Future Attempts (future + attempt)

Distribution by Scientific Domains

Selected Abstracts

Unraveling the Role of Mitochondria During Oxidative Stress in Plants

IUBMB LIFE, Issue 4 2001
Harvey Millar
Abstract The sedentary habit of plants means that they must stand and fight environmental stresses that their mobile animal cousins can avoid. A range of these abiotic stresses initiate the production in plant cells of reactive oxygen and nitrogen species that ultimately lead to oxidative damage affecting the yield and quality of plant products. A complex network of enzyme systems, producing and quenching these reactive species operate in different organelles. It is the integration of these compartmented defense systems that coordinates an effective response to the various stresses. Future attempts to improve plant growth or yield must consider the complexity of inter-organelle signaling and protein targeting if they are to be successful in producing plants with resistance to a broad range of stresses. Here we highlight the role of pre-oxidant, anti-oxidant, and post-oxidant defense systems in plant mitochondria and the potential role of proteins targeted to both mitochondria and chloroplasts, in an integrated defense against oxidative damage in plants. [source]

DNA aptamers developed against a soman derivative cross-react with the methylphosphonic acid core but not with flanking hydrophobic groups

John G. Bruno
Abstract Twelve rounds of systematic evolution of ligands by exponential enrichment (SELEX) were conducted against a magnetic bead conjugate of the para -aminophenylpinacolylmethylphosphonate (PAPMP) derivative of the organophosphorus (OP) nerve agent soman (GD). The goal was to develop DNA aptamers that could scavenge GD in vivo, thereby reducing or eliminating the toxic effects of this dangerous compound. Aptamers were sequenced and screened in peroxidase-based colorimetric plate assays after rounds 8 and 12 of SELEX. The aptamer candidate sequences exhibiting the highest affinity for the GD derivative from round 8 also reappeared in several clones from round 12. Each of the highest affinity PAPMP-binding aptamers also bound methylphosphonic acid (MPA). In addition, the aptamer with the highest overall affinity for PAPMP carried a sequence motif (TTTAGT) thought to bind MPA based on previously published data (J. Fluoresc 18: 867,876, 2008). This sequence motif was found in several other relatively high affinity PAPMP aptamer candidates as well. In studies with the nerve agent GD, pre-incubation of a large molar excess of aptamer candidates failed to protect human butyrylcholinesterase (BuChE) from inhibition. With the aid of three-dimensional molecular modeling of the GD derivative it appears that a hydrophilic cleft sandwiched between the pinacolyl group and the p -aminophenyl ring might channel nucleotide interactions to the phosphonate portion of the immobilized GD derivative. However, bona fide GD free in solution may be repulsed by the negative phosphate backbone of aptamers and rotate its phosphonate and fluorine moieties away from the aptamer to avoid being bound. Future attempts to develop aptamers to GD might benefit from immobilizing the pinacolyl group of bona fide GD to enhance exposure of the phosphonate and fluorine to the random DNA library. Copyright 2008 John Wiley & Sons, Ltd. [source]

Pursuing paradoxical proconvulsant prophylaxis for epileptogenesis

EPILEPSIA, Issue 7 2009
Caren Armstrong
Summary There are essentially two potential treatment options for any acquired disorder: symptomatic or prophylactic. For acquired epilepsies that follow a variety of different brain insults, there remains a complete lack of prophylactic treatment options, whereas at the same time these epilepsies are notoriously resistant, once they have emerged, to symptomatic treatments with antiepileptic drugs. The development of prophylactic strategies is logistically challenging, both for basic researchers and clinicians. Nevertheless, cannabinoid-targeting drugs provide a very interesting example of a system within the central nervous system (CNS) that can have very different acute and long-term effects on hyperexcitability and seizures. In this review, we outline research on cannabinoids suggesting that although cannabinoid antagonists are acutely proconvulsant, they may have beneficial effects on long-term hyperexcitability following brain insults of multiple etiologies, making them promising candidates for further investigation as prophylactics against acquired epilepsy. We then discuss some of the implications of this finding on future attempts at prophylactic treatments, specifically, the very short window within which prevention may be possible, the possibility that traditional anticonvulsants may interfere with prophylactic strategies, and the importance of moving beyond anticonvulsants,even to proconvulsants,to find the ideal preventative strategy for acquired epilepsy. [source]

Temperature-dependent stock-recruitment model for walleye pollock (Theragra chalcogramma) around northern Japan

Abstract Changes in fish year-class strength have been attributed to year-to-year variability in environmental conditions and spawning stock biomass (SSB). In particular, sea temperature has been shown to be linked to fish recruitment. In the present study, I examined the relationship between sea surface temperature (SST), SSB and recruitment for two stocks of walleye pollock (Theragra chalcogramma) around northern Japan [Japanese Pacific stock (JPS) and northern Japan Sea stock (JSS)] using a temperature-dependent stock-recruitment model (TDSRM). The recruitment fluctuation of JPS was successfully reproduced by the TDSRM with February and April SSTs, and February SST was a better environmental predictor than April SST. In addition, the JPS recruitment was positively related to February SST and negatively to April SST. The JSS recruitment modeled by the TDSRM incorporating February SST was also consistent with the observation, whereas the relationship between recruitment and February SST was negative, that is the opposite trend to JPS. These findings suggest that SST in February is important as a predictor of recruitment for both stocks, and that higher and lower SSTs in February act favorably on the recruitment of JPS and JSS respectively. Furthermore, Ricker-type TDSRM was not selected for either of the stocks, suggesting that the strong density-dependent effect as in the Ricker model does not exist for JPS and JSS. I formulate hypotheses to explain the links between SST and recruitment, and note that these relationships should be considered in any future attempts to understand the recruitment dynamics of JPS and JSS. [source]

Vertical distribution and behaviour of shrimp Pandalus borealis larval stages in thermally stratified water columns: laboratory experiment and field observations

Abstract By combining field data and laboratory observations of larvae in a simulated thermal gradient, we described the ontogenetic changes in vertical distribution and behaviour of early stages of shrimp Pandalus borealis in thermally stratified water columns. Both in the laboratory and at stations in the north-western Gulf of St Lawrence, the first two larval stages appear to actively select and maintain a position in the upper layer of warmer temperatures, within the thermocline and above the cold (<1C) intermediate layer. Stage III larvae were distributed deeper in the water column and in colder waters than the previous two stages. Stage IV and V larvae showed the highest degree of swimming activity in the laboratory and a much wider range (from surface to ,200 m) in vertical distribution in the field. The shift to deeper waters and settlement to the bottom habitat appears to happen after the fifth moult, at stage VI. We propose that the pattern of vertical distribution in the field reflects the adjustment of the different developmental stages to the distribution of preferred prey. The description of the ontogenetic change in the vertical distributions and movements of early stages of P. borealis should be valuable information for future attempts to model larval transport and dispersion, and for detecting settlement/recruitment areas using 3D ocean circulation models. The identification of the thermal habitat of the different larval stages and the timing for settlement at the bottom also provides important information for the development of temperature-dependent growth models up to the first juvenile stages. [source]

Patients' evaluations of the quality of care: influencing factors and the importance of engagement

Sophie H. Staniszewska BSc DPhil
Aims., This paper reports a study exploring the process of patient evaluation and identifying the factors which influence this. Background., Patient experiences of health care have become a central focus for researchers, policymakers, clinicians and patient groups in many countries. While surveys of patient experiences have become increasingly common internationally, concerns about the validity of concepts such as satisfaction have cast doubt on the utility of their findings. These concerns reflect our limited understanding of patient evaluation and the factors that can influence this process. Methods., A qualitative design was adopted, using semi-structured interviews with a sample of outpatients in their homes in one county in England. In total, 41 patients participated in the study and were interviewed before their appointment. Of these patients, 37 were interviewed again after their appointment. Six of the latter were then re-interviewed 6 weeks after the appointment to explore whether evaluations had changed. Findings., Patient evaluation was influenced by a number of factors, including gratitude, faith, loyalty, luck and equity. The overall effect was to prompt positive evaluation, even when care was poor. These factors should be accounted for in the interpretation of patient experiences surveys. Patient experiences were further influenced by their sense of engagement with the system. A negative sense of engagement could have a major impact on the patient, resulting in disappointment or fear and a desire to leave the health care system, and in a negative evaluation of a specific aspect of care. Conclusions., Engagement may provide a more appropriate indicator of negative experience than dissatisfaction. The influence of these factors should be considered in future attempts to develop more sensitive and appropriate methods of eliciting patient experiences. [source]

Predicting avian patch occupancy in a fragmented landscape: do we know more than we think?

Danielle F. Shanahan
Summary 1.,A recent and controversial topic in landscape ecology is whether populations of species respond to habitat fragmentation in a general fashion. Empirical research has provided mixed support, resulting in controversy about the use of general rules in landscape management. Rather than simply assessing post hoc whether individual species follow such rules, a priori testing could shed light on their accuracy and utility for predicting species response to landscape change. 2.,We aim to create an a priori model that predicts the presence or absence of multiple species in habitat patches. Our goal is to balance general theory with relevant species life-history traits to obtain high prediction accuracy. To increase the utility of this work, we aim to use accessible methods that can be applied using readily available inexpensive resources. 3.,The classification tree patch-occupancy model we create for birds is based on habitat suitability, minimum area requirements, dispersal potential of each species and overall landscape connectivity. 4.,To test our model we apply it to the South East Queensland region, Australia, for 17 bird species with varying dispersal potential and habitat specialization. We test the accuracy of our predictions using presence,absence information for 55 vegetation patches. 5.,Overall we achieve Cohen's kappa of 033, or ,fair' agreement between the model predictions and test data sets, and generally a very high level of absence prediction accuracy. Habitat specialization appeared to influence the accuracy of the model for different species. 6.,We also compare the a priori model to the statistically derived model for each species. Although this ,optimal model' generally differed from our original predictive model, the process revealed ways in which it could be improved for future attempts. 7.,Synthesis and applications. Our study demonstrates that ecological generalizations alongside basic resources (a vegetation map and some species-specific information) can provide conservative accuracy for predicting species occupancy in remnant vegetation patches. We show that the process of testing and developing models based on general rules could provide basic tools for conservation managers to understand the impact of current or planned landscape change on wildlife populations. [source]

De-escalation after repeated negative feedback: emergent expectations of failure

Brian J. Zikmund-FisherArticle first published online: 26 NOV 200
Abstract Research on willingness to make marginal investments (e.g., the escalation and sunk cost literatures) has often focused on project completion decisions, such as the "radar-blank plane." This paper discusses a fundamentally different type of marginal investment decision, that of couples deciding whether to continue infertility treatment in the face of repeated failures. Two experiments based on this context show that when people face multiple independent chances to achieve a valued goal but are unsure about chances of success, premature quitting or "de-escalation" is the norm. Repeated negative feedback appears to induce individuals to see each successive failure as more and more diagnostic. As a result, even a short series of failed attempts evokes beliefs that future attempts will also fail. These emergent expectations of failure, generated by causal attribution processes, associative learning, and/or discounting of ambiguous information, appear very compelling and induce people to forgo profitable marginal investments. Copyright 2004 John Wiley & Sons, Ltd. [source]

New Insights into the Neuromuscular Anatomy of the Ileocecal Valve

Tamas Cserni
Abstract The neuroanatomy of the ileocecal valve (ICV) is poorly understood. A better understanding of this important functional component of the gastrointestinal tract would enable surgeons to reconstruct an effective valve following surgical resection of the ICV. ICVs were examined in young pigs (N = 5) using frontal and transverse paraffin embedded and frozen sections. Hematoxylin+Eosin (H+E) staining, acetylcholinesterase (AchE), and NADPH-diaphorase (NADPH-d) histochemistry and protein gene product 9.5 (PGP 9.5) and C-kit immunohistochemistry were performed. The H+E staining revealed that the ICV consists of three muscle layers: an external circular muscle layer continuous with that of the ileal circular muscle layer, an inner circular muscle layer continuous with that of the cecal circular muscle layer, and a single longitudinal muscle layer, which appears to be secondary to a fusion of the ileal and cecal longitudinal muscle layers. The AchE, NADPH-d, and PGP 9.5 staining revealed two distinct coaxial myenteric plexuses, together with superficial and deep submucosal plexuses. The C-kit immunostaining showed a continuous myenteric ICC network within the ICV. The structure of the neuromuscular components within the ICV suggests that the valve is a result of a simple intussusception of the terminal ileum into the cecum. This knowledge may help surgeons in their future attempts at reconstructing more anatomically and functionally suitable ICVs following surgical resection of native ICVs. Anat Rec 2009. 2008 Wiley-Liss, Inc. [source]

Application and evaluation of classification trees for screening unwanted plants

Abstract Risk assessment systems for introduced species are being developed and applied globally, but methods for rigorously evaluating them are still in their infancy. We explore classification and regression tree models as an alternative to the current Australian Weed Risk Assessment system, and demonstrate how the performance of screening tests for unwanted alien species may be quantitatively compared using receiver operating characteristic (ROC) curve analysis. The optimal classification tree model for predicting weediness included just four out of a possible 44 attributes of introduced plants examined, namely: (i) intentional human dispersal of propagules; (ii) evidence of naturalization beyond native range; (iii) evidence of being a weed elsewhere; and (iv) a high level of domestication. Intentional human dispersal of propagules in combination with evidence of naturalization beyond a plants native range led to the strongest prediction of weediness. A high level of domestication in combination with no evidence of naturalization mitigated the likelihood of an introduced plant becoming a weed resulting from intentional human dispersal of propagules. Unlikely intentional human dispersal of propagules combined with no evidence of being a weed elsewhere led to the lowest predicted probability of weediness. The failure to include intrinsic plant attributes in the model suggests that either these attributes are not useful general predictors of weediness, or data and analysis were inadequate to elucidate the underlying relationship(s). This concurs with the historical pessimism that we will ever be able to accurately predict invasive plants. Given the apparent importance of propagule pressure (the number of individuals of an species released), future attempts at evaluating screening model performance for identifying unwanted plants need to account for propagule pressure when collating and/or analysing datasets. The classification tree had a cross-validated sensitivity of 93.6% and specificity of 36.7%. Based on the area under the ROC curve, the performance of the classification tree in correctly classifying plants as weeds or non-weeds was slightly inferior (Area under ROC curve = 0.83 0.021 (SE)) to that of the current risk assessment system in use (Area under ROC curve = 0.89 0.018 (SE)), although requires many fewer questions to be answered. [source]

In vitro induction of T cells that are resistant to A2 adenosine receptor-mediated immunosuppression

Akio Ohta
Background and purpose:, The increased levels of extracellular adenosine in inflamed tissues down-regulate activated immune cells via the A2A adenosine receptor. This A2A adenosine receptor-mediated immunosuppression is a disqualifying obstacle in cancer immunotherapy as it protects cancerous tissues from adoptively transferred anti-tumour T cells. The aim of this study was to test whether the negative selection of T cells will produce T cells that are resistant to inhibition by extracellular adenosine. Experimental approach:, Cytotoxic T lymphocytes (CTL) were developed by mixed lymphocyte culture in the presence or absence of the adenosine receptor agonist 5,-N-ethylcarboxamidoadenosine (NECA). The sensitivity of CTL to adenosine analogues was characterized by cAMP induction, interferon-, production and cytotoxicity. Key results:, CTL that could proliferate even in the presence of NECA were less susceptible to inhibition by A2A adenosine receptor agonists, as shown by a much smaller accumulation of cAMP and less inhibition of interferon-, production compared with control CTL. The successful protocol to produce CTL that are both resistant to adenosine-mediated immunosuppression and maintain strong cytotoxicity and interferon-, secretion required NECA to be added only during the expansion stage after the establishment of CTL. In contrast, the priming of resting T cells in the presence of NECA resulted in T cells with impaired effector functions. Conclusions and implications:, Adenosine-resistant effector T cells were successfully obtained by exposure of activated T cells to NECA. These in vitro studies form the basis for future attempts to produce anti-tumour T cells that are more effective in adoptive immunotherapy. [source]

Molecular interactions between Plasmodium and its insect vectors

R. E. Sinden
Summary Our understanding of the intricate interactions between the malarial parasite and the mosquito vector is complicated both by the number and diversity of parasite and vector species, and by the experimental inaccessibility of phenomena under investigation. Steady developments in techniques to study the parasite in the mosquito have recently been augmented by methods to culture in their entirety the sporogonic stages of some parasite species. These, together with the new saturation technologies, and genetic transformation of both parasite and vector will permit penetrating studies into an exciting and largely unknown area of parasite,host interactions, an understanding of which must result in the development of new intervention strategies. This microreview highlights key areas of current basic molecular interest, and identifies numerous lacunae in our knowledge that must be filled if we are to make rational decisions for future control strategies. It will conclude by trying to explain why in the opinion of this reviewer understanding malaria,mosquito interactions may be critical to our future attempts to limit a disease of growing global importance. [source]