尿中肌酐排泄稳定性的研究

分析在自由饮水条件下７７３个健康人的一次点尿样，６２人的２４ｈ尿样及８人连续５天收集的２４ｈ尿样，对这些尿样分别测定比重、肌酐浓度及肌酐排泄量，以揭示尿肌酐排泄的稳定性。研究发现，尿肌酐浓度与尿比重之间具有一定的相关性，尿肌酐排泄存在明显的个性差异和体内变异。可以认为，肌酐排泄的稳定性较差，用肌酐作为尿毒物浓度的校正参数，其适合性和可靠性值得怀疑。     

The effect of lecithin supplementation on plasma choline concentrations during a marathon

BACKGROUND: Previous studies have shown that plasma and urinary free choline concentrations decrease significantly during a marathon, and that these decreases may be associated with decreased performance. OBJECTIVE: In a pilot study, we sought to determine whether lecithin supplementation prior to a marathon would maintain plasma free and urinary choline concentrations and improve performance versus placebo. METHODS: 12 accomplished marathon runners, males (7) and females (5), 21 to 50 years of age were randomized to receive lecithin (4 capsules BID; PhosChol 900) or placebo beginning one day prior to the 2000 Houston-Methodist Health Care Marathon. The lecithin supplement provided approximately 1.1 g of choline on a daily basis (2.2 g total). Runners estimated finish time based on recent performance and training. Fasting, pre- and post-marathon plasma and a five-hour urine collection were analyzed for free choline and plasma for phospholipid-bound choline. Pre-race predicted, as well as the actual finish time, were recorded. RESULTS: All subjects completed the marathon. Plasma free choline decreased significantly in the placebo group and increased significantly in the lecithin group (9.6 +/- 3.6 to 7.0 +/- 3.6 nmol/mL vs. 8.0 +/- 1.2 to 11.7 +/- 3.6 nmol/mL, p = 0.001 for the delta between groups). No significant changes in plasma phospholipid-bound choline concentration were observed. There was a non-significant decrease in urine free choline in both groups. Actual finish time was 256.3 +/- 46.3 minutes for the lecithin group vs. 240.8 +/- 62.0 for the placebo group and the actual:predicted time was 1.03 +/- 0.06 (lecithin) and 1.07 +/- 0.08 (placebo), p = 0.36. CONCLUSION: Short-term lecithin supplementation prior to a marathon maintains normal plasma free choline concentration during the race, but failed to improve performance.     

Effect of coffee feeding on the duodenal transport and bile excretion of calcium in the rat

Caffeine administration increases endogenous fecal calcium and urinary calcium excretion resulting in a deterioration of calcium balance. The aim of the current study was to investigate the effect of coffee feeding on the intestinal transport of calcium and the mechanism of enhancement of endogenous calcium secretion. A group of rats were fed a diet containing 4% instant coffee and their calcium metabolism was compared to a control group fed the same diet with cellulose replacing the instant coffee. The results of the calcium balance study showed that 3 weeks of coffee consumption caused an increase in endogenous fecal calcium and urinary calcium excretion without a change in the absorption coefficient of calcium. We used an in vivo ligated loop technique to fractionate the calcium of the bile from that of the mucosal efflux and pancreatic secretions. The results indicated that the enhancement of endogenous calcium secretion into the duodenal lumen was from an increase in bile secretion and in mucosal efflux. When the bile flow rate was measured by direct cannulation of the bile duct, we were able to demonstrate that chronic coffee feeding resulted in a 45% increase in the bile flow rate without a change in the calcium concentration in the bile fluid.     

The influence of rat endogenous nitrogen excretion on the assessment of bean protein quality

The main objective of the present work was to study the interference of rat endogenous nitrogen excretion with the assessment of digestibility and biological value of dry bean (Phaseolus vulgaris, L.) protein. Dry bean plants were cultivated under (15NH4)2SO4 fertilization and at harvest dry beans had 1.080 atoms % of 15N-excess. Nitrogen balance studies indicated that bean protein digestibility and biological value were higher when N-balance was based on 15N-excess as compared to total nitrogen, both for undenaturated and heat-denaturated protein. The 15N-balance also showed that heat treatment significantly improved (p less than or equal to 0.05) the digestibility of bean protein in the integral flour and in protein isolate while the biological value decreased for both materials. The results permitted the conclusion that the conventional methods employed for calculation of bean protein digestibility and biological value, based on total nitrogen balance and protein-free diet, underestimate these indices of protein quality.     

Changes in organ growth with feeding pattern. The influence of feeding frequency on the circadian rhythm of protein synthesis in the rat

The effect of eating one large meal rather than several small meals per day on protein metabolism and the growth of individual organs was investigated in young male rats. Meal-eating did not affect the rate of protein catabolism in liver, kidney, small intestine, or spleen in vivo compared with continously fed control animals that consumed the same total amount of food. A circadian rhythm of protein synthesis was found in liver and kidney slices taken from normal rats killed at various times; starvation reduced the magnitude of protein synthesis but did not alter its cyclical nature. Consumption of the daily food all in one meal distorted the circadian rhythm, particularly when it was taken in the morning, and a morning meal increased the total 24 hour synthesis of protein in liver whereas an evening meal did not. Meal-feeding in the morning increased the weights of the liver, small intestine and tibia compared with continuously fed rats, but meal-feeding in the evening did not.     

Urinary chromium excretion, diurnal changes, and relationship to creatinine excretion in healthy and sick individuals of different ages.

Since urine is the main excretory pathway for chromium, this study was conducted to compare in normal individuals the daily urinary chromium excretion with a 4 hr sample, to investigate diurnal fluctuations of urinary chromium and age-dependent relationship between urinary chromium and creatinine excretion. The results can be summarized as 1) there was no significant difference between the observed 24 hr chromium excretion and 24 hr excretion calculated from the one 4 hr samples, 2) a diurnal variation was observed when urinary excretion was expressed as chromium per minute, but no time-related variation could be established when chromium/creatinine (Cr/Cre) ratios in samples from three different periods of the same day were compared, although a significant positive correlation existed between urinary chromium and creatinine concentration, 3) the Cr/Cre ratio was found to be age-dependent, 4) in malnourished children the Cr/Cre ratio was very high and significantly different from that of normal infants, 5) This ratio for the eight diabetics was found to be significantly higher when compared with normal adults. On the basis of these results, it is suggested that morning 4 hr urinary chromium reflects the daily chromium excretion and that the Cr/Cre ratio of single urine samples obtained during this period is a reliable criterion in the evaluation of chromium nutrition of individuals in different conditions, provided that the influence of age is taken into consideration.     

Urinary excretion of polyamines: importance of circadian rhythm, age, sex, menstrual cycle, weight, and creatinine excretion

The urinary excretion of putrescine, spermidine, spermine, and N1- and N8-acetylspermidines was measured in 95 volunteers. The 24-h excretion, split in four consecutive periods, was analyzed for circadian rhythm in eight volunteers. Circadian rhythm was observed in total polyamine and in N1- and N8-acetylspermidine excretions. The excretion rates of these polyamines were highest in the morning. The normal values for 24-h urinary excretion of polyamines were determined in 87 volunteers. Men excreted significantly more spermidine (P less than 0.001), N8-acetylspermidine (P less than 0.05), and spermine (P less than 0.001) than did women; putrescine excretion was higher in women (P less than 0.001). This variation was only partially explained by differences between sexes in body or muscle mass because most differences remained significant even after normalization for creatinine excretion and body weight. No correlation between the polyamine excretions and age or menstrual cycle was found.     

The influence of race on breast feeding

We evaluated the beginning of lactogenesis and the milk quantity until the fifth post-delivery day, before discharge, in 10 primiparae and 11 pluriparae Gypsies, as compared to 12 primiparae and 11 pluriparae Italian women. The results showed that both in primiparae and in pluriparae Gypsies, the lactogenesis started significantly earlier and the milk quantity was significantly greater than in Italian women.     

The influence of cooked kidney beans (Phaseolus vulgaris) on intestinal cell turnover and faecal nitrogen excretion in the rat

Male Wistar rats were fed on semi-synthetic diets containing cooked white kidney beans (Phaseolus vulgaris) or equivalent levels of protein and carbohydrate. No change was observed in over-all nitrogen balance in animals fed on the bean diet, but there was a two- to three-fold increase in their faecal excretion, compared with control rats. This was compensated by a decrease in urinary-N excretion. Homogenized small intestinal mucosa, prepared from bean-fed animals, showed a 28% increase in protein content compared with control material. Measurements of 3H-labelled thymidine turnover indicated that mucosal cell exfoliation was increased by approximately 35% in the small intestines of bean-fed rats compared with controls. It is concluded that though a diet rich in cooked P. vulgaris leads to some increase in mucosal cell turnover in the small intestine of rats, the consequent increase in mucosal protein loss could not account for the increased faecal-N excretion seen in these animals.     

The effect of choline supplementation on hepatic steatosis in the parenterally fed rat

Information regarding hepatic function during total parenteral nutrition in rats is often extrapolated to the clinical situation, but the steatosis observed in that species may simply reflect choline deficiency and be irrelevant to man. The effect of choline supplementation on hepatic lipid content and triglyceride secretion was examined in parenterally fed rats. Eighty to 90-day-old rats were randomized into three groups; group I received oral Purina Chow ad libitum, groups II and III received identical total parenteral nutrition regimens with the exception that group III received supplemental choline. After 7 days, peripheral triglyceride uptake was inhibited with Triton WR1339, the rate of secretion of 14C-labeled triglyceride measured after a bolus injection of 1-14C-palmitic acid, and total hepatic lipid content was measured. Total hepatic lipid content was elevated in group II (86.3 mg/g) and group III (83.3 mg/g), and both differed significantly from the control group I (35.2 mg/g, p less than 0.01), but the choline supplementation appeared to make no difference. Hepatic secretion of 14C-palmitic acid as 14C-triglyceride was reduced in group II (0.73%/ml plasma), and group III (0.72%/ml plasma) compared to group I (1.06%/ml plasma, p less than 0.05), and was unaffected by choline. The hepatic steatosis produced in the parenterally fed rat did not appear to be due to choline deficiency but to some other factors which may be important in man.     

Effects of age, feeding regimen, and glucocorticoids on catecholamine and cortisol excretion in preterm infants

BACKGROUND: The sympathoadrenal system is important in maintaining normal physiologic functioning in infants and increased output also can reflect stress. We sought to determine the effects of age, feeding regimen, and glucocorticoids on catecholamine and cortisol excretion in preterm infants and to assess whether a particular strategy of feeding enhanced sympathoadrenal development or was stressful. METHODS: Preterm infants (26-30 wk gestation; n = 171) were assigned randomly to begin trophic feedings from day 4 through 14 (trophic group) or to start feedings at day 15 (standard group) with feedings administered either by bolus every 3 hours (bolus) or continuously over 24 hours (continuous). At 10, 28, 40, 50, and 60 days of age, urine was collected continuously for 6 hours for measurement of catecholamines (norepinephrine, epinephrine, dopamine), cortisol, and creatinine. Data were available for 98 infants. RESULTS: Norepinephrine excretion increased with postnatal age. The increase with age was significantly greater in the trophic group compared with that in the standard group. Epinephrine excretion did not change with age, and there were no differences between trophic and standard groups. Dopamine excretion increased with age but was similar between trophic and standard groups (borderline significantly greater in the trophic group). Cortisol excretion increased with age and also was similar between trophic and standard groups. There was no effect on catecholamine or cortisol excretion of bolus vs continuous feedings, antenatal or postnatal corticosteroids, gestational age at birth, age at which full feedings were attained, or use of human milk compared with preterm formula. CONCLUSIONS: The greatest determinant of catecholamine and cortisol excretion is postnatal age. Feeding method, type of feeding, and glucocorticoid administration in the amounts customarily used have little significant effect on catecholamine or cortisol excretion. The apparent link between early feeding and norepinephrine (and possibly dopamine) excretion warrants further investigation.