6,963 publications from this institution
Chronic obstructive pulmonary disease is prominent in, but not restricted to, smokers and prior-smokers. Smoking cessation, reduction of exposure to biomass fuel smoke and particular atmospheric pollutants are important for their beneficial effects on comorbidities as well as pulmonary disease.
Seventeen patients with coronary artery disease were studied with cineangiography and simultaneous tip manometry at resting heart rate and submaximal tachycardia induced by atrial pacing. During early diastole, defined as the interval from the opening of the mitral valve to the point of minimal left ventricular pressure, 20 percent of total ventricular filling took place at resting heart rate, but 62 percent occurred during tachycardia. Minimal pressure was significantly correlated with the time constant of pressure decay during the isovolumic phase (r = 0.75 at resting heart rate and r = 0.81 during tachycardia). The measured minimal pressure could be predicted by extrapolating the exponential decay of ventricular isovolumic pressure to the time of occurrence of the minimal pressure, which occurred on average 2.7 time constants from the peak negative rate of change of pressure. At resting heart rate the time constant of relaxation was inversely correlated with ventricular inflow volume (r = −0.64) and inflow rate (r = −0.72). It is concluded that left ventricular relaxation has a relevant role in early diastolic pressure-volume relations and increases during tachycardia.
Alpha-adrenoceptor subtypes in canine tracheal smooth muscle were investigated by radioligand binding and by in vitro responses of muscle strips to electrical field stimulation and exogenous alpha-agonists. [3H]Yohimbine identified a high density of alpha 2-receptors (51.4 +/- 4.9 fmoles/mg of protein; n = 5) in tracheal smooth muscle membranes, whereas [3H]prazosin revealed a low density of alpha 1-receptors (11.1 +/- 2.9 fmoles/mg of protein; n = 5). In peripheral lung membranes, however, alpha 1-receptors predominated (46.8 +/- 7.7 fmoles/mg of protein; n = 4) over alpha 2-receptors (4.1 +/- 1.5 fmoles/mg of protein; n = 4). After pretreatment with atropine and propranolol and precontraction with serotonin or histamine, the contractile response of tracheal smooth muscle to electrical field stimulation was partially inhibited by 0.3 microM prazosin (16%), potently inhibited by 0.3 microM yohimbine (89%), and abolished by a combination of the two drugs. The response to neuronally released norepinephrine is therefore mediated predominantly by alpha 2-receptors. The rank order of potency for adrenergic agonists was clonidine greater than norepinephrine greater than phenylephrine in both competition studies with [3H]yohimbine and in contraction studies, signifying a predominance of postsynaptic alpha 2-receptors. The contractile responses to exogenous norepinephrine, clonidine, and phenylephrine were only weakly inhibited by 0.3 microM prazosin but markedly inhibited by 0.3 microM yohimbine, with a Kb of 1.2 nM, which was similar to the Kd of [3H]yohimbine binding to airway smooth muscle membranes (2.7 nM).
Platelet-activating factor (PAF) was first shown to be released from rabbit basophils during an acute allergic IgE-mediated response with the capacity of activa- ting platelets, hence its name.'Full chemical char- acterization of the PAF molecule as an ether- linked phospholipid, 1-O-alkyl-2-acetyl-sn-glyceryl-3phosphorylcholine was later obtained.24There does not seem to be general agreement as to naming this molecule which is also referred to as Paf-acether, acetyl glyceryl ether phosphorylcholine (AGEPC), or anti-hypertensive polar renomedullary lipid (ARPL).However, the term platelet-activating factor or PAF
Histamine H3‐receptor agonists inhibit excitatory neuro‐transmission in human and guinea‐pig airways. Since neural bronchoconstriction may be important in asthma we have studied the effect of a specific H3‐ receptor agonist R‐alpha‐methylhistamine (alpha MeHA) on bronchoconstriction induced by the inhaled irritant sodium metabisulphite (MBS) in six mild asthmatic subjects in a randomised double‐blind crossover study. Subjects received either alpha MeHA, 10 mg (as a chloride salt) or matched placebo (P) and were then challenged with doubling concentrations of MBS (0.3‐80 mg ml‐1) nebulised from a dosimeter at 5 min intervals with measurement of specific airway conductance (sGaw) and FEV1 at 2 and 4 min respectively after each inhalation. There was no effect of alpha MeHA on baseline airway calibre and the log concentrations of MBS required to lower sGaw by 50% (log PC50) and FEV1 by 20% (log PC20) were not significantly different after alpha MeHA when compared with placebo, suggesting that selective stimulation of airway H3‐receptors does not inhibit MBS‐induced bronchoconstriction.