ISSN:1059-910X    

DOI:10.1002/jemt.1070310502

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

年代:1995

数据来源: WILEY

摘要:

AbstractGap junctions were discovered more than three decades ago, and since this time, enormous strides have been made in understanding their structure and function. This article summarises the part played by microscopy, within the context of multidisciplinary research, in the historical development of our knowledge of the gap junction. © 1995 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070310503

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

年代:1995

数据来源: WILEY

摘要:

AbstractRecent advances in understanding lens fiber gap junction formation are reviewed. These include studies of junctional protein expression in the embryonic lens, and of age related changes affecting gap junction structure and composition in the adult lens. An in vitro assembly system based on detergent solubilized pore complexes and endogenous lipids has been developed to provide information on the molecular interactions involved in gap junction formation and to provide material for structure analysis. Important information on the electrical properties of lens gap junction channels is obtained using electrophysiological techniques including planar lipid bilayer analysis and patch clamping. © 1995 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070310504

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

年代:1995

数据来源: WILEY

摘要:

AbstractElectrical activation of the heart requires intercellular transfer of current through gap junctions connecting individual cardiac myocytes. Using a combination of light and electron microscopic techniques and molecular approaches, we have characterized the number, size, and spatial distribution of intercellular connections at gap junctions in cardiac myocytes and have also cloned, sequenced, and elucidated the subcellular distribution of three physiologically distinct gap junction channel proteins. In this review, we present evidence to suggest that the spatial distribution of myocyte interconnections and the molecular composition of gap junction channels may confer distinct conduction properties on specific tissues of the mammalian heart such as atrial and ventricular myocardium, and the nodes and bundles of the cardiac conduction system. © 1995 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070310505

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

年代:1995

数据来源: WILEY

摘要:

AbstractWe have taken several approaches to study the role of gap junctional communication during preimplantation mouse development. Firstly, the normal expression pattern of gap junctions has been characterized using immunostaining in conjunction with laser scanning confocal microscopy. Changes in junctional distribution have been correlated with developmental events. We have gone on to study development and junctional organization in mice which naturally exhibit reduced cell to cell communication (DDK syndrome), and in normal mice in which gap junction permeability has been artificially manipulated. Furthermore, anti‐peptide antibodies hae been tested for their ability to block gap junction communication and for the effects of such a block on subsequent development. Collectively, the results demonstrate that gap junctional communication plays an important role in the maintenance of compaction and the differentiation of an organized epithelium within an embryo, features which are vital for preimplantation development to progress successfully. © 1995 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070310506

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

年代:1995

数据来源: WILEY

摘要:

AbstractIschemia causes an increase in myocardial resistivity and a decrease in conduction velocity, thereby enhancing cardiac contractile dysfunction and arrhythmic tendency. Myocardial gap junctions, as principal determinants of conduction velocity, may, therefore, be expected to be deranged in ischemia. Despite a lack of consensus, attempts at correlating gap junction ultrastructural morphology with functional state have revealed the component connexons of gap junctions in freeze‐fractured myocardium to be in multiple small hexagonal arrays, tending to become randomly distributed and compacted under uncoupling conditions. Further hypoxic uncoupling causes ultrastructural damage and a reduction in gap‐junctional surface area. Immunohistochemical detection of connexin43 gap junctions in chronically ischemic non‐infarcted human myocardium demonstrates a reduction in junctional surface area within a normal number of intercalated disks per myocyte, and with a normal distribution of junction sizes. In healed canine infarction there are smaller and fewer gap junctions in the fibrotic myocardium adjacent to infarcts, with reductions in overall gap‐junctional content and the proportion of side‐to‐side vs. end‐to‐end intercellular connections. Immunohistochemical examination of intact human ventricular myocardium shows the myocytes immediately abutting healed infarcts to hve connexin43 gap junctions spread longitudinally over the cell surfaces, and not in discrete transversely orienated intercalated disks as in normal myocardium. Early after canine infarction, and before fibrotic healing, the connexin43 gap junctions in myocytes abutting the infarct show disorganization similar to that described in healed human infarcts, suggesting that this disturbance is an early pathophysiological cellular response, and not simply due to later fibrotic distortion. Such changes in gap‐junctional organization in myocardial ischemia and infarction may be implicated in the elusive link between subcellular structure, contractile dysfunction and arrhythmogenesis. © 19

ISSN:1059-910X    

DOI:10.1002/jemt.1070310507

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

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the use of a photobleach method and confocal microscopy to compare the cell‐to‐cell transfer rate of 5,6 carboxyfluorescein in dissociated embryonic chick lens cells with those in the anterior epithelium of the whole embryonic chick lens. The average cell‐to‐cell transfer rates obtained were 7.9 × 10−3sec−1in the dissociated cells and 2.6 × 10−3sec−1in the anterior epithelium in an intact lens. © 19

ISSN:1059-910X    

DOI:10.1002/jemt.1070310508

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

年代:1995

数据来源: WILEY

摘要:

AbstractMore than ten research groups have now reported the presence of gap junctions in blood‐forming tissue or cultured cells. It is time to accept that these cell‐coupling structures are present in this tissue. To find out what they are doing here we need to develop appropriate experimental techniques. This review covers the particular problems of investigating direct cell‐cell communication by gap or other junction in undisturbed haemopoietic tissue. It then describes and assesses the published reports of haemopoietic gap junctions. Recently, in the author's laboratory, three means of increasing the number of gap junctions 50‐ to 100‐fold in mouse marrow have been described, as well as techniques for doing so in culture. There is a complete report of this work here. At present it is quite unclear what function gap junctions serve in blood‐formation, perhaps it is some consolation that 30 years after their ultramicroscopic discovery it is also true for all other unexcitable tissues. Possibly the ability to up‐regulate their expression in haemopoietic tissue will help us find out what their role is in blood formation. © 1995 W

ISSN:1059-910X    

DOI:10.1002/jemt.1070310509

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe vertebrate retina is a highly laminated assemblage of specialized neuronal types, many of which are coupled by gap junctions. With one interesting exception, gap junctions are not directly responsible for the ‘vertical’ transmission of visual information from photoreceptors through bipolar and ganglion cells to the brain. Instead, they mediate ‘lateral’ connections, coupling neurons of a single type or subtype into an extended, regular array or mosaic in the plane of the retina. Such mosaics have been studied by several microscopic techniques, but new evidence for their coupled nature has recently been obtained by intracellular injection of biotinylated tracers, which can pass through gap junctional assemblies that do not pass Lucifer Yellow. This evidence adds momentum to an existing paradigm shift towards a population‐based view of the retina, which can now be envisagedbothas an array of semi‐autonomous vertical processing modules, each extending right through the retina,andas a multi‐layered stack of interacting planar mosaics, bearing some resemblance to a set of interleaved neural networks. Junctional conductance across mosaics of horizontal cells is known to be controlled dynamically with a circadian rhythm, and other dynamically‐regulated conductance changes are also likely to make important contributions to signal processing. The retina is an excellent system in which to study such changes because many aspects of its structure and function are already well understood. In this review, we summarize the microscopic appearance, coupling properties and functions of gap junctions for each cell type of the neural retina, the regulatory properties that could be provided by selective expression of different connexin proteins, and the evidence for gap junctional coupling in retinal development. © 1995

ISSN:1059-910X    

DOI:10.1002/jemt.1070310510

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

年代:1995

数据来源: WILEY

摘要:

AbstractUsing immunohistochemical staining, the distribution of connexin40 (Cx40) and connexin43 (Cx43) was studied in rat, guinea pig, porcine, bovine and human hearts. These species display differences in the degree of morphological differentiation of the conduction system. This study was performed in the anticipation that comparison of the distributions of Cx40 and Cx43 in young and adult specimens may provide clues as to the physiological role of connexins in the heart. To a large extent, the distribution patterns of Cx40 and Cx43 are comparable between species. In neonates and adults, Cx43 was immunolocalized throughout the working myocardium, but in the conduction system Cx43 was detected only after birth. Cx40 was found to appear slightly earlier in development than Cx43 and to disappear when levels of Cx43 became more abundant. This time course was seen in working myocardium and in the ventricular conduction system. Together these data suggest that expression of Cx40 induces or facilitates expression of Cx43, while abundant expression of Cx43 in turn leads to suppression of Cx40 expression. The exceptions to this may represent blocks in this potential regulatory sequence. A second conclusion is that Cx40 and Cx43 containing gap junctions appear in the ventricular conduction system from distal to proximal and only after birth. This indicates that terminal differentiation of the conduction system occurs unexpectedly late in development. © 1995 Wiley‐Liss, I

ISSN:1059-910X    

DOI:10.1002/jemt.1070310511

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

年代:1995

数据来源: WILEY