AN IMPROVED APPROACH TO PREPARE HUMAN BRAINS FOR RESEARCH

We describe two protocols for preparing human brains collected for res earch and diagnosis. In both protocols, one half brain is processed fo r research and the other for neuropathological evaluation. Clinical, n europathological and tissue mRNA retention data are used for sample ca tegorization. In protocol 1, coronal, whole hemisphere slices cut at s tandardized landmarks are frozen with a cooling device at -90 degrees C, which yields discrete anatomical structures. In selected instances, small blocks of brain are frozen at -160 degrees C in liquid nitrogen vapor. Cooling device or liquid nitrogen vapor frozen samples are sui table for in situ hybridization, protein blotting or immunohistochemis try. Morphological freezing artifacts are minimal. In protocol 2, one half brain is frozen en bloc on dry ice; this tissue is suitable for r egional evaluation of gene expression or neurochemistry. Morphological freezing artifacts are severe. In both protocols, the other half brai n is fixed in formalin prior to sectioning and diagnostic evaluation. The standardized selection of paraffin blocks from each brain allows p recise diagnoses to be established, including identification of danger ous infectious processes; moreover, it makes it possible to produce a set of uniformly selected blocks and slides for comparative studies. T hese protocols lead to standardized tissue preparation for research an d reduce variables impairing interpretation and comparison of data.