ISSN:1059-910X    

DOI:10.1002/jemt.1070270302

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

年代:1994

数据来源: WILEY

摘要:

AbstractMitochondria are semi‐autonomous organelles which are endowed with the ability to change their shape (e.g., by elongation, shortening, branching, buckling, swelling) and their location inside a living cell. In addition they may fuse or divide. These dynamics are discussed. Dislocation of mitochondria may result from their interaction with elements of the cytoskeleton, with microtubules in particular, and from processes intrinsic to the mitochondria themselves. Morphological criteria and differences in the fate of some mitochondria argue for the presence of more than one mitochondrial population in some animal cells. Whether these reflect genetic differences remains obscure. Emphasis is laid on the methods for visualizing mitochondria in cells and following their behaviour. Fluorescence methods provide unique possibilities because of their high resolving power and because some of the mitochondria‐specific fluorochromes can be used to reveal the membrane potential. Fusion and fission often occur in short time intervals within the same group of mitochondria. At sites of fusion of two mitochondria material of the inner membrane, the matrix compartment seems to accumulate. The original arrangement of the fusion partners is maintained for some minutes. Fission is a dynamic event which, like fusion, in most cases observed in vertebrate cell cultures is not a straightforward process but rather requires several “trials” until the division finally occurs. Regarding fusion and fission hitherto unpublished phase contrast micrographs, and electron micrographs have been included. © 1994 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070270303

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

年代:1994

数据来源: WILEY

摘要:

AbstractOur present understanding of mitochondrial division can be summarized as follows:Mitochondria contain a specific genome, synthesize their own DNA, and multiply semi‐autonomously. Strands of mitochondrial DNA (mt‐DNA) in the in vivo organelles of all eukaryotes are organized to form mitochondrial nuclei (nucleoids) (mt‐nuclei) with specific proteins including a histone‐like protein and transcription factors at the central region of the mitochondrion. We can easily observe the mt‐nucleus in vivo mitochondria in various organisms such as fungi, algae, plants, and animals by using high‐resolution epifluorescence microscopy. Therefore, the process of mitochondrial division can be clearly separated into two main events: division of the mt‐nuclei and mitochondriokinesis analogous to cytokinesis.Mitochondria undergo binary division which is accompained by the division of the mt‐nucleus. A remarkable characteristic of mitochondrial multiplication during the mitochondrial life cycle is that mitochondria can multiply the mt‐chromosome by endoduplication until 50–100 copies are present. Mitochondria can then divide without mitochondrial DNA synthesis to eventually contain 1–5 copies of the mt‐chromosome. This characteristic phenomenon can be observed during cell differentiation, such as during the formation of plasmodia and sclerotia ofPhysarum polycephalumand during embryogenesis and the formation of meristematic tissues in plants.The mitochondrial chromosome has a mitochondrial “kinetochore (centromere)” which is A‐T rich and contains specific sequences such as topoisomerase binding sites, tandem repeats, and inverted repeats. A bridge of proteins may exist between the kinetochore DNA and membrane systems. Mitochondrial chromosomes can divide according to the growth of a membrane system between the kinetochores.Mitochondriokinesis progresses steadily along with mitochondrial nuclear division. As the membrane at the equatorial region of a mitochondrion contracts, the neck of the cleavage furrow narrows, and eventually the daughter mitochondria are separated. An actin‐like protein may power mitochondriokinesis by separating the daughter mitochondria. In general, mitochondriokinesis occurs by contraction rather than by partition of the inner m

ISSN:1059-910X    

DOI:10.1002/jemt.1070270304

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule‐associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule‐associated proteins to porin‐containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross‐bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross‐bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria. © 1994 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070270305

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

年代:1994

数据来源: WILEY

摘要:

AbstractA new preparation method permits the production of large‐area, electron‐transparent, transmission electron microscopy (TEM) specimens in cross section of free‐standing, thick, multilayered structures. Such production often has been difficult in the past because of large chemical differences between the component layers in the multilayer. This difference usually results in a large difference in thinning rates between the layers. A unique combination of electroplating, lapping, dimpling, and low‐angle ion milling is a successful and reproducible technique for producing high‐quality TEM specimens of these complex materials. Procedures and results presented here are for a 304 stainless‐steel/copper multilayer having a repeat period of 20 nm and a total thickness of 20 μm. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United St

ISSN:1059-910X    

DOI:10.1002/jemt.1070270306

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.1070270307

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.1070270301

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

年代:1994

数据来源: WILEY