Biomedical subjects

G Chieffi

Publications and source records attributed to G Chieffi.

At least 37 records · Page 2Linked to original sources

PubMed1990

Indirect evidence for a physiological role exerted by a "testicular gonadotropin-releasing hormone" in the frog, Rana esculenta.

The possible physiological role of a putative testicular gonadotropin-releasing hormone (GnRH)-like material was studied in the frog, Rana esculenta. We have investigated (a) changes of mitotic index (MI) of primary spermatogonia (SPG) in GnRH agonist (GnRH-Ag)-treated testes in vitro; (b) changes of androgen concentrations in testes of intact frogs treated with a GnRH antagonist (GnRH-Ant); (c) variations of mitotic index of primary SPG in intact GnRH-Ant-injected animals and in testes incubated with GnRH-Ant; (d) changes of MI in hypophysectomized (PDX) animals treated with hypophysis (PD) homogenate, and hCG alone or in combination with GnRH-Ant; and (e) changes of androgen concentrations in plasma PDX frogs treated with hCG and hCG plus GnRH-Ant. Our results indicate that while GnRH-Ag induced accumulation of primary SPG mitosis, GnRH-Ant inhibited androgen production and natural occurring mitosis accumulation. Therefore, GnRH-Ant may counteract an endogenous peptide working into the testis.

Androgens↗

PubMed1990

Regulation of the testicular activity in the marine teleost fish, Gobius paganellus.

Seasonal variations of intratesticular steroid hormones (androgens and estradiol-17 beta) and spermatogenic activity have been studied in the marine teleost fish, Gobius paganellus. In addition, in vivo and in vitro experiments have been carried out in order to investigate the control of androgen production by the testis. While estradiol was never detected, androgens were at low values in autumn and reached maximal levels in spring concomitantly with the highest testis weight and the highest efficiency of the spermatogenic wave. In vitro incubations were carried out using ovine luteinizing hormone (oLH) (400, 4000, and 40,000 micrograms/liter; 20 degrees for 6 and 24 hr). The effective dose 40,000 micrograms/liter was used to induce androgen stimulation in both autumn and spring testes. The responsiveness to oLH was enhanced in spring testis. Estradiol and a gonadotropin-releasing hormone analog GnRHA (HOE766) were ineffective in modulating androgen production either alone (1-1000 nmol/liter) or in concert with oLH during short-term incubations. In intact animals, GnRHA elicited, 3 hr after the injection (10 micrograms), a three-fold increase of intratesticular androgen content. In conclusion, we show that the annual androgen profile in G. paganellus parallels the spermatogenic activity and that the androgen production is not affected in these experimental conditions by putative intratesticular factors (e.g., estradiol-17 beta and GnRH-like substances) which, conversely, are effective in inducing androgen changes in several vertebrate species.

Androgens↗

PubMed1990

Influence of light and temperature on the secretory activity of the Harderian gland of the green frog, Rana esculenta.

1. The secretory activity of the Harderian gland in Rana esculenta varies during the year, reaching its highest activity during the hottest period (July-August). Therefore, secretion may be modulated by temperature and/or photoperiod. 2. Adult males and females were placed under several combinations of light and temperature in two different periods of the year (February and July) in order to elucidate their respective roles, if any, on the stimulation of secretion. 3. Under experimental conditions, high temperature (24 degrees C), irrespective of the photoperiod selected, stimulates secretion shown both at histological and histochemical levels. 4. Low temperature (8 degrees C) impairs secretory activity, again independently of the photoperiod selected. 5. This data suggests that the secretion of the Harderian gland in Rana esculenta is modulated mainly by temperature.

Animals↗

PubMed1989

Seasonal fluctuations of estrogen-binding activity in the testis of the frog, Rana esculenta.

We have studied the annual cycle of estrogen-binding activity in the frog, Rana esculenta, testis to evidence possible fluctuations. The testicular binding for [3H]estradiol-17 beta shows high affinities (cytosolic Kd = 1.94 +/- 0.43 x 10(-9) M; nuclear Kd = 2.72 +/- 1.20 x 10(-9) M) and low capacity (cytosolic: 7.56 +/- 0.66 fmol/mg protein; nuclear: 9.27 +/- 2.5 fmol/mg protein). Nuclear-binding activity appears in spring concomitantly with the estradiol peak in plasma and testes, while, in the remaining periods, binding capacity was extremely low or absent. Present data strongly support an important role played by estrogens as an intratesticular control factor in vertebrates.

Animals↗

PubMed1989

Molecular forms of immunoreactive gonadotropin-releasing hormone in hypothalamus and testis of the frog, Rana esculenta.

The hypothalamus and the testis of the frog, Rana esculenta, contain gonadotropin-releasing hormone (Gn-RH)-like peptides which are recognized by an antiserum raised against mammalian Gn-RH. Two molecular forms which coelute with synthetic chicken II and salmon Gn-RH from reverse-phase HPLC were distinguished in the hypothalamus. A single peak coeluting with synthetic chicken II Gn-RH was present in the testis.

Animals↗

PubMed1989

Effects of intratesticular injections of estradiol and gonadotropin-releasing hormone (GnRHA, HOE 766) on plasma androgen levels in intact and hypophysectomized Torpedo marmorata and Torpedo ocellata.

The effect of a gonadotropin-releasing hormone analog (GnRHA, HOE766) was studied in hypophysectomized elasmobranch fish Torpedo marmorata and T. ocellata. In addition, estradiol (E2) effects were studied in intact and hypophysectomized (HPX) animals. Plasma androgen concentrations were measured 2 or 6 hr after GnRHA (100 ng or 10 micrograms) or 6 hr after E2 (10(-9) or 10(-6) M) intratesticular injections. Both GnRHA and E2 induced the increase of plasma androgen levels in HPX fish. E2 also enhanced androgen levels in intact animals. It is concluded that GnRH-like substances and E2 may modulate testicular activity in elasmobranch fish.

Androgens↗

PubMed1989

A sexual dimorphism of the harderian gland of the toad, Bufo viridis.

The Harderian gland of the toad, Bufo viridis, is an acinar gland located at the medial corner of the orbit. The columnar glandular cells show considerable variation in height depending upon their functional state. During July they are taller than in November and May, and filled with secretory seromucous granules. The glandular cells of the female toad, only, contain at their base numerous lipid droplets dispersed in a smooth endoplasmic reticulum. This is the first observation of sexual dimorphism in the Harderian gland of a nonmammalian vertebrate. The secretion of the gland is mainly merocrine. Although the secretion of the Harderian gland is mainly concerned with lubrication of the eyeball, the presence of lipid secretion only in the female glandular cells suggests a pheromonale function, which may influence the sexual behaviour of the male.

Animals↗

PubMed1989

The harderian gland of the frog, Rana esculenta, during the annual cycle: histology, histochemistry and ultrastructure.

The Harderian gland in Rana esculenta has been studied during the annual cycle at the histological, histochemical and ultrastructural levels. The Harderian gland has an acinar structure and is the only orbital gland in anuran amphibia. It develops at the medial corner of the orbit from the conjunctival epithelium at the premetamorphic stage. In the adult the glandular secretion reaches a maximum during the months of July and August, drops in September and resumes slowly from October onwards. The secretion is seromucoid and the secretory granules are released into the acinar lumen, mainly by exocytosis. Porphyrins were not detected. No sexual dimorphism was observed in the glandular cells. The resumption of secretory activity in October and the enhancement of secretion in May are marked by the appearance of "blue nuclei" (Mallory stain) in a relatively high percentage of glandular cells. This unusual blue colour, using the Mallory stain (by which nuclei stain red), disappears after digestion of paraffin sections with RNAase, but not with DNAase and trypsin. The blue staining may, therefore, indicate an increased amount of nuclear RNA. The Harderian gland in the frog most probably serves to lubricate and moisten the eye in the absence of the lacrimal gland. However, the gland may also represent an immunoactive organ owing to the presence of numerous mast cells and plasma cells in the interacinar spaces.

Animals↗

PubMed1988

Relationship between estradiol-17 beta seasonal profile and annual vitellogenin content of liver, fat body, plasma, and ovary in the frog (Rana esculenta).

The seasonal plasma estradiol-17 beta (E2-17 beta) profile and annual vitellogenin content of liver, fat body, plasma, and ovary were investigated in Rana esculenta. Concomitant with the increase in E2-17 beta, vitellogenin peaked in liver, plasma, and ovary during autumn and winter, while it remained at a relatively high concentration in fat body during spring. In vitro experiments showed that E2-17 beta (10(-9) M) is ineffective in inducing vitellogenin production in fat body, but is effective in inducing vitellogenin production in liver. As fat bodies do not produce the vitellogenin they contain, we suggest that fat bodies are involved in the transfer of vitellogenin to the ovary.

Animals↗

PubMed1988

Hypothalamus-hypophysis and testicular GnRH control of gonadal activity in the frog, Rana esculenta: seasonal GnRH profiles and annual variations of in vitro androgen output by pituitary-stimulated testes.

The binding of a gonadotrophin-releasing hormone (GnRH) long acting analog (GnRHA), D-Ser (But)6,Pro9-NEt GnRH (HOE 766), to pituitary and testicular extracts and the presence of GnRH-like material in testes and hypothalamuses were measured in the frog, Rana esculenta. Also, the cellular localization of immunoreactive GnRH was investigated in testes by immunohistochemical staining. Furthermore, lyophilized preparations of pituitary crude homogenates from animals caught monthly were tested in vitro for their ability to stimulate androgen production by December testes. Satisfactory results on specific 125I-GnRH binding were difficult to obtain in view of its low binding capacity. Moreover, binding in testicular homogenates was of the same order of magnitude (about 2%) as that found in pituitaries. In a cospecific radioimmunoassay for GnRH nonapeptide, both hypothalamic and testicular extracts gave displacement parallel to the standard curve. Immunoreactive GnRH did not significantly fluctuate in hypothalamuses, while it peaked in testes during December and July. Immunoreactive GnRH was evidenced in June and September testes employing immunohistochemical staining. In particular, the interstitial cells and the Sertoli cells were faintly stained. Testes of December animals stimulated by February pituitaries produced larger quantities of androgens as compared with testes stimulated with hypophyseal preparations from the remaining periods of the year. In conclusion, the present results are consistent with the idea that seasonal changes of the hypothalamus-hypophyseal activity play an important role in regulating the hormonal response in vertebrate testes. Moreover, we report that, in addition to rats, GnRH-like material is present in frog testes and for the first time it has been shown that such putative intratesticular material undergoes seasonal fluctuations in a vertebrate.

Androgens↗

PubMed1988

Fat body involvement in vitellogenin fate in the green frog, Rana esculenta.

1. Since, in Rana esculenta, fat bodies contain vitellogenin, the present study was performed in order to determine whether or not fat bodies are involved in the fate of vitellogenin. 2. The experiment of November shows that fat body excision provokes plasma vitellogenin increase even in animals treated with estradion-17 beta + pituitary crude homogenate (as compared with relative control). The same picture has been shown in the April experiment. 3. The result on protein-bound phosphate in ovaries from the April experiment has shown that fat body extirpation causes a decrease of protein-bound phosphate in the ovary. 4. This results indicates that fat bodies play an important role in sequestrating circulating vitellogenin by the ovary.

Animals↗

PubMed1988

A gonadotropin-releasing hormone (GnRH) antagonist decreases androgen production and spermatogonial multiplication in frog (Rana esculenta): indirect evidence for the existence of GnRH or GnRH-like material receptors in the hypophysis and testis.

The effects of a GnRH antagonist (GnRHA) on GnRH agonist (GnRH*)-induced androgen production and spermatogonial multiplication were studied in the frog, Rana esculenta, in vivo and in vitro. Intact and hypophysectomized (PDX) animals were kept at 22 +/- 2 C and treated with GnRH (45 ng/g BW) and GnRH* plus 1X and 10X concentrations of GnRHA on alternate days for 2 weeks. Androgen concentration in GnRH* plus GnRHA-treated animals decreased in the testis by about 50% with the 10X dose whereas the increase obtained in GnRH*-treated PDX group was completely abolished with the 1X dose. Histological sections were evaluated with respect of the mitotic index (MI) of the primary spermatogonia. Both GnRHA-treated intact and PDX frogs showed a dose-dependent MI decrease which reached 59% and 57% of control, respectively. In vitro incubations were carried out on testis halves at 15 C for 0, 2, 4, 6, and 8 h with the addition of 1 microgram GnRH* and 1 microgram GnRH* plus 1 or 10 micrograms GnRHA. The stimulatory effect of GnRH* and the inhibitory effect of GnRHA were apparent within 2 h. The basal mitogenic activity was affected by antagonist treatment and the inhibitory effect on the MI was evident within 2-4 h in the 10X-treated groups or within 6-8 h in the 1X treated groups. Since GnRH* and GnRHA bind to the same receptor these data strongly indicate that the effects of putative GnRH-like materials in the frog, Rana esculenta, are mediated throughout stereospecific recognition sites in both pituitary and testis.

Androgens↗

PubMed1987

Seasonal plasma and intraovarian sex steroid profiles, and influence of temperature on gonadotropin stimulation of in vitro estradiol-17 beta and progesterone production, in Rana esculenta (Amphibia: Anura).

Seasonal plasma and intraovarian estradiol-17 beta (E) and progesterone (P) fluctuations were studied by specific radioimmunoassay in the frog, Rana esculenta. Moreover, incubations of ovine-luteinizing hormone (oLH)-stimulated ovarian pieces at two different temperatures (15 and 24 degrees) have been carried out in order to evaluate the dependence of E and P output on this exogenous factor. Estradiol showed similar changes in plasma and ovaries, while P profile was better evidenced in the gonads since this hormone fluctuated in plasma, giving pulses of difficult interpretation. A shift from E to P production by the ovary near the ovulatory period (February-March) was noted. In vitro experiments were carried out using approximately equal-sized ovarian fragments containing follicles ranging from 0.7 to 1 mm and classified as early vitellogenic. High temperature induced oLH-stimulated P production within 6 h, while E increased after 24 h concomitantly with a P decline. At 15 degrees the stimulatory effect of oLH was achieved only on E output in the incubation medium after 24 h. In conclusion, our results in the frog, R. esculenta, show that E and P intervene at peak values separately during the annual cycle and that the temperature has an important role in the regulation of the steroid hormone-releasing activity.

Animals↗

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↗

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↗