Nuclear compartmentalization in transcriptionally activated hypothalamic neurons

Abstract

Transcription of cell-specific vasopressin and oxytocin genes as well as transcription of those housekeeping genes responsible for general metabolic activation and cellular hypertrophy is induced in supraoptic hypothalamic neurons by rises in plasma osmolarity. In this study, the nuclear volume, the ultrastructure of chromatin and the number and distribution of nuclear particles in the cell nuclei of supraoptic neurons of 3-month-old male Sprague-Dawley rats were analyzed after osmotically induced activation of transcription by periods of acute (1 day) and chronic (6 days) dehydration, and after halting the stimulation by rehydration of animals. The nuclear volume and the ultrastructure of chromatin were assessed on ultrathin sections. The number and distribution of nuclear particles were assessed on freeze-fracture replicas. The initial phase of osmotically induced enhancement of transcription was accompanied by an increase in nuclear volume and by a partial replacement of nuclear particles of large diameter (> 11 nm) by smaller nuclear particles. This latter change affected predominantly the nuclear periphery (0-1,000 nm from the nuclear membrane) and occurred simultaneously with a partial decondensation of chromatin clusters that may be related to chromatin unfolding. In chronically stimulated animals, the decondensation of chromatin and the replacement of large nuclear particles by smaller ones was enhanced in the nuclear periphery and was partially propagated to the interior of the nucleus. After suppression of cellular activation by rehydration of animals, the number of nuclear particles returned to control levels in the nuclear periphery while in the center of the nucleus the number of small particles decreased and the number of large particles increased as compared to control values. These results, together with the observation that in unstimulated cells the nuclear periphery and the nuclear interior differ in their composition of nuclear particles, evidence a structural and functional compartmentalization in the cell nucleus of supraoptic neurons.

The effect of prenatal X‐irradiation on the developing cerebral cortex of rats. II: A quantitative assessment of glial cells in the somatosensory cortex

“…However, no apparent vestigial signs of glial cell death were observed in the present study. Second, refuting the above, increased nuclear size might also imply larger amount of protein synthesis because the structural changes in the nucleus are also known to occur while facilitating the actions of locally expressed transcription regulatory molecules (Garcia‐Segura et al, 1993; Pena et al, 2001). In particular, astrocytes are known to be activated by various insults and/or degenerative changes.…”

Age‐related changes in growth hormone‐immunoreactive cells in the anterior pituitary gland of Jcl: Wistar‐TgN (ARGHGEN) 1Nts rats (Mini rats)

“…2003). It is conceivable that such an observation might also imply a lesser amount of protein synthesis because alterations in the structure of the nucleus are also known to occur in facilitating the actions of locally expressed transcription regulatory molecules (Garcia‐Segura et al . 1993; Pena et al .…”

“…The reduction in the size of the nucleus might be considered an indicator of retardation in cell maturity as nuclei of more mature cells are known to be larger (Miller & Peters 1981;Berciano et al 2002;McMahon et al 2003). It is conceivable that such an observation might also imply a lesser amount of protein synthesis because alterations in the structure of the nucleus are also known to occur in facilitating the actions of locally expressed transcription regulatory molecules (Garcia-Segura et al 1993;Pena et al 2001). Therefore, it is highly probable that the morphological changes observed in the GH-IR cells in Mini rats might indicate a more severe impact on the function of these cells.…”

Genome and stress-reaction in animals and humans

“…Так, фармакологическая активация ней-ронов вызывает перераспределение гетерохроматина в ядре солитарного тракта [119], действие нейроток-синов приводит к продолжительным изменениям со-стояния и расположения гетерохроматиновых блоков в нейронах неокортекса крыс [120]. Хронический стресс низкой интенсивности вызывает структурные изменения в ядерном хроматине клеток гипофиза крыс [121], а по-сле транскрипционной активации в гипоталамических нейронах происходит ультраструктурная реорганизация хроматина [122].…”