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H I Mosberg

Publications and source records attributed to H I Mosberg.

At least 91 records · Page 5Linked to original sources
PubMed1985

Studies in vitro with ICI 174,864, [D-Pen2, D-Pen5]-enkephalin (DPDPE) and [D-Ala2, NMePhe4, Gly-ol]-enkephalin (DAGO).

The interactions of a proposed, selective delta receptor antagonist (ICI 174,864) and selective agonists at mu and delta receptors, [D-Ala2, NMePhe4, Gly-ol]-enkephalin (DAGO) and [D-Pen2, D-Pen5]-enkephalin (DPDPE), respectively, have been studied using the electrically-stimulated mouse isolated vas deferens (MVD) and the guinea-pig isolated ileum (GPI). Incubation of increasing concentrations of ICI 174,864 (10,30,100 and 300 nM) produced a dose-related and parallel rightward displacement of the DPDPE dose-response curve in the MVD. In contrast, ICI 174,864 (300-3000 nM) failed to affect the DAGO dose-response curve in the same tissue. Analysis of the DPDPE-ICI 174,864 interaction in the MVD using the pA2 method revealed a Schild plot slope of -0.68 suggesting the involvement of more than one population of receptors. ICI 174,864 (300 nM) failed to antagonize DPDPE in the GPI at doses up to 30 microM. These results suggest that (a) ICI 174,864 acts as a selective delta antagonist in the MVD; (b) DPDPE interacts with mu receptors in the MVD but only at very high concentrations, and (c) delta receptors appear not to be of functional importance in the GPI.

Animals↗
PubMed1985

Characterization of [3H][2-D-penicillamine, 5-D-penicillamine]-enkephalin binding to delta opiate receptors in the rat brain and neuroblastoma--glioma hybrid cell line (NG 108-15).

Specific binding properties of the tritium-labeled delta opiate receptor agonist [3H][2-D-penicillamine, 5-D-penicillamine]enkephalin [( 3H][D-Pen2, D-Pen5]enkephalin) were characterized in the rat brain and in a mouse neuroblastoma-rat glioma hybrid cell line (NG 108-15). Saturation isotherms of [3H][D-Pen2, D-Pen5]enkephalin binding to rat brain and NG 108-15 membranes gave apparent Kd values of 1-6 nM. These values are in good agreement with the Kd value obtained from the kinetic studies. The Bmax value in NG 108-15 membranes was 235.3 fmol/mg of protein. An apparent regional distribution of [3H][D-Pen2, D-Pen5]enkephalin binding was observed in the rat brain. A number of enkephalin analogues inhibited [3H][D-Pen2, D-Pen5]enkephalin binding with high affinity (IC50 values of 0.5-5.0 nM) in both NG 108-15 and rat brain membranes. However, putative mu receptor-selective ligands such as morphine, [D-Ala2, MePhe4, Gly5-ol]enkephalin, [MePhe3, D-Pro4]morphiceptin, and naloxone were less effective inhibitors of [3H][D-Pen2, D-Pen5]enkephalin binding in both systems tested. These data suggest that [3H][D-Pen2, D-Pen5]enkephalin is a potent and selective ligand for the delta opioid receptor.

Animals↗
PubMed1984

Electroencephalographic assessment of the role of delta receptors in opioid peptide - induced seizures.

DPDPE ([D-Pen2, D-Pen5]-Enkephalin) and DPLPE ([D-Pen2, L-Pen5]-Enkephalin) are conformationally-constrained cyclic analogs of enkephalin with high selectivity for delta opioid receptors. Intracerebroventricular (i.c.v.) administration of each analog acutely produces a complex EEG response in rats characterized by a dose-related increase in spectral power and HVSA (peak frequency of 5.0 Hz) during behavioral stupor, and a theta driving (5.25-8.0 Hz) associated with intense behavioral arousal. These effects were antagonized by high (10 mg/kg), but not low (1.0 mg/kg), doses of naloxone. Both analogs failed to cause EEG or convulsive seizures. In contrast, i.c.v. administration of DADLE ([D-Ala2, D-Leu5]-Enkephalin), an enkephalin analog with activity at both mu and delta binding sites, caused initial nonconvulsive EEG seizures followed by HVSA (3.0 Hz); theta driving was not evident. The incidence of the seizures was dose-related and antagonized by very low doses of naloxone (0.01-1.0 mg/kg). Collectively, the inability of DPDPE and DPLPE to cause seizure activity, and the marked sensitivity of DADLE-induced EEG seizures to naloxone, suggest that delta receptors are not directly responsible for DADLE-induced EEG seizure activity. Furthermore, these data implicate mu opioid receptors as the primary sites responsible for enkephalin-induced seizures.

Animals↗
PubMed1984

1H n.m.r. investigation of conformational features of cyclic enkephalinamide analogs.

The conformational basis for the differing opioid receptor selectivities of the cyclic cystine-containing analogs, [D-Cys2, D(or L)-Cys5] enkephalinamide and the related penicillamine-containing analogs, [D-Pen2, D(or L)-Cys5] enkephalinamide (penicillamine = beta, beta dimethylcysteine) was investigated by 1H n.m.r. in aqueous solution. Comparison of chemical shift, temperature dependence of amide proton chemical shift, and coupling constant data suggests similar overall conformations for corresponding penicillamine- and cystine-containing analogs. Differences in conformation and flexibility do appear in the carboxamide terminal region of the corresponding analogs, which may account for their selectivities for different classes of opioid receptors.

Enkephalins↗
PubMed1984

Roles of mu, delta and kappa opioid receptors in spinal and supraspinal mediation of gastrointestinal transit effects and hot-plate analgesia in the mouse.

The opioid receptors involved in the mediation of thermal analgesia (55 degrees C hot-plate) and inhibition of gastrointestinal transit at the spinal and supraspinal levels were studied in unanesthetized mice. Five receptor-selective compounds were evaluated for effectiveness in eliciting analgesia and inhibiting transit after both i.c.v. and intrathecal administration; these included the proposed mu agonist, [D-Ala2, N-methyl-Phe4, Gly5-ol]enkephalin (DAGO), the proposed delta agonists, [D-Pen2, L-Pen5]enkephalin (DPLPE), [D-Pen2, D-Pen5]enkephalin (DPDPE) (conformationally constrained delta selective enkephalin analogs) and [D-Thr2, Thr6, Leu5]enkephalin (DTTLE), and the proposed kappa agonist, trans-3,4-dichloro-N-methyl-N-[2-(1-pyrolidinyl)-cyclohexyl]- benzeneacetamide methanesulfonate (U-50,488H), as well as the nonselective mu-acting agonist, morphine. All compounds were found to produce analgesia after i.c.v. administration; the rank order of potency by the i.c.v. route was DAGO greater than DTTLE greater than morphine greater than DPLPE greater than DPDPE greater than U-50,488H. The analgesic effectiveness of most of these agonists given i.c.v. was evident for up to 40 min, with only DTTLE and U-50,488H having briefer time courses. Similarly, all the compounds produced analgesic responses after intrathecal administration, with the rank order of potency by this route being DTTLE greater than morphine greater than DAGO greater than DPLPE greater than DPDPE greater than U-50,488H, and all compounds (except U-50,488H) had durations of action of up to 20 to 40 min. These agonists also inhibited gastrointestinal transit after intrathecal administration, with a rank order of potency of DAGO greater than DTTLE greater than DPLPE greater than morphine greater than DPDPE greater than U-50,488H.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1984

Cerebral delta opioid receptors mediate analgesia but not the intestinal motility effects of intracerebroventricularly administered opioids.

Conformationally constrained cyclic enkephalin analogs which possess a high selectivity for the delta opioid receptor were used to determine the relative contribution of mu and delta receptors to brain-mediated changes in small intestinal propulsion and increases in hot-plate response time. Receptor preferences were determined by comparing the relative potencies of several opioid agonists in suppressing the electrically evoked contractions of the guinea-pig ileum and mouse vas deferens preparations. The ratio of IC50 values obtained in the guinea-pig ileum and the mouse vas deferens was used as an index of delta receptor selectivity. Effects on intestinal transit were determined in rats in which a silastic cannula had been implanted in the proximal duodenum and a polyethylene cannula in the right lateral cerebral ventricle (i.c.v.). Movement of a radioactive marker along the length of the small intestine after instillation into the duodenum was used to evaluate drug-induced changes in intestinal transit. The analgesic effects of i.c.v. administered opioids were determined in a second group of rats in which i.c.v. cannulas alone had been implanted. After i.c.v. administration of the agonist, the rats were placed on a 55 degrees C hot plate and the latency to rear paw-lick was timed. Compounds which showed a preference for the mu receptor [( D-Ala2, N-methyl-Phe4, Gly5 -ol]enkephalin and morphine/normorphine) were the most potent agonists at producing thermal analgesia and inhibition of small intestinal transit, whereas nonselective compounds (beta-endorphin and [D-Ala2, Met5]enkephalinamide) were slightly less potent in these assays.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesia↗
PubMed1983

Conformationally constrained cyclic enkephalin analogs with pronounced delta opioid receptor agonist selectivity.

The enkephalin analogs, [D-Pen2,L-Cys5]- and [D-Pen2,D-Cys5]-enkephalin are cyclic compounds, conformationally constrained by virtue of their 14-membered, disulfide containing rings and by the rigidizing effect of the beta, beta dimethyl substituents of the penicillamine side chain. The analogs exhibit profound delta receptor specificity as assessed by their relative potencies in the guinea pig ileum (GPI) and mouse vas deferens (MVD) assays, exhibiting, respectively, 666 and 215 times higher potency in the latter assay system. By contrast, the receptor selectivities measured in rat brain binding assays in the absence of sodium were much more modest, the cyclic analogs being, respectively, 15.2 and 6.0 times more effective at displacing [3H] [D-Ala2,D-Leu5]enkephalin than [3H]naloxone. However, for binding assays performed in the presence of a sodium concentration equivalent to that used in the GPI and MVD assays, these binding selectivities increased to 167 and 49, respectively.

Animals↗
PubMed1983

Cyclic penicillamine containing enkephalin analogs display profound delta receptor selectivities.

The cyclic, penicillamine(beta, beta dimethylcysteine)-containing enkephalin analogs, [D-Cys2, L-Pen5]-and [D-Cys2, D-Pen5]enkephalin and the corresponding bis-penicillamine analogs, [D-Pen2, L-Pen5]-and [D-Pen2, D-Pen5]enkephalin were synthesized and evaluated for opioid activity in the guinea pig ileum (GPI) and mouse vas deferens (MVD) bioassays and in rat brain and neuroblastoma-glioma cell membrane binding assays. These analogs all displayed delta receptor selectivity as assessed by IC50(GPI)/IC50(MVD) ratios and by their relative potencies for displacing [3H]naloxone (NAL) vs. [3H] [D-Ala2, D-Leu5]enkephalin (DADLE) from rat brain membrane preparations. For [D-Pen2, L-Pen5]- and [D-Pen2, D-Pen5]enkephalin the observed IC50(GPI)/IC50 (MVD) ratios (1088 and 3164) and IC50NAL/IC50DADLE ratios (371 and 175) represent a vast improvement over previously reported delta receptor selective ligands.

Animals↗
PubMed1983

A comparison of the analgesic and gastrointestinal transit effects of [D-Pen2, L-Cys5]enkephalin after intracerebroventricular and intrathecal administration to mice.

Intrathecal (i.t.) administration of the highly delta selective peptide, [D-Pen2, L-Cys5]enkephalin (DPLCE) (1-10 micrograms), effectively inhibited gastrointestinal transit of an orally-given radiolabelled marker in mice. By contrast, the same doses did not affect marker transit after intracerebroventricular (i.c.v.) administration. I.c.v. or i.t. administration of the peptide effectively increased the latency to hindpaw lick using the 55 degrees C hot-plate as the nociceptive stimulus. Maximum analgesic effects were seen with 0.3 micrograms given i.t. or 10 micrograms given i.c.v. Time-response studies showed activity for as long as 20 min after administration by either route. The differential gastrointestinal effects of DPLCE after i.c.v. and i.t. administration to mice suggest that delta receptors in the brain may mediate analgesic but not gut effects while spinal cord receptors may be less functionally selective.

Analgesia↗
PubMed1983

Bis-penicillamine enkephalins possess highly improved specificity toward delta opioid receptors.

The conformationally restricted, cyclic, disulfide-containing, enkephalin analogs [2-D-penicillamine, 5-L-penicillamine]enkephalin [(D-Pen2,L-Pen5]enkephalin) and [2-D-penicillamine, 5-D-penicillamine]enkephalin [(D-Pen2,D-Pen5]enkephalin) were synthesized by solid-phase methods. Selectivities of these analogs for a single class of opioid receptor were investigated by examining relative potencies in the mouse vas deferens assay, in which the functional receptor is the delta receptor, versus the guinea pig ileum assay, in which the mu receptor is the functional receptor, and by determining their relative abilities to displace the prototypical delta receptor ligand [D-Ala2, D-Leu5]enkephalin and the prototypical mu receptor ligand naloxone from rat brain membrane preparations. Based on these comparisons [D-Pen2,L-Pen5]- and [D-Pen2,D-Pen5]enkephalin exhibited delta receptor selectivities of 1,088 and 3,164, respectively, in the bioassays, and 371 and 175, respectively, in the binding assays. Compared with the previously reported delta receptor selective analogs, [D-Ala2,D-Leu5]enkephalin, [D-Ser2,Leu5,Thr6]enkephalin, and [D-Thr2,Leu5,Thr6]enkephalin, the bis-Pen-containing analogs provide an order of magnitude increase in delta receptor selectivity.

Animals↗
PubMed1982

Conformational comparisons of oxytocin agonists, partial agonists, and antagonists using laser Raman and circular dichroism spectroscopy. Examination of 1-penicillamine and diastereoisomeric analogues.

The biological activity of peptide hormones and analogues depends on the structural and conformational properties of these compounds. A comparative study of the conformational properties of diastereoisomeric analogues of oxytocin with weak agonist activities (fully active but low potency), partial agonist activity (only able to partially induce biological response), and of conformationally restricted 1-penicillamine analogues with potent antagonist activity (no intrinsic activity, but can block the hormone's activity) was made using circular dichroism and laser Raman spectroscopies. Conformational information regarding the peptide amide, disulfide, and tyrosine chromophores was obtained, and indicates differences in the hormone agonists and antagonists. The diastereoisomeric oxytocin analogues [1-hemi-D-cystine]-, [2-D-tyrosine]-, and [5-D-asparagine]-oxytocin, have spectral features consistent with overall backbone conformations similar to oxytocin itself, but with differences in side chain moieties. This suggests that the substantial decrease in potency of the diastereoisomeric oxytocin analogues is due to changes in the relative orientations of the side chains. In contrast, the 1-penicillamine analogues of the present study, [1-penicillamine, 4-threonine]- and [1-penicillamine, 2-phenylalanine, 4-threonine]-oxytocin, like 1-penicillamine oxytocin analogues previously examined, have different backbone and disulfide conformations than oxytocin. All the 1-penicillamine oxytocin derivatives thus far examined appear, from laser Raman and CD data, to have similar topologies. However, those of the present study seem to have more rigid conformations as evidenced by very intense amide n-pi* and tyrosine pi-pi* CD transitions.

Circular Dichroism↗
PubMed1981

Conformational study of the potent peptide hormone antagonist [1-penicillamine,2-leucine]oxytocin in aqueous solution.

[1-Penicillamine,2-leucine]oxytocin is a conformationally restricted analogue of oxytoxin in which the half-cystine-1 and tyrosine-2 residues of the native hormone are replaced by half-penicillamine (beta, beta-dimethyl-half-cystine) and leucine, respectively. This analogue is a surprisingly potent oxytocin antagonist [Hruby, V. J., Deb, K. K., Yamamoto, D. M., Hadley, M. E., & Chan, W. Y. (1979) J. Med. Chem. 22,7]. Extensive proton magnetic resonance experiments were performed to determine the conformational properties of this analogue in aqueous solution, and the results were compared with the previously published model for the conformation of [1-penicillamine]oxytocin. The results are consistent with a conformation similar to that of [1-penicillamine]oxytocin except that, while [1-penicillamine]oxytocin in aqueous solution possesses two 1 comes from 3 (C7) type turns involving the isoleucine-3 peptide amide proton and the half-penicillamine-1 carbonyl and the asparagine-5 peptide amide proton and the isoleucine-3 carbonyl, [1-penicillamine,2-leucine)oxytocin has only the latter 1 comes from 3 turn. This difference between the antagonists is reflected in the different phi and psi angles in the three N-terminal residues of the two inhibitor analogues and in differences in the preferred side-chain conformations for several residues. One particular result of these conformational differences is that, whereas for [1-penicillamine]oxytocin the tyrosine-2 side chain is unable to assume the rotamer for maximal binding to the uterine receptor, [1-penicillamine,2-leucine]oxytoxin retains conformational and dynamic properties at residues two and three which are more similar to those of oxytocin. It is postulated that these conformational and dynamic properties are consistent with the stronger binding and, hence, greater antagonist activity for this penicillamine analogue relative to [1-penicillamine]oxytocin.

Amino Acids↗
PubMed1980

Binding of nickel and zinc ions to bacitracin A.

Bacitracin A is a cyclic dodecapeptide antibiotic produced by Bacillus licheniformis. Bacteriocidal activity requires the presence of divalent cations such as Zn2+. The metal-bacitracin A complex binds to bactoprenyl pyrophosphate, a lipid intermediate required for cell wall biosynsthesis which is found within the bacterial membrane. In this paper, the pH dependence of the metal binding to bacitracin A is investigated in an effort to define the sites of metal coordination. Most of the studies described in this report were performed with Ni2+ and Zn2+. Metal binding was monitored by observing changes in the ultraviolet absorption spectrum of bacitracin A and by monitoring the proton release which is concomitant with metal binding to the peptide. It was determined that both Ni2+ and Zn2+ form 1:1 complexes with bacitracin A in solution. These complexes are soluble in acidic solutions, but above approximately pH 5.5 they become insoluble. On the basis of the data reported as well as results previously reported from other laboratories, a model for divalent metal ion binding to bacitracin is suggested. It is proposed that the metal coordinates directly to the glutamate carboxyl, the histidine imidazole, and the thiazoline ring. The aspartate carboxyl and N-terminal amino group are not directly involved in metal binding. It is further proposed that due to the proximity of the metab, the pK of the N-terminal amino is shifted from 7.7 to 5.7 upon metal binding. Deprotonation of this group is suggested to cause precipitation of the bacitracin A-metal complex. This model is consistent with all the metal binding data and, furthermore, is consistent with the 1H NMR data presented in the accompanying paper [Mosberg, H. I., Scogin, D. A., Storm, D. R., & Gennis, R. B. (1980) Biochemistry (following paper in this issue)].

Bacitracin↗