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M Ruberg

Publications and source records attributed to M Ruberg.

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

Apoptosis and autophagy in nigral neurons of patients with Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive cell loss confined mostly to dopaminergic neurons of the substantia nigra. Several factors, including oxidative stress, and decreased activity of complex I mitochondrial respiratory chain, are involved in the degenerative process. Yet, the underlying mechanisms leading to dopaminergic cell loss remain elusive. Morphological assessment for different modes of cell death: apoptosis, necrosis or autophagic degeneration, can contribute significantly to the understanding of this neuronal loss. Ultrastructural examination revealed characteristics of apoptosis and autophagic degeneration in melanized neurons of the substantia nigra in PD patients. The results suggest that even at the final stage of the disease, the dopaminergic neurons are undergoing active process of cell death.

Aged↗
PubMed1997

[Neuronal death caused by apoptosis in Parkinson disease].

The identity of the neuronal populations (dopaminergic, noradrenergic, serotoninergic, cholinergic) that die in Parkinson's disease is well established. The cause of this degeneration, and the mechanism by which it takes place is still unknown, although there is data, at least for the dopaminergic neurons, suggesting that oxidative stress might play a role. In addition, recent ultrastructural studies of dopaminergic neurons in patients with Parkinson's disease have shown that these neurons die by apoptosis, and immunocytochemical studies have shown that the cytokine TNF-alpha, observed in microglial cells in the substantia nigra of patients post-mortem, might play a role, as might the transcription factor NF-kappa B, which is translocated into the nucleus of dopaminergic neurons in patients, a sign of its activation. We have developed an in vitro model of dopaminergic cell death that accounts for these observations. In both differentiated PC12 cells and primary cultures of mesencephalic neurons, we have shown that when the sphingomyelin-dependent signaling pathway is activated, these cells die by apoptosis, preceded by the production of superoxide radicals in the mitochondria and the nuclear translocation of NF-kappa B. TNF-alpha is known to induce all three such events: apoptosis, activation of the sphingomyelin pathway, free radical production. Our results suggest that the superoxide radicals are used as signalling molecules within the sphingomyelin pathway. These observations may help to explain the origin of the evidence, in postmortem brain from parkinsonian patients, for oxidative stress, hypothesized to be an etiological factor in this disease.

Apoptosis↗
PubMed1996

Ceramide induces apoptosis in cultured mesencephalic neurons.

The death of dopaminergic and other neurons in primary cultures of the mesencephalon could be induced by treatment with ceramide, as in lymphocytes where it mediates activation by the cytokines tumor necrosis factor-alpha and interleukin-1 beta of a novel sphingomyelin-dependent signaling pathway leading to apoptosis. The morphological hallmarks of this form of cell death-bleb formation, cell body shrinkage, nuclear chromatin condensation, and fragmentation--were observed in degenerating neurons. Internucleosomal DNA degradation could also be evidenced by gel electrophoresis. The C2 and C6 analogues as well as native ceramide, administered in a dodecane suspension, had a similar effect, whereas the closely related C2-dihydroceramide, which lacks the 4-5 trans double bond in the sphingosine chain, failed to induce apoptosis. Neuronal death could be delayed by serum factors, dibutyryl cyclic AMP, and the protein synthesis inhibitor cycloheximide.

Animals↗
PubMed1996

Subthalamotomy in parkinsonian monkeys. Behavioural and biochemical analysis.

Nineteen Macaca fascicularis monkeys were divided into four different groups: Group A (n = 3), control; Group B (n = 3), monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP); Group C (n = 8), animals treated with MPTP in which the subthalamic nucleus (STN) was unilaterally lesioned by kainic acid injection; in Group D (n = 5), the STN was lesioned prior to MPTP administration. Subthalamotomy resulted in a bilateral improvement of tremor, spontaneous activity, bradykinesia (evaluated by a manual motor test) and freezing in Group C. All these monkeys developed hemichorea contralateral to the lesion. The improvement was maintained and the hemichorea continued until death. The monkeys in group D showed severe hemiballism which persisted throughout MPTP administration and developed parkinsonian signs mainly on the side ipsilateral to the lesion. Analysis of the in situ hybridization of the mRNA coding for glutamic acid decarboxylase (GAD) of MPTP monkeys showed a significant increase in the mean density of silver grains over every labelled neuron in the globus pallidum lateralis (56.8% over control) as well as the globus pallidus medialis (GPM) (45.7% over control) and the substantia nigra reticulata (SNR) (35.8% over control). No significant change was observed in the thalamic nucleus reticularis. Subthalamotomy (Groups C and D) produced a significant reduction in mRNA GAD expression on the side of the lesion in the GPM and the SNR (34% and 42.3%, respectively) with respect to the ipsilateral (non-lesioned) side and also when compared with parkinsonian monkeys. These results confirm and expand, at the cellular level, the paramount role of STN hyperactivity in the pathophysiology of parkinsonism. The therapeutic consequences of these findings for surgical treatment of Parkinson's disease are discussed.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1996

Consequences of nigrostriatal denervation on the gamma-aminobutyric acidic neurons of substantia nigra pars reticulata and superior colliculus in parkinsonian syndromes.

To examine the effects of nigrostriatal denervation on the substantia nigra pars reticulata (SNpr), one of the main outputs of the basal ganglia, we used quantitative in situ hybridization to analyze the messenger RNA coding for Mr 67,000 glutamic acid decarboxylase (GAD67 mRNA) in the SNpr neurons from patients with Parkinson's disease (PD), monkeys rendered parkinsonian by 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP), and their respective controls. In MPTP-intoxicated monkeys, the expression of GAD67 mRNA was increased in the SNpr neurons, and the increase was reversed by L-dopa treatment. There were no differences in the level of GAD67 mRNA between PD patients who had been treated with L-dopa and control subjects. Combined with the previously reported increased expression of GAD67 mRNA in the internal segment of the pallidum of MPTP-intoxicated monkeys, these data suggest that the gamma-aminobutyric acid (GABAergic) activity of the output system of the basal ganglia is globally increased by nigrostriatal denervation. We also analyzed the level of GAD67 mRNA expression in the superior colliculus, a structure that receives the inhibitory influence of the GABAergic neurons of the SNpr and that is involved in eye movement control. GAD67 mRNA expression was reduced in both MPTP-intoxicated monkeys, whether or not they received L-dopa therapy, and PD patients, compared to their respective controls. This decrease may result from the hyperactivity of the inhibitory nigrotectal pathway, but also from other influences since it was not corrected by L-dopa therapy. These changes may account for the slight ocular motor and visuospatial cognitive impairment occurring in PD, even after L-dopa therapy.

Animals↗
PubMed1996

Consequence of nigrostriatal denervation and L-dopa therapy on the expression of glutamic acid decarboxylase messenger RNA in the pallidum.

To examine the consequences of nigrostriatal denervation and L-dopa treatment on the basal ganglia output system, we analyzed, by quantitative in situ hybridization, the messenger RNA coding for glutamic acid decarboxylase (Mr 67,000) (GAD67 mRNA) in pallidal cells from patients with Parkinson's disease (PD), monkeys rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) receiving or not receiving L-dopa, and their respective control subjects. In MPTP-treated monkeys, the expression of GAD67 mRNA was increased in cells from the internal pallidum, and this effect was abolished by L-dopa treatment. There were no differences in the levels of GAD67 mRNA between patients with PD, who were all treated with L-dopa, and control subjects. These results indicate that the level of GAD67 mRNA is increased in the cells of the internal pallidum after nigrostriatal dopaminergic denervation and that this increase can be reversed by L-dopa therapy.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1996

Creutzfeldt-Jakob disease from contaminated growth hormone extracts in France.

We diagnosed Cruetzfeldt-Jakob disease in 34 patients (16 definite, 18 probable) who had received human growth hormone extract for various period of time (mean +/- SD, 2.9 years), but particularly during the period between January 1984 and July 1985, a potential high-risk factor. Disease duration for deceased patients (n = 30) was 17 +/- 9 months. The clinical picture was homogeneous, starting with cerebellar ataxia and ocular motor disorders in about 90% of the patients. Neurologic deterioration, including dementia and myoclonic jerks, occurred within months. The high number of cases (1.5% of those treated between 1959 and 1988, 3% of those treated during the putative high-risk period) is still unexplained. We discuss the possibility that new cases will be detected,the risk of contaminating the general public, and the sanitary measures undertaken to prevent this.

Adolescent↗
PubMed1995

Effects of nigrostriatal denervation and L-dopa therapy on the GABAergic neurons in the striatum in MPTP-treated monkeys and Parkinson's disease: an in situ hybridization study of GAD67 mRNA.

The effects of nigrostriatal denervation and L-dopa therapy on GABAergic neurons were analysed in patients with Parkinson's disease and in monkeys rendered parkinsonian by MPTP intoxication. The expression of the messenger RNA coding for the 67 kDa isoform of glutamic acid decarboxylase (GAD67 mRNA), studied by quantitative in situ hybridization, was used as an index of the GABAergic activity of the striatal neurons. A significant increase in GAD67 mRNA expression, generalized to all GABAergic neurons, was observed in MPTP-treated monkeys compared to control monkeys in the putamen and caudate nucleus (+44 and +67% respectively), but not in the ventral striatum. L-Dopa therapy significantly reduced GAD67 mRNA expression in the putamen and caudate nucleus to levels similar to those found in control monkeys. However, the return to normal of GAD67 mRNA expression was not homogeneous across all neurons since it was followed by an increase of labelling in one subpopulation of GABAergic neurons and a decrease in another. These data suggest that in MPTP-treated monkeys the degeneration of nigrostriatal dopaminergic neurons results in a generalized increase in GABAergic activity in all the GABAergic neurons of the striatum, which is partially reversed by L-dopa therapy. As the expression of GAD67 mRNA is less intense in the ventral than in the dorsal striatum, this increase in striatal GABAergic activity may be related to the severity of nigrostriatal denervation. In parkinsonian patients who had been chronically treated with L-dopa, GAD67 mRNA expression was significantly decreased in all GABAergic neurons, in the caudate nucleus (by 44%), putamen (by 43.5%) and ventral striatum (by 26%). The opposite variation of GAD67 mRNA in patients with Parkinson's disease, compared with MPTP-treated monkeys, might be explained by the combination of chronic nigrostriatal denervation and long-term L-dopa therapy.

Aged↗
PubMed1995

Alterations of GABAergic neurons in the basal ganglia of patients with progressive supranuclear palsy: an in situ hybridization study of GAD67 messenger RNA.

We analyzed postmortem GABAergic neurons in the basal ganglia of three patients with progressive supranuclear palsy (PSP) and four matched controls by means of glutamic acid decarboxylase (M(r) 67,000 [GAD67]) mRNA in situ hybridization. In PSP, we found a 50 to 60% decrease in the number of neurons expressing GAD67 mRNA in the caudate nucleus, ventral striatum, and the external and internal pallidum. The expression of GAD67 mRNA per neuron was reduced in the caudate nucleus and putamen (-43%), the ventral striatum (-55%), and the external and internal pallidum (-59% and -68%). Our data indicate that striatal and pallidal GABAergic neurotransmission is markedly reduced in PSP and we suggest that this alteration may account for the motor and cognitive symptoms observed in PSP. Furthermore, the destruction of the basal ganglia output systems may explain the lack of responsiveness to L-dopa therapy of PSP patients.

Aged↗
PubMed1994

Morphological and molecular characterization of the response of differentiated PC12 cells to calcium stress.

The mechanisms that lead ultimately to neuronal death in pathological ageing of the brain remain mostly unknown as in the case of Parkinson's disease where there is a progressive and selective loss of dopaminergic neurons within the substantia nigra. Dopamine-expressing PC12 cells that were neuronally differentiated by nerve growth factor treatment were chosen as a culture model in which to study some of the changes that may occur during the course of the degenerative process. They were exposed to the calcium ionophore A23187 in order to produce a sustained rise in cytoplasmic calcium, a phenomenon related to various pathological conditions. The degenerative effects of the ionophore were dose- and time-dependent. They were characterized by early fragmentation of the neurites followed ultimately by a loss in cell viability. Biochemical changes, such as a decrease in [3H]dopamine uptake and modulations of the tyrosine hydroxylase gene, were detected before macroscopic evidence of cell suffering (e.g. neurite fragmentation) could be observed. Although an ongoing degenerative process was occurring in cell somata, PC12 cells were able to recover upon ionophore withdrawal. Characteristics of apoptosis such as chromatin condensation and DNA fragmentation were detectable in a small population of dying cells. DNA fragmentation could be prevented by the endonuclease inhibitor aurintricarboxylic acid. New protein synthesis was not required, as cycloheximide failed to prevent degeneration. Taken together, these results suggest that differentiated PC12 cells react to calcium stress through a sequence of regulatory processes which appears to be independent of the apoptotic pathway.

Animals↗
PubMed1994

Characterization and expression of the cDNA coding for the human myelin/oligodendrocyte glycoprotein.

We report here the characterization of a full-length cDNA encoding the human myelin/oligodendrocyte glycoprotein (MOG). The sequence of the coding region of the human MOG cDNA is highly homologous to that of other previously cloned mouse, rat, and bovine MOG cDNAs, but the 3' untranslated region differs by an insertion of an Alu sequence between nucleotides 1,590 and 1,924. Accordingly, northern blot analyzes with cDNA probes corresponding to the coding region or the 3' untranslated Alu-containing sequence revealed a single band of 2 kb, rather than the 1.6 kb of bovine, rat, or mouse MOG cDNA(s). Immunocytochemical analysis of HeLa cells transfected with human MOG cDNA, which was performed using a specific antibody raised against whole MOG, clearly indicated that MOG is expressed at the cell surface as an intrinsic protein. These data are in accordance with the predicted amino acid sequence, which contains a signal peptide and two putative transmembrane domains. The knowledge of the human MOG sequence should facilitate further investigations on its potential as a target antigen in autoimmune demyelinating diseases like multiple sclerosis.

Amino Acid Sequence↗
PubMed1994

A third locus for autosomal dominant cerebellar ataxia type I maps to chromosome 14q24.3-qter: evidence for the existence of a fourth locus.

The autosomal dominant cerebellar ataxias (ADCA) type I are a group of neurological disorders that are clinically and genetically heterogeneous. Two genes implicated in the disease, SCA1 (spinal cerebellar ataxia 1) and SCA2, are already localized. We have mapped a third locus to chromosome 14q24.3-qter, by linkage analysis in a non-SCA1/non-SCA2 family and have confirmed its existence in a second such family. We suggest designating this new locus "SCA3". Combined analysis of the two families restricted the SCA3 locus to a 15-cM interval between markers D14S67 and D14S81. The gene for Machado-Joseph disease (MJD), a clinically different form of ADCA type I, has been recently assigned to chromosome 14q24.3-q32. Although the SCA3 locus is within the MJD region, linkage analyses cannot yet demonstrate whether they result from mutations of the same gene. Linkage to all three loci (SCA1, SCA2, and SCA3) was excluded in another family, which indicates the existence of a fourth ADCA type I locus.

Adult↗
PubMed1993

In situ hybridization of GAD mRNA in monkey and human brain: quantification at both regional and cellular levels.

GAD mRNA was detected in human and monkey brain postmortem by in situ hybridization with an [35S]-labelled copy RNA corresponding to a 2.7-kb fragment of the coding region of human GAD mRNA. A characteristic and reproducible pattern of hybridization was obtained with the anti-sense, but not the sense probe in both monkey and human brain. Microscopic examination of tissue sections showed that only neuronal perikarya, not glial cells, were labelled. The data confirm the heterogeneity of GAD mRNA distribution reported in rodent brain and non-human primate brain.

Aged↗
PubMed1993

Does neuromelanin contribute to the vulnerability of catecholaminergic neurons in monkeys intoxicated with MPTP?

The question has been raised as to whether neuromelanin, a by-product of catecholamine metabolism which accumulates during aging in primate midbrain neurons, contributes to the selective vulnerability of subgroups of dopaminergic neurons in Parkinson's disease. 1-Methyl-4-phenylpyridinium (MPP+) a metabolite of 1-methyl, 4-phenyl, 1,2,3,6-tetrahydropyridine (MPTP) is toxic to dopaminergic neurons, particularly in primates, producing a motor syndrome similar to that observed in Parkinson's disease. To test whether this neurotoxin preferentially affects melanized neurons, the survival of melanized and non-melanized catecholaminergic neurons was analysed after MPTP intoxication in the midbrain of the cynomolgus monkey (Macaca fascicularis). Experiments were performed on six animals chronically treated with MPTP (two were severely disabled, four moderately affected) and two age-matched control monkeys. Two populations of neurons were examined on regularly spaced sections throughout the midbrain: catecholaminergic neurons, identified by tyrosine hydroxylase immunohistochemistry and neuromelanin-containing neurons, visualized by Masson's method. The total number of neurons of each type was estimated in the different midbrain catecholaminergic cell groups using computer assisted image analysis. In the midbrains of control animals not all catecholaminergic neurons contained neuromelanin. The percentage of melanized neurons compared to the total population of tyrosine hydroxylase-positive neurons was high in the substantia nigra pars compacta (81.5%) and in the locus coeruleus (98%), intermediate in the substantia nigra pars lateralis (70%), in the catecholaminergic cell group A8 (50%), and in the ventral tegmental area (41.5%) and almost nil in the central gray substance. In MPTP-treated monkeys, the severity of the loss of catecholaminergic neurons was variable within the different midbrain cell groups, though of similar intensity in severely and mildly disabled monkeys. A relationship was found between the loss of dopaminergic neurons in the different mesencephalic cell groups of MPTP-intoxicated animals and the percentage of melanized neurons they normally contain (r = 0.98; P = 0.04). The percentage loss of catecholaminergic neurons in the locus coeruleus, the only noradrenergic cell group studied, was lower than expected from the correlation curve obtained for dopaminergic cell groups. Altogether, these findings indicate: (i) that dopaminergic neurons are more vulnerable to MPTP-toxicity than noradrenergic neurons; and (ii) that among dopaminergic neurons, those containing neuromelanin are more susceptible, indicating a possible role of neuromelanin in MPTP-toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗