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Biomedical subjects

S M Chung

Publications and source records attributed to S M Chung.

At least 19 recordsLinked to original sources
PubMed1992

Effects of vanadate on vascular contractility and membrane potential in the rabbit aorta.

Isolated rabbit aortic ring with intact endothelial cell preparations precontracted with NE (10(-7) M) were relaxed by vanadate in a dose dependent manner (from 0.2 to 2 mM). Application of vanadate and ACh during the tonic phase of high K+(100 mM)-induced contraction showed a slight relaxation in contrast to that in NE-induced contraction, but sodium nitroprusside (10 microM) more effectively relaxed the aortic ring preparations in high K+ contraction than that of vanadate. Vanadate-induced relaxation in NE-contracted aortic rings was reversed by application of BaCl2 (50 microM) or glibenclamide (10 microM). Furthermore, Vanadate hyperpolarized membrane potential of smooth muscle cells in endothelium-intact aortic strips and this effect was abolished by application of glibenclamide. The above results suggest that vanadate release EDHF (Endothelium-Derived Hyperpolarizing Factor), in addition to EDRF (Endothelium-Derived Relaxing Factor) from endothelial cell. This EDHF hyperpolarize the smooth muscle cell membrane potential via opening of the ATP-sensitive K+ channel and close a voltage dependent Ca++ channel. So it is suggested that the vanadate-induced relaxation of rabbit thoracic aortic rings may be due to the combined effects of EDRF and EDHF.

Animals↗
PubMed1992

Bilateral internuclear ophthalmoplegia in a patient with Wernicke's encephalopathy.

The most common cause of bilateral internuclear ophthalmoplegia is multiple sclerosis. Wernicke's encephalopathy has been reported as a cause of unilateral internuclear ophthalmoplegia but not of bilateral internuclear ophthalmoplegia. In this report, we present the case of a patient with a history of alcohol abuse and acute onset of bilateral internuclear ophthalmoplegia whose clinical course and diagnostic studies are most consistent with a diagnosis of Wernicke's encephalopathy.

Adult↗
PubMed1991

Management of the hearing-impaired adults in Singapore.

A preliminary study to investigate that the pure-tone air-conduction hearing threshold level which is not an accurate index of amplification need profile applies to the hearing-impaired population in Singapore. Results obtained from a sample of twenty users of monaural amplification indicate that the hearing-impaired patients showed a significant reduction in communication difficulties with their hearing aids and are overall satisfied with their monaural amplification despite certain problems with background noise, regardless of the severity of their hearing losses.

Adult↗
PubMed1990

Characterization of a cathepsin L-like enzyme secreted from human pancreatic cancer cell line HPC-YP.

Spent culture medium from the human pancreatic carcinoma cell line HPC-YP, which can propagate in a protein-free, chemically defined medium without any other supplements, was analyzed for the presence of the cysteine protease, cathepsin L. The secreted form of cathepsin L was distinguished from the lysosomal form by its increased stability at alkaline pH, by its strong thermostability, and by its larger molecular size. HPC-YP cathepsin L was still stable at pH 7.4 and at 56 degrees C after 60-min preincubation. The molecular weight of this enzyme was estimated to be 68,000, compared with a molecular weight of 29,000 for normal liver cathepsin L. By Western blot analysis, HPC-YP enzyme was found to be composed of two components, one with a molecular weight of 37,000 and the other of 31,000. This result suggests that HPC-YP enzyme in the spent medium may be a complex of the proenzyme (in the case of liver proenzyme; Mr 39,000) and the mature enzyme (in the case of liver mature enzyme; Mr 29,000). Interestingly, an intrinsic inhibitor was also separated from the spent medium by gel filtration. The molecular weight of this inhibitor was estimated to be approximately 13,000. The cathepsin L of HPC-YP proved more resistant toward leupeptin than did liver cathepsin L. On the other hand, the former was more sensitive than the latter toward the diazomethane inhibitors, Z-Phe-Phe-CHN2 and Z-Phe-Ala-CHN2. These results indicate that cathepsin L secreted from cancer cell lines may play a role in the destruction of basal lamina, invasion of tissue, and formation of metastasis.

Blotting, Western↗
PubMed1990

Variant cathepsin L activity from gastric cancer tissue.

Cathepsin L activity was partially purified by S-Sepharose FF chromatography, concanavalin-A Sepharose chromatography, phenyl-Superose column chromatography, Mono S column chromatography, and TSK G3000SWXL column chromatography from gastric cancer tissue. The optimal pH of cathepsin L from gastric cancer tissue was 7.4, and the activity was retained even at alkaline pH. Heat stability tests showed that cathepsin L from gastric cancer tissue was heat stable; that is, 65% activity was retained after incubation at 56 degrees C for 60 min. The molecular weight of cathepsin L from gastric cancer tissue was estimated as 115 kD by gel filtration or 110 kD by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme showed a different affinity for wheat germ agglutinin-Sepharose than cathepsin L from gastric normal mucosa. These results suggest that cathepsin L from gastric cancer tissue may play an important role in gastric cancer invasion through the destruction of the surrounding extracellular matrix by its proteolytic activity.

Cathepsin L↗
PubMed1990

[Protease activities in gastric and colon cancer tissues].

Activities of cathepsin B, cathepsin L, and plasminogen activators (urinary type plasminogen activator and tissue type plasminogen activator) were assayed in homogenates of cancer tissue, normal tissue closely surrounding the cancer tissue, and normal tissue distant from the cancer tissue from 30 patients undergoing surgery for gastric cancers and 10 patients undergoing surgery for colon cancers. Activities of those proteases were also assayed in homogenates of adenoma tissue from 10 patients undergoing polypectomy for colon polyps. In the gastric cancer tissue homogenates, the activities of cathepsin B, cathepsin L and tissue type plasminogen activator were significantly higher than in normal tissues. By contrast, the activities of urinary type plasminogen activator of gastric cancer tissues were significantly lower than normal tissues. In the colon cancer tissue homogenates, the activities of cathepsin, B, cathepsin L, and urinary type plasminogen activator were significantly higher than in normal tissues. On the other hand, the activities of tissue type plasminogen activator of cancer tissues were significantly lower than normal tissues. But there were no significant differences in the activities of plasminogen activators between the cancer tissues and adenoma tissues. These results suggest that cathepsin B and cathepsin L play an important role in gastric and colon cancer proliferation and evolution, although the roles of plasminogen activators in gastric and colon cancer proliferation and evolution and in the colon adenoma-carcinoma sequence are still unknown.

Cathepsin B↗
PubMed1989

Variant cathepsin B activity secreted from human pancreatic cancer cell lines into protein-free chemically defined medium.

Cathepsin B activity was found in serum-free spent media of human pancreatic cancer cell lines, Panc-1 and MiaPaca. Cathepsin B activity was partially purified by gel filtration on TSK G3000SW, Con-A Sepharose chromatography, Phenyl-Superose column chromatography, and Mono S column chromatography. The optimal pH of cathepsin B was 7.4, and the activity was retained even at alkaline pH. Heat stability test showed that the enzyme was heat stable; that is, 50% activity was retained after incubation at 56 degrees C for 60 min. These results suggest that cathepsin B secreted from human pancreatic cancer cell is a variant type and may play an important role in pancreatic cancer invasion or metastasis through destruction of the surrounding extracellular matrix by its proteolytic activity.

Cathepsin B↗
PubMed1989

Characterization of variant gamma-glutamyl transpeptidase produced by pancreatocholangiocarcinoma cell lines in a protein-free, chemically defined medium.

Four pancreatocholangiocarcinoma cell lines (HPC-Y1, HPC-YT, MIA PaCa-2, and HChol-Y1) were established to propagate in a protein-free, chemically defined medium. High gamma-glutamyl transpeptidase (GGTP) activities were showed in their spent media (designated as the secreted (GGTP). Their GGTP activities in the spent media were 125, 85, 110, and 153 IU/L/mg of lyophilized spent media, whereas GGTP activities extracted from their cancer cell lines with bromelain were 105, 37, 86, and 112 IU/L/1 x 10(6) cells, respectively. The chemical characteristics of the GGTPs in the spent media from these cell lines resembled one of the GGTPs, sialic acid-rich GGTP, extracted from normal human pancreas with bromelain treatment as follows: the GGTPs secreted from the cancer cell lines bound to an anion exchange column moved fast on electrophoresis and then showed decreased electrophoretic mobility with neuraminidase treatment, showed a high affinity for concanavalin A and lentil lectin columns, and had an acidic isoelectric point. However, the elution patterns of erythroagglutinating phytohemagglutinin (E-PHA) column chromatography and thermostability tests demonstrated clear differences between the carcinoma GGTPs both in the spent media and cell lines and the sialic acid-rich GGTP of normal pancreas, namely the carcinoma GGTPs treated with neuraminidase showed affinity to E-PHA columns, and, in addition, the GGTPs in the spent media showed an apparent heat resistance at 56 degrees C. These findings indicate that the carcinoma GGTPs have a different oligosaccharide structure from that in normal pancreatic GGTPs.

Adenoma, Bile Duct↗
PubMed1988

Purification of human pancreatic gamma-glutamyltranspeptidase by lectin affinity chromatography.

Two types of pancreatic gamma-glutamyltranspeptidase (GGTP) (EC 2.3.2.2), sialic acid poor and sialic acid rich, were purified by the following: anion-exchange chromatography, wheat germ agglutinin (WGA)-Sepharose chromatography, gel filtration chromatography, phenyl-Superose chromatography, and hydroxylapatite chromatography. Among these, WGA-Sepharose chromatography helped to increase the specific activity of the GGTPs by approximately 20-30-fold in one effort. On dodecyl sulfate polyacrylamide gel electrophoresis, the two pancreatic GGTPs had different molecular weights. Sialic acid-rich GGTP had two subunits of Mr 67,000 and 27,000; however, the sialic acid-poor type had two subunits of Mr 72,000 and 29,000. The pI value of the sialic acid-poor GGTP was 5.9, and that of the sialic acid-rich GGTP 3.6.

Chromatography, Affinity↗
PubMed1988

Management of pregeniculate anterior visual pathway gliomas.

Gliomas of the pregeniculate anterior visual pathways comprise about 5% of all intracranial tumors that occur in the first decade of life. Gliomas are the most common primary optic nerve tumor. Diagnosing a glioma of the anterior visual pathways is much easier since the advent of computerized tomography (CT) and magnetic resonance imaging (MRI); the continuing problem is appropriate management. Improved guidelines for management are suggested based on a review of the literature and the authors' experience. These guidelines include both the need to characterize accurately the location of the tumor and its clinical and radiologic progression, and the imperative to employ active intervention only when there is a specific therapeutic goal that can be used for measuring the success of the treatment.

Child↗
PubMed1986

Diseases of the developing hip joint.

The best treatment for diseases of the hip can begin if one diagnoses the disorder as soon as possible after onset. In many cases, successful management of the disease will prevent permanent damage to the hip joint. If injury occurs to the developing hip joint, major hip surgery may be necessary in adult life.

Adolescent↗
PubMed1986

Factors influencing binaural hearing aid use.

Two hundred patients who had been fitted with binaural hearing aids were chosen as subjects for a questionnaire survey to determine the factors which would influence the use of binaural hearing aids. From the analysis of the 16 factors used which included audiological, physical and social factors, the following results were obtained: (1) A significantly greater proportion of male patients used binaural hearing aids than female patients. (2) A significantly greater proportion of patients with a different hearing loss configuration in the two ears used binaural hearing aids as compared with those with a symmetrical hearing loss. (3) Frequent users of binaural hearing aids were males, who had had additional help to reduce their hearing disability, and had a more severe hearing loss in the better ear. The use of binaural hearing aids in noisy situations and in localising sounds was also investigated.

Auditory Threshold↗
PubMed1986

Cholinergic stimulation of phosphatidic acid formation by rat cornea in vitro.

The cornea has one of the highest acetylcholine (ACh) concentrations of any tissue but the function of the ACh has remained enigmatic. During studies on corneal arachidonic acid metabolism, we observed that ACh stimulates formation of labeled phosphatidic acid in rat corneas whose phospholipids were prelabeled with [14C]arachidonate. ACh did not affect the metabolism of free [14C]arachidonate. [14C]Arachidonyl-phosphatidic acid formation was doubled after 10 min of incubation in the presence of ACh concentrations of 10(-4) M or greater. The stimulation by ACh could be completely blocked by atropine and scopolamine and partially blocked by d-tubocurarine. These studies suggest that intact rat cornea has muscarinic cholinergic receptors and that the enzymes of the inositol phospholipids pathway are present since phosphatidic acid is an obligatory intermediate in that cycle of reactions.

Acetylcholine↗
PubMed1985

Deoxycholate induces the preferential hydrolysis of polyphosphoinositides by human platelet and rat corneal phospholipase C.

Deoxycholate promotes phospholipase C degradation of endogenous phosphatidyl[3H]inositol (Pl), phosphatidyl[3H]inositol monophosphate (PIP) and phosphatidyl[3H]inositol bisphosphate (PIP2) in rat cornea and human platelets. Hydrolysis of phosphatidyl[3H]inositol significantly lags polyphospho[3H]inositide degradation. Concomitantly, formation of [3H]inositol monophosphate (IP1) lags behind [3H]inositol bisphosphate (IP2) and [3H]inositol trisphosphate (IP3) production. These results demonstrate that rat cornea and human platelet phospholipase C cause a preferential hydrolysis of the endogenous polyphosphoinositides rather than phosphatidylinositol.

Animals↗
PubMed1978

The histological characteristics of congenital coxa vara: a case report of a five year old boy.

In a 51/2 year old boy with unilateral coxa vara who died of unrelated causes histological sections were made of the proximal femora and pelvic growth plates. The proximal femora were also perfused to study the pattern of arterial supply. Evidence of active endochondral ossification was not detectable in growth plates of the affected right femur, the clinically and roentgenographically normal left femur and the pelvis, including a Salter Type II fissure fracture. The endochondral ossification defect found in growth plates of the proximal right femur and pelvis was associated with a reduction in the number and caliber of intraosseous arteries supplying the metaphyseal sides of the growth plates in the proximal femur and those supplying the subchondral region and extraosseous medial ascending cervical arteries on the surface of the femoral neck. This deficiency in endochondral ossification resembles a form of dwarfism associated with a coxa vara and a generalized growth plate disorder.

Cartilage, Articular↗