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Biomedical subjects

S Y Cho

Publications and source records attributed to S Y Cho.

At least 37 records · Page 2Linked to original sources
PubMed2001

Solid- and solution-phase synthesis of vancomycin and vancomycin analogues with activity against vancomycin-resistant bacteria.

Vancomycin, the prototypical member of the glycopeptide family of antibiotics, is a clinically used antibiotic employed against a variety of drug-resistant bacterial strains including methicillin-resistant Staphylococcus aureus (MRSA). The recent emergence of vancomycin resistance, viewed as a growing threat to public health, prompted us to initiate a program aimed at restoring the potency of this important antibiotic through chemical manipulation of the vancomycin structure. Herein, we describe the development of synthetic technology based on the design of a novel selenium safety catch linker, application of this technology to a solid-phase semisynthesis of vancomycin, and the solid- and solution-phase synthesis of vancomycin libraries. Biological evaluation of these compound libraries led to the identification of a number of in vitro highly potent antibacterial agents effective against vancomycin-resistant bacteria. In addition to aiding these investigations, the solid-phase chemistry described herein is expected to enhance the power of combinatorial chemistry and facilitate chemical biology and medicinal chemistry studies.

Anti-Bacterial Agents↗
PubMed2001

Synthesis and biological evaluation of vancomycin dimers with potent activity against vancomycin-resistant bacteria: target-accelerated combinatorial synthesis.

Based on the notion that dimerization and/or variation of amino acid 1 of vancomycin could potentially enhance biological activity, a series of synthetic and chemical biology studies were undertaken in order to discover potent antibacterial agents. Herein we describe two ligation methods (disulfide formation and olefin metathesis) for dimerizing vancomycin derivatives and applications of target-accelerated combinatorial synthesis (e.g. combinatorial synthesis in the presence of vancomycin's target Ac2-L-Lys-D-Ala-D-Ala) to generate libraries of vancomycin dimers. Screening of these compound libraries led to the identification of a number of highly potent antibiotics effective against vancomycin-suspectible, vancomycin-intermediate resistant and, most significantly, vancomycin-resistant bacteria.

Anti-Bacterial Agents↗
PubMed2001

Potential role of leptin in angiogenesis: leptin induces endothelial cell proliferation and expression of matrix metalloproteinases in vivo and in vitro.

Leptin, the product of ob gene, is an endocrine hormone that regulates adipose tissue mass. Recently, leptin has been found to generate a growth signal involving a tyrosine kinase-dependent intracellular pathway and promote angiogenic processes via activation of leptin receptor (Ob-R) in endothelial cells. However, it is not clear how leptin functions to promote multi-step processes involved in the neovascularization at the atherosclerotic plaque. We have examined the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) and Ob-R in human atherosclerotic lesions, leptin-mediated angiogenesis in vivo and in vitro. Immunohistochemical analysis of human atherosclerotic aorta revealed an increased expression of Ob-R in the intima of neorevascularized regions and of both MMPs and TIMPs predominantly in the endothelial lining of intimal neovessels and macrophages/foam cells. In the rat corneal angiogenesis assay, leptin elicited a comparable sensitivity of angiogenic activity to those of vascular endothelial growth factor (VEGF). The immunohistological analysis of the leptin-treated rat cornea showed definitive rises in Ob-R, MMPs and TIMPs expression as well as those of VEGF receptor (VEGFR-1). Leptin (10-40 ng/ml) induced proliferation of the human umbilical vein endothelial cells (HUVECs) and elevation of MMP-2, MMP-9, TIMP-1, and TIMP-2 expression in a dose-dependent manner. Leptin also induced increases of MMP-2, MMP-9, TIMP-1, and Up-regulated the human coronary artery smooth muscle cells (HCASMCs). These findings suggest that leptin, a hormone with pluralistic properties including a mitogenic activity on vascular endothelial cells, plays a role in matrix remodeling by regulating the expression of MMPs and TIMPs. Taken together, our findings further provide evidences for leptin's role as an angiogenesis inducer in the normal organ (rat cornea) and in aberrant vasculature under duress like atherosclerosis.

Animals↗
PubMed2001

A novel recombinant basic fibroblast growth factor and its secretion.

Basic fibroblast growth factor (FGF-2) is a pleiotropic mitogen which plays an important role in cell growth, differentiation, migration, and survival in different cells and organ systems. Recently, several clinical applications for FGF-2 gene transfer are being evaluated in wound healing and collateral artery development to relieve myocardial and peripheral ischemia due to the ability of FGF-2 to regulate the growth and function of vascular cells. However, FGF-2 lacks a classical hydrophobic secretion signal peptide, the FGF-2 chimeras containing various signal sequences have been explored. In this study, a novel recombinant 4sFGF-2 was constructed by replacing nine residues from the amino-terminus of native FGF-2 (Met1 to Leu9) with eight amino acid residues of signal peptide of FGF-4 (Met1 to Ala8) to better increase the secretion level of FGF-2. When the recombinant FGF-2 gene, cloned into the expression vector with CMV promoter, was expressed in COS-7 cells, the recombinant 4sFGF-2 was highly secreted into the media. The secreted 4sFGF-2 showed the same biological activity as the native FGF-2 in the dose-response effects on DNA synthesis and cell growth of rat aortic smooth muscle cells (RASMCs) and NIH3T3 cells. The 4sFGF-2 also was able to activate MAPK as wild FGF-2 in RASMCs. These results indicate that a novel recombinant 4sFGF-2 may be useful as clinical applicability of angiogenic growth factor gene transfer.

3T3 Cells↗
PubMed2001

Purification and characterization of a plasmin-like protease from Tenodera sinensis (Chinese mantis).

A novel type of protease (mantis egg fibrinolytic enzyme, MEF-2) was isolated from the egg cases of Tenodera sinensis. The protease was homogeneous by SDS-PAGE and its apparent molecular mass was 32,900 Da. The amino acids in the N-terminal region were Ile-Val-Gly-Gly-Glu-Glu-Ala-Val-Ala-Gly-Asp-Phe-Pro-Ile-Val-Ser-Leu-Gln-Glu. The enzyme was inhibited by PMSF, TLCK, aprotinin, benzamidine, soybean trypsin inhibitor and also slightly by elastatinal, EDTA, EGTA, cysteine and beta-mercaptoethanol, but TPCK, iodoacetate and E-64 did not affect the activity. MEF-2 was not sensitive to alpha(1)-antitrypsin but antithrombin III and alpha(2)-antiplasmin inhibited the enzyme. MEF-2 preferentially cleaved the oxidized B-chain of insulin between Arg(22) and Gly(23). Among chromogenic protease substrates, the most susceptible to MEF-2 hydrolysis was benzoyl-Phe-Val-Arg-p-nitroanilide with maximal activity at 30 degrees C and pH 5.0. These results indicate that MEF-2 belongs to the trypsin family. Upon incubation of crosslinked fibrin with MEF-2, a steady increase of D-dimer suggests that the enzyme has a strong fibrinolytic activity. In conclusion, MEF-2 is a new type of proteolytic enzyme and has some potential for practical application in fibrinolysis.

Amino Acid Sequence↗
PubMed2001

Differences in sensitivity of vanilloid receptor 1 transfected to human embryonic kidney cells and capsaicin-activated channels in cultured rat dorsal root ganglion neurons to capsaicin receptor agonists.

Heterologously expressed vanilloid receptor 1 (VR1), a cloned cDNA encoding for capsaicin (CAP)-sensitive currents, resembles the native CAP channels in cultured sensory neurons in channel property. But, the pharmacological profile of VR1 to various CAP analogs is not known. The stable expression of VR1 in human embryonic kidney (HEK) cells was generated and confirmed by reverse transcription-polymerase chain reaction and Western blots. VR1 expressed in HEK cells retained single-channel properties similar to those of the native channels. When concentration-response relationships were compared, CAP and DA-5018.HCl, a synthetic analog of CAP, exhibited a greater potency in activating VR1 than the native channels in sensory neurons. In contrast, resiniferatoxin and its analog, phorbol 12-phenylacetate 13-acetate 20-homovanillate, was more potent in activating the CAP-activated channels in cultured sensory neurons than VR1. Thus, the difference in pharmacological profiles of VR1 and the native channels suggests the possible presence of subtypes of the CAP receptor or regulatory mechanisms associated with VR1.

Analgesics, Non-Narcotic↗
PubMed2001

A single gene (yes) controls pigmentation of eyes and scales in Heliothis virescens.

A yellow-eyed mutant was discovered in a strain of Heliothis virescens, the tobacco budworm, that already exhibited a mutation for yellow scale, y. We investigated the inheritance of these visible mutations as candidate markers for transgenesis. Yellow eye was controlled by a single, recessive, autosomal factor, the same type of inheritance previously known for y. Presence of the recombinant mutants with yellow scales and wild type eyes in test crosses indicated independent segregation of genes for these traits. The recombinant class with wild type scales and yellow eyes was completely absent and there was a corresponding increase of the double mutant parental class having yellow scales and yellow eyes. These results indicated that a single factor for yellow eye also controlled yellow scales independently of y. This gene was named yes, for yellow eye and scale. We hypothesize that yes controls both eye and scale color through a deficiency in transport of pigment precursors in both the ommochrome and melanin pathways. The unlinked gene y likely controls an enzyme affecting the melanin pathway only. Both y and yes segregated independently of AceIn, acetylcholinesterase insensitivity, and sodium channel hscp, which are genes related to insecticide resistance.

Acetylcholinesterase↗
PubMed2001

Effects of left atrial compliance on left atrial pressure in pure mitral stenosis.

In mitral stenosis (MS), left atrial (LA) pressure is commonly elevated because of increased LA afterload. There is a wide spectrum of LA pressure in patients with MS, however, despite a similar mitral valve orifice area. LA compliance is an important determinant of both cardiovascular performance and pathological physiology. Few data are available, however, regarding the effects of LA compliance on LA pressure. We hypothesized that LA pressure may be higher in patients with decreased LA compliance. We analyzed the right heart and transseptal catheterization data in 47 patients (41 female, mean age 40 +/- 10 years) with pure MS and sinus rhythm. The magnitude of LA a and v waves was measured from transseptal catheterization. Fick's method was used to determine cardiac output. LA compliance was calculated by dividing the systolic rise in LA pressure (DeltaP(LA) = P(LA(v)) - P(LA(x))) into the stroke volume. LA size, mitral valve area (MVA), mean diastolic pressure gradient (MG), left ventricular (LV) end-diastolic and end-systolic dimensions were obtained by using two-dimensional and Doppler echocardiography. Multiple regression analysis was performed to identify independent factors determining LA pressure. The mean MVA was 0.95 +/- 0.22 cm(2). MG and LA dimension were 11.2 +/- 5.2 mm Hg and 50.6 +/- 5.2 mm, respectively. The mean LA pressure and cardiac output obtained by cardiac catheterization were 23.4 +/- 8.4 mm Hg and 4.3 +/- 1.5 L/min, respectively. The calculated LA compliance was 4.9 +/- 2.8 cm(3)/mm Hg. Univariate analysis showed that factors associated with increased LA pressure were smaller MVA (r = -0.33, P < 0.05), higher MG (r = 0.69, P < 0.01) and lower LA compliance (r = -0.55, P < 0.01); among them, MG (beta coefficient 0.59, SE 0.19, P < 0.01) and LA compliance (beta coefficient -0.26, standard error 0.34, P < 0.05) were the strongest predictors of LA pressure. In conclusion, LA compliance, along with MG that reflects the severity of MS, is an important contributing factor determining LA pressure in patients with pure MS and sinus rhythm.

Adult↗
PubMed2001

Clonorchis sinensis: molecular cloning and characterization of 28-kDa glutathione S-transferase.

A 28-kDa glutathione S-transferase (Cs28GST) was purified from a Clonorchis sinensis cytosolic fraction through anion-exchange and glutathione-affinity column chromatographies. A monoclonal antibody raised against Cs28GST reacted specifically to the C. sinensis antigen among trematode proteins. A putative peptide of 212 amino residues deduced from a cDNA clone appeared homologous with 28-kDa GST of trematodes, and its secondary structural elements predicted a GSH-binding site. Recombinant Cs28GST showed GST enzyme activity with CDNB substrate and was sensitive to the model inhibitors. The recombinant Cs28GST was antigenically indistinguishable from the native form and was recognized specifically by C. sinensis-infected human sera. The Cs28GST was localized in the tegument and underlying mesenchymal tissues. It is suggested that Cs28GST may play significant physiological roles against bioreactive molecules and be a useful reagent for serodiagnosis of clonorchiasis.

Amino Acid Sequence↗
PubMed2001

Lesions of the entorhinal cortex impair acquisition of hippocampal-dependent trace conditioning.

Rabbits with the electrolytic lesions of bilateral entorhinal cortex (EC) were trained with the hippocampal-dependent trace conditioning of the nictitating membrane response. The multiple-unit activity of the hippocampal CA1 region was recorded during conditioning. The conditioned stimulus was a tone (1 kHz, 85 dB, 200-ms duration), the unconditioned stimulus was a corneal air puff (3 psi, 150-ms duration), and the interstimulus interval was 750 ms. The EC-lesioned animals showed only 30% conditioned response (CR) by the ninth session while the sham-operated animals showed above 80% CR. The lesioned animals did not show learning-related changes in the hippocampal activity. When the training was switched to the 300-ms interstimulus interval trace conditioning, both groups learned above 80% CR. The EC-lesioned animals, however, showed less learning-related activity in the hippocampus than the sham-operated animals. These results suggest that the development of the learning-related activity in the hippocampus depends on the intact EC, and that the EC may provide a possible pathway conveying learning information from the cerebellum or cerebral cortex to the hippocampus during the trace conditioning.

Animals↗
PubMed2001

Purification and characterization of calobin II, a second type of thrombin-like enzyme from Agkistrodon caliginosus (Korean viper).

In our previous report, we purified and cloned the gene of a thrombin-like enzyme, calobin, from the venom of Agkistrodon caliginosus (Hahn, B.S., Yang, K.Y., Park, E.M., Chang, I.M., Kim, Y. S., 1996. Purification and molecular cloning of calobin, a thrombin-like enzyme from Agkistrodon caliginosus (Korean viper). J. Biochem. 119, 835-843.). During the purification of calobin, a second type of thrombin-like protease was found and it was purified using Affi-Gel Blue and Mono-S cation-exchange chromatography. It was identified as a serine protease with a molecular weight of 41, 000 on SDS-PAGE and its isoelectric point was determined to be 7.4 by isoelectric focusing. It showed little azocaseinolytic and fibrinolytic activity. However, this enzyme acted on fibrinogen to form fibrin with a specific activity of 7,587 NIH equivalent units and also exhibited arginine esterase activity. Amino acid sequencing of the N-terminal region established a primary structure composed of Val-Ile-Gly-Gly-Asp-Glu-Cys-Asn-Ile-Asn-Glu-His-Arg-Phe-Leu-Val-Ala-X -Tyr. This sequence was entirely consistent with that of calobin and showed a high homology with other thrombin-like enzymes, such as ancrod, batroxobin and gyroxin. Based on the biochemical properties such as molecular weight and isoelectric point, we can demonstrate a second thrombin-like protein showing a high potent clotting activity from the venom of Korean viper.

Agkistrodon↗
PubMed2001

STATT: a titrate-to-goal study of simvastatin in Asian patients with coronary heart disease. Simvastatin Treats Asians to Target.

BACKGROUND: Most published studies on the use of lipid-lowering agents to treat hypercholesterolemia have focused on Western populations, with few data on Asian populations. OBJECTIVE: The Simvastatin Treats Asians to Target (STATT) study used a titrate-to-goal protocol to evaluate the efficacy and tolerability of simvastatin 20 to 80 mg/d in the treatment of Asian patients with coronary heart disease. METHODS: This was a multicenter, open-label, uncontrolled, 14-week study in patients with coronary heart disease and serum low-density lipoprotein cholesterol (LDL-C) levels of 115-180 mg/dL and triglyceride levels of < or = 400 mg/dL. The dose of simvastatin was titrated from 20 to 80 mg/d to achieve the National Cholesterol Education Program (NCEP) LDL-C target of < or = 100 mg/dL. The primary efficacy measure was the percentage of patients achieving the NCEP target. Among secondary measures were the percentage of patients achieving European Society of Cardiology/European Atherosclerosis Society/European Society of Hypertension target LDL-C levels of < or = 115 mg/dL and the percentage change from baseline in lipid parameters. Tolerability was assessed in terms of the overall incidence of adverse experiences and the incidences of the most commonly reported adverse experiences. RESULTS: The intent-to-treat analysis included 133 Asian patients (93 men, 40 women; mean age, 59.5 years), of whom 125 completed 14 weeks of therapy. Their mean blood pressure was 130.2/79.4 mm Hg. Overall, 104 (78.2%) patients treated with simvastatin achieved LDL-C levels < or = 100 mg/dL at week 14, and 125 (94.0%) achieved this target at some point during the study. Similarly, 122 (91.7%) patients achieved an LDL-C level < or = 115 mg/dL at week 14, and 130 (97.7%) achieved this target at some point during the study. Treatment with simvastatin had favorable effects on the lipid profile, producing significant percentage changes from baseline in all parameters (P < 0.001). Simvastatin was well tolerated across the dose range. Overall, 40 patients (30.1%) had > or = 1 clinical adverse experience. Only 14 (10.5%) had adverse experiences that were possibly, probably, or definitely related to study drug; none of these experiences were considered serious. The most common adverse experiences (> or = 3% incidence) were abdominal pain (6%); chest pain (5%); dizziness (4%); and asthenia/fatigue, fibromyalgia, headache, insomnia, and upper respiratory tract infection (3% each). No new or unexpected adverse experiences were seen at the higher doses. CONCLUSIONS: Simvastatin was effective and well tolerated at doses of 20, 40, and 80 mg/d in Asian patients with coronary heart disease. Titration enabled the majority to achieve target LDL-C levels of < or = 100 mg/dL.

Aged↗
PubMed2001

Molecular cloning and characterization of a mu-class glutathione S-transferase from Clonorchis sinensis.

In biliary passages, Clonorchis sinensis causes epithelial hyperplasia and is assumed to promote carcinogenesis. Glutathione S-transferase (GST) is an antioxidant enzyme involved in phase II defense in trematodes. A clone (pcsGSTM1) encoding a GST was identified by screening a C. sinensis cDNA library with a PCR-synthesized cDNA probe. The predicted amino acid sequence encoded by pcsGSTM1 cDNA had a high degree of sequence identity and folding topology similar to the mu-class GSTs. The estimated molecular mass of the protein, 26 kDa, was consistent with an expression by pcsGSTM1 cDNA. The bacterially expressed recombinant csGSTM1 protein possessed an enzymatic GST activity and conjugated GSH to reactive carbonyls of lipid peroxidation. The recombinant csGSTM1 protein did not share antigenic epitope(s) with GSTs of Fasciola hepatica, Paragonimus westermani and Schistosoma japonicum. The csGSTM1 was identified to a mu-class GST in C. sinensis.

Amino Acid Sequence↗
PubMed2001

Isolation of neuronal precursors from differentiating P19 embryonal carcinoma cells by neuronal T alpha 1-promoter-driven GFP.

The induction of pluripotent P19 embryonal carcinoma (EC) cells with retinoic acid results in their differentiation into cells that resemble neurons, glia, and fibroblasts. To isolate and enrich the developing neurons from heterogeneously differentiating P19 EC cells, we used a recently introduced protocol combining the expression of green fluorescent protein (GFP) driven by a tissue-specific promoter and fluorescence-activated cell sorting. Cells were transfected with the gene for GFP, which is under the control of the neuronal T alpha 1 tubulin promoter. After four days of retinoic acid treatment, GFP was specifically detected in cells undergoing neuronal differentiation. Sorting of fluorescent differentiating P19 EC transfectants yielded populations highly enriched in neuronal precursors and neurons. Immunoreactivity for nestin and neurofilament was observed in 80 and 25% of the sorted cell population, respectively. These results demonstrate that differentiated neuronal precursor cells can be efficiently isolated from differentiating pluripotent embryonic cells in vitro, suggesting that this method can reproducibly provide homogeneous materials for further studies on neurogenesis.

Antineoplastic Agents↗
PubMed2001

Deficient long-term synaptic depression in the rostral cerebellum correlated with impaired motor learning in phospholipase C beta4 mutant mice.

Long-term depression (LTD) at parallel fibre-Purkinje cell synapse of the cerebellum is thought to be a cellular substrate for motor learning. LTD requires activation of metabotropic glutamate receptor subtype 1 (mGluR1) and its downstream signalling pathways, which invariably involves phospholipase Cbetas (PLCbetas). PLCbetas consist of four isoforms (PLCbeta1-4) among which PLCbeta4 is the major isoform in most Purkinje cells in the rostral cerebellum (lobule 1 to the rostral half of lobule 6). We studied mutant mice deficient in PLCbeta4, and found that LTD was deficient in the rostral but not in the caudal cerebellum of the mutant. Basic properties of parallel fibre-Purkinje cell synapses and voltage-gated Ca2+ channel currents appeared normal. The mGluR1-mediated Ca2+ release induced by repetitive parallel fibre stimulation was absent in the rostral cerebellum of the mutant, suggesting that their LTD lesion was due to the defect in the mGluR1-mediated signalling in Purkinje cells. Importantly, the eyeblink conditioning, a simple form of discrete motor learning, was severely impaired in PLCbeta4 mutant mice. Wild-type mice developed the conditioned eyeblink response, when pairs of the conditioned stimulus (tone) and the unconditioned stimulus (periorbital shock) were repeatedly applied. In contrast, PLCbeta4 mutant mice could not learn the association between the conditioned and unconditioned stimuli, although their behavioural responses to the tone or to the periorbital shock appeared normal. These results strongly suggest that PLCbeta4 is essential for LTD in the rostral cerebellum, which may be required for the acuisition of the conditioned eyeblink response.

Animals↗
PubMed2001

Histo-topographic distribution of acute inflammation of the human umbilical cord.

Acute inflammation of the umbilical cord, acute funisitis, is a sign of fetal inflammatory response, and the clinicopathological need for its identification is increasing. This study was conducted in order to describe the topographic distribution of acute funisitis, and thereby to provide more information on the intrinsic nature of acute funisitis and find a better way of pathologically examining the umbilical cord. A total of 10 umbilical cords affected by acute funisitis were histopathologically examined throughout their entire lengths at 1 mm intervals. Pathological examination was done to characterize the extent of the funisitis, the involvement of the vein (phlebitis) or of one or both arteries (arteritis), and the presence of inflammation in Wharton's jelly. Umbilical cord plasma interleukin (IL)-6 was measured by specific immunoassay to assess whether or not the severity of acute funisitis correlates with fetal cytokine response. It would appear that the inflammatory reaction begins as a discrete, multifocal process which eventually becomes contiguous as the inflammatory reaction proceeds. Umbilical cord plasma IL-6 concentrations tended to correlate with the extent of umbilical cord inflammation. The initial phase of acute funisitis involves discrete and multiple foci along the length of the umbilical cord. Moreover, the extent of acute funisitis reflects the severity of systemic fetal cytokine response. Therefore, adequate sampling using multiple sections would facilitate the identification of acute funisitis. We propose a standard sampling procedure taking one section from each third of the umbilical cord.

Acute Disease↗