Orientation of acidic polysaccharides and rhodopsin-oligosaccharides in frog retinal rod outer segments

Electron microscopic demonstration of Romhányi's aldehyde-bisulphite-toluidine blue (ABT)-topo-optical staining reaction

Romhányi's aldehyde-bisulphite-toluidine blue (ABT) topo-optical reaction was checked electron microscopically. The reaction product was found localized on the sarcolemma membrane and intercalated disc. The findings suggest that the topo-optical ABT-reaction is suitable for molecular analysis. In addition to confirming the electron microscopic suitability of the ABT-reaction it has also offered ultrastructural evidence for the reliability of the topo-optical method.

The relevance of the aldehyde bisulfite toluidine blue reaction and its variants in the submicroscopic carbohydrate research

Carbohydrates are chemical compounds that contain only oxygen, hydrogen and carbon. They are classified by their number of sugar units: monosaccharides (such as glucose and fructose), and disaccharides (such as sucrose and lactose) are simple carbohydrates; oligosaccharides and polysaccharides (such as starch, glycogen and cellulose) are complex carbohydrates. Carbohydrates play a crucial role in diverse biological systems [Hricovín M. Structural aspects of carbohydrates and the relation with their biological properties. Curr Med Chem 2004;11:2565-83]. According to Roseman [Sugars of the cell membrane. In: Weissmann G, Clairborn E, editors. Cell membranes. Biochemistry, Cell Biology, Pathology. New York: H. P. Publ. Co; 1975. p. 55-64], two classes of glycoproteins are described. Free glycoproteins are localised in the surface coat of the membranes and form a thick mobile layer, without any association to the membrane itself. Functionally, however, they are located in a close association with the membrane (e.g. in the duodenal mucosa). The other group consists of the membrane glycoproteins, which are integral to the membranes and are located in the outer layer. The oligosaccharide chains are bound to the N-terminal part of proteins, and are situated in the hydrophilic zone. Glycoproteins have diverse functions. They are important in specific receptor functions, in immunological cell destruction and play a significant role in reactions with lectins, antibodies, as well as in cell association and mutual recognition of the cells. This paper focuses on aspects of a summary of polarisation optical investigations and biological functions of the following three groups of carbohydrates: oligosaccharides, glycoproteins and glycosaminoglycans.

George Romhányi (1905-1991): pioneer in amyloid research and polarization microscopy, on the 100th anniversary of his birth

George Romhányi was an outstanding pathologist, university teacher and a renowned scientist of the 20th century. After studying medicine and pathology, his scientific interest focused on haemochromogenic reactions and submicroscopic structure research. He was among the first to describe the fibrillar-micellar structure of amyloid, as well as the helical-fibrillar structure of elastic fibres. Between 1951 and 1976 Romhányi held the chair of pathology at the University of Pécs. During this time he published numerous topo-optical reactions leading to a renaissance of polarization microscopy. Romhányi's topo-optical reactions possess a high molecular specificity and enabled submicroscopic structural analysis. He and his disciples analysed the biomembrane, collagen fibres, the extracellular matrix of connective tissues, cell walls of bacteria and fungi, the ergastoplasmatic membrane, RNA and DNA. Romhányi's investigation of a range of amyloid depositions was a milestone and led to intensive immuno-biologic research in this area. He firmly held the opinion that polarization microscopy is, along with the electron and fluorescent microscopy, indispensable for solving fundamental questions of molecular biology.

Polarization optical analysis of blood cell membranes

The present study deals with investigations of membrane structure using polarization topo-optical reactions. Polarization microscopy is a special field of biological submicroscopic morphology. It represents a powerful tool well able to reveal the features of organization of biological structures, and the regularity of macromolecules building cells and tissues - properties that cannot directly be studied by other approaches to complex biological systems. Only in "pure" systems can X-ray diffraction, or the analysis of circular dichroism and the dispersion of optical rotability provide data equivalent to those obtained by polarization microscopy in complex systems. One of the main drawbacks of molecular biology is that most information is relevant to isolated, purified particles or macromolecules. Thus, no conclusions can be drawn concerning the original arrangement of molecules. The gap between biochemical-biophysical and morphological approaches to molecular arrangement in complex structures is bridged by the polarization optical technique. As was pointed out in the introduction, polarization microscopy became a routine biological research method following the pioneering work of Romhányi. His enlightening topo-optical reactions (Romhányi 1960, 1963, 1966) were based on the oriented dye binding of the original charge carriers of regularly arranged tissue constituents. The second group of Romhányi's topo-optical reactions comprised procedures such as sulfation (Romhányi et al. 1973, 1974), the aldehyde-bisulfite-toluidine blue (ABT) reaction (Romhányi et al. 1974, 1975), the permanganate-bisulfite-toluidine blue (PBT) reaction (Fischer 1979, 1979a), and the sialic acid-specific reaction (Makovitzky 1980) all of which operate with induced dye-binding groups; i.e. dye-binding moieties on biological macromolecules are produced by specific chemical reactions.

Acid polysaccharide content of frog rod outer segments determined by metachromatic toluidine blue staining

Sulfonation of periodate-oxidized vicinal hydroxyl groups on a polysaccharide backbone allows binding of toluidine blue (aldehyde bisulfite-toluidine blue or ABT staining) with a concurrent metachromatic shift of the dye's absorption peak from 630 nm (monomer) to 580 nm (isolated dimer interaction at vicinal sulfonate groups) or 540 nm (dye polymer interaction). A molar absorptivity of 2.358 +/- 0.134 X 10(4) at 540 nm for polymeric toluidine blue O chloride (TB) aggregates was determined by spectrophotometry of TB bound to hyaluronic acid (HA) and sulfonated glycogen (SG) in water. Microspectrophotometry of ABT stained frog rod outer segments (FROS) showed spectra similar to TB in aqueous HA and SG solutions with absorbances corresponding to 0.063 M dye bound to sugar. Given two dye molecules bound per sugar residue and a rhodopsin concentration of 3.25 mM in FROS, the above indicates 10 stainable sugars per rhodopsin are contained in these cells. Half of these sugars are sensitive to hyaluronidase digestion implying 5 glycosaminoglycan (GAG) repeating units and 5 stainable oligosaccharide sugar residues per rhodopsin in FROS. The GAGs in FROS appear to be primarily HA. Birefringence measurements at 475 nm indicate that this HA and the oligosaccharide of rhodopsin are anisotropically oriented in these cells.

Erythrocyte membrane topo-optical staining reflects glycoprotein conformational changes

The study is concerned with the relationship of induced birefringence to conformational alterations of glycocalyx glycoproteins. Human erythrocytes washed with phosphate-buffered saline (PBS) and fixed with glutaraldehyde exhibit the most intense topo-optical staining, which is thought to reflect the lipid bound state of glycophorins. Incubations at reduced pH, in hypotonic media or in the presence of procaine resulted in a significant decline of induced anisotropy. The effects were not due to degradation of glycocalyx constituents. Erythrocytes subjected to treatments with procaine or at pH 6x2 suffered from loss of electrophoretic velocity, a finding indicative of rearrangement of cell surface glycoproteins. by example of the red blood cell the findings of this study confirm the premised suggestion of the sensible detection by topo-optical toluidine blue staining of the conformational state of glycoproteins of the glycocalyx.

The carbohydrates in frog retinal rod outer segments

Frog retinal rod outer segments appear to contain uncharacterized chemical components whose mass is roughly equivalent to 12--51% of the rhodopsin mass. Available data suggest that such components include soluble proteins and complex polysaccharides, and that hyaluronic acid accounts for a substantial fraction of this mass. Electron microscopic histochemical staining studies suggest that these polysaccharide components are located within the ROS disks. The oligosaccharide moieties of rhodopsin also appear localized within the disks. The interdisk cytoplasm may contain carbohydrates, but their quantity and identity are uncertain. Rhodopsin oligosaccharides as well as some fraction of the intradisk polysaccharide appear to have extended saccharide chains preferentially oriented perpendicular to the surface of the disk membrane. Possible roles for these polysaccharides in disk development and photoexcitation are discussed. The immediate need for complete rod outer segment chemical composition data is emphasized.

Studies on the molecular arrangement of RNA in tissues with a selective topo-optical reaction of RNA

Selective demonstration of RNA in tissues was achieved by treating tissue sections with potassium permanganate followed by bisulfite and toluidine blue at pH 1.0 (PBT reaction). It is suggested that this reaction is due to aldehyde groups which are formed by the oxidative cleavage of the pyrimidine rings of RNA which can be selectively demonstrated using bisulfite-toluidine blue as the aldehyde reagent. The specificity of the reaction was tested after RNAase treatment, after acid hydrolysis, and on pure RNA droplets. The aldehyde nature of the reacting groups was checked, after permanganate oxidation, by Schiff's leucofuchsin reagent, and by aldehyde blocking reactions. Two types of intracellular molecular arrangement of RNA molecules could be distinguished by polarization optics after application of the PBT reaction: 1) The strong birefringence, dichroism and metachromatic staining of membrane-bound RNA in ergastoplasm of pancreas, liver and plasma cells indicate a linear (planar) molecular order of RNA molecules on the surface of the membranes, and 2) the isotropic, basophilic staining of RNA not organized in membrane structures (Nissl substance, nucleoli) suggest a random distribution of their dye binding sites.

Ultrastructure of elastic fibers as shown by polarization optics after the topo-optical permanganate-bisulfite-toluidine blue (PBT) reaction

Permanganate-bisulfite-toluidine blue (PBT) reaction proved to be a highly selective and sensitive method for demonstration of elastic structures in tissue sections. Permanganate oxidation liberates a great amount of aldehyde groups in young and adult elastic fibers both in bovine ligamentum nuchae which can be demonstrated with the bisulfite-toluidine blue (pH = 1.0) staining procedure. There are suggestive evidences that the aldehyde groups are liberated from the desmosine and isodesmosine cross bondings of elastin. The dichroism and the strong birefringence of the elastic fibers induced by the PBT reaction indicate a high degree of linear fibrillar molecular order of the reacting elastin molecules which are assumed to be arranged helically in the aortic elastic fibers and they are assumed to show 2 different micellar textures in ligamentum nuchae fibers as reported with other topo-optical reactions earlier by Romhanyi.