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Biomedical subjects

R R White

Publications and source records attributed to R R White.

At least 37 records · Page 2Linked to original sources
PubMed1997

Prostatic ductal system in rats: tissue-specific expression and regional variation in stromal distribution of transforming growth factor-beta 1.

BACKGROUND: Regional variations in stromal-epithelial interactions, mediated through soluble growth factors, may be responsible for differences in epithelial growth and death observed between regions of the rat prostatic ductal system. Since transforming growth factor-beta 1 (TGF-beta 1) can induce prostatic epithelial cell death in vitro and in vivo, we examined the localization and production of TGF-beta 1 with respect to the functional regions of the rat prostatic ductal system. METHODS: The distribution of TGF-beta 1 in the rat ventral prostate was examined by immunohistochemistry. Cell type-specific expression of TGF-beta 1 was determined using RT-PCR analysis of prostate epithelial and stromal cell fractions separated by Percoll gradient centrifugation. RESULTS: Immunohistochemical staining of normal prostate revealed regional variations in stromal TGF-beta 1 protein, which was most abundant in the stroma surrounding the degenerative proximal ducts. TGF-beta 1 staining was also tightly associated with the prostatic smooth muscle. Results of RT-PCR experiments confirmed the major source of TGF-beta 1 mRNA in normal rat prostate to be the stroma, with lesser expression by the epithelium. CONCLUSIONS: Stromal TGF-beta 1 was associated with cell death in the adjacent epithelial cell compartment in the prostatic ductal system, and alpha-smooth muscle actin-positive stromal cells may play a negative growth-regulatory role in the rat ventral prostate through production of TGF-beta 1.

Animals↗
PubMed1997

Residual antimicrobial activity after canal irrigation with chlorhexidine.

We previously reported that the in vitro antimicrobial activity of a 2.0% chlorhexidine endodontic irrigant was equivalent to that of 5.25% sodium hypochlorite. The purpose of this study was to determine if chlorhexidine irrigants could instill substantive antimicrobial activity in instrumented root canals in vitro. Human teeth were instrumented using 2.0% or 0.12% chlorhexidine as irrigants. After instrumentation, the root canals were filled with sterile water, and samples of the root canal fluid were absorbed with paper points at 6, 12, 24, 48, and 72 h after treatment. The paper points were assayed for antimicrobial activity by placing them on agar plate surfaces inoculated with Streptococcus mutans and measuring zones of inhibition. Antimicrobial activity was present in all 2.0% chlorhexidine-treated teeth throughout the 72-h testing period and in most teeth, in relatively lower concentrations, for 6 to 24 h after irrigation with 0.12% chlorhexidine. These results indicate that chlorhexidine instills substantive antimicrobial activity when used as an endodontic irrigant.

Analysis of Variance↗
PubMed1996

Progression of inflammatory myofibroblastic tumor (inflammatory pseudotumor) of soft tissue into sarcoma after several recurrences.

We report a case of inflammatory myofibroblastic tumor (inflammatory pseudotumor) arising in the soft tissue of the right forearm and progressing into frank spindle cell sarcoma after five recurrences and a total span of 12 years. Myofibroblastic nature of the neoplastic spindle cells was shown by electron microscopy and immunohistochemistry. The patient developed multiple pulmonary metastases and died. Although five cases of metastasizing inflammatory myofibroblastic tumors were reported, association of sarcomatous transformation of this entity with metastatic capability was not previously described.

Disease Progression↗
PubMed1996

Effect of immediate and delayed post preparation on apical dye leakage using two different sealers.

Eighty freshly extracted teeth were endodontically prepared and filled with gutta-percha and either a zinc oxide-eugenol-based sealer or AH26 to determine what effect these sealers, with widely differing properties, would have on apical microleakage after either immediate or delayed dowel space preparation. The teeth were randomly assigned to 1 of 4 groups, and the post space was made either immediately after filling or after being stored in 100% humidity for 1 wk. They were then immersed in a 2% methylene blue solution under vacuum, washed, and split longitudinally. The extent of dye penetration was read by five independent observers and the results analyzed. The only significant difference was in the delayed preparation group with zinc oxide-eugenol sealer, which showed greater leakage than the other groups.

Analysis of Variance↗
PubMed1996

Angiomatoid fibrous histiocytoma.

This article reports a case of angiomatoid fibrous histiocytoma (AFH), a rare fibrous tissue tumor with unique clinical characteristics. Formerly, this tumor was classified as angiomatoid malignant fibrous histiocytoma. First described in 1979, AFH was felt to be a variant of malignant fibrous histiocytoma (MFH). One dominant characteristic that differentiates this tumor from the remainder of MFH subtypes is that it most often presents in individuals younger than 20 years of age. The usual MFH occurs in the seventh decade of life. Because of its rarity, AFH has been difficult to classify and, during this current year, has been designated as a separate entity, rather than a subtype of MFH. Clinically, the tumor presents as a soft-tissue mass in the subcutis or deep dermal layers of the body, often presenting on the extremities or neck. Local recurrence has been reported, but mortality figures are very favorable and wide local removal is sufficient treatment.

Age Factors↗
PubMed1995

Failure of ethylene oxide to sterilize extracted human teeth.

OBJECTIVES: The purpose of this study was to determine if ethylene oxide could sterilize extracted human teeth to be used in research. METHODS: An occlusal preparation was cut in freshly extracted molars and a small hole was drilled into the pulp chamber. A suspension of Bacillus subtilis (globigii) endospores, the standard biological monitor used for ethylene oxide sterilization, was injected into the pulp cavity, and the pulp cavity access was filled with composite material and sealed with a light-cured sealant. The teeth were exposed to either a 30 degrees C or 63 degrees C ethylene oxide sterilization process. Following exposure, the teeth were aseptically split and cultured to reveal viable spores. RESULTS: Sixty-four percent of the teeth exposed to "cold" ethylene oxide treatment and 80% of the teeth exposed to the "warm" treatment still contained viable spores. SIGNIFICANCE: Ethylene oxide cannot be relied on to sterilize extracted human teeth. Therefore, before they are used in research, other methods should be used to ensure killing of bloodborne pathogens that may be present within the teeth.

Bacillus subtilis↗
PubMed1995

Infection control in general practice: results of a questionnaire survey.

BACKGROUND: Infection control is an important aspect of quality of care. General practitioners (GPs) have a high throughput of patients, some attending because of a communicable disease, others for investigations or minor operations. This situation provides an opportunity for the spread of infections. This study looked at the development of practice policies on infection control and the need for further information and guidelines. METHODS: A postal questionnaire was sent to 117 practices in a single Family Health Services Authority. The questionnaire contained sections to be completed by a GP and a practice nurse in each surgery. RESULTS: A response rate of 74.5 per cent was obtained. Of the practices replying, 85 per cent did not have a written infection control policy. Sterilization of instruments was carried out in over 90 per cent of surgeries. Autoclaves were used in almost four-fifths of these practices; most did not have any written procedures covering their use. Few practices provided information on procedures for infected patients or staff. A third of practices did not have a needlestick policy, and sharps incidents were not recorded in 42 per cent of surgeries. Three-quarters of practices said that they would welcome guidelines on infection control. Half of the practice nurses thought that more training on infection control was required. CONCLUSIONS: The need for more training and the implications of the information from the study on the development and implementation of guidelines are discussed. Recommendations are made which aim to increase the awareness of this issue by means of guidelines and training focused on practice nurses.

Disinfection↗
PubMed1994

Neuropeptides are potent modulators of human in vitro immunoglobulin E synthesis.

We determined the effect of adrenocorticotropin hormone (ACTH) on the regulation of IgE synthesis. Depending on the concentration, ACTH enhanced or inhibited IgE synthesis in a culture system where IgE synthesis was induced with interleukin-4 (IL-4) and anti-CD40 monoclonal antibody in peripheral blood mononuclear cells. Similar effects on IgE synthesis were observed by adding ACTH-related peptides, e.g. corticotropin-releasing factor (CRF), the inducer of ACTH, or alpha-melanocyte stimulating hormone (alpha-MSH), a cleavage product of ACTH. However, ACTH had no effect on IgG or IgM synthesis in this culture system. ACTH did not act directly on either B or T cells as there was no influence on IgE synthesis in a system using purified B cells alone or co-cultured with T cells. The effect of ACTH on IgE synthesis was mediated by accessory cells. This was shown by priming purified CD14-positive monocytes with ACTH and reconstitution experiments. Therefore, these findings suggest that ACTH and the related peptides CRF and alpha-MSH can influence the microenvironment modulating an IL-4 and anti-CD40 monoclonal antibody driven class switching to IgE via accessory cells.

Adrenocorticotropic Hormone↗
PubMed1994

A comparison of 2.0% chlorhexidine gluconate and 5.25% sodium hypochlorite as antimicrobial endodontic irrigants.

Sodium hypochlorite, as an endodontic irrigant, poses problems including toxicity, odor, and discoloration of operatory items. An equally effective, but safer irrigant is desirable. Therefore, we compared the antimicrobial activity of 2.0% chlorhexidine gluconate with that of 5.25% sodium hypochlorite in an in vitro root canal system. Freshly extracted human teeth with pulpal pathosis were instrumented using chlorhexidine, sodium hypochlorite, or saline as irrigants. Microbiological samples were taken from the teeth immediately after accessing the canal, after instrumentation and irrigation, and after standing in an anaerobic atmosphere for 24 h. Irrigation with chlorhexidine or sodium hypochlorite significantly reduced the numbers of postirrigant positive cultures and colony-forming units compared with saline-irrigated teeth. The number of postirrigant positive cultures and the number of colony-forming units in positive cultures obtained from chlorhexidine-treated teeth were lower than the numbers obtained from sodium hypochlorite-treated teeth, but the differences were not statistically significant.

Analysis of Variance↗
PubMed1993

Crotalidae envenomation in children.

Poisonous snakebites cause a severe envenomation syndrome in children, yet treatment remains controversial. Sixty-seven patients were treated for poisonous snakebites at our institution between 1975 and 1990; 18 were children < or = 12 years old. There were 13 rattlesnake bites, 4 copperhead bites, and 1 unidentified bite. Initial management included intravenous fluids and antibiotic administration, laboratory studies, tetanus prophylaxis, affected limb elevation, and a limited excision of the bite site in the emergency room. Antivenin was administered only if signs of systemic involvement such as shock, coagulopathy, gastrointestinal cramping, or neurological involvement were present. Children developed systemic involvement 72% of the time, 9 children (50%) developed coagulopathy. Consequently, 11 (61%) children received antivenin. The dose of antivenin they received was 3.2 ml/kg and the children tolerated it well with only 36% of them demonstrating adverse reactions to the antivenin. Clinically, the pediatric patients demonstrated signs and symptoms of a fulminant envenomation syndrome (8 days, average hospital stay), yet, they had a good eventual outcome. Only 11% of children reported long-term morbidity. No deaths occurred and 100% of patients were able to return to full preinjury activities. We conclude that Crotalidae envenomation in children is a serious disease and warrants hospitalization, early surgical involvement, and frequent use of antivenin.

Animals↗
PubMed1993

A possible late onset variation of Papillon-Lefèvre syndrome: report of 3 cases.

Three unusual cases of Papillon-Lefèvre syndrome with late onset of features and relatively mild periodontal disease are presented. These examples confirm some of the late onset of features and mild periodontal presentation of a previous case report. Bacteriologic associations, polymorphonuclear leukocyte chemotactic, phagocytic, and bactericidal activity, and therapeutics with regard to this syndrome are discussed.

Adult↗
PubMed1992

Comparative tissue tolerance of a new endodontic sealer.

An experimental radiopaque resin root canal sealer was tested for tissue biocompatibility in rat connective tissue. The controls were four widely used sealers: Sealapex, Kerr's sealer, AH-26, and Roth's sealer. Polyethylene tubes were filled with the sealers and allowed to set for 24 hours in 100% humidity. Each sealer was implanted in the connective tissue of Sprague-Dawley rats and removed after 3, 10, 20, 30, and 60 days, fixed, and histologically prepared for light microscope evaluation. At each time period there was practically no difference in the reaction of all the sealers. By 60 days, the total picture was one of well-tolerated biocompatibility.

Animals↗
PubMed1992

Microleakage--full crowns and the dental pulp.

Recent studies have described microleakage under full crowns cemented with several different cements. This study tested three different types of crown margin preparations--a chamfer, a shoulder, and a shoulder plus a bevel to determine whether or not the margin preparation could affect microleakage. All crowns were cemented with zinc phosphate cement. The crowns were tested for leakage in thermocycled dye. All crowns demonstrated significant leakage following the path of the dentinal tubules into the pulp. This could possibly be one of the causes of pulpal inflammation and even pulpal death under full crowns.

Crowns↗