Cardiovascular variability after rilmenidine challenge: assessment of acute dosing effects by means of spectral analysis

Summary— Short-term fluctuations in blood pressure (BP) and heart rate (HR) were analysed in a group of twelve subjects with mild hypertension. Indirect finger BP was measured by a Finapres® device. The effects of an oral dose of rilmenidine (1 mg) were studied in a double-blind cross-over placebo-controlled study. Compared with placebo, rilmenidine reduced the variability of standing BP after 2 hours as estimated from the standard deviation of systolic BP which diminished by 20%. Spectral analysis of fluctuations in BP showed this reduction predominated in the mid frequency (MF) region corresponding to 10-second period oscillations, which depend on the activity of the autonomic nervous system. The average reduction in MF component for standing systolic BP was 24%. In addition the MF component for HR was reduced by 17%. This frequency domain analysis demonstrates a modified BP and HR variability profile with an acute dosing of rilmenidine. This effect being limited to the MF fluctuations in standing position orients towards an effect of the drug on the sympathetic cardiovascular control.     

Bronchial impaction in lobar collapse: CT demonstration and pathologic correlation

Bronchial (or mucoid) impaction refers to the accumulation of inspissated secretions (mucus and/or inflammatory products) within a bronchus, usually accompanied by bronchial dilatation. This process may be caused by abnormal mucociliary transport and excessive production of mucus. In other cases, a discrete lesion may be present that obstructs the bronchus with inspissated secretions accumulating distal to the obstructing lesion. Lobar collapse may result in either case if a lobar bronchus is occluded by the excessive mucus or a discrete obstructing lesion. The CT manifestations of bronchial impaction in four patients with lobar collapse are described. In two patients, the lobar collapse and distal bronchial impaction were produced by a central obstructing bronchogenic carcinoma, whereas the other two patients had an abnormal mucus accumulation without a discrete bronchial obstruction. On CT, the impacted bronchi, best seen on postcontrast images, appeared as relatively low-attenuation branching structures extending from the hilum peripherally into the more opaque enhancing atelectatic lung. In the three patients who had surgical resection of the involved lobe, pathologic examination confirmed the dilated bronchi, filled with mucus (one patient), fibrinopurulent exudate (one), or mucous plugs with Aspergillus hyphae (one). This unique pattern of impaction within a collapsed lobe should be recognized on CT and prompt a search for a possible central obstructing lesion.     

Calcium antagonist properties of the bisbenzylisoquinoline alkaloid cycleanine

Summary— The alkaloid cycleanine ([12aR-(12aR,24aR)]-2,3,12a,13,14,15,24,24a-octahydro-5,6,17,18-tetramethoxy-1,13-dimethyl-8,11: 20,23-dietheno-1H,12H [1,10]dioxacyclooctadecino[2,3,4-ij: 11,12,13-i'j']diisoquinoline) was extracted from the bulbs of Stephania glabra (Roxb) Miers and its effects on cardiac and smooth muscle preparations were studied and compared to those of nifedipine (1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridine dicarboxylic acid dimethylesther). Cycleanine inhibited the KCl-induced contraction of rabbit aortic rings with higher potency than nifedipine. IC50s for cycleanine and nifedipine were 0.8 and 7·10⁻⁹ M respectively. Cycleanine had minor effects on the norepinephrine-induced contraction of rabbit aortic rings. Cycleanine and nifedipine also depressed the contraction of rat ventricular preparations but with lower potency (IC50 = 3 and 0.03·10⁻⁶ M respectively). Action potential duration of rat right ventricular strips was decreased by both compounds. L-type Ca-current (I_CaL) of single rat ventricular cardiomyocytes was inhibited by cycleanine in a voltage- and frequency-dependent manner. With a higher potency nifedipine inhibited I_CaL in a tonic and almost frequency-independent manner. The results suggest that cycleanine can act as a potent vascular selective Ca-antagonist.