Biopersistence of silver nanoparticles in tissues from Sprague-Dawley rats

Silver nanoparticles are known to be distributed in many tissues after oral or inhalation exposure. Thus, understanding the tissue clearance of such distributed nanoparticles is very important to understand the behavior of silver nanoparticles in vivo. For risk assessment purposes, easy clearance indicates a lower overall cumulative toxicity. Accordingly, to investigate the clearance of tissue silver concentrations following oral silver nanoparticle exposure, Sprague–Dawley rats were assigned to 3 groups: control, low dose (100 mg/kg body weight), and high dose (500 mg/kg body weight), and exposed to two different sizes of silver nanoparticles (average diameter 10 and 25 nm) over 28 days. Thereafter, the rats were allowed to recover for 4 months. Regardless of the silver nanoparticle size, the silver content in most tissues gradually decreased during the 4-month recovery period, indicating tissue clearance of the accumulated silver. The exceptions were the silver concentrations in the brain and testes, which did not clear well, even after the 4-month recovery period, indicating an obstruction in transporting the accumulated silver out of these tissues. Therefore, the results showed that the size of the silver nanoparticles did not affect their tissue distribution. Furthermore, biological barriers, such as the blood–brain barrier and blood-testis barrier, seemed to play an important role in the silver clearance from these tissues.

Recovery from silver-nanoparticle-exposure-induced lung inflammation and lung function changes in Sprague Dawley rats

In a previous study, the lung function, as indicated by the tidal volume, minute volume, and peak inspiration flow, decreased during 90 days of exposure to silver nanoparticles and was accompanied by inflammatory lesions in the lung morphology. Therefore, this study investigated the recovery from such lung function changes in rats following the cessation of 12 weeks of nanoparticle exposure. Male and female rats were exposed to silver nanoparticles (14-15 nm diameter) at concentrations of 0.66 × 10(6) particles/cm(3) (49 μg/m(3), low dose), 1.41 × 10(6) particles/cm(3) (117 μg/m(3), middle dose), and 3.24 × 10(6) particles/cm(3) (381 μg/m(3), high dose) for 6 h/day in an inhalation chamber for 12 weeks. The rats were then allowed to recover. The lung function was measured every week during the exposure period and after the cessation of exposure, plus animals were sacrificed after the 12-week exposure period, and 4 weeks and 12 weeks after the exposure cessation. An exposure-related lung function decrease was measured in the male rats after the 12-week exposure period and 12 weeks after the exposure cessation. In contrast, the female rats did not show a consistent lung function decrease either during the exposure period or following the exposure cessation. The histopathology showed a gradual recovery from the lung inflammation in the female rats, whereas the male rats in the high-dose group exhibited persistent inflammation throughout the 12-week recovery period. Therefore, the present results suggest a potential persistence of lung function changes and inflammation induced by silver nanoparticle exposure above the no observed adverse effect level.

The influence of patient position on withdrawal force of thoracic epidural catheters

We investigated the forces required to remove thoracic epidural catheters to determine the effect of patient position on removal. Eighty-four patients undergoing open thoracotomy and thoracic patient-controlled epidural analgesia were enrolled. Catheterisation was performed under fluoroscopic guidance before surgery, and the patients were allocated to one of three position groups for removal: prone; sitting; and lateral. On the third postoperative day, the peak tension during withdrawal in the assigned position was measured. No differences in mean (SD) forces were found between groups: prone 1.61 (0.39) N, supine 1.62 (0.61) N and lateral 1.36 (0.56) N (p = 0.140). The withdrawal forces required to remove thoracic epidural catheters were not affected by the position. Thus, the position for removal can be determined by patient's choice and clinical judgement.

Anatomical Analysis of Computed Tomography Images for Determining the Optimal Oblique Fluoroscope Angle for Percutaneous Coeliac Plexus Block

This retrospective study used abdominal computed tomography (CT) scan images to determine the optimal safe oblique angle for fluoroscopy in fluoroscope-assisted coeliac plexus block (CPB). Abdominal CT scans from 131 patients were included in the study: 42 patients with cancer of the pancreas head, 45 with cancer of the pancreas body and tail and 44 with chronic pancreatitis. The oblique angle and entry distance from the midline were measured at the T12 and L1 levels, and the safe angle range that avoided puncture of the organs was also measured. The optimal angle varied between the T12 and L1 levels, and between the right and left sides at the T12 level. There was no difference in the oblique angle between the patient groups. The optimal oblique angle for fluoroscopy was determined to be 17° for right T12, 18° for left T12, and 19° for both left and right L1.

Development of a new pre- and post-processing tool (SADAPT-TRAN) for nonlinear mixed-effects modeling in S-ADAPT

Mechanistic modeling greatly benefits from automated pre- and post-processing of model code and modeling results. While S-ADAPT provides many state-of-the-art parametric population estimation methods, its pre- and post-processing capabilities are limited. Our objective was to develop a fully automated, open-source pre- and post-processor for nonlinear mixed-effects modeling in S-ADAPT. We developed a new translator tool (SADAPT-TRAN) based on Perl scripts. These scripts (a) automatically translate the core model components into robust Fortran code, (b) perform extensive mutual error checks across all input files and the raw dataset, (c) extend the options of the Monte Carlo Parametric Expectation Maximization (MC-PEM) algorithm, and (d) improve the numerical robustness of the model code. The post-processing scripts automatically summarize the results of one or multiple models as tables and, by generating problem specific R scripts, provide an extended series of standard and covariate-stratified diagnostic plots. The SADAPT-TRAN package substantially improved the efficiency to specify, debug, and evaluate models and enhanced the flexibility of using the MC-PEM algorithm for parallelized estimation in S-ADAPT. The parameter variability model can take any combination of normally, log-normally, or logistically distributed parameters and the SADAPT-TRAN package can automatically generate the Fortran code required to specify between occasion variability. Extended estimation features are available to avoid local minima, estimate means with negligible variances, and estimate variances for fixed means. The SADAPT-TRAN package significantly facilitated model development in S-ADAPT, reduced model specification errors, and provided useful error messages for beginner and advanced users. This benefit was greatest for complex mechanistic models.

Simultaneous determination of fimasartan, a novel antihypertensive agent, and its active metabolite in rat plasma by liquid chromatography-tandem mass spectrometry

Fimasartan, 2-butyl-5-dimethylaminothiocarbonylmethyl-6-methyl-3-[[2'-(1H tetrazol -5-yl)biphenyl-4-yl]methyl]pyrimidin-4(3H)-one (BR-A-657), is a novel angiotensin II receptor blocker exhibiting potent and selective AT1 receptor blocking activity. This study reports the liquid chromatography-tandem mass spectrometry assay for the simultaneous determination of fimasartan and its active metabolite, BR-A-557, in rat plasma. The assay was validated to demonstrate the specificity, linearity, recovery, lower limit of quantification, accuracy, precision and stability. The multiple reaction monitoring was based on the transition of m/z 502.1 → 207.1 for fimasartan, 486.2 → 207.1 for BR-A-557 and 526.1 → 207.1 for BR-A-563 (internal standard). The assay utilized a simple precipitation procedure with acetonitrile and isocratic elution. The LLOQ was 0.2 ng/mL for fimasartan and BR-A-557 using 50 μL plasma samples. The assay was linear over a concentration range from 0.2 to 500 ng/mL for fimasartan and BR-A-557, with correlation coefficients >0.9995. The intra- and inter-day assay accuracies were 93.6-108.0 and 90.8-101.4% for fimasartan and 102.2-107.1 and 99.6-103.3% for BR-A-557, respectively. The intra- and inter-day precision were 2.4-4.4 and 3.0-13.4% for fimasartan and 3.1-5.2 and 2.8-9.8% for BR-A-557, respectively. The developed assay may be used to study the metabolism and mechanistic pharmacokinetics of fimasartan in future studies.

Prediction of human pharmacokinetics and tissue distribution of apicidin, a potent histone deacetylase inhibitor, by physiologically based pharmacokinetic modeling

PURPOSE

The objectives of this study were to develop physiologically based models for the pharmacokinetics (PK) and organ distribution of apicidin in rats and mice and to predict human PK in blood and organs.

METHODS

The PK of apicidin was characterized in rats and mice after i.v. bolus injection, and distribution to various tissues was determined in rats following i.v. infusions at steady state. The developed models were prospectively validated within rat and within mouse and by scaling from rat to mouse using data after multiple i.v. injections. Human PK was predicted by the physiologically based modeling using intrinsic clearance data for humans from in vitro experiments.

RESULTS

The Cl(s) predicted for human (9.8 ml/min/kg) was lower than those found in mice (116.9 ml/min/kg) and rats (61.6 ml/min/kg), and the V(ss) predicted for human (1.9 l/kg) was less than in mice (2.0 l/kg) and rats (2.5 l/kg). Consequently, the predicted t (1/2) was longer in human (2.3 h) than in mice and rats (0.4 and 0.9 h, respectively). The highest concentrations of apicidin were predicted in liver followed by adipose tissue, kidney, lung, spleen, heart, arterial blood, venous blood, small intestine, stomach, muscle, testis, and brain.

CONCLUSIONS

The developed models adequately described the PK of apicidin in rats and mice and were applied to predict human PK. These models may be useful in predicting human blood and tissue concentrations of apicidin under different exposure conditions.

Assessment of bisphenol A exposure in Korean pregnant women by physiologically based pharmacokinetic modeling

The objective of this study was to predict the exposure to bisphenol A (BPA) after oral intake in human blood and tissues using physiologically based pharmacokinetic (PBPK) modeling. A refined PBPK model was developed taking into account of glucuronidation, biliary excretion, and slow absorption of BPA in order to describe the second peak of BPA observed following oral intake. This developed model adequately described the second peak and BPA concentrations in blood and various tissues in rats after oral administration. A prospective validation study in rats additionally supported the proposed model. For extrapolation to humans, a daily oral BPA dose of 0.237 mg/70 kg/d or 0.0034 mg/kg/d was predicted to achieve an average steady-state blood concentration of 0.0055 ng/ml (median blood BPA concentration in Korean pregnant women). This dose was lower than the reference dose (RfD, 0.016 mg/kg/d) and the tolerable daily intake established by the European Commission (10 μg/kg/d). Data indicate that enterohepatic recirculation may be toxicologically important as this pathway may increase exposure and terminal half-life of BPA in humans.

Determination of zearalenone by liquid chromatography/tandem mass spectrometry and application to a pharmacokinetic study

Zearalenone, a mycotoxin biosynthesized by various Fusarium fungi, is widely found as a contaminant in grains and animal feeds. This study describes a rapid and sensitive LC/MS/MS assay method for the quantification of zearalenone in rat serum. The assay was validated to demonstrate the specificity, linearity, recovery, lower limit of quantification (LLOQ), accuracy and precision. The multiple reaction monitoring was based on the transition of m/z 317.0 --> 130.9 for zearalenone and 319.0 --> 204.8 for zearalanone (internal standard). The assay utilized a single liquid-liquid extraction with t-butyl methyl ether and isocratic elution, and the LLOQ was 0.5 ng/mL using 0.1 mL rat serum. The assay was linear over a concentration range from 0.5 to 200 ng/mL, with correlation coefficients >0.9996. The mean intra- and inter-day assay accuracy was 101.2-112.9 and 96.3-108.0%, respectively. The mean intra- and inter-day precision was between 1.3-7.6 and 3.6-10.6%, respectively. The developed assay was applied to a pharmacokinetic study after a bolus intravenous injection of zearalenone in rats.

Interspecies scaling of oleanolic acid in mice, rats, rabbits and dogs and prediction of human pharmacokinetics

This study was conducted to predict the pharmacokinetics of oleanolic acid in humans based on animal data by allometry and several species-invariant time methods. Oleanolic acid was injected intravenously to mice, rats, rabbit and dogs (dose 1 mg/kg). The serum concentration-time profiles of oleanolic acid were best described by bi-exponential equation in all animal species. The average Cl, V ( ss ) and t ( 1/2 ) were 0.065 L/h, 0.019 L and 28.7 min in mice, 0.47 +/- 0.06 L/h, 0.117 +/- 0.029 L and 29.7 +/- 12.2 min in rats, 2.77 +/- 0.88 L/h, 1.83 +/- 0.60 L and 84.4 +/- 16.9 min in rabbits and 14.0 +/- 0.7 L/h, 9.2 +/- 10.1 L and 54.5 +/- 57.2 min in dogs, respectively. Based on animal data, human pharmacokinetic parameters of Cl, V ( ss ) and t (1/2) were predicted by simple allometry. In addition, actual concentration-time profiles obtained from animals were transformed to human profiles by species-invariant times of kallynochron, apolysichron and dienetichron. The predicted human pharmacokinetic parameters of Cl, V ( ss ) and t (1/2) by using simple allometry and species-invariant time transformation method ranged from 48.3-97.2 L/h, 49.1-92.9 L and 45.6-187.2 min, respectively. Those predicted parameters of oleanolic acid may be useful in designing dosing schedules of oleanolic acid in future clinical studies.

Use of an anti-vascular endothelial growth factor antibody in a pharmacokinetic strategy to increase the efficacy of intraperitoneal chemotherapy

The efficacy of intraperitoneal chemotherapy for ovarian cancers is limited by poor penetration of drug into peritoneal tumors. Based on pharmacokinetic theory that suggests that penetration depth is primarily determined by the rate of drug removal via tumor capillaries, we have hypothesized that co-administration of antiangiogenic therapy will allow for decreased drug removal, increased drug concentrations in tumor, and increased efficacy of intraperitoneal chemotherapy. Pharmacokinetic modeling was conducted to simulate the effect of tumor blood flow on tumor concentrations of topotecan. Simulations predicted that tumor blood flow reductions, as potentially achieved by antiangiogenic therapy, would lead to substantial increases in tumor concentrations after intraperitoneal chemotherapy but would lead to a slight decrease after systemic chemotherapy. Pharmacokinetic studies performed using the A2780 xenograft tumor model showed that animals receiving combined intraperitoneal topotecan and an anti-vascular endothelial growth factor (VEGF) monoclonal antibody had approximately 6.5-fold higher (p = 0.0015) tumor topotecan concentrations compared with animals receiving intraperitoneal topotecan alone, whereas there was no significant (p = 0.16) difference for systemic topotecan. Therapeutic studies conducted with two different drugs, topotecan and cisplatin, showed that animals receiving combined intraperitoneal chemotherapy and anti-VEGF therapy displayed superior survival relative to animals treated with chemotherapy alone (i.e., cisplatin or topotecan), anti-VEGF alone, or intravenous chemotherapy with concomitant anti-VEGF therapy. Combined intraperitoneal topotecan and anti-VEGF resulted in the complete cure of four of 11 mice. The proposed combination of antiangiogenic therapy and intraperitoneal chemotherapy, which was predicted to be beneficial by pharmacokinetic simulations, may provide substantial benefit to patients with peritoneal malignancies.

Disposition, oral bioavailability, and tissue distribution of zearalenone in rats at various dose levels

This study was conducted to characterize the disposition, oral bioavailability, and tissue distribution of zearalenone in rats. The pharmacokinetics and tissue distribution of zearalenone were studied after intravenous (i.v.) or oral (p.o.) administration at doses ranging from 1 to 8 mg/kg in intact and bile duct-cannulated rats. Serum, bile, and urine concentrations were determined by liquid chromatography and mass spectroscopy (LC/MS/MS) and tissue concentrations by high-performance liquid chromatography (HPLC)/fluorescence detection assays. Noncompartmental methods were used for pharmacokinetic analysis. Average Cl(s) (range 5.0-6.6 L/h/kg) and V(dss) (range 2-4.7 L/kg) remained unaltered over an i.v. dose range from 1 to 8 mg/kg, and area under the concentration-time curve (AUC) and initial peak concentrations increased linearly with dose. Minimal quantities of zearalenone were excreted unchanged in urine (f(e,urine) 0.5 +/- 0.2%) and bile (f(e,bile) 0.91 +/- 0.64%). After p.o. administration of 8 mg/kg, zearalenone was rapidly absorbed and serum concentration-time profiles showed a distinct second peak. The absolute oral bioavailability was low (2.7%). Comparing bile duct-cannulated to intact rats at a dose of 8 mg/kg, the impact of biliary excretion on overall pharmacokinetics was more pronounced after p.o. than after i.v. administration. Upon i.v. infusion to steady state, the highest zearalenone concentration was found in small intestine, followed by kidneys, liver, adipose tissue, and lung. Zearalenone concentrations in stomach, heart, brain, spleen, muscle, and testes were lower than those found in serum. The pharmacokinetics and tissue distribution data from this study may be useful to develop physiologically based pharmacokinetic (PBPK) models for zearalenone and subsequently to predict the pharmacokinetics and toxicity in humans.

Physiologically based pharmacokinetics of zearalenone

The objectives of this study were to (1) develop physiologically based pharmacokinetic (PBPK) models for zearalenone following intravenous (i.v.) and oral (p.o.) dosing in rats and (2) predict concentrations in humans via interspecies scaling. The model for i.v. dosing consisted of vein, artery, lung, liver, spleen, kidneys, heart, testes, brain, muscle, adipose tissue, stomach, and small intestine. To describe the secondary peak phenomenon observed after p.o. administration, the absorption model was constructed to reflect glucuronidation, biliary excretion, enterohepatic recirculation, and fast and slow absorption processes from the lumenal compartment. The developed models adequately described observed concentration-time data in rats after i.v. or p.o. administration. Upon model validation in rats, steady-state zearalenone concentrations in blood and tissues were simulated for rats after once daily p.o. exposures (0.1 mg/kg/d). The average steady-state blood zearalenone concentration predicted in rat was 0.014 ng/ml. Subsequently, a daily human p.o. dose needed to achieve the same steady-state blood concentration found in rats (0.014 ng/ml) was determined to be 0.0312 mg/kg/d or 2.18 mg/70 kg/d. The steady-state zearalenone concentration-time profiles in blood and tissues were also simulated for human after multiple p.o. administrations (dose 0.0312 mg/kg/d). The developed PBPK models adequately described the pharmacokinetics in rats and may be useful in predicting human blood and tissue concentrations for zearalenone under different p,o, exposure conditions.