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Biomedical subjects

R Levy

Publications and source records attributed to R Levy.

At least 271 records · Page 15Linked to original sources
PubMed1995

The peripheral cannabinoid receptor: adenylate cyclase inhibition and G protein coupling.

Two cannabinoid receptors, designated neuronal (or CB1) and peripheral (or CB2), have recently been cloned. Activation of CB1 receptors leads to inhibition of adenylate cyclase and N-type voltage-dependent Ca2+ channels. Here we show, using a CB2 transfected Chinese hamster ovary cell line, that this receptor binds a variety of tricyclic cannabinoid ligands as well as the endogenous ligand anandamide. Activation of the CB2 receptor by various tricyclic cannabinoids inhibits adenylate cyclase activity and this inhibition is pertussis toxin sensitive indicating that this receptor is coupled to the Gi/G(o) GTP-binding proteins. Interestingly, contrary to results with CB1, anandamide did not inhibit the CB2 coupled adenylate cyclase activity and delta 9-tetrahydrocannabinol had only marginal effects. These results characterize the CB2 receptor as a functional and distinctive member of the cannabinoid receptor family.

Adenylate Cyclase Toxin↗
PubMed1995

Striatal expression of substance P and methionin-enkephalin in genes in patients with Parkinson's disease.

The striatal expression of substance P (SP) and methionin-enkephalin (met-enk) genes was studied post mortem by in situ hybridization in patients with Parkinson's disease and a group of control subjects. No significant difference in striatal expression of these two neuropeptide messenger RNAs (mRNAs) was found in the patients compared with control subjects. This contrasts with animal models of parkinsonism, where expression of SP mRNA is decreased and met-enk mRNA increased. Possible explanations include: (1) compensatory mechanisms, which may develop during the long term evolution of Parkinson's disease; (2) normalized expression of the two genes resulting from chronic L-DOPA therapy.

Aged↗
PubMed1995

Preferential use of the VH4 Ig gene family by diffuse large-cell lymphoma.

Ig heavy chain variable region (VH) genes expressed by human diffuse large-cell lymphoma (DLC) and follicular lymphoma (FL) were identified and analyzed with respect to germline gene families. In 67 cases of FL, VH region genes were expressed in a pattern similar to that of normal B cells, with a predominance of the large VH3 gene family being used. In contrast, of the 17 cases of DLC, there was an extremely biased use of VH genes. Of these DLC tumors, 88% expressed genes from the small VH4 gene family; and even among these tumors, there was a limited use of genes, with 11 cases producing Igs derived from the VH4.21 germline gene. Although most of the VH genes expressed by DLC tumor cells contained mutations with respect to their germline counterparts, almost all of these mutations occurred before the clonal expansion of the tumor. This contrasts with our previous findings of ongoing mutations in FL and represents a fundamental difference between these two malignancies. This preferential gene use implies an important role for the VH4 gene family, and specifically for VH4.21, in the genesis of DLC.

Adolescent↗
PubMed1995

Autoradiographic localization and density of [125I]ferrotransferrin binding sites in the basal ganglia of control subjects, patients with Parkinson's disease and MPTP-lesioned monkeys.

Degeneration of the nigro-striatal dopaminergic neurons occurring in Parkinson's disease is associated with an increase in iron concentrations in the substantia nigra. As this metal catalyzes the production of free radicals, and oxidative stress may participate in the cascade of events ending in cell death, this increase in iron content may be involved in dopaminergic neuronal death. The localization and number of receptors for transferrin were investigated postmortem by quantitative autoradiography of iodinated-ferrotransferrin binding in the basal ganglia from controls, parkinsonian patients and MPTP-lesioned monkeys. In human controls, specific [125i] ferrotransferrin binding-site density was highest in the putamen and the caudate nucleus, and lowest in the globus pallidus. In parkinsonian patients, it was increased in the putamen and caudate nucleus, while in MPTP-intoxicated monkeys, there was a tendency for levels to decrease in these two regions. An inverse relationship between binding density and iron content reported in the studied regions supports the assumption of a possible capture of iron at the level of dopaminergic terminals and, in parkinsonian patients, on other cellular elements as well. These results suggest an involvement of transferrin receptors in iron uptake in the striatum of patients with Parkinson's disease, with differences between the 'acute' nigro-striatal MPTP-induced degeneration syndrome and the chronic long lasting human disease.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1995

White matter signal hyperintensities in the brains of patients with late paraphrenia and the normal, community-living elderly.

We determined the prevalence and anatomical location of areas of white matter hyperintensity visualized by magnetic resonance imaging in the brains of 38 late paraphrenic patients with an onset of psychotic illness after the age of 60 and 31 healthy aged community volunteers. All degrees of white matter signal hyperintensity were very common in both groups, and there was no excess of such changes in the brain of patients. Periventricular white matter and subcortical grey matter hyperintensities were significantly associated with both measured diastolic and systolic blood pressure in patients and control subjects. Periventricular and deep white matter, together with subcortical grey matter hyperintensities, were significantly associated with increased age. The excess of such presumed brain-imaging abnormalities previously reported in patients with an onset of psychosis late in life may be a consequence of earlier authors' failure to include examination of appropriate community control populations and to carefully exclude patients with evidence of stroke.

Aged↗
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

NMR mapping of the antigenic determinant recognized by an anti-gp120, human immunodeficiency virus neutralizing antibody.

The 24-amino-acid peptide RP135 (NNTRKSIRIQRGPGRAFVTIGKIG) corresponds in its amino acid sequence to the principal neutralizing determinant of the human immunodeficiency virus type-1, IIIB isolate (HIV-1IIIB, residues 308-331 of the envelope glycoprotein gp120). In order to map the antigenic determinant recognized by 0.5 beta, the complex of RP135 with an anti-gp120 HIV neutralizing antibody, 0.5 beta, which cross reacts with the peptide, was studied by using two-dimensional NMR spectroscopy. A combination of homonuclear Hartmann Hahn two-dimensional experiment and roating-frame Overhauser enhancement spectroscopy of the Fab/peptide complex measured in H2O was used to eliminate the resonances of the Fab and the tightly bound peptide residues and to obtain sequential assignments for those parts of the peptide which retain considerable mobility upon binding. In this manner, a total of 14 residues (Ser6-Thr19) were shown to be part of the antigenic determinant recognized by the antibody 0.5 beta. Lys5 and Ile20 were found to retain considerable mobility in the bound peptide while their amide protons undergo significant change in chemical shift upon binding. This observation suggests that these two residues are at the boundaries of the determinant recognized by the antibody. Competitive binding experiments using truncated peptides strongly support the NMR observations.

Amino Acid Sequence↗
PubMed1995

Induction of autoantibody responses to GM-CSF by hyperimmunization with an Id-GM-CSF fusion protein.

Fusion proteins consisting of an Ig containing xenogenic constant regions and granulocyte-macrophage colony stimulating factor (Id-GM-CSF) are potent immunogens capable of inducing anti-idiotypic Abs after two immunizations, without the usual need for adjuvants or carrier proteins. In this study, we investigated the effects of hyperimmunization with Id-GM-CSF and found that it induces anti-GM-CSF Abs that could bind to GM-CSF and neutralize its bioactivity in vitro. However, no detrimental effects of the anti-GM-CSF activity were apparent on the general health of the animals or on their base line white blood cell counts. Mice with the anti-GM-CSF activity reconstituted their peripheral white blood cells with identical kinetics as control mice after high dose cyclophosphamide treatment, sublethal irradiation, or lethal irradiation followed by syngeneic bone marrow transplantation. Primary and secondary Ab responses to a variety of protein Ags, including an unrelated Ig Id, were not affected. However, the anti-Id response induced by an unrelated GM-CSF fusion protein that is dependent upon the GM-CSF bioactivity was impaired. To avoid any potential problems associated with inducing anti-GM-CSF Abs, we show that priming with the Id-GM-CSF protein and boosting with the Id protein alone were sufficient to induce comparable anti-Id titers without inducing anti-GM-CSF Abs. We conclude that although hyperimmunization of mice with the GM-CSF fusion protein induced neutralizing anti-GM-CSF Abs, this was of little consequence to the animals. Nevertheless, we have devised a strategy to overcome this potential limitation on the use of GM-CSF fusion proteins for immunization.

Animals↗
PubMed1995

kappa-Opioid receptor-transfected cell lines: modulation of adenylyl cyclase activity following acute and chronic opioid treatments.

The opioid receptors mu, delta and kappa have recently been cloned. Here we show that kappa-agonists inhibit adenylyl cyclase activity in Chinese hamster ovary cells stably transfected with rat kappa-opioid receptor cDNA. Chronic exposure of the cells to kappa-agonists did not lead to significant desensitization of the capacity of the agonists to inhibit adenylyl cyclase. On the other hand, withdrawal of the agonist following the chronic treatment led to the phenomenon of supersensitivity ('overshoot') of adenylyl cyclase activity. Both the inhibition of adenylyl cyclase activity by the acute opioid treatment and the chronic agonist-induced supersensitivity are pertussis toxin sensitive, demonstrating involvement of Gi/Go proteins in both processes.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1995

CD18 (beta 2 leukocyte integrin) promoter requires PU.1 transcription factor for myeloid activity.

Normal cellular differentiation is linked to tightly regulated gene transcription. However, the DNA elements and trans-acting factors that regulate transcription in myeloid cells are poorly defined. CD18, the beta chain of the leukocyte integrins, is transcriptionally regulated during myeloid differentiation. The CD18 promoter is active after transfection into myeloid cells. We demonstrate that a region of the CD18 promoter that contains two binding sites for the PU.1 transcription factor is required for activity in myeloid cells. These sites are bound by in vitro translated PU.1 and by PU.1 from myeloid nuclear extracts. Mutagenesis of these sites abrogates binding by PU.1 and substantially decreases promoter activity in myeloid cells. Thus, the leukocyte-specific transcription factor PU.1 is required for myeloid activity of CD18.

Base Sequence↗
PubMed1995

Decreased phospholipase A2 activity in Alzheimer brains.

Phospholipase A2 (PLA2) is a key-enzyme in the metabolism of membrane phospholipids. In cholinergic neurons PLA2 controls the physico-chemical properties of neuronal membranes as well as the breakdown of phosphatidylcholine to produce choline for acetylcholine synthesis. Moreover PLA2 influences the processing and secretion of the amyloid precursor protein, which gives rise to the beta-amyloid peptide, the major component of the amyloid plaque in Alzheimer's disease (AD). In the present study PLA2 activity was investigated in post-mortem brains from 23 patients with AD and 20 nondemented elderly controls. In AD brains PLA2 activity was significantly decreased in the parietal and to a lesser degree in the frontal cortex. Lower PLA2 activity correlated significantly with an earlier onset of the disease, higher counts of neurofibrillary tangles and senile plaques and an earlier age at death, indicating a relationship between abnormally low PLA2 activity and a more severe form of the illness. The present results provide new evidence for a disordered phospholipid metabolism in AD brains and suggest that reduced PLA2 activity may contribute to the cholinergic deficit and to the production of amyloidogenic peptides in the disease.

Aged↗
PubMed1995

Two-dimensional NMR studies of the interactions between a peptide of cholera toxin and monoclonal antibodies.

To increase our understanding of the molecular basis for antibody specificity and for the cross-reactivity of antipeptide antibodies with native proteins, it is important to study the three-dimensional structure of antibody complexes with their peptide antigens. For this purpose it may not be necessary to solve the structure of the whole antibody complex but rather to concentrate on elucidating the combining site structure, the interactions of the antibody with its antigen, and the bound peptide conformation. To extract the information about antibody-peptide interactions and intramolecular interactions in the bound ligand from the complicated and unresolved spectrum of the Fab-peptide complex (Fab: antibody fragment made of Fv--the antibody fragment composed of the variable regions of the light and heavy chains forming a single combining site for the antigen--the light chain, and the first heavy chain constant regions), an nmr methodology based on measurements of two-dimensional transferred nuclear Overhauser effect (NOE) difference spectra was developed. Using this methodology the interactions of three monoclonal antibodies with a cholera toxin peptide were studied. The observed interactions were assigned to the antibody protons involved by specific deuteration of aromatic amino acids and specific chain labeling, and by using a predicted model for the structure of the antibody combining site. The assigned NOE interactions were translated to restraints on interproton distances in the complex that were used to dock the peptide into calculated models for the antibodies' combining sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Long-term follow-up of HIV positive asymptomatic patients having received cyclosporin A.

The data of the 27 asymptomatic HIV-1 seropositive patients with CD4+ cell count between 300 and 600/microliters treated by Cyclosporin A (CSA) (7.5 mg/kg/day) in our institution between October 1985 and 1987 were reviewed in October 1993. Hemoglobin concentration, platelet count, total lymphocytes, CD4+ and CD8+ cell counts and serum core protein p24 antigenemia, as well as creatininemia measured before CSA onset, at CSA cessation and twice a year were recorded as well as clinical signs and CSA toxicities. In October 1993 median duration of CSA treatment was 11 months, median follow-up after CSA cessation was 45 months and median total follow-up was 67 months. Toxicities of CSA were those commonly encountered in other pathologies. Under CSA no patient progressed toward clinical AIDS (1987 definition). The mean CD4+ cell count of the 27 patients remained unchanged (gain of 1 cell/year) under CSA treatment, while it decreased at a rate of 50 cells/year after CSA cessation (p < 0,005). On the other hand CSA treatment had no significant impact on the evolution of total lymphocyte count, CD8+ cell counts, and P24 antigenémia.

Adult↗
PubMed1995

Oligohydramnios, intrauterine growth retardation and fetal death due to umbilical cord torsion.

Intrauterine fetal death was observed in a woman at 35 gestational weeks shortly after she was admitted to hospital due to suspected placental insufficiency expressed by oligohydramnios and fetal growth retardation. The pathologic examination showed umbilical cord torsion and an organized thrombus at the site of the torsion. This findings could imply that both the fetal death and the placental insufficiency were the results of the cord torsion.

Adult↗