Do tsetse flies ‘see’ zebras? A field study of the visual response of tsetse to striped targets

Abstract A field study in Zimbabwe of Glossina pallidipes Austen and G. morsitans morsitans Westwood supported Waage's (1981) hypothesis that the striped pattern of zebras may protect them from being bitten by blood-sucking flies. In addition, the results suggest that the orientation of the stripes may be crucially important for the unattractiveness of zebras. The relative attractiveness of five different stationary targets (black, white, grey, vertically-striped and horizontally-striped; stripe width = 5 cm) were each tested on their own and in pairs of all combinations, with artificial host odour (CO₂ plus acetone) always present. Electric nets were used to catch flies as they attempted to land on or circle the targets. The results were similar for the two species of tsetse. When tested on their own, grey and vertically-striped targets caught similar numbers of flies and both caught significantly fewer than black or white targets (c. 36% as many). Horizontally-striped targets caught <10% as many flies as any other single target. Although there was no significant difference between the attractiveness of grey and vertically striped targets when they were presented together, when paired with the other targets, grey was as attractive as black or white, but the vertically-striped target was significantly less attractive than black or white (P < 0.001). In other words, a difference between grey and vertical stripes was found only in their attractiveness in relation to other targets. The horizontally-striped target, however, always caught the fewest flies, regardless of whether it was presented alone or alongside another target.     

Protective Effect of Cannabidiol on Hydrogen Peroxide-Induced Oxidative Damage in Human Umbilical Vein Endothelial Cells (HUVECs)

Natural antioxidants play an important role in promoting good health because of their prevention for oxidative damage. The work aimed to explore the antioxidant mechanism and activity of cannabidiol (CBD) at the cellular level. The human umbilical vein endothelial cell (HUVEC) with oxidative damage was employed as the model to study the protective capability of CBD. The results showed that CBD pre-treatment before the cells were exposed to hydrogen peroxide (H₂O₂) resulted in an obvious increase of cell viability (about 100 %) and antioxidant related enzymes activity, and a decline of malondialdehyde (MDA) level. Besides, CBD could alleviate the increase of intracellular reactive oxygen species (ROS) content, the contraction of nucleus, and condensation of chromatin. The changes showed a dose-dependent effect. Additionally, the free radicals scavenging capacity of CBD was comparable to that of typical natural antioxidant, anthocyanidins. In summary, CBD could be employed as a potent antioxidant source for avoiding the oxidative damage. These results could provide the foundation for the development of CBD antioxidant products.     

医院设备的接地方式探讨

本文根据某些医院设备接地方式上存在的问题提出了十条改进意见，并建议制订了《医院设备接地方式指南》强制性规范，改善防电击安全性。     

外源硒对低温胁迫下铁皮石斛幼苗的缓解效应及其抗氧化生理特征变化

以3个不同品系的铁皮石斛幼苗为材料,分别于叶面喷施不同浓度的亚硒酸钠溶液处理,并结合人工控温生长条件下的低温胁迫试验,探讨外源硒对铁皮石斛幼苗耐冷性和恢复生长能力的影响作用及其与有关抗氧化生理指标间的关系。结果表明:(1)耐冷性表现较强的品系其幼苗在低温胁迫下的叶绿素、MDA及脯氨酸含量变化幅度相对小于耐冷性较弱的品系。(2)适量浓度(0.05～0.10mg.L-1)外源硒处理对低温胁迫下铁皮石斛幼苗叶绿素降解具有缓解效应,可降低MDA含量,增加脯氨酸含量,同时显著提高GSH-AsA循环活性,从而提高铁皮石斛幼苗的耐冷性,但过高浓度的外源硒处理(>0.20mg.L-1)则效果相反。(3)低温胁迫解除后,0.10mg.L-1的外源硒处理能引起铁皮石斛‘ZD-1’幼苗中AsA含量显著下降并促进其GSH合成积累,有效提升铁皮石斛幼苗在恢复生长期的综合抗氧化防御能力。