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| Yuri Koutcherov |
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Prince of Wales Medical Research Institute, Barker Street Randwick NSW 2031, Australia
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Presentation: |
| 2002-10-07, 09:00-09:45 |
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| Development of the human hypothalamus. |
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| Structural differentiation of the human hypothalamus was studied in 33 brains aged from 9 weeks of gestation (w.g.) to newborn, using immunohistochemistry for parvalbumin, calbindin, calretinin, neuropeptideY, neurophysin, growth associated protein GAP43, synaptophysin and glycoconjugate, 3-fucosyl-N-acetyl-lactosamine. The use of chemoarchitecture in the human fetus permitted a depiction of differentiation process with high degree of structural resolution but not a high accuracy of timing and not of functional aspects of the hypothalamic structures. The analysis also allowed the identification of interspecies nuclei homologies which otherwise remain concealed in cytoarchitecture. Developmental stages, established by this study, are described in relation to obstetric trimesters. The first trimester (morphogenetic periods 9-10 w.g. and 11-14 w.g.), is characterized by differentiating structures of the lateral hypothalamic zone, which give rise to the lateral hypothalamus (LH) and posterior hypothalamus. The perifornical nucleus differentiates at 18w.g., from LH neurons which remain anchored in the perifornical position while most of the LH cells are displaced laterally. A transient supramamillary nucleus was apparent at 14 w.g. but not after 16 w.g. As the ventromedial nucleus differentiated at 13-16 w.g., three principal parts; the ventrolateral, the dorsomedial and the shell were revealed by distribution of calbindin, calretinin and GAP43 immunoreactivity. The second trimester (morphogenetic periods 15-17 w.g., 18-23 w.g. and 24-33 w.g.), is characterized by differentiation of the hypothalamic core, in which calbindin positive neurons revealed the medial preoptic nucleus at 16 w.g. abutted laterally by the intermediate nucleus. The dorsomedial nucleus was clearly defined at 10 w.g. and consisted of compact and diffuse parts, an organisation that was lost after 15 w.g. Differentiation of the medial mamillary body into lateral and medial was seen at 13-16 w.g. Late second trimester was marked by differentiation of periventricular zone structures including suprachiasmatic, arcuate and paraventricular nuclei. The subnuclear differentiation of these nuclei extends into the third trimester. |
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