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'Volvox carteri' in keywords
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1984 (2)
1982 (1)
1Author    Rainer Gilles, Lothar JaenickeRequires cookie*
 Title    Differentiation in Volvox carteri: Study of Pattern Variation of Reproductive Cells  
 Abstract    Asexual spheroids of the multicellular green alga Volvox are composed o f two types o f cells: non-flagellated reproductive gonidia and Chlamydomonas-\ike flagellated somatic cells. They are committed by a differentiating cleavage during embryogenesis. The gonidia o f the adult spheroids form a symmetrical pattern consisting o f four layers o f four gonidia each; their position is established already in the embryos by the gonidial initials. Whereas, generally, the 16-gonidia pattern is assumed to be the basic one, most o f the spheroids have fewer gonidia (down to 8). The nine possible gonidial patterns (8 to 16 gonidia) are described and correlated to the gonidial stem cells which have been differentiated. Defects in gonidial pattern are o f particular interest, since any model of differentiation has to explain not only the basic pattern formed, but also its systematic variations. Our study shows that the pattern reduction is by no means random, but governed by an intrinsic mechanism which shifts the first unequal cleavage from the 32-celled stage to the 16-celled stage. All the patterns formed can be deduced from cleavage pathways involving non-synchronous differentiation of the stem cells. Thus, pattern formation can be correlated to timing and spacing signals regulating events during embryogenesis. 
  Reference    Z. Naturforsch. 37c, 1023—1030 (1982); received June 1 1982 
  Published    1982 
  Keywords    Volvox carteri, Differentiation, Embryogenesis, Cell Lineages, Pattern Formation 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-1023.pdf 
 Identifier    ZNC-1982-37c-1023 
 Volume    37 
2Author    Bernd Weisshaar, Rainer Gilles, Regina Moka, Lothar JaenickeRequires cookie*
 Title    A High Frequency Mutation Starts Sexual Reproduction in Volvox carteri  
 Abstract    Pheromone-initiated sexual reproduction of Volvox carteri f. nagariensis is started by a "spontaneous" generation of sexual male spheroids at a rate of 10~4. As previously suggested, these males are mutants (5e.vc) which become independent of pheromone-controlled sex-induction. Unequivocal evidence for a mutative event now comes from the observation that the sex0 trait is transmitted through cell lineages during embryogenesis, thus confirming earlier 
  Reference    Z. Naturforsch. 39c, 1159—1162 (1984); received July 6 1984 
  Published    1984 
  Keywords    Cell Lineages, Mutation, Sexual Induction, Volvox carteri 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-1159.pdf 
 Identifier    ZNC-1984-39c-1159 
 Volume    39 
3Author    Rainer Gilles, Claudia Gilles, Lothar JaenickeRequires cookie*
 Title    Pheromone-Binding and Matrix-Mediated Events in Sexual Induction of Volvox carteri  
 Abstract    Sexual differentiation o f the reproductive cells (gonidia) o f the green alga Volvox carteri f. nagariensis Iyengar is triggered by a glycoprotein inducer which is released into the medium by sexual male spheroids. If added, it induces the next generation cycle to becom e sexual. About 3000 pheromone molecules per spheroid will give full induction. Specific binding sites for the pheromone have been identified in the extracellular matrix in which characteristic events take place. Inducer binding and action are reversible for a certain tim e period until the start o f cell division; thereafter, determination o f the gonidia is final. Extent o f sexual induction is proportional to the duration o f inducer pulses. Inhibition o f sexual induction reveals as essential extracellular components o f the induction system high m olecular acidic glycoproteins, cyclic nucleotides, Ca2+/calm odulin, and pherom one-controlled gene products. Low matrix levels o f cyclic AMP and cyclic GMP seem to stim ulate induction; high levels to inhibit. 
  Reference    Z. Naturforsch. 39c, 584 (1984); received March 7. 1984 
  Published    1984 
  Keywords    Volvox carteri, Sexual Induction, Extracellular Matrix, Pherom one, Cyclic N ucleotides 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0584.pdf 
 Identifier    ZNC-1984-39c-0584 
 Volume    39