In Vitro-In Vivo Extrapolation of Hepatic Biotransformation Data for Fish. III. An In-depth Case Study with Pyrene.

Computational models that predict chemical bioaccumulation in fish generally account for biotransformation using an apparent first-order whole-body rate constant (k ; d ). The use of such models requires, therefore, that methods exist for estimating k , ideally without the need to expose live animals. One promising approach for estimating k involves the extrapolation of measured in vitro intrinsic clearance (CL ) to the whole animal (in vitro-in vivo extrapolation, [IVIVE]).

International Country-Level Trends, Factors, and Disparities in Compassionate Use Access to Unlicensed Products for Patients With Serious Medical Conditions.

Importance: Compassionate use (CU) is a treatment option for patients with serious or life-threatening medical conditions that provides access to locally unlicensed medications (generally free of charge) when all available treatment options have been exhausted and enrollment in a clinical trial is not possible.

Objective: To examine the disparity in CU access observed across countries and explore the key driving factors.

Design Settings And Participants: This study analyzed all Novartis CU requests (for individual/named patients and cohort programs) received between January 1, 2018, and December 31, 2020, and investigated selected country-specific factors for association with request activity.

Biotransformation Potential of Cationic Surfactants in Fish Assessed with Rainbow Trout Liver S9 Fractions.

Biotransformation may substantially reduce the extent to which organic environmental contaminants accumulate in fish. Presently, however, relatively little is known regarding the biotransformation of ionized chemicals, including cationic surfactants, in aquatic organisms. To address this deficiency, a rainbow trout liver S9 substrate depletion assay (RT-S9) was used to measure in vitro intrinsic clearance rates (CL ; ml min g liver ) for 22 cationic surfactants that differ with respect to alkyl chain length and degree of methylation on the charged nitrogen atom.

Addition of Phenylmethylsulfonyl Fluoride Increases the Working Lifetime of the Trout Liver S9 Substrate Depletion Assay, Resulting in Improved Detection of Low Intrinsic Clearance Rates.

The activity of a trout liver S9 substrate depletion assay has been shown to decline over time, presumably due to proteolytic degradation of biotransformation enzymes. To address this problem, assay performance was evaluated following the addition of phenylmethylsulfonyl fluoride (PMSF) or a general-purpose protease inhibitor cocktail to liver homogenization buffers and/or S9 reaction mixtures. Addition of PMSF to liver homogenization buffers and/or S9 reaction mixtures had little or no effect on clearance of phenanthrene, a model cytochrome P450 substrate, in short-term (25 or 30 min) depletion experiments but resulted in significant improvements in retention of this initial activity over time.

In vitro-in vivo extrapolation of hepatic and gastrointestinal biotransformation rates of hydrophobic chemicals in rainbow trout.

Hepatic in vitro biotransformation assays, in combination with in vitro-in vivo extrapolation (IVIVE) and bioaccumulation modeling, can be used to support regulatory bioaccumulation assessments. In most applications, however, these methods ignore the possibility of extrahepatic metabolism. Here we evaluated intestinal biotransformation in rainbow trout using S9 fractions prepared from the upper intestinal (GIT) epithelium.

Biotransformation of Polycyclic Aromatic Hydrocarbons by Trout Liver S9 Fractions: Evaluation of Competitive Inhibition Using a Substrate Depletion Approach.

Environmental contaminants frequently occur as part of a chemical mixture, potentially resulting in competitive inhibition among multiple substrates metabolized by the same enzyme. Trout liver S9 fractions were used to evaluate the biotransformation of 3 polycyclic aromatic hydrocarbons (PAHs): phenanthrene, pyrene, and benzo[a]pyrene, tested as binary mixtures. Initial rates of biotransformation were determined using a substrate-depletion approach.

Allometric scaling of hepatic biotransformation in rainbow trout.

Biotransformation may substantially impact the toxicity and accumulation of xenobiotic chemicals in fish. However, this activity can vary substantially within and among species. In this study, liver S9 fractions from rainbow trout (4-400 g) were used to evaluate relationships between fish body mass and the activities of phase I and phase II metabolic enzymes.

Toxicokinetics of the neonicotinoid insecticide imidacloprid in rainbow trout (Oncorhynchus mykiss).

Studies were conducted to determine the distribution and elimination of imidacloprid (IMI) in rainbow trout. Animals were injected with a low (47.6 μg/kg), medium (117.

Measurement of kinetic parameters for biotransformation of polycyclic aromatic hydrocarbons by trout liver S9 fractions: Implications for bioaccumulation assessment.

substrate depletion methods developed by the pharmaceutical industry are being used with increasing frequency to support chemical bioaccumulation assessments for fish. However, the application of these methods to high log chemicals poses special challenges. Biotransformation of three polycyclic aromatic hydrocarbons (PAHs) was measured using trout liver S9 fractions.

Comparison of trout hepatocytes and liver S9 fractions as in vitro models for predicting hepatic clearance in fish.

Isolated hepatocytes and liver S9 fractions have been used to collect in vitro biotransformation data for fish as a means of improving modeled estimates of chemical bioaccumulation. To date, however, there have been few direct comparisons of these 2 methods. In the present study, cryopreserved trout hepatocytes were used to measure in vitro intrinsic clearance rates for 6 polycyclic aromatic hydrocarbons (PAHs).

Optimization of a UDP-glucuronosyltransferase assay for trout liver S9 fractions: activity enhancement by alamethicin, a pore-forming peptide.

1. An existing assay for UDP-glucuronosyltransferase (UGT) activity in trout liver microsomes was optimized using trout liver S9 fractions. Individual experiments were conducted to determine the time dependence of UGT activity as well as optimal levels of S9 protein, uridine 5'-diphosphoglucuronic acid (UDPGA), substrate (p-nitrophenol) and alamethicin, a pore-forming agent added to eliminate latency.

Toxicokinetics of perfluorooctane sulfonate in rainbow trout (Oncorhynchus mykiss).

Rainbow trout (Oncorhynchus mykiss) confined to respirometer-metabolism chambers were dosed with perfluorooctane sulfonate (PFOS) by intra-arterial injection and sampled to obtain concentration time-course data for plasma and either urine or expired water. The data were then analyzed using a 2-compartment clearance-volume model. Renal and branchial clearance rates (mL/d/kg) determined for all experiments averaged 19% and 81% of total clearance, respectively.

Measurement of charged-particle stopping in warm dense plasma.

We measured the stopping of energetic protons in an isochorically heated solid-density Be plasma with an electron temperature of ∼32  eV, corresponding to moderately coupled [(e^{2}/a)/(k_{B}T_{e}+E_{F})∼0.3] and moderately degenerate [k_{B}T_{e}/E_{F}∼2] "warm-dense matter" (WDM) conditions. We present the first high-accuracy measurements of charged-particle energy loss through dense plasma, which shows an increased loss relative to cold matter, consistent with a reduced mean ionization potential.

A Daily Process Analysis of Physical Activity, Sedentary Behavior, and Perceived Cognitive Abilities.

Objectives: This study evaluated the role of both physical activity and sedentary behavior in daily perceptions of cognitive abilities and whether these relations exist within-person, between-person, or both.

Design: Non-experimental, intensive longitudinal research using ecological momentary assessments.

Method: College students wore accelerometers and provided end-of-day reports on physical activity, sedentary behavior, and perceived cognitive abilities for 14 days.

Toxicokinetics of perfluorooctanoate (PFOA) in rainbow trout (Oncorhynchus mykiss).

Rainbow trout (Oncorhynchus mykiss) confined to respirometer-metabolism chambers were dosed with perfluorooctanoate (PFOA) by intra-arterial (i.a.) injection and sampled to obtain concentration time-course data for plasma, urine, and expired water.

A readability assessment of online stroke information.

Background: Patients and carers increasingly access the Internet as a source of health information. Poor health literacy is extremely common and frequently limits patient's comprehension of health care information literature. We aimed to assess the readability of online consumer-orientated stroke information using 2 validated readability measures.

Optimizing the use of rainbow trout hepatocytes for bioaccumulation assessments with fish.

Biotransformation rates measured using cryopreserved trout hepatocytes can be extrapolated to the whole animal to predict metabolism impacts on chemical bioaccumulation. Future use of these methods within a regulatory context requires, however, that they be optimized and standardized. Specifically, questions exist concerning gender differences in metabolism, cryopreservability of cells, and the accuracy of in vitro-in vivo scaling factors.

Hepatic clearance of 6 polycyclic aromatic hydrocarbons by isolated perfused trout livers: prediction from in vitro clearance by liver S9 fractions.

Isolated perfused trout livers were used to evaluate in vitro-in vivo metabolism extrapolation procedures for fish. In vitro depletion rates for 6 polycyclic aromatic hydrocarbons (PAHs) were measured using liver S9 fractions and extrapolated to the intact tissue. Predicted hepatic clearance (CLH) values were then compared with values exhibited by intact livers.

Enantiomer-specific in vitro biotransformation of select pharmaceuticals in rainbow trout (Oncorhynchus mykiss).

The occurrence of pharmaceuticals in the environment represents a challenge of emerging concern. Many pharmaceuticals are chiral compounds; however, few studies have examined the relative toxicity of pharmaceutical enantiomers to wildlife. Further, our understanding of stereospecific pharmacokinetics remains largely informed by research on humans and a few well-studied laboratory test animals, and not by studies conducted with environmentally relevant species, including fish.