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I Park

Publications and source records attributed to I Park.

At least 19 recordsLinked to original sources
PubMed1998

Size characterization of liposomes by flow field-flow fractionation and photon correlation spectroscopy. Effect of ionic strength and pH of carrier solutions.

The effect of ionic strength and pH of carrier solutions on the separation of liposomes by flow field-flow fractionation (flow FFF) has been studied for the determination of accurate vesicle size distribution of liposomes. Retention behaviors of liposomes (PC/PG/cholesterol) are observed in typical buffer solutions (PBS and Tris-HCl) of various ionic strengths as carrier liquids in flow FFF. The average diameters of collected fractions at each flow FFF run are measured by photon correlation spectroscopy (PCS) for the comparison with FFF calculations at corresponding time interval of collected fractions. A reasonable separation of liposomes is observed at I = 0.016 M for both buffer solutions. Retention of liposomes is found to be elongated at ionic strengths higher than an optimum condition found experimentally, but it is shortened at a lower ionic strength due to the electrostatic interaction between the channel wall and the liposomes. Finally, size distributions of liposomes are provided comparing the liposome preparations by flow FFF.

Drug Carriers↗
PubMed1998

Glycopeptide antibiotic resistance genes in glycopeptide-producing organisms.

The mechanism of high-level resistance to vancomycin in enterococci consists of the synthesis of peptidoglycan terminating in D-alanyl-D-lactate instead of the usual D-alanyl-D-alanine. This alternate cell wall biosynthesis pathway is ensured by the collective actions of three enzymes: VanH, VanA, and VanX. The origin of this resistance mechanism is unknown. We have cloned three genes encoding homologs of VanH, VanA, and VanX from two organisms which produce glycopeptide antibiotics: the A47934 producer Streptomyces toyocaensis NRRL 15009 and the vancomycin producer Amycolatopsis orientalis C329.2. The predicted amino acid sequences are highly similar to those found in VRE: 54 to 61% identity for VanH, 59 to 63% identity for VanA, and 61 to 64% identity for VanX. Furthermore, the orientations of the genes, vanH, vanA, and vanX, are identical to the orientations found in vancomycin-resistant enterococci. Southern analysis of total DNA from other glycopeptide-producing organisms, A. orientalis 18098 (chloro-eremomycin producer), A. orientalis subsp. lurida (ristocetin producer), and Amycolatopsis coloradensis subsp. labeda (teicoplanin and avoparcin producer), with a probe derived from the vanH, vanA, and vanX cluster from A. orientalis C329.2 revealed cross-hybridizing DNA in all strains. In addition, the vanH, vanA, vanX cluster was amplified from all glycopeptide-producing organisms by PCR with degenerate primers complementary to conserved regions in VanH and VanX. Thus, this gene sequence is common to all glycopeptide producers tested. These results suggest that glycopeptide-producing organisms may have been the source of resistance genes in vancomycin-resistant enterococci.

Actinobacteria↗
PubMed1998

[Catheter intervention for adult congenital heart diseases].

The efficacy of catheter intervention for adult congenital heart diseases was evaluated in 27 patients aged 20 to 52 years (mean age at catheterization 25 +/- 7 years) from 1986 to 1996. Four patients had pulmonary valve stenosis, four had aortic valve stenosis, three had coarctation of the aorta, 10 had pulmonary artery stenosis, four had cyanotic heart diseases and aorto-pulmonary collateral arteries, one had patent ductus arteriosus, and one had cyanotic heart disease and stenotic Blalock-Taussig shunt. Balloon dilation was successful in all patients with pulmonary valve stenosis, and follow-up evaluation (1-8 years) showed no restenosis in any patients. Balloon dilation was successful in all patients with aortic valve stenosis, and follow-up evaluation (0.5-5 years) showed transvalvular pressure gradient < 50 mmHg. Stenosis was relieved successfully in all patients with coarctation of the aorta, and follow-up evaluation showed no restenosis. Balloon dilation was successful in eight of 13 locations (62%) in patients with pulmonary artery stenosis. Coil embolization was successful in all patients with cyanotic heart diseases and aortopulmonary collateral arteries. In a patient with patent ductus arteriosus, two coils were placed in the ductus arteriosus but were retrieved because hemolysis was observed after the embolization. These data indicate that catheter intervention in young adults with congenital heart diseases is as effective as in children.

Adult↗
PubMed1997

Diamond-dusted silicone cannula for epiretinal membrane separation during vitreous surgery.

PURPOSE: To report a diamond-dusted silicone cannula as a tool for membrane separation during vitreous surgery. METHODS: A diamond-dusted silicone cannula was fashioned from flexible silicone tubing with a beveled tip and coated with diamond fragments for use during vitreous surgery. RESULTS: The instrument was used successfully in seven eyes with idiopathic macular hole and was found to be particularly useful for removing residual vitreous cortex and epiretinal membranes from around the hole. It was also effective in removing "immature membranes" in three eyes with proliferative vitreoretinopathy. CONCLUSION: The diamond-dusted silicone cannula is a useful tool for removing thin epiretinal membranes and vitreous cortex that may be difficult or nearly impossible to remove safely using other techniques.

Catheterization↗
PubMed1997

Prognostic markers of intravesical bacillus Calmette-Guérin therapy for multiple, high-grade, stage T1 bladder cancers.

BACKGROUND: Prediction of a response to intravesical bacillus Calmette-Guérin (BCG) therapy for bladder cancer is clinically important. We determined whether several molecular markers have prognostic value in intravesical BCG therapy for multiple, high-grade, stage T1 bladder cancers. METHODS: The expressions of p53 (clone D07), bcl-2 (100-D5), cathepsin-D (C5), c-myc(9E11), c-erbB-2 (CB11) and Ki-67 (MM1) were determined by immunohistochemistry in paraffin-embedded tissues from 32 multiple, T1, grade II-III bladder cancer patients (15 BCG responders, 17 nonresponders) who had undergone a single course of BCG therapy (Pasteur strain, 5 x 10(8) CFU weekly for 6 weeks) after complete removal of the tumors. The association between the expression of these markers and the response to BCG was assessed by univariate and multivariate analyses. RESULTS: There was no difference in patient and tumor characteristics between the 2 groups. Using multivariate analysis, the only useful marker was p53, with the overexpression of the p53 protein inversely related to the response to BCG therapy (P = 0.0182). CONCLUSION: Our results suggest that the status of p53 expression offers significant clinical information and may be a useful tool in the selection of suitable candidates for BCG therapy in multiple, high-grade stage T1 bladder cancer patients.

Adjuvants, Immunologic↗
PubMed1996

Deoxycytidine kinase and deoxyguanosine kinase of Lactobacillus acidophilus R-26 are colinear products of a single gene.

Three of the four deoxynucleoside kinases required for growth of Lactobacillus acidophilus R-26 exist as heterodimeric pairs specific for deoxyadenosine (dAK) and deoxycytidine (dCK) or dAK and deoxyguanosine (dGK). However, only two tandem genes, dak/dgk, are found, and are expressed only as dAK/dGK in transformed Escherichia coli. Sequencing peptides spanning 63% of the native dCK subunit revealed a sequence identical to that deduced from dgk (beginning MTVIVL...), except that dCK lacks residues 2 and 3 (dCK is M..IVL; dGK is .TVIVL). Also, mass spectrometry indicates that native dCK and dGK subunits are identical in mass adjusted for the first three residues. Furthermore, the native enzymes have identical isoelectric pH values, indicating an equal number of charged residues. To enable E. coli to express peptide having the native dCK sequence, codons 2 and 3 were deleted from the dgk portion of the tandem genes, resulting in expression of protein having the specificities and regulatory properties of native dAK/dCK, including heterotropic stimulation of dAK activity by deoxycytidine or dCTP (not deoxyguanosine or dGTP) and end-product inhibition of the respective activities by dATP and dCTP. Subcloning normal and mutant dgk yielded homodimeric dGK and dCK, respectively. The dCK homodimer strongly resembles human dCK, with a low K(m) for deoxycytidine, the ability to phosphorylate deoxyadenosine and deoxyguanosine at much higher K(m) values, and end-product inhibition by dCTP. Thus two distinct and specific enzymes evidently are derived from a single Lactobacillus gene. The mechanism by which this occurs in vivo has yet to be elucidated.

Amino Acid Sequence↗
PubMed1996

Mutational analysis of RNA structures and sequences postulated to affect 3' processing of M1 RNA, the RNA component of Escherichia coli RNase P.

When the rnpB gene encoding M1 RNA, the RNA component of Escherichia coli RNase P, is transcribed, the primary M1 RNA transcript (pM1 RNA) is produced and subsequently processed at the 3' end to generate the mature M1 RNA. To study features of pM1 RNA thought to be involved in RNA processing, systematic mutations were introduced in sequence elements and secondary structures surrounding the processing site using p23 RNA, a truncated pM1 RNA transcribed from the internally deleted rnpB gene, as a model substrate and the processing of its mutant derivatives was analyzed in vivo and in vitro. Neither the alteration of two bases forming the processing site nor the disruption of secondary structures surrounding the site significantly affected the processing efficiency although the secondary structures were required for maintaining RNA stability. In contrast, mutations at the rne-dependent site, GAUUU, immediately 3' to the processing site inhibited the processing and the extent of the inhibition varied with the altered sequences. Furthermore, the processing of the mutants of the rne-dependent site as well as wild-type p23 RNA was inhibited in an E. coli rnets strain at the nonpermissive temperature.

Base Sequence↗
PubMed1996

A congenitally "poor" pulmonary artery is a major reason for exclusion from Fontan operation.

We reviewed the clinical records of 185 patients who were possible candidates for Fontan operation. We did this to clarify whether all patients with suitable anomalies ultimately underwent a Fontan operation. Of the 152 patients with decreased pulmonary blood flow, 38 (26%) did not fulfill the criteria for Fontan operation, and 17 of the 33 patients (52%) with increased pulmonary blood flow (P < 0.01) were excluded as candidates. Of 48 non-candidate survivors, 19 had high pulmonary artery (PA) pressure or resistance and small PA (which we term "poor PA"), 17 had pulmonary hypertension, 6 had a markedly distorted PA, and 6 had severe ventricular dysfunction. A significant proportion of possible candidates with a suitable anomaly ultimately did not undergo a Fontan operation, because of "poor PA", a congenital condition that precluded Fontan operation.

Adolescent↗
PubMed1996

Stimulation of renin secretion by the phosphodiesterase IV inhibitor rolipram.

It is now generally accepted that the renin secretory response to beta adrenoceptor stimulation is mediated by increased formation of cAMP in the juxtaglomerular cells. It is also known that renin secretion is increased when cAMP metabolism is decreased by phosphodiesterase inhibitors such as theophylline, but it is not known which isoforms of phosphodiesterase are involved. In the present study, we investigated the effect on renin secretion of the phosphodiesterase IV inhibitor rolipram in conscious rabbits. The i.v. administration of rolipram in a dose of 25 microgram/kg followed by infusion at 5 microgram/kg/min in eight rabbits increased mean arterial pressure from 82 +/- 5 to 93 +/- 6 mm Hg (P<.05), decreased HR from 242 +/- 7 to 204 +/- 10 bpm (P<.05) and increased plasma renin activity (PRA) from 6.9 +/- 1.3 to 29.0 +/- 4.2 ng/ml/2 h (P<.01). In a second series of experiments, i.v. infusion of isoproterenol at 0.05 microgram/kg/min increased PRA from 4.1 +/- 0.9 to 9.9 +/- 1.2 ng/ml/2 h (P<.01). Administration of rolipram again increased PRA, and infusion of isoproterenol in the presence of rolipram increased PRA from 30.2 +/- 7.0 to 58.9 +/- 12.6 ng/ml/2 h (P<.01), an increase significantly greater (P<.05) than that produced by isoproterenol alone. Rolipram also prolonged the PRA and HR responses to isoproterenol. These results demonstrate that inhibition of phosphodiesterase IV increases renin secretion and potentiates the renin secretory response to beta adrenoceptor stimulation, thus providing evidence for a role of phosphodiesterase IV in the regulation of renin secretion.

Animals↗
PubMed1996

[Common atrium].

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Diagnosis, Differential↗
PubMed1995

Phosphotyrosine-independent binding of a 62-kDa protein to the src homology 2 (SH2) domain of p56lck and its regulation by phosphorylation of Ser-59 in the lck unique N-terminal region.

A previously undescribed 62-kDa protein (p62) that does not contain phosphotyrosine but, nevertheless, binds specifically to the isolated src homology 2 (SH2) domain of p56lck has been identified. The additional presence of the unique N-terminal region of p56lck prevents p62 binding to the SH2 domain. However, phosphorylation at Ser-59 (or alternatively, its mutation to Glu) reverses the inhibition and allows interaction of the p56lck SH2 domain with p62. Moreover, p62 is associated with a serine/threonine kinase activity and also binds to ras GTPase-activating protein, a negative regulator of the ras signaling pathway. Thus, phosphotyrosine-independent binding of p62 to the p56lck SH2 domain appears to provide an alternative pathway for p56lck signaling that is regulated by Ser-59 phosphorylation.

Amino Acid Sequence↗
PubMed1995

Kinetic mechanism and end-product regulation of deoxyguanosine kinase from beef liver mitochondria.

Initial-rate kinetic measurements with the affinity purified 2-deoxyguanosine (dGuo) kinase from beef liver mitochondria yielded reciprocal plots which converged on the abscissa, with either dGuo or ATP as the varied substrate. The limiting Km for dGuo was 4.7 microM, and that for ATP was 780 microM. One product, dGMP, was competitive with both substrates, while the other, ADP, was competitive with ATP and non-competitive with dGuo. Qualitatively identical results were obtained with an alternative substrate, dTTP, and with alternative product inhibitors, dIMP and dTDP. These results are consistent with a random Bi Bi kinetic mechanism, judging from the formation of a dead-end complex of the enzyme, dGuo and ADP. dGTP competes very strongly with ATP (Ki = 0.03 microM), but is non-competitive towards dGuo. The more weakly-bound dGDP is competitive with both substrates.

Animals↗
PubMed1995

Extraction of extracellular L-asparaginase from Candida utilis.

L-Asparaginase was extracted from Candida utilis cells using various reducing agents, 2-mercaptoethanol, dithiothreitol, or cysteine. The extraction of the enzyme depended upon the kind and concentration of reducing agents, temperature, time of incubation, and pH of buffer used. The enzyme was typically extracted by incubating the cells at 50 degrees C for 4 h in extraction solution containing 20 mM 2-mercaptoethanol in 20 mM potassium phosphate buffer (pH 7.0). The enzyme can be extracted from either cell precipitate or cell culture broth. The yeast cells were viable after extraction of L-asparaginase.

Asparaginase↗
PubMed1994

Asynchronous volume changes of the two ventricles after Fontan operation in patients with a biventricular heart.

Coordinated contraction of the ventricle is an important determinant of pump function, which seems to be particularly important in Fontan circulation with one pumping ventricle. We analyzed the synchronism of contraction of the two ventricles in 11 patients with a biventricular heart who had undergone Fontan operation. Curves representing ventricular volume changes in a cardiac cycle measured on angiograms were smoothed and divided into 20 segments. We calculated the number of segments of the same directional volume changes (synchronous changes) between the two ventricles (synchronous ratio). We also calculated the total volume of the two ventricles (the two as one whole ventricle) by adding their volumes in each segment and calculated the ratio (stroke volume ratio) of the aortic stroke volume from the whole ventricle to the sum of stroke volumes of the morphological right and left ventricles. If the two ventricles ejected the blood in a completely synchronous manner, these ratios should be 1.0. In seven patients with synchronous ratios of 0.75 or greater and a stroke volume ratio of greater than 0.95, the cardiac index was 3.2 +/- 0.3 l/min/m2, the maximum total volume (corresponding to end-diastolic volume) was 106 +/- 45% normal, and the ejection fraction was 0.44 +/- 0.10. In four patients with ratios of less than 0.70 and 0.95, respectively, the parameters were 2.4 +/- 0.5 (P < 0.05), 193 +/- 92%, and 0.33 +/- 0.08, respectively. The synchronous ratio was inversely correlated with cardiac output. In conclusion, synchronism of the cardiac cycle of the two ventricles affects Fontan circulation in patients with a biventricular heart.

Adolescent↗
PubMed1994

A sibship with recurrent Kawasaki disease and coronary artery lesion.

Although epidemiologic studies of Kawasaki disease suggest an infectious etiology, the cause of this mysterious disease remains unclear. We describe the occurrence of five episodes of Kawasaki disease over a six-year period in three siblings. Two of the three children experienced recurrent Kawasaki disease and developed coronary artery lesions, which included giant coronary artery aneurysms in the youngest child. The non-contemporaneous occurrence of the disease in these three children emphasizes the importance of a genetic basis and/or environmental factors in the etiology of Kawasaki disease.

Child, Preschool↗
PubMed1994

Prediction of quality of life at long-term follow-up after Fontan operation by scoring risk factors.

Many factors will determine the quality of life at long-term follow-up after the Fontan operation. We tried to predict the long-term outcome of modified Fontan operation based on the combined assessment of various preoperative data. The preoperative condition was evaluated by a scoring system in which multilevel scores (from zero to 8 points) were given to a total of 14 morphological and physiological factors according to the contribution of each factor to mortality. The major factors were the association of the extracardiac total anomalous pulmonary venous connection, pulmonary arterial vascular resistance, mean pulmonary arterial pressure, PA index, ejection fraction of the main ventricle, and creatinine clearance. Points for each factor were determined according to surgical mortality, with zero points indicating no increased risk. The total score, i.e., the sum of the points for each item, in each patient was analyzed in relation to the patient's quality of life over a long-term follow-up, as evaluated by questionnaires. Twenty-six of 29 patients with scores of 5 or less showed normal or almost normal life long after the operation, whereas 5 of 10 with higher scores had restricted physical and daily activity. In conclusion, good preoperative condition predicts a good quality of life long after the Fontan operation. In addition, the concept of taking into account all possible risk factors as a comprehensive indicator may be useful in predicting long-term results.

Adolescent↗
PubMed1993

Phosphorylation of Ser-42 and Ser-59 in the N-terminal region of the tyrosine kinase p56lck.

Ser-42 and Ser-59 in the N-terminal region have been identified as the major phorbol ester-induced phosphorylation sites of p56lck. Phosphorylation of Ser-59 results in a gel shift from 56 kDa to 61 kDa. Simultaneous phosphorylation of Ser-42 and Ser-59 results in a further gel shift to 63 kDa. In vitro kinase assays show that Ser-59 can be uniquely phosphorylated by mitogen-activated protein kinase and that Ser-42 can be phosphorylated by either protein kinase A or protein kinase C.

Amino Acid Sequence↗