Effect of tongue-palate contact mode on food transport during mastication.

The physiological mechanisms underlying Stage II transport (STII), during which comminuted solid food is transported from the oral cavity into the meso-pharynx for aggregation into a pre-swallow bolus, have yet to be clarified. The purpose of the present study was to investigate relationships between tongue-palate contact during mastication and incidence of STII by synchronised analysis of tongue pressure production on a hard palate and video-endoscopic (VE) images during mastication. Tongue pressure at 5 measuring points with an ultra-thin sensor sheet attached to the hard palate and trans-nasal VE images while masticating corned beef was recorded for 12 healthy subjects. All recordings were divided into 2 groups: mastication with STII and without STII. Tongue pressure duration was longer at the anterior-median part in the group with STII than in the group without STII. Integrated values of tongue pressure were greater at the anterior-median parts and posterior circumferential part in the group with STII. Integrated values of tongue pressure per second were greater in late-stage mastication than in early-stage mastication in the group with STII. These results suggest that the tongue-palate contacting at the anterior-median and post-circumferential parts of the hard palate is related with the incidence of STII.

Effects of water viscosity and tongue ingestion site on tongue pressure during food bolus propulsion.

The purpose of this study was to help provide data to help to implement effective rehabilitation following surgery for oral cancer by comparing tongue pressure production for water and thickened water from the anterior and posterior parts of the tongue during swallowing. Ten healthy volunteers (7 men, 3 women; age 27.6 ± 1.5 years) participated in the experiments. Tongue pressure during 3 mL water and 3 mL thickened water at the anterior and posterior tongue during swallowing was measured using a sensor sheet system with five measuring points on the hard palate. The sequential order of the points, maximal magnitude and duration of tongue pressure at each point were compared based on water viscosity and tongue ingestion site. There was a common pattern in the sequential order of tongue pressure generation among the two swallowing conditions. The maximal magnitude of tongue pressure was significantly higher when swallowing thickened water than when swallowing water at all points except for the anterior-median and mid-median part. Moreover, the pressure at all sites during posterior ingestions was significantly lower than that during anterior ingestion. The present results provide mean values of tongue pressure during voluntarily triggered swallowing in anterior ingestion and posterior ingestion in young, healthy dentate individuals; these values can be clinically referenced for tongue pressure measurement in the evaluation of patients with dysphagia. The use of reference values may help streamline the diagnosis, treatment and rehabilitation of dysphagia.

Relationships between dysphagia and tongue pressure during swallowing in Parkinson's disease patients.

Although dysphagia is a life-threatening problem in patients with Parkinson's disease (PD), the pathophysiology of oropharyngeal dysphagia is yet to be understood. This study investigated the tongue motor function during swallowing in relation to dysphagia and the severity of PD. Thirty patients with PD (14 males and 16 females; average age, 69.4 years), Hoehn and Yahr stage II-IV, in Osaka University Hospital are participated in this study. During swallowing 5 ml of water, tongue pressure on the hard palate was measured using a sensor sheet with 5 measuring points. The maximal tongue pressure at each measuring point during swallowing was compared between patients with PD and healthy controls. Subjective assessment of oropharyngeal dysphagia was performed using Swallowing Disturbance Questionnaire-Japanese. The maximal tongue pressure at each measuring point was significantly lower in patients with PD than in healthy controls (8 males and 12 females; average age, 71.6 years). Furthermore, the maximal tongue pressure was significantly lower in dysphagic PD patients than non-dysphagic PD patients. Loss of tongue pressure production at the anterior part of the hard palate was strongly related to dysphagia in the oral phase as well as in the pharyngeal phase. An abnormal pattern of tongue pressure production was more frequently observed in dysphagic PD patients than in non-dysphagic PD patients. The results suggest that tongue pressure measurement might be useful for early and quantitative detection of tongue motor disability during swallowing in patients with PD.

Tongue pressure production during swallowing in patients with mandibular prognathism.

UNLABELLED: Abnormalities of swallowing in patients with mandibular prognathism have not been evaluated quantitatively. The aim of this study was to compare tongue pressure production for bolus transfer between volunteers with normal occlusion and patients with mandibular prognathism. The control group had 10 female volunteers with normal occlusion, and the patient group had 10 women with mandibular prognathism. Tongue pressure was measured by a palatal sensor sheet at five sites on swallowing 4 mL of a tasteless and odourless jelly. RESULTS: The tongue pressure waveform differed between the control and patient groups. The incidence of a double-peak tongue pressure waveform was more frequent in the patient group. In both groups, the exertion of tongue pressure began at the anterior point of the sensor sheet, followed by the peripheral parts. Although the order of expression of tongue pressure was the same for the two groups, maximum tongue pressure at all parts of the sensor sheet was lower in the patient group than in the control group. Furthermore, swallowing time was longer in the patient group than in the control group at the peripheral parts of the palate. These results clearly show the difference in tongue pressure production during swallowing between patients with mandibular prognathism and volunteers with normal occlusion. The current findings suggest that maxillofacial morphology may affect tongue movement during swallowing.

Differences in biomechanical features of tongue pressure production between articulation and swallow.

Summary The purpose of this study was to compare the tongue pressure against the hard palate during the articulation of a monosyllable with that during swallowing. The participants were 20 healthy adults without swallowing or articulation disorder (10 men and 10 women, mean age ± standard deviation: 22·5 ± 0·9 years). Tongue pressure during articulation of [ki] (articulatory pressure) and during dry swallowing (swallowing pressure) was recorded by a 0·1-mm-thick sensor sheet with five measuring points attached to the hard palate. Biomechanical parameters such as maximal magnitude, duration, integrated value and slope gradient were compared between articulatory pressure and swallowing pressure at each measuring point. Although swallowing pressure was produced at each measuring point, articulatory pressure was found only in the posterior circumferential parts of the hard palate and was smaller in magnitude (14·9-16·7% of swallowing pressure) and integrated value, which meant the amount of work by tongue pressing (7·0-7·9%), shorter in duration (26·6-31·8%) and shallower in slope gradient, which meant the speed of tongue pressing (26·9-27·4%). Maximal magnitude was closely correlated with duration (R(2) = 0·386) and slope gradient (R(2) = 0·843) for articulatory pressure. These results first show the biomechanical differences between articulation and swallowing in terms of tongue contact with the hard palate. The findings suggest that tongue pressure measurement might be a useful investigation for patients with tongue motor disorder.

Impact of lingual plates on the interocclusal free way space: a pilot study.

Palatal augmentation prostheses are commonly used in the treatment for dysphagia. By lowering the palatal contours, the tongue contact is increased and thus the bolus propulsion facilitated. However, the unfavourable weight of such appliances may be avoided when using lingual plates. Hence, the aim of this study is to investigate the effect of two different types of lingual plates on the vertical dimension in rest position. Eleven healthy dentate subjects with an average age of 35.5 years (26-60 years) volunteered in this pilot study. The vertical overbites were measured on plaster models. Two different designs of the experimental lingual plates were tested in this pilot study (P-type & D-type). The inter-occlusal freeway space was measured using the electromagnetic K7 jaw-tracking system (Myotronics, U.S.A.), while the subjects were seated in an upright position. They were asked to close from rest position into maximum intercuspation for about 2 s. Recordings were performed without the plates and subsequently with each of the two plate designs in situ. All recordings were performed three times and the second closing movement of each recording was used for the analysis. After averaging the repetitions without experimental lingual plates, with P-type and D-type plates, the differences were analysed using a Kruskall-Wallis test. The results showed no significantly increased freeway space while using both types of lingual plates. Hence, it can be concluded that any altered tongue pressure during swallowing with lingual plates is not related to an increase in vertical dimension.

Influence of human jaw movement on cerebral blood flow.

Temporal changes in cerebral blood flow induced by jaw movement have yet to be investigated. To assess the influence of pattern and intensity of muscle contraction during jaw movement on task-induced change in cerebral blood flow, we performed bilateral transcranial Doppler ultrasound examination during clenching, gum chewing, and tooth tapping in healthy volunteers. A random-effects model analysis revealed a significant increase in middle cerebral artery blood flow velocity during clenching (high muscle activity) and gum chewing (moderate muscle activity), compared with the preceding rest period; however, such an increase was not detected during tooth tapping (low muscle activity). Cerebral blood flow was greater on the working side during the intensive isometric contraction of the masseter muscle in clenching. These results suggest that task-induced change in cerebral blood flow during jaw movement is influenced by the change in peripheral circulation evoked by muscle contraction.

Coordination of tongue pressure and jaw movement in mastication.

The tongue plays an important role in mastication and swallowing by its contact with the hard palate. Using an experimental palatal plate with 7 pressure sensors, and recording jaw movement using mandibular kinesiography, we assessed, in healthy subjects, the coordination of tongue and jaw movements during the entire masticatory sequence of solids, by measuring tongue pressure against the hard palate. Tongue pressure appeared during the occlusal phase, reached a peak near the start of opening, and disappeared during opening. Specific patterns in order, duration, and magnitude of tongue pressure were seen at the 7 pressure sensors in each chewing stroke. Magnitude and duration were significantly larger in the late stage of chewing (8 strokes before initial swallowing) than in the early stage (until 8 strokes after starting mastication). The normal pattern of tongue contact against the hard palate, control of tongue activity, and coordination with jaw movement during mastication is described.

Different modes of interaction of two peptide fragments from subdomain 4 of rabbit skeletal muscle actin with actin promoters.

Previously, we reported that the 2.6 kDa peptide fragment extending from Arg-177 to Tyr-198 in rabbit skeletal muscle actin bound to actin itself and inhibited its polymerization, while the 9.1 kDa peptide extending from Ser-199 to Tyr-279 in actin did not. The 2.6 kDa segment of actin was reported to contain one of the important actin-actin contacts (Hori, K. and Morita, F. (1992) J. Biochem. 112, 401-408). In this paper, we show additional evidence that the rate of salt-induced increase in the fluorescence of pyrene-labeled actin was decreased in the presence of the 2.6 kDa peptide. Conventional actin filaments were only scarcely observed in the presence of the 2.6 kDa peptide under an electron microscope with a steady state of fluorescence increase. Furthermore, the 2.6 kDa peptide was found to sever F-actin into short filament fragments. The 9.1 kDa peptide, on the other hand, neither inhibited the fluorescence increment of pyrene-actin nor severed actin filaments. However, the 9.1 kDa peptide was found to increase the viscosity and fluorescence intensity of pyrene-G-actin and to form short actin filaments in the absence of salts. Contact sites in the 9.1 kDa segment in actin may have a different mode of interaction with adjacent actin promoters in actin filaments from that of the 2.6 kDa segment.

Actin-actin contact: inhibition of actin-polymerization by subdomain 4 peptide fragments.

F-Actin was digested with alpha-chymotrypsin in 6 M urea, and two peptide fragments from subdomain 4 of actin molecule [Kabsch, W., Mannherz, H.G., Suck, D., Pai, E.F., & Holmes K.C. (1990) Nature 347, 37-44] were purified by reverse-phase HPLC and Sephadex G-50 gel filtration. The peptide fragments were identified as segments from Arg-177 to Tyr-198 (2.6-kDa peptide) and from Ser-199 to Tyr-279 (9.1-kDa peptide). Their effects on actin polymerization induced by 50 or 100 mM KCl were studied by measuring the increase in viscosity by the falling ball method. The 2.6-kDa peptide decreased the rate of actin polymerization and increased the critical concentration for the polymerization. Based on the atomic model of the actin filament [Holmes, K.C., Popp, D., Gebhard, W., & Kabsch, W. (1990) Nature 347, 44-49], the peptide is presumed to bind to the barbed end of the actin filament and inhibit the polymerization. By assuming that the peptide affected the rate of association of the actin monomer to the end of the actin filament, well-fitting curves for the polymerization kinetics were calculated. Computer-assisted results indicated that the dissociation constant of the 2.6-kDa peptide for F-actin is 200 to 260 microM. In contrast, the 9.1-kDa peptide only slightly inhibited actin polymerization. These results suggest that the actin-actin interface in the region between Arg-177 and Tyr-198 has a stronger interaction than those between Ser-199 and Tyr-279. The amino acid sequence L-T-D-Y-L present in the 2.6-kDa segment is homologous to a common sequence in the F-actin capping domain of various actin-binding proteins.

Increased monoamine turnover in the subfornical organ area following body fluid depletion.

To clarify whether monoaminergic inputs to the subfornical organ (SFO) area participate in fluid regulatory systems, we examined the effects of body fluid depletion on monoamine turnover in the region of the SFO using microdialysis techniques in rats. An iso-osmotic reduction of fluid volume following subcutaneous treatment with polyethylene glycol (PEG) significantly increased dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) concentrations in the SFO area. 5-hydroxytryptamine (5-HT) in the SFO area could be detected after the PEG treatment, while 5-HT was undetectable before the treatment. The data imply that both dopaminergic and serotonergic systems in the SFO area may be involved in controlling body fluid balance.

Enhanced monoamine release in the median preoptic area following reduced extracellular fluid volume in rats.

The role of monoaminergic neural inputs to fluid regulatory systems in the median preoptic nucleus (MnPO) was investigated by examination of monoamine metabolism during reduction of systemic extracellular fluid volume in freely moving rats. Extracellular fluid volume was decreased iso-osmotically by subcutaneous polyethylene glycol (PEG), and extracellular noradrenaline (NA), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured using intracerebral microdialysis techniques. PEG treatments significantly increased NA, DA and DOPAC release in the MnPO area. The results suggest that monoaminergic neural systems in the region of the MnPO are important in the control of extracellular fluid balance.

Transfer function analysis of cerebral autoregulation dynamics during jaw movements.

Mastication as a mild but life-long exercise has been examined as a possibility for maintaining brain function in the elderly. Little is known, however, about the cerebral circulatory response during masticatory movement. The aim of this study was to develop a monitoring system for circulation dynamics during masticatory movement and to apply this system to the study of cerebral autoregulation. Cerebral blood flow, heart rate, and arterial blood pressure were simultaneously recorded, and changes in these circulatory systems were quantitatively evaluated in 38 young healthy volunteers. Transfer function analysis was also performed on blood pressure and cerebral blood flow for investigation of cerebral autoregulation during gum chewing. Although increases in cerebral blood flow, mean blood pressure, and heart rate suggested the activation of cerebral and systemic circulation during gum chewing, increased cerebral circulation was independent of systemic circulation. Our results suggest that cerebral autoregulation is well maintained during jaw movements.

Age-related changes in tongue pressure during swallowing.

Although swallowing movement is known to change with aging, age-related differences in the tongue pressure for propelling a bolus from the oral cavity into the pharynx have yet to be investigated in a physiological condition. We hypothesized that tongue pressure during swallowing changed with aging and, using a 0.1-mm-thick sensor sheet with 5 measuring points, measured it while a 15-mL quantity of water was swallowed by young and elderly dentate individuals. Both groups showed a similar order of tongue pressure production at each point. However, the elderly group showed longer duration at each point, lower maximal magnitude in the anterio-median part of the hard palate, and higher magnitude in the circumferential parts of the hard palate than the young group. These results provide the first quantitative evidence of the age-related changes in tongue movement during natural swallowing, which could be attributed to muscle weakening and morphological changes in the oropharynx.

Recovery of silver from radiographic fixer.

This study examined the silver content of 10 brands of dental x-ray film that are commercially available in Japan. Kodak Ektaspeed EP-22 (Eastman Kodak Co., Rochester, N.Y.) was found to have the highest silver content, and SD 100 Gold X-ray Film (San Dental Co., Ltd., Tokyo, Japan) had the lowest content of silver. Electrolysis and ion exchange were used as the methods of silver recovery from films in the general dental office. Ion exchange was more than 99% efficient in silver recovery from the radiographic fixer and resulted in an 80% reduction in biochemical oxygen demand and a 95% reduction in chemical oxygen demand. However, these levels and other environmental pollutants were still above the limits set by the Japanese Pollutant Control law.

Effect of dispersing oil phase on the biodegradability of a solid alkane dissolved in non-biodegradable oil.

Acinetobacter sp. CR was grown on a model oil, which consisted of an inert oil matrix of pristane with n-heneicosane dissolved in it as the sole carbon source, in a stirred-tank bioreactor. This bacterium takes up substrates from the oil phase by direct contact with the oil phase. A previously established mathematical model was applied to reveal the effect of agitation conditions on the growth and n-alkane degradation kinetics of the bacterium. Higher impeller speed resulted in both lower microbial growth and lower n-alkane degradation rate of the bacterium, although it increased the specific surface area of the oil, which was measured by a previously developed device. This result was due to the decreased number of cells adhering to the oil surface, i.e., intense agitation inhibited the adhesion of cells to the oil surface. The addition of a surfactant below a critical micelle concentration (CMC) inhibited the degradation of n-heneicosane dissolved in pristane, although the biodegradability of the substrate recovered gradually with the increase in the dose of surfactant over CMC. The results suggest that efforts to increase the specific surface area of the oil phase have the undesirable result of inhibiting oil degradation when the dominant microbial degraders take up substrates in oil by direct contact with the oil.

Fungal contribution to in situ biodegradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) film in soil.

The contribution of fungi to the microbial degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films in soil was studied. Various traces, cavities, and grooves observed on the dented surface of PHBV films demonstrated that the degradation was a concerted effect of a microbial consortium colonizing the film surface, including fungi, bacteria, and actinomycetes. The succession of microbial consortia in the soil around the PHBV films during the degradation showed a distinctive increase in the fungal population, resulting in its dominance. Comparison of the degradation ability of microbial strains isolated from soil where PHBV films were degraded, revealed that fungi showed the highest contribution to PHBV degradation, growing very rapidly along the film surface with their high degradation ability and then expanding their hyphae in a three-dimensional manner.

Disposition of tritium-labelled heparin in rats.

To evaluate the distribution of water soluble macromolecular compound in the body, heparin was selected as one of the model compounds. Urinary and fecal excretion, and plasma levels following intravenous administration of commercial 3H-heparin were investigated at three different dose levels. Whole-body autoradiography was also carried out periodically following intravenous administration of 3H-heparin at single dose level. The distribution of radioactivity following the administration of 3H-heparin was compared with that of 14C-polyethylene glycol 6000. The statistically significant but only very small differences in the pharmacokinetic parameters and in the urinary excretion were observed over the wide range of dose (0.20, 2.0 and 20 mg/kg). The decline of plasma radioactivity following the administration of 3H-heparin appeared to be biexponential with time and pharmacokinetic constants were calculated according to a two-compartment open model. Whole-body autoradiograms showed that the reticulo-endotherial system (R.E.S.) may play an important role in removal of the radioactivity of heparin from the circulating blood.