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Climate change is currently one of humanity's greatest threats. To help scholars understand the psychology of climate change, we conducted an online quasi-experimental survey on 59,508 participants from 63 countries (collected between July 2022 and July 2023). In a between-subjects design, we tested 11 interventions designed to promote climate change mitigation across four outcomes: climate change belief, support for climate policies, willingness to share information on social media, and performance on an effortful pro-environmental behavioural task. Participants also reported their demographic information (e.g., age, gender) and several other independent variables (e.g., political orientation, perceptions about the scientific consensus). In the no-intervention control group, we also measured important additional variables, such as environmentalist identity and trust in climate science. We report the collaboration procedure, study design, raw and cleaned data, all survey materials, relevant analysis scripts, and data visualisations. This dataset can be used to further the understanding of psychological, demographic, and national-level factors related to individual-level climate action and how these differ across countries., (© 2024. The Author(s).)

Effectively reducing climate change requires marked, global behavior change. However, it is unclear which strategies are most likely to motivate people to change their climate beliefs and behaviors. Here, we tested 11 expert-crowdsourced interventions on four climate mitigation outcomes: beliefs, policy support, information sharing intention, and an effortful tree-planting behavioral task. Across 59,440 participants from 63 countries, the interventions' effectiveness was small, largely limited to nonclimate skeptics, and differed across outcomes: Beliefs were strengthened mostly by decreasing psychological distance (by 2.3%), policy support by writing a letter to a future-generation member (2.6%), information sharing by negative emotion induction (12.1%), and no intervention increased the more effortful behavior-several interventions even reduced tree planting. Last, the effects of each intervention differed depending on people's initial climate beliefs. These findings suggest that the impact of behavioral climate interventions varies across audiences and target behaviors.

Misinformation online poses a range of threats, from subverting democratic processes to undermining public health measures. Proposed solutions range from encouraging more selective sharing by individuals to removing false content and accounts that create or promote it. Here we provide a framework to evaluate interventions aimed at reducing viral misinformation online both in isolation and when used in combination. We begin by deriving a generative model of viral misinformation spread, inspired by research on infectious disease. By applying this model to a large corpus (10.5 million tweets) of misinformation events that occurred during the 2020 US election, we reveal that commonly proposed interventions are unlikely to be effective in isolation. However, our framework demonstrates that a combined approach can achieve a substantial reduction in the prevalence of misinformation. Our results highlight a practical path forward as misinformation online continues to threaten vaccination efforts, equity and democratic processes around the globe., (© 2022. The Author(s).)

Collective behavior provides a framework for understanding how the actions and properties of groups emerge from the way individuals generate and share information. In humans, information flows were initially shaped by natural selection yet are increasingly structured by emerging communication technologies. Our larger, more complex social networks now transfer high-fidelity information over vast distances at low cost. The digital age and the rise of social media have accelerated changes to our social systems, with poorly understood functional consequences. This gap in our knowledge represents a principal challenge to scientific progress, democracy, and actions to address global crises. We argue that the study of collective behavior must rise to a "crisis discipline" just as medicine, conservation, and climate science have, with a focus on providing actionable insight to policymakers and regulators for the stewardship of social systems., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

Groups of organisms, from bacteria to fish schools to human societies, depend on their ability to make accurate decisions in an uncertain world. Most models of collective decision-making assume that groups reach a consensus during a decision-making bout, often through simple majority rule. In many natural and sociological systems, however, groups may fail to reach consensus, resulting in stalemates. Here, we build on opinion dynamics and collective wisdom models to examine how stalemates may affect the wisdom of crowds. For simple environments, where individuals have access to independent sources of information, we find that stalemates improve collective accuracy by selectively filtering out incorrect decisions (an effect we call stalemate filtering). In complex environments, where individuals have access to both shared and independent information, this effect is even more pronounced, restoring the wisdom of crowds in regions of parameter space where large groups perform poorly when making decisions using majority rule. We identify network properties that tune the system between consensus and accuracy, providing mechanisms by which animals, or evolution, could dynamically adjust the collective decision-making process in response to the reward structure of the possible outcomes. Overall, these results highlight the adaptive potential of stalemate filtering for improving the decision-making abilities of group-living animals.

Aggregating multiple non-expert opinions into a collective estimate can improve accuracy across many contexts. However, two sources of error can diminish collective wisdom: individual estimation biases and information sharing between individuals. Here, we measure individual biases and social influence rules in multiple experiments involving hundreds of individuals performing a classic numerosity estimation task. We first investigate how existing aggregation methods, such as calculating the arithmetic mean or the median, are influenced by these sources of error. We show that the mean tends to overestimate, and the median underestimate, the true value for a wide range of numerosities. Quantifying estimation bias, and mapping individual bias to collective bias, allows us to develop and validate three new aggregation measures that effectively counter sources of collective estimation error. In addition, we present results from a further experiment that quantifies the social influence rules that individuals employ when incorporating personal estimates with social information. We show that the corrected mean is remarkably robust to social influence, retaining high accuracy in the presence or absence of social influence, across numerosities and across different methods for averaging social information. Using knowledge of estimation biases and social influence rules may therefore be an inexpensive and general strategy to improve the wisdom of crowds., (© 2018 The Author(s).)

The pharmacokinetics and metabolism of 1-(4-((4-phenyl-5-trifluoromethyl-2-thienyl)methoxy)benzyl)azetidine-3-carboxylic acid (MRL-A), a selective agonist for the sphingosine-1-phosphate 1 (S1P1) receptor, were investigated in rats and dogs. In both species, more than 50% of the dose was excreted in bile. Specific to the rat, and observed in bile, were a taurine conjugate of MRL-A and a glucuronide conjugate of an azetidine lactam metabolite. In dogs, a smaller portion of the dose (54% of administered dose) was excreted intact in bile, and the major metabolites detected were an azetidine N-oxide of MRL-A and an acylglucuronide of an N-dealkylation product. This latter metabolite was also observed in rat bile. Stereoselective formation of the N-oxide isomer was observed in dogs, whereas the rat produced comparable amounts of both isomers. The formation of a unique glutathione adduct was observed in rat bile, which was proposed to occur via N-dealkylation, followed by reduction of the putative aldehyde product to form the alcohol, and dehydration of the alcohol to generate a reactive quinone methide intermediate. Incubation of a synthetic standard of this alcohol in rat microsomes fortified with reduced glutathione or rat hepatocytes resulted in formation of this unique glutathione adduct.

PER.C6, a cell line derived from human embryonic retinal cells transformed with the Adenovirus Type 5 (Ad5) E1A and E1B genes, is used to produce E1-deleted Ad5 vectors such as the MRKAd5 HIV-1 gag vaccine. While whole, live PER.C6 cells are capable of growing as tumours when transplanted subcutaneously into immunodeficient nude mice at a high dosage, the process for vaccine production includes filtration steps and other methods which effectively preclude contamination by intact viable substrate cells. However, because of the neoplastic nature of this cell line, we carried out a series of investigations to assess the tumorigenic risk posed by residuals from the cell substrate in a vaccine. To address concerns about transmission of oncogenic DNA, we demonstrated that purified PER.C6 cellular DNA does not induce tumours in newborn hamsters or nude mice. To address concerns about other potential residuals, including hypothetical adventitious tumour viruses, we demonstrated that a PER.C6 cell lysate and a MRKAd5 HIV-1 gag vaccine produced on PER.C6 cells do not induce tumours in newborn hamsters or newborn rats. These results, in conjunction with the wide panel of viral safety tests performed on these cells, support the safety of the PER.C6 as a cell substrate for vaccine production.

This study compared the effects of ad libitum (AL) overfeeding and moderate or marked dietary restriction (DR) on the pathogenesis of a metabolic syndrome of diabesity comprised of age-related degenerative diseases and obesity in a outbred stock of Sprague-Dawley (SD) rats [Crl:CD (SD) IGS BR]. SD rats were fed Purina Certified Rodent Diet AL (group 1), DR at 72-79% of AL (group 2), DR at 68-72% of AL (group 3) or DR at 47-48% of AL (group 4) for 106 weeks. Interim necropsies were performed at 13, 26, and 53 weeks, after a 7-day 5-bromo-2-deoxyuridine (BrdU)-filled minipump implantation. Body weights, organ weights, carcass analysis, in-life data including estrous cyclicity, and histopathology were determined. At 6-7 weeks of age SD rats had 6% body fat. AL-feeding resulted in hypertriglyceridemia, hypercholesterolemia, and dietary-induced obesity (DIO) by study week 14, with 25% body fat that progressed to 36-42% body fat by 106 weeks. As early as 14 weeks, key biomarkers developed for spontaneous nephropathy, cardiomyopathy, and degenerative changes in multiple organ systems. Early endocrine disruption was indicated by changes in metabolic and endocrine profiles and the early development and progression of lesions in the pituitary, pancreatic islets, adrenals, thyroids, parathyroids, liver, kidneys, and other tissues. Reproductive senescence was seen by 9 months with declines in estrous cyclicity and pathological changes in the reproductive organs of both sexes fed AL or moderate DR, but not marked DR. The diabesity syndrome in AL-fed, DIO SD rats was readily modulated or prevented by moderate to marked DR. Moderate DR of balanced diets resulted in a better toxicology model by significantly improving survival, controlling adult body weight and obesity, reducing the onset, severity, and morbidity of age-related renal, endocrine, metabolic, and cardiac diseases. Moderate DR feeding reduces study-to-study variability, increases treatment exposure time, and increases the ability to distinguish true treatment effects from spontaneous aging. The structural and metabolic differences between the phenotypes of DIO and DR SD rats indicated changes of polygenic expression over time in this outbred stock. AL-overfeeding of SD rats produces a needed model of DIO and diabesity that needs further study of its patterns of polygenic expression and phenotype.

This study compared the effects of ad libitum (AL) overfeeding and moderate or marked dietary restriction (DR) on the pathogenesis of aged-related pituitary gland changes in Sprague-Dawley (SD) rats. SD rats were fed Purina Certified Rodent Diet AL (group 1), DR at 72-79% of AL (group 2), DR at 68-72% of AL (group 3) or DR at 47-48% of AL (group 4) for 106 weeks. Interim necropsies were performed at 13, 26, and 53 weeks, after a 7-day 5-bromo-2-deoxyuridine (BrdU)-filled minipump implantation. Body weights, organ weights and insulin-like growth factor 1 (IGF-1) serum levels were measured at interim and final necropsies. Serum levels of prolactin (PRL), progesterone, estradiol, luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured at 53 and/or 106 weeks. In addition to the routine histopathologic examination, determination of 7 stereologic parameters after pituitary immunohistochemistry of PRL, growth hormone (GH) and BrdU was done in both sexes at 13, 26, and 53 weeks. Body and pituitary weights were proportional to the food intake. In AL-fed rats, hyperplastic and neoplastic changes developed early and progressed with age, affecting almost all animals by 106 weeks. These changes were associated with high PRL serum levels. Pituitary adenomas were the most common cause of death in both sexes. In DR rats, a delayed onset and a decreased incidence of pituitary tumors were observed in association with decreased serum IGF-1, PRL, estradiol, and LH levels. The results of the stereological analysis demonstrated that, compared to AL-fed rats, pituitary glands from DR rats contained lower PRL and GH secreting cell volumes, and a lower epithelial cell BrdU labeling index, which correlated with a lower incidence of pituitary tumors at study termination. Moderate and marked degrees of DR delayed the onset of pituitary tumors in a temporal- and dose-related manner. In contrast to marked DR, which dramatically reduced the incidence of hyperplastic and neoplastic pituitary gland changes, moderate DR delayed the onset but did not prevent the development of pituitary tumors.

This study compared the effects of ad libitum (AL) overfeeding and moderate or marked dietary restriction (DR) on aged-related degenerative and proliferative changes of the endocrine pancreas in Sprague-Dawley (SD) rats. SD rats were fed Purina Certified Rodent Diet AL (group 1), DR at 72-79% of AL (group 2), DR at 68-72% of AL (group 3) or DR at 47-48% of AL (group 4) for 106 weeks. Interim necropsies were performed at 13, 26, and 53 weeks, after a 7-day 5-bromo-2-deoxyuridine (BrdU)-filled minipump implantation. Before each necropsy, glucose and serum insulin levels were measured. In addition to the routine histopathologic examination performed in both sexes, determination of 9 pancreatic islet stereologic parameters was done in males at 13, 26, and 53 weeks. In AL-fed rats, early changes in the islet morphology occurred, which resulted in a high incidence of islet fibrosis, focal hyperplasias and adenomas by two years. DR was dose-proportionally associated with decreased glucose and serum insulin levels, and delayed the onset, and decreased the incidence and severity of islet fibrosis and hyperplasia. Results of the stereology supported the histopathologic and clinical chemistry findings. It demonstrated that, compared to AL-fed rats, DR-fed rats had smaller pancreas, smaller pancreatic islets, smaller insulin secreting cell volumes, a lower degree of islet fibrosis and a lower islet cell BrdU labeling index, which correlated with a lower incidence of islet adenoma and carcinoma at study termination. Moderate and marked degrees of DR delayed the onset and severity of islet hyperplasia and fibrosis in a temporal- and dose-related manner. In contrast to marked DR, which dramatically prevented these changes, moderate DR delayed but not prevented onset of islet tumors. These findings support the concept that moderate DR results in a better-controlled animal model with a lower incidence or delayed onset of chronic spontaneous endocrine diseases in the rat bioassay.

The early development and progression of chronic nephropathy and its amelioration by moderate and marked dietary restriction (DR) was determined in Sprague-Dawley (SD) rats at 20, 33, 60, and 113 weeks of age. Both sexes of SD rats were overfed ad libitum (AL) or DR-fed at 72-79%, 68-72%, or 47-48% of the adult AL intake. The AL-fed rats rapidly developed increased body and kidney size, increased glomerular area (GA) and urinary protein loss, followed by declining creatinine clearance. Early increased kidney growth and glomerular hypertrophy by 20 weeks preceded increases in glomerular sclerotic index (GSI), 7-day BrdU tubular labeling index (TLI), and the lesions associated with chronic nephropathy. The glomerular number (GN) or the number of nephrons did not differ between the groups over the course of the study. Moderate DR (68-79% of AL) prevented the increased kidney size and GA at 20 weeks and delayed increases in GSI and TLI until 60 weeks of age. Marked DR (47-48% of AL) prevented increases in kidney size, GA and TLI at 20 weeks, and GSI at 60 weeks of age. In AL-fed rats, the early increase in GA predicted the early onset of proteinuria and the later decrease in creatinine clearance, and increased GSI, TLI, and mortality from severe nephropathy. The temporal and dose-related effects of increasing degrees of DR demonstrated that while nephron numbers were unchanged with age, the early development of glomerular hypertrophy was the critical morphological biomarker predicting the progression and severity of chronic nephropathy. Caloric restriction by DR prevented or delayed the development of glomerulosclerosis, tubulointerstitial damage, functional changes, morbidity, and mortality associated with chronic nephropathy in AL-overfed SD rats by controlling initial body and kidney growth, glomerular size, and nephron hypertrophy. These results indicate that control of body and renal growth by DR may be essential to prevent the development and progression of glomerulosclerosis in spontaneous nephropathy of laboratory rats.

Many employer-sponsored health plans and multi-employer health benefit trusts have seen an increase in medical child support orders (MCSOs), and they can anticipate receiving a greater number in the future. Once regulations are final for the national medical support notice (NMSN) required by the Child Support Performance and Incentive Act of 1998, plans should also begin receiving these. In preparation, plan administrators should ensure that they have proper procedures in place for determining whether MCSOs and NMSNs constitute QMCSOs.

The diet can significantly alter the results of toxicity and carcinogenicity studies. Ad libitum (AL) overfeeding of excessive calories to sedentary adult rodents is one of the most poorly controlled variables affecting the current rodent bioassay. AL-overfed rodents develop an early onset of adverse metabolic events, endocrine-disruptive degenerative diseases, and tumors that result in early morbidity and mortality. AL food consumption is extremely variable, but has a strong correlation with adult body weight, obesity, and survival. AL feeding of diets with modified protein, fiber, and energy content are not as effective as simple, moderate dietary (caloric) restriction (DR) in controlling these study variables. Moderate DR (70-75% of adult AL) is operationally simple and controls adult body weights, prevents obesity, and improves health and survival by reducing or delaying diet-related endocrine, renal, and cardiac diseases. Moderate DR provides a uniform rodent model, increases treatment exposure time, and increases the statistical sensitivity of these chronic bioassays to detect true treatment effects. Feeding a balanced diet by a moderate DR regimen of 70-75% of the maximum, unrestricted adult AL food intake is recommended for conducting well-controlled toxicity and carcinogenicity studies.

Overfeeding by ad libitum (AL) food consumption is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. The correlation of food consumption, the resultant adult body weight and the 2-y survival in Sprague-Dawley rats is highly significant. Feeding natural ingredient diets that varied in protein, fiber and metabolizable energy content did not improve low 2-y survival if Sprague-Dawley rats were allowed AL food consumption. Moderate dietary restriction (DR) of all diets tested significantly improved survival and delayed the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. By 2 y, moderate DR resulted in an incidence of spontaneous tumors similar to that seen with AL consumption; however, the tumors were more likely to be incidental and did not result in early mortality. There was a decreased age-adjusted incidence in pituitary and mammary gland tumors, but tumor volume and growth time were similar in the AL and DR groups, indicating a similar tumor progression with a delay in tumor onset. Moderate DR did not significantly alter drug-metabolizing enzyme activities or the toxicologic response to five pharmaceuticals tested at maximum tolerated doses (MTD). However, moderate DR did require higher doses of compounds to be given before classical MTD were produced with four pharmaceutical drug candidates. Toxicokinetic studies of two of these compounds demonstrated steady-state systemic exposures that were equal or higher in moderate DR-fed rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for rodent bioassays used to assess human safety of candidate pharmaceuticals.

Ad libitum (AL) overfeeding is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. There is a highly significant correlation between AL food consumption, the resultant obesity and body weight, and low 2-yr survival in rodents. AL feeding of diets with lowered protein, metabolizable energy (ME), and increased fiber does not improve survival. Only dietary restriction (DR) of all diets tested significantly improves survival and delays the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. Moderate DR results in an incidence of spontaneous tumors similar to AL-fed rats, but the tumors are found incidentally and do not cause early mortality. There is a decreased age-adjusted incidence of pituitary and mammary gland tumors in moderate DR-fed rats, but tumor growth time is similar between AL and DR rats with only a delay in tumor onset time seen in DR-fed groups. Moderate DR does not significantly alter drug-metabolizing enzyme activities nor the toxicologic response to 5 pharmaceuticals tested at maximum tolerated doses (MTDs). However, moderate DR-fed rats did require much higher doses of 4 additional pharmaceutical compounds before classical MTDs were produced. Toxicokinetic studies of 2 of these compounds demonstrated equal or higher steady-state systemic exposures to parent drug and metabolites in moderate DR-fed rats. Markers of oxidative stress (lipid peroxidation, protein oxidation) are decreased and cytoprotective anti-oxidant markers are preserved in moderate DR-fed rats. But moderate DR does not delay reproductive senescence in female rats. Only marked DR delays reproductive senescence compared to AL and moderate DR-fed female rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for the rodent bioassay when used to assess pharmaceuticals for human safety and compounds for risk assessment.

L-695,256 is a novel 2-fluorenonyl carbapenem antibiotic with significant antimicrobial activity against strains of methicillin-resistant Staphylococci. This prototype compound was administered intravenously to rhesus monkeys (Macaca mulatta) at does of 50 or 200 mg/kg/day for 2 weeks to assess toxicity and found to induce a hemolytic anemia characterized by extravascular hemolysis and splenomegaly. A subsequent study in this species in which 100 mg/kg/day was administered i.v. for 4 weeks showed that all animals were direct antiglobulin test (Coombs' test) positive for IgG with 20-25% reductions in the erythron. Following 3 weeks of recovery, the erythron had returned to normal, although it took an additional 2 months for the Coombs' test to become negative. Challenge of these same animals with 0.5 million U/kg (300 mg/kg/day) of penicillin intravenously indicated no apparent cross-reactivity. Since attempts to establish a model for this immune-mediated hemolytic anemia with this drug in rats or mice were unsuccessful, a 2-week i.v. study in squirrel monkeys (Saimiri sciureus) was conducted at a dose of 200 mg/kg/day. All animals in this study remained Coombs' test negative with no changes in the erythron, suggesting an increased sensitivity to beta-lactam-induced anemia in rhesus monkeys compared to other species. Further support for this hypothesis was obtained using the cephalosporin antibiotic, cefotetan. This compound induced a high incidence of Coombs' test positive hemolytic anemia at clinically relevant doses in rhesus monkeys, despite a very low incidence of this adverse effect in patients with many years of clinical use. These data suggest that although rhesus monkeys respond in a qualitatively similar manner to humans with regard to high doses of beta-lactam antibiotics, their sensitivity may overestimate the risk of immune-mediated hemolytic anemia for clinical use.

The experience with the submission of a nonclinical (pharmacology and toxicology) computer-assisted New Drug Application (CANDA) is reviewed. This system consisted of a stand-alone personal computer running several commercial programs in Microsoft Windows to access both text and data. WordPerfect was used as the word processor that contained all the documents and data tables (in read-only format) that were submitted in hard copy, and Andyne GQL was used as a tool to query the data in an Oracle relational database. Microsoft Excel was provided as a spreadsheet for graphics and analysis of data. Documents appeared virtually identical to those in the hard copy NDA submission. Searching the text was facilitated by the use of buttons on the screen, which allowed the NDA to be searched for a particular term. Data could be located either in WordPerfect documents, or in an Oracle database (using Andyne GQL) by querying the data. The data queries could be performed ad hoc, in which the reviewer selected all the parameters for a search, or with predefined query buttons, which retrieved data for principal treatment-related changes. This type of system also could serve as a useful model for both in-house nonclinical review and the submission of INDs and IND amendments.

The effects of formaldehyde were determined using a behavioral technique that permits the estimation of the aversiveness of airborne chemical irritants. Eight mice were initially trained to terminate presentations of ammonia by poking their nose into a conical sensor; five pokes terminated the presentation and produced a facial shower of clean air. Ammonia (1000 ppm) or formaldehyde (1.0-10 ppm) was delivered to the mice for a maximum of 60 sec followed by a 60-sec washout period; this cycle repeated 25 times per session. All animals consistently terminated 100% of ammonia deliveries. Mice also terminated delivery of formaldehyde. At the lowest concentration examined (1.0 ppm), significantly (p < 0.0005) more deliveries of formaldehyde were terminated than were deliveries of air. Mice differed in their sensitivity to formaldehyde: one mouse failed to terminate any more than 10% of deliveries of formaldehyde up to concentrations of 10 ppm; graded concentration-related increases in the number of deliveries terminated were observed in five mice; the two remaining mice consistently terminated 80% or more of the deliveries at each concentration of formaldehyde. As the concentration of formaldehyde increased, the amount of time taken to terminate the exposure decreased. A significant shift to the left of the concentration-effect curves occurred on the second exposure to the series of formaldehyde concentrations. These studies indicate that formaldehyde is aversive to mice at concentrations which approximate those at which humans also report sensory irritation, and that enhanced sensitivity is associated with repeated exposure.

A 5-week study was carried out in rats using a leukotriene biosynthesis inhibitor (MK-886; 3-[1-(4-chlorobenzyl)-3-t-butylthio-5-isopropylindol-2-yl]-2,2- dimethylpropanoic acid) at a dose of 300 mg.kg-1 x day-1, this being sufficient to produce > 90% inhibition of ex vivo leukotriene B4 synthesis in rat blood, and a cyclooxygenase inhibitor (indomethacin, 4 and 6 mg.kg-1 x day-1) to ascertain whether inhibition of leukotriene biosynthesis would potentiate or inhibit the toxicity associated with the administration of nonsteroidal anti-inflammatory drugs (NSAIDs), in particular the gastrointestinal damage. Treatment with indomethacin alone or in combination with MK-886 resulted in the toxicity normally associated with NSAIDs, including gastrointestinal lesions. No toxicity was associated with the administration of MK-886 alone, and MK-886 had no significant effect on the incidence of gastrointestinal lesions produced by indomethacin. These results indicate that leukotrienes are not significant mediators of NSAID-induced gastroenteropathy in the rat.

Primary cultures of rat hepatocytes were used to explore the mechanisms of the toxicity of aryl halides. The sensitivity of the hepatocytes to chloro-, bromo-, and iodobenzene was enhanced by inhibition of glutathione reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). In each case, the increased cell killing depended on the metabolism of the toxicant, a result shown by the protective effect of SKF-525A, an inhibitor of mixed function oxidation. BCNU decreased the metabolism of [14C]bromobenzene and the covalent binding of its metabolites by 20%. Chelation by deferoxamine of a cellular source of ferric iron prevented the cell killing in the presence or absence of BCNU. Deferoxamine had no effect on the metabolism or the covalent binding of [14C]bromobenzene. Similarly, the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD) reduced the cell killing and had no effect on the metabolism of [14C]bromobenzene. Thus, the toxicity of the three aryl halides was manipulated in ways that modify the sensitivity of hepatocytes to an oxidative stress, and the changes in cell killing occurred without parallel changes in the metabolism of [14C]bromobenzene or the covalent binding of its metabolites.

This study was designed by the pediatric clinical pharmacy service to evaluate the accuracy of the nursing Medication Administration Record (MAR). Medications returned to the pharmacy in the exchanged medication carts were compared to those charted in the computer-generated MAR for 10 working days. Fourteen percent of the doses studied were categorized as charting errors. Charting inconsistencies were summarized in a personalized memorandum distributed to the nursing staff on the pediatric unit. A subsequent evaluation revealed a 10% charting discrepancy rate. The nursing memo did not effect a statistically significant change in the error rates between the two phases of the study. Inaccurate charting poses problems for therapeutic decision making and for methods of reimbursement that use the MAR. This problem should be assessed in individual institutions. Corrective measures should be implemented and evaluated.

The relationship was explored between the accumulation of single-strand breaks in DNA and the killing of cultured hepatocytes by an oxidative stress generated by either tert-butyl hydroperoxide (TBHP), glucose oxidase, or menadione. The accumulation of DNA strand breaks was measured fluorometrically by the rate of the alkaline unwinding of DNA. In each case, DNA strand breaks were detected before the loss of cell viability. DNA damage and cell killing depended on a cellular source of iron. Pretreatment of the hepatocytes with the ferric iron chelator deferoxamine prevented both, and the readdition of iron to the medium restored the DNA damage and the cell killing. In addition, the radical scavenger keto-methiolbutyric acid reduced the extent of DNA damage and prevented the cell killing. By contrast, the antioxidants N,N'-diphenyl-p-phenylenediamine and butylated hydroxytoluene prevented the cell killing but not the DNA single-strand breaks induced by TBHP. Similarly, acidification of the culture medium also prevented the cell killing, without any effect on the extent of the DNA damage by TBHP, glucose oxidase, and menadione. These data indicate that DNA damage and cell killing produced by an oxidative stress depend upon the iron-catalyzed formation of a potent oxidizing species. However, the accumulation of such damage can be dissociated from the mechanisms that lethally injure the cells.

Rats treated with a single 0.5 ml/kg dose (ip) of CCl4 exhibited a threefold increase in liver microsomal phospholipase C (PLC) activity that was enhanced by phenobarbital and diminished by metyrapone pretreatment, respectively. Hepatocytes and hepatocellular fractions exposed to 0.5 mM CCl4 in vitro also exhibited a rapid rise in PLC activity that was reduced by metyrapone. Metyrapone also reduced the CCl4-related increase in the PLC-mediated reductions in cellular phosphatidylcholine content. The influence of CCl4 biotransformation on the activation of liver cell PLC was assessed in vitro. Covalent binding of 14CCl4 metabolites to isolated hepatocyte proteins and lipids was linear through 20 min of incubation and then quickly plateaued. The association of CCl4 metabolites with cellular phospholipids was inhibited by metyrapone and preceded the CCl4-dependent rise in PLC activity. CCl4-mediated increases in PLC activity were rapid and preceded reductions in cell viability. The translocation of cytosolic PLC to membranes such as the endoplasmic reticulum may explain the rapid, metabolite-dependent activation of PLC.PLC activation by haloalkanes was proportional to dose and incubation time in the order of CBrCl3 greater than CCl4 greater than CHCl3 greater than CFCl3 which corresponds to the observed hepatotoxic potential of these agents in vivo and in vitro. Haloalkane-dependent increases in PLC activity were inhibited by metyrapone. These results suggest that chemical metabolites activate PLC in vitro and in vivo. Therefore, the activation of a PLC that degrades membrane phospholipids may represent an important step in the pathogenic scheme of chemical-mediated liver cell necrosis.

Toluene can have striking acute behavioral effects and is subject to abuse by inhalation. To determine if its actions resemble those of drugs used in the treatment of anxiety ("anxiolytics"), two sets of experiments were undertaken. Inasmuch as prevention of pentylenetetrazol-induced convulsions is an identifying property of this class of agents, we first demonstrated that pretreatment with injections of toluene delayed the onset of convulsive signs and prevented the tonic extension phase of the convulsant activity in a dose-related manner. Injections of another alkyl benzene, m-xylene, were of comparable potency to toluene. Inhalation of toluene delayed the time to death after pentylenetetrazol injection in a manner related to the duration and concentration of exposure; at lower convulsant doses, inhalation of moderate concentrations (EC50, 1311 ppm) prevented death. Treatment with a benzodiazepine receptor antagonist (Ro 15-1788) failed to reduce the anticonvulsant activity of inhaled toluene. Anxiolytics also attenuate the reduction in response rate produced by punishment with electric shock. Toluene increased rates of responding suppressed by punishment when responding was maintained under a multiple fixed-interval fixed-interval punishment schedule of reinforcement. Distinct antipunishment effects were observed after 2 hr of exposure to 1780 and 3000 ppm of toluene; the rate-increasing effects of toluene were related to concentration and to time after the termination of exposure. Thus, toluene and m-xylene resemble in several respects clinically useful drugs such as the benzodiazepines.

Carbon tetrachloride (CCl4) biotransformation and covalent binding was measured in 1000g liver fractions by determining the amount of 14CCl4 metabolites covalently bound to proteins and lipids at various (5-60 min) incubation times. Reactive intermediate binding to proteins and phospholipids peaked at 20 min, whereas CCl4 metabolites associated with neutral lipids (primarily diacylglycerol) were initially low (0-15 min) and then gradually increased from 20 to 60 min. The rise in labeled diacylglycerol was associated with a decrease in phospholipids containing covalently bound CCl4 metabolites, since CCl4 bioactivation increased phospholipase C (PLC) activity three- to fourfold. The major rise in PLC activity occurred after the plateau of CCl4 metabolite binding to cellular phospholipids. In contrast, when CCl4 bioactivation is absent, 0.5 mM CCl4 has little effect on PLC activity. At CCl4 concentrations of 1 mM and greater, the NADPH-dependent activation of PLC by CCl4 is reduced because CCl4 biotransformation is inhibited. Nevertheless, PLC is still activated by CCl4; however, PLC activation by high doses of CCl4 occurs by bioactivation-independent mechanisms. Therefore, there are two components of CCl4-induced PLC activation: one which is dependent on CCl4 biotransformation and one which is not. Under both conditions (+/- biotransformation), the activation of PLC may be a key event in CCl4 hepatotoxicity since PLC disrupts the functional and structural integrity of membranes by degrading membrane phospholipids.