中华猕猴桃的防癌作用——(七)阻断慢性萎缩性胃炎病人体内N-亚硝基脯氨酸合成

本文报导了中华猕猴桃汁阻断慢性萎缩性胃炎(CAG)病人体内N-亚硝基脯氨酸(NPRO)合成的作用。在11名CAG病人的自身对照研究中,病人食入300mg NaNO_3和500mg脯氨酸后,尿中NPRO从本底值26.3nmol升至63.9nmol;同时服4.1ml浓缩猕猴桃汁后,多数人尿中NPRO明显下降,阻断率达94.4％。此外,有2人体内NPRO合成水平很高,提示可能有较高的癌变危险性。     

中华猕猴桃的防癌作用 (五)阻断大鼠和健康人体内N-亚硝基脯氨酸的合成

本文报导中华猕猴桃对体内N-2硝基脯氨酸(NPRO)合成的阻断效果。研究对象为15只雄性Wistar大鼠和10名男性健康志愿者。用自身对照分期观察。大鼠实验表明,中华猕猴桃汁可阻断体内NPRO合成(阻断率59.6％),且效果优于同浓度维生素C溶液,志愿者食入150g含75mg维生素C的中华猕猴桃可完全阻断服300mgNaNO_3和500mg脯氨酸后体内的NPRO合成,而75mg维生素C仅部分阻断。     

中华猕猴桃汁阻断胃癌高发区人群的内源性N-亚硝基化合物合成

本文以空腹胃液中挥发性亚硝胺(VNA)和24小时尿N-亚硝基脯氨酸(NPRO)排出量为指标,观察中华猕猴桃汁(简称桃汁)阻断胃癌高发区人群内源性N-亚硝基化合物(NOC)合成的阻断作用。受试者服用30ml桃汁后,空腹胃液中VNA总量由平均2.08±1.06μg/L显著下降至0.42±0.43μg/L(P<0.01),阻断率为79.8％。在NPRO试验中,受试验者摄入300mg脯氨酸后,尿NPRO排出量由本底的3.3±1.2μg/d显著升高至9.4±4.7μg/d(P<0.001)。与脯氨酸同时服用30ml桃汁后,NPRO排出量显著降低至本底水平(2.9±1.9μg/d,P<0.001)。上述阻断作用在胃粘膜病变程度不同的三组人群间未见显著性差别(P>0.1)。本研究证实,中华猕猴桃汁能有效地阻断胃癌高危人群内源性NOC合成。     

Effect of ascorbic acid dose taken with a meal on nitrosoproline excretion in subjects ingesting nitrate and proline

We determined the dose of ascorbic acid (ASC) given to subjects with a standard 400‐calorie meal that inhibited N‐nitrosoproline (NPRO) formation when we gave 400 mg of nitrate one hour before and 500 mg of L‐proline with the standard meal. Volunteers consumed their normal US diets but restricted their intakes of nitrate, proline, NPRO, and ASC. NPRO and N‐nitrososarcosine (NSAR) were determined in the 18‐hour urines by methylation followed by gas chromatography‐thermal energy analysis. Mean NPRO yields were 10.7, 41.9, 33.2, 22.3, and 23.1 nmol for groups of 9–25 subjects taking proline alone, proline + nitrate, and proline + nitrate + 120, 240, and 480 mg of ASC, respectively. There was a significant trend to lower NPRO yields as the ASC dose was raised. These results correspond to inhibitions by ASC of 28%, 62%, and 60%, respectively. Pairwise comparison showed that each group taking ASC formed significantly less NPRO than the group given only proline + nitrate. Mean NSAR yields were 9.0 nmol when proline alone was taken and 16.9–24.0 nmol when proline + nitrate + ASC was taken, with no trend to increase as the ASC dose was raised. However, NPRO and NSAR yields in individual urines were correlated with each other. We concluded that 120 mg of ASC taken with each meal (360 mg/day) would significantly reduce in vivo nitrosamine formation, similar to tests by Leaf and co‐workers (Carcinogenesis 8, 791–795, 1987) in which the reactants were taken between meals. The inhibitory dose of ASC may be <120 mg/meal when doses of nitrate and proline are not taken.     

Endogenous nitrosation of L-proline by dietary-derived nitrate

Two studies were conducted to assess the availability of normal dietary sources of nitrate for endogenous nitrosation of an amino acid substrate, L-proline, and to investigate the potential for dietary ascorbic acid to inhibit such nitrosation. In the first study, 16 subjects consumed a salad meal (containing about 172 mg nitrate) with and without a loading dose of proline. A significant increase (10.8 compared with 2.7 micrograms/24 hrs, p less than 0.0001) in mean urinary N-nitrosoproline (NPRO) excretion following meal plus substrate ingestion was indicative of intragastric proline nitrosation by meal-derived nitrate. In the second study (19 different subjects), the mean urinary NPRO level was significantly decreased (15.8 micrograms compared with 28.4, p = 0.022) by inclusion of ascorbic acid sources in the meal. This demonstrated inhibition of proline nitrosation by dietary sources of the vitamin. Large interindividual variation in nitrosating ability was apparent that was associated with variation in meal nitrate to salivary nitrite conversion. Although meals containing fresh vegetables, as tested here, could provide sufficient nitrate to result in endogenous formation of N-nitroso compounds, there will be considerable inter- and intraindividual variation in the extent of this process.     

Dietary fat and N-nitrosation in the rat

1. Groups of four conventional (CV) rats ate natural or purified diets either with or without 100 g fat/kg and drank 0.235 M-sodium nitrate. The fats tested were butterfat, coconut oil, olive oil, maize oil and safflower oil. 2. Decreased urinary excretion of N-nitrosoproline (NPRO) was observed in rats fed on fat-supplemented diets compared with those fed on low-fat diets, with butterfat having the greatest effect of the fats tested. 3. Reduced excretion of NPRO was not the result of inhibition of the intragastric N-nitrosation reaction or absorption of nitrosamine from the gastrointestinal tract. 4. The availability of nitrite in aqueous solution was decreased by the fat diets but the effect was similar in all the fats tested. 5. Nitrate reductase activity was present in the forestomach contents of CV rats at pH greater than 4 and was apparently inhibited by feeding a fat diet. No nitrate reductase activity was detected in stomach contents of germ-free rats. 6. Nitrate reductase activity in stomach and small intestinal tissue was not altered by feeding a fat diet. 7. It was concluded that nitrate reductase activity in stomach contents was of microbial origin and the decreased urinary excretion of NPRO on feeding the fat diets was mainly due to the inhibition of nitrate reductase activity in stomach contents.     

透析液流量对透析充分性的影响作用研究

目的 分析不同透析液流量对维持性血液透析患者透析充分性的影响作用.方法 将48例维持性血液透析患者根据透析液流量的不同分为500ml/min组、600ml/min组、700ml/min组、800ml/min组,每组12例,均治疗6周.每组治疗前和治疗后采血检测白蛋白(Alb)、血红蛋白(Hb)、红细胞压积(Hct)、血尿素氮(BUN)、血清肌酐(SCr)、甲状旁腺激素(iPTH),并计算尿素清除指数(Kt/V)和尿素下降率(URR).结果 500 ml/min组和600 ml/min组的Kt/V比较差异无统计学意义(P＞0.05),即透析液流量由500ml/min增加至600ml/min不能提高Kt/V,即不能提高透析充分性;500ml/min组、600ml/min组、700ml/min组和800ml/min组Kt/V比较差异有统计学意义,800ml/min组对透析充分性的影响作用更佳.采用自身对照方式比较不同透析液流量对透析充分性的影响,Kt/V随着透析液流量的增加而增加,即透析充分性与透析液流量呈正相关.结论 高透析液流量透析能提高患者的Kt/V,对提高透析充分性的作用显著.

Abstract：

Objective To analyze the dialysis adequacy of the maintenance hemodialysis patients under different dialyzate flow.Methods Forty-eight patients under maintenance hemodialysis were divided into four groups according to dialyzate flow:500 ml/min group,600 ml/min group,700 ml/min group and 800 ml/min group,with 12 patients in each group.Each group was treated 6 weeks.The albumin (Alb),hemoglobin(Hb),hematocrit(Hct),blood urea nitrogen (BUN),serum creatinine(SCr) and parathyroid hormone(iPTH) levels before and after treatment were examined,Kt/V and urea reduction ratio(URR) were calculated separately.Results There was no significant difference in Kt/V between 500 ml/min group and 600 ml/min group.Kt/V was no increased when the dialyzate flow rate increased from 500 ml/min to 600 ml/min,that was to say they could not improve the dialysis adequacy.There was statistically significant difference in Kt/V among 500 ml/min group,600 ml/min group,700 ml/min group and 800 ml/min group,and 800 ml/min group on the dialysis adequacy was better.Different dialyzate flow on the impact of the dialysis adequacy was compared in self-control method.Kt/V increased along with the increase of dialyzate flow,and the dialysis adequacy and dialyzate flow showed positive correlation.Conclusion The high dialyzate flow of dialysis treatment can improve Kt/V and has significant effect in enhancing the dialysis adequacy.     

中华猕猴桃的防癌作用——(六)阻断孕鼠、孕妇体内N-亚硝基脯氨酸合成

本文报导,中华猕猴桃汁阻断孕鼠及孕妇体内N-亚硝基脯氨酸(NPRO)合成作用,并首次报道NPRO可通过胎盘进入胎内。21只孕鼠实验中,在体内合成高量NPRO的同时,胎内检出了NPRO。中华猕猴桃汁可通过阻断NPRO在体内合成从而阻止其进入胎内。27名孕妇观察也见到同样的结果,仅在4名未服猕猴桃汁孕妇的羊水中检出低量NPRO。     

Problems with folacin status with use of orange juice substitutes in a geriatric institution

An increased range of orange drinks is now available with varying proportions of orange juice. These have begun to appear in institutions for the care of elderly people. With evidence of folacin deficiency in such elderly people, we evaluated the effect of either 100% orange juice or an orange drink (at least 5% juice) on folacin status in 19 institutionalized elderly people over a 13-week period. Serum folacin increased from 8.5 ± 0.8 to 13.2 ± 0.8 nmol/l ( P < 0.001) in 13 weeks, with 100 ml orange juice daily, but did not change from baseline (8.9 ± 0.8 nmol/l) to 13 weeks (8.5%± 0.7 nmol/l) with orange drink. By 6 weeks the difference between orange juice (11.0 ± 1.0 nmol/l) and orange drink (8.6 ± 0.7 nmol/l) was significant. Thus, not only is the choice of orange drink important, but small regular orange juice supplements can produce a significant increase in biochemical folacin status.     

High phosphorus intake only slightly affects serum minerals, urinary pyridinium crosslinks and renal function in young women

OBJECTIVE: Assessment of the physiological effects of a diet rich in phosphorus in young women. DESIGN: Control period I--commercial basic diet containing 1700 mg P and 1500 mg Ca/day for 4 weeks. Supplementation period--a 6 week high-phosphorus period of 3008 mg P and 1995 mg Ca/day. Control period II--4 weeks washout with basic diet as in period I. SETTING: Institute of Nutritional Science, Friedrich Schiller University, Jena. SUBJECTS: Ten healthy women, aged 20-30y. INTERVENTIONS: Orange juice and tablets, containing supplements of Ca5(PO4)3OH and NaH2PO4, totalling 1436 mg elemental phosphorus per day. RESULTS: There was an increase of 10.7+/-13.7 pg/ml in serum PTH, a decrease of 0.6+/-0.6 ng/ml in serum osteocalcin, an increase of 73.6+/-136.6 nmol/mmol creatinine in urinary pyridinoline and of 19.3+/-36.0 nmol/ mmol creatinine in urinary deoxypyridinoline, and a decrease of 2.6+/-9.3 mg/l in urinary microalbumin. All changes were insignificant. There were no changes in serum levels of Ca, PO4 or Zn, in serum concentration of 1,25-(OH)2D3, and in urinary beta-2-microglobulin excretion. Phosphorus supplementation caused intestinal distress, soft stools or mild diarrhoea. CONCLUSIONS: In spite of a high phosphorus supplementation no significant changes in bone-related hormones, pyridinium crosslinks as markers of bone resorption and parameters of renal function in young women were found.