Recebido em 16/2/07; aceito em 7/3/08; publicado na web em 31/10/08Free radicals induce lipid peroxidation, playing an important role in patho logical processes. The injury mediated by free radicals can be measured by conjugated dienes, malon dial dehyde, 4-hydroxynonenal, and others. However, malondialdehyde has been pointed out as the main product to evaluate lipid peroxidation. Most assays determine malondialdehyde by its reaction with thiobarbituric acid, which can be mea sured by indirect (spectrometry) and direct methodologies (chromatography). Though there is some controversy among the methodologies, the selective HPLC-based assays provide a more reliable lipid peroxidation measure. This review describes significant aspects about MDA deter mination, its importance in pathologies and biological samples treatment.

Production of bacterial nanocellulose (BNC) is becoming increasingly popular owing to its environmentally friendly properties. Based on this benefit of BNC production, researchers have also begun to examine the capacity for cellulose production through microbial hosts. Indeed, several research groups have developed processes for BNC production, and many studies have been published to date, with the goal of developing methods for large-scale production. During BNC bioproduction, the culture medium represents approximately 30 % of the total cost. Therefore, one important and challenging aspect of the fermentation process is identification of a new cost-effective culture medium that can facilitate the production of high yields within short periods of time, thereby improving BNC production and permitting application of BNC in the biotechnological, medical, pharmaceutical, and food industries. In this review, we addressed different aspects of BNC production, including types of fermentation processes and culture media, with the aim of demonstrating the importance of these parameters.

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J Bras Patol Med Lab • v. 41 • n. 5 • p. 323-34 • outubro 2005 y unitermos u te os unitermos y y y y y key words resumo Introdução: A vitamina B12 é hidrossolúvel, não-sintetizada pelo organismo humano, presente em alimentos de origem animal. Sua deficiência é muito freqüente entre idosos, vegetarianos e indivíduos que adotam baixa dieta protéica ou apresentam problemas de absorção gastrintestinal. Fisiopatologia: A deficiência de vitamina B12 leva a transtornos hematológicos, neurológicos e cardiovasculares, principalmente, por interferir no metabolismo da homocisteína (Hcy) e nas reações de metilação do organismo. Muitas vezes a deficiência pode permanecer assintomática por longos períodos, desencadeando uma deficiência crônica que, se mantida, pode levar a manifestações neurológicas irreversíveis. Metodologias: Metodologias eficientes que permitam um diagnóstico precoce são imprescindíveis. Porém um método considerado padrão-ouro ainda não é consensual. A dosagem sérica de vitamina B12 sofre algumas restrições pelos problemas de sensibilidade e especificidade, podendo ocorrer sintomas de deficiência mesmo com vitamina B12 sérica dentro dos níveis normais ou, de outro modo, ocorrendo baixos níveis de vitamina B12 sérica sem, contudo, apresentar baixos níveis da fração de vitamina realmente disponível para as células e sem apresentar sintomatologia. Novas alternativas vêm surgindo, como a dosagem de transcobalamina II (Tc II), a única fração de vitamina B12 disponível para as células, ou a dosagem de ácido metilmalônico (MMA) e Hcy, metabólitos que aumentam quando ocorre diminuição de vitamina B12 intracelular. Estes testes apresentam algumas vantagens, mas também limitações importantes para uso rotineiro. Conclusão: Em casos subclínicos, um diagnóstico correto e precoce representa ainda um desafio, e futuros estudos são necessários para definir um método padrão para diagnóstico laboratorial da deficiência de vitamina B12. Vitamina B12 Diagnóstico Soro Transcobalaminas Hiper-homocisteinemiaÁcido metilmalônico abstract Introduction: The vitamin B12 is a water soluble vitamin, not synthetized by humans organisms, found in foods of animal origin. Its deficiency is very frequent among old people, vegetarians, subjects who use a low protein diet, or who present gastrointestinal absorption failure. Physiopathology: The vitamin B12 deficiency leads to hematologic, neurophatologic and cardiovascular disorders, mainly by interfering in the homocysteine (Hcy) metabolism and in the methylation reactions of organism. Often, the deficiency can remain without symptoms for long time, leading to a chronic deficiency that, if not treated, may yield irreversible neurologic manifestations. Methodology: Efficient methodologies that allow the early diagnosis are essential. However, a gold standard method is not consensus yet. The vitamin B12 serum measurement presents some restrictions for problems of sensitivity and specificity, being able to occur deficiency's symptoms even the serum vitamin B12 being in nor-r r mal range or, i...