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.

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.