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Biomedical subjects

E Y Choi

Publications and source records attributed to E Y Choi.

52 records · Page 3Linked to original sources
PubMed1996

Suppression of rat hepatic cytochrome P450 2E1 expression by isopropyl 2-(1,3-dithioetane-2-ylidene)-2-[N-(4-methyl-thiazol-2-yl)carbamoyl] acetate (YH439), an experimental hepatoprotectant: protective role against hepatic injury.

The expression of cytochromes P450 2E1, P450 2B and P450 1A was examined in rat hepatic tissue in response to YH439, an experimental hepatoprotective agent. P450 2E1 metabolic activities relatively specific for P450 2E1 were decreased up to 57% of control activities in the hepatic microsomes prepared from rats treated with YH439 for 3 days. Immunoblot analyses showed that P450 2E1 levels were decreased below the limit of detectability in hepatic microsomes prepared from YH439-treated rats. YH439 at doses from 25 to 100 mg/kg completely suppressed isoniazid-inducible P450 2E1 levels as monitored by both metabolic activities and immunoblot analysis. RNA hybridization analysis revealed that P450 2E1 mRNA levels failed to change after YH439 treatment. These results demonstrate the YH439 effectively suppresses P450 2E1 expression in the absence of transcriptional inactivation. YH439 failed to affect P450 2B1/2 expression, whereas this agent enhanced the hepatic P450 1A1/2 levels. The hepatoprotective effects of YH439 were also examined. Animals treated with CCl4 and ethanol for 9 weeks showed hepatic injury as demonstrated by 2.5- and 2-fold increases in serum alanine aminotransferase and alkaline phosphatase activities, respectively. Concomitant YH439 treatment resulted in a significant protective effect against the experimental hepatic injury. The toxicant-induced elevation in hepatic hydroxyproline level was completely blocked by YH439 treatment. These data indicate that YH439 suppresses the expression of P450 2E1 and protects the liver against chemical-induced hepatic injury and that the selective modulation of detoxifying enzymes by YH439 may contribute to the protection of liver from xenobiotic-induced intoxication.

Animals↗
PubMed1996

DN4: a novel cell surface molecule on cortical epithelial cells of the human thymus.

A novel cell surface molecule, DN4, defined by an mAb raised against human thymic epithelial cells, showed a specificity for epithelial cells of the thymic cortex. This antigen was not expressed at detectable levels on any other types of tissues in the human body except for the thymus and bone marrow. Immunohistochemical analysis revealed that the reactivity of anti-DN4 mAb was restricted to the thymic cortex, and the antigen-expressing cells were arranged in a reticular network with long processes between thymocytes. The cellular nature of DN4-positive cells was identified as cortical epithelial cells, as DN4 was expressed in a subpopulation of freshly prepared thymic stromal cells which contain a large amount of keratin and expression of DN4 was strictly confined to the cortical area within the thymus on immunohistochemical analysis of frozen tissues. Immunofluorescence and flow cytometric analysis revealed that a subpopulation of bone marrow cells was also positive for DN4 (20%). The large blasts of normal bone marrow cells were clearly labeled with anti-DN4 mAb, in contrast to small-sized bone marrow cells. This finding suggests that DN4 seems to be transiently expressed in certain blastic stages during the differentiation of bone marrow cells. Immunoprecipitation of 125I-labeled cell lysates from THP-1 and U937 cell lines with anti-DN4 mAb yielded a single chain glycoprotein with an approximate size of 80-85 kd. There was a reduction in apparent molecular weight of approximately 40 kd in the immunoprecipitation of cell lysates after endoglycosidase F treatment. Thus, DN4 seemed to have a considerable amount of carbohydrate group. DN4 appears to be a novel cortical epithelial cell antigen of the human thymus, and although the role of this molecule has not been well established experimentally, the possibility can be suggested that the DN4 molecule might be involved in the positive selection of thymocytes which occurs predominantly in the thymic cortical area.

Antibodies, Monoclonal↗
PubMed1995

A novel T-cell differentiation antigen expressed in immature human thymocytes and neuroglial cells.

We report a novel human thymocyte differentiation antigen ICT-1 with a molecular weight of 49 kDa that is noncovalently associated with another 12-kDa protein. The ICT-1 antigen is expressed in 50-70% of total thymocytes, but not in resting or PHA-activated peripheral blood T-cells and bone marrow cells. The thymocytes expressing ICT-1 antigen appear after the 18th week of gestation during fetal development. Since the distribution pattern of the ICT-1 antigen within thymus partly overlaps with that of the CD1 antigens, we investigated whether ICT-1 was one of the CD1 antigen family. However, the failure of anti-ICT-1 antibody to react with mouse L cells transfected with cDNA of CD1a, -b, and -c and the different histologic distribution patterns from that of CD1d strongly suggest that the anti-ICT-1 antibody recognizes an antigen distinct from CD1. Furthermore, ICT-1 is also expressed in human neuroglial cells such as oligodendroglioma, glioblastoma multiforme, Ewing's sarcoma, and cerebellar astrocyte. Hence we believe that the ICT-1 antigen may be a novel thymus-leukemia (TL) antigen or a nonclassical MHC class I antigen.

Animals↗
PubMed1995

Production and characterization of monoclonal antibodies to bovine brain succinic semialdehyde reductase.

Monoclonal antibodies against bovine brain succinic semialdehyde reductase were produced and characterized. A total of nine monoclonal antibodies recognizing different epitopes of the enzyme were obtained, of which two inhibited the enzyme activity and three stained cytosol of rat spinal cord neurons as observed by indirect immunofluorescence microscopy. When unfractionated total proteins of bovine brain homogenate were separated by gel electrophoresis and immunoblotted, the antibodies specifically recognized a single protein band of 34 kDa, which comigrates with purified bovine succinic semialdehyde reductase. Using the antisuccinic semialdehyde reductase antibodies as probes, we investigated the cross-reactivities of brain succinic semialdehyde reductases from some mammalian and an avian species. The immunoreactive bands on western blots appeared to be the same in molecular mass--34 kDa--in all animal species tested, including humans. The result indicates that brain succinic semialdehyde reductase is distinct from other aldehyde reductases and that mammalian brains contain only one succinic semialdehyde reductase. Moreover, the enzymes among the species are immunologically very similar, although some properties of the enzymes reported previously were different from one another.

Animals↗
PubMed1994

Large-scale analysis of gene expression, protein localization, and gene disruption in Saccharomyces cerevisiae.

We have developed a large-scale screen to identify genes expressed at different times during the life cycle of Saccharomyces cerevisiae and to determine the subcellular locations of many of the encoded gene products. Diploid yeast strains containing random lacZ insertions throughout the genome have been constructed by transformation with a mutagenized genomic library. Twenty-eight hundred transformants containing fusion genes expressed during vegetative growth and 55 transformants containing meiotically induced fusion genes have been identified. Based on the frequency of transformed strains producing beta-galactosidase, we estimate that 80-86% of the yeast genome (excluding the rDNA) contains open reading frames expressed in vegetative cells and that there are 93-135 meiotically induced genes. Indirect immunofluorescence analysis of 2373 strains carrying fusion genes expressed in vegetative cells has identified 245 fusion proteins that localize to discrete locations in the cell, including the nucleus, mitochondria, endoplasmic reticulum, cytoplasmic dots, spindle pole body, and microtubules. The DNA sequence adjacent to the lacZ gene has been determined for 91 vegetative fusion genes whose products have been localized and for 43 meiotically induced fusions. Although most fusions represent genes unidentified previously, many correspond to known genes, including some whose expression has not been studied previously and whose products have not been localized. For example, Sec21-beta-gal fusion proteins yield a Golgi-like staining pattern, Ty1-beta-gal fusion proteins localize to cytoplasmic dots, and the meiosis-specific Mek1/Mre4-beta-gal and Spo11-beta-gal fusion proteins reside in the nucleus. The phenotypes in haploid cells have been analyzed for 59 strains containing chromosomal fusion genes expressed during vegetative growth; 9 strains fail to form colonies indicating that the disrupted genes are essential. Fifteen additional strains display slow growth or are impaired for growth on specific media or in the presence of inhibitors. Of 39 meiotically induced fusion genes examined, 14 disruptions confer defects in spore formation or spore viability in homozygous diploids. Our results will allow researchers who identify a yeast gene to determine immediately whether that gene is expressed at a specific time during the life cycle and whether its gene product localizes to a specific subcellular location.

Base Sequence↗
PubMed1994

Application of scanning electron microscopy in assessing the prevalence of some Setaria species in Korean cattle.

The numbers of individual Setaria species in the peritoneal cavities of Korean cattle were estimated. The worms were tentatively identified under light microscopy, and then precisely classified by SEM on the basis of unique features at the anterior and posterior ends of the adult worms. The positive rate of Setaria species was 34.2% out of 1,074 Korean cattle surveyed; that of S. digitata was 25.1%, S. marshalli 2.9% and both species 6.2%, respectively. Out of a total of 1,254 worms collected, 66.8% were female and 19.1% were male S. digitata; 9.2% were female and 5.0% were male S. marshalli, respectively. The average length of S. marshalli was somewhat longer than that of S. digitata. S. marshalli was documented for the first time in Korea.

Animals↗
PubMed1993

Kinetics and mechanism of an NADPH-dependent succinic semialdehyde reductase from bovine brain.

An NADPH-dependent succinic semialdehyde reductase has been purified from bovine brain by several chromatographic procedures. The preparation appeared homogeneous on SDS/PAGE. The enzyme is a monomeric protein with a molecular mass of 28 kDa. A number of properties of the bovine brain enzyme, such as substrate specificity, specific activity, molecular mass, optimum pH, amino acid composition, and kinetic parameters, have been determined and compared with those reported for preparations from other sources. The results indicate that the enzyme isolated from bovine brain in the present study is different from those reported for preparations from other sources. The inhibition kinetic patterns obtained when the products of the reaction or substrate analogs are used as inhibitor of the reaction catalyzed by the enzyme are consistent with an ordered sequential mechanism involving the formation of an intermediate ternary complex and in which NADPH is the first substrate to bind the enzyme.

Amino Acids↗
PubMed1992

Role of spectrin in Amoeba proteus, as studied by microinjection of anti-spectrin monoclonal antibodies.

Spectrin is a major protein accounting for about 5% of whole-cell proteins in Amoeba proteus, and the precipitation of spectrin by intracellular injection of purified anti-spectrin monoclonal antibodies has a profound effect on cell morphology, motility, and movement-related cell activities in amoebae. Thus, amoebae injected with anti-spectrin antibodies show drastic changes in their shape and movement, suggesting that amoeba spectrin plays an important structural role, unlike nonerythroid spectrins in other cells. However, precipitation of spectrin does not affect the distribution of F-actin in amoebae.

Actins↗
PubMed1991

Elevated levels of stress proteins associated with bacterial symbiosis in Amoeba proteus and soybean root nodule cells.

Obligatory bacterial endosymbionts of Amoeba proteus and symbiotic Bradyrhizobium japonicum bacteroids in soybean-root nodules contained large amounts of 67-kDa and 65-kDa proteins, respectively, antigenically related to groEL of E. coli and the 58-kDa heat-shock protein of Tetrahymena. Monoclonal antibodies against the 67-kDa protein recognized groEL analogs from several different organisms. The quantity of the stress protein in symbiotic B. japonicum bacteroids was augmented seven times that in the free-living counterparts. The increase in these proteins in endosymbionts, as determined by immunoblot techniques, indicated that intracellular symbiosis is a stress condition even when the symbiotic relationship is considered to be mutually beneficial. Mitochondria and chloroplasts may also be under a stressed condition like endosymbionts in view of the presence of heat-shock proteins in these cell organelles.

Amoeba↗
PubMed1990

Odontometric variation among American black, European, and Mongoloid populations.

Quantified dental parameters (including root and pulp areas and shape variables) derived from periapical radiographs were used to make comparisons among a sample of American Black (8 males--124 teeth, 9 females--138 teeth), European derivative (31 males--304 teeth, 43 females--497 teeth) and Mongoloid populations (12 males--166 teeth, 19 females--252 teeth). The magnitude of sexual dimorphism within each ethnic stock was also examined. Teeth from American Black males were robust. Sexual dimorphism was unambiguous in all groups although a hierarchical order existed from the highly dichotomous American Black sample to the more homogeneous European sample. The female dental phenotype was down-scaled from their male counterparts, but not gracile in form. Easily obtained area and shape parameters derived from dental radiographs proved useful as discriminators among racial groups and the sexes. The relationships among these data lend further support to the hypothesis of an African origin of modern humans.

Adolescent↗
PubMed1989

A spectrin-like protein present on membranes of Amoeba proteus as studied with monoclonal antibodies.

Monoclonal antibodies against a spectrin-like membrane-associated protein of xD amoebae. (Amoeba proteus) were used to determine the distribution of the protein and some of its characteristics. A total of 34 monoclonal antibodies recognizing different epitopes of the protein were obtained, of which seven stained cell membranes by indirect immunofluorescence. The spectrin-like protein had two subtypes of 225 and 220 kDa and several monoclonal antibodies cross-reacted with human erythrocyte spectrin when checked by indirect immunofluorescence staining and immunoblotting. Some of the antibodies also cross-reacted with antigens in HeLa cells and chick embryo fibroblasts. Polyclonal and monoclonal antibodies against Drosophila and human erythrocyte spectrins cross-reacted with the spectrin-like protein from amoebae. On the basis of these results, it was concluded that the protein is a spectrin. The protein was found on most cellular membranes of amoebae, including the plasma, nuclear, and phagosomal membranes, as well as symbiosome membranes.

Amoeba↗
PubMed1983

Neonatal ethanol exposure: effects on adult behavior and brain growth parameters.

Neonatal rats were reared using an artificial feeding technique from postnatal day 4 through 18. On postnatal day 4 through 7, some animals were given ethanol in their milk formula with the remaining animals serving as controls. The ethanol was given in amounts that have been shown to induce microcephaly when animals are examined at 18 days after birth. In this study, on postnatal day 18, all animals were weaned and allowed ad lib food and water until they were sacrificed at 60 days of age. When the animals were 30 days old, they were tested on a battery of behavioral tasks (nose poke, passive avoidance, and open field). No differences were found between the ethanol exposed animals and their controls on passive avoidance or nose poke activity. Ethanol-exposed female animals showed increased activity compared to their controls in the open field. There were no differences in open field activity between the ethanol exposed males and their controls. An examination of brain growth parameters (wet weights, DNA, cholesterol and protein content) showed no difference between the brains of ethanol-exposed males compared to controls at 60 days of age, regardless of brain parameter or brain area studied (forebrain, cerebellum or brainstem). The brains of ethanol-exposed females, however, had considerably less catch-up growth, with the ethanol effect on the cerebellum being very similar to that observed at 18 days of age. The results imply that sex and the time of ethanol exposure may interact to determine the ability of the brain to develop following a neonatal alcohol insult.

Animals↗
PubMed1976

C1q deficiency associated with urticarial-like lesions and cutaneous vasculitis.

We describe a 46 year old women with a seven year history of urticarial-like symptoms and cutaneous vasculitis with marked deficiency of C1q in the presence of normal levels of C1r and C1s and high titers of low molecular weight (7S) C1q precipitins. Hemolytic C1 activity, which was greatly reduced, was restored upon the addition of purified C1q. The other complement components were present in moderately reduced or normal levels. This patient bears resemblance to several other persons previously described with urticarial-like lesions in association with selective deficiency of C1q. The similarity of the clinical features, pathologic diagnosis, C1q levels disproportionately deficient in relation to other complement components and low molecular weight C1q precipitins support the conclusion that these are causally related in a symptom complex. The underlying basis is yet to be defined.

Complement C1↗
PubMedDate not supplied

Human brain GABA transaminase is immunologically distinct from those of other mammalian brains.

Monoclonal antibodies (mAbs) to bovine brain gamma-aminobutyric acid (GABA) transaminase were characterized by epitope mapping analysis, and used as probes to compare the epitopes of the enzymes from several mammalian brains including man. From the epitope mapping analysis, three subgroups of mAbs recognizing different peptide fragments were identified. In the immunoblots probed with the mAbs, only one out of the three subgroups of mAbs reacted with a protein band of 50 kDa from human brain; the two other mAbs failed to detect any signal on the blots. In contrast, all of the mAbs did recognize a GABA-T protein band on immunoblots of all other mammalian brains tested. The results suggest that human brain GABA transaminase is immunologically distinct from those of other mammalian brains.

4-Aminobutyrate Transaminase↗
PubMedDate not supplied

Lysosomal membrane proteins of Amoeba proteus, as studied with monoclonal antibodies.

Monoclonal antibodies were prepared against lysosomal membrane proteins of amoebae and used to follow lysosome-phagosome fusion after induced phagocytosis. The specificity of antibodies was checked by indirect immunofluorescence microscopy, immunoelectron microscopy, and localization of the antigen in subcellular fractions. The antibody-recognized proteins started to appear on the membranes of phagolysosomes about 5 min after phagocytosis as detected by indirect immunofluorescence, and the intensity of fluorescence increased for up to 1 h. Results of injection experiments in which purified antibodies had been injected into living cells and probed by indirect fluorescence indicated that the antigens were located on the cytoplasmic side of the lysosomal membranes. Lysosomes fuse with phagosomes on the one hand but not with non-fusible vesicles such as symbiosomes on the other. The results support the view that a membrane component(s) of non-fusible vesicles somehow prevents lysosomes from fusing with them.

Acid Phosphatase↗