Suppression of metachromasia of galactogen by organic solvents and its relation to their dielectric constants

Summary In order to elucidate the relationship between the dielectric constants of various organic solvents and their capacity to abolish the metachromasia of galactogen localised in the albumen gland of a land snail, effects of various alcohols, ketones, esters and ethers on the metachromasia were investigated. The metachromasia was labile to all these solvents and its suppression depended on their dielectric constants. The higher the dielectric constant of a solvent the lower was its capacity to suppress the metachromasia of galactogen. Such a relationship was not a generalised phenomenon but it was true within a group of solvents with a specific reactive group. The four groups of solvents can be arranged in a series: ethers, esters, alcohols, ketones, in order of their increasing efficiency to abolish the metachromasia. Saturated or unsaturated nature of the solvent also affected such a suppression.     

Histochemical significance of green metachromasia to Toluidine blue

Summary The significance of green metachromasia to Toluidine blue O, exhibited by vitelline cells of monogeneans and epicuticle of millipedes is elucidated, as due to phenolacid mucopolysaccharide complex, as synthetic phenols or synthetic phenol in combination with heparin or hyaluronic acid gave likewise a green colour to Toluidine blue. The green colour is indicative of a metachromatic reaction is suggested, by its being eliminated or suppressed on treatment with metallic cations or detergent like Sodium oleate, as in other metachromatic reactions. A probable involvement of -OH groups in phenol-acid mucopolysaccharide complex is suggested.We thank Prof. G. Krishnan, Director, Department of Zoology, University of Madras for the many courtesies extended to us. Thanks are due to Dr. P. Shanmugam and Dr. S. M. Bose for the enlightening discussions and to Dr. (Miss) Lakshmi Chettur and Dr. D. Subramaniam for their help.     

Muscular fatigue: effects of hydrogen ions and inorganic phosphate

During muscular fatigue two metabolites, hydrogen ions (H+) and inorganic phosphate (Pi), increase in concentration. The effect of increase in [H+] has been modeled mathematically for a system containing creatine kinase (EC 2.7.3.2), adenylate kinase (EC 2.7.4.3), and the appropriate concentrations of their substrates. Assuming that no other equilibrium reactions are involved, the result of acidification should be a useful increase in the ratio [ATP]/[ADP]. It is also shown by a reanalysis of earlier 31P NMR studies that the observed combination of increased [H+] and increased [Pi] leads to an increase in the monobasic phosphate concentration [Pi-] that is inversely proportional to the force of contraction. This suggests that Pi- may be a direct inhibitor of the actomyosin ATPase system.     

A spin labeling study of the effects of inorganic ions and pH on the conformation of spectrin

The structure of spectrin from human erythrocytes has been investigated by the EPR technique measuring the mobility of the protein spin label, 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. Conformational changes in the protein induced by variation of the concentrations of NaCl, Na2SO4, KCl, CaCl2 and MgCl2 and of pH have been studied. It could be demonstrated that both Ca2+ and Mg2+ give rise to structural changes by binding to specific sites, whereas the monovalent cations (K+, Na+) seem to act via ionic strength. A model is used to correlate the spin label mobility with the radius of the protein. In the Ca2+- and Mg2+-binding experiments, the decrease in the spin label mobility has been interpreted on the basis of the theory of multiple chemical equilibria. These experiments have been compared with EPR spectra measured at different pH values. The results support the model in that binding of H+, Ca2+ or Mg2+ reduces the charges located on the protein surface: the 'discharging' reduces the repulsive forces on the surface of the molecule and consequently, the protein contracts in discrete steps.     

Histochemical localization of zinc ions in the epididymis of the rat

Summary In the present study, the autometallograpic zinc sulphide technique, an improved version of the original Timm sulphide-silver method, was used. This technique reveals a particular pool of ionic zinc that is chelatable by diethyldithiocarbamate. At the light microscopical level, no reaction for zinc was found in tissues of young prepubertal rats. In adult mating and non-mating rats low zinc staining was found in the head and intermediate epididymis whereas the tail of the epididymis demonstrated high levels of zinc ions. Sections from the epididymal tail revealed a compartmentalization, based on pronounced differences in staining intensity along the epididymal ducts. At higher magnification zinc ions were found in the apical part of the principal cell and in the lumen. At the ultrastructural level autometallographic grains were located in vesicles and in lysosome-like structures of the apical parts of the principal cells. The luminal grains were found either associated with sperm cells, with the surface of the large microvilli (stereocilia), or free in the seminal fluid. The variation in content of zinc ions in the epididymal epithelium and lumen suggests that zinc ions are secreted into the lumen from the epididymal tail and may somehow be involved in maturation of the sperm cells.     

Suppressive actions of inorganic ions on the bioactivity of aminoglycoside antibiotics.

Many independent studies have shown that inorganic salts can suppress the inhibitory activities of aminoglycoside antibiotics against various bacterial species. From studies on the nature and mechanism of this suppressive ion effect, several conclusions can be drawn. Both monovalent and divalent cation salts can inhibit aminoglycoside action. At least two different mechanisms are apparently involved. The first is divalent cation dependent and has been described with $\text{Pseudomonas aeruginosa}$ and $\text{Mycobacterium smegmatis}$. With $\text{M. smegmatis}$, the effect aappears to be dependent more on a double positive charge than on particular metal ion species. The second mechanism is related to ionic strength and is elicited by both monovalent and divalent cation salts against many different organisms. However, based on studies with $\text{M. smegmatis}$, it appears that each of the two mechanisms involves interferance with the initial instantaneous electrostatic binding of drug at the cell surface.