PFOS dominates PFAS composition in ambient fine particulate matter (PM2.5) collected across North Carolina nearly 20 years after the end of its US production

Contamination of drinking water by per- and polyfluoroalkyl substances (PFASs) emitted from manufacturing plants, fire-fighting foams, and urban waste streams has received considerable attention due to concerns over toxicity and environmental persistence; however, PFASs in ambient air remain poorly understood, especially in the United States (US). We measured PFAS concentrations in ambient fine particulate matter (PM_2.5) at 5 locations across North Carolina over a 1 year period in 2019. Thirty-four PFASs, including perfluoroalkyl carboxylic, perfluoroalkane sulfonic, perfluoroalkyl ether carboxylic and sulfonic acids were analyzed by UHPLC/ESI-MS/MS. Quarterly averaged concentrations ranged from <0.004-14.1 pg m^-3. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) ranged from <0.18 to 14.1 pg m^-3, comparable to previous PM_2.5 measurements from Canada and Europe (<0.02-3.5 pg m^-3). Concentrations above 1 pg m^-3 were observed in July-September at Charlotte (14.1 pg m^-3, PFOA), Wilmington (4.75 pg m^-3, PFOS), and Research Triangle Park (1.37 pg m^-3, PFOS). Notably, PM_2.5 has a short atmospheric lifetime (<2 weeks), and thus, the presence of PFOS in these samples raises questions about their sources, since PFOS production was phased out in the US ∼20 years ago. This is the first US study to provide insights into ambient PFAS concentrations in PM_2.5.

Interference by pH and Ca2+ ions during measurements of catecholamine release in slices of rat amygdala with fast-scan cyclic voltammetry

Fast-scan cyclic voltammetry (FSCV) at carbon-fiber microelectrodes was used to investigate catecholamine release and uptake induced by local electrical stimulation of rat brain slices containing the basolateral amygdaloid nucleus. The amygdala contains less catecholamine than the striatum, and the observed release is proportionately smaller. Stimulus trains of long duration were required to obtain a well-resolved concentration change in the basolateral amygdala. Voltammetric detection of catecholamines under these conditions was complicated by interference from two extracellular ions, H+ and Ca2+. Ion-selective microelectrodes were used in conjunction with carbon-fiber microelectrodes to monitor pH and Ca2+. The magnitude of the pH changes was correlated with stimulation length and followed the pattern of a brief alkaline shift followed by a longer acidic shift. Extracellular Ca2+ concentration decreased during stimulation and returned fairly rapidly to baseline after the stimulation was over. Because it was not possible to account for all of the ionic interferences using information in the voltammograms, other strategies were employed. Exposure of amygdala slices to L-DOPA or DA increased electrically evoked release of catecholamine, but the effect was transient, and uptake rates decreased during continued exposure to these agents. The most successful approach to remove the interferences was to subtract the response obtained after exposure of the slice to the catecholamine depleter, Ro 4-1284. This agent eliminates the catecholamine response but does not appear to alter the ionic changes.

Evoked extracellular dopamine in vivo in the medial prefrontal cortex

The measurement of evoked extracellular dopamine in the medial prefrontal cortex by using fast-scan cyclic voltammetry with carbon-fiber microelectrodes was established and release characteristics of mesoprefrontal dopamine neurons were examined in vivo in anesthetized rats. Despite the sparse dopaminergic innervation and the presence of more dense noradrenergic and serotonergic innervations overall in the medial prefrontal cortex, the measurement of extracellular dopamine was achieved by selective recording in dopamine-rich terminal fields and selective activation of ascending dopamine neurons. This was confirmed by electrochemical, pharmacological, and anatomical evidence. An increased release capacity for mesoprefrontal dopamine neurons was also demonstrated by the slower decay of the evoked dopamine response after inhibition of catecholamine synthesis and the maintenance of the evoked dopamine response at higher levels in the medial prefrontal cortex compared with the striatum during supraphysiological stimulation.

The subunit structure of the hemocyanin from the crayfish Jasus edwardsii

The hemocyanin from the crayfish Jasus edwardsii(=lalandii) has been studied using ultracentrifugation, viscosity, circular dichroism and oxygen binding techniques. Sedimentation velocity experiments at pH 7.0 indicated the presence of principal species with S 20w=16.4 S, and at higher pH the presence of a species with S20,w=5.2S. Sedimentation equilibrium experiments yielded molecular weights of 490 000 and 81 000 respectively, indicating that the larger unit is a hexamer of the monomer unit. However, preliminary experiments with gel filtration and electrophoresis under denaturing conditions indicate that more than one monomer species may be present with molecular weight in the range 76-100 000. Circular dichroism (CD) spectra are presented at pH 7.0,8.6,10.0 and 11.0 for oxy-, deoxy- and apo-hemocyanins. Slight differences were observed in the magnitude of the bands in the presence or absence of Mg++. Oxygen binding studies have been made at pH 6.1,7.0,8.8 and 10.6, in the presence of 0.01 M MgCl2. The extent of cooperative binding was indicated by a maximum value of n=3.7, and a pronounced bohr effect was observed.

Pyruvate kinase of Streptococcus lactis

The kinetic properties of pyruvate kinase (ATP:pyruvate-phosphotransferase, EC 2.7.1.40) from Streptococcus lactis have been investigated. Positive homotropic kinetics were observed with phosphoenolpyruvate and adenosine 5'-diphosphate, resulting in a sigmoid relationship between reaction velocity and substrate concentrations. This relationship was abolished with an excess of the heterotropic effector fructose-1,6-diphosphate, giving a typical Michaelis-Menten relationship. Increasing the concentration of fructose-1,6-diphosphate increased the apparent V(max) values and decreased the K(m) values for both substrates. Catalysis by pyruvate kinase proceeded optimally at pH 6.9 to 7.5 and was markedly inhibited by inorganic phosphate and sulfate ions. Under certain conditions adenosine 5'-triphosphate also caused inhibition. The K(m) values for phosphoenolpyruvate and adenosine 5'-diphosphate in the presence of 2 mM fructose-1,6-diphosphate were 0.17 mM and 1 mM, respectively. The concentration of fructose-1,6-diphosphate giving one-half maximal velocity with 2 mM phosphoenolpyruvate and 5 mM adenosine 5'-diphosphate was 0.07 mM. The intracellular concentrations of these metabolites (0.8 mM phosphoenolpyruvate, 2.4 mM adenosine 5'-diphosphate, and 18 mM fructose-1,6-diphosphate) suggest that the pyruvate kinase in S. lactis approaches maximal activity in exponentially growing cells. The role of pyruvate kinase in the regulation of the glycolytic pathway in lactic streptococci is discussed.