Carbonic anhydrase activity in a calcium-mobilizing epithelium of the crustacean Orchestia cavimana during molting

We investigated the involvement of the enzyme, carbonic anhydrase, in the calcification-decalcification processes occurring in the posterior caeca of the midgut of the terrestrial crustacean, Orchestia cavimana, before and after exuviation. This enzyme was ultrahistochemically localized throughout the membranes of the caecal epithelium as well as extracellularly, i.e., within pre-exuvial calcareous concretions and postexuvial calcified spherules. During the molt cycle, the pattern of carbonic anhydrase activity in the posterior caeca was correlated with the calcium content at this level. Acetazolamide treatment in vivo inhibited about 50% of the calcium uptake during both pre-exuvial secretion and postexuvial reabsorption. The role of carbonic anhydrase in this mineralizing-demineralizing epithelium is discussed and compared with that of other mechanisms involved in this calcium turnover.

[Fate of a fragment of madrepore coral skeleton implanted in the diaphysis of long bones in dogs]

A madrepore fragment implanted into Dog's long bone diaphysis is quickly vascularized and then progressively resorbed; this is due to an osteoclasic action. At the same time, in replacement of resorbed coral, cancellous bone grows which progressively let the place to compact bone. Injections of diamox given to formerly implanted Dogs, slacken the resorption of coral implants which seems to be the work of carbonic anhydrase contained in osteoclasts.

[Calcifying bacteria and carbonic anhydrase]

Carbonic anhydrase activity was measured on bacteria known for their calcifying power. The results obtained allow us to conclude that carbonic anhydrase is not present in their enzymatic equipment. Nevertheless, the addition of carbonic anhydrase in culture media increases the growth of the cultures and their calcifying power. This result is due to the direct action of the enzyme on the pH of the culture medium. The results obtained could be applied to the mechanism of dental plaque calcification.