Home About us Contact
|
Home About us Contact | ||
|
|
||
Indirect Consequence (indirect + consequence)
Selected AbstractsThe function of D1-H332 in Photosystem II electron transport studied by thermoluminescence and chlorophyll fluorescence in site-directed mutants of Synechocystis 6803FEBS JOURNAL, Issue 17 2004Yagut Allahverdiyeva The His332 residue of the D1 protein has been identified as the likely ligand of the catalytic Mn ions in the water oxidizing complex (Ferreira, K.N., Iverson, T.M., Maghlaoui, K., Barber, J. & Iwata, S. (2004) Science 303, 1831,1838). However, its function has not been fully clarified. Here we used thermoluminescence and flash-induced chlorophyll fluorescence measurements to characterize the effect of the D1-H333E, D1-H332D and D1-H332S mutations on the electron transport of Photosystem II in intact cells of the cyanobacterium Synechocystis 6803. Although the mutants are not photoautotrophic they all show flash-induced thermoluminescence and chlorophyll fluorescence, which originate from the S2QA, and S2QB, recombinations demonstrating that charge stabilization takes place in the water oxidizing complex. However, the conversion of S2 to higher S states is inhibited and the energetic stability of the S2QA, charge pair is increased by 75, 50 and 7 mV in the D1-H332D, D1-H332E and D1-H332S mutants, respectively. This is most probably caused by a decrease of Em(S2/S1). Concomitantly, the rate of electron donation from Mn to Tyr-Z, during the S1 to S2 transition is slowed down, relative to the wild type, 350- and 60-fold in the D1-H332E and D1-H332D mutants, respectively, but remains essentially unaffected in D1-H332S. A further effect of the D1-H332E and D1-H332D mutations is the retardation of the QA to QB electron transfer step as an indirect consequence of the donor side modification. Our data show that although the His residue in the D1-332 position can be substituted by other metal binding residues for binding photo-oxidisable Mn it is required for controlling the functional redox energetics of the Mn cluster. [source] Does character displacement initiate speciation?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2010Evidence of reduced gene flow between populations experiencing divergent selection Abstract Character displacement , trait evolution stemming from selection to lessen resource competition or reproductive interactions between species , has long been regarded as important in finalizing speciation. By contrast, its role in initiating speciation has received less attention. Yet because selection for character displacement should act only where species co-occur, individuals in sympatry will experience a different pattern of selection than conspecifics in allopatry. Such divergent selection might favour reduced gene flow between conspecific populations that have undergone character displacement and those that have not, thereby potentially triggering speciation. Here, we explore these ideas empirically by focusing on spadefoot toads, Spea multiplicata, which have undergone character displacement, and for which character displacement appears to cause post-mating isolation between populations that are in sympatry with a heterospecific and those that are in allopatry. Using mitochondrial sequence data and nuclear microsatellite genotypes, we specifically asked whether gene flow is reduced between populations in different selective environments relative to that between populations in the same selective environment. We found a slight, but statistically significant, reduction in gene flow between selective environments, suggesting that reproductive isolation, and potentially ecological speciation, might indeed evolve as an indirect consequence of character displacement. Generally, character displacement may play a largely underappreciated role in instigating speciation. [source] Sex differences in behaviour as an indirect consequence of mating systemJOURNAL OF FISH BIOLOGY, Issue 4 2000A. E. Magurran A considerable literature has been devoted to documenting differences between the sexes. However, relatively little attention has hitherto been directed towards those differences that arise as an indirect consequence of mating system even though they can have profound implications for the daily lives of the animals involved. In this review we focus on differences in the non-reproductive behaviour of fish and relate these to sexual dimorphism in size and morphology, and to variance in fitness between the sexes. In line with our expectation, differences in distributional ecology, schooling, aggression, predator avoidance and foraging are exaggerated in sexually dimorphic species and polygamous mating systems. Nonetheless, the behaviour of males and females may also differ in sexually monomorphic and monogamous species. We conclude by highlighting promising directions for further research. [source] HIV-1 neuropathogenesis: glial mechanisms revealed through substance abuseJOURNAL OF NEUROCHEMISTRY, Issue 3 2007Kurt F. Hauser Abstract Neuronal dysfunction and degeneration are ultimately responsible for the neurocognitive impairment and dementia manifest in neuroAIDS. Despite overt neuronal pathology, HIV-1 does not directly infect neurons; rather, neuronal dysfunction or death is largely an indirect consequence of disrupted glial function and the cellular and viral toxins released by infected glia. A role for glia in HIV-1 neuropathogenesis is revealed in experimental and clinical studies examining substance abuse,HIV-1 interactions. Current evidence suggests that glia are direct targets of substance abuse and that glia contribute markedly to the accelerated neurodegeneration seen with substance abuse in HIV-1 infected individuals. Moreover, maladaptive neuroplastic responses to chronic drug abuse might create a latent susceptibility to CNS disorders such as HIV-1. In this review, we consider astroglial and microglial interactions and dysfunction in the pathogenesis of HIV-1 infection and examine how drug actions in glia contribute to neuroAIDS. [source] Asymptotic and spectral analysis of non-selfadjoint operators generated by a filament model with a critical value of a boundary parameterMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2003Marianna A. Shubov Abstract We consider a class of non-selfadjoint operators generated by the equation and the boundary conditions, which govern small vibrations of an ideal filament with non-conservative boundary conditions at one end and a heavy load at the other end. The filament has a non-constant density and is subject to a viscous damping with a non-constant damping coefficient. The boundary conditions contain two arbitrary complex parameters. In our previous paper (Mathematical Methods in the Applied Sciences 2001; 24(15) : 1139,1169), we have derived the asymptotic approximations for the eigenvalues and eigenfunctions of the aforementioned non-selfadjoint operators when the boundary parameters were arbitrary complex numbers except for one specific value of one of the parameters. We call this value the critical value of the boundary parameter. It has been shown (in Mathematical Methods in the Applied Sciences 2001; 24(15) : 1139,1169) that the entire set of the eigenvalues is located in a strip parallel to the real axis. The latter property is crucial for the proof of the fact that the set of the root vectors of the operator forms a Riesz basis in the state space of the system. In the present paper, we derive the asymptotics of the spectrum exactly in the case of the critical value of the boundary parameter. We show that in this case, the asymptotics of the eigenvalues is totally different, i.e. both the imaginary and real parts of eigenvalues tend to ,as the number of an eigenvalue increases. We will show in our next paper, that as an indirect consequence of such a behaviour of the eigenvalues, the set of the root vectors of the corresponding operator is not uniformly minimal (let alone the Riesz basis property). Copyright © 2003 John Wiley & Sons, Ltd. [source] What determines the molecular composition of abnormal protein aggregates in neurodegenerative disease?NEUROPATHOLOGY, Issue 4 2008Richard A. Armstrong Abnormal protein aggregates, in the form of either extracellular plaques or intracellular inclusions, are an important pathological feature of the majority of neurodegenerative disorders. The major molecular constituents of these lesions, viz., ,-amyloid (A,), tau, and ,-synuclein, have played a defining role in the diagnosis and classification of disease and in studies of pathogenesis. The molecular composition of a protein aggregate, however, is often complex and could be the direct or indirect consequence of a pathogenic gene mutation, be the result of cell degeneration, or reflect the acquisition of new substances by diffusion and molecular binding to existing proteins. This review examines the molecular composition of the major protein aggregates found in the neurodegenerative diseases including the A, and prion protein (PrP) plaques found in Alzheimer's disease (AD) and prion disease, respectively, and the cellular inclusions found in the tauopathies and synucleinopathies. The data suggest that the molecular constituents of a protein aggregate do not directly cause cell death but are largely the consequence of cell degeneration or are acquired during the disease process. These findings are discussed in relation to diagnosis and to studies of to disease pathogenesis. [source] Correlated evolution of fruit and leaf size in bird-dispersed plants: species-level variance in fruit traits explained a bit further?OIKOS, Issue 3 2002Carlos M. Herrera The astounding morphological diversity exhibited by the fruits of vertebrate-dispersed plants has been traditionally interpreted as the adaptive outcome of divergent selective pressures exerted on plants by the broad array of frugivorous animals involved in seed dispersal. Although the selective capacity of frugivores provides support to this interpretation, recent studies have challenged it by documenting a strong phylogenetic component associated to interspecific variation in most fruit characteristics. Size-related fruit traits provide a conspicuous exception to this pattern, because they exhibit considerable variation at the between-species level which is largely independent of phylogeny and is correlated with consumption by differently-sized dispersal agents. Substantial species-level variance in size-related traits may reflect genuine disperser-driven diversification, but may also be partly influenced by correlated evolution of fruit size with the size of other plant structures. This latter possibility is tested here for bird-dispersed plants of the Iberian Peninsula using phylogenetically independent contrasts. Results demonstrate the existence of correlated evolution of fruit and leaf size at the species level. As all the plant taxa considered have their fruits eaten, and seeds dispersed, by the same relatively reduced set of frugivorous bird species, results suggest that a significant fraction of the variation in fruit size represented in the species sample may be explained as an indirect consequence of variation in leaf size, rather than being associated with adaptive divergence related to seed dispersal agents. [source] Kinetics of bone protection by recombinant osteoprotegerin therapy in Lewis rats with adjuvant arthritisARTHRITIS & RHEUMATISM, Issue 7 2002Giuseppe Campagnuolo Objective To assess the effect of different dosages and treatment schedules of osteoprotegerin (OPG) on joint preservation in an experimental model of adjuvant-induced arthritis (AIA). Methods Male Lewis rats with AIA (6,8 per group) were treated with a subcutaneous bolus of recombinant human OPG according to one of the following schedules: daily OPG (an efficacious regimen) starting at disease onset (days 9,15), early intervention (days 9,11), delayed intervention (days 13,15), and extended therapy (days 9,22). Inflammation (hind paw swelling) was quantified throughout the clinical course; osteoporosis (bone mineral density [BMD], by quantitative dual x-ray absorptiometry) and morphologic appraisals of inflammation, bone damage, intralesional osteoclasts (by semiquantitative histopathologic scoring), and integrity of the articular cartilage matrix (by retention of toluidine blue stain) were determined in histology sections of arthritic hind paws. Results OPG provided dose- and schedule-dependent preservation of BMD and periarticular bone while essentially eliminating intralesional osteoclasts. Dosages ,2.5 mg/kg/day preserved or enhanced BMD and prevented essentially all erosions. A dosage of 4 mg/kg/day protected joint integrity to a comparable degree when given for 7 (days 9,15) or 14 (days 9,22) consecutive days. At this dosage, early intervention (days 9,11) was twice as effective as delayed intervention (days 13,15) at preventing joint dissolution. Erosions and osteoclast scores were greatly decreased for 26 days (measured from the first treatment) after 7 or 14 daily doses of OPG (4 mg/kg/day). OPG treatment also prevented loss of cartilage matrix proteoglycans, an indirect consequence of protecting the subchondral bone. No OPG dosage or regimen alleviated weight loss, inflammation, or periosteal osteophyte production. Conclusion These data indicate that OPG preserves articular bone and (indirectly) articular cartilage in arthritic joints in a dose- and schedule-dependent manner, halts bone erosion when given at any point during the course of arthritis, produces sustained antierosive activity after a short course, and is most effective when initiated early in the disease. [source] Offshore renewable energy: ecological implications of generating electricity in the coastal zoneJOURNAL OF APPLIED ECOLOGY, Issue 4 2005ANDREW B. GILL Summary 1Global-scale environmental degradation and its links with non-renewable fossil fuels have led to an increasing interest in generating electricity from renewable energy resources. Much of this interest centres on offshore renewable energy developments (ORED). The large scale of proposed ORED will add to the existing human pressures on coastal ecosystems, therefore any ecological costs and benefits must be determined. 2The current pressures on coastal ecology set the context within which the potential impacts (both positive and negative) of offshore renewable energy generation are discussed. 3The number of published peer-review articles relating to renewable energy has increased dramatically since 1991. Significantly, only a small proportion of these articles relate to environmental impacts and none considers coastal ecology. 4Actual or potential environmental impact can occur during construction, operation and/or decommissioning of ORED. 5Construction and decommissioning are likely to cause significant physical disturbance to the local environment. There are both short- and long-term implications for the local biological communities. The significance of any effects is likely to depend on the natural disturbance regime and the stability and resilience of the communities. 6During day-to-day operation, underwater noise, emission of electromagnetic fields and collision or avoidance with the energy structures represent further potential impacts on coastal species, particularly large predators. The wider ecological implications of any direct and indirect effects are discussed. 7Synthesis and applications. This review demonstrates that offshore renewable energy developments will have direct and, potentially, indirect consequences for coastal ecology, with these effects occurring at different scales. Ecologists should be involved throughout all the phases of an ORED to ensure that appropriate assessments of the interaction of single and multiple developments with the coastal environment are undertaken. [source] Density-dependent growth rate in an age-structured population: a field study on stream-dwelling brown trout Salmo truttaJOURNAL OF FISH BIOLOGY, Issue 10 2009R. Kaspersson A field experiment during autumn, winter and spring was performed in a small stream on the west coast of Sweden, aiming to examine the direct and indirect consequences of density-dependent intercohort competition in brown trout Salmo trutta. Individual growth rate, recapture rate and site fidelity were used as response variables in the young-of-the-year (YOY) age class, experiencing two different treatments: presence or absence of yearlings and over-yearlings (age , 1+ year individuals). YOY individuals in stream sections with reduced density of age , 1+ year individuals grew significantly faster than individuals experiencing natural cohort structure. In the latter, growth rate was negatively correlated with density and biomass of age , 1+ year individuals, which may induce indirect effects on year-class strength through, for example, reduced fecundity and survival. Movement of YOY individuals and turnover rate (i.e. proportion of untagged individuals) were used to demonstrate potential effects of intercohort competition on site fidelity. While YOY movement was remarkably restricted (83% recaptured within 50 m from the release points), turnover rate was higher in sections with reduced density of age ,1+ year individuals, suggesting that reduced density of age ,1+ year individuals may have released favourable microhabitats. [source] Genuine Episodic Memory Deficits and Executive Dysfunctions in Alcoholic Subjects Early in AbstinenceALCOHOLISM, Issue 7 2007Anne Lise Pitel Background: Chronic alcoholism is known to impair episodic memory function, but the specific nature of this impairment is still unclear. Moreover, it has never been established whether episodic memory deficit in alcoholism is an intrinsic memory deficit or whether it has an executive origin. Thus, the objectives are to specify which episodic memory processes are impaired early in abstinence from alcohol and to determine whether they should be regarded as genuine memory deficits or rather as the indirect consequences of executive impairments. Methods: Forty recently detoxified alcoholic inpatients at alcohol entry treatment and 55 group-matched controls underwent a neuropsychological assessment of episodic memory and executive functions. The episodic memory evaluation consisted of 3 tasks complementing each other designed to measure the different episodic memory components (learning, storage, encoding and retrieval, contextual memory, and autonoetic consciousness) and 5 executive tasks testing capacities of organization, inhibition, flexibility, updating, and integration. Results: Compared with control subjects, alcoholic patients presented impaired learning abilities, encoding processes, retrieval processes, contextual memory and autonoetic consciousness. However, there was no difference between the 2 groups regarding the storage capacities assessed by the rate of forgetting. Concerning executive functions, alcoholic subjects displayed deficits in each executive task used. Nevertheless, stepwise regression analyses showed that only performances on fluency tasks were significantly predictive of some of the episodic memory disorders (learning abilities for 40%, encoding processes for 20%, temporal memory for 21%, and state of consciousness associated with memories for 26%) in the alcoholic group. Discussion: At alcohol treatment entry, alcoholic patients present genuine episodic memory deficits that cannot be regarded solely as the consequences of executive dysfunctions. These results are in accordance with neuroimaging findings showing hippocampal atrophy. Moreover, given the involvement of episodic memory and executive functions in alcohol treatment, these data could have clinical implications. [source] Cytomegalovirus prophylaxis with valganciclovir in kidney, pancreas,kidney, and pancreas transplantationCLINICAL TRANSPLANTATION, Issue 4 2004Gaetano Ciancio Abstract:, Cytomegalovirus, seen in more than 50% of solid organ transplant recipients, is responsible for numerous direct and indirect consequences, including infection with opportunistic pathogens and allograft rejection. Prophylaxis with intravenous ganciclovir has been the gold standard for prevention; however, intravenous treatment is expensive and carries risks of its own. Oral ganciclovir, to be effective, must be given in large, divided doses. Valganciclovir, the valine ester of ganciclovir, at 900 mg/day, provides oral bioavailability equivalent to that of intravenous ganciclovir and superior to that of oral ganciclovir. This retrospective study assessed the efficacy of 3 months prophylaxis with valganciclovir in kidney, simultaneous pancreas,kidney, and pancreas transplantation. Of 161 patients, all of whom received potent immunosuppressive regimens and were followed for a mean of 440 days, only one developed cytomegalovirus infection, at 120 days post-transplantation. Two patients died, and two others lost their grafts. There were seven incidents of acute rejection. Only seven patients discontinued treatment early, five because of leukopenia. These results suggest that prophylaxis with 900 mg/day of valganciclovir for at least 3 months safely and effectively prevents cytomegalovirus infection in kidney, simultaneous pancreas,kidney and pancreas transplant recipients on highly potent immunosuppression. [source] | |||||||||||||