Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 5 de 5
Filter
Add more filters










Database
Language
Publication year range
1.
AJNR Am J Neuroradiol ; 41(2): 206-212, 2020 02.
Article in English | MEDLINE | ID: mdl-31948951

ABSTRACT

BACKGROUND AND PURPOSE: Brain CTP is used to estimate infarct and penumbra volumes to determine endovascular treatment eligibility for patients with acute ischemic stroke. We aimed to assess the accuracy of a Bayesian CTP algorithm in determining penumbra and final infarct volumes. MATERIALS AND METHODS: Data were retrospectively collected for 105 patients with acute ischemic stroke (55 patients with successful recanalization [TICI 2b/2c/3] and large-vessel occlusions and 50 patients without interventions). Final infarct volumes were calculated using DWI and FLAIR 24 hours following CTP imaging. RAPID and the Vitrea Bayesian CTP algorithm (with 3 different settings) predicted infarct and penumbra volumes for comparison with final infarct volumes to assess software performance. Vitrea settings used different combinations of perfusion maps (MTT, TTP, CBV, CBF, delay time) for infarct and penumbra quantification. Patients with and without interventions were included for assessment of predicted infarct and penumbra volumes, respectively. RESULTS: RAPID and Vitrea default setting had the most accurate final infarct volume prediction in patients with interventions ([Spearman correlation coefficient, mean infarct difference] default versus FLAIR: [0.77, 4.1 mL], default versus DWI: [0.72, 4.7 mL], RAPID versus FLAIR: [0.75, 7.5 mL], RAPID versus DWI: [0.75, 6.9 mL]). Default Vitrea and RAPID were the most and least accurate in determining final infarct volume for patients without an intervention, respectively (default versus FLAIR: [0.76, -0.4 mL], default versus DWI: [0.71, -2.6 mL], RAPID versus FLAIR: [0.68, -49.3 mL], RAPID versus DWI: [0.65, -51.5 mL]). CONCLUSIONS: Compared with RAPID, the Vitrea default setting was noninferior for patients with interventions and superior in penumbra estimation for patients without interventions as indicated by mean infarct differences and correlations with final infarct volumes.


Subject(s)
Algorithms , Image Interpretation, Computer-Assisted/methods , Neuroimaging/methods , Perfusion Imaging/methods , Stroke/diagnostic imaging , Adult , Aged , Aged, 80 and over , Bayes Theorem , Brain Ischemia/diagnostic imaging , Brain Ischemia/pathology , Diffusion Magnetic Resonance Imaging/methods , Female , Humans , Male , Middle Aged , Retrospective Studies , Stroke/pathology , Tomography, X-Ray Computed/methods
2.
Environ Sci Technol ; 38(2): 468-75, 2004 Jan 15.
Article in English | MEDLINE | ID: mdl-14750721

ABSTRACT

The potential to stimulate an indigenous microbial community to reduce a mixture of U(VI) and Tc(VII) in the presence of high (120 mM) initial NO3- co-contamination was evaluated in a shallow unconfined aquifer using a series of single-well, push-pull tests. In the absence of added electron donor, NO3-, Tc(VII), and U(VI) reduction was not detectable. However, in the presence of added ethanol, glucose, or acetate to serve as electron donor, rapid NO3- utilization was observed. The accumulation of NO2-, the absence of detectable NH4+ accumulation, and the production of N2O during in situ acetylene-block experiments suggest that NO3- was being consumed via denitrification. Tc(VII) reduction occurred concurrently with NO3- reduction, but U(VI) reduction was not observed until two or more donor additions resulted in iron-reducing conditions, as detected by the production of Fe(II). Reoxidation/remobilization of U(IV) was also observed in tests conducted with high (approximately 120 mM) but not low (approximately 1 mM) initial NO3- concentrations and not during acetylene-block experiments conducted with high initial NO3-. These results suggest that NO3(-)-dependent microbial U(IV) oxidation may inhibit or reverse U(VI) reduction and decrease the stability of U(IV) in this environment. Changes in viable biomass, community composition, metabolic status, and respiratory state of organisms harvested from down-well microbial samplers deployed during these tests were consistent with the conclusions that electron donor additions resulted in microbial growth, the creation of anaerobic conditions, and an increase in activity of metal-reducing organisms (e.g., Geobacter). The results demonstrate that it is possible to stimulate the simultaneous bioreduction of U(VI) and Tc(VII) mixtures commonly found with NO3- co-contamination at radioactive waste sites.


Subject(s)
Nitrates/analysis , Technetium/metabolism , Uranium/metabolism , Water Pollutants, Radioactive/metabolism , Biodegradation, Environmental , Biomass , Radioactive Waste , Soil , Water Microbiology , Water Supply
3.
Appl Environ Microbiol ; 67(8): 3750-2, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11472960

ABSTRACT

The dissimilatory iron-reducing bacterium Geobacter metallireducens was found to require iron at a concentration in excess of 50 microM for continuous cultivation on nitrate. Growth yield (approximately 3-fold), cytochrome c content (approximately 7-fold), and nitrate (approximately 4.5-fold) and nitrite (approximately 70-fold) reductase activities were all increased significantly when the growth medium was amended with 500 microM iron.


Subject(s)
Deltaproteobacteria/metabolism , Iron/metabolism , Nitrates/metabolism , Culture Media , Cytochrome c Group/metabolism , Deltaproteobacteria/growth & development , Gene Expression Regulation, Bacterial , Nitrate Reductase , Nitrate Reductases/metabolism , Nitrite Reductases/metabolism , Oxidation-Reduction
4.
Arch Microbiol ; 172(5): 313-20, 1999 Nov.
Article in English | MEDLINE | ID: mdl-10550473

ABSTRACT

Nitrate reduction in the dissimilatory iron-reducing bacterium Geobacter metallireducens was investigated. Nitrate reductase and nitrite reductase activities in nitrate-grown cells were detected only in the membrane fraction. The apparent K(m )values for nitrate and nitrite were determined to be 32 and 10 microM, respectively. Growth on nitrate was not inhibited by either tungstate or molybdate at concentrations of 1 mM or less, but was inhibited by both at 10 and 20 mM. Nitrate and nitrite reductase activity in the membrane fraction was not, however, affected by dialysis with 20 mM tungstate. An enzyme complex that exhibited both nitrate and nitrite reductase activity was solubilized from membrane fractions with CHAPS and was partially purified by preparative gel electrophoresis. It was found to be composed of four different polypeptides with molecular masses of 62, 52, 36, and 16 kDa. The 62-kDa polypeptide [a low-midpoint potential (-207 mV), multiheme cytochrome c] exhibited nitrite reductase activity under denaturing conditions. No molybdenum was detected in the complex by plasma-emission mass spectrometry.


Subject(s)
Deltaproteobacteria/enzymology , Heme/analogs & derivatives , Multienzyme Complexes/metabolism , Nitrate Reductases/metabolism , Nitrite Reductases/metabolism , Bacteria, Anaerobic/enzymology , Bacteria, Anaerobic/growth & development , Cytochrome c Group/metabolism , Deltaproteobacteria/growth & development , Electrophoresis, Polyacrylamide Gel , Heme/analysis , Iron/metabolism , Multienzyme Complexes/chemistry , Multienzyme Complexes/isolation & purification , Nitrate Reductase , Nitrate Reductases/chemistry , Nitrate Reductases/isolation & purification , Nitrates/metabolism , Nitrite Reductases/chemistry , Nitrite Reductases/isolation & purification , Nitrites/metabolism , Oxidation-Reduction
5.
Circ Shock ; 11(2): 149-58, 1983.
Article in English | MEDLINE | ID: mdl-6640858

ABSTRACT

The possible release of cardioinhibitory factors from the small intestine during severe hemorrhagic shock was examined by testing arterial and intestinal venous plasma samples obtained at various stages during the experiment in two groups of anesthetized dogs. One group of dogs was subjected to arterial hypotension at 35 +/- 5 mmHg for 3 h followed by reinfusion of all shed blood, while the other group was treated alike except that there was no hemorrhagic hypotension. The plasma samples were assayed for cardioinhibitory activity by utilizing the Langendorff guinea pig heart preparation. None of the plasma samples obtained from the sham operated dogs significantly alter the performance of the guinea pig heart. The arterial sample taken during the compensation phase of hemorrhagic hypotension increased, while the arterial and intestinal venous plasma taken at the terminal stage decreased the dP/dt. Plasma Na+, K+, total Ca2+, and Mg2+ concentration of all samples were within normal limits. It is concluded that the small intestine releases cardioinhibitory factors in severe hemorrhagic shock.


Subject(s)
Heart/drug effects , Jejunum/metabolism , Shock, Hemorrhagic/blood , Animals , Calcium/blood , Depression, Chemical , Dogs , Female , Guinea Pigs , Magnesium/blood , Male , Potassium/blood , Sodium/blood
SELECTION OF CITATIONS
SEARCH DETAIL
...