Search Results - "LEGAN, S. J"

Estrogen and progesterone do not activate Fos in AVPV or LHRH neurons in male rats by Hoffman, G.E., Le, W.W., Schulterbrandt, T., Legan, S.J.

“…In rodents, females but not males, in response to escalating levels of estrogen, express a luteinizing hormone (LH) surge that is prompted by a surge in…”
Get full text

Restricting feeding to the active phase in middle-aged mice attenuates adverse metabolic effects of a high-fat diet by Duncan, M.J, Smith, J.T, Narbaiza, J, Mueez, F, Bustle, L.B, Qureshi, S, Fieseler, C, Legan, S.J

“…Abstract Time-restricted feeding ameliorates the deleterious effects of a high-fat diet on body weight and metabolism in young adult mice. Because obesity is…”
Get full text

Oestrogen Receptor-α and -β Immunoreactivity in Gonadotropin-Releasing Hormone Neurones after Ovariectomy and Chronic Exposure to Oestradiol by Legan, S. J., Tsai, H.-W.

“…Oestradiol exerts negative‐ and positive‐feedback actions on luteinizing hormone (LH) secretion by modulating gonadotropin‐releasing hormone (GnRH) release…”
Get full text

Novel Wheel Running Blocks the Preovulatory Luteinizing Hormone Surge and Advances the Hamster Circadian Pacemaker by Legan, S.J, Franklin, K.M, Peng, X.-L, Duncan, M.J

“…In rodents, the preovulatory luteinizing hormone (LH) surge is timed by a circadian rhythm. We recently reported that a phenobarbital-induced delay of the…”
Get full text

Effect of arousing stimuli on circulating corticosterone and the circadian rhythms of luteinizing hormone (LH) surges and locomotor activity in estradiol-treated ovariectomized (ovx+EB) Syrian hamsters by Legan, S.J., Peng, X., Yun, C., Duncan, M.J.

“…In most proestrous hamsters, novel wheel exposure phase advances activity rhythms and blocks the preovulatory LH surge, which occurs 2h earlier the next day…”
Get full text

Chronic Elevation of Estradiol in Young Ovariectomized Rats Causes Aging-Like Loss of Steroid-Induced Luteinizing Hormone Surges by TSAI, Houng-Wei, LEGAN, Sandra J

“…This study was designed to test the hypothesis that the loss of LH surges in response to the stimulatory actions of estradiol and progesterone in middle-aged,…”
Get full text

Photoperiodic control of seasonal breeding in ewes: modulation of the negative feedback action of estradiol by Legan, S J, Karsch, F J

“…In ewes, a pivotal neuroendocrine event regulating seasonal breeding is a change in response of the hypothalamo-pituitary axis to the negative feedback action…”
Get full text

Patterns of circulating gonadotropins and ovarian steroids during the first periovulatory period in the developing sheep by Ryan, K.D. (University of Pittsburgh School of Medicine, Pittsburgh, PA), Goodman, R.L, Karsch, F.J, Legan, S.J, Foster, D.L

“…This report provides evidence that an increment in serum gonadotropin levels occurs at puberty in the sheep and that this reflects the critical hormonal event…”
Get full text

Neuroendocrine basis of seasonal reproduction by Karsch, F J, Bittman, E L, Foster, D L, Goodman, R L, Legan, S J, Robinson, J E

Get more information

Changes in LH pulse frequency and serum progesterone concentrations during the transition to breeding season in ewes by I'Anson, H, Legan, S J

“…To characterize the changes in LH pulse frequency during the transition to breeding season, LH pulse patterns and serum progesterone profiles were determined…”
Get full text

Progesterone ensures full-length luteal phases during the breeding season in ewes by Legan, S J, I'Anson, H, Neiser, P

“…To test the hypothesis that each luteal-phase increase in the serum concentration of progesterone throughout the breeding season prevents a short luteal phase…”
Get more information

Importance of retinal photoreceptors to the photoperiodic control of seasonal breeding in the ewe [Sheep reproductive cycles] by Legan, S.J, Karsch, F.J

“…Two experiments were performed to determine whether the eyes are necessary for photoperiodic control of reproduction in ewes. In the first, intact and…”
Get full text

Does the first LH surge of the breeding season initiate the first full-length cycle in the ewe? by I'Anson, H, Legan, S J

“…To determine whether the first LH surge of the breeding season initiates a transient rise in progesterone in most ewes, serum progesterone (daily) and LH…”
Get full text

Importance of variations in behavioural and feedback actions of oestradiol to the control of seasonal breeding in the ewe by Goodman, R L, Legan, S J, Ryan, K D, Foster, D L, Karsch, F J

“…Seasonal variations in the behavioural and feedback actions of oestradiol in the ewe were examined by determining the ability of various physiological…”
Get more information

Changes in patterns of luteinizing hormone secretion before and after the first ovulation in the postpartum mare by FITZGERALD, B. P, I'ANSON, H, LEGAN, S. J, LOY, R. G

“…To determine whether luteinizing hormone (LH) secretion during the first estrous cycle postpartum is characterized by pulsatile release, circulating LH…”
Get full text

Does the seasonal increase in estradiol negative feedback prevent luteinizing hormone surges in anestrous ewes by suppressing hypothalamic gonadotropin-releasing hormone pulse frequency? by LEGAN, S. J, I'ANSON, H, FITZGERALD, B. P, FITZOVICH, D

“…To test the hypothesis that the anestrous increase in estradiol negative feedback prevents estrous cycles by suppressing hypothalamic gonadotropin-releasing…”
Get full text

Importance of estradiol and progesterone in regulating LH [luteinizing hormone] secretion and estrous behavior during the sheep estrous cycle by Karsch, F.J, Legan, S.J, Ryan, K.D, Foster, D.L

“…Replacement of the ovaries of sheep shortly after ovulation with Silastic implants that simulated the physiological patterns and levels of estradiol and…”
Get full text

Evidence that changes in LH pulse frequency may regulate the seasonal modulation of LH secretion in ovariectomized mares by Fitzgerald, B P, I'Anson, H, Loy, R G, Legan, S J

“…To determine whether tonic LH secretion in ovariectomized mares is characterized by pulsatile release, frequent blood samples (every 15 min) were collected…”
Get full text

Importance of short luteal phases in the endocrine mechanism controlling initiation of estrous cycles in anestrous ewes by Legan, S J, I'Anson, H, Fitzgerald, B P, Akaydin, Jr, M S

“…A transient increase in serum progesterone concentrations (to 1 ng/ml for 1-2 days) is observed in the majority of ewes before the first estrous cycle of the…”
Get more information

Can the transition into anoestrus in the ewe be accounted for solely by insufficient tonic LH secretion? by Legan, S J, Goodman, R L, Ryan, K D, Foster, D L, Karsch, F J

“…It has been proposed that a seasonal increase in oestradiol negative feedback elicits anoestrus by preventing a key step in the preovulatory sequence of…”
Get more information