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61.
Capillary endothelial cell tropism of PVC-211 murine leukemia virus and its application for gene transduction. 总被引:1,自引:1,他引:0 下载免费PDF全文
M Masuda C A Hanson N V Dugger D S Robbins S G Wilt S K Ruscetti P M Hoffman 《Journal of virology》1997,71(8):6168-6173
PVC-211 murine leukemia virus (MuLV) causes neurodegenerative disease following inoculation of neonatal, but not adult, mice and rats. It was previously shown that tropism for brain capillary endothelial cells (CEC) was a determinant of the viral neuropathogenicity. In this study, we demonstrate that host age-dependent replication of PVC-211 MuLV in vivo occurs in CEC in the brain as well as in other organs, such as the liver, kidney, and heart. In contrast, primary explant cultures of CEC derived from brains and livers of adult and neonatal rats could be infected by PVC-211 MuLV, suggesting that the age-dependent susceptibility was abrogated in vitro. Although CEC were generally less susceptible to MuLV-mediated gene transduction than fibroblasts, treatment of CEC with 2-deoxyglucose followed by inoculation of a PVC-211 MuLV-pseudotyped vector in the absence of heparin improved the transduction efficiency. These observations support the possibility that PVC-211 MuLV may be useful for establishing models of CEC gene transduction. 相似文献
62.
Sara S. Tynan Niels H. Andersen Max T. Wills Laurence A. Harker Stephen R. Hanson 《Prostaglandins & other lipid mediators》1984,27(5):683-696
The ω-chain variant analogs of prostacyclin (PGI2) and PGD2 in which the n-amyl side-chain has been replaced by a cyclohexyl group have been prepared and their cardiovascular activities have been compared to those of BW-245C(Fig. 1)(1) a potent anti-aggregatory vasodilator bearing a cyclohexyl-terminated side-chain on a hydantoin skeleton. The cyclohexyl group has little effect on PGI2, but converts PGD2 to a long lasting hypotensive agent and increases the platelet anti-aggregatory potency of PGD2 by a factor of 8. The prostaglandin antagonist N-0164 selectively blocks the anti-aggregatory actions of PGD2, cyclohexyl-PGD2, and BW-245C; with essentially no effect on PGI2, cyclohexyl-PGI2 and PGE2 at comparably effective doses. The latter observation is contrary to an earlier report by MacIntyre (2,3), but supports the view that the anti-aggregatory effect of high doses of PGE2 () is mediated by the PGI2 receptor (4). The hydantoin acts at the platelet PGD2 receptor. 相似文献
63.
含单核中后期至后期花粉的蚕豆离体花药,经过2mM丁酸钠24小时预处理后,再漂浮培养于pH5.8或7.0的液体培养基。以不经预处理的作为对照。结果如下: 1.培养后9天内,丁酸钠预处理和培养基pH值并不明显影响花粉退化百分率。2.培养初期,pH7.0显著促进小孢子不等分裂。3.丁酸钠预处理抑制培养初期的小孢子有丝分裂,而后又显著增加小孢子均等分裂百分率。4.丁酸钠预处理导致小孢子有丝分裂类型的趋向改变。本文还对丁酸钠导致有丝分裂类型趋向改变的可能原因,进行了讨论。 相似文献
64.
在不同生境的松林中,人工补充寄主卵都能提高寄生效果。但林地生境不同,寄生率有明显差异。在松阔混交林中补充寄主,其寄生率比对照提高5.5—16.2倍。植被稀疏的纯松林效果较差,补充的寄生率比对照提高3.0倍。 卵蜂种群消长随季节温度而变化,全年以5月中旬至6月下旬和9月中旬至10月中旬为两个寄生高峰。卵蜂种群与松毛虫种群的消长存在较明显的相依关系,卵蜂种群随着松毛虫种群的消长而消长。施药对卵蜂种群有较大影响,施药区比对照区的寄生率约降低一倍。在混交林中填充寄主卵,能促进卵蜂种群世代延续。在逐步改善林地生境的基础上,利用人工补充寄主,可以代替人工繁蜂放蜂。 相似文献
65.
Several mutants have been isolated from the facultative methylotroph, Methylobacterium organophilum, using either N-methyl-N'-nitro-N-nitrosoguanidine or ultraviolet light as mutagens. One of these isolates, a glutamate auxotroph lacking isocitrate dehydrogenase, has been transformed to prototrophy, using wild-type DNA, at a frequency of 0-5%. Competence and DNA uptake occur only in cultures which are near the end of exponential growth, and maximal transformation requires a DNA concentration of 100 mug ml-1. 相似文献
66.
Comparison of Nitrogen Fixation Activity in Tall and Short Spartina alterniflora Salt Marsh Soils 总被引:7,自引:5,他引:2 下载免费PDF全文
Roger B. Hanson 《Applied microbiology》1977,33(3):596-602
A comparison of the N2 fixers in the tall Spartina alterniflora and short S. alterniflora marsh soils was investigated. Zero-order kinetics and first-order kinetics of acetylene reduction were used to describe the activity of the N2 fixers in marsh soil slurries. It was found that the Vmax values were approximately 10 times greater for the N2 fixers in the tall Spartina than in the short Spartina marsh when raffinose was used as the energy source. In addition, the (Ks + Sn) values were approximately 4 to 15 times lower for the N2 fixers in the tall Spartina than in short Spartina marsh. First-order kinetics of nitrogen fixation for several substrates indicate that the N2 fixers in the tall Spartina marsh were two to seven times more active than those in the short Spartina marsh. Ammonium chloride (25 μg/ml) did not inhibit nitrogen fixation in the tall Spartina marsh, but there was a 50% inhibition in nitrogen fixation in the short Spartina marsh. On the other hand, sodium nitrate inhibited nitrogen fixation almost 100% at 25 μg/ml in both soil environments. Amino nitrogen (25 to 100 μg/ml) had little or no effect on nitrogen fixation. The results indicate that the N2 fixers in the tall Spartina marsh were physiologically more responsive to nutrient addition than those in the short Spartina marsh. This difference in the two populations may be related to the difference in daily tidal influence in the respective areas and thus provide another explanation for the enhanced S. alterniflora production in the creek bank soil system. 相似文献
67.
Functional domains in introns: trans-acting and cis-acting regions of intron 4 of the cob gene 总被引:21,自引:0,他引:21
We have sequenced the mutational changes in eight mutants in the open reading frame of intron 4 of the cob gene on yeast mitochondrial DNA. Three have a cis-acting splicing defect, while the other inactivate a trans-recessive intron domain that specifies a trans-acting splicing factor. From phenotypic evidence, including analyses of the allele-specific extra proteins, we have identified a protein (P27) encoded wholly within the intron that appears to be the intron 4 splicing factor (maturase). The evidence suggests that P27 is a secondary translation product resulting from the proteolytic cleavage of a larger precursor encoded by exon and intron sequences, but an alternative model, in which P27 is a primary translation product, has not been ruled out. 相似文献
68.
Mosaic organization of a mitochondrial gene: evidence from double mutants in the cytochrome b region of Saccharomyces cerevisiae 总被引:5,自引:0,他引:5
The region coding for apocytochrome b in the mitochondrial genome of Saccharomyces cerevisiae is believed to exhibit a mosaic organization, consisting in certain strains of five exons and four introns. This model can be tested by the use of double mutants, each containing two physically, genetically and phenotypically defined mit- lesions in cis, (that is, in the same mitochondrial chromosome). Such mutants have been constructed, and the phenotypes of several examples of each of the four possible classes--exon-exon, exon-intron (downstream), intron (upstream)-exon and intron-intron--have been examined. Our results have shown that upstream mutations are always epistatic to downstream ones for polypeptide products, and that regulation of expression of cytochrome oxidase subunit I by introns is epistatic regardless of position. These findings have provided an independent verification of the mosaic model, and also suggest that at least the majority of novel polypeptides accumulating in intron mutants are hybrid products that contain sequences of the wild-type polypeptide. 相似文献
69.
Hypothalamic sarcoidosis and hypopituitarism 总被引:1,自引:0,他引:1
4 patients with presumed pituitary hypothalamic sarcoidosis are described. 3 had histological diagnoses compatible with sarcoidosis and in the other this diagnosis was strongly suspected from chest X-rays. 2 patients presented with diabetes insipidus. ACTH reserve was diminished in 3 out of 4 and growth hormone reserve was diminished in the 3 who were tested. All 4 patients developed secondary amenorrhea. 3 patients had hypothalamic hypothyroidism. Prolactin dynamics were intact. Tomograms of the sella turcica in all 4 and computerized tomography of the hypothalamic area in 2 patients failed to reveal any abnormality. 相似文献
70.