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101.
102.
103.
Peter W. Marks Benjamin A. Kruskal Frederick R. Maxfield 《Journal of cellular physiology》1988,136(3):519-525
The calcium-sensitive fluorescent indicator fura-2 and a microscope equipped for rapidly changing excitation wavelengths were used to look at the effects of growth factors on cytosolic free calcium ([Ca2+]i,) in NRK-49F cells. In these cells bradykinin induced a rapid increase in [Ca2+]i, which generally decayed to near basal [Ca2+]i within 3 minutes. The initial rise in [Ca2+]i in response to bradykinin was relatively independent of extracellular calcium; however, the decay to basal [Ca2+]i was more rapid in the absence of extracellular calcium. Measurements made on individual cells showed a heterogeneity in the response to bradykinin. Epidermal growth factor (EGF) had no effect on [Ca2+]i in NRK-49F cells when added alone in the presence of extracellular calcium. Simultaneous addition of bradykinin and EGF produced a more prolonged increase in [Ca2+]i than bradykinin alone. The prolongation was dependent on the presence of extracellular calcium and did not occur in its absence. Transient increases in [Ca2+]i occurring after the initial peak were occasionally seen in these cells. Our results indicate that there is rapid interaction between the signaling mechanisms for bradykinin and EGF. When this occurs, one effect is the transport of calcium into the cell from the extracellular environment, causing a more prolonged rise in [Ca2+]i. This effect occurs within 1 minute after combined addition of bradykinin and EGF. 相似文献
104.
Irina Zaitseva Vjacheslav Zaitsev Graeme Card Kirill Moshkov Benjamin Bax Adam Ralph Peter Lindley 《Journal of biological inorganic chemistry》1996,1(1):15-23
The X-ray structure of human serum ceruloplasmin has been solved at a resolution of 3.1?Å. The structure reveals that the molecule is comprised of six plastocyanin-type domains arranged in a triangular array. There are six copper atoms; three form a trinuclear cluster sited at the interface of domains 1 and 6, and there are three mononuclear sites in domains 2, 4 and 6. Each of the mononuclear coppers is coordinated to a cysteine and two histidine residues, and those in domains 4 and 6 also coordinate to a methionine residue; in domain 2, the methionine is replaced by a leucine residue which may form van der Waals type contacts with the copper. The trinuclear centre and the mononuclear copper in domain 6 form a cluster essentially the same as that found in ascorbate oxidase, strongly suggesting an oxidase role for ceruloplasmin in the plasma. 相似文献
105.
Genetic and structural analysis of a virulence determinant in polyomavirus VP1. 总被引:9,自引:5,他引:4 下载免费PDF全文
P H Bauer R T Bronson S C Fung R Freund T Stehle S C Harrison T L Benjamin 《Journal of virology》1995,69(12):7925-7931
The LID strain of polyomavirus differs from other laboratory strains in causing a rapidly lethal infection of newborn C3H/Bi mice. This virulent behavior of LID was attenuated by dilution, yet at sublethal doses LID was able to induce tumors at a high frequency, like its parent virus PTA. By constructing and assaying LID-PTA recombinant viruses and by DNA sequencing, the determinant of virulence in LID was mapped to the major viral capsid protein, VP1. The VP1s of LID and PTA differed at two positions: at 185, LID has phenylalanine and PTA has tyrosine, and at 296, LID has alanine and PTA has valine. Results obtained with viruses constructed by site-directed mutagenesis showed that alanine at position 296 is sufficient to confer a fully virulent phenotype regardless of which amino acid is at position 185. However, with valine at position 296, an effect of phenylalanine at position 185 is apparent, as this virus possesses an intermediate level of virulence. A crystal structure of polyomavirus complexed with 3'-sialyl lactose previously indicated van der Waals contacts between the side chain of valine 296 and the sialic acid ring (T. Stehle, Y. Yan, T. L. Benjamin, and S. C. Harrison, Nature [London] 369:160-163, 1994). When this interaction was modeled with alanine, these contacts were greatly reduced. Direct confirmation that the substitutions in VP1 affected receptor binding was obtained by studying virus hemagglutination behavior. The ensemble of results are discussed in terms of the idea that a lower affinity of the virus for its receptor can result in more rapid spread and increased pathogenicity. 相似文献
106.
Moran, R.C. & Øllgaard, B. 1995. Six new species of ferns (Polypodiopsida) from Ecuador. - Nord. J. Bot. 15: 177–185. Copenhagen. ISSN 0107–055X.
The following species of ferns from Ecuador are described as new: Blechnum mono-morphum. Bolbitis riparia, Hecistopteris pinnatifida, Hymenophyllum hemidimorphum, Polypodium latissimum , and Saccoloma laxum . 相似文献
The following species of ferns from Ecuador are described as new: Blechnum mono-morphum. Bolbitis riparia, Hecistopteris pinnatifida, Hymenophyllum hemidimorphum, Polypodium latissimum , and Saccoloma laxum . 相似文献
107.
Biosynthesis and action of nitric oxide in mammalian cells 总被引:26,自引:0,他引:26
Nitric oxide (NO) can act as a vasorelaxant, a modulator of neurotransmission and a defence against pathogens. However, under certain conditions, NO can also have damaging effects to cells. Whether NO is useful or harmful depends on its chemical fate, and on the rate and location of its production. Here, we discuss progress in NO chemistry and the enzymology of NO synthases, and we will also attempt to explai its actions in the cardiovascular, nervous and immune systems. 相似文献
108.
Chondroitin-sulfate containing proteoglycan (CSPG) of the extracellular matrix (ECM) was visualized in chick tissues and cell cultures with a monoclonal antibody, CS-56. Cultured cells of various origins contained dense punctate layers of CSPG on both the substrate and the cell surface, as determined by immunofluorescent and immunogold staining. Under culture conditions the CSPG-containing matrix was usually excluded from stable cell-to-substrate focal contacts. The substrate-attached CSPG exhibited remarkable chemical stability but could be successfully removed by pronase or chondroitinases ABC and AC. Incubation of living cells with CS-56 antibodies resulted in the clustering of surface CSPG into patches, indicating that the surface-bound CSPG is free to move laterally along the plasma membrane. The unique properties of the CSPG-containing ECM revealed by CS-56 antibodies and their relationships to specific types of cell contacts are discussed. 相似文献
109.
In prospectively evaluating 100 cases of adolescents with chest pain (along with two control groups), 91 were found to have recurrent chest pain; fewer than 5 had a serious organic cause. Significantly higher school absenteeism occurred in patients with either chest or abdominal pain than in patients without pain. Adolescents with chest and abdominal pain were more likely to be high users of medical services than those with no pain. Most adolescents believed that persons their age could have attacks; 44 of those with chest pain thought their symptom was due to a heart attack. The occurrence of chest pain was not influenced by an adolescent''s age, sex, race, smoking status or family structure, nor was it consistently associated with depression. Chest pain is thus a common problem of adolescence that produces considerable functional impairment not attributable to serious underlying disease. 相似文献
110.
George A. Carlson Benjamin A. Taylor Susan T. Marshall Arnold H. Greenberg 《Immunogenetics》1984,20(3):287-300
The genetic control of natural resistance in vivo to four natural killer (NK) cell-resistant H-2 homozygous lymphoid tumor cell lines was investigated by following the survival and organ distribution of cells prelabeled with radioactive iododeoxyuridine. Backcross mice derived from DBA/2J and CBA/J parents were injected with H-2
dtumor cells and tumor cell elimination was lowest in H-2
dhomozygotes. Natural killer cell activity was also reduced in mice with the H-2
dhaplotype, but no direct correlation between NK cell levels against YAC-1 or SL2-5 lymphoma cells and natural resistance in vivo was demonstrable. Analysis of 23 BXD recombinant inbred strains indicated that natural resistance to H-2
dtumors was restricted to H-2
bstrains. There was no direct association of NK cell activity with H-2 type in the BXD strains and NK cell levels did not correlate with tumor survival in vivo. By comparing natural resistance to H-2
dand H-2
btumors in DBA/2, C57BL/6, B6D2F1, and B10.D2 mice we found that H-2 nonidentity between the tumor and the host, rather than the host H-2 haplotype, determined whether natural resistance occurred. Again, NK cell activity against YAC-1 cells was not predictive of tumor survival in these strains. These results provide genetic evidence that NK cells alone cannot account for natural resistance to H-2 nonidentical cells of hemopoietic origin. 相似文献