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341.
Retinoic acid regulates growth hormone gene expression 总被引:16,自引:0,他引:16
342.
Putative transcription activator with alternative isoforms encoded by human ZFX gene 总被引:9,自引:0,他引:9
A Schneider-G?dicke P Beer-Romero L G Brown G Mardon S W Luoh D C Page 《Nature》1989,342(6250):708-711
343.
Clonal anergy induced in mature V beta 6+ T lymphocytes on immunizing Mls-1b mice with Mls-1a expressing cells 总被引:47,自引:0,他引:47
Tolerance to self-antigens has been shown to develop during ontogeny as a result of the clonal deletion of self-reactive T cells. Tolerance, or better 'nonresponsiveness', to specific antigens can also be induced in adult animals but the mechanism(s) involved are not well understood. Most murine T-helper cells that express the V beta 6 T-cell receptor gene segment are specific for Mls-1a antigens. We have therefore been able to use an anti-V beta 6 monoclonal antibody to follow the fate of Mls-1a specific T cells in adult Mls-1b mice made specifically unresponsive to Mls-1a. We show that the induced unresponsiveness is not due to clonal deletion, but rather to clonal anergy. The anergic V beta 6 T-helper cells express IL-2 receptors and undergo limited blastogenesis in vitro upon stimulation, but do not produce IL-2, in marked contrast to V beta 6 cells from naive mice. Our data appear to represent an in vivo correlate for the induction of anergy that has been observed in T-cell lines in vitro. 相似文献
344.
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346.
Sequence of an unusually large protein implicated in regulation of myosin activity in C. elegans 总被引:36,自引:0,他引:36
The Caenorhabditis elegans gene unc-22 encodes a very large muscle protein, called twitchin, which consists of a protein kinase domain and several copies of two short motifs. The sequence of twitchin has unexpected similarities to the sequences of proteins of the immunoglobulin superfamily, cell adhesion molecules and vertebrate muscle proteins, including myosin light-chain kinase. These homologies, together with results from earlier genetic and molecular analyses, indicate that twitchin is involved in a novel mechanism of myosin regulation. 相似文献
347.
Genetic imprinting suggested by maternal heterodisomy in nondeletion Prader-Willi syndrome 总被引:52,自引:0,他引:52
Prader-Willi syndrome (PWS) is the most common form of dysmorphic genetic obesity associated with mental retardation. About 60% of cases have a cytological deletion of chromosome 15q11q13 (refs 2, 3). These deletions occur de novo exclusively on the paternal chromosome. By contrast, Angelman syndrome (AS) is a very different clinical disorder and is also associated with deletions of region 15q11q13 (refs 6-8), indistinguishable from those in PWS except that they occur de novo on the maternal chromosome. The parental origin of the affected chromosomes 15 in these disorders could, therefore, be a contributory factor in determining their clinical phenotypes. We have now used cloned DNA markers specific for the 15q11q13 subregion to determine the parental origin of chromosome 15 in PWS individuals not having cytogenetic deletions; these individuals account for almost all of the remaining 40% of PWS cases. Probands in two families displayed maternal uniparental disomy for chromosome 15q11q13. This is the first demonstration that maternal heterodisomy--the presence of two different chromosome 15s derived from the mother--can be associated with a human genetic disease. The absence of a paternal contribution of genes in region 15q11q13, as found in PWS deletion cases, rather than a mutation in a specific gene(s) in this region may result in expression of the clinical phenotype. Thus, we conclude that a gene or genes in region 15q11q13 must be inherited from each parent for normal human development. 相似文献
348.
Gene inactivation triggered by recognition between DNA repeats 总被引:15,自引:0,他引:15
This chapter focuses on phenomena of gene inactivation resulting from the presence of repeated gene copies within the genome of plants and fungi, and on their possible relationships to homologous DNA-DNA interactions. Emphasis is given to two related premeiotic processes: Methylation Induced Premeiotically (MIP) and Repeat-Induced Point mutation (RIP) which take place in the fungiAscobolus immersus andNeurospora crassa, respectively. The relationships between these processes and genetic recombination are discussed. 相似文献
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Nonlinear forecasting as a way of distinguishing chaos from measurement error in time series 总被引:49,自引:0,他引:49
An approach is presented for making short-term predictions about the trajectories of chaotic dynamical systems. The method is applied to data on measles, chickenpox, and marine phytoplankton populations, to show how apparent noise associated with deterministic chaos can be distinguished from sampling error and other sources of externally induced environmental noise. 相似文献