Haematopoiesis in snakes (Ophidia) in early postnatal development

A study on the vertebral column of the dice snake Natrix tessellata (Serpentes, Natricidae) from Denizli (western Anatolia, Turkey)

The vertebral anatomy of snakes has attracted the attention of researchers for decades and numerous studies have been made for extinct and extant species. The present study investigated the morphological variations in vertebral structure among different vertebral regions in the dice snake Natrix tessellata, and provides a detailed anatomical and microstructural description of the vertebral column. Vertebrae were analyzed and compared using x-ray imaging, scanning electron microscopy, micro-computed tomography, and histological techniques. The vertebral column of N. tessellata is divided into three regions: precloacal, cloacal, and caudal. Unlike in many other tetrapods and snakes, the atlas of N. tessellata does not form a complete ring. It has a flat and roughly trilobate shape with a prominent middle lobe. The axis has two hypapophyses. The anterior precloacal region of the vertebral column has longer and more paddle-shaped hypapophyses, distinguishing it from the posterior and mid-trunk vertebrae. The anterior cloacal vertebrae have a short hypapophysis rather than a hemal keel, and the lymphapophysis extends outward, curving slightly. The cotyle and condyle of the caudal vertebrae exhibited a closer resemblance to a rounded shape, while the pleurapophysis extended ventrolaterally and curved ventrally near its distal end. Paired hemapophyses were present at the posterior-most point of the centrum instead of a hypapophysis. In light of previous fossil findings, our anatomical comparison of the vertebral and transverse processes indicates that the extant Natrix has a more flexible and less rigid spine than its ancestors. Overall, the vertebral differences among snake anatomical regions or taxa are a testament to the remarkable diversity and adaptability of these fascinating reptiles.

Left shift and toxic change in heterophils and neutrophils of non-mammalian vertebrates: A comparative review, image atlas, and practical considerations

Heterophils and neutrophils are important first cellular responders to inflammatory conditions. In addition to quantitative shifts in the numbers of these cells in blood, inflammatory disease states often have accompanying increases in immature precursor stages (left shift) and/or evidence of toxic change on blood film evaluation. Recognition of left shift and toxic change morphologies is a salient diagnostic finding with clinical relevance across species. The objectives of this report are to (a) review heterophil and neutrophil function and structure across the vertebrate animal kingdom, (b) compare morphologic features of left shift and toxic change in heterophils and neutrophils of non-mammalian vertebrates (NMV) to mammals, (c) provide an image guide demonstrating the breadth of morphologic diversity of heterophil and neutrophil lineages in health and disease across taxa, and (d) discuss practical considerations for clinical pathologists and other professionals involved in the recognition and interpretation of observations in the inflammatory leukogram of NMV.

Characteristic Distribution of Hematopoietic Cells in Bone Marrow of Xenopus Laevis

Bone marrow is the principal site of hematopoiesis in mammals. Amphibians were the first phylogenetic group in vertebrates to acquire bone marrow, but the distribution of hematopoietic cells in the bone marrow of the primitive frog, Xenopus laevis (X. laevis) has not been well documented. The purpose of this study was to perform a histological investigation of the distribution of hematopoietic cells in femoral bone marrow at various stages of development in X. laevis. Hematopoietic cells showed preferential distribution on the endosteal surface of cortical bone throughout all stages of development, from tadpole to aged frog. In mature frogs, hematopoietic cells appeared at the boundary between the epiphysis and the bone marrow. The distribution of hematopoietic cells around the blood vessels was limited to a small number of vessels in the bone marrow. Abundant adipose tissue was observed in the bone marrow cavity from the tadpole stage to the mature frog stage. Hematopoietic cells showed preferential distribution in a belt-like fashion on the surface of newly-formed bones in a bone regeneration model in the diaphysis of X. laevis. These results indicate that the distribution of hematopoietic cells in bone marrow in X. laevis differs from that in mammals, and that the bone marrow of X. laevis constitutes a useful model for exploring the mechanism underlying the phylogenetic differentiation of bone marrow hematopoiesis.

Does the Spleen Have a Function in Digestion? Medical History, Phylogenetic and Embryological Development of the Splenogastric System

BACKGROUND

Before the spleen was discovered to be a lymphatic blood organ, it had for centuries been considered to be a digestive organ. Concepts of a regulative, secretory and resorptive function in the digestive system were based mainly on a postulated connection between the stomach and the spleen. Splenogastric vascular connections have recently been rediscovered by modern surgery.

SUMMARY

To test the hypothesis that the spleen has a digestive function, this article reviews the literature focusing on the interaction between the spleen and the stomach. We examine the historical medical view of the spleen and stomach system and the reasons why a digestive function was abandoned in the 17th and 18th centuries. We then review the rediscovery of the splenogastric system and the present-day state of knowledge (anatomical origin, variability, haemodynamics) and present it in terms of the phylogenetic and embryological development of the spleen and stomach system. Key Message: Splenogastric arteries and gastrosplenic veins form a portal system which directly connects the spleen and stomach parenchyma. Despite its mesodermal anlage, phylogenetically and embryologically the spleen is intimately interconnected with the entodermal stomach parenchyma but detaches from this in the course of development. Further study is required to establish whether the splenogastric system is merely an evolutive remnant or actually a part of a functioning spleen-stomach system as postulated in complementary and integrative medicine.

Diverse of Erythropoiesis Responding to Hypoxia and Low Environmental Temperature in Vertebrates

Erythrocytes are responsible for transporting oxygen to tissue and are essential for the survival of almost all vertebrate animals. Circulating erythrocyte counts are tightly regulated and respond to erythrocyte mass and oxygen tension. Since the discovery of erythropoietin, the erythropoietic responses to environment and tissue oxygen tension have been investigated in mice and human. Moreover, it has recently become increasingly clear that various environmental stresses could induce the erythropoiesis via various modulating systems, while all vertebrates live in various environments and habitually adapt to environmental stress. Therefore, it is considered that investigations of erythropoiesis in vertebrates provide a lead to the various erythropoietic responses to environmental stress. This paper comparatively introduces the present understanding of erythropoiesis in vertebrates. Indeed, there is a wide range of variations in vertebrates' erythropoiesis. This paper also focused on erythropoietic responses to environmental stress, hypoxia, and lowered temperature in vertebrates.

Phylogenetic and Ontogenetic View of Erythroblastic Islands

Erythroblastic islands are a hallmark of mammalian erythropoiesis consisting of a central macrophage surrounded by and interacting closely with the maturing erythroblasts. The macrophages are thought to serve many functions such as supporting erythroblast proliferation, supplying iron for hemoglobin, promoting enucleation, and clearing the nuclear debris; moreover, inhibition of erythroblastic island formation is often detrimental to erythropoiesis. There is still much not understood about the role that macrophages and microenvironment play in erythropoiesis and insights may be gleaned from a comparative analysis with erythropoietic niches in nonmammalian vertebrates which, unlike mammals, have erythrocytes that retain their nucleus. The phylogenetic development of erythroblastic islands in mammals in which the erythrocytes are anucleate underlines the importance of the macrophage in erythroblast enucleation.

Evolution of B cell immunity

Two types of adaptive immune strategies are known to have evolved in vertebrates: the VLR-based system, which is present in jawless organisms and is mediated by VLRA and VLRB lymphocytes, and the BCR/TCR-based system, which is present in jawed species and is provided by B and T cell receptors expressed on B and T cells, respectively. Here we summarize features of B cells and their predecessors in the different animal phyla, focusing the review on B cells from jawed vertebrates. We point out the critical role of nonclassical species and comparative immunology studies in the understanding of B cell immunity. Because nonclassical models include species relevant to veterinary medicine, basic science research performed in these animals contributes to the knowledge required for the development of more efficacious vaccines against emerging pathogens.