Effect of pineal indoles on the chick embryo

Ooi, V C; Lee, DorothyW.M; Ng, Tzi Bun

doi:10.1016/s0306-3623(98)00182-7

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…following should be pointed out: elevated toxicity in chicken embryos [192], inhibition of reproductive function, delay of puberty onset, variations in the circadian cycle of the foetus and of the newborn [193], increment in the myelotoxicity in certain oncological treatments [194]. Moreover, melatonin has been reported to exaggerate collagen induced arthritis [195] and promote T cell leukemia [196].…”

Section: Sub-epithelial Mechanismsmentioning

confidence: 99%

New Issues About Melatonin and its Effects on the Digestive System

Motilva¹,

Deogracias²,

Lastra

2001

CPD

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In human beings, melatonin is secreted in a cyclic way by the pineal gland, although it has been detected in other tissues. Synthesis of melatonin takes place in the pinealocyte. It depends on adrenergic stimulation, and its secretion is related to the photoperiod in a circadian model of low activity during light phase and high activity at night time. Former studies aimed to establish the mechanisms by which melatonin carries out its biological function, proved the existance of high affinity binding sites. However, melatonin can pass through the plasmatic membrane; this property suggested a possible activity of the hormone inside the cell trough activation of nuclear receptors. Moreover, melatonin can act by itself as a potent oxygen-free-radical scavenger, which renders it a very strong antioxidant. It is currently accepted that melatonin plays an important role in numerous physiological processes. The gastrointestinal tract of numerous animal species contains melatonin, which is synthesized essentially by intestinal enterochrommaffin cells. Some investigations have revealed that its liberation follows also a circadian rhythm, although its secretion pattern might be influenced by nutritional factors. Receptors for melatonin have been identified in the digestive system, therefore the indolamine might play a leading role in different aspects of the vast digestive physiopathology. The hormone may interact with receptors and subsequently stimulate the synthesis of gastroprotective hormones and also exerts a direct defense on the epithelium, enhances submucosal blood flow and prevents the damage induced by ischemia followed by reperfusion. Moreover, studies have shown that treatment with melatonin reduces the severity of the lesions induced by NSAIDs on gastric mucosa suggesting a beneficial role of melatonin in preventing this gastropathy related to antiinflammatories.

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Section: Sub-epithelial Mechanismsmentioning

confidence: 99%

New Issues About Melatonin and its Effects on the Digestive System

Motilva¹,

Deogracias²,

Lastra

2001

CPD

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Melatonin receptor genes (mel‐1a, mel‐1b, mel‐1c) are differentially expressed in the avian germ line

Kawashima¹,

Stępińska²,

Kuwana³

et al. 2008

Molecular Reproduction Devel

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The presence of melatonin receptor transcripts (mel-1a, mel-1b and mel-1c) was investigated in primordial germ cells (PGCs), immature and mature oocytes, and sperm of Japanese quail by reverse transcription--polymerase chain reaction (RT-PCR). The mel-1a transcript was detected in as few as in a thousand PGCs. Significant differences in the expression of melatonin receptor genes were found in differentiating germ cells: in PGCs only the mel-1a receptor was expressed, in blastoderms and immature oocytes all three transcripts (mel-1a, mel-1b, mel-1c) were present, while in mature ovulated oocytes the predominant transcript was mel-1c (with sporadic occurrence of mel-1a and mel-1b). In sperm, mel-1a and mel-1c were present but mel-1b was absent. This indicates that the expression of melatonin receptor genes changes throughout the differentiation of PGCs into adult gametes: during oocyte differentiation two additional transcripts, mel-1b and mel-1c, are synthesized in addition to mel-1a, but at oocyte maturation, mel-1a and mel-1b are degraded and only mel-1c remains. During male line (spermatozoa) differentiation mel-1c is transcribed in addition to mel-1a, with mel-1b being completely absent. Since melatonin and the activities of enzymes participating in melatonin synthesis are present in the avian yolk, it is reasonable to suggest a role for this molecule in early avian development and germ line differentiation. We propose that melatonin may act as a signaling molecule regulating some differentiation processes (e.g., cell proliferation, migration, etc.) before the formation of neural and hormonal systems.

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