[Age related staining pattern of acid mucopolysaccharides in human rib cartilage by alcianblue-acridinorange following different fixation methods (author's transl)]

How best to preserve and reveal the structural intricacies of cartilaginous tissue

No single processing technique is capable of optimally preserving each and all of the structural entities of cartilaginous tissue. Hence, the choice of methodology must necessarily be governed by the nature of the component that is targeted for analysis, for example, fibrillar collagens or proteoglycans within the extracellular matrix, or the chondrocytes themselves. This article affords an insight into the pitfalls that are to be encountered when implementing the available techniques and how best to circumvent them. Adult articular cartilage is taken as a representative pars pro toto of the different bodily types. In mammals, this layer of tissue is a component of the synovial joints, wherein it fulfills crucial and diverse biomechanical functions. The biomechanical functions of articular cartilage have their structural and molecular correlates. During the natural course of postnatal development and after the onset of pathological disease processes, such as osteoarthritis, the tissue undergoes structural changes which are intimately reflected in biomechanical modulations. The fine structural intricacies that subserve the changes in tissue function can be accurately assessed only if they are faithfully preserved at the molecular level. For this reason, a careful consideration of the tissue-processing technique is indispensable. Since, as aforementioned, no single methodological tool is capable of optimally preserving all constituents, the approach must be pre-selected with a targeted structure in view. Guidance in this choice is offered.

Age-related histochemical staining patterns of glycosaminoglycans in cell nuclei of different regions of the rat brain: a pilot study

The brains of 6 rats aged 12 months (adult) and 6 rats aged 24 months (aged) were embedded in paraffin following steady state perfusion with fixation solution. Glycosaminoglycans (GAGs) were demonstrated by histochemical methods using the Alcian blue CEC method in combination with the Feulgen reaction and testis hyaluronidase. Cell nuclei revealed different patterns of GAGs in different layers of the brain cortex and in different cell types. In neuronal cell nuclei of layer 2, no GAGs are found and this may be the case also in certain types of pyramidal cells. There was a reduction of the blue staining components of the chromatin network by hyaluronidase, and also a reduction of the electronmicroscopic contrast by this enzyme in pilot study using a specimen of one animal. The enzyme effects were found to be more marked or even exclusively present in the group of aged animals. Thus, the contents of chrondroitin sulfates or hyluronate which are substrates of the enzyme may be increased either relatively or absolutely in cell nuclei of aged brains whereas GAGs resistant to the enzyme may be reduced in activity. Since GAGs are known to influence DNA activity, the variations demonstrated may be assumed to be of significance for the aging process in postmitotic cells.

[Histochemical studies on the structure and the age changes of Descemet's membrane in cattle (author's transl)]

Descemet's membrane of 15 cattle-corneas, aged 6 month to 13 years was studied by various histochemical and morphometric methods. 3 zones could be differentiated. Zone 1 is relatively small and does not show significant changes with age; zone 2 comprises the main part of Descemet's membrane, its diameter increased with age. Zone 2 is rich in sulfated glycosaminoglycans. Zone 3, below the endothelial lining, does not develop before the 3rd and 5th year of life and stains different from zone 2.