Effects of oxygen fraction in inspired air on force production and electromyogram activity during ergometer rowing

Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired air, F _IO₂ 0.209), in hyperoxia (F _IO₂ 0.622) and in hypoxia (F _IO₂ 0.158) in a randomized single-blind fashion. Oxygen consumption (V˙O₂), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Maximal force of a stroke (F _max) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P<0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P<0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between F _max and V˙O₂ was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P<0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F _IO₂ did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas. The lack of a significant correlation between F _max and V˙O₂ during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors in addition to V˙O₂. Accepted: 2 June 1997     

Dynamic changes in glucose and lactate in the cortex of the freely moving rat monitored using microdialysis

These experiments for the first time examine simultaneous changes in glucose and lactate in unanaesthetised animals during moderate hypoxia. Unanaesthetised rats were exposed to moderate hypoxia for a period of 15 min by reducing inspired oxygen to 8%. Changes in glucose and lactate were monitored in rat cortex using microdialysis and a novel dual enzyme-based assay. Samples of dialysate collected at 3-min intervals were assayed for both glucose and lactate. There was an early rapid rise of lactate that reached a peak at the end of the period of hypoxia followed by a steep decline. Glucose showed a very much smaller delayed increase that started during the period of hypoxia and continued beyond it. The origin of the rise in glucose is discussed, using the temporal relationship between the lactate and glucose changes.     

Polymer displacement/shielding in protein chromatography

An overview of different applications of polymer interactions with ion-exchange and dye-affinity chromatographic matrices is presented here. The strength of interaction between the ligand and the polymer plays a crucial role in deciding the mode of chromatographic application. Charged, non-ionic and thermosensitive polymers such as poly(ethylene imine), poly(N-vinyl pyrrolidone) and poly(vinyl caprolactam) respectively, show different degrees of interaction with the dye molecules in dye ligand chromatography. Polymers, with their ability of multipoint and hence strong attachment to the chromatographic matrices, were used as efficient displacers in displacement chromatography. The polymer displacement resulted in better recoveries and sharper elution profiles than traditional salt elutions. The globule–coil transition of the thermosensitive reversible soluble–insoluble polymer, poly(vinyl caprolactam), can be exploited in dye-affinity columns for the temperature induced displacement of the bound protein. In another situation, prior to the column chromatography of crude protein extract, polymers formed complexes with the dye matrix and “shielded” the column. The polymer shielding decreased the nonspecific interactions without affecting the specific interactions of the target protein to the dye matrix.     

不同海拔牦牛骨骼肌中乳酸脱氢酶三种亚基基因表达的比较

为了阐明高原低氧对牦牛（Bos mutus）骨骼肌中乳酸脱氢酶（LDH）三种亚基基因（LDHA、LDHB和LDHC）表达的影响,本实验分别选取高海拔（4 200 m）、中海拔（3 200 m）和低海拔（1 900 m）三个海拔位置养殖的临床健康成年雄性牦牛各5头,采用实时荧光定量PCR(qRT-PCR)和蛋白质印迹法检测牦牛骨骼肌中LDH三种亚基基因的m RNA表达和蛋白表达水平。结果表明,随海拔的升高,牦牛骨骼肌中LDHA m RNA的表达逐渐下降;LDHB m RNA先降低后升高,在高海拔组牦牛中表达最高,相对表达量为2.82±0.12,与低海拔组（1.01±0.07）、中海拔组（0.73±0.06）牦牛LDHB mRNA表达量差异显著（P <0.05）;LDHC mRNA的表达量随海拔的升高呈下降趋势,且低海拔组（1.10±0.16）、中海拔组（0.86±0.16）、高海拔组（0.69±0.12）组间两两相比均差异显著（P <0.05）。LDHA和LDHC蛋白表达量随海拔的升高呈下降趋势,且LDHA蛋白表达量在低海拔组（1.00±0.00）、中海拔组（0.88±0.0...     

A quantitative approach for understanding small-scale human mesenchymal stem cell culture – implications for large-scale bioprocess development

Human mesenchymal stem cell (hMSC) therapies have the potential to revolutionise the healthcare industry and replicate the success of the therapeutic protein industry; however, for this to be achieved there is a need to apply key bioprocessing engineering principles and adopt a quantitative approach for large-scale reproducible hMSC bioprocess development. Here we provide a quantitative analysis of the changes in concentration of glucose, lactate and ammonium with time during hMSC monolayer culture over 4 passages, under 100% and 20% dissolved oxgen (dO₂), where either a 100%, 50% or 0% growth medium exchange was performed after 72h in culture. Yield coefficients, specific growth rates (h^-1) and doubling times (h) were calculated for all cases. The 100% dO₂ flasks outperformed the 20% dO₂ flasks with respect to cumulative cell number, with the latter consuming more glucose and producing more lactate and ammonium. Furthermore, the 100% and 50% medium exchange conditions resulted in similar cumulative cell numbers, whilst the 0% conditions were significantly lower. Cell immunophenotype and multipotency were not affected by the experimental culture conditions. This study demonstrates the importance of determining optimal culture conditions for hMSC expansion and highlights a potential cost savings from only making a 50% medium exchange, which may prove significant for large-scale bioprocessing.     

Breaking the boundary — The key to bottom recovery? The role of mysid crustaceans in oxygenizing bottom sediments

Large areas of the Baltic Sea bottoms suffer from low oxygen conditions and anoxia, impoverishing the benthic macrofauna. The important macrofaunal function bioturbation, which improves the transport of oxygen into the sediment does not occur in an absence of benthic macrofauna. The objective of this study was to investigate if a semi-pelagic species, like the mysid crustacean Mysis relicta, is able to improve the oxygen conditions of the sediment and thereby acts as a facilitator for re-colonization of azoic sediments by benthic species. We also wanted to study the potential of M. relicta in breaking the diffusive boundary layer under varying degrees of oxygen deficiency. Three types of sediment qualities were used to mimic the severity of oxygen deficiency. Under normoxia, moderate hypoxia (40% O₂) and hypoxia, (20% O₂) M. relicta's bioturbation activity was studied by recording oxygen profiles in sediments with and without mysids. In normoxia the mysids were able to oxygenize the sediment independent of sediment quality. The results show that mysids are able to bioturbate the sediment to some extent in hypoxia independent of the sediment quality. In all treatments with mysids the diffusive boundary layer was more or less completely broken down. In normoxia treatment with sediment of very low quality the mysids prevented growth of the sulphur bacteria Beggiatoa spp. which usually occurs on anoxic bottoms. The ability of this semi-pelagic species to improve benthic oxygen conditions can be seen as an important first step in re-colonization by real benthic species.     

Ultrastructural detection of proteins, lipids and carbohydrates in oocytes of Amblyomma triste (Koch, 1844) (Acari; Ixodidae) during the vitellogenesis process

The ovary of the tick Amblyomma triste is classified as panoistic, which is characterized by the presence of oogonia without nurse and follicular cells. The present study has demonstrated that the oocytes in all developmental stages (I-IV) are attached to the ovary through a pedicel, a cellular structure that synthesizes and provides carbohydrate, lipids and proteins supplies for the oocytes during the vitellogenesis process. The lipids are deposited during all oocyte stages; they are freely distributed as observed in stages II, III and IV or they form complexes with other elements. The proteins are also deposited in all stages of the oocytes, however, in lower concentration in the stage IV. There is carbohydrate deposition from oocytes in the stage II as well as in stages III and IV. In addition, the present work has demonstrated that the oocyte yolk of A. triste has a glycolipoprotein nature and the elements are deposited in the following sequence: firstly the lipids and proteins, and finally the carbohydrates.     

Isolation of saccharolytic dissimilatory sulfate-reducing bacteria

Abstract Four unidentified saccharolytic dissimilatory sulfate-reducing strains were isolated from an anaerobic digester. Cells were Gram-negative, motile, nonsporulating rods which differ markedly from known sulfate reducers especially with respect to carbon source utilisation and sulfur sources which can be reduced. The strains were capable of metabolising at least 26 out of 50 carbohydrates tested. Carbohydrates were, in the absence of exogenous sulfate, fermented to acetate, ethanol, lactate, carbon dioxide and hydrogen. In the presence of excess sulfate carbohydrates were fermented to acetate, ethanol, carbon dioxide, hydrogen and hydrogen sulfide, but lactate was not detected. An oxidized organic or inorganic sulfur source, including elemental sulfur, was not required as a prerequisite for growth on carbohydrates, Lactate was, in the presence of sulfate, converted to acetate, ethanol, carbon dioxide, hydrogen and hydrogen sulfide. In the absence of sulfate no lactate was utilised and no growth was observed.     

P-31 Nuclear Magnetic Resonance Analysis of Brain: II. Effects of Oxygen Deprivation on Isolated Perfused and Nonperfused Rat Brain

Phosphatic metabolite (perchloric acid extractable) concentrations of cerebral tissues were analyzed by phosphorus-31 nuclear magnetic resonance (P-31 NMR) spectroscopy following external perfusion of the isolated rat brain (30 min or 60 min) under the following conditions: (a) constant perfusion pressure with either fluorocarbon- or erythrocyte-based medium, and (b) constant perfusate flow rate (3 ml/min) with the erythrocyte-based medium. Metabolite concentrations of control perfused brains were compared with those in nonperfused controls to provide a basis for detecting any qualitative or quantitative changes in cerebral metabolite composition. Metabolic responses of perfused brains to ischemia (incomplete ischemia, 83% reduction in flow for 10 min; transient complete ischemia for 1.5 or 2 min) were evaluated immediately after the ischemic episode and at selected time points during reperfusion (3 and 15 min). Alterations in cerebral metabolite levels induced by hypoxia were analyzed using a nonperfused rat brain model. Irrespective of the perfusion method employed, the phosphatic metabolites of control perfused rat brains were identical quantitatively to those of the nonperfused controls. Cerebral ischemia resulted in significantly increased levels of ADP, AMP + IMP, Pi, fructose 1,6-diphosphate, and glycerol 3-phosphate (global ischemia only), whereas ATP and phosphocreatine (PCr) levels declined significantly. The magnitude of these changes varied with the severity of the ischemia; however, following 15 min of control reperfusion metabolite levels had reverted to preischemic values. Significant perturbations in tissue phosphoethanolamine (3.84 delta resonance) content were evident at various time points during ischemia and postischemic recovery, which varied according to the perfusion conditions. In contrast to the changes observed in response to ischemia, hypoxia affected only cerebral high-energy phosphate levels. ATP and PCr levels were reduced, while a concomitant, essentially equimolar, increase in Pi and ADP was observed. The present studies indicate that in terms of phosphatic metabolites, the control equilibrated isolated perfused rat brain is quantitatively and qualitatively indistinguishable from the nonperfused rat brain in vivo regardless of the perfusion conditions (constant flow versus constant pressure). The metabolic responses to ischemia and hypoxia, as measured by P-31 NMR, were consistent with the pattern of changes reported elsewhere. Overall, P-31 NMR spectroscopic evaluation of the intact rat brain provides a potential experimental context for dynamic measures of cerebral metabolism under exogenously controlled conditions. Th     

新疆冬春麦区小麦地方品种贮藏蛋白遗传多样性研究

采用SDS-聚丙烯酰胺凝胶电泳（SDS-PAGE）对236份新疆小麦地方品种的高分子量麦谷蛋白亚基(HMW-GS)的组成进行了分析。结果表明：Glu-1位点共有19种等位基因,其中Glu-A1位点3种,Glu-B1位点7种,Glu-D1位点9种;亚基null、7+8、2+12在各自的位点上出现频率最高,分别达到91.95％、85.17％、80.93％;亚基组成类型共有21种,主要为null/7+8/2+12,频率达70.34％;同时筛选出33份含有1、2*、13+16、14+15、5+10、1.5+10、17+18等优质亚基的材料,可作为优质基因源。利用酸性聚丙烯酰胺凝胶电泳（A-PAGE）对其中的65份地方品种进行醇溶蛋白多样性分析。结果表明：电泳出现64条迁移率不同的谱带,构成65种组合,其中ω区出现的谱带最多,达17条,其次是β和γ区各16条,α区出现的谱带数最少,为15条。从每条谱带在65份材料中出现的频率看,总的变异范围为1.54%~93.85%;α、β、γ和ω四个分区多样性指数（H′）分别为0.498、0.386、0.523和0.348。这表明新疆麦区小麦地方品种贮藏蛋白位点存在丰富的遗传多样性。     

Effects of feeding and hypoxia on cardiac performance and gastrointestinal blood flow during critical speed swimming in the sea bass Dicentrarchus labrax

Previous studies have shown that if European sea bass are exercised after feeding, they can achieve a significantly higher maximum metabolic rate (MMR) than when fasted. They can meet combined metabolic demands of digestion (specific dynamic action, SDA) and maximal aerobic exercise, with no decline in swimming performance. If, however, exposed to mild hypoxia (50% saturation), bass no longer achieve higher MMR after feeding but they swim as well fed as fasted, due to an apparent ability to defer the SDA response. This study explored patterns of cardiac output (Q_A) and blood flow to the gastrointestinal tract (Q_GI) associated with the higher MMR after feeding, and with the ability to prioritise swimming in hypoxia. Sea bass (mean mass ~ 325 g, forklength ~ 27 cm) were instrumented with flow probes to measure Q_A and Q_GI during an incremental critical swimming speed (U_crit) protocol in a tunnel respirometer, to compare each animal either fasted or 6 h after a meal of fish fillet equal to 3% body mass. Feeding raised oxygen uptake (M_O2) prior to exercise, an SDA response associated with increased Q_A (+ 30%) and Q_GI (+ 100%) compared to fasted values. As expected, when exercised the fed bass maintained the SDA load throughout the protocol and achieved 14% higher MMR than when fasted, and the same U_crit (~ 100 cm s^-1). Both fed and fasted bass showed pronounced increases in Q_A and decreases in Q_GI during exercise and the higher MMR of fed bass was not associated with higher maximum Q_A relative to when fasted, or to any differences in Q_GI at maximum Q_A. In hypoxia prior to exercise, metabolic and cardiac responses to feeding were similar compared to normoxia. Hypoxia caused an almost 60% reduction to MMR and 30% reduction to U_crit, but neither of these traits differed between fed or fasted bass. Despite hypoxic limitations to MMR and U_crit, maximum Q_A and patterns of Q_GI during exercise in fasted and fed bass were similar to normoxia. Estimating GI oxygen supply from Q_GI indicated that the ability of bass to prioritise aerobic exercise over SDA when metabolically limited by hypoxia was linked to an ability to defer elements of the SDA response occurring outside the GI tract.     

大鼠脑损伤后非损伤区域缺氧诱导因子与乳酸的变化研究

目的：研究大鼠脑损伤后非损伤区域缺氧诱导因子（hypoxia-inducible factor-1α,HIF-1α）与乳酸的表达变化。方法：取雄性SD大鼠36只,体重200-300g,参照统计学随机数字表将大鼠随机平均分为正常对照组（6只）、假手术组（6只）、造模组（24只）,3组,造模组分四个时间点12h、72h、1w、2w处死动物（每时间点6只）。使用立体定位仪和液压打击装置,靶向打击大脑中动脉,造大鼠脑外伤模型。采用免疫组织化学法检测脑外伤后不同时间点损伤临近区域脑组织中HIF-1α蛋白表达及乳酸含量的变化。结果：正常组和假手术组脑组织神经细胞HIF-1α表达和乳酸含量无明显变化,而模型组损伤临近区域HIF-1α的表达及乳酸含量的变化规律基本一致,12 h时增多,72h时达到高峰,1w表达下降至2w时恢复正常。造模组12h、72h、1w3个亚组与正常对照组比较差异具有统计学意义p〈0.01,造模组2w亚组与正常对照组比较差异无统计学意义p〉0.01。结论：脑外伤后非损伤区域也有缺血、缺氧的改变,可能与脑外伤后的脑萎缩有相关性。