Biomedical subjects

I S Park

Publications and source records attributed to I S Park.

At least 19 recordsLinked to original sources

PubMed1998

Thiolated Salmonella antibody immobilization onto the gold surface of piezoelectric quartz crystal.

An improved antibody-coated sensor system based on quartz crystal microbalance analysis on Salmonella spp. was developed making use of thiolated antibody immobilization onto one gold electrode of the piezoelectric quartz crystal surface. The best results in sensitivity and stability were obtained with the thin layer of a thiol-cleavable, heterobifunctional cross-linker, sulfosuccinimidyl 6-[3-(2-pyridyldithio)propionamido]hexanoate (sulfo-LC-SPDP). The long bridge of this reagent could function as a spacer, facilitating antibody-Salmonella interaction on the gold electrode. After the addition of a S. typhimurium suspension into a reaction cell with 0.1 M sodium phosphate buffer, pH 7.2, the resonant frequency decreased conspicuously. The time required for maximum frequency shift was about 30-90 min. Sensor response was observed for the microbial suspensions ranging from 9.9 x 10(5) to 1.8 x 10(8) CFU/ml.

Antibodies, Bacterial↗

PubMed1998

Cell kinetics of surgically induced spinal open neural tube defect in chick embryos.

In an attempt to understand cell kinetics of open neural tube defects (ONTDs) in the embryonic stages, chronological changes of cell proliferation and cell death patterns in the surgically induced spinal ONTDs of chick embryos were investigated using proliferating cell nuclear antigen (PCNA) staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) method. ONTDs were induced at Hamburger and Hamilton stages 17-19. Compared with the control group, the surgery group showed a lower PCNA labeling index for 5 days after surgery and demonstrated more TUNEL-positive cells at 6 h, 3 and 5 days after surgery. Decreased cell proliferation and enhanced apoptosis were seen in the ventral as well as in the dorsal spinal cord. These results partly explain the functional deficits of ONTDs.

Animals↗

PubMed1998

Radiofrequency pulmonary valvotomy using a new 2-French catheter.

We report the usefulness of a new 2-French (F) electrode catheter for perforating the atretic pulmonary valve in patients with pulmonary atresia and intact ventricular septum, using radiofrequency energy. The new 2-F electrode catheter was used in three patients. The first patient, weighing 2.1 kg, with pulmonary atresia and an intact ventricular septum, underwent transcatheter valvotomy at the age of 18 days. Due to massive left ventricular volume overload, the patient required surgical ligation of the ductus arteriosus, but she was discharged uneventfully after that. The second patient, weighing 2.2 kg, had Ebstein's anomaly with pulmonary atresia and an intact ventricular septum. She underwent transcatheter valvotomy at the age of 30 days. Although she was weaned from prostaglandin E1 infusion, she died suddenly (presumed septicemic). A postmortem examination showed a split pulmonary valve. The third patient, weighing 2.3 kg, with pulmonary atresia and an intact ventricular septum, underwent transcatheter valvotomy at the age of 17 days. Prostaglandin E1 infusion was discontinued on the 3rd day after the transcatheter valvotomy and she was discharged uneventfully.

Angiography↗

PubMed1998

NMDA receptor antagonists enhance 5-HT2 receptor-mediated behavior, head-twitch response, in mice.

The purpose of this study was to characterize behavioral interactions between glutamatergic and serotonergic 5-HT2 receptors. Both competitive (AP-5 [D-2-amino-5-phosphovalerate] and D-CPP [3-(2carboxypiperazine-4yl)-propylphosphonate]) and noncompetitive (MK-801 [dizocilpine], ketamine, dextrorphan and dextromethorphan) N-methyl-D-aspartate (NMDA) receptor antagonists markedly enhanced a selective serotonergic behavior, the head twitch response (HTR), in mice. In contrast, NMDA itself inhibited 5-hydroxytryptamine (5-HT)-induced HTR in mice. These results suggest that glutamatergic neurotransmission may modulate serotonergic function at the 5-HT2 receptor.

Animals↗

PubMed1998

Preferential expression of insulin-like growth factor binding proteins-1, -3, and -5 during early diabetic renal hypertrophy in rats.

The renal insulin-like growth factor-I (IGF-I) system has been implicated in the pathogenesis of renal hypertrophy, altered hemodynamics, and extracellular matrix expansion associated with early diabetes. The relative abundance of IGF binding proteins (IGFBPs) in the renal microenvironment may modulate IGF-I actions. However, the precise IGFBPs expressed in the glomerular and tubulointerstitial compartments during diabetic renal growth have not been characterized. In the present study, in situ hybridization studies were performed to examine the expression of IGFBP-1 to -6 messenger RNAs (mRNAs) 3, 7, and 14 days after streptozotocin (STZ) injection in rats. In control, nondiabetic kidneys, all six IGFBP mRNAs were differentially expressed with a predominance of IGFBP-5. The onset of renal hypertrophy in STZ-induced diabetes was associated with a rapid and site-specific induction of IGFBP-1, -3, and -5 mRNAs. In contrast, basal expression of IGFBP-2, -4, and -6 mRNAs was not altered in diabetic rats. IGFBP-5 mRNA expression increased in diabetic glomeruli, cortical, and inner medullary peritubular interstitial cells at days 3, 7, and 14. Although normal glomeruli failed to express IGFBP-3, it was induced concomitantly with IGFBP-5 in diabetic glomeruli and cortical peritubular interstitial cells. IGFBP-1 mRNA levels also increased in cortical tubular cells at each time point tested. Peak induction of IGFBP-3 and -5 was observed at day 3, whereas IGFBP-1 was delayed until day 7. IGFBP-1, -3, and -5 mRNA levels declined by day 14, but remained persistently elevated above control. By immunoperoxidase staining, similar alterations in the pattern of IGFBP-3 and -5 protein expression were observed at each time point. The preferential and site-specific increase in IGFBP-1, -3, and -5 suggest that these IGFBPs may regulate the local autocrine and/or paracrine actions of IGF-I and contribute to the pathogenesis of the early manifestations of diabetic nephropathy.

Animals↗

PubMed1998

Active-site mutants of the VanC2 D-alanyl-D-serine ligase, characteristic of one vancomycin-resistant bacterial phenotype, revert towards wild-type D-alanyl-D-alanine ligases.

BACKGROUND: The rising number of vancomycin-resistant enterococci (VREs) is a major concern to modern medicine because vancomycin is currently the 'last resort' drug for life-threatening infections. The D-alanyl-D-X ligases (where X is an hydroxy or amino acid) of bacteria catalyze a critical step in bacterial cell-wall peptidoglycan assembly. In bacteria that produce glycopeptide antibiotics and in opportunistic pathogens, including VREs, D-, D-ligases serve as switches that confer antibiotic resistance on the bacteria themselves. Peptidoglycans in vancomycin-sensitive bacteria end in D-alanyl-D-alanine, whereas in vancomycin-resistant bacteria they end in D-alanyl-D-lactate or D-alanyl-D-serine. RESULTS: We demonstrate that the selective utilization of D-serine by the Enterococcus casseliflavus VanC2 ligase can be altered by mutagenesis of one of two residues identified by homology to the X-ray structure of the Escherichia coli D-alanyl-Dalanine ligase (DdlB). The Arg322-->Met (R322M) and Phe250-->Tyr (F250Y) ligase mutants show a 36-44-fold decrease in the use of D-serine, as well as broadened specificity for utilization of other D-amino acids in place of D-serine. The F250Y R322M double mutant is effectively disabled as a D-alanyl-D-serine ligase and retains 10% of the catalytic activity of wild-type D-alanyl-D-alanine ligases, reflecting a 6,000-fold switch to the D-alanyl-D-alanine peptide. Correspondingly, the Leu282-->Arg mutant of the wild-type E. coli DdlB produced a 560-fold switch towards D-alanyl-D-serine formation. CONCLUSIONS: Single-residue changes in the active-site regions of D-, D-ligases can cause substantial changes in recognition and activation of hydroxy or amino acids that have consequences for glycopeptide antibiotic efficacy. The observations reported here should provide an approach for combatting antibiotic-resistant bacteria.

Amino Acid Sequence↗

PubMed1998

Transient expression of clusterin (sulfated glycoprotein-2) during development of rat pancreas.

Clusterin has been known to play important roles not only in remodeling damaged tissues, but also in tissue reorganization during embryonic development. In the present study, we have investigated the expression of clusterin in the endocrine pancreas during embryonic development. Although a weak immunoreaction was detected in some pancreatic primordial cells at day 14 of gestation, distinct clusterin expression was identified by immunocytochemistry and Northern blot analysis at the 16th day of gestation. Clusterin-producing cells, which corresponded to insulin-containing cells, accounted for the major portion of the developing islet of Langerhans up to 18 days of gestation. Thereafter, clusterin-producing cells display similar distribution and morphological features to glucagon-producing cells. Clusterin expressed in the pancreas was shown by Western blot analysis to be a disulfide-linked heterodimer of 70 kDa with an alpha-subunit of 32 kDa. During early developmental stages, however, we found that proteolytic internal cleavage of the clusterin molecule occurred from the 18th day of gestation. Only one 70 kDa band on the 16th day and two bands (32 kDa and 70 kDa) on the 18th day of gestation were detected by Western blot analysis even in reducing conditions, while only a single 32 kDa band was detected on the second day after birth. The levels of clusterin mRNA in the pancreas transiently increased from the 16th day of gestation to the second day after birth, during the period when active cellular reorganization takes place to form the classic cellular features of the islet. Among various tissue (kidney, brain, liver, heart, lung and pancreas) the levels of clusterin mRNA were the highest in the pancreas from the 18th day of gestation to the second day after birth. In contrast, the lowest expression was observed in adult pancreatic tissue. The higher expression of clusterin in developing pancreas must indicate its involvement in tissue organization during development.

Animals↗

PubMed1998

Digital infrared thermographic imaging in patients with gastroesophageal reflux disease.

We performed a thermographic study to observe any possible interaction between the esophageal acid perfusion and the temperature changes of skin surface in patients with gastroesophageal reflux disease (GERD). Twenty-seven patients with GERD were categorized as group I(globus symptoms with posterior laryngitis) and group II (heartburn and/or regurgitation symptoms). Patients and 6 healthy volunteers underwent Bernstein test (BT) and digital infrared thermographic imaging (DITI) simultaneously. The positive rate for BT in group I and group II was 22.2% and 55.6%, respectively, and the DITI positive rate was 55.6% for group I and 50.0% for group II. None of healthy control were positive in BT or DITI. All subjects with DITI positive were hypothermic. The overall accordance rate between DITI and BT was 69.7%. All group I patients showed a diffuse type, while in group 11, 4 patients showed diffuse type and 5 patients showed localized type (p<0.05). In patients with DITI (+)/BT (-), 83.3% showed diffuse type, whereas equal numbers of diffuse and localized type were noted in patients with DITI (+)/BT (+). In conclusion, add contact with a sensitive mucosa leads to an activation of the sympathetic nervous system in some patients with GERD, inducing skin surface hypothermia.

Adult↗

PubMed1998

Cytokinetic pattern in the thoracic spinal cord of chick embryos (incubation day 5-13) using PCNA staining and TUNEL method.

For the cytokinetic studies using spinal cords of chick embryos, chronological patterns of cell proliferation and programmed cell death (apoptosis) should be known. Information in the early stages of chick embryos is available while data on later stages are seldom available. To investigate the chronological patterns of cell proliferation and apoptosis in the thoracic spinal cord of normal chick embryos on incubation day 5, 6, 8, 10 and 13 (Hamburger and Hamilton stage 26-40), proliferating cell nuclear antigen (PCNA) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method were used. Cell proliferation was active at the germinal layer on days 5 and 6. It markedly declined on day 8 and became negligible on day 13. TUNEL-positive cells were mainly found in the germinal layer, the ventrolateral part of the mantle layer and the dorsal root ganglion. Compared to PCNA-positive cells, TUNEL-positive cells were sparse, especially after day 10, when only a few positive cells were scattered. These results will be used as a control data for the studies such as an experimental research for neural tube defects.

Animals↗

PubMed1998

Comparative study of bentiromide test and endoscopic retrograde pancreatography in patients with chronic pancreatitis.

We performed a bentiromide test in 25 patients with chronic pancreatitis and 7 normal controls to evaluate pancreatic exocrine function, and compared the test results of patients with their endoscopic retrograde pancreatography(ERP) findings. The cumulative 6-hour recovery rate of para-aminobenzoic acid(PABA) in the urine was significantly lower in patients with chronic pancreatitis(55.8 +/- 24.2%) than in controls(82.0 +/- 10.0%). Among 25 patients with chronic pancreatitis, however, 7 patients showed normal recovery rates of PABA. Pancreatograms of the patients represented 4 mild changes, 5 moderate changes, and 16 marked changes. The average 6-hour recovery rates of PABA of the groups were 56.9 +/- 21.6%, 78.4 +/- 10.5%, and 47.2 +/- 23.7%, respectively. Urinary PABA recovery rates were found subnormal as follows: 3(75%) in the mild changes group; 1(20%) in the moderate changes group; and 14(87.5%) in the marked changes group. We found hardly any correlation between the degree of functional impairment and the changes noted by ERP. These findings suggest that both the pancreatic function test and morphologic study are required to evaluate the degree of functional impairment in patients with chronic pancreatitis.

4-Aminobenzoic Acid↗

PubMed1998

Acute gastroparesis in Duchenne's muscular dystrophy.

Duchenne's muscular dystrophy (DMD) is an X-linked recessive disease. Clinical descriptions of the disorder focus principally on skeletal muscle degeneration. Another manifestation, which involves the gastrointestinal tract, may be fatal. But its prevalence remains undefined. We report here a case of acute gastroparesis associated with Duchenne's muscular dystrophy. In our case, the patient's symptoms were improved by prokinetic agents and timely decompression in life-threatening acute gastric dilatation.

Acute Disease↗

PubMed1998

Induction of apoptosis in colon cancer cells by nonsteroidal anti-inflammatory drugs.

Epidemiological studies have demonstrated that nonsteroidal anti-inflammatory drugs (NSAIDs) decrease the incidence of colon cancer. In addition, NSAIDs reduce the number and size of polyps in patients with familial adenomatous polyposis. The mechanisms of the anti-neoplastic effect of NSAIDs are still far from complete understanding, but one possible mechanism is the induction of apoptosis. Several lines of evidence suggest that NSAIDs-induced apoptosis in colon cancer cells are mediated through the cyclooxygenase (COX)-independent pathway. In this study we explored the mechanism of NSAIDs-induced apoptosis in the colon cancer cell line, HT-29. We confirmed that NSAIDs induce apoptosis in HT-29 cells irrespective of their COX-selectivity. Indomethacin enhanced the expression of p21waf-1 in HT-29 cells. However the expression of apoptosis-related genes such as Fas, bcl-2 and bax was not affected by indomethacin. Intra- and extra-cellular calcium chelators, protein tyrosine kinase (PTK) inhibitor, protein kinase A (PKA) inhibitor and protein kinase C (PKC) inhibitors did not influence indomethacin-induced apoptosis in HT-29 cells. We concluded that NSAIDs-induced apoptosis in colon cancer cells may be independent from signals transducted through [Ca++]i, PTK, PKA, PKC or the expression of apoptosis-related genes. In contrast, our results demonstrating the induction of p21waf-1 transcription by NSAIDs suggest the possible association of NSAIDs-induced apoptosis and cell-cycle control in colon cancer cells.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1997

Bacterial resistance to vancomycin: overproduction, purification, and characterization of VanC2 from Enterococcus casseliflavus as a D-Ala-D-Ser ligase.

The VanC phenotype for clinical resistance of enterococci to vancomycin is exhibited by Enterococcus gallinarum and Enterococcus casseliflavus. Based on the detection of the cell precursor UDP-N-acetylmuramic acid pentapeptide intermediate terminating in D-Ala-D-Ser instead of D-Ala-D-Ala, it has been predicted that the VanC ligase would be a D-Ala-D-Ser rather than a D-Ala-D-Ala ligase. Overproduction of the E. casseliflavus ATCC 25788 vanC2 gene in Escherichia coli and its purification to homogeneity allowed demonstration of ATP-dependent D-Ala-D-Ser ligase activity. The kcat/Km2 (Km2 = Km for D-Ser or C-terminal D-Ala) ratio for D-Ala-D-Ser/D-Ala-D-Ala dipeptide formation is 270/0.69 for a 400-fold selection against D-Ala in the C-terminal position. VanC2 also has substantial D-Ala-D-Asn ligase activity (kcat/Km2 = 74 mM-1min-1).

Bacterial Proteins↗

PubMed1997

Rare variants of divided right ventricle with sequestered apical trabecular component.

The right ventricle may be divided into two or more compartments by various structures in various ways. Rarely, the apical trabecular component may be sequestered from the rest of the right ventricle. We report 4 cases with different underlying lesions that share a common pathology of apical sequestration of the right ventricle resulting in diverse hemodynamic consequences. Case 1 had pulmonary valve stenosis. The apical sequestration of the right ventricle resulted in no significant hemodynamic consequence. Case 2 had multiple defects in the muscular ventricular septum. The volume of left-to-right shunt seemed to be reduced because of the commitment of some of the defects to the sequestered cavity. Case 3 had a large defect in the trabecular septum. As the defect involved the whole septum that was related to the sequestered right ventricular apex, the left ventricle together with the sequestered right ventricle formed a boot-shaped chamber. Hemodynamically, the muscular shelf was an interventricular septum. Case 4 had a coronary artery fistula to an isolated cavity that occupied the apical region of the right ventricle. The pathology was similar to the case that was reported as a five-chambered heart. The abnormal cavity was, in fact, the sequestered right ventricular apex.

Adolescent↗

PubMed1997

D-Alanyl-D-lactate and D-alanyl-D-alanine synthesis by D-alanyl-D-alanine ligase from vancomycin-resistant Leuconostoc mesenteroides. Effects of a phenylalanine 261 to tyrosine mutation.

The Gram-positive bacterium Leuconostoc mesenteroides, ATCC 8293, is intrinsically resistant to the antibiotic vancomycin. This phenotype correlates with substitution of D-Ala-D-lactate (D-Ala-D-Lac) termini for D-Ala-D-Ala termini in peptidoglycan intermediates in which the depsipeptide has much lower affinity than the dipeptide for vancomycin binding. Overproduction of the L. mesenteroides D-Ala-D-Ala ligase (LmDdl) 2 in E. coli and its purification to approximately 90% homogeneity allow demonstration that the LmDdl2 does have both depsipeptide and dipeptide ligase activity. Recently, we reported that mutation of an active site tyrosine (Tyr), Tyr216, to phenylalanine (Phe) in the E. coli DdlB leads to gain of D-Ala-D-Lac depsipeptide ligase activity in that enzyme. The vancomycin-resistant LmDdl2 has a Phe at the equivalent site, Phe261. To test the prediction that a Tyr residue predicts dipeptide ligase while an Phe residue predicts both depsipeptide and dipeptide ligase activity, the F261Y mutant protein of LmDdl2 was constructed and purified to approximately 90% purity. F216Y LmDdl2 showed complete loss of the ability to couple D-Lac but retained D-Ala-D-Ala dipeptide ligase activity. The Tyr-->Phe substitution on the active site omega-loop in D-Ala-D-Ala ligases is thus a molecular indicator of both the ability to make D-Ala-D-Lac and intrinsic resistance to the vancomycin class of glycopeptide antibiotics.

Alanine↗

PubMed1997

D-alanine:D-alanine ligase: phosphonate and phosphinate intermediates with wild type and the Y216F mutant.

The crystallographic structure of the D-alanine:D-alanine ligase of the ddlB gene of Escherichia coli complexed with a D-Ala-D-alpha-hydroxybutyrate phosphonate and the structure of the Y216F mutant ligase complexed with a D-Ala-D-Ala phosphinate have been determined to 2.2 and 1.9 A resolution, respectively, and refined to R factors of 0.156 and 0.158. In each complex the inhibitor has reacted with ATP to produce ADP and a tight-binding phosphorylated transition state intermediate. Comparison of these two structures with the known crystal structure of the phosphinate intermediate of the wild-type ligase shows no major conformational changes, but B factors indicate differences in mobility of loops covering the binding site. The weaker inhibition of the Y216F mutant by both inhibitors is thought to be due in part to the loss of an interloop hydrogen bond. A similar mechanism may account for poor inhibition of VanA, the homologous D-Ala:D-lactate ligase produced by vancomycin-resistant enterococci.

Binding Sites↗

PubMed1997

Effect of erythromycin on gastric emptying in healthy individuals assessed by radio-opaque markers and plasma acetaminophen levels.

We simultaneously recorded gastric emptying of radio-opaque markers (ROMs) and monitored serial changes in plasma acetaminophen (AAP) levels to demonstrate the relationship between the ROM and the AAP methods, and we investigated the effect of a single intravenous dose of erythromycin (EM) on gastric emptying in healthy human subjects. After an overnight fast, subjects were randomized to receive either placebo or EM lactobionate (Abbott, North Chicago, IL, USA) 250 mg intravenously in a single dose, given immediately before a standard meal. Subjects ingested 1.5 g of AAP and ROMs with the test meal. A supine plain abdominal radiograph was taken 1, 2, 3, and 6 h after ingestion of the test meal. Peripheral blood samples were obtained 0, 0.5, 1, 1.5, 2, 3, and 6 h after ingestion of the test meal. EM significantly accelerated gastric emptying of ROMs. By 6 h, no markers remained in the stomach in any of the subjects in the placebo or EM groups. By 120 min, half of the ROMs had passed into the duodenum in 12.5% of subjects after placebo, whereas EM injection resulted in gastric emptying of half of the ROMs in all subjects. There was no difference in plasma AAP concentration between the placebo and EM groups. There were significant correlations between maximum plasma AAP concentration and gastric emptying of ROMs 120 min after ingestion (r = 0.546; P = 0.019), and between time of maximum plasma AAP concentration and gastric emptying of ROMs 120 min after ingestion (r = -0.568; P = 0.014). The time taken to reach the peak concentrations ranged from 30 to 90 min after ingestion, whereas most ROMs were emptied 120 min after ingestion. We conclude that the gastric emptying assessed by ROMs and by serial changes in plasma AAP level are good, non-invasive, clinically applicable tests, with a significant correlation between the two tests. A single intravenous dose of EM had a prokinetic effect on gastric emptying, assessed by ROMs, in healthy human subjects.

Acetaminophen↗

PubMed1997

Role of rebamipide on induction of heat-shock proteins and protection against reactive oxygen metabolite-mediated cell damage in cultured gastric mucosal cells.

Reactive oxygen metabolites (ROM) have been reported to be important in the pathogenesis of ischemia/ reperfusion-, ethanol-, nonsteroidal antiinflammatory drug-, or Helicobacter pylori-induced gastric mucosal injury. Rebamipide, a novel antiulcer agent, has been reported either to prevent various acute experimental gastric mucosal lesions or to accelerate the healing of chronic gastric ulcers. The underlying mechanism by which rebamipide exerts its cytoprotective effect in the damaged stomach is not fully determined. We investigated the role of rebamipide in protecting against ROM-mediated cell damage in gastric mucosal cells and in inducing cytoprotective proteins. Cells were exposed to ROM enzymatically generated by hypoxanthine-xanthine oxidase. Cytotoxicity was quantified by measuring specific 51Cr release from prelabeled cells. ROM caused dose-dependent increase in cytotoxicity and amount of thiobarbituric acid-reactive substances (TBA-RS). ROM-induced cytotoxicity and TBA-RS were dose-dependently decreased by the addition of rebamipide and/or catalase, but not by superoxide dismutase alone. The effects of rebamipide on electric spin resonance signal were investigated. We found that the DMPO spin adduct ESR signal of hydroxyl radicals (DMPO-OH) was significantly attenuated by rebamipide. Western blot analysis showed that induction of heat-shock protein (HSP70) was significantly increased following rebamipide administration in a dose-dependent manner. Based on these results, it is concluded that rebamipide exerted a protective effect on HX-XO-induced gastric mucosal cell cytotoxicity through one or more of the following mechanism(s): (1) inhibition of lipid peroxidation of the cell membrane; (2) hydroxyl radical scavenging activity; and (3) induction of cellular cytoprotective protein such as HSP70.

Alanine↗