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It has recently been established that both acute human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections are accompanied by a dramatic and selective loss of memory CD4+ T cells predominantly from the mucosal surfaces. The mechanism underlying this depletion of memory CD4+ T cells (that is, T-helper cells specific to previously encountered pathogens) has not been defined. Using highly sensitive, quantitative polymerase chain reaction together with precise sorting of different subsets of CD4+ T cells in various tissues, we show that this loss is explained by a massive infection of memory CD4+ T cells by the virus. Specifically, 30-60% of CD4+ memory T cells throughout the body are infected by SIV at the peak of infection, and most of these infected cells disappear within four days. Furthermore, our data demonstrate that the depletion of memory CD4+ T cells occurs to a similar extent in all tissues. As a consequence, over one-half of all memory CD4+ T cells in SIV-infected macaques are destroyed directly by viral infection during the acute phase-an insult that certainly heralds subsequent immunodeficiency. Our findings point to the importance of reducing the cell-associated viral load during acute infection through therapeutic or vaccination strategies. 相似文献
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The discrete nature of crystal lattices plays a role in virtually every material property. But it is only when the size of entities hosted by a crystal becomes comparable to the lattice period--as occurs for dislocations, vortices in superconductors and domain walls--that this discreteness is manifest explicitly. The associated phenomena are usually described in terms of a background Peierls 'atomic washboard' energy potential, which was first introduced for the case of dislocation motion in the 1940s. This concept has subsequently been invoked in many situations to describe certain features in the bulk behaviour of materials, but has to date eluded direct detection and experimental scrutiny at a microscopic level. Here we report observations of the motion of a single magnetic domain wall at the scale of the individual peaks and troughs of the atomic energy landscape. Our experiments reveal that domain walls can become trapped between crystalline planes, and that they propagate by distinct jumps that match the lattice periodicity. The jumps between valleys are found to involve unusual dynamics that shed light on the microscopic processes underlying domain-wall propagation. Such observations offer a means for probing experimentally the physics of topological defects in discrete lattices--a field rich in phenomena that have been subject to extensive theoretical study. 相似文献
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R. B. Hill 《Cellular and molecular life sciences : CMLS》1992,48(9):797-800
The Editors wish to thank Prof. R. B. Hill for having coordinated this Multi-author Review. 相似文献
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Summary Mouse embryo cells can be plated directly from single-cell suspensions of fresh embryos. For randomly bred Swiss mice, there is an increase in plating efficiency as a function of gestational age. Colony-forming units appear at about day 10 and there is an exponential increase in colony-forming ability up to day 16, after which there is no further increase.The technical assistance of Ms.Helen Sandza is gratefully acknowledged. This work was supported by a grant from the National Cancer Institute (No. CA13053). 相似文献
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R. B. Hill Elizabeth Marantz B. A. Beattie J. M. Lockhart 《Cellular and molecular life sciences : CMLS》1968,24(1):91-92
Zusammenfassung Der Radula Protractormuskel vonBusycon canaliculatum unterscheidet sich vom Herzmuskel, aber er verhält sich wie andere glatte Muskeln von andern Mollusken in der Beziehung zwischen passiver und aktiver Kraft. 相似文献
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