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Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA. 相似文献
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In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity. 相似文献
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The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration. 相似文献
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Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas. 相似文献
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Cepaea hortensis (Mull) is found in Spain only in the western part of the Iberian mountain range. This is the southernmost limit of its range. The most frequent colour is yellow, brown being very rare. The most frequent band patterns are 12345, fused banded and unbanded. There are associations between maximum and minimum temperatures and pink and effectively unbanded yellow phenotypes. The populations may be grouped into two zones, one located in the north and the other in the south of the sampled area. Visual predation was not observed. The marginal populations studied by us were compared with others from Northern Europe, and it was observed that pink snails are more frequent at the southern limit, and unbanded ones at the northern limit. This was interpreted as a climatic selection. 相似文献
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葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义。综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望。 相似文献
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Seasonal variation in alkalinity in pans in Central Africa 总被引:3,自引:3,他引:0
J. S. Weir 《Hydrobiologia》1968,32(1-2):69-80
Summary The alkalinity and pH of lakes (pans) in Central Africa on Kalahari Sand, varies with the physical nature of the pan. Natural pans show a range of pH from 6.1 to 8.7, and of total alkalinity from 10 mg/l to 580 mg/l. This range is attributable to local soil differences. Some pans have been deepened or have had water pumped into them to provide drinking points for game animals. The alkalinity of pumped pans is determined by the alkalinity of the water pumped into the pan and the time during which this has taken place. All these types of pan show cyclic seasonal variation in alkalinity and pH. The range in these factors is similar from one year to the next. Animals living either in permanent (deepened or pumped) pans or in temporary (natural) pans have to withstand a wide range of alkalinity fluctuation in the course of the year. 相似文献
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Parvalbumin in mouse muscle in vivo and in vitro 总被引:1,自引:0,他引:1
Marion S. Ecob-Prince Ekkehard Leberer 《Differentiation; research in biological diversity》1989,40(1):10-16
Parvalbumin is a cytosolic calcium-binding protein found in adult fast-twitch mammalian muscle. Using an antibody to paravalbumin, we have shown that its distribution in adult mouse muscles is associated with certain fibre types. It is absent from slow-twitch type 1 fibres, is absent or at low levels in fast-twitch type 2A fibres, but is present at moderate or high levels in fast-twitch type 2B fibres. When adult mouse muscle is cultured with embryonic mouse spinal cord, the regenerated fibres become innervated, express the adult fast isoform of myosin heavy chain and appear histochemically as fast-twitch fibres. We therefore investigated whether these apparently mature fibres also contained parvalbumin. Parvalbumin was not found in any fibres of twenty mature cultures, suggesting that neurotrophic activity in the absence of specific adult nerve activity patterns was insufficient to cause the expression of parvalbumin in the cultures. 相似文献
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2017年中国植物科学若干领域重要研究进展 总被引:1,自引:0,他引:1
2017年中国植物科学继续保持高速发展态势, 重大成果频出, 具体表现在中国植物学家在国际顶级学术期刊发表的文章数量平稳上升。中国植物科学领域的研究工作者成果精彩纷呈, 如新型广谱抗病机制的发现、水稻广谱抗病遗传基础及机制和疫霉菌诱发病害成灾机制研究等。2017年中国生命科学领域十大进展评选中, 有两项植物科学领域的研究成果入选。水稻生物学、进化与基因组学和激素生物学等领域学科发展突出。另外, 值得一提的是, 长期从事高等植物与代谢途径调控分子网络研究和水稻品种设计育种的李家洋院士的研究成果“水稻高产优质性状形成的分子机理及品种设计”荣获2017年国家自然科学一等奖。这一具有重大国际影响的开创性贡献标志着中国植物科学在该领域的国际科学前沿居于引领和卓越地位。该文对2017年中国本土科学家在植物科学若干领域取得的重要研究成果进行了系统梳理, 旨在全面追踪和报道当前中国植物科学领域发展的最新前沿动态, 与广大读者共同分享我国科学家所取得的辉煌成就。 相似文献