bluuebunny/crossref_metadata_2025 huggingface dataset:
The formation of a complex between calmodulin and neuronal nitric oxide synthase is determined by ESI-MS
Authors: Shirran Sally , Garnaud Pierre , Daff Simon , McMillan Derek , Barran Perdita
Published: August 2005

Calmodulin (CaM) is an acidic ubiquitous calcium binding protein, involved in many intracellular processes, which often involve the formation of complexes with a variety of protein and peptide targets. One such system, activated by Ca
2+
loaded CaM, is regulation of the nitric oxide synthase (NOS) enzymes, which in turn control the production of the signalling molecule and cytotoxin NO. A recent crystallographic study mapped the interaction of CaM with endothelial NOS (eNOS) using a 20 residue peptide comprising the binding site within eNOS. Here the interaction of CaM to the FMN domain of neuronal nitric oxide synthase (nNOS) has been investigated using electrospray ionization mass spectrometry (ESI-MS). The 46 kDa complex formed by CaM–nNOS has been retained in the gas-phase, and is shown to be exclusively selective for CaM.4Ca
2+
. Further characterization of this important biological system has been afforded by examining a complex of CaM with a 22 residue synthetic peptide, which represents the linker region between the reductase and oxygenase domains of nNOS. This nNOS linker peptide, which is found to be random coil in aqueous solution by both circular dichroism and molecular modelling, also exhibits great discrimination for the form of CaM loaded with 4[Ca
2+
]. The peptide binding loop is presumed to be configured to an α-helix on binding to CaM as was found for the related eNOS binding peptide. Our postulate is supported by gas-phase molecular dynamics calculations performed on the isolated nNOS peptide. Collision induced dissociation was employed to probe the strength of binding of the nNOS binding peptide to CaM.4Ca
2+
. The methodology taken here is a new approach in understanding the CaM–nNOS binding site, which could be employed in future to inform the specificity of CaM binding to other NOS enzymes.
On chaotic wave patterns in periodically forced steady-state KdVB and extended KdVB equations
Authors: Cox E.A , Mortell M.P , Pokrovskii A.V , Rasskazov O
Published: August 2005

The periodically forced KdVB and extended KdVB equations are considered. We investigate the structure of the totality of steady profiles. The existence of profiles that are close to any shuffling of two basic profiles is proved, and hence the existence of spatially chaotic and recurrent solutions. The proofs are based on topological degree theory to analyse chaotic behaviour. These proofs combine ideas suggested by P. Zgliczyński (

Zgliczyński 1996
Topol. Methods Nonlinear Anal
.
8
, 169–177

) with the method of topological shadowing. The results are also applicable to the classical problem of a quite general model of a forced nonlinear oscillator with viscous damping.
The quasi Eshelby property for rotational symmetrical inclusions of uniform eigencurvatures within an infinite plate
Authors: Xu Baixiang , Wang Minzhong
Published: August 2005

Although the Eshelby property does not hold for the non-ellipsoidal inclusions, some special properties have been found for the rotational symmetrical inclusions recently. In the present paper, an infinite plate containing a rotational symmetrical inclusion with uniform eigencurvatures is investigated. We mathematically prove that the rotational symmetrical inclusion in an infinite plate possesses the quasi Eshelby property. Namely, for anN-fold rotational symmetrical inclusion (Nis an integer greater than 2 and unequal to 4), the arithmetic mean of curvatures atNrotational symmetrical points in the inclusion is identical with that of a circular inclusion and independent of the orientation of the inclusion. Meanwhile, in two corollaries, we point out that the curvature at the centre, the averaged curvature over the inclusion domain, and the line integral average of curvatures along any concentric circle of the inclusion are all the same as the arithmetic mean.
Prenatal androgen exposure modulates cellular and humoral immune function of black-headed gull chicks
Authors: Müller Wendt , Groothuis Ton G.G , Kasprzik Alice , Dijkstra Cor , Alatalo Rauno V , Siitari Heli
Published: August 2005

Avian eggs contain considerable amounts of maternal yolk androgens, which have been shown to beneficially influence the physiology and behaviour of the chick. As androgens may suppress immune functions, they may also entail costs for the chick. This is particularly relevant for colonial species, such as the black-headed gull (Larus ridibundus), in which the aggregation of large numbers of birds during the breeding season enhances the risk of infectious diseases for the hatching chick.

To test the effect of maternal yolk androgens on the chick's immune function, we experimentally manipulated, in a field study, yolk androgen levels within the physiological range by in ovo injection of either androgens (testosterone and androstenedione) or sesame oil (control) into freshly laid eggs. We determined cell-mediated immunity (CMI) and humoral immunity of the chicks at the beginning of the nestling period to evaluate early modulatory effects of yolk androgens on immune function.

Embryonic exposure to elevated levels of androgens negatively affected both CMI and humoral immunity in nestling gull chicks. Consequently, maternal yolk androgens not only entail benefits of enhanced competitiveness and growth as previously shown, but also costs in terms of immunosuppression. The outcome of embryonic yolk androgen exposure thus likely depends on the post-hatching circumstances for the developing offspring such as parasite exposure and degree of sibling competition.
A poor start in life negatively affects dominance status in adulthood independent of body size in green swordtails
Xiphophorus helleri
Authors: Royle Nick J , Lindström Jan , Metcalfe Neil B
Published: August 2005

Whilst there is an abundance of studies revealing how dominance interactions affect access to resources critical for survival and reproductive success, very little is known about how dominance status is influenced by early life experiences. However, there is increasing evidence that early developmental trajectories can shape the physiology and behaviour of the adult. In particular, compensatory growth following a period of poor nutrition can have long-term effects on the phenotype. Since catch-up growth increases daily energy requirements and hence the motivation to acquire sufficient resources, it might either increase or decrease competitive ability and aggression. Here we test whether growth compensation early in life subsequently affects the dominance status of adult male swordtail fishes
Xiphophorus helleri
, a species with strong sexual dimorphism and male–male competition. Males that experienced a period of restricted food early in life subsequently caught up and achieved the same adult body and ornament size as control males that had been raised on
ad libitum
food throughout development, but were subordinate to size-matched controls, suggesting a trade-off between sexual attractiveness and competitive ability. This indicates that early life history and/or growth trajectory can be an important determinant of competitive ability independent of current body size.
Vortex core identification in viscous hydrodynamics
Authors: Finn Lucas I , Boghosian Bruce M , Kottke Christopher N
Published: August 2005

We describe a software package designed for the investigation of topological fluid dynamics with a novel algorithm for locating and tracking vortex cores. The package is equipped with modules for generating desired vortex knots and links and evolving them according to the Navier–Stokes equations, while tracking and visualizing them. The package is parallelized using a message passing interface for a multiprocessor environment and makes use of a computational steering library for dynamic user intervention.
Precision spectroscopy of hydrogen and femtosecond laser frequency combs
Authors: Hänsch T.W , Alnis J , Fendel P , Fischer M , Gohle C , Herrmann M , Holzwarth R , Kolachevsky N , Udem Th , Zimmermann M
Published: August 2005

Precision spectroscopy of the simple hydrogen atom has inspired dramatic advances in optical frequency metrology: femtosecond laser optical frequency comb synthesizers have revolutionized the precise measurement of optical frequencies, and they provide a reliable clock mechanism for optical atomic clocks. Precision spectroscopy of the hydrogen 1S–2S two-photon resonance has reached an accuracy of 1.4 parts in 10
14
, and considerable future improvements are envisioned. Such laboratory experiments are setting new limits for possible slow variations of the fine structure constant
α
and the magnetic moment of the caesium nucleus
μ
Cs
in units of the Bohr magneton
μ
B
.
Changes of structure and tilth mellowing in a Vertisol due to wet/dry cycles in the liquid and vapour phases
Authors: HUSSEIN J. , ADEY M.A.
Published: August 2005

Development of a fine tilth in Vertisols increases infiltration, plant‐available water and ease of cultivation and produces a fine seed bed. The tilth‐mellowing properties of a strongly self‐mulching Vertisol from Zimbabwe were investigated by applying different types of wetting to a worked soil and examining macromorphological features, size, density, strength and friability of the resulting clods/aggregates, developed through successive wet/dry cycles. Wetting regimes were chosen to simulate likely field conditions and included rapid flood‐, slow and fast capillary‐, simulated rainfall‐ and vapour‐wetting. Tilth development was compared to that of field soils.

All wetting treatments in the liquid phase resulted in decreases in aggregate density. Fast capillary wetting rapidly reduced size and strength of aggregates to below that of field soils whereas slow capillary wetting similarly rapidly decreased size but reduced strength more slowly. Flood wetting caused little change in size but aggregates showed a small decrease in strength. Rainfall wetting resulted in changes intermediate between these extremes. There was a significant linear relationship between strength and porosity of aggregates! For rainfall‐ and flood‐wetting, friabilities were at a maximum after one wet/dry cycle but subsequently decreased.

Vapour wet/dry cycles reduced strength but not density of worked soils, implying changes in internal microstructure without measurable porosity change.

Hypotheses to explain these changes are put forward.
Comparison of ceramic suction cups and KC1 extraction for the determination of nitrate in soil
Authors: DJURHUUS J. , JACOBSEN O.K.
Published: August 2005

Comparisons of nitrate concentrations in soil core extracts and ceramic suction cup isolates were made on a coarse sand and a sandy loam to evaluate the methods for estimating nitrate concentrations percolating through the root zone. On the coarse sand the comparisons were made at 80 cm on three dates during the winter of 1988/89. For each date, 103 soil samples and 101 or 102 suction cup isolates were taken. On the sandy loam the comparisons were made at 25 and 80 cm on two dates in March 1990. For each date and depth, 57 soil samples and 55–57 suction cup isolates were taken. On the coarse sand the mean nitrate concentrations were the same for the two methods. On the sandy loam the results obtained using the two methods differed significantly in only one of the four comparisons. However, the results indicated that the suction cup isolates differed slightly from the volume‐averaged concentrations obtained from the soil samples. The type of frequency distribution, normal or lognormal, seemed to be influenced both by the mean nitrate concentration and by the soil structure, and thus by the pattern of percolation. The size of sample required to estimate the mean nitrate concentration with a probability of 95% and a precision of 10% varied from 7 to 106.
Characterization of clay–organic‐matter complexes resistant to oxidation by peroxide
Authors: RIGHI D. , DINEL H. , SCHULTEN H.‐R. , SCHNITZER M.
Published: August 2005

In an acid soil, amounts or organic carbon resistant to peroxidation with hydrogen peroxide were strongly related to the proportions of expandable phyllosilicate (vermiculite, smectite) in the clay fraction, as measured by its K2O content and cation exchange capacity. This was taken to indicate that a substantial part of the organic matter resistant to oxidation was interlayered. The organic compounds in the clay‐organic matter complexes were identified by Pyrolysis Field Ionization Mass Spectrometry (Py‐FIMS).

Alkyl‐aromatics as well as carbohydrates, phenols, lignins, lipids and N‐compounds were found in the C‐horizon sample, whereas mainly alkyl‐aromatics and N‐compounds, more resistant to chemical oxidation, were associated with the A1 and Bw fine‐clay fraction. This was interpreted as being due either to the evolution of the clay‐associated compounds paralleling the mineralogical transformations, or to the selective adsorption of the more stable components.
Immobilization of 15N in forest litter studied by 15N CPMAS NMR spectroscopy
Authors: CLINTON P.W. , NEWMAN R.H. , ALLEN R.B.
Published: August 2005

Solutions labelled with 15N were applied as (15NH4)2SO4 or K15NO3 to isolated microplots in the floor of mountain beech forest (Nothofagus solandri var. cliffortioides) and incubated for 135 days under field conditions of moisture and temperature. Solid state 15N CPMAS NMR spectra of the forest litter layer showed that more than 80% of the total signal intensity was attributable to the secondary amide‐peptide peak. The degree of 15N enrichment or form of N did not alter the relative intensity of signals attributable to 15N in peptides, nucleic acids and aliphatic amine groups (amino sugars and free NH2 on amino acids). Combinations of 13C and 15N‐NMR spectra, edited by a process that exploited differences in proton spin properties between distinct categories of organic matter, indicated incorporation of 15N in humified organic matter rather than partly degraded plant material. This application demonstrated that solid state 15N CPMAS NMR has potential for use in studies of N immobilization under field conditions and with materials containing little N and small 15N enrichment.
Estimating temporal change in soil monitoring: I. Statistical theory
Authors: PAPRTTZ A. , WEBSTER R.
Published: August 2005

Detecting small temporal change of spatially varying soil properties demands precise estimation. Design– and model–based methods are compared for estimating temporal change of soil properties over finite areas. Analytical expressions for the estimators and their variances arc derived for the two approaches, and formulae for the expectations of the variances under the random–process model are developed. Among the randomized designs simple, stratified, and systematic random sampling using the arithmetic mean as estimator have been studied. Pairing the sampling positions on the different occasions increases the precision of design–based estimation if the observations are positively cross–correlated. The relative precisions of the means of stratified and systematic samples depends on the spatial correlation. Neither is more precise than the other in all circumstances. The stratified design provides an unbiased estimator for the sampling error, which is not available from systematic samples. Theoretically, the geostatistical global estimator is more precise than the estimates derived from any of the classical designs when many realizations arc repeatedly sampled at random. In practice, with only a single realization of the process, this is no longer relevant. Moreover, errors in estimating the variograms add to the total error of the method. It seems that only by sampling from large auto–correlated random fields can the precisions of the methods be compared in practice.
13C NMR studies of organic matter in whole soils: I. Quantitation possibilities
Authors: KINCHESH P. , POWLSON D. S. , RANDALL E. W.
Published: August 2005

A detailed discussion of the quantitative nature of 13C CPMAS NMR spectra as applied to solid samples, such as soil, is given. In particular, the influence of the cross‐polarization (CP) time constant (TCH), the relaxation time constant of protons in the rotating frame (T1pH) and the contact time (tc) in the CPMAS experiment are considered. Three distinct quantitation regimes are numerically identified according to sample parameters tCH and T1PH > and the experimental choice of tc: (i) quantitation obtainable from a single CPMAS spectrum; (ii) quantitation obtainable from a series of CPMAS spectra; and (iii) quantitation not possible using CPMAS. Strategies for the measurement of sample parameters TCH and TipH are reviewed. When quantitation is not possible using CPMAS it is necessary to regress to the direct polarization (DP) of 13C nuclei. The sensitivity problems of DPMAS are discussed, as too are general factors that affect the quantitation of 13C data such as spinning sidebands. More specifically in relation to soil samples, the effects on quantitation arising from the presence of paramagnetics and the actual methods for the measurement of signal intensities are covered.
Measuring the millimetre‐scale oxygen diffusivity in soil using microelectrodes
Authors: RAPPOLDT C.
Published: August 2005

The diffusivity of oxygen in soil was measured by periodically changing the gas above a soil core from nitrogen to air and vice versa. The concentration wave was measured as a function of depth with an oxygen electrode. For different Fourier components in the signal, phase shifts were calculated. The diffusivity follows from the increase of the phase shift with depth. Phase shifts are more suitable than signal amplitudes for the derivation of diffusivity. They are also easier to measure and do not require electrode calibration.

For a clay soil with an air–filled porosity of about 0.05 m3 m−3 a local diffusivity of 0.9 × 10−9 m2 s−1 was measured. This is several orders of magnitude smaller than macroscopic values for entire core samples of the same soil type. This low value can be explained by the presence of locally water–saturated clay.
Processes of structural crust formation on coarse‐textured soils
Authors: BIELDERS C.L. , BAVEYE P.
Published: August 2005

In order to understand better the mechanisms of structural crust formation on coarse‐textured soils, mixtures of 92.5% sand and 7.5% Ca2+‐kaolinite are exposed to simulated rainfall in experiments‐ involving a range of sand particle sizes, drop diameters and drop kinetic energies. For each combination of these variables, clay illuviation is measured and the changes in surface structure are observed on thin sections. The intensity of clay illuviation is inversely proportional to sand particle size and is shown to be determined by both rainfall and drop kinetic energy. A washed‐out layer forms at the surface of all samples exposed to drop impact. The lower boundary of this layer is generally marked by a relative concentration of clay micro‐aggregates in the form of a band. These micro‐aggregates are probably fragments derived from grain coatings initially present in the washed‐out layer. They accumulate at a depth that increases, on average, with drop kinetic energy and with the particle size of the sand fraction. Based on similarities with natural crusts, it is proposed that clay‐band formation in structural crusts formed on coarse‐textured soils may be initiated by the displacement of micro‐aggregates or other small particles from the washed‐out layer, followed by their accumulation due to mechanical straining. The experiments also point to the potential importance of the particle size of the sand fraction on the morphology of structural crusts.
Study of immobilization and remobilization of nitrogen fertilizer in cultivated soils by hydrolytic fractionation
Authors: SULÇE S. , PALMA‐LOPEZ D. , JACQUIN F. , VONG P.C. , GUIRAUD G.
Published: August 2005

Nitrogen immobilization and remobilization from a fertilizer were determined by hydrolytic fractionation of organic nitrogen with 6 M HC1 into acid–soluble distillable nitrogen (NSAD), acidsoluble nondistillable nitrogen (NSAnD) and nonhydrolysable nitrogen (NnH) on the Ap horizons of eight different soils from Myzeqe (Albania), eastern France, and tropical Mexico. The soils were fertilized with K15NO3 and then incubated at 28°C and 80% of the water holding capacity for 1 month. Mineral N was removed by extraction with a solution of CaCl2 after which rye grass was sown. The nitrogen taken up by rye grass was thus derived from soil organic matter. The three NSAD, NSAnD and NnH fractions participate in both immobilization and remobilization. The NSAnD fraction was shown to be the most active fraction. Remobilization of the biomass was greater in the sandy brown soils than in the clayey soils, in which intraaggregate immobilization would predominate. Evidently, the physical and chemical properties of the soils have a real bearing on immobilization and remineralization of nitrogen fertilizer in cultivated soils.
Extracellular enzyme activity in soil: effect of pH and ionic strength on the interaction with montmorillonite of two acid phosphatases secreted by the ectomycorrhizal fungus Hebeloma cylindrosporum
Authors: LEPRINCE F. , QUIQUAMPOIX H.
Published: August 2005

The interaction of extracellular enzymes with the solid phase of the soil affects their mobility and their catalytic properties. In particular, adsorption on clay minerals is known to shift the optimum pH of the catalytic activity towards alkaline values. Two conflicting interpretations of this phenomenon have been proposed: a surface pH effect and a pH–dependent modification of the conformation of the adsorbed enzyme. To assess the two mechanisms, we studied the adsorption on montmorillonite of two extracellular acid phosphatases of the ectomycorrhizal fungus Hebeloma cylindrosporum, and its consequences on catalytic activities. The results obtained are better interpreted by a pH–dependent modification of enzyme conformation due mainly to electrostatic interactions with the clay surface. At low pH, the two positively charged enzymes unfold on the negatively charged montmorillonite surface. At high pH, both the enzymes and the clay are negatively charged, and adsorption decreases. Adsorption and modification of conformation are largely irreversible, which should be taken into account when considering the fate of enzymes in soil. Finally, the comparison with the effect of clays on the catalytic activities of intracellular enzymes raises the hypothesis of a selection pressure of the soil solid phase leading to more stable extracellular enzymes.
Study of the distribution of copper in an acid sandy vineyard soil by three different methods
Authors: FLORES‐VÉLEZ L.M. , DUCAROIR J. , JAUNET A.M. , ROBERT M.
Published: August 2005

Copper sulphate (Bordeaux mixture) has been used as a fungicide against mildew in vineyards for more than a hundred years. This treatment has resulted in significant Cu accumulation in soils (from 100 to 1500 mg kg−1). It is desirable to determine the distribution of Cu in these soils to predict if this element is potentially toxic. Several speciation methods have been compared: sequential and single–step extractions, analytical transmission electron microscopy (ATEM, ASEM) and physical fractionation to study a profile of a vineyard acid soil in Beaujolais (France). Physical fractionation showed that copper is concentrated in the coarse organic fractions associated with plant residues and in the fine clay fraction. Analytical electron microscopy showed a great diversity of fixation sites (bacteria, amorphous organic and mineral compounds). Chemical sequential extractions showed that after the sequential extraction treatments, 60% of Cu was not extracted. Extraction data showed that in the case of an acid sandy soil, sequential chemical extraction did not seem to be sufficiently selective to speciate copper. In the single–step extractions study, the hydroxylamine treatment was the most selective. In the nonselective cases several phenomena may be responsible for the failure, the analytical electron microscopy study showed copper redistribution after certain single–step extractions were carried out.

After comparing three different distribution methods we conclude that the distribution of this element in acid soils should be investigated by several analytical methods to establish the true speciation.
Organic matter retention in an upland humic podzol; the effects of pH and solute type
Authors: KENNEDY J. , BILLETT M.F. , DUTHIE D. , FRASER A.R. , HARRISON A.F.
Published: August 2005

This paper discusses the effects of different horizons and soil solution compositions on dissolved organic matter retention in a moorland podzol and compares the results with previous studies of forest podzols. Adsorption isotherms were constructed for each of the major horizons of a freely draining, upland, moorland, humic podzol from north‐east Scotland, to investigate processes of retention and release of dissolved organic matter (DOM). Carbon retention of a range of solute types was studied, and phthalate was chosen as a model compound to measure carbon retention at three different pH values (3, 4.5 and 6). Retention and release of DOM was related to chemical, physical and mineralogical characteristics of the different soil horizons. All the mineral horizons retained DOM, with the Bs horizon most retentive. Solution pH did not significantly affect DOM retention in the O and A horizons. At pH 3 and 4.5 organic matter was weakly retained in the Bhs horizon, but strongly retained in the Bs and the Cx horizons. At pH 6 reversal of surface charge occurred in the Bs and Cx horizons resulting in the release of similar amounts of organic matter to that released from the O horizon at the same pH. The results demonstrate how podzols act as a ‘valve’ in controlling the input of dissolved organic compounds into surface and ground water, and how sensitive the controlling mechanisms are to pH change.
A hard sandy‐loam soil from semi‐arid Northern Cameroon: II. Geochemistry and mineralogy of the bonding agent
Authors: LAMOTTE M. , BRUAND A. , OHNENSTETTER D. , ILDEFONSE P. , PÉDRO G.
Published: August 2005

The hardening of soils containing little clay content has often been related to the cementing of skeleton grains. In sandy‐loam soils from the southern plain of the Chad basin the skeleton grains of the hard horizon are coated and bonded by wall‐shaped bridges. We have studied the bonding agent by X‐ray diffraction on extracted fractions (< 0·5 pm) and by quantitative in situ electron microprobe analysis on thin sections. The coatings and the wall‐shaped bridges are composed mainly of SO2 (mean = 60%), Al2O3 (29%) and FezO3 (7%). The TiO2 and K2O contents were small (1–2%), and the MgO, Na3O and CaO contents were less than 1%. The composition of the coatings and the wall‐shaped bridges is almost homogeneous, even if the Si/Al atomic ratio varies weakly with the morphology of the bridges. The bonding agent constituting the coatings and the wall‐shaped bridges seems to be a mixture of predominantly Al‐Fe beidellite with small contents of kaolinite, illite and quartz. A small content of fine clay minerals plays the major role of bonding agent and is responsible for hardness in sandy or sandy‐loam soils.
La matiére organique soluble à l'eau chaude et la stabilityé de l'agrégation. Aspects méthodologiques et application à des sols ferrallitiques du Congo
Authors: KOUAKOUA E. , SALA G.‐H. , BARTHÈS B. , LARRE‐LARROUY M.‐C. , ALBRECHT A. , FELLER C.
Published: August 2005

La stabilityé de la structure des horizons de surface et de profondeur de sols ferrallitiques du Congo est étudiée en fonction du mode de gestion des terres et de la teneur en carbone organique total des échantillons. Le rôle du carbone soluble à l'eau chaude dans l'agrégation est appréciéà partir de deux approches expérimentales, impliquant des extractions après chauffage en étuve ou en autoclave. Pour ce faire, des comparaisons sont faites entre les taux des macroagrégats stables (>200 pm) à l'eau froide et à l'eau chaude. Les résultats indiquent que les situations culturales étudiées induisent des variations significatives des teneurs en carbone total. Le taux des macroagégats stables à l'eau froide est très fortement corrélé aux teneurs en carbone total et en carbone solubiliséà l'eau chaude. Toutefois, les taux des macroagrégats stables obtenus avant et après extraction du carbone à l'eau chaude ne sont pas significativement différents, ce qui peut remettre en question les résultats sur la fonction agrégeante des matières organiques solubles, déduits des seules approches statistiques.

Hot‐water soluble organic matter and aggregate stability. Methodological aspects and application to ferrallitic soils of the Congo

The structural stability of surface and deeper horizons of ferrallitic soils of the Congo was studied in relation to the land use and the total organic carbon content of the samples. The role of hot‐water soluble carbon in aggregation was assessed with two experimental approaches, one by heating in an oven and the other in an autoclave under pressure. The proportion of aggregates (> 200 μm) stable in cold water were compared with that of macroaggregates stable in hot water. Cropping situation sunder study induced significant variations in total carbon content. Aggregate stability was highly correlated with both soluble and total carbon contents. However, amounts of water‐stable aggregates obtained before and after solubilization of organic matter in hot water were not significantly different. This result would infirm the supposed aggregating role of soluble organic matter, inferred from statistical data only.
Improvement of 13C and 15N CPMAS NMR spectra of bulk soils, particle size fractions and organic material by treatment with 10% hydrofluoric acid
Authors: SCHMIDT M.W.I. , KNICKER H. , HATCHER P.G. , KOGEL‐KNABNER I.
Published: August 2005

The small organic matter content of mineral soils makes it difficult to obtain 13C and 15N nuclear magnetic resonance (NMR) spectra with acceptable signal‐to‐noise ratios. Subjecting such samples to hydrofluoric acid removes mineral matter and leads to a relative increase in organic material. The effect of treatment with 10% hydrofluoric acid on bulk chemical composition and resolution of solid‐state 13C NMR spectra was investigated with six soils, some associated particle size fractions, plant litter and compost. The treatment enhanced the signal‐to‐noise ratio of the solid‐state 13C NMR spectra. The improvement in spectrum quality was greatest in the clay fraction of soil contaminated with coal ash. The removal of paramagnetic compounds associated with the ash may be the main reason for the improvement. Based on total C, total N, C/N ratio and intensity distribution of the solid‐state 13C NMR spectra, no changes in organic matter composition could be detected, except for a possible loss of carbohydrates. After treatment with HF, solid‐state 15N NMR spectra of particle size fractions were obtained and indicated that the observable nitrogen is present mostly as peptides and free amino groups. Extraction with hydrofluoric acid is recommended as a routine treatment prior to solid‐state 13C and 15N NMR on soil containing little C or N and soil samples containing paramagnetic compounds from natural or anthropogenic sources.
Species–area relationships of primates in tropical forest fragments: a global analysis
Authors: HARCOURT A. H. , DOHERTY D. A.
Published: August 2005

While in general the tropics and large‐bodied tropical forest mammals are poorly understood, the effects of fragmentation on tropical forest and the tropical mammalian order of primates are relatively well studied. Nevertheless, no quantitative synthesis exists of the response of primates to habitat fragmentation. We therefore conducted a meta‐analysis of the literature on the species–area relationships of primates in forest fragments in order to investigate regularities and differences among continents and sites.

The sample comprised 136 forest fragments (≤ 100 km2) at 33 sites in four continents (Africa, Asia, Madagascar and South America). We conducted our analysis at three spatial scales: global, continent and site. As richness (number of species) per site varied, we analysed both richness and proportional richness by area.

Study sites and size of fragments were unequally distributed across the globe. South America had three times as many sites as any other continent, for which we found less than 10 sites each. Fragment size was small in all continents (global median 1·0 km2).

Despite considerable noise in the data, primate richness and proportional richness generally declined significantly and linearly with fragment area at all spatial scales except in Africa.

Neither isolation (distance of fragment from main forest block) nor age of fragment was an obvious influence on proportional richness. However, the global median isolation was only 2 km.

Synthesis and applications. Fragmentation of habitat clearly threatens the survival of primates. However, study of the effects of fragmentation on primates might be directed in the wrong place. Estimates of minimum area requirements for primate species exceed tens of km2, yet most forest fragments studied measure less than 1 km2. Both to elucidate the biology of contrasts between species in susceptibility to fragmentation and to use research sites for associated conservation efforts, it might be better to direct more attention to fragments of a size in which long‐term persistence of some species is possible.
Long‐term interval burning alters fine root and mycorrhizal dynamics in a ponderosa pine forest
Authors: HART STEPHEN C. , CLASSEN AIMÉE T. , WRIGHT ROBERT J.
Published: August 2005

Plant roots and their mycorrhizal symbionts are critical components of forest ecosystems, being largely responsible for soil resource acquisition by plants and the maintenance of soil structure, as well as influencing soil nutrient cycling. Silvicultural treatments should be guided by knowledge of how these below‐ground components respond to different forest management practices.

We examined the cumulative effects of 20 years of prescribed burning at 2‐year intervals. We measured fine root length density and fine root and mycorrhizal root biomass in the upper 15 cm of mineral soil in a south‐western ponderosa pine forest over a complete burn cycle.

Repeated burning reduced fine root length, fine root biomass and mycorrhizal root biomass, as well as the amount of nitrogen and phosphorus stored in these below‐ground pools.

Estimates of fine root production, fine root decomposition and nutrient dynamics were similar in burned and control plots.

Synthesis and applications. Although repeated‐prescribed fire may be an effective, low‐cost approach for reducing fuel loads and lessening the chance of a catastrophic wildfire in ponderosa pine forests, our results suggest that this strategy may negatively affect below‐ground biomass pools and nutrient cycling processes in the long term. We recommend that mechanical reductions in fuel loads be conducted in these and similar forests that have not experienced fire for decades, before fire is reintroduced as a management tool.
Gap‐crossing decisions of woodland songbirds in Scotland: an experimental approach
Authors: CREEGAN HELEN P. , OSBORNE PATRICK E.
Published: August 2005

Recent declines in woodland birds in Britain have been linked to increasing habitat fragmentation. To understand the effects of fragmentation, data on avian dispersal across woodland gaps are essential but often lacking.

We used song thrush Turdus philomelos mobbing calls to attract songbirds across gaps ranging from 5 to 120 m in width and along comparable woodland edges. Responses were modelled against distance using generalized linear models. Such models have clear applied value for connecting fragmented landscapes.

We also calculated response indices and compared these with bird morphology. The gap‐crossing results were applied to a real landscape in central Scotland and landscape metrics were calculated to judge how perception of habitat connectivity varies interspecifically.

The chaffinch Fringilla coelebs and the robin Erithacus rubecula both responded more readily across gaps than through woodland. There was no difference between gap and edge response for the coal tit Parus ater, while the goldcrest Regulus regulus responded more readily along edges than across gaps. Maximum gap‐crossing distances ranged from 46 m (goldcrest) to 150 m (chaffinch).

There was a positive linear trend between mass of bird and the difference in the maximum response for gap and control experiments. Likewise there was a positive curvilinear relationship between wing area and the difference in probability of response between gap and control experiments at 50 m. These results may be interpreted in terms of manoeuvrability and ability to escape avian predation.

For the central Scotland landscape, the perceived number of patches in the landscape decreased exponentially with increasing gap‐crossing distance, while the median patch size and mean patch fractal dimension increased linearly with gap‐crossing distance.

Synthesis and applications. Our results show that an experimental approach using playback can be used to obtain data on avian gap crossing and the results applied to real landscapes to visualize interspecific differences in habitat perception. This has practical management applications, especially for designing forest habitat networks to maximize avian biodiversity, and potentially could help reverse the recent declines in woodland birds.
Seed inoculation with effective root‐nodule bacteria enhances revegetation success
Authors: THRALL PETER H. , MILLSOM DAVID A. , JEAVONS ALISON C. , WAAYERS MEIGAN , HARVEY GEOFFREY R. , BAGNALL DAVID J. , BROCKWELL JOHN
Published: August 2005

Extensive clearing of native vegetation in Australia has contributed to major environmental problems, including land degradation, dryland salinity, soil erosion and loss of biodiversity. Re‐establishing cover with deep‐rooted perennial species is a major focus for conservation and sustainable land management, particularly with regard to hydrological control of recharge and saline discharge areas. However, considerable expense is involved in large‐scale revegetation programmes and cost effectiveness is a real concern.

Low‐cost revegetation approaches are needed that require little maintenance yet can substantially enhance reliable establishment and growth of native trees and shrubs. We evaluated results from direct‐seeding field trials that examined the benefits of using native Australian Acacia species inoculated with effective strains of nitrogen‐fixing root‐nodule bacteria to revegetate degraded landscapes.

On average, inoculation led to a 118% increase in establishment of acacia seedlings, indicating that the use of elite strains of native bacteria can substantially reduce seed requirements. This is a major benefit given the expense of collecting sufficient native seed and the impacts of this activity on remnant population viability.

Particularly at sites experiencing harsher climatic conditions, subsequent survival of inoculated seedlings was significantly greater than for uninoculated controls. Moreover, inoculated acacias grew 10–58% faster than uninoculated controls during the critical early phase of establishment, although this varied among species and sites.

Synthesis and applications. Inoculation of Acacia species or other native leguminous shrubs and trees with elite strains of native rhizobia as part of direct‐seeding techniques has the potential to increase the scope, rate and success of land restoration world‐wide. Re‐establishment of important plant–soil interactions in degraded soils can contribute significantly to the development of biodiverse self‐regenerating native ecosystems in agricultural landscapes.
µ‐Opioid Receptor Preferentially Inhibits Oxytocin Release from Neurohypophysial Terminals by Blocking R‐type Ca2+ Channels
Authors: Ortiz‐Miranda S. , Dayanithi G. , Custer E. , Treistman S. N. , Lemos J. R.
Published: August 2005

Oxytocin release from neurophypophysial terminals is particularly sensitive to inhibition by the µ‐opioid receptor agonist, DAMGO. Because the R‐type component of the neurophypophysial terminal Ca2+ current (ICa) mediates exclusively oxytocin release, we hypothesised that µ‐opioids could preferentially inhibit oxytocin release by blocking this channel subtype. Whole‐terminal recordings showed that DAMGO and the R‐type selective blocker SNX‐482 inhibit a similar ICa component. Measurements of [Ca2+]i levels and oxytocin release confirmed that the effects of DAMGO and SNX‐482 are not additive. Finally, isolation of the R‐type component and its associated rise in [Ca2+]i and oxytocin release allowed us to demonstrate the selective inhibition by DAMGO of this channel subtype. Thus, µ‐opioid agonists modulate specifically oxytocin release in neurophypophysial terminals by selectively targeting R‐type Ca2+ channels. Modulation of Ca2+ channel subtypes could be a general mechanism for drugs of abuse to regulate the release of specific neurotransmitters at central nervous system synapses.
Laboratory study of the loads, speeds and times to finish and polish direct restorative materials
Authors: JONES C. S. , BILLINGTON R. W. , PEARSON G. J.
Published: August 2005

summary  This study investigated the loads, speeds and times required to achieve the smoothest surface on samples of amalgam, composite resin and glass–ionomer cement using the four grades of a disc polishing system. The tests were conducted on a specially constructed jig. The restorations were abraded with the appropriate disc using a range of loads, speeds and times based on a previous practitioner study. The surface roughness of each material was measured before and after abrading. The load was varied first, followed by speed and finally time. Photomicrographs were taken of a sample finished at the optimum load, speed and time and of loads above and below the optimum that produced the smoothest surface finish. In addition the fractured edge of a sample finished at the optimum values was examined. There was an optimum load, speed and time that produced the smoothest surface for each restorative material. For amalgam and composite the surface roughness value decreased as the discs became finer. There was a reduction in the roughness value for glass–ionomer cement using the two roughest discs. The values obtained were substantially in contrast from the earlier practitioner study. There were specific values for load, speed and time that produced a smoother surface for each material.
Microleakage of class V resin composite restorations after conventional and Er:YAG laser preparation
Authors: DELME K. I. M. , DEMAN P. J. , DE MOOR R. J. G.
Published: August 2005

summary  This in vitro study compared the microleakage of Class V resin composite restorations at bevelled enamel/composite and dentin/composite interfaces following Er:YAG laser (pre‐treatment modalities: laser‐etching and/or acid‐etching) or conventional preparation and acid‐etch, in association with two resin composite formulations and their three‐step adhesive system. Class V cavities with conventional bevel produced on the lingual and buccal surfaces of eighty extracted caries‐ and restoration‐free human teeth, were assigned to eight groups: cavities were or Er:YAG‐lased and acid‐etched (groups 1 and 5); or Er:YAG‐lased, laser‐etched and acid‐etched (groups 2 and 6); or Er:YAG‐lased and only laser‐etched (groups 3 and 7); or cut by dental drill at high‐speed and acid‐etched (groups 4 and 8). The specimens were restored with Optibond FL + Herculite XRV (groups 1, 2, 3 and 4) or with Scotchbond MP + Z 100 (groups 5, 6, 7 and 8), stored in distilled water at 37 °C for 24 h, thermocycled 1500 times between 5 and 55 °C, placed in a 2% aqueous solution of methylene blue for 24 h at 37 °C, embedded in resin and sectioned. Microleakage was assessed according to the depth of dye penetration along the restoration. There were statistically significant differences between occlusal and cervical regions for all groups (P < 0·01) except for groups 3 and 7. Pair‐wise comparison of groups showed that acid‐etch is advocated when using resin composite in Er:YAG‐lased Class V cavities; the seal at enamel margins in Er:YAG‐lased and laser‐etched cavities depended on the resin composite formulation and corresponding adhesive (P < 0·05).
Leukaemia‐Derived Dendritic Cells Can Be Generated From Blood or Bone Marrow Cells From Patients With Myelodysplasia: A Methodological Approach Under Serum‐Free Culture Conditions
Authors: Kufner S. , Zitzelsberger H. , Kroell T. , Pelka‐Fleischer R. , Salem A. , De Valle F. , Schmid C. , Schweiger C. , Kolb H. J. , Schmetzer H. M.
Published: August 2005

Functional dendritic cells (DC) are professional antigen‐presenting cells (APC) and can be generated in vitro from healthy as well as from leukaemic cells from AML patients giving rise to APC of leukaemic origin presenting leukaemic antigens. In a comparative methodological analysis of 50 AML samples, we could already show that leukaemia‐derived DC can regularly be generated under serum‐free culture conditions. In this study, we describe the generation and characterization of DC from different mononuclear cell (MNC) fractions from 24 myelodysplastic syndrome (MDS) patients under those different serum‐free culture conditions, determine the optimal culture conditions and compare the results with that from 23 healthy donors. In parallel cultures, we compared DC harvests after 7‐ or 14‐day culture, with total or adherent MNC or T‐cell‐depleted MNC or PB or BM–MNC, thawn or fresh MNC, in Xvivo or CellGro serum‐free media, ±10% autologous plasma or ±FL. In detail, we could show that MDS–DC harvests compared to healthy DC were higher after 10‐ to 14‐day culture; total or adherent PB or BM–MNC fractions yield comparable DC counts; however, from MACS‐depleted MNC fractions or thawn MNC lower DC counts can be generated. Whereas the addition of FL increases the DC harvest, the addition of autologous plasma in many cases has inhibitory influence on DC maturation, CellGro and Xvivo media yield comparable DC counts. Optimal harvest of vital and mature DC from MDS samples was obtained with a GM‐CSF, IL‐4, FL and TNF‐α containing serum‐free Xvivo medium after 10–14 days of culture (18/26% DC; 54/64% vital DC; 59/51% mature DC were generated from MDS/healthy MNC samples). Surface marker profiles (e.g. costimulatory antigen expression) of DC obtained from MDS samples were comparable with that of healthy DC. The leukaemic derivation of MDS–DC was demonstrated by the persistence of the clonal cytogenetic aberration in the DC or by coexpression of leukaemic antigens on DC. Autologous T‐cell activation of leukaemia‐derived DC was demonstrated in cases with MDS. Autologous T cells proliferate and upregulate DC‐contact‐relevant antigens. We are the first who demonstrate that the generation of leukaemia‐derived DC is feasible not only in AML but also in MDS under serum‐free culture conditions giving rise to DC with comparable characteristics as healthy DC and offering an antileukaemia‐directed immunotherapeutical vaccination strategy in AML and MDS.