Defibrillation efficacy of different electrode placements in a human thorax model.

The objective of this study was to measure the defibrillation threshold (DFT) associated with different electrode placements using a three-dimensional anatomically realistic finite element model of the human thorax. Coil electrodes (Endotak DSP, model 125, Guidant/CPI) were placed in the RV apex along the lateral wall (RV), withdrawn 10 mm away from the RV apex along the lateral wall (RVprox), in the RV apex along the anterior septum (RVseptal), and in the SVC. An active pulse generator (can) was placed in the subcutaneous prepectoral space. Five electrode configurations were studied: RV-->SVC, RVprox-->SVC, RVSEPTAL-->SVC, RV-->Can, and RV-->SVC + Can. DFTs are defined as the energy required to produce a potential gradient of at least 5 V/cm in 95% of the ventricular myocardium. DFTs for RV-->SVC, RVprox-->SVC, RVseptal-->SVC, RV-->Can, and RV-->SVC + Can were 10, 16, 7, 9, and 6 J, respectively. The DFTs measured at each configuration fell within one standard deviation of the mean DFTs reported in clinical studies using the Endotak leads. The relative changes in DFT among electrode configurations also compared favorably. This computer model allows measurements of DFT or other defibrillation parameters with several different electrode configurations saving time and cost of clinical studies.

Extracting isovolumes from three-dimensional torso geometry using PROLOG.

Three-dimensional (3-D) finite element torso models are widely used to simulate defibrillation field quantities, such as potential, gradient, and current density. These quantities are computed at spatial nodes that comprise the torso model. These spatial nodes typically number between 10(5) and 10(6), which makes the comprehension of torso defibrillation simulation output difficult. Therefore, the objective of this study is to rapidly prototype software to extract a subset of the geometric model of the torso for visualization in which the nodal information associated with the geometry of the model meets a specified threshold value (e.g., minimum gradient). The data extraction software is implemented in PROLOG, which is used to correlate the coordinate, structural, and nodal data of the torso model. A PROLOG-based environment has been developed and is used to rapidly design and test new methods for sorting, collecting, and optimizing data extractions from defibrillation simulations in a human torso model for subsequent visualization.

A family exhibiting heteroplasmy in the human mitochondrial DNA control region reveals both somatic mosaicism and pronounced segregation of mitotypes.

A family exhibiting heteroplasmy at position 16355 in hypervariable region I of the human mtDNA control region has been identified. This family consists of a mother, daughter, and son. DNA samples extracted from blood stains, buccal swabs, and hairs from these individuals were amplified by PCR and sequenced utilizing fluoresence-labeled dye terminator chemistry in an automated DNA sequencer. In both the daughter and mother, heteroplasmy was observed in DNA extracted from blood stains, buccal swabs, and hairs. In the blood stains, the proportion of cytosine was greater than thymine in both individuals. Buccal swab extracts showed a more balanced contribution from the two nucleotides. Telogenic hair root and hair shaft samples exhibited a wide range of nucleotide contributions at this position, from predominately cytosine in some samples to predominately thymine in others. The apparent stochastic segregation of mitotypes in hair samples is discussed from a forensic viewpoint, and the mechanism of mtDNA heteroplasmy is considered.

Extraction, PCR amplification and sequencing of mitochondrial DNA from human hair shafts.

Techniques have been developed for extracting, amplifying and directly sequencing mitochondrial DNA (mtDNA) from human hair shafts. The hair shaft is ground in a glass micro-tissue grinder, and the DNA is extracted with organic solvent and purified by filtration. The filtrate subsequently provides the mtDNA template for the PCR. The two hypervariable segments of the mtDNA control region are amplified in four separate reactions. After a purification step to remove unincorporated PCR primers, amplified products are quantitated by capillary electrophoresis and subjected to cycle sequencing. The products are separated and analyzed on an automated DNA sequencer. The mtDNA sequences from the hair shaft match the mtDNA sequences from blood samples taken from the same donor.

Validation of mitochondrial DNA sequencing for forensic casework analysis.

Two sets of studies were performed to evaluate the forensic utility of sequencing human mitochondrial DNA (mtDNA) derived from various tissues and amplified by the polymerase chain reaction (PCR). Sequencing was performed on a Perkin-Elmer/Applied Biosystems Division (PE/ABD) automated DNA sequencer (model 373A). The first set of experiments included typical validation studies that had previously been conducted on forensic DNA markers, such as: chemical contaminant effects on DNA from blood and semen and the effect of typing DNA extracted from body fluid samples deposited on various substrates. A second set of experiments was performed strictly on human hair shafts. These studies included typing mtDNA from hairs that were: (1) from different body areas, (2) chemically treated, (3) from deceased individuals, and (4) deliberately contaminated with various body fluids. The data confirm that PCR-based mtDNA typing by direct automated sequencing is a valid and reliable means of forensic identification.

Identification of host DNA by amplified fragment length polymorphism analysis: preliminary analysis of human crab louse (Anoplura: Pediculidae) excreta.

The ability to identify individual hosts of hematophagous arthropods via bloodmeal analyses is a continuing pursuit in both medical and forensic entomology. Characterization of human DNA from blood-feeding arthropods has been advanced substantially by preparation techniques, such as the polymerase chain reaction (PCR). Successful application of amplified fragment length polymorphism (AMP-FLP) analysis to excreta obtained from adult crab lice, Pthirus pubis (L.), fed on human volunteers is reported herein. Human DNA derived from crab louse excreta was typed successfully for two human DNA genetic markers, D1S80 and HUMTH01. Although preliminary, these results illustrate the ability of AMP-FLP analyses to provide individual human locus characterizations from desiccated arthropod excrement.

Supporting rehabilitation for the impaired healthcare employee: a case study.

A case study describing detection, intervention and treatment of a chemically dependent hospital pharmacist, leading to generalizations and conclusions concerning the handling of impaired health care workers. The willingness of one hospital's management and administration to offer continued employment and support to an impaired pharmacist throughout an extended period of rehabilitation has resulted in a story of success on both a personal and an institutional level. From this experience, the authors have concluded that this humane reaction to an employee in need is a viable alternative to more typical reactions involving legal prosecution.