Biomedical subjects

W S Choi

Publications and source records attributed to W S Choi.

At least 91 records · Page 5Linked to original sources

PubMed1997

Colocalization of dopamine D1 and D2 receptor mRNAs in rat placenta.

Dopamine is present in the human placenta. The major function of dopamine is the inhibition of human placental lactogen (hPL) release from human trophoblastic cells. This effect is mediated by cAMP through dopamine D2 receptors. However, studies on the effects of cAMP in the control of hPL release have yielded conflicting results. The purpose of this study is to explore the distribution of dopamine receptors in the rat placenta. Dopamine D1 and D2 receptor mRNAs were colocalized in the rat placenta by in situ hybridization histochemistry using radiolabeled cRNA probes. Dopamine D1 and D2 receptor mRNAs were detected in large cells of the endometrium of the uterus on day 10 of gestation. On days 12-16 of gestation, hybridization signals were localized mainly in the spongiotrophoblast and giant cells of the junctional zone of the placenta. With the development of the placenta, signals were moving from the junctional zone to the labyrinth zone. Pit-1 mRNA was detected in the placental lactotrophs and was also colocalized in neighboring placental sections. Our results clearly showed that dopamine D1 and D2 receptor mRNAs were coexpressed in the placental lactotrophs that express Pit-1 mRNA.

Animals↗

PubMed1997

Prolonged ethanol intake increases D2 dopamine receptor expression in the rat brain.

Dopamine via interaction with its receptor is known to be involved in the behavioral and endocrine actions in the mammalian brain. Behavioral effects produced by ethanol appear to be due to its actions on the dopaminergic system. In the present study using in situ hybridization histochemistry and RNase protection assay, the effect of prolonged ethanol intake on the expression of D2 dopamine receptor mRNA was examined in the rat brain. Specific D1 and D2 receptor mRNA signals were detected in the caudate putamen, nucleus accumbens, olfactory tubercle, hippocampus, dentate gyrus, and amygdaloid complex of the rat brain. Within the hypothalamus, the level of receptor mRNA was low in most nuclei with a somewhat higher level in the arcuate nucleus. Only the supurachiasmatic nucleus showed moderate to dense dopamine receptor mRNAs. Prefrontal cortex showed hybridization signals but their intensity was very low. A considerable amount of D2 mRNA was localized in the substantia nigra but D1 mRNA was not. Ethanol (10%) intake for 5 weeks increased both the density of hybridization signal and number of cells expressing D2 dopamine receptor mRNA in the caudate putamen, and nucleus accumbens, but not in the olfactory tubercle. RNase protection assay revealed about a 1.5-fold increase in the D2 dopamine receptor mRNA level in the corpus striatum. These results provide a basis for the involvement of dopamine D2 receptor expression in alcoholism.

Alcohol Drinking↗

PubMed1997

Identification of nitric oxide synthase in Staphylococcus aureus.

The presence of nitric oxide synthase (NOS) in Staphylococcus aureus ATCC6538P was established by western blot analysis. The identity of citrulline formed from L-arginine by the NOS was confirmed by both TLC and HPLC and the other product, NO, by directly measuring the production of nitrogen oxides (NOx) in the reaction mixture. The activity was inhibited by typical NOS inhibitors such as N-nitro-L-arginine methylester and NG,NG-dimethyl-L-arginine with the IC50 of 4.9 x 10(-4) and 2.5 x 10(-4) M, respectively. The NOS activity was maximum at pH 6.5 and at 47.5 degrees C. These results indicate that the NOS of S. aureus ATCC6538P is an isoform distinct from mammalian NOS.

Blotting, Western↗

PubMed1997

A novel 90-kDa stress protein induced in fish cells by fish rhabdovirus infection.

A 90 kDa cellular protein in a fish cell, CHSE-214, showed increased expression by the infection of infectious hematopoietic necrosis virus (IHNV), heat shock, 2-mercaptoethanol, copper sulfate, and cadmium sulfate, and was detected in various kinds of cells such as human, rat, and mouse cells. The molecular mass of the 90 kDa protein was different from those of the hsp90 and grp94. In addition, all the anti-stress protein MAbs did not react with the 90 kDa protein. Finally, the subcellular distribution of the 90 kDa protein, determined by Western blots of subcellular fractions, was found to be mainly nuclear, both in normal and IHNV-infected CHSE-214 cells. The present results indicate that the 90 kDa protein is a kind of stress protein. However, based on its molecular mass, antigenic characteristics, and subcellular distribution, it is likely that this protein is a novel stress protein that has not been previously described in animal systems, especially in fish systems.

Animals↗

PubMed1997

Maternal cocaine treatment alters dynorphin and enkephalin mRNA expression in brains of fetal rhesus macaques.

Cocaine exposure in utero is known to cause a variety of behavioral and motor deficits that may be attributable to alterations in the dopamine neurocircuitry. To ascertain cocaine effects in the fetus, we developed a nonhuman primate model in which pregnant monkeys were administered cocaine from day 20 through day 60 or 70 of gestation. Fetuses from these pregnancies develop a repertoire of neural deficiencies, including decreased mRNA expression of tyrosine hydroxylase in the midbrain and increased mRNA expression of dopamine receptor subtypes in the rostral forebrain. Presently, we studied the effects of maternal cocaine treatment on the mRNA expression of the endogenous opioids preprodynorphin (PPD) and preproenkephalin (PPE) in fetal monkey brains. Fetuses exposed to saline (0.9%) or cocaine (3 mg/kg) were delivered by Caesarean section, the fetal brains were dissected, and tissue RNA was extracted and quantified using ribonuclease protection assay analysis. The opioid peptides PPD and PPE were expressed in the fetal monkey brain by day 60, and even higher levels were found in day 70 fetuses. Maternal exposure to cocaine increased gene expression of PPD and PPE in the fetus at both day 60 and day 70 of gestation. Dynorphin mRNA levels were significantly elevated in the striatum, whereas enkephalin mRNA was elevated in both the frontal cortex and the striatal area of fetuses whose mothers received cocaine. Changes in the expression of these opioid peptides in presumed dopamine target neurons, which mediate motivation and reward, as well as motor control, provide further evidence for profound consequences of in utero cocaine exposure on the developing dopamine neurocircuitry.

Animals↗

PubMed1997

Cigarette smoking predicts development of depressive symptoms among U.S. adolescents.

To examine whether adolescent cigarette smoking predicts the development of depressive symptoms, we used a longitudinal follow-up survey of 6,863 adolescents ages 12 to 18 in the U.S. who did not report notable depressive symptoms at baseline. This study used a self-report measure of six depressive symptoms experienced within the past twelve months at follow-up as the outcome of interest. Results indicated that 11.5% developed notable depressive symptoms at follow-up. There were marked gender differences with 15.3% of girls developing notable depressive symptoms compared to 8.1% of boys. Gender differences in depressive symptoms were consistent across all age groups and were apparent by the age of twelve. For both genders, smoking status was the most significant predictor of developing notable depressive symptoms. Several other risk factors including involvement in organized athletics, availability of social support, and personality characteristics were also found to be associated with development of depressive symptoms. Adolescent cigarette smoking may have marked health consequences in terms of depressive symptoms. The reduction of cigarette smoking among adolescents should be a focus of depression prevention interventions. In addition, the development of gender-specific components of prevention interventions may be warranted.

Adolescent↗

PubMed1997

Stability, blood partition, and pharmacokinetics of a new reversible proton pump inhibitor, YJA-20379-1.

The pharmacokinetics of YJA-20379-1 were evaluated after intravenous (i.v.) administration to rats (10-50 mg/kg) and rabbits (10-50 mg/kg), and oral administration to rats (200 and 500 mg/kg). The stability and blood partition between plasma and blood cells were also investigated. After i.v. administration of YJA-20379-1, 10-50 mg/kg, to rats, the pharmacokinetic parameters of YJA-20379-1 were dose-independent, however, they were dose-dependent in rabbits. After oral administration of YJA-20379-1 to rats, the AUC of YJA-20379-1 seemed to increase with increasing doses (73.4 +/- 28.5 and 130 +/- 100 micrograms min/ml for 200 and 500 mg/kg, respectively). The extent of absorption after oral administration (F) was 6.47 and 4.74% for 200 and 500 mg/kg, respectively. The low F values were not due to incomplete absorption and could be due to extensive first-pass metabolism. YJA-20379-1 was unstable in pH solutions of 2-5, 12, and 13, very unstable in pH solutions of 1 and 14, however, stable in pH solutions of 6-11. YJA-20379-1 reached equilibrium rapidly between plasma and blood cells of rabbit blood at 1-5 micrograms/ml, an the mean blood cells/plasma concentration ratio was 5.24 +/- 1.21.

Administration, Oral↗

PubMed1997

Determination of a new antiulcer agent, YJA-20379-1 in plasma, urine, blood, and tissue homogenates by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the determination of a new antiulcer agent, YJA-20379-1, in human plasma and urine, and rat blood and tissue homogenates. The sample preparation was simple: a 2.5-volume of acetonitrile was added to the biological sample to deproteinize it. A 50-microliter aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase employed was methanol--0.1 M Sørensen phosphate buffer of pH7.0--H2O (80:2:15, v/v/v), and was run at a flow-rate of 0.7 ml/min. The column effluent was monitored by ultraviolet detector at 254 nm. The retention time for YJA-20379-1 was approximately 6.3 min. The detection limits for YJA-20379-1 in human plasma and urine, and rat tissue homogenate (including blood) were 50, 100, and 100 ng/ml, respectively. The coefficients of variation of the assay (within-day and between-day) were generally low (below 9.44%) for the human plasma and urine, and rat blood and tissue homogenate. No interference from endogenous substances were found.

Animals↗

PubMed1996

Effects of in utero cocaine exposure on the expression of mRNAS encoding the dopamine transporter and the D1, D2 and D5 dopamine receptor subtypes in fetal rhesus monkey.

The effects of in utero cocaine exposure on the development of the mRNAs encoding the dopamine transporter (DAT) and the D1, D2 and D5 dopamine receptor subtypes were determined in fetal monkey brains at day 45 and day 60 of gestation. Pregnant monkeys were treated with cocaine 3 mg/kg or saline i.m., four times a day from day 18 of gestation until the pregnancy was terminated at day 45 or day 60. The fetal brains were dissected, and tissue RNA extracted and quantified using ribonuclease protection assay analysis. In day 45 fetal monkeys, dopamine D1 and D2 receptor subtype mRNAs and DAT mRNA were found in low quantities both in control and cocaine-treated subjects. In day 60 fetal monkeys, D1 receptor mRNA levels were highest in the frontal cortex/striatal area, and low to moderate quantities were found in diencephalic and mesencephalic fetal brain regions. Dopamine D2 receptor mRNA levels were highest in the frontal cortex/striatal area, diencephalon and the midbrain, moderate in the brainstem and low in the caudal temporal lobe and surrounding cortical areas. Dopamine D5 receptor mRNA was expressed in low quantities throughout the day 60 fetal monkey brain, whereas DAT mRNA was found in the midbrain only. In utero cocaine exposure caused a significant increase in dopamine D1, D2 and D5 receptor subtype mRNAs in the frontal cortex/striatal area of day 60 fetal monkeys. These results support the hypothesis that dopamine synthesis and release may be reduced in cocaine-treated fetuses, which results in dopamine receptor up-regulation.

Animals↗

PubMed1996

Local expression of a POU family transcription factor, Pit-1, in the rat placenta.

A pituitary-specific trans-acting factor, Pit-1 regulates transcriptional activity of growth hormone (GH) and prolactin (PRL) genes. Pit-1 can bind and activate the promoters of human chorionic somatomammotropin (hCS-A) and placental GH variants (hGH-V) as well. However, expression of Pit-1 in the rat placenta has not yet been elucidated. The present study aims to determine whether the Pit-1 gene is locally expressed in the rat placenta using reverse transcription-polymerase chain reaction (RT-PCR), Northern blot and Western blot hybridization, in situ hybridization and immunohistochemistry. PCR products were further analyzed by Southern hybridization and DNA sequencing. The estimated size of Pit-1 mRNA in placenta was very similar to that in anterior pituitary (AP). PCR products from placenta were exactly the same size with that from AP and confirmed as Pit-1-specific by Southern hybridization. The Pit-1 specific sequence was also confirmed by sequencing of partial amplification fragments. Immunoreactive 33 kDa Pit-1 was present in the placenta as well as in AP. Pit-1 specific mRNA and protein were localized in the trophoblast cells of placenta. These data suggest that Pit-1 is locally synthesized in the rat placenta and may be involved in the regulation of GH- and/or PRL-like gene expression in the placenta.

Animals↗

PubMed1996

Myxoma of the mandible.

Myxoma of the jaw bone is a peculiar and rare tumor. A case of myxoma of the mandible is described in a 38-year-old man. The plain X-ray showed multiple osteolytic destructive lesions in the molar root area. CT scans demonstrated osteolytic expansile lesions with mild enhancement of the solid portion of the mass. Histologically, the tumor is composed of plump stellate cells with abundant amorphous myxoid stroma.

Adult↗

PubMed1996

Validation of susceptibility as a predictor of which adolescents take up smoking in the United States.

Smoking onset has 4 levels, with a "susceptibility" level preceding early experimentation. This study assessed the predictive validity of smoking susceptibility in a longitudinal study of a nationally representative sample of 4,500 adolescents who at baseline reported never having puffed on a cigarette. At follow-up 4 years later, 40% of the sample had experimented with smoking, and 8% had established a smoking habit. Baseline susceptibility to smoking, defined as the absence of a firm decision not to smoke, was a stronger independent predictor of experimentation than the presence of smokers among either family or the best friend network. However, susceptibility to smoking was not as important as exposure to smokers in distinguishing adolescents who progressed to established smoking from those who remained experimenters at follow-up.

Adolescent↗

PubMed1996

Regional differences in the incidence and treatment of carcinoma in situ of the breast.

Greater use of mammography in the United States in recent years has increased the detection of early neoplasms of the breast, including carcinoma in situ. However, the occurrence and treatment of diagnosed carcinoma in situ of the breast has not been fully described. Our goal was to examine temporal, geographic, and demographic patterns in the incidence and treatment of in situ breast cancer. The study included data from all women with in situ breast cancer that had been detected in the nine Surveillance, Epidemiology, and End Results areas of the United States from 1975 through 1990 (Surveillance Program, Cancer Statistics Branch, Bethesda, MD: National Cancer Institute, November, 1993). We calculated age-adjusted incidence rates (1970 United States standard) using data on histology and treatment from the Surveillance, Epidemiology, and End Results data tape. We assessed predictors of treatment by mastectomy using multiple logistic regression. From 1975-1979 to 1986-1990, the age-adjusted incidence rate of in situ breast cancer increased from 4.7 to 16.9/100,000 women. The increase occurred in all age groups and among both white and black women. However, there was nearly a 2-fold difference in incidence rates across geographic areas in 1986-1990, ranging from < 12/100,000 in Iowa and New Mexico to > 20/100,000 in San Francisco and Seattle. Geographic variability in treatment was also evident, with mastectomy, rather than breast-conserving therapy, performed on 46% of the women with in situ breast cancer in San Francisco and on 66% of those in Iowa. The incidence of diagnosed in situ breast cancer increased markedly during the 1980s, and there was substantial geographic variability in the rates of detection of these tumors and in the type of therapy received. Although mastectomy became a less common treatment over time, it was still performed on a high proportion of women with in situ breast cancer during the latter part of the decade.

Adult↗

PubMed1996

Determination of a new antiulcer agent, YJA-20379-2, in human plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the determination of a new antiulcer agent, YJA-20379-2, in human plasma and urine. The sample preparation was simple: 2.5-volume of acetonitrile was added to the biological sample to deproteinize. A 50-microliter aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase employed was methanol-0.1M Sørensen phosphate buffer of pH 7.0-H2O (75:2:25, v/v/v), and was run at a flow-rate of 1.0 ml/min. The column effluent was monitored by ultraviolet detector at 295 nm. The retention time for YJA-20379-2 was approximately 7.0 min. The detection limits for YJA-20379-2 in human plasma and urine were both 100 ng/ml. The coefficients of variation of the assay (within-day and between-day) were generally low (below 9.16%) for both the human plasma and urine. No interference from endogenous substances was found.

Anti-Ulcer Agents↗

PubMed1995

Well-differentiated, low-grade osteosarcoma of the clivus.

A case of well-differentiated osteosarcoma of the sphenoid bone was reported. The pathological differentiation of this rare entity from fibrous dysplasia, the radiographic appearance, and the differential diagnosis were discussed.

Diagnosis, Differential↗

PubMed1995

Distribution of dopamine D1, D2, and D5 receptor mRNAs in the monkey brain: ribonuclease protection assay analysis.

The distribution of the mRNAs encoding the dopamine D1, D2 and D5 receptors was determined in brain tissues obtained from intact female rhesus monkeys, using a ribonuclease protection assay. Tissue blocks from the frontal cortex, striatum, thalamus, hippocampus and substantia nigra were dissected and total RNA was extracted. Dopamine D2 and D5 receptor DNA fragments were generated from rhesus monkey genomic DNA using polymerase chain reaction. To generate dopamine receptor subtype-specific cRNA probes, DNA fragments corresponding to the carboxy terminus of the rhesus monkey D1 and D2 receptor genes and to the putative transmembrane domain regions (IV-VI) of the D5 receptor gene, were subcloned into the pGEM3Z/4Z vectors. Expression of D1 receptor mRNA exhibited significant regional differences: striatum > > > cerebral cortex > or = hippocampus > or = lateral thalamus. D1 receptor mRNA was found in low quantities in the medial thalamus, but was not consistently expressed in the substantia nigra area. In contrast, D2 receptor mRNA was detected in all regions that were studied: striatum > > > substantia nigra > > hippocampus > or = cerebral cortex > or = medial thalamus > or = lateral thalamus. D5 receptor mRNA was also expressed in all regions, with highest levels in the cerebral cortex, striatum and lateral thalamus, and moderate levels in the substantia nigra, medial thalamus and the hippocampus. The D5 receptor mRNA appears to be widely distributed in the monkey brain. Most interesting is the expression of D5 receptor mRNA in tissues of the substantia nigra area.

Animals↗

PubMed1995

Fusacandins A and B; novel antifungal antibiotics of the papulacandin class from Fusarium sambucinum. I. Identity of the producing organism, fermentation and biological activity.

The fuscandins, antifungal agents of the papulacandin class, are produced by a strain of Fusarium sambucinum. Fermentation yielded 60 mg/liter of fusacandin A and minor amounts of fusacandin B. As expected, the fusacandins inhibit (1,3)-beta-glucan synthesis. Fusacandin A is slightly less active than papulacandin B against Candida albicans and, like papulacandin, loses activity in the presence of serum.

Aminoglycosides↗

PubMed1995

Stage specific identification of the expression of GnRH mRNA and localization of the GnRH receptor in mature rat and adult human testis.

PURPOSE: To identify the expression of gonadotropin-releasing hormone (GnRH) messenger ribonuclueic acid (mRNA) and localize GnRH receptors in mature rat and adult human testes. MATERIALS AND METHODS: In situ hybridization and enzymatic receptor binding localization were performed. RESULTS: GnRH mRNA was expressed within the seminiferous tubules in both mature rat and adult human testis. In rats, expression of GnRH mRNA was identified in the Sertoli cells and spermatogenic cells of some seminiferous tubules, but the other tubules did not express any hybridization signal. In humans, expression of GnRH mRNA was identified only in some spermatogenic cells in some seminiferous tubules. The receptors for GnRH were localized to cells in the interstitial tissues of the testis, probably Leydig cells. CONCLUSION: The authors believe that the mature rat and adult human seminiferous tubular cells produce GnRH at the same specific stage of the spermatogenic cycle and that GnRH produced within seminiferous tubules, including Sertoli cells and spermatogenic cells, reacts with neighboring GnRH receptors in interstitial cells, including Leydig cells. The GnRH produced from the Sertoli cells in seminiferous tubules would react with GnRH receptors in interstitial cells as a paracrine hormone.

Adult↗