Increased body size confers greater fitness at lower experimental temperature in male Drosophila melanogaster

Genetic variation of body size along latitudinal clines is found globally in Drosophila melanogaster, with larger individuals encountered at higher latitudes. Temperature has been implicated as a selective agent for these clines, because the body size of laboratory populations allowed to evolve in culture at lower temperatures is larger. In this study, we investigated the hypothesis that larger size is favoured at lower temperature through natural selection on adult males. We measured life‐span and age‐specific fertility of males from lines of flies artificially selected for body size at two different experimental temperatures. There was an interaction between experimental temperature and body size selection for male fitness; large‐line males were fitter than controls at both temperatures, but the difference in fitness was greater at the lower experimental temperature. Smaller males did not perform significantly differently from control males at either experimental temperature. The results imply that thermal selection for larger adult males is at least in part responsible for the evolution of larger body size at lower temperatures in this species. The responsible mechanisms require further investigation.     

Relative bioactivities of cholecystokinins-8 and -33 on rat pancreatic acini

The relative potencies of cholecystokinin (CCK-33) and its carboxyl terminal octapeptide (CCK-8) for stimulation of amylase release from rat pancreatic acini was measured. Porcine CCK-33 and synthetic CCK-8 were initially subjected to high pressure liquid chromatography to assess purity. Concentrations of each peptide were determined by amino acid analysis. The relative immunoreactivities of CCK-33 and CCK-8 were compared using an antibody that recognizes the common carboxyl terminus of these forms. This antibody bound CCK-8 and CCK-33 with nearly equal affinity. The relative potencies of CCK-33 and CCK-8 were then measured by comparing their abilities to stimulate amylase release from isolated rat pancreatic acini. Statistical analysis of the relative potencies of the two hormones indicated that CCK-8 was 36% more potent than CCK-33 in this assay system. These data suggest that differences in biological activities between large and small forms of CCK are not as great as previously reported.     

Private Governance, Public Purpose? Assessing Transparency and Accountability in Self-Regulation of Food Advertising to Children

Reducing non-core food advertising to children is an important priority in strategies to address childhood obesity. Public health researchers argue for government intervention on the basis that food industry self-regulation is ineffective; however, the industry contends that the existing voluntary scheme adequately addresses community concerns. This paper examines the operation of two self-regulatory initiatives governing food advertising to children in Australia, in order to determine whether these regulatory processes foster transparent and accountable self-regulation. The paper concludes that while both codes appear to establish transparency and accountability mechanisms, they do not provide for meaningful stakeholder participation in the self-regulatory scheme. Accordingly, food industry self-regulation is unlikely to reflect public health concerns or to be perceived as a legitimate form of governance by external stakeholders. If industry regulation is to remain a feasible alternative to statutory regulation, there is a strong argument for strengthening government oversight and implementing a co-regulatory scheme.     

Purification of Somatostatin from Frog Brain: Coisolation with Retinal Somatostatin-Like Immunoreactivity

Somatostatin-like immunoreactivity (SLI) was purified from frog brain and retina, and the structure of the brain peptide was determined. Frog brain (101 g) and retinal (45 g) tissues were extracted with 3% acetic acid, yielding 9.6 and 0.44 nmol of SLI, respectively. SLI was further purified by chromatography on a somatostatin immunoaffinity column followed by sequential application to reverse-phase C-18 HPLC columns. The brain and retinal peptides, purified roughly 100,000-fold with net yields of 7.5 and 2.3%, respectively, appeared identical in the final steps of purification. The amino acid sequence of brain SLI, as determined by a gas-phase automated Edman degradation technique, was as follows: Ala-Gly-(Cys)-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-Thr-Ser-(Cys). Our data indicate that despite structural variations in somatostatins of other lower vertebrates, the amino acid sequence of frog brain and, by deduction, retinal SLI is identical to that of somatostatin tetradecapeptide. These findings support the physiological relevance of studies directed at elucidating the neurotransmitter function of somatostatin using the well-established models of frog brain and retina.     

Inversion and deletion mutants in Bacillus subtilis bacteriophage SPP1 as a consequence of cloning

Summary Properties of an inversion and a deletion mutant of B. subtilis phage SPP1 which arose during cloning are described. The results are related to the biology of this bacteriophage.In preceding communications from our laboratories (Heilmann and Reeve 1982, Behrens et al. 1983) we reported the properties of genetically engineered SPP1 bacteriophages, which could be used as cloning vehicles in B. subtilis. These phages contain a unique restriction site within a dispensable region of their genomes. In the course of cloning experiments using these phage vectors, we have occasionally observed the appearance of not only the original vector and desired hybrid phages, but also of SPP1 phages which had undergone extensive genomic rearrangements. Properties of two such phages, SPP1 inv1, which was found to contain a large inversion and of SPP1 delV, a deletion mutant, which defines an additional dispensable region of the SPP1 genome, are described in this communication.     

Predation and bark beetle dynamics

Bark beetle populations may undergo dramatic fluctuations and are often important pests in coniferous forests. Their dynamics are thought to be primarily driven by factors affecting the resistance of the host tree to attack, i.e., bottom-up forces, while natural enemies are usually assigned a minor role in these systems. I present behavioral experiments that suggest that the clerid beetle Thanasimus dubius may be an important source of mortality for the bark beetle Dendroctonus frontalis during attack of the host tree, and determine the nature of the functional response of T. dubius under conditions close to natural. I also examine the numerical response of T. dubius to large-scale fluctuations in D. frontalis density, and the relationship between bark beetle population trends and predator density, and find that beetle populations tend to decline when predator densities are high. Combined with the effects of clerid larvae on bark beetle broods, these results suggest that top-down forces generated by natural enemies could also be an important component of bark beetle dynamics. The implications of these results for bark beetle dynamics are discussed in relation to the prolonged life-cycle of clerid beetles. Received: 23 January 1997 / Accepted: 5 April 1997