摘要:

Summary—In dinoflagellates, as in many eukaryotes, several kinds of nanofilaments have been described: some are organized in bundles showing a strict periodicity, some are not; most are contractile upon a rise in Ca2+concentration, some are not. In any case, their contractile properties appear to be ATP independent. They are present in all cell types studied so far, and are typically found in association with the centrioles‐basal bodies where they are suggested to play a role in MTOC structure, position and function. Nanofilaments are all about 2–4 nm in diameter, interact with microtubules, and are insoluble filaments, though to a variable extent. We propose that the nanofilaments may play a structural and/or active role complementary to intermediate fila

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90048-5

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—Polyglutamylation, a posttranslational modification which consists of the sequential addition of one to six glutamyl units in the carboxy‐terminal domain of both tubulin subunits, is a major event in neurons. Its structure has been investigated by using monoreactive polyclonal antibodies directed against distinct glutamylation motifs,ieα‐ and γ‐linkages between glutamyl units. It is shown that, beside α‐linkages previously characterized, γ‐Linkages also occur in glutamyl chains of brain tubulin. The co‐existence of these two basic motifs leads to a conception of the polyglutamyl chain with a very sophisticated structure which could, through its complexity, help the microtubule to reach its structure and ful

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90049-3

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—The behavior of the primary cilia of 3Y1 cells in the interphase was investigated by indirect immunofluorescence microscopy and transmission electron microscopy, using an antibody for tubulin. At 4.5 h after scraping a part of a confluent cell sheet, the primary cilia of cells facing the wound were located predominantly forward of the nucleus on the wounded side, and were oriented in the direction of the leading lamellae. Cytoplasmic microtubules (MTs), emanating from around the base of the cilia, were well developed in the leading lamellae on the wounded side. On the other hand, in the cells of an unperturbed area away from the wounded edge, the primary cilia remained randomly distributed near the nucleus. The position and a certain well‐defined orientation of a pair of centrioles seem to play an important role for the development of cytoplasmic MTs, and consequently the orientation of the centrioles is controlled by the primary ci

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90050-7

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—PC12 cells which overexpress transfected liver‐type phosphofructokinase (PFKL) have previously been described as a model system for PFKL overexpression in Down's syndrome and have been shown to perform glycolysis at enhanced rates. Here we report that levels of protein kinase C (PKC) in PC 12‐PFKL cells were almost doubled, as estimated fromin vitroactivity and phorbol ester binding experiments and from an increase found in PKC‐alpha mRNA levels. Most of the added PKC was found to be associated with the cellular membrane while the cytoplasmic levels of PKC were barely increased. The steady‐state levels of 1,2‐sn‐diacylglycerol in PC12‐PFKL cells were found to be unaltered, suggesting that enhanced glycolysis in these cells did not influence PKC by altering the amounts of this compound. PFKL is one of several genes known to be overexpressed in Down's syndrome. Upregulation of PKC due to PFKL overexpression could result in widespread disturbances of gene expression and play a part in causing some of the many symptoms

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90051-5

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—The clonal rat rhabdomyosarcoma cell line BA‐HAN‐IC is composed of proliferating mononuclear cells, some of which spontaneously fuse to terminally differentiated myotube‐like giant cells. This cell line has been shown to be susceptible to differentiation induction with all‐transretinoic acid (RA). Since it is still unknown whether exclusively all‐transRA itself or also its metabolites can act as inductive compounds in our cell line, we exposed BA‐HAN‐1C cells to the metabolites 4‐hydroxy RA, 4‐oxo RA and 5,6epoxy RA. Exposure to these RA metabolites resulted in a significant inhibition of proliferation (P<0.001) and induction of cellular differentiation, as evidenced by a significant increase in the number of myotube‐like giant cells (P<0.05) and a significant increase in creatine kinase activity (P<0.05). However, differences in the inductive potency of these RA metabolites became apparent. Furthermore, RA metabolites exhibited a significantly weaker (P<0.05) inductive activity when compared to all‐transRA. Summarizing our results we could demonstrate that the endogenous metabolites 4‐hydroxy RA, 4‐oxo RA and 5,6‐epoxy RA are not merely deactivated cellular excretion products of all‐transRA, but potent inducers of differentiation and inhibitors of proliferation, possibly contributing to the complex physiol

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90052-3

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—Immunofluorescence and immunoelectron microscopy indicated that the antibody raised against the nuclear antigen Ki‐67 of mammalian cells recognized antigenic determinants of earlyDrosophilaembryos, localized on the outside of the nuclear envelope. Hence, the nuclear envelope ofDrosophilaappears to share a similar epitope with the chromosome scaffold of mitotic mammalian cells. With the progression of mitosis the antigen persisted around the mitotic spindle region and was also found in the pole regions at metaphase and anaphase. The antibody also stained the equatorial regions of the spindles from anaphase to late telophase. The antibody may therefore be used as a biochemical marker of the nuclear envelope for studying nuclear membrane biogenesis and behavior during the mitotic divisions of theDrosophilaemb

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90053-1

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—In the sperm nuclei the DNA is packaged into a highly condensed form and is not organized into nucleosome and solenoid but is bound and stabilized mainly by the protamines that arrange the DNA in an almost crystalline state. As demonstrated for somatic cells, the sperm DNA has been reported to be organized in loop domains attached to the nuclear matrix structures. However, the possible role of the sperm head matrix in maintaining the loop organization in absence of a typical nucleosomal structures has not been fully elucidated. By usingin situnick translation at confocal and electron microscope level, we analyzed the organization of the DNAprotamine complex and its association with the sperm nuclear matrix. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interactions with the nuclear matrix at fixed sites. The fine stucture of sperm nucleus and of sperm nuclear matrix, investigated on sections and replicas of freeze‐fractured specimens, suggests that the lamellar array, observed by freeze‐fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures possibly involved in the maintenance of chromatin domains in highly condensed sperm nuclei

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90054-X

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—Lentil seedlings were grown for 28 h in space, on board Spacelab (IML I Mission) and growth of the primary root was analysed. The length of cortical cells was less in near weightlessness than on the1 gcentrifuge (flight control) and mitotic index was lower but there was no apparent perturbation in the mitosis. To further investigate which phase of cell cycle was modified, densitometric analysis of nuclear DNA content in cortical cells was carried out by the mean of an image processing system (SAMBA). In microgravity there was a decrease in DNA synthesis and a promotion of the arrest in the G2 phase of cell cycle. These results, and other ones obtained elsewhere on a slowly rotating clinostat, led us to think that in microgravity the perturbation of the gravisensing cells and/or the absence of convection could account for the modification of cell growth registered in the primary roo

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90055-8

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—The intra‐cellular distribution of eight halogen glucocorticoids was investigated by ion microscopy in two cellular varieties of cultured non‐cancer cells (fibroblast 3T3) and cancer cells (human breast tumor cells MCF‐7). Two types of ion microscopy helped to determine this distribution, a direct imaging ion microscope (SMI 300) with low spatial resolution, and a scanning ion microscope (IMS4F), featuring high resolution, serving to obtain maps representing the intra‐cellular distribution of the fluorine elements and drugs present in these monolayer cultured cells. The fluorine images representative of the drugs containing fluorine showed that these drugs are essentially concentrated in the cell nuclei. In these nuclei, the distribution of these drugs is different from that of heterochromatin and of the

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90056-6

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Summary—The increase in galectin‐3 lectin content observed in tumours or inin vitrotransformed cells suggests that this lectin is important in the transformation process. In the present study, we investigated the mRNA expression level of the galectin‐3, galectin‐I and macrophage mannose receptor in normal andras‐transformed NIH 3T3 cells in relation to their transformation state. The galectin3 mRNA content inras‐transformed cells is increased in fully transformed cells, with a maximum inras‐transformed cells that have lost their growth anchorage‐dependence. Under the same conditions, the galectin‐1 mRNA level which was high in normal cells, increased slightly in transformed cells. The mRNA for the macrophage mannose receptor was not detected in 3T3 cells or in theirras‐trans

ISSN:0248-4900    

DOI:10.1016/0248-4900(94)90057-4

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY