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M H Tuszynski

Publications and source records attributed to M H Tuszynski.

At least 55 records · Page 3Linked to original sources
PubMed1997

Robust growth of chronically injured spinal cord axons induced by grafts of genetically modified NGF-secreting cells.

Little spontaneous regeneration of axons occurs after acute and chronic injury to the CNS. Previously we have shown that the continuous local delivery of neurotrophic factors to the acutely injured spinal cord induces robust growth of spinal and supraspinal axons. In the present study we examined whether chronically injured axons also demonstrate significant neurotrophin responsiveness. Adult rats underwent bilateral dorsal hemisection lesions that axotomize descending supraspinal pathways, including the corticospinal, rubrospinal, and cerulospinal tracts, and ascending dorsal spinal sensory projections. One to three months later, injured rats received grafts of syngenic fibroblasts genetically modified to produce nerve growth factor (NGF). Control subjects received unmodified cell grafts or cells transduced to express the reporter gene beta-galactosidase. Three to five months after grafting, animals that received NGF-secreting grafts showed dense growth of putative cerulospinal axons and primary sensory axons of the dorsolateral fasciculus into the grafted lesion site. Growth from corticospinal, raphaespinal, and local motor axons was not detected. Thus, robust growth of defined populations of supraspinal and spinal axons can be elicited in chronic stages after spinal cord injury by localized, continuous transgenic delivery of neurotrophic factors.

Animals↗
PubMed1996

Somatic gene therapy for nervous system disease.

Neurotrophic factors are target-derived molecules that prevent neuronal degeneration during development and, in some cases, during adulthood. They offer substantial promise as therapeutic agents in neurological disease by preventing cell loss and promoting axonal regeneration. However, the optimal means of delivering neurotrophic factors to the nervous system, and the CNS in particular, is an unresolved issue. Neurotrophic factors rarely influence only a single target neuronal population, hence broad delivery of neurotrophic factors to the nervous system may results in effects on multiple non-targeted neuronal populations. Ideally, neurotrophin delivery to the nervous system should be target-specific, regionally restricted, chronic, safe, well-tolerated and of sufficient concentration to elicit responses from target neurons. In this paper we discuss the use of somatic gene transfer methods to deliver neurotrophic factors to the CNS in a manner that seeks to meet the above criteria.

Animals↗
PubMed1996

Nerve growth factor delivery by gene transfer induces differential outgrowth of sensory, motor, and noradrenergic neurites after adult spinal cord injury.

Several neurotrophic factors have been identified that influence neuronal populations during central nervous system development, maturation, and senescence. To examine the responsiveness of the intact and the lesioned adult mammalian spinal cord to neurotrophic factors, primary rat fibroblasts were genetically modified to produce and secrete human nerve growth factor (NGF). These NGF-producing cells were then grafted to nonlesioned or lesioned adult rat spinal cords for periods of up to 1 year in vivo. Robust outgrowth of sensory and noradrenergic neurites was elicited by grafts in the previously nonlesioned spinal cord. Equally robust growth of sensory and noradrenergic neurites was observed in the lesioned spinal cord; in addition, partial sprouting of local motor neurites was elicited in the lesioned spinal cord. Thus, multiple neuritic populations of the adult spinal cord respond to neurotrophic factors by extending neurites, and this responsiveness is maintained and extended after major injury. Nerve growth factor delivered by somatic gene transfer may be a useful means of promoting axon regrowth in the injured spinal cord.

Adrenergic Fibers↗
PubMed1996

Central infusions of brain-derived neurotrophic factor and neurotrophin-4/5, but not nerve growth factor and neurotrophin-3, prevent loss of the cholinergic phenotype in injured adult motor neurons.

Neurotrophic factors are molecules that prevent neuronal degeneration and regulate neuronal phenotype during either development or adulthood. Relatively little is known about the comparative responsiveness of injured adult central nervous system motor neurons to various neurotrophic factors. In the present study we examined the effects of four members of the neurotrophin family on injured adult motor neurons. Nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3 or neurotrophin-4/5 were infused intracerebroventricularly into adult rats following transection of the motor hypoglossal nerve. Two weeks after axotomy, brain-derived neurotrophic factor and neurotrophin-4/5 completely prevented the loss of the cholinergic phenotype in hypoglossal motor neurons (97 +/- 11% and 99 +/- 5%, respectively) as assessed by choline acetyltransferase immunolabeling. In contrast, nerve growth factor and neurotrophin-3 exerted no protective effect. The low-affinity p75 neurotrophin receptor, capable of binding all four neurotrophins, was re-expressed in injured hypoglossal neurons; the majority of injured hypoglossal neurons also express trkB receptors but not trkA or trkC receptors. Thus, injury-induced responses to neurotrophins in adult motor neurons are mediated by trk receptors and their agonists, but may or may not also require low-affinity p75 neurotrophin receptors. Intracerebroventricular infusions of trkB agonists may be a useful means of targeting multiple and distantly separated populations of motor neurons for neurotrophic factor therapy.

Animals↗
PubMed1996

A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease.

A 1-year, double-blind, placebo-controlled, randomized, parallel-group study compared the efficacy and safety of acetyl-L-carnitine hydrochloride (ALCAR) with placebo in patients with probable Alzheimer's disease (AD). Subjects with mild to moderate probable AD, aged 50 or older, were treated with 3 g/day of ALCAR or placebo (1 g tid) for 12 months. Four hundred thirty-one patients entered the study, and 83% completed 1 year of treatment. The Alzheimer's Disease Assessment Scale cognitive component and the Clinical Dementia Rating Scale were the primary outcome measures. Overall, both ALCAR- and placebo-treated patients declined at the same rate on all primary and most secondary measures during the trial. In a subanalysis by age that compared early-onset patients (aged 65 years or younger at study entry) with late-onset patients (older than 66 at study entry), we found a trend for early-onset patients on ALCAR to decline more slowly than early-onset AD patients on placebo on both primary endpoints. In addition, early-onset patients tended to decline more rapidly than older patients in the placebo groups. Conversely, late-onset AD patients on ALCAR tended to progress more rapidly than similarly treated early-onset patients. The drug was very well tolerated during the trial. The study suggests that a subgroup of AD patients aged 65 or younger may benefit from treatment with ALCAR whereas older individuals might do more poorly. However, these preliminary findings are based on past hoc analyses. A prospective trial of ALCAR in younger patients is underway to test the hypothesis that young, rapidly progressing subjects will benefit from ALCAR treatment.

Acetylcarnitine↗
PubMed1996

Gene therapy in the adult primate brain: intraparenchymal grafts of cells genetically modified to produce nerve growth factor prevent cholinergic neuronal degeneration.

Gene therapy may be a useful means of delivering substances to the brain that are capable of preventing neuronal degeneration. In the present experiment, we determined whether intraparenchymal transplants of primary autologous cells genetically modified to produce nerve growth factor (NGF) would prevent injury-induced degeneration of cholinergic neurons. Cultured primary monkey fibroblasts were genetically modified to produce human NGF, and secreted 13.2 ng NGF/10(6) cells/h in vitro. Adult monkeys then underwent fornix transections to induce degeneration of basal forebrain cholinergic neurons, and received autologous grafts of either NGF-producing or control, beta-galactosidase-producing fibroblasts directly into the basal forebrain region. One month later, 61.7 +/- 8.9% of cholinergic neurons remained indentifiable in NGF-graft recipients compared to 26.2 +/- 5.0% in control graft recipients (P < 0.02). Neuronal protection correlated with the accuracy of graft placement: up to 92% protection from neuronal degeneration occurred when NGF-secreting grafts were accurately placed immediately adjacent to injured neurons. Thus, intraparenchymal NGF delivery to the adult primate brain by gene transfer can prevent the degeneration of basal forebrain cholinergic neurons. Gene therapy can target intraparenchymal brain sites for regionally specific neurotrophin delivery, thereby avoiding limitations imposed by diffusion of substances across the blood-brain barrier and through CNS parenchyma, while avoiding adverse effects of neurotrophic factors delivered in a non-directed manner to the central nervous system. The delivery of NGF by gene transfer to the brain merits further study as a means of preventing cholinergic neuronal degeneration in human disorders such as Alzheimer's disease.

Animals↗
PubMed1995

Bridging grafts and transient nerve growth factor infusions promote long-term central nervous system neuronal rescue and partial functional recovery.

Grafts of favorable axonal growth substrates were combined with transient nerve growth factor (NGF) infusions to promote morphological and functional recovery in the adult rat brain after lesions of the septohippocampal projection. Long-term septal cholinergic neuronal rescue and partial hippocampal reinnervation were achieved, resulting in partial functional recovery on a simple task assessing habituation but not on a more complex task assessing spatial reference memory. Control animals that received transient NGF infusions without axonal-growth-promoting grafts lacked behavioral recovery but also showed long-term septal neuronal rescue. These findings indicate that (i) partial recovery from central nervous system injury can be induced by both preventing host neuronal loss and promoting host axonal regrowth and (ii) long-term neuronal loss can be prevented with transient NGF infusions.

Acetylcholinesterase↗
PubMed1995

Regional differences in responsiveness of adult CNS axons to grafts of cells expressing human neurotrophin 3.

Neurotrophin 3 (NT3) belongs to the neurotrophin family, which also includes nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 4/5. NT3 mRNA is widely expressed in the rodent nervous system, but the physiological function of the native protein is still unclear. Genetically modified cell lines that produce physiological amounts of NT3 can provide a useful tool in the elucidation of the NT3 effects in the adult central nervous system (CNS). Genetically modified rat primary skin fibroblasts expressing and secreting human NT3 (hNT3) were prepared and characterized. In vitro, cell lines derived from different retroviral constructs expressed hNT3 mRNA, as determined by PCR and RNA blot analysis. Secretion of biologically active hNT3 was confirmed by specific elicitation of neurite outgrowth from cultured chick primary sympathetic and sensory neurons and from rat fetal locus coeruleus neurons in the presence of hNT3-producing cell conditioned media. In vivo, implanted fibroblasts survived well up to the maximal experimental time points of 6 weeks (brain) and 4 weeks (spinal cord) and continued to express hNT3 mRNA in vivo. As early as 2 weeks postgrafting, specific sprouting of host sensory neurites in response to hNT3-producing grafts was observed in the spinal cord. In contrast, hNT3-producing cerebral grafts did not induce a sprouting response different from that observed with control grafts. These findings establish the existence of a regionally different responsiveness of the CNS axons to local hNT3 overexpression.

Animals↗
PubMed1994

Neurotrophic factors and diseases of the nervous system.

Neuronal degeneration and death occur in mammals in the course of nervous system development, during senescence, and as a consequence of pathological events throughout life. Neurotrophic factors are natural target-derived molecules that prevent neuronal degeneration and death during development and promote neuronal recovery from injury and age-related atrophy. One neurotrophic factor--nerve growth factor-prevents the death of cells that are a target of varicella-zoster virus: dorsal root sensory neurons. Delivery of neurotrophic factors to dysfunctional neurons may be a useful therapeutic strategy for promoting neuronal recovery in a number of diseases, including varicella-zoster virus infection.

Animals↗
PubMed1994

Fibroblasts genetically modified to produce nerve growth factor induce robust neuritic ingrowth after grafting to the spinal cord.

The influences of neurotrophic factors on adult mammalian spinal cords are incompletely understood. In the present experiment, we utilized somatic gene transfer to examine the effects of nerve growth factor (NGF) on the unlesioned spinal cords of adult Fischer rats. Fischer 344 rat primary fibroblasts were genetically modified in vitro to produce and secrete NGF, then grafted to spinal cords at the T7 level. Grafts survived in vivo for periods of up to 1 year, and induced an extremely robust ingrowth of spinal neurites. Control and basic fibroblast growth factor-producing grafts did not promote extensive neurite growth. Neurites penetrating the NGF grafts were of sensory origin, since they labeled immunocytochemically for calcitonin gene-related peptide but not markers of other neuronal transmitter phenotypes. Electron microscopy revealed that neurites within NGF-secreting grafts were enveloped in glial cell processes and that axons frequently became myelinated. These results indicate that (i) genetically modified cell grafts are a useful model for studying trophic factor effects in the adult mammalian spinal cord, (ii) sensory neurites maintain robust NGF responsiveness into adulthood, and (iii) sprouting neurites can follow glial channels and become myelinated in the adult spinal cord. Grafts of fibroblasts genetically modified to secrete trophic factors merit study as potential tools for promoting regeneration after spinal cord injury.

Animals↗
PubMed1994

Somatic gene transfer to the adult primate central nervous system: in vitro and in vivo characterization of cells genetically modified to secrete nerve growth factor.

Somatic gene transfer offers a means of delivering substances to the central nervous system (CNS) in a regionally specific, high-dose, chronic and well-tolerated manner. Studies in rats have shown that genetically modified cell grafts can prevent neuronal degeneration and promote functional recovery after injury and can improve cognitive function in aged subjects. To assess the potential utility of somatic gene transfer techniques in primate models, retroviral vectors were used to modify genetically monkey and human primary skin fibroblasts to produce and secrete human nerve growth factor (NGF). In vitro, all cell types produced NGF and sustained this production through cell growth to confluency, as determined by both Northern blot analysis and ELISA. Adult human fibroblasts produced as much NGF as did young human fibroblasts. Monkey fibroblasts genetically modified to produce NGF were then grafted to intact adult rhesus and cynomolgous monkey brains. Among nine primates that received a total of 76 grafts, surviving cells were found in all subjects up to the maximal experimental timepoint of 6 months. Cholinergic fibres from the host brain penetrated NGF-secreting grafts up to 6 months after grafting, but showed little penetration in control grafts lacking the NGF gene. Autografts survived better than allografts. These findings indicate that both human and primate fibroblasts can be transduced to produce and secrete NGF, can maintain this production whether in a growing or quiescent state and can elicit robust sprouting responses when primate fibroblasts are grafted to the adult brain. Cells genetically modified to produce trophic factors are a useful model for studying in vitro and in vivo CNS plasticity and for testing potential therapies for neurodegenerative conditions.

Animals↗
PubMed1992

Ataxia in epidural spinal cord compression.

Nine patients presented with ataxia as the primary manifestation of epidural spinal cord compression. Eight had known cancer, the ninth an epidural abscess. Lower-extremity dysmetria, gait ataxia, or both, were the only neurologic signs in five patients. An incorrect initial diagnosis led to delay in treatment and subsequent neurologic deterioration in six patients. Failure to recognize isolated, painless ataxia as the initial manifestation of spinal cord compression and appropriately treat the disorder can result in irreversible spinal cord deterioration.

Abscess↗
PubMed1991

Recombinant human nerve growth factor infusions prevent cholinergic neuronal degeneration in the adult primate brain.

Atrophy of cholinergic neurons is a prominent component of Alzheimer's disease, and may explain in part the profound memory loss that is characteristic of patients with this disorder. Previous studies in animal models have shown that infusions of nerve growth factor into the adult brain can prevent both age-related and lesion-induced cholinergic neuronal atrophy. Recently, recombinant human nerve growth factor was found biologically active in nonprimate animal models. In the present experiment, recombinant human nerve growth factor infusions into the brains of adult primates prevented lesion-induced cholinergic neuronal degeneration and promoted cholinergic neurite sprouting. These findings provide additional support for potential therapeutic trials of human nerve growth factor in patients with Alzheimer's disease.

Alzheimer Disease↗
PubMed1990

Basal forebrain cell loss following fimbria/fornix transection.

Following fimbria/fornix transection, cells in the medial septum appear to undergo retrograde degeneration as shown by Nissl and acetylcholine esterase (AChE) staining. Recent studies using immunocytochemical techniques have also demonstrated loss of choline acetyltransferase (ChAT) and nerve growth factor receptor (NGFr) labeling of neurons in this region. Whether the apparent loss of ChAT- and NGFr-positive neurons is the result of the actual death of these neurons, or is instead a loss of ChAT enzyme or NGFr expression below levels detectable by immunocytochemical methods, remains an unresolved issue. In order to address this question, rhodamine-labeled fluorescent latex microspheres were injected into the hippocampus where they retrogradely transported to the cell bodies of the medial septum. Five days later these animals received either unilateral or bilateral fimbria/fornix lesions and were allowed to survive an additional 4 weeks. Compared to unlesioned control animals, unilaterally lesioned animals showed a 91% loss of fluorescently labeled cells and bilaterally lesioned animals showed a 93% loss. The inability to detect the fluorescent microspheres in the medial septum suggests that the majority of medial septal cells die after fimbria/fornix transection. ChAT and NGFr immunohistochemical staining were also performed. Cells stained for ChAT were reduced in number by 92% in animals with unilateral lesions and by 75% in animals with bilateral lesions, while NGFr-stained cells were reduced in number by 75% in animals with unilateral lesions and by 68% in animals with bilateral lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1990

Human beta nerve growth factor obtained from a baculovirus expression system has potent in vitro and in vivo neurotrophic activity.

A baculovirus expression vector, which contains the coding sequences for human prepro (beta) nerve growth factor under control of the viral polyhedrin promoter, was constructed. Upon infection of insect cells with the recombinant virus, mature human beta nerve growth factor (rhNGF) was released into the culture fluid. The mature rhNGF was biologically active since rat pheochromocytoma (PC12) and human neuroblastoma (SH-SY5Y) cells were induced to extend neurites upon treatment with this material. This activity was abolished by treating with antiserum prepared against mature mouse beta NGF (mNGF). When compared with mNGF, rhNGF more rapidly elicited the differentiation response in both PC12 and SH-SY5Y cells. In an in vivo assay of cholinergic cell survival, rhNGF was nearly as potent as mNGF in protecting cholinergic neurons from degeneration following a fimbria-fornix lesion. These results show that the baculovirus expression system provides quantities of biologically potent human beta NGF suitable for a comprehensive program of research to ascertain beta NGF's potential as a therapeutic agent for the treatment of Alzheimer's disease.

Animals↗
PubMed1990

Nerve growth factor infusions combined with fetal hippocampal grafts enhance reconstruction of the lesioned septohippocampal projection.

A combination of intracerebral grafting and intraventricular infusion of nerve growth factor was used to attempt to reconstruct the cholinergic component of the septohippocampal pathway following fimbria-fornix lesions in the rat. Four groups were tested: lesion only, lesion plus fetal hippocampal graft, lesion plus nerve growth factor, and lesion plus graft plus nerve growth factor. Choline acetyltransferase immunoreactivity, acetylcholinesterase fiber staining and behavior-dependent theta activity on electroencephalogram were used to assess the extent of pathway reconstruction. Nerve growth factor was infused for the first two weeks following the fimbria-fornix lesion, while electrophysiological measurements and histological analysis were conducted six to eight months later. The lesion plus graft plus nerve growth factor infusion group had long-term savings of choline acetyltransferase-immunoreactive cells as compared to the lesion only or lesion plus graft groups. In addition the lesion plus graft plus nerve growth factor infusion group had more extensive reinnervation of the hippocampus compared to all other groups. Behavioral-dependent theta activity on electroencephalogram was observed in some animals of both lesion plus graft and lesion plus graft plus nerve growth factor infusion groups, but not in other groups; however, unlike intact animals, the restored theta could be blocked completely by scopalamine. These results demonstrate that a combination of short-term intraventricular nerve growth factor infusion and fetal hippocampal grafts enhances reconstruction of the damaged septohippocampal circuit.

Animals↗