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  • 2000-2004  (1)
  • 1975-1979  (1)
  • Head formation  (1)
  • hepadnaviruses  (1)
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  • 2000-2004  (1)
  • 1975-1979  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of morphogenetic mutants of hydra (1977)
    Springer
    Development genes and evolution 183 (1977), S. 193-206 
    Details
    ISSN: 1432-041X
    Keywords: Hydra mutant ; Morphogenetic substances ; Head formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A mutant ofHydra attenuata is analysed, theaberrant, which is distinct from the wild type in having a smaller head with fewer tentacles and only half the number of head-specific cells. The rate of head and foot regeneration and the doubling time are slower inaberrants than in normal hydra. The lower head-forming potential is paralleled by a reduced concentration of head-specific morphogens: compared to the wild type, in theaberrant the concentration of head activator is reduced to 70% in the head and to 50% in the body, the concentration of head inhibitor is reduced to 50% in the head and to 80% in the body. Theaberrant is more sensitive (3 times) to added head activator and less sensitive (〉5 times) to added head inhibitor than the wild type. The slower rate of foot regeneration is paralleled by a lower content of foot-specific morphogens: compared to the wild type, in theaberrant the foot activator is reduced to 40% and the foot inhibitor to 70%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00867320
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Immune Escape by Hepatitis B Viruses (2000)
    Springer
    Virus genes 21 (2000), S. 27-37 
    Details
    ISSN: 1572-994X
    Keywords: HBV ; infection ; liver ; hepadnaviruses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Hepatitis B viruses are DNA viruses characterized by their very small genome size and their unique replication via reverse transcription. The circular genome has been efficiently exploited, thereby limiting genome variation, and leaves no space for genes in addition to those essentially needed during the viral live cycle. Hepatitis B viruses are prototype non-cytopathic viruses causing persistent infection. Human hepatitis B virus (HBV), as well as the closely related animal viruses, most frequently are transmitted vertically from mothers to their offspring. Because infection usually persists for many years, if not lifelong, hepatitis B viruses need efficient mechanisms to hide from the immune response of the host. To escape the immune response, they exploit different strategies. Firstly, they use their structural and non-structural proteins multiplely. One of the purposes is to alter the immune response. Secondly, they replicate by establishing a pool of stable extrachromosomal transcription templates, which allow the virus to react sensitively to changes in its microenvironment by up- or downregulating gene expression. Thirdly, hepatitis B viruses replicate in the liver which is an immunopriviledged site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008128212380
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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