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61.
Immortalization of human endothelial cells by murine sarcoma viruses, without morphologic transformation 总被引:3,自引:0,他引:3
D V Faller S Kourembanas D Ginsberg R Hannan T Collins B M Ewenstein J S Pober R Tantravahi 《Journal of cellular physiology》1988,134(1):47-56
Amphotropic murine leukemia virus pseudotypes of murine sarcoma viruses containing the ras or mos oncogenes were constructed to permit efficient introduction of the sarcoma virus genome into early-passage human umbilical vein endothelial cells. The resulting cell lines were morphologically and phenotypically unchanged, retaining properties characteristic of differentiated endothelial cells. For example, the cells in a Kirsten sarcoma virus-modified line were found to biosynthesize and secrete von Willebrand factor in both a constitutive and regulated manner, and they contained ultrastructurally identifiable Weibel-Palade bodies, an endothelial cell-specific organelle. In contrast to the parent cultures, sarcoma virus-modified cells were able to proliferate indefinitely in culture. Examination of both Kirsten sarcoma and Moloney leukemia virus-modified lines indicated that the immortalized cells retained a diploid female karyotype after over 18 months in culture. In addition, the sarcoma virus-modified cells were able to grow independently of added endothelial cell growth factor. This growth factor autonomy does not appear to be due to autocrine production of a biologically cross-reactive growth factor. These immortal, virus-modified endothelial cells express large amounts of sarcoma virus-specific mRNA but no detectable helper virus or transforming virus activity. This technique for immortalization of primary human cells without alteration of the differentiated characteristics of the cell type is readily applied to a variety of human cell types. Moreover, the ability to separate the immortalizing and transforming activities of viral oncogenes should provide further understanding as to mechanisms of oncogene action. 相似文献
62.
R Peto R Gray R Collins K Wheatley C Hennekens K Jamrozik C Warlow B Hafner E Thompson S Norton J Gilliland R Doll 《BMJ (Clinical research ed.)》1988,296(6618):313-316
A six year randomised trial was conducted among 5139 apparently healthy male doctors to see whether 500 mg aspirin daily would reduce the incidence of and mortality from stroke, myocardial infarction, or other vascular conditions. Though total mortality was 10% lower in the treated than control group, this difference was not statistically significant and chiefly involved diseases other than stroke or myocardial infarction. Likewise, there was no significant difference in the incidence of non-fatal myocardial infarction or stroke—indeed, disabling strokes were somewhat commoner among those allocated aspirin. The lower confidence limit for the effect of aspirin on non-fatal stroke or myocardial infarction, however, was a substantial 25% reduction. Migraine and certain types of musculoskeletal pain were reported significantly less often in the treated than control group, but as the control group was not given a placebo the relevance of these findings was difficult to assess. There was no apparent reduction in the incidence of cataract in the treated group.The lack of any apparent reduction in disabling stroke or vascular death contrasts with the established value of antiplatelet treatment after occlusive vascular disease. 相似文献
63.
Forest succession following fire in a forest mosaic of northwestern Quebec has been studied in order to: (1) describe the successional pathways using communities of different ages and (2) evaluate convergence of successional pathways and possible effect of fire suppression on the establishment of steady-state communities. As a first step, ordination and classification techniques were used in order to remove changes in forest composition which are related to abiotic conditions. Then, ordinations based on tree diameter distributions were used to study shifts in species composition in relation to time since the last fire.Even under similar abiotic conditions, successional pathways are numerous. However, regardless of forest composition after fire, most stands show convergence toward dominance of Thuja occidentalis and Picea mariana on xeric sites and dominance of Abies balsamea and Thuja occidentalis on more mesic sites. Stable communities of >300 yr occur on xeric sites while on mesic sites directional succession still occurs after 224 yr. Nearly all species involved in succession are present in the first 50 yr following fire. Only Abies balsamea and Thuja occidentalis increase significantly in frequency during succession. Following initial establishment, successional processes can generally be explained by species longevity and shade tolerance. Early successional species may be abundant in the canopy for more than 200 yr while the rapid decrease of Picea glauca, a late successional species could be related to spruce budworm outbreaks. Considering the short fire rotation observed (about 150 yr), a steady-state forest is unlikely to occur under natural conditions, though it may be possible if fire is controlled. 相似文献
64.
We investigated the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator on insulin receptors and insulin action in freshly isolated and primary cultures of rat hepatocytes. PMA (1 x 10–7 M) did not alter insulin receptor numbers or affinity either acutely or chronically but within 60 minute inactivated insulin stimulated tyrosine kinase of the insulin receptor. PKC activation inhibitied insulin (1 x 10–7M) stimulation of glycogen and lipid synthesis with a decrease or no change in basal glycogenesis and lipogenesis respectively. However, PKC activation did not alter insulin stimulated or basal amino acid transport even though PCK activation inhibited insulin stimulation of the insulin. receptor tyrosine kinase. Thus, within one tissue, PKC activation has differential effect on insulin action depending on which pathway is examined. Furthermore, insulin stimulation of the insulin receptor tyrosine kinase may not be a necessary step for all insulin signaling pathways. 相似文献
65.
Susan H. Woods Gregory C. Phillips John E. Woods Glenn B. Collins 《Plant cell reports》1992,11(5-6):257-261
An efficient protocol has been developed for the in vitro propagation of Mexican Weeping Bamboo through somatic embryogenesis from zygotic embryo explants. Mature seeds and excised embryos were cultured in the light or in the dark on both Murashige and Skoog's and Gamborg's B5 basal media with various supplements. Optimal somatic embryogenesis and plant regeneration were obtained by culture in the dark on Murashige and Skoog's basal medium supplemented with 3 mg/1 2,4-dichlorophenoxyacetic acid, 0.5 mg/1 6-benzylaminopurine and 2.0% sucrose. More than 95% of the germinating somatic embryos developed shoots and roots, and were transferred to soil with 85% success. 相似文献
66.
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68.
L M Kayes W T Schroeder D A Marchuk F S Collins V M Riccardi M Duvic K Stephens 《Genomics》1992,14(2):369-376
Recently the M17S1 gene, encoding an epidermal antigen thought to play a role in cell adhesion, was mapped to chromosome bands 17q11-q12, placing it in the vicinity of the gene for the genetic disorder neurofibromatosis 1 (NF1). The pleomorphic cutaneous lesions of NF1 and the precedent for other genes being embedded within the NF1 gene prompted us to investigate whether the M17S1 gene mapped near, or within, the NF1 gene. Genetic linkage analyses revealed that M17S1 was tightly linked to NF1 and mapped within the interval bounded by D17S58 and D17S54. Physical mapping of an M17S1 cDNA on somatic cell hybrids, yeast artificial chromosomes, and an NF1 patient with a deletion involving an entire NF1 allele demonstrated that M17S1 is located at least 180 kb centromeric to the NF1 gene. The distance between the genes suggests that M17S1 is unlikely to contribute to the NF1 phenotype since a gross chromosomal rearrangement would be required to disrupt expression of both genes. 相似文献
69.
This study examines the analysis of arthropod orientation data. Three problems are discussed: (1) dealing with time as it applies to spatial data, (2) determining the appropriate movelength to be used in collecting and in analyzing data, and (3) defining a turn, to discriminate between "gait noise" and course changes. The main objective is to determine the solution to defining the most appropriate movelength for comparisons between variables and between species. The technique described here for selecting the appropriate movelength that has relevance to both the locomotory rate of the animal and its body length, reduces variation resulting from lateral translational movements, prevents the use of movelengths that lead to artifactual or unrealistic turning values per move, and permits comparisons of species and individuals under various stimulus conditions. 相似文献
70.
R. J. Collins P. J. Boyle A. E. Clague A. E. Barr S. C. Latham 《Biological trace element research》1991,30(3):233-244
Patients with phenylketonuria (PKU) are frequently deficient in the essential trace element selenium (Se), because of their very low protein diet. Using two approaches to investigate T-cell response to proliferative signaling, viz, mitogenesis caused by the monoclonal antibody OKT3 and the plant lectin phytohaemagglutinin (PHA), we demonstrated significantly reduced responses to optimal concentrations of OKT3 in a group of PKU patients with reduced serum Se compared with a normal group (p = 0.0005) and with a group of PKU patients whose serum Se was normal (p = 0.0023). The response of the Se-deficient group to optimal levels of PHA did not differ from that of the normal controls or from that of Se-normal PKU patients. A dose-dependent relationship between serum Se levels and mitogenic response was evident for OKT3 (r = 0.34, p = 0.0154), but not for PHA (r = -0.02, p = 0.9086). We suggest that the reduced response to OKT3 mitogenesis in Se-deficient PKU patients is possibly the consequence of impaired Se-dependent metabolic activity, which affects mitogenic signaling via the T cell antigen receptor (TCR/CD3) complex. 相似文献