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91.
92.
During recent years, ceramide has received a lot of attention as a possible mediator of the cellular responses to a variety of apoptotic stimuli. In a manner analogous to generation of its sibling diacylglycerol, ceramide is generated by a phospholipase-C-type reaction from its lipid precursor sphingomyelin. Two observations led to the proposal that ceramide plays a role in apoptosis: (1) treatment of cells with tumor necrosis factor or other inducers of apoptosis leads to activation of sphingomyelinases and to an increase in cellular ceramide levels; (2) ectopic generation or administration of ceramide can mimic apoptotic cell death. Recently, several observations have challenged the notion that ceramide is an important cell-death mediator and have prompted a re-evaluation of previously published results. 相似文献
93.
NS Silverman MW Sullivan DL Jungkind V Weinblatt K Beavis RJ Wapner 《Canadian Metallurgical Quarterly》1994,84(6):1021-1024
OBJECTIVE: To assess the frequency of transient bacteremia among women undergoing transabdominal and transcervical chorionic villus sampling (CVS). METHODS: One hundred fourteen women undergoing CVS consented to participate in a university review board-approved study protocol. Exclusion criteria included known cardiac valve anomaly or replacement (or other prosthetic) and antibiotic use within the preceding 21 days. Blood cultures (aerobic and anaerobic) were drawn by a single operator on all patients, before CVS and within 15 minutes after completing CVS. Either the catheter tip or needle tip aspirate from each procedure was also sent for culture. RESULTS: Post-procedure bacteremia was detected in two (1.8%) of the patients undergoing CVS. These two patients both had their procedures performed transcervically, resulting in a 4.1% (two of 49) bacteremia rate after transcervical CVS, compared to none (zero of 65) in the transabdominal group (P = .36). The incidence of positive cultures from sampling instruments was also higher in the transcervical group (16.3 versus 0%; P = .003), but did not result in comparable rates of bacteremia among patients with positive instrument cultures. CONCLUSIONS: In this study, CVS was associated with a low rate of bacteremia, regardless of the procedure route. Recommendations for antibiotic prophylaxis in women with abnormal cardiac valves should parallel those for spontaneous vaginal delivery and other comparable genitourinary procedures. 相似文献
94.
Mutations in the p53 gene, which codes for a cell division regulatory protein, have been identified in approximately one-third of adult astrocytomas. We evaluated 35 astrocytic tumors (17 pilocytic, 4 diffuse low grade, 12 anaplastic, and 2 glioblastoma) in pediatric patients for p53 mutations, using polymerase chain reaction-single-stranded conformation polymorphism analysis as a screening technique. Additionally, those tumors identified with homozygosity in the area of the p53 gene on chromosome 17 by Southern blotting were sequenced to look for p53 mutations. No tumors were identified with polymerase chain reaction-single-stranded conformation polymorphism analysis shifts indicative of mutations in the p53 gene. Five of 21 tumors were homozygous in the region of the p53 gene on chromosome 17; no mutations in exons 5 to 8 were found in any of these tumors. The frequency of p53 mutation in pediatric astrocytomas is significantly less than the frequency for adult tumors, regardless of tumor grade. Furthermore, the frequency of p53 mutations in high-grade astrocytomas is significantly lower in pediatric tumors than in adult tumors. These results suggest that p53 is not important in the oncogenesis of pediatric astrocytomas. Oncogenesis in pediatric astrocytomas may occur by different mechanisms than those of similar tumors in adults. 相似文献
95.
AP Sandhu RP Symonds AG Robertson NS Reed SG McNee J Paul 《Canadian Metallurgical Quarterly》1998,40(3):575-581
BACKGROUND: The Quebec Neuroblastoma Screening (QNS) Project completed a 5-year program for measuring urinary vanillylmandelic acid (VMA)/homovanillic acid (HVA) levels at age 3 weeks and/or 6 months in 89% of 476,603 Quebec-born infants from 1989-1994; 45 screening positive preclinical cases (S-positive cases) and 20 congenital/neonatal (C/N) cases were identified. As of April 1997, an additional 59 cases in the same birth cohort were diagnosed clinically; these neuroblastomas developed after screening verified normal VMA/HVA levels (S-negative cases). METHODS: Pathology specimens from 45 of 59 S-negative cases were reviewed centrally and classified according to the Shimada system. Results were compared with clinical data and also with S-positive and C/N cases. RESULTS: Of 45 S-negative cases, 27 tumors had favorable histology (FH) and 18 had unfavorable histology (UH). Approximately 52% of FH tumors were diagnosed before age 1 year, whereas UH tumors were nearly exclusively (94%) diagnosed after age 1 year (P < 0.01). Approximately 89% of FH tumors were Stage I, II, or IV-S, whereas 72% UH tumors were Stage III or IV (P < 0.001). All children with FH tumors were alive at last follow-up (range of follow-up period: 9-79 months; median, 35 months), whereas 8 children with UH tumors died of disease even after limited follow-up (range of follow-up period: 0-60 months; median, 20 months). By contrast, S-positive and C/N cases were predominantly (97%) FH tumors, often (76%) Stage I, II, or IV-S, with excellent clinical outcome (survival rate of 98%). CONCLUSIONS: The majority of the UH neuroblastomas that developed in the birth cohort of the QNS Project were included in the group of S-negative cases and could not be detected by the screening at age 3 weeks and/or 6 months. 相似文献
96.
CJ Perrons JD Fox SB Lucas NS Brink RS Tedder RF Miller 《Canadian Metallurgical Quarterly》1996,32(3):205-209
Characterization of the region between HLA-B and the TNF loci in the human MHC revealed the presence of duplicated loci, named CL1 and CL2, that included repeat sequences. Development and use of a PCR typing methodology that amplified both CL microsatellites simultaneously indicated that PCR product patterns analysed on native agarose gels were allelic (Abraham et al., 1992). The purpose of the current study was to determine the molecular explanation for the unique patterns achieved. Sequence analysis of the CL1 locus from 32 chromosomes representing 10 ancestral haplotypes indicated that six alleles were present. The CL microsatellites also provided an opportunity to study the evolutionary relationships between MHC haplotypes from different racial groups. Sequence comparison of closely related ancestral haplotypes from different racial groups suggested that the CL1 microsatellite has not changed in the period since divergence. 相似文献
97.
BACKGROUND/AIMS: The number of perisinusoidal myofibroblasts has been shown to be increased in hepatocellular carcinoma, as compared to cirrhosis. This increase might suggest a cooperative relationship between tumour cells and myofibroblasts. To assess this relationship, we undertook: (a) an immunohistochemical study to confirm the existence of an increased number of perisinusoidal myofibroblasts in human hepatocellular carcinoma, as compared to cirrhosis with or without liver cell dysplasia, (b) an in vitro study testing the role of normal or tumoral human hepatocytes in myofibroblast proliferation. METHODS: Forty explanted cirrhotic livers, including 14 with hepatocellular carcinoma and 24 with liver cell dysplasia, were studied. Myofibroblasts were detected by immunohistochemistry using an antibody directed against alpha-smooth muscle actin. Hepatic myofibroblasts in culture were obtained by outgrowth from human liver explants. RESULTS: There was a progressive increase in the number of perisinusoidal myofibroblasts, from cirrhotic nodules without dysplasia to liver cell dysplasia and hepatocellular carcinoma. Conditioned medium from isolated normal human hepatocytes had only minor mitogenic effects on myofibroblasts, as assessed by measuring DNA synthesis and cell growth. In contrast, conditioned medium from a human hepatoma cell line (HepG2 cells) markedly stimulated the proliferation of human myofibroblasts. This mitogenic activity was stored in HepG2 cells and secreted in the extracellular medium rather than being simply released following cell lysis. CONCLUSIONS: These results suggest that the increased number of myofibroblasts in hepatocellular carcinoma might be due to a paracrine mechanism involving soluble mitogenic factor(s) secreted by tumour cells. 相似文献
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100.
FA Atik GJ Lopes Filho Mde M Linhares J Seda Neto NS Mansur 《Canadian Metallurgical Quarterly》1998,116(4):1781-1783
The authors report a case of a 25 year old Brazilian man with a history of crampy abdominal pain in the left iliac fossa for 2 weeks, abdominal distention, mucous diarrhea and anorexia. The patient presented signs of hemodynamic instability and a hard mass palpated in the left iliac fossa presented peritoneal irritation. At laparotomy, fecal peritonitis and a punched-out perforation of the midsigmoid colon were found. A left hemicolectomy was performed with terminal colostomy. Specimen examination revealed a thickened rectosigmoid wall, narrow lumen and multiple mucosal polyps. Microscopically, chronic granulomatous colitis with Schistosoma mansoni eggs confirmed the etiology. To the authors' knowledge, this is the first case of obstruction complicated with perforation due to mansoni schistosomiasis reported in the literature. 相似文献