Biomedical subjects

D Shipley

Publications and source records attributed to D Shipley.

5 recordsLinked to original sources

PubMed2006

Perturbation correction factors for the NACP-02 plane-parallel ionization chamber in water in high-energy electron beams.

Recent dosimetry protocols for clinical high-energy electron beams recommend measurements of absorbed dose-to-water with a plane-parallel or cylindrical ionization chamber. For well-guarded plane-parallel ionization chambers, the ionization chamber perturbation factor in water, p(Q), has a recommended value of unity in all protocols. This assumption was investigated in detail in this study for one of the recommended ionization chambers in the protocols: the Scanditronix NACP-02 plane-parallel ionization chamber. Monte Carlo (MC) simulations of the NACP-02 ionization chamber with the EGSnrc code were validated against backscatter experiments. MC simulations were then used to calculate p(wall), p(cav) and p(Q) perturbation factors and water-to-air Spencer-Attix stopping powers in 4-19 MeV electron beams of a calibration laboratory (NPL), and in 6-22 MeV clinical electron beams from a Varian CL2300 accelerator. Differences between calculated and the currently recommended (Burns et al 1996 Med. Phys. 23 383-8) stopping powers, water-to-air, were found to be limited to 0.9% at depths between the reference depth z(ref) and the depth where the dose has decreased to 50% of the maximum dose, R50. p(wall) was found to exceed unity by 2.3% in the 4 MeV NPL calibration beam at z(ref). For higher energy electron beams p(wall) decreased to a value of about 1%. Combined with a p(cav) about 1% below unity for all energies at z(ref), this was found to cause p(Q) to exceed unity significantly for all energies. In clinical electron beams all three perturbation factors were found to increase with depth. Our findings indicate that the perturbation factors have to be taken into account in calibration procedures and for clinical depth dose measurements with the NACP-02 ionization chamber.

Aluminum↗

PubMed2006

Atypical cutaneous leishmaniasis in two patients receiving low-dose methotrexate.

Cutaneous leishmaniasis is a protozoan disease that has high morbidity. There have been increasing reports of leishmaniasis in patients with an underlying immunosuppressed state. We present two cases of cutaneous leishmaniasis caused by Old World species in patients on methotrexate therapy. We postulate that the T-cell-mediated response to leishmaniasis infection could be modulated by methotrexate and may render an immunosuppressed individual more susceptible to developing clinical disease.

Adult↗

PubMed2001

Drug-induced urticaria. Recognition and treatment.

Urticaria is the second most common cutaneous manifestation of drug allergy. Drug-induced urticaria is seen in 0.16% of medical inpatients and accounts for 9% of chronic urticaria or angioedema seen in dermatology outpatient departments. Occurring within 24 hours of drug ingestion, it is most commonly caused by penicillins, sulfonamides and nonsteroidal anti-inflammatory drugs. Drug-induced urticaria is seen in association with anaphylaxis, angioedema, and serum sickness. Diagnosis requires a detailed history, knowledge of the most likely agents sometimes supplemented with in vitro and skin testing. For mild reactions, avoidance of the causative drug and treatment with antihistamines will suffice. For anaphylactic shock, treatment with epinephrine (adrenaline), corticosteroids and antihistamines is required. Patients should be educated to inform medical staff about previous drug reactions, and to avoid these and cross-reacting drugs if possible. Medical staff need to routinely enquire about allergy and avoid unnecessary prescriptions.

Algorithms↗

PubMed1997

Moderate alcohol consumption does not augment bone density in ovariectomized rats.

Moderate levels of alcohol consumption have been reported to have a beneficial effect on bone mineral density in postmenopausal women. The objective of this study was to examine the effect of a moderate level of alcohol consumption on bone density in a rigorously controlled animal model of osteoporosis. Ovariectomized and nonovariectomized rats were placed on standard lab pellets with free access to deionized water ad libitum. Alcohol-treated animals were given 0.38 g/kg of alcohol daily by intubation in the mid-afternoon and free access to standard lab pellets for 6 weeks. The amount of the alcohol solution was calculated daily to give the human equivalent of 2 glasses of wine/day. Pair-fed control animals were given, on the following day, an equal volume of the diet consumed by individual ethanol-fed rats. They received daily intubation solutions, with the ethanol replaced by isocaloric and isovolumetric amounts of maltose-dextrin. Chow-fed control animals received no intubations and were given access to standard lab pellets ad libitum. Ovariectomized animals had increased weight and decreased femur density and bone volume per total volume. They also had decreased total trabecular area, trabecular area, and number, as well as increased trabecular separation. Significant differences were found between the ovariectomized and nonovariectomized animals in the parameters under discussion, but there were no differences between diet groups. No beneficial effects were found after daily alcohol treatments.

Aged↗

PubMed1992

The haemoglobin-like protein (HMP) of Escherichia coli has ferrisiderophore reductase activity and its C-terminal domain shares homology with ferredoxin NADP+ reductases.

Three soluble ferrisiderophore reductases (FsrA, FsrB and FsrC) were detected in Escherichia coli. FsrB was purified and identified as the haemoglobin-like protein (HMP) by size and N-terminal sequence analyses. HMP was previously isolated as a dihydropteridine reductase and is now shown to have ferrisiderophore reductase activity. Database searches revealed that the C-terminal region of HMP (FsrB) is homologous to members of a family of flavoprotein oxidoreductases which includes ferredoxin NADP+ reductase (FNR). The combination of FNR-like and haemoglobin-like regions in HMP (FsrB) represents a novel pairing of functionally and structurally distinct domains. Structure-function properties of other FNR-like proteins, including LuxG and VanB, are also discussed.

Bacterial Proteins↗