大蒜阻断人体内N-亚硝基脯氨酸的合成

本文采用Ohshima以GC-TEA定量测定尿中N-亚硝基脯氨酸排出量的方法,以9名健康志愿者为对象,研究大蒜阻断人体内N-亚硝基脯氨酸的合成。受试者食生大蒜5g能完全阻断300mg硝酸钠与500mgL-脯氨酸在人体内合成N-亚硝基脯氨酸,平均阻断率为114.68％,为人群食大蒜预防内源性N-亚硝基化合物的合成及由此造成的致癌性危害提供科学依据。     

监测尿中N-亚硝基氨基酸作为内源性亚硝化的指标

自Magee和Barnes发现二甲基亚硝胺(NDMA)能引起大鼠肝癌以来,N-亚硝基化合物的致癌性得以广泛研究。已知N-亚硝基化合物是一类强致癌物。目前已对300多种这类化合物进行了研究,其中90％以上已被证明对多种动物有致癌作用。在所试动物中(包括灵长类在内),尚未见对N-亚硝基化合物致癌作用有抵抗力的报道,因而尽管目前尚无N-亚硝基化合物对人致癌的直接证据,但人们对N-亚硝基化合物在人类肿瘤病因中所起的     

从食物中每日摄入N-亚硝基化合物的量

N-亚硝基化合物广泛分布于环境和食物中,1982年Druckrey等首先报告,该化合物对多种动物显示强烈的致癌作用。其后Sandar等报道胺和亚硝酸可在机体内生成亚硝胺,自此引起食品卫生学界的关注。有人曾按各种食物的分析值,用数据处理机推断N-亚硝基化合物的摄入量。本文报告日本人平时饮食中,摄入N-亚硝基化合物的程度,以及含大量N-亚硝基化合物的前驱物质的食物,经混合、加热后N-亚硝基化合物的生成情况。     

柿科植物叶对亚硝胺体内外合成的阻断作用

本文研究了柿科植物叶对N-亚硝基脯氨酸(NPRO)体内外合成的阻断作用,从而得出如下结论:每天饮用5～10g多维茶就可阻断人体内源性亚硝基化合物的合成。对N-亚硝化反应起阻断作用的主要成分为还原型抗坏血酸,此外多酚类或其它成分也可能在其中起部分作用。     

虾米、咸鱼、咸蛋、咸菜中亚硝酸盐含量调查分析

亚硝酸盐是N-亚硝基化合物的前体物.现已确定N-亚硝基化合物对动物有较强的致癌作用[1].亚硝酸盐可以经过化学或生物学的途径合成多种多样的N-亚硝基化合物,而亚硝胺的形成浓度和亚硝酸盐的平方成正比[2].     

亚硝化农肥水中N-亚硝基化合物的分析

目的分析亚硝化农肥水中N-亚硝基化合物的种类。方法使用特异的高效液相色谱—光水解、热裂解—热能分析仪联机技术(HPLC-PHPS-TEA)进行分析检测。结果在亚硝化农肥水中发现N-亚硝基甲基脲(MNU),二甲基亚硝胺(NDMA);结论农肥水中含N-亚硝基化合物的胺类、酰胺类前体物:二甲胺和甲基脲。亚硝化农肥水中含有N-亚硝基化合物:二甲基亚硝胺和N-亚硝基甲基脲。这是两种能引起动物胃癌、食管癌和肝癌的N-亚硝基化合物。因此,从环境微生物、环境化学角度为"食管癌、胃癌和肝癌的氮循环——N-亚硝基化合物前体物病因假说"提供了有力的佐证。另外,使用我们的专利《消除饮用水中N-亚硝基化合物及其前体物的方法》作为干预措施,经过干预处理的农肥水,不管是否亚硝化,均无N-亚硝基化合物。证明专利方法有效,可以直接应用于食管癌、胃癌和肝癌的病因预防。     

啤酒中N-亚硝基化合物含量调查

N-亚硝基化合物对动物是强致癌物质。合成的100多种N-亚硝基化合物中,已证明其中80％左右可使动物致癌。国内外的一些流行病学调查资料也证明人类的某些癌症可能与N-亚硝基化合物有关。我们用气相色谱-质谱联用仪(系日本产JMS-D300双聚焦质     

环境中亚硝基类化合物的卫生学意义

环境中存在的亚硝基类化合物种类很多,污染食品后可形成对人类健康的威胁。N-亚硝基化合物对动物是一种强的致癌物,据报导还没有任何一种动物对此类化合物有抵抗力。由于实验动物的大多数器官对N-亚硝基化合物较为敏感,所以应该考虑到人类是易感的。动物实验证实,N-亚硝基化合物是诱发食管癌的化学物质。因此,这一大类化合物作为人类癌肿的可疑病因已受到高度重视,特别在一些食管癌高发地区。     

列车餐车食物中亚硝酸盐含量调查

亚硝酸盐是N-亚硝基化合物的前体物,现已确定N-亚硝基化合物对动物有较强的致癌作用〔1〕。亚硝酸盐可以经过化学或生物学的途径合成多种多样的N-亚硝基化合物,而亚硝胺的形成浓度和亚硝酸盐的平方成正比〔2〕。因此,必须控制食物中亚硝酸盐的含量。为了解列车餐车上食物中亚硝     

亚硝胺类化合物的危害及控制

1 前 言 亚硝胺类化合物属亚硝基化合物,包括亚硝胺与亚硝酰胺两类,是亚硝酸盐与胺类特别是仲胺合成的一大类化学物质,均含有N-亚硝基基团。大多数可致人体中毒甚至有极强的致癌性,对人类健康造成极大危害。     

EGCG和红茶多酚对HepG_2细胞脂质代谢相关基因表达的影响

目的:探讨表没食子儿茶素没食子酸酯(EGCG)和红茶多酚对人肝细胞癌HepG2细胞脂质代谢相关基因表达的影响。方法:HepG2细胞经EGCG(5μmol/L),红茶多酚(5μg/ml)或0.1%二甲亚枫(对照组)处理8h后,抽提RNA,并杂交至人14kcDNA芯片进行基因表达谱分析。应用实时RT-PCR技术对芯片结果进行验证。结果:HepG2细胞经EGCG和红茶多酚处理后表达差异的脂质代谢相关基因数分别为13条和29条,其中表达差异一致的基因有6条。实时RT-PCR结果与芯片结果一致。结论:EGCG和红茶多酚影响脂质代谢的机制是复杂的,此次实验发现的新靶标为今后茶多酚降脂作用研究提供了新的依据。     

Proline-rich proteins moderate the inhibitory effect of tea on iron absorption in rats

Tea inhibits iron absorption in studies in which tea is given with radiolabeled iron to humans as a single dose. Our objective was to test the hypothesis that proline-rich proteins (PRPs) may act as a defense against this effect by forming complexes with tannins, thereby preventing them from inhibiting iron absorption. Two studies were conducted. In study 1, rats were given test solutions containing (59)FeCl(3) in water, tea, or tea + gelatin (T/G). In study 2, the rats were divided into 3 groups and assigned to one of 3 nutritionally complete diets: control, tea (5 g tea tannin/kg diet), or T/G (5 g tea tannin + 60 g gelatin/kg diet). Rats were fed the respective diets for 5 d and then given a single (59)Fe-labeled meal of the diet. Iron absorption was measured by whole-body retention of the (59)Fe over a 2-wk period. Iron absorption in study 1 was lower in the tea group (24 +/- 9.6%, P < 0.05) than in the T/G (42 +/- 19.4%) or water groups (50 +/- 7.5%). In study 2, iron absorption did not differ among the groups. Rats fed the tea diet had dramatic hypertrophy of the parotid salivary glands. Adding gelatin as a proxy for salivary PRPs to the tea eliminated the inhibitory effect of tea on iron absorption. The results suggest that PRPs, whether from salivary glands or diet, can protect against the inhibition of iron absorption by tea.     

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。     

几种中草药及绿茶抗香烟焦油的致突变作用

为了深入研究开发利用中药资源，本实验用人外周血淋巴细胞的非程序ＤＮＡ合成试验（ＵＤＳ试验），对几种中草药及绿茶抗香烟焦油的致突变作用进行了研究。结果表明，白花蛇舌草、半枝莲、绿茶、茶多酚及犀黄丸均有不同程度的抗突变作用。先提取香烟焦油凝聚物后，再加１２５ｇ／Ｌ的白花蛇舌草，１２５ｇ／Ｌ的半枝莲，７８ｇ／Ｌ的绿茶，２５ｇ／Ｌ的茶多酚及３２５ｇ／Ｌ的犀黄丸就可以明显地对抗香烟焦油凝聚物对淋巴细胞ＤＮＡ的损伤作用；将中草药及绿茶先注入香烟内，再提取香烟凝聚物（内含中草药或绿茶），结果显示以上各浓度的中草药及绿茶同样能保护淋巴细胞的ＤＮＡ，且保护作用较前者更强。这一结果与其他抗突变试验结果基本一致。     

Association of green tea consumption with mortality from all-cause,cardiovascular disease and cancer in a Chinese cohort of 165,000 adult men

Tea is the most ancient and popular beverage in the world, and its beneficial health effects has attracted tremendous attention worldwide. However, the prospective evidence relating green tea consumption to total and cause-specific mortality is still limited and inconclusive. We recruited 164,681 male participants free of pre-existing disease during 1990–1991, with green tea consumption and other covariates assessed by the standardized questionnaire and mortality follow up continued until 2006 (mean 11 years; total person-years: 1,961,791). Cox regression analyses were used to quantify the associations of green tea consumption with all-cause (n = 32,700), CVD (n = 11,839) and cancer (n = 7002) mortality, adjusting simultaneously for potential confounders. At baseline, 18 % reported regular consumption of green tea. Compared with non-green tea drinkers, regular drinkers had significantly lower all-cause mortality, with adjusted hazard ratios (HRs) being 0.94 (95 % CI 0.89, 0.99) for ≤5 g/day, 0.95 (0.91, 0.99) for 5–10 g/day and 0.89 (0.85, 0.93) for >10 g/day. For CVD mortality, the corresponding HRs were 0.93 (0.85, 1.01) 0.91 (0.85, 0.98) and 0.86 (0.79, 0.93), respectively, while for cancer they were 0.86 (0.78, 0.98), 0.92 (0.83, 1.00) and 0.79 (0.71, 0.88), respectively. The patterns of these associations varied by smoking, alcohol drinking and locality. This large prospective study shows that regular green tea consumption is associated with significantly reduced risk of death from all-cause, CVD and cancer among Chinese adults.     

中国慢性病前瞻性研究:10个项目地区成年人群饮茶行为特征差异分析

目的 描述中国慢性病前瞻性研究(CKB)10个项目地区成年人群饮茶行为特征的地区差异。方法 分析CKB 10个项目地区512 891名30～79岁队列成员基线调查时饮茶行为信息,重点描述饮茶者每周饮茶行为特征的地区差异。结果 10个项目地区全部队列成员中,男性每周饮茶率(50.7%)高于女性(21.3%)。其中湖南项目地区调查人群每周饮茶率最高(男性74.3%,女性76.6%),河南项目地区最低(男性5.5%,女性1.0%)。除浙江和海口以外的其他8个项目地区,每周饮茶者以饮绿茶为主。青岛项目地区平均每次(男性3.8 g,女性3.1 g)、每日(男性6.2 g,女性4.1 g)和每周(男性38.4 g,女性25.0 g)茶叶消耗量均最高。结论 CKB 的10个项目地区研究人群在饮茶频率、品种、消耗量和浓淡喜好等特征上均存在较为明显的地区差异。     

The effect of tea on iron and aluminium metabolism in the rat

Weanling male Wistar rats were fed for 28 d on a semi-synthetic diet containing normal (38 micrograms/g) or low (9 micrograms/g) levels of iron. They were given water or tea infusion (20 g leaves/l water) to drink. Two further groups were given a normal- or low-Fe diet containing added tea leaves (20 g/kg diet). At the end of the study period, all rats given the low-Fe diet were severely anaemic, as assessed by haemoglobin, packed cell volume and liver Fe. Those given tea or the diet with added tea leaves showed a greater degree of Fe depletion. The blood and liver aluminium levels were not increased as a result of consuming tea or tea leaves, despite the higher Al intakes. Fe deficiency per se had no effect on Al absorption or retention from tea. It was concluded that the Al in tea was very poorly absorbed but that tea, either in the form of an infusion or as tea leaves, had an adverse effect on Fe status.     

Levels of Selected Heavy Metals in Black Tea Varieties Consumed in Saudi Arabia

The metal contents (Fe, Cu, Zn, Mn, Cr, Pb, Ni, Cd, Co) of 17 black tea samples were analyzed by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Among the investigated metals Mn was the highest (1,071.7 microg/g), whereas Pb showed minimum levels (0.30 microg/g). Iron was the second highest element found in black tea samples. Lowest Pb concentration (0.30 microg/g) was found in Abu Jabal tea; whereas maximum (2.2 microg/g) was found in Manasul tea. Lowest Cd concentration was found in Lipton whereas maximum level was observed for Al-Diafa tea. The concentrations of Co and Zn in the analyzed samples were in the range of 4.5-17.4 and 23.7-122.4 microg/g, respectively. Metal-to-metal correlation studies showed strong correlations between iron-chromium, iron-cadmium and lead-copper pairs. The data obtained in the present work compared well with the counterpart data reported internationally. Based upon the present safety standards, the tea versions selected in the present study were found to be safe for human consumption.     

山茶籽联合雌二醇对去卵巢大鼠骨重建和骨代谢酶的影响

目的:了解山茶籽联合雌二醇对去卵巢大鼠骨重建和骨代谢酶的影响,为山茶籽联合雌二醇治疗Ⅰ型骨质疏松症提供实验依据。方法:将90只5月龄健康雌性大白鼠分成假手术组(sham)、去卵巢模型组(OVX)、山茶籽组、雌二醇组(E2)、小剂量山茶籽+雌二醇组(Ts+E2),每组各18只。各实验组在第8、12、16周,随机处死6只大鼠,取左股骨切片观察骨组织,取右股骨测量骨密度,取左心血测量血清雌二醇、碱性磷酸酶。数据进行统计学分析。结果:OVX组的血清雌二醇和骨密度明显低于sham组(P<0.01),而血清碱性磷酸酶明显高于sham组(P<0.01);3个治疗组与sham组相比,各时间的血清雌二醇、碱性磷酸酶、骨密度均无显著性差异(P>0.05)。结论:小剂量的雌二醇联合山茶籽对去卵巢大鼠的骨质疏松症的治疗效果与单独使用较大剂量的山茶籽或较大剂量的雌二醇的治疗效果相近。     

Association between soy and green tea (Camellia sinensis) diminishes hypercholesterolemia and increases total plasma antioxidant potential in dyslipidemic subjects

OBJECTIVE: To evaluate the hypolipemic and antioxidant effects of soy and green tea alone and/or in association in dyslipidemic subjects. METHODS: One hundred dyslipidemic individuals were allocated into four groups. The soy group ingested 50 g of soy (kinako) daily, and the green tea group ingested 3 g of green tea in 500 mL of water per day. A third group ingested 50 g of soy and 3 g of green tea daily, and the control group had a hypocholesterolemic diet. Evaluations were performed at baseline and after 45 and 90 d. Plasma levels of total cholesterol, high-density lipoprotein, and triacylglycerols were evaluated by automated methods. Low-density lipoprotein (LDL) cholesterol was calculated using the Friedewald equation. LDL was isolated by ultracentrifugation. Total plasma antioxidant capacity and plasma levels of total lipid hydroperoxides and those linked to LDL were evaluated by chemiluminescence. The results were expressed as median values and their 25th to 75th percentiles, with a 5% level of significance. RESULTS: No significant difference occurred in LDL, high-density lipoprotein cholesterol, and triacylglycerol levels across groups. However, a statistically significant difference in total cholesterol occurred within the soy/green tea group 45 and 90 d after intervention. No statistically significant difference occurred in plasma levels of lipid hydroperoxides or those linked to LDL in any of the groups studied. All the groups that used soy and/or green tea presented increased total plasma antioxidant potential. CONCLUSION: Soy and green tea, alone or in combination, increased the total antioxidant potential of hypercholesterolemic patients, whereas only the combination decreased total cholesterol levels.