摘要:

AbstractIn vivo labeling of infant rat and mouse glomerular basement membranes (GBMs) with polyclonal anti‐laminin IgGs results in binding across the full widths of GBMs at all stages of development. These stages include the pre‐fusion, double basement membranes found beneath endothelial cells and podocytes in early glomeruli, and the subepithelial matrix outpockets where newly synthesized GBM is spliced into fused basement membrane during glomerular maturation. Identical binding results are obtained either with peroxidase or post‐embedding immunogold techniques. Although injected cationized ferritin also binds abundantly to all developing GBMs, it quickly disappears and, 24 hours after injection, is generally absent from GBMs but remains within mesangial matrices. Injection of newborn mice with monoclonal anti‐laminin IgGs results in dense labeling of pre‐fusion GBMs but post‐fusion GBMs and subepithelial outpockets are weak‐negative. Although masking can not be excluded, these results indicate that laminin epitopes are removed during GBM fusion and splicing, either by isoform substitution or proteolytic processing. The loss of bound cationized ferritin is believed to occur mainly through rapid turnover of GBM proteoglycans. © 1994 W

ISSN:1059-910X    

DOI:10.1002/jemt.1070280202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this contribution is to summarize our knowledge of the morphology of the basement membrane (BM). The first step in this direction is the attempt to define this term. The BM is composed of the Lamina lucida, densa, and fibroreticularis. Subsequently, the historical development of this term is discussed. Our main interest is, of course, focused on the description of the BM‐structure up to the macromolecular level and the special forms of this structure. This is supplemented by discussing its chemical composition and establishing a relationship between morphology and biochemistry. The obtained findings yielded some indications as to the molecular composition of the BM which may serve for the construction of “models.” The composition of the Lamina lucida (L.l.) and the Lamina or Pars fibroreticularis (L.f.) must be discussed separately, since, if present, they show a different and strongly varying structure (L.f.). An important aspect is the function of this extracellular layer which comprises mechanical tasks up to inductive effects. Finally, the concepts of the formation of the BM, especially of the Lamina densa (L.d.), are summarized. It obviously consists of a sequence of individual steps which starts with expression and secretion of the L.d.‐components and is followed by an induction of integrin expression. © 1994 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070280203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe application of cationic probes for the ultrastructural detection of proteoglycans in basement membranes is reviewed. Proteoglycans are highly negatively charged macromolecules due to their glycosaminoglycan side chains. The interaction of cationic probes with proteoglycans is of an electrostatic nature. Methods are discussed to increase the specificity of probes for proteoglycans. The use of phthalocyanin‐like dyes such as Cuprolinic blue, according to the critical electrolyte concentration method, results in a selective staining of proteoglycans. Enzymatic or chemical digestions, however, should be done to validate the proteoglycan nature of the dye‐positive granules/filaments, and to establish the class of proteoglycan. The value of cationic probes in basement membrane research on development and pathology is discussed. The potential for deducting molecular information from the ultrastructural appearance of stained proteoglycans is indicated. © 1994 Wiley‐Lis

ISSN:1059-910X    

DOI:10.1002/jemt.1070280204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn respiratory epithelium, the mucus is densely packed inside the secretory granules (SG) of secretory cells (SC) before being released by exocytosis in the airway lumen. We have previously shown that the frog palate is a representative model of respiratory epithelium and that rapid cryofixation is a very effective technique in preserving the integrity of the mucus SG. The concentration of phosphorus (P), sulphur (S), and calcium (Ca) were analysed inside the SG of the SC of frog palate after quick freezing, cryosubstitution, and embedding in Lowicryl resin at low temperature. The experiments were carried out using X‐ray microanalysis conducted with energy dispersive spectrometry (EDS) at 100 kV. The quantitation was carried out using the continuum method with reference to Agar standards. The cryofixation permitted us to distinguish two types of SG depending on whether they were electron dense (serous cells) or electron‐lucent (mucous cells). A significant (P<0.001) difference in the S concentration was observed between the individual serous (239 ± 79 mmol.kg−1) and the mucous SG (161 ± 48 mmol.kg−1). No significant difference could be identified in the Ca concentration between the two SG phenotypes. In the serous SG, the P content was high (41 ± 17 mmol.kg−1) compared with the mucous SG where it was not measurable. The comparison of the three element concentrations in each type of secretory cells showed that significant differences in concentration of S and Ca concentration could be observed from one SC cell to another. A significant correlation (r = 0.76,P<0.01) was observed between the S concentration and the topographical position of the SG inside the SC, the more proximal to the lumen, the higher the S concentration, suggesting that the maturation of the SG involves an increase in the protein content possibly due to a maturation process before the mucus exocytosis. Therefore, these results suggest that the elemental composition of granules varies according to the phenotype of the secretory cells and that changes in the S content from one SG to another or even inside the same cell may reflect a differential state in the functional activity of the secretory cells. © 1994 Wi

ISSN:1059-910X    

DOI:10.1002/jemt.1070280205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn the present study europium chelates were introduced as alternative fluorescent labels for microscopy and their effect on enhanced autofluorescence caused by the glutaraldehyde fixative was investigated. Glutaraldehyde fixation was used to stabilize the cells for a permanent mount after the immunocytochemical reaction. The europium signal in time‐resolved fluorescence microscopy was shown to be free of autofluorescence when strong cross‐linking fixation with glutaraldehyde was used and the signal‐to‐background ratio obtained was 2,400 or better. It was also shown that the europium signal was stable in daylight and at room temperature. Fluorescent europium chelate used in this experiment provides excellent contrast and long‐term stability for the samples with glutaraldehyde fixation and permanent mounting. © 1994 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070280206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe detection of elemental distributions within ultrastructural cellular components presents a number of challenges. There are many technical questions that need to be resolved including optimal fixation protocols. Another is the impact of heavy metals, such as osmium tetroxide (OsO4), on the detectability of other elements when OsO4is used in chemical fixation protocols for biological samples. OsO4was examined by varying its concentrations from 0% to 1% and time of fixation from 5 to 30 minutes with hamster alveolar macrophages. The morphological quality of cellular images observed and the detectability of iron using electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS) were evaluated. One percent OsO4for 30 minutes in the chemical fixation protocol enhances the quality of the ESI and does not interfere with the ESI or EELS signal of iron. Positive results from both methods indicate the presence of the specific element. The loss of59Fe during the chemical fixation procedure was also studied. Less than 10% was lost during the primary fixation step, but minimal losses occurred through dehydration, embedding, and sectioning. Careful technical assessment of the presence of an element as well as factors which might interfere with its detection is an important step in the application of any analytical microscopic technique. © 1994 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070280207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070280201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY