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Biomedical subjects

J A Davis

Publications and source records attributed to J A Davis.

At least 217 records · Page 12Linked to original sources
PubMed1983

Contrasting cardiovascular and respiratory responses to exercise in mitral valve and chronic obstructive pulmonary diseases.

The role of cardiovascular and pulmonary limitation in performing maximal exercise is contrasted in patients with mitral valve disease (MVD) and chronic obstructive pulmonary disease (COPD). The ventilatory (VE) gas exchange (VO2 and VCO2) and heart rate (HR) responses to an incremental cycle ergometer exercise were measured in six patients with MVD, seven patients with COPD, and six normal subjects. The VE requirement for the work (VE-VO2 relationship) was increased in both COPD and MVD groups compared with control subjects, but the breathing reserve was significantly lower in COPD (13 percent) compared with MVD (49 percent) and control groups (44 percent). In contrast, the VO2 at the anaerobic threshold was significantly lower in MVD (12.2 +/- .5 ml/kg) compared with COPD (15.7 +/- 1.2 ml/kg) and control subjects (16.6 +/- .9 ml/kg). Also, the heart rate reserve and the VO2-HR slope were significantly reduced in MVD (9 +/- 6 percent and 6.9 +/- 1.0 ml/min/beat, respectively) compared with COPD patients (44 +/- 7 percent and 2.0 ml/min/beat, respectively). Both patient groups experienced an acidosis in their terminal work rate, but the acidosis was primarily respiratory in the COPD and totally metabolic in the MVD group. These studies indicate that at maximal work rate, MVD but not COPD patients, manifest compromised O2 delivery to the muscles, while COPD but not MVD patients were unable to increase VE sufficiently to match the exercise-induced CO2 production.

Acid-Base Equilibrium↗
PubMed1982

Obstetrics.

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Family Practice↗
PubMed1982

Cervical intraepithelial neoplasia and 'wary' atypia: a study of colposcopic, histological and cytological characteristics.

Colposcopic, histological and cytological characteristics of 168 consecutive patients attending a colposcopy clinic were reviewed. A group of patients demonstrated a cluster of histological features previously related to possible human papilloma virus infection of cervical epithelium, including particularly koilocytosis, double nucleation and dyskeratosis. These patients had a significantly greater occurrence of colposcopic 'finger-like' lesion outline and colposcopic impression of warty change, but not of other specific colposcopic features. Over two-thirds of patients with histological warty features did not show these colposcopic changes. Cytological changes previously related to warty lesions did not occur commonly, and appeared to underestimate the histological occurrence of such changes. Histological changes considered to represent CIN were uncommon in patients who said that they had begun sexual activity less than 10 years ago, whereas patients with warty characteristics on histology showed no such bias.

Cervix Uteri↗
PubMed1982

Treatment of cervical intraepithelial neoplasia by colposcopically directed cryosurgery and subsequent pregnancy experience.

Of 420 patients attending a colposcopy clinic 204 were treated with outpatient cryosurgery for cervical intraepithelial neoplasia. It was possible to assess a definite outcome of therapy in 159 patients, and the lesion was successfully eradicated in 87% of them. Treatment failure appeared to be more common in patients of high parity, when the lesion extended into the cervical canal, and in those patients with large lesions. Failure appeared to be unrelated to patient age and to the histological grade of the lesion. In subsequent pregnancies utero-cervical function was preserved.

Adult↗
PubMed1982

The place of birth.

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Delivery, Obstetric↗
PubMed1982

Selective sympathetic neural changes in hypertrophied right ventricle.

Selective pressure overload of the right ventricle in guinea pigs resulted in early and sustained reductions in tyrosine hydroxylase and dopamine-beta-hydroxylase activities in the right ventricle. No changes in tyrosine hydroxylase activity were detected in stellate ganglia sinoatrial (SA) nodal region, atrioventricular (AV) nodal region, or left ventricle. Reductions in tyrosine hydroxylase activity in stressed right ventricle were similar regardless of duration of pulmonary artery constriction, extent of hypertrophy, presence or absence of hepatic congestion, and preservation or depletion of catecholamines. The changes may represent localized loss of sympathetic nerve fibers; factors involved directly in the process of pressure-overload-induced hypertrophy may be responsible. However, sympathetic nerves remaining in hypertrophied ventricle respond normally to cold-induced sympathetic activation. The reduction in tyrosine hydroxylase activity and the maintenance of norepinephrine turnover in residual innervation to hypertrophied right ventricle support the concept that sympathetic neural regulation of hypertrophied cardiac tissue is altered but not lost.

Animals↗
PubMed1982

Parameters of ventilatory and gas exchange dynamics during exercise.

To determine the precise nonsteady-state characteristics of ventilation (VE), O2 uptake (VO2), and CO2 output (VCO2) during moderate-intensity exercise, six subjects each underwent eight repetitions of 100-W constant-load cycling. The tests were preceded either by rest or unloaded cycling ("0" W). An early component of VE, VO2, and VCO2 responses, which was obscured on any single test by the breath-to-breath fluctuations, became apparent when the several repetitions were averaged. These early responses were abrupt when the work was instituted from rest but were much slower and smaller from the 0-W base line and corresponded to the phase of cardiodynamic gas exchange. Some 20 s after the onset of the work a further monoexponential increase to steady state occurred in all three variables, the time constants of which did not differ between the two types of test. Consequently, the exponential behavior of VE, VO2, and VCO2 in response to moderate exercise is best described by a model that incorporates only the second phase of the response.

Adult↗
PubMed1982

A comparison of gas exchange indices used to detect the anaerobic threshold.

This study was undertaken to determine which of four commonly used ventilatory or gas exchange indices provides the most accurate and reliable detection of the anaerobic threshold (AT). Sixteen subjects performed two cycle ergometer tests to volitional fatigue. After 4 min of unloaded cycling, the work rate was increased 20 W/min. Ventilatory and gas exchange measurements were made every 30 s throughout each test. During one of the two tests (randomly assigned), venous blood was also sampled every 30 s for subsequent determinations of blood lactate (HLa) concentration. Four ventilatory and gas exchange indices (VE, VCO2, R, VE/VO2) were used separately to detect the AT. The AT determined from systematic increases in HLa concentration was used as the criterion measure. AT values (means +/- SE) (VO2, l/min) using VE, VCO2, R, VE/VO2, and HLa were 1.79 +/- 0.11, 1.74 +/- 0.11, 1.58 +/- 0.06, 1.84 +/- 0.11, and 1.85 +/- 0.11 l/min, respectively. The highest correlation between a ventilatory or gas exchange AT and ATHLa (i.e., criterion measure) was found for VE/VO2 (r=0.93, P less than 0.001). The VE/VO2 also provided the highest test-retest correlation for detection of the AT (r = 0.93, P less than 0.001). Multiple correlational analyses did not significantly enhance detection of the AT. These results favor the use of VE/VO2 for noninvasive detection of the AT because it proved to be the most sensitive and reliable ventilatory or gas exchange index studied.

Adult↗
PubMed1982

Increased exercise performance in patients with severe COPD following inspiratory resistive training.

Six patients with severe chronic obstructive pulmonary disease underwent a six-week outpatient program to train their respiratory muscles with an inspiratory resistive device. Exercise performance was measured using a cycle ergometer. Maximum exercise capacity, represented by VO2 max, increased 15 percent. The maximum work rate increased 37 percent, and the minute ventilation attained during exercise increased 17 percent after training. Respiratory muscle endurance increased 56 percent. All patients reported an increased ability to perform the activities of daily living. No changes were reported in three patients who underwent sham training.

Breathing Exercises↗
PubMed1982

The Med-COR study: preparing high school students for health careers.

Recognizing the need for adequate representation of minorities in the health field, many professional schools initiated special recruitment efforts to attract minority students and developed programs to provide academic enrichment. Between 1971 and 1977, 480 black and Hispanic high school students from four inner-city schools in Los Angeles participated in the Med-COR Program (Medical Counseling, Organizing, and Recruiting) at the University of Southern California School of Medicine. The program was designed to increase the number of minority health professionals by offering enriched courses in the sciences and field experience in hospitals and laboratories. The positive results of a follow-up of 480 Med-COR students support the rationale that the number of minority health professionals can be increased by high school recruitment programs.

Adolescent↗
PubMed1982

Effect of ramp slope on determination of aerobic parameters from the ramp exercise test.

The effect of ramp slope on determination of aerobic parameters from the ramp exercise test. Med. Sci. Sports Exercise, Vol. 14, No. 5, pp. 339-343, 1982. We have previously demonstrated that the four parameters of aerobic function (maximal oxygen uptake (muVO2), VO2 at the anaerobic threshold (theta an), the time constant for VO2 kinetics (tau VO2), and work efficiency (eta)) may all be determined reliably from a single test in which the work rate increases continuously at a constant rate, i.e., ramp. That study, however, utilized a single ramp slope of 50 W X min-1, which may not be appropriate for subjects with very low or very high work tolerances. We therefore studied the effect of different ramp slopes on the determination of these parameters. Ramp slopes of 20, 30, 50, and 100 W X min-1 were generated on a cycle ergometer, and each was assigned randomly to 14 healthy subjects. Ventilatory and gas exchange variables were measured breath-by-breath utilizing on-line digital computation. Ramp slopes of 20, 30, and 50 W X min-1 yielded the same values for each aerobic parameter. The 100 W X min-1 ramp yielded muVO2 and eta an values that were the same as those found for the other ramp slopes, but tau VO2 and eta could not be discerned validly from this ramp slope. We conclude that valid assessment of the four parameters of aerobic function is possible with ramp slopes between 20 and 50 W X min-1; no further information on the parameters is to be gained by prolonging the tests with ramps slower than 20 W X min-1.

Adult↗
PubMed1981

Radioenzymatic assay of platelet serotonin, dopamine and norepinephrine in subjects with normal and increased serotonin production.

Platelet serotonin, dopamine and norepinephrine concentrations were determined with sensitive and specific radioenzymatic methods in normal volunteers and in sick subjects with both normal and increased serotonin production. In the assays, a 3H-labeled methyl group is transferred from [3H]S-adenosyl methionine to the monoamine under investigation by a semi-purified enzyme. The platelet serotonin concentration (expressed as pmol serotonin/mg platelet protein) was significantly higher in the patients with increased serotonin production from carcinoid tumors (5400 +/-0 500) than in the normal volunteers (900 +/- 100) or the sick subjects with normal serotonin production (900 +/- 100). Although eight of the subjects with increased serotonin production had symptoms of the carcinoid syndrome such as flushing and diarrhea, two of the subjects with increased serotonin production did not have these symptoms. The radioenzymatic method of platelet serotonin measurement was as effective as a conventional fluorometric technique for serum serotonin in detecting patients with serotonin overproduction from carcinoid tumors, and had the advantages of being more sensitive and specific. The great sensitivity and specificity of the radioenzymatic techniques suggest that it might be useful in evaluating disease states in which platelet serotonin is decreased. Using these techniques we found that dopamine and norepinephrine were also present in platelets, although in much lower amounts than serotonin. Despite the markedly increased serotonin concentration in the platelets of subjects with serotonin overproduction from carcinoid tumors, there was no alteration in the dopamine or norepinephrine concentration of their platelets.

Adult↗
PubMed1981

Dry artificial lung surfactant and its effect on very premature babies.

Artificial lung surfactant prepared with pure dipalmitoylphosphatidylcholine and phosphatidylglycerol in a ratio of 7:3 was made as a dry powder and then blown down an endotracheal tube into the lungs of 22 very premature babies at birth. Only one dose was given. The treated babies did better than their 33 controls. Fewer needed ventilation, and those who did required lower pressures in the first six hours of life. None of the treated babies died, compared with 8 of the controls.

Clinical Trials as Topic↗
PubMed1981

Abnormalities of pulmonary vascular dynamics and inflammation in early progressive systemic sclerosis.

Abnormalities of pulmonary function were studied in 10 patients with progressive systemic sclerosis (PSS) and 3 control subjects. All underwent 81M krypton lung scanning and total body gallium scanning. Immune complexes were measured by Raji cell radioimmunoassay and polyethylene glycol (PEG) assay. Perfusion scans were abnormal in 7 of 9 patients, and 5 of 9 showed a decrease in pulmonary perfusion after cold challenge. Increased gallium uptake was noted in the lungs of 6 of 9 patients. Krypton scans were normal in the control group. Elevated immune complexes were noted in 8 of 10 patients by the Raji assay and in 5 of 10 with the PEG assay. Efforts to separate patients with PSS into subgroups may lead to a better understanding of and advances in therapy for PSS.

Adult↗
PubMed1981

A case of clear cell adenocarcinoma of the vagina in pregnancy.

The case is described of a 20 year old pregnant woman with clear cell adenocarcinoma of the vagina who had been exposed to diethyl stilboestrol in utero. This is the second of three cases known to have occurred in Britain. The importance of radical treatment is discussed. Neither cervical nor vaginal intra-epithelial neoplasia were seen histologically, although squamous metaplasia was widespread, and in some areas was immature and showed atypical features which could be misinterpreted as intra-epithelial neoplasia. An area of atypical adenosis was noticed, a hitherto rarely observed feature.

Adenocarcinoma↗