General Phenomenon (general + phenomenon)

Distribution by Scientific Domains
Distribution within Life Sciences

Selected Abstracts

Functional studies of an evolutionarily conserved, cytochrome b5 domain protein reveal a specific role in axonemal organisation and the general phenomenon of post-division axonemal growth in trypanosomes

CYTOSKELETON, Issue 1 2009
Helen Farr
Abstract Eukaryotic cilia and flagella are highly conserved structures composed of a canonical 9+2 microtubule axoneme. Several recent proteomic studies of cilia and flagella have been published, including a proteome of the flagellum of the protozoan parasite Trypanosoma brucei. Comparing proteomes reveals many novel proteins that appear to be widely conserved in evolution. Amongst these, we found a previously uncharacterised protein which localised to the axoneme in T. brucei, and therefore named it Trypanosome Axonemal protein (TAX)-2. Ablation of the protein using RNA interference in the procyclic form of the parasite has no effect on growth but causes a reduction in motility. Using transmission electron microscopy, various structural defects were seen in some axonemes, most frequently with microtubule doublets missing from the 9+2 arrangement. RNAi knockdown of TAX-2 expression in the bloodstream form of the parasite caused defects in growth and cytokinesis, a further example of the effects caused by loss of flagellar function in bloodstream form T. brucei. In procyclic cells we used a new set of vectors to ablate protein expression in cells expressing a GFP:TAX-2 fusion protein, which enabled us to easily quantify protein reduction and visualise axonemes made before and after RNAi induction. This establishes a useful generic technique but also revealed a specific observation that the new flagellum on the daughter trypanosome continues growth after cytokinesis. Our results provide evidence for TAX-2 function within the axoneme, where we suggest that it is involved in processes linking the outer doublet microtubules and the central pair. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source]

Corticolous arthropods under climatic fluctuations: compensation is more important than migration

ECOGRAPHY, Issue 1 2005
Andreas Prinzing
Animals can cope with fluctuating climates by physiological tolerance, tracking of climatic fluctuations (migration) and compensatory redistribution among (micro)habitats (compensation). Compensation is less demanding and thus more important than migration at large geographic scales. It is not clear however which strategy is more important at the small scale of a microhabitat landscape. I investigated how six arthropod species (Collembola, Oribatei, Psocoptera, Isopoda) respond to microclimatic fluctuations at the surface of exposed tree trunks. Across a nine-month period I characterized the microclimatic zonation of 299 trunks, and focally sampled the arthropods from different microhabitat types (different cryptogam species and bark crevices) within different microclimatic zones. I found that compensatory microhabitat-use was a general phenomenon. The distribution of all species across microhabitats was influenced significantly by ambient microclimate. Also, the arthropods' microhabitat use changed throughout their ontogeny, and microhabitats were used even if they were rare. Most interestingly, the arthropods responded to microclimatic fluctuations primarily by redistribution among microhabitats and less by fluctuations of overall abundances across all microhabitats. Hence compensation was more important than migration. The animals moved for centimeters to decimeters rather than for decimeters to meters; they perceived and utilized their environment primarily at the finest, but also most complex scale. This has implications for the resilience of arthropod populations, their interactions with cryptogams and the turnover of species between macrohabitats. [source]

Hierarchical ZnS-In2S3 -CuS Nanospheres with Nanoporous Structure: Facile Synthesis, Growth Mechanism, and Excellent Photocatalytic Activity

Yingxuan Li
Abstract Without using any templates or surfactants, hierarchical ZnS-In2S3 -CuS nanospheres with nanoporous structure are successfully synthesized via a simple and convenient process. The nanospheres are aggregations of densely packed nanoparticles and nanorods. Different to the oriented attachment (OA) mechanism reported in the literature, the formation of these nanorods is believed to follow a lateral OA mechanism (nanoparticles attach along the direction perpendicular to the crystallographic axes with lateral planes as the juncture) based on the experimental data. This process could be a general phenomenon and would provide a new insight into the OA mechanism. A detailed time-resolved TEM kinetic study of the formation of the complex structure is shown. The dipole mechanism and electric field-induced growth are found to be responsible for the final architecture. Photocatalytic activities for water splitting are investigated under visible-light irradiation (, > 400 nm) and an especially high photocatalytic activity (apparent yield of 22.6% at 420 nm) is achieved by unloaded ZnIn0.25Cu0.02S1.395 prepared at 180 °C for 18 h because of their high crystallinity, large pore volume, and the presence of nanorods with special microstructures. [source]

Earnings management following chief executive officer changes: the effect of contemporaneous chairperson and chief financial officer appointments

Mark Wilson
M40; M41 Abstract Using a sample of listed Australian firms from 1999 to 2007, we examine the relationship between discretionary accruals and concurrent senior management appointments. Employing panel data regression models and focusing on a measure of discretionary accruals that excludes the effect of transparent write-downs such as restructuring charges, we find that chief executive officer (CEO) appointments, as a general phenomenon, are not significantly associated with opaque earnings management in the year of appointment or the following year. However, we find that CEO changes accompanied by a concurrent change in board chairperson are associated with significant income-decreasing earnings management in the year of appointment. We detect no significant relationship between contemporaneous CEO and chief financial officer changes and discretionary accruals. We find no evidence of earnings management in the first compete financial period following CEO appointment, regardless of whether or not concurrent Chair or chief financial officer appointments occurred. [source]

Interpretation of knockout experiments: the congenic footprint

L. C. Schalkwyk
In gene targeting experiments, the importance of genetic background is now widely appreciated, and knockout alleles are routinely backcrossed onto a standard inbred background. This produces a congenic strain with a substantial segment of embryonic stem (ES)-cell-derived chromosome still flanking the knockout allele, a phenomenon often neglected in knockout studies. In cholecystokynin 2 (Cckbr) knockout mice backcrossed with C57BL/6, we have found a clear ,congenic footprint' of expression differences in at least 10 genes across 40 Mb sequence flanking the Cckbr locus, each of which is potentially responsible for aspects of the ,knockout' phenotype. The expression differences are overwhelmingly in the knockout-low direction, which may point to a general phenomenon of background dependence. This finding emphasizes the need for caution in using gene knockouts to attribute phenotypic effects to genes. This is especially the case when the gene is of unknown function or the phenotype is unexpected, and is a particular concern for large-scale knockout and phenotypic screening programmes. However, the impact of genetic background should not be simply viewed as a potential confound, but as a unique opportunity to study the broader responses of a system to a specific (genetic) perturbation. [source]

Polyploidy-Associated Genomic Instability in Arabidopsis thaliana

Yixing Wang
Formation of polyploid organisms by fertilization of unreduced gametes in meiotic mutants is believed to be a common phenomenon in species evolution. However, not well understood is how species in nature generally exist as haploid and diploid organisms in a long evolutionary time while polyploidization must have repeatedly occurred via meiotic mutations. Here, we show that the ploidy increased for two consecutive generations due to unreduced but viable gametes in the Arabidopsis cyclin a1;2-2 (also named tardy asynchronousmeiosis-2) mutant, but the resultant octaploid plants produced progeny of either the same or reduced ploidy via genomic reductions during meiosis and pollen mitosis. Ploidy reductions through sexual reproduction were also observed in independently generated artificial octaploid and hexaploid Arabidopsis plants. These results demonstrate that octaploid is likely the maximal ploidy produced through sexual reproduction in Arabidopsis. The polyploidy-associated genomic instability may be a general phenomenon that constrains ploidy levels in species evolution. [source]

Above-ground forest biomass is not consistently related to wood density in tropical forests

GLOBAL ECOLOGY, Issue 5 2009
James C. Stegen
ABSTRACT Aim, It is increasingly accepted that the mean wood density of trees within a forest is tightly coupled to above-ground forest biomass. It is unknown, however, if a positive relationship between forest biomass and mean community wood density is a general phenomenon across forests. Understanding spatial variation in biomass as a function of wood density both within and among forests is important for predicting changes in stored carbon in response to global change, and here we evaluated the generality of a positive biomass,wood density relationship within and among six tropical forests. Location, Costa Rica, Panama, Puerto Rico and Ecuador. Methods, Individual stem data, including diameter at breast height and spatial position, for six forest dynamics plots were merged with an extensive wood density database. Individual stem biomass values were calculated from these data using published statistical models. Total above ground biomass, total basal area and mean community wood density were also quantified across a range of subcommunity plot sizes within each forest. Results, Among forests, biomass did not vary with mean community wood density. The relationship between subcommunity biomass and mean wood density within a forest varied from negative to null to positive depending on the size of subcommunities and forest identity. The direction of correlation was determined by the associated total basal area,mean wood density correlation, the slope of which increased strongly with whole forest mean wood density. Main conclusions, There is no general relationship between forest biomass and wood density, and in some forests, stored carbon is highest where wood density is lowest. Our results suggest that declining wood density, due to global change, will result in decreased or increased stored carbon in forests with high or low mean wood density, respectively. [source]

An analytical solution of one-dimensional consolidation for soft sensitive soil ground

Yun-Min Chen
Abstract An analytical solution of one-dimensional consolidation for soft sensitive soil ground is presented. The moving boundary is introduced to indicate the notable change of consolidation behaviour of sensitive soil with the increase of stress level. It is assumed that the soil structure of the upper subsoil gradually destroys downwards with the dissipation of pore pressure, and the coefficient of consolidation as well as the coefficient of permeability of the upper subsoil become small, which hinders the dissipation of pore pressure of the lower subsoil. The consolidation degree curve obtained from the present solution is found to lie between the two curves obtained from Terzaghi one-dimensional consolidation solution with the parameters of the undisturbed soil and the remolded soil. The calculated results provide a new explanation for a general phenomenon in the consolidation of soft sensitive soil ground, as that for high loadings the consolidation is longer than for small ones. It should be pointed out from this study that both the deep mixing method and the long vertical drains methods are effective techniques for improving deep sensitive soil ground. Copyright © 2004 John Wiley & Sons, Ltd. [source]

A New Scenario in Probe Local Oxidation: Transient Pressure-Wave-Assisted Ionic Spreading and Oxide Pattern Formation,

N. Xie
A new mechanism based on transient shock-wave-assisted lateral ionic spreading and oxide growth is reported for atomic force microscopy probe local oxidation (see figure). Transitory high pressure waves generated in the nanoscopic tip,sample junction significantly extend the distribution of hydroxyl oxidants to facilitate micrometer-scale disk-oxide growth on a silicon substrate. The results show that shock propagation may be a general phenomenon in AFM nanolithography. [source]

Acceleration of nitric oxide autoxidation and nitrosation by membranes

IUBMB LIFE, Issue 4-5 2007
Matias N. Möller
Abstract The reaction between nitric oxide (,NO) and oxygen yields reactive species capable of oxidizing and nitrosating proteins, as well as deaminating DNA bases. Although this reaction is considered too slow to be biologically relevant, it has been shown that membranes, lipoproteins, mitochondria and possibly proteins can accelerate this reaction. This effect stems from the higher solubility of both ,NO and O2in the hydrophobic phase of these biological particles, leading to a concentration of both reagents and so a higher rate of reaction. It has been determined that this reaction occurs from 30 to 300 times more rapidly within the membrane, while even higher values have been suggested for proteins. The autoxidation of ,NO in membranes is not the main route for cellular ,NO consumption but an important consequence of this phenomenon is to focus the generation of significant amounts of oxidizing and nitrosating molecules (nitrogen dioxide and dinitrogen trioxide) in the small volume comprised by cellular membranes. Even so, these reactive species are diffusible and their ultimate fate will depend on the reactivity towards available substrates rather than on physical barriers. The acceleration of ,NO autoxidation by biological hydrophobic phases may thus be a general phenomenon that increases in importance in cases of ,NO overproduction. IUBMB Life, 59: 243-248, 2007 [source]

Blunt egg pole holds cues for alien egg discrimination: experimental evidence

L. Pola, iková
Eggshell colour patterns play a crucial role in avian host,parasite coevolution. In contrast to many experiments investigating general host egg discrimination abilities, studies testing where specific recognition cues are located on the eggshells (on blunt, sharp or both egg poles) are lacking. Previous studies suggested that discrimination cues might be located at the blunt egg pole, where the shell patterning is typically concentrated. We tested this hypothesis experimentally in species subject to interspecific (great reed warblers Acrocephalus arundinaceus, reed warblers A. scirpaceus), and also intraspecific parasitism (song thrushes Turdus philomelos, blackbirds T. merula). We examined host responses towards two types of intraspecific eggs painted non-mimetic immaculate blue either at blunt or sharp poles. All four species rejected eggs manipulated at the blunt pole at significantly higher rates, indicating that they perceive the critical recognition cues in the same egg part. Thus, the presence of egg recognition cues at the blunt egg pole may be a general phenomenon in birds parasitized by both intraspecific and interspecific parasites. [source]

Methyl palmitate inhibits lipopolysaccharide-stimulated phagocytic activity of rat peritoneal macrophages

Swapna Sarkar
Abstract Macrophages, in general, are critical effectors of body's immune system. Chemical inhibition of phagocytic activity of such macrophages as Kupffer cells has been extensively studied. We have earlier shown that methyl palmitate (MP) inhibits the activation of Kupffer cells. To evaluate the potential of MP to inhibit the activation of other macrophages, we treated rat peritoneal macrophages with varying concentrations of MP. Its treatment led to a dose-dependent inhibition of phagocytic activity, which was found to be 34%, 47%, and 66% at 0.25, 0.50, and 1.0 mM MP, respectively, as measured by latex bead uptake. When MP-treated peritoneal macrophages were stimulated with lipopolysaccharide (LPS), the nitric oxide (.NO) release was inhibited at 6 h, while cyclooxygenase-2 expression decreased after 24 h. The treatment with MP increased the release of interleukin (IL)-10 in the LPS-treated cells at 6 h, while IL-6 and tumor necrosis factor-, were significantly increased both at 6 and 24 h. Our data suggest that MP inhibits phagocytic activity and . NO production similar to that observed in isolated Kupffer cells. Therefore, inhibition of phagocytosis by MP may be a general phenomenon, and it could be used as an inhibitor of macrophage function. © 2006 Wiley Periodicals, Inc. J Biochem Mol Toxicol 20:302,308, 2006; Published online in Wiley InterScience ( DOI 10.1002/jbt.20150 [source]

Molecular basis for the antiandrogen withdrawal syndrome

Hiroshi Miyamoto
Abstract In patients with prostate cancer who manifest disease progression during combined androgen blockade therapy, discontinuation of antiandrogen treatment might result in prostate-specific antigen decline, often associated with clinical improvement. The response called antiandrogen withdrawal syndrome is thus acknowledged as a general phenomenon. However, molecular mechanisms responsible for this syndrome are not completely understood. This article outlines the proposed mechanisms, including alterations of androgen receptor gene and its coregulatory proteins and activation of the signal transduction pathway, and the potential therapeutic approaches based on the specific mechanisms. © 2003 Wiley-Liss, Inc. [source]

The value increment of mass-customized products: an empirical assessment

Martin Schreier
The primary argument in favour of mass customization is the delivery of superior customer value. Using willingness-to-pay (WTP) measurements, Franke and Piller (2004), Journal of Product Innovation Management, 21, 401,415 have recently shown that customers designing their own watches with design toolkits are willing to pay premiums of more than 100% (,WTP). In the course of three studies, we found that this type of value increment is not a singular occurrence but might rather be a general phenomenon, as we again found average ,WTPs of more than 100% among customers designing their own cell phone covers, T-shirts and scarves. Building on this, we discuss the sources of benefits that are likely to explain this tremendous value increment. We argue that compared to conventional standard products, a mass-customized product might render the following utilitarian and hedonic benefits: (1) First, the output might be beneficial as self-designed products offer a much closer fit between individual needs and product characteristics. In addition to this mere functional benefit, extra value might also stem from (2) the perceived uniqueness of the self-designed product. As the customer takes on the role of an active co-designer, there may also be two general ,do-it-yourself effects': (3) First, the process of designing per se is likely to allow the customer to meet hedonic or experiential needs (process benefit). (4) Customers may also be likely to value the output of self-design more highly if they take pride in having created something on their own (instead of traditionally buying something created by somebody else). This is referred to as the ,pride of authorship' effect. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Changes in vertebral structure during growth of reared rainbow trout, Oncorhynchus mykiss (Walbaum): a new approach using modelling of vertebral bone profiles

M-H Deschamps
Abstract Severe bone resorption of the vertebral body in reared rainbow trout was thought to be a dysfunction in mineral balance induced by increased growth rate in unfavourable rearing conditions. To verify this assumption, we sampled market-sized trout (c. 250 g) from 20 fish farms with different rearing conditions. Growth rate was also studied by sampling trout reared in three different water temperatures from fry to market-size. Transverse sections of vertebrae were microradiographed, then digitized. Total bone area (Tt-B.Ar.) and bone profiles were obtained using BONE PROFILER 3.23 software and a mathematical model was developed to statistically compare bone profiles using 12 parameters in four vertebra regions. Tt-B.Ar. and bone profiles were found to vary with rearing conditions and growing temperatures, indicating obvious influences of these factors on bone remodelling. However, vertebral resorption was found to be a general phenomenon. In trout from 190 to 235 mm in length, vertebrae underwent important remodelling resulting in large resorption of the middle area, while the transition and peripheral areas showed an increase in bone deposition. Changes in vertebra architecture seem to be a good compromise between the need to mobilize stored minerals during growth while maintaining vertebral biomechanical properties. [source]

Crystallite and Grain-Size-Dependent Phase Transformations in Yttria-Doped Zirconia

Arun Suresh
In pure zirconia, ultrafine powders are often observed to take on the high-temperature tetragonal phase instead of the "equilibrium" monoclinic phase. The present experiments and analysis show that this observation is one manifestation of a much more general phenomenon in which phase transformation temperatures shift with crystallite/grain size. In the present study, the effect of crystallite (for powders) and grain (for solids) size on the tetragonal , monoclinic phase transformation is examined more broadly across the yttria,zirconia system. Using dilatometry and high-temperature differential scanning calorimetry on zirconia samples with varying crystallite/grain sizes and yttria content, we are able to show that the tetragonal , monoclinic phase transformation temperature varies linearly with inverse crystallite/grain size. This experimental behavior is consistent with thermodynamic predictions that incorporate a surface energy difference term in the calculation of free-energy equilibrium between two phases. [source]

Impact of Nanoscale Confinement on Crystal Orientation of Poly(ethylene oxide)

Haopeng Wang
Abstract Using a layer-multiplying coextrusion process to fabricate films with thousands of alternating polymer nanolayers, we report here a new crystalline morphology in confined polymer nanolayers and an abrupt transition in the crystallization habit. At higher temperatures, poly(ethylene oxide) crystallizes as large, in-plane lamellae. A 5,°C change in the crystallization temperature produces an on-edge lamellar orientation. The results point to a transition from heterogeneous nucleation to substrate-assisted nucleation. This may be a general phenomenon that accounts for previously unexplained differences in the preferred chain alignment of confined polymer crystals. [source]

Intraspecific competition drives multiple species resource polymorphism in fish communities

OIKOS, Issue 1 2008
Richard Svanbäck
It has been hypothesized that inter-specific competition will reduce species niche utilization and drive morphological evolution in character displacement. In the absence of a competitor, intra-specific competition may favor an expansion of the species niche and drive morphological evolution in character release. Despite of this theoretical framework, we sometimes find potential competitor species using the same niche range without any partitioning in niche. We used a database on test fishing in Sweden to evaluate the factors (inter- and intraspecific competition, predation, and abiotic factors) that could influence habitat choice of two competitor species. The pattern from the database shows that the occurrence of perch and roach occupying both littoral and pelagic habitats of lakes in Sweden is a general phenomenon. Furthermore, the results from the database suggest that this pattern is due to intra-specific competition rather than inter-specific competition or predation. In a field study, we estimated the morphological variation in perch and roach and found that, individuals of both species caught in the littoral zone were more deeper bodied compared to individuals caught in the pelagic zone. Pelagic perch fed more on zooplankton compared to littoral perch, independent of size, whereas the littoral perch had more macroinvertebrates and fish in their diet. Pelagic roach fed more on zooplankton compared to littoral roach, whereas littoral individuals fed more on plant material. Furthermore, we sampled littoral and pelagic fish from another lake to evaluate the generality of our first results and found the same habitat associated morphology in both perch and roach. The results show a consistent multi-species morphological separation in the littoral and pelagic habitats. This study suggests that intra-specific competition is possibly more important than inter-specific competition for the morphological pattern in the perch-roach system. [source]

Surnames in Siberia: A study of the population of Yakutia through isonymy

L. Tarskaia
Abstract We studied the isonymic structure of the Republic of Sakha (Yakutia), in the Russian Federation, using the surname distributions of 491,259 citizens above 18 years registered as residents in 2002. These were distributed in 35 districts and 497 towns and settlements of the Republic. The number of different surnames was 44,625. Matrices of isonymic distances between the 35 districts were tested for correlation with the geographic distance between the population centers of gravity of thedistricts. We found that, for the whole of Yakutia, Nei's distance was correlated with geographic distance (r = 0.693 ± 0.027). A dendrogram of the 35 districts was built from the distance matrix, using the UPGMA method. The clusters identified by the dendrogram correlate with the geographic position of the districts. The correlation of random inbreeding calculated from isonymy, FST, with latitude was positive and highly significant but weak (r = 0.23). So, inbreeding was highest in the Arctic districts, and lowest in the South. Average , for 497 towns was 107, for 35 districts it was 311, and for the Republic 433. The value of , was higher for Russian than for the local languages. The geographical distribution of ,, high in the Center and South-East and lower in the North-West, is compatible with the settlement of groups of migrants moving from the South-East toward the center and the North of Yakutia. It is proposed that low-density demic diffusion of human populations results in high inbreeding and may have been a general phenomenon in the early phases of human radiations. Am J Phys Anthropol 2009. © 2008 Wiley-Liss, Inc. [source]

Self and nonself recognition of chiral catalysts: The origin of nonlinear effects in the amino-alcohol catalyzed asymmetric addition of diorganozincs to aldehydes

Ryoji Noyori
Abstract Asymmetric addition of dialkylzincs to aldehydes in the presence of (2S)-3- exo -(dimethylamino)isoborneol [(S)-DAIB] exhibits various nonclassical phenomena. The enantiomeric excess (ee) of the alkylation product, obtained with partially resolved DAIB, is much higher than that of the chiral amino alcohol, while the rate decreases considerably as the ee of DAIB is lowered. The asymmetric amplification effects reflect the relative turnover numbers of two enantiomorphic catalytic cycles, where an essential feature is the reversible homochiral and heterochiral dimerization of the coexisting enantiomeric DAIB-based Zn catalysts. The interplay between the thermodynamics of the monomer/dimer equilibration and the kinetics of alkylation reaction strongly affect the overall profile of asymmetric catalysis. The self and nonself recognition of the chiral Zn catalysts is a general phenomenon when (S)-DAIB is mixed with its enantiomer, diastereomer, or even an achiral ,-amino alcohol. The degree of nonlinearity is highly affected not only by the structures and purity of catalysts but also by various reaction parameters. The salient features have been clarified on the basis of molecular weight measurements, NMR and X-ray crystallographic studies of organozinc complexes, and kinetic experiments, as well as computer-aided quantitative analysis. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:85,100, 2001 [source]

Cryopreservation technique: comparison of Test yolk buffer versus SpermCryo and vapour versus computerised freezing

ANDROLOGIA, Issue 1 2008
L. Paras
Summary Semen cryopreservation offers the possibility to maintain fertility over a long time period e.g. for male cancer patients. Although its use expands worldwide, there is no established method that can be referred to as an entrenched standard for routine laboratory use. Cryodamage is still a general phenomenon and the success of cryopreservation is affected on one side by the cryoprotective agent and on the other side by the technique of freezing. In this methodological study, we compared the newly offered SpermCryo (SC) with the standard used cryoprotectant Test yolk buffer (TYB). We could show that TYB is superior to SC. In addition, we compared the two mainly used techniques for cryopreservation: computerised slow-stage freezing versus nitrogen vapour fast freezing. Regarding the sperm post-thaw motility and viability, no significant difference was found between these two methods. In conclusion, TYB can be recommended as a cryomedium of first choice and the appropriate freezing technique can be selected according to the local facilities of the institution. [source]

Resprouting of saplings following a tropical rainforest fire in north-east Queensland, Australia

Abstract In 2002, fire burnt areas of Mesophyll- and Notophyll Vine Forest in the Smithfield Conservation Park near Cairns, Australia. We assessed the ability of rainforest plant species to persist through fire via resprouting. Natural rates of mortality and resprouting in unburnt areas were assessed for all saplings (stems < 2 m) via 13, 2 × 50 m belt transects, and compared to estimates of mortality and resprouting in 26 transects in burnt areas. We also tested the resprouting ability per-individual stem of each species against all other stems with which it co-occurred. Totals of 1242 stems (138 species) were sampled in burnt transects and 503 stems (95 species) in unburnt transects (total number of unique species = 169). There was no difference in the number of stems existing prior to the fire in burnt and unburnt areas when expressed on a per-sample area basis. Resprouting from basal shoots and root suckers was significantly greater in burnt than in unburnt areas, but rates of stem sprouting were not different. In burnt areas 72 species were tested for resprouting ability and most (65/72) resprouted at similar rates. All species analysed contained individuals that resprouted. The resprouting response of five species was significantly lower, and in two species was significantly higher. For these species especially, fire may act as a mechanism altering relative abundances. The fire coincided with an extreme El Niño event. Current predictions indicate El Niño conditions may become increasingly common, suggesting fire events within rainforest could become more frequent. Resprouting as a general phenomenon of rainforest species, and differential resprouting ability between species should therefore be an important consideration in assessing the potential path of vegetation change in rainforests after fire. [source]

Increased exposure to bacterial antigen RpL7/L12 in early stage colorectal cancer patients

CANCER, Issue 17 2010
Annemarie Boleij MSc
Abstract BACKGROUND: Intestinal bacteria have long been implicated in colorectal cancer pathology, and many reports point to a close linkage between Streptococcus bovis biotype I (recently renamed Streptococcus gallolyticus) infections and tumors of the human colon. This work aims to investigate the humoral immune response to this bacterium during different stages of colorectal cancer. METHODS: The presence of serum antibodies against S. bovis antigen RpL7/L12, previously assigned as a potential diagnostic antigen, was evaluated in Dutch (n = 209) and American (n = 112) populations using a newly developed enzyme-linked immunosorbent assay. RESULTS: The analyses consistently showed that an immune response against this bacterial antigen was increased in polyp patients and stage I/II colorectal cancer patients as compared with asymptomatic individuals. This was not paralleled by increased antibody production to endotoxin, an intrinsic cell wall component of the majority of intestinal bacteria, which implies that the humoral immune response against RpL7/L12 is not a general phenomenon induced by the loss of colonic barrier function. Notably, increased anti-RpL7/L12 levels were not or were only mildly detected in late stage colorectal cancer patients having lymph node or distant metastasis. CONCLUSIONS: These findings are indicative of an increased exposure to antigen RpL7/L12 during early stages of colon carcinogenesis and suggest that intestinal bacteria such as S. bovis constitute a risk factor for the progression of premalignant lesions into early stage carcinomas. Clearly, the current findings emphasize the necessity for further studies on the possible etiologic relationship between intestinal bacteria and human colorectal cancer. Cancer 2010. © 2010 American Cancer Society. [source]

Tests of a Dynamic Systems Account of the A-not-B Error: The Influence of Prior Experience on the Spatial Memory Abilities of Two-Year-Olds

John P. Spencer
Recently, Smith, Thelen, and colleagues proposed a dynamic systems account of the Piagetian "A-not-B" error in which infants' errors result from general processes that make goal-directed actions to remembered locations. Based on this account, the A-not-B error should be a general phenomenon, observable in different tasks and at different points in development. Smith, Thelen, et al.'s proposal was tested using an A-not-B version of a sandbox task. During three training trials and three "A" trials, 2-year-olds watched as a toy was buried in a sandbox at Location A. Following a 10-s delay, children searched for the object. Across five experiments, children's (total N= 92) performance on the A trials was accurate. After the A trials, children watched as a toy was hidden at Location B, 8 to 10 inches from Location A. In all experiments, children's searches after a 10-s delay were significantly biased in the direction of Location A. Furthermore, this bias toward Location A decreased with repeated trials to Location B, as well as when children completed fewer trials to Location A. Together, these data suggest that A-not-B,type errors are pervasive across tasks and development. [source]