The mammalian urinary bladder exhibits transepithelial Na+ absorption that contributes to Na+ gradients established by the kidney. Electrophysiological studies have demonstrated that electrogenic Na+ absorption across the urinary bladder is mediated in part by amiloride-sensitive Na+ channels situated within the apical membrane of the bladder epithelium. We have used a combination of in situ hybridization, Northern blot analysis, and immunocytochemistry to examine whether the recently cloned epithelial Na+ channel (ENaC) is expressed in the rat urinary bladder. In situ hybridization and Northern blot analyses indicate that α-, β-, and γ-rat ENaC (rENaC) are expressed in rat urinary bladder epithelial cells. Quantitation of the levels of α-, β-, and γ-rENaC mRNA expression in rat urinary bladder, relative to β-actin mRNA expression, indicates that, although comparable levels of α- and β-rENaC subunits are expressed in the urinary bladder of rats maintained on standard chow, the level of γ-rENaC mRNA expression is 5- to 10-fold lower than α- or β-rENaC mRNA. Immunocytochemistry, using an antibody directed against α-rENaC, revealed that ENaCs are predominantly localized to the luminal membrane of the bladder epithelium. Together, these data demonstrate that ENaC is expressed in the mammalian urinary bladder and suggest that amiloride-sensitive Na+ transport across the apical membrane of the mammalian urinary bladder epithelium is mediated primarily by ENaC.

Recent investigations have demonstrated that exercise-induced asthma (EIA) can be prevented by inspiration of warm, fully humidified air during exercise. We evaluated the success of a surgical face mask, used to retain warm, humidified, expired air, in preventing EIA in ten asthmatic children. subjects underwent six minutes of exercise on a treadmill during two sessions, in one session breathing room air and in another wearing a mask covering the nose and mouth. On the control day, average group forced expiratory volume in 1 s (FEV1) and maximal midexpiratory flow rate (MMEF) decreased from the preexercise baseline value to 66% and 47% of baseline, respectively, at six minutes; on the mask day, FEV1 and MMEF were 91% and 82% of the baseline values (increased in all subjects). A simple face mask may be an inexpensive, nonpharmacologic alternative for alleviation of EIA.

We continuously monitored esophageal (Pes) and gastric (Pga) pressures and used these measurements in a three-component model to estimate instantaneous diaphragmatic (DIA), inspiratory accessory muscle (IAM), and postexpiratory recoil (PER) pressures at various times during inspiration. We validated our model both by volume-pressure relationships of the respiratory system (Vrc-Pga and Vab-Pga, where Vrc and Vab are the rib cage and abdominal volumes, respectively) as well as electromyography of the respiratory muscles. Measurements were carried out at rest and during graded treadmill exercise in 11 subjects with chronic obstructive pulmonary disease (COPDs) and 8 age-matched normal subjects (AMNs). AMNs were 59 +/- 2 (SE) yr and had a forced expiratory volume at 1 s (FEV1.0) of 3.6 +/- 0.2 liters; COPDs were 66 +/- 2 yr and had a FEV1.0 of 1.0 +/- 0.1 liters. We noted the following. At rest, both AMNs and COPDs exhibited an increasing DIA pressure (PDIA) across inspiratory time (TI) at rest. As expired minute ventilation increased with exercise intensity, AMNs continued to maintain this PDIA ramp across inspiration; in contrast, COPDs exhibited higher values of PDIA during the first half of TI than during the second half. At all intensities of exercise, COPDs exhibited higher IAM and PER pressures than the AMNs.

This study examined the strategy utilized by patients with cardiovascular disease to regulate exercise intensity using the Rating of Perceived Exertion (RPE) and tested if a step-up procedure would reduce overshoot of target heart rate (HR). Also the study investigated if Prescription Congruence and Intensity Discrimination, components of the Intensity Self-regulation Model, could be validated for these patients. An estimation and production paradigm was used. HR was measured at 2-min. intervals during 6-min. stationary cycle ergometer exercise trials. Data for four experimental trials were compared: (1) a work intensity set by experimenter to achieve a target RPE of 11 (Estimation 11), (2) an intensity set by experimenter to achieve a target RPE of 13 (Estimation 13), (3) an intensity varied by participant every 2 min. to produce a target RPE of 13 (Production 13), and (4) a Step-up Procedure with the intensity varied by participant, first producing a target RPE of 11 during the first 2 min., followed by producing a target RPE of 13 from min. 2 to 6 of exercise (Production 11 + 13). A very small effect size was found for HR between Production 13 and Estimation 13, and a moderate effect size was noted for the increased HR when patients produced a target RPE of 13 as compared to 11. The participants could be divided into 2 groups: 10 patients comprised a Higher group whose HR at 2 min. during Production 13 was greater than HR at 2 min. during Estimation 13, and 6 patients in a Lower group with HR at 2 min. during Production 13 less than or equal to HR during Estimation 13. A large effect size was found at 6 min. for the reductions of the Higher group's HR overshoot and for the Lower group's HR undershoot during Production 13. All participants in the Higher group (n=10) had a clinically significant HR overshoot of 5 beats x min.(-1) at 2 min. during Production 13. Using a Step-up Procedure (Production 11 + 13), a large effect size was found for the reduced number of patients (n=3) with an overshoot of 5 beats x min.(-1) at 2 min. This supports the ability of participants in cardiac rehabilitation programs to meet the Prescription Congruence and Intensity Discrimination components of the Intensity Self-regulation Model in the RPE 11-13 zone. Evidence was found for overshoot/undershoot of target HR at 2 min., supporting a proposed third component, Production Strategy, of the Intensity Self-regulation Model. The 2-min. Step-up Procedure reduced some patients' tendency to "overshoot" target intensity.