Livres sur le sujet « TRP receptors »

The landmark paper discussed in this chapter is ‘The capsaicin receptor: A heat activated ion channel in the pain pathway’, published by Caterina et al. in 1997. The identification of the molecular basis for the sensitivity of a major proportion of nociceptive primary sensory neurons for capsaicin, the pungent agent in chilli pepper, was undoubtedly one of the most significant pain-related discoveries in the twentieth century, for at least three reasons. First, the mechanism for capsaicin-induced responses could unequivocally be explained. Second, the discovery heralded the starting point for the development of a highly promising, mechanism-based means of analgesia. Third, the discovery also sparked studies which resulted in the discovery of the major cation channel family, the transient receptor potential (TRP) ion channel family, several members of which have also become putative targets for the development of analgesics.

The paper discussed in this chapter describes the first mapping of neurotrophin receptors in adult sensory neurons. Neurotrophins and their receptors were a particularly hot topic at the time, but the primary focus of interest had been in their role in development. In this paper, McMahon and colleagues characterized both mRNA and protein expression of the recently discovered trk receptors on defined populations of adult sensory neurons, correlating trk expression with other primary afferent projection neuron properties such as cell size and neuronal function. Furthermore, by showing clear correlations between the expression of different trk receptors and the physical and functional properties of defined primary afferent projections, the authors provided key evidence suggesting that nerve growth factor and neurotrophin-3 acted on functionally distinct populations of adult sensory neurons. This paper provided the basis for subsequent research on neurotrophin signalling and function in both the healthy and the diseased nervous system.

Touch and taste provide information about objects in contact with, and inside, the body for use in detection and manipulation of food items. Four main types of touch receptors are found distributed in most parts of the body but some birds have ‘bill tip organs’ with very high concentrations of touch receptors. Three main types of bill tip organs are found in waterfowl, parrots, shorebirds, ibises, and kiwi. They allow birds to locate hidden objects with the bill alone and parrots to use their bills as third limbs. Seven types of taste receptors exist in birds, mainly in the mouth cavity but also within the gut. Information from these receptors play key roles in food intake and aids shorebirds in detecting profitable feeding locations. Detection of the geomagnetic field, by means of two known mechanisms, is probably widespread among birds. It plays a key role in direction and position finding.

A panoply of pharmacological and nonpharmacological strategies are currently employed to attenuate the risk of postoperative nausea and vomiting (PONV) in children, including 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists. 5-HT3 receptor antagonists can prolong the QT interval, which can be a precursor of torsades de pointes (TdP), particularly in children with congenital or acquired prolonged QT interval. This chapter summarizes the causes of prolonged QT interval, the potential interactions of prolonged QT interval with antiemetics and anesthetics, and strategies to prevent PONV.

This chapter describes the means that have been and can be used as management tools to limit chemical emissions and exposures to humans and other receptors that result in adverse effects. They include top-down mandates specified in enforceable exposure and/or emission standards (regulatory controls), bottom-up approaches involving control of access or requirements for the use of personal protective equipment (administrative controls), and various technologies that limit the use of chemicals (e.g., materials substitution) and/or capture and treat chemical wastes before their emissions to environmental media (engineering controls).

Thyroid hormones act on most tissues via nuclear T3 receptors. Thyroid hormones stimulate oxygen consumption and heat production, influence cell growth and maturation (central nervous system, bone), and modulate metabolism (carbohydrates, lipids, proteins, drugs). Treatment for presumed thyroid disease frequently has to be initiated before the results of diagnostic tests are available. Treatment of hyperthyroidism should result in the reduction of serum thyroid hormone levels and their action on peripheral tissues with concurrent treatment of the precipitating event. In severe hypothyroidism the choice of thyroid hormone (thyroxine or tri-iodothyronine), optimal dosing, and the route of administration remain controversial

Ischaemic heart disease and stroke are major causes of death and morbidity worldwide. Coronary and cerebrovascular events are mainly a consequence of a sudden thrombotic occlusion of the vessel lumen. Arterial thrombosis usually develops on top of a disrupted atherosclerotic plaque because of the exposure of thrombogenic material, such as collagen fibrils and tissue factor (TF), to the flowing blood. TF, either expressed by subendothelial cells, macrophage- and/or vascular smooth muscle-derived foam-cells in atherosclerotic plaques, is a key element in the initiation of thrombosis due to its ability to induce thrombin formation (a potent platelet agonist) and subsequent fibrin deposition at sites of vascular injury. Adhered platelets at the site of injury also play a crucial role in the pathophysiology of atherothrombosis. Platelet surface receptors (mainly glycoproteins) interact with vascular structures and/or Von Willebrand factor triggering platelet activation signalling events, including an increase in intracellular free Ca2+, exposure of a pro-coagulant surface, and secretion of platelet granule content. On top of this, interaction between soluble agonists and platelet G-coupled protein receptors further amplifies the platelet activation response favouring integrin alpha(IIb)beta(3) activation, an essential step for platelet aggregation. Blood-borne TF and microparticles have also been shown to contribute to thrombus formation and propagation. As thrombus evolves different circulating cells (red-blood cells and leukocytes, along with occasional undifferentiated cells) get recruited in a timely dependent manner to the growing thrombus and further entrapped by the formation of a fibrin mesh.

Under normal circumstances, the somatosensory system contributes more to shaping movements than to perception. Yet damage to the somatosensory system can result in spontaneous pain and other abnormal somatic perceptions. An exploration of the mechanisms and pathways involved in touch perception is slanted toward understanding the contribution of the dorsal column–medial lemniscus pathway to the generation of paresthesia and dysesthesia. Peripheral somatosensory afferents that contribute to the perception of sharp or aching pain, temperature, and itch are described. The properties of transient receptor potential (TRP) channels on nociceptors and thermoreceptors are described. Physiological and pharmacological mechanisms that lead to neurogenic inflammation are considered. How peripheral and central changes triggered by acute injury or disease can lead to long-lasting changes that support chronic pain is described. Persistent pain that occurs independently of any stimulus is termed neuropathic. Mechanisms of referred pain from deep structures including viscera are introduced.

Situated at the southern edge of the Tibetan Plateau (TP), the Hindu-Kush-Himalayas-Gangetic (HKHG) region is under the clear and present danger of climate change. Flash-flood, landslide, and debris flow caused by extreme precipitation, as well as rapidly melting glaciers, threaten the water resources and livelihood of more than 1.2 billion people living in the region. Rapid industrialization and increased populations in recent decades have resulted in severe atmospheric and environmental pollution in the region. Because of its unique topography and dense population, the HKHG is not only a major source of pollution aerosol emissions, but also a major receptor of large quantities of natural dust aerosols transported from the deserts of West Asia and the Middle East during the premonsoon and early monsoon season (April–June). The dust aerosols, combined with local emissions of light-absorbing aerosols, that is, black carbon (BC), organic carbon (OC), and mineral dust, can (a) provide additional powerful heating to the atmosphere and (b) allow more sunlight to penetrate the snow layer by darkening the snow surface. Both effects will lead to accelerated melting of snowpack and glaciers in the HKHG region, amplifying the greenhouse warming effect. In addition, these light-absorbing aerosols can interact with monsoon winds and precipitation, affecting extreme precipitation events in the HKHG, as well as weather variability and climate change over the TP and the greater Asian monsoon region.

Vibrio parahaemolyticus es la principal causa de gastroenteritis transmitida por mariscos en todo el mundo. La virulencia de V. parahaemolyticus se ha atribuido hasta ahora principalmente a la hemolisina directa termoestable (TDH) y la hemolisina relacionada con TDH (TRH). Recientemente el Sistema de Secreción de tipo III del cromosoma II (T3SS2), el cual codifica para varios efectores, ha sido relacionado con citotoxicidad y enterotoxicidad. Después de la aparición y posterior caída de la cepa pandémica, se han notificado casos de diarrea producidos por cepas clínicas que carecen de los genes tdh, trh y T3SS2 en muchos países, incluido Chile. Estas cepas, llamadas “no toxigénicas”, constituyen el 9-10% de los casos de diarrea a nivel mundial y aunque se han hecho avances en la descripción de los factores de virulencia de V. parahaemolyticus, la capacidad de las cepas no toxigénicas para causar enfermedad no ha sido completamente entendida. El hecho de que los genes tdh y trh se utilizan para estimar la carga de cepas patógenas en los mariscos durante el análisis de riesgo llama la atención sobre cuán fiables son estos análisis para detectar la gran variedad de cepas potencialmente patógenas presentes en las aguas y productos marinos. Por otra parte se conoce que en Vibrio, la evolución de la virulencia, parece estar estrechamente asociada a su capacidad para generar diversidad genética, en parte, a través de la modificación de la expresión génica, aunque mayoritariamente a través de transferencia genética horizontal (HGT). Con base en lo descrito anteriormente, esta propuesta hipotetiza que las cepas no toxigénicas de Vibrio parahaemolyticus han adquirido nuevos factores de virulencia mediante transferencia genética horizontal. Es por ello que el objetivo de esta tesis es: Identificar y caracterizar nuevos factores de virulencia en cepas chilenas no toxigénicas de Vibrio parahaemolyticus adquiridos mediante transferencia génica horizontal. Esta tesis está organizada en tres capítulos, el capítulo 1 comprende el marco teórico, el planteamiento del problema, la hipótesis y los objetivos. El capítulo 2, correspondiente al desarrollo del objetivo 1, en el cual se caracteriza el genoma de seis cepas no toxigénicas de V. parahaemolyticus aisladas del Sur de Chile. Uno de los principales hallazgos de este estudio fue la variabilidad genética de estas cepas al analizar su genoma accesorio. Este análisis mostró además la presencia de nuevas islas genómicas y elementos tipo profagos que codifican toxinas como zonula occludens (Zot) y repeats-in-toxin (RTX), ambas descritas en otros patógenos como V. cholerae donde se consideran factores de virulencia, aunque últimamente se ha descrito que la pérdida de RTX no afecta la virulencia de esta bacteria. En el capítulo 3 y final de esta tesis, se aborda el objetivo 2 que corresponde a la caracterización de posibles nuevos factores de virulencia, en este caso, la toxina Zonula Occludens (Zot). Aunque se sabe que Zot aumenta la permeabilidad epitelial intestinal por interacción con el receptor celular de zonulina PAR2 y esta unión desencadena una cascada de eventos intracelulares que conducen al desensamblaje de las uniones estrechas intercelulares, lo que se ha asociado con la producción de la diarrea en V. cholerae, el potencial patógeno de Zot de V. parahaemolyticus no se ha investigado aún. La cepa clínica PMC53.7, tdh/trh/T3SS2/negativa, resultó ser altamente citotóxica en cultivo celular de Caco-2 y contiene en su genoma accesorio un gen homólogo de zot. Con este antecedente, se caracterizó la toxina Zot en la cepa clínica PMC53.7 de V. parahaemolyticus y sus efectos sobre la barrera epitelial intestinal. El gen zot de PMC53.7 se clonó y se expresó en Escherichia coli BL21(DE3) y los efectos sobre la barrera epitelial intestinal se examinaron usando el modelo celular Caco-2. Se evaluó el cambio en la distribución de las proteínas de transmembrana asociadas a uniones estrechas (ZO-1 y ocludina), y en la distribución de actina en monocapas de Caco-2. Tras el tratamiento con Zot, se observó una modificación de la morfología celular. El cambio en las distribuciones de ocludina y F-actina se observó como una fragmentación de los límites brillantes de las células, con áreas de baja y alta intensidad, lo que indica una pérdida y redistribución de las proteínas asociadas a uniones estrechas. Los resultados de este trabajo sugieren que V. parahaemolyticus Zot puede contribuir a la virulencia de cepas no toxigénicas. En resumen, estos estudios han arrojado información sobre la diversidad de cepas de V. parahaemolyticus del sur del Pacífico, en especial aquellas que no poseen los principales factores de virulencia descritos para este microorganismo. Además, se caracteriza por primera vez una toxina Zot de V. parahaemolyticus en una cepa aislada de un paciente. Finalmente, los ensayos preliminares realizados en cultivo celular demostraron un posible potencial patógeno de esta toxina en la barrera epitelial intestinal.