61 resultados para Signs of adaptation
Resumo:
The shallow water equations are solved using a mesh of polygons on the sphere, which adapts infrequently to the predicted future solution. Infrequent mesh adaptation reduces the cost of adaptation and load-balancing and will thus allow for more accurate mapping on adaptation. We simulate the growth of a barotropically unstable jet adapting the mesh every 12 h. Using an adaptation criterion based largely on the gradient of the vorticity leads to a mesh with around 20 per cent of the cells of a uniform mesh that gives equivalent results. This is a similar proportion to previous studies of the same test case with mesh adaptation every 1–20 min. The prediction of the mesh density involves solving the shallow water equations on a coarse mesh in advance of the locally refined mesh in order to estimate where features requiring higher resolution will grow, decay or move to. The adaptation criterion consists of two parts: that resolved on the coarse mesh, and that which is not resolved and so is passively advected on the coarse mesh. This combination leads to a balance between resolving features controlled by the large-scale dynamics and maintaining fine-scale features.
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This study compares associations between demographic profiles, long bone lengths, bone mineral content, and frequencies of stress indicators in the preadult populations of two medieval skeletal assemblages from Denmark. One is from a leprosarium, and thus probably represents a disadvantaged group (Naestved). The other comes from a normal, and in comparison rather privileged, medieval community (AEbelholt). Previous studies of the adult population indicated differences between the two skeletal collections with regard to mortality, dental size, and metabolic and specific infectious disease. The two samples were analyzed against the view known as the "osteological paradox" (Wood et al. [1992] Curr. Anthropol. 33:343-370), according to which skeletons displaying pathological modification are likely to represent the healthier individuals of a population, whereas those without lesions would have died without acquiring modifications as a result of a depressed immune response. Results reveal that older age groups among the preadults from Naestved are shorter and have less bone mineral content than their peers from AEbelholt. On average, the Naestved children have a higher prevalence of stress indicators, and in some cases display skeletal signs of leprosy. This is likely a result of the combination of compromised health and social disadvantage, thus supporting a more traditional interpretation. The study provides insights into the health of children from two different biocultural settings of medieval Danish society and illustrates the importance of comparing samples of single age groups.
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Insoluble calcium salts were added to milk to increase total calcium by 30 mM, without changing properties influencing heat stability, such as pH and ionic calcium. There were no major signs of instability associated with coagulation, sediment formation or fouling when subjected to ultra high temperature (UHT) and in-container sterilisation. The buffering capacity was also unaltered. On the other hand, addition of soluble calcium salts reduced pH, increased ionic calcium and caused coagulation to occur. Calcium chloride showed the largest destabilising effect, followed by calcium lactate and calcium gluconate. Milk became unstable to UHT processing at lower calcium additions compared to in-container sterilisation.
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Plant secondary metabolites glucosinolates (GSL) have important functions in plant resistance to herbivores and pathogens. We identified all major GSL that are accumulated in S-cells in Arabidopsis by MALDI-TOF MS, and estimated by LC-MS that the total GSL concentration in these cells is above 130 mM. The precise locations of the S-cells outside phloem bundles in rosette and cauline leaves and in flower stalks were visualised using sulphur mapping by cryo-SEM/EDX. S-cells contain up to 40% of total sulphur in flower stalk tissues. S-cells in emerging flower stalks and developing leaf tissues show typical signs of Programmed Cell Death (PCD) or apoptosis, such as chromatin condensation in the nucleus and blebbing of the membranes. TUNEL staining for DNA double strand breaks confirmed PCD in S-cells in postmeristematic tissues in the flower stalk as well as in the leaf. Our results show that S-cells in postmeristematic tissues proceed to an extreme degree of metabolic specialisation besides PCD. Accumulation and maintenance of a high concentration of GSL in these cells are accompanied by degradation of a number of cell organelles. The substantial changes in the cell composition during S-cell differentiation indicate the importance of this particular GSL-based phloem defence system. The specific anatomy of the S-cells and ability to accumulate specialised secondary metabolites is similar to that of the non-articulated laticifer cells in latex plants and thus indicates a common evolutionary origin.
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Seed set of rice (Oryza sativa L.) is highly sensitive to short episodes of high temperature at anthesis events that are likely to be more frequent in future climates. Breeding for tolerance is therefore an essential component of adaptation to climate variability and change. Experiments were conducted in 2003 and 2004 at optimum (30 degrees C daytime) and high (35 and 38 degrees C) air temperature using parents of some prominent mapping populations (i) to determine whether there were differences in the daily flowering pattern and hence a potential heat avoidance mechanism, and (ii) to identify rice genotypes having true heat tolerance during anthesis, that is, high seed set in spikelets exposed to high temperature. Rice cultivar CG14 (O. glaberrima) reached peak anthesis earlier in the morning (1.5 h after dawn) under both control (30 degrees C) and high (38 degrees C) temperature conditions than O. sativa genotypes (>= 3 h after dawn). Exposure to high temperature (centered on the time of peak anthesis) for 6 h reduced spikelet fertility more than exposure for 2 h, and fertility was lower at 38 degrees C than at 35 degrees C. Genotypic ranking for spikelet fertility at 35 and 38 degrees C was highly correlated in both 2003 and 2004. Fertility was also highly correlated across years, suggesting a consistent and reproducible response of spikelet fertility to temperature. The check cultivar N22 was the most heat tolerant genotype (64-86% fertility at 38 degrees C) and cultivars Azucena and Moroberekan the most susceptible (<8%).
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In this paper, Bayesian decision procedures are developed for dose-escalation studies based on bivariate observations of undesirable events and signs of therapeutic benefit. The methods generalize earlier approaches taking into account only the undesirable outcomes. Logistic regression models are used to model the two responses, which are both assumed to take a binary form. A prior distribution for the unknown model parameters is suggested and an optional safety constraint can be included. Gain functions to be maximized are formulated in terms of accurate estimation of the limits of a therapeutic window or optimal treatment of the next cohort of subjects, although the approach could be applied to achieve any of a wide variety of objectives. The designs introduced are illustrated through simulation and retrospective implementation to a completed dose-escalation study. Copyright © 2006 John Wiley & Sons, Ltd.
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The conventional method for the assessment of acute dermal toxicity (OECD Test Guideline 402, 1987) uses death of animals as an endpoint to identify the median lethal dose (LD50). A new OECD Testing Guideline called the dermal fixed dose procedure (dermal FDP) is being prepared to provide an alternative to Test Guideline 402. In contrast to Test Guideline 402, the dermal FDP does not provide a point estimate of the LD50, but aims to identify that dose of the substance under investigation that causes clear signs of nonlethal toxicity. This is then used to assign classification according to the new Globally Harmonised System of Classification and Labelling scheme (GHS). The dermal FDP has been validated using statistical modelling rather than by in vivo testing. The statistical modelling approach enables calculation of the probability of each GHS classification and the expected numbers of deaths and animals used in the test for imaginary substances with a range of LD50 values and dose-response curve slopes. This paper describes the dermal FDP and reports the results from the statistical evaluation. It is shown that the procedure will be completed with considerably less death and suffering than guideline 402, and will classify substances either in the same or a more stringent GHS class than that assigned on the basis of the LD50 value.
Statistical evaluation of the fixed concentration procedure for acute inhalation toxicity assessment
Resumo:
The conventional method for the assessment of acute inhalation toxicity (OECD Test Guideline 403, 1981) uses death of animals as an endpoint to identify the median lethal concentration (LC50). A new OECD Testing Guideline called the Fixed Concentration Procedure (FCP) is being prepared to provide an alternative to Test Guideline 403. Unlike Test Guideline 403, the FCP does not provide a point estimate of the LC50, but aims to identify an airborne exposure level that causes clear signs of nonlethal toxicity. This is then used to assign classification according to the new Globally Harmonized System of Classification and Labelling scheme (GHS). The FCP has been validated using statistical simulation rather than byin vivo testing. The statistical simulation approach predicts the GHS classification outcome and the numbers of deaths and animals used in the test for imaginary substances with a range of LC50 values and dose response curve slopes. This paper describes the FCP and reports the results from the statistical simulation study assessing its properties. It is shown that the procedure will be completed with considerably less death and suffering than Test Guideline 403, and will classify substances either in the same or a more stringent GHS class than that assigned on the basis of the LC50 value.
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Mathematical modeling of bacterial chemotaxis systems has been influential and insightful in helping to understand experimental observations. We provide here a comprehensive overview of the range of mathematical approaches used for modeling, within a single bacterium, chemotactic processes caused by changes to external gradients in its environment. Specific areas of the bacterial system which have been studied and modeled are discussed in detail, including the modeling of adaptation in response to attractant gradients, the intracellular phosphorylation cascade, membrane receptor clustering, and spatial modeling of intracellular protein signal transduction. The importance of producing robust models that address adaptation, gain, and sensitivity are also discussed. This review highlights that while mathematical modeling has aided in understanding bacterial chemotaxis on the individual cell scale and guiding experimental design, no single model succeeds in robustly describing all of the basic elements of the cell. We conclude by discussing the importance of this and the future of modeling in this area.
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Meeting the demand for independent living from the increasing number of older people presents a major challenge for society, government and the building industry. Older people's experience of disabling conditions can be affected by the design and layout of their accommodation. Adaptations and assistive technology (AT) are a major way of addressing this gap between functional capacity and the built environment. The degree of adaptability and the differences in the average cost of adaptation of different types of property are large and there is major variation within property type. Based on a series of user profiles, it was found that a comprehensive package of adaptations and AT is likely to result in significant economies arising from a reduction in the need for formal care services. This finding is sensitive to assumptions about how long an individual would use the adaptations and AT, as well as to the input of informal care and the nature of their accommodation. The present study, which focused on social housing, has implications for how practitioners specify ways of meeting individual needs as well as providing a case to support the substantial increase in demand for specialist adaptation work.
Resumo:
We examined how far, and at what cost, the housing stock could be modified to accommodate the assistive technology (AT) necessary to enable older people to remain in their own homes. A multidisciplinary team devised seven hypothetical user profiles for 10 case study areas, with five local authorities and five housing associations in England and Wales. Each profile was considered at two times, five years apart, with the users' functional abilities deteriorating in between. In addition, in-depth interviews were carried out with a sample of 67 older people in the case study areas about their use and experience of a wide range of AT. The interviews showed the need to listen to older people and that they welcomed AT when it addressed a perceived need. The results showed that the extent of adaptation required of buildings to accommodate a user's needs varied greatly. It was also found that there was confusion about the terminology of AT, including the idea of the 'smart house'. The study shows that the adaptability of the housing depends on a range of factors and costs.
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Baby leaf salads are gaining in popularity over traditional whole head lettuce salads in response to consumer demand for greater variety and convenience in their diet. Baby lettuce leaves are mixed, washed and packaged as whole leaves, with a shelf-life of approximately 10 days post-processing. End of shelf-life, as determined by the consumer, is typified by bruising, water-logging and blackening of the leaves, but the biological events causing this phenotype have not been studied to date. We investigated the physiological and ultrastructural characteristics during postharvest shelf-life of two lettuce varieties with very different leaf morphologies. Membrane disruption was an important determinant of cell death in both varieties. although the timing and characteristics of breakdown was different in each with Lollo rossa showing signs of aging such as thylakoid disruption and plastoglobuli accumulation earlier than Cos. Membranes in Lollo rossa showed a later, but more distinct increase in permeability than in Cos. as indicated by electrolyte leakage and the presence of cytoplasmic fragments in the vacuole, but Cos membranes show distinct fractures towards the end of shelf-life. The tissue lost less than 25% fresh weight during shelf-life and there was little protein loss compared to developmentally aging leaves in an ambient environment. Biophysical measurements showed that breakstrength was significantly reduced in Lollo rossa, whereas irreversible leaf plasticity was significantly reduced in Cos leaves. The reversible elastic properties of both varieties changed throughout shelf-life. We compared the characteristics of shelf-life in both varieties of bagged lettuce leaves with other leafy salad crops and discuss the potential targets for future work to improve postharvest quality of baby leaf lettuce. (C) 2007 Elsevier B.V. All rights reserved.
Resumo:
Background N-3 polyunsaturated fatty acids (PUFAs) from oily fish protect against death from cardiovascular disease. We aimed to assess the hypothesis that incorporation of n-3 and n-6 PUFAs into advanced atherosclerotic plaques increases and decreases plaque stability, respectively. Methods We did a randomised controlled trial of patients awaiting carotid endarterectomy. We randomly allocated patients control, sunflower oil (n-6), or fish-oil (n-3) capsules until surgery. Primary outcome was plaque morphology indicative of stability or instability, and outcome measures were concentrations of EPA, DHA, and linoleic acid in carotid plaques; plaque morphology; and presence of macrophages in plaques. Analysis was per protocol. Findings 188 patients were enrolled and randomised; 18 withdrew and eight were excluded. Duration of oil treatment was 7-189 days (median 42) and did not differ between groups. The proportions of EPA and DHA were higher in carotid plaque fractions in patients receiving fish oil compared with those receiving control (absolute difference 0.5 [95% CI 0.3-0.7], 0.4 [0.1-0.6], and 0.2 [0.1-0.4] g/100 g total fatty acids for EPA; and 0.3 [0.0-0.8], 0.4 [0.1-0.7], and 0.3 [0.1-0.6] g/100 g total fatty acids for DHA; in plaque phospholipids, cholesteryl esters, and triacylglycerols, respectively). Sunflower oil had little effect on the fatty acid composition of lipid fractions. Fewer plaques from patients being treated with fish oil had thin fibrous caps and signs of inflammation and more plaques had thick fibrous caps and no signs of inflammation, compared with plaques in patients in the control and sunflower oil groups (odds ratio 0.52 [95% CI 0.24-0.89] and 1.19 [1.02-1.57] vs control; 0.49 [0.23-0.90] and 1.16 [1.01-1.53] vs sunflower oil). The number of macrophages in plaques from patients receiving fish oil was lower than in the other two groups. Carotid plaque morphology and infiltration by macrophages did not differ between control and sunflower oil groups. Interpretation Atherosclerotic plaques readily incorporate n-3 PUFAs from fish-oil supplementation, inducing changes that can enhance stability of atherosclerotic plaques. By contrast, increased consumption of n-6 PUFAs does not affect carotid plaque fatty-acid composition or stability over the time course studied here. Stability of plaques could explain reductions in non-fatal and fatal cardiovascular events associated with increased n-3 PUFA intake.
Resumo:
A mixture of organic acids and lactulose for preventing or reducing colonization of the gut by Salmonella Typhimurium was evaluated in pigs. A total of 63 4-week-old commercial piglets were randomly distributed into three different experimental dietary groups: a plain diet without additives (PD) and the same diet supplemented with either 0.4% (w/v) formic acid and 0.4% lactic acid (w/v) (AC) or 1% (w/v) lactulose (LC). After 7 days of adaptation, two-thirds of the pigs (14 from each diet) were challenged with a 2-mL oral dose of 10(8) CFU/mL of Salmonella Typhimurium, leaving the remaining animals unchallenged (UC). After 4 and 10 days post-challenge, pigs were euthanized and the ileum and caecum content were aseptically sampled to (a) quantify lactic, formic, and short-chain fatty acids (SCFA), (b) quantify bacterial populations and Salmonella by fluorescence in situ hybridization and (c) qualitatively analyse bacterial populations through denaturing gradient gel electrophoresis (DGGE). Modification of fermentation products and counts of some of the bacterial groups analysed in the challenged pigs receiving the treatments AC and LC were minimal. Treatments only influenced the bacterial diversity after 10 days post-challenge, with AC generating a lower number of DGGE bands than UC(P < 0.05). Neither the inclusion of a mixture of 0.4% (w/v) formic and 0.4% (w/v) lactic acids nor of 1% (w/v) lactulose in the feed influenced numbers of Salmonella in the ileum and caecum of experimentally challenged pigs. (C) 2009 Elsevier B.V. All rights reserved.
The effects of maternal social phobia on mother-infant interactions and infant social responsiveness
Resumo:
Background: Social phobia aggregates in families. The genetic contribution to intergenerational transmission is modest, and parenting is considered important. Research on the effects of social phobia on parenting has been subject to problems of small sample size, heterogeneity of samples and lack of specificity of observational frameworks. We addressed these problems in the current study.Methods: We assessed mothers with social phobia (N = 84) and control mothers (N = 89) at 10 weeks in face-to-face interactions with their infants, and during a social challenge, namely, engaging with a stranger. We also assessed mothers with generalised anxiety disorder (GAD) (N = 50). We examined the contribution to infant social responsiveness of early infant characteristics (neonatal irritability), as well as maternal behaviour. Results: Mothers with social phobia were no less sensitive to their infants during face-to-face interactions than control mothers, but when interacting with the stranger they appeared more anxious, engaged less with the stranger themselves, and were less encouraging of the infant's interaction with the stranger; infants of index mothers also showed reduced social responsiveness to the stranger. These differences did not apply to mothers with GAD and their infants. Regression analyses showed that the reduction in social responsiveness in infants of mothers with social phobia was predicted by neonatal irritability and the degree to which the mother encouraged the infant to interact with the stranger.Conclusions: Mothers with social phobia show specific parenting difficulties, and their infants show early signs of reduced social responsiveness that are related to both individual infant differences and a lack of maternal encouragement to engage in social interactions.