In vitro Tau Aggregation Inducer Molecules Influence the Effects of MAPT Mutations on Aggregation Dynamics.

Alzheimer's disease (AD) and Alzheimer's disease-related dementias (ADRDs) affect 6 million Americans, and they are projected to have an estimated health care cost of $355 billion for 2021. A histopathological hallmark of AD and many ADRDs is the aberrant intracellular accumulation of the microtubule-associated protein tau. These neurodegenerative disorders that contain tau aggregates are collectively known as tauopathies, and recent structural studies have shown that different tauopathies are characterized by different "strains" of tau filaments. In addition, mutations in the gene that encodes for tau protein expression have been associated with a group of tauopathies known as frontotemporal dementias with parkinsonism linked to chromosome 17 (FTDP-17 or familial frontotemporal dementia). In vitro studies often use small molecules to induce tau aggregation as tau is extremely soluble and does not spontaneously aggregate under typical laboratory conditions, and the use of authentic filaments to conduct in vitro studies is not feasible. This study highlights how different inducer molecules can have fundamental disparities to how disease-related mutations affect the aggregation dynamics of tau. Using three different classes of tau aggregation inducer molecules, we characterized disease-relevant mutations in tau's PGGG motifs at positions P301S, P332S, and P364S. When comparing these mutations to wild-type tau, we found that depending on the type of inducer molecule used, we saw fundamental differences in total aggregation, aggregation kinetics, immunoreactivity, and filament numbers, length, and width. These data are consistent with the possibility that different tau aggregation inducer molecules make different structural polymorphs, although this possibility would need to be confirmed by high-resolution techniques such as cryo-electron microscopy. The data also show that disease-associated missense mutations in tau impact tau aggregation differently depending on the mechanism of aggregation induction.

A review of the effectiveness of vegetated buffers to mitigate pesticide and nutrient transport into surface waters from agricultural areas.

A relatively large number of studies have investigated the effectiveness of vegetated buffer strips at reducing the movement of pesticides and nutrients from agriculture fields. This review outlines the observed influence of different factors (e.g., buffer width, slope, runoff intensity, soil composition, plant community) that can influence the efficacy of vegetated buffers in pesticide and nutrient retention. The reported effectiveness of vegetated buffers reducing the movement of pesticides and nutrients ranged from 10 to 100% and 12-100%, respectively. Buffer width is the factor that is most frequently considered by various jurisdictions when making recommendations on vegetated buffer strip implementation. However, the literature clearly illustrates that there is a great deal of variation in pesticide or nutrient reduction for a given buffer width. This indicates that other factors play an important role in buffer efficacy (e.g., ratio of source area to buffer area, soil composition and structure, runoff intensity, plant community structure) in addition to the width of the vegetative buffer area. These factors need to be considered when making recommendations on vegetated buffer strip construction in agroecosystems. This review has also identified a number of other gaps in the understanding of the effectiveness of vegetated buffers at reducing the movement of pesticides and nutrients from the areas of application.

The role of vegetated buffers in agriculture and their regulation across Canada and the United States.

A vegetated buffer, barrier, or filter strip is a parcel of land that is designated to separate land used for agriculture from valued aquatic or terrestrial habitats. It exists partly with the intent to diffuse runoff and to impeded sediment, nutrients, pesticides, and other constituents from reaching off-site surface waters. Mandatory buffer implementation is regulated at various levels of government in North America - from the federal to the state and provincial levels, and by some municipalities and counties. To better understand the degree and breadth of oversight, we undertook a comprehensive search and review of vegetative buffer regulations across North America. We determined the width of buffer required, under what habitat or field conditions, for which pesticides, and application type, amongst other attributes. For ground application, margins ranged from 1 m to upwards of greater than 4000 m depending on protection goals, with some being compound specific and others being generally applied to all registered pesticides/compounds. These buffers tended to be used most often to protect surface water, groundwater (e.g. drinking water wells), and nearby sensitive crops, but the required distances are generally not consistent between jurisdictions, regardless of the stated protection goals. We recommend that a thorough science-based review take place, with input from relevant stakeholders, to harmonize vegetated buffer size for effective surface water protection where ecological, climatic, and agricultural conditions are sufficiently similar in North America.

Ruthenium Complexes Stabilized by Bidentate Enamido-Phosphine Ligands: Aspects of Cooperative H2 Activation.

Four bidentate, hybrid ligands ((R)(NP)(R')H) featuring imine-nitrogen and alkyl-phosphine donors linked by a cyclopentyl ring were synthesized. The ortho position of the aryl group attached to nitrogen is varied such that R is Me or Pr(i); additionally, the groups decorating phosphorus (R') are varied between Bu(t) or Pr(i). The addition of each ligand to RuHCl(PPr(i)3)2(CO) in the presence of KOBu(t) generates four enamido-phosphine complexes RuH{(R)(NP)(R')}(PPr(i)3)(CO) that were characterized by NMR spectroscopy, elemental analyses, and, in the case of R = Pr(i) and R' = Bu(t) or Pr(i), X-ray crystallography. Depending on R', the reaction of RuH{(R)(NP)(R')}(PPr(i)3)(CO) with H2 generates varying amounts of the imine-phosphine complex RuH2{(R)(NP)(R')H}(PPr(i)3)(CO). Insights into the mechanism of H2 activation by these enamido derivatives were explored using RuH{(Pr)(NP)(Pri)}(PPr(i)3)(CO), for which an intermediate was identified as the dihydrogen-dihydride complex, RuH2(H2){(Pri)(NP)(Pri)H}(PPr(i)3)(CO), on the basis of the T1,min value of 22 ms for the (1)H NMR resonance at δ -7.2 at 238 K (measured at 400 MHz). The N donor of the enamine tautomeric form of the ligand is protonated by H2 or D2 and dissociates from Ru. Tautomerization of the enamine to the imine form of the dissociated arm is involved in formation of the final product.

Vortex formation in a shock-accelerated gas induced by particle seeding.

An instability forms in gas of constant density (air) with an initial nonuniform seeding of small particles or droplets as a planar shock wave passes through the two-phase medium. The seeding nonuniformity is produced by vertical injection of a slow-moving jet of air premixed with glycol droplets or smoke particles into the test section of a shock tube, with the plane of the shock parallel to the axis of the jet. After the shock passage, two counterrotating vortices form in the plane normal to that axis. The physical mechanism of the instability we observe is peculiar to multiphase flow, where the shock acceleration causes the second (embedded) phase to move with respect to the embedding medium. With sufficient seeding concentration, this leads to entrainment of the embedding phase that acquires a relative velocity dependent on the initial seeding, resulting in vortex formation in the flow.

New cyclopentenyl-linked [NPN] ligands and their coordination chemistry with zirconium: synthesis of a dinuclear side-on-bound dinitrogen complex.

The synthesis and characterization of two 1,2-cyclopentyl-bridged diiminophosphine proligands, (CY5)[NPN](DMP)H(2) (CY5 = cyclopentylidene; DMP = 2,6-Me(2)C(6)H(3)) and (CY5)[NPN](DIPP)H(2) (DIPP = 2,6-(i)Pr(2)C(6)H(3)), are presented, and tautomerization to the corresponding 1,2-cyclopentenyl-bridged enamineimine phosphine precursors is reported. These two new proligands are obtained by deprotonation of N-DMP- or N-DIPP-cyclopentylideneimine (N-DMP, 2,6-dimethylphenyl; N-DIPP, 2,6-diisopropylphenyl) and the subsequent addition of 0.5 equiv of dichlorophenylphosphine. Each ligand precursor exists as a mixture of isomers that consist of the diimine, enamineimine, and dienamine tautomers and corresponding stereoisomers, each of which could be identified. The bis(dimethylamido)zirconium complexes (CY5)[NPN](DMP)Zr(NMe(2))(2) and (CY5)[NPN](DIPP)Zr(NMe(2))(2) were prepared directly from the neutral proligands and Zr(NMe(2))(4) via protonolysis. Exchange of the dimethylamido ligands in the latter complexes for chlorides and iodides takes place upon reaction with excess Me(3)SiCl and Me(3)SiI, respectively. A dinuclear zirconium-dinitrogen complex, {(CY5)[NPN](DMP)Zr(THF)}(2)(µ-η(2):η(2)-N(2)), was obtained via KC(8) reduction of (CY5)[NPN](DMP)ZrCl(2) under 4 atm of N(2). On the basis of single-crystal X-ray analysis, N(2) has been reduced to a side-on-bound hydrazido (µ-η(2):η(2)-N(2)(4-)) unit. This dinitrogen complex is thermally unstable and decomposes in solution.

Dalton's and Amagat's laws fail in gas mixtures with shock propagation.

A shock propagating through a gas mixture leads to pressure, temperature, and density increases across the shock front. Rankine-Hugoniot relations correlating pre- and post-shock quantities describe a calorically perfect gas but deliver a good approximation for real gases, provided the pre-shock conditions are well characterized with a thermodynamic mixing model. Two classic thermodynamic models of gas mixtures are Dalton's law of partial pressures and Amagat's law of partial volumes. We measure post-shock temperature and pressure in experiments with nonreacting binary mixtures of sulfur hexafluoride and helium (two dramatically disparate gases) and show that neither model can accurately predict the observed values, on time scales much longer than that of the shock front passage, due to the models' implicit assumptions about mixture behavior on the molecular level. However, kinetic molecular theory can help account for the discrepancy. Our results provide starting points for future theoretical work, experiments, and code validation.

An in situ thermo-mechanical rig for lattice strain measurement during creep using neutron diffraction.

A long-term high-temperature testing stress rig has been designed and fabricated for performing in situ neutron diffraction tests at the ENGIN-X beamline, ISIS facility in the UK. It is capable of subjecting metals to high temperatures up to 800 °C and uniaxial loading under different boundary conditions including constant load, constant strain, and elastic follow-up, each with minimum of external control. Samples are held horizontally between grips and connected to a rigid rig frame, a soft aluminium bar, and a stepper motor with forces up to 20 kN. A new three zone split electrical resistance furnace which generates a stable and uniform heat atmosphere over 200 mm length was used to heat the samples. An 8 mm diameter port at 45° to the centre of the furnace was made in order to allow the neutron beam through the furnace to illuminate the sample. The entire instrument is mounted on the positioner at ENGIN-X and has the potential ability to operate continuously while being moved in and out of the neutron diffraction beam. The performance of the rig has been demonstrated by tracking the evolution of lattice strains in type 316H stainless steel under elastic follow-up control at 550 °C.

Nitrogen and phosphorus runoff losses from variable and constant intensity rainfall simulations on loamy sand under conventional and strip tillage systems.

Further studies on the quality of runoff from tillage and cropping systems in the southeastern USA are needed to refine current risk assessment tools for nutrient contamination. Our objective was to quantify and compare effects of constant (Ic) and variable (Iv) rainfall intensity patterns on inorganic nitrogen (N) and phosphorus (P) losses from a Tifton loamy sand (Plinthic Kandiudult) cropped to cotton (Gossypium hirsutum L.) and managed under conventional (CT) or strip-till (ST) systems. We simulated rainfall at a constant intensity and a variable intensity pattern (57 mm h(-1)) and collected runoff continuously at 5-min intervals for 70 min. For cumulative runoff at 50 min, the Iv pattern lost significantly greater amounts (p < 0.05) of total Kjeldahl N (TKN) and P (TKP) (849 g N ha(-1) and 266 g P ha(-1) for Iv; 623 g N ha(-1) and 192 g P ha(-1) for Ic) than did the Ic pattern. However, at 70 min, no significant differences in total losses were evident for TKN or TKP from either rainfall intensity pattern. In contrast, total cumulative losses of dissolved reactive P (DRP) and NO3-N were greatest for ST-Ic, followed by ST-Iv, CT-Ic, and CT-Iv in diminishing order (69 g DRP ha(-1) and 361 g NO3-N ha(-1); 37 g DRP ha(-1) and 133 g NO3-N ha(-1); 3 g DRP ha(-1) and 58 g NO3-N ha(-1); 1 g DRP ha(-1) and 49 g NO3-N ha(-1)). Results indicate that constant-rate rainfall simulations may overestimate the amount of dissolved nutrients lost to the environment in overland flow from cropping systems in loamy sand soils. We also found that CT treatments lost significantly greater amounts of TKN and TKP than ST treatments and in contrast, ST treatments lost significantly greater amounts of DRP and NO3-N than CT treatments. These results indicate that ST systems may be losing more soluble fractions than CT systems, but only a fraction the total N (33%) and total P (11%) lost through overland flow from CT systems.

Variable rainfall intensity and tillage effects on runoff, sediment, and carbon losses from a loamy sand under simulated rainfall.

The low-carbon, intensively cropped Coastal Plain soils of Georgia are susceptible to runoff, soil loss, and drought. Reduced tillage systems offer the best management tool for sustained row crop production. Understanding runoff, sediment, and chemical losses from conventional and reduced tillage systems is expected to improve if the effect of a variable rainfall intensity storm was quantified. Our objective was to quantify and compare effects of a constant (Ic) intensity pattern and a more realistic, observed, variable (Iv) rainfall intensity pattern on runoff (R), sediment (E), and carbon losses (C) from a Tifton loamy sand cropped to conventional-till (CT) and strip-till (ST) cotton (Gossypium hirsutum L.). Four treatments were evaluated: CT-Ic, CT-Iv, ST-Ic, and ST-Iv, each replicated three times. Field plots (n=12), each 2 by 3 m, were established on each treatment. Each 6-m2 field plot received simulated rainfall at a constant (57 mm h(-1)) or variable rainfall intensity pattern for 70 min (12-run ave.=1402 mL; CV=3%). The Iv pattern represented the most frequent occurring intensity pattern for spring storms in the region. Compared with CT, ST decreased R by 2.5-fold, E by 3.5-fold, and C by 7-fold. Maximum runoff values for Iv events were 1.6-fold higher than those for Ic events and occurred 38 min earlier. Values for Etot and Ctot for Iv events were 19-36% and 1.5-fold higher than corresponding values for Ic events. Values for Emax and Cmax for Iv events were 3-fold and 4-fold higher than corresponding values for Ic events. Carbon enrichment ratios (CER) were or=1.0 for CT plots (except for first 20 min). Maximum CER for CT-Ic, CT-Iv, ST-Ic, and ST-Iv were 2.0, 2.2, 1.0, and 1.2, respectively. Transport of sediment, carbon, and agrichemicals would be better understood if variable rainfall intensity patterns derived from natural rainfall were used in rainfall simulations to evaluate their fate and transport from CT and ST systems.

Optimization of in vitro conditions to study the arachidonic acid induction of 4R isoforms of the microtubule-associated protein tau.

The microtubule-associated protein tau exists in six different isoforms that accumulate as filamentous aggregates in a wide spectrum of neurodegenerative diseases classified as tauopathies. One potential source of heterogeneity between these diseases could arise from differential tau isoform aggregation. in vitro assays employing arachidonic acid as an inducer of aggregation have been pivotal in gaining an understanding of the longest four repeat tau isoform (2N4R). These approaches have been less successful for modeling the shorter 1N4R and 0N4R tau isoforms in vitro. Through a careful analysis of in vitro conditions for aggregation, we found that the differences in the acidity of tau isoform N-terminal projection domains determine whether tau filaments cluster into larger assemblies in solution. Beyond the potential biological implications of filament clustering, we provide optimized conditions for the arachidonic acid induction of shorter 4R tau isoforms aggregation in vitro that greatly reduce filament clustering and improved modeling results.

Effect of boundary conditions on the evolution of lattice strains in a polycrystalline austenitic stainless steel.

The effect of boundary conditions (constant load, constant strain and elastic follow-up) on lattice strain evolution during creep in a polycrystalline austenitic stainless steel was studied using in situ neutron diffraction at 550 °C. The lattice strains were found to remain constant under constant load control. However, under constant strain and elastic follow-up control, the lattice strains relaxed the most in the elastically softest lattice plane {200} and the least in the elastically stiffest lattice plane {111}. The intergranular stresses created between different grain families were constant during creep tests irrespective of the boundary conditions with the initial applied stresses of 250 MPa.

Antibiotic Transport via Runoff and Soil Loss.

Research has verified the occurrence of veterinary antibiotics in manure, agricultural fields, and surface water bodies, yet little research has evaluated antibiotic runoff from agricultural fields. The objective of this study was to evaluate the potential for agricultural runoff to contribute antibiotics to surface water bodies in a worst-case scenario. Our hypothesis was that there would be significant differences in antibiotic concentrations, partitioning of losses between runoff and sediment, and pseudo-partitioning coefficients (ratio of sediment concentration to runoff concentration) among antibiotics. An antibiotic solution including tetracycline (TC), chlortetracycline (CTC), sulfathiazole (STZ), sulfamethazine (SMZ), erythromycin (ERY), tylosin (TYL), and monensin (MNS) was sprayed on the soil surface 1 h before rainfall simulation (average intensity = 60 mm h(-1) for 1 h). Runoff samples were collected continuously and analyzed for aqueous and sediment antibiotic concentrations. MNS had the highest concentration in runoff, resulting in the highest absolute loss, although the amount of loss associated with sediment transport was <10%. ERY had the highest concentrations in sediment and had a relative loss associated with sediment >50%. TYL also had >50% relative loss associated with sediment, and its pseudo-partitioning coefficient (P-PC) was very high. The tetracyclines (TC and CTC) had very low aqueous concentrations and had the lowest absolute losses. If agricultural runoff is proven to result in development of resistance genes or toxicity to aquatic organisms, then erosion control practices could be used to reduce TC, ERY, and TYL losses leaving agricultural fields. Other methods will be needed to reduce transport of other antibiotics.

Synthesis of a sterically bulky diphosphine synthon and Ru(ii) complexes of a cooperative tridentate enamide-diphosphine ligand platform.

In order to generate tridentate enamido diphosphine ligand platforms, we developed procedures for the preparation of tBu2PCH2CH2P(tBu)I, which involve low temperatures, pentane solvent and addition of 4 equiv. of tBuLi to Cl2PCH2CH2PCl2 or 2 equiv. of tBuLi to known Cl(tBu)PCH2CH2P(tBu)Cl also at low temperatures in pentane; an alternate method involves the inverse addition of Cl(tBu)PCH2CH2P(tBu)Cl to 2 equiv. of tBuLi in pentane at 0 °C; all of these methods generate good yields of the tetraphosphine dimer (tBu2PCH2CH2P(tBu))2 contaminated by small amounts of tBu2PCH2CH2PtBu2 (dtbpe), which can be conveniently separated by sublimation. Subsequent oxidative cleavage of the P-P bond with I2 or 1,2-diiodoethane results in the formation of the desired tBu2PCH2CH2P(tBu)I, which undergoes C-P bond formation when added to 1 equiv. of the lithium N-2,6-diisopropylphenylenamide of cyclopentylidene imine to generate the HNPP ligand precursor; this species exists as a tautomeric mixture of the corresponding enamine and imine, the ratio of which depends on workup conditions used. This enamine-imine mixture can be used directly to form Ru(ii) species either directly with heating to generate the five-coordinate (NPP)RuCl(CO) via loss of H2 or by inclusion of 1 equiv. of KOtBu to generate (NPP)RuH(CO). X-ray crystallographic studies confirm that the geometry in the solid state matches the solution spectroscopic data. Subsequent studies of (NPP)RuH(CO) indicate that it reacts with benzaldehyde, benzyl alcohol, and H2 in a cooperative manner to generate a series of hydride carbonyls that have been characterized fully by NMR spectroscopy and X-ray crystallography.

Serum concentrations of tacrine hydrochloride predict its adverse effects in Alzheimer's disease.

OBJECTIVE: To assess the value of serum measurements of tacrine hydrochloride and its metabolite in predicting risk of adverse reaction in Alzheimer's disease. METHODS: The study was an outpatient-based controlled clinical trial. Study subjects were 35 female and 31 male patients who were receiving 50 to 150 mg tacrine hydrochloride per day. RESULTS: Serum concentration of tacrine hydrochloride and ratio of tacrine hydrochloride to metabolite were significantly higher in the 45 patients with symptomatic adverse effects (p < 0.001). The tacrine hydrochloride to metabolite ratio was significantly higher (p < 0.05) in the 30 patients in whom abnormal liver function developed, but concentration of tacrine hydrochloride was not significantly higher. Women showed a higher incidence of adverse effects (p < 0.05), and tacrine hydrochloride concentrations were higher (p < 0.05). Tacrine hydrochloride concentration and tacrine hydrochloride to metabolite ratio were higher in both men and women in whom adverse effects developed. CONCLUSION: Tacrine hydrochloride concentration is valuable in predicting the development of adverse effects, and its measurement may improve the use of the drug.

Pharmacokinetics of tacrine hydrochloride in Alzheimer's disease.

The clinical pharmacokinetics of tacrine hydrochloride have been characterized in patients who have Alzheimer's disease. Serum concentrations of the drug and of its probable metabolite were monitored in eight patients after a 25 mg oral dose, in six patients after a 50 mg oral dose, in four patients after repeated administration of 50 mg, and in two patients after a small intravenous dose. Urinary excretion of drug and metabolite for 24 hours was measured in one of the patients who received a small intravenous dose. The serum half-life was 1.59 +/- 0.15 hours (mean +/- SEM) after the 25 mg dose, 2.14 +/- 0.24 hours after the 50 mg dose, and 2.91 +/- 0.39 hours after continuous treatment. After intravenous administration, clearance was above 600 ml/min in both patients, and oral bioavailability was calculated at below 5%. Urine recovery was less than 3% of the dose. The low bioavailability of tacrine hydrochloride is partly explained by presystemic metabolism.

Comorbidity of attention deficit hyperactivity disorder with early- and late-onset bipolar disorder.

OBJECTIVE: The relationship between attention deficit hyperactivity disorder (ADHD) and earlier age at onset of affective illness was examined in probands with a history of bipolar disorder. METHOD: The authors assessed 56 adult bipolar subjects. Those with a history of childhood ADHD (N=8) were age and sex matched with bipolar subjects without a history of childhood ADHD (N=8). RESULTS: The age at onset of the first affective episode was lower for the subjects with bipolar disorder and a history of childhood ADHD (mean=12.1 years, SD=4.6) than for those without a history of childhood ADHD (mean=20. 0 years, SD=11.3). CONCLUSIONS: ADHD in children of bipolar probands might identify children at highest risk for development of bipolar disorder.

Comparison of the chromatographic characteristics of metabolites of tacrine hydrochloride in human serum and urine with those of in vitro metabolic products from hepatic microsomes.

There may be as many as five metabolites of THA in man, four corresponding to products in the rat. The study provides some evidence that one of major metabolites is 1-hydroxy-THA but lends no support to the putative oxidative deamination pathway.

High speed optical tomography system for imaging dynamic transparent media.

We describe the design and operation of a high speed optical tomography system for measuring two-dimensional images of a dynamic phase object at a rate of 5 kHz. Data from a set of eight Hartmann wavefront sensors is back-projected to produce phase images showing the details of the inner structure of a heated air flow. The tomographic reconstructions have a spatial resolution of approximately 2.0 mm and can measure temperature variations across the flow with an accuracy of about 0.7 C. Series of animated reconstructions at different downstream locations illustrate the development of flow structure and the effect of acoustic flow forcing.

Modified cytotoxic T lymphocyte precursor frequency assay by measuring released europium in a time resolved fluorometer.

The frequency of cytotoxic T lymphocyte precursors (CTLpf) can be quantified by using the principle of limiting dilution analysis (LDA). Chromium 51 (51Cr) and europium (Eu) release assays are based on the measurement of marker release after lysis of targets by the effector cells. Although, 51Cr release has been widely used to quantify cell lysis since its introduction, it has several disadvantages such as handling and disposal of radioisotopes as well as health risk to personnel involved performing the assay. This situation has led us to adopt a non-radioactive cytotoxicity assay. After 7 days culture the PHA-stimulated targets are labeled with europium DTPA chelate. Lysis of labeled targets by effectors releases the Eu-DTPA complex in culture medium--a highly fluorescent substance. The amount of fluorescence can be measured in a time resolved fluorometer. We describe here some modifications of the original protocol which include optimising IL-2 requirements, reduction of incubation times, addition of an extra spin before 37 degrees C incubation, readjustment of target cells per volume of labeling buffer and other crucial parameters increasing the specificity and sensitivity of CTLpf assay. We are in agreement with others that the Eu-release assay is specific and reproducible. It can be used for the CTLpf estimation as well as other T cell and non-T cell cytotoxicity assays.