Mario Biciotti

Cutaneous osmoregulation in Triturus cristatus carnifex (Laur.) (Urodela)

Abstract In the crested newt ( Triturus cristatus carnifex Laur.), osmotic permeability and active sodium transport (the latter studied by the short-circuit current technique) in the isolated skin change cyclically during the year. The lowest values for both parameters are recorded in winter (aquatic phase), while the highest values are recorded in summer (terrestrial phase). Prolactin (24 IU of ovine prolactin subdivided into three injections delivered on alternate days) administered during the terrestrial phase (coincident with the low rate of hormone release) induces a drastic drop in both osmotic permeability and active sodium uptake. Conversely, hypophysectomy performed during the aquatic phase increases both the osmotic permeability and active transport of sodium across the skin. The role played by the skin in the osmoregulatory mechanism of the crested newt is discussed.

On the activating effect of prolactin on thyroid metabolism in the crested newt. Comparison between the effect of prolactin and methylthiouracil

In the crested newt exogenous prolactin promotes the increase of thyroidal uptake of radioactive iodine which is paralleled by enhanced T4 production while the MIT:DIT and (MIT + DIT):I− ratios do not substantially differ from those of control animals. Evaluation of the serum content in iodinated compounds (separated by filtration on Sephadex G-25) has shown that both protein-bound iodine and free thyronines occur in higher amounts in the serum of prolactin-treated animals than in normal contros. Parallel investigations carried out on methylthiouracil-treated animals have demonstrated that this drug, besides drastically reducing the radioactive iodine uptake by the thyroid, induced pronounced alterations in the MIT:DIT and (MIT + DIT):I− ratios. The thyroid cytologic pattern in the thiouracil-treated animals differs markedly from the thyroid pattern found in the prolactin-treated animals. Through comparison of the results obtained in the two experimental treatments, further support is gained for the concept of prolactin activating action on thyroid metabolism in the newt.

Mesure du volume total et du pourcentage du sang chez le triton crete (Triturus cristatus carnifex Laur.) Dosage par dilution radio-Isotopique

ZusammenfassungDurch die Methode der radium-isotopischen Verdünnung haben die Autoren das Totalvolumen und den Prozentsatz des Blutes von Triturus cristatus carnifex Laur. gemessen. Die Befunde ergaben, daß eine lineare Beziehung zwischen dem Prozentsatz des Blutes und dem Gewicht des Körpers in den Grenzen der untersuchten Gewichte vorhanden ist.Der Prozentsatz des Blutes nimmt nämlich ab, während das Körpergewicht in entsprechender Weise zunimmt.Außerdem haben die Autoren festgestellt, daß eine lineare Beziehung zwischen dem Körpergewicht und dem Logarithmus des Totalvolumens des Blutes vorhanden ist.

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...

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.

Osmoregulatory adaptation of renal function in the terrestrial- and aquatic-phase crested newt (Triturus cristatus carnifex Laur)

Abstract Renal function (including rates of glomerular filtration (GFR), tubular water reabsorption, and urine production) was studied in normally hydrated crested newts at different stages of their annual cycle. GFR, estimated as clearance of 3H-inulin, ranged from 54 μl/g.h during the terrestrial phase to 16 μl/g.h in the aquatic phase. Rates of urine flow paralleled those of GRF. These results are in close agreement with the circumannual values for skin osmotic permeability, indicating that differential kidney activity is the major mechanism for the disposal of excess water taken on osmotically. Rates of water reabsorption by the renal tubules were not correlated with season of the year or habitat, thus suggesting greater “flexibility” in this process during the annual cycle.