Structural and functional relationships between nuclear bodies and the nucleolus-DNA body complex in the oocyte of Amphiporus lactifloreus

Silver-stained nucleolar organizer regions in adenocarcinoma of the cervix--a light and electron microscopic study

An increase in the number of Ag-NORs has been described as a possible marker for histopathological cancer diagnosis. The ultrastructural correlation of the reaction, however, has never been elucidated. In tissue samples of the endocervix of the uterus, we compared the ultrastructural configuration of Ag-NORs with the number of Ag-NORs dots. Light microscopic studies showed that the number of Ag-NORs in adenocarcinoma cells significantly increased, but the relation to the bromodeoxyuridine labeling index was not determined. By electron microscopy, Ag-NORs were only observed in the nucleoli and the nuclear bodies of nuclei. Ag-NORs were localized on all components of the nucleolar structure, but the dense fibrillar component was the predominant site in several cases. The nuclear bodies were exclusively found in adenocarcinoma cells and were argyrophilic. A spotted distribution of Ag-NORs was often found in the nucleoli of adenocarcinoma cells that showed an increased Ag-NOR count. The number of Ag-NORs was attributed not only to the number of nucleoli and nuclear bodies in a nucleus but also to the speckled distribution of silver deposits in a nucleolus. These results imply that the Ag-NOR count is a more definitive indicator of a hyperactive state of the cells than the combined number of nucleoli and nuclear bodies in adenocarcinoma of the uterine cervix.

A new version of the Ag-NOR technique. A combination with DAPI staining

The Ag-NOR staining technique is widely used for visualizing nucleolar organizer regions (NORs) in various plant and animal tissues. We describe a simple and time-saving combination of Ag-NOR staining with DNA detection by fluorescence microscopy. This modification was tested on cultured cells and semi-thin sections of plastic-embedded tissues. Of the different fixatives and embedding media used in our studies, the best results (i.e., high selectivity of staining, and lack of or very low background precipitation) were obtained with fixation in methanol-acetone at-20 degrees C for cultured cells, and fixation in 4% formaldehyde followed by embedding in Histocryl resin for tissue sections. The optimal time of Ag-NOR staining was determined experimentally for all materials tested. The specificity of the staining was checked at the electron microscopical level. Especially good results were obtained by mixing epifluorescence with standard bright-field illumination. In such a combination, Ag-NOR-positive nucleoli, or their fibrillar centres and dense fibrillar components, were clearly visible against a bright background of nuclear DNA.

Light and electron microscopic analysis of bovine embryos derived by in vitro and in vivo fertilization

PURPOSE

The aim of this study was to examine the morphological features of in vitro fertilization-derived bovine embryos (IVt) and compare them with those of in vivo fertilization-derived (IVv) ones.

RESULTS

Light microscopy showed the blastomeres of IVv embryos to have a tendency to be rounder up to the 16-cell stage and to form a more compact mass at the morula stage than in their IVt counterparts. Electron microscopy revealed that as development progressed, some structures (such as microvilli, phagosomes/lysosomes, intercellular junctions and intermediate filaments) appeared or reappeared while others (such as lipid droplets, vesicles with flocculent materials, cortical granules, nuclear annulate lamellae, nuclear envelope blebs) decreased or disappeared. These changes were observed about one cell stage later in IVt than in IVv embryos. Other structures were present in both IVt and IVv embryos, and they morphologically either changed (such as mitochondria, endoplasmic reticulum, Golgi apparatus and nucleoli) or did not change (cytoplasmic annulate lamellae). In contrast to previous reports, vacuolated nucleoli in both IVt and IVv embryos were observed from the two-cell stage.

CONCLUSIONS

It was concluded that (1) the development of bovine embryos to the blastocyst stage is like that of other mammalian embryos; (2) IVt and IVv embryos did not show consistent differences in morphological features; (3) although IVt embryos appear delayed in development, this may reflect different definition of age in vivo and in vitro.

Intranuclear inclusions in paramyxovirus-induced encephalitis: evidence for altered nuclear body differentiation

Intranuclear inclusion bodies (INB) are frequently encountered in viral infections, where they are thought to be accumulations of viral particles. However, for RNA viruses replicating in the cytoplasm, this compartmentalization represents a paradox not consistent with the viral replication cycle. To define the basis for intranuclear paramyxoviral inclusion bodies in astrocytes, natural cases of canine distemper virus subacute encephalitis were examined by light and transmission electron microscopy, and by quantitative confocal immunofluorescence microscopy. Although INB were viral antigen positive, they were not composed of structurally recognizable paramyxoviral nucleocapsids. The structural basis for the INB was instead viral antigen-associated forms of nucleolar development known as nuclear bodies. Three variants of the light microscopic Cowdry type A INB were complex nuclear bodies, giant beaded nuclear bodies (sphaeridia), and nuclear body-associated granulofilamentous matrices. In the latter, the granulofilamentous matrix frequently filled the nucleus, resulting in a fourth morphological INB variant, and was associated with morphological evidence of nuclear degeneration. These findings suggest a novel mechanism of virus-induced cytopathology whereby intranuclear viral protein exerts deleterious effects upon nucleolar differentiation in infected cells and hence altered host cell RNA metabolism.

Genome reactivation in developing early pig embryos: an ultrastructural and autoradiographic analysis

The onset of RNA synthesis in developing early pig embryos from 1-cell to 8-cell and morula stages was studied using high-resolution autoradiography of (5-3H)uridine incorporation. No transcriptional activity was detected in nuclei of 1- and 2-cell stage embryos with this technique. In these embryos nucleolus-like bodies (NLB) consist of sharply delineated, round, electron dense fibrillar masses. In the 4-cell stage embryos, the first uridine-3H incorporation in the nucleoplasm was detected and localized mainly near the regions of condensed chromatin. The first signs of reticulation and chromatin association were observed at the periphery of NLBs. In the next cell cycle (5- to 8-cell embryos) uridine-3H labelling was detected in the nucleoplasm and nucleoli. In these embryos, nucleoli consist of a central dense fibrillar mass without any transcriptional activity and fibrillo-granular cortex over which label was localized. The degree of functional restructure of nucleoli was variable within one blastomere or among different blastomeres, some nucleoli being more reticulated and showing more transcriptional activity than others. Fully developed nucleoli were present in early morulae. Electron dense unidentified structures described here as small dense round-shaped bodies (RDB) often surrounded by blocks of large chromatin granules were observed in intact 2-cell and alpha-amanitin treated 4-cell stage embryos. These structures did not show any transcriptional activity.