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Biomedical subjects

Y S Lee

Publications and source records attributed to Y S Lee.

At least 19 recordsLinked to original sources
PubMed1992

Purification, characterization, and molecular cloning of a 60-kDa phosphoprotein in rabbit skeletal sarcoplasmic reticulum which is an isoform of phosphoglucomutase.

A 60-kDa substrate of calmodulin-dependent protein kinase in rabbit "heavy" skeletal sarcoplasmic reticulum (SR) was characterized by purification and cDNA cloning. Purification was achieved by column chromatography using DEAE-Sephacel, heparin-agarose, and hydroxylapatite in 0.5% 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonic acid (CHAPS). Analyses of amino acid sequence and composition indicated that the CHAPS-soluble 60-kDa protein is an isoform of phosphoglucomutase (PGM). cDNAs encoding two isoforms of PGM were isolated from rabbit skeletal muscles. The translated amino acid sequences show that the isoforms, PGM1 and PGM2, differ in the N-terminal 77 amino acids and that PGM2 is identical to the 60-kDa protein in the SR. Northern blot analysis showed that the size of the mRNA encoding PGM2 is 2.4 kilobases. The PGM enzyme activity was markedly inhibited in SR membranes, while perturbation of the membranes with CHAPS or guanidine-HCl recovered the enzyme activity. KCl (0.15-1 M) led to a partial recovery of the enzyme activity suggesting that the charge interaction is not the primary force for PGM-SR interaction. PGM is localized in the heavy fraction of SR, where calsequestrin and Ca2+ release channel are enriched. Our results demonstrate that an isoform of PGM localized in junctional skeletal SR is the 60-kDa substrate of calmodulin-dependent protein kinase.

Amino Acid Sequence↗
PubMed1992

Regulation of Ca2+ release from sarcoplasmic reticulum in skeletal muscles.

Ca2+ release from skeletal sarcoplasmic reticulum (SR) could be regulated by at least three mechanisms: 1) Ca2+, 2) calmodulin, and 3) Ca2+/calmodulin-dependent phosphorylation. Bell-shaped Ca(2+)-dependence of Ca2+ release from both actively- and passively-loaded SR vesicles suggest that opening and closing of the Ca2+ release channel could be regulated by [Ca2+o]. The time- and concentration-dependent inhibition of Ca2+ release from skeletal SR by calmodulin was also studied using passively-Ca2+ loaded SR vesicles. Up to 50% of Ca2+ release was inhibited by calmodulin (0.01-0.5 microM); this inhibition required 5-15 min preincubation time. The hypothesis that Ca2+/calmodulin-dependent phosphorylation of a 60 kDa protein regulates Ca2+ release from skeletal SR was tested by stopped-flow fluorometry using passively-Ca2+-loaded SR vesicles. Approximately 80% of the initial rates of Ca(2+)-induced Ca2+ release was inhibited by the phosphorylation within 2 min of incubation of the SR with Mg-ATP and calmodulin. We identified two types of 60 kDa phosphoproteins in the rabbit skeletal SR, which was distinguished by solubility of the protein in CHAPS. The CHAPS-soluble 60 kDa phosphoprotein was purified by column chromatography on DEAE-Sephacel, heparin-agarose, and hydroxylapatite. Analyses of the purified protein indicate that the CHAPS-soluble 60 kDa protein is an isoform of phosphoglucomutase (PGM). cDNAs encoding isoforms of PGM were cloned and sequenced using synthetic oligonucleotides. Two types of PGM isoforms (Type I and Type II) were identified. The translated amino acid sequences show that Type II isoform is SR-form.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Studies on re-entrant arrhythmias and ectopic beats in excitable tissues by bifurcation analyses.

A phase-plane bifurcation analysis is a useful way to theoretically understand how various types of arrhythmias may arise from excitable tissues. In this paper, we have performed phase-plane bifurcation analysis to characterize arrhythmogenic states in excitable tissues. To achieve this, we have first formulated a model which is simple enough to be mathematically tractable, yet captures the non-linear features of cardiac excitation and conduction. In this model, single cells are connected in a circular fashion by gap conductances. Each cell carries the following two types of currents: a passive outward current and an inward "excitable" current which contains an activation and an inactivation gate. The activation gate is responsible for the upstroke of action potential and inactivation gate is responsible for the termination of the plateau potential. With this model, we have constructed bifurcation diagrams as a function of a bifurcation parameter. The parameter chosen as the bifurcation parameter has the property of raising maximum diastolic potential while shorting the refractory period. Our analysis revealed the existence of three distinct multi-stable phases in certain ranges of the bifurcation parameter: (1) bistability between a rotor and a quiescent state, (2) bistability between rotor and ectopic beats, and (3) three stable states co-existing among quiescent state, rotor, and ectopic beats. In these three regions, external impulses exert very distinct effects: In region 1, a brief current pulse can annihilate a re-entrant arrhythmia to quiescence. To initiate re-entry from a quiescent tissue, however, it takes two pulses (a primary pulse followed by a premature pulse at a site different from the "primary" site). In region 2, a brief pulse can convert a re-entrant arrhythmia to ectopic beats. To convert the ectopic beats back to circus movement, these beats have to be suppressed by a few brief current pulses to initiate one-way propagation. Depending on the frequency and strength of impulses in region 3, the tissue can switch back and forth among quiescence, circus movement, and ectopic beats. For comparison, we have also included a more complete Beeler-Reuter cardiac cell model in our analysis and obtained essentially the same results. From the behavioral similarities of these models, we conclude that re-entrant and ectopic arrhythmias must be intrinsic properties of excitable tissues and external stimuli can convert one mode of arrhythmia to another in the multistability regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

HLA-DR antigen expression in intestinal-type and diffuse-type gastric carcinoma.

The expression of the HLA-DR antigen, a Class II HLA antigen, was analyzed in 41 cases of gastric carcinoma (23 intestinal-type and 18 diffuse-type according to a modified Lauren classification) using a monoclonal antibody that is reactive to this antigen in routinely formalin-fixed, paraffin-embedded tissue sections. Seventeen cases of intestinal-type gastric carcinoma and two cases of diffuse-type gastric carcinoma were positive for the HLA-DR antigen. The staining in intestinal-type carcinoma generally was stronger and more extensive than in diffuse-type carcinoma, which showed only weak and focal staining. The difference in the frequency and pattern of staining between intestinal and diffuse-type gastric carcinoma supports the concept that these are two distinct subtypes of gastric carcinoma.

Adenocarcinoma↗
PubMed1992

Budd-Chiari syndrome treated successfully by percutaneous transluminal balloon angioplasty: two cases followed-up for 6 years.

We report 2 cases of Budd-Chiari syndrome that are due to complete membranous obstruction between the junction of the inferior vena cava and the right atrium. Both cases were treated successfully by King's bioptome breakthrough followed by balloon dilatation of the membrane. The patients showed remarkable symptomatic improvement and promising hemodynamic and angiographic results immediately after the procedure and 6 years later. We conclude that balloon angioplasty is a safe and effective method for treating this rare disease in selected cases.

Adult↗
PubMed1992

Adhesion molecules in skeletogenesis: I. Transient expression of neural cell adhesion molecules (NCAM) in osteoblasts during endochondral and intramembranous ossification.

We report that neural cell adhesion molecules (NCAM) are expressed transiently in developing chicken osteoblasts during osteogenesis using immunostaining on cryostat sections. NCAM is strongly expressed in most osteoblasts along bone trabeculae that coincide with the presence of collagen I and alkaline phosphatase activity. In endochondral ossification, NCAM is highly expressed in osteogenic buds as seen in the epiphysis and diaphysis of tibia and vertebrae. In intramembranous ossification, NCAM is seen in osteogenic condensation of calvaria and in the periosteum of tibial diaphysis. The expression is transient because NCAM is not expressed in mesenchymal cells before osteogenic condensation and NCAM expression is lost in osteocytes in later stages. The staining pattern suggests that NCAM is present on the cell membrane of osteoblasts. Using a specific monoclonal antibody, the osteoblast NCAM is shown to contain polysialic acid, which is enriched in embryonic brain. Northern blot analysis using chicken brain NCAM cDNA as probes showed two major sizes of mRNA at 6.4 and 4.2 kb in calvarial mRNA as opposed to bands at 7.2, 6.4, and 4.2 kb in the brain. An immunoblot showed major proteins at Mr 165 and 110 kd, unlike brain NCAM, which are 180, 140, and 120 kD. That NCAM is involved in bone morphogenesis is consistent with the general hypothesis that NCAM plays pivotal roles in mesenchymal condensation, as shown in the formation of muscle, kidney, skin, and cartilage. The results establish NCAM as a cell surface molecule expressed transiently during osteoblast lineage. The implication that NCAM may mediate osteoblast interaction and regulate skeletal morphogenesis is discussed.

Animals↗
PubMed1992

A comparison between intravenous streptokinase and tissue plasminogen activator with early intravenous heparin in acute myocardial infarction.

To compare the effects of two thrombolytic agents, streptokinase and recombinant tissue-type plasminogen activator (rTPA) with early heparinization, on left ventricular function, coronary patency and reinfarction rates, bleeding complications, and short- and long-term mortality, we studied 122 patients with acute myocardial infarction prospectively. All of them fulfilled the standard criteria for thrombolytic therapy. One group (n = 63) received 1,500,000 units of streptokinase over 1 hour, and one group (n = 59) received 100 mg of rTPA over 3 hours. Baseline data showed no significant differences between the streptokinase and rTPA groups. Results of predischarge studies 10 to 14 days after infarction revealed that there was no difference in left ventricular ejection fraction between the two groups (48.3% in the streptokinase group and 49.9% in the rTPA group; p = 0.67). The patency rate of the infarct-related artery tended to be higher in the rTPA group compared with the streptokinase group (77% vs 57%, p = 0.19). In-hospital spontaneous bleeding occurred after streptokinase in seven patients (11.1%) and after rTPA in eight (13.6%; p = 0.89). One patient had intracranial bleeding after rTPA and died 13 hours later. The early mortality rate within 30 days of acute myocardial infarction was 5 of 63 (7.9%) for the streptokinase group and 2 of 59 (3.4%) for the rTPA group (p = 0.49). During the 19.3-month follow-up period, reinfarction occurred in seven patients (11%) in the streptokinase group and in three (5%) in the rTPA group (p = 0.3). The mortality rates were 10 of 63 (16%) and 3 of 59 (5%), respectively (p = 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Aspirin↗
PubMed1992

Chain substituted polymerizable ether lipids: synthesis of sorbyl and diacetylenic ether glycerophosphocholine.

Three novel polymerizable ether lipids, 1,2-O-bis[10(2',4'-hexadienoyloxy)decyl]-rac, 1,2-O-bis(10,12-tricosadiynyl)-rac, and (-)-2,3-O-bis(10,12-tricosadiynyl)-sn-glycero-1-phosphocholine, were synthesized from 3-O-benzyl-rac, 3-O-trityl-rac and (-)-1-O-trityl-sn-glycerol as starting materials, respectively. All the reactions employed in these multi-step syntheses are straightforward giving an overall yield of 21% for the sorbyl, 42% for the racemic diacetylenic and 44% for the chiral diacetylenic lipid. All the lipids form bilayer assemblies on hydration and show transitions from gel to liquid-crystalline phases at 11.4 degrees, 27.6 degrees and 30.0 degrees C, respectively. Bilayer assemblies of each are photoreactive and are readily polymerized by irradiation with 254 nm light. Tubules of the chiral diacetylenic ether lipid were observed.

Phospholipid Ethers↗
PubMed1992

Humic acid: inhibitor of plasmin.

Synthetic humic acid, well water humic acid and commercial humic acid (Aldrich) all have the ability to inhibit human plasmin activity. At a concentration of 20 micrograms/ml, all three species will result in 93%, 70% and 40% of residual plasmin activity, respectively. The components of humic acid, such as protocatechuic acid, resorcinol, vanillic acid and ferulic acid do not have such inhibitory activities. The ability of humic acid to inhibit human plasmin has not been reported. It is, therefore, a new plasmin inhibitor.

Coumaric Acids↗
PubMed1992

Transesophageal echocardiography in adults with a continuous precordial murmur.

In order to assess the ability of echocardiography in the detection of intracardiac and extracardiac shunts, we studied 11 patients (aged 22-64 yr) with a continuous precordial murmur using transthoracic and transesophageal echocardiography, and correlated the results with the subsequent angiographic and surgical findings. We found that only in 5 of 6 patients with a patent arterial duct could the continuous flow pattern be detected in pulmonary artery using transthoracic echocardiography, whereas it could be readily and accurately identified by transesophageal echocardiography in all patients. The diameters of the patent arterial duct were also measured and found to be in good correlation with subsequent surgical findings (r = 0.98, p less than 0.05). In 2 patients with a ruptured aneurysm of sinus of Valsalva which originated from the right coronary sinus and perforated into the right ventricle, transesophageal echocardiography gave a better image than transthoracic echocardiography. In 2 patients with coronary artery fistula, the origin and site of drainage of the coronary artery could be imaged using transesophageal echocardiography, but the course of coronary artery fistula was more easily detected by transthoracic echocardiography. In one patient with aortopulmonary window, the defect between ascending aorta and main pulmonary artery could readily be imaged by transesophageal echocardiography. We therefore recommend transesophageal echocardiography when evaluating patients with precordial continuous murmur in whom intracardiac and extracardiac shunts or defects are suspected.

Adult↗
PubMed1992

Combination of 5-fluorouracil and recombinant interferon alpha-2B in advanced gastric cancer. A phase I study.

Based on recent preclinical data suggesting synergism between 5-fluorouracil (5-FU) and interferon alpha (IFN-alpha) and clinical activity of the combination therapy in colon cancer, 14 patients with advanced gastric cancer were treated with combination therapy of 5-FU and recombinant interferon alpha-2b (rIFN alpha-2b) (Intron A, Schering, Kenilworth, NJ, U.S.A.). The maximum tolerated dose was 5-FU 750 mg/m2/day given as a continuous infusion daily for 5 days followed by weekly bolus injection of the same initial daily dose, plus rIFN alpha-2b 5 X 10(6) U given subcutaneously 3 times weekly starting day 1 of 5-FU infusion. The dose-limiting toxicities were fatigue/weakness, diarrhea, and neurologic toxicities such as somnolence and confusion. The other common side effects were nausea, fever, leukocytopenia, thrombocytopenia, and the darkening of the skin. Of 13 evaluable patients, 4 had a partial response (duration 6, 14, 24, and 28 weeks). These data suggest that combination therapy of 5-FU plus rIFN alpha-2b is tolerable and has manageable side effects in patients with advanced gastric cancer. Further Phase II study will be needed to define the antitumor activity of this combination.

Adult↗
PubMed1992

Effects of iron limitation on production of a siderophore, outer membrane proteins, and hemolysin and on hydrophobicity, cell adherence, and lethality for mice of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is one of the most important enteropathogens in Taiwan, Japan, and other coastal regions. The pathogenesis of V. parahaemolyticus disease is not clearly understood. The expression of some factors by V. parahaemolyticus in iron-rich and iron-limited media was analyzed. In the clinical hemolytic strains, the production of a siderophore, two outer membrane proteins (77 and 80 kDa), and thermostable direct hemolysin was significantly enhanced in iron-limited culture, and hemolytic activities, cell hydrophobicity, HEp-2 cell adherence, and lethality for mice were also enhanced. The environmental nonhemolytic strain CCRC12958 that was cultured in iron-limited medium exhibited lethal activity for mice, and other factors except hemolysis were also enhanced like the responses of clinical strains were. These results suggested that a virulent factor(s) of V. parahaemolyticus may be induced or enhanced under iron-limited conditions. The iron-regulated factors reported in this paper may be important in the pathogenesis of V. parahaemolyticus disease.

Animals↗
PubMed1992

Mechanism of skin morphogenesis. II. Retinoic acid modulates axis orientation and phenotypes of skin appendages.

The factors that determine the axial orientation and phenotypes of skin appendages were analyzed by studying the effect of retinoic acid (RA) on embryonic chicken skin explant cultures. With RA uniformly distributed in the culture media, the feather buds became smaller, were disoriented or were transformed into scale-like structures in a concentration-dependent manner (from 0.05-2.5 microM). With RA distributed as a gradient created by a RA-soaked anion exchange bead, a radial zone of inhibition with a rim of disoriented buds was observed. The new axis of the disoriented buds appeared to be determined by a combination of the original feather axis determining force and a new axial force pointing centrifugally away from the RA source. This observed result can be simulated with a computer model using a vectorial sum of different feather axial determination forces. The size of the inhibited zone is linearly correlated to the RA concentration and may be used to quantify the morphogenetic activity of retinoids. These effects are specific to developmental stages (Hamburg and Hamilton stage 31-34). Both all-trans and 13-cis RA have morphogenetic activity. Retinol has no effect and retinal has a small inhibitory effect but neither phenotypic transformation nor axial disorientation were observed. The antero-posterior gradient of homeoprotein XlHbox 1 in feather buds became diffusive after RA treatment. RA dissolves dermal condensations and the distribution of N-CAM is altered from an anterior localized pattern to a diffusive presence in the bud cores. Endogenous retinoids in developing skins show developmental stage-dependent changes both quantitatively and qualitatively. The results suggest that RA either is or can modulate the endogenous morphogen(s) that determine the orientation and phenotype of skin appendages, and that this morphogenetic pathway involves Hox genes and adhesion molecules.

Animals↗
PubMed1992

Imaging of multiple coronary artery fistulas to right ventricle by transthoracic and transesophageal echocardiography.

A 20-year-old woman presented with extremely rare multiple coronary artery fistulas with left circumflex and right coronary arteries as the feeding vessels and two distinct sites of drainage into the posterior wall of the right ventricle near the apex in close proximity. The large left fistula was well depicted by transthoracic echocardiography, whereas the transesophageal approach better delineated part of the smaller right fistula.

Adult↗
PubMed1992

Lung adenoma development and NK activity in mice treated with multiple carcinogens.

A wide-spectrum initiation model was investigated in mice. Sequential treatments with diethylnitrosamine, urethane and N-methylnitrosourea, with or without a promoter, phenobarbital, resulted in tumor formation in the lungs in 85-90% of animals, but did not produce any tumorous lesions in other organs. The lung tumors were adenomas and the mean number of adenomas was 2.2-2.6 per mouse. Phenobarbital combination had no additive effect on lung tumor incidence and multiplicity. Splenic NK cell activity showed inconsistent increment in the carcinogen plus phenobarbital-treated group during the experiment (P less than 0.05).

Adenoma↗
PubMed1992

Distribution of prostaglandin E2 in gastric and duodenal mucosa: possible role in the pathogenesis of peptic ulcer.

BACKGROUND: Prostaglandin E which is present abundantly in the gastric mucosa is a powerful inhibitor of gastric acid secretion and a stimulus to gastric mucus production. In addition, prostaglandin E2 inhibits ulcer formation in animals, and the synthetic analogues of prostaglandin E have successfully been used in the treatment of patients with gastric and duodenal ulcer disease. To evaluate the role of endogenous prostaglandin E2 in the pathogenesis of the peptic ulcer disease, we measured mucosal prostaglandin E2 levels in patients with gastric and duodenal ulcer disease and compared with that of non-ulcer control persons. METHODS: The study population was made up of 44 non-ulcer persons, 36 patients with a benign gastric ulcer, and 48 with a duodenal ulcer. Every mucosal specimen, taken from the antrum and from the duodenal bulb, were homogenized, mixed with 1 M HCl, and centrifuged. After removal of the supernatant, precipitate was eluted with ethyl acetate in the Amprep C18 minicolumn. Then the extracted prostaglandin E2 in the ethyl acetate fractions was converted into its methyl oximate derivatives, and the prostaglandin E2 level was measured by radioimmunoassay. During the procedure any homogenized specimen which was looking grossly bloody was removed from the assay in order to avoid any possible contamination or prostaglandin E2 in blood. RESULTS: In non-ulcer persons, the mean values was 258.17 +/- 127.03 pg/mg. tissue in antrum and 121.07 +/- 67.46 pg/mg. tissue in duodenal bulb. The corresponding values were 186.42 +/- 70.51 pg/mg. tissue, 79.44 +/- 39.04 pg/mg. tissue in gastric ulcer patients and 204. 94 92.03 pg/mg. tissue, 99.66 +/- 56.10 pg/mgl. tissue in duodenal ulcer patients respectively. Gastric ulcer patients have the significantly lower level of the antral and duodenal prostaglandin E2 (p < 0.005). Those levels of duodenal ulcer patients were also significantly lower than those of non-ulcer persons (p < 0.025 & 0.05). Antral prostaglandin E2 level increased to 305.21 +/- 104.91 pg/mg. tissue in the gastric ulcer patients (p < 0.005) and to 271.02 +/- 93. 23 pg/mg. tissue in the duodenal ulcer (p < 0.005) when the ulcer crater was healed. The duodenal bulb prostaglandin E2 level was also increased in the healed stage of ulcer, e. g., 128.84 +/- 57.62 (p < 0.005) and 112.60 +/- 42.25 pg/mg. tissue, respectively. CONCLUSION: These results suggest that prostaglandin deficiency in the antral and duodenal bulb mucosa may have an important role in the pathogenesis of peptic ulcer disease.

Adult↗