Temperature-Dependent Effects of ATP on Smooth and Skeletal Muscles

ATP acting via different subtypes of P2X and P2Y receptors induces contractions or relaxation of mammalian smooth muscles, while in skeletal muscles, ATP can pre- and postsynaptically modulate effect of acetylcholine. It was shown that effects of ATP on both types of the muscle are significantly changed when the temperature shifts from physiological condition. For example, contractile responses of rodent urinary bladder and vas deferens mediated by P2X receptors are markedly increased with the decrease of the temperature. Similarly, in frog skeletal muscles, ATP-induced inhibition of acetylcholine release became more pronounced at low temperatures. In case of mammalian skeletal muscle, effect of temperature on ATP-induced responses depends on the type of muscle—slow and fast. In this chapter, we will discuss temperature-dependent effects of ATP on different muscle contractility and their possible mechanisms

Training Young Russian Physicians in Uganda: A Unique Program for Introducing Global Health Education in Russia

Background: Global health is a new concept in Russia. There has been an ongoing academic collaboration between the Yale School of Medicine in the United States and Makerere University College of Health Sciences in Uganda since 2010, and the US Western Connecticut Health Network/University of Vermont College of Medicine since 2012, to introduce global health concepts to Kazan State Medical University (KSMU) in Russia. The purpose was to educate Russian physicians and medical trainees about the practice of clinical medicine and medical education, as well as the general practice of global health in culturally diverse, resource-limited settings. Objectives: The aim of this study was to evaluate the initial outcomes of this multi-institutional partnership and to assess the impact of the global health elective on the participants and on KSMU. Methods: Participants were selected to attend a 6-week elective in global health at Mulago Hospital in Kampala, Uganda. The elective consisted of clinical experience, education about Uganda's common diseases, and region-specific sociocultural classes. It included a predeparture orientation and, upon return, completion of a standard questionnaire to assess the program's impact. Results: Since 2010, there have been 20 KSMU members (4 medical students, 4 interns, 9 residents, 2 fellows, and 1 faculty member) who have participated in the program. As a result of the elective, the participants reported increased knowledge of tropical medicine (70%) and HIV/AIDS (75%), and 95% reported increased cultural sensitivity and desire to work with the underserved. The majority noted a very positive impact of their careers (90%) and personal life (80%). KSMU established the first successful collaborative program in global health education in Russia, leading to the integration of tropical medicine and global health courses in medical school curriculum. Conclusion: This elective has proven highly effective in introducing the concept of global health to faculty, fellows, residents, and medical students at KSMU. It trained these participants to address the challenges faced by physicians in culturally diverse and resource-limited countries

P2 Receptor Signaling in Motor Units in Muscular Dystrophy

The purine signaling system is represented by purine and pyrimidine nucleotides and nucleosides that exert their effects through the adenosine, P2X and P2Y receptor families. It is known that, under physiological conditions, P2 receptors play only a minor role in modulating the functions of cells and systems; however, their role significantly increases under some pathophysiological conditions, such as stress, ischemia or hypothermia, when they can play a dominant role as a signaling molecule. The diversity of P2 receptors and their wide distribution in the body make them very attractive as a target for the pharmacological action of drugs with a new mechanism of action. The review is devoted to the involvement of P2 signaling in the development of pathologies associated with a loss of muscle mass. The contribution of adenosine triphosphate (ATP) as a signal molecule in the pathogenesis of a number of muscular dystrophies (Duchenne, Becker and limb girdle muscular dystrophy 2B) is considered. To understand the processes involving the purinergic system, the role of the ATP and P2 receptors in several models associated with skeletal muscle degradation is also discussed

Effects of ATP on Time Parameters of Contractility of Rats’ Slow and Fast Skeletal Muscles in Normal and Hypothermic Conditions

We have previously shown that hypothermia leads to an increase in the synaptic modulating effects of ATP but not of adenosine in several different animal skeletal muscles. In this paper, we studied the effect of ATP on the amplitude–time parameters of single and tetanic contractions of rats’ isolated fast (1) and slow (2) muscles at different temperatures. We found that when muscles were stimulated by the electrical field (0.1 Hz, 0.5 ms, 10 V), with a decrease in the bath temperature from 37 °C to 14 °C (3), there was an increase in the half-relaxation time of the slow muscle (m. soleus), but not of the fast muscle (m. EDL). Similar effects were observed using a carbachol-induced contraction technique, which suggests the postsynaptic (4) nature of the expansion of the contractile response of the slow muscle induced by ATP (5). To confirm the postsynaptic nature of the observed phenomenon, experiments were performed at a high calcium level (7.2 mM), in which the presynaptic effects of ATP were shown to be offset. We found that the hypercalcium condition did not significantly change the effects of ATP on the measured parameters in both muscles. To record muscle tetanic contractions, we gradually increased the frequency of electrical impulses with the increment of 2.5 Hz to achieve the fusion frequencies of 12.5 Hz for m. soleus and 17.5 Hz for m. EDL at normal temperatures. ATP (100 μM) did not change the fusion frequency for both muscles at a normal temperature but decreased this parameter for the slow muscle to 5 Hz at 14 °C without affecting that for the fast muscle. We conclude that ATP potentiates a hypothermia-induced increase in the half-relaxation time of the contraction of rats’ slow, but not fast, skeletal muscles by acting on postsynaptic P2 receptors (6)

Modulatory Roles of ATP and Adenosine in Cholinergic Neuromuscular Transmission

A review of the data on the modulatory action of adenosine 5’-triphosphate (ATP), the main co-transmitter with acetylcholine, and adenosine, the final ATP metabolite in the synaptic cleft, on neuromuscular transmission is presented. The effects of these endogenous modulators on pre- and post-synaptic processes are discussed. The contribution of purines to the processes of quantal and non-quantal secretion of acetylcholine into the synaptic cleft, as well as the influence of the postsynaptic effects of ATP and adenosine on the functioning of cholinergic receptors, are evaluated. As usual, the P2-receptor-mediated influence is minimal under physiological conditions, but it becomes very important in some pathophysiological situations such as hypothermia, stress, or ischemia. There are some data demonstrating the same in neuromuscular transmission. It is suggested that the role of endogenous purines is primarily to provide a safety factor for the efficiency of cholinergic neuromuscular transmission

La Representación popular del maguey y el puilque en las artes

El artículo que se presenta a continuación aborda la construcción de la identidad nacional mexicana por medio de la interiorización de representaciones de las artes populares dentro del nacionalismo del siglo xx, si bien toma como base el desarrollo artístico académico del siglo xix. Los símbolos que estudia, el maguey y pulque, propios del centro del país, son vistos como representaciones de un pasado agrario que es necesario adaptar a las condiciones de la modernidad. El autor argumenta que la construcción de la idea de nación puede construirse por medio de representaciones culturales en las cuales el éxito de la integración del imaginario popular depende de la capacidad de las artes en dar un nuevo significado al pasado que se pierde