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Long-term Loss (long-term + loss)
Selected AbstractsEvaluation of Atrial Thrombus Formation and Atrial Appendage Function in Patients with Pacemaker by Transesophageal EchocardiographyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2006ABOLFATH ALIZADEH M.D. Background: Physiologic pacing is claimed to be superior to ventricular pacing in as much as it entails lower risk of atrial fibrillation, stroke, and atrial remodeling. There are few data on the relation between atrioventricular (AV) synchrony and atrial clot formation. Utilizing transesophageal echocardiography (TEE), this study sought to evaluate the effect of AV synchrony loss on left atrial physiology, atrial stasis, and clot formation. Methods: We conducted a cross-sectional study on patients with both AV and ventricular pacing with left ventricular ejection fraction (LVEF) >30%. TEE enabled us to explore atrial and pacing leads thrombi and measure left atrial appendage (LAA) flow velocity Results: A total 72 patients (mean age, 65 ± 11.7) were enrolled in the study. The pacing mode was VVI in 53% and AV sequential in 47% of patients. LVEF (mean ± SD; %) was 53.3 ± 6.2% in ventricular pacing mode and 52.2 ± 6.6 in physiologic pacing mode. Thrombus formation on pacing lead (<10 mm in 97% of patients) was observed in 32% of all the patients (23% in patients with AV sequential pacing mode and 39% with VVI mode). Left atrial appendage flow velocity (LAA-FV) was significantly higher among the patients with AV sequential pacing mode (49.44 ± 18 cm/s vs 40.94 ± 19.4 cm/s, P value = 0.02). LAA-FV >40 cm/s was detected in 60% of the patients, 60% of whom were in physiologic mode. Left atrial size was significantly larger among the patients with VVI pacing mode (42.3 ± 2.3 mm vs 37.79 ± 4.5 mm, P = 0.001). Multivariate analysis showed no relation between LAA-FV and age, hypertension, diabetes mellitus, left atrial size, and left ventricular function. Only one patient had right atrial clot. There was no thrombus in the ventricles and atrial appendage. Conclusion: Long-term loss of AV synchrony induced by VVI pacing is associated with the impairment of LAA contraction. Thrombus formation in the LAA is not increased by VVI pacing in patients with relatively good left ventricular (LV) function and sinus rhythm. [source] Seasonal dynamics of macrophytes and phytoplankton in shallow lakes: a eutrophication-driven pathway from plants to plankton?FRESHWATER BIOLOGY, Issue 3 2010CARL D. SAYER Summary 1. Seasonal relationships between macrophyte and phytoplankton populations may alter considerably as lakes undergo eutrophication. Understanding of these changes may be key to the interpretation of ecological processes operating over longer (decadal-centennial) timescales. 2. We explore the seasonal dynamics of macrophytes (measured twice in June and August) and phytoplankton (measured monthly May,September) populations in 39 shallow lakes (29 in the U.K. and 10 in Denmark) covering broad gradients for nutrients and plant abundance. 3. Three site groups were identified based on macrophyte seasonality; 16 lakes where macrophyte abundance was perennially low and the water generally turbid (,turbid lakes'); 7 where macrophyte abundance was high in June but low in August (,crashing' lakes); and 12 where macrophyte abundance was high in both June and August (,stable' lakes). The seasonal behaviour of the crashing and turbid lakes was extremely similar with a consistent increase in nutrient concentrations and chlorophyll- a over May,September. By contrast in the stable lakes, seasonal changes were dampened with chlorophyll- a consistently low (<10,15 ,g L,1) over the entire summer. The crashing lakes were dominated by one or a combination of Potamogeton pusillus, Potamogeton pectinatus and Zannichellia palustris, whereas Ceratophyllum demersum and Chara spp. were more abundant in the stable lakes. 4. A long-term loss of macrophyte species diversity has occurred in many shallow lakes affected by eutrophication. One common pathway is from a species-rich plant community with charophytes to a species-poor community dominated by P. pusillus, P. pectinatus and Z. palustris. Such compositional changes may often be accompanied by a substantial reduction in the seasonal duration of plant dominance and a greater tendency for incursions by phytoplankton. We hypothesise a slow-enacting (10,100 s years) feedback loop in nutrient-enriched shallow lakes whereby increases in algal abundance are associated with losses of macrophyte species and hence different plant seasonal strategies. In turn such changes may favour increased phytoplankton production thus placing further pressure on remaining macrophytes. This study blurs the distinction between so-called turbid phytoplankton-dominated and clear plant-dominated shallow lakes and suggests that plant loss from them may be a gradual process. [source] Theoretical Consequences of Fluctuating Versus Constant Liganding of Oestrogen Receptor-, in NeuronesJOURNAL OF NEUROENDOCRINOLOGY, Issue 6 2010D. W. Pfaff A theory is put forward that emphasises differences in neuronal responses to fluctuations in steroid hormone levels compared to constant hormone levels. We propose that neuronal functions that regulate gonadotrophin release from the anterior pituitary tend to be more sensitive to rapid increases in the levels of oestrogens than they are to constant oestrogen levels. By contrast, neurones that control certain behavioral functions are affected just as well by constant oestrogen levels as by positively accelerating levels of oestrogen. In addition to providing examples of data from recent experiments that examine actions of the long-term effects of oestrogen on mouse behaviour, we illustrate the behavioural effects of microinjections of adeno-associated viral vectors of small interfering RNA directed against the mRNA for oestrogen receptor-, (ER,). This manipulation provides for a long-term loss of ER, function in a neuranatomically specific manner. The theoretical distinction between temporal features of oestrogen sensitivity of neuroendocrine versus behavioural function is not absolute, but is intended to stimulate new experimentation that examines temporal features of oestrogen administration. [source] The Influence of Historical Land Use and Water Availability on Grassland RestorationRESTORATION ECOLOGY, Issue 2010Zhuwen Xu The ecological role of historical land use has rarely been explored in the context of grassland restoration. We conducted a 4-year field experiment in a steppe and an old field in Inner Mongolia in northern China to examine the influence of historical land use and water availability on ecosystem restoration. Species richness, evenness, and plant cover were higher in the steppe than in the old field. The steppe was more temporally stable compared with the old field in terms of species richness, evenness, plant density, and cover. Water addition increased peak aboveground biomass, belowground net primary productivity, species richness, plant density, and cover in both the steppe and the old field. Water addition also enhanced the stability of ecosystems and the restoration of grassland. Our findings suggested that historical land use determines community structure and influences the process of grassland restoration. Converting grasslands to farmland in semiarid areas can cause the long-term loss of biodiversity and instability of ecosystem with consequent impacts on ecosystem services. The amendment of limited resources is an effective practice to increase the success of ecosystem restoration. [source] A comparative study on the acute and long-term effects of MDMA and 3,4-dihydroxymethamphetamine (HHMA) on brain monoamine levels after i.p. or striatal administration in miceBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2005Isabel Escobedo 1This study investigated whether the immediate and long-term effects of 3,4-methylenedioxymethamphetamine (MDMA) on monoamines in mouse brain are due to the parent compound and the possible contribution of a major reactive metabolite, 3,4-dihydroxymethamphetamine (HHMA), to these changes. The acute effect of each compound on rectal temperature was also determined. 2MDMA given i.p. (30 mg kg,1, three times at 3-h intervals), but not into the striatum (1, 10 and 100 ,g, three times at 3-h intervals), produced a reduction in striatal dopamine content and modest 5-HT reduction 1 h after the last dose. MDMA does not therefore appear to be responsible for the acute monoamine release that follows its peripheral injection. 3HHMA does not contribute to the acute MDMA-induced dopamine depletion as the acute central effects of MDMA and HHMA differed following i.p. injection. Both compounds induced hyperthermia, confirming that the acute dopamine depletion is not responsible for the temperature changes. 4Peripheral administration of MDMA produced dopamine depletion 7 days later. Intrastriatal MDMA administration only produced a long-term loss of dopamine at much higher concentrations than those reached after the i.p. dose and therefore bears little relevance to the neurotoxicity. This indicates that the long-term effect is not attributable to the parent compound. HHMA also appeared not to be responsible as i.p. administration failed to alter the striatal dopamine concentration 7 days later. 5HHMA was detected in plasma, but not in brain, following MDMA (i.p.), but it can cross the blood,brain barrier as it was detected in the brain following its peripheral injection. 6The fact that the acute changes induced by i.p. or intrastriatal HHMA administration differed indicates that HHMA is metabolised to other compounds which are responsible for changes observed after i.p. administration. British Journal of Pharmacology (2005) 144, 231,241. doi:10.1038/sj.bjp.0706071 [source] Decision-Making Biases, Antisocial Personality, and Early-Onset AlcoholismALCOHOLISM, Issue 7 2000Carlos A. Mazas Background: Disinhibited, antisocial traits increase the risk for early-onset alcoholism. Research also suggests that decision biases which favor immediate large rewards regardless of long-term consequences may be important mechanisms associated with the biological substrates of antisocial traits. This study tested the hypothesis that early-onset alcoholism with antisocial personality (ASP) would be associated with favoring immediate larger rewards despite their being associated with long-term losses. Methods: Twenty-seven early-onset alcoholics with and without a diagnosis of ASP, eight subjects with ASP but no alcohol dependence, and 32 controls were tested on a task that manipulated the magnitude of immediate rewards and the magnitude of long-term punishments. The sample was recruited from the community via advertisements. Results: Compared with subjects without ASP, subjects with ASP favored larger immediate rewards despite long-term losses regardless of alcohol dependence; however, they learned to shift their decisions in a more advantageous direction over time. A disadvantageous decision bias also was associated with drinking greater quantities of alcohol and having a lower IQ. Conclusions: This study suggests that ASP in a young adult noninstitutionalized sample was associated with a pattern of disadvantageous decision making similar to that observed in patients with antisocial behavioral characteristics associated with lesions in the ventromedial frontal cortex. The data also suggest that this pattern of disadvantageous decision making is associated with consuming larger quantities of alcohol but not consuming alcohol more frequently. [source] | |||||||||||||