Storage of Blood in the Mammalian Spleen: an Evolutionary Perspective

Abstract

Splenic blood storage is usually considered a characteristic restricted to Carnivora, Perissodactyla, and Ruminantia. In these mammals, the red pulp comprises the major part of the organ and -within it -the cords show a vast extension, allowing the storage of a great quantity of erythrocytes. Moreover, well-muscularized capsule and trabeculae permit a strong contractility. In this way, a significant quantity of erythrocytes can be poured into the circulation in response to an increased demand of oxygen. These spleens are usually classified as the Bstoring type,î n contrast to the Bdefensive type,^characterized by negligible quantity of blood stored. Past evolutionary interpretations have seen the former type as derived from the latter one. This explanation was based on some ontogenetic observations, thus deriving from the approach of Haeckel's biogenetic law, and caused some contradictions that remained unsolved. An in-depth examination of the literature reveals that almost all mammalian species can store erythrocytes in their spleen. What changes is the quantity of this storage and the efficiency of its release. This means that the dichotomy between Bstorage^and Bdefensivet ypes is just an approximation -and not very useful. Splenic storage, indeed, is not a recently acquired character by some mammals, rather a primitive one, that underwent different quantitative and qualitative changes during the evolution of the different mammalian lineages. This review offers a new hypothesis on the evolution of this function (viewing the presence of splenic erythropoiesis as a biological constraint) and proposes it as a case of exaptation.

Clinical effects of immunization, bleeding, and albumin-based fluid therapy in horses used as immunoglobulin source to produce a polyspecific antivenom (Echitab-plus-ICP) towards venoms of African snakes

“…Despite the loss of blood associated with the bleeding protocol, no relevant variations of oxygen saturation (SpO 2 ≥ 90%), systolic pressure (140–190 mm Hg), diastolic pressure (90–110 mm Hg), heart rate (27–43 bpm), P wave duration (0.09–0.14 s), PR interval (0.21–0.33 s), or QRS duration (0.12–0.14 s) were detected during the bleeding of three horses studied for cardiorespiratory alterations ( Welch-Huston et al, 2020 ). The loss of RBCs during bleeding is likely to be compensated by splenic contraction and the consequent mobilization of cells into the intravascular compartment ( Udroiu, 2017 ). Further research is needed to understand the mechanisms involved in the recovery of hematological parameters after the bleeding protocols are carried out in antivenom production.…”

Short Communication: Erythrocytes and leukocytes profiles of bottlenose dolphins (Tursiops aduncus) at conservation site

“…The blood release from the spleen helps the distribution of sufficient oxygen while diving. However, this condition is not applied to bottlenose dolphins because they do not have the capacity to store blood in the spleen (Udroiu 2017). Therefore, there is no difference in HCT between captive and free-range bottlenose dolphin.…”

Size-Dependent In Vivo Transport of Nanoparticles: Implications for Delivery, Targeting, and Clearance

“…The spleen is a well-perfused and important lymphatic organ, composed of two major types of tissue called red pulp and white pulp. , The red pulp accounts for nearly 80% of the spleen parenchyma and is mainly made up of cords rich in venous sinus and macrophages, while the white pulp largely comprises lymph-related nodules. The primary role of the spleen is to perform blood filtration and serve as a reservoir for blood storage and immunocyte storage to some extent. , As a blood filtration system, the spleen possesses a plentiful of reticuloendothelial system (RES), and the RES in the spleen effectively isolates senescent erythrocytes and pathogens from the bloodstream because blood components must squeeze through the ∼200 nm wide fenestration in the RES. − Subsequently, the abundant macrophages in the spleen phagocytosed and eliminated these entities . It is generally noticed that nanoparticles with size larger than 200 nm tend to be retained in the spleen because they could not effectively sieve through the splenic RES. , In addition, nanoparticle transport in the spleen is simultaneously affected by other factors, such as shape, rigidity, , and affinity for immunocytes .…”

“…The primary role of the spleen is to perform blood filtration and serve as a reservoir for blood storage and immunocyte storage to some extent. 174,175 As a blood filtration system, the spleen possesses a plentiful of reticuloendothelial system (RES), and the RES in the spleen effectively isolates senescent erythrocytes and pathogens from the bloodstream because blood components must squeeze through the ∼200 nm wide fenestration in the RES. 176−178 Subsequently, the abundant macrophages in the spleen phagocytosed and eliminated these entities.…”