黄曲霉毒素B1诱导性大鼠肝癌超微结构观察及N-ras表达变化

目的探讨黄曲霉毒素B1(AFB1)诱导性大鼠肝癌模型超微病理特征及N-rasmRNA表达变化规律。方法 40只Wistar大鼠分为正常对照组(12只)和诱癌组(28只)用AFB1(400μg/kg)间断腹腔注射雄性Wistar大鼠制作肝癌模型,电镜观察大鼠肝组织超微结构。应用RT-PCR技术检测对照组大鼠肝组织,损伤病变、早期癌变和癌变肝组织中N-ras mRNA表达水平。结果本组大鼠肝癌模型中,肝细胞呈变性损伤,异型性到癌变;线粒体由增生肿胀到枯竭、空泡变;糖原颗粒呈逐渐减少等特征性变化。观察到典型肝细胞吞噬细胞现象。N-rasmRNA在早期癌变组织、癌变组织中表达水平均显著高于对照组大鼠肝组织和损伤病变肝组织(F=5.47,P=0.019;后者F=6.98,P=0.006)。结论 AFB1诱导性大鼠肝细胞出现变性、异型性及癌细胞渐变的超微结构特征,N-ras异常表达参与大鼠肝细胞癌变机制。     

银杏叶提取物对黄曲霉毒素B1诱发Wistar大鼠肝癌的影响

[目的]通过建立黄凿霉毒素B1(Aflatoxin B1,AFB1)诱发Wistar大鼠肝细胞癌(HCC)模型,用银杏叶提取物(extract of Ginkgo Biloba Leaf,EGb761)进行干预,观察EGb761对AFB1致大鼠HCC作用的影响. [方法]实验大鼠按体重随机分成3组:A组(AFB1组)、B组(AFBI+EGb761组)和C组(空白对照组).于实验第14、28、42及55周给予肝活检并于第64周全部处死大鼠,观察大鼠肝脏γ-GY灶及HCC发生情况. [结果]在出癌前期,第42及第55周时,A组每个γ-GT阳性灶的面积分别为(7.95±0.30)mm2及(17.87±0.71)mm2,单位面积(cm2)灶的个数分别为0.35±0.006及0.26±0.004,灶总面积分别为(2.54±0.05)mm2/cm2及(4.68±0.12)mm2/cm2;B组在相同时段的相应指标,分别为(4.65±0.16)mm3及(9.03 4±0.35)mm2, (0.21 4±0.006)及(0.20±0.005),(0.97±0.03)mm2/cm2及(1.62±0.06)mm2/cm2.除了55周A、B两组的单位面积γ-GY阳性灶的个数无统计学差异外,各时段B组各项指标都显著小于A组(P=0.000).两个实验组共有28只大鼠发生恶性肿瘤,对照组无肿瘤发生.B组HCC诱发率(7/26,26.92%)明显低于A组(19/25,76%) (P=0.000).另外,HCC及其他肿瘤的发生时间,B组明显推迟.[结论]EGb761能明显抑制AFB1诱发大鼠肝的癌前病变及延迟癌前病变向癌发展.     

影响三地居民黄曲霉毒素B1-白蛋白加合物的相关因素分析

[目的]分析影响存在肝癌发病率梯度的三地居民个体黄曲霉毒素生物效应的相关因素.[方法]对广西扶挼两个自然村农民、南宁和四川成都城市居民采用酶联免疫法检测血浆黄曲霉毒素B1-白蛋白加合物(AFB1-Albumin Adducts,AAA)水平、肝炎病毒(hepatitis virus,HV)标志物(HBV两对半,HCV、HDV、HEV和HGV抗体)及肝功能.[结果]扶挼47.2%(42/89)的居民至少1种HV感染标志物阳性;南宁和成都分别为15.8%(31/196)和22.7%(27/119).Log(AAA)水平(n,x±s)为扶挼(89,2.44±0.16)和南宁(196,2.45±0.15)均高于成都(118,2.20±0.24),(P=0.000);但扶挼与南宁间差别无显著性(P=0.859).南宁(P=0.023)、成都(P=0.026)两地男性AAA水平均高于女性.扶挼和成都两地HV感染者AAA水平均高于非感染者(P分别为0.447和0.041).HV(-)组中,AAA水平与年龄(r=-0.199,P=0.000)和BMI(r=-0.158,P=0.006)负相关.HV(+)组AAA分别与白蛋白(P=0.000)、球蛋白(P=0.012)和天冬氨酸转氨酶(P=0.052)相关,而HV(-)组AAA分别与直接胆红素、间接胆红素、白蛋白、γ-谷氨酰转肽酶、总胆汁酸和碱性磷酸酶相关(P＜0.05).[结论]AFB1暴露的生物效应可能受肝炎病毒感染、性别、年龄和代谢等因素的影响.AAA与肝功能指标的相关性提示AFBl对肝脏实质或胆道细胞的损害作用.     

黄曲霉毒素B1诱发肝癌的生物标记物检测技术

原发性肝癌是最常见的恶性肿瘤之一，除乙型肝炎病毒外，黄曲霉毒素B1(AFBl)是原发性肝癌的主要危险因素之一。在瑞士进行的一项肝癌发病率调查显示，作为肝癌的决定性影响因素，AFB1的暴露比HBV感染更严重。在中国南方进行的一个相似性研究发现，在25～64岁的男性人群中5年以上癌症总死亡率的51％是由原发性肝癌引起的，而其中由AFB1诱发的肝癌占多数。目前尚缺乏有效的方法来评估AFB1在个体中的暴露情况，     

花生油黄曲霉毒素B1的监测结果分析

黄曲霉毒素是黄曲霉和寄生曲霉产生的一类代谢产物 ,它对人类及某些动物具有很强的毒性和致癌性 ,其中以黄曲霉毒素B1 (AFB1 )的毒性和致癌性最强。花生是最易受污染的食品之一[1 ] ,由其制取的花生油AFB1 污染情况一直引起人们的关注。我们于 2 0 0 2年 1月至 12月对本地区的花生油进行质量分析 ,结果如下 :1　材料与方法1.1　样品来源　从惠安区域经营花生油的商店和农贸市场抽取样品 168份。1.2　检验方法及评价　检验方法依据食品卫生检验方法理化部分GB T5 0 0 9.2 2 -1996《食品中黄曲霉毒素B1 的测定方法》。评价标准依据中华人…     

冷冻饮品霉菌污染及黄曲霉毒素B1检测结果分析

冷冻饮品的种类不断增加、消费量也日益增大，新颁布国标GB2759．1－1996对冷冻饮品中的细菌指标的规定也愈加严格。可至今国家对冷冻饮品的霉菌及其毒素的限量标准却从未制定。现将我站近几年来对冷冻饮品霉菌及黄曲霉毒素B1（AFB1）的检测结果报道如下。1材料与方法1．1样品来自辖区范围内生产、销售的冷冻饮品，计含乳蛋类69件，含豆、花生类42件，含果蔬类55件，共3大类166件。1．2方法霉菌产毒培养基为大米培养基，大米应在紫外线下去除带荧光颗粒；AFb1酶联免疫检测试剂由中国预防医学科学院营养与食品卫生研究所提供；酶标仪为美…     

黄曲霉毒素B1分析方法

黄曲霉毒素是常见霉菌—黄曲霉和寄生曲霉中产菌毒株的代谢产物。黄曲霉在自然界的存在较寄生曲霉普遍,此菌能在受到侵染的粮食和油料作物(尤其是玉米和花生)上生长繁殖产生毒素。1060年,英国曾发生了约十万只火鸡幼仔短短几个月内相继死亡的严重事故,后来查明是由于火鸡吃了含有霉变花生饼的饲料引起的,并从霉变的花生饼中分离出黄曲霉产菌毒株,1961年即证实了喂饲含有黄曲霉毒素的花生饼可使大鼠发生原发性肝癌。此后,人们对黄曲霉毒素的种类、理化性质、毒素、致癌性、去毒方法以及与人类肝癌的关系等方面做了大量的研究。     

酶联免疫吸附法快速测定黄曲霉毒素B1

黄曲霉毒素 (AFT)是由黄曲霉产生的一类具有极强毒性和致癌性的代谢产物。LD50 为 0 2 4mg/kg ,主要诱发肝癌。测定AFTB1常用薄层荧光法、高效液相色谱法。 80年代初国外已开始研究ELISA法进行AFTB1分析。该方法特异性强 ,分析速度快 ,简化提取和纯化步骤 ,一次可测定大批样品。现报告如下。1　材料和方法1 1　仪器与试剂AFTB1测试盒 (江苏省微生物研究所研制 ) ;甲醇 ;三氯甲烷 ;石油醚 ;提取溶液 :甲醇∶水 (1∶1)。仪器 :酶标测定仪 (WellscanMk3型Labsys tems ,Dragon公司 ) ;移液器。1 2　样品来源　由无锡市惠山区卫生防…     

酶联免疫吸附法测定黄曲霉毒素B1误差分析

1　引言酶联免疫吸附法 (ＥＬＩＳＡ)已广泛用于食品、饲料、饮料、中药材中化学成分的测定[1-2 ] 。如ＥＬＩＳＡ法检测黄曲霉素Ｂ1(ＡＦＢ1) [3 -4 ] 。该方法具有灵敏度高 ,特异性好 ,操作简便 ,成本低廉 ,对操作人员和环境污染少等特点 ,正逐渐被广大分析工作者掌握运用[5-6] 。然而 ,由于样品的复杂多样 ,以及酶的不稳定性 ,使得分析人员在实际检测样品中 ,出现假阳、阴性结果。为此 ,本文以ＥＬＩＳＡ检测ＡＦＢ1测试盒为例 ,针对样品特性 ,探讨含盐量、酸碱性、金属离子含量、提取溶液组分四个主要因素对检测结果的影响 ,并提出消除…     

HPLC同时测定食品中黄曲霉毒素B1、B2、G1、G2

目的：分析常见种类食物中黄曲霉毒素的含量，为建立食品中黄曲霉毒素的限量指标提供数据，并为大众的健康饮食提供参考。方法：以黄曲霉毒素B1的平均含量为参考选择黄曲霉毒素含量较多的常见食物种类，使用高效液相色谱仪及荧光检测器分析食物中黄曲霉毒素B1、B2、G1、G2的含量。结果：花生酱中含有的黄曲霉毒素最多，平均为2．41μg／kg；大米中黄曲霉毒素的含量次之，平均为0．15μg／kg；花生中黄曲霉毒素的平均含量为0．04μg／kg。结论：高效液相色谱法测定食物中黄曲霉毒素其重现性较好，而且可以一次分别测定出黄曲霉毒素B1、B2、G1、G2的含量，从结果看来尽管多数食品中均含有黄曲霉毒素，但是其含量均没有超过国家限量标准，其中花生酱中的黄曲霉毒素含量较高。这些数据均可以为大众的健康饮食提供参考。     

Mutagenic effect of aflatoxin B1

The present work aimed to study the mutagenic effect of aflatoxin B1 on human chromosomes. The experiments showed that aflatoxin B1 is a strong chromosome damaging agent. The treated cells showed a high rate of aberrations mainly breaks and interchanges. Using Giemsa banding technique, the study showed that the distribution of breakage points on individual chromosomes was significantly non-random. The study of sister chromatid exchanges (SCEs) indicated that the high incidence of breakage rate was paralled by an increased SCE rate. Some chromosomes were very sensitive to the mutagenic effect of aflatoxin B1, while other chromosomes were very resistant. The present data provides an additional consideration in assessing the risks of exposure to this agent.     

Protective effect of soybean saponins and major antioxidants against aflatoxin B1-induced mutagenicity and DNA-adduct formation

Saponins from various plant sources have been suggested as possible anticarcinogens. Major dietary sources of saponins include legumes such as soybeans. This study was performed to determine the effect of soybean saponins on aflatoxin B(1)(AFB(1))-induced mutagenicity and AFB(1)-DNA adduct formation using Salmonella typhimurium and human liver hepatoma (HepG2) cells, respectively. Major antioxidants including L-ascorbic acid, alpha-tocopherol, all-trans-retinol, and butylated hydroxytoluene (BHT), previously reported to possess antimutagenic activity, were used as test materials to evaluate the relative effectiveness of saponins. Results indicated antimutagenicity was in the order of BHT > saponins > alpha-tocopherol > L-ascorbic acid. Soybean saponins exerted a significant effect, inhibiting the mutagenicity of AFB(1) by 52%, 64%, and 81% at concentrations of 600, 900, and 1,200 microg per plate, respectively. The amount of tritiated AFB(1) metabolites-DNA adducts formed in HepG2 cells was significantly reduced when cells were preincubated with 10 or 30 microg/ml of test materials. Soybean saponins inhibited AFB(1)-DNA adduct formation by 50.1% at a concentration of 30 microg/ml, whereas L-ascorbic acid and BHT reduced adduct formation by 38.4% and 32.6%, respectively, at the same concentrations. These results indicate that soybean saponins possess not only a significant antimutagenic activity but a strong inhibitory action against carcinogen-induced DNA damages. Soybean saponins possibly block the initiation stage of carcinogenesis, and further studies are required to elucidate the mechanisms of action.     

Effects of green tea extract on the development of aflatoxin B1-induced precancerous enzyme-altered hepatocellular foci in rats]

Three kinds of extracts of green tea (decoction extract of green tea, water extract of green tea and ethanol extract of green tea) were tested for their effects on aflatoxin B1 (AFB1)-induced hepatocarcinogenesis in rats. The results revealed that all these three extracts of green tea possessed the remarkable inhibitory effects on the development of precancerous enzyme-altered hepatocellular foci. These results indicated that the main components of the green tea responsible for cancer prevention were all soluble in water and ethanol and thus providing an important clue for the search of the effective components in green tea for cancer prevention.     

Chemoprevention of aflatoxin B1-initiated and carbon tetrachloride-promoted hepatocarcinogenesis in the rat by green tea

Maintaining tumor-bearing rats on total parenteral nutrition (TPN) for eight days significantly reduced mass, protein, and DNA in small intestine and colon. Coinfusion of glucagon-like peptide 2 (GLP-2) significantly increased each of these variables in the duodenum, jejunum, and ileum, but not in the colon. Histological analysis of tissue revealed normal mucosa thickness and villus height in the small intestine of GLP-2-treated rats, whereas non-treated rats maintained on TPN exhibited villus shortening and thinning of the mucosa. Compared with TPN alone, no significant effects of GLP-2 were noted on tumor growth, liver weight, or heart weight. Coinfusion of GLP-2 with TPN had no significant effect on TPN-associated immunosuppression, as measured by mitogen-induced proliferation of cultured splenocytes. Although translocation of bacteria to the mesenteric lymph nodes appeared to be reduced in GLP-2-treated rats, the difference between groups was not statistically significant. These results suggest that hormonal alterations may be more important than an absence of luminal nutrition in TPN-associated mucosa changes in tumor-bearing rats. Additionally, maintenance of gut integrity during TPN does not appear to be a sufficient condition for the avoidance of the negative sequelae associated with this route of supplemental nutrition.     

Trout hepatic enzyme activation of aflatoxin B1 in a mutagen assay system and the inhibitory effect of PCBs

In summary, it was demonstrated that the trout PMF may be successfully employed in the Ames mutagen assay method by utilization of proper salts solution and a metabolic preincubation period at 25 degrees C. It has also been observed that, unlike the rat, pretreatment of rainbow trout with various PCBs decrease the mutagen assay response to AFB.     

Dietary protein level and aflatoxin B1-induced preneoplastic hepatic lesions in the rat

Previous studies have shown that the development in rats of aflatoxin B1 (AFB1)-induced gamma-glutamyl transpeptidase-positive (GGT+) foci, indicators of early preneoplastic liver lesions, was markedly greater when a 20% casein diet was fed than when a 5% casein diet was fed during the postinitiation period. In the present study, the dose-response relationship between dietary protein level (dose) and emergence of AFB1-induced GGT+ foci (response) in livers of rats was determined. Male Fischer-344 rats fed a 20% casein diet were orally administered AFB1 at a dose level of 250 micrograms/(kg X d) (10 doses over 12 d). One week after the last dose, the animals were divided into eight groups and fed isoenergetic diets containing either 4, 6, 8, 10, 12, 15, 20 or 30% dietary casein for the remaining 12 wk of the study. The development of GGT+ foci, as measured by number and percent of liver volume occupied, displayed a response with three discrete phases. The lowest dietary protein levels, 4, 6, 8 and 10% casein, were associated with a minimal level of GGT+ foci development. Between 10 and 12% dietary casein, the development of GGT+ foci sharply increased, up to the 15-30% dietary casein level. The sudden increase in the formation of GGT+ foci at 10-12% dietary casein was just above the level of dietary casein (6-8%) required for maximum body weight gain. These results in this animal model suggest that protein intake in excess of that required to sustain maximum growth rate may enhance AFB1-induced cancer development.     

Effects of carotenoids on aflatoxin B1-induced mutagenesis in S. typhimurium TA 100 and TA 98

The effects of beta-carotene, canthaxanthin, and extracts of tomato paste (containing lycopene) and orange juice (containing cryptoxanthin) on aflatoxin B1 (AFB1)-induced mutagenesis in S. typhimurium TA 100 and TA 98 were investigated. Inhibition of mutagenesis was studied during and following completion of AFB1 metabolism (i.e., after the addition of menadione), thereby permitting separate examination of the metabolic activation and phenotypic expression phases. Each experimental carotenoid, except lycopene, inhibited AFB1-induced mutagenesis in both tester strains. Cryptoxanthin was the most potent inhibitor, being at least an order of magnitude more potent than the other carotenoids. Inhibition by beta-carotene and canthaxanthin was more prominent during the activation phase, whereas cryptoxanthin was more effective during the subsequent phenotypic expression phase. These inhibitory effects were not dependent on conversion to retinol.