Biomedical subjects

J W Wilson

Publications and source records attributed to J W Wilson.

At least 181 records · Page 10Linked to original sources

PubMed1992

Galactic cosmic ray transport methods and radiation quality issues.

An overview of galactic cosmic ray (GCR) interaction and transport methods, as implemented in the Langley Research Center GCR transport code, is presented. Representative results for solar minimum, exo-magnetospheric GCR dose equivalents in water are presented on a component by component basis for various thicknesses of aluminum shielding. The impact of proposed changes to the currently used quality factors on exposure estimates and shielding requirements are quantified. Using the cellular track model of Katz, estimates of relative biological effectiveness (RBE) for the mixed GCR radiation fields are also made.

Animals↗

PubMed1992

Track structure model for damage to mammalian cell cultures during solar proton events.

Solar proton events (SPEs) occur infrequently and unpredictably, thus representing a potential hazard to interplanetary space missions. Biological damage from SPEs will be produced principally through secondary electron production in tissue, including important contributions due to delta rays from nuclear reaction products. We review methods for estimating the biological effectiveness of SPEs using a high energy proton model and the parametric cellular track model. Results of the model are presented for several of the historically largest flares using typical levels and body shielding.

Animals↗

PubMed1992

Dose-response of bacillus Calmette-Guerin in the treatment of superficial bladder cancer.

Although bacillus Calmette-Guerin (BCG) has been recognized as an effective therapy for superficial bladder cancer, dose-response studies are not available. Such studies are important because the administration of the vaccine is not devoid of significant side effects when the standard dose of 120 mg. is used. It has been speculated that smaller doses may be equally effective but carry fewer side effects. A controlled study comparing 2 doses of BCG was conducted as an initial step to explore this possibility. A total of 97 patients with a diagnosis of superficial (stages TIS, Ta and T1) bladder cancer was assigned to receive either 60 or 120 mg. BCG intravesically weekly for 6 weeks. The higher dose resulted in a better response for stages TIS, Ta (for prophylaxis of recurrence) and T1. However, the differences were not statistically significant. When stage TIS and Ta tumors coexisted, a significantly better response was recorded for the high dose. The overall success for the 2 treatments was 67% and 37% for the high and low doses, respectively. These differences reached statistical significance (p less than 0.02). Side effects were significantly less in number and severity in patients receiving the smaller dose of the vaccine.

BCG Vaccine↗

PubMed1992

Inclusive inelastic scattering of heavy ions in the independent particle model.

We consider the inclusive inelastic scattering of heavy ions using the Glauber model and the independent particle approximation. Inclusive inelastic distributions for projectile excitation of the target and total inelastic scattering, where all projectile and target excited states are summed, are discussed using closure. The total inelastic distribution when integrated is shown to be equivalent to the absorption cross section found from applying the optical theorem to the elastic scattering amplitude in the coherent approximation. Calculations are presented for several heavy-ion pairs using realistic nuclear densities in a large mass number approximation.

Elementary Particles↗

PubMed1992

Multiple-scattering effects in quasielastic alpha-4He scattering.

A multiple-scattering series for describing the quasielastic peak in nucleus-nucleus collisions is derived using the high-energy optical model. The effects of multiple knockout of target nucleons and internal excitation of the projectile are studied and found to be important for large energy loss and momentum transfers in inclusive alpha-4He scattering at 7 GeV/c. An approximate evaluation of higher-order inelastic collision terms is considered for forward-peaked wave functions and is demonstrated to be accurate.

Helium↗

PubMed1992

Effect of inhaled platelet-activating factor on bronchial inflammation in atopic non-asthmatic subjects.

We have investigated the effect of inhaled platelet-activating factor (PAF) on bronchial mucosal inflammation in 6 atopic non-asthmatic subjects in a double-blind, placebo-controlled, randomised and crossover study. On 2 study periods at least 4 weeks apart, fiberoptic bronchoscopy was performed 24 h after inhalation of either 200 micrograms PAF or methacholine (control) to obtain endobronchial biopsies. Immunocytochemistry using antibodies for trypase (AA1) and eosinophil cationic protein (EG2) was performed to enumerate mast cells and eosinophils, respectively, in the bronchial submucosa. Median values of AA1+ cells and EG2+ cells did not differ significantly after inhalation of PAF or control (23.8 vs. 39 and 6 vs. 8/mm2, respectively, PAF vs. control, non-significant). Our findings suggest that within 24 h of inhaling a bronchoconstrictor dose of PAF, this agonist does not induce bronchial hyperresponsiveness or mucosal inflammation in atopic non-asthmatic subjects. However, because of the small number of subjects studied, these preliminary data should be interpreted with caution.

Administration, Inhalation↗

PubMed1992

Effect of an inhaled corticosteroid on airway inflammation and symptoms in asthma.

The effect of inhaled corticosteroid therapy on airway mucosal inflammation was investigated in 10 symptomatic atopic asthmatic patients treated with inhaled albuterol and whose disease severity required preventative antiinflammatory treatment. Endobronchial biopsies were obtained by fiberoptic bronchoscopy before and after 6 wk of therapy with inhaled beclomethasone dipropionate (2,000 micrograms/day for 2 wk followed by 1,000 micrograms/day for 4 wk). Following treatment, there was a significant increase in mean morning peak expiratory flow (p less than 0.05) and baseline FEV1 measured on the day of methacholine challenge (p less than 0.05) and a decrease in asthma symptoms (p less than 0.01), peak expiratory flow variation (p less than 0.05), and albuterol usage (p less than 0.05). This was accompanied by a sevenfold decrease in airway responsiveness (p = 0.001). The clinical improvement in asthma was associated with a significant (p less than 0.05) reduction in epithelial and mucosal mast cells and eosinophils and submucosal T lymphocytes, but electron microscopy did not identify any changes in the extent of mast cell and eosinophil degranulation following treatment. Because of the association between the decrease in inflammatory cell numbers and the improvement in all the measured clinical and physiologic indices of asthma, we suggest that the beneficial effect of inhaled corticosteroids in asthma may be attributed to their antiinflammatory action in the bronchial mucosa.

Administration, Inhalation↗

PubMed1992

Lymphocyte activation in bronchoalveolar lavage and peripheral blood in atopic asthma.

To study the role of T lymphocytes in atopic asthma we have examined cell populations in peripheral blood and bronchoalveolar lavage (BAL) from 12 atopic asthmatics and 10 healthy volunteers using flow cytometry and a panel of monoclonal antibodies directed toward T-cell surface antigens. BAL from asthmatics contained more eosinophils (mean, 0.54 +/- 11.2 x 10(6) versus 0.06 +/- 0.08 x 10(6) absolute count, p less than 0.05), but no greater total or percent of T lymphocytes. There was no difference between the two groups in the relative numbers of CD4+ or CD8+ T cells. However, there was a significant increase in the mean number of BAL CD3+ lymphocytes expressing the activation markers interleukin-2 receptor (IL-2R, CD25) (8.48 versus 4.37%, p less than 0.01) and human lymphocyte antigen-DR (11.08 versus 7.74%, p less than 0.05) in the asthmatics. In contrast to lavage cells, there was no difference in CD3+ cell activation markers in the peripheral blood. These findings suggest that T-lymphocyte activation occurs within the airways in symptomatic atopic asthma.

Adult↗

PubMed1992

Stockless inventory systems for the health care provider: three successful applications.

Three large hospital-based stockless inventory systems are described. First, the method of stockless inventory is described in some detail and differentiated from the just-in-time (JIT) method of inventory management. Second, three hospital case studies involving successful stockless systems are summarized and evaluated. Finally, some important implications for the implementation of stockless inventory systems are summarized for hospital management.

Contract Services↗

PubMed1992

Risk analyses for the solar particle events of August through December 1989.

The solar particle events of August through December 1989, among the largest ever recorded, are analyzed to assess the potential hazards to humans on interplanetary missions from events of these types. Using the coupled neutron-proton space radiation transport computer code, BRYNTRN, risk estimates for the effects of exposures to the skin, ocular lens, and bone marrow are made for nominal thicknesses of the spacecraft aluminum shielding. Risk assessment in terms of absorbed dose is made for each event. Also presented are estimates of organ absorbed dose and dose equivalent for pairs of events which occurred within 30-day periods, and for the cumulative August through December 1989 period.

Elementary Particles↗

PubMed1992

Bronchial mucosal manifestations of atopy: a comparison of markers of inflammation between atopic asthmatics, atopic nonasthmatics and healthy controls.

We studied the role of atopy, as defined by positive skin tests to common inhalant allergens, in allergic bronchial inflammation. Endobronchial biopsies were taken via the fibreoptic bronchoscope in 13 symptomatic atopic asthmatics, 10 atopic nonasthmatics, and 7 normals. The numbers of mast cells, identified in the submucosa by immunohistochemistry using the AA1 monoclonal antibody against tryptase, were no different between the three groups, but electron microscopy showed that mast cell degranulation, although less marked in atopic nonasthmatics, was a feature of atopy in general. The numbers of eosinophils, identified by immunohistochemical staining using the monoclonal anti-eosinophil cationic protein antibody, EG2, were greatest in the asthmatics, low or absent in the normals and intermediate in the atopic nonasthmatics. In both atopic groups eosinophils showed ultrastructural features of degranulation. Measurements of subepithelial basement membrane thickness on electron micrographs showed that the collagen layer was thickest in the asthmatics, intermediate in the atopic nonasthmatics and thinnest in the normals. The results suggest that airways eosinophilia and degranulation of eosinophils and mast cells, as well as increased subepithelial collagen deposition, are a feature of atopy in general and suggest that the degree of change may determine the clinical expression of this immune disorder.

Adult↗

PubMed1992

Interplanetary crew exposure estimates for galactic cosmic rays.

Using the Langley Research Center galactic cosmic-ray transport computer code and the Computerized Anatomical Man model, initial estimates of interplanetary exposure of astronauts to galactic cosmic rays, during periods of solar minimum activity, are made for a realistic human geometry shielded by various thickness of spacecraft aluminum shielding. Conventional dose assessment in terms of total absorbed dose and dose equivalent is made for the skin, ocular lens, and bone marrow. Included in the analyses are separate evaluations of the contributions from the incident primary ions, from subsequent-generation fragmentation products, and from target fragments. In all cases considered, the equivalent sphere approximation yielded conservative overestimates for the actual organ exposures.

Cosmic Radiation↗

PubMed1991

Pyrophosphate inhibition of Proteus mirabilis-induced struvite crystallization in vitro.

Struvite (MgNH4PO4.6H2O) crystals, the major mineral component of infectious urinary calculi, were produced in vitro by growth of a clinical isolate of Proteus mirabilis in artificial urine. P. mirabilis growth and urease-induced struvite production were monitored by phase contrast light microscopy and measurements of urease activity, pH, ammonia concentrations, turbidity, and culture viability. In the absence of pyrophosphate, struvite crystals appeared within 3-5 h due to the urease-induced elevation of pH and initially assumed a planar or 'X-shaped' crystal habit (morphology) characteristic of rapid growth. When pyrophosphate was present, initial precipitation and crystal appearance were significantly impaired and precipitates were largely amorphous. When crystals did appear (usually after 7 or 8 h) they were misshapen or octahedral in shape indicative of very slow growth. X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) identified all crystals as struvite. Trace contaminates of carbonate-apatite (Ca10(PO4)6CO3) or newberyite (MgHPO4.H2O) were produced only in the absence of pyrophosphate. P. mirabilis viability and culture pH elevation were unaffected by the addition of pyrophosphate, whereas urease activity and ammonia concentrations were marginally reduced. Struvite could also be produced chemically by titration of the artificial urine with NH4OH. If pyrophosphate was present during titration, the same inhibitory effect on crystal growth occurred, so it is unlikely that urease inhibition is important. Lowering of pyrophosphate concentration from 13-0.45 mumol/l did not reduce its inhibitory activity so it is unlikely to act by chelating free Mg2+. We propose that pyrophosphate inhibits struvite growth principally through direct interference with the chemical mechanisms involved in crystal nucleation and growth, because of its effectiveness at very low concentrations.

Ammonia↗

PubMed1991

Effect of circumferential bands on cortical vascularity and viability.

Wire cerclage devices do not restrict cortical vascularity; however, bands, because they are flat and wide, have been implicated as the cause of fracture nonunion by disruption of cortical vascularity. This experiment evaluated the effect of cerclage bands on the cortical vascularity of bones that had not been fractured. Stainless-steel bands of four sizes (2.5, 5.0, 7.5, and 10.0 mm wide) and nylon bands of five sizes (2.5, 3.6, 4.8, 7.6, and 9.0 mm wide) were applied 1 cm apart to both femoral diaphyses of four mature dogs. In two additional dogs, 18-gauge cerclage wires were applied 5 mm apart on one femur and nylon bands were applied immediately adjacent to one another on the other femur to cover 3 cm of the length of each femoral diaphysis. These six dogs were euthanatized and perfused 7 days postoperatively and specimens were studied by microangiography and correlated histology. Two additional dogs were studied 4 and 15 weeks after application of nylon and metal bands. There was no evidence of complete cortical devascularization under any size or type of cerclage appliance at any time interval. Numerous examples of vessels traversing the cortex directly beneath all the cerclage appliances were observed. Cerclage devices, even when flat and wide, do not restrict cortical vascularity when applied to intact bones.

Angiography↗

PubMed1991

Analytical relationships of nuclear field and microdosimetric quantities for target fragmentation in tissue systems.

A simple analytic formula for the nuclear fields formed by target fragmentation in tissue systems is derived using the continuous slowing down approximation (CSDA). The energy fluctuations in sensitive localized sites within the tissue system caused by these nuclear events are defined by microdosimetry. In that CSDA is used, the energy fluctuations exclude the role of secondary electrons. The relations also relate to the response of microdosimetric devices to nuclear fragmentation fields.

Ions↗

PubMed1991

Nuclear reaction effects in use of newly recommended quality factor.

The biological risk for energetic ion exposure cannot be reliably estimated exclusive of the target nuclear reaction products produced within the local tissue. A theoretical basis is derived for evaluating target fragment contributions that are evaluated for the newly proposed quality factor.

Humans↗

PubMed1991

Optical model description of momentum transfer in relativistic heavy ion collisions.

An optical model description of momentum transfer in relativistic heavy ion collisions, based upon composite particle multiple-scattering theory, is presented. The imaginary component of the complex momentum transfer, which comes from the absorptive part of the optical potential, is shown to be the main contributor to the momentum loss of the projectile. Within the context of the Goldhaber formalism, predictions of fragment momentum distribution observables are made and compared with experimental data. Use of the model as a tool for estimating collision impact parameters is also discussed.

Ions↗

PubMed1991

Momentum transfer in relativistic heavy ion charge-exchange reactions.

Relativistic heavy ion charge-exchange reactions yield fragments (delta Z = +1) whose longitudinal momentum distributions are downshifted by larger values than those associated with the remaining fragments (delta Z = -1, -2, ...). Kinematics alone cannot account for the observed downshifts; therefore, an additional contribution from collision dynamics must be included. In this work, an optical model description of collision momentum transfer is used to estimate the additional dynamical momentum downshift. Good agreement between theoretical estimates and experimental data is obtained.

Ions↗