Urea production during prolonged swimming

Male interscholastic swimmers (n = 8) completed a 4572 m training swim in 62 ±1.1 min (x ± s.e.) with terminal heart rate and blood lactate of 152 ± 6 beats min^‐1 and 6.9±0.89 mM, respectively. Sweat rate (0.48±0.0951. h^‐1) was lower than similar intensity cycling (1.5±0.13 1. h^‐1) or running (1.1 ± 0.14 l.h^‐1). Post‐swim serum urea N (11.6±0.71 mM) was elevated (P<0.05) vs pre‐swim (4.6±0.39 mM). Post‐swim urine volume (860±75 ml 24 h^‐1) was reduced (P<0.07) and resulted in an elevated (P<0.05), but delayed (24–84 h), post‐exercise urea N excretion. Although the reduced urine and sweat production during the swim undoubtedly contributed to the elevated serum urea, there must be another explanation because together they could only account for 38% of the observed increase. On the basis of the magnitude of serum urea increase, it appears that the swim caused an increase in urea production (amino acid oxidation). The failure to observe larger increases in urinary urea during recovery indicates that either urea excretion following exercise continues for prolonged periods of time (>48 h) or another significant mode of nitrogen excretion exists.     

Optimization of insulin-mediated creatine retention during creatine feeding in humans

Abstract

The aim of this study was to determine whether creatine ingested in combination with relatively small quantities of essential amino acids, simple sugars, and protein would stimulate insulin release and augment whole-body creatine retention to the same extent as a large bolus of simple sugars. Seven young, healthy males underwent three randomized, 3-day experimental trials. Each day, 24-h urine collections were made, and on the second day participants received 5 g creatine + water (creatine trial), 5 g creatine + ～95 g dextrose (creatine + carbohydrate) or 5 g creatine + 14 g protein hydrolysate, 7 g leucine, 7 g phenylalanine, and 57 g dextrose (creatine + protein, amino acids, and carbohydrate) via naso-gastric tube at three equally spaced intervals. Blood samples were collected at predetermined intervals after the first and third naso-gastric bolus. After administration of the first and third bolus, serum insulin concentration was increased by 15 min (P < 0.05) in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials compared with creatine alone, and plasma creatine increased more following creatine alone (15 min, P < 0.05) than in the creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate trials. Urinary creatine excretion was greater with creatine alone (P < 0.05) than with creatine + carbohydrate and creatine + protein, amino acids, and carbohydrate. Administration of creatine + protein, amino acids, and carbohydrate can stimulate insulin release and augment whole-body creatine retention to the same extent as when larger quantities of simple sugars are ingested.     

补充不同剂量支链氨基酸对运动大鼠下丘脑5-羟色胺及其前体的影响

观察补充支链氨基酸(BCAA)后大鼠力竭游泳运动恢复期下丘脑细胞外液BCAA、游离色氨酸(f-Trp)和5-羟色胺(5-HT)的变化,分析补充BCAA是否能够提高大鼠的运动能力,比较补充BCAA的效果,探索补充BCAA的最佳剂量。方法:将32只大鼠随机分为对照组、小剂量补充组[1.25g/(kg·BW-1)]、中剂量补充组[2.5g/kg·BW-1)]和大剂量补充组[5g/(kg·BW-1)],每组8只。BCAA补充方案为:每天上午补充一次,每周6次(周日暂停),持续6周。6周后,在大鼠进行力竭游泳运动前一天下午取大鼠尾血测试血氨。采用毛细管电泳-激光诱导荧光法检测大鼠下丘脑细胞外液BCAA、f-Trp和5-HT的浓度。结论:血氨随着BCAA补充剂量的增加而升高,小剂量补充BCAA对机体血氨的生成无影响;补充BCAA能提高大鼠力竭游泳运动能力,但并不随BCAA补充剂量的增加而提高;补充BCAA可能提高了血浆BCAA与f-Trp竞争通过血脑屏障的能力且具有推迟和减少脑5-HT生成的作用;小剂量[1.25g/(kg·BW-1)]补充BCAA对提高大鼠运动能力效果最佳。     

Long-term high fructose and saturated fat diet affects plasma fatty acid profile in rats

As the consumption of fructose and saturated fatty acids (FAs) has greatly increased in western diets and is linked with an increased risk of metabolic syndrome, the aim of this study was to investigate the effects of a moderate (10 weeks) and a prolonged (30 weeks) high fructose and saturated fatty acid (HFS) diet on plasma FA composition in rats. The effects of a few weeks of HFS diet had already been described, but in this paper we tried to establish whether these effects persist or if they are modified after 10 or 30 weeks. We hypothesized that the plasma FA profile would be altered between 10 and 30 weeks of the HFS diet. Rats fed with either the HFS or a standard diet were tested after 10 weeks and again after 30 weeks. After 10 weeks of feeding, HFS-fed rats developed the metabolic syndrome, as manifested by an increase in fasting insulinemia, total cholesterol and triglyceride levels, as well as by impaired glucose tolerance. Furthermore, the plasma FA profile of the HFS group showed higher proportions of monounsaturated FAs like palmitoleic acid [16:1(n-7)] and oleic acid [18:1(n-9)], whereas the proportions of some polyunsaturated n-6 FAs, such as linoleic acid [18:2(n-6)] and arachidonic acid [20:4(n-6)], were lower than those in the control group. After 30 weeks of the HFS diet, we observed changes mainly in the levels of 16:1(n-7) (decreased) and 20:4(n-6) (increased). Together, our results suggest that an HFS diet could lead to an adaptive response of the plasma FA profile over time, in association with the development of the metabolic syndrome.     

Active-learning versus teacher-centered instruction for learning acids and bases

The prevalence of the ideas of Year I undergraduate biology students about the consequences, causes and cures of the 'greenhouse effect' was determined using a closed-form questionnaire, and the results compared with a parallel study undertaken nearly 10 years ago. Many of the students in the present study were unaware of the potential effect of global warming on the distribution of crop pests, or that ground level ozone acts as a 'greenhouse gas'. Prevalent misconceptions were that global warming is caused by increased penetration of solar radiation, that it is connected with holes in the ozone layer, that it would result in increased skin cancer, and that use of unleaded petrol would reduce it. There appeared to be a general conflation of thinking about global warming and ozone layer depletion. Despite an increased certainty about the existence and effects of global warming among experts, the results are broadly similar to, and certainly no better than, those obtained with an equivalent group of students in a previous study, suggesting that despite media publicity and inclusion of the issue of global warming in the formal curriculum, insecure knowledge and misconceptions persist.     

AMINO ACIDS' PROTECTIVE EFFECTS ON EXPERIMENTAL ACUTE RENAL FAILURE

This study was carried out to elucidate the nephroprotective effects from a mixture of 8 L-amino acids and the possible mechanism of protection by this amino acid mixture. Acute renal failure model was induced by an intravenous administration of 10 mg/kg cisplatin to male Sprague-Dawley rats. A mixture of 8 L-amino acids or 0.9% saline was infused at a rate of 2 ml/h for 3 h, starting with a 2 ml bolus injection before cisplatin administration. Amino acids showed no acute effect on renal morphology. The infusion of a mixture of 8 L-amino acids increased GFR by 85% in control rats. The abnormalities of urine sodium and potassium excretion caused by cisplatin were markedly attenuated by the administration of the amino acid mixture. With the infusion of this amino acid mixture, cisplatin-induced abnormal state 4 respiration returned to control levels and the depressed state 3 respiration, respiratory control ratio and carbonyl cyanide p-trifluoromethoxyphenyl hydrazone-uncoupled respiration were ameliorated remarkably. A mixture of 8 L-amino acids showed marked nephroprotection against cisplatin-induced acute renal failure in rats and might function through augmentation of the cisplatin-injured renal mitochondrial electron transport-oxidative phosphorylation sequence, probably via stabilizing the membrane (including inner mitochondrial membrane) protein tertiary structure. In addition, this amino acid mixture remarkably increased GFR and decreased urine sodium excretion in rats.     

磺酰化氮取代氨基酸配合物的合成与结构研究进展

本文综述了磺酰化氮取代氨基酸配合物的合成、配位结构方式的研究进展。     

Degradation of collagen in parchment under the influence of heat-induced oxidation: Preliminary study of changes at macroscopic,microscopic, and molecular levels

This paper examines the impact of heat-induced oxidation for new and historical parchment with the purpose of improving diagnostic tools for use in practical parchment conservation. Oxidation was generated by heat aging at 120°C in a dry oven for 24, 48, and 96 hours, respectively. The degradation was assessed on all samples at macrolevel by measuring color changes, at microlevel by measuring the shrinkage temperature as well as by performing a visual assessment of the fibers’ morphology and determining the amount of damaged fibers, and finally, at molecular level where amino acid analysis was used to reveal changes in the oxidized collagen. The study shows that the heat-induced oxidation leads to significant color changes, decrease in hydrothermal stability, as well as changes in the amino acid composition. Surprisingly, the results show that the historical parchment is more sensitive towards dry heat oxidation on a molecular level than is the new parchment. Furthermore, for the first time, we can show that physical damage reflected in the morphological characteristics of fibers can be attributed to oxidation by dry heat.     

Assessment of indoor air quality and the risk of damage to cultural heritage objects using MEMORI® dosimetry

Air pollution is one of the environmental influences that degrade cultural heritage objects situated indoors. Other essential influences, such as temperature, relative humidity, and light are often well monitored. The presence of air pollutants is less often measured or included in risk assessment. The MEMORI^® technology presented in this paper was developed as a tool for easy measurement and assessment of the general risk of degradation of heritage objects situated indoors due to indoor exposure to air pollutants. MEMORI dosimetry was performed in locations belonging to English Heritage and Tate (both located in London) and the National Archives of Norway in Oslo, to assess air quality. The related damage risk for collection objects and the protection offered by display and storage designs was assessed. A high level of acidic effect was observed inside a number of showcases, and a high level of oxidizing effect was observed in some room locations. Relatively simple mitigation measures, such as constructing tightly sealed showcases using low emitting materials, installing active carbon absorbing media inside a ‘microclimate’ frame, and using cardboard storage boxes for paper, significantly improved air quality. Overall, implementation of such measures is likely to improve the preservation of objects and reduce conservation costs.     

山茶和油茶种子中脂肪酸的分析

[目的]了解山茶和油茶种子中脂肪酸的组成和含量.[方法]气相色谱法测定山茶和油茶种子中脂肪酸的组成和含量.[结果]两种种子都含有4种脂肪酸:棕榈酸(8.45%和8.49%)、硬脂酸(2.67%和1.84%)、油酸(79.92%和81.62%)、亚油酸(8.95%和8.05%).[结论]油酸在山茶和油茶种子中的含量均很高.