Much of what we know about the role of biodiversity in mediating ecosystem processes and function stems from manipulative experiments, which have largely been performed in isolated, homogeneous ...environments that do not incorporate habitat structure or allow natural community dynamics to develop. Here, we use a range of habitat configurations in a model marine benthic system to investigate the effects of species composition, resource heterogeneity and patch connectivity on ecosystem properties at both the patch (bioturbation intensity) and multi-patch (nutrient concentration) scale. We show that allowing fauna to move and preferentially select patches alters local species composition and density distributions, which has negative effects on ecosystem processes (bioturbation intensity) at the patch scale, but overall positive effects on ecosystem functioning (nutrient concentration) at the multi-patch scale. Our findings provide important evidence that community dynamics alter in response to localized resource heterogeneity and that these small-scale variations in habitat structure influence species contributions to ecosystem properties at larger scales. We conclude that habitat complexity forms an important buffer against disturbance and that contemporary estimates of the level of biodiversity required for maintaining future multi-functional systems may need to be revised.
Whilst there is a wealth of empirical studies that indicate negative ecosystem consequences of biodiversity loss, much debate remains over the existence, strength and importance of the same patterns ...in natural systems. We used a gradient of organic enrichment as a means of defining non-random species loss in the marine benthos and, using partial linear regression, determined the relative importance of macrofaunal biodiversity and the abiotic environment in affecting a benthic ecosystem process (bioturbation intensity; indicated by sediment mixing depth), that is important in mediating benthic functioning. Of the abiotic and biotic variables tested (n = 8), species richness and sediment total organic carbon (TOC) content together explained 65% of the variability in this ecosystem process, with more than half of this variability explained solely by species richness. Importantly, the relative importance of biodiversity decreased at low levels of species richness and/or high levels of TOC. These results have profound implications for manipulative field experiments, where environmental factors are likely to dominate ecosystem processes, because the extent and importance of biological mediation could be underestimated. Our results also revealed that a large proportion of the explained variability in the ecosystem process is explained by the underlying reciprocal relationship (shared variability) between biodiversity and sediment TOC, highlighting the importance of species–environment interactions. If we are to fully appreciate the role of biodiversity in natural systems, our findings suggest that the intimate relationship between species and their environment needs to be more prominently featured in future studies that consider the ecosystem consequences of biodiversity loss.
To determine the prognostic significance and pathophysiologic implication of intraventricular extension of supratentorial intracerebral hemorrhage.
Prospective study.
Acute stroke and neurointensive ...care units of a tertiary care hospital.
One hundred twenty-nine patients with supratentorial intracerebral hemorrhage, managed medically.
Two patients had intraventricular catheters placed for external drainage. No patient received thrombolytics or surgical evacuation of clot.
Of the 129 patients, 47 had intraventricular extension of their hemorrhages. These patients had larger intraparenchymal hemorrhages (36.6 cm3 vs. 15.0 cm3) and lower initial Glasgow Coma Scale scores (mean, 9.6 vs. 13.7). Their 30-day mortality rate was 43% compared with only 9% among those without ventricular extension. Univariate and multivariate logistic regression modeling was used to assess the prognostic significance of various measures of intraventricular hemorrhage. The presence of intraventricular hemorrhage, the number of ventricles containing blood, fourth ventricular blood, and intraventricular hemorrhage volume were each related to 30-day mortality in a univariate analysis, but only intraventricular hemorrhage volume contributed significantly to outcome prediction in the presence of Glasgow Coma Scale score.
Volume of intraventricular hemorrhage is an important determinant of outcome in supratentorial intracerebral hemorrhage.
Continental shelf sediments are globally important for biogeochemical activity. Quantification of shelf-scale stocks and fluxes of carbon and nutrients requires the extrapolation of observations made ...at limited points in space and time. The procedure for selecting exemplar sites to form the basis of this upscaling is discussed in relation to a UK-funded research programme investigating biogeochemistry in shelf seas. A three-step selection process is proposed in which (1) a target area representative of UK shelf sediment heterogeneity is selected, (2) the target area is assessed for spatial heterogeneity in sediment and habitat type, bed and water column structure and hydrodynamic forcing, and (3) study sites are selected within this target area encompassing the range of spatial heterogeneity required to address key scientific questions regarding shelf scale biogeochemistry, and minimise confounding variables. This led to the selection of four sites within the Celtic Sea that are significantly different in terms of their sediment, bed structure, and macrofaunal, meiofaunal and microbial community structures and diversity, but have minimal variations in water depth, tidal and wave magnitudes and directions, temperature and salinity. They form the basis of a research cruise programme of observation, sampling and experimentation encompassing the spring bloom cycle. Typical variation in key biogeochemical, sediment, biological and hydrodynamic parameters over a pre to post bloom period are presented, with a discussion of anthropogenic influences in the region. This methodology ensures the best likelihood of site-specific work being useful for up-scaling activities, increasing our understanding of benthic biogeochemistry at the UK-shelf scale.
A time series from 1977–1989 and 2000–2002 of scientific trawl surveys in the Porcupine Seabight and adjacent abyssal plain of the NE Atlantic was analysed to assess changes in demersal fish biomass ...and length frequency. These two periods coincide with the onset of the commercial deep-water fishery in the late 1970s and the onset of the regulation of the fishery in the early 2000's, which allowed us to investigate changes in the relationship between total demersal fish biomass and depth between the pre- and post commercial fishing periods, as well as changes in the biomass (kg km−2) depth distribution and length frequency distribution of the most dominant fish species. Our results show a decline in total demersal fish biomass of 36% within the depth range of the commercial fishery (< 1500 m). Whilst there were significant declines in target (e.g. Coryphaenoides rupestris decreased by 57%) and non-target (e.g. C. guentheri and Antimora rostrata) species, not all species declined significantly. Changes in the overall length-frequency distribution were detected for 5 out of the 8 dominant species occupying depth ranges both within and outside the maximum depth for commercial trawling. This suggests that whilst there is evidence for likely fishery impacts on the biomass distribution of the demersal fish population as a whole, species-specific impacts are highly variable. It is clear that changes in population structure can extend beyond the depth at which fishing takes place, highlighting the importance for also considering the indirect effects on deep-sea fish populations.
Although the use of pesticides in inner-city homes of the United States is of considerable magnitude, little is known about the potentially adverse health effects of such exposure. Recent animal data ...suggest that exposure to pesticides during pregnancy and early life may impair growth and neurodevelopment in the offspring. To investigate the relationship among prenatal pesticide exposure, paraoxonase (PON1) polymorphisms and enzyme activity, and infant growth and neurodevelopment, we are conducting a prospective, multiethnic cohort study of mothers and infants delivered at Mount Sinai Hospital in New York City. In this report we evaluate the effects of pesticide exposure on birth weight, length, head circumference, and gestational age among 404 births between May 1998 and May 2002. Pesticide exposure was assessed by a prenatal questionnaire administered to the mothers during the early third trimester as well as by analysis of maternal urinary pentachlorophenol levels and maternal metabolites of chlorpyrifos and pyrethroids. Neither the questionnaire data nor the pesticide metabolite levels were associated with any of the fetal growth indices or gestational age. However, when the level of maternal PON1 activity was taken into account, maternal levels of chlorpyrifos above the limit of detection coupled with low maternal PON1 activity were associated with a significant but small reduction in head circumference. In addition, maternal PON1 levels alone, but not PON1 genetic polymorphisms, were associated with reduced head size. Because small head size has been found to be predictive of subsequent cognitive ability, these data suggest that chlorpyrifos may have a detrimental effect on fetal neurodevelopment among mothers who exhibit low PON1 activity.
To investigate the analgesic efficacy of lamotrigine in the treatment of painful HIV-associated distal sensory polyneuropathy (DSP).
The pathogenesis of HIV-associated DSP is unknown and there is no ...effective treatment. A novel anticonvulsant, lamotrigine, blocks voltage-sensitive sodium channels and inhibits the release of glutamate and aspartate. There have been anecdotal reports of efficacy of lamotrigine in the treatment of painful neuropathy and trigeminal neuralgia.
In a multicenter, randomized, double-blind, placebo-controlled study, lamotrigine was initiated at 25 mg per day and slowly titrated over 7 weeks to 300 mg per day. Study duration was 14 weeks. The primary outcome measure was change in pain on the modified Gracely scale with secondary outcome measures including change in neurologic examination, use of concomitant analgesic medications, and global pain relief.
Of 42 enrolled subjects, 13 did not complete the 14-week study endpoint. In five of these, rash was the cause for dropout. In the remaining 29 evaluable subjects, 20 patients received placebo and 9 received lamotrigine. The pain scores at baseline were not significantly different. The reduction in average pain from baseline to week 14 was greater (p = 0.03) in the lamotrigine group (-0.55) than in the placebo group (-0.18), adjusting for baseline levels of pain. There was no difference between the groups on the change in peak worst pain.
In this small trial, lamotrigine showed promise in the treatment of pain associated with HIV-related DSP. The frequency of rash was greater than in lamotrigine studies in epilepsy. A larger controlled study of lamotrigine is warranted.
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