Development and validation of a herring gull embryo toxicokinetic model for PCBs

A toxicokinetic model was developed to describe polychlorinated biphenyl (PCB) accumulation by herring gull (Larus argentatus) embryos during development. The model consists of two components, a bioenergetics model that predicts the lipid mass balance of embryo and yolk compartments with time and an empirical toxicokinetic model that describes PCB partitioning between lipid compartments in the egg. The model was calibrated using data on PCB and lipid partitioning between embryo and yolk+albumen at four time points during incubation in herring gull eggs injected with a PCB mixture, combined with data sets on herring gull embryo growth rates and bioenergetic demands with time. The model was validated using independent data consisting of maternally exposed, field-incubated Lake Superior herring gull eggs that varied in incubation ages over the range of 8.5 d to pipping age (26–28 days). PCB concentrations in 6–9 d embryos were nearly an order of magnitude less than predicted by equilibrium lipid partitioning between the embryo and yolk+albumen compartments of the eggs. PCB concentrations in embryos were adequately predicted by equilibrium partitioning, however, for eggs incubated for 23–28 d. An empirical relationship was developed to account for the apparent non-equilibrium behaviour of PCBs during early development. The model was sensitive to the mass of yolk lipids and the mass of PCBs deposited to fresh eggs and much of the variability in embryo PCB concentrations could by explained by accounting for variability in these input parameters. Consistent with experimental data for other avian species, the model predicts that the highest PCB concentrations in the embryo/chick occur during pipping or soon after when yolk lipids have been completely resorbed by the embryo.     

Development and validation of a non-linear IVIVC model for a diltiazem extended release formulation

To develop and validate internally an in vitro-in vivo correlation (IVIVC) for a diltiazem multi-particulate bead extended release formulation. In vitro dissolution of diltiazem capsules was examined using the following methods: USP Apparatus II (paddle) at 100 rpm and USP Apparatus III at 30 dpm. Seven healthy subjects received three diltiazem formulations (90 mg): slow (S), moderate (M), fast (F) releasing and an oral solution (90 mg). Serial blood samples were collected over 48 h and analyzed by a validated HPLC assay using ultraviolet detection. The f(2) metric (similarity factor) was used to analyze the dissolution data. Linear and non-linear (quadratic, cubic, and sigmoid functions) correlation models were developed using pooled fraction dissolved (FRD) and fraction absorbed (FRA) data from various combinations of the formulations. Predicted diltiazem concentrations were obtained by convolution of the in vivo dissolution rates. Prediction errors were estimated for C(max) and AUC to determine the validity of the correlation. Apparatus II using purified water was found to be the most discriminating dissolution method. Significant intersubject (CV%>50) was observed for C(max) and AUC. The quadratic M/F IVIVC model provided a significant relationship between FRD and FRA when using either two or three of the formulations. An average percent prediction error for C(max) and AUC for all formulations was 12.4% and 9.2%, respectively. The prediction errors observed for C(max) and AUC suggest that the predictability of the quadratic IVIVC model is inconclusive, as such, external validation studies are required.     

Development and validation of a chronic copper biotic ligand model for Ceriodaphnia dubia

A biotic ligand model (BLM) to predict chronic Cu toxicity to Ceriodaphnia dubia was developed and tested. The effect of cationic competition, pH and natural organic matter complexation of Cu was examined to develop the model. There was no effect of cationic competition using increasing Ca and Na concentrations in our exposures. However, we did see a significant regression of decreasing toxicity (measured as the IC25; concentration at which there was a 25% inhibition of reproduction) as Mg concentration increased. However, taking into account the actual variability of the IC25 and since the relative increase in IC25 due to additional Mg was small (1.5-fold) Mg competition was not included in the model. Changes in pH had a significant effect on Cu IC25, which is consistent with proton competition as often suggested for acute BLMs. Finally, natural organic matter (NOM) was added to exposures resulting in significant decreases in toxicity. Therefore, our predictive model for chronic Cu toxicity to C. dubia includes the effect of pH and NOM complexation. The model was validated with Cu IC25 data generated in six natural surface waters collected from across Canada. Using WHAM VI, we calculated Cu speciation in each natural water and using our model, we generated "predicted" IC25 data. We successfully predicted all Cu IC25 within a factor of 3 for the six waters used for validation.     

Aurora kinase inhibitors: identification and preclinical validation of their biomarkers

Aurora kinases are key regulators of mitosis and inhibitors being developed by a wide range of pharmaceutical and biotechnology companies for the treatment of cancer. Tumor cells respond differentially on inhibition of different Aurora kinase family members and these differences have to be considered in the clinical development of small-molecule inhibitors with respect to the chosen indications, the schedules or the selection of appropriate end points and they should also guide the development of biomarkers. Preclinical validation of potential biomarkers for Aurora kinase inhibitors led to a first application in clinical trials, as exemplified for the phosphorylation of histone H3 to follow Aurora-B inhibition. This review discusses the criteria for translation into the clinic and the value of pharmacodynamic biomarkers and their potential, but also their limitations to be used as surrogate markers for clinical end points.     

Development and validation of a novel IL-10 deficient cell transfer model for colitis

A number of rodent models for inflammatory bowel disease (IBD) have been developed, but most cannot be used to develop and validate new therapies for IBD. From the models developed, the IL-10 deficient mouse model is the one that results in a disease similar to human IBD; however, in this model, colitis occurs with variable incidence taking 3-4 months to develop. These are serious problems with the model when evaluating a new therapy because of the large-scale experiments required and the difficulty in performing an accurate pharmacological analysis. In this study, the IL-10 deficient mouse model was modified by transferring whole spleen and mesenteric lymph node cells from IL-10 deficient mice to CB-17 SCID mice. In this IL-10 deficient cell transfer model, chronic intestinal inflammation developed in all recipients within 2-3 weeks, which was far earlier than in donor IL-10 deficient mice. The pathological phenotypes were similar to those of IL-10 deficient mice and CD45RBhi T cell-transfer models. In addition, we assessed several agents for inflammatory bowel disease to validate the general utility of this cell transfer model. It is worth noting that TNFR-Ig or prednisolone, which is effective for treatment of patients with severe-fulminant Crohn's disease, markedly attenuated pathological clinical indices in this colitis model, whereas the immunosuppressive agents, azathioprine, tacrolimus, and cyclosporine A produced no significant effect. These results suggest that the IL-10 deficient cell transfer model is a good experimental model to use for developing new and effective therapies for active IBD.     

Development of a canine model to enable the preclinical assessment of pH-dependent absorption of test compounds

A preclinical canine model capable of predicting a compound's potential for pH-dependent absorption in humans was developed. This involved the surgical insertion of a gastrostomy feeding tube into the stomach of a beagle dog. The tube was sutured in position to allow frequent withdrawal of gastric fluid for pH measurement. Therefore, it was possible to measure pH in the stomach and assess the effect of gastric pH-modifying agents on the absorption of various test compounds. Fasted gastric pH in the dog showed considerable inter- and intra-animal variability. Pretreatment of pentagastrin (6 μg/kg intramuscularly) 20 min prior to test compound administration was determined to be adequate for simulating fasting stomach pH in humans. Pretreatment with famotidine [40 mg orally] 1 h prior to test compound administration was determined to be adequate for simulating human gastric pH when acid-reducing agents are coadministered. Pentagastrin and famotidine pretreatments were used to test two discovery compounds and distinct differences in their potential for pH-dependent absorption were observed. The model described herein can be used preclinically to screen out compounds, differentiate compounds, and support the assessment of various formulation- and prodrug-based strategies to mitigate the pH effect.     

Development and validation of a measure and a model of general practitioner attitudes toward collaboration with pharmacists

BackgroundCollaboration between general practitioners (GPs) and community pharmacists has been shown to be effective in improving patient outcomes. However, little is known about GP attitudes toward collaborating with their pharmacist counterparts and variables that influence this interprofessional collaboration.ObjectivesTo develop and validate, in the context of primary care in Australia 1) an instrument to measure GP attitudes toward collaborating with pharmacists and 2) a model that illustrates how GP attitudes (and other variables) influence GP-pharmacist collaborative behavior.MethodsThe “Attitudes Toward Collaboration Instrument for GPs” (ATCI-GP) was developed to measure GP attitudes toward GP-pharmacist collaboration based on existing literature and qualitative interviews with GPs and community pharmacists. The ATCI-GP and a previously validated behavioral measure “Frequency of Interprofessional Collaboration Instrument for GPs” (FICI-GP) were included in a survey and administered to a sample of 1145 GPs in 12 divisions of general practice across Australia. Principal component analysis (PCA) was used to assess the structure of the ATCI-GP. Structural equation modeling was used to determine how attitudes (measured by the ATCI-GP) and other variables, influence collaborative behavior (measured by the FICI-GP).ResultsThree hundred and seventy-six surveys were completed and returned for a response rate of 33%. PCA of the ATCI-GP suggested a two factor (“interactional and practitioner determinants” and “role for pharmacist in medication management”) solution accounting for 66.2% of the variance. The model for GP-pharmacist collaboration demonstrated adequate fit (χ²/df = 2.27, CFI = .99, RMSEA = .060, 90% CI [.052–.069]). Factors found to predict collaboration included: 1) Interactional and practitioner determinants 2) environmental determinants and 3) GP perception of the pharmacists' role in medication management.ConclusionsThe study provides evidence for the validity of the ATCI-GP for measuring GP-pharmacist collaboration from the GPs perspective and supports a model for collaboration in which collaborative behavior is influenced by a number of variables.     

A preclinical model of binge eating elicited by yo-yo dieting and stressful exposure to food: effect of sibutramine,fluoxetine, topiramate,and midazolam

Rationale  Preclinical models are needed to investigate the neurobiology and psychobiology of binge eating and to identify innovative pharmacotherapeutic strategies. Objectives  A modification of the model based on the combination of cyclic caloric restrictions and acute stress was developed to further increase its face validity and reliability and, for the first time, to assess its predictive value. Materials and methods  Four groups of female rats were employed: group 1 was normally fed and not stressed on the test day (25th); group 2 was fed normally but was exposed to an acute stress on day 25; group 3 was exposed to three cycles (4 days 66% of chow intake + 4 days food ad libitum) of yo-yo dieting but not stressed; and group 4 was exposed to cyclic yo-yo dieting and then stressed. All groups were fed highly palatable food (HPF) for 2 h on days 5–6 and 13–14. Acute stress was elicited by exposing rats to HPF, but preventing them from access to it for 15 min. Results  The combination of cyclic food restriction and stressful exposure to food markedly increased HPF intake. Sibutramine and fluoxetine inhibited food intake in all conditions. Topiramate selectively inhibited compulsive HPF intake in rats submitted to caloric restriction and stress. Midazolam increased HPF intake. Conclusions  Pharmacological results suggest that this model, in addition to face validity as an isomorphic model of human binge eating, is endowed with good predictive validity.     

Development and validation of transtheoretical model measures for Bulgarian adolescent non-smokers

The goal of this study was to develop, translate, and evaluate measures for decisional balance and situational temptations for Bulgarian adolescent nonsmokers and to test the predicted relationships with stages of change. Students in the last grades of high school (15-19 years old) recruited in 12 randomly selected schools participated in the study. Data from the 369 nonsmokers (61.8% female, mean age 16.4 years, 97.1% Bulgarian) were used in the measurement development. A two-factor model for decisional balance (CFI=.94) and a hierarchical three-factor model for temptations (CFI=.90) demonstrated the best fit. The predicted crossover pattern for decisional balance and decreasing trend for temptations across the stages of change was verified. Both measures demonstrated tau-equivalent invariance across gender, in addition to good psychometric properties. These results, with the caveat of the noted limitations, support the cross-cultural validity of these transtheoretical model (TTM) constructs and indicate that they can be used as a basis for development of smoking prevention interventions.     

Operant self-administration of alcohol and nicotine in a preclinical model of co-abuse

Rationale and objectives

Alcohol and nicotine are often taken together. In humans, intake of nicotine, via smoked tobacco, increases alcohol drinking, and alcohol increases smoking. Chronic nicotine treatment increases alcohol self-administration (SA) in laboratory animals; the reverse relationship is less clear. Most animal work modeling this has used passive administration, which lacks relevance to human co-abuse. Here, we describe a model based on sequential operant SA of alcohol and nicotine.

Methods

Animals are first trained on alcohol SA (0.19 ml of 12 % alcohol (w/v)/delivery) and then receive separate alcohol (8 %, w/v) and nicotine (15 μg/kg/infusion) SA sessions on the same day (“daily dual access”). Animals then receive access to alcohol and then to nicotine (or in the reverse order) in alternating 5-min periods in 2-h sessions (“alternating access”). We then determine if alternating access modifies the effects of naltrexone on responding for alcohol and nicotine.

Results

We found that with daily dual access, nicotine significantly increased alcohol SA when alcohol access occurred prior to nicotine access and that nicotine SA significantly decreased when the alcohol SA session preceded it. During alternating access, nicotine also significantly increased alcohol intake. Naltrexone (0.3 or 1 mg/kg) significantly reduced alcohol SA during these alternating access sessions in animals that also received nicotine SA, but had minimal effects on animals receiving alcohol SA alone. Naltrexone did not affect nicotine SA under any condition.

Conclusions

This sequential access procedure effectively models the effects of nicotine on alcohol intake noted in humans.     

Development of a self-emulsifying formulation that reduces the food effect for torcetrapib

Torcetrapib is a highly lipophilic (Clog P=7.45) and water insoluble cholesteryl ester transfer protein (CETP) inhibitor developed for the treatment of atherosclerosis. Self-emulsifying drug delivery system (SEDDS) formulations have been developed to reduce the food effect observed in early clinical trials using medium chain triglyceride (MCT) softgels and to increase the dose per capsule. MCT/Triacetin/Polysorbate 80/Capmul MCM (20/30/20/30) (MTPC) increased fasted exposure and thus reduced the food effect from 5- to 3-fold in dogs at a dose of 90 mg. Self-emulsifying formulations also accelerated absorption and generally decreased variability. Use of the lipophilic, GRAS cosolvent triacetin allowed a 2-fold increase in the dose per capsule. For the three formulations evaluated in dogs that showed significant differences in absorption, emulsion droplet size did not appear to play a significant role. Absorption did increase with Cremophor RH40 content, and at 50% Cremophor RH40 there was no food effect (at 30 mg). High polar surfactant content also resulted in poor dose proportionality, while there was good dose proportionality for MTPC. Studies of in vitro lipolysis are being conducted to aid in understanding the in vitro/in vivo relationships for torcetrapib SEDDS absorption.     

肠道转运Caco-2细胞单层模型的建立及验证评价

目的建立Caco-2细胞单层模型用于药物转运研究。方法按照常规的细胞培养方法,将Caco-2细胞接种到Millicell小室内(接种密度1×10⁶个·mL^-1),培养21 d。定期用细胞电位仪监测跨上皮细胞电阻（TEER）,评价细胞单层的紧密性与完整性;通过荧光黄转运实验检查Caco-2细胞单层模型细胞旁路转运通透性;通过普萘洛尔转运实验验证Caco-2细胞单层模型跨细胞被动转运通透性。结果培养21 d后,TEER值达到（981±123）Ω·cm²,荧光黄和普萘洛尔的表观通透系数分别为0.33×10及16.7×10^-6cm·s^-1。结论本研究建立的Caco-2细胞单层模型紧密、完整,具有良好通透性,可用于药物转运研究。     

Development and validation of a model to predict blood alcohol concentrations: Updating the NHTSA equation

ObjectsTo date, multiple models have been developed to estimate blood or breath alcohol concentration (BAC/BrAC). Several factors have been identified that affect the discrepancy between BACs/BrACs and retrospective estimation (eBAC) with existing equations. To the best of our knowledge, a model to quantify the effects of factors on the discrepancy between BAC/BrAC and eBAC is still nonexistent. The goal of this work was to develop a model to provide a more accurate retrospective estimation of breath alcohol concentration (eBAC).MethodA laboratory study with alcohol consumption and a driving task was conducted with 30 participants (17 male and 13 female) to explore the factors that may contribute to the discrepancy between BrAC and eBAC obtained with existing models. A new eBAC model was developed to improve the estimation of BrAC by modeling effects of gender, weight, and the delay of BrAC measurement on the discrepancy. The validity of the model was tested and established with the data from the experiment conducted in this study and two published research studies, and compared with existing eBAC models.ResultsResults of the model validity examination indicated that the developed model had higher R squares and lower root-mean-squared errors (RMSE) in estimating BrAC in three experiments compared with the existing eBAC models, including the NHTSA equation, the Matthew equation, the Lewis equation, the Watson equation, and the Forrest equation.ConclusionThe developed eBAC model had a better performance of BrAC estimation compared with existing eBAC models. The validation of the model with the data from three empirical studies indicated a high level of generalizability in estimating BrAC.     

Development of a placebo effect model combined with a dropout model for bipolar disorder

The aim of this study was to develop a placebo model for bipolar disorder to help optimize clinical trial designs for studies targeting manic episodes in bipolar disorder. A bipolar disease database was built based on individual longitudinal data collected from over 3,000 patients in 11 clinical trials for 5 approved bipolar drugs. An empirical placebo effect model with an exponential decay process plus a linear progression process was developed to quantify the time course of the Young Mania Rating Scale total score based on only placebo data from the database. In order to describe the dropout pattern during the trials, a parametric survival model was developed and the Weibull distribution was identified to be the best distribution to describe the data. Based on the likelihood ratio test, it was found that patients with higher baseline score, slower disease improvement and more rapid disease progression tended to dropout earlier, and the trial features such as trial starting year and trial site were also significant covariates for dropout. A combination of the placebo effect model and the dropout model was applied to simulate new clinical trials through Monte-Carlo simulation. Both the placebo effect model and dropout model described the observed data reasonably well based on various diagnostic plots. The joint placebo response and dropout models can serve as a tool to simulate the most likely level of placebo response with the expected dropout pattern to help design a new clinical trial.     

Development of an in vivo preclinical screen model to estimate absorption and bioavailability of xenobiotics.

The purpose of this study was to develop an in vivo screening method for rapid preclinical characterization of absorption and bioavailability of large numbers of compounds. This effort involved several steps. First, a pharmacokinetic characterization of a reference compound was conducted in the monkey. These data were used to verify theoretical calculations of a maximal portal dose-normalized area under the concentration-time curve. Next, a monkey screen was implemented using mixtures of up to five compounds each (i.e., cassettes) to estimate the bioavailability of approximately 200 compounds. Cassettes were administered as a single intraduodenal dose to a single monkey followed by simultaneous portal and systemic blood sampling. Definitive studies were then conducted to determine absolute bioavailability of 14 of these compounds. The studies with the reference compound demonstrated that the theoretical methodology based on a single intraduodenal dose with portal and systemic sampling provided consistent estimates of bioavailability. In the screen studies, approximately 75% of the test compounds were excluded from further evaluation due to poor absorption. Of the 14 compounds selected for follow-up evaluation from both well and poorly absorbed compounds, the absolute bioavailability of 10 of them were correctly classified from the screening data. The remaining 4 compounds were false positives, which showed low bioavailability; no false negatives were encountered. This approach allows for a rapid and reliable screen to evaluate absorption and bioavailability using a single dose in a preclinical model.     

Combined effect of recombinant CD19 x CD16 diabody and thalidomide in a preclinical model of human B cell lymphoma

Combining different treatment strategies offers the possibility of improving treatment results for cancer patients. The aim of our study was therefore to investigate the combination of treatment of established s.c. human B non-Hodgkin's lymphoma in severe immune deficient mice using a recombinant bispecific CD19 x CD16 diabody (targeting natural killer cells to CD19 cells) and the angiogenesis inhibitor thalidomide. Monotherapy with either thalidomide or diabody caused an approximate 50% reduction in tumor growth rate. The combined treatment showed evidence for a synergistic effect resulting in a 74% reduction in median tumor size. In the combined treatment group, two of five animals had complete remissions of their s.c. tumor. These results suggest that a combination treatment with recombinant diabodies and angiogenesis inhibition represents a useful approach in cancer therapy.     

Development and initial validation of a caffeine craving questionnaire

Craving for caffeine has received little empirical attention, despite considerable research into the potential for caffeine dependence. The main aim of this study was to develop, and initially validate, a multi-item, multidimensional instrument to measure cravings for caffeine. Participants were 189 caffeine consumers who completed the Questionnaire of Caffeine Cravings, which was based on the Questionnaire of Smoking Urges (QSU), in one of five naturally occurring periods of abstinence; 1-15 min; 16-120 mins; 3-7 h; 12-48 h and +48 h. Exploratory factor analysis suggested a three-factor solution best described the data; Factor 1 reflected strong desires, intentions and positive reinforcement; Factor 2 reflected mild/general positive and negative reinforcement and Factor 3 reflected functional/mood-based negative reinforcement. Significantly higher Factor 1 and Factor 2 scores were recorded for high frequency users; significantly higher Factor 1 and Factor 3 scores were recorded as a function of increased levels of dependence. Duration of abstinence did not significantly effect cravings across all three factors. Regression analyses suggested level of dependence best predicted both current cravings and frequency of daily use. These findings suggest caffeine cravings may be conceptualized multidimensionally and further validates the use of multidimensional, multi-item instruments. Cravings for caffeine may manifest and be detected across varying levels of dependence and, frequency of use and independently of duration of abstinence.     

Development and validation of a capsule filling machine simulator

Apart from some published work on instrumented (commercially available) capsule filling machines and compaction simulators for tablets, the use of simulators to study the capsule filling machines and compaction simulators for tablets, the use of simulators to study the capsule filling process hasnot been reported. This paper describes the development and validation of such a simulator.