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T H Kramer

Publications and source records attributed to T H Kramer.

At least 19 recordsLinked to original sources
PubMed1992

Ring substituted and other conformationally constrained tyrosine analogues of [D-Pen2,D-Pen5]enkephalin with delta opioid receptor selectivity.

The conformationally restricted, cyclic disulfide-containing delta opioid receptor selective enkephalin analogue [D-Pen2,D-Pen5] enkephalin (DPDPE) was modified by 2' (CH3) and 3' (I, OCH3, NO2, NH2) ring substitutions and by beta-methyl conformationally constrained beta-methyltyrosine derivatives in the 1 position. The potency and selectivity of these analogues were evaluated by bioassay in the mouse vas deference (MVD, delta receptor assay) and guinea pig ileum (GPI, mu receptor assay) assays and by radioreceptor binding assays in the rat brain using [3H]CTOP (mu ligand) and [3H][p-ClPhe4]DPDPE (delta ligand). The analogues showed highly variable potencies in the binding assays and in the bioassays. Aromatic ring substituents with positive Hammett constants had decreased potency, while substituents with negative Hammett constraints has increased potency for the opioid receptor. The most potent and most selective compound based on the binding was [2'-MeTyr1]DPDPE (IC50 = 0.89 nM and selectivity ratio 1310 in the binding assays). The 6-hydroxy-2-aminotetralin-2-carboxylic acid-containing analogue, [Hat1]DPDPE, also was highly potent and selective in both assays, demonstrating that significant modifications of tyrosine in enkephalins are possible with maintenance of high potency and delta opioid receptor selectivity. Of the beta-methyl-substituted Tyr1 analogues, [(2S,3R)-beta-MeTyr1]DPDPE was the most potent and the delta receptor selective. The results with substitution of beta-MeTyr or Hat instead of Tyr also demonstrate that topographical modification in a conformationally restricted ligand can significantly modulate both potency and receptor selectivity of peptide ligands that have multiple sites of biological activity.

Amino Acid Sequence↗
PubMed1992

Topographical requirements for delta opioid ligands: common structural features of dermenkephalin and deltorphin.

We propose a common topographical model for the bioactive conformation of deltorphin and dermenkephalin at the delta opioid receptor. In this model a hydrophilic surface from the N- to C-termini is surrounded by lipophilic residues ("hot dog" structure). The important element that orients the N-terminal tyramine is the interaction of the N-terminal amino group, with the carboxyl group of Asp4 in deltorphin I and with Asp7 through His4 (as a triad) in dermenkephalin. The biological properties of synthetic analogues designed to test this model demonstrate that the hydrophilic amino acid residues of these peptides are interchangeable. In addition, incorporation of Aib residues that change the lipophilic topography of these molecule, strongly reduces affinity for the delta opioid receptor.

Amino Acid Sequence↗
PubMed1992

Synthesis and biological activities of linear and cyclic enkephalin analogues containing a psi (E,CH = CH) or psi (CH2CH2) isosteric replacement.

The peptide CO-NH function was replaced by a trans carbon-carbon double bond or by a CH2-CH2 isostere in enkephalin analogues of DADLE, DCDCE-NH2 or DPDPE. In DADLE the 2-3 and the 3-4 peptide bond was modified, whereas in the cyclic analogues the Gly3-Phe4 bond was replaced by the isosteres Gly psi (E,CH = CH)Phe [5-amino-2-(phenylmethyl)-3(E)-pentenoic acid] or Gly psi (CH2CH2)Phe [5-amino-2-(phenylmethyl)pentanoic acid]. In general, the modification results in a drop in potency which is the largest for the flexible CH2-CH2 replacement. The Gly3 psi (E,CH = CH)Phe4 DCDCE-NH2 analogue retains considerable potency. These results confirm the importance of the peptide function at the 2-3 and 3-4 position in enkephalin analogues for biological potency.

Amino Acid Sequence↗
PubMed1992

I.v. versus non-i.v. drug use and selected patient variables related to AIDS risk behaviors.

A sample of 206 drug users volunteered for a survey questionnaire of AIDS-related risk behaviors. The Risk Behavior Inventory (RBI) was used to elicit self-report information on risk behaviors including drug use, needle use, and sexual practices. Non-IV cocaine users reported less risk behaviors than patients involved in IV drug use. Nevertheless, non-IV users remained substantially at risk for HIV exposure because of sexual practices and sexual interaction with IV drug users. Multiple regression analysis indicated that method of drug administration (IV vs non-IV) was the major contributor of accountable variance in risk behaviors, while other patient variables, such as age, gender, educational level, employment, and marital status, did not contribute significantly to the explained variance.

Acquired Immunodeficiency Syndrome↗
PubMed1992

AIDS awareness and risk behaviors among dually disordered adults.

An exploratory needs assessment was conducted among 50 clients of an abstinence-oriented outpatient clinic for adults experiencing coexisting drug abuse and chronic mental disorders. Findings revealed that, despite education and prevention efforts, sample members possessed considerable misinformation about AIDS and continued to engage in high risk heterosexual practices. Their knowledge level was not associated significantly with their admission diagnoses. Knowledge level also did not correlate significantly with safer sexual practices. These findings have implications for the development of AIDS education and prevention programs for dually disordered clients. To be effective, AIDS prevention and education efforts must be targeted at the clients' specific needs. Clear, explicit information about AIDS must be provided. In addition, behavioral-attitudinal change strategies that focus on the high-risk situations encountered by the clients and teach them alternative safer sex practices are required.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Norepinephrine and ATP are synergistic in the mouse vas deferens preparation.

Norepinephrine (NE) and ATP are thought to be neurotransmitters involved with contractions of the mouse vas deferens (MVD) in vitro. The EC50 values of exogenously administered NE and ATP were 5.16 +/- 1.37 and 315.32 +/- 221.18 microM, respectively. Contractions of MVD induced by electrical field stimulation were blocked by alpha,beta-methylene adenosine-5'-triphosphate (purinergic desensitizer) and not by prazosin (alpha 1-adrenoceptor antagonist), suggesting that ATP is the predominant transmitter in this preparation. However, because the EC50 value for ATP was over 100-fold greater than that for NE, we performed isobolographic analysis comparing NE and ATP actions separately and together. Our results demonstrated a synergistic interaction of ATP and NE. At all ratios of ATP:NE examined, exogenous NE enhanced contractile responses to ATP. These data indicate that the co-transmitters, NE and ATP, in the MVD interact postjunctionally in a synergistic manner.

Adenosine Triphosphate↗
PubMed1991

Changes in opioid receptor selectivity following processing of peptide E: effect on gut motility.

Peptide E is a mu-selective opioid peptide derived from proenkephalin A which contains [Met5]-enkephalin at the amino end and [Leu5]-enkephalin at the carboxyl end. Peptide E is further processed both centrally and peripherally to a [Leu5]-enkephalin-containing fragment which was investigated to determine if processing leads to alterations in receptor selectivity. Peptide E-(15-25) inhibited electrically stimulated contractions in both the mouse vas deferens, longitudinal muscle, myenteric (IC50 = 459 nmol/L), and guinea pig ileum (IC50 = 2630 nmol/L), indicating a sixfold delta-receptor selectivity. When administered intracerebroventricularly to mice, peptide E-(15-25) also produced potent analgesia which was completely antagonized by naloxone pretreatment, but the peptide had no effect on intestinal transit as measured by the radiochromium geometric center method. This is consistent with earlier findings that intracerebroventricular delta-opioid-selective agents are analgesic but do not inhibit intestinal transit. In vitro radioligand binding assays were performed using male Sprague-Dawley rat whole brain homogenates. The IC50 for peptide E against [3H]naloxone was 1.8 nmol/L compared with the delta-opioid ligand, [3H] [D-Pen2, D-Pen5]-enkephalin of 38.8 nmol/L. The IC50 for peptide E-(15-25) against [3H]naloxone was 497 nmol/L, but for [3H] [D-Pen2, D-Pen5]-enkephalin it was 50.6 nmol/L. Therefore, peptide E loses mu-opioid receptor affinity (1.8-497 nmol/L) after proteolytic processing and the loss of the amino terminal tyrosine but maintains a high delta-opioid affinity (38.8-50.6 nmol/L). These studies demonstrate that enzymatic peptide processing of peptide E to peptide E-(15-25) leads to a shift from mu- to delta-receptor selectivity and a different spectrum of biological effects on gut motility.

Animals↗
PubMed1991

Influence of peptidase inhibitors on the apparent agonist potency of delta selective opioid peptides in vitro.

Several peptides of diverse structure, reported to possess high affinity and selectivity for the delta opioid receptor, were studied using the mouse isolated vas deferens preparation to determine the effect of peptidase inhibition on their apparent potency. The peptides evaluated included [Leu5] enkephalin, the cyclic enkephalin analogs [D-Pen2,D-Pen5]enkephalin (DPDPE) and [D-Pen2,p-F-Phe4,D-Pen5]enkephalin (F-DPDPE), the linear enkephalin analogs [D-Ala2,D-Leu5]enkephalin (DADLE) and [D-Ser2(O-tBu), Leu5,Thr6]enkephalin (DSTBULET), and the naturally occurring amphibian peptides Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 (dermenkephalin), Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2 (deltorphin I) and Tyr-D-Ala-Phe-Glu-Val-Val-Gly-NH2 (deltorphin II). Concentration-response curves were determined for each peptide in the absence and presence of a combination of the peptidase-inhibiting agents bacitracin, bestatin, and captopril. A wide range of potencies was observed, both in the control state and in the presence of peptidase inhibition. The synthetic enkephalin analogs demonstrated small increases in potency with peptidase inhibition (no increase in the case of DPDPE), whereas the naturally occurring peptides were markedly increased in potency, up to as much as 123-fold for dermenkephalin. In the presence of peptidase inhibition, deltorphin II was the most potent peptide tested (IC50 = 1.13 x 10(-10) molar), and as such is the most potent delta opioid agonist reported to date. Stability to metabolism must be considered in the design and evaluation of in vitro experiments using peptides of this type.

Amino Acid Sequence↗
PubMed1991

Condom knowledge, history of use, and attitudes among chemically addicted populations.

The need for behavioral change of risky sexual practices has been of the highest priority since the onset of the AIDS epidemic. The major focus of education for safe sex has been emphasis on condom use. We surveyed 124 individuals applying to treatment for various chemical dependencies and 60 individuals applying for non-chemical-dependency medical treatment on various aspects of condom knowledge, history of use, and attitudes. Respondents reported that AIDS has motivated them to increase their use of condoms, however, only 13.9% always use them. Education is needed in the areas of increasing protection. Along with the use of a condom, the need for a reservoir tip and the risks associated with multiple sex partners should be stressed.

Adult↗
PubMed1991

Topographically designed analogues of [D-Pen,D-Pen5]enkephalin.

The conformationally restricted, cyclic disulfide-containing delta opioid receptor selective enkephalin analogue [D-Pen2,D-Pen5]enkephalin (1, DPDPE) was systematically modified topographically by addition of a methyl group at either the pro-S or pro-R position of the beta carbon of an L-Phe4 or D-Phe4 residue to give [(2S,3S)-beta-MePhe4]DPDPE (2), [(2R,3R)-beta-MePhe4]DPDPE (3), [(2S,3R)-beta-MePhe4]DPDPE (4), and [(2R,3S)-beta-MePhe4]DPDPE (5). The four corresponding isomers were prepared in which the beta-methylphenylalanine residue was p-nitro substituted, that is with a beta-methyl-p-nitrophenylalanine (beta-Me-p-NO2Phe) residue, to give [(2S,3S)-beta-Me-p-NO2Phe4]DPDPE (6), [(2R,3R)-beta-Me-p-NO2Phe4]DPDPE (7), [(2S,3R)-beta-Me-p-NO2Phe4] DPDPE (8), and [(2R,3S)-beta-Me-p-NO2Phe4]DPDPE (9), respectively. The potency and selectivity (delta vs mu opioid receptor) were evaluated by radioreceptor binding assays in the rat brain using [3H]CTOP (mu ligand) and [3H]DPDPE (delta ligand) and by bioassay with mouse vas deferens (MVD, delta receptor assay) and guinea pig ileum (GPI, mu receptor assay). The eight analogues of DPDPE showed highly variable binding and bioassay activities particularly at the delta opioid receptor (4 orders of magnitude), but also at the mu opioid receptor, which led to large differences (3 orders of magnitude) in receptor selectivity. For example, [(2S,3S)-beta-MePhe4]DPDPE (2) is 1800-fold selective in binding to the delta vs mu receptor, making it one of the most selective delta opioid receptor ligands in the enkephalin series as assessed by the rat brain binding assay, whereas the corresponding (2R,3R)-beta-Me-p-NO2Phe-containing analogue 9 is only 4.5-fold selective (nonselective) in this same assay. On the other hand, in the bioassay systems, [(2S,3S)-beta-Me-p-NO2Phe4]DPDPE (5) is more potent than DPDPE and 8800-fold selective for the MVD (delta receptor) vs the GPI (mu receptor), making it the most highly selective ligand in this series for the delta opioid receptor on the basis of these bioassays. In these assay systems, the (2R,3S)-beta-MePhe4-containing analogue 5 had very weak potency and virtually no receptor selectivity (4.4-fold). These results demonstrate that topographical modification alone in a conformationally restricted peptide ligand can significantly modulate both potency and receptor selectivity of peptide ligands that have multiple sites of biological activity and suggest that this approach may have general application to peptide ligand design.

Amino Acid Sequence↗
PubMed1991

Distribution and analgesia of [3H][D-Pen2, D-Pen5]enkephalin and two halogenated analogs after intravenous administration.

To improve pharmacological characteristics of the delta-selective, cyclic peptide [D-Pen2, D-Pen5]enkephalin (DPDPE), modification by halogenation at the Phe4 residue was undertaken. The present study was to determine the extent [3H]DPDPE, [3H][p-Cl-Phe4]DPDPE and [p-125IPhe4]DPDPE crosses the blood-brain barrier, elicits analgesia and to characterize selective organ distribution and stability after i.v. administration. A significantly greater percentage of total [3H][p-Cl-Phe4]DPDPE reached the brain after 10, 20 and 40 min as compared to [3H]DPDPE and both peptides were significantly displaced by pretreatment with naloxone or naltrindole. The amount of [3H]DPDPE detected in the brain was greater than that of [p-125IPhe4]DPDPE. Distribution results revealed large amounts of the administered peptides were sequestered rapidly in the gall bladder and secreted into the small intestine. Hot-plate antinociception tests 5 min after i.v. administration (30 and 60 mg/kg) revealed [p-Cl-Phe4]DPDPE to elicit a much greater analgesic effect as compared to DPDPE or [p-125IPhe4]DPDPE. These results provide evidence that [p-Cl-Phe4]DPDPE has a greater apparent distribution to the brain and has a greater effect on the antinociception threshold as tested on the hot-plate than DPDPE or [p-125IPhe4]DPDPE. Stability of unlabeled and tritiated DPDPE and [p-Cl-Phe4]DPDPE was determined both in vitro and in vivo; both unlabeled and tritiated DPDPE and [p-Cl-Phe4]DPDPE remain intact.

Analgesics↗
PubMed1990

Outpatient treatment of adults with coexisting substance use and mental disorders.

This study examined the six-month and one-year treatment statuses of 118 patients admitted to an abstinence-oriented, outpatient facility serving dually disordered adults. Findings revealed that persons who have been underserved by the mental health and substance abuse fields can be engaged in treatment and will respond favorably to it. Overall, demographic characteristics, admission diagnoses, and past treatment history did not predict treatment outcomes. Rather, patients who participated more fully in treatment had better recoveries than did those who did not engage in treatment. In addition, patients who complied and responded to treatment during their first six months in treatment were more likely to comply and respond to treatment during the second six months of treatment. These results should encourage other clinicians to develop innovative services that meet the needs of dually disordered adults.

Adaptation, Psychological↗