The finger length ratio (2D:4D) is a biomarker for the prenatal levels of testosterone. The prenatal effects of testosterone on the development of brain hemispheres are considered as a key factor in the etiology of left-handedness. We tested whether 2D:4D correlates with the type of handedness in males (18 right-handers and 18 left-handers). Right hand 2D:4D, left hand 2D:4D, average 2D:4D, and the difference between right and left 2D:4D (D(r-l)) were compared. The value of D(r-l) in left-handers was significantly lower than D(r-l) in right-handers. This result can be interpreted as proof that left-handers were subjected to higher levels of testosterone in utero.
Geschwind and Galaburda (1985a, 1985b) suggested that the season of conception is a non-genetic random variable that may affect laterality and handedness, probably due to seasonal variations in the hormonal influences on the foetal brain. According to this suggestion it is logical to expect seasonal anisotropy in the incidence of birth of right- and non-right-handers. The present study analysed data obtained from a sample of 3182 young Bulgarians: 2825 right-handers and 357 non-right-handers. Significant difference in the seasonal distribution of births of right- and non-right-handers was found in males only. The incidence of non-right-handedness was highest among participants born in winter. In right-handers increased birth rate was observed in spring and summer. The results in males seem to support the Geschwind and Galaburda suggestion. One can speculate that the high levels of mother's androgens during spring and early summer play the role of a "left shift" factor for the male foetuses with genetic potential for non-right-handedness.
This study examines the influence of melatonin on the PC anticoagulant pathway in rats. The experiment was performed on 52 male white Wistar rats weighing 200-220 g. Animals were equally divided into 4 groups. They were treated in three consecutive days, every 12 hours, subcutaneously: 1 st group -with saline solution (solvent for melatonin and luzindole); 2 nd group -with melatonin, daily dose 0.2 mg/kg body weight; 3 rd group -with luzindole, nonstop dose of 0.4 mg/kg body weight; 4th group -melatonin, one hour after pretreatment with luzindole. The required amount of blood was taken under urethane narcosis via direct cardiac puncture. After three days of administration of melatonin, a significant decrease in the antigen concentration of protein C, protein C activity, activated protein C and thrombomodulin was observed. The soluble form of the endothelial receptor for protein C, activity of protein S and free protein S were significantly elevated. The competitive melatonin receptor antagonist -luzindole, when administered alone and in pretreatment, effectively removes the observed effects of melatonin by blocking exogenous, as well as endogenous melatonin. In conclusion, our data give us reason to assume that melatonin significantly reduces the activity of the protein C anticoagulant pathway in rats.
The thymus and pineal gland (epiphysis) are endocrine glands with pivotal role in the maintenance of normal physiological processes. Their hormonal activity has been the subject of many studies, but on most occasions, each gland has been considered separately. Surveys that identify the link between these two glands, as well as the connection between their hormones, appeared only recently. The growing body of data about the morphology and the functions of the thymus and epiphysis reveals not only the bi-directional links between these glands but also common involutionary mechanisms. The immune activity of the thymus is wellknown, and the results indicate that melatonin has significant immunomodulatory potential as well. The hormones of both glands play a role in the antioxidant and antitumor defense of the organism, as well as in the hemostasis processes. Some studies confirm the existence of a functional relationship between the endocrine, immune, and nervous systems and the contribution of thymic and pineal hormones to its establishment. The association between thymus and epiphysis is important not only for the normal immune response but also for the regulation of aging and the occurrence of age-related conditions and diseases.
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