Foetal brain development

Lazzaro D, Price M, de Felice M, Di Lauro R. The transcription factor TTF-1 is expressed at the onset of thyroid and lung morphogenesis and in restricted regions of the foetal brain. Development. 1991 113 1093-1104. 

C.H. Hua, B.G. Gragg and B.D. Hetzel, The effect of maternal thyroidectomy prior to conception on foetal brain development in sheep,... 

Foetal mesencephalic tissue has been implanted in the striatum of patients with the juvenile form of Parkinson s disease and has been shown to develop functional axons this has enabled the dose of L-dopa to be reduced. Both imaging and pharmacological studies have now shown that functional dopaminergic neurons can develop in the brain of the patient following tissue transplantation. However, a major ethical objection has been raised to such transplants as six to seven foetal brains are required to obtain sufficient tissue. In addition, only about 20% of neurons survive transplantation. The ethical problem may be overcome by using brain transplants from domestic animals such as pigs. Such xenotransplants have been shown to survive in the human brain but the main problem with the extensive use of such transplants is the possible spread of viruses and prion infections. 

G. Morreale de Escobar, F. Escobar del Rey, R. Pastor, J. Mallol and M.J. Obregon, Effects of maternal thyroidectomy or iodine deficiency on T4 and T3 concentrations in rat concepta, before and after onset of foetal thyroid function, iji lodine nutrition, thyroxine and brain development", N. Kochupillai, M.G. Karmakar and V. Ramalingaswami eds., Tata McGraw-Hill Publ., New Dehli (1986), pp. 109-117. 

Segment 111 peri- and post-natal study. This concentrates on the late part of gestation, not covered by the teratogenicity study, on parturition and on the period of lactation. The study can be particularly useful in detecting subtle effects on the brain, which continues physical and functional development during the foetal and post-natal period, after dosing has ceased in the teratogenicity study. The test animal is usually the rat. 

Tetrahydrocannabinol is metabolized in the liver to form active metabolites which are further metabolized to inactive polar compounds these are excreted in the urine. Some metabolites are excreted into the bile and then recycled via the enterohepatic circulation. Because of their high lipophilicity, most active metabolites are widely distributed in fat deposits and the brain, from which sources they are only slowly eliminated. The half-life of elimination for many of the active metabolites has been calculated to be approximately 30 hours. Accordingly, accumulation occurs with regular, chronic dosing. Traces of the cannabinoids can be detected in the blood and urine of users for many days after the last administration. There is some evidence of metabolic tolerance occurring after chronic use of the drug. THC and related cannabinoids readily penetrate the placental barrier and may possibly detrimentally affect foetal development. 

All forms of mercury are acutely toxic to humans and animals, accumulating in the liver, kidney and brain, and some forms may cause abnormalities in foetal development (teratogenic). The main forms of mercury in the environment are the native nietal, inorganic salts of the (-1-1) and (-1-2) oxidation states and... 

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