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Biomedical subjects

H S Yoon

Publications and source records attributed to H S Yoon.

At least 19 recordsLinked to original sources
PubMed2001

Compaction in preimplantation mouse embryos is regulated by a cytoplasmic regulatory factor that alters between 1- and 2-cell stages in a concentration-dependent manner.

Present studies were performed to investigate what factors affect the morphogenesis of preimplantation mouse embryos, and to find the action mechanism of that factor by using cytoplasm removal and its reconstitution from a different developmental stage embryo. Half (HP group) or one-third of cytoplasm (TP group) was removed from 1-cell mouse embryos by micromanipulation, and their morphogenesis and genome expression were compared with sham-operated embryos (SP group). The compaction and blastocoel formation of embryos in both the HP and TP groups were accelerated in time and cell stage when compared with those of the SP group. However, the total activity and time of RNA synthesis, and gene expression of ZO-1alpha+ isoform were not different. To change the cytoplasm composition without altering the nucleus/cytoplasmic ratio, half a 1-cell embryo with both pronuclei was reconstituted with the half enucleated cytoplasm of 1-cell embryo (P + P group), 2-cell (P + 2 group) or 4-cell (P + 4 group) by electrofusion. Embryonic compaction, timing of RNA synthesis, and stage-specific gene expression of the ZO-1alpha(+) isoform in the P + 2 and P + 4 groups were accelerated in time and cell stage than that in the P + P group, but not different between the P + 2 and P + 4 groups. In addition, a blastomere of 2-cell embryo was reconstituted with the enucleated cytoplasm of 1-cell embryo (2 + P group) or 2-cell (2 + 2 group) in equal volume by electrofusion. Also, the karyoplast of 2-cell was fused with the enucleated 1-cell embryo (2 + PP group). Embryonic development, total activity of RNA synthesis, and gene expression of the ZO-1alpha(+) isoform of embryos in the 2 + P and 2 + PP groups were delayed when compared with those of the 2 + 2 group. Also, the phenomena of compaction and blastocoel formation were delayed in the development time and cell stage. From these results, the nucleus/cytoplasm ratio was found to have no direct effect on the regulation of embryonic morphogenesis, although it accelerated compaction and blastocoel formation. However, cytoplasmic factors that altered between 1- and 2-cell stages regulate embryonic morphogenesis, especially compaction, of preimplantation mouse embryos in concentration-dependent manner.

Animals↗
PubMed2001

Solution structure of the antiapoptotic protein bcl-2.

The structures of two isoforms of Bcl-2 that differ by two amino acids have been determined by NMR spectroscopy. Because wild-type Bcl-2 behaved poorly in solution, the structures were determined by using Bcl-2/Bcl-x(L) chimeras in which part of the putative unstructured loop of Bcl-2 was replaced with a shortened loop from Bcl-x(L). These chimeric proteins have a low pI compared with the wild-type protein and are soluble. The structures of the two Bcl-2 isoforms consist of 6 alpha-helices with a hydrophobic groove on the surface similar to that observed for the homologous protein, Bcl-x(L). Comparison of the Bcl-2 structures to that of Bcl-x(L) shows that although the overall fold is the same, there are differences in the structural topology and electrostatic potential of the binding groove. Although the structures of the two isoforms of Bcl-2 are virtually identical, differences were observed in the ability of the proteins to bind to a 25-residue peptide from the proapoptotic Bad protein and a 16-residue peptide from the proapoptotic Bak protein. These results suggest that there are subtle differences in the hydrophobic binding groove in Bcl-2 that may translate into differences in antiapoptotic activity for the two isoforms.

Amino Acid Sequence↗
PubMed2001

Transformation of kidney epithelial cells by a quinol thioether via inactivation of the tuberous sclerosis-2 tumor suppressor gene.

Although hydroquinone (HQ) is a rodent carcinogen, because of its lack of mutagenicity in standard bacterial mutagenicity assays it is generally considered a nongenotoxic carcinogen. 2,3,5-Tris-(glutathion-S-yl)HQ (TGHQ) is a potent nephrotoxic metabolite of HQ that may play an important role in HQ-mediated nephrocarcinogenicity. TGHQ mediates cell injury by generating reactive oxygen species and covalently binding to tissue macromolecules. We determined the ability of HQ and TGHQ to induce cell transformation in primary renal epithelial cells derived from the Eker rat. Eker rats possess a germline inactivation of one allele of the tuberous sclerosis-2 (Tsc-2) tumor suppressor gene that predisposes the animals to renal cell carcinoma. Treatment of primary Eker rat renal epithelial cells with HQ (25 and 50 microM) or TGHQ (100 and 300 microM) induced 2- to 4-fold and 6- to 20-fold increases in cell transformation, respectively. Subsequently, three cell lines (The QT-RRE 1, 2, and 3) were established from TGHQ-induced transformed colonies. The QT-RRE cell lines exhibited a broad range of numerical cytogenetic alterations, loss of heterozygosity at the Tsc-2 gene locus, and loss of expression of tuberin, the protein encoded by the Tsc-2 gene. Only heterozygous (Tsc-2(EK/+)) kidney epithelial cells were susceptible to transformation by HQ and TGHQ, as wild-type cells (Tsc-2(+/+)) showed no increase in transformation frequency over background levels following chemical exposure. These data indicate that TGHQ and HQ are capable of directly transforming rat renal epithelial cells and that the Tsc-2 tumor suppressor gene is an important target of TGHQ-mediated renal epithelial cell transformation.

Animals↗
PubMed2001

Ovarian expression of melatonin Mel(1a) receptor mRNA during mouse development.

Melatonin, secreted by the pineal gland, is involved in the regulation of many physiological functions of various species of animals. In the present study, the expression of gene for melatonin Mel(1a) receptor (MelR) was evaluated in the ovary, hypothalamus, and pituitary according to the developmental stages in female mice. Semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) and in situ PCR techniques were applied. According to the developmental stages, gene for MelR was differently expressed on ovary, hypothalamus, and pituitary. MelR gene was first expressed on pituitary prior to the expression in hypothalamus and ovary. Ovarian MelR gene started to express at birth. Unlike hypothalamic expression of MelR gene which was identified after birth, in pituitary, it was expressed at 16 days post coitum. In the ovary, the expression signal of MelR gene was identified on granulosa cells. However, the signal was not detected in the theca cells. It was weak in the primordial and atretic follicles. Taken together, it can be considered that melatonin has a pivotal role in the folliculogenesis.

Animals↗
PubMed2001

Phylogeny of Alariaceae, Laminariaceae, and Lessoniaceae (Phaeophyceae) based on plastid-encoded RuBisCo spacer and nuclear-encoded ITS sequence comparisons.

Concatenated sequences from the plastid-encoded RuBisCo spacer and nuclear-encoded rDNA ITS region of the Alariaceae, Laminariaceae, and Lessoniaceae as currently recognized were used to determine the phylogeny of kelps (Phaeophyceae). Our analyses indicate that all taxa in the Alariaceae, Laminariaceae, and Lessoniaceae form a monophyletic lineage (the Laminariales sensu stricto). The phylogenetic analyses show that the kelps form eight well-supported clades (represented by Egregia, Laminaria, Hedophyllum, Macrocystis, Alaria, Agarum, Ecklonia, and Lessonia) that conform to the tribes of the current morphological classification system of the "advanced" kelps. Our results suggest that the kelps should be classified into eight families rather than the three that are presently used. The interrelationships among the eight lineages were, however, unresolved in the phylogenetic analyses. In all trees, Egregia diverged first and is the sister to the other kelp taxa. Our phylogenetic analyses also indicate that Kjellmaniella and Laminaria do not form a monophyletic group. Taken together, the RuBisCo spacer and rDNA ITS prove useful for understanding the evolutionary history of the advanced kelps and provide a new framework for establishing the systematics of these commercially important brown algae.

Cell Nucleus↗
PubMed2001

Synthetic bile acid derivatives induce nonapoptotic death of human retinal pigment epithelial cells.

PURPOSE: To study whether the synthetic ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) derivatives, which we have synthesized and have reported their apoptosis-inducing effect, have the effect on the proliferation of retinal pigment epithelial cells. METHODS: UDCA, CDCA, and their synthetic derivatives were administered in culture to the human retinal pigment cell line, ARPE-19. The effect on cell viability and growth was assessed by trypan blue dye exclusion. In order to evaluate the type of cell death, mitochondrial membrane potential assay, DNA electrophoresis, TUNEL assay, nuclear staining and Western blotting for caspase-3 and poly(ADP-ribose) polymerase (PARP) activities were conducted. RESULTS: Unlike UDCA and CDCA, which did not exhibit a significant effect on viability, their synthetic derivatives decreased the viability of ARPE-19 cells in a concentration-dependent manner. The cells treated with the synthetic derivatives did not demonstrate the characteristic findings of apoptosis, such as DNA ladder, DNA fragmentation, nuclear condensation or fragmentation, and caspase-3 and PARP activation. The reduction of mitochondrial membrane potential was shown. In electron microscopical study nuclear condensation was not shown. CONCLUSIONS: The synthetic UDCA and CDCA derivatives induced nonapoptotic death of ARPE-19 cells.

Blotting, Western↗
PubMed2001

Phosphatidylinositol 3-kinase regulates proliferation of RAW 264.7 macrophages.

Phosphatidylinositol 3-kinase (P13-kinase) is an enzyme that acts as a direct biochemical link between a novel phosphatidylinositol pathway and a number of proteins containing intrinsic or associated kinase activities. Here we demonstrate that wortmannin, P13-kinase inhibitor, decreases the proliferation of RAW 264.7 macrophages and that another structurally unrelated inhibitor of P13-kinase, LY294002. also inhibits the proliferation. These results indicate a possible involvement of P13-kinase in RAW 264.7 macrophages growth regulation. Wortmannin stimulation of RAW 264.7 macrophages is followed by sustained expression of the mRNA of c-fos and a transient expression of the mRNA of c-jun. We also show that the wortmannin and LY294002 induce a cell cycle arrest in asynchronously growing cells leading to an inhibition of cell proliferation after 12 h of treatment. In addition, wortmannin or LY294002 inhibited the phorbol 12-myristate 13-acetate-induced macrophages proliferation potently. These results suggest that P13-kinase plays an important role in growth regulation of RAW 264.7 macrophages and that protein kinase C is a down stream effector of P13-kinase.

Androstadienes↗
PubMed2001

PatS and products of nitrogen fixation control heterocyst pattern.

The filamentous cyanobacterium Anabaena sp. strain PCC 7120 forms a developmental pattern of single heterocysts separated by approximately 10 vegetative cells. Heterocysts differentiate from vegetative cells and are specialized for nitrogen fixation. The patS gene, which encodes a small peptide that inhibits heterocyst differentiation, is expressed in proheterocysts and plays a critical role in establishing the heterocyst pattern. Here we present further analysis of patS expression and heterocyst pattern formation. A patS-gfp reporter strain revealed clusters of patS-expressing cells during the early stage of heterocyst differentiation. PatS signaling is likely to be involved in the resolution of these clusters. Differentiating cells were inhibited by PatS during the time period 6 to 12 h after heterocyst induction, when groups of differentiating cells were being resolved to a single proheterocyst. Increased transcription of patS during development coincided with expression from a new transcription start site. In vegetative cells grown on nitrate, the 5' end of a transcript for patS was localized 314 bases upstream from the first translation initiation codon. After heterocyst induction, a new transcript with a 5' end at -39 bases replaced the vegetative cell transcript. A patS mutant grown for several days under nitrogen-fixing conditions showed partial restoration of the normal heterocyst pattern, presumably because of a gradient of nitrogen compounds supplied by the heterocysts. The patS mutant formed heterocysts when grown in the presence of nitrate but showed no nitrogenase activity and no obvious heterocyst pattern. We conclude that PatS and products of nitrogen fixation are the main signals determining the heterocyst pattern.

Anabaena↗
PubMed2001

The effects of particle size distribution on the settleability of CSOs pollutants.

Over the past decades, flocculation and/or sedimentation processes have been adopted to remove pollutants from CSOs. It has been learned that major factors affecting settlement of pollutants are the particle size distribution, their settling velocities and their specific gravity. It is, therefore, a good idea to analyze the particle size distribution and settleability of CSOs pollutants in order to develop details in designing a process. Discussed in this study are pollutant characteristics of CSOs such as particle size distribution and settleability of pollutants. The power law function is applied and is found to be an effective and reliable index for expressing the particle size distribution of pollutants in CSOs. Based on the particle size spectrum analysis, the tendency toward settling and simultaneous flocculation-settling phenomenon of CSOs pollutants is described. Based on the regression analysis it is observed that the derived constants of curves representing settling velocity profile are proportional to the initial concentration of particles and to the beta-values of power law distributions. It is also revealed that the simultaneous flocculation-settling processes are effectively described by the changes of the average particle diameter and of the beta-values of power law distributions.

Geologic Sediments↗
PubMed2000

Genistein induces apoptosis of RPE-J cells by opening mitochondrial PTP.

Although previous studies demonstrated that genistein-induced apoptosis of various cell types including RPE-J cells, the involvement of mitochondrial events in such types of apoptosis has not been demonstrated to date. In this investigation of genistein-induced apoptosis of RPE-J cells, genistein induced the reduction of the mitochondrial membrane potential and the release of cytochrome c to cytosol. A mitochondrial permeability transition pore (PTP) blocker bongkrekic acid prevented the reduction of the mitochondrial membrane potential and cytochrome c release, and consequently abolished caspase-3 activation, nuclear condensation, and DNA fragmentation. On the other hand, zVAD-fmk did not inhibit the mitochondrial event such as the reduction of the mitochondrial membrane potential and cytochrome c release although it prevented caspase-3 activation, nuclear condensation, and DNA fragmentation. Taken together, genistein induces apoptosis of RPE-J cells by opening the mitochondrial PTP, and the mitochondrial event in this type of apoptosis is caused independently of caspase.

Animals↗
PubMed2000

Expression of protein kinase C genes in normal (+/+) and W mutant alleles (Wsh/Wsh, W/Wv) mice testes.

In the present study, we investigated the expression of mRNA of protein kinase C (PKC) isoenzymes (alpha, beta, gamma, delta, epsilon, zeta, eta, and theta) in normal (+/+) and W mutant alleles mice testes. In +/+ mice testes, abundant expression of PKCdelta and PKCtheta was observed, while other PKCs (alpha, beta, gamma, epsilon, zeta, and eta) generally were not detected by Northern blotting. The PKCdelta and PKCtheta isoenzymes demonstrated a distinctive cellular distribution when evaluated by in situ hybridization. We have previously shown that PKCdelta gene was selectively expressed in spermatid of +/+ testes. Here we show that PKCdelta gene is also present in spermatid of Wsh/Wsh mice testes and PKCtheta gene was present in interstitial cells of +/+, Wsh/Wsh, and W/Wv mice testes. These studies provide the evidence of selective cell distributions of the PKC isoenzymes and suggest that PKC has the functional significance in testes.

Alleles↗
PubMed2000

Genistein produces reduction in growth and induces apoptosis of rat RPE-J cells.

PURPOSE: To investigate the effect of the tyrosine kinase inhibitor, genistein, on the growth of the retinal pigment epithelial (RPE) cell. METHODS: The tyrosine kinase inhibitor, genistein, was administered in culture to the rat retinal pigment epithelial cell line, RPE-J. The effect on cell viability and growth was assessed by trypan blue dye exclusion. Induction of apoptosis was confirmed morphologically by light and electron microscopy and oligonucleosomal fragmentation was assessed by TUNEL and DNA ladder. Quantitation was undertaken by propidium iodide staining and photometric enzyme immunoassay. Western blot was performed to study poly-(ADP-ribose)-polymerase cleavage (PARP). To confirm the involvement of caspase, the caspase inhibitor z-VAD-fmk was employed. In addition, cell cycle phase was determined by flow cytometry. RESULTS: We here demonstrate that genistein treatment of RPE-J cells produces a dose- and time-dependent growth inhibition. Genistein in higher concentration induces apoptosis of rat RPE-J cell. z-VAD-fmk inhibited this type of apoptosis and cleavage of PARP enzyme was demonstrated. Ten micromolar genistein inhibited cell proliferation by G(0)/G(1) arrest without inducing apoptosis of the major population. Whereas 50 microM genistein caused growth inhibition of RPE-J cells by G(2)/M arrest and subsequent apoptotic death. CONCLUSIONS: Genistein inhibits RPE cell growth and induces apoptosis. The ability of genistein to inhibit the proliferation and to induce apoptosis of RPE cells could be potentially therapeutic for proliferative vitreoretinopathy.

Amino Acid Chloromethyl Ketones↗
PubMed1998

Heterocyst pattern formation controlled by a diffusible peptide.

Many filamentous cyanobacteria grow as multicellular organisms that show a developmental pattern of single nitrogen-fixing heterocysts separated by approximately 10 vegetative cells. Overexpression of a 54-base-pair gene, patS, blocked heterocyst differentiation in Anabaena sp. strain PCC 7120. A patS null mutant showed an increased frequency of heterocysts and an abnormal pattern. Expression of a patS-gfp reporter was localized in developing proheterocysts. The addition of a synthetic peptide corresponding to the last five amino acids of PatS inhibited heterocyst development. PatS appears to control heterocyst pattern formation through intercellular signaling mechanisms.

Amino Acid Sequence↗
PubMed1998

Heterocyst formation in Anabaena.

Heterocystous cyanobacteria grow as multicellular organisms with a distinct one-dimensional developmental pattern of single nitrogen-fixing heterocysts separated by approximately ten vegetative cells. Several genes have been identified that are required for heterocyst development and pattern formation. A key regulator, HetR, has been recently shown to be aserine-type protease.

Anabaena↗
PubMed1998

Expression of DAZ (deleted in azoospermia), DAZL1 (DAZ-like) and protamine-2 in testis and its application for diagnosis of spermatogenesis in non-obstructive azoospermia.

Spermatogenesis is regulated by hormones, local regulatory factors in the testes and specific gene expression of spermatogenic cells in humans. In this study, we have detected the expression of the deleted in azoospermia (DAZ), the DAZ-like autosome (DAZL1), and the protamine-2 genes in spermatogenic cells. Spermatogenesis in 38 male infertility patients was evaluated by the semen analysis and histological examination. Patients were diagnosed as Sertoli cell-only syndrome (n = 20), maturation arrest (n = 6), hypospermatogenesis (n = 6), and obstructive azoospermic patients with normal spermatogenesis (n = 6). After microscopic observation of the wet preparation of the testis tissues, seminiferous tubule contents were used for reverse transcription-polymerase chain reaction (RT-PCR) analysis of DAZ, DAZL1 and protamine-2. In cases with Sertoli-cell only syndrome, we found spermatogenic cells in 30% of patients (6/20) by the wet preparation method. There was no difference between the histology and the wet preparation results in maturation arrest and obstructive azoospermia; however, in one case of hypospermatogenesis, spermatozoa were not detectable by the wet preparation method. Using in-situ hybridization with DAZ and protamine-2 ribonuclear probes, we confirmed spermatogenic cell-specific expression of DAZ (spermatogonia/early spermatocyte) and protamine-2 (spermatid/spermatozoon). DAZ and protamine-2 expression can therefore be considered spermatogenic cell markers and could be useful in molecular diagnosis of spermatogenesis. In 13 patients with spermatozoa under the wet preparation, the expression of DAZ, DAZL1 and protamine-2 was detected in all the preparations. In one wet preparation showing only spermatogonia/spermatocyte, only DAZ and DAZL1 RNA were detected. In 14 wet preparations showing no spermatogenic cells, DAZ, DAZL1 and protamine-2 were not detected except in one preparation where DAZL1 expression was detected. In 10 wet preparations representing spermatogonia/spermatocyte to spermatids, but showing no spermaozoa, DAZ and DAZL1 were detected in eight and nine preparations respectively, and protamine-2 was detected in six preparations. These results of gene expression were similar to the wet preparation results. RT-PCR for DAZ, DAZL1 and protamine-2 was informative for the existence of germ cells, germ cell physiology and differentiation. From these results, we suggest that the analysis of DAZ, DAZL1 and protamine-2 expression by RT-PCR and wet preparation might offer a better method for finding the spermatogenic cells compared to the histological method.

Actins↗
PubMed1998

Determination of encephalomyocarditis viral diabetogenicity by a putative binding site of the viral capsid protein.

The molecular mechanism by which some, but not all, variants of encephalomyocarditis (EMC) virus selectively infect pancreatic beta-cells in mice and induce IDDM has been an enigma for more than a decade. We report here that the binding site of the EMC viral capsid protein VP1 determines viral diabetogenicity. Recombinant chimeric EMC viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 of the major capsid protein VP1 bind poorly to beta-cells. In contrast, recombinant chimeric EMC viruses containing alanine or glycine at position 152 of the VP1 bind efficiently to and infect beta-cells, resulting in the development of diabetes. Three-dimensional molecular modeling reveals that the van der Waals interactions are greater and the residues surrounding position 152 of the VP1 are more closely packed in recombinant chimeric viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 than in recombinant chimeric viruses containing alanine or glycine at the same position. Our studies reveal that the surface areas surrounding alanine or glycine at position 152 of the VP1 are more accessible, thus increasing the availability of the binding sites for attachment to beta-cell receptors and resulting in viral infection and the development of diabetes.

Animals↗
PubMed1997

Effect of a novel saponin adjuvant derived from Quillaja saponaria on the immune response to recombinant hepatitis B surface antigen.

Adjuvant activity of saponins extracted from the South American tree Quillaja saponaria has been demonstrated with many antigens. Recently, four saponin fractions (designated as QS-7, QS-17, QS-18, and QS-21) with adjuvant activity were purified by reverse phase chromatography. In particular, efficacy of the less toxic QS-21 fraction has been demonstrated with several recombinant viral antigens including HIV gp120. Here, we report a novel saponin fraction (designated as QS-L1) derived from Quillaja saponaria. Unlike previously identified saponins, QS-L1 had a different chemical structure and showed adjuvant activity only when administered in the presence of alum-precipitated antigen. Interestingly, the QS-L1 greatly increased not only a humoral immune response but also cellular immune response to recombinant hepatitis B virus surface antigen (HBsAg). Furthermore, QS-L1 showed lower toxicity in vivo and in vitro than the previously identified saponin fraction, QS-21. Finally, we examined the chemical structure of the QS-L1 using mass spectroscopic analysis, carbohydrate composition analysis and NMR spectroscopic analysis. Thus, our results indicated that this novel QS-L1 saponin fraction had several desirable properties required for an effective adjuvant.

Adjuvants, Immunologic↗