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The liver acts as a master regulator of metabolic homeostasis in part by performing gluconeogenesis. This process is dysregulated in type 2 diabetes, leading to elevated hepatic glucose output. The parenchymal cells of the liver (hepatocytes) are heterogeneous, existing on an axis between the portal triad and the central vein, and perform distinct functions depending on location in the lobule. Here, using single cell analysis of hepatocytes across the liver lobule, we demonstrate that gluconeogenic gene expression ( Pck1 and G6pc ) is relatively low in the fed state and gradually increases first in the periportal hepatocytes during the initial fasting period. As the time of fasting progresses, pericentral hepatocyte gluconeogenic gene expression increases, and following entry into the starvation state, the pericentral hepatocytes show similar gluconeogenic gene expression to the periportal hepatocytes. Similarly, pyruvate-dependent gluconeogenic activity is approximately 10-fold higher in the periportal hepatocytes during the initial fasting state but only 1.5-fold higher in the starvation state. In parallel, starvation suppresses canonical beta-catenin signaling and modulates expression of pericentral and periportal glutamine synthetase and glutaminase, resulting in an enhanced pericentral glutamine-dependent gluconeogenesis. These findings demonstrate that hepatocyte gluconeogenic gene expression and gluconeogenic activity are highly spatially and temporally plastic across the liver lobule, underscoring the critical importance of using well-defined feeding and fasting conditions to define the basis of hepatic insulin resistance and glucose production.
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Background and Aims: The visceral organ-brain axis, mediated by vagal sensory neurons in the vagal nerve ganglion, is essential for maintaining various physiological functions. In this study, we investigated the impact of liver-projecting vagal sensory neurons on energy balance, hepatic steatosis, and anxiety-like behavior in mice under obesogenic conditions. Methods: We performed single-nucleus RNA sequencing of vagal sensory neurons innervating the liver. Based on our snRNA-Seq results, we used the Avil CreERT2 strain to identify vagal sensory neurons that innervate the liver. Results: A small subset of polymodal sensory neurons innervating the liver was located in the left and right ganglia, projecting centrally to the nucleus of the tractus solitarius, area postrema, and dorsal motor nucleus of the vagus, and peripherally to the periportal areas in the liver. Male and female control mice developed diet-induced obesity (DIO) during high-fat diet feeding. Deleting liver-projecting advillin-positive vagal sensory neurons prevented DIO in male and female mice, and these outcomes are associated with increased energy expenditure. Although males and females exhibited improved glucose homeostasis following disruption of liver-projecting vagal sensory neurons, only male mice displayed increased insulin sensitivity. The loss of liver-projecting vagal sensory neurons limited the progression of hepatic steatosis in male and female mice fed a steatogenic diet. Finally, mice lacking liver-innervating vagal sensory neurons exhibited less anxiety-like behavior compared to the control mice. Conclusions: The liver-brain axis contributes to the regulation of energy balance, glucose tolerance, hepatic steatosis, and anxiety-like behavior depending on the nutrient status in healthy and obesogenic conditions.
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Hepatic lipid metabolism is regulated by the autonomic nervous system of the liver, with the sympathetic innervation being extensively studied, while the parasympathetic efferent innervation is less understood despite its potential importance. In this study, we investigate the consequences of disrupted brain-liver communication on hepatic lipid metabolism in mice exposed to obesogenic conditions. We found that a subset of hepatocytes and the bile duct are innervated by parasympathetic nerves originating from the dorsal motor nucleus of the vagus. The elimination of the brain-liver axis by deleting parasympathetic cholinergic neurons innervating the liver prevents hepatic steatosis and promots browning of inguinal white adipose tissue (ingWAT). The loss of the brain-liver axis also raises hepatic Cyp7b1 expression and fasting serum bile acid levels. Furthermore, knockdown of the G protein-coupled bile acid receptor 1 gene in ingWAT reverses the beneficial effects of the loss of the brain-liver axis, leading to the reappearance of hepatic steatosis in the experimental groups. However, deleting the brain-liver axis has a small but significant effect on body weight, which is accompanied by an increase in energy expenditure. Therefore, altering parasympathetic cholinergic innervation of the liver could offer a potential therapeutic approach for enhancing hepatic lipid metabolism in obesity and diabetes.
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Semaglutide is a well-designed drug with a special coating that allows for oral administration to patients with type 2 diabetes mellitus. However, patients taking oral semaglutide complain of its bitter taste. We therefore considered suggesting that patients take oral semaglutide with hot water. When the hot water temperature was increased to above 46.0°C but below 52.0°C, no bitter taste was perceived, with the daily mean interstitial glucose level remaining at the target range. Taking oral semaglutide with hot water helps reduce its bitter taste.
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Diabetes Mellitus Tipo 2 , Peptídeos Semelhantes ao Glucagon , Temperatura Alta , Humanos , Peptídeos Semelhantes ao Glucagon/administração & dosagem , Administração Oral , Diabetes Mellitus Tipo 2/tratamento farmacológico , Masculino , Feminino , Idoso , Pessoa de Meia-Idade , Temperatura Alta/efeitos adversos , Água , Hipoglicemiantes/administração & dosagem , Paladar/efeitos dos fármacosRESUMO
Imeglimin has not been well studied as an oral agent for the treatment of latent autoimmune diabetes of adults (LADA). We treated 2 cases of LADA with imeglimin. The case 1 patient was originally diagnosed with type 2 diabetes (T2D) at age 50 years and was treated with sulfonylurea, biguanide, canagliflozin, imeglimin, and dulaglutide. Before imeglimin, his glycated hemoglobin A1c (HbA1c) change was 94.0â mmol/mol (8.6%) in November 2022, but it dropped to 71.0â mmol/mol (6.5%) in May 2023 after imeglimin was added. The case 2 patient was originally diagnosed with T2D when she was aged 48 years. She was treated with vildagliptin, biguanide, luseogliflozin, and imeglimin. Her HbA1c before imeglimin was 92.9â mmol/mol (8.5%) in January 2023, which decreased to 75.4 mmol/mol (6.9%) in July 2023 after imeglimin was added. Although imeglimin has not been approved for treating type 1 diabetes and LADA, adding imeglimin to the current medication was effective in improving and controlling the patients' plasma glucose.
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BACKGROUND: Atrial anti-tachycardia pacing (aATP) has been shown to be effective for the termination of atrial tachyarrhythmias, but its success rate is still not high enough. OBJECTIVE: The main objective of this study was to investigate the mechanisms of atrial flutter (AFL) termination by aATP and the transition from AFL to atrial fibrillation (AF) during aATP. METHODS: We developed a multi-scale model of the human atrium based on magnetic resonance images and examined the atrial electrophysiology of AFL during aATP with a ramp protocol. RESULTS: In successful cases of aATP, paced excitation entered the excitable gap and collided with the leading edge of the reentrant wave front. Furthermore, the excitation propagating in the opposite direction collided with the trailing edge of the reentrant wave to terminate AFL. The second collision was made possible by the distribution of the wave propagation velocity in the atria. The detailed analysis revealed that the slowing of propagation velocity occurred at the exit of the sub-Eustachian isthmus, probably due to source-sink mismatch. During the transition from AFL to AF, the excitation collided with the refractory zone of the preceding wave and broke into multiple wave fronts to induce AF. A similar observation was made for the transition from AF to sinus rhythm. In both cases, the complex anatomy of the atria played an essential role. CONCLUSION: The complex anatomy of atria plays an essential role in the maintenance of stable AFL and its termination by aATP, which were revealed by the realistic three-dimensional simulation model.
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Fibrilação Atrial , Flutter Atrial , Humanos , Flutter Atrial/terapia , Fibrilação Atrial/terapia , Estimulação Cardíaca Artificial , Taquicardia/terapia , Átrios do CoraçãoRESUMO
BACKGROUND: Current implantable cardioverter defibrillators (ICDs) require electric conduction with high voltage and high energy, which can impair cardiac function and induce another malignant arrhythmia. As a result, there has been a demand for an ICD that can effectively operate with lower energy to mitigate the risks of a strong electric shock. METHODS: A pair of sheet-shaped electrodes covering the heart were analyzed in three configurations (top-bottom, left-right, and front-back) using a heart simulator. We also varied the distance between the two electrodes (clearance) to identify the electrode shape with the lowest defibrillation threshold (DFT). We also investigated the ICD shock waveform, shock direction, and the effect of the backside insulator of the electrode. RESULTS: The DFT was high when the clearance was too small and the DFT was high even when the clearance was too large, suggesting that an optimal value clearance. The top-bottom electrodes with optimal clearance showed the lowest DFT when the biphasic shocks set the top electrode to a high potential first and then the bottom electrode was set to a high potential. An interval between a first shock waveform and a second shock waveform should be provided for low-energy defibrillation. Because the insulator prevents unnecessary current flow to the backside, the DFT of the electrodes with insulators is less than those without insulators. CONCLUSION: Painless defibrillation using sheet-shaped electrodes on the epicardium is predicated on the basis of results using a heart simulator.
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Desfibriladores Implantáveis , Cardioversão Elétrica , Humanos , Cardioversão Elétrica/métodos , Fibrilação Ventricular , PericárdioRESUMO
The purpose of this study was to determine the differences in muscle synergy between skilled and unskilled participants using various loading conditions for power clean. Nineteen participants (ten skilled and nine unskilled) performed power clean at 60-90% one repetition maximum (1RM), while measured 12 muscles across the entire body. The vertical impulse was calculated for the unweighting associated with the double-knee bend (DKB) manoeuvre in power clean. Muscle synergies were extracted using non-negative matrix factorization. The weighting of muscle synergies was subsequently compared between the two groups for all loads, and confidence intervals were calculated. The number of muscle synergies in both groups was three, and the functions of all muscle synergies were similar. Muscle synergy 1 involved the first pull, muscle synergy 2 involved the transition and the second pull, and muscle synergy 3 involved DKB. No significant difference in either muscle synergy was observed at 60-80% 1RM weight, while the 90% 1RM showed significantly active in the ankle plantar flexor and knee extensor muscles for muscle synergy 3, which involved DKB only in the skilled group. This indicates that increased joint stiffness during DKB may minimize unweighting. Unskilled individuals may acquire such muscle synergies to lift greater weights.
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Joelho , Músculo Esquelético , Humanos , Músculo Esquelético/fisiologia , Extremidade Inferior/fisiologia , Articulação do Joelho/fisiologia , AtletasRESUMO
AIMS: Sodium load increases endogenous glucagon-like peptide-1 (GLP-1) levels in humans. Therefore, patients with an increased amount of dietary sodium intake are supposed to have higher endogenous GLP-1 levels compared to those with less dietary sodium intake. Therefore, it can be hypothesized that patients with type 2 diabetes mellitus (T2DM) with more dietary sodium intake show better dipeptidyl peptidase-4 inhibitor (DPP-4i) effect on glycemic control because of the expected higher GLP-1 level. Thus, we performed a single-center cohort study to explore this idea. METHODS: Medical records of patients with T2DM prescribed DPP-4i in the last 11 years were investigated. Dietary sodium intake was measured before the DPP-4i prescription with Tanaka's formula using casual spot urine samples. The effect of DPP-4i on glycemic control was estimated by the subtraction of glycated hemoglobin (HbA1c) before DPP-4i initiation from HbA1c 1 year after DPP-4i administration. We analyzed 50 patients. RESULTS: DPP-4i improved HbA1c by -0.41% ± 0.66%. The effect of DPP-4i on glycemic control was significantly negatively correlated with the dietary sodium intake (r = -0.400). Thus, the more dietary sodium intake, the better the glycemic control by DPP-4i. CONCLUSIONS: Thus, patients can expect better plasma glucose control by DPP-4is if patients are taking increased dietary sodium intake.
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Diabetes Mellitus Tipo 2 , Inibidores da Dipeptidil Peptidase IV , Sódio na Dieta , Humanos , Inibidores da Dipeptidil Peptidase IV/uso terapêutico , Inibidores da Dipeptidil Peptidase IV/farmacologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Hemoglobinas Glicadas , Estudos de Coortes , Hipoglicemiantes , Peptídeo 1 Semelhante ao Glucagon , Dipeptidil Peptidases e Tripeptidil PeptidasesRESUMO
ABSTRACT: Nishioka, T and Okada, J. Ballistic exercise versus heavy resistance exercise protocols: which resistance priming is more effective for improving neuromuscular performance on the following day? J Strength Cond Res 37(10): 1939-1946, 2023-This study aimed to determine whether ballistic exercise priming (BEP) or heavy resistance priming (HRP) is more effective for improving ballistic performance after 24 hours. Ten resistance-trained men performed BEP and HRP conditions 72-144 hours apart in a randomized and counterbalanced order. Jumping performance was assessed before and 24 hours after the BEP and HRP sessions using 0 and 40% one-repetition maximum (1RM) squat jump (SJ), 0 and 40% 1RM countermovement jump (CMJ), and drop jump (DJ) reactive strength index (RSI). Statistical significance was accepted at p ≤ 0.05. In the BEP condition, 0% 1RM CMJ height (+3.62%) as well as theoretical maximum velocity (+5.14%) and theoretical maximum power (+2.55%) obtained from CMJ 24 hours after the priming session were significantly greater than those at the baseline ( p ≤ 0.05), but 0% 1RM SJ height and DJ RSI ( p > 0.05) were not greater than those at the baseline. In the HRP condition, the jump performances were not improved ( p > 0.05). The percentage change in 0% 1RM CMJ height in the BEP condition was significantly greater than that seen in the HRP condition ( p = 0.015) but did not differ for 0% 1RM SJ height and DJ RSI ( p > 0.05). These results suggest that the BEP is more effective than HRP in improving CMJ performance after 24 hours. Therefore, practitioners should consider prescribing resistance priming using low-load ballistic exercises rather than high-load traditional exercises when planning to enhance athlete performance on the following day.
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Desempenho Atlético , Treinamento Resistido , Masculino , Humanos , Treinamento Resistido/métodos , Força Muscular , Exercício Físico , PosturaRESUMO
The rating of perceived exertion (RPE) scale has been found to reflect physiological responses, and this study aimed to assess the validity of using the Borg CR-10 scale and velocity loss to evaluate muscle fatigue quantified by surface electromyography during back squat (BS) exercise. A total of 15 collegiate male athletes underwent three non-explosive BS tasks comprising low, medium, and high volumes at 65% of their one-repetition maximum. RPEs, spectral fatigue index (SFI), and velocity loss during BS exercise were assessed throughout the trials. Significant differences in overall RPE (p < 0.001) and average SFI (p < 0.05) were observed between the conditions, whereas no significant difference was observed in average velocity loss. Significant increases in RPE and SFI (p < 0.001) were observed within the exercise process, whereas a significant increase in velocity loss was not observed. Correlation analyses indicated a significant correlation between RPE and SFI obtained during exercise (r = 0.573, p < 0.001). However, no significant correlation was observed between velocity loss and SFI. These results demonstrated that RPE could be used as a muscle fatigue predictor in BS exercise, but that velocity loss may not reflect muscle fatigue correctly when participants cannot and/or are not required to perform BS explosively. Furthermore, practitioners should not use velocity loss as a muscle fatigue indicator in some resistance exercise situations, such as rehabilitation, beginner, and hypertrophy programs.
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BACKGROUND AND AIMS: Triiodothyronine reduces sodium glucose cotransporter 2 expression in the kidney and increased glucose excretion in urine of alloxan-induced diabetic rats. Free thyroxine is also negatively associated with islet beta-cell function in euthyroid subjects. However, the influence of sodium glucose cotransporter 2 inhibitor on thyroid function in patients with type 2 diabetes mellitus has not been established. METHODS: We investigated thyroid function in patients with type 2 diabetes mellitus in the presence or absence of sodium glucose cotransporter 2 inhibitor in a multicenter retrospective study conducted between 2019 and 2021. All participants visited the hospital monthly for type 2 diabetes mellitus treatment and plasma glucose and glycated hemoglobin level measurements. Furthermore, thyroid-stimulating hormone, free triiodothyronine, and free thyroxine levels were measured annually. RESULTS: Free triiodothyronine level and the free triiodothyronine:free thyroxine ratio in the group treated with sodium glucose cotransporter 2 inhibitor were significantly higher than the levels in the group not treated with sodium glucose cotransporter 2 inhibitor. Free triiodothyronine levels in the group treated with sodium glucose cotransporter 2 inhibitor were significantly higher than the levels in the group not treated with sodium glucose cotransporter 2 inhibitor (p = 0.040). Free thyroxine levels in the group treated with sodium glucose cotransporter 2 inhibitor were significantly lower than the levels in the group not treated with sodium glucose cotransporter 2 inhibitor (p = 0.002). Thyroid-stimulating hormone levels did not differ significantly between the two groups. CONCLUSIONS: Our findings show that sodium glucose cotransporter 2 inhibitor affects free triiodothyronine levels free thyroxine levels, and the free triiodothyronine:free thyroxine ratio.
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Diabetes Mellitus Experimental , Diabetes Mellitus Tipo 2 , Inibidores do Transportador 2 de Sódio-Glicose , Estudos Retrospectivos , Tireotropina , Tiroxina , Tri-Iodotironina , HumanosRESUMO
Understanding the properties associated with the vertical force-velocity (F-v) profiles is important for maximizing jump performance. The purpose of this study was to evaluate the associations of maximum and reactive strength indicators with the F-v profiles obtained from squat jump (SJ) and countermovement jump (CMJ). On the first day, 20 resistance-trained men underwent measurements for half squat (HSQ) one-repetition maximum (1RM). On the second day, jump performances were measured to calculate the drop jump (DJ) reactive strength index (RSI) and the parameters of F-v profiles (theoretical maximum force [F0], velocity [V0], power [Pmax], and slope of the linear F-v relationship [SFv]) obtained from SJ and CMJ. The DJ RSI was not significantly correlated with any parameter of the vertical F-v profiles, whereas the relative HSQ 1RM was significantly correlated with the SJ F0 (r = 0.508, p = 0.022), CMJ F0 (r = 0.499, p = 0.025), SJ SFv (r = -0.457, p = 0.043), and CMJ Pmax (r = 0.493, p = 0.027). These results suggest that maximum strength is a more important indicator than reactive strength in improving vertical F-v profiles. Furthermore, the importance of maximum strength may vary depending on whether the practitioner wants to maximize the performance of SJ or CMJ.
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Desempenho Atlético , Força Muscular , Masculino , Humanos , Postura , Músculo EsqueléticoRESUMO
BACKGROUND: Previously, AF-956, which contains S356 of FAM83G and an N-terminal antenna peptide for entry into colon cancer cells, is markedly antiproliferative compared to a control peptide (AF-859), which lacks the N-terminal antenna peptide, by inducing apoptosis via the inhibition of HSP27 phosphorylation at residues S15 and S82. OBJECTIVE: Because FAM83G-derived peptides are promising lead compounds for colon cancer treatment, we reanalyzed the effect of AG-066, which contains S356 of FAM83G and an N-terminal antenna peptide for entry into the liver cancer cells. METHODS: HepG2 liver cancer cells were incubated with either AF-859 or AG-066 at a concentration of 54 µM at 37 °C for 24, 48, and 72 h. The effects of AF-859 and AG-066 on the cultured HepG2 cells were estimated using an inverted light microscope. Furthermore, the DNA ladder method and the dead cell assay were performed by applying Live/Dead Cell Staining Kit II. Erk phosphorylation was estimated by western blotting. RESULTS: Treatment with AG-066 markedly reduced HepG2 viable cell counts compared to the AF- 859-treated HepG2 cells, as evident from the significantly increased number of dead cells in the culture medium. Additionally, AG-066 treatment increased cellular DNA laddering. We found no difference in Erk phosphorylation status between the AG-066- and AF-859-treated groups. CONCLUSION: This study illustrated that the peptide with a structure based on FAM83G functions as a spontaneous apoptosis inducer for liver cancer cells. Hence, it is a promising lead compound for the treatment of liver cancer.
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Carcinoma Hepatocelular , Neoplasias do Colo , Neoplasias Hepáticas , Humanos , Neoplasias Hepáticas/tratamento farmacológico , Apoptose , Células Hep G2 , Peptídeos/farmacologia , Proliferação de CélulasRESUMO
Changes in intracellular calcium concentrations regulate heart beats. However, the decline in the left ventricular pressure during early diastole is much sharper than that of the Ca2+ transient, resulting in a rapid supply of blood to the left ventricle during the diastole. At the tissue level, cardiac muscles have a distinct characteristic, known as stretch activation, similar to the function of insect flight muscles. Stretch activation, which is a delayed increase in force following a rapid muscle length increase, has been thought to be related to autonomous control in these muscles. In this numerical simulation study, we introduced a molecular mechanism of stretch activation and investigated the role of this mechanism in the pumping function of the heart, using the previously developed coupling multiple-step active stiffness integration scheme for a Monte Carlo (MC) cross-bridge model and a bi-ventricular finite element model. In the MC cross-bridge model, we introduced a mechanism for trapping the myosin molecule in its post-power stroke state. We then determined the rate constants of transitions for trapping and escaping in a thermodynamically consistent manner. Based on our numerical analysis, we draw the following conclusions regarding the stretch activation mechanism: (i) the delayed force becomes larger than the original isometric force because the population of trapped myosin molecules and their average force increase after stretching; (ii) the delayed force has a duration of more than a few seconds owing to a fairly small rate constant of escape from the trapped state. For the role of stretch activation in heart pumping, we draw the following conclusions: (iii) for the regions in which the contraction force decreases earlier than the neighboring region in the end-systole phase, the trapped myosin molecules prevent further lengthening of the myocytes, which then prevents further shortening of neighboring myocytes; (iv) as a result, the contraction forces are sustained longer, resulting in a larger blood ejection, and their degeneration is synchronized.
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Muscle co-contraction between the agonist and antagonist muscles often causes low energy efficiency or movement disturbances. Surface electromyography biofeedback (sEMG-BF) has been used to train muscle activation or relaxation but it is unknown whether sEMG-BF reduces muscle co-contraction. We hypothesized that auditory sEMG-BF improves muscle co-contraction. Our purpose was to investigate whether auditory sEMG-BF is effective in improving muscle co-contraction. Thirteen participants pedaled on a road bike using four different auditory sEMG-BF conditions. We measured the surface electromyography at the lower limb muscles. The vastus lateralis (VL) and the semitendinosus (ST) activities were individually transformed into different beep sounds. Four feedback conditions were no-feedback, VL feedback, ST feedback, and both VL and ST feedback. We compared the co-contraction index (COI) of the knee extensor-flexor muscles and the hip flexor-extensor muscles among the conditions. There were no significant differences in COIs among the conditions (p = 0.83 for the COI of the knee extensor-flexor; p = 0.32 for the COI of the hip flexor-extensor). To improve the muscle co-contraction by sEMG-BF, it may be necessary to convert muscle activation into a muscle co-contraction. We concluded that individual sEMG-BF does not immediately improve muscle co-contraction during pedaling.
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Contração Muscular , Músculo Esquelético , Biorretroalimentação Psicológica , Eletromiografia , Humanos , Articulação do Joelho/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologiaRESUMO
To fully understand the health and pathology of the heart, it is necessary to integrate knowledge accumulated at molecular, cellular, tissue, and organ levels. However, it is difficult to comprehend the complex interactions occurring among the building blocks of biological systems across these scales. Recent advances in computational science supported by innovative high-performance computer hardware make it possible to develop a multiscale multiphysics model simulating the heart, in which the behavior of each cell model is controlled by molecular mechanisms and the cell models themselves are arranged to reproduce elaborate tissue structures. Such a simulator could be used as a tool not only in basic science but also in clinical settings. Here, we describe a multiscale multiphysics heart simulator, UT-Heart, which uses unique technologies to realize the abovementioned features. As examples of its applications, models for cardiac resynchronization therapy and surgery for congenital heart disease will be also shown.
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Coração , Simulação por Computador , Análise de Elementos Finitos , HumanosRESUMO
BACKGROUND: The rating of perceived exertion (RPE) is correlated with physiological variables. The purpose of this study was to assess the validity of using the Borg CR-10 scale and velocity to predict muscle fatigue assessed by surface electromyography during single joint resistance exercises. METHODS: Fifteen healthy males underwent different fatigue levels of unilateral elbow flexion (EF) and knee extension (KE), consisting of low, medium, and high volumes at 65% of their one-repetition maximum. The RPEs, spectral fatigue index (SFI), and mean velocity of the experimental exercises were assessed throughout the trials. RESULTS: Significant differences in overall RPE (p < 0.001) and average SFI (p < 0.001) were observed between the conditions in both exercises. Significant changes in RPE and SFI (p < 0.001) were observed throughout the EF, whereas a SFI increase (p < 0.001) was only observed at the end point of KE. Multiple regression analyses revealed two significant models (p < 0.001) for the prediction of muscle fatigue during EF (R2 = 0.552) and KE (R2 = 0.377). CONCLUSIONS: Muscle fatigue resulted in similar increases in perceptual responses, demonstrating that RPE is useful for assessing fatigue when resistance exercise is performed. However, velocity changes may not reflect muscle fatigue correctly when exercise is no longer performed in an explosive manner. We recommend combining RPE responses with velocity changes to comprehensively assess muscle fatigue during clinical and sports situations.
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Fadiga Muscular , Treinamento Resistido , Masculino , Humanos , Esforço Físico/fisiologia , Treinamento Resistido/métodos , Exercício Físico , Levantamento de Peso/fisiologiaRESUMO
ABSTRACT: Nishioka, T and Okada, J. Influence of strength level on performance enhancement using resistance priming. J Strength Cond Res 36(1): 37-46, 2022-The current study aimed to investigate (a) whether resistance priming was effective in enhancing jump performance for both stronger and weaker individuals and (b) how resistance priming influences the lower-body force-velocity profile. A total of 20 resistance-trained men performed priming and control conditions 72-144 hours apart in a randomized and counterbalanced order. Jump performances (0 and 40% 1 repetition maximum [1RM] squat jump, 0 and 40% 1RM countermovement jump [CMJ] and drop jump) were assessed before and 24 hours after the priming session, and before and 24 hours after rest (control). Priming session-induced percentage change in 0% 1RM CMJ height was positively correlated with the individual's relative half squat 1RM (r = 0.612, p ≤ 0.05). Using the median split method, subjects were divided into stronger (relative half squat 1RM = 1.93-2.67 kg·kg-1) and weaker (relative half squat 1RM = 1.37-1.92 kg·kg-1) groups and subsequently analyzed. The stronger group showed specific improvement in 0% 1RM CMJ performance 24 hours after the priming session (p ≤ 0.05), whereas the weaker group showed no improvement in any of their jump performances. Moreover, the priming session enhanced the theoretical maximum velocity (p ≤ 0.05), but not the theoretical maximum force during CMJ in the stronger group; whereas none of the force-velocity profile variables were enhanced in the weaker group. These results suggest that stronger individuals are more likely to experience performance enhancement using resistance priming, which may be movement- and velocity-specific.