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Biomedical subjects

S F Davies

Publications and source records attributed to S F Davies.

At least 37 records · Page 2Linked to original sources
PubMed1989

Comparative effects of transdermal clonidine and oral atenolol on acute exercise performance and response to aerobic conditioning in subjects with hypertension.

We compared the effects of transdermal clonidine and oral atenolol on acute exercise performance and on conditioning response to an 8-week program of regular aerobic exercise in young, otherwise healthy subjects with mild hypertension. The study was a double-blind, randomized, parallel-group study with placebo control. Twenty-seven subjects (11 receiving transdermal clonidine, 8 receiving oral atenolol, and 8 receiving placebo) completed the study. Atenolol controlled blood pressure in all 8 subjects, vs 6 of 11 in the transdermal clonidine group and 0 of 8 in the placebo group. Both active drugs lowered systolic blood pressure during exercise. With clonidine treatment, the antihypertensive effect during exercise was smaller and was observed only at low and moderate workloads. Acute exercise performance (subjects receiving drug but still unconditioned) was assessed by endurance time at a constant workload equal to the highest workload completed on a previous 2-minute incremental exercise test. Endurance time was reduced 35% by atenolol but not by transdermal clonidine or placebo. Neither active drug interfered with the progress of the conditioning program, as measured by gradual lengthening of exercise time. However, as assessed by change in oxygen uptake standardized to a heart rate of 170 beats per minute, the improvement in conditioning was twice as great in subjects receiving transdermal clonidine and placebo (+20%, +18%) as it was in those receiving atenolol (+8%). Subjects receiving placebo and transdermal clonidine lost weight; subjects receiving oral atenolol gained weight. The changes in weight were small.

Administration, Cutaneous↗
PubMed1989

The effect of phenylpropanolamine on blood pressure during upright bicycle exercise in normal subjects.

We studied the effect of a single oral dose (37.5 mg immediate release) of phenylpropanolamine (PPA) in six normal subjects during upright incremental bicycle exercise to symptom tolerance. The study was double blind and placebo controlled with a crossover design. The patients rested supine for 90 minutes after dosing, sat quietly on the bicycle for five minutes, and then began exercise. After PPA systolic blood pressure was increased during supine rest (135 +/- 14 mmHg vs 120 +/- 10 mmHg for placebo; P less than 0.01) and while sitting on the bicycle prior to exercise (131 +/- 8 mmHg vs 121 +/- 8 mmHg for placebo; P less than 0.05). However, PPA did not alter the expected increase in systolic blood pressure with progressive exercise. Systolic blood pressure at maximum exercise (254 +/- 43 watts) was 185 +/- 14 mmHg for PPA vs 182 +/- 13 mmHg for placebo (difference not significant). This suggests that the physiological factors controlling blood pressure during exercise (increased cardiac output, vasodilation of vessels in exercising muscles and vasoconstriction of non-exercising vascular beds) are not altered significantly by a dose of PPA sufficient to increase resting systolic blood pressure, at least in normal subjects.

Adult↗
PubMed1988

Diagnosis of pulmonary fungal infections.

The diagnosis of pulmonary fungal infections is reviewed. An overview of the major endemic and opportunistic fungal infections is followed by a brief discussion of the available diagnostic tools. These include: (1) direct microscopic examination of secretions or body fluids; (2) histopathologic examination of tissue biopsies; (3) cultures of secretions, body fluids, or ground-up tissue; and (4) immunological tests ("fungal serologies"). In the final section, a current diagnostic approach is given that identifies the diagnostic tests more likely to be helpful for each infection.

Aspergillosis↗
PubMed1988

Granulomatous diseases of the lung that mimic respiratory infections.

Granulomatous diseases of the lung may have clinical, roentgenographic, and pathological features that closely mimic respiratory tract infections. The protean manifestations of sarcoidosis allow confusion with a wide variety of infectious diseases. Acute hypersensitivity pneumonitis closely mimics an infectious illness; even subacute or chronic presentations may be mistaken for infections. Less commonly, the manifestations of intravenous talc granulomatous disease may also mimic infection.

Alveolitis, Extrinsic Allergic↗
PubMed1987

Extreme dyspnea from unilateral pulmonary venous obstruction. Demonstration of a vagal mechanism and relief by right vagotomy.

A 43-yr-old woman developed severe exertional dyspnea after an unsuccessful attempt to correct a total right anomalous pulmonary venous connection. A clotted anastomosis resulted in unilateral pulmonary venous obstruction. Investigation excluded airway disease, left ventricular failure, and severe pulmonary hypertension as the cause of dyspnea. Exercise studies demonstrated a markedly abnormal ventilatory pattern consistent with excess vagal stimuli to the respiratory center. Temporary and then permanent vagal interruption markedly altered the respiratory pattern and improved her functional status from New York Heart Association Class III to Class I, confirming that vagal afferents were the cause of the dyspnea.

Adult↗
PubMed1987

An overview of pulmonary fungal infections.

An overview of important pulmonary mycoses is presented. Four endemic mycoses occur in restricted geographic areas: histoplasmosis, blastomycosis, coccidioidomycosis, and paracoccidioidomycosis. Three opportunistic mycoses have causative agents that are ubiquitous in nature but cause infection only in compromised hosts: aspergillosis, mucormycosis, and candidiasis. Cryptococcosis is acquired by inhalation but usually presents as a chronic meningitis. Pulmonary sporotrichosis is rare; the usual subcutaneous form of the disease is acquired by inoculation. The clinical features of these infections are discussed, with special emphasis on recent advances in diagnosis and treatment.

Antifungal Agents↗
PubMed1987

Role of serodiagnostic tests and skin tests in the diagnosis of fungal disease.

Serodiagnostic tests have a significant role in the diagnosis of a number of fungal infections. The bases for these tests are reviewed and their sensitivity, specificity, and applications are discussed. Skin test antigens are also reviewed. Their diagnostic role is currently limited, but they have some utility as epidemiological tools.

Antibodies, Fungal↗
PubMed1986

Effect of respiratory alkalosis during exercise on blood lactate.

A biofeedback model of hyperventilation during exercise was used to assess the independent effects of pH, arterial CO2 partial pressure (PaCO2), and minute ventilation on blood lactate during exercise. Eight normal subjects were studied with progressive upright bicycle exercise (2-min intervals, 25-W increments) under three experimental conditions in random order. Arterialized venous blood was drawn at each work load for measurement of blood lactate, pH, and PaCO2. Results were compared with those from reproducible control tests. Experimental conditions were 1) biofeedback hyperventilation (to increase pH by 0.08-0.10 at each work load); 2) hyperventilation following acetazolamide (which returned pH to control values despite ventilation and PaCO2 identical to condition 1); and 3) metabolic acidosis induced by acetazolamide (with spontaneous ventilation). The results showed an increase in blood lactate during hyperventilation. Blood lactate was similar to control with hyperventilation after acetazolamide, suggesting that the change was due to pH and not to PaCO2 or total ventilation. Exercise during metabolic acidosis (acetazolamide alone) was associated with blood lactate lower than control values. Respiratory alkalosis during exercise increases blood lactate. This is due to the increase in pH and not to the increase in ventilation or the decrease in PaCO2.

Acetazolamide↗
PubMed1986

Comparison of the enzyme immunoassay, immunodiffusion, and complement fixation tests in detecting antibody in human serum to the A antigen of Blastomyces dermatitidis.

Using a new enzyme immunoassay (EIA) and standard immunodiffusion (ID) and complement fixation techniques for antibody to the A antigen of Blastomyces dermatitidis, we tested serum from 27 patients with blastomycosis diagnosed histopathologically or by culture; 20 with diagnoses made during 1981 through 1983 (Group A) and 7 during 1974 through 1976 (Group B). We also studied 30 control subjects with Mycoplasma pneumoniae infection (17 subjects), histoplasmosis (6 subjects), coccidioidomycosis (1 subject) and no known disease (6 subjects). Detectable antibody by all 3 tests was present more often for Group A than for Group B, possibly because of delay in testing. Enzyme immunoassay was the most sensitive test; a 1:8 or greater titer was present in acute-phase serum of all Group A patients tested, and a 1:64 or greater titer was associated with disseminated disease (p = 0.003). A positive ID was also more common in disseminated (88%) than in localized (33%) disease. Enzyme immunoassay titers of 1:16 were present in 4 control subjects, 3 with histoplasmosis. The 100% predictive values of a negative EIA and positive ID suggest that these tests are useful for serologic screening (EIA) and serologic confirmation (ID) of suspected blastomycosis, particularly in disseminated disease. Enzyme immunoassay titers of 1:32 or greater strongly support the diagnosis and titers of 1:16 or less may indicate localized disease or be nonspecific. None of the serologic tests predicted disease progression or reactivation.

Antibodies, Fungal↗
PubMed1986

A possible mechanism for mixed apnea in obstructive sleep apnea.

Hypopneas or pauses in respiratory effort frequently precede episodes of obstructive sleep apnea resulting in mixed apneas. We studied five subjects after chronic tracheostomy for obstructive sleep apnea. During stable non-REM (NREM) sleep, subjects breathed entirely through the tracheostomy. Tracheostomy occlusion caused experimental obstructive apnea which lasted 13.9 +/- 4.7 sec and ended with transient arousal and pharyngeal opening. At the end of the apnea there was marked hyperventilation (inspired minute ventilation rose 21.6 +/- 3.5 L on the first breath) followed by hypocapnia, hypopnea, and pauses in inspiratory effort as the subjects resumed NREM sleep. Hypocapnia was greater before inspiratory pauses lasting at least 5 sec than before shorter pauses (PETco2, 4.2 +/- 1.8 mm Hg below baseline vs 1.2 +/- 2.5 mm Hg below baseline). In three patients, pauses in inspiratory effort following experimental obstructive apnea were prevented by administration of 4 percent CO2 and 40 percent O2 inspired gas. This study suggests that: hyperventilation with hypocapnia occurs at the termination of obstructive apneas, and hypocapnia may be responsible for the attenuation or cessation of respiratory effort initiating the subsequent cycle of obstruction.

Adult↗
PubMed1986

Serodiagnosis of histoplasmosis.

The standard serologic tests for diagnosis of histoplasmosis include the complement fixation test (CF), which is quite sensitive, and the immunodiffusion test (ID), which is fairly specific. Radioimmunoassay (RIA) is an experimental serological test even more sensitive than CF, but also less specific. Problems with the specificity of serodiagnosis are addressed followed by a discussion of the sensitivity of the three tests in the different forms of histoplasmosis-chronic cavitary histoplasmosis, progressive disseminated histoplasmosis, and acute pulmonary histoplasmosis. Next, serologic results from a large point-source outbreak of acute pulmonary histoplasmosis in Orono, Minn, are presented. These results are used to define the sensitivity of the three tests in acute symptomatic pulmonary histoplasmosis and also to detail the time course of the appearance of antibodies measurable by each test. Finally, a case of sporadic severe acute pulmonary histoplasmosis is presented in which the approach to serodiagnosis was based on lessons learned from the Orono outbreak.

Adult↗
PubMed1986

Self-limited blastomycosis: a report of 39 cases.

We report 39 patients with pulmonary blastomycosis who were not treated with specific antifungal chemotherapy. Fourteen of these patients were recognized during an epidemic of blastomycosis in 1972 and did not have culturally proven disease. The remaining 25 patients were all proven instances of blastomycosis, 24 of whom had pulmonary disease only. Over a median observation period of 42 months (range: 12 to 168) one patient relapsed 52 months after the original diagnosis, while all of the others have remained clinically well. It is our belief that certain patients with blastomycosis limited to the lungs may safely be followed without specific antifungal chemotherapy until clearing occurs. These include patients with mild or no symptoms and those who have been more symptomatic but are already improving when the diagnosis is established. Worsening of the clinical picture, or evidence of extrapulmonary disease requires immediate antifungal chemotherapy.

Adolescent↗
PubMed1986

Blastomycosis.

Explore the source record for details and available documents.

Blastomyces↗
PubMed1984

Elevated serum angiotensin-converting enzyme (SACE) activity in acute pulmonary histoplasmosis.

Serum angiotensin-converting enzyme (SACE) levels were measured in 44 subjects six weeks after acute pulmonary histoplasmosis. All patients were infected in a common-source outbreak of histoplasmosis which occurred on one day. All patients had both strictly defined clinical and serologic evidence of infection. The SACE activity was elevated at six weeks compared to normal controls, and seven of the 44 had levels more than 2 SD above the normal mean. SACE levels were also measured at three and 24 weeks after acute infection in a smaller number of the same subjects. Serial observations demonstrated that all subjects (including those with normal and elevated SACE at six weeks) had a rise and fall in SACE activity following symptomatic acute pulmonary histoplasmosis. Our findings suggest that elevated SACE does not reliably separate sarcoidosis from histoplasmosis, although elevations in histoplasmosis are much less common and may occur only briefly following acute pulmonary histoplasmosis. More important, it seems that SACE activity rises acutely in all patients with symptomatic acute histoplasmosis and then falls gradually toward baseline over several months, coinciding temporally with the granulomatous response.

Acute Disease↗
PubMed1984

Alveolar hemorrhage syndromes: diffuse microvascular lung hemorrhage in immune and idiopathic disorders.

We have reviewed the alveolar hemorrhage (AH) syndromes, defined as immune or idiopathic disorders associated with diffuse microvascular hemorrhage into the acinar portion of the lung. The disorders that are most often associated with AH include antibasement membrane antibodies (ABMA) disease, idiopathic pulmonary hemosiderosis, systemic lupus erythematosus, systemic vasculitides, and idiopathic rapidly progressive glomerulonephritis. An approach to the recognition, diagnosis, and treatment of the AH syndromes has been outlined and several illustrative case studies have been presented. Recognition of AH is not usually difficult, but does require a high index of suspicion, since many disease processes may give rise to hemoptysis with infiltrates on chest roentgenogram. Recognition of AH is aided by careful clinical and laboratory assessment for evidence of extrapulmonary disease; simple hematologic studies such as sequential hemoglobins and iron studies; and measurement of carbon monoxide uptake by the lungs. Early recognition of AH may decrease the likelihood of respiratory failure and end-stage renal disease. The specific etiology of AH is usually determined by clinical examination, serologic assay for ABMA, and percutaneous renal biopsy by immunofluorescence. Open-lung biopsy is required in a minority of cases. High-dose pulse methylprednisolone appears to effectively control AH of diverse etiology. Combined plasma exchange and immunosuppression controls AH in ABMA disease and is the treatment of choice in this disorder. Cyclophosphamide is used for Wegener's granulomatosis, and sometimes in systemic necrotizing vasculitis, in an attempt to prevent irreversible damage to the kidneys.

Adult↗