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Biomedical subjects

A C Jackson

Publications and source records attributed to A C Jackson.

125 records · Page 7Linked to original sources
PubMed1981

Serial distribution of bronchoconstriction induced by vagal stimulation or histamine.

We compared the relative site of airway responses with histamine aerosol and electrical stimulation of the vagi in dogs that were anesthetized, vagotomized, mechanically ventilated, and treated with propranolol. We made measurements of pulmonary resistance by forced oscillations and of dead-space volume as indirect indicators of airway size. Direct measures of airway size were obtained from radiographic bronchograms and from acoustically equivalent airway areas as a function of distance, computed from pulse response data. During vagal stimulation there were marked increases in pulmonary resistance, decreases in dead space, and reduction in acoustic cross-sectional area at all distances. In contrast, after inhalation of enough aerosol histamine to increase pulmonary resistance approximately as much as it did during vagal stimulation, we observed little ro no reduction in dead space and reductions in acoustic cross-sectional area that were most marked in distal airways. The findings were confirmed by the radiographic bronchograms and are consistent with observations reported by others. These observations confirm previous data and demonstrate the utility of this technique for in vivo measurements.

Airway Resistance↗
PubMed1980

Smoothing of MEFV curves by digital filtering of flow as a function of volume.

Noise in flow records limits the degree to which one can characterize local features of maximum expiratory flow-volume (MEFV) curves, i.e., the volume dependence of flow over small volume intervals such as 5-10% of the vital capacity. Such noise includes instrument noise, cardiogenic pulsations, and rapid flow oscillations due to audible turbulence. Noise removal by analog filtering of the flow vs. time signal often is unacceptable because the initial rapid onset of flow can be severely distorted. A digital technique for directly filtering the flow vs. volume record that does not distort the initial rapid flow transient has been developed. Flow values are determined at 256 volume points equally spaced over the vital capacity. This sequence of flow values is passed through a linear phase, finite impulse response, Hamming window filter. The output sequence of filtered flow values, plotted against the corresponding volumes, quantitatively retains the local shape features of the MEFV curve without the noise.

Computers↗
PubMed1980

Comparison of direct and acoustical area measurements in physical models of human central airways.

Total cross-sectional areas were computed from direct measurements made on two human central airway casts. Acoustic pulse-response measurements were obtained on rigid-walled positive replicas of these casts. From the acoustic response data of each cast, we computed the area-distance function of the acoustically equivalent structure (i.e., the structure with regular branching and negligible viscous losses, but with similar acoustic properties). The acoustic data predicted equivalent areas that compared favorably to the total cross-sectional areas in the casts at all points from the beginning of the trachea to distances about 6 cm beyond the carina corresponding to airways of the third, fourth, or fifth generation. These results indicate that, at least in the central airways, branching asymmetry and internal energy losses introduced negligible errors in estimates of cross-sectional areas derived from acoustic pulse-response measurements. This rapid noninvasive technique thus shows promise as a method of detecting upper and central airway obstruction.

Acoustics↗
PubMed1980

Lung growth and airway function after lobectomy in infancy for congenital lobar emphysema.

To characterize the outcome of lobectomy in infancy and the low expiratory flows which persist after lobectomy for congenital lobar emphysema, 15 subjects with this history were studied at age 8-30 yr. Total lung capacity was normal in all, but higher values (P < 0.05) were observed in nine subjects with upper lobectomy than in five subjects with right middle lobectomy. Ratio of residual volume to total lung capacity was correlated (P < 0.05) with the amount of lung missing as estimated from normal relative weights of the respective lobes. Xe(133) radiospirometry in eight subjects showed that the operated and unoperated sides had nearly equal volumes at total lung capacity, but that the operated side was larger than the unoperated side at residual volume. Perfusion was equally distributed between the two sides. Similar findings were detected radiographically in four other subjects. Forced expiratory volume in 1 s and maximal midexpiratory flow rate averaged 72 and 45% of predicted, respectively. Low values of specific airway conductance and normal density dependence of maximal flows in 12 subjects suggested that obstruction was not limited to peripheral airways. Pathologic observations at the time of surgery and morphometry of the resected lobes were not correlated with any test of pulmonary function. These data show that lung volume can be completely recovered after lobectomy for congenital lobar emphysema in infancy. The volume increase occurs on the operated side, and probably represents tissue growth rather than simple distension. The response to resection is influenced by the particular lobe resected and may be associated with decreased lung recoil near residual volume. Low expiratory flows in these subjects could be explained by several mechanisms, among which a disproportion between airway and parenchymal growth in infancy (dysanaptic growth) is most compatible with our data.

Adolescent↗
PubMed1980

Serial distribution of airway geometry from acoustic impedance data.

Cross-sectional areas of airways vary with distance from the airway opening to alveoli. Existing techniques for estimating the serial distribution of airway cross section are invasive or depend on interpretations of indirect measurements. A rapid, noninvasive technique based on acoustic impedance data for estimating airway cross section as a function of distance has been described. Cross-sectional areas returned by this technique from measurements in a positive cast of human central airways out to subsegmental bronchi corresponded closely with areas determined from direct measurements. In vagotomized dogs, measurements indicate that vagal stimulation results in reduction of airway cross section at all distances, whereas histamine aerosol caused bronchoconstriction only at larger distances (i.e., peripheral airways). Vagotomy in the dog results in an apparent dilation in most airways to areas twice those in the control state. This increase in airway cross section is larger than has been reported previously. Measurements in humans indicate an apparent overestimation in tracheal cross-sectional areas. These findings might be caused by overestimations in area due to airway wall compliance in the intact human and in the dog without vagal tone. This technique may still be capable of providing useful information about the serial distribution of airway properties.

Acoustic Impedance Tests↗
PubMed1979

A technique for measuring frequency response of pressure, volume, and flow transducers.

A device and methodology is presented for testing the frequency response of pressure, volume, or flow transducers. Also reported are responses of selected transducers of all three types over the range of 2--120 Hz. Several pressure transducers tested had good frequency response when connected to the test system with a minimum of interconnecting fittings; others did not. Use of additional connectors degraded the response as did the addition of air-filled catheters. The frequency response of the pneumotachometers tested were influenced largely by the response characteristics of the associated pressure transducer and interconnecting fittings. These results emphasize the need to test the response characteristics of any transducer with specific connectors and fittings that are to be used to make the actual measurements of pressure, volume, or flow.

Mathematics↗
PubMed1977

Surgical treatment of male genital lymphedema.

The etiologic classification and history of the surgical treatment of male genital lymphedema are presented. Two case reports and their results illustrate the surgical technique of skin flaps and split thickness skin grafting.

Adult↗
PubMed1977

Airway geometry by analysis of acoustic pulse response measurements.

Serial distribution of airway properties determines in part the response of the lung to high frequency oscillations. We measured the response of excised dog lungs and lobes between 156 and 10,000 Hz and determined the area-distance function of the acoustically equivalent structure having rigid walls, regular branching, and negligible internal losses. The utility of this techique was tested by determining the effects of air trapping, removal of pleura from a dried lung, central airway smooth muscle tone. A strong correlation was found between relative changes in equivalent acoustic area and relative area changes measured radiographically in individual airways at corresponding distances. We conclude that despite departures of the properties of the real lung from the characteristics of the acoustically equivalent structure, changes in the area-distance function computed by this technique provide reasonable estimates of the magnitude and serial distribution of actual changes in airway cross-sectional area.

Acoustic Impedance Tests↗
PubMed1977

Effects of androgen and estradiol administration on the weight of the ventral prostate, seminal vesicles, and testes of immature rats.

This study was designed to investigate the effects of pharmacologic doses of estradiol on th biologic actions of testosterone and 5alpha-dihydrotestosterone when administered to immature (21 to 28 of age) male rats. The weights of the prostate, seminal vesicles, and testes were used as the indicators of androgen effects. Estradiol had no effects on the testosterone- or 5alpha-dihydrotestosterone-induced increases in prostate weight over the 12 days after the androgen injection. Estradiol acted synergistically with testosterone but not 5alpha-dihydrotestosterone on the increases in seminal vesicle weight. Estradiol had no effect, by itself, on the rate of testes growth. Both androgens resulted in a decreased rate of testicular growth and this was not infuenced by estradiol.

Animals↗
PubMed1976

Cytology in the diagnosis and followup of transitional cell carcinoma of the urothelium: a review with a case series.

Acceptance of the value of urinary cytology in transitional cell carcinoma has been mixed. Over-all accuracy is only fair to good and the results in mass screening are poor. However, cytology can be valuable in the serial evaluation of selected patients by the collection of multiple specimens. It is an important adjunct in upper tract lesions, in carcinoma in situ and in the evaluation of the patient with unexplained hematuria. Herein we analyze patients with transitional cell carcinoma of the urothelium with special reference to the use of cytology irrigation specimens from the bladder and the renal pelvis as an initial diagnostic tool and as an adjunctive technique for the evaluation of recurrence.

Adult↗
PubMed1975

Glottal aperture during panting with voluntary limitation of tidal volume.

A disadvantage of the forced oscillatory technique for measuring total respiratory resistance (namely, that it is usually done during quiet breathing or breathing holding--breathing patterns where the glottic aperture may be highly variable) was overcome by making the measurement during panting. The imposed forced oscillations (Hz) were distinguished from the spontaneous quiet breathing and panting frequencies by ensemble averaging. However, when panting was voluntary restricted so as to standardize the quiet breathing and panting flow amplitudes, resistance values frequently increased. The suggestion that partial glottal closure occurred during voluntarily restricted panting was confirmed by simultaneous inspection of the glottis with a fiberoptic bronchoscope. Thus, maximal opening of the glottis is assured only during unrestricted panting.

Glottis↗
PubMedDate not supplied

Serial distribution of airway diameters from input impedance and computed tomography.

Indirect measures of airway diameter such as respiratory system input impedance (Zin) have been widely used to infer or quantify bronchoconstriction, or bronchodilation. One such measure, Zin above 100 Hz has been shown to be primarily influenced by airway geometry and airway walls but not by lung and chest wall tissues. We used a recently developed method based on a complex asymmetrically branched network of tubes with nonrigid walls to analyze Zin from 100 to 2,000 Hz in control and bronchoconstricted (histamine injection) dogs. The resulting estimates of airway diameters indicated that peripheral airways were constricted far more (approximately 30% of their control diameters) than central airways (i.e., 0% in the trachea). Separate measurements of changes in airway diameters were made in an excised dog lung using high resolution computed tomography. The observed changes in airway diameter between lung volumes of total lung capacity (TLC) and functional residual capacity (FRC) were quantitatively consistent with those obtained from Zin data in our control dogs at FRC. We conclude that this systems identification method can be used to estimate the distribution of airway diameters from Zin.

Airway Resistance↗
PubMedDate not supplied

Spontaneous recovery from the encephalomyelitis in mice caused by street rabies virus.

Recovery from rabies was studied in an experimental model. Young adult mice were inoculated in a hindlimb footpad with street rabies virus (fox salivary gland isolate). In a group of 62 mice, 97% developed clinical rabies with paresis of the extremities and spasticity, and 37% recovered with neurological sequelae. There was an acute inflammatory reaction in the brainstem and grey matter of the spinal cord, and degeneration of myelinated axons in the white matter of the cord and in the dorsal roots. Rabies virus antigen was found in the central nervous system of all mice examined between day 5 and 13, and also in trigeminal and dorsal root ganglia. Surviving mice had neutralizing antibodies in serum and brain tissue, and 90% survived an intracerebral challenge with the CVS strain of fixed rabies virus. Spontaneous recovery from rabies encephalomyelitis was demonstrated with evidence of viral replication and pathological changes in the central nervous system.

Animals↗