111 research outputs found
Ontogenesi della risposta interrenalica allo stress nell'orata (Sparus aurata) e nell'ombrina (Umbrina cirrosa)
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Indicatori di stress in spigole (Dicentrarchus Labrax) provenienti da tre tipologie di allevamento
No full textSex steroids in Tapes philippinarum (Adams and Reeve 1850) during gametogenic cycle: Preliminary results
No full textIt is well known that a wide variety of endocrine-disrupting chemicals (EDCs) (e.g. organotin compounds, heavy metals, herbicides, xenoestrogen compounds) can induce endocrine alterations in aquatic invertebrates, often causing reproductive disorders. Although these phenomena are of great concern, mostly in coastal and estuarine environments, few data are available about the mechanism of action of EDCs, mainly due to lack of knowledge about the invertebrate endocrine system. To understand the possible mechanism of action of EDCs better, the presence and patterns of variation of sexual steroids, progesterone, testosterone and 17β-estradiol were measured in the whole body of the clam Tapes philippinarum by specific and opportunely validated microtitre radioimmunoassays (RIAs). Female steroid concentrations showed similar trends, with higher values during spawning and lower ones in post-spawning and gametogenesis periods. Conversely, in males, sexual steroids varied over the year: progesterone remained unchanged, with values similar to those of females in gametogenesis, whereas testosterone and 17β-estradiol showed a significant decrease during gametogenesis only. Seasonal variations in clam steroid levels may reflect their role in modulating reproduction. All hormones were unexpectedly high in the resting/early developing stage, during which gonadal tissue is scarce, indicating that digestive gland may have a biosynthetic steroid capacity or accumulation. Although these results are preliminary, evaluation of sexual steroids in T. philippinarum during the gametogenic cycle represent the first step for future research aimed at understanding the physiological role of these hormones and their potential interaction with EDCs
POSTPARTUM PROGESTERONE PROFILES AND REPRODUCTIVE PERFORMANCES OF DAIRY COWS TREATED WITH GnRH OR PROGESTERONE
No full textInfluence of a new slow-release GnRH analogue implant on reproduction in the Budgerigar (Melopsittacus undulatus, Shaw 1805)
No full textThe neuroendocrine conditioning of reproduction in birds could perform a very important role in captive breeding, especially in endangered species. Whereas in domestic and wild mammals pharmacological reproductive conditioning is well developed, in birds an effective method is not available. The aim of this study was to test the influence of a new slow-release GnRH analogue (buserelin acetate) implant on the reproductive activity of the Budgerigar (Melopsittacus undulatus), used as model species for captive-bred endangered birds. The effects were assessed by looking at reproductive parameters (egg-laying rate, egg fertility rate) and measuring excreted sex steroid metabolite concentrations in male and female birds. Modification of reproductive parameters and steroid metabolites excretion patterns were observed among birds administered with a GnRH analogue implant and maintained under artificial photoperiod (group I; 16L:8D). Implanted birds showed higher rates of egg-laying, potentially a higher proportion of fertile eggs and higher excreted steroid metabolite concentrations than birds maintained under natural photoperiod (group II; 10L:14D) and birds maintained under artificial photoperiod (group III; 16L:8D). Thus, it is concluded that the new slow-release GnRH analogue implant may represent an innovative and practicable treatment to rapidly induce reproductive activity in the Budgerigar, and that excreted sex hormone metabolites detection permits to monitor male and female gonadal activity
Welfare and quality of farmed trout fed high plant protein diets. 3 alternative indicators to evaluate stress in fish
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Extraglandular hormonal steroidogenesis in aged rats.
No full textWe have examined the metabolisM in Vitro of [4-C-14]pregnenolone by the following organs of 2.4-year-old rats: submandibular gland, stomach, duodenum, liver, lung, heart, spleen, kidney, skin, prostate, testis and adrenal. All tissues converted pregnenolone to progesterone, the highest yields being observed with adrenal, testis and skin. Androgen formation was intense in the testis and absent in the adrenal. Moreover, 17alpha-hydroxylation of pregnenolone occurred moderately in kidney, skin and submandibular gland and markedly in duodenum and stomach, which also produced high amounts of dehydroepiandrosterone and/or 5-androstene-3beta,17beta-diol. Extratesticular synthesis of androstenedione and testosterone was very low. A significant formation of 20alpha-dihydropregnenolone was observed in all tissues but stomach, duodenum and steroidogenic endocrines. Corticosteroids were not synthesized extraadrenally, except a small amount of 11-deoxycorticosterone in the testis. These results indicate that key steroid-biosynthetic enzymes, such as 3beta-hydroxysteroid dehydrogenase/DELTA5-DELTA4 isomerase, 17beta- and 20alpha-hydroxysteroid dehydrogenases and steroid 17alpha-monooxygenase/17,20-lyase are also expressed extraglandularly in the rat
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