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991.
JD Pierce CJ Wysocki EV Aronov JB Webb RM Boden 《Canadian Metallurgical Quarterly》1996,21(2):223-237
Cross-adaptation, the decrease in sensitivity to one odorant following exposure to a different odorant, is affected by odorant similarity, both perceptual and structural, but the precise relationship is obscure. The present series of studies was designed to explore various aspects of perceptual and structural similarity as they relate to cross-adaptation. In Experiment 1, cross-adaptation was assessed between androstenone and five odorants that share a common urinous note with androstenone, but retain unique perceptual characteristics; only the compound judged most perceptually similar to androstenone cross-adapted it. In Experiment 2, odorants both perceptually and structurally similar (androstenone and androstanone) displayed significant, mutual cross-adaptation. Furthermore, magnitude estimates for androstanone were significantly reduced following exposure to 3-methylidene-5 alpha-androstane (3M5A), a structurally similar, perceptually odorless compound. This finding appears to be the first demonstration that an odorless compound can affect, via cross-adaptation, the perception of an odorous compound. Finally, in Experiment 3, significant, asymmetric cross-adaptation was observed between compounds that are perceptually and structurally dissimilar (4-cyclohexylcyclohexanone [4-CHCH] and androstenone). These findings indicate that the role of similarity in cross-adaptation is difficult to quantify and emphasize the numerous odorant characteristics that can affect cross-adaptation. 相似文献
992.
DS Greenfield RM Siatkowski NJ Schatz JS Glaser 《Canadian Metallurgical Quarterly》1996,122(2):280-281
PURPOSE: We examined a 28-year-old woman who developed incongruous binasal and bitemporal visual field defects one week after having a febrile gastroenteritis characterized by severe diarrhea while traveling in Mexico. METHODS: The patient was treated with intravenous methylprednisolone sodium succinate, 1 g daily for three days, followed by an eight-week course of oral prednisone. RESULTS: Neuroradiologic examination demonstrated bilaterally increased signal intensity within the lateral geniculate bodies. Cerebrospinal fluid analysis disclosed isolated protein increase. CONCLUSION: Severe diarrhea may be associated with an aseptic bilateral lateral geniculitis resulting in hourglass-shaped visual fields. Corticosteroid therapy may provide mild improvement. 相似文献
993.
K Hashimoto SJ Sohn SD Levin T Tada RM Perlmutter T Nakayama 《Canadian Metallurgical Quarterly》1996,184(3):931-943
The nonreceptor protein tyrosine kinase p56lck (Lck) serves as a fundamental regulator of thymocyte development by delivering signals from the pre-T cell receptor (pre-TCR) that permit subsequent maturation. However, considerable evidence supports the view that Lck also participates in signal transduction from the mature TCR. We have tested this conjecture by expressing a dominant-negative form of Lck under the control of a promoter element (the distal lck promoter) that directs high expression in CD4+CD8+ thymocytes, mature thymocytes, and peripheral T cells, thereby avoiding, complications that result from the well-documented ability of dominant-negative Lck to block very early events in thymocyte maturation. Here we report that expression of the catalytically inactive Lck protein at twice normal concentrations inhibits thymocyte positive selection by as much as 80%, while leaving other aspects of cell maturation intact. This effect was studied in more detail in mice simultaneously bearing the male-specific H-Y alpha/beta TCR transgene and ovalbumin-specific DO10 alpha/beta TCR transgene, where even equimolar expression of the dominant-negative Lck protein substantially vitiated the positive selection process. Although deletion of H-Y alpha/beta thymocytes proceeded normally in male mice despite the presence of catalytically inactive Lck, modest inhibition of superantigen-mediated deletion was in some cases observed. These data further implicate Lck in the propagation of all TCR-derived signals, and indicate that even very modest deficiencies in the representation of functional Lck molecules could in humans, profoundly alter the character of the peripheral TCR repertoire. 相似文献
994.
995.
996.
RM Greene SF Betz S Hilgen-Willis DS Auld JB Fencl GJ Pielak 《Canadian Metallurgical Quarterly》1993,51(3):663-676
We have examined the F82Y;C102T variant of Saccharomyces cerevisiae iso-1-cytochrome c using high-resolution proton nuclear magnetic resonance spectroscopy, chemical denaturation, and differential scanning calorimetry. Comparison of proton chemical shifts, paramagnetic shifts, and nuclear Overhauser effects indicates structural changes are localized to the vicinity of position 82. One alteration involves the rearrangement of the side chain of leucine-85. Using many more proton assignments than were available in the initial report [G. J. Pielak, R. A. Atkinson, J. Boyd, and R. J. P. Williams, Eur. J. Biochem. 177, 179-185 (1988)], a second alteration involving an interaction between arginine-13 and tyrosine-82 is observed. The interaction appears to involve a hydrogen bond with the eta-protons of arginine's guanido group acting as donor and tyrosine's phenolic eta-oxygen as acceptor. In spite of this potentially-stabilizing interaction, the free energy of denaturation decreases by approximately 2.4 kcal mol-1. Results are discussed with respect to alterations in the native and denatured states. 相似文献
997.
HM Cox K Cheung AJ Fletcher RM Whitby PE Hickman 《Canadian Metallurgical Quarterly》1995,27(4):362-364
Controversy over appropriate disinfection of endoscopes continues with the most commonly utilized solution in Australian hospitals, despite concern over its efficacy, being 1% glutaraldehyde (AIDAL). Review of the in-use concentrations of glutaraldehyde at Princess Alexandra Hospital has documented a significant dilutional effect in 1% glutaraldehyde by gastrointestinal endoscopes. Each hospital should determine the minimum in-use concentration acceptable for any given disinfecting solution and any given range of endoscopes. Once this level is reached, a solution change should routinely occur. Such decisions can only be made by regularly monitoring in-use concentrations of disinfectants. 相似文献
998.
KI Ahammadsahib RM Hollingworth JP McGovren YH Hui JL McLaughlin 《Canadian Metallurgical Quarterly》1993,53(14):1113-1120
Bullatacin, a compound isolated from plants of the Annonaceae, and its analogues show in vivo potential as antitumor agents based on their efficacy in normal mice bearing L1210 murine leukemia and athymic mice bearing A2780 conventional ovarian cancer xenografts. These compounds also have interesting potential as insecticides and inhibit respiration in insect-derived Sf9 cells with high potency. Their toxicity in both cases probably arises from their strong inhibition of mitochondrial electron transport with a specific action at complex I. 相似文献
999.
Portal-systemic encephalopathy (PSE) is characterized by neuropsychiatric symptoms progressing through stupor and coma. Previous studies in human autopsy tissue and in experimental animal models of PSE suggest that alterations in levels of brain amino acids may play a role in the pathogenesis of PSE. To assess this possibility, levels of amino acids were measured using in vivo cerebral microdialysis in frontal cortex of portacaval-shunted rats administered ammonium acetate (3.85 mmol/kg, i.p.) to precipitate severe PSE. Sham-operated rats served as controls. Portacaval shunting resulted in significant increases of levels of extracellular glutamine (threefold, p < 0.001), alanine (38%, p < 0.01), aspartate (44%, p < 0.05), phenylalanine (170%, p < 0.001), tyrosine (140%, p < 0.001), tryptophan (63%, p < 0.001), leucine (75%, p < 0.001), and serine (60%, p < 0.001). Administration of ammonium acetate to sham-operated animals led to a significant increase in extracellular glutamine and taurine content, but this response was absent in shunted rats. The lack of taurine release into extracellular fluid following ammonium acetate administration in portacaval-shunted rats could relate to the phenomenon of brain edema in these animals. Ammonium acetate administration resulted in significant increases in the extracellular concentrations of phenylalanine and tyrosine in both sham-operated and portacaval-shunted rats. Severe PSE was not accompanied by significant increases in extracellular fluid concentrations of glutamate, aspartate, GABA, tryptophan, leucine, or serine, suggesting that increased spontaneous release of these amino acids in cerebral cortex is not implicated in the pathogenesis of hepatic coma. 相似文献
1000.
RM Elledge S Lock-Lim DC Allred SG Hilsenbeck L Cordner 《Canadian Metallurgical Quarterly》1995,1(10):1203-1208
A substantial portion of patients with estrogen receptor-positive breast cancer fail to respond to estrogen depletion or to the antiestrogen tamoxifen. The molecular changes that lead to tamoxifen resistance and estrogen-independent growth are unknown. To test the hypothesis that a p53 mutation could result in tamoxifen resistance and estrogen-independent growth, the MCF-7 cell line was transfected with p53 cDNA which was mutated at codon 179 (histidine to glutamine). MCF-7 is an estrogen receptor-positive, estrogen-dependent, tamoxifen-sensitive cell line with only wild-type p53. The presence of transfected mutant p53 cDNA was verified by the PCR, and overexpression of p53 protein was assessed by Western blotting. Five separate mutant-transfected clones were selected and tested in subsequent growth experiments. In monolayer culture, there was no consistent evidence of estrogen-independent growth or tamoxifen resistance in the mutant transfectants compared with vector-only controls or the parental cell line. In soft agar growth experiments, four of five mutant transfectants remained sensitive to tamoxifen in a dose-dependent manner. In the presence of wild-type p53, mutant 179 p53 protein does not result in estrogen-independent growth or tamoxifen resistance. These results do not exclude the possibility that other p53 mutational types could result in tamoxifen resistance, or that loss of the remaining wild-type allele may be necessary to result in this phenotype. 相似文献