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.     

Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo

The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis.     

Barotolerant variant of Streptococcus faecalis with reduced sensitivity to glucose catabolite repression

Physiological characterization of the APR-11 variant of Streptococcus faecalis ATCC 9790 revealed that the variant has reduced sensitivity to glucose catabolite repression. This reduced sensitivity was indicated by the synthesis of enzymes for catabolism of lactose or arginine in cultures growing at 0.1, 40, or 70 MPa in media with levels of glucose highly repressive for the parent strain. Reduced catabolite repression appeared to be due to reduced activity of the glucose-specific, phosphotransferase system in APR-11 cells. Conversion of pyruvate to lactate or to acetate and ethanol did not appear to be altered in the variant. The APR-11 variant produced a greater final yield of biomass than the parent at all pressures tested, and its barotolerance was especially marked in media with low levels of glucose and high levels of lactose in which derepression of the lactose catabolic system was necessary for full growth. Overall, the greater barotolerance of the APR-11 strain appeared to be due to its enhanced capacity for catabolism related to its reduced sensitivity to catabolite repression by glucose.     

Genetic and physical maps of Klebsiella aerogenes genes for histidine utilization (hut)

Summary Deletion derivatives of the hut-containing plasmid pCB101 were tested against point mutants defective in individual genes of the histidine utilization (hut) operons using a complementation/recombination assay. Location of the genes of the right operon, hutU and hutH, was confirmed by direct assay of the gene products, urocanase and histidase; location of the repressor gene was identified by measuring the ability of the plasmid-carried genes to repress the formation of histidase from a chromosomal location. The analysis of eight deletion plasmids unambiguously confirms the map order of the hut genes as hutI-G-C-U-H, and demonstrates that, in Klebsiella aerogenes, the hutU and hutH genes are transcribed from their own promoter. In addition, the genetic map of hut can be aligned with the restriction map of the hut DNA in plasmid pCB101. One of the deletion plasmids studied apparently encodes a defective histidase subunit that is trans-dominant to active histidase. Another deletion, which completely removes the left operon, hutIG, allows high level expression of the hutUH operon and thus overproduction of a toxic intermediate.     

Evidence that S-formylglutathione hydrolase and esterase D polymorphisms are identical

Summary From the analyses of families, populations, and somatic cell hybrids it could be concluded that the S-formylglutathione hydrolase (FGH) and esterase D (ESD) polymorphisms are identical.