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We report a search for time variations of the solar ^{8}B neutrino flux using 5804 live days of Super-Kamiokande data collected between May 31, 1996, and May 30, 2018. Super-Kamiokande measured the precise time of each solar neutrino interaction over 22 calendar years to search for solar neutrino flux modulations with unprecedented precision. Periodic modulations are searched for in a dataset comprising five-day interval solar neutrino flux measurements with a maximum likelihood method. We also applied the Lomb-Scargle method to this dataset to compare it with previous reports. The only significant modulation found is due to the elliptic orbit of the Earth around the Sun. The observed modulation is consistent with astronomical data: we measured an eccentricity of (1.53±0.35)%, and a perihelion shift of (-1.5±13.5) days.
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OBJECTIVE: This study aimed to use short-form visual analogue scale cochlear implantation questionnaires to evaluate subjective aspects at each out-patient visit. The correlation between subjective hearing tests using the short-form visual analogue scale and objective hearing outcomes was evaluated. METHOD: This study was conducted in a single centre. Cochlear implant users (n = 199) evaluated their hearing on a scale of 0 to 100 for the right, left and both ears. The Japanese speech perception test (CI-2004) Japanese monosyllable speech perception test (67-S) and cochlear implantation threshold were used for the objective cochlear implantation evaluation. RESULTS: A significant correlation was found between the short-form visual analogue scale questionnaire and objective hearing outcome, for words (r = 0.64) and sentences (r = 0.62) in CI-2004 and 67-S (r = 0.56) tests. No significant correlation was found between the short-form visual analogue scale score and cochlear implantation threshold (r = -0.18). CONCLUSION: Short-form visual analogue scale cochlear implantation questionnaires mean cochlear implant users spend less time answering subjective visual analogue scale questionnaires, and clinicians estimate a patient's cochlear implantation hearing and abnormality by chronological evaluation.
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Implantación Coclear , Implantes Cocleares , Percepción del Habla , Humanos , Escala Visual Analógica , AudiciónRESUMEN
This corrects the article DOI: 10.1103/PhysRevLett.130.031802.
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We report a search for cosmic-ray boosted dark matter with protons using the 0.37 megaton×years data collected at Super-Kamiokande experiment during the 1996-2018 period (SKI-IV phase). We searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the Galactic Center. No such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. This is the first experimental search for boosted dark matter with hadrons using directional information. The results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 10^{-33}cm^{2} and 10^{-27}cm^{2} for dark matter mass from 1 MeV/c^{2} to 300 MeV/c^{2}.
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BACKGROUND: Hypoxia has been noted as a key factor for induction and maintenance of cancer stemness thereby leading to therapy resistance. Three-dimensional (3D) spheroid models demonstrate a heterogeneity of hypoxic regions replicating the in vivo situation within tumors. Utilizing an established 3D spheroid model, we investigated whether extrinsic hypoxia reinforced chemoresistance in malignant pleural mesothelioma (MPM) spheroids. MATERIALS AND METHODS: Tumor spheres were generated from Meso-1 (a typical human MPM cell line) cells having high spheroid-forming ability. To induce hypoxia condition, we utilized a hypoxia chamber with regulation of O2 and CO2 levels. Cell viability was estimated by a WST-8 assay. Real-time polymerase chain reaction and Western blot were performed to evaluate the expression at mRNA and protein levels. RESULTS: Compared with cells cultured in the two-dimensional monolayer model, tumor sphere cells showed elevated mRNA levels of cancer stemness markers (CD26, CD44 and ABCG2) and protein levels of the stemness and hypoxia adaptation markers (ABCG2, ALDH1A1 and HIFs). Correlating with this, 3D spheroid cells were more resistant to permetrexed and topotecan than the two-dimensional cells, indicative of their potential for hypoxic adaptation. Furthermore, significantly stronger resistance to both chemotherapeutic agents was observed in spheroid cells upon hypoxic challenge compared to spheroid cells under normoxia. CONCLUSION: From the present data, it is concluded that hypoxia adaptation of MPM cells from tumor spheres could enhance their chemoresistance.
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Mesotelioma Maligno , Mesotelioma , Línea Celular Tumoral , Resistencia a Antineoplásicos/genética , Humanos , Hipoxia/metabolismo , Mesotelioma/tratamiento farmacológico , Mesotelioma/genética , Mesotelioma/patología , ARN Mensajero , Esferoides Celulares/metabolismo , Esferoides Celulares/patologíaRESUMEN
OBJECTIVES: Although it has been shown that specific foods and nutrients are associated with sleep quality, few studies have examined the association of dietary variety and appetite with sleep quality in older adults. DESIGN AND SETTING: A cross-sectional study was conducted that examined the association of dietary variety and appetite with sleep quality in Japanese adults aged ≥70 years who resided in the metropolitan area of Tokyo, Japan. PARTICIPANTS: Data were collected in two steps: a mailed interview survey and an on-site survey. Those who responded to the surveys and met the inclusion criteria were included. MEASUREMENTS: Dietary variety, appetite, and sleep quality were assessed using a Dietary Variety Score (DVS), Council on Nutrition Appetite Questionnaire (CNAQ) score, and sleep efficiency, respectively. The sleep efficiency is the ratio of sleep duration to total time in bed (retiring time-awakening time). We defined the individuals with a sleep efficiency less than 75% as having poor sleep quality. RESULTS: Mean DVS and CNAQ score were 3.8 and 29.6 points, respectively. The rate of individuals with poor sleep quality was 11.7%. In the fully adjusted model, the odds ratios (OR) for low sleep efficiency in the middle and highest group categories of the DVS were 0.83 (95% confidence interval [CI], 0.54-1.29) and 0.50 (95% CI, 0.28-0.90), respectively, in reference to the lowest group category (p for trend = 0.023). The OR for low sleep efficiency in the middle and highest group categories of the CNAQ score were 0.73 (95% CI, 0.47-1.14) and 0.54 (95% CI, 0.30-0.96), respectively, in reference to the lowest group category (p for trend = 0.031). CONCLUSIONS: The higher DVS and CNAQ scores were significantly associated with higher sleep efficiency. Thus, dietary variety and good appetite might help maintain good sleep quality in urban-dwelling older Japanese adults.
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Apetito/fisiología , Dieta/métodos , Trastornos del Inicio y del Mantenimiento del Sueño/dietoterapia , Anciano , Anciano de 80 o más Años , Estudios Transversales , Femenino , Humanos , Japón , Masculino , Población UrbanaRESUMEN
It has been shown that the tissue oxygen index (TOI) measured by near-infrared spectroscopy oscillates at very low frequencies during recovery after exercise and that this oscillation is derived from interactions among biochemical substances involved in oxidative metabolism in skeletal muscle. As a further step, we examined whether TOI in muscle interacts through oscillation with factors related to oxygen in the cardiorespiratory system. For this examination, coherence and phase difference between the TOI in the vastus lateralis and heart rate (HR) and between TOI and arterial oxygen saturation (SpO2) were sequentially determined during recovery (2-60 min) after severe cycle exercise with a workload of 7.5% of body weight for 20 s. Significant coherence between TOI and HR was obtained in the very low-frequency band (approximate range: 0.002-0.03 Hz) and in the low-frequency band (approximate range: 0.06-0.12 Hz). The phase difference was negative in the low-frequency band and positive in the very low-frequency band. The coherence between TOI and SpO2 was significant in the very low-frequency band. The phase difference was negative. There were no sequential changes in these coherences and phase differences. The results suggest that TOI in skeletal muscle interrelates with factors related to the heart and lungs.
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Ejercicio Físico/fisiología , Corazón/fisiología , Pulmón/fisiología , Músculo Esquelético/fisiología , Consumo de Oxígeno/fisiología , Oxígeno/metabolismo , Adulto , Análisis de los Gases de la Sangre/métodos , Prueba de Esfuerzo/métodos , Frecuencia Cardíaca/fisiología , Humanos , Pulmón/metabolismo , Masculino , Contracción Muscular/fisiología , Músculo Esquelético/metabolismo , Músculo Cuádriceps/metabolismo , Músculo Cuádriceps/fisiología , Adulto JovenRESUMEN
Endoscopic image diagnosis assisted by machine learning is useful for reducing misdetection and interobserver variability. Although many results have been reported, few effective methods are available to automatically detect early gastric cancer. Early gastric cancer have poor morphological features, which implies that automatic detection methods can be extremely difficult to construct. In this study, we proposed a convolutional neural network-based automatic detection scheme to assist the diagnosis of early gastric cancer in endoscopic images. We performed transfer learning using two classes (cancer and normal) of image datasets that have detailed texture information on lesions derived from a small number of annotated images. The accuracy of our trained network was 87.6%, and the sensitivity and specificity were well balanced, which is important for future practical use. We also succeeded in presenting a candidate region of early gastric cancer as a heat map of unknown images. The detection accuracy was 82.8%. This means that our proposed scheme may offer substantial assistance to endoscopists in decision making.
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Neoplasias Gástricas , Automatización , Detección Precoz del Cáncer , Gastroscopía , Humanos , Aprendizaje Automático , Redes Neurales de la Computación , Sensibilidad y Especificidad , Neoplasias Gástricas/diagnósticoRESUMEN
The purpose of this study was to concomitantly determine oxidative DNAdamage and bone resorption following a rapid body mass reduction in association with energy restriction and exercise training, considering 17ß-estradiol level, in female collegiate judokas. Eighteen nationally ranked university female judokas were enrolled as participants in this study. All participants continuously managed to reduce their body mass 8 days just before a competition. To detect cumulative effects of oxidative DNA damage and bone resorption, urinary samples were collected in the morning on three different days (Day 1= the beginning of body mass reduction; Day 4=mid-term of body mass reduction; Day 7=the day before the competition) for the later analysis of 8-hydroxy-2- deoxyguanosine (8-OHdG) as well as cross-linked N-terminal telopeptides of Type I collagen (NTx). Urinary 8-OHdG and NTx levels were determined with high performance liquid chromatography and enzyme-linked immunosorbent assay, respectively. No significant alterations were observed in urinary 8-OHdG or NTx levels over a rapid body mass reduction period. The findings of the present study indicate that female judokas appear to have relatively less oxidative DNA damage determined by quantification of 8-OHdG and bone resorption over a rapid body mass reduction period, potentially due to the enhanced endogenous defense responses (training adaptation). These data can provide athletes and coaches with valuable information in considering an optimal body mass management program to avoid detrimental physiological and biological conditions.
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Atletas , Peso Corporal/fisiología , Resorción Ósea , Daño del ADN/fisiología , Ejercicio Físico/fisiología , 8-Hidroxi-2'-Desoxicoguanosina , Composición Corporal/fisiología , Restricción Calórica , Colágeno Tipo I/orina , Desoxiguanosina/análogos & derivados , Desoxiguanosina/orina , Femenino , Humanos , Artes Marciales , Estrés Oxidativo/fisiología , Adulto JovenRESUMEN
AIMS: To test the hypothesis that treatment with a sodium-glucose co-transporter-2 inhibitor would reverse ventricular repolarization heterogeneity, a predictor of cardiovascular mortality, in people with Type 2 diabetes. METHODS: We retrospectively analysed changes in indices of ventricular repolarization before and after treatment with a sodium-glucose co-transporter-2 inhibitor in 46 people with Type 2 diabetes. RESULTS: Sodium-glucose co-transporter-2 inhibitor treatment reduced HbA1c concentration [62±13 mmol/mol (7.7±1.2%) vs 59±16 mmol/mol (7.5±1.4%)], body weight (77.8±13.9 vs 74.7±12.5 kg) and systolic blood pressure (133±18 vs 126±12 mmHg) in the study participants. Heart rate and QTc interval were not changed by sodium-glucose co-transporter-2 inhibitor treatment, but QTc dispersion was significantly reduced (median, 48.8 vs 44.2 ms). Sodium-glucose co-transporter-2 inhibitor treatment reversed QTc dispersion more in participants who had larger QTc dispersion before the treatment. Changes in systolic blood pressure (Spearman's ρ= 0.319; P=0.031), but not in HbA1c concentration, were correlated with changes in QTc dispersion after sodium-glucose co-transporter-2 inhibitor treatment. CONCLUSIONS: The findings suggest that sodium-glucose co-transporter-2 inhibitor treatment reverses ventricular repolarization heterogeneity in people with Type 2 diabetes, independently of its effect on glycaemic control. The favourable effect on ventricular repolarization heterogeneity could be the mechanism by which empaglifozin reduced cardiovascular events in a recent study.
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Diabetes Mellitus Tipo 2/tratamiento farmacológico , Angiopatías Diabéticas/tratamiento farmacológico , Hipoglucemiantes/uso terapéutico , Inhibidores del Cotransportador de Sodio-Glucosa 2 , Disfunción Ventricular/tratamiento farmacológico , Adulto , Anciano , Diabetes Mellitus Tipo 2/complicaciones , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Transportador 2 de Sodio-Glucosa , Resultado del Tratamiento , Disfunción Ventricular/etiologíaRESUMEN
Calcineurin inhibitors (CNIs) have been used off-label for the treatment of refractory Kawasaki disease (KD). However, it remains unknown whether CNIs show protective effects against the development of coronary artery lesions in KD patients. To investigate the effects of CNIs on coronary arteries and the mechanisms of their actions on coronary arteritis in a mouse model of KD, we performed experiments with FK565, a ligand of nucleotide-binding oligomerization domain-containing protein 1 (NOD1) in wild-type, severe combined immunodeficiency (SCID), caspase-associated recruitment domain 9 (CARD9)-/- and myeloid differentiation primary response gene 88 (MyD88)-/- mice. We also performed in-vitro studies with vascular and monocytic cells and vascular tissues. A histopathological analysis showed that both cyclosporin A and tacrolimus exacerbated the NOD1-mediated coronary arteritis in a dose-dependent manner. Cyclosporin A induced the exacerbation of coronary arteritis in mice only in high doses, while tacrolimus exacerbated it within the therapeutic range in humans. Similar effects were obtained in SCID and CARD9-/- mice but not in MyD88-/- mice. CNIs enhanced the expression of adhesion molecules by endothelial cells and the cytokine secretion by monocytic cells in our KD model. These data indicated that both vascular and monocytic cells were involved in the exacerbation of coronary arteritis. Activation of MyD88-dependent inflammatory signals in both vascular cells and macrophages appears to contribute to their adverse effects. Particular attention should be paid to the development of coronary artery lesions when using CNIs to treat refractory KD.
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Arteritis/tratamiento farmacológico , Inhibidores de la Calcineurina/uso terapéutico , Endotelio Vascular/efectos de los fármacos , Macrófagos/efectos de los fármacos , Síndrome Mucocutáneo Linfonodular/tratamiento farmacológico , Factor 88 de Diferenciación Mieloide/metabolismo , Oligopéptidos/uso terapéutico , Animales , Proteínas Adaptadoras de Señalización CARD/genética , Vasos Coronarios/patología , Citocinas/metabolismo , Modelos Animales de Enfermedad , Endotelio Vascular/inmunología , Humanos , Mediadores de Inflamación/metabolismo , Macrófagos/inmunología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Ratones SCID , Factor 88 de Diferenciación Mieloide/genética , Células RAW 264.7 , Transducción de SeñalRESUMEN
BACKGROUND: The role and phenotypic alterations of intrahepatic natural killer (NK) cells in liver disease were investigated. Although intrahepatic NK cells reportedly functionally deteriorate in the fibrotic liver, it remains unclear how the clinical severity of liver disease affects intrahepatic NK cells in patients with advanced liver failure. METHODS: We analyzed the phenotypic properties of intrahepatic NK cells by using mononuclear cells extracted from ex vivo liver perfusate effluents from patients who underwent liver transplantation. The relationship between the clinical severity of liver disease and the phenotype of intrahepatic NK cells in these patients was also evaluated. To estimate the immunological responsiveness of intrahepatic NK cells, phenotypic enhancement after interleukin-2 stimulation was analyzed. RESULTS: Intrahepatic NK cells from patients with advanced liver failure exhibited down-regulated monomodal expression of NKp46, a major activating molecule. Notably, the expression level of NKp46 decreased depending on the severity of liver disease, Model for End-Stage Liver Disease score, and Child-Pugh score rather than the etiology. After in vitro recombinant interleukin-2 stimulation, the enhancement of expression of cytotoxic molecules, NKp44, and tumor necrosis factor-related apoptosis-inducing ligand was significantly impaired in intrahepatic NK cells from patients with liver failure, concurrently with decreased expression of CD122 and interleukin-2 receptor beta. CONCLUSIONS: Our results suggest that terminal deterioration of liver environments by chronic liver disease impairs the potential of local NK cells, depending on the severity of the deterioration. These influences of advanced liver failure on intrahepatic NK cells may be attributed to multicentric carcinogenesis in patients with liver failure.
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Enfermedad Hepática en Estado Terminal/inmunología , Células Asesinas Naturales/inmunología , Trasplante de Hígado , Adulto , Femenino , Citometría de Flujo , Humanos , Masculino , Persona de Mediana EdadRESUMEN
The use of resonant whispering gallery modes (WGMs) for sensing exhibits various drawbacks and critical points related to the microsphere and tapered optical fiber fabrication tolerance. The uncertainty on the fiber taper and microsphere geometry or the gap between the microsphere and the fiber taper can complicate or limit the actual use of these devices for sensing, requiring peculiar calibration of the WGM based sensing set-up. An alternative double-step approach is proposed in this paper. In particular, the geometrical parameters of the set-up are recovered preliminarily and then the rare earth parameters are recovered via simple transmittance/gain measurements. The method is based on a refined electromagnetic model of the device suitably integrated with a particle swarm optimization (PSO) approach. The percent errors made on the up-conversion coefficients Cup and C3 are extremely low, being 0.75%, 0.05%, respectively. The procedure is very robust. It can be applied more in general, allowing the sensing of other physical parameters via simple transmittance measurements instead of wavelength shift ones, in both microsphere and microbubble based set-up.
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OBJECTIVE: Bright light therapy is widely used as the treatment of choice for seasonal affective disorder. Nonetheless, our understanding of the mechanisms of bright light is limited and it is important to investigate the mechanisms. The purpose of this study is to examine the hypothesis that bright light exposure may increase [(18) F]-fluorodeoxyglucose (FDG) uptake in olfactory bulb and/or hippocampus which may be associated neurogenesis in the human brain. METHOD: A randomized controlled trial comparing 5-day bright light exposure + environmental light (bright light exposure group) with environmental light alone (no intervention group) was performed for 55 participants in a university hospital. The uptake of [(18) F]FDG in olfactory bulb and hippocampus using FDG positron emission tomography was compared between two groups. RESULTS: There was a significant increase of uptake in both right and left olfactory bulb for bright light exposure group vs. no intervention group. After adjustment of log-transformed illuminance, there remained a significant increase of uptake in the right olfactory bulb. CONCLUSION: The present findings suggest a possibility that 5-day bright light exposure may increase [(18) F]FDG in the right olfactory bulb of the human brain, suggesting a possibility of neurogenesis. Further studies are warranted to directly confirm this possibility.
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Fluorodesoxiglucosa F18/farmacocinética , Hipocampo/metabolismo , Hipocampo/efectos de la radiación , Bulbo Olfatorio/metabolismo , Bulbo Olfatorio/efectos de la radiación , Trastorno Afectivo Estacional/metabolismo , Trastorno Afectivo Estacional/terapia , Adulto , Femenino , Hipocampo/efectos de los fármacos , Humanos , Luz , Masculino , Persona de Mediana Edad , Bulbo Olfatorio/diagnóstico por imagen , Fototerapia/métodos , Tomografía de Emisión de Positrones/métodos , Radiofármacos/farmacocinética , Trastorno Afectivo Estacional/diagnóstico por imagen , Resultado del Tratamiento , Adulto JovenRESUMEN
It was hypothesized that an oscillation of tissue oxygen index (TOI) determined by near-infrared spectroscopy during recovery from exercise occurs due to feedback control of adenosine triphosphate and that frequency of the oscillation is affected by blood pH. In order to examine these hypotheses, we aimed 1) to determine whether there is an oscillation of TOI during recovery from exercise and 2) to determine the effect of blood pH on frequency of the oscillation of TOI. Three exercises were performed with exercise intensities of 30 % and 70 % peak oxygen uptake (V(.)o(2)peak) for 12 min and with exercise intensity of 70 % V(.)o(2)peak for 30 s. TOI during recovery from the exercise was analyzed by fast Fourier transform in order to obtain power spectra density (PSD). There was a significant difference in the frequency at which maximal PSD of TOI appeared (Fmax) between the exercises with 70 % V(.)o(2)peak for 12 min (0.0039+/-0 Hz) and for 30 s (0.0061+/-0.0028 Hz). However, there was no significant difference in Fmax between the exercises with 30 % (0.0043+/-0.0013 Hz) and with 70 % V(.)o(2)peak for 12 min despite differences in blood pH and blood lactate from the warmed fingertips. It is concluded that there was an oscillation in TOI during recovery from the three exercises. It was not clearly shown that there was an effect of blood pH on Fmax.
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Relojes Biológicos/fisiología , Ejercicio Físico/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Consumo de Oxígeno/fisiología , Adolescente , Análisis de los Gases de la Sangre/métodos , Prueba de Esfuerzo/métodos , Humanos , Masculino , Adulto JovenRESUMEN
The purpose of the present study was to examine how oscillation of tissue oxygen index (TOI) in non-exercising exercise is affected during high-intensity and low-intensity exercises. Three exercises were performed with exercise intensities of 30% and 70% peak oxygen uptake (Vo(2)peak) for 12 min and with exercise intensity of 70% Vo(2)peak for 30 s. TOI in non-exercising muscle (biceps brachii) during the exercises for 12 min was determined by nearinfrared spectroscopy. TOI in the non-exercising muscle during the exercises was analyzed by fast Fourier transform (FFT) to obtain power spectra density (PSD). The frequency at which maximal PSD appeared (Fmax) during the exercise with 70% Vo(2)peak for 12 min (0.00477 ± 0.00172 Hz) was significantly lower than that during the exercise with 30% Vo2peak for 12 min (0.00781 ± 0.00338 Hz). There were significant differences in blood pH and blood lactate between the exercise with 70% Vo(2)peak and the exercise with 30% Vo(2)peak. It is concluded that TOI in nonexercising muscle oscillates during low-intensity exercise as well as during high-intensity exercise and that the difference in Fmax between the two exercises is associated with the difference in increase in blood lactate derived from the exercise.
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Ejercicio Físico , Contracción Muscular , Músculo Esquelético/metabolismo , Consumo de Oxígeno , Oxígeno/sangre , Biomarcadores/sangre , Humanos , Concentración de Iones de Hidrógeno , Cinética , Ácido Láctico/sangre , Masculino , Oscilometría , Espectroscopía Infrarroja por Transformada de Fourier , Espectroscopía Infrarroja Corta , Adulto JovenRESUMEN
The purpose of this study was to determine whether tissue oxygen indices (TOIs) in two muscle groups oscillated and were synchronized in repetition of impulse exercise with high intensity. Five impulse exercises of 400 watts for 10 s were repeated with intervals of 6 min. During this period, TOI was determined by near-infrared spectroscopy in the vastus lateralis and gastrocnemius muscles. TOIs in the two muscles oscillated at rest. The TOIs rapidly decreased during each impulse exercise and then recovered and overshot after each impulse. The TOIs oscillated during each interval period. During this test period, coherent and phase differences were determined. There was high coherence between TOIs in the two muscles with a peak value at 0.019 Hz. There was a phase difference of -45 ± 32.4 degrees between TOIs in the two muscles. This phase difference corresponded to about 6 s in time scale. It seemed from this time delay that impulse exercise was not a trigger factor for the starting point of TOIs in the two muscles. It has been concluded that TOIs oscillate and are synchronized between two muscles in repetition of impulse exercise with high intensity.
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Ejercicio Físico , Contracción Muscular , Consumo de Oxígeno , Oxígeno/metabolismo , Músculo Cuádriceps/metabolismo , Adulto , Ciclismo , Prueba de Esfuerzo , Humanos , Masculino , Espectroscopía Infrarroja Corta , Factores de Tiempo , Adulto JovenRESUMEN
The aim of this study was to investigate the effects of heat exposure in the absence of hyperthermia on power output during repeated cycling sprints. Seven males performed four 10-s cycling sprints interspersed by 30 s of active recovery on a cycle ergometer in hot-dry and thermoneutral environments. Changes in rectal temperature were similar under the two ambient conditions. The mean 2-s power output over the 1st-4th sprints was significantly lower under the hot-dry condition than under the thermoneutral condition. The amplitude of the electromyogram was lower under the hot-dry condition than under the thermoneutral condition during the early phase (0-3 s) of each cycling sprint. No significant difference was observed for blood lactate concentration between the two ambient conditions. Power output at the onset of a cycling sprint during repeated cycling sprints is decreased due to heat exposure in the absence of hyperthermia.
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AIM: The purpose of this study was to examine whether the muscle pump in the supine position is attenuated during light prolonged exercise. METHODS: After rest for 5 min, constant-load exercise with 50% of peak oxygen uptake (VO2) determined by incremental exercises in the supine position was performed for 60 min with a pedaling rate of 60 rpm. Total hemoglobin and myoglobin (total Hb) in the vastus lateralis was determined by using a near-infrared spectroscopy (NIRS) system. The instrument was operating at 2 Hz. VO2, heart rate (HR), mean blood pressure (MBP) and muscle deep temperature (Tm) were measured in the constant-load exercise. RESULTS: After an increase at the onset of exercise, VO2 showed a steady state, HR showed a significant gradual increase and MBP significantly decreased. After an increase until 20 min of exercise, Tm showed a steady state. Level of total Hb increased until 20 min and showed a steady state in all subjects. Average Tm was significantly related to average total Hb (r=0.978). Total Hb oscillated, but its oscillation occasionally disappeared. Peak amplitude of oscillation in total Hb for 30 s after the start of exercise was significantly higher than that for 1 min before the end of exercise. CONCLUSION: The results suggest that the muscle pump operates in light exercise but is attenuated in the vastus lateralis in the supine position at the late phase of prolonged exercise.