Attenuation of cardiovascular remodeling in DOCA-salt rats by the vasopeptidase inhibitor, omapatrilat

Omapatrilat, a vasopeptidase inhibitor, inhibits both neutral endopeptidase and angiotensin-converting enzyme with similar potency. The aim of this study was to investigate whether omapatrilat prevents or reverses cardiovascular remodeling and hypertension in deoxycorticosterone acetate (DOCA)-salt rats. Male Wistar rats (313 2 g, n=114) were uninephrectomized (UNX) with or without further treatment with DOCA and 1% NaCl in the drinking water. Compared with UNX control rats, DOCA-salt rats developed hypertension, cardiovascular hypertrophy, perivascular and interstitial cardiac fibrosis and inflammation, endothelial dysfunction, and the prolongation of ventricular action potential duration within four weeks. The administration of omapatrilat (40 mg/kg/day po) for two weeks commencing two weeks after surgery attenuated the development of cardiovascular hypertrophy, inflammation, fibrosis, and ventricular action potential prolongation. In contrast, omapatrilat treatment did not lower systolic blood pressure nor improve endothelial dysfunction. This study concludes that the renin-angiotensin-aldosterone, natriuretic peptide, and bradykinin systems are directly involved in the pathogenesis of cardiovascular remodeling in the DOCA-salt model of hypertension in rats, which may be independent of their effects on blood pressure.

Improved cardiovascular function with aminoguanidine in DOCA-salt hypertensive rats

1 The ability of aminoguanidine (AG), an inhibitor of collagen crosslinking, to prevent changes in cardiac and vascular structure and function has been determined in the deoxycorticosterone acetate (DOCA)-salt hypertensive rat as a model of the cardiovascular remodelling observed in chronic human hypertension. 2 Uninephrectomized rats (UNX) administered DOCA (25 mg every fourth day s.c.) and 1% NaCl in drinking water for 28 days developed cardiovascular remodelling shown as systolic hypertension, left ventricular hypertrophy, increased thoracic aortic and left ventricular wall thickness, increased left ventricular inflammatory cell infiltration together with increased interstitial collagen and increased passive diastolic stiffness, impaired contractility, prolongation of the action potential duration and vascular dysfunction. 3 Treatment with AG (0.05-0.1% in drinking water; average 182 +/- 17 mg kg(-1) day(-1) in DOCA-salt rats) decreased blood pressure (DOCA-salt 176 +/- 4; + AG 144 +/- 5 mmHg; *P < 0.05 vs DOCA-salt), decreased left ventricular wet weights (DOCA-salt 3.17 +/- 0.07; + AG 2.66 +/- 0.08 mg g(-1) body wt*), reduced diastolic stiffness constant (DOCA-salt 30.1 +/- 1.2; + AG 24.3 +/- 1.2* (dimensionless)), improved cardiac contractility (DOCA-salt 1610 +/- 130; + AG 2370 +/- 100 mmHg s(-1)*) and vascular reactivity (3.4-fold increase in maximal contractile response to noradrenaline, 3.2-fold increase in maximal relaxation response to acetylcholine, twofold increase in maximal relaxation response to sodium nitroprusside) and prolonged the action potential duration at 50% repolarization without altering collagen content or inflammatory cell infiltration. 4 Thus, cardiovascular function in DOCA-salt hypertensive rats can be improved by AG independent of changes in collagen content. This suggests that collagen crosslinking is an important cause of cardiovascular dysfunction during cardiovascular remodelling in hypertension.

Rainfall salt accessions in the Queensland Murray-Darling Basin

Two east - west transects were established in southern Queensland to quantify rainfall inputs of chloride and associated ions. Electrical conductivity, pH, and major and minor ions were measured at 9 sites within the Queensland Murray - Darling Basin and 1 site to the east. Variability at some sites was high, possibly a function of the sample collection method. Ionic concentrations decreased with distance inland, a trend similar to that observed elsewhere in Australia, although values closer to the coast were higher than observed in southern and western Australia. Equations to predict both annual average rainfall chloride mass deposition and total salt deposition were derived.

Rosuvastatin attenuates hypertension-induced cardiovascular remodeling without affecting blood pressure in DOCA-salt hypertensive rats

The pleiotropic effects of statins represent potential mechanisms for the treatment of end-organ damage in hypertension. This study has investigated the effects of rosuvastatin in a model of cardiovascular remodeling, the DOCA-salt hypertensive rat. Male Wistar rats weighing 300 to 330 g were uninephrectomized (UNX) or UNX and treated with DOCA (25 mg subcutaneously every fourth day) and 1% NaCl in the drinking water. Compared with UNX controls, DOCA-salt rats developed hypertension, cardiovascular hypertrophy, inflammation with perivascular and interstitial cardiac fibrosis, endothelial dysfunction, and prolongation of ventricular action potential duration at 28 days. Rosuvastatin-treated rats received 20mg/kg/d of the drug in 10% Tween 20 by oral gavage for 32 days commencing 4 days before uninephrectomy. UNX and DOCA-salt controls received vehicle only. Rosuvastatin therapy attenuated the development of cardiovascular hypertrophy, inflammation, fibrosis, and ventricular action potential prolongation, but did not modify hypertension or vascular dysfunction. We conclude that the pleiotropic effects of rosuvastatin include attenuation of aspects of cardiovascular remodeling in the DOCA-salt model of hypertension in rats without altering systolic blood pressure.

Vascular remodelling in the internal mammary artery graft and association with elevated endothelin-1 expression

Introduction: The vasoconstricting peptide Endothelin-1 (ET-1) has been associated with atherosclerotic cardiovascular disease, AAA, hypertension and hypercholesterolemia. It is known to stimulate quiescent vascular smooth muscle cells (VSMC) into the growth cycle and has been linked to intimal thickening following endothelial injury and is associated with vessel wall remodelling in salt-sensitive hypertension models. Enhanced ET-1 expression has been reported in the internal mammary artery (IMA) and was markedly higher in patients undergoing cardiac bypass surgery who were diabetic and /or hypercholesterolemic. Aims: To firstly review the histopathology of the IMA and secondly, determine the relationship between ET-1 expression in this vessel and mitogenic activity in the medial VSMC. Methods: Vessel tissue collected at the time of CABG surgery was formalin-fixed and paraffin-embedded for histological investigation. Cross sections of the left distal IMAwere stained with Alcian Blue/Verhoeff’s van Gieson to assess medial degeneration and identify the elastic lamellae and picrosirius red to determine the collagen content (specifically type I and type III). Immunohistochemistry staining was used to assess VSMC growth (PCNA label), tissue ET-1 expression, VSMC (SMCa-actin) area and macrophage/monocyte (anti-CD68) infiltration. Quantitative analysis was performed to measure the VSMC area in relation to ET-1 staining. Results: Fifty-five IMA specimens from the CABG patients (10F; 45M; mean age 65 years) were collected for this study. Fourteen donor IMAspecimens were used as controls (7F; 7M; mean age 45 years). Significant medial hypertrophy, VSMC disorganisation and elastic lamellae destruction was detected in the CABG IMA. The amount of Alcian blue staining in the CABG IMA was almost double that of the control (31.85+/14.52% Vs 17.10+/9.96%, P= .0006). Total collagen and type I collagen content was significantly increased compared with controls (65.8+/18.3% Vs 33.7 + / 13.7%, P= .07), (14.2 + /10.0% Vs 4.8 + /2.8%, P= .01), respectively. Tissue ET-1 and PCNA labelling were also significantly elevated the CABG IMA specimens relative to the controls (69.99 + /18.74%Vs 23.33 + /20.53%, P= .0001, and 37.29 + /12.88% Vs 11.06 + /8.18, P= .0001), respectively. There was mild presence of macrophages and monocytes in both CABG and control tissue. Conclusions: The IMA from CABG patients has elevated levels of type I collagen in the extracellular matrix indicative of fibrosis and was coupled with deleterious structural remodelling. Abnormally high levels of ET-1 were measured in the medial SMC layer and was associated with VSMC growth but not related to any chronic inflammatory response within the vessel wall.

Bile-salt-induced aggregation of poly(N-isopropylacrylamide) and lowering of the lower critical solution temperature in aqueous solutions

The effect of sodium cholate (NaC; concentration 1-16 mM), a biological surfactant, on the aggregation behavior of 1% (w/v, 2.2 × 10(-3) M) poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions was studied as a function of temperature. From turbidity, dynamic light scattering, viscosity, and fluorescence measurements, it was observed that (i) there is NaC-induced nanoscale aggregation of PNIPAM in its sol state and (ii) the lower critical solution temperature corresponding to sol-gel transition shifts to a lower temperature by about 2 °C.

Renal dopamine and salt-retaining states

Although generally regarded as a neurotransmitter, dopamine is also known to be secreted by the kidney whereby it promotes sodium excretion in its role as a natriuretic honnone. Peripheral dopamine may be formed by two alternative pathways; the decarboxylation of circulating L-Dopa by L-aromatic amino acid decarboxylase (LAAAD), and the desulphation of dopamine sulphate by arylsulphatase A (ASA), the latter being poorly represented in the literature. In many conditions and diseases with which sodium retention is associated, a reduced urinary excretion of dopamine has been noted implicating the involvement of dopamine in the maintenance of sodium homeostasis.This study investigates renal dopamine production via the desulphation of dopamine sulphate in a sample cohort during normal unregulated dietary sodium intake and following a low sodium regimen. After dietary salt restriction urinary dopamine sulphate levels were significantly increased, indicating that dopamine sulphate is indeed a physiological reservoir of active free dopamine, the necessity for which is reduced during self depletion. This confirmed the dopamine/dopamine sulphate pathway as one which may be relevant to the maintenance of sodium homeostasis. The activity of urinary ASA was investigated in diabetes mellitus as an example of a sodium-retaining state, and compared with that in a matched normal control group. A decreased ASA activity was anticipated, given the blunted dopamine excretion observed in many sodium-retaining states, however an unexpected increase in activity in the diabetic group was observed. Enzyme kinetic analysis of ASA showed that this was not due to the existence of an isoform having an altered affinity for dopamine sulphate. This rather paradoxical situation, that urinary-dopamine is decreased while ASA activity is increased, may be explained by the sequestering of free dopamine by autoxidation to 6-hydroxydopamine as has been hypothesised recently to occur in diabetes mellitus. To confirm the homogeneity of ASA in the normal and diabetic groups, four amplicons spanning the 3637bp intronic and exonic regions of the gene were generated by PCR. These were sequence utilising a fluorescent-dye terminator reaction using the forward PCR primer as sequencing primer. Although single nucleotide polymorphisms were observed between the two groups these occurred either in intronic regions or, when exonic, generated silent mutations, supporting the enzyme kinetic data. The expression of ASA was investigated to determine the basis of the increased activity observed in diabetes mellitus. Although a validated comparative RT-PCR assay was developed for amplification of arsa transcripts from fresh blood samples, expression analysis from archived paraffin-embedded renal tissue was complicated by the low yield and degradation of unprotected mRNA. Suggestions for the development of this work using renal cell-culture are discussed.

Improving the solubility and dissolution of poorly soluble drugs by salt formation and the consequent effect on mechanical properties

The bioavailability of BCS II compounds may be improved by an enhanced solubility and dissolution rate. Four carboxylic acid drugs were selected, which were flurbiprofen, etodolac, ibuprofen and gemfibrozil. The drugs were chosen because they are weak acids with poor aqueous solubility and should readily form salts. The counterions used for salt formation were: butylamine, pentylamine, hexylamine, octylamine, benzylamine, cyclohexylamine, tert-butylamine, 2-amino-2-methylpropan­2-ol, 2-amino-2-methyl propan-1,3-ol and tromethamine. Solubility was partially controlled by the saturated solution pH with the butylamine counterion increasing the solution pH and solubility and dissolution to the greatest extent. As the chain length increased, solubility was reduced due to the increasing lipophilic nature of the counterion. The benzylamine and cyclohexylamine counterions produced crystalline, stable salts but did not improve solubility and dissolution significantly compared to the parent compound. The substitution of hydroxyl groups to tert-butylamine counterions produced an increase in solubility and dissolution. AMP2 resulted in the most enhanced solubility and dissolution compared to the parent drug but using the tris salt did not further improve solubility due to a very stable crystal lattice structure. The parent drugs were very difficult to compress due to orientation effects and lamination. Compacts were prepared of each parent drug and salt and their modulus of elasticity values were measured using a three-point bend (Young’s modulus, E0) were extrapolated to zero porosity and compared. Compressibility and E0 were improved with the butylamine, tert-butylamine, cyclohexylamine and AMP2 counterions. The most significant improvement in compression and E0 was with the AMP2 salts. Mechanical properties were related to the hydrogen bonding within the crystal lattice structure for the gemfibrozil salt series.

A greenhouse integrating desalination, water saving and rainwater harvesting for use in salt-affected inland regions

This study proposes a new type of greenhouse for water re-use and energy saving for agriculture in arid and semi-arid inland regions affected by groundwater salinity. It combines desalination using reverse osmosis (RO), re-use of saline concentrate rejected by RO for cooling, and rainwater harvesting. Experimental work was carried at GBPUAT, Pantnagar, India. Saline concentrate was fed to evaporative cooling pads of greenhouse and found to evaporate at similar rates as conventional freshwater. Two enhancements to the system are described: i) A jet pump, designed and tested to use pressurized reject stream to re-circulate cooling water and thus maintain uniform wetness in cooling pads, was found capable of multiplying flow of cooling water by a factor of 2.5 to 4 while lifting water to a head of 1.55 m; and ii) Use of solar power to drive ventilation fans of greenhouse, for which an electronic circuit has been produced that uses maximum power-point tracking to maximize energy efficiency. Re-use of RO rejected concentrate for cooling saves water (6 l d-1 m-2) of greenhouse floor area and the improved fan could reduce electricity consumption by a factor 8.

Molecular mechanisms of salt effects on carbon nanotube dispersions in an organic solvent (N-methyl-2-pyrrolidone)

We consider the effects of salt (sodium iodide) on pristine carbon nanotube (CNT) dispersions in an organic solvent, N-methyl-2-pyrrolidone (NMP). We investigate the molecular-scale mechanisms of ion interactions with the nanotube surface and we show how the microscopic ion-surface interactions affect the stability of CNT dispersions in NMP. In our study we use a combination of fully atomistic Molecular Dynamics simulations of sodium and iodide ions at the CNT-NMP interface with direct experiments on the CNT dispersions. In the experiments we analyze the effects of salt on the stability of the dispersions by photoluminescence (PL) and optical absorption spectroscopy of the samples as well as by visual inspection. By fully atomistic Molecular Dynamics simulations we investigate the molecular-scale mechanisms of sodium and iodide ion interactions with the nanotube surface. Our simulations reveal that both ions are depleted from the CNT surface in the CNT-NMP dispersions mainly due to the two reasons: (1) there is a high energy penalty for the ion partial desolvation at the CNT surface; (2) NMP molecules form a dense solvation layer at the CNT surface that prevents ions to come close to the CNT surface. As a result, an increase of the salt concentration increases the "osmotic" stress in the CNT-NMP system and, thus, decreases the stability of the CNT dispersions in NMP. Direct experiments confirm the simulation results: addition of NaI salt into the NMP dispersions of pristine CNTs leads to precipitation of CNTs (bundle formation) even at very small salt concentration (∼10 -3 mol L -1). In line with the simulation predictions, the effect increases with the increase of the salt concentration. Overall, our results show that dissolved salt ions have strong effects on the stability of CNT dispersions. Therefore, it is possible to stimulate the bundle formation in the CNT-NMP dispersions and regulate the overall concentration of nanotubes in the dispersions by changing the NaI concentration in the solvent. © 2012 The Royal Society of Chemistry.

I.~Synthesis, isolation, and characterization of 1-(2-anthryl)-2-cyclopropylethylene and 1-(2-naphthyl)-2-cyclopropylethylene. II.~Titanium dioxide photocatalysis of haloethers: A mechanistic study

I. The target molecules are classified as 1-aryl 2-cyclopropyl substituted ethylene. In the ground state, these molecules have a number of conformers, which are in equilibrium through rotation about single bonds. Once excited, the conformers have fixed conformation and are no longer in equilibrium and can be distinguished by their UV-vis as well as fluorescence spectra. The synthetic strategy involves standard steps. Both 2-methylanthracene and 2-methylnaphthalene were brominated using N-bromosuccinimide to give the bromomethyl adduct, which then was reacted with triphenylphosphine to form the phosphonium salt. This was followed by the formation of the phosphorus ylide, which upon treatment with cyclopropanecarboxaldehyde gave the product.^ II. The degradation of three aliphatic haloethers: bis-(2-chloroethyl) ether, bis-(2-chloroisopropyl) ether, and bis-(2-chloroethoxy)methane and two aromatic haloethers: 4-chlorodiphenyl ether and 4-bromodiphenyl ether was studied. Product studies have been conducted on the titanium dioxide photocatalysis of these compounds including mass balance, monitoring and identifying intermediates to establish the reaction pathways to deduce a mechanism for their degradation. The extent of mineralization was determined from the measurement of halogen anion (Cl$\sp-$/Br$\sp-$) as well as total organic carbon. The relative rates of disappearance of the individual haloethers appear to be related to the hydrophobic character of the given compound. Reaction mechanisms involving hydroxyl radical are proposed to explain the observed results. ^

Tracking rates of ecotone migration due to salt-water encroachment using fossil mollusks in coastal South Florida

We determined the rate of migration of coastal vegetation zones in response to salt-water encroachment through paleoecological analysis of mollusks in 36 sediment cores taken along transects perpendicular to the coast in a 5.5 km2 band of coastal wetlands in southeast Florida. Five vegetation zones, separated by distinct ecotones, included freshwater swamp forest, freshwater marsh, and dwarf, transitional and fringing mangrove forest. Vegetation composition, soil depth and organic matter content, porewater salinity and the contemporary mollusk community were determined at 226 sites to establish the salinity preferences of the mollusk fauna. Calibration models allowed accurate inference of salinity and vegetation type from fossil mollusk assemblages in chronologically calibrated sediments. Most sediments were shallow (20–130 cm) permitting coarse-scale temporal inferences for three zones: an upper peat layer (zone 1) representing the last 30–70 years, a mixed peat-marl layer (zone 2) representing the previous ca. 150–250 years and a basal section (zone 3) of ranging from 310 to 2990 YBP. Modern peat accretion rates averaged 3.1 mm yr)1 while subsurface marl accreted more slowly at 0.8 mm yr)1. Salinity and vegetation type for zone 1 show a steep gradient with freshwater communities being confined west of a north–south drainage canal constructed in 1960. Inferences for zone 2 (pre-drainage) suggest that freshwater marshes and associated forest units covered 90% of the area, with mangrove forests only present along the peripheral coastline. During the entire pre-drainage history, salinity in the entire area was maintained below a mean of 2 ppt and only small pockets of mangroves were present; currently, salinity averages 13.2 ppt and mangroves occupy 95% of the wetland. Over 3 km2 of freshwater wetland vegetation type have been lost from this basin due to salt-water encroachment, estimated from the mollusk-inferred migration rate of freshwater vegetation of 3.1 m yr)1 for the last 70 years (compared to 0.14 m yr)1 for the pre-drainage period). This rapid rate of encroachment is driven by sea-level rise and freshwater diversion. Plans for rehydrating these basins with freshwater will require high-magnitude re-diversion to counteract locally high rates of sea-level rise.

Effect of arginine and oscillatory calcium ion (II) on vascular response mediated via nitric oxide signaling in normal and salt sensitive hypertensive rat mesenteric arterioles

Hypertension, a major risk factor in the cardiovascular system, is characterized by an increase in the arterial blood pressure. High dietary sodium is linked to multiple cardiovascular disorders including hypertension. Salt sensitivity, a measure of how the blood pressure responds to salt intake is observed in more than 50% of the hypertension cases. Nitric Oxide (NO), as an endogenous vasodilator serves many important biological roles in the cardiovascular physiology including blood pressure regulation. The physiological concentrations for NO bioactivity are reported to be in 0-500 nM range. Notably, the vascular response to NO is highly regulated within a small concentration spectrum. Hence, much uncertainty surrounds how NO modulates diverse signaling mechanisms to initiate vascular relaxation and alleviate hypertension. Regulating the availability of NO in the vasculature has demonstrated vasoprotective effects. In addition, modulating the NO release by different means has proved to restore endothelial function. In this study we addressed parameters that regulated NO release in the vasculature, in physiology and pathophysiology such as salt sensitive hypertension. We showed that, in the rat mesenteric arterioles, Ca2+ induced rapid relaxation (time constants 20.8 ± 2.2 sec) followed with a much slower constriction after subsequent removal of the stimulus (time constants 104.8 ± 10.0 sec). An interesting observation was that a fourfold increase in the Ca 2+ frequency improved the efficacy of arteriolar relaxation by 61.1%. Our results suggested that, Ca2+ frequency-dependent transient release of NO from the endothelium carried encoded information; which could be translated into different steady state vascular tone. Further, Agmatine, a metabolite of L-arginine, as a ligand, was observed to relax the mesenteric arterioles. These relaxations were NO-dependent and occurred via &agr;-2 receptor activity. The observed potency of agmatine (EC50, 138.7 ± 12.1 ± μM; n=22), was 40 fold higher than L-arginine itself (EC50, 18.3 ± 1.3 mM; n = 5). This suggested us to propose alternative parallel mechanism for L-arginine mediated vascular relaxation via arginine decarboxylase activity. In addition, the biomechanics of rat mesentery is important in regulation of vascular tone. We developed 2D finite element models that described the vascular mechanics of rat mesentery. With an inverse estimation approach, we identified the elasticity parameters characterizing alterations in normotensive and hypertensive Dahl rats. Our efforts were towards guiding current studies that optimized cardiovascular intervention and assisted in the development of new therapeutic strategies. These observations may have significant implications towards alternatives to present methods for NO delivery as a therapeutic target. Our work shall prove to be beneficial in assisting the delivery of NO in the vasculature thus minimizing the cardiovascular risk in handling abnormalities, such as hypertension.

Tracking the Effects of Salt Water Encroachment on South Florida Coastal Ecotones Using Mollusks

Many coastal wetland communities of south Florida have been cut off from freshwater sheet flow for decades and are migrating landward due to salt-water encroachment. A paleoecological study using mollusks was conducted to assess the rates and effects of salt-water encroachment due to freshwater diversion and sea level rise on coastal wetland basins in Biscayne National Park. Modem mollusk distributions taken from 226 surface sites were used to determine local habitat affinities which were applied to infer past environments from mollusk distributions found in soil cores. Mollusks species compositions were found to be strongly correlated to habitat and salinity, providing reliable predictions. Wetland soils were cored to bedrock at 36locations. Mollusks were abundant throughout the cores and 15 of the 20 most abundant taxa served as bioindicators of salinity and habitat. Historic accounts coupled with mollusk based inference models indicate (1) increasing salinity levels along the coast and encroaching into the interior with mangroves communities currently migrating westward, (2) replacement of a mixed graminoid-mangrove zone by a dense monoculture of dwarf mangroves, and (3) a confinement of freshwater and freshwater graminoid marsh to landward areas between urban developments and drainage canals.