关键词： INSECTIVORES (Mammals)   MAMMALS   PHYLOGENY  

摘要： The order Insectivora, including living taxa (lipotyphlans) and archaic fossil forms, is central to the question of higher-level relationships among placental mammals(1). Beginning with Huxley(2), it has been argued that insectivores retain many primitive features and are closer to the ancestral stock of mammals than are other living groups(3). Nevertheless, cladistic analysis suggests that living insectivores, at least, are united by derived anatomical features(4). Here we analyse DNA sequences from three mitochondrial genes and two nuclear genes to examine relationships of insectivores to other mammals. The representative insectivores are not monophyletic in any of our analyses. Rather, golden moles are included in a clade that contains hyraxes, manatees, elephants, elephant shrews and aardvarks. Members of this group are of presumed African origin(5,6). This implies that there was an extensive African radiation from a single common ancestor that gave rise to ecologically divergent adaptive types. 12S ribosomal RNA transversions suggest that the base of this radiation occurred during Africa's window of isolation in the Cretaceous period before land connections were developed with Europe in the early Cenozoic era.

关键词： multipurpose trees   Acacia angustissima   Acacia saligna   Chamaecytisus palmensis   Leucaena pallida   Sesbania sesban   ciliate protozoa   rumen pH  

摘要： The effect of five multipurpose trees (MPTs), Acacia angustissima, Acacia saligna, Chamaecytisus palmensis, Leucaena pallida and Sesbania sesban on ciliate protozoa was investigated in rumen cannulated Ethiopian sheep. Both entodiniomorphs and holotrichs were counted. The protozoa counts from S. sesban supplemented diet were significantly (P < 0.04) higher than from other diets. Maize stover alone and maize stover supplemented with C. palmensis or L. pallida did not have any significant (P > 0.05) effect on the numbers of ciliate protozoa. A. saligna supplemented diet reduced the numbers of protozoa from 1.60 X 10(5) to 0.62 x 10(5) cells ml(-1) rumen fluid. Differences in ciliate numbers among other MPT supplements barely failed to reach significance (P < 0.06). Entodiniomorphs dominated (93.3%) the protozoa population in all diets, with Entodinium species being the most predominant (80.7%). None of the MPTs tested eliminated protozoa. Effect of eating S. sesban and placing it in the rumen on protozoa was tested. Protozoa numbers decreased in the sheep in which S. sesban was placed in the rumen while they remained high in the sheep that were allowed to eat the supplement. Relationships between protozoal numbers and in sacco fibre degradation and neutral detergent fibre (NDF) digestibility were also examined. Degradation rate (c) increased with increase in protozoa numbers. NDF digestibility was significantly (P<0.01) lower in A. saligna supplemented diet than in others. No significant relationship was observed between ruminal pH and protozoal numbers with all diets. The animals on A. angustissima died after 9 and 21 days of the experiment. (C) 1997 Elsevier Science B.V.

关键词： Foraging   Herbivory  

摘要： We evaluated palatability of winter dormant tree twigs to the mountain hare Lepus timidus and the grey-sided vole Clethrionomys rufocanus with captive animals. We tested differences among trees within sites, among sites, and between two tree species (the mountain birch Betula pubescens ssp. czerepanovii and the tea-leaved willow Salix phylicifolia). In one of the sites, we also measured growth rates of autumnal moth Epirrita autumnata larvae on the same trees that were used in preference trials with the hares and voles. The differences in palatability to hares and voles were greatest al the level of tree species;both hares and voles preferred birches over willows, but with the hare there was some overlap in palatability between the tree species. There were also large and significant differences among sites and among trees within sites. Within sites, variation in tree palatability seemed to be larger among willows than among birches. Hares and voles may select willows at least partly on the same basis, but there was no correlation between palatability of the trees to the mammals and the growth rate of the larvae of the autumnal moth on the same trees. Variation in twig palatability to the hares and voles was so large at all levels (among trees within sites, among sites and between tree species) that we suggest it also has implications for food selection of these mammalian herbivores under natural conditions.

摘要： We investigated the effects of prescribed burning on the composition, abundance, species richness and diversity of oak savanna arthropod communities in a replicated, large-scale, 30-y experiment We employed four sampling methods over 3 y and caught 11,215 arthropods of 551 species. Species had varied and often negatively correlated short vs. longterm responses to burning. In the years savannas were burned, species richness and abundance of arthropods, especially Homoptera and Lepidoptera, were reduced and species compositions were sometimes more similar. However, despite its major effect on vegetation, frequency of burning did not affect arthropod abundance and species richness, but sometimes caused savannas to be similar in species or taxonomic order composition. The Shannon diversity index was unaffected by burning. On the whole, prescribed burns necessary to maintain grasslands and savannas do not appear to be harmful to, or to greatly impact, the arthropod fauna.

关键词： competition   Cynomys ludovicianus   herbivory   mesquite   prairie dogs   Prosopis glandulosa   seed disappearance   seedling establishment   succession   tree-grass dynamics  

摘要： Explanations for documented increases in woody plant dominance in grasslands and savannas of North America include atmospheric CO2 enrichment and changes in climate, livestock grazing, and fire regimes. However, tree/shrub encroachment has also coincided with the eradication of a once widespread native herbivore, the black-tailed prairie dog (Cynomys ludovicianus). We used field experiments and repeat aerial photography to demonstrate that prairie dogs, and the herbivores and granivores associated with their colonies, probably maintained grassland and savanna by preventing woody species such as Prosopis glandulosa (honey mesquite) from establishing or attaining dominance. Prosopis seed and pod disappearance was 3-99 times greater within prairie dog colonies. Ants were the primary agent of seed removal, whereas prairie dogs and associated vertebrates were the primary agents of pod removal. Survival of Prosopis seedlings protected from vertebrate herbivory was similar on and off prairie dog colonies (approximate to 60%), whereas survival of unprotected seedlings was 3 times greater off- than on-colony. On-colony, prairie dogs and associated herbivores girdled and destroyed all Prosopis saplings within 2 d of planting;survival of 1-yr-old seedlings was reduced by 50% after 3 mo of exposure to on-colony herbivores. Despite high levels of woody plant seed disappearance and seedling herbivory, on-colony ''seedling'' reserves were substantial (950 plants/ha). Thus, prairie dogs and the fauna that occur on their colonies suppressed rather than eliminated Prosopis from the colony site. Removal of prairie dogs led to rapid development of Prosopis stands. Repeat aerial photography showed that Prosopis canopy cover on a colony eradicated in 1950 (27%) increased to a level (61%) comparable to that of off-colony Prosopis stands (65%) within 23 yr. These data illustrate how transitions from grassland to woodland vegetation can be mediated by a rodent herbivore. They further demons

关键词： 结核杆菌   毒力   动物模型   菌株   感染  

摘要： 采用标准毒力的Ｈ３７ＲＶ菌株和经Ｌ－Ｊ培基传代减毒的菌株，对Ｃ５７ＢＬ／６Ｎ小鼠进行尾静脉注射和腹腔注射感染，就树造动物各器官的结核菌实验模型进行了探讨。结果表明，树造胸腔器官（肺和心脏）的动物模型以尾静脉感染为好，树造肝、脾和腹股沟淋巴结结核的动物模型以腹腔注射感染为宜。如要成功地树造结核感染的动物模型，最好将所购回的标准菌株在实验动物体内恢复毒力后再使用。

关键词： Acer pseudoplatanus   amino acids   aphids   CO2   Fagus sylvatica   leafhoppers   populations  

摘要： Five species of sap-feeding homoptera were studied on Fagus sylvatica and Acer pseudoplatanus and exposed to elevated concentrations of carbon dioxide (600 mu L L(-1)). The concentration of total soluble amino acids in foliage of F. sylvatica was unaffected by growing saplings in elevated atmospheric CO2 concentrations. Although experiments on individual aphids indicated poorer performance of Phyllaphis fagi (fewer, smaller nymphs produced), resultant populations did not differ from those in ambient (350 mu L L(-1)) conditions. The area of beech foliage stippled by the leafhopper Fagocyba cruenta was similar at ambient and elevated CO2 concentrations. The concentration of total amino acids and that of serine of A. pseudoplatanus foliage were significantly lower at elevated CO2 concentrations. However, the relative growth rates of two aphid species Drepanosiphum platanoidis and Periphyllus testudinaceus and one leafhopper Ossiannilssonola callosa were not significantly different in elevated CO2. No evidence was found that, under the conditions of these experiments, populations of aphids and leafhoppers will change as concentrations of CO2 increase.

关键词： Animals   Body Constitution   Bronchi   Lung Volume Measurements   Mice   Rats   Rodentia   Species Specificity  

摘要： Size-dependent structural patterns in the conductive bronchial tree of four species of myomorph rodents of different body weight were determined by lung casts. The lungs of the harvest mouse, Micromys minutus, body weight 5-7 g, the house mouse, Mus musculus, body weight 35-45 g, the brown rat, Rattus norvegicus, body weight 200-400 g, and the African giant pouched rat, Cricetomys gambianus, body weight 1,200-1,800 g, were inflated to 20 cm H2O, frozen, freeze-dried, hardened, and filled with silicone rubber. The casts were pruned, and branching pattern, diameter, and volume of the conductive bronchial tree were determined using a binocular magnifier. All four species have four lobes on the right lung and an undivided left lung, and the central bronchial tree on either side shows an identical monopodial branching pattern. Although the ramification of the central conductive bronchi is not size-dependent, the diameter and volume are. The diameter of the left main bronchus equals 1.24% of body length in Micromys and 0.6% in Cricetomys, and the conductive bronchial tree makes up 13% of the total lung volume in Micromys and 6% in Cricetomys. Relatively wider airways and a decline in airway resistance with declining body mass in small mammals compared to large ones result in a high ventilatory dead space, which is compensated for by a higher breathing frequency. (C) 1996 Wiley-Liss, Inc.

关键词： 乙型肝炎   疾病模型   免疫组化  

摘要： 目的：观察树是否可成为感染人ＨＢＶ的动物模型。方法：应用免疫组化及原位杂交技术，对实验组及对照组树肝组织进行研究分析。结果：应用羊抗－ＨＢｓ多抗检测树肝组织中的ＨＢｓＡｇ时，出现假阳性反应，阳性物为非目的抗原，应用生物素标记的ＨＢＶＤＮＡ探针进行肝组织原位杂交时，出现非特异性的显色反应，结论：提示在动物模型实验中，应设立严格的对照实验和应用不同反应系统进行校对考核。

关键词： Amino Acid Sequence   Animals   Base Sequence   Blotting   Northern   DNA   Complementary   Female   Gene Expression   Gonadorelin   Immunohistochemistry   In Situ Hybridization   Male   Mesencephalon   Molecular Sequence Data   Oligonucleotide Probes   Protein Precursors   RNA   Messenger   Research Support   U.S. Gov't   P.H.S.   Tupaiidae  

摘要： Reproductive maturation and regulation is centrally orchestrated by gonadotropin-releasing hormone (GnRH). GnRH produced in the vertebrate hypothalamus acts on the pituitary to regulate gonadotropins. In nonplacental mammalian species, it has recently been shown that a second GnRH gene is expressed in mesencephalic cells. Here, we report the cDNA sequences and expression patterns for two distinct genes encoding the hypothalamic and mesencephalic GnRH forms in the brain of a placental mammal, the tree shrew (Tupaia glis belangeri). The novel mammalian GnRH form, designated here as [His(5)Trp(7)Tyr(8)]GnRH (often sailed chicken GnRH II), is expressed in neurons of the mesencephalon and is the first nonhypothalamic form to be isolated from a mammal. Its peptide sequence is identical to the form previously reported in fish, amphibians, reptiles, and birds, revealing that it has remained unchanged for 500 million years. In contrast, the sequences of the hypothalamic GnRH decapeptides vary by as much as 50% across vertebrate species. The remarkable sequence conservation of mesencephalic GnRH suggests that it has been highly constrained throughout evolution, perhaps indicating an important, consented nongonadotropic role. The discovery and localization of two mRNAs encoding distinct GnRH forms in an advanced mammal suggest that other mammals, including primates, may also have a second GnRH gene with expression localized in the midbrain. (C) 1996 Academic Press, Inc.