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.     

黄曲霉毒素B1诱发大鼠肝癌及硒心癌机理的研究

Liver cancers of rats were induced by aflatoxin B1. Two other groups were given 3 ppm and 6 ppm selenium in water. It was found that Selenium had distinct inhibitory effect on carcinogenesis. 61% of rats not given selenium came down with liver carcinoma, whereas those given selenium no carcinogenetic changes were found. In the early stage selenium inhibited the formation of liver hyperplastic foci, in the late stage its effect was on the carcinogenetic change of the hyperplastic foci.     

Protective effect of some tropical vegetables against CCl4-induced hepatic damage

In the present study, ethanolic extracts of some tropical vegetables were investigated for their hepatoprotective effect against CCl4-induced liver damage in rats. CCl4 at a dose of 0.5 mL/kg of body weight produced liver damage in rats as manifested by the rise in the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total protein in serum (40.60 +/- 3.50 IU/L, 80.60 +/- 5.10 IU/L, and 73.20 +/- 1.87 g/L, respectively) and in liver homogenate (1,300.00 +/- 7.38 IU/L, 1,660.00 +/- 13.69 IU/L, and 250.00 +/- 7.51 g/L, respectively) compared to the control. The extracts at doses of 250 and 500 mg/kg of body weight were administered to the CCl4-treated rats. The vegetables at a dose of 250 mg/kg of body weight produced a significant hepatoprotective effect by decreasing the serum levels of ALT, AST, and total protein to values in the range of 11.21 +/- 1.90-16.22 +/- 1.00 IU/L, 29.00 +/- 2.70-48.00 +/- 2.10 IU/L, and 62.10 +/- 2.40-70.13 +/- 2.00 g/L and at a dose of 500 mg/kg of body weight to 13.00 +/- 1.20-21.00 +/- 1.30 IU/L, 40.00 +/- 2.5-59.00 +/- 2.20 IU/L, and 68.00 +/- 2.40-72.00 +/- 2.10 g/L, respectively. Similar results were obtained for liver homogenate levels of ALT, AST, and total protein with decreasing values compared with the CCl4-treated rats: 900.00 +/- 3.05-1,020.00 +/- 4.25 IU/L, 1,150.00 +/- 5.57-1,530.00 +/- 4.99 IU/L, and 150.00 +/- 3.12-185.00 +/- 3.00 g/L and 900.00 +/- 3.05-1,030.00 +/- 8.80 IU/L, 1,400.00 +/- 6.95-1,530.00 +/- 8.50 IU/L, and 165.0 +/- 5.50-210.00 +/- 4.41 g/L, respectively, at doses of 250 and 500 mg/kg of body weight, respectively. Furthermore, the effect of the extracts on lipid peroxidation, measured as malondialdehyde (MDA), was estimated on the liver homogenate. A significant hepatoprotective effect was also noticed with a decreased value of the MDA levels: 46.00 +/- 0.08-52.00 +/- 0.06 and 47.00 +/- 0.07-60.00 +/- 0.10 nmol of thiobarbituric acid-reactive substances/g of liver protein at doses of 250 and 500 mg/kg of body weight, respectively. It could be concluded that all the evaluated vegetables exhibit good hepatoprotective activities, though to varying degrees.     

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.     

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。     

抗黄曲霉毒素M1抗体制备及检测方法建立

目的制备针对黄曲霉毒素M1的单克隆抗体并建立针对黄曲霉毒素M1的间接竞争酶联免疫吸附试验检测方法。方法利用B细胞杂交瘤技术。建立能分泌抗黄曲霉毒素M1单克隆抗体的杂交瘤细胞株，制备抗黄曲霉毒素M1单克隆抗体，建立间接竞争酶联免疫吸附试验检测方法。结果研制出1株能特异性分泌抗黄曲霉毒素M1单克隆抗体的杂交瘤细胞株，命名为2F2。该单克隆抗体的Ig亚类为IgG1，亲和常数为2．8×10^-11mol／L。该抗体与黄曲霉毒素B1、黄曲霉毒素B2、黄曲霉毒素G1、黄曲霉毒素G2和黄曲霉毒素M2等结构类似物有微弱的交叉反应，具有较高的特异性。在此基础上建立了间接竞争酶联免疫吸附试验检测方法。该方法的最低检出浓度为0．07ng／ml。校正曲线的线性范围为0．02～2ng／ml，线性方程y=-0．4364x＋0．2693（R^2=0．9949）。方法的加标回收率为72．5％～131．3％。结论制备了具有高特异性和亲和力的抗黄曲霉毒素M1单克隆抗体，并建立了快速、灵敏的针对黄曲霉毒素M1的酶联免疫吸附试验检测方法。     

Protective effects of free radical scavengers and antioxidants against smokeless tobacco extract (STE)-induced oxidative stress in macrophage J774A.1 cell cultures

Previous studies have demonstrated that an aqueous smokeless tobacco extract (STE) administered in an acute oral dose to rats induces an enhanced induction of hepatic mitochondrial and microsomal lipid peroxidation, hepatic nuclear DNA single strand breaks, enhanced excretion of urinary lipid metabolites, including malondialdehyde, formaldehyde, acetaldehyde and acetone, and increased production of nitric oxide (NO) by peritoneal macrophage cells. These observations indicate that STE induces the production of oxygen free radicals. We have therefore examined the in vitro incubation of cultured J774A.1 macrophage cells with STE on the release of the enzyme lactate dehydrogenase (LDH) into the media as an indicator of cellular membrane damage and cytotoxicity. The amount of LDH released by STE was both concentration- and time-dependent. The cytotoxicity of STE to macrophage J774A.1 cells in culture was further determined from percent viability after various periods of incubation. The addition of 250 g STE/ml to the cultured J774A.1 cells resulted in a 2.9-fold increase in the release of LDH. Individual coincubation with superoxide dismutase (SOD), catalase, mannitol, and allopurinol had no significant effect on the release of LDH into the culture medium, while a combination of the four free radical scavengers resulted in a 59% decrease in the STE-induced release of LDH. At 75 M concentrations of viramine E and vitamin E succinate, approximately 28% and 41% inhibitions were observed in STE-induced LDH leakage, respectively. Taken together with previous studies, the results indicate that STE activates macrophage cells, resulting in the production of reactive oxygen species. These oxygen free radicals may be responsible for tissue damaging effects including membrane damage, and selected oxygen free radical scavengers and antioxidants can attenuate these tissue damaging effects.     

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.     

The protective effect of hydrated sodium calcium aluminosilicate against the adverse effects of aflatoxin B1 on D. melanogaster

The main aim of this study was to investigate the effects of Aflatoxin B1 (AFB1) and Aflatoxin B1 + hydrated sodium calcium aluminosilicate (HSCAS) on various developmental stages of Drosophila melanogaster. Different concentrations of AFB1 and HSCAS + AFB1 were administered during the developmental periods of the fly (egg, larvae and pupae). When the F1 progeny of control and application groups were compared, AFB1 was found to extend the process of metamorphosis and decrease the total number of offspring. However, these negative effects were inhibited with HSCAS treatment at different concentrations (5.0 and 10.0 ppm). These results suggest that HSCAS could effectively inhibit AFB1-induced abnormalities in the developmental stages of D. melanogaster.     

Protective effect of red-stemmed type of Ipomoea aquatica Forsk against CCl4-induced oxidative damage in mice

Water spinach (Ipomoea aquatica Forsk; I. aquatica) of the green-stemmed type (green type) is widely consumed, but there also exists a red-stemmed variety (red type). In the present study, the antioxidant capacity of the red type was compared to that of the green type in carbon tetrachloride (CCl(4))-treated mice. CCl(4)-induced thiobarbituric acid reactive substrate (TBARS) formation in the liver was significantly suppressed in mice fed 5% red-type I. aquatica, while the green type showed no effect. Hydrophobic oxygen radical absorbance capacity (H-ORAC(FL)) in the red type showed a lower level than that in the green type; however, lipophilic ORAC (L-ORAC(FL)) and total-ORAC(FL) levels were significantly higher in the red type than in the green type. α-Tocopherol, anthocyanidin/proanthocyanidin, and β-carotene contents were all significantly higher in the red type than in the green type. These results suggest that the wild red-type I. aquatica contains certain lipophilic components that exert antioxidant capacities not only in vitro but also in vivo. Such effective components in the red type would be beneficial phytochemicals for suppressing several diseases related to oxidative stress.     

抗黄曲霉毒素M1的单克隆抗体细胞株的建立

本研究建立了抗黄曲霉素素ＡＦＭ１的单克隆抗体细胞株,用ＡＦＭ１－肟＝朱血清白蛋白（ＡＦＭ１－ｏｘｉｍｅ－ＢＳＡ）ＷＪＭ ＢＵ ＴＲ ＱＫＵＭ本研究建立     

Protective effect of vaccination against chickenpox

In a group of student volunteers vaccinated at the age of 13-17 years with vaccine produced by SmithKline Beecham Biologicals which contains the live attenuated strain of the Oka virus of varicella zoster the period of the protective effect of vaccination was assessed. In the course of 310,000 man-days of detailed investigation the authors revealed in 55 vaccinated subjects close exposure to a patient with varicella, and six of the vaccinated subjects contracted the disease after exposure. In the course of the subsequent three years no further case of varicella was recorded. Subjects vaccinated only by a single dose of the vaccine with low post-vaccination levels of specific antibodies contracted the disease.     

Suppression of lipid-hydroperoxide and DNA-adduct formation by isoflavone-containing soy hypocotyl tea in rats

Objective Phytoestrogen isoflavones (IFs) are considered to suppress estrogen-related cancers through their antiestrogenic activity. The antioxidant effect of IFs, however, has not been confirmed in anin vivo system, so suppression of hydroperoxide formation and resultant DNA adduct formation were studied. Methods The antioxidant effects of the soya-hypocotyl tea (SHT), which contained daidzein (14+/−1.5 mg/l) and genistein (3+/−0.5 mg/l), were examined in Wistar rats fed the AIN-76 control diet or iron deficient diet (FeD) for 4 weeks. The intake amount of the diet and IFs were measured daily. Urinary excretion of IFs was measured for 3 days before sacrifice. In addition to the serum lipid analyses, phosphatidylcholine hydroperoxide (PCOOH), and phosphatidylethanolamine hydroperoxide (PEOOH) production in red blood cells and the liver were measured as a biomarker of oxidants. Production of DNA adducts by oxidative stress was measured by the amount of 8-hydroxy-2′-deoxyguanosine (oh⁸dG) in the liver and kidney, and urine. Histological changes were checked by H&E staining and immunohistochemistry for oh⁸dG. Results FeD rats showed anemia, growth retardation, hyperlipidemia. IFs only lowered the triacylglycerol level and did not change the cholesterol level. Rats fed the normal diet did not show suppression of PCOOH and PEOOH production in either red blood cells or the liver, while groups administered SHT showed suppressed production of PCOOH and PEOOH in the liver. The cumulative intake of daidzein, genistein and the total amount of IFs showed significant inverse associations with urinary excretion of oh⁸dG. oh⁸dG in the kidney showed an inverse association with the amount of oh⁸dG in the urine. Enzymehistochemically, a strong localization of oh⁸dG was found in the epithelial cells of the bile canaliculi and proximal tubules of the kidney. Conclusion IFs and SHT showed antioxidant effects at physiological concentrations in anin vivo system. The antioxidant effects of IFs decreased oxidation stress to the nuclear DNA, which was shown by the decreased oh⁸dG production. It is suggested that to prevent various cancers, in addition to the known antiestrogenie, antityrosin kinase, and other effects. IFs appeared to promote excretion of oh⁸dG.     

Protective effect of Indigofera oblongifolia in CCl4-induced hepatotoxicity

The present study aimed at assessing the protective effect of Indigofera oblongifolia on carbon tetrachloride (CCl4-induced hepatotoxicity. Hepatotoxicity was induced in male Wistar rats using CCl4 (1 mL/day at an interval of 72 hours). CCl4-induced animals were treated with I. oblongifolia at different doses. Hepatoprotection was assessed from activities of marker enzymes in serum and antioxidant status in the liver after an experimental period of 10 days. The activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and lactate dehydrogenase were significantly (P < .001) increased in serum of CCl4-induced animals when compared with control animals. Antioxidant status was significantly lowered in CCl4-treated animals with a significant (P < .001) increase in the levels of lipid peroxides [thiobarbituric acid-reactive substances (TBARS)], significantly lower levels of glutathione (GSH), and lowered activities of superoxide dismutase (SOD), catalase (CAT), and GSH peroxidase (GPx). The protective effect of I. oblongifolia was evident from lowering of levels of marker enzymes in serum and maintenance of antioxidant status in the liver as seen from lowered levels of TBARS, increased levels of GSH, and increased activities of SOD, CAT, and GPx. These results show the protective effect of I. oblongifolia and suggest the antioxidant property of the extract.     

Protective effects of soybean isoflavone against gamma-irradiation induced damages in mice

In the present work, we investigated the radioprotective efficacy of soybean isoflavone (SI) in mitigating gamma-irradiation-induced oxidative damage to the livers and blood systems of adult Swiss albino mice. We administered various doses of SI (50 mg/kg b.wt, 100 mg/kg b.wt, and 400 mg/kg b.wt) to the mice for seven consecutive days before exposing them to a single dose of 4.56 Gy 60Co-gamma whole-body irradiation. The irradiated mice continued to receive SI for two or seven days before sacrifice. The SI treatments significantly elevated liver catalase (CAT) and glutathione peroxidase (GPx) enzyme activities and mRNA abundances, and decreased the malonaldehyde (MDA) levels. The SI treatments also accelerated the recovery of circulating white blood cells (WBCs) and reticulocytes (RETs) seven days following irradiation. These effects were dose-dependent, and the strongest effect on most biomarkers (but not on histopathology) was seen with an intermediate dose. Our results provide useful information for future investigations, and strongly implicate a clinical application for SI.     

应用超声波法提取大米中黄曲霉毒素B1

目的：建立一种超声波快速提取大米中黄曲霉毒素B1的方法,并对提取方法的回收率和准确度进行评价。方法：采用ELISA方法,研究和评价了超声波提取大米中黄曲霉素B1的提取效率。结果：与普通振荡处理相比,采用超声波处理明显增大了提取效率,缩短了提取时间,超声波处理10 min时达到最大提取率,振荡处理30 min才能达到,而且超声波最大提取浓度比振荡处理提高了30.5%。在针对0.1、1和10μg/kg这3个浓度水平做加标回收试验,回收率达到83.0%-95.2%,比振荡处理提高10%左右。结论：超声频率20 KHz,时间为10 min,为提取黄曲霉毒素B1的最佳条件,而且不同超声频率对结果产生的影响不显著。     

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.     

Aspergillus flavus and aflatoxin B1 in flour production

This paper discusses the results of investigations of contamination with aflatoxin — producing fungi and aflatoxin B₁ affecting 545 samples of wheat grains, 475 samples of intermediate products of wheat grain being milled to flour (like middlings) and 238 samples of flour. A significant contamination with moulds was detected in analyzed samples. AlthoughAspergillus (34.87%) and Penicillium (32.37%) dominated, other types were also present, e.g.,Cladosporium, Fusarium, Mucor, Alternaria, Rhizopus, Absidia andTrichoderma (listed in order of frequency). The presence ofAspergillus flavus, the known aflatoxin producer, was detected in 9.94% of analyzed samples. Isolates of A.Flavus were capable of producing aflatoxin B₁ under favourable conditions. Aflatoxin B₁ was found in 76.8% of samples contaminated withA. flavus. The highest contamination with aflatoxin B₁ was detected in wheat grain samples (mean value of 16.3 µg/kg) and in intermediate products of wheat grain being milled to flour (mean value of 11.13 µg/kg). Contamination was lower in flour samples (mean value of 4.13 µg/kg). With regard to proposed standards given by the FAO and WHO, under which the content of aflatoxin should not exceed 30 µg/kg in food products, only two of 96 samples did not meet these criteria.