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991.
Sindbis virus induces apoptotic cell death in cultured cell lines, raising the possibility that apoptosis of infected neurons and other target cells in vivo may contribute to the resulting disease and mortality. To investigate the role of apoptosis in Sindbis virus pathogenesis, infected mouse brains were assayed by the in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling technique and for DNA ladder formation. Infection with recombinant Sindbis virus strain 633 resulted in widespread apoptosis in newborn mouse brains and spinal cords, but few apoptotic cells were observed following infection of 2-week-old animals. This finding correlates with the age-dependent mortality observed in mice. The more neurovirulent virus TE, which differs from 633 by a single amino acid in the E2 glycoprotein, induced significant apoptosis in brains and spinal cords of 2-week-old animals, consistent with its ability to cause fatal disease in older animals. Double-labeling experiments demonstrated that the apoptotic cells were also infected with Sindbis virus. Thus, Sindbis virus-induced apoptosis appears to be a result of virus infection and is likely to reflect pathogenic mechanisms for other viruses. 相似文献
992.
DE Bierer LG Dubenko P Zhang Q Lu PA Imbach AW Garofalo PW Phuan DM Fort J Litvak RE Gerber B Sloan J Luo R Cooper GM Reaven 《Canadian Metallurgical Quarterly》1998,41(15):2754-2764
Cryptolepine (1) is a rare example of a natural product whose synthesis was reported prior to its isolation from nature. In the previous paper we reported the discovery of cryptolepine's antihyperglycemic properties. As part of a medicinal chemistry program designed to optimize natural product lead structures originating from our ethnobotanical and ethnomedical field research, a series of substituted and heterosubstituted cryptolepine analogues was synthesized. Antihyperglycemic activity was measured in vitro and in an NIDDM mouse model to generate the first structure-bioactivity study about the cryptolepine nucleus. 相似文献
993.
994.
JW Cohen AC Monheit KM Beauregard SB Cohen DC Lefkowitz DE Potter JP Sommers AK Taylor RH Arnett 《Canadian Metallurgical Quarterly》1996,33(4):373-389
This article describes the Medical Expenditure Panel Survey (MEPS), the third in a series of nationally representative surveys of medical care use and expenditures sponsored by the Agency for Health Care Policy and Research. The MEPS is designed to provide extensive data on the types of health care services American use, how frequently they use them, how much is paid for the services, and who pays for them. It also will provide information on the types and costs of private health insurance available to the U.S. population. The survey is unparalleled in its degree of detail, as well as its ability to link medical care use, payments, and health insurance coverage to specific survey respondents and their families. It allows analysts to examine how individual and family characteristics, including the characteristics of their health insurance, affect medical care use and spending. This article discusses each of the MEPS components, focusing on design enhancements that have been made since the survey was last conducted nearly a decade ago. 相似文献
995.
996.
997.
SM Dimitrijevi? U Humer M Shehadeh WJ Ryves NM Hassan FJ Evans 《Canadian Metallurgical Quarterly》1996,15(3):393-401
For the first time a normal-phase HPLC method using photodiode-array detection is described for the analysis and purification of phorbol esters. The use of the method is demonstrated with examples of 10 different tigliane and daphnane esters (TPA, DOPP, DOPPA, Sap A, Sap B, Sap C, Sap D, Thy A, Ro and Rx). Both analytical and semipreparative techniques were developed. The method has been used in the final purification of DOPP and Rx from plant extracts. The method can be employed in the areas of phytochemistry, biochemistry and pharmacology/toxicology, where small samples of the toxic materials are required for research. 相似文献
998.
Heng C. Cao Marc De Graef Anthony G. Evans 《Journal of the American Ceramic Society》1993,76(12):3019-3023
In advanced actuator systems, ferroelectric ceramics are usually made into multilayered stacks to obtain optimum performance. This is done by interlacing noble metals (such as Pt/Pd) with ceramic green sheet and cofiring. The present study proposes an alternative, more economic electrode. Copper has been successfully diffusion bonded to several PZT-based ferroelectric ceramics in a multilayer configuration. The microstructure and the relevant physical properties of the interfaces have been investigated. This has been achieved by using microscopy, as well as by mechanical and electrical characterization. These studies indicate that no reaction product forms at the interface and, furthermore, that the interface exhibits good cohesion. 相似文献
999.
Combined handover algorithm for dynamic satellite constellations 总被引:1,自引:0,他引:1
A combined handover algorithm is proposed for a dynamic mobile satellite system. Handover decisions are based on user terminal (UT) position and signal strength measurement. The handover performances considered are handover position and call termination probability 相似文献
1000.
I Kim CJ Phillips JA Monjeau EC Birney K Noack DE Pumo RS Sikes JA Dole 《Canadian Metallurgical Quarterly》1998,7(6):667-678
The effects of terrestrial habitat islands on gene flow and genetic diversity in animal populations have been predicted and discussed in theoretical terms, but empirical data are needed to test these predictions and provide an understanding of the relationships of life-history characteristics to genetics of insular species. We studied saxicolous mice (Phyllotis xanthopygus) in Patagonia to explore genetic structure, phylogeography, and gene flow in a species inhabiting natural habitat islands. Phylogeographic analyses based on mtDNA sequences revealed two haplotype clades, which presumably reflect early Pleistocene factors that temporarily separated the mice into two geographically isolated groups. The Río Chubut, which lies within a glacial drainage basin bisecting northern Patagonia, might have affected gene flow in the species. Although we anticipated isolation by distance and founder phenomena associated with habitat islands, in some habitat patches we found evidence of high local genetic diversity. The amount of divergence in the mitochondrial cytochrome b gene (approximately 3.4%) in animals at a single locality could best be explained through a combination of historical factors and metapopulation source-sink theory. Demographic shifts, dispersal, and episodic recolonization are important in the life history and genetic population structure of P. xanthopygus. 相似文献