Efeito tóxico dos praguicidas maneb e paraquat sobre a atividade da enzima antioxidante catalase em ratos / Toxic effect of pesticides maneb and paraquat on catalase antioxidant enzyme activity in rats

Os radicais livres estão envolvidos em um grande número de enfermidades do ser humano.O cérebro tem níveis baixos de enzimas antioxidantes e um conteúdo lípidico elevado, tornando-se muito susceptível ao ataque de espécies reativas de oxigênio.Neste trabalho avaliou-se a lipoperoxidação em hipocampo e a atividade da enzima catalase em estriado e hipocampo de ratos tratados com o fungicida maneb (30 mg/kg) e o herbicida paraquat (10 mg/kg).Não houve alteração na lipoperoxidação nem na atividade enzimática no hipocampo dos animais tratados com ambos os praguicidas, porém foi observada uma inibição da catalase no estriado dos ratos tratados com maneb e com paraquat.Com estes resultados pode-se sugerir, de forma preliminar, uma ação tóxica maior sobre centros dopaminérgicos.Estudos sobre a toxicidade destes compostos são essenciais na compreensão do papel destes praguicidas e dos radicais livres na etiologia das doenças

Molecular characterization of a unique patient with epimerase-deficiency galactosaemia.

Inherited deficiencies of UDP-galactose 4-epimerase (GALE) have been associated with two distinct phenotypes. The vast majority of North American patients are clinically asymptomatic, are identified through newborn screening programmes for classical galactosaemia, and are of African-American descent. At least two symptomatic patients have been reported, one Pakistani and the other Asian Muslim, both with severe complications in the neonatal period and subsequent mental retardation. Through newborn screening, we have identified a GALE-deficient patient who is of mixed Pakistani/caucasian ancestry. He was clinically well in the neonatal period on a lactose-containing diet, and biochemical studies, including urine reducing sugars and galactitol, were consistent with a diagnosis of peripheral GALE deficiency. Although early developmental milestones were met normally, he now shows significant developmental delays in both motor and language skills. Mutational analysis revealed this patient to be a compound heterozygote at the GALE locus, with mutations N34S and L183P identified in the patient and confirmed in the parents. This report represents the first characterization of specific mutations in a GALE-deficient patient in conjunction with biochemical and clinical phenotype, and facilitates further studies of the GALE enzyme and its role in the different clinical forms of epimerase-deficiency galactosaemia.

Characterization of two mutations associated with epimerase-deficiency galactosemia, by use of a yeast expression system for human UDP-galactose-4-epimerase.

UDP-galactose-4-epimerase (GALE) is a highly conserved enzyme that catalyzes the interconversion of UDP-galactose and UDP-glucose. Impairment of this enzyme in humans results in one of two clinically distinct forms of epimerase-deficiency galactosemia-one benign, the other severe. The molecular and biochemical distinction between these disorders remains unknown. To enable structural and functional studies of both wild-type and patient-derived alleles of human GALE (hGALE), we have developed and applied a null-background yeast expression system for the human enzyme. We have demonstrated that wild-type hGALE sequences phenotypically complement a yeast gal10 deletion, and we have biochemically characterized the wild-type human enzyme isolated from these cells. Furthermore, we have expressed and characterized two mutant alleles, L183P-hGALE and N34S-hGALE, both derived from a patient with no detectable GALE activity in red blood cells but with approximately 14% activity in cultured lymphoblasts. Analyses of crude extracts of yeast expressing L183P-hGALE demonstrated 4% wild-type activity and 6% wild-type abundance. Extracts of yeast expressing N34S-hGALE demonstrated approximately 70% wild-type activity and normal abundance. However, yeast coexpressing both L183P-hGALE and N34S-hGALE exhibited only approximately 7% wild-type levels of activity, thereby confirming the functional impact of both substitutions and raising the intriguing possibility that some form of dominant-negative interaction may exist between the mutant alleles found in this patient. The results reported here establish the utility of the yeast-based hGALE-expression system and set the stage for more-detailed studies of this important enzyme and its role in epimerase-deficiency galactosemia.