Chemical stability and aggregation activity of assembly pheromone of argasid ticks and its synthetic purine analogues were studied during long-lasting storage at room temperature as the potential components of attractant/acaricide mixtures. Guanine spherules from dry excreta of Omithodoros moubata Murray, 1877 were very stable in their chemical composition and did not suffer from purine degradation. However, an intensive purine conversion into uric acid occurred in samples of the fluid of the excreta of Argas persicus (Oken, 1818) and to a lesser extent also in an artificial mixture of synthetic guanine, xanthine and hypoxanthine in saline. The presence of bacteria Bacillus sp. and the moulds Talaromyces flavus (syn. Pénicillium dangeardii) and Aspergillus carbonarius, isolated from some samples, might explain the enzymic degradation of purines. The suspension of guanine hydrochloride in saline or in saline with ethanol (1 : 1 v/v) as a potential acaricide solvent, and with diatomaceous earth as the pheromone carrier, was very stable and no guanine degradation occurred. This proved to be suitable for potential use mixed with acaricides for tick control. The assembly of A. persicus males, on most of the substrates tested, was very high up to day 77 of experiment but decreased significantly on day 114-119 in samples of synthetic analogue of assembly pheromone variant 1 in which the absolute amount of guanine in solutions strongly decreased or disappeared completely.
Nitric oxide (NO) plays a crucial role not only in regulation of blood pressure but also in maintenance of cardiac autonomic tone and its deficiency induced hypertension is accompanied by cardiac autonomic dysfunction. However, underlying mechanisms are not clearly defined. We hypothesized that sympathetic activation mediates hemodynamic and cardiac autonomic changes consequent to deficient NO synthesis. We used chemical sympathectomy by 6-hydroxydopamine to examine the influence of sympathetic innervation on baroreflex sensitivity (BRS) and heart rate variability (HRV) of chronic NG-nitro-L-arginine methyl ester (L-NAME) treated adult Wistar rats. BRS was determined from heart rate responses to changes in systolic arterial pressure achieved by intravenous administration of phenylephrine and sodium nitroprusside. Time and frequency domain measures of HRV were calculated from 5-min electrocardiogram recordings. Chronic L-NAME administration (50 mg/kg per day for 7 days orally through gavage) in control rats produced significant elevation of blood pressure, tachycardia, attenuation of BRS for bradycardia and tachycardia reflex and fall in time as well as frequency domain parameters of HRV. Sympathectomy completely abolished the pressor as well as tachycardic effect of chronic L-NAME. In addition, BRS and HRV improved after removal of sympathetic influence in chronic L-NAME treated rats. These results support the concept that an exaggerated sympathetic activity is the principal mechanism of chronic L-NAME hypertension and associated autonomic dysfunction., M. Chaswal, S. Das, J. Prasad, A. Katyal, M. Fahim., and Obsahuje bibliografii