硒对水稻的生态毒理效应及临界指标研究

通过土壤添加硒盆栽试验,研究了黄棕壤不同浓度Se对水稻生物量、叶绿素含量、抗氧化酶系统的影响.结果表明,低浓度Se(<8mg·kg^-1)对水稻根和地上生物量、叶绿素a含量、叶绿素a/b有促进作用,并整体提高了作物抗氧化酶系统,使MDA下降,SOD、CAT、POD、GSHPx活性相应提高.而高浓度Se(>16mg·kg^-1)对水稻根和地上生物量、叶绿素a含量、叶绿素a/b有明显的抑制作用,对抗氧化酶系统产生胁迫效应,使GSHPx明显上升,MDA上升,SOD、CAT、POD酶活性明显下降.各项生理指标与土壤Se处理浓度之间相关分析表明,土壤Se浓度与地上部干重相对百分率、根干重百分率、叶绿素a/b、MDA、SOD、CAT、POD之间有显著相关性.比较胁迫效应10%值的临界指标EC10值表明,作物地上部干重抑制率作为土壤临界值制定的依据更为可靠,EC10为21mg·kg^-1.     

Heteroskedasticity as a leading indicator of desertification in spatially explicit data

Regime shifts are abrupt transitions between alternate ecosystem states including desertification in arid regions due to drought or overgrazing. Regime shifts may be preceded by statistical anomalies such as increased autocorrelation, indicating declining resilience and warning of an impending shift. Tests for conditional heteroskedasticity, a type of clustered variance, have proven powerful leading indicators for regime shifts in time series data, but an analogous indicator for spatial data has not been evaluated. A spatial analog for conditional heteroskedasticity might be especially useful in arid environments where spatial interactions are critical in structuring ecosystem pattern and process. We tested the efficacy of a test for spatial heteroskedasticity as a leading indicator of regime shifts with simulated data from spatially extended vegetation models with regular and scale‐free patterning. These models simulate shifts from extensive vegetative cover to bare, desert‐like conditions. The magnitude of spatial heteroskedasticity increased consistently as the modeled systems approached a regime shift from vegetated to desert state. Relative spatial autocorrelation, spatial heteroskedasticity increased earlier and more consistently. We conclude that tests for spatial heteroskedasticity can contribute to the growing toolbox of early warning indicators for regime shifts analyzed with spatially explicit data.     

Combination stem cell therapy using dental pulp stem cells and human umbilical vein endothelial cells for critical hindlimb ischemia

Narrowing of arteries supplying blood to the limbs provokes critical hindlimb ischemia (CLI). Although CLI results in irreversible sequelae, such as amputation, few therapeutic options induce the formation of new functional blood vessels. Based on the proangiogenic potentials of stem cells, in this study, it was examined whether a combination of dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs) could result in enhanced therapeutic effects of stem cells for CLI compared with those of DPSCs or HUVECs alone. The DPSCs+ HUVECs combination therapy resulted in significantly higher blood flow and lower ischemia damage than DPSCs or HUVECs alone. The improved therapeutic effects in the DPSCs+ HUVECs group were accompanied by a significantly higher number of microvessels in the ischemic tissue than in the other groups. In vitro proliferation and tube formation assay showed that VEGF in the conditioned media of DPSCs induced proliferation and vessel-like tube formation of HUVECs. Altogether, our results demonstrated that the combination of DPSCs and HUVECs had significantly better therapeutic effects on CLI via VEGF-mediated crosstalk. This combinational strategy could be used to develop novel clinical protocols for CLI proangiogenic regenerative treatments.     

Gas exchange and habitat selection in the aquatic salamanders Necturus maculosus and Cryptobranchus alleganiensis

Summary The standard metabolic rate (SMR) and critical O₂ tension (P_c) of water-breathing mudpuppies and hellbenders were determined at 20° C using open-system respirometry. Both species are metabolic O₂ regulators, although the P_c of hellbenders (90 mmHg) is much higher than that of mudpuppies (40 mmHg). The SMR of the two species in water saturated with air was similar (19.5 and 20.0 l O₂/g·h for Cryptobranchus and Necturus, respectively) and not different from that of salamanders in general. Both species were able to survive for at least 5–11 days in severely hypoxic water (9–10 mmHg) by breathing air, indicating that the lungs are functional accessory respiratory structures.We conclude that hellbenders are restricted to relatively cool and flowing waters because of their limited gas exchange capabilities, particularly with regard to their limited aerobic scope for activity and slow recovery from exercise. Necturus maculosus is much more tolerant of hypoxia, but it is not known if they can inhabit areas were hypoxia is combined with hypercarbia.     

eNOS基因治疗促进大鼠缺血后肢的血管新生

目的:评估内皮型一氧化氮合酶(Endothelial nitric oxide synthase,eNOS)基因治疗对大鼠缺血后肢血管新生的影响。方法:局麻下将30只雄性SD大鼠后肢缺血模型制作后,随机分成实验组和对照组,每组15只。模型制作后1周,采用肌肉注射的方法,实验组缺血后肢接受载有eNOS基因的5型重组腺病毒治疗,对照组接受生理盐水治疗。eNOS基因治疗后4周,评估SD大鼠踝部动脉压、微循环灌注、数字减影血管造影、组织微血管计数以及eNOS蛋白的表达。结果:eNOS基因治疗后4周,和对照组相比,接受eNOS基因治疗的大鼠缺血肢体,表现了更好的血流恢复(踝部动脉压(mmHg):58.2±4.7 vs 86.8±4.3,P0.01;微循环灌注:142.0%±21.5%vs 219.6%±26.2%,P0.01)、侧枝开放和血管新生(血管造影:6.7±1.1 vs 14.4±1.7,P0.01;微血管/肌纤维比值:0.34±0.03 vs 0.56±0.02,P0.01)以及eNOS蛋白的高表达(0.46±0.02 vs 0.73±0.02,P0.01)。结论:eNOS基因治疗促进SD大鼠缺血后肢的血管新生。     

Situación funcional como factor independiente asociado con el mal pronóstico de pacientes ancianos ingresados en Cuidados Intensivos

Objective

To assess the association of previous functional status in elderly patients admitted to the ICU, estimated by the Barthel and Short Form-Late Life Function and Disability instrument scales, and the relationship with prognosis and functional capacity at hospital discharge.

Unexpected spatial stability of water chemistry in headwater stream networks

Understanding how water and solutes enter and propagate through freshwater landscapes in the Anthropocene is critical to protecting and restoring aquatic ecosystems and ensuring human water security. However, high hydrochemical variability in headwater streams, where most carbon and nutrients enter river networks, has hindered effective modelling and management. We developed an analytical framework informed by landscape ecology and catchment hydrology to quantify spatiotemporal variability across scales, which we tested in 56 headwater catchments, sampled periodically over 12 years in western France. Unexpectedly, temporal variability in dissolved carbon, nutrients and major ions was preserved moving downstream and spatial patterns of water chemistry were stable on annual to decadal timescales, partly because of synchronous variation in solute concentrations. These findings suggest that while concentration and flux cannot be extrapolated among subcatchments, periodic sampling of headwaters provides valuable information about solute sources and subcatchment resilience to disturbance.     

Effect of end-point cadence on the maximal work-time relationship

This study examined the effect of end-point cadence on the parameters of the work-time relationship determined for cycle ergometry. Eight male subjects completed four maximal tests on an electrically-braked cycle ergometer that regulated a constant power output independent of cadence. The power outputs imposed ranged between an average of 259 W and 403 W, whereas the corresponding durations ranged between 139 s and 1691 s. During each test subjects were required to maintain a cadence of 80–90 rpm. Accumulated time to end-point cadences of 70, 60 and 50 rpm were recorded. The four work-time determinations for each of three end-point cadences were used to determine linear relationships between work and time, yielding both a y-intercept, which represents anaerobic work capacity, and a slope, which is termed critical power (CP), for each end-point cadence. There was a significant increase in the y-intercept as end-point cadence decreased from 70 to 60 rpm (F[1,7]=36.7, p < 0.001) or 70 to 50 rpm (F[1,7]=80.1, p < 0.001), but not from 60 rpm to 50 rpm (F[1,7]=3.28, p > 0.05). In contrast, there was no effect of end-point cadence on CP (F[2,14]=1.89, p < 0.05). These results demonstrate that the end-point cadence selected to terminate tests only affects the y-intercept of the work-time relationship. To control for this effect, the cadence at which each test is terminated should be standardised if determination of anaerobic work capacity, as represented by the y-intercept, is required.     

对重症医学科进修生的临床教学体会

重症医学在我国发展较为滞后,多数重症医学科医生来自于其他专业,缺乏重症医学专业知识及临床实践经验。建立完善、科学、有效的重症医学科进修生管理和培养模式对于进一步提高危重症救治专业人才的水平至关重要。我科室通过总结多年的进修生教学经验,以"病例分析学习(case based learning,CBL)+多学科协作(multiple department team,MDT)"教学模式为主导,以病例幻灯竞赛为契机激发进修医生学习的主观能动性;以专业英语为特色;重视临床科研教学;制定规范化培训制度,实行导师负责制,开展定期考核。显著提高了重症医学科进修生的医疗及科研水平。