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  • 1
    Digitale Medien
    Digitale Medien
    On the finding of a mass occurrence of Serpula narconensis Baird, 1885 (Polychaeta, Serpulidae) in South Georgia (Antarctica) (1999)
    Springer
    Polar biology 22 (1999), S. 379-383 
    Details
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A new “reef ” of the serpulid polychaete Serpula narconensis Baird, 1885 is reported from the South Georgia Island shelf. This particular mass occurrence is the second serpulid “reef” reported in the Antarctic region. Its location, at 91- to 105-m depth, is very different from those serpulid reefs previously reported, usually sited at intertidal zone or at low depth, and this may be one of the largest, if not the largest, serpulid reef in the world.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003000050432
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Phase transition for absorbed Brownian motion with drift (1997)
    Springer
    Journal of statistical physics 86 (1997), S. 213-231 
    Details
    ISSN: 1572-9613
    Schlagwort(e): Absorbed Brownian motion ; quasistationary distributions ; conditioned Brownian motion with drift
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study one-dimensional Brownian motion with constant drift toward the origin and initial distribution concentrated in the strictly positive real line. We say that at the first time the process hits the origin, it is absorbed. We study the asymptotic behavior, ast→∞, ofm t , the conditional distribution at time zero of the process conditioned on survival up to timet and on the process having a fixed value at timet. We find that there is a phase transition in the decay rate of the initial condition. For fast decay rate (subcritical case)m t is localized, in the critical casem t is located around $$\sqrt t$$ , and for slow rates (supercritical case)m t is located aroundt. The critical rate is given by the decay of the minimal quasistationary distribution of this process. We also study in each case the asymptotic distribution of the process, scaled by $$\sqrt t$$ , conditioned as before. We prove that in the subcritical case this distribution is a Brownian excursion. In the critical case it is a Brownian bridge attaining 0 for the first time at time 1, with some initial distribution. In the supercritical case, after centering around the expected value—which is of the order oft—we show that this process converges to a Brownian bridge arriving at 0 at time 1 and with a Gaussian initial distribution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02180205
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Validation of a high-performance chromatographic method for determination of cefotaxime in biological samples (1999)
    Springer
    Fresenius' journal of analytical chemistry 363 (1999), S. 289-293 
    Details
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An analytical method for detecting and quantifying cefotaxime in plasma and several tissues is described. The method was developed and validated using plasma and tissues of rats. The samples were analyzed by reversed phase liquid chromatography (HPLC) with UV detection (254 nm). Calibration graphs showed a linear correlation (r 〉 0.999) over the concentration ranges of 0.5–200 μg/mL and 1.25–25 μg/g for plasma and tissues, respectively. The recovery of cefotaxime from plasma standards prepared at the concentrations of 25 μg/mL and 100 μg/mL was 98.5 ± 3.5% and 101.8 ± 2.2%, respectively. The recovery of cefotaxime from tissue standards of liver, fat and muscle, prepared at the concentration of 10 μg/g was: 89.8 ± 1.2% (liver), 103.9 ± 6.5% (fat) and 97.8 ± 2.1% (muscle). The detection (LOD) and quantitation (LOQ) limits for plasma samples were established at 0.11 μg/mL and 0.49 μg/mL, respectively. The values of these limits for tissues samples were approximately 2.5 times higher: 0.3 μg/g (LOD) and 1.25 μg/g (LOQ). For plasma samples, the deviation of the observed concentration from the nominal concentration was less than 5% and the coefficient of variation for within-day and between-day assays was less than 6% and 12%, respectively. The method was used in a pharmacokinetic study of cefotaxime in the rat and the mean values of the pharmacokinetic parameters are given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002160051190
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  • 4
    Digitale Medien
    Digitale Medien
    Transitive actions of semigroups in semi-simple Lie groups (1999)
    Springer
    Semigroup forum 58 (1999), S. 142-151 
    Details
    ISSN: 1432-2137
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: G be a connected semi-simple Lie group with finite center and S⊂G a semigroup with interior points. It is proved that S is transitive on a homogenous space G/L only if the action of L on B is minimal and contracting, where B=G/Pis the flag manifold of G asssociated with S. In [5, Thm.6.4] the authors claimed another necessary condition in case G is simple, namely, that L is discrete. It is shown by means of an example that this condition is wrong without the further assumption that G/L is compact.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002339900004
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  • 5
    Digitale Medien
    Digitale Medien
    “Errant” polychaetes of the Livingston Island shelf (South Shetlands, Antarctica), with the description of a new species (1997)
    Springer
    Polar biology 17 (1997), S. 285-295 
    Details
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Spanish cruise “Bentart 94” was the first of two devoted to the study of the benthic marine fauna off Livingston and Deception Islands, South Shetland Islands, Antarctica. In this paper, the taxonomic results of the examination of the “errant” families of the polychaetes collected during that cruise are presented. A total of 834 specimens have been examined, belonging to 34 species of 31 genera and 11 families. A new species, Micronereis anaramosae, is described, and Eusyllis kerguelensis McIntosh is referred to the genus Pionosyllis. The specimens were found in 109 samples of muddy sand, mud, stones, rocks, gravel, and mixed sediments, by scuba diving, Van Veen grab, rock trawl and anchor dredge.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00013370
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  • 6
    Digitale Medien
    Digitale Medien
    A new type of polytetrafluoroethylene prosthesis (Mycro Mesh): an experimental study (1996)
    Springer
    Journal of materials science 7 (1996), S. 475-478 
    Details
    ISSN: 1573-4838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract Comparisons were made of the tissue response to the implantation of two different polytetrafluoroethylene prostheses: Soft Tissue Patch (STP) and Mycro Mesh (MM). A 7 × 5 cm prosthesis of STP (n=12) or MM (n=12) was implanted into a defect of the same size (involving all layers except skin) created in the anterior abdominal wall in 24 New Zealand rabbits. The prostheses were anchored to the recipient tissue, in direct contact with the intestinal loops and connective tissue. After 14, 30, 60 and 90 days, groups of six implants were studied macroscopically and samples were taken to be processed by light microscopy, scanning electron microscopy (SEM), immunohistochemical studies and tensiometry. All animals were valid for the study. In three cases STP implants presented very loose adhesions in the peripheral zones corresponding to the sutures. They were also observed on three MM implants, in the area of the perforations. Light and scanning microscopy revealed the formation of a capsule of scar tissue surrounding both types of prosthesis. At day 90, bridges of connective tissue had formed in the perforated areas of MM. Good vascularization was established in the areas of recipient tissue corresponding to both implants. The macrophage reaction to both biomaterials was maximal at 14 days, after which it progressively decreased until day 90. Tensile testing revealed no significant differences between the two biomaterials. It is concluded that (a) behaviour in the peritoneal interface is similar in the two prostheses, (b) both biomaterials become encapsulated rather than integrated into the recipient tissue, (c) the foreign body reaction does not determine the success or failure of the implants, (d) The perforations of the MM prosthesis do not increase its resistance to stress, or at least not after 90 days of implantation into rabbit abdominal wall.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00705428
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  • 7
    Digitale Medien
    Digitale Medien
    The compound 14-keto-stypodiol diacetate from the algae Stypopodium flabelliforme inhibits microtubules and cell proliferation in DU-145 human prostatic cells (1998)
    Springer
    Molecular and cellular biochemistry 187 (1998), S. 191-199 
    Details
    ISSN: 1573-4919
    Schlagwort(e): Stypopodium flabelliforme ; 14-keto-stypodiol diacetate ; DU-145 cell line ; microtubule assembly ; cell proliferation ; plasminogen activator (u-PA) ; tumor invasiveness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract We investigated the effects of the drug 14-keto-stypodiol diacetate (SDA) extracted from the seaweed product Stypopodium flabelliforme, in inhibiting the cell growth and tumor invasive behavior of DU-145 human prostate cells. In addition, the molecular action of the drug on microtubule assembly was analyzed. The effects of this diterpenoid drug in cell proliferation of DU-145 tumor cells in culture revealed that SDA at concentrations of 5 μM decreased cell growth by 14%, while at 45 μM a 61% decrease was found, as compared with control cells incubated with the solvent but in the absence of the drug. To study their effects on the cell cycle, DU-145 cells were incubated with increasing concentrations of SDA and the distribution of cell-cycle stages was analyzed by flow cytometry. Interestingly, the data showed that 14-keto-stypodiol diacetate dramatically increased the proportion of cells in the G2/M phases, and decreased the number of cells at the S phase of mitosis, as compared with appropriate controls. Studies on their action on the in vitro assembly of microtubules using purified brain tubulin, showed that SDA delayed the lag period associated to nucleation events during assembly, and decreased significantly the extent of polymerization. The studies suggest that this novel derivative from a marine natural product induces mitotic arrest of tumor cells, an effect that could be associated to alterations in the normal microtubule assembly process. On the other hand, a salient feature of this compound is that it affected protease secretion and the in vitro invasive capacity, both properties of cells from metastases. The secretion of plasminogen activator (u-PA) and the capacity of DU-145 cells to migrate through a Matrigel-coated membrane were significantly inhibited in the presence of micromolar concentrations of SDA. These results provide new keys to analyze the functional relationships between protease secretion, invasive behavior of tumor cells and the microtubule network.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006879308861
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  • 8
    Digitale Medien
    Digitale Medien
    Quantitative analysis of macrobenthic soft-bottom assemblages in South Shetland waters (Antarctica) (1997)
    Springer
    Polar biology 17 (1997), S. 393-400 
    Details
    ISSN: 1432-2056
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Macrobenthic assemblages were investigated at 26 stations located around Livingston Island, Deception Island and the Bransfield Strait at depths ranging from 42 to 671 m. Representatives of 30 major taxa were found. The maximal density was 5,260 specimens·m−2 at Livingston Island; the mean abundance per station ranged from 160 to 4,380 specimens·m−2. The total biomass of the macrozoobenthos declined with depth, with mean values of 3,201 g·m−2 at shallower depths (〈 100 m) and 210 g·m−2 further down (〉 100 m). After multivariate analysis (cluster analysis, MDS) based on Bray-Curtis dissimilarities, most stations could be assigned to one of three groups on the basis of distinct biomass differences between sites. The first cluster with a rich Ascidiacea biomass is common on shallower bottoms. The second, with Ophiuroidea as a characteristic group, is common on deeper bottoms. The absence of an ‘indicator’ taxon is characteristic of the remaining cluster of those stations with the lowest biomass values. No significant correlations were detected between macrobenthic biomass and any sediment parameters measured, probably because part of the benthos (i.e. the epifauna) could be better explained by the coupling with a highly productive water column. The role of the epi-infauna sensu Gallardo as the main factor structuring benthic assemblages in the investigated area is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/PL00013382
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  • 9
    Digitale Medien
    Digitale Medien
    Correlation between gender and spontaneous C-cell tumors in the thyroid gland of the Wistar rat (1999)
    Springer
    Cell & tissue research 297 (1999), S. 451-457 
    Details
    ISSN: 1432-0878
    Schlagwort(e): Key words Thyroid gland ; Calcitonin ; C-cell hyperplasia ; C-cell carcinoma ; Medullary thyroid carcinoma ; Sexual dimorphism ; Rat (Wistar)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract  In many rat strains, C-cell hyperplasia occurs in an age-dependent manner and is often associated with multifocal C-cell carcinoma. The purpose of this study was to investigate the spectrum of spontaneous, proliferative C-cell disorders by gender in Wistar rats throughout their lifespan. The incidence of C-cell hyperplasia shows a significant increase with age (P〈0.001) and is much higher in female rats than in male rats (P〈0.05). From 3 to 24 months of life, 27.5% of female rats showed a normal C-cell pattern, 55.0% showed C-cell hyperplasia, and 17.5% showed C-cell tumors; while 57.5% of male rats showed a normal C-cell pattern, 32.5% showed C-cell hyperplasia, and 10% showed C-cell tumors. Although the overall frequency of C-cell neoplasms in females was nearly double that in males, these data are not statistically significant. However, the number of C-cell tumors showed a significant increase with age (P〈0.05). Therefore, we can conclude that there were significant differences in the incidence of the total spectrum of C-cell proliferative abnormalities in the thyroid gland of Wistar rats that were both age-dependent and gender-dependent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004410051371
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Morpho-ecological study on the South American species of the genus Nothofagus (1997)
    Springer
    Plant ecology 130 (1997), S. 101-109 
    Details
    ISSN: 1573-5052
    Schlagwort(e): Distribution ; Ecology ; Morphology ; Nothofagus ; South American
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The morphology of the 11 taxa of South American Nothofagus are compared. Thirty eight characteristics were taken into account: 12 from leaves, 3 from stipules, 3 from buds, 6 from cupules, 7 from fruits, 4 from petioles and 3 from male flowers. The data matrix, with average values of 100 measurements per taxon, was analyzed with multivariate statistical methods of classification and polar and spatial ordination. Five groups were established: The first one (Nothofagus obliqua, N. obliqua var. macrocarpa, N. leoni and N. alessandrii), with deciduous leaves, is adapted to mediterranean climatic conditions. The second groups (N. dombeyi, N. nitida and N. antarctica), with small leaves which are evergreen for the first two species and deciduous for the last, develops under temperate humid conditions typical of the Valdivian region. The three remaining groups correspond to isolated species with different requirements: N. glauca, has large deciduous leaves and colonizes the most xerophytic biotope that a Nothofagus in central Chile can tolerate. N. pumilio, with mid-sized deciduous leaves, is adapted to the cold and dry zones of the southern Andes. Finally, N. betuloides, with small evergreen leaves, grows in the cold/humid somewhat boggy conditions of the Magellanic region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009735821549
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