The renin-angiotensin system plays a major role in the regulation of blood pressure and electrolyte homeostasis in mammals. In this study, we subjected transgenic mice containing a human renin genomic construct to a variety of pharmacological and physiological manipulations to test whether expression of the human renin gene and release of active human renin in appropriately regulated in this model. These manipulations were designed to test major regulators of renin release, including angiotensin II, the macula densa, renal perfusion pressure, and beta-adrenergic receptors. We used human plasma renin concentration and human renal renin mRNA levels to document the response of the transgene to these stimuli. Human plasma renin concentration increased in response to both angiotensin-converting enzyme inhibition with captopril and isoproterenol and decreased after a high salt diet. A low salt or sodium-deficient diet did not stimulate renin release. Human renin mRNA levels in kidney increased after captopril but were unchanged in the other experimental groups. We also measured the levels of human renin mRNA in double transgenic mice containing the same human renin gene in addition to the human angiotensinogen gene. These mice are chronically hypertensive and have increased circulating levels of angiotensin II. Human renin mRNA levels in the kidney were paradoxically elevated compared with their single transgenic normotensive counterparts. These transgenic mice provide a model for examination of human renin regulation and may help elucidate the molecular mechanisms that regulate the gene in response to physiological cues.
To evaluate whether cervical spinal neurons can influence cardiac indices and myocyte viability in the acutely ischemic heart, the hearts of anesthetized rabbits subjected to 30 min of LAD coronary arterial occlusion (CAO) were studied 3 hours after reperfusion. Control animals were compared to those exposed to pre-emptive high cervical cord stimulation (SCS; the dorsal aspect of the C1-C2 spinal cord was stimulated electrically at 50 Hz; 0.2 ms; 90% of motor threshold, starting 15 min prior to and continuing throughout CAO). Four groups of animals were so tested: 1) neuroaxis intact; 2) prior cervical vagotomy; 3) prior transection of the dorsal spinal columns at C6; and 4) following pharmacological treatment [muscarinic (atropine) or adrenergic (atenolol, prazosin or yohimbine) receptor blockade]. Infarct size (IS) was measured by tetrazolium, expressed as percentage of risk zone. C1-C2 SCS reduced acute ischemia induced IS by 43%, without changing the incidence of sudden cardiac death (SCD). While SCS-induced reduction in IS was unaffected by vagotomy, it was no longer evident following transection of C6 dorsal columns or atropinization. Beta-adrenoceptor blockade eliminated ischemia induced SCD, while alpha-receptor blockade doubled its incidence. During SCS, myocardial ischemia induced SCD was eliminated following vagotomy while remaining unaffected by atropinization. These data indicate that, in contrast to thoracic spinal neurons, i) cranial cervical spinal neurons affect both adrenergic and cholinergic motor outflows to the heart such that ii) their activation modifies ventricular infarct size and lethal arrhythmogenesis.
Cellular network service providers often have to conduct small scale testing in the operational network before a change (e.g., a new feature) is fully rolled out across the entire network. This is referred to as the First Field Application (FFA). However, assessing the effectiveness of FFA changes is challenging because of overlapping external factors: seasonality (foliage, leaves budding), weather (rain, snow, hurricanes, storms), traffic pattern changes due to big events (e.g., games at stadiums, students returning to school after holidays), and network events such as outages or other maintenance activities in different regions. In this paper, we first highlight the technical challenges in assessing the service performance impact of changes in operational cellular networks. We then propose Litmus, a new approach based on a spatial dependency model for robust assessment of changes. We evaluate the effectiveness of Litmus using real-world data from operational cellular networks (GSM, UMTS and LTE). Our operational experiences demonstrate accurate inferences of the service performance impact of changes in the field.
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