DOI: 10.14704/nq.2012.10.1.431

Distribution of Particles in the Z-axis of Tissue Sections: Relevance for Counting Methods

Christopher S. von Bartheld

Abstract


The distribution of particles in the z-axis of thick tissue sections has gained considerable attention, primarily because of implications for the accuracy of modern stereological counting methods. Three major types of tissue section artifacts can affect particle quantification: loss of particles from the surfaces of tissue sections (lost caps), homogeneous collapse in the z-axis, and differential deformation in the z-axis. Initially it was assumed that thick sections were not compromised by differential shrinkage or compression (differential uniform deformation). Studies in the last decade showed that such artifacts are common and that they depend on the type of embedding media and sectioning devices. Paraffin, glycolmethacrylate and vibratome sections are affected by this artifact, but not celloidin- or cryosections. Differential distribution of particles in the z-axis is likely due to compression of the surface areas (margins) during sectioning, resulting in differential particle densities in the core and margins of tissue sections. This deformation of tissue sections can be rapidly quantified by measuring the position of particles in the z-axis. The analysis is complicated by potential secondary effects on section surfaces through loss of particles, the so-called “lost caps” phenomenon. Use of guard spaces can reduce the bias caused by secondary effects, while their use in case of primary effects (compression due to sectioning) would enhance the artifact’s impact on bias. Symmetric versus asymmetric patterns of z-axis distortion can give clues to distinguish primary and secondary effects. Studies that use the optical disector need to take these parameters into account to minimize biases.

NeuroQuantology | March 2012 | Volume 10 | Issue 1 | Page 66-75

Keywords


Stereology, morphology, histology, particle counting, bias, optical dissector, sampling, cell count, lost caps

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