Influence of short-term aerobic training and hydration status on tolerance during uncompensable heat stress

The purpose of the present study was to determine the separate and combined effects of a short-term aerobic training program and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40°C, 30% relative humidity). Males of moderate fitness [<50 ml · kg⁻¹ · min⁻¹ maximal O₂ consumption (V˙O_{2 max} )] were tested while euhydrated or hypohydrated by ≈2% of body weight through exercise and fluid restriction the day preceding the trials. Tests were conducted before and after either a 2-week program of daily aerobic training (1 h treadmill exercise at 65% V˙O_{2 max} for 12 days; n = 8) or a control period (n = 7), which had no effect on any measured variable. The training increased V˙O_{2 max} by 6.5%, while heart rate (f _c) and the rectal temperature (T _re) rise decreased during exercise in a thermoneutral environment. In the heat, training resulted in a decreased skin temperature and increased sweat rate, but did not affect f _c, T _re or tolerance time (TT). In both training and control groups, hypohydration significantly increased T _re and f _c and decreased the TT. It was concluded that the short-term aerobic training program had no benefit on exercise-heat tolerance in this uncompensable heat stress environment. Accepted: 12 November 1997     

Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges

Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges.     

每搏量变异度在围手术期容量治疗监测中的应用

每搏量变异度是动态的容量监测指标.机械通气患者心肺的相互作用是每搏量变异度的产生基础,通过动脉压力波形分析技术可以进行连续监测.每搏量变异度能够准确预测容量治疗反应,与静态的血流动力学参数相比,对于优化心输出量和组织氧供更有优势,但也存在一定的局限性.每搏量变异度受多种因素影响且不能用于自主呼吸和心律失常的患者.临床应用时应该综合考虑其影响因素,结合其他的指标和方法指导容量治疗.     

A rhizosphere fungus enhances Arabidopsis thermotolerance through production of an HSP90 inhibitor

The molecular chaperone HEAT SHOCK PROTEIN90 (HSP90) is essential for the maturation of key regulatory proteins in eukaryotes and for the response to temperature stress. Earlier, we have reported that fungi living in association with plants of the Sonoran desert produce small molecule inhibitors of mammalian HSP90. Here, we address whether elaboration of the HSP90 inhibitor monocillin I (MON) by the rhizosphere fungus Paraphaeosphaeria quadriseptata affects plant HSP90 and plant environmental responsiveness. We demonstrate that MON binds Arabidopsis (Arabidopsis thaliana) HSP90 and can inhibit the function of HSP90 in lysates of wheat (Triticum aestivum) germ. MON treatment of Arabidopsis seedlings induced HSP101 and HSP70, conserved components of the stress response. Application of MON, or growth in the presence of MON, allowed Arabidopsis wild type but not AtHSP101 knockout mutant seedlings to survive otherwise lethal temperature stress. Finally, cocultivation of P. quadriseptata with Arabidopsis enhanced plant heat stress tolerance. These data demonstrate that HSP90-inhibitory compounds produced by fungi can influence plant growth and responses to the environment.     

Performance analysis of elite Rugby League match play using global positioning systems

The aim of this study was (a) to examine the physiological demands of competitive Rugby League match play using portable Global Positioning Systems (GPSs) to monitor players' movement patterns and heart rate (HR) and (b) examine positional comparisons to determine if players' physiological requirements are influenced by their playing position during Rugby League match play. Twenty-two elite male Rugby League players were monitored during 5 regular season competition matches using portable GPS software. There was no difference in the total distance traveled between backs (5,573 ± 1,128 m) and forwards (4,982 ± 1,185 m) during match play. Backs and forwards had an average HR of approximately 80% of their maximum (162 ± 11 and 165 ± 12 b · min(-1), respectively) throughout each match. Backs achieved greater maximum running speed (8.6 ± 0.7 m · s(-1)), completed a greater number of sprints (18 ± 6), had less time between sprints (3.2 ± 1.1 minutes), achieved a greater total duration of sprinting (44.7 ± 9.1 seconds), and covered more distance sprinting (321 ± 74 m) than forwards did (6.8 ± 0.7 m · s(-1), 11 ± 5, 5.2 ± 2.2 minutes, 25.8 ± 9.2 seconds, and 153 ± 38 m, respectively). The GPS successfully provided real-time feedback to identify significant positional differences in distances covered, running speed characteristics, and the physiological demands of competitive Rugby League match play.     

Neuroprotection against CCl4 induced brain damage with crocin in Wistar rats

Owing to its lipophilic property, carbon tetrachloride (CCl₄) is rapidly absorbed by both the liver and brain. We investigated the protective effects of crocin against brain damage caused by CCl₄. Fifty rats were divided into five groups of ten: control, corn oil, crocin, CCl₄ and CCl₄ + crocin. CCl₄ administration decreased glutathione (GSH) and total antioxidant status (TAS) levels, and catalase (CAT) activity, while significant increases were observed in malondialdehyde (MDA) and total oxidant status (TOS) levels and superoxide dismutase (SOD) activity. The cerebral cortex nuclear lamina developed a spongy appearance, neuronal degeneration was observed in the hippocampus, and heterochromatic and pyknotic neurons with increased cytoplasmic eosinophilia were observed in the hippocampus after CCl₄ treatment. Because crocin exhibits strong antioxidant properties, crocin treatment increased GSH and TAS levels and CAT activities, and decreased MDA and TOS levels and SOD activity; significant improvements also were observed in histologic architecture. We found that crocin administration nearly eliminated CCl₄ induced brain damage by preventing oxidative stress.     

Conservation of pregnancy-specific glycoprotein (PSG) N domains following independent expansions of the gene families in rodents and primates

Background  

Rodent and primate pregnancy-specific glycoprotein (PSG) gene families have expanded independently from a common ancestor and are expressed virtually exclusively in placental trophoblasts. However, within each species, it is unknown whether multiple paralogs have been selected for diversification of function, or for increased dosage of monofunctional PSG. We analysed the evolution of the mouse PSG sequences, and compared them to rat, human and baboon PSGs to attempt to understand the evolution of this complex gene family.     

Quantifying maintenance requirements from the steady-state operation of a two-phase partitioning bioscrubber

An innovative method for directly and explicitly quantifying the maintenance energy requirements of pure cultures growing on volatile organic compound (VOC) substrates in a two-phase partitioning bioscrubber is described. Direct evidence of maintenance energy requirements of Achromobacter xylosoxidans Y234 is provided both through observed reductions in the macroscopic biomass-to-substrate yield with decreasing specific growth rates, but more remarkably through achievement of steady-state operation. The data conclusively show that maintenance activities do occur in the two-phase partitioning bioscrubber and clearly illustrate the importance of this phenomenon to the operation of this process, and similar bioreactor systems. While benzene was selected as the principal, sole substrate of interest in this study, ethylbenzene degradation experiments were also subsequently performed to illustrate and confirm the general applicability of the proposed technique, as well as the potential capabilities of the two-phase partitioning bioscrubber for the continuous treatment of waste gases containing various VOCs. The proposed method has been shown to generate maintenance energy estimates that are consistent with those obtained while employing more widely recognized estimation strategies, further validating its capabilities. The proposed steady-state mode also offers key operational advantages in terms of decreased disposal requirements in two-phase partitioning bioscrubbers. (c) 2005 Wiley Periodicals, Inc.