Genomic DNA from mice: a comparison of recovery methods and tissue sources.

Our aim is to identify an extraction method and the source of mouse tissue(s) that could allow a high-resolution genomic scan from a living mouse. We compared and optimized two methods for yield, purity of DNA, and their use in the polymerase chain reaction (PCR) of DNA extracted from different mouse tissues. In addition to whole blood, tissue samples from the brain, liver, testis, and tail were included in this study. The Rapid Method (RM) is preferable for the whole blood samples and testis and brain tissue samples because it is quicker, less toxic, and more cost-effective than the proteinase K method (PM). For liver the PM produced higher yields of DNA with less degradation than the RM. For tail tip, the PM produced a higher yield of DNA, but the RM resulted in a higher yield of PCR product. From a living mouse, a tail snip generated a sufficient amount of DNA for several hundred PCRs but not a complete genomic scan. We suggest that the RM can be used to extract genomic DNA for a complete genomic scan which requires either testicular tissues or repeated blood samples from the suborbital sinus over several months without sacrificing the animal.

Antinutritional effects and ecological significance of dietary condensed tannins may not be due to binding and inhibiting digestive enzymes.

The digestive enzymes alkaline phosphatase and 5'-nucleotide phosphodiesterase, solubilized from bovine intestinal mucosa and purified to homogeneity, were found to be strongly inhibited in vitro by condensed tannins (proanthocyanidins) purified from sorghum seeds and from quebracho. Tannin inhibition was prevented and reversed by the detergent Triton X-100 (protein-binding agent), by soluble polyvinylpyrrolidone (tannin-binding agent), or by phosphatidylcholine (membrane component). When tested as a crude particulate membrane fraction more characteristic of their in vivo condition, both enzymes were inhibited much less than either purified enzyme at the same tannin concentration. Because the enzymes appear to be relatively insensitive to inhibition by tannin in conditions which mimic in vivo conditions, and because the proportion of the dietary tannin which is available to interact with these enzymes in the digestive tract is likely to be rather small, we suggest that the antinutritional effects and ecological significance of dietary tannins are not due to tannin inhibition of these or other digestive enzymes by direct binding to them.