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Biomedical subjects

L K Brown

Publications and source records attributed to L K Brown.

At least 91 records · Page 5Linked to original sources
PubMed1985

Pulmonary function in singers and wind-instrument players.

Previous studies suggest that pulmonary function of singers and wind-instrument players may be better than normal control subjects due to breath-control training; however, prior studies were poorly controlled or limited in scope. In the present study, we compare 34 singers and 48 wind instrumentalists with a control group of 31 string or percussion instrumentalists using a pulmonary questionnaire, measurements of inspiratory and expiratory pressures, and spirometry. We found no significant difference between groups in maximum voluntary ventilation, forced expiratory volume in one second (FEV1), forced vital capacity (FVC), mean forced expiratory flow during the middle half of the FVC, the FEV1/FVC, peak expiratory pressure, or peak inspiratory pressure, independently or when corrected for age, sex, height, weight, years performing, smoking, presence or absence of cough, or sputum production. Smoking correlated negatively with measurements of pulmonary function in all groups. There was evidence of a heightened awareness of health among singers, who exercised more and smoked less than their colleagues. The differences in health habits may account in part for the myth of improved pulmonary volumes among singers.

Adult↗
PubMed1985

Stenosis of main bronchi mimicking fixed upper airway obstruction in sarcoidosis.

An unusual site and cause of disabling inspiratory and expiratory airflow limitation mimicking fixed upper airway obstruction is reported in two patients with sarcoidosis who had stenosis of almost the entire lengths of both main bronchi. The observed flows were consistent with a cross sectional airway diameter of 3 mm. The lumen of the trachea and proximal airways was not compromised.

Adult↗
PubMed1985

Quantitation of protein 3 content of circulating erythrocytes at the single-cell level.

The density and size of human erythrocytes has been roughly correlated with cell age, with the denser and smaller cells being older. Observations of this type have led to a hypothesis that the membranes of circulating erythrocytes are dynamic with respect to composition and that material is lost from the membrane during cell maturation and circulation. In this study, flow cytofluorimetry was used to investigate the distribution of the human erythrocyte anion transport protein (protein 3) in heterogeneous samples of circulating red cells. We verified that protein 3 can be specifically and quantitatively labeled in intact human erythrocytes with eosin-5-maleimide, a luminescent probe. Individual cells were accordingly analyzed for size by forward light scattering and for protein 3 content by quantitation of eosin fluorescence. Initial results indicated that the smallest erythrocytes had a protein 3 content equal to that of the largest circulating erythrocytes. This result was independently verified by light scatter-activated cell sorting; direct measurement of cell diameters by microscopy verified that the cell sizes of erythrocytes showing the 10% greatest and 10% smallest light-scattering signal were indeed distinct. Independent analysis of the size-sorted erythrocytes for protein 3 content was accomplished by gel electrophoresis of stroma from 150,000 large and small erythrocytes. Quantitative scanning densitometry of silver-stained gels of prepared stroma showed that protein 3 content of each set of fractionated cells was equal and did not vary as a function of cell size. Taken in combination with the reported correlation between increasing red blood cell age and decreasing cell size, these results indicate that any loss of membranous material during the cell aging process is not random.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1984

Percutaneous gastrostomy: use of intragastric balloon support.

To facilitate catheter entrance into the stomach during percutaneous gastrostomy, we sutured a balloon to a nasogastric tube and inflated the balloon in the stomach. The balloon provides support and firmness for the compliant stomach, and prevents the gastric wall from being pushed away by incoming needles and catheters. The balloon frequently becomes palpable in the left upper quadrant and offers a good target fluoroscopically or sonographically. Trocar catheters were easier to insert when the target balloon technique was used, and trocar puncture shortened procedure time. The technique initially was developed in the laboratory and then tested in cadavers. Presently it is used with patients. To date, no specific complications have occurred with this procedure.

Animals↗
PubMed1984

Quantitative variation of the common acute lymphoblastic leukemia antigen (gp100) on leukemic marrow blasts.

Marrow blasts from children with B cell precursor acute lymphoblastic leukemia (ALL) were studied for differences in quantitative expression of the common ALL antigen (CALLA). Of 42 untreated patients, 35 had detectable amounts of CALLA by flow cytometric (FCM) analysis of J-5 monoclonal antibody binding. Using an FCM technique that provides correlated measurements of a given cell surface antigen, cell size, and DNA content, we detected increased CALLA expression as lymphoblasts moved from G0/G1 phase through S phase of the cell cycle. The density of the antigen (per unit of blast surface area) remained relatively constant over the same interval, indicating that the change was not due to S phase-specific enhancement of CALLA expression. Eight cases had hyperdiploid cellular DNA content and in seven of these, only cells with clonal abnormalities of DNA content expressed the CALLA marker. Mean amounts of CALLA for each patient ranged widely within the study group, from very high to marginally detectable. This variation had no discernible relation to cell size, stem-line DNA content, percentage of cells in S phase, or the presence or absence of cytoplasmic immunoglobulin. Results of a univariate proportional hazards analysis showed that both quantitative level of CALLA for S phase cells (P = 0.048) and white blood cell count (P = 0.012) had made significant contributions to treatment outcome. Patients with relative amounts of CALLA less than the median value for the entire CALLA+ group had a higher rate of failure, which was virtually identical to that for the seven HLA-DR+ patients whose blasts lacked detectable CALLA. The observed interpatient variation in quantitative expression of CALLA is consistent with recognized steps in B cell precursor differentiation and may be useful in distinguishing patients with a less favorable prognosis.

Antibodies, Monoclonal↗
PubMed1984

Two-color flow cytometric measurement of DNA distributions of rat megakaryocytes in unfixed, unfractionated marrow cell suspensions.

The ploidy distribution of megakaryocytes shifts in response to platelet demand and thus provides a sensitive index of megakaryocytopoiesis. Flow cytometry (FCM) is a potentially valuable method for rapid determination of ploidy distributions of megakaryocyte populations; however, because megakaryocytes constitute only a very small proportion of the cells in unfractionated marrow, other rare events, such as cell clumping, complicate FCM analysis. We describe the measurement of cellular DNA distributions of megakaryocytes by two-color FCM in unfixed, unfractionated marrow--a method based on the resistance of megakaryocytes to hypotonic lysis in the cold for at least 2 days. Specific platelet antiserum was used to label megakaryocytes by indirect immunofluorescence with fluorescein (green fluorescence), and DNA was stained with propidium iodide (red fluorescence) in hypotonic citrate solution. The ploidy distribution of megakaryocytes was selectively determined with two-color, green-gated FCM, with which the red and green fluorescence of all cells is analyzed, but only the red fluorescence (DNA content) of cells that specifically bound the platelet antibody is recorded. We demonstrate that this method can readily detect changes in megakaryocyte DNA distributions due to experimental thrombocytopenia or platelet hypertransfusion and, therefore, should be useful for both experimental and clinical investigations of megakaryocytopoiesis.

Animals↗
PubMed1983

Aerosol rebreathing method for assessment of airway abnormalities: theoretical analysis and validation.

An aerosol rebreathing method which determines total aerosol deposition in the lung by rebreathing non-radioactive inert aerosol was investigated theoretically for its performance characteristics. The method was then validated experimentally by examining a system response to various operating parameters, its reproducibility and convenience in clinical use. It was found from the theoretical analysis that an optimum performance would be achieved by breathing an aerosol of particles 1 micrometer in diameter with a 500-cm3 tidal volume at the breathing rate of 30 breaths/min. With these optimum parameters, experimental results of 10 normals and 10 patients with obstructive airway disease revealed an excellent measurement reproducibility within subjects (+/- 10% from means). There was a wide separation between the two groups in terms of number of rebreathing breaths to reach 90% aerosol deposition (N90) (mean +/- S.E. = 10.8 +/- 1.6 for normals vs. 3.9 +/- 1.1 for patients) and cumulative percentage of aerosol deposition at the fourth breath (AD4) (mean +/- S.E. = 68 +/- 4.4% for normals vs. 90 +/- 3.5% for patients).

Adult↗
PubMed1983

Deposition of aerosol particles and flow resistance in mathematical and experimental airway models.

Aerosol deposition and flow resistance in obstructed airways were determined from five mathematical and experimental airway models. The first three models were theoretical and based upon Weibel's symmetrical lung model with 1) uniform reduction of airway diameter in various groups of airway generations; 2) obstruction of a few major airways such that a severe uneven flow distribution occurs in the lung; 3) focal constriction of selected large airways. In model 3, an empirical formula was utilized to assess deposition and resistance in the constricted airways. The remaining two models were tested experimentally; 4) oscillation of a compliant wall in a straight tube and 5) two-phase gas-liquid flow utilizing human sputum in a rigid branching tube. In models 1, 2, and 3, airway resistance increased to a greater extent than did the increase of aerosol deposition except when small airways were obstructed in model 1. Here, the increase of aerosol deposition was slightly higher than the rise in airway resistance. A sharp increase of aerosol deposition with a minimal increase of flow resistance was demonstrated in models 4 and 5. These data indicate that aerosol deposition may be a more sensitive indicator of airway abnormalities than overall airway resistance in small airways obstruction, during oscillation of large and medium airway walls, and when excessive secretions within the airways move with a wave or slug motion.

Aerosols↗
PubMed1980

Disopyramide (Norpace)-induced hypoglycemia.

Disopyramide (Norpace) is a recently released antiarrhythmic agent with quinidine-like actions, but structurally unique. We describe a patient in whom impressive hypoglycemia developed following treatment with this agent. Blood glucose levels returned to normal after cessation of therapy, but dropped again following rechallenge with the drug. The pathogenesis of the hypoglycemia was investigated by assessment of serum insulin, plasma glucagon and serum alanine levels during disopyramide rechallenge. Clinicians should be aware of fasting hypoglycemia as an unusual but potentially serious complication of disopyramide therapy.

Aged↗
PubMed1976

Pneumatosis coli associated with sigmoid volvulus and colonoscopy.

A case of interstitial emphysema involving the mesentery and serosa of the sigmoid colon after volvulus reduced by colonoscopy is presented. The case is reported as a form of pneumatosis intestinalis although it does not conform to the classical clinicopathologic picture of pneumatosis cystoides intestinalis. The infrequent occurrence of this condition in association with volvulus and/or colonoscopy is discussed.

Aged↗
PubMedDate not supplied

Respiratory drive and pattern during inertially-loaded CO2 rebreathing: implications for models of respiratory mechanics in obesity.

Chest wall inertance (Iw) constitutes a mechanical load which is small in normal individuals, but increases in the morbidly obese. The effect of increased Iw on respiratory drive and pattern has not previously been investigated. We studied this effect by measuring rebreathing CO2 response in 10 normal subjects with and without a 45.5 kg inertial load. Changes in inspiratory occlusion pressure (P0.1), ventilation, respiratory rate, mean inspiratory flow (VT/TI) duty cycle (TI/TT), inspiratory and expiratory times, and [P0.1/(VT/TI)] were assessed. The P0.1 vs. PETCO2 response shifted to the left during inertial loading, while the slope remained unchanged (x-intercept = 36.7 +/- 4.9 mm Hg unloaded vs. 32.7 +/- 7.5 mm Hg loaded, P less than 0.05), increasing P0.1 from 18.5 +/- 8.0 to 21.0 +/- 7.6 cm H2O at PETCO2 = 6.5 mm Hg (P less than 0.005). Respiratory pattern was unchanged with the inertial load except for a slight decrease in tidal volume. The inspiratory transfer characteristic [P0.1/(VT/TI)] at PETCO2 = 65 mm Hg increased significantly (8.3 +/- 2.0 to 10.5 +/- 2.9 cm H2O.(L.sec-1)-1, P less than 0.025) illustrating the strategy of maintaining similar ventilation by increasing inspiratory force against the load.

Adult↗