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Biomedical subjects

J S Han

Publications and source records attributed to J S Han.

At least 73 records · Page 4Linked to original sources
PubMed2000

Ras GTPase is essential for fas-mediated activation of phospholipase D in A20 cells.

We have previously reported that Fas cross-linking resulted in an increase in phospholipase D activity in A20 murine cells (J.-S. Han et al., Arch. Biochem. Biophys. 367, 233-239, 1999). In an attempt to explore the Fas downstream factor contributing to the activation of phospholipase D, we have investigated the possible involvement of a small GTP biding protein Ras in signaling events that were triggered by Fas cross-linking. Upon adenoviral expression of dominant negative mutant of Ras (N17Ras), an increase in phospholipase D activity by anti-Fas monoclonal antibody was diminished. Also, the Fas downstream signaling events triggered by Fas cross-linking such as the activation of phosphatidylcholine-specific phospholipase C, the increase in diacylglycerol level, and the translocation of protein kinase C to membrane fraction were all reduced by N17Ras expression. When parallel experiments were performed with manumycin-A, a Ras farnensyltransferase inhibitor, almost identical inhibitory effects on Fas downstream signaling were exhibited. These data suggest that Ras GTPase is essential in transmitting phospholipase D activation signal induced by Fas cross-linking and is located at phosphatidylcholine-specific phospholipase C upstream in Fas signaling cascades.

Adenoviridae↗
PubMed2000

Peripheral electric stimulation inhibits morphine-induced place preference in rats.

Conditioned place preference (CPP) is a commonly used model to detect rewarding effect of drugs. To observe the effect of peripheral electric stimulation (PES) on morphine-induced CPP, we trained the rats with morphine in a CPP paradigm. Twelve hours before the testing phase, rats were given PES via stainless-steel needles with frequencies of 2, 100, or 2/100 Hz, respectively. PES of 2 and 2/100 Hz significantly decreased CPP in morphine-trained animals in a naloxone reversible manner, while PES of 100 Hz, foot shock, needle insertion, or plain restraining, showed no effect. Thus, PES with a low-frequency component (2 Hz) could specifically inhibit the expression of morphine-induced CPP, presumably via activation of opioid receptors.

Acupuncture Therapy↗
PubMed2000

Decreased GDNF mRNA expression in dorsal spinal cord of unilateral arthritic rat.

It is now well established that nerve growth factor (NGF) plays a key role in inflammation-induced hyperalgesia. It was also reported that brain derived neurotrophic factor (BDNF), another member of neurotrophins, contributed to the pain pathway as a neurotransmitter in the CNS. The present work demonstrated a down-regulation of glial cell line-derived neurotrophic factor (GDNF) mRNA expression in dorsal spinal cord in complete Freund's adjuvant-induced unilateral arthritic rats serving as a chronic pain model. The fast occurring and long lasting down-regulations suggest that GDNF might contribute to pain pathway in a way different from neurotrophins and might play a role in the maintenance of chronic pain status.

Animals↗
PubMed2000

A comparison of mechanical properties of all-ceramic alumina dental crowns prepared from aqueous- and non-aqueous-based tape casting.

Alumina-glass dental composites were prepared by aqueous- and non-aqueous-based tape casting and sintering at 1120 degrees C, followed by glass infiltration at 1100 degrees C. Flexural strength and fracture toughness of the composites were investigated in terms of influence of tape constituents, namely, alumina powder, binder, and plasticizer on the mechanical properties. For the alumina-glass composites prepared from the aqueous-based tapes, both strength and toughness increased with increasing alumina fraction ratio in tape constituents including organic substances, a/a+o, and binder content ratio in binder/binder + plasticizer mixture, b/b+p. For the composites prepared from the non-aqueous-based tapes, on the other hand, both strength and toughness increased with increasing the a/a+o ratio but decreased with increasing the b/b+p ratio. These observations were consistent with influence of the constituents on mean alumina particle distance in tapes, suggesting that high strength of the glass infiltrated alumina composites is related to toughening by crack bowing. The optimized strength of the aqueous and nonaqueous tape cast composites was 559 and 508 MPa, and the fracture toughness was 3.3 and 3.1 MPam(1/2), respectively.

Aluminum Oxide↗
PubMed2000

Mechanical properties, phase stability, and biocompatibility of (Y, Nb)-TZP/Al(2)O(3) composite abutments for dental implant.

ZrO(2)/Al(2)O(3) composites were prepared by mixing a tetragonal ZrO(2), stabilized by 5.31 mol% Y(2)O(3) and 4.45 mol% Nb(2)O(5), and various amounts of Al(2)O(3). Influence of the amount of Al(2)O(3) on strength and toughness and tetragonal phase stability in the composites under autoclave conditions was investigated. In addition, in vitro and in vivo biocompatibility of the composites was examined. The composite, prepared with addition of 20 vol% Al(2)O(3), exhibited the highest strength of 700 MPa and toughness of 8.1 MPa. m(1/2) and showed no hydrothermal degradation while aging in an autoclave. The biocompatibility of the composite exhibited no cytotoxicity and no significant adverse soft-tissue response for up to 3 months implant period in guinea pigs.

Aluminum Oxide↗
PubMed2000

A new method for the representation of articular surfaces using the influence surface theory of plates.

The traditional approach to the representation of an articular surface is by using piecewise polynomial functions with a limited continuity to fit the surface from ordered data points. In this study, we introduce a new method, which is based on the influence surface theory of plates, for the representation of articular surfaces. The most significant advantage of this method is that it can effectively represent an articular surface from non-ordered data points. The effectiveness of the present method was shown by reconstruction of a human femoral surface and a mathematical cone.

Algorithms↗
PubMed2000

Functional studies using antibodies against orphanin FQ/nociceptin.

Orphanin FQ/nociceptin (OFQ) is a recently discovered endogenous ligand for the novel opioid receptor-like receptor (ORL-1). There are numerous reports in the literature demonstrating paradoxical effects of exogenous OFQ on pain modulation. For example, OFQ produces a pronociceptive effect in the brain and an analgesic effect in the spinal cord. In order to better understand the physiological actions of OFQ, the present study focused on the pain-modulatory effect of endogenously released OFQ measured using antibody microinjection techniques. We found that electroacupuncture analgesia (EA) was increased by intracerebroventricular (i.c.v.) injection of an OFQ-antibody and decreased following intrathecal injection. Furthermore, i.c.v. OFQ-antibody partially reversed tolerance to both chronic morphine and chronic EA. These data suggest that endogenously released OFQ plays an important role in pain modulation, where pain sensitivity in the brain and spinal cord is increased and decreased, respectively.

Analgesics, Opioid↗
PubMed2000

Phosphatidylcholine-specific phospholipase C-mediated induction of phospholipase D activity in Fas-expressing murine cells.

We have previously reported that Fas cross-linking resulted in the activation of phosphatidylcholine-specific phospholipase C (PC-PLC) and the subsequent activation of protein kinase C (PKC) and phospholipase D (PLD) in A20 cells. In an attempt to correlate the existence of PC-PLC activity and activation of PLD by Fas activation among various Fas-expressing murine cell lines, we have investigated the effect of anti-Fas monoclonal antibody on PC-PLC and PLD activities in A20, P388D1 and YAC-1 cell lines. Upon treatment of anti-Fas monoclonal antibody to these three cell lines, the activation of PLD was only observed in A20 cells. When the effect of anti-Fas monoclonal antibody on PKC and PC-PLC activities in Fas-expressing clones were investigated, the activation of PKC and PC-PLC was detected only in A20 clones. Results presented here also show that exogenous addition of Bacillus cereus PC-PLC activates PC hydrolysis, PKC and PLD in all three murine cell lines. These findings suggest that the activation of PC-PLC is a necessary requirement for the activation of PLD by Fas cross-linking and cell lines devoid of functional PC-PLC activity could exhibit enhanced PLD activity by exogenous addition of PC-PLC.

Animals↗
PubMed2000

Diminished adenylate cyclase activity and aquaporin 2 expression in acute renal failure rats.

BACKGROUND: The present study was aimed at investigating the changes of aquaporin 2 (AQP2) expression and its underlying mechanisms in ischemic acute renal failure (ARF). METHODS: ARF was induced by clamping the both renal arteries for 60 minutes in rats. Two or seven days later, AQP2 expression and trafficking were determined in the kidney by Western blot analysis and immunohistochemistry. The activity of adenylate cyclase was also measured. RESULTS: The urinary flow rates in ARF-2 and ARF-7 day were significantly increased in association with decreases of urine osmolality. While there was decreased expression of AQP2 in the cortex, outer medulla, and inner medulla in ARF, it was most pronounced in the outer medulla. The AQP2 expression was reduced in the apical membrane-enriched fraction as well the subapical vesicle-enriched fraction in ARF; however, the degree was greater in the former than in the latter. Immunohistochemical study also showed a markedly decreased expression of AQP2 in the collecting duct in ARF. cAMP generation in response to arginine vasopressin (AVP) in the kidney was attenuated in ARF, most prominently in the outer medulla. cAMP generation in the outer medulla in response to forskolin was not affected, but sodium fluoride was significantly blunted in ARF. CONCLUSIONS: The AVP-stimulated adenylate cyclase activity is impaired in ARF, secondary to a defect at the level of the G protein. The expression of AQP2 was reduced as a consequence, which may in part account for urinary concentration defect in ARF.

Acute Kidney Injury↗
PubMed2000

Decreased abundance of major Na(+) transporters in kidneys of rats with ischemia-induced acute renal failure.

Ischemia-induced acute renal failure (ARF) is known to be associated with significant impairment of tubular Na reabsorption. We examined whether temporary bilateral renal ischemia (30, 40, or 60 min) and reperfusion (1-5 days) affect the abundance of several renal Na transporters and urinary Na excretion (U(Na)V) in rats. In rats with mild ARF (30 min), immunoblotting revealed that proximal tubule type 3 Na(+)/H(+) exchanger (NHE-3) and type II Na-P(i) cotransporter (NaPi-II) were significantly decreased to 28 +/- 6 and 14 +/- 6% of sham levels, respectively, at day 1. Moreover, Na(+)-K(+)-ATPase levels were also significantly decreased (51 +/- 11%), whereas there was no significant decrease in type 1 bumetanide-sensitive cotransporter (BSC-1) and thiazide-sensitive cotransporter (TSC) levels. Consistent with reduced Na transporter abundance, fractional urinary Na excretion (FE(Na)) was significantly increased in mild ARF (30 min) and U(Na)V was unchanged, despite a marked reduction in glomerular filtration rate. Na transporter levels and renal Na handling were normalized within 5 days. Severe ischemic injury (60 min) resulted in a marked decrease in the abundance of Na(+)-K(+)-ATPase, NHE-3, NaPi-II, BSC-1, and TSC at both days 1 and 5. Consistent with this, FE(Na) was significantly increased at days 1 and 5. Intravenous K-melanocyte-stimulated hormone treatment partially prevented the ischemia-induced downregulation of renal Na transporters and reduced the high FE(Na) to control levels. We conclude that reduced levels of Na transporters along the nephron may play a critical role in the impairment of tubular Na reabsorption, and hence increased Na excretion, in ischemia-induced ARF.

Acute Kidney Injury↗
PubMed2000

Detection of Hantaan and Seoul viruses by reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP) in renal syndrome patients with hemorrhagic fever.

BACKGROUND: Hemorrhagic fever with renal syndrome (HFRS), also called Korean hemorrhagic fever (KHF), is the most common cause of acute renal failure in the Far East. Two serotypes of hantavirus, Hantaan and Seoul viruses are known pathogens for HFRS in Korea. PURPOSE: To elucidate the diagnostic applicability for the serotype diagnosis in HFRS patients, we used nested reverse transcriptase-PCR and restriction fragment length polymorphism (nRT-PCR/RFLP) to screen 2 prototype viruses, 11 virus isolates from HFRS patients, and 69 specimens obtained from 31 HFRS patients. METHODS: The nRT-PCR was performed using primers specific for the G1 segments of the Hantaan (HF3 1140-1163, HB14 1363-1342) and Seoul (SF2 809-832, SB3 1200-1177) viruses. The initial PCR products were then further amplified using nested primers for the Hantaan (HF4 1141-1164, HB13 1360-1339) and Seoul (SF7 863-884, SB1 1165-1142 ) viruses. Amplified segments were then digested with restriction enzymes specific for either Hantaan (C1a I) or Seoul (Sac I) virus sequences. RESULTS: In all cultured viruses, the serotypes identified by nRT-PCR/RFLP were consistent with those of PRNT. nRT-PCR/RFLP results indicated the presence of Hantaan virus in 10 patients and of Seoul virus in 15 patients. In 3 patients, both Hantaan- and Seoul-specific amplified bands were visualized in serially collected samples, and in 4 patients no amplicon was detected. Among 69 specimens, 55 were positive; these positive specimens were obtained between days 3 and days 33 of illness. The positive rate was not affected by the clinical phase, day of illness, or severity of HFRS. CONCLUSIONS: nRT-PCR/RFLP is a rapid and convenient method for serotype diagnosis in most HFRS patients. It could also allow detection of genetic variation of hantavirus within the same serotype.

Adult↗
PubMed1999

Suppression of morphine withdrawal by electroacupuncture in rats: dynorphin and kappa-opioid receptor implicated.

Our previous work has demonstrated that 100-Hz electroacupuncture (EA) or 100-Hz transcutaneous electrical nerve stimulation (TENS) was very effective in ameliorating the morphine withdrawal syndrome in rats and humans. The mechanism was obscure. (1) Rats were made dependent on morphine by repeated morphine injections (5-140 mg/kg, s.c., twice a day) for eight days. They were then given 100-Hz EA for 30 min 24 h after the last injection of morphine. A marked increase in tail flick latency (TFL) was observed. This effect of 100-Hz EA could be blocked by naloxone (NX) at 20 mg/kg, but not at 1 mg/kg, suggesting that 100-Hz EA-induced analgesia observed in morphine-dependent rats is mediated by kappa-opioid receptors. (2) A significant decrease of the concentration of dynorphin A (1-17) immunoreactivity (-ir) was observed in the spinal perfusate in morphine-dependent rats, that could be brought back to normal level by 100-Hz EA. (3) 100-Hz EA was very effective in suppressing NX-precipitated morphine withdrawal syndrome. This effect of EA could be prevented by intrathecal administration of nor-BNI (2.5 micrograms/20 microliters), a kappa-opioid receptor antagonist, or dynorphin A (1-13) antibodies (25 micrograms/20 microliters) administered 10 min prior to EA. In conclusion, while the steady-state spinal dynorphin release is low in morphine-dependent rats, it can be activated by 100-Hz EA stimulation, which may be responsible for eliciting an analgesic effect and ameliorating morphine withdrawal syndrome, most probably via interacting with kappa-opioid receptor at spinal level.

Animals↗
PubMed1999

Endomorphin-1 mediates 2 Hz but not 100 Hz electroacupuncture analgesia in the rat.

This work was designed to elucidate the possible involvement of endogenous endomorphin-I (EM1) in analgesia induced by electroacupuncture of low or high frequencies. Taking radiant heat tail flick latency (TFL) as an indication of nociception, rats were subjected to intrathecal (i.t.) injection of 10 microl antiserum against EM1 (EM1-AS) or normal rabbit serum (NRS, as control) and then followed by 2 or 100 Hz electroacupuncture stimulation for 30 min. The analgesia induced by 2 Hz electroacupuncture was attenuated by i.t. injection of EM1-AS at 1:10 and 1:100 but not at 1:1000 dilution. No such suppressive effect was observed for 100 Hz EA analgesia when EM1-AS was injected i.t. at any dilutions. These results indicate that EM1 is involved in 2 Hz but not 100 Hz electroacupuncture analgesia at spinal level.

Acupuncture Analgesia↗
PubMed1999

Effect of ceramide on apoptosis and phospholipase D activity in FRTL-5 thyroid cells.

Ceramide, a product of sphingomyelin hydrolysis, is now recognized as an intracellular lipid messenger, which mediates the effects of extracellular agents on cellular growth, differentiation and apoptosis. Recently, ceramide has been implicated in the regulation of phospholipase D (PLD). In this study, we examined the effects of ceramide on the activity and mRNA level of PLD during apoptotic process in FRTL-5 thyroid cells. C2-ceramide (N-acetyl sphingosine) induced apoptosis in FRTL-5 thyroid cells. Fluorescent staining showed that ceramide induced the typical features of apoptosis including condensed or fragmented nuclei. DNA fragmentation was also observed by agarose gel electrophoresis. Flow cytometric cell cycle analysis showed more clearly that ceramide induced apoptotic cell death in FRTL-5 thyroid cells. The treatment of FRTL-5 thyroid cells with thyroid-stimulating hormone (TSH) resulted in an increased PLD activity in a dose- and time-dependent manner. However, the TSH-induced increase in PLD activity was down-regulated within 2 h after ceramide treatment. Furthermore, the levels of PLD mRNA were found to be decreased throughout apoptotic process as inferred by reverse transcription-polymerase chain reaction. However, the decreases in PLD mRNA levels were not correlated with those in PLD activities after ceramide treatment. Taken together, these data suggest that ceramide inhibits the PLD activity in an early apoptotic phase and down-regulation of the levels of PLD mRNA may be implicated in apoptotic process in FRTL-5 thyroid cells.

Animals↗
PubMed1999

Ku autoantigen affects the susceptibility to anticancer drugs.

The Ku70/80 autoantigens (Ku) are the DNA-binding components of a DNA-dependent protein kinase (PK) involved in DNA double strand breaks repairing a V(D)J recombination. Because apoptosis is associated with DNA fragmentation and, consequently, creation of double strand breaks, and a variety of DNA-damaging drugs kill tumor cells by apoptosis, we tested the impact of Ku deficiency on the sensitivity of anticancer drugs. Ku-null mutant cell lines Ku70-/- and Ku80-/- were highly sensitive to anticancer drugs, compared with their wild-type cells. Ku-deficient cells were more sensitive to bleomycin-induced DNA fragmentation and exhibited a higher level of c-jun NH2-kinase/stress-activated PK activity than wild-type cells, whereas R7080-6 cells overexpressing both human Ku70 and Ku80 were resistant to bleomycin-induced apoptosis and exhibited a lower level of c-jun NH2-kinase/stress-activated PK activity. The Ku-protein level and Ku DNA binding activity were decreased after treatment with bleomycin, adriamycin, or vincristine, and the decreases were blocked by the treatment of z-DEVD-fmk, a specific inhibitor of caspase-3, suggesting that loss of Ku DNA binding is, in part, due to a caspase-mediated decrease in Ku protein levels. By contrast, HSF1 DNA-binding activity was increased by the treatment of these anticancer drugs and, subsequently, mitochondrial heat shock protein HSP75 was specifically induced. Our data suggest that Ku can affect the susceptibility to anticancer drug-induced apoptosis.

Animals↗
PubMed1999

Fas-mediated activation of phospholipase D is coupled to the stimulation of phosphatidylcholine-specific phospholipase C in A20 cells.

The activation of phospholipase D in murine B cell lymphoma A20 cells treated with anti-Fas monoclonal antibody has been investigated. Fas cross-linking resulted in a both dose- and time-dependent increases in phospholipase D activity. There was a nearly maximum saturated rise in phospholipase D activity at the dose of 200 ng/ml anti-Fas monoclonal antibody showing a fourfold increase within 3 h. Fas activation also caused an approximately twofold increase of phosphatidylcholine-specific phospholipase C activity and 1,2-diacylglycerol release, which could be blocked by 30 min pretreatment with the phosphatidylcholine-specific phospholipase C inhibitor D609 (50 microgram/ml). Pretreatment of D609 also effectively inhibited the translocation of protein kinase C betaI and betaII from the cytosol to the membrane and the activation of phospholipase D induced by Fas cross-linking, suggesting that 1, 2-diacylglycerol released from the cellular phosphatidylcholine pool through phosphatidylcholine-specific phospholipase C plays a major role in protein kinase C/phospholipase D activation. Anti-Fas monoclonal antibody failed to elicit phosphoinositide-specific phospholipase C activation and any changes in the intracellular Ca2+ level in A20 cells, indicating that the phosphoinositide-mediated pathway is not involved in this Fas signaling. Therefore, these results suggest that Fas-mediated phospholipase D activation may be a consequence of primary stimulation of phosphatidylcholine-specific phospholipase C and that phospholipase D may play a role in Fas cross-linking signaling downstream from phosphatidylcholine-specific phospholipase C.

Animals↗
PubMed1999

Accelerated release and production of orphanin FQ in brain of chronic morphine tolerant rats.

Orphanin FQ has been shown to possess anti-opioid activity at supraspinal level. Our previous work revealed that chronic morphine tolerance could be reversed by intracerebroventricular (i.c.v.) injection of OFQ IgG to rats. In this study, we used radioimmunoassay (RIA) to assess the changes of Orphanin FQ immunoreactivity (OFQ-ir) in cerebroventricular perfusate, periaqueductal gray (PAG) and amygdala of rats made tolerance to morphine (10-60 mg/kg, s.c., t.i.d., for 5 days). The results indicated that: (1) In rats administrated with morphine for 3 and 5 days, the content of OFQ-ir in cerebroventricular perfusate increased by 25% and 52% over the NS control group. (2) The content of OFQ-ir in PAG of rats receiving 1d, 3d and 5d injections of morphine showed an increase of 17%, 48% and 81% respectively over NS group. (3) The content of OFQ-ir in amygdala of rats given 3d and 5d of morphine showed a 36% and 55% increase compared with corresponding control group. It is suggested that continuous use of high doses of morphine accelerated the release and biosynthesis of OFQ in rat brain to antagonize the effect of opioids, which may play a role in the development of morphine tolerance, and that brain OFQ may serve as a delayed negative feedback control on opioid analgesia.

Amygdala↗