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排序方式: 共有3611条查询结果,搜索用时 31 毫秒
81.
82.
In search for new antitumor agents, twelve 6-aziridinylbenzimidazole derivatives were synthesized and their cytotoxicities were tested against three cancer cell lines (mouse lymphocytic leukemia P388 and B16, and human gastric carcinoma SNU-16). From 4-amino-3-nitrotoluene as the starting material, 2-(acetoxymethyl)benzimidazoles (5a-d) were obtained by Phillips reaction. These benzimidazoles were then reacted with Fremy's salt to give a mixture of three 2-(acetoxymethyl) (8a-c) and four 2-(hydroxymethyl)benzimidazole-4,7-diones (9a-d). Addition of these quinones with aziridine afforded 6-aziridinyl-2-(acetoxymethyl) (10a-c) and 6-aziridinyl-2-(hydroxymethyl)benzimidazole-4,7-diones (11a-d). Utilizing 2-(hydroxymethyl)benzimidazole-4,7-diones (9b,d), esters 10d and 13e-h were prepared by the sequential reactions of esterification and addition. The synthesized compounds show potent cytotoxicity against all of three cell lines tested. The cytotoxicities of 10a-d or 11a-d against SNU-16 were superior to those of 13e-h, and were equal to or slightly higher than that of mitomycin C. Compounds 11a-d were slightly more cytotoxic than 10a-d in all cell lines tested. 相似文献
83.
84.
TA Woolsey CM Rovainen SB Cox MH Henegar GE Liang D Liu YE Moskalenko J Sui L Wei 《Canadian Metallurgical Quarterly》1996,6(5):647-660
How neuronal activity changes cerebral blood flow is of biological and practical importance. The rodent whisker-barrel system has special merits as a model for studies of changes in local cerebral blood flow (LCBF). Stimulus-evoked changes in neural firing and 'intrinsic signals' recorded through a cranial window were used to define regions of interest for repeated flow measurements. Whisker-activated changes in flow were measured with intravascular markers at the pia. LCBF changes were always prompt and localized over the appropriate barrel. Stimulus-related changes in parenchymal flow monitored continuously with H2 electrodes recorded short latency flow changes initiated in middle cortical layers. Activation that increased flow to particular barrels often led to reduced flow to adjacent cortex. Dye was injected into single penetrating arterioles from the pia of the fixed brain and injected into arterioles in slices of cortex where barrels were evident without stains. Arteriolar and venular domains at the surface were not directly related to underlying barrels. Capillary tufts in layer IV were mainly coincident with barrels. The matching between a capillary plexus (a vascular module) and a barrel (a functional neuronal unit) is a spatial organization of neurons and blood vessels that optimizes local interactions between the two. The paths of communication probably include: neurons to neurons, neurons to glia, neurons to vessels, glia to vessels, vessels to vessels and vessels to brain. Matching a functional grouping of neurons with a vascular module is an elegant means of reducing the risk of embarrassment for energy-expensive neuronal activity (ion pumping) while minimizing energy spent for delivery of the energy (cardiac output). For imaging studies this organization sets biological limits to spatial, temporal and magnitude resolution. Reduced flow to nearby inactive cortex enhances local differences. 相似文献
85.
R Kneen NG Pham T Solomon TM Tran TT Nguyen BL Tran J Wain NP Day TH Tran CM Parry NJ White 《Canadian Metallurgical Quarterly》1998,27(4):845-850
PURPOSE: To review the University of Florida experience in treating ependymomas, analyze prognostic factors, and provide treatment recommendations. METHODS AND MATERIALS: Forty-one patients with ependymoma and no metastases outside the central nervous system received postoperative radiotherapy with curative intent between 1966 and 1989. Ten patients had supratentorial lesions, 22 had infratentorial lesions, and 9 had spinal cord lesions. All patients had surgery (stereotactic biopsy, subtotal resection, or gross total resection). Most patients with high-grade lesions received radiotherapy to the craniospinal axis. Low-grade intracranial lesions received more limited treatment. Spinal cord lesions were treated using either partial spine or whole spine fields. RESULTS: Of 32 intracranial tumors, 21 recurred, all at the primary site; no spinal cord tumors recurred. Overall 10-year survival rates were 51% (absolute) and 46% (relapse-free); by tumor site: spinal cord, 100%; infratentorial, 45%; supratentorial, 20% (p = 0.002). On multivariate analysis, tumor site was the only factor that influenced absolute survival (p = 0.0004); other factors evaluated included grade, gender, age, duration of symptoms, resection extent, primary tumor dose, treatment field extent, surgery-to-radiotherapy interval, and days under radiotherapy treatment. CONCLUSIONS: Patients with supratentorial or infratentorial tumors receive irradiation, regardless of grade. Craniospinal-axis fields are used when spinal seeding is radiographically or pathologically evident. Spinal cord tumors are treated using localized fields to the primary site if not completely resected. Failure to control disease at the primary site remains the main impediment to cure. 相似文献
86.
Except for subjective clinical criteria, there is no formal definition of distal radius fracture instability in the literature. The purposes of this ex vivo biomechanical study were (1) to provide an objective mechanical definition of fracture instability and (2) to demonstrate a noninvasive method that allows for direct measurement of instability. The following 3 questions are addressed: (1) Can the stability of distal radius fractures be measured using computed tomography (CT)? (2) Are the stability measurements reproducible? (3) How does external fixation change stability? A CT technique is described that was used to measure displacement of fracture fragments and measure the compliance of ex vivo distal radius fractures before and after external fixation. Validation studies of the CT technique revealed a mean coefficient of variation of 0.38. There was a linear relationship between measured and known displacements for all 3 orthogonal planes (coefficient of determination 0.99; p < .01). There was significant fracture displacement with loads as small as 20 N. The slope of the load-displacement curve (structural compliance) provided a quantitative measure of fracture instability. Fracture compliance decreased up to 69% after application of an external fixator. 相似文献
87.
S Bergamaschi F Battaini M Trabucchi M Parenti CM Lopez S Govoni 《Canadian Metallurgical Quarterly》1995,12(6):497-503
The effect of prolonged (72 h) ethanol (200 mM) exposure on the labeling of L-type (using tritiated PN 200-110) and N-type (using iodinated omega-conotoxin) voltage-dependent calcium channels was investigated in cultured NG 108-15 cells. In undifferentiated cells ethanol produced an 80% increase in PN 200-110 Bmax and no changes in omega-conotoxin binding. Differentiation had a profound effect on the response of cells to ethanol, which in differentiated neuron-like cells decreased omega-conotoxin binding (-53.5%) leaving PN 200-110 labeling of L-type channels unaffected. The effect was time dependent and reversible upon ethanol withdrawal. The decreased omega-conotoxin binding was accompanied by a reduced ability of omega-conotoxin to inhibit K+ -stimulated calcium uptake. The results demonstrate that in cultured NG 108-15 cells ethanol differentially affects DHP and omega-conotoxin-sensitive, voltage-dependent calcium channels and that the effect is also modulated by differentiation of the cell to a neuronal phenotype. 相似文献
88.
89.
D Matecka RB Rothman L Radesca BR de Costa CM Dersch JS Partilla A Pert JR Glowa FH Wojnicki KC Rice 《Canadian Metallurgical Quarterly》1996,39(24):4704-4716
The design, synthesis, and biological evaluation of compounds related to the dopamine (DA) uptake inhibitors: 1-[2-(diphenylmethoxy)ethyl]-4-(3-phenylpropyl)piperazine (1) and 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (2) (GBR 12395 and GBR 12909, respectively), directed toward the development and identification of new ligands interacting with high potency and selectivity at the dopamine transporter (DAT) is reported. The substitution of the piperazine ring in the GBR structure with other diamine moieties resulted in the retention of the high affinity of new ligands for the DAT. Some of the modified GBR analogs (e.g. 8, 10, (-)-49, or (-)-50) displayed substantially higher selectivity (4736- to 693-fold) for the dopamine (DA) versus the serotonin (5HT) reuptake site than the parent compounds. The bis(p-fluoro) substitution in the (diphenylmethoxy)ethyl fragment slightly increased the affinity of the ligands at the DA reuptake site but reduced their selectivity at this site (e.g. 9 and 8, 11 and 10, or 17 and 16, respectively). Congeners, such as the series of monosubstituted and symmetrically disubstituted piperazines and trans-2,5-dimethylpiperazines, which lack the (diphenylmethoxy)ethyl substituent lost the affinity for the DAT yet exhibited very high potency for binding to the sigma receptors (e.g.28). The chiral pyrrolidine derivatives of 1, (-)-49, and (+)-49, exhibited an enantioselectivity ratio of 181 and 146 for the inhibition of DA reuptake and binding to the DAT, respectively. 相似文献
90.
N Reinisch S Kiechl C Mayr P Schratzberger S Dunzendorfer CM K?hler T Buratti J Willeit CJ Wiedermann 《Canadian Metallurgical Quarterly》1998,28(10):787-792
BACKGROUND: In atherosclerosis, both reductions and elevations in plasma levels of antioxidants have been reported. This study investigated total antioxidant capacity of plasma from subjects with atherosclerotic disease. MATERIALS AND METHODS: The study population consisted of 48 men with or without carotid atherosclerosis. At baseline (1990) carotid arteries were evaluated by duplex sonography and plasma samples were obtained for testing antioxidant capacity by two different test systems. One assay system used neutrophils from healthy volunteers as a source of oxygen free radicals activating the non-fluorescent dichlorofluorescin diacetate in the presence of antioxidant containing plasma from study subjects. In the other test system, total plasma antioxidants were detected colorimetrically by using 2,2'-azino-di-(3-ethylbenzthiazoline sulphonate), metmyoglobin and superoxide in the presence of plasma. Carotid arteries were re-evaluated for the development of new plaques 5 years later (1995). RESULTS: Increased baseline total antioxidant capacity of plasma was significantly associated with the development of new atherosclerotic lesions during a period of 5 years. CONCLUSIONS: Endogenous antioxidant capacity of plasma is increased in patients with active atherosclerotic disease. As scavenging of oxygen free radicals is thought to protect from atherogenesis, elevated antioxidative capacity may represent an adaptive mechanism. 相似文献