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An effect of environmental factors on foetal development in mammals
Sedláčková, Lucie ; Bartoš, Luděk (advisor) ; Bučková, Katarína (referee)
The development of fetus begins with merging of male and female sex cells, of the sperm with the egg, and with the formation of zygote. This moment triggers a complex process of prenatal development, a period very sensitive to changes and adverse conditions in the mothers surroundings. Such circumstances may include poor nutrition, sudden changes in the mothers social environment, a high occurrence of predators, stressful experiences due to inadequate handling and many other factors. All of these are connected by a frequently spelled term - stress.
It is stress that causes excessive discharge of glucocorticoid hormones, for example cortisol. This glucocorticoid is necessary for fetal growth and for induction of certain enzymes, such as lung surfactants. Under certain conditions, maternal cortisol can reach abnormal values. Consequently, the excess of cortisol impacts the fetus in high concentrations, which may negatively influence the growth of the fetus and its development.
In mammals, the mothers stress during her pregnancy not only increases her own cortisol levels, but also decreases the expression and activity of glucocorticoid barrier enzyme 11beta-HSD2 in the placenta; therefore, the fetus is less protected. On the other hand, this affects placental production and metabolism of other proteins and hormones sensitive to glucocorticoid, such as prostaglandins, progesterone, estrogens, glucose transporter and placental lactogen. Additionally, inhibition of 11beta-HSD2 by prenatal stress might contribute to low birth weight and to pregnancy diseases, such as premature birth.
Prenatal stress mainly affects brain development. The effects of prenatal stress in mammals have been observed with increased latency for games, indirect locomotion behavior, anxiety and impaired memory. Prenatal stress is also associated with greater volatility and attention disorders, which are also connected with a reduced learning ability. It has been ascertained that prenatally stressed individuals may exhibit increased aggressive behavior, demasculinized and feminized behavior has been observed in males.
The effects of prenatal stress are transmissible to the next generation and there is evidence that these are manifested to a greater extent in the following generations.
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