Belen Torondel - Academia.edu (original) (raw)

Papers by Belen Torondel

Vascular Medicine, Mar 10, 2010

Arteriosclerosis, Thrombosis, and Vascular Biology, 2012

Objective— The overproduction of vascular NO contributes toward the circulatory collapse observed... more Objective— The overproduction of vascular NO contributes toward the circulatory collapse observed in patients with septic shock. Dimethylarginine dimethylaminohydrolase (DDAH), which has 2 isoforms, metabolizes asymmetrically methylated arginines (asymmetric mono- or di-methylarginine), endogenously produced NO synthase inhibitors. We wished to investigate whether reducing DDAH1 activity, using genetic and pharmacological approaches, is protective during lipopolysaccharide-induced endotoxic shock. Methods and Results— Experiments were conducted in DDAH1 heterozygous knockout mice (DDAH1 +/− ) or naive rats treated with a synthetic pharmacological DDAH inhibitor (L-257). We demonstrate for the first time that L-257 is DDAH1 selective using recombinant human DDAH proteins. DDAH1 mRNA was expressed in aortic but not macrophage cDNA, and consistent with this expression profile, L-257 selectively inhibited NO production from lipopolysaccharide-treated aorta but not macrophages, in cultur...

Archives of Disease in Childhood - Fetal and Neonatal Edition, 2010

IntroductionImpaired utero-placental perfusion leads to fetal growth restriction. The authors hav... more IntroductionImpaired utero-placental perfusion leads to fetal growth restriction. The authors have shown a significant increase in blood flow in the uterine arteries (UAs) of pregnant sheep and a significantly reduced contractile response following local transduction with an adenovirus encoding VEGF-A165 (Ad.VEGF-A). The authors have now studied the effects of local over-expression of the VEGF-DΔNΔC isoform and investigated the mechanism behind

PloS one, 2015

Menstrual hygiene management (MHM) practices vary worldwide and depend on the individual's so... more Menstrual hygiene management (MHM) practices vary worldwide and depend on the individual's socioeconomic status, personal preferences, local traditions and beliefs, and access to water and sanitation resources. MHM practices can be particularly unhygienic and inconvenient for girls and women in poorer settings. Little is known about whether unhygienic MHM practices increase a woman's exposure to urogenital infections, such as bacterial vaginosis (BV) and urinary tract infection (UTI). This study aimed to determine the association of MHM practices with urogenital infections, controlling for environmental drivers. A hospital-based case-control study was conducted on 486 women at Odisha, India. Cases and controls were recruited using a syndromic approach. Vaginal swabs were collected from all the participants and tested for BV status using Amsel's criteria. Urine samples were cultured to assess UTI status. Socioeconomic status, clinical symptoms and reproductive history, an...

Arteriosclerosis, Thrombosis, and Vascular Biology, 2015

Nitric oxide is a key to numerous physiological and pathophysiological processes. Nitric oxide pr... more Nitric oxide is a key to numerous physiological and pathophysiological processes. Nitric oxide production is regulated endogenously by 2 methylarginines, asymmetric dimethylarginine (ADMA) and monomethyl-l-arginine. The enzyme that specifically metabolizes asymmetric dimethylarginine and monomethyl-l-arginine is dimethylarginine dimethylaminohydrolase (DDAH). The first isoform dimethylarginine dimethylaminohydrolase 1 has previously been shown to be an important regulator of methylarginines in both health and disease. This study explores for the first time the role of endogenous dimethylarginine dimethylaminohydrolase 2 in regulating cardiovascular physiology and also determines the functional impact of dimethylarginine dimethylaminohydrolase 2 deletion on outcome and immune function in sepsis. Mice, globally deficient in Ddah2, were compared with their wild-type littermates to determine the physiological role of Ddah2 using in vivo and ex vivo assessments of vascular function. We show that global knockout of Ddah2 results in elevated blood pressure during periods of activity (mean [SEM], 118.5 [1.3] versus 112.7 [1.1] mm Hg; P=0.025) and changes in vascular responsiveness mediated by changes in methylarginine concentration, mean myocardial tissue asymmetric dimethylarginine (SEM) was 0.89 (0.06) versus 0.67 (0.05) μmol/L (P=0.02) and systemic nitric oxide concentrations. In a model of severe polymicrobial sepsis, Ddah2 knockout affects outcome (120-hour survival was 12% in Ddah2 knockouts versus 53% in wild-type animals; P<0.001). Monocyte-specific deletion of Ddah2 results in a similar pattern of increased severity to that seen in globally deficient animals. Ddah2 has a regulatory role both in normal physiology and in determining outcome of severe polymicrobial sepsis. Elucidation of this role identifies a mechanism for the observed relationship between Ddah2 polymorphisms, cardiovascular disease, and outcome in sepsis.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2015

Sentinel toys are increasingly used as a method of assessing young children&a... more Sentinel toys are increasingly used as a method of assessing young children's exposure to faecal pathogens in households in low-income settings. However, there is no consensus on the suitability of different approaches. We evaluated three types of toy balls with different surfaces (plastic, rubber, urethane) in the laboratory to compare the uptake of faecal indicator bacteria (Escherichia coli) on their surface. We performed bacteria survival analysis under different environmental conditions and tested laboratory methods for bacteria removal and recovery. In a field study we distributed sterile urethane balls to children <5 from 360 households in rural India. After 24 hours, we collected and rinsed the toys in sterile water, assayed for thermotolerant coliforms (TTC) and explored associations between the level of contamination and household characteristics. In the laboratory, urethane foam balls took up more indicator bacteria than the other balls. Bacteria recovery did not differ based on mechanic vs no agitation. Higher temperatures and moisture levels increased bacterial yield. In the field, the only factor associated with a decreased recovery of TTC from the balls was having a soil (unpaved) floor. Sentinel toys may be an effective tool for assessing young children's exposure to faecal pathogens. However, even using methods designed to increase bacterial recovery, limited sensitivity may require larger sample sizes.

Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced ami... more Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced amino acids that inhibit all three isoforms of nitric oxide synthase (NOS) 1 . ADMA accumulates in various disease states, including renal failure, diabetes and pulmonary hypertension, and its concentration in plasma is strongly predictive of premature cardiovascular disease and death 2-4 . Both L-NMMA and ADMA are eliminated largely through active metabolism by dimethylarginine dimethylaminohydrolase (DDAH) 5 and thus DDAH dysfunction may be a crucial unifying feature of increased cardiovascular risk. However, despite considerable interest in this pathway and in the role of ADMA as a cardiovascular risk factor, there is little evidence to support a causal role of ADMA in pathophysiology. Here we reveal the structure of human DDAH-1 and probe the function of DDAH-1 both by deleting the Ddah1 gene in mice and by using DDAH-specific inhibitors that, as we demonstrate by crystallography, bind to the active site of human DDAH-1. We show that loss of DDAH-1 activity leads to accumulation of ADMA and reduction in NO signaling. This in turn causes vascular pathophysiology, including endothelial dysfunction, increased systemic vascular resistance and elevated systemic and pulmonary blood pressure. Our results also suggest that DDAH inhibition could be harnessed therapeutically to reduce the vascular collapse associated with sepsis.

American Journal of Hypertension, 2001

Background: Plasma levels of endogenous guanidine compounds are increased in various pathologic c... more Background: Plasma levels of endogenous guanidine compounds are increased in various pathologic conditions, including chronic renal failure. In the present study we tested the effects of some of these compounds on basal and stimulated nitric oxide activity in human renal arteries. Methods: Rings from human renal arteries were obtained from 22 patients undergoing nephrectomy. The rings were suspended in organ baths for isometric recording of tension. We then studied the effects of N G -monomethyl-L-arginine (L-NMMA), N G ,N G -dimethyl-L-arginine (asymmetrical dimethylarginine [ADMA]), aminoguanidine (AG), and methylguanidine (MG) on artery rings under basal and stimulated conditions. Results: In precontracted arteries, L-NMMA (1 mol/L to 1 mmol/L) and ADMA (1 mol/L to 3 mmol/L) caused concentration-and endothelium-dependent contractions (median effective concentrations [EC 50 ] ϭ 13.3 mol/L and 17.5 mol/L, respectively; Emax ϭ 15 Ϯ 4% and 17 Ϯ 4% of the response to 100 mmol/L KCl, respectively). Aminoguanidine (0.01 to 3 mmol/L) and MG (0.01 to 3 mmol/L) produced endothelium-independent contractions (Emax ϭ 9 Ϯ 3% and 16 Ϯ 2% of the response to 100 mmol/L KCl, respectively). L-arginine (1 mmol/L) but not D-arginine (1 mmol/L) prevented the contractions by L-NMMA and ADMA, but did not change contractions induced by AG and MG. In precontracted arteries, the relaxation to acetylcholine was decreased but not abolished by L-NMMA and ADMA. The remaining relaxation was reduced by charybdotoxin (0.1 mol/L) and tetraethylammonium (1 mmol/L).

BMC Research Notes, 2014

Background: Our group conducted a cluster-randomised trial in 100 villages of Orissa, India to me... more Background: Our group conducted a cluster-randomised trial in 100 villages of Orissa, India to measure the impact of a rural sanitation intervention implemented under the government of India's Total Sanitation Campaign, on diarrhoea and soil-transmitted helminth infections. This paper reports on a process evaluation conducted in the context of the trial. Methods: Process evaluation data were collected through review of key documentation, quantitative surveys, direct observations, and semi-structured interviews with staff from implementing NGOs and community members. Between March 2011 and March 2012, trained enumerators recorded observations on latrine construction status every 6-8 weeks in the 50 intervention villages and noted activities reported to have taken place based on NGO staff interviews and review of NGO records. A survey among 10% of households in intervention and control villages was conducted to compare levels of awareness of key intervention components. In addition, 10% of village water and sanitation committee (VWSC) members were interviewed to measure their level of involvement in the intervention delivery.

Vascular Medicine, 2010

Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an en... more Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an endogenously produced nitric oxide (NO) synthase inhibitor. In mammals, two isoforms of DDAH, DDAH1 and DDAH2, are expressed in the cardiovascular system, suggesting that ADMA concentrations are actively regulated in blood vessels, raising the possibility that cardiovascular metabolism of ADMA constitutes a novel mechanism for the regulation of NO production. The purpose of this study was to determine the role of DDAH-catalyzed asymmetric methylarginine metabolism in the regulation of vascular function. We developed adenoviral vectors for the expression of human DDAH1 and 2. Overexpression of DDAH1 or 2 in human umbilical vein endothelial cells (HUVEC) increases DDAH activity, reduces ADMA concentrations and increases NO production. Similarly, overexpression of DDAH1 or 2 in DDAH1 +/mice carotid vessels increases NO production and attenuates the response to phenylephrine (PE), enhances acetylcholine (ACh) relaxation and attenuates the effect of exogenously applied ADMA. Finally, overexpression of either DDAH1 or 2 completely reversed the vascular dysfunction seen in DDAH1 +/mice. These data indicate that basal concentrations of ADMA in blood vessels are sufficient to regulate NO production, that increases in the level of either DDAH1 or 2, improves vascular function and that overexpression of either DDAH1 or 2 is sufficient to compensate for life-long exposure to elevated ADMA. Thus, therapeutic manipulation of DDAH expression or activity may represent a novel approach to improve vascular dysfunction in various cardiovascular diseases.

PLoS ONE, 2013

The disposal of human excreta in latrines is an important step in reducing the transmission of di... more The disposal of human excreta in latrines is an important step in reducing the transmission of diarrhoeal diseases. However, in latrines, flies can access the latrine contents and serve as a mechanical transmitter of diarrhoeal pathogens. Furthermore, the latrine contents can be used as a breeding site for flies, which may further contribute to disease transmission. Latrines do not all produce flies, and there are some which produce only a few, while others can produce thousands. In order to understand the role of the latrine in determining this productivity, a pilot study was conducted, in which fifty latrines were observed in and around Ifakara, Tanzania. The characteristics of the latrine superstructure, use of the latrine, and chemical characteristics of pit latrine contents were compared to the numbers of flies collected in an exit trap placed over the drop hole in the latrine. Absence of a roof was found to have a significant positive association (t=3.17, p=0.003) with the total number of flies collected, and temporary superstructures, particularly as opposed to brick superstructures (z=4.26, p<0.001), and increased total solids in pit latrines (z=2.57, p=0.01) were significantly associated with increased numbers of blowflies leaving the latrine. The number of larvae per gram was significantly associated with the village from which samples were taken, with the largest difference between two villages outside Ifakara (z=2.12, p=0.03). The effect of latrine superstructure (roof, walls) on fly production may indicate that improvements in latrine construction could result in decreases in fly populations in areas where they transmit diarrhoeal pathogens.

PLoS ONE, 2014

Background: More than 761 million people rely on shared sanitation facilities. These have histori... more Background: More than 761 million people rely on shared sanitation facilities. These have historically been excluded from international sanitation targets, regardless of the service level, due to concerns about acceptability, hygiene and access. In connection with a proposed change in such policy, we undertook this review to identify and summarize existing evidence that compares health outcomes associated with shared sanitation versus individual household latrines.

Nature Medicine, 2007

Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced ami... more Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced amino acids that inhibit all three isoforms of nitric oxide synthase (NOS) 1 . ADMA accumulates in various disease states, including renal failure, diabetes and pulmonary hypertension, and its concentration in plasma is strongly predictive of premature cardiovascular disease and death 2-4 . Both L-NMMA and ADMA are eliminated largely through active metabolism by dimethylarginine dimethylaminohydrolase (DDAH) 5 and thus DDAH dysfunction may be a crucial unifying feature of increased cardiovascular risk. However, despite considerable interest in this pathway and in the role of ADMA as a cardiovascular risk factor, there is little evidence to support a causal role of ADMA in pathophysiology. Here we reveal the structure of human DDAH-1 and probe the function of DDAH-1 both by deleting the Ddah1 gene in mice and by using DDAH-specific inhibitors that, as we demonstrate by crystallography, bind to the active site of human DDAH-1. We show that loss of DDAH-1 activity leads to accumulation of ADMA and reduction in NO signaling. This in turn causes vascular pathophysiology, including endothelial dysfunction, increased systemic vascular resistance and elevated systemic and pulmonary blood pressure. Our results also suggest that DDAH inhibition could be harnessed therapeutically to reduce the vascular collapse associated with sepsis.

Molecular Biology of the Cell, 2009

Address correspondence to: Beata Wojciak-Stothard (B.Wojciak-Stothard@ucl.ac.uk).

Journal of Hepatology, 2004

Background/Aims: The liver plays a prominent role in the metabolism of asymmetric dimethyl-L-argi... more Background/Aims: The liver plays a prominent role in the metabolism of asymmetric dimethyl-L-arginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase. This study was designed to determine whether plasma levels of ADMA and NO production are altered in patients with compensated and decompensated alcoholic cirrhosis.

Journal of Endocrinology, 2004

The functional properties of the endothelium of human thyroid arteries remain unexplored. We inve... more The functional properties of the endothelium of human thyroid arteries remain unexplored. We investigated the intervention of nitric oxide (NO), prostacyclin (PGI 2 ) and endothelium-derived hyperpolarizing factor (EDHF) in the responses to acetylcholine and noradrenaline in isolated thyroid arteries obtained from multi-organ donors. Artery rings were suspended in organ baths for isometric recording of tension. The contribution of NO, PGI 2 and EDHF to endothelium-dependent relaxation was determined by the inhibitory effects of N G -monomethyl--arginine (-NMMA), indomethacin, and K + channel inhibitors respectively. Acetylcholine induced concentrationdependent relaxation; this effect was not modified by indomethacin and was only partly reduced by -NMMA, but was abolished in endothelium-denuded rings. The relaxation resistant to indomethacin and -NMMA was abolished by using either apamin combined with charybdotoxin, ouabain plus barium, or a high-K + solution. Noradrenaline induced concentration-dependent contractions which were of greater magnitude in arteries denuded of endothelium or in the presence of -NMMA.

Journal of Cell Science, 2007

Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide production associated with abn... more Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide production associated with abnormal blood vessel growth and repair, however, the mechanism of action of ADMA is not well understood. We studied the role of exogenous and endogenous ADMA in the regulation of cell motility and actin cytoskeleton in porcine pulmonary endothelial cells (PAECs) and pulmonary microvascular endothelial cells (PMECs) from knockout mice that lack one of the enzyme metabolising ADMA, dimethylarginine dimethylaminohydrolase I (DDAHI) as well as endothelial cells overexpressing DDAH in vitro. We show that ADMA induced stress fibre and focal adhesion formation and inhibited cell motility in primary pulmonary endothelial cells. The effects of ADMA depended on the activity of RhoA and Rho kinase and were reversed by overexpression of DDAH, nitric oxide donors and protein kinase G activator, 8-bromo-cGMP. ADMA also inhibited the activities of Rac1 and Cdc42 in cells but these changes had a minor effect on cell motility. Endogenous ADMA increased RhoA activity and inhibited cell motility in PMECs from DDAHI knockout mice and inhibited angiogenesis in vitro. These results are the first demonstration that metabolism of cardiovascular risk factor ADMA regulates endothelial cell motility, an important factor in angiogenesis and vascular repair.

British Journal of Pharmacology, 2000

Sildena®l (0.1 ± 30 mM), a cyclic GMP phosphodiesterase 5 (PDE 5) inhibitor, induced inhibition o... more Sildena®l (0.1 ± 30 mM), a cyclic GMP phosphodiesterase 5 (PDE 5) inhibitor, induced inhibition of electrically evoked contractions of ring segments of human vas deferens from 34 vasectomies. Zaprinast (0.1 ± 100 mM), another PDE 5 inhibitor, and the nitric oxide (NO) donor sodium nitroprusside (SNP) (0.1 ± 100 mM) had no eect on neurogenic contractions. The inhibition induced by sildena®l was not modi®ed by the inhibitor of guanylate cyclase 1H-[1,2,4]oxadiazolo[4,3-a] quinoxaline-1-one (ODQ) (1 ± 30 mM) but it was abolished by the K + channel blockers tetraethylammonium (TEA, 1 mM), iberiotoxin (0.1 mM) and charybdotoxin (0.1 mM). Sildena®l, zaprinast and SNP did not aect the contractions induced by noradrenaline. SNP (10 mM) caused elevation of cyclic GMP levels that was potentiated by sildena®l (10 mM) and zaprinast (100 mM). ODQ (10 mM) inhibited the increase in cyclic GMP. Sildena®l inhibits adrenergic neurotransmission in human vas deferens. The inhibition is not related to accumulation of cyclic GMP but is probably due to activation of prejunctional large-conductance Ca 2+ -activated K + channels.

Vascular Medicine, Mar 10, 2010

Arteriosclerosis, Thrombosis, and Vascular Biology, 2012

Objective— The overproduction of vascular NO contributes toward the circulatory collapse observed... more Objective— The overproduction of vascular NO contributes toward the circulatory collapse observed in patients with septic shock. Dimethylarginine dimethylaminohydrolase (DDAH), which has 2 isoforms, metabolizes asymmetrically methylated arginines (asymmetric mono- or di-methylarginine), endogenously produced NO synthase inhibitors. We wished to investigate whether reducing DDAH1 activity, using genetic and pharmacological approaches, is protective during lipopolysaccharide-induced endotoxic shock. Methods and Results— Experiments were conducted in DDAH1 heterozygous knockout mice (DDAH1 +/− ) or naive rats treated with a synthetic pharmacological DDAH inhibitor (L-257). We demonstrate for the first time that L-257 is DDAH1 selective using recombinant human DDAH proteins. DDAH1 mRNA was expressed in aortic but not macrophage cDNA, and consistent with this expression profile, L-257 selectively inhibited NO production from lipopolysaccharide-treated aorta but not macrophages, in cultur...

Archives of Disease in Childhood - Fetal and Neonatal Edition, 2010

IntroductionImpaired utero-placental perfusion leads to fetal growth restriction. The authors hav... more IntroductionImpaired utero-placental perfusion leads to fetal growth restriction. The authors have shown a significant increase in blood flow in the uterine arteries (UAs) of pregnant sheep and a significantly reduced contractile response following local transduction with an adenovirus encoding VEGF-A165 (Ad.VEGF-A). The authors have now studied the effects of local over-expression of the VEGF-DΔNΔC isoform and investigated the mechanism behind

PloS one, 2015

Menstrual hygiene management (MHM) practices vary worldwide and depend on the individual's so... more Menstrual hygiene management (MHM) practices vary worldwide and depend on the individual's socioeconomic status, personal preferences, local traditions and beliefs, and access to water and sanitation resources. MHM practices can be particularly unhygienic and inconvenient for girls and women in poorer settings. Little is known about whether unhygienic MHM practices increase a woman's exposure to urogenital infections, such as bacterial vaginosis (BV) and urinary tract infection (UTI). This study aimed to determine the association of MHM practices with urogenital infections, controlling for environmental drivers. A hospital-based case-control study was conducted on 486 women at Odisha, India. Cases and controls were recruited using a syndromic approach. Vaginal swabs were collected from all the participants and tested for BV status using Amsel's criteria. Urine samples were cultured to assess UTI status. Socioeconomic status, clinical symptoms and reproductive history, an...

Arteriosclerosis, Thrombosis, and Vascular Biology, 2015

Nitric oxide is a key to numerous physiological and pathophysiological processes. Nitric oxide pr... more Nitric oxide is a key to numerous physiological and pathophysiological processes. Nitric oxide production is regulated endogenously by 2 methylarginines, asymmetric dimethylarginine (ADMA) and monomethyl-l-arginine. The enzyme that specifically metabolizes asymmetric dimethylarginine and monomethyl-l-arginine is dimethylarginine dimethylaminohydrolase (DDAH). The first isoform dimethylarginine dimethylaminohydrolase 1 has previously been shown to be an important regulator of methylarginines in both health and disease. This study explores for the first time the role of endogenous dimethylarginine dimethylaminohydrolase 2 in regulating cardiovascular physiology and also determines the functional impact of dimethylarginine dimethylaminohydrolase 2 deletion on outcome and immune function in sepsis. Mice, globally deficient in Ddah2, were compared with their wild-type littermates to determine the physiological role of Ddah2 using in vivo and ex vivo assessments of vascular function. We show that global knockout of Ddah2 results in elevated blood pressure during periods of activity (mean [SEM], 118.5 [1.3] versus 112.7 [1.1] mm Hg; P=0.025) and changes in vascular responsiveness mediated by changes in methylarginine concentration, mean myocardial tissue asymmetric dimethylarginine (SEM) was 0.89 (0.06) versus 0.67 (0.05) μmol/L (P=0.02) and systemic nitric oxide concentrations. In a model of severe polymicrobial sepsis, Ddah2 knockout affects outcome (120-hour survival was 12% in Ddah2 knockouts versus 53% in wild-type animals; P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Monocyte-specific deletion of Ddah2 results in a similar pattern of increased severity to that seen in globally deficient animals. Ddah2 has a regulatory role both in normal physiology and in determining outcome of severe polymicrobial sepsis. Elucidation of this role identifies a mechanism for the observed relationship between Ddah2 polymorphisms, cardiovascular disease, and outcome in sepsis.

Transactions of the Royal Society of Tropical Medicine and Hygiene, 2015

Sentinel toys are increasingly used as a method of assessing young children&amp;amp;amp;amp;a... more Sentinel toys are increasingly used as a method of assessing young children&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s exposure to faecal pathogens in households in low-income settings. However, there is no consensus on the suitability of different approaches. We evaluated three types of toy balls with different surfaces (plastic, rubber, urethane) in the laboratory to compare the uptake of faecal indicator bacteria (Escherichia coli) on their surface. We performed bacteria survival analysis under different environmental conditions and tested laboratory methods for bacteria removal and recovery. In a field study we distributed sterile urethane balls to children &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;5 from 360 households in rural India. After 24 hours, we collected and rinsed the toys in sterile water, assayed for thermotolerant coliforms (TTC) and explored associations between the level of contamination and household characteristics. In the laboratory, urethane foam balls took up more indicator bacteria than the other balls. Bacteria recovery did not differ based on mechanic vs no agitation. Higher temperatures and moisture levels increased bacterial yield. In the field, the only factor associated with a decreased recovery of TTC from the balls was having a soil (unpaved) floor. Sentinel toys may be an effective tool for assessing young children&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s exposure to faecal pathogens. However, even using methods designed to increase bacterial recovery, limited sensitivity may require larger sample sizes.

Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced ami... more Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced amino acids that inhibit all three isoforms of nitric oxide synthase (NOS) 1 . ADMA accumulates in various disease states, including renal failure, diabetes and pulmonary hypertension, and its concentration in plasma is strongly predictive of premature cardiovascular disease and death 2-4 . Both L-NMMA and ADMA are eliminated largely through active metabolism by dimethylarginine dimethylaminohydrolase (DDAH) 5 and thus DDAH dysfunction may be a crucial unifying feature of increased cardiovascular risk. However, despite considerable interest in this pathway and in the role of ADMA as a cardiovascular risk factor, there is little evidence to support a causal role of ADMA in pathophysiology. Here we reveal the structure of human DDAH-1 and probe the function of DDAH-1 both by deleting the Ddah1 gene in mice and by using DDAH-specific inhibitors that, as we demonstrate by crystallography, bind to the active site of human DDAH-1. We show that loss of DDAH-1 activity leads to accumulation of ADMA and reduction in NO signaling. This in turn causes vascular pathophysiology, including endothelial dysfunction, increased systemic vascular resistance and elevated systemic and pulmonary blood pressure. Our results also suggest that DDAH inhibition could be harnessed therapeutically to reduce the vascular collapse associated with sepsis.

American Journal of Hypertension, 2001

Background: Plasma levels of endogenous guanidine compounds are increased in various pathologic c... more Background: Plasma levels of endogenous guanidine compounds are increased in various pathologic conditions, including chronic renal failure. In the present study we tested the effects of some of these compounds on basal and stimulated nitric oxide activity in human renal arteries. Methods: Rings from human renal arteries were obtained from 22 patients undergoing nephrectomy. The rings were suspended in organ baths for isometric recording of tension. We then studied the effects of N G -monomethyl-L-arginine (L-NMMA), N G ,N G -dimethyl-L-arginine (asymmetrical dimethylarginine [ADMA]), aminoguanidine (AG), and methylguanidine (MG) on artery rings under basal and stimulated conditions. Results: In precontracted arteries, L-NMMA (1 mol/L to 1 mmol/L) and ADMA (1 mol/L to 3 mmol/L) caused concentration-and endothelium-dependent contractions (median effective concentrations [EC 50 ] ϭ 13.3 mol/L and 17.5 mol/L, respectively; Emax ϭ 15 Ϯ 4% and 17 Ϯ 4% of the response to 100 mmol/L KCl, respectively). Aminoguanidine (0.01 to 3 mmol/L) and MG (0.01 to 3 mmol/L) produced endothelium-independent contractions (Emax ϭ 9 Ϯ 3% and 16 Ϯ 2% of the response to 100 mmol/L KCl, respectively). L-arginine (1 mmol/L) but not D-arginine (1 mmol/L) prevented the contractions by L-NMMA and ADMA, but did not change contractions induced by AG and MG. In precontracted arteries, the relaxation to acetylcholine was decreased but not abolished by L-NMMA and ADMA. The remaining relaxation was reduced by charybdotoxin (0.1 mol/L) and tetraethylammonium (1 mmol/L).

BMC Research Notes, 2014

Background: Our group conducted a cluster-randomised trial in 100 villages of Orissa, India to me... more Background: Our group conducted a cluster-randomised trial in 100 villages of Orissa, India to measure the impact of a rural sanitation intervention implemented under the government of India's Total Sanitation Campaign, on diarrhoea and soil-transmitted helminth infections. This paper reports on a process evaluation conducted in the context of the trial. Methods: Process evaluation data were collected through review of key documentation, quantitative surveys, direct observations, and semi-structured interviews with staff from implementing NGOs and community members. Between March 2011 and March 2012, trained enumerators recorded observations on latrine construction status every 6-8 weeks in the 50 intervention villages and noted activities reported to have taken place based on NGO staff interviews and review of NGO records. A survey among 10% of households in intervention and control villages was conducted to compare levels of awareness of key intervention components. In addition, 10% of village water and sanitation committee (VWSC) members were interviewed to measure their level of involvement in the intervention delivery.

Vascular Medicine, 2010

Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an en... more Dimethylarginine dimethylaminohydrolase (DDAH) degrades asymmetric dimethylarginine (ADMA), an endogenously produced nitric oxide (NO) synthase inhibitor. In mammals, two isoforms of DDAH, DDAH1 and DDAH2, are expressed in the cardiovascular system, suggesting that ADMA concentrations are actively regulated in blood vessels, raising the possibility that cardiovascular metabolism of ADMA constitutes a novel mechanism for the regulation of NO production. The purpose of this study was to determine the role of DDAH-catalyzed asymmetric methylarginine metabolism in the regulation of vascular function. We developed adenoviral vectors for the expression of human DDAH1 and 2. Overexpression of DDAH1 or 2 in human umbilical vein endothelial cells (HUVEC) increases DDAH activity, reduces ADMA concentrations and increases NO production. Similarly, overexpression of DDAH1 or 2 in DDAH1 +/mice carotid vessels increases NO production and attenuates the response to phenylephrine (PE), enhances acetylcholine (ACh) relaxation and attenuates the effect of exogenously applied ADMA. Finally, overexpression of either DDAH1 or 2 completely reversed the vascular dysfunction seen in DDAH1 +/mice. These data indicate that basal concentrations of ADMA in blood vessels are sufficient to regulate NO production, that increases in the level of either DDAH1 or 2, improves vascular function and that overexpression of either DDAH1 or 2 is sufficient to compensate for life-long exposure to elevated ADMA. Thus, therapeutic manipulation of DDAH expression or activity may represent a novel approach to improve vascular dysfunction in various cardiovascular diseases.

PLoS ONE, 2013

The disposal of human excreta in latrines is an important step in reducing the transmission of di... more The disposal of human excreta in latrines is an important step in reducing the transmission of diarrhoeal diseases. However, in latrines, flies can access the latrine contents and serve as a mechanical transmitter of diarrhoeal pathogens. Furthermore, the latrine contents can be used as a breeding site for flies, which may further contribute to disease transmission. Latrines do not all produce flies, and there are some which produce only a few, while others can produce thousands. In order to understand the role of the latrine in determining this productivity, a pilot study was conducted, in which fifty latrines were observed in and around Ifakara, Tanzania. The characteristics of the latrine superstructure, use of the latrine, and chemical characteristics of pit latrine contents were compared to the numbers of flies collected in an exit trap placed over the drop hole in the latrine. Absence of a roof was found to have a significant positive association (t=3.17, p=0.003) with the total number of flies collected, and temporary superstructures, particularly as opposed to brick superstructures (z=4.26, p<0.001), and increased total solids in pit latrines (z=2.57, p=0.01) were significantly associated with increased numbers of blowflies leaving the latrine. The number of larvae per gram was significantly associated with the village from which samples were taken, with the largest difference between two villages outside Ifakara (z=2.12, p=0.03). The effect of latrine superstructure (roof, walls) on fly production may indicate that improvements in latrine construction could result in decreases in fly populations in areas where they transmit diarrhoeal pathogens.

PLoS ONE, 2014

Background: More than 761 million people rely on shared sanitation facilities. These have histori... more Background: More than 761 million people rely on shared sanitation facilities. These have historically been excluded from international sanitation targets, regardless of the service level, due to concerns about acceptability, hygiene and access. In connection with a proposed change in such policy, we undertook this review to identify and summarize existing evidence that compares health outcomes associated with shared sanitation versus individual household latrines.

Nature Medicine, 2007

Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced ami... more Asymmetric dimethylarginine (ADMA) and monomethyl arginine (L-NMMA) are endogenously produced amino acids that inhibit all three isoforms of nitric oxide synthase (NOS) 1 . ADMA accumulates in various disease states, including renal failure, diabetes and pulmonary hypertension, and its concentration in plasma is strongly predictive of premature cardiovascular disease and death 2-4 . Both L-NMMA and ADMA are eliminated largely through active metabolism by dimethylarginine dimethylaminohydrolase (DDAH) 5 and thus DDAH dysfunction may be a crucial unifying feature of increased cardiovascular risk. However, despite considerable interest in this pathway and in the role of ADMA as a cardiovascular risk factor, there is little evidence to support a causal role of ADMA in pathophysiology. Here we reveal the structure of human DDAH-1 and probe the function of DDAH-1 both by deleting the Ddah1 gene in mice and by using DDAH-specific inhibitors that, as we demonstrate by crystallography, bind to the active site of human DDAH-1. We show that loss of DDAH-1 activity leads to accumulation of ADMA and reduction in NO signaling. This in turn causes vascular pathophysiology, including endothelial dysfunction, increased systemic vascular resistance and elevated systemic and pulmonary blood pressure. Our results also suggest that DDAH inhibition could be harnessed therapeutically to reduce the vascular collapse associated with sepsis.

Molecular Biology of the Cell, 2009

Address correspondence to: Beata Wojciak-Stothard (B.Wojciak-Stothard@ucl.ac.uk).

Journal of Hepatology, 2004

Background/Aims: The liver plays a prominent role in the metabolism of asymmetric dimethyl-L-argi... more Background/Aims: The liver plays a prominent role in the metabolism of asymmetric dimethyl-L-arginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase. This study was designed to determine whether plasma levels of ADMA and NO production are altered in patients with compensated and decompensated alcoholic cirrhosis.

Journal of Endocrinology, 2004

The functional properties of the endothelium of human thyroid arteries remain unexplored. We inve... more The functional properties of the endothelium of human thyroid arteries remain unexplored. We investigated the intervention of nitric oxide (NO), prostacyclin (PGI 2 ) and endothelium-derived hyperpolarizing factor (EDHF) in the responses to acetylcholine and noradrenaline in isolated thyroid arteries obtained from multi-organ donors. Artery rings were suspended in organ baths for isometric recording of tension. The contribution of NO, PGI 2 and EDHF to endothelium-dependent relaxation was determined by the inhibitory effects of N G -monomethyl--arginine (-NMMA), indomethacin, and K + channel inhibitors respectively. Acetylcholine induced concentrationdependent relaxation; this effect was not modified by indomethacin and was only partly reduced by -NMMA, but was abolished in endothelium-denuded rings. The relaxation resistant to indomethacin and -NMMA was abolished by using either apamin combined with charybdotoxin, ouabain plus barium, or a high-K + solution. Noradrenaline induced concentration-dependent contractions which were of greater magnitude in arteries denuded of endothelium or in the presence of -NMMA.

Journal of Cell Science, 2007

Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide production associated with abn... more Asymmetric dimethylarginine (ADMA) is an inhibitor of nitric oxide production associated with abnormal blood vessel growth and repair, however, the mechanism of action of ADMA is not well understood. We studied the role of exogenous and endogenous ADMA in the regulation of cell motility and actin cytoskeleton in porcine pulmonary endothelial cells (PAECs) and pulmonary microvascular endothelial cells (PMECs) from knockout mice that lack one of the enzyme metabolising ADMA, dimethylarginine dimethylaminohydrolase I (DDAHI) as well as endothelial cells overexpressing DDAH in vitro. We show that ADMA induced stress fibre and focal adhesion formation and inhibited cell motility in primary pulmonary endothelial cells. The effects of ADMA depended on the activity of RhoA and Rho kinase and were reversed by overexpression of DDAH, nitric oxide donors and protein kinase G activator, 8-bromo-cGMP. ADMA also inhibited the activities of Rac1 and Cdc42 in cells but these changes had a minor effect on cell motility. Endogenous ADMA increased RhoA activity and inhibited cell motility in PMECs from DDAHI knockout mice and inhibited angiogenesis in vitro. These results are the first demonstration that metabolism of cardiovascular risk factor ADMA regulates endothelial cell motility, an important factor in angiogenesis and vascular repair.

British Journal of Pharmacology, 2000

Sildena®l (0.1 ± 30 mM), a cyclic GMP phosphodiesterase 5 (PDE 5) inhibitor, induced inhibition o... more Sildena®l (0.1 ± 30 mM), a cyclic GMP phosphodiesterase 5 (PDE 5) inhibitor, induced inhibition of electrically evoked contractions of ring segments of human vas deferens from 34 vasectomies. Zaprinast (0.1 ± 100 mM), another PDE 5 inhibitor, and the nitric oxide (NO) donor sodium nitroprusside (SNP) (0.1 ± 100 mM) had no eect on neurogenic contractions. The inhibition induced by sildena®l was not modi®ed by the inhibitor of guanylate cyclase 1H-[1,2,4]oxadiazolo[4,3-a] quinoxaline-1-one (ODQ) (1 ± 30 mM) but it was abolished by the K + channel blockers tetraethylammonium (TEA, 1 mM), iberiotoxin (0.1 mM) and charybdotoxin (0.1 mM). Sildena®l, zaprinast and SNP did not aect the contractions induced by noradrenaline. SNP (10 mM) caused elevation of cyclic GMP levels that was potentiated by sildena®l (10 mM) and zaprinast (100 mM). ODQ (10 mM) inhibited the increase in cyclic GMP. Sildena®l inhibits adrenergic neurotransmission in human vas deferens. The inhibition is not related to accumulation of cyclic GMP but is probably due to activation of prejunctional large-conductance Ca 2+ -activated K + channels.