Flexibility in basal metabolic rate and evaporative water loss among hoopoe larks exposed to different environmental temperatures

The 'energy demand' hypothesis for short-term adjustments in basal metabolic rate (BMR) posits that birds adjust the size of their internal organs relative to food intake, a correlate of energy demand, We tested this hypothesis on hoopoe larks (Alaemon alaudipes), inhabitants of the Arabian desert, by acclimating birds for 3 weeks at 15 degreesC and at 36 degreesC, then measuring their BMR and total evaporative water loss (TEWL), Thereafter, we determined the dry masses of their brain, heart, liver, kidney, stomach, intestine and muscles of the pectoral region. Although mean body mass did not differ initially between the two groups, after 3 weeks, birds in the 15 degreesC group had gained mass (44.1+/-6.5g), whereas larks in the 36 degreesC group had maintained a constant mass (36.6+/-3.6g; means +/- S.D., N=6). Birds in the 15 degreesC group had a mean BMR of 46.8+/-6.9kJday(-1), whereas birds in the 36 degreesC group had a BMR of 32.9+/-6.3kJday(-1), values that were significantly different when we controlled for differences in body mass. When measured at 35 degreesC, larks in the cold-exposure group had a TEWL of 3.55+/-0.60gH(2)Oday(-1), whereas TEWL for birds in the 36 degreesC group averaged 2.23+/-0.28gH(2)Oday(-1), a difference of 59,2%, Mass-independent TEWL differed significantly between groups, Larks in the 15 degreesC group had a significantly larger liver, kidney and intestine than larks in the 36 degreesC group. The total increase in organ mass contributed 14.3 % towards the total mass increment in the cold exposure group, Increased food intake among larks in the cold group apparently resulted in enlargement of some of the internal organs, and the increase in mass of these organs required a higher rate of oxygen uptake to support them. As oxygen demands increased, larks apparently lost more evaporative water, but the relationship between increases in BMR and TEWL remains unresolved

Another Sogdian-Chinese bilingual epitaph

AbstractTwo stone tablets in the Wangye Museum, Shenzhen, contain a bilingual Sogdian and Chinese epitaph for a Sogdian merchant and his wife, who lived in the northern Chinese city of Ye 鄴 in the late sixth centuryce. The two texts are published here for the first time and accompanied by a detailed commentary on philological and historical points of interest.</jats:p

Efficient Mixing at low Reynolds numbers using polymer additives

Mixing in fluids is a rapidly developing field of fluid mechanics \cite{Sreen,Shr,War}, being an important industrial and environmental problem. The mixing of liquids at low Reynolds numbers is usually quite weak in simple flows, and it requires special devices to be efficient. Recently, the problem of mixing was solved analytically for a simple case of random flow, known as the Batchelor regime \cite{Bat,Kraich,Fal,Sig,Fouxon}. Here we demonstrate experimentally that very viscous liquids at low Reynolds number, $Re$. Here we show that very viscous liquids containing a small amount of high molecular weight polymers can be mixed quite efficiently at very low Reynolds numbers, for a simple flow in a curved channel. A polymer concentration of only 0.001% suffices. The presence of the polymers leads to an elastic instability \cite{LMS} and to irregular flow \cite{Ours}, with velocity spectra corresponding to the Batchelor regime \cite{Bat,Kraich,Fal,Sig,Fouxon}. Our detailed observations of the mixing in this regime enable us to confirm sevearl important theoretical predictions: the probability distributions of the concentration exhibit exponential tails \cite{Fal,Fouxon}, moments of the distribution decay exponentially along the flow \cite{Fouxon}, and the spatial correlation function of concentration decays logarithmically.Comment: 11 pages, 5 figure

Lorentz Invariance Violation in Modified Gravity

We consider an environmentally dependent violation of Lorentz invariance in scalar-tensor models of modified gravity where General Relativity is retrieved locally thanks to a screening mechanism. We find that fermions have a modified dispersion relation and would go faster than light in an anisotropic and space-dependent way along the scalar field lines of force. Phenomenologically, these models are tightly restricted by the amount of Cerenkov radiation emitted by the superluminal particles, a constraint which is only satisfied by chameleons. Measuring the speed of neutrinos emitted radially from the surface of the earth and observed on the other side of the earth would probe the scalar field profile of modified gravity models in dense environments. We argue that the test of the equivalence principle provided by the Lunar ranging experiment implies that a deviation from the speed of light, for natural values of the coupling scale between the scalar field and fermions, would be below detectable levels, unless gravity is modified by camouflaged chameleons where the field normalisation is environmentally dependent.Comment: 8 pages, extended discussio

Physiological adjustments to arid and mesic environments in larks (Alaudidae)

Because deserts are characterized by low food availability, high ambient temperature extremes, and absence of drinking water, one might expect that birds that live in these conditions exhibit a lower basal metabolic rate ( BMR), reduced total evaporative water loss (TEWL), and greater ability to cope with high air temperatures than their mesic counterparts. To minimize confounding effects of phylogeny, we compared the physiological performance of four species of larks at ambient temperatures (T-a's) ranging from 0degrees to 50degreesC: hoopoe larks (Alaemon alaudipes) and Dunn's larks ( Eremalauda dunni) live in hot and dry deserts, whereas skylarks (Alauda arvensis) and woodlarks (Lullula arborea) occur in temperate mesic areas. Mass-adjusted BMR and TEWL were indistinguishable between hoopoe lark and Dunn's lark and between skylark and woodlark. When grouping the data of the two desert larks in one set and the data of the two mesic larks in another, desert larks are shown to have 43% lower BMR levels and 27% lower TEWL values than the mesic species. Their body temperatures (T-b's) were 1.1degreesC lower, and the minimal dry heat transfer coefficients ( h) were 26% below values for the mesic larks. When T a exceeded T-b, the h of hoopoe larks and Dunn's larks was high and indistinguishable from h at 40 degreesC, in contrast to the prediction that h should be decreased to minimize heat gain through conductance, convection, or radiation from the environment when T-a exceeds T-b

A plasma membrane template for macropinocytic cups

Macropinocytosis is a fundamental mechanism that allows cells to take up extracellular liquid into large vesicles. It critically depends on the formation of a ring of protrusive actin beneath the plasma membrane, which develops into the macropinocytic cup. We show that macropinocytic cups in Dictyostelium are organised around coincident intense patches of PIP3, active Ras and active Rac. These signalling patches are invariably associated with a ring of active SCAR/WAVE at their periphery, as are all examined structures based on PIP3 patches, including phagocytic cups and basal waves. Patch formation does not depend on the enclosing F-actin ring, and patches become enlarged when the RasGAP NF1 is mutated, showing that Ras plays an instructive role. New macropinocytic cups predominantly form by splitting from existing ones. We propose that cup-shaped plasma membrane structures form from self-organizing patches of active Ras/PIP3, which recruit a ring of actin nucleators to their periphery

Voltage-gated Na+ Channel Activity Increases Colon Cancer Transcriptional Activity and Invasion Via Persistent MAPK Signaling

Functional expression of voltage-gated Na+ channels (VGSCs) has been demonstrated in multiple cancer cell types where channel activity induces invasive activity. The signaling mechanisms by which VGSCs promote oncogenesis remain poorly understood. We explored the signal transduction process critical to VGSC-mediated invasion on the basis of reports linking channel activity to gene expression changes in excitable cells. Coincidentally, many genes transcriptionally regulated by the SCN5A isoform in colon cancer have an over-representation of cis-acting sites for transcription factors phosphorylated by ERK1/2 MAPK. We hypothesized that VGSC activity promotes MAPK activation to induce transcriptional changes in invasion-related genes. Using pharmacological inhibitors/activators and siRNA-mediated gene knockdowns, we correlated channel activity with Rap1-dependent persistent MAPK activation in the SW620 human colon cancer cell line. We further demonstrated that VGSC activity induces downstream changes in invasion-related gene expression via a PKA/ERK/c-JUN/ELK-1/ETS-1 transcriptional pathway. This is the first study illustrating a molecular mechanism linking functional activity of VGSCs to transcriptional activation of invasion-related genes

Physiological responses of Houbara bustards to high ambient temperatures

Desert birds often experience a scarcity of drinking water and food and must survive episodes of high ambient temperature (T-a). The physiological mechanisms that promote survival during extended periods of high T-a have received little attention. We investigated the physiological responses of wild-caught and captive-reared Houbara bustards, Chlamydotis macqueenii, to Ta values ranging from below 0 degreesC to 55 degreesC, well above those in most previous studies of birds. Captive-reared Houbara bustards (mass 1245 +/- 242 g, N = 7, mean +/- S.D.) in summer have a resting metabolic rate (RMR) of 261.4 kJ day(-1), 26% below allometric predictions, and a total evaporative water loss (TEWL) at 25 degreesC of 25.8 g day(-1), 31% below predictions. When T-a exceeded body temperature (T-b), the dry heat transfer coefficient decreased, a finding supporting the prediction that birds should minimize dry heat gain from the environment at high T-a values. Houbara bustards withstand high T-a values without becoming hyperthermic; at 45 degreesC, T-b was on average 0.9 degreesC higher than at 25 degreesC. RMR and TEWL of captive-bred Houbara bustards were 23% and 46% higher in winter than in summer, respectively. Captive-reared Houbara bustards had a 17% lower RMR and a 28% lower TEWL than wild-born birds with similar genetic backgrounds. Differences in body composition between wild-caught and captive-reared birds were correlated with differences in physiological performance

Environmental proxies of antigen exposure explain variation in immune investment better than indices of pace of life.

Investment in immune defences is predicted to covary with a variety of ecologically and evolutionarily relevant axes, with pace of life and environmental antigen exposure being two examples. These axes may themselves covary directly or inversely, and such relationships can lead to conflicting predictions regarding immune investment. If pace of life shapes immune investment then, following life history theory, slow-living, arid zone and tropical species should invest more in immunity than fast-living temperate species. Alternatively, if antigen exposure drives immune investment, then species in antigen-rich tropical and temperate environments are predicted to exhibit higher immune indices than species from antigen-poor arid locations. To test these contrasting predictions we investigated how variation in pace of life and antigen exposure influence immune investment in related lark species (Alaudidae) with differing life histories and predicted risks of exposure to environmental microbes and parasites. We used clutch size and total number of eggs laid per year as indicators of pace of life, and aridity, and the climatic variables that influence aridity, as correlates of antigen abundance. We quantified immune investment by measuring four indices of innate immunity. Pace of life explained little of the variation in immune investment, and only one immune measure correlated significantly with pace of life, but not in the predicted direction. Conversely, aridity, our proxy for environmental antigen exposure, was predictive of immune investment, and larks in more mesic environments had higher immune indices than those living in arid, low-risk locations. Our study suggests that abiotic environmental variables with strong ties to environmental antigen exposure can be important correlates of immunological variation.Financial support came from the Schure-Beijerinck-Poppings Fonds (to NPCH and AH), BirdLife Netherlands (to BIT), NSF grant IBN 0212587 (to JBW), and VENI and VIDI grants from the Netherlands Organisation for Scientific Research (to KDM and BIT).This is the accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007%2Fs00442-014-3136-y