To assess chemical toxicity, current high throughput screening (HTS) assays rely primarily on in vitro measurements using cultured cells. Responses frequently differ from in vivo results due to the lack of physical and humoral interactions provided by the extracellular matrix, cell-cell interactions, and other molecular components of the native organ. To more accurately reproduce organ complexity in HTS, we developed an organotypic assay using the cryopreserved precision cut lung slice (PCLS) from rats and mice. Compared to the never-frozen PCLS, their frozen-thawed counterpart slices showed viability or metabolic activity that is decreased to an extent comparable to that observed in other cryopreserved cells and tissues, but shows no differences in further changes in cell viability, mitochondrial integrity, and glutathione activity in response to the model toxin zinc chloride (ZnCl2). Notably, these measurements were successfully miniaturized so as to establish HTS capacity in a 96-well plate format. Finally, PCLS responses correlated with common markers of lung injury measured in lavage fluid from rats intratracheally instilled with ZnCl2. In summary, we establish that the cryopreserved PCLS is a feasible approach for HTS investigations in predictive toxicology.

Altered reinforcement sensitivity is hypothesized to underlie symptoms of attention deficit hyperactivity disorder (ADHD). Here we evaluate the behavioral sensitivity of Brazilian children with and without ADHD to a change in reward availability. Forty typically developing children and 32 diagnosed with DSM-IV ADHD completed a signal-detection task in which correct discriminations between two stimuli were associated with different frequencies of reinforcement. The response alternative associated with the higher rate of reinforcement switched, without warning, after 30 rewards were delivered. The task continued until another 30 rewards were delivered. Both groups of children developed a response bias toward the initially more frequently reinforced alternative. This effect was larger in the control group. The response allocation of the two groups changed following the shift in reward availability. Over time the ADHD group developed a significant response bias toward the now more frequently reinforced alternative. In contrast, the bias of the control group stayed near zero after an initial decline following the contingency change. The overall shift in bias was similar for the two groups. The behavior of both groups of children was sensitive to the asymmetric reward distribution and to the change in reward availability. Subtle group differences in response patterns emerged, possibly reflecting differences in the time frame of reward effects and sensitivity to reward exposure.

Aim of study: Metal contaminants contribute to adverse human health effects via acute and chronic exposures. Acute metal exposures followed by prolonged secondary metal exposures may elicit exaggerated inflammatory responses in certain individuals. The aim of this study is to determine whether repeated pulmonary exposures to zinc chloride (ZnCl2) alters subsequent responses to zinc or cerium exposures. Materials and Methods: Rats were intratracheally (IT) instilled with physiologic saline (n=24) or 0.05 mg/kg ZnCl2 (n=16) twice weekly for 4 weeks. Four days after last dosing, the saline group was divided into 3 subgroups, each IT-instilled with either saline, ZnCl2 or CeCl3 (both at 0.1 mg/kg). The ZnCl2 pre-instilled rats were divided into 2 subgroups, each instilled with 0.1 mg/kg ZnCl2 or CeCl3. Biomarkers of lung injury/inflammation were assessed in bronchoalveolar lavage (BAL) fluid collected 24 hours later. Oxidative stress was evaluated as total and reduced glutathione in BAL. Results: Increases in inflammatory cells, LDH, albumin, leptin, MCP-1, IP-10, fractalkine, TNFα and RANTES were observed in rats instilled with multiple PBS and then with 0.1 mg/kg ZnCl2 and CeCl3. However, rats pre-exposed repeatedly to 0.05 mg/kg ZnCl2 and then challenged with 0.1 mg/kg ZnCl2 or CeCl3 showed even more eosinophils, lymphocytes, and increased concentrations of hemoglobin and MIP-1α. Significant reduction in GSH/GSSG ratios in BAL in response to all ZnCl2 or CeCl3 exposures indicated oxidative stress. Conclusion: Previous exposure to zinc ions increases responsiveness to subsequent exposures to zinc and cerium ions. These findings suggest enhanced sensitization possibly due to a reduction in antioxidant defenses.