Melatonin supplementation can ameliorate the detrimental effects of heat stress on performance and carcass traits of Japanese quail

Melatonin, the major pineal hormone, modulates growth in poultry by influencing hormones involved in growth. We investigated the effects of dietary melatonin supplementation on performance, carcass characteristics, and excretion of nitrogen and some minerals in broiler Japanese quails (Coturnix coturnix japonica) exposed to high-ambient-temperature stress (34°C). One hundred twenty Japanese quails (10 d old) were randomly assigned to 4 treatment groups, 3 replicates of 10 birds each. The birds were kept in either an environment-controlled room at a constant 22°C or were kept at 22°C for 16 h/d and at 34°C for 8 h/d (9:00 am to 5:00 pm). At both temperatures birds were fed either a basal diet or the basal diet supplemented with 40 mg of melatonin per kilogram of diet. The experiment lasted for 32 d. Melatonin improved feed efficiency in both temperatures groups compared with their corresponding controls. Although feed intake was similar in all groups, the improvement in feed efficiency was more noticable in melatonin-fed quails kept at high temperature (p<0.01). Supplemental melatonin significantly increased live weight gain and carcass characteristics under stress conditions (p<0.01) but did not show the same effect at thermoneutral conditions (p>0.05). Heat exposure increased excretion of N, Ca, P, Zn, Fe, and Cr and decreased retention rates for them. Dietary melatonin supplementation returned these values to normal (p<0.01). No interactions between melatonin and temperature were found in the parameters measured. The results of the study show that melatonin supplementation attenuated the retardation in performance as well as the excretion of minerals caused by heat stress in broiler quails. Our data suggest that melatonin might offer protection against heat-stress-related depression in the performance of broiler quails.     

Brain melatonin content and polyethism in adult workers of Apis mellifera and Apis cerana (Hym., Apidae)

Abstract:  Radioimmunoassay showed that melatonin, N -acetyl-5-methoxytryptamine, was synthesized in the brain of workers of Apis mellifera ligustica Spinola, and related to the polyethism of the workers. Statistically significant differences were found in melatonin levels between workers at different ages and between workers performing different tasks. The level in foragers was higher than that in young nurses. The highest melatonin level was found in 21-day-old adult workers (213.15 pg per worker head) and the lowest level in 1-day-old adult workers (6.08 pg per worker head); and the highest level in pollen-collecting workers (404.13 pg per worker head) and the lowest in nurse workers (13.10 pg per worker head). Apis cerana cerana Fabricius showed a similar pattern, but the nectar foragers had the highest melatonin levels. The melatonin level also showed a daily rhythm. In 30-day-old adult workers there were two peaks, at 7:00 and 19:00 hours, and three troughs at 15:00, 21:00 and 1:00 hours respectively.     

叶面喷施褪黑素对低温胁迫下南瓜幼苗生长和生理特性的影响

以南瓜品种‘永安2号’幼苗为试验材料,采用室内盆栽实验,在叶面喷施不同浓度(0、50、100、150、200和300μmol·L^(-1))褪黑素(MT)后进行低温(10℃/7℃)胁迫处理,考察幼苗生长指标以及相对电导率、抗氧化酶活性、渗透调节物质含量等抗逆生理指标的变化,初步探讨外源褪黑素缓解南瓜幼苗低温冷害的生理机制。结果表明:(1)在低温胁迫条件下,南瓜幼苗出现叶片萎蔫失水、边缘失绿褪色、向内卷曲等冷害症状;幼苗株高、茎粗、鲜重、干重和壮苗指数等生长指标及叶片相对叶绿素含量均显著降低;叶片相对电导率、MDA含量和O^(-)·_(2)产生速率显著升高50%以上,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶、脱氢抗坏血酸还原酶活性以及可溶性糖、可溶性蛋白和脯氨酸含量也大多显著升高。(2)与低温胁迫处理相比,叶面喷施不同浓度褪黑素后,南瓜幼苗叶片冷害症状均得到不同程度恢复,并以100μmol·L^(-1) MT处理生长状态最好,植株形态表型与对照已没有明显差异;幼苗生长指标以及叶片相对叶绿素含量、6种抗氧化酶活性、3种渗透调节物质含量均不同程度提高,并随着MT浓度升高均先升后降,且均在100μmol·L^(-1) MT处理最高。研究发现,外源褪黑素能通过提高叶片叶绿素含量、增强抗氧化酶活性、增加渗透调节物质积累,显著降低低温冷害造成的膜质过氧化程度,有效减轻低温胁迫对南瓜幼苗的伤害,增强其抵抗低温能力,恢复幼苗的正常生长,且喷施浓度为100μmol·L^(-1)时效果最佳。     

Melatonin Promotes Rice Seed Germination under Drought Stress by Regulating Antioxidant Capacity

Drought stress is a serious threat to the germination of plant seeds and the growth of seedlings. Melatonin has been proven to play an important role in alleviating plant stress. However, its effect on seed germination under drought conditions is still poorly understood. Therefore, we studied the effects of melatonin on rice seed germination and physiological characteristics under drought stress. Rice seeds were treated with different concentrations of melatonin (i.e., 0, 20, 100, and 500 μM) and drought stress was simulated with 5% polyethylene glycol 6000 (PEG6000). The results showed that 100 μM melatonin can effectively improve the germination potential, rate and index; the vigor index of rice seeds; and the length of the shoot and root. In addition, that treatment also increased the activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and reduced the content of malondialdehyde (MDA). The grey relational grade between the shoot MDA content and the melatonin seed-soaking treatment was the highest, which could be useful for evaluating the effect of melatonin on drought tolerance. Two-way analysis of variance showed that the effect of single melatonin treatment on rice seeds was more significant than that of single drought stress and interaction treatment of drought and melatonin (p < 0.05). The subordinate function results showed that 100 μM melatonin significantly improved the germination and physiological indexes of rice seeds and effectively alleviated the adverse effects of drought stress on rice seedlings. The results helped to improve the understanding of the morphological and physiological involvement of melatonin in promoting seed germination and seedling development under drought stress.     

褪黑素对盐胁迫下普通菜豆芽期核酸修复的调控机制

普通菜豆(Phaseolus vulgaris)是重要的食用豆作物, 然而其极易受盐胁迫危害, 导致产量下降。褪黑素能提高植物耐盐能力。为探明外源褪黑素调控普通菜豆耐盐能力的机制, 以普通菜豆品种奶花芸豆(GZ-YD014)为实验材料, 设置水(W, 对照)、盐胁迫(S)和盐胁迫+100 µmol∙L^-1褪黑素(M+S) 3个处理。结果发现, 盐胁迫抑制了普通菜豆胚根的生长, 使其长度、表面积、体积以及直径显著降低, 外源褪黑素可缓解盐胁迫对普通菜豆胚根生长的抑制。外施褪黑素显著降低盐胁迫下活性氧积累和丙二醛(MDA)含量, 提高保护酶(过氧化物酶、超氧化物歧化酶、过氧化氢酶以及抗坏血酸过氧化物酶)活性, 增加渗透调节物质(可溶性糖和可溶性蛋白)以及生长素(IAA)、赤霉素(GA)和玉米素(ZT)的含量, 降低脱落酸(ABA)含量。通过转录组分析挖掘出217个差异表达基因(DEGs), DEGs在GO富集中显著(P-value<0.05)富集到核酸相关条目上, 在KEGG富集中显著(P-value<0.05)富集到核酸损伤修复(包括碱基切除修复、错配修复以及核苷酸切除修复)通路。qRT-PCR以及RAPD分析结果表明, 核酸损伤修复通路为外源褪黑素调控普通菜豆耐盐能力的一种机制。该研究揭示了外源褪黑素对普通菜豆芽期耐盐能力的调控机制, 可为褪黑素应用于盐胁迫下普通菜豆增产提供理论依据。     

High Intensity Light Increases Olfactory Bulb Melatonin in Venezuelan Equine Encephalitis Virus Infection

In mice infected with the Venezuelan equine encephalomyelitis (VEE) virus and exposed to high intensity light (2500 lux) with a 12 h light: 12 h dark photoperiod, a significant increase in the levels of melatonin in the olfactory bulb was observed. The significance of these findings deserves further studies to understand the mechanisms involved in this effect since the olfactory bulbs have been proposed as first portal for VEE virus entry into the CNS. The increase in melatonin content could represent one of the mechanisms of defense against the viral attack.     

Stereoselective effects of (R)- and (S)-carvedilol in humans

Carvedilol is currently used as the racemic mixture, (R,S)-carvedilol, consisting of equal amounts of (R)-carvedilol, an alpha-blocker, and (S)-carvedilol, an alpha- and beta-blocker, which have never been tested in their optically pure forms in human subjects. We performed a randomized, double-blind, placebo-controlled, crossover study in 12 healthy male volunteers. Subjects received single oral doses of 25 mg (R,S)-carvedilol, 12.5 mg (R)-carvedilol, 12.5 mg (S)-carvedilol, and placebo at 8 AM as well as at 8 PM. Exercise was performed at 11 AM, and heart rate and blood pressure were measured at rest and after 10 min of exercise. Urine was collected between 10 AM and 6 PM, as well as between 10 PM and 6 AM, and the amounts of urinary 6-hydroxy-melatonin sulfate (aMT6s) were determined by RIA. Compared to placebo, (R)-carvedilol increased heart rate during exercise (+4%, P < 0.05) and recovery (+10%, P < 0.05); (S)-carvedilol decreased heart rate during exercise (-14%, P < 0.05) and recovery (-6%, P < 0.05), and systolic blood pressure during exercise (-12%, P < 0.05); (R,S)-carvedilol decreased heart rate during exercise (-11%, P < 0.05), and systolic blood pressure at rest (-7%, P < 0.05) and during exercise (-10%, P < 0.05). None of the agents had any significant effect on the release of aMT6s. Our results indicate that only (S)-carvedilol causes beta-blockade, whereas (R)-carvedilol appears to increase sympathetic tone, presumably as a physiological reaction to the decrease of blood pressure caused by alpha-blockade. None of the drugs had any influence on melatonin release. The weak clinical net effect of beta-blockade of (R,S)-carvedilol at rest might be one reason why this drug causes fewer side effects than other beta-blockers, such as a reduction of nocturnal melatonin release.     

Studies of the interactions between melatonin and 2 Hz, 0.3 mT PEMF on the proliferation and invasion of human breast cancer cells

Interactions between the hormone melatonin at pharmacological concentrations (10(-3) M) and 2 Hz, 0.3 mT pulsed electromagnetic fields (PEMF) on the proliferation and invasion of human breast cancer cells were studied in vitro. Three types of human breast cancer cells were used in this study: MDA-MB-435, MDA-MB-231, and MCF-7. Results showed that cellular growth of MDA-MB-231 cells, which were reported to be lowly metastatic, and MCF-7 cells, which were reported to be nonmetastatic, were both significantly reduced by melatonin regardless of the presence of the field. Results also showed that MDA-MB-435 and MDA-MB-231 cells were invasive, with MDA-MB-231 cells being more invasive than the MDA-MB-435 cells for both unexposed and experimental-PEMF groups. In addition, invasion studies showed that MCF-7 cells were not invasive and that melatonin did not have any effects on the invasion of these cells, with or without the PEMF. It is also suggested that since metastasis requires growth and invasion into tissue, anti-invasion agents can be used in conjunction with melatonin to prevent formation of secondary metastases. The overall studies suggest that PEMF at 2 Hz, 0.3 mT does not influence cancer metastasis; while having clinical merit in the healing of soft tissue injury, this field has shown no influence on cancer cells as 60 Hz power line fields have.     

Circadian rhythms in the retina of rats with photoreceptor degeneration

Previous studies have demonstrated that the mammalian retina contains a circadian clock system that controls several retinal functions. In mammals the location of the retinal circadian clock is unknown whereas, in non-mammalian vertebrates, earlier work has demonstrated that photoreceptor cells contain the circadian clock. New experimental evidence has suggested that in mammals the retinal circadian clock may be located outside the photoreceptor cells. In this study we report that circadian rhythms in Aa-nat mRNA (in vivo) and melatonin synthesis (in vitro) are still present in the retina of rats lacking photoreceptors. The circadian pacemaker(s) controlling such rhythms is probably located in kainic acid sensitive neurons in the inner retina since kainic acid injections abolished the rhythmicity. These data are the first direct demonstration that circadian rhythmicity in the mammalian retina can be generated independently from the photoreceptors and the suprachiasmatic nuclei of the hypothalamus.     

Amelioration of methotrexate-induced enteritis by melatonin in rats

The anti-tumour drug methotrexate (MTX) induces intestinal mucosa injury resulting in malabsorption and diarrhoea. The purpose of this study was to investigate whether exogenous melatonin could protect the gut from MTX-induced damage in rats. A single dose of MTX (20 mg kg(-1), i.p.) was followed by i.p. saline or melatonin injections (10 mg kg(-1), MTX + Mel) for the next 5 days. On the fifth day, intestinal transit was assessed using charcoal propagation. Rats were decapitated and small intestinal segments were fixed for light (LM) and scanning electron microscope (SEM) examinations. Other intestinal segments were stored to measure glutathione (GSH) and malondialdehyde (MDA) levels, myeloperoxidase (MPO) and ATPase activity. MTX led to loss of more than 10% of the initial body weight (p < 0.01). Conversely, weight loss was markedly less in the melatonin-treated MTX group (p < 0.05). Bowel motility was increased in MTX-treated rats, while the transit index in the MTX-Mel group was not different from the control group. MTX caused decreases in GSH levels and ATPase activity, with increases in MDA levels and MPO activity. These changes were reversed in MTX-Mel-treated rats (p < 0.05-p < 0.001). LM and SEM in the MTX group revealed desquamation of surface epithelium and glandular degeneration, while the epithelium was slightly damaged in the MTX-Mel group. In conclusion, the present study demonstrates that melatonin is capable of reversing MTX-induced intestinal dysfunctions, indicating that it may be beneficial in ameliorating the symptoms of chemotherapy-induced enteritis.