***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Although reports of decreased plasma taurine in trauma , sepsis and critical illness are available , very little is known about the relationships among changes in plasma taurine , other amino acid levels and metabolic variables . We analyzed a large series of plasma amino acid profiles obtained in trauma patients with sepsis who were undergoing total parenteral nutrition .  The correlations between plasma taurine , other amino acid levels , parenteral substrate doses and metabolic and cardiorespiratory variables were assessed by regression analysis . Post-traumatic hypotaurinemia was followed by partial recovery toward less abnormal values when sepsis developed . Levels of taurine were directly and significantly related to levels of glutamate , aspartate , beta-alanine and phosphoethanolamine ( and unrelated to other amino acids ) . Levels of these amino acids increased simultaneously with increasing doses of leucine , isoleucine and valine in total parenteral nutrition . Decreasing taurine was associated with increasing lactate , arteriovenous O(2 ) concentration difference and respiratory index , and with decreasing cholesterol and cardiac index . These results characterize the relationships between plasma taurine and other amino acid levels in sepsis , provide evidence of amino acid interactions that may support taurine availability and show more severe decreases in plasma taurine with the worsening of metabolic and cardiorespiratory patterns Objective : l-arginine supplementation in sepsis is controversial . Septic shock has been alternatively viewed as an l-arginine-deficient state or as a syndrome caused by excess nitric oxide , an end-product of l-arginine metabolism . Design : R and omized , placebo-controlled , and double-blinded ( investigators , veterinarians , and pharmacists ) . Setting : Laboratory . Subjects : Purpose -bred , 1- to 2-yr-old , 10- to 12-kg beagles . Interventions : The effects of parenteral l-arginine alone or in combination with N-acetylcysteine were compared with vehicle alone in a well-characterized canine model of Escherichia coli peritonitis . Two doses were studied that delivered approximately 1.5-fold ( 10 mg·kg−1·hr−1 ) and 15-fold ( 100 mg·kg−1·hr−1 ) the l-arginine dose typically administered with st and ard total parenteral nutrition . Animals in the low- and high-dose l-arginine arms were further r and omized to receive vehicle alone or N-acetylcysteine ( 20 mg·kg−1·hr−1 ) as an antioxidant to prevent peroxynitrite formation . Measurements and Main Results : The main measurements were hemodynamics , plasma arginine and ornithine , serum nitrate/nitrite , laboratory studies for organ injury , and survival . Both doses of l-arginine similarly increased mortality ( p = .02 ) , and worsened shock ( p = .001 for reduced mean arterial pressure ) . These effects were associated with significant increases in plasma arginine ( p = .0013 ) and ornithine ( p = .0021 ) . In addition , serum nitrate/nitrite ( p = .02 ) , liver enzymes ( p = .08 ) , and blood urea nitrogen/creatinine ratios ( p = .001 ) rose , whereas arterial pH ( p = .001 ) and bicarbonate levels ( p = .001 )  fell . N-acetylcysteine did not significantly decrease any of the harmful effects of l-arginine . Thus , parenteral l-arginine monotherapy was markedly harmful in animals with septic shock . Conclusions : These findings suggest that supplemental parenteral l-arginine , at doses above st and ard dietary practice s , should be avoided in critically ill patients with septic shock Asymmetric  dimethylarginine ( ADMA ) is an endogenous inhibitor of endothelial nitric oxide ( NO ) synthase . Its concentration is elevated in patients with end-stage renal disease ( ESRD ) , in part because it is excreted via the kidneys . In this study , the plasma concentrations of ADMA , symmetric dimethylarginine , and L-arginine  were determined in relation to plasma nitrate levels ( as an index of NO formation ) for a group of 80 patients with ESRD . The effects of two treatment methods , i.e. , hemodialysis ( HD ) and peritoneal dialysis ( PD ) , and the role of the presence of atherosclerotic disease were evaluated . Forty-three patients receiving HD and 37 patients receiving PD were compared with healthy control subjects .  Plasma L-arginine and dimethylarginine levels were determined by HPLC , using precolumn derivatization with o-phthaldialdehyde . Plasma nitrate levels were determined by gas chromatography-mass spectrometry . Predialysis ADMA concentrations in HD-treated patients were approximately sixfold higher than those in the control group ( 6.0+/-0.5 versus 1.0+/-0.1 micromol/L ; P < 0.05 ) . Plasma nitrate concentrations were significantly lower in HD-treated patients , which suggests that ADMA may inhibit NO synthase . In contrast , plasma ADMA levels and nitrate concentrations in PD-treated patients were similar to those in control subjects . Plasma L-arginine concentrations were not significantly decreased in patients with ESRD .  ADMA concentrations were significantly decreased 5 h after HD , compared with baseline values . ADMA levels were significantly higher in HD-treated patients with manifest atherosclerotic disease than in HD-treated patients without atherosclerotic disease ( 7.31+/-0.70 versus 3.95+/-0.52 micromol/L ; P < 0.05 ) . This study confirms that ADMA is accumulated in ESRD . PD-treated patients exhibit significantly lower ADMA levels than do HD-treated patients . Accumulation of ADMA may be a risk factor for the development of endothelial dysfunction and cardiovascular disease in patients with ESRD Objective To investigate the role of nitric oxide in the regulation of vascular tone in patients with the sepsis syndrome . Design Prospect i ve , intervention study . Setting Tertiary care hospital . Patients Fifteen patients admitted to our medical intensive care unit with the diagnosis of sepsis syndrome by defined criteria . Interventions Eight patients received Nω-nitro-L-arginine was followed by hypertension ( mean blood pressure increased from 89 ± 8 to a maximum of 140 ± 12 mm Hg ) accompanied by a decrease in cardiac index ( from 3.51 ± 0.39 to a minimum of 2.65 ± 0.21 L/min/m2 ) and an increase in right atrial and pulmonary artery occlusion pressure . Systemic vascular resistance index increased from 1871.1 ± 302.3 to 3825.6 ± 244.4 dyne·sec/cm5·m2 , and pulmonary vascular resistance increased from 533.2 ± 125.8 to 816.0 ± 117.3 dyne·sec/cm5·m2 . These changes induced by Nω-nitro-L-arginine were reversed by the administration of L-arginine . The administration of L-arginine to another group of patients caused transient hypotension ( from 103 ± 6 to 81 ± 10 mm Hg ) and an increase in cardic index ( from 3.57 ± 0.15 to 4.74 ± 0.54 L/min/m2 ) . Both systemic and pulmonary vascular resistance indices decreased ( from 1987.6 ± 163.9 to 1251.4 ± 231.5 dyne·sec/cm5·m2 , and from 486.1 ± 65.2 to 380.5 ± 70.3 dyne·sec/cm5·m2 ) . Parallel to the increase in oxygen transport due to the increase in cardiac output , oxygen consumption index increased significantly 1 min after L-arginine ( from 127.0 ± 19.0 to 182.5 ± 37.3 mL/min/m2 ) . All mentioned changes were statistically significant ( p<.05 ) . Conclusions A continuous basal release of nitric oxide plays a role in the regulation of systemic and pulmonary vascular tone in patients with sepsis syndrome . L-arginine has systemic and pulmonary vasodilatory actions . ( Crit Care Med 1993 ; 21:1287–1295 Vascular risk factors increase the risk of developing Alzheimer 's disease . Increased concentrations of circulating homocysteine are associated with an increased risk of both vascular disease and Alzheimer 's disease .  Asymmetric dimethylarginine  (  ADMA  ) is an endogenous inhibitor of nitric oxide synthase . There is an increase in the concentration of ADMA in the circulation in vascular disease . We measured the concentrations of  homocysteine , ADMA and nitric oxide  ( as nitrate and nitrite ) in the plasma of 25 patients with Alzheimer 's disease and 25 control subjects . There was a highly significant increase in the plasma concentration of homocysteine ( P<0.001 ) and ADMA ( P<0.0001 ) and a highly significant decrease in the plasma concentration of nitric oxide ( P<0.0001 ) among the Alzheimer 's patients . In the combined patient and control groups a highly significant positive correlation was found between the plasma concentrations of homocysteine and ADMA ( r=0.782 , P<0.0001 ) . In addition , significant negative correlations were detected between the plasma concentration of nitric oxide and the plasma concentration of homocysteine ( r=-0.592 , P<0.0001 ) and ADMA ( r=-0.789 , P<0.0001 ) . These significant correlations were found to persist , even when they were restricted to the Alzheimer 's patients . The inhibition of endothelial nitric oxide synthesis by ADMA impairs cerebral blood flow , which may contribute to the development of Alzheimer 's disease . Endothelial dysfunction is also associated with atherosclerosis and stroke , which are important risk factors for Alzheimer 's disease . Inflammation plays an important role in Alzheimer 's disease and the inhibition of endothelial nitric oxide by ADMA may increase the concentration of inflammatory mediators in the brain . The inhibition of neuronal nitric oxide synthesis by ADMA may cause cognitive dysfunction in Alzheimer 's disease Sepsis has been associated with specific plasma amino acid patterns . Sixty-five patients were prospect ively investigated as to whether these patterns are indeed sepsis specific , or specific for metabolic stress without concomitant sepsis , or associated with the presence of organ failure . Virtually all aminoacid levels were decreased by 10–30 % ( p < 0.05 ) , whereas cystine and phenyl-alanine were significantly elevated . These changes were more pronounced in severe sepsis . Organ failure was not associated with significantly altered amino acid profiles . No differences were found between sepsis and stress without signs of sepsis . In addition , imminent death was not associated with aberrant amino acid profiles . We conclude that sepsis and metabolic stress are associated with changes in plasma amino acid profiles , but that such changes are aspeciflc and therefore poor indicators of disease severity Acute inflammation impairs vascular function . Based on the association between endothelial dysfunction and plasma concentrations of L-arginine and the endogenous nitric oxide synthase inhibitor ADMA ( asymmetrical dimethylarginine ) , we hypothesized that the ratio between L-arginine and ADMA could be affected by experimental inflammation . Plasma concentrations of L-arginine , ADMA and SDMA ( symmetrical dimethylarginine )  were studied at baseline and 3.5 h after intravenous administration of Escherichia coli endotoxin [ LPS ( lipopolysaccharide ) , 20 units/kg of body mass ; n = 8 ] or placebo ( n = 9 ) in healthy males .  L-Arginine and dimethylarginines  were quantified after solid-phase extraction by reversed-phase HPLC . Body temperature , heart rate and leucocyte count increased after LPS administration ( P < 0.01 for all ) . LPS administration decreased plasma concentrations of L-arginine from 66 micromol/l [ 95 % CI ( confidence interval ) : 56 , 88 ] at baseline to 48 micromol/l ( CI : 40 , 60 ) after 3.5 h ( P < 0.02 ) , but did not affect ADMA and SDMA concentrations . Consequently , the L-arginine/ADMA ratio declined significantly from a median of 159 ( CI : 137 , 193 ) to 135 ( CI : 103 , 146 ) ; a decrease of 25 ( CI : -68 , -13 ; P < 0.02 ) . L-Arginine , ADMA , SDMA and the L-arginine/ADMA ratio remained constant over time in controls . Acute inflammation reduces the L-arginine/ADMA ratio which could contribute to impaired vascular function Objective To determine the effect of trauma on arginase , an arginine-metabolizing enzyme , in cells of the immune system in humans . Summary Background Data Arginase , classically considered an enzyme exclusive to the liver , is now known to exist in cells of the immune system . Arginase expression is induced in these cells by cytokines interleukin ( IL ) 4 , IL-10 , and transforming growth factor 
    Output:
    
Plasma concentrations of plasma L-arginine are substantially decreased in patients with sepsis in the absence of trauma or surgery .