Microanatomy and ultrastructure of kidney interstitial cells and nephron in brown trout (Salmo trutta Linnaeus, 1758) at different stages of the life cycle

The study focuses on the microanatomy and ultrastructural changes in the trunk kidney interstitium cells and nephrons in parr, smolt and spawning brown trout Salmo trutta Linnaeus, 1758 sampled in Luga River and Solka River, the tributaries of the Baltic Sea. Regardless of the type of cells or their structure, there were changes in their areas and the number and structure of organelles responsible for the transport, synthetic and energetic function of cells. Our data on the morphology of the nephron combined with data on its physiology suggest a fundamental change in kidney function during the parr-smolt transformation before migration; this could be a preadaptation for a successful life in saltwater where urine output is sharply reduced. Thus, detected structural features of the trunk kidney in brown trout S. trutta are cytological markers of the migration process. The numbers of lymphocytes, neutrophils and eosinophils with segmented nuclei increased from parr to smolts and then to spawners; only monotypic specific granules in neutrophils were found in smolts and spawners. Cells with radially arranged vesicles were described for the first time in brown trout S. trutta renal interstitium. Their origin has not yet been established. The shape of these cells changed from spherical to trihedral during fish maturation. All the above ultrastructural changes of renal interstitium cells could be considered cytological markers of cell maturity.

Erythrocyte profile of circulating blood of Neogobius melanostomus (Pallas, 1814) under conditions of experimental hypothermia

The influence of hypothermia on erythrocyte profile of thermophile teleost species round goby, Neogobius melanostomus (Pallas, 1814), has been studied. Fish were acclimated to temperature 1-2^оС, 15-16^оС and 19-20^оС (control group) and held at given conditions for 5 days. The number of red blood cell precursors (pronormoblasts, basophilic and polychromatophilic normoblasts) in circulating blood has been estimated. Also, the number of abnormal erythrocytes, i.e. cells with micronuclei, nuclei invaginations, red blood cell shades, dacryocytes and cells undergoing amitosis has been determined on smears. The number of immature erythrocytes increased more than two times (p < 0,001) at 1-2^оС. The number of low-differentiated precursors, pronormoblasts and early basophilic normoblasts, increased for the most part. The number of abnormal erythrocytes did not change substantially, The changes in cellular blood composition were accompanied with the increase of plasma lactate concentration, indicating hypoxic state of fish. The results of the present work indicate that hematopoietic tissue remains sensitive to controlling factors at hypothermia, such as hypoxia, and may enhance proliferation and differentiation of erythroid cells.

Hematopoietic stem cells debut in embryonic lymphomyeloid tissues of elasmobranchs

The evolutionary initiation of the appearance in lymphomyeloid tissue of the hemopoietic stem cell in the earliest (most primitive) vertebrate model, i.e. the elasmobranch (chondroichthyan) Torpedo marmorata Risso, has been studied. The three consecutive developmental stages of torpedo embryos were obtained by cesarean section from a total of six pregnant torpedoes. Lymphomyeloid tissue was identified in the Leydig organ and epigonal tissue. The sections were treated with monoclonal anti-CD34 and anti-CD38 antibodies to detect hematopoietic stem cells. At stage I (2-cm-long embryos with external gills) and at stage II (3-4 cm-long embryos with a discoidal shape and internal gills), some lymphoid-like cells that do not demonstrate any immunolabeling for these antibodies are present. Neither CD34+ nor CD38+ cells are identifiable in lymphomyeloid tissue of stage I and stage II embryos, while a CD34+CD38- cell was identified in the external yolk sac of stage II embryo. The stage III (10-11-cm-long embryos), the lymphomyeloid tissue contained four cell populations, respectively CD34+CD38-, CD34+CD38+, CD34-CD38+, and CD34-CD38- cells. The spleen and lymphomyeloid tissue are the principal sites for the development of hematopoietic progenitors in embryonic Torpedo marmorata Risso. The results demonstrated that the CD34 expression on hematopoietic progenitor cells and its extraembryonic origin is conserved throughout the vertebrate evolutionary scale.

Morphological and functional characterization of hemocytes in cultivated mussel (Mytilus galloprovincialis) and effect of hypoxia on hemocyte parameters

The circulating hemocytes of cultivated marine mussel (Mytilus galloprovincialis) were investigated using light microscopy and flow cytometry. In mussels two cell types, granulocytes and agranulocytes, were identified based on the existence of two subpopulations of cells differing by size and granularity level on light-scattered plots. Light microscopic observation confirmed the presence of cells with cytoplasmic granules and cells without granulation in hemolymph of mussels. The main type of cells in hemolymph were agranular cells amounting 78.4 ± 8.9% in mussels. Flow cytometry showed that the agranular hemocytes of the mollusks produce significantly less reactive oxygen species compared to granulocytes. Mussel were exposed for 24 h of hypoxia and immune functions including hemocyte mortality, proliferation and reactive oxygen species (ROS) production were analysed using flow cytometric methods. Granulocyte number was higher at low oxygen concentration than that at normoxia; agranulocytes number decreased, in contrast. The ROS production after hypoxic treatment was decreased compared to normoxia level. No significant changes in hemocyte mortality and proliferation were observed.

Cellular Composition and Proliferation Levels in the Hematopoietic Tissue of Black Scorpionfish (Scorpaena porcus L.) Head Kidney and Spleen During the Spawning and Wintering Periods

To identify cells and analyze proliferative activity of hematopoietic tissue, black scorpionfish head kidney and spleen cells were characterized by light microscopy and flow cytometry. Hematopoiesis of black scorpionfish head kidney was formed by the following series: erythropoietic, granulopoietic, lymphopoietic, and thrombopoietic. Flow cytometric analysis allowed dividing blood cells in hematopoietic organs into subpopulations differing by size, granularity, and proliferative activity. Three distinct subpopulations were observed during the wintering period. The number of small low-granulated cells, identified as lymphocytes and thrombocytes, was 41% ± 4% in both wintering and spawning fish. Proliferating subpopulation of blast (high-granulated) cells amounted to about 36% of the total cell count with 50% ± 5% of proliferating cells; the largest low-granulated cells (10% of total cells) comprised maturing white blood cells, monocytes, and macrophages. The spawning period was accompanied with an increase of maturing neutrophils and enhancement of blast cell proliferation. In the spleen three distinct subpopulations were observed. The subpopulation of small low-granulated cells comprised lymphocytes and thrombocytes similar to the head kidney and amounted 33% ± 4%. Other cells with larger diameter were identified as red blood cells. No proliferation was observed during the wintering period in the spleen, however, spawning induced cell proliferation of erythroblasts (small granulated cells) with the number of dividing cells 84% ± 1%. Anat Rec, 302:1136-1143, 2019. © 2018 Wiley Periodicals, Inc.