten Daueröstrus und Zunahme des Gewichts der Uteri und der Nebennieren. Die Ovarien enthielten Follikel verschiedener Grösse, aber keine reifen Corpora lutea. Diese Wirkungen des Adreno-Ephedrins werden auf fettige Infiltration des Leberparenchyms zurückgeführt.     

Sequence of reovirus haemagglutinin predicts a coiled-coil structure

The use of modern techniques has led to new insights into the molecular mechanisms of viral pathogenesis. Although the infectious process is quite complex, it is clear that one critical stage, the interaction of viral attachment proteins with cell-surface receptors, often has a major role in determining the pattern of infection. The mammalian reoviruses have served as useful models for understanding the molecular basis of viral pathogenesis. The mammalian reovirus haemagglutinin (sigma 1 protein), which is an outer capsid protein, has been shown to be a major factor in determining virus-host cell interactions. To further our understanding of the structure and function of the haemagglutinin, we have cloned a complementary DNA copy of the reovirus type 3 S1 double-stranded RNA gene which encodes the virus haemagglutinin and have sequenced the DNA complementary to the S1 gene. Analysis of the predicted amino-acid sequence of the virus haemagglutinin has allowed us to determine that the amino-terminal portion contains an alpha-helical coiled-coil structure and that the carboxy-terminal portion contains the receptor-interacting domains. Using this information, we propose here a model of how the reovirus haemagglutinin is attached to the virus particle.     

Subwavelength-diameter silica wires for low-loss optical wave guiding

Silica waveguides with diameters larger than the wavelength of transmitted light are widely used in optical communications, sensors and other applications. Minimizing the width of the waveguides is desirable for photonic device applications, but the fabrication of low-loss optical waveguides with subwavelength diameters remains challenging because of strict requirements on surface roughness and diameter uniformity. Here we report the fabrication of subwavelength-diameter silica 'wires' for use as low-loss optical waveguides within the visible to near-infrared spectral range. We use a two-step drawing process to fabricate long free-standing silica wires with diameters down to 50 nm that show surface smoothness at the atomic level together with uniformity of diameter. Light can be launched into these wires by optical evanescent coupling. The wires allow single-mode operation, and have an optical loss of less than 0.1 dB mm(-1). We believe that these wires provide promising building blocks for future microphotonic devices with subwavelength-width structures.