It should be noted that, in the absence of a control group of women receiving no zidovudine during pregnancy, it is impossible to evaluate the actual impact of zidovudine from 35 wk of gestation until delivery. It is likely that, in the absence of zidovudine exposure, the values of haemato logical parameters at delivery would have been higher, and this may explain, in part, the apparent convergence of the two groups at delivery. Interestingly, the 37.4% prevalence of anaemia at delivery, observed in our study was similar to recent national estimates of 38.6% in Thailand. A subject of intensive research, many problems remain in the adult stem cell field. Among these, one important point is that the somatic stem cells that have been identified in most organs and tissues including skin, liver, brain, bone marrow, blood vessels, muscles, are always present in poor numbers. In addition, the possible sources of somatic stem cells, their percentage in various tissues and often their origins are as yet not well defined and the basic mechanisms of plasticity and/or the molecules regulating the proliferation and the differentiation are not completely determined. Potential answers concerning these problems could be derived from studies of somatic stem cells in culture. Clearly cell culture would be an invaluable and potent method for studying somatic stem cells from a morphological, immunocytochemical, biochemical and molecular point of view, although many technical hurdles must be overcome: in fact it is difficult to isolate somatic stem cells from the surrounding tissues, and to find markers to Tubeimoside-I characterize them. Here we have focused on an alternative animal model, the leech, which has the important advantages of being an economic invertebrate suitable for experimental manipulation, easily manipulated and without significant emotional or regulatory restrictions. The leech has a relative anatomical simplicity and is a reliable model for studying a variety of basic events, such as tissue Rebaudioside-D repair, which has a striking similarity to those of vertebrate responses even if the major draw-back to this model to date has been the difficulty in isolating cells for culture and maintenance of sterility. Although the wound healing process in leeches is a dynamic continuum, however, it can be classified into three principal phases consisting of a complex series of overlapping events.