Biomedical subjects
Publications and source records attributed to N Katakura.
Photochemical artificial nitrogen cycle was reported to produce dinitrogen and dihydrogen by photodecomposing ammonia with platinized TiO2, and its application to a photofuel cell with a nanoporous TiO2 film electrode, a new concept of a fuel cell to photochemically produce electricity and H2 from ammonia, was proposed.
This paper presents some research results pertaining to the application of solidified coal ash (SCA) for improving the stability of soft ground. The results pertain to the physical properties of SCA required for use as an alternative to sand in sand compaction piles (SCPs), and the assessment of possible environmental impacts resulting from construction of SCA piles in marine environments. The results of field tests indicate that the physical properties of SCA (permeability, internal friction angle, and grain-size distribution) are favorable for use in soil improvement applications. Also, the results show that SCA is sufficiently suitable as an alternative to sand in SCPs, although SCA piles cannot be compacted to the same extent as sand piles. Finally, test results showed no adverse environmental impacts on natural benthos resulting from placement of SCA piles in marine environments. Thus, the results of this study confirm that SCA is a viable alternative material to sand in SCPs that are used for ground improvement in marine environments, and that large quantities of SCA may be required for such applications resulting in an alternative use for an otherwise waste material.
The central pattern generator (CPG) for masticatory movements has been located in the medial bulbar reticular formation, by using cortically induced rhythmical jaw and tongue movements as a model. To analyze how stationary input from the cortex is transformed into rhythmical output in the neuronal population comprising the CPG, rhythmical neural activities representing rhythmical food ingestive movements were experimentally induced in vitro. Bath-application of N-methyl-D-aspartate (NMDA) induced rhythmical activities in the trigeminal (V), facial (VII) and hypoglossal (XII) nerves of in vitro brainstem-spinal cord preparations isolated from newborn rats and mice. This paper will review evidence for the notion that (1) the rhythmical XII nerve activity represents rhythmical sucking movements; (2) the population of neurons critically involved in the rhythm generation of the XII nerve is localized in the ventromedial medulla oblongata on both sides, and can induce rhythmical XII nerve activity on the same side independently of each other; (3) the rhythmical activities in the V, VII, and XII motoneurons are induced by separate CPGs, which are located segmentally at the respective level of the V motor, VII, and XII nuclei. In addition, rhythmical masticatory-like EMG activity of jaw muscles can be induced by repetitive stimulation of the pyramidal tract in the in vitro brainstem isolated from adult mice together with the oral-facial structures. We propose that the in vitro brainstem preparation is a useful tool for longitudinal analysis of postnatal development of the central pattern generation of food ingestive movements, including conversion from sucking to mastication.
Multiple epsilon subunits are major determinants of the NMDA receptor channel diversity. Based on their functional properties in vitro and distributions, we have proposed that the epsilon 1 and epsilon 2 subunits play a role in synaptic plasticity. To investigate the physiological significance of the NMDA receptor channel diversity, we generated mutant mice defective in the epsilon 2 subunit. These mice showed no suckling response and died shortly after birth but could survive by hand feeding. The mutation hindered the formation of the whisker-related neuronal barrelette structure and the clustering of primary sensory afferent terminals in the brainstem trigeminal nucleus. In the hippocampus of the mutant mice, synaptic NMDA responses and longterm depression were abolished. These results suggest that the epsilon 2 subunit plays an essential role in both neuronal pattern formation and synaptic plasticity.
We tried to induce rhythmical oro-facial motor activities in an isolated brain stem-spinal cord preparation from newborn rats. Neural activities were monitored from the hypoglossal nerve (XII N) and the ventral roots of the cervical cord. Bath application of N-methyl-D-aspartate (NMDA) as well as glutamate induced rhythmical burst activity in XII N distinct from and much faster than respiratory rhythm. This NMDA-induced rhythmical activity was blocked by simultaneous application of 2-amino-5-phosphonovalerate (AP5). The results demonstrate that NMDA receptor activation can induce rhythmical XII N activity different from respiration in an isolated mammalian CNS. This preparation will be useful for the investigation of neural mechanisms underlying the central generation of food ingestive movements.
Mastication is a typical rhythmical behavior in mammals. Like respiration, it is now generally accepted that the motor command for the basic pattern of rhythmical oral-facial movements is generated by a neuronal population in the brainstem (central pattern generator, CPG). The central pattern generation of rhythmical masticatory movements can be divided into three processes: (1) generation of the masticatory rhythm, (2) generation of a pattern of activities of the jaw, tongue and facial muscles, and (3) coordination of the activities of these muscles. There are several lines of evidence that the masticatory CPG is functionally subdivided into two neuronal groups: one for generation of the masticatory rhythm, giving the timing signal for rhythmical alternation of jaw closing and jaw opening (central rhythm generator, CRG), and the other for generation of the spatiotemporal pattern of activities of the jaw, tongue and facial muscles. This review will deal, first of all, with the localization of the CRG for rhythmical masticatory jaw movements, sources for its activation, and the premotor neurons mediating its output to the trigeminal motoneurons. Next, we will discuss the neurochemical basis for rhythmical trigeminal motoneurons activity as well as central masticatory rhythm generation. Finally, our recent attempt at induction of neural activities reflecting sucking movements (fictive sucking) in an in vitro preparation is presented.
This study illustrates morphologic changes of the pharyngeal airway after mandibular setback osteotomy. Twenty-six patients with prognathism were evaluated preoperatively and postoperatively with standard lateral cephalograms to assess craniofacial morphology--in particular, airway size. Subjects were classified into two groups: those with mandibular prognathism and those with mandibular prognathism accompanied by maxillary hypoplasia caused by cleft palate. In the postoperative period, the width of the pharyngeal airway significantly diminished in both groups; the airway widths of those with maxillary hypoplasia were narrower than those without maxillary hypoplasia. These results indicate that mandibular setback osteotomy induces the narrowing of the pharyngeal airway, and the narrowing effect of this surgery was more pronounced in prognathic patients accompanied by maxillary hypoplasia caused by cleft palate.
This study was undertaken to simplify the preparation procedures for test specimens by applying whole blood collected on filter paper disks. The results of ELISA obtained using specimens collected in this way for the detection of Sendai virus and mouse hepatitis virus antibodies in mice were comparable to those for ordinary ELISA using serum samples.
This study investigated the effects of iontophoretic application of excitatory amino acid (EAA) and norepinephrine (NE) agonists and antagonists on synaptic transmission to individual jaw-opener motoneurons (digastric) during activation of the jaw-opening reflex (JOR) evoked by stimulation of either fibers within the oral mucosa (OM), or tooth-pulp (TP). During both OM and TP stimulation, kynurenic acid (KYN), a wide-spectrum EAA antagonist, suppressed jaw-opener motoneuron discharge. Application of APV, an NMDA receptor antagonist, also suppressed motoneuron discharge evoked by TP stimulation, but produced minimal effects on motoneuron discharge evoked by OM stimulation. These data suggest a role of EAA in mediating synaptic transmission from last-order interneurons to jaw-opener motoneurons during the jaw-opening reflex evoked by intra-oral stimulation. Iontophoretic application of NE produced dual effects (facilitation or suppression) on motoneuronal discharge evoked by OM or TP stimulation. The effects were not related to the mode of motoneuronal activation. Iontophoretic application of the alpha 1 agonist, phenylephrine, facilitated motoneuronal discharge. In contrast, application of the alpha 2 agonist, clonidine, suppressed motoneuronal discharge during intra-oral stimulation. These effects were antagonized by prior iontophoretic application of the alpha 1 antagonist, prazosin, or the alpha 2 antagonist, yohimbine, respectively. In those cells in which the predominant effect of NE application on synaptic transmission was either facilitation or suppression of motoneuronal discharge, prior iontophoretic application of prazosin or yohimbine, respectively, antagonized the effects of NE application. These data suggest that NE can modulate synaptic transmission to jaw-opener motoneurons evoked by intra-oral stimulation via activation of alpha 1 or alpha 2 adrenoreceptors on trigeminal motoneurons.
1. The effects of iontophoretic application of the excitatory amino acid antagonists kynurenic acid (KYN) and DL-2-amino-5-phosphonovaleric acid (APV), as well as the monoamines serotonin (5-HT) and norepinephrine (NE), on extracellularly recorded jaw opener motoneuron [digastric motoneuron (DIG)] discharge during cortically induced rhythmical masticatory-like activity (RMA) were examined in the anesthetized guinea pig. 2. Iontophoretic application of KYN, a broad-spectrum amino acid antagonist, suppressed the motoneuronal discharge evoked by short pulse train stimulation of the cortex for most cells tested. In contrast, iontophoretic application of APV, a specific N-methyl-D-aspartate (NMDA) antagonist, was usually without effect on the motoneuronal discharge evoked by short pulse train stimulation. 3. During RMA evoked by repetitive cortical stimulation, both KYN and APV suppressed rhythmical DIG motoneuronal discharge in many cells tested. 4. These data suggest that excitatory amino acid receptors on jaw opener motoneurons are involved in activation of RMA. It is proposed that the short-latency rapid excitation of jaw opener motoneurons, which occurs during both short pulse train cortical stimulation and RMA induced by repetitive cortical stimulation, is mediated, at least in part, by non-NMDA receptors. It is further suggested that the large-amplitude, long-duration slow rhythmical oscillations, which occur in the membrane potential of jaw opener motoneurons during RMA induced by repetitive cortical stimulation, are mediated, at least in part, by NMDA receptors. 5. Iontophoretic application of NE or 5-HT with low currents (less than 20 nA) produced a facilitation of digastric motoneuronal discharge during cycle-triggered glutamate application, short pulse train cortical stimulation, and RMA evoked by repetitive cortical stimulation. These facilitatory effects on motoneuronal discharge started within 1 min of drug application, reached a peak at approximately 3 min that persisted for several minutes after the application period, and recovered to control levels within 10-15 min. Direct application of NE or 5-HT, in the absence of chemical or synaptic activation, failed to activate these motoneurons. However, iontophoretic application of either monoamine could facilitate and bring to threshold rhythmical motoneuronal discharges during subthreshold repetitive cortical stimulation. 6. Iontophoretic application of methysergide, a 5-HT antagonist, and phentolamine, an alpha adrenoreceptor blocker, both produced a selective and reversible blockade of the facilitatory effects of 5-HT and NE, respectively, on motoneuronal discharge during cortically induced RMA. In contrast, iontophoretic application of sotalol, a beta adrenoreceptor blocker, had no effect on the NE-induced facilitation of RMA.(ABSTRACT TRUNCATED AT 400 WORDS)
The effect of quartz filler content on viscosity, dynamic viscoelasticity and tensile stress of polyaddition-type silicone impression materials were investigated. A hydrogen polydimethylsiloxane (H-silicone) and two vinyl polydimethylsiloxane (V-silicone) silicone prepolymers were prepared. Quartz fillers were mixed to them at contents between 0 and 50% by weight. The viscosity of these rubber compounds and mechanical properties of set materials were measured by a cone and plate viscometer, the dynamic shear test and the tension test, respectively. Viscosity eta storage modulus G' and tensile stress sigma increased with the amount of filler increase. G' and sigma were decreased by use of a V-silicone prepolymer which had a high average molecular weight and the material was more flexible. This suggests that the characteristics of the silicone prepolymer greatly affect the mechanical properties of the impression materials. Therefore, the appropriate molecular design for silicone prepolymer and reasonable filler content should be considered to make impression materials that have suitable properties for clinical use.
The viscoelastic properties of new experimental tissue conditioners which consist of synthesized poly (butyl methacrylate) PBMA and a liquid of aromatic-ester plasticizer, without alcohol, were investigated to evaluate the effects of the molecular weight of polymer. The master curves of storage modulus G', dynamic viscosity eta' and loss tangent tan delta were constructed from the viscoelastic data at different temperatures. The effects of the molecular weight of polymer on the viscoelastic properties G' and tan delta were observed particularly, in a low frequency range. However, the dynamic viscosity eta' was not very sensitive to the molecular weight. These results suggest that PBMA produces more desirable properties for tissue conditioners, and that it is possible to manufacture new materials without alcohol.
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In the first series of experiments, we studied whether or not strychnine (STR)-resistant inhibition of masseter motoneurons (MASS . MNS) was involved in their rhythmical inhibition that occurs during masticatory activity, induced by repetitive stimulation of the cortical masticatory area (CMA) in the cat. After systemic STR injection, repetitive CMA stimulation induced rhythmically alternating activity in the masseteric and anterior digastric nerves with a shorter cycle time than before STR-administration. The short-latency IPSPS in the MASS . MNS evoked by single shocks applied to the CMA were abolished. In contrast, repetitive CMA stimulation still induced a rhythmical alternation of EPSPS and IPSPS in the MASS . MNS, although the IPSPS were significantly reduced in amplitude. In the second series, we attempted to abolish the STR-resistant component of the rhythmical IPSP with tetanus toxin (TT). This was injected into one superficial masseter muscle of the guinea pig. In the majority of animals, repetitive CMA stimulation induced a tonic EMG superimposed by rhythmical bursts in the TT-intoxicated masseter muscle. Repetitive CMA stimulation induced a rhythmical sequence of EPSPS and superimposed spikes in the MASS . MNS innervating the TT-intoxicated masseter muscle in paralyzed guinea pigs. It was concluded that: (1) the cortically-evoked short-latency inhibition of MASS . MNS is STR-sensitive, as is part of the rhythmical inhibition during CMA-induced mastication; and (2) rhythmical inhibition is not essential for the central generation of the rhythmical activity in the MASS . MNS.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.