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The objective of this study was to evaluate the effect of long-term melatonin treatment applied during the non-breeding season on semen characteristics, endocrine function of testicles and baseline level of insulin-like growth factor-I (IGF-I) in Awassi rams kept in the temperate continental zone of Europe and used as semen donors in an artificial insemination (AI) programme. On 23 February (day 0), slow-release melatonin implants were inserted subcutaneously into rams (n = 8). Control animals (n = 8) received no treatment. In both groups, basic semen parameters (concentration, total motility, fast and slow forward motility, morphology), GnRH-induced testosterone response and basal IGF-I concentration were evaluated on days 0, 47 and 71. No differences were found in concentration of spermatozoa, total motility, and numbers of spermatozoa with fast and slow progressive motility and normal/abnormal morphology between the melatonin-treated and the control group. However, in melatonin-treated animals, basal and GnRH-induced testosterone levels were slightly elevated on day 47 and became significantly higher on day 71 (P < 0.05) as compared to controls. There was no difference in plasma IGF-I levels between the groups. In conclusion, slow-release melatonin applied during the non-breeding season improves testicular testosterone production but does not influence the semen characteristics and the IGF-I level of semen donor Awassi rams used in an AI programme and kept in the temperate continental zone of Europe.
Follicular development and oocyte quality were assessed by laparoscopic observation and in vitro fertilisation, respectively, in melatonin-treated (Group M) and control (Group C) anoestrous Chios ewes (n = 10 in each group). Fourteen days after melatonin insertion, all ewes had laparoscopic evaluation of the follicular population followed by oocyte pick-up (OPU); on day 22 intravaginal progestagen sponges were inserted for 14 days. Two days after sponge removal the follicular population was re-evaluated and a second follicular aspiration was performed. Collected oocytes from the second OPU underwent in vitro maturation, fertilisation and culture. The number of large follicles was higher in Group M than in the control ewes during the first OPU and tended to be so (P = 0.06) at the second. Morphologically, oocytes collected from controls were of better quality than those from Group M; however, more oocytes collected from melatonintreated animals fertilised and developed in vitro . These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.
Thin-layer chromatography (TLC) methods coupled with densitometric detection were employed in analyses for the presence of nonhallucinogenic indole compounds in methanol extracts from the garlic (Allium sativum L.) bulbs originating from China, Georgia, Spain, Mexico, and Poland, and from granulated garlic in the form of seasoning (commercial product). Four indole compounds for which the garlic bulbs were analyzed, were detected: 5-methyltryptamine, L-tryptophan, 5-hydroxy-L-tryptophan, and melatonin, the amounts of which ranged from 4.2 to 199.6 mg kg−1 dry weight. In contrast, only 3 indole compounds were found in the garlic bulbs from Spain: 5-methyltryptamine, L-tryptophan and melatonin (85.7, 120.1, and 9.6 mg kg−1 dry weight, respectively). The total amount of indole compounds in the extracts from the garlic bulbs from China was the highest (415.4 mg kg−1 dry weight), while the amounts in the others (from Georgia, Spain, Mexico, Poland) were similar and ranged from 215.4 to 283 mg kg−1 dry weight. The granular, freeze-dried garlic contained the lowest content of indole compounds, and their total amount was only 207 mg kg−1 dry weight.
In order to examine the effect of exogenous melatonin on selected biochemical variables of the blood in ruminants, dairy cows were given the pineal gland hormone in the dose of 0.1 mg/kg body weight. One and four hours after melatonin administration blood samples were collected from the cows in the control and the treated group in order to determine the levels of glucose, insulin, total cholesterol, triglycerides, free fatty acids, as well as the activities of alanine and aspartate aminotransferase. The pineal gland hormone caused a significant increase in the levels of total cholesterol and triglycerides, slight increases in glucose and insulin levels, and a significant decrease in the concentration of free fatty acids. Melatonin did not exert an effect on the activity of liver enzymes.
Alonso-Vale, M. I. C., Andreotti, S., Peres, S. B., Anhe, G. F., Borges-Silva, C. N., Neto, J. C., Lima, F. B. (2005) Melatonin enhances leptin expression by rat adipocytes in the presence of insulin. Am. J. Physiol. Endocrinol. Metab. 288 , E805–E
Introduction Breeding cycles in horses are influenced by daylight, environmental temperature and nutritional intake level. On one hand, the main trigger is the increasing daylight in spring which results in a lower mean melatonin concentration and
melatonin on thyroid hormones in rats. Toxicology 195 , 69–75. Ugur A. Opposite effects of zinc and melatonin on thyroid hormones in rats Toxicology
Introduction Melatonin (N-acetyl-5-methoxytryptamine) is an endogenous indoleamine hormone structurally related to some substances such as tryptophan, serotonin, and indole-3-acetic acid. In mammals, melatonin is a biological regulator of various
serious medical, social, and economic burden for the society ( 4 ). Risk factors include hypertension, diabetes, generalized atherosclerosis, smoking, and heart diseases ( 29 ). Melatonin (N-acetyl-5-methoxytryptamine) is a key endogenous
Bartness, T. J., Powers, J. B., Hastinas, M. (1993) The timed infusion paradism for melatonin delivery: What has it taught us about the melatonin signal, its reception, and the photoperiodic control of seasonal responses? J. Pineal Res. 15 , 161
