Efficacy of a 'functional energy drink' in counteracting driver sleepiness

Driver sleepiness is a major cause of serious road crashes. Coffee is often used as an effective countermeasure to driver sleepiness. However, the caffeine levels in coffee are variable, whereas certain proprietary "functional energy drinks" (FEDs) contain known levels of caffeine (and other ingredients). We investigated the effectiveness of a well-known FED in reducing sleepiness in drivers. Twelve healthy young adults drove an instrumented car simulator between 14:00 and 17:00 h. Their sleepiness was enhanced by sleep restriction to 5 h the night before. Following a pretreatment 30-min drive and at the beginning of a 30-min break, participants were given double-blind 250-ml FED (containing sucrose, glucose, 80-mg caffeine, taurine, glucuronolactone and vitamins) vs. a control drink with the same volume and same taste but without caffeine, taurine and glucuronolactone. Two hours of continuous driving ensued. Lane drifting, subjective sleepiness and the electroencephalogram (EEG) were monitored throughout. Compared with the control, the FED significantly reduced sleep-related driving incidents and subjective sleepiness for the first 90 min of the drive. There was a trend for the EEG to reflect less sleepiness during this period. It was concluded that the FED is beneficial in reducing sleepiness and sleep-related driving incidents under conditions of afternoon monotonous driving following sleep restriction the night before.     

Thermogenic effect of adrenaline: interaction with insulin

Summary The contribution of insulin (3.6 pmol sd kg body mass^–1·min^–1 to adrenaline-induced (0.164 nmol · kg fat free mass^–1·min^–1) thermogenesis was studied in ten postabsorptive healthy volunteers using two sequential protocols. Variables considered were oxygen consumption as well as carbon dioxide production, heart rate, blood pressure, plasma concentrations of glucose, insulin, glycerol, free fatty acids,-HO-butyrate and lactate. Adrenaline increased plasma concentrations of glucose, glycerol, free fatty acids, and-HO-butyrate, and heart rate and metabolic rate during normo-insulinaemia [61.3 (SEM 6.6) pmol·^–1]. Similar effects were observed during hyperinsulinaemia [167.9 (SEM 18.7) pmol·^–1], but the effect of adrenaline on oxygen consumption was reduced. On average, metabolic rate increased by 12.9% during normo-insulinaemia and by 8.9% during hyperinsulinaemia. We concluded that relative hyperinsulinaemia resulted in decreased adrenaline-induced thermogenesis and therefore increased whole body anabolism.     

Effect of intravenous immunoglobulin treatment on the Th1/Th2 balance in women with recurrent spontaneous abortions

PROBLEM: The way by which intravenous immunoglobulin (IvIg) acts to prevent immunlogically mediated recurrent spontaneous abortions (RSA) has not been clarified. In the present study, a possible effect of IvIg on the T helper cell (Th1/Th2) balance was investigated in abortions of either alloimmune or autoimmune abnormalities. METHOD OF STUDY: The study included 21 women treated with IvIg before conception because of a history of RSA characterized by alloimmune abnormalities (n = 15) or associated with anti-phospholipid antibodies (APA) (n = 6). Peripheral blood samples, collected before and 5 days after the first IvIg infusion, were stimulated, and Th1 and Th2 cells were detected by flow-cytometric analysis using a combination of monoclonal antibodies against T-cell surface markers and intracellular interferon (IFN)-gamma and interleukin (IL)-4. The percentage of IFN-gamma-producing (Th1) and IL-4-producing (Th2) cells and the Th1/Th2 ratio were compared between pre- and post-infusion samples. RESULTS: A decrease of Th1 percentage in 66.6% of the cases and a concurrent Th2 percentage increase (47.61%) resulted in a decrease in the Th1/Th2 ratio in most of the cases (76.1%) (p < 0.01). Similar results were found in Group A (Th1/Th2 decreased in 60% of the cases, p < 0.05), while in Group B the effect of IvIg was not clear (Th1/Th2 increased in three and decreased in another three cases). CONCLUSION: Our finding suggests that IvIg administration in women with alloimmune RSA enhances Th2 polarization. This is not always the case with APA-associated abortions.     

失血性休克及复苏后不同组织代谢变化与组织损伤差异性的研究

目的：从能量代谢的角度探讨肠组织与心肌、骨骼肌等肠外组织在失血性休克及复苏后组织损伤的差异性。方法：采用大鼠失血性休克复苏模型，高效液相色谱法测定三磷酸腺苷（ATP）、二磷酸腺苷（ADP）和一磷酸腺苷（AMP）含量；生化及比色法测定黄嘌呤氧化酶（XO）、丙二醛（MDA）和超氧化物歧化酶（SOD）水平。结果：失血性休克后肠组织、心肌和骨骼肌ATP含量明显低于对照组，分别为对照的26.3%、30.7%和62.8%；复苏后,心肌、骨骼肌ATP含量明显高于休克组；失血性休克及复苏后，肠组织XO活化及MDA含量均明显高于对照组，SOD活力则明显低于对照组，其脂质过氧化程度较心肌和骨骼肌严重。结论：失血性休克及复苏后不同组织能量代谢变化及组织损伤程度存在差异性，肠组织能量代谢障碍及损伤程度重于心肌、骨骼肌等肠外组织。     

In-vivo quantification of myocardial Na-K pump rate during β-adrenergic stimulation of intact pig hearts

Maintenance of adequate electrical activity of the heart depends critically on the ability of the Na-K pump to compensate for normal passive sodium and potassium fluxes. Using sudden injections of [³H]ouabain into the left coronary artery in anaesthetized open-chest pigs, we monitored transient changes in myocardial potassium balance by PVC-valinomycin mini-electrodes. When related to the number of pumps blocked and fractional inhibition, these data provided estimates of total Na-K pump capacity as well as actual pump rate and perturbations of the Na-K balance. Experiments were performed in hearts with and without intracoronary isoprenaline infusion (2.5 nmol min^-1). After injection of 120 nmol [³H]ouabain into the left coronary artery, myocardial [³H]ouabain concentrations were 118 (74–178) and 103 (76–145) pmol g^-1 and total concentrations of [³H]oubain binding sites were 893 (752–1076) and 785 (691–877) pmol g^-1 (median, 95% confidence interval) in isoprenaline-treated and control hearts respectively (differences not significant). The [³H]ouabain injection caused a net potassium release of 81 (56–132) and 43 (23–75) μcool 100 g^-1 (median, 95% confidence interval) in isoprenaline-treated and control hearts respectively (n= 6–8; significance of difference, P= 0.03). Na–K pump rate estimated from mono-exponential release curves was 6363 (3942–10,858) K⁺ ions min^-1 site^-1 during β-adrenoceptor stimulation and 2514 (1380–4322) in control (significance of difference, P= 0.03). This corresponds to 40 and 16%, respectively, of the maximum possible pump rate determined from ATP hydrolysis. Comparison of accumulated potassium release and relative Na-K pump rate indicates that catecholamines enhance the sensitivity of the Na-K pump for intracellular sodium.     

Effects of marathon running on running economy and kinematics

The present study was designed to investigate interactions between running economy and mechanics before, during, and after an individually run marathon. Seven experienced triathletes performed a 5-min submaximal running test on a treadmill at an individual constant marathon speed. Heart rate was monitored and the expired respiratory gas was analyzed. Blood samples were drawn to analyze serum creatine kinase activity (S-CK), skeletal troponin I (sTnI), and blood lactate (B-La). A video analysis was performed (200 frames · s⁻¹) to investigate running mechanics. A kinematic arm was used to determine the external work of each subject. The results of the present study demonstrate that after the marathon, a standardized 5-min submaximal running test resulted in an increase in oxygen consumption, ventilation, and heart rate (P < 0.05), with a simultaneous decrease in the oxygen difference (%) between inspired and expired air, and respiratory exchange ratio (P < 0.05). B-La did not change during the marathon, while sTnI and S-CK values increased (P < 0.05), peaking 2 h and 2 days after the marathon, respectively. With regard to the running kinematics, a minor increase in stride frequency and a similar decrease in stride length were observed (P < 0.01). These results demonstrate clearly that weakened running economy cannot be explained by changes in running mechanics. Therefore, it is suggested that the increased physiological loading is due to several mechanisms: increased utilization of fat as an energy substrate, increased demands of body temperature regulation, and possible muscle damage. Accepted: 20 March 2000     

Can energy drinks reduce the depressor effect of ethanol? An experimental study in mice

Although the popularization of the combined use of alcoholic beverages and energy drinks (ED) containing caffeine, taurine and other substances has increased, there are no controlled experimental studies on the effects of ED alone or combined with ethanol. This work aimed at evaluating the effects of different doses of ED combined or not with ethanol, on the locomotor activity of Swiss mice. The administration of 3.57, 10.71 or 17.86 ml/kg of ED alone increased the locomotor activity of the animals in relation to a control group. Low doses of ethanol (0.5, 1.0 and 1.5 g/kg) alone or in combination with 10.71 ml/kg of ED did not affect their locomotor activity. However, the reduction of activity observed after 2.5 g/kg of ethanol was antagonized by 10.71 ml/kg of ED. Further studies on the mechanisms of this interaction are still needed.     

Optimum cycle frequencies in hand-rim wheelchair propulsion

Summary To study the effect of different cycle frequencies on cardio-respiratory responses and propulsion technique in hand-rim wheelchair propulsion, experienced wheelchair sportsmen (WS group; n=6) and non-wheel chair users (NW group; n=6) performed wheelchair exercise tests on a motor-driven treadmill. The WS group wheeled at velocities of 0.55, 0.83, 1.11 and 1.39 m · s^–1 and a slope of 2°. The NW group wheeled at 0.83, 1.11 and 1.39 m · s^–1 and a 1° slope. In each test, a 3-min period at a freely chosen cycle frequency (FCF: 100%) was followed by four 3-min blocks of paced cycle frequencies at 60%, 80%, 120% and 140% FCF. Effects of both cycle frequency and velocity on physiological and propulsion technique parameters were studied.Analysis of variance showed a significant effect (p<0.05) of cycle frequency on oxygen cost and gross mechanical efficiency in both the WS and NW group. This indicated the existence of an optimum cycle frequency which is close to the FCF at any given velocity. The optimum cycle frequency increased with velocity from 0.67 to 1.03 cps over the range studied (p< 0.05). Oxygen cost was 10% less at 100% FCF than at 60% or 140% FCF. Gross mechanical efficiency for the WS group at 100% FCF was 8.5%, 9.7%, 10.4% and 10.1%, respectively, at the four velocities. The similarity in the trend of oxygen cost and gross mechanical efficiency data in both the WS and NW groups suggests that an optimum cycle frequency is not merely a consequence of practice alone, but also reflects a physiologically determined optimum, dependent on muscle mechanics, e.g. velocity of contraction and power output of the muscles used.     

丹酚酸B对缺血小鼠脑能量代谢和脑水肿的影响

目的： 通过探讨丹酚酸B（SalB）对缺血小鼠脑能量代谢的影响，研究其对脑水肿的作用。方法：将NIH小鼠分为假手术组、缺血组、SalB治疗组和尼莫地平（Nim）治疗组，测定缺血30 min时脑组织能荷（EC）、磷酸肌酸（PCr）、ATP酶活性、兴奋性氨基酸（EAA）含量以及脑含水量。结果：SalB治疗组EC（0.520±0.034）和PCr［（98.344±13.249）μmol/g］的含量、Na⁺-K⁺-ATPase［（0.593±0.013）×10³ U/g］和Ca²⁺-ATPase［（0.484±0.053）×10³ U/g］的活性明显高于缺血组EC（0.465±0.037）、PCr［（81.614±9.919）μmol/g］的含量、Na+-K+-ATPase［（0.244±0.065）×10³ U/g］和Ca²⁺-ATPase［（0.321±0.086）×10³ U/g］ 的活性，2者相比显著差异（P<0.01）；而SalB治疗组Glu［（0.405±0.110）μmol/g］和Asp［（0.141±0.020）μmol/g］的含量和脑含水量［（38.1±0.1）%］ 则明显低于缺血组Glu［（0.550±0.140）μmol/g］、Asp［（0.287±0.050）μmol/g］的含量和脑含水量［（44.1±0.1）%］，2者比较亦有显著差异（P<0.05,P<0.01）。结论：增强脑组织能量代谢和ATP酶活性，并降低脑组织中兴奋性氨基酸的含量，可能是SalB减轻小鼠缺血性脑水肿的作用机制。