Respiratory sinus arrhythmia,shyness, and effortful control in preschool-age children

Resting respiratory sinus arrhythmia (RSA) and shyness were examined as predictors of effortful control (EC) in a sample of 101 preschool-age children. Resting RSA was calculated from respiration and heart rate data collected during a neutral film; shyness was measured using parents’, preschool teachers’, and classroom observers’ reports; and EC was measured using four laboratory tasks in addition to questionnaire measures. Principal components analysis was used to create composite measures of EC and shyness. The relation between RSA and EC was moderated by shyness, such that RSA was positively related to EC only for children high in shyness. This interaction suggests that emotional reactivity affects the degree to which RSA can be considered a correlate of EC. This study also draws attention to the need to consider the measurement context when assessing resting psychophysiology measures; shy individuals may not exhibit true baseline RSA responding in an unfamiliar laboratory setting.     

Functional Expression of the Human Receptor for Colony-Stimulating Factor 1 (CSF-1) in Hamster Fibroblasts: CSF-1 Stimulates Na+/H+ exchange and DNA-Synthesis in the Absence of Phosphoinositide Breakdown

Abstract

The human CSF-1 receptor (c-fms protooncogene product) was introduced into CSF-1 -unresponsive Chinese hamster lung fibroblasts (CCL39 cell line) in order to study its coupling to biochemical signal-transducing systems and to compare the growth-regulating properties of CSF-1 to those of other growth factors. Independent clones expressing different levels of CSF-1 receptors were isolated and characterized. CSF-1 increased pH|thymidine incorporation in serum-starved cells and potentiated the mitogenic effects of FGF and thrombin. As already observed for other growth factors activating receptor tyrosine kinases (EGF, FGF, 1GF-I), CSF-1 alone did not trigger inositol phosphate formation, but slightly enhanced the activity of phospholipase C agonists (thrombin, AIF₄- complex). Activation of the CSF-1 receptor by its ligand was evidenced by the rapid activation of the Na⁺/H⁺ exchanger resulting in amiloride-sensitive cytoplasmic alkalinization (0.1-0.2 pH units) within minutes after stimulation. Whereas pertussis toxin does not affect the action of EGF, FGF, or IGF-I in CCL39 cells, it partially inhibited both DNA synthesis reinitiation and activation of Na⁺/H⁺ exchange by CSF-1, indicating that the CSF-1 receptor can communicate with a signal-transducing GTP binding protein. A point-mutated form of the c-fms gene product, in which Tyr 969, a residue negatively modulating signal transduction, had been replaced with Phe [fms (F969)], did not generate responses significantly different from those obtained with the wild-type c-fms gene product. In the absence of CSF-1, cells expressing either wild-type or fms (F969) showed a considerably higher basal level of thymidine incorporation and decreased anchorage dependence compared with parental CCL39 cells. Monoclonal antibodies that interfere with signal transduction by the human CSF-1 receptor inhibited both basal [³H] thymidine incorporation and soft agar colony formation, indicating that relaxation of growth control was dependent on CSF-1 receptor expression.     

Outbreak of Mycoplasma pneumoniae at a military academy

In 2019,an outbreak of Mycoplasma pneumoniae (M.pneumoniae) occurred at a military academy in China.The attack rate (10.08％,60/595) was significantly different among the units.High-intensity training and crowded environments to which cadets are exposed are the high risk factors for the outbreak of M.pneumoniae.In-time prevention and control measures effectively controlled the spread of the epidemic.     

Athletes with an ACL reconstruction show a different neuromuscular response to environmental challenges compared to uninjured athletes

BackgroundEvidence suggests that neuromuscular alterations in patients with an anterior cruciate ligament reconstruction (ACLR) are rooted in neurocognitive and proprioceptive deficits. The aim of this study was to assess neuromuscular control of athletes with ACLR under increased cognitive and environmental challenges.Research questionDo athletes with ACLR show a different neuromuscular response to cognitive and environmental challenges relative to controls?MethodsCross-sectional study. Twenty athletes who had an ACLR (age: 23.7 ± 4.3 years, 14 males, time post-surgery: 258.6 ± 54 days) and twenty uninjured controls (age: 21.4 ± 1.5 years, 14 males) performed a stepping down-task in four environmental conditions: no additional challenges, while performing a cognitive dual-task, while undergoing an unpredictable support surface perturbation, and with the cognitive dual-task and unpredictable perturbation combined. Muscle activations of the vastus medialis (VM), vastus lateralis, hamstrings medialis (HM), hamstrings lateralis (HL), gastrocnemius medialis, gastrocnemius lateralis (GL) and gluteus medius were recorded with surface EMG. A three-way ANOVA with main effects for group, dual-task and perturbation was used to compare muscle activations.ResultsAthletes with ACLR show larger HM (ES = 0.45) and HL activation (ES = 1.32) and lower VM activation (ES = 0.72), compared to controls.Athletes with ACLR show a significantly smaller increase in VM (ES = 0.69), VL (ES = 0.53) and GL activation (ES = 0.52) between perturbed and unperturbed tasks compared to controls. Furthermore, under cognitive loading a significantly larger decrease in HM activation (ES = 0.40) and (medial) co-contraction (ES = 0.75) was found in athletes with ACLR compared to controls.SignificanceAthletes with ACLR show an altered neuromuscular response which might represent an arthrogenic muscle response. They show less additional adaptation to perturbed tasks compared to controls, potentially as result of altered proprioceptive input. Furthermore a larger influence of increased cognitive loading on the neuromuscular control was found in athletes with ACLR, indicating that also neurocognitive limitations may contribute to altered neuromuscular control.     

Advanced characterization of static postural control dysfunction in persons with multiple sclerosis and associated neural mechanisms

BackgroundMultiple sclerosis (MS) is an autoimmune-based chronic inflammatory disease characterized by the neurodegeneration of the central nervous system and produces postural dysfunction. Quiet or static standing is a complex task carried out through afferent sensory inputs and efferent postural corrective outputs. Currently the mechanisms underlying these outputs remain largely unknown.Research questionAssess the relationship between multi-dimensional measures of postural control and microstructural integrity of the cortical sensorimotor pathway (CSP) in persons with MS (PwMS) and neurotypical adults.MethodsPostural control performance was assessed by both overall and directional time-to-boundary measures across four manipulated sensory stance conditions (eyes open/closed; stance firm/foam) in twenty-nine neurotypical and twenty-seven PwMS. These postural outcomes were evaluated with mixed-model repeated measures analysis of variance across group (MS and control) and stance condition. Postural performance was also correlated with magnetic resonance imaging diffusion tensor-derived measures of microstructural integrity of the CSP.ResultsPwMS displayed significantly (p = 0.026) worse anterior-posterior postural control compared to their neurotypical counterparts across sensory testing conditions and poorer CSP microstructural integrity in comparison to neurotypical adults (p = 0.008). Additionally, PwMS displayed a significant association (2D (rho = -0.384, p = 0.048), AP (rho = -0.355, p = 0.035), and ML (rho = -0.365, p = 0.030) between integrity of the CSP and postural control performance during proprioceptive-based balance, such that those with worse cortical structure had poorer balance control.SignificanceThis is the first study to establish connections between the microstructural integrity of the CSP and multi-dimensional postural control performance. Results indicate that a reduction in the CSP microstructural integrity is associated with poorer postural control in PwMS. These outcomes identify neural underpinnings of postural control dysfunction in PwMS and provide new avenues for evaluating the efficacy of postural rehabilitation strategies in PwMS that express proprioceptive-based postural deficits.     

Effects of simulated peripheral visual field loss on the static postural control in young healthy adults

BackgroundIntegration of visual, vestibular, and proprioceptive sensations contributes to postural control. People with peripheral visual field loss have serious postural instability. However, the directional specificity of postural stability and sensory reweighting caused by gradual peripheral visual field loss remain unclear.Research questionWhat are the effects of peripheral visual field loss on static postural control?MethodsFifteen healthy young adults participated in this study. The participants were asked to stand quietly on a foam surface. Three conditions of virtual visual field loss (90°, 45°, and 15°) were provided by a head-mounted display, and ground reaction forces were collected using a force plate to calculate the displacements of the center of pressure (COP).ResultsThe root mean square (RMS), mean velocity, and 95% ellipse area of COP displacements in the horizontal plane increased, and RMS in the anteroposterior (AP) direction was unchanged under the smallest visual field condition compared to the largest one. The power spectrum density of COP displacements in the low-frequency band was decreased and that in the medium-frequency band was increased in the AP direction.SignificanceDuring quiet standing of young healthy adults with peripheral visual field loss, increased peripheral visual field loss resulted in lower postural stability. Postural stability in the AP direction was maintained contrary to the functional sensitivity hypothesis. Peripheral visual field loss reduced the weighting of the visual input and increased that of the vestibular input in the AP direction to maintain equilibrium.     

Effects of social anxiety on static and dynamic balance task assessment in older women

BackgroundSocial anxiety caused by the presence of an evaluator can impair balance performance in older women. However, it is unknown whether co-performing balance tasks with a partner mitigates this effect.Research questionDoes the presence of a partner mitigate the effect of social anxiety on static and dynamic balance assessment in older women?MethodsTwenty-one older women (mean age 66.5 (SD = 5.2) years) performed nine balance tasks under three conditions: (a) Alone (no evaluator present); (b) Evaluator (male evaluator present); (c) Partner (evaluator + performing tasks in parallel with partner). Participants were split into two groups post-hoc: Affected (n = 10) and Unaffected (n = 11), based on their emotional response to the presence of the evaluator (increased self-reported anxiety and fear).ResultsThe affected group took a longer time to complete tandem walking with eyes open in the Evaluator vs. Alone condition, but not in the Partner condition. Both groups increased anterior-posterior trunk angular velocity during tandem walking with eyes closed in the Evaluator vs. Alone condition, but not in the Partner condition.SignificanceSocial anxiety impairs the balance performance of older women, particularly in those most affected by the evaluator, and during more dynamic modified gait tasks that challenge balance while walking. However, co-performing balance tasks with a partner reduced the effects of social anxiety, suggesting that social support may help to mitigate some of the potential ‘white coat’ effects experienced during clinical balance assessments.     

Maturation of the postural control in adolescent girls: A 3-year follow-up study

BackgroundStable posture is a manifestation of the appropriate functioning of the neuromuscular system that is essential for proper motor development and control. Balance and stability of the erect posture are shaped during the entire childhood to culminate in its full efficiency in adolescent subjects.MethodsIn this 3-year follow-up study, the process of the postural control maturation has been assessed in a group of 18 girls at the transition period between childhood to adolescence. Their balance and postural stability control were assessed using standard static posturography supplemented by two postural stability tests: the rising-on-toes (ROT), and the maximum forward lean (MFL), all performed with (EO) and without vision (EC). Balance control was analyzed with the sway vector (SV) and sway directional indices, whereas the anteroposterior trajectories of the center-of- pressure (COP) during forward-leaning and the raise-on-toes tests were used to determine changes in postural stability control.ResultsThe study documented that stability control in girls aged 11–13 is shaped according to their own pace of development. Their postural sway was characterized by the lower COP velocity but very sensitive to visual input. The directional sway measures remained at the same level for the entire period of observation. MFL and ROT tests provided similar information on postural stability and its dependence on visual input. These tests allow for more thorough assessment of postural stability to compare with quiet stance testing.SignificanceSubtle changes in postural control in adolescents could be assessed based on the results of combined static and dynamic tests. In particular, the ROT test can be recommended for the assessment of postural stability.     

Cortical activity and gait parameter characteristics in people with multiple sclerosis during unobstructed gait and obstacle avoidance

BackgroundPeople with Multiple Sclerosis (PwMS) present higher cortical activity during walking. However, the cortical activity during gait while avoiding an obstacle is still not clear.ObjectiveTo investigate cortical activity and gait spatial-temporal parameters in PwMS during two different gait tasks (i.e., unobstructed and obstacle avoidance).MethodFifteen PwMS and 15 healthy controls (CG) were recruited. Participants performed ten trials in each gait condition, wearing a 64-electrode cap electroencephalogram (EEG) at 1024 Hz. Kinematic data were obtained through 10 Vicon® cameras at 200 Hz. EEG was analyzed through four cortical areas (frontal, motor, parietal, and occipital cortex areas) and five frequency bands (delta, theta, alpha, beta, and gamma) obtained through the power spectral density. In addition, spatial-temporal gait parameters (e.g., step length and velocity) were measured. Two-way ANOVA (group x gait condition) and MANOVA (group x gait condition) were used to compare gait and EEG parameters, respectively. One-way ANOVA was used to compare groups in the crossing phase of the obstacle avoidance condition.ResultsPwMS presented lower step length and velocity, and higher cortical activity in frontal (beta and gamma) and parietal (gamma) cortical areas in both gait conditions compared to CG. Moreover, PwMS presented increased cortical activation (frontal and parietal) and decreased step length and velocity in obstacle avoidance compared with unobstructed gait. In addition, PwMS required more cortical resources (frontal and parietal) than CG to accomplish both gait conditions. During the obstacle avoidance task, it was further observed that PwMS positioned their feet closer to the obstacle, before and after the task, compared to CG.ConclusionPwMS demand higher cortical resources to accomplish gait tasks, mainly when it is necessary to negotiate an obstacle in the pathway. This higher cortical activity may be a compensatory mechanism to deal with damage in subcortical structures caused by multiple sclerosis.     

The feasibility and efficacy of a serial reaction time task that measures motor learning of anticipatory stepping

BackgroundMotor learning has been investigated using various paradigms, including serial reaction time tasks (SRTT) that examine upper extremity reaching and pointing while seated. Few studies have used a stepping SRTT, which could offer additional insights into motor learning involving postural demands. For a task to measure motor learning, naïve participants must demonstrate a) improved performance with task practice, and b) a dose-response relationship to learning the task.Research questionIs a stepping SRTT feasible and efficacious for measuring motor learning?MethodsIn this prospective study, 20 participants stood on an instrumented mat and were presented with stimuli on a computer screen. They stepped to the corresponding positions on the mat as quickly as possible. Presented stimuli included random sequences and a blinded imbedded repeating sequence. Three days after completing the randomly assigned practice dose [high dose group (n = 10) performed 4320 steps; low dose group (n = 10) performed 144 steps], a retention test of 72 steps was performed. Feasibility was measured as the proportion of participants who completed the assigned practice dose without adverse events. Efficacy was measured as within-group performance improvement on the random sequences and on the repeating sequence (paired t-tests), as well as a dose-response relationship to learning both types of sequences (independent t-tests).ResultsAll participants (mean age 26.8 years) completed all practice sessions without adverse events, indicating feasibility. High dose practice resulted in performance improvement while low dose did not; a dose-response relationship was found, with high dose practice resulting in greater learning of the task than low dose practice, indicating efficacy.SignificanceThis stepping SRTT is a feasible and efficacious way to measure motor learning, which could provide critical insights into anticipatory stepping, postural control, and fall risk. Future research is needed to determine feasibility, efficacy, and optimal practice dosages for older and impaired populations.