THE EFFECTS OF THREE DIFFERENT REAR KNEE ANGLES ON KINEMATICS IN THE SPRINT START

The purpose of this study was to investigate the rear knee angle range in the set position that allows sprinters to reach greater propulsion on the rear block during the sprint start. Eleven university-track team sprinters performed the sprint start using three rear knee angle conditions: 90°, 115° and 135°. A motion capture system consisting of 8 digital cameras (250 Hz) was used to record kinematic parameters at the starting block phase and the acceleration phase. The following variables were considered: horizontal velocity of the centre of mass (COM), COM height, block time, pushing time on the rear block, percentage of pushing time on the rear block, force impulse, push-off angle and length of the first two strides. The main results show that first, horizontal block velocity is significantly greater at 90° vs 115° and 135° rear knee angle (p<0.05 and p<0.001 respectively) at block clearance and the first two strides; second, during the pushing phase, the percentage of pushing time of the rear leg is significantly greater at 90° vs 135° rear knee angle (p<0.01). No significant difference was found for block time among the conditions. These results indicate that block velocity is the main kinematic parameter affected by rear knee angle during the starting block phase and acceleration phase. Furthermore, the 90° rear knee angle allows for a better push-off of the rear leg than larger angles at the set position. The findings of this study provide some direction and useful practical advice in defining an efficient rear leg biomechanical configuration at the set position.     

山蝠和黑斑蛙乳酸脱氨酶同工酶及血糖浓度的季节变化

本工作采用聚丙烯酸胺凝胶电泳等方法,对山蝠（Ｎｙｃｔｕｓｎｏｃｔｕｌａ）和黑斑蛙（Ｒａｎａｎｉｇｒｏｍａｃｕｌａｔａ）在冬眠或蛰伏期与活动期的血清、脑、骨胳肌中的乳酸脱氢酶（ｌａｃｔａｔｅｄｅｈｙｄｒｏｇｅｎａｓｅ,ＬＤＨ）同工酶和血糖浓度进行了比较研究。ＬＤＨ同工酶及血糖浓度表现出明显的季节变化。与活动期的动物相比,在冬眠或蛰伏期中的动物的ＬＤＨ１缺乏、ＬＤＨ５明显增多（Ｐ＜０．００１）,血糖浓度明显升高（Ｐ＜０．００１）。此外,ＬＤＨ同工酶和血糖浓度的季节变化在冬眠动物和蛰伏动物之间还存在着明显的差异。这些结果提示,ＬＤＨ同工酶含量和血糖浓度的季节变化不仅与动物的能量代谢水平相适应,而且显示了冬眠和蛰伏两种生理过程中的可能差异。     

ACUTE EFFECTS OF MOVEMENT VELOCITY ON BLOOD LACTATE AND GROWTH HORMONE RESPONSES AFTER ECCENTRIC BENCH PRESS EXERCISE IN RESISTANCE-TRAINED MEN

This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL⁻¹) relative to the FEV group (0.1 ± 0.0 ng · mL⁻¹). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response.     

INDEPENDENT HIGH-FREQUENCY OSCILLATIONS IN THE AMOUNTS OF INDIVIDUAL ISOZYMES OF LACTATE DEHYDROGENASE IN HL60 CELLS

Early studies, using kinetic methods, suggested that the isozyme pattern of lactate dehydrogenase in various cells oscillated with time. More recent electrophoretic studies on murine erythroleukaemic cells (which exhibit only one isozyme) indicated very high frequency variations (period 2min or less) in the amount of the lone active isozyme. We now show that in HL60 cells, the activity stain intensities of the two major isozyme bands both oscillate but the temporal variations are distinct. As with other cellular rhythms, each of the two periodicities seem to be modulated in cyclic fashion with respect to period, amplitude and mean levels, the periods of both the primary and modulating rhythms being of the order of 10–15min or probably much less.     

THE EFFECT OF SALT CONCENTRATION ON THE GROWTH OF BACTERIA IN DILUTE NUTRIENT SOLUTIONS

SUMMARY: In dilute nutrient solutions Bacterium coli and Streptococcus faecalis were able to grow only over a narrow range of salt concentrations.     

THE EFFECT OF CYANIDE AND OF VARIATION IN ALKALINITY ON THE OXIDATION-REDUCTION POTENTIAL OF THE HEMOGLOBIN-METHEMOGLOBIN SYSTEM

The potentiometric method was applied to the study of the influence of cyanide and of hydroxyl ion on methemoglobin. Both of these ions appear to combine with the iron of the methemoglobin molecule and reduce its oxidant activity. From the magnitude of the effect produced by cyanide and by variation in pH on the oxidation-reduction potential of the methemoglobin-hemoglobin system, it is concluded that cyanmethemoglobin and alkaline methemoglobin are undissociated ferric compounds, the first with cyanide and the second with hydroxyl. Electronic formulas, based on the electrical properties of the hemoglobin derivatives, are suggested.     

急、慢性缺氧对大鼠凝血机能的影响

本文讨论了实验性缺氧对大鼠凝血机能产生的影响。实验结果表明,大鼠在模拟8000米高度两小时后,血小板凝聚性、血小板因子3活性明显增加,纤溶活性下降,同时,纤维蛋白原含量和因子X也明显下降。大鼠在模拟7000米经36天间歇性慢性缺氧,血小板计数、血小板凝聚性,血小板因子3活性、纤维蛋白原含量、因子X活性均显著增加,部分凝血活酶时间缩短、纤溶活性下降,明显地出现凝血增强的趋势。本文还讨论了抗缺氧药物复方党参、异叶青兰对人鼠急性缺氧时凝血机能的影响。     

斯氏并殖吸虫乳酸脱氢酶,苹果酸脱氢酶及酯酶同工酶的研究

本文采用Disc-PAGE电泳,首次对我国独有的斯氏并殖吸虫(Paragonimus skrjabini Chen,1959)成虫、童虫、囊蚴的乳酸脱氢酶(以下简称LDH)、苹果酸脱氢酶(以下简称MDH)和酯酶(以下简称EST)同工酶进行了研究。 在成虫、童虫、囊蚴间,LDH、MDH、EST同工酶在酶带数、排列型式、Rf值、相对活性和优势酶带的位置都存在差异。 根据虫体和宿主组织同工酶谱的不同,可以认为是本虫本身所具有。 同工酶作为其分类指标时,不仅要比较不同虫种成虫稳定的同工酶谱,也要比较同工酶在个体发育型式间的差异。     

EVOLUTION OF SPRINT SPEED IN LACERTID LIZARDS: MORPHOLOGICAL,PHYSIOLOGICAL, AND BEHAVIORAL COVARIATION

Organismal performance abilities occupy a central position in phenotypic evolution; they are determined by suites of interacting lower-level traits (e.g., morphology and physiology) and they are a primary focus of natural selection. The mechanisms by which higher levels of organismal performance are achieved during evolution are therefore fundamentally important for understanding correlated evolution in general and coadaptation in particular. Here we address correlated evolution of morphological, physiological, and behavioral characteristics that influence interspecific variation in sprint speed in a clade of lacertid lizards. Phylogenetic analyses using independent contrasts indicate that the evolution of high maximum sprinting abilities (measured on a photocell-timed racetrack) has occurred via the evolution of (1) longer hind limbs relative to body size, and (2) a higher physiologically optimum temperature for sprinting. For ectotherms, which experience variable body temperatures while active, sprinting abilities in nature depend on both maximum capacities and relative performance levels (i.e., percent of maximum) that can be attained. With respect to temperature effects, relative performance levels are determined by the interaction between thermal physiology and thermoregulatory behavior. Among the 13 species or subspecies of lizards in the present study, differences in the optimal temperature for sprinting (body temperature at which lizards run fastest) closely matched interspecific variation in median preferred body temperature (measured in a laboratory photothermal gradient), indicating correlated evolution of thermal physiology and thermal preferences. Variability of the preferred body temperatures maintained by each species is, across species, negatively correlated with the thermal-performance breadth (range of body temperatures over which lizards can run relatively fast). This pattern leads to interspecific differences in the levels of relative sprint speed that lizards are predicted to attain while active at their preferred temperatures. The highest levels of predicted relative performance are achieved by species that combine a narrow, precise distribution of preferred temperatures with the ability to sprint at near-maximum speeds over a wide range of body temperatures. The observed among-species differences in predicted relative speed were positively correlated with the interspecific variation in maximum sprinting capacities. Thus, species that attain the highest maximum speeds are (1) also able to run at near-maximum levels over a wide range of temperatures and (2) also maintain body temperatures within a narrow zone near the optimal temperature for sprinting. The observed pattern of correlated evolution therefore has involved traits at distinct levels of biological organization, that is, morphology, physiology, and behavior; and trade-offs are not evident. We hypothesize that this particular trait combination has evolved in response to coadaptational selection pressures. We also discuss our results in the context of possible evolutionary responses to global climatic change.     

THE EFFECT OF PHYSOSTIGMINE AND NEOSTIGMINE ON THE CONCENTRATION OF GLYCOGEN IN VARIOUS BRAIN STRUCTURES OF THE RAT

Abstract—

• 1 Hypothalamus, mesencephalon, cerebral cortex, cerebellar cortex and medulla oblongata of the rat brain contain varying amounts of glycogen. The highest concentration was found in the medulla, and the lowest in the hypothalamus.
• 2 Low doses of physostigmine produced a significant decrease in the concentration of glycogen in mesencephalon, cerebral cortex, cerebellar cortex and medulla. Higher doses of physostigmine were necessary to produce glycogenolysis in the hypothalamus. In the first four structures glycogen stores were almost equally sensitive to the action of physostigmine. Neostigmine did not affect brain glycogen. The glycogenolytic effect of physostigmine was dose-dependent.
• 3 Both atropine and propranolol were found to block the glycogenolytic effect of physostigmine in brain.
• 4 It is concluded that probably both cholinergic and adrenergic processes participate in the glycogenolytic effect of physostigmine. It is suggested that physostigmine initiates the cholinergic processes which then trigger adrenergic processes.

     

甘蔗组织培养中染色体数目变异的初步研究

本文通过甘蔗桂糖11号组培腋芽苗与其原种的染色体数目的比较,研究了腋芽苗染色体数目的变化情况。发现腋芽苗82％的细胞的染色体数目仍在其原种染色体数目变异的高峰之内。     

NO EFFECT OF ENVIRONMENTAL HETEROGENEITY ON THE MAINTENANCE OF GENETIC VARIATION IN WING SHAPE IN DROSOPHILA MELANOGASTER

Theory suggests that heterogeneous environments should maintain more genetic variation within populations than homogeneous environments, yet experimental evidence for this effect in quantitative traits has been inconsistent. To examine the effect of heterogeneity on quantitative genetic variation, we maintained replicate populations of Drosophila melanogaster under treatments with constant temperatures, temporally variable temperature, or spatially variable temperature with either panmictic or limited migration. Despite observing differences in fitness and divergence in several wing traits between the environments, we did not find any differences in the additive genetic variance for any wing traits among any of the treatments. Although we found an effect of gene flow constraining adaptive divergence between cages in the limited migration treatment, it did not tend to increase within‐population genetic variance relative to any of the other treatments. The lack of any clear and repeatable patterns of response to heterogeneous versus homogeneous environments across several empirical studies suggests that a single general mechanism for the maintenance of standing genetic variation is unlikely; rather, the relative importance of putative mechanisms likely varies considerably from one trait and ecological context to another.     

重复热处理对大鼠精子发生的影响研究:光学和电子显微镜观察

大鼠睾丸每月重复接受43℃热处理(每次处理25分钟)。第一次加温后24小时,光学和电镜观察指出,生殖细胞对加热反应并非是一种特异性效应。电镜观察指出,所有发育期的生殖细胞的胞核均受损伤,但其他细胞器,如细胞膜和线粒体却很完整。本实验表明,加热原初损伤是细胞核,而不是胞质的膜系统。 首次加温后24小时,具空泡化胞核的早期精细胞已有一个小顶体,而胞质的特征却相似于分裂的精母细胞。表明加热能引起精母细胞的核——质非同步发育,即加速胞核分裂和分化。 每月一次,二次加温后182天,绝大多数精小管内无生殖细胞,但在一些部分恢复的精细管中,还发现空泡化的多核巨细胞,本结果表明,一些休止期精原细胞也受潜在损伤,并能生存相当长时间;一旦细胞进行分裂之后,就出现退行性交。     

THE EFFECT OF EXTRACELLULAR POTASSIUM CONCENTRATION ON PROTEIN SYNTHESIS IN GUINEA-PIG HIPPOCAMPAL SLICES1,2

Abstract— We have measured the effect of small variations in extracellular potassium concentrations ([K⁺]) upon the incorporation of radioactively labelled amino acid into the protein of the isolated guinea-pig hippocampal slice. The slice is super-perfused with glucose fortified buffer and maintains an ATP concentration of 33–36 nmol/mg protein and incorporates lysine into protein at a rate of 0.82 pmol/(ig protein/h. Within the range of extracellular K⁺ from 1.3 to 8.1 mil the change in the rate of lysine incorporation into protein is proportional to the logarithm of the extracellular K⁺ concentration. Incorporation increases by about 100% over this range. Measurements of the specific activity of the presumed intracellular amino acid pool indicate that the effect of changes in extracellular [K⁺] is to alter the rate of protein synthesis rather than alter the availability of radioactively labelled precursor. Altering extracellular [K⁺] does not affect tissue levels of ATP or creatine phosphate, indicating that the effect on amino acid incorporation does not result from an effect upon energy metabolism. It is suggested that this effect of extracellular [K.⁺] may be a means by which changes in cerebral electrical activity lead to changes in the rate of protein synthesis in brain.