Effects of commercial chlorophenolate, 2,3,7,8-TCDD,and pure phenoxyacetic acids on hepatic peroxisome proliferation,xenobiotic metabolism and sister chromatid exchange in the rat

The induction of hepatic peroxisome proliferation and drug metabolizing enzymes and of sister chromatid exchange (SCE) in lymphocytes was studied in male Han/Wistar rats after exposing them for 2 weeks to a commercial chlorophenolate formulation (Ky-5) (100mg/kg/ day), to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD; 0.05–5 g/kg/wk) and to the pure phenoxyacetic acids, 2,4-dichlorophenoxyacetic acid (2,4-D; 100 mg/kg/day) and 2-chloro-4-methylphenoxyacetic acid (MCPA; 100 mg/kg/day). The chlorophenolate formulation and pure 2,4-D and MCPA caused significant increases in the number of peroxisomes in liver cells, although the average size of peroxisomes was not affected, whereas the effect of even the highest dose of 2,3,7,8-TCDD remained small. This finding indicates that dioxin impurities do not account for the peroxisome proliferation induced by chlorophenolate. The relative weight of the liver increased significantly in rats treated with the chlorophenolate formulation and with 2,3,7,8-TCDD (5.0 and 0.5 g/kg). The pattern of induction of xenobiotic metabolizing enzymes showed some differences between chlorophenolate treatment and 2,3,7,8-TCDD treatment. Furthermore, the effects of pure phenoxyacetic acids were different from that seen with chlorophenolate and 2,3,7,8-TCDD. The highest dose of 2,3,7,8-TCDD increased the frequency of SCE in circulating lymphocytes slightly, but significantly.     

Immunochemical characterization of cytochrome P-450 isozymes responsible for benzene oxidation in the rat liver

The contribution of cytochrome P-450 isozymes to benzene metabolismin liver microsomes from fed, fasted, pyrazole-, pbenobarbital(PB)- and ethanol-treated rats and in respective isocaloriccontrols was investigated using monoclonal antibodies (mAbs).Clone 1-7-1 mAb did not inhibit benzene metabolism, whereasclone 2-66-3 inhibited only in PB-induced microsomes at a highconcentration of benzene (6.26 mM), and clone 1-91-3 mAb inhibitedbenzene metabolism in all cases. The degree of inhibition wasas follows: fed isocaloric control PB < fasted < pyrazole ethanol. The pattern of inhibition was similar with clone 1-91-3for low (0.23 mM) and high concentrations of benzene, exceptin PB-induced mkrosomes. Western blot analysis showed that clone1-7-1 mAb did not bind any liver mkrosomal protein in the regionof cytochrome P-450s, whereas with clone 2-66-3 a clear-cutband was seen only in liver microsomes from PB-treated rats,with clone 1-98-1, a band was detected in mkrosomes from alltreated groups, in the following order: PB = isocaloric control< fed < fasted < pyrazole < ethanol. These resultsindicate that (i) cytochromes P-450b,e and P-450J contributeto benzene metabolism in rat liver; (ii) the former has a lowaffinity to benzene and is induced by PB; and (iii) P-450J hasa high affinity to benzene and is induced by 1-day fasting,pyrazole and ethanol, but decreased by PB treatment.     

Ethical challenges in surgery as narrated by practicing surgeons

Background  

The aim of this study was to explore the ethical challenges in surgery from the surgeons' point of view and their experience of being in ethically difficult situations.     

Expression of bcl-6 and CD10 protein is associated with longer overall survival and time to treatment failure in follicular lymphoma

Follicular lymphomas (FLs) are a heterogeneous group of tumors, but prognostic factors are evaluated insufficiently in this common hematologic neoplasm. While bcl-6 and CD10 are expressed characteristically in FLs, their significance for biologic behavior of FL has not been studied previously. Samples from 73 patients with FL and clinical follow-up from 7 to 231 months were evaluated by immunohistochemical analysis. Patients with high levels of bcl-6 expression had favorable overall survival (OS) (P = .003), disease-specific survival (DSS) (P = .033), and time to treatment failure (P = .003) compared with patients with low levels of bcl-6 expression. Multivariate analysis showed that the results for OS, DSS, and time to treatment failure were independent of the international prognostic index. Patients with CD10+ FLs also had longer OS (P = .001), DSS (P = .007), and time to treatment failure (P = .004), and grade 1 FL was associated with better OS (P = .01) and a statistical trend for longer DSS (P = .05) and time to treatment failure (P = .05), but these results were not independent of bcl-6 expression or the international prognostic index in multivariate analysis.     

CDK4 is a probable target gene in a novel amplicon at 12q13.3-q14.1 in lung cancer

Several chromosomal regions are recurrently amplified or deleted in lung tumors, but little is known about the underlying genes, which could be important mediators in tumor formation or progression. In lung cancer, the RB1-CCND1-CDKN2A pathway, involved in the G1-S transition, is damaged in nearly all tumors. In the present study, we localized a novel amplicon in lung tumors to a fragment of less than 0.5 Mb at 12q13.3-q14.1 by using comparative genomic hybridization (CGH) on cDNA microarrays. This approach enabled us to identify 10-15 genes with the most consistent amplifications. Semiquantitative RT-PCR analyses of 13 genes in this region showed that four of them (CDK4, CYP27B1, METTL1, and TSFM) were also highly up-regulated. Immunohistochemical (IHC) analysis of 141 tumor samples on a tissue microarray showed that CDK4 was expressed at a high level in 23% of lung tumors. Six (21.4%) of the tumors with high CDK4 expression (n = 28) were shown by fluorescence in situ hybridization (FISH) to contain the 12q13.3-q14.1 amplification. For CDK4, a positive correlation was found between gene copy number (FISH and CGH array), mRNA expression (RT-PCR), and level of protein expression (IHC). CDK4 expression did not correlate with CDKN2A methylation status. Amplification of CDK4 has been described in other tumor types, but its role in lung cancer remains to be elucidated. Although CDK4 amplification seems to be a relatively rare event (4.3%) in lung tumors, it indicates the significance of the RB1-CCND1 pathway in lung tumorigenesis.     

A mouse model for alpha-methylacyl-CoA racemase deficiency: adjustment of bile acid synthesis and intolerance to dietary methyl-branched lipids

alpha-Methylacyl-CoA racemase (Amacr) deficiency in humans leads to sensory motor neuronal and liver abnormalities. The disorder is recessively inherited and caused by mutations in the AMACR gene, which encodes Amacr, an enzyme presumed to be essential for bile acid synthesis and to participate in the degradation of methyl-branched fatty acids. To generate a model to study the pathophysiology in Amacr deficiency we inactivated the mouse Amacr gene. As per human Amacr deficiency, the Amacr(-/-) mice showed accumulation (44-fold) of C27 bile acid precursors and decreased (over 50%) primary (C24) bile acids in bile, serum and liver, however the Amacr(-/-) mice were clinically symptomless. Real-time quantitative PCR analysis showed that, among other responses, the level of mRNA for peroxisomal multifunctional enzyme type 1 (pMFE-1) was increased 3-fold in Amacr(-/-) mice. This enzyme can be placed, together with CYP3A11 and CYP46A1, to make an Amacr-independent pathway for the generation of C24 bile acids. Exposure of Amacr(-/-) mice to a diet supplemented with phytol, a source for branched-chain fatty acids, triggered the development of a disease state with liver manifestations, redefining the physiological significance of Amacr. Amacr is indispensable for the detoxification of dietary methyl-branched lipids and, although it contributes normally to bile acid synthesis from cholesterol, the putative pMFE-1-mediated cholesterol degradation can provide for generation of bile acids, allowing survival without Amacr. Based upon our mouse model, we propose elimination of phytol from the diet of patients suffering from Amacr deficiency.