Zur Sauerstoffabhängigkeit der Rate strahleninduzierter Chromosomenaberrationen in Oozyten vonDrosophila melanogaster
SummaryAbrahamson's (1959) results concerning the influence of oxygen on the frequency of X-ray induced structural changes (half-translocations) inDrosophila oocytes were generally reproduced, especially the demonstration of a “reverse” oxygen effect (under special experimental conditions protecting action of oxygen, sensitization by nitrogen). In the course of our investigations the following new findings were obtained: 1. The added aberration frequencies of the 3rd and 4th day after the various treatments generally tend to decrease as compared with those of the first two days (dependence on state of maturity of the treated oocytes). 2.Preirradiation treatment by nitrogen increases the aberration frequency significantly. Possible explanations of this effect are discussed.
On Judging the Significance of a Difference Obtained by Averaging Essentially Different Series
It is supposed that data on the frequency (p) of events of a given type have been obtained in the form of a number of series (1-k), which may differ determinately from one another, and that each series consists of two lots, representing the contrasting conditions A and B, while the total numbers observed (n) vary irregularly from series to series as well as from lot to lot. Formulae (1, 3) are given for calculating the best weighted average frequencies (p) in the two sets of lots, obtained under the two conditions, for the purpose of comparison of the results under the two conditions with one another. The error of the difference between these averages is given (2) and formula (7) is developed for ascertaining the minimum chance of the sets of lots showing as bad a fit as they do to one another, if the difference in conditions A and B had no real influence on the frequency (p). The purpose of these formulae, then, is to determine to what extent the results indicate that a difference in these conditions influences the frequency.
Cross talk between redox signalling and metabolic activity of osteoblasts and fibroblasts in the presence of hydroxyapatite-based biomaterials influences bone regeneration
Regeneration of bone tissue defects that result from metabolic disorders, including periodontal diseases, can be supported by biomaterials based on hydroxyapatite. Despite of good biocompatibility of biomaterials they can cause oxidative stress and inflammatory processes as a result of mechanical interaction with surrounding tissues. Because osteoblasts are responsible for bone regeneration process in which gingival fibroblasts may also participate, the aim of the work was to investigate the influence of hydroxyapatite-based biomaterials (allogeneic and xenogeneic) and biomaterials combined with enamel matrix derivative (Emdogain) on osteoblast and fibroblast redox balance in the context of osteoblast proliferation and differentiation.
The results showed that examined substitutes were not cytotoxic in vitro, but affected redox balance of osteoblasts and fibroblasts (ROS level increase and GSH level decrease) which led to oxidative stress (MDA and protein carbonyl groups level increase) resulting in an increase of the Nrf2 and NFκB expression. The consequence of these changes was partial inhibition of proliferation and osteoblast differentiation. Emdogain alone and combined with biomaterials decreased ROS generation and increased GSH level in both osteoblasts and fibroblasts leading to reduction of transcription factors expression especially proinflammatory NFκB, which promoted osteoblast differentiation and mineralization process.