Measurement of boundaries using a digitizer tablet

Estimating volumes from common carp hepatocytes using design-based stereology and examining correlations with profile areas: Revisiting a nutritional assay and unveiling guidelines to microscopists

Assessing fish liver status is common in aquaculture nutrition assays. This often implies determining hepatocytes profile areas in routine thin (5-7 μm) histological sections. However, there are theoretical problems using planar morphometry in thin sections: inherent sampling cells biases, too small numbers of sampled cells, under/overestimation of size, measuring size as areas when cells are three-dimensional (3D) entities. The gold standard for assessing/validate cell size is stereology using thick sections (20-40 μm). Here, we estimated the volume of hepatocytes and their nuclei by the nucleator and optical disector stereological probes (in thick sections), and, innovatively, in thin sections too (using single-section disectors). The liver of common carp eating feed containing either low or high level of lipids was targeted. Results were compared with prior profile areas from planar morphometry using thin sections, and with profile areas estimated here with the two-dimensional (2D) nucleator. Ratios between nucleus and cell/cytoplasm (N/C) areas and volumes were calculated and compared. There was high positive correlation between volumes in thin and thick sections (r = .85 to .89; p < .001), empirically validating the single-section disector. Strong correlations existed between profile-derived versus 2D-nucleator areas (r = .74 to .83; p < .001). There was systematic underestimation of cells and nucleus size using planar morphometry. The N/C ratios derived from the 2D-nucleator data were higher than those from planar morphometry. Despite theoretical premises for using simple planar morphometry in thin sections are flawed, our results support that such morphometry on carp/fish hepatocytes may offer some valid biological conclusions. Anyway, we advanced guidelines for implementing proper methods.

Stereology, morphometry, and mapping: the whole is greater than the sum of its parts

The latest developments in computer-based stereology build upon the similarities of classical stereology and computer microscopy to provide refined and effective spatial analyses that also permit mapping of anatomical regions. Classical stereology and computer microscopy have developed along independent pathways as methodologies to provide a quantitative understanding of the structure of the brain. They approach brain morphology and brain morphometry from different points of view. On one hand, stereology has concentrated upon the unbiased numerical estimation of parameters, such as length, area, volume, and population size that characterize entire regions of the brain, e.g. hippocampus, as well as individual elements within them, e.g. cell volume. On the other hand, computer microscopy has concentrated upon providing accurate three-dimensional maps of the morphology of entire regions of the brain as well as of individual elements within them, e.g. neuronal dendrite and axon systems. The differences in point of view are not so extensive as to keep the two methodologies separate. They share, after all, a similar manner of controlling microscope data input and analyzing the images the microscope provides. The incorporation of data archiving permits easier access to previous studies, as well as the sharing of stereological findings and their related maps throughout the scientific community. Some of the stereological systems now integrate spatial mapping with stereological analyses to provide more comprehensive methods to analyze brain tissue.

Simple PC-based system for morphometric analysis of synapses

The computer system designed for synaptic morphometry of aksosomatic and aksospine synapses of brain is described in the present paper. It is based on an AT-comparable personal computer equipped with low-cost frame grabber. This hardware configuration allows to input images from any TV source such as TV camera, videorecorder for further processing. The appropriate software was written in Microsoft Quick Basic to measure the main morphometric parameters of axon ending, dendritic spines, total contact, active zone and mitochondria. Number of synaptic vesicles (total and active) were also counted using a mouse as a pointing device. The derivative parameters (vesicle density, mitochondrial density) are then calculated. All measured data are stored in ASCII format, allowing ease in editing and export into other application programs. Statistical evaluation and calculation of histograms is performed by associated program also written in Quick Basic. The advantages and disadvantages of this approach are discussed.

Approximation of surfaces in quantitative 3-D reconstructions

In serial section reconstructions a series of planar profiles are taken representing curves on the surface of the structure to be reconstructed. For a number of quantitative serial section methods, approximation of a surface is done by the formation of tiles between points of adjacent profiles. As generally proposed, finding this approximation has been difficult due to the inordinately large number of possible solutions resulting from different combinations of tiles between points. Current algorithms have either applied heuristic criteria to force the formation of only one solution or have searched all acceptable combinations for one that minimizes some cost function. The algorithm presented has been developed to choose the tiling which minimizes the estimated error when the tile approximation of the surface is used in subsequent quantitative algorithm such as the calculation of surface area.