Genetic toxicology testing of Di(2-ethylhexyl) terephthalate

Di(2-ethylhexyl) terephthalate (DEHT) is a commercially produced chemical (Kodaflex® DOTP) that is used as a general purpose, low-volatility plasticizer for polyvinyl chloride and other polymeric materials. Less than 30 million kilograms of DEHT are produced annually. DEHT is isomeric with di(2-ethylhexyl) phthalate (DEHP), a nongenotoxic rodent carcinogen whose mode of action has been suggested to derive from its ability to produce hepatocellular proliferation and/or hepatic peroxisome proliferation. Thus it is important to know the behavior of DEHT in genotoxicity assays in order to compare it with that of DEHP and other phthalate ester plasticizers. It is known from previously published studies that rats fed DEHT in the diet at 2,000 mg/kg produce urine that is negative in the Ames Salmonella bacterial mutagenicity assay in the presence and absence of induced rat liver S-9 and in the presence and obsence of β-glucuronidase/aryl sulfatase. Reported here are the results of direct testing of DEHT in the Ames plate incorporation assay, the Chinese hamster ovary/hypoxanthine guanine phosphoribosyl transferase (CHO/HGPRT) in vitro mammalian cell mutagenicity assay, and an in vitro chromosome aberrations assay using CHO cells. The results for mono(ethylhexyl) terephthalate (MEHT), a metabolite of DEHT, in the Ames Salmonella bacterial mutagenicity assay are also presented. All test results for both DEHT and MEHT were found to be negative, and it is therefore concluded that DEHT, like its isomeric relative DEHP, is not genotoxic. © 1994 Wiley-Liss, Inc.     

Biochemical characterization of I-Ak proteins from mutant antigen-presenting B-cell--B-lymphoma hybridomas

Chemically induced mutants of an I-Ak,d expressing antigen-presenting B-cell--B-lymphoma hybridoma have recently been generated by immunoselection in vitro and were found to possess alterations in some of their serologically and functionally defined I-Ak region dependent functions. In order to identify at the structural level the origin of the differences in serological and functional properties of these mutants, I-Ak molecules from several of these mutant hybridomas were compared biochemically to wild-type I-Ak polypeptides by two-dimensional gel electrophoresis and high-pressure liquid chromatographic tryptic peptide analyses. Two-dimensional gel electrophoresis indicated that no major structural alterations, resulting in changes in mol. wt or charge, had occurred in the Ak alpha or Ak beta polypeptides from the mutant cells. Likewise, Ak alpha peptide maps of the mutants were indistinguishable from the normal Ak alpha peptide maps. However, two of the three mutants studied did exhibit one additional peptide in their Ak beta peptide maps. These results suggest that the major deficiencies in T-cell-activating functions of these mutants are a result of a limited alteration in the Ak beta polypeptide primary structure.     

氟吗啉诱发V79和CHL细胞基因突变和染色体畸变的研究

目的 探讨氟吗啉的致突变性。方法 首先测定氟吗啉对V79和CHL的细胞毒性，然后在非代谢活化和代谢活化条件下，进行氟吗啉诱发V79细胞HGPRT基因突变试验和CHL细胞染色体畸变试验。结果 以氟吗啉500、100、20和4μg/mL浓度处理V79细胞，处理组诱变率与阴性对照组突变率比较，差异无显著性(P≥0．05)；以500、250、125和62．5μg／mL浓度处理CHL细胞24、48h后，在非代谢活化条件下，处理组染色体畸变均小于5％，但在代谢活化条件下，处理组染色体畸变率均大于5％，而且呈剂量．反应关系，通过G-显带发现断裂集中发生于4q上，是断裂热点。结论 可以认为应用氟吗啉100～200mg／L防治植物病害不会对人类健康造成危害，但是职业人群应注意防护。     

Treatment of Lesch–Nyhan disease with S-adenosylmethionine: Experience with five young Malaysians,including a girl

Background: Lesch–Nyhan disease (LND) is a rare X-linked recessive neurogenetic disorder caused by deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8) which is responsible for recycling purine bases into purine nucleotides. Affected individuals have hyperuricemia leading to gout and urolithiasis, accompanied by a characteristic severe neurobehavioural phenotype with compulsive self-mutilation, extrapyramidal motor disturbances and cognitive impairment. Aim: For its theoretical therapeutic potential to replenish the brain purine nucleotide pool, oral supplementation with S-adenosylmethionine (SAMe) was trialed in 5 Malaysian children with LND, comprising 4 related Malay children from 2 families, including an LND girl, and a Chinese Malaysian boy. Results: Dramatic reductions of self-injury and aggressive behaviour, as well as a milder reduction of dystonia, were observed in all 5 patients. Other LND neurological symptoms did not improve during SAMe therapy. Discussion: Molecular mechanisms proposed for LND neuropathology include GTP depletion in the brain leading to impaired dopamine synthesis, dysfunction of G-protein-mediated signal transduction, and defective developmental programming of dopamine neurons. The improvement of our LND patients on SAMe, particularly the hallmark self-injurious behaviour, echoed clinical progress reported with another purine nucleotide depletion disorder, Arts Syndrome, but contrasted lack of benefit with the purine disorder adenylosuccinate lyase deficiency. This first report of a trial of SAMe therapy in LND children showed remarkably encouraging results that warrant larger studies.     

HBV适应性杂交细胞株的建立和初步研究

目的方法诱导HepG₂细胞产生HGPRT基因突变,将筛选出的HGPRT阴性的HepG2细胞与携带HBV的人原代肝细胞进行融合得杂交细胞,用HAT培养基筛选出异核体杂交细胞,再利用有限稀释法进行克隆,通过核型分析方法鉴定所得细胞。对所得杂交细胞及培养上清液进行HBV DNA和HBsAg、HBeAg的检测。实验同时,用未杂交的HepG2和人原代肝细胞作对照。结果经筛选后,有一杂交细胞株(HepCHLine3)克隆成功。HepCHLine3在形态学上与HGPRT^-HepG₂细胞相似,能体外传代培养,染色体核型分析示HepCHLine3杂交细胞染色体众数为99条,证明为融合细胞株,含所有来自HepG₂和人原代肝细胞的基因数。传代培养的HepCHLine3和其培养上清液用巢式PCR分别可检测到HBV DNA,培养上清液内检测到HBsAg和HBeAg。对照组的HepG₂和人原代肝细胞相应结果为阴性。提示该细胞携带并分泌HBV DNA。结论该杂交细胞兼具HepG₂细胞体外传代和人原代肝细胞对HBV易感的特性,是一新型杂交细胞系,为进一步建立新型HBV感染细胞模型奠定了基础。     

Genotoxicity testing of arsenobetaine, the predominant form of arsenic in marine fishery products

Marine fishery products may contain high levels of arsenic, mainly in the form of organic arsenic compounds. Arsenobetaine has been identified as the predominant form occurring in marine fishery products. The potential initiating and promoting capacities of this compound were therefore investigated in vitro. In the Salmonella typhimurium assay, no mutagenicity was observed in strains TA97, TA98 and TA100 without activation or after addition of a liver-enzyme fraction or gut-flora extract. The compound was also negative in the forward mutation assay of the HGPRT gene and in the test for sister chromatid exchanges in V79 Chinese hamster cells. No inhibition of metabolic co-operation between V79 Chinese hamster cells was observed at arsenobetaine concentrations up to 10 mg/ml. In addition, arsenobetaine had no synergistic or antagonistic effects on the action of the positive controls benzo[a]pyrene and tetradecanoylphorbol-13-acetate.     

Abnormal Property of Human Mutant Hypoxanthine-Guanine Phosphoribosyltransferase: Insensitivity of Fibroblast Enzyme to Stabilization against Freezing and Thawing by 5-Phosphoribosyl-1-Pyrophosphate

Abstract. Freezing and thawing of dilute normal human fibroblast suspensions causes partial inactivation of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and adenine phosphoribosyltransferase (APRT). Phosphoribosyl-pyrophosphate (PRPP) stabilizes both phosphoribosyltrans-ferases against this inactivation. Mutant HGPRT enzymes from a patient with the Lesch-Nyhan syndrome and from a gouty patient with partial HGPRT deficiency were similarly inactivated by freezing and thawing, but only the former mutant enzyme could be stabilized by PRPP. The insensitivity of the mutant HGPRT from the patient with partial enzyme deficiency to PRPP stabilization indicates a structural enzyme alteration. The different sensitivity of the two HGPRT mutants to PRPP stabilization reflects the heterogeneity of HGPRT mutations in man.     

鱼露致中国仓鼠卵巢细胞HGPRT位点突变作用

背景与目的:研究鱼露及亚硝化鱼露对中国仓鼠卵巢(CHO)细胞HGPRT位点突变的影响.材料与方法:分别将鱼露和亚硝化鱼露分成4个不同剂量处理组:5 μl/ml、2.5μl/ml、1.25 μl/ml、0.625 μl/ml,另设阳性对照组(EMS:0.75 μg/ml,不需代谢活化;MCA:4 μg/ml,需代谢活化)和溶剂对照组(三蒸水),应用CHO/HGPRT基因突变试验,采用琼脂平皿法,检测鱼露和亚硝化鱼露对CHO细胞的毒性及突变体频率,评价鱼露及亚硝化鱼露引起突变的可能性.结果:经S9系统活化和未经S9系统活化的所有处理组突变体频率差异均有统计学意义(X2S9-=41.115;FS9 =19.528;P均＜0.01);亚硝化鱼露及经S9系统代谢活化后的鱼露组处理突变体频率均显著高于溶剂对照组(P＜0.05或P＜0.01),且存在剂量-效应关系(S9-:r 亚硝化鱼露=0.986,P＜0.05;S9 :r鱼露=0.950,P=0.05;r亚硝化鱼露=0.997,P＜0.01);而未经S9系统活化的鱼露处理组与溶剂对照组间差异均无统计学意义(P＞0.05).结论:鱼露经亚硝化后对CHO/HGPRT位点有致突变作用,经S9系统活化后可能也有此作用.     

Genetic toxicology studies with glutaraldehyde.

Glutaraldehyde (GA; CAS no. 111-30-8) has a wide spectrum of industrial, scientific and biomedical applications, with a potential for human exposure particularly in its biocidal applications. The likelihood for genotoxic effects was investigated in vitro and in vivo. A Salmonella typhimurium reverse mutation assay showed no evidence for mutagenic activity with strains TA98, TA1535, TA1537 and TA1538, with or without metabolic activation. However, there was a weak mutagenic response (1.9-2.3-fold at the highest non-toxic concentration) with TA100 in the presence of metabolic activation. In a Chinese hamster ovary (CHO) forward gene mutation assay (HGPRT locus) there were no consistent, statistically significant, reproducible or dosage-related increases in the frequency of 6-thioguanine resistant cells. There were no reproducible or dosage-related increases in sister chromatid exchanges in an in vitro test in CHO cells. An in vitro cytogenetics study in CHO cells showed no evidence for an increase in chromosomal aberrations on treatment with GA, either in the presence or absence of metabolic activation. In vivo, a mouse peripheral blood micronucleus test showed no increase in micronucleated polychromatophils at sampling times of 30, 48 and 72 h after acute gavage dosing with GA at 40, 80 and 125 mg kg(-1) (corresponding to 25, 50 and 85% of the LD(50)). The absence of an in vivo clastogenic potential was confirmed by no increase in chromosomal aberrations in a rat bone marrow cytogenetics study with sampling at 12, 24 and 48 h after acute gavage dosing with GA (12.5, 30 or 60 mg kg(-1) with males, and 7.5, 20 or 40 mg kg(-1) with females). Thus, in this series of tests, GA produced genotoxic effects in vitro only in a bacterial reverse mutation assay with no evidence for in vivo genotoxicity.     

Effects of spermine on formation of HGPRT− mutants induced by ethylmethanesulfonate,methylmethanesulfonate, and mitomycin C in V79 chinese hamster cells

Spermine is a polyamine found in bacteria, animal, and plant tissues. It is involved in a variety of biological processes, and its interaction with DMA stabilizes the secondary structure of the double helix. Spermine is one of the first reported antimutagens, reducing the mutation rate in several prokaryotic test systems, while in eukaryotic organisms conflicting results have been obtained. In light of the significant antimutagenic effect of spermine, it is important to evaluate its activity in mammalian cells in culture. The present study was undertaken to evaluate the ability of spermine to suppress the level of HGPRT mutants induced by ethylmethanesulfonate, methylmethanesulfonate, and mitomycin C. Spermine reduced the mutation frequency induced by ethylmethanesulfonate and methylmethanesulfonate but did not affect survival; with mitomycin C survival was reduced but mutation rate was not influenced.