The concept of the foeto-placental unit as an integrated endocrine organ has been defined recently by many in vivo studies at the 17th- 20th week of gestation. A functioning foeto-placental unit is necessary for most of the increased oestrogen production of pregnancy and for the provision of glucocorticoids and aldosterone to the foetus. Neither the foetus nor the placenta alone have the necessary enzyme systems for the synthesis of these groups of steroids. However, when the foetus and placenta function as a unit, all of the enzyme systems are present for the synthesis of these steroids from circulating cholesterol. The placenta, but not the mid-gestation foetal adrenal, can synthesize physiologically significant amounts of pregnenolone from circulating cholesterol. Part of the pregnenolone is converted to progesterone in the placenta by the 3~-HSD system (absent in the foetus). The progesterone is transferred to the foetus where it is transformed by C-II, C-17, C-18 and C-21 hydroxylases (all absent in the placenta) to cortisol, corticosterone and aldosterone. Pregnenolone transferred from the placenta to the foetus undergoes 171X-hydroxylation, side chain splitting and sulfurylation (absent in the placenta) and is converted to DHAS. The DHAS may undergo 161X-hydroxylation (absent in the placenta) in the foetal liver and be transported to the placenta as 161X-OH-DHAS. There it is subjected to a neutral steroid sulfatase (absent in the foetus) and is converted to oestriol by action of the 3~-HSD system and the aromatizing enzyme system.
Erscheinungsdatum: 14.10.2011

lgrsnf/A:\Springer\bok%3A978-94-010-3428-9.pdf

nexusstc/Aspects of Praematurity and Dysmaturity: Groningen 10–12 May 1967/870dbfa9ded73d7a4f43d9f12da26da1.pdf

zlib/Medicine/John W. Reynolds (auth.), J. H. P. Jonxis M.D., H. K. A. Visser M.D., J. A. Troelstra M.D. (eds.)/Aspects of Praematurity and Dysmaturity: Groningen 10–12 May 1967_2241709.pdf

Springer Science + Business Media BV

Nutricia Symposium, 2, Dordrecht, 1968

Netherlands, Netherlands

Oct 14, 2011

2012

lg1072743

{"edition":"1","isbns":["9401034281","9401034303","9789401034289","9789401034302"],"last_page":368,"publisher":"Springer Netherlands","series":"Nutricia Symposium 2"}

Source title: Aspects of Praematurity and Dysmaturity: Groningen 10-12 May 1967 (Nutricia Symposia)

Front Matter....Pages I-XI
Front Matter....Pages 1-1
Aspects of Steroid Metabolism in the Foeto-Placental Unit and the Newborn Infant....Pages 3-20
Problems in the Pathologic Study of the Placenta....Pages 21-23
Back Matter....Pages 25-34
Front Matter....Pages 35-35
Growth Pattern of the Normal and the Deprived Fetus....Pages 37-45
The Assessment of Foetal age by the Examination of the Central Nervous System....Pages 46-56
Developmental Changes in Fetal Hemoglobin....Pages 57-67
Developmental Changes in Liver Enzyme Activities with Special Reference to the Perinatal Period of Life....Pages 68-90
Development of Enzymes and Absorption Processes in the Small Intestine of Human Fetus....Pages 91-98
Back Matter....Pages 99-116
Front Matter....Pages 117-117
Dysmaturity in the Experimental Animal....Pages 119-126
Effects of Prematurity and Dysmaturity in Animals....Pages 127-137
Back Matter....Pages 139-146
Front Matter....Pages 147-147
Factors Influencing Fetal Growth....Pages 149-166
The Regulation of Foetal Growth....Pages 167-188
Back Matter....Pages 189-197
Front Matter....Pages 199-199
The Metabolic Rate in Praemature, Dysmature and Sick Infants in Relation to Environmental Temperature....Pages 201-209
Glucose Control in the Newborn Infant....Pages 210-227
Neuropathological Findings in Severe Neonatal Hypoglycaemia with Remarks Concerning Lesions Due to Hypoxia....Pages 228-234
Hyperbilirubinaemia in Dysmature Versus Premature Infants....Pages 235-244
Back Matter....Pages 245-259
Front Matter....Pages 261-261
The Obstetrician and Dysmaturity....Pages 263-280
Back Matter....Pages 281-284
Front Matter....Pages 285-285
Causes of Handicap in the Low Weight Infant....Pages 287-302
Neurological Findings in Newborn Infants After Pre- and Paranatal Complications....Pages 303-321
Back Matter....Pages 323-328
Back Matter....Pages 329-356

2013-12-12