Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    The superstructure of chromatin and its condensation mechanism (1988)
    Springer
    European biophysics journal 16 (1988), S. 177-185 
    Details
    ISSN: 1432-1017
    Keywords: X-ray solution scattering ; synchrotron radiation ; sea urchin chromatin ; solubility ; condensation ; electric dichroism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Comparison between the internucleosomal distance found by X-ray solution scattering for chicken erythrocyte (23 nm) and sea urchin (30 nm) chromatin indicates that this distance is proportional to the linker length. The diameter of the condensed sea urchin chromatin fibers is about 45 nm which is significantly larger than in chicken erythrocyte chromatin (35 nm). Trivalent cations (Gd, Tb, Cr) and the polyamines spermine and spermidine were found to induce compaction at much lower concentrations than the divalent cations but Gd, Tb and Cr induce aggregation before full compaction of the fibers. The influence of hydrogen bonding is illustrated by comparison of the effects of NaCl, ammonium chloride and alkylammonium chlorides on condensation. Solubility experiments indicate that there is a nearly linear dependence of the Mg-- concentration at which precipitation occures on chromatin concentration and confirm the differences between cations observed by X-ray scattering. The chicken erythrocyte chromatin samples were further characterized by their reduced electric dichroism. The values found are consistent with the model derived from X-ray scattering and are compared with those reported in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261903
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Influence of sperm density and contact time on herring egg fertilization (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of applied ichthyology 4 (1988), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In order to standardize fish egg incubation techniques for bioassay application, fertilization procedures need to be included into the protocols. Nothing is known about the necessary sperm concentrations required to achieve optimal fertilization rates. The tests described here for the herring Clupea harengus L. include trials with 10 different sperm densities and 4 contact times (15, 30, 60 and 120 seconds). The variability of fertilization rates in eggs from different females was also investigated. Fertilization success was mainly influenced by sperm density and less by the actual contact time between unfertilized eggs and sperm containingmedia. Dilution in sperm density to 9.6 × 106 cells ml-1 or less resulted in reduced fertilization success. There was considerable variability in fertilization rates between females.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0426.1988.tb00470.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Invertebrate bioassays with North Sea water samples. I. Structural effects on embryos and larvae of serpulids, oysters and sea urchins (1985)
    Springer
    Helgoland marine research 39 (1985), S. 1-19 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Structural effects of bottom and surface water samples from two dumping grounds in the inner German Bight on the development of three meroplanktonic organisms(Pomatoceros triqueter: Polychaeta,Psammechinus miliaris: Echinodermata andCrassostrea gigas, Mollusca) were investigated. The titaniumdioxide dumping site was sampled immediately after dumping (within the visible waste trail 1 km behind the vessel), and 10 h after dumping. Samples were taken in the sewage sludge deposition area in the intervals between the usual dumping activities, regardless of the exact dumping schedule. The preserved bioassay test organisms were inspected microscopically to count percentages of “normal” larval hatch in test water samples, reference water samples and laboratory aged control water samples (5 to 10 replicates). The relative water quality at various dumping sites was expressed in terms of “net risk”-values (Woelke, 1972) compared to hatching rates observed in the controls. Larval development ofP. triqueter was significantly suppressed (up to −22 % “net risk”) in trail water of the titanium dioxide dump site while the development of sea urchin larvae was still affected in the 10 h surface samples. Hatching of all test organisms in bottom-water samples from the centre of the sewage sludge dump site was affected to different degrees when compared to reference areas about 4 km north or 6 km northwest of the dumping area. The general usefulness of standardized bioassay procedures in pollution monitoring programmes is discussed. The results presented here call for further verification to minimize experimental background variability and to enlarge the catalogue of suitable effects criteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01997515
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...