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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Inorganic chemistry 23 (1984), S. 4072-4075 
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The marine demosponge Suberites domuncula is abundantly present on muddy sand bottoms, both in the open sea and in harbors. In the present study it is shown that exposure of S. domuncula to cadmium (CdCl2) in concentrations ranging from 0.01 to 5.0 g ml−1 for up to 5 d results in apoptotic fragmentation of DNA. Kinetics experiments revealed that after 24 h a significant increase of DNA fragmentation already occurred. Besides cadmium a second stimulus was identified to also cause apoptosis in this species, namely exposure to heat-treated Escherichia coli. In order to support the finding that both cadmium and E. coli induce apoptosis in the sponge, expression of the apoptotic gene MA-3 was studied. The cDNA, SDMA3, was isolated and found to be 2247 nucleotides long. The deduced amino acid sequence (Mr 50 765) shares high similarity with the corresponding mouse molecule. Like the mouse gene, the sponge MA-3 gene undergoes increased expression in response to apoptotic stimuli. While the specimens remained alive after treatment with cadmium, the sponges treated with E. coli died after approximately 12 d. The E. coli-treated animals started to form gemmules 10 to 12 d after addition of the bacteria. Hence, the process of apoptosis in sponges is triggered by two different pathways, one which is initiated by exogenous factors, e.g. heavy metals, and a second one, caused by endogenous factors, which leads to gemmule formation and a shift of the presumably immortal cells to mortal cells. The latter assumption is supported by the finding that during the process of bacteria-induced apoptosis, which results in the death of the specimens, the activity of the telomerase drops. It is concluded that the cells which appear to be immortal and telomerase-positive undergo apoptosis during the process of gemmule formation. In consequence cells not involved in the production of gemmules become mortal. Based on these data, it is proposed that apoptosis is a suitable biomarker in the bioindicator organism S. domuncula to monitor unfavorable environmental conditions, at least in this animal phylum.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is known that species belonging to the lowest metazoan phylum, the Porifera (sponges), do not develop tumors. Sponge cells share with tumor cells of higher animals at least one characteristic; they contain high levels of telomerase activity, suggesting that they possess a high proliferation capacity. This assumption, however, has not been substantiated experimentally. In addition, sponges show a specific bauplan, leading us to postulate that they undergo apoptosis to replace a given set of cells at a given time. In the present study, 17β-estradiol (βE2) was used as a defined agent to assess its effect on both the telomerase activity and the process of apoptosis in the marine sponge Geodia cydonium (Jameson). It was found that βE2 (100 to 500 ng ml−1) caused increased expression (i) of the heat-shock protein HSP70 (Mr=70 000), a cytoplasmic chaperone; and (ii) of the nuclear chaperone thioredoxin (TRX), a protein involved in the control of cancer cell growth. For this purpose the gene of G. cydonium encoding TRX was cloned, and the cDNA was applied for the determination of the expression. Verapamil, an inhibitor of both the mammalian multidrug resistance pump and the invertebrate multixenobiotic resistance pump, was used in co-incubation experiments with βE2 to increase the uptake of βE2. The experiments revealed that verapamil augmented the βE2 effect on the expression of the two chaperones, HSP70 and TRX. In addition, the tissue of G. cydonium underwent apoptosis, and the cells lost their telomerase activity. In parallel with the induction of the apoptotic process, the number of DNA strand breaks increased. It is concluded that βE2 displays its effect via the production of reactive oxygen species (ROS). At physiological concentrations ROS cause the expression of HSP70 and TRX, while at higher ROS levels, generated during the co-incubation period of βE2 with verapamil, the cells undergo apoptosis and lose telomerase activity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Halichondria panicea (Pallas) is a marine sponge, abundantly occurring in the Adriatic Sea, North Sea, and Baltic Sea. It was the aim of the present study to investigate if this sponge species harbors bacteria. Cross sections through H. panicea were taken and inspected by electron microscopy. The micrographs showed that this sponge species is colonized by bacteria in its mesohyl compartment. To identify the bacteria, polymerase chain reaction (PCR) analysis of the 16S rRNA gene segment, typical for bacteria, was performed. DNA was isolated from sponge material that had been collected near Rovinj (Adriatic Sea), Helgoland (North Sea), and Kiel (Baltic Sea) and was amplified with bacterial primers by PCR. The data gathered indicate that in all samples bacteria belonging to the genus Rhodobacter (Proteobacteria, subdivision α) are dominant, suggesting that these bacteria live in symbiotic relationship with the sponge. In addition, the results show that the different samples taken contain further bacterial species, some of them belonging to the same genus even though found in sponges from different locations. The possibility of the presence of toxic bacteria was supported by the finding that organic extracts prepared from sponge samples displayed toxicity, when analyzed in vitro using leukemia cells.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments were carried out with the marine sponge Suberites domuncula to determine whether sponges may express-like mammalian tumor cells-a multidrug-like transporter system. The results demonstrate that sponge cells possess such a protective system termed multixenobiotic resistance (MXR) pump or P-glycoprotein-like pump. The protein was identified by antisera for the mammalian P170 multidrug resistance protein as a 130 kDa molecule. Binding studies were performed with 3H-vincristine (3H-VCR) and membrane vesicles; this process is ATP-dependent and inhibited by verapamil, which is known to reverse the multidrug-resistance phenotype in mammalian systems. Accumulation experiments were performed to demonstrate that the uptake of 3H-VCR is time-dependent, and increases at elevated extracellular levels of 3H-VCR. Application of the dyeing technique with calcein-AM, a suitable functional assay for multidrug transporter systems in mammal cells, also revealed the existence of the MXR pump in S. domuncula plasma membranes. These data demonstrate that S. domuncula is provided with a multidrug-like transporter, the MXR pump, which might function as a protection system for sponges in polluted environments.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 551 (1989), S. 363-367 
    ISSN: 0005-2736
    Keywords: (Geodia cydonium) ; Aggregation factor ; Circular proteid particle ; Dissociation ; Self-aggregation ; Sponge
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0921-8734
    Keywords: DNA relaxation activity ; Hen oviduct ; Nuclear matrix ; Poly(ADP-ribose) synthetase ; Protein Kinase NII ; Protein kinase C
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Parasitology Today 8 (1992), S. 61-66 
    ISSN: 0169-4758
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 18 (2003), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In auditory maps of the primary auditory cortex, neural response properties are arranged in a systematic way over the cortical surface. As in the visual system, such maps may play a critical role in the representation of sounds for perception and cognition. By recording from single neurons in the central nucleus of the inferior colliculus (ICC) of the mouse, we present the first evidence for spatial organizations of parameters of frequency sweeps (sweep speed, upward/downward sweep direction) and of whole-field tone response patterns together with a map of frequency tuning curve shape. The maps of sweep speed, tone response patterns and tuning curve shape are concentrically arranged on frequency band laminae of the ICC with the representation of slow speeds, build up response types and sharp tuning mainly in the centre of a lamina, and all (including high) speeds, phasic response types and broad tuning mainly in the periphery. Representation of sweep direction shows preferences for upward sweeps medially and laterally and downward sweeps mainly centrally in the ICC (either striped or concentric map). These maps are compatible with the idea of a gradient of decreasing inhibition from the centre to the periphery of the ICC and by gradients of intrinsic neuronal properties (onset or sustained responding). The maps in the inferior colliculus compare favourably with corresponding maps in the primary auditory cortex, and we show how the maps of sweep speed and direction selectivity of the primary auditory cortex could be derived from the here-found maps of the inferior colliculus.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3007-3009 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermally induced transition from the ordered to the disordered state of Ga0.52In0.48P/(Al0.35Ga0.65)In0.5P layers was investigated by means of rapid thermal annealing and photoluminescence spectroscopy. The annealing temperature and annealing time dependence of the luminescence was studied in the temperature range from 500 up to 1050 °C and for annealing times between 5 and 600 s. Within a very small temperature range of less than 40° we observe an emission energy blue shift of the GaInP luminescence band by about 100 meV. The shift occurs due to a complete disordering of the previously ordered layers without a simultaneous destruction of the heterostructure. The photoluminescence of the quaternary AlGaInP barrier was also observed and shows a simultaneous blue shift of about 90 meV due to an order-disorder transition.
    Type of Medium: Electronic Resource
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