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H Perfusion (h + perfusion)
Selected AbstractsDevelopment of an Improved Technique for the Perfusion of the Isolated Caudal Lobe of Sheep LiverEXPERIMENTAL PHYSIOLOGY, Issue 5 2000A. M. Ali The study was designed to develop an improved technique for perfusing the isolated caudal lobe of sheep liver. Twenty caudal lobes were perfused for 3-4 h, in a non-recirculating mode, with Krebs-Henseleit bicarbonate buffer. The perfusion system was designed to give a constant flow. The hepatic viability and functional normality of the perfused lobe were assessed by measuring the perfusion flow rate, pH, K+ efflux, O2 uptake, substrate uptake, gluconeogenesis from propionate and amino acids, and ureagenesis from ammonia and amino acids. Liver tissue was sampled for histological examination, as well as for the determination of liver glycogen and wet: dry weight ratio. The perfusion flow rate and pH were both stable throughout the perfusion. The potassium concentration in the effluent perfusate did not increase during the perfusion, suggesting that there was no loss of viability or hypoxia. The perfused lobe extracted more than 50% of the O2 supply. The rate of oxygen consumption was comparable to the rate reported in vivo. The initial glycogen content was reduced by about 40% after 4 h perfusion. The wet: dry weight ratio was 3.6, consistent with the absence of tissue oedema. Urea production was stimulated when NH4Cl (0.3 mM) was added to the medium but there was no significant increase in urea release when alanine (0.15 mM), glutamine (0.2 mM) or lysine (0.2 mM) was added. Urea production, however, increased by about 171% when a physiological mixture of amino acids was added. Propionate (0.5 mM), alanine and glutamine stimulated glucose production but not lysine or the complete amino acid mixture. Glutamine release was lower than that reported in the rat liver. Changing the direction of flow also revealed an apparent difference between livers from sheep and rats in their metabolism of ammonia. The improved technique offers a simple practical and inexpensive approach to many problems in ruminant physiology and nutritional biochemistry. [source] A novel in vitro flat-bed perfusion biofilm model for determining the potential antimicrobial efficacy of topical wound treatmentsJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2009R.M.S. Thorn Abstract Aims:, To develop an in vitro flat-bed perfusion biofilm model that could be used to determine the antimicrobial efficacy of topically applied treatments. Methods and Results:,Pseudomonas aeruginosa and Staphylococcus aureus biofilms were grown within continuously perfused cellulose matrices. Enumeration of the biofilm density and eluate was performed at various sampling times, enabling determination of the biofilm growth rate. Two antimicrobial wound dressings were applied to the surface of mature biofilms and periodically sampled. To enable real-time imaging of biofilm growth and potential antimicrobial kinetics, a bioluminescent Ps. aeruginosa biofilm was monitored using low-light photometry. Target species produced reproducible steady-state biofilms at a density of c. 107 per biofilm support matrix, after 24-h perfusion. Test dressings elicited significant antimicrobial effects, producing differing kill kinetic profiles. There was a good correlation between photon and viable count data. Conclusions:, The model enables determination of the antimicrobial profile of topically applied treatments against target species biofilms, accurately differentiating bactericidal from bacteriostatic effects. Moreover, these effects could be monitored in real time using bioluminescence. Significance and Impact of the Study:, This is the first in vitro biofilm model which can assess the antimicrobial potential of topical therapies in a dynamic growth environment. [source] Are Standard Human Coagulation Tests Suitable in Pigs and Calves During Extracorporeal Circulation?ARTIFICIAL ORGANS, Issue 7 2001Xavier M. Mueller Abstract: The thrombogenicity of membrane oxygenators as well as clotting parameters profiles, using standard human clotting tests, was analyzed in calves and pigs during 6 h perfusion. Three calves and 3 pigs were connected to extracorporeal circulation with standard heparinization. Blood samples were taken for coagulation variables throughout perfusion, and oxygenators were examined for clot deposits at the end of the experiment. Two out of 3 oxygenators of the calf group presented clot deposits while none in the pig group did. Baseline coagulation variables of pigs showed values similar to those of humans while neither extrinsic nor intrinsic pathways could be activated in calves with standard human coagulation tests. The calf model, in conclusion, was confirmed to be a difficult model for the testing of extracorporeal circulation device resistance to thrombus formation, which is, however, not reflected by standard human coagulation tests. The pig model is a better model in which both coagulation pathways could be activated with standard human coagulation tests. [source] Development of a small-scale bioreactor: Application to in vivo NMR measurementBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2005Dorra Gmati Abstract A perfused bioreactor allowing in vivo NMR measurement was developed and validated for Eschscholtzia californica cells. The bioreactor was made of a 10-mm NMR tube. NMR measurement of the signal-to-noise ratio was optimized using a sedimented compact bed of cells that were retained in the bioreactor by a supporting filter. Liquid medium flow through the cell bed was characterized from a mass balance on oxygen and a dispersive hydrodynamic model. Cell bed oxygen demand for 4 h perfusion required a minimal medium flow rate of 0.8 mL/min. Residence time distribution assays at 0.8,2.6 mL/min suggest that the cells are subjected to a uniform nutrient environment along the cell bed. Cell integrity was maintained for all culture conditions since the release of intracellular esterases was not significant even after 4 h of perfusion. In vivo NMR was performed for 31P NMR and the spectrum can be recorded after only 10 min of spectral accumulation (500 scans) with peaks identified as G-6P, F-6P, cytoplasmic Pi, vacuolar Pi, ATP, and ADP,, ATP, and ADP,, NADP and NDPG, NDPG and ATP,. Cell viability was shown to be maintained as 31P chemical shifts were constant with time for all the identified nuclei, thus suggesting constant intracellular pH. © 2004 Wiley Periodicals, Inc. [source] A rapid and transient synthesis of nitric oxide (NO) by a constitutively expressed type II NO synthase in the guinea-pig suprachiasmatic nucleusBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2001Sarah J Starkey We have measured extracellular NO/NO2, concentrations in guinea-pig suprachiasmatic nucleus (SCN) brain slices using fast cyclic voltammetry. A rapid and transient signal equivalent to 2.2±0.2 ,M NO/NO2, (mean±s.e.mean, n=13) was detected at 1.26 V, the peak oxidation potential for NO, following local electrical stimulation (five pulses of 0.1 ms duration at 100 Hz, delivered every 5 min). The NO/NO2, signal was inhibited by the non-selective nitric oxide synthase (NOS) inhibitors L -NAME, L -NMMA and the highly selective type II NOS (iNOS) inhibitor 1400 W (Garvey et al., 1997) in a concentration-dependent manner. IC50 values were 229 ,M (65 , 801, n=3, geomean and 95% confidence intervals (C.I.)), 452 nM (88 , 2310, n=5), and 14.2 ,M (3.6 , 54.4, n=5), with maximum inhibitions of 82.8±6.7, 46.0±8.1, and 90.6±3.6%, respectively. Exposure of the slices to the protein synthesis inhibitor cyclohexamide or the inhibitor of type II NOS induction dexamethasone immediately following slice cutting, and for a subsequent 4 , 5 h, did not inhibit the NO/NO2, signal. The evoked NO/NO2, signal was not reduced following 6 h perfusion in Ca2+ -free media, consistent with a Ca2+ -independent type II NOS activity. PCR for type II NOS revealed the presence of this isotype in the SCN, even immediately following removal of the brain. These studies provide the first evidence to suggest a functional, constitutively-active type II NOS within the brain of normal, healthy adult animals, and add type II NOS to the multiple isotypes of NO synthase playing a role within the mammalian SCN. British Journal of Pharmacology (2001) 134, 1084,1092; doi:10.1038/sj.bjp.0704330 [source] | |||||||||||||