Molecular recognition can be mediated by protein (lectin)-carbohydrate interaction, explaining the interest in this topic. Plant lectins and, more recently, chemically glycosylated neoglycoproteins principally allow to map the occurrence of components of this putative recognition system. Labelled endogenous lectins and the lectin-binding ligands can add to the panel of glycohistochemical tools. They may be helpful to derive physiologically valid conclusions in this field for mammalian tissues. Consequently, experiments were prompted to employ the abundant beta-galactoside-specific lectin of human nerves in affinity chromatography and in histochemistry to purify and to localize its specific glycoprotein ligands. In comparison to the beta-galactoside-specific plant lectins from Ricinus communis and Erythrina cristagalli, notable similarities were especially detectable in the respective profiles of the mammalian and the Erythrina lectin. They appear to account for rather indistinguishable staining patterns in fixed tissue sections. Inhibitory controls within affinity chromatography, within solid-phase assays for each fraction of lectin-binding glycoproteins and within histochemistry as well as the demonstration of crossreactivity of the three fractions of lectin-binding glycoproteins with the biotinylated Erythrina lectin in blotting ascertained the specificity of the lectin-glycoprotein interaction. In addition to monitoring the accessible cellular ligand part by the endogenous lectin as probe, the comparison of immunohistochemical and glycohistochemical detection of the lectin in serial sections proved these methods for receptor analysis to be rather equally effective. The observation that the biotinylated lectin-binding glycoproteins are also appropriate ligands in glycohistochemical analysis warrants emphasis.(ABSTRACT TRUNCATED AT 250 WORDS)
Protein-carbohydrate recognition may be involved in an array of molecular interactions on the cellular and subcellular levels. To gain insight into the role of proteins in this type of interaction, surgically removed specimens of human endomyocardial tissue were processed for histochemical and biochemical analysis. The inherent capacity of these sections to bind individual sugar moieties, which are constituents of the carbohydrate part of cellular glycoconjugates, was assessed using a panel of biotinylated neoglycoproteins according to a standardized procedure. Together with appropriate controls, it primarily allowed localization of endogenous lectins. Differences in lectin expression were observed between layers of endocardial tissue, myocardial cell constituents, connective-tissue elements, and vascular structures. The endocardium proved to be positive with beta-galactoside-bearing probes; with neoglycoproteins carrying beta-xylosides, alpha-fucosides, and galactose-6-phosphate moieties; and with probes containing a carboxyl group within the carbohydrate structure, namely sialic acid and glucuronic acid. In contrast, only fucose-and maltose-specific receptors were apparent in the elastic layers of the endocardium. Aside from ascertaining the specificity of the protein-carbohydrate interaction by controls, i.e., lack of binding of the probe in the presence of the unlabelled neoglycoprotein and lack of binding of the labelled sugar-free carrier protein, respective sugar receptors were isolated from heart extracts by using histochemically effective carbohydrates as immobilized affinity ligand. Moreover, affinity chromatography using immobilized lactose as affinity ligand as well as the use of polyclonal antibodies against the predominant beta-galactoside-specific lectin of heart demonstrated that the lactose-specific neoglycoprotein binding was due to this lectin. Remarkably, the labelled endogenous lectin, preferred to plant lectins for detecting ligands of the endogenous lectin, localized ligands in tissue parts where the lectin itself was detected glycohistochemically as well as immunohistologically. This demonstration of receptor-ligand presence in the same system is a further step toward functional assignment of the recorded protein-carbohydrate interaction. Overall, the observed patterns of lectin expression may serve as a guideline to elucidate the precise physiological relevance of lectins and to analyze pathological conditions comparatively.
Morphological changes are shown in the muscle biopsy specimens of an 8-year-old girl who suffered from a triosephosphate isomerase (TPI) deficiency, resulting in a chronic, nonspherocytic, hemolytic anemia, mental retardation and neuromuscular impairment. The newly introduced enzyme histochemical reaction for TPI demonstrated a total lack of histochemically detectable enzyme activity, whereas biochemical analysis of muscle tissue revealed less than 10% of the normal enzyme activity. Electron microscopy showed a degenerative myopathy with an increase in the amount of intracellular glycogen. Additionally, mitochondrial changes within the muscle fibers were observed to be similar to those in mitochondrial myopathies. The disturbed balance between glycerin-aldehyde phosphate and dihydroxyacetone phosphate, due to the deficiency of the TPI enzyme, is interpreted as the biochemical background of an impaired electron transport across the mitochondrial membrane, resulting in the coexistence of an impaired glycolytic pathway and an impaired mitochondrial metabolism of muscle cells.
Inhalation anaesthetic agents are known to depress phagocytic functions such as mobilization, attachment, chemotactic motility, engulfment and intracellular killing. Mannose-specific sugar receptors on the surface of leukocytes are involved in a series of phagocytosis-related activities. To investigate the effect of anaesthesia on the expression of this type of sugar receptor, mice were anaesthetized with halothane, enflurane and isoflurane. The presence of mannose-binding receptors on peripheral blood polymorphonuclear leukocytes was examined glycocytochemically using the biotinylated neoglycoprotein mannosylated bovine serum albumin. Prolonged administration of inhalation anaesthetic agents, especially halothane, markedly depressed expression of mannose-specific receptors. This reduction may possibly contribute to postoperative immunodepression, resulting from the impaired cellular interaction which is involved in the phagocytic function of granulocytes.
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