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  • 1
    Electronic Resource
    Electronic Resource
    Control of molecular weight distribution of the biopolymer pullulan produced byAureobasidium pullulans (1993)
    Springer
    Journal of polymers and the environment 1 (1993), S. 3-9 
    Details
    ISSN: 1572-8900
    Keywords: Biopolymer ; pullulan ; polysaccharide ; molecular weight
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The influence of carbon, nitrogen, and phosphate source, along with concentration, was determined for effect on the weight average molecular weight, molecular weight distribution, and yield of pullulan produced byAureobasidium pullulans NRRL-Y 6220. Batch systems, scale-up batch, and continuous fermentations of 1 L and 10 L were also evaluated as were processing variables, including solvents, and extraction conditions. Products with weight average molecular weight from 1.0 × 105 to 4.0 × 106 were produced in 100-g quantities by varying fermentation conditions such as constituents of the culture medium, pH, and length of incubation. Three sets of culture conditions were defined for the formation of low (〈5.0×105), medium (1.0–2.0×106), and high (〉2.0×106) weight average molecular weight polymer. These defined molecular weight fractions of pullulan were used in further studies in producing films and fibers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01457648
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of sodium bicarbonate ingestion on plasma ammonia accumulation during incremental exercise in man (1993)
    Springer
    European journal of applied physiology 66 (1993), S. 49-54 
    Details
    ISSN: 1439-6327
    Keywords: High-intensity exercise ; Metabolic alkalosis ; Ammonia ; Adenine nucleotide metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This investigation evaluated the influence of metabolic alkalosis on plasma ammonia (NH3) accumulation during incremental exercise. On two occasions separated by at least 6 days, six healthy men cycled at 70, 80, and 90%g of maximum oxygen consumption ( $$\dot VO_{2\max } $$ ) for 5 min; each exercise period was followed by 5 min of seated recovery. Exercise was then performed at 100% $$\dot VO_{2\max } $$ until exhaustion. Beginning 3 h prior to exercise, subjects ingested 3.6 mmol · kg body mass− NaHCO3 (test, T) or 3.0 mmol · kg body mass−1 CaCO3 (placebo, P) (both equivalent to 0.3 g · kg−1) over a 2-h period. Trials were performed after an overnight fast and the order of treatments was randomized. Arterialized venous blood samples for the determination of acid-base status, blood lactate and plasma NH3 concentrations were obtained at rest before treatment, 15 s prior to each exercise bout (Pre 70%, Pre 80%, Pre 90%, and Pre 100%), and at 0, 5 (5′Post), and 10 (10'Post) min after exhaustion. Additional samples for blood lactate and plasma NH3 determination were obtained immediately after each exercise bout (Post 70%, Post 80%, Post 90%) and at 15 min after exercise (15′Post). Time to exhaustion at 100% of $$\dot VO_{2\max } $$ was not significantly different between treatments [mean (SE): 173 (42) s and 184 (44) s for T and P respectively]. A significant treatment effect was observed for plasma pH with values being significantly higher on T than on P Pre 70% [7.461 (0.007) vs 7.398 (0.008)], Pre 90% [7.410 (0.010) vs 7.340 (0.016)], and 10'Post [7.317 (0.032) vs 7.242 (0.036)]. The change in plasma pH was significantly greater following the 90%g bout (Pre 100% Pre 90%) for T [−0.09 (0.02)] than for P [−0.06 (0.01)]. Blood base excess and plasma bicarbonate concentrations were significantly higher for T than P before each exercise bout but not at the point of exhaustion. During recovery, base excess was higher for T than P at 5′Post and 10′Post while the bicarbonate concentration was higher for T than P at 10′Post. A significant treatment effect was observed for the blood lactate concentration with T on the average being higher than P [7.0 (1.0) and 6.3 (1.1) mmol · l−1 for T and P averaged across the 12 sampling times]. Plasma NH3 accumulation was not different between treatments at any point in time. In addition, no differences were observed between treatments in blood alanine accumulation. The results suggest that under the conditions of the present investigation metabolic alkalosis does not influence plasma NH3 accumulation or endurance capacity during intense incremental exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863399
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  • 3
    Electronic Resource
    Electronic Resource
    The acute reversal of a diet-induced metabolic acidosis does not restore endurance capacity during high-intensity exercise in man (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 105-112 
    Details
    ISSN: 1439-6327
    Keywords: High-intensity exercise ; Diet Bicarbonate ; Acid-base status
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present experiment was designed to investigate whether a diet-induced metabolic acidosis was a major factor in the earlier onset of fatigue during high-intensity exercise. Six healthy males cycled to exhaustion at a workload equivalent to 95% of maximum oxygen uptake on four separate occasions. Exercise tests were performed after an overnight fast and each test was preceded by one of four experimental conditions. Two experimental diets were designed, either to replicate each subject's own normal diet [N diet, mean (SD) daily energy intake (E) = 13 (0.7) MJ, 14.5 (0.8)% protein (Pro), 37.5 (2.2)% fat (Fat) and 47.5 (2.1)% carbohydrate (CHO)], or a low-carbohydrate diet [E = 12.6 (0.8) MJ, 33.6 (1.3)% Pro, 64.4 (1.5)% Fat and 2.2 (0.4)% CHO]. These diets were prepared and consumed within the department over a 3-day period. Over a 3-period prior to the exercise trial subjects ingested either NaHCO3 or CaCO3 (3.6 and 3.0 mmol · kg body mass), thus giving four experimental conditions: N diet and treatment, N diet and placebo, low-CHO diet and treatment and low-CHO diet and placebo. Treatments were assigned using a randomised protocol. Arterialised venous blood samples were taken for the determination of acid-base status and metabolite concentrations at rest prior to exercise and at intervals for 30 min following exhaustion. Consumption of the low-CHO diet induced a mild metabolic acidosis which was reversed by the ingestion of NaHCO3. Blood pH, bicarbonate (HCO3 − ) and base excess (BE) were higher following NaHCO3 ingestion after the normal diet than all of the other experimental conditions (P 〈 0.01). Exercise time following the low-CHO diet was less than on the normal diet conditions (P 〈 0.05): bicarbonate ingestion had no effect on exercise time on either of the diet conditions. Post-exercise blood pH, HCO3 − and BE were higher following the ingestion of NaHCO3 irrespective of the pre-exercise diet (P 〈 0.05). Blood lactate concentration was higher 2 min after exercise following the N diet with NaHCO3 when compared to the low-CHO diets with either NaHCO3 or placebo (P 〈 0.05). Plasma ammonia accumulation was not significantly different between experimental conditions. These data confirm previous data showing that the ingestion of a low-CHO diet reduces the capacity to perform high-intensity exercise, but it appears that the metabolic acidosis induced by the low-CHO diet is not the cause of the reduced exercise capacity observed during high-intensity exercise under these conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262817
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  • 4
    Electronic Resource
    Electronic Resource
    Human power output during repeated sprint cycle exercise: the influence of thermal stress (1999)
    Springer
    European journal of applied physiology 79 (1999), S. 360-366 
    Details
    ISSN: 1439-6327
    Keywords: Key words Temperature ; Power output ; High-intensity exercise ; acid-base status
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thermal stress is known to impair endurance capacity during moderate prolonged exercise. However, there is relatively little available information concerning the effects of thermal stress on the performance of high-intensity short-duration exercise. The present experiment examined human power output during repeated bouts of short-term maximal exercise. On two separate occasions, seven healthy males performed two 30-s bouts of sprint exercise (sprints I and II), with 4 min of passive recovery in between, on a cycle ergometer. The sprints were performed in both a normal environment [18.7 (1.5)°C, 40 (7)% relative humidity (RH; mean SD)] and a hot environment [30.1 (0.5)°C, 55 (9)% RH]. The order of exercise trials was randomised and separated by a minimum of 4 days. Mean power, peak power and decline in power output were calculated from the flywheel velocity after correction for flywheel acceleration. Peak power output was higher when exercise was performed in the heat compared to the normal environment in both sprint I [910 (172) W vs 656 (58) W; P 〈 0.01] and sprint II [907 (150) vs 646 (37) W; P 〈 0.05]. Mean power output was higher in the heat compared to the normal environment in both sprint I [634 (91) W vs 510 (59) W; P 〈 0.05] and sprint II [589 (70) W vs 482 (47) W; P 〈 0.05]. There was a faster rate of fatigue (P 〈 0.05) when exercise was performed in the heat compared to the normal environment. Arterialised-venous blood samples were taken for the determination of acid-base status and blood lactate and blood glucose before exercise, 2 min after sprint I, and at several time points after sprint II. Before exercise there was no difference in resting acid-base status or blood metabolites between environmental conditions. There was a decrease in blood pH, plasma bicarbonate and base excess after sprint I and after sprint II. The degree of post-exercise acidosis was similar when exercise was performed in either of the environmental conditions. The metabolic response to exercise was similar between environmental conditions; the concentration of blood lactate increased (P 〈 0.01) after sprint I and sprint II but there were no differences in lactate concentration when comparing the exercise bouts performed in a normal and a hot environment. These data demonstrate that when brief intense exercise is performed in the heat, peak power output increases by about 25% and mean power output increases by 15%; this was due to achieving a higher pedal cadence in the heat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050521
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