Search for the presence of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin in bovine milk

Conclusion Surveillance samples of milk from the states of Oklahoma, Arkansas, and Missouri were collected from cows grazing on pasture or rangeland treated with normal applications of 2,4,5-T. These samples and control samples were analyzed for TCDD by GC/MS. A detection limit of 1 ppt was achieved. With this sensitivity the control samples were indistinguishable from those from treated areas. Hence, TCDD was not found.     

2,3,7,8-四氯二苯并二噁英对人芳香烃受体和转化生长因子α mRNA表达的影响

目的 研究2,3,7,8-四氯二苯并二嗯英(TCDD)染毒对表皮细胞芳香烃受体(AhR)和转化生长因子(TGF-α)表达的影响.方法 利用半定量逆转录PCR技术(RT-PCR)对24 h TCDD染毒组进行AhR和TGF-α基因表达的测定,并分析两者之间的相互关系.结果 以β-actin为内参照,测定细胞中AhR和TGF-α mRNA表达的相对含量.结果 显示随着TCDD浓度的增高,细胞中AhR mRNA的相对表达量呈现下降的趋势,r=-0.548,各染毒组与对照组相比差异有统计学意义(F=4.124,P=0.021),两两比较7×10-10 mol/L组(0.0620±0.0085)和7×10-9 mol/L组(0.0518±0.0194)与对照组(0.1138±0.9227)之间的差别有统计学意义(t=-3.48,P＜0.05;t=-4.17,P＜0.01),且其相对表达量分别为对照组的55%和45%.TGF-α mRNA的相对表达量随浓度的增加则呈现上升的趋势,相关系数r=0.695(P＜0.01),各组之间差异有统计学意义(F=15.789,P=0.000),在7×10-10 mol/L组(0.1474±0.0390)和7×10-9 mol/L组(0.2133±0.0364)相对表达量与对照组(0.0561±0.0100)的差别具有统计学意义(t=4.49,P＜0.01;t=7.74,P＜0.01),且其相对表达量是对照组的2.6倍和3.8倍.同时对AhR与TGF-α mRNA相对表达水平进行相关分析,两者呈负相关,r=-0.561(P＜0.05).结论 TCDD对细胞增殖过程中可影响基因表达,AhR表现为下调,TGF-α表现为上调,且两基因表达量之间存在负相关关系.     

哺乳期暴露2,3,7,8-四氯二苯并-p-二(噁)英的子代小鼠生殖发育以及肺组织CYP1A1水平

目的 探讨哺乳期暴露2,3,7,8-四氯二苯并-P-二(噁)英(TCDD)对子代小鼠生长发育及细胞色素P4501A1(CYP1A1)表达的影响.方法 采用清洁级昆明小鼠,设40μg/kg和20μg/kg TCDD染毒组,并分设相应的两个溶剂对照组及-个动物空白对照组.每组母鼠3只,仔鼠25～28只.母鼠分娩后的第1、3、5天腹腔注射TCDD,子代小鼠通过乳汁暴露于TCDD.观察不同生长期仔鼠的体重改变和生殖系统发育等.仔鼠生后第35天被处死,采用免疫组化法分析肺组织CYP1A1的表达.结果 TCDD染毒组的仔鼠体重明显降低,雌性仔鼠的阴道平均开放时间明显缩短,雄性仔鼠的睾丸平均下降时间明显延长.TCDD染毒组的肺泡结构紊乱,炎症细胞浸润,肺泡壁增厚水肿,CYP1A1表达量明显升高,并且雌性仔鼠的肺组织反应比雄性仔鼠严重.而对照组中雌雄间差异没有显著性.结论 单一哺乳期暴露于TCDD可使子代小鼠体重下降,雌性仔鼠性成熟提前,雄性仔鼠性成熟延缓.仔鼠肺组织CYP1A1表达明显增加,并存在性别差异.     

Metabolic stability of 2, 3, 7, 8-tetrachlorodibenzo-P-dioxin in mammalian liver microsomal systems and in living mice

Dibenzo-p-dioxin is rapidly converted by microsome-NADPH systems, prepared from mouse, rat, and rabbit liver, and by intraperitoneally treated mice into unidentified, polar metabolite(s) that, in living mice, appear in the urine. In contrast, not any of these three liver microsome-NADPH systems convert 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin into either trichlorodibenzo-p-dioxin or water-soluble products. In living mice, the tetrachloro compound, injected at the LD₅₀ dose, is either not at all or not extensively converted to water-soluble products; the feces are the major route of elimination, possibly via the bile. A large proportion of the administered tetrachlorodibenzo-p-dioxin persists in unmetabolized form in the liver, partially concentrated in the microsomal fraction, 11 to 20 days after treatment. The metabolic stability and localization of the tetrachloro material indicate that the unmetabolized compound, rather than a metabolite, probably is responsible for its toxic effects in mammals and that the endoplasmic reticulum of the liver is a possible site of action.     

Health hazard assessment for chlorinated dioxins and dibenzofurans other than 2, 3, 7, 8-TCDD

EPA is faced with the need to perform health risk assessments of environmental materials containing mixtures of chlorinated dioxins and -dibenzofurans. Preferably, such an assessment must be based on the direct evaluation of chronic health effects of the mixture or on a knowledge of the toxic effects of each of the components. In the absence of such data, the authors have developed two pragmatic approaches that can reasonably be applied to mixtures such as flyash or contaminated soil. The details of these approaches, viewed as interim procedures, are compared and contrasted with those used by other regulatory and public health authorities.     

Acute toxicity of 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 2,6-dinitrotoluene in the adult bullfrog (Lithobates catesbeiana)

2,4,6-Trinitrotoluene (TNT) is one of the most prevalent high explosives in the environment. 2,4-Dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) are the most common isoforms of dinitrotoluene. The goal of this study was to determine the acute toxic effects of TNT, 2,4-DNT, and 2,6-DNT in adult male bullfrogs. The LD(50) for TNT was 1,060 mg/kg BW while the LD(50 )for 2,4-DNT and 2,6-DNT was 1,098 mg/kg BW. All three compounds elicited similar symptoms of toxicity including changes of skin color, body weight, development of seizures, liver and kidney necrosis, and lung cyanosis. Relative organ weights did not show significant change.     

Toxicity and persistence of low-level PCB in adult wistar rats,fetuses, and young

Aroclor 1254 was fed to female and male rats daily for 9 weeks at a dose of 6.4 mg/kg in their drinking water. Control animals received plain tap water plus the emulsifier (0.15% Tween 80). Elevated mixed function oxidase (MFO) activity appeared to be due to 2,4,5,2,4,5- and 2,4,5,234-hexachlorobiphenyls, since only these compounds were present to any degree in the tissues of the animals when MFO activity persisted after termination of exposure. The placenta apparently is an effective barrier to PCB transfer.We also appreciate the advice, help, and facilities furnished by Dr. Melvin K. Abelseth, Director, Laboratories for Veterinary Science, New York State Department of Health.     

Toxicity of model aliphatic amines and their chlorinated forms

Aliphatic amines can be found in many wastewater effluents from industry, agriculture, pharmacy, and food processing. Amines can induce toxicological responses that are relevant in biochemical treatment processes, as well as in natural waters. This research compared the toxicity and inhibition caused by three aliphatic amines (n-propylamine, ethylmethylamine, and trimethylamine) and their chlorinated derivatives. The chemistry of chlorine interactions with these compounds was characterized by using membrane introduction mass spectrometry (MIMS). Acute toxicity assays were conducted by using a Microtox system with Phosphobacterium phosphoreum (also known as Vibrio fischeri) for the aliphatic amine compounds and their corresponding chlorinated derivatives, as identified by MIMS. Inhibition tests were conducted by using the oxygen utilization rate test with an enhanced nitrifier culture. The median effective concentration (EC50) values for chloropropylamine, chloroethylmethylamine, and chlorodimethylamine obtained by Microtox with a contact time of 15 min were 12.68, 19.72, and 15.92 microM, respectively. The EC50 values of these aliphatic chloramines from the Microtox test decreased by roughly one order of magnitude as a result of chlorination. Inhibition of nitrifiers also was observed in these amines. Trimethylamine and n-propylamine caused greater inhibition to nitrifiers than did ethylmethylamine under similar concentrations. Nitrifier inhibition from these amines increased after chlorination. The results of these tests indicated that aliphatic amines and their chlorinated derivatives could induce environmentally relevant toxicity responses in treatment settings and in receiving waters.     

Toxicity and persistence of low-level PCB in adult wistar rats, fetuses, and young.

Aroclor 1254 was fed to female and male rats daily for 9 weeks at a dose of 6.4 mg/kg in their drinking water. Control animals received plain tap water plus the emulsified (0.15% Tween 80). Elevated mixed function oxidase (MFO) activity appeared to be due to 2,4,5,2',4',5'- and 2,4,5,2'3'4'-hexachlorobiphenyls, since only these compounds were present to any degree in the tissues of the animals when MFO activity persisted after termination of exposure. The placenta apparently is an effective barrier to PCB transfer.     

Toxicity of 2-methyl-4-chlorophenoxyacetic acid to the adult crested newt

The toxicity of the herbicide Agroxone 3, a commercial formulation of the sodium salt of 2-methyl-4-chlorophenoxyacetic acid (MCPA), in the adult newt (Triturus cristatus carnifex) was tested after percutaneous exposure. At the concentration of 3200 ppm, the LT50 values were 17 and 21 hr for male and female newts. At 1600 ppm, the LT50 values were 35 and 45.5 hr. At 800 ppm, most of the animals were still alive after the 3 months of experimentation. There were no deaths at 400 and 200 ppm. Severe neuromuscular disorders were observed in animals exposed to lethal concentrations.     

Toxicity to Daphnia magna, Hyalella azteca, Oncorhynchus kisutch, Oncorhynchus mykiss, Oncorhynchus tshawytscha, and Rana catesbeiana of Atrazine, Metolachlor, Simazine, and Their Formulated Products

No abstract available.     

Immunogenicity and safety of a hexavalent meningococcal outer-membrane-vesicle vaccine in children of 2-3 and 7-8 years of age

To study the reactogenicity and immunogenicity of a hexavalent meningococcal outer-membrane-vesicle vaccine (OMV), two different dosages of this vaccine (7.5 and 15 microg of individual PorA proteins) consisting of vesicles expressing class 1 outer-membrane proteins (OMPs) of subtypes P1.7,16; P1.5,2; P1.19,15 and P1.5(c), 10; P1.12,13; P1.7(h),4 were administered to a group of 7-8 year (n=165) and a group of 2-3 year old children (n=172). Control groups of children with similar ages were vaccinated against hepatitis B. All participants received three injections. Pre- and postimmunisation sera were tested for bactericidal antibodies against six isogenic meningococcal vaccine strains expressing different PorA proteins. Antibody titres against OMP of the two different vesicles (PL16215 and PL10124) were measured by ELISA. The meningococcal hexavalent OMV vaccine was well tolerated. No statistically significant differences were seen between the high and low dose of hexavalent meningococcal OMV vaccine. The percentage of children showing a fourfold increase of bactericidal antibody titres against the specific serosubtype varied in toddlers from 28 to 98% and in older children from 16 to 100%. Both ELISA antibody titres and bactericidal activity showed the highest level in the youngest age-group.     

DQ2, DQ7 and DQ8 Distribution and Clinical Manifestations in Celiac Cases and Their First-Degree Relatives

HLA-linked genes are relevant to celiac disease (CD); the potential genetic differences present worldwide are not fully understood. Previous results suggest that the distribution of HLA-DQ2/DQ7/DQ8 in Chile may differ from that in Europe and North America. In celiac patients and their first-degree relatives (FDRS), we assessed their clinical, serological and histological characteristics, determined HLA-DQ2, HLA-DQ7 and HLA-DQ8 alleles and genotypes, and evaluated the relations between them. A total of 222 individuals were assessed (56 cases, 166 FDRs). 16.9% of FDRs were tTG positive; 53.6% of them showed overweight/obesity and 3% undernourishment; they spontaneously declared being asymptomatic, but detailed questioning revealed that 60.7% experienced symptoms, which had not been investigated. DQ2 was present in 53.9% and 43.9.0% of cases and FDRs (p < 0.05). The most frequent genotype distribution was DQ2/DQ7 (fr 0.392 (cases) and 0.248 (FDRs), respectively, p < 0.02). The next most common genotypes were HLA-DQ2/DQ8 (fr 0.236 in FDRs and 0.176 in cases, p < 0.05). 3.92% cases were not HLA-DQ2/DQ8 carriers. Among tTG positive FDRs, 57.4%, 22.3% and 20.2% carried DQ2, DQ7 and DQ8, respectively. In cases, 72.7% of the biopsies classified Marsh ≥3 carried at least one DQ2; 91.7% of DQ2/DQ2 and 88.3% of DQ2/DQ7 were Marsh ≥3. Thus, DQ2 frequency is lower than reported; the higher frequency found for DQ8 and DQ7 concur with recent publications from Argentine and Brazil. These results suggest that although CD may manifest clinically in ways similar to those described in other populations, some genetic peculiarities in this region deserve further study.