Structure-activity relationships in polycyclic aromatic hydrocarbons: induction of microsomal aryl hydrocarbon hydroxylase and its possible importance in chemical carcinogenesis

The results of quantitative structure-activity analysis show that the potency of polycyclic hydrocarbons as inducers of microsomal arylhydrocarbon hydroxylase (AHH) can be quantitatively described in terms of hydrophobic interactions, chemical reactivity, and the ability to participate in charge-transfer interactions. The rate-determining step in enzyme induction is probably the formation of a reactive K-region metabolite of the hydrocarbons which then reacts with a specific repressor. The same mechanism is proposed for chemical carcinogenesis on the ground of similarities in structure-activity relationships for both processes. It is suggested that AHH induction is the first step in chemical carcinogenesis.     

From the beginning to the present state of molecular microbial pathogenesis—A tribute to Pascale Cossart

The universe of Molecular Microbial Pathogenesis is filled with many female and male stars. But there are two particularly bright shining supernovae-like stars: the late Stanley Falkow and the very lively and creative Pascale Cossart. These two outstanding luminaries, surrounded by numerous planets, do not only belong to different scientific generations but their splendor also comes from very different scientific concepts. Stanley Falkow, often referred to as the ‘Father of Molecular Microbial Pathogenesis’, made many groundbreaking contributions to this field by addressing almost all important bacterial pathogens. Pascale Cossart, who could be called in analogy the ‘Queen of Modern Molecular Microbial Pathogenesis’ by combining the Microbiology and Cell Biology, concentrates in her similarly impressive scientific work essentially on a single bacterial species which she studied and still studies in great depth: the facultative intracellular bacterial pathogen Listeria monocytogenes—and the vast majority of her most prominent publications deals with this pathogen in almost all facets. It is certainly not an exaggeration to say that she together with her co-workers and collaborators developed this model bacterium into a paradigm among the intracellular bacterial pathogens.     

The Organization of Slave Raids in Dulotic Ants — a Comparative Study (Hymenoptera; Formicidae)

Slavemaking occurs in 8 genera or ants belonging to 2 subfamilies. Their raiding behaviour is described and compared. The basic organisation of a raid comprises scouting, recruitment, fight, and brood transportation. These elements can ordinarily be derived from the behaviour of the independent host species. Certain trends in the evolution of recruitment and fighting behaviour are discussed. “Intraspecific slavery”, which has been described by various authors, probably belongs to territorial behaviour. We doubt whether it represents an evolutionary precursor of true, interspecific slavery.     

Pollenanalytische Untersuchungen über die Fichtenwälder des Bayerischen Waldes

Ohne ZusammenfassungMit 11 Textabbildungen.     

How meiotic cells deal with non-exchange chromosomes

The chromosomes which segregate in anaphase I of meiosis are usually physically bound together through chiasmata. This association is necessary for proper segregation, since univalents sort independently from one another in the first meiotic division and this frequently leads to genetically unbalanced offspring. There are, however, a number of species where genetic exchanges in the form of meiotic cross-overs, the prerequisite of the formation of chiasmata, are routinely missing in one sex or between specific chromosomes. These species nevertheless manage to segregate these non-exchange chromosomes. There are four direct modes for associating achiasmatic chromosomes: (a) modified SC, (b) adhesion of chromatids comparable to somatic pairing, (c) ‘stickiness’ of heterochromatin or (d) specific ‘segregation bodies’, consisting of material structurally different from chromatin. There is also the possibility that the spindlepossibly joining forces with the kinetochores-carries out the faithful segregation of univalents which are not directly physically attached to one another. Finally, amphitelic orientation of univalents in metaphase I and pairing of the chromatids in meiosis II appear to ensure correct segregation as well.