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Biomedical subjects

Y Kang

Publications and source records attributed to Y Kang.

At least 163 records · Page 9Linked to original sources
PubMed1996

Prophylactic effects of taurine and diltiazem, alone or combined, on reperfusion arrhythmias in rats.

AIM: To study the effects of taurine (Tau) and diltiazem (Dil), alone or in combination, on reperfusion arrhythmias in anesthetized rats. METHODS: The arrhythmias were produced by coronary artery ligation for 15 min followed by reperfusion. Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were measured by thiobarbituric acid fluorescence assay and colorimetric determination. RESULTS: Tau 70 mg.kg-1 in combination with Dil 1 mg.kg-1 were more effective on prevention of the reperfusion arrhythmias than each drug alone. The combination of both drugs not only decreased the content of MDA, but also increased the activity of SOD in reperfusion myocardium. CONCLUSION: The inhibition of lipoperoxides formation as well as the inhibition of the calcium influx was involved in the anti-arrhythmic effect of both Tau and Dil.

Animals↗
PubMed1995

Impairment of motor coordination, Purkinje cell synapse formation, and cerebellar long-term depression in GluR delta 2 mutant mice.

Of the six glutamate receptor (GluR) channel subunit families identified by molecular cloning, five have been shown to constitute either the AMPA, kainate, or NMDA receptor channel, whereas the function of the delta subunit family remains unknown. The selective localization of the delta 2 subunit of the GluR delta subfamily in cerebellar Purkinje cells prompted us to examine its possible physiological roles by the gene targeting technique. Analyses of the GluR delta 2 mutant mice reveal that the delta 2 subunit plays important roles in motor coordination, formation of parallel fiber-Purkinje cell synapses and climbing fiber-Purkinje cell synapses, and long-term depression of parallel fiber-Purkinje cell synaptic transmission. These results suggest a close relationship between synaptic plasticity and synapse formation in the cerebellum.

Animals↗
PubMed1995

Effects of tamoxifen on growth and apoptosis of estrogen-dependent and -independent human breast cancer cells.

BACKGROUND: Apoptosis ("programmed cell death") is an active process characterized by prominent nuclear changes and DNA cleavage, which distinguishes it from cellular necrosis. In this study we investigated whether tamoxifen (TAM) treatment of estrogen receptor ER(+) MCF-7 and ER(-) MDA-231 human breast cancer cells resulted in cytotoxicity and cellular changes typical of apoptosis. METHODS: Cytotoxicity was measured using a tetrazolium assay. Cellular morphologic changes were observed using transmission electron microscopy. DNA cleavage was assessed using 1.6% agarose gel electrophoresis and was also quantitated biochemically. RESULTS: Exposure of cells to TAM for 24 h resulted in dose-dependent cytotoxicity, and MCF-7 cells were somewhat more sensitive to TAM. TAM induced chromatin condensation around the nuclear periphery in both cell lines, changes typical of apoptosis. TAM-induced cytotoxicity correlated with dose-dependent DNA cleavage, which showed the characteristic "internucleosomal ladder." DNA cleavage occurred at a slightly lower TAM dose and occurred somewhat sooner in MCF-7 cells. TAM-induced DNA cleavage in MCF-7 cells was inhibited by the protein synthesis inhibitor cycloheximide, the RNA synthesis inhibitor actinomycin D, and by 17 beta-estradiol. However, in MDA-231 cells, DNA cleavage was inhibited by cycloheximide, partially but not significantly inhibited by actinomycin D, and not inhibited by 17 beta-estradiol. CONCLUSIONS: TAM induces typical apoptosis in ER(+) or ER(-) human breast cancer cells. TAM induction of apoptosis in MCF-7 cells involves the estrogen receptor, and requires the synthesis of new protein and mRNA. TAM induction of apoptosis in MDA-231 cells depends primarily on protein synthesis. TAM-induced cytotoxicity and DNA damage appear to be explained in part by the induction of apoptosis.

Apoptosis↗
PubMed1995

Sequence heterogeneity of the C-terminal, Cys-rich region of the merozoite surface protein-1 (MSP-1) in field samples of Plasmodium falciparum.

Recent results with primate plasmodia and rodent models of infection have focused attention on the C-terminal region of the merozoite surface protein-1 (MSP-1) as one of the leading candidates for vaccination against the erythrocytic stages of malaria. However, sequence heterogeneity of this region may compromise its use as a vaccine candidate. While the C-terminal region of MSP-1 from the two prototypic alleles of P. falciparum has been shown to be relatively conserved in laboratory-maintained strains, little data exist on sequence heterogeneity of this region in field isolates from diverse geographic areas. To address this question, DNA encoding the C-terminal, Cys-rich region of P. falciparum MSP-1 from field samples was analyzed by a polymerase chain reaction (PCR)-direct sequencing method. Sequence data were consistent with those obtained from laboratory-maintained strains. In 15 isolates from Africa, Asia and Latin America, only a few nucleotide changes were found leading to amino-acid alterations at four positions out of 102 residues. All the variations corresponded to the predicted amino-acid sequence of the other prototype, suggesting that these changes were possibly due to allelic recombinations. The four changes were E-->Q at position 1644 and TSR-->KNG, or KNG-->TSR at positions 1691, 1700 and 1701. Thus, only three patterns of the C-terminal, Cys-rich region of MSP-1, E-TSR, Q-KNG and Q-TSR, were detected. All the Cys residues were conserved. These results support the potential utility of the C-terminal region of MSP-1 as a vaccine candidate.

Alleles↗
PubMed1995

Sequestration of insecticyanin, a blue hemolymph protein, into the egg of the hawkmoth Manduca sexta. Evidence for receptor-mediated endocytosis.

Sequestration of the blue biliprotein, insecticyanin, into developing oocytes of the hawkmoth, Manduca sexta was investigated. Immunodiffusion assays revealed that insecticyanin concentration in mature eggs (29.6 microM) is slightly higher than that in hemolymph (25.8 microM). The endocytotic uptake of insecticyanin was visualized at the light microscopic level using autoradiography. Uptake of 125I-insecticyanin by isolated oocytes was saturable. Analysis of in vitro uptake data estimated that the value of K(uptake) (insecticyanin concentration at half-maximal uptake rate) is 4.2 microM and that the Vmax (maximum rate of uptake) is 1 pmol follicle-1 h-1. Labeled insecticyanin was shown to bind to sonicated follicle membranes with high specificity and affinity. The KD (equilibrium dissociation constant) and the Bm (total number of binding sites per follicle), were estimated as 4 x 10(-8) M and 8 x 10(7) respectively. Competition studies showed that binding of labeled insecticyanin to oocyte membranes was blocked by excess amounts of unlabeled insecticyanin but not by lipophorin and vitellogenin of M. sexta. Additional membrane binding experiments demonstrated that receptors for insecticyanin are only present in the oocytes membranes, not in fat body or gut tissue.

Animals↗
PubMed1995

Relationship between tamoxifen-induced transforming growth factor beta 1 expression, cytostasis and apoptosis in human breast cancer cells.

Previously we have shown that tamoxifen (TAM) induces morphological and biochemical changes typical of apoptosis in oestrogen receptor (ER)-positive MCF-7 or ER-negative MDA-231 human breast cancer cells. In this study the effects of TAM on expression of transforming growth factor beta 1 (TGF-beta 1) were correlated with the effects on cell cycle kinetics and apoptosis. TAM had similar biphasic effects on both cell lines. Short-term (< 6 h) TAM incubation resulted in a slight decrease in TGF-beta 1 protein despite an increase in TGF-beta 1 mRNA and was associated with an increase in cells in S-phase. No apoptotic effects were noted. Longer (> or = 12 h) TAM incubation induced TGF-beta 1 protein (about 3-fold) and mRNA expression (about 2-fold) in both cell lines, and was associated with G1/G0 blockade and induction of apoptosis. The accumulation of TAM-induced TGF-beta 1 mRNA was increased by cycloheximide, but was not affected by 17 beta-oestradiol. Long-term incubation with TAM had no significant effect on TGF-beta 1 gene copy number. TAM-induced internucleosomal DNA cleavage was inhibited in both cell lines by the addition of an anti-TGF-beta 1 antibody. TAM has dose- and time-dependent effects on TGF-beta 1 expression associated with changes in cell cycle kinetics. These effects are independent of ER status and may be the result of a direct regulatory effect of TAM on TGF-beta 1 transcription. It also appears that induction of TGF-beta 1 plays an important role in TAM-induced apoptosis in breast cancer cells.

Antibodies, Neoplasm↗
PubMed1995

Cloning and expression of the VP1 major capsid protein of diabetogenic encephalomyocarditis (EMC) virus and prevention of EMC virus-induced diabetes by immunization with the recombinant VP1 protein.

The development of diabetes in mice induced by encephalomyocarditis (EMC) virus provides the best experimental evidence that viruses have an aetiological role in the pathogenesis of this disease. The major capsid protein (VP1) of EMC virus is important for both the attachment of the virus to pancreatic beta cells and for the determination of antigenicity. This experiment was initiated to clone the gene for the major capsid protein, VP1, of the diabetogenic EMC (EMC-D) virus, express the VP1 protein, and test whether the recombinant VP1 protein can prevent development of EMC-D virus-induced diabetes in mice. We successfully cloned the VP1 gene of the EMC-D virus in the expression vector pRSET and subsequently expressed the protein in Escherichia coli. The recombinant VP1 protein was then purified by affinity chromatography. Five- to six-week-old male SJL/J mice were immunized intraperitoneally with purified VP1 protein and then challenged after various intervals with highly diabetogenic EMC-D virus. None of the VP1-immunized mice developed diabetes, irrespective of the interval between immunization and virus challenge, whereas 80 to 95% of the EMC-D virus-infected control mice did develop diabetes. All of the VP1-immunized mice showed intact pancreatic islet architecture, whereas most of the infected control mice showed severe beta cell necrosis and lymphocytic infiltration of their pancreatic islets. On the basis of these observations, we conclude that the recombinant VP1 protein of EMC-D virus can completely prevent the development of EMC-D virus-induced diabetes in mice.

Amino Acid Sequence↗
PubMed1995

Effects of taurine on slow action potentials in papillary muscles of guinea pig.

AIM: To examine the effects of taurine on the slow action potentials induced by KCl 24 mmol.L(-1) or tetrodotoxin 40 mumol.L(-1) in guinea pig papillary muscles. METHODS: The transmembrane AP was recorded by a conventional glass microelectrode filled with KCl 3 mmol.L(-1). The muscles were exposed to high K(+)-Tyrode's solution or perfused with Tyrode's solution containing tetrodotoxin. Ouabain was added in order to induce oscillatory afterpotentials. RESULTS: Taurine 20 mmol.L(-1) decreased the maximal upstroke velocity of slow action potential and prolonged the action potential duration at 50% of repolarization. The amplitude of slow action potential and the maximal upstroke velocity both increased by CaCl(2)3 mmol.L(-1) were antagonized by taurine. Taurine increased the concentration of ouabain for oscillatory afterpotential and prolonged the onset time of oscillatory afterpotential. CONCLUSION: Taurine possesses a calcium antagonistic property.

Action Potentials↗
PubMed1995

Differential paired pulse depression of non-NMDA and NMDA currents in pyramidal cells of the rat frontal cortex.

Excitatory postsynaptic currents (EPSCs) were induced in layer II-V pyramidal cells in the frontal cortex of the young rat (postnatal day 14-21) by stimulation of layers II/III in the presence of bicuculline using the whole-cell patch-clamp technique. EPSCs usually consisted of fast and slow components that were sensitive to CNQX and APV, respectively. In response to paired stimuli of identical strength, paired pulse depression (PPD) was seen for these EPSCs. The PPD of fast EPSCs was most pronounced at an interstimulus interval (ISI) of 200-300 msec and ceased to occur at ISIs greater than 3-5 sec, while the PPD of slow EPSCs became most pronounced at an ISI of 500-1000 msec and ceased to occur at ISIs greater than 10 sec. The PPD of fast EPSCs was attenuated by (-)-baclofen (1-5 microM) and removed by 2-hydroxy-saclofen (0.2-0.4 mM). By contrast, the PPD of slow EPSCs consisted of early and late components that were attenuated by (-)-baclofen and muscarine (1-5 microM), respectively. The late PPD of slow EPSCs induced in the presence of baclofen was removed by pirenzepine (1-3 microM). Thus, fast and slow components of glutamatergic EPSCs displayed two distinct PPDs. These results suggest that a part of the glutamatergic afferents likely arising from layer II/III pyramidal cells may terminate predominantly on NMDA receptors in pyramidal cells of the frontal cortex and receive distinct presynaptic inhibition through at least the muscarinic receptors.

Animals↗
PubMed1995

Glutaminase-positive and glutaminase-negative pyramidal cells in layer VI of the primary motor and somatosensory cortices: a combined analysis by intracellular staining and immunocytochemistry in the rat.

Pyramidal neurons in layer VI of the primary motor and somatosensory cortices were examined by a combined method of intracellular recording, biocytin injection, and immunocytochemistry using in vitro slice preparations of rat brain immunofluorescence staining revealed that biocytin-injected pyramidal cells in layer VI were separated into glutaminase (PAG)-immunopositive and PAG-immunonegative cells. Although the two groups of pyramidal cells showed no statistically significant differences in passive membrane properties and spike characteristics, a clear difference was found in spike afterpotentials. Ten of 12 PAG-positive pyramidal cells showed no or a small fast afterhyperpolarization (fAHP), whereas 10 of 11 PAG-negative pyramidal cells displayed a large fAHP. Depolarizing afterpotentials were observed only in PAG-positive pyramidal cells than in PAG-negative cells. In contrast, the arborization of basal dendrites was more developed in PAG-positive pyramidal cells than in PAG-negative cells. The main axons of all the pyramidal cells entered the subcortical axons of all the pyramidal cells entered the subcortical white matter. The local axon collaterals of PAG-positive pyramidal cells were widely spread in the horizontal direction, whereas those of PAG-negative cells were distributed vertically along the dendritic tree. Since PAG is considered to be a marker of glutamatergic neurons in the cerebral cortex, the present results indicate that layer VI pyramidal cells are separated into glutamatergic and nonglutamatergic neurons that have different electrical properties and input-output organizations. Thus, cortical outputs from layer VI are suggested to use at least two distinct systems.

Animals↗
PubMed1995

Depressant effect of taurine on triggered activity induced by cesium chloride in rabbit hearts in vivo.

AIM: To study the effects of taurine (Tau) and tetrodotoxin (Tet) on cesium chloride (CsCl)-induced triggered activity and arrhythmia in anesthetized rabbits. METHODS: With a cuffed endotracheal tube, the rabbit ventilation was maintained by a respirator. A Franzy's contact electrode catheter was advanced into the right ventricle through the right external jugular vein and positioned against the anteroapical endocardial surface to record the monophasic action potential (MAP). A catheter was placed into femoral vein for systemic drug administration. RESULTS: CsCl (1 mmol L-1 iv) produced a decrease in the amplitude of MAP from 42.2 +/- 2.1 to 37.0 +/- 3.8 mV (P < 0.01), a prolongation of MAPD50 (156 +/- 22 to 209 +/- 26 ms, P < 0.01) or MAPD90 (205 +/- 25 to 250 +/- 20 ms, P < 0.01) and an early afterdepolarization (EAD) developed within 30 s after CsCl injection. The ventricular premature (VP) resulted from EAD triggered by CsCl. In the Tau (100 mg kg-1)- or Tet (10 micrograms kg-1)-pretreated group, not only was the amplitude of EAD decreased (Tau, 4.2 +/- 2.7; or Tet, 5.2 +/- 2.6, respectively vs 16.1 +/- 8.3 mv, P < 0.01), but also the duration of EAD was shortened (Tau, 695 +/- 164; or Tet, 492 +/- 172, respectively, vs 1068 +/- 166 ms, P < 0.01). The severity of triggered arrhythmia (TA) was alleviated and the incidence of TA was lowered within 30 min after iv CsCl by either Tau or Tet. CONCLUSION: The depressant effects of Tau and Tet on EAD and VP induced by CsCl were involved in an increase of outward current or a decrease of an inward current.

Action Potentials↗
PubMed1994

Effect of modification of connecting peptide of proinsulin on its export.

The production of a high yield of proinsulin using a secretion vector has been difficult, even with such modifications to the vector as a strong promoter and a good ribosome binding site. This investigation was therefore initiated to see whether modification of the connecting peptide of proinsulin has any effect on the export of proinsulin. We constructed three types of proinsulin secretion vectors: (a) pEZZ18-PI, by inserting the proinsulin gene into pEZZ18 vector; (b) pEZZ18-PI-C, by modifying ZZ-proinsulin by addition of the carboxy terminal peptide region of human insulin-like growth factor I (hIGFI) to the carboxy terminal end of proinsulin; and (c) pEZZ18-PI analogues, by sequentially deleting the connecting peptide region of proinsulin. The highest export yield of proinsulin was obtained when the connecting peptide region of the proinsulin was similar in size to that of hIGFI, or when most of the connecting peptide region of the proinsulin was deleted. The amount of exported ZZ-proinsulin analogues in these clones was over 25-times higher than that of ZZ-proinsulin with an unmodified connecting peptide in the secretion/expression vector pEZZ18-PI. On the basis of these observations, we conclude that modification of the mature domain of proinsulin is a critical factor for determination of the export of proinsulin.

Amino Acid Sequence↗
PubMed1994

Effect of alpha-interferon on P-glycoprotein expression and function and on verapamil modulation of doxorubicin resistance.

Human alpha-interferon (IFN-alpha) is one of the three major classes of interferons which possess antiviral, antiproliferative, and immunomodulatory activities. We recently reported synergism between IFN-alpha and tamoxifen in the modulation of doxorubicin (DOX) cytotoxicity and accumulation in multidrug resistant Chinese hamster ovary ChR C5 cells (Y. Kang and R. R. Perry, Cancer Res., 53: 3040-3045, 1993), but the mechanism was uncertain. In the present study, IFN-alpha (500 units/ml) pretreatment of ChR C5 cells similarly increased verapamil (VPL) modulation of DOX cytotoxicity in a time-dependent manner. Measurement of intracellular DOX fluorescence showed a parallel increase in DOX accumulation. Western blot analysis revealed that IFN-alpha induced a time-dependent increase in p-glycoprotein (p-gp) expression, accompanied by an increase of mdr-1 mRNA as measured using Northern analysis. MDR-1 gene copy number measured using Southern analysis remained unchanged. Assay of specific photoaffinity labeling of p-gp by [3H]-azidopine showed that, although IFN-alpha is not a substrate of p-gp, it significantly increased the ability of VPL to bind to p-gp. These data suggest that IFN-alpha may effect the expression of p-gp in multidrug-resistant ChR C5 cells by transcriptional or posttranscriptional control of mdr-1 gene expression. IFN-alpha enhances the ability of VPL to modulate DOX cytotoxicity and accumulation, possibly by altering the accessibility of p-gp binding site(s) to VPL. By using relatively low concentrations of IFN-alpha and VPL it may be possible to develop less toxic regimens to reverse multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Liver transplantation without the use of blood products.

OBJECTIVES: To examine the techniques and the outcome of liver transplantation with maximal conservation of blood products and to analyze the potential benefits or drawbacks of blood conservation and salvage techniques. DESIGN: Case series survey. SETTING: Tertiary care, major university teaching hospital. PATIENTS AND METHODS: Four patients with religious objections to blood transfusions who were selected on the basis of restrictive criteria that would lower their risk for fatal hemorrhage, including coagulopathy, a thrombosed splanchnic venous system requiring extensive reconstruction, active bleeding and associated medical complications. All patients were pretreated with erythropoietin to increase production of red blood cells. All operations were performed at the same institution, with a 36-month follow-up. INTERVENTIONS: Orthotopic liver transplantation that used blood salvage, plateletpheresis, and autotransfusion and the withholding of the use of human blood products with the exception of albumin. MAIN OUTCOME MEASURES: Survival and postoperative complications, with the effectiveness of erythropoietin and plateletpheresis as secondary measures. RESULTS: All patients are alive at 36 months after orthotopic liver transplantation. One patient, a minor (13 years of age), was transfused per a state court ruling. Erythropoietin increased the production of red blood cells as shown by a mean increase in hematocrit levels of 0.08. Platelet-pheresis allowed autologous, platelet-rich plasma to be available for use after allograft reperfusion. Three major complications were resolved or corrected without sequelae. Only one patient developed postoperative hemorrhage, which was corrected surgically. The mean charge for bloodless surgery was $174,000 for the three patients with United Network for Organ Sharing (UNOS) status 3 priority for transplantation. This result was statistically significant when these patients were compared with all the patients with UNOS status 3 priority during the same period who met the same restrictive guidelines (P < .05). Only 19 of 1009 orthotopic liver transplantations performed at our institution were similar according to the UNOS status and the fulfillment of the guidelines. The mean charge for these comparison patients was $327,000, 3.8% of which was related to transfusions. CONCLUSIONS: Orthotopic liver transplantation without the use of blood products is possible. Blood conservation techniques do not increase morbidity or mortality and can result in fewer transfusion-related, in-hospital charges.

Adolescent↗
PubMed1994

Complete nucleotide sequence of a strain of coxsackie B4 virus of human origin that induces diabetes in mice and its comparison with nondiabetogenic coxsackie B4 JBV strain.

The E2 strain of coxsackie B4 virus (CB4), which is of human origin, can induce a diabetes-like syndrome in mice. The cDNA of the genome of the E2 strain was cloned and sequenced. The E2 viral genome was found to comprise 7,396 bases, which appear to encode a polyprotein of 2,183 amino acids with an overall similarity of 94.91% to nondiabetogenic CB4 prototype JBV strain. The E2 genome is organized like other enteroviruses. It has a 5' noncoding region of 744 nucleotides, a single long open translational reading frame starting at nucleotide 745 and extending to nucleotide 7293, a 3' noncoding region of 100 nucleotides, and a poly (A) tract. Genomic sequence comparison of the E2 and JBV strains showed 1,369 nucleotide substitutions in the genome of the E2 strain, most of which are single and silent. There were 111 resultant amino acid changes arising from some of these substitutions, including 82 amino acid changes in the noncapsid proteins, and 29 amino acid changes in the capsid proteins VP1, VP2, VP3, and VP4, which showed 11, 13, 4, and 1 substitution(s), respectively. Noncapsid protein P2-C showed eight amino acid substitutions. On the basis of the sequence comparison of E2 and JBV strains of CB4, we suggest that some of the amino acid changes in the capsid and noncapsid proteins of the E2 strain may be involved in the determination of its diabetogenicity.

Amino Acid Sequence↗