Search NEL Online

Journal Article 2001; 22(6): 441-447 PubMed PMID: 11781542 Citation  Keywords:  Age Factors, Animals, Antioxidants:pharmacology, Female, Gene Expression Regulation, Neoplastic:drug effects, Mammary Neoplasms, Experimental:drug therapy, Melatonin:pharmacology, Mice, Mice, Transgenic, Photoperiod, RNA, Messenger:analysis, Receptor, Erb.   

OBJECTIVES AND DESIGN: The effect and the mechanism of light regimen and melatonin on the development of mammary tumors in HER2/neu transgenic mice were investigated. Female HER-2/neu mice starting from the age of 2 months were kept under standard light/dark regimen (LD) or constant light illumination (LL) and a part of each group was given melatonin (20 mg/l) during the night time.

RESULTS: The exposure to LL failed to change the incidence of spontaneous mammary adenocarcinoma development, the size of mammary tumors, as well as the incidence and size of lung metastases. However, the number of tumors per mouse was significantly increased in the LL group as compared to the LD group. The number of mice bearing 4 and more tumors was higher in the LL group than in the LD group, whereas the number of mice bearing 1 to 3 tumors was lower in the LL group in comparison with the LD group. Melatonin decreased the incidence and size of mammary adenocarcinomas, and the incidence of lung metastases in the LD group but not in the LL group. The mean number of tumors per mouse was not changed by melatonin treatment in both light regimens. The number of mice bearing 4 and more tumors was reduced by melatonin more significantly in the LL group than in LD group. Melatonin treatment resulted in a 2.5-fold reduction in the expression of HER-2/neu mRNA in mammary tumors from HER-2 /neu transgenic mice.

CONCLUSION: The data demonstrate the influence of the LD light regiment and melatonin treatment in the development of spontaneous mammary tumors in HER-2/neu mice suggesting a melatonin-dependent modulation of HER-2/neu gene expression in mammary adenocarcinoma....

Read abstract  Full text PDF

Journal Article 2001; 22(3): 169-174 PubMed PMID: 11449194 Citation  Keywords:  Animals, Humans, Hypothalamus:drug effects, In Vitro Techniques, Melatonin:pharmacology, Oxytocin:biosynthesis, Photoperiod, Pineal Gland:physiology, Pituitary Gland, Posterior:drug effects, Vasopressins:biosynthesis,.   

: The present paper reviews the findings accumulated on the role of pineal gland and its hormone - melatonin - in regulation of the hypothalamo-neurohypophysial system activity. Effects of modified photoperiod, pinealectomy or treatment with melatonin on the vasopressin and oxytocin biosynthesis and/or secretion have been described. Taken together, the in vivo and in vitro data suggest that the effect of melatonin on the vasopressin and oxytocin secretion depends on this pineal hormone concentration and experimental conditions....

Read abstract  Full text PDF

Journal Article 2018; 39(4): 277-280 PubMed PMID: 30531704 Citation  Keywords:  Animals, Hypothalamus:enzymology, Light, Male, Neprilysin:metabolism, Photoperiod, Pituitary Gland:enzymology, Rats,.   

OBJECTIVES: Enkephalins functions are partly modulated by enkephalinases especially membrane-bound alanyl aminopeptidase (EC-3.4.11.2) considered as the major enkephalin-degrading enzyme in brain. The analysis of its activity in standard and non-standard light/dark conditions may help the understanding of the regulatory mechanisms of enkephalins. METHODS: Enkephalinase activity was determined fluorometrically, using an arylamide derivative as substrate, in hypothalamus and pituitary of adult male rats, in a standard 12:12 h light/dark cycle; samples were collected at 10:00 h, 13:00 h and 16:00 h of the light period (light on from 7:00 to 19:00 h) and at 22:00 h, 01:00 h and 04:00 h of the dark one (light off from 19:00 h to 07:00 h). For comparison, the enzymatic activity was also measured in the same locations at the same time-points but under constant light conditions. RESULTS: In standard light/dark conditions, the results demonstrated an opposite daily rhythm in hypothalamus and pituitary. While the highest levels of AlaAP or enkephalinase activities were measured in hypothalamus during the dark period, they were the highest in the pituitary during the light one. In contrast, the lowest levels of activity were observed in the light period in the hypothalamus whereas they were in the dark one in the pituitary. A similar pattern was observed under constant light. The differences were however higher in hypothalamus and lower, but still significant, in pituitary. CONCLUSION: These results may reflect the behaviour of the endogenous substrates of enkephalinase and consequently be involved in their functions. This observation may affect the chronotherapeutic strategies....

Read abstract  Full text PDF