Introduction: Quantitative histochemistry

Abstract

A PANEL on histochemical technologies, applicable to neurochemical pathology, is especially germane at this Conference because of the complex microscopic anatomy of the central nervous system and the consequent compelling need for analytical methods capable of establishing correlations between chemical composition and histological structure. Three major principles and congruent technical measures have been employed for this purpose :l (1) Qualitative histo- and cytochemistry enabling in situ identification of biochemical constituents in light and electron microscopic preparations. This classical form of histochemistry is elaborated and exemplified by other panelists. (2) Use of differential gradient density techniques for preparation (with subsequent macro analysis) of subcellular cytological constituents (nuclei, mitochrondia, synaptosomes etc.) and of enriched fractions of neurons, astrocytes, oligodendrocytes, myelin sheaths and axons. With respect to the nervous system, important contributions in these spheres have been those of V. Whitaker (U.K.), E. de Robertis (Argentina), S. Rose (U.K.) and W. Norton (U.S.A.) (3) Quantitative histochemistry based on the preparation of microgram or sub-microgram sized tissue samples of known histological composition on which direct analyses for chemical structural components or enzyme activities can be carried out using miniaturized forms of standard biochemistry. Procedures of this sort were developed originally by LinderstromLang and Holter in the Carlsberg Laboratories, Copenhagen.2 Remarkable extensions and refinements of such techniques to levels permitting single cell analysis we owe especialiy to Lowry3 and HydCn4. Our laboratory has been concerned for many years with applying microgram level quantitative histochemical techniques, applicable to samples of histological dimensions, to the normal and diseased nervous system. Within this context a central program has been the one dealing with the microchemical anatomy and pathology of mammalian cerebral cortex referred to in my earlier presentation at this Conference. Its objectives have been to analyze cortical biochemical fine structure in terms of its microscopic anatomy, and to search for chemoarchitectonic alterations in disease. The results also permit inferential correlations between biochemical composition and histological structure, normal and otherwise. The experimental design serving these objectives has consisted in preparing from fresh,