Biomedical subjects

M Tokuda

Publications and source records attributed to M Tokuda.

At least 37 records · Page 2Linked to original sources

PubMed1997

Involvement of calmodulin-dependent protein kinases-I and -IV in long-term potentiation.

Multifunctional Ca2+/calmodulin-dependent protein kinases (CaMKs) are thought to be involved in the induction of long-term potentiation (LTP). In the present study, LTP was induced by theta burst stimulation in the Schaffer collateral area of the stratum radiatum in the hippocampal CA1 region of the rat hippocampus. LTP-induced and control hippocampal slices were studied by Western blot and immunohistochemical analyses using CaMK-I, -II and -IV antibodies. Increased amounts of all three CaMKs were found in LTP-induced hippocampal slices as indicated by Western blot as well as by the density of their immunoreactivity. Our data clearly shows that not only CaMK-II but also CaMK-I and -IV contribute to synaptic plasticity formed in LTP.

Animals↗

PubMed1997

Reticalmin: a novel calcium/calmodulin-dependent protein kinase IV-like protein in rat retina.

Western blot analysis of 100,000 g supernatant of rat retina using a polyclonal anti-Ca2+/ calmodulin-dependent protein kinase IV (CaM-kinase IV) antibody revealed an immunoreactive mass of 35 kDa, termed reticalmin. Lower amount of a isoform of CaM-kinase IV was also expressed in rat retina. Reticalmin did not react with anti-CaM-kinase IV C-terminal peptide antibody which recognized alpha and beta isoforms of CaM-kinase IV and calspermin. Immunohistochemically reticalmin was shown to be localized mainly in the outer segment of photo-receptor cells, and in dendrites of inner plexiform layers and may be in nuclei of ganglion cells and some inner nuclear layer cells.

Animals↗

PubMed1997

Changes in the expression of novel Cdk5 activator messenger RNA (p39nck5ai mRNA) during rat brain development.

We previously reported that a neuron-specific Cdk5 activator, p35nck5ai, was most prominent in the newborn rat brain. In the adult brain, the expression decreased in most regions except hippocampus and primary olfactory cortex. A novel neuron-specific Cdk5 activator, p39nck5ai, has been recently cloned. To clarify whether two activators were differentially distributed throughout brain development, in this study, we examined the spatial and temporal expression of p39nck5ai in the development rat brain. Northern blot analysis showed that p39nck5ai expression was low in 15-day old fetuses and newborn, and was most prominent in the 1-3 week-old rat brains. In the adult rat brain, expression declined to the same level as in newborn rat brain. In situ hybridization showed that p39nck5ai mRNA was weakly expressed in all neurons of all regions in the newborn rat brain and the transcriptional level was highest in all regions in the 3 week-old rat brain. In the adult, expression was decreased in most neurons except Purkinje and granule cells in the cerebellum which retained high levels. These results suggest that p35nck5a and p39nck5ai may have different functional roles in distinct brain regions during different states of the rat brain development.

Aging↗

PubMed1997

Embryonic transplantation and ischemic memory deficit.

Transient forebrain ischemia is associated with selective neuronal vulnerability and persistent memory deficit. This study compares functional outcome and morphological changes in rats subjected to post-ischemic CA1 or hilus/dentate gyrus region hippocampal fetal transplantation. Ischemia was produced by bilateral common carotid artery occlusion with hypotension. Fetal hippocampal neurons were transplanted into both sides of the CA1 or hilus/dentate gyrus region of the dorsal hippocampus, 1 week post-ischemia. Four weeks post transplantation, the rats underwent behavioral testing for 5 consecutive days using the water maze trial. All animals were perfusion fixed for morphological studies. Transplants in the CA1 region of the dorsal hippocampus were associated with memory and morphological recovery, while grafts placed into the hilus/dentate gyrus region of the dorsal hippocampus were not. Similarly, neurons transplanted in the CA1 region of the dorsal hippocampus were morphologically similar to CA1 pyramidal cell neurons and stained positive with calbindin D(28k). In contrast the grafts transplanted into the hilus/dentate gyrus region of the dorsal hippocampus were morphologically heterogeneous and staining with calbindin D(28k) was not as robust. Post-ischemic transplantation in the CA1 region of the dorsal hippocampus is effective in improving memory and morphological function.

Animals↗

PubMed1997

Multiple colonization defects in a cysteine protease mutant of Porphyromonas gingivalis.

A cysteine protease mutant, G-102, of Porphyromonas gingivalis 381 defective in the rgp-1 gene has been recently constructed in this laboratory. In order to evaluate the role of the protease in the virulence properties of P. gingivalis, a number of putative periodontopathic properties of the mutant were evaluated. Relative to the parental strain, mutant G-102 was demonstrated to be defective in interacting with Gram-positive bacteria as well as cultured epithelial cells. In addition, the mutant was altered in attaching to the protein components of extracellular matrix as well as to type I collagen. Some of these alterations could result from the decreased autoaggregation displayed by mutant G-102 relative to strain 381. However, since the epithelial cell attachment assays were carried out at very low bacterial densities, it is unlikely that reduced autoaggregation of the mutant is responsible for its decreased ability to attach to these eucaryotic cells. Electron microscopic examination of the cells also revealed that mutant G-102 was altered in normal fimbrae expression. In addition, reduced expression of the 43 kDa fimbrial subunit in the mutant was detected with both Western and Northern blotting. These results indicated that the rgp-1 gene product can play either a direct or indirect role in the colonization properties of P. gingivalis.

Adhesins, Bacterial↗

PubMed1997

Fos induction in rat brain neurons after stimulation of the hepatoportal Na-sensitive mechanism.

Responses of hepatic afferent nerves to intraportal bolus injection of hypertonic solutions were examined in anesthetized rats. Hepatic afferent nerve activity increased in response to an intraportal injection of 0.75 M NaCl or NaHCO3 but did not respond to a similar injection of 1.5 M mannitol, 0.75 M LiCl, or 0.15 M NaCl, implying that nerves in the hepatoportal area are sensitive to increases in Na concentrations and that this leads to stimulation of hepatic afferent nerve activity. To study central activation in response to stimulation of the hepatic Na-sensitive mechanism, c-fos induction was monitored. After electrical stimulation of hepatic afferent nerves, neurons containing Fos-like immunoreactivity (Fos-li) were found in the area postrema, nucleus of the solitary tract, paraventricular hypothalamic nucleus, and supraoptic nucleus at 90 min after stimulation. Induction of Fos-li was also studied after simultaneous infusion of 0.45 M NaCl into the portal vein and distilled water into the inferior vena cava in conscious rats so as to keep the total amount of solution introduced into the systemic circulation isotonic, thus avoiding changes in mean arterial pressure, plasma osmolality, and plasma NaCl concentrations. Fos-li-containing neurons were found in the same regions in which they were found after electrical stimulation. However, few, if any, Fos-li-containing cells were found if the rats were hepatically denervated or if they received an intraportal infusion of hypertonic LiCl or mannitol. These data provide evidence for involvement of the brain stem and forebrain structures in NaCl regulatory functions induced by stimulation of the hepatoportal Na-sensitive mechanism. However, stimulation of the hepatoportal osmosensitive mechanism does not activate these central structures.

Afferent Pathways↗

PubMed1997

Adult Still's disease with myocardial dysfunction induced by microangiopathy.

A 52-year-old man with inflammatory disease of unknown origin but no specific laboratory abnormalities was referred to our hospital. He has subsequently diagnosed as having adult Still's disease. During an episode of severe inflammation he suffered reversible myocardial damage as revealed by electrocardiography, echocardiography and 201Tl myocardial scintigraphy; this was ameliorated by treatment with steroids and immunosuppressive drugs. No significant stenosis of the coronary artery was observed on coronary angiography. Interstitial mononuclear infiltration was apparent in the right ventricle on endomyocardial biopsy. Myocardial injury with adult Still's disease, which may result in heart failure, has rarely been reported. We report a case of adult Still's disease with myocardial dysfunction that may have been caused by microangiopathy.

Heart↗

PubMed1997

Total anomalous pulmonary vein drainage in an adult diagnosed by helical computed tomography.

A 41-year-old man visited our hospital with the complaint of palpitation by atrial flutter. He was finally diagnosed as total anomalous pulmonary vein drainage by helical computed tomography (CT). This case is very unusual due to the lack of symptoms until the age of 41. The absence of pulmonary artery stenosis, and the presence of atrial septal defect providing sufficient right to left shunt flow to maintain the output of left ventricle are some of the reasons to explain the lack of symptoms and very slight impact on daily life. Helical CT, in particular 3-dimensional imaging, is very useful in diagnosing complicated cardiovascular deformation as in this case.

Adult↗

PubMed1997

[A successful surgical treatment of coronary to pulmonary artery fistula with coronary steal phenomenon due to large volume of shunt: a case report].

A successful surgical treatment of right and left coronary to pulmonary artery fistula was presented. The patient was 61-year-old female, who was admitted for evaluation of cardiac murmur and chest pain. Cardiac catheterization and coronary artery angiogram revealed a large fistula both from RCA and LAD to the main pulmonary artery and distal LAD flow was sealed by this fistula. The left to right shunt ratio was calculated to be 55.1%. Preoperative BMIPP scintigram showed low uptake in the apex of the heart. Operation was indicated, because it was considered that angina pectoris was originated from coronary steal phenomenon. At the operation each right and left coronary shunt flow was measured to be 100 ml/min respectively. The fistulas were ligated and an opening of fistulas draining into the main pulmonary artery was closed through pulmonary arteriotomy under total cardiopulmonary bypass. Postoperative angiogram showed complete disappearance of the fistulas, postoperative BMIPP scintigram became to be normal, and her chest pain disappeared.

Angina Pectoris↗

PubMed1996

Molecular cloning of the novel human G protein-coupled receptor (GPCR) gene mapped on chromosome 9.

A novel human GPCR gene was cloned by PCR with degenerate primers designed from cannabinoid type 1 receptor (CB1) sequences and a full-length clone was isolated by screening of a human genomic DNA library. This gene, termed EDG-3, is highly homologous (51.9 % overall and 69.2 % in seven transmembrane regions) to human EDG-1, 47.9 % to rat AGR16 but only 28.0 % to human CB1 receptor. The Northern hybridization analysis showed that a 2.8 kb transcript of EDG-3 is abundantly expressed in the heart followed by placenta, kidney and liver. The EDG-3 gene was mapped on the human chromosome 9q22.1-q22.2 by fluorescence in situ hybridization analysis. Although the ligand and physiological role of this receptor is unknown, this gene may be a new member of the EDG family.

Amino Acid Sequence↗

PubMed1996

Distinct cellular compartment of cyclin-dependent kinase 5 (Cdk5) and neuron-specific Cdk5 activator protein (p35nck5a) in the developing rat cerebellum.

We have elucidated the spatial and temporal localization of Cdk5 and p35nck5a in the developing rat postnatal cerebellum. Both proteins were highly expressed in cell bodies of post mitotic and immature neurons. The localization of Cdk5 in cellular compartment was changed from cell body to the axon in development. On the other hand, p35nck5a was always expressed in the cell body throughout cerebellum development. The Cdk5 kinase activity was correlated with the expression of p35nck5a rather than that of Cdk5. These results indicate that p35nck5a is a physiological activator of Cdk5 in immature neurons and further suggest that Cdk5 has another function in mature neurons.

Aging↗

PubMed1996

Expression of calbindin-D28K by reactive astrocytes in gerbil hippocampus after ischaemia.

Calbindin-D28K (Calbindin) is a member of the superfamily of calcium-binding proteins that is implicated in the regulation of intracellular calcium. In the adult mammalian brain, calbindin was thought to be present only in neurones, where it is believed to serve a neuroprotective role. We now report the expression of calbindin after ischaemia in reactive astrocytes in the CA1 subfield of the hippocampus. Since other calcium-binding proteins, such as S-100 and calmodulin, which induce transformation or proliferation of glia, occur in astrocytes, it is conceivable that the expression of calbindin after ischaemia might be an important part of the process of gliosis.

Animals↗

PubMed1996

Calcineurin inhibitors, FK506 and cyclosporin A, suppress the NMDA receptor-mediated potentials and LTP, but not depotentiation in the rat hippocampus.

The effects of FK506, a Ca2+/calmodulin-dependent phosphatase 2B (calcineurin) inhibitor, on the NMDA receptor-mediated potentials and synaptic plasticity were investigated in the CA1 region of the rat hippocampus. Bath application of FK506 (50 microM) produced a 45% inhibition on the NMDA receptor-mediated potentials. FK506 also inhibited the induction of long-term potentiation (LTP), but had no effect on the depotentiation in the CA1 hippocampus. Cyclosporin A (100 microM), another calcineurin inhibitor, mimicked the effects of FK506 on the NMDA responses and synaptic plasticity. These results suggest that FK506 inhibits the activity of NMDA receptors via the involvement of calcineurin. The differential effects of FK506 on LTP and depotentiation may attribute to the partial inhibition on the activity of NMDA receptors and the subsequent attenuation of intracellular Ca2+ increase.

Animals↗

PubMed1996

Protective effect of vagus nerve stimulation on forebrain ischaemia in gerbil hippocampus.

The left vagus nerve was stimulated during transient forebrain ischaemia in gerbils. The animals were exposed to 3 min of forebrain ischaemic insult at 37.5 degrees C. On day 5 post-ischaemia, the animals were perfusion-fixed for qualitative and quantitative histopathological analyses. High current stimulation of the vagus nerve inhibited ischaemic neuronal damage in the hippocampal CA1 sector (p < 0.01), but low current stimulation did not (p < 0.01). These effects might have been due to inhibition of the effects of excitatory amino acids during ischaemia. These results indicate that vagus nerve stimulation might be protective to neurones subjected to ischaemic insult.

Animals↗

PubMed1996

Evaluating systemic lupus erythematosus disease activity using molecular markers of hemostasis.

OBJECTIVE: To determine the usefulness of measuring sensitive markers of the coagulation-fibrinolysis system (i.e., thrombin-antithrombin III complex [TAT], D dimer fragments [DD], and plasmin-alpha2-plasmin inhibitor complex [PIC]) for evaluating disease activity in patients with systemic lupus erythematosus (SLE). METHODS: We studied 57 SLE patients. Plasma concentrations of DD were measured by latex agglutination using monoclonal antibodies; TAT and PIC were determined by sandwich enzyme-linked immunosorbent assay. Disease activity was determined by using the SLE Disease Activity Index (SLEDAI). RESULTS: Levels of TAT, DD, and PIC were higher in SLE patients than in healthy controls (P<0.05). Levels of TAT and DD showed good correlations with SLEDAI scores (for TAT r=0.66, P<0.001; for DD r=0.50, P<0.001). Elevated levels of TAT, DD, and PIC were decreased following treatment. CONCLUSION: These results strongly suggest that measurement of molecular markers of hemostasis is useful for evaluating disease activity in patients with SLE.

Adult↗

PubMed1996

Immunosuppressant FK506 prevents mossy fiber sprouting induced by kindling stimulation.

Kindling stimulation induces expansive growth of the axons of the dentate granule cells, the mossy fiber, into several areas of the hippocampus. An intraperitoneal injection of the immunosuppressant drug FK506, which is a specific inhibitor of Ca(2+)-calmodulin dependent phosphatase, calcineurin, prevented the full development of kindling as well as mossy fiber sprouting. The results show a correlation between mossy fiber sprouting and the development of kindling. The results suggest also that calcineurin may have a promoting role in mossy fiber sprouting and subsequent synaptogenesis.

Animals↗

PubMed1996

Localization and developmental changes in the neuron-specific cyclin-dependent kinase 5 activator (p35nck5a) in the rat brain.

Mammalian brains contain a cde2-like protein kinase which is a heterodimer of cyclin-dependent kinase 5 (Cdk5) and a brain-specific regulatory subunit with a molecular weight of 35,000. In this study, we examined the temporal and spatial expression patterns of p35nck5a in the developing rat brain. Northern blot analysis showed that p35nck5a messenger RNA expression was low in the brain of 12-day postcoitum rats, and increased to a much higher level from 18 days postcoitum to two weeks after birth, and then declined at three weeks after birth. These developmental changes in p35nck5a expression correlated with the changes in Cdk5-associated kinase activity during brain development. These data suggest that p35nck5a is the specific activator for Cdk5 in the brain. Immunohistochemical and in situ hybridization studies demonstrated the presence of p35nck5a protein in postmitotic neurons but not in glial cells at all stages of brain development, indicating that p35nck5a is a neuron-specific protein. In the adult brain, the protein was rich in cell bodies and dendrites, and only very low amounts were detected in axons. In fetal and neonatal brains, however, axonal pathways such as the corpus callosum and external capsule were also stained with anti-p35nck5a antibody. Our findings suggest that p35nck5a is neuron specific, and a specific activator for Cdk5, and the subcellular localization of the two is strictly regulated depending on brain development. Neuronal Cdc2-like kinase may play key roles in neuronal maturation, synaptic formation, and neuronal plasticity.

Animals↗

PubMed1996

Interleukin-8 gene expression by human dental pulp fibroblast in cultures stimulated with Prevotella intermedia lipopolysaccharide.

Interleukin (IL)-8 mRNA expression was investigated in human dental pulp fibroblast cultures after stimulation with lipopolysaccharide (LPS) prepared from Prevotella intermedia and inflammatory cytokines. The expression of IL-8 mRNA and the release of IL-8 induced by P. intermedia LPS in pulpal fibroblast cultures were detected by Northern blot analysis and ELISA, respectively. The sufficient concentration of P. intermedia LPS on the IL-8 mRNA expression was 0.1 microgram/ml in pulpal fibroblast cultures. IL-8 mRNA levels began to increase after 2 h of exposure, reached a maximum at 4 to 8 h, and declined after 48 h, reaching the unstimulated level by 60 h. IL-8 production by the pulpal fibroblasts began to increase after 8 h of exposure upon stimulation with 10 microgram/ml of P. intermedia LPS. By contrast Salmonella LPS and synthetic lipid A did not increase IL-8 mRNA concentrations in pulpal fibroblast cultures. Recombinant human IL-1 alpha, beta, and tumor necrosis factor-alpha were capable of stimulating these cells to express IL-8 mRNA but natural human interferon-beta, gamma, and recombinant human IL-6 were incapable in our assay. These results suggest that pulpal fibroblasts are immunoresponsive cells and can elaborate IL-8 upon stimulation with P. intermedia LPS.

Adolescent↗