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Biomedical subjects

A Davis

Publications and source records attributed to A Davis.

At least 451 records · Page 25Linked to original sources
PubMedDate not supplied

Comparison of the polyvinyl alcohol sponge and expanded polytetrafluoroethylene subcutaneous implants as models to evaluate wound healing potential in human beings.

Our current understanding of the complex processes involved in wound healing is based mainly on studies of animal models. Although this information has been useful, it may not totally reflect the response found in human beings. For example, human beings have a tendency to either "overheal," as seen in keloids and hypertrophic scar formation, or have deficient healing, as seen in chronic ulcer formation. No animal models are available to analyze these human clinical pathologic conditions. Therefore the objective of this study was to analyze the wound healing response in a large population (n = 40) of normal healthy human beings as a first step to begin studies of abnormal human wound healing. Simultaneously, a comparison was made between the polyvinyl alcohol implant and the expanded polytetrafluoroethylene implant model. Under sterile conditions with the use of local anesthesia, two preweighed polyvinyl alcohol implants and two standard 6 cm expanded polytetrafluoroethylene implants were placed subcutaneously in the upper arm of each subject. High-performance liquid chromatography was used to quantitate isoleucine and hydroxy-l-proline in acid hydrolysates of each implant. Isoleucine was used as an indicator of protein content in the tissue sample, whereas hydroxyproline reflected collagen content. No infectious or hemorrhagic complications were found in the 40 volunteers included in the study. No significant difference was found in isoleucine or hydroxy-l-proline content between postoperative day 7 polyvinyl alcohol implants and day 14 polyvinyl alcohol implants. In contrast, both isoleucine and hydroxy-l-proline content were significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 implants (p < 0.005 and p < 0.001, respectively). In addition, the ratio of hydroxy-l-proline to isoleucine was significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 expanded polytetrafluoroethylene and both day 7 and day 14 polyvinyl alcohol implants (p < 0.001). This observation suggests that by 14 days implantation of expanded polytetrafluoroethylene stimulated an increased deposition of collagen. No significant differences were found in the hydroxy-l-proline to isoleucine ratios among day 7 expanded polytetrafluoroethylene, day 7 polyvinyl alcohol, and day 14 polyvinyl alcohol implants. Histologic analyses correlated with the biochemical findings. These results suggest that expanded polytetrafluoroethylene may be the preferred implant for studies designed to examine pathologic processes associated with retarded wound healing. In contrast, the polyvinyl alcohol implant may be better suited for studies where a low background response is required. Moreover, the extreme variability in normal healthy volunteers seen in this study correlates clinically with the finding that, among the normal adult human population, there is a heterogeneous wound healing response.

Journal Article↗
PubMedDate not supplied

Immunoassay for detection of cocaine/metabolites in oral fluids.

There is growing interest in the use of alternate biological fluids for drug testing. An advantage of oral fluids is that collection can be made from individuals under direct observation without undue embarrassment or invasion of privacy. This study evaluated the STC Cocaine Metabolite MICRO-PLATE EIA for use in detection of cocaine and metabolites in oral fluids. Intra- and interassay precision of the EIA was < 10%. The EIA was cross-reactive to benzoylecgonine (100%), cocaine (> 12.9%), and cocaethylene (13.8%), but did not demonstrate detectable cross-reactivity with other commonly encountered medicants. Evaluation of a series of potential adulterants of oral fluids indicated that common household chemicals and foodstuffs did not alter the outcome of EIA testing for cocaine metabolite. Analysis by EIA and by gas chromatography-mass spectrometry (GC-MS) of oral fluids and urine specimens collected from current drug users in treatment programs and subjects participating in research studies involving controlled dosing of cocaine provided assessment of the clinical sensitivity and specificity of the STC Cocaine Metabolite EIA. Analysis of the data by means of receiver operating characteristic (ROC) plot indicated that the optimal cutoff concentration for the oral fluids EIA was 10 ng/mL. In comparison to GC-MS (10-ng/mL combined cutoff concentration for cocaine and benzoyleogonine), the EIA (10-ng/mL cutoff concentration) demonstrated a sensitivity, specificity, and accuracy of 95%, 82%, and 88%, respectively. The oral fluids EIA was slightly less sensitive than the urine EIA (300-ng/mL cutoff concentration) for the detection of cocaine metabolite with a sensitivity, specificity, and accuracy of 73%, 85%, and 88%, respectively. Overall, testing of oral fluids for cocaine metabolite with the STC Cocaine Metabolite MICRO-PLATE EIA appears to offer a viable alternative to urine for detection of recent cocaine use.

Cocaine↗
PubMedDate not supplied

Structured skin care regimen to prevent perineal dermatitis in the elderly.

A preliminary investigation was conducted to determine the efficacy of a structured skin care regimen to prevent perineal dermatitis in incontinent geriatric psychiatry patients. A 10-week, prospective, clinical trial was conducted (n = 15). Four weeks (weeks 2 to 5) were devoted to monitoring the unstructured pretreatment nursing skin care practice and to determining the incidence of perineal dermatitis in incontinent patients. Four weeks (weeks 7 to 10) were also spent implementing and observing the structured nursing skin care regimen. The study revealed that 33% (three) of the subjects in the unstructured skin care group and 33% (two) of the subjects in the structured skin care group had perineal dermatitis. In subjects with a combination of urine and stool incontinence perineal dermatitis developed within 2 days. The findings suggest that perineal dermatitis occurs quickly in the presence of urine and stool incontinence. Further research is needed to validate the efficacy of a structured skin care regimen to prevent perineal dermatitis.

Aged↗
PubMedDate not supplied

A rapid screening-level method to optimize location of infiltration ponds.

A rapid-screening technique was developed to identify lithologies that best disperse artificial recharge via surface infiltration and minimize effects on ground water chemistry. The technique prospectively evaluates basin infiltration rates and water chemistry influences by integrating geotechnical, hydraulic, and water quality data with column test data and numerical modeling. The technique was validated using field data collected from surface infiltration basins designed to recharge ground water pumped from the Pipeline pit gold mine in Nevada. Observed recharge rates at these infiltration sites correlated most significantly with depth to groundwater, with basins in coarse-grained lithologies performing better (0.45 to 0.85 m/day) than those with fine-grained layers (< 0.30 m/day). Observed water quality resulting from leaching of the previously unsaturated vadose zone showed a transitory (< six months) increase in solute concentrations followed by a decrease to baseline conditions, a phenomenon also observed in column tests that leached native soils with local ground water. Leaching of fine-grained soils with evaporites resulted in greater solute concentrations (TDS > 2000 mg/L) than coarse-grained soils (< 1200 mg/L). The results of HYDRUS_2D simulations using the accumulated data as input were in agreement with observed ground water chemistry downgradient of the infiltration basins for a variety of lithologies. Sites for infiltration basins can be rapidly screened to include areas with greatest depth to groundwater and in coarsest alluvial sediments, and impact to ground water chemistry can be reliably predicted using computer modeling and column test results.

Computer Simulation↗
PubMedDate not supplied

Estimating recharge distribution by incorporating runoff from mountainous areas in an alluvial basin in the Great Basin region of the southwestern United States.

A method is described to estimate the distribution of ground water recharge within hydrographic basins in the Great Basin region of the southwestern United States on the basis of estimated runoff from high mountainous areas and subsequent infiltration in alluvial fans surrounding the intermontane basins. The procedure involves a combination of Geographic Information System (GIS) analysis, empirical surface-runoff modeling, and water-balance calculations. The method addresses the need to develop and incorporate constraints on the distribution of recharge in regional-scale ground water flow modeling of arid and semiarid environments. The conceptual approach and methodology were developed for Crescent Valley, Nevada. However, the concept and method are generally applicable to any region where excess precipitation in upland areas is conveyed to lower elevations before it infiltrates to recharge the ground water system. Application of the procedure to a ground water flow model of Crescent Valley appears both qualitatively and quantitatively to result in a more accurate representation of actual recharge conditions than might otherwise have been prescribed.

Environmental Monitoring↗
PubMedDate not supplied

The use of modular nutrients in pediatrics.

BACKGROUND: Nutrient modules are commonly used by pediatricians and dietitians. There is no readily available current literature to which those using nutrient modules can refer. Therefore, we review nutrient module composition, module use in pediatrics, and complications associated with the use of nutrient modules. METHODS: Using an online database, Meduline, we searched the literature from 1996 through 1995. RESULTS: Nutrient modules are single or multiple nutrients that can be combined with a diet to add nutrients or to change the composition of the diet. These nutrients exist as a food or as medically compounded elements of a diet but alone are not complete foods. DISCUSSION: The addition of modules to a diet can alter the composition of a diet so that a single nutrient may become deficient and the diet cannot support normal growth and development. With use of nutrient modules, diets can be prepared to meet the specific needs of children with common or rare nutritional problems. CONCLUSION: Health care providers who use nutrient modules must understand the importance of diet composition and the careful monitoring of pediatric patients.

Child↗
PubMedDate not supplied

Hearing aid possession in the population: lessons from a small country.

The results of several studies on hearing aid use in the Welsh population were considered to investigate some general principles on determinants of such use within the general populations of developed countries. Overall hearing aid possession and use were not found to have changed significantly over the past 18 years, remaining at 4 per cent having obtained hearing aids and 3 per cent using them. The possession figures were consistent across all methodologies used. Higher hearing aid use in the post-industrial valleys (in which the traditional industries of coal mining and steel production had disappeared) was explained entirely by a higher level of reported hearing difficulties there. In all populations, less than 20 per cent of those reporting difficulties possessed hearing aids. Whether a hearing aid had been obtained free of charge from the National Health Service or purchased privately did not influence whether it was still used. It was concluded that an effort to improve the acceptability of hearing aids and reduce their stigma is required.

Aged↗
PubMedDate not supplied

Comparability of hamster with human faecal unconjugated bile acids in a model of colorectal cancer.

The relationship between experimental colorectal carcinogenesis and bile acids has usually been investigated in the rat, a species with a markedly different bile acid profile from man. In this study, we show that the hamster faecal bile acid profile is similar to that in man. Rectal cancer was induced in hamsters using twice weekly instillations of N-methyl-N-nitro-N-nitrosoguanidine (MNNG) for 4 weeks at doses of 1-8 mg kg-1. The medcian (range) faecal bile acid concentrations of tumour-bearing hamsters (0.52, 0.46-0.84 mumoles g-1 faeces) was reduced compared to controls (1.08, 0.95-1.65, mumoles g-1) and non-tumour bearing MNNG treated hamsters (1.18, 0.64-1.42 mumoles g-1), largely due to a decrease in cholic acid derivatives (all p less than 0.05) at least). This model may be more suitable for studying the relationship between colorectal cancer and bile acids.

Animals↗
PubMedDate not supplied

Effects of dietary N-3 and saturated fats on growth rates of the human colonic cancer cell lines SW-620 and LS 174T in vivo in relation to tissue and plasma lipids.

Ninety nude mice were inoculated subcutaneously with 1 x 10(7) cells of the human colonic cancer cell lines, SW-620 and LS174T. Tumour growth was assessed weekly for three weeks whilst the animals were receiving one of three diets: control (4.6% fat), coconut (20% fat, saturated fatty acids) and Maxepa (20% fat; n-3 fatty acids). At the end of the study SW-620 tumour weights (mean +/- SD, gm) were: control = 0.38 +/- 0.22, coconut = 0.43 +/- 0.31, Maxepa 0.20 +/- 0.16; the LS174T tumour weights were control = 1.33 +/- 1.27, coconut = 0.47 +/- 0.74, Maxepa = 0.38 +/- 0.56 (p less than 0.001, analysis of covariance). The Maxepa diet produced significant retardation in tumour growth (p less than 0.001). This was associated with reduced levels of linoleic acid and arachidonic acid in adipose tissue and tumour lipids with incorporation of n-3 fatty acids (all p less than 0.01 at least, analysis of variance). Moreover, the Maxepa diet produced significant reductions of plasma cholesterol, phospholipids and triglycerides (all p less than 0.01).

Adipose Tissue↗
PubMedDate not supplied

Weekend college.

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Curriculum↗