Are all measures of liver Kpuu a function of FH, as determined following oral dosing, or have we made a critical error in defining hepatic drug clearance?

Here we present, utilizing universally accepted relationships for hepatic clearance at steady state, that for all models of hepatic elimination the ratio of unbound liver drug concentration to unbound systemic blood concentration, Kpuu, is a function of or related to the hepatic bioavailability for that drug, FH. According to the derivation for the well-stirred model, Kpuu can never exceed unity, can frequently be a function of hepatic blood flow, and is equivalent to the value of FH as determined following oral dosing. For the parallel tube model, Kpuu will not equal FH but will be a function of FH and will also never be a value greater than 1. When hepatic clearance is rate limited by basolateral transporters, Kpuu will be less than 1, and less than FH. We believe that such outcomes are highly unlikely, and that the error arises from a basic assumption concerning hepatic clearance that leads to the mechanistic models of hepatic elimination, the well-stirred, parallel tube and dispersion models. That basic assumption is that the steady-state systemic concentration multiplied by the hepatic systemic clearance is equal to the product of the average unbound liver steady-state concentration and the intrinsic hepatic clearance (Css · CL = CH,u · CLint). Calculations of Kpuu and FH based on present methods of analysis provide a strong argument as to why this universally accepted relationship is not correct. Alternatively, we have shown in recent publications that hepatic clearance may be adequately determined based on Kirchhoff's Laws where no assumption of the above equality concerning hepatic intrinsic clearance is required, and where Kpuu is independent of hepatic extraction ratio and FH.

The development of a consensus statement for the prescription of powered wheelchair standing devices in Duchenne muscular dystrophy.

PURPOSE: To develop a consensus statement for the prescription of a Powered Wheelchair Standing Device (PWSD) in young people with Duchenne muscular dystrophy (DMD). MATERIALS AND METHODS: An international multidisciplinary panel comprising clinicians and users (young people with DMD) along with their parents was consulted. A literature review was undertaken and a Delphi method was utilised to generate consensus statements. To supplement limited literature, round one of the Delphi process comprised questions consistent with the International Classification of Functioning, Disability and Health model of disability to generate items based on expert opinion and was completed by 38 clinicians and nine users. Thirty-seven participants completed two further rounds rating the importance of each item with a five-point scale. Agreement of 70% or more participants for items indicated consensus. RESULTS: Consensus was reached for 47 of 80 items. Tolerance and comfort in supported standing for at least 10 min, ankle contracture less than 10 degrees and user goals reflecting motivation to use the standing function were agreed as necessary in guiding the decision to trial a PWSD. Evidence of family, therapist and servicing support were also considered critical in enabling continuity of PWSD use. CONCLUSIONS: PWSD is a mobility option that offers choice, control and opportunity for independence. This consensus statement can assist clinicians with decision-making around factors influencing successful implementation and optimisation of PWSD for young people with DMD.Implications for RehabilitationTolerance and comfort in supported standing for at least 10 minutes, ankle contracture limited to less than 10 degrees and the child's goals reflecting motivation to use the standing position were agreed to be necessary considerations in guiding the decision to trial a PWSD.Trialling a PWSD when the child is predicted to lose the ability to walk within a one to two year period was recommended although a PWSD could be suitable for a child who was unable to walk.Evidence of family, therapist and servicing support was considered critical in enabling continuity of PWSD use.

Association of CYP2C9*2 with bosentan-induced liver injury.

Bosentan (Tracleer) is an endothelin receptor antagonist prescribed for the treatment of pulmonary arterial hypertension (PAH). Its use is limited by drug-induced liver injury (DILI). To identify genetic markers of DILI, association analyses were performed on 56 Caucasian PAH patients receiving bosentan. Twelve functional polymorphisms in five genes (ABCB11, ABCC2, CYP2C9, SLCO1B1, and SLCO1B3) implicated in bosentan pharmacokinetics were tested for associations with alanine aminotransferase (ALT), aspartate aminotransferase (AST), and DILI. After adjusting for body mass index, CYP2C9*2 was the only polymorphism associated with ALT, AST, and DILI (ß = 2.16, P = 0.024; ß = 1.92, P = 0.016; odds ratio 95% CI = 2.29-∞, P = 0.003, respectively). Bosentan metabolism by CYP2C9*2 in vitro was significantly reduced compared with CYP2C9*1 and was comparable to that by CYP2C9*3. These results suggest that CYP2C9*2 is a potential genetic marker for prediction of bosentan-induced liver injury and warrants investigation for the optimization of bosentan treatment.

Pericardial effusion following esophageal variceal sclerotherapy.

We report a 37-year-old man with portal cavernoma who developed pericardial effusion two weeks following sclerotherapy for esophageal varices. It responded to conservative management.

Prediction of novel and analogous folds using fragment assembly and fold recognition.

A number of new and newly improved methods for predicting protein structure developed by the Jones-University College London group were used to make predictions for the CASP6 experiment. Structures were predicted with a combination of fold recognition methods (mGenTHREADER, nFOLD, and THREADER) and a substantially enhanced version of FRAGFOLD, our fragment assembly method. Attempts at automatic domain parsing were made using DomPred and DomSSEA, which are based on a secondary structure parsing algorithm and additionally for DomPred, a simple local sequence alignment scoring function. Disorder prediction was carried out using a new SVM-based version of DISOPRED. Attempts were also made at domain docking and "microdomain" folding in order to build complete chain models for some targets.

Prediction and functional analysis of native disorder in proteins from the three kingdoms of life.

An automatic method for recognizing natively disordered regions from amino acid sequence is described and benchmarked against predictors that were assessed at the latest critical assessment of techniques for protein structure prediction (CASP) experiment. The method attains a Wilcoxon score of 90.0, which represents a statistically significant improvement on the methods evaluated on the same targets at CASP. The classifier, DISOPRED2, was used to estimate the frequency of native disorder in several representative genomes from the three kingdoms of life. Putative, long (>30 residue) disordered segments are found to occur in 2.0% of archaean, 4.2% of eubacterial and 33.0% of eukaryotic proteins. The function of proteins with long predicted regions of disorder was investigated using the gene ontology annotations supplied with the Saccharomyces genome database. The analysis of the yeast proteome suggests that proteins containing disorder are often located in the cell nucleus and are involved in the regulation of transcription and cell signalling. The results also indicate that native disorder is associated with the molecular functions of kinase activity and nucleic acid binding.

Omeprazole as adjuvant therapy to endoscopic combination injection sclerotherapy for treating bleeding peptic ulcer.

BACKGROUND: Therapeutic endoscopy has provided a new means of treating bleeding peptic ulcers. Additional medical therapy may enhance the therapeutic benefit. Hemostasis is highly pH dependent and is severely impaired at low pH. Proton pump inhibitors, by achieving a significantly higher inhibition of gastric acidity, may improve the therapeutic outcomes after endoscopic treatment of ulcers. PATIENT AND METHODS: We enrolled 166 patients with hemorrhage from duodenal, gastric, or stomal ulcers and signs of recent hemorrhage, as confirmed by endoscopy. Twenty-six patients had ulcers with an arterial spurt, 41 patients had active ooze, 37 had a visible vessel, and 62 patients had an adherent clot. All patients received endoscopic injection sclerotherapy using 1:10,000 adrenaline and 1% polidocanol and were randomly assigned to receive omeprazole (40 mg orally) every 12 hours for 5 days or an identical-looking placebo. The outcome measures used were recurrent bleeding, surgery, blood transfusion, and hospital stay. RESULTS: Six (7%) of 82 patients in the omeprazole group had recurrent bleeding, as compared with 18 (21%) in the placebo group (P = 0.02). Two patients in the omeprazole group and 7 patients in the placebo group needed surgery to control their bleeding (P = 0.17). One patient in the omeprazole group and 2 patients in the placebo group died (P = 0.98). Twenty-nine patients (35%) in the omeprazole group and 61 patients (73%) in the placebo group received blood transfusions (P <0.001). The average hospital stay was 4.6 +/- 1.1 days in the omeprazole group and 6.0 +/- 0.7 days in the placebo group (P <0.001). CONCLUSION: The addition of oral omeprazole to combination injection sclerotherapy decreases the rate of recurrent bleeding, reduces the need for surgery and transfusion, and shortens the hospital stay for patients with stigmata of recent hemorrhage.

Circadian rhythms of renal phosphohydrolases analysed by Cosinor method.

Rhythmometric analysis of hydrolytic enzymes of mouse kidney has been performed on circadian time scale using the F test. Significant rhythms were detected in glucose-6-phosphatase (G6Pase), inorganic pyrophosphatase (InPPase) and alkaline phosphatase (AlPase) on protein and fresh weight basis. Acrophase (time for peak activity) of G6Pase, InPPase and AlPase per mg protein was at 9.9 degrees (1.0 hr), 88.5 degrees (6.0 hr) and at 342.3 degrees (20 hr) respectively. ATPase, which did not show significant rhythm (mean +/- SD = 4.51 +/- 0.30), had a peak value at 32.1 degrees (2.14 hr) with an amplitude of 0.31 units on protein basis. However, G6Pase and AlPase oscillated with high amplitudes (0.18 and 0.71) across the mean value (mesor) of 0.68 +/- 0.3 and 1.43 +/- 0.46 units respectively and with a phase shift of 5 hr. Since G6Pase is a multicomponent and multifunctional enzyme having several overlapping enzyme activities (viz. InPPase), coordinated events of G6Pase, InPPase and ATPase in the regulation of daily renal functions have been mapped in the intact animals, along a physiologic time scale.

Changes in interstitial adenosine during hypoxia: relationship to oxygen supply:demand imbalance, and effects of adenosine deaminase.

OBJECTIVE: The aim was to determine the changes in coronary blood flow and intramyocardial interstitial fluid (ISF) adenosine and adenosine metabolites during systemic hypoxia, and to evaluate (1) whether the increase in ISF adenosine during hypoxia is augmented if the hypoxic hyperaemia is prevented, and (2) the effects of adenosine deaminase on ISF adenosine and coronary blood flow during sustained hypoxia. METHODS: Anaesthetised dogs were instrumented with a flow probe around the left anterior descending coronary artery to measure coronary blood flow and with a microdialysis probe in the myocardium perfused by this artery to sample intramyocardial ISF. Dialysate purine metabolite levels were used as indices of ISF levels. Systemic hypoxia was induced by a reduction in the FIO2. RESULTS: Acute systemic hypoxia (PaO2 approximately 3.9 kPa) resulted in a 60% increase in dialysate adenosine, along with increases in dialysate levels of the adenosine metabolites inosine (74%), hypoxanthine (33%), and xanthine (32%). If the hypoxic hyperaemia was prevented, dialysate adenosine increased by 180% during hypoxia, and the increases in adenosine metabolites were augmented as well. During sustained hypoxia, intracoronary administration of adenosine deaminase decreased dialysate adenosine below prehypoxia levels, but did not alter the hypoxic hyperaemia. CONCLUSIONS: While ISF adenosine is increased during acute systemic hypoxia and is increased in relation to the oxygen supply:demand imbalance, consistent with a role of adenosine in hypoxic hyperaemia in the heart, adenosine is not necessary for the maintenance of a sustained increase in coronary blood flow during hypoxia.

Circadian rhythmometric analysis of hepatic phosphohydrolases with special reference to glucose-6-phosphatase and inorganic pyrophosphatase.

Rhythmometric analysis of a group of phosphohydrolases in mouse liver has been performed along a single 24 hr time scale. The presence of the rhythm was conducted by F test. Statistically significant circadian rhythm was detected in glucose-6-phosphatase (G6Pase) and inorganic pyrophosphatase (InPPase) activity expressed on fresh weight and protein basis. Both G6Pase and InPPase oscillated with a high amplitude of 0.44 U and 1.15 U respectively across the mean value (mesor) of 0.40 +/- 0.42 U and 2.81 +/- 1.14 U per mg protein and with a phase shift of 80 degrees (5.34 hr) among them. On the other hand, alkaline phosphatase (AlPase) did not show any rhythm whereas adenosine triphosphatase (ATPase) showed rhythmic activity on protein basis and oscillated across mesor of 1.84 +/- 0.5 U with an amplitude of 0.52. Acrophase (time for peak activity/mg protein) of G6Pase, InPPase and ATPase was found at 194.2 degrees (13.34 hr), 114.1 degrees (8.0 hr) and at 306.1 degrees (20.4 hr) respectively. AlPase, though did not show significant rhythm, had peak value at 231.8 degrees. Since hepatic G6Pase is a multicomponent and multifunctional enzyme with several overlapping activities (viz. InPPase), coordinated action of G6Pase and InPPase in the regulation of hepatic cell functions has been suggested.

Cardiac microdialysis to estimate interstitial adenosine and coronary blood flow.

The purpose of this study was twofold: 1) to investigate the feasibility and usefulness of cardiac microdialysis for the simultaneous estimation of regional cardiac interstitial fluid (ISF) adenosine (ADO) concentration and coronary blood flow (CBF); and 2) to determine the changes in the ISF levels of ADO and CBF during cardiac stimulation or regional myocardial ischemia. Cardiac microdialysis probes were implanted in the left ventricular myocardium of chloralose-urethan-anesthetized dogs and perfused with Krebs-Henseleit buffer. The concentration of ADO in the effluent dialysate was used as an index of intramyocardial ISF ADO concentration while local CBF was measured by H2 clearance via a platinum wire within the dialysis fiber. Dialysate ADO was elevated immediately after insertion of the microdialysis probe, declined rapidly in the first 20 min, stabilized by 60 min, and remained constant for 2 h. Based on the relationship in vitro and in vivo between microdialysis probe perfusion rate and dialysate ADO concentration, ISF ADO concentration within the left ventricular myocardium was estimated to be 0.9-1.3 microM. Dobutamine (10 micrograms.kg-1.min-1) infusion resulted in a 36% increase in CBF and a 2.5-fold increase in dialysate ADO (n = 9; P less than 0.05). Regional myocardial ischemia, induced by occlusion of the left anterior descending artery (LAD), caused a 13-fold increase in dialysate ADO in the LAD perfused myocardium (n = 9; P less than 0.05). These results are consistent with the ADO hypothesis and suggest that cardiac microdialysis provides a reliable technique for the sampling of regional intramyocardial ISF.

Effect of pyruvate on regional ventricular function in normal and stunned myocardium.

The prolonged ventricular dysfunction following brief periods of coronary artery occlusion that does not produce irreversible damage has been termed the "stunned" myocardium. Although ventricular function returns to preischemic values by 1 to 7 days after reperfusion is established, inotropic therapy may be necessary to enhance contractility in the stunned heart. The purpose of this study was to determine the effect of pyruvate on ventricular function in normal and stunned myocardium. Eight chloralose/urethane anesthetized dogs were instrumented with ultrasonic crystals to measure systolic wall thickening in the left anterior descending artery (LAD) and left circumflex artery perfused regions of the left ventricle. Pyruvate (1 ml/min of 150 mM sodium pyruvate, pH 7.4) was infused directly into the LAD prior to and 30 minutes after a 10 minute LAD occlusion. Prior to LAD occlusion, LAD pyruvate infusion increased systolic wall thickening in the LAD-perfused region from 16.2% +/- 4.3% to 23.4% +/- 5.1% (p less than 0.05). Thirty minutes after LAD occlusion, regional wall thickening was depressed (3.3% +/- 2.6%; p less than 0.05), which is indicative of stunned myocardium. Subsequent LAD pyruvate infusion increased wall thickening in the stunned myocardium to 12.7% +/- 2.5%. The improvement of regional ventricular function was maintained only during the pyruvate infusion, as function returned to prepyruvate levels within 20 minutes after cessation of pyruvate infusion. These data indicate that pyruvate exerts a positive inotropic effect in normal and stunned myocardium. If pyruvate, a key intermediate in energy-producing pathways, exerts its inotropic effect through an enhancement of the energy state of the heart, it may have advantages over traditional inotropic agents in the treatment of postischemic contractile dysfunction.