Physiological responses to maximal intensity intermittent exercise

Physiological responses to repeated bouts of short duration maximal-intensity exercise were evaluated. Seven male subjects performed three exercise protocols, on separate days, with either 15 (S15), 30 (S30) or 40 (S40) m sprints repeated every 30 s. Plasma hypoxanthine (HX) and uric acid (UA), and blood lactate concentrations were evaluated pre- and postexercise. Oxygen uptake was measured immediately after the last sprint in each protocol. Sprint times were recorded to analyse changes in performance over the trials. Mean plasma concentrations of HX and UA increased during S30 and S40 (P less than 0.05), HX increasing from 2.9 (SEM 1.0) and 4.1 (SEM 0.9), to 25.4 (SEM 7.8) and 42.7 (SEM 7.5) mumol.l-1, and UA from 372.8 (SEM 19) and 382.8 (SEM 26), to 458.7 (SEM 40) and 534.6 (SEM 37) mumol.l-1, respectively. Postexercise blood lactate concentrations were higher than pretest values in all three protocols (P less than 0.05), increasing to 6.8 (SEM 1.5), 13.9 (SEM 1.7) and 16.8 (SEM 1.1) mmol.l-1 in S15, S30 and S40, respectively. There was no significant difference between oxygen uptake immediately after S30 [3.2 (SEM 0.1) l.min-1] and S40 [3.3 (SEM 0.4) l.min-1], but a lower value [2.6 (SEM 0.1) l.min-1] was found after S15 (P less than 0.05). The time of the last sprint [2.63 (SEM 0.04) s] in S15 was not significantly different from that of the first [2.62 (SEM 0.02) s]. However, in S30 and S40 sprint times increased from 4.46 (SEM 0.04) and 5.61 (SEM 0.07) s (first) to 4.66 (SEM 0.05) and 6.19 (SEM 0.09) s (last), respectively (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Improvement of nitrogen-removal efficiency using immobilized microorganisms with oxidation–reduction potential monitoring

The use of an immobilized-cell reactor for simultaneous carbon–nitrogen removal in wastewater with the monitoring of oxidation–reduction potential (ORP) in an intermittent aeration (IA) process was investigated. Under alternating aerated and nonaerated conditions, the ORP-time profile showed distinctive turning points that directly correlated with changes in the system chemistry and biological activity. The aeration ratio, defined as aeration time/cycle time, was optimum at 50% for obtaining the maximum efficiency of denitrification accompanied by sufficient nitrification. High simultaneous carbon–nitrogen removal efficiency could be achieved using the immobilized-cell reactor by applying the IA process. More than 90% of COD-removal efficiency and over 80% of total-nitrogen-removal efficiency were obtained using three aerobic–anoxic cycles per day at an aeration ratio of 50% and with a hydraulic retention time of 10 h. Journal of Industrial Microbiology & Biotechnology (2000) 25, 229–234. Received 26 January 2000/ Accepted in revised form 08 August 2000     

Flight reconstruction of two European enantiornithines (Aves,Pygostylia) and the achievement of bounding flight in Early Cretaceous birds

Intermittent flight through flap‐gliding (alternating flapping phases and gliding phases with spread wings) or bounding (flapping and ballistic phases with wings folded against the body) are strategies to optimize aerial efficiency which are commonly used among small birds today. The broad morphological disparity of Mesozoic birds suggests that a range of aerial strategies could have evolved early in avian evolution. Based on biomechanics and aerodynamic theory, this study reconstructs the flight modes of two small enantiornithines from the Lower Cretaceous fossil site of Las Hoyas (Spain): Concornis lacustris and Eoalulavis hoyasi. Our results show that the short length of their wings in relation to their body masses were suitable for flying through strict flapping and intermittent bounds, but not through facultative glides. Aerodynamic models indicate that the power margins of these birds were sufficient to sustain bounding flight. Our results thus suggest that C. lacustris and E. hoyasi would have increased aerial efficiency through bounding flight, just as many small passerines and woodpeckers do today. Intermittent bounding appears to have evolved early in the evolutionary history of birds, at least 126 million years ago.     

Porphobilinogen deaminase and uroporphyrinogen III synthase: Structure,molecular biology,and mechanism

Porphobilinogen deaminase (hydroxymethylbilane synthase) and uroporphyrinogen III synthase (uroporphyrinogen III cosynthase) catalyze the transformation of four molecules of porphobilinogen, via the 1-hydroxymethylbilane, preuroporphyrinogen, into uroporphyrinogen III. A combination of studies involving protein chemistry, molecular biology, site-directed mutagenesis, and the use of chemically synthesized substrate analogs and inhibitors is helping to unravel the complex mechanisms by which the two enzymes function. The determination of the X-ray structure ofE. coli porphobilinogen deaminase at 1.76 Å resolution has provided the springboard for the design of further experiments to elucidate the precise mechanism for the assembly of both the dipyrromethane cofactor and the tetrapyrrole chain. The human deaminase structure has been modeled from theE. coli structure and has led to a molecular explanation for the disease acute intermittent porphyria. Molecular modeling has also been employed to simulate the spiro-mechanism of uroporphyrinogen III synthase.     

Effects of medium sterilization on the production of zaragozic acids by the fungusLeptodontidium elatius

The production of zaragozic acids by fermentation of the fungusLeptodontidium elatius was examined at the 800-L fermentor scale under two different production medium batch sterilization conditions. Low production-medium heat input (R₀=33.4 min) resulted in a 4-desacetoxy zaragozic acid C:4-O-desacetyl zaragozic acid C:zaragozic acid C ratio of 0.53:0.60:1.0. At a higher heat input (R₀=50.5 min), the ratio shifted to 1.0:0.66:1.0 with a corresponding 26% increase in total zaragozic acid production. This higher total zaragozic acid titer resulted from an increase in the amount of 4-desacetoxy zaragozic acid C produced while the levels of the other two analogues remained unchanged. Batch sterilization conditions also resulted in differences in growth, carbon substrate consumption, and oxygen uptake rates. The structures of the zaragozic acids produced suggest a precursor/end product relationship. A biosynthetic model describing the synthesis of the three zaragozic acids listed above is postulated and used to explain the effects of production-medium heat input during sterilization.     

Relationship between prostaglandin in peritoneal fluid and pelvic venous congestion after sterilization

Pelvic congestion may cause chronic pelvic pain in women. The aim of the study is to elucidate a possible role in this condition for prostaglandin. Prostaglandin levels in peritoneal fluid were measured in 18 women with pelvic pain caused by pelvic congestion following sterilization, 10 women without pain following sterilization, and 10 normal healthy women. Peritoneal fluid was aspirated by a silastic catheter from the cul-de-sac under laparoscopic direct vision. Concentration of 6-keto-PGF_1α, TXB₂, PGF_2α and PGE₂ were measured with the standard radioimmunoassay method in all samples. Results showed that 6-keto-PGF,. levels in peritoneal fluid from patients with pelvic congestion were markedly higher than those from two control women (P < 0.05); 6-keto-PGF_1α/TXB₂ in pelvic congestion and control groups were markedly different (P < 0.05); the total amounts of peritoneal fluid was higher in pelvic congestion than that in two control groups (P < 0.001). These data suggested that 6-ketoPGF_1α is increased in peritoneal fluid of women with pelvic congestion and the change might play an important role in attack of this disease.     

Activated charcoal does not catalyze sucrose hydrolysis in tissue culture media during autoclaving

Tissue culture media or aqueous sucrose solutions containing activated charcoal buffered to pH 5.5 and autoclaved did not undergo appreciable sucrose hydrolysis as reported. Rather, the extent of sucrose hydrolysis in media containing activated charcoal was found to be directly proportional to the hydrogen ion concentration (pH). This finding is consistent with the known mechanism of acid-catalyzed hydrolysis of acetals such as sucrose. Several types of charcoal were identified that acidified culture media to the extent that considerable acid-catalyzed sucrose hydrolysis occurred under autoclave conditions, making it appear as though activated charcoal was responsible for catalyzing sucrose hydrolysis. A simple mathematical expression was empirically derived that can be used to predict the extent of sucrose hydrolysis based on the post-autoclave pH of the media. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fish metacommunity responses to experimental drought are determined by habitat heterogeneity and connectivity

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