Ultrastructural and morphometric analysis of nuclear and nuclear changes during the early growth period in hamster facial neurons

Pamela Clark, Kathryn J. Jones, Arthur LaVelle

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In this study, progressive developmental changes in the nucleus and associated organelles, including the nucleolus, coiled bodies, nuclear envelope, and nucleoplasm, of hamster facial motor neurons were characterized by two parallel analyses: ultrastructural and morphometric. Golden hamsters (Mesocricetus auratus) used for this series were the 14‐day fetus, newborn (<6 hr), and 1, 2, 3, 4, 5, 7, 9, 11, and 13 days postnatal ages, with 3 animals per group. Following anesthesia and perfusion fixation, facial nuclear groups were dissected and processed for electron microscopy. Electron micrographs and camera lucida tracings of nuclear profiles were collected and analyzed. The ultrastructural analysis revealed progressive changes in the nucleolus from a compact, segregated type to a reticulated form characteristic of actively protein‐secreting cells. Nucleolar microbodies and fibrillar centers were seen at all ages; the latter structures appeared to decrease in size and increase with age in the series. The nucleolus‐associated chromatin became less condensed, suggesting an increase in the incorporation of rDNA into the nucleolus proper. Coiled bodies, both free and attached to nucleoli, were found in varying frequencies. The nucleoplasm of neurons at the earliest stages contained large numbers of heterochromatin clumps, which decreased concomitantly with an increase in interchromatin granules and fibrils during the later stages. Nuclear envelope imaginations, polarized along one side of the nucleus, increased throughout the developmental period examined. These changes occurred in concert with a 61% increase in nuclear size and a 47% increase in the length of nuclear envelope. The sequence of nuclear changes observed during this early period of normal facial neuronal growth completes the study of a series of distinctly defined cytomorphic events in this cell type, the lability of which can be experimentally tested for their functional roles in neuronal development.

Original languageEnglish (US)
Pages (from-to)749-760
Number of pages12
JournalJournal of Comparative Neurology
Volume302
Issue number4
DOIs
StatePublished - Dec 22 1990

Fingerprint

Nuclear Envelope
Coiled Bodies
Cricetinae
Mesocricetus
Neurons
Growth
Microbodies
Imagination
Heterochromatin
Motor Neurons
Ribosomal DNA
Organelles
Chromatin
Electron Microscopy
Fetus
Anesthesia
Perfusion
Electrons

Keywords

  • coiled bodies
  • facial motoneurons
  • microspherules
  • neuronal development
  • nuclear envelope invaginations
  • nucleolus

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Ultrastructural and morphometric analysis of nuclear and nuclear changes during the early growth period in hamster facial neurons. / Clark, Pamela; Jones, Kathryn J.; LaVelle, Arthur.

In: Journal of Comparative Neurology, Vol. 302, No. 4, 22.12.1990, p. 749-760.

Research output: Contribution to journalArticle

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abstract = "In this study, progressive developmental changes in the nucleus and associated organelles, including the nucleolus, coiled bodies, nuclear envelope, and nucleoplasm, of hamster facial motor neurons were characterized by two parallel analyses: ultrastructural and morphometric. Golden hamsters (Mesocricetus auratus) used for this series were the 14‐day fetus, newborn (<6 hr), and 1, 2, 3, 4, 5, 7, 9, 11, and 13 days postnatal ages, with 3 animals per group. Following anesthesia and perfusion fixation, facial nuclear groups were dissected and processed for electron microscopy. Electron micrographs and camera lucida tracings of nuclear profiles were collected and analyzed. The ultrastructural analysis revealed progressive changes in the nucleolus from a compact, segregated type to a reticulated form characteristic of actively protein‐secreting cells. Nucleolar microbodies and fibrillar centers were seen at all ages; the latter structures appeared to decrease in size and increase with age in the series. The nucleolus‐associated chromatin became less condensed, suggesting an increase in the incorporation of rDNA into the nucleolus proper. Coiled bodies, both free and attached to nucleoli, were found in varying frequencies. The nucleoplasm of neurons at the earliest stages contained large numbers of heterochromatin clumps, which decreased concomitantly with an increase in interchromatin granules and fibrils during the later stages. Nuclear envelope imaginations, polarized along one side of the nucleus, increased throughout the developmental period examined. These changes occurred in concert with a 61{\%} increase in nuclear size and a 47{\%} increase in the length of nuclear envelope. The sequence of nuclear changes observed during this early period of normal facial neuronal growth completes the study of a series of distinctly defined cytomorphic events in this cell type, the lability of which can be experimentally tested for their functional roles in neuronal development.",
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