Effects of 4-h ischemia and 1-h reperfusion on rat muscle sarcoplasmic reticulum function

To investigate the hypothesis that ischemia and reperfusion would impair sarcoplasmic reticulum (SR) Ca(2+) regulation in skeletal muscle, Sprague-Dawley rats (n = 20) weighing 290 +/- 3.5 g were randomly assigned to either a control control (CC) group, in which only the effects of anesthetization were studied, or to a group in which the muscles in one hindlimb were made ischemic for 4 h and allowed to recover for 1 h (I). The nonischemic, contralateral muscles served as control (C). Measurements of Ca(2+)-ATPase properties in homogenates and SR vesicles, in mixed gastrocnemius and tibialis anterior muscles, indicated no differences between groups on maximal activity, the Hill coefficient, and Ca(50), defined as the Ca(2+) concentration needed to elicit 50% of maximal activity. In homogenates, Ca(2+) uptake was lower (P < 0.05) by 20-25%, measured at 0.5 and 1.0 microM of free Ca(2+) ([Ca(2+)](f)) in C compared with CC. In SR vesicles, Ca(2+) uptake was lower (P < 0.05) by 30-38% in I compared with CC at [Ca(2+)](f) between 0.5 and 1.5 microM. Silver nitrate induced Ca(2+) release, assessed during both the initial, early rapid (phase 1), and slower, prolonged late (phase 2) phases, in homogenates and SR vesicles, indicated a higher (P < 0.05) release only in phase 1 in SR vesicles in I compared with CC. These results indicate that the alterations in SR Ca(2+) regulation, previously observed after prolonged ischemia by our group, are reversed within 1 h of reperfusion. However, the lower Ca(2+) uptake observed in long-term, nonischemic homogenates suggests that altered regulation may occur in the absence of ischemia.     

Effects of preexercise snack feeding on endurance cycle exercise

We studied the effects of ingesting either a snack food (S) (260 kcal) or placebo (P) 30 min before intermittent cycle exercise at 70% maximal O2 consumption on endurance performance and muscle glycogen depletion in eight healthy human males. Immediately before exercise there were significantly greater increases in plasma glucose (PG) (S +28 +/- 9.7; P +0.1 +/- 0.8 mg/dl) and insulin (S +219 +/- 61.5; P -7 +/- 5.5 pmol/l) (P less than 0.05) following S feeding compared with P. These differences were no longer present by the end of the first exercise period. There were no differences in endurance times (S 52 +/- 6.4; P 48 +/- 5.6 min) or in the extent of muscle glycogen depletion following exercise (S 56 +/- 14.7; P 50 +/- 15.5 micrograms/mg protein) between the two groups. PG was maintained at base-line (prefeeding) concentrations following S, whereas there was a tendency for PG to steadily decrease after P. Total grams of carbohydrate oxidized during exercise did not differ between the two groups (S 120; P 118 g). These results demonstrate that the ingestion of a mixed-macronutrient snack 30 min before exercise does not impair endurance performance nor increase the extent of muscle glycogen depletion during high-intensity cycle exercise in untrained adult male subjects.     

Glucose feedings and exercise in rats: glycogen use, hormone responses, and performance

This study compared the effects of glucose feeding and water on endurance performance, glycogen utilization, and endocrine responses to exhaustive running in rats. Forty-eight trained rats ran at approximately 70% peak O2 consumption (VO2) while receiving, via gavage, 1 ml of an 18% glucose solution or water every 30 min. Glucose- (GF) and water-fed rats (WF) were pair matched and killed at rest, at 25 or 50% of their previously determined run time to exhaustion, or at exhaustion. Run times to exhaustion were 4.6 +/- 1.0 and 3.0 +/- 0.9 h in GF and WF rats, respectively. In WF rats, plasma glucose declined continuously from a resting value of 7.4 +/- 0.5 to 1.8 +/- 0.5 mM at exhaustion and was lower than in GF rats at all exercise time points. In GF rats, glucose was maintained at 7.4 +/- 0.5 mM for 3 h before dropping to 3.9 +/- 0.6 mM at exhaustion. In both groups, liver and muscle glycogen decreased dramatically during the 1st h and changed only slightly thereafter. During the 3rd h, glycogen levels were maintained in GF rats but continued to decrease in WF rats (P less than 0.05). Insulin decreased during exercise and was not significantly different between groups. Glucagon, epinephrine, norepinephrine, and corticosterone increased to a greater extent in WF than in GF rats during the first 3 h of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of pre-exercise carbohydrate feedings on muscle glycogen use during exercise in well-trained runners

The purpose of this study was to examine the effects of pre-exercise glucose and fructose feedings on muscle glycogen utilization during exercise in six well-trained runners (VO2max = 68.2 +/- 3.4 ml X kg-1 X min-1). On three separate occasions, the runners performed a 30 min treadmill run at 70% VO2max. Thirty minutes prior to exercise each runner ingested 75 g of glucose (trial G), 75 g of fructose (trial F) or 150 ml of a sweetened placebo (trial C). During exercise, no differences were observed between any of the trials for oxygen uptake, heart rate or perceived exertion. Serum glucose levels were elevated as a result of the glucose feeding (P less than 0.05) reaching peak levels at 30 min post-feeding (7.90 +/- 0.24 mmol X l-1). With the onset of exercise, glucose levels dropped to a low of 5.89 +/- 0.85 mmol X l-1 at 15 min of exercise in trial G. Serum glucose levels in trials F and C averaged 6.21 +/- 0.31 mmol X l-1 and 5.95 +/- 0.23 mmol X l-1 respectively, and were not significantly different (P less than 0.05). There were also no differences in serum glucose levels between any of the trials at 15 and 30 min of exercise.     

Isolation and structural characterisation of 8-O-4/8-O-4- and 8-8/8-O-4-coupled dehydrotriferulic acids from maize bran

Two new dehydrotriferulic acids were isolated from saponified maize bran insoluble fiber using Sephadex LH-20 chromatography followed by semi-preparative RP-HPLC. Based on UV-spectroscopy, mass spectroscopy and one- and two-dimensional NMR experiments, the structures were identified as 8-O-4,8-O-4-dehydrotriferulic acid and 8-8(cyclic),8-O-4-dehydrotriferulic acid. Which of the possible phenols in the initially formed 8-8-dehydrodiferulate was etherified by 4-O-8-coupling with ferulate has been unambiguously elucidated. The ferulate dehydrotrimers which give rise to these dehydrotriferulic acids following saponification are presumed, like the dehydrodiferulates, to cross-link polysaccharides. Neither dehydrotriferulic acid described here involves a 5-5-dehydrodiferulic acid unit; only the 5-5-dehydrodimer may be formed intramolecularly. However, whether dehydrotriferulates are capable of cross-linking more than two polysaccharide chains remains open. Although the levels of the isolated ferulate dehydrotrimers are lower than those of the ferulate dehydrodimers, the isolation now of three different dehydrotriferulates indicates that trimers contribute to a strong network cross-linking plant cell wall polysaccharides.     

Improvements in exercise performance: effects of carbohydrate feedings and diet

In an effort to determine the effects of carbohydrate (CHO) feedings immediately before exercise in both the fasted and fed state, 10 well-trained male cyclists [maximum O2 consumption (VO2 max), 4.35 +/- 0.11 l/min)] performed 45 min of cycling at 77% VO2 max followed by a 15-min performance ride on an isokinetic cycle ergometer. After a 12-h fast, subjects ingested 45 g of liquid carbohydrate (LCHO), solid carbohydrate confectionery bar (SCHO), or placebo (P) 5 min before exercise. An additional trial was performed in which a high-CHO meal (200 g) taken 4 h before exercise was combined with a confectionery bar feeding (M + SCHO) immediately before the activity. At 10 min of exercise, serum glucose values were elevated by 18 and 24% during SCHO and LCHO, respectively, compared with P. At 0 and 45 min no significant differences were observed in muscle glycogen concentration or total use between the four trials. Total work produced during the final 15 min of exercise was significantly greater (P less than 0.05) during M + SCHO (194,735 +/- 9,448 N X m), compared with all other trials and significantly greater (P less than 0.05) during LCHO and SCHO (175,204 +/- 11,780 and 176,013 +/- 10,465 N X m, respectively) than trial P (159,143 +/- 11,407 N X m). These results suggest that, under conditions when CHO stores are less than optimal, exercise performance is enhanced with the ingestion of 45 g of CHO 5 min before 1 h of intense cycling.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of postexercise carbohydrate-protein feedings on muscle glycogen restoration.

The purpose of this investigation was to determine the effects of postexercise eucaloric carbohydrate-protein feedings on muscle glycogen restoration after an exhaustive cycle ergometer exercise bout. Seven male collegiate cyclists [age = 25.6 +/- 1.3 yr, height = 180.9 +/- 3.2 cm, wt = 75.4 +/- 4.0 kg, peak oxygen uptake (VO(2 peak)) = 4.20 +/- 0.2 l/min] performed three trials, each separated by 1 wk: 1) 100% alpha-D-glucose [carbohydrate (CHO)], 2) 70% carbohydrate-20% protein (PRO)-10% fat, and 3) 86% carbohydrate-14% amino acid (AA). All feedings were eucaloric, based on 1.0 g. kg body wt(-1). h(-1) of CHO, and administered every 30 min during a 4-h muscle glycogen restoration period in an 18% wt/vol solution. Muscle biopsies were obtained immediately and 4 h after exercise. Blood samples were drawn immediately after the exercise bout and every 0.5 h for 4 h during the restoration period. Increases in muscle glycogen concentrations for the three feedings (CHO, CHO-PRO, CHO-AA) were 118 mmol/kg dry wt; however, no differences among the feedings were apparent. The serum glucose and insulin responses did not differ throughout the restoration period among the three feedings. These results suggest that muscle glycogen restoration does not appear to be enhanced with the addition of proteins or amino acids to an eucaloric CHO feeding after exhaustive cycle exercise.     

Immediate effects of an 8-h advance shift of the rest-activity cycle on 24-h profiles of cortisol

To investigate the adaptation of plasma cortisol profiles to an abrupt phase advance of the rest-activity cycle, eight normal young subjects were submitted in a sleep laboratory to an 8-h advance shift of their sleep-wake and dark-light cycles. The shift was achieved by advancing bedtimes from 2300-0700 to 1500-2300. Blood samples were obtained at 20-min intervals for 68 consecutive hours. The shift resulted within 6-9 h in a 3- to 4-h advance of timings of the nadir of the cortisol profile and of the end of the quiescent period but had no immediate effect on the timing of cortisol acrophase. The quiescent period of cortisol secretion was shortened and fragmented. Thus a major advance shift achieved without enforcing sleep deprivation results in a rapid partial adaptation of the temporal profiles of cortisol but also in a marked disruption of the cortisol quiescent period. Sleep onset was consistently followed by a decrease in cortisol concentrations. Conversely, both sleep-wake and dark-light transitions were consistently associated with cortisol secretory pulses.     

Effects of 3 days of carbohydrate supplementation on muscle glycogen content and utilisation during a 1-h cycling performance

This study compared the effects of supplementing the normal diets of six trained cyclists [maximal oxygen uptake O_2max) 4.5 (0.36)l · min⁻¹; values are mean (SD)] with additional carbohydrate (CHO) on muscle glycogen utilisation during a 1-h cycle time-trial (TT). Using a randomised crossover design, subjects consumed either their normal diet (NORM) for 3 days, which consisted of 426 (137) g · day⁻¹ CHO [5.9 (1.4) g · kg⁻¹ body mass (BM)], or additional CHO (SUPP) to increase their intake to 661 (76) g · day⁻¹ [9.3 (0.7) g · kg⁻¹ BM]. The SUPP diet elevated muscle glycogen content from 459 (83) to 565 (62) mmol · kg⁻¹ dry weight (d.w.) (P < 0.05). However, despite the increased pre-exercise muscle glycogen stores, there was no difference in the distance cycled during the TT [40.41 (1.44) vs 40.18 (1.76) km for NORM and SUPP, respectively]. With NORM, muscle glycogen declined from 459 (83) to 175 (64) mmol · kg⁻¹ d.w., whereas with SUPP the corresponding values were 565 (62) and 292 (113) mmol · kg⁻¹ d.w. Accordingly, both muscle glycogen utilisation [277 (64) vs 273 (114) mmol · kg⁻¹ d.w.] and total CHO oxidation [169 (20) vs 165 (30) g · h⁻¹ for NORM and SUPP, respectively] were similar. Neither were there any differences in plasma glucose or lactate concentrations during the two experimental trials. Plasma glucose concentration averaged 5.5 (0.5) and 5.6 (0.6) mmol · l⁻¹, while plasma lactate concentration averaged 4.4 (1.9) and 4.4 (2.3) mmol · l⁻¹ for NORM and SUPP, respectively. The results of this study show that when well-trained subjects increase the CHO content of their diet for 3 days from 6 to 9 g · kg⁻¹ BM there is only a modest increase in muscle glycogen content. Since supplementary CHO did not improve TT performance, we conclude that additional CHO provides no benefit to performance for athletes who compete in intense, continuous events lasting 1 h. Furthermore, the substantial muscle CHO reserves observed at the termination of exercise indicate that whole-muscle glycogen depletion does not determine fatigue at this exercise intensity and duration. Accepted: 25 November 1996     

About 8- and approximately 84-h rhythms in endotheliocytes as in endothelin-1 and effect of trauma

Population densities (PD) of capillaries (C) and endotheliocytes (E) were determined in pinnal dermis of C57BL mice before and after trauma. Moving (and overall) least-squares spectra before trauma detected in EPD (versus CPD) pronounced 3.5-day (circasemiseptan) and 8-h oscillations corresponding to components of the endothelin-1 chronome in human blood plasma reported earlier. Circadians were more pronounced in CPD. After trauma, circasemiseptan oscillations appeared also in CPD; their period gradually shortened and in two weeks split into about 2.5- and about 4.5-day oscillations; and circadian components became very pronounced. The pre-traumatic chronome was not restored within three weeks following trauma.     

C(4)-h and c(5)-h Tautomers of Amthamine and Histamine Monocations

Tautomers and conformers (T/C's) involving the C4 and C5 atoms of the thiazole or imidazole rings were characterized in amthamine (2-amino-5-(2'-aminoethyl)-4-methylthiazole) and histamine (4(5)-2'-aminoethylimidazole), respectively. Critical points of the potential energy surfaces were calculated at the RHF/6-31G** level, using analytical gradients. Conformers were also determined at the MP2/6-31G**//6-31G** and MP2/6-31G**//MP2/6-31G** levels. In amthamine, a gauche conformer of C(5)-H tautomer, I+, turns out to be the second most stable T/C in the gas phase in the RHF approach. MP2 calculations generally yield larger potential energy. Topology of the charge density shows internal electrostatic interactions between S1 ... N for some of the gauche conformers (I+ and L+). Transition state structures for conformational changes and internal proton transfer reactions have also been characterized. In histamine, the C(4)-H tautomers are more stable than the C(5) -H ones, and they have a much higher potential energy than the most stable tautomers of amthamine. N(1) C(i)-H tautomers present similar electronic features to those of amthamine. Internal hydrogen bonds (HyB) and the ring formed in the gauche structures with internal HyB's have been characterized by using the charge density topology procedures. MP2 results are approximately similar to the RHF results, especially with respect to the conformational angles, the potential energy being larger than that from the RHF wavefunction. MP2 distances of HyB's reveal stronger HyB's than the RHF ones.     

The 4-6-8 method of sequence analysis

A new method to obtain more sequence data from a single gel run is described. This method allows the reading of over 500 bases of sequence data from a single gel by taking advantage of the differential migration of specific sized dideoxy terminated chain lengths in sequencing gels containing variable percentages of acrylamide. The method is easy to use, requires no special equipment and requires no special technical abilities. We feel the methodology described will be useful for the average laboratory doing sequencing work.     

Functional characterization of MHC class II-restricted CD8+CD4- and CD8-CD4- T cell responses to infection in CD4-/- mice

Classical CD4(+) and CD8(+) T cells recognize Ag presented by MHC class II (MHCII) and MHC class I (MHCI), respectively. However, our results show that CD4(-/-) mice mount a strong, readily detectable CD8(+) T cell response to MHCII-restricted epitopes after a primary bacterial or viral infection. These MHCII-restricted CD8(+)CD4(-) T cells are more similar to classical CD8(+) T cells than to CD4(+) T cells in their expression of effector functions during a primary infection, yet they also differ from MHCI-restricted CD8(+) T cells by their inability to produce high levels of the cytolytic molecule granzyme B. After resolution of a primary infection, epitope-specific MHCII-restricted T cells in CD4(-/-) mice persist for a long period of time as memory T cells. Surprisingly, upon reinfection the secondary MHCII-restricted response in CD4(-/-) mice consists mainly of CD8(-)CD4(-) T cells. In contrast to CD8(+) T cells, MHCII-restricted CD8(-)CD4(-) T cells are capable of producing IL-2 in addition to IFN-gamma and thus appear to have attributes characteristic of CD4(+) T cells rather than CD8(+) T cells. Therefore, MHCII-restricted T cells in CD4(-/-) mice do not share all phenotypic and functional characteristics with MHCI-restricted CD8(+) T cells or with MHCII-restricted CD4(+) T cells, but, rather, adopt attributes from each of these subsets. These results have implications for understanding thymic T cell selection and for elucidating the mechanisms regulating the peripheral immune response and memory differentiation.     

Effects of substrate and substrate analogues on the trinitrophenylation of myosin

The effects of ATP, ATP analogues, Mg²⁺ and actin on the trinitrophenylation of myosin and on the enzymic properties of trinitrophenylated samples were studied.

1. 1. Trinitrophenylation of myosin was inhibited by the presence of ATP and its analogues during the treatment in the order ADP > ATP > pyrophosphate > AMP.

2. 2. The alteration of the enzymic properties due to trinitrophenylation of myosin was prevented by the presence of ATP or ADP and somewhat less by that of pyrophosphate and AMP during trinitrophenylation, but only if Mg²⁺ was also present.

3. 3. Neither the degree of trinitrophenylation nor the enzymic properties of the trinitrophenylated myosin were influenced by the presence of actin during the treatment of myosin.

Metabolic and performance effects of raisins versus sports gel as pre-exercise feedings in cyclists

Research suggests that pre-exercise sources of dietary carbohydrate with varying glycemic indexes may differentially affect metabolism and endurance. This study was designed to examine potential differences in metabolism and cycling performance after consumption of moderate glycemic raisins vs. a high glycemic commercial sports gel. Eight endurance-trained male (n = 4) and female (n = 4) cyclists 30 +/- 5 years of age completed 2 trials in random order. Subjects were fed 1 g carbohydrate per kilogram body weight from either raisins or sports gel 45 minutes prior to exercise on a cycle ergometer at 70% V(.-)O2max. After 45 minutes of submaximal exercise, subjects completed a 15-minute performance trial. Blood was collected prior to the exercise bout, as well as after the 45th minute of exercise, to determine serum concentrations of glucose, insulin, lactate, free fatty acids (FFAs), triglycerides, and beta-hydroxybutyrate. Performance was not different (p > 0.05) between the raisin (189.5 +/- 69.9 kJ) and gel (188.0 +/- 64.8 kJ) trials. Prior to exercise, serum concentrations of glucose and other fuel substrates did not differ between trials; however, insulin was higher (p < 0.05) for the gel (110.0 +/- 70.4 microU x ml(-1)) vs. raisin trial (61.4 +/- 37.4 microU x ml(-1)). After 45 minutes of exercise, insulin decreased to 14.2 +/- 6.2 microU x ml(-1) and 13.3 +/- 18.9 microU x ml(-1) for gel and raisin trials, respectively. The FFA concentration increased (+0.2 +/- 0.1 mmol x L(-1)) significantly (p < 0.05) during the raisin trial. Overall, minor differences in metabolism and no difference in performance were detected between the trials. Raisins appear to be a cost-effective source of carbohydrate for pre-exercise feeding in comparison to sports gel for short-term exercise bouts.     

Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling

Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [VO2max = 57.8 (SE 4.1) ml kg-1 min-1] cycled for up to 255 min at a power output corresponding to VO2 at lactate threshold (approximately 68% VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg-1 body wt-1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P < 0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feed consumption and performance of dairy cows with alternate feedings of grass silage and maize silage

A feeding experiment was conducted with 10 dairy cows of the Fleckvieh breed and the cross Red Holstein Friesian × Fleckvieh, to study whether feeding with grass silage at the morning meal and maize silage at the evening meal (treatment B: alternating forage allocation) affects forage intake and milk production, in comparison with combined feeding with these two silages at each meal (treatment A). In order to prevent a selective forage consumption in treatment A, the two silages were given as a homogeneous mixture of nearly equal portions (51.6% maize silage, 48.4% grass silage) of dry matter (DM). The experiment was of switch-back design, with the treatment sequences ABA and BAB, and three experimental periods of 6 weeks.The daily forage consumption averaged 12.3 kg DM when the silages were given as a mixture and was significantly higher than the total forage consumption of 11.8 kg DM (P < 0.05) during the alternating allocation of the silages. In treatment B, daily intake of maize silage (7.10 kg DM) was greater than that of grass silage (4.70 kg DM/day). Furthermore, variation between cows in forage intake was significantly higher in this treatment than in treatment A. Average daily milk yield for treatment A was 18.75 kg with 3.84% fat and 3.70% protein, and 18.10 kg with 3.76% fat and 3.68% protein for treatment B. Production was significantly higher (P < 0.05), by 0.65 kg milk or 0.90 kg FCM, for treatment A.