University of Louisville

About: University of Louisville is a education organization based out in Louisville, Kentucky, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 24600 authors who have published 49248 publications receiving 1573346 citations. The organization is also known as: UofL.

Resistance and resilience of lotic algal communities: importance of disturbance timing and current'

Abstract: We examined effects of disturbance timing on resistance and resilience of epilithic algal communities growing in fast- (29 cm/s) and slow- (12 cm/s) current outdoor experimental stream channels in Kentucky, USA that were either left undisturbed (control) over 33 d following a simulated spate, or were subjected to an additional spate after either 9, 18, 27, or 33 d. On day 33, all channels were subjected to a final spate to assess effects of short-term disturbance history on resistance, independently of seasonal influences. Suc- cession proceeded from a sparsely populated community dominated by a small, monora- phid diatom (Achnanthes minutissima) immediately after the initial spate, to dominance by dense floating mats of filamentous green algae (Zygnematales: Mougeotia and Spirogyra) and Synedra spp. by day 21-24. Resistance was generally lower in slow-current commu- nities, both in terms of cell-density reduction and displacement of taxonomic structure, than in fast-current communities. Resistance in slow-current communities varied tem- porally, with communities least resistant on day 18, when community composition and physiognomy was changing rapidly, and on day 33, when green algal mats began to senesce. On day 33, slow-current communities that had not been recently disturbed (control, D9) exhibited greatest spate-induced loss of algal biomass. Additionally, slow-current com- munities with high pre-disturbance phaeophytin content (an indicator of algal senescence) also changed most in diatom assemblage structure across the final spate. No such rela- tionship was noted in fast current, suggesting that autogenic factors influenced communities in slow current more than those in fast. Resilience was higher in slow-current communities than in fast current, with disturbed communities reaching biomass and taxonomic structure similar to controls after 3-9 d. High resilience in slow current resulted from enhanced reproduction in some populations following spate-induced biomass reduction and pre- sumed release from nutrient and light limitation, and low shear stress relative to fast- current channels where biomass accrual was limited by current. Interactions between dis- turbance timing, successional state, and habitat affect the susceptibility of epilithic algal communities to disturbance and likely influence temporal and spatial heterogeneity in stream ecosystems.

Bacteraemia following periodontal procedures

Abstract: Introduction Transient bacteraemias are frequently detected following dental manipulation. Infective endocarditis (IE) can arise in susceptible individuals and antibiotic prophylaxis is routinely performed for certain procedures considered to be "at risk" of IE. Evidence is emerging that periodontal disease may be a significant risk factor for the development of certain systemic diseases such as cardiovascular disease. These systemic conditions could be initiated or detrimentally influenced by the repeated entry of bacteria into the bloodstream. Materials and methods The present study comprised a single blind parallel study of 2 weeks duration. A baseline blood sample was obtained from 30 volunteers with untreated periodontal disease following which a periodontal probing depth chart was collected. A further blood sample was taken following this procedure, and each subject was recalled 2 weeks later. A blood sample was collected, the subject carried out toothbrushing and a further blood sample taken. Full-mouth ultrasonic scaling was then performed and a final blood sample taken. Blood samples were analysed for bacteraemia using conventional microbiological culture and polymerase chain reaction (PCR) using universal bacterial primers that target the 16S ribosomal RNA gene of the vast majority of bacteria. Results Using culture methods, the incidence of bacteraemias was as follows: following ultrasonic scaling (13%), periodontal probing (20%) and toothbrushing (3%). PCR analysis revealed bacteraemia incidences following ultrasonic scaling, periodontal probing and toothbrushing of 23%, 16% and 13%, respectively. Conclusion These findings suggest that detectable dental bacteraemias induced by periodontal procedures are at a lower level than previously reported.

Evidence that late preconditioning against myocardial stunning in conscious rabbits is triggered by the generation of nitric oxide.

Abstract: Recent studies in conscious pigs and rabbits have demonstrated that a series of brief coronary occlusions renders the heart relatively resistant to myocardial “stunning” 24 hours later (late preconditioning [PC] against stunning). The mechanism of this powerful cardioprotective response is unknown. The goal of the present study was to test the hypothesis that the development of late PC against stunning is triggered by increased generation of NO during the first ischemic challenge. Conscious rabbits underwent a sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles for 3 consecutive days (days 1, 2, and 3). On day 1, rabbits received either an intravenous infusion of the NO synthase inhibitor Nω-nitro-l-arginine (L-NA, 13 mg/kg before the first occlusion) (group II, n=10) or vehicle (group I [control], n=10). In the control group, on day 1 systolic wall thickening (WTh) in the ischemic/reperfused region remained significantly depressed for 4 hours after the sixth reperfusion, indi...