Characterization of sinusoidal endothelial cells of the liver and bone marrow using an intravital lectin injection method.

The vascular endothelia express a variety of structural and biological phenotypes. We used an intravital injection method of plant derived lectins (Lycopersicon esculentum lectin (LEL), Ricinus communis Agglutinin-I (RCA-I), Ulex europaeus Agglutinin-I (UEA-I) and Concanavalin A (ConA)) to elucidate the morphology and function of the sinusoidal endothelium of the liver and bone marrow. All four lectins stained the sinusoidal endothelia of the liver and bone marrow in a patchy granular pattern which differed from the uniform and smooth staining pattern of non-sinusoidal vessels in other organs. By transmission electron microscopy, the granular pattern was identified as internalization of these lectins and subsequent accumulation within the endothelial cells, suggesting their active endocytosis. The endocytosis of these lectins emphasizes the fact that sinusoidal endothelial cells of the liver and bone marrow belong to the reticuloendothelial system (RES), a cell system characterized by internalization of foreign material. We introduce this intravital lectin injection as a useful technique to discriminate sinusoidal endothelial of the liver and bone marrow from other vascular endothelia.

The selective distribution of LYVE-1-expressing endothelial cells and reticular cells in the reticulo-endothelial system (RES).

LYVE-1, a receptor molecule for hyaluronan, is expressed in the lymphatic endothelium, blood sinus endothelium, and certain macrophage lineages. The present immunohistochemical study revealed a broader distribution of LYVE-1 in vascular endothelial cells of the murine lung, adrenal gland, and heart as well as the liver and spleen. In addition, sinus reticular cells-including sinuslining cells-in the medulla of the lymph node also intensely expressed LYVE-1. Ultrastructurally, immuno-gold particles for LYVE-1 were localized on the entire length of plasma membrane in all cell types. Most of these LYVE-1-expressing cells had previously been classified as the reticuloendothelial system (RES) specialized for eliminating foreign particles. An LPS stimulation decreased the LYVE-1 expression in macrophages but elevated the expression at mRNA and protein levels in the liver and lung, major organs for the elimination of blood-born waste substances. LYVE-1-expressing endothelial cells in these organs participated in the endocytosis of exogenous particles, and the uptake ability was conspicuously enhanced by the LPS challenge. Although the expression of the degrading enzyme, hyaluronidase, was generally low in the LYVE-1-expressing cells, they were topographically associated with a dense distribution of macrophages possessing hyaluronidase activities in each tissue. These findings suggest that the LYVE-1-expressing cells might be involved in the uptake of hyaluronan and other waste products as well as foreign particles circulating in the blood and lymph while participating in the subsequent degradation in relay with adjacent macrophage populations.

Morphological Analysis of Reticuloendothelial System in Capuchin Monkeys (Sapajus spp.) after Meso-2,3-Dimercaptosuccinic Acid (DMSA) Coated Magnetic Nanoparticles Administration.

Magnetic nanoparticles can be used for numerous in vitro and in vivo applications. However, since uptake by the reticuloendothelial system represents an obstacle for the achievement of nanoparticle diagnostic and therapeutic goals, the aim of the present study was to evaluate the uptake of dimercaptosuccinic acid coated magnetic nanoparticles by reticuloendothelial system phagocytic cells present in lymph nodes, spleen, and liver tissue and how the presence of these particles could have an impact on the morphology of these organs in capuchin monkeys (Sapajus spp.). Animals were intravenously injected with dimercaptosuccinic acid coated magnetic nanoparticles and euthanized 12 hours and 90 days post-injection. Organs were processed by transmission electron microscopy and histological techniques. Samples of spleen and lymph nodes showed no morphological changes. Nevertheless, liver samples collected 90 days post-administration showed slight morphological alteration in space of Disse. Moreover, morphometrical analysis of hepatic mitochondria was performed, suggesting a clear positive correlation between mitochondrial area and dimercaptosuccinic acid coated magnetic nanoparticles administration time. The present results are directly relevant to current safety considerations in clinical diagnostic and therapeutic uses of magnetic nanoparticles.

Development and histogenesis of the thymus in dog. A light and electron microscopical study.

The development of the thymus was studied with histological, transmission electron microscopic (TEM) and histochemical methods in 100 dog fetuses (beagle), between day 19 of gestation and day 21 after birth. Thymus development could be divided in three stages: 1/Formation of epithelial palisades; 2/Initiation of lymphopoiesis; 3/Differentiation of the medulla and Hassall's bodies (HB). The epithelial anlagen were seen at day 23 of gestation showing the characteristic palisade structure of the endodermally derived epithelium. Ten days later the beginning of lymphoiesis and the reticularization of the epithelial cells could be seen. The first HB could be found at day 38 when cortical-medullary differentiation is recognized. The histochemical observation demonstrated a rich content of PAS positive coarse granules in the cytoplasm of reticulo-epithelial (RE) cells. On the other hand, the HB showed a diffuse PAS positive reaction. The ultrastructural investigations demonstrated the presence of desmosomes connecting RE cells to one another. Desmosomes were not found between RE and lymphocytes. The growth of the developing thymus into the mesenchymal matrix resulted in the lobulation of the organ by connective tissue cells and fibers. The first mast cells were seen at day 35 of gestation, most abundantly in the interlobular connective tissue (ICT) although a few were present in the cortex and somewhat more in the medulla, near the HB. At the end of development small groups of neutrophil cell precursors appeared in the ICT and the cortex. Cysts were not present up to day 21 after birth.

Mechanisms of splenic control of murine malaria: cellular reactions of the spleen in lethal (strain 17XL) Plasmodium yoelii malaria in BALB/c mice, and the consequences of pre-infective splenectomy.

The splenic response in lethal 17XL Plasmodium yoelii murine malaria is vigorous, displaying marked phagocytosis, erythropoiesis, lymphopoiesis, plasmacytopoiesis, and, from day 3 of infection, increasing levels of parasitized erythrocytes. There is also a pronounced response of newly characterized fibroblastic stromal cells which branch and fuse with one another, forming extensive, complex, irregular, syncytial membranous sheets which provide a variety of barriers. Hence, I term these barrier cells (BC), and their fusion results in barrier-forming complexes (BFC). BC form adherent surfaces, trapping parasitized erythrocytes and monocytes-macrophages, facilitating phagocytosis. They envelop single plasma cells, erythrocytes, erythroblasts, lymphocytes, reticulocytes, monocytes-macrophages, or clusters of them. They surround blood vessels, forming blood-spleen barriers. They are insinuated into the circumferential reticulum at the periphery of white pulp, isolating white pulp. They form channels in red pulp, directing blood flow. They are associated with collagen. There appear to be several sources of BC. They may originate by activation of established reticular cells which form the filtration beds, by activation of reticular cells covering the pulp surface of capsule and trabeculae, and as a major source in this malaria, from circulating progenitors entering the splenic pulp from the vasculature. In non-lethal malaria, these barrier systems protect splenic reticulocytes from parasitization. In the lethal 17XL malaria they do not, and there follows a considerable increase in parasitization in the spleen with a corresponding increase in active macrophages. Large-scale parasitization and parasite recycling through the great stores of splenic reticulocytes in the lethal malaria, and the failure of parasitization of these splenic reticulocytes reserves on the non-lethal malaria, suggests that the actions of the spleen aggravate the lethal malaria and ameliorate the non-lethal. This is supported by the finding that non-lethal malaria is aggravated and lethal malaria ameliorated by splenectomy.

Male lupus: prevalence of IgA deficiency, 7S IgM and abnormalities of reticuloendothelial system Fc-receptor function.

Serological studies conducted on sera from a group of 31 male SLE patients revealed a 32% prevalence of 7S IgM and a 9.7% prevalence of IgA deficiency. Previous reports using similar methods indicated a higher (43-50%) prevalence of 7S IgM than was found in studies involving predominantly females with SLE (15-18%), and an overall prevalence of IgA deficiency ranging from 0.95% to 4.6%. Males resembled females in the prevalence of Fc-receptor specific reticuloendothelial system dysfunction, correlating with levels of circulating immune complex-like material and disease activity.

Ultrastructure and visceral distribution of lipopigments in infantile neuronal ceroid-lipofuscinosis.

After an uneventful psychomotor development, a Jordanian boy developed increasing blindness, deafness, myoclonic jerks, tetraspasticity and dementia beginning at the age of 8 months and finally resulting in coma during which he died at the age of 3 years and 4 months. Two of his older siblings had possibly suffered from the same disease, but one of them had died in the Near East without adequate diagnosis. Autopsy revealed infantile neuronal ceroid-lipofuscinosis (NCL). Lipopigments showing typical autofluorescence and PAS staining granules were abundant in the markedly atrophic brain and numerous visceral organs, especially in cells of the reticulo-endothelial system, intestinal tunica propria, the bone marrow and hepatic von Kupffer cells. Ubiquitous accumulation of these NCL-typical lipopigments were found in adventitial mesenchymal cells of small vessels, particularly in lungs, liver and lymphatic organs. Lipopigments had accreted to a lesser degree in podocytes of renal glomerula and Sertoli cells, and in striated muscle fibers only around nuclei. Lymphocytes, smooth muscle cells and stratified epithelial cells did not contain lipopigments. The ultrastructure of the membrane-surrounded osmiophilic cytosomes consisted predominantly of finely granular lipofuscin although short membranous profiles were occasionally embedded within this granular matrix. These morphological findings emphasize the diagnostic importance of lymph node, rectal and bone marrow biopsies and, to a lesser degree, of liver biopsy in infantile neuronal ceroid-lipofuscinosis. The nosology of infantile NCL, independent of the ethnic background, was further clarified by our studies on ultrastructure and visceral distribution of these lipopigments. Morphological damage to parenchymal cells of visceral organs, contrary to the widespread loss of cortical neurons in the brain could not be demonstrated.

Fibroblastic reticulum cells in human lymph nodes. An ultrastructural study.

The ultrastructural characteristics of the fibroblastic reticulum cell (FRC) in human reactive lymph nodes, which were studied electron microscopically, indicate a myofibroblastic cell with unique properties. Its contractile element is probably useful in controlling the volume of the lymph node and possibly in the movement of antigens and antibodies. The FRC may also play a role in other immunologic functions and seems to be preponderant in some lymphomas.

The role of zinc in pre- and postnatal mammalian thymic immunohistogenesis.

Mammalian thymic histogenesis can be morphologically divided into three consecutive stages: a) epithelial, b) lymphopoietic or lympho-epithelial, and 3) differentiated cellular microenvironmental, with formation of Hassall's bodies (HBs). Immunomorphological changes characteristic of human thymic involution begin during or soon after the first year after birth, and continue progressively throughout the entire life span. The 3% to 5% annual reduction in the number of cells of the human thymic microenvironment continues until middle age, when it slows down to less than 1% per year. According to the extrapolation of these results, total loss of thymic reticulo-epithelial (RE) tissue and the associated thymocytes should occur at the age of 120 years in humans. The marked reduction of the thymic cellular microenvironment is a well- controlled physiological process and is presumably under both local and global regulation by the cells of the RE meshwork and by the neuroendocrine axis, respectively. In humans, the age related decline of facteur thymique serique (FTS) levels in blood begins after 20 years of age and FTS completely disappears between the 5th and 6th decade of life. In contrast, serum levels of thymosin-alpha 1 and thymopoietin seem to decline earlier, starting as early as 10 years of age. The influences of a variety of other hormones on the involution of the thymus have also been characterized: testosterone, estrogen, and hydrocortisone treatment results in marked involution, cortisone and progesterone administration have a slight to moderate effect while use of desoxycorticosterone has no effect. The experimental administration of thyroxin yielded dose dependent results: low doses resulted in thymic hypertrophy, higher doses produced a slight hypertrophy, while the highest employed doses caused thymic atrophy. The atrophy was of apicnotic type, very different from that detected after treatment with corticoid hormones. Thymus transplantation experiments indicate that age-related, physiological thymic involution has been genetically preprogrammed. Grafting of the thymus from one week old C3H leukemic strain mice into 6 month old hosts resulted in changes in thymic weight and involution patterns that were synchronous in all recipients, in direct correlation with the glands in the donor, but not in the host. These data strongly suggest that the stimulus for thymus cell proliferation and differentiation is genetically determined within the organ implant. Since the thymus is the primary T-lymphopoietic organ during mammalian ontogenesis, its age-related involution with typical immunomorphological alterations can be held responsible only for the decline in antigen-specific T lymphocyte immune functions. Thymic involution and diminished T lymphocyte proliferation can be partially restored by thymic tissue transplantation or use of thymic hormones. The only partial reconstitution of CD4+ T helper lymphocyte subset after antineoplastic chemotherapy and bone marrow transplantation represents a significant, therapy complicating, clinical problem. After high-dose chemotherapy, restoration of thymus dependent CD4+ T lymphocyte genesis was reported only in children. Our radiation, stem cell transplantation, and hormone treatment experiments in animals strongly suggest age and time dependent regeneration of the cytoarchitecture of the thymic cellular microenvironment, as well as intrathymic lymphopoiesis. The human body's zinc pool undergoes progressive reduction, resulting in low zinc plasma levels and a negative crude zinc balance in older rodents, as well as humans. Previous research suggests that the diminished bioavailability of zinc in older mammals may represent one of the major factors for the involution of the thymus and consequent cellular immunological dysfunction. In PBMCs, zinc induces several cytokines, predominantly IL-1, IL-6 and TNF-alpha, and therefore, has an immense immunoregulative capacity. (ABSTRACT TRUNCATED)

Electron microscopic studies on tissue distribution of lipid microspheres used as drug delivery carriers.

The tissue distribution of lipid microspheres (LMs), drug carriers for targeting therapy of anti-inflammatory drugs, was morphologically studied by electron microscope. In areas of inflammation in rats and mice, LMs were taken up by macrophages and accumulated around endothelial cells of blood vessels, and were observed to penetrate to the outer layer of blood vessels. LMs were also observed in reticuloendothelial cells such as Kupffer cells and splenic macrophages. Furthermore, the uptake of LMs by polymorphonucleocytes (PMNs) in areas of inflammation was enhanced 2-3 fold when LMs were coated with homogeneous IgG. These findings are in agreement with the tissue distribution results previously reported by the authors in studies using radioisotope-labelled LMs. The present and previous reports indicate that LMs could be used as a novel drug carrier, similarly to liposomes, in a drug delivery system specific for areas of inflammation and reticuloendothelial systems.

Ultrastructural and morphometrical studies on the reticular framework and reticular fibers in the reticuloendothelial system of rats.

The reticular framework and reticular fibers in the thymus, cervical lymph node, spleen and bone marrow of Wistar rats were studied by transmission electron microscopy and morphometrical method. The reticular framework was usually observed in these organs as a common structure that consisted mainly of the slender cytoplasmic processes of the fibroblastic reticular cells interconnected with tight junction. Ultrastructurally, the reticular fibers were a mixture of collagen fibrils and amorphous materials, and were almost completely ensheathed by the cytoplasm of fibroblastic reticular cells. Such characteristic structure of the reticular fibers was found not only in the thymus, lymph node and spleen, but also in the bone marrow where it has not been clearly demonstrated previously. Morphometrical analysis revealed that the content of collagen fibrils in the reticular fiber in the lymphoid tissues (the thymus, lymph node and splenic white pulp) was much greater than that in the hematopoietic tissues (the bone marrow and splenic red pulp). Based on these evidences, it was reasonably considered that the reticular framework and reticular fiber ensheathed by the cytoplasm of the fibroblastic reticular cells were the most representative common structure in the reticuloendothelial system (RES) and played some important roles in the functions of RES.

[Myocardial biopsy in congestive myocardiopathies of apparently primary origin]. / La biopsie myocardique dans les myocardiopathies congestives en apparence primitives

38 patients with congestive cardiomyopathy of apparantly primary origin had a myocardial biopsy. The histology of the fragment of myocardium was studied both by light microscopy and electron microscopy. The results were compared with those from 3 "control" cases and with 16 cases of congestive asystole secondary to a known cause. The non-specific patternss which were observed were of 3 types: patterns of degeneration, pattern of hypertrophy, and interstitial fibrosis. Chronic alcholism had no modifying effect on the ultrastructure. Finally, the group in which the morphology was altered had a higher mortality, but the prognostic significance of the degree of severity of the morphological change must be treated with caution in each individual case.

[An ultrastructural study of the changes of the liver and spleen induced by experimental E. coli endotoxin shock--with special reference to effects of the low-dose heparin therapy].

Firstly, the author has investigated how low-dose heparin had influence on reticuloendothelial system of the normal Wistar rats. Secondly, the effect of the low-dose heparin therapy on E. coli endotoxin shock was investigated as to the ultrastructural changes of the liver and spleen of rats. Activation of the phagocytosis which was substantiated by increased uptake of the carbon was observed in heparin administered rats. In this group, abundant development of intra-cellular organellae was noted in the cytoplasm of the hepatic Kupffer cells, macrophages and reticulum cells of the spleen. The E.coli endotoxin administration resulted in formation of micro-thrombi in sinusoidal spaces of the liver at 4 hours after administration. The Kupffer cells also involved in striking disintegration and necrosis. Similarly the sinusoidal lining cells were denudated with disintegration and necrosis. The above-mentioned changes persisted for long term, while the changes less in heparin administered group. The active phagocytic process was discernible in the latter group. Cellular preservation was also excellent in the spleen. The mortality was lower in initial heparin-treated group in comparison with that of untreated control group.

Reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.): an ultrastructural and cytochemical study.

BACKGROUND: Head-kidney, considered the major fish lympho-haemopoietic tissue, consists of cells of the different haemopoietic series supported by a network of stromal cells whose morphofunctional properties have not been established. We report the ultrastructure and cytochemical features of the reticulo-endothelial stroma of the head-kidney from the seawater teleost gilthead seabream (Sparus aurata L.). METHODS: Samples of head-kidney were processed for electron microscopic study. Some of the samples were incubated for acid and alkaline phosphatase, peroxidase, glucose-6-phosphatase, or ATPase. RESULTS: The reticulo-endothelial stroma of gilthead seabream head-kidney consists of sinusoidal cells (endothelial and adventitial cells) and reticular cells (macrophage-type reticulum and fibroblast-like reticular cells). Transcytosis vesicles and rounded medium electron-dense granules were observed in the cytoplasm of the endothelial cells. The adventitial cells partially covered the outside surface of the endothelial cells and were joined by desmosomes. The macrophage-type reticulum cells were characterized by their cytoplasmic processes and acid phosphatase positive lysosomes. The fibroblast-like reticular cells were joined by desmosomes and formed an extensive network between the haemopoietic parenchyma. They were peroxidase negative and acid and alkaline phosphatase, glucose-6-phosphatase, beta-glucuronidase, and ATPase positive. CONCLUSIONS: The ultrastructural and cytochemical features of the reticulo-endothelial stroma of the gilthead seabream head-kidney are similar to those of mammalian bone marrow, suggesting phylogenetic analogies between both tissues.