急性捕食风险不能完全限制饥饿 雌性长爪沙鼠的觅食活动

觅食活动是动物生存和繁殖所必需的基本的活动,受个体生理状态（如饥饿）和环境状况（如捕食、食物可利用性）时空变化的影响,能量状态-风险分配假说指出,动物在应对不同风险时会优化觅食和反捕食努力的时间和能量分配。然而,有关啮齿动物觅食决策的能量状态-捕食风险分配假说的研究结论尚不统一。本研究在野外实验室以艾鼬（Mustela eversmannii）气味作为捕食风险刺激源,以非捕食者（马）气味源作为对照,首先通过Y型观测箱检验雌性饥饿长爪沙鼠（Meriones unguiculatus）对捕食者气味的辨别能力（Wilcoxon 秩检验）;在此基础上通过中立场行为观测箱分别测定饥饿雌鼠在“有食物和天敌气味源”与“有食物和非天敌气味源”环境下的觅食活动,采用Mann-Whitney Z检验比较两者间的行为差异,以验证急性捕食风险限制饥饿沙鼠觅食活动的假设,并探讨动物在饥饿风险与捕食风险共存情况下的觅食行为对策。结果显示,（1）长爪沙鼠对天敌气味反应明显,厌恶和回避有较高潜在捕食风险的空间;（2）虽然觅食潜伏期在捕食风险存在时有所增加,但急性捕食风险并未影响饥饿沙鼠的觅食频次,沙鼠通过缩短每次觅食的持续时间来应对捕食风险;与此同时,（3）饥饿沙鼠在急性捕食风险条件下对环境探究的次数明显增加,一定程度上提高反捕食努力,且自我修饰表现显著,以缓释捕食压力的恐惧效应。这些结果表明,急性捕食风险不能完全抑制饥饿沙鼠的觅食努力,在有捕食风险情况下,饥饿的长爪沙鼠会权衡觅食获取能量和避免捕食的收益和代价,优化觅食策略。本研究结果支持能量状态-风险分配假说关于在短期高风险情况下反捕食努力分配更多,但当动物在饥饿风险持续时间比例显著增加时,动物最终也必须在高风险情况下觅食的预测,也反映了长爪沙鼠对食物资源不可预测及捕食风险高的干旱半干旱荒漠环境的行为适应对策。     

Morphological Alteration of Golgi Apparatus and Subcellular Compartmentalization of TGF-β1 in Golgi Apparatus in Gerbils Following Transient Forebrain Ischemia

Golgi apparatus (GA) is a very important organelle involved in the metabolism of numerous proteins. TGF-β1 plays an important role in supporting neuronal survival after ischemic insults. Little is known, however, about the morphological alteration of GA and subcellular compartmentalization of TGF-β1 in brain after ischemia. Therefore, our present study was designed to check for GA morphological alterations and TGF-β1 subcellular localization. GA immunoreactivities were examined in the somatosensory cortex of gerbils after 10 min transient forebrain ischemia. Confocal Immunofluorographs of TGF-β1 and TGN38 were also taken. Results indicated that no fragmentation of GA was found in gerbils of norm, shams and 6, 24 and 72 h postocclusion, but some of the cortical cells showed fragmentation of GA in gerbils 7 days postocclusion. TGF-β1 was colocalized with TGN38, a marker molecule for the GA. We conclude that there was morphological alterations of GA and TGF-β1 was present in GA in the somatosensory cortex after 10 min ischemia.     

Association between sequence polymorphism in an epitope of Babesia divergens Bd37 exoantigen and protection induced by passive transfer

In Europe, Babesia divergens is the major agent responsible for babesiosis in cattle and can occasionally infect splenectomised humans. Recently, we reported the characterisation of a 37 kDa exoantigen (Bd37) anchored in the merozoite membrane of B. divergens by a glycosylphosphatidyl-inositol. After phospholipase hydrolyse of the glycosylphosphatidyl-inositol anchor, the Bd37 antigen could be isolated in the plasma of the infected host and from the in vitro culture supernatants. Immunisation of mice with a gel-filtration protective fraction of B. divergens exoantigens, produced a monoclonal antibody (MAb), called F4.2F8-INT, directed against Bd37. In the present study, we report data on passive protection using MAb F4.2F8-INT. This MAb was able to completely protect against virulent challenges with B. divergens isolates Rouen 1987 (Rouen87) and Weybridge 8843 (W8843) but had no protective effect against another French isolate from Massif Central (6303E). Physical characterisation of the epitope recognised by F4.2F8-INT allowed us to explain the differences observed between these isolates by western blotting and passive protection. These results suggest that the antigen carrying this epitope could be used as a target in the development of a recombinant vaccine against B. divergens babesiosis.     

Redescription of Besnoitia tarandi (Protozoa: Apicomplexa) from the reindeer (Rangifer tarandus)

Besnoitia tarandi tissue cysts were found in naturally-infected reindeer (Rangifer tarandus) from Finland. Infectivity of its tissue cysts, bradyzoites, and tachyzoites to animals and cell culture was studied. The bradyzoites and tissue cysts were not infectious to out-bred mice, rabbits or gerbils. When fed tissue cysts, neither cats nor dogs excreted oocysts. However, the parasite was lethal to interferon-gamma gene knock out mice irrespective of the route of inoculation. The parasite was grown successfully in African Green Monkey cells from tissues of two reindeer for the first time. Non-dividing, uninucleate tachyzoites from smears from cell cultures were 5.6 x 1.4 microm (4.5-7.4 x 1.0-1.9, n=50) in size. Longitudinally-cut bradyzoites in tissue sections measured 7.4 x 1.3 microm (6.5-7.8 x 1.0-1.6, n=30). Ultrastructurally, tachyzoites and bradyzoites were similar to those in other Besnoitia species, and in particular to parasites described from cattle (Besnoitia besnoiti) and equids (Besnoitia bennetti) in that their bradyzoites lacked enigmatic bodies. Based on comparative analysis of three portions of nuclear ribosomal DNA (the small and large subunits and the first internal transcribed spacer) B. tarandi was found to be more closely related to the other congeners described from ungulates. The parasite was formally redescribed and specimens deposited in the US National Parasite Collection.     

Biologic, morphologic, and molecular characterisation of Neospora caninum isolates from littermate dogs

Isolation and biologic and molecular attributes of Neospora caninum from three littermate dogs are described. Tissue cysts were confined to the brain and striated muscles. N. caninum was isolated (isolates NC-6, NC-7, and NC-8) in rodents and cell culture that had been inoculated with brain tissue from the dogs. Schizont-like stages reactive with N. caninum antibodies were seen in cell cultures seeded with bradyzoites released from Percoll-isolated N. caninum tissue cysts from the brain of one dog. Tissue cysts were infective orally to mice and gerbils, but not to cats and dogs. The isolates were also identified as N. caninum by PCR and sequence analysis.     

沙鼠亚科物种空间分布格局及其与环境因素的关系

通过查阅大量文献和标本采集记录 ,获得我国 7种沙鼠的分布资料。借助中国资源环境数据库( 1∶4 0 0 0 0 0 0 ) ,运用GIS软件 ,通过沙鼠亚科的生境分析 ,确认该类群的物种分布数据。在分布资料基础上 ,绘制物种数字化空间分布图 ,获得较为准确的物种地理分布信息。按 12 3 92 4km2 的等面积栅格收集物种分布和相关的地理要素数据 ,然后进行因子分析 ,确定影响动物空间分布的主要因素。结果表明 ,我国沙鼠亚科物种分布在 3 4 4～ 5 0 2°N ,74 1～ 12 4 1°E ,多分布在海拔 10 0 0～ 15 0 0m的荒漠和荒漠草原地带。分布区西部的物种丰富度相对高于东部。自阿拉山口 ,沿天山北麓至将军戈壁一带 ,以及河西走廊西段和弱水流域的荒漠区为物种丰富度高值区。因子分析表明 ,影响沙鼠亚科空间分布的决定因素是以土壤、植被、地貌和高度差为主的要素所构成的基本景观因子 ,其次是体现年总辐射量、年均降雨量和沙漠化程度的干旱和沙漠化程度因子 ,以及温度因子。变量分析表明 ,沙鼠亚科的物种丰富度与年均温度和沙漠化程度有着直接的联系 ;栅格因子得分分析表明 ,在沙鼠亚科物种丰富度高值区 ,干旱和沙漠化程度较高 ,年均温度较高 ,生境相对复杂。     

The effect of barn owls (Tyto alba) on the activity and microhabitat selection of Gerbillus allenbyi and G. pyramidum

Predation plays an important role in ecological communities by affecting prey behavior such as foraging and by physical removal of individual prey. In regard to foraging, animals such as desert rodents often balance conflicting demands for food and safety. This has been studied in the field by indirectly manipulating predatory risk through the alteration of cues associated with increased risk such as cover or illumination. It has also been studied by directly manipulating the presence of predators in aviaries. Here, we report on experiments in which we directly manipulated actual predatory risk to desert rodents in the field. We conducted a series of experiments in the field using a trained barn owl (Tyto alba) to investigate how two species of coexisting gerbils (Gerbillus allenbyi and G. pyramidum) respond to various cues of predatory risk in their natural environment. The gerbils responded to risk of predation, in the form of owl flights and owl hunger calls, by reducing their activity in the risky plot relative to the control plot. The strongest response was to owl flights and the weakest to recorded hunger calls of owls. Furthermore, when risk of predation was relatively high, as in the case with barn owl flights, both gerbil species mostly limited their activity to the safer bush microhabitat. The response of the gerbils to risk of predation disappeared very quickly following removal of the treatment, and the gerbils returned to normal levels of activity within the same night. The gerbils did not respond to experimental cues (alarm clock), the presence of the investigators, the presence of a quiet owl, and recorded white noise. Using trained barn owls, we were able to effectively manipulate actual risk of predation to gerbils in natural habitats and to quantify how gerbils alter their behavior in order to balance conflicting demands of food and safety. The method allows assessment of aspects of behavior, population interactions, and community characteristics involving predation in natural habitats.     

Histaminergic H2 Action Protects Hippocampal CA1 Neurons by Prolonging the Onset of the Anoxic Depolarization in Gerbils

Abstract: The central histaminergic action on ischemia-induced neuronal damage was examined by evaluating the histological outcome and the direct current (DC) potential shift in the hippocampal CA1 region in gerbils. An intracerebroventricular administration of histamine (10–100 nmol) improved the delayed ischemic damage in hippocampal CA1 pyramidal cells produced by 3 min of transient forebrain ischemia. A high dose (75 nmol) of mepyramine, an H₁ antagonist, aggravated ischemia-induced neuronal damage, but not a low dose (0.75 nmol). Administration of cimetidine (4 nmol) and ranitidine (3 nmol), H₂ antagonists, aggravated the neuronal damage. An injection of histamine (100 nmol) prolonged the onset time of the ischemia-induced sudden shift in the extracellular DC potential (anoxic depolarization; AD) to 133% of that in control animals. Administration of mepyramine (75 nmol) did not markedly change the AD, whereas injections of cimetidine (40 nmol) and ranitidine (3 nmol) reduced the onset latency to 47 and 45%, respectively. These findings suggest that the central H₂ action serves to protect neurons by delaying the onset of AD in gerbils.     

Alterations in the γ-Aminobutyric Acid-Gated Chloride Channel Following Transient Forebrain Ischemia in the Gerbil

The role of inhibitory neurotransmission in selective neuronal degeneration after transient forebrain ischemia was studied by binding of t-[35S]butylbicyclophosphorothionate ([35S]TBPS) to the gamma-aminobutyric acid (GABA)-gated chloride channel and measurement of GABAA receptor function in Mongolian gerbil brain. [35S]TBPS binding to the hippocampus, striatum, and cortex quantified by autoradiography and muscimol-stimulated 36Cl- uptake in synaptoneurosomes of the same regions were examined 1, 4, and 29 days after a 5-min bilateral carotid occlusion. [35S]TBPS binding was decreased in the pyramidal cell dendritic layers, stratum oriens, and stratum lacunosum-moleculare of the CA1 hippocampus, 4 and 29 days after occlusion, and in the stratum radiatum 29 days after occlusion. [35S]TBPS binding sites in the lateral striatum decreased 47% 4 days after occlusion. At the same time, there was a corresponding decrease in muscimol-stimulated 36Cl- uptake in the striatal synaptoneurosomes. Muscimol-stimulated 36Cl- uptake in the hippocampus decreased slightly 4 days after occlusion and more so after 29 days, although these decreases were not significant. No changes were observed in somatosensory cortex at any time point. These data suggest that a portion of GABAA receptors in areas sensitive to ischemic insult are associated with degenerating neurons, whereas other GABAA) receptors are spared.     

Hepatic tissue damage induced in Meriones ungliculatus due to infection with Babesia divergens-infected erythrocytes

Babesia divergens is an intraerythrocytic parasite which is capable of infecting a wide range of vertebrates causing huge economic losses.Histopathological, hematological and biochemical changes during B. divergens infection in female Meriones ungliculatus were reported. Animals were challenged with 5 × 10⁶B. divergens-infected erythrocytes. Parasitemia were maximum at day 5 postinfection where all gerbils died. Infection of gerbils with Babesia induced a significant decrease in erythrocytic count as well as the hemoglobin concentration and hematocrit percentage but leucocytes were increased significantly when compared to uninfected gerbils. Liver enzymes aspartate aminotransferase (AST) and aniline aminotransferase (ALT) were significantly increased while albumin and total bilirubin were significantly decreased at day 5 postinfection with B. divergens-infected erythrocytes. Histopathological scores of inflammation after infection of gerbils were done using Ischak’s activity index and indicated that the liver was severely affected. In conclusion, the study indicated that the course of infection by B. divergens-induced alternations in hematology, biochemistry and histopathology of the hepatic tissue.