bluuebunny/crossref_metadata_2025_split huggingface dataset:
Causes and consequences of post‐growth age‐dependent differences in small intestine size in a migratory sandpiper (Calidris mauri, Western Sandpiper)
Authors: STEIN R. W. , WILLIAMS T. D. 
Published: March 2006

SummaryCalidris mauriCabanis (Western Sandpiper) exhibits a pronounced post‐growth age‐dependent difference in small intestine size during southward migration, such that the later‐migrating juveniles have larger small intestines than do the adults. Potential causes and consequences of this age‐dependent difference are examined.Premigrant juveniles of full structural size had small intestines that were 10% longer than those of the premigrant adults, even though the juveniles had not attained asymptotic body mass. The elongated small intestines of premigrant juveniles appear to be growth‐related.Adults and juveniles exhibited parallel increases in intestinal length (7·0%) and circumference (9·5%) in association with the initiation of migration; these effects are consistent with migratory hyperphagia.Refuelling juveniles had small intestines that were 8·5% longer than those of the refuelling adults. Retaining an enlarged small intestine during migration confers increased digestive capacity to the juveniles, which may be under selection to minimize stopover duration.Refuelling juveniles had a higher prevalence of cestode infection than refuelling adults in one of two years, and the length‐corrected mass of the small intestine was 9·7% heavier in infected individuals. Cestode infection may be an important determinant of migration‐related mortality for juveniles, by compromising their health and increasing stopover duration.
Huddling in groups leads to daily energy savings in free‐living African Four‐Striped Grass Mice, Rhabdomys pumilio
Authors: SCANTLEBURY M. , BENNETT N. C. , SPEAKMAN J. R. , PILLAY N. , SCHRADIN C. 
Published: March 2006

Summary

Free‐living animals make complex decisions associated with optimizing energy and nutrient intake. In environments where ambient temperatures fall below the thermoneutral zone, homeotherms must choose whether or not to forage, how long and what to forage for, and whether or not to perform activities that conserve energy.
Huddling in groups has long been thought of as a possible means of conserving energy. Laboratory studies have shown that at low ambient temperatures individuals in groups expend less energy than individuals by themselves. However, studies have yet to demonstrate that thermoregulatory savings can have an impact on the overall daily energy expenditure (DEE) of free‐living animals.
Here we show that, in the laboratory, African Four‐Striped Grass Mice (Rhabdomys pumilio) expend less energy per individual in large groups than smaller groups. We also show that when free‐living groups were experimentally reduced to one‐half of their original size, DEE and water turnover increased by 19% and 37%, respectively.
The magnitudes of the reduction in free‐living DEE were comparable with calculated energy savings from the laboratory. One of the reasons why this species may sometimes occur in groups is that energetic benefits can be gained through huddling in habitats in which food and water are scarce.
Root strength and trampling tolerance in the grass Paspalum dilatatum and the dicot Lotus glaber in flooded soil
Authors: STRIKER G. G. , INSAUSTI P. , GRIMOLDI A. A. , LEÓN R. J. C. 
Published: March 2006

Summary

We studied the differences in root strength of species with contrasting root structural types (the grass Paspalum dilatatum and the dicot Lotus glaber), and their relationship with tolerance to simulated cattle trampling under flooding conditions.
Root strength was analysed through measurement of the pressure required to cause root collapse. The responses of aerenchyma and plant mass to flooding and trampling were studied.
Root aerenchyma increased from 28·0 to 40·2% in P. dilatatum and from 12·9 to 19·7% in L. glaber under flooding conditions. The increase in aerenchyma did not affect root strength in the relatively trampling‐resistant roots of P. dilatatum: roots cracked at >380 kPa in all treatments. In contrast, roots of L. glaber were weaker, cracking at 260 kPa; flooded roots with air spaces irregularly dispersed in the cortex cracked at 115 kPa.
Trampling, flooding or their combination did not affect the biomass of P. dilatatum. Conversely, the isolated effects of either trampling or flooding both decreased biomass accumulation in L. glaber. The combination of both treatments killed all Lotus plants.
In conclusion, root strength was positively associated with soil trampling tolerance. The effect of aerenchyma tissue generation on root strength varies among root structural types. Aerenchyma tissue increases root weakness in the less stable structural type of the dicot species, but had no effect on the strength of the grass.
Possible fitness consequences of experimentally advanced laying dates in Great Tits: differences between populations in different habitats
Authors: GIENAPP P. , VISSER M. E. 
Published: March 2006

Summary

In birds, early breeding individuals generally reproduce more successfully than late breeding individuals. The lack of response to this selection could be explained by resource constraints during the egg production period.
Parus species can learn from the mismatch experienced between breeding time and nestling food availability and subsequently adjust their breeding time accordingly. In two Great Tit populations, breeding time was manipulated by creating an artificial food peak. This allowed us to study fitness consequences of manipulated breeding time in the following year without the confounding effects of food supplementation.
In one population, manipulated females advanced their laying dates in response to the artificial food peak. However, sample sizes were too low to quantify fitness consequences. In the other population, no response to the treatment was found. This difference could be caused by differences in resource availability in early spring between the two habitats. Low resource availability in early spring could also explain the lack of response to selection observed in one population.
Does parental age affect offspring performance through differences in egg quality?
Authors: BOGDANOVA M. I. , NAGER R. G. , MONAGHAN P. 
Published: March 2006

SummaryPoorer performance in young compared with older age classes is common among iteroparous animals, and may result from age effects acting on different phases of reproduction. However, such effects have generally not been teased apart, and as a result their separate consequences for offspring fitness have remained unclear.We tested whether young and mature Herring Gulls produce offspring of different quality due to differences in their egg‐production capacity. An experimental protocol was used to standardize incubation and rearing conditions.Eggs laid by young females were smaller than eggs of mature birds. They had a reduced absolute amount of albumen, which reflected mainly lower water content.Within the young age class, female eggs were smaller than male eggs and had significantly paler yolk. This was due to young birds having reduced water content of the albumen, as well as carotenoid content in eggs containing a female embryo. In the mature class there were no such differences in resource allocation in relation to embryo sex. The sex ratio of clutches did not vary with parental age.Hatchlings from eggs produced by young pairs were smaller skeletally but had similar mass to hatchlings from eggs laid by mature birds. When reared by mature foster parents, they did not differ in structural growth or survival. However, they showed a different pattern of growth in body mass.Our results suggest that poorer reproductive performance of young breeders is not simply a consequence of poorer egg quality, as this was largely compensated for when the eggs of young pairs were incubated and reared by mature foster parents. However, it is also possible that adverse effects of lower egg quality are not manifest in the offspring until later in life.
Diffraction patterns of artificial two‐dimensional crystals synthesized in situ in an environmental scanning transmission electron microscope
Authors: VAN DORP W. F. , VAN SOMEREN B. , HAGEN C. W. , KRUIT P. , CROZIER P. A. 
Published: March 2006

SummaryIn this study, we demonstrated the use of electron‐beam‐induced deposition for synthesis of artificial two‐dimensional crystals with an in situ scanning transmission electron microscope. The structures were deposited from W(CO)6 in an environmental scanning transmission electron microscope on a 30‐nm‐thick Si3N4 substrate. We present clear electron beam diffraction patterns taken from those structures. The distance between the diffraction peaks corresponded to the dot spacing in the self‐made surface crystal. We propose using these arrays of dots as anchor points for making artificial crystals for diffraction analysis of weakly scattering or beam‐sensitive molecules such as proteins.
Accurate measure of laser irradiance threshold for near‐infrared photo‐oxidation with a modified confocal microscope
Authors: DENTON MICHAEL L. , SCHUSTER KURT J. , ROCKWELL BENJAMIN A. 
Published: March 2006

SummaryFemtosecond mode‐locked lasers are now being used routinely in multiphoton fluorescence and autofluorescence spectroscopy, are just beginning to be used in refractive surgery, and may be used in the future diagnosis of skin cancer. Pulses from these lasers induce non‐linear effects in resultant tissue interactions. Using a modified confocal microscope with dispersion compensation and accurate measurements of beam diameter, a very low threshold was measured for photochemical oxidation in cultured cells. The measured threshold showed non‐linear photo‐oxidation at a peak irradiance and photon‐flux density of 8.4 × 108 W cm−2 and 3.4 × 1027 photons cm−2 s−1, respectively (90‐fs pulse). The impact of these findings is significant to those using ultrashort lasers because they provide a tangible reference point (microscope‐independent) for the generation of photo‐oxidative stress in laser‐exposed tissues, and because they highlight the importance of dispersion compensation in minimizing collateral tissue damage.
Methods of studying the planar distribution of objects in histological sections of brain tissue
Authors: ARMSTRONG R. A. 
Published: March 2006

SummaryThis article reviews the statistical methods that have been used to study the planar distribution, and especially clustering, of objects in histological sections of brain tissue. The objective of these studies is usually quantitative description, comparison between patients or correlation between histological features. Objects of interest such as neurones, glial cells, blood vessels or pathological features such as protein deposits appear as sectional profiles in a two‐dimensional section. These objects may not be randomly distributed within the section but exhibit a spatial pattern, a departure from randomness either towards regularity or clustering. The methods described include simple tests of whether the planar distribution of a histological feature departs significantly from randomness using randomized points, lines or sample fields and more complex methods that employ grids or transects of contiguous fields, and which can detect the intensity of aggregation and the sizes, distribution and spacing of clusters. The usefulness of these methods in understanding the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and Creutzfeldt‐Jakob disease is discussed.
The Western Mediterranean lamproitic magmatism: origin and geodynamic significance
Authors: Peccerillo Angelo , Martinotti Giorgio 
Published: March 2006

AbstractUltrapotassic lamproitic rocks in the Western Alps, Tuscany‐Corsica and SE Spain (c. 30 to 1 Ma) show high MgO, Ni and Cr denoting a mantle origin, but also have incompatible element and radiogenic isotope abundances that resemble upper crustal rocks, such as local metapelites and global subducting sediments. The coexistence of mantle and crustal signatures in lamproites indicates a genesis in a lithospheric mantle, which had been contaminated by crustal rocks. The occurrence of lamproitic magmatism along the Alpine collision front suggests that mantle contamination occurred during east‐verging Cretaceous‐Oligocene subduction of the European plate beneath the African margin. We suggest that crustal material originated from the overriding continental margin, which was eroded by the low‐angle subducting European slab. Mantle melting and generation of lamproites took place later, during diachronous opening of Western Mediterranean basins, contemporaneously with a new cycle of magmatism, which was genetically related to the west‐north‐dipping Apennine‐Maghrebian subduction.
Transgressive segregation reveals two Arabidopsis TIR‐NB‐LRR resistance genes effective against Leptosphaeria maculans, causal agent of blackleg disease
Authors: Staal Jens , Kaliff Maria , Bohman Svante , Dixelius Christina 
Published: March 2006

SummaryIn a cross between the two resistant accessions Col‐0 and Ler‐0, a 15:1 segregation was found in F2, suggesting the presence of unlinked resistance loci to Leptosphaeria maculans. One hundred Col‐4 × Ler‐0, and 50 Ler‐2 × Cvi‐1 recombinant inbred lines, and seven susceptible Ler‐0 × Ws‐0 F2 progenies were examined to identify the two loci. Resistance in Col‐4, Ws‐0 and Cvi‐1 (RLM1) was mapped to the marker m305 on chromosome 1. Col‐4 × Ler‐0 and Ler‐2 × Cvi‐1 mapping populations located RLM2Ler on the same arm of chromosome 4. A tight physical location of RLM2 was established through near‐isogenic lines. This region was found to correspond to an ancient duplication event between the RLM1 and RLM2 loci. Two independent T‐DNA mutants in a TIR‐NB‐LRR R gene (At1g64070) displayed susceptibility, and L. maculans susceptible mutant phenotypes were confirmed to be allelic for rlm1 in F1 after crosses with susceptible rlm1Lerrlm2Col plants. Complementation of rlm1Lerrlm2Col with the genomic Col‐0 sequence of At1g64070 conferred resistance. In addition, two T‐DNA mutants in a neighbouring homologous TIR‐NB‐LRR gene (At1g63880) displayed moderate susceptibility to L. maculans. Sequence analysis revealed that At1g64070 was truncated by a premature stop codon, and that At1g63880 was absent in Ler‐0. RNA interference confirmed that Ler‐0 resistance is dependent on genes structurally related to RLM1. Camalexin was identified as a quantitative co‐dominant resistance factor of Col‐0 origin, but independent of RLM1. RLM1/RLM2 resistance was, however, found to require RAR1 and partially HSP90.1.
External K+ modulates the activity of the Arabidopsis potassium channel SKOR via an unusual mechanism
Authors: Johansson Ingela , Wulfetange Klaas , Porée Fabien , Michard Erwan , Gajdanowicz Pawel , Lacombe Benoît , Sentenac Hervé , Thibaud Jean‐Baptiste , Mueller‐Roeber Bernd , Blatt Michael R. , Dreyer Ingo 
Published: March 2006

SummaryPlant outward‐rectifying K+ channels mediate K+ efflux from guard cells during stomatal closure and from root cells into the xylem for root–shoot allocation of potassium (K). Intriguingly, the gating of these channels depends on the extracellular K+ concentration, although the ions carrying the current are derived from inside the cell. This K+ dependence confers a sensitivity to the extracellular K+ concentration ([K+]) that ensures that the channels mediate K+ efflux only, regardless of the [K+] prevailing outside. We investigated the mechanism of K+‐dependent gating of the K+ channel SKOR of Arabidopsis by site‐directed mutagenesis. Mutations affecting the intrinsic K+ dependence of gating were found to cluster in the pore and within the sixth transmembrane helix (S6), identifying an ‘S6 gating domain’ deep within the membrane. Mapping the SKOR sequence to the crystal structure of the voltage‐dependent K+ channel KvAP from Aeropyrum pernix suggested interaction between the S6 gating domain and the base of the pore helix, a prediction supported by mutations at this site. These results offer a unique insight into the molecular basis for a physiologically important K+‐sensory process in plants.
Fecundity and spawning of the Atlantic horseshoe crab,Limulus polyphemus, in Pleasant Bay, Cape Cod, Massachusetts, USA
Authors: Leschen Alison S. , Grady Sara P. , Valiela Ivan 
Published: March 2006

AbstractThis study provided the first comprehensive analysis of Atlantic horseshoe crab (Limulus polyphemus) fecundity.Limulusappear to be a determinate spawner, maturing all eggs for the breeding season before spawning begins. On average, larger females held a larger number of eggs (63,500) than smaller females (14,500). By the end of the breeding season there was an average of 11,600 mature eggs per female left undeposited, regardless of female size. Larger females laid a higher percentage of the eggs they contained. Thus they not only contain more eggs, but are more effective at laying them as well. Size of spawning females ranged from about 185–300 mm prosomal width, with by far the highest concentration in the mid‐size ranges. Although on an individual basis large females carry and lay the greatest number of eggs, mid‐size crabs as a group contributed more to the horseshoe crab population in Pleasant Bay because they were more plentiful (net fecundity was highest for mid‐size crabs). These results have implications for the management of this important species, which is harvested for bait, scientific, and biomedical uses. Incorporation of these results into models and other management tools can help predict growth rates, effects of size‐selective harvest, reproductive value, and stable stage distribution of populations.
Latitudinal and bathymetric trends in egg size variation: a new look at Thorson's and Rass's rules
Authors: Laptikhovsky Vladimir 
Published: March 2006

AbstractThe inverse relationship between egg size in marine animals and water temperature was simultaneously described by two outstanding marine scientists: G. Thorson and T.S. Rass. This rule consists of two different phenomena. Thorson's rule describes ecological processes related to changes in larval biology and morphology that are caused by a selective pressure of natural selection on the different types of larval development. It belongs to the realm of macro‐evolution. Rass's rule describes physiological processes within populations and species, and between closely related species. This is not related to changes in reproductive strategy, and therefore belongs to the realm of micro‐evolution and to the early stages of macro‐evolution. Populations begin to produce larger eggs in colder environments because of phenotypic plasticity. Thorson's rule describes temperature‐dependent changes in the relative abundance of small‐ and large‐egged species, whereas Rass's rule describes a temperature‐dependent relative position of both groups within an adaptive range of reproductive strategies.
Assessment of reactions of diverse maize inbred lines to Striga hermonthica (Del.) Benth
Authors: Menkir A. 
Published: March 2006

Abstract Striga hermonthica is the most widespread and destructive obligate root parasite infecting maize and other cereals in Africa. Maize inbred lines supporting reduced S. hermonthica emergence can form an important basis for developing Striga‐resistant maize cultivars. Twenty new inbred lines selected for field resistance to S. hermonthica, and five inbred checks with known resitance, tolerance and susceptibility reactions to S. hermonthica were evaluated in pots, greenhouse and field experiments under artificial Striga infestation for 3 years. The experiments were conducted to determine the extent of variation in parasite attachment to the roots of these lines and its relationship with emerged Striga plants and other traits. Significant differences (P < 0.0001) were detected among the inbred lines for the numbers of attached and emerged Striga plants and the results were consistent across test environments. Also, the lines exhibited significant differences for Striga damage symptom ratings and other traits recorded in the field. Parasite attachment to the roots was significantly correlated with emerged Striga count in the screenhouse (r = 0.67–0.68, P < 0.001) and in the field (r = 0.82–0.84, P < 0.0001) and with levels of grain yield reduction due to Striga (r = 0.71, P < 0.0001). Regression analysis of the numbers of attached parasites on the first principal component axis scores that integrated several traits recorded in the field was significant (P < 0.0001) and accounted for 62% of the total variation in numbers of attached parasites. The new inbred lines and the resistant inbred check were the least affected by S. hermonthica and exhibited yield losses of 0–37% compared with the yields of the tolerant and the susceptible inbred checks, which were reduced by 40–85%. Sixteen new inbred lines supported significantly fewer attached parasites compared with the susceptible inbred check. Some of these lines also supported significantly fewer emerged parasites and sustained lower damage symptoms and percentage yield losses due to Striga compared with the susceptible inbred check. These inbred lines would be useful in breeding programmes for developing resistant maize cultivars.
Diplotaxis erucoides‐induced cytoplasmic male sterility in Brassica juncea is rescued by the Moricandia arvensis restorer: genetic and molecular analyses
Authors: Bhat S. R. , Vijayan P. , Ashutosh  , Dwivedi K. K. , Prakash S. 
Published: March 2006

AbstractAn alloplasmic cytoplasmic male sterile (CMS) line of Brassica juncea was developed by repeated backcrossing of the sexual hybrid (Diplotaxis erucoides × Brassica rapa) with B. juncea cv. ‘Pusa Bold’. The CMS line is comparable to the B. juncea nuclear donor line for all morphological traits except male fertility. Southern and cleaved amplified polymorphic sequence (CAPS) analyses showed that the CMS line carries organellar genomes from the wild species that differ from the organellar genomes of B. juncea. Northern analysis with three mitochondrial gene probes revealed altered atpα transcription pattern associated with male sterility. The restorer of CMS (Moricandia arvensis) B. juncea was found to restore male fertility to the new CMS system. The mode of fertility restoration was found to be monogenic and gametophytic. The study identified CAPS markers for the psbB gene that could be useful in quick identification of the erucoides CMS line. Broad similarities and important differences observed at the molecular level between M. arvensis and D. erucoides CMS systems of B. juncea are discussed.
A molecular marker linked to the Prv1 gene that confers resistance to Papaya ringspot virus‐type W in melon
Authors: Teixeira A. P. M. , Camargo L. E. A. 
Published: March 2006

AbstractPapaya ringspot virus‐type W (PRSV‐W) is the most prevalent and important viral pathogen of cucurbits in Brazil. It can be effectively controlled by the incorporation of genetic resistance into susceptible melon cultivars. The present study identified amplified fragment length polymorphic (AFLP) markers linked to the PRSV‐W resistance Prv1 allele. The susceptible yellow‐fleshed melon‐breeding line AF426prv1 and its nearly isogenic‐resistant line AF426Prv1, which carries the Prv1 allele resident in the Indian cantaloupe U.S. Plant Introduction (PI) 180280, were screened for AFLP marker polymorphisms. Of 30 251 AFLP loci, only three were polymorphic between the nearly isogenic lines. Segregation analyses for these three polymorphic markers and the Prv1 allele using a BC1 population of 197 plants indicated close linkage (0.5% recombination frequency) between marker EK190 (HindIII‐CGA and MseI‐GTG; 190 bp) and Prv1. Thus, EK190 might be a useful marker in breeding programmes aiming to develop melon cultivars resistant to PRSV‐W. The other two markers are closely linked to each other, but distantly linked to Prv1.