Histological procedure

The nervous system contains an unusually diverse set of intermediate filaments (Table 8-2) with distinctive cellular distributions and developmental expression [21, 22]. Despite their molecular heterogeneity, all intermediate filaments appear as solid, rope-like fibers 8-12 nm in diameter. Neuronal intermediate filaments (NFs) can be hundreds of micrometers long and have characteristic sidearm projections, while filaments in glia or other nonneuronal cells are shorter and lack sidearms (Fig. 8-2). The existence of NFs was established long before much was known about their biochemistry or properties. As stable cytoskeletal structures, NFs were noted in early electron micrographs, and many traditional histological procedures that visualize neurons are based on a specific interaction of metal stains with NFs. 

Understanding of the intracellular localization of steroid receptors has gone through a number of phases, beginning with the view that receptors translocated from cytoplasm to nucleus in the presence of hormone. Indeed, with the exception of thyroid hormone receptors, which are exclusively nuclear in location, cell fractionation studies have revealed that in the absence of hormone, steroid receptors are extracted in the soluble or cytosolic fraction. However, when steroid is present in the cell, many occupied receptors are retained by purified cell nuclei. Histological procedures, such as immunocytochemistry, have confirmed the largely nuclear localization of occupied receptors, but... 

Embed the tissues in paraffin wax by routine histological procedures as soon as possible to avoid excessive hardening. 

Proceed using standard histology procedures for paraffin embedding and sectioning (see Note 21). 

Thereafter, the brain is fixed by perfusion with PBS followed by 4 % buffered PFA. The perfusion is carried out under deep anesthesia (ketamine, 100 mg/kg i.p.), through the ascending aorta. The brain should be carefully removed, post-fixed for 2—4 h in the same fixative at 4 °C, and stored in PBS at 4 °C until the histological procedure is carried out (r Sect. 3.1.3). If you plan to cut the tissue on a freezing microtome, an intermediate step of... 

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