Dynamics of mercury stable isotope compounds in Arctic seals: New insights from a controlled feeding trial on hooded seals Cystophora cristata.

Accurate interpretation of mercury (Hg) isotopic data requires the consideration of several biotic factors such as age, diet, geographical range, and tissue metabolic turnover. A priori knowledge of prey-predator isotopic incorporation rates and Hg biomagnification is essential. This study aims to assess Hg stable isotopes incorporation in an Arctic species of Phocidae, the hooded seal Cystophora cristata, kept in human care for 24 months (2012-2014) and fed on a constant diet of Norwegian Spring Spawning herring Clupea harengus. We measured THg, MMHg and iHg levels, as well as Hg stable isotope composition with both mass dependent (MDF) and mass independent (MIF) fractionation (e.g. δ202Hg and Δ199,200,201,204Hg) in hooded seal kidney, liver, hair and muscle, in addition to herring muscle. We then calculated Hg MDF and MIF isotopic fractionation between hooded seals and their prey. We found a significant shift in δ202Hg between hooded seal hair (+0.80‰) and kidney (-0.78‰), and herring muscle. In hooded seals tissues δ202Hg correlated positively with MMHg percentage. These findings suggest that tissue-specific Hg speciation is the major driver of changes in Hg isotopic fractionation rates in this Arctic predator. Δ199Hg, Δ200Hg, Δ201Hg and Δ204Hg values did not vary between herring and hooded seal tissues, confirming their utility as tracers of Hg marine and atmospheric sources in top predators. To our knowledge, this represents the first attempt to assess complex Hg isotope dynamics in the internal system of Arctic Phocidae, controlling the effects of age, diet, and distribution. Our results confirm the validity of Hg stable isotopes as tracers of environmental Hg sources even in top predators, but emphasize the importance of animal age and tissue selection for inter-study and inter-species comparisons.

Trace element concentrations in common dolphins (Delphinus delphis) in the Celtic Seas ecoregion: Interelement relationships and effects of life history and health status.

Given the increased extraction of trace elements for use by new and emerging technologies, monitoring the environmental fate and potential effects of these compounds within the aquatic environment has never been more critical. Here, hepatic trace element concentrations were assessed in a key sentinel predator, the common dolphin (Delphinus delphis), using a long-term dataset. Variation in concentrations were assessed in relation to other elements, time period, decomposition state, sex, age, total body length, sexual maturity and nutritional status, and cause of death. Additionally, mercury toxicity thresholds for evaluating risk were reviewed and employed. Concentrations of elements which bioaccumulate, THg, MeHg, Cd, and Pb, in addition to Se and V, were strongly correlated with age, and/or body length. An association was observed between Zn concentrations and disease status, with significantly higher concentrations measured in individuals that died from infectious disease, compared to other causes. Strong inter-elemental relationships were detected, namely between Hg and Se, MeHg and Se, Cd and Se, and Cu and Zn. While THg:Se molar ratio values were observed to increase with age and body length, approaching equimolarity. THg was largely comprised of inorganic Hg in older individuals, potentially bound to Se, therefore the effects from THg toxicity may possibly be less important than originally assumed. In contrast, higher MeHg:Hg ratio values were reported in juveniles, suggesting a poorer efficiency in demethylation and a higher sensitivity. The generation of data on proportions of hepatic MeHg and inorganic Hg is highly informative to both future toxicity threshold assessments within pollutant indicator assessments, and to understanding the ultimate fate of mercury in the marine web.

Cobalt(II)-Catalyzed Synthesis of γ-Diketones from Aryl Alkenes and Its Utilization in the Synthesis of Various Heterocyclic Compounds.

An earth-abundant Co(II) salt-catalyzed mild and affordable synthetic route has been developed for the synthesis of industrially relevant 1,4-dicarbonyl compounds (or γ-diketones) via oxidative coupling between aryl alkenes and ketones (both cyclic and acyclic) using TBHP and DBU as the oxidant and base, respectively. 1,4-Dicarbonyl compounds are known to be synthesized using expensive metal catalysts, dual catalysts, or low-cost metal complexes combined with an additive or ligand template, which further needs to be synthesized. Herein, we report the synthesis of 1,4-dicarbonyl compounds using cobalt(II) acetate as a catalyst without any expensive co-catalyst or ligand templates. This methodology has a broad substrate scope with significant yields and good functional group tolerance. Generation of unsymmetrical 1,4-dicarbonyls at room temperature and its versatile synthetic expansion to produce synthetically and biologically valuable heterocyclic compounds are salient features of this novel methodology. In addition, various controlled experiments such as primary kinetic isotope effect study, Hammett analysis with variation of the nature of the substituents on the styrene ring, and theoretical calculations (density functional theory) unravel the mechanistic intricacies involved in this new, simple, and atom-economic methodology.

Sustainable adsorbent frameworks based on bio-resourced materials and biodegradable polymers in selective phosphate removal for waste-water remediation.

Phosphorus to an optimum extent is an essential nutrient for all living organisms and its scarcity may cause food security, and environmental preservation issues vis-à-vis agroeconomic hurdles. Undesirably excess phosphorus intensifies the eutrophication problem in non-marine water bodies and disrupts the natural nutrient balance of the ecosystem. To overcome such dichotomy, biodegradable polymer-based adsorbents have emerged as a cost-effective and implementable approach in striking a "desired optimum-undesired excess" balance pertaining to phosphate in a sustainable manner. So far, the reports on adopting such adsorbent-approach for wastewater remediation remained largely scattered, unstructured, and poorly correlated. In this background, the contextual review comprehensively discusses the current state-of-the-art in utilizing biodegradable polymeric frameworks as an adsorbent system for phosphate removal and its efficient recovery from the aquatic ecosystem, while highlighting their characteristics-specific functional efficiency vis-à-vis easiness of synthetic and commercial viability. The overview further delves into the sources and environmental ramifications of excessive phosphorus in water bodies and associated mechanistic pathways of phosphorus removal via adsorption, precipitation, and membrane filtration enabled by biodegradable (natural and synthetic) polymeric substrates. Finally, functionality optimization, degradability tuning, and adsorption selectivity of biodegradable polymers are highlighted, while aiming to strike a balance in "removal-recovery-reuse" dynamics of phosphate. Thus, the current review not only paves the way for future exploration of biodegradable polymers in sustainable cost-effective adsorbents for phosphorus removal but also can serve as a guide for researchers dealing with this critical issue.

Long-term neuropsychological trajectories in children with epilepsy: does surgery halt decline?

Neuropsychological impairments are common in children with drug-resistant epilepsy. It has been proposed that epilepsy surgery might alleviate these impairments by providing seizure freedom; however, findings from prior studies have been inconsistent. We mapped long-term neuropsychological trajectories in children before and after undergoing epilepsy surgery, to measure the impact of disease course and surgery on functioning. We performed a retrospective cohort study of 882 children who had undergone epilepsy surgery at Great Ormond Street Hospital (1990-2018). We extracted patient information and neuropsychological functioning [obtained from IQ tests (domains: full-scale IQ, verbal IQ, performance IQ, working memory and processing speed) and tests of academic attainment (reading, spelling and numeracy)] and investigated changes in functioning using regression analyses. We identified 500 children (248 females) who had undergone epilepsy surgery [median age at surgery = 11.9 years, interquartile range = (7.8, 15.0)] and neuropsychological assessment. These children showed declines in all domains of neuropsychological functioning in the time leading up to surgery (all P-values ≤0.001; e.g. ßFSIQ = -1.9, SEFSIQ = 0.3, PFSIQ < 0.001). Children lost on average one to four points per year, depending on the domain considered; 27%-43% declined by ≥10 points from their first to their last preoperative assessment. At the time of presurgical evaluation, most children (46%-60%) scored one or more standard deviations below the mean (<85) on the different neuropsychological domains; 37% of these met the threshold for intellectual disability (full-scale IQ < 70). On a group level, there was no change in performance from pre- to postoperative assessment on any of the domains (all P-values ≥0.128). However, children who became seizure free through surgery showed higher postoperative neuropsychological performance (e.g. rrb-FSIQ = 0.37, P < 0.001). These children continued to demonstrate improvements in neuropsychological functioning over the course of their long-term follow-up (e.g. ßFSIQ = 0.9, SEFSIQ = 0.3, PFSIQ = 0.004). Children who had discontinued antiseizure medication treatment at 1-year follow-up showed an 8- to 13-point advantage in postoperative working memory, processing speed and numeracy, and greater improvements in verbal IQ, working memory, reading and spelling (all P-values ≤0.034) over the postoperative period compared with children who were seizure free and still receiving antiseizure medication. In conclusion, by providing seizure freedom and the opportunity for antiseizure medication cessation, epilepsy surgery might not only halt but reverse the downward trajectory that children with drug-resistant epilepsy display in neuropsychological functioning. To halt this decline as soon as possible or, potentially, to prevent it from occurring in the first place, children with focal epilepsy should be considered for epilepsy surgery as early as possible after diagnosis.

Silylation of 2H-indazoles by photoinduced hydrogen atom transfer catalysis.

A metal-free, visible-light-mediated C-H silylation of 2H-indazoles with triphenylsilane has been developed employing 4CzIPN as a photocatalyst and triisopropylsilanethiol as a hydrogen atom transfer (HAT) reagent under aerobic reaction conditions. This method shows tolerance toward many functional groups and affords a variety of silylated indazoles at up to 89% yield. The experimental results suggest that the reaction progresses through a radical pathway.

Prognostic variables predict clinical outcome after decompressive craniectomy: A single institute experience; A retrospective study.

Decompressive craniectomy (DC) is a well-established neurosurgical intervention in patients with high intracranial pressure who fail to respond to medical treatment. Data on predictive factors for functional outcomes in patients with DC who have malignant middle cerebral artery (MCA) infarction as opposed to intracranial hemorrhage (ICH) are scarce. Eighty-four patients who underwent DC treatment for ICH and malignant MCA infarction were examined. All patients underwent surgery in the Bahrain Salmaniya Medical Complex Neurosurgery Unit between January 2017 and June 2021. To determine whether any of these demonstrated a link to the functional outcome, radiographic factors were compared with clinical data. The postsurgical midline shift (MLS) (ICH group) showed the strongest correlation (ρ = 0.434; P = .006), as in the MCA infarction group as well (ρ = 0.46; P = .005). Further analyses using binary logistic regression with postsurgical basal cistern status and ∆ MLS, and it was observed to be statistically significant (odds ratios: 0.067, 95% CI: 0.007, 0.67; P = .021). The initial Glasgow coma scale, postsurgical MLS, basal cistern status, and ∆ are Measurable variables that can be used to predict outcomes in the groups with ICH and MCA infarction.