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Biomedical subjects

J H Yun

Publications and source records attributed to J H Yun.

14 recordsLinked to original sources
PubMed2001

Phenotypic variation of a Thr704Met mutation in skeletal sodium channel gene in a family with paralysis periodica paramyotonica.

OBJECTIVES: Patients with paralysis periodica paramyotonica exhibit a clinical syndrome with characteristics of both hyperkalaemic periodic paralysis and paramyotonia congenita. In several types of periodic paralysis associated with hyperkalaemia, mutations in the skeletal muscle sodium channel (SCN4A) gene have been previously reported. Phenotypic variations of mutations in SCN4A, however, have not been described yet. The present study aimed to evaluate genetic variations in a family with clinical and electrophysiological characteristics of paralysis periodica paramyotonia. METHODS: Seven members of a family affected with symptoms of paralysis periodica paramyotonia were studied by electrophysiological and genetic analyses. There were increased serum potassium concentrations in four members during paralytic attacks induced by hyperkalaemic periodic paralysis provocation tests. Short exercise tests before and after cold immersion were carried out in four patients to distinguish electrophysiological characteristics of hyperkalaemic periodic paralysis and paramyotonia. Sequencing analyses of SCN4A were performed on one patient and a normal control to identify polymorphisms. Restriction fragment length polymorphism (RFLP) analysis was then performed at the identified polymorphic sites. RESULTS: Electrophysiological studies showed both exercise sensitivity and temperature sensitivity. Compound motor action potential (CMAP) amplitudes were decreased (7.3%-28.6%) after short exercise tests. The CMAP amplitudes were even more severely decreased (21.7%-56.5%) in short exercise tests after cold exposure. Three polymorphic sites, Gln371Glu, Thr704Met, and Aspl376Asn were identified in SCN4A. RFLP analyses showed that all affected patients carried the Thr704Met mutation, whereas unaffected family members and a normal control did not. CONCLUSION: Phenotypic variation of the Thr704Met mutation, which was previously reported in patients with hyperkalaemic periodic paralysis, is described in a family affected with paralysis periodica paramyotonia.

Adult↗
PubMed2000

Duplication of genes encoding non-clathrin coat protein gamma-COP in vertebrate, insect and plant evolution.

Coatomer is a major component of COPI vesicles and consists of seven subunits. The gamma-COP subunit of the coatomer is believed to mediate the binding to the cytoplasmic dilysine motifs of membrane proteins. We characterized cDNAs for Copg genes encoding gamma-COP from mouse, zebrafish, Drosophila melanogaster and Bombyx mori. Two copies of Copg genes are present in vertebrates and in B. mori. Phylogenetic analysis revealed that two paralogous genes had been derived from a single ancestral gene by duplication independently in vertebrates and in B. mori. Mouse Copg1 showed ubiquitous expression with the highest level in testis. Zebrafish copg2 was biallelically expressed in hybrid larvae in contrast to its mammalian ortholog expressed in a parent-of-origin-specific manner. A phylogenetic analysis with partial plant cDNA sequences suggested that copg gene was also duplicated in the grass family (Poaceae).

Amino Acid Sequence↗
PubMed2000

Mit1/Lb9 and Copg2, new members of mouse imprinted genes closely linked to Peg1/Mest(1).

Two mouse genes, Mit1/Lb9 and Copg2, linked to Peg1/Mest on mouse chromosome 6, were identified to be imprinted maternally and paternally, respectively. Mit1/Lb9 encoding untranslated transcripts resides within the intron 20 of Copg2. The gene is maternally imprinted in adult mouse brain, partially imprinted in other tissues. Copg240 kb genomic region, being expressed ubiquitously in mouse tissues with a partial imprinting pattern in embryos, neonates, and adult brain in contrast to maternally imprinted human COPG2. In addition, we identified an antisense transcript of Copg2, Copg2AS, which overlaps 3'-UTRs of Copg2 and Peg1/Mest. The Copg2AS transcript is maternally imprinted in embryos, neonates, and adult tissues.

Amino Acid Sequence↗
PubMed2000

Characterization of JDP genes, an evolutionarily conserved J domain-only protein family, from human and moths.

We characterized evolutionarily conserved J domain containing protein (JDP) genes from human, Bombyx mori, and Manduca sexta. Each of the JDP proteins contains a J domain at its N-terminus and a highly conserved C-terminal domain. Southern blot analysis revealed that the human JDP1 gene is present as a single copy in the human genome. Expression was higher in brain, heart, and testis than in kidney or stomach. Human JDP1 was mapped in silico to chromosome 10q21.1, which exhibits a conserved synteny with the central region of mouse chromosome 10. Drosophila jdp is located at 99F4-99F11 on the right arm of the third chromosome.

Amino Acid Sequence↗
PubMed1998

Isolation of a new member of DnaJ-like heat shock protein 40 (Hsp40) from human liver.

A new member of Hsp40, HLJ1, consisting of 337 amino acids, was cloned from a human liver cDNA library. The deduced amino acid sequence of HLJ1 has an 84% homology (69% identity) with that of HDJ-1 isolated from human placenta. Northern analysis showed that expression of the HLJ1 gene is heat-inducible and its transcription shows some degree of preference in heart, skeletal muscle, and pancreas.

Amino Acid Sequence↗
PubMed1996

A new method of measuring heparin levels in whole blood by protamine titration using a heparin-responsive electrochemical sensor.

OBJECTIVE: To determine the ability of a new electrochemical sensor to determine heparin levels in whole blood and to correlate the heparin levels as determined by this heparin-responsive sensor (HRS) with heparin levels as determined by the Hepcon assay system (Medtronic Hemotec, Parker, CO). DESIGN: Methods comparison study. SETTING: A large academic medical center. INTERVENTIONS: The heparin levels of 162 samples from 24 patients undergoing cardiopulmonary bypass were determined by the HRS system and by the Hepcon system. In 21 samples, heparin levels as measured by anti-Xa activity were determined as well. MEASUREMENTS AND MAIN RESULTS: HRS-determined values correlated highly with Hepcon-determined values (r = 0.942) and with anti-Xa determined values (r = 0.905). Bias +/- precision comparing the HRS and Hepcon methods was 0.211 +/- 0.478 U/mL. CONCLUSIONS: HRS determined that whole blood heparin levels correlate well with Hepcon-determined levels. These limited results indicate that further development and testing of this new technology are warranted.

Anticoagulants↗
PubMed1996

Selective monitoring of peptidase activities with synthetic polypeptide substrates and polyion-sensitive membrane electrode detection.

A novel method to monitor specific peptidase activities in biological samples as complex as undiluted plasma/blood is described. The approach is based on the design of synthetic polypeptide substrates in which di- or triarginine sequences are linked to each other via one or more other amino acids recognized specifically by the peptidase to be determined. Detection of chymotrypsin and renin activities using synthetic substrates P4 (F-R-R-R-F-V-R-R-F-NH2) and P5 (R-R-R-L-L-R-R-L-L-R-R-R), respectively, serves to demonstrate the principles of this new assay system. A polyion-sensitive membrane electrode, prepared by doping polymer films with dinonylnaphthalene-sulfonate (DNNS), is shown to exhibit significant nonequilibrium electromotive force (EMF) responses toward these and other polycationic substrates at microgram/milliliter levels under physiological conditions. The same electrode, however, exhibits much smaller total EMF response toward the shorter fragments of the synthetic peptides generated by peptidase activity; hence, the addition of peptidase to a solution containing the synthetic substrate yields a change in electrode EMF response, the rate of which is proportional to the activity of peptidase present. Other synthetic polycationic peptides as well as natural polycationic peptides (e.g., protamine) that lack specific cleavage sites for chymotrypsin and renin, yet are detected by the DNNS-based membrane electrode, do not elicit any significant change in EMF response in the presence of the peptidases, confirming the feasibility and utility of the proposed bioanalytical method.

Amino Acid Sequence↗
PubMed1995

Protamine-sensitive polymer membrane electrode: characterization and bioanalytical applications.

A polymeric membrane electrode that exhibits significant and analytically useful potentiometric response to submicromolar levels of the heparin antagonist, protamine, is reported. The sensor is prepared by incorporating a lipophilic cation exchanger, potassium tetrakis(4-chlorophenyl)borate (KTpClPB) (at 1 wt%), within a specially formulated polymer membrane composed of 33 wt% 2-nitrophenyl octyl ether (2-NPOE), and 66 wt% poly(vinyl chloride) (PVC). When the polymer film is mounted in an appropriate electrode body, the resulting membrane electrode responds reproducibly to protamine via a nonequilibrium quasi-steady-state change in the phase boundary potential at the membrane/sample interface. Such response can be used to directly monitor, via classical potentiometric titrations, the binding between protamine and a variety of native (porcine and beef) as well as low-molecular-weight heparins. Scatchard analysis of the EMF titration data provides binding constants and stoichiometries for protamine-heparin interactions. The electrode can be further used to follow the enzymatic digestion of protamine by trypsin. In the presence of a given level of protamine, initial rates of potential decrease (-dE/dt) are shown to be linearly related to trypsin activity in solution over the range of 0-130 units/ml. The speed and simplicity of the protamine sensor make it an attractive alternative to classical methods for studying the interaction of protamine with other biologically important macromolecules as well as the proteolytic activity and reaction kinetics of trypsin.

Electrodes↗
PubMed1994

Response mechanism of polymer membrane-based potentiometric polyion sensors.

The potentiometric response mechanism of a previously reported polymer membrane-based electrode sensitive to the polyanion heparin is established. Based on transport and extraction studies, the heparin response is attributed to a nonequilibrium change in the phase boundary potential at the sample/membrane interface. While true equilibrium polyion response, obtained for low heparin concentrations only after very long equilibration times (> 20 h), yields the expected Nernstian response slope of < 1 mV/decade, the observed large and reproducible EMF response to clinically relevant heparin concentrations (approximately 10(-7) M) during typical measurement periods (2-5 min) is ascribed to a steady-state kinetic process defined by the flux of the polyion both to the surface and into the bulk of the polymer membrane. A model describing this nonequilibrium response is presented. With this model, the uniqueness of the polymer membrane composition (e.g., very low plasticizer content, strictly controlled cationic site concentration, etc.) required to achieve analytically useful heparin response becomes clear. Practical working conditions and limitations of the sensor are discussed. To support the generality of the steady-state model proposed, corresponding EMF response data for a newly developed membrane electrode sensitive to a polycationic protein (protamine) are also presented. It is shown that the protamine-responsive membrane electrode appears to operate via the exact same kinetic mechanism as the heparin sensing system.

Biosensing Techniques↗
PubMedDate not supplied

A disposable, coated wire heparin sensor.

The development of an ion-selective electrode heparin sensor consisting of a specially formulated polymer membrane doped with tridodecylmethylammonium chloride as the heparin complexing agent was recently reported. Because of the simple nature of the membrane technology used, the authors envisioned that the sensor could be configured as a disposable single-use device for rapid clinical or bedside measurement of heparin in a small, discrete sample. To explore this possibility, an inexpensive, disposable heparin sensor was created by dip-coating a copper wire with the specially formulated heparin-sensing polymeric membrane. Coated wire heparin sensors with a broad range of membrane thicknesses, prepared by repeatedly dipping the wire in the membrane solution for various times, were examined. Data show that increasing the membrane thickness of the sensor to a certain degree (more than 10 microns) enhanced the sensor's potentiometric response to heparin, although the time required to achieve 90% of the steady-state potential change was also prolonged. In addition, increasing membrane thickness also magnified the stirring effect on the sensor's response. In undiluted plasma samples, the coated-wire sensor with an optimized membrane thickness yielded a significant (5 to 30 mV) and reproducible response to heparin in a clinically relevant concentration range (0.5 to 12 units/ml, respectively). The clinical utility of the coated wire heparin sensor was shown using the sensor during protamine titration of heparinized plasma to assess the titration end-point. Preliminary results showed that the titration end-points determined by the heparin sensor strongly correlated with those determined by the activated partial thromboplastin time clotting assay. The overall time requirement to complete the titration process using a set of prefabricated coated wire heparin sensors, however, was less than 3 minutes. Further titration studies using undiluted clinical whole blood samples are in progress.

Biotechnology↗
PubMedDate not supplied

Cryopreservation of Taxus chinensis suspension cell cultures.

A simple cryopreservation method for suspension cells of Taxus chinensis was established. In this procedure 7 days old suspension cells were used without any pre-culture treatment. At first, cells were incubated in cryoprotectant solution (0.5M DMSO and 0.5M glycerol) on ice for 30 min and then frozen at a cooling rate of 1 degree C/min to -40 degrees C prior to immersion in liquid nitrogen. The average viability of frozen-thawed cells was between 30 to 40%. The recovery of cryopreserved cells in liquid nitrogen for 1 month was accomplished. After rapid thawing, cells were transferred to solid medium and cultivated for 4-6 weeks. The treatment of trehalose as a cryoprotectant enhanced re-growth of frozen-thawed cells. The stable maintenance of paclitaxel biosynthetic ability in cryopreserved cells was confirmed by comparing with that of regularly sub-cultured suspension cells.

Cell Survival↗
PubMedDate not supplied

A protamine filter for extracorporeal heparin removal. Development, testing, blood compatibility evaluation, and future direction.

The authors previously developed a filter device containing immobilized protamine (termed "protamine filter") that could be used to remove heparin during extracorporeal perfusion. In vivo studies involving dogs showed that the protamine filter removed more than 50% of heparin from the animals' blood circuit in less than 20 min. In addition, the use of the protamine filter did not elicit statistically significant protamine induced hemodynamic and thrombocytopenic responses. Biocompatibility of the protamine filter was also evaluated, with the focus on its effect on the coagulation cascade, the complement system, and the blood antithrombin III levels. Results showed that heparin adsorbed to the protamine coated surface retained 20% of its original activated partial thromboplastin time activity, rendering the coated surface antithrombotic. Activation of the coagulation system by the protamine coated membrane and the untreated cellulose membrane, as measured by the elevation of prothrombin fragment F1 + 2 levels, was statistically identical. The CH50 hemolytic assay showed that the protamine coated membrane produced a reduction of 1.2 +/- 0.8% of the total complement levels, as compared to 9.4 +/- 1.6% by the untreated membrane. In addition, the change in C3a des Arginine levels after 30 min of circulation was 1.5 +/- 0.2 mg/ml by the protamine filter, as compared to 2.1 +/- 0.1 mg/ml by the untreated membrane. Unlike native heparin that would bind with antithrombin, heparin adsorbed on the protamine coated surface was devoid of such activity, and produced no depletion of circulating antithrombin. Because of the limited capacity of the protamine filter, the future system is envisioned to consist of two filters; while one filter is removing heparin the other will be regenerated. With a recently developed heparin sensor, it should be possible to design a sensor directed, biofeedback, two filter heparin removal system.

Adsorption↗
PubMedDate not supplied

Clinical application of disposable heparin sensors. Blood heparin measurements during open heart surgery.

The authors previously reported the development of an ion selective electrode type heparin sensor consisting of a specially formulated polymer membrane doped with tridodecylmethylammonium chloride as the heparin complexing agent. They also demonstrated the feasibility of measuring blood heparin levels by protamine titration, using a disposable copper wire sensor coated with the heparin sensing membrane to probe the titration end point. In this article, the results of further titration studies conducted on 44 clinical whole blood specimens obtained from 8 patients undergoing open heart surgery were reviewed. Samples were taken from patients at four different stages during the bypass surgery: 1) before heparin administration; 2) immediately after heparin administration; 3) within 30 min to 3 hr after heparin administration; and 4) within 30 min after protamine administration. Heparin anticoagulant activity in these samples was monitored by the activated clotting time assay, whereas heparin concentrations were measured by protamine titration using either the Hepcon HMS Titrator (Medtronic HemoTec Inc., Englewood, CO) or the coated wire heparin sensor to determine titration end points. Results indicate that heparin levels determined by the sensor method were in good agreement with those determined by the Hepcon HMS Titrator. When the heparin concentrations estimated by the two methods show significant discrepancy (> 1.0 unit/ml), the sensor method seems to provide more precise values, as verified by an additional chromogenic heparin assay. The overall time required to complete the titration process and heparin measurement with a pre made heparin sensor was less than 3 min. Clinically, the heparin sensor could be used as a safeguard to precisely monitor heparin levels during surgical procedures. Alternatively, the sensor could be used to assess the accurate protamine dose required for full heparin reversal.

Blood Chemical Analysis↗