Uma exposição acidental aos raios X de um difratômetro / Accidental exposure to the X-ray of a diffractometer

As mãos de três trabalhadores foram irradiadas acidentalmente numa indústria em Camaçari, Estado da Bahia, Brasil. O diagnóstico clínico de radiodermite aguda foi possível, antes mesmo da confirmação dosimétrica da ocorrência, em virtude das manifestações cutâneas exibidas, precedidas por um eritema, e também pelas histórias ocupacionais. As avaliações das doses recebidas pelos acidentados, usando-se restituições com dosímetros termoluminescentes, tiveram boa correlação com as doses estimadas em função das manifestações clínicas. A causa imediata do acidente foi a má manutenção do equipamento que levou a sua janela posterior a ficar permanentemente aberta, porém foram fatores contributórios importantes a falta de informação dos empregados sobre os possíveis efeitos biológicos das radiações ionizantes e o não seguimento dos procedimentos operacionais corretos. A descrição deste acidente é importante, face ao grande número de difratômetros existentes em laboratórios, universidades, centros de pesquisa e indústrias. Tais aparelhos são considerados "virtualmente isentos de risco ocupacional", o que não é verdadeiro, como comprova a ocorrência que descrevemos. A evolução médica dos pacientes tem sido satisfatória, especialmente em virtude da baixa energia do feixe de raios X do difratômetro e, em conseqüência, da sua pequena penetração tissular.

Cellular signalling in vertebrate pigment cells

Chromatophores are specialized integumental stellate cells that synthesize and store pigments. Pigment granules are translocated within chromatophores of poikilothermic vertebrates and crustaceans in response to photic, thermal and/or neurohormonal stimuli, allowing the animal to rapidly change color for thermoregulation, adaptation to light and background, and social behavior display. Birds and mammals do not show color changes, but may present slow long-term responses, such as melanocyte proliferation, melanin synthesis and melanin granule translocation into feathers, hair and surrounding keratinocytes. Pigment translocation in lower vertebrates as well as pigment production in all vertebrates are modulated by a variety of hormones and neurotransmitters acting on transmembrane receptors located on the cell surface. Alpha-melanocyte-stimulating hormone (alpha-MSH), melanin-concentrating hormone (MCH), melatonin and catecholamines are the most important pigment cell agonists in vertebrates. The major signalling pathway leading to pigment dispersion and melanin synthesis appears to involve stimulation of adenylate cyclase followed by an increase in the cAMP level and activation cAMP-dependent protein kinases (PKAs). Another melanogenesis related intracellular pathway involves the activation of protein kinase C (PKC) by diacylglycerol, and the increase in cytosolic Ca2+ by inositol triphosphate. Growth factors such as basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and mast cell growth factor (MGF or KIT tigand), and UV radiation modulate the melanogenic and mitogenic processes in vertebrates melanocytes as well.

Quality control of food products purchased by the National School-Feeding Programme in Pernambuco, northeast Brazil, from 1985 to 1988

The effectiveness of the Quality Control System (QCS) implemented by the Fundaçäo de Assistência ao Escolar (FAE) for quality control of food products from different types and origins purchased by the National School-Feeding Programme (NSFP) in Pernambuco, Northeast Brazil, was evaluated. Physicochemical, microbiological, microscopical and organopetical analyses were performed in 4,860 food samples and the main causes of alterations were detected. Perishability was the characteristic used for distribution of food items into 3 main groups: A, B, and C. In accordance with 972 Quality Certificates between 1985 and 1988, 31.89 of the samples were rejected. The main reasons for rejection were innacuracies of net weight and drained weight and high moisture contents. Group B presented the smallest number of altered samples (27%); for Groups A and C these values were 33% and 44%, respectively. Our data lead to the conclusion that the QCS implemented by FAE is of paramount importance for an adequate quality control of foods provided to beneficiaries and for a good cost effectiveness of the school-feeding programme