What distinguishes cosmopolitan and endemicDrosophila species?

Summary CosmopolitanDrosophila species can survive wide ecological tolerances measured by resistance to desiccation/temperature extremes compared with endemic rain forest species. This, rather than any genetic features, is important in helping to explain the widespread distributions of cosmopolitan species.We thank Dr Lee Ehrman for cultures ofD. paulistorum, and the Australian Research Grants Committee for financial support.     

Cooperative tandem binding of met repressor of Escherichia coli

We present biochemical and genetic data to support the hypothesis that the Escherichia coli met repressor, MetJ, binds to synthetic and natural operator sequences in tandem arrays such that repression depends not only on the affinity of the DNA-protein interaction, but also on protein-protein contacts along the tandem array. This represents a novel form of regulatory switch. Furthermore, there seems to be homology between the organization of the met and trp operators.     

Habitat marking: males attracted to residual odors of twoDrosophila species

Summary We have found that males of the sibling speciesD. melanogaster andD. simulans are preferentially attracted to sites marked by the residual odors of conspecific females, especially if non-virgin. In natural populations, this could enhance sexual selection among males, and cause some isolation at the microhabitat level.     

The effects of a substituted sulphamoyl diuretic ‘clopamide’ (DT 327) on insulin release in vitro

Résumé Un diurétique sulphamyl Brinaldix (Clopamide DT327) fut expérimenté pour savoir si on pouvait reproduire in vitro une hypoglycémie observée après injection. L'expérience fut effectuée avec des cellules isolées d'ilots et un radio-immunoessai pour mesurer la libération d'insuline. Différentes concentrations de glucose et de diurétique furent utilisées et ni inhibition ni stimulation ne furent observées dans la libération d'insuline.     

Clindamycin and lincomycin alter miniature endplate current decay.

Antibiotic-induced muscle paralysis has frequently been found in both experimental animals and man with three distinct classes of antibiotic: (1) streptomycin and related aminoglycoside compounds, (2) polymyxins and (3) tetracyclines. Recently lincomycin and its chemical congener, clindamycin, have been reported to produce muscle paralysis which has different characteristics from those seen with other classes of antibiotic. Although closely related in chemical structure, lincomycin and clindamycin also seem to produce muscle paralysis by different mechanisms. Clindamycin is considered to exert a direct depressant action on muscle contractility whereas the action of lincomycin is considered to be primarily a depression of neuromuscular transmission. We report here that each of these antibiotics had a significant but different influence on endplate channel behaviour. Clindamycin increased the rate of miniature endplate current (m.e.p.c.) decay and reduced its voltage sensitivity without altering its exponential nature. Lincomycin split m.e.p.c. decay into an initial rapid phase followed by a prolonged phase.