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排序方式: 共有169条查询结果,搜索用时 15 毫秒
1.
Epstein-Barr virus transmission via the donor organs in solid organ transplantation: polymerase chain reaction and restriction fragment length polymorphism analysis of IR2, IR3, and IR4. 下载免费PDF全文
Two organ transplant recipients who received organs from a common donor and were diagnosed as having an Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disorder were studied to determine the mode of EBV transmission. The results of restriction fragment length polymorphism, polymerase chain reaction, and minisatellite DNA analyses demonstrate that both patients had a common strain of EBV and that this strain was transmitted from the donor's organs to both recipients. Posttransplant lymphoproliferative disorder resulted from the proliferation of EBV-immortalized B lymphocytes of the recipient, not those of the donor. 相似文献
2.
Failure of seed sterilization methods and breakdown in sterile technique can result in catabolism of thymidine by microorganisms during seedling incubation in radioisotope. The effectiveness of some sterilizing agents was monitored by microbiological methods and by thin layer chromatography for the presence of thymidine degradation products. Sodium hypochlorite and ethylene oxide each sterilized pea and sunflower seeds. Sodium hypochlorite failed to sterilize onion seeds while ethylene oxide was only occasionally effective and often retarded germination. Captan, commonly used before germination to prevent fungal blight of seedlings, did not reduce the bacterial flora of onion seeds. 相似文献
3.
Abstract: Methylmercury (MeHg) increases the concentration of intracellular Ca2+ ([Ca2+]i) and another endogenous polyvalent cation in both synaptosomes and NG108-15 cells. In synaptosomes, the elevation in [Ca2+]i was strictly dependent on extracellular Ca2+ (Ca2+e); similarly, in NG108-15 cells, a component of the elevations in [Ca2+]i was Ca2+e dependent. The MeHg-induced elevations in endogenous polyvalent cation concentration were independent of Ca2+e in synaptosomes and NG108-15 cells. The pattern of alterations in fura-2 fluorescence suggested the endogenous polyvalent cation may be Zn2+. Using 19F-NMR spectroscopy of rat cortical synaptosomes loaded with the fluorinated chelator 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N′,N′-tetraacetic acid (5F-BAPTA), we have determined unambiguously that MeHg increases the free intrasynaptosomal Zn2+ concentration ([Zn2+]i). In buffer containing 200 µM EGTA to prevent the Ca2+e-dependent elevations in [Ca2+]i, the [Zn2+]i was 1.37 ± 0.20 nM; following a 40-min exposure to MeHg-free buffer [Zn2+]i was 1.88 ± 0.53 nM. Treatment of synaptosomes for 40 min with 125 µM MeHg yielded [Zn2+]i of 2.69 ± 0.55 nM, whereas 250 µM MeHg significantly elevated [Zn2+]i to 3.99 ± 0.68 nM. No Zn2+ peak was observed in synaptosomes treated with the cell-permeant heavy metal chelator N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN, 100 µM) following 250 µM MeHg exposure. [Ca2+]i in buffer containing 200 µM EGTA was 338 ± 26 nM and was 370 ± 64 nM following an additional 40-min exposure to MeHg-free buffer. [Ca2+]i was 498 ± 28 or 492 ± 53 nM during a 40-min exposure to 125 or 250 µM MeHg, respectively. None of the values of [Ca2+]i differed significantly from either pretreatment levels or buffer-treated controls. 相似文献
4.
mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species 总被引:4,自引:0,他引:4
Reconstructions of the human-African great ape phylogeny by using
mitochondrial DNA (mtDNA) have been subject to considerable debate. One
confounding factor may be the lack of data on intraspecific variation. To
test this hypothesis, we examined the effect of intraspecific mtDNA
diversity on the phylogenetic reconstruction of another Plio- Pleistocene
radiation of higher primates, the fascicularis group of macaque (Macaca)
monkey species. Fifteen endonucleases were used to identify 10 haplotypes
of 40-47 restriction sites in M. mulatta, which were compared with similar
data for the other members of this species group. Interpopulational,
intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of
divergence time and branching order incorporating this variation were
substantially different from those based on single representatives of each
species. We conclude that intraspecific mtDNA diversity is substantial in
at least some primate species. Consequently, without prior information on
the extent of genetic diversity within a particular species, intraspecific
variation must be assessed and accounted for when reconstructing primate
phylogenies. Further, we question the reliability of hominoid mtDNA
phylogenies, based as they are on one or a few representatives of each
species, in an already depauperate superfamily of primates.
相似文献
5.
A M Douglas A M Georgalis L R Benton K L Canavan B A Atchison 《Analytical biochemistry》1992,201(2):362-365
A rapid nontoxic method for the purification of DNA from human leucocytes is described. Preliminary experiments which tested different methods of DNA purification indicated that digestion of proteins with proteinase K was unnecessary. This led to the development of a simple procedure involving lysis of the cells in SDS followed by extraction with 6 M NaCl. The method described overcomes the requirement for lengthy incubations in the presence of expensive proteinase K and subsequent extraction with toxic chemicals. 相似文献
6.
Dissociation of the CD4 downregulation and viral infectivity enhancement functions of human immunodeficiency virus type 1 Nef. 总被引:16,自引:14,他引:2 下载免费PDF全文
M A Goldsmith M T Warmerdam R E Atchison M D Miller W C Greene 《Journal of virology》1995,69(7):4112-4121
Recent evidence indicates that the nef gene of human immunodeficiency virus type 1 augments rather than inhibits viral replication in both cell culture and in vivo models. In addition, nef alters various normal cellular processes, including the display of CD4 on the cell surface. However, it remains unknown whether the enhancement of infectivity and the downregulation of CD4 represent linked or independent biologic properties of this single protein. In the present studies, mutational analyses were performed to define structure-function relationships within the Nef protein that mediate these effects. To assess the functional consequences of these mutations, sensitive and reliable assays were developed to quantitate the viral infectivity enhancement and CD4 downregulation functions of Nef. The results indicate that membrane-targeting sequences at the N terminus of Nef are important for both functions of Nef, while certain other conserved regions are dispensable for both functions. A conserved proline-X-X repeat segment in the central core of the protein, which is reminiscent of an SH3-binding domain, is critical for the enhancement of infectivity function but is dispensable for CD4 downregulation. However, the downregulation of CD4 by Nef appears to involve a two-step process requiring the initial dissociation of p56lck from CD4 to permit engagement of the endocytic apparatus by CD4. Together, these findings demonstrate that the infectivity enhancement and CD4 downregulation activities of human immunodeficiency virus type 1 Nef can be dissociated. Thus, these processes may be independent of one another in the viral replication cycle. 相似文献
7.
Between about ages 40 and 55 years, women experience a transition known as the menopause, which marks the end of their childbearing years. Although the most striking feature of the menopause is the cessation of menstruation, other biologic and psychosocial events occur and can be classified as stressors and "facilitators". For a predisposed group of women the stressors are likely to cause psychiatric disorders. At the same time, the facilitators are opportunities for personal growth and development. Physicians who understand both types of events during this phase of life and who are sensitive to the overall effects of ageing on marital partners can provide comprehensive care to the menopausal patient rather than automatically pursuing drug therapy (substitution hormonal therapy) alone. 相似文献
8.
Low-molecular-weight (4.5S) ribonucleic acid in higher-plant chloroplast ribosomes. 总被引:11,自引:2,他引:9 下载免费PDF全文
A species of RNA that migrates on 10% (w/v) polyacrylamide gels between 5S and 4S RNA was detected in spinach chloroplasts. This RNA (referred to as 4.5 S RNA) was present in amounts equimolar to the 5S RNA and its molecular weight was estimated to be approx. 33 000. Fractionation of the chloroplast components showed that the 4.5S RNA was associated with the 50 S ribosomal subunit and that it could be removed by washing the ribosomes with a buffer containing 0.01 M-EDTA and 0.5 M-KCl. It did not appear to be a cleavage product of the labile 23 S RNA of spinach chloroplast ribosomes. When 125I-labelled 4.5 S RNA was hybridized to fragments of spinach chloroplast DNA produced by SmaI restriction endonuclease, a single fragment (mol.wt. 1.15 times 10(6)) became labelled. The same DNA fragment also hybridized to chloroplast 5 S RNA and part of the 23 S RNA. It was concluded that the coding sequence for 4.5 S RNA was part of, or immediately adjacent to, the rRNA-gene region in chloroplast DNA . A comparable RNA species was observed in chloroplasts of tobacco and pea leaves. 相似文献
9.
Avoidance reactions of chironomid larvae to contaminated sediment taken from a heavy metal impacted lake were studied. Heavy metal levels in the test sediment ranged from background of 0.6 parts per million (ppm) cadmium, 77 ppm zinc and 17 ppm chromium to a maximum of 1,029 ppm cadmium, 17,262 ppm zinc and 2,106 ppm chromium. A linear relationship was established between cadmium and zinc levels in the sediment and avoidance by chironomids.An approximate threshold avoidance of metals in the sediment was determined to be between 213–422 ppm cadmium, 4385–8330 ppm zinc and 799–1513 ppm chromium.Supported by NIH Training Grant Number 5T01-ES00071 from National Institute of Environmental Health Sciences and in part by an NSF (RANN) Grant Number GI-35106.Purdue University Agricultural Experiment Station, Jour. No. 6474. 相似文献
10.
The impact of an industrially contaminated lake on heavy metal levels in its effluent stream 总被引:2,自引:1,他引:1
Levels of cadmium and zinc in various components of Williamson Ditch (an industrially contaminated stream flowing into Palestine Lake), Trimble Creek (a stream draining Palestine Lake) and the Tippecance River (a river receiving Trimble Creek) were determined. Water, sediment, plant, fish and clam samples were analyzed for cadmium and zinc content by atomic absorption spectrophotometry. Unweighted mean metal concentrations in Trimble Creek were the following: water, 51 µg Zn/1 and 4.2 µg Cd/1; sediment, 592 µg Zn/g and 48.8,µg Cd/g; plants, 375 µm Zn/g and 7.91 µg Cd/g; fish, 145 µg Zn/g and 6.02 µg Cd/g. These concentrations were generally lower than those found in Williamson Ditch and higher than those found in the Tippecanoe River or background levels previously reported for other aquatic ecosystems. 相似文献