Dimethyl-Benz(a)anthracene: A mammary carcinogen and a neuroendocrine disruptor.

Polycyclic Aromatic Hydrocarbons (PAHs) are potent carcinogens. Among these, dimethylbenz(a)anthracene (DMBA) is well known for its capacity to induce mammary carcinomas in female Sprague-Dawley (SD) rats. Ovariectomy suppresses the susceptibility of this model to DMBA, thus suggesting that the inducible action of the carcinogen depends on ovarian hormones.

Short term changes in melatonin and cortisol serum levels after a single administration of estrogen to menopausal women.

Objectives: It has been well-documented that serum melatonin levels are insensitive to estrous or menstrual ovarian steroid variations in the female rat or the human. However, a negative coupling has been already demonstrated between the nocturnal serum melatonin peak and serum E2 concentration during the late premenopausal period in the woman. The objection of the present study was designed to determine if diurnal serum melatonin values can be also lowered by a single administration of estrogen.

Substance P plasma concentration during the LH preovulatory surge of the menstrual cycle in the human.

Objectives: In order to determine the exact pattern of plasma Substance P (SP) concentration during the LH preovulatory surge and the functional correlates which could exist between plasma SP, LH, 17 beta-estradiol (E2) and Progesterone, we performed a detailed analysis of changes in plasma SP concentration, during the critical phases of the LH preovulatory surge in the Human.

Methods: The experimental study was performed in 21 women between the ages of 26 and 35 years. For each subject, blood samples were taken every 15 min, between 07:00 a.

ACTH-cortisol activity during the 17beta-estradiol and LH preovulatory surges of the menstrual cycle.

Objectives: A strong positive coupling has been already documented between the adrenocortical axis and the gonadal axis at the time of the initiation of the preovulatory LH surge of the menstrual cycle in the human. The LH preovulatory surge starts in the morning at the time of the acrophase (maximal plasma cortisol values) of the cortisol circadian rhythm. Also, it was shown that morning maximal plasma cortisol values were higher during the follicular phase than during the luteal phase.

Trisomy 21: from chromosomes to mental retardation.

The first descriptions of the trisomy 21 phenotype were by Jean-Etienne-Dominique Esquirol (1838), Edouard Séguin (1846) and later by John L. H. Down in 1862.

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague-Dawley rat.

Introduction: It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague-Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented.

Long term inhibition by estradiol or progesterone of melatonin secretion after administration of a mammary carcinogen, the dimethyl benz(a)anthracene, in Sprague-Dawley female rat; inhibitory effect of Melatonin on mammary carcinogenesis.

A single intragastric administration of 7,12-dimethylbenz(a)anthracene (DMBA) has been shown to induce mammary tumors in young cycling female Sprague-Dawley rats. The appearance of the tumors is preceded by a series of neuroendocrine disturbances, including attenuation of the preovulatory Luteinizing Hormone surge and Gonadotropin-Releasing Hormone release and amplification of the preovulatory 17beta-Estradiol (E2) surge. In this study, we examined the hypothesis that a single administration of DMBA increases the E2 and Progesterone inhibition of the spontaneous and Isoproterenol-induced Melatonin (MT) secretion from the pineal gland, during the latency phase.

Timing of initiation of the preovulatory luteinizing hormone surge and its relationship with the circadian cortisol rhythm in the human.

The relationship between the hypothalamo-pituitary-gonadal (HPG) axis and the hypothalamo-pituitary-adrenal (HPA) axis has been well documented in the rat. In most cases, a negative coupling was observed and an inhibitory effect of the HPA axis upon the HPG was shown. In the female rat, a marked circadian rhythm of corticosterone plasma values is observed during each day of the estrous cycle, with maximal values around 08:00 p.