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Biomedical subjects

S Akers

Publications and source records attributed to S Akers.

10 recordsLinked to original sources
PubMed1998

Cold exposure regulates the renin-angiotensin system.

The effect of cold exposure on the systemic renin-angiotensin system and on regulation of the angiotensin II (Ang II) receptor was examined in target organs for Ang II with cardiovascular relevance (left ventricle, kidney, lung) and metabolic relevance [interscapular brown adipose tissue (ISBAT), liver] to the functional consequences of cold exposure. In time course studies, the effects were examined of 4 hr or 1, 3 and 7 days of exposure to cold (4 degrees C) on plasma Ang II concentration and Ang II receptor binding characteristics in rat liver. Plasma Ang II concentration increased 10-fold after 4 hr of cold exposure, returned to control levels at days 1 and 3 of cold exposure, and was again increased (2-fold) at 7 days of cold exposure. The affinity of [125I]Sar1, Ile8-Ang II binding in membranes prepared from rat liver was not altered in cold-exposed rats. The density (Bmax) of binding sites in liver from cold-exposed rats was increased by day 1 and remained elevated over time-matched controls. Alterations in Ang II receptor density did not parallel plasma Ang II concentration in their time course, suggesting that cold-induced regulation of the Ang II receptor was not substrate mediated. In rats from the 7-day time point of cold exposure, Ang II receptor binding characteristics were examined in ISBAT and lung. Increases in Ang II receptor density were evident in ISBAT but not lung. To determine whether cold-induced increases in food intake contributed to elevations in plasma Ang II concentration and/or Ang II receptor density, a group of cold-exposed rats (7 days) were pair-fed to food intake levels of control rats. Pair-feeding of cold-exposed rats eliminated increases in plasma Ang II and norepinephrine concentration but did not prevent increases in Ang II receptor density in liver, ISBAT, kidney and left ventricle. Moreover, increases in Ang II receptor density were augmented in kidney and left ventricle from cold-exposed rats that were pair-fed. Results from these studies demonstrate that cold exposure resulted in an increase in plasma Ang II concentration through mechanisms related to increased food intake. Elevations in food intake in cold-exposed rats contributed to tissue-specific increases in Ang II receptor density. Moreover, cold-induced increases in Ang II receptor density were not related to plasma Ang II concentration.

Adipose Tissue↗
PubMed1993

An algorithmic approach to chronic cough.

OBJECTIVES: To evaluate a stepwise approach to chronic cough that emphasized initial treatment of all patients with an antihistamine-decongestant for postnasal drip and to determine the value of routine bronchoprovocation challenge in the evaluation of chronic cough. DESIGN: Prospective trial using an algorithm for chronic cough in immunocompetent nonsmoking out-patients. SETTING: University-based pulmonary practice. PATIENTS: Forty-five patients met the inclusion criteria. The mean duration of cough was 140 weeks (range, 3 to 2080 weeks), and the mean severity of cough as assessed by patients on a four-point scale was "severe." RESULTS: Marked improvement and resolution (mean, 3.1 and 7.1 weeks, respectively), with resolution in 96% of patients. Antihistamine-decongestant therapy was beneficial in 39 of 45 patients and was the only therapy needed for 16 patients. Bronchoprovocation challenge had a negative predictive value of 100% and a positive predictive value of 74% for cough caused by asthma. No significant relationship was found between the time to cough resolution and duration or severity of cough. Eighteen percent of patients experienced a recurrence of cough at a follow-up interval of 3 months. CONCLUSIONS: A sequential approach to chronic cough that emphasizes initial treatment with an antihistamine-decongestant is effective. Bronchoprovocation challenge is useful in evaluating patients with chronic cough but can be delayed until the initial response to antihistamine-decongestant therapy has been assessed. The 18% incidence of recurrence highlights the fact that cough often is the manifestation of a chronic or recurring process that requires chronic or episodic therapy.

Adolescent↗
PubMed1992

Specificity and sensitivity of the assay for elastin-derived peptides in chronic obstructive pulmonary disease.

One prediction of the protease-antiprotease hypothesis of chronic obstructive pulmonary disease (COPD) pathogenesis is the appearance of elastin-derived degradation products in the plasmas of affected patients that are due to the breakdown of alveolar interstitial elastin by an excess of elastolytic activity in the lung. We previously demonstrated a significant elevation of plasma elastin-derived peptides (EDP) in subjects with COPD in comparison with asymptomatic smokers with normal spirometry or normal nonsmokers. To better determine the selectivity of the assay for EDP as a marker of COPD, we measured plasma EDP levels in different patient populations. These included subjects with COPD, subjects with diseases that may involve accelerated elastolysis (pneumonia, atherosclerotic vascular disease, and inflammatory arthritis), subjects with diseases hypothesized to involve pulmonary inflammation without elastolysis (asthma and acute tracheobronchitis), asymptomatic smokers with normal spirometry, and healthy, nonsmoking subjects. Mean plasma EDP levels in subjects with COPD were elevated above those in all other subjects (p less than 0.01). The prospective analyses of specificity and sensitivity of plasma EDP levels as markers of COPD gave values of 91 and 65%, respectively. Utilizing receiver operating characteristic curve analysis to assess the diagnostic and screening performance of plasma EDP as a test for COPD (perfect test equals an area under the curve of 1.0), the area under the curve was 0.87, which compares favorably with many widely used clinical tests. These data demonstrate that the assay for plasma EDP is a quantitative, easily measured, and highly specific marker for subjects with COPD.

Adult↗
PubMed1992

Biliary lithotripsy can be enhanced with proper ultrasound probe position.

We have demonstrated in our in vitro system that an extracorporeal lithotripter utilizing a movable ultrasound probe can fragment gallstones more effectively when the ultrasound probe is not partially blocking shock waves. Using a pressure transducer we measured the pressures in the focal volume of a Wolf Piezolith 2300 lithotripter with the ultrasound probe fully extended and fully retracted. We also chose 12 pairs of twin gallstones, each taken from the same gallbladder. One stone from each pair was subjected to shock waves while the ultrasound probe was fully extended and the other treated while the probe was fully retracted. Shock wave pressures (which are converted to a measurable voltage output by our transducer) were clearly lower when the ultrasound probe was extended (5.45 volts; SEM = 0.10 volts) as compared to when the ultrasound scanner was retracted (6.7 volts: SEM = 0.08 volts). Significantly more shock waves were required to completely fragment stones when the ultrasound scanner was extended than when it was retracted (p = 0.01 using the nonparametric Wilcoxon's signed rank test). These results show that, in the lithotripter tested, an extended in-line ultrasound scanner can partially block shock waves. Retraction of an extendible ultrasound probe may enhance stone fragmentation when operating at the highest shock wave intensity.

Cholelithiasis↗
PubMed1987

Altered therapy of suspected pulmonary embolism using leg venography.

The traditional approach to the diagnosis of pulmonary embolism involves attempts to document the embolus in the lungs. An alternative diagnostic approach is to document the source of the embolus in the iliofemoral venous system. The present case shows how a search for leg thrombosis in suspected pulmonary embolism can also have an impact in choosing the optimal therapy to prevent recurrent embolization.

Aged↗
PubMed1984

The effect of nifedipine on serum digoxin concentrations in patients.

Drug interactions with digoxin are being increasingly recognized. Some calcium antagonists have been shown to alter digoxin kinetics and changes in digoxin dosage have been recommended. To determine whether nifedipine affects serum digoxin concentrations in patients during combined drug administration, serum digoxin concentrations were determined before and during concomitant drug administration in 14 cardiac patients. The mean (+/- SD) digoxin concentration was 0.92 +/- 0.5 ng/ml before and 0.96 +/- 0.5 ng/ml after 4 days of nifedipine therapy in eight inpatients. For the group of 14 patients, the mean level was 0.78 +/- 0.4 ng/ml before nifedipine and 0.8 +/- 0.4 ng/ml after 1 week of combined drug administration, and 0.84 +/- 0.5 ng/ml after 2 weeks of combined drug administration. These data suggest that nifedipine does not significantly alter serum digoxin concentrations in cardiac patients receiving combined digoxin and nifedipine in the clinical setting.

Aged↗
PubMed1983

Inhibition of airway reactivity by nifedipine in patients with coronary artery disease.

Nine patients with coronary artery disease were challenged with aerosolized methacholine before and 3 days after the daily oral administration of 30 mg of nifedipine. Resting airway tone appeared to be generally unaffected by nifedipine, as there were no significant changes in the baseline ventilatory functions. Serial measurements of spirometry and airway resistance were made after cumulative methacholine doses of 1.25, 3.75, and 8.75 mg. Identical doses of methacholine induced smaller changes in specific airway conductance (p less than 0.02), airway resistance (p less than 0.001), FEV1 (p less than 0.02), and FEF25-75% (p less than 0.01) after nifedipine therapy than before. These differences were significant at all methacholine dosage levels by paired t test except for FEV1 at the 3.75 mg dose. This study demonstrated that the bronchospastic response to methacholine in patients with coronary artery disease is reduced after the administration of nifedipine. This salutary effect on ventilatory function may be of importance to cardiac patients with concomitant chronic airway obstruction who are intolerant of beta-adrenergic blocking agents.

Airway Resistance↗