Contraction Time Research Articles

Plank exercise improves respiratory capacity through positive changes in body composition, abdominis function, and autonomic nerves' activities

AbstractThis research aimed to explore the impact of plank exercise training (PET) on respiratory function, body composition, abdominis performance, and autonomic nervous system (ANS). Sixty‐one young adults participated and were divided into a control group (CG, n = 31) and an exercise group (EG, n = 30), wherein PET was administered 3 days per week for 12 weeks. After the experiment, the body composition of the CG deteriorated, whereas that of the EG improved (p < 0.001). The EG exhibited a reduction of ∼34% in the mean maximum displacement and a rise of ∼20% in the mean contraction time of the abdominis. The sit‐up in the EG demonstrated a significant increase of ∼55%. In the EG, there was a substantial increase in peak expiratory force by ∼24% and forced expiratory volume in 1 s by ∼14%, accompanied by a reduction in resting respiratory rate by ∼ −9%. When compared to the CG, these alterations were significant between the two groups (p = 0.001). In the EG, there was a significant decrease in resting heart rate by ∼2%, accompanied by a decrease in sympathetic nervous activity by ∼ −5% and by an increase in parasympathetic nervous activity by ∼5%. When compared to the CG, these alterations were significant between the two groups (p = 0.001). The findings of this study revealed that implementing PET in young adults, while controlling for dietary intake and physical activity, resulted in noteworthy changes in respiratory capacity. These changes were coupled with improvements in body composition, abdominal functions, and the ANS.

Subclinical central hypothyroidism in patients with hypothalamic-pituitary disease: does it exist?

Central hypothyroidism (CH) is characterized by decreased thyroid hormone production due to insufficient stimulation of an otherwise normal thyroid gland by TSH. In patients with established hypothalamic-pituitary disease, a low FT4 concentration is considered highly specific, although poorly sensitive, for the diagnosis of CH. That would be comparable to diagnosing primary hypothyroidism in patients at risk only when serum FT4 concentrations are below the reference range, missing all patients with subclinical primary hypothyroidism and preventing proper therapy in patients in which thyroxine replacement is clearly beneficial. Cardiac time intervals, especially the isovolumic contraction time (ICT), have been considered the gold standard of peripheral thyroid hormone action. Using Doppler echocardiography, we have previously shown a very high proportion of prolonged ICT in patients with hypothalamic-pituitary disease and serum FT4 levels indistinguishable from controls. As ICT decreased/normalized after thyroxine-induced increases in FT4 concentrations within the normal reference range, prolonged ICT was considered a bona fide diagnostic biomarker of subclinical CH. Those findings challenge the usual interpretation that FT4 concentrations in the mid-reference range exclude hypothyroidism in patients with hypothalamic-pituitary disease. Rather, subclinical central hypothyroidism, a state analogous to subclinical primary hypothyroidism, seems to be frequent in patients with hypothalamic-pituitary disease and normal FT4 levels. They also challenge the notion that thyroid function is usually the least or the last affected in acquired hypopituitarism. The relevance of Doppler echocardiography to correctly diagnose and monitor replacement therapy in both clinical and subclinical forms of CH should improve quality of life and decrease cardiovascular risk, as already demonstrated in patients with clinical and subclinical primary hypothyroidism.

Assessment of fetal cardiac function in early fetal life: feasibility, reproducibility, and early fetal nomograms

BackgroundFetal cardiology has shown a rapid development in the last decades. Fetal echocardiography is not only used for the detection of structural anomalies but also to assess fetal cardiac function. Assessment of the fetal cardiac function is performed mostly at second and third trimester. The study of fetal cardiac function at the end of first timester has not been properly investigated and there is a lack of reference values at early gestational weeks. ObjectiveTo assess whether the measurement of time related parameters of cardiac function in the left ventricle of the fetal heart is feasible and reproducible at the end of the first trimester. If possible, we provide nomograms of these parameters from 11 to 13.6 gestational weeks. Study designWe conducted a prospective observational study from March to September 2022. The study was carried out in two hospitals (Hospital Universitari Dexeus, Barcelona and Hospital VITAHS 9 Octubre, Valencia). The scans were performed by 3 specialists in fetal medicine. Exclusion criteria were: fetal cardiac rhythm abnormalities, abnormal nuchal translucency, abnormal ductus venosus, fetal malformations, stillbirth, estimated fetal weight< 10 centile, diabetes and gestational hypertensive disorders. The cardiac function parameters studied in the left ventricle were: isovolumetric contraction time, isovolumetric relaxation time, ejection time, filling time, cycle time, myocardial performance index, ejection time fraction and filling time fraction. We study the feasibility and intra- and inter-observer reproducibility of this parameters using the interclass correlation coefficient (ICC). Nomograms were made and the percentiles of the values of the different parameters were calculated. Results409 cases were recruited but only 296 could be included in the statistical analysis once exclusion criteria were applied. The intra-observer reproducibility study was excellent (ICC>0.900) and the inter-observer reproducibility study was good (ICC>0.700). Data regression analysis showed that cycle time, filling time, isovolumetric contraction time and filling time fraction increased with gestational age, whereas ejection time fraction decreased with gestational age and myocardial performance index (mean 0.43±0.08), isovolumetric relaxation time (mean 0.04±0.01) and ejection time (mean 0.16±0.01) remained constant from 11 to 13 weeks. ConclusionsThe study of fetal cardiac function is feasible and reproducible at 11 to 13+6 gestational weeks. Nomograms of the studied parameters are provided.

Muscle contraction time after caffeine intake is faster after 30 minutes than after 60 minutes.

This study aimed to determine the optimal time point, either 30 or 60 minutes, at which muscle reactivity to caffeine administration is highest. Unlike previous studies that focused on the nervous system response, we employed tensiomyography (TMG) to directly assess the effects of caffeine on muscle fibers. TMG measurements were performed on the gastrocnemius medialis muscle of 42 male athletes who regularly consumed caffeine. Participants received a dose of 6 mg/kg body weight and TMG measurements were taken prior to caffeine intake, as well as 30 and 60 minutes afterward. Analysis of TMG parameters including time to contraction (Tc), time delay (Td), and maximal displacement (Dm) revealed that muscles exhibited faster contractions and greater stiffness at the 30-minute mark compared to both pre-caffeine intake and the 60-minute time point. Time exerted a significant main effect on Tc (F(2, 246) = 12.09, p < .001, ή2p = 0.09), Td (F(2, 246) = 3.39, p = .035, ή2p = 0.03), and Dm (F(2, 246) = 6.83, p = .001, ή2p = 0.05), while no significant effect of body side was observed. The findings indicate that muscle contraction time (Tc) and delay time (Td) are influenced by the time elapsed since caffeine ingestion, with the fastest responses occurring after 30 minutes. Additionally, a systemic effect of caffeine was observed, as there were no discernible differences in measurements between the two sides of the body. TMG proves to be an effective noninvasive method for assessing muscle responses following caffeine administration.

The kinematic analysis of the straight punch in two ways for amateur boxing players in Jordan

This study aimed to identify some kinematic variables (distance between the feet, arm movement, punch speed, punch time, punch distance, ankle angle, knee angle, elbow angle, shoulder angle, pelvis angle) for the straight punch between two methods. The first method: performing a straight punch with the right hand towards the target without changing the distance between the feet and being on a straight line. The second method: performing a straight punch with the right hand towards the target without changing the distance between the feet, and the left foot is ahead of the right foot. A total of 8 amateur boxers in Jordan who were photographed using an iPhone camera at a frequency of 60 frames per second, participated in this study. The researchers downloaded videos on a computer (LAPTOP), which contains the Kinovea software (Kinovea. Setup.0.8.15.), and determined the best attempts for each player by watching the videos. Then, the researchers analyzed the attempts through the kinetic analysis program (Kinovea. Setup.0.8.15.) and extracted the study variables. The shorter the muscle contraction time of the straight punch, the greater the kinetic momentum and speed of the punch in both styles, and the greater the knee angle, the greater the punch and speed of the punch in both styles. Also, momentum and punch speed were better in the second method. We recommend a climatic and other clinical study of the straight stroke. We also recommend to use the second method in the straight punch.

Experimental and numerical simulation investigation of cavitation phenomenon during bubble pulsation process

The current research on the cavitation phenomenon in the underwater explosion process is focused on the shock wave phase. In this study, it was found that there was also significant cavitation during bubble pulsation. Underwater explosion experiments were carried out at the bottom of a sheet using 2.5 g of TNT, which also showed that: (a) Cavitation lasts for the same duration as the bubble contraction time, (b) A cavitation closure pressure, the peak of which is greater than the bubble pulsation pressure, is produced by the closing of the cavitation zone. A tensile cut-off model was introduced to simulate the cavitation phenomenon during bubble pulsation, and the formation mechanism was investigated. The numerical simulation results show that: (a) The cavitation phenomenon is visible when the sheet above the explosive and the explosion distance are between 0.93 and 1.17 times the radius of the largest bubble, or between 0.69 and 1.85 times the maximum radius of the bubble when the sheet below the explosive, (b) The cavitation region and cavitation closure pressure increase and decrease with increasing explosion distance, peaking at a value close to one times the theoretical maximum bubble radius, and (c) The cavitation zone shrinks and the cavitation closing pressure drops as sheet thickness increases.

Acute Effects of Short-Term Massage Procedures on Neuromechanical Contractile Properties of Rectus Femoris Muscle.

Background and Objectives: In many sports, maintaining muscle work at an optimal level despite fatigue is crucial. Therefore, it is essential to discover the most efficient way of recovery. This study aimed to evaluate and compare the acute effects of four different recovery methods on muscle neuromechanical properties. Materials and Methods: The research was conducted using a randomized, quasi-experimental, repeated-measures design. Fourteen healthy and active male students of the Faculty of Sport and Physical Education (age 25.1 ± 3.9 years) were included in this study. The tensiomyography was used to evaluate muscle responses after four different types of short-term recovery methods (passive rest, percussive mechanical, vibro-mechanical, and manual massage) on the rectus femoris muscle on four occasions: baseline, post fatigue, post recovery and prolonged recovery. Results: The ANOVA revealed that muscle fatigue decreased maximal vertical muscle displacement (Dm) and muscle contraction time (Tc) in post fatigue compared to the baseline. The most important finding shows that only the vibro-mechanical massage resulted in an increase in Tc in the prolonged recovery compared to the post fatigue (p = 0.028), whereas only manual massage showed no differences in Dm from the baseline in post-recovery (p = 0.148). Moreover, both manual and vibro-mechanical massages increased Dm and Tc in prolonged recovery, indicating no differences from the baseline (all p > 0.05), thus showing signs of muscle recovery. Percussion mechanical massage and passive rest did not show indices of muscle recovery. Conclusions: Manual massage could induce immediate positive changes in Dm by reducing muscle stiffness. In addition, vibro-mechanical and manual massage improved muscle tissue by rapidly returning Dm and Tc values to baseline at prolonged recovery measurement (5 min after the fatigue protocol). These findings can benefit sports practitioners, and physical therapists in developing the best recovery method after muscle fatigue.

Impact of the Panama Canal on the Panamanian economy: analysis with input-output tables

The effects of canal activity not only prevent a greater economic contraction derived from the pandemic, but also allow for rapid economic recovery in Panama. The objective of the study is to determine the economic impact of the Canal in relation to production, added value, employment and salary income. The methodology used is the analysis of direct, indirect and induced impact attributed to the Input-Output Tables (IOT) method, for which the 45X45 IOTs have been developed in the years 2019, 2020, 2021 and 2022, incorporating the financial information from the Panama Canal Authority and the Supply and Use Tables at 2018 prices and with chained volume measurements provided by the National Institute of Statistics and Census. The results indicate that at the time of the considerable economic contraction in the country, estimated at 17.9%, the Canal grew by 7.2% of its production compared to fiscal year 2019, maintaining that the weight of this activity for this referenced year reached 5.5% of the GDP when adding indirect and induced effects; while in 2020 it reached 7.6%, gaining 2.1 units of this magnitude. For its part, the added value exceeds the growth in production, setting an evolution in its growth of 11.1%, with a less intense participation than in production, going from 4.2% in 2019 to 5.8% in 2020 of the value total added; However, the results in employment and salary income show a different dynamic when compared to 2019, with the former falling by 2% and the latter by 5%, considering that by 2019 canal employment included all the effects between 0.5% and 1.2% of total employment; improving this relationship in 2020 with a range between 0.6% and 1.5%. In subsequent years, the behavior of this service activity provides an important contribution to the aforementioned indicators in the country, ignoring the negative impacts of the container crises, the war between Russia and Ukraine; and the increase in interest rates.

Research on evaluation of fetal right ventricular function in normal and diabetic pregnant women during mid to late pregnancy using automated MPI ultrasound detection technology.

Objective: fetal circulatory characteristics differ from those after birth; the right ventricle assumes more than 60% of the workload in the systemic circulation before birth. The right ventricle automated myocardial performance index (AM+MPI) is a simple, time-efficient, and stable assessment method used to evaluate overall cardiac function. This study aimed to apply the right ventricle AM+MPI technique to explore its role in normal mid-to-late pregnancy fetal cardiac function and compare the AM+MPI differences between diabetic and normal fetuses. Methods: A total of 150 pregnant women who visited the obstetric outpatient department at Daxing Hospital, Xi'an, from January 2022 to June 2022 were selected. We excluded 42 patients with comorbid conditions other than diabetes, fetal anomalies, and unclear last menstrual periods, resulting in 85 healthy pregnant patients and 17 diabetic pregnant patients. Using a Samsung WS80A color Doppler ultrasound diagnostic device, we measured the fetal right ventricle AM+MPI, isovolumic contraction time (ICT), isovolumic relaxation time (IRT), and ejection time (ET) in RMPI mode. We performed variability and correlation analyses within the normal group and compared these parameters with those of the diabetic group. Results: In the healthy pregnant group, there was no significant variability in the fetal MPI, ET, or ICT values among the groups (p > 0.05). However, the IRT was positively correlated with gestational age (p < 0.05), with a linear fit formula of IRT = 29.78 + 0.49 × gestational age (DW value 1.87; F = 32.25, p < 0.05), indicating that the IRT increases with gestational age. The right ventricle MPI in the diabetic group was significantly greater than that in the normal group (p < 0.05). Conclusion: The right ventricle AM+MPI technique is simple, time-efficient, and stable and can objectively assess fetal right ventricle function, providing a theoretical basis for the early diagnosis of intrauterine cardiac function abnormalities. Additionally, there are significant differences in the right ventricle MPI between diabetic and normal fetuses, providing evidence for predicting fetal developmental issues and postnatal complications. The right ventricle AM+MPI holds promise as a new method for prenatal evaluation of fetal right heart function.

Effects of Repeated Jump Testing and Diurnal Changes on Subsequent Countermovement Jump and Squat Jump Output and Force-Time Characteristics

Abstract Harrison, PW, James, LP, Jenkins, DG, Holmberg, PM, and Kelly, VG. Effects of repeated jump testing and diurnal changes on subsequent countermovement jump and squat jump output and force-time characteristics. J Strength Cond Res 38(1): 174–179, 2024—The aim of this brief study was to investigate the effects of repeated jump testing on performance over 2 consecutive days while considering the possibility of diurnal changes. Fourteen male subjects and 14 recreationally active female subjects completed countermovement jump (CMJ) and squat jump (SJ) testing on 5 occasions (baseline [0,800], 5 minutes [0,820], 8 hours [1,600], 24 hours [0,800], and 32 hours [1,600]) over 32 hours. An additional rested baseline test was conducted on a separate day in the afternoon (1,600) to compare jump performance between morning and afternoon baseline values. Excluding small decreases in CMJ height at 24 hours (p = 0.292, Cliff’s delta = −0.225) in male subjects and similar decreases in CMJ height at 5 minutes (p = 0.034, Cliff’s delta = −0.245) in addition to SJ height:contraction time at 32 hours (p = 0.126, Cliff’s delta = 0.153) in female subjects, findings generally showed no changes in jump performance over multiple assessments. Squat jump metrics may have showed small improvements between morning and afternoon baseline values in male subjects (SJ height:contraction time [p = 0.030, Cliff’s delta = 0.225]) and female subjects (SJ height [p = 0.013, Cliff’s delta = 0.173] and SJ height:contraction time [p = 0.091, Cliff’s delta = 0.163)]. As jump performance was largely unaffected by repeated jump testing, the present findings support the use of monitoring practices and research designs that require multiple jump assessments within acute periods (∼32 hours).

Exploring the reticulo-ruminal motility pattern in goats through medical barium meal imaging technology.

The motility pattern of the reticulo-rumen is a key factor affecting feed intake, rumen digesta residence time, and rumen fermentation. However, it is difficult to study reticulo-ruminal motility using general methods owing to the complexity of the reticulo-ruminal structure. Thus, we aimed to develop a technique to demonstrate the reticulo-ruminal motility pattern in static goats. Six Xiangdong black goats (half bucks and half does, body weight 29.5 ± 1.0 kg) were used as model specimens. Reticulo-ruminal motility videos were obtained using medical barium meal imaging technology. Videos were then analyzed using image annotation and the centroid method. The results showed that reticulo-ruminal motility was divided into primary (stages I, II, III, and IV) and secondary contraction, and the movements of ruminal digesta depended on reticulo-ruminal motility. Our results indicated common motility between the ruminal dorsal sac and ruminal dorsal blind sac. We observed that stages I (3.92 vs. 3.21 s) (P < 0.01), II (4.81 vs. 4.23 s) (P < 0.01), and III (5.65 vs. 5.15 s) (P < 0.05); interval (53.79 vs. 50.95 s); secondary contraction time (10.5 vs. 10 s); and were longer, whereas stage IV appeared to be shorter in the bucks than in the does (7.83 vs. 14.67 s) (P < 0.01). The feasibility of using barium meal imaging technology for assessing reticulo-ruminal and digesta motility was verified in our study. We determined the duration of each stage of reticulo-ruminal motility and collected data on the duration and interval of each stage of ruminal motility in goats. This research provides new insights for the study of gastrointestinal motility and lays a solid foundation for the study of artificial rumen.

Quantifying muscle contraction with a conductive electroactive polymer sensor: introduction to a novel surface mechanomyography device

ABSTRACT Clinicians seek an accurate method to assess muscle contractility during activities to better guide treatment. We investigated application of a conductive electroactive polymer sensor as a novel wearable surface mechanomyography (sMMG) sensor for quantifying muscle contractility. The radial displacement of a muscle during a contraction is detected by the physically stretched dielectric elastomer component of the sMMG sensor which quantifies the changes in capacitance. The duration of muscle activation times for quadriceps, hamstrings, and gastrocnemius muscles demonstrated strong correlation between sMMG and EMG during a parallel squat activity and isometric contractions. A moderate to strong correlation was demonstrated between the sMMG isometric muscle activation times and force output times from a dynamometer. The potential wearable application of an electroactive polymer sensor to measure muscle contraction time is supported.

Cost and Time Analysis Using Earned Value Method in The Construction of Sports Facilities in Kecamatan Kedewan Kabupaten Bojonegoro

The implementation of construction work has the main targets in construction management, such as construction costs, quality of construction work and construction implementation time. Construction activities can be declared successful in their management if they produce work products with the quality criteria that have been determined, on time, and according to the agreed costs. Using EVM (Earned Value Method) in project management can be used to determine cost performance and implementation time during the project and the indicators used for analysis include: BCWP (Budget Cost of Work Performance), BCWS (Budget Cost of Work Schedule), ACWP (Actual Cost of Work Performance), SV (Schedule Variance), CV (Cost Variance), SPI (Schedule Performance Index), CPI (Cost Performance Index), EAS (Estimated At Schedule) and ETS (Estimated Temporary Schedule).By using this method in the Sports Facilities Construction Project, Kecamatan Kedewan, Kabupaten Bojonegoro, the ACWP (Actual Cost of Work Performed), BCWP (Budgeted Cost of Work Performed), and BCWS (Budgeted Cost of Scheduled) values were obtained. The CV value obtained &lt;0 in weeks 1 to 7 indicates that the costs incurred were greater than the plan, but in weeks 8 to 15 the CV value &gt;0 means that in that week the costs incurred were less than the plan. Meanwhile, the SV value for the 15th week is SV&lt;0, meaning the project is experiencing a delay from plan. The estimated of the completion budget requirement obtained from the ETC (Estimate to Compile) value is IDR. 3,345,105,521.28, while the estimated final total project cost obtained from the EAC (Estimate at Complete) value is IDR. 5,680,868,593.22. The results of the TE (Time Estimate) value in week 15 show 33 calendar days, so it takes 243 (Two hundred and forty three) calendar days to complete the project from week 15 to completion or 33 days later than the contract time of 210 calendar days.

A model for the contraction kinetics of cytoskeletal gel slabs

Cytoskeletal gels are engineered prototypes that mimic the contractile behavior of a cell in vitro. They are composed of an active polymer matrix and a liquid solvent. Their contraction kinetics is governed by two dynamic phenomena: mechanotransduction (molecular motor activation) and solvent diffusion. In this paper, we solve the transient problem for the simple case of a thin gel slab in uniaxial contraction under two extreme conditions: motor-limited or slow motor (SM) activation regime, and diffusion-limited or fast motor (FM) activation regime. The former occurs when diffusion is much faster than mechanotransduction, while the latter occurs in the opposite case. We observe that in the SM regime, the contraction time scales as t/t0∼(λ/λ0)−3, with t0 being the nominal contraction time, and λ and λ0 being the final and initial stretches of the slab. t0 is proportional to 1/w˙, where w˙ is the average mechanical power generated by the molecular motors per unit reference (dry polymer) volume. In the FM regime, the contraction time scales as t/t1∼(1−λ/λ0)2, with t1 being the nominal contraction time, here proportional to the ratio L2/D, where L is the reference (dry polymer) thickness, and D is the diffusivity of the solvent in the gel. The transition between the SM and FM regimes is defined by a characteristic power density w˙∗, where w˙≪w˙∗ gives the SM regime and w˙≫w˙∗ gives the FM regime. Intuitively, w˙∗ is proportional to D/L2, where, at a given power density w˙, a thinner gel slab (smaller L) or including smaller solvent molecules (higher D) is more likely to be in the SM regime given that solvent diffusion will occur faster than motor activation.

Night labour, social reproduction and political struggle in the ‘Working Day’ chapter of Marx's Capital

This essay offers a new reading of Marx's chapter on ‘the working day’ in Capital Volume One by exploring the textual theme of night-time work. Even as Marx emphasises how the lengthening workday enables the super-exploitation of producers’ wage labour, his depictions of nocturnal experiences highlight more forcefully the destruction of workers’ reproductive resources, capacities and relationships. Night comes to represent the contracted time, condensed space, petrified relational bonds and thwarted desires for human reproduction in a free, fulsome sense that includes reinvigorating oneself, caring for others and enjoying experiences apart from work or care. Night's role as a privileged signifier and catalyst of these changes comes through in key passages about women, children and vampires, and in theoretically meaningful variances between Marx's German paraphrasing of English sources and those original texts, which replace Marx's phrases in English translations of Capital. Contemplating Marx's ambivalent reflections on legal-political action to limit workday hours, I argue for making struggles over social reproduction in a capacious sense central to working-class politics today. I demonstrate the power of this Marxian analytic by considering the compression of social-reproductive time among today's microworkers, who fuel the digital economy by performing platform-based ‘tasks’ at all hours for very low wages.

KUS121, a VCP modulator, has an ameliorating effect on acute and chronic heart failure without calcium loading via maintenance of intracellular ATP levels

AimsAs heart failure (HF) progresses, ATP levels in myocardial cells decrease, and myocardial contractility also decreases. Inotropic drugs improve myocardial contractility but increase ATP consumption, leading to poor prognosis. Kyoto University Substance 121 (KUS121) is known to selectively inhibit the ATPase activity of valosin-containing protein, maintain cellular ATP levels, and manifest cytoprotective effects in several pathological conditions. The aim of this study is to determine the therapeutic effect of KUS121 on HF models. Methods and resultsCultured cell, mouse, and canine models of HF were used to examine the therapeutic effects of KUS121. The mechanism of action of KUS121 was also examined. Administration of KUS121 to a transverse aortic constriction (TAC)-induced mouse model of HF rapidly improved the left ventricular ejection fraction and improved the creatine phosphate/ATP ratio. In a canine model of high frequency-paced HF, administration of KUS121 also improved left ventricular contractility and decreased left ventricular end-diastolic pressure without increasing the heart rate. Long-term administration of KUS121 to a TAC-induced mouse model of HF suppressed cardiac hypertrophy and fibrosis. In H9C2 cells, KUS121 reduced ER stress. Finally, in experiments using primary cultured cardiomyocytes, KUS121 improved contractility and diastolic capacity without changing peak Ca2+ levels or contraction time. These effects were not accompanied by an increase in cyclic adenosine monophosphate or phosphorylation of phospholamban and ryanodine receptors. ConclusionsKUS121 ameliorated HF by a mechanism totally different from that of conventional catecholamines. We propose that KUS121 is a promising new option for the treatment of HF.

The effect of iron deficiency anemia on myocardial function in pediatrics

BackgroundIron deficiency is one of the most common types of anemia in children. Anemia leads to tissue hypoxia, which activates compensatory mechanisms such as increased cardiac output. Tissue Doppler imaging (TDI) is a useful echocardiographic technique for evaluation of regional and global myocardial systolic and diastolic function. ObjectivesThis study aimed to determine whether iron deficiency anemia (IDA) affects myocardial function in pediatric patients using conventional echocardiography and TDI. MethodsThis case-control study was conducted at an outpatient general pediatric clinic in cooperation with the Cardiology Unit of the Pediatric Department of Fayoum University Hospital from May 2021 to February 2022. The study included 30 cases with IDA and 30 apparently healthy children. The two study groups were matched for age and sex. ResultsThere was an increase in left ventricular end-diastolic diameter (LVEDD), while the control group showed increased ejection time (ET). There was a statistically significant lower mean E/A ratio among cases. There was a positive correlation between serum iron levels, ET, and isovolumetric contraction time (IVCT) among the cases. Additionally, there was a negative correlation between hemoglobin levels and LVEDD in the entire study group. No significant difference was found between the two study groups regarding the Tei index. ConclusionMinimal alterations in LV function parameters may occur due to IDA. A decrease in serum iron levels was significantly associated with further decreases in ET and IVCT. Additionally, there was a statistically significant lower mean E/A ratio among cases.

Oscillation Dynamics of Dielectric Polymer Droplets during Electrohydrodynamic Jetting in a Wide Range of Viscosities.

The electrohydrodynamic (EHD) jetting of fluids is used for several applications such as inkjet printing, atomization of analyte in mass spectrometry, liquid metal alloy ion sources, and electrospinning of polymer fibers. Historically, the bulk of research has focused on nonviscous, highly conductive fluids which are most suitable for EHD spray and printing, while there is relatively little experimental work on EHD jetting of highly viscous liquid dielectrics. We studied the dynamics of oscillation and pulsating jetting from a suspended drop of polydimethylsiloxane (PDMS) polymers in an electric field, with particular attention to the viscosity dependence of the oscillation period and meniscus elongation and contraction time over a wide viscosity range (102-105 cSt). The reported results could help the appropriate design of EHD processes and may open new possibilities for the rheological characterization of liquid polymers using small volumes at the scale of nanoliters.

Longitudinal assessment of skeletal muscle functional mechanics in the DE50-MD dog model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin (DMD) gene, is associated with fatal muscle degeneration and atrophy. Patients with DMD have progressive reductions in skeletal muscle strength and resistance to eccentric muscle stretch. Using the DE50-MD dog model of DMD, we assessed tibiotarsal joint (TTJ) flexor and extensor force dynamics, and the resistance of dystrophic muscle to eccentric stretch. Male DE50-MD and wild-type (WT) dogs were analysed every 3 months until 18 months of age. There was an age-associated decline in eccentric contraction resistance in DE50-MD TTJ flexors that discriminated, with high statistical power, WT from DE50-MD individuals. For isometric contraction, at the majority of timepoints, DE50-MD dogs had lower maximum absolute and relative TTJ flexor force, reduced TTJ muscle contraction times and prolonged relaxation compared to those in WT dogs. Cranial tibial muscles, the primary TTJ flexor, of 18-month-old DE50-MD dogs had significant numbers of regenerating fibres as expected, but also fewer type I fibres and more hybrid fibres than those in WT dogs. We conclude that these parameters, in particular, the eccentric contraction decrement, could be used as objective outcome measures for pre-clinical assessment in DE50-MD dogs.

The Effect of SARS-CoV-2 Spike Protein RBD-Epitope on Immunometabolic State and Functional Performance of Cultured Primary Cardiomyocytes Subjected to Hypoxia and Reoxygenation

Cardio complications such as arrhythmias and myocardial damage are common in COVID-19 patients. SARS-CoV-2 interacts with the cardiovascular system primarily via the ACE2 receptor. Cardiomyocyte damage in SARS-CoV-2 infection may stem from inflammation, hypoxia–reoxygenation injury, and direct toxicity; however, the precise mechanisms are unclear. In this study, we simulated hypoxia–reoxygenation conditions commonly seen in SARS-CoV-2-infected patients and studied the impact of the SARS-CoV-2 spike protein RBD-epitope on primary rat cardiomyocytes to gain insight into the potential mechanisms underlying COVID-19-related cardiac complications. Cell metabolic activity was evaluated with PrestoBlueTM. Gene expression of proinflammatory markers was measured by qRT-PCR and their secretion was quantified by Luminex assay. Cardiomyocyte contractility was analysed using the Myocyter plugin of ImageJ. Mitochondrial respiration was determined through Seahorse Mito Stress Test. In hypoxia–reoxygenation conditions, treatment of the SARS-CoV-2 spike RBD-epitope reduced the metabolic activity of primary cardiomyocytes, upregulated Il1β and Cxcl1 expression, and elevated GM-CSF and CCL2 cytokines secretion. Contraction time increased, while amplitude and beating frequency decreased. Acute treatment with a virus RBD-epitope inhibited mitochondrial respiration and lowered ATP production. Under ischaemia-reperfusion, the SARS-CoV-2 RBD-epitope induces cardiomyocyte injury linked to impaired mitochondrial activity.