WITHDRAWAL OF ENDOGENOUS SYMPATHETIC DRIVE LOWERS BLOOD PRESSURE IN PRIMARY ALDOSTERONISM

We were able to observe the effect of withdrawal of endogenous sympathetic drive in a hypertensive patient with an aldosterone-secreting adrenal adenoma. Acute stimulation of both carotid sinus nerves lowered blood pressure to normotensive or hypotensive levels by reducing peripheral resistance. When chronic carotid sinus nerve stimulation was discontinued, peripheral resistance and blood pressure increased. These data suggest that the sympathetic nervous system is important in the maintenance of hypertension in established primary aldosteronism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73780/1/j.1365-2265.1981.tb00663.x.pd

Diminished finger volume pulse in borderline hypertension: Evidence for early structural vascular abnomality

Digital volume pulse during maximum dilation was determined in 27 patients with borderline essential hypertension (BHT) and 28 age-matched normotensive controls (NT). Finger pulse volume (PV) and finger systolic pressure (SBP) were measured by pneumoplethysmography during vasodilation induced by combining direct and reflex heat dilation and reactive hyperemia. Finger SBP was higher (p p -3). Pulse volume correlated inversely with SBP in BHT (r = -0.40, p < 0.05) but was unrelated to SBP in NT. Pulse volume was not altered by high or low sodium intake in BHT or NT despite significant changes in plasma renin activity (PRA). In BHT finger vessels are less distensible at a higher pressure than in NT. This abnormality is demonstrable during maneuvers to withdraw sympathetic tone and is not influenced by alteration of PRA. These data support the concept that BHT can produce structural vascular change, and demonstrate that this abnormality can be detected by a relatively simple method.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24137/1/0000394.pd

EVIDENCE AGAINST AN INTERACTION OF ANGIOTENSIN II WITH THE SYMPATHETIC NERVOUS SYSTEM IN MAN

Animal experiments indicate that angiotensin II can, under some circumstances stimulate the sympathetic nervous system at a number of different sites. In order to determine whether such a relationship of the renin-angiotensin and sympathetic nervous system exists in man, we increased (by intravenous infusion), or decreased (by administering the oral converting enzyme inhibitor captopril) circulating angiotensin II levels and monitored plasma adrenaline and nor-adrenaline responses. Angiotensin II infusions did not increase plasma catechol-amines, and lowering of angiotensin II by captopril treatment in patients with severe hypertension or congestive heart failure failed to alter plasma adrenaline or nor-adrenaline levels. Whether physiological levels of angiotensin II are capable of interacting directly with the sympathetic nervous system in man remains to be demonstrated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73600/1/j.1365-2265.1981.tb00684.x.pd

Book reviews

Teaching/Communication/Extension/Profession,

Clinical syndromes associated with disorders of renal tubular chloride transport: Excess and deficiency of a circulating factor?

Two contrasting patients are described, one with pseudo-Bartter's syndrome induced by frusemide abuse and the other a case of hyporeninaemic hypoaldosteronism.The clinical and biochemical features of these two conditions are the opposite of each other and, in the first patient, the effects of frusemide were antagonised by treatment with indomethacin while in the second frusemide itself corrected the syndrome.The decreased pressor sensitivity to infused angiotensin II seen in the patient with pseudo-Bartter's syndrome was corrected with indomethacin and the enhanced pressor sensitivity seen in hyporeninaemic hypoaldosteronism was reversed with frusemide.Frusemide, an agent which blocks chloride transport at the ascending limb of Henle's loop, was respectively thus the cause and the cure of these conditions. On the basis of this the suggestion is made that Bartter's syndrome and hyporeninaemic hypoaldosteronism represent respectively an excess and a deficiency of a circulating factor similar to frusemide capable of blocking renal tubular chloride transport.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24748/1/0000170.pd

Analysis of Granular Flow in a Pebble-Bed Nuclear Reactor

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a major impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6cm-diameter spheres draining in a cylindrical vessel of diameter 3.5m and height 10m with bottom funnels angled at 30 degrees or 60 degrees. We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.Comment: 18 pages, 21 figure

Demographics and microbiological profile of Pneumonia in United Arab Emirates

Background. Pneumonia is a common respiratory disease, which has a mortality rate of approximately 14% worldwide. The management of pneumonia is based on the patient and microbiological profile existing in the community. There is a paucity of data regarding patient demographics and the microbiological profile for pneumonia in the United Arab Emirates (UAE). Methods. We conducted a retrospective analysis of inpatients with pneumonia in the UAE. Epidemiological, clinical and microbiological data was collected from patients over the age of 16 years admitted to a single university hospital with a diagnosis of pneumonia between the years 1997 and 2002. Patients were categorised as having community acquired (CAP) or hospital acquired pneumonia (HAP). Results. Among the 361 patients, 186 were females and 175 males. The mean age (±SEM) of the males was 59±1.6 years and of the females, 56.9±1.5 years. The annual hospital admission rate for pneumonia increased from 410 per million population in 1997 to 760 in 2002. The pneumonia was community acquired in 289 (80%) and hospital acquired in 72 (20%). Hospitalisation for CAP showed a significant seasonal variation with peak admission rates in March and April and the nadir in August and September. The overall mortality rate was 13%, and was significantly higher for HAP (24%) than for CAP (10%, p<0.01). The common microorganisms isolated from sputum culture in CAP were Haemophilus.influenzae (18.6%) and Streptococcus.pneumoniae (10%). The common pathogen in HAP was Pseudomonas.aeruginosa in (50%). 4 out of 17 (23%) H. influenzae isolates were resistant to amoxicillin and 2 of 9 S. pneumoniae isolates (22%) were resistant to penicillin. Conclusions. The hospitalisation rate for CAP has increased over the years and showed a clear seasonal trend in the UAE. H. influenzae was the most common organism among patients with CAP and P. aeruginosa in HAP. The mortality rate for HAP was significantly higher than for CAP. The drug resistance pattern was similar to reports from centres elsewhere in South East Asia

Responses to Dehydration in the One-Humped Camel and Effects of Blocking the Renin-Angiotensin System

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP

Effect of B-type natriuretic peptide-guided treatment of chronic heart failure on total mortality and hospitalization: an individual patient meta-analysis

Aims Natriuretic peptide-guided (NP-guided) treatment of heart failure has been tested against standard clinically guided care in multiple studies, but findings have been limited by study size. We sought to perform an individual patient data meta-analysis to evaluate the effect of NP-guided treatment of heart failure on all-cause mortality. Methods and results Eligible randomized clinical trials were identified from searches of Medline and EMBASE databases and the Cochrane Clinical Trials Register. The primary pre-specified outcome, all-cause mortality was tested using a Cox proportional hazards regression model that included study of origin, age (45%) as covariates. Secondary endpoints included heart failure or cardiovascular hospitalization. Of 11 eligible studies, 9 provided individual patient data and 2 aggregate data. For the primary endpoint individual data from 2000 patients were included, 994 randomized to clinically guided care and 1006 to NP-guided care. All-cause mortality was significantly reduced by NP-guided treatment [hazard ratio = 0.62 (0.45-0.86); P = 0.004] with no heterogeneity between studies or interaction with LVEF. The survival benefit from NP-guided therapy was seen in younger (<75 years) patients [0.62 (0.45-0.85); P = 0.004] but not older (≥75 years) patients [0.98 (0.75-1.27); P = 0.96]. Hospitalization due to heart failure [0.80 (0.67-0.94); P = 0.009] or cardiovascular disease [0.82 (0.67-0.99); P = 0.048] was significantly lower in NP-guided patients with no heterogeneity between studies and no interaction with age or LVEF. Conclusion Natriuretic peptide-guided treatment of heart failure reduces all-cause mortality in patients aged <75 years and overall reduces heart failure and cardiovascular hospitalizatio

Active to Sterile Neutrino Mixing Limits from Neutral-Current Interactions in MINOS

Results are reported from a search for active to sterile neutrino oscillations in the MINOS long-baseline experiment, based on the observation of neutral-current neutrino interactions, from an exposure to the NuMI neutrino beam of 7.07×10^(20) protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of 754±28(stat)±37(syst) for oscillations among three active flavors. The fraction f_s of disappearing ν_μ that may transition to ν_s is found to be less than 22% at the 90% C.L