bluuebunny/crossref_metadata_2025 huggingface dataset:
Daily activity patterns of Whiptail Lizards (Squamata: Teiidae: Aspidoscelis): a proximate response to environmental conditions or an endogenous rhythm?
Authors: WINNE C. T. , KECK M. B.
Published: May 2004

The hypothesis that high soil temperatures are required to induce both initiation and cessation of daily activity in Whiptail Lizards (Aspidoscelis; formerly Cnemidophorus), as well as the hypotheses that hunger thresholds and high rates of evaporative water loss influence daily activity patterns, were experimentally tested in A. inornata and A. gularis.

Although a critical soil temperature was required to elicit the initiation of morning activity, high temperature was not a necessary stimulus for the cessation of activity.

Access to prey did not influence the pattern of daily activity; moreover, evaporative water loss did not appear to explain the cessation of afternoon activity.

Reversing the photoperiod during our experiments led only to a change in the time of initiation of daily activity (i.e. activity began 12 h later), not a significant change in the duration of daily activity.

These results provide strong evidence that circadian cycles can play a critical role in not only the initiation but also the cessation of activity.

While the ultimate cause (i.e. selective advantage, if any) of this unusual circadian rhythm may be related to extreme temperature, limited water supplies or some other exogenous factor, clearly, the rhythm persists in the absence of limiting environmental conditions.
Direct and indirect impacts of fire on isoprenoid emissions from Mediterranean vegetation
Authors: ALESSIO G. A. , DE LILLIS M. , FANELLI M. , PINELLI P. , LORETO F.
Published: May 2004

Fire is often associated with episodes of air pollution, possibly involving the release of biogenic isoprenoids (isoprene and monoterpenes). The direct and indirect impacts of fire on isoprenoid emission by plants of the Mediterranean vegetation were studied. Leaves of Arbutus unedo, Phillyrea latifolia, Cistus incanus, Cistus mospeliensis, Pistacia lentiscus, Quercus ilex, Quercus suber, Quercus pubescens, Myrtus communis and Pinus halepensis were exposed to direct fire or to the fire‐consequent wave of elevated temperature.

Half the tested plant species did not emit isoprenoids and the treatments did not induce isoprenoid emission. In contrast, isoprene was emitted by intact leaves of Q. pubescens and M. communis, while monoterpenes were emitted by intact leaves of Q. ilex, Q. suber and P. halepensis.

The two treatments rapidly reduced isoprene emission by isoprene‐emitting species and monoterpene emission by Quercus spp. This inhibition was associated with photosynthetic inhibition, and recovery was seen in Quercus spp. within days of treatment. Recovery was also associated with the recovery of photosynthesis, suggesting that emitted isoprenoids continue to be formed predominantly from photosynthetic intermediates after a fire episode.

In Q. pubescens leaves, however, recovery from the elevated‐temperature treatment caused a sustained increase of isoprene emission which was not mirrored by a similar increase in photosynthesis. Whether this represents the induction of alternative metabolic pathways or an increase of the flux of photosynthetic carbon in the isoprene pathway is not known. Isoprene‐emitting species in areas surrounding fire may emit a substantially larger hydrocarbon flux for several days after fire.

The elevated‐temperature treatment induced the emission of α‐pinene from Myrtus leaves, and the fire treatment stimulated the emission of several monoterpenes from Pinus needles. The emission began to decrease within minutes in Myrtus, while it increased within the first 100 min in Pinus, where it was detectable the day after the event although the flux was smaller than in prestressed needles.

Exposure to fire and to the associated elevated temperature may induce bursts of monoterpenes from plants that regularly do not emit these compounds and temporarily increase the load of monoterpenes in the atmosphere by pine species. These emissions may contribute to photochemical reactions involved in smog and ozone formation.
Linking fine root traits to maximum potential growth rate among 11 mature temperate tree species
Authors: COMAS L. H. , EISSENSTAT D. M.
Published: May 2004

There is limited understanding of patterns of variation that exist among root traits of different species, especially under field conditions. We contrasted 11 fast‐ and slow‐growing species paired within five evolutionary lineages to investigate whether root traits associated with soil resource acquisition were related to species’ potential growth rate.

Measurements of root morphology, architecture, nitrogen and phenolic concentration, respiration and phosphorus uptake were taken on fine, non‐woody roots sampled from forest stands in central Pennsylvania, USA.

Across all five contrasts, roots of fast‐growing species generally had higher specific root length, smaller diameters, greater degree of branching, and lower phenolic concentrations than those of slow‐growing species. This suggests differences in potential soil exploration and root defences among species differing in potential growth rate.

There were no significant differences between fast‐ and slow‐growing species in root tissue density, respiration or P uptake. Lack of root physiological differences between species differing in growth rate contrasted with previous research on chamber‐grown seedlings.

These results imply that, while roots of fast‐growing species may be constructed for more rapid soil exploration and shorter life span than those of slow‐growing species, root physiology is either more closely tied to overall plant physiology, which is more similar among mature trees, or masked by variation in soil microsites, root age or interactions with mycorrhizal fungi.
Morphological dynamics in the foraging apparatus of a deposit feeding marine bivalve: phenotypic plasticity and heritable effects
Authors: DRENT J. , LUTTIKHUIZEN P. C. , PIERSMA T.
Published: May 2004

Design considerations dictate that systems work most efficiently when the separate components have processing capacities adjusted to each other, a principle known as symmorphosis. Adjustments in response to a variable environment are most likely to occur at the interface between the environment and integrated systems. In deposit‐feeding bivalves, the interface of the alimentary canal with the foraging environment consists of a siphon (intake), gills (flow generation) and palps (particle sorting).

Among European populations of the Baltic Tellin, Macoma balthica, the gill‐to‐palp mass‐ratio was positively correlated with the foraging environment, characterized by median grain size of the ambient sediment (R = 0·71).

In laboratory‐reared M. balthica gill‐to‐palp mass‐ratio responded plastically to changes in ambient sediment characteristics, resulting in large ratios in coarse sediment and small ratios in fine sediment.

In a common garden experiment, relative differences in gill‐to‐palp mass‐ratios of laboratory‐reared M. balthica from four populations appeared similar to those in the field, indicating a heritable component to the variation in integrated organ systems.

Phenotypically plastic adjustments ensure a close match between the integrated system of the alimentary canal to the local foraging environment. Heritable variation among populations may reflect different selective optima related to consistent differences in the environment between the populations.
Species‐level effects more important than functional group‐level responses to elevated CO2: evidence from simulated turves
Authors: HANLEY M. E. , TROFIMOV S. , TAYLOR G.
Published: May 2004

Using mixtures of 14 calcareous grassland plant species drawn from three functional groups, we looked at the effects of elevated atmospheric CO2 on contrasting levels of ecosystem performance (species, functional group and community). Experimental communities were subjected to ambient (≈350 µmol mol−1) or elevated CO2 (≈600 µmol mol−1) in controlled environments, with grazing simulated by clipping at monthly intervals for 546 days.

We assessed the effect of elevated CO2 on plant performance by quantifying the productivity (biomass) and cover of component species. We also examined the effect of elevated CO2 on the vertical structure of the plant canopy. Elevated CO2 resulted in a significant increase in total community biomass only following nutrient addition. Within functional groups, non‐leguminous forb species had significantly greater biomass and cover in elevated CO2 both before and after nutrient addition, although the effect was mainly due to the influence of one species (Centaurea nigra). Grasses, in contrast, responded negatively to elevated CO2, although again significant reductions in biomass and cover could mainly be ascribed to a single species (Brachypodium pinnatum). Legumes exhibited increased biomass and cover in elevated CO2 (the effects being particularly marked for Anthyllis vulneraria and Lotus corniculatus), but this response disappeared following nutrient addition. Vertical structure was little affected by CO2 treatment.

We conclude that due to the idiosyncratic responses of individual species, the categorization of plants into broad functional groups is of limited use in guiding our understanding of the impacts of elevated atmospheric CO2 on plant communities.
Allocation of nitrogen to cell walls decreases photosynthetic nitrogen‐use efficiency
Authors: ONODA Y. , HIKOSAKA K. , HIROSE T.
Published: May 2004

Nitrogen (N) is an essential limiting resource for plant growth, and its efficient use may increase fitness. We investigated photosynthetic N‐use efficiency (photosynthetic capacity per unit N) in relation to N allocation to Rubisco and to cell walls in Polygonum cuspidatum Sieb. et Zucc. which germinated in May (early germinators) and August (late germinators).

There was a significant difference between early and late germinators in photosynthetic capacity as a function of leaf N content per unit area. Higher photosynthetic N‐use efficiency in late germinators was caused primarily by a larger allocation of N to Rubisco.

Nitrogen allocation to cell walls was smaller in late germinators. The shorter growth period in late germinators was associated with higher photosynthetic capacity, which was achieved by allocating more N to photosynthetic proteins at the expense of cell walls.

The trade‐off between N allocation to photosynthesis and to structural tissues suggests that plants change N allocation to increase either the rate or duration of carbon assimilation. Such plastic change would help plants maintain themselves and cope with environmental changes.
Microparasite manipulation of an insect: the influence of theegtgene on the interaction between a baculovirus and its lepidopteran host
Authors: CORY J. S. , CLARKE E. E. , BROWN M. L. , HAILS R. S. , O'REILLY D. R.
Published: May 2004

Parasites and pathogens manipulate their hosts in a variety of ways that are thought to enhance their fitness. However, it is rare to be able to link such phenotypic changes to specific genes.

Here the effect of a single pathogen gene is examined. The ecdysteroid UDP‐glucosyltransferase (egt) gene of insect baculoviruses produces an enzyme that interferes with host moulting.

The effect of theegtgene was examined by comparing two baculoviruses that differed only in the expression of this gene. All three fitness traits examined – pathogenicity, infection duration and pathogen productivity – were affected by deletion of the gene.

Trichoplusia nilarvae in all five instars died earlier when infected with theegt‐minus virus compared with those infected by the wild‐typeAutographa californicanucleopolyhedrovirus.

Unexpectedly, theegt‐minus virus was more pathogenic to final instar larvae than the wild‐type virus. Virus genotype and dose both influenced insect development.

Wild‐type infected insects had a significantly higher yield of virus at death, cadaver weight and yield of virus per unit weight than those infected with theegt‐minus virus.

The size of the virus challenge had a major influence on the outcome of the interaction. The consequences of these data for pathogen fitness are discussed.
Down regulation of Hsp70 expression level prolongs the duration of heat‐induced male sterility in Drosophila buzzatii
Authors: SARUP P. , DAHLGAARD J. , NORUP A.‐M. , JØRGENSEN K. T. , HEBSGAARD M. B. , LOESCHCKE V.
Published: May 2004

The relationship between heat shock protein Hsp70 expression level and the duration of heat‐induced male sterility was investigated in four populations of Drosophila buzzatii Patterson and Wheeler. The effect of heat hardening on the duration of sterility was further examined after flies developed at either 25 or 31 °C. In addition, Hsp70 expression was measured in testes after development at three different thermal regimes.

Four main hypotheses were tested: (i) Hsp70 is expressed in testes of D. buzzatii males even at non‐stressful temperatures, and the level of expression increases with increasing rearing temperature. (ii) Hsp70 expression level differs between populations and is negatively correlated with the duration of poststress sterility. (iii) Experimentally induced Hsp70 expression at the pupal stage shortens the sterility period of flies reared above the temperature threshold of sterility. (iv) In contrast, a hardening treatment during the pupal stage of flies reared at 25 °C results in a longer time to fertility.

The results matched the hypotheses, leading to the conclusion that higher Hsp70 expression reduces the duration of heat‐induced male sterility.
Does testis size track expected mating success in yellow dung flies?
Authors: BLANCKENHORN W. U. , HELLRIEGEL B. , HOSKEN D. J. , JANN P. , ALTWEGG R. , WARD P. I.
Published: May 2004

We quantitatively compare the fitness function linking male mating success in the field to body size and the allometric relationship linking testis length (estimating sperm production) to body size, both empirically derived, for the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae).

We find that both relationships are similarly non‐linear (quadratic) and increasing. The most parsimonious interpretation of this congruence is that the evolution of testis size (and hence sperm numbers) evolutionarily ‘tracks’ the number of copulations a male of a given size can expect, resulting in the particular non‐linear testis size‐body size allometry evident.

We offer a general, two‐tiered statistical approach for this kind of quantitative comparison.
Net spinning caddisflies as stream ecosystem engineers: the influence of Hydropsyche on benthic substrate stability
Authors: CARDINALE B. J. , GELMANN E. R. , PALMER M. A.
Published: May 2004

Organisms that physically modify or create habitat (ecosystem engineers) can have a profound influence on community and ecosystem dynamics.

Here evidence is presented that one of the most abundant and widely distributed lotic insects could act as an ecosystem engineer in streams by increasing the stability of benthic substrates during flooding.

Natural densities of larval net spinning caddisflies (Hydropsychidae) were established in stream channels that had standardized physical properties. The mobility of three particle sizes were measured during simulated flooding and the fraction of particles eroded compared with that of control streams.

Larvae increased the initial velocity required to erode sediments by 10–30%. At velocities sufficient to scour 87% of particles from control channels, 57–100% remained stable in channels colonized by larvae.

Assuming larvae have similar effects in natural streams, caddisflies could be expected to increase the recurrence interval of a substrate scouring flood from 1·67 year to 2·41 year, corresponding to a 17% decrease in the probability of bed scour per year.

Our study suggests these insects could play an important role in generating the spatial ‘refuges’ that moderate the resistance of lotic communities to flooding. It is argued that, as has occurred in marine systems, a better understanding of how freshwater organisms engineer their physical environment has much potential to complement our historical focus on the abiotic forces that constrain populations and communities.
Sex‐specific differences in cardiovascular performance of a centrarchid fish are only evident during the reproductive period
Authors: COOKE S. J.
Published: May 2004

Although in birds and mammals sex‐specific differences in organismal performance and physiology are well documented, comparatively little is known about the influence of sex or reproductive status on fish performance or metabolism.

In this study, the resting cardiovascular performance of male and female Largemouth Bass Micropterus salmoides was contrasted across three seasons and different reproductive states including the spring when nesting males provide sole parental care. Doppler flow probes were used to monitor resting cardiac output (Q) and its two components (heart rate, fH and stroke volume, SVH).

During the spring when Largemouth Bass were engaged in reproduction (at 21 °C), parental male nesting fish had heightened resting cardiovascular rates (both Q and fH) relative to non‐nesting males and females. In the summer at higher water temperatures (24 °C), and in the autumn at water temperatures similar to the reproductive period (21 °C), resting cardiovascular variables were similar between sexes.

This study found that there are sex‐based differences in fish physiological performance. However, the sex‐specific differences were evident only during the reproductive period, and in particular for male fish actively engaged in the nesting phase of parental care, indicating a likely role of the endocrine system.
Endocrinology & Dialysis. Testosterone Metabolism and Replacement Therapy in Patients with End‐Stage Renal Disease
Authors: Holley JL , Johansen Kirsten L.
Published: May 2004

Hypogonadism is common among men with end‐stage renal disease (ESRD), beginning before the need for dialysis and not improved with the initiation of dialysis. Many of the manifestations of hypogonadism, such as bone disease and muscle wasting, are also frequently seen among dialysis patients. There have been few studies of testosterone replacement therapy in this patient population, but available data suggest that testosterone can be administered without adjustment of the doses used in hypogonadal men with normal renal function. Extrapolation from results of treatment of hypogonadal older men with normal renal function suggests that testosterone replacement could improve libido and could have salutary effects on muscle mass and bone mineral density in patients with kidney disease. However, caution is warranted because of the potential side effects of testosterone therapy, and further research is needed to more precisely define the balance of risk and benefit in patients with chronic kidney disease. Specifically it will be important to determine the prevalence and clinical significance of hypogonadism in ESRD patients in the modern era and to measure the effects of replacement therapy on various symptoms of hypogonadism as well as on overall quality of life, physical functioning, and survival.
Hypothesis: The Body Mass Index Paradox and an Obesity, Inflammation, and Atherosclerosis Syndrome in Chronic Kidney Disease
Authors: Beddhu Srinivasan
Published: May 2004

The association of high body mass index (BMI) with better survival in chronic kidney disease (CKD) is considered a “risk factor paradox” or “reverse epidemiology.” Since malnutrition is a powerful predictor of death and cardiovascular disease is its leading cause, it has been suggested that malnutrition and atherosclerosis must be associated. Thus the current paradigm is that malnutrition is a risk factor for atherosclerosis and obesity is protective in CKD patients. We recently showed that high‐BMI patients with inferred high body fat have an increased prevalence of atherosclerosis and subsequent cardiovascular and all‐cause mortality. Prior cross‐sectional studies also showed that high BMI in CKD is associated with higher C‐reactive protein (CRP) levels and increased coronary calcification on electron beam computed tomography (CT) scan. These apparently conflicting data on better survival but increased inflammation and atherosclerosis in high‐BMI CKD patients could be explained as follows. It is hypothesized that nutrition exerts a much stronger influence on survival than atherosclerosis in CKD. Malnutrition strongly augments the hazard of death from coexistent diseases, while better nutrition has the opposite effect. Thus the risk of death is highest in malnourished patients (low muscle and low fat mass) and lowest in well‐nourished patients (high BMI, high muscle mass). Obesity (high BMI, high fat mass) is associated with inflammation and atherosclerosis. The risk of death from obesity and atherosclerosis is increased, but not so much as occurs with malnutrition. Therefore high body fat patients have intermediate survival. Thus it is postulated that an association of obesity, inflammation, and atherosclerosis (OIA syndrome) might exist in CKD.
Fellows’ Forum in Dialysis. Depression: A Common but Underrecognized Condition Associated with End‐Stage Renal Disease
Authors: Perazella Mark A. , Wang Pei‐Li , Watnick Suzanne G.
Published: May 2004

We describe a patient with end‐stage renal disease (ESRD) who developed depression over the period of dialysis initiation. Depression is an extremely common but underrecognized disorder in the dialysis population, which is one of the rationales for this case report. Here we present the epidemiology, mechanisms for diagnosis, associations with medical morbidity, and treatment modalities specifically for patients on dialysis.
Improved Survival with Higher Hematocrits: Where is the Evidence?
Authors: Cotter Dennis J. , Stefanik Kevin , Zhang Yi , Thamer Mae
Published: May 2004

The Centers for Medicare and Medicaid Services (CMS) is reviewing Medicare coverage policy for recombinant human erythropoietin (epoetin) therapy. CMS officials are concerned that “Medicare spending on EPO may be higher than necessary without resulting in optimal patient benefit.” Approximately 190 end‐stage renal disease (ESRD) patients die each day—a mortality rate that has remained essentially unchanged since 1994—despite improvements in the “adequacy of dialysis, vascular access, and anemia management”. To date, the evidence cited in support of a survival benefit of epoetin confuses the relationship between treatment response and outcomes with a causal effect of epoetin. A variety of mechanisms may account for a non‐causal association between hematocrit and mortality can occur. We conclude that there is no basis for inferring the survival benefits (or detriments) of increasing a patient's hematocrit by adjusting the dosing of epoetin. Furthermore, we note that caution is required in administering large doses of epoetin to unresponsive patients in order to achieve the target hematocrit. A better understanding of the epoetin/survival relationship, well‐grounded in science, is needed to provide a basis for CMS to improve its current epoetin policies, and may help to improve patient mortality.
Environmental and spatial variables influence the composition of frog assemblages in sub‐tropical eastern Australia
Authors: Parris Kirsten M.
Published: May 2004

In community ecology, contrasting theories suggest that the distribution and abundance of species, and thus the composition of assemblages, are influenced by i) environmental gradients, or ii) contagious biotic processes such as predation, competition, dispersal and disease. In the former case, sites with similar environments would tend to support similar assemblages, while in the latter, geographically proximate sites would tend to support more similar assemblages than widely separated sites. I investigated the relative influence of environmental variables and spatial position on the composition of frog assemblages at forest streams in sub‐tropical eastern Australia using redundancy analysis (RDA) and partial RDA. Data on the maximum abundance of the frog species at 65 survey sites were transformed such that RDA would yield the Hellinger distance between sites. The following analysis identified 11 environmental variables that explained 45% of the variation in the abundance of species at the survey sites (the species matrix), as a proportion of total variance. The geographic co‐ordinates of the survey sites accounted for 12%, while the environmental and spatial variables combined accounted for 47% of the variation in the species matrix. Partial redundancy analysis indicated that of the explained variation, 74% was purely environmental, 5% was purely spatial and 21% was spatial environmental variation. This study is the first to quantify the relative influence of environmental and spatial variables on the composition of amphibian assemblages. It provides support for both the environmental control model and the biotic control model of species’ distributions and assemblage composition, although environmental variables appear to have the greater effect at this scale of analysis.
Benthic diatom communities in boreal streams: community structure in relation to environmental and spatial gradients
Authors: Soininen Janne , Paavola Riku , Muotka Timo
Published: May 2004

An important goal for community ecology is the characterization and prediction of changes in community patterns along environmental gradients. We aimed to identify the major environmental correlates of diatom distribution patterns in boreal running waters. We classified 197 stream sites based on their diatom flora. Direct ordination methods were then used to identify the key environmental determinants of this diatom‐based stream typology. Finally, we tested whether a regional classification scheme based on terrestrial landscapes (ecoregions) provides a reasonable framework for a regional grouping of streams based on their diatom flora. Two‐way indicator species analysis produced 13 site groups, which were primarily separated by chemical variables, mainly conductivity, total P and water colour. In partial CCA, the environmental and spatial factors accounted for 38% and 24%, respectively, of explained variation in community composition. A high proportion (almost 40%) of variation explained by the combined effect (spatially‐structured environmental) indicated that diatom communities of boreal streams incorporate a strong spatial component. At the level of subecoregions, classification strength was almost equally strong for all sites as for near‐pristine reference sites only. Procrustes analysis indicated that spatial factors and patterns in diatom community structure were strongly concordant. Our data support the argument that diatom communities are strongly spatially structured, with distinctly different communities in different parts of the country. Because of the strong spatial patterns of community composition, bioassessment programs utilising lotic diatoms would clearly benefit from regional stratification. A combination of regional stratification and the prediction of assemblage structure from local environmental features might provide the most robust framework for diatom‐based assessment of the biological integrity of boreal streams.
Elevational gradients, area and tropical island diversity: an example from the palms of New Guinea
Authors: Bachman Steven , Baker William J. , Brummitt Neil , Dransfield John , Moat Justin
Published: May 2004

The factors causing spatial variation in species richness remain poorly known. In this study, factors affecting species richness of palms (Palmae/Arecaceae) were studied along the elevational gradient of New Guinea. Interpolated elevational ranges were calculated from a database of all known collections for 145 species in 32 genera. The amount of land area at different elevations greatly affects the species richness gradient. If assessed in equal‐elevation bands species richness appears to decline monotonically, but when assessed in equal‐area bands species richness shows a pronounced mid‐elevation peak, due to the large proportion of lowlands in New Guinea. By randomising species ranges within the total elevational gradient for palms and accounting for area, we found the mid‐elevation peak to be consistent with a mid‐domain effect caused by the upper and lower limits to palm distribution. Our study illustrates the importance of accounting for area in macroecological studies of richness gradients and introduces a novel yet simple method for doing this through the use of equal‐area bands. Together, the effect of area and the mid‐domain effect explain the majority of variation in species richness of New Guinea palms. We support calls for the multivariate assessment of the mid‐domain effect on an equal footing with other potential explanations of species richness.
Landscape structure and locust swarming: a satellite's eye view
Authors: Despland Emma , Rosenberg Jane , Simpson Stephen J.
Published: May 2004

Desert locust Schistocerca gregaria outbreaks consistently start in the same places, suggesting that certain landscapes are particularly favourable for outbreaking. Outbreaks are generated by multiplication, concentration and gregarisation of locust populations. Previous research has shown how small‐scale vegetation patterns in desert ecosystems influence locust gregarisation; the present study examines the effects of large‐scale landscape structure on locust multiplication and concentration. NOAA/AVHRR satellite imagery was used to relate abundance and spatial distribution of resources at the landscape scale to the historical record of locust outbreaks. Threshold NDVI values were investigated to define what constitutes ‘resource’ for locusts. The first part of the study showed that abundance and spatial distribution of resource were not sufficient to distinguish between outbreak and non‐outbreak areas in the western part of the locust distribution area. Thus, outbreak danger zones cannot be identified by landscape structure at this spatial resolution. The second analysis investigated spatio‐temporal patterns of vegetation growth in two locust breeding areas with very different landscape structure; in both cases, the patterns differed significantly between outbreaking and non‐outbreaking years. In Mauritania, a flat homogeneous desert landscape, both resource abundance and fragmentation were higher in outbreaking years. On the Red Sea coast, a fragmented landscape, resource spatial distribution was consistent between years, and abundance alone was a significant predictor of outbreaking. High resource abundance promotes locust multiplication, and contraction of resource into small patches increases locust concentration; these two mechanisms explain how landscape structure influences locust outbreaking.
Life cycle period and activity of prey influence their susceptibility to predators
Authors: Molinari‐Jobin A. , Molinari P. , Loison A. , Gaillard J.‐M. , Breitenmoser U.
Published: May 2004

In a multi‐prey system, predators kill different kinds of prey according to their availability, where “availability” is a function of prey abundance and vulnerability (e.g. anti‐predator behavior). We hypothesized that prey availability changes seasonally, for instance because reproduction leads to a higher abundance of young in spring and summer or because changes in behavior such as during the mating season makes the prey periodically more vulnerable. We tested this hypothesis in a simple predator‐prey system in the Jura Mountains of Switzerland and France, where a single large mammalian predator, the Eurasian lynx, preys upon two ungulate species, the roe deer and the chamois. In 1996 and 1997 we were able to assign a total of 190 roe deer and 54 chamois killed by lynx to a specific age and sex class (males, females or juveniles). As expected, the proportion of juveniles killed varied considerably among periods, being at the highest from 1st of June to 15th of August. No significant seasonal differences were detected regarding the frequency of predation on males versus females. In particular, the interaction between species and period, expected because of different timing of the rutting period between roe deer and chamois, was not significant. Females were killed only slightly more often during gestation. The relationship between prey abundance and vulnerability is highly complex, as the lynx’ prey selection needs to be analyzed not only horizontally (changes of a specific prey category with season) but also vertically (an increase in the vulnerability of one category releases predation pressure on others). Second, we predicted that certain activities, such as feeding, expose prey to predation more than others. We found more chamois predated when feeding, whereas roe deer were predated mainly when ruminating. This interspecific discrepancy reflects differences either in the anti‐predator behavior of roe deer and chamois or in the relative time allocation to feeding and ruminating between the two species.
Language, Learning, and Color Perception
Authors: Özgen Emre
Published: May 2004

People perceive colors categorically. But what is the role of the environment (or nurture)—specifically, language—in color perception? The effects of language on the way people categorize and perceive colors have been considered to be minimal, but recent evidence suggests that language may indeed change color perception. Speakers of languages with different color-name repertoires show differences in the way they perceive color. Research shows that categorical effects on color perception can be induced through laboratory training and suggests language can similarly change color perception through the mechanism of perceptual learning.
Why Socioeconomic Status Affects the Health of Children
Authors: Chen Edith
Published: May 2004

This article provides an overview of research on socioeconomic status (SES) and physical health in childhood. SES has a gradient relationship with children's health, such that for each incremental increase in SES, there is a comparable benefit in children's health. In this article, I discuss psychosocial mechanisms underlying this association and argue that it is important to utilize knowledge about how the relationship between SES and health changes with age to inform a developmentally plausible search for mediators of this relationship. Furthermore, SES at different points in a child's lifetime may have different effects on health. I advocate an interdisciplinary approach to searching for mediators that would allow researchers to understand how characteristics of society, the neighborhood, the family, and the individual child are involved in the processes linking SES and children's health.
The centrosomal protein Lats2 is a phosphorylation target of Aurora‐A kinase
Authors: Toji Shingo , Yabuta Norikazu , Hosomi Toshiya , Nishihara Souichi , Kobayashi Toshiko , Suzuki Susumu , Tamai Katsuyuki , Nojima Hiroshi
Published: May 2004

Human Lats2, a novel serine/threonine kinase, is a member of the Lats kinase family that includes the Drosophila tumour suppressor lats/warts. Lats1, a counterpart of Lats2, is phosphorylated in mitosis and localized to the mitotic apparatus. However, the regulation, function and intracellular distribution of Lats2 remain unclear. Here, we show that Lats2 is a novel phosphorylation target of Aurora‐A kinase. We first showed that the phosphorylated residue of Lats2 is S83 in vitro. Antibody that recognizes this phosphorylated S83 indicated that the phosphorylation also occurs in vivo. We found that Lats2 transiently interacts with Aurora‐A, and that Lats2 and Aurora‐A co‐localize at the centrosomes during the cell cycle. Furthermore, we showed that the inhibition of Aurora‐A‐induced phosphorylation of S83 on Lats2 partially perturbed its centrosomal localization. On the basis of these observations, we conclude that S83 of Lats2 is a phosphorylation target of Aurora‐A and this phosphorylation plays a role of the centrosomal localization of Lats2.
Heat‐shock induced nuclear retention and recycling inhibition of importin α
Authors: Furuta Maiko , Kose Shingo , Koike Makiko , Shimi Takeshi , Hiraoka Yasushi , Yoneda Yoshihiro , Haraguchi Tokuko , Imamoto Naoko
Published: May 2004

Heat‐shock induces a strong stress response and modifies all aspects of cellular physiology, which involves dynamic changes in the nucleocytoplasmic distributions of a variety of proteins. Many distinct nucleocytoplasmic transport pathways exist in eukaryotic cells, but how a particular transport pathway is regulated under different cellular conditions remains elusive. The finding of this study indicate that conventional nuclear import, which is mediated by importin α/β, is down‐regulated, while the nuclear import of 70 kD heat‐shock cognate protein is up‐regulated in heat‐shock cells. Among the factors involved in the mediation of the conventional nuclear import, significant levels of importin α accumulate in the nucleus in response to heat‐shock. An analysis of the behaviour of importin α with fluorescence recovery after photobleaching and fluorescence loss in photobleaching studies show that nuclear importin α becomes less mobile and its nucleocytoplasmic recycling is impaired in heat‐shock cells. These data coincided well with biochemical and cytological studies. Our present data show that heat‐shock induces the nuclear accumulation, nuclear retention, and recycling inhibition of importin α, resulting in the suppression of conventional nuclear import. This suggests a new regulatory mechanism for the adaptation of cells to environmental changes, such as heat‐shock.
Transcriptional co‐activator activity of SYT is negatively regulated by BRM and Brg1
Authors: Ishida Michiko , Tanaka Shinya , Ohki Misao , Ohta Tsutomu
Published: May 2004

The t(X;18)(p11.2;q11.2) translocation found in synovial sarcomas results in the fusion of the SYT gene on chromosome 18 to the SSX gene on chromosome X. Although the SYT‐SSX fusion proteins may trigger synovial sarcoma development, the biological functions of SYT, SSX and SYT‐SSX genes are unclear. Transfections of Gal4 DNA binding domain fusion protein constructs demonstrate that SYT protein acts as a transcriptional co‐activator at the C‐terminal domain and that the activity is repressed through the N‐terminus. The N‐terminal 70 amino acids of SYT bind not only to BRM, but also to Brg1, both of which are subunits of SWI/SNF chromatin remodelling complexes. Here, we have investigated the functions of BRM and Brg1 on the repression of SYT activity. The negative regulation of SYT transcriptional co‐activator activity is dependent on the ATP‐hydrolysis of BRM and Brg1 in the protein complexes. This indicates that the SWI/SNF protein complexes regulate SYT activity using the chromatin remodelling activity.
Over-expression of TATA binding protein (TBP) and p53 and autoantibodies to these antigens are features of systemic sclerosis, systemic lupus erythematosus and overlap syndromes
Authors: Chauhan R , Handa R , Das T P , Pati U
Published: May 2004

The aim of this study was to determine the expression levels of p53 and TATA binding protein (TBP) and the presence of autoantibodies to these antigens in Asian Indian patients with systemic sclerosis (SSc), overlap syndromes (OS) and systemic lupus erythematosus (SLE). Fifty patients with SSc, 20 with OS, including mixed connective tissue diseases (MCTD), 20 with SLE, 10 disease controls (DC) and 25 controls (C) were studied. The over-expression of p53 and TBP antigen was determined quantitatively by sandwich enzyme-linked immunosorbent assay (ELISA), varies between four- and sevenfold higher in patients with SSc, OS and SLE, in comparison to DC and C. The expressed protein antigens were not present as free antigens but as immune-complexes. Autoantibodies to p53 were detected by ELISA in 78% subjects with SSc, 100% with OS and 80% with SLE. Autoantibodies to TBP were observed in 28% patients with SSc, 25% with OS and 15% with SLE. In comparison to healthy controls, the titre of antibodies to p53 was significantly higher in patients with SSc (P = 0·00001) than the patients with OS (P = 0·00279) and SLE (P = 0·00289), whereas the titre of antibodies to TBP was higher in patients with OS (P = 0·00185) than the SLE (P = 0·00673) and the SSc (P = 0·00986) patients. Autoantibodies to p53 and TBP were detected in all these patients and the levels of these two autoantibodies showed weak negative correlation with each other. We propose that the over-expression of these antigens might be due to hyperactive regulatory regions in the p53 and TBP gene.
Expression and subcellular distribution of toll-like receptors TLR4, TLR5 and TLR9 on the gastric epithelium in Helicobacter pylori infection
Authors: SCHMAUßER B , ANDRULIS M , ENDRICH S , LEE S K , JOSENHANS C , MÜLLER-HERMELINK H-K , ECK M
Published: May 2004

Toll-like receptors (TLRs) expressed by mucosal epithelium play an essential role in the defense against microbes by recognizing conserved bacterial molecules. For the first time TLR4, TLR5 and TLR9 have been microanatomically localized in patients with noninflamed gastric mucosa and Helicobacter pylori gastritis by immunohistochemistry. Because polarized expression of TLRs in apical and basolateral epithelial compartments is thought to modulate mucosal immunity, subcellular TLR distribution by gastric epithelium was investigated using confocal microscopy. TLR4, TLR5 and TLR9 were expressed by gastric epithelium in antrum and corpus of all patients with H. pylori gastritis (n = 14) and with noninflamed gastric mucosa (n = 5). TLR4 was expressed at the apical and the basolateral pole of the gastric epithelium as well in noninflamed gastric mucosa as in H. pylori gastritis. TLR5 and TLR9 expression in the noninflamed gastric mucosa was identical to that of TLR4 with localization at the apical and the basolateral epithelial pole. However, in H. pylori gastritis TLR5 and TLR9 expression on the gastric epithelium changed to an exclusive basolateral localization without detectable expression at the apical pole. In the human stomach, the gastric epithelium expressed TLR4, TLR5 and TLR9, which gives it the possibility to interact with H. pylori. Furthermore, gastric epithelial TLR4 expression is highly polarized in an apical and a basolateral compartment, whereas TLR5 and TLR9 polarization seems to be a process dynamically influenced by H. pylori infection. This polarized and dynamically regulated gastric epithelial expression of TLRs supports a sentinel role for these receptors in the mucosal immunity to H. pylori.
Constitutive expression of Interleukin-18 and Interleukin-18 receptor mRNA in tumour derived human B-cell lines
Authors: LOREY S L , HUANG Y C , SHARMA V
Published: May 2004

Interleukin-18 (IL-18) is a pro-inflammatory cytokine involved in the Th1 immune response and expressed by a variety of cell types. IL-18 is a member of the IL-1 family and plays an important role in autoimmune diseases and inflammation. Using reverse transcriptase-polymerase chain reaction (RT-PCR) mRNA expression of IL-18, IL-18 receptor alpha (IL-18Rα), and beta (IL-18Rβ) were studied in tumour derived human B-cell lines. Furthermore, we investigated IL-18 protein secretion by using enzyme linked immunosorbent assay (ELISA). The results, as presented in this report, suggest that IL-18, IL-18Rα, and IL-18Rβ mRNA are constitutively and ubiquitously expressed in human B-cell lines, but secretion of the functional protein does not occur. We therefore speculate that IL-18 possibly affects B-cells through paracrine actions.
Langerhans cells from human oral epithelium are more effective at stimulating allogeneic T cellsin vitrothan Langerhans cells from skin
Authors: HASSÉUS B , JONTELL M , BERGENHOLTZ G , DAHLGREN U I
Published: May 2004

This report is focused on the functional capacity of Langerhans cells (LC) in the epithelium of skin and oral mucosa, which both meet different antigenic challenges. The capacity of LC from human oral and skin epithelium to provide co-stimulatory signals to T cells in vitro was compared. LC in a crude suspension of oral epithelial cells had a significantly enhanced T cell co-stimulatory capacity compared to skin epithelial cells. This applied both to cultures with concanavalin A (con-A)-stimulated syngeneic T cells and to a mixed epithelial cell lymphocyte reaction involving allogeneic T cells. The co-stimulatory capacity of oral and skin epithelial cells was reduced by >70% if monoclonal antibodies against HLA-DR, -DP and -DQ were added to the cultures with allogeneic T cells, indicating the involvement of HLA class II expressing LC. Immunohistochemistry revealed that 6% of the epithelial cells were CD1a + LC in sections from both oral and skin epithelium. Interleukin (IL)-8 production was higher in cultures of oral epithelial cells and con-A stimulated T cells than in corresponding cultures with skin epithelial cells as accessory cells. The results suggest that LC in human oral epithelium are more efficient at stimulating T cells than those of skin.
Redox status and immune function in type I diabetes families
Authors: MATTEUCCI E , MALVALDI G , FAGNANI F , EVANGELISTA I , GIAMPIETRO O
Published: May 2004

Because abnormalities in redox balance cluster in type I diabetes families and the intracellular thiol redox status seems to modulate immune function, we aimed to investigate the relationship between oxidative stress and immunological features. We measured oxidative markers, serum proinflammatory cytokines, soluble cytokine receptors and subsets of peripheral blood lymphocytes (by varying combinations of CD4, CD8, CD23 or low-affinity IgE receptor, and CD25 or IL-2 receptor) from 38 type I patients, 76 low-risk (i.e. without underlying islet autoimmunity) non-diabetic first-degree relatives of diabetic patients, and 95 healthy subjects. In type I diabetes families, protein and lipid oxidation was confirmed by the presence of reduced sulphhydryl groups, increased advanced oxidation protein products, and increased plasma and erythrocyte malondialdehyde. Relatives had decreased counts of monocytes, of cells co-expressing CD23 and CD25 and of CD25+ cells in peripheral blood. Patients with TIDM had similar defects and, in addition, showed decreased counts of peripheral CD4+CD8+ lymphocytes and increased serum levels of soluble receptors for interleukin (IL)-6 and IL-2. Abnormal indicators of oxidative stress were related in part to immune abnormalities. In the whole study group, we found a correlation (multiple R 0·5, P < 0·001) of CD23+CD25+ cells with blood counts of monocytes, CD4+CD8+ cells, CD25+ cells, basal haemolysis and plasma levels of thiols. In type I diabetics, anti-GAD65 antibody levels were associated (multiple R 0·6, P = 0·01) positively with sIL-6R, negatively with duration of diabetes and CD23+CD25+ counts; plasma creatinine correlated positively (multiple R 0·6, P < 0·001) with both sIL-2R and tumour necrosis factor (TNF)-α concentration. Our study reports the first evidence that the oxidative stress observed in type I families is related to immunological hallmarks (decreased peripheral numbers of monocytes as well as cells bearing a CD4+CD8+, CD23+CD25+ and CD25+ phenotype) from which the involvement of some immunoregulatory mechanisms could be suspected. It remains to be elucidated the course of events culminating in the loss of physiological immune homeostasis and disease pathology.