The role of glucose,long-chain triglycerides and amino acids for promotion of amino acid balance across peripheral tissues in man

The role of amino acids, glucose and lipids in improving amino acid balance in peripheral tissues was evaluated. Primed constant infusion of L -[ring-²H₅]phenylalanine in combination with flux measurements of glucose, free fatty acids (FFA) and amino acids across arm and leg tissues were applied in male volunteers after an overnight fast with subsequent primed constant infusions of amino acids (0·2 g N kg^?1 body weight day^?1), long-chain triglycerides (0·98–1·079 g kg^?1 day^?1) and glucose (3·13–3·62 g kg^?1 day^?1). Amino acids and phenylalanine tracer infusion continued for 6 h; the lipid infusion was provided during 2–6 h from the start, and glucose infusion was provided between 4 and 6 h. Flux measurements were performed at steady state before the next infusion started. Arterial concentrations of infused substrates increased during provision, but remained constant thereafter. Plasma insulin increased when glucose was provided, whereas insulin-like growth factor (IGF) I was unchanged during all infusions. Blood flow was unchanged in arm tissue during all infusions, while leg blood flow increased during fat and glucose infusion. FFA and glucose balance were unchanged during amino acid infusion but improved during lipid and glucose infusions. Amino acid balance was negative across arm and leg tissues in the fasted state, but reached balance during amino acid infusion. This effect was equally dependent on protein synthesis and protein degradation without any contribution from lipids and glucose. 3-Methylhistidine release from tissues was not influenced by any substrate. Our results suggest that extracellular amino acid concentrations determine amino acid balance across peripheral tissues independently of non-protein calories, insulin and IGF-I.     

The separate and combined effect of leucine and insulin on muscle free amino acids

Summary. The effect of insulin and leucine on amino acid and protein metabolism in muscle is not fully understood. To characterize their separate and combined effects on free amino acids in muscle and plasma, 11 volunteers received an infusion of either leucine (1 g h^-1, Group 1) or glucose (20 g h^-1, Group 2) for 2 h followed by a combination of the two infusions for an additional 2-h period. In muscle both the leucine infusion and the leucine plus glucose infusion increased the concentration of free leucine significantly, while the sum of the other branched chain amino acids (BCAA), of the aromatic amino acids and of the basic amino acids decreased. Glucose infusion alone decreased the sum of the essential amino acids, the BCAA and the aromatic amino acids. The combination of leucine and glucose augmented the decreases, while the concentrations of glutamate, glutamine and alanine were unaffected. In plasma the leucine infusion doubled the leucine concentration and decreased alanine, valine, methionine, tyrosine, phenylalanine and the sum of the aromatic amino acids. Glucose infusion decreased methionine, serine, isoleucine and the sum of the essential amino acids and of the BCAA. The combination of leucine infusion and hyperinsulinaemia augmented the decreases. The plasma concentrations of the keto acids of valine and isoleucine decreased by the leucine infusion while the concentrations of the keto acid of leucine and isoleucine decreased by glucose infusion. The combination of leucine and glucose had an additive effect. These effects are attributed to a specific effect of leucine on the other two BCAA and a depression of muscle proteolysis by both leucine and insulin, resulting from glucose infusion.     

Protective effects of triflusal on secondary thrombus growth and vascular cyclooxygenase-2

Summary. Background: Carotid residual mural thrombus predisposes to recurrent thrombosis and/or distal embolization (i.e. cerebrovascular ischemia). Objectives: Our aims were (i) to analyze and compare the efficacy of aspirin, triflusal, and its main metabolite 2‐hydroxy‐4‐trifluorometylbenzoic acid (HTB) on secondary thrombus growth; and (ii) evaluate to what extent the three Cox‐1 inhibitors influenced vascular Cox‐1/Cox‐2 expression and endothelial prostacyclin synthesis. Methods: In a rabbit model of ex vivo thrombosis, a fresh mural thrombus was formed on damaged vessels at flow conditions typical of mild and severe carotid stenoses. The effects of Cox‐1 inhibitors administered both intravenously (i.v.) (aspirin 5 mg kg^?1, triflusal 10 mg kg^?1, and HTB 10 mg kg^?1) and orally (p.o.) (8 days; aspirin 30 mg kg^?1 day^?1, and triflusal 40 mg kg^?1 day^?1) on secondary thrombus growth were assessed by In‐¹¹¹deposited platelets and compared with a placebo control. Arterial Cox‐1/Cox‐2 expression after 8‐day treatment was evaluated at mRNA and protein levels. Additionally, a drug‐related dose‐dependent in vitro assay was performed for endothelial PGI₂ release measurement (Cox‐2 activity). Results: All Cox inhibitors similarly and significantly (P < 0.05) reduced secondary thrombus formation after i.v. and p.o. administration versus placebo control. Treatments exerted no effect on vascular Cox‐1 mRNA whereas Cox‐2 mRNA was moderately reduced by aspirin and triflusal (placebo 100% ± 9%, aspirin 70% ± 2% and triflusal 70% ± 2%; P < 0.05). Cox‐2 protein levels were slightly higher in the triflusal versus aspirin group (placebo 100% ± 6%, aspirin 35% ± 10% and triflusal 61% ± 9%; P < 0.005 versus placebo). Interestingly, in vitro, HTB solely maintained endothelial PGI₂ synthesis levels similar to the control. Conclusions: At a similar level of efficacy in inhibiting secondary thrombosis, triflusal seems to better preserve Cox‐2 expression than aspirin and its metabolite HTB was able to protect endothelial prostacyclin production.     

Essential and non-essential amino acid requirement in injured patients receiving total parenteral nutrition

The metabolic derangements of injury are known to influence nitrogen (N) requirements whilst less is known about individual amino acid (AA) requirements. This study was designed to investigate prospectively N vs AA requirement in 36 injured patients treated with total parenteral nutrition (TPN). The non-protein caloric input was 30 kcal kg^-1 day^-1 and three AA solutions were assessed containing the same AAs but in different proportion. Overall N intake was set at 0.35 g N kg^-1 day^-1 for solution A and B and 0.24 g N kg^-1 day^-1 for solution C. Solution B was similar to A, both being enriched in branched chain AAs (BCAA: 0.69 g kg^-1 day^-1 in B compared with 0.55 g kg^-1 day^-1 in A) while decreased in aromatic and sulphurated forms (1.75 times the normal need). Solution C was designed to maintain a daily input of BCAA similar to A (0.52 g kg^-1 day^-1) but with the supply of aromatic and sulphurated AA between solutions A and B, the supply of other AAs (lysine, theonine, histidine, arginine, glycine) being dependent on the selected N intake. For all the essential AAs the supply was always greater than normal allowances. Increasing BCAA over 0.55 g kg^-1 day^-1 did not improve N balance when N intake was 0.35 g kg^-1 day^-1, whilst nutrition with solution C was unable to maintain N balance. Moreover we found indirect evidence that this N intake, 0.52g kg^-1 day^-1 was more sparing than 0.37 g kg^-1 day^-1 of BCAA. N balance of the three groups suggests that injured patients need more than 0.24 g N kg^-1 day^-1 probably for non-essential AA synthesis. The study of plasma AA values support the increased non-essential N need in group C and allows us to suggest the proper AA composition of the overall optimal daily N intake (0.28–0.30 g N kg^-1 day^-1) in catabolic patients: BCAA about 0.5 g kg^-1 day^-1, phenylalanine, methionine, tryptophane, threonine and lysine from 2–3 to 5–10 times the normal allowance, the remainding N supply (about 0.14 g kg^-1 day^-1) should be made up from histidine, arginine, tyrosine, serine, proline, glycine, glutamic and aspartic acid. Presented in abstract form at the 3rd European Congress on Intensive Care Medicine, Hamburg, June 11–14, 1986     

Renal metabolism of amino acids and ammonia in subjects with normal renal function and in patients with chronic renal insufficiency.

The net renal metabolism of amino acids and ammonia in the post absorptive state was evaluated in subjects with normal renal function and in patients with chronic renal insufficiency by measuring renal uptake and release, and urinary excretion of free amino acids and ammonia. In normal subjects the kidney extracts glutamine, proline, citrulline, and phenylalanine and releases serine, arginine, taurine, threonine, tyrosine, ornithine, lysine, and perhaps alanine. The renal uptake of amino acids from arterial blood occurs by way of plasma only, whereas approximately a half of amino acid release takes place by way of blood cells. Glycine is taken up from arterial plasma, while similar amounts of this amino acid are released by way of blood cells. In the same subjects total renal ammonia production can be largely accounted for by glutamine extracted. In patients with chronic renal insufficiency (a) the renal uptake of phenylalanine and the release of taurine and ornithine disappear; (b) the uptake of glutamine and proline, and the release of serine and threonine are reduced by 80--90%; (c) the uptake of citrulline and the release of alanine, arginine, tyrosine, and lysine are reduced by 60--70%; (d) no exchange of glycine is detectable either by way of plasma or by way of blood cells; (e) exchange of any other amino acid via blood cells disappears, and (f) total renal ammonia production is reduced and not more than 35% of such production can be accounted for by glutamine extracted, so that alternative precursors must be used. A 140% excess of nitrogen release found in the same patients suggests an intrarenal protein and peptide breakdown, which eventually provides free amino acids for ammonia production.     

Influence of branched-chain amino acid infusion on arterial concentrations and brain exchange of amino acids in patients with hepatic cirrhosis

Summary.

• 1 The influence of branched-chain amino acid (BCAA) infusion on arterial concentrations and brain exchange of amino acids was studied in seven patients with hepatic cirrhosis and in six healthy control subjects. Arterial levels and arterial-jugular venous (A-JV) concentration differences for amino acids, glucose, ketone bodies and lactate were measured in the basal state and during a constant rate, 150 min intravenous infusion of a BCAA solution (250 fmiol/min, 70% L-leucine, 20% L-valine and 10% L-isoleucine).
• 2 In the basal state the arterial whole blood concentrations of tyrosine, phenylalanine and methionine were 40–130 % higher in the cirrhotic patients compared to the controls, while the levels of the BCAA were 20–35 % lower. The patients' concentration of aspartic acid was 70% below the corresponding control value.
• 3 During BCAA infusion the arterial leucine concentration rose 4–5 fold while valine increased 60–95% and isoleucine rose 45–50%. The arterial levels of several amino acids decreased progressively in a similar manner in patients and controls. At the end of the 150 min infusion period methionine had decreased 35% (P<001), tyrosine 25% (P<0–001) and phenylalanine 35% (P<0–001) in the patient group.
• 4 Positive A-JV differences in amino acid concentration–indicating net brain uptake–were seen for leucine, isoleucine, valine, serine, tyrosine and lysine in both groups in the basal state. The patients had a greater A-JV difference than the controls for tyrosine (P<0–05) while the uptake of the other amino acids, including the BCAA, was similar in the two groups. The fractional uptake of leucine and valine was significantly increased in the patients.
• 5 During BCAA infusion the A-JV difference for leucine increased 2–3 fold in both patients and controls and the net uptake to the brain of tyrosine and phenylalanine was abolished in the patient group.
• 6 It is concluded that (a) patients with hepatic cirrhosis show a decreased whole blood concentration of aspartate indicating a reduced intracellular concentration of this amino acid, (b) brain uptake of tyrosine and fractional uptake of leucine and valine is augmented in patients with hepatic cirrhosis, demonstrating abnormal brain amino acid uptake in this disorder, and (c) BCAA infusion effectively lowers the arterial concentrations for tyrosine, phenylalanine and methionine in cirrhotic patients as well as in healthy controls and blocks the abnormal brain uptake of tyrosine. These findings provide a biochemical background to the suggested beneficial effect of BCAA infusion in patients with hepatic cirrhosis and portal systemic encephalopathy.

     

Skeletal Muscle Protein and Amino Acid Metabolism in Experimental Chronic Uremia in the Rat: ACCELERATED ALANINE AND GLUTAMINE FORMATION AND RELEASE

The kinetics and factors regulating alanine and glutamine formation and release were investigated in skeletal muscle preparations from control and experimentally uremic rats. These preparations maintained phosphocreatine and ATP levels in vitro which closely approximated levels found in vivo. Alanine and glutamine release from uremic muscle were increased 45.8 and 36.0%, respectively, but tissue levels were unaltered. The increased release of alanine by uremic muscle was not accounted for by decreased rates of medium alanine reutilization via oxidation to CO₂ or incorporation into muscle protein. The maximal capacity of added amino acids such as aspartate, cysteine, leucine, and valine to stimulate net alanine and glutamine formation was the same in uremic and control muscle. Epitrochlearis preparations were partially labeled in vivo with [guanido-¹⁴C]-arginine. On incubation, preparations from uremic animals showed a 54.6% increase in the rate of loss of ¹⁴C-label in acid precipitable protein. Correspondingly, these same uremic preparations showed a 62.7% increase in ¹⁴C-label appearance in the acid-soluble fraction of muscle and in the incubation media. Insulin decreased alanine and glutamine release to an extent threefold greater in uremic than in control preparations, and increased muscle glucose uptake approximately threefold in all preparations. Although basal rates of [4,5-³H]leucine incorporation into protein were decreased 25% in uremic muscles as compared with control muscles, insulin stimulated [³H]leucine incorporation nearly equally in both preparations.     

L‐Amino acid load to enhance PET differentiation between tumor and inflammation: an in vitro study on 18F‐FET uptake

Labeled amino acids (AA) are tumor tracers for use in nuclear medecine. O‐(2‐[¹⁸F]fluoroethyl)‐L ‐tyrosine (FET) is transported by the L ‐system, known to function as an exchanger. In vitro utilization of FET, after a preload or prior to an afterload of non radioactive L ‐amino acids, was evaluated in order to measure the potential effects of AA content on the distinction between tumor and inflammatory lesions. Cellular uptake of FET was studied on rat osteosarcoma cells (ROS 17/2.8) and human leukocytes, initially loaded with nonradioactive L ‐tyrosine or L ‐methionine. FET efflux was evaluated from cells loaded with nonradioactive L ‐phenylalanine after tracer uptake. ROS 17/2.8 showed a higher sensitivity to preload and afterload effects on cellular FET content as compared with the leukocytes. We conclude that preload with L ‐tyrosine, prior to the administration of FET, may be a potential procedure to improve PET differentiation between tumor and inflammatory lesions. Copyright © 2006 John Wiley & Sons, Ltd.     

Prevention of colonic fibrosis by Boswellia and Scutellaria extracts in rats with colitis induced by 2,4,5-trinitrobenzene sulphonic acid

Background Currently, no effective preventive measures or medical therapies are available for intestinal fibrosis and, thus, surgery remains the only available strategy in the management of fibrostenotic enteropathies, especially Crohn's disease. The aim of this study was to evaluate the efficacy of a combined therapy of anti‐inflammatory Boswellia and antifibrotic Scutellaria extracts on the development of colonic fibrosis in rats. Materials and methods Chronic colonic inflammation‐associated fibrosis was induced in rats by intracolonic administration of 2,4,5‐trinitrobenzene sulphonic acid (TNBS). Sixty‐four healthy male Sprague‐Dawley rats were assigned to five groups: 8 controls, 14 TNBS, 14 TNBS orally treated with Boswellia extracts (50 mg kg^?1 day^?1), 14 TNBS orally treated with Scutellaria extracts (150 mg kg^?1 day^?1), and 14 TNBS orally treated with both Boswellia (50 mg kg^?1 day^?1) and Scutellaria extracts (150 mg kg^?1 day^?1). The colon was removed after 21 days of treatment and assessed by macroscopic, histological, morphometric and immunohistochemical analyses. For immunohistochemical analysis, alpha‐smooth muscle actin (α‐SMA), collagen types I–III, connective tissue growth factor (CTGF), transforming growth factor‐beta1 (TGF‐β1), Smad3, Smad7 and CD3 antibodies were used. Results Combined oral administration of Boswellia and Scutellaria significantly improved the course and macroscopic findings of TNBS‐induced chronic colitis assessed by disease activity index, colon weight, length, adhesions, strictures, dilatation, thickness, oedema, ulcerations and extension of damage. The histological severity of the colonic fibrosis was also notably improved by the treatment and associated with a significant reduction in the colonic expression of α‐SMA, collagen I–III, CTGF, TGF‐β1, Smad3, and Smad7. Conclusions These data demonstrate that the prophylactic administration of anti‐inflammatory Boswellia and antifibrotic Scutellaria extracts is effective in preventing colonic fibrosis in TNBS‐induced colitis. Their antifibrotic mechanism of action seems to be mediated by the inhibition of TGF‐β1/Smad3 pathway.     

Respiratory compensation point during incremental test in overweight and normoweight boys: is it useful in assessing aerobic performance? A longitudinal study

The purpose of this study was to investigate the characteristics of the respiratory compensation point (RCP) in overweight and normoweight boys and to clarify changes in the RCP over 4 years. This study was conducted with 11 overweight boys and 14 boys with normal weight. The boys performed the graded test every 2 years (three series) beginning at the age of 9–10 years and finishing at the age of 13–14 years. During the test, the RCP was detected. In every series, the RCP occurred earlier in the overweight boys than in the normoweight boys and at a significantly (P<0·05) lower rate relative to body mass power output (P kg^?1). Relative oxygen uptake (VO₂ kg^?1) at the RCP in all studies was also significantly (P<0·05) lower in the group of overweight boys. The maximum level of analysed indicators (VO₂max; Pmax) differentiated both groups in similar ways as their level noted at RCP. This study showed significant (P<0·05) correlation between the values VO₂max kg^?1 and VO₂ kg^?1 at RCP in each series of the test and between Pmax kg^?1 and P kg^?1 at RCP. The respiratory compensation point seems to be a good method for evaluating aerobic performance in children (also overweight). During puberty, a decreasing tendency in aerobic performance was observed in both groups.     

Antithrombotic effects of S 18886, a novel orally active thromboxane A2 receptor antagonist

Summary. Platelet activation and thrombus formation play a critical role in the onset of acute coronary syndromes. Thromboxane A₂ (TxA₂) is among the different chemical modulators released by activated platelets. TxA₂ is considered one of the most powerful agonists for platelet activation. In addition, TxA₂ exerts a vasoconstrictor effect by serving as an agonist of the thromboxane receptor (TP) on the vascular smooth muscle cell membranes. The putative effect of TxA₂ on thrombosis is demonstrated by the clinical effectiveness of acetylsalicylic acid (ASA) in the prevention of acute coronary syndromes. Among the clinically used antiplatelet agents, clopidogrel has shown to be slightly more effective than ASA in the prevention of atherothrombotic events in patients with peripheral arterial disease, and is one of the most widely used after aspirin. The aims of the study were to study the antithrombotic effects of escalating doses of the TP‐receptor antagonist, S 18886 and to compare its effects with those achieved by the administration of ASA (5 mg kg^?1 day^?1), and clopidogrel (3 mg kg^?1 day^?1). The study was undertaken at high and low shear rate conditions using the Badimon perfusion chamber in a porcine model. Antithrombotic effects were assessed as changes on platelet and fibrin(ogen) deposition. The doses of 30 and 100 µg kg^?1 day^?1 were selected based on a previous platelet aggregation study. S 18886 shows a dose‐dependent antithrombotic response. The dose of S‐100 develops similar antithrombotic effects to those of clopidogrel and superior to those of aspirin. The antithrombotic effects were statistically significant at both studied shear rate conditions. Therefore, the orally active TP‐receptor antagonist, S 18886, appears to be a new and effective agent to prevent atherothrombotic complications.     

Pulmonary function in rats dying from long‐term parenteral nutrition

Infusion of Vamin or Intralipid causes death in a rat model of continuous parenteral nutrition. Morphological investigations have shown vascular injury and thrombus formation in the lungs. In this study, lung function in rats was examined before death due to parenteral nutrition. The rats were fed saline intravenously (group I); 100?mL?kg^?1?day^?1 (controls); a 7% amino acid‐glucose solution (Vamin‐Glukos) (group II); 100?mL?kg^?1?day^?1, or 20% fat emulsion (Intralipid) (group III); 40?mL?kg^?1?day^?1. The infusion was stopped when the condition of the rats deteriorated. In a saline‐perfused, isolated lung model, pulmonary arterial pressure (Ppa), transpulmonary pressure (Ptp), endothelial function, measured as inactivation of serotonin (bioassay), and the capillary filtration coefficient (CFC) were determined. Haematological parameters were also evaluated. Constant findings in group II and III were central thrombus formation, anaemia and thrombocytopenia. Ppa increased from 0.7 (0.04)?kPa in group I to 1.4 (0.1)?kPa and 1.7 (0,1)?kPa in groups II and III, respectively (p<0.001). Inactivation of serotonin was reduced to 36% (2) in group II and 37% (2) in group III compared with 74% (5) in group I (p<0.002). CFC increased to 25?mg?min^?1 (5) (group II) and 30?mg?min^?1 (6) (group III) compared with 13?mg?min^?1 (2) in controls (p=0.01). The study shows that major pulmonary hypertension and severe reduction of the endothelial function are present when rats deteriorate after infusion of parenteral nutrition substrates.     

Transport kinetics of amino acids across the resting human leg.

Flux rates of amino acids were measured across the leg after an overnight fast in resting human volunteers. A balanced amino acid solution was, after a primed infusion, continuously infused for 2 h at each of three step-wise and increasing rates corresponding to 8.3, 16.7, 33.2 mg N/kg per h that were equivalent to 0.2, 0.4, 0.8 g N/kg per d. Flux of amino acids across the leg was compared with the flux of glucose, glycerol, lactate, free fatty acids, and oxygen. The size of the muscular tissue pool of amino acids was measured. Whole body amino acid oxidation was estimated by means of the continuous infusion of a 14C-labeled mixture of amino acids. Arterial steady state levels were obtained for most amino acids within 30 to 45 min after the primed constant infusion. Leg flux of amino acids switched from a net efflux after an overnight fast to a balanced flux between infusion rates corresponding to 0.2-0.4 g N/kg per d. At 0.8 g N/kg per d essentially all amino acids showed uptake. The infusion of amino acids stimulated leg uptake of glucose and lactate production and decreased FFA release. Oxygen uptake and leg blood flow increased significantly with increased infusion of amino acids. There was significant variability in transport rate among individual amino acids. Branched chain amino acids showed rapid transport and methionine slow transport rate. Only small changes in the muscle tissue concentration of certain amino acids were registered after 6 h of amino acid infusion despite uptake for several hours. When amino acids were infused at a rate corresponding to 0.8 g N/kg per d, the leg uptake of amino acids was 6% and the simultaneous whole body oxidation of infused amino acids was approximately 10%. Net uptake of leucine across the leg per hour was 62% of the muscle pool of free leucine when amino acids were infused at a rate corresponding to 0.4 g N/kg per d. Multiple regression analysis showed that the arterial concentration of an amino acid was the most important factor for uptake, more so than insulin concentration and blood flow. It is concluded that leg exchange of amino acids is large enough to rapidly change the pool size of the amino acids in skeletal muscle, if not counter-regulated by changes in rates of protein synthesis and degradation. Estimates of the capacity for protein synthesis and transfer RNA acceptor sites in muscles agree in order of magnitude with the net uptake of amino acids at high infusion rates of amino acids. Therefore, measurements of the balance of tyrosine, phenylalanine, and particularly methionine at steady state may reflect net balance of proteins across skeletal muscles even in short-time experiments.     

Apixaban, an oral, direct and highly selective factor Xa inhibitor: in vitro, antithrombotic and antihemostatic studies

Summary. Background: Apixaban is an oral, direct and highly selective factor Xa (FXa) inhibitor in late‐stage clinical development for the prevention and treatment of thromboembolic diseases. Objective: We evaluated the in vitro properties of apixaban and its in vivo activities in rabbit models of thrombosis and hemostasis. Methods: Studies were conducted in arteriovenous‐shunt thrombosis (AVST), venous thrombosis (VT), electrically mediated carotid arterial thrombosis (ECAT) and cuticle bleeding time (BT) models. Results: In vitro, apixaban is potent and selective, with a K_i of 0.08 nm for human FXa. It exhibited species difference in FXa inhibition [FXa K_i (nm ): 0.16, rabbit; 1.3, rat; 1.7, dog] and anticoagulation [EC_2× (μm , concentration required to double the prothrombin time): 3.6, human; 2.3, rabbit; 7.9, rat; 6.7, dog]. Apixaban at 10 μm did not alter human and rabbit platelet aggregation to ADP, γ‐thrombin, and collagen. In vivo, the values for antithrombotic ED₅₀ (dose that reduced thrombus weight or increased blood flow by 50% of the control) in AVST, VT and ECAT and the values for BT ED_3× (dose that increased BT by 3‐fold) were 0.27 ± 0.03, 0.11 ± 0.03, 0.07 ± 0.02 and > 3 mg kg^?1 h^?1 i.v. for apixaban, 0.05 ± 0.01, 0.05 ± 0.01, 0.27 ± 0.08 and > 3 mg kg^?1 h^?1 i.v. for the indirect FXa inhibitor fondaparinux, and 0.53 ± 0.04, 0.27 ± 0.01, 0.08 ± 0.01 and 0.70 ± 0.07 mg kg^?1 day^?1 p.o. for the oral anticoagulant warfarin, respectively. Conclusions: In summary, apixaban was effective in the prevention of experimental thrombosis at doses that preserve hemostasis in rabbits.     

Amino acid uptake and release by colorectal cancer in man

Little information is available regarding the amino acid exchange by human tumors. To characterize this exchange in vivo, 21 patients with resectable colorectal carcinomas were studied during curative operations. Concerning the amino acid uptake and release by peripheral tissues, 20 non-cancer patients served as controls. Both groups of subjects were well-nourished, as indicated by anthropometric and biochemical variables. In the cancer patients, we cannulated a peripheral artery and vein as well as a central tumor-draining vein and the portal vein. Plasma concentrations and concentration differences were determined in mumol/l and in percentages of the total amino acid amounts. Peripheral glutamate uptake per liter plasma was reduced in the cancer patients (p = 0.02). In these patients, the central tumor-draining vein contained less glutamine (p = 0.002) and more glutamate (p = 0.002) than the peripheral vein. Glutamine uptake by the tumor occurred more often than glutamine release, while glutamate had a negative balance across the tumor in all but three cases. The qualitative differences between the peripheral tissues and the tumors with respect to glutamine and glutamate exchange reached high levels of significance (p = 0.002 for both of the amino acids). In addition, the tumors released more glycine, ornithine, and tyrosine than the periphery. As to glutamine and glutamate metabolism, there was a significant difference between the tumors and the portal-drained organs (p greater than or equal to 0.05). The discussion of the results emphasizes the contributions made by the periphery and the tumor to the plasma amino pattern. The role of glutamine as a potential high importance energy source for neoplastic tissues is delineated.     

Regulation of myocardial amino acid balance in the conscious dog.

The effects in vivo of physiologic increases in insulin and amino acids on myocardial amino acid balance were evaluated in conscious dogs. Arterial and coronary sinus concentrations of amino acids and coronary blood flow were measured during a 30-min basal and a 100-min experimental period employing three protocols: euglycemic insulin clamp (plasma insulin equaled 70 +/- 11 microU/ml, n = 6); euglycemic insulin clamp during amino acid infusion (plasma insulin equaled 89 +/- 12 microU/ml, n = 6); and suppression of insulin with somatostatin during amino acid infusion (plasma insulin equaled 15 +/- 4 microU/ml, n = 6). Basally, only leucine and isoleucine were removed significantly by myocardium (net branched chain amino acid [BCAA] uptake equaled 0.5 +/- 0.2 mumol/min), while glycine, alanine, and glutamine were released. Glutamine demonstrated the highest net myocardial production (1.6 +/- 0.2 mumol/min). No net exchange was seen for valine, phenylalanine, tyrosine, cysteine, methionine, glutamate, asparagine, serine, threonine, taurine, and aspartate. In group I, hyperinsulinemia caused a decline of all plasma amino acids except alanine; alanine balance switched from release to an uptake of 0.6 +/- 0.4 mumol/min (P less than 0.05), while the myocardial balance of other amino acids was unchanged. In group II, amino acid concentrations rose, and were accompanied by a marked rise in myocardial BCAA uptake (0.4 +/- 0.1-2.6 +/- 0.3 mumol/min, P less than 0.001). Uptake of alanine was again stimulated (0.9 +/- 0.3 mumol/min, P less than 0.01), while glutamine production was unchanged (1.3 +/- 0.4 vs. 1.6 +/- 0.3 mumol/min). In group III, there was a 4-5-fold increase in the plasma concentration of the infused amino acids, accompanied by marked stimulation in uptake of only BCAA (6.8 +/- 0.7 mumol/min). Myocardial glutamine production was unchanged (1.9 +/- 0.4-1.3 +/- 0.7 mumol/min). Within the three experimental groups there were highly significant linear correlations between myocardial uptake and arterial concentration of leucine, isoleucine, valine, and total BCAA (r = 0.98, 0.98, 0.92, and 0.97, respectively); P less than 0.001 for each). In vivo, BCAA are the principal amino acids taken up by the myocardium basally and during amino acid infusion. Plasma BCAA concentration and not insulin determines the rate of myocardial BCAA uptake. Insulin stimulates myocardial alanine uptake. Neither insulin nor amino acid infusion alters myocardial glutamine release.     

Reversal of the anti‐platelet effects of aspirin and clopidogrel

Summary. Background: Guidelines recommend stopping aspirin and clopidogrel 7 to 10 days before surgery to allow time for replacement of permanently inhibited platelets by newly released uninhibited platelets.Objectives: The purpose of the present study was to determine the rate of offset of the anti‐platelet effects of aspirin and clopidogrel after stopping treatment and the proportion of untreated donor platelets that are required to reverse their anti‐platelet effects.Methods: Cohort 1 consisted of 15 healthy subjects who received aspirin 81 mg day^?1 or clopidogrel 75 mg day^?1 for 7 days and underwent serial blood sampling until platelet function testing results normalized. Cohort 2 consisted of 36 healthy subjects who received aspirin 325 mg day^?1, clopidogrel 75 mg day^?1, aspirin 81 mg day^?1 plus clopidogrel 75 mg day^?1 or no treatment for 7 days and underwent a single blood sampling.Results: In cohort 1, arachidonic acid (AA)‐induced light transmission aggregation (LTA) returned to baseline levels in all subjects within 4 days of stopping aspirin, coinciding with the partial recovery of plasma thromboxane B₂ concentrations. ADP‐induced LTA did not return to baseline levels until 10 days after stopping clopidogrel. In cohort 2, AA‐induced LTA in patient treated with aspirin reached control levels after mixing with 30% untreated donor platelets whereas ADP‐induced LTA in patients treated with clopidogrel reached control levels only after the addition of 90% or more donor platelets.Conclusions: Platelet aggregation recovers within 4 days of stopping aspirin but clopidogrel must be stopped for 10 days to achieve a normal aggregatory response.     

Does proteolysis explain glutamine release from the septic brain?

Berg and colleagues report on amino acid exchange across the human brain during endotoxin infusion. Lipopolysaccharide infusion induced a decrease in the ratio between branched chain amino acids and aromatic amino acids, increased unidirectional phenylalanine uptake, and increased net brain glutamine release. Cerebral proteolysis is suggested to play a role, but the question is whether this is the case and why this would happen.     

Plasma and albumin-free recombinant factor VIII: pharmacokinetics, efficacy and safety in previously treated pediatric patients

Summary. Background: The pharmacokinetics of factor VIII replacement therapy in preschool previously treated patients (PTPs) with hemophilia A have not been well characterized. Objectives: To assess the pharmacokinetics, efficacy and safety of a plasma‐free recombinant FVIII concentrate, ADVATE [Antihemophilic Factor (Recombinant), Plasma/Albumin‐Free Method, rAHF‐PFM], in children < 6 years of age with severe hemophilia. Patients/methods: Fifty‐two boys, one girl, mean (± SD) age 3.1 ± 1.5 years and ≥ 50 days of prior FVIII exposure, were enrolled in a prospective study of ADVATE rAHF‐PFM at 23 centers. Results: The mean terminal phase half‐life (t_1/2) was 9.88 ± 1.89 h, and the mean adjusted in vivo recovery (IVR) was 1.90 ± 0.43 IU dL^?1 (IU kg^?1)^?1. Over the 1–6‐year age range, t_1/2 of rAHF‐PFM increased by 0.40 h year^?1. IVR increased by 0.095IU dL^?1(IU kg^?1)^?1 (kg m^?2)^?1 in relation to body mass index (BMI). Patients primarily received prophylaxis. Median (range) annual joint bleeds were 0.0 (0.0–5.8), 0.0 (0.0–6.1) and 14.2 (0.0–34.5) for standard prophylaxis, modified prophylaxis and on‐demand treatment, respectively. Bleeds were managed in 90% (319/354) of episodes with one or two rAHF‐PFM infusions; response was rated excellent/good in 93.8% of episodes. Over a median 156 exposure days, no FVIII inhibitors were detected and no related severe adverse events or unusual non‐serious adverse events were seen. Conclusions: Children < 6 years of age appear to have shorter FVIII t_1/2 and lower IVR values than older subjects. However, these parameters increased with age (t_1/2) and BMI (adjusted IVR), respectively. rAHF‐PFM was clinically effective and well tolerated, with no signs of increased immunogenicity in previously treated young children with hemophilia A.     

Outpatient-based physical rehabilitation for survivors of prolonged critical illness: A randomized controlled trial

Introduction: The physical and psychological impact of critical illness is well documented. Recovery may take many months and is often incomplete. The optimal way of addressing these important sequelae following hospital discharge remains unclear. Methods: Single center, randomized controlled trial in patients invasively ventilated for ≥5 days. The treatment group (TG) underwent a 7-week, outpatient-based exercise and education program, with the control group (CG) receiving no intervention during the study period. Primary outcome measures were changes in functional capacity assessed using the cardiopulmonary exercise testing parameters, peak VO₂, and anaerobic threshold (AT). Secondary outcome measures were changes in and health-related quality of life assessed using the Short Form 36 version 2 questionnaire. Assessors remained blinded to group allocation. Results: Sixty-three patients completed the study (target n = 90). Improvements in both peak VO₂ and AT were seen in both TG and CG but no significant difference between groups was evident. AT improved by 11.7% in CG (baseline 10.3 ml O₂ kg^?1 min^?1, follow-up 11.5 ml O₂ kg^?1 min^?1), and by 14.6% in TG (baseline 10.3 ml O₂ kg^?1 min^?1, follow-up 11.8 ml O₂ kg^?1 min^?1; ANCOVA p = 0.74). Peak VO₂ improved by 14.0% in CG (baseline 13.6 ml O₂ kg^?1 min^?1, follow-up 15.5 ml O₂ kg^?1 min^?1), and by 18.8% in TG (baseline 13.8 ml O₂ kg^?1 min^?1, follow-up 16.4 ml O₂ kg^?1 min^?1; ANCOVA p = 0.68). Significant improvements were seen in both groups for physical component summary scores (PCS) (TG 39.6 versus 31.0; CG 36.1 versus 32.6) and mental component summary scores (MCS) (TG 48.6 versus 38.4; CG 41.3 versus 37.0). The degree of improvement was significantly higher in the treatment group in comparison to control subjects (PCS p = 0.048; MCS p = 0.017). This improvement was most marked in the subgroup ventilated for >14 days. Conclusions: A 7-week, outpatient-based exercise and education program resulted in improved health-related quality of life scores but not improved exercise capacity.