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Biomedical subjects

S J Ireland

Publications and source records attributed to S J Ireland.

At least 19 recordsLinked to original sources
PubMed1998

Subtle neurological deficits and psychopathological findings in substance-abusing homeless and non-homeless veterans.

This study evaluated the hypothesis that homeless individuals would display higher levels of neurological deficits than non-homeless individuals, particularly in frontal lobe or executive functions. Eighteen acutely homeless, 15 chronically homeless, and 20 non-homeless individuals admitted to an inpatient psychiatric service received a battery of neurological and psychosocial measures. In comparison to non-homeless subjects with comparable levels of psychopathology, homeless individuals showed higher levels of hostility, prior criminal activity, and family history of psychiatric illness, but lower levels of depression. A positive relationship between hostility and neurological soft signs was observed among chronically homeless subjects. These results suggest that a substantial subset of nonpsychotic homeless veterans suffers from "occult" neurological deficits.

Adult↗
PubMed1997

HIV/AIDS risk in heterosexual college students. A review of a decade of literature.

Empirical studies dealing with the psychosocial correlates of HIV risk among heterosexual college students are reviewed, including findings related to such theoretical variables as HIV/AIDS-related knowledge, personal and partner's attitudes toward condom use, perceived susceptibility, communication with sex partners, and sexual self-efficacy. Although college students are highly knowledgeable about basic HIV/AIDS facts, they retain some misperceptions about disease transmission. They hold neutral-to-negative hedonistic and practical attitudes about using condoms: those who have engaged in risky behavior accurately perceive their greater susceptibility to infection and experience anxiety regarding transmission of HIV infection. Heterosexual college students communicate infrequently with their partners about safer sex, but they often agree to a partner's suggestion that they use condoms. Higher levels of sexual self-efficacy among college students have been associated with a lower risk for HIV transmission. Limitations and clinical implications of the findings and recommendations for future interventions are discussed.

Condoms↗
PubMed1996

HIV risk correlates among non-injection cocaine dependent men in treatment.

Guided by the AIDS Risk Reduction Model (ARRM), psychosocial correlates of HIV risk behavior were examined among noninjection cocaine dependent, heterosexual men (NI-CD-HM) in treatment. Subjects (N = 111) completed a structured interview to measure ARRM mediating variables and HIV risk behaviors. The results indicated that greater perceived susceptibility to contracting HIV, lower sexual self-efficacy, higher lifetime incidence of sexually transmitted diseases, and being under the influence of alcohol or other drugs during sex predicted having more sexual partners in the month prior to admission. Despite adequate knowledge of safer sex guidelines, subjects remained misinformed regarding certain aspects of HIV transmission. Men who perceived that their partners viewed condoms more positively and who exchanged drugs for sex were more likely to use condoms, yet condom use skills were typically inadequate to ensure effective prevention. These results suggest that HIV prevention interventions among NI-CD-HM should focus on improving knowledge, enhancing beliefs in the capacity to enact safer sex behaviors for preventing HIV and other STDs, building relevant skills (e.g., condom use, open sexual communication between partners), and emphasizing psychoactive substance abstinence. Couple interventions, in which partners actually rehearse safer sex negotiations, may be particularly effective in this regard.

Acquired Immunodeficiency Syndrome↗
PubMed1994

GR138676, a novel peptidic tachykinin antagonist which is potent at NK3 receptors.

GR138676, a conformationally constrained analogue of neurokinin B, is a novel, potent NK3 receptor antagonist. GR138676 was a competitive antagonist of neurokinin B-dependent arachidonic acid mobilization from prelabelled Chinese hamster ovary cells stably transfected with a human NK3 receptor gene (pKB 8.3) and of contractions induced by senktide in rat portal vein (pKB 8.2). However, GR138676 was also a competitive antagonist of the increase in intracellular calcium evoked by the selective NK1 agonist, GR73632, in the human astrocytoma U373MG cell-line (pKB 8.3). GR138676 had little activity at NK2 receptors, inhibiting binding of the NK2 antagonist radioligand [3H]-GR100679 to Chinese hamster ovary cells transfected with the human ileum NK2 receptor with a pKi of 6.0. In summary, despite its activity at NK1 receptors, GR138676 will be a useful tool for characterizing NK3 receptors as well as defining the physiological and pathophysiological function of this receptor subtype.

Amino Acid Sequence↗
PubMed1992

Conformationally constrained tachykinin analogues: potent and highly selective neurokinin NK-2 receptor agonists.

The design and synthesis of potent and selective neurokinin NK-2 receptor agonists 12 (GR64349) and 31 are described, together with structure-activity relationships for related analogues. Compound 12 (EC50 = 3.7 nM at NK-2 receptors in the rat colon; selectivity > 1000- and > 300-fold with respect to NK-1 and NK-3 receptors, respectively) was derived by incorporation of a Gly-Leu gamma-lactam conformational constraint into the C-terminal region of the neurokinin A octapeptide analogue [Lys3]-NKA(3-10). Compound 31 (EC50 = 15 nM in rat colon) contains a novel fused-bicyclic constraint at the corresponding site in the substance P hexapeptide analogue [Ava6]-SP(6-11).

Amino Acid Sequence↗
PubMed1992

Substituted imidazo[1,2-b]pyridazines. New compounds with activity at central and peripheral benzodiazepine receptors.

A large range of substituted imidazo[1,2-b]pyridazines have been synthesized, and a number of potent ligands at central benzodiazepine (Bz) receptors on rat brain membranes have been identified in initial binding screens using [3H]diazepam. For those tested more extensively, binding studies conducted in the presence and absence of gamma-aminobutyric acid suggest that they were full receptor agonists. Some preliminary evidence was found suggesting some species selectivity, i.e. several of the compounds were more active in in vivo tests in rats than in mice. The agonist activity of these 2-phenyl (and substituted phenyl) imidazo[1,2-b]pyridazines is consistent with the model of Bz receptor ligands as proposed by Fryer [Raven Press, 1983, pp. 7-20]. Several compounds were identified which had more selective activity at peripheral-type (mitochondrial) Bz binding sites. Thus, substituted imidazo[1,2-b]pyridazines represent yet another class of low molecular mass compounds which have activity at Bz receptor sites.

Animals↗
PubMed1992

Highly potent and selective heptapeptide antagonists of the neurokinin NK-2 receptor.

Incorporation of D-Pro9 into substance P related peptides is known to enhance neurokinin NK-2 receptor agonist potency and selectivity with respect to other neurokinin receptors. We now report that replacement of D-Trp9 by D-Pro9 in the nonselective neurokinin antagonist [Arg5,D-Trp7,9, Nle11]-SP(5-11) gave a partial agonist with NK-2 receptor selectivity. Further incorporation of Pro10 provided the weak but selective NK-2 antagonist Arg-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH2 (compound 4; NK-2 pKB = 5.9; NK-1 pKB = 4.7; NK-3 pKB less than 4.6). Addition of a suitable lipophilic N-terminal substituent (e.g. Boc, PhCO, cyclohexylcarbonyl) to this compound greatly enhanced NK-2 antagonist activity (compound 10, GR 83074; NK-2 pKB = 8.2), and combined with further optimization of the N-terminal amino acids, provided the extremely potent and selective NK-2 antagonist PhCO-Ala-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH2 (compound 34, GR 94800; NK-2 pKB = 9.6; NK-1 pKB = 6.4; NK-3 pKB = 6.0). Compounds of this class produced a potent inhibition of NK-2 agonist-induced bronchoconstriction in the anaesthetized guinea-pig.

Amino Acid Sequence↗
PubMed1992

Characterization of tachykinin-induced ventral root depolarization in the neonatal rat isolated spinal cord.

Depolarization responses to tachykinin receptor agonists were recorded extracellularly from lumbar ventral roots of spinal cord isolated from neonatal rats (one to eight days post partum). All spinal cords were hemisected in the sagittal plane. In addition, in some hemisected cords, the dorsal horns were removed by means of a further cut, perpendicular to the first. In both hemisected and quadrisected spinal cords, reproducible depolarization responses were induced by low concentrations of the neurokinin-1-selective agonist substance P methylester (10 nM-1 microM) or of the neurokinin-3-selective agonist senktide (3-300 nM). On both types of preparation, responses to substance P methylester (1 microM) or senktide (300 nM) were of comparable size. The amplitude of the response to senktide (300 nM) was reduced by at least 88% in spinal cord preparations exposed to tetrodotoxin (0.5 microM) or to physiological medium containing magnesium chloride (20 mM). In contrast, under either of these conditions, concentration-response curves to substance P methylester were shifted rightward by 2.8-8.5-fold, with little effect on the maximum response. Responses to senktide were blocked selectively by the N-methyl-D-aspartate antagonist 3-[(+-)-2-carboxypiperazine-4-yl]propyl-1-phosphonic acid (100 microM); the antagonist had little effect on substance P methylester-induced depolarization (mean concentration ratio 2.0). These results suggest that in the neonatal rat spinal cord, application of exogenous tachykinin agonists can induce ventral root depolarization by activation of neurokinin-1 and/or neurokinin-3 receptors. The response to stimulation of neurokinin-1 receptors has a major component likely to be due to a direct action at motoneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Ontogeny and characterization of [125I]Bolton Hunter-eledoisin binding sites in rat spinal cord by quantitative autoradiography.

The distribution and characteristics of [125I]Bolton Hunter-eledoisin binding sites in rat lumbar spinal cord were studied during postnatal development by in vitro receptor autoradiography. At three, six and 10 days of age, specific [125I]eledoisin binding was distributed throughout the dorsal and ventral horns of the spinal cord. In contrast, from day 24 onwards, specific binding of [125I]eledoisin was confined to superficial layers of the dorsal horn, with negligible amounts of specific binding in the ventral horn. [125I]Eledoisin binding to neonatal (three day) and adult (eight to 12 weeks) spinal cord sections was characterized using tachykinin agonists. In both dorsal and ventral horns of neonatal spinal cord, the rank order of potency of agonists indicated that the majority (64%) of specific [125I]eledoisin binding was to neurokinin-3 binding sites. The identity of the non-neurokinin-3 sites labelled by [125I]eledoisin remains to be determined. In adult rat spinal cord, [125I]eledoisin appeared to bind exclusively to neurokinin-3 binding sites. These results suggest that major changes take place in the localization of neurokinin-3 receptors during postnatal ontogeny of the rat spinal cord. These changes may reflect an important role for tachykinins in neuronal plasticity of the developing spinal cord.

Animals↗
PubMed1991

Lipidic peptides. III: Lipidic amino acid and oligomer conjugates of morphine.

A series of lipidic morphine esters 1b-1f with enhanced membrane-like character were synthesized by coupling the lipidic amino acids 2a-2e to the phenolic hydroxyl group of the opioid analgesic morphine (1a). The antinocioceptive activity of the esters 1b-1f was determined in vivo following both iv and oral dosing. After iv administration, four of the conjugates, 1b, 1c, 1d, and 1f, exhibited antinocioceptive activity in the mouse abdominal constriction test, with a potency similar to that of the parent compound 1a. Conjugate 1b showed activity following oral administration.

Administration, Oral↗
PubMed1991

Receptor-selective, peptidase-resistant agonists at neurokinin NK-1 and NK-2 receptors: new tools for investigating neurokinin function.

The pharmacological profiles of two novel neurokinin agonists have been investigated. delta Ava[L-Pro9,N-MeLeu10]SP(7-11) (GR73632) and [Lys3,Gly8-R-gamma-lactam-Leu9] NKA(3-10) (GR64349) are potent and selective agonists at NK-1 and NK-2 receptors respectively. In the guinea-pig isolated trachea preparation, contractions induced by these agonists were largely unaffected by inclusion of peptidase inhibitors in the bathing medium, indicating that these agonists are resistant to metabolism by peptidases. In the anaesthetised guinea-pig, both agonists were more potent bronchoconstrictor agents than either NKA or the SP analogue, SP methylester. In the anaesthetised rat, the NK-1 agonist, GR73632 was more potent than SP, NKA or NKB at causing the histamine-independent extravasation of plasma proteins into the skin after intradermal administration. The NK-2 agonist, GR64349 and the NK-3 agonist, senktide were without significant effect in this model. These agonists are useful tools for characterizing neurokinin receptor-mediated actions both in vitro and in vivo.

Administration, Cutaneous↗
PubMed1991

Receptors mediating tachykinin-induced contractile responses in guinea-pig trachea.

1. The classification of tachykinin receptors in the guinea-pig trachea has been investigated. This was of interest because, from previous studies, it was not clear whether the guinea-pig trachea contains either a mixture of NK1 and NK2 receptors or, alternatively, a single type of novel tachykinin receptor. 2. In the present study, the guinea-pig trachea was contracted by tachykinin agonists selective for NK1 receptors (substance P methylester (SPOMe) and GR73632) or NK2 receptors (GR64349) but not NK3 receptors (senktide). 3. Against SPOMe and GR73632, the NK1 antagonist, GR71251, behaved as a reversible competitive antagonist having apparent affinity (pKB 7.05 vs SPOMe) consistent with action at NK1 receptors. GR71251 (3 microM) did not antagonize responses to GR64349. 4. The NK2 antagonists L-659,877 and Ac-Leu-Asp-Gln-Trp-Phe-Gly-NH2 (R396) antagonized GR64349 although only R396 appeared to behave competitively (pKB 5.73). Neither L-659,877 (30 microM) nor R396 (30 microM) blocked responses to SPOMe. 5. For L-659,877 and R396, comparison was made between activity in guinea-pig trachea and in preparations known to contain tachykinin receptors predominantly of the NK2 type. In the rabbit trachea, both L-659,877 and R396 had effects similar to those in guinea-pig trachea. In contrast, in the rat colon muscularis mucosae, both L-659,877 and R396 appeared to behave competitively with pKB values against GR64349 of 7.83 and 6.90 respectively. 6. It is concluded that in guinea-pig trachea, contractile responses can be induced by activation of both NK1 and NK2 receptors. The present data are discussed with reference to the proposed existence of subtypes of the NK2 receptor.

Animals↗
PubMed1991

Investigation into species variants in tachykinin NK1 receptors by use of the non-peptide antagonist, CP-96,345.

The affinity of the non-peptide antagonist CP-96,345 for tachykinin NK1 receptors has been estimated in a range of species by use of both radioligand binding and functional assays. CP-96,345 was 30-120 fold less active at NK1 receptors in rat and mouse than in the other species examined, including man. These results demonstrate the existence of species variations in NK1 receptors.

Animals↗
PubMed1991

Influence of zeranol and breed on growth, composition of gain, and plasma hormone concentrations.

Seven Angus and six Brangus steers averaging 225 and 245 kg, respectively, were assigned randomly to zeranol (36 mg) implant (I) and no implant (NI) treatments. Steers had ad libitum access to a corn silage diet plus .68 kg of a soybean meal-based supplement fed daily. Steers were bled via jugular catheters on d 0, 28, 56, and 84 at 15-min intervals for 4 h before and 4 h after feeding. Concentrations of growth hormone (GH), insulin (INS), triiodothyronine (T3), thyroxine (T4), and glucose were determined. Whole-body protein and fat contents were monitored. A breed x I interaction (for d 56 to 84 and d 0 to 84) was observed for ADG (P less than .05 and P less than .07, respectively), feed conversion (P less than .05 and P less than .07, respectively), and protein deposition (for d 0 to 29 and d 0 to 84; P less than .07 and P less than .05, respectively). These interactions were attributed to a greater response to I by Angus than by Brangus steers. A feeding x period interaction (P less than .10) was observed for mean GH concentration, and INS, T4, and T3 concentrations were higher (P less than .05) during the 4-h postfeeding period than during the 4-h prefeeding period. The implant increased (P less than .08) mean GH concentration but did not alter the frequency, duration, or amplitude of plasma GH peaks. Steers that were implanted had lower (P less than .05) plasma T3. Brangus steers had lower (P less than .05) plasma glucose, T3, and T4 concentrations than Angus steers. Results indicate that growth factors beyond those measured are responsible for the anabolic response to zeranol.

Adipose Tissue↗
PubMed1990

The pharmacological characterization of 5-HT3 receptors in three isolated preparations derived from guinea-pig tissues.

1. The pharmacological characterization of the 5-HT3 receptors in guinea-pig isolated tissues is described. The tissues used were ileum (longitudinal muscle-myenteric plexus), colon and vagus nerve. The guinea-pig isolated colon is a novel preparation. 2. In the guinea-pig isolated ileum, 5-hydroxytryptamine (5-HT, 1 x 10(-8)-3 x 10(-5) M) and the selective 5-HT3 receptor agonist 2-methyl-5-HT (3 x 10(-7)-1 x 10(-4) M) caused concentration-related contractions. The 5-HT concentration-response curve was biphasic whilst the 2-methyl-5-HT curve was monophasic. The EC50 value for the low potency portion of the 5-HT curve was 4.1 x 10(-6) M. The EC50 for 2-methyl-5-HT was 1.23 x 10(-5) M. Selective 5-HT3 receptor antagonists caused rightward shifts of the 2-methyl-5-HT curve and the lower potency portion of the 5-HT curve. Neither ketanserin (1 x 10(-6) M) nor methysergide (1 x 10(-5) M) antagonized the responses to 5-HT or 2-methyl-5-HT. 3. In the guinea-pig isolated colon, 5-HT (3 x 10(-7)-3 x 10(-5) M; EC50 2.4 x 10(-6) M) caused contractions which were mimicked by 2-methyl-5-HT (1 x 10(-6)-1 x 10(-4) M; EC50 7.2 x 10(-6) M). Selective 5-HT3 receptor antagonists caused rightward displacements of the 5-HT concentration-response curves. Neither ketanserin (1 x 10-6 M) nor methysergide (1 x 10- 5M) had any effect on responses to 5-HT or 2-methyl- 5-HT. 4. In the guinea-pig isolated vagus nerve, 5-HT (1 x 10-6-3 x 1O-4M) and 2-methyl-5-HT (1 x i0-S- 1 X 10-3m; EC50 7.6 x 10- M) caused depolarizations; at higher concentrations there were afterhyperpolarizations. The maximum response to 2-methyl-5-HT was less than half that to 5-HT. Selective 5-HT3 receptor antagonists caused rightward displacements of the 5-HT concentration-response curves. Antagonists at other 5-HT receptors (ketanserin, 1 x 10- M and methysergide, 1 x 10-6 M) had no effect. 5. The estimated affinity values of 5-HT3 receptor antagonists correlated well between the three models. Phenylbiguanide was inactive as an agonist or antagonist (up to 1 x 1O-4M) in each preparation. 6. Comparisons with antagonist affinity values obtained in the rat isolated vagus nerve revealed marked differences. Antagonists were generally more potent on the rat isolated vagus nerve, although the differences varied considerably between antagonists. 7. The results are discussed in terms of species-related receptor differences.

Animals↗