Assessment of functional gametes in chickens after transfer of primordial germ cells

The ability of primordial germ cells (PGCs) transferred from donor to recipient embryos to form functional gametes was assessed using feather colour as a phenotypic marker. Donor primordial germ cells were obtained in blood samples taken from Dwarf White Leghorn embryos, homozygous for the dominant allele at the locus for 'dominant white' plumage (I), which had been incubated for 52 h. Blood samples containing PGCs were transferred by intravascular injection to Barred Plymouth Rock embryos (ii) incubated for 53, 72 and 96 h. Of the embryos which hatched, 28 were male and 31 were female. All chicks were raised to sexual maturity and test mated with Barred Plymouth Rock fowl. All of the 3117 offspring exhibited the typical Barred Plymouth Rock phenotype; no Barred Plymouth Rock x Dwarf White Leghorn chicks were obtained. The results of this study suggest that the frequency of transmission of the donor line genotype after PGC transfer must be improved for this technique to be useful for the routine development of transgenic poultry.     

Hypertension in obesity may reflect a homeostatic thermogenic response

Systemic hypertension of mild to moderate degree is often associated with obesity. The hypothesis is that over-eating leads to increased sympathetic activity targeted at the peripheral vasculature as well as other tissues in an attempt (that in many cases may be futile) to stimulate facultative thermogenesis and burn-off the excess energy. This hypothesis represents an important modification of one proposed by Landsberg and is supported by: 1) recent observations that carbohydrate feeding to humans specifically increases muscle sympathetic vasoconstrictor activity in the peroneal nerve, and 2) studies with animal models in which active vasoconstriction in the limbs and elsewhere is associated with marked increases in oxygen consumption (energy expenditure).     

Molecular cloning of a GTPase activating protein specific for the Krev-1 protein p21rap1

The rap1/Krev-1 gene encodes a ras-related protein that suppresses transformation by ras oncogenes. We have purified an 88 kd GTPase activating protein (GAP), specific for the rap1/Krev-1 gene product, from bovine brain. Based on partial amino acid sequences obtained from this protein, a 3.3 kb cDNA was isolated from a human brain library. Expression of the cDNA in insect Sf9 cells resulted in high level production of an 85-95 kd rap1GAP that specifically stimulated the GTPase activity of p21rap1. The complete deduced amino acid sequence is not homologous to any known protein sequences, including GAPs specific for p21ras. Northern and Western blotting analysis indicate that rap1GAP is not ubiquitously expressed and appears most abundant in fetal tissues and certain tumor cell lines, particularly the Wilms' kidney tumor, SK-NEP-1, and the melanoma, SK-MEL-3, cell lines.     

Cleavage and gastrulation in the shrimp Sicyonia ingentis: invagination is accompanied by oriented cell division.

Embryos of the penaeoidean shrimp Sicyonia ingentis were examined at intervals during cleavage and gastrulation using antibodies to beta-tubulin and DNA and laser scanning confocal microscopy. Cleavage occurred in a regular pattern within four domains corresponding to the 4-cell-stage blastomeres and resulted in two interlocking bands of cells, each with similar spindle orientations, around a central blastocoel. Right-left asymmetry was evident at the 32-cell-stage, and mirror-image embryos occurred in a 50:50 ratio. Gastrulation was initiated by invagination into the blastocoel at the 62-cell-stage of two mesendoderm cells, which arrested at the 32-cell-stage. Further invagination and expansion of the archenteron during gastrulation was accompanied by rapid and oriented cell division. The archenteron was composed of presumptive naupliar mesoderm and the blastopore was located at the site of the future anus of the nauplius larva. In order to trace cell lineages and determine axial relationships, single 2- and 4-cell-stage blastomeres were microinjected with rhodamine-dextran. The results showed that the mesendoderm cells which initiated gastrulation were derived from the vegetal 2-cell-stage blastomere, which could be distinguished by its slightly larger size and the location of the polar bodies. The mesendoderm cells descended from a single vegetal blastomere of the 4-cell-stage. This investigation provides the first evidence for oriented cell division during gastrulation in a simple invertebrate system. Oriented cell division has previously been discounted as a potential morphogenetic force, and may be a common mechanism of invagination in embryos that begin gastrulation with a relatively small number of cells.     

Isolation, DNA sequence, and regulation of a Saccharomyces cerevisiae gene that encodes DNA strand transfer protein alpha.

DNA strand transfer protein alpha (STP alpha) from meiotic Saccharomyces cerevisiae cells promotes homologous pairing of DNA without any nucleotide cofactor in the presence of yeast single-stranded DNA binding protein. This gene (DNA strand transferase 1, DST1) encodes a 309-amino-acid protein with a predicted molecular mass of 34,800 Da. The STP alpha protein level is constant in both mitotic and meiotic cells, but during meiosis the polypeptide is activated by an unknown mechanism, resulting in a large increase in its specific activity. A dst1::URA3/dst1::URA3 mutant grows normally in mitotic media; however, meiotic cells exhibit a greatly reduced induction of both DNA strand transfer activity and intragenic recombination between his1 heteroalleles. Spore viability is normal. These results suggest that DST1 is required for much of the observed induction of homologous recombination in S. cerevisiae during meiosis but not for normal sporulation.     

The Evolution of the Y Chromosome with X-Y Recombination

A theoretical population genetic model is developed to explore the consequences of X-Y recombination in the evolution of sex chromosome polymorphism. The model incorporates one sex-determining locus and one locus subject to natural selection. Both loci have two alleles, and the rate of classical meiotic recombination between the loci is r. The alleles at the sex-determining locus specify whether the chromosome is X or Y, and the alleles at the selected locus are arbitrarily labeled A and a. Natural selection is modeled as a process of differential viabilities. The system can be expressed in terms of three recurrence equations, one for the frequency of A on the X-bearing gametes produced by females, one for each of the frequency of A on the X- and Y-bearing gametes produced by males. Several special cases are examined, including X chromosome dominance and symmetric selection. Unusual equilibria are found with the two sexes having very different allele frequencies at the selected locus. A significant finding is that the allowance of recombination results in a much greater opportunity for polymorphism of the Y chromosome. Tighter linkage results in a greater likelihood for equilibria with a large difference between the sex chromosomes in allele frequency.     

Structure and phosphorylation of eukaryotic initiation factor 2. Casein kinase 2 and protein kinase C phosphorylate distinct but adjacent sites in the beta-subunit

Eukaryotic initiation factor 2 (eIF-2) from rabbit reticulocytes can be phosphorylated on its beta-subunit by two different protein kinases, protein kinase C and casein kinase 2. Phosphorylation by these kinases is additive, suggesting that they phosphorylate different sites (serine residues) in eIF-2 beta. Two-dimensional peptide mapping of the phosphopeptides generated from labelled eIF-2 beta by digestion with trypsin, cyanogen bromide or Staphylococcus aureus V8 proteinase showed that protein kinase C and casein kinase 2 phosphorylated distinct and different sites in this protein. This conclusion was supported by the results of analysis of the phosphopeptides on reverse-phase chromatography. Analysis of the phosphopeptides derived from eIF-2 beta labelled by both kinases together strongly suggested that the sites labelled by protein kinase C and casein kinase 2 are adjacent in the primary sequence. These data are discussed in the light of the present understanding of the sequence specificity of the kinases. Rat liver eIF-2 beta was also found to be a substrate for protein kinase C and casein kinase 2, which were again shown to label different serine residues.     

Adhesion-mediating molecules of human monocytes

Adhesion of monocytes to each other and to T cells and substrates is increased by phorbol esters. In the presence of these compounds monocyte aggregation was almost completely inhibited (greater than 90%) by monoclonal antibody 60.3. This antibody recognizes GP90 (CD18), a leukocyte surface glycoprotein which is separately and noncovalently associated to either GP160 (CD11a), GP155 (CD11b), or GP130 (CD11c). Anti-LFA-1 antibody (CD11a) was only partially inhibitory (35%) while antibodies 60.1 (CD11b) and anti-Leu-M5 (CD11c) had a minimal inhibitory effect (10%). Antibody LB-2 recognizing a single glycoprotein distinct from the GP90-GP160 complex and expressed on activated B and T cells, monocytes, and vascular endothelial cells was partially inhibitory (22%). Monoclonal antibodies anti-C3bR (CD35), T29/33 (CD45, leukocyte common antigen 200). TA-1 (CD11a), OKM1 (CD11b), F10-44-2 (brain-leukocyte antigen), OKM5 (monocyte-endothelial cell antigen) and to class I or class II molecules exerted no inhibition on the monocyte aggregation. Fab fragments of antibody 60.3 efficiently inhibited not only monocyte aggregation in the absence or presence of phorbol esters but also adhesion of these cells to autologous or allogeneic T lymphocytes and, to a lesser extent, to plastic surfaces. It is thus concluded that GP90, either alone or associated to the larger glycoproteins, and LB-2 antigen mediate monocyte adhesion.