Cell and tissue research
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Cell and tissue research · Jun 2009
ReviewRole of neurotrophin signalling in the differentiation of neurons from dorsal root ganglia and sympathetic ganglia.
Manipulation of neurotrophin (NT) signalling by administration or depletion of NTs, by transgenic overexpression or by deletion of genes coding for NTs and their receptors has demonstrated the importance of NT signalling for the survival and differentiation of neurons in sympathetic and dorsal root ganglia (DRG). Combination with mutation of the proapoptotic Bax gene allows the separation of survival and differentiation effects. These studies together with cell culture analysis suggest that NT signalling directly regulates the differentiation of neuron subpopulations and their integration into neural networks. ⋯ Its role in the specification of other neuronal properties is less well analysed. In vitro analysis suggests the involvement of NT signalling in the choice between the noradrenergic and cholinergic transmitter phenotype, in the expression of various classes of ion channels and for target connectivity. In vivo analysis is required to show the degree to which NT signalling regulates these sympathetic neuron properties in developing embryos and postnatally.
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Cell and tissue research · Sep 2007
Photic induction of c-Fos in enkephalin neurons of the rat intergeniculate leaflet innervated by retinal PACAP fibres.
The brain's biological clock, located in the suprachiasmatic nucleus (SCN), is synchronised with the cyclic environment by photic and non-photic cues. Photic information to the SCN is mediated by pituitary adenylate-cyclase-activating polypeptide (PACAP)-containing retinal ganglion cells (RGCs), whereas non-photic input originates primarily from neuropeptide Y (NPY) cells in the ipsilateral thalamic intergeniculate leaflet (IGL). ⋯ In the present study, we have used anterograde tracing from both eyes, bilateral eye enucleation, double-immunofluorescence histochemistry, high-resolution confocal laser scanning microscopy and three-dimensional computer analysis to show that (1) PACAP-containing RGCs project to the IGL and are the only source for the PACAP-immunoreactive fibres in the IGL; (2) a few NPY-containing neurons in the IGL are innervated by PACAP-containing retinal nerve fibres and the contacts are both axodendritic and axosomatic; (3) most enkephalin-immunoreactive neurons in the IGL are innervated by PACAP-containing retinal afferents and the contacts are mainly axodendritic; (4) light stimulation at various time points activates (as evidenced by c-Fos induction) enkephalin-positive neurons but not NPY-immunoreactive neurons. The findings suggest that PACAP-immunoreactive retinal afferents in the IGL primarily innervate enkephalin-immunoactive neurons and that the enkephalin-containing neurons, which project locally and to the contralateral IGL, are activated by light independent of diurnal time.
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Cell and tissue research · Feb 2007
Dermal matrix proteins initiate re-epithelialization but are not sufficient for coordinated epidermal outgrowth in a new fish skin culture model.
We have established a new culture system to study re-epithelialization during fish epidermal wound healing. In this culture system, fetal bovine serum (FBS) stimulates the epidermal outgrowth of multi-cellular layers from scale skin mounted on a coverslip, even when cell proliferation is blocked. The rate of outgrowth is about 0.4 mm/h, and at 3 h after incubation, the area occupied by the epidermal sheet is nine times larger than the area of the original scale skin. ⋯ In addition, the leading-edge cells do not have apparent "purse string"-like actin bundles. The outgrowth stimulated by FBS is inhibited by laminin. These results suggest that dermal substrates such as type I collagen and fibronectin are able to initiate epidermal outgrowth but require other factors to enhance such outgrowth, together with coordinated alterations in cellular phenotype.
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Cell and tissue research · Oct 2006
Localization of cholinergic innervation and neurturin receptors in adult mouse heart and expression of the neurturin gene.
Neurturin (NRTN) is a neurotrophic factor required during development for normal cholinergic innervation of the heart, but whether NRTN continues to function in the adult heart is unknown. We have therefore evaluated NRTN expression in adult mouse heart and the association of NRTN receptors with intracardiac cholinergic neurons and nerve fibers. Mapping the regional distribution and density of cholinergic nerves in mouse heart was an integral part of this goal. ⋯ GFRalpha2 was present in most cholinergic nerve fibers and in Schwann cells and their processes throughout the heart. Some cholinergic nerve fibers, such as those in the sinus node, also exhibited Ret immunoreactivity. These findings provide the first detailed mapping of cholinergic nerves in mouse heart and suggest that the neurotrophic influence of NRTN on cardiac cholinergic innervation continues in mature animals.
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During the last decade deep brain stimulation (DBS) has become a routine method for the treatment of advanced Parkinson's disease (PD), leading to striking improvements in motor function and quality of life of PD patients. It is associated with minimal morbidity. The rationale of targeting specific structures within basal ganglia such as the subthalamic nucleus (STN) or the internal segment of the globus pallidus (GPi) is strongly supported by the current knowledge of the basal ganglia pathophysiology, which is derived from extensive experimental work and which provides the theoretical basis for surgical therapy in PD. ⋯ The main hypotheses for the mechanism of high-frequency stimulation are: (1) depolarization blocking of neuronal transmission through inactivation of voltage dependent ion-channels, (2) jamming of information by imposing an efferent stimulation-driven high-frequency pattern, (3) synaptic inhibition by stimulation of inhibitory afferents to the target nucleus, (4) synaptic failure by stimulation-induced neurotransmitter depletion. As the hyperactivity of the STN is considered a functional hallmark of PD and as there is experimental evidence for STN-mediated glutamatergic excitotoxicity on neurons of the substantia nigra pars compacta (SNc), STN-DBS might reduce glutamatergic drive, leading to neuroprotection. Further studies will be needed to elucidate if STN-DBS indeed provides a slow-down of disease progression.