Sympathetic nerves in adult rats regenerate normally and restore pilomotor function during an anti-NGF treatment that prevents their collateral sprouting.

We have used anti-nerve growth factor (anti-NGF) [corrected] administration to study the NGF dependency of the reinnervation of denervated skin by sympathetic nerves in the adult rat. Sympathetic pilomotor fields were revealed by electrical stimulation of selected dorsal cutaneous nerves; the affected skin rapidly assumed a "gooseflesh" appearance, sharply demarcated from surrounding unstimulated skin. Examined 2-5 days after section of neighboring nerves, the "isolated" pilomotor field of the spared nerve was found to be coextensive with an area of amine-fluorescent fibers that were associated with pilomotor muscles and blood vessels. After its isolation, a pilomotor field begins to expand into the surrounding deprived territory, reaching a maximum size at approximately 40 days. Fluorescence studies confirmed that new sympathetic fiber growth had occurred into the expanded regions of such fields. Daily injections of polyclonal anti-NGF serum completely prevented these pilomotor field expansions. Following termination of the anti-NGF treatment, expansion proceeded normally. Finally, if the onset of anti-NGF treatment was delayed until pilomotor field expansion had already commenced, further expansion was halted. Regeneration of sympathetic fibers was evoked by crushing a selected nerve. Recovery of pilomotor function in the totally denervated skin was first detected at about 20 days postcrush, and the field progressively enlarged over the next 40 days. Although the imposed NGF deprivation is known to cause a demonstrable shrinkage, and presumably atrophy, of sympathetic ganglia, the anti-NGF treatment appeared to impair neither the restoration of a pilomotor field after nerve crush, nor its continued expansion into skin regions well beyond that originally supplied by the nerve, i.e., into territory whose invasion by collateral sprouts would have been totally prevented by the treatment. During such NGF deprivation, fluorescent regenerating fibers were visualized in the nerve trunk. We conclude that even though the regenerating and collaterally sprouting sympathetic fibers probably utilise the same degenerating dermal pathways to reach and functionally reinnervate the same denervated targets, only the collateral sprouting of the uninjured axons is dependent upon endogenous NGF. These findings extend the results described earlier for nociceptive fibers, and suggest that the contrasting dependencies upon growth factors of sprouting and regeneration might apply throughout the adult nervous system.     

Loss of cell polarity causes severe brain dysplasia in Lgl1 knockout mice

Disruption of cell polarity is seen in many cancers; however, it is generally considered a late event in tumor progression. Lethal giant larvae (Lgl) has been implicated in maintenance of cell polarity in Drosophila and cultured mammalian cells. We now show that loss of Lgl1 in mice results in formation of neuroepithelial rosette-like structures, similar to the neuroblastic rosettes in human primitive neuroectodermal tumors. The newborn Lgl1(-/-) pups develop severe hydrocephalus and die neonatally. A large proportion of Lgl1(-/-) neural progenitor cells fail to exit the cell cycle and differentiate, and, instead, continue to proliferate and die by apoptosis. Dividing Lgl1(-/-) cells are unable to asymmetrically localize the Notch inhibitor Numb, and the resulting failure of asymmetric cell divisions may be responsible for the hyperproliferation and the lack of differentiation. These results reveal a critical role for mammalian Lgl1 in regulating of proliferation, differentiation, and tissue organization and demonstrate a potential causative role of disruption of cell polarity in neoplastic transformation of neuroepithelial cells.     

香烟烟雾暴露对未成年小鼠齿状回神经发生和小胶质细胞的影响

为探讨香烟烟雾暴露(cigarette smoking exposure,CSE)对未成年小鼠的神经发生及学习记忆的影响,本研究用亲和组织化学方法,以5-溴脱氧尿苷(5-bromodeoxyuridine,BrdU)和西非单叶豆同工凝集素-B4(Bandeirae SimplicifoliaIsolectin-B4,BSI-B4)分别标记新生细胞和小胶质细胞(microglia,MG),观察了CSE小鼠齿状回内的神经发生及MG数目的变化,并通过Morris水迷宫训练测验其空间学习能力。结果显示:CSE下小鼠齿状回内的神经发生降低,MG数目显著减少;而在水迷宫的学习中,CSE组的逃避潜伏期亦明显长于对照组(P<0.05)。上述结果表明CSE损害了未成年小鼠齿状回内的神经发生,抑制了MG的激活,同时小鼠的空间学习能力与神经发生及激活的MG数量平行变化。此结果提示CSE造成的学习能力降低可能与齿状回神经发生及MG减少有关。     

大鼠海马内注射β淀粉样蛋白促进神经细胞增殖

目的观察脑内β淀粉样蛋白(β-amyloid,AB)沉积对神经细胞增殖的影响。方法将Aβ_(1-42)定位注射至大鼠双侧海马,对照组注射反序列Aβ_(42-1)或PBS。腹腔注射Brdu标记增殖细胞。用免疫组化和免疫荧光检测溴脱氧尿苷(Bromodeoxyuridine,Brdu)标记细胞和doublecortin(DCX)阳性细胞。结果海马内注射Aβ_(1- 42)后引起海马齿状回颗粒下层(subgranular zone,SGZ)和侧脑室下层(subventricular zone,SVZ)Brdu标记细胞及DCX阳性细胞显著增加(P<0.01)。双免疫荧光分析表明许多Brdu标记细胞表达DCX。结论Aβ沉积可以促进脑内的神经细胞增殖,提示这种现象可能为阿尔茨海默病的一种代偿性应答。促进神经细胞增殖的措施对于治疗阿尔茨海默病具有重要的价值。     

营养不良可增加幼鼠齿状回颗粒下层的细胞增殖和神经生发(英文)

为了观察营养不良对幼鼠海马齿状回 (DG)和脑室下层 (SVZ)的细胞增殖和神经发生的影响 ,采用 5 -溴 -2 -脱氧尿苷(Brd U)标记结合免疫组织化学方法对脑切片分别进行 Brd U、Tu J1(β tubulin,β微管蛋白 )及 GFAP(胶质纤维酸性蛋白 )反应或双重反应。结果表明 ,营养不良幼鼠齿状回的细胞增殖和神经生发明显高于营养良好的幼鼠而脑室下层的细胞增殖数量在两者却无明显差异。在齿状回 ,新生的细胞中大约有 5 0 %为新生的神经元 ,10～ 2 0 %为神经胶质细胞。本文结果提示 ,幼鼠海马齿状回的细胞增殖和神经生发可能因营养不良而增加 ,这些新生的细胞可能对日后某些海马依赖性行为产生一定的影响     

Neurogenesis of the climbing fibers in the human cerebellum: a Golgi study

The prenatal and early postnatal neurogenesis of the human climbing fibers of the lateral cerebellar hemispheres have been studied, with the rapid Golgi method, and correlated with the developmental stages of Purkinje cells. A transitional phase has been established in the neurogenesis of the human Purkinje cell between the second and third stages of Cajal. This phase coincides with the arrival of the climbing fibers. It is characterized by the reabsorption and subsequent transformation of Purkinje cell's basal dendrites into somatic spines. Following the arrival of the climbing fibers and the establishment of contacts, the Purkinje cell is progressively transformed from an immature stellate and nonoriented cell into a monopolar and spatially oriented one which acquires all of its mature morphological and functional features. The human climbing fibers arrive at the Purkinje cell plate by the 28th week of gestation and establish a transient paraganglionic plexus before contacts with these neurons can be recognized. They start to form pericellular nests by the 29th week, and by the 31st week of gestation all Purkinje cells of the lateral hemispheres have pericellular nests around their bodies. These pericellular nests are progressively and rapidly transformed into supracellular "capuchones" which themselves are also short-lived because the climbing process starts readily in them. Supracellular "capuchones" are recognized by the 34th seek and their fibrils start to climb the dendrites of Purkinje cells (young climbing phase) by the 36th week of gestation. The process of climbing the dendrites of the Purkinje cells will continue through late prenatal and early postnatal life. The human climbing fibers are distributed, in the internal granular layer, within narrow and long vertical territories which are transverse to the long axis of the follium. A single climbing fiber is (1) able to establish contacts with many Purkinje cells located within its narrow territory of distribution; (2) has a tendency to establish contacts with small groups of Purkinje cells rather than with isolate neurons; (3) able to send collaterals to several contiguous cerebellar folia; and (4) able to send collaterals to the internal granular layer and to form pericellular nests in it. The human cerebellum may be considered to be subdivided into a series of parallel, narrow, and transverse structural/functional planes, each one characterized by the distribution of a climbing fiber.(ABSTRACT TRUNCATED AT 400 WORDS)     

Enhanced neurogenesis after transient global ischemia in the dentate gyrus of the rat

The dentate gyrus is one of the few areas of the mammalian brain where new neurons are continuously produced in adulthood. Certain insults such as epileptic seizures and ischemia are known to enhance the rate of neuronal production. We analyzed this phenomenon using the temporary occlusion of the two carotid arteries combined with arterial hypotension as a method to induce ischemia in rats. We measured the rate of cell production and their state of differentiation with a mitotic indicator, bromodeoxyuridine (BrdU), in combination with the immunohistochemical detection of neuronal markers. One week after the ischemic episode, the cell production in dentate gyrus was increased two- to threefold more than the basal level seen in control animals. Two weeks after ischemia, over 60% of these cells became young neurons as determined by colabeling with BrdU and a cytoplasmic protein (CRMP-4) involved in axonal guidance during development. Five weeks after the ischemia, over 60% of new neurons expressed calbindin, a calcium-binding protein normally expressed in mature granule neurons. In addition to more cells being generated, a greater proportion of all new cells remained in the differentiated but not fully mature state during the 2- to 5-week period after ischemia. The maturation rate of neurons as determined by the calbindin labeling and by the rate of migration from a proliferative zone into the granule cell layer was not changed when examined 5 weeks after ischemia. The results support the hypothesis that survival of dentate gyrus after ischemia is linked with enhanced neurogenesis. Additional physiological stimulation after ischemia may be exploited to stimulate maturation of new neurons and to offer new therapeutic strategies for promoting recovery of neuronal circuitry in the injured brain.