中西医观解读时间生物学

时间生物学是一门研究生命活动节律的科学。在西方医学中,研究时间生物学是利用分子生物学实验来阐释其机制,以西医的思维方法解释时间生物学的生理及病理过程;中医对时间生物学的记载有两千多年的历史,阴阳理论、子午流注学说以及五运六气学说一直以来都在指导中医的诊断和治疗。中西医观的不同对时间生物学的研究提供了新的研究思路,同时时间生物学也为研究中西医结合提供了广阔的前景。     

一种简单有效的非损伤观测根瘤和根系形态的方法

实时观测根瘤及根系形态对于豆科植物研究具有重要意义, 但目前还缺乏一个便于观测根系、高效结瘤、适宜生长且经济实用的豆科植物培养体系。以蒺藜苜蓿(Medicago truncatula)为植物材料, 建立了一种可实时观测根瘤及根系形态的纸袋水培法, 并与其它常用方法进行对比。结果表明, 依赖于石英砂等固体介质栽培蒺藜苜蓿对根瘤和根系形态的实时观测造成障碍, 而水培和喷雾培养等方法的根瘤菌接种效率不高, 且不便观测侧根发育情况。采用纸袋水培法探讨了褪黑素对蒺藜苜蓿根系发育的影响, 发现褪黑素具有降低根瘤形成效率、抑制侧根伸长、增加侧根数目以及增大侧根与主根之间夹角等作用。因此, 纸袋水培法能够高效接种根瘤菌且为实时无损伤观测根瘤及根系形态提供了可能, 是一种适用于豆科植物简单有效的培养方法。     

高温胁迫下外源褪黑素对黄瓜幼苗活性氧代谢的影响

以黄瓜品种‘津春4号’为试材,用叶面喷施的方法,研究了高温胁迫条件下外源褪黑素(melatonin,MT)对黄瓜幼苗活性氧（ROS）代谢的影响.结果表明：外源MT能显著降低高温胁迫下黄瓜叶片超氧阴离子自由基（O₂^-.）产生速率、过氧化氢（H₂O₂）含量、电解质漏渗率（relative electric conductivity, REC）及丙二醛(MDA)含量,增强黄瓜幼苗叶片中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性,提高抗坏血酸（AsA）、谷胱甘肽（GSH）及可溶性蛋白质含量.说明MT预处理能抑制高温胁迫条件下黄瓜幼苗体内ROS的产生,提高抗氧化酶系的活性及抗氧化物质的含量,降低膜质过氧化水平,保护脂膜的完整性,减少电解质的外渗,减轻高温胁迫对幼苗造成的伤害,提高幼苗抗高温胁迫的能力.     

褪黑激素的研究进展

褪黑激素是一种在多个物种的多个组织中广泛存在并具有重要生理作用的激素。本文拟就褪黑激素在体内的分布,褪黑激素受体的分子结构、药理学特性、生物功能及调控模式作一简述。     

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+100μmol·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。...     

Regulation effects of melatonin on bone marrow mesenchymal stem cell differentiation

Melatonin’s therapeutic potential has been highly underestimated because its biological functional roles are diverse and relevant mechanisms are complicated. Among the numerous biological activities of melatonin, its regulatory effects on pluripotent mesenchymal stem cells (MSCs), which are found in bone marrow stem cells (BMSCs) and adipose tissue (AD-MSC), have been recently proposed, which has received increasingly more attention in recent studies. Moreover, receptor-dependent and receptor-independent responses to melatonin are identified to occur in these cells by regulating signaling pathways, which drive the commitment and differentiation of MSCs into osteogenic, chondrogenic, or adipogenic lineages. Therefore, the aim of our current review is to summarize the evidence related to the utility of melatonin as a regulatory agent by focusing on its relationship with the differentiation of MSCs. In particular, we aimed to review its roles in promoting osteogenic and chondrogenic differentiation and the relevant signaling cascades involved. Also, the roles that melatonin and, particularly, its receptors play in these processes are highlighted.     

Role of melatonin on electromagnetic radiation-induced oxidative stress and Ca2+ signaling molecular pathways in breast cancer

Aims: Exposure to electromagnetic radiation (EMR) may increase breast cancer risk by inducing oxidative stress and suppressing the production of melatonin. Aim of the present review is to discuss the mechanisms and risk factors of EMR and oxidative stress-induced breast cancer, to summarize the controlled studies evaluating measures for prevention, and to conclude with evidence-based strategies for prevention.

Materials: Review of the relevant literature and results from our recent basic studies, as well as critical analyses of published systematic reviews were obtained from the Pubmed and the Science Citation Index.

Results: It has been proposed that chronic exposure to EMR may increase the risk of breast cancer by suppressing the production of melatonin; this suppression may affect the development of breast cancer either by increasing levels of circulation of estrogen or through over production of free oxygen radicals. Most epidemiological studies have also indicated overall effect of EMR exposure in premenopausal women, particularly for estrogen receptor positive breast tumors. Enhanced voltage-dependent Ca²⁺ current and impaired inhibitory G-protein function, and derangement of intracellular organelles with a Ca²⁺ buffering effect, such as endoplasmic reticulum and mitochondria have been also shown to contribute to disturbed Ca²⁺ signaling in breast cancer.

Conclusion: Melatonin may modulate breast cancer through modulation of enhanced oxidative stress and Ca²⁺ influx in cell lines. However, there is not enough evidence on increased risk of breast cancer related to EMR exposure.     

Effects of exposure to a circularly polarized 50-Hz magnetic field on plasma and pineal melatonin levels in rats

We sought to determine whether a 6-week exposure to a 50-Hz rotating magnetic field influences melatonin synthesis by 11–18 week-old Wistar-King male rats. Rats were exposed continuously to a rotating magnetic field at 1, 5, 50, or 250 μT (spatial vector rms) for 6 weeks, except for twice-weekly breaks of about 2 h for cleaning of cages and feeding. The rats were housed in exposure and sham-exposure facilities, which were located in the same room, under a 12:12 light-dark photoperiod (lights on at 06:00 h). The room was constantly illuminated by 4 small, dim red lights (< 0.07 lux in dark period). Levels of plasma and pineal gland melatonin were determined by radioimmunoassay. A significant decrease of melatonin was observed between the control group and groups exposed to a magnetic field at a flux density in excess of l μT during the night time, but no statistical differences were found among the exposed groups. These results indicate that subchronic exposure of albino rats to a 50-Hz rotating magnetic field influences melatonin production and secretion by the pineal gland. © 1993 Wiley-Liss, Inc.     

Prophylactic administration of carnosine and melatonin abates the incidence of renal toxicity induced by an over dose of titanium dioxide nanoparticles

The alleviative effects of two antioxidants, carnosine (Car) and melatonin (Mel), against titanium dioxide nanoparticles (TiO₂‐NPs) toxicity‐induced oxidative and inflammatory renal damage were examined in rats. Administration of these antioxidants along with TiO₂‐NPs effectively reduced serum urea, uric acid, creatinine, glucose, tumor necrosis factor‐α, interleukin‐6, C‐reactive protein, immunoglobulin G, vascular endothelial growth factor, and nitric oxide, as well as a significant amelioration of the decrease in glutathione levels in renal tissue was observed, compared to those in rats treated with TiO₂‐NPs alone. The renoprotective properties of the antioxidants were confirmed by reduced intensity of renal damage as demonstrated by histological findings. In conclusion, Car and Mel play protective roles against TiO₂‐NPs‐induced renal inflammation and oxidative injury, likely due to their antioxidant and anti‐inflammatory properties.     

Daily profiles of serum and gastrointestinal melatonin in response to daytime or night-time supply of tryptophan-rich diet in carp (Catla catla)

Influences of daytime (~10:00 h) or night-time (~22:00 h) supply of L-tryptophan (Trp)-rich diet on daily rhythm features of melatonin and arylalkylamine-N-acetyltransferase (AANAT) protein (key regulator of melatonin biosynthesis) in gastrointestinal (gut) tissue extracts, and melatonin in serum were studied in carp (Catla catla). Analysis of obtained data revealed that the mesor and amplitude values of both melatonin and AANAT in gut tissue-extracts were higher in daytime-fed fish than those supplied with food at night, and their acrophase varied from ~2 h in the daytime-fed carp to ~10 h in night-time-fed fish. Notably, initiation of stimulatory response of melatonin and AANAT in gut to Trp-rich diet varied from ~2 h (following food supply in day) to ~6 h (after food supply during night). However, in either case, their elevated levels were maintained for ~12 h. Trp-rich diet also caused increase in serum melatonin levels, and the duration of such response varied with the time of food supply. Collectively, present study not only demonstrates the role of Trp-rich diet as a potential inducer of gut melatoninergic system and modulator of daily serum melatonin profiles, but underlines the importance of the time of food supply as a determining factor of its influence as well.