H. U. Zacharias

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Acute kidney injury (AKI) is a frequent complication of sepsis, major surgery or nephrotoxic medication use. It is associated with high morbidity and mortality. In an effort to identify novel biomarkers capable of predicting the development of AKI after cardiac surgery with cardiopulmonary bypass use, urine specimens were collected before and at 4 and 24 h(More)
Data normalization is an essential step in NMR-based metabolomics. Conducted properly, it improves data quality and removes unwanted biases. The choice of the appropriate normalization method is critical and depends on the inherent properties of the data set in question. In particular, the presence of unbalanced metabolic regulation, where the different(More)
Nontargeted metabolite fingerprinting is increasingly applied to biomedical classification. The choice of classification algorithm may have a considerable impact on outcome. In this study, employing nested cross-validation for assessing predictive performance, six binary classification algorithms in combination with different strategies for data-driven(More)
MOTIVATION In biomedicine, every molecular measurement is relative to a reference point, like a fixed aliquot of RNA extracted from a tissue, a defined number of blood cells, or a defined volume of biofluid. Reference points are often chosen for practical reasons. For example, we might want to assess the metabolome of a diseased organ but can only measure(More)
Acute kidney injury (AKI) is a frequent complication after cardiopulmonary bypass, but early detection of postoperative AKI remains challenging. Protein biomarkers predict AKI excellently in homogeneous cohorts but are less reliable in patients suffering from various comorbidities. We employed nuclear magnetic resonance spectroscopy in a prospective study(More)
  • 2011
Abbreviations 1D One-dimensional 1 H Hydrogen-1 (proton) 2D Two-dimensional 13 C Carbon-13 31 P Phosphorus-31 ADPKD Autosomal dominant polycystic kidney disease Acetyl-CoA Acetyl coenzyme A ANOVA Analysis of variance ATP Adenosine triphosphate BHBA Beta-hydroxybutyric acid °C Degrees Celsius Ca Calcium ck Choline kinase CPMG Carr, Purcell, Meiboom, Gill DIM(More)
The high reliability of NMR spectroscopy makes it an ideal tool for large-scale metabolomic studies. However, the complexity of biofluids and, in particular, the presence of macromolecules poses a significant challenge. Ultrafiltration and protein precipitation are established means of deproteinization and recovery of free or total metabolite content, but(More)
Reliable identification of features distinguishing biological groups of interest in urinary metabolite fingerprints requires the control of total metabolite abundance, which may vary significantly as the kidneys adjust the excretion of water and solutes to meet the homeostatic needs of the body. Failure to account for such variation may lead to(More)
Obesity is a complex multifactorial phenotype that influences several metabolic pathways. Yet, few studies have examined the relations of different body fat compartments to urinary and serum metabolites. Anthropometric phenotypes (visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), the ratio between VAT and SAT (VSR), body mass index (BMI),(More)
Motivation: Metabolomics data is typically scaled to a common reference like a constant volume of body fluid, a constant creatinine level, or a constant area under the spectrum. Such normalization of the data, however, may affect the selection of biomarkers and the biological interpretation of results in unforeseen ways. Results: First, we study how the(More)
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