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Biomedical subjects

K Mizuno

Publications and source records attributed to K Mizuno.

At least 199 records · Page 11Linked to original sources
PubMed1999

Thiazolidinediones down-regulate plasminogen activator inhibitor type 1 expression in human vascular endothelial cells: A possible role for PPARgamma in endothelial function.

The effect of peroxisome proliferator-activated receptor (PPAR) gamma activators, thiazolidinediones, on plasminogen activator type 1 (PAI-1) was examined in cultured human umbilical vein endothelial cells (HUVEC). Tumor necrosis factor alpha (TNF-alpha) enhanced PAI-1 secretion and mRNA expression by approximately 2-fold. The thiazolidinediones, troglitazone and pioglitazone, decreased basal and TNF-alpha-stimulated PAI-1 secretion and mRNA expression in HUVEC in a dose-dependent fashion. PPARgamma mRNA in HUVEC could be detected by reverse transcriptase-polymerase chain reaction using specific primers. These results suggest that PPARgamma may regulate PAI-1 expression in HUVEC and that thiazolidinediones have a therapeutic potential for improving endothelial dysfunction observed in insulin resistance.

Base Sequence↗
PubMed1999

Dual specificity protein kinase activity of testis-specific protein kinase 1 and its regulation by autophosphorylation of serine-215 within the activation loop.

TESK1 (testis-specific protein kinase 1) is a protein kinase with a structure composed of an N-terminal protein kinase domain and a C-terminal proline-rich domain. Whereas the 3.6-kilobase TESK1 mRNA is expressed predominantly in the testis, a faint 2.5-kilobase TESK1 mRNA is expressed ubiquitously. The kinase domain of TESK1 contains in the catalytic loop in subdomain VIB an unusual DLTSKN sequence, which is not related to the consensus sequence of either serine/threonine kinases or tyrosine kinases. In this study, we show that TESK1 has kinase activity with dual specificity on both serine/threonine and tyrosine residues. In an in vitro kinase reaction, the kinase domain of TESK1 underwent autophosphorylation on serine and tyrosine residues and catalyzed phosphorylation of histone H3 and myelin basic protein on serine, threonine, and tyrosine residues. Site-directed mutagenesis analyses revealed that Ser-215 within the "activation loop" of the kinase domain is the site of serine autophosphorylation of TESK1. Replacement of Ser-215 by alanine almost completely abolished serine autophosphorylation and histone H3 kinase activities. In contrast, replacement of Ser-215 by glutamic acid abolished serine autophosphorylation activity but retained histone H3 kinase activity. These results suggest that autophosphorylation of Ser-215 is an important step to positively regulate the kinase activity of TESK1.

Alanine↗
PubMed1999

Differential effects of GDNF and BDNF on cultured ventral mesencephalic neurons.

Previous studies have shown that brain derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) can enhance the survival of dopaminergic neurons in the ventral mesencephalon (VM). Here we compared several non-survival functions of the two factors in VM neurons in culture. We found that both BDNF and GDNF elicited an increase in the depolarization-induced release of dopamine, but had no effect on GABA release, in the VM cultures. BDNF, but not GDNF, significantly enhanced the expression of the calcium binding protein calbindin and synaptic protein SNAP25. In contrast, treatment of the cultures with GDNF, but not BDNF, elicited a marked fasciculation of the processes of the VM neurons. Thus, although both act on VM neurons, BDNF and GDNF have distinct functions.

Actins↗
PubMed1999

Low intensity pulsed ultrasound exposure increases prostaglandin E2 production via the induction of cyclooxygenase-2 mRNA in mouse osteoblasts.

Both prostaglandin E2 (PGE2) and low intensity pulsed ultrasound (U/S) exposure have been reported to accelerate fracture repair. We hypothesized that these two pathways are interactive. To verify this hypothesis, we examined the regulation of PGE2 production by U/S exposure (sine wave of 1.5MHz repeating at 1kHz, 30mW/cm2, 20 minutes) in mouse osteoblastic cell line, MC3T3-E1. The production of PGE2 in osteoblasts was augmented by U/S, which was threefold at 60 min. in comparison with unexposed samples. Then we evaluated the expression of cyclooxygenase-2 (COX-2) mRNA, which is a critical enzyme for PGE2 production. U/S rapidly up-regulated the expression of COX-2 mRNA in a time dependent manner. In addition, PGE2 production by U/S was drastically suppressed by a selective inhibitor of COX-2. These results provide strong evidence that PGE2 production in osteoblasts is dependent upon the induction of COX-2 mRNA expression by U/S and offer a mechanistic insight into how U/S accelerates fracture repair.

Animals↗
PubMed1999

Nuclear export of LIM-kinase 1, mediated by two leucine-rich nuclear-export signals within the PDZ domain.

LIM-kinase 1 (LIMK1) is a serine/threonine kinase that phosphorylates cofilin and regulates actin-filament dynamics. LIMK1, which contains two LIM domains and a single PDZ domain, localizes predominantly in the cytoplasm, but its mutant, deleted with the PDZ domain, localizes mainly in the nucleus, thereby indicating that the PDZ domain plays a role in the cytoplasmic localization of LIMK1. Here we provide evidence that the PDZ domain of LIMK1 contains two functional leucine-rich nuclear-export signals (NESs). The PDZ domain of LIMK1 fused with glutathione S-transferase (GST-PDZ), when injected into the nucleus, was rapidly excluded from the nucleus, but its mutant with replacements of conserved hydrophobic residues in two putative NESs by alanines remained in the nucleus. The nuclear export of GST-PDZ was sensitive to leptomycin B (LMB), a specific inhibitor of nuclear export mediated by leucine-rich NESs. Malfunctional mutation of two NESs or LMB treatment prevented the nuclear export of full-length LIMK1 and induced its nuclear accumulation. These results suggest that the predominant localization of LIMK1 in the cytoplasm is supported by two NESs within the PDZ domain and that LIMK1 normally shuttles between the cytoplasm and the nucleus. We also provide evidence that a short basic cluster sequence within the protein-kinase domain is involved in the nuclear import of LIMK1.

Amino Acid Sequence↗
PubMed1999

STAT3 is required for the gp130-mediated full activation of the c-myc gene.

The signal transducers and activators of transcription (STAT) family members have been implicated in regulating the growth, differentiation, and death of normal and transformed cells in response to either extracellular stimuli, including cytokines and growth factors, or intracellular tyrosine kinases. c-myc expression is coordinately regulated by multiple signals in these diverse cellular responses. We show that STAT3 mostly mediates the rapid activation of the c-myc gene upon stimulation of the interleukin (IL)-6 receptor or gp130, a signal transducing subunit of the receptor complexes for the IL-6 cytokine family. STAT3 does so most likely by binding to cis-regulatory region(s) of the c-myc gene. We show that STAT3 binds to a region overlapping with the E2F site in the c-myc promoter and this site is critical for the c-myc gene promoter- driven transcriptional activation by IL-6 or gp130 signals. This is the first identification of the linkage between a member of the STAT family and the c-myc gene activation, and also explains how the IL-6 family of cytokines is capable of inducing the expression of the c-myc gene.

Animals↗
PubMed1999

Requirement of PEST domain tyrosine phosphatase PEP in B cell antigen receptor-induced growth arrest and apoptosis.

Signaling events leading to B cell growth or apoptosis are beginning to be unravelled, but detailed information is still lacking. To identify signaling molecules involved in B cell antigen receptor (BCR)-initiated pathways, we used the immature B cell line, WEHI-231, to investigate protein tyrosine phosphatases (PTP) whose expression was modulated by BCR ligation. Among the PTP cloned by reverse transcription-PCR, mRNA expression of the proline-, glutamic acid-, serine- and threonine-rich (PEST) domain phosphatase (PEP) was selectively elevated 3.1-fold within 3 h after anti-IgM antibody stimulation. In contrast, expression of another PEST domain phosphatase, PTP-PEST, was unaffected. Western blot analysis revealed that 71% of PEP was located in the cytosolic fraction, while 29% was in the membrane fraction. To examine the direct contribution made by PEP to BCR-initiated signal transduction, we transfected an antisense PEP cDNA into WEHI-231 cells. Two stable clones were established in which PEP expression was reduced by 34% and 47%, respectively. Strikingly, BCR-mediated inhibition of DNA synthesis was significantly rescued in the clones, and G1 phase cell cycle arrest and apoptosis were almost completely ablated. Considered collectively, these results indicate that PEP is a positive, crucial regulator in determining B cell fate triggered by BCR engagement.

Amino Acid Sequence↗
PubMed1999

Specific and non-specific effects of transcranial magnetic stimulation on simple and go/no-go reaction time.

The effects of subthreshold transcranial magnetic stimulation (TMS) on simple and go/no-go reaction time (RT) tasks were studied in seven healthy volunteers. Subjects were asked to respond by abducting the thumb in a warning-imperative signal paradigm. TMS was randomly delivered at variable delays to the imperative signal (IS). Simple RT was significantly shortened when TMS was delivered to the left motor cortex and parietal regions simultaneously with IS. In the go/no-go paradigm, a similar trend to shorter RT was seen at a delay of 0 ms. Additionally, a significant shortening was observed at a delay of 90 ms with TMS over the contralateral motor cortex only. Movement-related potentials (MRPs) in the two paradigms showed a predominantly contralateral negativity approximately 80 ms preceding EMG onset. Our findings support the existence of two differentiated effects of TMS on RT: (1) one non-specific effect, evidenced in both the simple and go/no-go paradigms at a 0 ms delay, which can be at least partially explained by intersensory facilitation; and (2) a motor-specific effect of TMS, unveiled in the go/no-go paradigm at a 90 ms delay.

Adult↗
PubMed1999

Efficacy of the axially loaded pivot shift test for the diagnosis of a meniscal tear.

Although magnetic resonance imaging (MRI) has improved the diagnostic accuracy of meniscal pathology, the authors believe that physical examination remains essential to the evaluation of knee pathology. In this study, the diagnostic accuracy of five clinical tests for meniscal pathology was prospectively evaluated in 160 patients, who thereafter underwent arthroscopy. 69% (109 knees) of the knees tested had associated ACL deficiency. There were 144 meniscal lesions in 130 of the 160 knees which were examined. The sensitivity of the tests was lower than the specificity. Conventional tests such as McMurray and Apley tests showed a low accuracy rate of 45% and 28% respectively. The diagnostic value of the axially loaded pivot shift test was significantly higher, indicating that this remains a useful diagnostic aid.

Adolescent↗
PubMed1999

Inhibitory effect of orally administered aldose reductase inhibitor SNK-860 on corneal polyol accumulation in galactose-fed rats.

BACKGROUND: Diabetic keratopathy, frequently observed after vitreous surgery, has been thought to be related to the aldose reductase-catalyzed reaction. However, few reports have been published on the chronological changes in polyol accumulation and the effect of the aldose reductase inhibitor in the corneal epithelium or endothelium of galactosemic rats. Consequently, the polyol accumulation in corneal epithelium and endothelium with stroma of 50% galactose-fed rats and the preventive effect of an aldose reductase inhibitor, SNK-860, were biochemically analyzed. METHODS: Four-week-old male Sprague-Dawley rats were fed a 50% galactose diet without supplement or supplemented with a low (3 mg/kg b.w.) or high (30 mg/kg b.w.) dose of SNK-860 (Sanwa Kagaku Kenkyusho, Japan), or a normal diet. Polyol contents in the corneal epithelium or endothelium with stroma were individually measured using gas-liquid chromatography. RESULTS: Polyol in corneal epithelia accumulated quickly in the 1st week, reached a maximum at the 3rd week of feeding and then gradually decreased. Low- and high-dose SNK-860 treatment significantly inhibited polyol accumulation in the epithelium and endothelium with stroma, respectively. Changing to the normal or SNK-860 supplemented diets significantly inhibited polyol accumulation. CONCLUSION: This finding indicates that oral administration of a new aldose reductase inhibitor, SNK-860, or systematic treatment of diabetes may be effective in preventing polyol pathway-induced corneal damage by quickly reducing the polyol level.

Administration, Oral↗
PubMed1999

Expression of platelet-derived growth factor proteins and their receptor alpha and beta mRNAs during fracture healing in the normal mouse.

Platelet-derived growth factor (PDGF), abundant in bone tissue, has been reported to stimulate mesenchymal cell proliferation and migration. To elucidate the functional roles of PDGF during fracture healing, we investigated the expression of PDGF-A and -B chain proteins and receptor alpha and beta mRNAs in fractured mouse tibiae. Twelve-week-old male BALB/c mice were operated on to make a closed fracture on the proximal tibia. On days 2, 4, 7, 10, 14, 21, and 28 after the operation, the fractured tibiae were excised, fixed with 4% paraformaldehyde, decalcified with 20% EDTA, and embedded in paraffin to prepare 7-microm sections. Immunohistochemistry using polyclonal antibodies against human PDGF-A and -B chains was carried out by the avidin-biotin-peroxidase method. For in situ hybridization, we used digoxigenin-labeled single-stranded DNA probes specific for mouse PDGF receptors alpha and beta generated by unidirectional polymerase chain reaction. In the inflammatory phase on days 2-4 after the fracture, mesenchymal cells gathering at the fracture site expressed the PDGF-B chain and beta receptor mRNA. At the stage of cartilaginous callus formation on day 7, the immunoreactivity for PDGF-A and -B chains on proliferating and hypertrophic chondrocytes and the signals of alpha and beta receptor mRNAs on proliferating chondrocytes became manifest. At the stage of bony callus and bone remodeling on days 14-21, the predominant expression of the PDGF-B chain and beta receptor was observed on both osteoclasts and osteoblasts. On day 28, signals for PDGF ligand proteins and receptor mRNAs diminished. The coincidental localization of PDGF ligands and their receptors implies a paracrine and autocrine mechanism. Our data suggested that PDGF contributed in part to the promotion of the chondrogenic and osteogenic changes of mesenchymal cells from the early to the midphase of fracture healing; the functions mediated by the beta receptor, including cell migration, might be prerequisites to the recruitment of mesenchymal cells in the initial step and to the interaction between osteoclasts and osteoblasts in the bone remodeling phase.

Animals↗
PubMed1999

Experimental vaccine activities of recombinant E1 and E2 glycoproteins and hypervariable region 1 peptides of hepatitis C virus in chimpanzees.

A chimpanzee was immunized with two recombinant envelope glycoproteins E1 and E2 of hepatitis C virus (HCV), strain HCV-N2, and the hypervariable region 1 (HVR1) peptides of a different isolate, HCV-#6, then received an intravenous inoculation of 10 chimpanzee infectious doses of HCV-#6. With high humoral immune response against E1 and E2 but a low response against HVR1, the vaccinee became infected with the HCV. However, after increasing the titer of anti-HVR1 against HCV-#6, the vaccinee showed protection. Neutralization of HCV-#6 with the antiserum from this protected vaccinee was achieved by inoculation of this mixture into another chimpanzee. These results suggest that vaccination with a peptide-vaccine of homologous HVR1 is effective in the chimpanzee.

Amino Acid Sequence↗
PubMed1999

Compatibility problems in frontal, side, single car collisions and car-to-pedestrian accidents in Japan.

Compatibility problems in car-to-car frontal, side, single car and car-to-pedestrian collisions in Japan are discussed using traffic accident data. The number of serious and fatal injuries is investigated for the subject car and other cars, which are categorized by their class and mass. The aggressivity of the cars is calculated by the number of fatalities, fatality rates and by the number of car registrations. The results show that in car-to-car frontal collisions, cars with a mass of 1150 kg are the most compatible among the current car population. In both car-to-car frontal and side collisions, the sports utility vehicle and mini car are found to be the most incompatible car types with high and low aggressivity, respectively. On the other hand, the accident data show that the wagon and midsize sedan are the most compatible car types. The compatibility of fixed objects in the road environment with cars and cars with pedestrians is also discussed. In a single car collision with a fixed object, the guardrail is the most compatible object and can reduce the fatality rate on prefecture roads by about 60%. The front geometry of the car has large effect on compatibility with a pedestrian.

Accidents, Traffic↗
PubMed1999

Interaction between purinoceptor subtypes on hippocampal serotonergic transmission using in vivo microdialysis.

The effects of purinoceptor subtypes on hippocampal extracellular serotonin levels were determined by using in vivo microdialysis. Perfusion with adenosine-5'-triphosphate (ATP) for 20 min produced concentration-dependent changes in hippocampal extracellular serotonin levels, which consisted of an initial rise phase, with levels increasing to 309% of control with 100 microM ATP, followed by a later rebound reduction phase, with levels decreasing to 6% of control. The P2X1-7 active P2 purinoceptor agonist, 2-methylthioATP (2-MeSATP: 100 microM) increased the extracellular serotonin level drastically (638%), while the P2X1,3 active P2 purinoceptor agonist, alpha, beta-methylene-L-ATP (alpha, beta-meATP: 100 microM) produced a small increase (132%) in the serotonin level. The P2X1,2,3,5,7 active P2 purinoceptor antagonist, suramin (100 microM), reduced the basal serotonin level (86%) and the ATP-evoked initial rise phase (from 309 to 254%) without affecting the late reduction phase. The adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (CPT: 50 microM) potentiated the rising phase (167%) and abolished the subsequent ATP-evoked reduction phase. Perfusion with CPT and an adenosine A2 receptor antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX: 10 microM), reduced the ATP-evoked initial rise (to 181%) and abolished the late reduction phases of serotonin release. These results indicate that ATP-evoked hippocampal serotonin release is composed of an initial rise phase and a later reduction phase. The ATP-evoked initial rise phase might be produced by an activation of P2X purinoceptor function, whereas the late reduction phase was modulated by the activation of adenosine A1 receptor function by adenosine, metabolized from ATP in the synaptic cleft.

Adenosine Triphosphate↗
PubMed1999

Enhanced Fas/CD95-mediated apoptosis by epidermal growth factor in human endometrial epithelial cells.

Epidermal growth factor (EGF) has been reported to regulate apoptosis in various cell lineages. Throughout the menstrual cycle overexpression of the EGF receptor in the secretory epithelium and constitutive expression of EGF in all types of endometrial cells were identified by immunohistochemical study of normal human endometrial tissues. However, it is not known whether EGF also regulates endometrial apoptosis. This study examined the regulatory functions of EGF in endometrial apoptosis by using a human endometrial epithelial cell line HHUA which is susceptible to Fas-mediated apoptosis. Although EGF alone did not affect the cell growth of HHUA, EGF pretreatment of HHUA enhanced Fas-mediated growth suppression and Fas-mediated DNA fragmentation in the cells. Flowcytometric analyses demonstrated that EGF did not induce Fas expression on the cell surface while expressions of the EGF receptor were down-regulated. These results suggest that EGF may enhance apoptotic susceptibility of the endometrial epithelium, especially in the secretory epithelium.

Apoptosis↗
PubMed1999

Serial electroencephalographic findings in patients with MELAS.

To clarify the electroencephalographic characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS), the medical records and electroencephalograms of six patients with MELAS and two of their relatives with MELA (mitochondrial myopathy, encephalopathy, and lactic acidosis, without strokelike episodes) were retrospectively reviewed. All have a point mutation in the mitochondrial DNA at nucleotide position 3243. The electroencephalograms (n = 79) were divided into four groups according to the time relation to the strokelike episode: (1) before the first strokelike episode, (2) within 5 days after the strokelike episode (acute stage), (3) between 6 days and 1 month after the strokelike episode (subacute stage), and (4) more than 1 month after the strokelike episode (chronic stage). In the acute stage, 10 of the 11 electroencephalograms (9 strokelike episodes in four patients) revealed focal high-voltage delta waves with polyspikes (FHDPS), which were recognized as ictal electroencephalogram. Ictal events during FHDPS included focal clonic or myoclonic seizure and migrainous headache. In the subacute and chronic stages, focal spikes or sharp waves and 14- and 6-Hz positive bursts were frequently recorded. The authors' results suggest that FHDPSs present a reliable and accurate indicator of a strokelike episode in patients with MELAS.

Adolescent↗
PubMed1999

Biphasic effects of zonisamide on serotonergic system in rat hippocampus.

To study the mechanisms of antiepileptic action of zonisamide (ZNS), we determined the effects of ZNS on extracellular, total levels and re-uptake activity of serotonin (5-HT) in rat striatum and hippocampus. After acute administrations, plasma ZNS concentrations associated with anticonvulsive action (effective concentrations) increased the total levels of 5-HT, its metabolise (5-hydroxyindoleacetic acid: 5-HIAA) and precursor (5-hydroxytryptophan: 5-HTP). After chronic administration of ZNS, effective plasma concentrations also increased the extracellular and total levels of 5-HT, 5-HIAA, and 5-HTP. On the other hand, after both acute and chronic administrations of ZNS, a supra-effective ZNS concentration either decreased or did not affect the total levels of these substances. Therefore, the stimulatory effects of ZNS on the 5-HT system were reduced by an increase in ZNS concentration to supra-effective concentrations. ZNS concentrations of 30-1000 microM did not affect hippocampal 5HT re uptake activity in vitro. These results suggest that ZNS has biphasic effects on the 5-HT system, in that effective concentrations of ZNS enhance and supra-effective concentrations of ZNS reduce the function of the 5-HT system. These biphasic effects of ZNS on the 5-HT system may be involved in the mechanisms of action of the antiepileptic and psychotropic effects, and side effects of ZNS.

5-Hydroxytryptophan↗