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.
The Production of Translocations in Drosophila Oocytes.
Attached-X female Drosophila oocytes of various ages were irradiated, and the frequency of detachment deter mined in females of various ages. There is an increase in radiation sensttivity of oocytes with aging up to three days, after which there is no evident increase. A two hit formation of detachments ts found both in young and oid oocytes. Dose fractionation experiments show breaks in stage 7 rejoin in about ten minutes, whiie those in stage 14 do not rejoin untii fertilizatton. There is evidently a change in the proportions of the various kinds of exchanges obtained when females are aged before treatment. Speculations are made as to the possibie roie of cytochrome oxidase activity in the changing sensitivity of oocytes. (auth)
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.