Electrically stimulated in vitro heart cell mimic of acute exercise reveals novel immediate cellular responses to exercise: Reduced contractility and metabolism, but maintained calcium cycling and increased myofilament calcium sensitivity.

Cardiac cellular responses to acute exercise remain undescribed. We present a model for mimicking acute aerobic endurance exercise to freshly isolated cardiomyocytes by evoking exercise-like contractions over prolonged periods of time with trains of electrical twitch stimulations. We then investigated immediate contractile, Ca2+ , and metabolic responses to acute exercise in perfused freshly isolated left ventricular rat cardiomyocytes, after a matrix-design optimized protocol and induced a mimic for acute aerobic endurance exercise by trains of prolonged field twitch stimulations. Acute exercise decreased cardiomyocyte fractional shortening 50%-80% (p < .01). This was not explained by changes to intracellular Ca2+ handling (p > .05); rather, we observed a weak insignificant Ca2+ transient increase (p = .11), while myofilament Ca2+ sensitivity increased 20%-70% (p < .05). Acidic pH 6.8 decreased fractional shortening 20%-70% (p < .05) because of 20%-30% decreased Ca2+ transients (p < .05), but no difference occurred between control and acute exercise (p > .05). Addition of 1 or 10 mM La- increased fractional shortening in control (1 mM La- : no difference, p > .05; 10 mM La- : 20%-30%, p < .05) and acute exercise (1 mM La- : 40%-90%, p < .01; 10 mM La- : 50%-100%, p < .01) and rendered acute exercise indifferent from control (p > .05). Intrinsic autofluorescence showed a resting NADstate of 0.59 ± 0.04 and FADstate of 0.17 ± 0.03, while acute exercise decreased NADH/FAD ratio 8% (p < .01), indicating intracellular oxidation. In conclusion, we show a novel approach for studying immediate acute cardiomyocyte responses to aerobic endurance exercise. We find that acute exercise in cardiomyocytes decreases contraction, but Ca2+ handling and myofilament Ca2+ sensitivity compensate for this, while acidosis and reduced energy substrate and mitochondrial ATP generation explain this.

Runx1 Deficiency Protects Against Adverse Cardiac Remodeling After Myocardial Infarction.

BACKGROUND: Myocardial infarction (MI) is a leading cause of heart failure and death worldwide. Preservation of contractile function and protection against adverse changes in ventricular architecture (cardiac remodeling) are key factors to limiting progression of this condition to heart failure. Consequently, new therapeutic targets are urgently required to achieve this aim. Expression of the Runx1 transcription factor is increased in adult cardiomyocytes after MI; however, the functional role of Runx1 in the heart is unknown. METHODS: To address this question, we have generated a novel tamoxifen-inducible cardiomyocyte-specific Runx1-deficient mouse. Mice were subjected to MI by means of coronary artery ligation. Cardiac remodeling and contractile function were assessed extensively at the whole-heart, cardiomyocyte, and molecular levels. RESULTS: Runx1-deficient mice were protected against adverse cardiac remodeling after MI, maintaining ventricular wall thickness and contractile function. Furthermore, these mice lacked eccentric hypertrophy, and their cardiomyocytes exhibited markedly improved calcium handling. At the mechanistic level, these effects were achieved through increased phosphorylation of phospholamban by protein kinase A and relief of sarco/endoplasmic reticulum Ca2+-ATPase inhibition. Enhanced sarco/endoplasmic reticulum Ca2+-ATPase activity in Runx1-deficient mice increased sarcoplasmic reticulum calcium content and sarcoplasmic reticulum-mediated calcium release, preserving cardiomyocyte contraction after MI. CONCLUSIONS: Our data identified Runx1 as a novel therapeutic target with translational potential to counteract the effects of adverse cardiac remodeling, thereby improving survival and quality of life among patients with MI.

Developing transmissible vaccines for animal infections.

Intrinsically safe designs and a staged transparent development process will be essential.

GLUT4 translocation and dispersal operate in multiple cell types and are negatively correlated with cell size in adipocytes.

The regulated translocation of the glucose transporter, GLUT4, to the surface of adipocytes and muscle is a key action of insulin. This is underpinned by the delivery and fusion of GLUT4-containing vesicles with the plasma membrane. Recent studies have revealed that a further action of insulin is to mediate the dispersal of GLUT4 molecules away from the site of GLUT4 vesicle fusion with the plasma membrane. Although shown in adipocytes, whether insulin-stimulated dispersal occurs in other cells and/or is exhibited by other proteins remains a matter of debate. Here we show that insulin stimulates GLUT4 dispersal in the plasma membrane of adipocytes, induced pluripotent stem cell-derived cardiomyocytes and HeLa cells, suggesting that this phenomenon is specific to GLUT4 expressed in all cell types. By contrast, insulin-stimulated dispersal of TfR was not observed in HeLa cells, suggesting that the mechanism may be unique to GLUT4. Consistent with dispersal being an important physiological mechanism, we observed that insulin-stimulated GLUT4 dispersal is reduced under conditions of insulin resistance. Adipocytes of different sizes have been shown to exhibit distinct metabolic properties: larger adipocytes exhibit reduced insulin-stimulated glucose transport compared to smaller cells. Here we show that both GLUT4 delivery to the plasma membrane and GLUT4 dispersal are reduced in larger adipocytes, supporting the hypothesis that larger adipocytes are refractory to insulin challenge compared to their smaller counterparts, even within a supposedly homogeneous population of cells.

Run for your life: can exercise be used to effectively target GLUT4 in diabetic cardiac disease?

The global incidence, associated mortality rates and economic burden of diabetes are now such that it is considered one of the most pressing worldwide public health challenges. Considerable research is now devoted to better understanding the mechanisms underlying the onset and progression of this disease, with an ultimate aim of improving the array of available preventive and therapeutic interventions. One area of particular unmet clinical need is the significantly elevated rate of cardiomyopathy in diabetic patients, which in part contributes to cardiovascular disease being the primary cause of premature death in this population. This review will first consider the role of metabolism and more specifically the insulin sensitive glucose transporter GLUT4 in diabetic cardiac disease, before addressing how we may use exercise to intervene in order to beneficially impact key functional clinical outcomes.

GLUT4 expression and glucose transport in human induced pluripotent stem cell-derived cardiomyocytes.

Induced pluripotent stem cell derived cardiomyocytes (iPSC-CM) have the potential to transform regenerative cardiac medicine and the modelling of cardiac disease. This is of particular importance in the context of diabetic cardiomyopathy where diabetic individuals exhibit reduced cardiac diastolic contractile performance in the absence of vascular disease, significantly contributing towards high cardiovascular morbidity. In this study, the capacity of iPSC-CM to act as a novel cellular model of cardiomyocytes was assessed. The diabetic phenotype is characterised by insulin resistance, therefore there was a specific focus upon metabolic parameters. Despite expressing crucial insulin signalling intermediates and relevant trafficking proteins, it was identified that iPSC-CM do not exhibit insulin-stimulated glucose uptake. iPSC-CM are spontaneously contractile however contraction mediated uptake was not found to mask any insulin response. The fundamental limitation identified in these cells was a critical lack of expression of the insulin sensitive glucose transporter GLUT4. Using comparative immunoblot analysis and the GLUT-selective inhibitor BAY-876 to quantify expression of these transporters, we show that iPSC-CM express high levels of GLUT1 and low levels of GLUT4 compared to primary cardiomyocytes and cultured adipocytes. Interventions to overcome this limitation were unsuccessful. We suggest that the utility of iPSC-CMs to study cardiac metabolic disorders may be limited by their apparent foetal-like phenotype.

Cardiac SNARE Expression in Health and Disease.

SNARE proteins are integral to intracellular vesicular trafficking, which in turn is the process underlying the regulated expression of substrate transporters such as the glucose transporter GLUT4 at the cell surface of insulin target tissues. Impaired insulin stimulated GLUT4 trafficking is associated with reduced cardiac function in many disease states, most notably diabetes. Despite this, our understanding of the expression and regulation of SNARE proteins in cardiac tissue and how these may change in diabetes is limited. Here we characterize the array of SNARE proteins expressed in cardiac tissue, and quantify the levels of expression of VAMP2, SNAP23, and Syntaxin4-key proteins involved in insulin-stimulated GLUT4 translocation. We examined SNARE protein levels in cardiac tissue from two rodent models of insulin resistance, db/db mice and high-fat fed mice, and show alterations in patterns of expression are evident. Such changes may have implications for cardiac function.

Recruitment issues and potential solutions to increase rehabilitation science applications.

Recruitment of academically gifted students for Communication Sciences and Disorders, (Speech Language Pathology) Occupational Therapy and Physical Therapy programs has been a challenge for the past few years. A student survey was created to provide insight as to when in their academic development and what methods are used by students to make program selections. Outcomes from this study include: (1) when students made career choices; (2) what influenced them in their career choice, (3) how and why they selected their future profession, (4) the number of programs applied to, and (5) the reasons they selected our university. As a result of this survey, recruitment methods have been enhanced to more actively recruit students during high school and to ensure that personal, volunteer or work-experience is included in the recruitment process.

Use of simulated patients and reflective video analysis to assess occupational therapy students' preparedness for fieldwork.

Educators must determine whether occupational therapy students are adequately prepared for Level II fieldwork once they have successfully completed the didactic portion of their coursework. Although studies have shown that students regard the use of video cameras and simulated patient encounters as useful tools for assessing professional and clinical behaviors, little has been published in the occupational therapy literature regarding the practical application of simulated patients or reflective video analysis. We describe a model for a final Comprehensive Practical Exam that uses both simulated patients and reflective video analysis to assess student preparedness for Level II fieldwork, and we report on student perceptions of these instructional modalities. We provide recommendations for designing, implementing, and evaluating simulated patient experiences in light of existing educational theory.

Ergonomics work assessment in rural industrial settings: a student occupational therapy project.

This case study describes a student occupational therapy (OT) program, the creation of a worksite assessment project as a part of a Community Connections: Partners for Learning and Service grant funded by Health Resources and Services Administration. The primary goals were to design occupation-based community learning experiences in a variety of rural community settings, so that students might benefit from participating in the community based learning and: based on the results, embed occupation-based learning into existing occupational therapy curriculum. The components of the project and the ergonomics content of the OT education program are described; details of the work assessment are presented with analysis of data from the student evaluation of this project.

The clinical impact of the presence or absence of the fifth finger flexor digitorum superficialis on grip strength.

Previous studies have determined abnormalities in the fifth small finger flexor digitorum superficialis (FDS) tendons as interconnected (common) to the fourth finger (FDS) or absent. This study examined the effect of FDS-absent and FDS-common presentations of the fifth finger on grip strength in a mixed-gender group of rehabilitation science students and faculty members from the Medical University of South Carolina. This study evaluated 171 subjects. After controlling for gender, age, and hand dominance, the grip strength of subjects in the FDS-absent group was 6.9 lb weaker than the FDS-common group and 8.14 lb weaker than the FDS-independent group. The common group was 1.2 lb weaker than the normal group. Absence of the FDS occurred in 18.6% of female subjects and 15.3% of male subjects. Our findings suggest that hand therapists should expect lower results when measuring grip strength of FDS-absent or FDS-common individuals.