Cloning and pharmacological characterization of a rat mu opioid receptor

We have isolated a rat cDNA clone that displays 75% amino acid homology with the mouse delta and rat kappa opioid receptors. The cDNA (designated pRMuR-12) encodes a protein of 398 amino acids comprising, in part, seven hydrophobic domains similar to those described for other G protein-linked receptors. Data from binding assays conducted with COS-1 cells transiently transfected with a CMV mammalian expression vector containing the full coding region of pRMuR-12 demonstrated mu receptor selectivity. In situ hybridization mRNA analysis revealed an mRNA distribution in rat brain that corresponds well to the distribution of binding sites labeled with mu-selective ligands. Based upon these observations, we conclude that pRMuR-12 encodes a mu opioid receptor.

The distribution of dopamine D2 receptor heteronuclear RNA (hnRNA) in the rat brain

Conventional in situ hybridization methods have been useful in characterizing the anatomical distribution of cells in the central nervous system that express dopamine D2 receptor mRNA. However, due to the large size of the D2 mRNA pool, this method may be insensitive to changes in D2 gene transcription. We have developed a method of hybridizing a 35S-labelled cRNA probe to an intron in the D2 receptor gene in order to measure the amount of primary transcript or heteronuclear RNA (hnRNA) in D2-expressing cells. Introns are found uniquely in hnRNA and are thought to be short-lived intermediates. Thus, monitoring introns could represent a more direct measure of D2 gene transcription. The anatomical distribution of the D2 hnRNA is similar to the distribution of D2 mRNA in the rat brain. D2 heteronuclear RNA was found in the nuclei of cells in the caudate putamen, nucleus accumbens, hippocampus, olfactory tubercle, substantia nigra, ventral tegmental area, and zona incerta. Other regions that contain D2 mRNA, but do not demonstrate intronic signal, include the globus pallidus, prefrontal, cingulate, entorhinal, and piriform cortex, septum, and amygdala. However, these areas have low amounts of D2 mRNA and may contain levels of D2 hnRNA that are below detection. Heteronuclear RNA quantitation by solution hybridization followed by RNase protection was performed on striatum, substantia nigra, cerebral cortex, hippocampus, hypothalamus, and pituitary using a D2 intron 7/exon 8 border probe. These results corroborate the distribution of hnRNA revealed with intronic in situ hybridization. In addition, protection assays were able to detect hnRNA in areas that express low levels of D2 like the cortex, hippocampus and hypothalamus. hnRNA/mRNA ratios calculated from intron/exon border probe protection assays were not equivalent for all the tissue areas studied, indicating that transcription and/or hnRNA half lives may differ between tissues that express D2 receptors. The combined use of intronic in situ hybridization and intron/exon border protection assay as an index of D2 gene transcription and RNA processing provides more information than measuring the mRNA pool alone. It may also prove to be a more useful measure of gene regulation, allowing for evaluation of gene responses to acute treatments.

Cloning and pharmacological characterization of a rat kappa opioid receptor

A full-length cDNA was isolated from a rat striatal library by using low-stringency screening with two PCR fragments, one spanning transmembrane domains 3-6 of the mouse delta opioid receptor and the other unidentified but homologous to the mouse delta receptor from rat brain. The novel cDNA had a long open reading frame encoding a protein of 380 residues with 59% identity to the mouse delta receptor and topography consistent with a seven-helix guanine nucleotide-binding protein-coupled receptor. COS-1 cells transfected with the coding region of this clone showed high-affinity binding to kappa opioid receptor-selective ligands such as dynorphin A and U-50,488 and also nonselective opioid ligands such as bremazocine, ethylketocyclazocine, and naloxone. Not bound at all (or bound with low affinity) were dynorphin A-(2-13), enantiomers of naloxone and levophanol [i.e., (+)-naloxone and dextrorphan], and selective mu and delta opioid receptor ligands. Activation of the expressed receptor by kappa receptor agonists led to inhibition of cAMP. Finally, in situ hybridization revealed a mRNA distribution in rat brain that corresponded well to the distribution of binding sites labeled with kappa-selective ligands. These observations indicate that we have cloned a cDNA encoding a rat kappa receptor of the kappa 1 subtype.

Effects of cocaine on dopamine receptor gene expression: a study in the postmortem human brain

The effects of chronic cocaine exposure on dopamine D1 and D2 receptor gene expression in the human brain were studied in postmortem samples from chronic cocaine abusing and matched control subjects. Using in situ hybridization of receptor autoradiography to examine messenger ribonucleic acid (RNA) and binding sites, respectively, neither D1 nor D2 receptor expression was found to be changed in the nucleus accumbens, caudate, putamen, or substantia nigra of the cocaine-exposed subjects. Although chronic cocaine exposure can produce alterations in dopaminergic neurotransmission, sustained compensatory changes in dopamine receptor expression do not appear to occur in the human.

Extrapulmonary tuberculosis in children

OBJECTIVE

To investigate an apparent increase in the number of children admitted to the Royal Alexandra Hospital for Children with extrapulmonary tuberculosis (TB). Further, to highlight both the seriousness of this disease and the difficulty of its diagnosis, and to draw attention to factors such as ethnic origin in identifying children at risk.

DESIGN

Clinical and microbiological data were collected for all children admitted to the hospital with a confirmed diagnosis of TB. A standardised incidence ratio (SIR) was used to analyse the number of children admitted with extrapulmonary TB in 1990-1991 compared with 1982-1989, and in 1987-1991 compared with 1982-1986.

RESULTS

Eleven children (five of these in 1990 and 1991) had extrapulmonary TB (4, central nervous system; 3, osteomyelitis; 2, cervical lymphadenitis; 2, abdominal). One was Aboriginal and 10 were from families of overseas origin. Twenty-one others had pulmonary TB and 17 of these were from families of overseas origin. The apparent increase in the number of admissions for extrapulmonary TB was not statistically significant.

CONCLUSION

There has been a recent increase in the number of children hospitalised with extrapulmonary TB but when this is compared with the increase in children hospitalised for all causes, the increase is not significant. Immigration and the continuing contact of children with infected adults appear to account for most cases of TB in this series.

Corticosteroids regulate brain hippocampal 5-HT1A receptor mRNA expression

Using in situ hybridization techniques, the expression of 5-HT1A receptor mRNA was measured within the hippocampal formation after bilateral adrenalectomy (ADX). After 24 hr ADX, 5-HT1A receptor mRNA expression was significantly increased in all hippocampal subfields in ADX animals relative to sham-operated controls (SHAM). The magnitude of the increase was most pronounced within CA2 (127%) and CA3/4 (94%)-subfields of dorsal hippocampus, intermediate in the dentate gyrus (73%), and least within CA1 (60%). Administration of exogenous corticosterone (CORT) at the time of ADX maintained the level of 5-HT1A receptor mRNA expression within the range of SHAM animals. In vitro receptor autoradiographic analysis of 5-HT1A receptors in adjacent sections from the same animals indicated a simultaneous increase in 5-HT1A binding throughout the hippocampus in response to ADX. 5-HT1A binding increased to a similar extent (approximately 30%) in CA subfields and dentate gyrus but remained within SHAM levels in CORT-replaced animals. 5-HT1A receptor mRNA levels were also increased in hippocampal subregions of 1 week ADX animals relative to SHAM animals. Within both CA1 and CA2 subfields, the increments were approximately double those observed after 1 d ADX. 5-HT1A receptor binding was increased in every hippocampal subfield to a similar extent as that observed after 1 d ADX. Increases in both 5-HT1A receptor mRNA expression and 5-HT1A receptor binding were preventable by administration of exogenous CORT at the time of ADX. Hippocampal 5-HT1C receptor mRNA and D1 receptor mRNA expression were not significantly altered by either acute or chronic ADX treatment. These data indicate that adrenal steroids may selectively regulate hippocampal 5-HT1A receptors at the level of 5-HT1A receptor mRNA expression.

Distribution of D5 dopamine receptor mRNA in rat brain

The distribution of the messenger RNA encoding the dopamine D5 receptor was determined in the rat brain by in situ hybridization. Using [35S]-labelled riboprobes to either the rat or human D5 receptor, this mRNA was localized to the hippocampus and the parafascicular nucleus of the thalamus. This mRNA could not be visualized in the more traditional brain regions associated with dopaminergic cell bodies or projection fields. This unusual distribution suggests a novel function in the brain for this subtype of the dopamine receptor.

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.

Site-directed mutagenesis of the human dopamine D2 receptor

Based on amino acid sequence and computer modeling, two conflicting three-dimensional models of the dopamine D2 receptor have been proposed. One model (Dahl et al., 1991, Proc. Natl. Acad. Sci. USA 88, 8111) suggests that dopamine interacts with aspartate 80 of transmembrane (TM) 2 and asparagine 390 of TM6 with the transmembranes arranged in a clockwise manner, while a second model (Hibert et al., 1991, Mol. Pharmacol. 40, 8) suggests that dopamine interacts with aspartate 114 of TM3 and the serines of TM5 (194 and 197) with the transmembranes arranged in a counterclockwise manner when viewed from the extracellular space. The present study tests the latter model by selectively mutating aspartate 114 and serines 194 and 197 of the human dopamine D2 receptor by site-directed mutagenesis. In addition, two methionines (116 and 117) were mutated to evaluate whether residues near aspartate (114) of the dopamine D2 receptor are critical in differentiating dopamine receptor agonists from adrenoceptor agonists. Removal of the negative charge with the mutation of aspartate (114) to either asparagine or glycine led to a total loss of both agonist and antagonist binding. Individual or dual methionine mutations in positions 116 and 117, to make the dopamine D2 binding pocket more closely resemble the beta 2-adrenoceptor, did not result in a change in selectivity toward noradrenergic agonists or antagonists. The serine mutations revealed interesting differences between the dopamine D2 receptor and the adrenoceptors. In particular, serine 197 appeared more important than serine 194 for agonist binding. In addition, the binding of one agonist (N-0437) was unaffected by individual serine mutations, while the binding of some antagonists, such as raclopride and spiperone, was significantly altered. These findings are discussed in relation to ligand structure and their interactions with the putative binding pocket.

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 mRNA in adjacent rat brain sections. D1 receptor binding sites were labeled using the selective antagonist [3H](R)-(+)-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzaz epin- 7-ol (SCH23390) (4.6 nM), in the presence of 1 microM ketanserin, while the D1 receptor mRNA was visualized with a 35S-labeled riboprobe corresponding to a region between transmembrane domains III and VI of the rat D1 receptor (base pairs 383-843). Analysis of serial sections suggested a good agreement between D1 receptor binding and mRNA in several brain regions, including the paleocortex, caudate-putamen, nucleus accumbens, amygdala, and suprachiasmatic nucleus. Marked discrepancies between D1 receptor binding and mRNA 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 probably due to the differential localization of D1 receptor mRNA 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 mRNA 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.

Precholecystectomy endoscopic cholangiography and stone removal is not superior to cholecystectomy, cholangiography, and common duct exploration

Thirty-four patients with suspected common bile duct stones were randomized to undergo endoscopic cholangiography and stone removal prior to open cholecystectomy or to have open cholecystectomy, operative cholangiography, and common bile duct exploration. Sixteen underwent the first protocol, and 18 the second. Analysis of the ability to clear stones from the common bile duct, morbidity, mortality, hospital stay, length of operation, and hospital cost showed no difference in outcome between patients treated by either method. These data suggest there is neither an advantage nor a disadvantage to treating patients with suspected duct stones by precholecystectomy endoscopic cholangiography and stone removal.

t-butylated hydroxytoluene enhances intracellular levels of glutathione and related enzymes of rat lens in vitro organ culture

Studies were undertaken to investigate the effect of t-butylated hydroxytoluene (BHT) on reduced glutathione (GSH) levels and related enzymes in rat ocular tissues. GSH levels were significantly enhanced when 1 microM BHT was included in the medium of rat lens cultures. BHT had a dose-dependent effect on GSH levels of lenses in cultures. Inclusion of 10 microM BHT in the culture medium resulted in a twofold increase in GSH levels of the lens within 24 hr. Increased gamma-glutamylcysteine synthetase activity concomitant with the increased amount of [35S]methionine incorporation in GSH strongly suggested that BHT caused enhanced levels of GSH in lenses by increasing de novo biosynthesis. A significant increase was also observed in glutathione S-transferase (GST) levels of lenses in culture containing BHT in the medium. Present studies also demonstrated that rat lens expresses only the mu and pi class GST isoenzymes and both these classes of isoenzymes were elevated by BHT. Oral administration of BHT to rats also resulted in enhanced in vivo levels of GSH in lens, retina and cornea. In addition, a significant in vivo increase in the levels of GST, GSH-peroxidase, GSH-reductase, gamma-glutamylcysteine synthetase, and glucose 6-phosphate dehydrogenase was observed in the lens, retina, and cornea of BHT-fed rats.

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.

A. E. Bennett Award paper. Expression of the dopamine D2 receptor gene in brain

The cloning of the dopamine (DA) D2 receptor now permits the characterization and regulation of D2 messenger RNA (mRNA) in the brain. In this article, the authors describe their studies delineating the distribution of D2 receptor mRNA in the rodent and primate brain, and compare the distribution of message to D2 receptor binding sites. The effects of chronic DA agonist and antagonist treatment on D2 receptor mRNA are also presented, and provide insights into receptor regulation. Finally, the autoreceptor role of D2 receptors located in the midbrain is examined with a combination of 6-hydroxydopamine lesions and anatomic colocalization studies with tyrosine hydroxylase. These preclinical results provide a framework for subsequent investigation into the nature of D2 receptor gene expression in postmortem brains from patients with disorders putatively associated with dopaminergic dysfunction, especially schizophrenia. They also lay the groundwork for a more profound understanding of DA neurocircuitry by combining molecular biological and traditional anatomical techniques.

Minimal access surgery for gastroesophageal reflux: laparoscopic placement of the Angelchik prosthesis in pigs

Conventional surgery for gastroesophageal reflux is effective but requires laparotomy. Minimal access surgery for gastroesophageal reflux could provide a decrease in morbidity. The Angelchik antireflux prosthesis is an alternative to fundoplication for the treatment of this ailment. We evaluated the results of laparoscopic placement of the Angelchik prosthesis in 10 pigs. The duration of the procedure averaged 44 min. The mean lower esophageal sphincter pressure increased from 12.2 +/- 2.8 mmHg at baseline to 45.2 +/- 7.8 (P less than 0.05), 32.1 +/- 3.9 (P less than 0.05), and 25.1 +/- 6.5 mmHg (P greater than 0.05) as measured immediately postoperatively, at 1 week, and at 3 weeks, respectively, following placement of the prosthesis. There was no instance of prosthetic migration or esophageal perforation. One postoperative death due to distention and perforation of the colon occurred. Two animals developed distal esophageal impaction of food. We conclude that the antireflux prosthesis can be safely and effectively placed using laparoscopic methods in a porcine model. Further development of this technique is warranted.

Improved technique for establishing pneumoperitoneum for laparoscopy

The establishment of a pneumoperitoneum is essential for laparoscopy. Anatomical features of the umbilicus can be used to reduce associated complications and improve the ease of creating a pneumoperitoneum.

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.

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.

Localization of dopamine D2 receptor mRNA and D1 and D2 receptor binding in the rat brain and pituitary: an in situ hybridization-receptor autoradiographic analysis

Several lines of evidence suggest the existence of multiple dopamine receptor subtypes, referred to as D1 and D2. The present study examines the distribution of these dopamine binding sites in the rat brain and pituitary in relation to the distribution of D2 receptor mRNA using a combination of in vitro receptor autoradiographic and in situ hybridization techniques. 3H-Raclopride and 3H-SCH23390 (in the presence of 1 microM ketanserin) were used to label D2 and D1 receptor binding sites, respectively, while a 495 bp cRNA probe synthesized from the Sac I-Bgl II fragment of a rat D2 receptor cDNA was used to visualize the D2 receptor mRNA. Analysis of adjacent tissue sections in which receptor autoradiography and in situ hybridization had been performed revealed several brain regions where the D2 binding site and corresponding mRNA appear to be similarly distributed, including the caudate-putamen, nucleus accumbens, olfactory tubercle, globus pallidus, substantia nigra, and ventral tegmental area. In the pituitary gland, D2 binding sites and mRNA appear to be codistributed with very dense levels in the intermediate lobe and individually labeled cells in the anterior lobe. Brain regions demonstrating a lack of correspondence between the distribution of the D2 binding site and D2 receptor mRNA include the olfactory bulb, neocortex, paleocortex, hippocampus, and zona incerta. Several hypotheses are discussed to explain the lack of correspondence in certain brain regions; these include the localization of receptor binding sites on both fibers and cell bodies and receptor transport. These studies provide a better understanding of the anatomical distribution of the D2 receptor and serve as a framework for future regulatory and anatomical mapping studies. By focusing on specific brain regions, such as the nigrostriatal system, hippocampus, and olfactory bulb, they provide insights into D2 receptor synthesis, transport, and insertion into cell membranes.