Search results for "Pregnenolone"
showing 7 items of 17 documents
Neurosteroids in the Retina
2003
Steroids may have a powerful role in neuronal degeneration. Recent research has revealed that steroids may influence the onset and progression of some retinal disorders as well as neurodegenerative diseases and, as in brain, they accumulate in the retina via a local synthesis (neurosteroids) and metabolism of blood-circulating steroid hormones. Their crucial role as neurodegenerative and neuroprotective agents has been also upheld in a retinal excitotoxic paradigm. These findings are reviewed especially from the emerging perspective that after an insult local changes in steroidogenic responses and consequent neurosteroid availability might turn out to be offensive or defensive cellular adap…
Screening of Ovarian steroidogenic pathway in Ciona intestinalis and its modulation after Tributyltin exposure
2010
In this study, we have identified several ovarian steroids in Ciona with high similarity to vertebrate steroids and showed that cholesterol, corticosterone, dehydroepiandrosterone, estrone, estradiol-17beta, testosterone, pregnenolone, progesterone, have identical molecular spectra with vertebrate steroids. In addition, we have studied the effects of an endocrine disruptor (tributyltin: TBT) on these sex hormones and their precursors, ovarian morphology, and gene expression of some key enzymes in steroidogenic pathway in the ovary of Ciona. Ovarian specimens were cultured in vitro using different concentrations of TBT (10{sup -5}, 10{sup -4} and 10{sup -3} M). Ethanol was used as solvent co…
Pregnenolone sulphate (PREGS) affects spatial learning and memory in two different cognitive tasks in adult rats. Influence of the emotional state.
2009
Pregnenolone sulphate (PREGS) is one of the most potent memory-enhancing neurosteroids in rodent learning studies, also involved in the modulation of the emotional state (Valleè et al 2001). Neurosteroids exert an important role as modulators of the neuronal activity by interacting with different receptors or ion channels (Urani et al 1998). Indeed PREGS acts as negative modulator of GABAA- and as positive modulator of NMDA -receptors. Altered levels of PREGS have also been reported during aging and in human neurodegenerative pathologies like Alzheimer’s disease. The aim of this study was to investigate, in adult male rats, the effects of a single injection of PREGS (10 mg/kg s.c.) on: i) o…
Induction of neurosteroid synthesis by NMDA receptors in isolated rat retina: a potential early event in excitotoxicity
1998
Here we investigated the possible regulation of neurosteroidogenesis by N-methyl-D-aspartic acid (NMDA) receptor activation and addressed the hypothesis that neurosteroid synthesis may be involved in acute excitotoxicity. In the isolated retina, exposure to NMDA modified pregnenolone and pregnenolone sulphate formation. This effect was dose and time dependent, the synthesis being increased by relatively moderate NMDA doses (1-100 microM) within 30 min exposure and reduced to its control value by 60 min or by raising drug concentrations. NMDA-stimulated neurosteroid synthesis was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclo-hepten-5,10-imine hydrogen maleate (MK-801) and 3(2-ca…
Pregnenolone sulfate modulates NMDA receptors, inducing and potentiating acute excitotoxicity in isolated retina
1998
Pregnenolone sulfate (PS) acts as a positive allosteric modulator of N-methyl-D-aspartate (NMDA) receptor-mediated responses. In the retina, we previously observed that the synthesis of pregnenolone and PS increases after stimulation of NMDA receptors and blockade of the synthesis reduces retinal cell death. This study was carried out to explore in the isolated and intact retina the possible role of PS in NMDA-induced excitotoxicity. Lactate dehydrogenase (LDH) measurements and morphological analysis revealed that a 90-min exogenous application of PS at 0.1-500 microM concentrations potentiated NMDA-induced cell death and at 50-500 microM concentrations caused cytotoxicity. After 45 min, ei…
A caspase-3-dependent pathway is predominantly activated by the excitotoxin pregnenolone sulfate and requires early and late cytochrome c release and…
2002
This study investigates the implication of mitochondria- and caspase-dependent pathways in the death of retinal neurones exposed to the neurosteroid pregnenolone sulfate (PS) shown to evoke apoptosis and contribute to amplification and propagation of excitotoxicity. After a brief PS challenge of intact retinas, caspase-3 and caspase-2 activation and cytochrome c release occur early and independent of changes in the oxidative state measured by superoxide dismutase activity. The temporal and spatial relationship of these events suggests that a caspase-3-dependent pathway is activated in response to cytochrome c release and requires caspase-2 activation and a late cytochrome c release in speci…
Preliminary identification and quantification of steroid hormones in the red palm weevil, Rhynchophorus ferrugineus
2012
In the present preliminary study, we used a gas chromatography–mass spectroscopy (GC-MS) method to identify and quantify steroid hormones, their precursors and metabolites in whole body of red palm weevil (RPW) R. ferrugineus adults. We identified a total of seven steroids by single ion monitoring mode (SIM) analysis and compared them to the National Institute of Standards and Technology (NIST) library. The steroids include: dehydroepiandrosterone (DHEA), estrone, estradiol-17β, testosterone, progesterone, cortisol and cholesterol, whereas pregnenolone, pregnan-20-one-17-hydroxy and corticosterone were not detected. This study shows that some invertebrate groups seem to use partially or tot…