Search PubMed⌕ Search

Biomedical subjects

S J Watson

Publications and source records attributed to S J Watson.

At least 181 records · Page 10Linked to original sources
PubMed1992

Diurnal corticotropin-releasing hormone mRNA variation in the hypothalamus exhibits a rhythm distinct from that of plasma corticosterone.

The hypothalamopituitary-adrenal axis exhibits a diurnal rhythm as witnessed by the daily excursion of corticosterone in plasma. The rhythm appears to be mediated largely by the stimulation of CRH neurons in the paraventricular nucleus (PVN) of the hypothalamus. In the present study, we investigated the effects of circadian influence on CRH mRNA levels in the paraventricular hypothalamus. Animals were sacrificed through a 24-hour period to establish a detailed time course of CRH mRNA fluctuations. Levels of both type I and type II corticosterone receptor mRNAs were also measured in this area to see whether changes correlate with that of CRH mRNA. Plasma levels of ACTH were quantified as an index for CRH peptide secretion. The results indicate that changes in ACTH closely paralleled alterations in corticosterone levels with an increasing trend starting at 1 PM, suggesting that the diurnal secretory drive commences around this time. The CRH mRNA rhythm as determined by RNase protection assays appeared to change in an anticipatory fashion to these endocrine fluctuations, increasing during the light phase and reaching maximal levels just prior to dark (5-6 PM). An abrupt decrease of 30% in the CRH mRNA content was detected in the hypothalamus within 2 h after dark (8 PM) and coincided with the peak of plasma corticosterone levels. However, other periodic variations in the CRH mRNA content were not accompanied by changes in plasma corticosterone. Neither types of corticosterone receptor mRNAs showed any diurnal change suggesting that the expression of steroid receptors in the hypothalamus is not regulated by circadian influences. We conclude that CRH mRNA levels fluctuate diurnally but are inversely related to corticosterone levels only in the early evening.

Adrenocorticotropic Hormone↗
PubMed1992

Localization and quantification of pro-opiomelanocortin mRNA and glucocorticoid receptor mRNA in pituitaries of suicide victims.

Suicidal behavior has been associated with hypothalamic-pituitary-adrenal overactivity in humans, as measured by increased corticosteroid secretion. To investigate whether this overactivity is reflected at the pituitary level, we have studied the localization of pro-opiomelanocortin (POMC) mRNA, and glucocorticoid receptor (GR) mRNA, in human anterior pituitaries, and quantified these messages relative to controls. Pituitaries from 7 suicide victims and 11 cardiac deaths were sectioned into 10-microns slides, stained with thionin and processed for in situ hybridization using a riboprobe complementary to human POMC mRNA. To correct for possible postmortem cell loss, hybridization with P1B15, a cDNA complementary to rat cyclophillin mRNA, was used in adjacent sections. POMC mRNA containing cells were found to be localized in clusters and were highly associated with corticotropin-releasing hormone (CRH) receptors. In contrast, GR mRNA containing cells were distributed through the pituitary, although areas of increased density were associated with POMC mRNA cells. Quantification with a computerized image analysis system revealed a 25% increase in POMC message in suicide victims. Analysis of the corticotrophic cell clumps showed that the suicide victims had higher POMC mRNA density per cell (p = 0.04) and larger corticotrophic cell size (p = 0.04) than the cardiac death victims. No differences in GR mRNA were detected between the two groups, although GR and POMC mRNA levels were highly and significantly correlated (r = 0.8, p < 0.001). There were no differences in P1B15 message between the two groups. We conclude that in situ hybridization is a useful tool to study gene regulation in human neuroendocrine tissue and that suicide victims show evidence of chronic hypothalamic-pituitary-adrenal axis activation.

Adult↗
PubMed1992

Distribution and regulation of the prohormone convertases PC1 and PC2 in the rat pituitary.

PC1 and PC2 are enzymes involved in the activation of prohormones via the cleavage of pairs of basic amino acids. The expression levels of each of these enzymes were evaluated in the rat anterior and neurointermediate pituitary lobes by in situ hybridization and Northern gel analysis and after various pharmacological manipulations. All intermediate lobe melanotrophs expressed high levels of PC2 mRNA and lower levels of PC1 mRNA. PC1 mRNA was highly expressed throughout the anterior lobe; however, appreciable PC2 mRNA levels were also found. Based on colocalization studies, anterior lobe corticotrophs were found to express PC1 mRNA, but very little PC2 mRNA. Neurointermediate lobe levels of PC1, PC2, and POMC mRNA increased 2- to 6-fold in rats treated with haloperidol, while they decreased to 10-25% of their control values after bromocriptine treatment. These results indicate that in the intermediate lobe, dopamine is involved in the regulation of PC1 and PC2. In the anterior lobe, haloperidol had a strong effect on PC2 mRNA, increasing its levels by 8- to 12-fold compared to the control value, while PC1 mRNA was unaffected. Both PC1 and PC2 mRNA levels were increased 5- to 9-fold in animals made hypothyroid by treatment with 6-n-propyl-2-thiouracil. Adrenalectomy had no significant effect on anterior lobe PC1 mRNA levels. However, both PC1 and PC2 mRNA levels were responsive to dexamethasone treatment in the AtT-20 cell lines. Our results indicate that dopamine, thyroid hormones, and corticosteroids are involved in PC1 and/or PC2 gene expression. These data are also consistent with the role of PC1 and PC2 as prohormone-processing enzymes.

Amino Acid Sequence↗
PubMed1992

Rapid regulation of corticotropin-releasing hormone gene transcription in vivo.

Regulation of corticotropin-releasing hormone (CRH) gene expression in vivo was assessed via in situ hybridization histochemistry, using probes directed against an intronic sequence of the CRH gene. Initial characterization of the CRH intron (CRHin) probe revealed specific localization of signal to the nuclear compartment of neurons in the medial parvocellular paraventricular hypothalamus, which are known to produce CRH peptide and mRNA. Abundance of CRHin signal was low, commensurate with a low resting pool of CRH heteronuclear RNA (hnRNA), representing CRH primary transcript. Regulation of CRH hnRNA levels was assessed after acute glucocorticoid synthesis blockade by injection of metyrapone. Metyrapone inhibits the conversion of 11-deoxycorticosterone to corticosterone, thereby rapidly depleting glucocorticoids and serving as a discrete stimulus for hypothalamo-pituitary-adreno-cortical activation. Plasma hormone measurements verified the efficacy of treatment, as metyrapone-treated rats showed extremely low basal corticosterone levels at all postinjection time points, while exhibiting progressive increases in plasma ACTH release over the 60-min postinjection period. CRH hnRNA levels were markedly increased 15-30 min after metyrapone injection, consistent with a rapid induction of CRH gene transcription in response to the stimulatory event. CRH mRNA, on the other hand, did not exceed control levels until 60 min post metyrapone, illustrative of a temporal lag between transcriptional changes and detectable changes in mRNA pools. Additional sections from metyrapone-and vehicle-treated rats were hybridized with probes complementary to mRNA encoding the immediate-early gene c-fos. c-fos was not present under unstimulated conditions yet was rapidly induced upon metyrapone treatment or vehicle injection (15 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Expression of peptidylglycine alpha-amidating monooxygenase (EC 1.14.17.3) in the rat central nervous system.

An important step in the posttranslational modification of many bioactive neuropeptides, the carboxy-terminal amidation of glycine-extended peptides, is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3). The expression of the gene encoding this enzyme was examined in adult rat brain by in situ hybridization histochemistry and immunocytochemistry. PAM mRNA transcripts and PAM-like immunoreactivity were detected in all major brain areas with the exception of the cerebellum. Very high levels of PAM mRNAs were found in the hypothalamic magnocellular neurons, the hippocampal formation, and olfactory cortex. These areas also showed strong PAM-like immunoreactivity. Regions known to contain high levels of amidated neuropeptides also expressed high levels of PAM mRNA. The observed heterogeneous PAM mRNA levels may reflect differences in the peptidergic activity of different neuronal systems. Interestingly, all pyramidal neurons of the hippocampus expressed very high levels of PAM mRNA, although no identified amidated peptide matches this distribution completely. Furthermore, PAM was not expressed exclusively in neuronal tissue but was also present in non-neuronal tissue. PAM transcripts could be localized in certain ventricular ependymal cells, with the highest expression in the lateral ventricle. Localization of PAM to non-neuronal cells and neurons not known to produce alpha-amidated peptides suggests that these cells may be producing as yet unidentified amidated neuropeptides.

Animals↗
PubMed1991

Comparative anatomical distribution of 5-HT1A receptor mRNA and 5-HT1A binding in rat brain--a combined in situ hybridisation/in vitro receptor autoradiographic study.

The present study examined the comparative distribution of 5-HT1A receptor mRNA and 5-HT1A receptors in rat brain using a combination of in situ hybridisation histochemistry and in vitro receptor autoradiography. 5-HT1A mRNA was visualized using a 910 bp cRNA probe synthesised from a BalI-PvuII fragment of the rat 5-HT1A reetor gene, while 5-HT1A receptors were labelled with the 5-HT1A-selective ligand 8-OH-DPAT. In general terms, there was a complementary distribution of cells expressing 5-HT1A receptor mRNA and 5-HT1A receptor sites. High levels of both 5-HT1A mRNA and 5-HT1A receptors were evident in the hippocampal formation (CA1, CA3, dentate gyrus), entorhinal cortex, and raphe nuclei and lower levels in neocortex and thalamus. Although 5-HT1A mRNA was not expressed in any regions which did not also exhibit 5-HT1A receptors, within both the diagonal band and the medial septal nucleus mRNA levels were proportionately higher than 5-HT1A receptor levels, possibly reflecting receptor transport or a heterogeneity in 5-HT1A receptor turnover mechanisms. 5-HT1A receptor mRNA and 5-HT1A binding sites were undetectable in caudate/putamen and cerebellar regions. The present data indicate the synthesis of 5-HT1A receptors both in raphe serotonergic cells and anatomically specific serotonergic projection areas, further supporting both a presynaptic autoregulatory and postsynaptic modulatory role for this receptor in serotonergic transmission.

Animals↗
PubMed1991

Atypical prodynorphin gene expression in corticosteroid-producing cells of the rat adrenal gland.

Prodynorphin (proDyn) gene expression was examined in the rat adrenal gland. In situ hybridization revealed a heterogenous proDyn mRNA distribution limited almost exclusively to the adrenal cortex; the inner cortical layers contained the highest amounts. In the adrenal medulla, only scattered single cells were seen. By Northern (RNA) blot analysis, adrenocortical proDyn mRNA levels were highly abundant but of smaller size than proDyn transcripts found in the brain. Low levels of the brain-size proDyn mRNA transcript were detected but restricted to the medulla. A discrepancy was suggested when comparing the high abundance of proDyn mRNA levels with the low levels of proDyn-derived peptide in the adrenal. A hypothesis of nontranslation of the shorter proDyn mRNA by adrenocortical cells was rejected because polysomal loading analysis suggests that the mRNA is translated. We propose that adrenocortical proDyn-derived peptides are not targeted for storage but are released shortly after synthesis, thus accounting for low peptide levels. We also measured proDyn mRNA levels in response to stimuli known to affect adrenocortical cells and their most important function--steroidogenesis. Adrenals from hypophysectomized rats had less proDyn mRNA by a factor of 5 than adrenals from normal sham-operated rats. Normal levels were restored by adrenocorticotrophic hormone administration, indicating a potential importance of adrenal proDyn in the hypothalamic-adrenal-pituitary axis.

Adrenal Cortex↗
PubMed1991

Heterogeneity in the beta-endorphin immunoreactivity response to electroconvulsive therapy.

Electroconvulsive therapy is accompanied by an activation of the hypothalamic-pituitary-adrenal axis, resulting in a release of beta-endorphin from the anterior pituitary corticotrophs of humans. As a group, patients in our study demonstrated similar plasma beta-endorphin immunoreactivity response to their initial and final treatments. However, approximately half of the patients demonstrated greater beta-endorphin immunoreactivity release with their first seizure compared with their last seizure, and half of the patients demonstrated the opposite pattern. This difference was not explained by age, sex, unilateral vs bilateral treatments, sine wave vs brief pulse, or psychotropic or anticholinergic medication. Patients with constant seizure duration during the first and final treatments demonstrated a greater release of beta-endorphin immunoreactivity with the final treatment compared with the first treatment. Individuals with decreasing seizure duration during the course of the electroconvulsive therapy demonstrated a decreased beta-endorphin immunoreactivity response during their final treatment.

Adult↗
PubMed1991

Loss of glucocorticoid fast feedback in depression.

A rate-sensitive fast-feedback inhibition of stress-induced corticotropin secretion by glucocorticoids is well documented in rats. Studies in patients with Cushing's disease or adrenal insufficiency have also supported the existence of fast feedback in humans. However, few studies exist in normal healthy subjects or depressed patients. This study compared fast-feedback inhibition of beta-endorphin/beta-lipotropin secretion by hydrocortisone in 16 control subjects and 16 depressed patients. A fast-feedback effect of hydrocortisone on beta-endorphin/beta-lipotropin secretion during the hour of the hydrocortisone infusion was demonstrated in control subjects. Depressed patients demonstrated no increase in beta-endorphin/beta-lipotropin concentrations during the infusion. These data suggest a decreased sensitivity to glucocorticoid fast feedback in depressed patients and complement existing studies demonstrating decreased sensitivity to proportional feedback by dexamethasone in depressed patients. We believe the data presented herein are the first demonstration that abnormal feedback occurs at the level of the brain rather than pituitary in depressed patients.

Adrenocorticotropic Hormone↗
PubMed1991

Distribution of D2 dopamine receptor mRNA in the primate brain.

1. The distribution of the messenger RNA (mRNA) encoding the D2 dopamine receptor has been mapped in the monkey brain by in situ hybridization. 2. Using [35S]-labelled riboprobes corresponding to the region of the D2 dopamine receptor spanning the third cytosolic loop and the sixth and seventh transmembrane domains, specific hybridization was observed in a number of neural structures. 3. High levels of mRNA expression were observed in the caudate, putamen, and claustrum. Significant amounts were also identified in the hippocampus, lateral geniculate nucleus, much of the cortex, amygdala, pons, and thalamus. High levels of this mRNA were also visualized in the substantia nigra, likely reflecting autoreceptor synthesis. 4. While the distribution of D2 dopamine receptor mRNA was similar between the monkey and previously published maps in the rat, several differences were noted. 5. These results demonstrate the feasibility of visualizing this mRNA in the primate brain, and suggest that a similar analysis of human postmortem brain material may be possible.

Animals↗
PubMed1991

A comparison of D1 receptor binding and mRNA in rat brain using receptor autoradiographic and in situ hybridization techniques.

D1, a subtype of the dopamine receptors, is widely distributed in the nervous system and has been shown to be positively coupled to adenylate cyclase. Using a combination of in vitro receptor autoradiographic and in situ hybridization techniques, the present study examines the co-distribution of D1 receptor binding sites and D1 receptor messenger RNA in adjacent rat brain sections. D1 receptor binding sites were labeled using the selective antagonist [3H]SCH23390 (4.6 nM) in the presence of 1 microM ketanserin, while the D1 receptor messenger RNA was visualized with a 35S-labeled riboprobe corresponding to a region between transmembrane domains III and VI of the rat D1 receptor (bp 383-843). Analysis of serial sections suggested a good agreement between D1 receptor binding and messenger RNA in several brain regions, including the paleocortex, caudate-putamen, nucleus accumbens, amygdala and suprachiasmatic nucleus. Marked discrepancies between D1 receptor binding and messenger RNA were observed in other brain regions including the entopeduncular and subthalamic nuclei, substantia nigra (pars reticulata), hippocampus and cerebellum. While technical considerations may contribute to these results, much of the discordance between the distributions is likely due to the differential localization D1 receptor messenger RNA in cell bodies and receptor binding sites on fibers and may provide insights into receptor synthesis, transport and membrane insertion. In the basal ganglia, for instance, D1 receptors are synthesized in the striatum and are either transported to efferent projections in areas such as the substantia nigra, or remain localized in striatal cells bodies. Ibotenic acid lesions in the striatum are consistent with these conclusions and demonstrate a coordinate loss of D1 receptor binding and messenger RNA in the caudate-putamen that is accompanied by a degeneration of fibers projecting to substantia nigra and a loss of D1 binding in the pars reticulata. Neurons in the dentate gyrus and in the granular layer of the cerebellum, on the other hand, synthesize D1 receptors and transport them entirely to either their dendritic or axonal fields, respectively, in the molecular layer. This analysis provides a better understanding of dopaminergic receptor systems in the CNS and their anatomical organization.

Adenylyl Cyclases↗
PubMed1991

Pro-opiomelanocortin mRNA and peptide co-expression in the developing rat pituitary.

Pro-opiomelanocortin (POMC) is synthesized in both the pituitary gland and the brain. Various peptide products of this precursor, namely beta-endorphin, ACTH and alpha-MSH are co-localized in the anterior lobe corticotrophs, all intermediate lobe cells and in hypothalamic neurons. Messenger RNA (mRNA) for POMC has further been shown to exist in these tissues. In this study, we have shown that POMC mRNA, and peptide accumulation as detected by in situ hybridization and immunocytochemistry, respectively, occur simultaneously within the rat pituitary gland during ontogeny and that their maturation occurs in parallel during prenatal and early postnatal development.

Adrenocorticotropic Hormone↗
PubMed1991

An analysis of the concept of experience.

This paper is an analysis of the concept of experience. It begins with an examination of some of the methods used in concept analysis. Following this, an eclectic approach is taken by the combination of many aspects from some of the analysis methods discussed. It shows that the term experience is used in four ways in normal nursing usage: exposure to a particular event, emotion, information or situation; time spent in the service of nursing; the amount of knowledge gained over a period of time; and an event, situation or emotion. Various methods are used then to define experience and to delineate the meaning of experience in the profession of nursing. It is made clear that the measurement of experience in quantitative terms is widespread, but that measurement in qualitative terms is less well understood, but may prove to be more important.

Clinical Competence↗
PubMed1991

Neuroanatomical and functional studies of peptide precursor-processing enzymes.

An overview of in situ hybridization mapping studies comparing the brain distributions of mRNA transcripts encoding the proprotein convertase Furin, PC1 and PC2 in relation to transcripts encoding carboxypeptidase H (CPE) and peptidylglycine alpha-amidating monooxygenase (PAM) is presented. Furin mRNA was detected in both neurons and non-neuronal cells throughout all brain areas. The cellular localization of PC1 and PC2 was primarily neuronal, with PC2 generally more widely distributed, although many regional variations were detected. The detection of specific combinations of the convertases, CPE and PAM in peptide-rich brain regions suggests that specific enzymatic pathways are involved in neuropeptide processing. Results are also described from a series of functional studies on the processing of pro-opiomelanocortin (POMC) in a heterologous neuronal cell line, Neuro-2A, which expresses low levels of PC2 mRNA but no detectable PC1 mRNA. Two contrasting POMC-processing patterns were observed: one where the precursor was processed at a number of cleavage sites to produce several peptides, and another where POMC was processed at a single cleavage site to produce beta E only. If PC2 is responsible for POMC processing in transfected cells, this enzyme may have favored cleavage of the amino terminal-processing site above other sites in the latter type of cell line.

Animals↗
PubMed1991

In situ hybridization analysis of arginine vasopressin gene transcription using intron-specific probes.

In situ hybridization histochemistry with a probe directed against an intron sequence of the rat arginine vasopressin (AVP) gene was used to demonstrate localization and regulation of AVP heteronuclear RNA in discrete brain regions. Hybridization with an AVP intron I (AVPinI) probe revealed specific hybridization confined to cell nuclei of paraventricular nucleus, supraoptic nucleus (SON), and suprachiasmatic nucleus neurons of the rat hypothalamus. Grain counts revealed that the signal generated by the AVPinI probe represented 1.9% of that derived from an AVP exon C probe (AVPexC) in the SON. Interestingly, in the suprachiasmatic nucleus the proportion of AVPinI to AVP exon C ratio was much higher (12%), suggesting either increased transcription of the AVP gene or changes in posttranscriptional RNA processing. Regulatory experiments revealed that 2.6-fold increases in AVPinI signal could be visualized in the SON as little as 30 min after an acute salt load, a period during which no significant change in cytoplasmic AVP mRNA could be observed. In response to chronic salt loading, both AVP heteronuclear RNA and AVP mRNA were up-regulated. These data compared favorably with transcription rate values determined by nuclear run-on assay, suggesting that intronic in situ hybridization affords a relatively reliable method for assessment of rapid changes in gene transcription in individual central nervous system neurons.

Animals↗
PubMed1991

Comparison of the distributions of D1 and D2 dopamine receptor mRNAs in rat brain.

The distributions of messenger RNAs encoding both the D1 and D2 dopamine receptors have been determined in the rat brain by in situ hybridization. High levels of both mRNAs were found in the traditional dopaminoceptive regions of brain, including the caudate-putamen, nucleus accumbens, and olfactory tubercle; lower levels of both were found in a number of other neural structures, such as the lateral septum, olfactory bulb, hypothalamus, and cortex. High levels of D2 but not D1 receptor mRNA were identified in the midbrain dopamine cell groups, suggesting that the autoreceptors found in the substantia nigra and ventral tegmental area are exclusively D2. Other areas demonstrating differential distribution of these two mRNAs included the pituitary, amygdala, and hippocampus. Quantitative densitometric analysis revealed that in most of the brain regions studied in which both messages exist, the amounts of D1 and D2 receptor mRNAs were approximately equal. Finally, using thin (2.5-micron) sections through the caudate-putamen, about half of all cells were found to be positive for D1 receptor mRNA, and approximately 75% of cells contained D2 receptor mRNA. Subsequent analysis in sequential sections revealed that co-localization of D1 and D2 receptor mRNA occurred in 33% +/- 7% of all caudate-putamen cells: about half of all cells containing D1 receptor mRNA also contained D2 receptor mRNA, and approximately half of all D2 receptor mRNA-positive cells also contained D1 receptor mRNA. These results indicate that there is considerable overlap between D1 and D2 dopaminoceptive cells, and provide a basis for future regulatory studies of dopamine systems in brain within a defined anatomic context.

Animals↗
PubMed1990

Beta-lipotropin-beta-endorphin response to low-dose ovine corticotropin releasing factor in endogenous depression. Preliminary studies.

Studies in depression using a maximal stimulatory dose of corticotropin releasing factor have concluded that elevated resting cortisol levels in depressed patients exert a negative feedback effect on the corticotroph, resulting in a decreased corticotropin response. In this preliminary report, we examine the effects of a submaximal dose of corticotropin releasing factor on the release of another corticotroph secretory product, beta-lipotropin-beta-endorphin. We observed a decreased beta-lipotropin-beta-endorphin response in depressed subjects, but a normal adrenal cortisol response. Although the total beta-lipotropin-beta-endorphin response was decreased, the initial secretory response did not differ between patients and normal controls. Rather, the patients appeared to turn off secretion faster. This rapid shutoff was seen in all patients regardless of resting cortisol levels, suggesting that resting cortisol levels alone do not explain the decreased response seen in depressed patients.

Adult↗