Gian Emilio Andreoletti

Sex steroid profile and plasma vitellogenin during the annual reproductive cycle of the crested newt (Triturus carnifex laur.)

The annual reproductive cycle of the crested newt, Triturus carnifex, has been studied in the field. Temperatures, rainfall, humidity, and photoperiod were recorded throughout the year. Adult male and female newts were sampled monthly; snout vent lengths, crest heights of males, and body ovarian, oviducal, testicular, and abdominal gland weights were recorded. Plasma samples were assayed for androgen, estradiol-17 beta, and progesterone by radioimmunoassay and for vitellogenin by enzyme-linked immunosorbent assay. Air, deep water, water surface, and soil temperatures were low from October to March, but increased in April and May without consistent summer variations. Ovarian and oviducal weights increased in October to reach maximum values between January and March (reproductive period). Crest height and abdominal gland weight in males mirrored the ovarian and oviducal pattern, while testicular weights were maximal in October and November. In females, plasma androgens were high during the reproductive period, and plasma estradiol peaked sharply in March, while plasma progesterone changed little. In the males plasma androgen and estradiol concentrations were similar to those of females, while plasma progesterone was significantly correlated with the cycle in testicular weight. In both sexes androgens showed a significantly negative correlation with air and water surface temperature. Plasma vitellogenin peaked in March but it did not correlate with either ovarian weight or plasma estradiol concentrations. These data support and confirm those previously reported for newts under laboratory conditions. The negative correlation between androgens and temperature suggests that this hormone may trigger the reproductive process. Moreover the correlations between plasma progesterone and testicular weight may indicate that this hormone is involved in male newts reproduction.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Anatomical organization of CRF- and AVT-like systems in the newt hypothalamus and the effects of localized lesion to the posterior hypothalamus on serum aldosterone and corticosterone

Abstract The anatomical organization of the preoptico‐hypophysial systems, and in particular of CRF‐like and AVT‐like fibres, throughout the posterior hypothalamus of the crested newt, Triturus crista‐tus carnifex Laur. was investigated immunohistochemically. The effects on interrenal activity of central and bilateral lesions in the posterior hypothalamus were also evaluated immunohistochemically and biochemically. Bilateral lesions which interrupted both CRF‐like and AVT‐like fibre systems resulted in a decrease in serum corticosterone and aldosterone, while central lesions rostral to the median eminence caused slighter decreases in the steroid levels and did not affect so dramatically the CRF‐like afferences to the median eminence; the pars nervosa was frequently atrophied.

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.

Effects of permanent deafferentation of the anterior preoptic area on serum aldosterone levels in the crested newt (Triturus cristatus carnifex Laur.)

By cutting off the fiber systems running along the medial forebrain bundle of the urodele amphibian Triturus cristatus, a wide deafferentation of the preoptic area was evoked. This operation elicited a decrease in aldosterone serum level, probably through a reduction of ACTH secretion. At present we are not able to ascertain whether such reduction was prompted by changes in the hypothalamic production of the neurohypophysial hormones or the corticotropin-releasing factor (CRF).

Regulation of ACTH and MSH production in amphibians: An immunocytochemical study on autografted pituitary in Triturus carnifex

Abstract To ascertain whether the pituitary intermediate lobe is able to produce adrenocorticotropic factors in vivo in Triturus carnifex, two groups of animals were subjected to ectopic pituitary auto‐graft. Animals of one group were sacrificed two months after the autograft; those of the second group one year after the operation. Immunocytochemical study of ACTH and MSH revealed that, in the autograft, only in the second group was the intermediate lobe immunopositive to an antiserum against synthetic ACTH (anti‐ACTH). This result supports the hypothesis that the pituitary intermediate lobe can produce adrenocorticotropic factors in vivo.

Sedimentation characteristics of thyroglobulin in some amphibians after 131I lodination in vivo

Abstract The radioiodine uptake and sedimentation characteristics of thyroglobulin labeled in vivo with 131 I were studied in Triturus cristatus, Rana esculenta, Bufo viridis , and Bufo bufo after different iodination times. It was seen (a) that 131 I uptake, which is a function of iodination time, is lower in the anurans than in Triturus cristatus , despite the fact that iodine binding is consistently fairly rapid; (b) that by assigning a sedimentation coefficient of 19.5 S to rat thyroglobulin, the same value is found for Triturus cristatus and Bufo viridis thyroglobulin, whereas in Rana esculenta and Bufo bufo thyroglobulin attains a sedimentation coefficient of 21.5 S and 18.7 S, respectively; (c) that after short iodination times small amounts of light iodination protein fractions are present; (d) that in Bufo bufo and Bufo viridis an iodinated protein fraction is also present whose concentration rises with increasing iodination times and whose sedimentation coefficient is equal to 26 S in Bufo bufo and 27.5 S in Bufo viridis . In each of these two species the ratio of the sedimentation coefficient of the heavy fraction to that of the quantitatively predominating fraction is 1.41.

Enzyme activities in the integument of amphibia: Biochemical, histochemical and electrophysiological data on Rana kl. esculenta and Xenopus laevis

Abstract The enzymatic activities related to Rana kl. esculenta and Xenopus laevis skin, and in particular to an unstirred layer in the epidermis surface (subcorneal space) where mitochondria‐rich cells (MR cells) and principal cells (PC cells) expose their apical membrane, are studied; histochemical, biochemical and electro‐physiological data are compared. The organization of PAS (Periodic Acid Schiff)/PASM (Periodic Acid, Silver Methenamine) positive material and some ectoenzymes in the subcorneal space and in the apical surface of living and active cells, both MR and PC are described. Subcorneal space appears to be a specialized structure, forming an unstirred layer at the limiting surface of amphibians living in water. This layer may function as an efficient barrier to capture ions and small molecules diffusing from living cells in the skin, so forming the space where active reuptake of ions and small diffusible organic molecules may take place, but in thermo‐dynamically favourable conditions.