Biomedical subjects

M Yoshida

Publications and source records attributed to M Yoshida.

At least 505 records · Page 28Linked to original sources

PubMed1999

Antimalarial use of volatile oil from leaves of Virola surinamensis (Rol.) Warb. by Waiãpi Amazon Indians.

The Amazon Indians Waiãpi living in the West of Amapá State of Brazil, treat malaria with an inhalation of vapor obtained from leaves of Viola surinamensis. The essential oil obtained from adult and plantlet leaves was analyzed by GC/MS and 11 monoterpenes, 11 sesquiterpenes and three phenylpropanoids were identified. Plantlet essential oil caused 100% of growth inhibition after 48 h in the development of the young trophozoite to schizont stage and the sesquiterpene nerolidol (100 microg/ml) was identified as one of the active constituents (100% of growth inhibition was obtained). In addition, examination of [U14C]-glucose incorporation showed that activity of nerolidol is related to the inhibition of glycoprotein biosynthesis.

Adult↗

PubMed1999

Distribution and retention of mercury in metallothionen-null mice after exposure to mercury vapor.

We studied the role of metallothionein (MT) in the distribution and retention of mercury in the brain, lung, liver and kidney of MT-null and wild-type mice after exposure to mercury (Hg0) vapor. Mice were exposed to Hg0 vapor at 5.5-6.7 mg/m3 for 3 h and killed at 1, 24, 72 or 168 h after exposure. One hour after exposure to Hg0 vapor, there were no differences in mercury concentrations in these organs from MT-null and wild-type mice. However, the elimination rate of mercury from the organs, except the brain, were remarkably faster in MT-null mice than in wild-type mice. MT-I and -II levels in the lung and kidney were increased significantly in wild-type mice but not in MT-null mice at 24 h after exposure to Hg0 vapor. At this time point, over 65% of the mercury was retained in the MT fraction of the cytosol of organs from wild-type mice. In contrast, mercury appeared mainly in the high-molecular-weight protein fractions in the cytosol of organs from MT-null mice. In the brain, a large amount of mercury was bound to MT in both strains of mice immediately after exposure. No difference was observed in the elimination rate of mercury from the brain between both strains of mice. Brain MT levels were elevated slightly in wild-type mice at 168 h after exposure but could not be detected in MT-null mice. These data suggest that no detectable MT-I and -II levels were found in the brain of MT-null mice and that mercury was apparently bound to MT-III. Using MT-null mice, we showed also that MT-III may play an important role in the retention of mercury in the brain.

Administration, Inhalation↗

PubMed1999

Epsilon subunit, an endogenous inhibitor of bacterial F(1)-ATPase, also inhibits F(0)F(1)-ATPase.

Since the report by Sternweis and Smith (Sternweis, P. C., and Smith, J. B. (1980) Biochemistry 19, 526-531), the epsilon subunit, an endogenous inhibitor of bacterial F(1)-ATPase, has long been thought not to inhibit activity of the holo-enzyme, F(0)F(1)-ATPase. However, we report here that the epsilon subunit is exerting inhibition in F(0)F(1)-ATPase. We prepared a C-terminal half-truncated epsilon subunit (epsilon(DeltaC)) of the thermophilic Bacillus PS3 F(0)F(1)-ATPase and reconstituted F(1)- and F(0)F(1)-ATPase containing epsilon(DeltaC). Compared with F(1)- and F(0)F(1)-ATPase containing intact epsilon, those containing epsilon(DeltaC) showed uninhibited activity; severalfold higher rate of ATP hydrolysis at low ATP concentration and the start of ATP hydrolysis without an initial lag at high ATP concentration. The F(0)F(1)-ATPase containing epsilon(DeltaC) was capable of ATP-driven H(+) pumping. The time-course of pumping at low ATP concentration was faster than that by the F(0)F(1)-ATPase containing intact epsilon. Thus, the comparison with noninhibitory epsilon(DeltaC) mutant shed light on the inhibitory role of the intact epsilon subunit in F(0)F(1)-ATPase.

Adenosine Triphosphate↗

PubMed1999

In vivo gene transfer of an extracellular domain of platelet-derived growth factor beta receptor by the HVJ-liposome method ameliorates bleomycin-induced pulmonary fibrosis.

A number of investigators have reported augmented expression of PDGF in lungs with idiopathic pulmonary fibrosis (IPF) or with other types of pulmonary fibrosis. To accomplish such a regulation of PDGF activity, we constructed an expression plasmid of the extracellular domain of PDGF receptor beta chain (XR), which lacks intracellular tyrosine kinase domain and transmembrane portions, and estimated the therapeutic effects of XR gene transfer through the trachea on bleomycin-induced lung fibrosis of C57BL/6 mice using the hemagglutinating virus of Japan(HVJ)-liposome method. The XR gene transfer ameliorated the increases in the wet weight and hydroxyproline content and the histopathologic changes of the lung induced by bleomycin. These findings suggest that PDGF plays a crucial role in the pathogenesis of pulmonary fibrosis, and that XR gene transfer using the HVJ-liposome method may limit the progression of pulmonary fibrosis.

Animals↗

PubMed1999

Dark aerobic growth conditions induce the synthesis of a high midpoint potential cytochrome c8 in the photosynthetic bacterium Rubrivivax gelatinosus.

In several strains of the photosynthetic bacterium Rubrivivax gelatinosus, the synthesis of a high midpoint potential cytochrome is enhanced 4-6-fold in dark aerobically grown cells compared with anaerobic photosynthetic growth. This observation explains the conflicting reports in the literature concerning the cytochrome c content for this species. This cytochrome was isolated and characterized in detail from Rubrivivax gelatinosus strain IL144. The redox midpoint potential of this cytochrome is +300 mV at pH 7. Its molecular mass, 9470 kDa, and its amino acid sequence, deduced from gene sequencing, support its placement in the cytochrome c8 family. The ratio of this cytochrome to reaction center lies between 0.8 and 1 for cells of Rvi. gelatinosus grown under dark aerobic conditions. Analysis of light-induced absorption changes shows that this high-potential cytochrome c8 can act in vivo as efficient electron donor to the photooxidized high-potential heme of the Rvi. gelatinosus reaction center.

Aerobiosis↗

PubMed1999

Effects of NKH477 on renal nerve stimulation-induced responses in anesthetized dogs.

We evaluated the effects of an adenylate cyclase activator, N, N-dimetyl-beta-alanine[3R-(3alpha,4alphabeta,5beta+ ++,6beta,6aalpha, 10alpha,10abeta,10balpha)]-5(acetyloxy)-3-eth enyldodecahydro-10, 10b-dihydroxy-3,4a,7,7,10a-pentamethyl-1-oxo-1H-naphtho[2, 1-b]pyran-6-yl ester hydrochloride (NKH477), on neural control of renal functions in anesthetized dogs. Renal nerve stimulation (2 Hz) increased renal norepinephrine efflux and reduced renal blood flow, glomerular filtration rate, urine flow rate, urinary Na(+) excretion and fractional Na(+) excretion. Intrarenal arterial infusion of NKH477 (300 ng/kg/min) suppressed the stimulation-induced reductions in renal blood flow and glomerular filtration rate and attenuated the reductions in urine flow rate and urinary Na(+) excretion but not the changes in renal norepinephrine efflux and fractional Na(+) excretion. Infusion of NKH477 did not affect the urinary responses induced by renal nerve stimulation at a lower frequency (0.5-1 Hz) which had little influence on renal blood flow and glomerular filtration rate. The present results demonstrate that NKH477 inhibits renal vasoconstriction and hypofiltration but not the enhanced tubular Na(+) reabsorption during activation of the renal sympathetic nervous system.

Adenylyl Cyclases↗

PubMed1999

Improved liquid chromatographic separation of different proteins by designing functional surfaces of cattle bone-originated apatite.

Spherical particles of cattle bone-originated hydroxyapatite (r-HAp) were prepared by dissolution-precipitation, spray-drying using a two fluid-nozzle apparatus, and subsequent heat treatment. The product had effective pore structures for liquid chromatographic separation of albumin, myoglobin, ribonuclease, lysozyme and cytochrome c. The activated surfaces of the r-HAp particles were easily prepared with desired proportions of P- and C-sites and appropriate acid-basic strength for selective protein adsorption by optimizing the synthesis conditions. Liquid chromatography columns packed with the particles exhibited high resolution and durability in protein separation, reflecting stable distribution of pore size.

Animals↗

PubMed1999

Psychological stress selectively increases extracellular dopamine in the 'shell', but not in the 'core' of the rat nucleus accumbens: a novel dual-needle probe simultaneous microdialysis study.

In order to compare psychological stress-induced dopamine (DA) release in two subterritories (e.g. shell and core) of the nucleus accumbens of the same animal, a novel dual-needle microdialysis probe has been developed. The two needles were placed in the ipsilateral shell and core subterritories of the nucleus accumbens under pentobarbital anesthesia and 24 h later the microdialysis was started. Basal DA output was not significantly different between the shell and the core. Psychological stress for 20 min significantly increased extracellular DA levels in the shell of the nucleus accumbens, however, the levels of dopamine remained almost unaltered in the core. This finding suggests that DA transmission in the shell of the nucleus accumbens was selectively activated during psychological stress, and that the shell plays an important role in emotional responses. The results further show that microdialysis using the novel dual-needle probe could be very useful to differentiate neurochemical changes occurring in neighboring areas in the brain.

Animals↗

PubMed1999

Tax oncoprotein of HTLV-1 binds to the human homologue of Drosophila discs large tumor suppressor protein, hDLG, and perturbs its function in cell growth control.

HTLV-1 Tax oncoprotein interacts with various cellular factors and modulates transcription and the cell cycle. To identify more cellular targets, we employed the yeast two hybrid system with Tax using a human cDNA library, and isolated a cDNA encoding the human counterpart of Drosophila discs large tumor suppressor protein, hDLG. Tax binding to hDLG was confirmed in vitro and also in HTLV-1-infected T-cells. Furthermore, hDLG was found to be efficiently phosphorylated in Tax-transfected cells and HTLV-1-infected T-cells. The C-terminus of Tax and the PDZ domain of hDLG were responsible for the binding of Tax to hDLG. The C-terminal peptide of Tax prevented the binding of hDLG to APC tumor suppressor gene product, suggesting inhibition of hDLG function by Tax. Over-expression of hDLG in NIH3T3 cells by microinjection induced a reduction of BrdU incorporation into DNA, but co-expression of Tax suppressed this inhibitory effect of hDLG. These results suggest that hDLG arrested the cell cycle and that Tax canceled this inhibitory action of hDLG through targeting hDLG. Therefore, Tax affects this novel regulatory pathway of the cell cycle alteration, of which seems to play a role in the development of human cancer.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Interaction of polystyrene microspheres with liver cells: roles of membrane receptors and serum proteins.

Our previous studies have demonstrated that serum would play an important role in the hepatic disposition of polystyrene microspheres (MS) and that complement C3 should be involved as the serum opsonin. In this study, we tried to identify the entity of other serum opsonins and dysopsonin for the hepatic uptake of MSs with particle sizes of 50 nm (MS-50) and 500 nm (MS-500) by isolated liver perfusion studies using a recirculation procedure in rats. Pretreatment of the liver by trypsin significantly suppressed the serum-dependent hepatic uptake of both MSs, suggesting that some protein components on the cell surface should be necessary for the serum-dependent phagocytosis of MSs. Pretreatment of the serum by the anti-fibronectin antibody resulted in a significant reduction in the hepatic disposition of MS-500 (49% of control), suggesting that fibronectin should also work as the opsonin for the hepatic uptake of MS-500. The hepatic disposition of both MSs in the presence of serum was inhibited by the addition of N-acetylgalactosamine into the perfusate, suggesting the possible involvement of lectin in the serum-dependent hepatic uptake of MSs. Furthermore, a more intensive hepatic disposition of MSs was observed in the presence of plasma compared with that in the presence of serum in the perfusate, suggesting the possible involvement of blood coagulation factors, such as fibrinogen, as the opsonin in the hepatic disposition of MSs.

Animals↗

PubMed1999

Role of calcium channels in catecholamine secretion in the rat adrenal gland.

1. We elucidated the contribution of voltage-dependent Ca2+ channels to cholinergic control of catecholamine secretion in the isolated perfused rat adrenal gland. 2. Nifedipine (0.3-3 microM) inhibited increases in noradrenaline output induced by transmural electrical stimulation (1-10 Hz) and acetylcholine (6-200 microM), whereas it only slightly inhibited the adrenaline output responses. Nifedipine also inhibited the catecholamine output response induced by 1, 1-dimethyl-4-phenyl-piperazinium (DMPP; 5-40 microM) but not by methacholine (10-300 microM). 3. omega-Conotoxin MVIIC (10-1000 nM) inhibited the catecholamine output responses induced by electrical stimulation but not by acetylcholine, DMPP and methacholine. 4. omega-Conotoxin GVIA (50-500 nM) had no inhibitory effect on the catecholamine output responses. 5. These results suggest that L-type Ca2+ channels are responsible for adrenal catecholamine secretion mediated by nicotinic receptors but not by muscarinic receptors, and that their contribution to noradrenaline secretion may be greater than that to adrenaline secretion. P/Q-type Ca2+ channels may control the secretion at a presynaptic site.

Acetylcholine↗

PubMed1999

alpha3beta3gamma complex of F1-ATPase from thermophilic Bacillus PS3 can maintain steady-state ATP hydrolysis activity depending on the number of non-catalytic sites.

Homogeneous preparations of alpha(3)beta(3)gamma complexes with one, two or three non-competent non-catalytic site(s) were performed as described [Amano, Hisabori, Muneyuki, and Yoshida (1996) J. Biol. Chem. 271, 18128-18133] and their properties were compared with those of the wild-type complex. The ATPase activity of the complex with three non-competent non-catalytic sites decayed rapidly to an inactivated state, as reported previously [Matsui, Muneyuki, Honda, Allison, Dou, and Yoshida (1997) J. Biol. Chem. 272, 8215-8221]. In contrast, the complex with one or two non-competent non-catalytic sites displayed a substantial steady-state phase activity depending on the number of non-competent non-catalytic sites in the complex. This result indicates that one competent non-catalytic site can maintain the continuous catalytic turnover of the enzyme and can potentially relieve all three catalytic sites from inhibition by MgADP(-). Furthermore, the results suggest that the interaction between three non-catalytic sites might not be as strong as that between catalytic sites, which are all strictly required for a continuous catalytic turnover.

Adenosine Triphosphate↗

PubMed1999

Mechanisms of hepatic disposition of polystyrene microspheres in rats: effects of serum depend on the sizes of microspheres.

To study the mechanisms of the hepatic disposition of polystyrene microspheres (MS), effects of serum on their hepatic disposition characteristics were investigated for MSs with particle sizes of 50 nm (MS-50) and 500 nm (MS-500) by isolated liver perfusion experiments. It was revealed that serum in the perfusate inhibited and promoted the hepatic disposition of MS-50 and MS-500 at 37 degrees C, respectively. However, pre-heating at 56 degrees C or pre-treatment with anti-C3 antibody of serum reduced the promotive effect of serum on the hepatic uptake of MS-500, suggesting that the complement system should be involved as opsonins for the hepatic uptake of MS-500. Hepatic disposition of both MSs at 4 degrees C was reduced by the addition of serum into the perfusate, which could be ascribed to the reduction of the surface hydrophobicity of MSs due to the adsorption of serum proteins onto the surface of MSs and to resultant decrease in non-specific disposition to the liver. From these results, serum was found to function both as the opsonin to enhance the hepatic uptake of MSs and as the inhibitor by reducing non-specific interaction between MSs and the plasma membrane. Whether serum promotes or inhibits the hepatic disposition of MSs would be dependent on the particle sizes of MSs.

Animals↗

PubMed1999

Experimental spinal fusion using sintered bovine bone coated with type I collagen and recombinant human bone morphogenetic protein-2.

STUDY DESIGN: Posterolateral lumbar transverse process fusion using recombinant human bone morphogenetic protein (rhBMP)-2 carried by sintered bovine bone and Type I collagen complex was compared with fusion achieved using autogeneous bone graft or sintered bovine bone alone. OBJECTIVES: This study examined the efficacy of sintered bovine bone coated with Type I collagen as a carrier of rhBMP-2 for lumbar intertransverse process arthrodesis. SUMMARY OF BACKGROUND DATA: Posterolateral intertransverse process arthrodesis using osteoinductive growth factors is performed experimentally in the lumbar spine. The previous studies revealed the efficacy of osteoinductive factors applied to carriers having no bony structures, such as collagen sheet or polylactic acid polymer, for the spinal fusion. However, in their studies, a large amount of osteoinductive proteins have been applied for the spinal fusion. We used the sintered bovine bone "True Bone Ceramics" (TBC; Koken Co., Tokyo, Japan) coated with type I collagen as the carrier. True Bone Ceramics is the only biomaterial possessing a natural trabecular structure and an organized crystal of bone minerals. METHODS: Twenty-two adult rabbits underwent bilateral lumbar intertransverse process arthrodesis at L4-L5. The animals were divided into four groups and had materials implanted as follows: autologous bone group, grafted autologous corticocancellous bone harvested from the posterior iliac crest; implanted TBC group; TBC collagen group, implanted TBC coated with Type I collagen infiltrating into the porous space; and BMP group, implanted sintered bovine bone coated with Type I collagen infiltrated with 100 micrograms of rhBMP-2. Spinal fusion was evaluated by radiographic analysis, manual palpation, biomechanical testing, and histologic examination 6 weeks after surgery. RESULTS: Two rabbits were killed because of infection and lumbar plexus palsy. Radiographs of the BMP group showed a homogeneous fusion mass at the intertransverse area, and stability was confirmed by dynamic radiographs at 3 and 6 weeks after surgery. In the BMP group, a bony mass in the intertransverse area was more prominent than in the other groups. The BMP group had a higher fusion rate based on manual palpation than the-other groups, and BMP fusions showed significantly higher tensile strength and stiffer fusion. The histologic findings in the BMP group demonstrated membranous bone and endochondral bone formations between the transverse process and the fusion mass. In the other groups, continuous trabecular bone formation was observed in the area surrounding the transverse process, but gaps between grafted fragments and less mature bone formation were present in the intertransverse area. CONCLUSIONS: Sintered bovine bone coated with Type I collagen and rhBMP-2 resulted in a higher fusion rate than the autograft and can be used as a carrier for rhBMP-2 in spinal fusion.

Animals↗

PubMed1999

Motoneurons of the axial swimming muscles in hatchling Xenopus tadpoles: features, distribution, and central synapses.

Xenopus tadpole motoneurons make cholinergic synapses within the spinal cord. This excitation changes with longitudinal position and contributes to the excitation that controls motor activity and its longitudinal spread during swimming. To explore the anatomic constraints on this excitation, backfilling has been used to examine the anatomy and distribution of the whole population of spinal motoneurons, to define the extent of their central axons and to find where they make synapses. Motoneuron features show considerable variation but do not allow their separation into primary and secondary. Most motoneurons have descending central axons and it is likely that central synapses are made from these axons as longitudinal dendritic extent is very limited. Motoneuron density reaches a broad plateau over the mid-trunk region at 12-13 per 100 microm. Soma size does not change with longitudinal position, but the dorsoventral extent of the dendrites decreases caudally, whereas the central axon length increases. Motoneuron distribution data were used to estimate the longitudinal distribution of central motoneuron axons. This has a broad plateau at 12-14 per 100 microm over much of the trunk and only decreases significantly caudal to the anus. This distribution correlates with cholinergic excitation during swimming. Transmission electron microscopy of motoneurons backfilled with horseradish peroxidase was used to show that central motoneuron axons make en passant synapses with motoneuron dendrites and the dendrites of other unstained neurons. By using measures of synapse frequency and total dendrite length, trunk motoneurons are estimated to each receive 100-200 synapses.

Acetylcholine↗

PubMed1999

Three isoforms of mammalian hyaluronan synthases have distinct enzymatic properties.

Three mammalian hyaluronan synthase genes, HAS1, HAS2, and HAS3, have recently been cloned. In this study, we characterized and compared the enzymatic properties of these three HAS proteins. Expression of any of these genes in COS-1 cells or rat 3Y1 fibroblasts yielded de novo formation of a hyaluronan coat. The pericellular coats formed by HAS1 transfectants were significantly smaller than those formed by HAS2 or HAS3 transfectants. Kinetic studies of these enzymes in the membrane fractions isolated from HAS transfectants demonstrated that HAS proteins are distinct from each other in enzyme stability, elongation rate of HA, and apparent K(m) values for the two substrates UDP-GlcNAc and UDP-GlcUA. Analysis of the size distributions of hyaluronan generated in vitro by the recombinant proteins demonstrated that HAS3 synthesized hyaluronan with a molecular mass of 1 x 10(5) to 1 x 10(6) Da, shorter than those synthesized by HAS1 and HAS2 which have molecular masses of 2 x 10(5) to approximately 2 x 10(6) Da. Furthermore, comparisons of hyaluronan secreted into the culture media by stable HAS transfectants showed that HAS1 and HAS3 generated hyaluronan with broad size distributions (molecular masses of 2 x 10(5) to approximately 2 x 10(6) Da), whereas HAS2 generated hyaluronan with a broad but extremely large size (average molecular mass of >2 x 10(6) Da). The occurrence of three HAS isoforms with such distinct enzymatic characteristics may provide the cells with flexibility in the control of hyaluronan biosynthesis and functions.

Animals↗

PubMed1999

Enzymatic repair of 5-formyluracil. II. Mismatch formation between 5-formyluracil and guanine during dna replication and its recognition by two proteins involved in base excision repair (AlkA) and mismatch repair (MutS).

5-Formyluracil (fU), a major methyl oxidation product of thymine, forms correct (fU:A) and incorrect (fU:G) base pairs during DNA replication. In the accompanying paper (Masaoka, A., Terato, H., Kobayashi, M., Honsho, A., Ohyama, Y., and Ide, H. (1999) J. Biol. Chem. 274, 25136-25143), it has been shown that fU correctly paired with A is recognized by AlkA protein (Escherichia coli 3-methyladenine DNA glycosylase II). In the present work, mispairing frequency of fU with G and cellular repair protein that specifically recognized fU:G mispairs were studied using defined oligonucleotide substrates. Mispairing frequency of fU was determined by incorporation of 2'-deoxyribonucleoside 5'-triphosphate of fU opposite template G using DNA polymerase I Klenow fragment deficient in 3'-5' exonuclease. Mispairing frequency of fU was dependent on the nearest neighbor base pair in the primer terminus and 2-12 times higher than that of thymine at pH 7.8 and 2.6-6.7 times higher at pH 9.0 with an exception of the nearest neighbor T(template):A(primer). AlkA catalyzed the excision of fU placed opposite G, as well as A, and the excision efficiencies of fU for fU:G and fU:A pairs were comparable. In addition, MutS protein involved in methyl-directed mismatch repair also recognized fU:G mispairs and bound them with an efficiency comparable to T:G mispairs, but it did not recognize fU:A pairs. Prior complex formation between MutS and a heteroduplex containing an fU:G mispair inhibited the activity of AlkA to fU. These results suggest that fU present in DNA can be restored by two independent repair pathways, i.e. the base excision repair pathway initiated by AlkA and the methyl-directed mismatch repair pathway initiated by MutS. Biological relevance of the present results is discussed in light of DNA replication and repair in cells.

Adenine↗

PubMed1999

Developmental expression of sarcoglycan gene products in cultured myocytes.

The sarcoglycan complex consists of four membrane-spanning proteins and was shown to be exclusively distributed in striated muscles. In this study, we analyzed the pattern of expression of the mRNAs and proteins of the sarcoglycan subunits during cell differentiation in a culture of myocytes. All four sarcoglycan mRNAs were detectable in proliferating cells, and expression of the alpha- and gamma-subunits was up-regulated by 20- and 50-fold following muscle cell fusion. However, sarcoglycan proteins were scarcely detectable in proliferating cells and were first detected 2 days after the induction to be differentiated. The accumulation of the sarcoglycan protein subunits was accompanied by cell differentiation. The discrepancy between the expression of the mRNAs and proteins of the sarcoglycan subunits in proliferating cells may be ascribed to rapid degradation of the protein.

Animals↗