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Biomedical subjects

V I Teichberg

Publications and source records attributed to V I Teichberg.

At least 37 records · Page 2Linked to original sources
PubMed1989

Kainyl-bovine serum albumin: a novel ligand of the kainate sub-type of glutamate receptor with a very high binding affinity.

Bovine serum albumin has been conjugated with kainylaminooxyacetylglycine to afford a multivalent kainylated protein called kainyl-bovine serum albumin (KA-BSA). This derivative, radiolabelled with 125I to more than 5000 Ci/mmol, was found to interact in the chick, goldfish and rat brain to specific membranous sites displaying the pharmacological properties attributed to the kainate sub-type of glutamate receptor. Measurements of the kinetics of association and dissociation of KA-BSA showed a quasi-irreversible binding with dissociation constants in the subpicomolar and nanomolar range. The chemical properties and the binding characteristics of KA-BSA suggest that it interacts mainly with kainate binding sites present in clusters in the membrane. Localization of the KA-BSA binding sites, by autoradiography in the chick cerebellum and by immunoperoxidase staining in the goldfish cerebellum, revealed an exclusive association with the molecular layer.

Animals↗
PubMed1989

A microtest plate assay of functional excitatory amino acid receptors.

A microtest plate assay of functional excitatory amino acid receptors present on cultured chick embryo retinal cells has been developed. It is based on measurements of excitatory amino acid-mediated increase in 22Na+ influx into retinal cells adhering to each of the 96 wells of microtest plates. Dose-dependent responses to L-glutamate, kainate and N-methyl-D-aspartate but not to quisqualate can be measured. These responses are selectively inhibited by antagonists of excitatory amino acids. The assay is reliable, fast to perform and parsimonious in terms of the volume and thus of amount of the drug applied. It allows a single investigator to perform, in one day, measurements of the effects of known or putative glutamatergic ligands in more than 100 different conditions.

Animals↗
PubMed1989

Patterns of expression of a 15K beta-D-galactoside-specific lectin during early development of the avian embryo.

We have determined, by immunohistochemical and biochemical techniques, the distribution of an endogenous beta-D-galactoside-binding lectin between the early primitive streak stage and the 5th day of embryonic development of the chick. The lectin, which was purified from the pectoral muscle of 16-day-old chick embryos, migrates on SDS-PAGE as a single polypeptide of relative molecular mass 15 x 10(3). Antibodies to this pure lectin interact with the 15K (K = 10(3) M(r)) polypeptide as well as with a 6.5K polypeptide; this second component appears to be antigenically related to the 15K lectin, as antibodies affinity purified on the 15K band recognize both polypeptides. In early stages of development, lectin immunoreactivity was present in most cells of the epiblast and hypoblast in the region of the primitive streak, while towards the edge of the area pellucida the epiblast was stained less intensely. During gastrulation, strong immunoreactivity was present also in migrating cells and in the mesoblast, while at the margin of the area pellucida the epiblast was negative. Up to the 10-somite stage, lectin immunoreactivity was present in the somites, neural tube and presumptive cardiac region; the non-neural ectoderm and the extracellular matrix were not labeled; the predominant immunoreactive component at this stage of development was the 6.5K polypeptide. Later in development, the lectin immunoreactivity gradually disappeared from the dermamyotome and nervous system to reappear conspicuously as soon as a differentiated myotome could be detected. Immunoreactivity was very high in the myotome, skeletal and cardiac muscles and transient in smooth muscles. The only region of the nervous system that continued to express the lectin throughout development was the trigeminal (semilunar) ganglion; in all regions of the nervous system, the lectin immunoreactivity disappeared early in development to be re-expressed only much later. The lining epithelium of the digestive tract and other endodermal derivatives expressed the lectin transiently. In the extraembryonic membranes, immunoreactivity to the lectin was observed in the yolk sac and in both layers of the amnion. The striking regulation of the expression of this endogenous lectin suggests that its functions are linked to cell proliferation and/or to the selective expression of a developmentally-timed cell phenotype.

Animals↗
PubMed1988

Affinity-repulsion chromatography. Principle and application to lectins.

The interactions of proteins with their immobilized ligands in an electrically charged microenvironment were studied. The binding of lectins to erythrocytes and to affinity matrices was used as a model system. Lectins bind and agglutinate erythrocytes in the presence of at least 10 mM NaCl or 1 mM CaCl2, but not in deionized water. The salt dependence of the agglutination process is due to the ability of salts to provide counterions neutralizing the forces of repulsion between the electrostatic charges of similar sign present on the erythrocyte cell surface and on the lectins. The same salt dependence is observed for the binding of lectins to affinity matrices. These observations are the basis of a protein separation process coined affinity-repulsion chromatography in which the electrostatic charges present, or purposely introduced, on affinity matrices are exploited and allow the elution, by electrostatic repulsion, of proteins carrying electrostatic charges of the same sign as that of the matrix. In this process, proteins are loaded on the affinity matrix in a salt solution and eluted with deionized water. Affinity-repulsion chromatography has been successfully applied here to the isolation of several lectins. Its physicochemical basis, merits, and potential applications are discussed.

Animals↗
PubMed1988

Isolation, immunochemical characterization and localization of the kainate sub-class of glutamate receptor from chick cerebellum.

The low-affinity kainate binding sites, present at high density in chick cerebellar membranes, were solubilized with Triton X-100 and purified 41-fold. The purified kainate binding sites, therein referred to as the kainate receptor, displayed the expected pharmacological specificity: domoate = kainate much greater than L-glutamate much greater than D-glutamate, quisqualate, N-methyl-D-aspartate. Analysed by SDS-PAGE under reducing conditions, a single polypeptide with a Mr = 49,000 was observed. Western blots of membranes prepared from different brain areas and animal species were analysed using a monoclonal antibody, named mAb IX-50, raised against the purified kainate receptor. The mAb IX-50 stained the 49,000 polypeptide in chick, goldfish and mammalian brain tissues indicating its conservation during evolution. The staining intensity correlated with the density of kainate binding sites. The mAb IX-50 stained also a 93,000 polypeptide but the latter did not copurify with the 49,000 polypeptide. The kainate binding activity was selectively immunoadsorbed on mAb IX-50 coupled to Sepharose which, upon elution, released a 49,000 polypeptide. The immunohistochemical localization of mAb IX-50 binding sites in the chick cerebellar molecular layer coincided with that of the kainate receptor. We conclude that the 49,000 polypeptide is part of the kainate receptor and carries the kainate recognition site.

Animals↗
PubMed1988

Involvement of excitatory neurotransmitters in the damage produced in chick embryo retinas by anoxia and extracellular high potassium.

Chick embryo retinas were exposed for 40 min to anoxic conditions and the resulting histological changes were studied by light microscopy. A strong edematous response with severe swelling of the inner nuclear, inner plexiform and ganglion cell layers and numerous cells with pyknotic nuclei but very few dead cells were observed. These changes were qualitatively similar to those observed on retinas exposed to high potassium concentration or to glutamic acid. The deleterious effects of anoxia and high potassium concentration were not affected by the removal of calcium ions from the retina incubation medium but were prevented by gamma-D-glutamylglycine, an antagonist of excitatory amino acid receptors. These results suggest that the damage observed in retinas maintained under anoxia for 40 min is likely to be due to the release, from non-synaptic pools, of excitatory neurotransmitters, possibly glutamic and/or aspartic acids, evoked by the dissipation of the membrane ionic gradients. These events would be the first in a chain of toxic damage leading ultimately to cell death.

Animals↗
PubMed1987

Extensive amino acid sequence homologies between animal lectins.

We have established the amino acid sequence of the beta-D-galactoside binding lectin from the electric eel and the sequences of several peptides from a similar lectin isolated from human placenta. These sequences were compared with the published sequences of peptides derived from the beta-D-galactoside binding lectin from human lung and with sequences deduced from cDNAs assigned to the beta-D-galactoside binding lectins from chicken embryo skin and human hepatomas. Significant homologies were observed. One of the highly conserved regions that contains a tryptophan residue and two glutamic acid residues is probably part of the beta-D-galactoside binding site, which, on the basis of spectroscopic studies of the electric eel lectin, is expected to contain such residues. The similarity of the hydropathy profiles and the predicted secondary structure of the lectins from chicken skin and electric eel, in spite of differences in their amino acid sequences, strongly suggests that these proteins have maintained structural homologies during evolution and together with the other beta-D-galactoside binding lectins were derived from a common ancestor gene.

Amino Acid Sequence↗
PubMed1986

Absence of side-effects in the anticonvulsant action of cortically applied antagonists of N-methyl-D-aspartate.

Three compounds reportedly blocking the N-methyl-D-aspartate (NMDA) receptor, namely 2-amino-5-phosphonovalerate, gamma-D-glutamylglycine and 3-hydroxy-2-quinoxalinecarboxylic acid, were injected subdurally onto the cortex of freely moving rats. All 3 compounds effectively suppressed behavioral and electrographic seizure activity induced by strychnine, morphine and picrotoxin that were administered via the same route. The cortical application of the NMDA-receptor antagonists did not induce behavioral or electrographic changes, and behavioral side-effects commonly observed following intracerebroventricular administration of these compounds were absent. The anatomical separation of anticonvulsant action and side-effects induced by these compounds suggests that this class of compounds may eventually be useful as antiepileptic drugs.

2-Amino-5-phosphonovalerate↗
PubMed1985

Peptides derived from kainic acid as antagonists of N-methyl-D-aspartate-induced neuroexcitation in rat brain.

The effects of dipeptides and an amide chemically derived from kainic acid (KA) on the response of rat striatal slices to excitatory amino acids were studied. Some of the gamma-peptides of KA were found to antagonize the response to N-methyl-D-aspartate (NMDA) more than that to quisqualate and glutamate and not to have any effect on the response to kainate. The least potent antagonists among the tested compounds were the gamma-amide of KA and the peptides of KA with beta-alanine and gamma-aminobutyric acid, whereas the gamma-kainyl peptides of the alpha-amino acids glycine, tyrosine, glutamate and KA were more active. The latter are the best blockers of the response to NMDA among the tested compounds.

Animals↗
PubMed1985

Anticonvulsant properties of 3-hydroxy-2-quinoxalinecarboxylic acid, a newly found antagonist of excitatory amino acids.

Various aromatic acids have been investigated as putative ligands of excitatory amino acid receptors. 3-Hydroxy-2-quinoxalinecarboxylic acid (HQC), at 1 mM, was found to antagonize the 22Na+ efflux produced in 22Na+-preloaded brain slices by N-methyl-D-aspartate and kainate. The response to glutamate was also affected but not that to quisqualate. The apparent KI value of HQC for suppression of the N-methyl-D-aspartate response was 0.27 mM. The anticonvulsant action of HQC was investigated in mice and rats. HQC administered intracerebroventricularly caused a dose dependent delay in the occurrence of picrotoxin induced convulsions and afforded protection against picrotoxin induced death. These results confirm the proposition that antagonists of excitatory amino acids possess anticonvulsant properties.

Animals↗
PubMed1985

Isolation and characterization of chicken thymic electrolectin.

We have detected the presence of a beta-D-galactoside-binding lectin (electrolectin) in extracts of the thymus of adult chickens. This lectin was purified by affinity chromatography on a lactosyl-Sepharose column to yield 1.4 mg of pure protein from 230 g of thymus. The chicken thymic electrolectin (CTE) has an Mr of 15 300 when analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and of 30 000 when analysed by gel filtration. The amino acid composition of CTE is similar to that of other electrolectins purified from human and rat lung. CTE cross-reacts immunologically, but is not identical, with electrolectins from electric-eel electric organ and from chick-embryo pectoral muscle. CTE agglutinates chicken thymocytes but does not appear to promote their mitosis.

Amino Acids↗
PubMed1985

A dipeptide derived from kainic and L-glutamic acids: a selective antagonist of amino acid induced neuroexcitation with anticonvulsant properties.

The dipeptide N-[[[2'S-(2' alpha, 3' beta, 4' beta)]-2'-carboxy-4'-(1"-methylethenyl)-3'-pyrrolidinyl)acetyl]-L- glutamic acid (6) has been synthesized by a route that involves the selective protection of the alpha-carboxyl function of kainic acid. This dipeptide inhibits the stimulation of Na+ fluxes induced in brain slices by the neuroexcitant N-methyl-D-aspartic acid. Administered intracerebroventricularly, it is also effective in protecting mice from picrotoxin-induced convulsions with an ED50 of 0.17 mumol.

Animals↗
PubMed1984

An evaluation of selected brain constituents as putative excitatory neurotransmitters.

Searching for the endogenous ligands of the 4 classes of excitatory amino acid receptors detected in the mammalian CNS, we have measured, using a 22Na+ efflux receptor assay, the excitatory activity of 42 brain constituents or analogs and established the receptor specificity of those substances which possess excitatory properties. Among the substances tested were methyltetrahydrofolate and N-acetylaspartylglutamate, two putative ligands of the kainate and glutamate receptors. These compounds were found to have very little or no excitatory activity, respectively. The 8 brain constituents possessing excitatory properties displayed a receptor specificity similar to either that of N-methyl-D-aspartate (e.g. quinolinate) or glutamate (e.g. cysteine sulfinate) but not of kainate or quisqualate. These results are discussed in relation with the problem of the identification of brain excitatory neurotransmitters.

Animals↗
PubMed1984

Differential sensitivity of selected rat brain areas to excitatory neurotransmitters released by K+ depolarization.

The depolarization of brain slices by high K+ concentrations in the presence of Ca2+ ions leads to the release from nerve terminals of endogenous excitatory neurotransmitters that interact with subsynaptic receptors controlling the neuronal membrane permeability to Na+ ions. This interaction has been studied by following the K+-evoked Ca2+-dependent 22Na+ efflux from 22Na+-preloaded slices from the cortex, striatum, hippocampus, cerebellum, substantia nigra and hypothalamus of the rat. The results indicate that the so-called N-methyl-D-aspartate receptor mediates the bulk of the excitatory transactions in the cortex and striatum whereas a subsynaptic glutamate receptor may mediate those in the hippocampus and cerebellum.

Animals↗
PubMed1984

gamma-Aminobutyric acid activation of 36Cl- flux in rat hippocampal slices and its potentiation by barbiturates.

gamma-Aminobutyric acid (GABA) increases the rate of 36Cl- efflux from preloaded rat hippocampal slices in a dose-dependent manner (EC50: 400 microM). This action has the pharmacological specificity expected of activation of GABA receptors in that it is mimicked by the agonists muscimol and 3-aminopropanesulfonic acid, and blocked by the antagonists bicuculline and picrotoxinin. GABA uptake inhibitors, nipecotic acid and 2,4-diaminobutyric acid, fail to increase 36Cl- flux. Pentobarbital produces a dose-dependent activation (EC50 = 1.5 mM) of 36Cl- efflux with maximal response greater than that of GABA. The effect of pentobarbital can be mimicked by 1,3-dimethylbutylbarbiturate, secobarbital, (+)hexobarbital but not (-)hexobarbital, and is blocked by bicuculline and picrotoxinin. Pentobarbital and the other active barbiturates also potentiate the action of GABA. Phenobarbital does not have any effect independently or in combination with GABA. It is suggested that GABA increases 36Cl- permeability by activation of a postsynaptic receptor which is in turn functionally coupled to a barbiturate receptor.

Animals↗
PubMed1984

The distribution of electrolectin in mouse: genetic and ontogenic variations.

Electrolectins are beta-D-galactoside binding lectins found in teleosts, avians and mammals. We have studied the distribution of electrolectin in several inbred strains of mice and have followed the changes in electrolectin activity occurring during development. Electrolectin activity is present in skeletal muscle, kidney, lung, heart, thymus and spleen of the young animal. The levels of electrolectin activity present in skeletal muscle, heart, lung, kidney and liver keep increasing up to 14 days after birth and then steadily decrease. In contrast, the level of electrolectin activity in the thymus and in the spleen remain constant during development. These results are discussed in view of the possible role of electrolectin in differentiation.

Aging↗
PubMed1984

Barbiturates, alcohols and the CNS excitatory neurotransmission: specific effects on the kainate and quisqualate receptors.

The effects of barbiturates and straight-chain aliphatic alcohols on the responses of rat striatal neurons to excitatory amino acids have been investigated. The responses to N-methyl-D-aspartate, quisqualate, kainate, L-glutamate and L-aspartate were measured by the increase in 22Na+ efflux rate that they produce in brain slices. The responses to quisqualate and kainate, measured in the 22Na+ efflux assay, were found to be partially blocked by barbiturates whereas the responses to N-methyl-D-aspartate, glutamate and aspartate were not. The kainate and quisqualate-induced increases in 22Na+ efflux rate were much more readily blocked by the presence of aliphatic alcohols than were the responses to N-methyl-D-aspartate, glutamate and aspartate. These results strengthen the idea of the existence of 4 distinct receptors for excitatory amino acids in the rat striatum. They are consistent with the presence on the kainate and quisqualate receptors, but not on the N-methyl-D-aspartate and glutamate/aspartate receptors of a hydrophobic domain which would provide a site of interaction for barbiturates and alcohols. They suggest that receptors for excitatory amino acids can be targets for the actions of barbiturates and alcohols on the central nervous system, and may mediate some of the anesthetic and hypnotic effects of these drugs.

Alcohols↗