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Y Dudai

Publications and source records attributed to Y Dudai.

At least 55 records · Page 3Linked to original sources
PubMed1987

The cAMP cascade in the nervous system: molecular sites of action and possible relevance to neuronal plasticity.

Many intercellular messages regulate the activity of their target cells by altering the intracellular level of cAMP and, as a consequence, the phosphorylation state of proteins which serve as substrates for cAMP-dependent protein kinase. Such regulation plays a crucial role in neuronal development, neuronal function, and neuronal plasticity (e.g., elementary learning mechanisms). Ample information has been accumulated in recent years on the enzymes that regulate the level of cAMP or respond to it, on the regulation of cAMP synthesis by neurohormones, neurotransmitters, ions, and toxins, on neuronal-specific substrate proteins that are phosphorylated by the cAMP-dependent kinase, and on the interaction of the cAMP-cascade with other second-messenger systems within neurons. Such data, obtained by a combination of molecular-biological, biochemical, and cellular approaches, shed light on the detailed mechanisms by which modulation of a ubiquitous molecular cascade leads to a great variety of short-term as well as long-term specific neuronal responses and alterations.

Animals↗
PubMed1985

Multiple defects in the activity of adenylate cyclase from the Drosophila memory mutant rutabaga.

Adenylate cyclase in homogenates of Drosophila melanogaster is heterogeneous with respect to its affinity toward MgATP and its subcellular distribution. Km values for MgATP range, under similar assay conditions, from approximately 10(-5) M to approximately 10(-3) M, depending on the body region and on the subcellular localization of the enzyme. The majority of the enzyme in whole-body preparations is particulate, but various body regions differ in the relative proportion of the soluble enzyme. The memory mutant rutabaga lacks up to 35% of the total particulate activity. Even ligands that stimulate directly the catalytic subunit are incapable of bringing the activity of the mutant's enzyme to normal levels. The defect is differentially pronounced in various body parts and is associated with an altered responsiveness of the enzyme to Mg2+, to Ca2+, and to forskolin. It is suggested that rutabaga is lesioned in a subpopulation, or a functional state, of adenylate cyclase, which may play a role in memory formation.

Abdomen↗
PubMed1985

Defective responsiveness of adenylate cyclase to forskolin in the Drosophila memory mutant rutabaga.

The Drosophila memory mutant rutabaga (rut) has been previously shown to have a defective subpopulation (or functional state) of the enzyme adenylate cyclase. We report here that the reduced adenylate cyclase activity is also associated with a defective responsiveness of the enzyme to forskolin. Forskolin activation isotherms of the enzyme in normal membranes reveal low- and high-affinity forskolin-interacting components; the residual enzyme in the mutant shows a smaller proportion of the high-affinity response. In addition, in mutant membrane preparations, forskolin fails to shift the Km of the enzyme for free Mg2+ and for MgATP, in contrast to the situation in the normal tissue. The defect in the responsiveness to forskolin in rut is even more pronounced in a Lubrol-solubilized enzyme preparation, and is due to intrinsic properties of the cyclase system rather than to the absence (or presence) of a soluble, or detergent solubilized, factor in rut. The reduced forskolin responsiveness maps to the X chromosomal segment 12F5-6 to 13A1-5, within the region previously reported to span the locus that controls both the abortive memory and the lack of Ca2+-stimulation of adenylate cyclase in rut17. The possible relevance of the findings to postulated molecular mechanisms of short-term memory formation is discussed.

Adenylyl Cyclases↗
PubMed1984

Enkephalin degrading enzymes are present in the electric organ of Torpedo californica.

Two proteolytic activities that degrade [Leu5]enkephalin were found in Torpedo californica electric organ. One is a soluble aminopeptidase that degrades enkephalin at the Tyr1-Gly2 peptide bond, and the second is an endopeptidase that degrades enkephalin at the Gly3-Phe4 peptide bond. The aminopeptidase is inhibited by low concentrations of puromycin and bestatin. More than 60% of the endopeptidase is associated with the particulate fraction and is almost completely inhibited by low concentrations of captopril (SQ 14225) or SQ 20881 (potent inhibitors of angiotensin converting enzyme). Thiorphan and phosphoramidon (potent enkephalinase inhibitors) are much less effective. The pattern of cleavage and inhibition of the particulate endopeptidase thus resembles that of angiotensin converting enzyme.

Aminopeptidases↗
PubMed1984

[3H]serotonin binds to two classes of sites in Drosophila head homogenate.

[3H]serotonin binds to two classes of sites in a crude membrane preparation of Drosophila melanogaster heads, with apparent Kd values of 1.4 and 130 nM, and a concentration of 0.2 and 1.5 pmol/mg protein, respectively. High salt concentration and a guanyl nucleotide decrease the number of the high-affinity binding sites. Low concentrations of ergot alkaloids, various tryptamine derivatives, neuroleptic drugs, but not of phentholamine , propranolol and dopamine, displace [3H]serotonin from its high affinity sites. The relevance of the [3H]serotonin-binding sites to serotonin receptors in Drosophila is discussed.

Animals↗
PubMed1984

High-affinity [3H]octopamine-binding sites in Drosophila melanogaster: interaction with ligands and relationship to octopamine receptors.

[3H]Octopamine binds to a particulate preparation from heads of Drosophila melanogaster at a level of 0.5 +/- 0.1 pmol/mg protein, with an apparent dissociation constant of 6.0 +/- 0.9 x 10(-9) M at 26 degrees C. The binding is reduced or abolished by heat, trypsin, detergents, sulfhydryl reagents and EDTA. Low concentrations of MgCl2 or CaCl2 increase binding but high ionic strength is inhibitory. Low concentrations of dihydroergotamine, phentolamine, clonidine, chlorimipramine and chlorpromazine, but not of serotonin and propranolol, displace the labeled biogenic amine from its binding sites. The stable GTP analogue, guanosine-5'-(beta-gamma-imido)triphosphate (Gpp(NH)p), at the microM range, decreases the maximal number of the high-affinity [3H]octopamine-binding sites. The properties of the [3H]octopamine-binding sites are compared to the properties of octopamine receptors as revealed by stimulation of adenylate cyclase in insects, including Drosophila.

Animals↗
PubMed1983

Glycoprotein properties of benzodiazepine receptors from calf cerebral cortex.

Several lectins (concanavalin A, wheat germ agglutinin, wax bean agglutinin, and phytohemagglutinin) induce aggregation and precipitation of deoxycholate-solubilized benzodiazepine receptors from calf cerebral cortex. These receptors were also retained on columns of immobilized lectins. Photoaffinity labeling of the soluble benzodiazephine receptors prevented their interaction with lectins. Periodate treatment caused inactivation of benzodiazepine receptors which was partially prevented by diazepam and/or gamma-aminobutyric acid. The possible association of the drug-binding site and the carbohydrate moiety is discussed.

Animals↗
PubMed1983

Diethylpyrocarbonate modification of benzodiazepine receptors from calf cerebral cortex.

Diethylpyrocarbonate (DEP), an amino acid modifying reagent, causes complete inactivation of particulate and deoxycholate-solubilized benzodiazepine-receptors from calf cerebral cortex. No heterogeneity was observed in DEP-sensitivity of the receptors. Protection from DEP-induced inactivation was provided by the centrally active benzodiazepines, diazepam and nitrazepam, but not by the peripherally active Ro5-4864, suggesting that DEP modifies a residue which is essential for the central actions of benzodiazepines. GABA did not protect against inactivation or influence the protection afforded by diazepam, indicating that the DEP-modifiable residue is independent of GABA binding sites, or that GABA binding sites are also sensitive to DEP. DEP-induced inactivation of benzodiazepine-receptors proceeds much faster at pH 10.1 than at pH 8.1 or 6.0, indicating the modification of a high pKa side group, possibly the phenol of a tyrosyl residue. This postulation is in accord with our previous findings with the modifying reagents tetranitromethane and N-acetylimidazole.

Animals↗
PubMed1983

Heterogeneity in the physicochemical properties of deoxycholate-solubilized benzodiazepine receptors from calf cerebral cortex.

The hydrodynamic behaviour of benzodiazepine receptors solubilized by deoxycholate from calf cerebral cortex reveals two molecular forms. The Stokes radii are 46.5 A and 67.2 A, and the sedimentation coefficients are 10.9 S and 14.6 S. The calculated apparent molecular weights and frictional ratios suggest either two nearly globular proteins of ca. 200K and 400K daltons each, or two ca. 300K daltons proteins which differ significantly in their degree of asymmetry. The benzodiazepine binding site is located on ca. 51K daltons component(s) in both forms.

Animals↗
PubMed1983

Mutations affect storage and use of memory differentially in Drosophila.

The behavior of normal Drosophila and of X-linked olfactory conditioning mutants was analyzed by using an olfactory memory choice task. Memory in normal flies was optimal at 5-12 min after training and then decayed slowly. Memory in the mutants was 40-80% of normal when tested 30 sec after training but it decayed rapidly and was very low after 7 min. Successive conditioning experiments indicated that some types of mutants can behave as though they store information for a longer period than that revealed by straightforward memory tests, but this information reveals itself only by interaction with newly acquired information in a conflict situation. It thus seems that the mutations can either prevent the formation of normal memory or prevent memory from evoking a normal behavioral response.

Journal Article↗
PubMed1983

Production of a high affinity antiserum to benzodiazepines.

Antibodies specific for benzodiazepines were raised in rabbits by immunization with a conjugate of a benzodiazepine derivative, Ro 7-1986/1, with bovine serum albumin. The presence of anti-Ro 7-1986/1 antibodies in the sera was demonstrated by a radioimmunoassay using the radioligand [3H]flunitrazepam ([3h]FNZ). The antibodies displayed a high-affinity for [3H]FNZ (KD = 0.073 +/- 0.003 nM) and and cross-reacted with a broad spectrum of benzodiazepine derivatives. Benzodiazepine levels in samples of sera and urine of benzodiazepine-treated humans were determined. Due to the high sensitivity of the assay only minute volumes (microliter quantities) of body fluids are employed and, therefore, no extraction of the drugs is required. Nitrazepam and diazepam levels as low as 20 picograms can be easily observed. Intoxicating levels of benzodiazepines can be detected by a single measurement in less than 10 min. This radioimmunoassay is advantageous for pharmacokinetic studies, toxicological examinations and forensic medicine due to its high sensitivity, wide-range specificity and technical simplicity.

Animals↗
PubMed1982

High-affinity octopamine receptors revealed in Drosophila by binding or [3H]octopamine.

The study describes, for the first time, detection of a putative, high-affinity octopamine receptor by direct binding studies with a radiolabeled ligand. Crude membranes prepared from heads of Drosophila melanogaster bind [3H]octopamine at a level of 0.4 pmol per mg protein with an apparent Kd of 5 nM. Low concentrations of dihydroergotamine, phentolamine and chloropromazine, but not of propranolol and serotonergic ligands, were potent displacers of [3H]octopamine binding. The [3H]octopamine binding assay may prove useful in assessing the potency of novel octopaminergic ligands.

Animals↗
PubMed1982

Aminergic receptors in Drosophila melanogaster: responsiveness of adenylate cyclase to putative neurotransmitters.

Adenylate cyclase in Drosophila melanogaster heads is stimulated 5-6-fold by low concentrations of octopamine. The octopamine stimulation is inhibited by low concentrations of the alpha-adrenergic ligands phentolamine and dihydroergotamine and of chlorpromazine, but not by low concentrations of the beta-antagonist propranolol and by the alpha-antagonist yohimbine. d-Tubocurarine enhances the octopamine effect. Tyramine, norepinephrine, and epinephrine also stimulate the cyclase, probably via the octopamine receptor. Serotonin and dopamine stimulate Drosophila adenylate cyclase 1.3-1.4-fold; at least the latter putative neurotransmitter seems to interact with a receptor distinct from the octopamine receptor. Prolonged incubation with dopamine in vitro abolishes adenylate cyclase basal activity as well as responsiveness to guanyl nucleotides, NaF, and putative neurotransmitters.

Adenylyl Cyclases↗
PubMed1982

Aminergic receptors in Drosophila melanogaster: properties of [3H]dihydroergocryptine binding sites.

[3H]Dihydroergocryptine ([3H]DHE) binds to a particulate preparation from Drosophila melanogaster heads at a level of 2.4 +/- 0.4 pmol/mg protein, with an apparent dissociation constant of 2.0 +/- 0.5 nM. The binding sites are inactivated by heat, pronase treatment, and sulfhydryl and disulfide reagents. [3H]DHE binding is inhibited by low concentrations of serotonergic and alpha-adrenergic ligands. The specificity of the binding sites, as revealed by displacement studies, differs from that of [3H]DHE binding sites in various vertebrate tissues. The [3H]DHE binding sites may correspond to serotonergic receptors, and possibly, to additional classes of receptors for putative neurotransmitters in Drosophila.

Animals↗