Detection of ATP by “in line” 31P magnetic resonance spectroscopy during oxygenated hypothermic pulsatile perfusion of pigs’ kidneys

Object

To demonstrate that adenosine triphosphate (ATP), which provides a valuable biomarker for kidney viability in the context of donation after cardiac death (DCD) transplantation, can be detected by means of ³¹P magnetic resonance spectroscopy (MRS) if kidneys are perfused with oxygenated hypothermic pulsatile perfusion (O₂+HPP).

Materials and methods

Porcine kidney perfusion was carried out using a home made, MR-compatible HPP-machine. Consequently, kidney perfusion could be performed continuously during magnetic resonance imaging and magnetic resonance spectroscopy recording. ³¹P MR spectroscopy consisted of 3-dimensional chemical shift imaging (CSI), which allowed for the detection of ATP level in line. ³¹P CSI was performed at 3?tesla in 44?min with a nominal voxel size of 6.1?cc.

Results

³¹P CSI enabled the detection of renal ATP when pO₂ was equal to 100?kPa. With pO₂ of 20?kPa, only phosphomonoester, inorganic phosphate and nicotinamide adenine dinucleotide could be found. Semi-quantitative analysis showed that ATP level was 1.3?mM in normal kidney perfused with pO₂ of 100?kPa.

Conclusions

This combined technology may constitute a new advance in DCD organ diagnostics prior to transplantation, as it allows direct assessment of ATP concentration, which provides a reliable indicator for organ bioenergetics and viability. In this study, kidneys presenting no warm ischemia were tested in order to establish values in normal organs. The test could be easily integrated into the clinical environment and would not generate any additional delay into the transplantation clinical workflow.     

Computerized single-breath nitrogen washout: predicted values in a rural French community

The role of the cholecystokinergic input to the rat's dorsal lateral geniculate nucleus (dLGN) was studied by examining the effect of iontophoretically administered CCK-8S on the neuronal response to stimulation of the receptive field center. Peristimulus activity was recorded extracellularly from 108 neurons grouped according to the type of receptive field (OFF, ON, or ON-OFF) and classified with respect to their Y, X, or W properties by means of discriminant analysis. CCK affected the response to a center-sized spot of light in two thirds of the neurons investigated. The center response decreased in 50 of 73 CCK-sensitive neurons (69%), predominantly in Y OFF and X OFF center cells (17 of 19). In the remaining 23 cells the center response increased, most consistently (11 of 17) in W ON center cells. Center and surround responses were similarly influenced. Inhibitions and excitations induced by CCK-8S were reproducible, dose dependent, and receptor mediated. The CCKB antagonist PD 135158 reduced the CCK effects in 10 of 14 cells; the CCKA antagonist KL 1001 reduced the CCK effects in 17 of 36 cells. The CCK-induced inhibition was B-receptor specific in 4 of 8 cells, A-receptor specific in 2 of 8 cells, and partially mediated by each of the two types of receptor in the remaining 2 cells. Blocking by the CCKA antagonist was more frequently observed in W cells than in cells with Y or X characteristics. The data show that CCK modifies the activity of dLGN cells in a variable direction depending on the specific cell type (Y, X, W) and response pattern (OFF, ON). The effects of CCK are discussed in relation to proposed functions of the superior collicular input to the dLGN.     

Trust and persistence [software agents]

We rely on computers to control our power plants and water supplies, our automobiles and transportation systems, and soon our economic and political systems. Increasingly, software agents are enmeshed in these systems, serving as the glue that connects distributed components. Clearly, we need mechanisms to determine whether these agents are trustworthy. What do we need to establish trust? Agents are often characterized by features such as autonomy, sociability, proactiveness, and persistent identity. This latter feature is key in determining trust. When agents operate over an extended period, they can earn a reputation for competence, timeliness, ease of use, and trustworthiness, which is something ephemeral agents cannot do. Along with persistence, we need a reliable way to identify an agent and ensure that its true identity is not concealed. How can we assess an agent's trustworthiness? As with other aspects of agents and multiagent systems, we can take our cue from the human domain. Our reputations for trustworthiness are determined and maintained by the people we deal with. Analogously, a software agent's reputation will reside within the other agents with whom it interacts. For some agent interactions, such as those involving commerce, agents will simply inherit the reputation of their human owner, sharing, for example, their owner's credit rating and financial capability. For other types of interactions, such as those involving information gathering, an agent will determine its own reputation through its efforts at gathering and distilling information. An agent with a reputation for conducting thorough searches will be trusted by other agents wishing to use its Web search results     

Wideband radio channel characteristics in alpine regions

Radio channel time dispersion parameters of three adjacent base stations located in a mountainous area have been measured. The measured paths, subdivided into 100 m segments, were evaluated with a 9 dB delay window. A substantial number of critical locations were observed. Coverage based on tolerable time dispersion turns out to be different to coverage prediction based on the field strength only.<>