Molecular characterization of a radiation-induced reverse mutation at the dilute locus in the mouse

SummaryIrradiation has been employed successfully to increase the reverse mutation rate at the agouti and dilute loci in the mouse. The dilute allele has previously been shown to be due to the insertion of an ecotropic-specific murine leukaemia virus in the vicinity of the dilute locus, and its instability to be due to the excision of the proviral sequence (Jenkinset al.1981). Molecular analysis of the recovered radiation-induced revertant at the dilute locus indicated excision of all but approximately 500 bp of the proviral sequence. The proviral sequence remaining in the mouse genome hybridizes to a probe specific for the proviral long terminal repeat (LTR) sequence. Previous characterization of two spontaneous reverse dilute mutations indicated precise proviral excision of all but a single LTR, and suggests homologous recombination between the proviral LTR sequences as the mechanism of proviral excision (Hutchison, Copeland & Jenkins 1984). The present results indicate that radiation and increases the reverse mutation rate at the dilute locus acts by a similar mechanism, and suggest that mutagenic treatment may be employed to produce genetic variants of interest.

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Applications of ultramicrotomy for materials characterization

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100147004 ◽

1993 ◽

Vol 51 ◽

pp. 232-233

Author(s):

R.T. Blackham ◽

J.J. Haugh ◽

C.W. Hughes ◽

M.G. Burke

Keyword(s):

Materials Science ◽

Microstructural Analysis ◽

Analytical Electron Microscopy ◽

Austenitic Stainless Steels ◽

Specimen Preparation ◽

Preparation Technique ◽

Thermally Induced ◽

Radiation Induced ◽

Characterization Of Materials

Essential to the characterization of materials using analytical electron microscopy (AEM) techniques is the specimen itself. Without suitable samples, detailed microstructural analysis is not possible. Ultramicrotomy, or diamond knife sectioning, is a well-known mechanical specimen preparation technique which has been gaining attention in the materials science area. Malis and co-workers and Glanvill have demonstrated the usefulness and applicability of this technique to the study of a wide variety of materials including Al alloys, composites, and semiconductors. Ultramicrotomed specimens have uniform thickness with relatively large electron-transparent areas which are suitable for AEM anaysis.Interface Analysis in Type 316 Austenitic Stainless Steel: STEM-EDS microanalysis of grain boundaries in austenitic stainless steels provides important information concerning the development of Cr-depleted zones which accompany M23C6 precipitation, and documentation of radiation induced segregation (RIS). Conventional methods of TEM sample preparation are suitable for the evaluation of thermally induced segregation, but neutron irradiated samples present a variety of problems in both the preparation and in the AEM analysis, in addition to the handling hazard.

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