Biomedical subjects

K Pope

Publications and source records attributed to K Pope.

12 recordsLinked to original sources

PubMed2004

Observation of parity nonconservation in møller scattering.

We report a measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A(PV)=[-175+/-30(stat)+/-20(syst)] x 10(-9). This first direct observation of parity nonconservation in Møller scattering leads to a measurement of the electron's weak charge at low energy Q(e)(W)=-0.053+/-0.011. This is consistent with the standard model expectation at the current level of precision: sin((2)theta(W)(M(Z))((-)MS)=0.2293+/-0.0024(stat)+/-0.0016(syst)+/-0.0006(theory).

Journal Article↗

PubMed2003

Realistic human head model for EEG from both the geometry and conductivity aspects.

This paper describes modelling and simulation of a had model which incorporates both the geometries and conductivities of the human head. It focuses on the inclusion of tissue conductivity inhomogeneity in a realistically-shaped head model, and investigates the impact of this inclusion on the potential distribution within the model. The result show that the impact, which has been neglected in realistic head models so far, is significant.

Brain↗

PubMed2001

Influence of nozzle-to-skin distance in cryogen spray cooling for dermatologic laser surgery.

BACKGROUND AND OBJECTIVE: Cryogen sprays are used for cooling human skin during various laser treatments. Since characteristics of such sprays have not been completely understood, the optimal atomizing nozzle design and operating conditions for cooling human skin remain to be determined. MATERIALS AND METHODS: Two commercial cryogenic spray nozzles are characterized by imaging the sprays and the resulting areas on a substrate, as well as by measurements of the average spray droplet diameters, velocities, temperatures, and heat transfer coefficients at the cryogen-substrate interface; all as a function of distance from the nozzle tip. RESULTS: Size of spray cones and sprayed areas vary with distance and nozzle. Average droplet diameter and velocity increase with distance in the vicinity of the nozzle, slowly decreasing after a certain maximum is reached. Spray temperature decreases with distance due to the extraction of latent heat of vaporization. At larger distances, temperature increases due to complete evaporation of spray droplets. These three variables combined determine the heat transfer coefficient, which may also initially increase with distance, but eventually decreases as nozzles are moved far from the target. CONCLUSIONS: Sprayed areas and heat extraction efficiencies produced by current commercial nozzles may be significantly modified by varying the distance between the nozzle and the sprayed surface.

Cryotherapy↗

PubMed2001

Cryogen spray cooling in laser dermatology: effects of ambient humidity and frost formation.

BACKGROUND AND OBJECTIVE: Dynamics of cryogen spray deposition, water condensation and frost formation is studied in relationship to cooling rate and efficiency of cryogen spray cooling (CSC) in combination with laser dermatologic surgery. STUDY DESIGN/MATERIALS AND METHODS: A high-speed video camera was used to image the surface of human skin during and after CSC using a commercial device. The influence of ambient humidity on heat extraction dynamics was measured in an atmosphere-controlled chamber using an epoxy block with embedded thermocouples. RESULTS: A layer of liquid cryogen may remain on the skin after the spurt termination and prolong the cooling time well beyond that selected by the user. A layer of frost starts forming only after the liquid cryogen retracts. Condensation of ambient water vapor and subsequent frost formation deposit latent heat to the target site and may significantly impair the CSC cooling rate. CONCLUSIONS: Frost formation following CSC does not usually affect laser dosage delivered for therapy of subsurface targets. Moreover, frost formation may reduce the risk of cryo-injury associated with prolonged cooling. The epidermal protection during CSC assisted laser dermatologic surgery can be further improved by eliminating the adverse influence of ambient humidity.

Aerosol Propellants↗

PubMed2000

Use of bolus intraperitoneal aminoglycosides for treating peritonitis in end-stage renal disease patients receiving continuous ambulatory peritoneal dialysis and continuous cycling peritoneal dialysis.

Peritonitis is the most common complication of peritoneal dialysis (PD) and accounts for the most drop-out from PD among patients with end-stage renal disease (ESRD). Antibiotic protocols to treat peritonitis recommend initial treatment for both gram-positive and gram-negative infections, pending culture results. Current literature also suggests comparable therapeutic success using bolus (single-dose) parenteral aminoglycosides to treat systemic gram-negative infections compared to conventional divided-dose aminoglycosides. The single bolus dose antibiotic regimen has the potential for reduced nephrotoxicity and ototoxicity. We therefore hypothesized that intermittent bolus dose intraperitoneal (i.p.) aminoglycosides may be superior to conventional continuous dose i.p. aminoglycosides in treating dialysis-associated peritonitis, and have fewer side effects. Six patients with clinical peritonitis were treated with single, bolus-dose, i.p. gentamicin or tobramycin (5 mg/kg ideal body weight), range 250-440 mg (mean: 355 +/- 68.25 mg) at the start of therapy. No patient grew gram-negative organisms; aminoglycosides were therefore not repeated. Three patients used four continuous ambulatory peritoneal dialysis (CAPD) exchanges per day; three patients used six nightly continuous cycling peritoneal dialysis (CCPD) exchanges with a daytime dwell. Mean PD aminoglycoside clearance was 6.75 +/- 2.27 mm3/min; mean urinary aminoglycoside clearance was 5.75 +/- 1.14 mm3/min. Mean blood aminoglycoside elimination t1/2 was 29.27 +/- 3.55 hours, with a mean blood level of 3.18 +/- 1.45 micrograms/mL 72 hours after initial therapy, and 1.52 +/- 0.81 micrograms/mL 96 hours after initial therapy. Peritoneal equilibration test (PET) scores before and after aminoglycoside administration (performed a mean of 4.6 months apart) were 0.672 +/- 0.097 and 0.705 +/- 0.092 respectively (p = 0.321). Comparative audiograms using pure-air tone conduction with frequencies from 250-12,000 Hz were done within 24 hours of aminoglycosides and again when therapy was complete (mean: 17 days). No significant changes were seen. While efficacy of bolus versus conventional-use aminoglycosides could not be definitely established, the kinetics of bolus aminoglycosides suggests that therapeutic blood levels persist for 72-96 hours and that the risk for oto/vestibular toxicity is negligible. We conclude that use of bolus i.p. aminoglycosides is safe, achieves therapeutic blood levels for extended intervals, demonstrates no clinical oto/vestibular toxicity, is cost-effective, and is a convenient strategy for patients and nursing staff.

Anti-Bacterial Agents↗

PubMed1999

Use of bolus intraperitoneal iron dextran in continuous ambulatory peritoneal dialysis or continuous cyclic peritoneal dialysis patients receiving recombinant human erythropoietin.

Impaired erythropoiesis in continuous ambulatory peritoneal dialysis (CAPD) or continuous cyclic peritoneal dialysis (CCPD) patients receiving recombinant human erythropoietin (rHuEPO) is most often secondary to iron deficiency, either as a result of poor intestinal absorption or failure to take oral supplements as prescribed. The inconvenience of giving intravenous (i.v.) iron dextran (ID) to CAPD/CCPD patients precluded its use in this population. We therefore examined the efficacy of bolus intraperitoneal (i.p.) iron dextran (1000 mg) on erythropoiesis in a pilot study of 14 CAPD/CCPD patients. The patients ranged in age from 23-81 years, and all had iron deficiency (transferrin saturation 6%-23%; mean: 15.2% +/- 1.34%). Of the 14 patients studied, 13 were receiving rHuEPO. Pre-treatment hematocrit (Hct) ranged from 21%-38% (mean: 30.2% +/- 1.37%). After infusion of 2 L Dianeal (Baxter Healthcare Corp., Deerfield, Illinois, U.S.A.), 500 mg of undiluted ID was administered directly into the Tenckhoff catheter and subsequently flushed with 30 mm3 normal saline. The peritoneal dialysis (PD) exchange containing ID then dwelled for a period not < 6 hours before standard PD resumed. A second 500 mg dose ID was given to each patient by the same protocol 3-86 days later (mean: 14 days). No complications were seen. No patient complained of abdominal pain or other subjective symptoms during infusion or during the dwell. Repeat iron studies done 1-7 months post ID (mean: 2.8 months) showed a 1.1-fold to 4.9-fold increase (mean: 1.4-fold) in mean iron levels (40.4 +/- 3.9 mg/dL versus 57.5 +/- 5.5 mg/dL, p = 0.036); a 1.1-fold to 5.2-fold increase (mean: 1.6-fold) in mean transferrin saturation (15.2% +/- 1.3% versus 24.5% +/- 2.6%, p = 0.008); a 1.01-fold to 1.60-fold increase (mean: 1.12-fold) in mean Hct (30.2% +/- 1.37% versus 33.8% +/- 1.5%; p = 0.042). The mean dose of rHuEPO was statistically unchanged (170.0 +/- 47.4 U/kg body weight versus 178.8 +/- 49.6 U/kg body weight per week; p = 0.841). Peritoneal equilibration test (PET) score 1-4 months post ID (mean: 2 months) was 0.778 +/- 0.02 compared with a PET score at baseline of 0.767 +/- 0.03 (p = 0.734). No significant delta was observed in blood urea nitrogen (BUN) or creatinine values. We conclude that use of bolus i.p. ID is safe, effective, and convenient, and demonstrates no short-term negative effect on peritoneal membrane integrity. Long-term effects have yet to be determined.

Adult↗

PubMed1995

Combined ultrasound and fluorescence spectroscopy for physico-chemical imaging of atherosclerosis.

This paper describes a combined ultrasonic and spectroscopic system for remotely obtaining physico-chemical images of normal arterial tissue and atherosclerotic plaque. Despite variations in detector-tissue separation, R, fluorescence powers corresponding to pixels in the image are converted to the same set of calibrated units using distance estimations from A-mode ultrasound reflection times. An empirical model, validated by Monte Carlo simulations of light propagation in tissue, is used to describe changes in fluorescence power as a function of R. Fluorescence spectra of normal and atherosclerotic human aorta obtained with this system are presented as a function of R. To compensate for changes in fluorescence power with R, the empirical model was used in each case to calculate the fluorescence power at a constant reference value of R(Rref = 1.67 mm). Prior to compensation, tissue fluorescence power decreased more than a factor of two as R was increased from 2.5 to 5 mm. Following compensation, the fluorescence power varied less than +/- 10% of the average compensated peak. The chemical composition of each sample was determined by fitting its fluorescence spectrum (in calibrated units) to a model of tissue fluorescence incorporating structural protein and ceroid fluorescence, as well as structural protein and hemoglobin attenuation. Parameters of the fit were used to classify tissue type. Without compensation for distance variation, classification of tissue type was frequently incorrect; however, with compensation, predictive value was high. A 1-D chemical image of a section of human aorta containing both normal and atherosclerotic regions obtained with this system is also presented. After compensation for detector-sample separation, tissue classifications along the cross-section closely resemble those obtained from histology. Regions of elevated ceroid concentration and intimal thickening are clearly observable in the resultant chemical image. The potential value of this type of system in the diagnosis and treatment of coronary artery disease is discussed.

Aorta↗

PubMed1993

Monte Carlo fluorescence verification of experimental results for the combined ultrasonic and spectroscopic imaging of coronary artery disease.

A system is being tested that combines fluorescence spectroscopy and intravascular ultrasound to image both chemical composition and structure of arterial tissue in vitro. In this system, distances obtained from A-mode ultrasound will be used to compensate for decreases in fluorescence intensity due to the detector-sample separation distance r. For concentrated rhodamine, a fluorescent dye, compensation has been experimentally achieved assuming fluorescence is emitted isotropically and decreases as 1/r2. For dilute rhodamine and human arterial tissue, however, compensation must be achieved with different models, since light penetration into the sample is more significant. Using optical properties consistent with those of the aforementioned samples, experimental results are successfully simulated with a Monte Carlo model for tissue fluorescence. Angular profiles are presented that demonstrate the quantitative difference between the fluorescence of these mediums. The profiles support the hypothesis that, although fluorescence is emitted isotropically within tissue, the angular distribution of light exiting the tissue is not isotropic due to reabsorption events.

Aorta↗

PubMed1990

Pesticides and their control.

1. Pesticides account for a small but important number of acute human poisonings. 2. When considering interventions for pesticide poisoning in the workplace, interaction may occur on a continuum from a one-to-one encounter to planning or educating in the context of the aggregate. 3. Occupational health nurses need to be aware of the potential harm inherent in human exposure to pesticides and to be prepared to initiate intervention strategies at all phases of injury--pre-event, event, and post-event.

Health Education↗

PubMed1986

Expression in Escherichia coli of synthetic human interleukin-1 alpha genes encoding the processed active protein, mutant proteins, and beta-galactosidase fusion proteins.

We have synthesized, cloned, and expressed the coding region for the C-terminal 159 amino acids (aa) of the human active interleukin polypeptide hormone IL-1 alpha. The sequence was assembled in stages and includes preferred Escherichia coli codons and unique restriction sites. The coding region was cloned on a multicopy plasmid vector adjacent to signals for transcription and translation that directed synthesis of 6% of total E. coli protein as IL-1 alpha. Active IL-1 alpha mutants that have a C-terminal additional eleven aa and that have N-terminal deletions of six and fourteen aa are described. Plasmids expressing beta-galactosidase fusion proteins with various parts of IL-1 alpha at their N-termini were constructed.

Base Sequence↗

PubMed1982

Building a ladder.

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Career Mobility↗

PubMed1977

Differential effect of pre- and postnatal litter size reduction on body weight and development of stress response in the rat.

The postnatal development of pups belonging to the small, prenatally reduced litters (PRN) was compared to that of pups of the postnatally reduced litters (PST) and to that of pups of intact, normal-size litters (CON). Body adrenal and pituitary weight gain as well as maturation of the pituitary-adrenal system were enhanced in the PRN and PST pups as compared to the CON pups in the 3 postnatal weeks. However, significant differences in some data between the PRN and PST pups were found, indicating the more pronounced beneficial effect of the prenatal reduction of litter size. The postnatal litter size reduction abolished the weight gain of the testes. The prenatal reduction of litter size resulted in a similar, although less pronounced negative effect.

Adrenal Glands↗