Abstract
A procedure is described that prepares chemically untreated biological sections for X-ray microanalysis in the scanning electron microscope (SEM). The method aims to retain and localize labile components in tissue sections by a procedure that is both rapid and routine. Large quantities of fresh tissue can be processed for analysis within a single day. Thick cryosections are cut with a steel knife in a conventional cryostat, freeze-dried, and then ashed by either low or high temperature incineration procedures. Controlled microincineration attenuates the organic matrix to reveal sufficient surface relief for effective SEM of some cytological structure and microanalysis of the residual inorganic components. The detectability of various elements is enhanced because the relative concentrations in the residues are increased and the level of nonspecific background in the X-ray spectra is reduced. The technique is applied to different tissues from the visceral complex of the marine prosobranch Littorina littorea. In animals exposed to elevated levels of zinc it can be demonstrated tht the metal is localized both as an insoluble form in granules and as a labile form within the cytoplasm. Other metals, including magnesium, potassium, calcium, manganese, and iron, have been identified and localized. The effectiveness of this technique for retaining labile elements is compared, in outline, with that of conventional fixation procedures.