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Biomedical subjects

T Miyasaka

Publications and source records attributed to T Miyasaka.

At least 19 recordsLinked to original sources
PubMed2001

Molecular analysis of mutant and wild-type tau deposited in the brain affected by the FTDP-17 R406W mutation.

Frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) is a familial neurological disorder, characterized genetically by autosomal dominant inheritance, clinically by behavioral abnormalities and parkinsonism, and neuropathologically by tauopathy. Linkage analyses of affected families have led to identification of several exonic and intronic mutations in the tau gene. In this study, we analyzed molecular species of tau in the soluble and insoluble fractions of brain affected by the FTDP-17 R406W mutation. Protein chemical analysis and Western blotting using site-specific antibodies indicated that almost equal amounts of wild-type and mutant tau were present in the Sarkosyl-insoluble fraction of the R406W brain. Consistent with this, wild-type and mutant tau colocalized in neurofibrillary tangles in the frontal cortex and hippocampus of the R406W brain. In contrast to soluble R406W tau, which was less phosphorylated than soluble wild-type tau, the Sarkosyl-insoluble mutant tau was highly phosphorylated as well as the insoluble wild-type tau.

Aged↗
PubMed2001

The proton uptake channel of bacteriorhodopsin as studied by a photoelectrochemical method.

A series of the mutant proteins (D96N, D96N/D85N, D115N, L93T, T46V, V49A) where the residues are located at the cytoplasmic domain of bacteriorhodopsin (bR) were studied photoelectrochemically and their photocurrent response characteristics at the electrode/electrolyte interface were compared with those of the wild-type bR. While the wild-type bR of normal proton pumping activity yields symmetrical cathodic (positive) and anodic (negative) responses, corresponding to proton release and proton uptake, respectively, these mutants, with the exception of D115N, showed diminished amplitudes in the negative response. This indicates retardation of proton translocation from the cytoplasmic surface to the retinal Schiff base. The mutation that gave the strongest influence on the negative response was D96N while moderate influence was obtained with L93T, T46V, and V49A. These results suggest that residues other than D96 also participate in the cytoplasmic proton uptake channel, either by interacting with D96 directly or by forming a hydrogen-bonded network with water molecules. The D96N/D85N double mutant yielded little response at neutral pH, but the response was partially recovered by addition of azide, while it was fully recovered in the single mutant D96N. The D115N mutant showed the response profile that closely resembles the wild-type, indicating that D115 is not crucially involved in the event of proton transfer relay at the cytoplasmic region. It was also found that every mutant in this study releases protons prior to uptake at the other membrane surface, as does the wild-type.

Azides↗
PubMed2001

Platelet-derived growth factor is involved in the augmentation of airway responsiveness through remodeling of airways in diesel exhaust particulate-treated mice.

BACKGROUND: Thickening of the region adjacent to the basement membrane is a key component of the remodeling of the asthmatic airway and is caused by collagen deposition in the region. OBJECTIVE: We sought to clarify the role of platelet-derived growth factor (PDGF), a competence factor of fibroblast, in the enhanced airway responsiveness and remodeling in a murine model. METHODS: Diesel exhaust particulates (DEPs) were administered intranasally every other day for 2 weeks with or without anti-PDGF-beta neutralizing antibody or goat IgG. Pulmonary function was then analyzed by using whole-body plethysmography before and after acetylcholine inhalation. RESULTS: Anti-PDGF-beta neutralizing antibody significantly inhibited both the elevation of airway resistance elicited by 1.25 and 2.5 mg/mL acetylcholine and the increase in the airway wall thickening induced by DEPs. In addition, bronchoalveolar lavage fluid cell analysis revealed that anti-PDGF-beta neutralizing antibody did not affect cellular infiltration at the airways. CONCLUSION: PDGF plays an important role in the process of remodeling brought about by DEP exposure in mice.

3T3 Cells↗
PubMed2000

Induction of apoptosis in bronchial eosinophils: beneficial or harmful?

BACKGROUND: Prominent eosinophil infiltration takes place in asthmatic bronchi, and damages bronchial epithelial cells. AIM: This study was designed to investigate whether induction of apoptosis in infiltrated cells in the airways is beneficial or harmful. METHODS: A/J mice, which are genetically predisposed to be hyperresponsive to acetylcholine, were immunized with ovalbumin (OA) and alum. Thereafter, they were subjected to a 2-week regimen of OA inhalation, during which they were also administered either hamster anti-mouse Fas monoclonal antibody or hamster IgG (sham control) intranasally. Pulmonary function was then analyzed using whole-body plethysmography. RESULTS: Inhalation of OA increased both airway responsiveness to acetylcholine and infiltration of eosinophils. Administration of anti-Fas antibody induced apoptosis in the infiltrating eosinophils and abolished the increase in airway responsiveness to acetylcholine. CONCLUSION: Induction of apoptosis in eosinophils infiltrating asthmatic bronchi has a beneficial effect on airway hyperresponsiveness.

Acetylcholine↗
PubMed2000

A diffuse alveolar hemorrhage in a human T-lymphotropic virus type I carrier with acute cerebellar ataxia and interstitial pneumonitis: an autopsy case report.

A 76-year-old HTLV-I-positive male with acute cerebellar ataxia was suffering from dyspnea on exertion. Chest CT suggested interstitial pneumonitis. Methylprednisolone pulse therapy improved his symptoms and chest CT findings. Twelve months after discharge, when the prednisolone dose was tapered to 5 mg every other day, his lung lesion recurred. The lesion responded initially to steroid therapy. However, hypoxemia intractable to steroid pulse therapy developed and the patient died of respiratory failure. The autopsy revealed diffuse alveolar hemorrhage with no finding of vasculitis. This is the first case report of diffuse alveolar hemorrhage in an HTLV-I carrier.

Acute Disease↗
PubMed2000

Effect of binary and ternary filler mixtures on the mechanical properties of composite resins.

The mechanical strength of experimental light cure composites containing binary filler mixtures with various combinations of irregular and spherical macrofillers in various mixes, and the microfilled ternary system fillers were measured. The compressive strength of the binary mixtures between different shaped fillers was not related to mixing ratios, although it significantly increased as the filler size decreased. The mixing ratio was immaterial within the irregular filler mixture. The compressive strength of the binary mixtures within the spherical fillers increased as the mixing ratio increased while the filler size was relatively large, then the mixing ratio became insignificant as the filler size decreased under 1.4 microns. The compressive strength of the microfilled ternary fillers increased with the decrease in the macrofiller size and with the increase in the mixing ratio. A large diametrical tensile strength was found in several microfilled ternary mixtures containing different shaped macrofillers.

Analysis of Variance↗
PubMed1999

Ku80 can translocate to the nucleus independent of the translocation of Ku70 using its own nuclear localization signal.

Ku antigen is a complex of Ku70 and Ku80 subunits and plays an important role in not only DNA double-strand breaks (DSB) repair and V(D)J recombination, but also in growth regulation. Ku is generally believed to always form and function as heterodimers on the basis of in vitro observations. Here we demonstrate that the localization of Ku80 does not completely coincide with that of Ku70. Ku70 and Ku80 were colocalized in the nucleus in the interphase but not in the late telophase/early G1 phase of the cell cycle. Since the in vivo function of Ku might be partially regulated by the control of its transport, we attempted to investigate the molecular mechanisms underlying the nuclear translocation of Ku. The nuclear translocation of Ku80 started during the late telophase/early G1 phase after the nuclear envelope was formed and this was preceded by the nuclear translocation of Ku70. Furthermore, we found that the Ku80 protein was transported to the nucleus without heterodimerization with Ku70. To understand in detail the mechanism of transport of Ku80, we attempted to identify the nuclear localization signal (NLS) of Ku80 and defined to a region spanning nine amino acid residues (positions 561 - 569). The Ku80 NLS was demonstrated to be mediated to the nuclear rim by two components of PTAC58 and PTAC97. All these findings support the idea that Ku80 can translocate to the nucleus using its own NLS independent of the translocation of Ku70.

Amino Acid Sequence↗
PubMed1999

The nuclear localization signal of the human Ku70 is a variant bipartite type recognized by the two components of nuclear pore-targeting complex.

Ku protein is a complex of two subunits, Ku70 and Ku80. Ku is suspected to participate in both DNA double-strand break repair and transcription. Since both of these processes take place in the cell nucleus, we have been investigating the subcellular localization and nuclear transport of Ku proteins. In the present study, we analyzed the subcellular localization and nuclear localization signal (NLS) of Ku70. Fusion proteins of Ku70 and green fluorescent protein (GFP) transiently expressed in cells were clearly localized in the nuclei of interphase cells. Ku70 staining was distributed throughout both the nucleus and the cytoplasm in late telophase to early G1 phase cells. The NLS of Ku70 was located at the region composed of 18 amino acid residues (positions 539 to 556). This region overlapped with the Ku80-independent DNA-binding domain reported previously. The Ku70 NLS consisted of two basic subregions and a nonbasic intervening region. All the subregions were necessary for complete NLS activity. The amino acids in the nonbasic intervening region of Ku70 might be important for full NLS activity not only to provide sufficient length between the two separated clusters of basic amino acids but also to have an adequate amino acid sequence. All of the basic amino acid residues in the basic subregions were conserved among mammalian and avian homologues, confirming their importance in the nuclear translocation of Ku70. The structure of the Ku70 NLS resembled the consensus of a bipartite-type NLS. The Ku70 NLS was mediated to target to the nuclear rim by two components of the nuclear pore-targeting complex, PTAC58 and PTAC97.

Amino Acid Sequence↗
PubMed1999

Diesel exhaust particulate induces airway hyperresponsiveness in a murine model: essential role of GM-CSF.

BACKGROUND: Inhaled pollutants were recently shown to be responsible for an increased incidence of airway allergic diseases, including asthma. A common feature of all forms of asthma is airway hyperresponsiveness. OBJECTIVE: Our purpose was to elucidate the effects of diesel exhaust particulate (DEP), one of the most prevalent inhaled pollutants, on airway responsiveness. METHODS: A/J and C57Bl/6 mice were used; the former are genetically predisposed to be hyperresponsive to acetylcholine, whereas the latter are not. DEP was administered intranasally for 2 weeks, after which pulmonary function was analyzed by whole-body plethysmography. RESULTS: Intranasal administration of DEP increased airway responsiveness to acetylcholine in both A/J and C57Bl/6 mice and induced displacement of ciliated epithelial cells by mucus-secreting Clara cells. The effect was mediated by M(3) muscarinic receptors. Acetylcholine-evoked bronchial constriction was reversed by administration of terbutaline, a beta(2)-adrenergic antagonist, which is also characteristic of human asthma. Intranasal administration of antibody raised against GM-CSF abolished DEP-evoked increases in airway responsiveness and Clara cell hyperplasia. The antibody raised against IL-4 also inhibited DEP-evoked increases in airway responsiveness. However, it was to a lesser extent compared with antibody against GM-CSF. In addition, DEP stimulated GM-CSF messenger RNA expression in the lung. CONCLUSION: DEP induces airway hyperresponsiveness by stimulating GM-CSF synthesis.

Acetylcholine↗
PubMed1999

Accompanying arteries of the lesser saphenous vein and sural nerve: anatomic study and its clinical applications.

The arteries adjacent to the lesser saphenous vein and sural nerve were investigated in 10 fresh cadavers that had been systemically injected with a lead oxide-gelatin mixture. The accompanying arteries were found to lie along the lesser saphenous vein and sural nerve and to nourish the skin through venocutaneous and neurocutaneous perforators. On the basis of the anatomy of these accompanying arteries, the lesser saphenous venoadipofascial (VAF) pedicled fasciocutaneous flap and the lesser saphenous-sural veno-neuro adipofascial (V-NAF) pedicled fasciocutaneous flap have been developed and applied to 23 cases of various reconstructions of the lower extremity with proximal and distal bases. Survival of the flaps has been extremely good, and the flaps have been clinically useful.

Adult↗
PubMed1999

[Vasculo-Behcet's disease with fatal massive hemoptysis].

A 39-year-old man was admitted to our hospital because of hemoptysis. A chest X-ray film on admission showed a patchy shadow in the left lower lung field. Computed tomography revealed nodular opacities in the left pulmonary artery. The patient had history of oral ulcers, erythema nodosum, pustular lesions, and genital ulcers. Furthermore, the needle reaction was positive. Our diagnosis was an incomplete type of Behcet's disease. A radionuclide-venography and lung-perfusion study disclosed deep-vein thrombosis. Combined therapy with prednisolone, colchicine, and indomethacin farnesil was initiated, but the patient died of massive hemoptysis. Pathological examination revealed a ruptured aneurysm in the bronchus segmentalis apacalis and thrombotic angitis in the inferior vena cava. Behcet's disease is rarely a cause of hemoptysis. However, the prevalence of hemoptysis due to pulmonary vasculitis in patients with Behcet's disease has been reported to be 5 to 10% which is not so rare. Because of the poor prognosis, we want to emphasize Behcet's disease as a cause of hemoptysis.

Adult↗
PubMed1998

Subcellular localization and protein-protein interaction regions of Ku proteins.

The Ku protein is a complex of Ku70 and Ku80 subunits and is capable of binding promoters in a sequence-specific manner, although it remains unclear whether Ku is involved in transcriptional regulation. We examined the subcellular localization and determined the interaction regions of Ku. Our results indicate that heterodimers of Ku70 and Ku80 are localized in the nucleus, and that the stretches from amino acid (aa) 378 to 482 of Ku70 and from aa 374 to 502 of Ku80 are necessary for heterodimerization. These interaction regions do not contain any previously recognized protein-protein interaction motifs. To determine whether Ku contains a potential transcriptional activation domain, we examined N- and C-terminal deletion mutants of Ku70 and Ku80 for their ability to activate transcription in the GAL4-based one-hybrid system. We found that the whole Ku protein had no transcriptional activity, although the N-terminal peptide fragment of Ku70 was capable of activating transcription of the HIS3 and lacZ reporter genes in yeast cells.

Antigens, Nuclear↗
PubMed1998

Inhibitory projections from pronator teres to biceps brachii motoneurones in human.

Neural projections from the pronator teres (PT) muscle to biceps brachii (BB) motoneurones were studied in three healthy human subjects using a post-stimulus time histogram method. In 25 BB motor units, electrical stimulation to the PT nerve with intramuscular needle electrodes induced inhibition in nine units (36%), whereas facilitation was produced in 18 units (72%) by stimulation to the median nerve trunk with surface electrodes at the distal end of the intermuscular septum of the arm or in the cubital fossa. Six motor units (24%) received both inhibition (PT nerve stimulation) and facilitation (median nerve trunk stimulation). In the six, the latency of the inhibition was, on average, 1.2 ms longer than that of the facilitation. The stimulation site for the inhibition was, on average, 4.8 cm distal to that for the facilitation. The inhibition was evoked with an intensity well below the motor threshold. These findings suggest that BB motoneurones receive oligosynaptic inhibition of group I afferents from PT in human.

Adult↗
PubMed1998

[The involvement of cytokines, chemokines and inducible nitric oxide synthase (iNOS) induced by a transient ischemia in neuronal survival/death in rat brain].

Inflammatory/immunological processes underlie the survival/damage of neurons after brain ischemia. In glial cells, cytokines such as IL-1 beta and TNF-alpha are produced following ischemic stresses. On the other hand, it is suggested that NO/iNOS is involved in neuronal apoptosis. We here review the ischemia-induced production of cytokine/iNOS and the neurotrophic/neurotoxic effects. It is not clear whether or not the neuronal death after brain ischemia is apoptosis or necrosis. Under the condition of transient forebrain ischemia, however, we obtained results suggesting apoptosis in the delayed neuronal death of the CA1 pyramidal neurons. The time course and cellular localization of postischemic iNOS expression depend on the properties of the ischemic insult. The iNOS induction is detected primarily in astrocytes after the transient forebrain ischemia when the neuronal apoptosis is observed. We discuss a variety of cytokines with neurotrophic/neurotoxic actions that are produced by ischemia or environmental stresses in glial cells. From the neurotoxicological aspect of the neuro-glial interaction, we also review recent findings on signalling pathways of the iNOS induction in glial cells and the mechanisms of the cytotoxic actions of NO.

Animals↗
PubMed1998

Allosteric inhibitors against HIV-1 reverse transcriptase: design and synthesis of MKC-442 analogues having an omega-functionalized acyclic structure.

Based on X-ray crystallographic analysis of MKC-442/human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) complex, analogues in which the N1-substituent is replaced with omega-functionalized alkyl groups were designed to improve the affinity for the enzyme. Synthesis of these compounds was carried out starting from MKC-442 by a sequence of reactions (N3-protection, removal of N1-ethoxymethyl group, alkylation, and N3-deprotection). The compounds were evaluated for anti-HIV activity. Structure-activity relationships are discussed in terms of the possible interaction with the enzyme.

Allosteric Site↗