ABSTRACT
The biology of sialic acids has been an object of interest in many models of acquired and inherited skeletal muscle pathology. The present study focuses on the sialylation changes in mouse skeletal muscle after invasion by the parasitic nematode Trichinella spiralis (Owen, 1835). Asynchronous infection with T. spiralis was induced in mice that were sacrificed at different time points of the muscle phase of the disease. The amounts of free sialic acid, sialylated glycoproteins and total sialyltransferase activity were quantified. Histochemistry with lectins specific for sialic acid was performed in order to localise distribution of sialylated glycoconjugates and to clarify the type of linkage of the sialic acid residues on the carbohydrate chains. Elevated intracellular accumulation of α-2,3- and α-2,6-sialylated glycoconjugates was found only within the affected sarcoplasm of muscle fibres invaded by the parasite. The levels of free and protein-bound sialic acid were increased and the total sialyltransferase activity was also elevated in the skeletal muscle tissue of animals with trichinellosis. We suggest that the biological significance of this phenomenon might be associated with securing integrity of the newly formed nurse cell within the surrounding healthy skeletal muscle tissue. The increased sialylation might inhibit the affected muscle cell contractility through decreased membrane ion gating, helping the parasite accommodation process.
ABSTRACT
Fixation techniques preserving morphological fidelity, protein antigenicity and integrity of nucleic acids can have a high impact on both basic and applied biomedical sciences and diagnostic pathology. Different types of mouse tissues were fixed with neutral buffered formalin, ethanol supplemented with acetic acid and modified methacarn (methanol-Carnoy) fixative. The alcohol-fixed samples were processed in an Autotechnicon tissue processor or in an incubator. The preservation of tissue morphology was assessed in all specimens and the immunoreactivity was evaluated with antibodies specific for proteins with nuclear, membrane or cytoplasmic localization. RNA was extracted from all groups of fixed hind limb skeletal muscle specimens and was assessed versus unfixed tissue for preservation of its quantity and quality by amplification of gene-specific fragments of different lengths. Both alcohol-based fixatives preserved the tissue architecture and the specificity of immunoreactivity in excellent quality; the trimming approach did not result in detectable differences. Oligonucleotide fragments of length between 108 and 577 base pairs were amplified from all groups of alcohol-fixed skeletal muscle specimens in amounts comparative to the unfixed muscle tissue. We conclude that both alcohol-based fixatives are an excellent tool for storage of tissue samples designed for immunohistochemical and mRNA expression studies when the access to fresh samples is limited.
