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Biomedical subjects

P Walker

Publications and source records attributed to P Walker.

312 records · Page 18Linked to original sources
PubMedDate not supplied

[N-acetyl-aspartate abnormalities in internal-temporal epileptic foci using proton magnetic resonance spectroscopy].

The aim of this study was to characterize the neurochemical abnormalities related to N-acetyl-aspartate which is a neuronal marker, within an epilepticus focus located in the internal-temporal area, using proton magnetic resonance spectroscopy. Eleven patients with a mono-hippocampal epileptics focus on clinical and per-critical electroencephalographical criteria, were matched with 11 controls by age, sex and laterality. Proton spectroscopy of a volume of 8 cm3 was performed within the ipsilateral and the contralateral internal-temporal area and within the 2 hippocampus of controls. Volumetry of the ipsilateral and the contralateral hippocampus and of the 2 hippocampus of controls was performed using resonance magnetic imaging. All these measurements were performed during the interictal stage. The results were concordant to show a decrease of the ratio N-acetyl-aspartate/choline and N-acetyl-aspartate/creatine within the epilepticus focus, in relation with a hippocampal atrophy. This study finds similar results to those of other previous works. The decrease of N-acetyl-aspartate levels within the epilepticus focus could be related to a decrease of the neuronal cell density. This procedure is able to show a decrease of the levels of this metabolite within an internal temporal epilepticus focus and associated with a hippocampal atrophy.

Adolescent↗
PubMedDate not supplied

Left ventricular contractility after hypothermic preservation: predictive value of phosphorus 31-nuclear magnetic resonance spectroscopy.

Early graft failure accounts for a substantial portion of the mortality after heart transplantation. This factor underscores the need for the development of reliable methods for predicting graft performance and thus ensuring optimal clinical outcome. The aim of this study was to describe the link between myocardial metabolism evaluated throughout preservation with the use of phosphorus 31-nuclear magnetic resonance spectroscopy and ventricular contractility after reperfusion. Thirteen pig hearts were excised and preserved from 3 to 12 hours with clinical techniques. During preservation the hearts underwent phosphorus 31-nuclear magnetic resonance spectroscopy. After reperfusion, left ventricular contractility was evaluated with an isolated heart model undergoing isovolumetric contraction. Throughout storage, beta-adenosine triphosphate remained stable and intracellular pH and phosphocreatine decreased exponentially, whereas inorganic phosphate increased exponentially. Intracellular pH, phosphocreatine, inorganic phosphates measured at the onset of preservation, and intracellular pH and phosphocreatine measured at the end of preservation correlated significantly with the left ventricular contractility after reperfusion. We conclude that the metabolic state of myocardium at excision is especially important and that phosphorus 31-nuclear magnetic resonance evaluation of the heart during preservation appears to provide reliable indexes for predicting subsequent ventricular contractility after reperfusion.

Animals↗
PubMedDate not supplied

Patellar tendon-to-patella ratio in children.

Patellofemoral problems are common in skeletally immature patients. In the evaluation of this condition, it is important to determine the position of the patella on lateral radiographs. There are no normal values to determine this ratio (patellar tendon-to-patella ratio). In this study, 225 anteroposterior (AP) and lateral radiographs of skeletally immature knees were examined and bone ages determined. The patellar tendon-to-patella ratio was then calculated for each age group until skeletal maturity. These ratios allow a more accurate assessment of patella alta in the pediatric population, assisting in diagnosis and surgical planning.

Adolescent↗