摘要:

During development of the vertebrate lens, the lens epithelium undergoes a final stage of differentiation into lens fibre cells, during which the major lens proteins, the crystallins, are synthesised. Lentoids, comprising clusters of lens fibre cells can also be produced by transdifferentiation from certain non‐lens tissues, including neural retina and pigmented retinal epithelium. We have isolated an alpha A2‐crystallin genomic probe and used it to study the transcription and processing of alpha A2‐crystallin mRNA both during lens development and transdifferentiation. We relate these results to earlier measurements in this laboratory of delta‐crystallin transcription and alpha‐ and delta‐crystallin protein synthesis, to compare the expression of these two sets of genes. Tissue specific differences in gene expression were found. delta‐crystallin mRNA is transcribed before alpha A2‐crystallin RNA in the lens, but after it in transdifferentiating neural retina and pigm

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00385.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The estrogenic induction of vitellogenesis in avian and amphibian liver has been well characterized at the target gene level. Comparatively little however, is known about cognate nuclear events associated with the response, particularly those involving large‐scale structural changes and the non‐histone proteins (NHP). We have examined these aspects further in primary stimulated roosters. In the first 24 hr post induction with estradiol, hepatocyte nuclei enlarged by 50% and exhibited sharp rises in total protein and RNA content. In particular, the mass of residual NHP rose about 40%. Extensive internal reorganization was evident, including partial disaggregation of chromatin, proliferation of interchromatin components and de novo appearance of prominent “nuclear bodies”. These changes were accompanied by quantitative fluctuations in nucleoplasmic and several matrix fraction proteins. A marked relative decrease was evident in all three lamins, as well as approximately 75 and approximately 175 kD proteins. Hn‐RNP‐associated polypeptides however, and various unidentified components became much more prominent. By 24 hr, cells were fully differentiated for bulk export of vitellogenin and low density lipoproteins. All changes persisted for several days before gradually regressing to normal over a 2‐4 week period. Many key nuclear modifications, however, did not regress fully, including persistent enlargement, elevated NHP content and modified matrix fraction proteins. Collectively, these may reflect part of the “memory” effect, commonly observed in steroid target tissues, whereby a second, more pronounced response can be triggered long after primary induc

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00386.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Autoimmune serum from a patient with scleroderma was shown by indirect immunofluorescence to label nucleoli in a variety of cells tested including: rat kangaroo PtK2, Xenopus A6, 3T3, HeLa, and human peripheral blood lymphocytes. Immunoblot analysis of nucleolar proteins with the scleroderma antibody resulted in the labeling of a single protein band of 34 kD molecular weight with a pI of 8.5. Electron microscopic immunocytochemistry demonstrated that the protein recognized by the scleroderma antiserum was localized exclusively in the fibrillar region of the nucleolus which included both dense fibrillar and fibrillar center regions. Therefore, we have named this protein “fibrillarin”. Fibrillarin was found on putative chromosomal nucleolar organizer regions (NORs) in metaphase and anaphase, and during telophase fibrillarin was found to be an early marker for the site of formation of the newly forming nucleolus. Double label indirect immunofluorescence and immunoelectron microscopy on normal, actinomycin D‐segregated, and DRB‐treated nucleoli showed that fibrillarin and nucleolar protein B23 were predominantly localized to the fibrillar and granular regions of the nucleolus, respectively. RNase A and DNase I digestion of cells in situ demonstrated that fibrillarin was partially removed by RNase and completely removed by DNase. These results suggest that fibrillarin is a widely occurring basic nonhistone nucleolar protein whose location and nuclease sensitivity may indicate some structural and/or functional role in the rDNA‐containing dense fibrillar and fibrillar center regions of the

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00387.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Nuclear rotation is observed in a variety of cell types. However, few quantitative analyses are reported and the significance of this phenomenon is still unclear. To investigate this type of nuclear movement, we performed a quantitative analysis in mouse L‐929 fibroblasts, a cell line chosen since it displays a high nuclear rotational activity. Analyses were performed using time‐lapse microcinematography. The relationship between nuclear rotation and other cellular phenomena such as the cell cycle and locomotion were studied. Then, we investigated the rotation in a population of sister cells to study whether it is genetically determined. Finally, we performed a qualitative analysis of nuclear rotation in different cultured cell lines. Results show that nuclear rotations preferentially occur during the phases of the cell cycle which surround mito

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00388.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Reprecipitated fibrils from collagen solutions assemble into aggregates often showing a remarkable twisted structure. We first observed these aggregates in collagen gels prepared to facilitate culture of epithelial cells. We verified that these structures form in the absence of cells and correspond to a process of self‐assembly. Studies on reconstructed fibrils of collagen are generally based on the examination of thin specimens mounted onto coated grids prepared for electron microscopy. We rather applied the classical methods of fixation, embedding and ultramicrotomy, which allowed us to analyze the structure of these aggregates, several microns in diameter. Our gels were prepared from 2.5 mg/ml tropocollagen solutions usually chosen for cell and organ cultures. The time required to obtain twisted architectures, in these aggregates, depends on temperature and the presence of factors such as fetal calf serum proteins. Twist is observed at two different levels of organization. Microfibrils are gathered into twisted bundles which condense into cross‐striated fibrils. These fibrils themselves aggregate and show a mutual twist whose orientation is left‐handed as is the twist observed within each microfibril bundle. Several models of these architectures are presented. Planar twist, cylindrical twist and toroidal twist are described and their relation to the structure of certain liquid crystals is considered. Examples of orthogonal packing also have been observed. These structures obtained in vitro are very close to patterns already described in vivo in numerous collagen mat

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00389.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Thyroid ultrastructure changes were studied during the course of a low iodine diet in rats. At day 20, follicles were normal, but a number of them contained cells of higher density and with greatly elongated microvilli. Endoplasmic reticulum cisternae were frequently dilated. From day 20 until day 80, the most characteristic changes in the thyroid cells were the progressive accumulation of subapical peroxidase‐positive exocytotic vesicles. After 80 days of the low iodine treatment, Golgi apparatuses were very active. Cell division could be observed. At this stage, exocytotic vesicles were generally very abundant. These data suggest that the remarkable accumulation of subapical exocytotic vesicles between day 20 and day 120 might represent an adaptation to the moderate and gradual increase in TSH stimulation that occurs in the conditions of low iodine die

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00390.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The ultrastructure of prostatic secretory cells was studied with the osmium impregnation technique in order to determine if the ER reactivity, or its absence, and its three‐dimensional organization correspond to specific functions possibly hormono‐dependent. Thick sections (0.3 micron) of rat ventral prostate were made after a five‐day impregnation with osmium tetroxide and examined by standard transmission electron microscopy at 80 kV. Studies were performed in normal adult rats, between the 3rd and 26th day following castration and in castrated rats treated with 5‐alpha‐dihydrotestosterone. In normal rats the impregnation technique delineated three secretory cell types (dark, greyish and clear), representing various degrees of reactivity in ER cisternae; however, despite this quantitative variation, they had similar morphological characteristics. In a longitudinal section, the ER network appeared to be made of saccules running parallel along the length of the cell and forming whorl‐like patterns around the nucleus. Comparison of sections taken at various angles suggests that the ER network is made of concentric parallel saccules extending from the base to the apex of the cell and encircling the nucleus and the Golgi apparatus like a large multilayered cylinder. Whereas in dark cells the Golgi apparatus contained mostly clear vesicles, it was always heavily impregnated in clear cells. Noteworthy, osmium deposits were rarely observed on the nuclear envelope of secretory cells but were always present in basal cells. After castration, secretory cells became progressively cubic and the most conspicuous cytoplasmic change was observed in association with the ER. The Golgi apparatus decreased markedly in volume and became heavily stained with metallic osmium.(ABSTRACT TRUNCATED A

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00391.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The populations of interstitial cells in the testis of three 2‐3 month old monkeys and of three 5‐6 years old adults (Macaca fascicularis) were analyzed: percentage, mitotic index and labeling index after 3H‐thymidine injection. In the young monkey and the adult well differentiated Leydig cells incorporate the precursor as fibroblast‐like cells. This demonstrates their ability of

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00392.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The intranucleolar localization of fibrillar centers and their relationships with nucleolus‐associated chromatin were determined in stereopairs of human oocyte nucleoli obtained by computer reconstruction of serial sections. This study showed that there was no numerical relationship between the number of fibrillar centers and the number of chromosomal NORs. The three‐dimensional reconstruction demonstrated that the majority of fibrillar centers was directly connected with the nucleolus‐associated chro

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00393.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The organization of encapsidated herpes simplex viral DNA in situ was examined by use of the osmium‐amine stain specific for DNA. After either formaldehyde or glutaraldehyde fixation the DNA is packaged in a compact toroid without inner structure with Epon or GMA embedment but revealed a complex inner structure with Lowicryl K4M embedment. In the latter there was an inner cylindrical core, 50 × 80 nm, around which were apposed one or more thick filaments of 5‐8 nm diameter. Thinner DNA filaments of 3‐4 nm diameter form a cage of loose coils around the core with an intervening space of approximately 15 nm. Lowicryl embedding may be considered as a tool to investigate the packaging of viral DNA in v

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1985.tb00394.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY