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1.
The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments. 相似文献
2.
A physical domain of herpes simplex virus ICP8 is expressed and active in Escherichia coli. 下载免费PDF全文
In this report, we describe a series of procedures to assay the function of fusion genes in Escherichia coli and the specific application to the carboxy-terminal third of the herpes simplex virus type 1 (HSV-1) DNA-binding protein ICP8. E. coli cells containing the cloned HSV-1 BamHI G fragment with the HSV-1 BamHI-G-V site, map unit 0.388, nearest the tet promoter in pBR322 synthesized an active product containing a portion of ICP8. The new product induced phenotypic alterations in recipient hosts that were measurable and stable yet limited to the stability of the plasmid. The corresponding cloned DNA from the characterized HSV-1 DNA-binding protein mutant tsHA1 exhibited a predictable temperature-sensitive phenotype. Screening procedures based on the loss of induction of the parental plasmid-induced phenotype in E. coli cells allowed us to select additional mutations. One of these, which conferred a phenotype different from that of tsHA1, was transferred to the viral genome by marker transfer techniques. We suggest that any mutant could be isolated in any sequence, provided that the wild-type coding sequences induce alterations in E. coli cells. The observed alterations should have relevance in determining the mode of action of the protein in its normal environment. 相似文献
3.
Immune deficiency in the X-linked lymphoproliferative syndrome. I. Epstein-Barr virus-specific defects 总被引:8,自引:0,他引:8
S Harada K Sakamoto J K Seeley T Lindsten T Bechtold J Yetz G Rogers G Pearson D T Purtilo 《Journal of immunology (Baltimore, Md. : 1950)》1982,129(6):2532-2535
Eleven males with XLP were evaluated for EBV-specific antibodies during periods of 2 to 7 yr. Variable responses to EBV-specific antigens were found. All 11 patients had subnormal anti-EBNA titers, which probably reflected a T cell deficiency. The patients showed four different patterns in their anti-VCA response: 1) two boys who had experienced malignant lymphoma mounted no antibodies at all; 2) two patients showed intermittent anti-VCA titers; 3) four males had persistently elevated anti-VCA titers; and 4) three patients showed normal anti-VCA titers. ADCC against EBV-infected cells was abnormally low in six patients and was elevated in two patients given gamma-globulin. ADCC titers did not correlate with anti-VCA titers. However, most patients with XLP failed to effect regression of autologous EBV-infected lymphoblastoid cell lines, indicating a deficiency in long-lived T cell-mediated immunity to EBV. 相似文献
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Sixteen patients with an early dense hemiplegia due to cerebrovascular accidents were shown to have a greater degree of hypoxia than 16 matched control patients. The patients with hemiplegia had a reflex compensatory fall in arterial carbon dioxide tensions (PaCO2) with possible reduction in cerebral blood flow. Oxygen treatment led to an increase in PaCO2 in the patients with hemiplegia, but the increase in oxygen tensions in these patients was significantly less than that in the control group, suggesting increased pulmonary shunting as the cause for the hypoxia. Oxygen treatment may improve cerebral blood flow and oxygenation and have a useful role in the early management of patients with a dense hemiplegia. 相似文献
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R. H. Pearson 《BMJ (Clinical research ed.)》1988,297(6644):309-310
9.
Summary A spore-free parasporal crystal suspension was prepared fromBacillus thuringiensis subsp.israelensis by an aqueous biphasic separation technique and the waste fractions quantified with regard to spore numbers and insecticidal potencies. The technique proved efficient in selectively removing spores from the spore-crystal mixture. The final crystal suspension was used to develop a novel bioassay system which allowed rapid determination of crystal effectiveness in 1/8 to 1/6 of the time required in the conventional mortality versus concentration bioassay. 相似文献
10.
The macro-invertebrate communities of temporary pools in an intermittent stream in tropical Queensland 总被引:2,自引:1,他引:1
Nine pools were studied in an intermittent stream. They were close to each other but differed in size, substratum, amount of shade and duration of water presence. Initial conditions were set by wet season flooding, following which each pool developed its own character. Cluster analysis showed that communities changed substantially with time in both species composition and abundance, and that some initially similar communities diverged while some initially dissimilar ones converged.Principal Components Analysis showed that these community changes were due largely to the drying of the pools, and to seasonal effects. Specialised drying communities developed in the pools of longer duration (up to 8 months), but not in the short-lived pools (3–4 months). Apparently similar numerical responses in different pools were often caused by different suites of predominant species.The diversity of the fauna (total of 78 species) was high in comparison with similar habitats in non-tropical regions.The pattern of development of the pools' communities was much as expected from island biogeography theory, except that there was no relationship between species richness and duration and size of pools. The species complements were largely opportunistic, being governed by extreme environmental disturbance. 相似文献