Neuronal differentiation

The most significant of the abnormalities observed in a hypothyroid brain is a hypoplastic neuropile, i.e., a marked reduction in the number of connections between neurons [102], This has been observed both in the cerebrum and the cerebellum. For instance a permanent and dramatic reduction in the arborization of the dendritic tree of the Purkinje cell is observed in the hypothyroid cerebellum [103]. The length of the primary dendritic trunk is increased and a deficit in the number, density and branching of the dendritic spines is noticed. In contrast neonatal hyperthyroidism accelerates development of spines. Similar findings have been reported for the cerebrum, i.e., reduction in length and branching of pyramidal neurons, of the density of axonal terminals and of the number of spines [102], 

Direct counting of the microtubules present both in the dendrites of the Purkinje cells [118] and in the sciatic nerve [119] have recently confirmed that hypothyroidism markedly decreases microtubule assembly and/or stability. 

Little is known about the mechanism of action of thyroid hormones on microtubule assembly. It might be that, as in other cell types, thyroid hormones regulate the expression of the specific TAU mRNAs and/or their accumulation. One has also to take into account that a large number of other molecules are required to build up neurites during neuronal differentiation (membranes, components of the growth cone, etc.). 

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Jia C. and Halpem M. (1996). Subclasses of vomeronasal receptor neurons differential expression of G-proteins (Gi-alpha2 Go-alpha) and segregated projections to the accessory olfactory-bulb. Brain Res 719, 117-128. 

Neary JT Department of Veterans Affairs, Medical Center, Miami, FL Effects of lead on nerve growth factor-induced neurite outgrowth and branching due to an interaction of lead with signal transduction mechanisms important for neuronal differentiation Department of Veterans Affairs, Research and Development... 

Zawia NH, Harry GJ. 1996. Developmental exposure to lead interferes with glial and neuronal differential gene expression in the rat cerebellum. Toxicol Appl Pharmacol 138 43-47. 

As to the primary developmental actions of testosterone, growth and differentiation appear to be involved. Testosterone or estradiol stimulates outgrowth of neurites from developing hypothalamic neurons that contain estrogen receptors [14, 15]. This is believed to be one of the principal aspects of testosterone action that increases the number and the size of neurons within specific hypothalamic nuclei in males, compared to females [1, 14, 15]. 5a-DHT may have a similar effect on androgen-sensitive neurons. Differentiation of target neurons also occurs in adult brain tissue, hormones like estradiol can evoke responses that differ between adult male and female rats [1,14,15],... 

Inokoshi J, Katagiri M, Arima S, Tanaka H, Hayashi M, et al. 1999. Neuronal differentiation of Neuro 2a cells by inhibitors of cell cycle progression, trichostatin A and butyr-olactone I. Biochem Biophys Res Commun 256 372-376. 

Makeyev EV, Zhang J, Carrasco MA et al (2007) The MicroRNA miR-124 promotes neuronal differentiation by triggering brain-specific alternative pre-mRNA splicing. Mol CeU 27 435-448... 

Fricker, R.A., Carpenter, M.K., Winkler, C., Greco, C., Gates, M.A., and Bjorklund, A. (1999) Site-specific migration and neuronal differentiation of human neural progenitor cells after transplantation in the adult rat brain. / Neurosci 19 5990-6005. 

Chao MV Neurotrophic receptors a window into neuronal differentiation. Neuron 9 583-593, 1992... 

Young, M.J., Ray, J., Whiteley, S.J., Klassen, H., Gage, F.H. (2000). Neuronal differentiation and morphological integration of hippocampal progenitor cells transplanted to the retina of immature and mature dystrophic rats. Mol Cell Neurosci, 16, 197-205. 

Tozuka, Y., Fukuda, S., Namba, T. (2005) GABAergic excitation promotes neuronal differentiation in adult hippocampal progenitor cells. Neuron 47, 803-15. 

Y. Nagai and S. Tsuji, Significance of ganglioside-mediated glycosignal transduction in neuronal differentiation and development, Prog. Brain Res. 101 119 (1993). 

Novitskaya V, Grigorian M, Kriajevska M, Tarabykina S, Bronstein I, Berezin V, Bock E, Lukanidin E. 2000. Oligomeric forms of the metastasis-related Mtsl (S100A4) protein stimulate neuronal differentiation in cultures of rat hippocampal neurons. J Biol Chem 275(52) 41278 11286. 

PEDF, first purified from human retinal pigment epithelial cultures as a factor that induces neuronal differentiation of cultured retinoblastoma cells (Tombran-Tink et al., 1991 Steele et al., 1993), has been recently shown to regulate normal angiogenesis in the eye (Dawson et al., 1999). PEDF is found both intracellularly and extracellularly in the fetal and early adult eye but is lost at the onset of senescence (Becerra, 1997 Araki et al., 1998). It is down-regulated by hypoxia and induced in the retina as a result of... 

The biochemistry of odor detection involves at least three types of protein odor receptors (ORs) odorant binding proteins (OBPs) and odor degrading enzymes (ODEs). ORs are expressed by olfactory receptor neurons (ORNs) and localized in the membranes of the ciliated dendrites (Figure 14.1). The result of detection is translated into neuronal electrical activity by transductory proteins. But while transductory proteins are more or less common for all olfactory neurons, differential expression of ORs, OBPs and ODEs allows the neurons to detect specific odor molecules. 

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