Chemical and physical analyses of wax ester properties

Wax esters are major constituents of the surface lipids in many terrestrial arthropods, but their study is complicated by their diversity. We developed a procedure for quantifying isomers in mixtures of straight-chain saturated and unsaturated wax esters having the same molecular weights, using single-ion monitoring of the total ion current data from gas chromatography-mass spectrometry. We examined the biological consequences of structural differences by measuring the melting temperatures, T(m), of >60 synthetic wax esters, containing 26–48 carbon atoms. Compounds containing saturated alcohol and acid moieties melted at 38–73°C. The main factor affecting T(m) was the total chain length of the wax ester, but the placement of the ester bond also affected T(m). Insertion of a double bond into either the alcohol or acid moiety decreased T(m) by ∼30°C. Simple mixtures of wax esters with n-alkanes melted several °C lower than predicted from the melting points of the component lipids. Our results indicate that the wax esters of primary alcohols that are most typically found on the cuticle of terrestrial arthropods occur in a solid state under physiological conditions, thereby conferring greater waterproofing. Wax esters of secondary alcohols, which occur on melanopline grasshoppers, melted >60°C below primary esters of the same molecular weight and reduced T(m) of the total surface lipids to environmental values

Institutional history as an element of community history : Civilian Conservation Corps in the Okanogan country

Gerald W. Williams Collectio

Starvation Resistance is Associated with Developmentally Specified Changes in Sleep, Feeding and Metabolic Rate

Food shortage represents a primary challenge to survival, and animals have adapted diverse developmental, physiological and behavioral strategies to survive when food becomes unavailable. Starvation resistance is strongly influenced by ecological and evolutionary history, yet the genetic basis for the evolution of starvation resistance remains poorly understood. The fruit fly Drosophila melanogaster provides a powerful model for leveraging experimental evolution to investigate traits associated with starvation resistance. While control populations only live a few days without food, selection for starvation resistance results in populations that can survive weeks. We have previously shown that selection for starvation resistance results in increased sleep and reduced feeding in adult flies. Here, we investigate the ontogeny of starvation resistance-associated behavioral and metabolic phenotypes in these experimentally selected flies. We found that selection for starvation resistance resulted in delayed development and a reduction in metabolic rate in larvae that persisted into adulthood, suggesting that these traits may allow for the accumulation of energy stores and an increase in body size within these selected populations. In addition, we found that larval sleep was largely unaffected by starvation selection and that feeding increased during the late larval stages, suggesting that experimental evolution for starvation resistance produces developmentally specified changes in behavioral regulation. Together, these findings reveal a critical role for development in the evolution of starvation resistance and indicate that selection can selectively influence behavior during defined developmental time points

The Effect of Selection for Desiccation Resistance on Cold Tolerance of Drosophila Melanogaster

Low Temperature and Desiccation Stress Are Thought to Be Mechanistically Similar in Insects, and Several Studies Indicate that There is a Degree of Cross-Tolerance between Them, such that Increased Cold Tolerance Results in Greater Desiccation Tolerance and Vice Versa. This Assertion is Tested at an Evolutionary Scale by Examining Basal Cold Tolerance, Rapid Cold-Hardening (RCH) and Chill Coma Recovery in Replicate Populations of Drosophila Melanogaster Selected for Desiccation Resistance (With Controls for Both Selection and Concomitant Starvation) for over 50 Generations. All of the Populations Display a RCH Response, and There is No Effect of Selection Regime on RCH or Basal Cold Tolerance, Although There Are Differences in Basal Cold Tolerance between Sampling Dates, Apparently Related to Inter-Individual Variation in Development Time. Flies Selected for Desiccation Tolerance Recover from Chill Coma Slightly, But Significantly, Faster Than Control and Starvation-Control Flies. These Findings Provide Little Support for Cross-Tolerance between Survival of Near-Lethal Cold and Desiccation Stress in D. Melanogaster. © 2007 the Authors

Matter-wave bistability in coupled atom-molecule quantum gases

We study the matter-wave bistability in coupled atom-molecule quantum gases, in which heteronuclear molecules are created via an interspecies Feshbach resonance involving either two-species Bose or two-species Fermi atoms at zero temperature. We show that the resonant two-channel Bose model is equivalent to the nondegenerate parametric down-conversion in quantum optics, while the corresponding Fermi model can be mapped to a quantum optics model that describes a single-mode laser field interacting with an ensemble of inhomogeneously broadened two-level atoms. Using these analogy and the fact that both models are subject to the Kerr nonlinearity due to the two-body s-wave collisions, we show that under proper conditions, the population in the molecular state in both models can be made to change with the Feshbach detuning in a bistable fashion.Comment: 6 pages, 5 figure

Role of ecdysone signaling in fat body remodeling

Climate change is fundamentally connected to animal development and survival, and the life history of an organism must be coordinated with predictable seasonal changes of the environment. Climate change affects the life cycle of plants, a major food source for insects. If photoperiod, the primary environmental queue that insects utilize to determine the proper emergence time, and food availability becomes out of sync, many populations of insects and other animals could be threatened. Understanding animal development can provide insight into this issue and could provide clues that may help the scientific community predict how insect populations may respond to climate change. During Drosophila metamorphosis, most of the larval tissues are destroyed, but the fat body is an exception. The larval fat body escapes destruction and is instead remodeled from flat, polygonal and attached sheets of cells to round, spherical and detached free-floating cells (Nelliot, et. al, 2006). It has been hypothesized that Ecdysone signaling is necessary for fat cell detachment. To test the hypothesis that Ecdysone signaling is necessary for fat cell detachment, I am using genetic techniques to create mosaic animals. These techniques will allow me to generate clones of cells that are deficient or hyperactive in certain Ecdysone signaling targets. Currently, I am trying to establish animals for the first part of a two-step cross. Next, using the FLP/FRT and the Mosaic Analysis with a Repressible Cell Marker system (MARCM), I will generate mitotic clones of cells. These clones will be comprised of small populations of cells mutant for Ecdysone signaling factors and will be surrounded by normal (wild type) cells. I predict that the populations which are deficient in Ecdysone signaling factors will not undergo fat body remodeling while the surrounding pools of wild type cells will complete the remodeling program. These two types of cells can be distinguished from each other because I will also label the Ecdysone signaling-defective cells with green fluorescent protein. The data will be procured on the Confocal Microscope in the Center for Biological Imaging

Expression of Thor does not increase desiccation resistance in Drosophila melanogaster

Using microarray analysis of Drosophila melanogaster, the Gibbs lab has identified several hundred candidate genes that may be involved in desiccation resistance. One of these genes is Thor, an important downstream target of the TOR/insulin signaling pathway. Preliminary results confirm that Thor plays a role in desiccation resistance. Further research will be needed to verify these results and understand the mechanism by which Thor increases desiccation resistance. This research will also serve as a proof-of-principle for testing microarray-derived hypotheses. A previous microarray analysis found evidence that down-regulation of protein synthesis might be a cellular response to desiccation through the up-regulation of Thor. When Drosophila melanogaster adult males are exposed to desiccation, Thor expression increases 6.5-fold. Thor codes for the D. melanogaster 4Ebinding protein (4E-BP), which inhibits translation by binding to the eukaryotic initiation factor 4E (eIF-4E). Thus, a reduction in protein synthesis might function to reduce energy expenditures during desiccation. To test whether THOR plays a role in the response to desiccation, we measured desiccation resistance in flies with altered Thor expression. We measured desiccation resistance in flies with Thor expression reduced through P-element mutagenesis (Thork13517 and Thor2) and RNA interference (RNAi). Using the GAL4/UAS system (Brand and Perrimon, 1993), desiccation resistance was also measured in flies with increased expression of wild-type Thor and constitutively-active Thor (4EBP( AA)). We found that Thor hypomorph mutant males (Thork13517) are desiccation sensitive. However, we found no difference in desiccation sensitivity between Thor null mutants (Thor2) and control flies (Thor1rv1). Knocking down expression of Thor with RNAi increased desiccation sensitivity. However, desiccation resistance did not increase in male flies that over-expressed Thor or a constitutively-active Thor (4E-BP(AA)) using the GAL4/UAS system. These mixed results do not support the hypothesis that Thor expression increases desiccation resistance

Synchrotron X-Ray Visualisation of Ice Formation in Insects during Lethal and Non-Lethal Freezing

Although the biochemical correlates of freeze tolerance in insects are becoming well-known, the process of ice formation in vivo is subject to speculation. We used synchrotron x-rays to directly visualise real-time ice formation at 3.3 Hz in intact insects. We observed freezing in diapausing 3rd instar larvae of Chymomyza amoena (Diptera: Drosophilidae), which survive freezing if it occurs above −14°C, and non-diapausing 3rd instar larvae of C. amoena and Drosophila melanogaster (Diptera: Drosophilidae), neither of which survive freezing. Freezing was readily observed in all larvae, and on one occasion the gut was seen to freeze separately from the haemocoel. There were no apparent qualitative differences in ice formation between freeze tolerant and non-freeze tolerant larvae. The time to complete freezing was positively related to temperature of nucleation (supercooling point, SCP), and SCP declined with decreasing body size, although this relationship was less strong in diapausing C. amoena. Nucleation generally occurred at a contact point with the thermocouple or chamber wall in non-diapausing larvae, but at random in diapausing larvae, suggesting that the latter have some control over ice nucleation. There were no apparent differences between freeze tolerant and non-freeze tolerant larvae in tracheal displacement or distension of the body during freezing, although there was markedly more distension in D. melanogaster than in C. amoena regardless of diapause state. We conclude that although control of ice nucleation appears to be important in freeze tolerant individuals, the physical ice formation process itself does not differ among larvae that can and cannot survive freezing. This suggests that a focus on cellular and biochemical mechanisms is appropriate and may reveal the primary adaptations allowing freeze tolerance in insects

On the Approach to the Equilibrium and the Equilibrium Properties of a Glass-Forming Model

In this note we apply some theoretical predictions that arise in the mean field framework for a large class of infinite range models to structural glasses and we present a first comparison of these predictions with numerical results.Comment: 22 pages, 15 figure

A Screen for Sleep and Starvation Resistance Identifies a Wake-Promoting Role for the Auxiliary Channel UNC79

The regulation of sleep and metabolism are highly interconnected, and dysregulation of sleep is linked to metabolic diseases that include obesity, diabetes, and heart disease. Furthermore, both acute and long-term changes in diet potently impact sleep duration and quality. To identify novel factors that modulate interactions between sleep and metabolic state, we performed a genetic screen for their roles in regulating sleep duration, starvation resistance, and starvation-dependent modulation of sleep. This screen identified a number of genes with potential roles in regulating sleep, metabolism, or both processes. One such gene encodes the auxiliary ion channel UNC79, which was implicated in both the regulation of sleep and starvation resistance. Genetic knockdown or mutation of unc79 results in flies with increased sleep duration, as well as increased starvation resistance. Previous findings have shown that unc79 is required in pacemaker for 24-hours circadian rhythms. Here, we find that unc79 functions in the mushroom body, but not pacemaker neurons, to regulate sleep duration and starvation resistance. Together, these findings reveal spatially localized separable functions of unc79 in the regulation of circadian behavior, sleep, and metabolic function