Extranuclear recombination in Aspergillus nidulans: closely-linked multiple chloramphenicol- and oligomycin-resistance loci.

Summary A nuclear, chloramphenicol-sensitive mutant cas-1 has been isolated which is cross sensitive to a number of drugs, including oligomycin and cycloheximide. Approximately one-third of the chloramphenicol-resistant mutants isolated from mutagenized conidia of this strain were found to be extranuclear, and exhibited a variety of phenotypes. One of these mutants, designated (camB51), was slow growing on drug-free medium and recombined at low frequency with the previously described mutant (camA112) (Gunatilleke et al., 1975).The majority of extranuclear oligomycin-resistant mutants isolated from cas-1 were indistinguishable from (oliA1) (Rowlands and Turner, 1973). Two mutants, (oliB322) and (oliB332), with similar but not identical phenotypes to (oliA1), recombined with the latter at low frequency but not with each other, thus representing a new class of extranuclear mutants.     

The role of activity in anticipating and confronting stressful situations.

This paper is an analytical review of studies comparing stress reactions in threatening situations during which the person can or cannot take action. The studies reviewed were conducted mainly in real-life situations and involved diverse forms of coping activities under various conditions of danger and distress. To achieve a better understanding of the effect of activity on stress reactions, several distinctions are made: between various types of stress reactions; between various indices and measurements of stress reactions; between activity which is directly related to the source of threat and activity which is not; and between various personality dimensions. The adaptive potential of activity in stressful situations is discussed in terms of: the sense of mastery and control provided by activity; activity as a means of attention diversion; and activity as a means of discharging energy generated by mobilization. It is suggested that taking action under stressful conditions, as opposed to remaining passive, is a powerful coping tool.     

THE POLLINATION ECOLOGY OF DELPHINIUM TRICORNE (RANUNCUL ACEAE)

The pollination ecology of Delphinium tricorne, a spring-ephemeral herb of eastern deciduous forests, was studied at eight sites in the Ohio River basin from West Virginia to southern Illinois. The plant was found to be obligately dependent for its pollination on queen bumblebees (Bombus Latr. spp.) and hummingbirds, to which the flowers are closely adapted in form, color, function, and blooming phenology. Other bees, including Anthophora ursina, Osmia bucephala, Ptilothrix bombiformis, and Xylocopa virginica; Lepidoptera, including Amphion nessus, Danaus plexippus, Epargyreus clams, Erynnis juvenalis, Hemaris thysbe, Papilio glaucus, P. philenor, P. troilus, Poanes zabulon, Vanessa atalanta, and V. cardui; and the beefly Bombylius major foraged for nectar and/or pollen on the flowers without pollinating them. Techniques employed in the study included insect exclosures to test fertility of plants in the absence of pollinators, analysis of floral colors by reflectance spectrophotometry and ultraviolet photography, analysis of pollinator behavior by cinematography and close-range stereophotography, collection and identification of visitors to flowers, and identification of pollen types carried by foragers on the flowers.     

Cupin: A candidate molecular structure for the Nep1-like protein family

Background  

NEP1-like proteins (NLPs) are a novel family of microbial elicitors of plant necrosis. Some NLPs induce a hypersensitive-like response in dicot plants though the basis for this response remains unclear. In addition, the spatial structure and the role of these highly conserved proteins are not known.     

Increased secretion of type beta transforming growth factor accompanies viral transformation of cells.

Cells transformed by Harvey or Moloney sarcoma virus secrete at least 40 times as much type beta transforming growth factor as their respective untransformed control cells. The transformed cells bind only 20 to 50% as much type beta transforming growth factor as the control cells, suggesting that transformation causes down-regulation of the type beta transforming growth factor receptor.     

The effects of luteinizing hormone, oestrogen and ovariectomy on the agonistic behaviour of female Quelea quelea

Previous work with male Quelea showed that agonistic behaviour in relation to individual distance is controlled by luteinizing hormone (LH), rather than by testosterone, and that males are more aggressive than females. Experiments with female groups are reported which show that: (a) LH injections increase aggressive encounter frequency; (b) ovariectomy in the breeding season (but not outside it) also increases encounter frequency; and (c) oestrogen injections decrease encounter frequency. The effects of LH were shown to be specific to agonistic responses rather than mediated through changes in activity. Correlations between changes in natural hormone levels and encounter frequency support the injection findings. These results are consistent with the hypothesis that LH controls aggressive encounters over individual distance in the female as in the male and that oestrogenic inhibition of this LH-mediated aggressiveness is a cause of female subordination and the lower encounter frequency found in female groups. The annual cycle of encounter frequency is described and the significance of different systems of hormonal control is discussed.