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Biomedical subjects

Y S Cho

Publications and source records attributed to Y S Cho.

At least 91 records · Page 5Linked to original sources
PubMed1998

Absence of H(+)-ATPase in the intercalated cells of renal tissues in classic distal renal tubular acidosis.

Proton-secretory defect is thought to be a major pathophysiologic mechanism leading to classic distal renal tubular acidosis (dRTA). However, there have been only two case reports demonstrating the absence of proton pump in renal tissues of the patients with Sjögren's syndrome. This study presents two cases of classic dRTA in which the absence of intact H(+)-ATPase was shown in their renal biopsy tissues by immunohistochemistry using a rabbit polyclonal antibody against the 70 kDa catalytic subunit of H(+)-ATPase from bovine brain clathrin-coated vesicles; one of the cases is diagnosed as subclinical Sjögren's syndrome and the other is idiopathic dRTA. A normal human kidney (NC) and the renal biopsy tissues from a patient with chronic tubulointerstitial nephritus whose proton secretory capacity was intact (DC) were compared as controls. The first patient, a 26-year-old woman, presented with quadriparesis. Her serologic tests revealed positive autoantibodies (ANA, SSA; SSB & RF), and a lower lip biopsy confirmed the diagnosis of Sjögren's syndrome. The second patient, a 43-year-old woman, who initially presented with a pathologic fracture of both femoral necks was referred for an evaluation for hypokalemia by the Department of Orthopedic Surgery. Her renal ultrasonography showed medullary calcification, and no autoantibodies were positive. Serum electrolytes and blood gas analyses of the two patients indicated severe hypokalemia and metabolic acidosis, and proton secretory defects were shown by a failure to lower the urine pH during marked acidemia induced by NH4Cl loading and an abnormally low urine-blood pCO2 difference during bicarbonate administration. While stainings with the anti-H(+)-ATPase antibody in NC and DC were strongly positive in intercalated cells in the connecting tubules and collecting ducts, the tissues from both patients with dRTA were devoid of any anti-H(+)-ATPase staining in the intercalated cells. These results support that the pathophysiologic basis of impaired H+ secretion in idiopathic classic dRTA as well as Sjögren's syndrome is the absence of intact H(+)-ATPase pumps in the intercalated cells.

Acidosis, Renal Tubular↗
PubMed1997

Hepatitis C virus E2 protein purified from mammalian cells is frequently recognized by E2-specific antibodies in patient sera.

The envelope protein of hepatitis C virus (HCV) is composed of two membrane-associated glycoproteins, E1 and E2. To obtain HCV E2 protein as a secretory form at a high level, we constructed a recombinant chinese hamster ovary (CHO) cell line expressing a C-terminal truncated E2 (E2t) fused to human growth hormone (hGH), CHO/hGHE2t. The hGHE2t fusion protein was purified from the culture supernatant using anti-hGH mAb affinity chromatography at approximately 80% purity. The purified hGHE2t protein appeared to be assembled into oligomers linked by intermolecular disulfide bond(s) when density gradient centrifugation and SDS-polyacrylamide gel electrophoresis were employed. When the purified fusion protein was used for testing its ability to bind to antibodies specific for HCV by enzyme-linked immunosorbent assay, the protein was recognized by antibodies in sera from 90% of HCV-positive patients. Treatment of hGHE2t protein by beta-mercaptoethanol, but not by heat and SDS, significantly reduced its reactivity to the antibodies of patient sera, suggesting that intermolecular and/or intramolecular disulfide bonds are important for its ability to recognize its specific antibody and that the E2 protein contains discontinuous antigenic epitope(s).

Animals↗
PubMed1997

Intracytoplasmic sperm injection (ICSI) versus conventional IVF on abattoir-derived and in vitro-matured equine oocytes.

Conventional IVF as well as several assisted microfertilization techniques have shown limited success in the horse. After recent positive results achieved with intracytoplasmic injection of a single spermatozoon (ICSI) in human IVF, we chose to try the method in the horse. We compared conventional IVF to ICSI by fertilization rates of oocytes with compact and expanded cumuli and by developmental potential of the resulting embryos. Cumulus-oocyte complexes (COCs) were obtained by aspirating the follicular fluid from the ovaries of slaughtered mares. Complexes showing complete cumulus investment, either compact or expanded, were randomly assigned to IVF or ICSI trials and separately cultured for IVM. Frozen-thawed stallion spermatozoa were prepared for IVF with a swim-up procedure conducted in Talp-Hepes with heparin or for ICSI in Earle's balanced salt solution (EBSS) supplemented with human serum albumin (HSA). Oocytes for IVF were partially decumulated by pipetting, whereas those for ICSI were totally denuded with 80 UI/ml hyaluronidase. Oocytes were fixed, stained and examined for signs of fertilization the day after IVF or ICSI. The percentage of normally fertilized oocytes showing 2 pronuclei or cleavage was significantly higher with ICSI than IVF (29.8%, 17/57 vs 8.7%, 9/103 ; P < 0.01). Significantly higher fertilization rates were observed in oocytes retrieved with an expanded cumulus when submitted to ICSI procedure as compared with IVF (52.2%, 12/23 vs 17.1%, 6 35 ; P < 0.01), whereas in oocytes recovered with a compact cumulus, fertilization rates were low (14.7%, 5/34 with ICSI and 4.4%, 3 68 with IVF; NS). Embryonal development did not occur after culture following IVF, as indicated by absence of cleavage in any of the 93 inseminated oocytes. Following ICSI, 7 of 55 injected oocytes cleaved, 5 of which had shown expanded cumuli; of the 5, 2 were at the 16-cell stage and one each at the 8-, 3- and 2-cell stage, respectively. The other 2 fertilized oocytes, originating from compact cumuli, reached 4- and 8- cell stages, respectively. These results indicate that ICSI can be applied successfully to in-vitro matured equine oocytes to increase the fertilization rates. In addition, it seems that in vitro cytoplasmic maturation of oocytes issuing from a compact cumulus may not be complete enough to lead to a successful fertilization and that ICSI may be a tool to evaluate ooplasmic maturation.

Journal Article↗
PubMed1997

Role of Rho GTPase in the endothelin-1-induced nuclear signaling.

Binding of Endothelin-1 (ET-1) to its heterotrimeric G protein-coupled receptors stimulates various signaling cascades involving the activation of phospholipase C-beta, phospholipase D, protein kinase C (PKC), tyrosine kinases, Ca2+/calmodulin-dependent kinase (CaMKs), and Ras, a small molecular weight G-protein, but, the role of Rho GTPase remains unclear. In this project, we examined whether RhoA contributes to the ET-1-induced signaling cascade to c-fos SRE activation in Rat-2 fibroblast cells. Our results demonstrate that Rho activation is critical for the signal transduction of ET-1 to c-fos SRE.

Animals↗
PubMed1997

Effects of follicular fluid supplementation of in-vitro maturation medium on the fertilization and development of equine oocytes after in-vitro fertilization or intracytoplasmic sperm injection.

The aim of this study was to compare the effect of the addition of follicular fluid (FF) collected from preovulatory follicles with that of oestrous mare serum (EMS) (acting as the control) to TCM-199 medium on the in-vitro maturation, fertilization and development of equine cumulus-enclosed oocytes. Oocytes (<30 mm in diameter) were obtained from the ovaries of slaughtered mares. After in-vitro maturation in the presence of the two supplements, their fertilization, cleavage and developmental potential were compared after conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) using frozen-thawed spermatozoa. Follicular fluid did not increase the maturation of oocytes to metaphase II stage compared to control. After IVF, there was no difference in fertilization rates between FF-supplemented oocytes and controls (7/87, 8.4% of oocytes showing two pronuclei with FF versus 7/116, 6% with EMS; not significant). However, after ICSI, FF-supplemented oocytes showed significantly increased normal fertilization (32/85, 37.6% of two-pronuclear oocytes) and developmental potential (15/31, 48% cleavage) compared to the control oocytes (7/47, 14.9%, P < 0.01; and 2/48, 4%, P < 0.01, respectively). Overall, ICSI resulted in increased fertilization rates compared to IVF, regardless of the presence or absence of FF (39/132, 29.5% with ICSI versus 14/203, 6.9%). These results suggest that follicular fluid supplementation may improve the maturity of equine cumulus-enclosed oocytes sufficiently for the successful use of ICSI, but not sufficiently for normal sperm-egg interaction occurring during IVF.

Animals↗
PubMed1997

Effect of chaotropic salt on the secondary structure of pigskin gelatin.

Pigskin gelatin was prepared and its molecular weight profile was examined by SDS-PAGE. The major molecular weights of gelatin were 214 kDa, 135 kDa, and 122 kDa. The secondary structure of a gelatin solution in the presence of chaotropic salt was studied by using circular dichroism (CD). The CD study clearly showed that the chaotropic salt increased the ordered secondary structure of the gelatin solution due to the altered water structure.

Animals↗
PubMed1997

The role of thiols in protecting against simultaneous toxicity of menadione to platelet plasma and intracellular membranes.

Our previous study suggested that menadione (MEN) is cytotoxic to platelets of rats due to oxidative stress. To elucidate the mechanism of this toxicity, MEN-induced depletion of total cellular thiols or depletion of gutathione was studied in intact rat platelets. Treatment with MEN resulted in dose and time dependent damage to plasma (assessed by lactate dehydrogenase leakage) and intracellular (assessed by serotonin release) membranes. These events were well correlated with total cellular thiol depletion by MEN treatment, however MEN-induced glutathione depletion occurred rapidly and before plasma and intracellular membrane damage. Unlike hepatocytes, oxidized glutathione was not formed, suggesting that protein arylation, rather than oxidative stress, might be the ultimate mechanism for MEN cytotoxicity in platelets. Platelets were pretreated with dithiothreitol to supplement the total cellular thiol pool or with 1-chloro-2,4-dinitrobenzene to deplete glutathione, a soluble thiol. Dithiothreitol pretreatment to platelets protected against MEN-induced toxicity to both plasma membranes (prevented lactate dehydrogenase leakage and changes in platelet turbidity) and intracellular membranes (prevented serotonin release), although 1-chloro-2,4-dinitrobenzene pretreatment potentiated these toxicities. These results indicate that the total cellular pool of thiols plays a vital role in maintaining plasma and intracellular membrane integrity.

Animals↗
PubMed1996

Chemopreventive effect of chlorophyllin on mutagenicity and cytotoxicity of 6-sulfooxymethylbenzo[a]pyrene.

The chemopreventive activity of chlorophyllin (CHL) was monitored by using 6-sulfooxymethylbenzo[a]pyrene (SMBP) which is an ultimate metabolite of benzo[a]pyrene (B[a]P). CHL was quite effective in reducing both cytotoxicity and mutagenicity for SMBP in dose dependent manner up to 12.5 mM CHL in Chinese hamster V79 cells. The inhibitory patterns of CHL for SMBP were also confirmed in Salmonella typhimurium strains TA98 and TA100. Mutation frequency caused by SMBP was diminished almost to a control level at a 50 nmol CHL. A similar but less effective prevention of CHL was indicated in the mammalian and the bacterial mutagenicity assays with 6-hydroxymethylbenzo[a]pyrene (HMBP). The inhibitory effect of CHL against assault of SMBP on V79 cells was found to be related to the reduced cellular uptake of SMBP and further the remarkably lowered DNA adducts.

Animals↗
PubMed1996

Regulation of NAD+ glycohydrolase activity by NAD(+)-dependent auto-ADP-ribosylation.

NAD+ glycohydrolase (NADase; EC 3.2.2.5) is an enzyme that catalyses hydrolysis of NAD+ to produce ADP-ribose and nicotinamide. Its physiological role and the regulation of its enzymic activity have not been fully elucidated. In the present study, the mechanism of self-inactivation of NADase by its substrate, NAD+, was investigated by using intact rabbit erythrocytes and purified NADase. Our results suggest that inactivation of NADase was due an auto-ADP-ribosylation reaction. ADP-ribosylated NADase of rabbit erythrocytes was deADP-ribosylated when incubated without NAD+, and thus enzyme activity was simultaneously restored. These findings suggest that reversible auto-ADP-ribosylation of NADase might regulate the enzyme's activity in vivo.

Adenosine Diphosphate Ribose↗
PubMed1995

Impact of childhood cancer on Korean families.

A health care system that includes institutions such as the home, clinic, or hospital as well as interpersonal relationships between providers and receivers of health care is a part of any culture. Clinical issues are a part of all cultures, and cross-cultural comparisons are useful in understanding health care. With immigration and travel, a better understanding of the situation of families who have a child with cancer in various countries, different health care systems, and different cultures is needed. Understanding the situation for families with a child who has cancer in South Korea will lead one to a better understanding of a Korean family who has immigrated to the west and has a child develop cancer or is in need of treatment.

Adolescent↗
PubMed1994

Intraocular hemocoagulase in human vitrectomy.

A prospective study was performed to establish the effects on the bleeding time and the ocular toxicity of the use of intravitreal hemocoagulase (1 NIH thrombin unit/100 ml in BSS Plus) in patients undergoing vitrectomy. Sixty patients with diabetic retinopathy, penetrating ocular injury or non-diabetic retinal vascular disorder, in whom electroretinograms were recordable, were assigned to a study of Hemocoagulase-BSS Plus versus BSS Plus. The bleeding time was measured after cutting the proliferative attachments to the underlying retina. Intravitreal hemocoagulase significantly reduced the bleeding time, and this reduction of bleeding facilitated the surgery. A washout of hemocoagulase at the completion of the vitrectomy was not carried out. Hemocoagulase in the vitreous cavity assisted in maintaining hemostasis during the first week after diabetic vitrectomy. Postoperative electroretinography data did not show any disadvantage for the hemocoagulase infusate. Clinical study showed no adverse effect on the cornea, lens or visual acuity.

Adolescent↗
PubMed1993

Selectivity of phospholipase C isozymes in growth factor signaling.

Xenopus laevis oocytes were injected with mRNA extracted from growth factor-responsive CCL39, Chinese hamster lung fibroblasts. The expression of functional growth factor receptors on the oocytes was demonstrated by growth factor-induced 45Ca2+ efflux. To determine the isozyme(s) of phospholipase C (PLC) coupled to growth factor receptors, growth factor-induced 45Ca2+ efflux were measured following coinjection of mRNA from CCL39 cells with PLC antibodies. PLC-gamma 1 antibody did not lead to loss of 45Ca2+ efflux induced by thrombin but resulted in loss of that induced by platelet-derived growth factor (PDGF). In contrast, PLC-delta 1 antibody did not block PDGF-induced 45Ca2+ efflux but led to inhibition of thrombin-induced 45Ca2+ efflux. PLC-beta 1 antibody did not affect Ca2+ efflux by the treatment of either thrombin or PDGF. These results suggest that these growth factor receptors are coupled to specific effectors, i.e. thrombin receptor to PLC-delta 1 and PDGF receptor to PLC-gamma 1.

Animals↗
PubMed1993

Failed oocyte retrieval in in-vitro fertilization with documented positive serum beta-human chorionic gonadotrophin (HCG) concentration on day HCG+1.

No oocytes were obtained at ovum retrieval in a 33-year-old patient with secondary tubal infertility, whereas in a previous cycle nine oocytes were obtained under the same ovarian stimulation protocol as used in the studied cycle. Oocyte retrieval failed in spite of the correct administration of human chorionic gonadotrophin (HCG) as demonstrated by serum beta-HCG concentration (58.6 mIU/ml) on day HCG+1. However, it was shown that progesterone failed to rise even after the administration of exogenous HCG as the luteinizing hormone signal. Therefore, when ovum retrieval fails, the serum progesterone as well as beta-HCG concentrations may be useful to help identify the cause of this unusual event.

Adult↗