Structure of an HIF-1alpha -pVHL complex: hydroxyproline recognition in signaling

The ubiquitination of the hypoxia-inducible factor (HIF) by the von Hippel-Lindau tumor suppressor (pVHL) plays a central role in the cellular response to changes in oxygen availability. pVHL binds to HIF only when a conserved proline in HIF is hydroxylated, a modification that is oxygen-dependent. The 1.85 angstrom structure of a 20-residue HIF-1alpha peptide-pVHL-ElonginB-ElonginC complex shows that HIF-1alpha binds to pVHL in an extended beta strand-like conformation. The hydroxyproline inserts into a gap in the pVHL hydrophobic core, at a site that is a hotspot for tumorigenic mutations, with its 4-hydroxyl group recognized by buried serine and histidine residues. Although the beta sheet-like interactions contribute to the stability of the complex, the hydroxyproline contacts are central to the strict specificity characteristic of signaling.     

School food environments and the obesity issue: content,structural determinants,and agency in Canadian high schools

To understand the phenomenon of the rapidly increasing prevalence of overweight and obese children and youth, it is especially important to examine the school food environment, the role of structural factors in shaping this environment, and the resulting nutrition and health outcomes. The paper examines research on school food environments in the US and Canada. It notes evidence of widespread availability of poor nutrition products in both environments and delineates reasons for the situation, and examines initiatives presently being undertaken in a number of jurisdictions in both countries to encourage healthy eating in schools. Empirical data are presented from a pilot study of high schools in the Canadian province of Ontario. The study documents the extent of student purchasing of nutrient-poor foods and beverages, and the structural factors internal and external to the school that appear responsible for the availability of such products in food environments in this critical institutional sphere. The paper also examines positive local initiatives in high schools that seek to encourage healthy eating in schools.

Taste nerve fibers: a random distribution of sensitivities to four tastes

The numbers of rat glossopharyngeal and chorda tympani fibers responding to one, two, three, or four taste stimuli of different quality (sodium chloride, hydrochloric acid, quinine, and sucrose) and to each of the six possible pairs of these stimuli can be predicted if there are four independent sensitivities randomly distributed among innervating fibers.     

Action spectra for phase shifts of a circadian rhythm in Drosophila

Action spectra were determined for lightinduced phase shifts of the circadian rhythm of adult emergence in Drosophila pseudoobscura. The action spectra for advance and delay phase shifts are similar; the most effective wavelengths are in the blue region, with a sharp cutoff above 500 nanometers. This similarity suggests that the same photoreceptive pigment mediates both advance and delay phase shifts.     

The illusion of control: industrialized agriculture,nature, and food safety

I explore the role of nature in the agrifood system and how attempts to fit food production into a large-scale manufacturing model has lead to widespread outbreaks of food borne illness. I illustrate how industrial processing of leafy greens is related to the outbreak of E. coli 0157:H7 associated with spinach in the fall of 2006. I also use this example to show how industry attempts to create the illusion of control while failing to address weaknesses in current processing systems. The leafy greens industry has focused efforts on sterilizing the growing environment and adopting new technologies, while neglecting to change the concentrated structure of processing systems. Repeated breakdowns in these systems illustrate a widening fault line between attempted and failed control of nature in industrial food production.

Intestinal calcium transport: stimulation by low phosphorus diets

Rats maintained on a low phosphorus diet supplemented with 25-hydroxyvitamin D(3) show high intestinal calcium transport activity as compared to rats similarly treated but fed a diet containing adequate phosphorus. This increased transport activity is correlated with an increased biosynthesis of 1,25-dihydroxyvitamin D(3), the probable metabolically active form of the vitamin in the intestine.