Biomedical subjects

Y Ishiwata

Publications and source records attributed to Y Ishiwata.

At least 19 recordsLinked to original sources

PubMed2004

Possible role of VEGF in the progression of kidney disease in streptozotocin (STZ)-induced diabetic rats: effects of an ACE inhibitor and an angiotensin II receptor antagonist.

Two endothelium-derived factors, endothelin (ET), a vasoconstrictor, and vascular endothelial growth factor (VEGF), an angiogenic factor are thought to be involved in the pathogenesis of diabetic vascular complications. The aim of this study was to determine the effects of an angiotensin II type I (AT-1) receptor antagonist and an ACE inhibitor on the pathogenesis of VEGF and ET-1-mediated kidney disease in STZ-induced diabetic rats. Two days after STZ administration, diabetic rats were treated for 8 weeks with enalapril maleate, an ACE inhibitor, candesartan cilexetil, an AT-1 receptor antagonist, or saline. Urinary albumin and N-acetyl beta-D glucosaminidase (NAG) excretion as well as the VEGF protein content in the kidney were all found to be elevated in diabetic rats. Administration of enalapril maleate or candesartan cilexetil decreased the level of microalbuminuria and NAG excretion in diabetic rats. Administration of enalapril maleate also suppressed the elevated renal VEGF protein content in these animals while candesartan cilexetil treatment had no effect. Serum ET-1 and VEGF levels were unchanged by these treatments. These data support a role for AT-1 receptor antagonists and ACE inhibitors in the prevention of diabetic nephropathy, and suggest that the former may work by reducing renal VEGF levels.

Albuminuria↗

PubMed2003

First night effect of an interocclusal appliance on nocturnal masticatory muscle activity.

The purpose of this study was to examine the effect of an interocclusal appliance on nocturnal masticatory muscle activities. Six healthy Japanese males (mean age: 26.8 years) participated in this study. Electromyographic (EMG) activities of the right anterior temporalis and masseter muscles were recorded using a portable EMG recording unit at night both with and without an interocclusal appliance. In both muscles, the maximal EMG activity and the number of bruxing events decreased significantly by wearing the appliance. Moreover, the duration of a higher level of muscle activity was decreased while that of a lower level of muscle activity increased by wearing the appliance in both muscles. These findings suggest that nocturnal masticatory muscle activity is significantly reduced by wearing an interocclusal appliance, and that the use of such an appliance at night could help to relax masticatory muscles.

Adult↗

PubMed2003

Hemispheric dominance of tongue control depends on the chewing-side preference.

Blood-oxygenation-level-dependent (BOLD)-functional magnetic resonance imaging (fMRI) is known to be a non-invasive technique for studying human brain function. The purpose of this study was to apply BOLD-fMRI to identify brain areas responsible for producing tongue movements and their relation to chewing-side preference in 15 normal right-handed volunteers. A marked increase in BOLD signals was detected in primary sensorimotor cortices upon protrusion and in rightward and leftward tongue movements compared with at rest. In 10 subjects with an evident chewing-side preference, the BOLD signal change in the primary sensorimotor cortex was significantly greater on the side contralateral to the preferred chewing side. The results suggest that there is a relationship between hemispheric dominance and chewing-side preference in primary sensorimotor cortices responsible for tongue movements.

Adult↗

PubMed2002

Observation of fluorapatite formation under hydrolysis of tetracalcium phosphate in the presence of KF by means of soft X-ray emission and absorption spectroscopy.

The effect of fluoride on the hydrolysis of tetracalcium phosphate (TTCP; Ca4(PO4)2O) in 0.1 mol/l KH2PO4 containing 62-83 mmol/l KF was studied with the help of X-ray fluorescence measurements. Fluorine X-ray emission and absorption spectra of the final product of hydrolysis and reference samples (CaF2 and Ca5(PO4)3F) were measured at Beamline BL-2C of Photon Factory (PF, Tsukuba). Based on these measurements we concluded that hydrolysis of TTCP in the presence of KF converts it into fluorapatite. Formation of CaF2, which is often found in the hydrolysis of hydroxyapatite at high fluoride concentration, was not observed.

Journal Article↗

PubMed2002

Breathing modes, body positions, and suprahyoid muscle activity.

AIM: To determine (1) how electromyographic activities of the genioglossus and geniohyoid muscles can be differentiated, and (2) whether changes in breathing modes and body positions have effects on the genioglossus and geniohyoid muscle activities. METHOD: Ten normal subjects participated in the study. Electromyographic activities of both the genioglossus and geniohyoid muscles were recorded during nasal and oral breathing, while the subject was in the upright and supine positions. The electromyographic activities of the genioglossus and geniohyoid muscles were compared during jaw opening, swallowing, mandibular advancement, and tongue protrusion. RESULTS: The geniohyoid muscle showed greater electromyographic activity than the genioglossus muscle during maximal jaw opening. In addition, the geniohyoid muscle showed a shorter (P < 0.05) latency compared with the genioglossus muscle. Moreover, the genioglossus muscle activity showed a significant difference among different breathing modes and body positions, while there were no significant differences in the geniohyoid muscle activity. CONCLUSION: Electromyographic activities from the genioglossus and geniohyoid muscles are successfully differentiated. In addition, it appears that changes in the breathing mode and body position significantly affect the genioglossus muscle activity, but do not affect the geniohyoid muscle activity.

Adult↗

PubMed2001

Effects of a titratable oral appliance on supine airway size in awake non-apneic individuals.

STUDY OBJECTIVES: To define morphological changes in the upper airway and its surrounding structures after the insertion of a titratable mandibular repositioner. DESIGN: Ten non-apneic adult males participated in this study. A set of supine lateral cephalograms was taken for each subject at the end of expiration with a titratable oral appliance in place in four mandibular positions: most retruded (RP), maximum protrusion (MAX), 33% of MAX (MAX33), and 67% of MAX (MAX67). Changes in the anteroposterior width of the upper airway, positions of the hyoid bone and the third cervical vertebra were compared between the four mandibular positions. An ANOVA was used to test for statistical significance. SETTING: N/A. PATIENTS OR PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The anteroposterior width of the velopharynx significantly increased when the mandible was advanced from RP to MAX67 and MAX. However, there were no significant changes in the anteroposterior width of the oropharynx. Significant forward displacement of the hyoid bone and third cervical vertebra together with the mandible was found in MAX67 and MAX compared to RP. CONCLUSION: Especially in MAX67 and MAX, the titratable oral appliance significantly enlarges upper airway size in the velopharynx and results in a forward displacement of the hyoid bone and the third cervical vertebra.

Adult↗

PubMed2001

Modulation of the stretch reflex of jaw-closing muscles in different modes and phases of respiration.

The objective of this study was to investigate whether and how changes in the mode of respiration affect the electromyographic activity of human jaw-closing muscles. Fifteen men were examined in this study. A pair of surface electrodes was attached bilaterally to the masseter and anterior and posterior temporalis muscles for electromyographic recording. Respiratory movements of the chest wall and nasal airflow were recorded simultaneously. Recordings were performed with subjects in the sitting position during quiet nasal and oral respiration. The stretch reflex of jaw-closing muscles was elicited by randomly tapping the chin with an impulse hammer. In 11 subjects, we measured nasal resistance with a rhinomanometer. The amplitude of electromyographic activities of the masseter and anterior temporalis muscles during oral respiration was significantly less than that during nasal respiration, whereas that of the posterior temporalis muscle showed no significant difference between the different modes of respiration. Furthermore, the reduction in the amplitude of the electromyographic activity was more evident in the inspiratory phase during oral respiration. There was a significant positive correlation between the ratio of the reflex amplitude during inspiration in the 2 respiratory modes and nasal resistance for the masseter muscle, but not for the anterior temporalis muscle. These results suggest that the reflexive electromyographic activity of some human jaw-closing muscles is modulated during oral respiration.

Adult↗

PubMed2001

Changes in mandibular position and upper airway dimension by wearing cervical headgear during sleep.

We previously reported that the wearing of cervical headgear induced forward displacement of the mandible in awake subjects. However, it was unclear whether such mandibular displacement also occurred during sleep. The purpose of this study was to examine changes in mandibular position and oropharyngeal structures that were induced by the wearing of cervical headgear during sleep. Ten healthy adults (7 male and 3 female) who gave their informed consent were included in this study. A pair of lateral cephalograms was taken with the patient in the supine position with and without cervical headgear at end-expiration during stage 1 to 2 non-rapid-eye-movement sleep. The Wilcoxon signed-rank test was used for a statistical analysis. The amount of jaw opening was significantly decreased by the wearing of the cervical headgear (P <.05), although no significant anteroposterior mandibular displacement was induced. The sagittal dimension of the upper airway was significantly reduced (P <.05); however, no significant changes were observed in the vertical length of the upper airway. Although the hyoid bone and the third cervical vertebra moved significantly forward by the wearing of the cervical headgear (P <.05), the relationship among the mandibular symphysis, the hyoid bone, and the third cervical vertebra did not change. These results suggest that cervical headgear significantly reduced the sagittal dimension of the upper airway during sleep, although there was no significant anteroposterior displacement of the mandible.

Adult↗

PubMed2001

An anti-inflammatory drug, propagermanium, may target GPI-anchored proteins associated with an MCP-1 receptor, CCR2.

Monocyte chemoattractant protein-1 (MCP-1) promotes the migration and activation of monocytes and plays a pivotal role in the development of chronic inflammation. Propagermanium (3-oxygermylpropionic acid polymer) has been used as a therapeutic agent against chronic hepatitis B in Japan. We report here that propagermanium specifically inhibits in vitro chemotactic migration of monocytes by MCP-1. Propagermanium did not inhibit binding of MCP-1 to a human monocytic cell line, THP-1 cells, or affect intracellular Ca(2+) mobilization or the cAMP concentration in MCP-1-treated THP-1 cells. The effect of propagermanium seems to require glycosylphosphatidylinositol (GPI)-anchored proteins, as cleavage of GPI anchors by phosphatidylinositol-phospholipase C (PI-PLC) eliminated the inhibitory activity of propagermanium. Anti-GPI-anchored protein antibodies, such as anti-CD55 and anti-CD59, reduced staining of C-C chemokine receptor 2 (CCR2) with an anti-CCR2 antibody against the N-terminus of CCR2 in a flow cytometric analysis, and these antibodies also selectively inhibited MCP-1-induced migration of THP-1 cells. Furthermore, under fluorescence microscopy, GPI-anchored proteins colocalized with CCR2 on THP-1 cells. These results suggest that propagermanium may target GPI-anchored proteins that are closely associated with CCR2 to selectively inhibit the MCP-1-induced chemotaxis, thus providing a mechanistic basis for the anti-inflammatory effects of the drug.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

Synthesis and anti-influenza virus activity of tricyclic compounds with a unique amine moiety.

Several novel tricyclic compounds with a unique amine moiety (1, 2a--i) were designed and prepared based on the structure of triperiden for the development of anti-influenza virus agents. An in vitro antiviral assay showed that 1-(1-azabicyclo[3.3.0]octan-5-yl)-1-(4-fluorophenyl)-1-(2-tricyclo[3.3.1.1(3.7)]decyl)methan-1-ol hydrochloride (2f) has a potent anti-influenza A virus activity. Furthermore, since 2f was well tolerated in mice, 2f is promising as a novel anti-influenza virus agent for humans.

Animals↗

PubMed2000

Supine cephalometric study on sleep-related changes in upper-airway structures in normal subjects.

The purpose of this study was to examine sleep-related changes in the upper airway and surrounding structures including the mandible, hyoid bone, and cervical vertebra in normal subjects using lateral cephalograms in the supine position. Eleven male and nine female healthy adults participated in this study. Supine cephalograms were taken at end-expiration during wakefulness and in stage 1-2 non-rapid-eye-movement (NREM) sleep judged from the electroencephalogram and respiratory monitoring. A paired t-test was used to compare differences between the values measured during wakefulness and sleep. A significant increase in the amount of jaw opening was observed during sleep. The anteroposterior width of the upper airway was significantly decreased during sleep. The distances between the hyoid bone and the mandibular symphysis and between the cervical vertebra and the hyoid bone were significantly decreased during sleep. Consequently, the distance between the cervical vertebra and the mandibular symphysis was significantly decreased. These results suggest that the upper-airway dimension is significantly decreased and relatively small structural changes are induced during sleep in normal subjects.

Adult↗

PubMed2000

Functional divergence of human genioglossus motor units with respiratory-related activity.

The genioglossus muscle has at least two types of motor unit with respiratory-related activity. Inspiratory motor units show phasic activity during inspiration, whereas inspiratory/expiratory motor units show phasic inspiratory activity superimposed on tonic activity. The purpose of this study was to investigate the physiological roles of these different genioglossus motor units. The unitary activities of 12 inspiratory and 12 inspiratory/expiratory motor units were recorded using fine-wire electrodes during quiet nasal breathing in eight normal adult males. The mean interspike interval and the SD of successive spikes were calculated for inspiratory and inspiratory/expiratory motor units, respectively. Scattergrams of the mean interspike interval versus SD were constructed for the two groups of motor units. The effects of changes in head position on the firing activity and the patterns of distribution of the mean interspike interval versus its SD were significantly different for inspiratory and inspiratory/expiratory motor units. These results suggest that the inspiratory and inspiratory/expiratory motor units have different functional roles in respiration; inspiratory motor units may be phasically active to counteract intraluminal negative pressure during inspiration, whereas inspiratory/expiratory motor units may be tonically active to maintain tongue posture.

Action Potentials↗

PubMed2000

Respiratory-related genioglossus electromyographic activity in response to head rotation and changes in body position.

The purpose of this study was to assess the effect of changes in body and head positions on respiratory-related activity of the genioglossus muscle in normal subjects in 8 body and head positions: (1) upright body with head straight, (2) upright body with head rotated to the right, (3) upright body with head rotated to the left, (4) supine body with head straight, (5) supine body with head rotated to the right, (6) supine body with head rotated to the left, (7) lateral recumbent body to the right, and (8) lateral recumbent body to the left. Phasic activity of the genioglossus muscle decreased significantly when subjects rotated their heads and moved from the supine to the lateral recumbent position. It is therefore concluded that genioglossus muscle activity is modulated in response to head rotation and changes in body position.

Adult↗

PubMed2000

Neuromuscular and skeletal adaptations following mandibular forward positioning induced by the Herbst appliance.

The purpose of this study was to examine neuromuscular and skeletal adaptations to changes in sagittal jaw relationships induced by the Herbst appliance. Six patients (age, 9 years and 5 months to 11 years and 2 months) with Angle Class II, division 1 malocclusions were studied longitudinally. The structural changes were determined by analyzing serial lateral cephalograms. Electromyographic recordings of specific masticatory muscles were used to evaluate neuromuscular adaptations. Similar cephalometric changes were observed in all patients. In all patients, lateral pterygoid muscle activity increased immediately after insertion of the appliance, but the activity decreased markedly after 4 to 6 months of treatment. In 4 of the 6 patients studied, however, the condyles were located in a slightly more downward and forward position. These findings indicate that the adaptation of muscular function occurs within a relatively short period and precedes the compensatory morphological changes produced through functional appliance therapy.

Adaptation, Physiological↗

PubMed2000

Genioglossus muscle activity during rhythmic open-close jaw movements.

The purpose of this study was to examine genioglossus muscle activity during rhythmic open-close jaw movements. The electromyographic activity of the genioglossus muscle was recorded with a bipolar fine-wire electrode in six healthy males. The electromyographic activities of the ipsilateral masseter and digastric muscles were simultaneously recorded with bipolar surface electrodes. The subjects were instructed to perform rhythmic open-close jaw movements in time with a metronome set at 23, 27, 33, 42 and 50 beats/min. In all of the subjects, rhythmic electromyographic activity of the genioglossus muscle was recorded in both the jaw-opening and jaw-closing phases. The activity of the genioglossus muscle was predominantly recorded in the jaw-opening phase in two subjects, and in the jaw-closing phase in two subjects. The burst duration of the electromyographic activity of the genioglossus muscle changed linearly in accordance with the cycle duration. However, the latency from the onset of the electromyographic activity of the masseter or digastric muscle to that of the genioglossus muscle was almost constant, independent of the cycle duration. Based on these findings, we conclude that the activity of the human genioglossus muscle is closely linked to that of masticatory muscles under the control of a closely related central pattern generator.

Adult↗

PubMed2000

Effect of wearing cervical headgear on tongue pressure.

The purpose of this study was to examine whether wearing cervical headgear affected tongue pressure on the lingual surface of mandibular incisors, with particular attention to suprahyoid muscle activity. Tongue pressure was recorded using a miniature pressure sensor without cervical headgear and with two cervical headgears with traction forces of 500 and 1200 g, respectively. Electromyographic activity of suprahyoid muscles and respiratory-related movement were recorded simultaneously. Wearing cervical headgear significantly affected tongue pressure and suprahyoid muscle activity in the short-term. A significant increase in tongue pressure was observed in association with an increase in traction force from 500 to 1200 g, whereas no significant difference in suprahyoid muscles activity was seen between these force levels. These results suggest that wearing cervical headgear increases tongue pressure on the lingual surface of mandibular incisors, and this increase in tongue pressure may result from changes in the electromyographic activity of suprahyoid muscles to maintain adequate pharyngeal patency.

Adaptation, Physiological↗

PubMed2000

Jaw-tongue reflex: afferents, central pathways, and synaptic potentials in hypoglossal motoneurons in the cat.

The tongue position is reflexively controlled by the jaw position (the jaw-tongue reflex). The purpose of this study was to clarify the mechanism of this reflex in terms of afferents, central pathways, and synaptic potentials in hypoglossal motoneurons in the cat. Intracellular recordings from hypoglossal motoneurons revealed that electrical stimulation of the temporalis muscle nerve evoked excitatory and inhibitory post-synaptic potentials in hypoglossal motoneurons. The threshold of temporalis muscle nerve stimulation for evoking the synaptic potentials was higher than 2.0 times the nerve threshold. The amplitude of the potentials increased with stimulus intensity up to 5.0 times the nerve threshold. Punctate light pressure applied to the temporalis muscle induced a tonic depolarizing potential in hypoglossal motoneurons on which action potentials as well as depolarizing synaptic activation noise were superimposed. On the other hand, electrical stimulation of the temporalis muscle during jaw-opening could slightly inhibit the electromyographic activities in the genioglossus and styloglossus muscles. Lesions including the Probst's tract at the level caudal to the trigeminal motor nucleus abolished both excitation and inhibition in hypoglossal motoneurons induced by tonic depression of the lower jaw, but exerted no effects on either the tonic stretch reflex or the trigemino-hypoglossal reflex. In contrast, lesions including the trigeminal spinal tract produced no changes in either excitation or inhibition of hypoglossal motoneurons induced by temporalis muscle afferents, whereas the excitation of hypoglossal motoneurons was abolished by the lesions. We conclude that the group II muscle spindle afferents from the temporalis muscle are primarily responsible for evoking the jaw-tongue reflex.

Afferent Pathways↗

PubMed1999

Proposed standard for human blood vitamin B1 value using HPLC. The Committee for Vitamin Laboratory Standards, Japan.

Standard reference ranges for all laboratory test values are mandatory. This study was designed to establish a reference range for blood vitamin B1 levels, since the normal range has not been determined in the Japanese population. We founded the Japan Committee for Vitamin Laboratory Standards, which was incorporated with the Vitamin Society of Japan and the Japanese Society of Nutrition and Food Science. We standardized whole blood vitamin B1 levels using three HPLC techniques (post-column reverse-phase HPLC, pre-column reverse-phase HPLC, and precolumn GP-HPLC). The reference range was obtained in 54 volunteers administered a 1,800 kcal diet with 2 mg of vitamin B1 (1.74 mg measured) daily to avoid marginal vitamin B1 deficiency in the population. The range for each assay was 26-47, 28-51, and 28-56 ng/ml, respectively. Our data suggest that 26-28 ng/ml is the lower limit of normal for whole blood vitamin B1, but further studies in a larger population are needed in order to obtain more definitive results.

Chromatography, High Pressure Liquid↗