Effects of brain and mesenchyme upon the cytogenesis of XXXX adenohypophysis in vitro. II. Differentiation of LH cells.

@entity35 @entity75 @entity1640
The objective of this in-vitro study was to examine whether the @entity1640 floor or the mesenchyme is involved in differentiation of LH cells in the developing @entity35 adenohypophysis. Overall growth of the adenohypophysial tissue was retarded when the adenohypophysial primordium was cultivated after enzymatic removal of the @entity1640 floor on days 11.5 and 12.5 of gestation. This malgrowth was more marked when the brain was separated on day 11.5; most explants retained a simple cystiform structure that consisted of a few layers of undifferentiated cells. @entity75 also caused a highly significant decrease (P less than 0.001) in the number of immunoreactive LH cells, if it was performed on day 11.5 but not day 12.5. Mesenchyme had little effect on the adenohypophysial growth or the number of immunopositive cells. Cultivation of the adenohypophysial primordium with the @entity1640 floor resulted in the appearance of many immunoreactive LH cells. The number of LH cells significantly decreased, however, when the co-cultivated brain completely surrounded the adenohypophysial tissue. These results indicate that in 11.5-day-old fetal @entity35 the @entity1640 floor is indispensable for the initial proliferation of adenohypophysial primordial cells and for the early determinating process of LH cells. Once determined, the development of LH cells may proceed without the surrounding tissues. The cytodifferentiation seems to be rather inhibited when in contact with the brain. The significance of the intimate spatial relationship between developing LH cells and the surrounding mesenchyme is also discussed.
