Pasquale Usai

Renal Alkaline Phosphatase and osmoregulatory adaptations in Amphibians. I. Seasonal variations and action of an antidiuretic hormone (AVT).

Abstract 1. 1. The biochemical assay of alkaline phosphatase (EC 3.1.3.1) activity was achieved in the kidney of Triturus cristatus adult specimens treated with arginine vasotocin (AVT) and prolactin (PRL). 2. 2. In normal animals the activity of alkaline phosphatase in the terrestrial phase is almost half that in the aquatic phase. 3. 3. AVT treatment consistently elicited a marked reduction in the enzyme activity. 4. 4. No change in renal alkaline phosphatase activity was induced by PRL treatment in terrestrial animals.

Skin morphology and function in Xenopus laevis exposed to a saline environment for up to one week.

This study evaluated the skin adaptation response in Xenopus laevis to short- and medium-term stays (24 h, 48 h, 7 days) in brackish water. Morphological, histochemical, histoenzymological (alkaline phosphatase, carbonic anhydrase) and electrophysiological (short-circuit current, resistance) characteristics were examined. The results show that animals adapt to brackish water, implementing a variety of short and medium-term morphofunctional modifications of the epidermis and skin glands. These modifications form part of the defence mechanisms needed to protect the animal from an excess increase in the saline concentration of internal fluids.

Ion transport processes and alkaline phosphatase activity in the skin of the crested newt

Abstract The supposed relationship linking alkaline phosphatase (???) activity and selective transepithelial transport processes was investigated in the skin of the crested newt under various experimental conditions of ion transport stimulation and inhibition. The effects of rearing animals in deionized water and of treatment with aldosterone were analysed in the cold (10° C, winter) and warm seasons (22° C, summer); the effect of treatment with prolactin and prolactin plus aldosterone was analysed in the warm season. ??? activity was detected histochemically using Burstones method, ion transport processes were revealed electrophysiologically by determination of the transepithelial potential difference (PD), short‐circuit current (SCC), and electrical resistance (Rm). ??? activity in keratinocytes markedly increases during the transition from the winter to summer condition. In summer aldosterone significantly increases enzyme activity in keratinocytes compared to controls. In the same condition, prolacti...

Interrenal balance in Xenopus laevis Daudin females kept under dry conditions or dehydrated then replaced in aquaria

Abstract Xenopus laevis adult females exposed to progressive water deprivation and maintained under dry conditions for two weeks showed a statistically significant increase in serum aldosterone and cortico‐sterone levels in response to osmotic stress. These results are in accordance with those previously obtained by us in males from this typically aquatic species subjected to the same experimental conditions. In females returned to water for one week after a two week period of dehydration, serum aldosterone and corticosterone returned to values approximating those of control.

Active ion transport and morphofunctional organization in the skin of the alpine newt, Triturus alpestris during the life cycle

Electrophysiological techniques were used to study active ion transport across the skin in larval, pedomorphic and metamorphosed alpine newts (Triturus alpestris apuanus). Data were compared with morphological and histoenzymological studies (alkaline phosphatase - APH -) in the skin of the same animals. A short circuit current, which presumably corresponds to active sodium transport, apparently absent in larvae, develops in pedomorphic specimens during the adult epidermis differentiation process and appears to be sensitive to some extent to temperature changes. Flask cells appear early in pedomorphic forms and reveal intense APH activity, a characteristic which is also found in adult animals. Circumstantial evidence correlates APH activity with transport phenomena. These findings support the hypothesis that morphological and physiological differentiation form part of a single process occurring during metamorphosis.

Renal alkaline phosphatase and osmoregulatory adaptations in amphibians. II: Seasonal variations and action of arginine-vasotocin and prolactin in Triturus cristatus carnifex Laur. (Urodela) kidney

Abstract The biochemical assay of alkaline phosphatase (EC 3.1.3.1) activity in the kidney of the adult Triturus cristatus carnifex is reported. In normal animals the activity of renal alkaline phosphatase was notably depressed in the terrestrial compared with the aquatic phase. In both phases arginine-vasotocin (AVT) elicited a marked reduction in the enzyme activity. Exogenous prolactin (PRL) induced no change in activity when administered to terrestrial animals. which are known to have a large store of endogenous PRL in the hypophysis, but low levels in blood. Hypophysectomy on aquatic animals markedly depressed renal alkaline phosphatase, but PRL administration brought back to normal the values of enzymatic activity. Thus it would appear that renal alkaline phosphatase is involved in osmoregulatory processes in the adult Triturus cristatus.