Annual rhythmicity and maturation of physiological parameters in goats

This study was conducted to investigate seasonal rhythmicity and maturation of physiological parameters in goats. Five kids (Capra hircus, Maltese breed) were studied for 24 months, starting at 5 months of age. Rectal temperature and various blood-borne substances (melatonin, cholesterol, urea, total bilirubin, albumin, glucose, calcium, magnesium, phosphate, and sodium) were measured once a month at dawn and dusk. Serum bilirubin concentration exhibited statistically significant 12-month rhythmicity, and melatonin concentration exhibited 6-month rhythmicity. Changes in the dusk-to-dawn difference in rectal temperature during the course of the study provided suggestive evidence that the circadian rhythm of body temperature in goats is not fully developed until the end of the second year of life. The results documented also maturational changes in cholesterol production and blood glucose regulation.     

Pre-treatment with melatonin inhibits oleic acid-induced acute lung injury in rats

AIM: To assess the protective role of melatonin (MEL) in a rat model of oleic-induced acute lung injury.METHODS: Twenty-four rats were randomly allocated to three groups as follows: saline(NS) injection group, oleic acid(OA) injection group and MEL plus OA injection group, the lavage protein, lung wet-to-dry weight ratio, malondialdehyde(MDA) content, superoxide dismutase(SOD) activity and lung histopathology were examined. RESULTS: (1) Injection 0.15 mL/kg of OA led to a severe acute lung injury(ALI), characterized by significantly increasing in lavage protein, lung coefficient (P<0.01), and by histopathological alterations which presented hemorrhage, edema, thickened alveolar septum and the existence of inflammatory cells in alveolar spaces; (2) Infusion of MEL (20 mg/kg, intraperitoneally for 60 min before the oleic acid) markedly alleviated above-mentioned symptom induced by OA, consistent with decrease of MDA level (P<0.01) and the increase of SOD activty (P<0.01). CONCLUSION: Pre-treatment with MEL can attenuate the OA-induced ALI in rats via cleaning and preventing the formation of free radicals and further lessening the increase of alveolocapillary membrane permeability, these data suggest that MEL may be effective in the prevention of ALI.     

Expression analysis of melatonin receptor subtypes in the ovary of domestic chicken

Melatonin (N-acetyl-5-methoxytryptamine), an indole hormone, regulates various biological functions through three different receptor subtypes (Mel-1a, Mel-1b, and Mel-1c). However, the distribution of different melatonin receptor subtypes in chicken reproductive tissues was not known. In the present investigation, the partial sequences of ovarian melatonin receptor subtypes (Mel-1a, Mel-1b, and Mel-1c) were characterized. Further, the expression profile of melatonin receptor subtypes in the granulosa and theca layers of different preovulatory and postovulatory follicles (POF) were studied by semi-quantitative RT-PCR. The expression of all three subtypes of melatonin receptors were observed in the ovary of domestic chicken. Analysis of partial sequences of ovarian melatonin receptors revealed that the melatonin subtypes were identical to the brain receptors. In small white ovary follicles, we observed only the expression of mel-1b receptors, but not mel-1a or mel-1c receptors. In yellow follicles, all the three subtypes of receptors expression were noticed. Interestingly, we observed the expression of mel-1a receptor only in thecal layer, but not in granulosa layer. In contrast, mel-1b and -1c receptors were expressed in both granulosa and thecal layer. During the regression of POF, we observed significant upregulation of melatonin receptors (mel-1a and 1c) expression, that downregulated in the later stages of regression. We assume that the expression of melatonin receptors might have been influenced by the atresia or apoptosis of different follicular layers in POF. Our findings suggest that the differential distribution of melatonin receptor subtypes might have distinct downstream cellular functions in the ovarian tissues.     

Protection of melatonin on isoproterenol-induced hyperphosphorylation of tau and spatial memory impairment in rats

AIM: To study the in vivo effect of melatonin (MEL) on Alzheimer-like tau hyperphosphorylation and spatial memory retention impairment induced by isoproterenol (IP). METHODS: Simultaneous injection of 2 μL IP(10 mmol/L) or IP plus MEL(0.1 μg,1μg)into rat hippocampus bilaterally with stereotexin; The phosphorylation of tau was analyzed by immunohistochemistry and Western blot and the memory retention was tested by Morris Water Maze. RESULTS：Injection of IP induced hyperphosphorylation of tau at Tau-1 and PHF-1 epitopes and increased latency of rats to find the hidden platform in the Morris water maze. MEL significantly restored the IP-induced impairment in spatial memory（P＜0.05）and tau hyperphosphorylation determined by both immunocytochemistry and Western blot. CONCLUSION: MEL inhibits partially the IP-induced pathological processes in tau hyperphosphorylation and spatial memory impairment in rat brain.     

褪黑激素在毛皮动物生产上的应用

本文论述了褪黑激素（MT）植入物在水豹、狐猩、貉等毛皮运动生产上的应用，MT能促进其冬皮不同程度的早熟；也能让绒山羊、牦牛在非生绒期长绒、让安哥拉兔夏毛产量增加。     

Melatonin mitigates the adverse effect of hypoxia during myocardial differentiation in mouse embryonic stem cells

BackgroundHypoxia causes oxidative stress and affects cardiovascular function and the programming of cardiovascular disease. Melatonin promotes antioxidant enzymes such as superoxide dismutase, glutathione reductase, glutathione peroxidase, and catalase.ObjectivesThis study aims to investigate the correlation between melatonin and hypoxia induction in cardiomyocytes differentiation.MethodsMouse embryonic stem cells (mESCs) were induced to myocardial differentiation. To demonstrate the influence of melatonin under hypoxia, mESC was pretreated with melatonin and then cultured in hypoxic condition. The cardiac beating ratio of the mESC-derived cardiomyocytes, mRNA and protein expression levels were investigated.ResultsUnder hypoxic condition, the mRNA expression of cardiac-lineage markers (Brachyury, Tbx20, and cTn1) and melatonin receptor (Mtnr1a) was reduced. The mRNA expression of cTn1 and the beating ratio of mESCs increased when melatonin was treated simultaneously with hypoxia, compared to when only exposed to hypoxia. Hypoxia-inducible factor (HIF)-1α protein decreased with melatonin treatment under hypoxia, and Mtnr1a mRNA expression increased. When the cells were exposed to hypoxia with melatonin treatment, the protein expressions of phospho-extracellular signal-related kinase (p-ERK) and Bcl-2-associated X proteins (Bax) decreased, however, the levels of phospho-protein kinase B (p-Akt), phosphatidylinositol 3-kinase (PI3K), B-cell lymphoma 2 (Bcl-2) proteins, and antioxidant enzymes including Cu/Zn-SOD, Mn-SOD, and catalase were increased. Competitive melatonin receptor antagonist luzindole blocked the melatonin-induced effects.ConclusionsThis study demonstrates that hypoxia inhibits cardiomyocytes differentiation and melatonin partially mitigates the adverse effect of hypoxia in myocardial differentiation by regulating apoptosis and oxidative stress through the p-AKT and PI3K pathway.     

Effects of orexigenic peptides and leptin on melatonin secretion during different photoperiods in seasonal breeding ewes: an in vitro study

The pineal gland (PG) acts as a neuroendocrine transducer of daily and seasonal time through the nocturnal release of melatonin. Here, we examined the interaction of season, orexin, ghrelin, and leptin on melatonin secretion by pineal explants in short-term culture. Glands were collected after sunset from 12 ewes during long days (LD; April and May) and from an additional 12 ewes during short days (SD; October and November). Glands were transected sagittally into strips, with each equilibrated in 2.5 mL of Dulbecco's modified Eagle's medium for 60 min, followed by a 2-h incubation in control medium or medium containing orexin B (10 and 100 ng/mL), ghrelin (10 and 100 ng/mL), or 50 ng/mL of leptin. After a 3-h incubation, some PG explants treated previously with lower doses of orexin or ghrelin were challenged with 50 ng/mL of leptin and those treated with both doses of orexin were challenged with 300 nM of the β-agonist isoproterenol. One milliliter of medium was harvested and replaced from each well every 30 min. Treatment with the low dose of orexin during LD increased melatonin secretion about 110% (P<0.01); treatment with a high dose increased melatonin secretion about 47% (P<0.001). During the SD period, leptin stimulated (P < 0.05) melatonin secretion slightly compared with mean melatonin concentration in controls. However, together, orexin and leptin depressed (P<0.01) melatonin secretion. Both doses of ghrelin reduced (P < 0.01) melatonin concentration during the SD season compared with control culture. Addition of ghrelin and leptin to culture medium increased (P<0.01) melatonin concentration compared with ghrelin-treated culture and decreased melatonin concentration (P<0.01) compared with leptin-treated culture during SD. Isoproterenol stimulated (P<0.01) melatonin secretion compared with values observed during the pretreatment period. We conclude that orexigenic peptides (orexin B and ghrelin) and an anorectic peptide (leptin) affect PG directly. The responses of PG to those hormones depend on day length. Moreover, secretion of melatonin from the ovine PG is under an adrenergic regulation.     

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 (T(3)), and thyroxine (T(4)) 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 T(3) and T(4) 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 (r(day) = -0.645, P = 0.007; r(night) = -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.     

亚低温条件下外源褪黑素和Ca2+对西瓜幼苗生理特性的影响

以西瓜品种8424种子和幼苗为试材,利用人工气候室进行亚低温处理(昼/夜18℃/12℃)20 d,研究外源褪黑素(MT)和Ca²⁺浸种处理对亚低温条件下西瓜种子萌发,西瓜幼苗抗氧化酶SOD、POD和CAT等活性,渗透调节物质可溶性糖和脯氨酸含量的影响。结果表明,亚低温处理的西瓜种子发芽率和发芽势仅为46.5%和40.5%,外源100μmol·L^-1褪黑素和5 mmol·L^-1Ca²⁺复合浸种处理西瓜种子发芽率和发芽势分别达到62.3%和58.5%。外源褪黑素和Ca²⁺浸种处理显著提高了抗氧化酶SOD、POD、CAT和APX活性,促进了渗透调节物质可溶性糖和脯氨酸的积累,有效缓解亚低温对西瓜种子萌发和幼苗生长影响;褪黑素和Ca²⁺复合浸种西瓜幼苗在出苗第20天时植株鲜质量达到8.21 g·株^-1,达到对照处理的85.5%。综上,外源褪黑素和Ca²⁺能通过提高西瓜幼苗抗氧化酶活性和渗透调节能力等,缓解亚低温的不良影响,促进西瓜幼苗生长。