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Biomedical subjects

J T Sharp

Publications and source records attributed to J T Sharp.

At least 19 recordsLinked to original sources
PubMed1992

Acute ozone-induced lung injury in rats: structural-functional relationships of developing alveolar edema.

As part of a study on the effects of acute ozone stress on the lung surfactant system, we correlated morphometric, biochemical, and functional indices of lung injury using male rats exposed to 3 ppm ozone for 1, 2, 4, and 8 hr. Evaluation of lung mechanics, using the Pulmonary Evaluation and Diagnostic Laboratory System, revealed a significant decrease in dynamic lung compliance (ml/cmH2O/kg) from a control value of 0.84 +/- 0.02 (SEM) to 0.72 +/- 0.04 and 0.57 +/- 0.06 at 4 and 8 hr, respectively. At 2 hr there was a transient increase in PaO2 to 116 torr (control = 92 torr) followed by a decrease at 4 hr (65 torr) and 8 hr (55 torr). Morphometry of lung tissue, fixed by perfusion of fixative via the pulmonary artery at 12 cm H2O airway distending pressure, demonstrated an increase in the area of the intravascular compartment at 8 hr, in association with a 65 and 39% replacement of the alveolar area by fluid in ventral and dorsal lung regions, respectively. There was a positive correlation (r = 0.966) between alveolar edema and transudated proteins in lavage fluid. A stepwise multiple regression model, with edema as the dependent variable, suggested that pulmonary vasodilatation, hypoxemia, and depletion of surfactant tubular myelin in lavage fluid were indices for predicting alveolar edema. In a second model, with lavage protein concentration as the dependent variable, decreasing dynamic compliance and hypoxemia were predictors of progressive, intraalveolar transudation of plasma proteins. The above structural-functional relationships support the concept that ozone-induced high-protein alveolar edema is pathogenetically linked to pulmonary hyperemia, deficiency of surfactant tubular myelin, and associated lung dysfunctions.

Animals↗
PubMed1992

Structural change of the thorax in chronic obstructive pulmonary disease.

This study examines structural changes of the thorax in hyperinflated subjects with chronic obstructive pulmonary disease (COPD). Age-matched normal subjects were used for comparison. Thoracic dimensions were determined using anteroposterior and lateral chest radiographs performed at total lung capacity, functional residual capacity, and residual volume. Rib cage dimensions (lateral diameter, rib angle, anteroposterior diameter) and diaphragm position were determined at each lung volume. There were no significant differences in rib cage dimension between the COPD and normal subjects for all lung volumes. In contrast, the diaphragm was significantly lower in the COPD subjects. The change of rib cage dimensions in the COPD subjects (for a similar volume change) was not different from that in normal subjects, whereas the change of diaphragm position in the COPD subjects (for a similar volume change) was reduced. In conclusion, the primary structural change of the thorax in COPD with chronic hyperinflation is confined to the diaphragm, with no appreciable structural change in the rib cage.

Aged↗
PubMed1991

The progression of erosion and joint space narrowing scores in rheumatoid arthritis during the first twenty-five years of disease.

Erosions and cartilage destruction are nearly universal features in peripheral joints that have been chronically affected by rheumatoid arthritis. Scoring methods to measure the extent of these abnormalities in hands and wrists have been developed and have been thoroughly tested in several studies to establish their reproducibility. In this study, we utilized one of these scoring methods to examine the progression of radiologic damage as related to duration of disease. Two hundred ninety-two patients from 3 different participating centers in the Arthritis, Rheumatism, and Aging Medical Information System were included. Six hundred fifty films of the hands and wrists, obtained from 210 patients, were scored for erosions and joint space narrowing. The average annual rate of progression of the total radiologic score, which sums erosion and joint space abnormalities and has a maximum possible score of 314, was approximately 4 units per year over the first 25 years after onset; this progression was more rapid in the earlier years of disease and slightly slower in the later years. Data were insufficient to accurately determine the progression rate in disease of more than 25 years duration.

Arthritis, Rheumatoid↗
PubMed1979

Infectious arthritis.

One hundred thirteen patients with 120 episodes of septic arthritis were seen during a 14-year period. The most common bacteria cultured from joint fluid or blood during the acute episodes were gonococci, staphylococci, and streptococci. Seventeen other bacteria were the infecting organisms in one or more cases each. Other infections and medical conditions frequently were present. In some instances the septic arthritis was a complication of another infection. In other patients septic arthritis appeared to occur because of diminished resistance to infection. The majority of patients responded well to medical treatment, but eight died and 26 had persistence of articular pain at follow-up examination.

Adolescent↗
PubMed1978

Periodic respiration in erect posture in Shy-Drager syndrome.

Tilt-table polygraphic study in four patients with Shy-Drager syndrome demonstrated periodic apnoea in the erect posture. In one patient reduced hypercapneic ventilatory response and necropsy findings of neuronal loss and astrocytosis in the pontine tegmentum suggested dysfunctional respiratory neurones in the brainstem. One patient had Cheyne-Stokes respiration during the late stage of the illness.

Apnea↗
PubMed1978

Effects of lung volume and electrode position on the esophageal diaphragmatic EMG.

In anesthetized dogs studied both supine and prone, the electromyogram (EMG) of the diaphragm recorded directly from three portions of the diaphragm (crural, anterior, and costal) was compared with simultaneous recordings of the diaphragmatic EMG recorded from 10 sites in the esophagus and stomach. Effects upon the EMG of lung volume change and esophageal electrode position change were determined during bilateral supramaximal tetanic phrenic stimulation with airway occluded. Lung volume change had little effect upon the directly recorded EMG. The effect of lung volume change upon the EMG recorded from the esophagus was somewhat greater and marked change was noted as the esophageal recording site was varied. In supine dogs two sites of maximal signal were observed, one 1 cm above the cardia and the other 4--6 cm below the cardia. In prone dogs a single site for maximal signal was observed 3 cm above the cardia. An electrode site as close to the cardia as possible appears to be optimal from the point of view of variation in signal due to lung volume change and due to body position change. Gastric balloon stabilization is recommended. Proximity of the electrode and posterior gastric wall to the diaphragmatic crura may explain the maximal EMG signal recorded below the cardia.

Action Potentials↗
PubMed1978

Effects of body position change on thoracoabdominal motion.

With a linearized respiratory magnetometer, measurements of anteroposterior and lateral diameters of both the rib cage and the abdomen were made at functional residual capacity and continuously during tidal breathing. Twenty-five subjects with normal respiratory systems were studied in the sitting, supine, lateral decubitus, and prone body positions. When subjects changed from sitting to supine position anteroposterior diameters of both rib cage and abdomen decreased while their lateral diameters increased. Both anteroposterior and lateral tidal excursions of the rib cage decreased; those of the abdomen increased. When subjects turned from supine to lateral decubitus position both anteroposterior diameters increased and the lateral diameters decreased. This was associated with an increase in both lateral excursions and a decrease in the abdominal anteroposterior excursions. Diameters and tidal excursions in the prone position resembled those in the supine position. Diameter changes could be explained by gravitational effects. Differences in tidal excursions accompanying body position change were probably related to 1) differences in the distribution of respiratory muscle force, 2) differences in the activity or mechanical advantage of various inspiratory muscles, and 3) local compliance changes in parts of the rib cage and abdomen.

Abdomen↗
PubMed1978

Compliances of human rib cage and diaphragm-abdomen pathways in relaxed versus paralyzed states.

The respiratory magnetometer method of Konno and Mead was used to measure separately the rib cage and the diaphragm-abdomen components of the total respiratory system compliance in 11 subjects with normal respiratory systems. Measurements made in the awake, relaxed state by the method of Heaf and Prime were compared with similar measurements made in the anesthetized, paralyzed state by the supersyringe method. The rib cage component was greater in the paralyzed than the relaxed state in 9 of 11 subjects, but the diaphragm-abdomen component was greater in the relaxed than the paralyzed state in 8 of 11 subjects. We believe that these differences can be explained by respiratory muscle activity in the presumed relaxed state. The fraction of the tidal volume attributable to rib cage displacement compared to abdominal displacement was greater during mechanical ventilation in the paralyzed state than during awake, spontaneous breathing. This can be explained by the different distribution of inflating forces produced by diaphragmatic contraction compared to positive airway and alveolar pressure, in particular by the very different patterns of diaphragmatic displacement in the 2 states.

Abdomen↗
PubMed1978

Multicenter comparison of naproxen and indomethacin in rheumatoid arthritis.

In a double-blind, crossover study, naproxen, 250 mg twice a day, naproxen, 500 mg taken at bedtime, and indomethacin, 25 mg four times a day, were compared in 132 patients with rheumatoid arthritis; six centers participated in the study. Objective indices of arthritis activity, such as number of clinically active joints, walking time, and duration of morning stiffness, were nearly identical for the three treatment regimens. Of particular interest was the observation that efficacy of a single daily dose of naproxen was comparable to that of the twice-daily dosage. Naproxen was better tolerated than indomethacin, as shown by a statistically significant difference in the incidence of CNS complaints.

Adult↗
PubMed1977

Relationship between multicentric reticulohistiocytosis and tuberculosis.

Some cases presently classified as multicentric reticulohistiocytosis may represent unusual manifestations of tuberculosis. Antituberculous chemotherapy may be justified in patients who have clinical and histopathologic evidence of multicentric reticulohistiocytosis in association with a positive tuberculin skin test.

Arthritis↗
PubMed1977

Effect of plasma exchange on circulating immune complexes and antibody formation in patients treated with cyclophosphamide and prednisone.

A patient with systemic lupus erythematosus (SLE) and a patient with an immune complex disease resembling Goodpasture's syndrome were treated with cyclophosphamide, prednisone and repeated plasma exchanges. Circulating immune complexes decreased, and symptoms of central nervous system disease remitted for up to 15 to 20 days after plasma exchange in the patient with SLE. In vitro lymphocyte blastogenic responses to antigens were also transiently increased on two occasions following treatment. In the second patient, decreases in circulating immune complexes and clinical improvement were ascribed chiefly to immunosuppressive drug treatment. Serum antibody to keyhole limpet hemocyanin was relatively unaffected by plasma exchange in both patients. These results suggest that plasma exchange may help to deplete circulating immune complexes or alter the equilibrium between soluble antigen and antibody which causes complexes to form and circulate. It may be less effective in reducing circulating antibody levels in patients who continue to produce new antibody.

Adult↗