Asthma induced by house dust mites: benefits resulting from a correct environmental hygienization

Summary The aim of the present work has been the determination of the effectiveness of a primary prevention in the allergopathy induced by house dust mites weighing its benefits as regards asthmatic symptomatology.A sample of 56 subjects, aged 6 to 30 years, monosensitive to house dust mites (DTP and DTF) and with a diagnosis of bronchial asthma has been examined. The patients have entered a study plan whose purpose has been the evaluation of the effects of an environmental improvement on symptomatology. The diagnosis of asthma induced by house dust mites has been confirmed both by in vivo (Prick-test) and in vitro (PRIST and RAST) investigations.A follow-up after 3 months has shown that the hygienic measures have produced beneficial effects on symptomatology in as many as 22 patients (52.4%) out of a total of 42 who have put into practice the environmental improvement. These results encourage to proceed on this path in the choice of the therapy for those subjects affected by respiratory allergopathy to house dust mites.     

4-Aminopyridine: Effects on electrical activity during ischemia and reperfusion in perfused rat hearts

We investigated the effects of 2 and 4 mM 4-aminopyridine (4-AP, – blocker of the transient outward current I_to) on the electrophysiological response to regional ischemia and reperfusion. Spontaneously beating rat hearts were subjected to coronary occlusion (10 min) followed by reperfusion. The surface electrogram and the membrane potential from subepicardial left ventricular cells were recorded throughout. The basal effect of 4-AP was a dose dependent increase in the action potential duration (APD₉₀) without changes in the resting potential or the heart rate. During early ischemia resting depolarization (from 87.4 ± 1.9–70.1 ± 2.5 mV in the controls) was enhanced by 4 mM, 4-AP (84.3 ± 1.4 mV vs. 61.7 ± 1.3 mV) whereas APD₉₀ increased by 73.5%. These effects resulted in a marked reduction in the duration of diastolic intervals that led to conduction failure and aborted responses. A partial recovery was found by the end of ischemia concomitant with APD₉₀ shortening in both, control and 4-AP treated hearts. On reperfusion, 4-AP did not influence the initial incidence of ventricular tachyarrhythmias but decreased their duration from 531.5 ± 56.3–260.7 ± 100 sec (2 mM) and to 75.6 ± 10.5 sec (4 mM). These data confirm others obtained by Henry et al. [11] in isolated cells indicating that ischemia induces sequential changes in several K⁺ conductances. In addition, they show that changes in action potential characteristics may exert beneficial effects on reperfusion arrhythmias by acting on the arrhythmic substrate without suppressing the trigger mechanism.     

Anti-inflammatory effects of angiotensin II AT1 receptor antagonism prevent stress-induced gastric injury

Stress reduces gastric blood flow and produces acute gastric mucosal lesions. We studied the role of angiotensin II in gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats were pretreated for 14 days with the AT1 receptor antagonist candesartan before cold-restraint stress. AT1 receptors were localized in the endothelium of arteries in the gastric mucosa and in all gastric layers. AT1 blockade increased gastric blood flow by 40-50%, prevented gastric ulcer formation by 70-80% after cold-restraint stress, reduced the increase in adrenomedullary epinephrine and tyrosine hydroxylase mRNA without preventing the stress-induced increase in adrenal corticosterone, decreased the stress-induced expression of TNF-alpha and that of the adhesion protein ICAM-1 in arterial endothelium, decreased the neutrophil infiltration in the gastric mucosa, and decreased the gastric content of PGE2. AT1 receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, and anti-inflammatory effects (with reduction in TNF-alpha and ICAM-1 expression leading to reduced neutrophil infiltration) while maintaining the protective glucocorticoid effects and PGE2 release. Angiotensin II has a crucial role, through stimulation of AT1 receptors, in the production and progression of stress-induced gastric injury, and AT1 receptor antagonists could be of therapeutic benefit.     

Effects of barium and 5-hydroxydecanoate on the electrophysiologic response to acute regional ischemia and reperfusion in rat hearts

The aim of this work was to investigate the role of the inward rectifying (K₁) and the sarcolemmal ATP-sensitive K⁺ (K-ATP) channels in the electrical response to regional ischemia and the subsequent development of ventricular tachyarrhythmias on reflow (RA). Surface electrograms (ECG) and the transmembrane potential from subepicardial left ventricular cells were recorded in spontaneously beating rat hearts perfused with buffer alone (controls) or exposed to 100 M BaCl₂ or 100 M 5-hydroxydecanoate (5-HD) to block either K₁ or K-ATP channels respectively. After 20 min of equilibration and 10 min of control recordings, the left anterior descending coronary artery was occluded for 10 min. This was followed by reperfusion. The effects of regional ischemia as well as those of reperfusion (10 min) were recorded throughout. In the three groups, ischemia induced a modest decrease in heart rate and a sharp reduction in resting potential within 3 min. The latter as well as the accompanying depression of propagated electrical activity were enhanced by Ba²⁺. A partial recovery of the resting potential was observed in all groups during the last 2 min of coronary occlusion. Concomitantly, a slight reduction in the action potential duration was found in the control hearts. This effect was blocked by 5-HD. Under Barium the action potential duration increased by a factor of 3 and its ischemic variations were minimized. Severe sustained ventricular tachyarrhythmias developed on reflow in the controls and in the 5-HD exposed hearts. Barium limited the duration of arrhythmic episodes to a few seconds. Our data indicate that the initial electrical effects of ischemia are unrelated to activation of ATP sensitive K⁺ channels and that g_K1 dominates the K⁺ membrane conductance at this stage. Furthermore, they show that action potential lengthening limits the duration of arrhythmic episodes triggered by reperfusion. This suggests that electrical heterogeneity plays an important role in the perpetuation of reperfusion arrhythmias.     

Anti-stress and anti-anxiety effects of centrally acting angiotensin II AT1 receptor antagonists

The brain and the peripheral (hormonal) angiotensin II systems are stimulated during stress. Activation of brain angiotensin II AT(1) receptors is required for the stress-induced hormone secretion, including CRH, ACTH, corticoids and vasopressin, and for stimulation of the central sympathetic activity. Long-term peripheral administration of the angiotensin II AT(1) antagonist candesartan blocks not only peripheral but also brain AT(1) receptors, prevents the hormonal and sympathoadrenal response to isolation stress and prevents the formation of stress-induced gastric ulcers. The mechanisms responsible for the prevention of stress-induced ulcers by the AT(1) receptor antagonist include protection from the stress-induced ischemia and inflammation (neutrophil infiltration and increase in ICAM-1 and TNF-alpha) in the gastric mucosa and a partial blockade of the stress-induced sympathoadrenal stimulation, while the protective effect of the glucocorticoid release during stress is maintained. AT(1) receptor antagonism prevents the stress-induced decrease in cortical CRH(1) and benzodiazepine binding and is anxiolytic. Blockade of brain angiotensin II AT(1) receptors offers a novel therapeutic opportunity for the treatment of anxiety and other stress-related disorders.     

Differential electrophysiologic effects of global and regional ischemia and reperfusion in perfused rat hearts. Effects of Mg2+ concentration

The effects of regional and global ischemia on cellular electrical activity and on arrhythmias induced by reperfusion were studied at different Mg²⁺ concentrations (Mg²⁺ _o, 0, 1.2, and 4.8 mM) in perfused rat hearts. Surface electrograms and transmembrane potentials were recorded during control, 10 min of ischemia (perfusion arrest or coronary ligation), and reperfusion. Increasing Mg²⁺ _o from 0-4.8 mM decreased heart rate, did not alter action potential morphology, and had a strong antiarrhythmic action on reperfusion following coronary ligation. At low and normal Mg²⁺ _o, the incidence of tachyarrhythmias was between 70 and 80%. Global ischemia led to progressive atrioventricular block and the final ventricular beating rate was similar at all Mg²⁺ _o despite unequal initial values. The severity of arrhythmias was similar to that found after regional ischemia in Mg²⁺ _o = 0, but much lower at normal and high Mg²⁺ _o. The resting depolarization induced by coronary ligation decreased as Mg²⁺ _o was raised, but such a relation was not seen during global ischemia where the depolarization was less marked. The action potential duration did not vary with the ventricular rate between 160 and 380 beats per min but increased considerably when sinus rate was markedly slowed (40 to 80 bpm) by raising Mg²⁺ _o to 9.6 mM. Our data show that a high Mg²⁺ _o exerts a strong protection against reperfusion arrhythmias regardless of the type of ischemia. Modulation of the sinus rhythm by Mg²⁺ may contribute to its protective effect by decreasing K⁺ _o accumulation and Na⁺ _i loading during ischemia.     

Computational simulation of vibrationally resolved spectra for spin‐forbidden transitions

In this computational study, we illustrate a method for computing phosphorescence and circularly polarized phosphorescence spectra of molecular systems, which takes into account vibronic effects including both Franck‐Condon and Herzberg‐Teller contributions. The singlet and triplet states involved in the phosphorescent emission are described within the harmonic approximation, and the method fully takes mode‐mixing effects into account when evaluating Franck‐Condon integrals. Spin‐orbit couplings, which are responsible for these otherwise forbidden phenomena, are accounted for by means of a relativistic two‐component time‐dependent density functional theory method. The model is applied to two types of chiral systems: camphorquinone, a rigid organic system that allows for an extensive benchmark, and some members of a class of iridium complexes. The merits and shortcomings of the methods are discussed, and some perspectives for future developments are offered.     

Estrogen upregulates renal angiotensin II AT1 and AT2 receptors in the rat

We studied renal AT1 and AT2 receptors in male, female, ovariectomized and ovariectomized-estrogen-treated Wistar-Hanover and Wistar-Kyoto rats. AT1 receptors and AT1A receptor mRNA predominated, with no significant differences between males and females. AT2 receptor expression was restricted in female rats to the capsule, the transition zone between outer and inner medulla, the endothelium lining the papilla, and arcuate arteries and veins. There were no AT2 receptors in male rats, while male mice express substantial numbers of estrogen-dependent AT2 receptors. Arcuate arteries and veins expressed AT1B mRNA in males and females, and AT2 mRNA in females only. AT1 receptor and AT2 receptor expression were estrogen-dependent, with increases in AT1 and AT2 receptor expression after estrogen treatment in ovariectomized rats. Estrogen treatment increased prostaglandin E2 (PGE2) and cGMP concentrations in the renal medulla, and eNOS expression in cortical arteries. In rodents, expression of renal Angiotensin II receptor types is estrogen-dependent, with significant species, strain and area differences. Our results support an important role for AT2 receptors in the regulation of renal function and in the protective effects of estrogen in the kidney.