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Biomedical subjects

T Glaser

Publications and source records attributed to T Glaser.

At least 109 records · Page 6Linked to original sources
PubMed1987

Genes encoding alpha and beta subunits of Na,K-ATPase are located on three different chromosomes in the mouse.

We have made use of a panel of mouse-hamster somatic cell hybrids and restriction fragment length polymorphisms between two mouse species (Mus musculus and Mus spretus) to determine the chromosomal localization of genes encoding the alpha and beta subunits of the Na,K-ATPase (Na+,K+-activated ATP phosphohydrolase, EC 3.6.1.3). DNA probes for three distinct isoforms of the Na,K-ATPase alpha subunit mapped to three different mouse chromosomes: the alpha 1 gene (Atpa-1) cosegregated with the Egf gene on chromosome 3; alpha 2 (Atpa-2) with the cytochrome P-450PB gene family/coumarin hydroxylase locus on chromosome 7; alpha 3 (Atpa-3) with the alpha-spectrin gene on chromosome 1. The Na,K-ATPase beta-subunit gene (Atpb) mapped to the same region of chromosome 1, but it was not tightly linked to the Atpa-3 gene. These results indicate that three isoforms of the Na,K-ATPase alpha subunit are encoded by three distinct genes. The dispersion of Na,K-ATPase genes suggests that their expression is not likely to be controlled by a common cis-acting regulatory element.

Animals↗
PubMed1986

Calpain-calpastatin and fusion. Fusibility of erythrocytes is determined by a protease-protease inhibitor [calpain-calpastatin] balance.

Rat erythrocytes fuse when treated with the membrane mobility agent, 2-(2-methoxyethoxy)ethyl-cis-8-(2-octylcyclopropyl)octanoate (A2C) and Ca2+, whereas human cells do not. Membrane proteolysis promoted by calpain is required for rat cell fusion [(1986) Eur. J. Biochem., in press]. Human calpain induced a selective proteolysis in both the human and rat erythrocyte ghosts (mainly band 4.1 in the human, band 4.1 and band 3 in the rat cell) and rendered them fusible. Calpastatin (calpain inhibitor) prevented A2C-induced fusion in both ghosts, via inhibition of proteolysis. The human erythrocyte has excess calpastatin and resists A2C-promoted fusion. A regulatory role of calpastatin in membrane fusion is thus indicated.

Animals↗
PubMed1986

Fusion of rat erythrocytes by membrane-mobility agent A2C depends on membrane proteolysis by a cytoplasmic calpain.

The membrane-mobility agent 2-(2-methoxyethoxy)ethyl-cis-8-(2-octylcyclopropyl)octanoate (A2C) promotes fusion of rat, but not of human, erythrocytes. The difference in fusibility was shown to be correlated with membrane proteolysis, a process induced by Ca2+ in the rat erythrocytes or hemolysate-loaded ghosts, but not in the human cell. Membrane proteolysis is necessary but not sufficient for fusion. Fusion requires both Ca2+ and A2C [Kosower, N. S., Glaser, T. and Kosower, E. M. (1983) Proc. Natl Acad. Sci USA 80, 7542-7546]. Membrane proteolysis (Ca2+-dependent) and fusion (Ca2+ and A2C-dependent) requires a Ca2+-activated cytoplasmic thiol protease, as shown by the following observations. In intact rat erythrocytes, proteolysis and fusion are prevented by thiol alkylation and by inhibitors of Ca2+-dependent thiol proteases. Inhibitors to other proteases have no effect. Erythrocyte ghosts undergo proteolysis and fusion only when loaded with non-inhibited hemolysate, irrespective of membrane status (native or alkylated membrane). A partially purified cytosolic enzyme, identified as calpain I, promotes proteolysis in rat erythrocyte ghosts. A2C induces fusion only in such calpain-treated ghosts.

Animals↗
PubMed1986

Ontogenesis of serotonin (5-HT) binding sites in the choroid plexus of the rat brain.

The increase in density of 5-HT1c receptors in the choroid plexus of the third and lateral ventricles was analyzed in rats between the 1st and 90th postnatal days. An increase was found between the 3rd day and the 4th to 5th week, at which time adult values are attained. The development of the 5-HT1c receptors clearly differs from that of 5-HT1 receptors in other brain regions. The density in the choroid plexus is about 20% higher in the third ventricle than in the lateral ventricles.

Animals↗
PubMed1986

Quantitative autoradiography of transmitter binding sites with an image analyzer.

A computerized image processing system for quantitative receptor autoradiography on tritium-sensitive film is described. The method implements an image analyzer (IBAS 1 + 2) for the acquisition of an image which is evaluated with respect to the regional distribution of binding site densities by a small computer which is connected to a digitizer. Several methodological problems must be considered when using tritium-labelled compounds and an image analyzer. The use of tissue standards and shading procedures, the improvement of signal-to-noise ratio, the calibration of the system which establishes the non-linear relation between grey values and concentration of radioactivity, the contrast enhancement and the quenching problem are discussed. This method permits a quick and precise quantitative analysis of binding site distribution in receptor autoradiography.

Animals↗
PubMed1985

Autoradiographic identification and topographical analyses of high affinity serotonin receptor subtypes as a target for the novel putative anxiolytic TVX Q 7821.

TVX Q 7821 is a putative non-benzodiazepine anxiolytic which has a high affinity to 5-HT1 receptors. In this study some of the binding characteristics of the radiolabeled drug using rat brain cryostat sections and the autoradiographic localization of binding sites using the LKB-Ultrofilm technique have been investigated. Parallel experiments have been performed using [3H]serotonin ( [3H]5-HT). Both [3H]TVX Q 7821 and [3H]5-HT bound specifically and in a saturable manner to tissue sections, the Kd values being 6.8 and 3.7 nmol/l, respectively. Quantitative autoradiography using computer-assisted image analysis revealed a mean inhibition by TVX Q 7821 of [3H]5-HT binding of 56% in many brain areas. The inhibition ranged from 80% in the hippocampus and entorhinal area to practically none in the substantia nigra and the dorsal subiculum. Color coded autoradiograms obtained either with [3H]5-HT or [3H]TVX Q 7821 showed a nearly identical pattern of labeling with high receptor densities in the hippocampus, the entorhinal area, the septum, the interpeduncular nucleus and the dorsal raphe. However, in some brain areas striking differences in the intensity of labeling were found. [3H]5-HT but not [3H]TVX Q 7821 bound strongly in the substantia nigra, the dorsal subiculum and the globus pallidus. It is proposed that TVX Q 7821 binds to a subtype of 5-HT1 receptor (the so-called 5-HT1A sites as recently proposed). Thus, the putative anxiolytic TVX Q 7821 may provide a means for the study of the functional role of 5-HT1 receptors.

Animals↗
PubMed1985

The ontogenetic development of serotonin (5-HT1) receptors in various cortical regions of the rat brain.

The distribution of serotonin (5-HT1) receptors in various cortical regions of the rat brain has been examined during ontogenesis by quantitative autoradiography. An increase in binding site density between the first postnatal day and adult age was observed and could be approximated by a sigmoid shaped (logistic) growth curve. A marked heterochrony in the increase of binding site density is found in the 13 analyzed cortical regions. Binding sites develop earlier in neocortex than in allocortical areas. Fifty percent of the binding site density of adult age is reached in the motor cortex at the 9th postnatal day, followed by the primary somatosensory cortex one day later, by the medial prefrontal cortex on the 12th day, by the fascia dentata on the 14th day and by the CA 1-region on the 20th day. A detailed analysis of the frontal, medial prefrontal and hippocampal regions also shows a heterochrony within these regions. Adult values of binding site densities are also reached at different ages in the various cortical regions. The highest receptor densities were observed in the dorsal subiculum, the lowest in the primary somatosensory cortex.

Aging↗
PubMed1985

Binding of the putative anxiolytic TVX Q 7821 to hippocampal 5-hydroxytryptamine (5-HT) recognition sites.

The abilities of the putative non-benzodiazepine anxiolytic compound TVX Q 7821 in comparison to 5-HT and the 5-HT2 receptor antagonist ketanserin to displace 3H-5-HT from its binding sites in various regions of calf brain were studied. Binding affinities and capacities for 3H-5-HT were determined using membranes from different calf brain regions. Competition experiments with radiolabelled 3H-ketanserin using rat prefrontal cortex membranes were also performed. High affinity 3H-5-HT binding was found in all calf brain areas examined, with the hippocampus having the highest density of binding sites. TVX Q 7821 was a potent displacer (Ki-value 10 nmol/l) of 3H-5-HT binding in hippocampal membranes but not in membranes from other brain regions. No high affinity binding of TVX Q 7821 was found to the 5-HT receptors labelled with 3H-ketanserin. It is concluded, that TVX Q 7821 may bind preferentially to a special subtype of the 5-HT1 recognition site. Furthermore the results suggest that these sites may be involved in the mechanism of the anxiolytic action of TVX Q 7821.

Animals↗
PubMed1985

3H-TVX Q 7821: identification of 5-HT1 binding sites as target for a novel putative anxiolytic.

In order to clarify the mechanism of action of the putative nonbenzodiazepine anxiolytic TVX Q 7821 [2-(4-(4-(2-pyrimidinyl)-1-piperazinyl)butyl)-1, 2-benzisothiazol-3-(2H)one-1,1-dioxidehydrochloride], binding studies with the radio labelled compound were performed. 3H-TVX Q 7821 bound rapidly, reversibly and in a saturable manner with high affinity to calf brain structures with preference for the hippocampus (KD 1.62 nmol/l; Bmax 320 fmol/ mg protein). 3H-TVX Q 7821 binding was displaced only by 5-hydroxytryptamine and its agonists and antagonists including spiperone, but was not displaced by a variety of other neurotransmitters and drugs. The 5-HT2 receptor antagonist ketanserin was a weak displacer. The hippocampal binding sites for 3H-TVX Q 7821 were pharmacologically very similar to the 5-HT1-binding sites in this region. TVX Q 7821 is likely to be an important tool in research on functional aspects of 5-HT1 binding sites.

Animals↗
PubMed1985

Disulfide-linked and transglutaminase-catalyzed protein assemblies in platelets.

Energy depletion induces the formation of disulfide-linked and transglutaminase-catalyzed protein assemblies in platelets. The disulfide type polymers, formed following incubation at 37 degrees C in the absence of adenosine triphosphate (ATP)-generating precursors, are composed of cytoskeletal proteins and are associated with a decrease of reduced glutathione levels accompanying ATP depletion. The maintenance of ATP and reduced glutathione levels to, respectively, 34% and 47% of their original values is sufficient to prevent the formation of both polymer types. The transglutaminase-type cross-links are formed in the presence of calcium in either "energy-depleted" or thrombin stimulated platelets. 125I-surface-labeled membrane proteins, presumably transmembrane proteins, are incorporated into the transglutaminase-catalyzed cross-linked polymer of thrombin-stimulated platelets. Glycoproteins IIb and IIIa are not essential to the polymer formation, since thrombasthenic platelets treated with thrombin exhibit the same type of labeled polymer. The transglutaminase-catalyzed polymer formation following thrombin stimulation of platelets is inhibited by a calcium channel blocker, an intracellular calcium antagonist, as well as other inhibitors such as indomethacin, dibutyryl cyclic AMP, and prostaglandin E1. Although the evidence points to the formation of transglutaminase-catalyzed cross-linking in the cytoplasmic compartment, additional cross-linking of extruded components cannot be excluded.

Acyltransferases↗
PubMed1984

TVX 2706--a new phosphodiesterase inhibitor with antiinflammatory action. Biochemical characterization.

The effects of the anti-inflammatory and analgesic drug 3-ethyl-1-(3-nitrophenyl)-2,4[1H, 3H]-quinazolindione (TVX 2706) on neuronal and glial cell culture systems including neuroblastoma X glioma hybrid cells have been studied. This compound strongly enhances the increase in intracellular levels of cyclic AMP caused by appropriate effectors in all systems tested so far. EC50 values are in the submicromolar range. The effect is apparently neither due to an increased responsiveness of the hybrid cells for an effector like prostaglandin E1 nor to an increased activity of adenylate cyclase, but to an inhibition of both low and high affinity cyclic AMP phosphodiesterases. Half-maximal inhibition of enzyme activity is obtained at 10 microM TVX 2706. The drug is at least equipotent to or more potent than some other common phosphodiesterase inhibitors. Inhibition of phosphodiesterase activity is also observed in homogenates from rat polymorphonuclear leucocytes, where the low Km-enzyme is preferentially inhibited. TVX 2706 does not interfere with the calmodulin activation of phosphodiesterase. The role of phosphodiesterase inhibition as a possible mechanism of the anti-inflammatory action of TVX 2706 is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

Brain serotonin receptors as a target for the putative anxiolytic TVX Q 7821.

In animal behavioral tests of anxiolytic efficacy, TVX Q 7821 was active and equipotent with diazepam, but did not produce muscle relaxation or anti-convulsant effects. The high affinity, specific binding of 3H-TVX Q 7821 to calf hippocampal membranes was displaced by serotonin (5-HT) but not by diazepam. Similarly, unlabeled TVX Q 7821 displaced 3H-5-HT but not 3H-flunitrazepam binding. Since ketanserin (a putative 5-HT2 ligand) was equally weak in displacing labeled 5-HT or TVX Q 7821, TVX Q 7821 may preferentially bind to 5-HT1, receptors.

Aggression↗
PubMed1983

Vasoactive intestinal polypeptide: presence in neuroblastoma X glioma hybrid cells.

Extracts of neuroblastoma X glioma hybrid cells 108CC15 and their parental lines were investigated for the presence of vasoactive intestinal polypeptide (VIP). With the aid of a radioimmunoassay and a receptor binding assay, VIP activity was found in the hybrid cells, to a lesser extent in neuroblastoma cells, but not in glioma cells. These results suggest a neuronal function of VIP. Since the hybrid cells also contain acetylcholine and opioids, they may be useful in studies of co-release of neurohormones.

Animals↗
PubMed1983

Membrane-mobility agent-promoted fusion of erythrocytes: fusibility is correlated with attack by calcium-activated cytoplasmic proteases on membrane proteins.

Rat, but not human, erythrocytes undergo fusion promoted by the membrane-mobility agent 2-(2-methoxyethoxy)-ethyl cis-8-(2-octylcyclopropyl)octanoate (A2C). The difference in behavior is correlated with rat erythrocyte membrane protein degradation caused by Ca2+-activated proteases. The human erythrocyte is deficient in such protease activity. Membrane protein degradation is a necessary, but not sufficient, requirement for membrane fusion. Membrane protein degradation probably releases membrane components from certain constraints. In addition, the motion of membrane components precedes fusion and must be promoted by reagents such as A2C, leading to the creation of fusion-potent lipid areas. This sequence of chemical and physical events occurs in other fusion processes.

Animals↗