Anthropogenic control over wintertime oxidation of atmospheric pollutants.

During winter in the mid-latitudes, photochemical oxidation is significantly slower than in summer and the main radical oxidants driving formation of secondary pollutants, such as fine particulate matter and ozone, remain uncertain, owing to a lack of observations in this season. Using airborne observations, we quantify the contribution of various oxidants on a regional basis during winter, enabling improved chemical descriptions of wintertime air pollution transformations. We show that 25-60% of NOx is converted to N2O5 via multiphase reactions between gas-phase nitrogen oxide reservoirs and aerosol particles, with ~93% reacting in the marine boundary layer to form >2.5 ppbv ClNO2. This results in >70% of the oxidizing capacity of polluted air during winter being controlled, not by typical photochemical reactions, but from these multiphase reactions and emissions of volatile organic compounds, such as HCHO, highlighting the control local anthropogenic emissions have on the oxidizing capacity of the polluted wintertime atmosphere.

The Convective Transport of Active Species in the Tropics (CONTRAST) Experiment.

The Convective Transport of Active Species in the Tropics (CONTRAST) experiment was conducted from Guam (13.5° N, 144.8° E) during January-February 2014. Using the NSF/NCAR Gulfstream V research aircraft, the experiment investigated the photochemical environment over the tropical western Pacific (TWP) warm pool, a region of massive deep convection and the major pathway for air to enter the stratosphere during Northern Hemisphere (NH) winter. The new observations provide a wealth of information for quantifying the influence of convection on the vertical distributions of active species. The airborne in situ measurements up to 15 km altitude fill a significant gap by characterizing the abundance and altitude variation of a wide suite of trace gases. These measurements, together with observations of dynamical and microphysical parameters, provide significant new data for constraining and evaluating global chemistry climate models. Measurements include precursor and product gas species of reactive halogen compounds that impact ozone in the upper troposphere/lower stratosphere. High accuracy, in-situ measurements of ozone obtained during CONTRAST quantify ozone concentration profiles in the UT, where previous observations from balloon-borne ozonesondes were often near or below the limit of detection. CONTRAST was one of the three coordinated experiments to observe the TWP during January-February 2014. Together, CONTRAST, ATTREX and CAST, using complementary capabilities of the three aircraft platforms as well as ground-based instrumentation, provide a comprehensive quantification of the regional distribution and vertical structure of natural and pollutant trace gases in the TWP during NH winter, from the oceanic boundary to the lower stratosphere.

Formaldehyde production from isoprene oxidation across NOx regimes.

The chemical link between isoprene and formaldehyde (HCHO) is a strong, non-linear function of NOx (= NO + NO2). This relationship is a linchpin for top-down isoprene emission inventory verification from orbital HCHO column observations. It is also a benchmark for overall photochemical mechanism performance with regard to VOC oxidation. Using a comprehensive suite of airborne in situ observations over the Southeast U.S., we quantify HCHO production across the urban-rural spectrum. Analysis of isoprene and its major first-generation oxidation products allows us to define both a "prompt" yield of HCHO (molecules of HCHO produced per molecule of freshly-emitted isoprene) and the background HCHO mixing ratio (from oxidation of longer-lived hydrocarbons). Over the range of observed NOx values (roughly 0.1 - 2 ppbv), the prompt yield increases by a factor of 3 (from 0.3 to 0.9 ppbv ppbv-1), while background HCHO increases by a factor of 2 (from 1.6 to 3.3 ppbv). We apply the same method to evaluate the performance of both a global chemical transport model (AM3) and a measurement-constrained 0-D steady state box model. Both models reproduce the NOx dependence of the prompt HCHO yield, illustrating that models with updated isoprene oxidation mechanisms can adequately capture the link between HCHO and recent isoprene emissions. On the other hand, both models under-estimate background HCHO mixing ratios, suggesting missing HCHO precursors, inadequate representation of later-generation isoprene degradation and/or under-estimated hydroxyl radical concentrations. Detailed process rates from the box model simulation demonstrate a 3-fold increase in HCHO production across the range of observed NOx values, driven by a 100% increase in OH and a 40% increase in branching of organic peroxy radical reactions to produce HCHO.

Aqueous-phase mechanism for secondary organic aerosol formation from isoprene: application to the Southeast United States and co-benefit of SO2 emission controls.

Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA), but the mechanism and yields are uncertain. Aerosol is prevailingly aqueous under the humid conditions typical of isoprene-emitting regions. Here we develop an aqueous-phase mechanism for isoprene SOA formation coupled to a detailed gas-phase isoprene oxidation scheme. The mechanism is based on aerosol reactive uptake coefficients (γ) for water-soluble isoprene oxidation products, including sensitivity to aerosol acidity and nucleophile concentrations. We apply this mechanism to simulation of aircraft (SEAC4RS) and ground-based (SOAS) observations over the Southeast US in summer 2013 using the GEOS-Chem chemical transport model. Emissions of nitrogen oxides (NOx ≡ NO + NO2) over the Southeast US are such that the peroxy radicals produced from isoprene oxidation (ISOPO2) react significantly with both NO (high-NOx pathway) and HO2 (low-NOx pathway), leading to different suites of isoprene SOA precursors. We find a mean SOA mass yield of 3.3 % from isoprene oxidation, consistent with the observed relationship of total fine organic aerosol (OA) and formaldehyde (a product of isoprene oxidation). Isoprene SOA production is mainly contributed by two immediate gas-phase precursors, isoprene epoxydiols (IEPOX, 58% of isoprene SOA) from the low-NOx pathway and glyoxal (28%) from both low- and high-NOx pathways. This speciation is consistent with observations of IEPOX SOA from SOAS and SEAC4RS. Observations show a strong relationship between IEPOX SOA and sulfate aerosol that we explain as due to the effect of sulfate on aerosol acidity and volume. Isoprene SOA concentrations increase as NOx emissions decrease (favoring the low-NOx pathway for isoprene oxidation), but decrease more strongly as SO2 emissions decrease (due to the effect of sulfate on aerosol acidity and volume). The US EPA projects 2013-2025 decreases in anthropogenic emissions of 34% for NOx (leading to 7% increase in isoprene SOA) and 48% for SO2 (35% decrease in isoprene SOA). Reducing SO2 emissions decreases sulfate and isoprene SOA by a similar magnitude, representing a factor of 2 co-benefit for PM2.5 from SO2 emission controls.

Organic nitrate chemistry and its implications for nitrogen budgets in an isoprene- and monoterpene-rich atmosphere: constraints from aircraft (SEAC4RS) and ground-based (SOAS) observations in the Southeast US.

Formation of organic nitrates (RONO2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry of RONO2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO2) in the GEOS-Chem global chemical transport model with ∼25 × 25 km2 resolution over North America. We evaluate the model using aircraft (SEAC4RS) and ground-based (SOAS) observations of NOx, BVOCs, and RONO2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas- and particle-phase RONO2 species measured during the campaigns. Gas-phase isoprene nitrates account for 25-50% of observed RONO2 in surface air, and we find that another 10% is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10% of observed boundary layer RONO2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO3 accounts for 60% of simulated gas-phase RONO2 loss in the boundary layer. Other losses are 20% by photolysis to recycle NOx and 15% by dry deposition. RONO2 production accounts for 20% of the net regional NOx sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NOx emissions. This segregation implies that RONO2 production will remain a minor sink for NOx in the Southeast US in the future even as NOx emissions continue to decline.

Instrumentation and Measurement Strategy for the NOAA SENEX Aircraft Campaign as Part of the Southeast Atmosphere Study 2013.

Natural emissions of ozone-and-aerosol-precursor gases such as isoprene and monoterpenes are high in the southeast of the US. In addition, anthropogenic emissions are significant in the Southeast US and summertime photochemistry is rapid. The NOAA-led SENEX (Southeast Nexus) aircraft campaign was one of the major components of the Southeast Atmosphere Study (SAS) and was focused on studying the interactions between biogenic and anthropogenic emissions to form secondary pollutants. During SENEX, the NOAA WP-3D aircraft conducted 20 research flights between 27 May and 10 July 2013 based out of Smyrna, TN. Here we describe the experimental approach, the science goals and early results of the NOAA SENEX campaign. The aircraft, its capabilities and standard measurements are described. The instrument payload is summarized including detection limits, accuracy, precision and time resolutions for all gas-and-aerosol phase instruments. The inter-comparisons of compounds measured with multiple instruments on the NOAA WP-3D are presented and were all within the stated uncertainties, except two of the three NO2 measurements. The SENEX flights included day- and nighttime flights in the Southeast as well as flights over areas with intense shale gas extraction (Marcellus, Fayetteville and Haynesville shale). We present one example flight on 16 June 2013, which was a daytime flight over the Atlanta region, where several crosswind transects of plumes from the city and nearby point sources, such as power plants, paper mills and landfills, were flown. The area around Atlanta has large biogenic isoprene emissions, which provided an excellent case for studying the interactions between biogenic and anthropogenic emissions. In this example flight, chemistry in and outside the Atlanta plumes was observed for several hours after emission. The analysis of this flight showcases the strategies implemented to answer some of the main SENEX science questions.

Low molecular weight proteomic information distinguishes metastatic from benign pheochromocytoma.

Metastatic lesions occur in up to 36% of patients with pheochromocytoma. Currently there is no way to reliably detect or predict which patients are at risk for metastatic pheochromocytoma. Thus, the discovery of biomarkers that could distinguish patients with benign disease from those with metastatic disease would be of great clinical value. Using surface-enhanced laser desorption ionization protein chips combined with high-resolution mass spectrometry, we tested the hypothesis that pheochromocytoma pathologic states can be reflected as biomarker information within the low molecular weight (LMW) region of the serum proteome. LMW protein profiles were generated from the serum of 67 pheochromocytoma patients from four institutions and analyzed by two different bioinformatics approaches employing pattern recognition algorithms to determine if the LMW component of the circulatory proteome contains potentially useful discriminatory information. Both approaches were able to identify combinations of LMW molecules which could distinguish all metastatic from all benign pheochromocytomas in a separate blinded validation set. In conclusion, for this study set low molecular mass biomarker information correlated with pheochromocytoma pathologic state using blinded validation. If confirmed in larger validation studies, efforts to identify the underlying diagnostic molecules by sequencing would be warranted. In the future, measurement of these biomarkers could be potentially used to improve the ability to identify patients with metastatic disease.

Macromolecular solvation energies derived from small molecule crystal morphology.

The morphology of small molecule crystals provides a model for evaluating surface solvation energies in a system with similar packing density to that observed for amino acid residues in proteins. The solvation energies associated with the transfer of methylene and carboxyl groups between vacuum and aqueous phases are estimated to be approx. $40 and -260 cal/A2, respectively, from an analysis of the morphology of succinic acid crystals. These solvation energies predict values for contact angles in reasonable agreement with measurements determined from macroscopic monolayer surfaces. Transfer free energies between vapor and water phases for a series of carboxylic acids are also predicted reasonably well by these solvation energies, provided the surface exposure of different groups is quantitated with the molecular surface area rather than the more traditional accessible surface area. In general, molecular surfaces and molecular surface areas are seen to have important advantages for characterizing the structure and energetics of macromolecular surfaces. Crystal faces of succinic acid with the lowest surface energies in aqueous solution are characteristically smooth. Increasing surface roughness and apolarity are associated with higher surface energies, which suggests an approach for modifying the surface properties of proteins and other macromolecules.

Sensory aprosodia with left hemiparesis from subcortical infarction. Right hemisphere analogue of sensory-type aphasia with right hemiparesis?

We report a case of sensory aprosodia with left hemiparesis following an ischemic infarction of the right thalamus and posterior limb of the internal capsule. Bedside evaluation, confirmed by special quantitative tests, demonstrated normal spontaneous affective prosody and gesturing with marked impairment of affective repetition and comprehension of affective prosody and gestures. A left hemiparesis with sensory loss was also present. This combination of deficits appears to represent the right-side analog to the unusual syndrome of Wernicke-type aphasia with right hemiparesis occasionally observed following left subcortical injury, thus providing further support for the hypothesis that the functional-anatomic organization of affective language in the right hemisphere mirrors that of propositional language in the left.

The exercise test in Andersen syndrome.

BACKGROUND: Andersen syndrome is a rare form of periodic paralysis (PP) associated with dysmorphic features and potentially fatal cardiac dysrhythmias. To date, no electrodiagnostic abnormalities have been reported that can be used to confirm the presence of PP in this condition. OBJECTIVES: To determine if the exercise test could be used to confirm the diagnosis of PP in Andersen syndrome. To evaluate the exercise test as a means to assess neuromuscular status during treatment. METHODS: We performed the exercise test on 2 patients with Andersen syndrome. In 1 patient, we used a modified version of the test to document responsiveness to treatment with tocainide. RESULTS: Studies in both patients demonstrated a progressive decline in the compound muscle action potential amplitude after exercise that was characteristic of the phenomenon seen in other forms of PP. In 1 patient, improvement in interattack strength and a reduction in the number of attacks of weakness correlated with improvement in the test results. CONCLUSIONS: Our cases demonstrate that the exercise test can confirm the diagnosis of PP in Andersen syndrome. A modified version of exercise testing may also be considered as an objective method for documenting treatment responses in PP.

Chronic cryptogenic sensory polyneuropathy: clinical and laboratory characteristics.

BACKGROUND: Chronic sensory-predominant polyneuropathy (PN) is a common clinical problem confronting neurologists. Even with modern diagnostic approaches, many of these PNs remain unclassified. OBJECTIVE: To better define the clinical and laboratory characteristics of a large group of patients with cryptogenic sensory polyneuropathy (CSPN) evaluated in 2 university-based neuromuscular clinics. DESIGN: Medical record review of patients evaluated for PN during a 2-year period. We defined CSPN on the basis of pain, numbness, and tingling in the distal extremities without symptoms of weakness. Sensory symptoms and signs had to evolve for at least 3 months in a roughly symmetrical pattern. Identifiable causes of PN were excluded by history, physical examination findings, and results of laboratory studies. We analyzed clinical and laboratory data from patients with CSPN and compared findings in patients with and without pain. RESULTS: Of 402 patients with PN, 93 (23.1%) had CSPN and stable to slowly progressive PN syndrome. These patients presented with a mean age of 63.2 years and a mean duration of symptoms of 62.9 months. Symptoms almost always started in the feet and included distal numbness or tingling in 86% of patients and pain in 72% of patients. Despite the absence of motor symptoms at presentation, results of motor nerve conduction studies were abnormal in 60% of patients, and electromyographic evidence of denervation was observed in 70% of patients. Results of laboratory studies were consistent with axonal degeneration. Patients with and without pain were similar regarding physical findings and laboratory test abnormalities. Only a few patients (<5%) had no evidence of large-fiber dysfunction on physical examination or electrophysiologic studies. All 66 patients who had follow-up examinations (mean, 12.5 months) remained ambulatory. CONCLUSIONS: Cryptogenic sensory polyneuropathy is a common, slowly progressive neuropathy that begins in late adulthood and causes limited motor impairment. Isolated small-fiber involvement is uncommon in this group of patients. Management should focus on rational pharmacotherapy of neuropathic pain combined with reassurance of CSPN's benign clinical course.

Site of autonomic dysfunction in a patient with Ross' syndrome and postganglionic Horner's syndrome.

Ross' syndrome is a rare peripheral nervous system disorder defined by Adie's tonic pupil, hyporeflexia, and segmental anhidrosis. Injury to postganglionic cholinergic fibers is believed to account for the tonic pupil and sweating disturbance. We report a 47-year-old man found to have Ross' syndrome in combination with a complete postganglionic Horner's syndrome. Pharmacologic and sudomotor tests in this unique patient provide further evidence that Ross' syndrome results from injury to sympathetic and parasympathetic ganglion cells or to their postganglionic projections.

Myasthenia gravis activities of daily living profile.

The authors have developed an MG activities of daily living (ADL) profile (MG-ADL)-a simple eight-question survey of MG symptoms. In 254 consecutive encounters with established MG patients, the authors compared scores from the MG-ADL to the quantitative MG score (QMG)-a standardized, reliable scale used in clinical trials. The mean MG-ADL score was 4.89+/-3.63. The mean QMG score was 10.80+/-5.70. Pearson's correlation coefficient was 0.583 (p < 0.001). The MG-ADL is an easy-to-administer survey of MG that correlates well with the QMG and can serve as a secondary efficacy measurement in clinical trials.

Acetylcholine receptor antibodies in the Lambert-Eaton myasthenic syndrome.

Two patients were initially diagnosed with myasthenia gravis with elevated titers of acetylcholine receptor antibodies. Features including weakness that normalized with sustained contraction, areflexia, autonomic symptoms, and low-amplitude baseline compound muscle action potentials with abnormal increments following brief exercise and high-frequency repetitive stimulation, however, suggested that these patients had Lambert-Eaton myasthenic syndrome. One patient had antibodies directed against presynaptic calcium channels, confirming the diagnosis. The second patient was seronegative for these antibodies but had elevated titers of antistriated muscle antibodies. This shows that serologic studies can conflict with clinical and electrodiagnostic findings in patients with Lambert-Eaton syndrome. These cases also point out that acetylcholine receptor antibodies are not necessarily diagnostic of myasthenia gravis in patients with Lambert-Eaton syndrome. Instead, these antibodies could represent a nonpathogenic epiphenomenon.

Electrophysiologic findings in multifocal motor neuropathy.

We performed detailed electrophysiologic studies on 16 patients with clinically defined multifocal motor neuropathy and found a wide spectrum of demyelinating features. Only five patients (31%) had conduction block in one or more nerves. However, in 15 patients (94%) at least one nerve showed other features of demyelination. We also noted a significant degree of superimposed axonal degeneration in 15 patients. Eight patients (50%) had individual nerves with pure axonal injury, despite the presence of demyelinating features in other nerves. Antiganglioside antibodies were elevated in four of five patients with conduction block and five of 11 patients without conduction block. We conclude that multifocal motor neuropathy is characterized electrophysiologically by a wide spectrum of axonal and demyelinating features. Diagnostic criteria requiring conduction block may lead to underdiagnosis of this potentially treatable neuropathy.

Primary hyperparathyroidism and ALS: is there a relation?

BACKGROUND: An association between primary hyperparathyroidism (PHP) and amyotrophic lateral sclerosis (ALS) has been noted; however, a causal relation between these disorders has not been confirmed. PATIENTS/METHODS: We report five patients (three men, two women) meeting El Escorial criteria for ALS who also had PHP. In three patients, the diagnosis of PHP was made during the laboratory evaluation for motor neuron disease, and in one patient, the diagnosis of PHP preceded the onset of weakness by 5 months and in another by 2 years. Serum calcium levels in all five patients were elevated, ranging from 11.2 to 12.8 mg/dL (normal, <10.4 mg/dL), as were levels of parathyroid hormone (PTH). RESULTS: All five patients underwent parathyroid adenoma resection with subsequent normalization of serum calcium and PTH levels. Each patient had progressive weakness resulting in death 1 to 3 years following parathyroidectomy. CONCLUSION: Resection of parathyroid adenomas in patients meeting El Escorial criteria for ALS did not alter the course of ALS. PHP and ALS appear to be coexisting but unrelated disorders.

The wide spectrum of myofibrillar myopathy suggests a multifactorial etiology and pathogenesis.

BACKGROUND: Myofibrillar myopathy (MFM) is characterized by nonhyaline lesions (foci of myofibrillar destruction) and hyaline lesions (cytoplasmic inclusions composed of compacted myofibrillar residues) on light and electron microscopy. Immunocytochemistry demonstrates the abnormal expression of desmin and numerous other proteins. The clinical, laboratory, and histologic features of MFM are heterogeneous, making a diagnosis difficult. RESULTS: We diagnosed eight patients with MFM over the preceding 3 years. MFM was inherited in an autosomal dominant pattern in one patient, developed sporadically in five patients, and was induced by an experimental chemotherapy, Elinafide (Knoll, Parsippany, NJ), in two patients. Age at onset ranged from 14 to 64 years. The pattern of weakness was variable but involved proximal and distal muscles. Five patients had evidence of a cardiomyopathy. Electromyography demonstrated muscle membrane instability and small, polyphasic motor unit potentials. Serum creatine kinase levels were normal to moderately elevated (<10x normal). Light and electron microscopy demonstrated the characteristic pattern of nonhyaline and hyaline lesions and the associated abnormalities on immunocytochemistry. CONCLUSIONS: Patients demonstrate a wide spectrum of clinical, laboratory, and histologic abnormalities. Chemotherapy-induced MFM has abnormalities on immunocytochemistry similar to the those of hereditary and sporadic cases. The pathogenesis of MFM is likely heterogeneous. However, MFM is distinctive in that it can preferentially affect distal muscles and has a frequent association with cardiomyopathy. The cardiomyopathy may be amenable to treatment with pacemaker insertion or cardiac transplantation.

Axonal multifocal motor neuropathy without conduction block or other features of demyelination.

BACKGROUND: Conduction block is considered an essential finding for the distinction between motor neuropathies and lower motor neuron disorders. Only a small number of reports describe patients with multifocal motor neuropathies who lack overt conduction block, although in these cases other features of demyelination still suggest the presence of a demyelinating disorder. In contrast, a purely axonal multifocal motor neuropathy has not been described. METHODS: This report describes nine patients with slowly or nonprogressive multifocal motor neuropathies who had purely axonal electrodiagnostic features. RESULTS: GM1 antibodies titers were normal in all nine cases. Six patients were treated with either prednisone or IV immunoglobulin and three showed convincing improvement. CONCLUSIONS: These findings suggest an immune-mediated motor neuropathy with axonal electrophysiologic features that appears to be distinct from both multifocal motor neuropathy and established motor neuron disorders.

Brachial amyotrophic diplegia: a slowly progressive motor neuron disorder.

OBJECTIVE: To describe a sporadic motor neuron disorder that remains largely restricted to the upper limbs over time. BACKGROUND: Progressive amyotrophy that is isolated to the upper limbs in an adult often suggests ALS. The fact that weakness can remain largely confined to the arms for long periods of time in individuals presenting with this phenotype has not been emphasized. METHODS: We reviewed the records of patients who had a neurogenic "man-in-the-barrel" phenotype documented by examination at least 18 months after onset. These patients had severe bilateral upper-extremity neurogenic atrophy that spared lower-extremity, respiratory, and bulbar musculature. RESULTS: Nine of 10 patients meeting these criteria had a purely lower motor neuron disorder. During follow-up periods ranging from 3 to 11 years from onset, only three patients developed lower-extremity weakness, and none developed respiratory or bulbar dysfunction or lost the ability to ambulate. CONCLUSION: Patients presenting with severe weakness that is fully isolated to the upper limbs, without pyramidal signs, may have a relatively stable variant of motor neuron disease.