bluuebunny/crossref_metadata_2025 huggingface dataset:
Crack Growth in Soda–Lime–Silicate Glass near the Static Fatigue Limit
Authors: Wiederhorn Sheldon M. , Dretzke Achim , Rödel Jürgen
Published: February 2007

The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda–lime–silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water. Cracks were first propagated at a stress intensity factor above the crack growth threshold and then arrested for 16 h at a stress intensity factor below the threshold. The stress intensity factor was then raised to reinitiate crack growth. The cycle was repeated multiple times, varying the hold stress intensity factor, the hold time, and the propagation stress intensity factor. Examination of the fracture surface by optical microscopy showed surface features that marked the points of crack arrest during the hold time. These features were identical to those reported earlier by Michalske in a similar study of crack arrest. A study with the AFM showed these features to be a consequence of a bifurcation of the crack surface. During the hold period, waviness developed along the crack front so that parts of the front propagated out of the original fracture plane, while other parts propagated into the plane. Crack growth changed from the original flat plane to a bifurcated surface with directions of as much as 3° to 5° to the original plane. This modification of crack growth behavior cannot be explained by a variation in the far‐field stresses applied to the crack. Nor can the crack growth features be explained by chemical fluctuations within the glass. We speculate that changes in crack growth direction are a consequence of an enhancement in the corrosion rate on the flank of the crack at stresses below the apparent crack growth threshold in a manner described recently by Chuang and Fuller.
Thermal Shock Behavior of Silicon Oxycarbide Foams
Authors: Colombo Paolo , Hellmann John R. , Shelleman David L.
Published: February 2007

Silicon oxycarbide (SiOC) ceramic foams, obtained from the pyrolysis of a preceramic polymer, were subjected to thermal multiple cycles from 800°–1200°C to room temperature in a water bath. Flexural and compression strengths, as well as elastic modulus, were characterized before and after quenching. Excellent thermal shock and cycling resistance behavior was observed, with only moderate strength and stiffness degradation. The phase assemblage of the foam remained unchanged, and no crack formation in the foams was observed. However, microstructural characterization revealed the development of porosity in the struts and cell walls due to the oxidation of residual carbon in the amorphous SiOC material, thereby contributing to a small decrease in stiffness after quenching.
Cation Ordering in Pb(Mg1/3Nb2/3)O3–Pb(Sc1/2Nb1/2)O3 (PMN–PSN) Solid Solutions
Authors: Farber Leon , Valant Matjaz , Akbas Mehmet Ali , Davies Peter K.
Published: February 2007

Extended thermal annealing treatments were used to modify the B‐site cation order in the (1 −x)PMN–xPSN perovskite system (where PMN is lead magnesium niobate, Pb(Mg1/3Nb2/3)O3, and PSN is lead scandium niobate, Pb(Sc1/2Nb1/2)O3). Extensive 1:1 ordering could be induced in compositions with x≥ 0.1. The substitution of PSN into PMN produced a large increase in the thermal stability of the 1:1 ordered phase, with the maximum disordering temperature of ∼1360°C being observed for the x= 0.5 composition. By monitoring the change in the degree of order with temperature, the order–disorder boundary for the PMN–PSN system was established and the transition temperature for pure PMN was estimated to be ∼950°C. The changes in stability across the system were consistent with the “random‐site” description of the cation order. The change in enthalpy associated with the ordering was affected by the size difference of the two ordered cation sites and by the size and charge mismatch of the metal cations that occupy the random‐ site position.
Inhibition of Sintering and Surface Area Loss in Phosphorus‐Doped Corundum Derived from Diaspore
Authors: Smith Richard L. , Yanina Svetlana V. , Rohrer Gregory S. , Perrotta Anthony J.
Published: February 2007

The influence of magnesium, phosphorus, and iron additions on the low‐temperature (≤1000°C) sintering of nanocrystalline α‐Al2O3 derived from α‐AlOOH has been investigated. α‐AlOOH powder with a surface area of 50 m2/g yielded α‐Al2O3 products with surface areas of 150 and 80 m2/g after dehydration at temperatures of 400° and 500°C, respectively. However, these products were prone to sintering at >600°C, and the surface area was reduced to 15 m2/g within only 1 h at 1000°C. Although magnesium and iron doping had no discernible effect, the presence of phosphorus inhibited sintering and surface‐area loss significantly. Samples doped with 1%–2% phosphorus had surface areas of >31 m2/g after 100 h at 1000°C. Atomic force microscopy studies of α‐Al2O3 pseudomorphs derived from α‐AlOOH single crystals also demonstrated the inhibiting effect of phosphorus, as the rate of crack elimination was reduced on phosphorus‐modified surfaces. The effects of the dopants are discussed with regard to their potential influence on α‐Al2O3 surface energy and diffusivity.
Segregation Effects at Grain Boundaries in Fluorite‐Structured Ceramics
Authors: Lei Yuanyuan , Ito Yasuo , Browning Nigel D. , Mazanec Terry J.
Published: February 2007

The atomic‐scale structure, composition, and chemistry of grain boundaries in two fluorite‐structured ceramic materials were characterized by a combination of Z‐contrast imaging and electron energy‐loss spectroscopy (EELS). In the case of a symmetric 24° [001] tilt bicrystal of yttria‐stabilized‐zirconia (YSZ), a shift in the zirconium M‐edge onset and a change in the yttrium and zirconium M‐edge ratios at the boundary indicate an increase in the number of electrons in the boundary plane. A detailed study of the structure and composition indicates that this is caused by an increase in the number of oxygen vacancies in the grain boundary core that is partially compensated by yttrium segregation. Studies of grain boundaries in an industrial Gd‐doped ceria ceramic reveals similar changes in vacancy/dopant profiles indicating that these effects may be generic to grain boundaries in fluorite‐structured materials.
Glass‐Reduced SiAlONs with Improved Creep and Oxidation Resistance
Authors: Rosenflanz Anatoly
Published: February 2007

Ceramics containing α‐SiAlON with improved high‐temperature properties such as thermal stability and creep and oxidation resistance were synthesized. The influence of starting composition on the amount of residual grain‐boundary phase has been explored. Results have been interpreted in terms of compatibility phase relationships in the Si3N4–AlN–Al2O3–Re2O3 system and transient evolutions.
Genome‐wide screening of loci associated with drug resistance to 5‐fluorouracil‐based drugs
Authors: Ooyama Akio , Okayama Yoshihiro , Takechi Teiji , Sugimoto Yoshikazu , Oka Toshinori , Fukushima Masakazu
Published: February 2007

Resistance to chemotherapeutic agents represents the chief cause of mortality in cancer patients with advanced disease. Chromosomal aberration and altered gene expression are the main genetic mechanisms of tumor chemoresistance. In this study, we have established an algorithm to calculate DNA copy number using the Affymetrix 10K array, and performed a genome‐wide correlation analysis between DNA copy number and antitumor activity against 5‐fluorouracil (5‐FU)‐based drugs (S‐1, tegafur + uracil [UFT], 5′‐DFUR and capecitabine) to screen for loci influencing drug resistance using 27 human cancer xenografts. A correlation analysis confirmed that the single nuceotide polymorphism (SNP) showing significant associations with drug sensitivity were concentrated in some cytogenetic regions (18p, 17p13.2, 17p12, 11q14.1, 11q11 and 11p11.12), and we identified some genes that have been indicated their relations to drug sensitivity. Among these regions, 18p11.32 at the location of the thymidylate synthase gene (TYMS) was strongly associated with resistance to 5‐FU‐based drugs. A change in copy number of the TYMS gene was reflected in the TYMS expression level, and showed a significant negative correlation with sensitivity against 5‐FU‐based drugs. These results suggest that amplification of the TYMS gene is associated with innate resistance, supporting the possibility that TYMS copy number might be a predictive marker of drug sensitivity to fluoropyrimidines. Further study is necessary to clarify the functional roles of other genes coded in significant cytogenetic regions. These promising data suggest that a comprehensive DNA copy number analysis might aid in the quest for optimal markers of drug response. (Cancer Sci 2007; 98: 577–583)
Substrate choice of membrane‐type 1 matrix metalloproteinase is dictated by tissue inhibitor of metalloproteinase‐2 levels
Authors: Kudo Tomoya , Takino Takahisa , Miyamori Hisashi , Thompson Erik W. , Sato Hiroshi
Published: February 2007

Although tissue inhibitor of metalloproteinase‐2 (TIMP‐2) is known to be not only an inhibitor of matrix metalloproteinases (MMP) but also a cofactor for membrane‐type 1 MMP (MT1‐MMP)‐mediated MMP‐2 activation, it is still unclear how TIMP‐2 regulates MMP‐2 activation and cleavage of substrates by MT1‐MMP. In the present study we examined the levels of cell‐surface MT1‐MMP, MMP‐2 activation and cleavage of MT1‐MMP substrates in 293T cells transfected with the MT1‐MMP and TIMP‐2 genes. Co‐expression of TIMP‐2 at an appropriate level increased the level of cell‐surface MT1‐MMP, both the TIMP‐2‐bound and free forms, and generated processed MMP‐2 with gelatin‐degrading activity. In contrast, MT1‐MMP substrates testican‐1 and syndecan‐1 were cleaved by the cells expressing MT1‐MMP, which was inhibited by TIMP‐2 even at levels that stimulate MMP‐2 activation. These results suggest that TIMP‐2 environment determines MT1‐MMP substrate choice between direct cleavage of its own substrates and MMP‐2 activation. (Cancer Sci 2007; 98: 563–568)
Sources of natural resistance to plant viruses: status and prospects
Authors: MAULE ANDREW J. , CARANTA CAROLE , BOULTON MARGARET I.
Published: February 2007

Globally, virus diseases are common in agricultural crops and have a major agronomic impact. They are countered through the deployment of genetic resistance against the virus, or through the use of a range of farming practices based upon the propagation of virus‐free plant material and the exclusion of the virus vectors from the growing crop. We review here the current status of our knowledge of natural virus resistance genes, and consider the future prospects for the deployment of these genes against virus infection.
Rat salivary gland ligation causes reversible secretory hypofunction
Authors: Carpenter G. H. , Osailan S. M. , Correia P. , Paterson K. P. , Proctor G. B.
Published: February 2007

Aim:  To determine the influence of inflammation on salivary secretion. Secretion by salivary glands involves interactions between nerves, blood vessels and salivary cells. The present study investigated the effects of inflammation on rat submandibular gland function following acute ductal obstruction.

Methods:  Under recovery anaesthesia a metal clip was placed on the main duct of the submandibular gland. After 24 h salivary secretion was evoked by nerve and methacholine stimulation. For recovery experiments the clip was removed after 24 h and the animal left to recover for 3 days when salivary function was again assessed.

Results:  By 24 h of obstruction an inflammatory infiltrate had developed within the obstructed gland and stimulated salivary flows were just 20% of the normal secretion, whilst protein secretion and ion reabsorption were also severely impaired. If ductal obstruction was removed after 24 h the salivary function returned to normal after 3 days of recovery. In vitro analysis of cells from 24‐h ligated glands revealed normal changes in intracellular calcium (the main secondary messenger involved in fluid secretion) in response to methacholine stimulation. Protein secretion from isolated cells indicated some changes in particular to methacholine‐induced protein secretion although a significant protein secretion was still seen in response to isoprenaline – the main stimulus for protein secretion.

Conclusion:  This report demonstrates reversible salivary inhibition associated with an inflammatory infiltrate within the salivary gland.
Large‐scale glaciotectonic‐imbricated thrust sheets on three‐dimensional seismic data: facts or artefacts?
Authors: Rafaelsen Bjarne , Andreassen Karin , Hogstad Kai , Kuilman Luppo W.
Published: February 2007

Imbricate reflections commonly occur in the glacigenic section of seismic profiles from the Bjørnøya Trough. This was the main drainage pathway for fast‐flowing ice‐streams from the former Barents Sea and Scandinavian ice sheets. Industry three‐dimensional (3D) seismic data from the southern flank of the Bjørnøya Trough are used here to investigate these imbricate reflections. Integration of vertical seismic sections with 3D plan view images and attribute maps reveal that imbricate reflections at the SW Barents Sea Margin are mega‐scale sediment blocks with a glacigenic origin. Imbricate reflections in two regions to the east of the survey appear on plan‐view as well‐developed lineations of U‐shaped crescents; however, following detailed analysis of their location, geometry and relation to sailing direction during data acquisition, we can demonstrate that these are seismic artefacts. These artefacts are related to the straight parts of east–west‐trending plough marks on the sea floor, having a dip direction that is directly related to the sailing direction of the ship during seismic acquisition. By analysing both real glacigenic imbrications and false imbrications or artefacts, we are able to demonstrate the critical distinguishing criterion.
Modulation of glucocorticoid metabolism by the growth hormone – IGF‐1 axis
Authors: Agha Amar , Monson John P.
Published: February 2007

The growth hormone‐insulin‐like growth factor 1 (GH‐IGF‐1) axis plays an important role in modulating the peripheral metabolism of glucocorticoids mainly through its effect on the isoenzyme 11 β‐hydroxysteroid dehydrogenase 1 (11β‐HSD1) which, in vivo, functions as a reductase catalysing the conversion of cortisone to cortisol. Several in vivo and ex vivo studies have shown that the GH‐IGF‐I system inhibits the expression and activity of 11β‐HSD1 in adipose tissues and the liver resulting in reduced local regeneration of cortisol. This interaction has clinically significant implications as it may at least partly explain the phenotypes of acromegaly and adult GH deficiency and the effects that treatment of these conditions has on body composition. In addition, by accelerating the peripheral metabolism of cortisol, GH therapy may precipitate adrenal insufficiency in susceptible hypopituitary patients, and endocrinologists should be mindful of this phenomenon when starting hypopituitary patients on GH replacement therapy.
Increased insulin‐stimulated endothelin‐1 release is a distinct vascular phenotype distinguishing Cushing's disease from metabolic syndrome
Authors: Setola Emanuela , Losa Marco , Lanzi Roberto , Lucotti Pietro , Monti Lucilla D. , Castrignanò Tristana , Galluccio Elena , Giovanelli Massimo , Piatti PierMarco
Published: February 2007

Objective  Although much is known about the anti‐inflammatory effects of an acute corticosteroid therapy, little is known about the effects on chronic hypercortisolism on endothelial dysfunction and proinflammatory alterations in patients with Cushing's disease (CD).

Patients and methods  We studied 9 patients with CD, 10 patients with metabolic syndrome and 27 normal controls. The tests consisted of an intravenous bolus of 0·1 U/kg insulin combined with a euglycaemic clamp technique with an arterialized forearm and assessment of the training parameters deep‐venous balance of forearm glucose uptake (as an index of insulin sensitivity); NOx (nitric oxide end‐products), c‐GMP (second messenger of nitric oxide) and endothelin‐1 release, as indices of endothelial function and proinflammatory systemic markers.

Results  Forearm glucose uptake incremental area was significantly lower in Cushing's disease and in the metabolic syndrome than in controls, suggesting a state of severe insulin resistance. Compared to controls and to the metabolic syndrome, basal and insulin‐stimulated NOx release incremental areas were significantly reduced in Cushing's disease, while forearm c‐GMP release was similarly decreased in CD and metabolic syndrome. By contrast, endothelin‐1 incremental areas after insulin bolus were significantly higher in CD than in controls and the metabolic syndrome, in the presence of increased TNF‐alpha, IL‐6 and CRP levels. Forearm glucose uptake incremental area significantly correlated with NOx incremental area, forearm c‐GMP release incremental area, TNF‐alpha levels and ET‐1 incremental area.

Conclusions  In patients with CD, supraphysiological insulin levels are not able to overcome the insulin resistance due to chronic hypercortisolism. Furthermore, an increased proatherogenic risk profile is characterized by decreased nitric oxide synthesis and activity, enhanced endothelin‐1 levels and increased proinflammatory markers.
Effects of free fatty acids, growth hormone and growth hormone receptor blockade on serum ghrelin levels in humans
Authors: Gormsen Lars C. , Nielsen Charlotte , Gjedsted Jakob , Gjedde Signe , Vestergaard Esben Thyssen , Christiansen Jens S. , Jørgensen Jens Otto , Møller Niels
Published: February 2007

Background  Circulating ghrelin levels are reported to be suppressed by insulin, GH and free fatty acids (FFAs). However, insulin, GH and FFA levels are all interdependent, and it is therefore difficult to delineate their independent effects on ghrelin secretion.

Objective  To isolate and define the impact of GH, GH receptor (GHR) blockade and intravenous FFA infusion on total circulating ghrelin levels during a hyperinsulinaemic glucose clamp with identical insulin levels.

Design  In a randomized design, eight healthy males each underwent an 8‐h hyperinsulinaemic glucose clamp on four occasions together with either: (1) control (saline), (2) intravenous FFA infusion (intralipid/heparin infusion 4 h), (3) a GH bolus (0·5 mg i.v.) or (4) GHR blockade (pegvisomant, 30 mg s.c.).

Results  Hyperinsulinaemia per se resulted in a decrease in ghrelin concentrations of about 15%. During FFA exposure, ghrelin levels were suppressed by about 22% when compared with saline [area under the curve (AUC)ghrelin0−240 122·7 ± 10·9 vs. 97·6 ± 13·4 pg/ml/min, P = 0·001], followed by a rebound increase upon discontinuation of the infusion. Furthermore, average ghrelin concentration (AUCghrelin) was significantly inversely correlated to average FFA levels (AUCFFA) (r = −0·33, P < 0·05). Neither GH administration nor GHR blockade resulted in significant alterations in total ghrelin levels in the presence of unaltered insulin and FFA levels.

Conclusions  Elevation of FFAs by means of an intravenous infusion acutely suppresses ghrelin levels, whereas GH administration and GHR blockade have no detectable effect on ghrelin concentration when insulin and FFA levels are kept fixed.
Linkage of Graves’ disease to the human leucocyte antigen region in the Chinese‐Han population in Taiwan
Authors: Chen Pei‐Lung , Fann Cathy Shen‐Jang , Chang Chien‐Ching , Wu I‐Lin , Chiu Wei‐Yih , Lin Chin‐Yu , Yang Wei‐Shiung , Chang Tien‐Chun
Published: February 2007

Objective  To investigate whether markers in the candidate chromosome regions, including the human leucocyte antigen (HLA) region, are linked to Graves’ disease (GD).

Design  A familial linkage study with a candidate region approach.

Patients  A total of 536 individuals in 122 multiplex Chinese‐Han families with a GD proband and at least one other affected sibling, resulting in 270 affected sib‐pairs. Subjects with a family history of noniatrogenic hypothyroidism or Hashimoto's thyroiditis were excluded.

Measurements  We genotyped eight short tandem repeat polymorphism (STRP) markers in a 13·7 cM region covering the HLA region on chromosome 6p21 and 26 STRPs in four other candidate regions previously reported in the literature.

Results  Multipoint nonparametric linkage (NPL) analysis showed significant linkage to the HLA region [the marker UniSTS:239159, nonparametric log of odds (LOD) score 3·44, P = 0·00003; NPL Z‐score 4·1, P = 0·00002] from 270 affected sib‐pairs. The 1‐LOD support interval comprised the whole HLA region (ca. 4 Mb). By contrast, the maximal NPL Z‐scores of the markers of the other candidate regions (2q33, 5q31, 7q22 and 14q31) previously reported were all less than 1·0.

Conclusions  Our results provide strong support for linkage of GD to the HLA region. Further dissection of this region to identify the candidate gene for GD is warranted in our population.
The impact of salinity pulses on the emergence of plant and zooplankton from wetland seed and egg banks
Authors: NIELSEN DARYL L. , BROCK MARGARET A. , PETRIE ROCHELLE , CROSSLÉ KATHARINE
Published: February 2007

1. In this study we compared the emergence of aquatic biota from sediments under 14‐day pulses of high (5000 mg L−1) and low (1000 mg L−1) salinity with emergence under freshwater and equivalent constant salinity levels. We tested the hypothesis that pulses of high salinity and short duration have no impact on the emergence of aquatic plants and zooplankton from wetland sediment.

2. The way salt is moved through the landscape may alter the response of biota to increases in salinity. Under natural hydrological regimes in rivers and floodplains salinity pulses occur often at concentrations that exceed predicted tolerance levels for aquatic biota. The impacts of natural pulses of high salinity followed by rapid return to fresh conditions may be used to inform management guidelines for the potential release of non‐natural saline water into river systems with minimal impact.

3. For both aquatic plants and zooplankton the abundance and richness of the emerging taxa decreased at higher salinities kept at constant levels. In contrast, pulses of salinity followed by return to freshwater conditions did not have a negative impact on the emergence of aquatic plants or zooplankton. For many taxa of zooplankton a positive impact was demonstrated with higher emergence following the salinity pulse.

4. The responses of aquatic plant and zooplankton taxa are grouped into five response types. Type 1: negatively impacted by all salt regimes. Type 2: preference for constant salinities. Type 3: no difference between fresh and either pulse regime. Type 4: preference for high concentration pulses. Type 5: emergence higher under a low concentration pulse.

5. Although previous studies indicate that constant high‐level salinity in rivers and wetlands can decrease the species richness of aquatic communities, this current study shows pulses may not have the same impact. Our results support the hypothesis that pulses of high salinity and short duration do not impact on the emergence of aquatic plants and zooplankton from wetland sediments. For zooplankton, pulses of salt may trigger emergence.

6. These trends may be used to explore the potential to use managed water releases to move salt through the landscape with minimal impact of salinity on aquatic biota. However, before such preliminary results are applied in management of saline water releases we need to determine the implications for interacting processes in natural ecosystems.
Small lakes dominate a random sample of regional lake characteristics
Authors: HANSON PAUL C. , CARPENTER STEPHEN R. , CARDILLE JEFFREY A. , COE MICHAEL T. , WINSLOW LUKE A.
Published: February 2007

1. Lakes are a prominent feature of the Northern Highland Lake District (NHLD) of Wisconsin, covering 13% of the landscape. Summarising the physical, chemical, or biological nature of NHLD lakes at a regional scale requires a representative sample of the full size distributions of lakes. In this study, we selected at random 168 lakes from the full size distribution of lakes in the NHLD and sampled each lake for a broad suite of limnological variables.

2. Most lakes were small. The median lake area was 1.1 ha, however, half of the surface area of water was in a relatively small number of lakes larger than 162 ha. Smaller lakes tended to be low in dissolved inorganic carbon (DIC) and high in dissolved organic carbon (DOC). Inclusion of small lakes (<4 ha) in the survey resulted in an acid neutralising capacity (ANC) median (76.5 μEq L−1) much lower than previous estimates, and a DOC median (10.1 mg L−1) about 50% higher than it would have been without the smaller lakes. Unlike DOC, total P tended to be evenly distributed across lake sizes.

3. The implications of these findings are that regional summaries of lake characteristics for the NHLD are influenced by the inclusion of small lakes in the sample, even though most of the water surface area is in lakes larger than 162 ha. Excluding small lakes introduces bias in the estimates of organic carbon and inorganic carbon values, for example. Similar biases may be introduced for lake characteristics at the global scale if small lakes are not sampled, because the size distribution of lakes globally is dominated in number by small lakes.
Planktonic phosphorus pool sizes and cycling efficiency in coastal and interior British Columbia lakes
Authors: NOWLIN WESTON H. , DAVIES JOHN‐MARK , MAZUMDER ASIT
Published: February 2007

1. Limnologists have long acknowledged the importance of phosphorus (P) in determining the organism biomass and productivity of lake ecosystems. Despite a relatively large number of studies that have examined P cycling in lake ecosystems, there remain several substantial methodological issues that have impeded our understanding of P cycling in limnetic plankton communities. Two critical issues confronting ecologists are (1) a lack of precise measurements of the dissolved inorganic phosphorus (PO) and (2) accurate or complete measurements of dissolved P regeneration rates by plankton communities.

2. Here, we examine patterns of epilimnetic planktonic P pool sizes and turnover rates in eight lakes in British Columbia, Canada over a 2‐year period. We determine the concentrations and turnover times of P in various planktonic compartments (dissolved and various planktonic size fractions), using recently developed methods for estimating phosphate concentration and planktonic regeneration rates.

3. The pico‐ and nanoplankton size fraction (0.2–20 μm) played a central role in planktonic P cycling in lakes examined by this study. On average across lakes, pico‐ and nanoplankton contained >60% of the planktonic P, accounted for >90% PO uptake, and contributed 50% of the plankton community dissolved P regeneration rate.

4. PO concentrations determined by steady state bioassays (ssPO) were extremely low (87–611 pmol L−1) and were 2–3 orders of magnitude less than simultaneously measured colorimetric soluble reactive phosphorus estimates. Lake ssPO concentrations increased linearly with total phosphorus (TP), and the slope of this relationship was approximately 1, indicating that PO remained a consistent proportion of the TP pool across a range of TP concentrations.

5. Turnover rates of the total planktonic P pool and the <20 μm pool became more rapid with increasing lake TP, indicating that, according to this metric, planktonic P cycling efficiency increased with TP concentrations. We also detected a significant relationship between particulate phosphorus (PP) <20 μm turnover time and seston N : P ratios, with PP <20 μm turnover times becoming slower with increasing seston N : P. These findings suggest that long‐standing conceptual models of nutrient cycling that predict slower cycling rates and decreasing cycling efficiency with increasing TP concentrations require further empirical examination. We postulate that patterns in lake P turnover and cycling efficiency are a result of complex interactions between plankton biomass and composition, and the ratios of multiple nutrients (C, N, P), rather than solely a function of the TP pool.
Variation in sperm size within and between ejaculates in a cockroach
Authors: HARRIS W. E. , MOORE A. J. , MOORE P. J.
Published: February 2007

Interspecific diversity in the morphology of animal sperm suggests adaptive evolutionary changes in size and structure. Little attention has been directed at patterns of intraspecific phenotypic variation in sperm morphology, although such variation is a prerequisite for the extreme diversity seen among male gametes. Despite well‐developed sperm competition theory providing a basis for exploring how variation in sperm morphology may affect male fitness, the patterns of variation in sperm morphology remain unclear for most species.

We report systematic size variation in sperm length among different males and between successive ejaculates within the same male in the cockroach Nauphoeta cinerea. Both flagellum length and mid‐piece length decreased between the first and second ejaculate. However, within the same ejaculate the sperm head (acrosome and nucleus), midpiece (centriole adjunct region) and tail length exhibited less variation than that present between males for both first and second ejaculates.

Our findings, combined with previous studies, suggest a focus on episodes of selection and lifetime selection on ejaculates may be instructive in understanding the selective forces influencing sperm evolution in a predictive framework.
Disruption of theWolbachiasurface protein genewspBby a transposable element in mosquitoes of theCulex pipienscomplex (Diptera, Culicidae)
Authors: Sanogo Y. O. , Dobson S. L. , Bordenstein S. R. , Novak R. J.
Published: February 2007

Culex pipiens quinquefasciatusSay andCulex pipiens pipiensLinnaeus are sibling species incriminated as important vectors of emerging and re‐emerging infectious diseases worldwide. The two forms differ little morphologically and are differentiated mainly based upon ecological, behavioural, physiological and genetic traits. Within the North American zone of sympatry, populations ofCx. p. quinquefasciatusandCx. p. pipiensundergo extensive introgression and hybrid forms have been reported in nature. BothCx. p. quinquefasciatusandCx. p. pipiensare infected with the endosymbiotic bacteriaWolbachia pipientis.Here, we report the presence of a transposable element belonging to the IS256 family (IS256wPip) associated withWolbachiain bothCx. p. quinquefasciatusandCx. p. pipienspopulations. Using reverse transcriptase PCR and sequence analysis, we show that IS256wPip has disrupted thewspBlocus, a paralogue of theWolbachiaouter membrane protein (wspA) gene. The inactivation of thewspBappears to be specific toCx. p. quinquefasciatusand to hybrids of the two forms, and was not observed in the surveyedCx. p. pipiensmosquitoes. Our results support the hypothesis of a different origin of North AmericanCx. p. quinquefasciatusandCx. p. pipienspopulations. The flux of mobile genetic elements in theWolbachiawPip genome could explain the high level of crossing types observed among differentCulexpopulations. The insertion of IS256wPip intowspBmay comprise a genetic candidate for discriminatingWolbachiasymbionts inCulex.
Ixodes ticks belonging to the Ixodes ricinus complex encode a family of anticomplement proteins
Authors: Daix V. , Schroeder H. , Praet N. , Georgin J.‐P. , Chiappino I. , Gillet L. , De Fays K. , Decrem Y. , Leboulle G. , Godfroid E. , Bollen A. , Pastoret P.‐P. , Gern L. , Sharp P. M. , Vanderplasschen A.
Published: February 2007

The alternative pathway of complement is an important innate defence against pathogens including ticks. This component of the immune system has selected for pathogens that have evolved countermeasures. Recently, a salivary protein able to inhibit the alternative pathway was cloned from the American tick Ixodes scapularis (Valenzuela et al., 2000; J. Biol. Chem. 275, 18717–18723). Here, we isolated two different sequences, similar to Isac, from the transcriptome of I. ricinus salivary glands. Expression of these sequences revealed that they both encode secreted proteins able to inhibit the complement alternative pathway. These proteins, called I. ricinus anticomplement (IRAC) protein I and II, are coexpressed constitutively in I. ricinus salivary glands and are upregulated during blood feeding. Also, we demonstrated that they are the products of different genes and not of alleles of the same locus. Finally, phylogenetic analyses demonstrate that ticks belonging to the Ixodes ricinus complex encode a family of relatively small anticomplement molecules undergoing diversification by positive Darwinian selection.
Microsatellite flanking region similarities among different loci within insect species
Authors: Meglécz E. , Anderson S. J. , Bourguet D. , Butcher R. , Caldas A. , Cassel‐Lundhagen A. , D’Acier A. C. , Dawson D. A. , Faure N. , Fauvelot C. , Franck P. , Harper G. , Keyghobadi N. , Kluetsch C. , Muthulakshmi M. , Nagaraju J. , Patt A. , Péténian F. , Silvain J.‐F. , Wilcock H. R.
Published: February 2007

Although microsatellites are ubiquitous in eukaryota, the number of available markers varies strongly among taxa. This meta‐analysis was conducted on 32 insect species. Sequences were obtained from two assembled whole genomes, whole genome shotgun (WGS) sequences from 10 species and screening partial genomic libraries for microsatellites from 23 species. We have demonstrated: (1) strong differences in the abundance of microsatellites among species; (2) that microsatellites within species are often grouped into families based on similarities in their flanking sequences; (3) that the proportion of microsatellites grouped into families varies strongly among taxa; and (4) that microsatellite families were significantly more often associated with transposable elements – or their remnants – than unique microsatellite sequences.
Deposits and physical properties of pyroclastic density currents during complex Subplinian eruptions: the AD 472 (Pollena) eruption of Somma‐Vesuvius, Italy
Authors: SULPIZIO ROBERTO , MELE DANIELA , DELLINO PIERFRANCESCO , LA VOLPE LUIGI
Published: February 2007

Small‐scale pyroclastic density currents (PDCs) associated with the AD 472 (Pollena) eruption of Somma‐Vesuvius, Italy, were generated by both magmatic and phreatomagmatic explosive fragmentation. The resulting deposits were emplaced under flow boundary conditions dominated by varying combinations of grain interaction, fluid escape and traction processes. Stratigraphic and lithofacies analysis of these PDCs offers a new perspective on the en masse versus progressive aggradation debate for PDC deposition. In particular, the analyses indicate that PDCs were density stratified with a basal underflow dominated by grain interactions. The underflows comprised trains of self‐organized granular pulses of variable thickness and magnitude, depending on the overall particle concentration and fluid turbulence. A change in gradient between the upper and lower slopes of the volcano promoted deposition and the different pulses aggraded sequentially (stepwise). In this model each pulse stops en masse and the whole deposit aggrades progressively. Particle concentration, density, mean velocity, and flow height were assessed for the studied PDCs using differaent methods for massive and stratified deposits. The calculated mobility of the flows was 0·2 to 0·3, in the expected range for small‐scale PDCs.
Palaeoceanographic controls on reef deposition: the Messinian Cariatiz reef (Sorbas Basin, Almería, SE Spain)
Authors: SÁNCHEZ‐ALMAZO I. M. , BRAGA J. C. , DINARÈS‐TURELL J. , MARTÍN J. M. , SPIRO B.
Published: February 2007

The Cariatiz section lies at the toe of the palaeoslope of the Messinian Cariatiz fringing reef, at the northern margin of the Neogene Sorbas Basin in SE Spain. Distal‐slope reef deposits in the upper part of the section can be traced laterally to the reef core of the last episodes of reef progradation. The underlying deposits are alternating diatomitic marl, marl and silty marl that intercalate with sandstone beds. Combined lithological changes, variations in proportions of warm‐water planktic foraminifera and δ18O values suggest that at least seven, probably precessional, cycles are recorded throughout the Cariatiz section. The correlation of seven cycles in the pelagic deposits to seven reef progradation cycles, and associated vertical shifts in reef facies, indicates relative sea‐level oscillations of several tens of metres. Biostratigraphic and palaeomagnetic data suggest that both the Cariatiz section and the fringing reef formed during the reverse polarity Chron C3r. Surface‐water temperatures seem to be the major factor controlling carbonate production in the reef system. Deposition of bioclastic calcirudite and calcarenite, with no active coral growth, took place at the lowest sea‐level within each reef cycle during temperature minima within each precessional cycle. Porites framework and reef‐slope deposits with Halimeda gravel, in contrast, formed during temperature rises and thermal maxima within precessional cycles.
Identification of two novel alleles HLA‐B*3569 and ‐B*4450 and confirmation of HLA‐A*2631 in the Brazilian population†
Authors: Abdeen H. , McErlean C. , Moraes M. E. , Romero M. , Marques S. B. , Goncales A. C. , Guariento E. G. , Middleton D.
Published: February 2007

Two novel alleles, human leukocyte antigen (HLA)‐B*3569, ‐B*4450 and a confirmatory sequence of HLA‐A*2631 were identified during a routine typing for the Brazilian Bone Marrow Donor Registry. Sequence analysis of coding exons 2 and 3 revealed a single nucleotide substitution in HLA‐B*3569 and two single nucleotide substitutions in HLA‐B*4450, compared with closely related alleles. At the protein level, these substitutions result in a change of a single amino acid residue in each of HLA‐B*3569 and ‐B*4450 at positions 74 (Arg > Pro) and 80 (Thr > Ile), respectively. These variations are located in the highly polymorphic region at the end of the α1 domain of the HLA molecule. It appears that HLA‐B*3569 arose from the analogous HLA‐B*3510 through a point mutation. However, HLA‐B*4450 may have arisen from HLA‐B*440301 and ‐B*4425 by gene conversion.
MIC gene polymorphism and haplotype diversity in rhesus macaques
Authors: Doxiadis G. G. M. , Heijmans C. M. , Otting N. , Bontrop R. E.
Published: February 2007

Rhesus macaques (Macaca mulatta) mainly originating from India were analysed for their major histocompatibility complex class I‐related (MIC) gene repertoire. Thus far, three distinct genes, designated MIC1, MIC2 and MIC3, have been identified in the rhesus macaque. In addition, an MICD pseudogene has been described mapping apart from the other loci in a telomeric direction. Genomic comparisons and the presence of a characteristic microsatellite in exon 5 suggest that the MIC1 gene is the equivalent of the human MICA gene. Hence, the MIC2 gene, lacking the microsatellite – as do humans –, is considered to be the equivalent of human MICB. The MIC3 gene, a hybrid of MICA and MICB, seems to be generated by a crossing‐over event with one breakpoint in intron 3 and accordingly is named MICA/B. Apart from their human counterparts, MICA, MICB and MICA/B cluster in separate branches in the phylogenetic tree, confirming the hybrid character of the MICA/B gene. Population analyses have shown that the various genes display polymorphism, and six MICA, five MICB and three MICA/B alleles have been identified. In the panel of homozygous typing cells, two distinct haplotype configurations have been defined by segregation analyses. Each haplotype comprises an MICB gene in conjunction with either an MICA or an MICA/B gene. Furthermore, the presence of a polymorphic microsatellite in the MICA and MICA/B alleles facilitates speedy and accurate haplotyping.
Identification of a novel HLA‐B*56 allele, B*5618 and an extension of B*2736 by sequence‐based typing
Authors: Li Z. , Zou H.‐Y. , Shao C.‐P. , Tang S. , Wang D.‐M.
Published: February 2007

We report the identification of a novel human leukocyte antigen (HLA)‐B*56 allele, B*5618 and an extension of B*2736 that were found during routine high‐resolution sequence‐based typing in Chinese Han individual. The B*5618 allele has 4nt changes from B*5610 in exon 3, The B*2736 allele has 10nt changes from B*270401 in exons 3–4.
Occurrence and diversity of Frankia in Tunisian soil
Authors: Gtari Maher , Daffonchio Daniele , Boudabous Abdellatif
Published: February 2007

There is a lack of studies on the occurrence and diversity of Frankia in African soils, including those in northern African regions. The present study on Tunisian soils is an attempt to address this issue using Alnus glutinosa, Elaeagnus angustifolia and Casuarina glauca in a plant capturing bioassay on 30 soil samples, followed by amplified 16S ribosomal DNA restriction pattern analysis (ARDRA). A total of seven ARDRA haplotypes of Frankia have been detected in root actinorhizas that have been affiliated to theoretical ARDRA haplotypes upon in silico digestion of selected 16S ribosomal RNA (rRNA) gene sequences retrieved from GeneBank and confirmed by their partial 16S rRNA gene sequencing. Elaeagnus‐compatible Frankia isolates were widespread and form four ARDRA haplotypes affiliated to Frankia, colonizing Elaeagnaceae and Rhamnaceae in two different phylogenetic subgroups. Alnus‐compatible strains occurring in northern subhumid area were closely related to Alnus–Morella‐compatible strains and clustered in two ARDRA haplotypes. Casuarina‐compatible strains lack variability in several northern arboreta. The relatively wide diversity of Tunisian Frankia strains opens the perspective that African soil could be an interesting reservoir for the isolation of new actinorhizal strains that could be used as potential biofertilizers to counteract the progressive soil desertification which indeed is a crucial environmental problem in Northern Africa.
The distribution ofcopia‐type retrotransposons and the evolutionary history of tomato and related wild species
Authors: TAM S. M. , CAUSSE M. , GARCHERY C. , BURCK H. , MHIRI C. , GRANDBASTIEN M.‐A.
Published: February 2007

Retrotransposons are mobile genetic elements that amplify throughout the genome and may be important contributors of genetic diversity. Their distribution is influenced by element behaviour and host‐driven controls. We analysed the distribution of threecopia‐type retrotransposons, ToRTL1, T135 and Tnt1 using sequence‐specific amplification polymorphism in self‐compatible (SC) and incompatible (SI) species ofSolanumsubsectionLycopersicon, and genetically mapped polymorphic insertions inS. lycopersicum(tomato). The majority of polymorphic insertions (61%) are located in centromeric regions of the tomato genome. A significant positive relationship was detected between insertion polymorphisms and mating system, independent of selection as most insertions were found to be neutral. As insertion patterns successfully inferred interspecific relationships ofSolanumsubsectionLycopersicon, our results suggest that the distribution of ToRTL1, T135 and Tnt1 may essentially be determined by selection removing strongly deleterious insertions, with genetic drift and mating system, but not recombination rate, playing important roles.
A screen for immunity genes evolving under positive selection in Drosophila
Authors: JIGGINS F. M. , KIM K. W.
Published: February 2007

Genes involved in the immune system tend to have higher rates of adaptive evolution than other genes in the genome, probably because they are coevolving with pathogens. We have screened a sample of Drosophila genes to identify those evolving under positive selection. First, we identified rapidly evolving immunity genes by comparing 140 loci in Drosophila erecta and D. yakuba. Secondly, we resequenced 23 of the fastest evolving genes from the independent species pair D. melanogaster and D. simulans, and identified those under positive selection using a McDonald–Kreitman test. There was strong evidence of adaptive evolution in two serine proteases (persephone and spirit) and a homolog of the Anopheles serpin SRPN6, and weaker evidence in another serine protease and the death domain protein dFADD. These results add to mounting evidence that immune signalling pathway molecules often evolve rapidly, possibly because they are sites of host–parasite coevolution.
The evolution of conspecific gamete precedence and its effect on reinforcement
Authors: LORCH P. D. , SERVEDIO M. R.
Published: February 2007

Conspecific gamete precedence, the usage of conspecific sperm by a female that mates with both a conspecific and a heterospecific male, has been found in many taxa. We construct a population genetic model to examine the evolution of conspecific gamete precedence and its coevolution with premating isolation in the process of reinforcement. Our findings suggest that conspecific gamete precedence can evolve via a process very similar to reinforcement. We explore the nature of the selection against hybridization necessary to drive this evolution. Moreover, our results confirm the prediction ofMarshallet al.(Trends Ecol. Evol.2002;17:558–563)that conspecific gamete precedence will inhibit the evolution of reinforcement between two species. We further find that reinforcement will inhibit the evolution of conspecific gamete precedence. Both reinforcement and conspecific gamete precedence increase reproductive isolation and contribute to the process of speciation. We discuss factors that may affect which of these phenomena are likely to become predominant between incipient species.
Inference of parasite local adaptation using two different fitness components
Authors: REFARDT D. , EBERT D.
Published: February 2007

Estimating parasite fitness is central to studies aiming to understand parasite evolution. Theoretical models generally use the basic reproductive rate R0 to express fitness, yet it is very difficult to quantify R0 empirically and experimental studies often use fitness components such as infection intensity or infectivity as substitutes. These surrogate measures may be biased in several ways. We assessed local adaptation of the microsporidium Ordospora colligata to its host, the crustacean Daphnia magna using two different parasite fitness components: infection persistence over several host generations in experimental populations and infection intensity in individual hosts. We argue that infection persistence is a close estimator of R0, whereas infection intensity measures only a component of it. Both measures show a pattern that is consistent with parasite local adaptation and they correlate positively. However, several inconsistencies between them suggest that infection intensity may at times provide an inadequate estimate of parasite fitness.
β‐Aminobutyric Acid‐induced Resistance in Brassica juncea against the Necrotrophic Pathogen Alternaria brassicae
Authors: Kamble A. , Bhargava S.
Published: February 2007

β‐Aminobutyric acid (BABA) pretreatment of Brassica plants protected them against the necrotrophic pathogen Alternaria brassicae. The achieved resistance level was much higher than that seen after salicylic acid (SA) and jasmonic acid (JA) pretreatments. BABA pretreatment to the leaves, 1 day before inoculation, led to an inhibition of the oxidative burst and a decrease in SA levels, but did not influence lipoxygenase activity nor cause callose deposition at the site of inoculation. Expression of two marker genes of the SA and JA pathways, namely PR1 and PDF1.2, was enhanced in response to BABA pretreatment. Our results indicate that BABA‐induced resistance is mediated through an enhanced expression of pathogenesis‐related protein genes, independent of SA and JA accumulation.