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Murphy BA. Circadian and Circannual Regulation in the Horse: Internal Timing in an Elite Athlete. J Equine Vet Sci 2019; 76:14-24. [PMID: 31084748 DOI: 10.1016/j.jevs.2019.02.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 02/25/2019] [Indexed: 12/20/2022]
Abstract
Biological rhythms evolved to provide temporal coordination across all tissues and organs and allow synchronization of physiology with predictable environmental cycles. Most important of these are circadian and circannual rhythms, primarily regulated via photoperiod signals from the retina. Understanding the nature of physiological rhythms in horses is crucially important for equine management. Predominantly, they have been removed from exposure to their natural environmental stimuli; the seasonally changing photoperiod, continuous foraging and feeding activity, social herd interactions, and the continuous low-intensity exercise of a grassland dweller. These have been replaced in many cases with confined indoor housing, regimental feeding and exercise times, social isolation, and exposure to lighting that is often erratic and does not come close to mimicking the spectral composition of sunlight. Man has further altered seasonal timing cues through the use of artificial lighting programs that impact reproductive behavior, breeding efficiency, and the development of youngstock. Understanding how these new environmental cues (some stronger and some weaker) impact the internal physiology of the horse in the context of the natural endogenous rhythms that evolved over millennia is key to helping to improve equine health, welfare, and performance, now and into the future. This review provides an overview of the field, highlights the recent discoveries related to biological timing in horses, and discusses the implications that these findings may have for the production and management of the elite equine athlete.
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Affiliation(s)
- Barbara A Murphy
- School of Agriculture and Food Science, University College Dublin, Dublin, Ireland.
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Nolan MB, Walsh CM, Duff N, McCrarren C, Prendergast RL, Murphy BA. Artificially extended photoperiod administered to pre-partum mares via blue light to a single eye: Observations on gestation length, foal birth weight and foal hair coat at birth. Theriogenology 2017; 100:126-133. [PMID: 28708527 DOI: 10.1016/j.theriogenology.2017.06.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 05/19/2017] [Accepted: 06/06/2017] [Indexed: 10/19/2022]
Abstract
In seasonally breeding animals, photoperiod perception is crucial for timing of important physiological events. In the horse, long day photoperiod influences the onset of ovulation and cyclicity, shedding of the heavier winter coat and the timing of parturition. In this compilation of studies, conducted across three breeding seasons and two countries, the impact of artificially extended day length was investigated on gestation length, foal birth weight and foal hair coat at birth. The light therapy was administered to pre-partum mares via mobile head worn masks which provided short wavelength blue light to a single eye. In Study 1, reductions in gestation lengths were observed following administration of artificially extended day length (124.8 ± 15.11 days) in the final months of pregnancy to a group of Thoroughbred mares compared to controls (P < 0.05; 339.7 ± 9.56 days vs 350.6 ± 9.13). Study 2 revealed that pre-partum exposure to artificially extended day length (104.6 ± 9.89 days) increased foal birth weight compared to controls (47.13 ± 2.93 kg vs 43.51 ± 6.14 kg; P < 0.05) in mares bred early in the year. In Study 3, artificially extended day length (87.53 ± 19.6 days) administered to pre-partum mares affected the coat condition of foals at birth with respect to hair weight (P < 0.0001) and hair length (P < 0.0001) compared to controls (0.34 ± 0.20 μg vs 0.59 ± 0.12 μg and 1.93 ± 0.56 cm vs 2.56 ± 0.32 cm, respectively). Collectively, these studies serve to highlight the influential role of the circa-annual changes in photoperiod length on the pre-partum mare for normal foetal development during the natural breeding season. It also emphasizes the potential that exists to improve breeding efficiency parameters by artificially simulating this important environmental cue in the latter stages of gestation against the backdrop of an economically driven early breeding season.
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Affiliation(s)
- Margaret B Nolan
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Caroline M Walsh
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
| | - Noelle Duff
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Conor McCrarren
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland
| | - Ralph L Prendergast
- School of Electrical, Electronic and Mechanical Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Barbara A Murphy
- School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland.
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Relationships between blood hormonal concentrations and secondary fibre shedding in young cashmere-bearing goats at their first moult. ACTA ACUST UNITED AC 2016. [DOI: 10.1017/s1357729800054321] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractThe aim of this study was to evaluate secondary fibre shedding in relation to seasonal hormonal changes in young cashmere-bearing goats reared in southern Italy. We used 14 cashmere-bearing kids, seven males and seven females, of a Scottish breed-population of goats specialized in cashmere production. Monthly, a hair patch of 4 cm2was clipped from both left and right mid sides alternately and cashmere length and its yield were determined. Blood samples were taken every 2 weeks and plasma was assayed for prolactin (PRL), growth hormone (GH), tri-iodothyronine (T3), thyroxine (T4), progesterone and testosterone. With the same frequency, animals were monitored for onset of moult. Our data indicate that in young cashmere goats at their first moult, secondary fibre shedding is a seasonal event that is strictly related to changes in photoperiod and that PRL has a pivotal rôle in regulating this phenomenon. This corresponds with findings in adults. The observation that both thyroid hormones and sex steroids varied seasonally suggests that they are involved in the regulation of the moult cycle, but their precise rôle remains to be elucidated. Our data also indicate that GH seems to be implicated in the control of the moult cycle. The finding that maximal fibre shedding occurred earlier in males than females could be ascribed to differences in GH levels and to the earlier increase in plasma concentration of PRL observed in males.
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Choi D. Potency of melatonin in living beings. Dev Reprod 2013; 17:149-77. [PMID: 25949131 PMCID: PMC4282293 DOI: 10.12717/dr.2013.17.3.149] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Revised: 08/01/2013] [Accepted: 08/03/2013] [Indexed: 01/20/2023]
Abstract
Living beings are surrounded by various changes exhibiting periodical rhythms in environment. The environmental changes are imprinted in organisms in various pattern. The phenomena are believed to match the external signal with organisms in order to increase their survival rate. The signals are categorized into circadian, seasonal, and annual cycles. Among the cycles, the circadian rhythm is regarded as the most important factor because its periodicity is in harmony with the levels of melatonin secreted from pineal gland. Melatonin is produced by the absence of light and its presence displays darkness. Melatonin plays various roles in creatures. Therefore, this review is to introduce the diverse potential ability of melatonin in manifold aspects in living organism.
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Affiliation(s)
- Donchan Choi
- Department of Life Science, College of Environmental Sciences, Yong-In University, Yongin 449-714, Republic of Korea
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Kobayashi H, Kromminga A, Dunlop TW, Tychsen B, Conrad F, Suzuki N, Memezawa A, Bettermann A, Aiba S, Carlberg C, Paus R. A role of melatonin in neuroectodermal-mesodermal interactions: the hair follicle synthesizes melatonin and expresses functional melatonin receptors. FASEB J 2005; 19:1710-2. [PMID: 16030176 DOI: 10.1096/fj.04-2293fje] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Since mammalian skin expresses the enzymatic apparatus for melatonin synthesis, it may be an extrapineal site of melatonin synthesis. However, evidence is still lacking that this is really the case in situ. Here, we demonstrate melatonin-like immunoreactivity (IR) in the outer root sheath (ORS) of mouse and human hair follicles (HFs), which corresponds to melatonin, as shown by radioimmunoassay and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The melatonin concentration in organ-cultured mouse skin, mouse vibrissae follicles, and human scalp HFs far exceeds the respective melatonin serum level and is significantly increased ex vivo by stimulation with norepinephrine (NE), the key stimulus for pineal melatonin synthesis. By real-time PCR, transcripts for the melatonin membrane receptor MT2 and for the nuclear mediator of melatonin signaling, retinoid orphan receptor alpha (ROR)alpha, are detectable in murine back skin. Transcript levels for these receptors fluctuate in a hair cycle-dependent manner, and are maximal during apoptosis-driven HF regression (catagen). Melatonin may play a role in hair cycle regulation, since its receptors (MT2 and RORalpha) are expressed in murine skin in a hair cycle-dependent manner, and because it inhibits keratinocyte apoptosis and down-regulates ERalpha expression. Therefore, the HF is both, a prominent extrapineal melatonin source, and an important peripheral melatonin target tissue. Regulated intrafollicular melatonin synthesis and signaling may play a previously unrecognized role in the endogenous controls of hair growth, for example, by modulating keratinocyte apoptosis during catagen and by desensitizing the HF to estrogen signaling. As a prototypic neuroectodermal-mesodermal interaction model, the HF can be exploited for dissecting the obscure role of melatonin in such interactions in peripheral tissues.
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Affiliation(s)
- Hiromi Kobayashi
- Department of Dermatology, University Hospital Schleswig-Holstein, Campus Lübeck, University of Lübeck, Lübeck, Germany
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Wu P, Hou L, Plikus M, Hughes M, Scehnet J, Suksaweang S, Widelitz RB, Jiang TX, Chuong CM. Evo-Devo of amniote integuments and appendages. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2004; 48:249-70. [PMID: 15272390 PMCID: PMC4386668 DOI: 10.1387/ijdb.041825pw] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
Abstract
Integuments form the boundary between an organism and the environment. The evolution of novel developmental mechanisms in integuments and appendages allows animals to live in diverse ecological environments. Here we focus on amniotes. The major achievement for reptile skin is an adaptation to the land with the formation of a successful barrier. The stratum corneum enables this barrier to prevent water loss from the skin and allowed amphibian / reptile ancestors to go onto the land. Overlapping scales and production of beta-keratins provide strong protection. Epidermal invagination led to the formation of avian feather and mammalian hair follicles in the dermis. Both adopted a proximal - distal growth mode which maintains endothermy. Feathers form hierarchical branches which produce the vane that makes flight possible. Recent discoveries of feathered dinosaurs in China inspire new thinking on the origin of feathers. In the laboratory, epithelial - mesenchymal recombinations and molecular mis-expressions were carried out to test the plasticity of epithelial organ formation. We review the work on the transformation of scales into feathers, conversion between barbs and rachis and the production of "chicken teeth". In mammals, tilting the balance of the BMP pathway in K14 noggin transgenic mice alters the number, size and phenotypes of different ectodermal organs, making investigators rethink the distinction between morpho-regulation and pathological changes. Models on the evolution of feathers and hairs from reptile integuments are discussed. A hypothetical Evo-Devo space where diverse integument appendages can be placed according to complex phenotypes and novel developmental mechanisms is presented.
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Affiliation(s)
- Ping Wu
- Department of Pathology, University of Southern California, Los Angeles
| | - Lianhai Hou
- Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing
| | - Maksim Plikus
- Department of Pathology, University of Southern California, Los Angeles
| | - Michael Hughes
- Department of Pathology, University of Southern California, Los Angeles
| | - Jeffrey Scehnet
- Department of Pathology, University of Southern California, Los Angeles
| | - Sanong Suksaweang
- Department of Pathology, University of Southern California, Los Angeles
| | | | - Ting-Xin Jiang
- Department of Pathology, University of Southern California, Los Angeles
| | - Cheng-Ming Chuong
- Department of Pathology, University of Southern California, Los Angeles
- Corresponding author: Cheng-Ming Chuong, HMR 315B, Department of Pathology, Keck School of Medicine, University of Southern California, 2011 Zonal Avenue, Los Angeles, CA USA 90033, Tel: 323 442-1296, Fax: 323 442-3049,
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Frank LA, Hnilica KA, Oliver JW. Adrenal steroid hormone concentrations in dogs with hair cycle arrest (Alopecia X) before and during treatment with melatonin and mitotane. Vet Dermatol 2004; 15:278-84. [PMID: 15500479 DOI: 10.1111/j.1365-3164.2004.00372.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The purpose of the study was to evaluate intermediate adrenal steroid hormones (ISH) in neutered dogs with hair cycle arrest (Alopecia X) during treatment with melatonin, and to see if hair re-growth is associated with sex hormone concentrations within the normal ranges. Twenty-nine neutered, euthyroid, and normo-cortisolemic dogs were enrolled in the study (23 Pomeranians, three keeshonds, two miniature poodles, and one Siberian husky). Coat assessment and an ACTH stimulation test were performed pre-treatment and approximately every 4 months for a year post treatment. Melatonin was administered initially at 3-6 mg, every 12 h. Based on clinical progression, each dog was continued on the current dose of melatonin, given an increased dose of melatonin or changed to mitotane. Partial to complete hair re-growth occurred in 14/23 Pomeranians, and partial re-growth in 3/3 keeshond and 1/2 poodle dogs. A Siberian husky dog failed to re-grow hair. Fifteen dogs had partial hair re-growth at the first re-evaluation. Melatonin dosage was increased in eight dogs but only one had improved hair re-growth. On mitotane treatment, partial to complete hair re-growth was seen in 4/6 dogs and no re-growth in 2/6 dogs. No significant decrease in sex hormone concentrations were seen during melatonin or mitotane treatment. Concentrations of ISH in dogs with hair re-growth did not differ significantly from pre-treatment values. At the completion of the study, androstenedione, progesterone and 17-hydroxyprogesterone were still above reference ranges in 21, 64 and 36%, respectively, of dogs with partial to complete hair re-growth. In conclusion, 62% of dogs had partial to complete hair re-growth. However, not all dogs with hair re-growth had concentrations of ISH within the normal range.
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Affiliation(s)
- Linda A Frank
- Department of Small animal Clinical Sciences, University of Tennessee, C247 Veterinary Teaching Hospital, Knoxville, TN 37996-4544, USA.
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Abstract
A review of major studies of tetrapod skin development since the 1870s illustrates how knowledge of structure and mechanism progressed through phases emphasizing Natural History, morphology, endocrinology, and tissue manipulation prior to the prevailing "molecular era." Each successive phase of investigation, while suffering from its own limitations and constraints, has produced conceptual advances. At various times, different systems in various organisms have been research models of choice for practical and/or technical reasons. Comparative studies of scaled and non-scaled integuments and appendages thereof, e.g., nails, claws, glands, hair, and especially feathers, revealed data that suggested new directions for research programs. Some non-mammalian models still offer unique opportunities for pursuit of specific questions pertinent to studies of hair: arguments between American and British schools concerning feather development that originated in the 1930s remain unresolved and may thus affect interpretation of recent investigations. The current emphasis on the study of diffusible molecules involved in papilla-follicle interactions in hair development and replacement can only be understood in the context of the interwoven history of questions relating sequentially to evolutionary homology, physiological controls of tissue homeostasis, embryonic induction, and, most recently, molecular genetics.
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Affiliation(s)
- Paul F A Maderson
- Biology Department, Brooklyn College of CUNY, Brooklyn, NY 11210, USA.
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