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Biomedical subjects

S T Kim

Publications and source records attributed to S T Kim.

At least 127 records · Page 7Linked to original sources
PubMed1993

Effects of rehmanniae radix water extract on renal function and renin secretion rate in unanesthetized rabbits.

This study was undertaken to explore the effects of different preparations of Rehmanniae Radix on renal function and renin secretion rate. Steamed Rehmanniae showed a decrease in urine volume, renal hemodynamics, and urinary excretion of electrolytes confined to the infused kidney, and was followed by an increase in urinary excretion of electrolytes from both kidneys. Dried Rehmanniae showed a decrease in urine volume, glomerular filtration rate, and urinary excretion of electrolytes, while raw Rehmanniae showed only an increase in urinary excretion of electrolytes. Steamed Rehmanniae and dried Rehmanniae decreased renin secretion rate, but raw Rehmanniae tended to increase renin secretion. These results suggest that the Rehmanniae Radix preparations have different effects on renal function and renin secretion rate.

Animals↗
PubMed1993

Occlusive and reperfused myocardial infarction: detection by using MR imaging with gadolinium polylysine enhancement.

PURPOSE: To assess the capability of gadolinium polylysine-enhanced cardiac magnetic resonance (MR) imaging in depicting normal and ischemic myocardium during occlusion and reperfusion of the left anterior descending artery. MATERIALS AND METHODS: Contrast-enhanced MR images were obtained in 18 cats during 90 minutes each of occlusion and reperfusion. The change in signal intensity (SI) was compared among normal myocardium and central and peripheral ischemic zones. Results were compared with those of 2,3,5-triphenyltetrazolium chloride staining. RESULTS: During occlusion, the ischemic zone lacked enhancement while normal myocardium had gradual enhancement. During reperfusion, the ischemic zone had strong enhancement. In cats with large infarction, the central and peripheral ischemic zones had intermediate and high SI, respectively; in cats with focal or no infarction, the entire ischemic zone had high SI. CONCLUSION: Occlusive and reperfused myocardial infarction can be detected at gadolinium polylysine-enhanced MR imaging by means of differential SI changes in normal myocardium and central and peripheral ischemic zones.

Animals↗
PubMed1993

The thrombolytic effect of lumbrokinase is not as potent as urokinase in a rabbit cerebral embolism model.

The purpose of the present study is to determine whether lumbrokinase has an in vivo thrombolytic effect in a rabbit cerebral embolism model. In our previous studies, we found that lumbrokinase, an extract from Korean earth worms, has a strong in vitro fibrinolytic effect without the presence of plasminogen and significant in vivo thrombolytic effects of lumbrokinase in a rat human-clot-induced cerebral embolism model. We established the cerebral embolism model in rabbits by injecting a piece of human clot into the internal carotid artery via the external carotid artery and confirmed the occlusion with angiography. Twenty one rabbits were divided into three groups and 5cc of saline, urokinase of 50,000 u/ml, and equipotent LK were injected intraarterially for 30 minutes into each group of 7 animals. Ten minutes after the end of infusion, an angiogram was performed to confirm the recanalization. Clot lysis occurred in one, six, and one animals in the saline, urokinase and lumbrokinase treated groups respectively. With regard to its in vitro effect, lumbrokinase is not as potent in vivo. Further investigation should be performed to determine the cause of its weakened in vivo effect and to develop a method to potentiate it.

Animals↗
PubMed1992

Energy transfer (deazaflavin-->FADH2) and electron transfer (FADH2-->T <> T) kinetics in Anacystis nidulans photolyase.

DNA photolyases catalyze the photocycloreversion of cyclobutane pyrimidine dimers. The enzyme from the cyanobacterium Anacystis nidulans contains two chromophores, 1,5-dihydroflavin adenine dinucleotide (FADH2) and 7,8-didemethyl-8-hydroxy-5-deazariboflavin (8-HDF). The photophysical/photochemical reactions leading to DNA repair were investigated by using time-resolved and steady-state fluorescence spectroscopy. It was found that the excited singlet state of 8-HDF transfers energy to FADH2 at a rate of 1.9 x 10(10) s-1 and a quantum yield of 0.98. Using the Forster equation for long-range energy transfer and assuming random orientations of the donor and acceptor the interchromophore distance was calculated to be 15 A. The excited singlet FADH2 which forms either by energy transfer from 8-HDF or by direct absorption of a photon has a lifetime of 1.8 ns in the absence of substrate and 0.14 ns in the presence of the photodimer indicating electron transfer from the FADH2 excited singlet state to the dimer at a rate of 6.5 x 10(9) s-1 and quantum efficiency of 92%.

Cyanobacteria↗
PubMed1992

Roles of FAD and 8-hydroxy-5-deazaflavin chromophores in photoreactivation by Anacystis nidulans DNA photolyase.

DNA photolyase from the cyanobacterium Anacystis nidulans contains two chromophores, flavin adenine dinucleotide (FADH2) and 8-hydroxy-5-deazaflavin (8-HDF) (Eker, A. P. M., Kooiman, P., Hessels, J. K. C., and Yasui, A. (1990) J. Biol. Chem. 265, 8009-8015). While evidence exists that the flavin chromophore (in FADH2 form) can catalyze photorepair directly and that the 8-HDF chromophore is the major photosensitizer in photoreactivation it was not known whether 8-HDF splits pyrimidine dimer directly or indirectly through energy transfer to FADH2 at the catalytic center. We constructed a plasmid which over-produces the A. nidulans photolyase in Escherichia coli and purified the enzyme from this organism. Apoenzyme was prepared and enzyme containing stoichiometric amounts of either or both chromophores was reconstituted. The substrate binding and catalytic activities of the apoenzyme (apoE), E-FADH2, E-8-HDF, E-FAD(ox)-8-HDF, and E-FADH2-8-HDF were investigated. We found that FAD is required for substrate binding and catalysis and that 8-HDF is not essential for binding DNA, and participates in catalysis only through energy transfer to FADH2. The quantum yields of energy transfer from 8-HDF to FADH2 and of electron transfer from FADH2 to thymine dimer are near unity.

Apoenzymes↗
PubMed1992

The third chromophore of DNA photolyase: Trp-277 of Escherichia coli DNA photolyase repairs thymine dimers by direct electron transfer.

Photolyases repair pyrimidine dimers in DNA by converting the light energy of 300- to 500-nm photons into chemical energy. Enzymes from various organisms contain two chromophore cofactors (FADH2 and either methenyltetrahydrofolate or 8-hydroxy-5-deazaflavin) that absorb the low-energy photons and initiate splitting of the cyclobutane ring by a radical mechanism. Here, we show that, in addition to these two chromophores, in the far UV range, direct excitation of one specific tryptophan residue (out of 15 total) in the polypeptide chain of Escherichia coli photolyase leads to splitting of the cyclobutane ring with high quantum yield (phi = 0.56), independent of the other chromophores. The specific tryptophan residue responsible for photosensitized repair was identified as Trp-277 by site-specific mutagenesis.

Catalysis↗
PubMed1992

Pyrimidine dimer splitting in covalently linked dimer-arylamine systems.

Cyclobutadipyrimidines (pyrimidine dimers) undergo photosplitting which is sensitized by electron donors. We prepared a series of compounds in which a dimer is directly linked to an arylamine, which acts as sensitizer for dimer splitting. Two diastereomers of the dimer-arylamine exhibited very different splitting efficiencies. Also studied were N-methyl, ring methoxy, as well as deuterated derivatives of the sensitizer. These dimer-arylamines had an absorption band with lambda max approximately 300 nm. In each case intramolecular photosensitization of dimer splitting was highly dependent on the solvent, ranging in one instance from phi spl = 0.02 in water to a high value of 0.31 in the least polar solvent mixture examined (1,4-dioxane: isopentane, 1:99). A mechanism is proposed which involves photoinduced electron transfer from arylamine to dimer and splitting of the dimer radical anion. The dependence of splitting on the solvent was rationalized on the basis of retardation of back electron transfer due to Marcus inverted behavior of the charge-separated species. Photolyases might achieve their high efficiency of dimer splitting in part by employing a hydrophobic active site to slow back electron transfer in a similar manner.

Amines↗
PubMed1992

Splitting of cis-syn cyclobutane thymine-thymine dimers by radiolysis and its relevance to enzymatic photoreactivation.

The 137Cs-gamma-irradiation of cis-syn thymine-thymine cyclobutane type dimers has been studied in aqueous solution. The mechanism of thymine dimer cleavage by eaq-, CO2.-, OH.,SO4.-,Br2.- and isopropanol radicals was studied using high pressure liquid chromatography (HPLC). Evidence that the one-electron reductants studied induce dimer cleavage partially by a chain reaction is presented. Approximate values for the one-electron reduction potential of thymine-thymine are obtained and thermodynamic calculations are presented in order to predict the direction of electron transfer in the case of enzymatic photoreactivation.

Cesium Radioisotopes↗
PubMed1992

Adult T-cell leukemia/lymphoma (ATL)--clinical, histopathological, immunological and immunohistochemical characteristics.

Twenty-one patients with ATL were assessed. The predominant physical findings were lymph node and bone marrow involvement, skin involvement, hepatosplenomegaly and leukemic manifestations. The predominant histopathological findings in both skin and lymph node specimens were the diffuse medium-sized cell type and the diffuse mixed cell type. Some phenotypic discrepancy was found between the neoplastic cells in the peripheral blood, lymph nodes and skin of patients with ATL with respect to CD45RA and CD45RO, and CD7, CD29, CD25 and HLA-DR. That is, the predominant neoplastic cell phenotype was the helper T-cell, which was CD3+, CD4+, CD7+, CD25+, CD45RA+ and HLA-DR+, and CD29- and CD45RO- in peripheral blood and lymph nodes, and CD3+, CD4+, CD7+, CD29+, CD45RO+ and HLA-DR+, and CD45RA- in the skin. In other words, we have described the phenotypic heterogeneity of ATL cells and demonstrated the heterogeneity of CD45R isoform expression on ATL cells in different organs--the skin, peripheral blood and lymph nodes--of the same patient.

Adult↗
PubMed1992

Therapeutic effect of transcatheter oily chemoembolization therapy for encapsulated nodular hepatocellular carcinoma: CT and pathologic findings.

An emulsion of iodized oil and doxorubicin hydrochloride was intraarterially injected in 27 patients with encapsulated single nodular hepatocellular carcinoma (HCC). Computed tomography (CT) was performed 1-3 weeks after injection, and the lesions were resected 1-4 weeks thereafter. The percentages of tumor necrosis were evaluated in cut surfaces of resected specimens and were compared with the findings at iodized-oil CT. Six tumors with complete intratumor retention of iodized oil had 98% necrosis, and 21 tumors with incomplete retention had 64% necrosis. Two tumors with complete retention of iodized oil in the surrounding liver had 100% necrosis, while 16 tumors with partial retention and nine tumors without retention of iodized oil in surrounding liver had 74% and 62% necrosis, respectively. Complete retention of iodized oil in the tumor and surrounding liver demonstrated the best therapeutic effects. Evaluation of the pattern and distribution of iodized oil in the tumor and surrounding liver with iodized-oil CT is useful in the assessment of the therapeutic effects of transcatheter arterial embolization in encapsulated nodular HCCs.

Carcinoma, Hepatocellular↗
PubMed1991

Determination of rates and yields of interchromophore (folate----flavin) energy transfer and intermolecular (flavin----DNA) electron transfer in Escherichia coli photolyase by time-resolved fluorescence and absorption spectroscopy.

Escherichia coli DNA photolyase, which photorepairs cyclobutane pyrimidine dimers, contains two chromophore cofactors, 1,5-dihydroflavin adenine dinucleotide (FADH2) and 5,10-methenyltetrahydrofolate (MTHF). Previous work has shown that MTHF is the primary photoreceptor which transfers energy to the FADH2 cofactor; the FADH2 singlet excited state then repairs the photodimer by electron transfer. In this study, we have determined the rate constants for these photophysical processes by time-resolved fluorescence and absorption spectroscopy. From time-resolved fluorescence, we find that energy transfer from MTHF to FADH2 and FADH degrees occurs at rates of 4.6 x 10(9) and 3.0 x 10(10) s-1, respectively, and electron transfer from FADH2 to a pyrimidine dimer occurs at a rate of 5.5 x 10(9) s-1. Using Förster theory for long-range energy transfer and assuming K2 = 2/3, the interchromophore distances were estimated to be 22 A in the case of the MTHF-FADH2 pair and 21 A for the MTHF-FADH degrees pair. Picosecond absorption spectroscopy identified an MTHF single state which decays to yield the first excited singlet state of FADH2. The lifetimes of MTHF and FADH2 singlets and the rates of interchromophore energy transfer, as well as the rate of electron transfer from FADH2 to DNA measured by time-resolved fluorescence, were in excellent agreement with the values obtained by picosecond laser flash photolysis. Similarly, fluorescence or absorption lifetime studies of the folate-depleted enzyme with and without photodimer suggest that FADH2, in its singlet excited state, transfers an electron to the dimer with 89% efficiency. The distance between FADH2 and the photodimer was calculated to be ca. 14 A.

Apoenzymes↗
PubMed1991

Multiparameter optimizations in micellar liquid chromatography using the iterative regression optimization strategy.

An extension of the iterative regression optimization strategy to multi-parameter optimizations is described and applied to the separation of ionic compounds (amino acids and peptides) by means of micellar liquid chromatography. The parameters examined are the concentration of surfactant, the concentration of 2-propanol and pH. Fairly regular (linear, weakly curved) retention behaviour of the compounds as a function of the parameters results in an efficient optimization using a relatively small number of initial experiments.

Amino Acids↗
PubMed1991

Effect of base, pentose, and phosphodiester backbone structures on binding and repair of pyrimidine dimers by Escherichia coli DNA photolyase.

Photolyases reverse the effects of UV light on cells by converting cyclobutane dipyrimidine photoproducts (pyrimidine dimers, Pyr mean value of Pyr) into pyrimidine monomers in a light-dependent reaction. Previous work has suggested that, based on substrate preference, there are two classes of photolyase: DNA photolyase as exemplified by the Escherichia coli enzyme, and RNA photolyases found in plants such as Nicotiana tabacum and Phaseolus vulgaris. In experiments aimed at identifying substrate determinants, including the pentose ring, for binding and catalysis by E. coli DNA photolyase we tested several Pyr mean value of Pyr. We found that the enzyme has relative affinities for photodimers of T mean value of T greater than or equal to U mean value of T greater than U mean value of U much greater than C mean value of C and that the E-FADH2 form of the enzyme repairs these dimers at 366 nm with absolute quantum yields of 0.9 (T mean value of T), 0.8 (U mean value of T), 0.6 (U mean value of U), and 0.05 (C mean value of C). The enzyme also repairs an isolated thymine dimer and the synthetic substrate, 1,1'-trimethylene-bis (thymine) cyclobutane dimer. Unexpectedly, we found that this enzyme, previously thought to be specific for DNA, repairs uracil cyclobutane dimers in poly(rU). The affinity of photolyase for a uracil dimer in RNA is about 10(4)-fold lower than that for a U mean value of U in DNA; however, once bound, the enzyme repairs the photodimer with the same quantum yield whether the dimer is in ribonucleoside or deoxyribonucleoside form.

Base Composition↗
PubMed1991

Intraoperative sonography of hepatocellular carcinoma: detection of lesions and validity in surgical resection.

Eighty-six hepatocellular carcinomas (HCCs) in 67 patients were examined by intraoperative sonography. Sensitivity for detecting tumors with intraoperative sonography was compared with sonography, computed tomography (CT), hepatic angiography, and CT after intraarterial injection of iodized poppy-seed oil (Lipiodol-CT). The overall sensitivities were 76% with sonography, 86% with CT, 89% with angiography, 96% with Lipiodol-CT, and 98% with intraoperative sonography. The differences in sensitivity between intraoperative sonography and sonography (p less than 0.01), CT (p less than 0.01), and angiography (p less than 0.05) were significant. In 35 lesions smaller than 2 cm, the sensitivities of Lipiodol-CT and intraoperative sonography were high (91 and 94%, respectively). In operating field, tumors were invisible in 36 (42%) and nonpalpable in 31 of 86 cases (36%). In 35 tumors smaller than 2 cm, invisible tumors were 66% and nonpalpable tumors were 63%. However, 84 of 86 cases (98%) could be localized with intraoperative sonography. These results suggest that intraoperative sonography is the final diagnostic imaging procedure before surgical resection of tumors and in cases of invisible and nonpalpable tumors in the operating field, this procedure is mandatory to improve surgical results.

Carcinoma, Hepatocellular↗
PubMed1991

[Multiple pulmonary metastasis from histologically benign giant cell tumor of the right radial olecranon].

An unusual case of a benign giant cell tumor of bone with pulmonary metastasis is reported. A 23-year-old man had a painful tumor in the right radial olecranon that proved to be a histologically benign giant cell tumor. Curettage and bone-grafting were performed, but the tumor recurred twice, 8 months and 20 months after initial treatment. Histological examination of biopsy materials from the recurring tumor showed typical benign giant cell tumors. Five years later, wedge resections were performed for bilateral pulmonary nodules, which had been detected by chance. The pulmonary nodules turned out to be histologically similar to the primary tumor of the olecranon. Almost 7 years later, he was asymptomatic and the chest radiograph was clear, and there was no local recurrence of the lesion.

Adult↗
PubMed1990

Papillary cystic tumor of the liver. A case report with ultrastructural observation.

A case of primary tumor of the liver with pathologic features strikingly similar to those of the papillary cystic tumor of the pancreas in a 41-year-old woman is presented. Two large, well-demarcated, solid and cystic tumors with extensive hemorrhage and necrosis were located in the right and left lobes, measuring 30 x 27 x 7.5 cm and 5.5 x 4.0 x 2.5 cm, respectively. Microscopically, both tumor masses showed two basic patterns of cellular arrangement. One was a papillary pattern with fairly prominent fibrovascular stalks covered with one to three cell layers of tall to cuboidal cells. The other pattern was that of solid growth with microcystic degeneration. Ultrastructurally, the tumor cells were polyhedral and their oval shaped nuclei were occasionally indented. The cytoplasmic organelles varied in amount, and immature cell junctions and intercellular spaces were rarely present. A few cells contained zymogen-like secretory granules and annulate lamellae. The pancreas was free of tumor. To our knowledge, this tumor is a unique clinicopathologic entity of hepatic origin, and its similarity to the pancreatic papillary cystic tumor in clinical, gross, microscopic, and ultrastructural features together with their closely related organogenesis, suggests that this tumor derives from pluripotential cells transdifferentiating toward the pancreatic acinar cells and ductular cells, with the latter being indistinguishable from intrahepatic small bile ductular epithelial cells.

Adult↗