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Yusuke Morita

Publications and source records attributed to Yusuke Morita.

32 records · Page 2Linked to original sources
PubMed2003

Single eight-hour shift of light-dark cycle increases brain-derived neurotrophic factor protein levels in the rat hippocampus.

We previously reported that an eight hour phase advance in the light-dark (LD) cycle increases sleep in rats. Brain-derived neurotrophic factor (BDNF) is suggested to be one of the sleep and circadian regulating factors. We have therefore observed the responses of BDNF protein in the hippocampus, cerebellum and brainstem under conditions of LD change. BDNF protein was quantitatively measured using an ELISA kit. Under an 8-h LD phase advance, the levels of hippocampal BDNF were significantly increased on the day of the phase change, while the levels in the cerebellum and brainstem remained constant. Plasma corticosterone levels were not largely affected. Thus, a single LD shift acutely affects hippocampal BDNF metabolism with no large stress response.

Animals↗
PubMed2003

Changes in the expression of steroid metabolism-related genes in rat adrenal glands during selective REM sleep deprivation.

Selective REM sleep deprivation was carried out under the conditions designed to minimize the adverse influence of environmental conditions and restricted movement, and the influence of REM sleep deprivation on adrenocortical steroid metabolism was investigated by measuring the steady-state levels of mRNAs encoding steroid metabolism-related genes, steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme cytochrome P450 (P450scc) and steroid 5alpha-reductase (5alpha-R), in rat adrenal glands. Selective REM sleep deprivation caused a significant decrease in StAR mRNA and an increase in 5alpha-R mRNA levels without any notable change in P450scc mRNA levels in the adrenal gland. In contrast, non-selective sleep disturbance, resulting in the partial reductions of non-REM and REM sleep, tended to increase both StAR and P450scc mRNA levels without any statistical significance. These results indicate that REM sleep deprivation by itself may affect the expression of steroid metabolism-related genes in the adrenal gland, suggesting a possible relation between REM sleep and adrenocortical steroid metabolism.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2003

Premovement gating of somatosensory evoked potentials after tibial nerve stimulation.

Somatosensory evoked potentials (SEPs) are attenuated or gated during movement. The mechanism for this includes both centrifugal gating of afferent input and competition with other afferents caused by the movement (peripheral gating). Using a paradigm in which the signal for triggering movement is the electric stimulus for SEPs, we studied the gating of SEPs after tibial nerve stimulation prior to foot movement, and compared it with that during counting task. Significant gating was found for P40 component, which distributed centrally and ipsilaterally to the side of the stimulation, whereas the contralateral N40 component showed no changes. Dissociated gating of P40 and N40 indicates multiple generators of these components, in contrast to the previous view of a single generator dipole projecting tangentially. Together with the previous findings in median SEPs, these gating phenomena should represent a general mechanism for sensori-motor integration in preparation for limb movement.

Adult↗
PubMed2003

Tactile-visual cross-modal shape matching: a functional MRI study.

The process and location of integration of information from different sensory modalities remains controversial. We used functional MRI to investigate the neural representation of cross-modal matching between tactile and visual shape information in eleven normal volunteers. During the scan, patterns of 2D shapes were presented both tactually and visually, simultaneously. Four different matching tasks were performed: tactile-tactile with eyes closed (TT), tactile-tactile with visual input (TTv), visual-visual with tactile input (VVt), and tactile-visual (TV). The TT task activated the contralateral primary sensorimotor area, and the postcentral gyrus, superior parietal lobules, anterior portion of the intraparietal sulcus, secondary somatosensory cortex, thalamus, dorsal premotor area, cerebellum, and supplementary motor area bilaterally, without occipital involvement. Visual matching activated the primary visual cortex and the lingual and fusiform gyri bilaterally. A cross-modal area was identified by subtracting TTv images from TV images, subtracting VVt images from TV images, and then determining common active areas. There was one discrete area that was active bilaterally; the posterior intraparietal sulcus close to the parieto-occipital sulcus. These data suggest that shape information from different sensory modalities may be integrated in the posterior intraparietal sulcus during tactile-visual matching tasks.

Adult↗
PubMed2003

Short-term sleep disturbance enhances brain-derived neurotrophic factor gene expression in rat hippocampus by acting as internal stressor.

Rats were subjected to nonselective sleep disturbance for short periods under conditions designed to minimize the adverse influence of external stresses, such as environmental conditions and restricted movement, and both brain-derived neurotrophic factor (BDNF) protein and its mRNA levels in the brain were then determined to investigate the influence of sleep disturbance itself on BDNF gene expression. Total sleep duration was partially but significantly reduced by disturbing the sleep/wake cycle for 1 and 2 h, gradually increased according to the time of disturbance, then returned to control levels at 6 h after the beginning of sleep disturbance. Under these conditions, the slight but significant elevation of corticotrophin-releasing factor (CRF) mRNA levels in the paraventricular nucleus (PVN) was observed at an early stage of the sleep disturbance period. Sleep disturbance induced the elevation of both BDNF protein and its mRNA levels in the hippocampus but not in the cerebellum or the brainstem, and the elevated BDNF mRNA expression in the hippocampus returned toward basal levels during the sleep recovery period when the rebound of sleep duration was observed. These findings suggest the possibility that short-term disturbance of the sleep/wake cycle and, hence, the partial reduction of non-REM sleep duration, might exert a potential influence on neuronal and/or glial cells as an internal stressor, resulting in the elevation of BDNF gene expression in rat hippocampus.

Animals↗
PubMed2003

Effect of backchannel utterances on facilitating idea-generation in Japanese think-aloud tasks.

The relation between backchannel utterance and idea-generation has hardly been studied. Based on preliminary investigations, we formulated a hypothesis that a listener's backchannel utterances facilitate a speaker's idea-generation. This study experimentally manipulated the frequency of backchannel utterances by listeners during speakers' idea-generation for think-aloud tasks. 16 Japanese female undergraduates participated. Analysis indicated that frequent backchannel utterances increased not only the number of ideas generated but also the speaking time for the tasks.

Adolescent↗
PubMed2003

Culture of chondrocytes in fibroin-hydrogel sponge.

Fibroin-hydrogel sponge and collagen gel were used as scaffold for in vitro cartilage regeneration. Fibroin-hydrogel sponge was formed by phase separation from freezed fibroin solution. Chondrocytes were harvested from proximal humerus, distal femur and proximal tibia of 4-week-old Japanese white rabbits and inoculated in the fibroin-hydrogel sponge and collagen gel. Those constructs were cultured in DMEM supplemented with 10% FCS and 50 ml L-ascorbate at 37 degrees C. Histological observation, measurement of sulfated glycosaminoglycan and cell density were carried out at 3, 7, and 14 days after the cultivation. Well-defined cartilage tissue can be seen both in the fibroin-hydrogel sponge and in the collagen gel. The matrix was intensely stained by safranin-O and showed a metachromatic reaction in both group. However, the quantity of sulfated glycosaminoglycan and cell density of the fibroin-hydrogel sponge group were increased more rapidly than these of the collagen gel group. Thus, the chondrocytes proliferated in the fibroin sponge without losing their differentiated phenotype. It is possible that culture environment in the fibroin sponge was suitable for chondrocytes regeneration.

Biomimetic Materials↗
PubMed2003

Evaluation of dynamic visco-elastic properties during cartilage regenerating process in vitro.

The dynamic visco-elastic properties of regenerated cartilage tissue were measured to evaluate its mechanical function during cultivation. Harvested chondrocytes from 4-week-old Japanese white rabbits were inoculated into fibroin sponge at a cell concentration of about 5 x 10(7) cells/ml. Dynamic visco-elasticity measurements were performed under compressive loading to evaluate the load bearing function of the articular cartilage. The dynamic modulus and the dynamic loss of the regenerated cartilage increased and the peak value of tandelta, as well as the frequency at the peak, decreased with increasing cultivation time. The pores of the fibroin sponge became filled with newly formed tissue as cultivation time increased. These changes in the visco-elastic properties of the regenerated cartilage were compared with those of a model system, ethylene propylene diene monomer sponge with interstitial fluid, and appear to be a result of increased fluid flow resistance and internal loss. We conclude that the changes in the dynamic visco-elastic properties of the regenerated cartilage were caused because of narrowing of the fluid path by synthesized extracellular matrix.

Animals↗
PubMed2002

Age-related changes in control of blood pressure and heart rate during sleep in the rat.

STUDY OBJECTIVES: The aim of this study was to determine age-related changes in the control of mean arterial pressure (MAP) and heart rate (HR) during sleep, and its relationship to the baroreflex in aging. DESIGN: MAP, HR, body temperature (TP), spontaneous activity (ACT), and sleeping/waking duration were monitored for 24 hours in groups of young (10-12 wk old) and old (23-24 mo old) rats. SETTING: The sleep laboratory at the University of Tokushima. PARTICIPANTS: Subjects were 8 young (10-12 wk old) and 7 old (23-24 mo old) Wistar rats. INTERVENTIONS: Reflex control of HR was evaluated by examining various pressure responses to an intravenous bolus injection of phenylephrine and sodium nitroprusside. MEASUREMENTS AND RESULTS: MAP and TP were recorded by a radiotelemetry system. HR was detected from the AP signal. ACT was counted by a photo-sensor system. In the case of old rats, the sensitivity of baroreflex control of HR was significantly depressed, and the spontaneous increase of MAP and HR during REM sleep and the MAP drop at the end of REM sleep were significantly enhanced. The old rats showed no large deterioration of the circadian profiles of MAP, HR, TP, and the amount of sleep. CONCLUSIONS: The baroreflex dysfunction is considered to appear in an early stage of the aging process, and to affect the control of MAP and HR during sleep.

Age Factors↗
PubMed2002

Mesolimbic dopaminergic system is involved in diurnal blood pressure regulation.

Parkinson's disease (PD) patients with autonomic failure show no nocturnal decrease in blood pressure (BP). At present, it is not clear if this symptom is attributable to the disturbance of the dopaminergic (DA) system that is responsible for PD. In the present study, we determined that the mesolimbic DA system is involved in diurnal profiles of the mean BP (MBP) by destroying the A10 DA system in rats with 6-hydroxydopamine. In control rats, a clear dip in the MBP and heart rate (HR) occurs during the light, that is, resting period, analogous to the nocturnal dip in normal humans. This normal daytime decrease in MBP and HR was disturbed by inducing a lesion of the ventral tegmental area (VTA) DA neurons, although the rhythms of wake-sleep duration and behavioral activity remained relatively intact. On the basis of this evidence, the absence of a nocturnal dip in BP in PD patients is attributed to impairment of the mesolimbic DA system.

Animals↗
PubMed2002

Effect of ultrasound application on fat mobilization.

The aim of this experimental trial was to study the effect of ultrasound application on the lipolysis in adipose tissue. Rats were administered to pentobarbital (Nembutal) anesthesia and their abdomens were shaved. Rat abdomen was subjected to 24 kHz-1 MHz ultrasound for 10 min to investigate frequency and power-intensity dependency for fat mobilization. Blood was taken from the tail vein to estimate plasma free fatty acids (FFA). For frequency dependency two regions around 100 kHz and 300-500 kHz were effective for fat mobilization. For power-intensity dependency, effective regions were found to be from 24 to 1090 kHz. In the effective regions on frequency and power-intensity, application of ultrasound caused increases in plasma FFA and norepinephrine concentration of extra-cellular fluid of perirenal adipose tissue. These results suggest that ultrasound application stimulates fat mobilization through a local increase in norepinephrine secretion under the conditions of effective frequency and intensity.

Journal Article↗
PubMed2002

Visco-elastic properties of cartilage tissue regenerated with fibroin sponge.

The mechanical properties of regenerated cartilage tissue were measured to evaluate changes in their visco-elastic properties during cultivation. An indentation test and dynamic visco-elasticity measurements were carried out on cartilage tissue cultured with rabbit chondrocytes that had been inoculated into the fibroin sponge. A 1.5-mm-diameter porous indentor was used for the indentation test, in which time-dependent strain curves were derived from measurements taken under several loading conditions. Dynamic visco-elasticity measurements were performed under compressive loading to evaluate the load-bearing function of the articular cartilage. Although the amount of permanent deformation was not influenced by the duration of cartilage regeneration, the amount of creep deformation increased with longer cultivation. The E' value of the regenerated cartilage increased and the peak value of tan delta and the frequency at the peak became lower with longer cultivation. It is suggested that the changes in the time-dependent strain curves and dynamic visco-elastic properties of the regenerated cartilage were caused by maturation of the cultured cartilage tissue.

Animals↗
PubMed2002

REM sleep deprivation suppresses acquisition of classical eyeblink conditioning.

STUDY OBJECTIVES: The aim of this study was to investigate the issue of whether REM sleep is involved in implicit learning through the cerebellum-related neural circuit via the use of classical eyeblink conditioning (CEC). DESIGN: Subjects were divided into three groups: control (sleep without interruption), REM sleep deprivation (RD), and slow wave sleep (stage 3+4) deprivation (SD). The CEC was performed after 8 hours of ordinary nocturnal sleep or sleep disrupted at a selected sleep stage. SETTING: A university-based sleep laboratory. PATIENTS OR PARTICIPANTS: Twenty-seven healthy volunteers (all men, aged 23.2+/-0.6 years). INTERVENTIONS: The CEC was measured after selective sleep deprivation or ordinary nocturnal sleep. MEASUREMENTS AND RESULTS: The eyeblink reflex was conditioned using a classical delay conditioning paradigm. The conditioned response (CR) was determined by electromyography measurements of the orbicularis oculi muscles. The rate of appearance of the CR was compared among the three groups. Compared with the control subjects, RD subjects were significantly deficient in their capacity to acquire conditioned eyeblinks, while no difference was found among the SD subjects. CONCLUSIONS: This study suggests that RD suppresses the cerebellar function in CEC and that REM sleep is closely linked with the learning function in the cerebellum.

Adult↗