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排序方式: 共有876条查询结果,搜索用时 15 毫秒
81.
VR Lord JW Cherwonogrodzky GG Schurig RD Lord MJ Marcano GE Meléndez 《Canadian Metallurgical Quarterly》1998,59(5):546-551
We have investigated the inter-relationship between the opioid and aminergic systems in the control of secretion of the pro-oestrous LH surge and the involvement of delta-opioid receptor subtypes in this process. Conscious female rats bearing a cannula in the femoral artery were injected i.p. with a selective delta-opioid receptor agonist (DPDPE) either alone or with the opioid antagonist (naloxone) at 1300 h on the day of pro-oestrus. Blood samples were collected hourly between 1500 h and 1900 h, and plasma LH levels were measured by RIA. At the end of this period (1900 h), the animals were autopsied and the concentrations of the amines (noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5HT)) and their metabolites (dihydroxyphenolglycol (DHPG) and 5-hydroxyindoleacetic acid (5HIAA), metabolites of NA and 5HT respectively) were determined by HPLC with electrochemical detection in the medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus. DPDPE abolished the LH surge and concomitantly decreased hypothalamic NA and DHPG concentrations in all the areas examined. The levels of DA, 5HT and 5HIAA were also reduced in all hypothalamic regions studied, except DA and 5HIAA in the suprachiasmatic nucleus. Naloxone reversed these inhibitory effects of the delta-agonist. We conclude that activation of delta-opioid receptors may exert an inhibitory effect on LH release. The effect is probably an indirect one mediated by the monoaminergic systems, as they are suppressed by DPDPE in nearly all the hypothalamic regions studied. 相似文献
82.
SL Anliker MS McClure TC Britton EA Stephan SR Maple GG Cooke 《Canadian Metallurgical Quarterly》1994,83(5):716-719
The anti-tumor agent gemcitabine hydrochloride, a beta-difluoronucleoside, is remarkably stable in the solid state. In 0.1 N HCI solution at 40 degrees C, deamination of gemcitabine occurs, yielding its uridine analogue. Approximately 86% of the initial gemcitabine remains after 4 weeks under these conditions. Cleavage of the N-glycosidic bond of gemcitabine or conversion to its alpha-anomer in 0.1 N HCI solution is not observed over a 4-week period. However, this work has shown that gemcitabine hydrochloride anomerizes in 0.1 N NaOH at 40 degrees C. Approximately 72% of the initial gemcitabine remains after 4 weeks under the basic conditions used. Uridine hydrolysis products are also formed under these conditions. The anormerization reaction, which is unusual under basic conditions, has been confirmed by characterization of the chromatographically isolated alpha-anomer by NMR and mass spectrometry. A mechanism involving an acyclic intermediate is proposed. 相似文献
83.
CC Helbing CL Wellington M Gogela-Spehar T Cheng GG Pinchbeck RN Johnston 《Canadian Metallurgical Quarterly》1998,17(12):1491-1501
When exposed to diverse growth conditions in vitro, cells can respond by entering states of proliferation, quiescence, differentiation or apoptosis. While the choices among these states can be influenced by proto-oncogene expression, how these disparate outcomes are achieved remains poorly understood. To address these issues, we have generated rodent fibroblast cell lines that harbor a human c-myc gene under the control of a tetracycline-regulated promoter. When Myc-induced cells are deprived of serum growth factors, they rapidly become apoptotic with the onset of apoptosis preceded by a large, transient increase in cdk2 kinase activity that is associated with the induction of cdc25A phosphatase and the later accumulation of p27Kip1 kinase inhibitor. Surprisingly, serum starvation in the absence of myc overexpression, (which leads to quiescence instead of apoptosis) also causes a marked transient elevation in cdk2 kinase activity, an induction of cdc25A and a delayed increase in p27Kip1. Transient elevations in cdk2 kinase activity and cdc25A abundance are required for cell cycle progression, but it is evident that these changes also precede entry to either apoptosis or quiescence in serum-starved cells. These findings suggest that the pathways to both quiescence and apoptosis share regulatory machinery with cell cycle control mechanisms. In addition, the abundance of Myc protein can be critical in the choices among these cellular states. 相似文献
84.
85.
An 8-year-old boy presented with precocious puberty and a mediastinal mass. A computer search showed that this rare presentation is most common with germ cell tumor of the mediastinum in children with Klinefelter syndrome. The tumor was completely resected after preoperative chemotherapy, and the patient is well 2 years after the operation. In patients with Klinefelter syndrome, germ cell tumors are 50 times more common than in patients without Klinefelter syndrome, usually contain nonseminomatous elements, present at an earlier age, and are seldom testicular in location. 相似文献
86.
BACKGROUND: Carisoprodol is a skeletal muscle relaxant with the potential for abuse. A carisoprodol overdose is rarely considered fatal. Nevertheless, we encountered carisoprodol in several cases, prompting review of our experience. METHODS: We did a retrospective study of cases examined at the Jefferson County Coroner/Medical Examiner Office from January 1, 1986, to October 31, 1997, reviewing investigative reports and autopsy findings. RESULTS: Carisoprodol was present in 24 cases. Seventeen decedents died of acute drug intoxication. Carisoprodol was never the sole drug detected at autopsy, nor was it ever the sole cause of death. Propoxyphene was a co-intoxicant in 8 of the 24 cases. CONCLUSIONS: Carisoprodol causes respiratory depression. Since the mechanism of death was respiratory depression in 82% of the decedents who died of acute intoxication, we consider that carisoprodol was probably responsible, in part, for those deaths. The simultaneous use of propoxyphene and carisoprodol seems to be especially dangerous. 相似文献
87.
Kinetics and products of peroxynitrite anion O=NOO- reactions, catalyzed by water-soluble manganese and iron porphyrins, were studied under basic and neutral conditions. In the absence of organic substrates peroxynitrite decomposes catalytically to give nitrite and dioxygen as major products. Catalytic decomposition competes with direct oxidation of sulfoxide to sulfone, while phenol is catalytically nitrated in o- and p-positions. A reaction mechanism is proposed. 相似文献
88.
Vascular MADs: two novel MAD-related genes selectively inducible by flow in human vascular endothelium 总被引:2,自引:0,他引:2
JN Topper J Cai Y Qiu KR Anderson YY Xu JD Deeds R Feeley CJ Gimeno EA Woolf O Tayber GG Mays BA Sampson FJ Schoen MA Gimbrone D Falb 《Canadian Metallurgical Quarterly》1997,94(17):9314-9319
Vascular endothelium is an important transducer and integrator of both humoral and biomechanical stimuli within the cardiovascular system. Utilizing a differential display approach, we have identified two genes, Smad6 and Smad7, encoding members of the MAD-related family of molecules, selectively induced in cultured human vascular endothelial cells by steady laminar shear stress, a physiologic fluid mechanical stimulus. MAD-related proteins are a recently identified family of intracellular proteins that are thought to be essential components in the signaling pathways of the serine/threonine kinase receptors of the transforming growth factor beta superfamily. Smad6 and Smad7 possess unique structural features (compared with previously described MADs), and they can physically interact with each other, and, in the case of Smad6, with other known human MAD species, in endothelial cells. Transient expression of Smad6 or Smad7 in vascular endothelial cells inhibits the activation of a transfected reporter gene in response to both TGF-beta and fluid mechanical stimulation. Both Smad6 and Smad7 exhibit a selective pattern of expression in human vascular endothelium in vivo as detected by immunohistochemistry and in situ hybridization. Thus, Smad6 and Smad7 constitute a novel class of MAD-related proteins, termed vascular MADs, that are induced by fluid mechanical forces and can modulate gene expression in response to both humoral and biomechanical stimulation in vascular endothelium. 相似文献
89.
90.
AL Okorokov KI Panov WA Offen VG Mukhortov AA Antson Karpeisky MYa AJ Wilkinson GG Dodson 《Canadian Metallurgical Quarterly》1997,10(3):273-278
We have developed a model of ischaemia-reperfusion injury in C57BL/6 mice involving ischaemia for 0.5 to 2.5 h with an elastic tourniquet on one hind limb and reperfusion for 24 h, analogous to a well-established model of ischaemia-reperfusion injury in the rat. Viability was assessed in tissue homogenates of the gastrocnemius muscles from the affected and contralateral control limb by a triphenyl tetrazolium chloride dye reaction, measuring the activity of the oxidative mitochondrial enzymes. After 1.5 h ischaemia and 24 h reperfusion, viability in the ischaemic-reperfused limb was 13%, with the control muscle regarded as 100% viable. Significant improvements in viability to 86% (P < 0.05) and 56% (P < 0.05) were achieved, with administration 30 min prior to tourniquet release, of the nitric oxide (NO) synthase inhibitor nitro-L-arginine methyl ester (L-NAME, 30 mg/kg) and the anti-inflammatory glucocorticoid dexamethasone (2.5 mg/kg) respectively, with similar findings in the rat tourniquet model. 相似文献