Biomedical subjects

S J Watson

Publications and source records attributed to S J Watson.

At least 109 records · Page 6Linked to original sources

PubMed1997

Neuroendocrine and behavioral responses and brain pattern of c-fos induction associated with audiogenic stress.

The present study determined simultaneously the behavioural, neuroendocrine and regional brain activity, using semi-quantitative analysis of c-fos mRNA induction, produced by 30 min of auditory stimulation at different white noise intensities (background 60 dB, 70, 80, 90 and 105 dBA), in rats. Only the highest noise intensities (90 and 105 dB) significantly increased corticosterone release after 30 min stimulation. Behaviourally, the 105 dB noise condition reliably reduced overall activity, and moderate noise intensities (70 and 80 dB) increased sleeping time. Three distinct patterns of c-fos mRNA induction were observed. First, following exposure to the experimental cages, a wide pattern of brain activation was obtained in experimental animals irrespective of noise intensity presentation, compared to the naive rats. Second, a number of auditory structures (cochlear nuclei, superior olivary complex, nuclei of the lateral lemniscus, inferior colliculus and the medial division of the medial geniculate body) displayed a clear intensity-dependent increase in c-fos induction. Third, compared to all other conditions, the stressed rats (90 and 105 dB conditions) displayed significantly higher c-fos induction in relatively few areas. Particularly intense c-fos induction was observed in the bed nucleus of the stria terminalis, especially its anterior medial and ventral aspects, the septohypothalamic nucleus, the ventral lateral septum, the ventral portion of the dentate gyrus, a number of hypothalamic nuclei including the lateral preoptic area, the medial preoptic nucleus and the paraventricular nucleus, the median raphe and the pedunculopontine tegmental nucleus. The involvement of a number of these structures in a specific audiogenic stress responsive circuit is discussed.

Acoustic Stimulation↗

PubMed1997

Key residues defining the mu-opioid receptor binding pocket: a site-directed mutagenesis study.

Structural elements of the rat mu-opioid receptor important in ligand receptor binding and selectivity were examined using a site-directed mutagenesis approach. Five single amino acid mutations were made, three that altered conserved residues in the mu, delta, and kappa receptors (Asn150 to Ala, His297 to Ala, and Tyr326 to Phe) and two designed to test for mu/delta selectivity (Ile196 to Val and Val202 to Ile). Mutation of His297 in transmembrane domain 6 (TM6) resulted in no detectable binding with [3H]DAMGO (3H-labeled D-Ala2, N-Me-Phe4, Gly-ol5-enkephalin), [3H]bremazocine, or [3H]ethylketocyclazocine. Mutation of Asn150 in TM3 produces a three- to 20-fold increase in affinity for the opioid agonists morphine, DAMGO, fentanyl, beta-endorphin1-31, JOM-13, deltorphin II, dynorphin1-13, and U50,488, with no change in the binding of antagonists such as naloxone, naltrexone, naltrindole, and nor-binaltorphamine. In contrast, the Tyr326 mutation in TM7 resulted in a decreased affinity for a wide spectrum of mu, delta, and kappa agonists and antagonists. Altering Val202 to Ile in TM4 produced no change on ligand affinity, but Ile196 to Val resulted in a four- to fivefold decreased affinity for the mu agonists morphine and DAMGO, with no change in the binding affinities of kappa and delta ligands.

Animals↗

PubMed1996

Moving from the orphanin FQ receptor to an opioid receptor using four point mutations.

It is unclear how receptor/ligand families that are evolutionarily closely related achieve functional separation. To address this question, we focus here on the newly discovered Orphanin FQ, a peptide homologous to the opioid peptide Dynorphin, and its receptor, the Orphanin FQ receptor, which is highly homologous to the opioid receptors. In spite of this high degree of homology in terms of both ligands and receptors, there is little direct cross-talk between the Orphanin FQ system and the endogenous opioid system. Thus, the opioid peptides show either relatively low affinity or no affinity toward the Orphanin FQ receptor; conversely, Orphanin FQ has no affinity toward any of the opioid receptors. We sought to investigate the molecular basis of such discrimination by attempting to reverse it and endowing the Orphanin FQ receptor with the ability to bind opioids. We report that by mutating as few as four amino acids, we can produce a receptor that recognizes pro-Dynorphin products with very high affinity and yet still binds Orphanin FQ as well as the wild-type receptor. This suggests that the Orphanin FQ receptor has developed features that specifically exclude the opioids and that these features are distinct from those required for the high affinity binding of its own endogenous ligand.

Analgesics↗

PubMed1996

Mapping the receptor domains critical for the binding selectivity of delta-opioid receptor ligands.

While a good deal has been learned about determinants of high affinity ligand/receptor interactions in G-protein-coupled receptors, less is known about mechanisms of ligand selectivity. The opioid receptors offer an excellent opportunity to study the mechanisms whereby structurally very similar receptors discriminate between different but structurally highly related ligands. In the current study, we use a series of chimeric constructs between the delta-opioid receptor and either the mu- or the kappa-opioid receptors to investigate the structural basis of binding selectivity of multiple classes of delta-opioid receptor selective ligands. Our results demonstrate that a region containing the sixth transmembrane domain (TM6) and the third extracellular loop (EL3) in the delta-opioid receptor is absolutely critical for delta-opioid receptor selectivity. The introduction of this region into the kappa-opioid receptor is sufficient to impart a delta profile for delta-opioid receptor selective alkaloids such as naltrindole and naltriben. In order to locate the amino acid residues that may be involved in ligand selectivity in TM6 and EL3 of the delta-opioid receptor, several mutations were introduced into that region. These mutations showed differential effects on peptide and alkaloid ligands. In addition, none of the individual mutations alone could account for the changes exhibited by the chimeric receptors. We conclude that the selectivity of most delta-opioid ligands is achieved through their interaction with many different residues in the TM6/EL3 region. Our results also support a view that the extracellular domains of peptide receptors may provide the basis of a sorting mechanism for ligand selectivity.

Binding, Competitive↗

PubMed1996

Dopaminergic regulation of progesterone receptors: brain D5 dopamine receptors mediate induction of lordosis by D1-like agonists in rats.

To characterize the signaling pathway by which the neurotransmitter dopamine modulates progesterone receptor (PR) activation, the steroid-dependent behavior lordosis was used in estrogen-primed ovariectomized Sprague-Dawley rats with stereotaxic implanted third ventricle cannulas. Lordosis was observed in response to solicitous males in females after central administration of the D1-like agonist SKF38393 and three of its analogs (SKF77434, SKF75640, and SKF85174). In contrast, D1-like antagonist SCH23390 and D1-like/D2 repopulation inhibitor EEDQ blocked behavior inducible by the D1-like agonists. Further, antisense oligonucleotides to D5, but not D1, dopamine receptor mRNA suppressed reproductive behavior associated with D1-like stimulation. This finding provides strong evidence that dopaminergic modulation of lordosis is mediated by the novel D5 dopamine receptor. Although D1, but not D5, dopamine receptor mRNAs were detected in the ventromedial nucleus (VMN) by in situ hybridization, agonists microinjected into the VMN, but not into the arcuate nucleus or preoptic area, induced lordosis, suggesting the functional presence of D5 dopamine receptors in the VMN. Also in support, D5 receptor mRNA antisense microinjected into the VMN blocked the subsequent induction of lordosis by D1-like agonists. Finally, facilitation of sex behavior by D1-like agonists was blocked by the antiprogestin RU38486 and PR antisense oligonucleotide. Collectively, the data provide strong evidence for dopaminergic modulation of reproductive behavior through D5 dopamine receptor-mediated modulation of PR-dependent behavior in rat CNS.

Animals↗

PubMed1996

Primary structure and tissue distribution of the orphanin FQ precursor.

The heptadecapeptide orphanin FQ (OFQ) is a recently discovered neuropeptide that exhibits structural features reminiscent of the opioid peptides and that is an endogenous ligand to a G protein-coupled receptor sequentially related to the opioid receptors. We have cloned both the human and rat cDNAs encoding the OFQ precursor proteins, to investigate whether the sequence relationships existing between the opioid and OFQ systems are also found at the polypeptide precursor level, in particular whether the OFQ precursor would encode several bioactive peptides as do the opioid precursors, and to study the regional distribution of OFQ sites of synthesis. The entire precursor protein displays structural homology to the opioid peptide precursors, especially preprodynorphin and preproenkephalin. The predicted amino acid sequence of the OFQ precursor contains a putative signal peptide and one copy of the OFQ sequence flanked by pairs of basic amino acid residues. Carboxyl-terminal to the OFQ sequence, the human and rat precursors contain a stretch of 28 amino acids that is 100% conserved and thus may encode novel bioactive peptides. Two peptides derived from this stretch were synthesized but were found to be unable to activate the OFQ receptor, suggesting that if they are produced in vivo, these peptides would likely recognize receptors different from the OFQ receptor. To begin analyzing the sites of OFQ mRNA synthesis, Northern analysis of human and rat tissues were carried out and showed that the OFQ precursor mRNA is mainly expressed in the brain. In situ hybridization of rat brain slices demonstrated a regional distribution pattern of the OFQ precursor mRNA, which is distinct from that of the opioid peptide precursors. These data confirm that the OFQ system differs from the opioid system at the molecular level, although the OFQ and opioid precursors may have arisen from a common ancestral gene.

Amino Acid Sequence↗

PubMed1996

Fos expression in forebrain afferents to the hypothalamic paraventricular nucleus following swim stress.

The paraventricular nucleus of the hypothalamus (PVN) serves as the origin of the final common pathway in the secretion of glucocorticoid hormones in response to stress. Various stress-related inputs converge upon the cells of the medial parvocellular division of the PVN. These neurons, which synthesize and release corticotropin-releasing hormone, arginine vasopressin, and other secretagogues, are responsible for a cascade of events which culminates in the adrenocorticotropin-induced release of corticosteroids from the adrenal cortex. Previous data have suggested complex afferent regulation of PVN neurons, although the neuronal pathways by which the effects of stress are mediated remain to be fully disclosed. The present experiment sought to identify forebrain areas potentially involved in afferent regulation of the PVN in response to an acute stressor. Discrete injections of the retrograde tracer Fluoro-gold were delivered to the PVN, and rats were subsequently subjected to an acute swim stress. Brains were processed immunocytochemically for the simultaneous detection of the tracer and Fos, the protein product of the immediate early gene c-fos, utilized as a marker for neuronal activation. The majority of Fluoro-gold/Fos labeled neurons were detected in the parastrial nucleus, the medial preoptic area, the anterior hypothalamic area, the dorsomedial hypothalamic nucleus and adjacent posterior hypothalamic area, and, to a lesser extent, the supramammillary nucleus. These findings are discussed in relation to neural pathways mediating activation and inhibition of the hypothalamic-pituitary-adrenocortical axis.

Afferent Pathways↗

PubMed1996

The effect of adrenalectomy on stress-induced c-fos mRNA expression in the rat brain.

Previously, we determined the pattern of stress-induced c-fos mRNA expression throughout the brain in order to gain further insight into the identification of the neural circuits mediating stress-induced regulation of the hypothalamic-pituitary-adrenal axis. In the present study, we determined if rapid effects of increased glucocorticoid levels after stress contribute to changes in c-fos mRNA expression. To this end, stress-induced c-fos expression was characterized in adrenalectomized (ADX) or adrenalectomized and corticosterone replaced (ADX/B) male rats. Animals were sacrificed 30 min post-onset of a 10 min swim stress, and in situ hybridization histochemistry was used to detect c-fos mRNA throughout the brain. The pattern of c-fos induction in the ADX and ADX/B animals was similar to that observed in the sham operated animals. Additionally, densitometric measurements were made to quantify the c-fos response in the paraventricular nucleus of the hypothalamus and the CA1/2 region of the hippocampus. We found that ADX did not alter the magnitude of the c-fos response to stress in these areas, but there was a slight dampening of the response in ADX/B animals. In sum, these results suggest that the pattern of c-fos expression observed 30 min post-stress is independent of stress-induced increases in circulating glucocorticoid concentrations.

Acute Disease↗

PubMed1996

Topical glyceryl trinitrate in the treatment of chronic anal fissure.

The aetiology of anal fissure is unclear, but there is an association with high maximum resting pressure (MRP). Internal sphincterotomy reduces MRP and heals fissure through an increase in local blood supply. Glyceryl trinitrate (GTN) is a nitric oxide donor which contributes to internal anal sphincter relaxation via a non-adrenergic non-cholinergic pathway. GTN ointment was applied topically in different concentration to the anal margin in patients with chronic anal fissure to monitor its effect primarily on MRP and secondarily on fissure healing. Nineteen patients with chronic anal fissure were treated with ointment containing increasing concentrations of GTN (0.2-0.8 per cent) to produce a reduction in MRP of greater than 25 per cent. The actual dose of GTN varied as no standard delivery system has been developed, but a 'typical amount' of GTN ointment weighed about 200 mg. In 15 of 19 patients, a concentration greater than 0.2 per cent was required to lower the MRP by at least 25 per cent. The minimum concentration of GTN that reduced the resting pressure by at least 25 per cent was prescribed and local application was carried out by the patient twice daily for 6 weeks. At 6 weeks, nine patients had healed, six required sphincterotomy and four were lost to follow-up. Eight of the nine patients with healed fistula required a GTN concentration of 0.3 per cent or more. Sixteen patients were resistant to the usually effective does of 0.2 per cent GTN. In three there was tachyphylaxis and the duration of action of GTN was less than the 12 h described previously in control patients. Two patients did not fulfil the study because of headache.

Administration, Topical↗

PubMed1996

Psychomotor stimulant- and opiate-induced c-fos mRNA expression patterns in the rat forebrain: comparisons between acute drug treatment and a drug challenge in sensitized animals.

Amphetamine-, cocaine-, and morphine-induced c-fos expression patterns were examined following an injection protocol that has previously been shown to produce behavioral sensitization and enhanced dopamine release in the striatal complex. Drug-specific c-fos patterns were observed in both acute and sensitization injection paradigms. A sensitization pretreatment schedule did, however, alter the c-fos expression patterns induced by all the drugs in the caudate putamen, nucleus accumbens, and the cerebral cortex. In some striatal and cortical regions, there was an increase or recruitment of cells expressing c-fos whereas in others there was an apparent decrease or inhibition. The somatosensory cortex was one area where pretreatment with all three drugs increased c-fos expression. The results suggest that the neuronal networks that are modulated by systemic drug injections in the sensitized animal differ from those affected by the initial drug exposure; areas of overlap may indicate common "sensitization' circuits.

Animals↗

PubMed1996

Immunohistochemical localization of the cloned kappa 1 receptor in the rat CNS and pituitary.

Several lines of evidence have demonstrated the presence of three opioid receptor types in the CNS and periphery. These receptors are referred to as mu, delta and kappa, and have been implicated in a wide variety of functions. The present study examines the localization of the kappa 1 receptor, a region of the receptor that has little homology with mu and delta receptors. Immunohistochemical studies in Zamboni-fixed rat tissue demonstrate immunoreactive perikarya and/or fibers in such regions as the deep layers of the parietal, temporal and occipital cortex, parasubiculum, central and medial amygdala, bed nucleus stria terminalis, nucleus accumbens, olfactory tubercle, endopiriform nucleus, claustrum, hypothalamic nuclei, median eminence, midline thalamic nuclei, zona incerta, central gray, caudal linear and dorsal raphe, substantia nigra, pars reticulata, ventral tegmental area, parabrachial nucleus, spinal trigeminal nucleus, nucleus of the solitary tract, spinal cord and the dorsal root ganglia. Specific kappa 1 receptor-like immunohistochemical staining is also observed in the pituitary, where immunoreactive perikarya and fibers are localized in the neural and intermediate lobes. Transfection and preabsorption controls suggest that the antibody is selective for the cloned kappa 1 receptor, and does not recognize mu or delta. This immunohistochemical localization corresponds well to previously described kappa 1 receptor mRNA and binding distributions and provides new insights into the cellular localization and pre- and postsynaptic organization of the kappa 1 receptor-like proteins in the rat brain and pituitary. The functional implications of these results are discussed in light of the kappa 1 receptors play in hormonal regulation, antinociception and reward.

Animals↗

PubMed1996

Dopamine receptor mRNA expression in human striatum and neocortex.

The distributions of the transcripts encoding the five dopamine receptors have been determined in the human striatum and selected regions of the neocortex. In the striatum significant levels of dopamine receptor expression are restricted to the D1, D2, and D3 receptors. D1 and D2 receptor messenger ribonucleic acids (mRNAs) are homogeneously distributed throughout the caudate, putamen, and nucleus accumbens. D3 receptor mRNA is particularly enriched in the nucleus accumbens, with moderate levels in the ventral putamen. In the prefrontal cortex D1 and D4 receptor mRNAs are the most abundant, although the other three transcripts are seen at lower levels. A similar pattern is seen in the temporal neocortex. In the occipital cortex, D1 receptor mRNA is the most abundant, D3 the rarest, while the other three transcripts are present at modest levels of expression. These data add to a growing understanding of the neuroanatomical distribution of these transcripts in the human brain. They are essential to understand in the context of the limbic circuitry of the brain, as new hypotheses of dysfunction of dopaminergic neurotransmission are advanced in psychiatry and as these receptor subtypes are targeted for development of novel pharmacological treatments.

Aged↗

PubMed1996

Expression of serotonin transporter mRNA in human brainstem raphe nuclei.

The distribution of the messenger RNA (mRNA) encoding the serotonin transporter was investigated in the entire extent of the ascending raphe systems of the human brainstem, using a sensitive cRNA probe. This mRNA is abundant in the neurons of the raphe nuclei, especially in the dorsal and median raphe. The subregional distribution of this mRNA closely corresponds to that described for tryptophan hydroxylase in immunocytochemical studies. It is expressed at the highest levels in ventral and ventrolateral subregions of the dorsal raphe, with lower levels of expression in the median raphe, oral pontine reticular nuclei, and the supralemniscal cell groups. These results provide a description of the distribution of this mRNA in normal subjects and will serve as the basis for future studies of the subregional distribution of this mRNA in the brains of depressed patients and those who have committed suicide.

Adult↗

PubMed1996

Interleukin-1 beta-mediated regulation of mu-opioid receptor mRNA in primary astrocyte-enriched cultures.

Opioids have been found to modulate the immune system by regulating the function of immunocompetent cells. Several studies suggest that the interaction between immune and opioid systems is not unidirectional, but rather reciprocal, in nature. In the CNS, one cellular target of immune system activation is the astrocytes. These glial cells have been shown to produce the opioid peptide, proenkephalin, to express the mu-, delta-, and kappa-opioid receptors, and to respond to the immune factor interleukin-1 beta (IL1 beta) with an increased proenkephalin synthesis. To characterize more completely the astrocytic opioid response to immune factor stimulation, we examined the effect of IL1 beta (1 ng/ml) on the mu-receptor mRNA expression in primary astrocyte-enriched cultures derived from rat (postnatal day 1-2) cortex, striatum, cerebellum, hippocampus, and hypothalamus. A 24-h treatment with IL1 beta produced a 70-80% increase in the mu-receptor mRNA expression in the striatal, cerebellar, and hippocampal cultures but had no effect on this expression in the cortical and hypothalamic cultures. This observation represents one of the few demonstrated increases in levels of the mu-receptor mRNA in vitro or in vivo, since the cloning of the receptor. The enhanced mu-receptor mRNA expression, together with the previous observation that IL1 beta stimulates proenkephalin synthesis in astrocytes, supports the IL1 beta-mediated regulation of an astroglial opioid peptide and receptor in vitro, a phenomenon that may be significant in the modulation of the gliotic response to neuronal damage. Therefore, the astroglial opioid "system" may be important in the IL1 beta-initiated, coordinated response to CNS infection, trauma, or injury.

Animals↗

PubMed1996

Determination of the relationship between the pH and conductivity of gastric juice.

Studies of gastric secretion were carried out on 14 subjects, some of whom had taken acid secretion inhibitors. In vitro studies were performed in an attempt to ascertain the effect of H+ and Na+ ions on conductivity. There is a strong correlation between intragastric pH and conductivity for pH < 2, but none of the gastric samples were isotonic. The measured conductivity of the samples was therefore considerably lower than predicted for isotonic gastric juice.

Adult↗

PubMed1996

[Hemorrhoidectomy: current status].

The many treatments for haemorrhoids highlight a lack of consensus. Differences in patients' and surgeons' priority make objective evaluation of haemorrhoid treatment difficult; different types of haemorrhoids are being treated in patients from different socio-economic backgrounds by surgeons of varying expertise from within different cultural settings. In this article we have reviewed the results of common treatments for haemorrhoids and give an outline of our operative technique when performing haemorrhoidectomy.

Hemorrhoids↗

PubMed1996

Transperineal repair of symptomatic rectocele with Marlex mesh: a clinical, physiological and radiologic assessment of treatment.

BACKGROUND: The aim of this study was to evaluate the operative repair of rectoceles in a defined group of women by a technique designed to deal with the cause (failure of the rectovaginal septum) rather than the effect (rectal and vaginal wall bulging). STUDY DESIGN: Only women whose defecation was aided by vaginal digitation and who had large rectoceles on proctography were included. Any other clinical symptoms in the absence of vaginal digitation, even when proctography demonstrated a rectocele, were not taken as indicators for surgery in this study. There were nine women, median age 50 years (range, 32 to 61). The rectovaginal septum was repaired with Marlex mesh through a perineal approach by one surgeon. The median follow-up period was 29 months. RESULTS: Eight of the nine women achieved successful evacuation after surgery without the need for vaginal digitation. Rectocele size, depth, and the percent of barium trapped in the rectocele on proctography were all improved. Anorectal physiology measurements were unchanged by surgery. CONCLUSIONS: Operative repair of the rectovaginal septum removes the need for vaginal digitation in most women with large rectoceles on proctography. Further studies in well-defined groups of women are needed to establish how well rectocele repair aids women with a variety of other pelvic and perineal symtoms.

Adult↗

PubMed1995

Primary astroglial cultures derived from several rat brain regions differentially express mu, delta and kappa opioid receptor mRNA.

The existence of opioid receptors within glial cell membranes has been proposed by several laboratories based on biochemical and radioligand binding data. The recent cloning of the mu, delta and kappa receptors has enabled us to directly examine the issue of opioid receptor expression in rat brain astroglia by using solution hybridization/ribonuclease protection assays to analyze the total RNA obtained from primary cultures of cortical, striatal, cerebellar, hippocampal and hypothalamic astrocytes. The results indicate that all five glial cultures expressed mu, delta and kappa receptor mRNA. The rank order of receptor mRNA abundance, expressed collectively across all five cultures, was determined to be delta > or = kappa >> mu. An analysis of the glial distribution profile for each receptor type revealed that mu receptor mRNA levels were the most abundantly expressed in cortical cultures, while the greatest levels of delta receptor mRNA were found in the cortical and hypothalamic cultures, and significant kappa receptor mRNA levels were produced by the cortical, hypothalamic and cerebellar cultures. Furthermore, the five glial cultures each expressed different levels of total opioid receptor (mu + delta + kappa) mRNA. The rank order of total opioid receptor mRNA expression across different astroglial cultures was found to be cortex > hypothalamus > cerebellum = hippocampus > striatum. An analysis of the relative expression profiles for mu, delta and kappa receptor mRNA within each culture revealed that all cultures manifested relatively high levels of delta and kappa receptor mRNA, but relatively low levels of mu receptor mRNA. Generally, cortical, hippocampal and hypothalamic cultures were characterized by comparable levels of delta and kappa receptor mRNA, and little, if any, mu receptor mRNA. However, striatal cultures were characterized by a high level of delta receptor mRNA which was approximately twice and four times that of the kappa and mu receptor mRNA, respectively. In contrast, cerebellar cultures expressed predominantly kappa receptor mRNA at a level which was almost twice that of the delta receptor mRNA, and expressed very little mu receptor mRNA. These data show that primary astroglial cultures not only express mu, delta and kappa receptor mRNAs, but they do so in a manner dependent upon receptor type and brain region. This suggests a regional heterogeneity of astrocytes with respect to opioid receptor expression, a characteristic previously described only for neurons. Furthermore, it suggests the existence of an additional anatomical component in CNS opioid systems.

Animals↗