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101.
Results from imaging and lesion studies of item recognition memory have suggested that the hippocampus supports memory for the arbitrary associations that form the basis of episodic recollection, whereas the perirhinal cortex (PRc) supports familiarity for individual items. This view has been challenged, however, by findings showing that PRc may contribute to associative recognition, a task thought to measure relational or recollective memory. Here, using functional magnetic resonance imaging, we demonstrate that PRc activity is increased when pairs of items are processed as a single configuration or unit and that this activity predicts subsequent familiarity-based associative memory. These results explain the discrepancy in the literature by showing that novel associations can be encoded in a unitized manner, thereby allowing PRc to support associative recognition based on familiarity. 相似文献
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D Wegmann M Norbury-Glaser B Bergman K Haskins 《Journal of immunology (Baltimore, Md. : 1950)》1992,149(1):77-82
There is compelling evidence from animal models that type I diabetes is a consequence of T cell-mediated destruction of islet beta-cells. The recent isolation of islet-specific T cell clones from nonobese diabetic mice provides a means of identification of the Ag on islet cells that are responsible for stimulation of autoreactive T cells. We describe an APC line constructed by fusion of spleen B cells obtained from nonobese diabetic mice to a B lymphoma that was transfected with the H and L chains of an IgM specific to the hapten TNP. Using this hybrid APC we have observed a dramatic increase in the efficiency of presentation of TNP-conjugated islet cell protein preparations compared to that seen with conventional APC. Our results illustrate the potential use of this APC line for isolation and characterization of islet Ag relevant to the T cell response. 相似文献
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Gengxiang Zhao Nantaporn Haskins Zhongmin Jin Norma M. Allewell Mendel Tuchman Dashuang Shi 《Biochemical and biophysical research communications》2013
Maricaulis maris N-acetylglutamate synthase/kinase (mmNAGS/K) catalyzes the first two steps in l-arginine biosynthesis and has a high degree of sequence and structural homology to human N-acetylglutamate synthase, a regulator of the urea cycle. The synthase activity of both mmNAGS/K and human NAGS are regulated by l-arginine, although l-arginine is an allosteric inhibitor of mmNAGS/K, but an activator of human NAGS. To investigate the mechanism of allosteric inhibition of mmNAGS/K by l-arginine, we have determined the structure of the mmNAGS/K complexed with l-arginine at 2.8 Å resolution. In contrast to the structure of mmNAGS/K in the absence of l-arginine where there are conformational differences between the four subunits in the asymmetric unit, all four subunits in the l-arginine liganded structure have very similar conformations. In this conformation, the AcCoA binding site in the N-acetyltransferase (NAT) domain is blocked by a loop from the amino acid kinase (AAK) domain, as a result of a domain rotation that occurs when l-arginine binds. This structural change provides an explanation for the allosteric inhibition of mmNAGS/K and related enzymes by l-arginine. The allosterically regulated mechanism for mmNAGS/K differs significantly from that for Neisseria gonorrhoeae NAGS (ngNAGS). To define the active site, several residues near the putative active site were mutated and their activities determined. These experiments identify roles for Lys356, Arg386, Asn391 and Tyr397 in the catalytic mechanism. 相似文献
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