Demonstration of bone resorbing cells in elasmobranchs: Comparison with osteoclasts.

We have previously shown that Elasmobranchs-characterized by a partially calcified cartilaginous endoskeleton-presented a bony vertebral arch containing osteoblasts, osteocytes and resorbing cells. The aim of this study is to test the ability of Elasmobranchs to resorb bone tissue. The subcutaneous implantation in dogfish (Scyliorhinus canicula) of devitalized mineral-containing bone particles, obtained from a bony fish (the eel, Anguilla anguilla) resulted, after 21 2 months, in the formation of mononucleated as well as multinucleated cells around and between the bone fragments.

[Effect of prolonged water deprivation on weight gain and water metabolism in a gerbillid rodent (Meriones shawi shawi)].

The effect of prolonged water deprivation, applied progressively since weaning, was studied on body weight in growing sub-desert rodents (Meriones shawi). Then, water metabolism, food consumption and kidney weight were measured in these adults animals. During partial water deprivation the weight curve was similar to that of controls, whereas with total water deprivation three different stages were noticed: a decrease, a stabilization and an increase in body weight as a function of age.

Evidence for the presence of osseous tissue in dogfish vertebrae.

The calcified cartilage of the dogfish vertebra has been studied by means of an undecalcified hard tissue method, including microradiography and tetracycline labelling, and electron microscopy. The transversely sectioned vertebra shows a centrum and neural and hemal arches. The mineralized area consists of a narrow but continuous band, which touches the perichondrium, and is formed by chondrocytes that participate in the mineralizaton of the surrounding matrix.

[Demonstration of bone tissue in the axial skeleton of a chondrichthian: the dogfish (Scyliorhinus canicula)].

Dogfish vertebra have been studied by means of an undecalcified hard tissue method, including microradiography and tetracycline labelling. The transversal section of Dogfish vertebra shows a centrum and two couples of neural and hemal arches. The mineralized area consists of a narrow but continuous band, just against the perichondrium, formed by chondrocytes that participate in the surrounding matrix mineralization.

[Calcitonin in the ultimobrancial body of Anguilla (Anguilla anguilla L.): cytologic localization by indirect immunofluorescence using human anti-salmon-calcitonin antibodies].

The localization of intracellular calcitonin has been achieved by immunofluorescence in the cytoplasm of all cells forming the epithelium of the ultimobranchial body of eels, using a human antiserum against synthetic Salmon calcitonin I. The specificity of the reaction is demonstrated by inhibition with synthetic salmon calcitonin (S.C.