Patterns of progesterone, melatonin and prolactin secretion in ewes maintained in four different photoperiods

1983 ◽  
Vol 97 (2) ◽  
pp. 229-242 ◽  
Author(s):  
D. J. Kennaway ◽  
L. M. Sanford ◽  
B. Godfrey ◽  
H. G. Friesen
Keyword(s):  
Pineal Gland ◽  
Endocrine System ◽  
Prolactin Secretion ◽  
Constant Light ◽  
Ovarian Activity ◽  
Dark Phase ◽  
Melatonin Secretion ◽  
Night Time ◽  
Serum Progesterone ◽  
Natural Photoperiod

Twenty-four-hour patterns of serum melatonin and prolactin levels were determined in ewes on nine occasions during a year. The sheep were maintained in four different photoperiods: room 1, simulated natural photoperiod; room 2, normal daylength extremes twice in 12 months, changes occurring in a regular fashion; room 3, alternating long (16 h) and short (8 h) days for 90 days; room 4, constant light. Cyclic ovarian activity, determined by twice-weekly determinations of serum progesterone, commenced in rooms 1, 2 and 3 after a transition from long to short daylength and terminated during long daylength. Thus in rooms 2 and 3 there were two periods of ovarian activity. In room 4 (constant light) ovarian activity began earlier than in room 1 and was of greater duration (240 days v. 190 days). Basal prolactin levels were highest (50–134 μg/l) during periods of long daylength and lowest (< 10 μ/l) in short daylength. Ewes maintained in constant light had an intermediate level (21–62 μg/l) throughout the study. Melatonin secretion was lowest during daylight (< 78 pmol/l) and highest during darkness. Night-time melatonin levels varied markedly from hour to hour and between individuals in rooms 1, 2 and 3. There was, however, no consistent seasonal change in the absolute levels of melatonin, although the duration of melatonin secretion did closely follow the length of the dark phase. There were no significant changes in melatonin levels during the oestrous cycle. Ewes kept in constant light had < 78 pmol melatonin/l throughout the period of study. If the pineal gland is involved in transmitting photoperiodic information to the endocrine system, then it is most likely to be by means of an interaction between duration of melatonin secretion and an underlying change in sensitivity of end organs to melatonin.

Melatonin Modulates Lactation by Regulating Prolactin Secretion Via Tuberoinfundibular Dopaminergic Neurons in the Hypothalamus- Pituitary System

2020 ◽  
Vol 21 (8) ◽  
pp. 744-750 ◽  
Author(s):  
Hongyang Li ◽  
JingyaWei ◽  
Fengtao Ma ◽  
Qiang Shan ◽  
Duo Gao ◽  
...  
Keyword(s):  
Pineal Gland ◽  
Pituitary Gland ◽  
Antioxidant Capacity ◽  
Dopaminergic Neurons ◽  
Growth And Development ◽  
Endocrine System ◽  
Mammary Glands ◽  
Prolactin Secretion ◽  
The Body ◽  
Stimulation Of

In-depth studies have identified many hormones important for controlling mammary growth and maintaining lactation. One of these is melatonin, which is synthesized and secreted by the pineal gland to regulate circadian rhythms, improve antioxidant capacity, and enhance immunity. Prolactin is secreted by the pituitary gland and is associated with the growth and development of mammary glands as well as initiation and maintenance of lactation. The hypothalamus-pituitary system, the most important endocrine system in the body, regulates prolactin secretion mainly through dopamine released from tuberoinfundibular dopaminergic neurons. This review provides a reference for further study and describes the regulation of lactation and prolactin secretion by melatonin, primarily via the protection and stimulation of tuberoinfundibular dopaminergic neurons.

scholarly journals Transcriptional regulation of hydroxyindole O-methyltransferase in the chicken pineal gland: day/night changes and long-term effects of light and darkness

1993 ◽  
Vol 290 (3) ◽  
pp. 661-664 ◽  
Author(s):  
M Bernard ◽  
J Guerlotte ◽  
M Cogne ◽  
P Greve ◽  
J P Collin ◽  
...  
Keyword(s):  
Pineal Gland ◽  
Gene Transcription ◽  
Cdna Probe ◽  
Constant Light ◽  
Constant Darkness ◽  
Mrna Levels ◽  
Long Term Effects ◽  
Night Time ◽  
Environmental Lighting ◽  
Time Fall

The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalysed by hydroxyindole O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. This transcriptional rhythm was not accompanied by day/night changes in HIOMT concentration, probably due to a slow turnover of this protein. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.

Photoperiod effects on the development of beef heifers

2003 ◽  
Vol 83 (4) ◽  
pp. 721-730 ◽  
Author(s):  
J. A. Small ◽  
N. D. Glover ◽  
A. D. Kennedy ◽  
W. P. McCaughey ◽  
D. R. Ward
Keyword(s):  
Body Weight ◽  
Body Weight Gain ◽  
Prolactin Secretion ◽  
Outdoor Environment ◽  
Serum Prolactin ◽  
Beef Heifers ◽  
Serum Progesterone ◽  
Ambient Temperatures ◽  
Natural Photoperiod ◽  
Sire Breed

Crossbred beef heifers (n = 144) were assigned at weaning (187 ± 14 d of age) by body weight (225 ± 23 kg) and sire breed (British/Continental) to one of two photoperiod treatments from 21 Decem ber 1998 (0 wk) until 10 May 1999 (20 wk): natural photoperiod (NP) that gradually increased from 8.1 h (0 wk) to 15.2 h (20 wk) and, extended photoperiod (EP) that consisted of natural + supplemental light (400 lx, 1 m above ground) to extend photoperiod to 16 h. Rations were formulated for two-steps of body weight gain (0.6 and 1.2 kg d-1) to achieve 60% of mature weight at 18 wk. Visual observations of estrus behavior were made twice daily and confirmed by serum progesterone. Body weight, backfat and serum prolactin data were determined for each 4-wk period. Ambient temperatures averaged -12.2 ± 6°C in winter (0 to 12 wk) and 4.2 ± 5°C in spring (12 to 20 wk). Gain in body weight was greater (P < 0.05) and backfat lower (P < 0.05) for EP than NP treatments from -2 to 6 wk and only 1% of heifers had attained puberty during this period. However, as yearlings at similar (P > 0.05) body weight and backfat, more (P < 0.05) EP than NP heifers had attained puberty (84.7% vs. 69.4%). Prolactin was greater (P < 0.05) for EP than NP treatments from 2 to 6 wk (10.3 vs 5.5 ± 1.2 ng mL-1). Management of photoperiod influences attainment of puberty and prolactin secretion in beef heifers housed in an outdoor environment. Key words: Photoperiod, puberty, estrus, beef heifers, prolactin

scholarly journals Response of Pre-pubertally Castrated Rams and Ewes to Artificial PhotoperiodChanges in Plasma LH and Prolactin

1986 ◽  
Vol 39 (4) ◽  
pp. 417
Author(s):  
AL Poulton
Keyword(s):  
Plasma Concentrations ◽  
Prolactin Secretion ◽  
Light Regime ◽  
Constant Light ◽  
Ovarian Activity ◽  
Artificial Light ◽  
Short Days

Castrate rams and ovariectomized ewes were maintained in the presence of entire rams and ewes and subjected to successive periods of alternating 6 h light: 18 h darkness ('short' days) and 18 h light: 6 h darkness ('long' days) preceeded by a period of 12 h light: 12 h darkness ('constant' light days). Plasma concentrations of LH and prolactin were measured in the castrate animals in order to determine how LH and prolactin secretion responded to (i) the artificial light regime and (ii) corresponding periods of elevated or depressed testicular and ovarian activity in the entire rams and ewes.

Night-time disability glare of constant-light LED traffic monitoring fill light

2021 ◽  
pp. 147715352098226
Author(s):  
X Cai ◽  
L Quan ◽  
J Wu ◽  
Y He
Keyword(s):  
Dynamic Range ◽  
Road Traffic ◽  
Reaction Times ◽  
High Dynamic Range ◽  
Luminance Contrast ◽  
Traffic Monitoring ◽  
Constant Light ◽  
Night Time ◽  
Disability Glare ◽  
Small Targets

Fill light, used to helps cameras capture road traffic conditions at night, can lead to serious visual consequences for drivers. Research on disability glare from LED fill light is scarce and therefore this study explored strategies for controlling disability glare of constant-light LED traffic monitoring fill light. The threshold increment was used as an index to evaluate disability glare. The effective disability glare area of LED traffic monitoring fill light was determined based on high dynamic range technology. According to visual efficacy theory, there is a relationship between disability glare conditions and reaction times. The influencing factors include background luminance, luminance contrast and fill light luminance. The results showed that disability glare was the most intense in a range of 20 m to 30 m in front of LED fill light. To reduce the effect of disability glare on drivers, luminance contrast between small targets and the road surface should be greater than 0.5. The fill light luminance should not be greater than 100,000 cd/m2.

scholarly journals Clock genes in calendar cells as the basis of annual timekeeping in mammals--a unifying hypothesis

2003 ◽  
Vol 179 (1) ◽  
pp. 1-13 ◽  
Author(s):  
GA Lincoln ◽  
H Andersson ◽  
A Loudon
Keyword(s):  
Gene Expression ◽  
Molecular Mechanism ◽  
Clock Genes ◽  
Prolactin Secretion ◽  
Secretory Cells ◽  
Dark Phase ◽  
Pars Tuberalis ◽  
Cry Protein ◽  
Wide Range

Melatonin-based photoperiod time-measurement and circannual rhythm generation are long-term time-keeping systems used to regulate seasonal cycles in physiology and behaviour in a wide range of mammals including man. We summarise recent evidence that temporal, melatonin-controlled expression of clock genes in specific calendar cells may provide a molecular mechanism for long-term timing. The agranular secretory cells of the pars tuberalis (PT) of the pituitary gland provide a model cell-type because they express a high density of melatonin (mt1) receptors and are implicated in photoperiod/circannual regulation of prolactin secretion and the associated seasonal biological responses. Studies of seasonal breeding hamsters and sheep indicate that circadian clock gene expression in the PT is modulated by photoperiod via the melatonin signal. In the Syrian and Siberian hamster PT, the high amplitude Per1 rhythm associated with dawn is suppressed under short photoperiods, an effect that is mimicked by melatonin treatment. More extensive studies in sheep show that many clock genes (e.g. Bmal1, Clock, Per1, Per2, Cry1 and Cry2) are expressed in the PT, and their expression oscillates through the 24-h light/darkness cycle in a temporal sequence distinct from that in the hypothalamic suprachiasmatic nucleus (central circadian pacemaker). Activation of Per1 occurs in the early light phase (dawn), while activation of Cry1 occurs in the dark phase (dusk), thus photoperiod-induced changes in the relative phase of Per and Cry gene expression acting through PER/CRY protein/protein interaction provide a potential mechanism for decoding the melatonin signal and generating a long-term photoperiodic response. The current challenge is to identify other calendar cells in the central nervous system regulating long-term cycles in reproduction, body weight and other seasonal characteristics and to establish whether clock genes provide a conserved molecular mechanism for long-term timekeeping.

Pineal Apoplexy: A Case Series and Review of the Literature

2021 ◽  
Author(s):  
Martin Majovsky ◽  
David Netuka ◽  
Radim Lipina ◽  
Jan Mraček ◽  
Vladimír Beneš
Keyword(s):  
Surgical Treatment ◽  
Pineal Gland ◽  
Clinical Significance ◽  
Obstructive Hydrocephalus ◽  
Case Series ◽  
Surgical Removal ◽  
Pineal Tumor ◽  
Review Of The Literature ◽  
Melatonin Secretion ◽  
Pubmed Database

Abstract Background Pineal apoplexy is a rare condition, with unknown incidence and clinical significance. To elucidate this clinical condition, we analyzed our own case series and performed a review of the literature. Methods We enrolled all patients with a hemorrhagic pineal apoplexy who were referred to our department between January 2000 and January 2020. Hemorrhagic pineal apoplexy was defined as the presence of fluid–fluid levels inside the pineal cyst (PC) on an axial or sagittal magnetic resonance scan. In one patient, after PC apoplexy, we performed a circadian melatonin sampling from peripheral blood to determine the function of the pineal gland. The PubMed database was searched for publications using the terms “pineal” and “apoplexy.” Results Eight patients were enrolled, of which three patients underwent surgical treatment and five patients were managed conservatively. One patient was tested for circadian melatonin secretion. Results confirmed melatonin secretion with preserved physiologic circadian rhythm.Our search of the literature led us to 31 studies that comprised 30 patients with apoplectic PC, 9 with apoplectic pineal tumor, and 1 with bleeding into the normal pineal gland. Most patients presented with headache, nausea, and vomiting, less frequently with acute hydrocephalus and gaze palsy. Twenty patients with a PC underwent resection or aspiration. Two patients underwent shunt placement as the only procedure and five received both shunt and surgical removal. Six patients with a PC were observed without surgical treatment. All the nine patients with a pineal tumor were operated on. In indicated cases, four patients received radiation therapy and one received chemotherapy. Conclusion Clinical significance of hemorrhagic pineal apoplexy ranges from an asymptomatic course to rapid deterioration and death. In patients with mild symptoms, observation is indicated, whereas surgical treatment is reserved for severe cases presenting with obstructive hydrocephalus and includes cerebrospinal fluid diversion, resection of apoplectic pineal lesions, or both.

Pattern of prolactin secretion and pituitary responsiveness to LRH in pseudopregnant rats maintained in constant light

1982 ◽  
Vol 99 (1) ◽  
pp. 31-38 ◽  
Author(s):  
T. R Koiter ◽  
A. A. van der Gugten ◽  
N. Pols-Valkhof ◽  
J. van Eekeren ◽  
G. A. Schuiling
Keyword(s):  
The Netherlands ◽  
Prolactin Secretion ◽  
Constant Light ◽  
Blood Samples ◽  
Lighting Conditions ◽  
Maximal Height ◽  
Netherlands Cancer Institute ◽  
The Right ◽  
Plasma Prl ◽  
Cervical Stimulation

Abstract. Secretion of LH in response to an LRH infusion (104 ng/h during 21 h), secretion of progesterone (P) and 20 α-dihydroprogesterone (DHP), as well as the 24 h rhythm of prolactin (Prl) secretion were investigated in rats rendered persistently oestrous by exposure to constant light and in which subsequently pseudopregnancy (PSP) had been induced by cervical stimulation after induction of ovulation by hCG. Similar persistently oestrous rats, but otherwise untreated, served as controls. LRH was infused through an intra-jugular cannula and blood samples for assay of LH were taken via an intra-carotid cannula. LH responses were judged on the basis of the mean maximal height (MH; ng LH ml plasma) and the rate of decrease or half life (t½ of the plasma LH concentrations after 2 h of LRH infusion. For assay of P and DHP blood samples were taken from the orbitalplexus. In another series of animals blood, for assay of Prl, was sampled every 2 h for 24 h from a cannula with the tip in the right atrium. It was observed that in persistently oestrous rats LH-responses were high (MH = 3326 ± 305) and steep (t½ = 65 ± 10 min). On the day after the night of ovulation (day 0 of PSP) and on days 1, 5 and 9 of PSP the responses were lower (MH between 1315 and 1041) and more blunted (t½ varied between 236 and 142 min), whilst on day 12 of PSP they were again higher (MH = 4416 ± 575) and steeper (t½ = 101 ± 12 min). P and DHP concentrations were low in persistently oestrous rats and high during days 5 and 8 of PSP. On day 12 of PSP P concentrations were low again, while the DHP concentrations had increased further. In persistently oestrous rats the plasma Prl levels were low with incidental elevations (up to 141 ng Prl/ml aAntoni van Leeuwenhoekhuis The Netherlands Cancer Institute, Amsterdam, The Netherlands plasma). During days 8 – 9 of PSP Prl was secreted at irregular intervals (1 to 3 peaks/24 h) with peak levels of up to 400 ng Prl/ml plasma. On days 11 – 12 of PSP, Prl peaks were lacking almost completely: only a few minor elevations (up to 41 ng Prl/ml plasma) were measured. It is concluded that during days 0 to 10 of pseudopregnancy under constant light the endocrine state of the animals (in terms of LRH-responsiveness and P and DHP secretion) differs significantly form that during the previous and the following days. As similar changes are observed in PSP rats maintained under standard lighting conditions, it is apparent that the lighting conditions do not influence these changes. The pattern of Prl secretion during PSP, on the other hand is affected by the lighting conditions.

CIRCA-ANNUAL RHYTHMS OF PROLACTIN SECRETION IN EWES AND THE EFFECT OF PINEALECTOMY

1980 ◽  
Vol 84 (1) ◽  
pp. 83-89 ◽  
Author(s):  
C. J. MUNRO ◽  
K. P. McNATTY ◽  
L. RENSHAW
Keyword(s):  
Plasma Concentration ◽  
Pineal Gland ◽  
Seasonal Variations ◽  
Reproductive Tract ◽  
Plasma Concentrations ◽  
Prolactin Secretion ◽  
Transitional Period ◽  
Short Photoperiod ◽  
Winter Period ◽  
Long Photoperiod

Changes in the plasma concentration of prolactin in intact, pinealectomized, shampinealectomized, ovariectomized and hysterectomized ewes were investigated over a period of 11 months. The concentrations of prolactin were consistently low (<20 ng/ml) during the winter months (short photoperiod) in the intact, sham-pinealectomized, ovariectomized and hysterectomized animals. In contrast, the concentrations of prolactin were consistently raised (> 50 ng/ml) during the summer months (long photoperiod) in the same groups. During the transitional period from winter to summer the concentrations of prolactin were correlated with the reproductive status of the animals. In the pregnant animals, the prolactin concentrations increased from low values during pregnancy to high values at parturition. During lactation, the concentrations of prolactin in these animals remained high, although they were lower than those found subsequently during the summer months when the ewes were no longer lactating. In the non-pregnant ewes (i.e. the ovariectomized and hysterectomized animals), the prolactin concentrations increased more gradually during the transitional period from winter to summer than was the case in the parturient animals. In the pinealectomized ewes, the plasma concentrations of prolactin were raised throughout the year, irrespective of whether the animals were pregnant, lactating or in anoestrus. In these animals, the only occasion when prolactin concentrations were consistently low was during the mid-winter period, although they were also low at times during the period of oestrous activity. It was concluded that the circa-annual pattern of prolactin concentrations in ewes is primarily determined by the photoperiod, and that the pineal gland in the ewe is an important translator of the photoperiod. Parturition and suckling have important, but secondary, influences. Moreover, it was concluded that the secretions from the reproductive tract and the seasonal variations in temperature normally have little influence by themselves on the circa-annual rhythm of prolactin.

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