Electron microscope study of the human neuromuscular junction

A preliminary electron microscope study of human neuromuscular junction is presented. The biopsy material was taken from the palmarus longus, and fixed routinely in osmium tetroxide and embedded in methacrylate. The structure of the motor endings and the relationship of the synaptic vesicles to the axolemmal membrane are described. The synaptic clefts are filled with an homogeneous material in continuity with the basement membrane covering the muscle fiber. The subneural apparatus is described, and special attention is paid to a vesicular component present in the sarcoplasm of the junctional area, which differs from synaptic vesicles and is presumed to be a derivate of the sarcoplasmic reticulum.     

Past vegetation changes in the Brazilian Pantanal arboreal–grassy savanna ecotone by using carbon isotopes in the soil organic matter

Measurements of the organic carbon inventory, its stable isotopic composition and radiocarbon content were used to deduce vegetation history from two soil profiles in arboreal and grassy savanna ecotones in the Brazilian Pantanal. The Pantanal is a large floodplain area with grass-dominated lowlands subject to seasonal flooding, and arboreal savanna uplands which are only rarely flooded. Organic carbon inventories were lower in the grassy savanna site than in the upland arboreal savanna site, with carbon decreasing exponentially with depth from the surface in both profiles. Changes in ¹³C of soil organic matter (SOM) with depth differed markedly between the two sites. Differences in surface SOM ¹³C values reflect the change from C₃ to C₄ plants between the sites, as confirmed by measurements of ¹³C of vegetation and the soil surface along a transect between the upland closed-canopy forest and lowland grassy savanna. Changes of ¹³C in SOM with depth at both sites are larger than the 3–4 per mil increases expected from fractionation associated with organic matter decomposition. We interpret these as recording past changes in the relative abundance of C₃ and C₄ plants at these sites. Mass balances with ¹⁴C and ¹³C suggest that past vegetational changes from C₃ to C₄ plants in the grassy savanna, and in the deeper part of the arboreal savanna, occurred between 4600 and 11 400 BP, when major climatic changes were also observed in several places of the South American Continent. The change from C₄ to C₃, observed only in the upper part of the arboreal savanna, was much more recent (1400 BP), and was probably caused by a local change in the flooding regime.     

Towards a monophyletic genus Albinaria (Gastropoda, Pulmonata): the first molecular study into the phylogenetic position of eastern Albinaria species

Recent molecular phylogenetic studies of the terrestrial snail genus Albinaria have caused a radical reassessment of its taxonomy. These studies, however, were limited to western species. This paper examines mitochondrial 12S sequences and nuclear ITS1 & 2 sequences of both eastern and western species, and demonstrates that Albinaria, in its most recent definition, is not monophyletic. Both molecular datasets place ' Albinaria ' hedenborgi from Lebanon in a well-supported clade with species of the genus Cristataria , distributed south-east of the vicariant range of Albinaria . The remaining species from Cyprus, Turkey and Greece constitute a well-supported monophyletic group. These two clades form geographical clusters, whereas Albinaria in the current definition (including ' A. '  hedenborgi ) has a disjunct distribution. ' A.' hedenborgi should therefore be classified with Cristataria , together with the morphologically similar and geographically close ' A. '  nadimi .  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 143 , 531−542.     

Home range, association and related aspects of elephants in the eastern Transvaal Lowveld

Home range and association patterns of elephants Loxodonta africana in private nature reserves adjacent to the Kruger National Park, South Africa, were determined over a period of six years by using radio telemetry. The minimum convex polygon (MCP) and harmonic mean (HM) methods were used for data processing. The minimum and maximum range areas required by females were estimated at 115 and 465 km², respectively, whilst those of males varied between 157 and 342 km². Core areas of females comprised on average 10·1% of the range areas as calculated by the MCP method. Range areas between females in the Klaserie and Timbavati Private Nature Reserves differed significantly. A significant difference in range size was also found between the male population (pooled data) and the females of the Klaserie Private Nature Reserve. Range areas increased from the wet to the dry season. Three male elephant categories were established, namely males utilizing the same area during the study period, those who shifted their range areas and individuals with very large range areas which frequented the area on an irregular basis. A loose relationship existed between males. Association between females can be attributed to kinship and not to the overlapping of range areas. Results indicated avoidance behaviour between females in their core areas, which might partially explain the ability of elephants to tolerate high densities. It is concluded that male elephant hunting should be approached with caution.     

大鼠胰腺发育过程中AFP动态表达的意义

目的:探索大鼠胰腺发育过程中AFP动态表达的意义.方法:采用高密度寡核苷酸芯片对胚胎12.5天(E12.5)、E15.5、E18.5、初生和成年大鼠胰腺进行基因转录水平分析.结果:AFP显著高表达于E18.5大鼠胰腺,AFP在胚胎期的动态表达趋势与胰腺功能细胞标志物以及可能介导AFP促细胞增殖效应的有关信号系统成员的表达趋势一致.结论:AFP在大鼠胰腺发育过程中动态表达的生物学意义可能在于参与胰腺发育调控.