ISSN:1059-910X    

DOI:10.1002/jemt.1070280102

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe fine structure of the renal (i.e., glomerular, tubular, and capillary) basement membranes was re‐evaluated with the aid of a deep‐etch replica method. The structure of the laminae rarae interna and externa of the rat glomerular basement membrane (GBM) and laminae lucida of other basement membranes were basically identical in that 6 to 8 nm fibrils were interconnected to form a three‐dimensional, polygonal network. By contrast, all of the laminae densa examined were composed of closely packed granules, and a filamentous substructure was identified only in a limited area. These granular components were demonstrated to be an integral component of the lamina densa. From additional observations on the trypsinized bovine GBM, it appeared that the basic structure of renal basement membranes was almost identical, namely, that a three‐dimensional fibrillar meshwork existed throughout the individual layers to form a structural framework upon which fine particles were variably attached. In addition, we observed some of the fine structure of the pars fibroreticularis; the laminae densa of the tubular and capillary basement membranes continued to the fibrillar meshwork resembling the structural backbone of the glomerular basement membrane. The network was sometimes directly connected to the extracellular matrix, but more often changed into a rough fibrillar framework and connected to the extracellular matrix. © 1994 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070280103

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

年代:1994

数据来源: WILEY

摘要:

AbstractHigh angle platinum/carbon (Pt/C) replication has proved to be a valuable tool in analyzing basement membrane structure in human amnion, bovine lens capsule, and the Engelbreth‐Holm‐Swarm (EHS) tumor. High resolution replicas for transmission electron microscopy (TEM) have been achieved by depositing 1.0 ± 0.1 nm thick Pt/C films backed with rotary deposited 12.5 ± 2.5 nm thick carbon films. The basement membrane collagen IV network was observed to consist of fine branching filaments containing globular domains intrinsic to the filaments. A second quasi‐regular network is formed by laminin. Unidirectional 45° angle Pt/C replication was used for most of this work. The merits and deficiencies of unidirectional vertical replication (80° angle), unidirectional 45° angle, and 20° low angle rotary replication are discussed. Vertical replication produces the highest resolution replicas and has the potential for revealing the overall pattern of basement membrane structural assembly if basement membrane preparations freeze‐dried in low salt can faithfully maintain their in vivo structure. © 1994 W

ISSN:1059-910X    

DOI:10.1002/jemt.1070280104

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

年代:1994

数据来源: WILEY

摘要:

AbstractA three‐dimensional network of irregular anastomosing strands, referred to as “cords,” was found to be the main component of the lamina densa of (a) common, “thin” basement membranes in tissues from diverse origins including foot pad epidermis, trachea, jejunum, seminiferous tubule and vas deferens of the rat, monkey seminiferous tubule, and mouse ciliary process, (b) a “double” basement membrane, the rat glomerular basement membrane, and (c) “thick” basement membranes including rat Reichert's membrane, mouse lens capsule and the Engelbreth‐Holm‐Swarm (EHS) tumor matrix. The average thickness of the cords was 3.2–4.8 nm, 4 nm, and 4.7–5 nm, respectively, in these three types of basement membranes. The mean diameter of the intercordal spaces, or openings of the network, averaged 14 nm with a range from 8 nm in the glomerular basement membrane to 21.9 nm in the lens capsule. After cryofixation followed by freeze substitution or freeze drying, similar cord networks were observed in all basement membranes examined which included two thin basement membranes, that of the rat epididymis and seminiferous tubules, and three thick basement membranes, that is, the lens capsule and the EHS tumor matrix of the mouse, and rat Reichert's membrane. In addition, following the co‐incubation of laminin, type IV collagen and heparan sulfate proteoglycan at 35°C, a precipitate was formed which was found to contain lamina densa‐like sheets and large semisolid masses. Both types of structures were found to be made up of a network of 3 nm wide cords, which resembled that of natural basement membranes. With the immunoperoxidase technique, these cords were stained for major basement membrane components including laminin, type IV collagen, heparan sulfate proteoglycan, entactin, and fibronectin. Ribbon‐like “double tracks” 4.5 nm in width and being distributed along cords have been identified as the form taken by heparan sulfate proteoglycan in basement membranes. Following mild plasmin treatment, most of the cord components were digested away leaving behind a network of fine filaments found to contain type IV collagen. Each cord, therefore, is organized by a type IV collagen core filament which is surrounded by a plasmin‐sensitive sheath containing other basement membrane components. Two types of minor structural components, that is, 7–10 nm wide straight “basotubules” and 3.5 nm wide particulate structures referred to as “pentosomes” were associated with cord network in some basement membranes. In summary, since a fine network of about 4 nm thick cords was always found to occupy a bulk of all basement membranes examined in tissues of a diverse origin and of different species, and also after the use of different preparative methods, such cord network is likely to be the basic structu

ISSN:1059-910X    

DOI:10.1002/jemt.1070280105

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn tissues prepared with chemical fixation followed by conventional dehydration, basement membranes have been observed to be laminated structures composed of a lamina lucida and lamina densa as well as a poorly limited transitional zone referred to as the pars fibroreticularis. Scattered attempts in the application of new techniques of tissue preparation such as cryofixation or freeze substitution for the study of the basement membrane structure have been made in recent years. From these studies, the possibility has arisen in which basement membranes are composed of only the lamina densa without a lamina lucida. In recent studies in this laboratory, the attempt was made to determine whether or not this lamina lucida is an artefact, and if so, which step in the conventional method of tissue preparation is responsible for its formation. Basement membranes from diverse sources in the mouse and rat including the testis, ductus epididymis, eye, thyroid, kidney, and skin, were observed after either cryofixation by slam freezing followed by freeze substitution, or aldehyde fixation followed by freeze substitution. The basement membranes after preservation with either of these two methods were composed of only the lamina densa with no lamina lucida. It indicates that an artefactual formation of the lamina lucida occurs during dehydration in conventional tissue preparation rather than during chemical fixation. In view of the well known superiority of freeze substitution over conventional dehydration, the lamina lucida of the basement membrane is likely to be an artefact. Therefore, it is concluded that the lamina lucida is an artefact formed during conventional tissue preparation, and in its original condition in the living state, the basement membrane is composed of a single layer made up of lamina densa material. © 1994 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070280106

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

年代:1994

数据来源: WILEY

摘要:

AbstractCobalt staining of primary afferents in frog spinal cord was combined with peroxidase‐antiperoxidase pre‐embedding or immunogold post‐embedding immunocytochemical labelling. Our results have shown that cobalt labelling can easily be distinguished from both of the immunoreaction end products. The protocol of cobalt labelling did not affect the immunoreactivity of structures. The morphology and synaptology of cobalt labelled and immunostained profiles in our sections were very similar to those reported in previous studies using different double labelling techniques. These results indicate that this new combined method could be used as an alternative double labelling technique in electron microscopic studies on nervous tissues. © 1994 Wiley‐L

ISSN:1059-910X    

DOI:10.1002/jemt.1070280107

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

年代:1994

数据来源: WILEY

摘要:

AbstractA procedure is described for forming a flat face on a frozen piece of plant tissue, which may then be observed fully‐hydrated or lightly etched, and coated or uncoated with a metal film, in scanning electron microscopy (SEM). The frozen sample was planed with a glass knife at ‐80°C in cryo‐ultramicrotome. The sections were discarded, and the planed block face placed on the cold stage in the microscope column, either for observation uncoated at low kV, or for light etching (‐90°C) to reveal the cell outlines. If a higher accelerating voltage was needed, the face was given an evaporative coating of Al in the cryo‐preparation chamber and returned to the column. The advantages of the planed face over the usual fracture face are illustrated: imaging at a chosen rather than a chance position; clearer cellular and subcellular detail; preservation of hydrated gels like mucilage and swollen cell walls; the possibility of making serial parallel sections through the same piece of tissue; opportunities for accurate morphometric analyses on the planed face; capacity to produce longitudinal sections; preservation of very delicate structures that are destroyed by fixation and drying. A major advantage of the Al‐coated planed face is the increased accuracy of energy‐dispersive X‐ray (EDX) microanalyses on a smooth rather than a rough surface. Tests are included which show that neither the light etching employed, nor successive planing, interferes with the analyses of elements in the frozen face. © 19

ISSN:1059-910X    

DOI:10.1002/jemt.1070280108

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.1070280109

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.1070280110

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.1070280111

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

年代:1994

数据来源: WILEY