Tyrosine hydroxylase and methionine-enkephalin in the human mesencephalon. Immunocytochemical localization and relationships

The immunocytochemical localization of tyrosine hydroxylase (TH) and methionine-enkephalin (met-enkephalin) was determined at two representative caudal and rostral levels of the human mesencephalon. Four main groups of catecholaminergic neurons were delineated, situated in the substantia nigra and the lateral, ventromedial and dorsomedial tegmentum, extending over several cytoarchitectonic divisions. They matched fairly well the dopaminergic cell groups described in monkey midbrain. TH-like immunoreactivity and neuromelanin were closely related in neurons of substantia nigra, but less so in the other groups. A widespread met-enkephalinergic innervation was observed in most areas containing catecholaminergic neurons. It followed a characteristic pattern: homogeneous and very dense in the lateral and posterior portions of substantia nigra; patchy and less dense in the other areas, the medio-ventral and periaqueductal gray being only sparsely innervated, in contrast to observations in rodents. Dopaminergic cell bodies surrounded by met-enkephalinergic varicosities were seen in most groups, particularly in the lateral substantia nigra and medioventral tegmentum. The topography of met-enkephali-like immunoreactive terminals in the substantia nigra was reminiscent of the distribution of neostriatal and pallidal afferents.     

Immunohistochemical studies of FMRF-amide-like immunoreactivity in rat brain

The anatomical distribution of neuronal perikarya and nerve fibres containing FMRF-amide-like immunoreactivity in the brain, spinal cord and pituitary of the rat has been studied by immunohistochemistry. In animals pretreated with colchicine, the highest concentration of nerve cell bodies occurred in hypothalamic nuclei. Cells were also present in the cortex, striatum, septum, thalamus and in the brainstem. Beaded nerve fibres were abundant in the septum, nucleus of the striae terminalis, hypothalamus, medial regions of the thalamus, the parabrachial nucleus, the ventrolateral medulla, the substantia gelatinosa of the spinal trigeminal nucleus and the dorsal horn of the spinal cord. Fibres were also present in the cortex, striatum, amygdala, pons, ventral spinal cord and the neural lobe of the pituitary. The localization was specific in that preabsorbtion of the antisera with FMRF-amide, but not structurally related molecules such as Met-Enk-Arg6Phe7, APP or BPP, completely abolished the localization. The mammalian counterparts of FMRF-amide may have a neurotransmitter or neuromodulatory role.     

Morphological differentiation and proteoglycan synthesis regulate Alzheimer amyloid precursor protein processing in PC-12 and human astrocyte cultures.

A morphologically differentiated strain of rat pheochromocytoma (PC-12H) metabolically labeled with [35S]methionine and incubated with a phorbol ester displayed reduced 140-kDa and increased 15 kDa bands relative to cells incubated without phorbol ester after immunoprecipitation with antisera elicited by the C-terminal peptide of the Alzheimer amyloid precursor protein (APP). These bands correspond to glycosylated full length APP and a C-terminal fragment previously reported by Anderson et al. (Neurosci. Lett. 120:126-128, 1991) to result from a cleavage within the amyloidotic A4 region of APP, which releases a 120 kDa extracellular fragment. The 15 kDa fragment, not immunoprecipitated with an antisera elicited by the N-terminal portion of A4 amyloid, is nonamyloidogenic. Incubation of these cells with p-nitrophenylxyloside, known to inhibit proteoglycan formation, also increased this nonamyloidogenic cleavage of APP. In contrast to these results, an undifferentiated low passage PC-12-L strain constitutively displayed rapid nonamyloidogenic APP cleavage. Incubation of PC-12-L with phorbol ester did not affect the relative abundance of 140 or 15 kDa bands. Growth of PC-12-L with 7 S NGF or dibutyryl cAMP resulted in increased morphological differentiation and decreased APP cleavage which was now phorbol-inducible. Similar analyses of dividing and senescent human astrocytes and normal and F-AD fibroblasts indicate 5-fold lower rates of mid-A4 APP cleavage. Phorbol esters decreased the 140 kDa APP band without affecting the intensity of the 15 kDa band in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

APP/PS1双转基因老年性痴呆小鼠早期病理和认知行为变化

【目的】探讨APP/PS1双转基因老年性痴呆(Alzheimer’s disease,AD)模型小鼠早期病理和行为学变化。【方法】选取5、7月龄的APP/PS1双转基因小鼠和非转基因小鼠,采用刚果红染色法和定量方法,并结合Morris水迷宫行为学测试,对其脑内淀粉样斑块积聚与学习记忆能力的月龄变化关系进行研究。【结果】(1)7月龄的双转基因组小鼠的空间辨别学习记忆能力与非转基因组小鼠比较差异有统计学意义(P<0.05);(2)APP/PS1双转基因组小鼠在5、7月龄时海马与脑皮质均观察到明显的橘红色斑块沉积,但非转基因组小鼠海马及脑皮质均未观察到淀粉样斑块沉积。【结论】7月龄APP/PS1双转基因小鼠的学习记忆能力下降,APP/PS1双转基因小鼠大脑皮层和海马部位淀粉样斑块的早期出现随年龄依赖性增加。     

辛伐他汀对铜和高胆固醇阿尔茨海默病家兔海马淀粉样肽前蛋白mRNA表达的影响

目的 研究辛伐他汀对铜和高胆固醇诱导的阿尔茨海默病(AD)家兔海马淀粉样肽前蛋白(APP)mRNA表达的影响.方法 采用Sparks方法复制铜和高胆固醇诱导的AD家兔模型.辛伐他汀(5 mg·kg-1·d-1)灌胃3 w,高效液相色谱法(HPLC)检测家兔海马胆固醇含量,实时定量RT-PCR法检测海马APP mRNA表达水平.分析海马胆固醇含量与海马APP mRNA表达的相关性.结果 模型组海马胆固醇含量及APP mRNA表达水平显著高于正常组(P＜0.05).辛伐他汀组海马胆固醇含量及APP mRNA表达水平显著低于模型组(P＜0.05);与正常组相无显著差别(P＞0.05).海马APP mRNA表达水平与海马胆固醇含量呈正相关(r=0.58,P＜0.05).结论 辛伐他汀可通过降低海马胆固醇含量减少APP转录,这可能是辛伐他汀降低AD发病的机制.     

Transient Axonal Injury in the Absence of Demyelination: A Correlate of Clinical Disease in Acute Experimental Autoimmune Encephalomyelitis

Axonal degeneration contributes to the transient and permanent neurological deficits seen in multiple sclerosis, an inflammatory disease of the central nervous system. To study the immunological mechanisms causing axonal degeneration, we induced experimental autoimmune encephalomyelitis (EAE) in wildtype Lewis rats and Lewis rats with a slowly progressive myelin degeneration due to proteolipid protein (PLP) overexpression. EAE was triggered either by the transfer of encephalitogenic T-cells alone or by the co-transfer of T-cells with demyelinating antibodies. Inducible nitric oxide synthase (iNOS) expression in perivascular macrophages was associated with a transient functional disturbance of axons, reflected by the focal and reversible accumulation of amyloid precursor protein. Clinical disease correlated with the numbers of APP positive axon spheroids. Demyelination was associated with a further increase of iNOS expression in macrophages and with a higher degree of axonal injury. Our studies suggest that nitric oxide and its metabolites contribute to axonal pathology and possibly also to subsequent neurological dysfunction in EAE.     

Searching for new animal models of Alzheimer′s disease

The pathophysiology of chronic neurodegenerative diseases, as Alzheimer′s diseases, has remained inaccessible till recently. But this situation is changing quickly. In the past decades, genes causing familiar forms of the disease have been identified and provided the genetic framework for the emerging amyloid hypothesis. On the basis of these findings, engineered mouse models have been developed and have allowed the understanding of crucial information about the pathogenic process. Certain observations obtained by transgenic mice, however, do not easily fit with the simplest version of the amyloid hypothesis. Even if there are transgenic lines that offer robust and relatively faithful reproductions of a subset of Alzheimer′s disease′s features, a mouse model that recapitulates all aspects of the disease has not yet been produced. Several still not completely known factors combine to produce highly variability across transgenic mouse models. Discrepancies in neuropathology and behaviour between transgenic mouse models and human Alzheimer′s disease, and among different transgenic-lines, suggest caution in the interpretation of the results. Here we try to analyze critically some of the information provided by transgenic mice but ascertaining which elements of the neuropathological and behavioural phenotype of these various strains of transgenic mice are relevant to that observed in Alzheimer′s disease continues to be a challenge.     

The ADAMs family: coordinators of nervous system development, plasticity and repair

A disintegrin and metalloprotease (ADAM) transmembrane proteins have metalloprotease, integrin-binding, intracellular signaling and cell adhesion activities. In contrast to other metalloproteases, ADAMs are particularly important for cleavage-dependent activation of proteins such as Notch, amyloid precursor protein (APP) and transforming growth factor alpha (TGFalpha), and can bind integrins. Not surprisingly, ADAMs have been shown or suggested to play important roles in the development of the nervous system, where they regulate proliferation, migration, differentiation and survival of various cells, as well as axonal growth and myelination. On the eleventh anniversary of the naming of this family of proteins, the relatively unknown ADAMs are emerging as potential therapeutic targets for neural repair. For example, over-expression of ADAM10, one of the alpha-secretases for APP, can prevent amyloid formation and hippocampal defects in an Alzheimer mouse model. Another example of this potential neural repair role is the finding that ADAM21 is uniquely associated with neurogenesis and growing axons of the adult brain. This comprehensive review will discuss the growing literature about the roles of ADAMs in the developing and adult nervous system, and their potential roles in neurological disorders. Most excitingly, the expanding understanding of their normal roles suggests that they can be manipulated to promote neural repair in the degenerating and injured adult nervous system.     

小鼠皮层和海马Aβ前体蛋白表达的增龄性改变

目的 探讨年龄对小鼠皮层和海马神经元Aβ前体蛋白(APP) 695表达的影响.方法 C57BL/6J雄性小鼠按照年龄随机分为3组:2月龄组、12月龄组和20月龄组;采用免疫组织化学和免疫印迹方法观测各组皮层和海马神经元APP695蛋白的表达.结果 与2月龄相比,12月龄组海马和皮层神经元APP695蛋白水平明显升高(P＜0.05);20月龄组APP水平较12月龄组明显升高(P＜0.05,P＜0.01).结论 小鼠皮层和海马神经元APP695的表达随着年龄的增长而增高.