Control of the antibody response of C57BL/6 Lyt-congenic strains to the Lyt-3.1 alloantigen by a gene linked to theLyt-2 locus

Congenic anti-Lyt-3.1 sera have recently been produced by immunizing B6-Lyt-2^a mice with thymocytes from either B6-Lyt-2^a, Lyt-3^a or B6-Lyt-2^a, Lyt-3^a, H-2^k mice (Boos et al. 1978). Surprisingly, mice of the congenic strain B6 failed to produce either anti-Lyt-2.1 or anti-Lyt-3.1 cytotoxic antibodies after identical immunizations. To determine the genetic basis for the difference in response to Lyt-3.1, (B6 × B6-Lyt-2^a)F_a mice and progeny of the backcross, (B6 × B6-Lyt-2^a)F₁ × B6-Lyt-2^a, were immunized with B6-Lyt-2^a, Lyt-3^a, H-2^k thymocytes. In addition, thymic biopsies of backcross progeny were performed and thymocytes tested for the Lyt-2.2 antigenic specificity. Results indicate that gene(s) governing the immune response to Lyt-3.1 is (are) linked to theLyt-2 locus, and that the responder allele (linked toLyt-2 ^a ) shows very poor penetrance in Lyt-2^a/Lyt-2^b mice.     

Links between global taxonomic diversity,ecological diversity and the expansion of vertebrates on land

Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.     

Rassenumwandlung bei Aspergillus niger

Zusammenfassung Es wurde versucht, zwei physiologisch durch die Oxalsäurebildung und die dadurch beeinflußte Richtung der Autolyse verschiedene Rassen von Aspergillus niger ineinander überzuführen. Dies gelang durch Einwirkung von Trocknen bzw. Erhitzen der Sporen und durch Passage über Tannin- und Oxalsäurelösung.Der Übergang der Rasse Göttingen neu (viel Oxalsäure, saure, helle Autolyse) in die Rasse Göttingen alt (wenig Oxalsäure, neutrale bzw. alkalische, dunkle Autolyse) ging bedeutend leichter als umgekehrt.Durch Oxalsäurepassage wird die Rasse Göttingen alt stärker in der Richtung der sauren, die Rasse Göttingen neu stärker in der Richtung der neutralen Autolyse beeinflußt.Die jeweiligen Veränderungen erwiesen sich drei bis acht Generationen, soweit untersucht, konstant.Mit Hilfe ähnlicher Methoden dürften die Veränderungen bei diesem Pilz der experimentellen Analyse zugänglich werden.Kurzer Auszug aus der Dissertation von Paul Hugo Kreutzmann, Untersuchungen über die Variabilität von Aspergillus niger. Göttingen 1935.