摘要:

Recent reports, both biochemical and morphological, have challenged the widely accepted two‐step model of steroid hormone action. This model proposed that steroid hormone receptors existed under two different forms: the unliganded receptor in the cytoplasm and the hormone‐bound receptor complex in the nucleus. A nuclear translocation mechanism was hypothesized as a necessary link between the two forms. In contradiction with this model, new studies have concluded to the absence of receptor in the cytoplasm and its presence in the nucleus under all hormonal conditions, thus rendering the hypothetical nuclear translocation unnecessary. In this review, we discuss how our concept of the mechanism of action of steroid hormone ought to be revised in the light of the new d

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00437.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Co‐isolated residual nuclear shells and residual nucleoli from membrane‐depleted rat liver nuclei were spread according to Kleinschmidt's method. Comparison of the spread residual structures isolated from nuclear shells and spread pore complex‐lamina isolated from nuclear envelopes showed that these residual structures are morphologically identical. Furthermore, our nuclear shell isolation procedure allowed visualization of DNA strands bound to a granular component of the lamina. The fragmentation of nuclear shells allowed us to obtain well‐spread nucleolar remnants, in which we observed DNA strands anchored on a residual nucleolar network attached to the lamina. The different molecular features revealed by the spreading of residual nucleolar structures suggest that both non‐transcribing nucleolar DNA and active ribosomal genes are linked to the nucleolar network. Although the exact nature of this network remains to be defined, the results of the present study strongly suggest that the DNA molecules of the chromosomes bearing ribosomal genes have many sites of attachment to a non‐chromatin nucleolar network which can be referred to as a nucleolar skele

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00438.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The localization of DNA polymerases in Xenopus laevis oocytes and eggs was studied. Oocytes have a high level of DNA polymerase alpha activity detected exclusively in the nuclei, while mitochondria contain all the DNA polymerase activity of the gamma type. No DNA polymerase beta activity is present in the nuclear fraction. Moreover, the beta activity is not present in unfertilized eggs. In oocytes, DNA polymerase alpha is weakly bound to the nucleoplasm. The leakage of the enzyme from whole nuclei can be prevented using polyvinylpyrrolidone, a nuclear pore sealing agent.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00439.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The morphology of intact or membrane‐deprived interphase nuclei has been analysed by freeze‐fracture electron microscopy. This method appears particularly useful for providing information on the distribution and organisation of chromatin and ribonucleoproteins in the absence of dehydration and embedding artifacts of conventional electron microscope techniques which, among other effects, appear to affect heterochromatin distribution, inducing its aggregation along the nuclear envelope. The main levels of chromatin superstructure, from nucleosome to solenoid fibres, are detectable in the replicas of freeze‐fractured nuclei on the basis of the size of their shadow, a parameter particularly suitable for automated image ana

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00440.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Bacterial DNA is organized as a compact nucleoid whose structure is maintained by membrane—DNA, protein—DNA and RNA—DNA interactions. We investigated the effect of the transcription inhibitor rifamycin on the structure of the nucleoid in B. subtilis. Decrease of nucleoid compactness and loss of DNA superhelicity were correlated with DNA transcription arrest, both in the wild‐type and in a rifamycin‐resistant strain. Moreover, the phospholipid content of the nucleoid does not change upon rifamycin

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00441.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A sugar‐binding component was shown to be present at the surface of endoerythrocytic Plasmodium berghei and P. chabaudi stages and merozoites by means of a panel of neoglycoproteins using fluorescence microscopy and flow cytofluorometry. The protein nature of this material was ascertained by the loss of sugar‐binding capacity upon trypsin treatment. This lectin‐like protein primarily bound neoglycoprotein‐borne N‐acetylglucosamine and secondarily bound neoglycoprotein‐borne alpha‐D‐glucose, beta‐D‐galactose and alpha‐L‐fucose. These results suggest the presence of at least one type of lectin‐like protein with an extended binding site accomodating several sugar units, and define its localizatio

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00442.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Synapse formation and maturation in the subcommissural organ (SCO) of Wistar rats were studied from birth to the end of the first month. Modifications of the secretory ependyma were analyzed over the same period. On the 1st postnatal day, the large varicosities in contact with the SCO ependymocytes appeared immature (absence or low density of vesicular population, no synaptic membrane differentiation). The synaptic contacts were formed from the 3rd postnatal day, near the glandular cell nuclei (0.1 micron distance); progressively, the content of the axonal boutons and the pre‐ and post‐synaptic specializations became similar to those of adults. From the 21st day on, the axo‐glandular innervation was considered analogous to that in the adult. Using immunocytochemistry, it was found that the increase in the serotonin‐immunoreactive fiber density in the whole organ was time‐dependent. Light and electron microscopy demonstrated changes in the morphology of SCO ependymocytes during the first postnatal weeks, notably in the endoplasmic reticulum and content ot apical protrusions. On postnatal day 14, two types of ependymal cells, neonatal‐like and adult‐like, coexisted. The evolution of SCO ependymocytes coincided with the progressive onset and maturation of axo‐glandular innervation taking pl

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00443.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

After stimulation of guinea pigs with estradiol to increase their Kurloff cell number, spleen imprints were prepared in order to detect non‐specific acid phosphatase (AcPase) activity by light microscopic cytochemistry using naphthol AS‐BI phosphate as substrate and pararosanilin or fast garnet GBC as coupler. For ultracytochemistry, Kurloff cells were prepared from spleens by filtration through a homogeneizer screen followed by repeated centrifugation. AcPase and trimetaphosphatase activities were tested using beta‐glycerophosphate, cytidine‐5′‐monophosphate and inorganic trimetaphosphate as substrates. Significant enzymatic activities were demonstrated with all the substrates used in the cytoplasmic inclusion body of the Ku

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00444.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The action of androgen (dihydrotestosterone‐DHT‐) on fibroblast growth was evaluated by 3H thymidine incorporation in DNA, by DNA assay using 3‐5 diaminobenzoic acid fixation, and by a more sophisticated technique: flow cytometry. Cell DNA and proteins were stained with propidium iodide and fluorescein isothyocyanate, respectively. We did not observe any detectable DNA variation when fibroblats were incubated in the presence of DHT. Moreover, DHT did not modify DNA and protein distribution, either in the total cell cycle or in each phase of the cell cycle. These results suggest that androgens do not induce total protein synthesis nor increase DNA in target cells. It is likely that they induce specific protein synt

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1986.tb00445.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY