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Biomedical subjects

D Dickey

Publications and source records attributed to D Dickey.

11 recordsLinked to original sources
PubMed1998

Radiance modelling using the P3 approximation.

Light dosimetry is an essential component of effective photodynamic therapy (PDT) of tumours. Present PDT light dosimetry techniques rely on fluence-based models and measurements. However, in a previous paper by Barajas et al, radiance-based light dosimetry was explored as an alternative approach. Although successful in demonstrating the use of Monte Carlo (MC) simulations of radiance in tissue optical characterization, the MC proved time consuming and impractical for clinical applications. It was proposed that an analytical solution to the transport equation for radiance would be desirable as this would facilitate and increase the speed of tissue characterization. It has been found that the P3 approximation is one such potential solution. Radiance and fluence expressions based on the P3 approximation were used to optically characterize an Intralipid-based tissue phantom of varying concentration of scatterer (Intralipid) and absorber (methylene blue) using a plane wave illuminated, semi-infinite medium geometry. The results obtained compare favourably with the Grosjean approximation of fluence (a modified diffusion theory) using the same optical parameters (mu(a), mu(s), g). The results illustrate that radiance-based light dosimetry is a viable alternative approach to tissue characterization and dosimetry. It is potentially useful for clinical applications because of the limited number of invasive measurements needed and the speed at which the tissue can be characterized.

Data Interpretation, Statistical↗
PubMed1992

The effects of biofeedback-assisted relaxation on cell-mediated immunity, cortisol, and white blood cell count in healthy adult subjects.

The effect of biofeedback-assisted relaxation on cell-mediated immunity, cortisol, and white blood cell count was investigated in healthy adults under low-stress conditions. Fourteen subjects were trained with biofeedback-assisted relaxation for 4 weeks, while 17 subjects were controls. The group trained in relaxation techniques showed increased blastogenesis, decreased white blood cell count, due to decreased neutrophils, and no change in cortisol in comparison to the control group. Subjects with lower initial anxiety scores and forehead muscle tension levels showed larger increases in blastogenesis and larger decreases in neutrophils than subjects with higher initial anxiety and muscle tension levels.

Adult↗
PubMed1992

Pulmonary transplant. Transplantation for end-stage lung disease: a nurse's perspective.

The types of lung transplants are single lung (performed on either side), double lung en bloc (which requires total cardiopulmonary bypass and myocardial protection), and bilateral-sequential lung transplant (which uses separate single lung transplants with separate main stem bronchial anastomoses). Single lung transplants are used for restrictive lung disorders, such as pulmonary fibrosis; double lung procedures are used for patients with obstructive lung disease, such as emphysema, and bilateral-sequential lung transplantation is used in patients diagnosed with generalized bronchiectasis, including cystic fibrosis, or any other chronically infected lung disease. The criteria for differentiating single versus bilateral transplantation is constantly being evaluated and redefined. The future of lung transplantation depends on continued research, improved methods of preservation, improved care to potential donors, and an increase in the availability of donors.

Humans↗
PubMed1990

The effects of N-cadherin misexpression on morphogenesis in Xenopus embryos.

N-cadherin is a calcium-dependent, cell adhesion molecule that has been proposed to play a role in morphogenesis in vertebrate embryos. Throughout early neural development, N-cadherin is expressed during the morphogenetic changes that occur when ectoderm, in response to neural induction, forms a neural plate and tube. To study the role of N-cadherin in these processes, cDNA clones encoding Xenopus laevis N-cadherin were isolated and used to study the expression of N-cadherin in frog embryos. These studies showed that N-cadherin RNA is not expressed at detectable levels in early cleavage embryos or in isolated ectoderm in the absence of neural induction. However, N-cadherin RNA rapidly appeared in ectoderm exposed to a heterologous neural inducer, indicating that N-cadherin expression, as an early response to induction, precedes the morphogenetic events associated with early neural development. The role of N-cadherin in these morphogenetic events was studied by ectopically expressing N-cadherin in the ectoderm of embryos prior to induction. The ectopic expression of this protein in ectoderm led to the formation of cell boundaries and to severe morphological defects. These results are consistent with the hypothesis that the morphogenetic changes associated with early neural development are controlled, in part, by the induced expression of N-cadherin in the neural plate.

Amino Acid Sequence↗
PubMed1990

Post-choledochoenterostomy 'sump syndrome'.

The 'sump syndrome' is an uncommon, late complication of a side-to-side choledochoenterostomy. Five patients with this syndrome were encountered over a 5-year period. Pain or cholangitis was the clinical presentation in four patients, whereas one patient presented with secondary septic arthritis and a hepatic abscess. Liver function tests were mildly abnormal in each patient. All patients had a stomal size of less than 1 cm as assessed by forward- or side-viewing endoscopy. Endoscopic retrograde cholangiography revealed either stones or debris in the distal common bile ducts of all patients. Four patients had a surgical clearance of their duct with concurrent closure of the choledochoduodenostomy in three patients and the creation of a Rouxen-Y end-to-side choledochojejunostomy in the fourth patient. The other patient had an endoscopic sphincterotomy performed. After 1-4 years of follow-up, four patients have had a total resolution of symptoms. The other patient with follow-up for 4 years has had one episode of cholangitis which resolved rapidly with antibiotic treatment. The pathogenesis and clinical spectrum of the sump syndrome are reviewed and current management strategies are discussed.

Abdominal Pain↗
PubMed1985

Early gastric cancer.

Thirty patients with early gastric cancer were studied as part of a consecutive series of 308 gastric cancers, giving a proportion of 9.7%. Twenty-eight of the early gastric cancer patients were symptomatic, pain being the most common symptom. Endoscopy proved more effective than barium studies as a first investigation but the diagnosis rate at first examination was still only 69%. Seven patients with early gastric cancer had lymph node spread at the time of presentation. Five patients eventually died of cancer metastases. There was a high incidence of benign peptic ulceration (50%) and this with lymph node metastasis was an unfavourable prognostic feature. Only four of the 26 patients submitted to standard surgical resections died of cancer. This study supports the concept that early gastric cancer does indeed occur in Western man and the five year survival rate (65%) is much higher than for late gastric cancer (13%). The high incidence of metastasis at the time of presentation may account for the difference between our survival rate for early gastric cancer, and that reported from Japan.

Adenocarcinoma↗
PubMed1985

Difficulties in the endoscopic diagnosis of gastric and oesophageal cancer.

A study was made of 116 patients with gastric or oesophageal cancer, in whom endoscopy was negative, or biopsy was negative or not performed. The most common problems were the presence of pyloric or oesophageal stricture (sometimes with excessive luminal content) and difficulty in obtaining diagnostic biopsy material in linitis plastica, early gastric cancer, lymphoma and sarcoma. Problems also occurred from failure to biopsy apparently benign conditions and from delay in a second endoscopy. Some cancers were regarded as benign ulcers and treated as such by drugs or surgery because more reliance was placed on endoscopic biopsy than on the endoscopist's opinion of the macroscopic appearance. In 17 of the 16 patients there was delay, incorrect management or further difficulty in diagnosis.

Diagnostic Errors↗