摘要:

We investigated the relationship between intermediate filaments (IFs) and other detergent‐ and nuclease‐resistant filamentous structures of cultured liver epithelial cells (T51B cell line) using whole mount unembedded preparations which were sequentially extracted with Triton X‐100 and nucleases. Immunogold labelling and stereoscopic observation facilitated the examination of each filamentous structure and their three‐dimensional relationships to each other. After solubilizing phospholipid, nucleic acid and soluble cellular protein, the resulting cytoskeleton preparation consisted of a network of cytokeratin and vimentin IFs linked by 3 nm filaments. The IFs were anchored to and determined the position of the nuclear lamina filaments (NLF) network and the centrioles. The NLF was composed of the nuclear lamina filaments measuring 3‐6 nm in diameter which radiated from and anchored to the skeleton of the nuclear pores. The IFs located in the nuclear region appeared to be interwoven with the NLF. At the cell surface, the IFs seemed to be attached to the putative actin filament network. They formed a focally interrupted plexus‐like structure at the cell periphery. Fragments of vimentin filaments were found among the filamentous network located at the cell surface, and some filaments terminated bl

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

We have characterized the junctions between endothelial cells of diverse blood vessels at the light and electron microscopic level using various antibodies to plakoglobin (polypeptide Mr 83,000) and vinculin. Endothelial cells from fenestrated and non‐fenestrated capillaries to large arteries are connected to each other by extended junctions that are coated on their cytoplasmic face by plaques of loosely matted filamentous material that form a continuous belt system along the cell circumference. These plaques are devoid of desmosome‐specific proteins such as desmoplakin(s) and desmoglein, but contain plakoglobin. Immunofluorescence microscopic reactions of these regions with vinculin antibodies have also been observed, although they are much weaker and less consistent. This composition, together with their association with actin microfilaments, classifies this extended plaque system as Zonulae adhaerentes. Our results also show that such endothelia may be distinguished from truly epithelial cells by the absence of desmosomes and intermediate filaments of the cytokeratin type. The relationship of the various kinds of adhering junctions and the physiological importance of these junctions are discus

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The dermis of the frog skin (Rana esculenta) displayed a remarkable organization of vertical and horizontal tracts. Vertical thick tracts connected the dermal Stratum spongiosum with the subcutaneous tissue. Horizontal thin tracts were found alongside and contiguous to them. The thick tracts were sheathed by collagen fibrils of the Stratum compactum which were vertically oriented (i.e. parallel to the axes of the tracts) according to the horizontal and orthogonal arrangement of the collagen bundles of the Stratum compactum. The thin tracts devoid of collagenous sheath were formed by clear spaces between superimposed collagen bundles of the dermal Stratum compactum. On vertical sections, the thick tracts were seen to contain fibronectin (FN), detected by indirect immunoperoxidase. Continuous vertical FN lines were centred in these tracts. On horizontal sections, a clear zone around these FN‐centred lines was also sheathed by FN. The thick tracts contained flattened pigmentary cells and fibroblasts; these cells were FN‐outlined. The thin tracts contained patches of FN and FN‐outlined fibroblasts. In culture, in vertical thick tracts, both pigmentary cells and fibroblasts disappeared when antiserum to FN was added to the culture medium. This suggested that thick tracts were pathways allowing pigmentary cells to move upward or downward between their usual upper dermal and lower subcutaneous localizations. Fewer fibroblasts were found in the thin tracts in the presence of antiserum

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Pre‐incubation of rat Sertoli cells with concentrations of follicle‐stimulating hormone (FSH) too low to stimulate plasminogen activator (PA) secretion, provoked an inhibition of its subsequent stimulation by an effective dose of the hormone. A kinetic study of this desensitization was performed using equine FSH (which exhibits prolonged stimulation of PA secretion) and porcine FSH (which like all other FSH tested, provokes a transient response). Low non‐stimulating concentrations of both hormones were shown to inhibit the subsequent PA response to each of them. Desensitization of rat Sertoli cells by low (non‐stimulating) concentrations of FSH did not modify the typical time course (transient or prolonged) of PA secretion under subsequent stimulation by porcine or equine FSH, respectively. Only the intensity of the response to each hormone was dramatically reduced. Besides, the induction of desensitization by these non‐stimulating concentrations of FSH was shown to be very rapid (10‐15 min). The precise mechanism of this desensitization is not yet clear but its abolishment by the cyclic nucleotide phosphodiesterase (PDE) inhibitor MIX is consistent with the hypothesis that activation of PDE occurs at lower FSH concentration than adenylate cyclase

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Because extended exposure of AtT‐20 corticotropin‐secreting cells to atrial natriuretic factor (ANF) results in a desensitization of ANF‐induced cGMP synthesis, we sought to establish whether pretreatment of AtT‐20 cells with the atrial peptide also led to an internalization process. In fact, by coupling an ultrastructural approach to cryoultramicrotomy, ANF‐immunoreactivity was detected at both the plasma membrane level and at intracellular sites in AtT‐20 cells. Internalization was observed within 5 min at which time labelling was observed in the plasma membrane level, in vacuole‐like structures in close proximity to the plasma membrane, in cytoplasmic matrix and sometimes in mitochondria. After 30 min exposure Golgi apparatus, mitochondria and nuclear euchromatin were also labelled. Following 1‐4 hr, labelling in other cell compartments, e.g. lysosomal, was increased, while it was reduced in plasma membranes and vacuole‐like structures. Secretory granules and endoplasmic reticulum were not labelled throughout the time course. Extraction of a intracellular [125I] ANF from AtT‐20 cells following 4 hr incubation suggested that about 90% of the peptide was intact. The data suggest that internalization of ANF may serve to terminate the biological response associated with ANF receptor activation; subcellular distribution of internalized, intact ANF suggests that the peptide may have other, as yet unidentified, in

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A study of the ultrastructural aspects of endocytosis of human erythrocytes by Entamoeba histolytica‐like amoebae (Laredo) revealed two different mechanisms of endocytosis. First, there is classical phagocytosis which consists of the formation of a phagocytotic pseudopod. This process begins with the engulfment of the red blood cell followed by its entrapment in a food vacuole of the same size as the erythrocyte. It is then digested in the food vacuole. The second means of endocytosis is achieved through a preliminary lytic attack on the red blood cell. Following attachment of the prey to the attacking cell, dendritic extensions elongate from the surface of the amoeba at the site of attachment. Intense folding and liquefaction of the red blood cell membrane is then observed. The fluid membrane is then sucked into the amoeba through a pinocytotic‐like channel. The end result is the formation of small vacuoles in the amoeba's cytoplasm, filled with the digested red blood c

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The aim of the present work is to gather new information on the ferritin molecule. Natural crystals of ferritin occurring in the yolk platelets of a mollusc oocyte were studied. Their crystallographic structure was found to be equivalent to one of the structures obtained by artificial crystallization (fcc; a = 15 nm). Individual ferritin particles isolated from horse spleen were studied by microdiffraction techniques, using field emission gun transmission electron microscopy. The iron core crystals display a hexagonal structure; our results confirm the value of the unit cell parameter a (0.51 nm) and, for the first time, we have been able to extract the value of the unit cell parameter c (0.95 nm). Thus, among the three models described in the literature for the crystalline structure of the iron complex, our results corroborate that of Towe and Bradley (J. Colloid. Interf. Sci., 1967, 25, 384‐392

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The effect of synthetic granular hydroxyapatite (HAP) on cultured fibroblastic cells (L929, human bone and gingiva cells) was studied. Phagocytosis of HAP particles and resulting morphological cell changes were demonstrated by microscopic examinations. Cell counts and [3H]thymidine uptake indicated significant increases in cell proliferation and DNA synthesis. These results could account for some of the alterations of the fibroblast behavior induced by changes in intracellular levels of calcium ions released from the material.

ISSN:0248-4900    

DOI:10.1111/j.1768-322X.1987.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY