Detection in vivo of protein-DNA interactions within the lac operon of Escherichia coli

Studies of the sequence-specific binding of proteins to DNA have so far relied on in vitro experiments using cloned restriction fragments containing the relevant DNA sequences. We have applied the genomic sequencing technique of Church and Gilbert to show that the interactions observed in vitro occur in vivo. We use this approach to study the binding of regulatory proteins to the lac operon in vivo and detect changes in the reactivity (inhibition or enhancement) of guanines to methylation by dimethyl sulphate caused by the proximity of proteins to the N-7 atom of these guanines. We can detect the simultaneous binding of the catobolite gene activator protein (CAP) and the Lac repressor to their specific recognition sequences, and following induction of the lac operon we observe effects that are related to RNA polymerase binding or RNA elongation. We have successfully used oligonucleotide probes as short as 17 bases to display genomic sequence.     

Hyperprolactinemia and estrogen-induced rhythms in LH and prolactin release in the ovariectomized rat

Short-term (9 days) hyperprolactinemia induced by pituitary grafts reduced basal plasma LH levels in ovariectomized rats whereas long-term (31 days) grafts increased basal LH levels. Although long-term grafts inhibited estradiol-induced prolactin surges, hyperprolactinemia had no effect on the LH surge. It is concluded that the estrogen-treated ovariectomized rat is not suitable for studying the effects of hyperprolactinemia on LH release.     

Negative phototaxis inDrosophila associated with a morphological change in the compound eye

Summary The ultrastructure of the compound eyes of several photonegative selection lines and their unselected photopositive controls of five species of themelanogaster subgroup was analyzed. A qualitative phenotypic change concerning the rhabdomeres in one of the photonegative selection lines ofD. mauritiana could be detected. It was proved that this structural aberration of the rhabdomeres is caused by a parallel mutation of the mutantora (outer rhabdomeres absent) ofD. melanogaster.     

Thiarubrine A, a bioactive constituent of Aspilia (Asteraceae) consumed by wild chimpanzees

Two African species of Aspilia (Asteraceae), which are used medicinally by man and which are eaten by wild chimpanzees in an unusual manner, were found to contain the potent antibiotic thiarubrine A as a major leaf phytochemical. Its presence in leaf material strengthens the view that the feeding behavior of wild chimpanzees is related to special physiological or pharmacological effects on the animals.     

Role of active oxygen species in diethyldithiocarbamate-induced gastric ulcer in the rat

Diethyldithiocarbamate, an inhibitor of Cu,Zn-superoxide dismutase, was recently found to be ulcerogenic in the rat stomach, and active oxygen species were found to be responsible for its ulcerogenicity. To clarify which active oxygen species play a role in ulcerogenesis, the effects of various scavengers and iron-chelators were studied. As superoxide dismutase and catalase reduced the ulcerogenesis induced by diethyldithiocarbamate, the superoxide radical and hydrogen peroxide were considered to play a pathogenic role in this ulcer model.