Biomedical subjects

M Yoshimura

Publications and source records attributed to M Yoshimura.

At least 181 records · Page 10Linked to original sources

PubMed1998

Capsaicin facilitates excitatory but not inhibitory synaptic transmission in substantia gelatinosa of the rat spinal cord.

Actions of capsaicin were examined on synaptic transmissions in the substantia gelatinosa (SG) of adult rat spinal cord slices using the whole-cell patch-recording technique. Bath-applied capsaicin at a concentration of 2 microM activated a slow inward current (having an amplitude of 33 pA at -70 mV), which was accompanied by an increase in the frequency of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs; by 234%); these actions were blocked by a capsaicin-receptor antagonist, capsazepine (10 microM). The capsaicin-induced increase in sEPSC frequency was resistant to tetrodotoxin (0.5-1 microM). On the other hand, capsaicin (2 microM) did not affect either glycine- or gamma-aminobutyric acid-mediated spontaneous synaptic transmission. The results indicate that capsaicin enhances excitatory but not inhibitory synaptic transmission, possibly through a direct action on primary afferent terminals in the SG. As the SG has been thought to participate in nociceptive pathway, it is suggested that such a presynaptic action of capsaicin contributes to nociceptive transmissions.

Animals↗

PubMed1998

Quantitative measurements for type 1 deiodinase messenger ribonucleic acid in human peripheral blood mononuclear cells: mechanism of the preferential increase of T3 in hyperthyroid Graves' disease.

To evaluate the regulatory mechanism of human Type 1 iodothyronine deiodinase (D1) gene expression, we measured the D1 mRNA levels in peripheral blood mononuclear cells (PBMC) in normal control subjects and in patients with Graves' disease. We used competitive reverse transcriptase-polymerase chain reaction with the deleted complimentary RNA of D1 as the standard for quantification. The D1 mRNA levels in PBMC were increased significantly in patients with Graves' disease compared with that in normal controls. There was a significant (p < 0.01) positive correlation (r=0.698) between D1 mRNA level and serum T3 concentration. When PBMC from the normal volunteers were cultured with various doses of T3, the quantity of D1 mRNA increased significantly in a dose-dependent manner. These findings indicate that PBMC D1 mRNA is actually up-regulated by T3 in vivo, and we postulate that a vicious spiral of increasing T3 and D1 is responsible for the exacerbation of thyrotoxicosis in hyperthyroid Graves' disease.

Gene Expression Regulation↗

PubMed1998

Modulation by chloramine-T of 4-aminopyridine-sensitive transient outward current in rabbit atrial cells.

The effects of an oxidizing agent, chloramine-T, on the 4-aminopyridine-sensitive transient outward current (ITO) were investigated in rabbit atrial myocytes by using patch-clamp techniques. Extracellular application of chloramine-T at 20 microM irreversibly slowed the time course of inactivation of the whole-cell ITO, and increased the peak by 19.3% (n = 19) at +40 mV. At 100 microM, chloramine-T decreased the peak by 22.5% (n = 9) of the control, and subsequently induced a glibenclamide-sensitive time-independent outward K+ current. Under superfusion with dithiothreitol (3 mM), chloramine-T (100 microM) produced no change in ITO. The chloramine-T-induced slowing of ITO inactivation was partially reversed by subsequent application of 3 mM dithiothreitol. In single-channel recordings with the cell-attached patch configuration, chloramine-T (20 microM) increased the open probability of the ITO channel from 0.15 to 0.46 at a potential 100 mV positive to the resting potential, and the mean open lifetime from 5.1 ms to 7.0 ms (n = 5). The unitary current amplitude was not affected. As a result, chloramine-T increased the ensemble current in amplitude and slowed its decay. These results indicated that: (1) inactivation of the native A-type channels of rabbit heart is susceptible to oxidation; and (2) oxidation of ITO channels may contribute to the genesis of arrhythmias.

4-Aminopyridine↗

PubMed1998

Agonist stimulation of B1 and B2 kinin receptors causes activation of the MAP kinase signaling pathway, resulting in the translocation of AP-1 in HEK 293 cells.

In response to bradykinin, phosphorylated MAP kinases (ERK-1 and ERK-2) were abundantly increased in HEK 293 cells, which overexpress the rat B2 kinin receptor. In a similar way des-Arg9-bradykinin stimulation of B1 kinin receptor-overexpressing HEK 293 cells caused activation of the same species of MAP kinase. Furthermore, nuclear translocation of transcription factor AP-1 was also found in the cells after stimulation with either agonist. PD98059, a MAP kinase kinase (MEK-1) inhibitor, blocked the agonist-induced AP-1 translocation as well as the phosphorylation of the MAP kinases. This communication provides the first evidence for both B1 and B2 kinin receptors mediating the MAP kinase signaling pathway to activate AP-1.

Animals↗

PubMed1998

Association of remnant lipoprotein levels with impairment of endothelium-dependent vasomotor function in human coronary arteries.

BACKGROUND: It remains undetermined whether triglyceride-rich lipoproteins are an independent risk factor for atherosclerosis. METHODS AND RESULTS: The correlation of responses of coronary arterial diameter (quantitative coronary angiography) and coronary blood flow (intracoronary flow wire technique) to intracoronary infusion of acetylcholine (10 and 50 microg/min) with coronary risk factors including remnant lipoprotein levels was statistically analyzed in 106 consecutive subjects with normal coronary angiograms. Remnant lipoproteins were isolated from fasting blood with an immunoaffinity mixed gel containing anti-apolipoprotein (apo) A-1 and anti-apoB-100 monoclonal antibodies. In multivariate stepwise regression analysis, remnant lipoprotein levels had the most significant correlation with abnormal epicardial coronary vasomotor responses to acetylcholine infusion, reflected by impaired dilation or constriction of the epicardial coronary arteries, and the levels also had an inverse and independent correlation with the coronary blood flow increase in response to acetylcholine. In a subgroup of 53 consecutive subjects, constrictor responses of epicardial coronary diameters to intracoronary infusion of NG-monomethyl-L-arginine (50 micromol/min for 4 minutes) at baseline, reflecting the presence of coronary nitric oxide bioactivity, had an inverse and independent correlation with remnant lipoprotein levels by use of multivariate analysis. CONCLUSIONS: Remnant lipoprotein levels were independently associated with abnormal endothelium-dependent vasomotor function in large and resistance coronary arteries in humans, indicating that remnant lipoproteins may impair endothelial vasomotor function in human coronary arteries. The decrease in coronary nitric oxide bioactivity may be responsible in part for the inhibitory effects of remnant lipoproteins.

Acetylcholine↗

PubMed1998

Dynein arms are oscillating force generators.

Eukaryotic flagella beat rhythmically. Dynein is a protein that powers flagellar motion, and oscillation may be inherent to this protein. Here we determine whether oscillation is a property of dynein arms themselves or whether oscillation requires an intact axoneme, which is the central core of the flagellum and consists of a regular array of microtubules. Using optical trapping nanometry, we measured the force generated by a few dynein arms on an isolated doublet microtubule. When the dynein arms on the doublet microtubule contact a singlet microtubule and are activated by photolysis of caged ATP8, they generate a peak force of approximately 6pN and move the singlet microtubule over the doublet microtubule in a processive manner. The force and displacement oscillate with a peak-to-peak force and amplitude of approximately 2 pN and approximately 30 nm, respectively. The geometry of the interaction indicates that very few (possibly one) dynein arms are needed to generate the oscillation. The maximum frequency of the oscillation at 0.75 mM ATP is approximately 70 Hz; this frequency decreases as the ATP concentration decreases. A similar oscillatory force is also generated by inner dynein arms alone on doublet microtubules that are depleted of outer dynein arms. The oscillation of the dynein arm may be a basic mechanism underlying flagellar beating.

Adenosine Triphosphate↗

PubMed1998

Intracoronary infusion of reduced glutathione improves endothelial vasomotor response to acetylcholine in human coronary circulation.

BACKGROUND: Oxygen free radicals have been shown to cause endothelial vasomotor dysfunction. This study examined the effect of reduced glutathione (GSH), an antioxidant, on human coronary circulation. METHODS AND RESULTS: Responses of epicardial diameter and blood flow of the left anterior descending coronary artery to intracoronary infusion of acetylcholine (ACh, 50 microg/min) were measured by quantitative coronary angiography and Doppler flow-wire technique, respectively, before and during combined intracoronary infusion of GSH (50 mg/min) or saline in 26 subjects with no significant coronary stenosis. GSH infusion suppressed the constrictor response of epicardial diameter to ACh and enhanced the increase in blood flow response to ACh. Furthermore, GSH potentiated the coronary dilator effect of nitroglycerin. A beneficial effect of GSH on the epicardial diameter response to ACh was observed in a subgroup of subjects with > or = 1 coronary risk factors but not in a subgroup without risk factors. Saline infusion did not have any effects. CONCLUSIONS: The results indicate that GSH improved coronary endothelial vasomotor function, particularly in subjects with coronary risk factors, and it potentiated the vasodilator effect of nitroglycerin in human coronary arteries.

Acetylcholine↗

PubMed1998

Bisecting GlcNAc structure is implicated in suppression of stroma-dependent haemopoiesis in transgenic mice expressing N-acetylglucosaminyltransferase III.

Several sugar structures have been reported to be necessary for haemopoiesis. We analysed the haematological phenotypes of transgenic mice expressing beta-1,4 N-acetylglucosaminyltransferase III (GnT-III), which forms bisecting N-acetylglucosamine on asparagine-linked oligosaccharides. In the transgenic mice, the GnT-III activity was elevated in bone marrow, spleen and peripheral blood and in isolated mononuclear cells from these tissues, whereas no activity was found in these tissues of wild-type mice. Stromal cells after long-term cultures of transgenic-derived bone marrow and spleen cells also showed elevated GnT-III activity, compared with an undetectable activity in wild-type stromal cells. As judged by HPLC analysis, lectin blotting and lectin cytotoxicity assay, bisecting GlcNAc residues were increased on both blood cells and stromal cells from bone marrow and spleen in transgenic mice. The transgenic mice displayed spleen atrophy, hypocellular bone marrow and pancytopenia. Bone marrow cells and spleen cells from transgenic mice produced fewer haemopoietic colonies. After lethal irradiation followed by bone marrow transplantation, transgenic recipient mice showed pancytopenia compared with wild-type recipient mice. Bone marrow cells from transgenic donors gave haematological reconstitution at the same level as wild-type donor cells. In addition, non-adherent cell production was decreased in long-term bone marrow cell cultures of transgenic mice. Collectively these results indicate that the stroma-supported haemopoiesis is compromised in transgenic mice expressing GnT-III, providing the first demonstration that the N-glycans have some significant roles in stroma-dependent haemopoiesis.

Acetylglucosamine↗

PubMed1998

Alterations with aging and ischemia in nicotinic acetylcholine receptor subunits alpha4 and beta2 messenger RNA expression in postmortem human putamen. Implications for susceptibility to parkinsonism.

Nicotine activates the dopaminergic system and acts to alleviate hypokinetic disorders (parkinsonism). The frequency of parkinsonism increases with age and is sometimes associated with multiple small infarcts (status lacunaris) in the putamen. To investigate changes with aging in control cases free from neurological disease and changes in cases with multiple small infarcts (status lacunaris) in the putamen, the present study determined nicotinic acetylcholine receptor (nAChR) subunit alpha4 and beta2 messenger RNA (mRNA) expression in the postmortem human putamen using the reverse transcription-polymerase chain reaction (RT-PCR). In controls, alpha4 subunit mRNA expression was unaltered, but beta2 subunit mRNA expression decreased significantly with age. In cases with status lacunaris, both beta2 and alpha4 subunit mRNA expressions were significantly lower than in the control cases. The reduction in beta2 mRNA expression alone, or in both alpha4 and beta2 mRNA expressions, suggests a reduction in functional nAChRs in the putamen, which may in part explain the susceptibility to hypokinetic disorders of the elderly and subjects with ischemic damage in the striatum.

Adult↗

PubMed1998

Age-related changes in nicotinic acetylcholine receptor subunits alpha4 and beta2 messenger RNA expression in postmortem human frontal cortex and hippocampus.

Age-related changes in nicotinic acetylcholine receptor (nAChR) subunit alpha4 and beta2 messenger RNA (mRNA) expression in the postmortem human frontal cortex and hippocampus was investigated using the reverse transcription-polymerase chain reaction (RT-PCR). In the frontal cortex, both alpha4 and beta2 subunit mRNA expression decreased with age. In the hippocampus, alpha4 subunit mRNA expression was unaltered, while beta2 subunit mRNA expression significantly decreased with age. These findings suggest that nAChR transcription decreases during aging with differing vulnerability between subunits and brain regions, which could in part contribute to the reduction in cognitive functions seen in the elderly.

Adult↗

PubMed1998

Muscarinic facilitation of GABA release in substantia gelatinosa of the rat spinal dorsal horn.

1. Blind patch clamp recordings were made from substantia gelatinosa (SG) neurones in the adult rat spinal cord slice to study the mechanisms of cholinergic modulation of GABAergic inhibition. 2. In the majority of SG neurones tested, carbachol (10 microM) increased the frequency (677 % of control) of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs). A portion of these events appeared to result from the generation of spikes by GABAergic interneurones, since large amplitude IPSCs were eliminated by tetrodotoxin (1 microM). 3. The effect of carbachol on spontaneous IPSCs was mimicked by neostigmine, suggesting that GABAergic interneurones are under tonic regulation by cholinergic systems. 4. The frequency of GABAergic miniature IPSCs in the presence of tetrodotoxin (1 microM) was also increased by carbachol without affecting amplitude distribution, indicating that acetylcholine facilitates quantal release of GABA through presynaptic mechanisms. 5. Neither the M1 receptor agonist McN-A-343 (10-300 microM) nor the M2 receptor agonist, arecaidine (10-100 microM), mimicked the effects of carbachol. All effects of carbachol and neostigmine were antagonized by atropine (1 muM), while pirenzepine (100 nM), methoctramine (1 microM) and hexahydrosiladifenidol hydrochloride, p-fluoro-analog (100 nM) had no effect. 6. Focal stimulation of deep dorsal horn, but not dorsolateral funiculus, evoked a similar increase in IPSC frequency to that evoked by carbachol and neostigmine. The stimulation-induced facilitation of GABAergic transmission lasted for 2-3 min post stimulation, and the effect was antagonized by atropine (100 nM). 7. Our observations suggest that GABAergic interneurones possess muscarinic receptors on both axon terminals and somatodendritic sites, that the activation of these receptors increases the excitability of inhibitory interneurones and enhances GABA release in SG and that the GABAergic inhibitory system is further controlled by cholinergic neurones located in the deep dorsal horn. Those effects may be responsible for the antinociceptive action produced by the intrathecal administration of muscarinic agonists and acetylcholinesterase inhibitors.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗

PubMed1998

Immunological assessment of the distribution of type VII adenylyl cyclase in brain.

The localization of the nine identified isoforms of adenylyl cyclase in brain has been largely based on determination of patterns of mRNA expression. A polyclonal antibody has now been developed that specifically recognizes Type VII adenylyl cyclase. This antibody was used for immunocytochemical analysis of the distribution of Type VII adenylyl cyclase in rat brain. Labeling of Type VII adenylyl cyclase was observed in several areas, including cerebellum, caudate-putamen, nucleus accumbens, hippocampus and cerebral cortex. In some of these areas, the staining of the adenylyl cyclase protein suggested the possibility of presynaptic localization. For example, in situ hybridization showed Type VII adenylyl cyclase mRNA concentrated in cerebellar granule neurons. The cerebellar granule cell layer, however, showed little immunostaining, while punctate immunostaining was observed in the molecular layer. These results suggested that protein synthesized in the granule neurons may be targeted to the neuron terminals. Punctate staining in the caudate-putamen, globus pallidus and nucleus accumbens also suggested the possibility of axonal and/or dendritic localization of Type VII adenylyl cyclase in these regions. Labeling of the soma of cerebellar Purkinje cells, cortical pyramidal and non-pyramidal cells and interneurons in the cerebellum and hippocampus was also observed. Type VII adenylyl cyclase, like the other adenylyl cyclase isoforms, has distinct regulatory characteristics, including sensitivity to stimulation by Gsalpha and G protein betagamma subunits, modulation by protein kinase C, and high sensitivity to stimulation by ethanol. These characteristics, and the discrete localization of this enzyme, may contribute to its ability to provide signal integration and/or control of neurotransmitter release in particular neurons or brain areas.

Adenylyl Cyclases↗

PubMed1998

Ectopic expression of N-acetylglucosaminyltransferase III in transgenic hepatocytes disrupts apolipoprotein B secretion and induces aberrant cellular morphology with lipid storage.

N-Acetylglucosaminyltransferase III (GnT-III) produces "bisecting-GlcNAc" and regulates the branching of N-glycans. GnT-III activity is elevated during hepatocarcinogenesis, which is in contrast to the undetectable level found in normal hepatocytes. To determine the biological significance of GnT-III in hepatocytes, transgenic mice that specifically express GnT-III in the liver were established and characterized. The transgenic hepatocytes had a swollen oval-like morphology, with many lipid droplets. Apolipoprotein B, which contained increased level of bisecting-GlcNAc accumulated in the transgenic hepatocytes. In the transgenic serum, triglycerides, the beta- and pre-beta-lipoprotein fractions, and apolipoprotein B100 were significantly decreased, compared with levels in nontransgenic serum. These abnormal phenotypes were more prominent in the mice with more copies of the transgene and a resulting high GnT-III activity. We demonstrate that aberrant glycosylation, as the direct result of the formation of bisecting-GlcNAc, disrupts the function of apolipoprotein B, leading to the generation of fatty liver. This observation suggests a novel mechanism for the pathogenesis of fatty liver.

Animals↗

PubMed1998

Age-related changes in D1 and D2 receptor mRNA expression in postmortem human putamen with and without multiple small infarcts.

Expression of messenger RNAs (mRNAs) encoding the D1 and D2 dopamine receptors as a function of age was determined in the human putamen using the reverse transcription-polymerase chain reaction (RT-PCR). In cases without multiple small infarcts (status lacunaris) in the putamen, D1 mRNA expression was unaltered, while D2 mRNA expression significantly decreased with age. Both D1 and D2 mRNA expression was lower in cases with status lacunaris. The reduction in D1 receptors primarily located on striatonigral neurons or D2 receptors primarily located on striatopallidal neurons may inhibit thalamocortical neurons. The decreased transcription of D1 and D2 receptor genes may in part account for increased susceptibility to hypokinetic disorders in the elderly.

Actins↗

PubMed1998

Transsynaptic cell death of neurons following striatopallidal lesions does not occur in substantia nigra pars reticulata in developing rats

In adult rats, combined lesions of the striatum and globus pallidus (GP) cause transsynaptic cell death of neurons in the substantia nigra pars reticulata (SNr) which becomes apparent 1-2 weeks after the lesions. This delayed cell death of SNr neurons has been explained to be caused by over-excitation of SNr neurons which results from an imbalance between excitatory and inhibitory inputs due to two simultaneous events: acceleration of the excitatory input from the disinhibited subthalamic nucleus (STN) and deprivation of the inhibitory input from the striatum. To examine whether the transsynaptic neuronal death in SNr is caused by the same lesions in developing rats, we destroyed the striatum and GP in rats on postnatal days 10 (P10), P15, P20, P25, P30, P35 and P60 by injecting ibotenic acid. We found that cell death did not occur in SNr neurons in rats younger than P20 and that Fos expression induced in STN neurons after these striatopallidal lesions in P10 and P20 rats was lower than that in P30 or P60 rats. These findings suggest that excitation of STN neurons is not enough to cause cell death of SNr neurons in rats younger than P20. Immature functional connection between the cerebral cortex and STN in the early developing animals may contribute to the resistivity of SNr neurons to transsynaptic delayed cell death.

Journal Article↗

PubMed1998

Transsynaptic cell death of neurons following striatopallidal lesions does not occur in substantia nigra pars reticulata in developing rats.

Animals↗

PubMed1998

Long-term follow-up of the vascularized iliac bone graft.

We retrospectively studied four patients who were treated with vascularized iliac bone graft for reconstruction of the tibia. The average length of the graft was 9.8 cm. The follow-up period was 11-18 years (average, 14.8 years). Although two of them were osteomyelitis, no recurrence occurred. We also studied four patients who were treated with nonvascularized iliac bone graft for anterior spinal interbody fusion (average, 10.8 years). Cosmetic problem slightly exists because the vascularized iliac bone still showed the original shape, which was prominent from the tibial contour. The vascularized iliac bone marrow showed iso intensity in both T1 and T2 image of the MRI. However, nonvascularized iliac bone graft on the spine showed high intensity in both T1 and T2 imaging. Since the vascularized iliac bone graft does not present fatty degeneration, it shows strong resistance against infection.

Adult↗

PubMed1998

Two cases of synchronous multiple thymoma.

We report two cases of synchronous double primary thymoma without myasthenia gravis. These cases suggest the possibility of multicentric thymoma and confirm the validity of a complete thymectomy.

Adult↗