摘要： Kava, an intoxicating beverage prepared from the pepper plant Piper methysticum, is widely consumed by the indigenous peoples in the islands of the South Pacific. As the first of a series of studies on the neuropharmacological interactions of kava with CNS receptors we tested purified pyrones and kava resin for activity on GABA and benzodiazepine binding sites in rat and mouse brain membranes. Only weak activity was observed on GABA(A) binding sites in washed synaptosomal membranes prepared from rat brain and this was abolished by extraction of the membranes with Triton X-100, suggesting that lipid soluble components were involved. No effects were observed on GABA(B) binding sites in rat brain membranes in vitro. Kava resin and pyrones exerted some weak effects on benzodiazepine binding in vitro but this did not correlate with pharmacological activity. In addition, in ex vivo studies, no effects were observed on [H-3]diazepam binding to brain membranes prepared from mice in which selected kava constituents were injected intraperitoneally, whereas similarly administered diazepam (5 mg/kg) inhibited [H-3]diazepam binding by > 95%. Similar lack of activity was observed in in vivo binding studies;injection of kava resin failed to influence the CNS binding of the benzodiazepine-receptor ligand [H-3]Ro15-1788 injected into mice prior to sacrifice. The pharmacological activities of kava resin and pyrones do not appear to be explained by any significant interaction with GABA or benzodiazepine binding sites.

关键词： Science   Humanities and Social Sciences   multidisciplinary  

摘要： Recent palaeontological discoveries and the correspondence between molecular and morphological results provide fresh insight on the deep structure of mammalian phylogeny. This new wave of research, however, has yet to resolve some important issues.

关键词： 树Qu   实验动物   哺乳动物  

摘要： 由于树鼩(Tupaia Belangeri,Tree Shrew)在分类学上的特殊地位,近几十年来日本、德国、英国等许多国家研究人员对其生物学、分类学特性进行了大量研究,与此同时,树鼩体小、价廉、新陈代谢远比啮齿类动物更接近人类,在医学科研中应用日渐增多,其作为实验动物的价值也日渐增大。

关键词： OPEROPHTERA-BRUMATA   TORTRIX-VIRIDANA   BUDBURST PHENOLOGY   QUERCUS-ROBUR   POPULATION DYNAMICS   SPATIAL HETEROGENEITY  

关键词： 计算机视觉   八元树   旋转  

摘要： 在计算机视觉中,八元树是三维物体表示的一种重要形式,本文利用线性八元树结构,提出一种通过平移处理代替旋转的方法,有效地解决了运动物体八元树表示中复杂的旋转问题。首先建立高层节点旋转后的标准八元树,低层的标准八元树可由高层标准八元树直接推出,然后将同层各节点的旋转变为该层标准八元树的平移。这种方法处理速度高,节省了存贮空间.

摘要： Although there has been much recent interest in ant-plant mutualisms, few data are available on the effects of foraging ants on herbivore numbers and levels of herbivory on plants that do not offer specific inducements to attract ant visitation. In forestry plantations and tropical crops, ants have erratic but sometimes dramatic effects on the numbers of insect herbivores but, in more natural habitats, their effects on levels of herbivory appear to be largely unknown. In Australia, where ants and Eucalyptus woodlands are ubiquitous and abundant and where considerable debate has occurred regarding levels of herbivory in Eucalyptus forests, very little work has been done to examine the effects of ants on densities of insect herbivores on eucalypts. In this study, ants were experimentally excluded from mature and immature foliage of saplings of the mallee Eucalyptus incrassata in South Australia, and herbivore numbers and levels of leaf herbivory were assessed during the next 6 months. No significant differences in herbivory were found between ant-access and ant-exclusion treatments. In spring and early summer, ants were found in associations with aggregations of eurymelid bugs on young foliage, and the effects of ants on bug densities were experimentally investigated. Bug densities decreased rapidly in ant-exclusion treatments compared with ant-access controls. Ants also quickly removed seeds of E. incrassata from experimental caches. The potential of ants to limit the numbers of insect herbivores on eucalypts seems limited given their tendency to form mutualistic associations with sap-feeding Homopterans and because of a lack of other herbivores that are particularly vulnerable to ant predation.

关键词： 树Qu   实验动物   体温   昼夜节律  

摘要： 对树鼩、大鼠、小鼠、豚鼠、家兔及家鸽体温的昼夜变动节律进行了比较观察树鼩、大鼠、小鼠、家鸽体温昼夜变动幅度较大。昼夜节律明显;豚鼠、家兔体温昼夜变动幅度较小.树鼩、家鸽的体温昼夜节律呈现昼行动物的相位特征,前者的峰、谷值分别位于19:00和5:00,后者的峰,谷值分别倍于15:00和5:00.大鼠体温的昼夜节律呈现典型的夜行性特征,其峰、谷值分别位于0:00和10:00.同为夜行动物的小鼠的体温昼夜节律、相位与大鼠不同。谷值位于8:00—0:00,其余时间几乎稳定于相同水平.豚鼠、家兔体温昼夜节律表现昼行性特点.

摘要： A community of small rodents was studied in thicket-clump and grassland savanna of Lengwe National Park, Malawi, from September 1984 to June 1985. Nine species were recorded on a 1.1 ha grid and five assessment lines, using a capture-mark-release technique. The three commonest species (and their percentage proportions) were Mastomys natalensis (47%), Acomys spinosissimus (24%) and Saccostomus campestris (11%). Population numbers on the grid fluctuated from 1-30 individuals/ha, and the numbers on the assessment lines fluctuated from 4-57 individuals. There were two peaks of population numbers during the year: the first was in the early wet season (when individuals emigrated from dry season refugia and there was limited reproduction) and the second was in the mid dry season (when young born at the end of the wet season entered the trappable population). The population was comprised mainly of subadults in the late dry season, adults and some young in the wet season, and young and subadults in the early and mid dry seasons. Population survival rates were low with only 30-50% of individuals surviving to the following month. The magnitude of population fluctuations are related to the strong seasonality of climate, flooding and grass characteristics;in this respect, the community of small mammals in Lengwe National Park shows similarities to those of the Kafue Valley in Zambia and the Chobe Valley in Botswana.

关键词： FIRE   OAK SAVANNA   TREE BARK   ARTHROPOD FAUNA   NORTH-AMERICA  

摘要： The arthropod communities living on the bark of the oak species Quercus macrocarpa and Q. ellipsoidalis were investigated in a North American oak savanna. Differences were found in the community structure of the arthropods living on the bark of these two tree species, although they have the same fissured bark type. In the North American oak savanna ecosystem the most important disturbance factor is fire, which maintains species richness. Highest numbers of species and specimens were found at moderately disturbed sites. Three main ecological groups of arthropods living on the bark of trees can be distinguished in relation to the degree of disturbance: (1) Inhabitants of bark of trees restricted to undisturbed sites: they do not occur in fire-disturbed areas;(2) Inhabitants of bark of trees adapted to a moderate degree of disturbance: many species occur in high numbers only in moderately disturbed areas;and (3) Specialist inhabitants of bark of trees in heavily disturbed areas. The number of specimens of these species increases per trunk with the frequency of disturbance.