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Serum thymidine activity and insulin-like growth factors in the neonatal period
Insights
Neonatal growth factors, including insulin-like growth factors (IGFs) and thymidine activity, were studied in newborns. Postnatal changes suggest infant production of these growth factors, potentially influencing fetal growth and neonatal development.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Molecular Biology
Background:
- Insulin-like growth factors (IGFs) I and II are crucial for fetal and postnatal growth.
- Thymidine incorporation into lymphocytes reflects cellular proliferation and growth activity.
Purpose of the Study:
- To investigate the levels and changes of IGF-I, IGF-II, and growth-promoting activity in neonatal blood.
- To explore the relationship between these parameters and birth weight.
- To understand the role of growth factors in fetal development and neonatal growth.
Main Methods:
- Radioimmunoassayable IGF-I and IGF-II were measured in cord and capillary blood from neonates.
- [3H] thymidine incorporation into lectin-activated lymphocytes was used to assess growth-promoting activity.
- Blood samples were collected at 30 minutes and 24 hours after birth.
Main Results:
- Cord blood levels of IGF-I, IGF-II, and thymidine activity were lower than in adults.
- Postnatally, IGF-I decreased, IGF-II remained stable, while thymidine activity increased above adult levels.
- Differences between cord and early capillary blood suggested infant growth factor production, correlating with birth weight.
Conclusions:
- IGFs and other factors contribute to fetal growth and neonatal development.
- Infant production of growth factors begins early postnatally.
- Factors beyond IGFs are involved in neonatal growth, as indicated by elevated thymidine activity.
Abstract:
Growth-promoting activity measured as [3H] thymidine incorporation into lectin-activated lymphocytes was determined simultaneously with radioimmunoassayable IGF I and IGF II in cord and capillary blood collected from human neonates 30 min and 24 h after birth. All the parameters studied in cord blood were lower than in normal adults. During the early postnatal period, IGF I decreased and IGF II remained unchanged, but thymidine activity increased above the normal adult level. The differences between the values found in cord blood and in capillary blood collected within the first 1/2 h after birth agree with a production of growth factors by the infant. All these growth factors may play a role in foetal growth, as suggested by their correlation with birth weight. Finally, factors other than IGFs contributing to thymidine activity may play a role in neonatal growth since they are higher in newborns than in adults.