绿茶抑制大鼠体内杂环胺-DNA加合物的形成

食物中的致突变物２－氨基－１－甲基－６－苯基咪唑并「４，５－ｂ」吡啶可诱发大鼠结肠和乳腺肿瘤，而且与人类癌症特别是结肠和直肠癌的密切关系。本研究以致癌物－ＤＮＡ加合物为生物标记物，观察绿茶对ＰｈＩＰ致癌作用的预防效果及机理。     

染苯小鼠DNA加合物的形成与剂量－反应关系

染苯小鼠ＤＮＡ加合物的形成与剂量－反应关系王春光，李桂兰，尹松年苯能导致骨髓造血组织的多种疾患且具致癌作用。我们曾以３２Ｐ后标记方法就腹腔注射染苯小鼠体内ＤＮＡ加合物的形成及持续时间进行了探讨，发现苯在体内可至少形成２种加合物［１］．然而小鼠吸入染苯...     

重量法测定血苯-白蛋白加合物的初步研究

苯进入人体内形成有很高活性的环氧化物，可与多种蛋白形成加合物。有研究用同位素标记的苯（Ｃ６２Ｈ６）白蛋白为内标衍生后，用气质联仪（ＧＣＭＳ）测定血液中的苯白蛋白加合物［１］。由于采用昂贵的仪器和同位素内标物，在一般实验室难以进行。本研究采用重...     

流感甲3（H3N2）和甲1（H1N1）型的临床反应的研究

１９９８年２月中旬至３月上旬，广西铁路百色地区某小学发生流感暴发流行，经病毒分离证实为混合型流感暴发流行，发病以甲１（Ｈ１Ｎ１）和甲３（Ｈ３Ｎ２）为主［１］。为此我们对甲１（Ｈ１Ｎ１）和甲３（Ｈ３Ｎ２）两种不同亚型毒株引起临床反应进行研究，结果报告如下。１　对象与方法１１　研究对象　随机抽取该时间内发病的患者双份血清３９人份，分别用流感毒株甲３型（Ａ／Ｓｈａｎｇｄｏｎｇ／９／９３）（Ｈ３Ｎ２），甲１型（Ａ／Ｔａｉｗａｎ／１／８６）（Ｈ１Ｎ１）做血凝抑制试验测定血凝抑制（ＨＩ）抗体滴度。凡ＨＩ…     

姜黄素抗突变抗癌作用研究进展

姜黄素是一种天然的食用色素，具有消炎，抗动脉粥样硬化等作用。近年来，发现其具有抗诱变及抗癌作用，其抗癌机理可能如下：１、抑制某些癌基因的表达；２．抑制致癌物的活化，诱导去毒酶。加快致癌物的排泄，阻止ＤＮＡ加合物的形成；３．具有抗氧化，清除自由基的作用。     

能量限制对体外~3H—AFB_1和~3H—MNU与大鼠肝细胞DNA结合的影响

能量限制对体外￣３Ｈ—ＡＦＢ＿１和￣３Ｈ—ＭＮＵ与大鼠肝细胞ＤＮＡ结合的影响曹盛丰近年来，营养毒理学的研究进展较快。有报道指出，能量限制能延长寿命［１，２］，延缓慢性退化性疾病的病程［３，４］，降低致癌化合物对癌症的诱导作用［５，６］。但是，能量水平...     

石棉与烟雾溶液对人胚肺细胞DNA的损伤作用

目的探讨石棉与烟雾溶液联合作用对人胚肺细胞ＤＮＡ的损伤作用。方法采用非程序ＤＮＡ合成试验，对石棉与烟雾溶液单独及联合作用时人胚肺细胞ＤＮＡ修复合成情况进行了观察。结果石棉与烟溶液单独作用时，均能诱导人胚肺细胞的非程序ＤＮＡ合成试验，且均有明显的剂量反应关系；当二者联合作用时，其造成的细胞３Ｈ标记的胸腺嘧啶核苷（［３Ｈ］－ＴｄＲ）参入量的增加量明显高于二者单独作用时引起的［３Ｈ］－ＴｄＲ参入量的增加量之和。此外，ＯＨ的清除剂二甲基亚砜可部分阻止石棉引起的［３Ｈ］－ＴｄＲ参入。结论石棉与烟溶液联合对人胚肺细胞ＤＮＡ的损伤具有协同作用，ＯＨ在石棉引起的细胞ＤＮＡ损伤中起一定作用。     

跳伞对空降兵血浆HSP70和肿瘤坏死因子的影响

生产和环境中的物理、化学、生物因素及其引发的体内生化、生理、病理反应和产生的代谢产物均可诱导热应激蛋白（ｈｅａｔｓｔｒｅｓｐｒｏｔｅｉｎｓ,ＨＳＰｓ）的合成增加［１３］,其中最为重要、诱导最强的是ＨＳＰ７０。伞兵在三维空间进行各种状态的变化,会受到...     

中国仓鼠肺成纤维细胞过氧化适应及其机理

目的为研究真核细胞过氧化适应反应及其可能机理。方法在中国仓鼠肺成纤维细胞（ＣＨＬ）上，通过低剂量Ｈ２Ｏ２预处理，观察细胞和ＤＮＡ对高剂量Ｈ２Ｏ２再处理的适应反应，同时测定ＣＡＴ酶和ＰＡＲＰ的变化及其在适应ＤＮＡ断裂中的作用。结果在细胞活力和ＤＮＡ断裂水平上均观察到非致死性适应反应，然而这两种水平的适应模式（条件）有所不同，提示两者可能存在不同的诱导适应的途径。低剂量Ｈ２Ｏ２可诱导ＣＡＴ酶活性增高，并与抑制ＤＮＡ断裂的适应效应具有相关性（ｒ＝０．９５，Ｐ＜０．０５），同时ＰＡＲＰ阻断剂３氨基苯胺（３ＡＢ）可明显抑制ＤＮＡ断裂水平的适应反应。结论ＣＨＬ细胞系存在细胞活力变化和ＤＮＡ断裂的过氧化非致死性适应。ＣＡＴ和ＰＡＲＰ参与过氧化ＤＮＡ断裂的适应诱导     

体外甲基丙烯酸环氧丙酯-DNA加合物的研究

目的 探讨新诱变剂甲基丙烯酸环氧丙酯（ＧＭＡ）与ＤＮＡ形成加合物的类型和特性。方法 在体外条件下,dＡＭＰ、dＣＭＰ、dＧＭＰ、dＴＭＰ及小牛胸腺ＤＮＡ与ＧＭＡ发生反应,反应产物经紫外光谱、反相高效液相色谱（ＲＰ－ＨＰＬＣ）和质谱先进方法分析。结果 ＧＭＡ能与dＡＭＰ、dＣＭＰ、dＧＭＰ及小牛胸腺ＤＮＡ形成专一性共价结合。已 被证实１捉ＧＭＡ－ＤＮＡ加合物为Ｎ３－甲基丙烯酸－２羟丙－基－脱氧胞嘧啶核苷一磷     

Tea as a potential chemopreventive agent in PhIP carcinogenesis: effects of green tea and black tea on PhIP-DNA adduct formation in female F-344 rats

The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed during the cooking of proteinaceous animal foods (meat, chicken, and fish). PhIP is a carcinogen in the Fischer 344 (F-344) rat; it induces mammary tumors in female rats and lymphomas and colon and prostate tumors in male rats. In F-344 rats, PhIP forms DNA adducts in various organs, including the target organs. Inhibition of PhIP-DNA adduct formation is likely to lead to inhibition of PhIP tumorigenicity. We have examined the chemopreventive properties of green tea and black tea in PhIP carcinogenesis by evaluating their effects on PhIP-DNA adduct formation in the female F-344 rat. Young adult animals were maintained on powdered AIN-76A diet while receiving regular drinking water or 2% (wt/vol) infusions of green tea or black tea for a total of six weeks. During Weeks 3, 4, and 5, all animals received PhIP by gavage (1 mg/kg/day). Three rats per group were euthanized on Days 1 and 8 after termination of PhIP exposure. DNA was isolated from a number of organs and analyzed for PhIP-DNA adducts by 32P-postlabeling assays. Compared with animals on regular drinking water, PhIP-DNA adduct formation was inhibited in small intestine, colon, liver, and mammary epithelial cells (MECs) of animals receiving green tea or black tea as the sole source of drinking fluid. Green tea inhibited adduct formation in colon, liver, and MECs (33.3-80.0%) on both days, but only on Day 8 (54.4%) in small intestine. Black tea inhibited adduct formation on both days in liver (71.4-80.0%), on Day 1 in colon (40.0%), and on Day 8 in small intestine (81.8%); it had no effect on MEC adducts. Neither green tea nor black tea had an effect on adduct levels in pancreas, lungs, white blood cells, heart, kidneys, spleen, cecum, or stomach. Similarly, these teas did not affect the rate of adduct removal (percent change from Day 1 to Day 8) in any organ. It is concluded that green tea and black tea are potential chemopreventive agents in PhIP-induced tumorigenesis in the F-344 rat.     

Inhibition of DNA adduct formation of PhIP in female F344 rats by dietary conjugated linoleic acid

The dietary mutagen 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) is a mammary carcinogen in the female Fischer (F344) rat and a colon carcinogen in the male F344 rat. To exert its carcinogenicity, it is believed that PhIP needs to form adducts with DNA, a process requiring N‐hydroxylation of PhIP by cytochromes P‐450 1A1 and/or 1A2 (CYP 1A1 and/or 1A2), as well as further esterification of the hydroxylamine thus formed. Dietary conjugated linoleic acid (CIA) inhibits chemical carcinogenesis in various experimental models. We have examined the effect of dietary CLA on PhIP‐DNA adduct formation in female F344 rats. Four‐week‐old animals were maintained on AIN‐76A diet without or with CLA (1%, 0.5%, and 0.1% wt/wt) for 57 days. PhIP was added to the diets (0.04% wt/wt) from Days 14–42. Animals were killed (4/group) on Days 43, 50, and 57. DNA isolated from liver, mammary epithelial cells (MEC), colon, and white blood cells (WBC) was analyzed for PhIP‐DNA adducts by ³²P‐postlabeling assays. On Day 43, CIA inhibited adduct formation in the liver (up to 58%) in a dose‐dependent manner. CIA also inhibited hepatic adduct levels (29–39%) on Day 50 (at 1.0% and 0.5% CIA) and on Day 57 (53% at 0.5% CLA). CLA significantly reduced adduct levels in the WBC on Day 50 (63–70%). Adducts in MEC and the colon were not affected by dietary CIA. On Day 57, adduct levels in MEC, liver, colon, and WBC were 0–30.3%, 8.6–41.7%, 21.5–50.7%, and 7.5–11.8%, respectively, of those on Day 43. Northern blot analysis of liver RNA showed that dietary CIA did not affect steady‐state levels of CYP 1A1 or 1A2 mRNA. It is concluded that dietary CLA inhibits PhIP‐DNA adduct formation in liver and WBC but that those in MEC and the colon are unaffected when a low‐level dietary regimen of carcinogen and inhibitor was used. In inhibiting PhIP‐DNA adduct formation, CIA does not appear to act by inhibiting CYP 1A1 or 1A2 expression.     

Effects of dietary conjugated linoleic acid on DNA adduct formation of PhIP and IQ after bolus administration to female F344 rats

Meats cooked at high temperatures contain mutagenic heterocyclic amines such as 2‐amino‐l‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) and 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ). In female Fischer 344 rats, IQ is a multiorgan carcinogen, whereas PhIP induces mammary adenocarcinomas. For IQ and PhIP, N‐hydroxylation, catalyzed by microsomal cytochrome P‐450 1A1 and/or 1A2, and then esterification, especially O‐acetylation, are the principal steps leading to DNA adduct formation. Conjugated linoleic acid (CLA) is a mixture of conjugated linoleic acid isomers found in various meat and dairy products. We have examined the effect of dietary CLA on DNA adduct formation by PhIP and IQ in female Fischer 344 rats. Four‐week‐old animals were maintained on AIN‐76A diet without or with CLA (4% wt/wt) and treated with IQ or PhIP (50 mg/kg by gavage) after two weeks. Animals were killed (4/group) one, four, and eight days later. DNA isolated from mammary epithelial cells, liver, colon, and white blood cells was analyzed for carcinogen‐DNA adducts by ³²P‐postla‐beling assays. On Day 1, dietary CLA significantly inhibited adduct formation (82.0%) in mammary epithelial cells in IQ‐but not in PhIP‐treated rats. In the colon, dietary CLA significantly inhibited PhIP‐DNA adduct formation (18.7%) on Day 8 but increased IQ‐DNA adduct formation (30.5%) on Day 8. Dietary CLA had no effect on adduct levels in liver or white blood cells. Calf thymus DNA was incubated with N‐hydroxy‐PhIP or ‐IQ in the presence of acetyl‐CoA. Enzymatic activation was catalyzed by liver or mammary cytosol. A two‐week pretreatment with 2% (wt/wt) dietary CLA had no effect on O‐acetyltransferase‐catalyzed IQ‐ or PhIP‐DNA adduct formation. It is concluded, under certain conditions, that dietary CLA can lower IQ‐ and PhlP‐DNA adduct formation. Overall, however, the major mode of action of CLA is probably by a mechanism other than the inhibition of the N‐hydroxylation and subsequent O‐acetylation of PhIP or IQ.     

Inhibition of DNA adduct formation of PhIP in female F344 rats by dietary conjugated linoleic acid

The dietary mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mammary carcinogen in the female Fischer (F344) rat and a colon carcinogen in the male F344 rat. To exert its carcinogenicity, it is believed that PhIP needs to form adducts with DNA, a process requiring N-hydroxylation of PhIP by cytochromes P-450 1A1 and/or 1A2 (CYP 1A1 and/or 1A2), as well as further esterification of the hydroxylamine thus formed. Dietary conjugated linoleic acid (CLA) inhibits chemical carcinogenesis in various experimental models. We have examined the effect of dietary CLA on PhIP-DNA adduct formation in female F344 rats. Four-week-old animals were maintained on AIN-76A diet without or with CLA (1%, 0.5%, and 0.1% wt/wt) for 57 days. PhIP was added to the diets (0.04% wt/wt) from Days 14-42. Animals were killed (4/group) on Days 43, 50, and 57. DNA isolated from liver, mammary epithelial cells (MEC), colon, and white blood cells (WBC) was analyzed for PhIP-DNA adducts by 32P-postlabeling assays. On Day 43, CLA inhibited adduct formation in the liver (up to 58%) in a dose-dependent manner. CLA also inhibited hepatic adduct levels (29-39%) on Day 50 (at 1.0% and 0.5% CLA) and on Day 57 (53% at 0.5% CLA). CLA significantly reduced adduct levels in the WBC on Day 50 (63-70%). Adducts in MEC and the colon were not affected by dietary CLA. On Day 57, adduct levels in MEC, liver, colon, and WBC were 0-30.3%, 8.6-41.7%, 21.5-50.7%, and 7.5-11.8%, respectively, of those on Day 43. Northern blot analysis of liver RNA showed that dietary CLA did not affect steady-state levels of CYP 1A1 or 1A2 mRNA. It is concluded that dietary CLA inhibits PhIP-DNA adduct formation in liver and WBC but that those in MEC and the colon are unaffected when a low-level dietary regimen of carcinogen and inhibitor was used. In inhibiting PhIP-DNA adduct formation, CLA does not appear to act by inhibiting CYP 1A1 or 1A2 expression.     

Effects of dietary conjugated linoleic acid on DNA adduct formation of PhIP and IQ after bolus administration to female F344 rats

Meats cooked at high temperatures contain mutagenic heterocyclic amines such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). In female Fischer 344 rats, IQ is a multiorgan carcinogen, whereas PhIP induces mammary adenocarcinomas. For IQ and PhIP, N-hydroxylation, catalyzed by microsomal cytochrome P-450 1A1 and/or 1A2, and then esterification, especially O-acetylation, are the principal steps leading to DNA adduct formation. Conjugated linoleic acid (CLA) is a mixture of conjugated linoleic acid isomers found in various meat and dairy products. We have examined the effect of dietary CLA on DNA adduct formation by PhIP and IQ in female Fischer 344 rats. Four-week-old animals were maintained on AIN-76A diet without or with CLA (4% wt/wt) and treated with IQ or PhIP (50 mg/kg by gavage) after two weeks. Animals were killed (4/group) one, four, and eight days later. DNA isolated from mammary epithelial cells, liver, colon, and white blood cells was analyzed for carcinogen-DNA adducts by 32P-postlabeling assays. On Day 1, dietary CLA significantly inhibited adduct formation (82.0%) in mammary epithelial cells in IQ--but not in PhIP-treated rats. In the colon, dietary CLA significantly inhibited PhIP-DNA adduct formation (18.7%) on Day 8 but increased IQ-DNA adduct formation (30.5%) on Day 8. Dietary CLA had no effect on adduct levels in liver or white blood cells. Calf thymus DNA was incubated with N-hydroxy-PhIP or -IQ in the presence of acetyl-CoA. Enzymatic activation was catalyzed by liver or mammary cytosol. A two-week pretreatment with 2% (wt/wt) dietary CLA had no effect on O-acetyltransferase-catalyzed IQ- or PhIP-DNA adduct formation. It is concluded, under certain conditions, that dietary CLA can lower IQ- and PhIP-DNA adduct formation. Overall, however, the major mode of action of CLA is probably by a mechanism other than the inhibition of the N-hydroxylation and subsequent O-acetylation of PhIP or IQ.     

Effect of dietary constituents with chemopreventive potential on adduct formation of a low dose of the heterocyclic amines PhIP and IQ and phase II hepatic enzymes

We conducted a study to evaluate dietary chemopreventive strategies to reduce genotoxic effects of the carcinogens 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). PhIP and IQ are heterocyclic amines (HCAs) that are found in cooked meat and may be risk factors for cancer. Typical chemoprevention studies have used carcinogen doses many thousand-fold higher than usual human daily intake. Therefore, we administered a low dose of [14C]PhIP and [3H]IQ and utilized accelerator mass spectrometry to quantify PhIP adducts in the liver, colon, prostate, and blood plasma and IQ adducts in the liver and blood plasma with high sensitivity. Diets supplemented with phenethylisothiocyanate (PEITC), genistein, chlorophyllin, or lycopene were evaluated for their ability to decrease adduct formation of [14C]PhIP and [3H]IQ in rats. We also examined the effect of treatments on the activity of the phase II detoxification enzymes glutathione S-transferase (GST), UDP-glucuronyltransferase (UGT), phenol sulfotransferase (SULT) and quinone reductase (QR). PEITC and chlorophyllin significantly decreased PhIP-DNA adduct levels in all tissues examined, which was reflected by similar changes in PhIP binding to albumin in the blood. In contrast, genistein and lycopene tended to increase PhIP adduct levels. The treatments did not significantly alter the level of IQ-DNA or -protein adducts in the liver. With the exception of lycopene, the treatments had some effect on the activity of one or more hepatic phase II detoxification enzymes. We conclude that PEITC and chlorophyllin are protective of PhIP-induced genotoxicity after a low exposure dose of carcinogen, possibly through modification of HCA metabolism.     

Effects of chemoprotective agents on the metabolic activation of the carcinogenic arylamines PhIP and 4-aminobiphenyl in human and rat liver microsomes

Carcinogenic aromatic amines, including the heterocyclic amines, may pose a significant health risk to humans. To determine the potential for chemoprotective intervention against the carcinogenicity of these arylamines and to better understand their mechanism of action, a range of agents, most of them natural dietary constituents, was examined in vitro for their ability to modulate the N-hydroxylation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 4-aminobiphenyl (ABP), an initial step in their bioactivation. Experiments were conducted with rat and human liver microsomes. The agents (diallyl sulfide, indole-3-carbinol, alpha-angelicalactone, cafestol/kahweol palmitates, cafestol, kahweol, benzylisothiocyanate, genistin, formononetin, daidzin, equol, biochanin A, Oltipraz, tannic acid, quercetin, ethoxyquin, green tea, and black tea) comprised a variety of chemical classes that included sulfur-containing compounds, antioxidants, flavonoids, phytoestrogens, diterpenes, and polyphenols. Several of these agents, quercetin, ethoxyquin, and black tea, were found to strongly inhibit PhIP N-hydroxylation in rat liver microsomes, resulting in a nearly 85-90% decrease in activity at 100 microM or 0.2%. Tannic acid and green tea, in addition to these agents, were also strong inhibitors of ABP N-hydroxylation. In human liver microsomes, each of these agents was strongly inhibitory (approx 85-95% at 100 microM or 0.02%) of PhIP and ABP N-hydroxylation. Theaflavins and polyphenols were judged to be the primary inhibiting components in the teas, the theaflavins showing the most potent effect. These results demonstrate that chemoprotective agents can inhibit the bioactivation of carcinogenic arylamines, and this is likely to be one of the mechanisms of protection.     

Comparison of white tea, green tea, epigallocatechin-3-gallate, and caffeine as inhibitors of PhIP-induced colonic aberrant crypts

There is growing interest in the possible health benefits of tea. We reported previously on the inhibition by white tea of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced colonic aberrant crypt foci (ACF) in the rat (4). To distinguish between blocking and suppressing effects, and thus provide mechanistic insights into prevention during the initiation versus post-initiation phases of carcinogenesis, white tea, and green tea were administered at 2% (w/v) as the sole source of drinking fluid either 2 wk before and 2 wk during PhIP dosing (100 mg/kg, every other day by oral gavage), or starting 1 wk after the carcinogen and continued until the study was terminated at 16 wk. In the former protocol, each tea produced marginal inhibition of colonic ACF, despite evidence for changes in several hepatic enzymes involved in heterocyclic amine metabolism. Post-initiation, however, the data were as follows (ACF/colon, mean +/- SE): PhIP/water 12.2 +/- 1.5; PhIP/white tea 5.9 +/- 0.9 (** P < 0.01); PhIP/caffeine 5.9 +/- 1.5 (** P < 0.01); PhIP/EGCG 3.5 +/- 0.8 (***P < 0.001); PhIP/green tea 8.9 +/- 1.2 (P = 0.22, not significant). In the latter study, apoptosis was determined using in situ oligo ligation and cleaved caspase-3 assays, whereas cell proliferation was assessed via bromodeoxyuridine (BrdU) incorporation. No consistent changes were seen in apoptosis assays, but BrdU labeling was as follows (percent of cells positive/colonic crypt, mean +/- SE): PhIP/water 10.4 +/- 0.6; PhIP/white tea 8.6 +/- 0.2 (*P < 0.05); PhIP/EGCG 6.0 +/- 0.85 (** P < 0.01); PhIP/caffeine 8.75 +/- 0.45 (*P < 0.05); PhIP/green tea 9.5 +/- 0.4 (P > 0.05, not significant). The data imply that white tea, caffeine, and EGCG may be most effective post-initiation, via the inhibition of cell proliferation in the colon and through the suppression of early lesions.