1,721,070 research outputs found
Cardiovascular complications of calcium supplementation in chronic kidney disease : are there arrhythmic risks?
No full textCalcium supplements may induce hypercalcaemia in patients with chronic kidney disease (CKD) or patients on hemodialysis. Even in the absence of overt hypercalcaemia, calcium supplementation may be associated with a positive calcium balance and intracellular calcium overload. There is an increased risk of complex supraventricular, ventricular arrhythmias or the risk of suffering a cardiac arrest in the presence of hypercalcaemia and calcium overload in subjects with impaired or absent renal function. A maximum intake of 1000 mg elemental calcium, combining supplements and dietary calcium, together with a 1.5 mmol/l level in the dialysate, may be a safer (opinion based) recommendation in CKD patients. This is especially the case if the patient already shows signs of extra-skeletal calcification or if they present cardiac comorbidities. Lower calcium levels in the dialysis fluid might reduce the positive calcium balance but can increase intradialytic plasma calcium changes and therefore increase the risk of arrhythmias
Renal chemoreceptors
No full textA study of the renal receptors and types of stimuli which give origin to supraspinal and spinal-mediated autonomic reflexes is presented. Multiunit and single unit recordings from the afferent renal nerves of male Sprague-Dawley rats have revealed two groups of renal chemosensitive receptors (chemoreceptors). These we have called renal R1 and R2 "chemoceptive" receptors. R1 receptors do not have a resting discharge but are activated after 38.7 ± 3.3 (S.E.) sec (n = 40) of complete renal ischemia (occlusion of the artery). Other activating stimuli are associated with a marked impairment in renal blood flow (prolonged occlusion of the renal vein and the hypotension of systemic asphyxia or hemorrhage). Their discharge is characterized by trains of impulses which cease abruptly upon re-entry of blood into the kidney. They are not responsive to increases or decreases in renal perfusion pressure or to increases in renal venous or ureteral pressure. In contrast, R2 receptors have a resting discharge and respond vigorously to backflow of normal urine (nondiuretic) into the renal pelvis. The results of the backflow into the pelvis of different test solutions (diuretic and nondiuretic urine, 1 M urea, 1 M mannitol and solutions of NaCl and KCl) indicate that this response is dependent upon the composition of the fluid bathing the renal pelvis rather than the increase in pelvic pressure or pelvic distension. The resting discharge rate is highest in nondiuretic conditions and declines substantially after diuresis is induced by extracellular volume expansion. R2 receptors are also activated by renal ischemia produced by clamping the renal artery. It is concluded that these two groups of afferent sensory units are renal chemosensitive receptors, (chemoreceptors) which respond to the chemical environment of renal interstitium
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Reno-renal and reno-adrenal reflexes in the rat
No full text1. Experiments were carried out to investigate whether the activation of renal chemoceptive receptors by natural stimuli might induce reflex alterations of efferent postganglionic activity to the ipsilateral kidney and preganglionic activity to the ipsilateral adrenal. 2. In anaesthetized rats with intact nervous system back-flow of urine and occlusion of the renal artery were accompanied by increments in efferent sympathetic activity both to the kidney and adrenal without concomitant changes in heart rate and blood pressure. 3. Greater excitatory responses in nerve activity to the same test stimuli were observed in rats with the spinal cord cut at C 1. 4. These results indicate that the natural activation of renal chemoceptive receptors might induce reno-renal and reno-adrenal excitatory reflexes which are likely to be integrated at spinal and supraspinal levels
Renal receptors in the rat sensitive to chemical alterations of their environment
No full textTwo major groups of renal chemosensory neural elements have been identified in the rat: one specifically activated by renal ischemia, the previously described 'R' chemoreceptors, and the other by backflow of nondiuretic urine into the renal pelvis. The latter group is the object of the present investigation. In anesthetized, male Sprague-Dawley rats, single-unit recordings were obtained by dissection of the centrally cut nerves of the right kidney. The responses of single units to backflow into the renal pelvis of nondiuretic urine, diuretic urine, and solutions containing urea, mannitol, or inorganic ions were compared. The excitatory effect of the backflow of nondiuretic urine was due to its chemical composition rather than to changes in pelvic pressure and pelvic distension. The same units were activated markedly by renal ischemia. The resting discharge rate of the units was very high in nondiuretic conditions, and it declined progressively when diuresis was induced by expansion of the extracellular fluid volume. It is concluded that this group of sensory elements responds to the chemical environment in the renal interstitium as modified by ions crossing the pelvic epithelium, by leakage of ions out of ischemic cells, and by alterations in the excretory function of the kidney and renal blood flow. This group of renal sensory nerve endings has been termed 'R2' chemoceptive receptors, to distinguish them from the previously described group of renal 'R' chemoreceptors
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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