Parasitology



Tritiated thymidine ([3H]-TdR) and immunocytochemical tracing of cellular fate within the asexually dividing cestode Mesocestoides vogae (syn. M. corti)


A. G. SMITH a1c1 and G. McKERR a1
a1 Cancer and Ageing Research Group, University of Ulster at Coleraine, Cromore Road, Coleraine, Co. Londonderry BT55 1SA, Northern Ireland

Abstract

This report documents the presence of an active thymidine kinase (TK) system within Mesocestoides vogae tetrathyridia as quantified by tritiated thymidine ([3H]-TdR) incorporation using liquid scintillation counting. A 100-fold increase in [3H]-TdR incorporation was observed at 37 °C when compared with its incorporation at 0 °C. Thymidine's competitive analogue, BrdU, competed for sites within newly replicated DNA. Immunohistochemical trials performed here using antibodies against BrdU identified cells that have entered and passed through S-phase. Positively stained nuclei were most numerous at the anterior tip of tetrathyridia especially within the ganglia, lesser numbers of these cells occurred along the growing commissure and amongst surface tegumental cytons suggesting that stem cells do not exist in one region but are found throughout the entire body. As M. vogae has no internal organ systems the major sites for cell proliferation are those exhibiting maximal cell recruitment and undergoing tissue repair. These results show that it is possible to monitor changes in the cell recruitment pattern within this cestode. Thus use of BrdU and immunohistochemistry demonstrates how spatial arrangement and cellular reorganization can be successfully traced within M. vogae.

(Received October 7 1999)
(Revised January 19 2000)
(Accepted January 24 2000)


Key Words: Mesocestoides vogae; [3H]-TdR; BrdU incorporation; immunohistochemistry; cellular reorganization.

Correspondence:
c1 Corresponding author: Tel: +01265 44141 Ex: 4759/4765. Fax: +01265 324906. E-mail: AG.Smith@ulst.ac.uk


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