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Biomedical subjects

P O'Brien

Publications and source records attributed to P O'Brien.

At least 91 records · Page 5Linked to original sources
PubMed1992

New directions in pediatric heart transplantation.

New developments in pediatric heart transplantation have influenced the nursing management of these patients. The patient population has changed over the past few years with an increase in patients with congenital heart disease and larger numbers of infants and young children. The management of patients prior to transplantation has become more complex, with new pharmacologic agents and the use of mechanical assist devices as a bridge to heart transplantation. The importance of accurate assessment and management of pulmonary hypertension both before and after transplantation have been recognized. FK506, a new immunosuppressant in clinical trial, appears promising as both a maintenance therapy and a rescue drug with fewer side effects than cyclosporine. The trend toward outpatient and home care for many transplant-related therapies reflects the wider trend in health care. The practice of the critical care nurse involved in pediatric heart transplantation has been influenced by these recent changes.

Adolescent↗
PubMed1991

Evidence for the generation of hydroxyl radicals from a chromium(V) intermediate isolated from the reaction of chromate with glutathione.

The formation of hydroxyl radicals from a chromium(V) complex isolated from the reaction of glutathione with chromate has been demonstrated in spin trapping experiments using dimethylsulfoxide and 3,5-dibromo-4-nitrosobenzene sulfonate. Mechanisms for the formation of radicals in such systems are discussed. These results help to explain the ability of solutions containing chromate and glutathione to cause strand breaks in DNA.

Chromates↗
PubMed1991

Reassessment of the association between Guillain-Barré syndrome and receipt of swine influenza vaccine in 1976-1977: results of a two-state study. Expert Neurology Group.

Although the original Centers for Disease Control study of the relation between A/New Jersey/8/76 (swine flu) vaccine and Guillain-Barré syndrome (polyradiculoneuritis) demonstrated a statistical association and suggested a causal relation between the two events, controversy has persisted. To reassess this association, the authors obtained medical records of all previously reported adult patients with Guillain-Barré syndrome in Michigan and Minnesota from October 1, 1976 through January 31, 1977. To identify previously unreported hospitalized cases with onset of symptoms during this period, the authors surveyed medical care facilities. A group of expert neurologists formulated diagnostic criteria for Guillain-Barré syndrome and then reviewed the clinical records in a blinded fashion. Of the 98 adult patients from the original Centers for Disease Control study eligible for consideration, three were found to have been misclassified by date of onset and were excluded. Of the remaining 95, the 28 (29%) who did not meet the diagnostic criteria were equally distributed between the vaccinated group (18 of 60, 30%) and the unvaccinated group (10 of 35, 29%). In addition to the 67 remaining cases who met the diagnostic criteria, six previously unreported cases (three of whom had been vaccinated) were found and included in this analysis. The relative risk of developing Guillain-Barré syndrome in the vaccinated population of these two states during the 6 weeks following vaccination was 7.10, comparable to the relative risk of 7.60 found in the original study. These findings suggest that there was an increased risk of developing Guillain-Barré syndrome during the 6 weeks following vaccination in adults. The excess cases of Guillain-Barré syndrome during the first 6 weeks attributed to the vaccine was 8.6 per million vaccinees in Michigan and 9.7 per million vaccinees in Minnesota. No increase in relative risk for Guillain-Barré syndrome was noted beyond 6 weeks after vaccination.

Causality↗
PubMed1991

Hodgkin's disease of the liver; prognosis and possible indications for radiotherapy.

A retrospective analysis of 56 patients presenting with Hodgkin's disease involving the liver between 1970 and 1984 revealed a 10-year survival probability of 44%. The actuarial 10-year continuous progression free survival was 42%. Presentation variables predicting for relapse in the liver included hepatomegaly (P less than 0.025) or focal lesions on isotope, ultrasound or CT scan (P less than 0.01). These factors may define a context for investigation of adjuvant hepatic irradiation following chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Current status of radiosurgery for arteriovenous malformations.

Cerebral arteriovenous malformations (AVM), regardless of the mode of discovery, have an annual risk of hemorrhage of approximately 4 percent. A progressive obliterative vasculitis culminating in the occlusion of an AVM may be induced by the administration of radiation doses of approximately 20 Gy given in a single fraction. The process takes about two years and occlusion occurs in approximately 80% of patients so treated. Such a dose may be accurately administered to AVMs up to 3 cm in diameter with very little radiation imparted to the adjacent brain by means of multiple highly collimated radially arranged cobalt sources (the Gamma Knife) or by means of a modified linear accelerator turned through an arc or arcs with the target AVM as the centre of rotation. The Gamma Knife and the modified linear accelerator have nearly equal accuracy. Recent experience with modified linear accelerators indicates efficacy equal to the Gamma Knife. Both devices are effective treatment for small AVMs but the cost of modifying a pre-existing linear accelerator is only a few percent of the acquisition and installation costs of the Gamma Knife.

Evaluation Studies as Topic↗
PubMed1991

Non-Hodgkin's lymphoma presenting with extradural spinal cord compression: functional outcome and survival.

Between 1971 and 1988, 20 patients with previously undiagnosed non-Hodgkin's lymphoma (NHL), of intermediate or high grade histology presented with extradural spinal cord compression. All had decompressive surgery. The first treatment after surgery was chemotherapy in nine and radiotherapy in 11 patients. At presentation 15% were ambulant and this improved to 55% after surgery; urinary continence improved from 30 to 80%. Mobility and sphincter control remained unchanged, regardless of subsequent therapy. Chemotherapy as the initial treatment modality after surgery, either alone or in combination with radiotherapy, did not jeopardise functional outcome. Mobility after surgery was an independent prognostic factor for survival, when corrected for age and stage at presentation (P = 0.04). The treatment of intermediate and high grade NHL presenting with spinal cord compression should be based on histology, extent of disease and age, as with other sites of presentation, but should also take into consideration the prognostic importance of post-surgical mobility.

Adolescent↗
PubMed1991

Studies of the binding of chromium(III) complexes to phosphate groups of adenosine triphosphate.

The binding of a number of chromium complexes to ATP has been studied by 31P NMR spectroscopy. The results are consistent with the formation of outer-sphere complexes between ATP and the chromium species. The magnitude of the binding constant has been determined as approximately 500 mol-1 dm3 (pH = 7.00) for the interaction of trisethylenediamine chromium(III) with ATP. Under our experimental conditions no NMR signals are observed from complexes in which chromium(III) is bound directly to the phosphate groups of ATP. The relative stability of the inner sphere complexes of chromium(III) and glutathione or ATP is probably not a significant factor in determining the toxicity of chromium(III) complexes.

Adenosine Triphosphate↗
PubMed1991

The reduction of chromate is a prerequisite of chromium binding to cell nuclei.

Isolated calf thymus nuclei bound a chromium(III) glutathione complex in a time-dependent manner. In contrast chromium(VI) (sodium chromate) did not bind. However, when chromate was incubated with the nuclei in the presence of glutathione, chromium adducts were detected. These observations indicate that the reduction of chromate, by a reducing agent such as glutathione, is a prerequisite for the generation of bonds between the metal and constituents of the cell nuclei in vitro. Chromium adducts with nuclei are probably one cause of DNA lesions and mutations.

Animals↗
PubMed1991

The prevalence of hearing impairment amongst Maori schoolchildren.

A survey of hearing amongst a population of Maori schoolchildren in the eastern North Island of New Zealand has demonstrated a high prevalence of hearing impairment. Out of 194 children undergoing audiometry an impairment of 20 dB or greater at 0.5, 1.2 and 4 kHz was found in the worse hearing ear in 29% and in the better hearing ear in 12%. Comparison with a similar survey done in the same valley in 1977 revealed an apparent reduction in the prevalence of hearing loss and the prevalence of otitis media. This improvement appears to be due to a reduced prevalence of otitis media. An unexpected finding was that at least 2% of the children had a bilateral sensorineural hearing impairment.

Adolescent↗
PubMed1991

Assessment of nutrient intake in association with weight loss after gastric restrictive procedures for morbid obesity.

Postoperative nutrient intakes were examined in patients who were losing weight in an early period following gastric restrictive surgery for morbid obesity (3 to 6 months post-surgery), and patients whose reduced weight was relatively stable at 1 to 2 years post-surgery. In association with weight loss, patients showed increased physical activity and reduced energy intakes which were frequently less than the Recommended Daily Intakes (RDI), particularly in the early period. Protein intake was also below recommended levels in the two post-operative phases. The intakes of iron, folate and calcium were below the recommended levels in the early postoperative phase. The intakes of iron and folate were also below recommended levels in the late postoperative phase. The study indicates the potential for deficiencies of iron, folate and calcium after gastric restrictive surgery and supports the importance of careful and prolonged follow-up of these patients, with particular attention to nutritional status.

Adult↗
PubMed1991

Myocardial biochemical and hemodynamic adaptations to chronic tachycardia.

The purpose was to determine the biochemical and hemodynamic adaptations of the myocardium to chronic tachycardia. Cardiac pacemakers were implanted in Yorkshire pigs and set at a rate of 180 beats/min for a period of 35-42 days. Animals were then anesthetized with pentobarbital sodium. Myocardial blood flow and hemodynamics were determined at three different heart rates (i.e., 120, 180, and 220 beats/min). Tissue samples were then taken for microsphere and biochemical analyses. Chronically paced hearts maintained better cardiac function and had consistently higher left ventricular blood flow with a higher endocardial-to-epicardial ratio. The activities of citrate synthase and 3-hydroxyacyl-CoA dehydrogenase were 23 and 45% greater in the paced hearts, respectively. The sarcoplasmic reticulum adenosinetriphosphatase activity was 55% greater in the paced hearts, whereas the myosin adenosinetriphosphatase was the same as in the control hearts. Polyacrylamide gels of the ventricular myosin isoforms showed only the V3 type to be present in both the control and paced hearts. These findings show that the heart of a large mammal adapts to chronic tachycardia (i.e., 180 beats/min) by elevating the aerobic and calcium-sequestering capacities without altering its myosin type.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1991

Competitive particle concentration fluorescence immunoassay for measuring 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (lometrexol) in serum.

A competitive particle concentration fluorescence immunoassay (PCFIA) is described for measuring 5,10-dideaza-5,6,7,8-tetrahydrofolic acid (lometrexol; Lilly) in human serum. b-Phycoerythrin-labeled lometrexol competes with free lometrexol for binding to a limiting concentration of lometrexol-specific antibodies immobilized by a second antibody to submicrometer-diameter polystyrene particles in specially designed 96-well plates. Reaction particles are washed and concentrated onto filter membranes in the wells of the plates and the fluorescence is measured at 575 nm. The method, including sample preparation and data reduction, is automated and can be completed in less than 2 h. The assay has a standard curve maximum measurable concentration of 1000 micrograms/L and a minimum detectable concentration of 0.1 microgram/L. Analytical recovery of lometrexol in serum is quantitative at concentrations greater than 1 micrograms/L. Intra- and interassay coefficients of variation at 50 micrograms/L in serum are 7.1% (n = 9) and 7.5% (n = 33), respectively. The cross-reactivity of naturally occurring folates, folic acid analogs, and the anti-cancer agent methotrexate is minimal. We report the use of the PCFIA during Phase I clinical studies designed to evaluate the pharmacokinetics of lomextrexol after intravenous administration to cancer patients.

Adult↗
PubMed1991

Disposition of cerebral metastases from malignant melanoma: implications for radiosurgery.

Radiosurgery is becoming more generally available and indications for its use continue to be defined. Cerebral metastases from malignant melanoma are often treated with whole-brain irradiation, but with limited benefit. Innovative treatments, such as radiosurgery, make possible the delivery of doses of radiation that are higher than usual. To determine how many patients might be candidates for radiosurgery, a retrospective analysis of computed tomographic brain scans performed on 41 patients with cerebral metastases from malignant melanoma was undertaken. One-third of these patients were found to have cerebral metastases amenable to a radiosurgical approach, as illustrated radiation dose-volume histograms. Patient and tumor characteristics suggest that this series is represent with cerebral metastases from malignant melanoma. The implications of radiosurgery for normal tissue radiation tolerance and its effects on melanoma are discussed.

Adult↗
PubMed1990

Pseudomonas colonization in cystic fibrosis: lack of correlation with secretion of ABO blood group antigens.

In cystic fibrosis, a majority of patients develop persistent lifelong respiratory tract colonisation with pseudomonas aeruginosa while a minority do not appear to become colonised. There is some evidence that non-secretion of ABO Blood Group antigens into body secretions is a marker for susceptibility to certain gram negative infections. Therefore, we studied 47 adult patients with cystic fibrosis to identify an association, if any, between secretor status and the presence or absence of pseudomonas aeruginosa in their sputum. Overall, we found no difference between the prevalence of non-secretors in our patient group and in the normal population. Furthermore, there was no association between secretor status and presence or absence of pseudomonas aeruginosa in sputum. We conclude that secretor status is unlikely to play a major role in susceptibility to pseudomonas aeruginosa infection in patients with cystic fibrosis.

ABO Blood-Group System↗