刺激家兔腹部迷走神经外周端降压效应中枢机制的研究

应用电解损毁和脑室内注射药物的方法研究了刺激家兔腹部迷走神经外周端所致降压效应的中枢机制。结果表明:1.电刺激延脑闩部尾侧1.5—2mm、中线旁开0.25mm、深1—2mm 处主要引起降压反应。2.电解损毁该部位可以使刺激腹部迷走神经外周端所引起的降压效应显著减弱(n=20,P<0.001),但对刺激减压神经所致降压反应无影响。3.在延脑闩部水平电解损毁减压神经纤维在孤束核的主要投射区可以使刺激减压神经所致降压反应显著减弱,而对刺激腹部迷走神经外周端所致降压反应无影响。4.第四脑室注射5,6-双羟色胺的动物较之注射人工脑脊液的动物颈、胸髓5-羟色胺含量明显降低、动物动脉压增高、心率明显增快、刺激减压神经所致降压反应未见减弱,而刺激腹部迷走神经外周端所致降压反应却明显减小。因此,我们认为家兔腹部迷走神经外周端所致降压效应依赖于延脑闩下部的中缝隐核及连合核等结构,而与减压神经的投射部位无关。延脑中缝核至脊髓的下行性5-HT能神经纤维抑制脊髓交感节前神经元的活动,是这个降压效应的中枢机制之一。     

Comparison of malate dehydrogenase isoenzymes in someAllium species by isoelectric focusing

Malate dehydrogenase isoenzymes were studied in tenAllium species and in six cultivars ofA. cepa by isoelectric focusing in polyacrylamide gel with Ampholine pH 3.5–10.0. Using this method better resolution was obtained than by polyacrylamide gel electrophoresis. The number of MDH isoenzymes obtained by isoelectric focusing is from five to ten in the range of pH 3.65 to 6.75. MDH isoenzymes can be used for characterization on the level of species and cultivars (inA. cepa), but its use on the level of sections and subgenera is questionable.     

The comparison of seed protein patterns within the genusArachis by polyacrylamide gel electrophoresis

The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard index. Results obtained confirm the close relationships established between members of the genus on morphological grounds and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly, the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value of seed protein pattern data appears to be in distinguishing species within sections.     

Cell surface changes and enzyme release during hypoxia and reoxygenation in the isolated, perfused rat liver

We examined the effects of hypoxia and reoxygenation in isolated, perfused rat livers. Hypoxia induced by a low rate of perfusion led to near anoxia confined to centrilobular regions of the liver lobule. Periportal regions remained normoxic. Within 15 min, anoxic centrilobular hepatocytes developed surface blebs that projected into sinusoids through endothelial fenestrations. Periportal hepatocytes were unaffected. Both scanning and transmission electron microscopy suggested that blebs developed by transformation of preexisting microvilli. Upon reoxygenation by restoration of a high rate of perfusion, blebs disappeared. Other changes included marked shrinkage of hepatocytes, enlargement of sinusoids, and dilation of sinusoidal fenestrations. There was also an abrupt increase in the release of lactate dehydrogenase and protein after reoxygenation, and cytoplasmic fragments corresponding in size and shape to blebs were recovered by filtration of the effluent perfusate. We also studied phalloidin and cytochalasin D, agents that disrupt the cytoskeleton. Both substances at micromolar concentrations caused rapid and profound alterations of cell surface topography. We conclude that hepatic tissue is quite vulnerable to hypoxic injury. The morphological expression of hypoxic injury seems mediated by changes in the cortical cytoskeleton. Reoxygenation causes disappearance of blebs and paradoxically causes disruption of cellular volume control and release of blebs as cytoplasmic fragments. Such cytoplasmic shedding provides a mechanism for selective release of hepatic enzymes by injured liver tissue.     

New subspecies ofSparganium erectum L. from Iran

From the Caspian coastal region of Iran a new taxon,Sparganium erectum L. subsp.mazanderanicum Ponert, is described and illustrated. This new subspecies in some of its characters is near toSparganium erectum L. subsp.microcarpum (Neumann)Domin (with its east distribution trend); in other characters it is near toSparganium erectum L. subsp.neglectum (Beeby)Schinz etThell. (with ist south distribution trend). A comparative table of diacritical characters of these three subspecies is appended.     

On the validity of the genusDactylococcopsis (Cyanophyceae)

Summary The genusDactylococcopsis Hansg. 1888 (Cyanophyceae) is based on the typeD. rupestris, which was later identified as a green algae. Most of the many species described later were also placed to other groups of algae. Several authors even doubted about the existence of the genus. As, however, some species of Cyanophyceae correspond to the original generic diagnosis, the name Dactylococcopsis Hansg. ex R. et F.Chod. 1925 has been proposed as a nomen conservandum, and a new type (D. smithii R. et F.Chod.) has been defined. Further speciesD. linearis Geitl. 1935 and D.Planctonica Teil. 1942 has been unambiguously described till now.     

Chromosome counts of some Mongolian plants

The paper gives the chromosome numbers of 45 species from 72 Mongolian localities, belonging to the genera:Amygdalus, Asparagus, Astragalus, Cancrinia, Caragana, Chamaerhodos, Chelidonium, Chesneya, Dianthus, Hypecoum, Lathyrus, Lilium, Oxytropis, Papaver, Potentilla, Schizonepeta, Sibbaldia, Thermopsis, Trifolium, Trigonella, Vicia. Chromosome morphology of three species ofChamaerhodos and taxonomical remarks on some other species are added. A new combinationSibbaldia sericea (Grubov) Soják is proposed.