Assessment of the mutagenicity of dichloroacetic acid in lacI transgenic B6C3F1 mouse liver

Dichloroacetic acid (DCA) is a chlorination byproduct found in finished drinking water. When administered in drinking water this chemical has been shown to produce hepatocellular adenomas and carcinomas in B6C3F1 mice over the animal's lifetime. In this study, we investigated whether mutant frequencies were increased in mouse liver using treatment protocols that yielded significant tumor induction. DCA was administered continuously at either 1.0 or 3.5 g/l in drinking water to male transgenic B6C3F1 mice harboring the bacterial lacI gene. Groups of five or six animals were killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of treatment, there was no significant difference in mutant frequency between the treated and control animals at either dose level. At 60 weeks, mice treated with 1.0 g/l DCA showed a 1.3-fold increase in mutant frequency over concurrent controls (P = 0.05). Mice treated with 3.5 g/l DCA for 60 weeks had a 2.3-fold increase in mutant frequency over the concurrent controls (P = 0.002). The mutation spectrum recovered from mice treated with 3.5 g/l DCA for 60 weeks contained G:C-->A:T transitions (32.79%) and G:C-->T:A transversions (21.31%). In contrast, G:C-->A:T transitions comprised 53.19% of the recovered mutants among control animals. Although only 19.15% of mutations among the controls were at T:A sites, 32.79% of the mutations from DCA-treated animals were at T:A sites. This is consistent with the previous observation that the proportion of mutations at T:A sites in codon 61 of the H-ras gene was increased in DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates DCA-associated mutagenicity in the mouse liver under conditions in which DCA produces hepatic tumors.      

Identification of differentially expressed genes in aflatoxin B1- treated cultured primary rat hepatocytes and Fischer 344 rats

Aflatoxin B1 (AFB1), a mutagen and hepatocarcinogen in rats and humans, is a contaminant of the human food supply, particularly in parts of Africa and Asia. AFB1-induced changes in gene expression may play a part in the development of the toxic, immunosuppressive and carcinogenic properties of this fungal metabolite. An understanding of the-role of AFB1 in modulating gene regulation should provide insight regarding mechanisms of AFB1-induced carcinogenesis. We used three PCR- based subtractive techniques to identify AFB1-responsive genes in cultured primary rat hepatocyte RNA: differential display PCR (DD-PCR), representational difference analysis (RDA) and suppression subtractive hybridization (SSH). Each of the three techniques identified AFB1- responsive genes, although no individual cDNA was isolated by more than one technique. Nine cDNAs isolated using DD-PCR, RDA or SSH were found to represent eight genes that are differentially expressed as a result of AFB1 exposure. Genes whose mRNA levels were increased in cultured primary rat hepatocytes after AFB1 treatment were corticosteroid binding globulin (CBG), cytochrome P450 4F1 (CYP4F1), alpha-2 microglobulin, C4b-binding protein (C4BP), serum amyloid A-2 and glutathione S-transferase Yb2 (GST). Transferrin and a small CYP3A-like cDNA had reduced mRNA levels after AFB1 exposure. Full-length CYP3A mRNA levels were increased. When liver RNA from AFB1-treated male F344 rats was evaluated for transferrin, CBG, GST, CYP3A and CYP4F1 expression, a decrease in transferrin mRNA and an increase in CBG, GST, CYP3A and CYP4F1 mRNA levels was also seen. Analysis of the potential function of these genes in maintaining cellular homeostasis suggests that their differential expression could contribute to the toxicity associated with AFB1 exposure.      

Total elbow arthroplasty is moving forward: Review on past,present and future

The elbow joint is a complex joint, which, when impaired in function, leads to severe disability. In some cases however, an arthroplasty might be an appropriate treatment. In the past four decades, large steps havebeen taken to optimize this treatment in order to achieve better post-operative outcomes. To understand these progresses and to discover aspects for upcoming improvements, we present a review on the past developments, the present state of affairs and future developments which may improve patient care further.     

Crossreaction of monoclonal Anti-T-cell antibodies: Implications for classifying B-cell leukemias

Summary Cell samples from 62 patients with B-cell leukemias (33 CLL, 8 IC, 6 PLL, 4 HCL, 2 ALL and 9 other NHL) were tested with a series of monoclonal antibodies (A50, T101, Lyt2, Leu1, M203) directed against T cells and shown to crossreact with B-CLL. The results demonstrate a heterogeneity of B-cell leukemias as all typical cases of CLL were reactive whereas most other cases were negative. Using the fluorescence-activated cell sorter, a somewhat stronger reaction was seen in early or benign cases of CLL, compared to advanced cases. All B-cell leukemias tested expressed the Ia antigen.     

Enhancement of chemotactic factor-stimulated neutrophil oxidative metabolism by leukotriene B4

Leukotriene B4 (LTB4) is a potent primary stimulator of neutrophil chemotaxis, aggregation, and degranulation and induces superoxide production at higher concentrations. In order to determine whether LTB4 modulates neutrophil responses to oxidative stimuli, human neutrophils (PMNs) were incubated with LTB4 prior to stimulation with f-Met-Leu-Phe (fMLP, 10(-7) mol/L), opsonized zymosan (OZ, 250 micrograms/mL), or phorbol myristate acetate (PMA, 32 nmol/L). Superoxide (O2-) production by stimulated PMNs was assessed by the superoxide dismutase-inhibitable reduction of cytochrome c. LTB4 alone did not stimulate O2- production in concentrations below 10(-7) mol/L and had no effect on the O2- assay. In the concentration range of 10(-12) to 10(-8) mol/L, LTB4 did not alter O2- release induced by OZ or PMA. In contrast, LTB4-treated cells demonstrated enhanced O2- production following exposure to fMLP, and in the presence of 10 nmol/LLTB4, generated 180% +/- 41% of O-2 quantities produced by control cells (n = 23). Enhancement was LTB4 dose-dependent, was maximal in the range of 1 to 10 nmol/L LTB4, was not reversed by removal of the lipid from the medium prior to fMLP stimulation, and was not dependent on the presence of Ca++ or Mg++ in the suspending medium. Chemiluminescence of fMLP-stimulated neutrophils was increased to 323% of controls in neutrophils preincubated with 10 nmol/L LTB4. Unlike augmentation of oxidative responses to fMLP seen with other degranulating stimuli, enhancement by LTB4 was not correlated with an increase in 3H-fMLP receptor binding. These results indicate that, in addition to its primary effects on neutrophil function, LTB4 modulates PMN oxidative responses to the chemotactic peptide and, thus, may amplify the release of oxygen metabolites at inflammatory foci.