bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical assessment affects aggression and competitive ability: a team-fighting strategy for the ant
Formica xerophila
Authors: Tanner Colby J
Published: August 2006

The relationship between numerical advantage and competitive ability is a fundamental component in contests between groups of social animals. An individual's ability to correctly assess the numerical state of its group is of vital importance. In addition to numerical dominance, the group's fighting ability also plays an important role in competitive interactions. By staging experimental fights between two
Formica
ant species, I show that
Formica xerophila
are able to assess their own group's strength prior to any competitive encounter. Ants that perceive themselves as part of a large group act more aggressively toward a competitor than ants that perceive themselves as isolated individuals. This increase in aggression improves
F. xerophila
's competitive ability. Furthermore, the number of individuals in a contest was found to affect competitive ability. In contests with equal number of competitors, groups of
F. xerophila
were more successful than individual
F. xerophila
. Contrary to previous predictions using Lanchester's laws of fighting,
F. xerophila
's ability to kill competitors increased nonlinearly with group size. This nonlinearity was due to the collective fighting strategy of an
F. xerophila
group isolating and engaging a single
Formica integroides
competitors.
Responding to environmental change: plastic responses vary little in a synchronous breeder
Authors: Reed Thomas E , Wanless Sarah , Harris Michael P , Frederiksen Morten , Kruuk Loeske E.B , Cunningham Emma J.A
Published: August 2006

The impact of environmental change on animal populations is strongly influenced by the ability of individuals to plastically adjust key life-history events. There is therefore considerable interest in establishing the degree of plasticity in traits and how selection acts on plasticity in natural populations. Breeding time is a key life-history trait that affects fitness and recent studies have found that females vary significantly in their breeding time–environment relationships, with selection often favouring individuals exhibiting stronger plastic responses. In contrast, here, we show that although breeding time in the common guillemot,
Uria aalge
, is highly plastic at the population level in response to a large-scale environmental cue (the North Atlantic Oscillation, NAO), there is very little between-individual variation—most individuals respond to this climate cue very similarly. We demonstrate strong stabilizing selection against individuals who deviate from the average population-level response to NAO. This species differs significantly from those previously studied in being a colonial breeder, in which reproductive synchrony has a substantial impact on fitness; we suggest that counter selection imposed by a need for synchrony could limit individuals in their response and potential for directional selection to act. This demonstrates the importance of considering the relative costs and benefits of highly plastic responses in assessing the likely response of a population to the environmental change.
Delayed feedback control of chaos
Authors: Pyragas Kestutis
Published: August 2006

Time-delayed feedback control is well known as a practical method for stabilizing unstable periodic orbits embedded in chaotic attractors. The method is based on applying feedback perturbation proportional to the deviation of the current state of the system from its state one period in the past, so that the control signal vanishes when the stabilization of the target orbit is attained. A brief review on experimental implementations, applications for theoretical models and most important modifications of the method is presented. Recent advancements in the theory, as well as an idea of using an unstable degree of freedom in a feedback loop to avoid a well-known topological limitation of the method, are described in detail.
Rep and PriA helicase activities prevent RecA from provoking unnecessary recombination during replication fork repair
Authors: Mahdi Akeel A. , Buckman Carol , Harris Lynda , Lloyd Robert G.
Published: August 2006

The rescue of replication forks stalled on the template DNA was investigated using an assay for synthetic lethality that provides a visual readout of cell viability and permits investigation of why certain mutations are lethal when combined. The results presented show that RecA and other recombination proteins are often engaged during replication because RecA is present and provokes recombination rather than because recombination is necessary. This occurs particularly frequently in cells lacking the helicase activities of Rep and PriA. We propose that these two proteins normally limit the loading of RecA on ssDNA regions exposed on the leading strand template of damaged forks, and do so by unwinding the nascent lagging strand, thus facilitating reannealing of the parental strands. Gap closure followed by loading of the DnaB replicative helicase enables synthesis of the leading strand to continue. Without either activity, RecA loads more frequently on the DNA and drives fork reversal, which creates a chickenfoot structure and a requirement for other recombination proteins to re-establish a viable fork. The assay also reveals that stalled transcription complexes are common impediments to fork progression, and that damaged forks often reverse independently of RecA.
Integrin αIIbβ3:ligand interactions are linked to binding‐site remodeling
Authors: Hantgan Roy R. , Stahle Mary C. , Connor John H. , Horita David A. , Rocco Mattia , McLane Mary A. , Yakovlev Sergiy , Medved Leonid
Published: July 2006

This study tested the hypothesis that high‐affinity binding of macromolecular ligands to the αIIbβ3 integrin is tightly coupled to binding‐site remodeling, an induced‐fit process that shifts a conformational equilibrium from a resting toward an open receptor. Interactions between αIIbβ3 and two model ligands—echistatin, a 6‐kDa recombinant protein with an RGD integrin‐targeting sequence, and fibrinogen's γ‐module, a 30‐kDa recombinant protein with a KQAGDV integrin binding site—were measured by sedimentation velocity, fluorescence anisotropy, and a solid‐phase binding assay, and modeled by molecular graphics. Studying echistatin variants (R24A, R24K, D26A, D26E, D27W, D27F), we found that electrostatic contacts with charged residues at the αIIb/β3 interface, rather than nonpolar contacts, perturb the conformation of the resting integrin. Aspartate 26, which interacts with the nearby MIDAS cation, was essential for binding, as D26A and D26E were inactive. In contrast, R24K was fully and R24A partly active, indicating that the positively charged arginine 24 contributes to, but is not required for, integrin recognition. Moreover, we demonstrated that priming—i.e., ectodomain conformational changes and oligomerization induced by incubation at 35°C with the ligand‐mimetic peptide cHarGD—promotes complex formation with fibrinogen's γ‐module. We also observed that the γ‐module's flexible carboxy terminus was not required for αIIbβ3 integrin binding. Our studies differentiate priming ligands, which bind to the resting receptor and perturb its conformation, from regulated ligands, where binding‐site remodeling must first occur. Echistatin's binding energy is sufficient to rearrange the subunit interface, but regulated ligands like fibrinogen must rely on priming to overcome conformational barriers.
A structural rationale for SV40 Vp1 temperature‐sensitive mutants and their complementation
Authors: Kasamatsu Harumi , Woo Jennifer , Nakamura Akiko , Müller Peter , Tevethia M. Judith , Liddington Robert C.
Published: August 2006

Two groups of temperature‐sensitive (ts) mutants, termed ts B and ts C, have mutations in the major capsid protein of SV40, Vp1. These mutants have virion assembly defects at the nonpermissive temperature, but can complement one another when two mutants, one from each group, coinfect a cell. A third group of mutants, termed ts BC, have related phenotypes, but do not complement other mutants. We found that the mutations fall into two structural and functional classes. All ts C and one ts BC mutations map to the region close to the Ca2+ binding sites, and are predicted to disrupt the insertion of the distal part of the C‐terminal invading arm (C‐arm) into the receiving clamp. They share a severe defect in assembly at the nonpermissive temperature, with few capsid proteins attached to the viral minichromosome. By contrast, all ts B and most ts BC mutations map to a contiguous region including acceptor sites for the proximal part of the C‐arm and intrapentamer contacts. These mutants form assembly intermediates that carry substantial capsid proteins on the minichromosome. Thus, accurate virion assembly is prevented by mutations that disrupt interactions between the receiving pentamer and both the proximal and distal parts of the C‐arms, with the latter having a greater effect. The distinct spatial localization and assembly defects of the two classes of mutants provide a rationale for their intracistronic complementation and suggest models of capsid assembly.
Energetics of aliphatic deletions in protein cores
Authors: Bueno Marta , Campos Luis A. , Estrada Jorge , Sancho Javier
Published: July 2006

Although core residues can sometimes be replaced by shorter ones without introducing significant changes in protein structure, the energetic consequences are typically large and destabilizing. Many efforts have been devoted to understand and predict changes in stability from analysis of the environment of mutated residues, but the relationships proposed for individual proteins have often failed to describe additional data. We report here 17 apoflavodoxin large‐to‐small mutations that cause overall protein destabilizations of 0.6–3.9 kcal.mol−1. By comparing two‐state urea and three‐state thermal unfolding data, the overall destabilizations observed are partitioned into effects on the N‐to‐I and on the I‐to‐U equilibria. In all cases, the equilibrium intermediate exerts a “buffering” effect that reduces the impact of the overall destabilization on the N‐to‐I equilibrium. The performance of several structure‐energetics relationships, proposed to explain the energetics of hydrophobic shortening mutations, has been evaluated by using an apoflavodoxin data set consisting of 14 mutations involving branching‐conservative aliphatic side‐chain shortenings and a larger data set, including similar mutations implemented in seven model proteins. Our analysis shows that the stability changes observed for any of the different types of mutations (LA, IA, IV, and VA) in either data set are best explained by a combination of differential hydrophobicity and of the calculated volume of the modeled cavity (as previously observed for LA and IA mutations in lysozyme T4). In contrast, sequence conservation within the flavodoxin family, which is a good predictor for charge‐reversal stabilizing mutations, does not perform so well for aliphatic shortening ones.
A model for the coupling of α‐helix and tertiary contact formation
Authors: Hausrath Andrew C.
Published: August 2006

Peptides corresponding to excised α‐helical segments of natural proteins can spontaneously form helices in solution. However, peptide helices are usually substantially less stable in solution than in the structural context of a folded protein, because of the additional interactions possible between helices in a protein. Such interactions can be thought of as coupling helix formation and tertiary contact formation. The relative energetic contributions of the two processes to the total energy of the folded state of a protein is a matter of current debate. To investigate this balance, an extended helix‐coil model (XHC) that incorporates both effects has been constructed. The model treats helix formation with the Lifson‐Roig formalism, which describes helix initiation and propagation through cooperative local interactions. The model postulates an additional parameter representing participation of a site in a tertiary contact. In the model, greater helix stability can be achieved through combinations of these short‐range and long‐range interactions. For instance, stronger tertiary contacts can compensate for helices with little intrinsic stability. By varying the strength of the nonlocal interactions, the model can exhibit behavior consistent with a variety of qualitative models describing the relative importance of secondary and tertiary structure. Moreover, the model is explicit in that it can be used to fit experimental data to individual peptide sequences, providing a means to quantify the two contributions on a common energetic basis.
The product complex of M. tuberculosis malate synthase revisited
Authors: Anstrom David M. , Remington S. James
Published: July 2006

Enzymes of the glyoxylate shunt have been implicated as virulence factors in several pathogenic organisms, notably Mycobacterium tuberculosis and Candida albicans. Malate synthase has thus emerged as a promising target for design of anti‐microbial agents. For this effort, it is essential to have reliable models for enzyme:substrate complexes. A 2.7 Å resolution crystal structure for M. tuberculosis malate synthase in the ternary complex with magnesium, malate, and coenzyme A has been previously described. However, some unusual aspects of malate and Mg++ binding prompted an independent determination of the structure at 2.3 Å resolution, in the presence of saturating concentrations of malate. The electron density map of the complex reveals the position and conformation of coenzyme A to be unchanged from that found in the previous study. However, the coordination of Mg++ and orientation of bound malate within the active site are different. The revised position of bound malate is consistent with a reaction mechanism that does not require reorientation of the electrophilic substrate during the catalytic cycle, while the revised Mg++ coordination is octahedral, as expected. The results should be useful in the design of malate synthase inhibitors.
Crystal structure of the human TRPV2 channel ankyrin repeat domain
Authors: McCleverty Clare J. , Koesema Eric , Patapoutian Ardem , Lesley Scott A. , Kreusch Andreas
Published: August 2006

TRPV channels are important polymodal integrators of noxious stimuli mediating thermosensation and nociception. An ankyrin repeat domain (ARD), which is a common protein–protein recognition domain, is conserved in the N‐terminal intracellular domain of all TRPV channels and predicted to contain three to four ankyrin repeats. Here we report the first structure from the TRPV channel subfamily, a 1.7 Å resolution crystal structure of the human TRPV2 ARD. Our crystal structure reveals a six ankyrin repeat stack with multiple insertions in each repeat generating several unique features compared with a canonical ARD. The surface typically used for ligand recognition, the ankyrin groove, contains extended loops with an exposed hydrophobic patch and a prominent kink resulting from a large rotational shift of the last two repeats. The TRPV2 ARD provides the first structural insight into a domain that coordinates nociceptive sensory transduction and is likely to be a prototype for other TRPV channel ARDs.
Role of prostaglandin D2 and E2 terminal synthases in chronic rhinosinusitis
Authors: Okano M. , Fujiwara T. , Yamamoto M. , Sugata Y. , Matsumoto R. , Fukushima K. , Yoshino T. , Shimizu K. , Eguchi N. , Kiniwa M. , Urade Y. , Nishizaki K.
Published: August 2006

Background
Prostaglandin (PG)D2 and E2, two major cyclooxygenase (COX) products, are generated by PGD2 synthase (PGDS) and PGE2 synthase (PGES), respectively, and appear to mediate airway inflammation.

Objective
We sought to determine the role of PGDS and PGES in the pathophysiology of chronic rhinosinusitis (CRS).

Methods
The study examined the expression of PGDS and PGES in nasal polyps of 22 CRS patients. As controls, uncinate process mucosae were obtained from 12 CRS patients not having nasal polyps and five subjects without sinusitis. Immunohistochemistry and quantitative real‐time PCR were used to evaluate the expression.

Results
Both PGDS and PGES were detected in nasal polyps by immunohistochemistry. Significantly greater levels of PGDS mRNA and lesser levels of PGES mRNA were observed in the nasal polyps as compared with uncinate process mucosae, and an inverse correlation between PGDS and PGES expression was observed. Levels of PGDS mRNA in nasal polyps were positively correlated with degree of infiltration by EG2+ eosinophils, whereas the levels of PGES were inversely correlated. Significantly increased levels of PGDS and conversely decreased levels of PGES were observed in asthmatics as compared with non‐asthmatics. In addition, PGDS and PGES levels were positively and inversely correlated with the radiological severity of sinusitis, respectively.

Conclusions
These results suggest that PGDS and PGES display an opposite and important role in the pathophysiology of CRS such as polyp formation, and more specifically, a biased expression of these synthases might contribute to the development of CRS by affecting eosinophilic inflammation.
Associations between antioxidant status, markers of oxidative stress and immune responses in allergic adults
Authors: Dunstan J. A. , Breckler L. , Hale J. , Lehmann H. , Franklin P. , Lyonso G. , Ching S. Y. L. , Mori T. A. , Barden A. , Prescott S. L.
Published: August 2006

Background
There has been growing interest in the role of antioxidant function in controlling inflammatory disease states, such as allergy. This study investigated the relationship between antioxidant status, markers of airways inflammation [exhaled nitric oxide (eNO)], oxidative stress (F2 isoprostanes) and immune responses in allergic adults.

Methods
Antioxidants (vitamins C, E, β‐carotene and selenium) and total antioxidant capacity (tAC) in serum were examined in relation to eNO, plasma F2 isoprostanes and peripheral blood mononuclear cell (PBMC) cytokine and lymphoproliferative response to house dust mite (HDM) allergen, Staphylococcus enterotoxin B (SEB), phytohaemaglutinin (PHA) and lipopolysaccharide (LPS) in 54 allergic adults.

Results
Firstly, levels of specific vitamins did not correlate with tAC. Secondly, we did not see any evidence that specific vitamin levels (or tAC) were associated with either polarization or attenuation of in vitro immune responses. If anything, there were positive correlations between antioxidant (vitamin C and selenium) levels and HDM allergen responses [lymphoproliferation (selenium; r=0.35, P=0.013) and both Th2 IL13 (vitamin C; τ=0.254, P=0.028) and Th1 IFN‐γ (vitamin C; τ=0.302, P=0.009) responses]. There were also significant positive relationships between antioxidant levels and IL‐10 responses to polyclonal stimulation by SEB (r=0.292, P=0.036) and LPS (r=0.34, P=0.015) (β‐carotene) and PHA (r=0.34, P=0.021) (tAC). Thirdly, although airways inflammation (eNO) was associated with both in vitro and in vivo (skin test reactivity) to HDM, we did not see any correlation between eNO and oxidative stress (F2‐isoprostanes). Finally, there were no consistent relationships between oxidative stress and immune responses.

Conclusion
There was no evidence that higher antioxidant levels were associated with reduced allergen responsiveness in allergic adults. If anything, antioxidant status was associated with increased immune responsiveness. The significance of this needs to be addressed in future intervention studies.
Associations between ghrelin levels in serum of preterm infants and enteral nutritional state during the first 6 months after birth
Authors: Hübler Axel , Rippel Constance , Kauf Eberhard , Hoyer Heike , Mainz Jochen , Schlenvoigt Dorothea , Schramm Dirk
Published: July 2006

Background  Previous studies have suggested a possible influence of ghrelin on foetal growth. After birth, the regulation of this newly discovered orexigenic peptide is largely unknown.

Objective  To study the relationship between circulating levels of ghrelin and enteral nutritional state in preterm infants during the first months of life.

Methods  Ghrelin levels were measured in a cross‐sectional study by radioimmunoassay on the second day after birth (n = 51), at 3 months (n = 63) and at 6 months (n = 53) of corrected postnatal age. Complete data sets of auxological parameters, biochemical values, perinatal diseases, nutritional management and therapy were determined.

Results  All infants showed levels of ghrelin in postnatal serum. In correlation analyses and multivariable linear regression models, ghrelin was strongly related to enteral caloric intake on the second day after birth (all P < 0·01). At 6 months of corrected postnatal age, infants who were exclusively breastfed/formula fed had significantly lower ghrelin levels than infants with solid foods (Mann–Whitney U‐test: P = 0·027).

Conclusion  Ghrelin levels were positively correlated with the enteral nutritional state in preterm infants on the second day after birth. The introduction of solid foods increased the ghrelin levels in a group of preterm infants at 6 months of corrected postnatal age.
A TECHNIQUE FOR SELECTIVE SOLUTION OF IRON OXIDES IN THIN SECTIONS OF SOIL
Authors: BULLOCK P. , LOVELAND P. J. , MURPHY C. P.
Published: July 2006

A technique to study optically the effects of three different extraction procedures for removing iron from thin sections of soil is described. The distribution of iron in each section is recorded before treatment. Silicone grease is then applied to all parts of the sections except those to be treated. The areas selected for treatment are immersed for 24 hours in one of three beakers containing dithionite‐citrate‐bicarbonate, 02M ammonium oxalate at pH3 and 01M K‐pyrophosphate at pH10. After treatment, the sections are degreased and the effects of the various treatments examined optically.
Vertical, lateral and longitudinal movement of zooplankton in a large river
Authors: JACK JEFFREY D. , FANG WEI , THORP JAMES H.
Published: July 2006

1. The spatial distribution and movement patterns of zooplankton in large rivers are little known compared with those in lake environments. We conducted a series of studies in the Ohio River (U.S.A.) during the low flow period to assess diel vertical (DVM), longitudinal and lateral movement of crustacean zooplankton.

2. The dominant large zooplankter, the copepod Eurytemora affinis, showed a consistent vertical migration pattern of daytime ascent and night‐time descent during all sampling periods – the reverse of the most common migratory pattern of zooplankton in lakes. The cladoceran Bosmina migrated in a similar way in two of the three sampling periods. Surveys taken longitudinally in the river showed similar trends for both taxa.

3. During the lateral surveys, E. affinis was significantly more abundant in the shallow littoral zone during the night than in the daytime. The combination of vertical and lateral movement patterns along with the diel distribution of zooplanktivorous fish suggest that these movements are a predator‐avoidance mechanism.

4. Sampling programmes in large rivers should consider that larger zooplankton such as E. affinis may not be randomly distributed in the river channel and behaviours such as diel vertical migration may be just as evident in river habitats as in lakes.
Mechanical branch constraints contribute to life‐history variation across tree species in a Bolivian forest
Authors: STERCK FRANK J. , VAN GELDER H. ARNOLD , POORTER LOURENS
Published: July 2006

Trade‐offs among plant traits may contribute to specialization for different environments and coexistence of plant species. This may be the first study that shows how trade‐offs among branch traits contribute to variation in crown size, light requirements and maximum height across multiple sympatric tree species in a tropical rain forest.

Ten saplings were selected for each of 30 tree species in a Bolivian rain forest. Sapling height and crown dimensions were measured and branch and stem samples were harvested. Fresh density, dry density, modulus of rupture, centre of mass, biomass and diameters were determined for those samples. For each species, cantilever theory predicted the mass needed to produce a stable 1‐m long horizontal branch.

Generally, shade‐tolerant species had denser and stronger branches, and produced a stable horizontal branch at lower resource costs. These species had branches with a higher resistance against mechanical failure, and a wide crown that favours effective light acquisition. Less shade‐tolerant species had low density and weak branches, short branches, high resource costs per unit branch length, and low resource costs per unit stem length. These traits seem advantageous under conditions of prolonged exposure to direct sunlight, where such species grow rapidly to reproductive size, while mechanical risks are low and light levels are favourable.

Branch (wood and bark) traits are good predictors for performance differences across tree species in heterogeneous forest light environments. Physical trade‐offs among branch traits contribute to the specialization of tree species for different light habitats and to tree species coexistence in tropical rain forests, even within classical functional groups such as pioneers and shade tolerants.
Microfauna associated with amoebic gill disease in sea‐farmed Atlantic salmon, Salmo salar L., smolts
Authors: Bermingham M L , Mulcahy M F
Published: August 2006

A study of microfauna, associated with pathological changes in the gills of Atlantic salmon, Salmo salar L., was conducted over 2001–2002. Monthly samples of 1+ salmon smolts were taken, protozoan populations were quantified and gill health was assessed histologically. Protozoan densities were correlated with pathological changes, in order to determine their possible role in lesions in the gills. The most severe gill tissue changes were observed in summer/autumn and the least in spring. A diverse polyphyletic protozoan community was observed colonizing the gills, including Neoparamoeba sp., other amoebae, scuticociliates, Ichthyobodo‐like flagellates, trichodinid ciliates and prostomatean ciliates. The earlier gill tissue changes in the gill were not always associated with the presence of these microorganisms, whereas amoebae (other than Neoparamoeba sp.), Ichthyobodo‐like flagellates and trichodinid ciliates correlated with augmenting gill lesions. Neoparamoeba sp. was present, but its abundance did not correlate with the disease. This study suggests that a diversity of protozoans including Ichthyobodo‐like flagellates, trichodinid ciliates and amoebae other than Neoparamoeba sp. are involved in the aetiology of amoebic gill disease in the Irish situation.
The Metabolic Syndrome: A Brain Disease?
Authors: Buijs Ruud M , Kreier Felix
Published: July 2006

The incidence of obesity with, as consequence, a rise in associated diseases such as diabetes, hypertension and dyslipidemia − the metabolic syndrome − is reaching epidemic proportions in industrialized countries. Here, we provide a hypothesis that the biological clock which normally prepares us each morning for the coming activity period is altered due to a modern life style of low activity during the day and late‐night food intake. Furthermore, we review the anatomical evidence supporting the proposal that an unbalanced autonomic nervous system output may lead to the simultaneous occurrence of diabetes type 2, dyslipidemia, hypertension and visceral obesity.
Effect of a cannabinoid agonist on gastrointestinal transit and postprandial satiation in healthy human subjects: a randomized, placebo‐controlled study
Authors: Esfandyari T. , Camilleri M. , Ferber I. , Burton D. , Baxter K. , Zinsmeister A. R.
Published: July 2006

Abstract  Cannabinoid receptor (CBR) stimulation inhibits motility and increases food intake in rodents. Effects of CBR stimulation in human gastrointestinal (GI) tract are unclear. We compared effects of dronabinol (DRO) and placebo (PLA) on GI transit, gastric volume and satiation in humans. In a double‐blind, randomized study, 30 healthy volunteers were randomly assigned to DRO 5 mg b.i.d. or PLA for three doses. We measured GI functions noninvasively: day 0, Ensure® satiation test to measure maximum tolerated volume (MTV) and 30‐min post‐Ensure® symptoms; day 1, scintigraphic transit (111In‐egg meal) and fasting and postprandial gastric volume (99Tcm‐SPECT); day 2, 24‐h colonic transit and repeat satiation test. ancova was used to compare treatment groups with gender, age, and, for the satiation test, the baseline MTV, as covariates. A log‐rank test was used to assess treatment effects on gastric emptying. Planned sample size had 80% power to detect 25–30% differences in primary end points. There was an overall retardation of gastric emptying with DRO (P = 0.018); this was more pronounced in females (P = 0.011), than in males (P = 0.184). No significant treatment differences were detected for gastric volumes, MTV, post‐Ensure® symptoms, small bowel and colonic transit. Fasting gastric volume was greater in males receiving DRO compared with PLA (238 ± 17 vs 185 ± 16, P = 0.04). DRO retards gastric emptying in humans; effects are gender‐related. Dronabinol also increases fasting gastric volumes in males.
Untersuchungen zum Abbau des Herbizids Chlorphenpropmethyl im Boden und durch Mikroorganismen
Authors: KÖCHER HELMUT , LINGENS FRANZ , KOCH WERNER
Published: August 2006

Das Herbizid 2‐Chlor‐3‐(4‐chlorphenyl)propionsauremethylester (Chlorphenprop‐methyl) wurde in Sand‐und Lehmboden bei 21°C innerhalb weniger Stunden hydrolysiert. Das Hydrolyseprodukt 2‐Chlor‐3‐(4‐chlorphenyl)propionsäure (CPP) wurde in beiden Böden bei 22.0 ppm Anfangskonzentration mit einer Halbwertszeit von 4 bis 8 Tagen. bei 4.4 ppm Anfangskonzenlralion mit einer Halbwertszeit von knapp einem Tag abgebaut. Als Zwischenprodukt des CPP‐Abbaus in Boden wurde 4‐Chlorbenzoesaure, in Mischkulturen von Bodenmikroorganismen ausserdem 4‐Chlorzimtsäure identifiziert. Tn autoklaviertem und mit NaN3 sterilisiertem Boden unterblieb der Abbau von CPP. Die Anreicherung und Isolierung von Mikroorganismen, die den ersten Schritt des CPP‐Abbaus vollziehen, war nicht möglich. Zwei aus den VersuchsbÖden isolierte und vorläufig den Gattungen Flavobacterium bzw. Brevibacterium zugeordnete Bakterienstämme bauten den Metaboliten 4‐Chlorzimtsäure zu 4‐ Chlorbenzoesäure ab, zwei de r Gattung Arthrobacter Zugeordnete Bakterienstämme wuchsen auf der 4‐Chlorbenzoesäure als alleiniger Kohlenstoffquelle. Die Ergebnisse sprechen insgesaml dafär, dass Chlorphenprop‐methyl im Boden zunächst zu CPP hydrolysiert wird, welches anschliessend über 4‐Chlorzimtsäure zu 4‐Chlorbenzoesäure abgebaut wird. Von der 4‐Chlorbenzoesäure aus erfolgt dann weiterer Abbau unter Ringspaltung.
Breaking dormancy of Avena fatua L. seed by treatment with ammonia
Authors: CAIRNS A. L. P. , de VILLIERS O. T.
Published: August 2006

Summary: Résumé: Zusammenfassung

Wild oat (Avena fatua L.) seed dormancy was broken by treating the air‐dry seed with ammonia. Loss of dormancy was proportional to the concentration and/or time of exposure to the gas. The dormancy of several other grass weed species was also broken by ammonia but the gas had no effect on the dormancy of dicotyledonous weed seeds. The dormancy‐breaking effect of ammonia was irrevocable and treated seeds could be stored for months without any decrease in germination. Germination of seed treated with sub‐optimal concentrations of ammonia increased with after‐ripening. Ammonia caused an increase in leakage of electrolytes from treated seeds, indicating an increase in permeability of the seed coat. The increase in permeability cannot, however, explain the loss of dormancy in deeply dormant wild oat where dormancy resides in the embryo.

Des traitements à l'ammoniaque pour lever la dormance de graines de Avena fatua L.

La dormance de graines de la folle avoine (Avena fatua L.) a pu être levée en traitant à l'ammoniaque les graines séchées à l'air. La perte de dormance s'est révélée fonction de la concentration et/ou du temps d'exposition au gaz. La dormance de plusieurs autres graminées a pu être levée par l'ammoniaque mais le gaz n'a pas eu d'effet sur les graines d'adventices dicotylédonées. L'effet de l'ammoniaque en levant la dormance était irréversible; le stockage des graines traitées pendant plusieurs mois n'a amené aucune diminution de la germination. La germination de graines traitées avec des concentrations d'ammoniaque sous‐optimales a augmenté suite à une maturation après la récolte. L'ammoniaque a amené une fuite d'électrolytes plus importante chez les graines traitées, ce qui indique une plus grande perméabilité du tégument. La plus forte perméabilité, cependant, n'explique pas la perte de dormance chez des folles avoines profondément dormantes, car chez cette espèce la dormance réside dans l'embryon.

Abbruch der Ruheperiode von Avena fatua L.‐Samen durch Behandlung mit Ammoniak

Die Behandlung lufttrockener Samen von Avena fatua L. mit Ammoniak führte zu einem Abbruch ihrer Ruhezeit. Der Verlust der Ruheperiode war proportional zu Konzentration und/oder Expositionszeit. Ammoniak brach ebenfalls die Samenruhe verschiedener anderer Ungrasarten, zeigte aber keine Wirkung bei zweikeimblättrigen Unkräutern. Die Beendigung der Samenruhe durch Ammoniak war unwiderruflich und behandelte Samen konnten während Monaten ohne Abnahme ihrer Keimfähigkeit gelagert werden. Mit zunehmender Dauer einer Nachreifung nahm die Keimung der Samen zu, die mit unteroptimalen Konzentrationen von Ammoniak behandelt worden waren. Ammoniak verursachte ein verstärktes Austreten von Elektrolyten aus den Samen, was auf eine erhöhte Permeabilität der Samenschale hinweist. Dieser Permeabilitätsanstieg kann jedoch den Verlust der Samenruhe bei Wildhafer nicht erklären, da die Ursache der Ruheperiode im Embryo zu suchen ist.
Community participation in organising rural general practice: Is it sustainable?
Authors: Taylor Judy , Wilkinson David , Cheers Brian
Published: July 2006

Objective:  We analysed community participation in organising rural general medical practice in order to suggest ways to extend and sustain it.

Design:  A multisite, embedded case‐study design collecting data through semistructured interviews, non‐participation observation and a document analysis.

Setting:  One remote and two rural communities in Australia.

Participants:  Community members, GPs, health professionals, government officers and rural medical workforce consultants.

Results:  High levels of community participation in recruiting and retaining GPs, organising the business model, and contributing to practice infrastructure were evident. Community participation in designing health care was uncommon. Participation was primarily to ensure viable general practice services necessary to strengthen the social and economic fabric of the community. There were factors about the decision‐making and partnership processes in each of the communities that threatened the viability of community participation.

Conclusions:  We recommend that a concept of community development and explicit facilitation of the processes involved is necessary to strengthen participation, create effective partnerships and ensure inclusive decision‐making.
Variation in drought resistance in adjacent edaphic populations of Eucalyptus viminalis Labill.
Authors: LADIGES PAULINE Y.
Published: July 2006

Population differences in growth rate, drought resistance, and aspects of tissue water relations in seedlings of two neighbouring populations of E. viminalis on basalt and granite soils have been reported previously (Ladiges 1974a, b). The present work has confirmed these differences and field studies have related them to differences in edaphic factors.

The granite soil supports the slower growing, more drought‐resistant population. Moisture contents for this soil were lower over a twelve‐month period than for the basalt soil. Estimated pF values for granitic top‐soil were higher and above 5 for six months of the year. During the drier months, leaf water potentials of mature trees on the granite were lower than for trees on the basalt and reached average values of ‐28 bars in March 1974.

A comparison of open‐pollinated seedlings on two areas of granite, 0–4 km and 2–0 km from the trees on the basalt, suggested that there is a degree of gene flow between trees on the basalt and trees on the nearer granite site. The results therefore suggest some outcrossing in E. viminalis. Prior to 1900, stands on the basalt area were probably continuous with those on the more distant granite site and a degree of gene flow would have occurred.

It appears that differential selection pressures have been primarily responsible for the population differences noted in growth rate and drought resistance.
Studies in the ecology of coastal heath in New South Wales
Authors: SIDDIQI M. Y. , MYERSCOUGH P. J. , CAROLIN R. C.
Published: July 2006

Effects of heating dry seed were investigated in Banksia serratifolia and B. ericifolia. Seeds were inviable after 7 min exposure at 150°C or higher temperatures but remained viable after exposure at 100°C and lower temperatures. Imbibed seeds show no dormancy, and seeds survive fire insulated from heat in the thick woody follicles which may persist unopened for several years on the parent plant but open following fire.

Effects of nutritional supplements were observed in the seed germination and seedling survival and growth of Banksia serratifolia, B. aspleniifolia and B. ericifolia. Germination with radicle and hypocotyls extension was not significantly affected by a wide range of mineral nutrient regimes. In pot experiments using a heath soil seedling survival and growth were adversely affected by moderate additions of phosphate with surviving seedlings showing toxicity symptoms and poor development of proteoid roots. Moderate supplements of potassium had no adverse effect, and in B. serratifolia and B. ericifolia lessened the adverse effects of phosphate addition. The slow growth of the seedlings accords with the normal low nutrient availability in heath soils but seedlings show little capacity for rapid exploitation of any temporary increase of available nutrients after fire.
Polyploidy, flowering phenology and climatic adaptation in Heteropogon contortus (Gramineae)
Authors: TOTHILL J. C. , HACKER J. B.
Published: July 2006

Chromosome numbers of 2n = 39, 40, 50, 60, 69, 70, 80 and 90 are reported for Heteropogon contortus from a world collection. The numbers 2n = 39, 69, 70 and 90 are new to the literature. The cytogeographic distribution indicates that the tropical latitudes are almost exclusively occupied by tetraploids while the sub‐tropical latitudes are characterized by a wide range of ploidy levels from tetraploid to nonaphid.

Observations on the time of flowering of these accessions using uniform grass garden techniques indicate that pan‐tropical populations are made up almost exclusively of late flowering lines and those from subtropical areas are of mixed lines showing great diversity from early to late flowering types. The association of polyploidy and flowering time are discussed in relation to the possible origin of H. contortus, to its adaptation and migration. It seems reasonable to suggest that polyploidy and the development of an earlier flowering response are both adoptively advantageous and have been selected for the species’migration into sub‐tropical latitudes.
Vegetation succession after fire in sclerophyll woodland communities in south‐eastern Australia
Authors: PURDIE ROSEMARY W. , SLATYER R. O.
Published: July 2006

The dynamics of vegetation regeneration after burning were examined in three dry sclerophyll communities near Canberra, in south‐eastern Australia. Changes in seedling and regrowth populations were followed in permanent quadrats during the first two years after burning, compared with both the preburn vegetation and population changes over the same period in adjacent, unburnt plots.

All species represented either by living plants in the tree and shrub strata and/or by seed in the soil and litter prior to burning regenerated during the first year after the fire treatments. No new species invaded the areas after burning. Species varied in their regenerative strategy and recovered after the fires either by germination of seed residual in the soil and ash or released from trees after burning, by regrowth from surviving vegetative organs, or by a combination of germination and regrowth. Both seedling input and the vegetative recovery of populations were higher during the first than second year after burning. The vegetative multiplication and seed gertnination of many species were stimulated by fire.

It was concluded that the regeneration of the communities studied, as well as the post‐fire recovery of numerous different communities reported in the literature, closely resembled an initial floristic composition model. It is considered that the process of vegetation redevelopment after a disturbance (i.e. secondary succession) will be influenced greatly by the species composition at the time of disturbance, and by the type of disturbing agent. A single model would not be expected to adequately describe secondary succession following disturbance by agents imposing different stress conditions on a community.
Resource partitioning and competition in honeyeaters of the genus Meliphaga
Authors: FORD HUGH A. , PATON D. C.
Published: July 2006

Six species of Meliphaga studied in detail in South Australia all differ in some important aspect of their ecology consistent with the concept of interspecific competition. Four species are very similar in their feeding ecology but show distinct habitat preferences. The two remaining species are rather different in their feeding ecology and frequently overlap with their congeners in habitat. Two other species, not studied in detail, also appear to have distinct habitat preferences.

One species has increased its range of habitat on Kangaroo Island, in the absence of potential competitors.

The case for interspecific competition playing a part in the moulding of the niches of species in this genus is thus strengthened.
Ecological paradoxes*
Authors: KIKKAWA JIRO
Published: July 2006

Two controversial areas of ecology are examined critically to ascertain the limits of some current theories. In the field of population ecology it is argued that no general theory can explain the regulation of animal numbers. Existing theories are considered inadequate because either (1) evidence points to multiple causes rather than a single cause, (2) propositions lose scientific appeal by accumulating qualifiers, or (3) conflicting theories are irrefutable in scientific inquiry. Different research strategies are required to discover generalities in population regulation. In the field of community organization it is pointed out that too much emphasis on the competitive exclusion principle has blinded ecologists from the clustering of resources and of species populations. Conditions of co‐existence as well as segregation are considered important in the organization of communities, which allow elements of chance in small scale distribution. The ecological world is likened to the physical world in which small scale disorder leads to order on a large scale. For the development of a global ecology the acceleration of studies in the tropics and the southern hemisphere is urged.
Variations in vegetation and soil pattern across the Hawkesbury Sandstone plateau from Barren Grounds to Fitzroy Falls, New South Wales
Authors: BURROUGH P. A. , BROWN L. , MORRIS E. C.
Published: July 2006

The regional variations of vegetation, soil and rainfall over the Hawkesbury Sandstone plateau from Barren Grounds Nature Reserve to Fitzroy Falls, N.S.W., were described by aerial photo interpretation, field surveys, ordination techniques and trend surface analysis. The results show that on well‐drained middle to upper slopes the regional gradient in mean annual rainfall is the main factor controlling soil morphology, vegetation formation and species composition. Local deviations from the regional patterns result from topographic modifications of the regional climate or variations in soil drainage impedance. Other minor variations in vegetation species composition may be the result of small differences in soil texture or fertility.
A comparison of some populations of Eucalyptus viminalis Labill. growing on calcareous and acid soils in Victoria, Australia
Authors: LADIGES PAULINE Y. , ASHTON D. H.
Published: July 2006

A study of populations of Eucalyptus viminalis found on both acid and alkaline soils showed that seedlings differ in their tolerance of calcareous soils and their susceptibility to lime chlorosis.

Seedlings from an open‐forest population on calcareous dunes in the Otway Ranges, Victoria, averaged a significantly greater yield than seedlings of three other populations found on acid soils when all were grown on calcareous soil of pH 6.8. A tall ribbon gum form of E. viminalis, from Paradise gully in the Otways, was the least tolerant of alkaline conditions and showed severe signs of chlorosis and reddening of leaf margins. The latter appeared to be related to high uptake of phosphorus. This population showed rapid growth on a fertile acid loam.

The data presented also emphasize the need to consider the variation in soils which can occur at any one site. Population differences were most marked when seedlings were grown on soils of pH near 7.0. Yield was reduced in the Otways calcareous population when seedlings were grown on the more leached soil from swales (pH 6.5) between dunes and on the highly calcareous soil from the dune crests (pH 7.8–8.0).

The failure of any of the populations of E. viminalis studied to grow well on soils of high pH suggest that this species is not tolerant of highly calcareous soils. This may in part explain the absence of this species from the drier calcareous areas on the Mornington Peninsula and the Yanakie Isthmus, Victoria. Since seedlings had reduced root development on the soil collected from the Peninsula, E. viminalis may be restricted, in effect because of drought stress, to non‐calcareous sites in the eastern part of Victoria.
Observations on changes in the quality of food eaten by the wild rabbit*
Authors: MYERS K. , BULTS H. G.
Published: July 2006

The quality of the food eaten by rabbits can be predicted from the quality of the recently ingested food in the anterior portion of the stomach using the equation: crude protein in food (% dry weight) = 1.42 × crude protein in stomach (% dry weight).

The relationship which food bears to the ecology of rabbits differs from population to population. In semi‐arid north‐western and mediterranean New South Wales changes in food quality are closely related to changes in climate and to various important aspects of rabbit biology. In southern Queensland and subalpine New South Wales, quality of food in the stomach is less significantly related to changes in climate and the biological parameters measured.
A note on the selection of seed types by harvester ants in northern Australia
Authors: MOTT J. J. , McKEON G. M.
Published: July 2006

Seed harvesting ants (mainly Pheidole spp.) in the Katherine area of the Northern Territory have been observed to actively forage seed in both native and sown pasture areas. Using discrete mixtures of seeds it was found that ants from colonies in both sown and native pastures would preferentially remove seed of the native grass species, Themeda australis and Digitaria ciliaris, to the introduced legume Stylosanthes humilis. This difference in selection could not be explained solely on a basis of size or weight differences between the species.

The preference for grass species over introduced legumes indicates that ant predation is not the main factor in the low seed survival to germination in introduced pastures.