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E J Simon

Publications and source records attributed to E J Simon.

At least 127 records · Page 7Linked to original sources
PubMed1981

Presence of leucine-enkephalin in organotypic explants of fetal mouse spinal cord.

Spinal cord explants with attached dorsal root ganglia (DRGs), from 14-day fetal mice were fixed at 1-3 weeks in vitro and incubated for leucine-enkephalin (LE) immunoreactivity by the peroxidase-anti-peroxidase (PAP) immunohistochemical method. Results show long processes with labeled varicosities seen more often in dorsal regions of the cord explants. Stained punctate bodies and varicosities were often seen close to large cells in these cultures, whereas no label was detected in neuronal perikarya. A prominent laminar array of stained punctate bodies was noted in one cord explant, concentric with the perimeter of the explant. No LE label was detected in the neuritic outgrowths from the cord-DRG explants, whereas high levels of opiate receptors develop in these outgrowths, primarily on the DRG neurites, by 1-2 weeks in culture. The results indicate the presence of LE in explants of fetal mouse spinal cord with attached DRGs and offer an in vitro model system in which the onset and development of peptidergic neurons can be studied as they form functional cellular interrelationships with neurons bearing opioid and monoaminergic receptors in these organotypic cultures.

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PubMed1981

Characterization and partial purification of solubilized active opiate receptors from toad brain.

Opiate receptors have been solubilized from toad brain membranes in active form by using digitonin. Between 40% and 50% of the stereospecific binding activity present in toad brain membranes is recoverable in the ultracentrifugal supernatant of digitonin extracts. Binding of opiates to the solubilized receptor is enhanced 4- to 5-fold by decreasing digitonin concentration to 0.1% or less prior to binding. The solubilized receptor is similar to the membrane-bound receptor in its affinity for various ligands and its sensitivity to heat, trypsin, and N-ethylmaleimide. Moreover, the sodium effect seen in membrane-bound receptor is retained in the solubilized preparation. Both membrane-bound and soluble toad receptors show weak binding of enkephalins, suggesting that they are predominantly of the mu type. The solubilized opiate receptor has an approximate molecular weight of 350,000-400,000. Purification of up to 20-fold has been achieved by gel filtration on Sepharose CL-6B.

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PubMed1981

Characterization of phospholipase A inhibition of stereospecific opiate binding and its reversal by bovine serum albumin.

Opiate receptor binding is inhibited by phospholipase A from some sources, whereas the enzyme from other sources is inactive even at much higher concentrations. Evidence is presented that an active enzymatic site is required for inhibition and that the degree of inhibition seems to correlate with the extent of phospholipolysis. The inhibition is reversed almost completely by treatment with 0.5 to 1% bovine serum albumin, even up to 90% inhibition by phospholipase. As more enzyme is added or incubation time is increased, the extent of reversal diminishes. Based on our evidence, the most likely explanation of these results is that the inhibition of opiate binding activity by phospholipase A is due to the toxicity of the products of phospholipolysis and that bovine serum albumin reverses the inhibition by removing these products from the membranes, thereby restoring the active conformation of the receptors.

Animals↗
PubMed1980

Benzodiazepine binding in chicken retina and its interaction with gamma-aminobutyric acid.

Chicken retina contains saturable, stereoselective high affinity binding sites for benzodiazepines. The density of binding sites in chicken retina exceeds that found in rat and cow retina. GABA and muscimol increase specific 3H-flunitrazepam binding in the chicken retina in a dose-dependent manner. This effect is reversed by bicuculline methiodide. The enhancement of specific binding caused by GABA was shown to be due to an increase in the affinity of flunitrazepam, while the number of binding sites remained unchanged.

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PubMed1980

Selective protection of stereospecific enkephalin and opiate binding against inactivation by N-ethylmaleimide: evidence for two classes of opiate receptors.

Stereospecific binding of 3H-labeled [D-Ala2,D-Leu5]enkephalin is irreversibly inactivated by the sulfhydryl group alkylating agent N-ethylmaleimide. This inactivation, like that of opiate binding, exhibits pseudo-first-order kinetics with a half-inactivation time of 10-12 min. The presence of opiates or enkephalins during incubation with N-ethylmaleimide provides good protection. Ouantitative studies of protection demonstrate that naltrexone and morphine are 20 and 8 times, respectively, more effective in protecting the binding of [3H]naltrexone than that of [3H]enkephalin. [D-Ala2,Leu]Enkephalin and [D-Ala2,Met]enkephalin, however, are more effective (7 and 30 times, respectively) for the protection of 3H-labeled [D-Ala2,D-Leu5]enkephalin binding. These results provide strong evidence for the existence of two classes of opiate receptor in rat brain.

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PubMed1980

Specific, high affinity [3H]ethylketocyclazocine binding in rat central nervous system: lack of evidence for kappa receptors.

The binding properties and distribution of the tritiated benzomorphan, [3H]ethylketocyclazocine, were studied in rat central nervous system (CNS). Specific binding is saturable and represents 75 to 90% of total binding. Scatchard analysis is consistent with the existence of two classes of binding sites with Kd values of 0.5 and 10.5 nM, respectively. Ethylketocyclazocine binding is increased in the presence of sodium chloride. This characteristic resembles that of opiate antagonists rather than that of other agonists. The distribution of ligands. The IC50 values of various opioid agonists and antagonists for competition with [3H]ethylketocyclazocine correlate well with their IC50 values for competition with [3H]naloxone. This evidence does not lend support to the existence of a separate kappa receptor in rat CNS.

Animals↗
PubMed1980

Opiate binding sites in the retina: properties and distribution.

The presence of opiate binding sites in rat retina was confirmed and their properties and distribution were investigated. Etorphine, naloxone and methionine enkephalin exhibit high affinity, saturable binding to retinal membrane preparations. Scatchard analysis of the binding data yielded linear plots for each ligand. The P1 subcellular fraction contains the greatest density of sites per milligram of protein. The response of the binding of all ligands to sodium ions was similar in the retina to that observed in the brain. Competition experiments using naloxone and methionine enkephalin indicated that a homogeneous class of binding sites exists in the rat retina. Opiate binding sites were also demonstrated in the retina of cow, toad and skate. Methionine enkephalin-like immunoreactivity was not clearly detectable in rat retina but was present in toad retina. The physiological role of the opiate binding sites in the retina remains to be elucidated.

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