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121.
F de Wolf J Goudsmit D A Paul J M Lange C Hooijkaas P Schellekens R A Coutinho J van der Noordaa 《BMJ (Clinical research ed.)》1987,295(6598):569-572
One hundred and ninety eight men seropositive for human immunodeficiency virus (HIV) antibody and 58 HIV antibody seroconverters were studied for an average of 19.3 (SEM 0.5) months to assess the relation between HIV antigenaemia and the risk of developing the acquired immune deficiency syndrome (AIDS) and AIDS related complex. Forty (20.2%) of the 198 HIV antibody seropositive men were antigen positive at entry and remained so during follow up. Eight (13.8%) of the 58 HIV antibody seroconverters and 20 (12.7%) of the remaining 158 HIV antibody seropositive men became antigen positive during follow up, resulting in an end point attack rate for HIV antigenaemia of 14.3%. AIDS related complex was diagnosed in 25 (15.8%) of the HIV antigen negative men and in 14 (20.7%) of the HIV antigen positive men. AIDS was diagnosed in 15 men, resulting in an end point attack rate for AIDS of 23.9% in the HIV antigen positive group and 1.3% in the antigen negative group. HIV antibody seropositive men without symptoms but with persistent HIV antigenaemia are at increased risk of developing AIDS and AIDS related complex. 相似文献
122.
Functional Changes Associated with Structural Alterations Induced by Mobilization of a P Element Inserted in the Sex-lethal Gene of Drosophila 总被引:22,自引:11,他引:11 下载免费PDF全文
Genetic analysis of rearrangements within the multifunctional sex determining gene Sex-lethal has allowed correlation of changes in specific functions with DNA alterations. Rearrangements were isolated by mobilization of a P element which is on the 5' side of the gene, at coordinate 0. Previous work has shown that rearrangements associated with alterations in Sxl gene function are found within an 11-kb region between coordinates-11 and 0. Here it is shown that insertion of foreign DNA, per se, at coordinate 0 is compatible with wild-type gene function. However, deletion of sequences on either side of this point generates a mutant phenotype. Deletions extending distally beyond coordinate -6.5 kb result in a null phenotype, whereas smaller distal deletions or proximal deletions eliminate only some Sxl functions. 相似文献
123.
Summary Dissociated single cells from chicken retina or tectum kept in rotation-mediated cell culture aggregate, proliferate and establish a certain degree of histotypical cellto-cell relationships (sorting out), but these systems never form highly laminated aggregates (nonstratified R- and T-aggregates). In contrast, a mixture of retinal plus pigment epithelial cells forms highly stratified aggregates (RPE-aggregates, see Vollmer et al. 1984). The present comparative study of stratified and nonstratified aggregates enables us to investigate the process of cell proliferation uncoupled from that of tissue stratification. Here we try to relate these two basic neurogenetic processes with patterns of expression of cholinesterases (AChE, BChE) during formation of both types of aggregates.During early aggregate formation, in both stratified and nonstratified aggregates an increased butyrylcholinesterase activity is observed close to mitotically active cells. Quantitatively both phenomena show their maxima after 2–3 days in culture. In contrast, AChE-expression in all systems increases with incubation time. In nonproliferative areas, in the center of RPE-aggregates, the formation of plexiform layers is characterized initially by weak BChE and then strong AChE-activity. These areas correspond with the inner (IPL) and outer (OPL) plexiform layers of the retina in vivo. Although by sucrose gradient centrifugation we find that the 6S- and the fiber-associated 11S-molecules of AChE are present in all types of aggregates, during the culture period the ratio of 11S/6S-forms increases only in RPE-aggregates, which again indicates the advanced degree of differentiation within these aggregates.It is thus demonstrated that cholinesterases first correlate with neuronal cell proliferation and later with stratification, which indicates functions of both enzymes during both developmental periods.Abbreviations
AChE
acetylcholinesterase
-
BChE
butyrylcholinesterase
-
iso-OMPA
specific inhibitor of BChE
-
BW 284C51
specific inhibitor of AChE
-
IPL
inner plexiform layer
-
OPL
outer plexiform layer 相似文献
124.
Glucose and amino acid metabolism in 1- and 30-day-old chick telencephalon slices was studied in two incubation media in the presence or in the absence of a continuous oxygenation. Medium 1 has a composition and a tonicity similar to cerebrospinal fluid, medium 2 is hypertonic and does not contain any K+ ions. The incorporation of glucose carbon into amino acids and the distribution of radioactivity between the different amino acids are close to the ones observed in the chick brain in vivo only when the slices are incubated in medium 1, with oxygen at 30 days and without oxygen for the 1-day-old chick. It also appears that if oxygenation is necessary for incubation of mature brain tissue in vitro, the absence of the medium oxygenation is more suitable for the study of glucose metabolism in 1-day-old chick brain slices. 相似文献
125.
Synopsis Woundfin, Plagopterus argentissimus, fed predominantly on simuliid larvae during the day, and shifted to the larger Hydropsyche spp. at night. Ephemeropteran larvae were eaten nearly uniformly throughout the 24 hour period. Mean weight of food consumed varied from 20–40 mg per individual (0.7–2.5% body weight) throughout the 24 h period. Our estimated daily ration of about 8% body weight, at temperatures that varied between 15–25°C, is based upon our measure of mean gut contents over a 24h period, combined with intestinal evacuation rates suggested for other cyprinids in the literature. The relatively continuous feeding pattern suggests a foraging strategy that would minimize competition with other species for food during June, a period of minimum annual food abundance in Virgin River. 相似文献
126.
Paul J. Chuba Myron A. Leon Amit Banerjee Sunil Palchaudhuri 《Molecular & general genetics : MGG》1989,216(2-3):287-292
Summary
Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters. 相似文献
127.
We have shown, in a preliminary report, that macrophages can induce strand breaks in the DNA of co-cultured tumor cells (Chong et al., 1988). The present study is designed to determine if oxygen-centered species generated by the cell-free enzyme-substrate combination of hypoxanthine and xanthine oxidase can induce similar lesions and to identify the specific mediator(s). We report that co-incubation of murine mammary tumor cell lines with hypoxanthine and xanthine oxidase leads to the induction of DNA-strand breaks as determined by fluorescence analysis of DNA unwinding (FADU) assay or alkaline elution techniques. This damage is preventable by catalase which removes hydrogen peroxide but no protection is provided by agents to remove or prevent the formation of superoxide anion (superoxide dismutase), or hydroxyl radical (mannitol or the iron chelator o-phenanthroline). Likewise, cyclooxygenase or lipoxygenase inhibitors of arachidonate metabolism (indomethacin, nordihydroguaiaretic acid, caffeic acid) or bromophenacyl bromide do not alter the degree of DNA scission. Treatment with higher doses of oxygen species leads to significant toxicity as determined by evaluation of cell growth potential or colony-forming ability. Again, toxicity is prevented only by the presence of catalase. Tumor cells are able to rejoin strand breaks at lower, less toxic doses. When comparing different tumor cell subpopulations at various stages of progression, i.e., metastatic vs. nonmetastatic, for sensitivity to hydrogen peroxide-induced strand breakage, we found that at lower concentrations (less than 5μM) metastatic populations are sensitive whereas nonmetastatic populations exhibit no significant breakage. At higher concentrations of hydrogen peroxide, all lines were sensitive, suggesting that a lower threshold of sensitivity may exist for more progressed tumour cell lines. 相似文献
128.
Basidiomycetous fungi, two saprophytes and three mycorrhizal, were used to assess the specificity of DNA hybridization for
distinguishing genera from one another. Interspecific comparisons were done with several isolates of mycorrhizal fungi,Laccaria bicolor andL. laccata, collected from diverse geographical sites. The DNAs were digested with four restriction nucleases and separated by gel electrophoresis
into patterns of DNA fragments called restriction fragment length polymorphisms (RFLPs). The RFLPs were hybridized with a
radioactively-labeled DNA probe encoding Basidiomycetous ribosomal RNA genes. The five genera were discernable using both
unprobed and probed RFLPs. Hybridization of probe DNA with RFLPs was isolate-specific for all nine Laccaria isolates examined.
The reclassification of aL. bicolor isolate is supported, demonstrating that hybridization of RFLPs offers an additional tool for taxonomy of ectomycorrhizal
fungi. The method may have field application for distinguishing known isolates if their DNA fingerprints are previously ascertained
and are distinct from RFLPs of indigenous organisms. 相似文献
129.
130.
The mouseIgK-VSer gene encodes an immunoglobulin light chain variable region which gives rise to two phenotypic polymorphisms of mouse chains. The nucleotide sequences of coding and flanking regions of theIgk-VSer
c
andIgk-VSer
d
alleles found in recently inbred strains of wild mice are compared with those of theIgk-VSer
a
andIgk-VSer
b
alleles described previously. Results suggest that the gene is evolving randomly and that framework 2 and complentarity determining region 2 are preserved, presumably for overall light chain structure. Results indicate that all four allels have an octamer motif upstream of the gene which should be functional and allow prediction of whether or not the product of the germ line gene will be detectable as either the IB-peptide or Ef1a phenotypic polymorphism. Southern hybridization of genomic DNA using as probe a 1-kbXba I-Xba I fragment located approximately 4 kb upstream of the BALB/cIgk-VSer
b
coding region demonstrated the presence of homologous DNA in mice bearing theIgk-VSer
a
allele and absence from mice bearing theIgk-VSer
c
andIgk-VSer
d
alleles. Nucleotide sequence comparison of BALB/c and SK/CamRk (Igk-VSer
d
) DNA in this region demonstrated that BALB/c contained an insertion 2.4 kb in length which was absent from SK/CamRk. Both strains contain DNA homologous to the reverse complement of the mouse Bam5 repetitive element at the point of the insertion, with BALB/c containing approximately 70 nucleotides more of the element than SK/CamRk. Surprisingly, the strains containing DNA related to theXba I-Xba I probe are not those determined to be the most similar by nucleotide sequence comparisons and by the Phylogenetic Analysis Using Parsimony program. The evolutionary relationship of the alleles and a possible basis for the inconsistency presented by theXba I-Xba
I fragment-related DNA are discussed. 相似文献