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[en] The possible relationship between exposure to extremely low electric and magnetic fields (EMF) and biological effects has become a public concern and a very active research topic. Many in vitro and in vivo studies have been carried out to explore the possible mechanism by which those fields can influence the functioning of living cells and whole animals. One of the ways in which electric or magnetic fields may effect animals and men is via melatonin. (author)
[en] A mixture of brominated melatonin derivatives has been synthesized for use as starting material for preparation of ring tritium labelled melatonin by catalytic hydrogenolysis. The high specific activity obtained makes this product useful in radioimmunoassay studies. (author)
[en] This study aimed to evaluate if melatonin implantation at the end of April and June was able to increase cashmere production in female Inner Mongolian cashmere goats and to search for contributing factors accounting for the melatonin increasing in cashmere production. One hundred and fifty female Inner Mongolian cashmere goats (initial body weight 37.2 ± 3.3 kg) were randomly assigned to either a control (n=75) or a treatment (n=75) group. Goats in the treatment group were implanted with melatonin (2 mg/kg of body weight) on April 30 and June 30, 2014 while goats in the control received no treatment. Melatonin implantation increased cashmere yield by 23.4% while increasing the length and density of the cashmere fiber by 19.8% and 11.4%, whereas it decreased cashmere fiber diameter by 4.4%. Melatonin treatment had no effect on doe growth, litter size or birth and weaning weights of kid. Melatonin implantation promoted cashmere yield by increasing fiber length and density without impacting the performance of goats and their offspring. Therefore, melatonin implantation during the cashmere non-growing period (late April and June) is an effective way to increase cashmere yield and improve cashmere characteristics of goats.
[en] Small ruminants from middle and high latitudes have a limited breeding season beginning in summer or autumn. Their reproductive capacity is thus lowered unless techniques for inducing oestrus and ovulation are used. The photoperiod is the main trigger (proximal factor) of reproductive activity in both male and female. The pineal gland is implicated in the response to photoperiod treatment because of the diurnal rhythm in the secretion of its hormone, melatonin. The combination of photoperiod treatment and administration of melatonin opens up new prospects for breeding period control. Small ruminants from the tropical and subtropical zones, on the other hand, are less seasonal in their reproductive activity. Other environmental factors (relationship between individuals; males-females and females-young, nutritional level, temperature, etc.) appear to have a regulatory role in this activity (termination or initiation). Alteration of these factors (male effect, for example) can improve breeding period control. (author)
[en] Alterations in size of the pineal body and melatonin secretion have been observed in cancer patients. The present study was carried out to evaluate pineal dimension in a group of cancer patients and their relation to melatonin blood levels. The study included 70 oncologic patients. As controls, 41 patients with acute or chronic disease other than cancer entered the study. Melatonin serum levels were measured by radioimmunoassay on venous blood samples collected at 9:00 a.m. Pineal size was determined by brain CT scan, by considering the product of the two longest perpendicular diameters, multiplied by the thickness of the stratum. The volume of the pineal body was found to be enlarged in 12/70 (17%) cancer patients, and its mean value was significantly higher than that observed in controls. Melatonin levels were also significantly higher in oncologic patients than in controls. However, there was no correlation between melatonin levels and pineal size in cancer patients. Finally, cancer patients did not show a higher degree of pineal calcifications than controls. The clinical significance of pineal enlargement in cancer patients remains to be understood
[en] Melatonin, a lipophilic molecule that is mainly synthesized in the pineal gland, performs various neuroprotective functions. However, the detailed role and mechanisms of promoting neuronal differentiation remains limited. This study demonstrated that 10 μM melatonin led to significant increases in the proliferation and neurite outgrowth of PC12 cells. Increased expression of microtubule-associated protein 2 (MAP2, a neuron-specific protein) was also observed. However, luzindole (melatonin receptor antagonist) and PD98059 (MEK inhibitor) attenuated these increases. LY294002 (AKT inhibitor) inhibited melatonin-mediated proliferation in PC12 cells and did not affect melatonin-induced neural differentiation. The expression of p-ERK1/2/ERK1/2 was increased by melatonin treatment for 14 days in PC12 cells, whereas luzindole or PD98059 reduced the melatonin-induced increase. These results suggest that the activation of both the MEK/ERK and PI3K/AKT signaling pathways could potentially contribute to melatonin-mediated proliferation, but that only the MEK/ERK pathway participates in the melatonin-induced neural differentiation of PC12 cells. Altogether, our study demonstrates for the first time that melatonin may exert a positive effect on neural differentiation via melatonin receptor signalling and that the MEK/ERK1/2 signalling may act down stream from the melatonin pathway. - Highlights: • Melatonin improves the proliferation of PC12 cells. • Melatonin induces neural differentiation of PC12 cells. • Melatonin-mediated proliferation in PC12 cells relies on the ERK and AKT pathways. • Activation of ERK is essential for melatonin-induced neural differentiation of PC12.
[en] Melatonin and Ca2+ have been implicated in growth, development and stress responses in plants. Here, we report the effects of exogenous melatonin and Ca2+ on growth, photosynthetic capacity, antioxidant potential and ion homeostasis in melon (Cucumis melon L. cv. Yangjiaosu) seedlings under salt stress. It was observed that salt stress significantly inhibited growth in melon seedlings, while exogenous application of melatonin and Ca2+ alleviated the inhibition. Further analysis showed that exogenous application of melatonin or Ca2+ promoted photosynthetic rate and water use efficiency in salt-stressed melon seedlings. In addition, exogenous melatonin or Ca2+ enhanced accumulation of Ca2+, but reduced accumulation of Na+ in both leaves and roots of melon seedlings under salt stress. Furthermore, exogenous melatonin or Ca2+ reduced oxidative damage, as demonstrated by decreased electrolyte leakage and MDA content, by stimulating activities of antioxidant enzymes, including SOD, POD, CAT and APX, in salt-stressed melon seedlings. Collectively, these results suggest that exogenous melatonin or Ca2+ acts in the alleviation of salt stress by improving photosynthesis, maintaining ion homeostasis and elevating antioxidant capacity in melon seedlings. Our work also provides a case study and melatonin or Ca2+ may serve as useful agent to relieve salt stress in agricultural production. (author)
[en] The impact of the non-visual action of light on the design of novel light sources is discussed. Therefore possible modifications of lamps dealing with spectral tailoring and their action on melatonin suppression in usual life situations are investigated. The results of melatonin suppression by plasma lamps are presented. It is shown that even short-time exposure to usual light levels in working areas has an influence on the melatonin onset.
[en] Melatonin, a pineal indolamine, participates in different body functions and is shown to possess diverse biological activities such as anti-tumor action. Angiogenesis inhibition is one of the mechanisms by which melatonin exerts its oncostatic effects. Increased angiogenesis is a major feature of tumor progression, thus angiogenesis inhibition is a critical step in cancer therapy. Melatonin employs a variety of mechanisms to target nutrients and oxygen supply to cancer cells. At the transcriptional level, hypoxia induced factor-1α (HIF-1α) and the genes under its control, such as vascular endothelial growth factor (VEGF) are the main targets of melatonin for inhibition of angiogenesis. Melatonin prevents translocation of HIF-1α into the nucleus thereby hindering VEGF expression and also prevents the formation of HIF-1α, phospho-STAT3 and CBP/p300 complex which is involved in the expression of angiogenesis-related genes. Angiostatic properties of melatonin could be also due to its ability to inhibit VEGFR2’s activation and expression. Other angiostatic mechanisms of melatonin include the inhibition of endothelial cell migration, invasion, and tube formation. In the present study, we have reviewed the molecular anti-angiogenesis pathways mediated by melatonin and the responsible mechanisms in various types of cancers both in vitro and in vivo.