ADENOSINE TRIPHOSPHATASE ACTIVITY IN RAT BRAIN FOLLOWING DIFFERENTIAL FIXATION WITH FORMALDEHYDE, GLUTARALDEHYDE, AND HYDROXYADIPALDEHYDE

Renaissance of cytochemical localization of membrane ATPases in the myocardium

ATPases of cardiac cells are known to be among the most important enzymes to maintain the fluxes of vital cations by hydrolysis of the terminal high-energy phosphate of ATP. Biochemically the activities of Ca(2+)-pump ATPase, Ca2+/Mg(2+)-ecto ATPase, Na+,K(+)-ATPase and Mg(2+)-ATPase are determined in homogenates and isolated membranes as well as in myofibrillar and mitochondrial fractions of various purities. Such techniques permit estimation of enzyme activities in vitro under optimal conditions without precise enzyme topography. On the other hand, cytochemical methods demonstrate enzyme activity in situ, but not under optimal conditions. Until recently several cytochemical methods have been employed for each enzyme in order to protect its specific activity and precise localization but the results are difficult to interpret. To obtain more consistent data from biochemical and cytochemical point of view, we modified cytochemical methods in which unified conditions for each ATPase were used. The fixative solution (1% paraformaldehyde-0.2% glutaraldehyde in 0.1 M Tris Base buffer, pH 7.4), the same cationic concentrations of basic components in the incubation medium (0.1 M Tris Base, 2 mM Pb(NO2)3, 5 mM MgSO4, 5 mM ATP) and selective stimulators or inhibitors were employed. The results reveal improved localization of Ca(2+)-pump ATPase, Na(+)-K+ ATPase and Ca2+/Mg(2+)-ecto ATPase in the cardiac membrane.

Electroreceptor functioning and morphology: functioning during histological fixation

The impact of chemical fixatives on electroreceptor functioning was studied electrophysiologically. The oxidative agents KMnO4 and OsO4 eliminate the sensory response within a few seconds, leaving a disturbed spike train pattern. Glutaraldehyde and formaldehyde eliminate the sensory response gradually in a period of several minutes; after that the afferent fibre shows repetitive activity. It is concluded that the physiological state of the electroreceptor is not preserved during chemical fixation; the ultimate morphological picture will reflect an unphysiological state, i.e. the response to the fixative.

Adenosine triphosphatases in electroreceptor organs (ampullary organs and mormyromasts) of Gnathonemus petersii Mormyridae

Cytochemical techniques were used for the light and electron microscopical localization of ATPase in the ampullary organ and the mormyromast, both cutaneous electroreceptors in Gnathonemus petersii (Mormyridae). At the right microscope level, two different techniques gave the same results, namely that high concentrations of the enzyme are present in the mormyromast and certain epidermal cells and weak concentrations in the ampullary organ. The enzyme was localized at the ultrastructural level using the lead capture method. It was found in the cytoplasm of type III accessory cells of the ampullary organ, in the apical cytoplasm of SC1 sensory cells and the accessory cells surrounding them and on the membrane of the SC2 sensory cells of the mormyromast. The ATPase of these various cells was inhibited by p-chloromercuribenzoate. The enzyme in the mormyromast SC1 and their accessory cells was not dependent on Mg2+ ions. However, that in the type III accessory cells of the ampullary organ and in the SC2 of the mormyromast was strictly dependent on Mg2+. In addition, there was a Ca2+-dependent ATPase in the microvilli of the SC2 of certain mormyromasts.

The cytochemical demonstration of NaK dependent adenosine triphosphatase at electrocyte level in Eigenmannia virescens (Gymnotidae)

ATPase activity (E.C. 3.6.1.3.) has been studied by electron microscopy with the help of several cytochemical techniques on Eigenmannia virescens electrocytes. Incubation was carried out with in two different media containing paranitrophenyl phosphate (p-NPP) or adenosine triphosphate (ATP) as substrate. With p-NPP the phosphate freed is captured at alkaline pH, either by strontium chloride or by lead citrate. With ATP the phosphate freed is captured at a pH close to neutrality by the lead nitrate. NaK ATPase activity was only demonstrated with the medium containing ATP; the positive results obtained with this technique were sensitive to ouabain. The enzyme is situated both on the membrane of the posterior face which is innervated and on that of the anterior face of the electrocytes. The cytoplasm of the anterior face is occupied by a strong concentration of tubules on whose membranes the enzyme is also present. The localisation of the enzyme on the tubules can explain biochemical results which indicate that 70% of the total NaK ATPase of the electrolytes is situated at the level of the anterior face.

Adenosine triphosphatase distribution in mammary tissue

Lactating mammary tissue from farm animals and small mammals was perfusion-fixed, prior to histochemical procedures, in an effort to localize the ouabain-sensitive Na+/K+-stimulated ATPase enzyme with the use of specific inhibitors. Histochemical evidence suggests that the Na+/K+-stimulated ATPase is located predominantly on the cytoplasmic side of the plasmalemma in myoepithelial and secretory cells of the alveolus and in epithelial cells of the ducts. Enzyme is not present on the apical plasmalemma of the secretory or duct cells. This substantiates the previous suggestions of localization of the sodium pumps on lateral and basal surface in lactating mammary secretory cells and duct cells.

Crystalline patterns of myelin lipids visualized by freeze fracture

Freeze fracture of rat optic nerve reveals smooth, particle-free regions on the lammellar fracture faces of myelin when prepared by standard procedures. When the fixed, glycerin-impregnated tissue is incubated at 6 degrees C for two or more days, crystalline patterns indicative of a phase transition can be seen in the particle-free regions. The crystalline patterns can be destroyed by subsequent incubation at 37 degrees C and are not seen when the initial incubation is at room temperature or 37 degrees C. Butylated hydroxytoluene has no effect on the formation of the crystalline patterns. The time course of the formation of the crystalline patterns suggest that the rate-limiting step in the process is not the phase transition itself. We propose that the lipids associated with the particles in vivo are involved in the formation of the crystalline patterns.

Cytochemical localization of adenosine triphosphatase and thiamine pyrophosphatase in the synapases of rat's cerebral cortex

Ultrastructural distribution of adenosine triphosphatase and thiamine pyrophosphatase in synapses of rat's cerebral cortex was studied. Adenosine triphosphatase activity in some synaptic vesicles and mitochondria, on pre- and postsynaptic membranes, as well as in the postsynaptic thickening was established. The reaction specificity was proved by means of some controls: various concentrations of ouabain, NaF, NiCl2, cysteine, substrate free medium and non-specific substrates - cocarboxylase and beta-glycerophosphate. At the thiamine pyrophatase reaction, the enzyme positive product was found on the membrane of some clear synaptic vesicles, on the singl sacs of smooth endoplasmic reticulum in the axon terminal, and bouton cell membrane. Substrate free medium, addition of cystein and substitution of orininal substrate with adenosine triphosphate and beta-glycerophosphate as controls were used. The fine structure localization of both enzymes in synaptic structures suggests their important role in the synaptic function.

Adenosine triphosphate hydrolysis in rat dental tissues. A histochemical study to differentiate the enzymes involved

The purpose of this study was to try to differentiate histochemically between the various enzymes which may catalyze the hydrolysis of ATP in developing rat dental tissues. Freeze cut and freeze dried sections of molar and incisor teeth were incubated in lead capture-based media at pH 5.0, 7.2 or 9.4 with one of the following substrates: beta-glycerophosphate, AMP, ADP, ATP, AMP-PNP and tetrasodium pyrophosphate. To establish the enzymatic nature of the hydrolysis parallel sections were incubated after prior fixation in either formaldehyde or glutaraldehyde. By comparing the enzymatic stainings obtained with the various substrates and at the different pH:s, it was concluded that ATP can be visibly hydrolyzed in rat dental tissues by alkaline phosphatase (stratum intermedium, apical part of maturation ameloblasts, basal part of all ameloblasts, odontoblasts and subodontoblastic layer), specific ATPase (apical and basal parts of secretory ameloblasts) and ATP pyrophosphatase and/or adenylate cyclase (stratum intermedium, odontoblasts). Acid phosphatase, specific ADPase, 5'-nucleotidase, inorganic pyrophosphatase, 3':5'-cyclic-AMP-phosphodiesterase and adenylate kinase on the other hand, seem not to be engaged in the ATP hydrolysis to such a degree as to complicate the interpretation of the histochemical staining. The alkaline phosphatase part of the ATP hydrolysis appeared to be rather insensitive to aldehyde fixation, while the hydrolysis effected by specific ATPase and ATP pyrophosphatase and/or adenylate cyclase was extinguished after fixation with formaldehyde for 4 h or glutaraldehyde for 10 min.

Differences in enzyme content of azurophil and specific granules of polymorphonuclear leukocytes. II. Cytochemistry and electron microscopy of bone marrow cells

In the previous paper we presented findings which indicated that enzyme heterogeneity exists among PMN leukocyte granules. From histochemical staining of bone marrow smears, we obtained evidence that azurophil and specific granules differ in their enzyme content. Moreover, a given enzyme appeared to be restricted to one of the two types. Clear results were obtained with alkaline phosphatase, but those with a number of other enzymes were suggestive rather than conclusive. Since the approach used previously was indirect, it was of interest to localize the enzymes directly in the granules. Toward this end, we carried out cytochemical procedures for five enzymes on normal rabbit bone marrow cells which had been fixed and incubated in suspension. The localization of reaction product in the granules was determined by electron microscopy. In accordance with the results obtained on smears, azurophil granules were found to contain peroxidase and three lysosomal enzymes: acid phosphatase, arylsulfatase, and 5'-nucleotidase; specific granules were found to contain alkaline phosphate. Specific granules also contained small amounts of phosphatasic activity at acid pH. Another finding was that enzyme activity could not be demonstrated in mature granules with metal salt methods (all except peroxidase); reaction product was seen only in immature granules. The findings confirm and extend those obtained previously, indicating that azurophil granules correspond to lysosomes whereas specific granules represent a different secretory product.