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Organism's Ability (organism + ability)
Selected AbstractsNucleus accumbens neurons encode Pavlovian approach behaviors: evidence from an autoshaping paradigmEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2006Jeremy J. Day Abstract Environmental stimuli predictive of appetitive events can elicit Pavlovian approach responses that enhance an organism's ability to track and secure natural rewards, but may also contribute to the compulsive nature of drug addiction. Here, we examined the activity of individual nucleus accumbens (NAc) neurons during an autoshaping paradigm. One conditioned stimulus (CS+, a retractable lever presented for 10 s) was immediately followed by the delivery of a 45-mg sucrose pellet to a food receptacle, while another stimulus (CS,, a separate retractable lever presented for 10 s) was never followed by sucrose. Approach responses directed at the CS+ and CS, were recorded as lever presses and had no experimental consequence. Rats (n = 9) selectively approached the CS+ on more than 80% of trials and were surgically prepared for electrophysiological recording. Of 76 NAc neurons, 57 cells (75%) exhibited increases and/or decreases in firing rate (i.e. termed ,phasically active') during the CS+ presentation and corresponding approach response. Forty-seven percent of phasically active cells (27 out of 57) were characterized by time-locked but transient increases in cell firing, while 53% (30 out of 57) showed a significant reduction in firing for the duration of the CS+. In contrast, the same excitatory subpopulation exhibited smaller increases in activity relative to CS, onset, while the inhibitory subpopulation showed no change in firing during the CS, period. The magnitude and prevalence of cue-related neural responses reported here indicates that the NAc encodes biologically significant, repetitive approach responses that may model the compulsive nature of drug addiction in humans. [source] PATTERNS OF PHENOTYPIC AND GENETIC VARIATION FOR THE PLASTICITY OF DIAPAUSE INCIDENCEEVOLUTION, Issue 7 2007Wade E. Winterhalter Phenotypic plasticity describes an organism's ability to produce multiple phenotypes in direct response to its environmental conditions. Over the past 15 years empiricists have found that this plasticity frequently exhibits geographic variation and often possesses a significant heritable genetic basis. However, few studies have examined both of these aspects of plasticity simultaneously. Here, we examined both the geographic and genetic variations of the plasticity for diapause incidence (the proportion of eggs that enter an arrested state of development capable of surviving over the winter) relative to temperatures and photoperiods associated with long and short season environments across six populations of the striped ground cricket, Allonemobius socius, using a half-sibling split brood quantitative genetic design. We found that plasticity, as measured by the slope of the reaction norm, was greater in the southern-low altitude region (where populations are bivoltine) relative to the southern-high and northern-low altitude regions (where populations are univoltine). However, the heritability of plasticity was only significantly different from zero in univoltine populations that experienced "intermediate" natal season lengths. These patterns suggest that selection may favor the plasticity of diapause incidence in bivoltine regions, but act against plasticity in regions in which populations are univoltine. Furthermore, our data suggest that under "intermediate" natal season length conditions, the interplay between local adaptation and gene flow may keep the plasticity of diapause incidence low (but still significant) while maintaining its genetic variation. As such, this study not only provides a novel observation into the geographic variation of phenotypic plasticity, but also provides much needed groundwork for tests of its adaptive significance. [source] Immunotoxicity of acute acephate exposure in control or IL-1-challenged rats: correlation between the immune cell composition and corticosteroid concentration in bloodJOURNAL OF APPLIED TOXICOLOGY, Issue 5 2002Ashok K. Singh Abstract Corticosterone concentration and the immune cell composition were measured in rats exposed by intraperitoneal (i.p.) injection to different doses (10,500 mg kg,1) of acephate (Ace) and 250 µg kg,1 of interleukin 1 (IL-1), either alone or in combination. Two different combination protocols were used: IL-1 and Ace were administered simultaneously; and IL-1 was injected 60 min after Ace administration (sequential exposure). Ace, in a dose- and time-dependent manner, inhibited blood and brain acetylcholinesterase (AChE) activities, increased blood corticosterone concentrations, suppressed blood CD4, CD8, B cell and monocyte contents and increased blood neutrophil counts. The Ace-induced changes lasted for up to 24 h after Ace exposure. Interleukin 1 increased blood corticosterone concentrations without affecting blood or brain AChE activities. The IL-1-induced corticosterone concentration returned to the basal level within 3,10 h after IL-1 exposure. The CD4, CD8, B cell and monocyte counts increased significantly at 10 min after IL-1 exposure. The cell counts decreased gradually thereafter and returned to the basal level within 30 min after IL-1 exposure. Simultaneous exposure of rats to Ace and IL-1 partially suppressed the IL-1-induced increase in the immune cell counts and decreased the immune cell numbers below the basal values. Sequential injection of Ace and IL-1 blocked the IL-1-induced increase in the immune cell numbers. Thus, Ace exposure would impair the normal distribution of immune cells and deregulate the IL-1 response in rats. This study therefore suggests that Ace would suppress the immune cell numbers in blood, thus decreasing an organism's immunity. Ace exposure occurring concurrent with injury would augment the acute-phase response, which would augment the toxic effects of IL-1 and other cytokines, and Ace exposure occurring prior to the injury would suppress or abolish the initial stimulatory effects of IL-1, which would decrease an organism's ability to combat infection or injury. Copyright © 2002 John Wiley & Sons, Ltd. [source] MicroReview: Growth versus maintenance: a trade-off dictated by RNA polymerase availability and sigma factor competition?MOLECULAR MICROBIOLOGY, Issue 4 2004Thomas Nyström Summary The regulatory design of higher organisms is proposed to comprise a trade-off between activities devoted to reproduction and those devoted to cellular maintenance and repair. Excessive reproduction will inevitably limit the organism's ability to resist stress whereas excessively devoted stress defence systems may increase lifespan but reduce Darwinian fitness. The trade-off is arguably a consequence of limited resources in any one organism but the nature and identity of such limiting resources are ambiguous. Analysis of global control of gene expression in Escherichia coli suggests that reproduction and maintenance activities are also at odds in bacteria and that this antagonism may be a consequence of a battle between transcription factors for limiting RNA polymerase. The outcome of this battle is regulated and depends on the nutritional status of the environment, the levels of the alarmone ppGpp, and RNA polymerase availability. This paper reviews how the concentration of RNA polymerase available for transcription initiation may vary upon shifts between growth and growth-arrest conditions and how this adjustment may differentially affect genes whose functions relate to reproduction and maintenance. [source] Bacteroides thetaiotaomicron: a dynamic, niche-adapted human symbiontBIOESSAYS, Issue 10 2003Laurie E. Comstock The coevolution of humans with their intestinal microflora has resulted in cooperative relationships that have shaped the biology and the genomes of these symbiotic partners. Bacteroides thetaiotaomicron is one such bacterial symbiont that is a dominant member of the intestinal microbiota of humans and other mammals. The recent report of the genome sequence of B. thetaiotaomicron1 is the first reported for an abundant Gram-negative organism of the human colonic microbiota and, as such, provides the first glimpse on a genomic scale of the genetic arsenal used by a Gram-negative symbiont to dominate in this ecosystem. The genome has revealed large expansions of many paralogous groups of genes that encode products essential to the organism's ability to successfully compete in this environment. Most noteable is the organism's abundant machinery for utilizing a large variety of complex polysaccharides as a source of carbon and energy. The proteome also reveals the organism's extensive ability to adapt and regulate expression of its genes in response to the changing ecosystem. These factors, as well as others highlighted below, suggest an incredibly flexible and adaptable organism that is exquisitely equipped to dominate in its challenging and competitive niche. BioEssays 25:926,929, 2003. © 2003 Wiley Periodicals, Inc. [source] Animal performance and stress: responses and tolerance limits at different levels of biological organisationBIOLOGICAL REVIEWS, Issue 2 2009Karin S. Kassahn ABSTRACT Recent advances in molecular biology and the use of DNA microarrays for gene expression profiling are providing new insights into the animal stress response, particularly the effects of stress on gene regulation. However, interpretation of the complex transcriptional changes that occur during stress still poses many challenges because the relationship between changes at the transcriptional level and other levels of biological organisation is not well understood. To confront these challenges, a conceptual model linking physiological and transcriptional responses to stress would be helpful. Here, we provide the basis for one such model by synthesising data from organismal, endocrine, cellular, molecular, and genomic studies. We show using available examples from ectothermic vertebrates that reduced oxygen levels and oxidative stress are common to many stress conditions and that the responses to different types of stress, such as environmental, handling and confinement stress, often converge at the challenge of dealing with oxygen imbalance and oxidative stress. As a result, a common set of stress responses exists that is largely independent of the type of stressor applied. These common responses include the repair of DNA and protein damage, cell cycle arrest or apoptosis, changes in cellular metabolism that reflect the transition from a state of cellular growth to one of cellular repair, the release of stress hormones, changes in mitochondrial densities and properties, changes in oxygen transport capacities and changes in cardio-respiratory function. Changes at the transcriptional level recapitulate these common responses, with many stress-responsive genes functioning in cell cycle control, regulation of transcription, protein turnover, metabolism, and cellular repair. These common transcriptional responses to stress appear coordinated by only a limited number of stress-inducible and redox-sensitive transcription factors and signal transduction pathways, such as the immediate early genes c-fos and c-jun, the transcription factors NF,B and HIF - 1,, and the JNK and p38 kinase signalling pathways. As an example of environmental stress responses, we present temperature response curves at organismal, cellular and molecular levels. Acclimation and physiological adjustments that can shift the threshold temperatures for the onset of these responses are discussed and include, for example, adjustments of the oxygen delivery system, the heat shock response, cellular repair system, and transcriptome. Ultimately, however, an organism's ability to cope with environmental change is largely determined by its ability to maintain aerobic scope and to prevent loss in performance. These systemic constraints can determine an organism's long-term survival well before cellular and molecular functions are disturbed. The conceptual model we propose here discusses some of the crosslinks between responses at different levels of biological organisation and the central role of oxygen balance and oxidative stress in eliciting these responses with the aim to help the interpretation of environmental genomic data in the context of organismal function and performance. [source] Applying a continua landscape approach to evaluate plant response to fragmentation: Primula vulgaris in the Cantabrian mountainsAPPLIED VEGETATION SCIENCE, Issue 4 2009Alicia Valdés Abstract Question: Continua landscape approaches conceptualize the effects of habitat fragmentation on the biota by considering fragmented landscapes as continuous gradients, departing from the view of habitat as either suitable (fragment) or unsuitable (matrix). They also consider the ecological gradients or the ,Umwelt' (species-specific perception of the landscape) to represent the processes that ultimately limit organisms' ability to colonize and persist within habitat remnants. Are these approaches suitable for evaluating the response of plant species to fragmentation? Location: Fragmented mid-elevation temperate forests, Cantabrian range, Spain. Methods: The presence, abundance and demographic structure of populations of the perennial herb Primula vulgaris were sampled across a continuous extent of 100 ha, subdivided into 400 50 m × 50 m sampling units. These variables were related to forest availability, forest subdivision and edge density, topography and the spatial clumpiness of populations (a measure of plant dispersal constraints and, hence, a major surrogate of plant Umwelt). Results: Fragmentation processes, especially habitat loss, negatively affect P. vulgaris, with a stronger effect on presence than on abundance and demography. Despite the importance of habitat availability, P. vulgaris does not occupy all potentially suitable forest habitat, mostly owing to dispersal constraints. A positive effect of slope on plant presence also suggests some effect of habitat quality in determining establishment and occupancy of forest landscape. Conclusions: Within-habitat dispersal constraints are as important as forest fragmentation in determining the landscape-scale distribution of P. vulgaris. By assessing the relative role of the diverse fragmentation processes, and of the species' landscape perception, a continua landscape approach proves to be a valuable tool for predicting plant response to landscape change. [source] | ||||||||||