60 research outputs found

    Translational toxicology in setting occupational exposure limits for dusts and hazard classification – a critical evaluation of a recent approach to translate dust overload findings from rats to humans

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    Background We analyze the scientific basis and methodology used by the German MAK Commission in their recommendations for exposure limits and carcinogen classification of “granular biopersistent particles without known specific toxicity” (GBS). These recommendations are under review at the European Union level. We examine the scientific assumptions in an attempt to reproduce the results. MAK’s human equivalent concentrations (HECs) are based on a particle mass and on a volumetric model in which results from rat inhalation studies are translated to derive occupational exposure limits (OELs) and a carcinogen classification. Methods We followed the methods as proposed by the MAK Commission and Pauluhn 2011. We also examined key assumptions in the metrics, such as surface area of the human lung, deposition fractions of inhaled dusts, human clearance rates; and risk of lung cancer among workers, presumed to have some potential for lung overload, the physiological condition in rats associated with an increase in lung cancer risk. Results The MAK recommendations on exposure limits for GBS have numerous incorrect assumptions that adversely affect the final results. The procedures to derive the respirable occupational exposure limit (OEL) could not be reproduced, a finding raising considerable scientific uncertainty about the reliability of the recommendations. Moreover, the scientific basis of using the rat model is confounded by the fact that rats and humans show different cellular responses to inhaled particles as demonstrated by bronchoalveolar lavage (BAL) studies in both species. Conclusion Classifying all GBS as carcinogenic to humans based on rat inhalation studies in which lung overload leads to chronic inflammation and cancer is inappropriate. Studies of workers, who have been exposed to relevant levels of dust, have not indicated an increase in lung cancer risk. Using the methods proposed by the MAK, we were unable to reproduce the OEL for GBS recommended by the Commission, but identified substantial errors in the models. Considerable shortcomings in the use of lung surface area, clearance rates, deposition fractions; as well as using the mass and volumetric metrics as opposed to the particle surface area metric limit the scientific reliability of the proposed GBS OEL and carcinogen classification.International Carbon Black Associatio

    Surface tension studies of ternary system: Copper soap plus benzene plus methanol at 313 K

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    1173-1176Colloidal behaviour of copper soap solution in benzene plus methanol mixture from the surface tension studies confirms that cmc values depend upon the composition of the solvent mixture and are found to decrease with increase in chain length of the soap anion. The results of the surface tensions have been explained on the basis of Szyszkowski's empirical equation and it is observed that the values X, Y, and (-X ln Y) lead to the confirmation of the fact that the change in the behaviour of the soap takes place at 50% methanol concentration. The plots of the parachor against the mole fraction of the soap are characterised by an intersection of two straightlines at the cmc of the soap. Hammic and Andrew's equation has been successfully applied to explain the behaviour of soap in benzene-methanol mixture

    Neuroprotective Potential of Peroxisome Proliferator Activated Receptor-α Agonist in Cognitive Impairment in Parkinson’s Disease: Behavioral, Biochemical, and PBPK Profile

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    Parkinson’s disease (PD) is a common neurodegenerative disorder affecting 1% of the population by the age of 65 years and 4-5% of the population by the age of 85 years. PD affects functional capabilities of the patient by producing motor symptoms and nonmotor symptoms. Apart from this, it is also associated with a higher risk of cognitive impairment that may lead to memory loss, confusion, and decreased attention span. In this study, we have investigated the effect of fenofibrate, a PPAR-α agonist in cognitive impairment model in PD. Bilateral intranigral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (100 ”g/1 ”L/side) produced significant cognitive dysfunctions. Fenofibrate treatment at 10, 30, and 100 mg/kg for twenty-five days was found to be neuroprotective and improved cognitive impairment in MPTP-induced PD model as evident from behavioral, biochemical (MDA, GSH, TNF-α, and IL-6), immunohistochemistry (TH), and DNA fragmentation (TUNEL positive cells) studies. Further, physiologically based pharmacokinetic (PBPK) modeling study was performed using GastroPlus to characterize the kinetics of fenofibric acid in the brain. A good agreement was found between pharmacokinetic parameters obtained from the actual and simulated plasma concentration-time profiles of fenofibric acid. Results of this study suggest that PPAR-α agonist (fenofibrate) is neuroprotective in PD-induced cognitive impairment
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