RÉSUMÉ
Nanodosimetry, a new discipline developed on the basis of microdosimetry, is based on the structural characteristics of particle tracks and studies on the probability distribution of ionization pairs in a specific volume to characterize the damage degree of DNA strand. Now nanodosimetric quantities, which may be measured, gradually form the concept such as ionization cluster size, ionizing cluster size distribution and complementary cumulative probability distribution etc. This paper aims to establish and explain the relationship between nanodosimetry and DNA damage and repair. On the basis of reviewing the current measurement and calculation method of nanodosimetry, this paper summarized the development trend and application prospect of nanodosimetry, and put forward the future research direction of nanodosimetry.
RÉSUMÉ
BACKGROUNDThe use of stem cells for various clinical applications is highly expected and the production of good quality stem cells is very critical for basic studies. In the bone marrow, hematopoietic and mesenchymal stem cells form a unique niche in which the oxygen tension is low. Hypoxia may have a role in maintaining stem cell fate, self renewal and multi-potency. We investigated whether low oxygen culture would be beneficial for hematopoietic stem cell stemness.METHODSBone marrow cells from 8-10 week aged mice were subjected to hypoxic conditioning by culture for 7days in 20%, 3% and 1% oxygen. For culture,1x105 cell/ml were seeded in colony forming assay in each dish. During the culturing, cell colonies were checked once every three days. Compared to normoxic cells, hypoxic cells weremorphologicallyundifferentiated and counted by Olympus IX71 microscope.RESULTSMore colonies were observed at 3% and 1% oxygen. Statistical significances were identified with granulocytes and macrophage colony (p<0.05) in hypoxic condition.CONCLUSIONSOur data suggests low physiological oxygen culture could improve the stemness of macrophage and granulocytes colony. Long term culture will be necessary to confirm whether low physiological oxygen levels also improve genomic stability.
RÉSUMÉ
Three types of microscopic operations were used in this study: 1. excision of the optic vesicle alone; 2. after excising the optic vesicle, a piece of forebrain tissue taken from another donor was inserted in between presumptive lens ectoderm and forebrain wall; 3. cut down the optic vesicle and portion of forebrain tissue and replaced them back in situ by turning over 180?. The operations were carried out on Rana nigromaculata at 15 and 16 stages, in order to bring the presumptive lens ectoderm to come into contact directly with the forebrain tissue for the purpose to analyse the possibility of eye cup formation from the brain wall. The results indicate that the forebrain wall which came into contact with the presumptive lens ectoderm could be induced and differentiated into a secondary eye cup or retina. A total of 81 cases of secondary eye cups among 282 operations (28.8%) were observed. The mechanism for the induction and its significance were discussed.