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W S Choi

Publications and source records attributed to W S Choi.

At least 109 records · Page 6Linked to original sources
PubMed1994

Presence of gonadotropin-releasing hormone mRNA in the rat olfactory piriform cortex.

Gonadotropin releasing hormone (GnRH) neurons are known to be originated from the olfactory placode and to enter the forebrain regions during embryonic development. The present study aims to ascertain whether GnRH is locally expressed in the olfactory cortex. Northern blot hybridization and reverse transcription-polymerase chain reaction revealed that GnRH mRNA was present in the rat olfactory cortex as well as in the olfactory bulb. The predicted size of GnRH mRNA is similar to that detected in the hypothalamus. In situ hybridization histochemistry also showed that GnRH mRNA is highly concentrated in the olfactory piriform cortex. The present data indicate that GnRH is synthesized in the olfactory piriform cortex.

Animals↗
PubMed1994

Effects of natural sequence variation on recognition by monoclonal antibodies neutralize simian immunodeficiency virus infectivity.

The determinants of immune recognition by five monoclonal antibodies (KK5, KK9, KK17, Senv7.1, and Senv101.1) that neutralize simian immunodeficiency virus infectivity were analyzed. These five neutralizing monoclonal antibodies were generated to native SIVmac251 envelope glycoprotein expressed by a vaccinia virus recombinant vector. All five recognize conformational or discontinuous epitopes and require native antigen for optimal recognition. These monoclonal antibodies also recognize SIVmac239 gp120, but they do not recognize gp120 of two natural variants of SIVmac239, 1-12 and 8-22, which evolved during the course of persistent infection in vivo (D.P.W. Burns and R.C. Desrosiers, J. Virol. 65:1843-1854, 1991). Recombinant viruses which were constructed by exchanging variable regions between SIVmac239 and variant 1-12 were used to define domains important for recognition. Radioimmunoprecipitation analysis demonstrated that sequence changes in variable regions 4 and 5 (V4/V5) were primarily responsible for the loss of recognition of the 1-12 variant. Site-specific mutants were used to define precise changes that eliminate recognition by these neutralizing antibodies. Changing N-409 to D, deletion of KPKE, and deletion of KEQH in V4 each resulted in loss of recognition by all five monoclonal antibodies. SIVs with these natural sequence changes are still replication competent and viable. Changing A-417 to T or A/N-417/418 to TK in V4 or Q-477 to K in V5 did not alter recognition detectably. These results define specific, naturally occurring sequence changes in V4 of SIVmac that result in loss of recognition by one class of SIVmac neutralizing antibodies.

Amino Acid Sequence↗
PubMed1994

Blockade of noradrenergic neurotransmission with diethyldithiocarbamic acid decreases the mRNA level of gonadotropin-releasing hormone in the hypothalamus of ovariectomized, steroid-treated prepubertal rats.

We have previously found that progesterone (P) augmented gonadotropin-releasing hormone (GnRH) mRNA levels in the hypothalamus of ovariectomized, estradiol-treated (OVX + E) prepubertal rats. In order to determine whether noradrenergic neurotransmission is involved in the stimulatory effect of P on GnRH gene expression, diethyldithiocarbamic acid (DDC, 500 mg/kg), a dopamine beta-hydroxylase inhibitor was administered i.p. 1 h before P (1 mg) injection into OVX + E treated rats, and the effect of DDC on the P-induced GnRH mRNA levels was examined. A single injection of P into OVX + E primed rats augmented norepinephrine (NE) content, while the administration of DDC effectively blocked the P-induced increase in NE content, along with the increase in dopamine content. Suppression of NE neurotransmission with DDC resulted in a marked decrease in the P-induced GnRH mRNA levels as well as GnRH release in vitro. These results clearly demonstrate that noradrenergic neurotransmission is involved in P-stimulated GnRH gene expression in the rat hypothalamus.

Animals↗
PubMed1994

Immunocytochemical mapping of a novel dopamine-releasing protein in the rat brain.

This report partially describes, for the first time, the immunocytochemical distribution of a novel dopamine-releasing protein (DARP) in the male rat brain. This glycoprotein detected specifically with a monoclonal antibody against DARP follows a close distribution to that of catecholamines (CA) in areas in the CNS rich in either CA fibers or CA neuron cell groups as previously reported by others using a tyrosine hydroxylase (TH) marker. The striking similarities in the topographic arrangement of the DARP-positive reaction product and the TH-positive reaction product is another argument favoring the view that DARP is involved in the regulation of catecholamine neurons.

Animals↗
PubMed1993

Encapsidation of genetically engineered poliovirus minireplicons which express human immunodeficiency virus type 1 Gag and Pol proteins upon infection.

The use of recombinant viruses for the expression of a wide array of foreign proteins has become commonplace during the last few years. Recently, we have described the construction and characterization of chimeric human immunodeficiency virus type 1 (HIV-1)-poliovirus genomes in which the gag and pol genes of HIV-1 have been substituted for the VP2 and VP3 capsid genes of the P1 capsid precursor region of poliovirus. Transfection of these RNAs into tissue culture cells results in replication of the RNA genome and expression of HIV-1-P1 fusion proteins (W. S. Choi, R. Pal-Ghosh, and C. D. Morrow, J. Virol. 65:2875-2883, 1991). Here we report on the encapsidation and amplification of the minireplicons to obtain sufficient quantities for biological characterization. To do this, HIV-1-poliovirus minireplicon genomes containing the gag or pol gene were transfected into cells previously infected with a recombinant vaccinia virus (VV-P1) which expresses the poliovirus capsid precursor protein, P1 (D. C. Ansardi, D. C. Porter, and C. D. Morrow, J. Virol. 65:2088-2092, 1991). The chimeric minireplicons replicated and expressed the appropriate HIV-1-P1 fusion proteins as determined by immunoprecipitation with HIV-1-specific antibodies. The encapsidated genomes were isolated by ultracentrifugation. Reinfection of cells with the encapsidated chimeric RNA genomes resulted in expression of the HIV-1-Gag-P1 or HIV-1-Pol-P1 fusion protein. Serial passaging of the encapsidated chimeric HIV-1-poliovirus genomes was accomplished by coinfecting cells with the encapsidated minireplicons and VV-P1, resulting in stocks of the encapsidated minireplicons. Northern (RNA) blot analysis of passaged material revealed that no detectable deletions of the chimeric genomes occurred during 14 serial passages. Infection of cells by the encapsidated minireplicons was blocked by antipoliovirus antibodies. Coinfection of cells with encapsidated minireplicons and type 1 Sabin poliovirus resulted in encapsidation of the chimeric genomes by wild-type poliovirus as measured by immunoprecipitation of the HIV-1-P1 fusion proteins with HIV-1-specific antibodies. The results of this study demonstrate the encapsidation of poliovirus minireplicons which express foreign proteins and point to the future use of this system as a potential vaccine vector.

Capsid↗
PubMed1993

Immunocytochemical localization of dopamine-releasing protein in the rat adrenal.

The mechanism by which adrenal medulla transplants to the brain of Parkinson's patients ameliorate the symptoms of this neurodegenerative disease is unknown. It has been postulated but not proven that these transplants secrete a neurotrophic factor(s) responsible for the activation of the dopamine (DA) neurons. DA-releasing protein (DARP) was identified by immunocytochemistry in cells of the adrenal gland but not in tissues such as the liver or spleen. In the adrenal gland the immunopositive DARP cells were distributed both in the cortex as well as in the medulla. In the former, the distribution was rather uniform covering a broad area of the zona glomerulosa and fasciculata without positive cells in the zona reticularis. In the adrenal medulla the DARP signal was found in segregated cells forming clusters similar to the homotypic distribution of norepinephrine and epinephrine cells. The immunopositive cells for DARP were oval or spindle in shape and the staining was localized in the cytoplasm surrounding the nucleus. In addition, in this paper we present evidence confirming that the adrenal gland is the source of a protein that after immunopurification in nanogram amounts releases DA from corpus striatum fragments superfused in vitro. These data clearly demonstrate the existence of DARP in the adrenal gland and support the hypothesis that the effectiveness of the adrenal medulla transplants to the brain of Parkinson's patients is in part due to the secretion of neurotrophic factors. We submit that DARP is one of such factors.

Adrenal Glands↗
PubMed1993

Mitomycin C in anterior chamber tube shunt to a surgical membrane.

To increase the success rate of intraocular pressure control in recalcitrant glaucoma, anterior chamber tube shunt to a surgical membrane (ACTSSM) surgery using silicone tube and expanded polytetrafluoroethylene (e-PTFE) can be performed. Applying mitomycin C (MMC) during ACTSSM surgery may increase the success rate by decreasing the fibroblast proliferation and collagen in the fibrous capsule. To evaluate the effects of MMC on the fibrous capsule formed after ACTSSM surgery, operations were performed on 18 white rabbits. Nine rabbits were treated with 0.04% MMC solution on the episclera for 5 minutes before ACTSSM (group A) and the others were not treated (group B). At postoperative 2, 4 and 8 weeks successively, 6 eyes of the 3 rabbits were enucleated from each group. Light microscopic examinations were performed after hematoxylin & eosin staining and Masson's trichrome staining. In group A (MMC application group), fibrous capsules were not so dense, moderately thick, and showed many microcystic spaces. Proliferating fibrous connective tissues ingrowing between twofold surgical membranes were scanty. In group B (MMC non-application group), fibrous capsules showed high cellular density and less microcystic spaces, comparing those of MMC application group, suggesting low permeability of fibrous capsule to aqueous humor. MMC may be useful in increasing the success rate of ACTSSM surgery.

Animals↗
PubMed1993

Meningioangiomatosis--a case report.

Meningioangiomatosis is a rare benign hamartomatous lesion. We describe a case of meningioangiomatosis in an 18-year-old boy with a 15 year history of seizures. Computed tomography reveals an irregular calcification density along the right temporal gyrus. Microscopically, irregularly branched blood vessels, surrounded by a concentric arrangement of proliferating spindle cells, are extending into the gray matter from the meningeal surface. Ultrastructural and immunohistochemical examination failed to demonstrate features of meningothelial cell origin in this case. This is the first case of meningioangiomatosis published in Korea along with immunohistochemical and electron microscopic studies. The pathogenesis and previous reports of this lesion will be discussed.

Adolescent↗
PubMed1991

Expression of human immunodeficiency virus type 1 (HIV-1) gag, pol, and env proteins from chimeric HIV-1-poliovirus minireplicons.

Recent studies have demonstrated that genomes of poliovirus with deletions in the P1 (capsid) region contain the necessary viral information for RNA replication. To test the effects of the substitution of foreign genes on RNA replication and protein expression, chimeric human immunodeficiency virus type 1 (HIV-1)-poliovirus genomes were constructed in which regions of the gag, pol, or env gene of HIV-1 were substituted for regions of the P1 gene in the infectious cDNA clone of type 1 Mahoney poliovirus. The HIV-1 genes were inserted between nucleotides 1174 and 2956 of the poliovirus cDNA so that the translational reading frame was maintained between the HIV-1 genes and the remaining poliovirus genes. The chimeric genomes were positioned downstream from a T7 RNA polymerase promoter and transcribed in vitro by using T7 RNA polymerase, and the RNA was transfected into HeLa cells. A Northern (RNA blot) analysis of the RNA from transfected cells demonstrated the appropriate-size RNA, corresponding to the full-length chimeric genomes, which increased over time. Immunoprecipitation with antibodies specific for poliovirus RNA polymerase or sera from AIDS patients demonstrated the expression of the poliovirus RNA polymerase and HIV-1 proteins as fusions with the poliovirus P1 protein. The expression of the HIV-1-poliovirus P1 fusion protein was dependent upon an intact RNA polymerase gene, indicating that RNA replication was required for efficient expression. A pulse-chase analysis of the protein expression from the chimeric genomes demonstrated the initial rapid proteolytic processing of the polyprotein from the chimeric genomes to give HIV-1-poliovirus P1 fusion protein in transfected cells; the HIV-1 gag-P1 and HIV-1 pol-P1 fusion proteins exhibited a greater intracellular stability than the HIV-1 env-P1 fusion protein. Finally, superinfection with wild-type poliovirus of HeLa cells which had been transfected with the chimeric genomes did not significantly affect the expression of chimeric fusion protein. The results are discussed in the context of poliovirus RNA replication and demonstrate the feasibility of using poliovirus genomes (minireplicons) as novel vectors for expression of foreign proteins.

Acquired Immunodeficiency Syndrome↗
PubMed1991

[Immunohistochemical observation on the antigens inducing IgG and IgM antibodies against sparganum].

Localization and characterization of the antigenic components of sparganum which induced IgG and IgM antibodies in the host were studied by immunohistochemical techniques and SDS-PAGE and Western blotting. The antigen recognized by IgG antibody of rats or mice which were immunized by infection or injection of crude extracts of metacestodes of Spirometra erinacei, was located in the parenchyma of sparganum, especially at the cortex and around the calcareous corpuscles. The immunoreaction was demonstrated not only in the encysted fibrous wall of host but around the arterioles or venules in the connective tissue of host. The antigen recognized by IgM antibody of rats or mice was also observed in the parenchyma of sparganum and in the connective tissue of host. By 5-20% gradient SDS-PAGE and EIBT, we detected antigenic components by IgG and IgM antibodies of the rat or mouse immunized by infection or injection of crude extract of spargana. Twenty-three antigenic bands from crude extracts of spargana were recognized by IgG antibody and 15 components by IgM antibody of immunized rats. Out of the bands recognized by IgG and IgM antibodies, 15 were cross-reacted each other. Twenty components of excretory-secretory proteins from spargana were recognized by IgG, and 5 components by IgM antibody of immunized rats. By IgG and IgM antibodies of immunized mice, 16 components of crude extracts were recognized by IgG antibody and 9 components by IgM antibody. Twenty components of excretory-secretory preparation were recognized by IgG antibody and 5 components by IgM antibody. Thirteen components of crude extracts were cross-reacted by IgG antibody of rats and mice.

Animals↗
PubMed1990

Medial extent of the posterior renal fascia. An anatomic and computed tomography study.

To study the medial extent of the posterior renal fascia and the perirenal space, the authors dissected two cadavers and reviewed 50 computed tomographic (CT) abdominal scans. The results demonstrated that the medial extent of the posterior renal fascia depends on the level in a vertical direction and its relationship to the kidney which varies at different levels. At the renal hilus, the fascia inserts posteromedially to the fascia of the quadratus lumborum along its lateral margin; more cranially, the line of insertion is more lateral, onto the diaphragmatic fascia; more caudally, the line of insertion is more medial, inserting onto the anterior surface of the quadratus lumborum. Therefore the posteromedial insertion of the posterior renal fascia extends medially, from the more laterally placed diaphragmatic fascia, to the lateral margin of the quadratus lumborum and then to the anterior surface of the quadratus lumborum, depending on the anatomic level. The clinical implication of these findings are discussed.

Cadaver↗
PubMed1990

Symptomatic subependymoma--a case report.

Subependymoma is a rare, slow-growing, benign noninvasive tumor of the central nervous system that may be located in the fourth ventricle, the septum pellucidum, the third and the lateral ventricles, the aqueduct, and the proximal spinal cord. Symptoms, if any, usually result either from direct compression of the brain stem or from acute hydrocephalus due to occlusion of the foramen of Monro or aqueduct of Sylvius. In this report, we describe a case of subependymoma of the lateral ventricle with headache in a young female patient. This is the first reported case subependymoma in Korea that was documented along with Magnetic resonance image.

Adult↗
PubMed1989

Evidence that brain prostaglandin E2 is involved in physiological sleep-wake regulation in rats.

We reported in previous studies that prostaglandin E2 (PGE2) has central effects of augmenting wakefulness and suppressing slow-wave sleep (SWS) and paradoxical sleep (PS) in rats. In the present study, we tested the effect of AH 6809, an antagonist of PGE2 receptors, on sleep-wake activities. AH 6809 in saline was infused continuously into the third ventricle of freely moving rats at a rate of 2.1, 6.3, and 21 pmol/min from 2300 to 0500 hr. During the infusion at 21 pmol/min, wakefulness decreased to 82%, and SWS and PS increased to 122% and 161%, of the respective baseline values. These changes can be explained by AH 6809 antagonizing the endogenous PGE2 that acts to augment wakefulness in the brain. This explanation is supported by the fact that the infusion of AH 6809 at 21 pmol/min inhibited the wakefulness-promoting effect of PGE2 infused at 10 pmol/min. Moreover, the PGE2-related mechanisms for regulating sleep-wake activities may be different from those producing hyperthermia, because AH 6809 at 21 pmol/min had no primary effect on brain temperature and did not antagonize the hyperthermia produced by the PGE2 infusion. A diurnal infusion (1200 to 1800 hr) of AH 6809 at 21 pmol/min produced similar effects on sleep-wake activities compared with the nocturnal infusion (2300 to 0500 hr), although the PS increase was not significant, suggesting that the PGE2-related mechanisms are acting all day long with or without a circadian rhythm. These findings strongly suggest that endogenous PGE2 in the brain is involved in the physiological mechanisms for regulating sleep-wake activities.

Animals↗
PubMed1988

Superior aspect of the perirenal space: anatomy and pathological correlation.

To study the anatomy of the superior aspect of the perirenal space, we analysed 50 computed tomographic (CT) scans with reference to the anatomy of Gerota's fascia, and dissected five cadavers laying special emphasis on the ascent of Gerota's fascia. We also reviewed 10 scans of patients with a large lesion in the right upper abdomen regarding localisation of the lesion. We conclude that Gerota's fascia does not cover the upper portion of the kidney and adrenal gland so that the superior aspect of the perirenal space is open towards the upper abdominal extraperitoneal space. Thus, a large lesion arising from the right adrenal gland or kidney easily invaginates the liver through the bare area mimicking a hepatic lesion, and vice versa. This explains the difficulty in localising a large lesion in the right upper abdomen.

Humans↗
PubMed1987

The effects of DNA methylation by Hha I methylase on the cleavage reactions by Hae II, Aha II and Ban I endonucleases.

The DNA methylated by Hha I methylase was resistant against cleavage of Hae II or Aha II endonuclease indicating that the methyl group of the C5 position of the inmost cytosine nucleotide interferes with the interaction between the enzyme and the hexameric recognition sequence. Considering that Hae II or Aha II methylase has not been isolated yet, the result explained above is a useful information for protecting a double stranded DNA from being cleaved by Hae II or Aha II endonuclease. In contrast to Hae II or Aha II endonuclease, Ban I endonuclease which also has Hha I sequence as its tetrameric core was able to cleave the same DNA normally. This result suggests that the C5 position of the inmost pyrimidine nucleotide is not an important contact point between Ban I endonuclease and its hexameric recognition sequence.

DNA (Cytosine-5-)-Methyltransferases↗