Nucleic Acids Extraction

The fixation of tissue samples in formalin leads to extensive cross-linking of all tissue components. As a result, the nucleic acids isolated from these specimens are highly fragmented. The extent of fragmentation depends on the tissue type and the condition of fixation. This fragmentation is enhanced in postmortem paraffin-embedded tissues. No modifications of the usual protocol of nucleic acid extraction are needed using postmortem archive tissues. For any type of formalin-fixed, paraffin-embedded tissue there is the possibility to easily isolate single cells or subpopulations of cells by microdissection. Methods for the extraction of DNA[4,9] and rna[5,8] from archive tissues propose the use of single or multiple 6-8-p.m histological sections from the paraffin blocks. The first step in the extraction protocols from paraffin-embedded tissues is the elimination of paraffin. Paraffin is soluble in organic solvents such as xylene. After the deparaffinization, tissues are then washed with ethanol several times to completely eliminate residual xylene, as even small amounts could block the activity of the enzymes used in the next steps.[8] To obtain DNA and RNA for further analysis it is necessary to digest the tissue sections by proteinase K or other proteolytic enzymes to remove the cross-linked proteins. The difference in the protocol for the isolation of RNA and DNA from archival autopsy tissues is the composition of the lysis buffer and proteinase K concentration as previously reported.[4,5,8,9] To purify nucleic acids from proteinase K and proteolysis residues, an extraction with phenol/chloroform is needed, for DNA we use phenol-Tris and for RNA phenol-H2O. Final samples are obtained by alcohol precipitation using glycogen as a carrier.[4,5,8,9] The concentration of nucleic acids is measured at the absorbance of 260 nm.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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