狗静脉注射高渗溶液后的血流动力学分析

在15只戊巴比妥钠麻醉的开胸狗身上观察高渗溶液对血流动力学的影响,主要结果如下:1.静脉内注射50%葡萄糖溶液(3m1/kg,15s 内注毕),规律地引起心动徐缓、动脉血压降低、左心室(-dp/dt)减小、左心室 dp/dt 和心输出量增加,以及肾和股薄肌的血流阻力降低。25%甘露醇溶液具有类似作用。2.切断两侧颈迷走神经后,注射高渗溶液不再能诱发动脉低血压以及肾和股薄肌血流阻力的反射性降低,提示此类效应的传入通路主要为迷走神经。3.在切断迷走神经后注射高渗溶液,还使左心室 dp/dt 进一步增加,表明高渗溶液增强心肌收缩性。根据以上结果似可认为,静脉注射高渗溶液所致动脉血压降低,实质上反映着心输出量的增加不足以抵销外周阻力的减小。     

蝮蛇抗栓酶治疗冠心病

应用蝮蛇抗栓酶治疗15例冠心病患者,其中12例为慢性冠心病患者,3例为急性心肌梗塞患者.治疗结果表明:治疗后心电图示心肌缺血改善者达72.7%,心脏 B 超示室壁运动改善者达80%,心阻抗血流图示 PEP/LVET 明显下降,P<0.01,CI 明显增高.P<0.05,说明蝮蛇抗栓酶具有明显的改善心肌缺血和左心室功能的作用。     

利用秆维管束进行中国散生竹类的聚类分析

本文是应用模糊聚类分析方法研究中国散生竹类分类的一次尝试。分类特征采用了竹秆上、中、下三段各类型维管束数,方法上使用了模糊(Fuzzy)直接聚类分析进行综合分析。经电子计算机运算后,不仅取得了与传统分类基本一致的分类结果,同时也表明这种方法较之其它一些植物数量分类方法简便易行,此外还讨论了一些中国散生竹类分类上的问题。     

Vegetation zonation in dune slacks on the Leba Bar,Polish Baltic Sea coast

Vegetation zones in dune slacks on the Leba Bar on the Polish Baltic Sea coast are described. Plant colonization starts on moist sand in eastern ends of slacks, in the wake of receding mobile dunes. Communities on deflation ribs, dominated by psammophytic grasses, sedges and lichens, are structurally simple. Communities in troughs, dominated by species of fresh habitats, become structurally more complex in a western direction and they culminate with the Pinus silvestris forest. The main lines of vegetation variation correlate with groundwa-ter depth, micro topography, soil profile build-up and substrate acidification.     

Xylem pathways in liana stems with variant secondary growth

FISHER, J. B. & EWERS, F. W., 1992. Xylem pathways in liana stems with variant secondary growth. The three-dimensional construction of stem xylem in tropical lianas (woody vines) was studied using several approaches: 1. observations of the xylem surface in stems with bark removed after NaOH treatment or natural retting; 2. reconstructions from serial transverse sections; 3. movement of dye solutions up isolated xylem sectors in intact plants, and 4. flow of dye solutions down branches and xylem sectors in isolated stem segments. Long distance (up to several metres) xylem pathways in unbranched stems and connections between lateral branches and main stems are described for !5 species in eight families which represented seven differnt patterns of secondary growth. The xylem in even the most complex stems is integrated by three-dimensional interconnections of xylem regions which may appear isolated in transverse section. Interconnections are most common at leaf and branch nodes. Some old stems have peripheral xylem that remains isolated over long distances in unbranched stems, but even these had structural and physiological interconnections between xylem regions at branch nodes.     

Distribution of chylomicron degradation products in the isolated,perfused rat heart

Chylomicron degradation by hearts from fed and fasted rats was studied using a perfusion technique, which allows the separate collection of coronary (Q_rv) and interstitial effluent (Q_i). Upon perfusion with [³H]-cholesterol-containing chylomicrons the tissue recovery of label was highest in the fasted state, while label recovered in Q_i was highest in the fed state. Density gradient centrifugation of Q_i indicated that the label was recovered in lipoproteins with higher densities: low density lipoproteins (1.019<d<1.050), high density lipoproteins (1.050<d<1.21) and a fraction of d>1.21. These particles probably represent chylomicron degradation products (remnants and “surface fragments”). Our results indicate that tissue cholesterol uptake during chylomicron degradation may be inhibited in the fed state. Furthermore, the role of the myocyte (or interstitial) lipoprotein lipase in chylomicron degradation is discussed.     

Correlations between net auxin and secondary xylem development in young Populus deltoides

Stems of cottonwood ( Populs deltoides Bartr. ex Marsh.) plants grown under different conditions were examined to determine the relation between net endogenous auxin yields and the acropetal advance of the primary-secondary vascular transition zone (TZ). In all treatments, the internode yielding maximum net auxin activity, as determined by the Avena curvature bioassay, closely corresponded with the internode in which the TZ occurred. Under short-day (SD) dormancy-inducing conditions, auxin yield declined steadily while the maximum auxin peak and the TZ shifted toward younger internodes. Auxin yields from these plants were extremely low after 5 weeks of SD compared with those from long-day (LD) plants. The only consistent auxin yield was obtained from internodes subtending young leaves beneath the apical bud. Plants placed in SD for 3 weeks and then returned to LD conditions showed an immediate increase in auxin yield in the stem, and the progressive acropetal advance of the TZ under SD was reversed. Therefore, within 7 LD the positions of the TZ and peak auxin yield corresponded to those observed before the imposition of SD Fully dormant plants placed in LD showed a dramatic rise in auxin yields during the first 2 weeks of renewed growth. Although low levels of auxin were found in the newly developing shoots after 6 LD, yields increased rapidly after 9 and 14 LD. The position of the TZ corresponded with the peak of net auxin activity after 9 and 14 LD.