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Toxicol Lett ; 341: 33-42, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33497768


Sulfur mustard (SM) is a lipid soluble alkylating agent that causes genotoxic injury. The eye is highly sensitive to SM toxicity and exposures exceeding 400 mg min/m3 can elicit irreversible corneal pathophysiologies. Development of medical countermeasures for ocular SM exposure has been hindered by a limited understanding of dose-dependent effects of SM on corneal injury. Here, clinical, histological and ultrastructural analyses were used to characterize the effects of SM dose on corneal injury progression. Corneas were evaluated for up to 20 wk following exposure to saturated SM vapor for 30-150 s, which corresponds to 300-1,500 mg min/m3. In acute studies, a ceiling effect on corneal edema developed at doses associated with full-thickness corneal lesions, implicating endothelial toxicity in corneal swelling. Recurrent edematous lesions (RELs) transiently emerged after 2 wk in a dose-dependent fashion, followed by the development of secondary corneal pathophysiologies such as neovascularization, stromal scarring and endothelial abnormalities. RELs appeared in 96 % of corneas exposed for ≥ 90 s, 52 % of corneas exposed for 60 s and 0 % of corneas exposed for 30 s. While REL latency was variable in corneas exposed for 60 s, REL emergence was synchronized at exposures ≥ 90 s. Corneas did not exhibit more than one REL, suggesting RELs are part of a programmed pathophysiological response to severe alkylating lesions. In post-mortem studies at 12 wk, corneal edema was positively correlated to severity of endothelial pathologies, consistent with previous findings that endothelial toxicity influences long-term outcomes. These results provide novel insight into long-term corneal pathophysiological responses to acute toxicity and identify exposure conditions suitable for therapeutic testing.

Substâncias para a Guerra Química/toxicidade , Córnea/efeitos dos fármacos , Lesões da Córnea/induzido quimicamente , Gás de Mostarda/toxicidade , Animais , Córnea/patologia , Relação Dose-Resposta a Droga , Esquema de Medicação , Feminino , Gás de Mostarda/administração & dosagem , Coelhos
Dementia (London) ; : 1471301220973067, 2020 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-33372553


BACKGROUND AND AIMS: Sensitivity to the rights of people with dementia is a key principle cited in the World Health Organisation's global action plan on dementia. Some critics question whether rights-based approaches embody loose and ill-defined ideas incapable of bringing about meaningful change. Exercising the right to autonomy is considered a core problem for people living with dementia. The tradition of individual sovereignty dominates ideas about autonomy, although the person as an individual is not a cross-culturally universal concept. This study explored the viewpoints of people with dementia and family carers regarding the meaning of autonomy with a view to informing rights-based practice. METHODS: Twenty participants, people living with dementia and family carers, each conducted a Q-sort of statements regarding the meaning of autonomy. A by-person factor analysis was used to identify patterns in how the range of statements about autonomy were ranked. RESULTS: Three factors emerged: retaining independence and self-expression, accepting dependence but being included and opportunity for connection. There was some agreement across these different views regarding the importance of being given time to think before making decisions and being kept active. CONCLUSIONS: This study highlights the need for a person-centred approach to supporting people with dementia to claim their rights and the importance of adopting a stance of curiosity and critical thinking in rights-based training and professional practice. The findings suggest a variety of meaningful stories of autonomy and the possibility of further developing existing rights-based frameworks for dementia care.

Arch Toxicol ; 94(11): 3877-3891, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32691075


Organophosphorus (OP) compounds inhibit central and peripheral acetylcholinesterase (AChE) activity, overstimulating cholinergic receptors and causing autonomic dysfunction (e.g., bronchoconstriction, excess secretions), respiratory impairment, seizure and death at high doses. Current treatment for OP poisoning in the United States includes reactivation of OP-inhibited AChE by the pyridinium oxime 2-pyridine aldoxime (2-PAM). However, 2-PAM has a narrow therapeutic index and its efficacy is confined to a limited number of OP agents. The bis-pyridinium oxime MMB4, which is a more potent reactivator than 2-PAM with improved pharmaceutical properties and therapeutic range, is under consideration as a potential replacement for 2-PAM. Similar to other pyridinium oximes, high doses of MMB4 lead to off-target effects culminating in respiratory depression and death. To understand the toxic mechanisms contributing to respiratory depression, we evaluated the effects of MMB4 (0.25-16 mM) on functional and neurophysiological parameters of diaphragm and limb muscle function in rabbits and rats. In both species, MMB4 depressed nerve-elicited muscle contraction by blocking muscle endplate nicotinic receptor currents while simultaneously prolonging endplate potentials by inhibiting AChE. MMB4 increased quantal content, endplate potential rundown and tetanic fade during high frequency stimulation in rat but not rabbit muscles, suggesting species-specific effects on feedback mechanisms involved in sustaining neurotransmission. These data reveal multifactorial effects of MMB4 on cholinergic neurotransmission, with the primary toxic modality being reduced muscle nicotinic endplate currents. Evidence of species-specific effects on neuromuscular function illustrates the importance of comparative toxicology when studying pyridinium oximes and, by inference, other quaternary ammonium compounds.

Cornea ; 39(5): 640-648, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32044824


PURPOSE: Ocular exposure to sulfur mustard (SM) vapor causes acute loss of corneal endothelial cells (CECs). Persistent corneal endothelial pathologies are observed in eyes that do not recover from SM exposure, suggesting that endothelial toxicity contributes to mustard gas keratopathy (MGK). Here, we evaluated the contributions of endothelial loss to acute and chronic corneal injuries in SM-exposed eyes. METHODS: Rabbit eyes were exposed in vivo to equivalent doses of SM using 9-, 11-, or 14-mm vapor caps. The effects of exposure area on corneal injury progression were longitudinally evaluated over 12 weeks using clinical evaluations. The effects of exposure area on CEC morphology, endothelial and epithelial ultrastructure, and endothelial barrier function were determined from 1 day to 12 weeks. RESULTS: SM exposure caused loss of CECs and failure of endothelial barrier integrity at 1 day, independent of exposure cap size. By 3 weeks, eyes exposed with the 14-mm vapor cap exhibited increased corneal permeability, repopulation of the endothelium by cells with fibroblastic morphology, and abnormal deposition of extracellular matrix. Eyes exposed with 9- or 11-mm vapor caps exhibited transient symptoms of injury that fully resolved, with the rate of recovery correlated with cap size. CONCLUSIONS: The nonlinear correlation between endothelial lesion size and probability of developing MGK suggests that the CEC loss is a determinative factor for emergence of MGK. These studies illustrate the importance of endothelial repair in preventing MGK. Furthermore, they exclude chemical modification of basement membrane as a mechanistic cause of recurrent epithelial erosions in MGK eyes.