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51.
The relationship between maternal age and chromosome size in autosomal trisomy. 总被引:8,自引:4,他引:4
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The pattern of maternal age-specific incidence of autosomal trisomy in spontaneous abortions was examined for each chromosome for which a sufficient number of trisomies was observed. This included chromosomes 2, 4, 7-10, 13-16, 18, and 20-22. The rate of increase after age 30 for each of the small chromosomes (groups D-G) was similar, with the exception of chromosome 16, which showed a significantly shallower rate. The C group chromosomes tended to have an intermediate rate of increase after age 30, with the exception of chromosome 7, which had a pattern similar to the smaller chromosomes. The larger chromosomes (2 and 4) had the smallest rate of increase. There was a significant relationship between chromosome size and rate of increase after age 30 (after excluding chromosome 16), but not with rate of increase before age 30. The results suggest that autosomal trisomies may be of heterogeneous origin, with a maternal age-related factor associated with chromosome size and other sources unrelated to chromosome size. Additional evidence for and against this hypothesis is discussed. 相似文献
52.
M A Chan L D Stein H M Dosch N H Sigal 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(1):106-112
Although most human B cells express receptors for Epstein Barr virus (EBV), few (usually less than 1%) are readily transformed into B lymphoblastoid cell lines after exposure to EBV. Transformable cells previously have been found to be mostly resting B lymphocytes. We recently developed a limiting dilution culture system which permits the growth of EBV-transformed B lymphocytes with high efficiency. Because in this system up to over 30% of peripheral blood- or tonsil-derived B cells respond to EBV, we re-examined the properties of EBV-transformable cells. Frequencies of transformable lymphocytes were determined by Poisson analysis. EBV-susceptible B cells committed to IgM, IgG, or IgA secretion were found to occur in the range of 3 to 27, 0.1 to 6, and 0.1 to 5 per 100 B cells, respectively. Under our culture conditions, a major proportion of the IgM-committed cells derived from large lymphocytes which appeared to have entered the cell cycle. This population contains most of the EBV-responsive cells detected and, therefore, most of the additional cells responding in our culture system. In contrast, precursors of IgG- or IgA-producing lymphoblast lines were small cells with DNA contents typical for the G0/G1 phases of the cell cycle. Anti-immunoglobulin antibodies were used in panning experiments to separate B cell subpopulations which expressed different immunoglobulin isotypes on their surface. In limiting dilution cultures of these purified B lymphocytes subsets, it was found that virtually all precursors of IgM-producing cell lines expressed surface IgM (sIgM) before their infection and transformation by EBV. The "cloning efficiency" of positively selected, large sIgM+ cells approached 100%. In contrast, sIgG or sIgA were found only on cells committed to the production of IgG or IgA, respectively. The expression of sIgD was examined by using sequential panning procedures. Virtually all IgM-committed lymphocytes and a subset of cells committed to IgA secretion were found among the sIgD+ cells. The majority of cells committed to IgA production and all IgG-committed cells were found in the sIgD- B cell population. Our findings indicate that the EBV-susceptible B cell subset of normal lymphocytes is heterogeneous with respect to cell size, cell cycle, sIg determinants, and efficiency of transformation. On the basis of our findings and previous reports, we propose a model in which transformability is a B cell-inherent property. Factors unrelated to the virus but present in our culture system appear responsible for the enhanced vulnerability to viral transformation in some cells which entered into the cell cycle.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
53.
Quantitative measurement of sn-1,2-diacylglycerols present in platelets, hepatocytes, and ras- and sis-transformed normal rat kidney cells 总被引:82,自引:0,他引:82
J Preiss C R Loomis W R Bishop R Stein J E Niedel R M Bell 《The Journal of biological chemistry》1986,261(19):8597-8600
A simple enzymatic method for the quantitation of the mass of sn-1,2-diacylglycerol (DAG) present in crude lipid extracts was developed to assess the function of DAGs as intracellular "second messengers" of extracellular agents and of oncogene products. The assay employed Escherichia coli DAG kinase which constituted approximately 15% of the membrane protein of a plasmid-bearing strain and defined mixed micellar conditions to solubilize the DAG present and allow its quantitative conversion to [32P]phosphatidic acid. The assay was proportional with the amount of DAG added over the range of 25 pmol to 25 nmol. The rapid rise of DAG in platelets stimulated with thrombin (210% over basal) and in hepatocytes stimulated with vasopressin (230% over basal) was quantitated and the values agreed with previous measurements. The amounts of DAG in normal rat kidney (NRK) cells grown at 34 and 38 degrees C, respectively, were 0.47 and 0.61 nmol/100 nmol of phospholipid. In K-ras-transformed NRK cells grown at 34 or 38 degrees C, DAG levels were elevated 168 or 138%, respectively. When a temperature-sensitive K-ras NRK cell line was investigated, the amount of DAG present was elevated at the permissive but not at the restrictive temperature. These data are consistent with the K-ras protein functioning in transmembrane signalling by activating phospholipase C. Protein kinase C (Ca2+/phospholipid-dependent enzyme) activation by DAG may play an important role in cellular transformation. 相似文献
54.
T Chajek-Shaul G Friedman H Knobler O Stein J Etienne Y Stein 《Biochimica et biophysica acta》1985,837(2):123-134
Lipoprotein lipase synthesized by cultured rat preadipocytes is present in three compartments: an intracellular, a surface-related 3-min heparin-releasable, and that secreted into the culture medium. 30 min after addition of 6 microM monensin, the lipoprotein lipase activity in the heparin-releasable compartment starts to decrease; by 4 h of monensin treatment the lipoprotein lipase activity in the heparin-releasable pool and in the culture medium is about 10% of that found in control dishes. The intracellular activity, which had been identified as lipoprotein lipase by an antiserum to lipoprotein lipase, increases slowly and doubles by 24 h. However, since the cellular compartment accounts for 10-25% of total activity, this increase does not account for the missing enzyme activity. To determine whether this enzyme molecule is synthesized but is not active, incorporation of labeled leucine, mannose and galactose into immunoadsorbable lipoprotein lipase was studied in control, monensin- or tunicamycin-treated cells. Addition of tunicamycin (5 micrograms/ml) for 24 h caused a 30-50% reduction in immunoadsorbable lipoprotein lipase, but the enzyme activity was reduced by 90%. On the other hand, 4 h monensin treatment reduced both incorporation of [3H]leucine into immunoadsorbable lipoprotein lipase and heparin-releasable and medium lipoprotein lipase activity by 57 to 77%. The immunoadsorbable lipoprotein lipase in the intracellular compartment has a [14C]mannose to [3H]galactose ratio of 0.15 and this ratio increased 6-fold in monensin-treated cells. The intracellular lipoprotein lipase in monensin-treated cells had the same affinity for both the native and synthetic substrate as the lipoprotein lipase in control cells, yet its spontaneous secretion into the culture medium and its release by 3 min heparin treatment was markedly decreased. The present results indicate that: the presence of asparagine-linked oligosaccharide (formation of which is inhibited by tunicamycin) is mandatory for the expression of lipoprotein lipase activity; lipoprotein lipase is active also in a high mannose form; and terminal glycosylation and oligosaccharide processing, which is inhibited by monensin, may be important for the appearance of heparin-releasable lipoprotein lipase and secretion of lipoprotein lipase into the medium. 相似文献
55.
Summary ThreeAlnus glutinosa (L.) Gaertn. clones, obtained byin vitro propagation techniques, were inoculated with four strains ofFrankia. The ability of these clones to nodulate and fix nitrogen was previously reported; this study deals with the performance of 12 different combinations of pairs of symbionts.Shoot fresh weight, shoot height and collar diameter were measured 60 and 82 days after inoculation. Shoot fresh weight seems to be more sensitive and reliable than the other parameters. Nitrogenase activity, measured by the acetylene reduction assay, was assayed 78 days after inoculation and was consistent with the biomass measurements.Better growth was observed when type N strains were used. Significant growth differences were observed between clones AG-2 and AG-8 on the one hand and clone AG-4 on the other. Thus, the use of genetically defined host plants and microsymbionts permitted the demonstration of significant performance variation even among cloned plants from the same provenance (AG-4 and AG-8).The duration of the experiment influenced the results with differences becoming less significant with time. This might be caused by an external limiting factor such as the pot size, competition for light,etc. But it could also be indicative of differences in nodulation speed among the treatments. 相似文献
56.
Traber D. L.; Adams T. Jr; Sziebert L.; Stein M.; Traber L. 《Journal of applied physiology》1985,58(3):1005-1009
We studied the effects of superoxide dismutase (SOD), an enzyme that converts superoxide into peroxide, on the cardiopulmonary response to endotoxin in sheep. Sheep (n = 18) were prepared for chronic measurement of cardiopulmonary variables, including lung lymph flow, by surgically implanting catheters under halothane anesthesia. Nine of the animals were studied before and after the administration of endotoxin (0.75 microgram/kg) with and without SOD. An additional nine animals received SOD without the lipopolysaccharide. Endotoxin produced an increase in lung lymph flow that was initially associated with a marked pulmonary arterial (PA) hypertension and reduced lymph-to-plasma protein ratio (L/P). The lymph flow remained elevated later in the response, but there was only a mild increase in PA pressure, and the L/P was normal. There was also a fall in blood neutrophils and in cardiac index. SOD increased this secondary elevation in lung lymph flow, and the corresponding L/P was greater than the preendotoxin value. The fall in neutrophil count, cardiac output, and the elevation in PA pressure seen with endotoxin were not affected by SOD. When administered in the absence of endotoxin, SOD produced no perceptible change in the cardiopulmonary and lymph values. We conclude that peroxide, hydroxyl ion, and/or other free radicals formed by the action of SOD must be responsible for a portion of the endotoxin response rather than superoxide itself. 相似文献
57.
The shear stress at the wall has been of interest as one of the possible fluid dynamic factors that may be damaging in the region of prosthetic valves. The purpose of this study was to measure the axial wall shear stresses in the region of a 29 mm tissue annulus diameter porcine stent mounted prosthetic aortic valve (Hancock, Model 242). Studies were performed in an in vitro pulse duplicating system. The axial wall shear stress was calculated from velocities obtained near the wall with a laser Doppler anemometer. The largest axial wall shear stress was 29 dyn cm-2 and it occurred at the highest stroke volume used (80 ml). At a stroke volume of 50 ml, the largest axial wall shear stress was 17 dyn cm-2 and at a stroke volume of 35 ml, it was 15 dyn cm-2. Stresses of these magnitudes are far below those reported to be damaging to the endothelial surface. These stresses may be high enough, however, to affect platelet function. 相似文献
58.
59.
We have previously reported that insulin binding is decreased in the olfactory bulb of both heterozygous (Fa/fa) and obese (fa/fa) Zucker rats. In the present study, we measured insulin binding in membranes prepared from the olfactory bulb, cerebral cortex, and hypothalamus of control (Fa/Fa) Wistar Kyoto rats; "fatty" (fa/fa) Wistar Kyoto rats; and phenotypically lean (Fa/?) Wistar Kyoto rats. Insulin binding was decreased in all brain regions, as well as the liver of the obese Wistar Kyoto fa/fa rats. Additionally, insulin binding was decreased in the liver and brain membranes from the Fa/? Wistar Kyoto rats. As most of the Fa/? rats were probably carriers of one 'fa' gene, but the population was only slightly hyperinsulinemic, we conclude that--as in the Zucker rat--it is the presence and expression of the 'fa' gene rather than downregulation which results in the decreased insulin binding. Thus, regulation of the brain insulin receptor appears to be independent of plasma or cerebrospinal fluid insulin levels. 相似文献
60.
Zeev Ronai Judith Shaham Joseph Stein Dov Sulitzeanu 《Cancer immunology, immunotherapy : CII》1986,22(1):72-75
Summary A polyethylene glycol precipitation technique was used to determine the levels of circulating immune complexes (CIC) in breast cancer and melanoma patients. All patients in the study had undergone surgery and were free of distant metastatic disease. CIC were measured at two to four time intervals, of 3 to 6 months each, over an average follow-up period of 13.5 months (range 7–20 months). In both groups of patients, metastatic disease developed with a higher frequency in patients who had undetectable CIC levels throughout the follow-up period or had become negative at the time metastases were discovered. 相似文献