摘要:

Summary—Adenocarcinoma cells often form intracellular lumens and intercellular cysts. In order to study the structural relationships between these lumens and the apical domain of normal enterocytes, we have applied electron microscopy and confocal microscopy to a cloned cell line derived from the human colon adenocarcinoma cell line LoVo which express a high number of intracellular lumens and intercellular cysts. Microvilli reminiscent of those detected in the brush border of small intestinal cells are formed in the two types of compartments. By immunofluorescence, we found that a 135 kDa membrane glycoprotein characterized by a monoclonal Ab and normally associated with the brush‐border of enterocytes is expressed at the surface of the intracellular lumens and intercellular cysts present in the adenocarcinoma cells. Comparison of fluorescence and reflection contrast micrographs obtained by confocal microscopy demonstrate the presence of spherical intracellular lumens in the juxtanuclear region of single cells, and of more complex shaped intercellular cysts located within clusters of cells. The later cells form junctional complexes limiting an apical plasma membrane domain in contact with the intercellular cyst. It is suggested that the intracellular lumens may represent the abortive form of an apical plasma membrane due to the lack of components required to establish epithelial cell contacts. As opposed to conventional fluorescence microscopy, confocal microscopy allows rapid inspection of the tridimensional organization of intracellular lumens and intercellular cysts even when they are located in cell multilay

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90339-5

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—In cold‐stressed oocytes ofPleurodeles waltl, lampbrush chromosome lateral loops exhibited important structural modifications which were visualized under light microscopy. Electron microscopy study revealed that the RNP particles associated with growing transcripts in the matrix of these loops were 15 nm at 8°C compared to 30 nm at normal temperature (20°C); hnRNP isolated from cold‐stressed oocytes sedimented at 15 S in sucrose, while those from control oocytes sedimented at 30 S, as expected. However, under both normal and cold stress conditions, hnRNP possessed a buoyant density of 1.38 g/cm3in CsCl, indicating that their typical RNA/protein ratio was maintained at 8°C. Our results demonstrate that cold stress affects the structure of hnRNP in amphibian

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90340-9

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—A major 26 kDa protein was identified in the cytoplasmic and nuclear compartments of axolotl thymocytes. A polyclonal antiserum was produced against the denatured form of this protein. High levels of 26 kDa were expressed by hydrocortisonesensitive lymphocytes which represent a major thymocyte subpopulation in young animals. However, no further expression of the 26 kDa protein was observed in involuted thymus of adult animals nor in thymus of young artificially metamorphosed axolotls. The 26 kDa was never expressed by splenic and blood peripheral lymphocytes at any stage of development. Partial N‐terminal amino acid sequence and amino acid composition demonstrate that the 26 kDa polypeptide is strongly homologous to HMGI‐2 proteins, the most abundant members of the high mobility group (HMG) non‐histone chromosomal proteins. HMG1‐2 are thought to be involved in the organization of chromatin structure, as well as in the stability, replication and transcription of DNA. It was confirmed that the 26 kDa axolotl polypeptide is recognized by a well characterized rabbit antiserum to rat HMG1

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90341-Y

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Endogenous albumin was revealed over cellular structures of rat ascendent aorta endothelia and mesothelium, with high resolution and specificity, by applying the protein A‐gold immunocytochemical approach. This approach allows albumin distribution to be studied under steady‐state conditions. The cellular layers evaluated were the aortic endothelium, the capillary endothelium (vasa vasorum), and the mesothelium externally lining the aorta at this level. Gold particles, revealing albumin antigenic sites, were preferentially located over plasmalemmal vesicles and intercellular clefts of endothelial and mesothelial cells, though with different labeling intensities. The interstitial space was also labeled. Morphometrical evaluation of plasmalemmal vesicles demonstrated a higher surface density for these structures in capillary endothelial cells (12%) compared with those in aortic endothelial (5%) and mesothelial cells (2%). Quantitation of gold labeling intensities over these structures revealed a higher labeling over plasmalemmal vesicles of capillary endothelium than over those of aortic endothelium and mesothelium. This result, together with the higher surface density of plasmalemmal vesicles found in capillary endothelium, suggest an important role of these structures in the transendothelial passage of endogenous albumin, particularly for capillary endothelium. On the other hand, labeling densities over mesothelial clefts were found to be higher than those of capillary and aortic endothelia. Results from this study concur with the proposal of a differential passage of albumin according to the cell lining considered, and suggest a role for mesothelial intercellular clefts in contributing to the presence of albumin in interstitial s

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90342-Z

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The location of lipopolysaccharide (LPS) was studied by immunofluorescence and immunoelectron microscopy in macrophages infected with a non‐invasiveShigella dysenteriae1 strain. Bacterial degradation began only 3 h after the end of infection. The first visible sign of degradation was detected by immunogold labelling at the level of LPS which detached from the bacterial surface and was transferred to the perinuclear lysosomes. After a few hours, it was found in small vesicles spread over the whole macrophage cytoplasm in which it remained visible for 72 h. These vesicles seemed to belong to a compartment in which slowly or non‐degradable compounds are stored. LPS separation from the bacterial surface was immediately followed by the degradation of the intrabacterial constituents. The long lag period observed before initiation of bacterial degradation was not due to a lack of phagosome acidification, since DAMP, a lysosomotropic drug was found in all phagosomes at the end of the ingestion period. Thefrequency of phagosome‐lysosome fusion was 30% forS dysenteriaeand 72% forB subtilisused as a reference of high fusion frequency. The low frequency of fusion ofS dysenteriaemay play an important role in the survival of the virulent strains in macrophage by providing bacteria enough time to lyse the phagosome membrane before lysosome fusion

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90343-2

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The effects of vitamin D on the intramuscular distribution of total and bound calcium, phosphate and on available cytosolic calcium, were investigated in skeletal muscle. Total calcium and phosphorus were measured on ashed subcellular fractions of muscles from vitamin D‐repleted and vitamin D‐deprived rats. The variations in available calcium were followed by determining the activities of calcium‐sensitive enzymes in isolated cytosol. Bound‐calcium was revealed ultra‐microscopically by pyroantimonate. In vitamin D‐repleted muscles, the pyroantimonate method revealed specific areas of intense bound‐calcium deposition: the myofibrils, where they formed pronounced lines parallel to the Z‐bands. In vitamin D‐deficient muscles, the calcium‐pyroantimonate deposits appeared clearly reduced. This loss was accompanied by a marked reduction in total calcium and phosphorus in all the subcellular fractions, as compared to vitamin D‐repleted muscles. Unexpectedly, the activity of the Ca2+‐activated isocitrate‐dehydrogenase was increased in the cytosol, while that of the Ca2+‐inhibited pyruvate‐kinase decreased. Prolonged vitamin D‐administration to vitamin D‐repleted rats led to an intensification of calcium‐pyroantimonate deposits and a general increase in total calcium and phosphorus, but no change in the cytosolic Ca2+‐sensitive enzyme activities. Cessation of vitamin D‐administration to vitamin D‐repleted rats produced a regression of calcium‐pyroantimonate deposits, a general decrease of total calcium and phosphate levels, and stimulation of the Ca2+‐activated isocitrate‐dehydrogenase accompanied by lowering of the Ca2+‐inhibited pyruvate‐kinase. The results clearly indicate a correlation between vitamin D‐repletion and the total and bound calcium content of skeletal muscle. In addition, they demonstrate an apparent contradiction between the decrease of total and bound calcium, and the activities of cytosolic Ca2+sensitive enzymes during vitamin D‐deprivation, which can only be explained by an increase in available calcium. It is suggested that vitamin D stimulates intramuscular mechanisms tending to lower available calcium by in

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90344-3

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—Human pancreatic cells of the Capan‐1 line form domes in culture during the stationary growth stage. The domes are thought to be a result of the transport of water and electrolytes by the Capan‐1 cells. In older Capan‐1 cultures, the epithelial sheets formed thickenings from several layers of cells of which the outermost ones were joined by tight type junctions. In the intracellular space, deposits of insoluble calcium salts were observed. Culture of Capan‐1 cells in the presence of fibroblasts prolonged survival of the cultures with intact domes for more than 80 days. The Capan‐1 cells proliferated forming multilayers and closed cavities which we called super‐domes. X‐ray spectrometry and electron diffraction analysis showed that the abundant deposits inside these cavities consisted of calcium phosphate in an apatite structure. The number of these deposits increased with time in culture, and they appeared to be formed at the sites of contact with an extracellular matrix consisting of cell debris. Deposits were not observed within the culture medium. Cells from domes were stained cytochemically for ATPases and alkaline phosphatases and examined by light and electron microscopy. The Capan‐1 cells surrounding the domes were differentiated, polarized cells containing placental type alkaline phosphatases on their apical membranes and Ca2+‐ATPases on their basolateral membranes. These enzymes were thought to play a role in the accumulation of phosphate and Ca2+ions in the dome cavities, which then formed crystals in the presence of organic compounds produced by lysis of cells of the deepest layers of the super‐domes. The crystals of hydroxyapatite observed in standard Capan‐1 cell cultures and those cocultured with fibroblasts were assumed to be a result of transepithelial transport of Ca2+and phosph

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90345-4

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The experimental induction of ε particles, retrovirus‐like structures corresponding to the small IA particles of the mouse, was studied by electron microscopy in rodent‐cultured cell lines. Among the chemicals tested, only IdUr was shown to be an effective inducer, but not cycloheximide, puromycine, deoxy‐fluorouracile or 5‐azacytine. However, only two mouse‐derived cell lines: KiBALB and FG 10, among 27 cell lines of mouse, rat and mink origins tested, expressed ε particles upon IdUr treatment. Epsilon particles thus respond to chemical inducers very differently in comparison with large IAP. Moreover, the addition of interferon previously shown to attenuate IAP production, had no effect on that o

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90346-5

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The expression of cytoskeletal isoactin genes in NIH 3T3 and L cells was studied byin situhybridization. Anti‐sense RNA probes specific for β‐ and γ‐actin were prepared byin vitrotranscription of the 3′‐untranslated regions of each cDNA which diverge in an isoactin‐specific manner. Both NIH 3T3 and L cells showed a higher expression of β‐and γ‐actin mRNAs in a growing state than in a stationary one. Among these changes, the suppression of γ‐actin mRNA in L cells was most prominent and that of β‐actin in 3

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90347-6

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Summary—The stroma‐vascular fraction (SVF) of inguinal and epididymal fat pads of 4 week‐old rats was studied by electron microscopy. Among the various cell types, endothelial cells and preadipocytes were found in both SVF, while mesothelial cells were only detected in the epididymal SVF. The resulting heterogeneity of primary culture and the adipoconversion of the fat cell precursors were studied in a serum‐supplemented medium enriched with insulin (14.5 nM) and exogeneous triglycerides. Despite the heterogeneity of the inoculum, the primary cultures were rather homogeneous, fat cell precursors being the main cell type. Distinctive contaminant fibroblast‐like cells were observed in both cultures, whereas epithelial‐like cells, which correspond most probably to mesothelial cells, were only found in epididymal cultures. Differentiation of fat cell precursors was assessed by the appearance of lipoprotein lipase (LPL) and glycerol‐3‐phosphate dehydrogenase (GPDH). LPL activity was found in the same level in cells of both deposits while GPDH activity was elevated in inguinal vs epididymal derived stroma‐vascular cells. The different adipose conversion pattern of both cultures was confirmed by morphological quantification: the maturation of epididymal fat cell precursors was faster but less extensive. These differences could be related mainly to regional localization rather than to different maturation of the

ISSN:0248-4900    

DOI:10.1016/0248-4900(90)90348-7

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY