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M Poltorak

Publications and source records attributed to M Poltorak.

At least 37 records · Page 2Linked to original sources
PubMed1990

Intracerebral adrenal medulla grafts: a review.

This review summarizes basic and clinical research on intracerebral adrenal medulla grafts, emphasizing potential applications to Parkinson's disease. Properties of intraventricular and intraparenchymal grafts are described, and cell survival and functional effects are compared. It is clear that adrenal medulla allografts survive poorly in the parenchyma of the corpus striatum and better in the lateral ventricle. Nerve growth factor (NGF) may improve the survival of adrenal medulla grafts. In the absence of added NGF even adrenal medulla grafts in the ventricle survive irregularly, and the factors required for graft survival in the ventricle are not well understood. In the 6-hydroxydopamine-lesioned rat model most evidence suggests, not surprisingly, that adrenal medulla grafts produce functional effects only when they survive. These effects may be related to production of catecholamines by the transplanted cells. In addition, adrenal medulla grafts may produce trophic effects on host brain. These effects are most evident in animals with MPTP-induced damage to dopaminergic systems and may be nonspecific, possibly related in part to the brain injury that is induced by graft implantation. Trophic effects may contribute to the functional effects of adrenal medulla grafts: For intraparenchymal grafts, trophic effects that do not require cell survival may contribute small functional changes, while additional behavioral effects may require substantial chromaffin cell survival. The evidence for direct dopamine-mediated effects as compared to trophic mechanisms of action for these grafts in animal models for Parkinson's disease is presented. Clinical studies of adrenal medulla grafts in human patients are examined and compared in detail. When inspected closely, the various clinical studies are in general agreement on most points, although there are differences in the degree of improvement found, both across different studies and individual patients. It is concluded that some beneficial clinical effects occur, with small to modest changes in most patients and substantial improvement in a minority of patients. There also seem to be larger or more consistent changes in durations of "on" and "off" times in L-dihydroxyphenylalanine-treated patients. There are substantial side effects, and it is not clear that the clinical changes are sufficient to justify performing adrenal medulla transplantation in human patients as a routine procedure.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Medulla↗
PubMed1990

Cell adhesion molecules (CAMs) in adrenal medulla in situ and in vitro: enhancement of chromaffin cell L1/Ng-CAM expression by NGF.

We have studied the expression of the cell adhesion molecules (CAMs) L1/Ng-CAM, N-CAM, J1/tenascin, and myelin-associated glycoprotein and their common carbohydrate L2/HNK-1 epitope in normal rat adrenal gland sections as well as in adrenal medulla cell culture with and without NGF stimulation. In situ L1/Ng-CAM was observed on the surface of some but not all chromaffin cell clusters, including their closely associated extracellular matrix (ECM). N-CAM immunoreactivity was present on all chromaffin cells and ECM. The ECM of whole medullas also expressed J1/tenascin molecules. In long-term cultures, nerve growth factor (NGF) stimulation enhanced L1/Ng-CAM, N-CAM, and Thy 1.1 immunolabeling on chromaffin cells and their processes. Process outgrowth was greater from chromaffin cell clusters containing S-100 positive Schwann cells as compared to dispersed single chromaffin cells. When long bundles of chromaffin cell fibers were present, S-100, L1/Ng-CAM, and N-CAM positive Schwann cells were always found and were grouped in distinct clusters in the intervals between the chromaffin cells. In some areas, however, after NGF stimulation some chromaffin cell process development occurred despite an apparent lack of close contact with Schwann cells. NGF-activated chromaffin cells also demonstrated neurofilament- and vimentin-like-immunoreactive filaments within cell bodies and their processes. Chromaffin cells were usually found on a layer of N-CAM and fibronectin positive fibroblasts, and often were associated with laminin-immunoreactive material. These data suggest a possible role of N-CAM and L1/Ng-CAM as well as ECM laminin in process outgrowth from chromaffin cells.

Adrenal Medulla↗
PubMed1990

Cell adhesion molecules in adrenal medulla grafts: enhancement of chromaffin cell L1/Ng-CAM expression and reorganization of extracellular matrix following transplantation.

Intracerebral adrenal medulla grafts have been used in human patients as an experimental treatment for Parkinson's disease, based on studies in animal models of this disorder. However, alterations in chromaffin cell properties after transplantation and the factors controlling graft survival are poorly understood. Since cell adhesion molecules (CAMs) are involved in regeneration and development of neural tissue in vivo and in vitro, the present study was undertaken to determine the expression of CAMs in adrenal medulla isografts. Fragments of rat adrenal medulla were implanted into the right lateral ventricle. The majority of grafts survived quite well, for up to 2 months (the longest studied period). The implanted chromaffin cells did not develop extensive processes. The cells retained tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) immunoreactivity, while phenylethanolamine N-methyltransferase (PNMT) expression was decreased. Surviving transplanted chromaffin cells showed enhancement and spreading of surface L1/Ng-CAM expression as compared to normal chromaffin cells in adrenal medulla. The implanted chromaffin cells demonstrated only partial conversion to neuronal phenotypes. These chromaffin cells did not develop extensive processes, but showed an enhancement of L1/Ng-CAM expression. Surviving chromaffin cells were accompanied by reorganization of their closely associated extracellular matrix (ECM). As compared to normal in situ adrenal medulla, graft ECM demonstrated a substantial increase of L1/Ng-CAM and laminin immunoreactivities and a distinct decrease in J1/tenascin expression. Some adrenal medulla grafts degenerated, particularly when misplaced within the host brain parenchyma. In these cases the grafts showed fragmentation of ECM and gradual disappearance of CAMs. These results suggest that surviving adrenal medulla grafts exhibit increased synthesis of certain CAMs by chromaffin cells, which may be involved in interactions between chromaffin cells and the surrounding ECM. It is speculated that both surviving and degenerating adrenal medulla grafts could provide CAMs and ECM components including laminin to host brain and this way contribute to functional effects of grafts.

Adrenal Medulla↗
PubMed1990

Prenatal exposure to ethanol causes a delay in the developmental expression of neurofilament epitopes in cerebellum.

The expression of nonphosphorylated neurofilaments (nPNFs) and phosphorylated neurofilaments (PNFs) was examined in cerebella during development of C57/Bl/6J mice prenatally exposed to ethanol. The length of nPNF immunoreactive portions of primary and secondary dendrites of Purkinje neurons was reduced during early postnatal developmental stages. This difference disappeared by 2 months of age. These results indicate a delay in the maturation of nPNFs in Purkinje neurons of ethanol-exposed mice. There also appeared to be some underdevelopment of basket cell axons in terms of PNF expression, during early postnatal stages, as compared to normal control litters. These findings may reflect a general delay in neuronal maturation after ethanol exposure. Prenatal exposure to ethanol may, therefore, have profound effects on developmental events occurring during early postnatal life. We could not, however, exclude the possibility that the disturbances in neurofilament expression were due to malnutrition in the alcohol-treated animals.

Animals↗
PubMed1989

Expression of cell adhesion molecules from the L2/HNK-1 family in cerebellar isografts in mice.

The expression of cell adhesion molecules and glial fibrillary acid protein (GFAP) was examined in isografts of embryonic mouse cerebellum. Donor embryonic cerebella with the meninges removed were implanted into the lateral cerebral ventricles of adult host animals and examined after 2-6 weeks. Indirect immunofluorescence staining was performed on fresh frozen sections, using antibodies against the cell adhesion molecules L1, N-CAM, J1, myelin associated glycoprotein (MAG), and their shared L2/HNK-1 carbohydrate epitope, as well as GFAP. Nissl staining revealed that a normal trilaminar cytoarchitecture developed in some areas of implanted cerebella. Antibodies against cell adhesion molecules showed patterns of immunoreactivity generally similar to those present during normal cerebellar development. Expression of the L2 epitope in normal cerebellum is transiently observed in the molecular layer and is primarily seen in the substantia medullaris of mature cerebellum. This pattern was altered in the grafts, with a persistent expression of the L2 epitope in the molecular layer and less pronounced L2 immunoreactivity in the substantia medullaris cerebelli. These results may reflect a retardation of granule neuron differentiation due to abnormal or missing efferents and afferents in transplanted cerebellum. Also, the characteristic GFAP-positive radially oriented elongated fibers of Bergmann glia were not detected, even though passage of granule cells from their germinating zone to the internal granular layer was observed. The data presented here suggest that the developmental appearance and pattern of expression of cell adhesion molecules during morphogenesis of the cerebellum occurs largely independently of the normal complement of afferent and efferent connections.

Animals↗
PubMed1989

Immunoreactive phosphorylated epitopes on neurofilaments in neuronal perikarya may be obscured by tissue preprocessing.

Monoclonal antibodies (SMI 31 and SMI 34) against phosphorylated epitopes on neurofilaments react almost exclusively with neuronal axons in paraffin sections of perfused animals. Using fresh frozen (unfixed) rodent brain sections the immunoreactivity with these antibodies was also present in numerous neuronal cell bodies. Both antibodies also recognized intracellular antigens in the soma of living cells of a human neuroblastoma clone. These data suggest that phosphorylation of neurofilaments in neuronal perikarya is common in vivo. The phosphorylated neurofilament epitopes in neuronal perikarya may become hidden during tissue preprocessing and fixation.

Animals↗
PubMed1989

Immunological reactions induced by intracerebral transplantation: evidence that host microglia but not astroglia are the antigen-presenting cells.

The immunological reactions to embryonic cerebellar xenografts (n = 16) and allografts (n = 8) in host rat brain were studied after 2, 4, and 6 weeks of survival and compared to a control group consisting of 10 rats with isografts. Indirect immunofluorescence was performed on fresh frozen brain sections using antibodies against antigen presenting cells (Ia/Ox-6+ cells) and T helper (W3/25+) cells. Massive infiltrations of both cell types were found within xenografts. Ia antigen was present in the walls of small vessels near the transplant as well as in the ventricles on supra- and subependymal cells. In host tissue surrounding the grafts, Ox-6+ immunoreactivity was also observed in a population of cells ranging from an irregular rod-like shape with short branching processes to more rounded cell bodies with retracted processes. The appearance of these cells was characteristic of microglia. These cells were GFAP-negative. These cellular reactions were associated with rejection of the grafts. In contrast, the allografts survived, but nevertheless cells expressing Ox-6+ and to a lesser extent W3/25+ immunoreactivity were found along the injection needle tract and in damaged host tissue surrounding the grafts. No Ox-6+ perivascular infiltrations were seen. Some staining was also found within the allografts, mainly associated with damaged tissue. Ox-6+ ramified cells were also observed. Both Ox-6+ and W3/25+ immunoreactivity decreased with the time of survival. Host and donor GFAP-positive astrocytes did not express Ox-6+ molecules, and therefore probably were not involved in presenting antigen to effector cells. The control isografts also survived very well, but nevertheless Ox-6+ and less widespread W3/25+ cells were present in surrounding injured host tissue. Ox-6+ perivascular infiltration was not found in the host brain of animals with isografts. Ox-6+ and W3/25+ immunoreactivities were present primarily in graft areas that appeared damaged, often closely associated with injured host tissue. These results indicate that the process of implantation of grafts and associated brain injury induces enhanced Ia/Ox-6+ immunoreactivity, primarily on microglia in brain parenchyma surrounding grafts, and suggest that host microglia may substantially contribute to the initiation of immune reactions against intracerebral grafts. Despite this predisposition to an immunological response, only in the case of xenografts did these reactions, with the addition of Ox-6+ perivascular cuffing and cell infiltrations within the grafts, lead ultimately to graft rejection.

Animals↗
PubMed1988

The expression of phosphorylated neurofilament epitopes in human brains.

The expression of phosphorylated neurofilaments (PNF) epitopes in hippocampal neurons was examined in 5 cases of Alzheimer's disease and 12 brains of schizophrenic patients. A control group (n = 17) consisted of 5 brains of patients with other acute or chronic neurologic disorders and 12 brains of persons who were free of any known neurologic disease. Immunocytochemistry with monoclonal antibodies to PNF was done on formalin-fixed, paraffin sections of hippocampus. Adjacent sections were impregnated with silver. Immunoreactivity to PNF was observed in tangles and plaques of the Alzheimer's brains and also in hippocampal pyramidal cells in 6 of the 12 schizophrenic brains and in 9 of the 17 control brains (2 with neurological disorders and 7 with non-neurological diseases). The positive PNF-stained cell bodies, in silver impregnated sections, generally did not show evident neurofibrillary abnormalities. Enzymatic dephosphorylation prior to immunostaining abolished PNF reactivity. These results suggest the widespread occurrence and relative non-specificity of perikaryonal PNF immunoreactivity in human post mortem brain tissue. We could not exclude the possibility that the hippocampal and brainstem neurons are predilection sites for normal perikaryonal phosphorylation in human brain.

Adult↗
PubMed1988

Cerebellar allografts in brain of quaking mice.

Fragments of normal embryonic cerebellum were transplanted into adult Quaking mice to examine using peroxidase-antiperoxidase immunocytochemistry the development of genetically normal tissue in an abnormal host environment. The Quaking mouse animals used as hosts are characterized by defective myelin associated glycoprotein. Normal characteristic expression and distribution of neurofilaments was observed in the cerebellar grafts. Nonphosphorylated epitopes of neurofilaments were seen in Purkinje cell bodies and dendrites. The phosphorylated epitopes of neurofilaments were observed in basket cell axons. Phosphorylated epitopes were also present in numerous myelinated axons, which were probably fibers from deep cerebellar nuclei. These data support the notion that neurogenesis with alternative connections can occur in transplants. Staining patterns with myelin associated glycoprotein and myelin basic protein also suggest that normal myelination occurs in grafts transplanted to the brains of Quaking mice.

Animals↗
PubMed1988

A comparison of intraventricular and intraparenchymal cerebellar allografts in rat brain: evidence for normal phosphorylation of neurofilaments.

Allografts of embryonic (E14-E15) rat cerebellum in adult brain were compared using the intraparenchymal and intraventricular transplantation techniques. We studied the expression and distribution of phosphorylated neurofilament (PNF) epitopes, nonphosphorylated neurofilament (nPNF) epitopes, synapse-associated antigens, glial fibrillary acidic protein (GFAP) and myelin basic protein (MBP). Both intraventricular and intraparenchymal grafts developed a clear trilaminar organization. Intraparenchymal grafts were much smaller and showed a large GFAP-positive glial scar and demyelination of host tissue. Nevertheless, myelinated fibers were present more often crossing the host-transplant border in intraparenchymal grafts. PNF and nPNF epitopes were present in both types of grafts. Staining patterns characteristic of normal rat cerebellum were seen. nPNF epitopes were present in Purkinje cell bodies and dendrites and PNF epitopes in basket cell axons surrounding Purkinje neurons. The appearance and distribution of PNF epitopes resembled that seen in normal postnatal cerebellar development and both PNF and nPNF epitopes were present at the same times in early development in both intraventricular and intraparenchymal grafts. In contrast to the situation in trauma and disease, PNF epitopes never appeared in perikarya of transplanted cerebellar neurons. The expression of synapse-associated antigens in grafted tissue was also similar to that seen in normal cerebellum.

Animals↗
PubMed1987

Normal neuronal cell bodies of the nucleus tractus mesencephalici nervi trigemini react with antibodies against phosphorylated epitopes on neurofilaments.

Reactivity to antibodies directed against phosphorylated neurofilament epitopes is normally present in axons. Phosphorylated neurofilament immunoreactivity is not generally found in neuronal perikarya, except in abnormal states such as Alzheimer's disease. We found that cytoplasm of neurons of the nucleus tractus mesencephalici nervi trigemini in normal mice and rats reacts with monoclonal antibodies against phosphorylated epitopes on neurofilaments. This suggests either that phosphorylated epitopes on neurofilaments are localized in the perikarya of some normal neurons or that the antibodies that were used (SMI 31 and SMI 34) recognize more than phosphorylated epitopes.

Animals↗
PubMed1987

Myelin-associated glycoprotein, a member of the L2/HNK-1 family of neural cell adhesion molecules, is involved in neuron-oligodendrocyte and oligodendrocyte-oligodendrocyte interaction.

A monoclonal antibody to the myelin-associated glycoprotein (MAG) was prepared and characterized to probe for the involvement of MAG in cell surface interactions among neural cells in vitro. The antibody reacts specifically with oligodendrocyte cell surface and myelin-rich brain regions as expected from previous investigations. Not all O4 antigen-positive oligodendrocytes express MAG in vitro. Fab fragments of the antibody interfere with neuron to oligodendrocyte and oligodendrocyte to oligodendrocyte adhesion, but not with oligodendrocyte to astrocyte adhesion. MAG-containing liposomes bind to the cell surfaces of the appropriate target cells by a mechanism that is specifically inhibitable by Fab fragments of monoclonal MAG antibodies, demonstrating that MAG is a neural cell adhesion molecule.

Animals↗
PubMed1986

Reactivity with neural cell adhesion molecules in sera from patients with demyelinating diseases.

Sera from 5 patients with IgM gammopathy and peripheral neuropathy reacted strongly by a sensitive immunospot enzyme-linked immunosorbent assay test with the myelin-associated glycoprotein (MAG) purified from human and bovine brains and the novel neural cell adhesion molecule J1 and associated glycoproteins from human brain. Two other members of the L2/HNK-1 family of cell adhesion molecules, the L1 glycoprotein and the neural cell adhesion molecule N-CAM, are not recognized significantly more strongly by these sera than by sera from patients with multiple sclerosis. Sera from patients with Guillain-Barré syndrome and amyotrophic lateral sclerosis and from healthy humans did not react with any of the glycoproteins tested at the serum concentrations used.

Animals↗
PubMedDate not supplied

In vitro properties of a newly established medulloblastoma cell line, MCD-1.

Medulloblastomas are poorly differentiated brain tumors believed to arise from primitive pleuripotential stem cells, and tend to express mixed neuronal and glial properties. In the present study, we examined immunohistochemical and neurotransmitter phenotypic properties in a newly established medulloblastoma cell line, MCD-1. MCD-1 cells were immortal, not contact-inhibited, but did not grow in soft agar. Immunohistochemical studies showed positive staining for neurofilament protein (NF), neuron-specific enolase (NSE), synaptophysin, MAP 2, tau, NCAM 180, vimentin, and S-100 protein. The cells expressed specific uptake of glutamate, serotonin, and choline, but not GABA or dopamine. A significant increase in process extension was seen in response to agents that enhance intracellular cyclic AMP, especially 3-isobutyl-1-methylxanthine (IBMX). Process formation induced by IBMX was associated with a decrease in cell proliferation as evidenced by a reduction in numbers of cells incorporating 5-bromo-2-deoxyuridine (BrdU). No increase in process extension was observed following exposure to NGF or retinoic acid. MCD-1 cells were shown to produce transforming growth factor beta (TGF beta), and were immunopositive for mutant p53. Transfection assays with the PG13-Luc reporter plasmid, which contains a p53-responsive enhancer element and a luciferase reporter gene, suggested MCD-1 cells are deficient in wild-type p53 and do not activate p53 on treatment with the anticancer agent adriamycin. The MCD-1 cell line is suggested to represent an abnormally differentiated cell type, which has some properties consistent with a multipotent neuronal phenotype while retaining some properties of immature cells of a glial lineage. The MCD-1 cell line can be used to provide a model of a medulloblastoma cell line that is resistant to growth-controlling and anticancer agents.

1-Methyl-3-isobutylxanthine↗
PubMedDate not supplied

Cerebral transplants for seizures: preliminary results.

Several critical brain regions have been identified in which application of gamma-aminobutyric acid (GABA) potentiating agents in small quantities can suppress or prevent generalized and kindled amygdala seizures, i.e., substantia nigra and deep prepiriform cortex. Severity of audiogenic seizures in the genetically epilepsy prone rat (GEPR) is reduced by injection of norepinephrine (NE) into the lateral ventricles and by GABA in inferior colliculus. The present investigation examines the potential for raising epileptic thresholds by increasing local GABAergic or NE inhibitory activity by means of brain transplants of tissue rich in GABA or NE neurons. Two models of epilepsy were used: amygdala-kindled seizures and sound-induced seizures in GEPRs. Transplantation of embryonic cerebellar or cortical tissue to the deep prepiriform area of amygdala kindled rats transiently raised seizure thresholds in three of the nine animals. Transplantation of embryonic cerebellar or cortical tissue to the inferior colliculus or adrenal medulla tissue to lateral ventricles of GEPRs did not appreciably reduce the intensity of audiogenic seizures in these animals.

Amygdala↗