Aurora Del Fa

Effects of L-carnitine, L-acetylcarnitine and gangliosides on the regeneration of the transected sciatic nerve in rats

Three pharmacological agents, L-carnitine, L-acetylcarnitine and gangliosides, were tested for their ability to enhance the regeneration of the rat sciatic nerve following transection and microsurgical repair. The drugs were administered intraperitoneally at the dose of 50 mg/kg/d for 28 and 56 d postoperatively. At the end of treatment, the motor function recovery of the peroneal component of the sciatic nerve was assessed and the regenerated nerves were analysed morphometrically on histological semi-thin sections. Also, the reinnervated extensor digitorum longus (EDL) muscles were studied histochemically using the adenosine-triphosphatase (ATP-ase) technique 56 d after surgery. Motor function assessment at 56 d after nerve repair revealed that L-acetylcarnitine-treated animals recovered a clinical grade significantly higher (p less than 0.05) than the control animals. Twenty-eight days after nerve repair, the number of myelinated fibres was significantly higher (p less than 0.05) in L-acetylcarnitine and ganglioside-treated animals than in control animals. However, 56 d after nerve repair the number of regenerated fibres in all the drug-treated groups was not significantly different from that of the control group. The EDL muscles of the drug-treated animals did not show significant differences from those of control animals with respect to fibre composition and fibre diameter although the L-acetylcarnitine-treated animals exhibited a significantly lower (p less than 0.05) degree of muscle atrophy than did the control animals. The results of the present work seem to indicate that L-acetylcarnitine and to a lesser extent gangliosides exert some favourable effect on the regeneration of the transected sciatic nerve in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Canine cognitive dysfunction and the cerebellum: Acetylcholinesterase reduction, neuronal and glial changes

The specific functional and pathological alterations observed in Alzheimers disease are less severe in the cerebellum than in other brain areas, particularly the entorhinal cortex and hippocampus. Since dense core amyloid-beta plaque formation has been associated with an acetylcholinesterase heterogeneous nucleator action, we examined if an acetylcholinesterase imbalance was involved in cerebellum plaque deposition. By using the canine counterpart of senile dementia of the Alzheimers type, a promising model of human brain aging and early phases of Alzheimers disease, we investigated how cerebellar pathology and acetylcholinesterase density could be related with cognitive dysfunction. As in Alzheimers disease, the late affectation of the cerebellum was evidenced by its lack of amyloid-beta plaque and the presence of diffuse deposition throughout all cortical grey matter layers. The highest acetylcholinesterase optic density corresponded to cerebellar islands of the granular layer and was predominantly associated with synaptic glomeruli and the somata of Golgi cells. Its reduction correlated with aging and loss of granule cells, whereas cognitive deficit only correlated with loss of Purkinje cells. The observed Bergmann glia alterations may correspond to a reactive response to the loss and damage of the Purkinje cells, their specific neuronal partner. Regarding the role of acetylcholinesterase mediation in amyloid-beta deposition, our data argue against an interaction between these two proteins because acetylcholinesterase reduction correlates with aging but not with cognitive deficit. Finally, our data support the use of companion dogs of all breeds to study aging and early phases of Alzheimers disease.

Reelin is transiently expressed in the peripheral nerve during development and is upregulated following nerve crush

Reelin is an extracellular matrix protein which is critical for the positioning of migrating post-mitotic neurons and the laminar organization of several brain structures during development. We investigated the expression and localization of Reelin in the rodent peripheral nerve during postnatal development and following crush injury in the adult stage. As shown with Western blotting, immunocytochemistry and RT-PCR, Schwann cells in the developing peripheral nerve and in primary cultures from neonatal nerves produce and secrete Reelin. While Reelin levels are downregulated in adult stages, they are again induced following sciatic nerve injury. A morphometric analysis of sciatic nerve sections of reeler mice suggests that Reelin is not essential for axonal ensheathment by Schwann cells, however, it influences the caliber of myelinated axons and the absolute number of fibers per unit area. This indicates that Reelin may play a role in peripheral nervous system development and repair by regulating Schwann cell-axon interactions.

Developmental distributive pattern of acetylcholinesterase in chick embryo ciliary ganglion

AChE cytochemistry was performed in the chick ciliary ganglion (CG) during various embryonic stages. AChE first appeared in the RER of the neurons at 5 days of incubation (d.i.). Synaptic AChE appeared only later, parallely to the appearance of the calyciform synapses, i.e. at 9 d.i. At first AChE was mainly localized at the calyx side facing the satellite cell, thereafter extending to the neuronal side and especially labeling synaptic contacts occurring at points along the presynaptic membrane. Finally, at 15 d.i., i.e. when the calyx is morphologically mature, AChE reaction labels the whole contour of the calyciform nerve terminal. At 10 d.i., limited AChE-positive extrasynaptic areas of the ciliary neurons surface first appeared, thereafter extending up to affect at 15 d.i. large neuronal surfaces. Some hypotheses can be drawn from our results: (i) the earliest appearance of cytoplasmic AChE seems somehow independent of the establishing of functional synaptic contacts; (ii) the pattern of development of neuronal AChE suggests the existence of a sort of transynaptic control by presynaptic nerve terminals. However, it is possible that concomitant retrograde iris-dependent influences on ganglionic AChE concur in modulating neuronal AChE; (iii) the functional role possibly played by AChE localized at extra-synaptic level still remains to be clarified.

Aquaporin 4 expression increases in the rat hippocampus and cortex during trimethyltin-induced neurodegeneration

Trimethyltin (TMT) is a neurotoxicant know to produce significant and selective neuronal degeneration in the rodent CNS (for review, 1). Magnetic resonance imaging (MRI) investigation in TMT-treated rats has evidenced dilation of lateral ventricles, possibly correlated to alterations in blood brain barrier permeability .In order to explore the molecular mechanisms involved in the phenomenon we have investigated in the hippocampus and cortex of TMT-treated rats the expression of aquaporin 4 (AQP4), a glial water channel protein believed to play a role in brain oedematous conditions. AQP4 expression was tested both by real-time PCR and western blotting analysis in hippocampus and cortex homogenates. To confirm molecular results and visualize the AQP4 cell distribution double-label immunofluorescence for AQP4 and GFAP was performed. Real-time PCR and western blotting data show a significant upregulation of AQP4 starting from 14 days of TMT treatment both in the hippocampus and the cortex. Accordingly, the immunofluorescence shows an intense astrogliosis and AQP4 immunoreactivity diffusely pronounced in the hippocampal and cortex areas starting from 14 days after intoxication. In particular, AQP4 immunolabelling was localized in astrocytic end-feet encircling the blood vessels. The study of the Rhodamine B fluorescent tracer, intraperitoneally administered, also revealed an intense vascular reaction, characterized by hypertrophic vessels with abnormal course and dimensions in the brain of TMT-treated rats, indicating a vascular involvement in the TMT-induced neurodegenerative processes.. AQP4 over-expression and astrogliosis occurring in the brain of TMT-treated rats might putatively play a role in alterations of vascular permeability and brain oedema formation evidenced by MRI studies.

Aquaporin 4 (AQP4) expression and blood brain barrier damage in an experimental model of neurodegeneration induced by trimethyltin

Trimethyltin (TMT) is well known to produce a distinct pattern of selective neuronal degeneration in the rodent CNS. TMT intoxication is also an important factor linked to induction of brain edema. Aquaporin-4 (AQP4), a water transporting protein, is thought to be the primary route through which water moves in and out astrocytes, is over-expressed in some pathological conditions, and is considered a marker of vascular permeability. The aim of our study was to investigate the integrity of the blood brain barrier (BBB), and the expression of AQP4 in astrocytes, after TMT intoxication. The brains of adult female Wistar rats, treated and untreated with TMT, were isolated and consecutive coronal sections obtained with a vibratome were incubated with primary fluorescent antibodies AQP4-Ig goat and GFAP-Ig rabbit. Imaging of fluorescence was performed on a confocal laser scanning microscope (Zeiss). In addition, dissected hippocampi and cortex were homogenized and the proteins were separated by SDS-PAGE. Although data in literature document absence of alterations of the BBB in TMT treated rats, our preliminary published data of the MRI investigation with Gd-DTPA suggested the presence of such alterations that concur with the passage of contrast into the damaged tissue. We have analyzed the AQP4 expression 7, 14, 21 and 35 days after TMT exposure. Immunofluorescence and Western Blotting analysis have showed an upregulation of the AQP4 in astrocytes after TMT intoxication., the expression levels of which progressively increased after TMT exposure, both in hippocampus and in brain cortex. All the data suggest that the astrocytes and their AQP4 protein are involved in the brain edema formation and in the possible alteration of the vascular permeability, in this TMT model of neurodegeneration.