Cytochemical Localization Of Ca2 Research Articles

Cytochemical Localization of Ca2+-, Mg2+-ATPase on the Limiting Membrane of Peroxisomes Isolated from Renal Tubules of Rats.

The cytochemical localization of Ca2+-, Mg2+-ATPase in peroxisomes isolated from rat renal tubules was investigated at the ultrastructural level. The reaction products were localized mainly on the cytoplasmic surface of the isolated peroxisomes, but also to some extent on the matrix, side of the limiting membrane. Neither Ca2+-nor Mg2+-ATPase activity was affected by treatment with levamisole, an inhibitor of alkaline phosphatase. Ca2+-ATPase activity was inhibited by thapsigargin and myricetin, but not by PCMB. Mg2+-ATPase activity was inhibited by PCMB. It was inhibited slightly by thapsigargin, but was not affected by myricetin.

Cytochemical localization of Ca(2+)-ATPases and demonstration of ATP-dependent calcium sequestration in giant smooth muscle fibres of Beroe.

A cytochemical analysis of the mechanisms underlying cytosolic calcium regulation was undertaken in the giant smooth muscle fibres of the marine invertebrate Beroe. The ability of the sarcoplasmic reticulum to accumulate Ca2+ was demonstrated on living skinned single cells. In the presence of oxalate, and physiological concentrations of Ca2+, calcium oxalate crystals were formed in the lumen of tubules and cisternae of the sarcoplasmic reticulum. The subcellular distribution of Ca(2+)-ATPase was studied with a cytochemical technique; a dense precipitate resulting from Ca(2+)-ATPase activity was found on the plasma membrane, on the membranes of tubules and cisternae of the sarcoplasmic reticulum, and in mitochondria.

Ultrastructural localization of calcium in mechanoreceptors of the oral mucosa.

Cytochemical localization of Ca2+ in Meissner corpuscles and Merkel cell-neurite complexes in the palatine mucosa of the Mongolian gerbil was studied by a combined oxalate antimonate-microwave irradiation procedure. The reaction products obtained were identified as calcium antimonate by EGTA solubility and X-ray microanalysis. Meissner corpuscles in the normal palatine rugae could be roughly classified into three types by amount and localization of Ca2+. Type I corpuscles were characterized by a high Ca2+ content in both the terminal axoplasm and caveolae of the lamellar plates, type II, by a low Ca2+ content in the terminal axoplasm and a high Ca2+ content in the lamellar cytoplasm. Type III corpuscles showed intermediate characteristics. Palatine rugae stimulated mechanically during fixation contained an increased number of type I corpuscles. On the other hand, two patterns were distinguished in the distribution of Ca2+ in Merkel cells in palatine rugae fixed under normal conditions. One showed abundant Ca2+ dispersed throughout the cell, while in the other, Ca2+ was specifically localized in the Golgi apparatus and mitochondria. Similar distribution patterns also were observed in palatine rugae that had received mechanical stimulus during fixation. Axon terminals of most Merkel cell-neurite complexes in normal palatine rugae were poor in axoplasmic Ca2+, whereas those in most Merkel cell-neurite complexes in mechanically stimulated palatine rugae contained abundant Ca2+ in their axoplasm.

Histochemical examination of adenosine nucleotidases in the developing rat spinal cord: Possible involvement in an enzymatic chain of ATP degradation.

In an attempt to characterize the membrane-associated Ca2+-ATPase activity in the roof and floor plates of the developing rat spinal cord (36), the effect of quercetin, a potent inhibitor of Ca2+-transporting ATPase was histochemically examined. Histochemical localization of ADPase and AMPase actvity was also investigated in relation to possible involvement in the enzymatic hydrolysis of ATP.When tissue specimens were incubated in media containing quercetin at a concentration of 0.1 or 0.5mM, the Ca2+-ATPase activity in both roof and floor plates appeared to be diminished, in a concentration-dependent manner, as seen under light microscopy. The inhibitory effect of quercetin was clearly evident in the floor plate. ADPase activity was also noted in both the roof and floor plates, particularly in the roof plate. Electron microscopic study revealed that the ADPase activity was mainly localized in the lateral and luminal plasma membranes of these plate-forming cells, resembli g the cytochemical localization of Ca2+-ATPase activity. There was, howover, no evidence of histochemical activity of AMPase in the developing spinal cord. These findings indicate that, in addition to activity of Ca2+-transporting ATPase, the roof and floor plate-forming cells during embryonic development may possess ecto-nucleotidases which hydrolyse ATP to AMP.

Variations in the morphology and Ca2+-ATPase activity of the ovarian surface epithelium in rats.

The ultrastructure and cytochemical localization of Ca2+-activated adenosine triphosphatase (Ca2+-ATPase) activity of the ovarian surface epithelium in immature rats and in adult rats during the estrous cycle and pregnancy were investigated at both light and electron microscopical levels. In the adult rat ovaries at all stages of the estrous cycle, the intensity of Ca2+-ATPase activity and ultrastructure of the surface epithelium were considerably varied in the different regions on the same ovary. The variations in the morphology and Ca2+-ATPase activity likely provide evidence for the differences in the functional activity of the surface epithelium, which are related to the topographical connection with adjacent structures of ovarian cortex, i.e., corpus luteum, preovulatory Graafian follicles, interstitium containing small follicles. In the adult rat ovaries at all reproductive stages, the cuboidal or columnar surface epithelial cells were found on the interstitium containing small follicles. In some places, the columnar surface epithelial cells, forming crypts of the epithelium, invaginated into the ovarian proper. This type of surface epithelial cell had well-developed microvilli on its apical membrane, and showed intense Ca2+-ATPase activity on its apical and lateral membranes. The squamous surface epithelial cells were found on the surface of corpus luteum and preovulatory Graafian follicles. These cells had a low number of microvilli and less activity of Ca2+-ATPase on the apical membrane. In the immature rat ovaries, the surface epithelial cells were in part squamous, in part cuboidal. Both types of surface epithelial cells had few microvilli. Ca2+-ATPase activity on the apical membrane was considerably less on all surfaces of the ovaries. It seems that the transport function of the surface epithelium in the immature ovary is not active as compared with the mature ovary.These results suggest that the surface epithelium may have an active function of local absorption and/or transepithelial transport between pelvic cavity and ovarian proper, and its functional activity is associated with the reproductive function of the ovary.

Cytochemical localization of Ca2+-Mg2+ adenosine triphosphatase in rat incisor ameloblasts during enamel secretion and maturation.

A modified Wachstein-Meisel medium containing lead or cerium as capturing ions was used to localize Ca2+-Mg2+ adenosine triphosphatase (ATPase; EC 3.6.1.3) in rat incisor ameloblasts during enamel formation. Sections representing different developmental stages were processed for electron microscopic cytochemistry. Distribution and intensity of the observed reaction product, which was almost exclusively associated with cell membranes, varied according to the stage of enamel formation. During the secretory stage, intense reaction product was evident along the entire plasma membrane of ameloblasts and papillary cells. The early transitional ameloblasts showed reaction product on their proximal and lateral cell membranes, but not distally. In late transitional (pre-absorptive) ameloblasts, distal cell membranes exhibited intense reaction product. During enamel maturation, smooth-ended ameloblasts showed reaction product proximally and laterally, but not distally. Ruffle-ended maturative ameloblasts exhibited intense reaction product along their lateral and distal membranes. The intensity of the latter was decreased but not eliminated by levamisole. In the transition from smooth-ended to ruffle-ended cells, the reaction product became evident distally, concomitant with the appearance of cell membrane invaginations. These data are consistent with a possible role for Ca2+-Mg2+ ATPase in controlling calcium availability at the enamel mineralization front.

Ca2+-binding sites and phosphatase activities in sieve element reticulum and P-protein of chick-pea phloem. A cytochemical and X-ray microanalysis survey

In stem ofCicer arietinum, the loss of ribosomes attached to the rough ER cisternae during sieve element ontogeny results in the formation of “sieve element reticulum” (SER). By enhancing contrast of the SER, the OsFeCN postfixation/staining of material prefixed in glutaraldehyde in presence of calcium enables a good visualization of this membrane system. The pattern of staining in the SER is slightly lower when Mg2+ is substituted for Ca2+. These results support the view that the OsFeCN staining requires divalent cations and that the SER can accumulate Ca2+. The detection of Ca2+ by means of the pyroantimonate method in conjunction with X-ray microanalysis and the cytochemical localization of Ca2+ -ATPase in the SER cisternae provides evidence for Ca2+ sequestration by the SER. On the other hand, Ca2+-binding sites and ATPase activity are localized in P-protein. The ability to bind Ca2+ seems to enable the SER to function as an effective Ca2+ sink which may participate—with the sieve tube plasma membrane and mitochondria—in the maintenance of low Ca2+ concentration in phloem sap. In addition, the close association between P-protein and SER membranes exhibiting Ca2+-binding capabilities suggests that a Ca2+-mediated functional relationship may exist between the two structures. It is postulated that the SER may play a role in putative Ca2+ control of P-protein organization.