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E. V. Lambert J. A. Hawley J. Goedecke T. D. Noakes S. C. Dennis 《Journal of sports sciences》2013,31(3):315-324
Carbohydrate ingestion before and during endurance exercise delays the onset of fatigue (reduced power output). Therefore, endurance athletes are recommended to ingest diets high in carbohydrate (70% of total energy) during competition and training. However, increasing the availability of plasma free fatty acids has been shown to slow the rate of muscle and liver glycogen depletion by promoting the utilization of fat. Ingested fat, in the form of long-chain (C 16-22 ) triacylglycerols, is largely unavailable during acute exercise, but medium-chain (C 8-10 ) triacylglycerols are rapidly absorbed and oxidized. We have shown that the ingestion of medium-chain triacylglycerols in combination with carbohydrate spares muscle carbohydrate stores during 2 h of submaximal (< 70% VO 2 peak) cycling exercise, and improves 40 km time-trial performance. These data suggest that by combining carbohydrate and medium-chain triacylglycerols as a pre-exercise supplement and as a nutritional supplement during exercise, fat oxidation will be enhanced, and endogenous carbohydrate will be spared. We have also examined the chronic metabolic adaptations and effects on substrate utilization and endurance performance when athletes ingest a diet that is high in fat (> 70% by energy). Dietary fat adaptation for a period of at least 2-4 weeks has resulted in a nearly two-fold increase in resistance to fatigue during prolonged, low- to moderate-intensity cycling (< 70% VO 2 peak). Moreover, preliminary studies suggest that mean cycling 20 km time-trial performance following prolonged submaximal exercise is enhanced by 80 s after dietary fat adaptation and 3 days of carbohydrate loading. Thus the relative contribution of fuel substrate to prolonged endurance activity may be modified by training, pre-exercise feeding, habitual diet, or by artificially altering the hormonal milieu or the availability of circulating fuels. The time course and dose-response of these effects on maximizing the oxidative contribution of fat for exercise metabolism and in exercise performance have not been systematically studied during moderate- to high-intensity exercise in humans. 相似文献
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晾晒烟感赤星病后游离氨基酸含量的研究 总被引：4，自引：0，他引：4
不同品种晾晒烟接种赤星菌后,游离氮基酸含量也不同。随品种抗病性由弱到强,碱性、芳香族、杂环族三类基酸全病程病健比下降,酸性、脂肪族、侧链为非极性、侧链不带电极性四类氨基酸则上升,酪、赖、精、胱等氨基酸下降,苯、组、脯、蛋、谷、天、丝、苏、甘、缬、亮等氨基酸上升。品种抗性越强,苯、酪、赖、精、组、脯、胱等氨基酸上升越早,消减也越快。游离氨基酸总增值量也随品种抗性增强而增大。 相似文献
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实验采用平皿培养法和抑菌圈法测定了稀土三元配合物RE(2-Cl-4-FBA)3bipy(RE=Nd、Sm、Ho、Eu)以及配体2-氯-4-氟苯甲酸(2-Cl-4-FHBA)、2,2‘-联吡啶(bipy)对黑曲霉生物活性的影响.通过比较抑菌圈直径的大小,发现合成的四种配合物对黑曲霉生长都存在选择性抑制,其中Sm的三元配合物抑制作用最明显;在相同条件下继续培养,每两周测量抑菌圈直径,其结果表明配合物的抑菌效果稳定持久.初步推测可将这种稀土配合物应用于那些具备适宜黑曲霉生长和繁殖条件的工业器械的灭菌. 相似文献
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海蒿子中脂肪酸组成的研究 总被引：1，自引：0，他引：1
本文用气相色谱法测定了中药海蒿子中主茎及侧枝叶两部分中脂肪酸种类和含量,结果表明海蒿子中含有丰富的不饱和脂肪酸,因此具有良好的营养保健作用,值得开发利用。 相似文献
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MMP-9和CD15s与胃癌血管生成的相关性研究及其临床意义 总被引：2，自引：0，他引：2
目的:探讨基质金属蛋白酶9(MMP-9)和唾液酸化Lewis X(CD15s)抗原与胃癌侵袭转移的相关性。方法:采用CD105,MMP-9,CD15s进行免疫组化S-P法染色,对47例胃癌根治性切除手术标本病理组织切片进行标记,检测CD105的微血管密度(MVD),并对MVD与MMP-9、CD15s的关系进行统计分析。结果:MMP-9、CD15s表达都呈阳性的胃癌组织微血管密度高于MMP-9和CD15s单阳性及二者均阴性的胃癌组织。结论:MMP-9高表达有利于癌组织局部浸润,CD15s高表达有利于癌细胞血行转移,MMP-9及CD15s检测对临床诊治胃癌及判断预后具有一定意义。 相似文献
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We investigated the pedagogical content knowledge (PCK) of nine experienced chemistry teachers. The teachers took part in
a teacher training course on students’ difficulties and the use of models in teaching acid–base chemistry, electrochemistry,
and redox reactions. Two years after the course, the teachers were interviewed about their PCK of (1) students’ difficulties
in understanding acid–base chemistry and (2) models of acids and bases in their teaching practice. In the interviews, the
teachers were asked to comment on authentic student responses collected in a previous study that included student interviews
about their understanding of acids and bases. Further, the teachers drew story-lines representing their level of satisfaction
with their acid–base teaching. The results show that, although all teachers recognised some of the students’ difficulties
as confusion between models, only a few chose to emphasise the different models of acids and bases. Most of the teachers thought
it was sufficient to distinguish clearly between the phenomenological level and the particle level. The ways the teachers
reflected on their teaching, in order to improve it, also differed. Some teachers reflected more on students’ difficulties;
others were more concerned about their own performance. Implications for chemistry (teacher) education are discussed.
Submitted to Research in Science Education 相似文献
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This study examined the effect of carbohydrate ingestion on metabolic and performance-related responses during and after a simulated 1h cycling time trial. Eight trained male cyclists (VO 2 peak = 66.5ml kg -1 min -1 ) rode their own bicycles mounted on a windload simulator to imitate real riding conditions. At a self-selected maximal pace, the cyclists performed two 1h rides (separated by 7 days) and were fed either an 8% carbohydrate or placebo solution. The beverages were administered 25 min before (4.5ml kg -1 ) and at the end (4.5ml kg -1 ) of the ride. With carbohydrate feeding, plasma glucose tended (P = 0.21) to rise before the time trial. Compared with rest, the plasma glucose concentration decreased significantly (P < 0.05) at the end of both rides, with no statistically significant difference being observed between treatments. Thereafter, plasma glucose increased significantly (P < 0.05) at 15 and 30 min into recovery, and was significantly higher at 30 min during the carbohydrate trial compared with the placebo trial. No significant changes in plasma free fatty acids were observed during the ride. However, a significant increase (P < 0.05) in free fatty acids was found at 15 and 30 min into recovery, with no difference between trials. Mean power output was significantly (P < 0.05) greater during the carbohydrate compared with the placebo trial (mean - S.E.: 277-3 and 269-3W, respectively). The greater distance covered in the carbohydrate compared with the placebo trial (41.5-1.06 and 41.0–1.06km, respectively; P < 0.05) was equivalent to a 44s improvement. We conclude that pre-exercise carbohydrate ingestion significantly increases endurance performance in trained cyclists during a 1h simulated time trial. Although the mechanism for this enhancement in performance with carbohydrate ingestion cannot be surmised from the present results, it could be related to a higher rate of carbohydrate oxidation, or to favourable effects of carbohydrate ingestion on the central component of fatigue. 相似文献
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采用索式提取法对螺旋藻中的脂肪油进行提取,并对脂肪酸进行甲酯化处理,利用气相色谱-质谱联用仪进行分析测定.螺旋藻共检测出6种脂肪酸,不饱和脂肪酸为4种,相对百分含量占检出所有脂肪酸的57.44%,其中,二十碳五烯酸（EPA）为12.17%,亚油酸为7.25%,5,8,11,14-二十碳四烯酸（花生四烯酸）为22.12%. 相似文献