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Biomedical subjects

C Rhodes

Publications and source records attributed to C Rhodes.

68 records · Page 4Linked to original sources
PubMed1975

Biochemical method for mapping mutational alterations in DNA with S1 nuclease: the location of deletions and temperature-sensitive mutations in simian virus 40.

S1 nuclease (EC 3.1.4.X), a single-strand-specific nuclease, can be used to accurately map the location of mutational alterations in simian virus 40 (SV40) DNA. Deletions of between 32 and 190 base pairs, which are at or below the limit of detectability by conventional electron microscopic analysis of heteroduplex DNAs, have been located in this way. To map a deletion, a mixture of unit length, linear DNA, prepared from the SV40 deletion mutant and its wild-type parent, are denatured and reannealed to form heteroduplexes. S1 nuclease can cut such heteroduplexes at the nonbase-paired region to produce fragments whose lengths correspond to the position of the deletion. Similarly, specific fragments are produced when S1 nuclease cleaves a heteroduplex formed from the DNAs of SV40 temperature-sensitive mutants and either their revertants or wild-type parents. Thus, the positions of the nonhomology between these DNAs can be determined.

Aspergillus↗
PubMed1971

Unsuitability of indoxyl acetate as a substrate for the assay of testicular hyaluronidase.

The most recently published method for the assay of testicular hyaluronidase preparations was based on the premise that the enzyme also exhibited carboxylesterase activity towards indoxyl acetate. Studies on the relative enzyme activities of various hyaluronidase preparations towards hyaluronate and indoxyl acetate, the relative stabilities towards pH, temperature and mechanical shaking and the behaviour towards a variety of inhibitors, showed that the activities towards the two substrates reflected the presence of at least two different enzyme systems in the preparations. Gel chromatography and polyacrylamide-gel-electrophoresis experiments confirmed these conclusions and the collective findings clearly establish that methods based on the use of indoxyl acetate cannot be employed to measure testicular hyaluronidase activity.

Acetates↗
PubMedDate not supplied

An in vitro skin corrosivity test--modifications and validation.

An in vitro rat epidermal slice technique has been developed for identifying chemicals with potential to cause a corrosive lesion in animal skin in vivo. This potential has been correlated with the ability to lyse stratum corneum and has been measured as a lowering of the electrical resistance of the skin slice. Initial validation of the technique with 63 chemicals resulted in a high sensitivity for corrosive chemicals but a lower specificity for irritant chemicals. Subsequent modification relating to chemical contact resulted in an improved specificity (i.e. fewer false positives) at the expense of a small loss in sensitivity (i.e. an increase in the number of false negatives). An intralaboratory double blind trial with 34 corrosive chemicals and 36 irritants showed the technique to have total sensitivity (i.e. no false negatives) and a specificity of 88%. The results of the initial validation and the double blind trial illustrate the robust nature and high reproducibility of this in vitro technique for identifying skin-corrosive chemicals. Overall the model has considerable potential as a pre-screen for conventional animal tests with the additional advantage of providing objective and quantifiable information.

Animals↗