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Masaki Yoshida

Publications and source records attributed to Masaki Yoshida.

At least 37 records · Page 2Linked to original sources
PubMed2004

Cross-modal integration and plastic changes revealed by lip movement, random-dot motion and sign languages in the hearing and deaf.

Sign language activates the auditory cortex of deaf subjects, which is evidence of cross-modal plasticity. Lip-reading (visual phonetics), which involves audio-visual integration, activates the auditory cortex of hearing subjects. To test whether audio-visual cross-modal plasticity occurs within areas involved in cross-modal integration, we used functional MRI to study seven prelingual deaf signers, 10 hearing non-signers and nine hearing signers. The visually presented tasks included mouth-movement matching, random-dot motion matching and sign-related motion matching. The mouth-movement tasks included conditions with or without visual phonetics, and the difference between these was used to measure the lip-reading effects. During the mouth-movement matching tasks, the deaf subjects showed more prominent activation of the left planum temporale (PT) than the hearing subjects. During dot-motion matching, the deaf showed greater activation in the right PT. Sign-related motion, with or without a lexical component, activated the left PT in the deaf signers more than in the hearing signers. These areas showed lip-reading effects in hearing subjects. These findings suggest that cross-modal plasticity is induced by auditory deprivation independent of the lexical processes or visual phonetics, and this plasticity is mediated in part by the neural substrates of audio-visual cross-modal integration.

Adult↗
PubMed2004

The application of independent component analysis to the multi-channel surface electromyographic signals for separation of motor unit action potential trains: part I-measuring techniques.

The purpose of this study is to examine whether or not the application of independent component analysis (ICA) is useful for separation of motor unit action potential trains (MUAPTs) from the multi-channel surface EMG (sEMG) signals. In this study, the eight-channel sEMG signals were recorded from tibialis anterior muscles during isometric dorsi-flexions at 5%, 10%, 15% and 20% maximal voluntary contraction. Recording MUAP waveforms with little time delay mounted between the channels were obtained by vertical sEMG channel arrangements to muscle fibers. The independent components estimated by FastICA were compared with the sEMG signals and the principal components calculated by principal component analysis (PCA). From our results, it was shown that FastICA could separate groups of similar MUAP waveforms of the sEMG signals separated into each independent component while PCA could not sufficiently separate the groups into the principal components. A greater reduction of interferences between different MUAP waveforms was demonstrated by the use of FastICA. Therefore, it is suggested that FastICA could provide much better discrimination of the properties of MUAPTs for sEMG signal decomposition, i.e. waveforms, discharge intervals, etc., than not only PCA but also the original sEMG signals.

Action Potentials↗
PubMed2004

The application of independent component analysis to the multi-channel surface electromyographic signals for separation of motor unit action potential trains: part II-modelling interpretation.

The purpose of this article was to investigate whether or not FastICA can separate identical motor unit action potential trains (MUAPTs) of the 8-channel surface electromyographic (sEMG) signals constructed by an sEMG model into the independent components. Firstly, we have examined how much the increase of motor units (MUs) in the simulated sEMG signals influenced the performance on the separation of MUAPTs by kurtosis. The decreased trend of mean kurtosis on both sEMG signals and their independent components were observed as MUs were increased. These data suggested that the separation performance decayed when MUs were increased. Secondary, the differences between the independent components and the principal components have been also applied to the simulated sEMG signals with or without time delay between the sEMG channels. FastICA could successfully separate identical MUAPTs with no time delay but principal component analysis (PCA) could not do so. Against it, both FastICA and PCA could not separate MUAPTs with some time delay. In conclusion, our results suggested that FastICA could separate identical MUAPTs with no time delay into the independent components by FastICA, which might offer a new technique for the separation of interfered MUAP waveforms based on statistical properties of sEMG signal distributions.

Action Potentials↗
PubMed2004

Management of detrusor dysfunction in the elderly: changes in acetylcholine and adenosine triphosphate release during aging.

Numerous studies have detailed age-related changes in the structure and function of the bladder that may contribute to the high prevalence of overactive bladder (OAB) in the elderly population, but the relation of these changes to OAB symptoms remains unclear. Physiologic and neurochemical studies have been conducted in human detrusor strips obtained from people of different ages, focusing on potential changes in cholinergic and purinergic neurotransmission, as well as the release and actions of acetylcholine (ACh) from nonneuronal bladder cells. Results from physiologic and microdialysis experiments indicate that purinergic transmission increases with age, whereas cholinergic transmission decreases. These effects are most likely because of decreased release of ACh and increased release of adenosine triphosphate (ATP) from postganglionic parasympathetic axons innervating the bladder. Immunohistochemical experiments showed that choline acetyltransferase in the human detrusor is contained not only in parasympathetic axons, but also in cells of the urothelium. The release of nonneuronal ACh increases with age and detrusor stretch. The age-related increase in purinergic transmission in the detrusor and other data indicating that responses to ATP are increased in detrusor overactivity suggest that purinergic receptor antagonists may provide a useful complement to muscarinic receptor antagonists in the treatment of older patients with OAB. Nonneuronal ACh release may play a key role in the storage phase of the micturition reflex, and this may explain, at least in part, the effectiveness of antimuscarinic agents for the treatment of OAB.

Acetylcholine↗
PubMed2004

Electroporation-mediated muscarinic M3 receptor gene transfer into rat urinary bladder.

BACKGROUND: Muscarinic M3 (M3) receptor has been recognized as a major muscarinic receptor for smooth muscle contractions of the urinary bladder. Under the hypothesis that overexpression of M3 receptor in the urinary bladder would enhance urinary bladder contractions, we have transferred the M3 receptor gene into rat bladders using electroporation (EP) and evaluated the functional expression of the transferred gene. METHODS: Plasmids expressing luciferase, a green fluorescence protein and M3 receptor were injected into the rat bladder and square-wave electric pulses were immediately applied. Two days after gene transfer, we analyzed gene expression. Immunohistochemical staining was performed and the contractile responses from isolated bladder strips, which were induced KCl, carbachol and electrical field stimulation (EFS), were evaluated. RESULTS: The optimal conditions of electroporation were 8 pulses, 45 voltages, 50 milliseconds/pulses and 1 Hz. Under these conditions, luciferase gene expression was enhanced approximately 300-fold, compared to an injection of DNA only. Regarding immunohistochemistry with an anti-M3 receptor, an increase in immunoactivity was observed in the M3 receptor gene transferred rat bladder, compared to the bladder of the control rat. In rats with the transferred M3 receptor gene, carbachol- and EFS-induced maximum contractile responses of bladder smooth muscle strips significantly increased. CONCLUSIONS: These findings suggest that an in vivo EP procedure is an useful method for gene transfer into the bladder and that an overexpression of M3 receptor in the rat bladder enhances bladder contractility. This technique may become a new treatment modality for detrusor underactivity.

Animals↗
PubMed2004

Chemohormonal therapy as primary treatment for metastatic prostate cancer: a randomized study of estramustine phosphate plus luteinizing hormone-releasing hormone agonist versus flutamide plus luteinizing hormone-releasing hormone agonist.

BACKGROUND: The present study was undertaken mainly to investigate whether chemohormonal therapy with estramustine phosphate plus luteinizing hormone-releasing hormone (LHRH) agonist has a more beneficial effect than the hormonal therapy with flutamide plus LHRH agonist for newly diagnosed patients with metastatic prostate cancer. METHODS: A total of 57 patients with metastatic prostate cancer aged 59-80 years (median 74 years) were entered in the study and were randomized to the treatment of estramustine phosphate (560 mg/day) plus LHRH agonist (estramustine group) or flutamide (375 mg/day) plus LHRH agonist (flutamide group) with stratification for the degree of performance status, histological differentiation and bone metastasis. RESULTS: Both of the treatment regimens were well tolerated with similar incidences of adverse drug reactions. The overall response rates (complete response plus partial response) at 12 weeks after treatment in the estramustine and flutamide groups were 76 and 55%, respectively. The median time to objective progression for the estramustine group (25.4 months) was longer than that of the flutamide group (14.6 months). The serum levels of follicle stimulating hormone and testosterone were significantly lower in the estramustine group. CONCLUSIONS: Chemohormonal therapy with estramustine phosphate plus LHRH agonist showed longer clinical progression-free survival than the hormonal therapy with flutamide plus LHRH agonist (P = 0.03), although there was no significant difference in the overall survival. A larger-scaled trial with more statistical power is required to clarify that the former regimen is more beneficial than the latter for newly diagnosed patients with advanced prostate cancer.

Aged↗
PubMed2004

[Gnathostomiasis caused by Gnathostoma spinigerum etiologically diagnosed upon extraction of the worm from the skin].

We report a patient with gnathostomiasis in whom a specific diagnosis of Gnathostoma spinigerum infestation was made morphologically upon removal of the worm. A 47-Year-old Japanese male on a business trip to Vietnam ate fried frog with a Vietnamese friend in January 2002, the friend was diagnosed with gnathostomiasis in June 2002. The patient noted swelling of the right leg with migration to the right arm, prompting him to our hospital in February 2003. Hematologic examination showed eosinophilia, and specific anti-gnathostome antibody was detected by a dot enzyme-linked immunosorbent assay (Dot ELISA) in the serum. He was diagnosed as gnathostomiasis, and was given albendazole 400 mg b.i.d. On day 11 of therapy the patient removed a larval worm from the right palmar lesion by pinching with his nails. The worm was identified as G. spinigerum based on morphologic characteristics including number of hooklets on its head-bulb. When gnathostomiasis is suspected, albendazole should be administered before incision of the skin lesion.

Albendazole↗
PubMed2004

Acetylcholine release from urinary bladder smooth muscles of non-insulin-dependent diabetic rats.

INTRODUCTION: To investigate the mechanism of voiding dysfunction in non-insulin-dependent diabetes mellitus, we attempted to measure the acetylcholine (ACh) release using an in vivo microdialysis technique and measuring the detrusor pressure after electrical field stimulation (EFS) of the pelvic nerve. MATERIALS AND METHODS: Eight- and 32-week-old female Goto-Kakizaki (GK) rats (non-insulin-dependent diabetes mellitus model) and age-matched female Wistar rats (controls) were used in this study. The pelvic nerve was exposed on a bipolar platinum electrode to EFS, and a cannula was inserted into the bladder to measure the detrusor pressure. The microdialysis probe was inserted into the bladder wall and was connected to a microinfusion syringe pump. Dialysate was constantly perfused, collected in a microtube, and then injected into the ACh assay system. Histological examinations were performed by staining with hematoxylin and eosin and S-100 immunohistochemical staining in bladder preparations of both GK and control rats. RESULTS: In 8-week-old rats, both detrusor pressures and amounts of ACh release of GK rats were not significantly different from those of control rats. In 32-week-old rats, both detrusor pressures and ACh releases were only significantly increased at 5 and 10 Hz of EFS. In the histological study, the number of nerve fibers or bundles of 32-week-old GK rats was significantly decreased as compared with control rats. CONCLUSION: The present data suggest that the decrease in EFS-induced ACh release in GK rats, which may be caused by the decreased number of nerve fibers, may contribute to the decrease in bladder contractions.

Acetylcholine↗
PubMed2004

[Retinopathy of prematurity in extremely low birth weight infants: a Tokyo multicenter study].

OBJECTIVE: To investigate how the increase in survival rate in extremely low birth weight (a birth weight of 1,000 g or less) infants had affected the incidence of retinopathy of prematurity (ROP) and the frequency of laser treatment. METHODS: We retrospectively reviewed the medical records of 122 surviving premature infants with birthweights less than 1,000 g to determine the severity of ROP observed at 16 neonatal intensive care units in Tokyo between April and October 2002. RESULTS: The survival rate was 85.6%. The mean gestational age was 26.74 weeks and the mean birth weight was 782.25 g. One-hundred-and-five infants (86.1%) developed ROP, fifty (41.0%) received laser treatment, and six (4.9%) had retinal detachment. The median postmenstrual age (gestational age at birth plus chronological age in weeks, PMA) at the onset of ROP was 32.5 weeks, and the first laser treatment was performed at the median PMA of 35.7 weeks. CONCLUSIONS: In these extremely low birth weight infants, there was an increase in the survival rate and in the incidence of severe ROP that progressed to the stage that required treatment.

Birth Weight↗
PubMed2004

[The visual pathways, from anatomical MRI to physiological with (f)MRI and tractography with diffusion tensor MRI (DTMRI)].

Advances in MRI technology have led to a better knowledge of visual pathways (1984-2004), with a new descriptive anatomy and functional model. The authors first describe the technical development of MRI over the last thirty years, then describe and illustrate the new descriptive anatomy. Cephalic MRI reveals brain structures that were previously invisible, on different encephalic planes, in the optic pathways, horizontally from the cornea to the calcarin fissure (neuro-ocular plane (NOP), oblique trans-hemispheric neuro-ocular (OTNOP) and neuro-opto-tractal planes (NOTP)), in their orthogonal orientation upon the oculomotor pathways: head and axonal optic nerve pack (visual deutoneurons in their meninges), optic tracts, lateral geniculate bodies, optic radiations and the calcarian fissure. Comparative anatomy with the rhesus macaque is mentioned. Functional neuroanatomy (physiology) benefits from cine-MRI for ocular motricity (OD MRI), growth by the observation of myelinization in children, blood and CSF circulation by MR angiography, local blood volumes by perfusion imaging, neuronal quantification with inflammation or myelin regeneration by spectroscopy (MRS), brain mapping by functional MR ((f)MRI) measuring local CBF enhancement by paradigmatic stimulations. The recent functional imaging method, tractography (or diffusion tensor MRI (DTMRI)), using diffusion MRI techniques, natural vector calculations with diffusion tensor and software power for morphological and statistical directional results, represents the direction of projection, association and commissural white matter tracts. Normal examples are shown and some common clinical consequences are discussed.

Adult↗
PubMed2003

Down-regulation of melanin synthesis by a biphenyl derivative and its mechanism.

Down-regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2'-dihydroxy-5,5'-dipropyl-biphenyl (DDB), down-regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse-chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down-regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation.

Animals↗
PubMed2003

Future research needs for the definition/diagnosis of interstitial cystitis.

In Workshop 8 at the International Conference on Interstitial Cystitis (Kyoto March 2003, future research needs for the definition/diagnosis of interstitial cystitis (IC) were discussed by the participants. To structure discussions a study proposal was used. This workshop decided that research should focus on identifying and validating classification criteria for the diagnosis of IC. This might well be done in a (multi-centre) study with a control group of urge-frequency patients without pain (OAB?). However, before doing so standards should be defined as on how to perform and interpret vaginal examination, urodynamic investigation, cystoscopy under anesthesia, potassium sensitivity test, and histopathology in these patients.

Biomedical Research↗
PubMed2003

Effects of castration on nitric oxide-mediated relaxations in male rat corpus cavernosum smooth muscle.

BACKGROUND: The effects of castration on nitric oxide- mediated relaxations and nitric oxide synthase activity in male rat corpus cavernosum smooth muscles. METHODS: Eight-week-old male rats were assigned to two groups: control (sham operated) and castrated animals. After 8 weeks, corpus cavernosum smooth muscle strips were mounted in an organ bath for isometric tension recordings. Electrical field stimulation (EFS) was applied to the strips precontracted with 30 microM phenylephrine. The microdialysis probe was inserted into the strip, and Krebs-Henseleit solution was perfused into the probe. The dialysate during EFS and cholinergic stimulation was collected, and the amount of NO(-)(2)/NO(-)(3) (NOx) released in the dialysate was measured by the Greiss method. Sodium nitroprusside and carbachol were cumulatively added to the strips precontracted with 30 microM phenylephrine. RESULTS: EFS caused frequency-dependent relaxations and NOx releases in the strips. Pretreatment with N(omega)-nitro-L-arginine (100 microM) and tetrodotoxin (1 microM) completely inhibited relaxations and NOx releases. The maximum relaxation in the castration group was significantly greater than that in the control group. The release of NOx was significantly greater in the castration group than in the control group. Sodium nitroprusside relaxed the tissues in both groups similarly. Carbachol failed either to relax the tissue or to increase the amount of NOx production in the tissue. CONCLUSION: The present data suggest that castration enhances nitric oxide synthase activity and nitric oxide-mediated relaxations in the male rat corpus cavernosum.

Animals↗
PubMed2003

Pharmacological effects of KRP-197 on the human isolated urinary bladder.

KRP-197, 4-(2-methylimidazol-l-yl)-2,2-diphenylbutyramide, is a newly synthesized antimuscarinic drug, developed for the treatment for overactive bladder. For evaluation of pharmacological characteristics of KRP-197, we investigated whether it influenced both prejunctional and postjunctional muscarinic receptors on the isolated human detrusor smooth muscles as compared with the effects of atropine, oxybutynin, and propiverine. Using the muscle bath technique, we investigated the effects of various antimuscarinic drugs on the contractions induced by carbachol, KCl, CaCl(2), and electrical field stimulation. Furthermore, using high-performance liquid chromatography with a microdialysis technique, we measured the acetylcholine release from the muscle strips during electrical field stimulation. The effects of various antimuscarinic drugs on acetylcholine releases were also evaluated. Pretreatment with various antimuscarinic drugs caused parallel shifts to the right in carbachol-induced concentration-response curves. The rank order of pA(2) values was KRP-197 > or = atropine > oxybutynin > propiverine. Atropine and KRP-197 did not cause significant inhibition of KCl- and CaCl(2)-induced contractions. All drugs caused concentration-dependent inhibitions in electrical field stimulation-induced contractions. Pretreatment with atropine and propiverine did not cause significant changes in electrical field stimulation-induced acetylcholine release. However, KRP-197, and oxybutynin caused significant decreases in acetylcholine release. The present study demonstrates that KRP-197 has an inhibitory effect on postjunctional muscarinic receptors as well as on prejunctional muscarinic receptors to modulate acetylcholine release in human detrusor smooth muscles. The findings suggest the usefulness of KRP-197 as a therapeutic drug for an overactive bladder with symptoms of frequency, urgency, and urge incontinence.

Aged↗
PubMed2003

Pharmacological effects of darifenacin on human isolated urinary bladder.

Darifenacin [(S)-2--2,2-diphenylacetamide] is a novel antimuscarinic drug currently undergoing phase III trials for the treatment of overactive bladder. We investigated the functional antagonist potency of darifenacin, and the antimuscarinic drugs propiverine, oxybutynin and atropine, on human detrusor smooth muscle. Urinary bladder specimens were obtained from 20 patients who underwent total cystectomy for malignant bladder tumor. Using an organ-bath technique, the effects of the compounds on carbachol-, KCl-, CaCl(2)- or electrical field stimulation (EFS)-induced contractions of the tissues were evaluated. The order of antagonist potency (pA(2 )values) at the muscarinic M(3) receptors was: darifenacin (9.34) > atropine (9.26) > oxybutynin (7.74) > propiverine (7.68). Darifenacin and atropine, at concentrations up to 10(-6) mol/l, did not inhibit the KCl- and CaCl(2)-induced contractions (concentrations 80 and 5 mmol/l, respectively), while propiverine and oxybutynin (10(-5) mol/l) significantly inhibited these contractions. Pretreatment with darifenacin (10(-9)-10(-6) mol/l), propiverine (10(-8)- 10(-5) mol/l), oxybutynin (10(-8)-10(-5) mol/l) and atropine (10(-9)-10(-6) mol/l) significantly inhibited maximum EFS-induced contractions. Darifenacin inhibited contractions of human detrusor smooth muscle only through its antimuscarinic action, while propiverine and oxybutynin had both antimuscarinic and Ca(2+) channel antagonist actions. These findings indicate that darifenacin is a potent antagonist at the M(3) receptor and support its use as a treatment for overactive bladder.

Aged↗
PubMed2003

Effects of diabetes on nitric oxide-mediated relaxations in male rat corpus cavernosum smooth muscle.

INTRODUCTION: We evaluated the effects of diabetes on nitric oxide-mediated relaxations and nitric oxide synthase activity in male rat corpus cavernosum smooth muscles. METHODS: Eight-week-old male rats were assigned to three groups: control (injected with the vehicle), DM (diabetes mellitus, induced by injection with 65 mg/kg streptozotocin), and TES (testosterone, testosterone supplemented after induction of diabetes). After 8 weeks, corpus cavernosum smooth muscle strips were mounted in an organ bath for isometric tension recordings. Electrical field stimulation (EFS, 2-ms pulse duration, 0.3-20 Hz and 3 s train) was applied to the strips precontracted with 30 microM phenylephrine. The microdialysis probe was inserted into the strip, and Krebs-Henseleit solution was perfused into the probe. The dialysate during EFS was collected, and the amount of NO(-)(2)/NO(-)(3) (NOx) released in the dialysate was measured by the Greiss method. Sodium nitroprusside (0.1 nM to 10 mM) and carbachol (1 nM to 10 mM) were cumulatively added to the strips precontracted with 30 microM phenylephrine. RESULTS: EFS caused frequency-dependent relaxations and NOx releases of the strips. Pretreatment with N(omega)-nitro-L-arginine (100 microM) and tetrodotoxin (1 microM) completely inhibited the relaxations and NOx releases. The maximum relaxation was significantly greater in the DM group than in the control or TES group. The release of NOx was significantly greater in the DM group than in the control or TES group. Sodium nitroprusside, the endothelium-independent vasodilator, relaxed the tissues in all three groups. There were no significant differences among control, DM and TES groups in the maximum relaxation to sodium nitroprusside. CONCLUSION: The present data suggest that diabetes enhances nitric oxide synthase activity and nitric oxide-mediated relaxations in the male rat corpus cavernosum by the reduced testosterone level in the diabetic animals.

Animals↗
PubMed2003

[Pharmacological analysis of neurotransmitters contributing to lower urinary tract function].

Lower urinary tract function is controlled by the autonomic nervous system, which consists of adrenergic, cholinergic, and non-adrenergic, non-cholinergic (NANC) neurons. We have measured the amount of various neurotransmitters (acetylcholine, ACh; noradrenaline, NA; adenosine triphosphate, ATP; and nitric oxide, NO) released from human and rabbit urinary tract smooth muscles by the microdialysis method coupled with HPLC. Muscle strips are isolated from human or rabbit bladder, urethra, and prostate. A microdialysis probe was inserted into each smooth muscle strip. Each muscle strip was connected to an isometric transducer, and tension development was measured. We have evaluated the changes in electrical field stimulation-induced neurotransmitter releases and functional responses in physiological and pathological conditions and the interactions between neurotransmitters or neurons. In this review, we present several of our results: 1) interactions between adrenergic and nitrergic neurons in rabbit urethra, 2) effect of NO on human bladder function, 3) effect of NO on human prostate function, and 4) effects of aging on acetylcholine and ATP releases from human bladder smooth muscles. These data may reveal physiological or pathological neurotransmitter control of lower urinary tract function and give us useful information for clinical intervention to treat lower urinary tract symptoms.

Animals↗