Biomedical subjects

M D'Antonio

Publications and source records attributed to M D'Antonio.

At least 19 recordsLinked to original sources

PubMed1995

Nature and distribution of gonadotropin-releasing hormone (GnRH) in the brain, and GnRH and GnRH binding activity in serum of the spotted dogfish Scyliorhinus canicula.

The distribution of different molecular forms of gonadotropin-releasing hormone (GnRH) in the brain and serum of the spotted dogfish, Scyliorhinus canicula, was investigated by an indirect immunofluorescence method, using antisera against salmon (s-), chicken-II (cII-) and mammalian (m-) GnRHs, and by reverse-phase high-performance liquid chromatography (RP-HPLC) coupled with radioimmunoassays. Five GnRH molecular forms were demonstrated on the basis of the retention time in the RP-HPLC system. The characteristics of four of these GnRH peptides are consistent with those of m-, cII-, dogfish (df-), and sGnRH. The fifth form appears to be novel. Immunoreactive sGnRH structures were confined to the diencephalon; whereas cIIGnRH and mGnRH were found in the telencephalon and diencephalon. cIIGnRH- and dfGnRH-like molecules were detected in the serum. Moreover, a specific, low-affinity GnRH binding protein (GnRH-BP) was found in the serum of the spotted dogfish. The binding of [125I]sGnRHA to the serum GnRH-BP was dependent on incubation time, equilibrium being reached within 1 hr at 4 degrees; binding was rapid and completely reversible. Scatchard analysis yielded a linear plot with a Kd of 7.9 x 10(-7) M. The presence of a GnRH-BP in spotted dogfish serum suggests a probable action of GnRH via the general circulation.

Animals↗

PubMed1995

Chicken GnRH-II and salmon GnRH effects on plasma and testicular androgen concentrations in the male frog, Rana esculenta, during the annual reproductive cycle.

In the frog, Rana esculenta, two molecular forms of GnRH, coeluting with chicken (c) GnRH-II and salmon (s) GnRH, have been detected using HPLC and radioimmunoassay. Mammalian (m) GnRH seems to be also present. In amphibians the role of cGnRH-II seems to be primarily the involvement in the regulation of neuroendocrine processes and, while the mGnRH has been postulated to act as a neurotransmitter and/or neuromodulator, the activity of sGnRH-like material has not been investigated. Therefore, we have treated the frogs with single or multiple injections of cGnRH-II or sGnRH (6 micrograms) or both peptides (6 micrograms of each) to detect differences in the response measured as testicular or plasma androgen (testosterone plus 5 alpha-dihydrotestosterone) concentration during the annual reproductive cycle. The basal profile of testicular and plasma androgen shows that the spring peak disappeared in control animals given multiple injections and kept in short-term captivity. We show in the treatment with cGnRH-II and/or sGnRH that the effects of the peptides depend on the season, the experimental design, and the tissue in which androgen levels were measured. In particular, both peptides strongly stimulate androgen production during the autumn-winter period, the time of the greater response to the GnRHs when basal levels of steroids are highest.

Analysis of Variance↗

PubMed1993

Dopamine regulation of testicular activity in intact and hypophysectomized frogs, Rana esculenta.

In intact frogs, both GnRHA and L-dopa were able to increase testicular and plasma androgen levels and to induce spermiation. The dopamine antagonist pimozide inhibited both the effects of L-dopa but not those of GnRHa. Hypophysectomy reduced androgen levels, but spermiation was still induced by both GnRHa and L-dopa, suggesting that these agents can directly influence the testis through a route not involving the pars distalis. Again, pimozide antagonised spermiation induced by L-dopa but not that induced by GnRHa.

Androgens↗

PubMed1993

Opioids and testicular activity in the frog, Rana esculenta.

The presence and activity of brain, pituitary and testicular beta-endorphin (beta-EP)-like material have been studied in the frog, Rana esculenta, using reverse-phase high-pressure liquid chromatography, coupled with radioimmunoassay and immunocytochemistry. In-vivo and in-vitro treatments with naltrexone were carried out to assess the putative physiological activity of opioid peptides. beta-EP(1-31) and (1-27), together with their acetylated forms, have been identified in brain, pituitary and testis. In particular, beta-EP(1-31) concentrations peaked during July in the brain and pituitary, whilst in testes maximum concentrations were found in April and November. beta-EP immunoreactivity was present in the brain within the nucleus preopticus and nucleus infundibularis ventralis while positive fibres in the retrochiasmatic regions projected to the median eminence. In the testis, interstitial cells, canaliculi of the efferent system, spermatogonia and spermatocytes showed positive immunostaining for beta-EP. In intact animals, naltrexone treatment increased plasma and testicular androgen levels and this effect was confirmed in in-vitro incubations of minced testes. Naltrexone also induced a significant increase in germ cell degeneration. Our results indicated that an opioid system modulates the hypothalamus-pituitary-gonadal axis in the frog, Rana esculenta and, for the first time, we have shown that the testicular activity of a non-mammalian species may be regulated by opiates locally.

Animals↗

PubMed1992

Effects of gonadotropin-releasing hormone variants on plasma and testicular androgen levels in intact and hypophysectomized male frogs, Rana esculenta.

The effects of vertebrate gonadotropin-releasing hormone (GnRH) variants on plasma and testicular androgen level in intact and hypophysectomized (PDX) male frogs, Rana esculenta, have been investigated. In intact animals, mammalian (m)-GnRH, m-GnRH analog (buserelin), salmon (s)-GnRH, chicken (c) I-GnRH, cII-GnRH, D-Arg6-cII-GnRH (cII-GnRHA), and lamprey (l)-GnRH (1.5 micrograms and 6 micrograms, total dose given on alternate days for 5 days) were able to enhance androgen production showing that specificity of pituitary responsiveness to GnRH variants appears to be low. Chicken II-GnRH was more effective than s-GnRH in eliciting testicular and circulatory androgen level increase. Moreover, in animals treated with 6 micrograms of cII-GnRH and s-GnRH in combination, androgens decreased as compared with animal treated with cII-GnRH only, suggesting that GnRH receptors bind preferentially the s-GnRH form. In PDX animals, buserelin (1.5 and 6 micrograms), cII-GnRH, and its analog (6 micrograms) were able to increase plasma androgen levels whereas testis androgen concentrations were increased by cII-GnRH (1.5 and 6 micrograms), D-Arg6-cII-GnRHA, and buserelin (6 micrograms). Since androgen production in PDX animals is influenced especially by peptides sharing cII-GnRH structure, it is suggested that a testicular cII-GnRH-like material play a role as local modulator of the gonadal activity in Rana esculenta.

Amino Acid Sequence↗

PubMed1992

Plasma and follicular tissue steroid levels in the elasmobranch fish, Torpedo marmorata.

Steroid concentrations in plasma and follicular tissues (theca plus granulosa layers) were determined by radioimmunoassay in the aplacental viviparous ray, Torpedo marmorata, during various stages of the reproductive cycle. Steroids in the uterine fluid of pregnant animals and in preovulatory atretic follicles were also measured. In the follicular tissue of cyclic animals, levels of progesterone were always lower than those of estradiol-17 beta and androgens (testosterone plus 5 alpha-dihydrotestosterone). Estradiol-17 beta and androgen levels increased as the animals approached the ultimate maturational stage before ovulation. Androgens were not detectable in plasma, while estradiol-17 beta increased dramatically before ovulation. In pregnant animals, only small ovarian follicles (less than 5 mm in diameter) were observed, and these had hormone concentrations that were similar to those of the small follicles of cyclic animals. Progesterone was the only steroid detected in the uterine fluid of pregnant animals. In completely sclerotic atretic follicles of pregnant animals, steroids were not detected. Progesterone was the main hormone in atretic follicles undergoing yolk resorption. This suggests that the latter may contribute to the elevated plasma progesterone concentrations of pregnant animals.

Animals↗

PubMed1992

Immunoreactive Met-enkephalin-like material in the testis of Rana esculenta: identification and localization.

Methionine-enkephalin (Met-Enk) has been detected in the testis of the frog, Rana esculenta, using a reverse-phase high-performance liquid chromatography system coupled with a specific radioimmunoassay. By means of immunocytochemical techniques Met-Enk positive cells have been localized in interstitial and germinal compartments. Particularly, spermatogonia, spermatocytes, and spermatozoa were stained in seminiferous tubules, and numerous interstitial cells showed strong cytoplasmic immunoreactivity in summer animals. Variations in the concentration of Met-Enk immunoreactive material occurred during the annual cycle. Our data show that Met-Enk is present in testes of nonmammalian vertebrate species. These results suggest that autocrine and/or paracrine mechanisms may regulate testicular activity in amphibians.

Amino Acid Sequence↗

PubMed1992

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

An androgen-binding activity has been identified in nuclear extracts of the testis of the frog, Rana esculenta. A single class of high affinity (Kd = 2.5 +/- 0.6 x 10(-9) M), low-capacity binding sites was found. The binding was specific for androgens; 17 beta-estradiol displaced [3H]testosterone with an ID50 of 0.1 microM. Cytosolic binding activity has a low affinity and a high capacity and lacks specificity. The seasonal fluctuations in binding capacity did not correlate with the androgen peaks in plasma and testes between February and June and in September; periods coinciding with the resumption of spermatogenesis and the development of spermatids, respectively. The present data strongly support androgenic control of intratesticular function in vertebrates generally.

Androgens↗

PubMed1992

Ovarian opioids and the reproductive cycle of the frog Rana esculenta.

In mammals, proopiomelanocortin-related peptides are involved in reproductive processes both at the hypothalamo-pituitary and ovarian levels. Using immunocytochemical, biochemical and physiological "in vitro" studies, we provide here evidence for a diffuse POMC-related opioid system in the frog Rana esculenta. Ovarian beta-endorphin (beta-EP) is expressed in thecal cells and changes during the reproductive cycle in an inverse relationship with follicular development. Seasonal changes in the ovary are different to those in the brain or in the pituitary. The ratio of acetylated vs native beta-EP in the ovary also changes over the reproductive period, affecting the biological activity of the peptide. During both the reproductive spring period and the summer post-reproductive phase pMol amounts of beta-EP stimulate follicular androgen secretion in vitro, in a naloxone-reversible way. In either period, an inhibition of estradiol, possibly mediated via other factors, is the result of opioid action. In conclusion, these data demonstrate for the first time the widespread presence of beta-EP-related peptides in the frog Rana esculenta. Both immunocytochemical and biochemical evidence, as well as in vitro responses, support a physiological role for beta-EP in ovarian seasonality during the reproductive cycle of this amphibian.

Amino Acid Sequence↗

PubMed1992

Resumption of testicular activity in Gobius paganellus after administration of ethane 1,2-dimethane sulfonate (EDS).

1. The effect of a single injection of ethane-1,2-dimethane sulfonate (EDS) was studied in the teleost fish, Gobius paganellus in two different periods of the year. 2. During June EDS did not induce any change, while during December the drug was highly effective in promoting testicular activity. 3. Nucleus/cytoplasm ratio of interstitial cells strongly decreased concomitantly with the detection of high testicular androgen levels. 4. The germinal compartment was well developed showing the appearance of all spermatogenic stages and the cavity of lobular compartments filled of spermatozoa. 5. Our data are the first evidence of a stimulatory activity of EDS on testes of a vertebrate species.

Androgens↗

PubMed1991

Sites of action of local estradiol feedback mechanism in the frog (Rana esculenta) testis.

The direct effect of estradiol on testicular androgen biosynthesis was studied in the frog, Rana esculenta, measuring progesterone, 17 alpha-OH-progesterone, androstenedione, and androgens (T + DHT) in supernatants and testes incubated (6 hr, 15 degrees) with estradiol alone (10(-6) M) or in combination with crude pituitary homogenate (1 pituitary equivalent/tube). Estradiol, either alone or in combination with pituitary homogenate, induced decreases of 17 alpha-OH-progesterone, androstenedione, and androgens but was ineffective in modulating progesterone levels. Pituitary homogenate was effective in inducing a significant increase of androstenedione and androgens but was ineffective in modulating both progesterone and 17 alpha-OH-progesterone production. It is concluded that estradiol acts by decreasing the activity of steroidogenic enzymes starting from 17 alpha-hydroxylase, while pituitary homogenate does not affect the 17 alpha-hydroxylase activity, but it acts starting from 17,20-lyase.

17-alpha-Hydroxyprogesterone↗

PubMed1991

2H-pyrano[3,2-d]-1-benzoxepin derivatives with platelet antiaggregating and other activities.

The synthesis of some N,N-disubstituted 4-amino-5,6-dihydro-3-phenyl-2H-pyrano[3,2-d]-1-benzoxepin-2 -ones by reaction of phenylchloroketene with a series of N,N-disubstituted (E)-4-aminomethylene-3,4-dihydro-1-benzoxepin-5(2H)-ones, followed by dehydrochlorination of the primary adducts with DBN, is described. Some of these compounds showed a platelet antiaggregating activity in vitro slightly superior to that of acetylsalicylic acid, as well as weak local anesthetic and antiinflammatory activities in mice and rats, respectively.

Anesthetics, Local↗

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

omega-Dialkylaminoalkyl ethers of 6-(benzyl or phenyl)-1,3,3-trimethyl-2-oxabicyclo [2.2.2]octan-6-ol with platelet antiaggregating and local anesthetic activities.

The synthesis of 1,3,3-trimethyl-6-phenyl-2-oxabicyclo[2.2.2]octan-6-ol 2 and 6-benzyl-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-ol 3 starting from (+)-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-one and phenylmagnesium bromide or benzylmagnesium chloride, respectively, is described. Alcohols 2 and 3 gave a series of omega-dialkylaminoalkyl ethers 4 by reaction as sodium salts with omega-chloroalkyldialkylamines in toluene solution. Some compounds 4, in particular those derived from alcohol 2, showed a strong platelet antiaggregating activity in vitro, superior to that of acetylsalicylic acid, as well as in general an appreciable local anesthetic activity and a weak sedative effect in mice.

Anesthesia↗

PubMed1990

[Endoscopic papillotomy today. Indications and results].

The therapeutic possibilities offered by endoscopic papillotomy have improved in comparison with the recent past by virtue of mounting experience and increasingly satisfactory results. The position of the surgeon in the face of this procedure is more serene and objective than those who concern themselves with the endoscopic method as such. In long-term personal experience, endoscopic papillotomy was indicated in 162 cases of biliary lithiasic pathology--associated and otherwise with Odditis--and angiocolitis, with and without the gall-bladder. The reference to endoscopic treatment was mainly confined to patients with associated pathologies, dependent and otherwise, that involved general or specific surgical risk, while evaluations of the lumen of the biliary excretory way, of the coexistence of more or less incisive biliary inflammation, of the age of the patient--all parameters to which are attributed special importance for the choice between derivative intervention and open papillotomy--do not possess particular significance for the endoscopic method. Results obtained and the low incidence of short and long-term morbility support the claim to absolute usefulness of the method when it is proposed on correct indications and carried out with expert technique.

Ampulla of Vater↗

PubMed1989

Intratesticular feedback mechanisms in the regulation of steroid profiles in the frog, Rana esculenta.

Testosterone (T), 5 alpha-dihydrotestosterone (DHT), estradiol-17 beta (E), and progesterone (P) were measured in the plasma of the frog, Rana esculenta, during the annual cycle. Moreover, in vitro experiments were carried out in order to investigate the local regulation of steroidogenesis. Testosterone and DHT showed high values during autumn and early spring and had a T/DHT ratio which increased during summer, while E peaked in midspring, remaining at detectable values thereafter. Progesterone increased in autumn, winter, and spring. In vitro incubations of minced testes showed that E, stimulated by pituitary factors, inhibited androgen synthesis while T did not. Our results indicate that paracrine and/or autocrine mechanisms operate in the frog testis to regulate annual steroid profiles.

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↗