Alpha-methyl-para-tyrosine pretreatment protects from striatal neuronal death induced by four-vessel occlusion in the rat

Rats were treated with alpha-methyl-para-tyrosine (AMT, 250 mg/kg, i.p), an hydroxylase inhibitor, in order to decrease brain levels of catecholamines. Six hours later, when cerebral dopamine (DA) and norepinephrine were reduced by about 80%, a transient forebrain ischemia of 30 min duration was induced by four-vessel occlusion technique. Evaluation of brain damage 72 hours after ischemia showed that AMT treatment significantly decreased neuronal necrosis in the striatum but had no cytoprotective effect in the CA1 sector of the hippocampus and in the neocortex. AMT treatment reduced mortality within the ischemic period but did not affect either the mortality within the recirculation period or the postischemic neurologic deficit. These results suggest that the striatal cytoprotective effect of AMT is linked to cerebral DA depletion and that excessive release of DA during ischemia or dopaminergic hyperactivity during recirculation play a detrimental role in the development of ischemic cell damage in the striatum.     

The osmotic/calcium stress theory of brain damage: Are free radicals involved?

This overview presents data showing that glucose use increases and that excitatory amino acids (i.e., glutamate, aspartate), taurine and ascorbate increase in the extracellular fluid during seizures. During the cellular hyperactive state taurine appears to serve as an osmoregulator and ascorbate may serve as either an antioxidant or as a pro-oxidant. Finally, a unifying hypothesis is given for seizure-induced brain damage. This unifying hypothesis states that during seizures there is a release of excitatory amino acids which act on glutamatergic receptors, increasing neuronal activity and thereby increasing glucose use. This hyperactivity of cells causes an influx, of calcium (i.e. calcium stress) and water movements (i.e., osmotic stress) into the cells that culminate in brain damage mediated by reactive oxygen species.Special issue dedicated to Dr. Frederick E. Samson     

External characteristics and associated developmental changes in two species of Sulawesi macaques,Macaca tonkeana andM. hecki,with special reference to hybrids and the borderland between the species

The degree of intergradation between two species of Sulawesi macaques,Macaca tonkeana andM. hecki, was studied by examining the diagnostic external characteristics of more than 100 monkeys kept as pets by natives. Two possible hybrid monkeys were found and both originated from the borderland between the two species, located in the most proximal region of the northern peninsula of Sulawesi. The previously postulated wide area of integradation between the two species at the possible contact zone was, however, not recognized, and typical examples oftonkeana orhecki were found to be present on the two sides of a narrow “hybrid” zone which was defined by direct observations. Furthermore, despite considerable individual variations, we were able to allocate most monkeys to one or other of the species. Each of ten external characteristics of the members of both species more or less encompassed the individual variations, but may undergo changes with the development of the monkeys. The mechanisms of reproduction of hybrid monkeys and the maintenance of differences between the species are discussed.     

Distribution and possible intergradation betweenMacaca tonkeana andM. ochreata at the borderland of the species in Sulawesi

Morphological observations of pet and wild monkeys were made in the area that was inferred to be the borderland betweenMacaca tonkeana andM. ochreata in Sulawesi. Almost all individual monkeys could be classified into one of two species by their external characteristics. The possible borderland was estimated to extend from the La River in the east and to around Karaena River in the west. These two species may make contact in the forest in the western area of the borderland. Some external characteristics exhibited wide individual variations in the two species. Some monkeys originating from the borderland showed external characteristics that were intermediate between those of the two species. The possible intergradation between these two species is discussed in terms of the morphological variations found in the two species.     

Ferritin enhances production of DNA strand breaks by 6-hydroxydopamine,ascorbic acid and H2O2 in CCC PM2 bacteriophage DNA

Damage of CCC PM2 DNA by 6-hydroxydopamine (6-OHDA) and ascorbic acid (AA), compounds that are both able to release iron from ferritin, was significantly enhanced in the presence of ferritin. H₂O₂, a product of 6-OHDA autoxidation, did not induce DNA strand breaks in the absence of ferritin and only to a minor extent in the presence of ferritin. DNA damage by 6-OHDA and AA could be reduced by the hydroxyl radical scavenger mannitol, the iron chelator desferrioxamine, and, partly, by a combination of superoxide dismutase and catalase. These inhibitory effects were clearly less pronounced in the presence of ferritin. Ferritin obviously played an important role as a source of iron in the pro-oxidative processes of 6-OHDA and AA. These features might be of importance in cancer therapy since many tumor cells contain elevated ferritin levels.     

甘肃马唧山地区榆中贝母(Fritillaria yuzhongensis)的生态学特性及种子发芽规律的初步研究

榆中贝母(Fritillaria yuzhongensis)生长于马啣山的高山地带,全生育期约100 d左右,是一种生育期较短的类短命植物。在果实成熟时,种子的胚发育不全,具有后熟作用的特点,包括形态后熟和生理后热两个阶段;因此,需要一定时期的低温处理,才能完成后熟过程,以解除休眠,促使种子发芽。本试验表明:榆中贝母完成形态后熟过程的最佳温度是7℃左右,经过100d以上的低温处理才能使原胚发育成熟,继续在7℃低温下处理70d以上,才能完成生理后熟过程。榆中贝母种子休眠时间长,需要经过170d以上的低温处理,种子才能萌发。本试验结果为榆中贝母种子的萌发提出了适宜的温度范围和低温处理时间,为提高种子的出苗率和缩短栽培年限提供了科学依据。     

湖泊和地下水中异养细菌群落结构和生理特征的比较研究

对武汉东湖三个定点观测站和潜江市一深水机井中异养细菌群落的种群组成、对不同基质的反应、菌株和群落的生理特征和活力水平等方面比较研究结果表明:环境差异较小的东湖Ⅰ、Ⅱ、Ⅲ站异养细菌群落间的差异亦较小,具有类似的结构特征和生理活力水平,对特定基质表现了相似的作用模式;地下水中的异养细菌群落在上述几方面均显示了明显的差别。此外,在异养细菌群落结构和功能研究方法上亦是有益的探讨。     

激光、血卟啉对肿瘤细胞DNA单链断裂及其重接的影响

用简化的Kohn氏碱洗脱法,观察了光敏剂血卟啉衍生物(HPD)对小鼠S-180肿瘤细胞DNA单链断裂及其重接修复的影响。激光HPD能导致S-180细胞DNA单链断裂明显增加,而且这种断裂随着保温时间的延长,继续增多。在本实验条件下没有观察到HPD对X线的增敏作用,HPD不能增加X线所致的DNA单链断裂,也不能影响其重接。单链断裂重接动力学的实验进一步证明了这个论点。