Role of nitric oxide in gonadotropin-releasing hormone-dependent prostaglandin F2 alpha synthesis by frog (Rana esculenta) interrenal gland during post-reproduction.

The aim of this study was to clarify the possible involvement of nitric oxide (NO) on prostaglandin (PG) E2-9-ketoreductase activity in the gonadotropin-releasing hormone (GnRH)-dependent PGF2 alpha synthesis by the interrenal gland of the female water frog, Rana esculenta, during the post-reproduction. Interrenal glands were incubated in vitro with GnRH, NO donor (sodium nitroprusside, SNP), and inhibitors of phospholipase C (compound 48/80), inositol triphosphate (decavanadate), calmodulin (calmidazolium), NO synthase (L-NAME), and PGE2-9-ketoreductase (palmitic acid). Production of PGE2 and PGF2 alpha and NO synthase and PGE2-9-ketoreductase activities were determined. GnRH and SNP increased PGF2 alpha production and PGE2-9-ketoreductase activity, and decreased production of PGE2 and GnRH increased NO synthase activity. GnRH effects were blocked by all inhibitors, except for palmitic acid, which did not affect NO synthase activity, which is increased by GnRH. This study indicates that NO may be involved in regulation of the R. esculenta post-reproduction through stimulation of PGE2-9-ketoreductase activity in GnRH-dependent PGF2 alpha synthesis by the frog interrenal gland.

Trace element determination-I Use of 2,9-dimethyl-1,10-phenanthroline in determination of copper in heavy matrices by carbon furnace atomic-absorption spectrometry.

A method for the determination of copper in complex matrices by electrothermal atomic-absorption spectrometry has been developed. It uses neocuproine as complexing agent. The detection limit is 0.2 ng/ml, and interferences are minimized.

[Emergency laboratory in the pediatric module]. / Il Laboratorio di Urgenza nel modulo pediatrico.

The emergency in the laboratory is a serious problem. The Authors, starting from management evaluations, try to analyse the problems related to the urgent examinations in the Laboratory of a Pediatric Hospital. They propose executive ways for the best working of the same laboratory.

[Urine analysis in a pediatric laboratory using reagent strips read visually (visual dip sticks)]. / L'esame delle urine in un laboratorio pediatrico effettuato mediante strisce reattive ad osservazione diretta (dip sticks visual).

The Authors studied the possibility of using some dip sticks visual for urinalysis. One hundred of urine samples have been analyzed at the beginning with the instrumental laboratory analytical system and then with the dip sticks visual; the results put in evidence that there is a real discrepancy as far as glucose is concerned. Glucose is overestimated in dip sticks visual method. Bilirubin, blood and proteins are in a decreasing order the most different items. Concerning to pH the results have been comparable. Specific weight cannot be compared to the laboratory method, on the other hand it can be used for screening. On the whole the Authors are quite satisfied about dip sticks visual method; it can be used in order to accelerate diagnosis and avoid pre-analytical mistakes.

A possible role of prostaglandin E2 in reproduction of the male water frog, Rana esculenta. In vivo and in vitro studies.

Plasma prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), androgens and estradiol-17 beta were measured in the male water frog, Rana esculenta, during the annual sexual cycle. In vivo experiments were carried out to study the effects of PGE2 and PGF2 alpha on plasma sex steroids during the following periods: prereproduction (April), reproduction (May), postreproduction (June) and recovery (October). In the same months, in vitro experiments were performed to evaluate the effects of these two prostaglandins (PGs) on testicular release of sex steroids. The PGE2 plasma levels peaked in April. PGE2 treatment in vivo increased androgens in April and October, while PGF2 alpha increased estradiol-17 beta in June and October. In in vitro experiments, PGE2 increased androgens in April, while PGF2 alpha increased estradiol-17 beta in October. These results suggest that PGE2 could induce the breeding activity, probably through androgens synthesis. PGF2 alpha could interrupt the breeding, through estradiol-17 beta secretion.

Relationships among mammalian gonadotropin-releasing hormone, prostaglandins, and sex steroids in the brain of the crested newt, Triturus carnifex.

The present study was carried out to evaluate the in vitro brain release of prostaglandin F2 alpha (PGF2 alpha), prostaglandin E2 (PGE2), androgens, and 17 beta-estradiol in male and female crested newt, Triturus carnifex, during three different periods of the annual sexual cycle; in addition, the effects of mammalian gonadotropin-releasing hormone (mGnRH), PGF2 alpha, and PGE2 on prostaglandins and steroids release by the brain were evaluated during the same periods. In brain incubations of both sexes, PGF2 alpha and estradiol were higher during postreproduction, while PGE2 and androgens were higher during reproduction. In both sexes, mGnRH increased PGF2 alpha and estradiol during postreproduction, and PGE2 during reproduction; PGF2 alpha increased estradiol secretion during postreproduction. Only in the male, did both mGnRH and PGE2 increase androgens during reproduction. It could be suggested that in Triturus carnifex, the regulation of the reproductive activity in the central nervous system (CNS) depends on the relationships among mGnRH, prostaglandins and steroids. In particular, PGF2 alpha and PGE2 seem to play different roles in the CNS of the newt: PGF2 alpha is involved in the postreproductive processes, through estradiol secretion, while PGE2 in the reproductive ones (through androgens secretion?).

Plasma prostaglandin F2 alpha and reproduction in the female Triturus carnifex (Laur.).

Plasma patterns of prostaglandin F2 alpha (PGF2 alpha) and sex hormones (progesterone, androgens and 17 beta-estradiol) have been studied in the female crested newt, Triturus carnifex (Laur.), during the annual sexual cycle. The effects of exogenous PGF2 alpha on sex hormones were determined. In addition, the effects of one week's captivity on plasma PGF2 alpha and sex hormones were reported. PGF2 alpha plasma level peaked in April, was low in summer, and progressively increased during the autumn to peak again in December. The April PGF2 alpha coincided with a 17 beta-estradiol rise, and with a progesterone drop. The autumn PGF2 alpha increase was coupled to a 17 beta-estradiol rise, and therefore it has been tentatively related to ovary and oviduct development. In newts collected in April, moreover, a PGF2 alpha-dependent 17 beta-estradiol synthesis could occur, since PGF2 alpha injection induced a significant 17 beta-estradiol plasma increase. These findings led us to suppose that PGF2 alpha intervenes in spring breeding season termination through the induction of a 17 beta-estradiol synthesis as in other amphibian species. PGF2 alpha injection caused a progesterone decrease, probably by inducing corpora lutea lysis. The patterns of plasma sex hormones were consistent with the results reported for the same newt species.

The effect of mammalian gonadotropins and homologous gonadotropins on the activity of delta 5-3 beta-hydroxy-steroid-dehydrogenase (HSD) in hypophysectomized Rana esculenta.

Mammalian gonadotropins and partially purified gonadotropins (FSH and LH) from an amphibian (Rana esculenta) were used to investigate their action on enzymatic activity of delta 5-3 beta-HSD in male and female hypophysectomized Rana esculenta in stage of genital activity (October) and in stasis or hibernation stage (January). Amphibian and equine LH stimulate delta 5-3 beta-HSD activity especially in females hypophysectomized in the stage of genital activity, while ovine FSH action is very low and amphybian FSH practically inactive. The present data suggested that control of gonadotropic activity in the reproductive cycle in Rana esculenta is LH-dependent.

Preliminary studies on the uptake of labeled mammalian gonadotropins by ovary and oviduct of the green frog, Rana esculenta, in vivo.

In hypophysectomized females, Rana esculenta, a significant uptake of labeled ovine FSH and LH was evident in both the ovary and oviduct. This binding was specific only for the ovary. Ovariectomy did not modify the affinity of the oviduct for these gonadotropins. The possibility of the presence of discrete receptor molecules for FSH and LH in the ovary of Rana esculenta is discussed.

Plasma sex hormones and post-reproductive period in the green frog, Rana esculenta complex.

The plasmatic profiles of androgens, estradiol, and progesterone, together with gonads and SSC modifications, have been followed, throughout the post-reproductive period in two Rana esculenta populations, inhabiting, respectively, a mountain pond (Colfiorito) and a sea level lagoon (Lesina). Testosterone and progesterone progressively decrease in the blood until July, while estradiol shows, in both sexes, an increase in the same month. Testosterone depletion accounts for thumb pad atrophy in the male and probably, in both sexes, for the summer interruption of sexual behavior. The estradiol increase could be linked to the induction of vitellogenin synthesis by the liver or, alternatively, could act through negative feed-back on the brain centers involved in GnRF synthesis and therefore it could be responsible for an inhibition of LH release and, in turn, of androgen synthesis/secretion by the gonads. The last function can be framed in the endocrine regulation of the so-called "refractory period" which interrupts the breeding during the summer. The hematic level of progesterone is higher during the ovulation period and this is consistent with the role assigned to the hormone, i.e., the induction of jelly release from oviductal glands. The hormonal trends in the blood of the two frog populations are very similar, although some differences exist in the levels of testosterone and progesterone.

Prostaglandins and corticosterone in the oviparous female lizard, Podarcis sicula sicula, during reproduction.

The in vitro effects of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) on corticosterone release by ovarian follicles, corpora lutea (CL), and interrenals were studied in the female lizard, Podarcis sicula sicula, during reproduction. Follicles and CL studied in the female lizard, Podarcis sicula sicula, during reproduction. Follicles and CL were divided according to their different developmental stages; follicles: previtellogenic, early-vitellogenic, mid-vitellogenic and fully-grown; CL: CL1 (unshelled eggs in the oviducts), CL2 (shelled eggs in the oviducts), CL3 (eggs laid 6 h previously) and CL4 (eggs laid 48 h previously). Interrenals were divided according to the reproductive stages: pre-vitellogenesis, vitellogenesis, ovulation, post-ovulation, and post-deposition. PGF2 alpha release was highest in fully-grown follicles and PGE2 in early-vitellogenic follicles, corticosterone was highest in pre-vitellogenic and lowest in early-vitellogenic follicles. PGE2 decreased corticosterone in pre-vitellogenic, mid-vitellogenic and fully-grown follicles. PGF2 alpha release was highest in CL4, and PGE2 in CL1 and CL2, corticosterone was highest in CL4. PGF2 alpha increased corticosterone in CL1, CL2 and CL3. In interrenals, PGF2 alpha release was highest and PGE2 lowest during ovulation, corticosterone was highest during ovulation. PGF2 alpha increased and PGE2 decreased interrenal corticosterone during vitellogenesis, ovulation, and post-ovulation. In the plasma, PGF2 alpha levels were highest and PGE2 lowest during ovulation, corticosterone was highest during ovulation. These results suggest that corticosterone, modulated by PGF2 alpha and PGE2, is implied in the reproductive processes with different roles. In fact this steroid could favour ovulatory and luteolytic processes. In addition the hypothesis of an anti-vitellogenic role of corticosterone is discussed.