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)

The aims of this study were to examine whether mouflons exposed to constant long and short day photoperiods are able to exhibit an annual cycle of hair growth and moult, and prolactin (PRL) secretion. Mouflon ewes were assigned to three groups of treatment. Ewes were maintained, either under natural photoperiod (control, n=9), or received a series of subcutaneous melatonin implants from December to April (n=8), or were exposed to a constant long day photoperiod (16-h light:8-h dark; 16L:8D) during 18 months (n=7). Blood was collected weekly to determine PRL concentrations, and hair samples were clipped weekly from the base of the neck to measure the length of predominant hair. Under constant long days and with melatonin implants, mouflons expressed an annual rhythm of PRL secretion, even though these treatments modified the times of rise or falling of PRL concentrations throughout the year. Hair growth initiation was almost coincident with the summer solstice in both control and melatonin-implanted mouflons but occurred two months earlier in long day hold mouflons (P<0.001). Long day hold mouflons had a lower hair growth rate than control and melatonin-implanted mouflons (P<0.001), and at the end of the experiment, a shorter hair length (3.4±0.24 cm; P<0.01) than control (4.3±0.17 cm), and melatonin-implanted mouflons (4.2±0.12 cm). Our data support the conclusion that in mouflon, an endogenous circannual rhythm of PRL secretion exists, and that the seasonal cycle of hair growth and moult appears to depend, at least in part, on circulating levels of PRL.     

Nocturnal melatonin concentrations vary dramatically between the two jugular veins in most individual sheep maintained under mimicked or natural photoperiod

Two experiments were designed to determine if melatonin concentrations differ between jugular veins. In a first experiment, blood was collected continuously every 30 min from each jugular during 12-h from 6 ewes. In a second experiment, 100 ewes were sampled twice at night simultaneously from the two jugular veins. In both experiments, mean melatonin concentrations were similar between right and left jugulars. However, within individuals, large differences were observed between the two sides (p < 0.001). This difference was stable over time and the higher side varies among individuals. The concentrations of prolactin and oxytocin, measured in the same samples did not show such differences. This observation raises the question of the origin of this phenomenon. Moreover, it has important implications for studies in which melatonin concentrations need to be assessed accurately. Indeed, a reliable quantitative assessment of melatonin production by the pineal gland requires sampling from both jugular veins.     

褪黑素调控绵羊季节性发情的研究进展

褪黑素是松果腺细胞合成的吲哚胺类激素中生物活性最高的1种神经激素,该激素调节着体内的多种生理活动。对褪黑素的合成、代谢、作用机制以及对绵羊的季节性发情的影响进行了阐述。     

低磷胁迫下外源褪黑素对大麦幼苗根系发育的调控作用

为探究低磷胁迫下外源褪黑素（Melatonin,MT）对大麦幼苗根系生长发育调控作用,以磷敏感型大麦品种GN42为试验材料,设置正常磷（CK）、低磷和低磷添加MT 3个处理,比较分析了不同处理间大麦幼苗根系表型特征、解剖构造和相关基因表达量的差异。结果表明,低磷胁迫后大麦幼苗根系生长受到抑制,表现为根系总长度、表面积和体积均不同程度下降,且根冠厚度减少,活性氧(ROS)过量积累,花青素含量增加,根系磷转运蛋白相关基因Hvpht1;1上调表达,花青素合成基因Hvant和MT合成基因Hvcomt均下调表达。低磷胁迫下添加外源MT后,幼苗根系生长受抑制程度缓解,根系总长、表面积和体积均显著增加,根冠厚度也显著增加,ROS积累量明显变少,且3种基因都不同程度上调表达。由此说明,外源MT可以有效缓解低磷胁迫对大麦幼苗生长发育的不利影响,提高植株对低磷胁迫的适应性。     

褪黑素对高温胁迫玉米叶片光合特性与抗氧化酶活性的调控

2022年以安科985为试验材料,在玉米灌浆期自然高温胁迫条件下(2022年夏高温持续时间长、范围广、强度大、极端性强),灌施不同浓度褪黑素(MT)溶液,0(CK)、100(MT100)、200(MT200)、300(MT300)μmol/L,研究不同处理下玉米叶片光合特性、荧光特性、抗氧化酶活性与产量形成的影响。结果表明,褪黑素处理显著增加了玉米行粒数、穗粗、穗长、百粒重和单株产量,降低了秃尖长度。褪黑素处理后叶片SPAD值、N含量、净光合速率、气孔导度和蒸腾速率显著增加,胞间二氧化碳浓度显著降低。与对照相比,褪黑素处理下ΦPSⅡ、ETR、qN、qP和Fv/Fm均显著上升,Y(N0)和F0显著下降。200μmol/L处理显著提高叶片抗氧化酶活性(SOD、POD、CAT),丙二醛MDA含量显著降低。褪黑素处理后,干物质积累量和干物质向子粒的分配比例显著增加。自然高温胁迫下,褪黑素处理可增强玉米抗性,以200μmol/L效果最佳。     

外源褪黑素处理对常温货架期梨果实贮藏品质的影响

【目的】明确褪黑素处理对采后常温货架期梨果实贮藏品质的影响。【方法】以新梨7号果实为试材,设置50、100、150、200、250μmol·L^-15个褪黑素浓度梯度处理,以清水处理为对照,测定了常温货架期果实失重率、硬度、可溶性固形物含量、乙烯释放速率、香气物质种类和含量等指标。【结果】从处理后5、10、15和20 d的测定结果可以看出,与对照相比,褪黑素处理减少了梨果实内水分的消耗,果实的失重率升高的幅度小,果实硬度较高,150μmol·L^-1褪黑素处理失重率和果实硬度与对照差异达显著水平;褪黑素处理能够使新梨7号果实的可溶性固形物含量稳定,处理20 d时,不同浓度褪黑素处理可溶性固形物含量显著高于对照;褪黑素处理新梨7号果实的乙烯释放速率均低于对照,以150μmol·L^-1褪黑素处理最低,较对照减少了87.05%,差异显著;不同浓度褪黑素处理对新梨7号果实香气物质种类和含量存在差异,褪黑素处理能调节果实香气种类和含量。【结论】外源褪黑素处理可延缓新梨7号梨果实失水,保持果实硬度和可溶性固形物含量,减少乙烯释放。适宜浓度褪黑素处理可调节香气物质的种类和含量,保证常温货架期贮藏品质,综合认为,150μmol·L^-1浓度褪黑素处理能够有效延缓梨果实的衰老,处理效果最好。     

褪黑素在卵巢中功能的研究进展

褪黑素是一种由哺乳动物松果体分泌的神经内分泌胺类激素,通过其高亲和性膜受体的参与调控动物生理节律、季节性繁殖和卵巢功能等生理过程。本文就褪黑素的相关特性及在卵巢中的功能研究进行综述,为其成为提高卵母细胞质量、治疗不孕疾病的开发药物提供理论依据。     

生物钟对哺乳动物生理代谢、繁殖和肠道菌群影响的研究进展

进化过程中生物钟通过将合成代谢和分解代谢两种代谢过程进行时间上的分离,优化代谢效率;同时使动物机体的代谢循环与睡眠/活动循环同步,维持基本的代谢节律。哺乳动物的繁殖性能主要受到下丘脑-垂体-性腺轴的调控。下丘脑视交叉神经上核的主生物钟能够产生自发性振荡并且感受光周期的变化,引发褪黑素分泌的变化。褪黑素(MT)作为一种重要的节律调节因子和生殖激素,介导下丘脑-垂体-性腺轴各部分激素的节律性变化,进而调控哺乳动物繁殖性能。同时肠道菌群的变化作为一种繁殖障碍的反映逐渐引起人们的关注。本文将重点阐述昼夜节律对宿主能量代谢、繁殖性能以及肠道菌群之间的相互作用,主要包括中枢生物钟视交叉神经上核(SCN)通过褪黑素介导的下丘脑-垂体-性腺轴各部分激素的节律性变化,进而调控哺乳动物的繁殖节律。     

褪黑素对雏鸡睾丸支持细胞体外增殖的影响

为研究褪黑素对雏鸡睾丸支持细胞增殖的影响,本实验以原代分离培养并鉴定的雏鸡睾丸支持细胞为研究对象,经不同浓度(1、10、100、1000 nmol/L)褪黑素处理细胞48 h后,使用Cell Counting Kit-8(CCK-8)、EdU和实时荧光定量PCR(RT-qPCR)检测雏鸡睾丸支持细胞的细胞活力、细胞增殖能力和增殖相关基因的表达。结果表明:与对照组相比,添加1000 nmol/L褪黑素可提高细胞活力和细胞增殖能力(P<0.05),上调PCNA、Cyclin B和Cyclin D基因的表达(P<0.05),下调P21基因的表达(P<0.05)。结果显示褪黑素可以促进支持细胞增殖。