The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue

Design-based stereology: Planning, volumetry and sampling are crucial steps for a successful study

Quantitative data obtained by means of design-based stereology can add valuable information to studies performed on a diversity of organs, in particular when correlated to functional/physiological and biochemical data. Design-based stereology is based on a sound statistical background and can be used to generate accurate data which are in line with principles of good laboratory practice. In addition, by adjusting the study design an appropriate precision can be achieved to find relevant differences between groups. For the success of the stereological assessment detailed planning is necessary. In this review we focus on common pitfalls encountered during stereological assessment. An exemplary workflow is included, and based on authentic examples, we illustrate a number of sampling principles which can be implemented to obtain properly sampled tissue blocks for various purposes.

Microscopy-based quantitative analysis of lung structure: application in diagnosis

INTRODUCTION

Stereology provides a set of methods that are appropriate for a microscopy-based quantitative assessment of lung structure. In general, the aim of stereology is to obtain information on three-dimensional structures from two-dimensional sections of these structures. The inherent impartiality of stereological principles is critical in order to meet the requirements of 'good laboratory practice'.

AREAS COVERED

This article is a systematic review of the applications of stereology to characterize pathological alterations of emphysema, fibrosis, acute lung injury and tumor grading. The reader is provided with a general overview of unbiased or design-based stereology and is provided with some examples of how these methods could be integrated into a diagnostic work-up of lung diseases in humans and animal models. The article also reviews the implications of a published statement, which defines standards for quantitative assessment of lung structure based on stereology, by the American Thoracic Society and the European Respiratory Society.

EXPERT OPINION

In view of the recently published standards for quantitative assessment of lung structure, unbiased stereological methods are strongly recommended, particularly as they provide valuable information in diagnosing lung diseases and allow a statistically valid quantitative comparison between different groups. Future developments will make the application of stereology in lung biology and pathology even more efficient. Moreover, there is also the potential for combing the principles of stereology with other imaging modalities (e.g., radiological), which will allow for non-invasive lung stereology.

Assessment of air space size characteristics by intercept (chord) measurement: an accurate and efficient stereological approach

The mean linear intercept (chord) length (L(m)) is a useful parameter of peripheral lung structure as it describes the mean free distance in the air spaces. It is often misinterpreted as a measure of "alveolar size," and its estimation is fraught with a number of pitfalls. We present two methods for the accurate estimation of L(m): 1) the indirect method, which derives L(m) from the volume-to-surface ratio of air spaces estimated by point counting methods, and 2) the direct method, which uses a set of random intercepts and calculates L(m) from their frequency distribution, for which we introduce a new and accurate method. Both methods are efficient and, with proper precautions, unbiased. The meaning of L(m) is assessed in two different examples. In a physiological study, the effect of different inflation levels is studied, showing that L(m) critically depends on lung inflation. In an experimental study on emphysema-like changes in a genetic mouse model, the effect of heterogeneity of air space size is assessed; these results are obtained partly because of differences in lung volume due to altered recoil in the emphysematous lungs. In conclusion, although L(m) is not a robust parameter of internal lung structure because it crucially depends on lung volume, it is still a valid measure for which accurate and efficient methods are available that yield additional parameters such as size distribution or alveolar surface area.

The Effect of Fixation and Histological Preparation on Coronary Artery Dimensions

Histometric data are necessary for quantifying the cellular and tissue structure which serves as a basis for the construction of mathematical and integrative models. However, fixation and histological processing of tissues such as dehydration, embedding, sectioning and staining can cause dimensional changes and tissue distortion. The present study was designed to analyze the effects of one widely used fixation and histological preparation protocol for muscle tissue on several morphometric parameters of the coronary arteries. A total of 110 left anterior descending (LAD) artery segments obtained from eight pig hearts were fixed in 6.25% glutaraldehyde and embedded in JB-4 solution. The dimensions of the fixed rings in the loaded and no-load states and histological sections were compared with those of the fresh tissue using Bland-Altman scatter diagrams; i.e., the percent differences between measurements in two different states of various morphometric parameters (inner and outer circumference and wall thickness and area) against their means. We found that vascular elastin cannot be fixed, as seen by the retraction of the vessel dimensions when the loading of the fixed ring was removed. This retraction is time dependent and can lead to significant differences in wall thickness. The differences in dimensions between the histological sections and the fresh tissues in the no-load state were small for the inner and outer diameter (5.6 and 5.2%, respectively) and wall thickness and area (13.4 and 13.1%, respectively). These results are important for establishing an accurate quantitative data base of histological structure that can be related to vascular function or dysfunction.

Liver of the brown trout, Salmo trutta (Teleostei, Salmonidae): a stereological study at light and electron microscopic levels

BACKGROUND

A quantitative study was undertaken for the first time on the normal liver of male and female 2-year-old brown trout, Salmo trutta.

METHODS

Liver was fixed by controlled perfusion. Organ-level morphometry provided weight and volume. A two-stage stereological approach was performed at light and electron microscopy levels. Systematic sampling and point-counting morphometry were used for estimating the relative volumes of the structural compartments. Total absolute volumes of these components were obtained by multiplying each volume density by the volume of its reference space.

RESULTS

Liver volume was 3,423.6 mm3 for males and 3,657.4 mm3 for females. Parenchyma accounted for 95% of hepatic volume. Veins and bile ducts occupied, respectively, 76% and 17% of the stroma, whereas arteries, connective tissue, and melanomacrophages together composed only 6%. Hepatocytes occupied 88% of the parenchyma. Nonhepatocytic cells (endothelium, biliary epithelial cells, Ito cells, and macrophages) composed 4% of the parenchyma, the capillary lumen 6%, and other spaces (Disse space, canaliculi, and lumina of preductules and ductules) composed 2%. Significant sexual differences were found: (1) Females showed a greater parenchymal volume density (0.85% vs. 0.35%) and absolute volume (29.5 mm2 vs. 11.7 mm3) of Ito cells; (2) macrophages of females also presented a greater parenchymal volume density (0.94% vs. 0.46%), but not absolute volume.

CONCLUSIONS

The need to analyze both relative and absolute stereological data was stressed. Similarities and differences were detected between brown trout and other species (fishes and mammals); the findings suggest that, despite architectural differences, some quantitative parameters of liver microanatomy were retained during phylogeny. Factors mediating sexual differences in Ito cells and macrophages were discussed and the need for further studies was highlighted.

Glycol methacrylate embedding of alginate-polylysine microencapsulated pancreatic islets

A method for processing and embedding alginate-polylysine microencapsulated pancreatic tissue in glycol methacrylate resin (GMA) is described. Fixation in 4% phosphate buffered formaldehyde, processing in ascending concentrations of glycol methacrylate monomer and embedding in Technovit 7100 results in well preserved morphological details of hydrogels, hydrogel-cell interfaces, and encapsulated pancreatic tissue. Routine staining with Loeffler's methylene blue, hematoxylin and eosin, and Romanovsky-Giemsa gave excellent images of the GMA embedded alginate polylysine membrane and tissues allowing cells on the outside of the capsule to be analyzed effectively as part of the foreign body reaction against the capsule membrane.

The biological reality of the interlacunar network in the embryonic, cartilaginous, skeleton: a thiazine dye/absolute ethanol/LR White resin protocol for visualizing the network with minimal tissue shrinkage

Third toe phalanges of chicks aged 8-13 days in ovo and 7-day post-natal rat femoral growth plate were examined to determine whether the interlacunar network (IN), a structure with no lipoprotein membrane component or cytoplasmic organelles, is a genuine component of young growth cartilage. In chick phalanges dehydrated by 70% (v/v) ethanol and LR White resin, variable metachromatic staining of the interlacunar network by toluidine blue and red staining by picro-Sirius red indicate the presence of glycosaminoglycans and collagen. The network in phalanges dehydrated by 80% (v/v) ethanol appears little different; however, the network is much less widely detectable in phalanges dehydrated by 90% (v/v) ethanol and, after dehydration by absolute ethanol, is almost completely undetectable. In contrast, when the young cartilage is permeated by a thiazine dye such as toluidine blue, using a solution of dye in the aldehyde fixative, the network is widely detectable, following dehydration by absolute ethanol, both in chick phalanges and in rat growth plate. Comparison of projected areas shows that the extent to which whole chick feet are found to have shrunk, by the time that they are photographed under LR White resin, is determined principally by the extent of dehydration, by 70% (v/v) or absolute ethanol; post-shrinkage areas are 33% or 35% of areas measured in buffer for 70% (v/v) ethanol/LR White resin and 71% or 75% for absolute ethanol/LR White resin (the higher value in each is for the toluidine blue treatment). The network is thus present in radically shrunk tissue, but, significantly, is also fully represented in tissue shrunk by only a conventional margin and is therefore not produced as an artefact by exceptional tissue shrinkage as has been suggested.

Estimation of capillary length density in skeletal muscle by unbiased stereological methods: II. Use of vertical slices of unknown thickness

BACKGROUND

The capillary network of the skeletal muscle was analyzed from a quantitative point of view with the purpose of determining the capillary length density--LV(cap/mus). A recent stereological method was applied to estimate this quantity using vertical slices of unknown thickness.

METHODS

First, the whole muscle was systematically sampled according to the fractionator method. The capillary length density was estimated on each chosen field of vision where the vertical axis was always identified as parallel to the major axis of the muscle fibers. Three measurements were performed: count of intersections between capillaries and cycloid test lines, count of intersections between capillaries and straight test lines, and count of capillary end points corresponding to the intersections of capillaries with the parallel planes of the vertical slices.

RESULTS

The estimated capillary length density was 1,578 mm per mm3 of skeletal muscle tissue. The average thickness of the vertical slices was also estimated as 23.4 microns, which is roughly 6% less than the thickness measured using the microcator information on the microscope stage displacement.

CONCLUSIONS

The advantages of this methodology were based on two main features: the method is assumption-free on the degree of capillary and muscle anisotropy, and the thickness of the vertical slices need not be known nor constant.