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541.
Between June 1984 and December 1986, 35 patients with acute myocardial infarction received streptokinase intravenously within 3 hours after the beginning of chest pain and underwent percutaneous transluminal coronary angioplasty (PTCA) either immediately (in 2 cases) or 1 to 19 (mean 4.4) days later (in 33). The rate of successful PTCA was 89%. Reocclusion occurred in one patient. The mean percentage of stenosis decreased from 86% to 11%. The mean trans-stenotic gradient was reduced from 41 to 11 mm Hg. The results suggest that in patients whose condition is stable, PTCA performed a few days after thrombolysis is a valuable alternative to more aggressive treatment with immediate PTCA. 相似文献
542.
The visual pigment rhodopsin has been purified and depleted of detergent. Under these conditions, the pigment strongly aggregates. When dried, a significant fraction of these aggregates appear insensitive to light. We have characterized them by means of absorption and photoacoustic spectroscopies and we find that their photochemical behavior is best explained by a limited activity that does not reach photointermediates beyond the lumirhodopsin step in the bleaching sequence of rhodopsin. We interpret this result as an indication of a significant conformational change of the protein during the transition from lumi- to meta-rhodopsin. 相似文献
543.
J F Hubert J Simard B Gagné N Barden F Labrie 《Molecular endocrinology (Baltimore, Md.)》1988,2(6):521-527
The effect of incubation with LHRH and its agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide has been measured on the concentrations of mRNAs for the common alpha-subunit of glycoprotein hormones and beta-LH in rat anterior pituitary cells in primary culture. After incubation, total RNA was analyzed by Northern blot or dot blot hybridization with alpha- and LH beta 32P-labeled cRNA probes and mRNA levels were quantified by autoradiography. Short-term treatment (4-6 h) of pituitary cells with 100 nM LHRH led to a marked stimulation of LH release but no effect was observed on alpha-subunit or LH beta mRNA levels. Longer (24-72 h) incubation periods with LHRH led to complete desensitization of the LH response to the neurohormone and induced 2- to 3-fold increases in alpha-mRNA cell content while LH beta mRNA levels remained unchanged. Maximal induction of alpha mRNA accumulation was observed with an LHRH concentration as low as 0.1 nM. Incubation with the LHRH agonist [D-Trp6, des-Gly-NH2(10)]LHRH ethylamide for 24-72 h also increased alpha mRNA but did not modify LH-beta mRNA levels. It is concluded that long-term exposure of anterior pituitary cells to LHRH or to an LHRH agonist positively regulates alpha-subunit gene expression in the absence of change in LH beta mRNA levels. This observation can provide an explanation for the high plasma levels of free alpha-subunits found in patients treated chronically with LHRH agonists. 相似文献
544.
Verónica Téllez Ariel Ahumada Juan Muro Soledad Sepúlveda Luis Izquierdo 《Development genes and evolution》1988,197(6):360-365
Summary Two-cell mouse ova, which were centrifuged for l h at 70 000–90 000xg, showed a precise stratification of the cytoplasm and an elongation of the nucleus. The ova were fixed at different times and observed by light and electron microscopy using cytochemical methods and detergent extractions. Within 40 min after centrifugation the normal-looking morphology was recovered except for the persisting lipid caps at the centripetal poles of the blastomeres. Cleavage, compaction and blastulation were not prevented by centrifugation. Treatments with colcemid or cytochalasin D delayed but did not impair recovery. These results suggest that a resilient cytoskeletal structure may be involved in this kind of embryonic regulation. 相似文献
545.
J. V. Priestley M. A. Hynes V. K. M. Han M. Réthelyi E. R. Perl P. K. Lund 《Histochemistry and cell biology》1988,89(5):467-479
Summary Methodological variables for in situ hybridization using 32P labelled oligodeoxyribonucleotides (oligomers) have been examined. Four different oligomers directed against proglucagon messenger RNA (mRNA) and two different oligomers against prosomatostatin mRNA have been used. Specific hybridization was obtained in adult rat brain, stomach and pancreas and in neonatal rat ileum. Tissue was perfusion fixed with 4% paraformaldehyde 0.2% glutaraldehyde and hybridization was carried out in 50% formamide for 72 h at 42° C. Using hybridization conditions of lower stringency (33% formamide) labelling was also obtained in guinea pig tissue. Other variables which affected hybridization signal intensity were the inclusion of a prehybridization dehydration stage, the probe concentration, the inclusion of ammonium acetate in the posthybridization dehydrating ethanols and in the autoradiographic emulsion, and the exposure time. The localisation of proglucagon mRNA in rat pancreas using a 20mer was used as a model tissue for testing these methodological variables and the results were found generally also to apply to the other probes and tissues tested. The methods described provide single cell resolution and show that 32P labelled oligomers may be used to localise neuropeptide and endocrine mRNAs in different types of tissue and in different mammalian species. 相似文献
546.
Summary In order to study mitogenic control during axolotl limb regeneration, we have developed a primary blastema cell culture as a very sensitive bioassay for blastema mitogens. Transferrin, an iron-binding glycoprotein which has been shown to be the neurotrophic factor for muscle cells, is the mitogen which has been analysed in the present report. Addition of approximately 2 g human transferrin/ ml of serum-free culture medium enhances blastema cell proliferation 11-fold over control levels and 2-fold over that produced by the addition of nerve extracts or purified growth factors extracted from nerve tissues (basic and acidic fetal growth factor, FGF). At a higher concentration (20 g/ml), transferrin alone has no mitogenic effect unless the medium is also supplemented with FeCl3 (100 M). The results are discussed with regard to the sensitivity of the blastema cell culture bioassay and in the context of the neurotrophic theory of urodele limb regeneration. 相似文献
547.
548.
Development and characterization of continuous avian cell lines depleted of mitochondrial DNA 总被引:6,自引:0,他引:6
Réjean Morais Paul Desjardins Chanta Turmel Karen Zinkewich-Péotti 《In vitro cellular & developmental biology. Plant》1988,24(7):649-658
Summary Populations of quail and chicken cells were treated with ethidium bromide, an inhibitor of mitochondrial DNA replication.
After long-term exposure to the drug, the cell populations were transferred to ethidium bromide (EtdBr)-free medium, and cloned.
Clones HCF7 (quail) and DUS-3 (chicken) were propagated for more than a year, and then characterized. Analysis of total cellular
DNA extracted from these cells revealed no characteristic mitochondrial DNA molecule by Southern blot hybridization of HindIII-
or AvaI-digested total cellular DNA probed with cloned mitochondrial DNA fragments. Reconstruction experiments, where a small
number of parental cells was mixed with HCF7 cells and DUS-3 cells before extraction of total cellular DNA, further strengthen
the notion that the drug-treated cells are devoid of mitochondrial DNA molecules. The cell populations were found to proliferate
at a moderately reduced growth rate as compared to their respective parents, to be auxotrophic for uridine, and to be stably
resistant to the growth inhibitory effect of EtdBr and chloramphenicol. At the ultrastructural level, mitochondria were considerably
enlarged and there was a severe reduction in the number of cristae within the organelles and loss of cristae orientation.
Morphometric analysis revealed a fourfold increase of the mitochondrial profile area along with a twofold decrease of the
numerical mitochondrial profiles. Analysis of biochemical parameters indicated that the cells grew with mitochondria devoid
of a functional respiratory chain. The activity of the mitochondrial enzyme dihydroorotate dehydrogenase was decreased by
95% and presumably accounted for uridine auxotrophy.
This work was supported by a grant from the Medical Research Council of Canada. 相似文献
549.
550.
P Mentré F Escaig 《Biology of the cell / under the auspices of the European Cell Biology Organization》1992,74(1):119-126
Flotation on hot water (about 60 degrees C) which is frequently employed to stretch semithin sections on substrates for SIMS (secondary ion mass spectrometry) microscopy, is the cause of numerous artefacts. In the case of epoxy resin-embedded tissue, one observes loss of potassium and sodium and accumulation of calcium. The relative contrast of cell nuclei in the ionic images, is rapidly affected by these ion migrations. After prolonged contact with hot water, tissue becomes uniformly emissive. In the case of hydrosoluble resin-embedded tissue, potassium and sodium do not appear to be affected by the action of water, which suggests that they are covalently bound with chelating sites buried beneath the layer of water bound to the surface of the macromolecules. Calcium accumulates, probably on widely exposed anionic sites. Moreover, the domains observed in hydrosoluble resin-embedded tissue shrink differently according to the proportion of water removed by melamine; this can provide interesting information on the initial equilibrium between water, ion sand macromolecules. Our results seem to support the assumption that bound water should play an important role in the preservation of both macromolecular architecture and ion distributions. 相似文献