Studies on erythropoesis in severely anaemic Xenopus

This Thesis reports studios on orythropoioois (rod blood sell formation) in Xenopus laovis in response to a phenylhydrazino induced anaemia. During this response, large numbers of immature red blood cells enter the peripheral circulation and differentiate as a seemingly homogeneous cohort. In the first part of this thesis, studios have centred on the rates of red cell production, of their cell division in circulation and of their biosynthetic activity. Changes in the patterns of biosynthetic activity, notably transcription of RNA molecules and translation of proteins, particularly haemoglobins, are observed during maturation of the red cell. A comparison between orythropoiesis and red blood cell maturation in Xenopus and other animals, notably other amphibians and mammals, is made. The second part of the thesis reports studios on the effects of 5'Bromodeoxyuridine (BUdR) on this Xenopus orythropoietic system. BUdR is a metabolic analogue of thymidine and on its incorporation into DNA in place of thymidine during DNA replication in differentiating cells, it has been found to have many interesting effects on their subsequent differentiation. Those effects have usually been observed as an inhibition of the synthesis of certain protein products normally associated with a terminally differentiated phenotype, although further studies show that transcription is also affected.The possible mechanisms by which BUdR might induce these effects are discussed.