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Nuclear compartmentalization in transcriptionally activated hypothalamic neurons
L M Garcia-Segura1, M T Berciano, M Lafarga
1Instituto Cajal, CSIC, Madrid, Spain.
Biology of the Cell
|January 1, 1993
Summary
Rises in plasma osmolarity increase transcription in supraoptic neurons. Nuclear changes, including chromatin decondensation and altered nuclear particle distribution, reflect this activation and its suppression.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Supraoptic neurons regulate water balance via vasopressin and oxytocin.
- Osmotic stimuli activate gene transcription in these neurons.
Purpose of the Study:
- To investigate nuclear structural and functional changes in supraoptic neurons during osmotic stimulation.
- To analyze alterations in nuclear volume, chromatin ultrastructure, and nuclear particle distribution.
Main Methods:
- Analysis of nuclear volume and chromatin ultrastructure on ultrathin sections.
- Assessment of nuclear particle number and distribution using freeze-fracture replicas.
- Study of male Sprague-Dawley rats subjected to acute (1 day) and chronic (6 days) dehydration, followed by rehydration.
Main Results:
- Osmotic stimulation increased nuclear volume and altered nuclear particle composition, with larger particles replaced by smaller ones, particularly in the nuclear periphery.
- Chronic stimulation led to enhanced chromatin decondensation and particle changes, extending into the nuclear interior.
- Rehydration reversed some changes, with nuclear periphery particle numbers returning to control levels, while the nuclear interior showed decreased small particles and increased large particles.
Conclusions:
- Osmotic activation of transcription in supraoptic neurons involves significant nuclear structural modifications.
- Evidence suggests structural and functional compartmentalization within the supraoptic neuron nucleus.
- These nuclear changes are dynamic and reversible upon cessation of osmotic stimulation.