1,721,026 research outputs found
Contraception as prevention and therapy: sex steroids and the brain
No full textThe brain is one of the specific target tissues for sex steroid hormones. Estrogens, progestins and androgens are able to induce several effects in brain areas of the central nervous system (CNS), through the binding with specific receptors. Specific receptors for gonadal steroids have been identified in the amygdala, hippocampus, basal forebrain cortex, cerebellum, locus ceruleus, midbrain rafe nuclei, glial cells, pituitary gland, hypothalamus and central gray matter.At the hypothalamic level, the principal target for sex steroids is those neurons producing the pulsatile release of the gonadotropin releasing hormone (GnRH), localized in the mediobasal hypothalamus and the arcuate nucleus.The GnRH release depends on the complex and co-ordinated interrelationships among gonadal steroids, pituitary gonadotropins and neuroactive transmitters, such as the noradrenaline, dopamine, opioid peptides (β-endorphin), acetylcholine, serotonin, γ-aminobutyrric acid, corticotropin releasing hormone and neuropeptide Y.The interplay of these control mechanisms is governed by peripheral feedback signals; as well as the input from higher brain centers they may modify the GnRH secretion. The anterior pituitary lobe is the best known target tissue for endogenous or exogenous sex steroid hormones, because it is possible to detect luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels in blood, as the expression of the pituitary cells' activity. The synthesis and release of FSH and LH by the gonadotropic cells depend upon the peripheral control of gonadal hormones and the GnRH hypothalamic release. In summary, during a woman's reproductive life, the interaction between neurotransmitters, neuropeptides and gonadal hormones modulates the hypothalamo-pituitary-gonadal axis by acting selectively on the synthesis and release of GnRH and of pituitary gonadotropic hormones.The increased use of oral contraceptives in the last 30 years and, in general, of sex steroid hormone derivative therapies, has led to the study of the biochemical and metabolic properties of the different progestin molecules available in hormonal therapies by focusing attention on the interactions between estrogens and progestins in the modulation of the hypothalamo-pituitary-gonadal axis.The different kinds of estrogen and progestin molecules used in oral contraceptives inhibit the ovulatory process and may interfere with other sex steroid hormone receptors, thus exerting multiple effects in each target tissue
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Endocrine, neuroendocrine and behavioral effects of oral dehydroepiandrosterone sulfate supplementation in postmenopausal women.
No full textAging in women and men is characterized by a progressive decline of circulating dehydroepiandrosterone (DHEA) levels and its sulfate ester (DHEAS). The improvement of wellbeing described in postmenopausal women treated with DHEA suggests that this steroid may exert specific actions on the central nervous system (CNS). The postmenopausal period is associated with several neuroendocrine modifications. The decrease of circulating levels of beta-endorphin is considered a hormonal marker of those changes. The aim of the present study was to investigate neuroendocrine and behavioral effects of three months of DHEAS supplementation in postmenopausal women. Postmenopausal women (n = 22) were divided in three groups: the first group was treated with oral DHEAS (n = 8) (50 mg/day), the second treated with the same dose of oral DHEAS + transdermal estradiol (n = 8) (DHEAS) 50 mg/day, estradiol 50 micrograms/patch) and the third with transdermal estradiol alone (n = 6) (50 micrograms/day). Before and after 1, 2 and 3 months of therapy, the following circulating steroid and protein hormone levels were evaluated: DHEA, DHEAS, androstenedione, testosterone, estrone, estradiol, 17-hydroxyprogesterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinizing hormone (LH), beta-endorphin, growth hormone (GH) and cortisol, and a Kupperman score was performed. Before and after treatments, plasma beta-endorphin levels were evaluated in response to three neuroendocrine tests: (a) clonidine, an alpha 2-presynaptic adrenergic agonist (1.25 mg i.v.) (b) naloxone, an opioid receptor antagonist (4 mg i.v.) and (c) fluoxetine, a serotonin selective reuptake inhibitor (30 mg p.o.). In both groups of women treated with DHEAS, mean basal serum DHEA, DHEAS, androstenedione, and testosterone levels significantly increased after treatment, while no changes were shown in the group receiving estradiol alone. Serum estradiol, estrone, GH and plasma beta-endorphin levels significantly increased progressively for the three months of treatment, with higher levels for estrone and estradiol in subjects receiving estradiol alone or plus DHEAS. Serum SHBG, cortisol, and 17-hydroxyprogesterone did not show significant variations under any treatment. Serum LH and FSH levels showed a significant decrease in groups treated with estradiol alone or plus DHEAS at the second and third months. The Kupperman score showed that all treatments were associated with similar and progressive improvement. Before therapy clonidine, naloxone and fluoxetine stimuli failed to modify circulating beta-endorphin levels. After each of the treatments, the beta-endorphin response was completely restored and was similar, independent of the kind of therapy. Restoration of the beta-endorphin response to specific stimuli suggests that DHEAS and/or its active metabolites modulates the neuroendocrine control of pituitary beta-endorphin secretion, which may support the therapeutic efficacy of the DHEAS on behavioral symptoms
Effect of different hormonal replacement therapies on circulating allopregnanolone and dehydroepiandrosterone levels in postmenopausal women.
No full textThe effects of hormone replacement therapy (HRT) on the central nervous system in postmenopausal women might be mediated by changes in neurosteroid synthesis and/or release. The aim of this study was to evaluate the impact of HRT on the levels of allopregnanolone, a sedative anxiolytic GABA(A) agonist steroid, and dehydroepiandrosterone (DHEA), a GABA(A) antagonist steroid. We evaluated allopregnanolone and DHEA circulating levels after 1, 3, 6, 9 and 12 months of HRT with ten different estrogen or estrogen-progestin molecules, regimens and routes of administration in 186 postmenopausal women. Cortisol, luteinizing hormone, follicle stimulating hormone, estradiol and progesterone levels were also evaluated. Allopregnanolone levels significantly increased during follow-up with all HRT preparations. The addition of progestin molecules (except for 19-nor derivatives) to transdermal estradiol administration alone determined a higher increase in allopregnanolone levels. Transdermal HRT showed a significantly higher percentage change in allopregnanolone levels compared with oral HRT. DHEA levels showed a progressive decline starting from the 3-month follow-up, without significant differences between the transdermal and oral groups, as well as among the ten groups, independently of the presence and type of progestin molecule used. In conclusion, HRT strongly modifies circulating neurosteroid levels in postmenopausal women
Increased midtrimester amniotic fluid activin A: a risk factor for subsequent fetal death
No full textOBJECTIVE:
The objective of this study was to determine whether concentrations of activin A and corticotropin-releasing factor in amniotic fluid can identify patients at risk of fetal death.
STUDY DESIGN:
A retrospective case-control study of women who have had a midtrimester amniocentesis was designed. Case subjects consisted of patients who had a spontaneous fetal death after the procedure, whereas the control group consisted of patients who had a normal pregnancy outcome after midtrimester amniocentesis. Dimeric activin A was measured by a specific 2-site enzyme immunoassay, and corticotropin-releasing factor was measured by a specific and sensitive radioimmunoassay after acidic extraction. Statistical analysis was performed with Mann-Whitney U test, Fisher's exact test, and chi2 tests and regression analysis.
RESULTS:
First, activin A was detectable in all amniotic fluid samples. Second, the concentration of activin A in amniotic fluid increased with advancing gestational age. Third, patients who subsequently had a fetal death had a higher median concentration of activin A than those with a normal pregnancy outcome (P <.01). Fourth, an amniotic fluid concentration of activin A greater than the 95th confidence interval for gestational age was found in 40% of patients who subsequently had a fetal death (odds ratio: 21.6; P <.005). Finally, the median concentration of corticotropin-releasing factor in amniotic fluid was not different in case subjects and control subjects.
CONCLUSIONS:
An elevated concentration of activin A in amniotic fluid identifies women at risk of fetal death
Dehydroepiandrosterone as neurosteroid: neuroendocrine effects in post-menopausal women.
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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