Heart Work Research Articles

The effect of evaporative cooling vests on the physiological and perceptual strain indices of construction workers

Aim: One of the most harmful agents in construction sites is heat exposure. The aim of this study was to evaluate the performance of new evaporative cooling vests in construction workers. Materials and Methods: This case–control study was implemented on 60 construction workers in hot conditions (air temperature 49.0°, relative humidity 5.5%) in the summer of 2019. In this study, 30 people with cooling vests (case group) and 30 people without cooling vests (control group) were working for 120 min in a hot environment. In both groups, heart rate oral temperature and wet bulb globe temperature (WBGT) index were measured. Moreover, the Perceptual Strain Index (PeSI) and Heat Strain Score Index (HSSI) questionnaires were completed by the workers. Data were analyzed after inter to SPSS16 software. Results: All of the WBGT values were higher than occupational exposure limit. The mean and standard deviation (SD) of the work heart rate in the case and control groups, was equal to 111.1 ± 7.6 beats per minute (bpm) and 114.3 ± 7.9 bpm respectively (P < 0.05). Also the average and SD of the oral temperature in the case and control groups, respectively, was equal to 36.36 ± 0.41 and 36.37 ± 0.55. There was no statistically significant difference. Mean and SD of Physiological Strain Index (PSI), in case and control groups, were 2.53 ± 0.66 and 3.64 ± 0.81, respectively. The mean and SD of the PeSI and the HSSI in the case group were 4.64 ± 0.79 and 10.12 ± 1.71, respectively, and in the control group, 6.41 ± 0.85 and 15.88 ± 0.1.43. Statistically, the difference between PSI, PeSI, and HSSI means was significant. Conclusions: This study results showed that hot environmental conditions were stressful for construction workers and also Iranian evaporative cooling vests (Hifitcool brand) were able to reduce perceptual and physiological heat strain in construction workers in the hot conditions.

RyR2 Serine-2030 PKA Site Governs Ca2+ Release Termination and Ca2+ Alternans.

PKA (protein kinase A)-mediated phosphorylation of cardiac RyR2 (ryanodine receptor 2) has been extensively studied for decades, but the physiological significance of PKA phosphorylation of RyR2 remains poorly understood. Recent determination of high-resolution 3-dimensional structure of RyR2 in complex with CaM (calmodulin) reveals that the major PKA phosphorylation site in RyR2, serine-2030 (S2030), is located within a structural pathway of CaM-dependent inactivation of RyR2. This novel structural insight points to a possible role of PKA phosphorylation of RyR2 in CaM-dependent inactivation of RyR2, which underlies the termination of Ca2+ release and induction of cardiac Ca2+ alternans. We performed single-cell endoplasmic reticulum Ca2+ imaging to assess the impact of S2030 mutations on Ca2+ release termination in human embryonic kidney 293 cells. Here we determined the role of the PKA site RyR2-S2030 in a physiological setting, we generated a novel mouse model harboring the S2030L mutation and carried out confocal Ca2+ imaging. We found that mutations, S2030D, S2030G, S2030L, S2030V, and S2030W reduced the endoplasmic reticulum luminal Ca2+ level at which Ca2+ release terminates (the termination threshold), whereas S2030P and S2030R increased the termination threshold. S2030A and S2030T had no significant impact on release termination. Furthermore, CaM-wild-type increased, whereas Ca2+ binding deficient CaM mutant (CaM-M [a loss-of-function CaM mutation with all 4 EF-hand motifs mutated]), PKA, and Ca2+/CaMKII (CaM-dependent protein kinase II) reduced the termination threshold. The S2030L mutation abolished the actions of CaM-wild-type, CaM-M, and PKA, but not CaMKII, in Ca2+ release termination. Moreover, we showed that isoproterenol and CaM-M suppressed pacing-induced Ca2+ alternans and accelerated Ca2+ transient recovery in intact working hearts, whereas CaM-wild-type exerted an opposite effect. The impact of isoproterenol was partially and fully reversed by the PKA inhibitor N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide and the CaMKII inhibitor N-[2-[N-(4-chlorocinnamyl)-N-methylaminomethyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide individually and together, respectively. S2030L abolished the impact of CaM-wild-type, CaM-M, and N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinoline-sulfonamide-sensitive component, but not the N-[2-[N-(4-chlorocinnamyl)-N-methylaminomethyl]phenyl]-N-(2-hydroxyethyl)-4-methoxybenzenesulfonamide-sensitive component, of isoproterenol.

Deleterious effects of cardiomyocyte-specific prostaglandin E2 EP3 receptor overexpression on cardiac function after myocardial infarction

AimsProstaglandin E2 (PGE2) is a lipid hormone that signals through 4 different G-protein coupled receptor subtypes which act to regulate key physiological processes. Our laboratory has previously reported that PGE2 through its EP3 receptor reduces cardiac contractility at the level of isolated cardiomyocytes and in the isolated working heart preparation. We therefore hypothesized that cardiomyocyte specific overexpression of the PGE2 EP3 receptor further decreases cardiac function in a mouse model of heart failure produced by myocardial infarction. Main methodsOur study tested this hypothesis using EP3 transgenic mice (EP3 TG), which overexpress the porcine analogue of human EP3 in the cardiomyocytes, and their wildtype (WT) littermates. Mice were analyzed 2 wks after myocardial infarction (MI) or sham operation by echocardiography, RT-PCR, immunohistochemistry, and histology. Key findingsWe found that the EP3 TG sham controls had a reduced ejection fraction, reduced fractional shortening, and an increased left ventricular dimension at systole and diastole compared to the WT sham controls. Moreover, there was a further reduction in the EP3 TG mice after myocardial infarction. Additionally, single-cell analysis of cardiomyocytes isolated from EP3 TG mice showed reduced contractility under basal conditions. Overexpression of EP3 significantly increased cardiac hypertrophy, interstitial collagen fraction, macrophage, and T-cell infiltration in the sham operated group. Interestingly, after MI, there were no changes in hypertrophy but there were changes in collagen fraction, and inflammatory cell infiltration. SignificanceOverexpression of EP3 reduces cardiac function under basal conditions and this is exacerbated after myocardial infarction.

Collaborative autoethnography and social work

Like autoethnography, (AE), collaborative autoethnography (CAE) results in highly personalised narrative accounts of the researcher’s engagement with specific sociocultural contexts. CAE adds a collective interpretation to that engagement. While CAE has thus far been little used in social work practice and education, it is an emerging methodological approach that offers new and different insights and opportunities. This paper discusses CAE and its relationship with social work practice and education. In it I discuss how CAE allows for a collective exploration of an individual experience and how these explorations, and the process of obtaining them, have many benefits for social work practitioners and social work students alike. The similarities between CAE and social work are highlighted, by focussing on some of the very core skills and values that lie at the heart of social work, such as listening, collaborating and showing empathy, CAE would seem a natural progression for inquiry within social work. This contribution to the special issue has implications for both social work practice and social work education.

Ergonomic Evaluation of a Walking Type Power Operated Maize Stalk Harvester

Background: Ergonomics is a science that focuses its study on improved design as a remedial measure to fatigue and discomfort in humans. Its objective is to optimize health, safety and productivity. Methods: In the current study, an ergonomic evaluation of walking type power operated maize stalk harvester was done with traditional system. Result: It was observed that the average working heart rate, working oxygen consumption rate, ODR, BPDS and, REBA score was 93.3 beats/min, 0.582 litre/min, 1.1 (uncomfortable), 23.5, 5.3 (medium risk) respectively. The working angles of different body parts like trunk, neck, leg, upper arm, lower arm and wrist were studied and are 9.1o, 7.3o, 41.8o, 23.6o, 48.2o and 7.9o for developed prototype respectively.

"Toda la tragedia y la comedia de la vida": sobre la mezcla de afectos y géneros en el Filebo de Platón

In Philebus 50b ff., for the first time, the pleasure that human beings take in the tragic is explicitly noted. Plato refers there to "all the tragedy and comedy of life", an expression that is at the heart of my work. In what follows I will first make some philological observations on the passage in context, then I outline Plato's conception of the tragic, illustrating it with the Phaedo. I will analyse the references to tragedy and comedy in Symposium and Laws VII. And finally I will return to the Philebus to show that in Plato's poetics "mixture" applies not only to the affections but also to the two dramatic genres, whose mixture occurs both on stage and in life.

Development and Ergonomic Assessment of Manually Operated Modified Linseed Crop Thresher

Manually operated modified linseed crop thresher was developed from ergonomics considerations. Anthropometric data were taken in selected age subjects 25-40 years for male workers. Anthropometric data regarding body dimensions were obtained for male workers from SHUATS, Prayagraj. During the methods of threshing operation (thresher and traditional method) the working heart rate was recorded with proper technique and oxygen consumption rate, energy expenditure rate and body parts discomfort scoring was obtained. The heart rate, oxygen consumption, energy expenditure rate and BPDS were obtained in the mean value 115.19 beats/min, 0.63 l/min, 9.59 kJ/min and 44.93 for thresher operating whereas 127.56 beats/min, 0.77 l/min, 11.56 kJ/min and 55.43 for traditional method operating.

Barbeques and shiny numbers: micro-ethical encounters in Sydney social housing estates

AbstractMicro-ethical practices are at the heart of community development work, however they are often subsumed within descriptions and reports focused on projects and outcomes. In this article, we examine the critical role played by micro-ethical practices in addressing exclusion and misrecognition with community members experiencing social disadvantage. In three vignettes drawn from a weekly food and social support programme, we discuss the ways in which micro-ethical practices in community development can address exclusion at a fundamental level in the everyday environment using relation-based principles and a framework of recognition.

Abstract 11262: Effect of Active Cancer/Cachexia on the Development of Cardiac Dysfunction in Mice

Introduction: Cancer is independently associated with the alteration of cardiac function prior to cardiotoxic chemotherapy (CCT) exposure. Similar to cancer associated cachexia (CAC), the elevation and the deleterious role of IL-6 in plasma was associated with a reduced cardiac function in heart failure (HF) patients subpopulation. Cancer cells manipulate BCL-2-associated athanogene 3 (BAG3)-HSP70-regulated pathways in tumor cells, which is a key regulator of protein turnover and contractility in cardiomyocyte. Hypothesis: Here, we aimed to characterize the progression of cardiac dysfunction and the expression of BAG3 and HSP70 in tumor-bearing mice. Methods: Colon-26 adenocarcinoma cells (C26; n=22) with/without shIL-6 (C26 shIL-6; n=22) were injected subcutaneously adult male BALB/c mice. Control mice were injected with PBS (n=13). Echocardiographic examinations and invasive hemodynamic measurements ( in vivo and ex vivo using isolated working hearts system) were performed at 10 (early) and 20 (late) days post injection, respectively. The expression of BAG3 and Hsp70 were determined by Western blot. Results: The tumor size was comparable between the cancer groups. However, only C26 group showed a significant loss of subcutaneous fat and skeletal muscle (p&lt;0.05, respectively), confirming cachectic condition. Echocardiography results show a tendency to decline of ejection fraction at the early phase (p~0.08 vs Control), and turned significance lower at late stage (p&lt;0.05 vs Control) in tumor-bearing mice. In line with that, invasive hemodynamic and isolated working heart measurements confirmed LV systolic and diastolic dysfunction (late stage, p&lt;0.05 vs Control, respectively). Interestingly, heart rate and aortic flow were predominantly declined in cachectic animals (p&lt;0.05 vs Control). Importantly, cardiac dysfunction was associated with a significant reduction in both BAG3 and Hsp70 in the myocardium independently of cachexia. Conclusions: Cancer rather than CAC is a main driver for the development of cardiac contractile dysfunction prior to CCT exposure. In addition, our data suggest that targeting BAG3-Hsp70 complex in the cardiomyocytes may provide a novel strategy to improve the cancer associated cardiac dysfunction.

Connecting academics’ disciplinary knowledge to their professional development as university teachers: a conceptual analysis of teacher expertise and teacher knowledge

Disciplinary knowledge lies at the heart of academic work. However, connecting academics’ disciplinary knowledge to their professional development as teachers has been a longstanding challenge for (research-intensive) universities. This is reflected in criticism of the practices that aim to support the professional development of university teachers. In order to create better connections, a deeper understanding is needed of how academics’ disciplinary knowledge relates to the development of their teaching. In this paper, we therefore aim to advance theoretical insights about how academics’ disciplinary knowledge connects to their professional development as university teachers. We do so by providing a conceptual analysis of teacher expertise and teacher knowledge perspectives. Literature discussed as part of the teacher expertise perspective provides insights into how knowledge is structured in order to perform teacher tasks. In our discussion of the teacher knowledge perspective, we include bodies of literature about teachers’ knowledge base to explore the role of disciplinary knowledge in how to teach and about powerful knowledge to explore the role of disciplinary knowledge in what to teach. Insights from these bodies of literature can, from a teacher knowledge perspective, offer theoretical underpinnings for connecting academics’ disciplinary knowledge to their professional development as university teachers. Adaptive expertise and practical knowledge are identified as concepts that include elements of both teacher expertise and teacher knowledge perspectives. Based on the conceptual analysis, we identify and discuss three aspects related to supporting the professional development of university teachers where attention to connection with teachers’ disciplinary knowledge is important.

Hypothermia yields favourable cardiac energetics in experimental ischemia/reperfusion – insights from non-invasive pressure-volume loops by CMR

Abstract Background/Introduction In experimental studies, mild hypothermia (&amp;lt;35°C) has reduced infarct size [1], potentially through reduced reperfusion injury [2], but human trials have been ambiguous [3]. Furthermore, a pressure-volume (PV) loop framework is the gold standard for assessing cardiac performance, but the invasive approach limits its clinical use. Therefore, we used a porcine model of ischemia/reperfusion with cardiovascular magnetic resonance (CMR) imaging throughout one week to acquire non-invasive PV loops. Purpose To quantify the cardioprotective effects of hypothermia at reperfusion by serial CMR imaging in a perspective of cardiac energy and mechanics. Methods Normothermia and Hypothermia groups (n=7+7 pigs) were imaged with CMR at baseline and subjected to 40 minutes of normothermic ischemia by catheter intervention. Thereafter, the Hypothermia group was rapidly cooled (&amp;lt;35°C) for 5 minutes before reperfusion. Additional imaging at two hours, 24 hours, and seven days were used to assess ventricular volumes and ischemic injuries. Infarct size was determined by high-resolution ex-vivo T1-weighted images. Results Figure 1 shows that stroke volume (SV: p=0.029; Friedmans test) and ejection fraction (EF: p=0.068) were notably reduced post-reperfusion in the Normothermia group. In contrast, the decreases were ameliorated in the Hypothermia group (SV: p=0.77; EF: p=0.13). Mean arterial pressure (MAP) was stable in the Normothermia group (p=0.77) but dropped two hours post-reperfusion in hypothermic animals (p=0.007). Over one week, both groups experienced the same decrease and partial recovery pattern for stroke work, external power, and ventricular-arterial coupling. Still, the adverse effects from ischemia were generally attenuated in the Hypothermia group. Although not significant, ischemia/reperfusion caused smaller infarcts in the Hypothermia group (10±8% vs 15±8%; p=0.32). The change in PV loop variables from baseline to 24 hours was compared with infarct size for each group. Though statistical power was limited, the general trend in analyses of covariance indicated that hypothermia has cardioprotective properties incremental to reducing infarct sizes (Figure 2), such as higher external power (p=0.061) and lower arterial elastance (p=0.015). Conclusion Using non-invasive PV loops by CMR, we observed that mild hypothermia before reperfusion results in favourable cardiac energetics that alleviates the heart's work after an ischemia/reperfusion injury during the first week. This study suggests that hypothermia has cardioprotective properties, incremental to reducing infarct size. The primary cardioprotective mechanism was likely an afterload reduction unloading the injured left ventricle. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Swedish Heart-Lung FoundationThe Medical Faculty of Lund University (ALF)

Correlates of Physical Activity among Preadolescent Filipinos

A resounding call for more contemporary research on the correlates of physical activity in low and middle-income countries has been documented over the years. It was, therefore, the aim of this study to examine the correlates of physical activity in terms of endurance, body mass index, and motivation. Study participants involved 257 students, specifically male (n=137) and female (n=120), ranging from 9 to 11 years old preadolescent Filipinos. The physical activity levels were determined by the Physical Activity Questionnaire for Children (PAQ-C), while the cardiorespiratory endurance was assessed by a 3-minute step test. A body mass index (BMI) was calculated and classified using the World Health Organization criteria. Both Behavioral Regulation in Exercise Questionnaire (BREQ) and the PAQ-C were used to measure motivation in physical activities. An interview was also conducted for data triangulation. This research yielded the following results: First, endurance (x1) had no direct positive effect on physical activity (y) (β=-.069). Second, BMI (x2) had no direct positive effect on Physical activity (y) (β=.023). Third, motivation (x3) had a direct positive effect on physical activity (y) (β=.237). Next, endurance (x1) had no direct positive effect on motivation (x3) (β=-.116). Subsequently, BMI (x2) had a direct negative effect on motivation (x3) (β =-.301). Finally, endurance (x1) had a direct positive effect on BMI (x2) (β =.515). Endurance-BMI was considered the most remarkable relationship, garnering the highest standard estimate score of .515. The results also showed that BMI (x1) positively affected endurance (x2). It suggests that higher levels of working heart rate are associated with higher BMI scores of overweight and obese Filipino preadolescents. They had a lower endurance level due to excess body weight.

The IGF-1R Inhibitor NVP-AEW541 Causes Insulin-Independent and Reversible Cardiac Contractile Dysfunction.

The antitumor treatment NVP-AEW541 blocks IGF-1R. IGF-1R signaling is crucial for cardiac function, but the cardiac effects of NVP-AEW541 are ill defined. We assessed NVP-AEW541′s effects on cardiac function and insulin response in vivo and in isolated working hearts. We performed a dose–response analysis of NVP-AEW541 in male, 3-week-old rats and assessed the chronic effects of the clinically relevant dose in adult rats. We performed glucose tolerance tests and echocardiography; assessed the expression and phosphorylation of InsR/IGF-1R and Akt in vivo; and measured substrate oxidation, contractile function, and insulin response in the isolated working hearts. NVP-AEW541 caused dose-dependent growth retardation and impaired glucose tolerance in the juvenile rats. In the adults, NVP-AEW541 caused a continuously worsening depression of cardiac contractility, which recovered within 2 weeks after cessation. Cardiac Akt protein and phosphorylation were unchanged and associated with InsR upregulation. An acute application of NVP-AEW541 in the working hearts did not affect cardiac power but eliminated insulin’s effects on glucose and fatty acid oxidation. The systemic administration of NVP-AEW541 caused dose- and time-dependent impairment of glucose tolerance, growth, and cardiac function. Because cardiac insulin signaling was maintained in vivo but absent in vitro and because contractile function was not affected in vitro, a direct link between insulin resistance and contractile dysfunction appears unlikely.

After the Wave, the Flood? Finding a New Autonomy and Relation to Work

How do changes in the perception of the arts stemming from activism, government policies, precarity and the ongoing crises unfolding in the world affect the autonomy of the artist? In this article, I analyse three cases of young and emerging theatre makers in Flanders and Brussels that each deal with the economic, social precarity of the arts, as well as the general precarious state of the world. Camping Sunset, Ne Mosquito Pas, and Anna Franziska Jäger and Nathan Ooms each explore new ways of maintaining autonomy, be it by collective collaboration, creating a network and an aesthetics of failures and cynicism or a performance of overpositivity and a revaluation of the comic. My claim is that these artists find autonomy in the ‘making’ of a work itself, placing poetics back at heart of artistic work instead of performance. I argue that their poetics can be described as a poetics of inoperativity (Agamben), which places resistance and criticality on the level of making theatre and performance itself instead of making large societal claims.

Assessment of Cardiac Toxicity of Manganese Chloride for Cardiovascular Magnetic Resonance

MRI is widely used in cardiology to characterize the structure and function of the heart. Currently, gadolinium-based contrast agents are widely used to improve sensitivity and specificity of diagnostic images. Recently, Manganese, a calcium analogue, has emerged as a complementary contrast agent with the potential to reveal remaining viable cells within altered tissue. Imaging applications may be limited by substantial toxicity of manganese. Indeed, cardiac safety of manganese is not yet comprehensively assessed. In this study we investigated the effect of MnCl2 (1–100 µM) on cardiac function. Hemodynamic function was determined ex vivo using an isolated working rat heart preparation. HL-1 cardiac myocytes were used to investigate cell viability (calcein AM) and calcium cycling (Cal-520 a.m.). Rat ventricular cardiomyocytes were dissociated by enzymatic digestion. Action potentials and calcium currents were recorded using the patch clamp technique. MRI experiments were performed at 1.5T on formalin-fixed rat hearts, previously perfused with MnCl2. MnCl2 perfusion from 1 up to 100 µM in isolated working hearts did not alter left ventricular hemodynamic parameters. Contractility and relaxation index were not altered up to 50 µM MnCl2. In HL-1 cardiac myocytes, incubation with increasing concentrations of MnCl2 did not impact cell viability. The amplitude of the calcium transients were significantly reduced at 50 and 100 µM MnCl2. In freshly isolated ventricular myocytes, action potential duration at 20, 50 and 90% of repolarization were not modified up to 10 µM of MnCl2. L-type calcium current amplitude was significantly decreased by 50 and 100 µM of MnCl2. MRI on heart perfused with 25 and 100 µM of MnCl2 showed a dose dependent decrease in the T1 relaxation time. In conclusion, our results show that low concentrations of MnCl2 (up to 25 µM) can be used as a contrast agent in MRI, without significant impact on cardiac hemodynamic or electrophysiology parameters.

Ergonomic and Workload Investigation of Tractor Operators Using Rotavator in Pulverization and Puddling Operations

The ergonomic investigation entails assessment of anthropometric dimensions, physiological variations and related workload of 120 respondents having age group between interval 20-50 years for seed bed operation (pulverization and puddling) using rotavator. The study indicated that the average resting heart rate of the tractor operators was 77.56 bpm for secondary tillage operation (pulverization) and 81.46 bpm for puddling operation (for further sowing of paddy crop). The average working heart rate throughout the pulverization and puddling operation were investigated as 95.43 and 103.86(bpm) respectively. The average EER and OCR values for the concerned operations were 6.45 and 7.79(kJ/min) and 0.41 and 0.52(L/min) respectively. The BPDS values of selected subjects were ascertained as 19.5 and 21.4respectively. The study reveals that diff erent farm operations have signifi cant eff ect on the physiological parameters of the respondents. The fi ndings conclude that the tractor operators were more compatible and comfortable in conducting pulverization by rotavator for given soil conditions. The performance of operators was found superlative for the same operation than by puddling operation. For the safer, smart and eff ective agricultural operation in rural parts of the nation, the need of ergonomics is onerous and is a key in predicting the daily working capacity of the respondents involved in various farm operations thereby ensuring the proper harmonious and eff ectual relationship in man-machine interface.

​Ergonomic Evaluation of Developed Manual Fruit Harvesting Device

Background: Ergonomics in agriculture assumes pronounced importance as it is a multidisciplinary science that endeavors to make a better fit between the job and the worker to ensure their health and safety. Methods: In the current study, a evaluation of developed manual fruit harvester was done suitable for selective harvesting and comparison was done with traditional system on ergonomic grounds. Result: The mean working heart rate (HR) during kinnow harvesting operation was 102.09 beats per min, and 108.53 beats per min for traditional and developed method respectively. The ODR (overall discomfort rating) value ranged from 4 to 5 and 0 to 4 and the BPDS value ranged from 40.66 to 59.58 and 30.91 to 51.33 in harvesting operation by traditional and developed system respectively The average RULA score for traditional method was found 7 and action level 4 which fall in the range of very high risk level and changes are required immediately. The average RULA score for developed method was found 4 and action level 2 which fall in the range of low risk level and changes may be required.

Assessment of cardiac toxicity of manganese chloride for cardiovascular magnetic resonance

MRI is widely used in cardiology to visualize the structure and function of the heart. Currently gadolinium is the contrast agents use to improve sensitivity and specificity of diagnostic images, enabling the assessment of scar and fibrosis. Manganese-based contrast molecules are being developed with the hope to improve the diagnosis of cardiac pathologies. Manganese, a calcium analogue, allows detection of viable cells within altered tissue. However, the cardiac safety of manganese is not fully assessed. To characterize the effect of MnCl2 on cardiac function and electrical parameters. Hemodynamic function was determined ex vivo using the isolated working rat heart preparation. HL-1 cell line was used to investigate cell viability (loading with calcein AM) and calcium cycling (loading with CAL-520 AM). Rat ventricular cardiomyocytes were dissociated by enzymatic digestion. Action potentials and calcium currents were recorded using the patch clamp technique. The effect of ascending concentrations of MnCl2 (1, 10, 25, 50 and 100 μM) were evaluated. MRI experiments (1.5 T and 9.4 T) were performed on formalin-fixed rat hearts, previously perfused with 25 or 100 μM of MnCl2. Left ventricular hemodynamic parameters from isolated working hearts show that heart rate is not modified by μM [MnCl2]. Similar observation was made for contractility index and aortic flow up to 50 μM; 100 μM MnCl2 induced a significant decrease of the two parameters. At the cellular level, μM [MnCl2] did not impact HL-1 cell viability. The amplitude of the calcium transients was significantly reduced only at 100 μM of MnCl2 ( P < 0.05). In isolated ventricular myocytes, action potential duration at 20%, 50% and 90% of repolarization were not modified up to 10 μM of MnCl2. A small but significant decrease of action potential duration was observed at 25, 50 and 100 μM (APD90 decrease by 23 ± 6% vs control). Peak L-type calcium current amplitude was significantly decreased by 50 and 100 μM of MnCl2. MRI on heart perfused with 25 μM of MnCl2 (no impact hemodynamic function) and 100 μM of MnCl2 showed a dose dependent decrease in the T1 relaxation time, a parameter for altered and disease state. Our results show that μM [MnCl2] (up to 25 μM) can be used as a contrast agent in MRI, without effects on cardiac hemodynamic parameters. MRI with manganese should therefore enable visualization of viable and stunned myocardium.

Exercise Preconditioning Preserves Cardiac Function and Enhances Cardiac Recovery Following Dobutamine Stimulation in Doxorubicin‐Treated Rat Hearts

Doxorubicin (DOX) is a chemotherapeutic drug used to treat a wide range of cancers, and its use is limited by cardiotoxicity. Exercise preconditioning has been shown to protect against DOX‐induced cardiac dysfunction when hearts are maintained under resting conditions. However, it is unclear whether this exercise‐induced protective effect is maintained when the heart is challenged during an acute exercise bout. It was hypothesized that preconditioning protects the heart against DOX cardiotoxicity when it is challenged with the β1‐adrenergic receptor agonist dobutamine (DOB), which mimics acute exercise stress.Fischer 344 rats were randomly assigned to sedentary (SED) or voluntary wheel running (WR) groups for 10 weeks. At week 11, rats were treated with either 15 mg/kg DOX or saline (SAL). Five days later, ex vivo cardiac function was assessed using an isolating working heart model at baseline, during the infusion of 7.5 μg/kg/min DOB, and during recovery.DOB infusion significantly increased left ventricular developed pressure (LVDP), maximal (dP/dtmax) and minimal (dP/dtmin) rate of left ventricular pressure development, and heart rate in all groups (p&lt;0.05). During the recovery phase (i.e., after DOB washout) LVDP was significantly lower than baseline in all groups except for SED+DOX (baseline vs. recovery: SED+SAL: 97±2 vs. 84±5 mmHg; WR+SAL: 116±7 vs. 90±7 mmHg; SED+DOX: 83±5 vs. 76±4 mmHg; WR+DOX: 109+2 vs. 100±4 mmHg, p&lt;0.05). SED+DOX also showed a lower baseline and recovery LVDP than WR+DOX (83±5 vs. 109±2 mmHg baseline, 76±4 vs. 100±4 mmHg recovery, p&lt;0.05). WR+DOX showed higher dP/dtmax and lower dP/dtmin when compared to SED+DOX during DOB infusion (7311±605 vs. 5167±508 mmHg/s and ‐4059±454 vs. ‐3158±416 mmHg/s, respectively). SED+DOX dP/dtmax was significantly lower during DOB infusion and during recovery when compared to all other groups (p&lt;0.05). During DOB and recovery, +DOX groups showed lower HR values than +SAL groups (p&lt;0.05).These data demonstrate that exercise preconditioning preserved cardiac function after DOX exposure even when the heart is challenged, and it appeared to preserve the heart’s ability to recovery from this functional challenge. Cardioprotection seems to extend beyond rest into conditions which challenge cardiac function. These observations support the premise that exercise training can protect against cardiac dysfunction that may occur during acute exercise in cancer patients undergoing DOX treatment.

Physiological workload of workers employed during motor-manual timber harvesting in young alder stands in different seasons.

This study examined the physiological strain experienced by workers employed in motor-manual timber harvesting performed in winter and summer, and the applicability of heart rate indices for estimating energy expenditure. The heart rates (HR) of 2 teams consisting of 2 persons working simultaneously during felling and forwarding, in both winter and summer, were measured. Heart rate at work (HRwork), resting heart rate (HRrest), relative heart rate (%HRR), ratio of working heart rate to resting heart rate, and 50% level were used to estimate the physiological workload in particular jobs. The HRindex (HRwork/HRrest) equation was used to estimate the energy expenditure (EE). For all jobs, significantly higher physiological workload and energy expenditure were recorded during winter. The season significantly affects the physiological workload during logging operations. If there is no possibility of harvesting wood in summer, in order to limit the workload of workers during winter activity, attention should be paid to the proper organization of work and selection of workers. Int J Occup Med Environ Health. 2022;35(4):437-47.