高温天数和吡虫啉互作对麦长管蚜世代内与世代间生态表型的影响

麦长管蚜Sitobion avenae是麦类作物主要的害虫之一,严重影响麦类作物的质量和产量.为了探究不同高温天数和农药互作对麦长管蚜世代内与世代间生活史性状的影响,调查了成蚜经高温事件34℃/3 h持续1d、3d和5d与低剂量吡虫啉互作,对生活史性状的影响.结果 表明,在世代内,随着高温天数增加,存活率随之下降,仅高温处理下由67.5％下降为12.5％,与农药结合后由70％下降为10％,但对寿命、繁殖却没有影响(P＞0.05).不同高温天数和吡虫啉的互作延迟效应主要加剧了对繁殖的负面影响,尤其是在高温天持续3d和5d(P＜0.05),显著抑制了母代种群参数的增长.在世代间,母代单独经历不同高温天数后,对子代存活、发育、繁殖和寿命均没有显著影响(P＞0.05).高温天数和吡虫啉的互作主要对子代存活产生了负面影响,下降率可达33.3％,但两者的互作却对子代成蚜寿命、繁殖产生了正面刺激作用,大大减缓对子代种群参数的影响.上述结果将为气候变暖和农药双重胁迫下麦长管蚜种群动态的预测、防控提供一定的理论指导.     

Plastic male mating behavior evolves in response to the competitive environment*

Male reproductive phenotypes can evolve in response to the social and sexual environment. The expression of many such phenotypes may also be plastic within an individual's lifetime. For example, male Drosophila melanogaster show significantly extended mating duration following a period of exposure to conspecific male rivals. The costs and benefits of reproductive investment, and plasticity itself, can be shaped by the prevailing sociosexual environment and by resource availability. We investigated these ideas using experimental evolution lines of D. melanogaster evolving under three fixed sex ratios (high, medium, and low male‐male competition) on either rich or poor adult diets. We found that males evolving in high‐competition environments evolved longer mating durations overall. In addition, these males expressed a novel type of plastic behavioral response following exposure to rival males: they both significantly reduced and showed altered courtship delivery, and exhibited significantly longer mating latencies. Plasticity in male mating duration in response to rivals was maintained in all of the lines, suggesting that the costs of plasticity were minimal. None of the evolutionary responses tested were consistently affected by dietary resource regimes. Collectively, the results show that fixed behavioral changes and new augmentations to the repertoire of reproductive behaviors can evolve rapidly.     

不同地理种群短额负蝗对环境温度的适应性

【目的】本研究旨在探明短额负蝗Atractomorpha sinensis不同地理种群对环境温度响应的适应性差异。【方法】以大豆叶片为食物饲养,在恒温16, 20, 24, 28和32℃, 相对湿度70%,光周期16L∶8D条件下,系统观测陕西延安、河南郑州、四川成都、云南曲靖和广东广州5个短额负蝗地理种群的生长发育过程,比较不同地理种群各虫态的发育历期、发育速率及发育起点温度和有效积温的差异性,分析种群生物学指标与栖息地环境温度的相关性。【结果】不同种群短额负蝗发育速率均随着温度升高而加快,但在16℃下成都和广州种群不能完成世代发育。随着不同种群栖息地纬度和海拔升高,其     

Solving the mystery of human sleep schedules one mutation at a time

Abstract

Sleep behavior remains one of the most enigmatic areas of life. The unanswered questions range from “why do we sleep?” to “how we can improve sleep in today’s society?” Identification of mutations responsible for altered circadian regulation of human sleep lead to unique opportunities for probing these territories. In this review, we summarize causative circadian mutations found from familial genetic studies to date. We also describe how these mutations mechanistically affect circadian function and lead to altered sleep behaviors, including shifted or shortening of sleep patterns. In addition, we discuss how the investigation of mutations can not only expand our understanding of the molecular mechanisms regulating the circadian clock and sleep duration, but also bridge the pathways between clock/sleep and other human physiological conditions and ailments such as metabolic regulation and migraine headaches.     

Effects of cholesterol levels on the excitability of rat hippocampal neurons

Changes in the cholesterol levels dynamically alter the microenvironment of the plasma membrane and have been shown to modify functions of ion channels. However, the cellular effect of these modifications is largely unknown. In this report, we demonstrate that cholesterol levels modulate neuronal excitability in rat hippocampal neurons. Reduction of cholesterol levels shortened the duration and increased the firing frequency and peak amplitude of action potentials, while enrichment of cholesterol reversed the effect. Furthermore, we showed that reduction of cholesterol levels increased, while enrichment of cholesterol decreased the amplitude of the delayed rectifier I_K currents. On the other hand, reduction of cholesterol levels slowed down the inactivation of the fast transient I_A currents, but enrichment of cholesterol had no significant effect on the I_A currents. Besides, alteration in cholesterol levels had no significant effect on the action potential in the presence of blockers for both I_K and I_A currents. These observations demonstrate that cholesterol levels bi-directionally regulate the neuronal excitability mainly through modifications of the I_K and I_A currents, suggesting an optimum level of cholesterol for the optimum excitability of neurons. Alterations in the neuronal cholesterol levels have been associated with aging, cognitive decline, neurodegenerative diseases, etc. Therefore, our findings are important for a deeper understanding of the relationship between the cholesterol level and dysfunctions of the brain at the molecular level.     

Independent coding of movement duration in a repetitive non-visually guided movement

The aim of the present study was to examine the association of high blood lactate levels, induced with a maximal cycling or with an intravenous infusion, with spinal cord excitability. The study was carried out on 17 male athletes; all the subjects performed a maximal cycling test on a mechanically braked cycloergometer, while 6 of them were submitted to the intravenous infusion of a lactate solution (3?mg/kg in 1?min). Before the exercise or the injection, also at the end as well as 5 and 10?min after the conclusion, venous blood lactate was measured and excitability of the spinal α-motoneurons was evaluated by using the H reflex technique. In both experimental conditions, it has been observed that an exhaustive exercise is associated with a strong increase of blood lactate (but not of blood glucose) and with a significant reduction of spinal excitability. Since a similar augment of blood lactate induced by an intravenous infusion, in subjects not performing any exercise, is not associated with significant changes of spinal excitability, it can be concluded that the increase of blood lactate levels during a maximal exercise is not per se capable of modifying the excitability of spinal α-motoneurons.     

Organization of meissner corpuscles in the glabrous skin of monkey and cat

Abstract

Purpose: Motor imagery, the process of imagining a physical action, has been shown to facilitate the excitability of spinal anterior horn cells. In the acute phase after a stroke, the excitability of spinal anterior horn cells is significantly reduced, which leads to motor deficits. This loss of movement can be prevented by increasing the excitability of spinal anterior horn cells immediately following an injury. Motor imagery is an effective method for facilitating the excitability of spinal anterior horn cells in patients with impaired movement; however, the optimal duration for motor imagery is unclear.

Materials and Methods: To investigate time-dependent changes in spinal anterior horn cell excitability during motor imagery, healthy adult participants were recruited to measure the F-wave, an indicator of anterior horn cell excitability. F-waves were measured from participants at baseline, during motor imagery, and post-motor imagery. During motor imagery, participants imagined isometric thenar muscle activity at 50% maximum voluntary contraction for 5?min. F-waves were measured at 1, 3, and 5?min after beginning motor imagery and analysed for persistence and F/M amplitude ratio.

Results: Persistence and F/M amplitude ratios at 1- and 3-min after motor imagery initiation were significantly greater than at baseline. The persistence and F/M amplitude ratio at 5-min after motor imagery initiation, however, was comparable to baseline levels.

Conclusion: Therefore, 1 to 3?min of motor imagery is likely sufficient to facilitate the excitability of spinal anterior horn cells.     

Interaction of Phospholipid and Antibiotic Ionophores,Gramicidin A′ and Valinomycin,in Mixed Monolayers

To obtain information concerning the effects of ionophores on biological membranes, the thermotropic behavior of ionophores such as gramicidin A′ and valinomycin in monolayers was investigated by measuring the surface pressure–area (π–A) and the surface viscosity-area (η_s–A) isotherms. Gramicidin A’ had an isotherm having the transition from a liquid-expanded through an intermediate to a condensed state, while valinomycin had a concave isotherm. The π–A isotherms for two ionophores had a decremental shift with increasing temperatures, depending upon a variety of their molecular structures. A distinct difference between the two ionophores in η_s–A isotherms was observed. In addition, the interaction of dimyristoylphosphatidylcholine (DMPC) with the two ionophores in mixed monolayers was investigated. When valinomycin was mixed with DMPC, no deviation from the additivity rule occurred below and above the phase transition temperature T_c of DMPC. However, when gramicidin A′ was mixed with DMPC, a considerable negative deviation from ideal mixing occurred below T_c, suggesting the formation of an irregular ripple structure.     

Direct Observation of Spin-Trapped Carbon Dioxide Radicals in Hepatocytes Exposed to Carbon Tetrachloride

Carbon dioxide radical adducts of the spin trapping agent, α-phenyl N-t-butyl nitrone (PBN), have been observed to occur in the urine and bile of rats exposed to carbon tetrachloride as well as in perfusates of liver in which the perfusion medium contained carbon tetrachloride (Connor er al., J. Biol. Chem., 261, 4542, (1986)). The carbon dioxide adduct was proven to be derived from CCI, by use of 13-C-labelled compound. These adducts were not observed in the liver itself suggesting that they might be rapidly secreted from the liver. However, using isolated hepatocytes, we have demonstrated that the carbon dioxide radical adduct can be observed directly in the liver cells as it is formed. Since this water-soluble adduct cannot be extracted by non-aqueous solvents such as chloroform or toluene, its formation in liver in vivo or in perfused livers was not detected. Lowering the oxygen tension in the system diminished the intensity of production of the carbon dioxide adduct, consistent with the adduct being produced as a result of ·OOCCl₃ generation. It is not clear the extent to which this adduct is formed as a result of the ·CO₂ radical or is produced by metabolic oxidation of the trichloromethyl radical adduct of PBN per se to the carbon dioxide radical adduct. The intensity of the signal of the carbon dioxide radical adduct suggests that adduct conversion may be the route of formation since it seems unlikely that a sufficient amount of the halocarbon could be metabolized to ·COCl or ·CO₂ radicals to generate a signal of the magnitude involved. The ·CO₂ adduct is readily observed in intact hepatocytes, but the ·CCl₃ adduct is not (although we know the ·CCl₃ adduct has been produced in these cells), indicating that the ·CO₂ adduct is present in considerable abundance compared to the ·CCl₃ adduct.