Restorative Neurology and Neuroscience - Volume 16, issue 2

Authors: Fansa, Hisham | Keilhoff, Gerburg | Horn, Thomas | Altmann, Silke | Wolf, Gerald | Schneider, Wolfgang

Article Type: Research Article

Abstract: Purpose: Nerve allografts are highly antigenic and, thus, require the continuous use of immunosuppressive drugs. FK 506 was found to pre-vent rejection successfully. However, clinically neurotoxic complications have been noted in the central and peripheral nervous system although an increased rate of axonal regeneration has also been shown after nerve crush experiments. To investigate whether a possible regeneration pro-moting potency of FK 506 is determined via an influence on Schwann cells, Schwann cells were cultured from …the sciatic nerve of the rat. Methods: The effect of 100 µM FK 506 administered daily on these cultures was assessed microscopically over a period of seven days and compared to an untreated control group of cultures. Additionally, the changes in intracellular calcium were recorded using a laser scanning microscope. In vivo regeneration of autologous rat sciatic nerve grafts was assessed clinically, histologically and morphometrically after two and six weeks. The animals received a daily administration of 0.6 mg FK 506/kg body weight, the control received saline. Results: In vitro FK 506 increased the Schwann cell number in culture significantly compared to non treated cultures, while the fibrocyte population was decreased. FK 506 caused a transient increase of intracellular calcium levels in cultured cells. In vivo, a significantly higher axon count was observed in the FK 506 treated grafts after two weeks regeneration compared with controls. Good regeneration was noted in all grafts after six weeks regeneration. Conclusions: The increased axon counts and decreased myelin debris in the FK 506 grafts after two weeks indicate an accelerated Wallerian degeneration and increased axon sprouting into the graft initially. The inhibition of calcineurin activity is not the mediator of the neurotrophic effect. FK 506 promotes axonal regeneration through binding to FKBP-12. The increase of intracellular calcium may induce Schwann cell pro-liferation via calmodulin. The therapeutic relevance for autologous nerve grafting, however, has to be defined in further studies. Show more

Keywords: FK 505, immunosuppression, Schwann cell, intracellular calcium, nerve graft, axonal regeneration

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 77-86, 2000

Authors: Dietrich, A. | Fülöp, Z.L. | Chambers, M. D. | Darrell, R.S. | Stein, D.G.

Article Type: Research Article

Abstract: Purpose: Ginkgo biloba extract (EGb 761) has been shown to facilitate behavioral and neuro-morphological recovery from brain injury, but less is known about its effects on glia. Since gliosis may be an important component of the recovery process, we tested the hypothesis that EGb 761 alters the time course and development of microglial activation and astrocytosis after brain injury. Methods: Rats were treated with either saline or EGb 761 and killed at 2 hrs, 1, 3, …7, and 14 days following unilateral entorhinal cortex (EC) lesions. Microglia and their precursors were visualized with a silver impregnation method, and astrocytes with GFAP. Results: Blood-borne monocytes/macrophages were seen as early as 2 hrs after injury in all animals. The side contralateral to the injury showed minimal microglial activation and there were no significant effects of drug treatment. On the side ipsilateral to the lesion EGb 761 enhanced microglial activation at 3, 7, and 14 days in the molecular layer and the hilus of the dentate gyrus; the areas of most profound deaf-ferentation after EC injury. Regions of the corpus callosum also showed enhanced microglial activation over the same time course. Reactive astrocytes were stained with GFAP and were found to be more numerous than activated microglia, particularly in the ipsilateral corpus callo-sum. EGb 761 treatment enhanced astrocytosis at 3 days in the molecular layer, the hilus, and the corpus callosum on the ipsilateral side. Conclusions: Taken together our results show that EGb 761 enhances, accelerates and prolongs the activation of microglia and astrocytosis at the site of injury. Show more

Keywords: Ginkgo biloba, microglia, astrocyte, neuronal death, entorhinal cortex, traumatic brain injury, stereology

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 87-96, 2000

Authors: Schneider, J.S. | Rothblat, David S.

Article Type: Research Article

Abstract: Purpose: This study was designed to assess differences in dopamine clearance rates and potassium chloride (KCl)-stimulated release in the striatum of cats that had either spontaneously recovered from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced Parkinsonism or recovered after receiving GM1 ganglioside treatment. Methods: A severe Parkinsonian motor disorder was produced in 17 adult cats by administration of MPTP for seven to ten days. Six MPTP-treated cats received daily GM1 administration (30 mg/kg, i.m.) for 6 weeks and …eleven MPTP-treated cats were allowed to spontaneously recover over the same period of time. High-speed chronoamperometric electrochemical measurements were obtained from dorsal and ventral striatal regions in all animals. Dopamine clearance rates were obtained by measuring the clearance of pressure-ejected dopamine from the extracellular space and local potassium-induced release was studied by applying KCl to the tissue. Results: Dopamine clearance rates recorded in all striatal areas in GM1-treated cats were significantly faster than dopamine clearance rates recorded in spontaneously recovered cats. In GM1-treated animals, electrochemical signals recorded in response to KCl stimulation were sig-nificantly greater in all striatal areas compared to spontaneously recovered animals. Reduction/oxidation (redox) ratios recorded in GM1- treated animals indicated dopamine to be the predominant electroactive species released in all striatal areas in response to KCl stimulation. Redox ratios recorded in the ventral striatum of spontaneously recovered cats also indicated dopamine to be the predominant electroactive spe-cies released in response to KCl stimulation. However, redox ratios recorded in the dorsal striatum of spontaneosuly recovered cats indicated serotonin to significantly contribute to the recorded signal. Conclusions: These results support previous observations that volume transmission may predominate dopaminergic signaling in the stria-tum of spontaneously recovered cats and suggest that a greater degree of synaptic transmission is possible in GM1-treated animals. While the functional significance of this partial restoration of dopaminergic synaptic transmission in the striatum remains to be determined, it may under-lie improved behavioral recovery observed following GM1 treatment. Show more

Keywords: Parkinsonism, MPTP, dopamine, GM1, ganglioside, striatum

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 97-104, 2000

Authors: Chau, Wai Kei | So, Kwok-Fai | Tay, David | Dockery, Peter

Article Type: Research Article

Abstract: Purpose: In the present study we have morphometrically examined a regeneration model in which axons normally residing in CNS have regrown and are interacting with Schwann cells from the PNS. This study will not only provide morphometric data on regenerated optic fibers but also shed light on possible factors in determining the fiber morphometry. Methods: The optic nerves of rats aged 6 weeks were cut intra-orbitally and replaced with a autologous sciatic nerve. After a survival …period of 9 months, the graft or regenerated nerves containing the regenerated optic axons and Schwann cells were processed for morphometric measurements. Results: The mean myelinated axon diameter of regenerated nerve (1.8 ± 0.2 µm) was significantly (P < 0.05) greater than that of the optic nerve (0.9 ± 0.03 µm). However, unmyelinated regenerated optic axons had a smaller mean axon diameter (0.49 ± 0.04 µm) than normal myelinated optic axons. This may suggest that myelinating glial cells exert an influence on axon caliber and Schwann cells seem to have greater effect than oligodendrocytes. The mean g-ratio showing the relative myelin sheath thickness was found to be the highest in the optic nerve (0.78 ± 0.003), least in the sciatic nerve (0.6 ± 0.009) and intermediate in the regenerated nerve (0.68 ± 0.01). The results indicated that Schwann cells myelinating the regenerated optic axons have produced a thinner myelin sheath. Intra-axonally, no significant difference was detected in the number of axonal microtubules and neurofilaments between the regenerated and optic nerves. Therefore the disposition of microtubules and neurofilaments into axon may be intrinsically determined. Conclusions: In this study, we have identified some of the extrinsic and intrinsic factors in determining the fiber morphometry of the regen-erated nerve. The axon-size and myelination by glial cells were determined through the external axon-glial interactions, whereas the number of axonal microtubules and neurofilaments were intrinsically determined. Show more

Keywords: Optic nerve, regenerated optic axons, schwann cells, axon-glial interaction, g-ratio, microtubules, neurofilaments

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 105-116, 2000

Authors: Dohm, Stephan | Streppel, Michael | Guntinas-Lichius, Orlando | Pesheva, Penka | Probstmeier, Rainer | Walther, Michael | Neiss, Wolfram F. | Stennert, Eberhard | Angelov, Doychin N.

Article Type: Research Article

Abstract: Purpose: A major reason for the poor functional recovery after peripheral nerve injury is the outgrowth of supernumerary axonal branches at the lesion site. Projecting within several nerve fascicles, the branches of one axon often re-innervate synchronously muscles with antagonis-tic functions and impair any coordinated activity. We hypothetized that accelerated axonal elongation through extracellular matrix proteins fos-tering neurite outgrowth might reduce axonal branching and improve recovery of function. Methods: In a control …group of rats, ramus zygomaticus, ramus buccalis, and ramus marginalis mandibulae of the facial nerve were transected and the stumps labeled with DiI, Fluoro-Gold (FG), and Fast Blue (FB). Results: Neuron counts showed that the zygomatic ramus contained axons of 204 ± 88 DiI-labeled motoneurons in the dorsal facial subnu-cleus. No perikarya were labeled by 2 or 3 tracers. After transection and suture of the facial nerve trunk, the zygomatic ramus contained axons of 328 ± 50 motoneurons dispersed throughout the whole facial nucleus. The occurrence of double-labeled (DiI+FG and DiI+FB) motoneu-rons showed that about 30 % of all axons in the zygomatic ramus had a twin branch projecting within the buccal and/or mandibular ramus. Conclusions: Entubulation of transected facial nerve in a silicone tube containing phosphate buffered saline, collagen type I, laminin, fibronectin, or tenascin did not reduce the portion of double-labeled motoneurons. We conclude that (i) axonal branching follows a rather con-stant pattern regardless of changes in the local microenvironment; (ii) despite their known effect to support neurite outgrowth, all tested extra-cellular matrix proteins do not suppress axonal branching in the rat facial nerve model. Show more

Keywords: Retrograde tracing, DiI, Fast Blue, Fluoro-Gold, neuron number, collagen, laminin, fibronectin, tenascin

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 117-126, 2000

Authors: ODell, Dianne M. | Muir, Judith K. | Zhang, Chen | Bareyre, Florence M. | Saatman, Kathryn E. | Raghupathi, Ramesh | Welsh, Frank | McIntosh, Tracy K.

Article Type: Research Article

Abstract: Purpose: One of the downstream consequences of glutamate-induced NMDA (N-methyl-D-aspartate) receptor activation following trau-matic brain injury (TBI) is production of nitric oxide (NO). In this study, we evaluated the ability of lubeluzole, a novel neuroprotective com-pound which downregulates the glutamate-activated nitric oxide pathway and blocks sodium and voltage-sensitive calcium channels, to improve behavioral and histological outcome in rats following TBI. Methods: Rats were anesthetized and subjected to moderate lateral fluid percussion brain …injury (2.42.6 atm) or were surgically prepared but not injured (sham). Fifteen minutes after injury, animals received a bolus of either vehicle (n = 12 injured, n = 14 uninjured) or lubeluzole (0.31 mg/kg, n = 12 injured, n = 8 uninjured) through the jugular vein followed by a one hour infusion of vehicle or lubeluzole (0.31 mg/kg). Animals were tested at 48 hours post-injury for cognitive performance in the Morris water maze, neuromotor function, and limb placing func-tion, and then sacrificed. Results: While brain injury resulted in significant cognitive and motor deficits, injured animals treated with lubeluzole did not differ in spa-tial memory performance, neuromotor score, or limb placing function from injured, vehicle-treated animals. Furthermore, there was no differ-ence in the mean number of ipsilateral hippocampal CA3 neurons between injured rats treated with vehicle and those treated with lubeluzole. Conclusions: This single-dose study failed to demonstrate a beneficial effect of lubeluzole on the acute behavioral or histological sequelae following TBI. Show more

Keywords: Hippocampus, lubeluzole, Morris water maze, nitric oxide, traumatic brain injury

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 127-134, 2000

Authors: Przedborski, Serge | Jackson-Lewis, Vernice | Djaldetti, Ruth | Liberatore, Gabriel | Vila, Miquel | Vukosavic, Slobodanka | Almer, Gabrielle

Article Type: Research Article

Abstract: MPTP causes damage to substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons as seen in Parkinsons disease (PD). After sys-temic administration of MPTP, its active metabolite, MPP + , accumulates within SNpc DA neurons, where it inhibits ATP production and stim-ulates superoxide radical formation. The produced superoxide radicals react with nitric oxide (NO) to produce peroxynitrite, a highly reactive tissue-damaging species that damages proteins by oxidation and nitration. Only selected proteins appear …nitrated, and among these, is found tyrosine hydroxylase (TH), the rate limiting enzyme in DA synthesis. The process of nitration inactivates TH and, consequently dopamine pro-duction. Peroxynitrite also nicks DNA, which, in turn, activates poly(ADP-ribose) polymerase (PARP). PARP activation consumes ATP, and thus acutely depletes cell energy stores. This latter event aggravates the preexisting energy failure due to MPP + -induced mitochondrial respira-tion blockade and precipitates cell death. Altogether, these findings support the view that MPTPs deleterious cascade of events include mito-chondrial respiration deficit, oxidative stress, and energy failure. Because of the similarity between the MPTP mouse model and PD, it is tempting to propose that a similar scenario applies to the pathogenesis of PD. Show more

Keywords: Free radicals, MPTP, neurodegeneration, NO, Parkinsons disease, poly(ADP-ribose) polymerase, tyrosine hydroxylase

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 135-142, 2000

Authors: Jain, S. | Mathur, R. | Sharma, R. | Nayar, U.

Article Type: Research Article

Abstract: Purpose: Amygdala plays a very important role in the mediation of emotional and affective components of pain. Bilateral amygdalectomy increases the threshold for vocalization, a measure of emotional reactivity, without any change in the tail flick latency. The present work was designed to study the recovery of emotional nociceptive behaviour following neural tissue transplantation in lesioned rats. Methods: In a group of adult wistar rats lesions of the central nucleus of amygdala (CeA) were produced …electrolytically. In a separate group of rats amygdalar tissue was transplanted at the lesioned site 2 days thereafter. The vocalization tests, viz. simple vocalization (SV) and vocalization after discharge (VA), which were used to study the emotional nociceptive behaviour were carried out both before and after pro-ducing lesion/transplant. Results: Bilateral CeA lesions increased the thresholds for SV and VA significantly (p < 0.001), indicating analgesia. Following amygdalar tissue transplantation a significant decrease (p < 0.05) in the thresholds were observed when compared with the lesioned group, although when compared with the basal data it showed an increase (p<0.05). Conclusions: The results indicate a partial recovery of the vocalization response following amygdalar tissue transplantation. Show more

Keywords: Amygdala, nociception, simple vocalization, vocalization after discharge, amygdalar tissue transplant

Citation: Restorative Neurology and Neuroscience, vol. 16, no. 2, pp. 143-147, 2000