1. Investigación

Many physiological events occurring during the estrous cycle, including folliculogenesis, oocyte maturation, ovulation, follicular atresia, corpus luteum development, luteolysis, steroidogenesis, and angiogenesis are associated with an increased expression of the renin–angiotensin–aldosterone system (RAAS) in uterus and ovarian follicles. This enhanced expression leads to a rise in plasma concentrations of these hormones in women and laboratory animals, and the same might happen in the mare. This study aims to assess if an activation of the RAAS occurs in mares around ovulation and if this activation is related to the diameter of the predominant follicle (DPF), packed cell volume (PCV), and electrolyte concentrations. Twenty-five healthy Spanish Purebred mares were sampled during the five days before ovulation, the day of ovulation, and the first five days after ovulation. Renin (REN) concentrations increased progressively during the five days before ovulation, achieving the highest values on the day of ovulation. Angiotensin (ANG) concentrations showed a sharp decrease after ovulation, with the lowest values the fifth day after it. Aldosterone (ALD) concentrations increased progressively, from the fifth day before ovulation until the fifth day after ovulation. The highest PCV values were found on the day of ovulation. There were no relevant correlations between the RAAS components and electrolytes concentrations. Before ovulation, there was a positive relationship between REN and ALD (r = 0.760) and after ovulation, a negative correlation between ANG and ALD (r = –0.660). The DPF was correlated with REN (r = 0.740) and with ALD (r = 0.800) concentrations. Ovulation in the mare is associated with high plasma REN concentrations, and therefore, with an activation of the RAAS. In addition, after ovulation, the sharp decrease in plasma REN and ANG concentrations might be a reflex of the modulation of the previously activated RAAS, although plasma ALD concentrations increased during this period.

Durante la gestación se producen ajustes de tipo metabólico y cardiovascular cuyo objetivo va encaminado a preservar la energía y disponer de la cantidad adecuada de nutrientes necesarios para el crecimiento y desarrollo del feto equino. Por tanto, este periodo representa un estrés metabólico en la yegua, que podría manifestarse en las características hematológicas, bioquímicas y hormonales. Por este motivo, los objetivos planteados en la presente investigación fueron los siguientes: 1) Establecer valores hematológicos, bioquímicos y hormonales de referencia para la yegua PRE gestante; 2) Analizar el efecto de la gestación sobre el perfil hemático, bioquímico y hormonal de las yeguas y 3) Valorar las modificaciones hematológicas, bioquímicas y hormonales asociadas al envejecimiento de las madres. Se ha estudiado un total de 31 yeguas reproductoras PRE a lo largo de la gestación, la cual fue dividida en tres periodos (I, II y III) de duración similar. Las yeguas fueron clasificadas en tres grupos de edad: A (entre 4 y 9 años, n=21), B (entre 10 y 14 años, n=7) y C (mayores de 15 años, n=3). Se obtuvieron muestras de sangre venosa a lo largo del periodo gestacional, por las mañanas, con una frecuencia mensual. De la extracción realizada a cada una de las yeguas, se separaron dos fracciones, almacenándose en cantidades similares en tubos con heparina-litio, y tubos de vidrio con activadores de la coagulación, para la extracción de plasma y suero, de forma respectiva. Previamente a la centrifugación de la sangre anticoagulada con heparina-litio, se procedió a la realización del microhematócrito. En plasma se analizaron las concentraciones de proteínas y electrolitos, sodio, potasio y cloro, empleando la espectrofotometría y el analizador con electrodos selectivos, respectivamente. Las concentraciones de renina, angiotensina, aldosterona, cortisol, sulfato de estrona y progesterona se analizaron en suero, empleando técnicas inmunoenzimáticas de competición. A nivel hematológico y bioquímico, la gestación en la yegua PRE se caracterizó por un aumento del valor hematócrito, sin modificaciones de las concentraciones de proteínas plasmáticas y electrolitos, sodio, potasio y cloro. A nivel hormonal, la gestación presentó incremento de las concentraciones de renina y aldosterona, disminución de la concentración de cortisol, y fluctuaciones de dirección variable de las concentraciones de progesterona y sulfato de estrona, sin modificaciones apreciables de los niveles de angiotensina II. El avance de la edad en la yegua reproductora PRE se caracterizó por la reducción de las concentraciones de angiotensina II, sodio y cloro, sin modificaciones del valor hematócrito, de las concentraciones de potasio, renina, aldosterona, progesterona, sulfato de estrona y cortisol. En conclusión, el estado fisiológico de la gestación modifica significativamente los parámetros hematológicos, bioquímicos y hormonales en la yegua PRE. La preñez se caracteriza por una marcada actividad del Sistema Renina Angiotensina Aldosterona. Este hecho posiblemente pueda estar relacionado con la interacción de determinados factores metabólicos y hormonales que acontecen durante la preñez en la yegua. En la yegua PRE, la gestación podría enmascarar los efectos hematológicos, bioquímicos y hormonales promovidos por la edad.

Myeloid disorders are conditions being characterized by abnormal proliferation and development of myeloid lineage including granulocytes (neutrophils, eosinophils and basophils), monocytes, erythroids, and megakaryocytes precursor cells. Myeloid leukemia, based on clinical presentation and proliferative rate of neoplastic cells, is divided into acute (AML) and myeloproliferative neoplasms (MPN). The most commonly myeloid leukemia reported in horses are AML-M4 (myelomonocytic) and AML-M5 (monocytic). Isolated cases of AML-M6B (acute erythroid leukemia), and chronic granulocytic leukemia have also been reported. Additionally, bone marrow disorders with dysplastic alterations and ineffective hematopoiesis affecting single or multiple cell lineages or myelodysplastic diseases (MDS), have also been reported in horses. MDSs have increased myeloblasts numbers in blood or bone marrow, although less than 20%, which is the minimum level required for diagnosis of AML. This review performed a detailed description of the current state of knowlegde of the myeloproliferative disorders in horses following the criteria established by the World Health Organization.

The process of fibrin clot formation is a series of complex and well-regulated reactions involving blood vessels, platelets, procoagulant plasma proteins, natural inhibitors, and fibrinolytic enzymes. Vasculitis can be caused by a variety of different agents as bacteria, viruses, protozoal, rickettsial organisms, toxic, drugs, medications, and neoplasms. The most common cause of vasculitis is the purpura hemorrhagica, which is associated with exposure to Streptococcus equi ssp. equi or less commonly, equine influenza. Deficiencies or defects of the hemostatic components may result in bleeding and/or thrombosis. Inherited alterations of primary hemostasis (von Willebrand disease: vWD and Glanzmann’s thrombasthenia: GT) and of secondary hemostasis (hemophilia A and prekallikrein: PK deficiency) are scarcely reported in equine clinic. On the contrary, acquired alterations of primary and secondary hemostasis are commonly found. They include thrombocytopenia, platelet dysfunction due to the administration of some drugs and targeted antiplatelet agents, decreased factor synthesis (liver disease or deficiency of vitamin K), release of inactive factors, inhibition of factor activity, or excessive consumption and depletion of factors (platelets, coagulation factors, and anticoagulants factors as antithrombin (AT) and protein C). Disseminated intravascular coagulation (DIC) is the most common and complex hemostatic disorder in horses and appears to be associated with sepsis, inflammatory and ischemic gastrointestinal tract disorders and other systemic severe diseases. These alterations are commonly found in patients in intensive care units.