Investigating effects of climate-induced changes in water temperature and diet on mercury concentrations in an Arctic freshwater forage fish

The amount of mercury (Hg) in Arctic lake food webs is, and will continue to be, affected by rapid, ongoing climate change. At warmer temperatures, fish require more energy to sustain growth; changes in their metabolic rates and consuming prey with potentially higher Hg concentrations could result in increased Hg accumulation. To examine the potential implications of climate warming on forage fish Hg accumulation in Arctic lakes, we quantified growth and Hg accumulation in Ninespine Stickleback Pungitius pungitius under different temperature and diet scenarios using bioenergetics models. Four scenarios were considered that examined the role of climate, diet, climate × diet, and climate × diet × elevated prey Hg. As expected, annual fish growth increased with warmer temperatures, but growth rates and Hg accumulation were largely diet dependent. Compared to current growth rates of 0.3 g⋅y^-1, fish growth increased at least 200% for fish consuming energy-dense benthic prey and decreased at least 40% for fish consuming pelagic prey. Compared to baseline levels, the Hg burden per kilocalorie of Ninespine Stickleback declined up to 43% with benthic consumption - indicating strong somatic growth dilution - but no more than 4% with pelagic consumption; elevated prey Hg concentrations led to moderate Hg declines in benthic-foraging fish and Hg increases in pelagic-foraging fish. Bioenergetics models demonstrated the complex interaction of water temperature, growth, prey proportions, and prey Hg concentrations that respond to climate change. Further work is needed to resolve mechanisms and rates linking climate change to Hg availability and uptake in Arctic freshwater systems.

Climate change and mercury in the Arctic: Biotic interactions

Global climate change has led to profound alterations of the Arctic environment and ecosystems, with potential secondary effects on mercury (Hg) within Arctic biota. This review presents the current scientific evidence for impacts of direct physical climate change and indirect ecosystem change on Hg exposure and accumulation in Arctic terrestrial, freshwater, and marine organisms. As the marine environment is elevated in Hg compared to the terrestrial environment, terrestrial herbivores that now exploit coastal/marine foods when terrestrial plants are iced over may be exposed to higher Hg concentrations. Conversely, certain populations of predators, including Arctic foxes and polar bears, have shown lower Hg concentrations related to reduced sea ice-based foraging and increased land-based foraging. How climate change influences Hg in Arctic freshwater fishes is not clear, but for lacustrine populations it may depend on lake-specific conditions, including interrelated alterations in lake ice duration, turbidity, food web length and energy sources (benthic to pelagic), and growth dilution. In several marine mammal and seabird species, tissue Hg concentrations have shown correlations with climate and weather variables, including climate oscillation indices and sea ice trends; these findings suggest that wind, precipitation, and cryosphere changes that alter Hg transport and deposition are impacting Hg concentrations in Arctic marine organisms. Ecological changes, including northward range shifts of sub-Arctic species and altered body condition, have also been shown to affect Hg levels in some populations of Arctic marine species. Given the limited number of populations and species studied to date, especially within Arctic terrestrial and freshwater systems, further research is needed on climate-driven processes influencing Hg concentrations in Arctic ecosystems and their net effects. Long-term pan-Arctic monitoring programs should consider ancillary datasets on climate, weather, organism ecology and physiology to improve interpretation of spatial variation and time trends of Hg in Arctic biota.

Treatment of ruptured intracranial aneurysms using the novel generation of flow-diverters with surface modification: A systematic review and meta-analysis

BACKGROUND

Surface modification of flow diverters (FDs) has been explored as a solution for reducing thrombotic risk of these devices, without necessarily using dual antiplatelet therapy (DAPT). If effective, this could pose a promising alternative for treatment of ruptured aneurysms not amenable to other modalities.

METHODS

We performed a comprehensive search of PubMed, MEDLINE, and Embase databases following Preferred Reporting Items for Systematic reviews and Meta-analyzes guidelines. We included articles reporting use of surface-modified FDs for treatment of ruptured aneurysms. Demographics, subarachnoid hemorrhage (SAH) severity, aneurysm characteristics, devices used, periprocedural complications, angiographic outcomes, and mortality were extracted for sample size-based weighted analysis.

RESULTS

Six studies comprising 59 patients with 64 aneurysms were included. Mean patient age was 56.6 ± 6.3 years and 60.6% (95% confidence interval [CI], 46.7-72.9%) were women. The anterior circulation was the location in 60.4% (95%CI, 45.5-73.5%) of aneurysms; 41.8% of the aneurysms were saccular (95%CI, 29.3-55.4%), 16.7% were fusiform (95%CI, 8.3-30.8%), 29.9% were dissecting (95%CI, 12.8-55.4%), 24.4% were blood-blister (95%CI, 15.2-36.7%), and 5.7% were mycotic (95%CI, 2-15.1%). Poor SAH grade was reported in 46.9% (95%CI, 33.3-60.9%). Adjunctive coiling was used in 33.2% (95%CI, 12.4-63.6%). Periprocedural thromboembolic and hemorrhagic complications occurred in 20% (95%CI, 7.1-45.1%) and 8.8% (95%CI, 3.7-19.5%), respectively. Complete occlusion was achieved in 76.4% (95%CI, 58.1-88.3%); no retreatments during follow-up were reported. Overall mortality was 15.1% (95%CI, 7.7-27.6%). There were no differences between single antiplatelet therapy (SAPT) and DAPT regimens with respect to periprocedural thromboembolic complications (P = 0.09), hemorrhagic (P = 0.834) complications, and mortality (P = 0.312).

CONCLUSION

Surface-modified FD treatment of ruptured aneurysms resulted in high rates of thromboembolic complications and acceptable rates of hemorrhagic complications. A considerable proportion of aneurysms were nonsaccular. Rates of complete occlusion were high and retreatment were low. Importantly, no statistically significant difference was found between SAPT and DAPT with respect to complications and mortality.

A systematic review and meta-analysis of the Derivo Embolization Device: a novel surface-modified flow diverter for intracranial aneurysm treatment

BACKGROUND

Surface-modified flow diverters (FDs) designed to reduce thrombogenicity represent the next frontier for intracranial aneurysm treatment. The Derivo Embolization Device (DED) is a novel FD with titanium oxide and titanium oxynitride finishing of the struts. We performed a systematic review of pertinent literature, aiming to evaluate the device's effectiveness and safety.

METHODS

A literature search of PubMed, Embase, and MEDLINE was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Five studies comprising 481 aneurysms were included. These studies were conducted in Turkey, Brazil, Germany, Poland, and Italy; two were prospective and three were retrospective. Twenty-six aneurysms (5.4%) were ruptured. The antiplatelet regimens were heterogeneous, but dual antiplatelet therapy was administered preprocedurally in all studies and maintained for 3-12 months before a switch to single antiplatelet therapy. The rate of periprocedural ischemic and hemorrhagic complications was 4.9% (95% CI 2.9% to 7%). Adjunctive coiling was used in 25.6% (95% CI 11.4% to 39.8%) of aneurysms. The complete angiographic occlusion rate was 81.4% (95% CI 71.3% to 91.5%), mortality rate was 2.1% (95% CI 0.4% to 3.9%), with follow-up ranging from 9 to 18 months. Delayed aneurysm rupture was reported in one patient.

CONCLUSIONS

The DED has been increasingly used in other countries. We identified low rates of periprocedural complications and mortality and a high rate of complete occlusion.

Fish growth rates and lake sulphate explain variation in mercury levels in ninespine stickleback (Pungitius pungitius) on the Arctic Coastal Plain of Alaska

Mercury concentrations in freshwater food webs are governed by complex biogeochemical and ecological interactions that spatially vary and are often mediated by climate. The Arctic Coastal Plain of Alaska (ACP) is a heterogeneous, lake-rich landscape where variability in mercury accumulation is poorly understood. Earlier research indicated that the level of catchment influence on lakes varied spatially on the ACP, and affected mercury accumulation in lake sediments. This work sought to determine drivers of spatial variation in mercury accumulation in lake food webs on the ACP. Three lakes that were a priori identified as "high catchment influence" (Reindeer Camp region) and three lakes that were a priori identified as "low catchment influence" (Atqasuk region) were sampled, and variability in water chemistry, food web ecology, and mercury accumulation was investigated. Among-lake differences in ninespine stickleback (Pungitius pungitius) length-adjusted methylmercury concentrations were significantly explained by sulphate concentration in lake water, a tracer of catchment runoff input. This effect was mediated by fish growth, which had no pattern between regions. Together, lake water sulphate concentration and fish age-at-size (proxy for growth) accounted for nearly all of the among-lake variability in length-adjusted methylmercury concentrations in stickleback (R²_adj = 0.94, p < 0.01). The percentage of total mercury as methylmercury (a proxy for net Hg methylation) was higher in sediments of more autochthonous, "low catchment influence" lakes (p < 0.05), and in the periphyton of more allochthonous, "high catchment influence" lakes (p < 0.05). The results indicate that dominant sources of primary production (littoral macrophyte/biofilm vs. pelagic phytoplankton) and food web structure (detrital vs. grazing) are regulated by catchment characteristics on the ACP, and that this ultimately influences the amount of methylmercury in the aquatic food web. These results have important implications for predicting future mercury concentrations in fish in lakes where fish growth rates and catchment inputs may change in response to a changing climate.

Lakes at Risk of Chloride Contamination

Lakes in the Midwest and Northeast United States are at risk of anthropogenic chloride contamination, but there is little knowledge of the prevalence and spatial distribution of freshwater salinization. Here, we use a quantile regression forest (QRF) to leverage information from 2773 lakes to predict the chloride concentration of all 49 432 lakes greater than 4 ha in a 17-state area. The QRF incorporated 22 predictor variables, which included lake morphometry characteristics, watershed land use, and distance to the nearest road and interstate. Model predictions had an r² of 0.94 for all chloride observations, and an r² of 0.86 for predictions of the median chloride concentration observed at each lake. The four predictors with the largest influence on lake chloride concentrations were low and medium intensity development in the watershed, crop density in the watershed, and distance to the nearest interstate. Almost 2000 lakes are predicted to have chloride concentrations above 50 mg L^-1 and should be monitored. We encourage management and governing agencies to use lake-specific model predictions to assess salt contamination risk as well as to augment their monitoring strategies to more comprehensively protect freshwater ecosystems from salinization.

Tooth development and replacement in the Atlantic Cutlassfish, Trichiurus lepturus, with comparisons to other Scombroidei

Atlantic Cutlassfish, Trichiurus lepturus, have large, barbed, premaxillary and dentary fangs, and sharp dagger-shaped teeth in their oral jaws. Functional teeth firmly ankylose to the dentigerous bones. We used dry skeletons, histology, SEM, and micro-CT scanning to study 92 specimens of T. lepturus from the western North Atlantic to describe its dentition and tooth replacement. We identified three modes of intraosseous tooth replacement in T. lepturus depending on the location of the tooth in the jaw. Mode 1 relates to replacement of premaxillary fangs, in which new tooth germs enter the lingual surface of the premaxilla, develop horizontally, and rotate into position. We suggest that growth of large fangs in the premaxilla is accommodated by this horizontal development. Mode 2 occurs for dentary fangs: new tooth germs enter the labial surface of the dentary, develop vertically, and erupt into position. Mode 3 describes replacement of lateral teeth, in which new tooth germs enter a trench along the crest of the dentigerous bone, develop vertically, and erupt into position. Such distinct modes of tooth replacement in a teleostean species are unknown. We compared modes of replacement in T. lepturus to 20 species of scombroids to explore the phylogenetic distribution of these three replacement modes. Alternate tooth replacement (in which new teeth erupt between two functional teeth), ankylosis, and intraosseous tooth development are plesiomorphic to Bluefish + other Scombroidei. Our study highlights the complexity and variability of intraosseous tooth replacement. Within tooth replacement systems, key variables include sites of formation of tooth germs, points of entry of tooth germs into dentigerous bones, coupling of tooth germ migration and bone erosion, whether teeth develop horizontally or immediately beneath the tooth to be replaced, and how tooth eruption and ankylosis occur. Developmentally different tooth replacement processes can yield remarkably similar dentitions.

Testosterone effects on functional amygdala lateralization: A study in adolescent transgender boys and cisgender boys and girls

The influence of testosterone on the development of human brain lateralization has been subject of debate for a long time, partly because studies investigating this are necessarily mostly correlational. In the present study we used a quasi-experimental approach by assessing functional brain lateralization in trans boys (female sex assigned at birth, diagnosed with Gender Dysphoria, n = 21) before and after testosterone treatment, and compared these results to the functional lateralization of age-matched control groups of cisgender boys (n = 20) and girls (n = 21) around 16 years of age. The lateralization index of the amygdala was determined with functional magnetic resonance imaging (fMRI) during an emotional face matching task with angry and fearful faces, as the literature indicates that boys show more activation in the right amygdala than girls during the perception of emotional faces. As expected, the lateralization index in trans boys shifted towards the right amygdala after testosterone treatment, and the cumulative dose of testosterone treatment correlated significantly with amygdala lateralization after treatment. However, we did not find any significant group differences in lateralization and endogenous testosterone concentrations predicted rightward amygdala lateralization only in the cis boys, but not in cis girls or trans boys. These inconsistencies may be due to sex differences in sensitivity to testosterone or its metabolites, which would be a worthwhile course for future studies.

Climbing towards recovery: investigating physically injured combat veterans' psychosocial response to scaling Mt. Kilimanjaro

PURPOSE

To explore physically injured combat veterans' psychosocial response to scaling Mt. Kilimanjaro.

METHOD

Participants (n = 4) were male and ranged in age from 22 to 44 years. They had all been wounded as a result of active duty in Afghanistan between 15 and 42 months (M = 27.25) before the study. Data were collected throughout a 9-day climb on Mt. Kilimanjaro using multiple sources of ethnographic data collection techniques including semi-structured interviews and detailed observations. Data were analyzed using cross case analysis.

RESULTS

The findings are divided into themes that were drawn out of the data to illustrate the participants' psychosocial response to their experience of climbing on Mt. Kilimanjaro. Key themes of self-determination, active coping and social support were identified from the data.

CONCLUSION

Support for those in recovery from trauma should foster psychosocial resources needed for healthy functioning. Future research should explore the role of meaningful and challenging activities as a way of improving the experience of recovery following serious injury.

Anomalous rise in algal production linked to lakewater calcium decline through food web interactions

Increased algal blooms are a threat to aquatic ecosystems worldwide, although the combined effects of multiple stressors make it difficult to determine the underlying causes. We explore whether changes in trophic interactions in response to declining calcium (Ca) concentrations, a water quality issue only recently recognized in Europe and North America, can be linked with unexplained bloom production. Using a palaeolimnological approach analysing the remains of Cladocera (herbivorous grazers) and visual reflectance spectroscopically inferred chlorophyll a from the sediments of a Nova Scotia (Canada) lake, we show that a keystone grazer, Daphnia, declined in the early 1990s and was replaced by a less effective grazer, Bosmina, while inferred chlorophyll a levels tripled at constant total phosphorus (TP) concentrations. The decline in Daphnia cannot be attributed to changes in pH, thermal stratification or predation, but instead is linked to declining lakewater [Ca]. The consistency in the timing of changes in Daphnia and inferred chlorophyll a suggests top-down control on algal production, providing, to our knowledge, the first evidence of a link between lakewater [Ca] decline and elevated algal production mediated through the effects of [Ca] decline on Daphnia. [Ca] decline has severe implications for whole-lake food webs, and presents yet another mechanism for potential increases in algal blooms.

Anomalous rise in algal production linked to lakewater calcium decline through food web interactions

Increased algal blooms are a threat to aquatic ecosystems worldwide, although the combined effects of multiple stressors make it difficult to determine the underlying causes. We explore whether changes in trophic interactions in response to declining calcium (Ca) concentrations, a water quality issue only recently recognized in Europe and North America, can be linked with unexplained bloom production. Using a palaeolimnological approach analysing the remains of Cladocera (herbivorous grazers) and visual reflectance spectroscopically inferred chlorophyll a from the sediments of a Nova Scotia (Canada) lake, we show that a keystone grazer, Daphnia , declined in the early 1990s and was replaced by a less effective grazer, Bosmina , while inferred chlorophyll a levels tripled at constant total phosphorus (TP) concentrations. The decline in Daphnia cannot be attributed to changes in pH, thermal stratification or predation, but instead is linked to declining lakewater [Ca]. The consistency in the timing of changes in Daphnia and inferred chlorophyll a suggests top-down control on algal production, providing, to our knowledge, the first evidence of a link between lakewater [Ca] decline and elevated algal production mediated through the effects of [Ca] decline on Daphnia . [Ca] decline has severe implications for whole-lake food webs, and presents yet another mechanism for potential increases in algal blooms.

Serotonin and dopamine transporters in relation to neuropsychological functioning, personality traits and mood in young adult healthy subjects

BACKGROUND

Serotonin and dopamine neurotransmitter systems are implicated in the regulation of mood, cognition and personality traits and their dysfunction is thought to be implicated in diverse psychopathologies. However, in healthy subjects the relationship between the serotonin and dopamine systems and neuropsychological functioning and personality traits is not clearly established. In the present study we investigated whether neuropsychological functioning, personality traits and mood states of a group of healthy subjects are associated with in vivo measures of serotonin transporters (SERTs) and dopamine transporters (DATs).

METHOD

A total of 188 young healthy subjects underwent neuropsychological and subjective measurements of memory function, depression and impulsivity. Participants' SERT and DAT availability in predefined regions of interest were assessed using single photon emission computed tomography (SPECT) with the radiotracer [123I]β-CIT. Individual magnetic resonance imaging (MRI) scans served as anatomic reference.

RESULTS

We did not find any significant association between SERT or DAT availability and neuropsychological test performance or self-reported impulsivity and mood. There were no significant sex differences in SERT or DAT availability, but men performed significantly better on some tests of visuospatial functioning than women.

CONCLUSIONS

Robust negative findings for striatal DAT availability seriously question earlier findings of positive associations between DAT availability and cognitive functions in healthy subjects. Our results also suggest that subcortical SERT availability is not associated with the neuropsychological functions and personality traits assessed. In summary, the present study suggests that neuropsychological and personality measurements in young healthy people are not associated with subcortical SERT or striatal DAT availabilities in the brain.

DNA microarray analysis of functionally discrete human brain regions reveals divergent transcriptional profiles

Transcriptional profiles within discrete human brain regions are likely to reflect structural and functional specialization. Using DNA microarray technology, this study investigates differences in transcriptional profiles of highly divergent brain regions (the cerebellar cortex and the cerebral cortex) as well as differences between two closely related brain structures (the anterior cingulate cortex and the dorsolateral prefrontal cortex). Replication of this study across three independent laboratories, to address false-positive and false-negative results using microarray technology, is also discussed. We find greater than a thousand transcripts to be differentially expressed between cerebellum and cerebral cortex and very few transcripts to be differentially expressed between the two neocortical regions. We further characterized transcripts that were found to be specifically expressed within brain regions being compared and found that ontological classes representing signal transduction machinery, neurogenesis, synaptic transmission, and transcription factors were most highly represented.

The clinical teacher. A critical link in competence development

Regardless of market conditions, staff development personnel are responsible for helping to meet the organization's need for competent staff. Collaboration between the organization's education and clinical staff is essential to effect a successful transfer from having knowledge to performing effectively. One organization's response to the challenge of competence development, and how a successful transfer of learning can be achieved by collaboration between clinical educators and clinical staff is reported.

The influence of black English on diagnosis of reading in learning disabled and normal readers

This study investigated the removal of black English dialect features from the error scores of three oral reading tests—the Gray Oral Reading Test, the Gilmore Oral Reading Test, and the Spache Diagnostic Reading Scales. The 40 children in the sample population (20 control children matched by age and sex with 20 children identified by the school as learning disabled) were given all three tests. Each test was scored first using test manual criteria and then rescored using those criteria but eliminating from the error count any dialect miscue. On all three tests, LD children scored lower than control children. Also, the effect of removing dialect miscues as errors caused an overall increase in reading scores on all three tests. On the Gray and Spache tests, but not on the Gilmore test, control children benefited more from the removal of dialect responses as errors than LD children. Additionally, the results indicated that dialect had a greater impact on the scores of the Gilmore than it did on the Gray and Spache tests.