• Vr Muthukkaruppan

      Articles written in Proceedings – Section B

    • Lymphoid differentiation and organization of the spleen in the lizard,Calotes versicolor

      P Kanakambika Vr Muthukkaruppan

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      InCalotes versicolor, splenic primordium appears at stage 30 as a protuberance of mesenchymal cells from the dorsal mesentery. Lymphopoiesis is initiated at stage 40, followed by an increase in the lymphoid population of the rudiment during the successive stages of development. In the adult, splenic pulp is poorly demarcated into white pulp and red pulp. The former is in the form of closely arranged lymphoid follicles and the latter is highly restricted to narrow strands of blood spaces. A comparative study on the lymphoid organization of the spleen of a few other species of reptiles was also carried out.

    • Procedure for thymectomy in the lizard,Calotes versicolor

      RM Pitchappan VR Muthukkaruppan

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      The procedure for thymectomy in the lizard,C. versicolor has been described. The thymus is situated in the cervical region, attached to the midventral aspect of the internal jugular vein. It is medial to the hypoglossal nerve, dorsal to the internal carotid artery, anterior to the ductus caroticus and caudal to the acute angle formed by the hypoglossal nerve and the internal jugular vein. Sodium pentobarbital and ether were used as anaesthetics. The thymus was approached through a lateral incision in the cervical region. The intervening sternomastoid muscle was pushed aside and the thymus was removed using a pair of fine forceps. Streptopenicillin powder was sprinkled over this area to avoid infection and the wound was closed with a film of kollodium. The feasibility of applying this surgical procedure for the ablation of other organs in the lizard is discussed.

    • In vitro properties of heterologous anti-lizard thymocyte serum

      RM Pitchappan VR Muthukkaruppan

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      A potent and specific antiserum was raised in rabbits by injecting a single cell suspension of thymocytes of the lizard,Calotes versicolor. Rabbit anti-Calotes thymocyte serum (ATS) was characterizedin vitro by using cytotoxicity assay and quantitative absorption analysis. The cytolytic activity of ATS was always higher towards thymocytes than towards lymphoid cells of spleen, bone-marrow and peripheral blood. Various absorption experiments indicate the existence of two antigens among thymocytes—one distinct for thymocytes and thymus derived cells and another, common to lymphocytes. Further, thymus-brain antigenic correlation has been demonstrated in this reptilian species. TheCalotes complement is less efficient than that of guinea pig in mediating the cytolysis of target cells by ATS. Further, ATS did not have cytotoxic effect on antibody producing cells. The significance of these findings has been discussed with reference to the dichotomy of lymphoid systems at this phylogenetic level.

    • Role of the thymus in the immune response to sheep erythrocytes in the lizardCalotes versicolor

      RM Pitchappan VR Muthukkaruppan

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      The role of the thymus in antibody response to sheep erythrocytes (SRBC) was investigated in the lizard,Calotes versicolor, by utilizing the experimental models of adult thymectomy and anti-thymocyte serum (ATS) treatment. When thymectomized lizards were treated with high dose regimen of ATS, plaque-forming cell (PFC) response to SRBC was abrogated; however, this response was not altered by the low dose. A definite recovery of anti-SRBC response after ATS treatment occurred in the presence of the thymus. On the other hand the PFC response to SRBC was enhanced one month after adult thymectomy and after low dose ATS treatment. Both low and high doses of normal rabbit serum suppressed the immune response to SRBC and it is suggested that this suppression might be due to antigenic competition.

      These results indicate that (i) anti-SRBC response is thymus dependent and (ii) there are two kinds of thymus derived cells: one ‘helper’ collaborating in anti-SRBC response and another ‘regulator’ governing the magnitude of the response which is involved in antigenic competition. The phylogenetic status on the dual role of the thymus in immune functions has been discussed.

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