TY  - JOUR
A1  - Schartl, Manfred
A1  - Schmidt, C. R.
A1  - Anders, A.
A1  - Barnekow, A.
T1  - Elevated expression of the cellular src gene in tumors of differing etiologies in Xiphophorus
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61889
ER  - 
TY  - JOUR
A1  - Hügle, Barbara
A1  - Scheer, Ulrich
A1  - Franke, Werner W.
T1  - Ribocharin: a nuclear M\(_r\) 40,000 protein specific to precursor particles of the large ribosomal subunit
N2  - Using a monoclonal antibody (No-194) we have identified, in Xenopus laevis and other amphibia, an acidic protein of M, 40,000 (ribocharin) which is specifically associated with the granular component of the nucleolus and nucleoplasmic 65S particles. These particles contain the nuclear 28S rRNA and apparently represent the precursor to the large ribosomal subunit in nucleocytoplasmic transit. By immunoelectron microscopy ribocharin has been localized in the granular component of the nucleolus and in interchromatin granules. During mitosis ribocharin-containing particles are associated with surfaces of chromosomes and are recollected in the reconstituting nucleoli in late telophase. We suggest that ribocharin is a specific component of precursor particles of the large ribosomal subunit, which dissociates from the 65S particle before passage through the nuclear envelope, and is reutilized in ribosome biogenesis.
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-41169
ER  - 
TY  - JOUR
A1  - Hügle, Barbara
A1  - Hazan, Rachel
A1  - Scheer, Ulrich
A1  - Franke, Werner W.
T1  - Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis
N2  - Using antibodies to various nucleolar and ribosomal proteins, we define, by immunolocalization in situ, the distribution of nucleolar proteins in the different morphological nucleolar subcompartments. In the present study we describe the nucleolar localization of a specific ribosomal protein (51) by immunofluorescence and immunoelectron microscopy using a monoclonal antibody (R5 1-105). In immunoblotting experiments, this antibody reacts specifically with the largest and most acidic protein of the small ribosomal subunit (51) and shows wide interspecies cross-reactivity from amphibia to man. Beside its localization in cytoplasmic ribosomes, this protein is found to be specifically localized in the granular component of the nucleolus and in distinct granular aggregates scattered over the nucleoplasm. This indicates that ribosomal protein 51, in contrast to reports on other ribosomal proteins, is not bound to nascent pre-rRNA transcripts but attaches to preribosomes at later stages of rRNA processing and maturation. This protein is not detected in the residual nucleolar structures of cells inactive in rRNA synthesis such as amphibian and avian erythrocytes. During mitosis, the nucleolar material containing ribosomal protein 51 undergoes a remarkable transition and shows a distribution distinct from that of several other nucleolar proteins. In prophase, the nucleolus disintegrates and protein 51 appears in numerous small granules scattered throughout the prophase nucleus. During metaphase and anaphase, a considerable amount of this protein is found in association with the surfaces of all chromosomes and finely dispersed in the cell plasm. In telophase, protein 51-containing material reaccumulates in granular particles in the nucleoplasm of the newly formed nuclei and, finally, in the re-forming nucleoli. These observations indicate that the nucleolus-derived particles containing ribosomal protein 51 are different from cytoplasmic ribosomes and, in the living cell, are selectively recollected after mitosis into the newly formed nuclei and translocated into a specific nucleolar subcompartment, i.e ., the granular component. The nucleolar location of ribosomal protein 51 and its rearrangement du'ring mitosis is discussed in relation to the distribution of other nucleolar proteins.
KW  - Cytologie
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39695
ER  - 
TY  - JOUR
A1  - Dandekar, Thomas
A1  - Gramsch, Christian
A1  - Houghton, Richard A.
A1  - Schultz, Rüdiger
T1  - Affinity purification of \(\beta\)-endorphin-like material from NG108CC15 cells by means of the monoclonal \(\beta\)-endorphin antibody 3-E7
N2  - No abstract available
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-29896
ER  - 
TY  - JOUR
A1  - Linsenmair, Karl Eduard
T1  - Individual and family recognition in subsocial arthropods, in particular in the desert isopod Hemilepistus reaumuri
N2  - Individual recogmtlon in the non-eusocial arthropods is, according to our present knowledge, predominantly found in the frame of permanent or temporary monogamy. In some cases, e. g. in stomatopods and possibly other marine crustaceans too, individual recognition may serve to allow identification of (i) individuals within dominance hierarchies or (ii) neighbours in territorial species thus helping to avoid the repetition of unnecessary and costly fights. Kin recognition is experimentally proven only in some isopod species (genera Hemilepistus and Porcel/io) and in the primitive cockroach (termite?) Cryptocercus. The «signatures» or «discriminators» used in the arthropods are chemical. It is assumed that the identifying substances are mainly genetically determined and in this paper I shall discuss possible evolutionary origins. The main part of this account is devoted to the presentation of some aspects of the highly developed individual and kin identification and recognition system in the desert isopod Hemilepistus reaumuri - a pure monogamous species in which pairs together with their progeny form strictly exclusive family units. Amongst other things problems of (i) mate choice, (ii) learning to recognize a partner, (iii) avoiding the un adaptive familiarization with aliens are treated. Monogamy under present conditions is for both sexes the only suitable way of maximizing reproductive success; an extremely strong selection pressure must act against every attempt to abandon monogamy under the given ecological conditions. The family «badges» which are certainly always blends of different discriminator substances are extremely variable. This variability is mainly due to genetical differences and is not environmentally caused. It is to be expected that intra-family variabiliry exists in respect of the production of discriminator substances. Since the common badge of a family is the result of exchanging and mixing individual substances, and since the chemical nature of these discriminators requires direct body contacts in order to acquire those substances which an individual does not produce itself, problems must arise with molting. These difficulties do indeed exist and they are aggravated by the fact that individuals may produce substances which do not show up in the common family badge. An efficient learning capability on the one hand and the use of inhibiting properties of newly molted isopods help to solve these problems. In the final discussion three questions are posed and - partly at least - answered; (i) why are families so strictly exclusive, (ii) how many discriminator substances have to be produced to provide a variability allowing families to remain exclusive under extreme conditions of very high population densities, (iii) what is the structure of the family badge and what does an individual have to learn apart from the badge in order not to mistake a family member for an alien or vice versa.
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33957
ER  - 
TY  - JOUR
A1  - Anders, F.
A1  - Schartl, Manfred
A1  - Barnekow, A.
A1  - Schmidt, C. R.
A1  - Luke, W.
A1  - Jaenel-Dess, G.
A1  - Anders, A.
T1  - The genes that carcinogens act upon
N2  - No abstract available.
KW  - Onkogen
Y1  - 1985
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-72704
ER  - 
TY  - JOUR
A1  - Barnekow, Angelika
A1  - Gessler, Manfred
T1  - Activation of the pp60\(^{c-src}\) kinase during differentiation of monomyelocytic cells in vitro
N2  - Tbe proto-oncogene c-src, the cellular homolog of the Rous sarcoma virus (RSV) transforming gene v-src, is expressed in a tissue-specific and age-dependent manner. Its physiological function, although still unknown, appears to be more closely related to differentiation processes than to proliferation processes. To obtain more information about the physiological role of the c-src gene in cells, we have studied differentiation-dependent alterations using the human HL-60 leukaemia cell line as a model system. Induction of monocytic and granulocytic differentiation of HL-60 cells by 12-0-tetradecanoylphorbol-13-acetate (TPA) and dimethylsulfoxide (DMSO) is associated with an activation of the pp60<sup>c-src</sup> tyrosine kinase, but not with increased c-src gene expression. Control experiments exclude an interaction of TPA and DMSO themselves with the pp60<sup>c-src</sup> kinase.
KW  - Biochemie
KW  - c-src
KW  - differentiation
KW  - protein tyrosine kinase
KW  - protooncogene
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59278
ER  - 
TY  - JOUR
A1  - Weich, H. A.
A1  - Sebald, Walter
A1  - Schairer, H. U.
A1  - Hoppe, J.
T1  - The human osteosarcoma cell line U-2 OS expresses a 3.8 kilobase mRNA which codes for the sequence of the PDGF-B chain
N2  - A cDNA clone of about 2500 basepairswas prepared from the human osteosarcoma cellline U-2 OS by hybridizing with a v-sis probe. Sequence analysis showed that this cDNA contains the coding region for the PDGF-B chain. Here we report that the mitogen secreted by these osteosarcoma cells contains the PDGF-B chain and is probably a homodimer of two B-chains.
KW  - Biochemie
KW  - Platelet-derived growthfactor
KW  - cDNA
KW  - Oncogene
KW  - Tumor cell
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62588
ER  - 
TY  - JOUR
A1  - Hoppe, J.
A1  - Gatti, D.
A1  - Weber, H.
A1  - Sebald, Walter
T1  - Labeling of individual amino acid residues in the membrane-embedded F\(_0\) part of the F\(_1\) F\(_0\) ATP synthase from Neurospora crassa. Influence of oligomycin and dicyclohexylcarbodiimide
N2  - Three F0 subunits and the F\(_1\) subunit P of the ATP synthase from Neurospora crassa were labeled with the lipophilic photoactivatable reagent 3-(trifluoromethyl)-3-(m-[\(^{125}\)I]iodophenyl)diazirine ([\(^{125}\)I]TID). In the proteolipid subunit which was the most heavily labeled polypeptide labeling was confmed to five residues at the NH2-terminus and five residues at the C-terminus ofthe protein. Labeling occurred at similar positions compared with the homologaus protein (subunit c) in the ATP synthase from Escherichia coli, indicating a similar structure of the proteolipid subunits in their respective organisms. The inhibitors oligomycin and dicyclohexylcarbodiimide did not change the pattern of accessible surface residues in the proteolipid, suggesting that neither inhibitor induces gross conformational changes. However, in the presence of oligomycin, the extent oflabeling in some residues was reduced. Apparently, these residues provide part of the binding site for the inhibitor. After reaction with dicyclohexylcarbodiimide an additional labeled amino acid was found at position 65 corresponding to the invariant carbodümide-binding glutamic acid. These results and previous observations indicate that the carboxyl side chain of Glu-65 is located at the protein-lipid interphase. The idea is discussed that proton translocation occurs at the interphase between different types if F\(_0\) subunits. Dicyclohexylcarbodiimide or oligomycin might disturb this essential interaction between the F\(_0\) subunits.
KW  - Biochemie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62598
ER  - 
TY  - JOUR
A1  - Hoppe, J.
A1  - Sebald, Walter
T1  - Topological studies suggest that the pathway of the protons through F\(_0\) is provided by amino acid residues accessible from the lipid phase
N2  - The structure of the F0 part of ATP synthases from E. coli and Neurospora crassa was analyzed by hydrophobic surface labeling with [125I]TID. In the E. co/i F0 all three subunits were freely accessible to the reagent, suggesting that these subunits are independently integrated in the membrane. Labeted amino acid residues were identified by Edman degradation of the dicyclohexylcarbodiimide binding (DCCD) proteins from E. coli and Neurospora crassa. The very similar patterns obtained with the two homologaus proteins suggested the existence of tightly packed cx-helices. The oligomeric structure of the DCCD binding protein appeared to be very rigid since little, if any, change in the labeling patternwas observed upon addition of oligomycin or DCCD to membranes from Neurospora crassa. When membrancs were pretrcated with DCCD prior to the reaction with [125I]TID an additionally labeled amino acid appeared at the position of Glu·65 which binds DCCD covalently, indicating the Jocation of this inhibitor on the outside of the oligomer. It is suggested that proton conduction occurs at the surface of the oligomer of the DCCD binding protein. Possibly this oligomer rotates against the subunit a or b and thus enables proton translocation. Conserved residues in subunit a, probably located in the Iipid bilayer, might participate in the pro· ton translocation mechanism.
N2  - La structure de la partie F0 de l'ATP synthase a ete analysee au moyen de marquage par /e reactif hydrophobe TJD[125 I]. Les trois sous-unites de E. coli F0 sont accessibles au reactif ce qui semble indiquer que ces sous-unites sont integrees dans Ia membrane defaron independante. Les amino-acides marques ont ete identifies par Ia degradation d'Edman des profeines d'E. coli et de Neurospora associees au dicyclohexylcarbodiimide (DCCD). L 'analogie des courbes obtenues pour /es deux proteines homologues suggere l'existence d'a-helices rangees de faron serree. La structure oligomerique de Ia proreine associee au DCCD semble etre tres rigide puisque pratiquement aucun changement dans /e marquage n 'a ete observe par addition d'oligomycine ou de DCCD aux membranes de Neurospora crassa. Quand /es membranes sont traitees avec /e DCCD avant Ia reaction avec TJD[125 I], un amino-acide additionnellement marque apparait a Ia position Glu·65 et forme avec le DCCD une Iiaison covalente. Ce dernier resu/tat indique Ia localisation de cet inhibiteur a /'exterieur de J'oligo· mere. II semble donc que Ia conduction des protons ait lieu a Ia surface de /'oligomere de Ia proteine associee au DCCD. II serait possib/e que l'o/igomere se retourne contre Ia sous-unite a ou b, permettunt de ce fait Ia translocation des protons. Les residus conserves de Ia sous-unite a, probab/ement Jocalises dans Ia double couche lipidique, pourraient participer au mecanisme de translocation des protons.
KW  - Biochemie
KW  - conduction de protons
KW  - proteines membranaires
KW  - carbenes
KW  - proton conduction
KW  - membrane proteins
KW  - carbenes
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62602
ER  - 
TY  - JOUR
A1  - Gabellini, N.
A1  - Sebald, Walter
T1  - Nucleotide sequence and transcription of the fbc operon from Rhodopseudomonas sphaeroides. Evaluation of the deduced amino acid sequences of the FeS protein, cytochrome b and cytochrome c\(_1\)
N2  - No abstract available
KW  - Biochemie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62615
ER  - 
TY  - JOUR
A1  - McCarthy, J. E.
A1  - Sebald, Walter
A1  - Gross, G.
A1  - Lammers, R.
T1  - Enhancement of translational efficiency by the Escherichia coli atpE translational initiation region: its fusion with two human genes
N2  - No abstract available
KW  - Biochemie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62626
ER  - 
TY  - JOUR
A1  - Kobelt, Frank
A1  - Linsenmair, Karl Eduard
T1  - Adaptations of the reed frog Hyperolius viridiflavus to its arid environment. I. The skin of Hyperolius viridiflavus nitidulus in wet and dry season conditions.
N2  - Hyperolius viridiflavus nitidulus inhabits parts of the seasonally very hot and dry West African savanna. During the long lasting dry season, the small frog is sitting unhidden on mostly dry plants and has to deal with high solar radiation load (SRL), evaporative water loss (EWL) and small energy reserves. It seems to be very badly equipped to survive such harsh climatic conditions (unfavorable surface to volume ratio, very limited capacity to störe energy and water). Therefore, it must have developed extraordinary efficient mechanisms to solve the mentioned Problems. Some of these mechanisms are to be looked for within the skin of the animal (e.g. protection against fast desiccation, deleterious effects of UV radiation and over-heating). The morphology of the wet season skin is, in most aspects, that of a "normal" anuran skin. It differs in the Organization of the processes of the melanophores and in the arrangement of the chromatophores in the Stratum spongiosum, forming no "Dermal Chromatophore Unit". During the adaptation to dry season conditions the number of iridophores in dorsal and ventral skin is increased 4-6 times compared to wet season skin. This increase is accompanied by a very conspicuous change of the wet season color pattern. Now, at air temperatures below 35° C the color becomes brownish white or grey and changes to a brilliant white at air temperatures near and over 40° C. Thus, in dry season State the frog retains its ability for rapid color change. In wet season State the platelets of the iridophores are irregularly distributed. In dry season State many platelets become arranged almost parallel to the surface. These purine crystals probably act as quarter-wave-length interference reflectors, reducing SRL by reflecting a considerable amount of the radiated energy input. EWL is as low as that of much larger xeric reptilians. The impermeability of the skin seems to be the result of several mechanisms (ground substance, iridophores, lipids, mucus) supplementing each other. The light red skin at the pelvic region and inner sides of the limbs is specialized for rapid uptake of water allowing the frog to replenish the unavoidable EWL by using single drops of dew or rain, available for only very short periods.
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30551
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
A1  - Hansmann, Paul
A1  - Falk, Heinz
A1  - Sitte, Peter
T1  - Ultrastructural localization of DNA in two Cryptomonas species by use of a monoclonal DNA-antibody
N2  - Immunogold cytochemistry - DNA localization - Cryptomonas nucleomorph The distribution and subcellular localization of DNA in the unicellular alga Cryptomonas has been investigated electron-microscopically by indirect immunocytochemistry, using a monoclonal DNA antibody and a gold-Iabeled secondary antibody. This technique proved to be very sensitive and entirely specific. DNA could be demonstrated in four different compartments (nucleus, nucleomorph, plastid, and mitochondrion). Within the plastid, DNA is concentrated in stroma regions that are localized preferentially around the center of the organelle. The mitochondrion contains several isolated DNA-containing regions (nucleoids). Within the nucleus, most of the DNA is localized in the 'condensed' chromatin. DNA was also detectable in small areas of the nucleolus, whereas the interchromatin space of the nucleus appeared almost devoid of DNA. Within the nucleomorph, DNA is distributed inhomogeneously in the matrix. DNA could furthermore be detected in restricted areas of the 'fibrillogranular body' of the nucleomorph, resembling the situation encountered in the nucleol us. The presence of DNA and its characteristic distribution in the nucleomorph provide additional, strong evidence in favour of the interpretation of that organelle as the residual nucleus of a eukaryotic endosymbiont in Cryptomonas.
KW  - Cytologie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39746
ER  - 
TY  - JOUR
A1  - Schultz, Rüdiger
A1  - Metzner, Katharina
A1  - Dandekar, Thomas
A1  - Gramsch, Christian
T1  - Opiates induce long-term increases in prodynorphin derived peptide levels in the guinea-pig myenteric plexus
N2  - No abstract available
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-29809
ER  - 
TY  - JOUR
A1  - Hadjiolova, Krassimira
A1  - Rose, Kathleen M.
A1  - Scheer, Ulrich
T1  - Immunolocalization of nucleolar proteins after D-galactosamine-induced inhibition of transcription in rat hepatocytes
N2  - No abstract available
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33205
ER  - 
TY  - JOUR
A1  - Reimer, Georg
A1  - Scheer, Ulrich
A1  - Peters, Jan-Michael
A1  - Tan, Eng M.
T1  - Immunolocalization and partial characterization of a nucleolar autoantigen (PM-Scl) associated with polymyositis / scleroderma overlap syndromes.
N2  - Precipitating anti-PM-Sel antibodies are present in sera from patients with polymyositis. scleroderma. and polymyositis/scleroderma overlap syndromes. By indirect immunofluorescence microscopy. anti-PM-Scl antibodies stained the nucleolus in cells of different tissues and species. suggesting that the antigen is highly conserved. By electron microscopy, anti-PM-Scl antibodies reacted primarily with the granular component of the nuc1eolus. Drugs that inhibit rRNA synthesis had a marked effect on the expression of PM-Scl antigen. In actinomycin D-treated cells, immunofluorescence staining by anti-PM-Scl was signüicantly reduced with residual staining restricted to the granular regions of nuc1eoli. Treatment with 5,6-dichloro-beta-D- ribofuranosylbenzimidazole (DRB) also selectively reduced nuc1eolar staining. On a molecular level, anti-PM-Sel antibodies precipitated 11 polypeptides with molecular weights (Mr) ranging from 110,000 to 20,000. The Mr 80,000 and 20.000 polypeptides were phosphorylated. Evidence suggests that the PM-Scl antigen complex may be related to a prerlbosomal particle.
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33191
ER  - 
TY  - JOUR
A1  - Linsenmair, Karl Eduard
T1  - Adaptations of the reed frog Hyperbolius viridiflavus to its arid environment: II. Some aspects of the water economy of H. viridiflavus nitidulus under wet and dry ...
N2  - Adaptations to aridity ofthe reedfrog Hyperolius viridiflavus nitidulus, living in different parts of the seasonally very dry and hot West African savanna, are investigated ...
KW  - Zoologie
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-78395
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
T1  - Injection of antibodies into the nucleus of amphibian oocytes: an experimental means of interfering with gene expression in the living cell
N2  - No abstract available
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-41182
ER  - 
TY  - JOUR
A1  - Mahsberg, Dieter
T1  - Contact chemoreception of prey in hunting scorpions
N2  - Scorpions commonly are assumed to hunt on living prey. But under laboratory conditions they also respond very sensitively to dead insects lying on the substrate. In many cases the motionless prey is seized and consumed. It was investigated how this behavior can be elicited. The buthid scorpions Androctonus australis (L.) and Buthus occitanus (Am.) not only find motionless prey again which was stung but managed to escape before dying: They also respond to extracts of the cuticle of prey insects. After touching prey marks' either with the tips of the chelae fingers or the tarsi of the walking legs or the pectine organs specific responses (searching, seizing, feeding) are released at a high rate. Behavioral experiments demonstrate for the first time the chemosensitivity of the pectine organs for which only mechanosensitivity had been proofed formerly. Mechanical as well as contact chemical stimulation of these organs cause scorpions to orient towards the stimulus source which is grasped, retained and consumed or rejected depending on its quality. The probably responsible chemosensitive receptors are already described in the literature. The possible adaptive value and the biological significance of contact chemoreception in prey catching and in other aspects of the life of scorpions is discussed.
KW  - Skorpion
Y1  - 1986
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-45784
ER  - 
TY  - JOUR
A1  - Maueler, W.
A1  - Eigenbrodt, E.
A1  - Schartl, Manfred
T1  - Intermediary metabolism of normal and tumorous tissue of Xiphophorus (Teleostei: Poeciliidae)
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61855
ER  - 
TY  - JOUR
A1  - Barnekow, A.
A1  - Schartl, Manfred
T1  - Comparative studies on the src proto-oncogene and its gene product pp60\(^{c-src}\) in normal and neoplastic tissues of lower vertebrates
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61869
ER  - 
TY  - JOUR
A1  - Kleene, R.
A1  - Pfanner, N.
A1  - Pfaller, R.
A1  - Link, T. A.
A1  - Sebald, Walter
A1  - Neupert, W.
A1  - Tropschug, M.
T1  - Mitochondrial porin of Neurospora crassa: cDNA cloning, in vitro expression and import into mitochondria
N2  - No abstract available
KW  - Biochemie
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62566
ER  - 
TY  - JOUR
A1  - Römisch, J.
A1  - Tropschug, M.
A1  - Sebald, Walter
A1  - Weiss, H.
T1  - The primary structure of cytochrome c\(_1\) from Neurospora crassa
N2  - No abstract available
KW  - Biochemie
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-62578
ER  - 
TY  - JOUR
A1  - Barnekow, A.
A1  - Paul, E.
A1  - Schartl, Manfred
T1  - Expression of the c-src protooncogene in human skin tumors
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61870
ER  - 
TY  - JOUR
A1  - Benavente, Ricardo
A1  - Rose, Kathleen M.
A1  - Reimer, Georg
A1  - Hügle-Dörr, Barbara
A1  - Scheer, Ulrich
T1  - Inhibition of nucleolar reformation after microinjection of antibodies to RNA polymerase I into mitotic cells
N2  - The formation of daughter nuclei and the reformation of nucleolar structures was studied after microinjection of antibodies to RNA polymerase I into dividing cultured cells (PtK2). The fate of several nucleolar proteins representing the three main structural subcomponents of the nucleolus was examined by immunofluorescence and electron microscopy. The results show that the RNA polymerase I antibodies do not interfere with normal mitotic progression or the early steps of nucleologenesis, i.e. , the aggregation of nucleolar material into prenucleolar bodies. However,they inhibit the telophasic coalescence of the prenucleolar bodies into the chromosomal nucleolar organizer regions, thus preventing the formation of new nucleoli. These prenucleolar bodies show a fibrillar organization that also compositionally resembles the dense fibrillar component of interphase nucleoli . We conclude that during normal nucleologenesis the dense fibrillar component forms from preformed entities around nucleolar organizer regions, and that this association seems to be dependent on the presence of an active form of RNA polymerase I.
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33247
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
A1  - Raska, I.
T1  - Immunocytochemical localization of RNA polymerase I in the fibrillar centers of nucleoli
N2  - No abstract available
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39618
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
T1  - Structure of lampbrush chromosome loops during different states of transcriptional activity as visualized in the presence of physiological salt concentrations
N2  - Lampbrush chromosomes of amphibian oocytes were isolated in the presence of near-physiological salt concentrations, to preserve their native state, and studied by electron microscopy of ultrathin s~dions. The transcriptional state of the lampbrush chromosomes was experimentally modulated by incubating the oocytes for various time periods in medium containing actinomycin D. The observations show that the structure of the lateral loops changes rapidly in response to alterations in transcriptional activity. During decreasing transcriptional activity and reduced packing density of transcripts, the chromatin axis first condensed into nucleosomes and then into an approximately 30 nm thick higher order chromatin fiber. Packaging of the loop axis into supranucleosomal structures may contribute to the foreshortening and retraction of the loops observed during inhibition of transcription and in later stages of meiotic prophase. The increasing packing density of the DNA during the retraction process of the loops could also be visualized by immunofluorescence microscopy using antibodies to DNA. The dependence of the loop chromatin structure on transcriptional activity is discussed in relation to current views of mechanisms involved in gene activation.
KW  - lampbrush chromosomes
KW  - chromatin structure
KW  - electron microscopy
KW  - immunofluorescence microscopy
KW  - DNA antibodies
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39304
ER  - 
TY  - JOUR
A1  - Dandekar, Thomas
A1  - Schulz, R.
T1  - Evidence for the expression of peptides derived from three opioid precursors in NG 108CC15 hybrid cells
N2  - No abstract available
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-29909
ER  - 
TY  - JOUR
A1  - Maschwitz, U.
A1  - Fiala, Brigitte
A1  - Dolling, W. R.
T1  - New trophobiotic symbioses of ants with South East Asian bugs
N2  - A trophobiotic relationship between two species of phloem-feeding plataspid bugs and an ant, Meranoplus mucronatus, was discovered on tree trunks in Malaysia. Similar relationships were found between coreid bugs and Crematogaster sp. and Anoplolepis longipes, on bamboo in the same area. The ants recruit to groups of the bugs and feed on the liquid, sugar-rich faeces of the larvae, stimulating release of the honeydew by tactile signals. They protect all stages of the bugs from disturbance by biting and by the use of defensive secretions. Phloem-feeding bugs in the families Plataspidae and Coreidae need long sty lets to pierce the thick bark of their host tree. The different methods of accommodating the resting stylets in these two families are described. The plataspids are described as Tropidotylus servus sp. novo and T. minister sp. novo A coreid previously reported in association with M. mucronatus in Malaya is described as Hygia cliens sp. novo The coreids on bamboo were determined as Cloresmus spp. and Notobitus affinis.
KW  - Ants
KW  - Coreidae
KW  - Heteroptera
KW  - Malaya
KW  - New Species
KW  - Plataspidae
KW  - Trophobiosis
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34030
ER  - 
TY  - JOUR
A1  - Reimer, Georg
A1  - Rose, Kathleen M.
A1  - Scheer, Ulrich
A1  - Tan, Eng M.
T1  - Autoantibody to RNA polymerase I in scleroderma sera
N2  - Autoantibodies to components of the nucleolus are a unique serological feature of patients with scleroderma. There are autoantibodies of several specificities; one type produces a speckled pattern of nucleolar staining in immunofluorescence. In actinomycin D and 5,6-dichloro-{j-D-ribofuranosylbenzimidazoletreated Vero cells, staining was restricted to the fibrillar and not the granular regions. By double immunofluorescence, specific rabbit anti-RNA polymerase I antibodies stained the same fibrillar structures in drug-segregated nucleoli as scleroderma sera. Scleroderma sera immunoprecipitated 13 polypeptides from (35S)methionine-labeled HeLa cell extract with molecular weights ranging from 210,000 to 14,000. Similar polypeptides were precipitated by rabbit anti-RNA polymerase I antibodies, and their common identities were confirmed in immunoabsorption experiments. Microinjection of purified IgG from a patient with speckled nucleolar staining effectively inhibited ribosomal RNA transcription. Autoantibodies to RNA polymerase I were restricted to certain patients with scleroderma and were not found in other autoimmune diseases.
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34294
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
A1  - Messner, Karin
A1  - Hazan, Rachel
A1  - Raska, Ivan
A1  - Hansmann, Paul
A1  - Falk, Heinz
A1  - Spiess, Eberhard
A1  - Franke, Werner W.
T1  - High sensitivity immunolocalization of double and single-stranded DNA by a monoclonal antibody
N2  - A monoclonal antibody (AK 30-10) is described which specifically reacts with DNA both in double and single-stranded forms but not with other molecules and structures, including deoxyribonucleotides and RNAs. When used in immunocytochemical experiments on tissue sections and permeabilized cultured cells, this antibody detects DNA-containing structures, even when the DNA is present in very small amounts. Examples of high resolution detection include the DNA present in amplified extrachromosomal nucleoli, chromomeres of lampbrush chromosomes, mitochondria, chloroplasts and mycoplasmal particles. In immunoelectron microscopy using the immunogold technique, the DNA was localized in distinct substructures such as the "fibrillar centers" of nucleoli and certain stromal centers in chloroplasts. The antibody also reacts with DNA of chromatin of living cells, as shown by microinjection into cultured mitotic cells and into nuclei of amphibian oocytes. The potential value and the limitations of immunocytochemical DNA detection are discussed.
KW  - Cytologie
KW  - DNA antibodies
KW  - monoclonal antibodies
KW  - DNA immunolocalization
KW  - chromatin
KW  - mycoplasma tests
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-41063
ER  - 
TY  - JOUR
A1  - Schartl, Manfred
A1  - Schröder, Johannes Horst
T1  - A new species of the genus Xiphophorus Heckel 1848, endemic to northern Coahuila, Mexico (Pisces: Poeciliidae)
N2  - Xiphophorus meyeri n. sp. is described as an endemic to Muzquiz, Coahuila, Mexico. It appears to be the northernmost species of the genus. The new species is related to X. couchianus and X. gordoni, but differs morphologically from those by dorsal fin ray number, by the expression of some gonopodial features and most markedly by the appearance of macromelanophores or tr-melanophores.
KW  - Schwertkräpfling
KW  - Coahuila
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-87117
ER  - 
TY  - JOUR
A1  - Peschke, Klaus
A1  - Mahsberg [geb. Krapf], Dieter
A1  - Fuldner, Dietrich
T1  - Ecological separation, functional relationships, and limiting resources in a carrion insect community
N2  - 1. Thr ecological separation of 19 carrion inscet species (adults and some of their larvae) was investigated at rabbit carcasses in North Bavaria (FRG) referring to 4 niche dimensions. In the (1.) macrohabitats (forest - clearing) the distribution of saprophageous beetle larvae was mainly considered, for (2.) seasonality the differential abundance of blow flies (Colliphoridae). (3.) The stages of decay were correlated with the temperature dependent development of blow fly maggots affecting the abundance of competing saprophageous beetles and of carnivors preying upon maggots of different size classes. By using ( 4.) microhabitats (spatial subdivision of a carcass) as further niche dimension, the dustering of speries using similar food resources was domonstrated in a niche overlap dendrogram.
2. The quantitative effect of predators on blow fly maggots was investigated both in field and laboratory experiments. Predation upon maggots rcduces their scramble competition, resulting in a higher pupal weight. Thus, the reproductive succcss of the blow flies seems to be buffered by the developmental flexibility of the calliphorids. The numerical effect of predators and parasitoids on the blow fly pupae was also quantified.
3. In a case study on the staphylinid beetle, Aleochara curtula, we investigated the diffenntial abundance of sexes. The ratio at which the males and females arrive at the carcass is balanced. Here the beetles feed and copulated. Females depart into the vicinity of the carrion much earlier than males, thus shifting the sex ratio to a maale bias. In the surroundings the females deposit their eggs, and the parasitoid first instar larvae search for scattered blow fly pupae. The temporal and spatial distribution of both sexes of A. curtula is thus not only affected by the food allocation of the adults, but a.lso by limiting resources of mating end egg laying sites as well as larval hosts.
KW  - Aaskäfer
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86361
ER  - 
TY  - JOUR
A1  - Foerster, Wolfgang
A1  - Schartl, Manfred
T1  - Karyotype and isozyme patterns of five species of Aulonocara REGAN, 1922
N2  - No abstract available.
KW  - Aulonocara
KW  - Karyotyp
KW  - Isoenzym
Y1  - 1987
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86774
ER  - 
TY  - JOUR
A1  - Adam, D.
A1  - Wittbrodt, J.
A1  - Telling, A.
A1  - Schartl, Manfred
T1  - RFLP for an EGF-receptor related gene associated with the melanoma oncogene locus of Xiphophorus maculatus
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61822
ER  - 
TY  - JOUR
A1  - Schartl, Manfred
A1  - Peter, R. U.
T1  - Progressive growth of fish tumors after transplantation into thymus-aplastic (nu/nu) mice
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61833
ER  - 
TY  - JOUR
A1  - Schartl, Manfred
T1  - A sex chromosomal restriction-fragment-length marker linked to melanoma-determining Tu loci in Xiphophorus
N2  - No abstract available
KW  - Physiologische Chemie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61842
ER  - 
TY  - JOUR
A1  - Gessler, Manfred
A1  - Bruns, Gail A. P.
T1  - Molecular mapping and cloning of the breakpoints of a chromosome 11p14.1-p13 deletion associated with the AGR syndrome
N2  - Chromosome 11p13 is frequently rearranged in individuals with the WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation) or parts of this syndrome. To map the cytogenetic aberrations molecularly, we screened DNA from cell Unes with known WAGR-related chromosome abnormalities for rearrangements with pulsed fleld gel (PFG) analysis using probes deleted from one chromosome 11 homolog of a WAGR patient. The first alteration was detected in a cell line from an individual with aniridia, genitourinary anomalies, mental retardation, and a deletion described as 11p14.1-p13. We have located one breakpoint close to probe HU11-164B and we have cloned both breakpoint sites as well as the junctional fragment. The breakpoints subdivide current intervals on the genetic map, and the probes for both sides will serve as important additional markers for a long-range restriction map of this region. Further characterization and sequencing of the breakpoints may yield insight into the mechanisms by which these deletions occur.
KW  - Biochemie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-59264
ER  - 
TY  - JOUR
A1  - Goebel, Werner
A1  - Chakraborty, T.
A1  - Kreft, Jürgen
T1  - Bacterial hemolysins as virulence factors
N2  - No abstract available
KW  - Biologie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60553
ER  - 
TY  - JOUR
A1  - Goebel, Werner
A1  - Kathariou, S.
A1  - Kuhn, M.
A1  - Sokolovic, Z.
A1  - Kreft, Jürgen
A1  - Köhler, S.
A1  - Funke, D.
A1  - Chakraborty, T.
A1  - Leimeister-Wächter, M.
T1  - Hemolysin from Listeria-biochemistry, genetics and function in pathogenesis
N2  - No abstract available
KW  - Biologie
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60563
ER  - 
TY  - JOUR
A1  - Thiry, Marc
A1  - Scheer, Ulrich
A1  - Goessens, Guy
T1  - Immunoelectron microscopic study of nucleolar DNA during mitosis in Ehrlich tumour cells
N2  - In order to investigate the DNA localization within Ehrlich tumor cell nucleoli during mitosis, two recent immunocytochemical methods using either an anti-DNA or an anti-bromodeoxyuridine (BrdU) monoclonal antibody have been applied. In both cases, the immunogold labeling has been performed on ultrathin sections of cells embedded either in Lowicryl K4M or in Epon, respectively. Identical results are observed with both immunocytochemical approaches. In the interphase nucleolus, besides the labeling of the perinucleolar chromatin shell and of its intranucleolar invaginations which penetrate into the nucleolar body and often terminate at the fibrillar centers, a few gold particles are also preferentially found towards the peripheral region of the fibrillar centers. In contrast, the dense fibrillar component and the granular component are never labeled. During mitosis, the fibrillar centers persist at the chromosomal nucleolus organizing regions (NOR's) and can be selectively stained by the silver method. However, these metaphase fibrillar centers are no longer decorated by the DNA- or BrdU antibodies. These results indicate that until the end of prophase, rRNA genes are present inside the fibrillar center material, disappear during metaphase and reappear in reconstituting nucleoli during telophase. Thus, fibrillar centers appear to represent structures sui generis, which are populated by rRNA genes only when the nucleolus is functionally active. In segregated nucleoli after actinomycin D treatment, the DNA labeling is exclusively restricted to the perinucleolar chromatin blocks. These findings also suggest that the DNA content of the fibrillar center material varies according to the rRNA transcription level of the cells. The results are discussed in the light of the present knowledge of the functional organization of the nucleolus.
KW  - Cytologie
KW  - Nucleolus
KW  - DNA
KW  - mitosis
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-40745
ER  - 
TY  - JOUR
A1  - Rose, Kathleen M.
A1  - Szopa, Jan
A1  - Han, Fu-Sheng
A1  - Cheng, Yung-Chi
A1  - Richter, Arndt
A1  - Scheer, Ulrich
T1  - Association of DNA topoisomerase I and RNA polymerase I: A possible role for topoisomerase I in ribosomal gene transcription
N2  - RNA polymerase I preparations purified from a rat hepatoma contained DNA topoisomerase activity. The DNA topoisomerase associated with the polymerase had an Mr of 110000, required Mg2+ but not ATP, and was recognized by anti-topoisomerase I antibodies. When added to RNA polymerase I preparations containing topoisomerase activity, anti-topoisomerase I antibodies were able to inhibit the DNA relaxing activity of the preparation as well as RNA synthesis in vitro. RNA polymerase II prepared by analogous procedures did not contain topoisomerase activity and was not recognized by the antibodies. The topoisomerase I: polymerase I complex was reversibly dissociated by column chromatography on Sephacryl S200 in the presence of 0.25 M (NH4hS04. Topoisomerase I was immunolocalized in the transcriptionally active ribosomal gene complex containing RNA polymerase I in situ. These data indicate that topoisomerase I and RNA polymerase I are tightly complexed both in vivo and in vitro, and suggest a role for DNA topoisomerase I in the transcription of ribosomal genes.
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33901
ER  - 
TY  - JOUR
A1  - Reimer, Georg
A1  - Raska, Ivan
A1  - Scheer, Ulrich
A1  - Tan, Eng M.
T1  - Immunolocalization of 7-2-ribonucleoprotein in the granular component of the nucleolus
N2  - Certain autoimmune sera contain antibodies against a nucleolar ribonucleoprotein particle associated with 7-2-RNA (R. Reddy et al. (1983) J. Bioi. Chem . 258, 1383; C. Hashimoto and J. A. Steitz (1983) J. Bioi. Chem. 258, 1379). In this study, we showed by immunofluorescence microscopy that antibodies reactive with 7-2-ribonucleoprotein immunolocalized in the granular regions of actinomycin D and 5,6-dichloro-I-j3-D-ribofuranosylbenzimidazole (DRB)-segregated nucleoli from Vero cells. By electron microscopic immunocytochemistry, antigen-antibody complexes were located in the granular component of transcriptionally active nucleoli from rat liver hepatocytes and HeLa cells. Anti-7- 2-RNP antibodies from two autoimmune sera immunoprecipitated a major protein of Mr 40,000 from e5S] methionine-Iabeled HeLa cell extract. The immunolocalization data suggest that 7-2-ribonucleoprotein may be involved in stages of ribosome biogenesis which take place in the granular component of the nucleolus, i.e., assembly, maturation, and/or transport of preribosomes
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-33890
ER  - 
TY  - JOUR
A1  - Benavente, Ricardo
A1  - Schmidt-Zachmann, Marion S.
A1  - Hügle-Dörr, B.
A1  - Reimer, G.
A1  - Rose, K. M.
A1  - Scheer, Ulrich
T1  - Identification and definition of nucleolus-related fibrillar bodies in micronucleated cells
N2  - Small nucleolus-related bodies which occur in the nUcleoplasm of " micronuclei" lacking nucleolar organizers have been studied by immunofluorescence microscopy. These bodies stained specifically with three different antibodies directed against proteins that are normally associated with the dense fibrillar component of functional nucleoli, but not with antibodies specific for certain proteins of the granular component or the fibrillar centers. Our data show that, in the absence of rRNA genes, the various constituent proteins characteristic of the dense fibrillar component spontaneously assemble into spherical entities but that the subsequent fusion of these bodies into larger structures is prevented in these micronuclei. The similarity between these nucleolus-related bodies of micronuclei and the prenucleolar bodies characteristic of early stages of nucleologenesis during mitotic telophase is discussed.
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39423
ER  - 
TY  - JOUR
A1  - Thiry, Marc
A1  - Scheer, Ulrich
A1  - Goessens, Guy
T1  - Localization of DNA within Ehrlich tumour cells nucleoli by immunoelectron microscopy
N2  - The distribution of DNA in Ehrlich tumour cell nucleoli was investigated by means of an immunocytochemical approach , involving a monoclonal antibody directed against double- and single-stranded DNA. Immunolabelling was performed . either before or after the embedding process. The postembedding labelling method allows better ultrastructural preservation than the preembedding labelling method. In particular, the various nucleolar components are well preserved and identifiable. In the nucleolus, labelling is particularly concentrated over the perinucleolar chromatin and over its intranucleolar invaginations, which penetrate the nucleolar body and often terminate at the fibrillar centres. In addition, aggregates of gold particles are found in the fibrillar centres, preferentially towards the peripheral regions. By contrast, the dense fibrillar component is completely devoid of labelling. The results seem to indicate that DNA containing the rDNA genes is located in the fibrillar centres, with a preference for the peripheral regions. This finding suggests that transcription of the rDNA genes should occur within the confines of the fibrillar centre, probably close to the boundary region of the surrounding dense fibrillar component. The results are discussed in the light of present knowledge of the functional organization of the nucleolus.
KW  - nucleolus
KW  - DNA
KW  - monoclonal antibody
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-39327
ER  - 
TY  - JOUR
A1  - Geise, W.
A1  - Linsenmair, Karl Eduard
T1  - Adaptations of the reed frog Hyperbolius viridiflavus to its arid environment. IV. Ecological significance of water economy with comments on thermoregulation and energy allocation
N2  - No abstract available
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30570
ER  - 
TY  - JOUR
A1  - Dabauvalle, Marie-Christine
A1  - Schulz, Barbara
A1  - Scheer, Ulrich
A1  - Peters, Reiner
T1  - Inhibition of nuclear accumulation of karyophilic proteins in living cells by microinjection of the lectin wheat germ agglutinin
N2  - No abstract available
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34288
ER  - 
TY  - JOUR
A1  - Scheer, Ulrich
A1  - Dabauvalle, Marie-Christine
A1  - Merkert, Hilde
A1  - Benavente, Ricardo
T1  - The nuclear envelope and the organization of the pore complexes
N2  - No abstract available
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-34275
ER  - 
TY  - JOUR
A1  - Linsenmair, Karl Eduard
A1  - Schmuck, R.
T1  - Adaptations of the reed frog Hyperbolius viridiflavus to its arid environment. III. Aspects of nitrogen metabolism and osmuregulation in the reed frog, H. viridiflavus taeniatus, with special reference to the role of iridophores
N2  - Reed frogs of the superspecies Hyperolius viridiflavus occur throughout the seasonally very dry and hot African savannas. Despite their small size (300-700 mg), estivating reed frogs do not avoid stressful conditions above ground by burrowing into the soil, but endure the inhospitable climate relatively unprotected, clinging to mostly dry grass sterns. They must have emcient mechanisms to enable them to survive e.g. very high temperatures, low relative hurnidities, and high solar radiation loads. Mechanisms must also have developed to prevent poisoning by the nitrogenous wastes that inevitably result from protein and nucleotide turnover. In contrast to fossorial amphibians, estivating reed frogs do not become torpid. Reduction in metabolism is therefore rather Iimited so that nitrogenous wastes accumulate faster in these frogs than in fossorial amphibians. This severely aggravates the osmotic problems caused by dehydration. During dry periods total plasma osmolarity greatly increases, mainly due to urea accumulation. Of the total urea accumulated over 42 days of experimental water deprivation, 30% was produced during the first 7 days. In the next 7 days rise in plasma urea content was negligible. This strong initial increase of urea is seen as a byproduct of elevated amino acid catabolism following the onset of dry conditions. Tbe rise in total plasma osmolarity due to urea accumulation, however, is not totally disadvantageous, but enables fast rehydration when water is available for very short periods only. Voiding of urine and feces eeases once evaporative water loss exceeds 10% of body weight. Tberefore, during continuous water deprivation, nitrogenous end products are not excreted. After 42 days of water deprivation, bladder fluid was substantially depleted, and urea coneentration in the remaining urine (up to 447 mM) was never greater than in plasma fluid. Feces voided at the end of the dry period after water uptake contained only small amounts of nitrogenous end products. DSF (dry season frogs) seemed not to be uricotelic. Instead, up to 35% of the total nitrogenous wastes produced over 42 days of water deprivation were deposited in an osmotically inert and nontoxic form in iridophore crystals. The increase in skin purine content averaged 150 µg/mg dry weight. If urea had been the only nitrogenous waste product during an estivation period of 42 days, lethal limits of total osmolarity (about 700 mOsm) would have been reached 10-14 days earlier. Thus iridophores are not only involved in colour change and in reducing heat load by radiation remission, but are also important in osmoregulation during dry periods. The seIective advantages of deposition of guanine rather than uric acid are discussed.
KW  - Biologie
KW  - Zoologie
KW  - Frosch
KW  - Hyperolius viridiflavus
KW  - Estivation
KW  - Osmoregulation
KW  - Nitrogen metabolism
KW  - lridophores
Y1  - 1988
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-78108
ER  -