Alterations of three-dimensional structure of nucleolar organizers during cell division and differentiation
| Project/Area Number |
09640793
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
生物形態・構造
|
|---|
| Research Institution | Ehime University |
|---|
Principal Investigator |
SATO Seiichi Ehime University, Faculty of Science, Professor, 理学部, 教授 (90108374)
|
|---|
| Project Period (FY) |
1997 – 1998
|
| Project Status |
Completed (Fiscal Year 1998)
|
| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1998: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1997: ¥2,100,000 (Direct Cost: ¥2,100,000)
|
|---|
| Keywords | nucleolus / higher plants / nucleolonema / dense granular component / granular component / EM histochemistry / solenoid / rDNA / ダイコン / タマネギ / イムノゴールド法 / オスミウムアミン-B法 / RNase-gold法 |
|---|
| Research Abstract |
The nucleoloneina of Raphanus sativus root-tip cells was studied with light and electron microscopy especially focusing on its three-dimensional structural organization. Its countour was very intricate and thc thickness showed a large variation in air-dried specimens. It usually appeared to coil or meander. Serial ultrathin sectioning of thc nucleolonema iii its longitudinal orientation first revealed the stack of short nucleolonema fragments, then a pair of knobbly frames with space in-between, and again the stack of the short nucleolonema segments. On the other hand, transversal sections revealed 'c'-shaped segments with the change of their openings' orientation. Morphometry of the nucleolonema indicated two categories of the nucleolonema ; each had an average thickness of 510 nm and 1.19mum, respectively. Taken together, the thin nucleolonema may coil or fold to form the thick one. The fibrillar centers including DNA-containing structures were closely associated with the thin nucleo
… More
lonem a and intermittently arranged along the nucleolonema.
Localization of intranucleolar DNA under hypoxic conditions was examined in excised loot tips of Allium cepa. Application of a silver impregnation technique to serial ultrathin sections indicated that the nucleolus segregated into two regions, the central core of the dense fibrillar component (DFC) and the periphery of the granular component (GC), and developed achromatic channels meandering within the DEC core. Electron microscopy showed that the Qccurrence of the achromatic channel was caused by development and/or fusion of the fibrillar centers (FCs), which are believed to contain the temporarily resting ribosomal-RNA genes (rDNA). The label of the DFC with anti-DNA antibodies was significantly strong compared with that of the cytosol and the labeling specificity was uniform throughout the DEC.Interestingly, the labeling specificity of the ECs and their surrounding region in the specimens exposed to hypoxic condition was almost the same as those grown under a normal condition. Concurrently with the development of the FCs under hypoxic conditions, the granules about 35 um in diameter (35 nm granules) were formed in the FCs. They were not labeled at all with anti-DNA antibodies and RNase-gold complexes, indicating that they contain neither DNA nor RNA.Altogether, the DFC containing the intranucleolar DNA probably engaged in the RNA transcription may gradually collapses to turn into the FCs and simultaneously releases the inactivated rDNA as clusters of chromatin-likemasses and Sonic nucleolar proteins as the 35 inn granules, when the cells are exposed to hypoxic conditions. Less
|
Report
(3 results)
Research Products
(15 results)
