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Erect Posture (erect + posture)
Selected AbstractsThe effect of single oral low-dose losartan on posture-related sodium handling in post-TIPS ascites-free cirrhosis,HEPATOLOGY, Issue 3 2006George Therapondos Post-TIPS ascites-free patients with cirrhosis and previous refractory ascites demonstrate subtle sodium retention when challenged with a high sodium load. This is also observed in pre-ascitic patients with cirrhosis. This phenomenon is dependent on an intrarenal angiotensin II (ANG II) mechanism related to the assumption of erect posture. We investigated whether similar mechanisms were involved in post-TIPS ascites-free patients, by studying 10 patients with functioning TIPS and no ascites. We measured the effect of changing from supine to erect posture on sodium excretion at baseline and after single oral low dose losartan (7.5 mg) which has been shown to blunt proximal and distal tubular sodium reabsorption in pre-ascites. At baseline, the assumption of erect posture produced a reduction in sodium excretion (from 0.30 ± 0.06 to 0.13 ± 0.02 mmol/min, P = .05), which was mainly due to an increase in proximal tubular reabsorption of sodium (PTRNa) (69.7 ± 3.1% to 81.1 ± 1.8%, P = .003). The administration of losartan resulted in a blunting of PTRNa (supine 69.7 ± 3.1% to 63.9 ± 3.9%, P = .01 and erect 81.1 ± 1.8% to 73.8 ± 2.4%, P = .01), accompanied by an increased distal tubular reabsorption of sodium in both postures, with no overall improvement in sodium excretion on standing. In conclusion, post-TIPS ascites-free patients with cirrhosis exhibit erect posture-induced sodium retention. We speculate that (1) this effect is partly mediated by the effect of ANG II on PTRNa and (2) that the inability of low dose losartan to block the erect posture-induced sodium retention may be related to the erect posture-induced rise in aldosterone which is unmodified by losartan. (HEPATOLOGY 2006;44:640,649.) [source] The mechanism of improved sodium homeostasis of low-dose losartan in preascitic cirrhosisHEPATOLOGY, Issue 6 2002Florence Wong 200 Elizabeth St. Renal sodium retention on standing is one aspect of the abnormal renal sodium handling in preascitic, well-compensated patients with cirrhosis. Recently, it has been shown that low doses (7.5 mg) of the angiotensin II (Ang II) receptor antagonist, losartan, can reverse renal sodium retention on high, 200-mmol sodium/d diet in these patients and restore them to sodium balance. Therefore, the effect of 7.5 mg of losartan on sodium excretion, when changing from supine to erect posture for 2 hours, was examined in 10 well-compensated patients with cirrhosis and 9 age- and sex-matched controls on the same sodium diet, under strictly controlled metabolic conditions. In contrast to control subjects, in whom sodium excretion was unaffected, single 7.5-mg doses of losartan again restored the preascitic patients with cirrhosis to sodium balance. In addition, it blunted the fall in erect posture, induced renal sodium excretion by a reduction in proximal and distal tubular reabsorption of sodium. These changes occurred without any significant changes in blood volumes, systemic and renal hemodynamics, or glomerular filtration rate (GFR) and filtered sodium load compared with controls, and despite activation of the systemic renin-angiotensin-aldosterone system, which was still within normal levels. In conclusion, the beneficial natriuretic effects of low-dose losartan on erect posture , induced sodium retention in preascitic cirrhosis supports the suggestion that the pathophysiology of sodium retention in preascites is in part caused by an intrarenal tubular effect of Ang II in that posture. [source] Mechanisms of Postural Control in Alcoholic Men and Women: Biomechanical Analysis of Musculoskeletal Coordination During Quiet StandingALCOHOLISM, Issue 3 2010Edith V. Sullivan Background:, Excessive sway during quiet standing is a common sequela of chronic alcoholism even with prolonged sobriety. Whether alcoholic men and women who have remained abstinent from alcohol for weeks to months differ from each other in the degree of residual postural instability and biomechanical control mechanisms has not been directly tested. Method:, We used a force platform to characterize center-of-pressure biomechanical features of postural sway, with and without stabilizing conditions from touch, vision, and stance, in 34 alcoholic men, 15 alcoholic women, 22 control men, and 29 control women. Groups were matched in age (49.4 years), general intelligence, socioeconomic status, and handedness. Each alcoholic group was sober for an average of 75 days. Results:, Analysis of postural sway when using all 3 stabilizing conditions versus none revealed diagnosis and sex differences in ability to balance. Alcoholics had significantly longer sway paths, especially in the anterior,posterior direction, than controls when maintaining erect posture without balance aids. With stabilizing conditions the sway paths of all groups shortened significantly, especially those of alcoholic men, who demonstrated a 3.1-fold improvement in sway path difference between the easiest and most challenging conditions; the remaining 3 groups, each showed a ,2.4-fold improvement. Application of a mechanical model to partition sway paths into open-loop and closed-loop postural control systems revealed that the sway paths of the alcoholic men but not alcoholic women were characterized by greater short-term (open-loop) diffusion coefficients without aids, often associated with muscle stiffening response. With stabilizing factors, all 4 groups showed similar long-term (closed loop) postural control. Correlations between cognitive abilities and closed-loop sway indices were more robust in alcoholic men than alcoholic women. Conclusions:, Reduction in sway and closed-loop activity during quiet standing with stabilizing factors shows some differential expression in men and women with histories of alcohol dependence. Nonetheless, enduring deficits in postural instability of both alcoholic men and alcoholic women suggest persisting liability for falling. [source] Benign prostatic hyperplasia due to venous drainage malfunction in the male reproductive system: a price of erect posture in humansANDROLOGIA, Issue 5 2008W.-B. Schill Editor-in-Chief No abstract is available for this article. [source] The evolution of bipedal postures in varanoid lizardsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009GORDON W. SCHUETT The bipedal posture (BP) and gait of humans are unique evolutionary hallmarks, but similar stances and forms of locomotion have had enormous influences on a range of phylogenetically diverse tetrapods, particularly dinosaurs and birds, and a range of mammalian lineages, including non-human apes. The complex movements involved in bipedalism appear to have modest evolutionary origins, and it is presumed that a stable and erect posture is a prerequisite for erect strides and other bipedal movements. Facultative bipedalism in several lineages of lizards is achieved by running, but some varanid lizards (genus Varanus) exhibit BPs without running. In these cases, BPs (BPstanding) are not used as a form of locomotion; rather, BPstanding is associated with defensive displays, and such postures also probably permit better inspection of the environment. Yet, in other varanids, BPs have been observed only during combat episodes (BPcombat), where both contestants rise together and embrace in the so-called clinch phase. Numerous other species, however, show neither type of BP. Past researchers have commented that only large-bodied varanids exhibit BP, a behaviour that appears to show phylogenetic trends. We termed this idea the King,Green,Pianka (KGP) bipedal hypothesis. In this article, we address two main questions derived from the KGP hypothesis. First, what is the phylogenetic distribution of BP in Varanus and close relatives (varanoids)? Second, is BP positively correlated with the phylogenetic distribution of large body size (e.g. snout,vent length, SVL)? In addition, we asked a related question: do the lengths of the femur and tail show body size-independent adaptive trends in association with BP? Because varanid species that show BPstanding also use these postures during combat (BPcombat), both types of BP were analysed collectively and simply termed BP. Using comparative phylogenetic analyses, the reconstruction of BP required three steps, involving a single gain and two losses. Specifically, BP was widespread in the monophyletic Varanus, and the single gain occurred at the most recent common ancestor of the African clade. The two losses of BP occurred in different clades (Indo-Asian B clade and Indo-Australian Odatria clade). BPs are absent in the sister group to Varanus (Lanthanotus borneensis) and the other outgroup species (Heloderma spp.). Our phylogenetic reconstruction supports the KGP prediction that BP is restricted to large-bodied taxa. Using the Hansen model of adaptive evolution on a limited, but highly relevant morphological dataset (i.e. SVL; femur length, FL; tail length, TL), we demonstrated that these characters were not equivalent in their contribution to the evolution of BP in Varanus. SVL was significantly correlated with BP when modelled in a phylogenetic context, but the model identified random processes as dominant over adaptive evolution, suggesting that a body size threshold might be involved in the evolution of BP. A Brownian motion (BM) model outperformed the selection model in our analysis of relative TL, suggesting that TL and BP evolved independently. The selection model for relative FL outperformed the BM model, indicating that FL and BP share an adaptive history. Our non-phylogenetic analyses involving regression residuals of FL and TL vs. SVL showed no significant correlation between these characters and BP. We suggest that BP in Varanus provides a convergent or analogue model from which to investigate various forms of bipedalism in tetrapod vertebrates, especially other reptiles, such as theropod dinosaurs. Because BPstanding in varanids is possibly an incipient stage to some form of upright locomotion, its inclusion as a general model in evolutionary analyses of bipedalism of vertebrates will probably provide novel and important insights. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 652,663. [source] Attracting endangered species to ,safe' habitats: responses of fairy terns to decoysANIMAL CONSERVATION, Issue 4 2001D. S. Jeffries The New Zealand fairy tern (Sterna nereis davisae) is considered an endangered subspecies. The aims of this study were to quantify fairy tern responses to decoys and sound recordings and determine the viability of decoys as a technique for re-establishment of this species in protected habitat. Sixteen decoy trials were conducted in an area suitable for nesting from 9 September to 2 October 1999 at Papakanui Spit, New Zealand (36°26,S, 174°13,E). The decoy models were effective in attracting fairy terns to a specific area. There was a significant effect due to decoys with >80% of landing episodes occurring in the decoy plots. There was no effect due to individual plots. A planned contrast between decoys with and without recordings showed no significant difference. The behaviour of the fairy terns towards the decoys paralleled live tern interactions, e.g., erect postures, one aggressive response and a possible courtship feeding. Fairy terns appear to be less social than other members of the Laridae family (although their population numbers make the level of gregariousness difficult to determine). Despite low numbers, the response to the decoys was highly significant. We suggest that decoy techniques could be used as a simple and effective management tool for a wide range of group-living species. Such techniques will become particularly important as the availability of suitable habitat declines owing to anthropogenic effects. Finally, regardless of whether the attraction of fairy terns towards these decoys encourages residence and nesting in this area, the effectiveness of attracting terns to a specific location results in a safe and efficient means of trapping adults away from the nest and/or outside the breeding season. [source] | |||||||||||||