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1.
A prospective study was conducted of 100 consecutive admissions to the neonatal intensive care unit of the Hospital for Sick Children, Toronto, of infants with respiratory distress syndrome or transient tachypnea of the newborn. It was found that in 15% of cases the illness was completely preventable, being the result of unintentionally premature termination of pregnancy. Significant intrapartum asphyxia occurred in 44% of the infants in whom respiratory distress syndrome developed. Factors placing the pregnancy at high risk were present antenatally in most cases, and most of the deliveries took place in hospitals without adequate facilities or staff, or both, for the requirements of the infant at and following birth. 相似文献
2.
NRK rat cells infected with a transformation-defective, temperature-sensitive (ts) mutant of the avian sarcoma virus could not proliferate in Ca2+-deficient medium at a nonpermissive temperature (40 °C) that inactivated the viral pp60v-scr-transforming product and rendered the cells phenotypically untransformed. However, these arrested cells were stimulated to initiate DNA replication with little or no delay while still in the Ca2+-deficient medium, either by adding Ca2+ or calmodulin at 40 °C or by reducing the temperature to 36 °C which restored the transformed phenotype by rapidly reactivating pp60v-src. The G1/S transition triggered by restoring the transformed phenotype was suppressed by three different anticalmodulin drugs (R24571, trifluoperazine, W7). The suppression by one of these drugs, trifluoperazine, was overcome by adding calmodulin. Thus, neoplastic transformation by the avian sarcoma virus sharply reduces the extracellular Ca2+ requirement for the initiation of DNA replication without bypassing a calcical-modulin-dependent mechanism also needed for the G1/S transition. 相似文献
3.
Jennifer H. Riddell Philip J. Whitfield M. A. Balogun Michael C. Thorndyke 《Acta zoologica》1991,72(1):1-5
FMRFamide-like immunoreactivity has been demonstrated in the digenean trematode Echinostoma liei. The functions of FMRFamide-like substances appear to be many and varied within the invertebrates, where they are involved in neurotransmission, cardiovascular regulation, muscular contraction and/or relaxation, and in co-ordination of growth and maturation. It is clearly indicated that FMRFamide-like substances function as neurotransmitter/neuromodulator in E. liei by the abundance of positively stained nerve fibres and perikarya seen throughout the CNS and PNS. A single endocrine-like cell also showing FMRFamide-like immunoreactivity is situated within the muscular cirrus pouch. 相似文献
4.
Summary Washed microsomal preparations (100 000 xg sediment) from the yeast Sporopachydermia cereana that had been grown on trimethylamine N-oxide as sole nitrogen source catalysed the NAD(P)H-dependent reduction of trimethylamine N-oxide to trimethylamine. Under anaerobic conditions, this was the sole reaction product, but under aerobic conditions only small amounts of trimethylamine accumulated, most being further metabolized to methylamine and formaldehyde (no detectable dimenthylamine accumulated due to its rapid turnover). In the absence of NAD(P)H, no formation of amines or formaldehyde from trimethylamine N-oxide was detected. The trimethylamine N-oxide reductase activity was inhibited by quinacrine, Cu2+ ions, triethylamine N-oxide (apparent K
i 0.43 mM) and dimethyl sulphoxide (K
i 0.94 mM). Chlorate and nitrate failed to inhibit the enzyme. The K
m for trimethylamine N-oxide was 29 M. Triethylamine N-oxide was also reduced by the microsomal preparation with the formation of acetaldehyde, and this reduction was sensitive to the same inhibitors as trimethylamine N-oxide, suggesting that both amine oxides are metabolized by the same enzyme(s). It is concluded that trimethylamine N-oxide is metabolized in this yeast via an NAD(P)H-dependent reductase.Abbreviations TMAO
triemthylamine N-oxide 相似文献
5.
Rat kidney (NRK) cells infected with a temperature-sensitive mutant of the Kirsten sarcoma virus were arrested in the G0/G1 phase of their cell cycle by incubation in serum-deficient medium at a p21-inactivating temperature of 41 degrees C. These quiescent ts K-NRK cells were then stimulated to transit G1 and initiate DNA replication by lowering the temperature to 36 degrees C, which rapidly reactivated p21. Reactivating the viral Ki-RAS protein by temperature shift led to an increase in adenylate cyclase activity in early G1 phase. The Ki-RAS protein increased the sensitivity of adenylate cyclase to guanyl nucleotides by a mechanism that seemed to involve inactivation of the enzyme's inhibitory G1 regulatory protein. 相似文献
6.
7.
PHYLOGENY OF THE SUBFAMILIES OF THE FAMILY BRACONIDAE (HYMENOPTERA: ICHNEUMONOIDEA): A REASSESSMENT 总被引:1,自引:0,他引:1
R.A. Wharton S.R. Shaw M.J. Sharkey D.B. Wahl J.B. Woolley J.B. Whitfield P.M. Marsh W. Johnson 《Cladistics : the international journal of the Willi Hennig Society》1992,8(3):199-235
Abstract— The recently published phylogeny of Braconidae by Quicke and van Achterberg is reassessed. Character-state definitions and character polarities are evaluated, and more rigorous methods are suggested. Our results indicate that there are many more parsimonious solutions to their data set, the consensus of which differs substantially from their results. Based on our reassessment, little can be said about the relationships among braconid subfamilies. Consensus trees show the cyclostomes as a largely unresolved basal grade. The two other major lineages which have been proposed, the helconoids and microgastroids, are somewhat better resolved, but not consistently so. Relationships among the helconoids vary considerably depending on the parameters used for parsimony analysis. 相似文献
8.
Protein kinase C increases the activity of the polyoma virus middle T antigen-associated phosphatidylinositol kinase 总被引:3,自引:0,他引:3
L Raptis J Bell J F Whitfield 《Biochemical and biophysical research communications》1988,154(1):306-311
Exposure of polyoma virus-transformed fibroblasts to the protein kinase C-stimulating phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) is known to increase the transforming potential of the virus's middle T antigen. Here it is shown that this TPA treatment also stimulates an 85 kDa phosphatidylinositol kinase associated with the middle T antigen. Since activation of this kinase is known to be necessary, although not by itself sufficient for the transformation of cells by polyoma virus, bursts of protein kinase C activity, triggered by TPA or various cellular receptors, might enhance the oncogenicity of polyoma virus by stimulating this middle T antigen-associated phosphatidylinositol kinase. 相似文献
9.
Characterization of monoclonal antibodies to histone 2B. Localization of epitopes and analysis of binding to chromatin 总被引:1,自引:0,他引:1
Two mouse monoclonal IgM antibodies have been isolated which bind to histone 2B (H2B), as shown by protein blotting and immunostaining and by solid-phase radioimmunoassay (RIA). One of these (HBC-7) was specific for H2B by both techniques whereas the other (2F8) cross-reacted with histone H1 by RIA. Both antibodies failed to recognize H2B limit peptides from trypsin-digested chromatin and did not bind to Drosophila H2B, which differs extensively from vertebrate H2B only in the N-terminal region. These findings indicate that both antibodies recognize epitopes within the trypsin-sensitive, N-terminal region comprising residues 1-20. Binding of antibody HBC-7 was inhibited by in vitro ADP-ribosylation of H2B at glutamic acid residue 2. This strongly suggests that the epitope recognized by HBC-7 is located at the N-terminus of H2B, probably between residues 1 and 8. We have used solid-phase radioimmunoassay to investigate factors which influence the accessibility of this epitope in chromatin. Removal of H1 ('stripping') from high-molecular-mass chromatin had no effect on HBC-7 binding, nor was any difference observed between binding to stripped chromatin and to 146-base-pair (bp) core particles derived from it by nuclease digestion. These results suggest that accessibility of the N-terminal region of H2B is not influenced by H1 itself or by the size or conformation of linker DNA. In contrast, binding of antibody HBC-7 to 146-bp core particles derived from unstripped chromatin was reduced by up to 70%. Binding was restored by exposure of these core particles to the conditions used for stripping. Analysis of the protein content of core particle preparations from stripped and unstripped chromatin suggests that these findings may be attributable to redistribution of non-histone proteins during nuclease digestion. Pre-treatment of high-molecular-mass chromatin or 146-bp core particles with the intercalating dye ethidium bromide resulted in a severalfold increase in binding of HBC-7. The major changes in nucleosome morphology induced by ethidium are therefore accompanied by an increase in accessibility of the N-terminal region of H2B, possibly as a direct result of changes in the spatial relationship between H2B and core DNA. 相似文献
10.