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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 513 (1987), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
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    Unknown
    Washington, D.C., etc. : Periodicals Archive Online (PAO)
    The Journal of economic education. 10:1 (1978:Fall) 18 
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 65 (1979), S. 31-39 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Toads pretreated for 2 months on either a dark or a light background were then exposed to lead nitrate at 50 ppm lead for 21 days, the illumination regimes being maintained. Metal analysis of dorsal skin showed significantly higher lead levels (p〈0.01) in dark-adapted toads. No precipitated lead deposits were observed at the ultrastructural level, necessitating X-ray microanalysis of sections containing melanophores, gland cells and general (non-melanophore) cytoplasm. Analysis showed the lead to be concentrated within the melanosomes of the melanophores, and to be significantly higher (p〈0.01) in individual melanosomes of dark-adapted toads than in light-adapted ones. Copper was also found to be concentrated in the melanosomes and was higher (p〈0.01) in the melanosomes of the dark-adapted toads. The results are consistent with the known affinity of melanin for heavy metals and the documented increase in melanophore number under prolonged dark background regimes. Since all toads received the same lead exposure, the melanosome results give rise to speculation that higher melanin levels might occur in individual melanosomes of dark-adapted skin.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We have determined the genomic organisation of the human chordin gene, CHRD, and have shown that it maps within a gene cluster at 3q27 containing THPO (thrombopoietin), CLCN2 (a voltage-gated chloride-channel gene) and EIF4G1 (a eukaryotic translation-initiation-factor-gamma gene). The CHRD and THPO genes are very close neighbours and are transcribed from opposing DNA strands from promoters that are spaced less than 2 kb apart. We considered that the CHRD gene and the chordin-regulating GSC (goosecoid) gene could be candidate genes for Cornelia de Lange syndrome (CDLS), a developmental malformation syndrome which is primarily characterised by mental handicap, growth retardation, distinctive facial features and limb-reduction defects. CDLS patients typically occur as sporadic cases, but several reports have suggested dominant inheritance. The candidacy of the CHRD and GSC genes was supported by several lines of evidence: prior evidence for a CDLS gene at 3q26.3–q27; a report suggesting a significant association between CDLS and thrombocytopenia; suspected genetic heterogeneity in CDLS; location of the GSC gene in close proximity to a 14q32 breakpoint detected in a CDLS patient with a balanced de novo translocation; known regulation of chordin expression by goosecoid; and the pattern of embryonic expression of the mouse GSC gene. Another candidate gene at 3q27, SOX2, was also considered because of its suspected role as a transcription factor in early development and because of known examples of SOX genes that are loci for dominantly inherited developmental disorders. However, mutation screening failed to identify CDLS patient-specific mutations in CHRD, GSC or SOX2.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 56 (1978), S. 55-64 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Control individuals contained no lead in the chloragocytes but high α-glycogen rosette reserves. Starvation of contaminated earthworms for 4d caused a lead loss and the chloragocytes possessed fewer debris vesicles than those of unstarved worms, suggesting that the debris vesicles may be the route for at least some of the lead loss. No glycogen deposits were observed in the chloragocytes of starved or unstarved earthworms from contaminated soil. Maintenance of contaminated earthworms in potting compost caused lead losses similar to those sustained by starvation, but the chloragocyte cytoplasm possessed β-glycogen reserves. Specimens maintained in lead-spiked potting compost showed lead levels similar to those of earthworms taken directly from contaminated soil. No β-glycogen accumulations were observed under this enriched regime. Although the possible interference of lead in carbohydrate metabolism is discussed, the results do not wholly support metabolic inhibition by lead. It is hypothesised that lead sequestration is energy-demanding and that in the absence of an energy-rich diet glycogen stores fail to accumulate. In the presence of an organic-rich medium, elevated lead levels preclude glycogen formation, because of the high sequestration-demand, but at lower lead levels β-glycogen deposits occur if a high organic diet is available.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lead content of whole earthworms, highest in contaminated site specimens, was significantly higher inDendrobaena rubida thanLubricus rubellus and a species difference in zinc was also recorded. Selective feeding and differential absorption are discounted and a species difference in maximum tolerance to body lead is suggested. Copper was low in all specimens. Chloragocytes and intestinal tissue showed significantly higher lead levels in contaminated earthworms than in control material. Ultrastructurally, chlorgocytes from contaminated earthworms showed electron dense flecks associated with the chroragosome peripheries and within the debis vesicles. Very fine flecks occurred in the nuclei, but mitochondria and Golgi were indistinguishable from control material. Preliminary X-ray microanalysis of contaminated chloragocytes revealed lead and phosphorus. The deposits within the chloragocytes might represent unbound lead precipitated by phosphate buffer; flecks being absent from contaminated, citrate buffered material and from control material. The chloragosomes are proposed as possible sites for sequestered lead. Chloragocyte and intestinal glycogen levels were significantly higher in control material where the chloragocyte cytoplasm was rich in α-glycogen rosettes, these being absent from lead contaminated cells. The glycogen-lead correlation suggests that the metabolism of contaminated chloragocytes is directed towards lead sequestration, though differing nutritional states cannot be ignored.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 33 (1977), S. 1120-1120 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An apparatus and method are described which facilitate the rapid and accurate visual relocation of specified areas within ordinary, circular, plastic petri-dishes.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Laboratory experiments were conducted to study the effects of the exposure to a sublethal concentration (500 p.p.m.) of lead on the ultrastructure and acid phosphatase compartmentalization of the chloragogenous tissue of earthworms,Eisenia foetida. For the cytochemical demonstration of acid phosphatase activity, lead and cerium were used as capturing agents. In both cases there was a change in the compartmentalization of acid phosphatase, the enzyme activity being localized within the chloragosomes in controls, but distributed throughout the cytosol in treated animals. In addition, acid phosphatase activity increased following lead exposure. At the ultrastructural level, disruption of the chloragosomal membranes, an increase in chloragosomal fusion processes and vesiculation of the cytoplasm were evident. Moreover, an enhanced release of chloragosomes to the extracellular space was found in lead-exposed worms.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Laboratory experiments were conducted to study the effects of the exposure to a sublethal concentration (500 p.p.m.) of lead on the ultrastructure and acid phosphatase compartmentalization of the chloragogenous tissue of earthworms, Eisenia foetida. For the cytochemical demonstration of acid phosphatase activity, lead and cerium were used as capturing agents. In both cases there was a change in the compartmentalization of acid phosphatase, the enzyme activity being localized within the chloragosomes in controls, but distributed throughout the cytosol in treated animals. In addition, acid phosphatase activity increased following lead exposure. At the ultrastructural level, disruption of the chloragosomal membranes, an increase in chloragosomal fusion processes and vesiculation of the cytoplasm were evident. Moreover, an enhanced release of chloragosomes to the extracellular space was found in lead-exposed worms.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cytochemical localization of the lysosomal marker enzyme acid phosphatase was studied in the chloragogenous tissue of earthworms. The Gomori lead technique and the cerium capture technique were utilized. Both techniques demonstrated the chloragosomal location of this enzyme. Only a small proportion of chloragosomes presented reactivity, which suggests that these organelles are distinctly heterogeneous. The reaction product was localized in the periphery of chloragosomes, suggesting a membrane-bound compartmentalization of acid phosphatase. In addition, degenerating mitochondria and membrane whorls were observed in some chloragosomes, indicating the possibility that these organelles perform autophagosomal functions.
    Type of Medium: Electronic Resource
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