Biomedical subjects

D H Han

Publications and source records attributed to D H Han.

At least 37 records · Page 2Linked to original sources

PubMed1999

Decreased insulin-stimulated GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats.

It was recently found that the effect of an exercise-induced increase in muscle GLUT-4 on insulin-stimulated glucose transport is masked by a decreased responsiveness to insulin in glycogen-supercompensated muscle. We evaluated the role of hexosamines in this decrease in insulin responsiveness and found that UDP-N-acetyl hexosamine concentrations were not higher in glycogen-supercompensated muscles than in control muscles with a low glycogen content. We determined whether the smaller increase in glucose transport is due to translocation of fewer GLUT-4 to the cell surface with the 2-N-4-(1-azi-2,2,2-trifluroethyl)-benzoyl-1, 3-bis(D-mannose-4-yloxy)-2-propylamine (ATB-[2-3H]BMPA) photolabeling technique. The insulin-induced increase in GLUT-4 at the cell surface was no greater in glycogen-supercompensated exercised muscle than in muscles of sedentary controls and only 50% as great as in exercised muscles with a low glycogen content. We conclude that the decreased insulin responsiveness of glucose transport in glycogen-supercompensated muscle is not due to increased accumulation of hexosamine biosynthetic pathway end products and that the smaller increase in glucose transport is mediated by translocation of fewer GLUT-4 to the cell surface.

Animals↗

PubMed1999

Insulin resistance of muscle glucose transport in male and female rats fed a high-sucrose diet.

It has been reported that, unlike high-fat diets, high-sucrose diets cause insulin resistance in the absence of an increase in visceral fat and that the insulin resistance develops only in male rats. This study was done to 1) determine if isolated muscles of rats fed a high-sucrose diet are resistant to stimulation of glucose transport when studied in vitro and 2) obtain information regarding how the effects of high-sucrose and high-fat diets on muscle insulin resistance differ. We found that, compared with rat chow, semipurified high-sucrose and high-starch diets both caused increased visceral fat accumulation and insulin resistance of skeletal muscle glucose transport. Insulin responsiveness of 2-deoxyglucose (2-DG) transport measured in epitrochlearis and soleus muscles in vitro was decreased approximately 40% (P < 0.01) in both male and female rats fed a high-sucrose compared with a chow diet. The high-sucrose diet also caused resistance of muscle glucose transport to stimulation by contractions. There was a highly significant negative correlation between stimulated muscle 2-DG transport and visceral fat mass. In view of these results, the differences in insulin action in vivo observed by others in rats fed isocaloric high-sucrose and high-starch diets must be due to additional, specific effects of sucrose that do not carry over in muscles studied in vitro. We conclude that, compared with rat chow, semipurified high-sucrose and high-cornstarch diets, like high-fat diets, cause increased visceral fat accumulation and severe resistance of skeletal muscle glucose transport to stimulation by insulin and contractions.

Adipose Tissue↗

PubMed1998

A high fat diet impairs stimulation of glucose transport in muscle. Functional evaluation of potential mechanisms.

A high fat diet causes resistance of skeletal muscle glucose transport to insulin and contractions. We tested the hypothesis that fat feeding causes a change in plasma membrane composition that interferes with functioning of glucose transporters and/or insulin receptors. Epitrochlearis muscles of rats fed a high (50% of calories) fat diet for 8 weeks showed approximately 50% decreases in insulin- and contraction-stimulated 3-O-methylglucose transport. Similar decreases in stimulated glucose transport activity occurred in muscles of wild-type mice with 4 weeks of fat feeding. In contrast, GLUT1 overexpressing muscles of transgenic mice fed a high fat diet showed no decreases in their high rates of glucose transport, providing evidence against impaired glucose transporter function. Insulin-stimulated system A amino acid transport, insulin receptor (IR) tyrosine kinase activity, and insulin-stimulated IR and IRS-1 tyrosine phosphorylation were all normal in muscles of rats fed the high fat diet for 8 weeks. However, after 30 weeks on the high fat diet, there was a significant reduction in insulin-stimulated tyrosine phosphorylation in muscle. The increases in GLUT4 at the cell surface induced by insulin or muscle contractions, measured with the 3H-labeled 2-N-4-(1-azi-2,2, 2-trifluoroethyl)-benzoyl-1,3-bis-(D-mannose-4-yloxy)-2-propyla min e photolabel, were 26-36% smaller in muscles of the 8-week high fat-fed rats as compared with control rats. Our findings provide evidence that (a) impairment of muscle glucose transport by 8 weeks of high fat feeding is not due to plasma membrane composition-related reductions in glucose transporter or insulin receptor function, (b) a defect in insulin receptor signaling is a late event, not a primary cause, of the muscle insulin resistance induced by fat feeding, and (c) impaired GLUT4 translocation to the cell surface plays a major role in the decrease in stimulated glucose transport.

3-O-Methylglucose↗

PubMed1998

Post-ischemic changes in the expression of Alzheimer's APP isoforms in rat cerebral cortex.

A significant porportion (25%) of patients with Alzheimer's disease (AD) also shows vascular pathology. Recent ultrastructural studies demonstrated characteristic and extensive angio-architectural distortions of cerebral capillaries in AD brains. We examined the expression of APP mRNA isoforms of cerebral cortex after transient ischemia by middle cerebral artery occlusion, using RT-PCR. Neuronal damage and glial fibrillary acidic protein immunohistochemistry were also examined histologically. After transient ischemia, the Kunitz protease inhibitor-bearing isoforms (KPI-APP) were increased whereas APP 695, which lacks KPI domain, was decreased. Neuronal damage and GFAP-immunoreactive astrocytes were also observed. These results show that focal, transient ischemia alters KPI-APP/APP 695 ratio in cerebral cortex and this shift in APP isoforms could be related to neurodegeneration and/or activation of astrocytes during the ischemic process.

Alzheimer Disease↗

PubMed1998

Gliomatosis cerebri: clinical features, treatment, and prognosis.

To clarify clinical features and to elucidate prognostic factors and prognosis, the authors retrospectively analyzed 16 cases of gliomatosis cerebri treated at Seoul National University Hospital between January 1988 and December 1995. Age at diagnosis ranged from 19 to 62 (median 34) years and male to female ratio was 10:6. Most presented with headache or seizure, and the mean duration of symptoms was 12.8 months. A poorly defined diffuse high signal intensity lesion, extending in T2-weighted images for two lobes or more, was the characteristic magnetic resonance (MR) image finding. On postcontrast T1-weighted MR imaging, focal enhancement of the lesion was detected in five cases. All patients underwent histological confirmation by craniotomy (9 cases) or stereotactic biopsy (7 cases). Histologically, all patients had compatible findings of gliomatosis cerebri which are the widespread infiltration of neoplastic glial cells with minimal destruction of pre-existing structures. After histological diagnosis, external radiation therapy was begun except in one case, who declined this treatment. Fourteen patients completed the whole procedure and received the planned dose (mean 5780 cGy). Median survival time after diagnosis was 38.4 months. In univariate analysis, the Ki-67 labelling index (> 1) showed significant correlation with the length of survival (p = 0.006). It is suggested that 1) gliomatosis cerebri can be diagnosed by a combination of MR imaging findings and histological examination; 2) histological diagnosis and external radiation therapy might be a good treatment modality; 3) the Ki-67 labelling index correlates significantly with survival time.

Adult↗

PubMed1998

DHEA treatment reduces fat accumulation and protects against insulin resistance in male rats.

The purpose of this study was to determine whether administration of dehydroepiandrosterone (DHEA) protects male rats against the accumulation of body fat the development of insulin resistance with advancing age. We found that supplementation of the diet with 0.3% DHEA between the ages of 5 months and approximately 25 months resulted in a significantly lower final body weight (DHEA, 593 +/- 18 g vs control, 668 +/- 12 g, p < 0.02), despite no decrease in food intake. Lean body mass was unaffected by the DHEA, and the lower body weight was due to a approximately 25% reduction in body fat. The rate of glucose disposal during a euglycemic, hyperinsulinemic clamp was 30% higher in the DHEA group than in the sedentary controls due to a greater insulin responsiveness. The DHEA administration was as effective in reducing body fat content and maintaining insulin responsiveness as exercise in the form of voluntary wheel running. The DHEA had no significant effect on muscle GLUT4 content. A preliminary experiment provided evidence suggesting that muscle insulin signaling, as reflected in binding of phosphatidylinositol 3-kinase to the insulin receptor substrate-1, was enhanced in the DHEA-treated and wheel running groups as compared to controls. These results provide evidence that DHEA, like exercise, protects against excess fat accumulation and development of insulin resistance in rats.

Adipose Tissue↗

PubMed1998

Amylin-mediated inhibition of insulin-stimulated glucose transport in skeletal muscle.

We examined the effects of amylin on 3-O-methyl-D-glucose (3-O-MG) transport in perfused rat hindlimb muscle under hyperinsulinemic (350 microU/ml, 2,100 pmol/l) conditions. Amylin at 100 nmol/l concentration inhibited 3-O-MG transport relative to control in all three basic muscle fiber types. Transport decreased in slow-twitch oxidative (from 5.65 +/- 1.13 to 3.46 +/- 0.71 micromol . g-1 . h-1), fast-twitch oxidative (from 6.84 +/- 0.90 to 4.84 +/- 0.76 micromol . g-1 . h-1), and fast-twitch glycolytic (from 1.27 +/- 0.20 to 0.60 +/- 0.05 micromol . g-1 . h-1) muscle. Amylin inhibition of insulin-stimulated glucose transport in skeletal muscle was accompanied by a 433 +/- 72% increase in intracellular glucose 6-phosphate (G-6-P) despite the absence of extracellular glucose. The source of hexose units for the formation and maintenance of G-6-P was likely glycogen. Amylin increased glycogenolysis, increased lactate formation, and decreased glycogen synthase activity. Furthermore, the kinetics of glycogen synthase suggest that this enzyme may control intracellular G-6-P concentration. Despite the large increase in G-6-P, no detectable increase in uridine diphosphate-N-acetylhexosamines occurred, suggesting that the proposed glucosamine pathway may not be involved in transport inhibition. However, decreases in uridine diphosphate hexoses were detected. Therefore, uridine or hexosamine-based metabolites may be involved in amylin action.

3-O-Methylglucose↗

PubMed1998

Clinical characteristics of vertebrobasilar artery dissection.

Sixteen patients with the diagnosis of vertebral or basilar artery dissection who were admitted at the Seoul National University Hospital from 1972 to 1996 are described. During the same period, we encountered 76 patients with posterior circulation aneurysms, so the vertebrobasilar artery dissection was 21% of posterior circulation aneurysms. The mean age was 44 years, and male predominated. Nine patients presented with subarachnoid hemorrhage (SAH) and seven with ischemic symptoms. The characteristic angiographic finding of patients with SAH was aneurysmal dilatation (pseudoaneurysm) in eight of nine cases. In cases of ischemic symptoms, only one case had aneurysmal dilatation. Some other angiographic findings were demonstrated such as string sign, tapered narrowing, complete occlusion, or double lumen. Clinical course of SAH group was much different from that of ischemic group. Rebleeding occurred in three patients of SAH group; immediately after the rebleeding all patients became comatose, but after extraventricular drainage, all patients with rebleeding recovered rapidly. In SAH group, four of nine cases died but there was no mortality in the ischemic group. These four patients showed signs of stem failure, when computed tomography (CT) demonstrated no evidence of additional bleeding and follow-up CT showed the infarction at a part of stem and/or cerebellum. Vasospasm or sudden extensive extension of dissection could be the cause of death. Surgical management was performed in three patients, endovascular intervention in four, and conservative management in two. The patients with incomplete embolization or conservative management had poor outcome. In ischemic group, all underwent conservative management including anticoagulation and/or antiplatelet therapy. On follow-up, most of the patients with ischemic symptoms made complete or very good recoveries.

Adolescent↗

PubMed1998

Removal of adenosine decreases the responsiveness of muscle glucose transport to insulin and contractions.

Adenosine in the extracellular space modulates stimulated glucose transport in striated muscle. In the heart and in adipocytes, adenosine potentiates insulin-stimulated glucose transport. There is controversy regarding the effect of adenosine in skeletal muscle, with reports of both an inhibitory effect and no effect, on insulin-stimulated glucose transport. We found that, in rat epitrochlearis and soleus muscles, removing adenosine with adenosine deaminase or blocking its action with the adenosine receptor blocker CPDPX markedly reduces the responsiveness of glucose transport to stimulation by 1) insulin alone, 2) contractions alone, and 3) insulin and contractions in combination. Measurement of the increase in GLUT4 at the cell surface in response to a maximally effective insulin stimulus in the epitrochlearis muscle, using the exofacial label ATB-[3H]BMPA, showed that adenosine deaminase treatment markedly reduces cell-surface GLUT4 labeling. The reduction in cell-surface GLUT4 labeling was similar in magnitude to the decrease in maximally insulin-stimulated glucose transport activity in adenosine deaminase-treated muscles. These results show that adenosine potentiates insulin- and contraction-stimulated glucose transport in skeletal muscle by enhancing the increase in GLUT4 at the cell surface and raise the possibility that decreased adenosine production or action could play a causative role in insulin resistance.

Adenosine↗

PubMed1998

Large glial cyst of the pineal gland: a possible growth mechanism. Case report.

The authors report on a patient who presented with a large symptomatic glial cyst of the pineal gland communicating with the third ventricle. The hole between the ventricle and the cyst, suspected on magnetic resonance images, was found at surgery. The to-and-fro flow mechanism is considered to be involved in the pathogenesis of growth in this unusual large glial cyst of the pineal gland, although this mechanism cannot be applied universally.

Adult↗

PubMed1997

Central neurocytoma: the role of radiation therapy and long term outcome.

BACKGROUND: It has been suggested that the biologic behavior of central neurocytoma is indolent, although little is known regarding the role of radiation therapy and long term outcome. To clarify the role of radiation therapy and long term outcome, the authors retrospectively analyzed 15 cases of central neurocytoma. METHODS: Clinical records and radiologic findings of 15 cases of central neurocytoma diagnosed at Seoul National University Hospital between January 1982 and February 1995 were carefully reviewed. The duration of follow-up was from 18-168 months (mean, 52 months); follow-up images were reviewed and the patient's Karnofsky performance scale (KPS) was assessed up to the time of last follow-up. RESULTS: The age of the patients ranged from 15 to 60 years (mean, 25 years) and the male to female ratio was 11:4. Macroscopic total resection of the tumor was performed in seven patients, two of whom received fractionated radiation therapy. Subtotal removal of the tumor was performed in eight patients, five of whom received this same therapy. In 2 of the 5 patients who did not receive radiation therapy after macroscopic total resection, the tumors recurred 8 and 21 months after surgery, respectively; in contrast, recurrence was not detected in the 2 patients who received fractionated radiation therapy after macroscopic total resection. In all five patients who received fractionated radiation therapy after subtotal resection, the tumor shrank (n = 3) or disappeared (n = 2) during the postsurgical follow-up period ranging from 27-113 months; the tumor began to shrink from 6 months to 2 years after radiation. No change was found in the three patients who did not receive radiation therapy after subtotal resection. At the time of last follow-up, the KPS was greater than 90 in all patients except one who required assistance in his daily activities because of complications from radiation therapy. CONCLUSIONS: It is suggested that even if the biologic behavior of a central neurocytoma is benign, radiation therapy appears to have an effect on tumor control. However, it should be carefully decided whether to use radiation therapy for a residual tumor because radiation can cause delayed complications and the clinical course of subtotally resected patients who do not receive radiation therapy is extremely benign.

Activities of Daily Living↗

PubMed1997

Mixed tumour of schwannoma and meningioma components in a patient with NF-2.

The authors present the case of an intracranial tumour consisting of both schwannoma and meningioma within the same tumour, in a patient with neurofibromatosis-2 (NF-2). A pre-operative diagnosis of this mixed tumour was not made. However, retrospectively, a meningiomatous area was found inside the acoustic neurinoma on magnetic resonance (MR) images. Predominant schwannoma with a minor component of meningioma was confirmed by histopathological and immunohistochemical examinations. The transitional zones of these two different tumours were macroscopically sharp but microscopically interdigitated. The patient had another meningioma and schwannoma in a separate section of the cranial cavity. Based on this patient, it is suggested that the collision of two kinds of tumours is the most likely hypothesis to explain the development of mixed components of schwannoma and meningioma within the same tumour.

Adolescent↗

PubMed1997

Epidemiological survey of moyamoya disease in Korea.

To both clarify the current clinico-epidemiological features of Moyamoya disease in Korea as well as compare these cases with Japanese patients, 451 cases were collected from 26 Korean major neurosurgical institutes and 296 definite cases were analyzed statistically. Although the Korean age distribution patterns of Moyamoya disease showed two peaks, similar to Japanese patients, the Korean pattern was shifted to the right thus indicating Korean adult population to be 20% higher than that of Japanese patients. The female/male ratio was 1:3, which was slightly less than that for Japanese. The family occurrence rate in Koreans was 1.8%. The incidence of cerebral infarction and bleeding in Koreans was higher while transient ischemic attack (TIA) and seizure were less than that of Japanese. The incidence of infarction in children and of hemorrhage in children and adults were also statistically higher in Koreans. The incidence of hemorrhage was higher in females than in males. Both the age at onset and sex affected the disease type. Single encephalo-duro-arterio-synangiosis (EDAS) was performed on 87.6% of all surgical cases. Although the incidence of bleeding was higher in Korea, the outcomes of the patients were similar to that of the Japanese patients. Although Korean Moyamoya disease showed a relatively higher incidence of hemorrhage and adult onset, the overall clinical background was similar to that of Japanese patients.

Adolescent↗

PubMed1997

Moyamoya disease in adults: characteristics of clinical presentation and outcome after encephalo-duro-arterio-synangiosis.

To determine the clinical characteristics and the effectiveness of encephalo-duro-arterio-synangiosis (EDAS) in adulthood-onset Moyamoya disease (MMD), the authors retrospectively reviewed 26 patients suffering from MMD who were admitted to Seoul National University Hospital between 1987 and 1995. When they showed major symptoms, all were more than 16 years-old. The most common presenting symptom was intracranial hemorrhage (ICrH), found in 12 patients or 46% of the total; the second was infarction and transient ischemic attack, each found in seven or 27% of them. Only one patient was found to have seizures, which were associated with a cerebral infarction. The Suzuki angiographic stage 3 and less than stage 3 accounted for 73% of all 52 hemispheres. A total of 15 patients underwent single photon emission computed tomography (SPECT) preoperatively. When the derangement of cerebral perfusion was estimated with four SPECT grades (SG), 70% of their hemispheres revealed normal (SG1) or localized decreased-perfusion (SG2). The other 30% had extensive decreased-perfusion or localized perfusion defects (SG3). There was no case who had extensive perfusion defects (SG4). A total of 17 patients underwent EDAS operations (EDAS group) and nine did not undergo any operation (no-op group). The EDAS group had significantly better clinical outcomes than the no-op group after a 12-month median follow-up period (P < 0.05). The angiographic and SPECT follow-up studies comprised six and seven cases, respectively. There was also satisfactory angiographic revascularization in all follow-up cases and improvement in cerebral perfusion at SPECT follow-up in six of seven cases. It is concluded that the involvement of posterior circulation of MMD is not frequent and cerebral perfusion is preserved in adulthood-onset MMD patients. These findings may explain the reason why hemorrhages are frequent and the late onset of symptoms in adulthood-onset MMD. Surgical treatment with EDAS seems to be effective in adulthood-onset MMD in terms of clinical improvement.

Adolescent↗

PubMed1997

Quantitative fit testing techniques and regulations for tight-fitting respirators: current methods measuring aerosol or air leakage, and new developments.

Until a few years ago, only two quantitative fit testing (QNFT) techniques were available and accepted by U.S. Occupational Safety and Health Administration (OSHA) regulations. In the 1980s and 1990s, several new and fundamentally different QNFT methods were developed. Two of the newer methods are commercially available and are accepted by OSHA as suitable alternatives. In this article the principles of operation of the OSHA-accepted and of some newly developed but not yet approved QNFT techniques are explained, and each technique's major advantages and disadvantages are pointed out. Emphasis is given to negative-pressure air-purifying respirators, as they are in most frequent use today. The requirements and recommendations for fit testing positive-pressure respirators are discussed as well. Finally, the presently available QNFT standards and regulations are summarized to assist the user in making fit testing decisions.

Aerosols↗

PubMed1997

DHEA protects against visceral obesity and muscle insulin resistance in rats fed a high-fat diet.

Visceral obesity is frequently associated with muscle insulin resistance. Rats fed a high-fat diet rapidly develop obesity and insulin resistance. Dehydroepiandrosterone (DHEA) has been reported to protect against the development of obesity. This study tested the hypothesis that DHEA protects against the increase in visceral fat and the development of muscle insulin resistance induced by a high-fat diet in rats. Feeding rats a diet providing 50% of the energy as fat for 4 wk resulted in a twofold greater visceral fat mass and a 50% lower rate of maximally insulin-stimulated muscle 2-deoxyglucose (2-DG) uptake compared with controls. Rats fed the high-fat diet plus 0.3% DHEA were largely protected against the increase in visceral fat (+ 11.3 g in high fat vs. + 2.9 g in high fat plus DHEA, compared with controls) and against the decrease in insulin-stimulated muscle 2-DG uptake (0.94 +/- 0.15 mumol.ml-1.20 min-1, controls; 0.46 +/- 0.06 mumol.ml-1.20 min-1, high-fat diet; 0.78 +/- 0.07 mumol.ml-1.20 min-1, high fat + DHEA). DHEA did not affect food intake. These results show that DHEA has a protective effect against accumulation of visceral fat and development of muscle insulin resistance in rats fed a high-fat diet.

Animals↗

PubMed1997

Effect of endurance exercise training on muscle glycogen supercompensation in rats.

The purpose of this study was to test the hypothesis that the rate and extent of glycogen supercompensation in skeletal muscle are increased by endurance exercise training. Rats were trained by using a 5-wk-long swimming program in which the duration of swimming was gradually increased to 6 h/day over 3 wk and then maintained at 6 h/day for an additional 2 wk. Glycogen repletion was measured in trained and untrained rats after a glycogen-depleting bout of exercise. The rats were given a rodent chow diet plus 5% sucrose in their drinking water and libitum during the recovery period. There were remarkable differences in both the rates of glycogen accumulation and the glycogen concentrations attained in the two groups. The concentration of glycogen in epitrochlearis muscle averaged 13.1 +/- 0.9 mg/g wet wt in the untrained group and 31.7 +/- 2.7 mg/g in the trained group (P < 0.001) 24 h after the exercise. This difference could not be explained by a training effect on glycogen synthase. The training induced approximately 50% increases in muscle GLUT-4 glucose transporter protein and in hexokinase activity in epitrochlearis muscles. We conclude that endurance exercise training results in increases in both the rate and magnitude of muscle glycogen supercompensation in rats.

Animals↗

PubMed1997

A clinical comparison of definite moyamoya disease between South Korea and Japan.

BACKGROUND AND PURPOSE: The goal of the present study was to clarify whether South Korean patients with moyamoya disease have clinical features similar to those of Japanese patients. METHODS: From 26 South Korean neurosurgical institutes, 296 definite cases were collected and analyzed statistically. These cases were then compared with 731 Japanese definite cases registered to the Research Committee on Moyamoya Disease of the Ministry of Health and Welfare, Japan. RESULTS: The Korean age distribution patterns showed two peaks that were similar to those seen in Japanese patients. The incidence of adult moyamoya disease in South Korea, however, was 20% higher than that in Japanese patients. The family occurrence rate was 1.8% in Koreans. The incidence of cerebral infarction and bleeding in Koreans was statistically higher, whereas transient ischemic attack and seizure were less than those in Japanese subjects. The incidence of infarction in children and that of hemorrhage in both children and adults were also statistically higher in Koreans. The incidence of hemorrhage was higher in females than in males. Both the age at onset and sex affected the disease type. Although most Japanese patients underwent direct bypass surgery and/or combined indirect bypass procedures, single encephaloduroar-teriosynangiosis was performed on 87.6% of all surgical cases in Koreans. Despite the higher incidence of hemorrhagic type in South Korea, the outcomes of the patients were similar to those of the Japanese patients. CONCLUSIONS: This study suggests that the clinical background of moyamoya disease in South Korea is essentially similar to that in Japan.

Adolescent↗