Neuronal apoptosis versus necrosis induced by glutamate or free radicals

The type of cell death encountered in neuronal cell cultures exposed to excitatory amino acids — such as glutamate, the major excitatory neurotransmitter in the central nervous system, or free radicals, such as nitric oxide (NO^.) and superoxide anoin (O2^{. –}), which react to form peroxynitrite (ONOO^–) — appears to depend on the intensity of the exposure and may involve two temporarily distinct phases. Following relatively fulminant insults, an initial phase of necrosis — associated with extreme energy depletion — may simply reflect the failure of neurons to carry out the default apoptotic death program used to efficiently dispose of aged or otherwise unwanted cells. Neurons recovering mitochondrial energy potential after an initial fulminant insult or following a more subtle inciting injury may subsequently undergo apoptosis, possibly associated with a factor released from mitochondria that triggers this death program. The maintenance of balanced energy production may be a decisive factor in detemining the degree, type, and progression of neuronal injury caused by excitotoxins and free radicals. Similar events could possibly occur in vivo after ischemia or other insults.     

Actin distribution in somatic embryos and embryogenic protoplasts of white spruce (Picea glauca)

Summary Examination of unfixed immature somatic embryos of white spruce (Picea glauca) with fluorescent rhodamine-labeled phalloidin revealed an extensive network of fine actin microfilaments (MFs) in the embryonal region which were not detected in specimens fixed with formaldehyde. Transition cells linking the embryonal region and suspensor cells contained fine MFs as well as bundles of MFs. The large, highly vacuolated suspensor cells were characterized by actin MF cables only. Treatment of embryos with cytochalasin B (CB) removed the fine MFs from the embryonal region and transition cells, but many MF cables in suspensor cells were resistant. Full recovery from CB treatment was observed in most somatic embryos. Embryogenic protoplasts capable of regenerating to somatic embryos in culture were released from only the embryonal region of somatic embryos. Both uninucleate and multinucleate embryogenic protoplasts retained the extensive network of fine actin MFs. In contrast, protoplasts derived from vacuolated suspensor cells and vacuolated free-floating cells contained thick MF bundles and were not embryogenic. Distinct MF cages enclosed nuclei in multinucleate protoplasts and may be responsible for preventing nuclear fusion. Microspectrophotometric analyses showed that the DNA contents of embryonal cells in the embryo and embryogenic protoplasts were similar and characteristic of rapidly dividing cell populations. However, transition and suspensor cells which released nonembryogenic protoplasts appeared to be arrested in G₁, and suspensor cells showed signs of DNA degradation.     

Force-dependent changes in movement-related cortical potentials

The purpose of this study was to compare movement-related cortical potentials (MRCPs) associated with different levels of isometric contractions by elbow flexors. Eight healthy, right-handed male subjects participated in this study and performed different levels (10 and 50% of maximal voluntary contraction) of isometric contractions by the right elbow flexors. Electroencephalogram (EEG) signals were recorded from Fz, C3, Cz and C4 of the international 10/20 system. Motor potential (MP) amplitudes (from −200 to approximately −50 ms before force onset) for C3 associated with both force generations was significantly greater (P < 0.01) than those for C4, indicating that contralateral predominance of MRCP was observed in the right arm flexion. In Fz, the potentials of negative slope (NS′) (from −600 to approximately −200 ms) and MPs for 50% MVC were significantly greater than those of 10% MVC. In Cz, the MP associated with 50% MVC revealed a significantly greater (P < 0.05) value than that with 10% MVC. In C3 and C4, the MP associated with 50% MVC tended to be greater than that with 10% MVC, but no statistically significant differences were found. These force-dependent changes in MRCPs imply increased activation of neural circuits involved in motor preparation and initiation. It is therefore suggested that the larger potentials from Fz and Cz for 50% MVC compared with 10% MVC reflect a greater activation of supplementary motor area for the preparation of the larger force generation.     

Nitric Oxide-Induced [3H]GABA Release from Cerebral Cortical Neurons Is Mediated by Peroxynitrite

Abstract: The functional significance of peroxynitrite in the release of [³H]GABA induced by nitric oxide (NO) liberated from NO generators was investigated using cerebral cortical neurons in primary culture. NO generators such as sodium nitroprusside (SNP) and S -nitroso- N -acetylpenicillamine (SNAP) increased [³H]GABA release in a dose-dependent manner. These increases in [³H]GABA release were significantly inhibited by hemoglobin, indicating that those NO generators evoke the release of [³H]GABA by the formation of NO. Two types of superoxide scavengers, Cu²⁺/Zn²⁺ superoxide dismutase and ceruloplasmin, significantly reduced the increase in [³H]GABA release induced by both SNP and SNAP, which assumes that NO requires superoxide to induce [³H]GABA release from the neurons. In addition, synthesized peroxynitrite induced a dose-dependent increase in [³H]GABA release from the neurons. These results indicate that NO-induced [³H]GABA release is mediated by peroxynitrite formed by the reaction of NO with superoxide.     

Pathological changes of myocardial cytoskeleton in cardiomyopathic hamster

Immunocytochemical investigation was performed on the cytoskeletal proteins in cardiac tissue of the cardiomyopathic hamster. Male cardiomyopathic UM-X7.1 hamsters at 180 days of age (n=8) and age- and sex-matched normal BIO-RB hamsters (n=8) were used in this study. Immunofluorescence microscopy using monoclonal antibodies against desmin, -actinin, titin, and vincullin was employed. The heart weight to body weight ratio was significantly increased in the heart of cardiomyopathic hamster compared with that of normal hamster. In cardiomyopathic hamster, the left ventricular cavity was markedly dilated. Light microscopically, hypertrophy and atrophy of myocytes and myocardial fibrosis were prominently observed in cardiomyopathic myocardium. Immunocytochemically, desmin, -actinin and titin showed the cross striations along the myofibers in normal myocardium. In contrast, in cardiomyopathic myocardium, desmin was irregularly distributed in myocytes and the amount of desmin was increased. Loss of cross striations of -actinin and titin were frequently observed. Immunofluorescence against vinculin was not significantly altered. We conclude that the alterations of cytoskeletal proteins in myocardial cells may relate to decreased myocardial function in cardiomyopathic hamster failing heart.     

鲨鱼软骨制剂抑制血管生成的研究

以鲨鱼软骨为原料,经盐酸胍抽提,丙酮分级沉淀, 超滤等步骤得到鲨鱼软骨制剂(shark cartilage preparation,SCP). 利用整装细胞扫描电镜方法测定SCP对血管内皮细胞骨架系统的影响,体外细胞迁移实验测定它对内皮细胞迁移的抑制效应,及鸡胚绒毛尿囊膜实验测定对血管生成的抑制效应. 结果表明SCP能显著抑制内皮细胞的骨架形成;显著抑制内皮细胞的迁移,并有明显的浓度依赖关系;显著抑制鸡胚绒毛尿囊膜的血管生成. 细胞骨架是细胞分裂增殖及运动迁移的基础,血管内皮细胞的运动迁移又是血管生成的基础,因此SCP的作用机理可能是通过抑制细胞骨架的形成,抑制内皮细胞的运动迁移,从而抑制血管生成.     

上海四膜虫接合生殖期间皮层细胞骨架蛋白的研究

本文采用生化抽提,结合电泳及显微技术,对上海四膜虫（Ｔｅｔｒａｈｙｍｅｎａｓｈａｎｇｈａｉｅｎｓｉｓ）Ｓ１皮层细胞骨架（ｃｏｒｔｉｃａｌｃｙｔｏｓｋｅｌｅｔｏｎ）的蛋白组份,及其在接合生殖期间的变化进行了一系列的研究,初次探索了Ｓ１株上海四膜虫在接合生殖中皮细胞骨架的蛋白组份及含量,并分析了它们与间期,接合分开时期同类蛋白相互间的差异,发现在接合生殖时期７６－８８ｋＤ蛋白有突出的表现,而９０ｋＤ和     

Ultrastructure of the Somatic and Buccal Cortex of the Tetrahymenine Hymenostome Glaucoma chattoni

SYNOPSIS The membranes, epiplasm, and fiber systems are described in the somatic cortex of Glaucoma chattoni strain HZ-1. Kinetodesmal fibers, postciliary and transverse microtubular ribbons, basal microtubules, transverse fibers and transverse accessory material are associated with kinetosomes. Longitudinal microtubular ribbons and mitochondria occur interkinetally. In the buccal cortex, the membranes, epiplasm and fibers of the 3 membranelles, the paroral kinety, the ribbed wall, and the cytostome are described. Comparisons between G. chattoni and other ciliates reveal ultrastructural differences of possible systematic significance. In the somatic cortex of this and other tetrahymenines. Iongitudinal microtubular ribbons and basal microtubules occur concurrently. In the buccal cortex, alveoli are absent in tetrahymenine membranelles. A table is presented of the fiber systems associated with single somatic kinetosomes of various ciliates whose cortical ultrastructure has been studied to date.     

Molecules and Morphologies: The Perpetuation of Pattern in the Ciliated Protozoa*†

SYNOPSIS. Three apparently conflicting generalizations concerning the relationships between molecules and cell structure may be derived from studies on cellular patterning in the ciliates. (A) Cells with identical genes and molecular composition may have different hereditary patterns. (B) Genes, through their prescribed molecular derivatives, constrain the modes of pattern permutation and define the states of greatest stability. (C) Cells with identical hereditary patterns may have entirely different genes and molecular compositions. These principles may be reconciled through the recognition that they are characteristically applicable over different time intervals. Hereditary differences within a clone and without related molecular differences (principle A) may persist for hundreds of cell generations, but they are resolved eventually within a constant environment (principle B) as the configuration of minimal free energy is approached. On an even longer time scale, molecular substitutions have occurred for many or most components of the cell, but these have been constrained by selective pressures on an ancient design (principle C) that disallow substitutions affecting certain form-function relations which have been elevated to an adaptive peak.