Freshwater and salt-water influence in human identification by analysis of DNA: an epidemiologic and laboratory study

Aim: To investigate the casuistry of drowning cases by reviewing the records from the Forensic Medicine Institute Nina Rodrigues in the city of Salvador, BA, Brazil, and to verify the potential of DNA recovery in human teeth immersed in water. Methods: An epidemiological survey was conducted followed by a laboratorial phase, in which 40 teeth were immersed in fresh and salt-water, the DNA was extracted by the organic method and amplified by polymerase chain reaction, using the amelogenin as initiator. The electrophoresis initially occurred in agarose gel and later in polyacrylamide gel. Results: In the present survey, 346 deaths from drowning were observed, most of them in salt-water (51.73%), with a predominance of male victims (86.13%) aged from 18 to 35 years-old (37.94%). Dentists identified 14.74% of the victims. DNA was recovered in 37.5% from the samples, most from teeth immersed in freshwater. Polyacrylamide gel analysis in samples that were amplified in agarose gel allowed correct gender identification in 83.3% of the cases. However, allele loss was observed in samples of two victims, jeopardizing gender determination. Conclusions: Dental exposure to water interfered in DNA recovery. The gender investigation using the amelogenin as initiator was effective.

Avaliaçäo de três métodos de extraçäo de DNA de material parafinado para amplificaçäo de DNA genômico pela técnica da PCR / Evaluation of three methods od DNA extraction from paraffin-embedded material for the amplification of genomic DNA by means of the PCR technique

Existem na literatura vários protocolos para extraçäo de DNA genômico a partir de material fixado em formal e embebido em parafina. A obtençäo de DNA genômico é importante para realizaçäo de experimentos em biologia molecular, dentre eles a PCR. Este trabalho teve por objetivo otimizar a extraçäo de DNA genômico a partir de material fixado (hiperplasia fibrosa inflamatória) e näo-fixado (mucosa bucal normal) em formol, comparando-se três metodologias diferentes: fenol com digestäo enzimática, partículas de sílica com e sem digestäo enzimática. Para amplificaçäo do DNA pela técnica da PCR, utilizou-se iniciadores para o éxon 7 da citoqueratina tipo 14. O sucesso da amplificaçäo foi verificado pela eletroforese do produto em gel de poliacrilamida 8 por cento contendo glicerol 5 por cento corado com prata. Obteve-se amplificaçäo do DNA genômico extraído com fenol/digestäo enzimática e com partículas de sílica/disgestäo enzimática, para ambos tecidos utilizados. O método padronizado tem potencial para auxiliar no diagnóstico histopatológico, assim como no estudo retrospectivo de material de arquivo