Effect of constant-release melatonin implants and prolonged exposure to a long day photoperiod on prolactin secretion and hair growth in mouflon (Ovis gmelini musimon)

Prolactin: A Mammalian Stress Hormone and Its Role in Cutaneous Pathophysiology

The hormone prolactin (PRL) is best recognised for its indispensable role in mammalian biology, specifically the regulation of lactation. Bearing in mind that the mammary gland is a modified sweat gland, it is perhaps unsurprising to discover that PRL also plays a significant role in cutaneous biology and is implicated in the pathogenesis of a range of skin diseases, often those reportedly triggered and/or exacerbated by psychological stress. Given that PRL has been implicated in over 300 biological processes, spanning reproduction and hair growth and thermo- to immunoregulation, a comprehensive understanding of the relationship between PRL and the skin remains frustratingly elusive. In an historical curiosity, the first hint that PRL could affect skin biology came from the observation of seborrhoea in patients with post-encephalitic Parkinsonism as a result of another global pandemic, encephalitis lethargica, at the beginning of the last century. As PRL is now being postulated as a potential immunomodulator for COVID-19 infection, it is perhaps timeous to re-examine this pluripotent hormone with cytokine-like properties in the cutaneous context, drawing together our understanding of the role of PRL in skin disease to illustrate how targeting PRL-mediated signalling may represent a novel strategy to treat a range of skin diseases and hair disorders.

Polymorphism of the MTNR1A Melatonin Receptor Gene in Goat Breeds of Northern Italy

Melatonin receptor MT1, encoded by the MTNR1A gene, is the main one involved in the seasonal regulation of reproductive activity. A correlation between this gene polymorphism and reproductive performance has been demonstrated in sheep. To date, no data about MTNR1A gene polymorphism are available regarding Italian goat breeds other than the Sarda goat. This study aimed to detect any PCR-RFLP polymorphic sites of MTNR1A using MnlI and RsaI enzymes in Northern Italian goat breeds, which are characterized by a pronounced reproductive seasonality. One-hundred-eight adult female goats belonging to four different breeds were included in the study (i.e., Frisa Valtellinese, n = 29; Orobica, n = 23; Lariana, n = 29; Camosciata delle Alpi, n = 27). Blood was sampled from each goat. Genomic DNA was extracted from each sample and the main part of exon II of MTNR1A gene was amplified by PCR and digested with MnlI and RsaI enzymes. Unexpectedly, none of the fragments were found to be polymorphic. The absence of polymorphism may be linked to the macro group of goat breeds that evolved during human migrations. Breeds of the Alpine-European strain would appear to show no polymorphism, as confirmed by our study, whereas breeds belonging to the Mediterranean-African or Asian-Middle Eastern strains do.

Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid

Noninflammatory alopecia is common in dogs and is a frequent cause to consult a veterinarian. It is also a common reason to take biopsies. Noninflammatory alopecia can be attributed to a decreased formation or cytodifferentiation of the hair follicle or the hair shaft in utero, resulting in congenital alopecia. Congenital alopecia often has a hereditary cause, and examples of such disorders are ectodermal dysplasias associated with gene variants of the ectodysplasin A gene. Noninflammatory alopecia may also be caused by impaired postnatal regeneration of hair follicles or shafts. Such disorders may have a clear breed predilection, and alopecia starts early in life. A hereditary background is suspected in those cases but has not been proven. They are referred to as follicular dysplasia although some of these disorders present histologically like a hair cycle disturbance. Late-onset alopecia is usually acquired and may be associated with endocrinopathies. Other possible causes are impaired vascular perfusion or stress. As the hair follicle has limited possible responses to altered regulation, and histopathology may change during the course of a disease, a detailed clinical history, thorough clinical examination including blood work, appropriate biopsy site selection, and detailed histological findings need to be combined to achieve a final diagnosis. This review aims to provide an overview about the known noninflammatory alopecic disorders in dogs. As the pathogenesis of most disorders is unknown, some statements are based on comparative aspects or reflect the authors' opinion.

Melatonin in Health and Disease: A Perspective for Livestock Production

Mounting evidence in the literature indicates an important role of endogenous and exogenous melatonin in driving physiological and molecular adaptations in livestock. Melatonin has been extensively studied in seasonally polyestrous animals whereby supplementation studies have been used to adjust circannual rhythms in herds of animals under abnormal photoperiodic conditions. Livestock undergo multiple metabolic and physiological adaptation processes throughout their production cycle which can result in decreased immune response leading to chronic illness, weight loss, or decreased production efficiency; however, melatonin’s antioxidant capacity and immunostimulatory properties could alleviate these effects. The cardiovascular system responds to melatonin and depending on receptor type and localization, melatonin can vasodilate or vasoconstrict several systemic arteries, thereby controlling whole animal nutrient partitioning via vascular resistance. Increased incidences of non-communicable diseases in populations exposed to circadian disruption have uncovered novel pathways of neurohormones, such as melatonin, influence health, and disease. Perturbations in immune function can negatively impact the growth and development of livestock which has been examined following melatonin supplementation. Specifically, melatonin can influence nutrient uptake, circulating nutrient profiles, and endocrine profiles controlling economically important livestock growth and development. This review focuses on the physiological, cellular, and molecular implications of melatonin on the health and disease of domesticated food animals.

Temporal and seasonal changes in mercury accumulation in Tatra chamois from West Carpathians

The main aim of this study was to determine the concentration of total mercury (T-Hg) in different tissues, hair, and faeces from a long-lived animal that actively lives in the subalpine and alpine zone within temperate climate zone throughout the year. Levels of T-Hg in samples from naturally deceased Tatra chamois (n = 72) from the Tatra Mountains (Slovakia) were determined using direct mercury analyses on the basis of dry weight. The mercury concentrations in hair samples were compared over the last three decades. Seasonal changes in mercury concentration and differences in the amounts of mercury in various tissues, hairs, and faeces between age and sex groups were also studied. The highest mercury concentrations in organs were found in the kidneys of Tatra chamois, with mean values of 0.45 ± 0.07 μg/g (dry weight) for adults (n = 18) and 0.39 ± 0.12 μg/g (dry weight) for juveniles (n = 6). These values are considerably high compared to expected Hg levels in wild ungulates from foothill and mountain areas in the temperate zone. Juveniles had higher levels of T-Hg in their muscles (0.011 ± 0.001 μg/g dry weight, n = 10) and faeces (0.189 ± 0.025 μg/g dry weight, n = 7) when compared to adults that had 0.007 ± 0.001 μg/g dry weight of T-Hg in muscles (n = 29) and 0.113 ± 0.015 μg/g dry of T-Hg weight in faeces (n = 19). T-Hg concentrations in individual tissues (heart, kidney, liver, lungs, spleen, tongue, muscle, bone), hairs, and faeces were not significantly different between males and females. Mercury levels in the hair of Tatra chamois have increased significantly since the 1990s (median value of T-Hg: 0.025 μg/g dry weight) with the highest values presenting during the 2000s (0.029 μg/g dry weight). Since 2010 (0.016 μg/g dry weight), levels have declined when compared to those observed during the 1990s and 2000s. Therefore, we can conclude that T-Hg deposition in alpine areas of the Tatra Mountains shows a declining trend since the 2010s. T-Hg concentrations in the heart, muscle, and hair were higher in summer compared to winter. Seasonal changes in mercury concentrations are likely most related to the seasonal availability of food, but may also be related to moulting periods, and this correlation must be explored further.

Expression of lipid-protein gene PLP2 in Liaoning cashmere goat

The relationship between PLP2 gene and cashmere fiber quality of Liaoning cashmere goat was investigated. The sheep fibroblast cells were treated with exogenous cytokines and melatonin, independently, and RNA interference, RT-PCR and in situ hybridization were utilized for investigating the PLP2 gene regulation mechanism underlying the Liaoning cashmere growth. The results showed that the expression of PLP2 gene in the prosperous and degenerative stage is higher than that of the primary follicle, indicating that the PLP2 gene promotes the secondary follicle, wherein the gene is expressed only in the inner root sheath, suggesting its correlation to hair loss. The results of RT-PCR showed that the trend of FGF5 expression in PLP2 gene was positively regulated. The influence of MT on the expression of PLP2 gene was negatively regulated, and the inhibition was gradually enhanced with the passage of time. Studies have confirmed that the Noggin gene is an inhibitor of the BMP signaling pathway. After the noggin gene interferes with the lentivirus infection, the expression of the PLP2 gene is downregulated. Therefore, the PLP2 gene, along with the other suppressor genes including the noggin gene, might affect the development of hair follicles by inhibiting the BMP（Bone morphogenetic proteins）pathway.

Long noncoding RNA and gene expression analysis of melatonin-exposed Liaoning cashmere goat fibroblasts indicating cashmere growth

Cashmere produced from Liaoning cashmere goat is highly valuable. Melatonin is an important factor affecting cashmere growth and can regulate the growth cycle via effects on gene expression. Long noncoding RNAs (lncRNAs) regulate gene expression, but detailed studies of their effect on hair growth are lacking. To explore how lncRNA mediates the effects of melatonin on cashmere growth, we used RNA-Seq including a control condition (C) and three melatonin treatments (1.0 g/L 24 h (M1_24H), 0.2 g/L 24 h (M2_24H), 0.2 g/L 72 h (M2_72H)). M1_24H, M2_24H, and M2_72H had 32, 10, and 113 differentially expressed lncRNAs, respectively. Gene ontology (GO) and pathway analyses results showed that melatonin was most beneficial to cashmere growth at 0.2 g/L 72 h, and nuclear factor (NF)-κB signaling corresponding to an effect of LncRNA MTC was involved in hair follicle development. We found that melatonin upregulated XLOC_005914 lncRNA (LncRNA MTC). Proliferation increased in the 0.2 g/L 72 h condition and cells with high LncRNA MTC expression, but it was reduced in fibroblasts with knocked down LncRNA MTC expression. This is the first report that LncRNA MTC promotes fibroblast proliferation and regulates hair follicle development and cashmere growth by activating NF-κB signaling.

Effect of Melatonin Implants during the Non-Breeding Season on the Onset of Ovarian Activity and the Plasma Prolactin in Dromedary Camel

To examine a possible control of reproductive seasonality by melatonin, continual-release subcutaneous melatonin implants were inserted 4.5 months before the natural breeding season (October-April) into female camels (Melatonin-treated group). The animals were exposed to an artificial long photoperiod (16L:8D) for 41 days prior to implant placement to facilitate receptivity to the short-day signal that is expected with melatonin implants. The treated and control groups (untreated females) were maintained separately under outdoor natural conditions. Ovarian follicular development was monitored in both groups by transrectal ultrasonography and by plasma estradiol-17β concentrations performed weekly for 8 weeks and then for 14 weeks following implant insertion. Plasma prolactin concentrations were determined at 45 and 15 days before and 0, 14, 28, 56, and 98 days after implant insertion. Plasma melatonin concentration was determined to validate response to the artificial long photoperiod and to verify the pattern of release from the implants. Results showed that the artificial long photoperiod induced a melatonin secretion peak of significantly (P < 0.05) shorter duration (about 2.5 h). Melatonin release from the implants resulted in higher circulating plasma melatonin levels during daytime and nighttime which persisted for more than 12 weeks following implants insertion. Treatment with melatonin implants advanced the onset of follicular growth activity by 3.5 months compared to untreated animals. Plasma estradiol-17β increased gradually from the second week after the beginning of treatment to reach significantly (P < 0.01) higher concentrations (39.2 ± 6.2 to 46.4 ± 4.5 pg/ml) between the third and the fifth week post insertion of melatonin implants. Treatment with melatonin implants also induced a moderate, but significant (P < 0.05) suppressive effect on plasma prolactin concentration on the 28th day. These results demonstrate that photoperiod appears to be involved in dromedary reproductive seasonality. Melatonin implants may be a useful tool to manipulate seasonality and to improve reproductive performance in this species. Administration of subcutaneous melatonin implants during the transition period to the breeding season following an artificial signal of long photoperiod have the potential to advance the breeding season in camels by about 2.5 months.

Genetic variability of myostatin and prolactin genes in popular goat breeds in Egypt

The genetic polymorphisms of two functional genes named: myostatin (MSTN) and prolactin (PRL) were investigated in three goat breeds (Barki, Damascus and Zaraibi) using Sanger nucleotide sequence and restriction fragment length polymorphism (RFLP) methods, in order to differentiate between these breeds. Nucleotide sequencing of 337 bp MSTN gene detected five SNPs in Barki breed, two SNPs in Damascus breed, while the Zaraibi breed did not show any SNPs. Moreover, MSTN-HaeIII/PCR-RFLP gave a single Genotype BB was found in all the studied breeds. Meanwhile, Nucleotide sequencing of 196 bp PRL gene showed two SNPs in Damascus breed, one SNPs in Zaraibi breed, while the Barki breed did not show any SNPs. Moreover, PRL-Eco24I/PCR-RFLP showed three genotypes (AA, AB and BB). The genotype AB showed the maximum frequency in all the studied breeds (0.75, 0.85, and 0.90 for Damascus, Barki and Zaraibi breeds, respectively). Observed heterozygosity (Ho) value was higher than expected heterozygosity (He) value all studied breeds. In addition, the values of both Ho and He were the highest in Zaraibi breed (0.90 and 0.51 respectively). Chi-square (χ²) value revealed a significant variation Hardy-Weinberg equilibrium (P < .05) in the three studied breeds. It is the highest in Zaraibi goats and lowest in Damascus breed. The results demonstrated that the PRL-Eco24I/PCR-RFLP polymorphism may be utilized as effective marker for genetic differentiation between goat breeds, but MSTN-HaeIII/PCR-RFLP revealed no polymorphism or variation, thus it is not recommended in the selection program. Moreover, these results open up interesting prospects for future selection programs, especially marker assisted selection. In addition, the results established that PCR-RFLP method is a suitable tool for calculating genetic variability.

Effects of melatonin implantation on cashmere growth, hormone concentrations and cashmere yield in cashmere-perennial-type Liaoning cashmere goats

The aim of the present study was to investigate the effects of melatonin implants on cashmere growth, the concentrations of plasma melatonin and prolactin and the total cashmere yield in cashmere-perennial-type Liaoning cashmere goats. Twenty female goats were assigned to two treatments (n = 10) including a control and a treatment in which melatonin (2 mg/kg bodyweight) was implanted in March and May, respectively. The experiment lasted for 153 days. Fibre samples were collected in July, August and April the following year (before cashmere harvest). Blood samples were taken monthly from March to August. Cashmere yield was recorded after harvest. In melatonin-treated goats, cashmere length and cashmere growth rate from April to July were significantly increased (P < 0.05), but no influence was observed (P > 0.05) in August. Implantation of melatonin significantly increased plasma melatonin concentrations (P < 0.05) and decreased prolactin concentrations from April to July compared with the control group (P < 0.05), but no difference was observed in August (P > 0.05). Administration of melatonin increased the cashmere yield by 6.2% and the maximum cashmere length by 8.4%, but the differences were not significant (P > 0.05). Moreover, the cashmere fibre diameter was not influenced by melatonin implantation (P > 0.05). The results also indicated that plasma melatonin concentrations were correlated with plasma prolactin in the regulation of cashmere growth. Implantation of melatonin was an effective way to promote cashmere growth, and administration during the cashmere slow-growing period improved cashmere production without changing cashmere fibre diameter in cashmere-perennial-type Liaoning cashmere goats.

Melatonin and cashmere growth in Inner Mongolian cashmere goats

The aim of the study was to investigate the effects of melatonin implants on cashmere growth and productive performance of cashmere goats. A total of thirty female goats were assigned to one of three treatments (n = 10), including control and two treatments where melatonin [2 mg kg−1 body weight (BW)] was implanted either in April and June or in June. Compared with the control, implantation in April and June increased cashmere yield and maximum cashmere length by 20.3% and 15.7%, respectively (P < 0.01), with an average initiation date of 22 May 2013 and cessation date of 26 Mar. 2014. In contrast, no cashmere growth was observed in control goats until 19 June 2013 and the growth ceased on 3 Apr. 2014. Melatonin only implanted in June had no effect on cashmere yield and maximum cashmere length, with an average initiation date of 5 June 2013 and cessation date of 27 Mar. 2014. Cashmere growth rate, cashmere fiber diameter, the final BW, and average daily gain were not influenced by melatonin implantation. Results suggested that melatonin implantation during the cashmere nongrowing period is an effective way to stimulate cashmere growth and extend the cashmere growth phase with April and June identified as the most appropriate time for implantation.

Alternative methods for feline fertility control: Use of melatonin to suppress reproduction

PRACTICAL RELEVANCE

Reversible contraceptives are highly desired by purebred cat breeders for managing estrous cycles and by scientists managing assisted reproduction programs. A variety of alternative medicine approaches have been explored as methods to control feline fertility.

SCOPE

In the field of veterinary homeopathy, wild carrot seed and papaya have been used for centuries. Both appear to be safe, but their efficacy as feline contraceptives remains anecdotal. In contrast, the use of melatonin in cats has been investigated in a number of studies, findings from which are reviewed in this article.

RATIONALE

Cats are seasonally polyestrous (they cycle several times during their breeding season) and are described as long-day breeders because endogenous melatonin negatively regulates estrous cyclicity. Exogenous melatonin administered parenterally also suppresses ovarian activity in cats, and long-term oral or subcutaneous melatonin administration is safe.

CHALLENGES

The therapeutic use of melatonin is limited by its short biological half-life (15-20 mins), its poor oral bioavailability and its central effects in reducing wakefulness. Research is required to determine whether higher doses, longer-release formulations, repeated administration or combination implants might overcome these limitations.

Photoperiod and melatonin treatments for controlling sperm parameters, testicular and accessory sex glands size in male Iberian ibex: A model for captive mountain ruminants

This study examines whether photoperiod and/or melatonin treatments can improve sperm variables outside the breeding season in the Iberian ibex-a model species for wild mountain ruminants-thus helping in the collection of high quality sperm beyond the normal breeding season for depositing in genetic resource banks. Adult Iberian ibex males (n=17) were divided into four treatment groups: (1) controls under the natural photoperiod (control group; n=4), (2) treatment with melatonin implants on December 22nd, February 22nd and April 22nd (group WS-M; n=5), (3) treatment with short photoperiod cycles, i.e., 2 months of long days followed by melatonin implants (to emulate 2 months of short days) throughout the year (group PHPld+M; n=4), and (4) treatment with melatonin implants on June 22nd and August 22nd (group SS-M; n=4). The interaction treatment x season had a strong influence on testis size (P<0.05), the size of the seminal vesicles (P<0.001), the percentage of abnormal sperms (P<0.05), and percentage non-progressive (P<0.05) and progressive (P<0.001) sperm motility. In groups WS-M and PHPld+M, the normal springtime physiological reductions in testis size, non-progressive sperm motility and acrosome integrity were prevented. The values for the studied sperm variables were, however, reduced in the natural breeding season at the end of the experimental period in group PHPld+M, although not in group WS-M. The pattern of melatonin administration in group SS-M conferred no advantages on reproductive functionality. These results suggest that lengthening the short day period after the winter solstice (the WS-M treatment) extends reproductive activity in this species, allowing good quality sperm to be recovered for conservation purposes during the non-breeding season.

Effects of tryptophan supplementation on cashmere fiber characteristics, serum tryptophan, and related hormone concentrations in cashmere goats

This study was designed to investigate the effects of tryptophan (Trp) supplementation on cashmere fiber characteristics and on serum Trp, melatonin (MEL), prolactin (PRL), insulin-like growth factor 1 (IGF-1), triiodothyronine (T3), and thyroxine (T4) concentrations in cashmere goats during the cashmere fast-growth period. Thirty-six Liaoning cashmere wether goats were stratified on the basis of body weight (28±0.8 kg) and assigned randomly to 1 of the following 4 rumen-protected Trp treatments: 0, 2.0, 4.0, and 6.0 g per goat per day. The experimental period lasted 137 d. Blood samples were collected monthly during the daytime (8:00 AM) and at night (8:00 PM). Tryptophan supplementation improved cashmere growth rates, cashmere weight, and body weight (P=0.001) and increased serum Trp levels, nighttime MEL concentrations, IGF-1, and T3 and T4 concentrations (P<0.05). Across the treatments and sampling months, a highly positive correlation between cashmere growth rate and nighttime serum MEL concentrations was observed (r=0.879, P=0.001). A moderately negative correlation between cashmere growth rates and serum PRL concentrations during the day and at night (rday=-0.645, P=0.007; rnight=-0.583, P=0.018) was observed. A moderately positive correlation between the cashmere growth rate and the daytime serum IGF-1 concentration (r=0.536, P=0.032) was observed, and no correlation was found between the cashmere growth rate and the other serum hormone concentrations. These data indicate that changes in serum concentrations of MEL, IGF-1, and PRL are related to cashmere growth in Liaoning cashmere goats during the cashmere fast-growth period. Under the experimental conditions of the current trial, we suggest that Trp may promote cashmere growth by increasing daytime IGF-1 and nighttime MEL secretion.

Identification of SNPs within the sheep PROP1 gene and their effects on wool traits

Regarding mutations of PROP1 (Prophet of POU1F1) gene significantly associating with combined pituitary hormone deficiency (CPHD) in human patients and animals, PROP1 gene is a novel important candidate gene for detecting genetic variation and growth, reproduction, metabolism traits selection and breeding. The aim of this study was to detect PROP1 gene mutation of the exon 1-3 and its association with wool traits in 345 Chinese Merino sheep. In this study, on the basis of PCR-SSCP and DNA sequencing methods, ten novel SNPs within the sheep PROP1 gene, namely, AY533708: g.45A>G resulting in Glu15Glu, g.1198A>G, g.1341G>C resulting in Arg63Ser, g.1389G>A resulting in Ala79Ala, g.1402C>T resulting in Leu84Leu, g.1424A>G resulting in Asn91Ser, g.1522C>T, g.1556A>T, g.1574T>C, g.2430C>G were reported. In addition, association analysis showed that three genotypes of P4 fragment were significantly associated with fiber diameter in the analyzed population (P=0.044). These results strongly suggested that polymorphisms of the PROP1 gene could be a useful molecular marker for sheep breeding and genetics through marker-assisted selection (MAS).

Novel SNP of the goat prolactin gene (PRL) associated with cashmere traits

Concentrations of the single-chain polypeptide hormone prolactin (PRL) are associated with wool or cashmere traits, and its seasonal changes may determine patterns of enzymatic activity and may affect cashmere fibre growth and moult. So, the PRL gene is a potential candidate gene for cashmere traits in marker-assisted selection (MAS). In this paper, we report a novel missense single-nucleotide polymorphism (SNP) within the goat PRL gene in 1367 individuals by PCR-SSCP (polymerase chain reaction with single-strand conformation polymorphism) analysis and DNA sequencing. The novel X76049:g.576C>A mutation is confirmed by Eco24I PCR-RFLP (restriction fragment length polymorphism) analysis and causes a missense codon (Pro176Thr). The frequencies of allele C varied from 0.79 to 0.93 in 9 analysed goat populations. C allele was correlated with higher fibre length (P=0.014).

Suppression of estrus in cats with melatonin implants

The objective of this study was to assess the efficacy of a subcutaneous melatonin implant to suppress estrus in queens (felis catus). The hypothesis was that this implant would temporarily and reversibly suppress estrus in queens without producing any clinically detectable side effects. Fourteen adult queens were maintained in cages under artificial illumination (14h light:10h dark) for 45 d and then randomly assigned to one of two treatments. At interestrus, queens received a single subcutaneous melatonin implant (18mg; Melovine [CEVA Sante Animal, Libourne, France]; MEL: n=9), or a single subcutaneous placebo implant without melatonin (0mg; PLA; n=5). At the next estrus, all queens received a second MEL (n=9) or PLA (n=5) implant. Blood samples were taken when queens displayed estrous signs and during interestrus to measure estradiol (E(2)) and progesterone (P(4)), respectively, by radioimmunoassay. There were no significant differences in duration of the interestrus interval in PLA cats, regardless of whether the implants were placed during interestrus or estrus (6.0+/-9.7 d vs. 6.0+/-9.7 d, respectively; least square means [LSM]+/-SEM). However, when MEL implants were placed during interestrus, the duration of interestrus was approximately twice as long as that occurring when MEL implants were placed during estrus (113.3+/-6.1 d vs. 61.1+/-6.8 d, respectively; P<0.01). Serum E(2) and P(4) concentrations were similar in queens with PLA and MEL implants and in queens that received implants in estrus and interestrus. In conclusion, a subcutaneous MEL implant effectively and reversibly suppressed estrus in queens for approximately 2 to 4 mo with no clinically detectable side effects.

Androgens and hair growth

Hair's importance in human communication means that abnormalities like excess hair in hirsutism or hair loss in alopecia cause psychological distress. Androgens are the main regulator of human hair follicles, changing small vellus follicles producing tiny, virtually invisible hairs into larger intermediate and terminal follicles making bigger, pigmented hairs. The response to androgens varies with the body site as it is specific to the hair follicle itself. Normally around puberty, androgens stimulate axillary and pubic hair in both sexes, plus the beard, etc. in men, while later they may also inhibit scalp hair growth causing androgenetic alopecia. Androgens act within the follicle to alter the mesenchyme-epithelial cell interactions, changing the length of time the hair is growing, the dermal papilla size and dermal papilla cell, keratinocyte and melanocyte activity. Greater understanding of the mechanisms of androgen action in follicles should improve therapies for poorly controlled hair disorders like hirsutism and alopecia.

A PstI polymorphism at 3'UTR of goat POU1F1 gene and its effect on cashmere production

POU1F1 is a positive regulator for prolactin (PRL) whose metabolites may directly or indirectly affect some aspects of the hair growth cycle, therefore, POU1F1 gene is an important candidate gene for cashmere traits selection through marker-assisted selection (MAS). Hence, in this study, the PCR-RFLP method was applied to detect a T>C transition determining a PstI polymorphism at the 3'UTR of POU1F1 locus and evaluate its associations with cashmere traits in 847 Inner Mongolia White Cashmere goats. In the analyzed population, the allelic frequencies for the T and C alleles are 0.959 and 0.041, respectively and the genotypic frequencies are in Hardy-Weinberg equilibrium (P > 0.05). Moreover, significant statistical relationships between the PstI polymorphism of POU1F1 gene and goat cashmere yields were found (*P < 0.05). When compared with TC genotype, TT genotype was associated with superior cashmere yields in 2, 4, and 5 years old individuals, as well as with average cashmere yield. Hence, TT genotype is suggested to be a molecular marker for senior cashmere yield.

Horn growth related to testosterone secretion in two wild Mediterranean ruminant species: The Spanish ibex (Capra pyrenaica hispanica) and European mouflon (Ovis orientalis musimon)

Seasonal variations in the horn development and testicular activity of the Spanish ibex (Capra pyrenaica hispanica) (n=6) and European mouflon (Ovis orientalis musimon) (n=5) were monitored to determine the role of increasing testosterone concentration on the arrest of horn growth during the rutting season. Marked seasonal variations in the rate of horn growth (P<0.01) and testicular activity (P<0.001) were seen in both species, although the magnitude and timing of these changes were different (P<0.01). Horn growth rate was inversely correlated to seasonal levels in testosterone plasma concentration in both species (ibex: R=-0.45, P<0.01; mouflon R=-0.51, P<0.01). In the mouflon, the increase in plasma testosterone concentration recorded in September (P<0.05 compared with the lowest concentration) coincided with a significant reduction in horn growth (P<0.05). In the ibex, the increase in plasma testosterone concentration in October (P<0.05 compared with the lowest concentration) was associated with a significant arrest of horn growth in November (P<0.05). These results appear to support the hypothesis that high peripheral plasma levels of testosterone are linked with the seasonal arrest of horn growth during the rutting period.

Melatonin-improved reproductive performance in sheep bred out of season

The effects of melatonin implants on out-of-season breeding in New Zealand Romney composite ewes, was determined by comparison of reproductive performance in ewes treated with progesterone+equine chorionic gonadotrophin (eCG) (control; n=107), melatonin+progesterone+eCG (n=97) or melatonin+progesterone (n=96). Conception rates in melatonin+progesterone+eCG-treated ewes (67%) were higher than in the control ewes (P<0.01; 47%). Pregnancy rates were higher in melatonin+progesterone+eCG-treated ewes (55%; P<0.001) compared with the control ewes (40%). Fewer melatonin+progesterone-treated ewes displayed oestrus (14%; P<0.001) and subsequently became pregnant (6%). Oestrus rates in melatonin+progesterone-treated ewes (14%) were lower than both the melatonin+progesterone+eCG-treated (82%) and control ewes (86%; P<0.001), which were similar to each other. The number of foetuses per pregnant ewe was similar in all three treatment groups. Serum melatonin concentrations at Day -9 were higher in the ewes treated with melatonin and there was a large variation between individual ewes, but concentrations were similar for pregnant and nonpregnant ewes. The combination of higher conception rate and the trend for more lambs per pregnant ewes resulted in more lambs being born per ewe treated in melatonin+progesterone+eCG-treated ewes compared to the other two treatment groups. These results suggest that melatonin implants, in conjunction with administration of progesterone and eCG, may be suitable as a means of increasing the number of lambs born per ewe treated in an out-of-season breeding program in New Zealand sheep flocks while melatonin and progesterone is not.

Hormonal regulation of hair follicles exhibits a biological paradox

Hair's importance for insulation and camouflage or human communication means that hairs need to change with season, age or sexual development. Regular, regenerating hair follicle growth cycles produce new hairs which may differ in colour and/or size, e.g., beard development. Hormones of the pineal-hypothalamus-pituitary axis coordinate seasonal changes, while androgens regulate most sexual aspects with paradoxically different effects depending on body site; compare beard growth and balding! Hormones affect follicular mesenchymal-epithelial interactions altering growing time, dermal papilla size and dermal papilla cell, keratinocyte and melanocyte activity. Greater understanding of these mechanisms should improve treatments for poorly controlled hair disorders, alopecia and hirsutism.

Seasonal Endocrine Changes and Breeding Activity in Mediterranean Wild Ruminants

The methods of assisted reproduction commonly used in domestic animals are currently being applied to non-domestic species. This is because of the limitation of maintaining the genetic variability in the wild, as it occurs in wild ruminants of the Mediterranean Basin. Despite the apparent progress of the technology, success of the offspring to grow and become healthy adult individuals has remained low in wild species. Difficulties usually arise from insufficient information about basic reproductive biology, such as the seasonal changes in ovarian and testicular activity. Directional adaptive evolution involves development of speciespecific physiological reproductive patterns to cope with various environmental factors. Thus, species originating and living at the same latitude display different reproductive strategies to entrain the breeding activity at an optimal time of the year. The aim of this paper was to present current knowledge on reproductive physiology of Mediterranean wild ruminants as a basic prerequisite for the successful use of assisted reproduction methods. Special emphasis is given to seasonal endocrine changes, ovarian cycles and testicular activity of Iberian wild ruminants, together with the role of social interactions on the regulation of these events.

Control of molt in birds: association with prolactin and gonadal regression in starlings

Despite the importance of molt to birds, very little is known about its environmental or physiological control. In starlings Sturnus vulgaris, and other species, under both natural conditions and experimental regimes, gonadal regression coincides with peak prolactin secretion. The prebasic molt starts at the same time. The aim of this series of experiments was to keep starlings on photo-schedules that would challenge the normally close relationship between gonadal regression and molt, to determine how closely the start of molt is associated with gonadal regression and/or associated changes in prolactin concentrations. In one series of experiments, photosensitive starlings were moved from a short photoperiod, 8 h light per day (8L), to 13 or 18L, and from 13 to 18L or 13 to 8L during testicular maturation. Later, photorefractory birds under 13L that had finished molting were moved to 18L. In another series of experiments, photorefractory starlings were moved from 18 to 8L for 7 weeks, 4 weeks, 2 weeks, 1 week, 3 days, 1 day, or 0 days, before being returned to 18L. There was no consistent relationship between photoperiod, or the increase in photoperiod, and the timing of the start of molt. Nor was there a consistent relationship with gonadal regression and the start of molt-molt could be triggered in the absence of a gonadal cycle. However, there was always an association between the start of molt and prolactin. In all cases where molt was induced, there had been an earlier increase in prolactin. However, the timing of molt was related to the time of peak prolactin, not the magnitude of that peak. This relationship between peak prolactin and the start of molt could explain the normally close relationship between the end of breeding activity and the start of molt.

The impact of body site, topical melatonin and brushing on hair regrowth after clipping normal Siberian Husky dogs

The aims of this study were to determine the impact of body site, vigorous brushing and topical melatonin treatment on hair regrowth after clipping normal dogs. Siberian Husky dogs were randomly assigned to three groups of eight dogs each. All dogs had the lumbosacral region and both lateral thighs clipped. The left thigh and lumbosacral area received no treatment and were compared in all 24 dogs. Eight dogs had the right thigh treated with 0.1% melatonin twice daily for 2 months, and hair regrowth was compared with the left thigh. Eight dogs had the right thigh brushed twice daily for 2 months, and hair regrowth was compared with the left thigh. Eight dogs had neither thigh treated. Hairs were plucked before and 2 months postclipping, and the proportion of hair growth from the original length was calculated and compared as described above. Biopsy samples were collected before and after treatment to determine if brushing induced dermal inflammation and melatonin increased the proportion of anagen follicles. Proportionally, left thigh hairs were significantly longer compared to lumbosacral hairs 2 months postclipping. No significant differences in hair regrowth were noted between the nontreated thigh and the thigh treated with melatonin or brushed. No significant difference in dermal inflammation was noted before and after brushing. No significant differences were observed in the proportion of anagen follicles before and after topical melatonin treatment. Our results showed that the hairs in the lumbosacral region were proportionally shorter than lateral thigh hairs 2 months postclipping. Moreover, topical melatonin and brushing had no impact on hair regrowth after clipping normal dogs.