Understanding the Impact of Mesh on Tank Overflow System Capacity.

A 2016 incident that resulted in damage to a water storage tank's roof motivated pilot-scale experiments to be conducted to determine the impact of mesh on tank overflow capacity. A clean mesh installed near the outlet of an overflow system did not reduce the capacity during the weir dominated flow regime. The impact of a mesh was found to be a reduction in the area available to flow, which was found to lower the achievable capacity through the system. Considering only the head loss or pressure drop associated with the mesh and not area reduction resulted in an overestimation of achievable capacity, which could lead to an undersized overflow system. The results and formulas presented will help water utilities ensure overflow systems with mesh are appropriately sized.

The case for increasing the statistical power of eddy covariance ecosystem studies: why, where and how?

Eddy covariance (EC) continues to provide invaluable insights into the dynamics of Earth's surface processes. However, despite its many strengths, spatial replication of EC at the ecosystem scale is rare. High equipment costs are likely to be partially responsible. This contributes to the low sampling, and even lower replication, of ecoregions in Africa, Oceania (excluding Australia) and South America. The level of replication matters as it directly affects statistical power. While the ergodicity of turbulence and temporal replication allow an EC tower to provide statistically robust flux estimates for its footprint, these principles do not extend to larger ecosystem scales. Despite the challenge of spatially replicating EC, it is clearly of interest to be able to use EC to provide statistically robust flux estimates for larger areas. We ask: How much spatial replication of EC is required for statistical confidence in our flux estimates of an ecosystem? We provide the reader with tools to estimate the number of EC towers needed to achieve a given statistical power. We show that for a typical ecosystem, around four EC towers are needed to have 95% statistical confidence that the annual flux of an ecosystem is nonzero. Furthermore, if the true flux is small relative to instrument noise and spatial variability, the number of towers needed can rise dramatically. We discuss approaches for improving statistical power and describe one solution: an inexpensive EC system that could help by making spatial replication more affordable. However, we note that diverting limited resources from other key measurements in order to allow spatial replication may not be optimal, and a balance needs to be struck. While individual EC towers are well suited to providing fluxes from the flux footprint, we emphasize that spatial replication is essential for statistically robust fluxes if a wider ecosystem is being studied.

Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach.

Quantifying landscape-scale methane (CH4 ) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH4 emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH4 uptake, in controlling landscape-level fluxes. We measured CH4 fluxes from multiple microtopographical subunits (sedge-dominated lawns, interhummocks and hummocks) within an aapa mire in subarctic Finland, as well as in drier ecosystems present in the wider landscape, lichen heath and mountain birch forest. An intercomparison was carried out between fluxes measured using static chambers, up-scaled using a high-resolution landcover map derived from aerial photography and eddy covariance. Strong agreement was observed between the two methodologies, with emission rates greatest in lawns. CH4 fluxes from lawns were strongly related to seasonal fluctuations in temperature, but their floating nature meant that water-table depth was not a key factor in controlling CH4 release. In contrast, chamber measurements identified net CH4 uptake in birch forest soils. An intercomparison between the aerial photography and satellite remote sensing demonstrated that quantifying the distribution of the key CH4 emitting and consuming plant communities was possible from satellite, allowing fluxes to be scaled up to a 100 km(2) area. For the full growing season (May to October), ~ 1.1-1.4 g CH4  m(-2) was released across the 100 km(2) area. This was based on up-scaled lawn emissions of 1.2-1.5 g CH4  m(-2) , vs. an up-scaled uptake of 0.07-0.15 g CH4  m(-2) by the wider landscape. Given the strong temperature sensitivity of the dominant lawn fluxes, and the fact that lawns are unlikely to dry out, climate warming may substantially increase CH4 emissions in northern Finland, and in aapa mire regions in general.

Dealing with disjunct concentration measurements in eddy covariance applications: a comparison of available approaches.

Using proton transfer reaction mass spectrometry equipped with a quadrupol mass analyser to quantify the biosphere-atmosphere exchange of volatile organic compounds (VOC), concentrations of different VOC are measured sequentially. Depending on how many VOC species are targeted and their respective integration times, each VOC is measured at repeat rates on the order of a few seconds. This represents an order of magnitude longer sample interval compared to the standard eddy covariance (EC) method (5-20 Hz sampling rates). Here we simulate the effect of disjunct sampling on EC flux estimates by decreasing the time resolution of CO2 and H2O concentrations measured at 20 Hz above a temperate mountain grassland in the Austrian Alps. Fluxes for one month are calculated with the standard EC method and compared to fluxes calculated based on the disjunct data (1, 3 and 5 s sampling rates) using the following approaches: i) imputation of missing concentrations based on the nearest neighbouring samples (iDECnn), ii) imputation by linear interpolation (iDECli), and iii) virtual disjunct EC (vDEC), i.e. flux calculation based solely on the disjunct concentrations. It is shown that the two imputation methods result in additional low-pass filtering, longer lag times (as determined with the maximum cross-correlation method) and a flux loss of 3-30 % as compared to the standard EC method. A novel procedure, based on a transfer function approach, which specifically corrects for the effect of data treatment, was developed, resulting in improved correspondence (to within 2 %). The vDEC method yields fluxes which approximate the true (20 Hz) fluxes to within 3-7 % and it is this approach we recommend because it involves no additional empirical corrections. The only drawback of the vDEC method is the noisy nature of the cross-correlations, which poses problems with lag determination - practical approaches to overcome this limitation are discussed.

The cardiac neural stem cell phenotype is compromised in streptozotocin-induced diabetic cardiomyopathy.

Neural stem cells were identified in the rat heart and during scar formation and healing participated in sympathetic fiber sprouting and angiogenesis. In the setting of diabetes, impaired wound healing represents a typical pathological feature. These findings provided the impetus to test the hypothesis that experimental diabetes adversely influenced the phenotype of cardiac neural stem cells. Streptozotocin (STZ)-induced diabetic rats were associated with elevated plasma glucose levels, significant loss of body weight and left ventricular contractile dysfunction. In the heart of STZ-diabetic rats, the density of nestin immunoreactive processes emanating from cardiac neural stem cells were reduced. The latter finding was reaffirmed as nestin protein expression was significantly decreased in the heart of STZ-diabetic rats and associated with a concomitant reduction of nestin mRNA. Employing the TUNEL assay, the loss of nestin expression in STZ-diabetic rats was not attributed to widespread cardiac neural stem cell apoptosis. Insulin administration to STZ-diabetic rats with established hyperglycaemia led to a modest recovery of nestin protein expression in cardiac neural stem cells. By contrast, the administration of insulin immediately after STZ injection improved plasma glucose levels and significantly attenuated the loss of nestin protein expression. These data highlight the novel observation that nestin protein expression in cardiac neural stem cells was significantly reduced in STZ-induced type I diabetic rats. The aberrant cardiac neural stem cell phenotype may compromise their biological role and predispose the diabetic heart to maladaptive healing following ischemic injury.

Infarct size is increased in female post-MI rats treated with rapamycin.

Rapamycin represents a recognized drug-based therapeutic approach to treat cardiovascular disease. However, at least in the female heart, rapamycin may suppress the recruitment of putative signalling events conferring cardioprotection. The present study tested the hypothesis that rapamycin-sensitive signalling events contributed to the cardioprotective phenotype of the female rat heart after an ischemic insult. Rapamycin (1.5 mg/kg) was administered to adult female Sprague-Dawley rats 24 h after complete coronary artery ligation and continued for 6 days. Rapamycin abrogated p70S6K phosphorylation in the left ventricle of sham rats and the noninfarcted left ventricle (NILV) of 1-week postmyocardial-infarcted (MI) rats. Scar weight (MI 0.028 +/- 0.006, MI+rapamycin 0.064 +/- 0.004 g) and surface area (MI 0.37 +/- 0.08, MI+rapamycin 0.74 +/- 0.03 cm2) were significantly larger in rapamycin-treated post-MI rats. In the NILV of post-MI female rats, rapamycin inhibited the upregulation of eNOS. Furthermore, the increased expression of collagen and TGF-beta3 mRNAs in the NILV were attenuated in rapamycin-treated post-MI rats, whereas scar healing was unaffected. The present study has demonstrated that rapamycin-sensitive signalling events were implicated in scar formation and reactive fibrosis. Rapamycin-mediated suppression of eNOS and TGF-beta3 mRNA in post-MI female rats may have directly contributed to the larger infarct and attenuation of the reactive fibrotic response, respectively.

The rat heart contains a neural stem cell population; role in sympathetic sprouting and angiogenesis.

Nestin-expressing cells were identified in the normal rat heart characterized by a small cell body and numerous processes and following an ischemic insult migrated to the infarct region. The present study was undertaken to identify the phenotype, origin and biological role of nestin-expressing cells during reparative fibrosis. A neural stem cell phenotype was identified based on musashi-1 expression, growth as a neurosphere, and differentiation to a neuronal cell. Using the Wnt1-cre; Z/EG transgenic mouse model, which expresses EGFP in embryologically-derived neural crest cells, the reporter signal was detected in nestin-expressing cells residing in the heart. In infarcted human hearts, nestin-expressing cells were detected in the viable myocardium and the scar and morphologically analogous to the population identified in the rat heart. Following either an ischemic insult or the acute administration of 6-hydroxydopamine, sympathetic sprouting was dependent on the physical association of neurofilament-M immunoreactive fibres with nestin-positive processes emanating from neural stem cells. To specifically study the biological role of the subpopulation in the infarct region, neural stem cells were isolated from the scar, fluorescently labelled and transplanted in the heart of 3-day post-MI rats. Injected scar-derived neural stem cells migrated to the infarct region and were used as a substrate for de novo blood vessel formation. These data have demonstrated that the heart contains a resident population of neural stem cells derived from the neural crest and participate in reparative fibrosis. Their manipulation could provide an alternative approach to ameliorate the healing process following ischemic injury.

Female rats fed a high-fat diet were associated with vascular dysfunction and cardiac fibrosis in the absence of overt obesity and hyperlipidemia: therapeutic potential of resveratrol.

It remains presently unknown whether vascular reactivity is impaired and whether maladaptive cardiac remodeling occurs before the onset of overt obesity and in the absence of hyperlipidemia. Normal female rats were fed a high-fat diet for 8 weeks and were associated with a modest nonsignificant increase of body weight (standard diet, 300 +/- 10, versus high-fat diet, 329 +/- 14 g) and a normal plasma lipid profile. In rats fed a high-fat diet, systolic (171 +/- 7 mm Hg) and diastolic blood pressures (109 +/- 3) were increased compared to a standard diet (systolic blood pressure, 134 +/- 8; diastolic blood pressure, 96 +/- 5 mm Hg), and acetylcholine-dependent relaxation of isolated aortic rings (high-fat diet, 22 +/- 5%, versus standard diet, 53 +/- 8%) was significantly reduced. Furthermore, perivascular fibrosis was detected in the heart of rats fed a high-fat diet. The exogenous addition of resveratrol (trans-3,5,4'-trihydroxystilbene) (0.1 microM) to aortic rings isolated from rats fed a high-fat diet restored acetylcholine-mediated relaxation (47 +/- 9%). The administration of resveratrol (20 mg/kg/day for 8 weeks) to rats fed a high-fat diet prevented the increase in blood pressure and preserved acetylcholine-dependent relaxation of isolated aortic rings. However, resveratrol therapy failed to attenuate the perivascular fibrotic response. These data have demonstrated that a high-fat diet fed to normal female rats can elicit a hypertensive response and induce perivascular fibrosis before the development of overt obesity and in the absence of hyperlipidemia. Resveratrol therapy can prevent the hypertensive response in female rats fed a high-fat diet but is without effect on the progression of perivascular fibrosis.

Dexamethasone treatment of post-MI rats attenuates sympathetic innervation of the infarct region.

Sympathetic fiber innervation of the damaged region following injury represents a conserved event of wound healing. The present study tested the hypothesis that impaired scar healing in post-myocardial infarction (post-MI) rats was associated with a reduction of sympathetic fibers innervating the infarct region. In 1-wk post-MI rats, neurofilament-M-immunoreactive fibers (1,116 +/- 250 microm(2)/mm(2)) were detected innervating the infarct region and observed in close proximity to a modest number of endothelial nitric oxide synthase-immunoreactive scar-residing vessels. Dexamethasone (Dex) treatment (6 days) of post-MI rats led to a significant reduction of scar weight (Dex + MI 38 +/- 4 mg vs. MI 63 +/- 2 mg) and a disproportionate nonsignificant decrease of scar surface area (Dex + MI 0.54 +/- 0.06 cm(2) vs. MI 0.68 +/- 0.06 cm(2)). In Dex-treated post-MI rats, the density of neurofilament-M-immunoreactive fibers (125 +/- 47 microm(2)/mm(2)) innervating the infarct region was significantly reduced and associated with a decreased expression of nerve growth factor (NGF) mRNA (Dex + MI 0.80 +/- 0.07 vs. MI 1.11 +/- 0.08; P < 0.05 vs. MI). Previous studies have demonstrated that scar myofibroblasts synthesize NGF and may represent a cellular target of Dex. The exposure of 1st passage scar myofibroblasts to Dex led to a dose-dependent suppression of [(3)H]thymidine uptake and a concomitant attenuation of NGF mRNA expression (untreated 3.47 +/- 0.35 vs. Dex treated 2.28 +/- 0.40; P < 0.05 vs. untreated). Thus the present study has demonstrated that impaired scar healing in Dex-treated post-MI rats was associated with a reduction of neurofilament-M-immunoreactive fibers innervating the infarct region. The attenuation of scar myofibroblast proliferation and NGF mRNA expression may represent underlying mechanisms contributing to the diminished neural response in the infarct region of Dex-treated post-MI rats.

Effects of resveratrol (trans-3,5,4'-trihydroxystilbene) treatment on cardiac remodeling following myocardial infarction.

Resveratrol (RES; trans-3,5,4'-trihydroxystilbene) has been shown to improve health and slow the progression of disease in various models. Several cardioprotective mechanisms have been identified including antioxidant, anti-inflammatory, and antifibrotic actions. Each of these actions is thought to have the ability to attenuate the pathophysiology underlying the deleterious cardiac structural remodeling that results from acute myocardial infarction (MI). Therefore, we evaluated the effect of resveratrol treatment on the progression of cardiac remodeling after MI. Four groups of rats (sham, n = 6; sham + RES, n = 21; MI, n = 26; MI + RES, n = 24) were treated for 13 weeks, starting 7 days before ligation of the left anterior descending coronary artery. Serial transthoracic echocardiography revealed that resveratrol had no effect on MI-induced left-ventricular and left-atrial dilatation or reduction in left-ventricular fractional shortening. Consistent with these findings, resveratrol did not improve the deterioration of hemodynamic function or reduce infarct size at 12 weeks post-MI. Resveratrol-treated animals did, however, show preserved cardiac contractile reserve in response to dobutamine administration. Radioligand binding revealed that MI reduced beta-adrenergic receptor density. Resveratrol administration increased beta-adrenoceptor density, so that resveratrol-treated MI rats had beta-adrenoceptor densities similar to normal rats. Real-time reverse transcription-polymerase chain reaction revealed that MI-induced changes in sarcoplasmic reticulum Ca2+-ATPase 2 and transforming growth factor beta-1 expression were unaltered by resveratrol, whereas MI-induced increases in atrial natriuretic factor (ANF) and connective tissue growth factor (CTGF) expression were attenuated. Resveratrol treatment does not improve cardiac remodeling and global hemodynamic function post-MI but does preserve contractile reserve and attenuate ANF and CTGF up-regulation.

What are the possibilities of spontaneous resorption of a thoracic disc herniation occupying more than 20% of the spinal canal in the asymptomatic subject? Comparative study.

Thoracic disc herniation is a rare pathology for which surgical treatment is difficult. The discovery of asymptomatic or only slightly symptomatic lesions can be problematic, especially in cases of marked canal stenosis. The possibility of spontaneous resorption has been documented by a few case reports but there is no study on this subject. Our objective was to compare the clinical and radiological data for two groups of patients with significant thoracic herniation (occupying more than 20% of the spinal canal): one showing spontaneous resorption (group 1) and the other persistence of the lesion during follow up (group 2). The physiological processes of thoracic herniation are also discussed. We present a retrospective study of our database of patients with thoracic hernia. Only subjects who initially showed signs of slight or absent myelopathy (Frankel D or E) were included. Group 1 and 2 are composed of 12 and 17 patients respectively. The clinical and radiological data are compared. The two groups were not different for the following parameters: age, sex ratio, disc calcification, size, trajectory, side, hernia level. Other parameters were evaluated and were not associated with a higher rate of resorption: disc calcification, intramedullary hypersignal in T2 sequence, calcification of the posterior common vertebral ligament, calcification of another disc and Scheuerman's disease. Asymptomatic thoracic disc herniation is a condition that can disappear spontaneously, even in the case of a large lesion. To date, there are no clinical or radiological data that can predict such an evolution.

Disparate regulation of signaling proteins after exercise and myocardial infarction.

INTRODUCTION: The signaling proteins extracellular signal-regulated kinase (ERK1/2) and protein kinase B (PKB) were implicated in the development of pathological cardiac hypertrophy. The present study examined whether the progression of physiological eccentric cardiac hypertrophy was associated with ERK1/2 and PKB recruitment. METHODS AND RESULTS: Following 1 and 3 wk of voluntary exercise, female Sprague-Dawley rats ran a total distance of 55 +/- 10 and 195 +/- 19 km, respectively. Left ventricular hypertrophy was detected in 3-wk-exercised rats, albeit prepro-ANP protein expression was unchanged. ERK1/2 was not recruited in the left ventricle (LV) of either 1-wk-exercised rats or the hypertrophied LV of 3-wk-exercised rats. In 1-wk-exercised rats, PKB Thr308 and Ser473 phosphorylation were significantly reduced, whereas a selective increase of PKB Ser473 phosphorylation was observed in the hypertrophied LV of 3-wk-exercised rats. In both 1- and 3-wk-exercised rats, an upward electrophoretic mobility band shift of p70 ribosomal S6 kinase (p70 S6K) was detected. In 1-wk post-myocardial-infarcted (MI) female Sprague-Dawley rats, scar formation was associated with increased left ventricular end-diastolic pressure. In the hypertrophied noninfarcted left ventricle (NILV), ERK1/2, p70 S6K, PKB Ser473, and Thr308 phosphorylation were increased. CONCLUSIONS: These data support the premise that ERK1/2 and PKB were differentially regulated during the development of eccentric physiological and pathological cardiac hypertrophy. It remains to be determined whether the chronic activation of either ERK1/2 and/or PKB in the NILV of post-MI rats may contribute in part to maladaptive cardiac remodelling.

A comparative analysis of simulated and observed photosynthetic CO2 uptake in two coniferous forest canopies.

Gross canopy photosynthesis (P(g)) can be simulated with canopy models or retrieved from turbulent carbon dioxide (CO2) flux measurements above the forest canopy. We compare the two estimates and illustrate our findings with two case studies. We used the three-dimensional canopy model MAESTRA to simulate P(g) of two spruce forests differing in age and structure. Model parameter acquisition and model sensitivity to selected model parameters are described, and modeled results are compared with independent flux estimates. Despite higher photon fluxes at the site, an older German Norway spruce (Picea abies L. (Karst.)) canopy took up 25% less CO2 from the atmosphere than a young Scottish Sitka spruce (Picea sitchensis (Bong.) Carr.) plantation. The average magnitudes of P(g) and the differences between the two canopies were satisfactorily represented by the model. The main reasons for the different uptake rates were a slightly smaller quantum yield and lower absorptance of the Norway spruce stand because of a more clumped canopy structure. The model did not represent the scatter in the turbulent CO2 flux densities, which was of the same order of magnitude as the non-photosynthetically-active-radiation-induced biophysical variability in the simulated P(g). Analysis of residuals identified only small systematic differences between the modeled flux estimates and turbulent flux measurements at high vapor pressure saturation deficits. The merits and limitations of comparative analysis for quality evaluation of both methods are discussed. From this analysis, we recommend use of both parameter sets and model structure as a basis for future applications and model development.

Comparison of the effects of an angiotensin-converting enzyme inhibitor and a vasopeptidase inhibitor after myocardial infarction in the rat.

OBJECTIVES: The goal of this study was to compare the effects of the vasopeptidase inhibitor omapatrilat and the angiotensin-converting enzyme inhibitor (ACEI) captopril in the postmyocardial infarction (MI) rat model. BACKGROUND; The cardioprotective effects of ACEIs after MI are thought to be partially due to an increase in bradykinin (BK). Vasopeptidase inhibitors inhibit both ACE and neutral endopeptidase (NEP), further reduce BK metabolism and increase natriuretic peptides, which may result in better cardioprotective effects than with ACEIs after MI. METHODS: Myocardial infarction was induced in 514 Wistar male rats by ligation of the anterior coronary artery. Rats surviving 4 h after MI (n = 282) were assigned to omapatrilat (40 or 80 mg/kg/day), captopril (160 mg/kg/day) or no treatment. After 56 days, neurohumoral, hemodynamic, ventricular remodeling, morphometry, immunohistochemistry and cardiac cytokine expression were measured. RESULTS: Omapatrilat and captopril resulted in similarly improved survival, cardiac hemodynamics and reduced cardiac fibrosis and hypertrophy after MI. The pattern of left ventricular (LV) remodeling differed, omapatrilat causing less attenuation of the rightward shift of the LV pressure-volume relation at lower filling pressures than captopril. Both interventions reduced messenger ribonucleic acid expression of the profibrotic cytokine transforming growth factor-beta(1); neither effected the anti-inflammatory cytokine interleukin-10, and only captopril reduced the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). Expression of TNF-alpha was in cardiomyocytes. Both medications reduced circulating endothelin-1, angiotensin II and catecholamines, but only omapatrilat increased atrial natriuretic peptides. CONCLUSIONS: This study indicates that both omapatrilat and captopril markedly improve post-MI survival, cardiac function and cardiac remodeling in the rat. It would appear that the addition of NEP inhibition to those of ACEIs does not result in significant further benefit after MI.

On the validation of models of forest CO2 exchange using eddy covariance data: some perils and pitfalls.

With the widespread application of eddy covariance technology, long-term records of hourly ecosystem mass and energy exchange are becoming available for forests around the world. These data sets hold great promise for testing and validation of models of forest function. However, model validation is not a straightforward task. The goals of this paper were to: (1) review some of the problems inherent in model validation; and (2) survey the tools available to modelers to improve validation procedures, with particular reference to eddy covariance data. A simple set of models applied to a data set of ecosystem CO2 exchange is used to illustrate our points. The major problems discussed are equifinality, insensitivity and uncertainty. Equifinality is the problem that different models, or different parameterizations of the same model, may yield similar results, making it difficult to distinguish which is correct. Insensitivity arises because the major sources of variation in eddy covariance data are the annual and diurnal cycles, which are represented by even the most basic models, and the size of the response to these cycles can mask effects of other driving variables. Uncertainty arises from three main sources: parameters, model structure and data, each of which is discussed in turn. Uncertainty is a particular issue with eddy covariance data because of the lack of replicated measurements and the potential for unquantified systematic errors such as flux loss due to advection. We surveyed several tools that improve model validation, including sensitivity analysis, uncertainty analysis, residual analysis and model comparison. Illustrative examples are used to demonstrate the use of each tool. We show that simplistic comparisons of model outputs with eddy covariance data are problematic, but use of these tools can greatly improve our confidence in model predictions.

Hyper-reactivity of cerebral arteries from ovariectomized rats: therapeutic benefit of tamoxifen.

1. An increased incidence of systemic hypertension has been documented in postmenopausal women and identified as an independent risk factor in the development of cerebrovascular stroke. The present study examined whether cerebrovascular reactivity was increased in the hypertensive ovariectomized rat, and explored the potential therapeutic benefit of the partial estrogen receptor agonist tamoxifen. 2. Female Sprague-Dawley rats were subjected to bilateral ovariectomy (OVX, n=16) or a sham operation (n=8). At 6-week postsurgery, rats were anesthetized to assess ventricular contractility and blood pressure. In a second series of experiments, OVX rats (n=8) were given tamoxifen starting 3 weeks postsurgery, and continued for 3 weeks. At the end of each protocol, the middle cerebral artery was harvested and rings were mounted in wire-myographs to measure isometric tension. 3. Systolic arterial pressure (SAP) was significantly increased (P<0.05) in the OVX rat (174+/-8 mmHg), as compared to sham (135+/-6 mmHg). The resting tension of isolated cerebral arteries from OVX rats (186+/-15 mg) was significantly elevated (P<0.05), as compared to sham (129+/-9 mg). Phenylephrine treatment did not elicit a constriction of cerebral arteries isolated from sham rats, whereas a potent response (P<0.05) was observed in OVX rats. Nitric oxide (NO) synthase inhibition with L-NNA led to a limited contraction in sham rats (8+/-3% of Emax), whereas a significant (P<0.05) increase was observed in OVX rats (34+/-12% of Emax). Lastly, vascular sensitivity (pD2) to sodium nitroprusside was significantly increased (P<0.05) in OVX rats, as compared to sham. 4. Tamoxifen therapy normalized the resting tension of isolated cerebral arteries from OVX rats, abrogated phenylephrine-mediated contraction, and modestly reduced SAP. By contrast, tamoxifen treatment of OVX rats did not attenuate L-NNA-mediated contractile response of cerebral arteries. 5. These data demonstrate that the cerebral artery isolated from the OVX rat was associated with an exaggerated vasoconstrictor response to phenylephrine, and altered NO-dependent vascular reactivity. The administration of tamoxifen to OVX rats normalized cerebral artery reactivity to phenylephrine. These findings provide the impetus to examine the potential therapeutic benefit of the partial estrogen receptor agonist tamoxifen to reduce the incidence of cerebrovascular stroke in postmenopausal women.

AT1 receptor antagonist therapy preferentially ameliorated right ventricular function and phenotype during the early phase of remodeling post-MI.

1. The influence of AII on contractile dysfunction, regulation of the tyrosine kinase-dependent signaling molecule extracellular signal-regulated kinase (ERK), and natriuretic peptide gene expression were examined in the noninfarcted left ventricle (NILV) and right ventricle (RV) during the early phase of remodeling post-myocardial infarct (MI) in the rat. The selective AT(1) receptor antagonist irbesartan was administered <10 h following coronary artery ligation, and rats were killed either at 4-day or 2-week post-MI. 2. At 4 days post-MI, left ventricular systolic pressure (LVSP: sham=125+/-12, MI=91+/-4 mmHg) was decreased, whereas left ventricular end-diastolic pressure (LVEDP: sham=9+/-2, MI=17+/-2 mm Hg), right ventricular systolic (RVSP: sham=26+/-1, MI=34+/-2 mm Hg), and end-diastolic pressures (RVEDP: sham=3+/-0.5, MI=7+/-1 mm Hg) were increased. ERK phosphorylation was significantly elevated in the NILV and RV. 3. Irbesartan (40 mg x kg(-1)/day(-1)) administration did not improve left ventricular function, or suppress increased ERK phosphorylation in the 4-day post-MI rat. By contrast, irbesartan therapy normalized RVSP (MI+irbesartan=25+/-1 mm Hg), RVEDP (MI+irbesartan=3+/-0.3 mm Hg), and reduced ERK1 (MI=3.0+/-0.6, MI+irbesartan=2.0+/-0.3-fold increase), and ERK2 (MI=3.8+/-0.8, MI+irbesartan=2.2+/-0.5-fold increase) phosphorylation. 4. In 2-week post-MI rats, biventricular dysfunction was associated with increased prepro-ANP, and prepro-BNP mRNA expression. Irbesartan therapy normalized RVSP, attenuated RVEDP, and abrogated natriuretic peptide mRNA expression (prepro-ANP; MI=9+/-2, MI+irbesartan=2+/-1-fold increase, prepro-BNP; MI=6+/-2, MI+irbesartan=1+/-1-fold increase), whereas both transcripts remained elevated in the NILV despite the partial attenuation of LVEDP. 5. These data suggest that the therapeutic benefit of irbesartan treatment during the early phase of remodeling post-MI was associated with the preferential amelioration of RV contractile function and phenotype.

Elevated mean arterial pressure in the ovariectomized rat was normalized by ET(A) receptor antagonist therapy: absence of cardiac hypertrophy and fibrosis.

1. The influence of menopause on ventricular function and remodelling remains undefined. The following study examined the effect of ovariectomy on ventricular contractility, cardiac hypertrophy and extracellular matrix protein expression. 2. Elevated circulating levels of the vasoconstrictor endothelin-1 have been reported in post-menopausal women. Moreover, endothelin-1 has been shown to influence blood pressure, ventricular function and cardiac remodelling. In this regard, the potential pathophysiological role of endothelin-1 in the ovariectomized rat was assessed via the administration of the selective endothelin(A) receptor (ET(A)) antagonist BMS-182874. 3. In 3 and 6 week ovariectomized female Sprague - Dawley rats, uterus atrophy was associated with a significant increase in mean arterial pressure, and left ventricular systolic pressure, as compared to sham. By contrast, right ventricular contractile indices were normal in the ovariectomized rat. Despite increased systolic load, left ventricular hypertrophy was not evident, prepro-atrial natriuretic peptide (prepro-ANP) mRNA levels and collagen protein content were similar to sham. 4. The treatment of ovariectomized rats with BMS-182874 (60 mg kg(-1) per day) did not reverse uterus atrophy. However, BMS-182874 normalized mean arterial pressure, and left ventricular systolic pressure in the ovariectomized rat. 5. Thus, despite elevated blood pressure, ovariectomized rats were not associated with either cardiac hypertrophy or fibrosis. Lastly, endothelin-1, acting via the stimulation of the ET(A) receptor represents an integral mechanism implicated in the increase of mean arterial pressure following ovariectomy.

Validation and application of a liquid chromatography-tandem mass spectrometric method for the determination of SCH 211803 in rat and monkey plasma using automated 96-well protein precipitation.

A rapid, sensitive, specific, accurate, and reproducible automated liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the quantitative determination of 1'-(2-amino-3-methylbenzoyl)-4-[[[(3-chlorophenyl)sulfonyl]phenyl]methyl]-1,4'-bipiperidine hydrochloride (SCH 211803) in plasma has been developed. The method was validated in rat and monkey plasma over the concentration range of 0.5-250 ng/ml using 2H(4)-SCH 211803 as the internal standard (IS). Automated 96-well plate protein precipitation (PP) with acetonitrile (ACN) was used for sample processing. The method employed a Betasil C18 column with a fast gradient for the separation of analyte and internal standard from the plasma matrix and a triple quadrupole mass spectrometer operated in positive ion multiple reaction monitoring (MRM) mode for detection. The method was used for the determination of SCH 211803 plasma concentrations to support pre-clinical studies.

Validation of a sensitive and automated 96-well solid-phase extraction liquid chromatography-tandem mass spectrometry method for the determination of desloratadine and 3-hydroxydesloratadine in human plasma.

To support clinical development, a liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed and validated for the determination of desloratadine (descarboethoxyloratadine) and 3-OH desloratadine (3-hydroxydescarboethoxyloratadine) concentrations in human plasma. The method consisted of automated 96-well solid-phase extraction for sample preparation and liquid chromatography/turbo ionspray tandem mass spectrometry for analysis. [2H(4)]Desloratadine and [2H(4)]3-OH desloratadine were used as internal standards (I.S.). A quadratic regression (weighted 1/concentration(2)) gave the best fit for calibration curves over the concentration range of 25-10000 pg/ml for both desloratadine and 3-OH desloratadine. There was no interference from endogenous components in the blank plasma tested. The accuracy (%bias) at the lower limit of quantitation (LLOQ) was -12.8 and +3.4% for desloratadine and 3-OH desloratadine, respectively. The precision (%CV) for samples at the LLOQ was 15.1 and 10.9% for desloratadine and 3-OH desloratadine, respectively. For quality control samples at 75, 1000 and 7500 pg/ml, the between run %CV was