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Biomedical subjects

H Park

Publications and source records attributed to H Park.

342 records · Page 19Linked to original sources
PubMed1979

Thrombotic thrombocytopenic purpura in early pregnancy. Remission after plasma exchange.

A 24-year-old Chinese female developed fever, fluctuating neurological and renal manifestations, microangopathic hemolytic anemia, and thrombocytopenia during the 11th week of her first pregnancy. Therapy for thrombotic thrombocytopenic purpura (TTP), initiated during the 15th week of her pregnancy, including corticosteroids, platelet aggregation inhibitors, hysterotomy, and splenectomy was ineffective. However, dramatic improvement and remission occurred after plasma exchange of 3,560 ml was performed with the Haemonetics Model 30 Blood Cell Separator.

Adrenal Cortex Hormones↗
PubMed1979

New technique for solid-phase immunoassay: application to hepatitis B surface antigen.

I describe a new technique for improving the sensitivity of the solid-phase "sandwich" assay, by using the through-passage receptacle in a novel flow-communication device. The technique allows a large volume of serum to flow through the antibody-coated receptacle repeatedly during the incubation and is thus termed the "flow-through large-volume incubation" method. Binding of 125I-labeled hepatitis B surface antigen to its corresponding antibody on a solid-phase by this method was more rapid and persistent than binding by the conventional method. When the method was applied to the first incubation of the sandwich assay, the test for the antigen was rendered four-, eight-, and 32-fold as sensitive as an accepted third-generation test for the antigen, by incubating 5-mL volumes of serum at (a) room temperature for 18 h, (b) 45 degrees C for 8 h, or (c) room temperature for seven days, respectively.

Hepatitis B Antigens↗
PubMed1978

A new plastic receptacle for solid phase immunoassays.

A new, simple, inexpensive plastic device for solid phase immunoassay, the through-passage receptacle (TPR), with a large ratio of surface area to volume, is described. It was substantially more efficient in non-specific protein adsorption and specific immunological binding than the conventional wells of microtiter plates. It was also easier to wash since washing was facilitated by a through-passage with a gravity flow. This device, which should be more conducive to automation than currently used receptacles, should increase the sensitivity and decrease the incubation time of the solid phase immunoassay technique.

Binding Sites, Antibody↗
PubMedDate not supplied

Proximal gastrectomy and jejunal pouch interposition: radiographic evaluation of postoperative findings.

BACKGROUND: We assessed the postoperative findings of proximal gastrectomy and jejunal pouch interposition with contrast radiography. METHODS: Eleven patients with proximal gastrectomy and jejunal pouch interposition for proximal gastric carcinoma underwent contrast radiography. We evaluated the radiographic findings of the remnant stomach and interposed jejunal pouch. RESULTS: The interposed jejunal pouch showed good expansion, and the motility of the remnant gastric antrum was normal in all patients. One patient had significant lumenal narrowing of the esophageal pouch anastomotic site. Leak at the anastomotic site was not found. Reflux into the esophagus from the pouch was observed in two patients. Gastric emptying time was considerably delayed in two patients. CONCLUSION: Follow-up upper gastrointestinal series of the proximal gastrectomy and jejunal pouch interposition showed different postoperative findings. Awareness of the normal and abnormal findings is essential in the accurate postoperative evaluation of these patients.

Adult↗
PubMedDate not supplied

Expression of lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in human preeclamptic placenta: possible implications in the process of trophoblast apoptosis.

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) was originally identified as a receptor for oxidatively modified low-density lipoprotein. It has been reported that oxidative stress and hyperlipidemia play important roles in the etiology of preeclampsia, and that placental oxidative stress may stimulate syncytiotrophoblast apoptosis in preeclampsia. In this study, we examined the expression of LOX-1 in the human placentas of normal pregnancies and in preeclampsia using immunohistochemistry and Western blot analysis, and proposed that LOX-1 has a role in trophoblast apoptosis. To analyze apoptotic activity, the expression of the specific caspase cleavage site within cytokeratin 18 was assessed immunohistochemically using the monoclonal antibody M30 CytoDeath. Both LOX-1 and M30 immunoreactivity occurred predominantly in syncytiotrophoblasts. A significantly higher number of LOX-1 and M30-positive cells were found in preeclamptic placentas than in normal placentas. The number of M30-positive cells correlated with the apoptotic index of trophoblasts determined by TdT-mediated dUTP nick-end labeling (TUNEL). Syncytiotrophoblasts showing apoptotic activity were immunopositive to LOX-1 by double immunohistochemical fluorescence. We suggest that the functional role of syncytiotrophoblasts in placental dysfunction results from the localization and upregulation of LOX-1 in the preeclamptic placenta, possible implications in upregulation of syncytiotrophoblast apoptotic activity in preeclampsia.

Adult↗
PubMedDate not supplied

Use of arsenic trioxide as an antivascular and thermosensitizing agent in solid tumors.

Arsenic trioxide, As2O3 (ATO), has been found to be an effective chemotherapeutic for acute promyelocytic leukemia but its effect on solid tumors has not been fully explored. In the present report, we describe our observation that ATO is a potent antivascular agent and that it markedly enhances the effect of hyperthermia on tumors. The tumor blood perfusion in SCK tumors of A/J mice and FSaII tumors of C3H mice was significantly suppressed for up to 24 hours after an i.p. injection of 8 mg/kg ATO. ATO was also found to be able to increase the thermosensitivity of tumor cells in vitro. As a probable consequence of these effects, ATO treatment markedly increased the tumor growth delay caused by hyperthermia at 41.5 to 42.5 degrees C. Immunohistochemical staining of tumor tissue revealed that the expression levels of several adhesion molecules and TNFalpha are noticeably increased in tumors 2 to 6 hours after systemic ATO treatment. It is concluded that ATO is potentially useful to enhance the effect of hyperthermia on tumors at a clinically relevant temperature.

Angiogenesis Inhibitors↗
PubMedDate not supplied

Adriana and Luisa Castellucci award lecture 1999: role of oxygen in the regulation of trophoblast gene expression and invasion.

Changes in oxygen levels characterize normal and pathological human placentation. For example, relatively low Po(2)values are present around the blastocyst during implantation and in the placenta of the first trimester of pregnancy, a time of maximal trophoblast invasion. Our studies have revealed that low oxygen levels stimulate the in vitro invasiveness of cultured first trimester trophoblasts. This increased invasive ability is linked to elevated expression of some components of the plasminogen activator system and requires the participation of a putative haem protein. As gestation proceeds beyond the first trimester, and the extent of trophoblast invasion decreases, placental oxygen levels rise with a corresponding increase in blood flow. However, during certain pathological conditions, such as pre-eclampsia/intrauterine growth restriction, impaired remodelling of the uterine spiral arterioles leads to vessels with reduced diameters and localized regions of placental ischaemia/hypoxia. Placental hypoxia in the second half of gestation, as a consequence of reduced uteroplacental blood flow, may result in aberrant expression of genes that contribute to the pathophysiology of pre-eclampsia. Some of these genes encode certain cytokines and vasoactive molecules. We have also identified other genes whose expression is regulated by oxygen. Expression of one of them is induced in trophoblast and other cell types cultured under low oxygen levels and the product of the gene is a 43-kDa protein which we have termed PROXY-1. Compared to placental tissues and membranes isolated from uncomplicated pregnancies, PROXY-1 expression is elevated in tissues from pre-eclamptic pregnancies such as chorionic villi of peri-infarct regions, basal plate and membrane decidua, as well as chorion. Overall, these observations suggest that oxygen levels play an important role in placentation and in the pathophysiology of certain complications of pregnancy.

Adult↗
PubMedDate not supplied

Arsenic trioxide induces selective tumour vascular damage via oxidative stress and increases thermosensitivity of tumours.

It has previously been found that the anti-leukaemia agent Arsenic Trioxide (ATO) causes vascular shutdown in solid tumours and markedly sensitizes tumours to hyperthermia. The present study was designed to evaluate the mechanism of action and dose-dependence of ATO-induced thermosensitization in FSaII and SCK murine tumours. The role of oxidative stress was studied by observing ATO-induced vascular shutdown in vivo and ATO-induced endothelial cell adhesion molecule expression in vitro in the presence or absence of an anti-oxidant. It was found that a dose as low as 2 mg/kg ATO impaired vascular function, as estimated by 86Rb uptake, in the tumour. The degree of tumour growth delay induced by 1 h of hyperthermia at 42.5 degrees C, applied 2 h after ATO injection, was proportional to the dose of ATO administered. In addition, it was found that ATO can directly thermosensitize tumour cells in vitro. The development of massive tissue necrosis in the tumour was observed in the days after treatment, especially with the combination of ATO and heating. ATO-induced adhesion molecule expression in vitro was abolished when the anti-oxidant n-acetyl-cysteine (NAC) was introduced prior to exposure, while the addition of NAC in vivo partially blocked ATO-induced vascular shutdown. These results suggest that the expression of adhesion molecules by the vasculature due to oxidative stress contribute to the ATO-induced selective tumour vascular effects observed and that the clinical use of ATO to increase tumour thermosensitivity via direct cellular and vascular effects appears feasible.

Animals↗
PubMedDate not supplied

Production and characterization of immortalized rat hepatocytes secreting hepatocyte growth factor/scatter factor.

BACKGROUND/AIMS: Hepatocyte transplantation is a recently attractive field in the treatment of liver failure and enzyme-deficient diseases. However, procurement of sufficient quantities of hepatocytes is almost impossible. We attempted to create a hepatocyte cell line that could be used for hepatocyte transplantation. METHODOLOGY: L2A2 is a conditionally immortalized rat hepatocyte cell line produced by transfection of temperature-sensitive simian virus T antigen to the hepatocytes in the Lewis rat. Hepatocyte Growth Factor/Scatter Factor (HGF/SF)-secreting L2A2 cells, designated as SF-21, was produced by transfecting human HGF/SF cDNA into L2A2 cells. RESULTS: This cell line was able to produce HGF/SF at the rate of 5-10 ng/10(6) cells/24 hrs, and the recombinant HGF/SF was of the expected size and was functionally active in that it could scatter Madin-Darby canine kidney cells. The SF-21 cells grew faster than its parental cell clone, and survived and proliferated at 37 degrees C in vitro. Also, the SF-21 cells were able to survive and proliferate when transplanted into the spleen of syngeneic rat, and expressed glucose-6-phosphatase. CONCLUSIONS: These HGF/SF-secreting hepatocytes can be used as a model system to test a feasibility of using genetically engineered hepatocyte cell line for hepatocyte transplantation in the rat.

Animals↗
PubMedDate not supplied

Biochemistry and physiology of overwintering in the mature larva of the pine needle gall midge, Thecodiplosis japonensis (Diptera: cecidomyiidae) in Korea.

The pine needle gall midge, Thecodiplosis japonensis, overwinters in the soil as a third instar mature larva. The metabolic and physiological compensations and adjustments during its overwintering and acclimation were studied. Field-sampled larvae in 1997/98 winter showed a significant increase in whole-body trehalose by January (5.71 +/- 0.09 vs. 9.41 +/- 0.42 mg/g wet weight) along with a more significant decrease in whole-body glycogen (16.25 +/- 0.18 vs. 5.65 +/- 0.45 mg/g wet weight). Afterwards, there was a partial reconversion of trehalose to glycogen. Moreover, trace amounts of glycerol and steady content of glucose as potential cryoprotectants were found during the overwintering period. Temperature acclimation of field-sampled larvae affects interconversion between trehalose and glycogen. Trehalose accumulation does not affect the larval supercooling capacity. The mean supercooling point of the larvae remained nearly constant at about -20 degree he winter and was unchanged after temperature acclimation. Low temperature survival experiment suggested that the larvae adopt a freeze-avoiding strategy for overwintering.

Journal Article↗
PubMedDate not supplied

Simultaneous liquid chromatographic screening of five coccidiostats in chicken liver.

A reverse-phase liquid chromatographic (LC) method is described for simultaneously determining 5 coccidiostats--aklomide, dinsed, ethopabate, nitromide, and zoalene in chicken liver. The method entails blender extraction of 10 g liver with ethyl acetate, column chromatography through Sephadex LH-20 and neutral alumina, and LC analysis on a C18 column with UV detection at 260 nm. The drugs were eluted from Sephadex with methanol-benzene (10 + 90), from alumina with methanol-dichloromethane (10 + 90), and from C18 with acetonitrile-water (linear gradient: 25% acetonitrile for 10 min, increasing to 55% over 15 min; flow rate 1 mL/min). Liquid chromatography was completed in 40 min and calculations were based on peak height measurements. Average recoveries of the coccidiostats from fortified liver ranged from 72 to 97%, except for dinsed, which showed a relatively constant average recovery of 57%. The detection limit for the standards was 2.5 ng on column. Levels as low as 50 ng/g were detected in fortified liver samples.

Animals↗