Developmental aspects of the XXXX brain @entity8683 : loss of @entity3167 and fluctuation in number characterize fetal development.

@entity3505 @entity3167 @entity7263 @entity8683 @entity35
In this study, I have investigated the structure of the @entity35 brain @entity8683 during fetal development. There is a progressive decrease in the apparent molecular size of the brain alpha-subunit during development: 130K on day 16 of gestation, 126K at birth, and 120K in the adult. Glycosylation was investigated as a possible reason for the observed differences in the alpha-subunit molecular size. The results show that the developmental decrease in the brain alpha-subunit apparent molecular size is due to a parallel decrease in @entity3167 content. This was further confirmed by measuring the retention of autophosphorylated insulin receptors on @entity3505 germ agglutinin (WGA)-Sepharose. An inverse correlation between developmental age and retention of @entity7263 -labeled insulin receptors on the lectin column was observed. Insulin binding increases 6-fold between 16 and 20 days of gestation [61 +/- 25 (+/- SE) fmol/mg protein and 364 +/- 42 fmol/mg, respectively]. Thereafter, binding in brain membranes decreases to 150 +/- 20 fmol/mg by 2 days after birth, then reaches the adult level of 63 +/- 15 fmol/mg. In addition, the degree of insulin-stimulated autophosphorylation closely parallels the developmental changes in insulin binding. Between 16 and 20 days of fetal life, insulin-stimulated phosphorylation of the beta-subunit increases 6-fold. Thereafter, the extent of phosphorylation decreases rapidly, reaching adult values identical with those in 16-day-old fetal brain. These results suggest that the embryonic brain possesses competent insulin receptors whose expression changes markedly during fetal development. This information should be important in defining the role of insulin in the developing nervous system.
