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71.
家兔面神经后核内侧区在呼吸节律起源中的作用 总被引:36,自引:8,他引:28
从腹侧面暴露家兔延髓,脑内微量注射1%普鲁卡因阻滞面神经后核内侧区(mNRF),全部动物(n=20)一次注射(0.3—1.0μl)后即能可逆地消除呼吸节律。区域对照显示此区非常局限,范围约1.0×1.0×1.0mm。组织学检查表明为面神经后核内侧区。本文分析了 mNRF的呼吸相关神经元(RRNs)的放电形式。在 mNRF 有较多的呼气(E)神经元和呼气-吸气跨时相(E-IPS)神经元。在阻滞 mNRF 引起呼吸停止期间,观察到低位延髓背侧呼吸群(DRG)和腹侧呼吸群(VRG)尾端区 RRNs 放电的节律性消失,表现连续放电或停止放电。电刺激DRG,VRG 尾端区,只能诱发短串的膈神经放电,而不能产生节律性发放。说明这些区域的RRNs 无自动节律性活动的能力。结果表明,面神经后核内侧区与呼吸节律发生有关,它可能是呼吸节律发生器的一个重要的所在部位。 相似文献
72.
The distribution of excreted flavonoid aglycones within the familyLabiatae was studied and differences were found, especially in the A-ring substitution patterns. Thus, 5,7-dihydroxy-6-methoxyflavones with substituted B-rings are characteristic of species ofSalvia (sect.Salvia),Rosmarinus andOcimum; 5,7-dihydroxy-6,8-dimethoxyflavones occur only inOcimum and 5,6-dihydroxy-7,8-dimethoxyflavones inThymus and related species. Members of the two subfamiliesLamioideae andNepetoideae produce exudate flavonoids, but some genera are devoid of these compounds. There is a correlation between the habitat where the plant grows and production of these compounds, the species from (semi-)arid habitats being those which generally accumulate external flavonoids. 相似文献
73.
Jonathan D. Hill 《Human ecology: an interdisciplinary journal》1988,17(1):1-25
This essay examines ritual and ceremonial activities among the Arawakspeaking Wakuénai of the Venezuelan Amazon as processes of constructing power relations in changing historical and ecological conditions. Ritual evocations of the vertical dimension of power relations between mythic ancestors and human descendants adapt local populations to conditions of relatively severe stress, such as epidemics and scarcity of fish in long wet seasons. Other rituals evoke the horizontal dimension of power relations between affinally-related groups as a way of expanding the local descent group in conditions of lowered stress. These two ways of exercising ritual power link human populations to specific natural habitats and provide flexibility needed to adjust to demographic and other historical changes. Through ritual performances, the Wakuénai transform the natural environment into a cultural landscape of socialized objects and, conversely, remember the history of political relations among peoples through spirit-naming of natural species, objects, places, and geographic landmarks. 相似文献
74.
The N-terminal -amino groups of 1-bungarotoxin (1-Bgt) fromBungarus multicinctus venom were modified with trinitrobenzene sulfonic acid and the modified derivative was separated by high performance liquid chromatography. The trinitrophenylated (TNP) derivative contained two TNP groups at the -amino groups of A chain and B chain and showed a marked decrease in enzymatic activity. Methionine residues at positions 6 and 8 of the A chain were oxidized with chloramine T or cleaved with cyanogen bromide to remove the N-terminal octapeptide. Oxidation of methionine residues and removal of the N-terminal octapeptide caused a precipitous decrease in enzymatic activity, whereas antigenicity remained unchanged. The presence of dihexanoyllecithin influenced the interaction between 1-Bgt and 8-antilinonaphthalene sulfonate (ANS) and revealed that 1-Bgt consists of two types of ANS-binding sites, one at the substrate binding site of the A chain and the other might be at the B chain. The modified derivatives still retained their affinity for Ca2+ and ANS, indicating that the N-terminal region is not involved in Ca2+ and substrate binding. A fluorescence study revealed that the -amino group of the A chain was in the vicinity of substrate binding site and that the TNP -amino groups were in proximity to Trp-19 of the A chain. In addition, the study showed that the N-terminal region is important for stabilizing the architectural environment of Trp-19. The results, together with the proposal that Trp-19 of the A chain is involved in substrate binding, suggest that the N-terminal region of the A chain plays a crucial role in maintaining a functional active site for 1-Bgt. 相似文献
75.
S. Živanović 《Human Evolution》1988,3(5):329-334
Studies of the morphological features of the temporal region of mesolithic skulls from Padina in the Iron Gate Gorge of the
Danube revealed a very prominent and large supramastoid ridge which is the most striking feature in skulls of both sexes.
Mastoid processes were larger in male skulls, but in 25% of the cases there was an overlap between the size of the processes
in male and female specimens. The mastoid ridge was prominent in both sexes. The digastric fossa was always well defined in
both sexes and in the two thirds of the skull specimens it was deep. The posterior root of the zygoma was prominent in all
the skulls, but it was better developed in the male specimens. The parietotemporal suture in both sexes rises above the level
of the pterion. There were no morphological or anthropometrical differences between the left and the right side of individual
skulls outside the limits of natural asymmetry. All these morphological characteristics of the temporal region may help in
racial and sexual diagnosis of the Mesolithic skulls from the Iron Gate Gorge. 相似文献
76.
77.
78.
木耳和毛木耳的极性研究 总被引:10,自引:0,他引:10
从木耳(Auricularia auricula)和毛木耳(A.polytricha)的同一子实体弹射、分离30个单孢子并发育成单核菌丝体,各自分成3组,以10×10方式进行单核体两两配对。取两配对单核体交结处菌丝体块到新的平板上继续发育并插入无菌的盖玻片让其菌丝爬上。后利用双苯并咪唑(Hoechst 33258)染色,在萤光显微镜下逐块检查配对后菌丝体细胞中核的数目。如果出现双核,再加以检查锁状联合以验证,则为配对亲和。不亲和者仍为单核。根据配对行为进行不亲和因子分配决定其交配型。检测结果表明,木耳和毛木耳担孢子的性别是由一对遗传因子A.a所控制。属典型性二极性(bipolar)异宗结合。 相似文献
79.
The leaf ultrastructure of NADP-malic enzyme type C4 species possessing different anatomical features in the Cyperaceae was examined: types were the Rhynchosporoid type, a normal
Kranz type in which mesophyll cells are adjacent to Kranz cells, and Fimbristyloid and Chlorocyperoid types, unusual Kranz
types in which nonchlorophyllous mestome sheath intervenes between the two types of green cells. They show structural characteristics
basically similar to the NADP-malic enzyme group of C4 grasses, that is, centrifugally located chloroplasts with reduced grana and no increase of mitochondrial frequency in the
Kranz cells. However, the Kranz cell chloroplasts of the Fimbristyloid and Chlorocyperoid types exhibit convoluted thylakoid
systems and a trend of extensive development of peripheral reticulum, although those of the Rhynchosporoid type do not possess
such particular membrane systems. The suberized lamella, probably a barrier for CO2 diffusion, is present in the Kranz cell walls of the Rhynchosporoid type and in the mestome sheath cell walls of the other
two types, and tightly surrounds the Kranz cells (sheaths) that are the sites of the decarboxylation of C4 acids. These ultrastructural features are discussed in relation to C4 photosynthetic function. 相似文献
80.
Detailed examination of a sample plot covered by the Lindero membranaceae-Fagetum crenatae association on Mt. Sanpoiwadake,
Hakusan National Park, revealed a number of correlations between the distribution of subassociations and environmental factors.
The subassociations on the south-facing slopes receive deep snow cover in winter with rapid melting in the spring. They occur
on porous, freely draining soils, typical of the general range of brown forest soils. Conversely, on the north-eastern slopes
there are widespread late-snow patches which delay leaf development and expansion and which provide an abundant water supply
well into early summer. Under these conditions, bleached soil horizons have developed with iron pan formation, resulting in
poor soil drainage, strongly correlated with quite different plant communities. 相似文献