PubMed Health⌕ Search

Biomedical subjects

Y D Park

Publications and source records attributed to Y D Park.

At least 19 recordsLinked to original sources
PubMed2005

Characterization of a pollen-preferential gene, BAN102, from Chinese cabbage.

We isolated and characterized a pollen-preferential gene, BAN102, from Chinese cabbage and analyzed the activity of its promoter. There were three or four copies of the BAN102 gene in the Chinese cabbage genome that specifically expressed in pollen and pollen tube. There were 2137 bp of BAN102 genomic clone comprising 186 bp of protein coding region, and 1178 bp of 5' and 773 bp of 3' non-coding regions. TATA box were located at 1071 nt of the promoter region while the polyadenylation signal and polyadenylation site were at 1470 and 1486 nt of the 3' non-coding region. BLAST search of BAN102 sequence showed that coding region of BAN102 gene was the greatest percent similarity with arabinogalactan protein (AGP23) gene from Arabidopsis thaliana. Promoter analysis using GUS gene as a reporter showed that the pollen-specificity of BAN102 resided within the -112 to -44 bp of proximal promoter from the transient expression in tobacco and Chinese cabbage plants.

Base Sequence↗
PubMed2002

Reduction of spin injection efficiency by interface defect spin scattering in ZnMnSe/AlGaAs-GaAs spin-polarized light-emitting diodes.

We report the first experimental demonstration that interface microstructure limits diffusive electrical spin-injection efficiency across heteroepitaxial interfaces. An inverse correlation be-tween spin-polarized electron injection efficiency and interface defect density is demonstrated for ZnMnSe/AlGaAs-GaAs spin-polarized light-emitting diodes that exhibit quantum well spin polarizations up to 85%. A theoretical treatment shows that the suppression of spin injection due to interface defects results from the contribution of the defect potential to the spin-orbit interaction, which increases the spin-flip scattering.

Journal Article↗
PubMed2002

Pathophysiology of altered consciousness during seizures: Subtraction SPECT study.

BACKGROUND: The mechanisms underlying altered consciousness during seizures are poorly understood. Previous clinicopathologic studies suggest a role for the thalamus and upper brainstem in consciousness mechanisms. OBJECTIVE: To examine blood flow changes associated with altered consciousness during seizures. METHODS: Seventy-one patients with epilepsy who underwent video-EEG monitoring and ictal/interictal SPECT were studied. Patients were divided into three groups depending on their conscious state during seizures: 1) complete impairment of consciousness (CI), 2) no impairment of consciousness (NI), or 3) uncertain impairment of consciousness (UI). The distribution of blood flow changes during these seizures was assessed by subtraction (ictal - interictal) SPECT co-registered to MRI. Conscious state was assessed in relation to secondary ictal hyperperfusion in subcortical regions (i.e., thalamus and upper brainstem). RESULTS: Impairment of consciousness showed a strong association with secondary hyperperfusion in the thalamic/upper brainstem region (p = 0.01), occurring in 92% (45/49) of CI, 69% (9/13) of UI, and 11% (1/9) of NI. CONCLUSIONS: These findings are consistent with a role for the thalamus and upper brainstem in consciousness mechanisms. The authors suggest that the spread of epileptic discharges or a trans-synaptic activation (diaschisis) of these structures is an important mechanism in the alteration of consciousness during seizures. Variance in the results may be due to differences in timing of radioisotope injection, sensitivity of the subtraction SPECT technique, and the ability to clinically assess the conscious state.

Adolescent↗
PubMed2002

A group-IV ferromagnetic semiconductor: MnxGe1-x.

We report on the epitaxial growth of a group-IV ferromagnetic semiconductor, Mn(x)Ge(1-x), in which the Curie temperature is found to increase linearly with manganese (Mn) concentration from 25 to 116 kelvin. The p-type semiconducting character and hole-mediated exchange permit control of ferromagnetic order through application of a +/-0.5-volt gate voltage, a value compatible with present microelectronic technology. Total-energy calculations within density-functional theory show that the magnetically ordered phase arises from a long-range ferromagnetic interaction that dominates a short-range antiferromagnetic interaction. Calculated spin interactions and percolation theory predict transition temperatures larger than measured, consistent with the observed suppression of magnetically active Mn atoms and hole concentration.

Journal Article↗
PubMed2001

Negative regulation of filamentous growth and flocculation by Lkh1, a fission yeast LAMMER kinase homolog.

We have isolated a full-length cDNA clone that encodes for a Schizosaccharomyces pombe homolog of the dual-specificity protein kinase of the LAMMER family, lkh1 (lammer kinase homolog). The proposed Lkh1 protein contains 575 amino acids. The lkh1(+) null mutant is viable, but exhibits flocculation upon reaching stationary phase in liquid media and filamentous adhesion growth on solid media. Analysis of the flocculation activity of the lkh1(+) null mutant indicates that asexual aggregation of S. pombe cells into floccules is divalent cation-dependent and galactose-specific. We also demonstrate that the Saccharomyces cerevisiae LAMMER kinase homolog, Kns1, can substitute for the Lkh1 function in S. pombe.

Amino Acid Sequence↗
PubMed2001

Unfolding and inactivation of fatty acid synthase from chicken liver during urea denaturation.

The inactivation and conformational changes of the multifunctional fatty acid synthase (acyl-CoA:malonyl-CoA C-acyltransferase (decarboxylating, oxoacyl- and enoyl-reducing and thioester-hydrolyzing), EC 2.3.1.85) from chicken liver have been studied in urea solution. The results show that complete inactivation of the fatty acid synthase occurs before obvious conformational changes with regard to the overall, beta-ketoacyl reduction and acetoacetyl-CoA reduction reactions. Significant conformational changes indicated by the changes of the intrinsic fluorescence emission and the circular dichroism spectra occurred at higher urea concentrations. The kinetic rate constants for the two phase inactivation and unfolding reactions were measured and semilogarithmic plots of the activity versus time gave curves which could be resolved into two straight lines, indicating that both the inactivation and unfolding processes consisted of fast and slow phases as a first-order reaction. The results from Lineweaver-Burk plots indicated that urea is a competitive inhibitor for acetyl-CoA and malonyl-CoA, with K(m) increasing with increasing urea concentrations. However, urea is a noncompetitive inhibitor for NADPH, the substrate of the overall reaction and beta-ketoacyl reduction reaction, and acetylacetate, the substrate of the beta-ketoacyl reduction reaction. Activation by low concentrations of urea was observed although this activation was only temporarily induced in an early stage of inactivation. The aggregation phenomenon of the fatty acid synthase in a certain concentration range of urea (3-4 M) was also observed during unfolding. This result shows that this multifunctional enzyme unfolds with competition with misfolding in the folding pathway. Comparison of inactivation and conformational changes of the enzyme as well as aggregation imply that unfolding intermediates may exist during urea denaturation. The possible unfolding pathway of fatty acid synthase is also discussed in this paper.

Animals↗
PubMed2001

Reactivation and refolding of rabbit muscle creatine kinase denatured in 2,2,2-trifluoroethanol solutions.

The unfolding and refolding of creatine kinase (ATP:creatine N-phosphotransferase (CK), EC 2.7.3.2) during denaturation and reactivation by trifluoroethanol (TFE) have been studied. Significant aggregation was observed when CK was denatured at TFE concentrations between 10% and 40% (v/v). 50% TFE (v/v) was used to study the denaturation and unfolding of CK. The activity loss of CK was a very quick process, as was the marked conformational changes during denaturation followed by fluorescence emission spectra and far-ultraviolet CD spectra. DTNB modification and size exclusion chromatography were used to find that CK dissociated and was in its monomer state after denaturation with 50% TFE. Reactivation and refolding were observed after 80-fold dilution of the denatured CK into 0.05 M Tris-HCl buffer, pH 8.0. The denatured CK recovered about 38% activity following a two phase course (k(1)=4.82+/-0.41x10(-3) s(-1), k(2)=0.60+/-0.01x10(-3) s(-1)). Intrinsic fluorescence maximum intensity changes showed that the refolding process also followed biphasic kinetics (k(1)=4.34+/-0.27x10(-3) s(-1), k(2)=0.76+/-0.02x10(-3) s(-1)) after dilution into the proper solutions. The far-ultraviolet CD spectra ellipticity changes at 222 nm during the refolding process also showed a two phase course (k(1)=4.50+/-0.07x10(-3) s(-1), k(2)=1.13+/-0.05x10(-3) s(-1)). Our results suggest that TFE can be used as a reversible denaturant like urea and GuHCl. The 50% TFE induced CK denaturation state, which was referred to as the 'TFE state', and the partially refolded CK are compared with the molten globule state. The aggregation caused by TFE during denaturation is also discussed in this paper.

Animals↗
PubMed2001

Intensification of chemotherapy using block therapies as consolidation and reinduction therapies for acute lymphoblastic leukemia during childhood.

Between April 1994 and March 1997, 143 children (age range, 1-15 years) with newly diagnosed acute lymphoblastic leukemia (ALL), except for those patients with t(9;22), were treated according to protocol-94 of the Osaka Childhood Leukemia Study Group. In this trial, the intensity of chemotherapy was enforced in the consolidation and reinduction phases by introducing AML-type block therapies consisting of concentrated administration of 4 to 6 drugs during 5 or 6 days. For patients in the higher risk groups, rotational combination chemotherapy was introduced following the early phase. A total of 124 children with B-cell precursor ALL (B-pre ALL) were classified into 3 groups, the ultrahigh-risk group (UHRG) (15 patients), the high-risk group (HRG) (61 patients), or the standard-risk group (SRG) (48 patients), based on age. leukocyte count, immunophenotype, central nervous system leukemia, response to treatment, and selected chromosomal abnormalities. The complete remission rate was 93%, and the 6-year event-free survival (EFS) rate was 79%+/-4%. EFS rates for the UHRG, HRG, and SRG groups were 67%+/-12%, 80%+/-6%, and 81%+/-6%, respectively. Nineteen patients with T-cell ALL were treated with the protocol for the UHRG. Thirteen patients (68%) attained complete remission, and the 6-year EFS rate was 55%+/-12%. Thus, intensification of chemotherapy improved the EFS rate and AML-type block therapies appeared to be effective as the consolidation and reinduction therapies for B-pre ALL.

Adolescent↗
PubMed2001

Upshaw-Schulman syndrome revisited: a concept of congenital thrombotic thrombocytopenic purpura.

Upshaw-Schulman syndrome (USS) is a congenital bleeding disorder characterized by repeated episodes of thrombocytopenia and microangiopathic hemolytic anemia that respond to infusions of fresh frozen plasma. Inheritance of USS has been thought to be autosomal recessive, because 2 siblings in the same family are often affected but their parents are asymptomatic. Recently, chronic relapsing thrombotic thrombocytopenic purpura (CR-TTP), reported almost exclusively in adults, was shown to be caused by inherited or acquired deficiency in the activity of a plasma von Willebrand factor-cleaving protease (vWF-CPase). The pathogenesis of USS is unknown, and a relationship between CR-YEP and USS has not been reported. We studied 3 unrelated USS patients (ST, SY, and KI) who presented with severe indirect neonatal hyperbilirubinemia. All 3 patients had undetectable vWF-CPase activity, and the inhibitors to vWF-CPase were all negative. In their parents with no clinical symptoms, vWF-CPase activities as a percentage of control samples (mother/father) were 17/20 for ST, 60/45 for SY, and 36/5.6 for KI. Thus, USS and vWF-CPase activity appear to be coinherited as autosomal recessive traits. Transfusion of fresh frozen plasma in 2 patients (ST and SY) resulted in the expected maximal increment of approximately 7% to 8% in vWF-CPase activity at 1 to 4 hours, but the levels became less than 3% within 2 days. After this decrease, platelet counts increased, plateaued in the normal range at 10 to 12 days, and declined thereafter. Thus, the 2 to 3 weeks of therapeutic benefit from plasma infusions will be discussed in relation to the intravascular lifetime of vWF-CPase.

ADAM Proteins↗
PubMed2001

Effects of Korean red ginseng and its mixed prescription on the high molecular weight dextran-induced blood stasis in rats and human platelet aggregation.

This study was undertaken to evaluate the antithrombotic effects of Korean Red Ginseng (KRG) and its new prescription (KRGP) consisting of five herbs such as Korean red ginseng, Ganoderma, Cinnamomi Cortex, Glycyrrhizae Radix and Laminaria. In rats with blood stasis induced by high molecular weight dextran, KRG and KRGP significantly restored not only the number of platelets and fibrinogen, but also suppressed the fibrin degradation products (FDP) to normal range. In platelet aggregation assay with human platelet rich plasma (PRP), KRG and KRGP significantly inhibited thrombin and collagen-induced platelet aggregation. The IC(50) values of KRG and KRGP were >2 and 0.23+/-0.01 mg/ml for thrombin, 0.32+/-0.01 and 0.17+/-0.02 mg/ml for collagen and 0.72+/-0.25 and >2 mg/ml for ADP, respectively. In coagulation assay, KRG and KRGP significantly prolonged activated partial prothrombin time (APPT) and prothrombin time (PT) as compared with control data. KRGP was found to be more effective than KRG alone on antithrombotic activity. These results suggest that KRGP may exert its antithrombotic activity due to inhibition of platelet aggregation and coagulation activity more than KRG.

Animals↗
PubMed2001

Aggregation of creatine kinase during refolding and chaperonin-mediated folding of creatine kinase.

The course of refolding and reactivation of urea-denatured creatine kinase (ATP; creatine N-phosphotransferase, EC 2.7.3.2) has been studied in the absence and presence of molecular chaperonin GroEL. The enzyme was denatured in Tris--HCl buffer containing 6 M urea for 1 h. In the refolding studies, the denatured enzyme was diluted 60-fold into the same buffer containing GroEL or not for activity, turbidity, fluorescence measurements and polyacrylamide gel electrophoresis. The results show that the reactivation process is dependent of creatine kinase concentration in the concentration range 2.5--4 microM. The levels of activity recovery decrease with increasing enzyme concentration because of the formation of wrong aggregates. The molecular chaperonin GroEL can bind the refolding intermediate of creatine kinase and thus prevent the formation of wrong aggregates. This intermediate is an inactive dimeric form that is in a conformation resembling the 'molten globule' state.

Animals↗
PubMed2001

Reactivation kinetics of guanidine hydrochloride-denatured creatine kinase measured using the substrate reaction.

Guanidine hydrochloride-denatured creatine kinase (CK) can very quickly form a dimer with reactivity when the denaturant is diluted into the reaction system in the presence of DTT or EDTA. Tsou's method and its applied equation [Tsou (1988), Adv. Enzymol. Rel. Areas Mol. Biol. 61, 381-436; Yang and Zhou (1998), Biochim. Biophys. Acta 1388, 190-198] were used to measure the kinetic reactivation rate constants and the reactivation degree for reassociated CK dimers. Partial reactivation (about 50% at best) occurred following a monophasic course during the substrate reaction when compared with previous time interval measurements. The reactivation degree increased with increasing DTT (0.1-5 mM) and EDTA (0.1-1 mM) concentrations. The apparent forward rate constants do not change with concentration, showing that the reactivation is a reversible first-order reaction, but not of complex formation type. However, the apparent forward rate constants do change with EDTA concentration, showing that the reactivation with EDTA is a reversible first-order reaction as well as of complex formation type. Excess DTT concentrations have an inhibitory effect, indicating that the excessive EDTA acts as a metal chealate not only for free Mg2+, but also for MgATP during the enzyme catalysis. This study shows that additional information about the reactivation of CK can be obtained from examining the substrate reaction. The possible refolding pathway of CK is discussed.

Creatine↗
PubMed2001

Molecular mechanism for osmolyte protection of creatine kinase against guanidine denaturation.

The effects of osmolytes, including dimethysulfoxide, sucrose, glycine and proline, on the unfolding and inactivation of guanidine-denatured creatine kinase were studied by observing the fluorescence emission spectra, the CD spectra and the inactivation of enzymatic activity. The results showed that low concentrations of dimethysulfoxide (< 40%), glycine (< 1.5 m), proline (< 2.5 m) and sucrose (< 1.2 m) reduced the inactivation and unfolding rate constants of creatine kinase, increased the change in transition free energy of inactivation and unfolding (Delta Delta G(u)) and stabilized its active conformation relative to the partially unfolded state with no osmolytes. In the presence of various osmolytes, the inactivation and unfolding dynamics of creatine kinase were related to the protein concentrations. These osmolytes protected creatine kinase against guanidine denaturation in a concentration-dependent manner. The ability of the osmolytes to protect creatine kinase against guanidine denaturation decreased in order from sucrose to glycine to proline. Dimethysulfoxide was considered separately. This study also suggests that osmolytes are not only energy substrates for metabolism and organic components in vivo, but also have an important physiological function for maintaining adequate rates of enzymatic catalysis and for stabilizing the protein secondary and tertiary conformations.

Anilino Naphthalenesulfonates↗
PubMed2001

Cutaneous mastocytosis associated with a mixed germ cell tumour of the ovary: report of a case and review of the literature.

A 10-year-old girl with a mixed germ cell tumour of the ovary, treated by surgery and chemotherapy, developed cutaneous mastocytosis approximately 8 months after starting chemotherapy. This is the sixth report of a germ cell tumour associated with mastocytosis. c-kit receptor point mutations, including Asp816Val and Val560Gly were absent in a biopsy specimen obtained from lesional skin.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

Echocardiographic features in a patient with primary oxalosis.

Primary oxalosis is a rare congenital disorder of oxalate metabolism characterized by deposits of calcium oxalate in several organs, including the heart. We present the case of a 38-year-old man with primary oxalosis who had unique echocardiographic findings. Two-dimensional echocardiography revealed the sparkling high intensity echocardiographic pattern and concentric thickening of myocardial walls. Microscopic examinations showed the extensive deposits of calcium oxalate crystals in the myocardium. Therefore, we suggest that primary oxalosis should be given important consideration in the differential diagnosis of a hypertrophied myocardium with high intensity echocardiograms.

Adult↗
PubMed2001

Chaperone-like activity of peptidyl-prolyl cis-trans isomerase during creatine kinase refolding.

Porcine kidney 18 kD peptidyl-prolyl cis-trans isomerase (PPIase) belongs to the cyclophilin family that is inhibited by the immunosuppressive drug cyclosporin A. The chaperone activity of PPIase was studied using inactive, active, and alkylated PPIase during rabbit muscle creatine kinase (CK) refolding. The results showed that low concentration inactive or active PPIase was able to improve the refolding yields, while high concentration PPIase decreased the CK reactivation yields. Aggregation was inhibited by inactive or active PPIase, and completely suppressed at 32 or 80 times the CK concentration (2.7 microM). However, alkylated PPIase was not able to prevent CK aggregation. In addition, the ability of inactive PPIase to affect CK reactivation and prevent CK aggregation was weaker than that of active PPIase. These results indicate that PPIase interacted with the early folding intermediates of CK, thus preventing their aggregation in a concentration-dependent manner. PPIase exhibited chaperone-like activity during CK refolding. The results also suggest that the isomerase activity of PPIase was independent of the chaperone activity, and that the proper molar ratio was important for the chaperone activity of PPIase. The cysteine residues of PPIase may be a peptide binding site, and may be an essential group for the chaperone function.

Creatine Kinase↗
PubMed2001

Folding pathway for partially folded rabbit muscle creatine kinase.

Rabbit muscle creatine kinase (CK) was modified by 5,5'-dithio-bis(2-nitrobenzoic acid) accompanied by 3 M guanidine hydrochloride denaturation to produce a partially folded state with modified thiol groups. The partially folded CK was in a monomeric state detected by size exclusion chromatography, native-polyacrylamide gel electrophoresis, circular dichroism, and intrinsic fluorescence studies. After dithiothreitol (DTT) treatment, about 70% CK activity was regained with a two-phase kinetic course. Rate constants calculated for regaining of activity and refolding were compared with those for CK modified with various treatments to show that refolding and recovery of activity were synchronized. To further characterize the partially folded CK state and its folding pathway, the molecular chaperone GroEL was used to evaluate whether it can bind with partly folded CK during refolding, and 1-anilinonaphthalene-8-sulfonate was used to detect the hydrophobic surface of the monomeric state of CK. The monomeric state of CK did not bind with GroEL, although it had a larger area of hydrophobic surface relative to the native state. These results may provide different evidence for the structural requirement of GroEL recognition to the substrate protein compared with previously reported results that GroEL bound with substrate proteins mainly through hydrophobic surface. The present study provides data for a monomeric intermediate trapped by the modification of the SH groups during the refolding of CK. Schemes are given for explaining both the partial folding CK pathway and the refolding pathway.

Anilino Naphthalenesulfonates↗