The nucleolar apparatus and neuronal reactivity to injury during development

LaVelle, Arthur; LaVelle, Faith W.

doi:10.1002/jez.1401370205

Cited by 68 publications

(16 citation statements)

References 21 publications

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“…LaVelle & LaVelle (1958) noted that no more than 100 axotomized facial motoneurones show degenerative signs even at the stage at which more than 1500 axotomized facial motoneurones are lost during a 24 h period in neonatal hamsters. This suggests that once the axotomized neurones have undergone degenerative changes, cell lysis follows rapidly (LaVelle & Lavelle, 1958). Thus, changes in the electrical properties of axotomized neurones associated with the 'prelethal stage' would not be detected unless the cell death proceeds on a daily basis, as in the case of facial motoneurones axotomized in neonatal animals.…”

Section: Discussionmentioning

confidence: 99%

Electrophysiological properties of axotomized facial motoneurones that are destined to die in neonatal rats.

Umemiya

Araki

Kuno

1993

The Journal of Physiology

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SUMMARY1. Rat facial motoneurones axotomized on the day after birth were examined morphologically, and their electrical properties were characterized using the wholecell recording technique in thin slices of the brainstem.2. About 40% of facial motoneurones were lost within 4 days of axotomy, and only about 20% of the neurones survived 9 days after axotomy.3. The surviving facial motoneurones examined 4 or 6 days after axotomy were reduced in size, and this was associated with a decrease in their input capacitance.4. Both the resting potential and the amplitude of action potentials remained unchanged in axotomized facial motoneurones.5. Facial motoneurones examined 4 or 6 days after axotomy showed an increase in the spike duration. When the preparation was superfused with a Ca2+-free solution, the spike duration of axotomized facial motoneurones was shortened, whereas the spike duration of control facial motoneurones was prolonged.6. The voltage-gated transient K+ current (IA) density was significantly reduced in axotomized motoneurones, whereas the Ca2+-dependent transient K+ current (K, Ca) density was not affected.7. Voltage-gated Ca2+ currents in facial motoneurones showed inactivation, displaying an initial transient phase followed by a sustained phase. The rate of inactivation of Ca2+ currents was significantly faster in axotomized neurones than in control neurones.8. A small subpopulation of facial motoneurones examined 4 or 6 days after axotomy had a disproportionately high input resistance and a significantly longer after-hyperpolarization. The probability of this occurring was correlated with the time course of cell death induced by axotomy.9. It is concluded that facial motoneurones axotomized in neonatal rats comprise two subpopulations. The subpopulation characterized by a markedly high input resistance is suggested to represent the neurones which are at the 'prelethal' stage or in the process of cell death.

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Section: Discussionmentioning

confidence: 99%

Electrophysiological properties of axotomized facial motoneurones that are destined to die in neonatal rats.

Umemiya

Araki

Kuno

1993

The Journal of Physiology

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“…FMN ranged from having no label over the nucleolus to having the entire nucleolus obscured by very intense labeling. In these cells, the nucleolus is very large in diameter (4-5 microns; LaVelle and LaVelle, 1958), relative to the section thickness of 12 microns. Histograms were therefore generated, with FMN grouped according to the degree of precursor rRNA expression in their nucleoli.…”

Section: In Situ Hybridization Quantitative Proceduresmentioning

confidence: 99%

Ribosomal RNA transcriptional activation and processing in hamster facial motoneurons: Effects of axotomy with or without exposure to testosterone

et al. 1998

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A key step in the ability of neurons to survive injury and successfully regenerate involves ribosomal RNA production. Testosterone propionate (TP), augments facial nerve regeneration in the adult hamster. TP modulates the nucleolar reaction in injured facial motoneurons, such that mature ribosome levels increase more rapidly and in greater magnitude than with injury only. In this study, molecular and electron microscopic stereologic approaches were used to determine the effects of axotomy and steroid treatment on ribosomal transcription and processing in facial motoneurons. Castrated adult male hamsters were subjected to right facial nerve transection at the stylomastoid foramen. Half the animals were subcutaneously implanted with one Silastic TP capsule, with the remainder sham implanted. For the in situ hybridization experiments, postoperative survival times were 0.5, 2, or 6 hours. In situ hybridization with a ribosomal DNA probe specific to the external transcribed spacer region located at the 5' end of the ribosomal gene was accomplished. Transcriptional activation of the rRNA gene occurred rapidly, within 2 hours, after injury only. Unexpectedly, TP treatment did not alter the time course or magnitude of rRNA transcriptional activity. For the electron microscope experiments, the postoperative time of 12 hours was selected. Stereologic analysis of 3 nucleolar subcomponents, fibrillar centers (site of rRNA transcription), nucleolonema (site of rRNA processing), and granular material (site of preribosome storage), was accomplished. TP decreased the nucleolonemal strands and the granular material, relative to injury only. These results suggest that, although rRNA transcription is rapidly activated by axotomy, rRNA processing is temporarily stalled. TP does not affect the early, axotomy-induced transcriptional activation of the ribosomal gene, but may, instead, prevent the subsequent disruption in rRNA processing. An hypothesis for the molecular mechanism by which steroids augment the regenerative capabilities of injured facial motoneurons is presented.

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“…The nuclear membrane was frequently folded. The nucleoli were structurally mature but often multiple [La Velle and La Velle, 1958a]. The Nissl substance was sparse and concentrated along the cell membrane.…”

Section: Observationsmentioning

confidence: 99%

“…La Velle and La Velle [1958a;1959] observed early nucleolar involution after axotomy in newborn hamsters and sug gested that the lack of regeneration was due to some kind of nucleolar insufficiency. However, in newborn rats the neuronal degeneration was equally rapid and severe, although the nucleoli were structurally mature at the time of the operation and no early nucleolar involution was observed.…”

Section: Transection O F the Facial Nervementioning

confidence: 99%

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Variations in the Axon Reaction in Animals of Different Ages

Søreide¹

1981

Cells Tissues Organs

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The retrograde nerve cell reaction was studied after crush lesion of the facial nerve in rats of different ages. Neuronal survival increased from 10% in newborn rats to 100% in adults. In 8- or 10-day-old animals axotomy caused central chromatolysis, nuclear eccentricity, folding of the nuclear membrane, and development of nuclear caps. Similar lesions in adult rats caused only minimal changes. The findings differ from those previously reported in hamsters [La Velle and La Velle, 1958a, b, 1959], where chromatolysis was most severe in adult animals. However, the neuronal survival followed the same age-related pattern in rats and hamsters. Thus, there are marked species differences in the chromatolytic response after axotomy, but these differences do not affect neuronal survival. It is concluded that chromatolysis is not a decisive factor for neuronal recovery after axon injury in young animals.

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The nucleolar apparatus and neuronal reactivity to injury during development

Cited by 68 publications

References 21 publications

Electrophysiological properties of axotomized facial motoneurones that are destined to die in neonatal rats.

Electrophysiological properties of axotomized facial motoneurones that are destined to die in neonatal rats.

Ribosomal RNA transcriptional activation and processing in hamster facial motoneurons: Effects of axotomy with or without exposure to testosterone

Variations in the Axon Reaction in Animals of Different Ages

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