Fast and simple DNA extraction from saliva and sperm cells obtained from the skin or isolated from swabs

The forensic scientist often has to cope with problematic samples from the crime scene due to their minute size and thus the low amount of extractable DNA. The retrieval of DNA from swabs taken from the surface of the skin, for example, in cases of strangulation, can be especially difficult. We systematically investigated swabs taken from the skin (to obtain a genetic profile from the victim and also from a possible offender) and from sperm cell containing swabs using two extraction kits: the Invisorb forensic and the Invisorb spin swab kit (both Invitek, Germany). DNA quality and quantity were tested on ethidium bromide containing agarose gels and in a highly sensitive duplex-PCR, which amplifies fragments specific for mitochondrial and nuclear DNA. Absolute quantification was done using real time PCR. Samples, which were positive in the duplex-PCR, were also employed to genetic fingerprinting using the Powerplex ES and the AmpFlSTRIdentifiler(TM) kits. Our study shows that the easy-to-use Invisorb spin swab kit is very suitable for DNA isolation from swabs taken from the skin and also from sperm cells. Retrieval of cells from the skin with swabs moistened in extraction buffer, not in distilled water, led to a significant higher DNA yield.     

Nachweis von DNA-Spuren an Schneide- und Stichwerkzeugen

Background

The DNA analysis of knives that may have been used as a weapon in criminal cases is usually done to link the perpetrator and/or the victim to the weapon. However, little is known about the amount of DNA that can be found on common household knives although that might complicate the interpretation of DNA trace analysis.

Material and methods

This study investigated 12 household knives and one pair of scissors used on a regular basis by laboratory personnel and 40 knives used as weapons in cases investigated by these institutes. Swabs of the handle as well as the blade were taken and DNA was extracted using routinely used methods. The DNA yield was quantified by real-time PCR. All samples were subjected to a multiplex PCR comprising 16 autosomal loci.

Results and discussion

The majority of swabs rendered complete DNA profiles. Household knives could be linked to the persons living in the respective households. Knives used as weapons showed predominantly the profiles of the perpetrator and/or the victim. In conclusion, knives are well suited for molecular analysis. However, the interpretation of the results obtained should be carried out carefully to avoid a false positive assessment.     

Further evidence for abnormal GABAergic circuits in amygdala-kindled rats

In amygdala-kindled rats, synaptosomal levels of γ-aminobutyric acid (GABA) and its synthesizing enzyme glutamate decar☐ylase as well as [³H]GABA binding to synaptic membranes were determined in several brain regions which, except for the amygdala, were pooled from both hemispheres to obtain enough tissue for the subcellular fractionations. Compared to controls, GABA synthesis was reduced in the ipsilateral (stimulated) amygdala and in corpus striatum and substantia nigra. GABA receptor binding was decreased in amygdala and substantia nigra but significantly increased in the striatum. The data suggest that abnormal GABAergic transmission in discrete brain areas may be involved in the generation and propagation of amygdala-kindled seizures.     

Conventional MRI and MR spectroscopy in nonclassical mitochondrial disease: report of three patients with mitochondrial DNA deletion

Objects The objectives were to present magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) findings in three patients with deletion on mitochondrial DNA (mtDNA) and nonclassical mitochondrial disorders (NCMD), correlating these findings with the percentage of deleted mtDNA.Results Our study confirms the high prevalence of white matter (WM), basal ganglia, and posterior fossa lesions in NCMD, ranging from mild to severe involvement. The subcortical WM, caudate, thalamus, globus pallidus, and dorsal brain stem were more frequently affected. A lactate peak was the most frequent finding at the MRS. We found a correlation between the percentage of mtDNA deletion and degree of MRS abnormalities.Conclusions Our findings showed that MRS is a useful investigational tool in patients with NCMD. Supplementary studies are necessary to elucidate the correlation of quantitative mtDNA deletion and neuroimaging phenotype.     

The distribution of intrinsic cortical axons in area 3b of cat primary somatosensory cortex

Summary The morphology of single neurons in area 3b of cat primary somatosensory (SI) cortex was examined after horseradish peroxidase (HRP) injections. Neurons were labeled either by intracellular injection of HRP following intracellular recording or by small extracellular iontophoretic HRP injections. Both pyramidal and nonpyramidal neurons were labeled and reconstructed from serial sections. Their axons had local, interlaminar and interareal patterns of termination. Most neurons formed local axonal fields around their cell bodies and dendrites. Pyramidal neurons in cortical layer IV sent axons up into layers II and III, neurons in layers II and III sent axons down to layer V, and layer V neurons sent axons to layer VI as well as back to the upper layers. Layer VI neurons sent axons back to the upper cortical layers in a unique bowl-shaped pattern. The horizontal distribution of axons of pyramidal cells in layer III was extremely widespread. Axons of layer III neurons in area 3b terminated within 3b and area 1, but not in other areas of SI. Layer III neurons in area 1 distributed axon collaterals to all fields of SI as well as projecting a main axon to motor cortex. In general, the axon collaterals of area 3b pyramidal cells outside layer III remained confined to area 3b. Most of the nonpyramidal neurons labeled were basket cells in layers III and VI. These neurons formed dense axonal fields around their cell bodies, and none of their axons could be followed into the underlying white matter. The results of the present study demonstrate that area 3b somatosensory cortical neurons and their axons are vertically organized in a manner similar to that reported for other sensory cortical areas. They also show that widespread horizontal connections are formed by pyramidal neurons of layer III, and that these horizontal axons can travel for great distances in the cortical grey matter.     

Treatment of trigeminal neuralgia associated with multiple sclerosis: case report

The incidence of trigeminal neuralgia (TN) in patients with multiple sclerosis is higher than in the general population. If pharmacologic therapy fails, invasive procedures in the gasserian ganglion are usually offered. Microvascular decompression is not routinely performed. The authors report a patient with persistent TN after repetitive trigeminal radiofrequency rhizotomy and finally successful microvascular decompression after demonstration of neurovascular compression with high-resolution MRI.     

Serotonergic mechanisms in amygdaloid-kindled seizures in the rat

The kindling model of epilepsy is based on a permanent alteration in brain function resulting from repeated subconvulsant stimulation. Because these alterations may be neurochemical in nature, the role of serotonin (5-HT) in the development of amygdaloid-kindled seizures was studied using female rats. Concentrations of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) were determined fluorometrically in the hypothalamus, amygdala, midbrain, and brain-stem regions. Amygdaloid kindling led to significant decreases of 5-HT and 5-HIAA in the midbrain region. The administration of 5-hydroxytryptophan (5-HTP), a 5-HT precursor, was found to retard the evolution of the kindling process and p-chlorophenylalanine (p-CPA), a depletor of brain 5-HT, facilitated the development of amygdaloid kindled seizures. Both 5-HTP and p-CPA produced an increase in afterdischarge duration of full kindled seizures. The data suggest that serotonergic mechanisms may play a suppressive role in the development of amygdaloid-kindled seizures.     

Cat medial interlaminar nucleus: retinotopy, relation to tapetum and implications for scotopic vision

The medial interlaminar nucleus (MIN) of the cat was electrophysiologically mapped in sufficient detail to resolve individual laminae and to allow reconstruction of isoazimuth and isoelevation lines in coronal, sagittal, and horizontal planes. The electrophysiologically defined laminar pattern was in agreement with that revealed anatomically in the same animal, as well as with the general pattern revealed by anatomical methods in several unmapped nuclei. The MIN is made up of three distinct layers, each receiving inputs from one hemi-retina but none representing an entire hemifield. We confirm the findings of Guillery et al. (19) that the contralateral hemifield is represented in layers 1 and 2 through the contralateral and ipsilateral eyes, respectively, and that layer 3 represents the ipsilateral hemifield through the contralateral eye. Elevation and absolute value of azimuth are represented continuously through the MIN. When an isoazimuth line crosses the border between layer 3 and either layer 1 or 2, the absolute value of azimuth is maintained but the sign of the azimuth changes. Adjacent points on either side of this border represent mirror symmetrical visual directions on opposite sides of the vertical meridian. This indicates that the distance from the vertical meridian is an independently coded parameter within the geniculate complex. There is virtually no nasotemporal overlap in any layer of the MIN. The function relating magnification (mm3 per steradian) to eccentricity is strikingly similar to the function relating retinal ganglion cell density to eccentricity, suggesting that a constant fraction of retinal ganglion cells project to the MIN at all eccentricities. Most of the volume of each MIN layer is devoted to lower visual fields. Analysis of the geniculate retinotopic maps of Sanderson (46) reveals no equivalent bias toward lower visual fields in the dorsal lateral geniculate nucleus. The MIN represents a region of retina roughly coincident with the tapetum, suggesting a role of the MIN in dim-light vision.