Biomedical subjects

J Y Su

Publications and source records attributed to J Y Su.

At least 37 records · Page 2Linked to original sources

PubMed1997

[Changes of calcium transport in rat liver nuclei during sepsis].

Calcium transport changes in rat liver nuclei were observed on the model of early sepsis (9 h after operation of cecal ligation and puncture). Calcium content in hepatocytes and nuclei were significantly increased by 20% and 36% respectively (P < 0.05) during sepsis. The activity of Ca(2+)-ATPase in hepatocytic nuclei was increased by 94% (P < 0.01) and 45Ca2+ transport accelerated by 32% (P < 0.01). There was a positive correlation between nuclear 45Ca2+ transport and nuclear Ca(2+)-ATPase activity (r = 0.914, P < 0.01). Calmodulin stimulated the activity of nuclear Ca(2+)-ATPase and 45Ca2+ transport; while calmodulin inhibitor trifluoperazine exerted an opposite effect. The above results suggest that liver nuclear calcium transport is strengthened during early sepsis as a result of changes of Ca(2+)-ATPase activity.

Animals↗

PubMed1997

[Effect of anoxic preconditioning on protein kinase C activity in neonatal rat cardiomyocytes].

In a model of anoxia/reoxygenation (A/R) of cultured rat cardiomyocytes, protection of cellular damage, activation of protein kinase C (PKC) and PKC-mediated protein phosphorylation by anoxic preconditioning (APC) can be demonstrated as shown by the increase of cell viability, attenuation of formation of lipid peroxides (MDA) and lowering of the leakage of lactate dehydrogenase (LDH) and protein from cells. The results also show that transient anoxia mimicked the outcomes of activation of PKC as shown by increased incorporation of 32P, especially in the 66 kD and 31 kD protein fractions. Preincubation of cardiomyocytes with H7 (an inhibitor of PKC) completely abolished these protective effects of transient anoxia. Protein phosphatase inhibitor OA mimicked the protective effects of A/R, while protein phosphatase activator BDM induced a complete abolishment. In short, we conclude that the protective effect of APC is medicated by activation of PKC.

Animals↗

PubMed1997

[Effects of basic fibroblast growth factor on anoxia/reoxygenation injury of rat neonatal cardiomyocytes].

The effects of basic fibroblast growth factor (bFGF) on anoxia/reoxygenation (A/R) injury and protein kinase C (PKC) activity were studied on a model of A/R injury of neonatal rat cardiomyocytes to investigate the possibility of its using as a substrate for pharmacological preconditioning. The data indicated that bFGF improved the viability of cardiomyocytes, lowered the deplection of ATP and leakage of intracellular lactate dehydrogenase (LDH) in a concentration-dependent manner. PKC inhibitor, H7, completely abolished the protective effects. It was also found that bFGF directely activated PKC in cardiomyocytes in a time course similar to that in hypoxic preconditioning. The data suggested that the protective effect of bFGF on cardiomyocyte A/R injury might be mediated by PKC.

Animals↗

PubMed1997

[Effects of hypoxia/reoxygenation on mitogen-activated protein kinase activity in cultured neonatal rabbit cardiac myocytes].

Cardiomyocytes subjected to brief episode of hypoxia possess a resistance to serious damaging effect exerted by a subsequent long-time hypoxia on these cells, which is called hypoxic preconditioning (PC). The pathway of intracellular signal transduction during hypoxia PC has not yet been validated. On a model of hypoxia/reoxygenation (H/R) of cultured neonatal rabbit cardiomyocytes, the present study is taken to investigate the changes of mitogen-activated protein kinase (MAPK) and ribosomal S6 kinase (S6K) activity. It was found that intracellular total MAPK and nuclear MAPK, after a 15-min period of reoxygenation preceded by a single 60-min period of hypoxia, were increased by 95% and 230%, respectively. Intracellular S6K activity increased by 142% at 30 min of H/R vs the control group (P < 0.01). Phosphatase 1 (PPase 1) inhibitor (ocadaic acid, OA 1 mumol/L) augmented the increase of MAPK and S6K activity induced by H/R. However, tyrosine kinase (Tyr K) inhibitor (genistein), protein kinase C (PKC) inhibitor (H7) and preincubation of cardiomyocytes with PKC activator PMA all reduced MAPK activation by H/R. Protein kinase A (PKA) inhibitor (H89), Ca2+/Calmodulin-dependent protein kinase (PKM) inhibitor (W7) or PPase 2a inhibitor (OA 10 nmol/L) had no significant effect on MAPK and S6K activity. The above results suggested that activation of MAPK and S6K activity during hypoxia/reoxygenation there might require participation of PKC, Tyr K and PPase 1, while PKA, PKM and PPase 2a were not involved.

Animals↗

PubMed1996

Cloning and characterization of a novel serine/threonine protein kinase expressed in early Xenopus embryos.

We have cloned from a Xenopus ovary cDNA library a novel protein kinase gene whose expression peaks in the oocyte and unfertilized egg, begins to decrease gradually after fertilization, and disappears during the gastrulation stage of embryogenesis. The cloned gene, termed XEEK1 (for Xenopus egg and embryo kinase), encodes a protein with a predicted molecular mass of 49 kDa. Bacterially expressed XEEK1 migrates at 57 kDa upon polyacrylamide gel electrophoresis analysis, and a XEEK1-specific antibody recognizes a protein of 57 kDa in Xenopus oocyte and egg extracts. The XEEK1 kinase domain shares 35% identity (approximately 65% similarity) with the yeast SNF1 kinase and related kinases. However, expression of XEEK1 does not complement a snf1 deletion mutation in yeast, which suggests that it is probably not a Xenopus homolog of SNF1. Recombinant XEEK1 protein autophosphorylates on threonine residues in vitro in a reaction that prefers Mn2+ to Mg2+ ions. Site-directed mutagenesis of the conserved lysine residue (Lys-81) within the kinase domain to isoleucine totally abolishes kinase activity, and threonine 192 has been identified as the autophosphorylation site. This site is distinct from the conserved threonine (Thr-215 in XEEK1) present in the protein kinase activation loop that is the site of autophosphorylation for many protein kinases. XEEK1 is a substrate for the cyclic AMP-dependent protein kinase both in vitro and in vivo, suggesting a possible mode of regulation of XEEK1. An immunoprecipitate of oocyte/egg extracts with anti-XEEK1 serum contains a protein of approximately 155 kDa that may be a substrate and/or a regulatory component of the kinase.

Amino Acid Sequence↗

PubMed1996

Mechanisms of action of isoflurane on contraction of rabbit conduit artery.

Isoflurane may cause differential effects on different vascular beds of the same animal species. The mechanisms of this action have not been elucidated. Accordingly, we compared in rabbit aorta and femoral artery the effects of isoflurane (1-3.3%) in isolated rings (endothelium denuded) activated by norepinephrine, and isoflurane effects on Ca2+ fluxes from the sarcoplasmic reticulum in skinned strips. When < 30 nM norepinephrine was used to cause ring contraction, isoflurane increased the force of contraction in aortic rings, but decreased force in femoral arterial rings. At 30 nM norepinephrine stimulation, 3.3% isoflurane decreased the force and, in the presence of verapamil, isoflurane actually increased the force in both arterial types. In skinned strips of both arterial types, isoflurane present during Ca2+ uptake decreased the caffeine-induced tension transients, whereas isoflurane present during Ca2+ release enhanced the transients. Isoflurane potentiated the depression of the tension transients by ryanodine. Isoflurane directly caused contracture even in the absence of caffeine. Thus, isoflurane has similar cellular mechanisms of action in the aortic and femoral arterial smooth muscle: inhibiting Ca2+ influx through the sarcolemma, decreasing Ca2+ uptake by the sarcoplasmic reticulum, and enhancing caffeine-induced Ca2+ release from the sarcoplasmic reticulum.

Animals↗

PubMed1996

Total knee arthroplasty in tuberculous arthritis.

Sixteen cases of tuberculosis of the knee treated by total knee arthroplasty with followup of 3.4 to 11 years were reviewed. Eight cases were treated with antituberculous chemotherapy for 2 to 20 months before and 1 year after the arthroplasty. Another 8 cases were not diagnosed primarily and therefore received only postoperative antituberculous chemotherapy. Five cases had a recurrence of tuberculosis. Four of these 5 cases did not receive preoperative antituberculous treatment. The infection in 1 case was controlled satisfactorily with chemotherapy alone, and for the other 3 cases, chemotherapy was supported by surgical debridements. The last case of recurrent infection occurred in a patient who had received long- standing corticosteroid therapy. He required an excisional arthroplasty to control the infection. The mean functional knee score was 30.5 points before surgery and 82.6 points at the time of the last followup. These results suggest that arthroplasty may be formed for knees badly damaged with tuberculous infection, and good results may be expected for those patients who have received effective antituberculous chemotherapy both before and after surgery. There is a substantial risk of reactivation of tuberculous infection for those patients not treated before surgery or for patients dependent on corticosteroids.

Adult↗

PubMed1996

Effects of Arg-Gly-Asp-Ser on Ca2+ transport of myocardial sarcoplasmic reticulum in rat septic shock.

AIM: To study the effects of Arg-Gly-Asp-Ser (RGDS), a synthetic short peptide of fibrinogen degradation, on the Ca2+ transport function of cardiac sarcoplasmic reticulum in rat septic shock. METHODS: RGDS 5 mumol.kg-1 was injected i.v. at 4 h and 14 h after cecal ligation and puncture (CLP) operation on rats. Highly purified membrane of sarcoplasmic reticulum (SR) was prepared from rat hearts. Assays were made of ATP-dependent Ca2+ uptake by cardiac SR and [3H] ryanodine binding to SR. RESULTS: The initial rate and the capacity of SR Ca2+ uptake were increased by 104% (P < 0.01) and 12% (P < 0.05), respectively, paralleled by an increase in Ca(2+)-ATPase activity and a decrease in calcium accumulation of myo- cardium of septic rats, whereas the Bmax and Kd values of Ca2+ activated [3H]ryanodine binding to SR were unaffected after RGDS administration. CONCLUSIONS: The results indicated that RGDS have cardioprotective effects of maintaining Ca2+ homeostasis of cardiac myocytes by enhancing SR Ca2+ uptake in rat septic shock.

Animals↗

PubMed1995

Cloning and characterization of the Xenopus cyclin-dependent kinase inhibitor p27XIC1.

We have isolated a gene encoding Xic-1, a 27-kDa cyclin-dependent kinase (Cdk) inhibitor from Xenopus ovary that shares significant homology with both mammalian CIP1 and Kip1/Kip2. The N- and C-terminal halves of Xic-1 are sufficient for interacting with Cdks and proliferating cell nuclear antigen, respectively. Recombinant Xic-1 inhibits Xenopus cyclin E/Cdk2, cyclin A/Cdk2 and cyclin B/Cdc2 activities, although with quite different IC50 values. Truncation of the N terminus of Xic-1 increases the IC50 value for cyclin A/Cdk2 50-fold with no effect on the inhibition of cyclin E/Cdk2 or cyclin B/Cdc2.Xic-1 inhibits both single-stranded and nuclear DNA synthesis in egg extracts, an effect reversed by proliferating cell nuclear antigen or cyclin E/Cdk2, respectively. These results suggest a function for Xic-1 in the control of DNA synthesis by cyclin E/Cdk2.

Amino Acid Sequence↗

PubMed1995

Cloning and expression of a Xenopus gene that prevents mitotic catastrophe in fission yeast.

In fission yeast the Wee1 kinase and the functionally redundant Mik1 kinase provide a regulatory mechanism to ensure that mitosis is initiated only after the completion of DNA synthesis. Yeast in which both Wee1 and Mik1 kinases are defective exhibit a mitotic catastrophe phenotype, presumably due to premature entry into mitosis. Because of the functional conservation of cell cycle control elements, the expression of a vertebrate wee1 or mik1 homolog would be expected to rescue such lethal mutations in yeast. A Xenopus total ovary cDNA library was constructed in a fission yeast expression vector and used to transform a yeast temperature-dependent mitotic catastrophe mutant defective in both wee1 and mik1. Here we report the identification of a Xenopus cDNA clone that can rescue several different yeast mitotic catastrophe mutants defective in Wee1 kinase function. The expression of this clone in a wee1/mik1-deficient mutant causes an elongated cell phenotype under non-permissive growth conditions. The 2.0 kb cDNA clone contains an open reading frame of 1263 nucleotides, encoding a predicted 47 kDa protein. Bacterially expressed recombinant protein was used to raise a polyclonal antibody, which specifically recognizes a 47 kDa protein from Xenopus oocyte nuclei, suggesting the gene encodes a nuclear protein in Xenopus. The ability of this cDNA to complement mitotic catastrophe mutations is independent of Wee1 kinase activity.

Amino Acid Sequence↗

PubMed1995

Modulation of the ryanodine receptor sarcoplasmic reticular Ca2+ channel in skinned fibers of fast- and slow-twitch skeletal muscles from rabbits.

This study was performed to compare skinned fibers from rabbit adductor magnus (AM) and soleus (SL) muscles with regard to the influence of caffeine, Ca2+ and Mg2+ on the depressive effects of ryanodine (RYA) on the caffeine-induced tension transients. Single skinned fibers were immersed in solutions to load Ca2+ into, and release Ca2+ from the SR (a load-release cycle). Three cycles were sequentially performed in each skinned fiber: (1) a control (no RYA), (2) a conditioning period in which activation was carried out in the presence of ryanodine plus various concentrations of the modulators, i.e. caffeine, Ca2+ or Mg2+, and (3) a test (no RYA) which monitored the release activity retained after the conditioning cycle. The depressive effect of RYA was found to be a function of [ryanodine], [caffeine], or [Ca2+], and an inverse function of [Mg2+], where [] denotes concentration. The half-maximal effects of RYA in AM (5 microM RYA) and SL (10 microM RYA), respectively, occurred at a pCa50 of 5.32 versus 5.43 without caffeine, or pCa50 of 7.24 versus 6.88 and pMg50 of 3.29 versus 3.61 with 25 mM caffeine, at a [caffeine] of 4.96 versus 7.29 mM, and at a [ryanodine] of 31.0 versus 101.6 microM. Thus, the RYA depression in skinned muscle fibers is modulated by caffeine, Ca2+, and Mg2+ in both muscle types, and AM is at least two- to fourfold more sensitive than SL.

Animals↗

PubMed1995

Effects of halothane on calcium(2+)-activated tension of the contractile proteins and calcium(2+) uptake and release by the sarcoplasmic reticulum in skinned human myocardial fibers.

Based on studies using skinned myocardial fibers from animals, it has been postulated that one of the major mechanisms by which halothane depresses myocardial contractility is by decreasing the Ca2+ content of the sarcoplasmic reticulum (SR). In this study we examined, in skinned human myocardial fibers, the effects of halothane on Ca(2+)-activated tension development of the contractile proteins and Ca2+ uptake and release by the SR. Left ventricular muscle samples obtained from patients undergoing aortocoronary bypass operations were mechanically skinned and immersed in test solutions equilibrated with N2 and halothane preceded and followed by immersion in control solution (no halothane). To study Ca(2+)-activated tension development of the contractile proteins, free Ca2+ concentrations in the bathing solutions were buffered by EGTA. To study Ca2+ uptake and release by the SR, Ca2+ was loaded into the SR and released with caffeine and the resulting tension transients were measured. Halothane (1%-3%) depressed maximum Ca(2+)-activated tensions (pCa = -log[Ca2+](M) = 3.8) by 5% for each 1% increase in concentration. Tensions generated by submaximum Ca2+ concentrations expressed as a percentage of maximum tension were not significantly decreased by halothane except at 3%. Halothane decreased Ca2+ uptake (IC50 = 1.7%), and increased (by approximately 50%) Ca2+ release by the SR. We conclude that decreased activation of the contractile proteins and Ca2+ uptake by the SR can both contribute to the myocardial depression produced by halothane. Of these, decreased Ca2+ uptake by the SR is probably a major mechanism for halothane depression of myocardium.

Animals↗

PubMed1995

[Impaired calcium uptake by cardiac sarcoplasmic reticulum and its underlying mechanism during rat septic shock].

The underlying mechanism of Ca2+ uptake function of cardiac sarcoplasmic reticulum (SR) was investigated in the rat septic shock model produced by cecal ligation and puncture (CLP). The results are as follows. During the early phase of sepsis, the initial rate of ATP-dependent Ca2+ uptake by SR was decreased, while both the capacity of Ca2+ uptake and the activity of Ca(2+)-ATPase were unaffected. In the late sepsis, the impairment in SR function was even greater as the initial rate and the capacity of Ca2+ uptake by SR were significantly decreased, and this was paralleled by a reduction in Ca(2+)-ATPase activity. Although Ca2+ affinity (Km value) to calcium pump and the A0.5 values for Mg2+ and ATP activation on the Ca2+ uptake rate were unchanged, during sepsis the phosphorylation of SR vesicles by adding of catalytic subunit of the cAMP-dependent protein kinase (PKA), calmodulin, or the fragment of PKC into Ca2+ uptake buffer, failed to stimulate Ca2+ uptake activities of SR isolated from early or late septic rats. These data suggest that depression of cardiac SR function is aggravated as sepsis develops, the impairment of SR Ca2+ uptake is possibly based on a mechanism of defective phosphorylation of SR rather than the ionic and energic regulatory actions of Ca2+, Mg2+, ATP on cardiac SR.

Animals↗

PubMed1995

Phosphofructokinase binding to myofibrils in fish muscle: influences of ionic strength and metabolite levels on enzyme complex formation.

The interaction of 6-phosphofructo-1-kinase (PFK) with myofibrils was assessed using the purified proteins from rainbow trout white skeletal muscle. More than 70% of PFK activity was bound at pH values between 6 and 7 but higher pHs dissociated the complex. Increasing salt concentrations also reduced PFK binding, with greater sensitivity to salt at pH 7.0 vs pH 6.6. Substrates and allosteric effectors also reduced enzyme binding to myofibrils; 50% of enzyme was released at 0.23, 0.24, 1.3, and 2.0 mM for fructose 6-phosphate, Mg.ATP, ATP and AMP, respectively. However, the addition of a protein crowding agent, poly(ethylene)glycol, greatly enhanced PFK binding to myofibrils, particularly at high pH (8.0) or high [KCl]. The studies suggest that reversible binding of PFK to myofibrils may be an important factor in the control of anaerobic glycolysis in vivo, especially under the cellular conditions of burst swimming exercise.

Actins↗

PubMed1995

Arthroscopic debridement for osteoarthritis of the knee: a seven years follow-up study.

We reviewed 32 knees with osteoarthritis of the knee treated by either arthroscopic debridement in association with drilling the subchondral bone or arthroscopic debridement alone and followed for 2.5 to 11 years. Eighteen knees had arthroscopic debridement and drilling the subchondral bone, and 14 knees had arthroscopic debridement alone. In the group treated with arthroscopic debridement and drilling the subchondral bone, 55.6% had good to excellent results, 22.2% had fair results, and 22.2% had poor results. In the group that had arthroscopic debridement alone, 57.2% had good to excellent results, 35.7% had fair results, and 7.1% had poor results. There was better relief of pain in the group with arthroscopic debridement alone.

Adult↗

PubMed1995

In Vitro antimicrobial susceptibilities of Streptococcus pneumoniae isolated from two teaching hospitals in Taiwan, 1989-1995.

The susceptibility of 46 pneumococcal isolates collected during October 1989 to May 1995 from National Taiwan University Hospital and Taipei Municipal Yang Ming Hospital was studied. Among these isolates, the resistant rate of penicillin G was 21.7%; the penicillin G-resistant strains were more frequently resistant than the penicillin-sensitive strains to other beta-lactam antimicrobial drugs. The minimum bactericidal concentrations (MBCs) of penicillin G for all isolates were equal to, or one dilution higher than, minimum inhibitory concentrations (MICs). Three strains were false positive for penicillin resistance among isolates of Streptococcus pneumoniae screened with oxacillin. On the other hand, resistance to penicillin G was often independent of resistance to erythromycin. Vancomycin was the most active agent tested.

Humans↗

PubMed1994

Effect of chain length on the formation and stability of synthetic alpha-helical coiled coils.

A series of polypeptides containing 9, 12, 16, 19, 23, 26, 30, 33, and 35 amino acid residues was designed to investigate the effects of peptide chain length on the formation and stability of two-stranded alpha-helical dimers or coiled coils. These peptides were synthesized by the solid-phase method, purified by reversed-phase high-performance liquid chromatography (RP-HPLC), and characterized by RP-HPLC, amino acid composition analysis, and mass spectrometry. The amphipathic alpha-helical peptides were designed to dimerize by interchain hydrophobic interactions at positions a and d and interchain salt bridges between lysine and glutamic acid residues at positions e and g of the repeating heptad sequence of Glu-Ile-Glu-Ala-Leu-Lys-Ala (g-a-b-c-d-e-f). The ability of these peptides to form alpha-helical structures in the presence and absence of a helix-inducing reagent (trifluoroethanol) was monitored by circular dichroism spectroscopy. The helicity of the peptides increased with increasing chain length in a cooperative manner. A minimum of three heptads corresponding to six helical turns was required for a peptide to adopt the two-stranded alpha-helical coiled coil conformation in aqueous medium. The increased stability of the peptides as a result of an increase in hydrophobic interactions (chain length) was demonstrated by the shift in the transitions of the guanidine hydrochloride (Gdn.HCl) denaturation and thermal unfolding profiles. The concentrations of denaturant (Gdn.HCl) required to achieve 50% denaturation are 3.2, 4.9, 6.9, and 7.5 M for peptides 23r, 26r, 30r, and 33r, respectively, in aqueous medium. However, the effect of a chain length increase on coiled-coil stability was not additive. The melting temperature, Tm, at which 50% of the helicity is lost, increased by 34 degrees C in changing the peptide chain length from 23 to 26; however, that shift was only 14 degrees C when the chain length was increased from 30 to 33 residues. These results are consistent with a chain length dependent cooperative folding of the peptides into coiled coils.

Amino Acid Sequence↗

PubMed1994

Identification of a Xenopus cDNA that prevents mitotic catastrophe in the fission yeast Schizosaccharomyces pombe.

A Xenopus total ovary cDNA library was constructed in a fission yeast expression vector. Using a genetic functional complementation method, we have identified a Xenopus cDNA clone that can rescue several different yeast mitotic catastrophe mutants defective in Wee1 kinase function at the restrictive temperature. The 3.0-kb cDNA clone contains an open reading frame (ORF) of 2226 nucleotides, encoding a predicted 82-kDa protein. The deduced amino acid (aa) sequence shows seven almost identical 30-aa tandem repeats, each of which contains a phosphorylation site meeting the consensus for both Cdc2 kinase and MAP kinase.

Amino Acid Sequence↗