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R2
Kinds of R2 Terms modified by R2 Selected AbstractsEffects of Habitat Disturbance on Stream Salamanders: Implications for Buffer Zones and Watershed ManagementCONSERVATION BIOLOGY, Issue 3 2003John D. Willson To minimize the impacts of development on aquatic habitats, numerous conservation measures have been implemented, including the use of riparian buffer zones along streams and rivers. We examined the effectiveness of current buffer-zone systems for management of small watersheds in conserving stream-dwelling salamander populations in 10 small streams ( draining <40.5 ha ) in the western Piedmont of North Carolina. We captured salamanders by means of funnel traps and systematic dipnetting and used a geographic information system to calculate the percentage of disturbed habitat within the watershed of each stream and within 10.7-, 30.5-, and 61.0 -m buffer zones around each stream, upstream from our sampling locations. Although the relative abundance of salamanders was strongly inversely proportional to the percentage of disturbed habitat in the entire watersheds ( R2 = 0.71 for Desmognathus fuscus and 0.48 for Eurycea cirrigera ), we found little to no correlation between the relative abundance of salamanders and the percentage of disturbed habitat present within buffer zones ( R2 = 0.06,0.27 for D. fuscus and 0.01,0.07 for E. cirrigera ). Thus, conservation efforts aimed at preserving salamander populations in headwater streams must consider land use throughout entire watersheds, rather than just preserving small riparian buffer zones. Resumen: La destrucción y degradación del hábitat se encuentra entre la mayores amenazas a la vida silvestre, junto con el aumento global de la población humana. Para minimizar los impactos del desarrollo sobre hábitats acuáticos, se han instrumentado numerosas medidas de conservación, incluyendo el uso de zonas de amortiguamiento riparias a lo largo de arroyos y ríos. Examinamos la efectividad de los actuales sistemas de zonas de amortiguamiento usados en el manejo de cuencas pequeñas para la conservación de poblaciones de salamandras de arroyo en 10 arroyos pequeños ( que drenan <40.5 ha ) al pie de monte del occidente de Carolina del Norte. Capturamos salamandras con trampas de embudo y mediante el uso sistemático de redes y utilizamos un sistema de información geográfica para calcular el porcentaje de hábitat perturbado dentro de la cuenca de cada arroyo y dentro de zonas de amortiguamiento de 10.7-, 30.5- y 61.0-m alrededor de cada arroyo, río arriba de nuestros sitios de muestreo. Aunque los valores de abundancia relativa de salamandras fueron inversamente proporcionales al porcentaje de hábitat perturbado en el total de las cuencas ( R2 = 0.71 para Desmognathus fuscus y 0.48 para Eurycea cirrigera ), encontramos una correlación débil o inexistente entre las abundancias relativas de salamandras y el porcentaje de hábitat perturbado en las zonas de amortiguamiento R2 = 0.06,0.27 para D. fuscus y 0.01,0.07 para E. cirrigera ). Por lo tanto, los esfuerzos de conservación dirigidos a preservar poblaciones de salamandras de arroyos de cabecera deben tomar en cuenta el uso de la tierra en la superficie entera de las cuencas, en lugar de preservar pequeñas zonas de amortiguamiento riparias. [source] Pulmonary diffusion and aerobic capacity: is there a relation?ACTA PHYSIOLOGICA, Issue 4 2010Does obesity matter? Abstract Aim:, We sought to determine whether pulmonary diffusing capacity for nitric oxide (DLNO), carbon monoxide (DLCO) and pulmonary capillary blood volume (Vc) at rest predict peak aerobic capacity (O2peak), and if so, to discern which measure predicts better. Methods:, Thirty-five individuals with extreme obesity (body mass index or BMI = 50 ± 8 kg m,2) and 26 fit, non-obese subjects (BMI = 23 ± 2 kg m,2) participated. DLNO and DLCO at rest were first measured. Then, subjects performed a graded exercise test on a cycle ergometer to determine O2peak. Multivariate regression was used to assess relations in the data. Results:, Findings indicate that (i) pulmonary diffusion at rest predicts O2peak in the fit and obese when measured with DLNO, but only in the fit when measured with DLCO; (ii) the observed relation between pulmonary diffusion at rest and O2peak is different in the fit and obese; (iii) DLNO explains O2peak better than DLCO or Vc. The findings imply the following reference equations for DLNO: O2peak (mL kg,1 min,1) = 6.81 + 0.27 × DLNO for fit individuals; O2peak (mL kg,1 min,1) = 6.81 + 0.06 × DLNO, for obese individuals (in both groups, adjusted R2 = 0.92; RMSE = 5.58). Conclusion:, Pulmonary diffusion at rest predicts O2peak, although a relation exists for obese subjects only when DLNO is used, and the magnitude of the relation depends on gender when either DLCO or Vc is used. We recommend DLNO as a measure of pulmonary diffusion, both for its ease of collection as well as its tighter relation with O2peak. [source] Kinetic analysis of hyaluronidase activity using a bioactive MRI contrast agentCONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2006Liora Shiftan Abstract One of the attractions of molecular imaging using ,smart' bioactive contrast agents is the ability to provide non-invasive data on the spatial and temporal changes in the distribution and expression patterns of specific enzymes. The tools developed for that aim could potentially also be developed for functional imaging of enzyme activity itself, through quantitative analysis of the rapid dynamics of enzymatic conversion of these contrast agents. High molecular weight hyaluronan, the natural substrate of hyaluronidase, is a major antiangiogenic constituent of the extracellular matrix. Degradation by hyaluronidase yields low molecular weight fragments, which are proangiogenic. A novel contrast material, HA-GdDTPA-beads, was designed to provide a substrate analog of hyaluronidase in which relaxivity changes are induced by enzymatic degradation. We show here a first-order kinetic analysis of the time-dependent increase in R2 as a result of hyaluronidase activity. The changes in R2 and the measured relaxivity of intact HA-GdDTPA-beads (r2B) and HA-GdDTPA fragments (r2D) were utilized for derivation of the temporal drop in concentration of GdDTPA in HA-GdDTPA-beads as the consequence of the release of HA-GdDTPA fragments. The rate of dissociation of HA-GdDTPA from the beads showed typical bell-shaped temperature dependence between 7 and 36 °C with peak activity at 25 °C. The tools developed here for quantitative dynamic analysis of hyaluronidase activity by MRI would allow the use of activation of HA-GdDTPA-beads for the determination of the role of hyaluronidase in altering the angiogenic microenvironment of tumor micro metastases. Copyright © 2006 John Wiley & Sons, Ltd. [source] Performance of the Panleucogating protocol for CD4+ T cell enumeration in an HIV dedicated laboratory facility in Barbados,,CYTOMETRY, Issue S1 2008Namrata Sippy-Chatrani Abstract Objective: To compare the Panleucogating (PLG) protocol with the routinely used four-color protocol for CD4+ T cell count enumeration. Design and Methods: One hundred fifty-three blood samples were randomly selected from samples received at the National HIV Laboratory for routine immunological monitoring. Samples were prepared using Coulter CYTO-STAT® tetraCHROME monoclonal antibodies and FlowCAREÔ PLG CD4 reagent for four-color and PLG, respectively, and analyzed on the Beckman Coulter EPICS XL flow cytometer. The PLG protocol used a sequential gating strategy where CD4+ T cells were identified using side scatter properties of cells and CD45 staining. The four-color protocol used CD45 and CD3 to identify CD4+ T cells. Results: Absolute CD4+ T cell counts and percentages ranged from 4 to 1,285 cells/,L and 0.9 to 46.7%, respectively. Linear regression analyses revealed good correlation of PLG with the four-color protocol (absolute counts, R2 = 0.95; percentages, R2 = 0.98) over the entire range including the clinically relevant range. Bland Altman statistics revealed no bias for CD4 counts <500 cells/,L and a slight underestimation by PLG for counts >500 cells/,L (Bias = ,32.7 cells/,L; 95% agreement limits = ,151.3, +86.0). CD4+ T cell percentages were the similar over the entire range (Bias = 0.6%; 95% agreement limits = ,1.97 ± 3.18). Conclusions: PLG is an accurate method for enumerating CD4+ T cells and has resulted in major cost savings to the Government of Barbados. This has implications for the sustainability of the National HIV containment program in Barbados and the other resource limited Caribbean countries. The PLG technique is now being routinely used in Barbados. © 2008 Clinical Cytometry Society [source] Evaluation of a single-platform microcapillary flow cytometer for enumeration of absolute CD4+ T-lymphocyte counts in HIV-1 infected Thai patients,,CYTOMETRY, Issue 5 2007Kovit Pattanapanyasat Abstract Background: Various assays are used to enumerate peripheral blood absolute CD4+ T-lymphocytes. Flow cytometry is considered the gold standard for this purpose. However, the high cost of available flow cytometers and monoclonal antibody reagents make it difficult to implement such methods in the resource-poor settings. In this study, we evaluated a cheaper, recently developed single-platform microcapillary cytometer for CD4+ T-lymphocyte enumeration, the personal cell analyzer (PCA), from Guava® Technologies. Methods: CD4+ and CD8+ T-lymphocyte counts in whole blood samples from 250 HIV-1 infected Thais were determined, using a two-color reagent kit and the Guava PCA, and compared with the results obtained with two reference microbead-based methods from Becton Dickinson Biosciences: the three-color TruCOUNTÔ tube method and the two-color FACSCountÔ method. Statistical correlations and agreements were determined using linear correlation and Bland,Altman analysis. Results: Absolute CD4+ T-lymphocyte counts obtained using the Guava PCA method highly correlated with those obtained using TruCOUNT method (R2 = 0.95, mean bias +13.1 cells/,l, limit of agreement [LOA] ,101.8 to +168.3 cells/,l). Absolute CD8+ T-lymphocyte counts obtained using the Guava PCA method also highly correlated with those obtained with the two reference methods (R2 = 0.92 and 0.88, respectively). Conclusion: This study shows that the enumeration of CD4+ T-lymphocytes using the Guava microcapillary cytometer PCA method performed well when compared with the two reference bead-based methods. However, like the two reference methods, this new method needs substantial technical expertise. © 2007 Clinical Cytometry Society. [source] R-wave Amplitude in Lead II of an Electrocardiograph Correlates with Central Hypovolemia in Human BeingsACADEMIC EMERGENCY MEDICINE, Issue 10 2006John G. McManus MD Abstract Objectives Previous animal and human experiments have suggested that reduction in central blood volume either increases or decreases the amplitude of R waves in various electrocardiograph (ECG) leads depending on underlying pathophysiology. In this investigation, we used graded central hypovolemia in adult volunteer subjects to test the hypothesis that moderate reductions in central blood volume increases R-wave amplitude in lead II of an ECG. Methods A four-lead ECG tracing, heart rate (HR), estimated stroke volume (SV), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured during baseline supine rest and during progressive reductions of central blood volume to an estimated volume loss of >1,000 mL with application of lower-body negative pressure (LBNP) in 13 healthy human volunteer subjects. Results Lower-body negative pressure resulted in a significant progressive reduction in central blood volume, as indicated by a maximal decrease of 65% in SV and maximal elevation of 56% in HR from baseline to ,60 mm Hg LBNP. R-wave amplitude increased (p < 0.0001) linearly with progressive LBNP. The amalgamated correlation (R2) between average stroke volume and average R-wave amplitude at each LBNP stage was ,0.989. Conclusions These results support our hypothesis that reduction of central blood volume in human beings is associated with increased R-wave amplitude in lead II of an ECG. [source] Brain functional changes during placebo lead-in and changes in specific symptoms during pharmacotherapy for major depressionACTA PSYCHIATRICA SCANDINAVICA, Issue 4 2009A. M. Hunter Objective:, Brain functional changes during placebo lead-in have been associated with antidepressant response in clinical trials for major depressive disorder (MDD); however, the relationship between such non-pharmacodynamic changes in brain function and changes in specific symptoms is unknown. Method:, Fifty-eight adults with MDD completed a 1-week single-blind placebo lead-in preceding 8 weeks of double-blind randomized treatment with fluoxetine or venlafaxine (n = 30) or placebo (n = 28). Brain functional change during lead-in was assessed using quantitative electroencephalographic (qEEG) prefrontal theta-band cordance. Symptoms were assessed using the Symptom Checklist-90-Revised (SCL-90-R). Results:, The multiple regression model examining the qEEG parameter in relation to SCL-90-R subscales was significant [F(9,9) = 4.27, P = 0.021, R2 = 0.81] in females, with a significant association for the interpersonal sensitivity subscale (beta coefficient = 1.94, P = 0.001). Conclusion:, Prefrontal neurophysiologic change during placebo lead-in may indicate subsequent antidepressant-related improvement in symptoms of interpersonal sensitivity. [source] Vascular gene expression and phenotypic correlation during differentiation of human embryonic stem cellsDEVELOPMENTAL DYNAMICS, Issue 2 2005Sharon Gerecht-Nir Abstract The study of the cascade of events of induction and sequential gene activation that takes place during human embryonic development is hindered by the unavailability of postimplantation embryos at different stages of development. Spontaneous differentiation of human embryonic stem cells (hESCs) can occur by means of the formation of embryoid bodies (EBs), which resemble certain aspects of early embryos to some extent. Embryonic vascular formation, vasculogenesis, is a sequential process that involves complex regulatory cascades. In this study, changes of gene expression along the development of human EBs for 4 weeks were studied by large-scale gene screening. Two main clusters were identified,one of down-regulated genes such as POU5, NANOG, TDGF1/Cripto (TDGF, teratocarcinoma-derived growth factor-1), LIN28, CD24, TERF1 (telomeric repeat binding factor-1), LEFTB (left,right determination, factor B), and a second of up-regulated genes such as TWIST, WNT5A, WT1, AFP, ALB, NCAM1. Focusing on the vascular system development, genes known to be involved in vasculogenesis and angiogenesis were explored. Up-regulated genes include vasculogenic growth factors such as VEGFA, VEGFC, FIGF (VEGFD), ANG1, ANG2, TGF,3, and PDGFB, as well as the related receptors FLT1, FLT4, PDGFRB, TGF,R2, and TGF,R3, other markers such as CD34, VCAM1, PECAM1, VE-CAD, and transcription factors TAL1, GATA2, and GATA3. The reproducibility of the array data was verified independently and illustrated that many genes known to be involved in vascular development are activated during the differentiation of hESCs in culture. Hence, the analysis of the vascular system can be extended to other differentiation pathways, allocating human EBs as an in vitro model to study early human development. Developmental Dynamics 232:487,497, 2005. © 2004 Wiley-Liss, Inc. [source] In humans the adiponectin receptor R2 is expressed predominantly in adipose tissue and linked to the adipose tissue expression of MMIF-1DIABETES OBESITY & METABOLISM, Issue 4 2010K. Kos In this study, the regional adipose tissue-adiponectin (AT-ADN) and adiponectin receptor (R1 and R2) expression and their relation with metabolic parameters, circulating and AT-derived cytokine expressions were compared. Paired subcutaneous adipose tissue (SCAT) and visceral adipose tissue (VAT) were taken from 18 lean and 39 obese humans, AT-mRNA expression of adipokines analysed by RT-PCR and corresponding serum levels by enzyme-linked immunosorbent assay (ELISA). R1 and R2 adipocyte expression was compared with 17 other human tissues. ADN-gene expression was lower in VAT than SCAT [mean (SD) 1.54 (1.1) vs. 2.84 (0.87); p < 0.001], and lower in obese subjects (VAT : p = 0.01;SCAT : p < 0.001). SCAT-ADN correlated positively with serum ADN (r = 0.33;p = 0.036) but not VAT-ADN. AT expressions of ADN and macrophage migration inhibiting factor (MMIF), IL18 and cluster of differentiation factor 14 (CD14) in both depots showed inverse correlations. R1 and R2 were expressed ubiquitously and R2 highest in SCAT, and this is much higher (×100) than R1 (×100). R expression was similar in lean and obese subjects and unrelated to the metabolic syndrome, however, receptors correlated with VAT-MMIF (R 1: r = 0.4;p = 0.008;R 2: r = 0.35,p = 0.02) and SCAT-MMIF expression (R 2: r = 0.43;p = 0.004). Unlike ADN, its receptors are expressed in many human tissues. Human R2 expression is not highest in the liver but in AT where it is associated with MMIF expression. The adiponectin-dependent insulin-sensitizing action of thiazolidinediones is thus probably to differ amongst species with weaker effects on the human liver. [source] Insulin resistance is not coupled with defective insulin secretion in primary hyperparathyroidismDIABETIC MEDICINE, Issue 10 2009F. Tassone Abstract Aims, An increased frequency of both impaired glucose tolerance and Type 2 diabetes mellitus (DM) has been reported in primary hyperparathyroidism (pHPT), thus we sought to investigate insulin sensitivity and insulin secretion in a large series of pHPT patients. Subjects and methods, One hundred and twenty-two consecutive pHPT patients without known DM were investigated [age (mean ± sd) 59.3 ± 13.6 years, body mass index (BMI) 25.7 ± 4.2 kg/m2; serum calcium 2.8 ± 0.25 mmol/l; PTH 203.2 ± 145.4 ng/l]. Sixty-one control subjects were matched, according to the degree of glucose tolerance, in a 2 : 1 patient:control ratio. Fasting- and oral glucose tolerance test-derived estimates of insulin sensitivity and secretion were determined by means of the quantitative insulin sensitivity check index (QUICKI) and the insulin sensitivity index (ISI) composite. Results, Both the QUICKI and ISI composite were lower in pHPT patients than control subjects (P < 0.03 and P < 0.05, respectively) after adjusting for age, systolic blood pressure and BMI. Conversely, all insulin secretion estimates were significantly increased in pHPT patients than in control subjects (P < 0.04 and P < 0.03, respectively) and after adjusting for age, systolic blood pressure and BMI. Log serum calcium levels were negatively associated with the QUICKI and log ISI composite (R = ,0.30, P = 0.001; R = ,0.23, P = 0.020, respectively) in pHPT patients. Serum calcium levels significantly and independently contributed to impaired insulin sensitivity in multivariate analysis (QUICKI as dependent variable: , = ,0.31, P = 0.004, R2 = 0.15; log ISI composite as dependent variable: , = ,0.29, P = 0.005, R2 = 0.16). Conclusions, Our study confirms a reduction in both basal and stimulated insulin sensitivity in primary hyperparathyroidism, in spite of increased insulin secretion. Moreover, our data show for the first time a significant relationship between hypercalcaemia and insulin sensitivity in this condition. [source] Statin therapy improves brachial artery vasodilator function in patients with Type 1 diabetes and microalbuminuriaDIABETIC MEDICINE, Issue 3 2005G. K. Dogra Abstract Aims Type 1 diabetes mellitus patients with microalbuminuria have endothelial dysfunction associated with the degree of albuminuria but not with LDL-cholesterol levels. Lipid-lowering agents such as statins may still be of benefit as they can correct endothelial dysfunction by both lipid and non-lipid mechanisms. We therefore examined the effects of atorvastatin on brachial artery endothelial dysfunction in these patients. Methods In a double-blind, randomized crossover study, 16 Type 1 diabetes mellitus patients with microalbuminuria received 6 weeks of atorvastatin 40 mg/day or placebo, separated by a 4-week washout. Brachial artery, endothelium-dependent, flow-mediated dilatation (FMD) and endothelium-independent, glyceryl trinitrate-mediated dilatation (GTNMD) were measured. Results Compared with placebo, atorvastatin produced a significant decrease in apolipoprotein B (34.2%), LDL-cholesterol (44.1%) (all P < 0.001), and oxidized-LDL (35.7%, P = 0.03). There was a non-significant increase in plasma cGMP (P = 0.13) on atorvastatin. FMD and GTNMD increased significantly on atorvastatin (FMD: atorvastatin +1.8 ± 0.4%; placebo +0.2 ± 0.4%, P = 0.007); (GTNMD: atorvastatin +1.3 ± 0.9%; placebo ,1.2 ± 0.6%, P = 0.04). An increase in cGMP was independently correlated with an increase in FMD on atorvastatin (adjusted R2 0.41, P = 0.02). Conclusion Atorvastatin improves endothelium-dependent and independent vasodilator function of the brachial artery in Type 1 diabetes mellitus patients with microalbuminuria. This may relate to pleiotropic effects of statins, in particular reduced oxidative stress and increased availability of nitric oxide. [source] Brachial-ankle pulse wave velocity measured automatically by oscillometric method is elevated in diabetic patients with incipient nephropathyDIABETIC MEDICINE, Issue 11 2003H. Yokoyama Abstract Aims To examine whether brachial-ankle pulse wave velocity (baPWV), a possible early marker of atherosclerotic vascular damage, is associated with albuminuria in patients with Type 2 diabetes. Methods BaPWV was measured by automatic oscillometric method in 346 Type 2 diabetic patients with normoalbuminuria (a mean level of three times measurements of albumin-to-creatinine (ACR) < 30 µg/mg creatinine; n = 200), incipient nephropathy (a mean level of ACR , 30 and < 300 µg/mg creatinine; n = 119), and clinical nephropathy (a mean level of ACR , 300 µg/mg creatinine; n = 27), and without peripheral vascular disease. Results BaPWV (cm/s) was significantly higher in patients with incipient nephropathy (1722 ± 382) and clinical nephropathy (1763 ± 322) than in patients with normoalbuminuria (1559 ± 343, P < 0.0001, respectively). By univariate analysis it correlated significantly with age (r = 0.44, P < 0.0001), systolic blood pressure (r = 0.55, P < 0.0001), diastolic blood pressure (r = 0.42, P < 0.0001), albuminuria (r = 0.24, P < 0.0001) and HbA1C (r = 0.11, P < 0.05). Albuminuria revealed an independent significant association with baPWV (P < 0.01) after adjustment for age, sex, smoking, BMI, HbA1C, hyperlipidemia, and hypertension. Multiple regression analysis showed age, diastolic blood pressure and albuminuria were independently associated with baPWV (adjusted R2 = 0.42, P < 0.0001). Conclusions The results might indicate a possible link between the pathogenesis of atherosclerosis and diabetic nephropathy. Future studies are needed to clarify the usefulness and its predictable value. [source] The rich generally get richer, but there are exceptions: Correlations between species richness of native plant species and alien weeds in MexicoDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004Francisco J. Espinosa-García ABSTRACT Studies on the resistance of communities to plant invasions at different spatial scales have yielded contradictory results that have been attributed to scale-dependent factors. Some of these studies argue either for or against Elton's notion of biotic resistance against invasions through diversity. We studied the correlation between alien weeds and native species, dividing the latter group into weedy and non-weedy species, integrating various factors that influence diversity into an analysis on the scale of the federal states of Mexico. The resulting multiple-regression models for native and alien weed species are robust (adjusted R2 = 0.87 and R2 = 0.69, respectively) and show a strong partial correlation of the number of weed species (native and alien) with the number of non-weed native species. These results agree with studies showing a positive correlation between the number of native and alien species on larger scales. Both models also include human population density as an important predictor variable, but this is more important for alien weeds (, = 0.62) than for native weeds (, = 0.32). In the regression model for native weed species richness, the non-cultivated (fallow) area (, = 0.24) correlated positively with native weed richness. In the model for alien weed species richness, the native weed species richness was an important variable (, = ,0.51), showing a negative partial correlation (rpart = ,0.4). This result is consistent with Elton's biotic resistance hypothesis, suggesting that biotic resistance is scale independent but that this may be masked by other factors that influence the diversity of both weeds and non-weeds. [source] Synthesis and calcium channel modulating effects of modified Hantzsch nitrooxyalkyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(pyridinyl or 2-trifluoromethylphenyl)-5-pyridinecarboxylatesDRUG DEVELOPMENT RESEARCH, Issue 4 2000Ramin Miri Abstract A group of racemic nitrooxyalkyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(pyridinyl or 2-trifluoromethylphenyl)-5-pyridinecarboxylates 8a,o were synthesized using modified Hantzsch reactions. In vitro calcium channel antagonist activities, determined using a guinea pig ileum longitudinal smooth muscle (GPILSM) assay, showed that compounds 8a,o exhibited weaker calcium antagonist activity (10,5 to 10,7 M range) than the reference drug nifedipine (IC50 = 1.43 × 10,8 M). Compounds 8 possessing a C-4 R1 = 2-pyridyl substituent were always more potent than the approximately equiactive analogs having an R1 = 3-pyridyl, 4-pyridyl or 2-CF3 -C6H4 -substituent, within each subgroup of nitrooxyalkyl compounds [R2 = , (CH2)nONO2 (n = 2, 3, 4) or ,CH(CH2ONO2)2]. Although the length of the R2 = ,(CH2)nONO2 substituent (n = 2,4) was not a determinant of smooth muscle calcium antagonist activity when the C-4 R1 -substituent was 2-pyridyl, when R1 was a 3-pyridyl, 4-pyridyl, or 2-CF3 -C6H4 -substituent, the relative potency order with respect to the R2 = ,(CH2)nONO2 substituent was n = 3 and 4 > n = 2. Replacement of the isopropyl substituent of the ester moiety of the calcium antagonist (±)-2-pyridyl 3a by a ,(CH2)nONO2 (n = 2,4) moiety increased calcium antagonist activity on GPILSM by 8-fold. In contrast, replacement of the isopropyl substituent of the ester moiety of the calcium agonists (±)-3-pyridyl 3b, (±)-4-pyridyl 3c or the methyl substituent of the ester moiety of Bay K8644 by a R2 nitrooxyalkyl substituent resulted in abolition of their calcium agonist effects on GPILSM that is replaced by a smooth muscle calcium antagonist effect. These calcium antagonist data support the concept that incorporation of a nitrooxyalkyl ester substituent constitutes a valuable drug design strategy to enhance Hantzsch 1,4-dihydropyridine calcium antagonist and/or abolish calcium agonist effects on smooth muscle. Replacement of the isopropyl (8b,c), or the methyl (8d) group by a ,CH2CH2ONO2 moiety resulted in retention of the cardiac positive inotropic effect where the relative potency order with respect to the C-4 substituent was 2-CF3 -C6H6 - (8d) > 3-pyridyl (8b) , 4-pyridyl (8c). Model hybrid (calcium channel modulation, ·NO release) compounds, that exhibit dual cardioselective agonist / smooth muscle selective antagonist activities, represent a novel type of 1,4-dihydropyridine CC modulator that offers a potential approach to drug discovery targeted toward the treatment of congestive heart failure and for use as probes to study the structure,function relationship of calcium channels. Drug Dev. Res. 51:225,232, 2000. © 2001 Wiley-Liss, Inc. [source] Spectrally based remote sensing of river bathymetryEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2009Carl J. Legleiter Abstract This paper evaluates the potential for remote mapping of river bathymetry by (1) examining the theoretical basis of a simple, ratio-based technique for retrieving depth information from passive optical image data; (2) performing radiative transfer simulations to quantify the effects of suspended sediment concentration, bottom reflectance, and water surface state; (3) assessing the accuracy of spectrally based depth retrieval under field conditions via ground-based reflectance measurements; and (4) producing bathymetric maps for a pair of gravel-bed rivers from hyperspectral image data. Consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate: the remotely sensed signal must be dominated by bottom-reflected radiance. We developed a simple algorithm, called optimal band ratio analysis (OBRA), for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong, linear relationships between an image-derived quantity X and flow depth d. OBRA of simulated spectra indicated that water column optical properties were accounted for by a shorter-wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer-wavelength denominator band subject to strong absorption by pure water. Field spectra suggested that bottom reflectance was fairly homogeneous, isolating the effect of depth, and that radiance measured above the water surface was primarily reflected from the bottom, not the water column. OBRA of these data, 28% of which were collected during a period of high turbidity, yielded strong X versus d relations (R2 from 0·792 to 0·976), demonstrating that accurate depth retrieval is feasible under field conditions. Moreover, application of OBRA to hyperspectral image data resulted in spatially coherent, hydraulically reasonable bathymetric maps, though negative depth estimates occurred along channel margins where pixels were mixed. This study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry. Copyright © 2009 John Wiley & Sons, Ltd. [source] Concentrated flow erosion rates reduced through biological geotextilesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2009T. Smets Abstract Soil erosion by concentrated flow can cause serious environmental damage. Erosion-control geotextiles have considerable potential for reducing concentrated flow erosion. However, limited data are available on the erosion-reducing potential of geotextiles. In this study, the effectiveness of three biological geotextiles in reducing soil losses during concentrated flow is investigated. Hereto, runoff was simulated in a concentrated flow flume, filled with an erodible sandy loam on three slope gradients (13·5, 27·0 and 41·5%). Treatments included three biological geotextiles (borassus, buriti and bamboo) and one bare soil surface. Darcy,Weisbach friction coefficients ranged from 0·01 to 2·84. The highest values are observed for borassus covered soil surfaces, followed by buriti, bamboo and bare soil, respectively. The friction coefficients are linearly correlated with geotextile thickness. For the specific experimental conditions of this study, borassus geotextiles reduced soil detachment rate on average to 56%, buriti geotextiles to 59% and bamboo geotextiles to 66% of the soil detachment rate for bare soil surfaces. Total flow shear stress was the hydraulic parameter best predicting soil detachment rate for bare and geotextile covered surfaces (R2 = 0·75,0·84, p <0·001, n = 12,15). The highest resistance against soil detachment was observed for the borassus covered soil surfaces, followed by buriti, bamboo and bare soil surfaces, respectively. Overall, biological geotextiles are less effective in controlling concentrated flow erosion compared with interrill erosion. Copyright © 2009 John Wiley & Sons, Ltd. [source] Interrill erosion on cultivated Greek soils: modelling sediment deliveryEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2006D. Dimoyiannis Abstract For interrill erosion, raindrop-induced detachment and transport of sediment by rainfall-disturbed sheet flow are the predominant processes, while detachment by sheet flow and transport by raindrop impact are negligible. In general, interrill subprocesses are inter-actively affected by rainfall, soil and surface properties. The objective of this work was to study the relationships among interrill runoff and sediment loss and some selected para-meters, for cultivated soils in central Greece, and also the development of a formula for predicting single storm sediment delivery. Runoff and soil loss measurement field experiments have been conducted for a 3·5-year period, under natural storms. The soils studied were developed on Tertiary calcareous materials and Quaternary alluvial deposits and were textured from sandy loam to clay. The second group of soils showed greater susceptibility to sealing and erosion than the first group. Single storm sediment loss was mainly affected by rain and runoff erosivity, being significantly correlated with rain kinetic energy (r = 0·64***), its maximum 30-minute intensity (r = 0·64***) and runoff amount (r = 0·56***). Runoff had the greatest correlation with rain kinetic energy (r = 0·64***). A complementary effect on soil loss was detected between rain kinetic energy and its maximum 30-minute intensity. The same was true for rain kinetic energy and topsoil aggregate instability, on surface seal formation and thus on infiltration characteristics and overland flow rate. Empirical analysis showed that the following formula can be used for the successful prediction of sediment delivery (Di): Di = 0·638,EI30tan(,) (R2 = 0·893***), where , is a topsoil aggregate instability index, E the rain kinetic energy, I30 the maximum 30-minute rain intensity and , the slope angle. It describes soil erodibility using a topsoil aggregate instability index, which can be determined easily by a simple laboratory technique, and runoff through the product of this index and rain kinetic energy. Copyright © 2006 John Wiley & Sons, Ltd. [source] Wind effects on sediment transport by raindrop-impacted shallow flow: a wind-tunnel studyEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2004G. Erpul Abstract In wind-driven rains, wind velocity and direction are expected to affect not only energy input of rains but also shallow ,ow hydraulics by changing roughness induced by raindrop impacts with an angle on ,ow and the unidirectional splashes in the wind direction. A wind-tunnel study under wind-driven rains was conducted to determine the effects of horizontal wind velocity and direction on sediment transport by the raindrop-impacted shallow ,ow. Windless rains and the rains driven by horizontal wind velocities of 6 m s,1, 10 m s,1, and 14 m s,1 were applied to three agricultural soils packed into a 20 by 55 cm soil pan placed on both windward and leeward slopes of 7 per cent, 15 per cent, and 20 per cent. During each rainfall application, sediment and runoff samples were collected at 5-min intervals at the bottom edge of the soil pan with wide-mouth bottles and were determined gravimetrically. Based on the interrill erosion mechanics, kinetic energy ,ux (Ern) as a rainfall parameter and product of unit discharge and slope in the form of qbSco as a ,ow parameter were used to explain the interactions between impact and ,ow parameters and sediment transport (qs). The differential sediment transport rates occurred depending on the variation in raindrop trajectory and rain intensity with the wind velocity and direction. Flux of rain energy computed by combining the effects of wind on the velocity, frequency, and angle of raindrop impact reasonably explained the characteristics of wind-driven rains and acceptably accounted for the differences in sediment delivery rates to the shallow ,ow transport (R2 , 0·78). Further analysis of the Pearson correlation coef,cients between Ern and qSo and qs also showed that wind velocity and direction signi,cantly affected the hydraulics of the shallow ,ow. Ern had a smaller correlation coef,cient with the qs in windward slopes where not only reverse splashes but also reverse lateral raindrop stress with respect to the shallow ,ow direction occurred. However, Ern was as much effective as qSo in the sediment transport in the leeward slopes where advance splashes and advance lateral raindrop stress on the ,ow occurred. Copyright © 2004 John Wiley & Sons, Ltd. [source] Analysis of determinants of mammalian species richness in South America using spatial autoregressive modelsECOGRAPHY, Issue 4 2004Marcelo F. Tognelli Classically, hypotheses concerning the distribution of species have been explored by evaluating the relationship between species richness and environmental variables using ordinary least squares (OLS) regression. However, environmental and ecological data generally show spatial autocorrelation, thus violating the assumption of independently distributed errors. When spatial autocorrelation exists, an alternative is to use autoregressive models that assume spatially autocorrelated errors. We examined the relationship between mammalian species richness in South America and environmental variables, thereby evaluating the relative importance of four competing hypotheses to explain mammalian species richness. Additionally, we compared the results of ordinary least squares (OLS) regression and spatial autoregressive models using Conditional and Simultaneous Autoregressive (CAR and SAR, respectively) models. Variables associated with productivity were the most important at determining mammalian species richness at the scale analyzed. Whereas OLS residuals between species richness and environmental variables were strongly autocorrelated, those from autoregressive models showed less spatial autocorrelation, particularly the SAR model, indicating its suitability for these data. Autoregressive models also fit the data better than the OLS model (increasing R2 by 5,14%), and the relative importance of the explanatory variables shifted under CAR and SAR models. These analyses underscore the importance of controlling for spatial autocorrelation in biogeographical studies. [source] Effects of radio-transmitter antenna length on swimming performance of juvenile rainbow troutECOLOGY OF FRESHWATER FISH, Issue 4 2004K. J. Murchie Abstract,,, Technological advances have lead to the production of micro radio-transmitters capable of being implanted in fish as small as c. 5 g. Although the actual tags are small, transmitters are equipped with long antennas that can increase drag and tangle in debris. We examined the effects of radio-transmitter antenna length on the swimming performance of juvenile rainbow trout, Oncorhynchus mykiss, (N = 156, mean mass = 34 g, mean fork length = 148 mm). Although we tested a variety of different antenna lengths up to a maximum of 300 mm, only the longest antenna significantly impaired swimming performance relative to control fish (P < 0.001). There was no difference in swimming performance between the sham (surgery, but no transmitter) and the control fish (handled, but no surgery), suggesting that the surgical procedure itself did not negatively affect the fish. Regression analysis, however, indicated that there was a significant decrease in swimming performance associated with increased antenna length (R2 = 0.11, P < 0.001). In addition, when held in laboratory tanks, fish with the three longest antennas (150, 225 and 300 mm) frequently became entangled with the standpipe. We suggest that researchers, under the guidance of the tag manufacturer, trim antennas to the shortest possible length required to detect fish in their specific study area. Antenna length is clearly an important issue for small fish, especially for species that inhabit complex habitats where antennas may become entangled, and where fish must attain speeds near limits of their swimming capacity. Resumen 1. Los avances tecnológicos han llevado a producir micro radio-trasmisores capaces de ser implantados en peces de muy pequeño tamaño (,5 g). Aunque las marcas actuales son pequeñas, los trasmisores están equipados con antenas largas que pueden llegar a enredarse en los restos de vegetación. Examinamos los efectos de la longitud de la antena sobre la rutina natatoria de juveniles de Oncorhynchus mykiss (n = 156, peso medio = 34 g, longitud furcal media = 148 mm). 2. Aunque analizamos varias longitudes de antena, hasta 300 mm, solamente las de mayor longitud alteraron la rutina natatoria en relación a los peces control (P < 0.001). No hubo diferencia en la rutina natatoria entre individuos bajo cirugía pero sin trasmisores respecto de los individuos control (manipulados pero sin cirugía) lo que sugiere que los procedimientos de cirugía no afectaron negativamente a los peces. Sin embargo, análisis de regresión indicaron un declive significativo en la rutina natatoria asociado a la longitud de la antena (R2 = 0.11, P < 0.001). Además, al ser mantenidos en tanques, los individuos con las tres antenas mas largas (150, 225, y 300 mm) frecuentemente se enredaron con las tuberías. 3. Sugerimos a los investigadores que, bajo la dirección de los productores de marcas y antenas, consideren el uso de las antenas más pequeñas que permitan detectar a los peces en sus respectivas áreas de estudio. La longitud de la antena es una cuestión importante para los pequeños peces, especialmente para especies en hábitats complejos donde las antenas pueden llegar a enredarse y donde los peces pueden alcanzar velocidades casi al limite de su capacidad natatoria. [source] Can hepatitis C virus prevalence be used as a measure of injection-related human immunodeficiency virus risk in populations of injecting drug users?ADDICTION, Issue 2 2010An ecological analysis ABSTRACT Background Human immunodeficiency virus (HIV) outbreaks occur among injecting drug users (IDUs), but where HIV is low insight is required into the future risk of increased transmission. The relationship between hepatitis C virus (HCV) and HIV prevalence among IDUs is explored to determine whether HCV prevalence could indicate HIV risk. Methods Systematic review of IDU HIV/HCV prevalence data and regression analysis using weighted prevalence estimates and time,series data. Results HIV/HCV prevalence estimates were obtained for 343 regions. In regions other than South America/sub-Saharan Africa (SAm/SSA), mean IDU HIV prevalence is likely to be negligible if HCV prevalence is <30% (95% confidence interval 22,38%) but increases progressively with HCV prevalence thereafter [linearly (, = 0.39 and R2 = 0.67) or in proportion to cubed HCV prevalence (, = 0.40 and R2 = 0.67)]. In SAm/SSA, limited data suggest that mean HIV prevalence is proportional to HCV prevalence (, = 0.84, R2 = 0.99), but will be much greater than in non-SAm/SSA settings with no threshold HCV prevalence that corresponds to low HIV risk. At low HCV prevalences (<50%), time,series data suggest that any change in HIV prevalence over time is likely to be much smaller (<25%) than the change in HCV prevalence over the same time-period, but that this difference diminishes at higher HCV prevalences. Conclusions HCV prevalence could be an indicator of HIV risk among IDUs. In most settings, reducing HCV prevalence below a threshold (30%) would reduce substantially any HIV risk, and could provide a target for HIV prevention. [source] Capillary electrophoresis-time of flight-mass spectrometry using noncovalently bilayer-coated capillaries for the analysis of amino acids in human urineELECTROPHORESIS, Issue 12 2008Rawi Ramautar Abstract A capillary electrophoresis-time of flight-mass spectrometry (CE-TOF-MS) method for the analysis of amino acids in human urine was developed. Capillaries noncovalently coated with a bilayer of Polybrene (PB) and poly(vinyl sulfonate) (PVS) provided a considerable EOF at low pH, thus facilitating the fast separation of amino acids using a BGE of 1,M formic acid (pH,1.8). The PB,PVS coating proved to be very consistent yielding stable CE-MS patterns of amino acids in urine with favorable migration time repeatability (RSDs <2%). The relatively low sample loading capacity of CE was circumvented by an in-capillary preconcentration step based on pH-mediated stacking allowing 100-nL sample injection (i.e. ca. 4% of capillary volume). As a result, LODs for amino acids were down to 20,nM while achieving satisfactory separation efficiencies. Preliminary validation of the method with urine samples showed good linear responses for the amino acids (R2 >0.99), and RSDs for peak areas were <10%. Special attention was paid to the influence of matrix effects on the quantification of amino acids. The magnitude of ion suppression by the matrix was similar for different urine samples. The CE-TOF-MS method was used for the analysis of urine samples of patients with urinary tract infection (UTI). Concentrations of a subset of amino acids were determined and compared with concentrations in urine of healthy controls. Furthermore, partial least squares,discriminant analysis (PLS,DA) of the CE-TOF-MS dataset in the 50,450,m/z region showed a distinctive grouping of the UTI samples and the control samples. Examination of score and loadings plot revealed a number of compounds, including phenylalanine, to be responsible for grouping of the samples. Thus, the CE-TOF-MS method shows good potential for the screening of body fluids based on the analysis of endogenous low-molecular weight metabolites such as amino acids and related compounds. [source] Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flowELECTROPHORESIS, Issue 10 2008Liya Ge Abstract In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25,min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8,1.9,,M) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples. [source] Enhanced separation of purine and pyrimidine bases using carboxylic multiwalled carbon nanotubes as additive in capillary zone electrophoresisELECTROPHORESIS, Issue 16 2006Xin Xiong Abstract This paper describes the enhanced separation of adenine (A), hypoxanthine (HX), 8-azaadenine (8-AA), thymine (T), cytosine (C), uracil (U) and guanine (G) by CZE dispersing carboxylic multiwalled carbon nanotubes (c-MWNTs) into the running buffer. The effect of important factors such as c-MWNT nanoparticle concentration, the acidity and concentration of running buffer, and separation voltage were investigated to acquire the optimum conditions. The seven purine and pyrimidine bases could be well separated within 16,min in a 35,cm effective length fused-silica capillary at a separation voltage of +8.0,kV in a 23,mM tetraborate buffer (pH,9.2) containing 8.0×10,5,g/mL c-MWNTs. Under the optimal conditions, the linear ranges were of 2,250,,g/mL for A (R2,=,0.995), 3,200,,g/mL for U (R2,=,0.990) and G (R2,=,0.992), 3,250,,g/mL for T (R2,=,0.998), 2,200,,g/mL for C (R2,=,0.985) and 4,200,,g/mL for HX (R2,=,0.988) and 8-AA (R2,=,0.990). The detection limits were 0.9,,g/mL for A (S/N,=,3), 2.4,,g/mL for U, 2.0,,g/mL for T, 1.5,,g/mL for C, 2.5,,g/mL for G and 3.0,,g/mL for HX and 8-AA. The proposed method was successfully applied for determining five purine and pyrimidine bases in yeast RNA. [source] Evaluation of Various Unstructured Kinetic Models for the Production of Protease by Bacillus sphaericus,MTTC511ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2008A. Rajendran Abstract Bacillus sphaericus,MTCC511 was used for the production of protease in submerged batch fermentation. Maximum protease activity of 1010,U/L was obtained during a fermentation period of 24,h under optimized conditions of 30,°C in a medium with an initial pH of 7 and at a shaking rate of 120,rpm. The maximum biomass obtained in the batch fermentation was 2.55,g/L after 16,h. Various unstructured models were analyzed to simulate the experimental values of microbial growth, protease activity and substrate concentration. The unstructured models, i.e. the Monod model for microbial growth, the Monod incorporated Luedeking-Piret model for the production of protease and the Monod-incorporated modified Luedeking-Piret model for the utilization of substrate were capable of predicting the fermentation profile with high coefficient of determination (R2) values of 0.9967, 0.9402 and 0.9729, respectively. The results indicated that the unstructured models were able to describe the fermentation kinetics more effectively. [source] Design and testing of ,genome-proxy' microarrays to profile marine microbial communitiesENVIRONMENTAL MICROBIOLOGY, Issue 2 2008Virginia I. Rich Summary Microarrays are useful tools for detecting and quantifying specific functional and phylogenetic genes in natural microbial communities. In order to track uncultivated microbial genotypes and their close relatives in an environmental context, we designed and implemented a ,genome-proxy' microarray that targets microbial genome fragments recovered directly from the environment. Fragments consisted of sequenced clones from large-insert genomic libraries from microbial communities in Monterey Bay, the Hawaii Ocean Time-series station ALOHA, and Antarctic coastal waters. In a prototype array, we designed probe sets to 13 of the sequenced genome fragments and to genomic regions of the cultivated cyanobacterium Prochlorococcus MED4. Each probe set consisted of multiple 70-mers, each targeting an individual open reading frame, and distributed along each ,40,160 kbp contiguous genomic region. The targeted organisms or clones, and close relatives, were hybridized to the array both as pure DNA mixtures and as additions of cells to a background of coastal seawater. This prototype array correctly identified the presence or absence of the target organisms and their relatives in laboratory mixes, with negligible cross-hybridization to organisms having , ,75% genomic identity. In addition, the array correctly identified target cells added to a background of environmental DNA, with a limit of detection of ,0.1% of the community, corresponding to ,103 cells ml,1 in these samples. Signal correlated to cell concentration with an R2 of 1.0 across six orders of magnitude. In addition, the array could track a related strain (at 86% genomic identity to that targeted) with a linearity of R2 = 0.9999 and a limit of detection of ,1% of the community. Closely related genotypes were distinguishable by differing hybridization patterns across each probe set. This array's multiple-probe, ,genome-proxy' approach and consequent ability to track both target genotypes and their close relatives is important for the array's environmental application given the recent discoveries of considerable intrapopulation diversity within marine microbial communities. [source] Elucidating the factors influencing the biodegradation of cylindrospermopsin in drinking water sourcesENVIRONMENTAL TOXICOLOGY, Issue 3 2008Maree J. Smith Abstract The cyanotoxin cylindrospermopsin (CYN) is produced by several species of cyanobacteria and can be persistent in drinking waters supplies, which is of major concern to water authorities because of its potential to severely compromise human health. Consequently, there is a need to fully understand the persistence of CYN in water supplies, in particular, to determine whether this toxin is readily degraded by endemic aquatic organisms. This study provides insights into the environmental factors that can influence the biodegradation of this toxin in Australian drinking water supplies. Biodegradation of CYN was only evident in water supplies that had a history of toxic Cylindrospermopsis raciborskii blooms. In addition, lag periods were evident prior to the onset of biodegradation; however, repeated exposure of the endemic organisms to CYN resulted in substantial decreases in the lag periods. Furthermore, the concentration of CYN was shown to influence biodegradation with a near linear relationship (R2 of 0.9549) existing between the biodegradation rate and the initial CYN concentration. Temperature was also shown to affect the biodegradation of CYN, which is important since CYN is now being detected in more temperate climates. The presence of copper-based algicides inhibited CYN degradation, which has significant implications since copper-based algicides are commonly used to control cyanobacterial growth in water bodies. The results from this study indicate that the biodegradation of CYN in natural water bodies is a complex process that can be influenced by many environmental factors, some of which include CYN concentration, temperature, and the presence of copper-based algicides. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Bioaccumulation and ROS generation in liver of freshwater fish, goldfish Carassius auratus under HC Orange No. 1 exposureENVIRONMENTAL TOXICOLOGY, Issue 3 2007Yuanyuan Sun Abstract HC Orange No. 1 (CAS No. 54381-08-7, 2-nitro-4,-hydroxydiphenylamine) is used as a color additive in hair dyes. In this study, laboratory experiment was carried out to determine HC Orange No. 1 bioaccumulation and oxidative stress in the liver of freshwater fish, goldfish Carassius auratus. Fish were exposed to different concentrations (0.05, 0.1, 0.2, 0.5, and 1.0 mg/L) of HC Orange No. 1 for 10 days, with one group assigned as control. The accumulation of HC Orange No. 1 in liver increased with the exposure concentration (R2 = 0.94). A secondary spin trapping technique was used followed by electron paramagnetic resonance (EPR) analysis to study the reactive oxygen species (ROS) production. On the basis of the hyperfine splitting constants and shape of the EPR spectrum, the ROS generated in fish liver after exposure was identified as hydroxyl radical (,OH). There is a good correlation between the exposure concentrations and ,OH generation (R2 = 0.92). The ,OH signal intensity of the EPR spectrum showed a significant increase (P < 0.05) when the HC Orange No. 1 concentration was 1.0 mg/L, compared with that of the control. A good positive relationship (R2 = 0.95) was found between the ,OH formation and accumulation level of HC Orange No. 1 in liver. The changes of the activities of catalase (CAT), superoxide dismutase (SOD), glutathione S -transferase (GST), and contents of reduced glutathione (GSH) were also detected. These observations indicated a possible mechanism of oxidative stress induced by HC Orange No. 1 on fish. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 256,263, 2007. [source] Summer changes in cyanobacterial bloom composition and microcystin concentration in eutrophic Czech reservoirsENVIRONMENTAL TOXICOLOGY, Issue 3 2006Petr Znachor Abstract In mid-July and August 2003 and 2004, 18 reservoirs in the Czech Republic were sampled for phytoplankton species composition and concentration of intracellular microcystins (MCs). As a consequence of high nutrient loading, most of the reservoirs experienced cyanobacterial blooms of various intensities, with the prevalence of cyanobacteria increasing markedly in August, along with a conspicuous shift in species composition toward dominance of Microcystis spp. Microcystins were detected in 90% of the samples, and their amount also increased considerably in August, reflecting the cyanobacterial biomass. In Microcystis -dominated samples, a significantly higher amount of MCs (p < 0.001) occurred than in samples in which other taxa prevailed. Microcystins were positively correlated with chlorophyll a and cyanobacterial biovolume (p < 0.05, R2 = 0.61 and 0.66, respectively), with the strongest correlation found for Microcystis spp. biovolume (p < 0.001, R2 = 0.87). This taxon was the most important producer of MCs in Czech reservoirs. The main structural variants of MCs were MC-LR, MC-RR, and MC-YR. This study's data also indicate that the relative share of MC variants (MC-LR and MC-RR) varies considerably with time, most likely as a consequence of different species and strain compositions during the summer. This study clearly demonstrates a high prevalence of MC-producing cyanobacteria in Czech reservoirs. Therefore, regular monitoring of these reservoirs is highly desirable in an effort to minimize potential health risks to the human population. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 236,243, 2006. [source] Determination and fate of oxytetracycline and related compounds in oxytetracycline production wastewater and the receiving river,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Dong Li Abstract This study investigated the occurrence and fate of oxytetracycline (OTC) and its related substances, 4-epi-oxytetracycline (EOTC), ,-apo-oxytetracycline (,-apo-OTC), and ,-apo-oxytetracycline (,-apo-OTC), in a wastewater treatment plant (WWTP) treating OTC production wastewater and a river receiving the effluent from the WWTP using liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). The percent removal of OTC in the WWTP was 38.0 ± 10.5%, and the concentration of OTC was still up to 19.5 ± 2.9 mg/L in the treated outflow. The concentration slightly decreased along the river, from 641 ± 118 ,g/L at site R2 (discharging point) to 377 ± 142 ,g/L at site R4 (,20 km from site R2), which was still higher than the minimal inhibition concentration of OTC reported (,250 ,g/L). On the other hand, the total amount of its related substances in the treated effluent was less than 5% of OTC. Concentrations of ,-apo-OTC and ,-apo-OTC increased along the river, from 5.76 ± 0.63 and 2.08 ± 0.30 ,g/L at site R2 to 11.9 ± 4.9 and 12.0 ± 4.6 ,g/L at R4, respectively, although EOTC decreased from 31.5 ± 3.8 to 12.9 ± 1.1 ,g/L, respectively. The mean concentration of ,-apo-OTC in river sediments was 20.8 ± 7.8 mg/kg, and its ratio to OTC was approximately 0.11, nearly twice the ratio of ,-apo-OTC and EOTC to OTC (0.058 ± 0.014 and 0.061 ± 0.015, respectively). [source] | |||||||||||||||||||||||||