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Biomedical subjects

Y G Kang

Publications and source records attributed to Y G Kang.

At least 19 recordsLinked to original sources
PubMed2003

Age-related change in serum concentrations of testosterone in middle-aged Korean men.

The objective of this study was to determine whether testosterone and sex hormone binding globulin (SHBG) levels are different between healthy men and men with chronic illness, and to evaluate the age-related changes of testosterone and SHBG in healthy men in Korea. enrollment took place between January 2000 and December 2001 at Pundang CHA General Hospital in Korea. All men who came for male climacteric and geriatric health screening examinations were eligible. Of the 762 men recruited, 136 men had at least one present or previous medical illness and 626 men were healthy. Higher serum concentrations of total testosterone (5.31 +/- 1.88 ng/ml vs. 4.96 +/- 1.43 ng/ml; p < 0.05), free androgen index (16.60 +/- 7.36 vs. 14.57 +/- 5.55; p < 0.01) and calculated bioavailable testosterone (8.88 +/- 3.52 nmol/l vs. 7.91 +/- 2.52 nmol/l; p < 0.01) were demonstrated in the healthy compared with the disease group. Total testosterone declined at a rate of 0.2% per year, SHBG increased by 1.74% per year, calculated bioavailable testosterone declined by 0.8% per year, and free androgen index declined by 1.15% per year in healthy subjects aged between 40 and 70. The above results seem to be consistent with previous Western studies, showing higher concentrations of testosterone in healthy men, that decline with increasing age.

Adult↗
PubMed2001

Blast-wave-sphere interaction using a laser-produced plasma: an experiment motivated by supernova 1987A.

We present x-ray shadowgraphs from a high Mach number ( approximately 20) laboratory environment that simulate outward flowing ejecta matter from supernovae that interact with ambient cloud matter. Using a laser-plastic foil interaction, we generate a "complex" blast wave (a supersonic flow containing forward and reverse shock waves and a contact discontinuity between them) that interacts with a high-density (100 times ambient) sphere. The experimental results, including vorticity localization, compare favorably with two-dimensional axisymmetric hydrodynamic simulations.

Journal Article↗
PubMed1998

Effect of 0.1% dexamethasone on epithelial healing in experimental corneal alkali wounds: morphological changes during the repair process.

BACKGROUND: The effect of 0.1% dexamethasone on epithelial healing was evaluated in corneal alkali wounds. METHODS: Epithelial wounds were induced by a 60-s application of a round filter paper (5.5 mm) soaked in 1 N NaOH onto the central cornea of the rabbit. Animals were treated with 0.1% dexamethasone 4 times each day for 8 weeks in one subgroup and only for the 1st week in the other subgroup. The control eyes were treated with a balanced salt solution. The repair processes of epithelium and its basement membrane were evaluated morphologically and morphometrically. RESULTS: Treatment with 0.1% dexamethasone was found to retard the repair process of epithelial healing compared with the control eyes. Morphologically, the basement membrane in the control cornea was damaged focally at 2 days, maximally disrupted at 4 weeks, and regained the normal integrity at 8 weeks after the initial alkali damage. In 0.1% dexamethasone-treated corneas, regardless of the application period, the basement membrane structure was visible up to 4 weeks but disappeared at 8 weeks after the initial alkali wounds. The eyes treated with 0.1% dexamethasone for 8 weeks showed an intense infiltration of inflammatory cells in the superficial stroma 4 weeks after treatment. CONCLUSION: A topical application of 0.1% dexamethasone retarded the corneal epithelial healing. The cornea treated with 0.1% dexamethasone only for the 1st week maintained a well-preserved basement membrane for as long as 4 weeks after initial damage without enhancement of the inflammatory cell infiltration. However, further study is needed to prevent late disintegration of the basement membrane.

Animals↗
PubMed1998

Prolonged release of tegafur from S/O/W multiple emulsion.

To develop a prolonged and sustained release preparation, we prepared an albumin microsphere-in-oil-in-water emulsion (S/O/W) and examined sustained release from it in comparison with other control preparations such as water-in-oil (W/O) emulsions and microspheres in vitro and in vivo, respectively. Tegafur was used as a model drug. A microsphere-in-oil emulsion was prepared by adding albumin microspheres to soybean oil containing 20% Span 80. To prepare an S/O/W emulsion, the microsphere-in-oil emulsion was added into an aqueous solution of hydroxypropyl methylcellulose containing Pluronic F68. The mean particle size of the albumin microspheres was 3 microns, and the ratio of entrapment of tegafur into albumin microspheres was about 25%. In an in vitro release test, the t75 of the S/O/W emulsion was fourfold greater and in an in vivo release test the mean residence time of tegafur from the S/O/W emulsion was more than twofold that from a W/O emulsion or microsphere system. The mean residence time of 5-fluorouracil (5-FU) from an S/O/W emulsion was also greater than with other dosage forms. These results suggest the possible usefulness of an S/O/W emulsion for the sustained and prolonged release of tegafur.

Animals↗
PubMed1989

Liver transplantation: intraoperative changes in coagulation factors in 100 first transplants.

Six intraoperative blood samples were obtained at intervals from each of 100 individuals undergoing their first liver transplants. The patients fell into the following diagnostic categories: postnecrotic cirrhosis 28, primary biliary cirrhosis 20, sclerosing cholangitis 19, miscellaneous diseases 14, carcinoma/neoplasia 12 and fulminant hepatitis 7. Coagulation factor values in the initial (baseline) blood samples varied by patient diagnosis. In general, all factor levels were reduced except factor VIII:C, which was increased to almost twice normal. The slight intraoperative changes in factors II, VII, IX, X, XI and XII suggested that a steady-state relationship existed between depletion (consumption/bleeding) and repletion (transfusion, transit from extra- to intravascular space), even in the anhepatic state. In contrast, there were rapid and very significant falls in factor VIII and fibrinogen and a less pronounced decrease in factor V, all reaching their nadirs in early to mid-Stage III. The cause of these coagulation changes appears to be activation of the fibrinolytic system.

Adolescent↗
PubMed1989

Intraoperative blood transfusions in highly alloimmunized patients undergoing orthotopic liver transplantation.

Intraoperative blood requirements were analyzed in patients undergoing primary orthotopic liver transplantation and divided into two groups on the basis of panel reactive antibody of pretransplant serum measured by lymphocytotoxicity testing. One group of highly sensitized patients (n = 25) had PRA values of over 70% and the second group of patients (n = 26) had 0% PRA values and were considered nonsensitized. During the transplant procedure, the 70% PRA group received considerably greater quantities of blood products than the 0% PRA group--namely, red blood cells: 21.1 +/- 3.7 vs. 9.8 +/- 0.8 units (P = 0.002), and platelets: 17.7 +/- 3.2 vs. 7.5 +/- 1.5 units (P = 0.003). Similar differences were observed for fresh frozen plasma and cryoprecipitate. Despite the larger infusion of platelets, the blood platelet counts in the 70% PRA group were lower postoperatively than preoperatively. Twenty patients in the 70% PRA group received platelet transfusions, and their mean platelet count dropped from 95,050 +/- 11,537 preoperatively to 67,750 +/- 8,228 postoperatively (P = 0.028). In contrast, nearly identical preoperative (84,058 +/- 17,297) and postoperative (85,647 +/- 12,445) platelet counts were observed in the 17 0% PRA patients who were transfused intraoperatively with platelets. Prothrombin time, activated partial thromboplastin time, and fibrinogen levels showed no significant differences between both groups. These data demonstrate that lymphocytotoxic antibody screening of liver transplant candidates is useful in identifying patients with increased risk of bleeding problems and who will require large quantities of blood during the transplant operation.

Adult↗
PubMed1989

Systemic effects of tissue plasminogen activator-associated fibrinolysis and its relation to thrombin generation in orthotopic liver transplantation.

Orthotopic liver transplantation is frequently associated with hyperfibrinolysis, the origin and clinical relevance of which is largely unknown. In 20 orthotopic liver transplantations, we studied the occurrence and systemic effects of hyperfibrinolysis. Severe fibrinolysis was defined to be present when the euglobulin-clot lysis time and the whole-blood-clot lysis time, as measured by thrombelastography, were shorter than 60 and 90 min, respectively, at some time during the operation. Based on these criteria, 7 patients had minimal fibrinolysis (group I), and 13 patients had severe fibrinolysis (group II). In group II a gradual increase of tissue-type plasminogen activator (t-PA) activity was seen during the anhepatic stage, followed by an "explosive" increase immediately after graft reperfusion (P = 0.0004, compared with group I), and a reduction of plasminogen activator inhibitor (PAI) activity. Plasma degradation products of fibrinogen and fibrin increased parallel to t-PA activity, and levels were significantly higher at 45 min after graft reperfusion in group II compared with group I (P less than 0.04). Thrombin-antithrombin III complexes showed an identical steady increase in both groups, indicating that increased t-PA activity was not related to thrombin formation. A combination of increased endothelial release and reduced hepatic clearance may have caused the increased t-PA activity. The t-PA-associated destruction of fibrinogen and fibrin after graft reperfusion is consistent with the clinical signs of severe oozing often seen in this period. These observations may have important clinical implications for the treatment of bleeding in patients undergoing orthotopic liver transplantation.

Adult↗
PubMed1987

Mechanisms of cerebrovascular dilation by ether in monkeys.

We hypothesized that when the depth of ether anesthesia is increased from 2 to 5%, cerebral vessels dilate secondary to circulating catecholamine stimulation of cerebral metabolism. Cerebral blood flow (CBF) by 133Xe clearance and cerebral metabolic rate for oxygen (CMRO2) were measured on 2% and then 5% ether in air in two groups of seven monkeys each during mechanical ventilation. Propranolol, 0.5 mg/kg i.v., was infused over 5 min in one group, and the other received saline. All measurements were repeated on 5% and 2% ether. Cerebrovascular resistance (CVR) fell by 30%, from 2.28 +/- 0.61 (mean +/- SD) to 1.51 +/- 0.28 mm Hg ml-1 100 g-1 min-1 (p less than 0.01), with the increase in ether from 2 to 5%. CBF and CMRO2 were unaltered from values of about 45 ml 100 g-1 min-1 and 2.3 ml 100 g-1 min-1, respectively. During 5% ether anesthesia, propranolol had no effect on CBF, CMRO2, or CVR. On 2% ether, it increased CVR twofold, from 1.5 +/- 0.30 to 3.0 +/- 1.0 mm Hg ml-1 100 g-1 min-1, and decreased CBF by 33%, from 48 +/- 8 to 32 +/- 10 ml 100 g-1 min-1. Plasma epinephrine was two-fold higher on 2% compared to 5% ether, both before and after saline or propranolol infusion. In monkeys, cerebrovascular dilation by ether at 5% compared to 2% is not secondary to catecholamine stimulation of CMRO2. It may result from a direct effect of either plasma catecholamines or ether on the cerebrovasculature.

Animals↗
PubMed1987

Glucose metabolism during liver transplantation in dogs.

Arterial and hepatic venous blood levels of glucose were studied in 12 dogs during orthotopic liver transplantation performed under ketamine anesthesia without exogenous glucose administration. During the early part of surgery, arterial blood glucose levels were stable: 161 +/- 12 mg/dl (mean +/- SEM) after laparotomy and 183 +/- 16 mg/dl 5 min before the anhepatic stage. During the anhepatic stage, arterial blood glucose levels decreased progressively to 135 +/- 9 and 88 +/- 8 mg/dl, 5 min in the anhepatic stage and 5 min before reperfusion of the graft liver, respectively (P less than 0.05). Reperfusion of the graft liver resulted in an increase in arterial glucose levels to 206 +/- 17 and 240 +/- 24 mg/dl, 5 and 30 min after reperfusion, respectively (P less than 0.05). Hepatic venous blood glucose levels increased after reperfusion (405 +/- 37 and 346 +/- 41 mg/dl, 5 and 30 min after reperfusion, respectively) and were significantly higher than in arterial blood (P less than 0.05). Arterial plasma insulin, measured in five animals, did not change significantly during the procedure, whereas plasma glucagon levels, stable during the preanhepatic and anhepatic stages, increased steadily after reperfusion of the graft liver, from 66.1 +/- 14.2 to 108.4 +/- 38.1 pg/ml (P less than 0.05). This study shows that in dogs with ketamine anesthesia mild hypoglycemia occurs during the anhepatic stage of liver transplantation without exogenous glucose administration followed by hyperglycemia on reperfusion of the graft liver, possibly secondary to the release of glucose from the donor liver.

Analysis of Variance↗
PubMed1987

Cardiovascular responses to acute loading with nifedipine alone and nifedipine plus propranolol during inhalation anesthesia in monkeys.

The cardiovascular effects of the administration of nifedipine and nifedipine combined with propranolol were examined in 15 monkeys during 0.75 and 1.25 MAC of anesthesia with isoflurane, enflurane, or halothane. Hemodynamic variables measured included heart rate (HR), mean arterial pressure (MAP), left ventricular end-diastolic pressure (LVEDP), maximum rate of increase of the Left ventricular pressure (max LV dP/dt), and thermodilution cardiac output (CO). The infusion of nifedipine at a rate adequate to produce therapeutic blood levels during 0.75 MAC with each anesthetic decreased MAP and SVR, but had no effect on cardiac index (CI), max LV dP/dt, or HR. Increasing the anesthetic concentration from 0.75 to 1.25 MAC during nifedipine administration decreased HR and MAP in all groups and decreased CI with halothane and enflurane, but not with isoflurane. Addition of propranolol by infusion in amounts adequate to produce 75% beta-adrenergic blockade caused a further depression of CI, max LV dP/dt, HR, and MAP. However, the hemodynamic depression was significantly greater with halothane and enflurane than with isoflurane. Intravenous administration of calcium chloride (10 mg/kg) after calcium channel and beta-adrenergic blockade only partially reversed the hemodynamic depression that occurred with all three anesthetics. It was concluded that acute loading with nifedipine with and without propranolol exerts a greater cardiovascular depressant effect during enflurane or halothane anesthesia than during isoflurane anesthesia. The myocardial depressant effects of nifedipine and propranolol myocardial depressant effects of nifedipine and propranolol may be synergistic with the depressant effects of potent inhalation anesthetics.

Anesthesia, Inhalation↗
PubMed1986

Cardiovascular depression secondary to ionic hypocalcemia during hepatic transplantation in humans.

Cardiovascular function, serum ionized calcium (Ca+2), and serum citrate were measured intraoperatively in patients (n = 9) undergoing orthotopic hepatic homotransplantation. Serum citrate increased 20-fold (P less than 0.0006) following transfusion of citrated blood products in the absence of a functional liver. Serum ionized calcium decreased (P less than 0.003) with concomitant decreases in cardiac index (P less than 0.005), stroke index (P less than 0.004), and left ventricular stroke work index (P less than 0.001). Hemodynamic depression and ionic hypocalcemia were reversed following the administration of CaCl2. In contrast to patients with normal hepatic function, who may tolerate large amounts of citrated blood, patients with end-stage liver disease demonstrate acute ionic hypocalcemia with concomitant hemodynamic depression when receiving citrated blood products during the course of hepatic transplantation.

Calcium Chloride↗