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排序方式: 共有399条查询结果,搜索用时 50 毫秒
391.
BB Little DA Roe RW Stettler VR Bohman KL Westfall S Sobhi 《Canadian Metallurgical Quarterly》1995,172(5):1441-1445
OBJECTIVE: The aim of this study was to analyze placental metabolism in a genetically controlled in vitro animal model. STUDY DESIGN: Placentas from Sprague-Dawley rats were centrifuged, and microsomes were isolated. Four treatment groups were incubated with cocaine over four time periods: placental microsomes + cocaine, placental microsomes + diisopropyl fluorophosphate (an anticholinesterase) + cocaine, placental microsomes + cocaine + butyrylcholinesterase, and a blank (cocaine only). Gas chromatography was used to quantify cocaine (Limit of quantitation = 19 ng/ml) and metabolites. Gas chromatography/mass spectrometry was used to verify the identity of the metabolites. RESULTS: Butyrylcholinesterase enhanced cocaine metabolism to ecgonine methyl ester. More than 40% of cocaine was metabolized to norcocaine by rat placental when diisopropyl fluorophosphate suppressed cocaine. Norcocaine is produced by hepatic N-demethylase action on methyl-bearing nitrogen in cocaine, suggesting that placenta and liver have this capacity. Gas chromatography/mass spectrometry was essential to the identification of norcocaine, because norcocaine is frequently not identified. CONCLUSIONS: This biotransformation of cocaine to norcocaine may be a primary metabolic pathway induced in the cholinesterase-deficient placenta. This has clinical implications because norcocaine is ninefold more active physiologically than cocaine or ecgononine methylesterase. 相似文献
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DM Moody WR Brown VR Challa DA Stump DM Reboussin C Legault 《Canadian Metallurgical Quarterly》1995,59(5):1304-1307
Emboli in brain tissue after cardiopulmonary bypass were reported in the literature 30 years ago, but there is little objective evidence confirming the presence of emboli in the brain after cardiopulmonary bypass with more modern equipment and techniques. Recently, with alkaline phosphatase vascular staining, we found an acellular fatty material in brain microvasculature from autopsy material of patients who died shortly after cardiopulmonary bypass. These fatty intravascular collections range in diameter from 10 to 70 microns, a size that lodges in the smallest vessels of the microvasculature. They have been found in numbers sufficient to cause detectable neurologic dysfunction and are believed, but not proved, to be emboli. By sequentially injecting colored microspheres, we can determine when emboli occur during experimental cardiopulmonary bypass. In ongoing related studies, magnetic resonance imaging was performed before cardiac valve replacement in 39 patients for whom preoperative and postoperative neurologic and neuropsychologic testing was available. Preliminary results suggest that magnetic resonance imaging evidence of prior stroke is not a significant risk factor for cognitive or motor decrement after cardiopulmonary bypass. 相似文献
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MY Zhou H Klitgaard B Saltin RR Roy VR Edgerton PD Gollnick 《Canadian Metallurgical Quarterly》1995,78(5):1740-1744
The influence of microgravity on the myosin phenotype of skeletal muscle fibers in the vastus lateralis of eight crew members was studied before and after 5-day (n = 3) and 11-day (n = 5) spaceflights (space shuttle flights: STS-32, -33 and -34). Single-fiber electrophoresis analyses showed that the proportion of fibers expressing only slow (type I) myosin heavy chain (MHC) in the vastus lateralis was significantly lower after than before 11 days of spaceflight. Although the family of type II MHC isoforms was elevated post- compared with preflight, the distribution among the isoforms of type II MHC was not statistically different. Based on monoclonal and polyclonal antibodies specific for three adult MHC isoforms and single-fiber electrophoresis, approximately 3% of the fibers analyzed coexpressed all three adult MHC isoforms. The results from immunohistochemical staining with two different sets of antibodies indicate a reduction in the percentage of fibers expressing type I MHC as a result of spaceflight. The mean difference, however, was significant only when the fibers were categorized simply as type I or II. These changes appeared to be highly individualized among the astronauts. These results suggest that a rapid change in MHC isoform expression can occur in some muscle fibers after a relatively brief exposure to spaceflight. 相似文献
397.
VR Ermolaev GM Shub EP Kusina GL Polianski? VI Sobolev 《Canadian Metallurgical Quarterly》1976,10(3):53-58
Recovery of spatial resolving capacity (acuity) of central vision after temporary blindness induced by prolonged (1.5, 3, 6 min) light adaptation to a sun or incandescence lamp (20, 40, 80 thous. lux) illuminated white screen was studied. The recovery time increased exponentially with an increase in energy light stimulation (product of brightness of the deadapting source by the time of action). A general formula describing the relationship between the time of recovery of acuity and brightness of the test table and energy of light stimulus was derived. 相似文献
398.
Novel amic acid diamines (AADs) (2‐carboxyterephthalamido‐bis(alkyl or aryl amine)s, H2N? X? NH(O?)C? C6H3(COOH)? C(?O)NH? X? NH2, where X is were synthesized by reacting trimellitic anhydride chloride with aromatic or aliphatic diamines in dimethylformamide at 5–10 °C. Poly(amide imide)s (PAIs) with an amide to imide ratio of three in the polymer chains were prepared by interfacial polycondensation of the AADs in aqueous alkaline solution with isophthaloyl chloride or terephthaloyl chloride in dichloromethane at ambient temperature to form poly(amide amic acid)s, followed by their subsequent thermal cycloimidization. All of the PAIs were soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide and N‐methylpyrrolidone, and have inherent viscosities in the range 0.15–0.48 dL g?1. The polymers were characterized by IR and NMR spectroscopy, TGA and DSC techniques. The PAIs have initial decomposition temperatures in the range 250–460 °C in air, and glass transition temperatures of 128–320 °C, depending upon the structures of the monomers. Composite membranes containing a poly(amide amic acid) and poly(amide imide) barrier layer on the top of a porous polyethersulfone support were prepared by in situ interfacial polymerization of the AADs in aqueous alkaline solution with trimesoyl chloride in hexane, and subsequent curing. The performances of these membranes were evaluated by using aqueous feed solutions containing 2000 ppm NaCl, Na2SO4 or CaCl2. Copyright © 2006 Society of Chemical Industry 相似文献
399.
TR Bilderback VR Gazula MP Lisanti RT Dobrowsky 《Canadian Metallurgical Quarterly》1999,274(1):257-263
Neurotrophins signal through Trk tyrosine kinase receptors and the low-affinity neurotrophin receptor p75(NTR). We have shown previously that activation of Trk A tyrosine kinase activity can inhibit p75(NTR)-dependent sphingomyelin hydrolysis, that caveolae are a localized site for p75(NTR) signaling, and that caveolin can directly interact with p75(NTR). The ability of caveolin to also interact with tyrosine kinase receptors and inhibit their activity led us to hypothesize that caveolin expression may modulate interactions between neurotrophin signaling pathways. PC12 cells were transfected with caveolin that was expressed efficiently and targeted to the appropriate membrane domains. Upon exposure to nerve growth factor (NGF), caveolin-PC12 cells were unable to develop extensive neuritic processes. Caveolin expression in PC12 cells was found to diminish the magnitude and duration of Trk A activation in vivo. This inhibition may be due to a direct interaction of caveolin with Trk A, because Trk A co-immunoprecipitated with caveolin from Cav-Trk A-PC12 cells, and a glutathione S-transferase-caveolin fusion protein bound to Trk A and inhibited NGF-induced autophosphorylation in vitro. Furthermore, the in vivo kinetics of the inhibition of Trk A tyrosine kinase activity by caveolin expression correlated with an increased ability of NGF to induce sphingomyelin hydrolysis through p75(NTR). In summary, our results suggest that the interaction of caveolin with neurotrophin receptors may have functional consequences in regulating signaling through p75(NTR) and Trk A in neuronal and glial cell populations. 相似文献