Simulating rewetting events in intermittent rivers and ephemeral streams: a global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56‐98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached organic matter. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter

Climate change and human pressures are changing the global distribution and the ex‐ tent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico‐chemical changes (precon‐ ditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experi‐ mentally simulated, under standard laboratory conditions, rewetting of leaves, river‐ bed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative character‐ istics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dis‐ solved substances during rewetting events (56%–98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contrib‐ uted most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental vari‐ ables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached sub‐ stances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying event

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Clinical Decision-Making

Eye removal surgery can be challenging clinically for the surgeon and emotionally for the patient. There are three main techniques of eye removal including evisceration (removal of the intraocular contents and cornea with retention of the patient’s sclera and natural extraocular muscle attachments), enucleation (removal of the entire globe with lysis of the natural attachments of the extraocular muscles and severing of the optic nerve proper), and exenteration (removal of the entire orbital contents, including the globe if present). The choice of technique is dependent upon the disease process being addressed and patient factors such as the condition of the native sclera, medical comorbidities, anticoagulation, and the presence and extent of traumatic damage

Prognostic Factors in Aneurysmal Subarachnoid Hemorrhage: Pooled Analyses of Individual Patient Data and Development of Novel Risk Scores in Large Cohorts of International Patients

Primary studies reporting prognostic associations in aneurysmal subarachnoid hemorrhage (SAH) are often insufficiently powered, use data of limited representativeness and scarcely examine the added value of prognostic factors above those of other known factors. Hence, considerable knowledge gaps and conflicting results exist in the literature on the nature and extent of prognostic associations in SAH. Prognostic factors have been combined to develop prediction models and risk scores for early outcome prediction after SAH. None is routinely applied in clinical or research settings; some major constraints relate to lack of evidence on the predictive accuracy, reliability and generalizability of reported risk scores. The global aim of this research was to address these challenges and contribute to improved understanding of prognostic associations in SAH by analysing large cohorts of SAH patients reflecting a broad spectrum of settings. Pooled analyses of patient-level data from multiple randomized clinical trials and prospective hospital registries involving 10963 patients demonstrated a strong prognostic effect of admission neurologic status on 3-month outcome according to Glasgow outcome score. Age had a moderate effect on outcome; premorbid hypertension and subarachnoid clot burden on the Fisher scale were weak predictors of outcome. Patient's sex had no independent predictive value. Prognostic effect of aneurysm size and location depended on treatment modality. Novel prognostic scores were developed combining these predictors for early prediction of mortality and unfavorable outcomes at 3 months, and demonstrated adequate performance at bootstrap (AUC: 0.77 - 0.83) and at cross validation. Using 2 nationally representative administrative datasets, socioeconomic status and race/ethnicity were explored as latent prognostic factors in SAH. Multinomial logistic regression analysis demonstrated socioeconomic status, measured as neighborhood income status, was associated with inpatient mortality risk after admission for SAH. The extent of the association could be related to health care system under which treatment was provided. Race/ethnicity was independently associated with inpatient mortality. Patients of Hispanic ethnicity had the best outcomes and Asia/Pacific Islanders experienced the worst outcomes during the inpatient course. This research has provided higher level evidence than prior studies on studied prognostic factors and reliable tools for early prediction of outcome after hospitalization for SAH.Ph.D

Headache with Aura: A case report of ocular melanoma

Background: Headaches and visual complaints are common conditions encountered in the emergency department. While a patient's age, risk factors, and comorbidities often aid in risk stratification and guide emergency department evaluation, atypical presentations of serious disease may still occur in young otherwise healthy patients Case: In this vignette we discuss a case of ocular (choroidal) melanoma in a 21 year-old female patient who presented with recurrent photopsia and headaches. Discussion: Ocular melanoma is the most common non-skin melanoma and should be considered by the emergency physician for patients with visual deficits. Likely presentations and risk factors for ocular melanoma will be discussed as well as emergency department and specialty management. Published by Elsevier Inc

Optic nerve sheath fenestration: a revised lateral approach for nerve access

Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, describes a disease of poorly understood pathophysiology with a specific set of signs and symptoms including potentially irreversible and blinding visual loss. Optic nerve sheath fenestration (ONSF) is a well-described surgical treatment for patients with IIH and progressive visual loss despite maximally tolerated medical therapy. A number of optic nerve access procedures have been described including medial transconjunctival, superomedial lid crease, and lateral orbitotomy with and without bone takedown. The purpose of this report is to describe a revised lateral approach for temporal optic nerve access that obviates the need to traverse through the intraconal fat of the central surgical space in the previously described lateral approach techniques

Cicatricial ectropion and madarosis associated with panitumumab treatment of metastatic colorectal cancer

To report a case of cicatricial ectropion and madarosis with the use of anti-epidermal growth factor receptor medication panitumumab. An 82-year-old man with metastatic colorectal cancer presented with cicatricial ectropion and madarosis after starting panitumumab, an anti-epidermal growth factor receptor medication used to treat metastatic colorectal cancer. His findings resolved several weeks after discontinuation of panitumumab and treatment with lubrication and antibiotic/steroid ointment. This case demonstrates the importance to consider potential medication side effects when treating periocular conditions in patients taking anti-epidermal growth factor receptor (anti-EGFR) agents