Early development of the kelp fly,Coelopa frigida (Diptera). II. Morphology of cleavage and blastoderm formation

Cleavage and blastoderm formation in Coelopa frigida are extremely rapid developmental processes. In short (6–7 minutes) successive cell cycles, nuclei multiply and spread out through the egg. The movement seems to be aided by endoplasmic vesicles and cisternae which are in direct contact with the nuclear membrane. The first cells to separate from the egg plasmodium in early superficial cleavage stages are the pole cells. Precursor material from multivesicular bodies forms the pole cell membranes. The primary nuclei from the posterior pole region are removed from the blastoderm by the pole cell segregation. Blastoderm nuclei from the regions adjacent to the posterior pole migrate into the residual periplasm after pole cell segregation has been completed and constitute the blastoderm nuclei in that region of the egg. Nucleoli are not revealed during internal cleavage. They appear in pole cells shortly after their segregation. The generation time of the blastoderm nuclei increases after the twelfth cleavage. Concurrently, nucleoli form in the blastoderm nuclei and permanent cell membranes separate individual blastoderm cells. After blastoderm cells have been separated from each other, they remain in contact with the interior yolk sac by means of cytoplasmic canals. This contact is maintained at least during the early phases of blastokinesis. Observations on nuclear migration and rapid membrane formation are discussed as examples of protein assembly from subunits as an alternative to de novo protein synthesis in early stages of development.     

The role of protein quality control in mitochondrial protein homeostasis under oxidative stress

Mitochondria contribute significantly to the cellular production of ROS. The deleterious effects of increased ROS levels have been implicated in a wide variety of pathological reactions. Apart from a direct detoxification of ROS molecules, protein quality control mechanisms are thought to protect protein functions in the presence of elevated ROS levels. The reactivities of molecular chaperones and proteases remove damaged polypeptides, maintaining enzyme activities, thereby contributing to cellular survival both under normal and stress conditions. We characterized the impact of oxidative stress on mitochondrial protein homeostasis by performing a proteomic analysis of isolated yeast mitochondria, determining the changes in protein abundance after ROS treatments. We identified a set of mitochondrial proteins as substrates of ROS‐dependent proteolysis. Enzymes containing oxidation‐sensitive prosthetic groups like iron/sulfur clusters represented major targets of stress‐dependent degradation. We found that several proteins involved in ROS detoxification were also affected. We identified the ATP‐dependent protease Pim1/LON as a major factor in the degradation of ROS‐modified soluble polypeptides localized in the matrix compartment. As Pim1/LON expression was induced significantly under ROS treatment, we propose that this protease system performs a crucial protective function under oxidative stress conditions.     

Extracellular polysaccharides of some basidiomycetes.

Culture filtrates of four basidiomycete fungi, Stereum strigoso-zonatum, Fomes australis, Trametes lilacinogilva and Polyporus tumulosus were fractionated and examined for polysaccharide content. Acid hydrolysis showed the presence of galactose, mannose, xylose, fucose and glucose. Their relative amounts were estimated by gas chromatography of the corresponding alditol acetates. Galactose and mannose were the major constituent sugars, amounting to more than 50% of the total. One of the polysaccharides, a fucogalactomannan elaborated by P. tumulosus, was isolated in a purified form. It was shown to have [alpha]D +42 degrees and contained galactose, mannose, fucose and xylose in the relative proportions 2 : 1 : 1 : 0-2.     

Myotonia congenita (Thomsen's disease) excluded from the region of the myotonic dystrophy locus on chromosome 19

Summary Linkage analysis has been carried out in six German families with autosomal dominantly inherited myotonia congenita (Thomsen's disease) using five chromosome 19 markers known to be linked to the gene for myotonic dystrophy (DM). Two of the markers, APOC1 and APOC2, are tightly linked to DM. Close linkage between these markers and myotonia congenita (MC) has been excluded to a distance of 9cM (z=-2.158). These data support the clinical suggestion that MC and DM are non-allelic disorders.