Ultrastructural association of the chromatin-containing lacunar spaces with the granular component of the interphase nucleolus in Allium cepa

1981 ◽  
Vol 59 (11) ◽  
pp. 2073-2076
Author(s):  
L. A. Chouinard
Keyword(s):  
Granular Material ◽  
Allium Cepa ◽  
Ultrastructural Level ◽  
Dense Fibrillar Component ◽  
Active Chromatin ◽  
Granular Component ◽  
Meristematic Cells ◽  
Partial Association ◽  
Root Meristematic Cells ◽  
Fibrillar Component

At the ultrastructural level, the interphase nucleolus in root meristematic cells of Allium cepa is characterized by the presence of chromatin-containing lacunar spaces associated with the dense-fibrillar component of the nucleolar mass. The present observations reveal that a number of these chromatin-containing lacunar spaces also exhibit partial association with the dense-granular component of the nucleolus. Under the electron microscope, such lacunar spaces are indeed seen to be enclosed or walled off, on one side, by dense-fibrillar material, and on the other side, by dense-granular material continuous with and indistinguishable from the dense-granular component of the nucleolus. The relevant observational evidence would be consistent with the view that loops of transcriptionally active chromatin, emanating from the nucleolar organizing region, project radially into either only the dense-fibrillar or both the dense-fibrillar and the dense-granular material bordering the lacunar spaces in question.

Ultrastructural association of the chromatin-containing lacunar spaces with the vacuolar component of the interphase nucleolus in Allium cepa

1982 ◽  
Vol 60 (12) ◽  
pp. 2624-2628 ◽  
Author(s):  
L. A. Chouinard
Keyword(s):  
Granular Material ◽  
Allium Cepa ◽  
Ultrastructural Level ◽  
Observational Evidence ◽  
The Other ◽  
Active Chromatin ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nucleolar Organizing Region ◽  
Root Meristematic Cells

At the ultrastructural level, some of the chromatin-containing lacunar spaces of the interphase nucleolus in root meristematic cells of Allium cepa are seen to be walled off, on one side, by dense-fibrillar material and to be contiguous, on the other side, to electron-transparent areas, of variable sizes and shapes, bordered by dense-granular material continuous with and indistinguishable from the dense-granular component of the nucleolar mass. These electron-transparent areas associated with the lacunar spaces are equated with nucleolar vacuoles since they contain scattered preribosomal-like granules and fibrils and are rimmed by dense-granular material. The relevant observational evidence would be consistent with the view that loops of transcriptionnally active chromatin emanating from the nucleolar organizing region project radially into either only the dense-fibrillar or both the dense-fibrillar and the interior of the electron-transparent vacuolar areas seen to be contiguous to the lacunar spaces in question. In relation to this problem, it is of interest to note that the vacuolar spaces of the interphase nucleolus in Allium cepa occasionally display within their confines discrete masses of fibrillar material, possibly chromatinic in character, and in various states of condensation and configuration.

scholarly journals Ultrastructural distribution of DNA and RNA within the nucleolus of human Sertoli cells as seen by molecular immunocytochemistry

1993 ◽  
Vol 105 (1) ◽  
pp. 33-39 ◽  
Author(s):  
M. Thiry
Keyword(s):  
Sertoli Cells ◽  
Ultrastructural Level ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Dense Fibrillar Component ◽  
Granular Component ◽  
Dna And Rna ◽  
Nucleotidyl Transferase ◽  
Immunocytochemical Techniques ◽  
Fibrillar Component

The precise distribution of DNA and RNA within the human Sertoli cell nucleolus has been investigated, at the ultrastructural level, by cytochemical and molecular immunocytochemical techniques. In Sertoli cells, the nucleolar components show a typical spatial distribution. The fibrillar centres are not surrounded by a layer of dense fibrillar component, but come in contact only with strands of dense fibrillar component. These fibrillar parts of strands are the extensions of granular strands connected to a large granular mass. These strands delimit numerous nucleolar interstices in which chromatin fibres are clearly obvious. Using the in situ terminal deoxynucleotidyl transferase/immunogold procedure for detecting DNA, we find evident label exclusively over the chromatin fibres enclosed in the nucleolar interstices and over the fibrillar centres, and no significant label over the dense fibrillar component and granular component of the nucleolus. Furthermore, using the polyadenylate nucleotidyl transferase/immunogold procedure for detecting RNA, we show that label is deposited not only over the granular component and dense fibrillar component, as expected, but also quite obviously over the fibrillar centres. No label is seen over the interstices containing chromatin.

scholarly journals Action of Ponceau 4R (E-124) food dye on root meristematic cells of Allium cepa L.

2015 ◽  
Vol 37 (1) ◽  
pp. 101 ◽  
Author(s):  
Gleuvânia Santana Marques ◽  
Josefa Janaína do Anjos Sousa ◽  
Ana Paula Peron
Keyword(s):  
Allium Cepa ◽  
Meristematic Cells ◽  
Food Dye ◽  
Root Meristematic Cells ◽  
Ponceau 4R

scholarly journals Sodium cacodylate as antimitotic agent

2014 ◽  
Vol 57 (3) ◽  
pp. 329-340
Author(s):  
Jadwiga A. Tarkowska
Keyword(s):  
Allium Cepa ◽  
Mitotic Spindle ◽  
Sodium Cacodylate ◽  
Antimitotic Agent ◽  
Ultrastructural Studies ◽  
Meristematic Cells ◽  
Cacodylate Buffer ◽  
Root Meristematic Cells ◽  
Dividing Cells

The effect of pure sodium cacodylate on dividing cells was studied. The root meristematic cells of <em>Allium cepa</em> L. (the roots were squashed in acetoorcein) and endosperm cells of <em>Haemanthus katherinae</em> Bak. (<em>in vitro</em> observations) were used. Serious disturbances in karyokinesis and cytokinesis were found that led most often to the formation of polyploid or multinucleate (<em>A. cepa</em>) cells. These results point to damage of the mitotic spindle and phragmoplast. Careful use of cacodylate buffer in ultrastructural studies of microtubules is advised.

Distinguishing the sites of pre-rRNA synthesis and accumulation in Ehrlich tumor cell nucleoli

1991 ◽  
Vol 99 (4) ◽  
pp. 759-767
Author(s):  
M. Thiry ◽  
G. Goessens
Keyword(s):  
Tumor Cell ◽  
Condensed Chromatin ◽  
Rrna Genes ◽  
Rrna Synthesis ◽  
Rrna Gene ◽  
Dense Fibrillar Component ◽  
Ehrlich Tumor ◽  
Granular Component ◽  
Fibrillar Component

The precise location of transcribing rRNA genes within Ehrlich tumor cell nucleoli has been investigated using two approaches: high-resolution autoradiography of cells pulse-labelled with tritiated uridine, varying the exposure time, and in situ-in vitro transcription coupled with an immunogold labelling procedure. When autoradiographic preparations are exposed for a short time, silver grains are found associated almost exclusively with interphasic cell nucleoli. Labelling of extranucleolar areas requires longer exposure. Within the nucleolus, the first sites to be revealed are in the dense fibrillar component. Prolonging exposure increases labelling over the dense fibrillar component, with label becoming more and more apparent over the fibrillar centers. Under these conditions, however, labelling does not extend into the granular component, and no background is observed. Initiation of transcription on ultrathin cell sections occurs preferentially at the borders of condensed chromatin blocks and in their close vicinity. The condensed chromatin areas themselves remain unlabelled. Inside most nucleoli, gold-particle clusters are mainly detected in the fibrillar centers, especially at their periphery, whereas the dense fibrillar component and the granular component remain devoid of label. These results, together with previous observations made on the same cell type, clearly indicate that the fibrillar centers are the sites of rRNA gene transcription in Ehrlich tumor cell nucleoli, while the dense fibrillar component is the site of pre-rRNA accumulation.

scholarly journals Simultaneous immunoelectron microscopic visualization of protein B23 and C23 distribution in the HeLa cell nucleolus.

1989 ◽  
Vol 37 (9) ◽  
pp. 1371-1374 ◽  
Author(s):  
M Biggiogera ◽  
S Fakan ◽  
S H Kaufmann ◽  
A Black ◽  
J H Shaper ◽  
...  
Keyword(s):  
Hela Cell ◽  
Immunoelectron Microscopy ◽  
Silver Staining ◽  
Dense Fibrillar Component ◽  
Specific Antibodies ◽  
Granular Component ◽  
Protein B23 ◽  
Reported Data ◽  
Fibrillar Component

The intranucleolar distribution of phosphoproteins B23 and C23 was visualized simultaneously by post-embedding immunoelectron microscopy in HeLa cell nucleoli, using specific antibodies. The data show that proteins B23 and C23 co-localize to the same nucleolar compartments, i.e., the dense fibrillar component and the granular component. Neither of the two antibodies is significantly associated with the fibrillar centers in these cells, although the fibrillar centers appear positive after silver staining. These findings suggest that other unidentified components must be responsible for the silver staining observed in the fibrillar centers of interphase nucleoli. The results are discussed in the light of previously reported data obtained by preembedding immunolabeling techniques and by silver staining, which both suggested a localization of protein C23 inside the fibrillar centers.

scholarly journals A LIGHT AND ELECTRON MICROSCOPE STUDY OF SMALL, SPHERICAL NUCLEAR BODIES IN MERISTEMATIC CELLS OF ALLIUM CEPA, VICIA FABA, AND RAPHANUS SATIVUS

1965 ◽  
Vol 26 (1) ◽  
pp. 1-17 ◽  
Author(s):  
J. G. Lafontaine
Keyword(s):  
Vicia Faba ◽  
Allium Cepa ◽  
Raphanus Sativus ◽  
Ultrastructural Level ◽  
Nuclear Bodies ◽  
Meristematic Cells ◽  
Azure B ◽  
The Common ◽  
Chromosomal Loci ◽  
Common Association

Interphase, preprophase, and prophase nuclei of meristematic cells of Allium cepa, Vicia faba, and Raphanus sativus are characterized by the presence of spherical bodies approximately 1 µ in diameter. These structures are Feulgen-negative but stain metachromatically with azure B, as the nucleolus, following fixation with glutaraldehyde. At the ultrastructural level, they consist predominantly of fibrils estimated to be between 70 and 100 A in diameter which greatly resemble those found within certain zones of the nucleolus in these plant species. Moreover, in Allium cepa, these spherules often exhibit dense particles which are also found within the fibrillar zones of the nucleolus in this species. The observations that the bodies in question are frequently located at the surface of the nucleolus and moreover show cytochemical and ultrastructural similarities with this organelle suggest that they may originate from the nucleolus. However, the common association of the spherules with chromosome strands may indicate instead that these bodies represent extranucleolar ribonucleoprotein materials synthesized by specific chromosomal loci.

Sign in / Sign up

Export Citation Format

Share Document