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L W Davidson

Publications and source records attributed to L W Davidson.

10 recordsLinked to original sources
PubMed1993

Role of the leukocyte in endotoxin-induced alterations of the red cell membrane. Second place winner of the Conrad Jobst Award in the Gold Medal paper competition.

Sepsis and endotoxemia are known to be associated with alterations in the red cell membrane that result in diminished flexibility. This decreased flexibility may be responsible, in part, for the microcirculatory abnormalities accompanying sepsis. The etiology of these sepsis-associated changes remains unclear. This study evaluates the role of the white blood cell in these abnormalities. Specimens were obtained from 44 volunteers and divided into two treatment groups. Group I specimens were incubated with Escherichia coli endotoxin (2 micrograms/ml) followed by removal of the white blood cells. The white blood cells were removed from group II specimens before endotoxin incubation. Paired, saline-incubated samples served as controls. After incubation, washed erythrocytes were evaluated for deformability and membrane viscosity. Deformability was assessed by filtration through 4.7-microns membranes. Red cell deformability was expressed as filtration rate (volume of cells per second per square centimeter). Membrane viscosity was assessed by fluorescent spectroscopy of cells into which the membrane probe 1(4-(trimethylamino)-phenyl)-6-phenyl-1,3,5-hexatriene had been incorporated. Results were expressed as anisotropy. Endotoxin resulted in a significant increase in erythrocyte membrane viscosity (experimental, 0.296 +/- 0.002 vs. control, 0.284 +/- 0.002, P < 0.001). This was reflected by a significant decrease in cellular deformability (experimental, 142.55 +/- 6.55 vs. control, 157.86 +/- 8.63, P < 0.01). However, these alterations are not a direct effect of endotoxin, but require the presence and participation of the white blood cell and/or its mediators (experimental, 0.301 +/- 0.002 vs. control, 0.300 +/- 0.001, P = NS).

Awards and Prizes↗
PubMed1979

The accumulation and elimination of diflubenzuron by fish.

In summary, diflubenzuron is accumulated from water into fish tissues at levels up to 80 fold within 24 hr when fish are exposed to concentrations of 10 ppb. Within the concentration range of 1-10 ppb, the amount accumulated in a 24 hr exposure is proportional to concentration. After 24 to 48 hr exposure fish degrade and eliminate diflubenzuron and the excretory products are neither the parent compound nor p-chlorophenylurea. The amount of diflubenzuron remaining in fish tissues with time is dependent on the reduction of residue concentration in water; however, the potential for degradation and elimination is very great.

Animals↗
PubMedDate not supplied

Outcomes of sudden cardiac arrest treated with defibrillation by emergency medical technicians (EMT-Ds) or paramedics in a two-tiered urban EMS system.

OBJECTIVE: Controversy exists as to the effectiveness of defibrillation by emergency medical technicians (EMT-Ds) in reducing mortality from cardiac arrest in two-tiered EMS systems. This study was performed to assess the impact of EMT-Ds on outcome of sudden cardiac death in a small, urban, modified two-tiered EMS system. METHODS: This was a retrospective, unmatched case-control study comparing the outcomes of patients suffering sudden cardiac death treated by EMT-Ds with paramedic (EMT-P) backup with the outcomes of patients treated by EMT-Ps as first responders. Outcomes were defined as survival to the following endpoints: hospital admission, hospital discharge, and discharge with normal neurologic function (neurologic survival). Differences between groups were considered significant if p < or = 0.05 by Fisher's exact test or t-test. RESULTS: Three hundred twenty-two patients suffered out-of hospital sudden cardiac deaths over a three-year period and met study inclusion criteria. There were no significant differences in mean age, sex distribution, or incidence of ventricular fibrillation as the presenting rhythm between the groups. Rates of survival to admission, survival to discharge, and neurologic survival were 25.8%, 8.1%, and 5.6%, respectively. Corresponding survival rates for 46 patients treated first by EMT-Ds were 19.6%, 8.7%, and 4.3%. For 276 patients treated by EMT-Ps as first responders, the rates were 26.8%, 8.0%, and 5.8%. There were no significant differences in survival rates between the two response modes, despite a significantly shorter response interval for EMT-Ds (3.6 +/- 1.8 min, vs 4.6 +/- 2.0 min for EMT-Ps). There were likewise no significant differences in survival rates between the two response modes when only patients in ventricular fibrillation or ventricular tachycardia were considered. There were no significant differences in survival rates grouped by presenting rhythm, with the exception of 9.6% neurologic survival in witnessed ventricular fibrillation as compared with 0% in asystole. CONCLUSION: EMT defibrillation had no impact on outcome of sudden cardiac death in this small, urban, two-tiered EMS system. Survival rates were similar to those reported for other such systems. However, power to detect significant differences was low, and further study is indicated. Controlled multicenter trials are recommended.

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