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101.
Lymphocytes obtained from the spleen of Balb/C mice have been subjected to transformation by LPS in the presence of varying concentrations of Pb2+, Cd2+, or Cr3+. Both DNA and protein turnover were followed. It was found that Pb2+ and Cr3+ are mitogenic over a broad range of concentrations, while Cd2+ is slightly mitogenic at very low (10?6M) concentration and rapidly becomes inhibitory of both [3H]TdR and [3H]ALA uptake. Pb2+ appears to stimulate the action of LPS, while Cr3+ appears to inhibit. Each of the metals protects the lymphocytes from cell death arising from incubation with LPS. The mechanism of the observed changes is as yet obscure. 相似文献
102.
103.
C. R. Müller K. E. Davies C. Cremer G. Rappold J. W. Gray H. H. Ropers 《Human genetics》1983,64(2):110-115
Summary Human Y chromosomes were purified by dual beam flow sorting from a human x Chinese hamster cell line retaining the Y as the only free human chromosome. DNA was extracted from the Y fraction and cloned into gtWES.B vector arms. More than 100 recombinant clones carrying human inserts have been characterised by Benton-Davis plaque screening and Southern blotting or in situ hybridisation. Several repetitive sequences were found to be predominantly located on the Y, whereas the majority also cross-hybridised with autosomal DNA. One repetitive clone gave a specific hybridisation signal with the X and the Y chromosome but not with autosomes. Preliminary evidence indicates that many clones contain single copy as well as repetitive sequences. However, no Y-specific single copy sequence has yet been identified. 相似文献
104.
A multicentre, randomized, double-blind trial compared the efficacy and safety of and tolerance to natural and synthetically produced prostaglandin E2 tablets in the induction of labour in 202 women. The compounds were similarly effective, inducing labour in approximately 66% of patients. The total dose required and the interval between induction and delivery were similar in the two groups, as were the Apgar scores at 1 and 5 minutes and the incidence of maternal and fetal side effects. 相似文献
105.
J.M. Katz S.J.M. Skinner T. Wilson D.H. Gray 《Prostaglandins & other lipid mediators》1983,26(4):545-555
Mouse calvaria were maintained in organ culture without serum additives. Basal active resorption, as measured by 45Ca and hydroxyproline release, was significantly inhibited to 74% control levels by indomethacin (1.4 × 10−7 M). Prostaglandin F and prostaglandin E2 production, determined by radioimmunoassay, were both significantly lowered by this concentration of indomethacin. DNA, protein and hydroxyproline synthesis, as indices of cell toxicity, were unaffected by low concentrations of indomethacin, while concentrations of 1.4 × 10−6M inhibited protein synthesis (p<0.005). In the presence of indomethacin (1.4 × 10−7M) both PGE2 and PGF2α stimulated resorption in a dose-dependent manner, with PGE2 being the more potent. Neither prostaglandin affected hydroxyproline synthesis at low concentrations, but PGE2 had a marked inhibitory action at a higher concentration (10−6M). In combination, the effects of PGE2 and PGF2α showed no evidence of synergism or any antagonistic action. The study shows that in vitro calcium and hydroxyproline resorption in the unstimulated mouse calvaria are inhibited by indomethacin at concentrations measured in serum during human therapy. The decreased PGF and PGE2 production associated with this decreased bone resorption in the presence of non-toxic concentrations of indomethacin would suggest a role for these prostaglandins in maintaining the basal resorption of cultured bone. 相似文献
106.
Seven residues implicated as acting directly in substrate binding in yeast hexokinase B have been identified in the crystallographic structure by chemical sequencing. The cysteine which is regarded as a residue critically maintaining the active conformation of yeast hexokinase has been selectively labelled and likewise located in the structure. In some parts of the amino acid sequence predicted from the high-resolution electron density map it is found that alignments of chemically sequenced peptides can be made unambiguously; however, the extent of matching to the predicted sequence varies considerably along the chain. 相似文献
107.
Several methods currently in use for measuring mean corpuscular volume include: centrifuged packed cell volume, electronic impedance, and light scattering methods. Although these techniques are widely used and accepted, there are problems inherent to each method which may produce systematic errors that are difficult to estimate. This paper describes a new flow cytometric method of cell volume determination, based on the principle of volume exclusion, which may overcome the systematic errors of the methods currently in use. This method requires that the cells be suspended in a fluorescent dye which is unable to penetrate the cell membrane. The level of fluorescence which is produced when a narrow stream of the cell suspension is excited by a focused laser beam will remain constant until a cell arrives in the illuminated region thereby causing a decrease in fluorescence which is directly proportional to the cell's volume. The volume exclusion method is shown to give an estimate of mean red cell volume which correlates well with existing methods. 相似文献
108.
Bordetella pertussis adenylate cyclase toxin and hemolytic activities require a second gene, cyaC, for activation. 总被引:15,自引:0,他引:15 下载免费PDF全文
E M Barry A A Weiss I E Ehrmann M C Gray E L Hewlett M S Goodwin 《Journal of bacteriology》1991,173(2):720-726
In these studies, the Bordetella pertussis adenylate cyclase toxin-hemolysin homology to the Escherichia coli hemolysin is extended with the finding of cyaC, a homolog to the E. coli hlyC gene, which is required for the production of a functional hemolysin molecule in E. coli. Mutations produced in the chromosome of B. pertussis upstream from the structural gene for the adenylate cyclase toxin revealed a region which was necessary for toxin and hemolytic activities of the molecule. These mutants produced the 216-kDa adenylate cyclase toxin as determined by Western blot (immunoblot) analysis. The adenylate cyclase enzymatic activities of these mutants were equivalent to that of wild type, but toxin activities were less than 1% of that of wild type, and the mutants were nonhemolytic on blood agar plates and in in vitro assays. The upstream region restored hemolytic activity when returned in trans to the mutant strains. This genetic complementation defined a gene which acts in trans to activate the adenylate cyclase toxin posttranslationally. Sequence analysis of the upstream region defined an open reading frame with homology to the E. coli hlyC gene. In contrast to E. coli, this open reading frame is oriented oppositely from the adenylate cyclase toxin structural gene. 相似文献
109.
A scaffold-associated DNA region is located downstream of the pea plastocyanin gene. 总被引:11,自引:2,他引:9 下载免费PDF全文
Chromosomal scaffold-associated DNA has been isolated from pea leaf nuclei treated with lithium diiodosalicylate to remove histones and then digested with restriction enzymes to remove the DNA in chromosomal loops. A scaffold-associated region (SAR) of DNA has been identified 8 to 9 kb downstream of the single-copy pea plastocyanin gene in proximity to a repetitive sequence present in 300 copies in the pea haploid genome. Isolated restriction fragments from within the SAR can bind to scaffold preparations in a binding assay in vitro. The nucleotide sequence of the SAR indicates a 540-bp 77% A+T-rich region containing many sequence elements in common with SARs from other organisms. Sequences with homology to topoisomerase II binding sites, A-box and T-box sequences, and replication origins are present within this AT-rich region. 相似文献
110.
The objective of an engineered reed bed is to manage the natural growth of the reeds in order to optimise the processing of the wastewater to be purified. Downflow reed beds, with two treatment stages, have been added in front of a previously installed horizontal flow bed on a dairy farm to treat parlour washings and standing yard wastewater. Recent results have shown that the BOD is being reduced from an average of 1006 mg/litre at the inlet to only 57 mg/litre at the exit from the small final lagoon. 相似文献