ABSTRACT
Melanosomes in retinal tissues of a human, monkey and rat were analyzed by EDX in the TEM. Samples were prepared by ultramicrotomy at different thicknesses. The material was mounted on Al grids and samples were analyzed in a Zeiss 912 TEM equipped with an Omega filter and EDX detector with ultrathin window. Melanosomes consist of C and O as main components, mole fractions are about 90 and 3-10 at.%, respectively, and small mole fraction ratios, between 2 and 0.1 at.%, of Na, Mg, K, Si, P, S, Cl, Ca. All elements were measured quantitatively by standardless EDX with high precision. Mole fractions of transition metals Fe, Cu and Zn were also measured. For Fe a mole fraction ratio of less than 0.1at.% was found and gives the melanin its paramagnetic properties. Its mole fraction is however close to or below the minimum detectable mass fraction of the used equipment. Only in the human eye and only in the retinal pigment epitelium (rpe) the mole fractions of Zn (0.1 at.% or 5000 microg/g) and Cu were clearly beyond the minimum detectable mass fraction. In the rat and monkey eye the mole fraction of Zn was at or below the minimum detectable mass fraction and could not be measured quantitatively. The obtained results yielded the chemical composition of the melanosomes in the choroidal tissue and the retinal pigment epitelium (rpe) of the three different species. The results of the chemical analysis are discussed by mole fraction correlation diagrams. Similarities and differences between the different species are outlined. Correlation behavior was found to hold over species, e.g. the Ca-O correlation. It indicates that Ca is bound to oxygen rich sites in the melanin. These are the first quantitative analyses of melanosomes by EDX reported so far. The quantitative chemical analysis should open a deeper understanding of the metabolic processes in the eye that are of central importance for the understanding of a large number of eye-related diseases. The chemical analysis also allows a correlation with structural changes observed at the various regions of the eye.
Subject(s)
Melanosomes/chemistry , Retina/chemistry , Aged , Animals , Calcium , Carbon/analysis , Female , Haplorhini , Humans , Metals/analysis , Microscopy, Energy-Filtering Transmission Electron , Oxygen/analysis , Rats , Species SpecificityABSTRACT
The shadow profile monitoring of etched enamel surfaces was used for the investigations of constitutional differences. This method allows a three dimensional projection of the partially demineralized human enamel.
Subject(s)
Acid Etching, Dental , Dental Bonding , Dental Enamel/ultrastructure , Histological Techniques , Humans , In Vitro Techniques , Microscopy, Electron/methodsABSTRACT
6-[3-[4-(o-Methoxyphenyl)-1-piperazinyl]-propylamino)-1, 3-dimethyluracil (urapidil, Ebrantil) is capable of significantly influencing the excitation processes of the mammalian myocardial cell in a dose-related manner. At a concentration of 10(-3) mol/l urapidil myocardial action potentials of guinea-pig and hypertrophied or nonhypertrophied rat hearts reveal substantial reduction of the maximum upstroke velocity and marked prolongation. All these effects can completely be washed out within 15 min. Decreased isometric peak tension and time to peak tension indicate that high urapidil concentrations exert an additional negative inotropic effect. Experimental blockade of the individual transmembrane ionic fluxes suggests that urapidil affects the cardiac excitation process in an antiarrhythmic-like manner with inhibition of the initial, rapid Na+ inward current; the repolarizing K+ efflux; and probably also the slow Ca++ inward current. 10(-6) mol/l urapidil does not induce any alteration in the electrical behaviour of myocardium. Since this concentration corresponds to the serum concentrations generally reached in oral therapy of hypertension with urapidil, antiarrhythmic side effects should only occur under exceptional conditions like parenteral administration of high dosage or increased myocardial sensitivity.