Restorative Neurology and Neuroscience - Volume 3, issue 2

Authors: Goldstein, Murray

Article Type: Other

DOI: 10.3233/RNN-1991-3201

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 53-53, 1991

Authors: Cassel, J.C. | Kelche, C. | Will, B.E.

Article Type: Research Article

Abstract: Long-Evans female rats sustained aspirative lesions of the fimbria-fornix pathways and part of the overlying structures (Lesion). Eight or 9 days later, one third of these lesioned rats received intrahippocampal septal cell suspension grafts (Sept-G) and another third received grafts of hippocampal origin (Hipp-G). Sham-operated rats (Sham) served as controls. For each surgical treatment, 3 subgroups were assigned to one of 3 experiments which differed by the delay separating grafting from testing. Three months (EXP1), seven months (EXP2) and twelve months (EXP3) after grafting, rats were tested for reactivity to pentylenetetrazol (PTZ, 30 mg/kg, i.p.) and to sound (10–20 kHz …peaks, 120 dB, 90 s), two models of generalized convulsive seizures. Three months after grafting, lesion-only rats showed increased reactivity to PTZ as compared to Sham rats; both types of grafts (Sept-G, Hipp-G) attenuated this lesion-induced effect. Whether 7 or 12 months after grafting, no significant between-group differences were observed anymore. Three months after grafting, reactivity to sound tended to increase in lesion-only rats and was significantly increased in both groups with grafts (Sept-G, Hipp-G) as compared to the Sham group. Seven months after grafting, only Hipp-G rats showed increased reactivity to sound compared to Sham or lesion-only rats. No significant between-group difference was observed at 12 months post-grafting. At all 3 delays, histological analyses revealed well integrated grafts, but only septal grafts provided the denervated hippocampus with an AChE-positive fiber ingrowth. Reactivity to PTZ or to sound was correlated neither with the size of the graft, nor with the acetylcholinesterase (AChE)-positive graft-derived reinnervation of the dorsal hippocampus. The present results suggest that hippocampal denervation may result in a temporary increase in reactivity to PTZ and susceptibility to sound, the former being transitorily attenuated and the latter being transitorily increased by both kinds of grafts. Our data confirm earlier reports showing that grafts may influence sensitivity to convulsive seizure-inducing treatments. In addition, these data indicate that this influence is not necessarily lasting and that the kind and duration of this influence is dependent upon the model of convulsive seizures used. Show more

Keywords: Audiogenic seizure, Septohippocampal lesion, Hippocampal graft, Pentylenetetrazol, Behavioral seizure, Septal graft

DOI: 10.3233/RNN-1991-3202

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 55-64, 1991

Authors: Carter, Deborah A. | Lisney, S.J.W.

Article Type: Research Article

Abstract: Counts of myelinated and unmyelinated axon profiles have been made from normal, uninjured rat sural nerves and from nerves injured 6 months earlier in one of two ways. In one group of rats the nerve was simply cut and left to regenerate, leading to the development of a neuroma in continuity, while in the second group the nerve was cut but then ligated as well to prevent regeneration; this led to stump neuroma formation. After nerve transection and regeneration, with subsequent formation of a neuroma in continuity, there was no change in the number of myelinated axon profiles found 25 …mm proximal to the old injury site when compared with control, but there was an 18% reduction (P < 0.05) in the number of unmyelinated axon profiles. Immediately proximal to the injury site the picture was similar, with there still being the same number of myelinated axon profiles as in control material but here the reduction in unmyelinated axon numbers was slightly greater at 24% (P < 0.05). In the proximal part of nerves that had been cut and stump neuroma formation induced there was a large increase (33%) in myelinated axon profiles over and above control values (P < 0.001) but the number of unmyelinated profiles was the same as in controls. Closer to the stump neuroma the number of myelinated axon profiles had increased yet further to be 88% (P < 0.001) above control while the number of unmyelinated ones remained no different from control. Our interpretation of these results is that after nerve transection and regeneration there is no loss of peripheral neurons supporting myelinated axons but some loss of those supporting unmyelinated ones. If a cut nerve is prevented from regenerating and a stump neuroma forms, however, a vigorous sprouting response is triggered in neurons with myelinated axons while those supporting unmyelinated axons are possibly prevented from dying. The reaction of peripheral neurons to injury is such that the number of axons they support varies along the nerve as one goes disto-proximally away from the injury site. Thus discrepancies in results from different laboratories have come about because material for axon counting has been taken from different points along the nerve relative to the injury site and also because the material has been taken from nerves injured in different ways. Show more

Keywords: Nerve regeneration, Myelinated axons, Unmyelinated axons, Neuroma formation, Axon sprouting

DOI: 10.3233/RNN-1991-3203

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 65-73, 1991

Authors: Romano, Victor M. | Blair, Sidney J. | Kerns, James M. | Wurster, Robert D.

Article Type: Research Article

Abstract: Regeneration of severed rat tibial nerves was functionally and morphologically compared with repair following the use of 3 anastomosis techniques: collagen guide tubes, fibrin glue and conventional microsurgical sutures. In addition, one tibial nerve was crushed in some rats. At ten weekly intervals, functional recovery, assessed by sciatic nerve stimulated evoked contraction of the flexor digitorum muscle, was quicker and more complete following nerve crush than following the anastomosis techniques which were not different from each other. Ten weeks following the surgery, the retrograde transport morphological technique indicated that the anastomosis techniques were not different from each other. The number …of labeled tibial motoneurons (tube and suture groups) was significantly less than the crush group, but the glue group was intermediate. Thus, although having less extensive recovery following crush, the quicker and easier techniques of nerve repair, i.e., collagen tubes or fibrin glue, produced comparable anatomical and functional recovery as the more time-consuming, technically demanding microsurgical repair with fine sutures. Show more

Keywords: Fibrin glue, Bioresorbable tubing, Peripheral nerve regeneration

DOI: 10.3233/RNN-1991-3204

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 75-80, 1991

Authors: Hines, Michael | Shrager, Peter

Article Type: Research Article

Abstract: Conduction in demyelinated and remyelinating axons has been simulated with a computational model. The calculations made use of recent determinations of ionic channel densities in the internodal axolemma of Xenopus fibers. Several new morphological measurements reduced the number of parameters not directly obtained from experimental data. Action potentials and ionic currents were calculated for a wide range of fiber diameters and internodal lengths. The earliest stage of remyelination, characterized by Schwann cell attachment and extension of processes, was simulated by covering just a small percentage of the internode by a single cell layer. Conduction invariably failed if the internodal Na+ …channel density was zero. The minimum density required for successful propagation agreed well with that measured in loose patch clamp experiments. Lateral diffusion of Na+ channels from nodes of Ranvier into the demyelinated internode did not restore conduction in blocked axons, and this was true regardless of the initial internodal Na+ channel density. Decreases in the internodal K+ channel density improved the safety factor for conduction, but this was significant only in the largest axons. Simulating minimal paranodal demyelination by eliminating the axo-glial junctional seals did not result in conduction block, but did produce large conduction delays. Show more

Keywords: Multiple sclerosis, Channels, Demyelinated, Axons, Conduction

DOI: 10.3233/RNN-1991-3205

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 81-93, 1991

Authors: Woerly, Stéphane | Marchand, Raymond

Article Type: Short Communication

Abstract: Collagen chondroitin-6-sulfate hydrogels containing embryonic striatal neurons were implanted into premade brain cavities of the rat striatum. The bioimplant was progressively transformed into a new matrix mostly by the deposition of newly formed collagen and by the ingrowth of glial cells and glial cell processes. At two months, the new matrix has partly restructured the lesion cavity. Cells co-implanted with the hydrogels attached, survived and differentiated while nerve fibers of the host striatum grew into the biomatrix.

Keywords: Collagen matrix, Chondroitin sulfate, Neural graft, Regeneration, Astrocyte, Glial repair

DOI: 10.3233/RNN-1991-3206

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 95-99, 1991

Authors: Hazell, J.W.P. | Pye, A.

Article Type: Research Article

DOI: 10.3233/RNN-1991-3207

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 2, pp. 101-107, 1991