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Biomedical subjects

R Pierantoni

Publications and source records attributed to R Pierantoni.

At least 73 records · Page 4Linked to original sources
PubMed1986

Plasma and testicular estradiol and plasma androgen profile in the male frog Rana esculenta during the annual cycle.

Seasonal plasma and testicular estradiol levels were measured in the male frogs, Rana esculenta, by radioimmunoassay. In plasma samples a simultaneous measurement of androgens was carried out in order to investigate a possible relationship between androgens and estradiol-17 beta. Concomitantly with the estradiol-17 beta peak in plasma and testes during the April-May period, plasma androgens sharply decreased.

Androgens↗
PubMed1986

Regulation of androgen production by frog (Rana esculenta) testis: an in vitro study on the effects exerted by estradiol, 5 alpha-dihydrotestosterone, testosterone, melatonin, and serotonin.

The possible role of estradiol-17 beta (E2), testosterone (T), 5 alpha-dihydrotestosterone (DHT), melatonin, and serotonin on the regulation of androgen (A) production by the frog, Rana esculenta, testes was studied in vitro. E2 (10(-6) M) inhibited A production whether alone or in combination with oLH (20 micrograms) after 6 hr incubation. After 24 hr incubation. A production was reduced by E2 concentration of around 10(-6) and 10(-9) M. Melatonin and serotonin did not induce any change whichever experimental condition was used. Preincubation for 6 hr with 10(-6) M T or DHT enhanced the oLH-stimulated A production after 18 hr incubation. These data suggest that steroids may regulate their intratesticular levels without passing into the blood stream.

Androgens↗
PubMed1986

In vivo and in vitro stimulatory effect of a gonadotropin-releasing hormone analog (HOE 766) on spermatogonial multiplication in the frog, Rana esculenta.

The effects of a GnRH analog (GnRHA), D-Ser-t-Bu6,desGly-NH2(10) (HOE 766) on spermatogenesis were analyzed in the frog, Rana esculenta. Intact animals caught at two different periods of the year (January and March) were treated with HOE 766 (GnRHA, 45 ng/g BW) at low (4 +/- 1 C) and high (22 +/- 2 C) temperatures. Hypophysectomized frogs were used also and, in addition to GnRHA, these animals were treated with crude pars distalis homogenate. In vitro incubations were carried out at 15 C, for 0, 6, and 24 h with the addition of 1 microgram GnRHA. Half of each testis was used as the untreated control. Histological sections of the testes were analyzed for the evaluation of the mitotic index of the primary spermatogonia. Intact March animals had mitotic indices higher than January animals. GnRHA treatment elicited an increase of the mitotic index in both intact and hypophysectomized animals. High temperature potentiated the GnRHA effect while low temperature favored pars distalis treatment. In conclusion, the present results are consistent with the fact that in the frog, R. esculenta, the magnitude of spermatogonial proliferation is temperature dependent, and for the first time it is shown that GnRH-like substances have direct stimulatory effect on the mitotic activity of the primary spermatogonia in a vertebrate.

Animals↗
PubMed1985

Effect of temperature and darkness on testosterone concentration in the testes of intact frogs (Rana esculenta) treated with gonadotrophin-releasing hormone analog (HOE 766).

Testicular testosterone was determined by radioimmunoassay in the frog (Rana esculenta) kept in total darkness, at a high or a low temperature (24 or 4 degrees C), and treated with a gonadotrophin-releasing hormone analog (GnRHa, HOE 766). Prolonged exposure to dark conditions seemed to inhibit hypotalamic functions. Moreover, it is shown that high temperature interacts positively with GnRHa treatment on testicular testosterone concentration.

Animals↗
PubMed1985

The outer horizontal cell of the frog retina: morphology, receptor input, and function.

The outer horizontal cell (OHC) of the frog Rana pipiens was studied by light and electron microscopy of Golgi-stained and horseradish peroxidase-injected cells. Responses of OHCs were recorded with intracellular electrodes. The OHCs are probably axonless cells. Their dendritic terminals are lateral processes at synaptic ribbons and are involved frequently in reciprocal invaginating contacts with receptors, ie, contacts characterized by invagination of receptor membrane deeply into the horizontal cell process. Two classes of OHC were distinguished on the basis of size and receptor contacts. Small OHCs (dendritic area about 5,000 micron2) contact all classes of receptor. These cells were not successfully penetrated with microelectrodes. Giant OHCs (dendritic area about 30,000 micron2) apparently contact only blue-sensitive rods and red-sensitive cones. They generate chromaticity or C-type responses, hyperpolarizing to short and depolarizing to long wavelength light.

Animals↗
PubMed1984

Seasonal plasma sex steroid levels in the female Rana esculenta.

Seasonal plasma progesterone, androstenedione, estrone, and 17 beta-estradiol concentrations in the female Rana esculenta were determined by radioimmunoassay during the 1979 and 1981 seasons. Plasma levels of these steroids were highest just before the first ovulatory wave in spring and lowest after the breeding season. In the 1979 season (during the 1981 season hormones were not assayed in January, November, and December) progesterone, androstenedione, and estradiol levels showed another peak in November-December. During the breeding months, i.e., late March to late June, progesterone, androstenedione, and estradiol levels showed intermittent ups and downs corresponding roughly to the ovulatory waves. In addition, during the breeding season progesterone and androstenedione levels had a higher average in frogs with "ripe" ovaries than in those with "spent" ovaries. Relationships between seasonal steroid levels and ovarian activity are briefly discussed.

Amphibians↗
PubMed1984

The effects of thyroidectomy on androgen and prolactin receptors in the dorsal skin and caudal fin of Triturus cristatus carnifex.

The interactions between thyroid hormones and receptors for steroid hormones and prolactin in dorsal skin and caudal fin of Triturus cristatus carnifex were studied during the annual cycle. Thyroidectomy induces an increase of prolactin binding in the dorsal skin and caudal fin in the animals captured in March. In these thyrodectomized animals the androgen receptors became undetectable. Results indicate that in Triturus cristatus carnifex the thyroid induces an increase of androgen receptors and a decrease, that is removed by thyroidectomy, of prolactin receptors.

Animals↗
PubMed1984

Stimulatory effect of a GnRH agonist (buserelin) in in vitro and in vivo testosterone production by the frog (Rana esculenta) testis.

The summary testicular effects of an agonistic analogue of gonadotropin-releasing hormone (buserelin, GnRHa) have been studied in vitro and in vivo in the frog, Rana esculenta. During 3 h incubation GnRHa (8 X 10(-7) M) potentiated pituitary factors in stimulating testosterone production by minced testes in vitro. After 6 h of incubation 8 X 10(-7) M GnRHa stimulated maximal testosterone output. Testes of 10-day hypophysectomized animals did not show any GnRHa effect in vitro. In vivo, a direct effect of GnRHa on testicular testosterone production was demonstrated in hypophysectomized animals, although this effect was temperature-dependent, requiring the frog to be maintained at a high temperature (24 degrees C). No effect of GnRHa was detectable in frogs kept at a low temperature (4 degrees C).

Animals↗
PubMed1984

Seasonal testosterone profile and testicular responsiveness to pituitary factors and gonadotrophin releasing hormone during two different phases of the sexual cycle of the frog (Rana esculenta).

Plasma and testicular testosterone concentrations in the frog, Rana esculenta, were studied by radioimmunoassay and showed similar seasonal fluctuations. The increase in testicular androgen during November preceded that occurring in the plasma by 2 months. Pituitary products and gonadotrophin releasing hormone, and the responsiveness of the testis to these substances play an important role in determining the hormone profile.

Animals↗
PubMed1984

The internal horizontal cell of the frog. Analysis of receptor input.

The inner horizontal cell (IHC) of the retina of Rana pipiens was studied by light and electron microscopy of Golgi stained or horseradish peroxidase injected cells. Responses of IHCs were recorded with intracellular electrodes. Both axon and dendritic terminals of the IHC make synaptic contact with all classes of receptor. The terminals occur as lateral or medial processes at synaptic ribbons. Reciprocal invaginations of receptor into horizontal cell process are common. Different classes of receptor are contacted in about the proportions with which they occur in the retina. No tendency for contacts of one type of receptor to occur on a particular part of the cell was found. The IHC generates L-type S-potentials. Both rod and cone input is evident in the waveform of the response, its spectral sensitivity, and the effect on it of adaptation.

Animals↗
PubMed1983

Post weaning plasma progesterone, prolactin and environmental influence in the resumption of ovarian activity in sows.

Plasma progesterone levels were determined three days after weaning in 151 sows Landrace x Large White. Furthermore, the influence of bromocriptine (Parlodel, Sandoz) was studied on the resumption of ovarian activity in 19 sows during the hot season. An increased progesterone base-line level was shown during the June-July-August period as compared with May and September-October. No correlation was found between progesterone levels and the percentage of sows which returned to estrus 10 days after weaning except when progesterone levels reached and exceeded 0.9 ng/ml; in this case, no sow resumed ovarian activity in normal time. Bromocriptine treatment had no influence on the resumption of ovarian activity, suggesting that prolactin is not involved in the lack of estrus after weaning. An influence of environmental factors is also suggested.

Animals↗
PubMed1983

Plasma levels of luteinizing hormone, estradiol and androstenedione in sows with inadequate plasma progesterone.

The authors report the profiles of luteinizing hormone (LH), estradiol (E2), progesterone (P) and androstenedione (A) in some female pigs with altered plasma hormonal levels. Twenty cycles are described and 19 out of them are characterized by low plasma P in luteal phase of different etiology, at least as measured by hormone concentrations. The following disorders are observed: a) possible impairment of follicular maturation; b) impaired LH secretion in presence of too high E2; c) low LH base-line values; d) inadequate luteal phase; e) short luteal phase; f) heat disorders. An attempt is made to correlate the altered hormonal profiles with the high rate of summer conception failure in sows.

Androstenedione↗