The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Alan J Tilbrook - One of the best experts on this subject based on the ideXlab platform.
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Role of estradiol in cortisol-induced reduction of luteinizing hormone Pulse Frequency.
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Alan J Tilbrook, Fred J KarschAbstract:Precise control of pulsatile GnRH and LH release is imperative to ovarian cyclicity but is vulnerable to environmental perturbations, like stress. In sheep, a sustained (29 h) increase in plasma cortisol to a level observed during stress profoundly reduces GnRH Pulse Frequency in ovariectomized ewes treated with ovarian steroids, whereas shorter infusion (6 h) is ineffective in the absence of ovarian hormones. This study first determined whether the ovarian steroid milieu or duration of exposure is the relevant factor in determining whether cortisol reduces LH Pulse Frequency. Prolonged (29 h) cortisol infusion did not lower LH Pulse Frequency in ovariectomized ewes deprived of ovarian hormones, but it did so in ovariectomized ewes treated with estradiol and progesterone to create an artificial estrous cycle, implicating ovarian steroids as the critical factor. Importantly, this effect of cortisol was more pronounced after the simulated preovulatory estradiol rise of the artificial follicular phase. The second experiment examined which component of the ovarian steroid milieu enables cortisol to reduce LH Pulse Frequency in the artificial follicular phase: prior exposure to progesterone in the luteal phase, low early follicular phase estradiol levels, or the preovulatory estradiol rise. Basal estradiol enabled cortisol to decrease LH Pulse Frequency, but the response was potentiated by the estradiol rise. These findings lead to the conclusion that ovarian steroids, particularly estradiol, enable cortisol to inhibit LH Pulse Frequency. Moreover, the results provide new insight into the means by which gonadal steroids, and possibly reproductive status, modulate neuroendocrine responses to stress.
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cortisol reduces gonadotropin releasing hormone Pulse Frequency in follicular phase ewes influence of ovarian steroids
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Iain J. Clarke, Fred J Karsch, Alan J TilbrookAbstract:Stress-like elevations in plasma glucocorticoids suppress gonadotropin secretion and can disrupt ovarian cyclicity. In sheep, cortisol acts at the pituitary to reduce responsiveness to GnRH but does not affect GnRH Pulse Frequency in the absence of ovarian hormones. However, in ewes during the follicular phase of the estrous cycle, cortisol reduces LH Pulse Frequency. To test the hypothesis that cortisol reduces GnRH Pulse Frequency in the presence of ovarian steroids, the effect of cortisol on GnRH secretion was monitored directly in pituitary portal blood of follicular phase sheep in the presence and absence of a cortisol treatment that elevated plasma cortisol to a level observed during stress. An acute (6 h) cortisol increase in the midfollicular phase did not lower GnRH Pulse Frequency. However, a more prolonged (27 h) increase in cortisol beginning just before the decrease in progesterone reduced GnRH Pulse Frequency by 45% and delayed the preovulatory LH surge by 10 h. To determine whether the gonadal steroid milieu of the follicular phase enables cortisol to reduce GnRH Pulse Frequency, GnRH was monitored in ovariectomized ewes treated with estradiol and progesterone to create an artificial follicular phase. A sustained increment in plasma cortisol reduced GnRH Pulse Frequency by 70% in this artificial follicular phase, in contrast to the lack of an effect in untreated ovariectomized ewes as seen previously. Thus, a sustained stress-like level of cortisol suppresses GnRH Pulse Frequency in follicular phase ewes, and this appears to be dependent upon the presence of ovarian steroids.
Fred J Karsch - One of the best experts on this subject based on the ideXlab platform.
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Role of estradiol in cortisol-induced reduction of luteinizing hormone Pulse Frequency.
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Alan J Tilbrook, Fred J KarschAbstract:Precise control of pulsatile GnRH and LH release is imperative to ovarian cyclicity but is vulnerable to environmental perturbations, like stress. In sheep, a sustained (29 h) increase in plasma cortisol to a level observed during stress profoundly reduces GnRH Pulse Frequency in ovariectomized ewes treated with ovarian steroids, whereas shorter infusion (6 h) is ineffective in the absence of ovarian hormones. This study first determined whether the ovarian steroid milieu or duration of exposure is the relevant factor in determining whether cortisol reduces LH Pulse Frequency. Prolonged (29 h) cortisol infusion did not lower LH Pulse Frequency in ovariectomized ewes deprived of ovarian hormones, but it did so in ovariectomized ewes treated with estradiol and progesterone to create an artificial estrous cycle, implicating ovarian steroids as the critical factor. Importantly, this effect of cortisol was more pronounced after the simulated preovulatory estradiol rise of the artificial follicular phase. The second experiment examined which component of the ovarian steroid milieu enables cortisol to reduce LH Pulse Frequency in the artificial follicular phase: prior exposure to progesterone in the luteal phase, low early follicular phase estradiol levels, or the preovulatory estradiol rise. Basal estradiol enabled cortisol to decrease LH Pulse Frequency, but the response was potentiated by the estradiol rise. These findings lead to the conclusion that ovarian steroids, particularly estradiol, enable cortisol to inhibit LH Pulse Frequency. Moreover, the results provide new insight into the means by which gonadal steroids, and possibly reproductive status, modulate neuroendocrine responses to stress.
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cortisol reduces gonadotropin releasing hormone Pulse Frequency in follicular phase ewes influence of ovarian steroids
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Iain J. Clarke, Fred J Karsch, Alan J TilbrookAbstract:Stress-like elevations in plasma glucocorticoids suppress gonadotropin secretion and can disrupt ovarian cyclicity. In sheep, cortisol acts at the pituitary to reduce responsiveness to GnRH but does not affect GnRH Pulse Frequency in the absence of ovarian hormones. However, in ewes during the follicular phase of the estrous cycle, cortisol reduces LH Pulse Frequency. To test the hypothesis that cortisol reduces GnRH Pulse Frequency in the presence of ovarian steroids, the effect of cortisol on GnRH secretion was monitored directly in pituitary portal blood of follicular phase sheep in the presence and absence of a cortisol treatment that elevated plasma cortisol to a level observed during stress. An acute (6 h) cortisol increase in the midfollicular phase did not lower GnRH Pulse Frequency. However, a more prolonged (27 h) increase in cortisol beginning just before the decrease in progesterone reduced GnRH Pulse Frequency by 45% and delayed the preovulatory LH surge by 10 h. To determine whether the gonadal steroid milieu of the follicular phase enables cortisol to reduce GnRH Pulse Frequency, GnRH was monitored in ovariectomized ewes treated with estradiol and progesterone to create an artificial follicular phase. A sustained increment in plasma cortisol reduced GnRH Pulse Frequency by 70% in this artificial follicular phase, in contrast to the lack of an effect in untreated ovariectomized ewes as seen previously. Thus, a sustained stress-like level of cortisol suppresses GnRH Pulse Frequency in follicular phase ewes, and this appears to be dependent upon the presence of ovarian steroids.
Amy E Oakley - One of the best experts on this subject based on the ideXlab platform.
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Role of estradiol in cortisol-induced reduction of luteinizing hormone Pulse Frequency.
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Alan J Tilbrook, Fred J KarschAbstract:Precise control of pulsatile GnRH and LH release is imperative to ovarian cyclicity but is vulnerable to environmental perturbations, like stress. In sheep, a sustained (29 h) increase in plasma cortisol to a level observed during stress profoundly reduces GnRH Pulse Frequency in ovariectomized ewes treated with ovarian steroids, whereas shorter infusion (6 h) is ineffective in the absence of ovarian hormones. This study first determined whether the ovarian steroid milieu or duration of exposure is the relevant factor in determining whether cortisol reduces LH Pulse Frequency. Prolonged (29 h) cortisol infusion did not lower LH Pulse Frequency in ovariectomized ewes deprived of ovarian hormones, but it did so in ovariectomized ewes treated with estradiol and progesterone to create an artificial estrous cycle, implicating ovarian steroids as the critical factor. Importantly, this effect of cortisol was more pronounced after the simulated preovulatory estradiol rise of the artificial follicular phase. The second experiment examined which component of the ovarian steroid milieu enables cortisol to reduce LH Pulse Frequency in the artificial follicular phase: prior exposure to progesterone in the luteal phase, low early follicular phase estradiol levels, or the preovulatory estradiol rise. Basal estradiol enabled cortisol to decrease LH Pulse Frequency, but the response was potentiated by the estradiol rise. These findings lead to the conclusion that ovarian steroids, particularly estradiol, enable cortisol to inhibit LH Pulse Frequency. Moreover, the results provide new insight into the means by which gonadal steroids, and possibly reproductive status, modulate neuroendocrine responses to stress.
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cortisol reduces gonadotropin releasing hormone Pulse Frequency in follicular phase ewes influence of ovarian steroids
Endocrinology, 2009Co-Authors: Amy E Oakley, Kellie M Breen, Elizabeth R Wagenmaker, Iain J. Clarke, Fred J Karsch, Alan J TilbrookAbstract:Stress-like elevations in plasma glucocorticoids suppress gonadotropin secretion and can disrupt ovarian cyclicity. In sheep, cortisol acts at the pituitary to reduce responsiveness to GnRH but does not affect GnRH Pulse Frequency in the absence of ovarian hormones. However, in ewes during the follicular phase of the estrous cycle, cortisol reduces LH Pulse Frequency. To test the hypothesis that cortisol reduces GnRH Pulse Frequency in the presence of ovarian steroids, the effect of cortisol on GnRH secretion was monitored directly in pituitary portal blood of follicular phase sheep in the presence and absence of a cortisol treatment that elevated plasma cortisol to a level observed during stress. An acute (6 h) cortisol increase in the midfollicular phase did not lower GnRH Pulse Frequency. However, a more prolonged (27 h) increase in cortisol beginning just before the decrease in progesterone reduced GnRH Pulse Frequency by 45% and delayed the preovulatory LH surge by 10 h. To determine whether the gonadal steroid milieu of the follicular phase enables cortisol to reduce GnRH Pulse Frequency, GnRH was monitored in ovariectomized ewes treated with estradiol and progesterone to create an artificial follicular phase. A sustained increment in plasma cortisol reduced GnRH Pulse Frequency by 70% in this artificial follicular phase, in contrast to the lack of an effect in untreated ovariectomized ewes as seen previously. Thus, a sustained stress-like level of cortisol suppresses GnRH Pulse Frequency in follicular phase ewes, and this appears to be dependent upon the presence of ovarian steroids.
K.l. Esbenshade - One of the best experts on this subject based on the ideXlab platform.
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Role of gonadotropin-releasing hormone Pulse Frequency in differential regulation of gonadotropins in the gilt.
Biology of reproduction, 1997Co-Authors: Friederike L. Jayes, Jack H. Britt, K.l. EsbenshadeAbstract:We tested the hypothesis that different GnRH Pulse frequencies will affect serum LH and FSH differently. Ovariectomized gilts (n = 6), immunized against GnRH, were given 200-ng Pulses of GnRH agonist (GnRH-A) every 180 min for 3 days (pretreatment), followed by GnRH-A Pulses every 30, 60, or 180 min for 3 days (treatment) in a Latin rectangle design. Mean gonadotropin concentrations did not change over time when GnRH Pulses were administered every 180 min. Initiation of high GnRH-A Pulse Frequency (30 min) caused a robust increase in serum LH to 265% of the pretreatment level (p < 0.007) and a more moderate increase in serum FSH to 127% of pretreatment level (p - 0.02). After 66 h of frequent pulsing, desensitization had occurred and serum LH concentrations were similar to pretreatment concentrations, but serum FSH had decreased to 53% of pretreatment levels (p < 0.0008). After 72 h of treatment, 5 pFg GnRH-A was infused to estimate residual releasable pools of LH and FSH, and the amounts of LH and FSH released were negatively correlated with GnRH-A Pulse Frequency. The results of this study imply that the LH surge is terminated because the pituitary gland becomes incapable of responding to an otherwise adequate stimulus, and not because of exhaustion of releasable LH pools. Our results confirm that in the pig the response to altered GnRH-A Pulse Frequency differs between LH and FSH. High GnRH Pulse Frequency is more effective in acutely releasing LH than FSH. Low Pulse Frequency of GnRH supports FSH synthesis and release, but is not as effective in increasing LH concentrations, while high GnRH Pulse Frequency inhibits FSH synthesis and release.
Willy Supatto - One of the best experts on this subject based on the ideXlab platform.
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Balancing signal and photoperturbation in multiphoton light-sheet microscopy by optimizing laser Pulse Frequency
2020Co-Authors: Vincent Maioli, Antoine Boniface, Pierre Mahou, Lamiae Abdeladim, Emmanuel Beaurepaire, Ferrer Ortas Julia, Willy SupattoAbstract:Improving the imaging speed of multiphoton microscopy is an active research field. Among recent strategies, light-sheet illumination holds distinctive advantages for achieving fast imaging in vivo. However, photoperturbation in multiphoton light-sheet microscopy remains poorly investigated. We show here that the heart beat rate of zebrafish embryos is a sensitive probe of linear and nonlinear photoperturbations. By analyzing its behavior with respect to laser power, Pulse Frequency and wavelength, we derive guidelines to balance signal and photoperturbation. We then demonstrate one order-of-magnitude signal enhancement over previous implementations by optimizing the laser Pulse Frequency. These results open new opportunities for fast live tissue imaging.
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Fast in vivo multiphoton light-sheet microscopy with optimal Pulse Frequency.
Biomedical optics express, 2020Co-Authors: Vincent Maioli, Antoine Boniface, Pierre Mahou, Júlia Ferrer Ortas, Lamiae Abdeladim, Emmanuel Beaurepaire, Willy SupattoAbstract:Improving the imaging speed of multiphoton microscopy is an active research field. Among recent strategies, light-sheet illumination holds distinctive advantages for achieving fast imaging in vivo. However, photoperturbation in multiphoton light-sheet microscopy remains poorly investigated. We show here that the heart beat rate of zebrafish embryos is a sensitive probe of linear and nonlinear photoperturbations. By analyzing its behavior with respect to laser power, Pulse Frequency and wavelength, we derive guidelines to find the best balance between signal and photoperturbation. We then demonstrate one order-of-magnitude signal enhancement over previous implementations by optimizing the laser Pulse Frequency. These results open new opportunities for fast live tissue imaging.
