Home About us Contact
|
Home About us Contact | ||
|
|
||
Equivalent Levels (equivalent + level)
Selected AbstractsSelective harvest of sooty shearwater chicks: effects on population dynamics and sustainabilityJOURNAL OF ANIMAL ECOLOGY, Issue 4 2005CHRISTINE M. HUNTER Summary 1Selectivity of harvest influences harvest sustainability because individuals with different characteristics contribute differently to population growth. We investigate the effects of selection based on chick weight on a traditional harvest of the sooty shearwater Puffinus griseus by Rakiura Maori in New Zealand. 2We develop a periodic stage-structured matrix population model and incorporate seasonal harvest of three weight classes of chicks. Intensity and selectivity of harvest are defined in terms of weight-specific hazard functions. 3We investigate the effect of harvest intensity and selectivity on population growth rate, ,, and the chick exploitation rate, E. We also consider the interaction of chick harvest and adult mortality. 4, decreases and E increases as harvest intensity increases. At low harvest intensities, selection has little effect on ,. At high harvest intensities, , increases as selectivity increases because of the non-linear relationship between harvest intensity and the probability of being harvested. 5, is determined almost completely by E, irrespective of the combination of harvest selectivity and intensity producing E. This is true for both general patterns of selectivity and specific patterns estimated from empirical data. 6The elasticities of ,, the net reproductive rate and the generation time are unaffected by selectivity and show only small responses to harvest intensity. 7Adult sooty shearwaters are killed as bycatch in long-line and driftnet fisheries. Such mortality of adults has an effect on , about 10-fold greater than an equivalent level of chick harvest. 8The sustainability of any combination of chick harvest and adult mortality depends on the resulting reduction in ,. We explore these results in relation to indices of sustainability, particularly the United States Marine Mammal Protection Act (MMPA) standards. [source] PPAR,1 synthesis and adipogenesis in C3H10T1/2 cells depends on S-phase progression, but does not require mitotic clonal expansionJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2004Young C. Cho Abstract Adipogenesis is typically stimulated in mouse embryo fibroblast (MEF) lines by a standard hormonal combination of insulin (I), dexamethasone (D), and methylisobutylxanthine (M), administered with a fresh serum renewal. In C3H10T1/2 (10T1/2) cells, peroxisome proliferator-activated receptor ,1 (PPAR,1) expression, an early phase key adipogenic regulator, is optimal after 36 h of IDM stimulation. Although previous studies provide evidence that mitotic clonal expansion of 3T3-L1 cells is essential for adipogenesis, we show, here, that 10T1/2 cells do not require mitotic clonal expansion, but depend on cell cycle progression through S-phase to commit to adipocyte differentiation. Exclusion of two major mitogenic stimuli (DM without insulin and fresh serum renewal) from standard IDM protocol removed mitotic clonal expansion, but sustained equivalent PPAR,1 synthesis and lipogenesis. Different S-phase inhibitors (aphidicolin, hydroxyurea, l -mimosine, and roscovitin) each arrested cells in S-phase, under hormonal stimulation, and completely blocked PPAR,1 synthesis and lipogenesis. However, G2/M inhibitors effected G2/M accumulation of IDM stimulated cells and prevented mitosis, but fully sustained PPAR,1 synthesis and lipogenesis. DM stimulation with or without fresh serum renewal elevated DNA synthesis in a proportion of cells (measured by BrdU labeling) and accumulation of cell cycle progression in G2/M-phase without complete mitosis. By contrast, standard IDM treatments with fresh serum renewal caused elevated DNA synthesis and mitotic clonal expansion while achieved equivalent level of adipogenesis. At most, one-half of the 10T1/2 mixed cell population differentiated to mature adipocytes, even when clonally isolated. PPAR, was exclusively expressed in the cells that contained lipid droplets. IDM stimulated comparable PPAR,1 synthesis and lipogenesis in isolated cells at low cell density (LD) culture, but in about half of the cells and with sensitivity to G1/S, but not G2/M inhibitors. Importantly, growth arrest occurred in all differentiating cells, while continuous mitotic clonal expansion occurred in non-differentiating cells. Irrespective of confluence level, 10T1/2 cells differentiate after progression through S-phase, where adipogenic commitment induced by IDM stimulation is a prerequisite for PPAR, synthesis and subsequent adipocyte differentiation. © 2003 Wiley-Liss, Inc. [source] Using the Distractor Categories of Multiple-Choice Items to Improve IRT LinkingJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 3 2006Jee-Seon Kim Simulation and real data studies are used to investigate the value of modeling multiple-choice distractors on item response theory linking. Using the characteristic curve linking procedure for Bock's (1972) nominal response model presented by Kim and Hanson (2002), all-category linking (i.e., a linking based on all category characteristic curves of the linking items) is compared against correct-only (CO) linking (i.e., linking based on the correct category characteristic curves only) using a common-item nonequivalent groups design. The CO linking is shown to represent an approximation to what occurs when using a traditional correct/incorrect item response model for linking. Results suggest that the number of linking items needed to achieve an equivalent level of linking precision declines substantially when incorporating the distractor categories. [source] Immunohistochemical characterization of guided bone regeneration at a dehiscence-type defect using different barrier membranes: an experimental study in dogsCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2008Frank Schwarz Abstract Objectives: The aim of the present study was to evaluate immunohistochemically the pattern of guided bone regeneration (GBR) using different types of barrier membranes. Material and methods: Standardized buccal dehiscence defects were surgically created following implant bed preparation in 12 beagle dogs. Defects were randomly assigned to six different GBR procedures: a collagen-coated bone grafting material (BOC) in combination with either a native, three cross-linked, a titanium-reinforced collagen membrane, or expanded polytetrafluorethylene (ePTFE), or BOC alone. After 1, 2, 4, 6, 9, and 12 weeks of submerged healing, dissected blocks were processed for immunohistochemical (osteocalcin , OC, transglutaminase II , angiogenesis) and histomorphometrical analysis [e.g., bone-to-implant contact (BIC), area of new bone fill (BF)]. Results: In general, angiogenesis, OC antigen reactivity, and new bone formation mainly arose from open bone marrow spaces at the bottom of the defect and invaded the dehiscence areas along the implant surface and BOC. At 4 weeks, membranes supporting an early transmembraneous angiogenesis also exhibited some localized peripheral areas of new bone formation. However, significantly increasing BIC and BF values over time were observed in all groups. Membrane exposure after 10,12 weeks was associated with a loss of the supporting alveolar bone in the ePTFE group. Conclusion: Within the limits of the present study, it was concluded that (i) angiogenesis plays a crucial role in GBR and (ii) all membranes investigated supported bone regeneration on an equivalent level. [source] Axoneme-dependent tubulin modifications in singlet microtubules of the Drosophila sperm tailCYTOSKELETON, Issue 4 2008Henry D. Hoyle Abstract Drosophila melanogaster sperm tubulins are posttranslationally glutamylated and glycylated. We show here that axonemes are the substrate for these tubulin C-terminal modifications. Axoneme architecture is required, but full length, motile axonemes are not necessary. Tubulin glutamylation occurs during or shortly after assembly into the axoneme; only glutamylated tubulins are glycylated. Tubulins in other testis microtubules are not modified. Only a small subset of total Drosophila sperm axoneme tubulins have these modifications. Biochemical fractionation of Drosophila sperm showed that central pair and accessory microtubules have the majority of poly-modified tubulins, whereas doublet microtubules have only small amounts of mono- and oligo-modified tubulins. Glutamylation patterns for different ,-tubulins experimentally assembled into axonemes were consistent with utilization of modification sites corresponding to those identified in other organisms, but surrounding sequence context was also important. We compared tubulin modifications in the 9 + 9 + 2 insect sperm tail axonemes of Drosophila with the canonical 9 + 2 axonemes of sperm of the sea urchin Lytichinus pictus and the 9 + 0 motile sperm axonemes of the eel Anguilla japonica. In contrast to Drosophila sperm, L. pictus sperm have equivalent levels of modified tubulins in both doublet and central pair microtubule fractions, whereas the doublets of A. japonica sperm exhibit little glutamylation but extensive glycylation. Tubulin C-terminal modifications are a prevalent feature of motile axonemes, but there is no conserved pattern for placement or amount of these modifications. We conclude their functions are likely species-specific. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Seasonal plasticity of brain aromatase mRNA expression in glia: Divergence across sex and vocal phenotypesDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2005Paul M. Forlano Abstract Although teleost fishes have the highest levels of brain aromatase (estrogen synthase) compared to other vertebrates, little is known of its regulation and function in specific brain areas. Previously, we characterized the distribution of aromatase in the brain of midshipman fish, a model system for identifying the neural and endocrine basis of vocal-acoustic communication and alternative male reproductive tactics. Here, we quantified seasonal changes in brain aromatase mRNA expression in the inter- and intrasexually dimorphic sonic motor nucleus (SMN) and in the preoptic area (POA) in males and females in relation to seasonal changes in circulating steroid hormone levels and reproductive behaviors. Aromatase mRNA expression was compared within each sex throughout non-reproductive, pre-nesting, and nesting periods as well as between sexes within each season. Intrasexual (male) differences were also compared within the nesting period. Females had higher mRNA levels in the pre-nesting period when their steroid levels peaked, while acoustically courting (type I) males had highest expression during the nesting period when their steroid levels peaked. Females had significantly higher levels of expression than type I males in all brain areas, but only during the pre-nesting period. During the nesting period, non-courting type II males had significantly higher levels of aromatase mRNA in the SMN but equivalent levels in the POA compared to type I males and females. These results demonstrate seasonal and sex differences in brain aromatase mRNA expression in a teleost fish and suggest a role for aromatase in the expression of vocal-acoustic and alternative male reproductive phenotypes. © 2005 Wiley Periodicals, Inc. J. Neurobiol, 2005 [source] Factor and item-response analysis DSM-IV criteria for abuse of and dependence on cannabis, cocaine, hallucinogens, sedatives, stimulants and opioidsADDICTION, Issue 6 2007Nathan A. Gillespie ABSTRACT Aims This paper explored, in a population-based sample of males, the factorial structure of criteria for substance abuse and dependence, and compared qualitatively the performance of these criteria across drug categories using item,response theory (IRT). Design Marginal maximum likelihood was used to explore the factor structure of criteria within drug classes, and a two-parameter IRT model was used to determine how the difficulty and discrimination of individual criteria differ across drug classes. Participants A total of 4234 males born from 1940 to 1974 from the population-based Virginia Twin Registry were approached to participate. Measurements DSM-IV drug use, abuse and dependence criteria for cannabis, sedatives, stimulants, cocaine and opiates. Findings For each drug class, the pattern of endorsement of individual criteria for abuse and dependence, conditioned on initiation and use, could be best explained by a single factor. There were large differences in individual item performance across substances in terms of item difficulty and discrimination. Cocaine users were more likely to have encountered legal, social, physical and psychological consequences. Conclusions The DSM-IV abuse and dependence criteria, within each drug class, are not distinct but best described in terms of a single underlying continuum of risk. Because individual criteria performed very differently across substances in IRT analyses, the assumption that these items are measuring equivalent levels of severity or liability with the same discrimination across different substances is unsustainable. Compared to other drugs, cocaine usage is associated with more detrimental effects and negative consequences, whereas the effects of cannabis and hallucinogens appear to be less harmful. Implications for other drug classes are discussed. [source] Good practice in plasma collection and fractionationISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue n1 2010C. Schärer The control strategy to ensure safety of blood products includes a combination of measures focusing on ensuring the quality and safety of starting material by careful donor selection and testing strategies at different levels, together with validated manufacturing processes, including steps to inactivate or remove potential contaminating agents. Using an approach based on good manufacturing practice (GMP) provides a manufacturing model that allows for a documented system of incorporating quality throughout the entire manufacturing process and describes the activities and controls needed to consistently produce products that comply with specifications and are safe for use. There are no doubts that the aim of providing safe and high-quality product to the patients should be the same for all products derived from human blood, independent of its use either as a blood component for direct transfusion or as industrially manufactured product. It would be difficult to justify whether for blood components the good practice standards and for plasma derivatives the GMP standards for manufacturing would not ensure equivalent levels of quality and safety. To ensure a high level of quality and safety of blood components and plasma derivatives, the implementation of double standards in blood establishments and fractionation industry would not be effective and should be avoided. Harmonized standards and good practices for collection and fractionation, based on the principles of GMP, should be envisaged in the whole chain of manufacturing blood components and plasma derivatives. Global initiatives to further promote the implementation of harmonized GMP for the collection in blood establishments and a stringent regulatory control are ongoing. This would further contribute to the global availability of plasma-derived medicinal products. [source] Affirmative action, duality of error, and the consequences of mispredicting the academic performance of african american college applicantsJOURNAL OF POLICY ANALYSIS AND MANAGEMENT, Issue 1 2002Jeryl L. Mumpower The implications of different potential affirmative action policies depend on three factors: selection rate from the applicant pool, base rate of qualified applicants, and accuracy of performance predictions. A series of analyses was conducted under various assumptions concerning affirmative action plans, causes of racial differences in average college admissions test scores, and racial differences in accuracy of performance predictions. Evidence suggesting a lower level of predictive accuracy for African Americans implies that, under a program of affirmative action, both proportionately more false positives (matriculated students who do not succeed) and proportionately more false negatives (rejected applicants who could have succeeded) will be found among African American applicants. Unless equivalent levels of predictive accuracy are achieved for both groups, no admission policy can be fair simultaneously to majority group applicants and African American applicants. © 2002 by the Association for Public Policy Analysis and Management. [source] Molecular evidence for a founder effect in invasive house finch (Carpodacus mexicanus) populations experiencing an emergent disease epidemicMOLECULAR ECOLOGY, Issue 1 2006DANA M. HAWLEY Abstract The impact of founder events on levels of genetic variation in natural populations remains a topic of significant interest. Well-documented introductions provide a valuable opportunity to examine how founder events influence genetic diversity in invasive species. House finches (Carpodacus mexicanus) are passerine birds native to western North America, with the large eastern North American population derived from a small number of captive individuals released in the 1940s. Previous comparisons using amplified fragment length polymorphism (AFLP) markers found equivalent levels of diversity in eastern and western populations, suggesting that any genetic effects of the founder event were ameliorated by the rapid growth of the newly established population. We used an alternative marker system, 10 highly polymorphic microsatellites, to compare levels of genetic diversity between four native and five introduced house finch populations. In contrast to the AFLP comparisons, we found significantly lower allelic richness and heterozygosity in introduced populations across all loci. Three out of five introduced populations showed significant reductions in the ratio of the number of alleles to the allele size range, a within-population characteristic of recent bottlenecks. Finally, native and introduced populations showed significant pairwise differences in allele frequencies in every case, with stronger isolation by distance within the introduced than native range. Overall, our results provide compelling molecular evidence for a founder effect during the introduction of eastern house finches that reduced diversity levels at polymorphic microsatellite loci and may have contributed to the emergence of the Mycoplasma epidemic which recently swept the eastern range of this species. [source] General and specific host responses to bacterial infection in Peyer's patches: a role for stromelysin-1 (matrix metalloproteinase-3) during Salmonella enterica infectionMOLECULAR MICROBIOLOGY, Issue 1 2007Scott A. Handley Summary Salmonella enterica serovar Typhimurium (S. typhimurium) and Yersinia enterocolitica are enteric pathogens capable of colonizing and inducing inflammatory responses in Peyer's patches (PPs) and mesenteric lymph nodes (MLNs). Although the tissue colonization pattern is similar between these two pathogens, their pathogenic lifestyles are quite different. For example, while S. typhimurium is primarily an intracellular pathogen, Y. enterocolitica survives primarily extracellularly. We determined and compared the transcriptional changes occurring in response to S. typhimurium and Y. enterocolitica colonization of PP using Affymetrix GeneChip technology. Both pathogens elicited a general inflammatory response indicated by the upregulation of cytokines and chemokines. However, specific differences were also observed, most notably in the transcriptional regulation of gamma interferon (IFN-,) and IFN-,-regulated genes in response to S. typhimurium but not Y. enterocolitica. Of particular note, a group of genes encoding matrix metalloproteinases (MMPs) had increased transcript numbers in the PPs following infection with both pathogens. The experiments described here compare oral S. typhimurium or Y. enterocolitica infection in stromelysin-1 (MMP-3)-deficient mice (mmp-3,/,) with mice possessing functional MMP-3 (mmp-3+/+). There was little difference in the survival of MMP-3-deficient mice infected with Y. enterocolitica when compared with littermate controls. Surprisingly though, mmp-3,/, mice were markedly more resistant to S. typhimurium infection than the control mice. S. typhimurium was able to colonize mmp-3,/, mice, albeit in a delayed fashion, to equivalent levels as mmp-3+/+ mice. Nevertheless, significantly lower levels of inflammatory cytokines were detected in tissues and serum in the mmp-3,/, mice in comparison with mmp-3+/+ mice. We hypothesize that MMP-3 is involved in initiating an early and lethal cytokine response to S. typhimurium colonization. [source] Suillus bovinus glutamine synthetase gene organization, transcription and enzyme activities in the Scots pine mycorrhizosphere developed on forest humusNEW PHYTOLOGIST, Issue 2 2004Jarmo T. Juuti Summary ,,Glutamine synthetase (GS) expression and activity is of central importance for cellular ammonium assimilation and recycling. Thus, a full characterization of this enzyme at the molecular level is of critical importance for a better understanding of nitrogen (N) assimilation in the mycorrhizal symbiosis. ,,Genomic and cDNA libraries of Suillus bovinus were constructed to isolate the GS gene, glnA, and corresponding cDNAs. The transcription initiation site was identified and transcription and enzyme activities were characterized in pure culture mycelium and mycorrhiza, and extramatrical mycelium samples harvested from Scots pine,Suillus bovinus microcosms grown on forest humus. ,,Pure culture mycelium, mycorrhiza and extramatrical mycelium all exhibited equivalent levels of GS transcription, translation and enzyme activities. However, levels of transcription and enzyme activity did not correlate as a large majority of detectable transcripts showed specific 5,-end truncation. ,,Our data suggest that GS is constitutively expressed and not directly affected by environmental conditions of the symbiotic N uptake. Any changes in the intracellular ammonium level are most likely handled by regulatory flexibility of GS at enzyme level. [source] Limitations to CO2 assimilation in ozone-exposed leaves of Plantago majorNEW PHYTOLOGIST, Issue 1 2002Y. Zheng Summary ,,The potential limitations on net leaf carbon assimilation imposed by stomatal conductance, carboxylation velocity, capacity for ribulose 1,5-bisphosphate regeneration and triose phosphate ultilization rate were derived from steady-state gas exchange measurements made over the life-span of two leaves on plants of an ,O3 -sensitive' population of Plantago major grown at contrasting atmospheric O3 concentrations. ,,Parallel measurements of chlorophyll fluorescence were used to monitor changes in the quantum efficiency of PSII photochemistry, and in vitro measurements of Rubisco activity were made to corroborate modelled gas exchange data. ,,Data indicated that a loss of Rubisco was predominantly responsible for the decline in CO2 assimilation observed in O3 -treated leaves. The quantum efficiency of PSII was unchanged by O3 exposure. ,,Stomatal aperture declined in parallel with CO2 assimilation in O3 -treated plants, but this did not account for the observed decline in photosynthesis. Findings suggested that O3 -induced shifts in stomatal conductance result from ,direct' effects on the stomatal complex as well as ,indirect effects' mediated through changes in intercellular CO2 concentration. Leaves on the same plant exposed to equivalent levels of O3 showed striking differences in their response to the pollutant. [source] Effect of morphology on barrier properties of poly(ethylene terephthalate),POLYMER ENGINEERING & SCIENCE, Issue 3 2005A.A. Natu The effects of morphology on the barrier properties of poly(ethylene terephthalate) (PET) have been investigated. Various levels of crystallinity can be developed in PET as a result of thermal exposure, orientation, and heat setting. The morphologies of the crystalline phase are affected by the conditions of their formation. As a result of morphological differences, samples with equivalent levels of crystallinity have been found to exhibit different oxygen barrier properties. These differences are most apparent at low and intermediate levels of crystallinity. For thermally crystallized systems, at the same crystalline content, increasing superstructure size in the crystalline phase leads to greater tortuosity for the permeant molecules, resulting in lower permeability. For stretched and heat set PET, transport properties can be correlated with birefringence as well as overall orientation, measured in terms of fraction of molecules in the trans or extended chain conformation. At high levels of crystallinity, where the spherulites become volume filling, permeation takes place primarily through the interlamellar regions of the crystalline phase and is controlled by level of crystallinity, independent of the mode of crystallization. The barrier properties of PET, before spherulitic impingement occurs, are governed by the size and number of spherulites as well as by the amorphous orientation present in non-crystalline regions. POLYM. ENG. SCI., 45:400,409, 2005. © 2005 Society of Plastics Engineers [source] Role of TNF, in Early Chemokine Production and Leukocyte Infiltration into Heart AllograftsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 1 2010D. Ishii The acute phase cytokines IL-1,, IL-6 and TNF, are produced early during inflammatory processes, including ischemia-reperfusion. The appearance and role of these cytokines in the early inflammation following reperfusion of grafts remain poorly defined. This study investigated the role of TNF, in the induction of early leukocyte infiltration into vascularized heart allografts. TNF, and IL-6 mRNA levels reached an initial peak 3 h posttransplant and a second peak at 9,12 h with equivalent levels in iso- and allografts. A single dose of anti-TNF, mAb given at reperfusion decreased neutrophil and macrophage chemoattractant levels and early neutrophil, macrophage and memory CD8 T-cell infiltration into allografts. Anti-TNF, mAb also extended graft survival from 8.6 ± 0.6 days to 14.1 ± 0.8 days. When assessed on day 7 posttransplant, the number of donor-reactive CD8 T cells producing IFN-, in the spleen was reduced almost 70% in recipients treated with anti-TNF, mAb. Whereas anti-CD154 mAb prolonged survival to day 21, administration of anti-TNF, and anti-CD154 mAb delayed rejection to day 32 and resulted in long-term (>80 days) survival of 40% of the heart allografts. These data implicate TNF, as an important mediator of early inflammatory events in allografts that undermine graft survival. [source] Pond characteristics as determinants of species diversity and community composition in desert batsANIMAL CONSERVATION, Issue 5 2010O. Razgour Abstract Although water availability is known to affect landscape-scale patterns of wildlife diversity and distribution in arid environments, little is known about the microhabitat characteristics that shape the local-scale distribution of desert bats. We examined the relative importance of pond microhabitat characteristics for the conservation of bats, and hypothesized that in arid environments, patterns of bat diversity and community composition relate to the size of the pond and its hydroperiod (the number of months a pond holds water), a term we use to distinguish between permanent, semi-permanent and temporary ponds. We combined acoustic monitoring with video recording and an experimental approach to study bat activity over natural ponds in the Negev Desert, Israel. We found that both within and between ponds bat species richness and activity significantly increased with pond size. An experimental reduction of pond size led to a significant reduction in bat species richness and activity and affected the bat community composition. In contrast to pond size, pond hydroperiod did not affect bat diversity, as temporary ponds had equivalent levels of bat species richness and activity to permanent ponds. However, hydroperiod did couple with pond size to affect the bat community composition, whereby non-desert bat species that have a higher frequency of drinking were associated with larger and more permanent ponds. Our results highlight the importance of larger temporary ponds (ponds over 15 m in length and 0.5 m in depth) for the conservation of biodiversity in arid environments. [source] Mirror Self-Recognition Beyond the FaceCHILD DEVELOPMENT, Issue 1 2006Mark Nielsen Three studies (N=144) investigated how toddlers aged 18 and 24 months pass the surprise-mark test of self-recognition. In Study 1, toddlers were surreptitiously marked in successive conditions on their legs and faces with stickers visible only in a mirror. Rates of sticker touching did not differ significantly between conditions. In Study 2, toddlers failed to touch a sticker on their legs that had been disguised before being marked. In Study 3, having been given 30-s exposure to their disguised legs before testing, toddlers touched the stickers on their legs and faces at equivalent levels. These results suggest that toddlers pass the mark test based on expectations about what they look like, expectations that are not restricted to the face. [source] | |||||||||||||