Application of cytochrome P450 reactivity on the characterization of chemical compounds and its association with repeated-dose toxicity.

Repeated-dose toxicity (RDT) studies are one of the critical studies to assess chemical safety. There have been some studies attempting to predict RDT endpoints based on chemical substructures, but it remains very difficult to establish such a method, and a more detailed characterization of chemical compounds seems necessary. Cytochrome P450s (P450s) comprise multiple forms with different substrate specificities and play important roles in both the detoxification and metabolic activation of xenobiotics. In this study, we investigated possible use of P450 reactivity of chemical compounds to classify the compounds. A total of 148 compounds with available rat RDT test data were used as test compounds and subjected to inhibition assays against 18 human and rat P450s. Among the tested compounds, 82 compounds inhibited at least one P450 form. Hierarchical clustering analyses using the P450 inhibitory profiles divided the 82 compounds into nine groups, some of which showed characteristic chemical and biological properties. Principal component analyses of the P450 inhibition data in combination with the calculated chemical descriptors demonstrated that P450 inhibition data were plotted differently than most chemical descriptors in the loading plots. Finally, association analyses between P450 inhibition and RDT endpoints showed that some endpoints related to the liver, kidney and hematology were significantly associated with the inhibition of some P450s. Our present results suggest that the P450 reactivity profiles can be used as novel descriptors for characterizing chemical compounds for the investigation of the toxicity mechanism and/or the establishment of a toxicity prediction model.

Solution structure of the major fish allergen parvalbumin Sco j 1 derived from the Pacific mackerel.

Although fish is an important part of the human diet, it is also a common source of food allergy. The major allergen in fish is parvalbumin, a well-conserved Ca2+-binding protein found in the white muscle of many fish species. Here, we studied the solution structure of the parvalbumin Sco j 1, derived from the Pacific mackerel, using nuclear magnetic resonance spectroscopy. We mapped the IgE-binding epitope proposed in a recent study onto the present structure. Interestingly, three of four residues, which were elucidated as key residues of the IgE-binding epitope, were exposed to solvent, whereas one residue faced the inside of the molecule. We expect that this solution structure can be used in future studies attempting to analyze the various IgE-binding modes of these allergens.

Construction of the Database of Rat Repeated-dose Toxicity Tests of Pesticides for the Toxicological Characterization of Hepatocyte Hypertrophy.

Liver and hepatocyte hypertrophy can be induced by exposure to chemical compounds, but the mechanisms and toxicological characteristics of these phenomena have not yet been investigated extensively. In particular, it remains unclear whether the hepatocyte hypertrophy induced by chemical compounds should be judged as an adaptive response or an adverse effect. Thus, understanding of the toxicological characteristics of hepatocyte hypertrophy is of great importance to the safety evaluation of pesticides and other chemical compounds. To this end, we have constructed a database of potentially toxic pesticides. Using risk assessment reports of pesticides that are publicly available from the Food Safety Commission of Japan, we extracted all observations/findings that were based on 90-day subacute toxicity tests and 2-year chronic toxicity and carcinogenicity tests in rats. Analysis of the database revealed that hepatocyte hypertrophy was observed for 37-47% of the pesticides investigated (varying depending on sex and testing period), and that centrilobular hepatocyte hypertrophy was the most frequent among the various types of hepatocyte hypertrophy in both the 90-day and 2-year studies. The database constructed in this study enables us to investigate the relationships between hepatocyte hypertrophy and other toxicological observations/findings, and thus will be useful for characterizing hepatocyte hypertrophy.

Optimization of drug viscosity used in gas-powered liquid jet injectors.

This paper describes the effect of drug viscosity on the performance of gas powered liquid jet injectors. The analysis is accomplished utilizing a Computational Fluid Dynamics (CFD) model that obtains the stagnation pressure at the nozzle outlet. The technique is based on previous work used to predict gas power driven injector piston velocity with time. The results depict the variation in average and peak injector stagnation pressure for three different driven pressures; driving injections which vary from 0.2 cP to 87 cP in viscosity. Furthermore, a numerical representation of jet shape is also obtained to verify the effect of viscosity on jet geometry. These results demonstrate that increasing viscosity by 10 times that of water produces only a slight decrease in injector stagnation pressure and produces jets with greater confinement, which will display better characteristics for puncturing the skin.

Reactive oxygen species-independent rapid initiation of mitochondrial apoptotic pathway by chelerythrine.

Chelerythrine, formerly identified as a protein kinase C inhibitor, has also been shown to inhibit the anti-apoptotic Bcl-2 family proteins. However, recent studies have now demonstrated that chelerythrine can induce the loss of mitochondrial membrane potential (ΔΨm), a membrane permeability transition (MPT), and the subsequent activation of the mitochondrial apoptotic pathway, even in the cells deficient in Bax and Bak. This suggests the existence of an alternative Bax/Bak-independent pathway for apoptosis. The generation of reactive oxygen species (ROS) from the mitochondrial electron transport chain (ETC) is also implicated in the cytotoxity elicited by chelerythrine. In our current study, we show that chelerythrine induces the rapid apoptotic death of H9c2 cardiomyocyte-derived cells within 8 min of treatment. The proteolytic activation of caspase9 and caspase3, crucial mediators of the mitochondrial apoptotic pathway, are also observed within 6 min of exposure to this drug. The generation of ROS is detected but at only marginal levels in the treated cells. The inhibition of the mitochondrial ETC by rotenone and malonate had almost no effects on ROS generation but in both cases effectively inhibited both cell death and the caspase activation induced by chelerythrine. Hence, chelerythrine initiates the rapid mitochondrial apoptotic death of H9c2 cardiomyoblastoma cells in a manner that is likely independent of the generation of ROS from mitochondria.

Reproducibility and variance of a stimulation-induced hemodynamic response in barrel cortex of awake behaving mice.

The present work evaluated the reproducibility and variance of the cerebral blood flow (CBF) response to natural whisker stimulation in the barrel cortex of awake behaving mice. The animal was placed on an air float ball that allowed the animal to walk, while the head of the animal was fixed in a custom-made stereotactic apparatus. Dynamic CBF changes in the barrel cortex and animal locomotion were simultaneously monitored with laser-Doppler flowmetry (LDF) and an optical motion sensor that detected the rotation distance of the ball, respectively. Whisker stimulation-induced CBF measured under daytime and nighttime conditions showed consistent responses (24% and 23% of the pre-stimulus baseline, respectively), whereas the amount of locomotion was 1.4 times higher during nighttime relative to daytime. Repeated longitudinal experiments over 7 days showed a reproducible, evoked CBF (13-26% relative to the baseline among 7 animals). The mean of the variance coefficient (i.e., standard deviation divided by mean) across multiple days was 0.11 and 0.75 for evoked CBF and locomotion, respectively. These results showed reproducible and reliable measurements of longitudinal CBF response in behaving mice regardless of day-to-day variations in locomotion. Furthermore, we confirmed that the CBF response to whisker stimulation was well localized and reproducible, measured with laser speckle imaging under awake condition. The results further show the capability of long-term hemodynamic imaging in normal and disease-model mice, which is of particular importance for understanding the longitudinal changes and plasticity of neurovascular coupling and behavioral performances such as during growth, development and aging.

Death due to blood transfusion-induced anaphylactic shock: A case report.

In medical practice, many clinical accidents due to blood transfusion reactions have been reported, among which, nonhemolytic transfusion reactions (NHTRs) have been mainly reported in recent years. NHTRs induce reactions such as anaphylactic shock and transfusion-related acute lung injury (TRALI); however, few forensic autopsy case reports with blood transfusion reactions including anaphylactic shock have been published. A marker for anaphylactic shock is serum tryptase, which indicates systematic mast cell activation in living patients. In forensic medicine, serum tryptase has been used in the postmortem diagnosis of anaphylactic shock. In this autopsy case report, the blood tryptase level was elevated to 49.0 ng/mL (reference standard level <13.5 ng/mL). When considered comprehensively with autopsy findings and blood typing, we concluded that this patient was suspected to have suffered from anaphylactic shock as a result of blood transfusion.