bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of DHA supplementation on digestible starch utilization by rainbow trout
Authors: Tapia-Salazar M. , Bureau W. , Panserat S. , Corraze G. , Bureau D. P.
Published: January 2006

Rainbow trout has a limited ability to utilize digestible carbohydrates efficiently. Trout feeds generally contain high levels of DHA, a fatty acid known to inhibit a number of glycolytic and lipogenic enzymes in animals. A study was conducted to determine whether carbohydrate utilization by rainbow trout might be affected by dietary DHA level. Two low-carbohydrate (<4% digestible carbohydrate) basal diets were formulated to contain 1 (adequate) or 4 (excess)g/100g DHA diet respectively. The two basal diets were diluted with increasing levels of digestible starch (0%, 10%, 20% and 30%, respectively) to produce eight diets. These diets were fed to fish for 12 weeks at 15°C according to a pair-fed protocol that consisted of feeding the same amount of basal diet but different amounts of starch. Live weight, N and lipid gains, hepatic glycogen and plasma glucose values significantly increased, whereas feed efficiency (gain:feed) significantly decreased, with increasing starch intake (P<0·05). The retention efficiency of N (N gain/digestible N intake) improved with starch supplementation but was not affected by DHA level (P>0·05). Starch increased the activity of glucokinase, pyruvate kinase, glucose 6-phosphate dehydrogenase and fatty acid synthase (P<0·05) but did not affect hexokinase and malic enzyme activity. DHA had no effect on growth but increased plasma glucose and reduced carcass lipid and liver glycogen contents (P<0·05). Glycolytic and lipogenic enzymes were not affected by DHA level, except for pyruvate kinase, which was reduced by increasing DHA level. These results suggest only a marginal effect of dietary DHA on the ability of fish to utilize carbohydrate.
Effects of defaunation on fermentation characteristics and biotin balance in an artificial rumen-simulation system (RUSITEC) receiving diets with different amounts and types of cereal
Authors: Abel H. , Schröder B. , Lebzien P. , Flachowsky G.
Published: January 2006

Biotin is required by rumen microbes for efficient fermentation. To evaluate the role of protozoa in ruminal biotin metabolism, five diets composed of grass hay or of grass hay/cereal grain mixtures were supplied to faunated or defaunated RUSITEC fermenters. In the mixed diets, hay was replaced to 33:67 or 67:33 w/w on an air-dried basis by either wheat or maize grain in order to simulate different cellulolytic and amylolytic fermentation conditions. Defaunation increased SCFA production, whereas NH4concentration and the release of CH4were reduced. Biotin input declined when cereal grain was used to replace the hay. With the exception of the high-wheat treatment, defaunated fermenters yielded higher biotin outputs than faunated fermenters. The biotin balance, calculated as the difference between the total biotin output (biotin in the solid residue contained in the nylon bags after fermentation plus the biotin in the effluent) and the biotin input with the feed, was negative for all the dietary treatments apart from fermenters supplied with the high-maize diet. It was less negative or, in the case of the high-maize diets, more positive for defaunated compared with faunated fermenters. It was concluded that, under normal faunated conditions, protozoa directly utilise or indirectly affect the bacterial synthesis and/or utilisation of biotin. With diets of a high fermentation potential, as realised with the high-wheat diet, protozoa prevent the development of a bacterial population that would utilise high or synthesise low amounts of biotin.
Influence of thePhaseolus vulgarisphaseolin level of incorporation, type and thermal treatment on gut characteristics in rats
Authors: Montoya Carlos A. , Lallés Jean-Paul , Beebe Stephen , Montagne Lucile , Souffrant Wolfgang B. , Leterme Pascal
Published: January 2006

Phaseolus vulgarisphaseolin has been shown to stimulate faecal losses of endogenous N in rats. Experiments with purified phaseolin were carried out in rats to test the hypothesis that these losses reflect intestinal disorders. Phaseolin composition varies depending on its constitutive subunits. Therefore, three phaseolin types (S, T, I) were tested. Phaseolin T was incorporated in varying levels (0, 33, 67 or 100% of the dietary protein) as raw material in experiment 1. In experiment 2, the three phaseolin types were incorporated at 50%, with or without previous thermic treatment. Raw casein was the basal protein source and was also heated in experiment 2. Faecal digestibility of phaseolin and gut integrity were evaluated in both experiments. The incorporation level or type of phaseolin had little effect on gross anatomy of gut segments but these factors influenced the weight and pH of fresh contents of the stomach and caecum (P<0·05). Raw phaseolin T incorporated at various levels led to an enlargement of duodenal villi together with a tendency for increased crypt depth in the jejunum (P=0·06). Activities of both alkaline phosphatase in the duodenum and aminopeptidase N in the ileum decreased (P<0·05) after thermal treatment of casein while they increased (P<0·05) for heat-treated phaseolin S and T, respectively. In conclusion, raw phaseolin had no effect on the tissue weight of gut segments and induced limited alterations in the small intestine. Differences due to phaseolin level or type were limited too.
Nutrient-stimulated glucagon-like peptide 1 release after body-weight loss and weight maintenance in human subjects
Authors: Adam Tanja C. M , Lejeune Manuela P. G. M. , Westerterp-Plantenga Margriet S.
Published: January 2006

Glucagon-like peptide 1 (GLP-1) is a peptide hormone that is released in response to nutrient ingestion. Postprandial GLP-1 release has been reported to be attenuated in obese subjects, but reports on the effect of weight loss on GLP-1 are conflicting. The aim of the present study was to clarify the effect of a weight-loss period and a consecutive weight-maintenance period on nutrient-stimulated GLP-1 release in obese subjects. Nutrient-stimulated (standard breakfast; 1·9MJ) GLP-1 release was investigated in thirty-two obese subjects on three occasions: before weight loss (T1) (BMI 30·0 (sd 2·5) kg/m2); after a 6-week very-low-energy diet (VLED) (T2) (BMI 27·6 (sd 2·3) kg/m2); after a 3-month weight-maintenance period (T3) (BMI 27·9 (sd 2·3) kg/m2). At each occasion, following a fasting blood sample the test meal was fed and blood was drawn every 30min for 2h relative to ingestion in order to determine plasma GLP-1, insulin, glucose and NEFA concentrations. Subjects lost 7 (sd 3·4) kg during the VLED (P<0·0001) and regained 1 (sd 3·2) kg during the weight-maintenance period (NS). The area under the curve for nutrient-stimulated plasma GLP-1 (pmol/l×h) was significantly decreased (P=0·01) at T2 (6·8 (sd 1)) compared with T1 (12·8 (sd 2·9)) and T3 (11·1 (sd 1·5)). Since we found a rebound of concentrations after a weight-maintenance period, decrease after weight loss seems to be transient and possibly due to a negative energy balance.
Is reversal of endothelial dysfunction by tea related to flavonoid metabolism?
Authors: Hodgson Jonathan M. , Puddey Ian B. , Burke Valerie , Croft Kevin D.
Published: January 2006

Dietary flavonoids can improve endothelial function, but the response varies between individuals. Wide variability is also seen in flavonoid O-methylation, a major pathway of flavonoid metabolism. The O-methylation of flavonoids could alter activity, and thus influence any effect on endothelial function. The objective of the current analysis was to investigate whether variability in the endothelial function response to ingestion of tea, a rich source of flavonoids, is related to the degree of O-methylation of flavonoids. This relationship was investigated in two studies in which endothelium-dependent flow-mediated dilatation (FMD) of the brachial artery was assessed and urinary 4-O-methylgallic acid (4OMGA) excretion was used as a marker of the O-methylation of tea-derived flavonoids. In the first study, amongst participants consuming five cups of tea per day for 4 weeks, the degree of increase in 4OMGA excretion was inversely associated with the change in FMD responses (r −078, p=0·008). In the second study, there was a significant difference in the FMD responses to acute ingestion of three cups of tea between individuals with a low (median) 4OMGA response (1·94 (sem 0·79) % and −0·25 (sem 0·53) %, respectively; p=0·03). That is, any improvement in FMD following ingestion of tea may be enhanced in individuals who O-methylate less of the absorbed flavonoids. The present results are consistent with the suggestion that differences in flavonoid metabolism may influence their effect on endothelial function. Thus, differences in flavonoid metabolism could be related to the level of benefit of dietary flavonoids on the risk of CVD.
Relationship between nutritional habits adopted by ulcerative colitis relevant to cancer development patients at clinical remission stages and molecular-genetic parameters
Authors: Rosman-Urbach Maya , Niv Yaron , Birk Yehudith , Morgenstern Sara , Schwartz Betty
Published: January 2006

UC (ulcerative colitis) patients have an increased risk of developing colorectal cancer compared with the normal population. The cause underlying this higher risk is not fully defined but includes nutritional and environmental factors concomitant with genetic alterations. We aimed to evaluate genetic stability in the colonic tissue of UC patients in clinical remission compared with the healthy population, and to establish a possible correlation between nutritional habits and these molecular assessments. UC patients (n 42) and healthy controls (n 37) participated in the study. All participants were histopathologically and medically diagnosed. Participants completed five separate 7d dietary records, food-frequency questionnaires and validated 24h recalls for nutritional assessment. The extent of chromosome 17 loss and the calculated chromosome index was determined in colon tissue biopsies by fluorescence in situ hybridisation. Correlations between the molecular and nutritional assessments were performed using Pearson's correlation coefficients. Significant differences in the nutritional intake of total fat (65 (SD 15) v. 89 (SD 25) g), cholesterol (330 (SD 168) v. 464 (SD 177) mg), dietary fibre (32 (SD 4·7) v. 9 (SD 4) g), vitamin A (1009 (SD 209) v. 506 (SD 204) μg), vitamin C (308 (SD 108) v. 72 (SD 53) mg) and folic acid (412 (SD 89 μg) v. 187 (SD 107)) were recorded for UC patients compared with controls. Significant correlations were found for the consumption of different food groups and the chromosome index for chromosome 17. The results of our study suggest that the nutritional habits adopted by UC patients during clinical remission may affect key cellular components of the colonic tissue, inducing a high degree of aneuploidy and genetic instability, and probably affecting the development of colon cancer.
Docosahexaenoic acid enhances the antioxidant response of human fibroblasts by upregulating γ-glutamyl-cysteinyl ligase and glutathione reductase
Authors: Arab Khelifa , Rossary Adrien , Flourié Françoise , Tourneur Yves , Steghens Jean-Paul
Published: January 2006

The chemopreventive effects of dietaryn-3 PUFA in various pathologies has so far remained controversial, and we were interested in studying their potential influence on cell redox status. DHA (22:6n-3), a typical highly unsaturatedn-3 PUFA, was used at 30µmol/l in a model of human fibroblast cell culture. A dose–response effect, roughly linear, was checked for DHA between 0 and 60µmol/l, and was accompanied by a large increase in intracellular GSH content. A time course study of this effect shows that, after a short fall, as soon as 4h after the beginning of the experiment, the large increase in the GSH content was associated with elevated catalytic activities of γ-glutamyl-cysteinyl ligase, glutathione reductase and glutathioneS-transferase. This coordinated response is characteristic of an antioxidant response and was confirmed by the induction of expression of mRNA for γ-glutamyl-cysteinyl ligase, glutathione reductase and haem-oxygenase. This large increase in the GSH content contributes to decreasing the reactive oxygen species level, as assessed by the decreased accumulation of dichlorofluorescein inside cells. To our knowledge, this is the first report on a specific and potent effect of DHA for decreasing the oxidative stress of human fibroblasts.
SUMOylation of the Corepressor N-CoR Modulates Its Capacity to Repress Transcription
Authors: Tiefenbach Jens , Novac Natalia , Ducasse Miryam , Eck Maresa , Melchior Frauke , Heinzel Thorsten
Published: January 2006

In the absence of ligands the corepressor N-CoR mediates transcriptional repression by some nuclear hormone receptors. Several protein–protein interactions of N-CoR are known, of which mainly complex formation with histone deacetylases (HDACs) leads to the repression of target genes. On the other hand, the role of posttranslational modifications in corepressor function is not well established. Here, we show that N-CoR is modified by Sumo-1. We found SUMO-E2–conjugating enzyme Ubc9 and SUMO-E3 ligase Pias1 as novel N-CoR interaction partners. The SANT1 domain of N-CoR was found to mediate this interaction. We show that K152, K1117, and K1330 of N-CoR can be conjugated to SUMO and that mutation of all sites is necessary to fully block SUMOylation in vitro. Because these lysine residues are located within repression domains I and III, respectively, we investigated a possible correlation between the functions of the repression domains and SUMOylation. Coexpression of Ubc9 protein resulted in enhanced N-CoR–dependent transcriptional repression. Studies using SUMOylation-deficient N-CoR RDI mutants suggest that SUMO modification contributes to repression by N-CoR. Mutation of K152 to R in RD1, for example, not only significantly reduced repression of a reporter gene, but also abolished the effect of Ubc9 on transcriptional repression.
Rab1 Defines a Novel Pathway Connecting the Pre-Golgi Intermediate Compartment with the Cell Periphery
Authors: Sannerud Ragna , Marie Michaël , Nizak Clément , Dale Hege Avsnes , Pernet-Gallay Karin , Perez Franck , Goud Bruno , Saraste Jaakko
Published: January 2006

The function of the pre-Golgi intermediate compartment (IC) and its relationship with the endoplasmic reticulum (ER) and Golgi remain only partially understood. Here, we report striking segregation of IC domains in polarized PC12 cells that develop neurite-like processes. Differentiation involves expansion of the IC and movement of Rab1-containing tubules to the growth cones of the neurites, whereas p58- and COPI-positive IC elements, like rough ER and Golgi, remain in the cell body. Exclusion of Rab1 effectors p115 and GM130 from the neurites further indicated that the centrifugal, Rab1-mediated pathway has functions that are not directly related to ER-to-Golgi trafficking. Disassembly of COPI coats did not affect this pathway but resulted in missorting of p58 to the neurites. Live cell imaging showed that green fluorescent protein (GFP)–Rab1A-containing IC elements move bidirectionally both within the neurites and cell bodies, interconnecting different ER exit sites and the cis-Golgi region. Moreover, in nonpolarized cells GFP-Rab1A-positive tubules moved centrifugally towards the cell cortex. Hydroxymethylglutaryl-CoA reductase, the key enzyme of cholesterol biosynthesis, colocalized with slowly sedimenting, Rab1-enriched membranes when the IC subdomains were separated by velocity sedimentation. These results reveal a novel pathway directly connecting the IC with the cell periphery and suggest that this Rab1-mediated pathway is linked to the dynamics of smooth ER.
A Genetic Dissection of Aip1p's Interactions Leads to a Model for Aip1p-Cofilin Cooperative Activities
Authors: Clark Michael G. , Teply Joseph , Haarer Brian K. , Viggiano Susan C. , Sept David , Amberg David C.
Published: January 2006

Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal β-propeller and a secondary actin binding site lies in a comparable location on its C-terminal β-propeller. Random mutagenesis followed by screening for separation of function mutants led to the identification of several mutants specifically defective for interacting with cofilin but still able to interact with actin. These mutants suggested that cofilin binds across the cleft between the two propeller domains, leaving the actin binding sites exposed and flanking the cofilin binding site. Biochemical, genetic, and cell biological analyses confirmed that the actin binding- and cofilin binding-specific mutants are functionally defective, whereas the genetic analyses further suggested a role for Aip1p in an early, internalization step of endocytosis. A complementary, unbiased molecular modeling approach was used to derive putative structures for the Aip1p-cofilin complex, the most stable of which is completely consistent with the mutagenesis data. We theorize that Aip1p-severing activity may involve simultaneous binding to two actin subunits with cofilin wedged between the two actin binding sites of the N- and C-terminal propeller domains.
CD99 Acts as an Oncosuppressor in Osteosarcoma
Authors: Manara Maria Cristina , Bernard Ghislaine , Lollini Pier-Luigi , Nanni Patrizia , Zuntini Monia , Landuzzi Lorena , Benini Stefania , Lattanzi Giovanna , Sciandra Marika , Serra Massimo , Colombo Mario Paolo , Bernard Alain , Picci Piero , Scotlandi Katia
Published: January 2006

CD99 was recently reported to be under control of the osteoblast-specific transcription factor Cbfa1 (RUNX2) in osteoblasts, suggesting a role in the phato-physiology of these cells. No extensive information is available on the role(s) of this molecule in malignant phenotype, and osteosarcoma, in particular, has never been studied. We report that in 11 different cell lines and 17 clinical samples CD99 expression is either undetectable or very low. Being expressed in the normal counterpart, we tested the hypothesis that CD99 down-regulation may have a role in osteosarcoma development and progression. CD99-forced expression in two osteosarcoma cell lines significantly reduced resistance to anoikis, inhibited growth in anchorage independence as well as cell migration, and led to abrogation of tumorigenic and metastatic ability. Therefore, the molecule acts as a potent suppressor of malignancy in osteosarcoma. CD99 gene transfection induces caveolin-1 up-regulation and the two molecules were found to colocalize on the cell surface. Treatment with antisense oligonucleotides to caveolin-1 abrogates the effects of CD99 on migration. The findings point to an antioncogenic role for CD99 in osteosarcoma, likely through the regulation of caveolin-1 and inhibition of c-Src kinase activity.
THE EFFECTS OF GOVERNMENT‐MANDATED FAMILY LEAVE ON EMPLOYER FAMILY LEAVE POLICIES
Authors: BAUM CHARLES L.
Published: January 2006

The 1993 Family and Medical Leave Act (FMLA) guarantees employees 12 weeks of unpaid leave. However, studies find either small or insignificant effects of the legislation on employment, work, leave‐taking, and wages. Perhaps employees are unable to use the leave because it is unpaid or they do not need family leave because they already may take off work via vacation, sick leave, and disability leave policies. If so, then family leave legislation may have increased employer‐provided family leave without corresponding effects on employment‐related outcomes. This article examines family leave legislation's effects on employers' family leave policies, finding positive effects. (JEL J1, J2, J3)
No‐Fault Divorce and the Compression of Marriage Ages
Authors: Allen Douglas W. , Pendakur Krishna , Suen Wing
Published: January 2006

We examine how no‐fault divorce law affects the age at first marriage, when everyone has a different value of marriage. The heterogeneity of individual values implies an unambiguous negative effect on the variance of marriage age. We test this hypothesis with marriage records from 1970 to 1995. Controlling for state‐level heterogeneity and for time trends, the standard deviation of the log age at first marriage drops by approximately 5% with the introduction of no‐fault divorce. We find that the mean age at first marriage increases slightly, suggesting that the mean person is slightly worse off with no‐fault divorce. (JEL K0, D1)
The International Constitutional Order
Authors: Wet Erika De
Published: January 2006

Constitutionalism is a deeply contested but indispensable symbolic and normative frame for thinking about the problems of viable and legitimate regulation of the complexily overlapping political communities of a post-Westphalian world.1
The Eu Asylum Qualification Directive, Its Impact on the Jurisprudence of the United Kingdom And International Law
Authors: Lambert HéLène
Published: January 2006

The new legal order in European asylum is being shaped by a key document: the Directive on minimum standards for the qualification and status of third-country nationals as refugees and persons otherwise in need of international protection and the content of the protection granted (hereinafter the Qualification Directive). The Qualification Directive was adopted by the Council of the European Union on 29 April 2004.2 It entered into force on 20 October 2004, that is 20 days after its publication in the Official Journal.3 The Member States have until 10 October 2006 to implement its provisions into national legislation.4 Meanwhile, they have a duty not to adopt measures contrary to it.5 For those countries that have already implemented the Qualification Directive, such as France,6 the judiciary will need to ensure compliance with it.7
Mitigation of Damage: A French Perspective
Authors: Le Pautremat Solène
Published: January 2006

‘Nothing ventured, everything gained!’ is an apt summary of the position recently adopted by the French Cour de Cassation towards the subject of mitigation of loss. In two seminal judgments of 19 June 2003,1 the French supreme court2 explicitly rejected the introduction of a general principle of mitigation in the French law of tort, thereby departing from the solutions reached in England and other neighbouring legal systems.
Experimental shift in hosts' acceptance threshold of inaccurate-mimic brood parasite eggs
Authors: Hauber Márk E , Moskát Csaba , Bán Miklós
Published: January 2006

Hosts are expected to evolve resistance strategies that efficiently detect and resist exposure to virulent parasites and pathogens. When recognition is not error-proof, the acceptance threshold used by hosts to recognize parasites should be context dependent and become more restrictive with increasing predictability of parasitism. Here, we demonstrate that decisions of great reed warblersAcrocephalus arundinaceusto reject parasitism by the common cuckooCuculus canorusvary adaptively within a single egg-laying bout. Hosts typically accept one of their own eggs with experimentally added spots and the background colour left visible. In contrast, hosts reject such spotted eggs when individuals had been previously exposed to and rejected one of their own eggs whose background colour had been entirely masked. These results support patterns of adaptive modulation of antiparasitic strategies through shifts in the acceptance threshold of hosts and suggest a critical role for experience in the discrimination decisions between inaccurate-mimic parasite eggs and hosts' own eggs.
Electromagnetic self-adaptive surfaces with shielded external support system
Authors: Arnaut Luk R
Published: January 2006

We analyse the electromagnetic (EM) characteristics of a self-adaptive material (SAM) surface whose support system is shielded from the SAM array by a perfectly conducting ground plane. This configuration enables subarrays consisting of EM sensors and actuators to be completely separated from the control unit, active components, beamformers, power hybrids and wiring harness. The radiation characteristics, spectral-domain Green dyadic function and array impedance are obtained in closed form, based on image theory. It is shown that the performance of a previously studied free-standing implementation can be achieved with the present implementation in a more practical manner. Numerical examples are given to illustrate the analytical results. An equivalent circuit representation is developed for a single sensor/actuator pair that takes all conductive and radiated EM interactions in this pair into account. The results find application in the design and operation of fully EM ‘intelligent’ surfaces, ‘smart’ antennas, and as novel active absorbing EM boundary conditions in computational electromagnetics.
Dynamic fibre sliding along debonded, frictional interfaces
Authors: Yang Q.D , Rosakis A , Cox B.N
Published: January 2006

The problem is considered of a fibre that is driven dynamically, by compression at one end, into a matrix. The fibre is not initially bonded to the matrix, so that its motion is resisted solely by friction. Prior work based on simplified models has shown that the combination of inertial effects and friction acting over long domains of the fibre–matrix interface gives rise to behaviour that is far more complex than in the well-known static loading problem. The front velocity may depart significantly from the bar wave speed and regimes of slip, slip/stick and reverse slip can exist for different material choices and loading rates. Here more realistic numerical simulations and detailed observations of dynamic displacement fields in a model push-in experiment are used to seek more complete understanding of the problem. The prior results are at least partly confirmed, especially the ability of simple shear-lag theory to predict front velocities and gross features of the deformation. Some other fundamental aspects are newly revealed, including oscillations in the interface stresses during loading; and suggestions of unstable, possibly chaotic interface conditions during unloading. Consideration of the experiments and two different orders of model suggest that the tentatively characterized chaotic phenomena may arise because of the essential nonlinearity of friction, that the shear traction changes discontinuously with the sense of the motion, rather than being associated with the details of the constitutive law that is assumed for the friction. This contrasts with recent understanding of instability and ill-posedness at interfaces loaded uniformly in time, where the nature of the assumed friction law dominates the outcome.
An underwater shock simulator
Authors: Deshpande V.S , Heaver A , Fleck N.A
Published: January 2006

An underwater shock simulator has been developed for the underwater shock loading of materials and test structures within the laboratory. The tube is struck at one end by a steel projectile, with the test structure placed at the opposite end of the tube. Realistic exponentially decaying pressure pulses are generated in the water with peak pressures in the range 15–70 MPa and decay times ranging from 0.1 to 1.5 ms. The peak pressure and the pulse duration are independently adjusted by varying the projectile velocity and mass, respectively. The underwater shock simulator is used to investigate the one-dimensional fluid–structure interaction of sandwich plates with steel face sheets and an aluminium foam core. The degree of core compression is measured as a function of both the underwater shock impulse and the Taylor fluid–structure interaction parameter. Fully coupled finite element simulations agree well with the measurements while decoupling the fluid–structure interaction phase from the core compression phase within the finite element analysis leads to an under-prediction of the degree of core compression.
Boundary layers in a dilute particle suspension
Authors: Foster M.R , Duck P.W , Hewitt R.E
Published: January 2006

The general problem of a boundary-layer flow carrying a dilute, mono-disperse suspension of small particles (together with gravitational effects) is considered. The problem is modelled using the ‘dusty-gas’ equations, which are a coupled equation set linking the fluid motion to that of the particle motion (both of which are modelled as continua). A number of qualitatively distinct potential scenarios are predicted. These include a variety of boundary-layer breakdowns, and the formation of shock transitions in the distribution of the particulate phase (together with the development of particle-free zones). Numerical results predicting these differing behaviours are confirmed through local asymptotic analyses of the governing equations. Although we consider a general class of boundary layer, our results are compared and contrasted with previous studies of specific cases, most notably the constant freestream fluid velocity case (akin to the ‘clean’ Blasius boundary layer). In the case of a boundary-layer flow driven by a linearly retarding free stream (the analogue of the classical ‘Howarth’ boundary-layer problem), the effects of the particle phase are surprisingly seen to (slightly) delay the separation of the boundary layer.
Mesoscale bounds in finite elasticity and thermoelasticity of random composites
Authors: Khisaeva Z.F , Ostoja-Starzewski M
Published: January 2006

Under consideration is the problem of size and response of the Representative Volume Element (RVE) in the setting of finite elasticity of statistically homogeneous and ergodic random microstructures. Through the application of variational principles, a scale dependent hierarchy of strain energy functions (i.e. mesoscale bounds) is derived for the effective strain energy function of the RVE. In order to account for thermoelastic effects, the variational principles are first generalized, and then analogous bounds on the effective thermoelastic response are derived. It is also shown that, in contradiction to results obtained for random linear composites, the hierarchy on the effective strain energy function in nonlinear elasticity cannot be split into volumetric and isochoric terms, while the hierarchy on the effective free energy function cannot be divided into purely mechanical and thermal contributions.
The Haantjes tensor and double waves for multi-dimensional systems of hydrodynamic type: a necessary condition for integrability
Authors: Ferapontov E.V , Khusnutdinova K.R
Published: January 2006

An invariant differential-geometric approach to the integrability of (2+1)-dimensional systems of hydrodynamic type,

is developed. We prove that the existence of special solutions known as ‘double waves’ is equivalent to the diagonalizability of an arbitrary matrix of the two-parameter family

Since the diagonalizability can be effectively verified by calculating the Haantjes tensor, this provides a simple necessary condition for integrability.
A scaling law for properties of nano-structured materials
Authors: Wang J , Duan H.L , Huang Z.P , Karihaloo B.L
Published: January 2006

In this brief communication, we identify intrinsic length scales of several physical properties at the nano-scale and show that, for nano-structures whose characteristic sizes are much larger than these scales, the properties obey a simple scaling law. The underlying cause of the size-dependence of these properties at the nano-scale is the competition between surface and bulk energies. This law provides a yardstick for checking the accuracy of experimentally measured or numerically computed properties of nano-structured materials over a broad size range and can thus help replace repeated and exhaustive testing by one or a few tests.
The greater than twofold cost of integration for retroviruses
Authors: Krakauer David C , Sasaki Akira
Published: January 2006

Sexual reproduction, typically conceived of as a puzzling feature of eukaryotes, has posed an extraordinary evolutionary challenge in terms of the twofold replicative advantage of asexual over sexual organisms. Here we show mathematically that a greater than twofold cost is paid by retroviruses such as HIV during reverse transcription. For a retrovirus, replication is achieved through RNA reverse transcription and the effectively linear growth processes of DNA transcription during gene expression. Retroviruses are unique among viruses in that they show an alternation of generations between a diploid free living phase and a haploid integrated phase. Retroviruses engage in extensive recombination during the synthesis of the haploid DNA provirus. Whereas reverse transcription generates large amounts of sequence variation, DNA transcription is a high-fidelity process. Retroviruses come under strong selection pressures from immune systems to generate escape mutants, and reverse transcription into the haploid DNA phase serves to generate diversity followed by a phase of transcriptional clonal expansion during the restoration of diploidy from a stable, long lived, DNA encoded provirus.
The introgression of a functional nuclear gene from
Poa
to
Festuca ovina
Authors: Ghatnekar Lena , Jaarola Maarit , Bengtsson Bengt O
Published: January 2006

In sheep's fescue,
Festuca ovina
, genes coding for the cytosolic enzyme phosphoglucose isomerase, PGIC, are not only found at the standard locus,
PgiC1
, but also at a segregating second locus,
PgiC2
. We have used PCR-based sequencing to characterize the molecular structure and evolution of five
PgiC1
and three
PgiC2
alleles in
F. ovina
. The three
PgiC2
alleles were complex in that they carried two gene copies: either two active genes or one active and one pseudogene. All the
PgiC2
sequences were very similar to each other but highly diverged from the five
PgiC1
sequences. We also sequenced
PgiC
genes from several other grass species. Phylogenetic analysis of these sequences indicates that
PgiC2
has introgressed into
F. ovina
from the distant genus
Poa
. Such an introgression may, for example, follow from a non-standard fertilization with more than one pollen grain, or a direct horizontal gene transfer mediated by a plant virus.
Evidence for adaptive male mate choice in the fruit fly
Drosophila melanogaster
Authors: Byrne Phillip G , Rice William R
Published: January 2006

Theory predicts that males will benefit when they bias their mating effort towards females of higher reproductive potential, and that this discrimination will increase as males become more resource limited. We conducted a series of experiments to test these predictions in a laboratory population of the fruitfly,
Drosophila melanogaster
. In this species, courtship and copulation have significant costs to males, and females vary greatly in fecundity, which is positively associated with body size. When given a simultaneous choice between small and large virgin females, males preferentially mated with larger, more fecund, females. Moreover, after males had recently mated they showed a stronger preference for larger females. These results suggest that male
D. melanogaster
adaptively allocate their mating effort in response to variation in female quality and provide some of the first support for the theoretical prediction that male stringency in mate choice increases as resources become more limiting.
Temperature-dependent transmission and latency ofHolospora undulata, a micronucleus-specific parasite of the ciliateParamecium caudatum
Authors: Fels Daniel , Kaltz Oliver
Published: January 2006

Transmission of parasites to new hosts crucially depends on the timing of production of transmission stages and their capacity to start an infection. These parameters may be influenced by genetic factors, but also by the environment. We tested the effects of temperature and host genotype on infection probability and latency in experimental populations of the ciliateParamecium caudatum, after exposure to infectious forms of its bacterial parasiteHolospora undulata. Temperature had a significant effect on the expression of genetic variation for transmission and maintenance of infection. Overall, low temperature (10 °C) increased levels of (multiple) infection, but arrested parasite development; higher temperatures (23 and 30 °C) accelerated the onset of production of infectious forms, but limited transmission success. Viability of infectious forms declined rapidly at 23 and 30 °C, thereby narrowing the time window for transmission. Thus, environmental conditions can generate trade-offs between transmission relevant parameters and alter levels of multiple infection or parasite-mediated selection, which may affect evolutionary trajectories of parasite life history or virulence.
Phylogenetic and ecological determinants of the neotropical dawn chorus
Authors: Berg Karl S , Brumfield Robb T , Apanius Victor
Published: January 2006

The concentration of avian song at first light (i.e. the dawn chorus) is widely appreciated, but has an enigmatic functional significance. One widely accepted explanation is that birds are active at dawn, but light levels are not yet adequate for foraging. In forest communities, the onset to singing should thus be predictable from the species' foraging strata, which is ultimately related to ambient light level. To test this, we collected data from a tropical forest of Ecuador involving 57 species from 27 families of birds. Time of first song was a repeatable, species-specific trait, and the majority of resident birds, including non-passerines, sang in the dawn chorus. For passerine birds, foraging height was the best predictor of time of first song, with canopy birds singing earlier than birds foraging closer to the forest floor. A weak and opposite result was observed for non-passerines. For passerine birds, eye size also predicted time of first song, with larger eyed birds singing earlier, after controlling for body mass, taxonomic group and foraging height. This is the first comparative study of the dawn chorus in the Neotropics, and it provides the first evidence for foraging strata as the primary determinant of scheduling participation in the dawn chorus of birds.
Outbreeding selects for spiteful cytoplasmic elements
Authors: Engelstädter Jan , Charlat Sylvain
Published: January 2006

In addition to their nuclear genome, the vast majority of eukaryotes harbour cytoplasmic genomes, e.g. in mitochondria or chloroplasts. In the majority of cases, these cytoplasmic genomes are transmitted maternally only, leading to selective pressures divergent from those that act on nuclear genes. In particular, cytoplasmic genes, which reduce the fitness of males that carry them, but have no fitness effect in females, are believed to be selectively neutral. Here, we go a step further and argue that in outbreeding populations (i.e. populations with inbreeding avoidance), ‘spiteful’ cytoplasmic elements that reduce the number of offspring produced by males are in fact selected for. We study this process by means of a stochastic model, analysing both the probability of spread and the impact that such a spiteful cytotype can have on population dynamics. Our results demonstrate that the probability of spread of the spiteful cytotype can be several times higher in outbreeding than in panmictic populations. Spread and fixation of the spiteful cytotype can lead to different qualitative effects on the population dynamics, including extinction, decreased or increased stable population size. We discuss our results in respect to cytoplasmically induced male infertility and cytoplasmic incompatibility.
Phenotypic plasticity in the scaling of avian basal metabolic rate
Authors: McKechnie Andrew E , Freckleton Robert P , Jetz Walter
Published: January 2006

Many birds exhibit short-term, reversible adjustments in basal metabolic rate (BMR), but the overall contribution of phenotypic plasticity to avian metabolic diversity remains unclear. The available BMR data include estimates from birds living in natural environments and captive-raised birds in more homogenous, artificial environments. All previous analyses of interspecific variation in BMR have pooled these data. We hypothesized that phenotypic plasticity is an important contributor to interspecific variation in avian BMR, and that captive-raised populations exhibit general differences in BMR compared to wild-caught populations. We tested this hypothesis by fitting general linear models to BMR data for 231 bird species, using the generalized least-squares approach to correct for phylogenetic relatedness when necessary. The scaling exponent relating BMR to body mass in captive-raised birds (0.670) was significantly shallower than in wild-caught birds (0.744). The differences in metabolic scaling between captive-raised and wild-caught birds persisted when migratory tendency and habitat aridity were controlled for. Our results reveal that phenotypic plasticity is a major contributor to avian interspecific metabolic variation. The finding that metabolic scaling in birds is partly determined by environmental factors provides further support for models that predict variation in scaling exponents, such as the allometric cascade model.
Dual degradation signals control Gli protein stability and tumor formation
Authors: Huntzicker Erik G. , Estay Ivette S. , Zhen Hanson , Lokteva Ludmila A. , Jackson Peter K. , Oro Anthony E.
Published: January 2006

Regulated protein destruction controls many key cellular processes with aberrant regulation increasingly found during carcinogenesis. Gli proteins mediate the transcriptional effects of the Sonic hedgehog pathway, which is implicated in up to 25% of human tumors. Here we show that Gli is rapidly destroyed by the proteasome and that mouse basal cell carcinoma induction correlates with Gli protein accumulation. We identify two independent destruction signals in Gli1, DN and DC, and show that removal of these signals stabilizes Gli1 protein and rapidly accelerates tumor formation in transgenic animals. These data argue that control of Gli protein accumulation underlies tumorigenesis and suggest a new avenue for antitumor therapy.
Implications of a simple mathematical model to cancer cell population dynamics
Authors: Garner A. L. , Lau Y. Y. , Jordan D. W. , Uhler M. D. , Gilgenbach R. M.
Published: January 2006

Abstract.  Recent research in cancer progression and treatment indicates that many forms of cancer arise from the development of a small subpopulation of abnormal cancer stem cells (CSCs) that promote cancer growth and spread. Many potential treatments preferentially interact with cells at certain stages of the cell cycle by either selective killing or halting the cell cycle, such as intense, nanosecond‐duration pulsed electric fields (nsPEFs). Simple mathematical models of unfed cancer cell populations at the plateau of their growth characteristics may estimate the long‐term consequences of these treatments on proliferating and quiescent cell populations. Applying such a model with no transition from the quiescent to proliferating state shows that it is possible for the proliferating cell population to fall below 1 if the quiescent cell population obtains a sufficient competitive advantage with respect to nutrient consumption and/or survival rate. Introducing small, realistic transition rates did not appreciably alter short‐term or long‐term population behaviour, indicating that the predicted small cell population behaviour (< 1 cell) is not an artefact of the simpler model. Experimental observations of nsPEF‐induced effects on the cell cycle suggest that such a model may serve as a first step in assessing the viability of a given cancer treatment in vitro prior to clinical application.
The tumour necrosis factor (TNF)‐α−308GA promoter polymorphism is related to prenatal growth and postnatal insulin resistance
Authors: Casano‐Sancho Paula , López‐Bermejo Abel , Fernández‐Real José Manuel , Monrós Eugènia , Valls Carme , Rodríguez‐González Francesc‐Xavier , Ricart Wifredo , Ibáñez Lourdes
Published: January 2006

Objective Variation in the tumour necrosis factor gene, (TNF) has been associated with insulin resistance traits. We questioned whether the TNF−308G/A polymorphism is associated with birthweight and insulin resistance in children born small for gestational age (SGA), a patient population known to be at risk for insulin resistance.

Design A cross‐sectional, hospital‐based study assessing insulin sensitivity in SGA children.

Patients One hundred and ninety‐eight school‐age children born either SGA (n = 90, age 7·4 ± 4·5 years) or appropriate for gestational age (AGA, n = 108, age 8·7 ± 4·0 years).

Measurements All children were genotyped for the TNF−308G/A polymorphism; a biochemical profile was also performed in prepubertal SGA (n = 58) and AGA (n = 57) subjects.

Results Genotype frequencies for the TNF−308G/A single nucleotide polymorphisms (SNPs) (GG and GA/AA) differed between SGA and AGA children (86%vs. 72% and 14%vs. 28%, respectively; P = 0·025). The GG genotype was associated with lower birthweight and birth length (2747·0 ± 23·3 g vs. 2851·0 ± 45·7 g, P = 0·045, and 47·0 ± 0·2 cm vs. 48·2 ± 0·4 cm, P = 0·011, respectively) and, in AGA but not in SGA children, with higher systolic blood pressure [103·3 (95% confidence interval (CI) 96·4–110·2) mmHg vs. 92·8 (84·9–100·7) mmHg; P = 0·028], higher blood glucose [4·8 (4·7–5·0) mmol/l vs. 4·5 (4·3–4·8) mmol/l; P = 0·042] and higher homeostasis model assessment for insulin resistance (HOMA‐IR) index [1·4 (1·1–1·7) vs. 0·9 (0·4–1·3); P = 0·005]. In multivariate analysis, the TNF−308GG genotype was an independent predictor of HOMA‐IR during childhood, explaining 8% of its variance.

Conclusion SGA children show increased frequency of the TNF−308G allele, an allele that is associated with prenatal growth and with postnatal insulin resistance. The TNF−308G/A polymorphism may have implications in the growth and metabolic abnormalities that characterise SGA children.