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Biomedical subjects

C Powell

Publications and source records attributed to C Powell.

At least 127 records · Page 7Linked to original sources
PubMedDate not supplied

Plasma membrane-resident glucocorticoid receptors in rodent lymphoma and human leukemia models.

The presence of the glucocorticoid (GC) receptor is required for GC-evoked apoptosis. However, the explicit mechanism of involvement of this receptor continues to be debated. Employing the murine (S-49) and human (CCRF-CEM) lymphoid cell lines, we demonstrated that this response requires a specialized form of the glucocorticoid receptor (GR) that resides in the plasma membrane (mGR). Our studies of mGR have been done in our stable mGR-enriched (by sequential cell separation--immunopanning, fluorescent cell sorting, soft agar cloning) S-49 and CCRF-CEM cells. Direct and indirect immunofluorescent studies of live intact cells showed GR-specific periplasma membrane staining. Immunoanalysis by flow cytometry demonstrated abundant mGR in mGR++ cells, but only barely detectable mGR in mGR-- cells. Western blot and autoradiographic analyses of immunoprecipitated membrane extracts from these cells show they contain immunoreactive and competitively labeled high Mr receptor ranging from 94 to 150 kDa. Using mGR++ CCRF-CEM cells and three synchronization procedures (double thymidine, thymidine/colcemid, and colcemid blocks), we have investigated the influence of cell cycle on regulation and function of mGR. Both mGR expression and GC-mediated lymphocytolysis appear highest at late S-G2/M. Analysis of mGR in lymphocytes of several leukemic patients indicated differences in the levels of receptor expression. These findings might provide diagnostic clues about patients' differential response to steroid therapy and potential therapeutic avenues for effective treatment of hormone-responsive leukemic patients.

Animals↗
PubMedDate not supplied

Engineering dental pulp-like tissue in vitro.

Injury or infection of adult dental pulp often necessitates root canal therapy. This terminates dentin formation and subsequent tooth maturation. In addition, the synthetic materials currently utilized to replace lost tooth structure are not capable of completely replacing the function of the lost tissue, and often fail over time. This report describes a technique to engineer new pulp-like tissues utilizing cultured cells and synthetic extracellular matrices. Fibroblasts were obtained from human adult dental pulps and multiplied in culture. These cells were subsequently seeded onto synthetic matrices fabricated from fibers (approximately 15 microns in diameter) of polyglycolic acid (PGA). The pulp-derived fibroblasts adhered to the fibers, proliferated, and formed a new tissue over 60 days in culture with a cellularity similar to that of native pulp. These tissues may find application in the regeneration of oral tissues and may provide novel systems in which to study the biocompatibility of materials and chemicals used in dentistry.

Adult↗
PubMedDate not supplied

Evaluation of Opsite catheter dressings for parenteral nutrition: a prospective, randomized study.

A prospective, randomized study compared the use of Opsite and standard gauze/tape dressings in 261 patients receiving parenteral nutrition. Eighty-four patients had a source of external drainage and were evaluated as a separate group. Catheter-related sepsis was assessed by blood culture, catheter tip culture, clinical sepsis, and clinical defervescence of fever after catheter removal. Although no statistically significant difference between Opsite and standard dressings could be identified, Opsite-treated patients consistently had increased parameters of catheter-related sepsis in all comparisons. As used here, Opsite is probably not a suitable catheter dressing system for parenteral nutrition.

Bandages↗
PubMedDate not supplied

Clinical effect of nonthrombotic total parenteral nutrition catheters.

Radiographic evidence of subclavian vein thrombosis has been shown to occur in 33% of total parenteral nutrition patients. This incidence can be significantly reduced to 8% when heparin is administered concomitantly in total parenteral nutrition solutions. To evaluate the thrombotic risk of a newly developed polyurethane catheter, 20 concurrent patient pairs were prospectively cannulated with either a standard polyethylene catheter plus heparin or a polyurethane catheter without heparin in a sequential statistical study. Radionuclide venograms (Tc99m) were performed within 72 hr of catheterization, at biweeky intervals, and at termination of total parenteral nutrition administration. No patient in either group developed clinical (pain, arm swelling, collateral veins) or venogram evidence of thrombosis after catheterization during an overall cannulation period of 820 days. Use of polyurethane catheters and elimination of heparin in total parenteral solutions may be particularly important since contraindications to heparin use are common. Additionally, heparin elimination can decrease admixture work and confusion (ie, subcutaneous heparin double dosing) without increasing the risk of subclavian vein thrombosis.

Adult↗
PubMedDate not supplied

Heparin does not reduce catheter sepsis during total parenteral nutrition.

Although it is recognized that the addition of heparin to total parenteral nutrition solutions reduces subclavian vein thrombosis from percutaneous polyethylene catheters, it does not affect the low thrombosis rate associated with polyurethane catheters. It has been suggested that heparin also reduces catheter sepsis during total parenteral nutrition. We reviewed the sepsis rate in 86 patients randomized to receive iv nutrition with or without heparin through polyethylene, polyvinyl, and polyurethane catheters. Blood was drawn from febrile patients for culture; if positive, catheters were removed and the tips cultured. Catheters were considered infected if blood and catheter tips were positive, or if fever disappeared within 48 hr after catheter removal, even if cultures were negative. Catheter sepsis occurred in two patients in both groups. It appears that heparin does not reduce sepsis from percutaneous subclavian vein catheters. Although its use may be indicated to reduce thrombosis associated with polyethylene catheters, there is no indication for its use to reduce sepsis with either type of catheter.

Bacterial Infections↗
PubMedDate not supplied

Risk of infection accompanying the use of single-lumen vs double-lumen subclavian catheters: a prospective randomized study.

A prospective study was undertaken to compare the risks of a multiple-lumen catheter to bilateral subclavian catheters in patients receiving total parenteral nutrition (TPN). All patients had one preexisting subclavian catheter. Patients were randomized into two groups: one group received a double-lumen catheter via a guidewire change of the preexisting single-lumen subclavian catheter. In the second group, a second single-lumen subclavian catheter was inserted and the preexisting single-lumen catheter was changed over a guidewire. Patients were followed by the Nutrition Support Service and were managed identically with regard to solutions given, catheter care, dressing changes, monitoring of mechanical complications, and evaluation of fever. Total infection rates in both groups were identical (22.7%). The difference in mechanical complication rates in the double-lumen catheter group (9%) and the group with bilateral single-lumen catheters (22.7%) was not significant by Fischer's exact test. The multiple-lumen catheter is superior in convenience and as safe as bilateral single-lumen catheters.

Catheters, Indwelling↗
PubMedDate not supplied

Effect of frequent guidewire changes on triple-lumen catheter sepsis.

Frequent guidewire changes of single-lumen (SLC) and triple-lumen (TLC) catheters have been proposed to decrease catheter sepsis. We placed TLC in 126 patients needing total parenteral nutrition (TPN) and multiple venous access, prospectively randomizing them to two groups: group I received a guidewire change every 3 days, and group II received guidewire changes for mechanical or septic complications only. Tips were cultured at each line change and tips and blood for each septic episode. Catheter sepsis was defined by the criteria of the Association for Practitioners in Infection Control (APIC). There were 67 positive cultures in 52 patients, but most produced very few colonies or grew the same organisms in other infection sites. Forty-seven% of all cultures grew Staphylococci, and 23% grew Candida. APIC-defined catheter sepsis was detected in 12.7% of group I and 15.9% of group II. Although we observed no statistically significant difference in the two techniques, if we assume that a 20% difference in the incidence of catheter-induced sepsis would be important to detect, the probability of failing to detect such a difference is 0.24 with an 0.05 level of significance (two-sided). Prophylactic guidewire changes did not alter the incidence of catheter sepsis in patients with TLC who required TPN. The high rate of sepsis and Candida infection may be due to the critical illness of the immunocompromised population studied.

Adult↗
PubMedDate not supplied

The challenge of the Children's Charter: rhetoric vs reality.

The rights of children are not enshrined in statute. However, over recent years, a number of organizations such as Action for Sick Children and The Children's Trust, Tadworth, have produced guidelines related to the rights of children and their families in hospital. The voluntary sector has led the way in influencing policy makers. This is exemplified in the publication of the Department of Health's draft Children's Charter. This article explores the strengths, weaknesses, opportunities and threats of this recent innovation.

Child↗
PubMedDate not supplied

Development of an introductory course in child protection.

The maltreatment of children is a significant public health and social problem. Healthcare professionals have a crucial role to play working with other agencies to protect children from abuse and neglect. The need for training, support and clinical supervision in this work has been identified. This article discusses the collaborative work that led to the establishment of an introductory course in child protection (English National Board 970) at one school of nursing and midwifery and outlines the benefits of undertaking such a course. The course has attracted participants from a range of healthcare settings and has proved to be well evaluated and oversubscribed. Practitioners have returned to their work setting with increased awareness of child maltreatment and an understanding of the need for a proactive approach to child protection.

Child↗