Neurotrophic factor therapy for nervous system degenerative diseases

The ability of neurotrophic factors to regulate developmental neuronal survival and adult nervous system planticity suggests the use of these molecuales to treat neurodegeneration associated with human diseases. Solid rationales exist for the use of NGF and neurotrophin-3 in the treatment of neuropathies of the peripheral sensory system, insulin-like growth factor and ciliary neurotrophic factor in motor neuron atrophy, and NGF in Alzheimer's disease. Growth factors have been identified for neurons affected in Parkinson's disease, Huntington's disease, and acute brain and spinal cord injury. Various strategies are actively pursued to deliver neurotrophic factors to the brain, and develop therapeutically useful molecules that mimic neurotrophic factor actions or stimulate their production or receptor mechanisms. 1994 John Wiley & Sons, Inc.     

人──板系统最佳蹬伸动作的控制模型及数值分析

本文基于Hanavan模型和人体测量学参数,以人体各环节间的相对运动作为控制量,建立了人-板系统中起跳蹬伸动作的数学模型,给出了模型的数值计算方法,在此基础上给出了实现最佳蹬伸用力过程的计算实验途径与运动技术诊断方法。     

一类单种群动态模型的稳定性

一、引言及引理考虑一类单种群动态模型对方程（1）总假设满足其中N（t）为种群在时刻t的数量或密度．由于方程（1）是描述种群增长的生态模型,因此我们考虑（1）的正解且满足初始条件：易证（1）和（2）有唯一正常数平衡点本文研究（1）关于N*的稳定性．（1）的特别情形是其中（1a）描述在食物资源严重不足种群数量充分大导致种群内部互相竞争残杀时的增长模型［1];（1b）描述种内既有竞争又有协作的所谓ALLEE效应的增长模型［2]．事实上,若β＞0,由（1b）式知,当N（t-r）充分小时,当N（t—r）充分大时,这正是ALLEE效应．文献…     

降钙素基因相关肽的研究进展

降钙素基因相关肽（ＣＧＲＰ）是由３７个氨基酸残基构成的生物活性多肽,与降钙素（ＣＴ）源子一个共同的基因。ＣＧＲＰ分布广泛,具有很强的血管扩张、降低血压以及心肌正性肌力作用等,并参与心血管系统稳态的调节。目前,ＣＧＲＰ已能人工合成,将为某些心血管疾病如高血压、心肌缺血、痉挛性或闭塞性周围血管疾病等的治疗提供一条崭新的途径。     

重组BCG口服免疫诱导的细胞和体液免疫应答

重组ＢＣＧ口服免疫诱导的细胞和体液免疫应答最近研究证明,外源基因能在牛分枝杆菌ＢＣＧ中表达,用这些重组分枝杆菌免疫小鼠可诱导抗外来蛋白的细胞和抗体免疫应答。近年来的许多研究也证实了肠道和呼吸道粘膜淋巴系统在防御感染方面的贡献,因此,迫切需要能够刺激粘...     

Histo-cytological study of the liver of the cabrilla sea bass, Serranus cabrilla (Teleostei, Serranidae), an available model for marine fish experimental studies

Livers of juvenile cabrilla sea basses ( Serranus cabrilla ) were subjected to light and electron transmission microscopy following different periods of maintenance in an aquarium. Since this fish is easy to feed in captivity and the hepatic structure was found to be comparable at the four periods tested (0, 5, 10 and 20 days), both at the histological and ultrastructural level, the liver of S. cabrilla could be an available model for marine contamination experimental studies. As in other fish species, it is not possible to distinguish the portal lobules and the triads. The Melano-Macrophage Centres contain tipofuscins, ceroids and haemosiderin, but they do not contain any melanin. The hepatocytes are arranged in cords (two cells thick), and, at the ultrastructural level, they show numerous microvilli in the perisinusoidal and canalicular areas. The hyaloplasm includes a considerable amount of glycogen and some lipid droplets are occasionally observed. Mitochondria, rough endoplasmic reticulum and the Golgi apparatus are relatively scarce.     

Simulation of the light-induced oscillations of the membrane potential in Potamogeton leaf cells

Summary An attempt has been made to simulate the light-induced oscillations of the membrane potential of Potamogeton lucens leaf cells in relation to the apoplastic pH changes. Previously it was demonstrated that the membrane potential of these cells can be described in terms of proton movements only. It is hypothesized that the membrane potential is determined by an electrogenic H⁺-ATPase with a variable H⁺/ATP stoichiometry. The stoichiometry shifts from a value of two in the dark to a value of one in the light. Moreover, this H⁺ pump shows the characteristics of either a pump or a passive H⁺ conductance: the mode of operation of the H⁺ translocator is considered to be regulated by the external pH. The pump conductance is assumed to be dominant at low or neutral pH, while the passive H⁺ conductance becomes more significant at alkaline pH. The pH dependence of the transport characteristic is expressed by protonation reactions in the plasma membrane. The proposed model can account for most features of the light-induced oscillations but not for the absolute level of the membrane potential.This research was supported by the Foundation of Biophysics, part of the Dutch Organization for Scientific Research (NWO) ECOTRANS publication No. 34.     

Time and biosequences

In this paper we discuss and demonstrate the importance of several factors relative to the relationship between time and evolution of biosequences. In both quantitative and qualitative measurements of the genetic distances, the compositional constraints of the nucleotide sequences play a very important role. We demonstrate that when homologous sequences significantly differ in base composition we get erratic branching order and/or wrong evaluation of the evolutionary rates. We must consider that every gene may have a different evolutionary dynamic along its sequence, generally linked to its functional constraints; this too can seriously affect its clocklike behavior. We report some cases showing how these factors can affect the quantitative measurements of the genetic distances of biosequences. Presented at the NATO Advanced Research Workshop onGenome Organization and Evolution, Spetsai, Greece, 16–22 September 1992     

Striatal L-DOPA Decarboxylase Activity in Parkinson's Disease In Vivo: Implications for the Regulation of Dopamine Synthesis

Abstract: L-DOPA is a large neutral amino acid subject to transport out of, as well as into, brain tissue. Competition between dopamine synthesis and L-DOPA egress from striatum must favor L-DOPA egress if decarboxylation declines relatively more than transport in Parkinson's disease. To test this hypothesis, we injected patients with Parkinson's disease with a radidabeled analogue of L-DOPA and recorded regional brain radioactivity as a function of time by means of positron emission tomography. We simultaneously estimated the activity of the decarboxylating enzyme and the amino acid transport. In the striatum of patients, we found the L-DOPA decarboxylase activity to be reduced in the head of the caudate nucleus and the putamen. However, the rate of egress of the DOPA analogue was unaffected by the disease and thus inhibited dopamine synthesis more than predicted in the absence of L-DOPA egress.     

Immunocytochemical Quantification of Tyrosine Hydroxylase at a Cellular Level in the Mesencephalon of Control Subjects and Patients with Parkinson's and Alzheimer's Disease

Abstract: Parkinson's disease is characterized by massive degeneration of the melanized dopaminergic neurons in the substantia nigra. The functional capacity of the surviving nigral neurons is affected, as indicated by the subnormal levels of tyrosine hydroxylase (TH) mRNA in these neurons and the presence in the parkinsonian mesencephalon of melanized neurons lacking TH immunoreactivity. This is apparently in contradiction with the known overactivity of dopamine synthesis and release that occurs in the remaining dopaminergic terminals. To test the ability of the surviving neurons to express TH protein, a semiquantitative immunocytochemical method was developed. The relative amounts of TH were estimated with a computer-assisted image analysis system in the dopaminergic neurons of representative mesencephalic sections of control and parkinsonian brains and for comparison in brains from patients with Alzheimer's disease. In control brains, the mean TH content per neuron differed from one subject to another and between the different dopaminergic cell groups of the mesencephalon in the same subject. Within a given dopaminergic region, the level of TH was variable among neurons. In patients with Parkinson's disease, the ratio of TH protein content per neuron in the substantia nigra by reference to that of the central gray substance was reduced. In patients with Alzheimer's disease, the amount of TH was selectively reduced in the remaining dopaminergic neurons of the ventral tegmental area, a region characterized by a loss in dopaminergic neurons. The decrease in cellular TH content might therefore be related to the presence of the neurodegenerative process in the area considered. In patients with Parkinson's disease, the incapacity of the surviving neurons to express normal TH levels may reduce the efficiency of the hyperactivity mechanisms that develop in the remaining striatal dopaminergic terminals.