Quantitative Assessment of Population Variability in Hepatic Drug Metabolism Using a Perfused Three-Dimensional Human Liver Microphysiological System.

In this work, we first describe the population variability in hepatic drug metabolism using cryopreserved hepatocytes from five different donors cultured in a perfused three-dimensional human liver microphysiological system, and then show how the resulting data can be integrated with a modeling and simulation framework to accomplish in vitro-in vivo translation. For each donor, metabolic depletion profiles of six compounds (phenacetin, diclofenac, lidocaine, ibuprofen, propranolol, and prednisolone) were measured, along with metabolite formation, mRNA levels of 90 metabolism-related genes, and markers of functional viability [lactate dehydrogenase (LDH) release, albumin, and urea production]. Drug depletion data were analyzed with mixed-effects modeling. Substantial interdonor variability was observed with respect to gene expression levels, drug metabolism, and other measured hepatocyte functions. Specifically, interdonor variability in intrinsic metabolic clearance ranged from 24.1% for phenacetin to 66.8% for propranolol (expressed as coefficient of variation). Albumin, urea, LDH, and cytochrome P450 mRNA levels were identified as significant predictors of in vitro metabolic clearance. Predicted clearance values from the liver microphysiological system were correlated with the observed in vivo values. A population physiologically based pharmacokinetic model was developed for lidocaine to illustrate the translation of the in vitro output to the observed pharmacokinetic variability in vivo. Stochastic simulations with this model successfully predicted the observed clinical concentration-time profiles and the associated population variability. This is the first study of population variability in drug metabolism in the context of a microphysiological system and has important implications for the use of these systems during the drug development process.

Physiome-on-a-Chip: The Challenge of "Scaling" in Design, Operation, and Translation of Microphysiological Systems.

Scaling of a microphysiological system (MPS) or physiome-on-a-chip is arguably two interrelated, modeling-based activities: on-platform scaling and in vitro-in vivo translation. This dual approach reduces the need to perfectly rescale and mimic in vivo physiology, an aspiration that is both extremely challenging and not substantively meaningful because of uncertain relevance of any specific physiological condition. Accordingly, this perspective offers a tractable approach for designing interacting MPSs and relating in vitro results to analogous context in vivo.

Quantitative Systems Pharmacology Approaches Applied to Microphysiological Systems (MPS): Data Interpretation and Multi-MPS Integration.

Our goal in developing Microphysiological Systems (MPS) technology is to provide an improved approach for more predictive preclinical drug discovery via a highly integrated experimental/computational paradigm. Success will require quantitative characterization of MPSs and mechanistic analysis of experimental findings sufficient to translate resulting insights from in vitro to in vivo. We describe herein a systems pharmacology approach to MPS development and utilization that incorporates more mechanistic detail than traditional pharmacokinetic/pharmacodynamic (PK/PD) models. A series of studies illustrates diverse facets of our approach. First, we demonstrate two case studies: a PK data analysis and an inflammation response--focused on a single MPS, the liver/immune MPS. Building on the single MPS modeling, a theoretical investigation of a four-MPS interactome then provides a quantitative way to consider several pharmacological concepts such as absorption, distribution, metabolism, and excretion in the design of multi-MPS interactome operation and experiments.

Systemic glucocorticoids in severe exacerbations of COPD.

OBJECTIVE: This study aimed to compare the efficacies of 3-day and 10-day courses of methylprednisolone (MP) treatment in severe COPD exacerbations necessitating hospitalization for respiratory failure. DESIGN: Prospective, randomized, single-blind study. SETTING: Tertiary-care center. PATIENTS AND METHODS: Thirty-six patients were included in the study and randomized into two groups: group 1 received MP, 0.5 mg/kg q6h for 3 days, and group 2 was administered the same dosage of MP for the first 3 days, after which it was tapered and terminated on the tenth day. There was no difference between the groups for age, baseline FEV(1), PaO(2), PaCO(2), and pH levels. One patient in group 1 who developed pneumothorax and one patient in group 2 who had steroid-related psychosis could not complete the study. RESULTS: Both groups showed significant improvements in PaO(2) and FEV(1) levels, but these were more marked in group 2 (p = 0.012 and p = 0.019, respectively). There was a significant increase in FVC levels in group 2 only (p = 0.003). Group 2 also had a more marked improvement in dyspnea on exertion. There was no difference between the two groups with regards to other parameters, including pH, PaCO(2) levels, and other symptom scores. Six patients in group 1 and five patients in group 2 developed new exacerbations within the following 6 months. Hyperglycemia occurred in two patients in each group. CONCLUSION: In severe COPD exacerbations, a 10-day course of steroid treatment is more effective than a 3-day course in improving the outcome, but has no benefit in reducing exacerbation rates.

Physicians' approach to the diagnosis and treatment of tuberculosis in Afyon, Turkey.

OBJECTIVE: To evaluate physicians' approaches to the diagnosis and treatment of tuberculosis in Afyon, Turkey. MATERIAL AND METHODS: A questionnaire on tuberculosis was filled out by 208 physicians (46 specialists and 162 general practitioners). RESULTS: Bacteriology was the preferred method of diagnosis among 75% (n = 156) of the physicians. For treatment of newly diagnosed tuberculosis, 64.4% prescribed a three-drug and 30.8% a four-drug combination. The combination most often selected was HRE (36.5%). Preferred treatment durations were 9 (38.5%) and 6 (34.6%) months. For patients with treatment failure, 20.2% of the physicians would add a new drug to the existing regimen, while 65.4% would refer the patient to a specialised tuberculosis unit. For the treatment of childhood tuberculosis, 38.5% of the physicians thought a two-drug treatment was adequate. For tuberculosis during pregnancy, 9.7% of the physicians offered treatment after the pregnancy, while 11.5% offered treatment after abortion. CONCLUSION: The knowledge of the physicians about the diagnosis and treatment of tuberculosis was deemed insufficient. Additional educational resources for physicians may contribute to improvements in tuberculosis control.

Effect of recombinant human erythropoietin (r-HuEPO) therapy on plasma FT3, FT4, TSH, FSH, LH, free testosterone and prolactin levels in hemodialysis patients.

The aim of this study was to evaluate the effect of r-HuEPO treatment on free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), free testosterone and prolactin levels in uremic hemodialysis patients. Twenty-four uremic hemodialysis patients were given r-HuEPO with a dose 60 U/kg as intravenous bolus injection at the end of each dialysis session. Once the hematocrit value of the patient had reached a range of 30-35%, the dose was adjusted so as to keep the hematocrit levels constant. Twenty uremic dialysis patients were taken as control group. The above-mentioned hormone levels of patients and control group were determined before and 4 months after r-HuEPO treatment. After the treatment, serum prolactin levels significantly decreased in both sexes (36.8 +/- 7.8 vs 22.9 +/- 6.3 ng/ml and 78.3 +/- 13.3 vs 37.4 +/- 10.4 ng/ml male and female, respectively). FT3 and FT4 significantly increased (1.17 vs 1.67 pg/ml, p < 0.05, and 0.64 vs 0.084 ng/dl, p < 0.05, respectively). TSH levels increased but those changes were not significant. There was no change in the level of any hormone in the control group. Also, the sexual functions of eight male patients treated with r-HuEPO improved and menstruation started again in four female patients. We concluded that r-HuEPO treatment especially decreases prolactin level in uremic hemodialysis patients. It is conceivable that correction of elevated prolactin levels could improve sexual disorders in these patients.

The efficiency of fractionated parenteral iron treatment in CAPD patients.

Some chronic renal failure patients respond poorly to recombinant human erythropoietin (rHuEPO). In continuous ambulatory peritoneal dialysis (CAPD) patients, such a poor response may indicate inadequate dialysis or low body iron stores. To correct iron deficiency, once-a-week intravenous iron supplementation is recommended. However, hemodialysis patients receive iron supplements three times a week. This study was designed to compare the efficacy of iron supplementation between once-weekly and twice-weekly regimens. In both groups, rHuEPO doses were similar. Seventeen CAPD patients were studied. All had hemoglobin levels less than 10 g/dL. Ten patients were given 100 mg intravenous iron once weekly, and 7 were given 50 mg intravenous iron twice weekly until a total iron dose of 600 mg was achieved (stage I). The patients were crossed over to receive another 600 mg iron (stage II). Hematocrit increased significantly in patients receiving twice-a-week iron supplementation (+3.8% and 6%) compared to those receiving once-a-week iron supplementation (+1.3% and 1.4%) during stages I and II. The ferritin levels were not different between the groups. In conclusion, rHuEPO is more effective when administered with intravenous iron.

Cryptosporidiosis and blastocystosis in renal transplant recipients.

Some intestinal parasitic infections are frequently seen in renal transplant recipients. Parasites such as Cryptosporidium spp. and Blastocystis hominis are often asymptomatic or responsible for limited infections in normals, but may cause prolonged and heavy infections with gastrointestinal complaints, mainly diarrhea, in immunocompromised patients. Such infections can often not be detected by routine diagnostic procedures, but special concentration and staining methods are needed. We investigated 115 fecal specimens from 69 renal transplant recipients and 42 fecal specimens from 42 control cases. Of the 69 recipients, 27 (39.1%) had B. hominis and 13 (18.8%) had Cryptosporidium spp. in at least one fecal specimen. Prevalence of symptomatic Cryptosporidium infections was significantly higher in the renal transplant recipients, when compared with the control group (p < 0.05). Special parasitological procedures must be performed in immunocompromised patients with chronic gastrointestinal complaints. Disappearance of symptoms after antiparastic drugs in some of 16 symptomatic patients are described, suggesting that these infections are more pathogenic in transplant recipients.

Disappearance of mitral and tricuspid regurgitation in haemodialysis patients after ultrafiltration.

BACKGROUND: Doppler echocardiography has recently revealed frequent occurrence of valvular (in particular mitral) regurgitation in dialysis (HD) patients. We hypothesized that this may be in part 'functional' and related to the cardiac dilatation which is also frequently present. Thus it would be possible to improve it by ultrafiltration. METHODS: Mitral and tricuspid regurgitation was detected in 21 haemodialysis patients who had cardiomegaly but no manifest cardiac failure. They were treated by intensified ultrafiltration sessions, as much as they could tolerate, while all antihypertensive drugs were stopped. Doppler echocardiograms were then repeated. RESULTS: Mitral regurgitation disappeared in 13 and tricuspid regurgitation in 14 patients, while lesser degrees of either of them persisted in seven. This was accompanied by decreases of body weight (5.4 +/- 2.7 kg) mean arterial pressure (125 +/- 15 to 95 +/- 11 mmHg), cardiothoracic index (from 0.57 to 0.47), and left atrial (28 +/- 4 to 22 +/- 3 mm/m2), left ventricular systolic (25 +/- 5 to 21 +/- 55 mm/m2) and left ventricular diastolic (31 +/- 5 to 27 +/- 5 mm/m2), and mitral annular diameters (19.4 +/- 2 to 16.6 +/- 2 mm/m2). Ejection fraction increased but remained below 50% in 11 patients. CONCLUSION: Most of the mitral and tricuspid regurgitations seen in HD patients are partly or completely functional, due to dilatation of the mitral annulus which is related to volume overload. A more aggressive approach, while discontinuing antihypertensive drugs can correct or improve many of them and also ameliorate cardiac function.

Regression of left ventricular hypertrophy in haemodialysis patients by ultrafiltration and reduced salt intake without antihypertensive drugs.

BACKGROUND: Left ventricular hypertrophy (LVH) is very frequent in haemodialysis patients. Only few investigations have reported its regression, and only by the use of antihypertensive drugs. Because volume load is at least as important as pressure load, we investigated whether persistent strict volume control by ultrafiltration alone may be effective in improving LVH METHODS: Using blood pressure (BP) and cardiac dimensions as a guide, we treated all hypertensive patients in our dialysis unit during the 3 times weekly dialysis sessions for 4 h per session with as much ultrafiltration as they could stand. If they gained too much weight an extra isolated ultrafiltration (UF) session was applied. Special attention was given to dietary salt restriction. The study group of all 15 patients in whom echocardiographic assessment had been made at least 1.5 years previously was selected retrospectively, and we acknowledge that important confounding factors might not have been controlled for. Cardiothoracic index (CTI) was estimated on the chest X-ray. Diameters of left atrium (LA), left ventricle systolic (LVS) and diastolic (LVD), interventricular septum (IVS), posterior wall (PW), and left ventricular mass index (LVMI) were estimated by standard echocardiographic methods. RESULTS: Mean arterial pressure of the study group had been lowered by UF before the first echocardiogram from predialysis 136+/-11 to 101+/-14 and from postdialysis 119+/-8 to 92+/-12 mmHg. During a mean follow-up period of 37+/-11 months LVMI decreased from 175+/-60 to 105+/-11 g/m2. CTI decreased further from 48+/-3 to 43+/-4%, while significant decreases of LA (22.5+/-3 to 19.9+/-4 mm/m2), LVS (18.7+/-4 to 15.9+/-3 mm/m2) and LVD (28.3+/-4 to 24.0+/-3 mm/m2) were seen in all patients. There also was a further decrease in both pre- and postdialysis BP to 116+/-12/73+/-7 and 105+/-7/65+/-3 mmHg respectively. CONCLUSION: The results of this uncontrolled retrospective study suggest that good long-term BP control and a decrease of LVM can be achieved by continuous efforts to control hypervolaemia. The decrease in volume may be even more important than pressure reduction to achieve this goal.

'Paradoxical' rise in blood pressure during ultrafiltration in dialysis patients.

In some hypertensive haemodialysis (HD) patients, blood pressure rises further during ultrafiltration (UF). We investigated seven such patients, who were not responsive to hypotensive drugs, including converting enzyme inhibitors. All had marked cardiac dilatation, but most were non-oedematous. They were treated with repeated intense UF while monitoring cardiac function by echocardiography. After a variable time period they all became (near) normotensive without medication. Mean systolic and diastolic blood pressure decreased by 46 +/- 18 and 22 +/- 9 mmHg respectively while bodyweight decreased by a mean of 6.7 +/- 3.0 kg. Plasma volume decreased by 22%, and mean albumin increased from 3.9 +/- 0.3 to 4.2 +/- 0.3 g/dl. Cardiothoracic index decreased from a 0.56 +/- 0.02 to 0.45 +/- 0.03. Mitral and tricuspid insufficiency was present in four patients and improved or disappeared in all of them. Diameters of the inferior vena cava, left atrium, and end systolic and diastolic left ventricle markedly decreased in all patients. Ejection fraction increased, but remained subnormal in some patients, while cardiac output increased in five and decreased in two patients. We conclude that paradoxical blood pressure rise with UF usually occurs in the presence overhydration and cardiac dilatation and should be treated by intensified UF. The explanation of this phenomenon remains speculative.