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Biomedical subjects

R Oliver

Publications and source records attributed to R Oliver.

At least 37 records · Page 2Linked to original sources
PubMed2000

Evidence that the cAMP pathway controls emergence of both primary and appressorial germ tubes of barley powdery mildew.

Development of conidia of barley powdery mildew involves the formation of a primary germ tube (PGT), an appressorial germ tube (AGT), and an appressorium. Previously, it was found that cyclic AMP (cAMP) was involved in these developmental processes. Comparison of development on the host surface with two types of cellulose membrane revealed that frequency of PGT emergence was surface independent. On one type of cellulose, where the frequencies of both AGT and appressorial differentiation were similar to that on the host surface, cAMP levels and protein kinase A (PKA) activities had a biphasic pattern with peaks at 15 min and 4 h after inoculation (prior to PGT and AGT emergence, respectively). The effect of manipulating cAMP levels was tested on another type of cellulose membrane, which stimulated a lower degree of AGT and appressorial formation than the host surface. Cholera toxin and forskolin, activators of adenylyl cyclase, significantly increased PGT emergence, but cAMP did not. Cholera toxin, forskolin, and cAMP increased the frequency of AGT and appressorial formation, but in a time-dependent manner.

Cellulose↗
PubMed2000

Bioavailability of orally administered micronised fluticasone propionate.

OBJECTIVE: The aim of this study was to determine the absolute oral bioavailability of fluticasone propionate (FP) in healthy volunteers. METHODS: A 3-period incomplete block crossover design was used. On separate occasions, 21 male volunteers received a single 250 microg intravenous dose of FP (n = 21) and twice daily oral doses of either micronised FP 0.1 mg (n = 9), 1 mg (n = 12), 10 mg (n = 11) or placebo (n = 9) for 4 days. RESULTS: FP was not measurable in the plasma after twice daily oral administration of a 0.1 mg dose. FP concentrations just above the limit of quantification could be measured in only 5 volunteers, and only at some time points, after administration of FP 1 mg twice daily. At a dose of 10 mg twice daily the absolute oral bioavailability of the drug was <1% when a liquid chromatography-mass spectrometry assay was used to assess plasma concentrations. Only oral doses of FP 10 mg twice daily, 10 times greater than the recommended maximum inhaled dose, produced any detectable change in urinary cortisol excretion. CONCLUSION: The results of this study confirm that oral absorption of FP into the systemic circulation is negligible. The swallowed portion of an inhaled dose of FP is unlikely to increase the systemic exposure to the drug, thus decreasing the likelihood of adverse systemic effects.

Administration, Oral↗
PubMed1999

A suggested method for sentinel node biopsy in squamous cell carcinoma of the head and neck.

BACKGROUND: Debate continues over the management of the N0 neck in head and neck malignancy. Therefore, the possibility of performing sentinel node biopsy in these patients was investigated to formulate a method for the procedure. METHODS: Patients undergoing prophylactic or therapeutic neck dissections were injected with either Patent Blue V dye alone or with blue dye and 99m-Tc labeled Albures. The latter group underwent preoperative lymphoscintigraphy. During surgery, blue stained lymphatics were followed to blue nodes, and a neoprobe was used to identify radioactive nodes. RESULTS: In 5 of 13 patients receiving blue dye, a blue node was identified, but none contained tumor. Metastases were identified in other neck nodes in 3 of 5. Sentinel nodes were identified in 15 of 16 patients receiving dye, and Albures. Sentinel node biopsy was accurate in 7 of 7 necks containing impalpable metastases when all nodes had been evaluated after dissection. DISCUSSION: Sentinel node biopsy using blue dye and radiocolloid may prove to be a reliable technique in the N0 neck and warrants further investigation.

Biopsy↗
PubMed1998

Quantitative heel ultrasound in 3180 women between 45 and 75 years of age: compliance, normal ranges and relationship to fracture history.

There is growing evidence to support the use of quantitative ultrasound (QUS) to identify fracture risk in late postmenopausal women but few data are available in younger women. In order to address this issue all women between 45 and 75 years of age registered in two general practices in Bournemouth, Dorset, UK were invited to attend for heel QUS. Measurements were made in 79% of the 4018 women identified. The mean QUS results for 5-year age groups were very similar to those from reported reference ranges from North America and the north of England. The odds ratios (95% confidence limits) for self-reported fractures after 45 years per standard deviation of age-adjusted QUS parameters were: broadband ultrasound attenuation (BUA) = 1.40 (1.26-1.56), speed of sound (SOS) = 1.56 (1.41-1.74) and Stiffness = 1.52 (1.37-1.68). The results suggest that QUS is associated with fracture history in early postmenopausal women.

Aged↗
PubMed1998

Recipient to donor conduction of atrial tachycardia following orthotopic heart transplantation.

We report a case of atrial tachycardia in a 60-year-old male 8 years postorthotopic heart transplantation. At electrophysiology study, the clinical rhythm was found to arise from the remnant of the recipient atrium and was successfully terminated by delivery of radiofrequency energy. Surgical scars formed at the anastomosis of the recipient and donor atrium during the time of orthotopic heart transplantation are thought to electrically isolate the two areas. Although rarely recognized, dysrhythmias originating from the recipient atrial remnant may occur more often than previously thought.

Catheter Ablation↗
PubMed1998

Quantitative ultrasound (QUS) of the heel predicts wrist and osteoporosis-related fractures in women age 45-75 years.

This study was designed to determine the ability of quantitative ultrasound (QUS) of the heel to predict fracture risk at different sites in postmenopausal women between the ages of 45 and 75 years. Heel QUS was measured at baseline using a Lunar Achilles scanner, and subsequent fractures were identified over 3 yr. The results were analyzed graphically after age adjustment and using Cox's proportional regression to estimate odds ratios for fracture risk; 3180 women were scanned (79% of sample). Sixty-three wrist, 12 hip, 4 vertebral, 7 proximal humerus, 3 pelvic, and 61 other fractures were identified over a mean followup of 31 mo. There was a fivefold difference in numbers of wrist and osteoporosis-related fractures (hip, vertebra, pelvis, and humerus combined) between the lowest and highest quartiles of QUS results adjusted for age. The odds ratios per 1 SD decline in QUS parameters adjusted for age were: wrist fractures BUA = 1.6, SOS = 1.5, stiffness = 1.8, osteoporosis-related fractures BUA = 1.9, speed of sound (SOS) = 1.6, stiffness = 2.2, and other fractures, BUA = 1.0, SOS = 1.1, stiffness = 1.1. When analyzed for each 10-yr age group, the odds ratios were generally higher in the 56-65 yr group than the other decades. In women between 45 and 75 yr, heel QUS can predict wrist and osteoporosis- related fractures at about the same level that dual-energy X-ray absorptiometry (DXA) of various sites can predict wrist fractures. This extends the current evidence that heel QUS can predict hip fracture risk in women over 75 yr to include other fracture sites in younger women. Heel QUS may be useful in the primary care assessment of osteoporotic fracture risk in women after the menopause.

Journal Article↗
PubMed1998

Transplantation of allogeneic islets of Langerhans in the rat liver: effects of macrophage depletion on graft survival and microenvironment activation.

Early impairment of islet function and graft loss limit the success of allogeneic islet transplantation. Nonspecific inflammatory events occurring at the transplant site immediately after grafting, involving the production of cytokines and free radicals and sinusoidal endothelial cell (SEC) activation, may contribute to islet cell damage. To evaluate whether Kupffer cell inactivation would result in prolonged allograft survival in a model system of intrahepatic islet transplantation in rats, we systemically administered either gadolinium chloride (GdCl3) or dichloromethylene diphosphonate (Cl2MDP) to assess the effects of macrophage inactivation on rejection and on the release of proinflammatory molecules, as well as to assess the functional profile of SEC. The results obtained were compared with those observed in untreated, sham-injected animals and in rats receiving intraportal infusions of microbeads. Transient macrophage inhibition, particularly in hepatic Kupffer cells, is associated with significant prolongation of graft survival after intraportal islet allotransplantation (ITx) in rats: 7.2 days in the control group versus 11.9 days in the GdCl3 group (P < 0.01) and 15.6 days in the Cl2MDP group (P < 0.0006), respectively. Although systemic release of inflammatory mediators was observed only when islet transplantations were performed and it could be inhibited by macrophage-targeting treatments, perturbation of the functional profile of endothelial cells was also observed when microembolization was induced by the use of microbeads and could not be prevented by macrophage inhibition. These experiments provide evidence to support the concept that macrophages play a key role in early inflammatory events known to adversely affect islet engraftment and suggest that manipulation of nonspecific immune activation by inhibition of macrophage function may facilitate hepatic engraftment of islet allografts. The mechanisms mediating this effect are likely to include prevention of release of tumor necrosis factor-alpha, interleukin-1beta, and NO and interference with the rate of immune response to the islets.

Animals↗
PubMed1997

Safety, functionality and acceptability of a prototype polyurethane condom.

Male condoms made from synthetic materials offer an alternative to latex condoms that may be more acceptable to users, thereby potentially resulting in more protected acts of intercourse. A prospective, noncomparative clinical study was conducted to evaluate the safety of using certain polyurethane materials to make condoms. Fifty-one healthy, contracepting, mutually monogamous couples were recruited between June 30 and November 24, 1993 to use a prototype roll-on polyurethane condom developed by Family Health International. Couples were to use the condoms for 10 consecutive acts of vaginal intercourse over a 4-week period. Baseline and postexposure genital examinations, including colposcopy for female participants, were performed. Fifty couples completed the study requirements and 517 acts of intercourse occurred using the condoms. Two adverse events were reported: irritation of introitus in a female participant and a small irritated erythematous lesion on a male participant's penis. Neither event was considered to be serious and both were resolved without treatment. Breakage and slippage rates were similar to those reported for latex condoms. These results suggest that polyurethane condoms represent a safe, functional and acceptable alternative to latex condoms.

Adult↗