摘要:

The review is focused on the molecular structure and function of the proteins composing the actin‐based cytokeletal cortex, located at the cytoplasmic face of plasma membranes of eucaryotic cells, which stabilizes integral membrane proteins in separate domains of cell membranes. It includes a survey of the molecular properties of teh proteins of the erythrocyte membrane skeleton such as spectrin, ankyrin, protein 4.1, and adducin. The properties of the immunological counterparts of erythroid cortical proteins found in nonerythroid tissues and cells are compared. The structural organization and function of the newly discovered class of calcium‐binding proteins, nonerythroid peripheral membrane proteins, calpactins, are also described. Finally, the discussion of some experimental models illustrates that the membrane skeleton of living cells is actively involved in a wide variety of essential biological functions ranging from differentiation, to maintenance of cell polarity and cell shape, and regulation of exocytotic proces

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90001-9

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Detergent extraction of human blood platelets pre‐treated with Taxol to stabilize microtubules allows isolation of marginal band (MB) cytoskeletons. We studied MB cytoskeleton structure using dark‐field light microscopy and negative stain electron microscopy (EM). Dark‐field illumination clearly demonstrated the “hoop” shape of MB cytoskeletons in unfixed suspension where the microtubule coils had a mean diameter of 2.87 μm (± 0.18 μm, SD). Microtubules were uncoiled by brief exposure to trypsin (2 mg/μg protein) or by NaCl (154–600 mM) but not by DNase I, which removed ∼40% of total actin, but had no effect on dark‐field images of microtubule coils. As microtubules uncoiled, a single fiber emerged from the hoop and gradually lengthened as the brightness of the hoop diminished; these fibers correspond to the single microtubules seen by EM. Polypeptides of coiled and uncoiled MB cytoskeletons were analyzed by SDS‐PAGE. When microtubules became uncoiled, no changes in the major components (α‐ and β‐tubulin, IEF‐51K, or actin) were found. However, a number (>10) of minor polypeptides, each<5% of total cytoskeletal protein and with an Mr ranging from 80,000≽ 260,000, were decreased in “uncoiled” MB cytoskeletons. These results implicate one or more of these minor polypeptides in maintenance of hoop integrity. Dark‐field light microscopy thus provides an approach toward investigating the mechanisms(s) involved in maintaining the microtubu

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90002-0

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

During the process of progestogen‐induced meiotic maturation in the goldfish oocyte, the oocyte nucleus (germinal vesicle, GV) migrates to the sperm entry site or micropyle at the animal pole. Following GV migration (GVM) to the micropyle, the nuclear membrane undergoes dissolution (GVD) and the cell enters metaphase I in preparation to generate the first polar body. Microtubule destabilizing drugs including colcemid, nocodazole and vinblastine were found to elicit GVM, mimicking the process which occurs just prior to the prophase I‐metaphase I transition during steroid induced oocyte meiotic maturation. In addition, these drugs enhanced the induction of GVM by 17 alpha, 20 beta dihydroxy‐4‐pregnen‐3‐one, a potent, naturally occurring meiotogenic steroid in this species. By contrast, taxol, a microtubule stabilizing drug, was found to inhibit steroid induced GVM. A new assay for centrifugation induced GVM was applied to the goldfish oocyte in order to assess effects of steroids and drugs on GVM, without the complication of GVD or the restrictions imposed by the slow time course of naturally occurring GVM. The effective centrifugal force (ECF) required to elicit GVM in 50% of the oocytes (ECF50) decreased significantly after short incubations (1–5 hr) of oocytes with either 17 alpha, 20 beta dihydroxy‐4‐pregnen‐3‐one or microtubule disrupting drugs (i.e., colcemid, nocodazole, or vinblastine). A working hypothesis, modeled after the effects of microtubule disrupting agents on intermediate filament arrays in somatic cells, is proposed in which a small number of microtubules or other polymeric tubulin units are responsible for maintaining a cytoskeletal array. The net effect of progestogen or microtubule disrupting drugs would be to collapse or reorganize t

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90003-2

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The spatial organization of microtubules in mitotic as well as in interphase cells and in axons has been investigatedin situin the embryonic nervous system of mice using high molecular weight polyethylene glycol‐embedded semithin sections and immunofluorescence with a tubulin‐specific polyclonal antibody.In situ, the overall process of mitosis appears nearly identical to that described in cell culture. All types of mitotic microtubules (kinetochore, interpolar and asterial) can be visualized at the different stages. The slight differences from observations in cell culture are explained by differences in cell interactions.In bipolar neuroepithelial cells, interphasic microtubules appear in the form of a framework surrounding the nucleus during its to‐and‐fro movements and which follows the modifications in shape of the cell processes. These microtubules seem to play an active role in the mechanism, indicating the modifications in length of the apical process.In the differentiating young neuron, tubulin increases in amount to be involved in the elongation of axonal microtubules. This increase seems to be independent of the presence of axons in the environment. Axonal microtubules are independent of a microtubule‐organizing center localized in the p

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90004-4

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

F‐actin and microtubule co‐distribution and interaction were studied during anaphase‐telophase. Rapid and drastic changes in the cytoskeleton during these particular stages were studied in isolated plant endosperm cells of the blood lily. These wall‐free cells can be considered as natural dividing protoplasts. As identified previously, an F‐actin cytoskeletal network characterized the plant cortex and formed an elastic cage around the spindle, remaining throughout interphase, mitosis and cytokinesis. Actin was specifically labeled by fluorescent phalloidin and/or monoclonal antibodies. Gold‐labeled secondary antibodies were used for ultrastructural observations and silver‐enhancement was applied for video‐enhanced microscopy. Microtubule and microfilament dynamics and interaction were studied using drug antagonists to actin (cytochalasins B, D) and to tubulin (colchicine). This permitted precise correlations to be made between chromosome movement inhibition and alteration in the actin/tubulin cytoskeleton. During anaphase chromosome migration, the cortical actin network was stretched along the microtubular spindle, while it remained homogeneous when anaphase was inhibited by colchicine. Cytochalasins did not inhibit chromosome movement but altered actin distribution. A new population of actin filaments appeared at the equator in late anaphase before the microtubular phragmoplast was formed and contributed to cell plate formation. Our conclusion is that F‐actin‐microtubule interaction may contribute to the regulatory mechanism o

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90005-6

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Cytohistochemical staining and RNase‐gold labelling have been applied to root‐tip meristematic cells ofVicia fabato study the origin and biological significance of 2 types of inclusions: one seen in the nucleoplasm and the other in the cytoplasm of early telophase cells. They have been termed “dense bodies” and “cytoplasmic nucleolus‐like bodies” (NLB), respectively. Both types of inclusions respond positively to silver staining and ribonucleoprotein (RNP) staining in a similar fashion to nucleolus. Interestingly, the dense bodies label heavily with the RNase‐gold complex, as does the nucleolus, while the cytoplasmic NLB have no affinity with the label. In most cases, the dense bodies label more heavily than the nucleolus. Light microscope surveys reveal that the dense bodies sometimes appear to be released from the surface of the nucleolus. On the other hand, prenucleolar material showing the same silver staining and RNP preferential staining characteristics as the dense bodies begin to accumulate on the surface of chromosomes in mid‐anaphase. This material does not label with RNase‐gold. These data are discussed in terms of the hypothesis that the dense bodies are derived from the nucleolus by direct budding or fragmentation, and the cytoplasmic NLB are composed of prenucleolar material that failed to at

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90006-8

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Little information exists on how various nucleolar proteins function in ribosome biogenesis. Of special interest is that group of nucleolar proteins which are not incorporated into mature ribosomes because they are candidates for a role in the regulation of ribosome construction. Non‐ribosomal nucleolar proteins can be analyzed using autoimmune sera from scleroderma patients which often contain antinuclear antibodies. One such serum, designated ScBr, is shown by indirect immunofluorescence to react specifically with nucleoli in cells of 3 different mammalian species, indicating that the antigen is at least partly conserved evolutionarily. It is not RNase‐sensitive, but is completely eliminated after incubation with pronase and 2 M NaCl. Immuno‐electron microscopy was carried out on Lowicryl ultrathin sections to localize the antigen. The labeling was observed over both the granular and the dense fibrillar component but not the fibrillar centers, indicating that the antigen is associated with ribosomal RNA transcription sites and ribosome assembly into precursor particles. In addition, the antibody was localized to small nucleoplasmic entities, termed dense nuclear bodies. This could indicate a relationship between nucleoli and dense nuclear bodies. By immunoprecipitation, only a single protein of 94 kDa molecular weight was revealed. By immunoblotting, the band at 94 kDa was found to be the only positive band for high ScBr dilutions. Observation of the behavior of the antigen during mitosis revealed that it became dispersed into the cytoplasm after breakdown of the nuclear envelope, lining most of the chromosomes rather that remaining associated with the NOR‐chromosomes. The antigen appeared to be restored to nucleoli only in late telophase; phase‐dense prenucleolar bodies of early telophase cells did not show positive staining for the antigen. During actinomycin‐D RNA synthesis inhibition as well as in non‐stimulated lymphocytes the positive staining is greatly decreased. These results were consistent with a role for the 94 kDa nucleolar protein in the process of preribo

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90007-X

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The distribution of 2 nuclear antigens in the interphase nuclei of liver ofPleurodeles waltlwas determined with the help of monoclonal antibodies, using immunofluorescence for light microscopy and indirect immunoperoxidase and immunogold labeling procedures for electron microscopic localization. The antibodies C36/1 and A33/22 label antigens with relative molecular masses of 270 kDa and 80 kDa, and isoelectric points of 7.0 and 6.4, respectively. The liver of urodels is characterized by the presence of a peripheral layer of hematopoietic cells around the parenchymatous tissue formed by typical hepatocytes. The antibody C36/1 labels the nuclei of both types of cells, whereas the antibody A33/22 labels the nuclei of hepatocytes but not those of the peripheral hematopoietic cells. With both these antibodies, labeling, whenever observed, is restricted to fibrillar structures in the interchromatin space,i.e., to peri‐ and inter‐chromatin fibrils; condensed chromatin, nucleoli, and nuclear envelope are not labe

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90008-1

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

During estrogen‐induced development of the quail oviduct, tubular glands are formed by evagination of epithelial cells into the stroma. The distribution of laminin was studied during the early stages by means of immunofluorescence and immunoperoxidase techniques. Ultrastructural changes in the basal lamina were studied by electron miscrocopy.Basement membranes at all stages of development were delineated with 3 polyclonal antilaminin antisera. However, in ovariectomized birds, laminin could not be detected by one of the polyclonal antilaminin antisera. Subsequently, this antibody detected laminin as epithellal cell evaginations were induced by estradiol benzoate. The heavy and light chains of Engelbreth Holm sarcoma (EHS) laminin were revealed in immunoblotting by all antibodies.By electron microscopy after the immunoperoxidase technique with antilaminin antisera laminin appears to be accumulated mainly in the lamina densa. Furthermore, the thickness of the basal lamina increases during oviduct development. These data indicate that basal lamina organization is modified during oviduct cell differentiation and that immunoreactivity of epithelial basement membrane laminin changes during developmen

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90009-3

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Excellent preservation and new structural details can be demonstrated in rust‐infected leaf tissue after high pressure freezing and freeze‐fracturing. A tubular‐vesicular complex was the most remarkable cytoplasmic structure observed in cells of the bean rust fungusUromyces appendiculatusvar.appendiculatusduring its establishement in its hostPhaseolus vulgaris. In fungal cells undergoing intensive synthesis of wall material, this membranous system extended throughout the cytoplasm; in addition, vesicles were accumulated adjacent to the plasma membrane. Here, membrane‐associated configurations were observed which seem to be involved in exo‐ and/or endocytotic processes. It is assumed that the tubular‐vesicular complex belongs to the endomembraneous system of the bean rust fungus and that it is involved in the synthesis and secretion of wa

ISSN:0248-4900    

DOI:10.1016/0248-4900(88)90010-X

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY