bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex differences in diving at multiple temporal scales in a size‐dimorphic capital breeder
Authors: Beck Carrie A. , Bowen W. Don , McMillan Jim I. , Iverson Sara J. 
Published: November 2003

Summary

Air‐breathing marine predators can modify their diving behaviour to accommodate different patterns of prey abundance and distribution and may do so at multiple temporal scales (individual dives, bouts of dives and foraging trips).
The grey seal, Halichoerus grypus, is a size‐dimorphic, capital breeding species in which sex differences in foraging ecology have previously been found at the scale of individual dives. In this study, diving behaviour of male and female adult grey seals was examined at the temporal scales of dive bouts (41 males/46 females) and foraging trips (7 males/9 females) during the 8‐month prebreeding foraging period between 1992 and 1999 to investigate whether sex differences were evident at longer temporal scales.
Foraging trip duration did not differ between males and females. However, females (the smaller sex) spent significantly more time diving and less time hauled‐out on land between trips than males. This suggests that females are more selective than males when searching for prey. These differences are consistent with the effects of body‐size dimorphism on diving behaviour.
Virtually all dives occurred in bouts. At this scale, males and females showed significantly different seasonal patterns of most bout characteristics, including bout duration, percentage of bout spent at depth and effort (hours spent in bouts day−1).
Grey seals used four different types of bouts, differing in duration, depth, percentage bout spent at depth and the shape of individual dives within the bout. Males and females differed in the proportion of each bout type used and in the seasonal and day–night distribution of bout types.
Few bout characteristics varied significantly among years, despite interannual variation in prey abundance. Where interannual differences did occur, both sexes behaved in a similar way.
Different seasonal patterns in bouts of diving by males and females could not be accounted for by body‐size dimorphism or niche divergence, but were consistent with the hypothesis that females must recover condition earlier in the year than males to support the energetic costs of reproduction.
Recovery rates of benthic communities following physical disturbance
Authors: Dernie K. M. , Kaiser M. J. , Warwick R. M. 
Published: November 2003

Summary

Despite numerous studies that have investigated the effects of physical disturbance on marine benthic communities, deducing the ecological significance of such events has been hampered by the specificity of individual studies. Less stable habitats (coarse, clean sands) are thought to recover more quickly than stable (muddy sands and mud) habitats but so far an empirical test of this paradigm has been lacking.
We describe a large‐scale field experiment that investigated the response of marine benthic communities within a variety of sediment types (clean sand, silty sand, muddy sand and mud) to physical disturbance. Sites were sampled for macrofauna and habitat characteristics (sediment organic content and water content, depth of water within disturbed pits) following disturbance, in order to examine any relationship between the rate of physical and biological recovery.
There were no detectable changes to the measured physical parameters following the disturbance with the exception of the water depth within disturbed areas. It was not possible to derive a linear relationship between the measured habitat characteristics (percentage silt and clay content) and the recovery trajectory of the associated community. However, the rate of sediment infilling of disturbed plots was strongly correlated to the recovery rate of the numbers of individuals within disturbed areas.
Clean sand communities had the most rapid recovery rate following disturbance, whereas communities from muddy sand habitats had the slowest physical and biological recovery rates. These findings concur with the predictions of a meta analysis of fishing disturbances for similar habitats.
We suggest that physical and biological recovery rates are mediated by a combination of physical, chemical and biological factors that differ in their relative importance in different habitats. Monitoring the infilling rate of physically disturbed patches of sediment has the potential to become a useful tool to predict the recovery rate of associated communities.
Territorial behaviour and population dynamics in red grouse Lagopus lagopus scoticus. II. Population models
Authors: Matthiopoulos Jason , Moss Robert , Mougeot François , Lambin Xavier , Redpath Steve M. 
Published: November 2003

Summary

Recent experiments on cyclic red grouse populations discovered that aggressiveness, induced by testosterone implants, depressed population density for more than a year after the implants were exhausted.
This confirms the observation, also made in previous studies of this territorial species, that aggressiveness can determine population density. Additionally, it hints at a form of social memory that sustains the effect of episodes of high aggressiveness after their cause has ceased to exist.
We explore the logical consequences of this observation with a simple model of the interaction between population density and aggressiveness. A flexible function describes how aggressiveness changes from year to year as a function of population density. At low densities animals are tolerant to conspecifics and aggressiveness falls from one year to the next. Conversely, at high densities aggressiveness rises.
In the model, current aggressiveness is set by aggressiveness in the previous year, and modified by last year's population density (first version) or by current population density (second version).
We assume no particular behavioural mechanism underlying this process but derive conditions under which changes in aggressiveness, effected by density, can generate unstable dynamics.
The two versions of the model give fluctuations that differ in period and amplitude but have similar conditions for unstable dynamics. Specifically, the more abrupt the transition from tolerant to intolerant behaviour with increasing density, the more likely are cycles to occur.
We show how a previous model of the kinship hypothesis for red grouse cycles can be recast in the current terminology, and how the new models offer a more general way of examining red grouse population dynamics.
High rates of extracellular superoxide production by lichens in the suborder Peltigerineae correlate with indices of high metabolic activity
Authors: BECKETT R. P. , MINIBAYEVA F. V. , VYLEGZHANINA N. N. , TOLPYSHEVA T. 
Published: November 2003

ABSTRACTRates of extracellular superoxide radical (O2· −) formation were measured in 34 species of lichens from different taxonomic groupings and contrasting habitats before and after desiccation stress. All 21 species from the suborder Peltigerineae produce O2· − extracellularly at high rates, even when they are not stressed. In addition, some species show a burst of O2· − production during rehydration following desiccation. Extracellular production of O2· − is almost absent in the species from other lichen groups. In general, production of high levels of O2· − and the existence of an inducible oxidative burst are best developed in species growing in wet microhabitats. Rates of O2· − production are also positively correlated to previously published indices of lichen metabolic activity. Preliminary studies on the identity of the O2· − producing enzymes suggest that they do not possess the classical characteristics of those suggested to produce reactive oxygen species in higher plants. Patterns of O2· − production are discussed in terms of the strategies used by different lichens groups in their defence against pathogenic fungi and bacteria.
Nitric oxide production in tobacco leaf cells: a generalized stress response?
Authors: GOULD K. S. , LAMOTTE O. , KLINGUER A. , PUGIN A. , WENDEHENNE D. 
Published: November 2003

ABSTRACTThe function of nitric oxide (NO), a gaseous free radical emitted by many plants, is incompletely understood. In the present study the hypothesis that NO generation, like that of the reactive oxygen species, occurs as a general response to different environmental cues was tested. Leaf peels and mesophyll cell suspensions of Nicotiana tabacum cv. Xanthi were loaded with the NO‐specific fluorophore, diaminofluorescein, and subjected to an abiotic stressor. Light stress and mechanical injury had no apparent effect on NO production. In contrast, high temperatures, hyperosmotic stress, salinity and epi‐illumination in a microscope all led to rapid surges in NO‐induced fluorescence. The fluorescence originated from cells of the palisade mesophyll and across all epidermal cell types, including guard cells, subsidiary cells, and long and short trichomes. Fluorescence was evident first in the plastids, then in the nucleus and finally throughout the cytosol. Nicotiana plumbaginifolia cell suspensions expressing the calcium reporter aequorin provided evidence that, under hyperosmotic stress, NO participates in the elevation of free Ca2+ in the cytoplasm. The physiological significance of NO production in response to abiotic stressors is discussed.
Comparative analysis of photosensitivity in photosystem I donor and acceptor side mutants of Chlamydomonas reinhardtii
Authors: SOMMER F. , HIPPLER M. , BIEHLER K. , FISCHER N. , ROCHAIX J.‐D. 
Published: November 2003

ABSTRACTElectron input from plastocyanin into photosystem I (PSI) is slowed down in the Chlamydomonas reinhardtii mutants affected at the donor side (PsaF or PsaB, lumenal loop j) of PSI. In contrast, electron exit from PSI to ferredoxin is diminished in the PSI acceptor side PsaC mutants K35E and FB1. Although, the electron transfer reactions are diminished to a similar extent in both type of mutants, the PsaC mutants K35E and FB1 are more light‐sensitive than the PsaF‐deficient strain 3bF or the PsaB mutants E613N and W627F. To assess the differential photosensitivity of donor and acceptor side mutants fluorescence transients, gross oxygen evolution and uptake, PSII photo‐inhibition and rate of recovery were measured as well as NADP+ photoreduction. The NADP+ photoreduction measurements indicated that the donor side is limiting the reduction rate. In contrast, measurements of gross oxygen evolution and uptake showed that the reducing side limits linear electron transfer. However, under high light, donor and acceptor side mutations lead to PSII photo‐inhibition and to a diminished rate of PSII recovery, cause lipid peroxidation and result in a decrease in the levels of PSI and PSII. The wild type is not affected under the same conditions. These responses are most pronounced in the PsaC‐K35E and PsaB‐W627F mutants, and they correlate with the light sensitivity of these strains. The correlation between limitation of electron transfer through PSI and the formation of reactive oxygen species as a cause for the light‐sensitivity is discussed.
Spatial patterning of pigmentation in evergreen leaves in response to freezing stress
Authors: NICOTRA A. B. , HOFMANN M. , SIEBKE K. , BALL M. C. 
Published: November 2003

ABSTRACTEvergreen leaves of temperate climate plants are often subject to frosts. Changes in carbon gain patterns arise from freezing‐related tissue damage, and from interactions between light and temperature stress. We examined relationships between spatial patterns in freezing and concentrations of chlorophyll. Spatial patterns in pigmentation in leaves that had or had not been exposed to naturally occurring frosts were determined by conventional extraction techniques combined with high‐resolution hyperspectral imaging of reflectance from intact leaves. Predictive indices were developed to relate reflectance to chlorophyll content and chlorophyll a/b ratios within intact leaves. Leaves exposed to frosts had lower chlorophyll contents and more variable a/b ratios than protected leaves. In frost‐affected leaves, chlorophyll content was highest near leaf centres and decreased toward leaf tips and margins. Decline in chlorophyll content was associated with shifts in chlorophyll a/b ratios and increases in red pigmentation due to anthocyanin, with effects being greater on leaf sides exposed directly to the sun. These altered pigmentation patterns were consistent with patterns in freezing. The present results illustrate the fine scale of spatial variation in leaf response to freezing, and raise important questions about impacts of freezing on photosynthetic function in over‐wintering evergreens.
Relationship between boron and calcium in the N2‐fixing legume–rhizobia symbiosis
Authors: REDONDO‐NIETO M. , WILMOT A. R. , EL‐HAMDAOUI A. , BONILLA I. , BOLAÑOS L. 
Published: November 2003

ABSTRACTBecause boron (B) and calcium (Ca2+) seem to have a strong effect on legume nodulation and nitrogen fixation, rhizobial symbiosis with leguminous plants, grown under varying concentrations of both nutrients, was investigated. The study of early pre‐infection events included the capacity of root exudates to induce nod genes, and the degree of adsorption of bacteria to the root surface. Both phenomena were inhibited by B deficiency, and increased by addition of Ca2+, resulting in an increase of the number of nodules. The infection and invasion steps were investigated by fluorescence microscopy in pea nodules harbouring a Rhizobium leguminosarum strain that constitutively expresses green fluorescent protein. High Ca2+ enhanced cell and tissue invasion by Rhizobium, which was highly inhibited after B deficiency. This was combined with an increased B concentration in nodules of plants grown on B‐free medium and supplemented with high Ca2+ concentrations, and that can be attributed to an increased B import to the nodules. Histological examination of indeterminate (pea) and determinate (bean) nodules showed an altered nodule anatomy at low B content of the tissue. The moderate increase in nodular B due to additional Ca2+ was not sufficient to prevent the abnormal cell wall structure and the aberrant distribution of pectin polysaccharides in B‐deficient treatments. Overall results indicate that the development of the symbiosis depends of the concentration of B and Ca2+, and that both nutrients are essential for nodule structure and function.
Characterization of Arabidopsis genes involved in biosynthesis of polyamines in abiotic stress responses and developmental stages
Authors: URANO K. , YOSHIBA Y. , NANJO T. , IGARASHI Y. , SEKI M. , SEKIGUCHI F. , YAMAGUCHI‐SHINOZAKI K. , SHINOZAKI K. 
Published: November 2003

ABSTRACTTo characterize the genes for enzymes involved in the biosynthesis of polyamines (PAs), their expression profiles were investigated and the levels of PAs in Arabidopsis thaliana quantified. In the Arabidopsis genome, eight genes involved in PAs biosynthesis were identified and the expression profiles of these genes were analysed, not only under abiotic stress to determine whether they were stress‐inducible, constitutive, or stress‐repressible, but also in various organs to show their tissue specificity. AtADC2 and AtSPMS mRNAs, encoding arginine decarboxylase and spermine synthase, clearly increased in response to NaCl and dehydration and abscisic acid treatments. Stress‐inducible accumulation of AtADC2 mRNA correlated with putrescine (Put) accumulation under NaCl and dehydration treatments. In a cold condition, AtSAMDC2 mRNA increased significantly. AtADC2 and AtSAMDC2 mRNA were expressed in sexual organs such as flowers, buds and immature siliques. PAs also accumulated in sexual organs. These results suggest that the transcripts of eight genes involved in PA biosynthesis show different profiles of expression not only in response to environmental stress but also during plant development.
Sequence‐specific, Golgi‐dependent vacuolar targeting of castor bean 2S albumin
Authors: Brown Joanna C. , Jolliffe Nicholas A. , Frigerio Lorenzo , Roberts Lynne M. 
Published: November 2003

SummaryThe targeting of the castor bean (Ricinus communis) 2S albumin precursor has been investigated by expressing cDNA in transformed tobacco (Nicotiana tabacum) leaf cells and by following biosynthesis in the native tissue. Correct targeting in both tissues was accompanied by processing of the precursor. Delivery to vacuoles was sensitive to brefeldin A (BFA) treatment in both tissues and to perturbation of COPII function in tobacco, supporting the view that transport through the Golgi is required. The targeting signal for this Golgi‐dependent routing lies within the propeptide of the first heterodimer of proalbumin. This propeptide directed a normally secreted reporter protein to the vacuoles of tobacco cells in a Golgi‐dependent manner in vivo, unless a critical Leu residue was mutated, supporting the view that a sequence‐specific signal was needed to target a seed storage protein to the vacuoles of a vegetative cell.
Application of a new enzyme‐linked immunosorbent assay for detection of total hepatitis C virus core antigen in blood donors
Authors: Cano H. , Candela M. J. , Lozano M. L. , Vicente V. 
Published: November 2003

Summary.  Recent studies have shown that total hepatitis C virus (HCV) core antigen, both free and antibody bound, is an accurate indirect marker of viral replication that can be used in clinical practice. The aim of the present study was to evaluate the performance of a new total HCV core antigen enzyme‐linked immunosorbent assay (ELISA) for detection and quantification of total core antigen in blood donors, testing positive for anti‐HCV antibodies and for prospective low‐risk population screening.A population comprising 257 samples, from blood donors detected reactive for anti‐HCV antibodies [137 recombinant immunoblot assay (RIBA) positive and 120 RIBA indeterminate], were tested by using a new total HCV core antigen ELISA. HCV‐RNA was quantified by using quantitative polymerase chain reaction (PCR) assays in all RIBA‐positive samples and RIBA‐indeterminate samples that were positive for the total core antigen. Specificity of the assay was studied in 1070 healthy blood donors negative for anti‐HCV antibodies.Compared with quantitative PCR assays, the total HCV core antigen assay showed 97·37% sensitivity. The three HCV‐RNA‐positive samples, which tested negative for the total core antigen, had a low viral load (<1·4 × 104 IU mL−1). All samples with more than 1·4 × 104 IU mL−1 of viral RNA were positive for total core antigen, independent of the HCV genotype. Concentration of total core antigen correlated significantly with those of HCV‐RNA (r = 0·614, P < 0·0001). Overall specificity in freshly collected blood donor specimens was 99·63%.Our data indicate that the total HCV core antigen ELISA has a sensitivity close to PCR assays in diagnosing HCV infection in blood donors with anti‐HCV antibodies and shows an excellent specificity in volunteer donors. This assay, in combination with anti‐HCV antibodies screening tests, could be an alternative to molecular assays for HCV infection screening in blood donors.
Effect of haemodilution with diaspirin cross‐linked haemoglobin on the oxygen reserve in a rodent model of surgical blood loss
Authors: D'Almeida M. S. , White M. , Martin C. M. , Sibbald W. J. , Chin‐Yee I. H. 
Published: November 2003

Summary.  The efficacy of pre‐operative haemodilution is limited by the reduction in haemoglobin concentration. Acellular haemoglobin‐based oxygen carriers provide an alternative to colloid as a haemodiluent, potentially extending the safe limits of this procedure. The aim of this investigation was to determine whether haemodilution with a cross‐linked haemoglobin solution, diaspirin cross‐linked haemoglobin solution (DCLHb), would enhance the oxygen reserve compared to pentastarch.Sprague Dawley rats were placed in a metabolic box to directly measure systemic oxygen consumption (VO2). Rats were randomized to be haemodiluted to a cellular haemoglobin of 80 g L−1 with either DCLHb or pentastarch. Oxygen reserve was assessed during isovolemic haemorrhage by determining the critical oxygen delivery (DO2crit) and haemoglobin concentration at the point of oxygen supply dependency (OSD).Following haemodilution and for the duration of the experiment, cardiac index (CI) was significantly lower and systemic vascular resistance was significantly higher in the DCLHb than the pentastarch group. The DO2crit (3·2 ± 0·4 mL minAg−1 and 3·4 ± 0·5 mL minAg−1, DCLHb versus pentastarch) and cellular haemoglobin concentration (51 ± 9 g L−1 and 48 ± 9 g L−1), at which rats entered OSD were similar in both groups. Total haemoglobin concentration (cellular and plasma DCLHb) and arterial oxygen content were significantly higher in the DCLHb group (total haemoglobin, 66 ± 8 g L−1 and arterial content, 9·2 ± 1·4 mL dL−1) compared to the pentastarch group (total haemoglobin, 48 ± 9 g L−1 and arterial content, 7·3 ± 1·4 mL dL−1). Oxygen extraction ratios increased from baseline levels to 0·53 ± 0·07 and 0·56 ± 0·1, for the DCLHb and pentastarch groups, respectively, and were not significantly different.The increase in arterial oxygen content from DCLHb in plasma was offset by the decrease in CI observed in this group. Plasma DCLHb did not extend the limits of haemodilution beyond the capacity of the cellular haemoglobin concentration.
Haemolytic disease of the newborn due to maternal irregular antibodies in the Chinese population in Taiwan
Authors: Wu K. H. , Chu S. L. , Chang J. G. , Shih M. C. , Peng C. T. 
Published: November 2003

Summary.  From 1991 to 2000, amongst 23 886 full‐term healthy Chinese babies delivered at our hospital, 2615 babies developed neonatal hyperbilirubinaemia. After excluding other causes of hyperbilirubinaemia and identifying the irregular antibodies, 15 cases of haemolytic disease of the newborn (HDN) due to maternal irregular antibodies were diagnosed; three cases were born in our hospital and 12 cases were referred. Amongst these 15 babies, six cases had HDN due to anti‐E, three cases due to anti‐E + c, three cases due to anti‐D, one case due to anti‐c and two cases due to ‘Mi’ antibodies reacting with MiIII phenotype cells (anti‐Hil and anti‐Mur). Although there were four cases of hydrops fetalis, only one of the patients expired.The prevalence of HDN caused by maternal irregular antibodies has been estimated to be 0·01%. Therefore, routine prenatal screening for irregular antibodies was not rational in the Chinese population in Taiwan. Anti‐E and anti‐E + c were the important irregular antibodies resulting in HDN. Although few cases of HDN due to anti‐‘Mi’ have been reported, Anti‐‘Mi’ is significant in regions with a high prevalence of the MiIII phenotype.