@article{BenaventeReimerRoseetal.1988, author = {Benavente, Ricardo and Reimer, Georg and Rose, Kathleen M. and H{\"u}gle-D{\"o}rr, Barbara and Scheer, Ulrich}, title = {Nucleolar changes after microinjection of antibodies to RNA polymerase I into the nucleus of mammalian cells}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40666}, year = {1988}, abstract = {After microinjection of antibodies against RNA polymerase I into the nuclei of cultured rat kangaroo (PtKz) and rat (RVF-SMC) cells alterations in nucleolar structure and composition were observed. These were detected by electron microscopy and double-label immunofluorescence microscopy using antibodies to proteins representative of the three major components of the nucleolus. The microinjected antibodies produced a progressive loss of the material of the dense fibrillar component (DFC) from the nucleoli which, at 4 h after injection, were transformed into bodies with purely granular component (GC) structure with attached fibrillar centers (FCs). Concomitantly, numerous extranucleolar aggregates appeared in the nucleoplasm which morphologically resembled fragments of the DFC and contained a protein (fibrillarin) diagnostic for this nucleolar structure. These observations indicate that the topological distribution of the material constituting the DFC can be experimentally influenced in interphase cells, apparently by modulating the transcriptional activity of the rRNA genes. These effects are different from nucleolar lesions induced by inhibitory drugs such as actinomycin D-dependent "nucleolar segregation". The structural alterations induced by antibodies to RNA polymerase I resemble, however, the initial events of nucleolar disintegration during mitotic prophase.}, language = {en} } @article{BarresSchmidSendtneretal.1993, author = {Barres, B. A. and Schmid, R. and Sendtner, Michael and Raff, Martin C.}, title = {Multiple extracellular signals are required for long-term oligodendrocyte survival}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42644}, year = {1993}, abstract = {We showed previously that oligodendrocytes and their precursors require continuous signalling by protein trophic factors to avoid programmed cell death in culture. Here we show that three classes of such trophic factors promote oligodendrocyte survival in vitro: (1) insulin and insulin-like growth factors (IGFs), (2) neurotrophins, particularly neurotrophin-3 (NT -3), and (3) ciliary-neurotrophic factor (CNTF), leukemia inhibitory factor (LIF) and interleukin 6 (IL-6). A single factor, or combinations of factors within the same class, promote only short-term survival of oligodendrocytes and their precursors, while combinations of factors from different classes promote survival additively. Long-term survival of oligodendrocytes in vitro requires at least one factor from each class, suggesting that multiple signals may be required for long-term oligodendrocyte survival in vivo. We also show that CNTF promotes oligodendrocyte survival in vivo, that platelet-derived growth factor (PDGF) can promote the survival of oligodendrocyte precursors in vitro by acting on a novel, very high affinity PDGF receptor, and that, in addition to its effect on survival, NT-3 is a potent mitogen for oligodendrocyte precursor cells.}, language = {en} } @article{DittrichThoenenSendtner1994, author = {Dittrich, Falk and Thoenen, Hans and Sendtner, Michael}, title = {Ciliary neurotrophic factor: pharmacokinetics and acute-phase response in rat}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42639}, year = {1994}, abstract = {No abstract available}, language = {en} } @article{KaupmannSendtnerStoecklietal.1991, author = {Kaupmann, Klemens and Sendtner, Michael and St{\"o}ckli, Kurt A. and Jockusch, Harald}, title = {The gene of ciliary neurotrophic factor (cntf) maps to murine chromosome 19 and its expression is not affected in the hereditary motoneuron disease 'wobbler' of the mouse}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42626}, year = {1991}, abstract = {The cDNA for ciliary neurotrophic factor (CNTF), a polypeptide involved in the survival of motoneurons in mammals, has recently been cloned (St{\"o}ckli et al., Nature, 342, 920 - 923, 1989; Lin et al. Science, 246, 1023 - 1025, 1989). We have now localized the corresponding gene Cntf to chromosome 19 in the mouse, using an interspecific cross between Mus spretus and Mus musculus domesticus. The latter was carrying the gene wobbler (wr) for spinal muscular atrophy. DNA was prepared from backcross individuals and typed for the segregation of species-specific Cntf restriction fragments in relation to DNA markers of known chromosomal location. The M.spretus allele of Cntf cosegregated with chromosome 19 markers and mapped closely to Ly-1, to a region of mouse chromosome 19 with conserved synteny to human chromosome 11q. Cntf is not linked to wr, and the expression of CNTF mRNA and protein appears close to normal in facial and sciatic nerves, of affected (wr/wr) mice, suggesting that motoneuron degeneration of wobbler mice has its origin in defects other than reduced CNTF expression.}, language = {en} } @article{SendtnerGnahnWakadeetal.1988, author = {Sendtner, Michael and Gnahn, H. and Wakade, A. and Thoenen, Hans}, title = {Is activation of the Na\(^+\)K\(^+\) pump necessary for NGF-mediated neuronal survival?}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42610}, year = {1988}, abstract = {The ability of nerve growth factor to cause rapid activation of the Na+K+ pump of its responsive cells was examined by measuring the uptake of 86Rb+. A significant increase in 86Rb+ uptake in Ea chick dorsal root ganglion sensory neurons after NGF treatment was seen only if the cells had been damaged during the preparation procedure. Such damaged cells could not survive in culture in the presence of NGF, and undamaged cells that did survive in response to NGF exhibited no increased 86Rb+ uptake rate. Furthermore, cultured calf adrenal medullary cells did not show an increase in 86Rb+ uptake after treatment with NGF, although these cells respond to NGF with an increased synthesis of catecholaminergic enzymes. These results are incompatible with the hypothesis that the mechanism of action of NGF that promotes neuronal survival and enzyme induction results from an initial stimulation of the Na+K+ pump.}, language = {en} } @article{LillienSendtnerRaff1990, author = {Lillien, Laura E. and Sendtner, Michael and Raff, Martin C.}, title = {Extracellular Matrix-associated molecules collaborate with ciliary neurotrophic factor to induce type-2 astrocyte development}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42602}, year = {1990}, abstract = {0-2A progenitor cells give rise to both oligodendrocytes and type-2 astrocytes in vitro. Whereas oligodendrocyte differentiation occurs constitutively, type-2 astrocyte differentiation requires extracellular signals, one of which is thought to be ciliary neurotrophic factor (CNTF). CNTF, however, is insufficient by itself to induce the development of stable type-2 astrocytes. In this report we show the following: (a) that molecules associated with the extracellular matrix (ECM) cooperate with CNTF to induce stable type-2 astrocyte differentiation in serumfree cultures. The combination of CNTF and the ECM-associated molecules thus mimics the effect of FCS, which has been shown previously to induce stable type-2 astrocyte differentiation in vitro. (b) Both the ECM-associated molecules and CNTF act directly on 0-2A progenitor cells and can induce them to differentiate prematurely into type-2 astrocytes. (c) ECM-associated molecules also inhibit oligodendrocyte differentiation, even in the absence of CNTF, but this inhibition is not sufficient on its own to induce type-2 astrocyte differentiation. (d) Whereas the effect of ECM on oligodendrocyte differentiation is mimicked by basic fibroblast growth factor (bFGF), the effect of ECM on type-2 astrocyte differentiation is not. (e) The ECM-associated molecules that are responsible for inhibitin~ oligodendrocyte differentiation and for cooperating with CNTF to induce type-2 astrocyte differentiation are made by non-glial cells in vitro. (f) Molecules that have these activities and bind to ECM are present in the optic nerve at the time type-2 astrocytes are thought to be developing.}, language = {en} } @article{SendtnerStoeckliCarrolletal.1992, author = {Sendtner, Michael and St{\"o}ckli, Kurt A. and Carroll, Patrick and Kreutzberg, Georg W. and Thoenen, Hans}, title = {More on motor neurons}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42598}, year = {1992}, abstract = {No abstract available}, language = {en} } @article{FrankeScheerTrendelenburgetal.1976, author = {Franke, Werner W. and Scheer, Ulrich and Trendelenburg, Michael F. and Spring, Herbert and Zentgraf, Hanswalter}, title = {Absence of nucleosomes in transcriptionally active chromatin}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40646}, year = {1976}, abstract = {The ultrastructure of twO kinds of transcription ally active chromatin, the lampbrush chromosome loops and the nucleoli from amphibian oocytes and primary nuclei of the green alga Acetabularia, has been examined after manual isolation and dispersion in low salt media of slightly alkaline pH using various electron microscopic staining techniques (positive staining, metal shadowing, negative staining, preparation on positively charged films, etc.) and compared with the appearance of chromatin from various somatic cells (hen erythrocytes, rat hepatocytes, ClIltured murine sarcoma cells) prepared in parallel. While typical nucleosomes were revealed with all the techniques for chromatin from the latter three cell system, no nucleosomes were identified in either the lampbrush chromosome structures or the nucleolar chromatin. Nucleosomal arrays were absent not only in maximally fibril-covered matrix units but also in fibril-free regions between transcriptional complexes, including the apparent spacer intercepts between different transcriptional units. Moreover, comparisons of the length of the repeating units of rDNA in the transcribed state with those determined in the isolated rDNA and with the lengths of the first stable product of rDNA transcription, the pre-rRNA, demonstrated that the transcribed rDNA was not significantly shortened and/or condensed but rather extended in the transcriptional units. Distinct granules of about nucleosomal size which were sometimes found in apparent spacer regions as well as within matrix units of reduced fibril density were shown not to represent nucleosomes since their number per spacer unit was not inversely correlated with the length of the specific unit and also on the basis of their resistance to treatment with the detergent Sarkosyl NL-30. It is possible to structurally distinguish between transcriptionally active chromatin in which the DNA is extended in a non-nucleosomal form of chromatin and condensed, inactive chromatin within the typical nucleosomal package. The characteristic extended structure of transcriptionally active chromatin is found not only in the transcribed genes but also in non-transcribed regions within or between ("spacer") transcriptional units as well as in transcriptional units that are untranscribed amidst transcribed ones and/or have been inactivated for relatively short time. It is hypothesized that activation of transcription involves a transition from a nucleosomal to an extended chromatin organisation and that this structural transition is not specific for single "activated" genes but may involve larger chromatin regions, including adjacent untranscribed intercepts.}, subject = {Cytologie}, language = {en} } @article{EckertFrankeScheer1972, author = {Eckert, W. A. and Franke, Werner W. and Scheer, Ulrich}, title = {Actinomycin D and the central granules in the nuclear pore complex: thin sectioning versus negative staining}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40636}, year = {1972}, abstract = {Thin section electron microscopy of Actinomycin D treated Tetrahymena cells and amphibian oocytes (Xenopus laevis, Triturus aZpestris) reveal no reduction in the central granules in the nuclear pore complexes. Possible reasons for the diversity between these results and earlier observations using negatively stained isolated nuclear envelopes from the same objects are discussed. The results clearly show that the presence of central granules within the nuclear pores does neither depend on nuclear RNA synthesis nor does indicate nucleocytoplasmic RNA transport. This conclusion leads to a reconsideration of the nature of the central granule. The functioning of the central granule of the nuclear pore complexes is further discussed in connection with recent studies on the ultrastructure of various types of cisternal pores.}, language = {en} } @article{FrankeScheer1971, author = {Franke, Werner W. and Scheer, Ulrich}, title = {Some structural differentiations in the HeLa cell: heavy bodies, annulate lamellae and cotte de maillet endoplasmic reticulum}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40614}, year = {1971}, abstract = {A small fraction of HeLa cells within an exponentially growing culture showed cisternal differentiations, such as cytoplasmic as well as intranuclear annulate lamellae and special smooth surfaced endoplasmic reticulum aggregates with a typical "Cotte de maillet" appearance. Additionally, clusters of dense granules were observed in the cytoplasm which were often associated with polysomes and strongly resembled the so-called "heavy bodies" known in particular in diverse oocytes. The functional meaning of these structures is discussed. Moreover, it is deduced from the ultrastructural identity of the pore complexes in the nuclear envelope and the cytoplasmic and intranuclear annulate lamellae that the pore complex material with its highly ordered arrangement is not a structure characteristic for nucleocytoplasmically migrating material, but rather is a general structural expression of a tight binding of ribonucleoprotein (RNP) to cisternal membranes. The pore complexes are thought of as representing sites of a RNP-storage. A similar functioning is hypothesized for the "heavy body"like aggregates. To the current hypotheses on the formation of annulate lamellae and the nuclear envelope, which are based on the concept of membrane continuities and constancies, the alternative view of a self assembly mechanism of membrane constituents on nucleoprotein structures is added.}, subject = {Cytologie}, language = {en} } @article{HughesSendtnerGoldfarbetal.1993, author = {Hughes, Richard A. and Sendtner, Michael and Goldfarb, Mitchell and Lindholm, Dan and Thoenen, Hans}, title = {Evidence that fibroblast growth factor 5 is a major muscle-derived survival factor for cultured spinal motoneurons}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42588}, year = {1993}, abstract = {We examined the potential role of fibroblast growth factor 5 (FGF-5) as a target-derived trophic factor for spinal motoneurons. Northern analysis of total RNA from rat skeletal muscle revealed an FGF-5 mRNA transcript both during the period of embryonic motoneuron death and in the adult. Recombinant human FGF-5 supported the survival of highly enriched cultures of embryonic chick motoneurons. Significant proportions of the motoneuron survival activity of rat skeletal muscle extracts could be immunoprecipitated using an antiserum to FGF-5. The immunoprecipitable activity was present in soluble and matrix-bound forms in embryonic muscle, but bound exclusively to the extracellular matrix in adult muscle. These results, along with the secretory nature of FGF-5, suggest that FGF-5 may act as a target-derived trophic factor for motoneurons.}, language = {en} } @article{SendtnerStoeckliThoenenetal.1992, author = {Sendtner, Michael and St{\"o}ckli, Kurt A. and Thoenen, Hans and Schmalbruch, H. and Carroll, P. and Kreutzberg, Georg W.}, title = {Ciliary neurotrophic factor prevents the degeneration of motor neurons in mouse mutant progressive motor neuronopathy}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42563}, year = {1992}, abstract = {CILIARY neurotrophic factor (CNTF) supports the survival of embryonic motor neurons in vitro and in vivo and prevents lesion-mediated degeneration of rat motor neuron~ during early post-natal stages. Here we report that CNTF greatly reduces all the functional and morphological changes in pmnlpmn mice5, an autosomal recessive mutant leading to progressive caudo-cranial motor neuron degeneration. The first manifestations of progressive motor neuronopathy in homozygous pmnl pmn mice become apparent in the hind limbs at the end of the third post-natal week and all the mice die up to 6 or 7 weeks after birth from respiratory paralysis. Treatment with CNTF prolongs- survival- and greatly Impoves motor function of these mice. Moreover, morphological manifestations, such as loss of motor axons in the phrenic nerve and degeneration of facial motor neurons, were greatly reduced by CNTF, although the treatment did not start until the first symptoms of the disease had already become apparent and substantial degenerative changes were already present. The protective and restorative effects of CNTF in this mouse mutant give new perspectives for the treatment of human degenerative motor neuron diseases with CNTF.}, language = {en} } @article{SpringTrendelenbrugScheeretal.1974, author = {Spring, Herbert and Trendelenbrug, Michael F. and Scheer, Ulrich and Franke, Werner W. and Herth, Werner}, title = {Structural and biochemical studies of the primary nucleus of two green algal species, Acetabularia mediterranea and Acetabularia major}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40600}, year = {1974}, abstract = {Primary (giant) nuclei of the green algae Acetabularia mediterranea and A. major were studied by light and electron microscopy using in situ fixed material as well as manually isolated nuclear components. In addition, cytochemical reactions of nuclear structures and biochemical determinations of nuclear and cytoplasmic RNA and of genome DNA content were performed. The data obtained and the structures observed are interpreted as demonstralions of transcriptional activities of different gene classes. The most prominent class is the nucleolar cistrons of precursors of ribosomal RNA which occur highly repeated in clusters in the form of regularly alternating intercepts on deoxyribonucleoprotein axes of transcribed rDNA, the fibril-covered matrix units, and the fibril-free "spacer" segments. A description and a classification of the various structural complexes which seem to represent transcriptional activities is given. Quantitative evaluations of these arrangements are presented. The morphology and the dimensions of such structures are compared with the RNA molecular weight determinations and with the corresponding data reported from various animal cell systems. It is suggested that the formation of the giant nucleus is correlated with, and probably due to, an enormous amplification of transcriptionally active rDNA and packing of the extrachromosomal copies into the large nucleolar aggregate bodies.}, subject = {Cytologie}, language = {en} } @article{SendtnerCarrollHoltmannetal.1994, author = {Sendtner, Michael and Carroll, P. and Holtmann, B and Hughes, R. A. and Thoenen, H.}, title = {Ciliary Neurotrophic Factor}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42545}, year = {1994}, abstract = {No abstract available}, language = {en} } @article{FrankeZentgrafScheer1973, author = {Franke, Werner W. and Zentgraf, Hanswalter and Scheer, Ulrich}, title = {Membrane linkages at the nuclear envelope}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40596}, year = {1973}, abstract = {Electron-opaque material is shown in the perinuclear cisternae of various cell types to connect the inner and outer nuclear membrane faces. Similar bridges were observed between the outer nuclear membrane and the outer mitochondrial membrane. The intracisternal bridges of the nuclear envelope appear to be important for the structural stability of the perinuclear cisterna. Stable structural linkage of mitochondria to the outer nuclear membrane might be relevant to the understanding of the characteristic juxtanuclear accumulation of mitochondria and also provide arguments for the discussions of certain biochemical activities found in nuclear and nuclear membrane fractions.}, subject = {Cytologie}, language = {en} } @article{FrankeScheerZentgraf1984, author = {Franke, Werner W. and Scheer, Ulrich and Zentgraf, Hanswalter}, title = {Organization of transcriptionally active and inactive chromatin}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-40588}, year = {1984}, abstract = {No abstract available}, subject = {Deutschland}, language = {en} } @article{WeisenbergerScheerBenavente1993, author = {Weisenberger, Dieter and Scheer, Ulrich and Benavente, Ricardo}, title = {The DNA topoisomerase I inhibitor camptothecin blocks postmitotic reformation of nucleoli in mammmalian cells}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-41434}, year = {1993}, abstract = {No abstract available}, subject = {Cytologie}, language = {en} } @article{SaadatSendtnerRohrer1989, author = {Saadat, S. and Sendtner, Michael and Rohrer, H.}, title = {Ciliary neurotrophic factor induces cholinergic differentiation of rat sympathetic neurons in culture}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32677}, year = {1989}, abstract = {Ciliary neurotrophic factor (CNTF) influences the levels of choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH) in cultures of dissociated sYmpathetic neurons from newborn rats. In the presence of CNTF both the total and specific activity of ChAT was increased 7 d after culture by 15- and 18-fold, respectively, as compared to cultures kept in the absence of CNTF. Between 3 and 21 d in culture in the presence of CNTF . the total ChAT activity increased by a factor of >100. Immunotitration demonstrated that the elevated ChAT levels were due to an increased number of enzyme molecules. In contrast to the increase in ChAT levels, the total and specific activity levels' of TH were decreased by 42 and 36 \%, respectively, after 7 d in culture. Half-maximal effects for both ChAT increase and TH decrease were obtained at CNTF concentrations of rvO.6 ng and maximal levels were reached at I ng of CNTF per milliliter of medium. The effect of CNTF on TH and ChAT levels were seen in serum-containing medium as well as in serum-free medium. CNTF was shown to have only a small effect on the long-term s.urviVal of rat sympathetic neurons. We therefore concluded that the effects of CNTF on ChAT and TH are not due to selective survival of cells that acquire cholinergic traits in vitro, but are rather due to the induction of cholinergic differentiation of noradrenergic sympathetic neurons.}, language = {en} } @article{FialaMaschwitz1991, author = {Fiala, Brigitte and Maschwitz, Ulrich}, title = {Extrafloral nectaries in the genus Macaranga (Euphorbiaceae) in Malaysia: comparative studies of their possible significance as predispositions for myrmecophytism.}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42863}, year = {1991}, abstract = {So me species of the paleotropical tree genus Macaranga (Euphorbiaceae) live in elose association with ants. Thc genus comprises the full range of species from those not regularly inhabited by ants to obligate myrmecophytes. In Malaysia (peninsular and Borneo) 23 ofthe 52 species areknown to be ant-associated (44\%). The simplest structural adaptation of plants to attract ants are extrafloral nectaries. We studied the distribution of extraflural nectaries in the genus Macaranga to assess the significance of this character as a possible predisposition for the evolution of obligate myrmecophytism. All species have marginal glands on the leaves. However, only the glands of nonmyrmecophytic species function as nectaries, whereas liquids secreted by these glands in myrmecophytic species did not contain sugar. Some non-myrmecophytic Macaranga and transitional Macaranga species in addition have extrafloral nectaries on the leaf blade near the petiole insertion. All obligatorily myrmecophytic Macaranga species, however, lack additional glands on the lamina. The non-myrmecophytic species are visited by a variety of different ant species, whereas myrmecophytic Macaranga are associated only with one specific ant-partner. Since these ants keep scale insects in the hollow sterns, reduction of nectary production in ant-inhabited Macaranga seems to be biologically significant. We interpret this as a means of (a) saving the assimilates and (b) stabilization of maintenance of the association's specificity. Competition with other ant species for food rewards is avoided and thereby danger ofweakening the protective function ofthe obligate antpartner for the plant is reduced. A comparison with other euphorb species living in the same habitats as Macaranga showed that in genera in which extrafloral nectaries are widespread, no myrmecophytes have evolved. Possession of extrafloral nectaries does not appear to be essential for the development of symbiotic ant-plant interactions. Other predispositions such as nesting space might have played a more important role.}, subject = {Macaranga}, language = {en} } @article{MaschwitzFialaLinsenmair1992, author = {Maschwitz, Ulrich and Fiala, Brigitte and Linsenmair, K. Eduard}, title = {A new ant-tree from SE Asia: Zanthoxylum myriacanthum (Rutaceae), the Thorny Ivy-Rue}, isbn = {0025-1291}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-42967}, year = {1992}, abstract = {Zanthoxylum myriacanthum, a small Rutaceous tree growing mainly in secondary hill forests in SE Asia, is a true myrmecophyte. It possesses stem domatia in the form of hollow branches with slitlike openings. Branch hollows and entrance slits are produced by the plant itself through pith degene~.tion ?u.d growth proceSses. If the entrance is not kept open by ants it closes again by growth ol the surrounding tissue after some time. The domatia are colonized opportunistic ally by different arboreous ants, e.g. Crematogaster and Campono tus. Additionally many small extrafloral nectaries are found on the leaflets of Zanthoxylum myriacanthum. Judging from herbarium studies and literature records at least four more true ant trees are found in the genus Zanthoxylum namely Z. rhetsa in SE Asia, Z. conspersipunctatum, Z. pluviatile and Z. vinkii in New Guinea. We could not confirm ant inhabitation in Drypetes pendula (Euphorbiaceae) on the Malay Peninsula, which has also been recorded to be an anttree.}, language = {en} }