bluuebunny/crossref_metadata_2025 huggingface dataset:
Intriguing compensation by adult female spiders for food limitation experienced as juveniles
Authors: Moya‐Laraño Jordi , Orta‐Ocaña Juan Manuel , Barrientos José Antonio , Bach Carmen , Wise David H.
Published: May 2003

We conducted a field experiment to test for food limitation in immature stages, and its consequences for mature females, in the territorial, cannibalistic spiderLycosa tarentula(L.). Randomly selected antepenultimate juveniles were provided supplemental prey until they matured, at which time supplemental feeding ceased. Immature stages ofL. tarentulaare food‐limited. Supplemented juvenile spiders decreased foraging activity, disappeared at a lower rate and grew faster than the control spiders, which had been exposed only to ambient prey levels. Fed juvenile females were less hungry at maturity, as judged by an index of body condition, and showed higher mating success as adults, as judged by cohabitation rates with mature males. Foraging theory predicts that in order to compensate for residual effects of food limitation, adult female spiders that had experienced a shortage of prey as juveniles – the controls – would have to exhibit a greater increase in foraging activity upon maturing than the prey‐supplemented group. Contrary to expectation, the control females did not increase their foraging activity, but the previously fed females did forage more actively as adults. Furthermore, the difference in mass gain during the mating period between the two groups was opposite from what the difference in change in foraging activity would predict. Control females, the spiders that had not changed their foraging activity, gained mass more rapidly than the previously fed females, with the result that the two groups were similar in mass by the end of the mating period. We hypothesize that an increased rate of sexual cannibalism may have been one mechanism by which control females compensated for the food limitation that they had experienced as immatures.
The ‘ghost of settlement past’ determines mortality and fecundity in the barnacle, Semibalanus balanoides
Authors: Hills Jeremy M. , Thomason Jeremy C.
Published: May 2003

Intraspecific competition is common in many organisms. For many sessile marine invertebrates high settlement densities can lead to competition with conspecifics that can affect the probability of mortality, morphology, and reproductive output. This work aims to determine the affect of recruit density on shell morphology and fecundity and the temporal nature of intraspecific competition for the acorn barnacle, Semibalanus balanoides. Two tile arrays were used; experiment 1 was deployed at the start of the settlement season (43,264 recruits, 4.1% survivorship to adult), experiment 2 was deployed in the middle of the season (5,454 recruits, 42.8% survivorship). Experiment 2 displayed density dependent mortality between recruits and juveniles and adults, whereas no relationship was found for exp. 1. Experiment 2 had higher egg production per individual, but also higher egg production per area of tile compared to exp. 1. A negative relationship was found between recruit density and egg production, however during the summer period, this relationship switched to a positive relationship between juvenile density and egg production, due to high mortality on tiles with high recruit density. Cumulative population density (CPD) was calculated as the cumulative mean density of barnacles per cm‐2 of tile and was used as an index of intraspecific competition. There was a linear negative relationship between mass of eggs per individual and CPD. However, CPD over the summer period more fully explained egg production per individual. A time window was identified when cumulative intraspecific competitive effects were shown to have a strong negative effect on egg production and an increase in mortality, causing a flip from density independent fecundity to density dependent fecundity. These results suggest that recruit density is an important driver of subsequent population processes.
Laws of nature and laws of ecology
Authors: Colyvan M. , Ginzburg L. R.
Published: May 2003

We address the question of whether there are laws in ecology. Although there has been a great deal of recent interest in this topic, much of the relevant debate has been conducted under some common misconceptions about what laws of nature are. Once these misconceptions are cleared up, the case for ecology having laws is much stronger. Indeed, we suggest that the case for laws in ecology is no better or worse than the case for laws in physics.
Current measures of nutrient resorption efficiency lead to a substantial underestimation of real resorption efficiency: facts and solutions
Authors: Van Heerwaarden L. M. , Toet S. , Aerts R.
Published: May 2003

Nutrient resorption is an important process during leaf senescence, which helps plants to minimize nutrient losses. To quantify nutrient resorption, the parameter resorption efficiency is commonly used. This parameter describes the percentage of the nutrient pool withdrawn before leaf abscission. The nutrient pool is generally expressed on the basis of leaf mass or leaf area, assuming that these bases do not change during senescence. In this paper we firstly present a mathematical formula describing the effect of change in measurement basis on the difference between the real resorption efficiency (RRE) value and the measured resorption efficiency (MRE). This formula shows that even moderate senescence‐related changes in a measurement basis can lead to considerable underestimation of RRE. Secondly, to estimate the general change in measurement basis we quantified leaf mass loss and leaf shrinkage during senescence from literature data. These data shows that mass loss percentages can be as high as 40%, and leaf shrinkage can be up to 20%. This level of change in basis seriously compromises the MRE when not corrected for. Using our formula and the reported average literature values of changes in leaf mass (21%) and leaf shrinkage (11%) during senescence, we calculated that the average RRE for nitrogen and phosphorous of terrestrial plants is 6% (leaf area) to 10% (leaf mass) higher than the 50%, respectively 52% as reported by Aerts (1996). This implies that nutrient resorption from senescing leaves is even more important for nutrient retention in terrestrial plants than thought so far. We advocate that preselecting leaves and monitoring the measurement basis throughout the duration of the experiment should minimize the difference between MRE and RRE.
Effects of selective episodes in the field on life history traits in the bumblebeeBombus terrestris
Authors: Baer Boris , Schmid‐Hempel Paul
Published: May 2003

Natural selection has different fitness consequences when it acts during different life cycle stages of an organism. In social insects, for example, the colony foundation and early colony growth is a critical time period with high probability of failure. Here we used colonies of the bumblebeeBombus terrestrisL. to test whether selective episodes at different life cycle stages result in differences in colony performance and fitness. The timing of a selective episode was varied by field exposure of colonies, either permanently or during a short period at three different colony life cycle stages – early, middle, or late in the cycle. We found that selective episodes at different life cycle stages did not affect maximal size, fitness or survival of colonies, or the time span between colony foundation and reproduction. Instead, the colonies were able to compensate for costs encountered by delaying reproduction. This might have important fitness consequences, since later emerging sexuals might be faced with harsher environmental conditions and increased costs of finding a mate. In addition, an important component of selection might be parasitism and the resulting resource allocation to the immune system. We here measured the generalized immune response (i.e. encapsulation response) of early produced workers as an indicator of a colony's capacity to defend against parasitism. Encapsulation response correlated positively with eventual colony size and fitness, indicating that this measure of “immunocompetence” correlates with important life history traits.
Effects of prey quality and availability on the life history of a trap‐building predator
Authors: Mayntz David , Toft Søren , Vollrath Fritz
Published: May 2003

Although generalist predators catch a great diversity of prey species, foraging theory has mostly been concerned with quantitative aspects and neglected questions about the nutrient quality of prey. Here, we test the hypothesis that the life history of a trap‐building predator is affected by both prey availability and by the nutrient quality of prey. Under controlled laboratory conditions, orb‐weaving spiders (Zygiella x‐notata) were raised from hatchlings to maturity on prey of different nutrient quality and in different amounts. Both prey nutrient quality and availability had significant but different effects on many important life history traits, such as instar duration, number of instars used in the development, body weight at maturation and development time. Prey availability was especially important for growth rates whereas prey nutrient quality had the most severe effects on juvenile survivorship and female fecundity. Furthermore, while prey of low quality tended to reduce the number of instars used in the development, prey availability induced sex‐specific responses in instar numbers. Thus, both prey nutrient quality and availability may be important factors shaping the evolution of life history traits in generalist predators.
Interactions between above‐ and belowground insect herbivores as mediated by the plant defense system
Authors: Bezemer T. M. , Wagenaar R. , Van Dam N. M. , Wäckers F. L.
Published: May 2003

Plants are frequently attacked by both above‐ and belowground arthropod herbivores. Nevertheless, studies rarely consider root and shoot herbivory in conjunction. Here we provide evidence that the root‐feeding insect Agriotes lineatus reduces the performance of the foliage feeding insect Spodoptera exigua on cotton plants. In a bioassay, S. exigua larvae were allowed to feed on either undamaged plants, or on plants that had previously been exposed to root herbivory, foliar herbivory, or a combination of both. Previous root herbivory reduced the relative growth rates as well as the food consumption of S. exigua by more than 50% in comparison to larvae feeding on the undamaged controls. We found no effects in the opposite direction, as aboveground herbivory by S. exigua did not affect the relative growth rates of root‐feeding A. lineatus. Remarkably, neither did the treatment with foliar herbivory affect the food consumption and relative growth rate of S. exigua in the bioassay. However, this treatment did result in a significant change in the distribution of S. exigua feeding. Plants that had been pre‐exposed to foliar herbivory suffered significantly less damage on their young terminal leaves. While plant growth and foliar nitrogen levels were not affected by any of the treatments, we did find significant differences between treatments with respect to the level and distribution of plant defensive chemicals (terpenoids). Exposure to root herbivores resulted in an increase in terpenoid levels in both roots as well as in mature and immature foliage. Foliar damage, on the other hand, resulted in high terpenoid levels in young, terminal leaves only. Our results show that root‐feeding herbivores may change the level and distribution of plant defenses aboveground. Our data suggest that the reported interactions between below‐ and aboveground insect herbivores are mediated by induced changes in plant secondary chemistry.
Measuring dispersal in a metapopulation using stable isotope enrichment: high rates of sex‐biased dispersal between patches in a mayfly metapopulation
Authors: Caudill Christopher C.
Published: May 2003

Dispersal affects a wide array of ecological and evolutionary processes, but has been difficult to estimate empirically. A 15Nitrogen stable isotope enrichment technique was used to passively mark all developing Callibaetis ferrugineus hageni (Eaton) mayfly larvae in a beaver pond that had previously been shown to be a patch in a source‐sink metapopulation. After enrichment during the larval stages, dispersal among ponds by adult females was demonstrated by the presence of unmarked females ovipositing in the labeled pond, and marked females in an unlabeled pond. Observed frequencies of marked females suggested incomplete mixing between ponds. In contrast, males rarely dispersed from their natal pond, which was consistent with the unusual mating system in this species – adult Callibaetis are short‐lived, do not feed, and females are sexually receptive immediately after emerging from the larval habitat. The frequent dispersal demonstrated using the stable isotope technique was a critical component of the source‐sink dynamic observed in this metapopulation, and further use of this technique will provide insights into patterns of dispersal in spatially structured habitats.
Variation in top‐down control of avian reproductive success across a fragmentation gradient
Authors: Patten Michael A. , Bolger Douglas T.
Published: May 2003

Understanding mechanisms that inhibit population persistence in fragmentation‐sensitive species is a key to conservation and management. It has become clear that species vary in their sensitivity to habitat fragmentation caused by urbanization and other land uses. We studied variation in avian reproductive success in coastal sage scrub habitat across a fragmentation gradient (interior of large habitat blocks (>2300 ha)→edge of large habitat blocks→large habitat fragments (37–80 ha)→small habitat fragments (5–17 ha)) in urban southwestern California. We focused on four species of birds: the shrub‐nesting wrentit (Chamaea fasciata) and California towhee (Pipilo crissalis) and the ground‐nesting spotted towhee (P. maculatus) and rufous‐crowned sparrow (Aimophila ruficeps). Snake abundance was the best predictor of nest failure in the ground‐nesting species, whereas abundance of avian predators (Corvidae, Mimidae) was associated with nest failure of the wrentit and a combination of snake and avian predator abundance was correlated with nest failure of the California towhee. Avian nest predator abundance increased across the fragmentation gradient; by contrast, snake abundance decreased across this gradient. As a result, top‐down control of reproductive success in populations of the spotted towhee and rufous‐crowned sparrow was largely absent in habitat fragments. These two species enjoyed much higher nest success on fragments yet, paradoxically, both species are sensitive to fragmentation whereas the shrub‐nesting species are not. Our findings suggest that another process – perhaps differential survivorship or dispersal – yields reduced abundance of ground‐nesting species in habitat fragments. Studies of top‐down control and trophic cascades in fragmented landscapes should reflect that the strength of top‐down forces across a landscape varies with characteristics of predator and prey and their autecological responses to ecological gradients.
Hypotonic buffer induces meiosis and formation of anucleate cytoplasmic islands in the egg of the two‐spotted cricket Gryllus bimaculatus
Authors: Sarashina Isao , Shinmyo Yohei , Hirose Ayumi , Miyawaki Katsuyuki , Mito Taro , Ohuchi Hideyo , Horio Tetsuya , Noji Sumihare
Published: May 2003

In insects, egg activation is known to occur in vivo and independently of fertilization, but its mechanisms are poorly understood. To gain understanding of these mechanisms, an attempt was made to activate the egg of Gryllus bimaculatus in vitro. It was found that meiosis resumed and was completed in unfertilized eggs treated with hypotonic buffer. Early developmental processes in activated, unfertilized eggs were investigated and compared with those in fertilized eggs. Mitosis did not progress, resulting in formation of anucleate cytoplasmic islands (pseudoenergids). Development in the activated, unfertilized eggs stopped at this stage and both yolk subdivision and cellularization did not occur. To elucidate the role of the nucleus in the developmental process to the syncytial stage in fertilized eggs, eggs were treated with aphidicolin to inhibit DNA polymerization. It was found that pseudoenergids also formed in these aphidicolin‐treated fertilized eggs. These results demonstrate that pseudoenergids can increase in number independently of nuclei, suggesting that the cytoplasm rather than the nucleus plays the primary role in development to the syncytial stage in G. bimaculatus.
Immunocytochemical study of activin type IB receptor (XALK4) in Xenopus oocytes
Authors: Fukui Akimasa , Komazaki Shinji , Miyoshi Osamu , Asashima Makoto
Published: May 2003

Studies have shown that the activin type IB receptor is specific for activin/nodal signaling. Activin is produced by follicle cells in the ovary, and is incorporated into the oocytes. Antisera against three peptides were prepared, encompassing the extracellular, intracellular and serine/threonine kinase domains of the Xenopus type IB activin receptor (XALK4). Immunocytochemistry was done using these antisera to investigate the distribution of XALK4 in the Xenopus ovary. All three antisera stained the mitochondrial cloud of Xenopus previtellogenic oocytes. Purified antibody against the intracellular domain also recognized the mitochondrial cloud. Immunoelectron microscopy localized XALK4 on the endoplasmic reticulum of the mitochondrial cloud, although not on mitochondria.
Nuclear localization of β‐catenin in vegetal pole cells during early embryogenesis of the starfish Asterina pectinifera
Authors: Miyawaki Kyojy , Yamamoto Masamichi , Saito Kyoko , Saito Shouichiro , Kobayashi Naoto , Matsuda Seiji
Published: May 2003

Recently, β‐catenin has been reported to control the expression of morphogenetic genes through the Wnt signaling pathway in invertebrate embryogenesis. In this study, the distribution pattern of β‐catenin during starfish embryogenesis was investigated using immunohistochemistry. In 16‐cell stage embryos, β‐catenin began to accumulate in some nuclei at the vegetal pole. During the early cleavage stage, the cells expressing nuclear β‐catenin increased in number in the vegetal pole region of the embryos, and the β‐catenin signal increased in intensity in each nucleus. At the blastula stage, signal for β‐catenin was also found in the cytoplasm of the cells with nuclear β‐catenin. At the vegetal plate stage, almost all vegetal plate cells expressed β‐catenin in both the nucleus and cytoplasm. When the embryos developed to early gastrulae, cells with nuclear β‐catenin were restricted to the archenteron tip, and the signal gradually faded in later stages. The localization and temporal change of β‐catenin expression suggests that β‐catenin has a pivotal role in archenteron formation in starfish embryos.
Specification of secondary mesenchyme‐derived cells in relation to the dorso‐ventral axis in sea urchin blastulae
Authors: Kominami Tetsuya , Takata Hiromi
Published: May 2003

To learn how the dorso‐ventral (DV) axis of sea urchin embryos affects the specification processes of secondary mesenchyme cells (SMC), a fluorescent dye was injected into one of the macromeres of 16‐cell stage embryos, and the number of each type of labeled SMC was examined at the prism stage. A large number of labeled pigment cells was observed in embryos in which the progeny of the labeled macromere were distributed in the dorsal part of the embryo. In contrast, labeled pigment cells were scarcely noticed when the descendants of the labeled macromere occupied the ventral part. In such embryos, free mesenchyme cells (probably blastocoelar cells) were predominantly labeled. CH3COONa treatment, which is known to increase the number of pigment cells, canceled such patterned specification of pigment cells and blastocoelar cells along the DV axis. Pigment cells were also derived from the ventral blastomere in the treated embryo. In contrast, a similar number of coelomic pouch cells was derived from the labeled macromere, irrespective of the position of its descendants along the DV axis. After examination of the arrangement of blastomeres in late cleavage stage embryos, it was determined that 17–20 veg2‐derived cells encircled the cluster of micromere descendants after the 9th cleavage. From this number and the numbers of SMC‐derived cells in later stage embryos, it was suggested that the most vegetally positioned veg2 descendants at approximately the 9th cleavage were preferentially specified to pigment and blastocoelar cell lineages. The obtained results also suggested the existence of undescribed types of SMC scattered in the blastocoele.
Screening for novel pancreatic genes from in vitro‐induced pancreas in Xenopus
Authors: Sogame Asako , Hayata Tadayoshi , Asashima Makoto
Published: May 2003

The processes of development and differentiation of the pancreas, an endoderm‐derived vital organ that consists of both endocrine and exocrine cells, are highly conserved across most vertebrates. Recently, an in vitro system has been reported to induce embryonic pancreas using multipotent Xenopus ectodermal cells treated with activin and retinoic acid. In this study, this system was first modified to eliminate the mesoderm‐derived pronephros. It was found that pronephros, which appeared with the use of low concentrations of activin, was eliminated at higher concentrations (400 ng/mL), while pancreas developed at a high frequency. Using this modified system, subtractive hybridization screening for novel pancreatic genes was done to better understand the molecular mechanisms of pancreas formation. Four novel genes were identified and characterized that were also found to be specifically expressed in the developing pancreas: carboxyl ester lipase, pancreatic elastase2, placental protein11 and protein disulfide isomerase A2 precursor. This in vitro pancreas‐induction system may provide a useful model for analysis of the molecular mechanisms that function during pancreas development.
Voltage‐clamp study of the activation currents and fast block to polyspermy in the egg of Xenopus laevis
Authors: Glahn David , Nuccitelli Richard
Published: May 2003

Voltage‐clamped mature, jelly‐intact Xenopus eggs were used to carefully examine the ionic currents crossing the plasma membrane before, during, and after fertilization. The bulk of the fertilization current was transient, of large amplitude, and reversed at the predicted Cl– reversal potential. However, the large amplitude fertilization current was preceded by a small, step‐like increase in holding current. This small increase in holding current is referred to in this paper as Ion to acknowledge its qualitative similarity to the Ion current previously described in the sea urchin. It was observed in both fertilized and artificially activated eggs, and was found to be unaffected by 10 mm tetra‐ethyl ammonium (TEA), a concentration found to block K+ currents in Rana pipiens. Current–voltage relationships are presented for the large fertilization potential, and show that the fertilization currents have a marked outward rectification and are voltage sensitive. These properties are in contrast to the total lack of rectification and slight voltage sensitivity seen before or after the fertilization currents. The time required for sperm to fertilize the egg was found to be voltage dependent with a relatively more depolarized voltage requiring a longer time for fertilization to occur. The percentage of eggs blocked with varying potential levels was determined and this information was fitted to a modified Boltzmann equation having a midpoint of −9 mV.
Retinoic acid increases the length and volume density of ducts in the rat embryonic pancreas
Authors: Erasmus Carene , Penny Clem , Kramer Beverly
Published: May 2003

In this study, the role of all‐trans retinoic acid (RA) on the proliferation of rat embryonic pancreas ducts and on the proportion of insulin cells was investigated. All‐trans RA (10−6 m) was added to Ham's F12.ITS serum‐free medium in which 12.5 day rat dorsal pancreatic buds were cultured on Matrigel. Control explants were cultured on Matrigel in Ham's F12.ITS alone or in Ham's F12.ITS containing ethanol (the diluent for RA). After a 7 day culture period, explants were incubated with bromodeoxyuridine (BrdU) for assessment of cell proliferation. Explants were processed for both morphometry and immunocytochemistry. The length density and volume density of the pancreatic ducts were assessed using an image analysis system. Cells positive for insulin, BrdU and glucagon were localized on adjacent serial sections. RA treatment caused a statistically significant increase in the volume density (P < 0.007) and length density (P < 0.008) of the ducts, as well as a 1.2‐fold increase (P < 0.0001) in the proportion of insulin to glucagon cells, compared to both control groups. Few insulin cells were BrdU positive, indicating that cells had a low proliferation rate. The increased proportion of insulin cells may relate to the increased volume density and length density of the ducts in RA‐treated explants. It is suggested that RA stimulated the production of additional progenitor cells and not proliferation of existing insulin cells.
Microarray analysis of murine palatogenesis: Temporal expression of genes during normal palate development
Authors: Brown Nathan L. , Knott Lynda , Halligan Eugene , Yarram Sarah J. , Mansell Jason P. , Sandy Jonathan R.
Published: May 2003

The mammalian face is assembled in utero in a series of complex and interdependent molecular, cell and tissue processes. The orofacial complex appears to be exquisitely sensitive to genetic and environmental influence and this explains why clefts of the lip and palate are the most common congenital anomaly in humans (one in 700 live births). In this study, microarray technology was used to identify genes that may play pivotal roles in normal murine palatogenesis. mRNA was isolated from murine embryonic palatal shelves oriented vertically (before elevation), horizontally (following elevation, before contact), and following fusion. Changes in gene expression between the three different stages were analyzed with GeneChip® microarrays. A number of genes were upregulated or downregulated, and large changes were seen in the expression of loricrin, glutamate decarboxylase, gamma‐amino butyric acid type A receptor beta3 subunit, frizzled, Wnt‐5a, metallothionein, annexin VIII, LIM proteins, Sox1, plakophilin1, cathepsin K and creatine kinase. In this paper, the changes in genetic profile of the developing murine palate are presented, and the possible role individual genes/proteins may play during normal palate development are discussed. Candidate genes with a putative role in cleft palate are also highlighted.
Development and gene expression of nuclear transplants generated by transplantation of cultured cell nuclei into non‐enucleated eggs in the medaka Oryzias latipes†
Authors: Ju Bensheng , Pristyazhnyuk Inna , Ladygina Tatiana , Kinoshita Masato , Ozato Kenjiro , Wakamatsu Yuko
Published: May 2003

To develop nuclear transplantation techniques for the medaka Oryzias latipes, nuclei of cultured cells from transgenic fish were transplanted into unfertilized eggs of the orange–red variety of O. latipes, without enucleation, in two experimental series. In the first experimental series, fibroblast cells cultured from the adult caudal fin were used as donors, which carried the green fluorescent protein (GFP) gene driven by the promoter of the medaka elongation factor 1α‐A gene. Wild‐type body color was another donor genetic marker used in this experimental series. In the second experimental series, cells cultured from 6‐day‐old embryos were used as donors, which carried the GFP genetic marker driven by the promoter of the medaka β‐actin gene. From more than 1000 eggs transplanted in each experiment, a considerable number of nuclear transplants developed to various embryonic stages showing stage‐ and tissue‐specific expression of the donor genetic markers, although the expression was mosaic in many cases. Three and six of the transplanted eggs in the first and second experimental series (0.3 and 0.5%, respectively) hatched, and the hatchlings expressing the genetic markers survived for up to 3 weeks. The chromosome number varied among cells in a single transplant embryo. The results obtained in these experiments may help future cloning efforts in fish.
Possible involvement of myosin‐X in intercellular adhesion: Importance of serial pleckstrin homology regions for intracellular localization
Authors: Yonezawa Satoshi , Yoshizaki Norio , Sano Mamoru , Hanai Atsuko , Masaki Shigeo , Takizawa Takenori , Kageyama Takashi , Moriyama Akihiko
Published: May 2003

Subcellular fractionation experiments with mouse hepatocytes, combined with sodium dodecylsulfate (SDS)–polyacrylamide gel electrophoresis (PAGE)–immunoblot analysis using antibodies against two different tail regions of mouse myosin‐X demonstrated a 240 kDa molecular mass to be associated with the plasma membrane‐rich P2 fraction. The basolateral plasma membrane fraction, but not the brush border fraction, isolated from renal cortices also contained the 240 kDa form of myosin‐X. In an attempt to assess relative contributions of possible functional domains in the tail of myosin‐X to localization and function, cDNA corresponding to all three pleckstrin homology (PH) domains and different regions (PH1, 2 and 3, and the two subdomains of PH1: PHS1 and PHS2), as well as the myosin tail homology 4 domain (MyTH4) and the band4.1/ezrin/radixin/moesin‐like domain (FERM) were separately inserted into the pEGFP vector and expressed in cultured COS‐1 cells. As a result, two distinct regions responsible for localization were identified with regard to PH: one covers all three forms that tends to localize to regions of dynamic actin, such as membrane ruffles, lamellipodia and thick cortical actin bundles at the sites of cell–cell adhesion in a Rac‐ and Cdc42‐dependent manner. The other covers PHS1 and PH2 that localizes to filopodia, filopodial puncta and the sites of intercellular adhesion in a Cdc42‐dependent manner. Expression of green fluorescent protein (GFP)‐MyTH4 fusion protein resulted in formation of phalloidin‐positive granules, while GFP‐FERM affected the actin cytoskeletal system in a distinctly different way. Taken altogether, the results lend support to the view that myosin‐X is involved in cell–cell adhesion‐associated signaling‐linked membrane and/or cytoskeleton reorganization.
Ontogeny of lipase expression in winter flounder
Authors: Murray H. M. , Gallant J. W. , Perez‐Casanova J. C. , Johnson S. C. , Douglas S. E.
Published: May 2003

The partial sequencing of two lipases from winter flounder Pseudopleuronectes americanus, one most closely related to gastric, lingual and lysosomal acid lipase from other vertebrates and one most closely related to bile salt‐activated lipase, is reported. Biochemical analyses of enzymatic activity demonstrated the greater contribution made by bile salt‐activated lipase relative to neutral bile salt‐independent lipase. Using molecular techniques, the tissue‐specific expression of bile salt‐activated lipase in pancreatic tissue and acid triacylglycerol lipase in a wide variety of organs was demonstrated. Furthermore, the developmental expression of these types of lipase in larval fish was established.
Reduced territorial defence in rainbow trout fry exposed to a paper mill effluent: using the mirror image stimulation test as a behavioural bioassay
Authors: Johnsson J. I. , Parkkonen J. , Förlin L.
Published: May 2003

Rainbow troutOncorhynchus mykissfry exposed to a paper mill effluent showed increased EROD (ethoxyresorufin‐O‐deethylase) activity and reduced territorial aggression in mirror image stimulation (MIS) tests. These results suggest that the MIS test could be a useful tool to detect sublethal behavioural effects of pollution in fish fry.
Utilization of the exotic cladoceran Daphnia lumholtzi by juvenile fishes in an Illinois River floodplain lake
Authors: Lemke A. M. , Stoeckel J. A. , Pegg M. A.
Published: May 2003

Daphnia lumholtzi comprises a substantial component of the zooplankton community during mid‐ to late‐summer in Lake Chautauqua, a floodplain lake along the Illinois River near Havana, Illinois. In order to quantify the utilization of D. lumholtzi by juvenile fishes, diet analyses were conducted for seven juvenile fish species collected from Lake Chautauqua during the 2001 annual drawdown period. Freshwater drum Aplodinotus grunniens and emerald shiner Notropis atherinoides demonstrated negative selectivity for D. lumholtzi relative to native zooplankton species whereas four species of fish (bluegill Lepomis macrochirus, white bass Morone chrysops, white crappie Pomoxis annularis and black crappie Pomoxis nigromaculatus) consumed substantial amounts of D. lumholtzi. Although selectivity values for D. lumholtzi varied among these fish species, positive selection for D. lumholtzi increased similarly among larger size classes of each fish species, and corresponded with ontogenetic shifts in diet. Mean body length of D. lumholtzi consumed by 20–69 mm LT juvenile fishes ranged from 0·75 to 0·99 mm with a calculated total length range of 2·0–2·6 mm. Results from this study provide evidence that high abundances of D. lumholtzi in mid‐ to late‐summer provide an additional food source for several juvenile fish species during a time when abundances of large native cladoceran species (i.e. Daphnia) are low, and juvenile fishes are searching for larger prey associated with ontogenetic shifts from zooplankton to macroinvertebrates and fishes. Because zooplankton production is typically lower in rivers than in lakes, survivorship of juvenile fishes produced in floodplain lakes may be higher in riverine systems if they are not reliant on zooplankton as a primary food resource. Therefore, high abundances of D. lumholtzi may benefit juvenile fishes in managed floodplain lakes, such as Lake Chautauqua, by increasing growth and facilitating the transition from zooplanktivory to insectivory or piscivory.
Nine‐year prospective relationship betweenparental smoking cessation and children's daily smoking
Authors: Bricker JonathanB. , Leroux Brian G. , V.Peterson Arthur , Kealey Kathleen A. , Sarason Irwin G. , Andersen M. Robyn , Marek Patrick M.
Published: May 2003

Aims  The first prospective investigation of the extent to which parentalsmoking cessation predicts their children's daily smoking.

Design  Parental smoking status was assessed when children were aged8/9 years and children's smoking status was assessedat age 17/18 years.

Setting  Twenty Washington State school districts in the control groupof the Hutchinson Smoking Prevention Project.

Participants and measurements 

Questionnaire data were gathered on 3012 children (49% femaleand 91% Caucasian) and both of their parents in a cohort witha 95% retention rate.

Findings  When both parents quit smoking, children's odds of dailysmoking were reduced by 39% (95% CI = 15%,56%) compared to when both parents were current smokers.Furthermore, when both parents never smoked then children’sodds of daily smoking were reduced by 71% (95% CI = 62%,78%).

Conclusions  Parental smoking cessation is associated with reduced risk oftheir children's daily smoking. Parents who quit stillplace children at substantially higher risk compared to parentswho never smoked.
A longitudinal study of the effects of adolescent cannabis use on high school completion
Authors: Lynskey Michael T. , Coffey Carolyn , Degenhardt Louisa , Carlin John B. , Patton George
Published: May 2003

Objective  To examine the extent to which weekly cannabis use during mid‐adolescence may increase the risk of early school‐leaving.

Setting  A prospective study of a general population sample of adolescents studied from ages 15–21 years in Melbourne, Australia.

Method  Computer‐assisted self‐completion questionnaires and telephone interviews conducted in six waves at ages 15–18 and again at age 21 in a sample of 1601 male and female school students.

Results  Weekly cannabis use, assessed prospectively, was associated with significantly increased risk of early school‐leaving. This effect remained after adjustment for a range of prospectively assessed covariates including demographic characteristics, other substance use, psychiatric morbidity and antisocial behavior. There was suggestive evidence of an interaction between weekly cannabis use and age with the effects of weekly cannabis use on early school‐leaving being strongest at the youngest ages and diminishing progressively with age.

Conclusions  Early regular cannabis use (weekly use at age 15) is associated with increased risk of early school‐leaving. These effects of regular cannabis use may diminish with increasing age and are likely to operate through the social context within which cannabis is used and obtained.
Treatments for spit tobacco use: a quantitative systematicreview
Authors: Ebbert JonO. , Rowland Leah C. , Montori Victor M. , Vickers Kristin S. , Erwin Patricia J. , Dale Lowell C.
Published: May 2003

Aims  Spit tobacco use is prevalent in the United States and is associatedwith adverse health consequences. Health‐care providers have neitherevidence summaries nor evidence‐based guidelines to assist themin treating patients who use spit tobacco.

Design  We completed a systematic review of the literature to determinethe efficacy and safety of pharmacological and behavioral interventionsfor the treatment of spit tobacco use.

Findings  We found six randomized controlled trials testing pharmacological interventionsand eight testing behavioral interventions. Using random‐effects meta‐analyses,bupropion sustained‐release (SR) increased point prevalence tobaccoabstinence at 12 weeks [odds ratio (OR) 2.1; 95% confidenceinterval (CI), 1.0–4.2]. Nicotine replacementtherapy with patch or gum increased point prevalence tobacco abstinenceat 6 months (OR 1.3; 95% CI, 1.0–1.6).Behavioral interventions increased long‐term (6 month)point prevalence tobacco abstinence (OR 1.7; 95% CI, 1.1–2.9).Studies including an oral examination followed by feedback to thepatient had the highest treatment effect.

Conclusions  Behavioral interventions for ST users are effective for increasing STabstinence rates. Bupropion SR is probably effective and nicotinereplacement therapy may be effective. This evidence from randomizedcontrolled trials provides health‐care professionals with informationnecessary to effectively treat spit tobacco use.
Alexander the Great's relationship with alcohol
Authors: Liappas J. A. , Lascaratos J. , Fafouti S. , Christodoulou G. N.
Published: May 2003

Aims  This study sought to clarify if Alexander the Great indulged pathologically in alcohol and whether it contributed to his death.

Design  The texts of the historians Diodorus of Sicily, Plutarch, Arrian, Curtius Rufus, Athenaeus, Aelian and Justin were studied, with their information concerning wine consumption by Macedonians, and especially Alexander, and were evaluated. The surviving historical texts, all later than Alexander's epoch, are based on a series of contemporary histories and especially on the ‘Royal Journals’, an official diary written in the imperial court.

Findings and conclusions  Alexander consumed large quantities of undiluted wine periodically, reaching pathological intoxication. However, the existing data do not provide convincing evidence that Alexander the Great manifested abuse of or dependence on alcohol according to DSM‐IV or ICD‐10 criteria and it seems unlikely that alcohol was involved in his untimely death.
Enhanced growth of sagebrush (Artemisia tridentata) in response to manipulated ecosystem warming
Authors: PERFORS TRACY , HARTE JOHN , ALTER S. ELIZABETH
Published: May 2003

Global models project impending climate changes that could significantly alter plant species composition in ecosystems. Climate manipulation experiments provide an opportunity to investigate such effects. Here we describe and apply a method for extracting the age‐detrended growth rate of sagebrush (Artemisia tridentata Nutt.) and show that experimental ecosystem warming enhances the growth rate of this shrub. Snowmelt date, not soil temperature or moisture, is demonstrated to be the dominant climate variable controlling the observed effect. Our findings suggest that global climate change will result in increased growth and range expansion of sagebrush near northern or high‐elevation range boundaries in the Western United States.
Effects of N‐fertilisation on CH4 oxidation and production, and consequences for CH4 emissions from microcosms and rice fields
Authors: KRÜGER MARTIN , FRENZEL PETER
Published: May 2003

The world's growing human population causes an increasing demand for food, of which rice is one of the most important sources. In rice production nitrogen is often a limiting factor. As a consequence increasing amounts of fertiliser will have to be applied to maximise yields. There is an ongoing discussion on the possible effects of fertilisation on CH4 emissions. We therefore investigated the effects of N‐fertiliser (urea) on CH4 emission, production and oxidation in rice microcosms and field experiments. In the microcosms, a substantial but short‐lived reduction of CH4 emission was observed after N‐addition to 43‐d‐old rice plants. Methane oxidation increased by 45%, demonstrated with inhibitor measurements and model calculations based on stable carbon isotope data (δ13CH4). A second fertilisation applied to 92‐d‐old plants had no effect on CH4 emission rates.

The positive effect of additional N on methanotrophic bacteria was also found in vitro for potential CH4 oxidation rates in soil and root samples from the microcosm and field experiments, indicated by elevated initial oxidation rates and reduced lag‐phases. Fertilisation did not affect methane production in the microcosms. In the field, the effects were diverse: methane production was inhibited in the topsoil, but stimulated instead in the bulk soil. Stimulation occurred probably in the anaerobic food chain at the level of hydrolytic or fermenting bacteria, because acetate, a methanogenic precursor, increased simultaneously.

Combining field, microcosm and laboratory experiments we conclude that any agricultural treatment improving the N‐supply to the rice plants will also be favourable for the CH4 oxidising bacteria. However, N‐fertilisation had only a transient influence and was counter‐balanced in the field by an elevated CH4 production. A negative effect of the fertilisation was a transient increase of N2O emissions from the microcosms. However, integrating over the season the global warming potential (GWP) of N2O emitted after fertilisation was still negligible compared to the GWP of emitted CH4.
Soil organic matter biochemistry and potential susceptibility to climatic change across the forest‐tundra ecotone in the Fennoscandian mountains
Authors: SJÖGERSTEN SOFIE , TURNER BENJAMIN L. , MAHIEU NATHALIE , CONDRON LEO M. , WOOKEY PHILIP A.
Published: May 2003

We studied soil organic carbon (C) chemistry at the mountain birch forest‐tundra ecotone in three regions of the Fennoscandian mountain range with comparable vegetation cover but contrasting degrees of continentality and latitude. The aim of the study was to identify functional compound classes and their relationships to decomposition and spatial variation across the ecotone and latitudinal gradient. Solid‐state 13C nuclear magnetic resonance (CPMAS 13C NMR) was used to identify seven functional groups of soil organic C: alkyls, N‐alkyls, O‐alkyls, acetals, aromatics, phenolics and carboxyls. N‐alkyls, O‐alkyls and acetals are generally considered labile substrates for a large number of saprotrophic fungi and bacteria, whilst phenolics and aromatics are mainly decomposed by lignolytic organisms and contribute to the formation of soil organic matter together with aliphatic alkyls and carboxyls. All soils contained a similar proportional distribution of functional groups, although relatively high amounts of N‐alkyls, O‐alkyls and acetals were present in comparison to earlier published studies, suggesting that large amounts of soil C were potentially vulnerable to microbial degradation. Soil organic matter composition was different at the most southerly site (Dovrefjell, Norway), compared with the two more northerly sites (Abisko, Sweden, and Joatka, Norway), with higher concentrations of aromatics and phenolics, as well as pronounced differences in alkyl concentrations between forest and tundra soils. Clear differences between mountain birch forest and tundra heath soil was noted, with generally higher concentrations of labile carbon present in tundra soils. We conclude that, although mesic soils around the forest‐tundra ecotone in Fennoscandia are a potential source of C to the atmosphere in a changing environment, the response is likely to vary between comparable ecosystems in relation to latitude and continentality as well as soil properties especially soil nitrogen content and pH.
Projecting future fire activity in Amazonia
Authors: CARDOSO MANOEL F. , HURTT GEORGE C. , MOORE BERRIEN , NOBRE CARLOS A. , PRINS ELAINE M.
Published: May 2003

Fires are major disturbances for ecosystems in Amazonia. They affect vegetation succession, alter nutrients and carbon cycling, and modify the composition of the atmosphere. Fires in this region are strongly related to land‐use, land‐cover and climate conditions. Because these factors are all expected to change in the future, it is reasonable to expect that fire activity will also change. Models are needed to quantitatively estimate the magnitude of these potential changes. Here we present a new fire model developed by relating satellite information on fires to corresponding statistics on climate, land‐use and land‐cover. The model is first shown to reproduce the main contemporary large‐scale features of fire patterns in Amazonia. To estimate potential changes in fire activity in the future, we then applied the model to two alternative scenarios of development of the region. We find that in both scenarios, substantial changes in the frequency and spatial patterns of fires are expected unless steps are taken to mitigate fire activity.
Effects of elevated carbon dioxide on green leaf tissue and leaf litter quality in an intact Mojave Desert ecosystem
Authors: BILLINGS SHARON A. , ZITZER STEPHEN F. , WEATHERLY HEATHER , SCHAEFFER SEAN M. , CHARLET T. , ARNONE JOHN A. , EVANS R. D.
Published: May 2003

The effects of elevated carbon dioxide (CO2) on plant litter are critical determinants of ecosystem feedback to changing atmospheric CO2 concentrations. We measured concentrations of nitrogen (N) and carbon (C) and calculated C : N ratios of green leaves of two desert perennial shrubs, and the same quality parameters plus lignin and cellulose content of leaf litter from four shrub species exposed to elevated CO2 (FACE technology; Hendrey & Kimball, 1994) for 3 years in an intact Mojave Desert ecosystem. Shrubs tested were Larrea tridentata, Lycium pallidum, Lycium andersonii and Ambrosia dumosa. We calculated resorption efficiency from green tissue and leaf litter N data and measured lignin and cellulose content in litter in the last year study. Green leaves of L. tridentata grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown in ambient conditions in 1999 (P < 0.05). Lycium pallidum green leaves grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown under ambient conditions in 2000 (P < 0.05). There was no CO2 effect on C content of either species. We found no effect of CO2 on N or C content, C : N ratios, or lignin or cellulose concentrations in leaf litter of L. tridentata, L. pallidum, L. andersonii, or A. dumosa. There was no significant effect of CO2 on estimates of shrub resorption efficiency. There was a seasonal effect on green tissue and litter tissue quality for L. tridentata, with lower tissue N content in summer than in spring or winter months. These data suggest that any productivity increases with elevated CO2 in desert ecosystems may not be limited by lower leaf litter quality and that resorption efficiency calculations are best performed on an individual leaf basis.