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Lymphopoiesis in the bursa of Fabricius without continuity and contiguity with the cloaca: preliminary studies
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CONTRIBUTION TO THE STUDY OF LYMPHOPOIESIS IN THE BURSA OF FABRICIUS IN GALLUS-DOMESTICUS
No full textIt has been proposed that the anatomical connection between the bursa of Fabricius and the cloaca is the pathway for unknown intestinal factors which are necessary for the induction of normal bursal lymphopoiesis. It has also been suggested that normal lymphopoiesis occurs only if nerve and vascular connections are intact. Experiments were performed to test these hypotheses. To test the influence of the intestinal contents, the bursal stalk was cut on the 16th day of incubation or at hatching. In this way, contact between the bursa and the intestinal flow in embryos was avoided and bacterial contamination of the bursa at hatching was also avoided. No change in the bursal follicles was observed. To study the influence of the nervous system on bursal lymphopoiesis, the bursa was isolated from the cloaca at hatching, and by maintaining vascularization the bursa was sutured to the peritoneum of the abdominal wall after scratching the contact surfaces. Once a new vascular network was established, one fragment of bursa was completely isolated from its normal anatomical site, causing interruption of the blood vessels and nerves of the bursa. The histological appearance of the bursa was not changed. It would appear that the integrity of the anatomical relation between bursa and cloaca and an intact nerve supply is not necessary for normal lymphopoiesis to occur in the bursa of Fabricius. In contrast, sufficient vascularization appears to be essential
A CONTRIBUTION TO THE STUDY OF THE LYMPHOID-FOLLICLE ASSOCIATED EPITHELIAL-CELLS
No full textThe esterase activity in the bursa of Fabricius in 10-day-old chicks is examined by means of serial sections obtained by cutting along the major axis of the lymphoid follicles. The positivity for this enzymatic reaction is not only confined to the FAE (follicle associated epithelial) cells of the epithelial frame-work and to isolated cells belonging to the medullary part of the follicle, but it extends in a club-shaped morphological continuity from the FAE cells towards the centre of the follicle. A similar image with a high affinity for acid stainings was also found by means of the H and E technique in suitably orientated sections. Morphological continuity between the FAE cells and the centre-medullary part leads us to suppose the FAE cells and the cells of the centre-medullary part may have a common origin. In the present work, we consider the possibility of FAE cells being of mesenchymatic origin because, besides the fact that they are in continuity with the centre-medullary cells, they appear after CFU (Colony Forming Units) migration, they have no basal lamina, they have certain features which are present in mesenchymatic cells belonging to the histiocytic line, like high esterase activity and micropinocytotic capability and, finally, they are sensitive to carrageenan and silica, which is a peculiarity of macrophages
DISTRIBUTION OF LYMPHOCYTES-B IN THE AREAS OF BURSAL AND CLOACAL LYMPHOID INFILTRATION
No full textThe present study was carried out on the Diffusely Infiltrated Area of the bursa of Fabricius (DIA) and the area of lymphoid infiltration of the dorsal wall of the cloaca, using immunoperoxidase and electron transmission microscopy, in order to verify the behaviour of antibody-producing cells and their distribution in the two organs. An anti-chicken Ig antiserum was used for this purpose, and the results obtained show that there is a progressive increase in the antibody-producing cells in the DIA, and subsequently also in the cloaca, during the first few weeks of life; the percentage values remain constantly higher in the DIA compared with the cloaca. Electron microscopy made it possible to detect numerous lymphocytes and some plasma cells in the epithelium. Many of the intra-epithelial lymphocytes were immunoperoxidase-positive. The possible role played by the B-lymphocytes found in both organs is discussed
Laminin and beta 1 integrin distribution in the early stages of human kidney development
No full textLaminin, an extracellular matrix molecule (EMM) widely expressed in the basal laminae, interacts with specific membrane receptors among which the integrin molecules are the best known. During embryo development laminin is the first synthesized EMM and plays a significant role in the morphogenesis of organs in which epithelial-mesenchymal interactions and branching take place. The present study describes the distribution of laminin and of beta-1 integrin receptors during the very early stages of human kidney development. The observations were carried out on paraffin sections of human embryos ranging between the 4th and the 7th gestational week. Laminin was detected within the basement membranes of mesonephric duct, vesicles, glomerular vessels and celomic epithelium. The metanephric anlage reacted with anti-laminin immunoglobulins in the basement membrane underlying the ampullae and in few blastemic cap cells. Low levels of beta-1 integrin reactivity were found in both the mesonephric and metanephric structures. This study provides for the first time data about the distribution of laminin and beta-1 integrin in the early stages of human renal organogenesis suggesting a key role for these molecules in the epithelial-mesenchymal interactions necessary for kidney development
THE BEHAVIOR OF BURSAL LYMPHOID FOLLICLE-ASSOCIATED CELLS AFTER TREATMENT WITH TESTOSTERONE
No full textAdministration of androgens produces damage in lymphoid tissue and in the bursa of Fabricius. After IM administration of 5 mg of testosterone propionate (TP) beginning at hatching and continued during the following 4 days, a significant reduction in the bursal weights is observed. Histologically, an increase in the connective tissue is observed and cystic formations are also found. In all cysts examined, there is continuity of the cystic lumen with the free surface. The follicle-associated epithelial (FAE) cells are on the bottom of the pseudocysts and form a separation between the pseudocystic cavity and the lymphoid tissue which is still further inwards. These cells do not lose their esterase activity, even though they are often flattened. Furthermore, they disappear in the pseudocysts deprived of lymphoid tissue. A new hypothesis is advanced that the FAE cells originate from the mesenchyme with differentiation in the histiocytic line
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