Alkaline phosphatase isozymes of Xenopus laevis embryos and tissues

Enzymatic and immunological properties of alkaline phosphatase of bullfrog

Enzymatic and immunological properties of alkaline phosphatase (ALPase) in several tissues of bullfrog (Rana catesbeiana) were investigated. Inhibition and thermal inactivation studies showed that bullfrog ALPases in kidney, liver, and intestine had similar enzymatic properties. In addition, mouse antiserum against bullfrog liver ALPase cross-reacted with kidney and intestine enzymes as well as with liver enzyme. These results suggest that a single phenotype of ALPase exists in all tissues of bullfrog in contrast to two or three isoenzymes in mammals.

Electron-microscopic cytochemistry of alkaline-phosphatase activity in endothelium, pericytes and oligodendrocytes in the rat brain

The fine structural localization of alkaline-phosphatase (ALP) activity was investigated in the endothelial cells and pericytes of blood vessels and in the oligodendrocytes of rat cerebral cortex and corpus callosum by means of electron-microscopic (EM) cytochemistry using the lead-citrate method. ALP activity was associated with both the luminal and abluminal plasma membranes of some endothelial cells, but in other endothelial cells, this activity was found inside the cytoplasm. In some pericytes, ALP activity was associated with the plasma membrane but in others, strong activity was exhibited within both the cytoplasm and nucleus. Light, medium and dark oligodendrocytes showed ALP activity on their plasma membranes; on the other hand, immature oligodendrocytes exhibited activity within the cytoplasm and on the part of their plasma membrane. Within the cytoplasm of these reacted immature cells, the rough endoplasmic reticulum, nuclear membrane and outer membrane of the mitochondria were the main sites of ALP reaction. Endothelial cells, pericytes and oligodendrocytes demonstrated ALP activity along their plasma membrane or within their cytoplasm, and pericytes showed it within their nuclei. In particular, oligodendrocytes retained ALP activity throughout their cell life, and the intracellular distribution of this activity altered as they matured.

Cellular commitment for post-gastrular increase in alkaline phosphatase activity in Xenopus laevis development

Xenopus embryos were dissociated into cells and cultured in Ca2+-free medium to study the relationship between the cell-to-cell interaction and macromolecular synthesis. Under the conditions, cells did not aggregate at all, and remained isolated even while they were dividing actively. Synthesis of DNA and protein as studied by the incorporation of (3H) thymidine and (3H) leucin proceeded as in the aggregating cells. Also, the activity to synthesize rRNA, 5S RNA, and heterogeneous RNA as determined by the incorporation of (3H) uridine was not impaired. Such as increase in the activity of alkaline phosphatase, as occurs in embryos after the gastrula stage, was found to be inhibited greatly when early-blastula cells were cultured in the non-aggregating conditions. However, we found here that the inhibition was not observed with cells isolated from late-blastulae. Therefore, it appears that the increase in the activity of alkaline phosphatase during post-gastrular stages is dependent on some cellular commitment which may be established by cell-to-cell contact during the blastula stage.