J. A. Lorente

Increasing DNA extraction yield from saliva stains with a modified Chelex method

Recovery, preservation and analysis of body fluid stains is an important aspect of forensic science. PCR-based typing of DNA extracted from recovered stains is often a crucial method to identify a perpetrator or exclude an innocent suspect. This paper reports an improved method of extracting genomic DNA from saliva stains deposited on human skin in simulated bite mark situations. Results of organic (phenol-chloroform) extraction and Chelex extraction were compared to a modified Chelex method developed by the authors. Modifications include pre-extraction preparation with proteinase K and incubations at 56 degrees C and 100 degrees C plus microconcentration of the solution. Quantification results using the classical Chelex extraction method showed that 31.9 +/- 4.22% of the deposited DNA was recovered, but using the modified Chelex extraction method DNA recovery was increased to 47.7 +/- 6.90%. The quantity and quality of extracted DNA was shown to be adequate for PCR-based typing at two STR loci.

Dandruff as a Potential Source of DNA in Forensic Casework

Dandruff is a clinical alteration of the skin that consists histologically of orthokeratotic clumps with minute parakeratotic foci found in inflammatory pathologies such as seborrheic dermatitis and psoriasis. Therefore, some nucleated cells should be found in dandruff and hence there is a possibility that forensically typeable DNA could be extracted from dandruff. Because of a particular case in which we were involved, a study was carried out to determine whether or not DNA could be extracted from dandruff, and if the two most widely used extraction techniques (Chelex and organic) would be applicable. Results show that sufficient quantities of DNA (more than 30 to 40 ng) can be obtained from as little as 1.0 to 1.5 mg of dandruff. Both methods yield DNA, although the organic procedure seems to yield more (72.5 ng Chelex vs. 183.3 ng organic). All the DNA samples extracted were typed correctly for the loci HUMTH01 and HUMvWA. Therefore, dandruff can be considered a potential source of DNA for forensic identification.

The usefulness of lung surfactant phospholipids (LSPs) in the diagnosis of drowning

The authors have studied the usefulness of some lung surfactant phospholipids (LSPs) isolated from lung tissues as markers of drowning. Two different groups of rabbits were sacrificed by drowning in fresh and salt water, and their phospholipid compositions were compared with those of a non-drowned control series. For the phospholipids studied in lung lavages (phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl glycerol) the proportions differed between the control group and the drowned group, and between the fresh-water and salt-water drowned animals. According to these results, the lipids we have analyzed can be employed as markers in forensic autopsies, where it is necessary to differentiate between death by drowning and postmortem immersion and between fresh-water and salt-water drowning. In lung tissue, only phosphatidyl choline and phosphatidyl inositol showed significative differences. These results also confirm that LSPs are strongly affected in drowning.

Plasmatic levels of atrial natriuretic peptide (ANP) in drowning. A pilot study

Bodies found in water may cause problems for forensic pathologists who have to differentiate drowning from postmortem immersion or fresh from salt water drowning. The exact physiopathology of drowning is still controversial and complementary tests can not exactly establish the exact cause of death if macroscopic findings at autopsy are not conclusive. We have employed atrial natriuretic peptide (ANP) as a marker in an experimental series of fresh and salt water drowning, comparing their results with a non-drowned control series. There are differences between the plasma basal levels of the control series (79 pg/ml) and the levels in animals drowned in fresh water (358 pg/ml, P less than 0.001) and between control and rabbits drowned in salt water (190 pg/ml, P less than 0.001). According to these values, there are also differences between fresh and salt water drowned animals (P less than 0.001). We propose this peptide as a new marker in cases of drowning, with the ability to differentiate drowning from postmortem immersion and fresh from salt water drowning.

Spanish population data on seven loci : D1S80, D17S5, HUMTH01, HUMVWA, ACTBP2, D21S11 and HLA-DQA1

Blood samples from 120 Spanish Caucasian individuals were amplified and typed by electrophoresis at six loci, and by reverse dot-blot hybridization at one locus. Results demonstrate the assumption of independence within and between the seven loci analyzed. Therefore, a Spanish population database has been established and statistical analysis shows that a high degree of discrimination can be obtained when all seven (or fewer) loci are used to characterize forensic biological evidence.

STR Data for the PowerPlex ® 16 Loci in Buenos Aires Population (Argentina)

DNA samples from 101 unrelated individuals were extracted by Chelex procedure (1) and then quantified using QuantiBlot® Human DNA Quantitation Kit according to the manufacturers instructions (2). DNA samples (1 ng) were amplified and typed by PowerPlex® 16 System (3). The electrophoresis was carried out on the ABI PRISM® 377 DNA Sequencer using GeneScan® Genotyper® and PowerTyper™ 16 Macro software. Data were analyzed using a program provided by R. Chakraborty (University of Texas School of Biomedical Sciences, Houston, Texas). Interclass correlations yielding p

STUDY OF CATHEPSIN A, B AND D ACTIVITIES IN THE SKIN WOUND EDGES. ITS APPLICATION TO THE DIFFERENTIAL DIAGNOSIS BETWEEN VITAL AND POSTMORTEM WOUNDS

The aims of the authors in this paper has been to check the diagnostic ability of the Cathepsin A, B and D concentrations in the skin wound edges to the differential diagnosis between vital and postmortem wounds. We have studied 56 domestic pigs grouped in seven experimental series consisting of 8 animals in each, according to the time (0, 5, 15, 30 min and 1, 3 and 6 h) after the injury. The enzymatic activities were investigated following the methods by Bowen and Davison Biochem. J., 131 (1973) 417-419, Suhar and Marks J. Biochem., 101 (1979) 23-30 and by Anson (modified by Yamamoto, Eur. J. Biochem., 95 (1979) 459-467) for Cathepsin A, B and D, respectively. For the differential diagnosis between vital and postmortem wounds, our results showed that the most useful markers studied are the Cathepsin A and D activities, Cathepsin D that of the first one.

Cathepsin D as a vitality marker in human skin wounds

SummaryThis paper shows the results obtained by studying the lysosomal enzyme Cathepsin D as a potential marker for the vitality of wounds in human specimens. We have analyzed 53 samples using enzymological and histological techniques. Our results show the ability of Cathepsin D to establish the vital origin of wounds inflicted 5 minutes or less before death, where the specific activity of cathepsin D reached 0.055 units at the wound edge and 0.01 units in their respective controls (P < 0.001). As previously demonstrated in an experimental series, Cathepsin D seems to be a very useful marker of high forensic interest in especially difficult cases. Further studies are in progress to check the influence of different factors such as drugs intake and clinical conditions on Cathepsin D activity.ZusammefassungDas Manuskript zeigt Ergebnisse, wie sie durch Untersuchung des lysosomalen Enzyms Cathepsin D als potentiellen Marker für Vitalität in menschlichen Hautwunden erzielt wurden. Wir haben 53 Proben mit Hilfe enzymatischer und histologischer Techniken untersucht. Die Ergebnisse zeigen die Fähigkeit von Cathepsin D, den vitalen Ursprung von Wunden zu etablieren, selbst wenn sie 5 Minuten oder geringere Zeit vor dem Tod gesetzt wurden. In den letzteren erreichte die spezifische Aktivität von Cathepsin D 0,055 Einheiten an den Wundränden und 0,01 Einheiten in den entsprechenden Kontrollen (P < 0,001). Wie früher in experimentellen Untersuchungen gezeigt wurde, scheint Cathepsin D ein sehr nützlicher Marker von hoher forensischer Bedeutung besonders in schwierigen Fällen zu sein. Weitere Studien sind in der Bearbeitung, um den Einfluß verschiedener Faktoren, wie Medikamenteneinnahme und klinischer Zustand, auf die Cathepsin D-Aktivität zu überprüfen.

Postmortem stability of some markers of intra-vital wounds

We have studied the diagnostic value of several markers of the intra-vital nature of wounds - cathepsin D (EC 3.4.23.5) and ions (Ca, Mg, Cu, Zn and Fe) - after the influence of putrefaction. For this purpose, we have inflicted vital wounds to six pigs, which were killed 20 min later. Ten minutes after death, wounds were excised with 5-6 cm of skin around the incision and maintained at three different temperatures (4, 18 and 28.5 +/- 13.4 degrees C). After varying periods of postmortem interval from 0 to 48 h, aliquots of each wound were taken and analyzed with atomic absorption spectrophotometry for ions and with UV-spectrophotometry for cathepsin D. Our results demonstrate that ions conserve their diagnostic ability to differentiate vital from postmortem wounds after the influence of putrefaction. Nevertheless, cathepsin D does not show this ability in these experimental conditions.

Paraguayan population data on the fifteen STR loci included in the PowerPlex 16 kit.

Blood samples were obtained by venipuncture from unrelated individuals (n = 168) living in Paraguay.