Metabolic activation of aryldialkyltriazenes in the mouse: induction of mitotic gene conversion in Saccharomyces cerevisiae in the host-mediated assay.
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Adenine↗
Biomedical subjects
R Fahrig
Publications and source records attributed to R Fahrig.
Acridine-induced mitotic gene conversion (paramutation) in Saccharomyces cerevisiae. The effect of two different modes of binding to DNA.
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Acridines↗
Nucleic acid content of a diploid and of a triploid strain of Drosophila melanogaster.
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Animals↗
Similar pigmentation characteristics in the specific-locus and the mammalian spot test. A way to distinguish between induced mutation and recombination.
Animals with the same genetic constitution have similar pigmentation characteristics in both the specific-locus and the mammalian spot test. By microscopical analysis it is possible to distinguish between the following genotypes: a/a, p/p--light gray spots; a/a, d/d--gray spots; a/a, cch/c--light brown spots; a/a, b/b--brown spots; a/a, p cch/p cch--near-white spots; a/a, P C/P C--black spots. Near-white and black spots are presumed products of reciprocal recombination, especially if appearing simultaneously as a twin spot.
Animals↗
Dynamic range requirements in digital mammography.
The dynamic range and the number of gray levels, gamma s, required for digital mammography has been evaluated using an energy transport model. The effects of molybdenum (Mo) and tungsten (W) target spectra and the energy-dependent attenuation by elemental filters, breast tissue, and a phosphor screen were included in the model. For detectors with ideal optical coupling and no inherent detector noise, 3,100 gray levels are discernable (requiring 12 bits per pixel), assuming a 40 kVp, W target spectrum (1.0 mm A1 filtration), a mean glandular dose to a 5 cm thick breast of 0.6 mGy, and an ideal observer with a 5 mm diam viewing aperture. The effects of inherent detector noise and realistic coupling efficiency on gamma s were also examined. For the 40 kVp, W spectrum, a detector with total coupling efficiency of 16 electrons (e-) per x-ray interaction and a dynamic range of 3000 (maximum carrier signal of 1.93 x 10(5) e-/pixel and inherent detector noise of 64 e- pixel) would decrease the number of gray levels that could be resolved by only 2% compared to a detector with ideal coupling and no inherent noise. A detector with a total coupling efficiency of 2.0 electrons per x-ray interaction and a dynamic range of 240 (maximum carrier signal 2.41 x 10(4) e-/pixel and inherent detector noise of 100 e-/pixel) would reduce the number of gray levels by 26% for the 40 kVp spectrum. On the basis of dynamic range, W spectra are preferable for digital mammography, since Mo spectra yielding the same signal-to-noise ratio require a detector with dynamic range twice as large, and with a 30% greater saturation signal. When no scatter rejection method is used, scattered radiation over a 254 cm2 imaging field reduces the number of discernable gray levels by 23% for a 5 cm thick breast and 34% for an 8 cm thick breast.
Breast↗
An analysis of the geometry of saccular intracranial aneurysms.
BACKGROUND AND PURPOSE: Our goal was to characterize the geometry of simple-lobed cerebral aneurysms and to find the absolute size of these lesions from angiographic tracings. METHODS: Measurements of angiographic neck width (N), dome height (H), dome diameter (D), and semi-axis height (S) were obtained from tracings of 87 simple-lobed lesions located at the basilar bifurcation (BB), middle cerebral (MCA), anterior communicating (AcomA), posterior communicating (PcomA), superior cerebellar (SCA), and posterior cerebral (PCA) arteries. The following ratios were analyzed as subgroups according to location and as a collective sample: dome diameter/dome height (D/H), dome height/neck width (H/N), dome diameter/neck width (D/N), and dome height/semi-axis height (H/S). Using the parent artery as a reference, aneurysm dimensions were normalized to absolute in vivo size. Estimations were validated using angiographic markers. RESULTS: For the entire sample, mean ratios were D/H = 1.11, D/N = 1.91, and H/N = 1.86. For the H/S ratio, the value was 1.98 for BB, MCA, and PcomA lesions and significantly smaller for the AcomA subgroup, at 1.52. The average sizes (in mm) for these dimensions were N = 3.4 for MCA, 3.0 for AcomA, 3.1 for PcomA, and 6.5 for BB; D = 6.1 for MCA, 5.9 for AcomA, 5.3 for PcomA, and 11.7 for BB; H = 5.6 for MCA, 5.0 for AcomA, 5.3 for PcomA, and 11.3 for BB. On average, BB aneurysms were twice as large as aneurysms at other locations. Good correlations were found between the scaled values for D and N, H and N, and H and D. CONCLUSION: These results have been used to characterize the typical simple-lobed aneurysm geometry and to provide a framework for the development of a method of assessment of treatment choice and outcome on the basis of lesion geometry.
Aneurysm, Ruptured↗