Various animals must cope with some specific extreme environmental conditions and, as a consequence, they developed extremely efficacious adaptive defence responses. The mechanisms of the specific defences are more clearly visible in some species than in humans. Therefore, animal models of the human defence mechanisms should be selected accordingly. The appropriate, well responding models may be regarded as "biological amplifiers". This review is focussed on examples of effective defence against: (i) parturitional asphyxia, which extends fertility of mammals; (ii) diving asphyxia, which extends access of food in aquatic birds and mammals; (iii) endotoxemia, which provides survival of the fittest in mammals showing top fertility; (iv) deep hypothermia, which enables hibernating mammals to arouse. Each of the defences needs close co-operation of the cardiovascular, respiratory and temperature regulatory systems. Underlined problems regarding a choice of appropriate experimental animal models should stimulate renaissance of comparative physiology.
Stem cells (SC) research is an important part of biotechnology that could lead to the development of new therapeutic strategies. A lot of effort has been put to understand biology of the stem cells and to find genes and subsequently proteins that are responsible for their proliferation, self-renewal and differentiation. Different cytokines and growth factors has been used to expand stem cells, but no combination of these factors was identified that could effectively expand the most primitive stem cells. Recently, however, genes and receptors responsible for SC proliferation and differentiation have been described. Ligands for these receptors or these genes themselves are being already used for ex vivo expansion of stem cells and the first data are very promising. New markers, such as CXCR4 and CD133, have been discovered and shown to be present on surface of hematopoietic stem cells. The same markers were recently also found to be expressed on neuronal-, hepatic- or skeletal muscle-stem cells. By employing these markers several laboratories are trying to isolate stem cells for potential clinical use. New characteristics of stem cells such as transdifferentiation and cell fusion have been described. Our team has identified a population of tissue committed stem cells (TCSC). These cells are present in a bone marrow and in other tissues and they can differentiate into several cell types including cardiac, neural and liver cells.
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