RESUMO
BACKGROUND/AIMS: A Bitot spot is a conjunctival lesion, classically associated with severe vitamin A deficiency. In this paediatric series, we describe conjunctival lesions indistinguishable from Bitot spots, seen in the presence of normal vitamin A levels. METHODS: This descriptive case series was performed by retrospective review of case notes, including all patients with Bitot-like spots found to have normal serum vitamin A levels, seen at the Hospital for Sick Children, Toronto, between 2006 and 2016. Data collected included age at presentation, ophthalmic and systemic diagnoses, and the presence of recognised genetic mutations. Histopathology was reviewed in one case. RESULTS: Ten patients with Bitot-like spots with laboratory-confirmed normal serum vitamin A levels were identified. The conjunctival lesions were indistinguishable clinically and histopathologically from classic Bitot spots and were noted to occur in a range of anterior segment pathologies, including aniridia, WAGR syndrome, Axenfeld-Rieger syndrome, and blepharokeratoconjunctivitis. CONCLUSIONS: Bitot-like spots are found in children with a number of anterior segment pathologies in the absence of vitamin A deficiency.
Assuntos
Anormalidades do Olho , Oftalmopatias Hereditárias , Deficiência de Vitamina A , Segmento Anterior do Olho , Criança , Anormalidades do Olho/complicações , Humanos , Vitamina A , Deficiência de Vitamina A/complicaçõesRESUMO
PURPOSE: The aim of this study was to investigate how glutathione reductase (GR) loses its activity during cataract formation and whether it is possible to revive it back to the normal levels. METHOD: In this study, endogenous as well as synthetic reducing systems (GSH, TTase, DTT, captopril) and alpha-crystallin at different concentrations were incubated with the soluble fraction of human cataract lens protein. The activity of glutathione reductase with or without the reducing agents and alpha-crystallin was tested, and the difference in activity gained was calculated. RESULTS: Five agents (GSH, DTT, TTase, captopril, alpha-low crystallin) were able to revive the activity of GR from human cataract lenses to different extents. CONCLUSION: This study shows that human lens GR activity was revived by different reducing agents as well as by a molecular chaperone (alpha-crystallin).
Assuntos
Catarata/enzimologia , Glutationa Redutase/metabolismo , Cristalino/enzimologia , Chaperonas Moleculares/farmacologia , Substâncias Redutoras/farmacologia , alfa-Cristalinas/farmacologia , Animais , Captopril/farmacologia , Bovinos , Ditiotreitol/farmacologia , Relação Dose-Resposta a Droga , Ativação Enzimática , Glutarredoxinas , Glutationa/farmacologia , Humanos , Técnicas In Vitro , Chaperonas Moleculares/administração & dosagem , Proteína Dissulfeto Redutase (Glutationa)/farmacologia , Substâncias Redutoras/administração & dosagem , alfa-Cristalinas/administração & dosagemRESUMO
In this study, endogenous as well as synthetic reducing systems were shown to reduce the disulphide bonds formed in glyceraldehyde 3-phosphate dehydrogenase, an important glycolytic enzyme previously reported to have lost its activity in human cataract lenses, resulting in reviving the activity of this enzyme. Disulphide bond formation is a non-specific posttranslational modification of proteins, which leads to a loss of function of the affected protein. When an enzyme is targeted, this harmful effect can be easily detected by monitoring the change of activity. Endogenous reducing systems are responsible for breaking these bonds and returning the protein (enzyme) to its natural state, when these mechanisms fail to do so, the loss of enzyme activity will be permanent.