Biomedical subjects

Henrik Olsen

Publications and source records attributed to Henrik Olsen.

4 recordsLinked to original sources

PubMed2005

Mixed messages: transcription patterns in failing and recovering human myocardium.

In previous studies, mechanical support of medically refractory hearts with a left ventricular assist device (LVAD) has induced regression of many morphological and functional abnormalities characteristic of failing human hearts. To identify transcriptional adaptations in failing and LVAD-supported hearts, we performed a comprehensive transcription analysis using the Affymetrix microarray platform and 199 human myocardial samples from nonfailing, failing, and LVAD-supported human hearts. We also used a novel analytical strategy that defines patterns of interest based on multiple intergroup comparisons. Although over 3088 transcripts exhibited significantly altered abundance in heart failure, most of these did not exhibit a consistent response to LVAD support based on our analysis. Of those 238 with a consistent response to LVAD support, more than 75% exhibited persistence or exacerbation of HF-associated transcriptional abnormalities whereas only 11%, 5%, and 2% exhibited partial recovery, normalization, and overcorrection responses, respectively. Even among genes implicated by previous reports of LVAD-associated myocardial improvements, partial or complete normalization of transcription did not predominate. The magnitude of differences in transcript abundance between nonfailing and failing hearts, and between failing an LVAD-supported hearts, tended to be low with changes greater than or equal to 2-fold infrequently observed. Our results indicate that morphological or functional myocardial improvements may occur without widespread normalization of pathological transcriptional patterns. These observations also suggest that many failure-associated transcriptional changes have only a limited role in regulating cardiac structure and function and may represent epiphenomena and/or nonspecific myocardial plasticity responses. Differences in mRNA localization, translation efficiency, and posttranslational protein modifications or interactions may be more pivotal in regulating myocardial structure and function.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed2005

High speed development work by preparation of an "in-hand" library of NMR-quantified degradation products.

Standard materials of impurities are needed in pharmaceutical development such as for validating impurity analytical methods. Most often the impurities possess structures, which are difficult and very time consuming to synthesize. In the present work, we demonstrate that a library of degradation products of ragaglitazar--a novel tricyclic-gamma-alkyloxyphenylpropionic acid with hypolipidemic and antidiabetic activity--observed in stability indicating samples of a solid dosage formulation by LC-MS can be produced in a one pot oxidation reaction. The library entities were isolated in small quantities (microg-mg) by preparative HPLC and structurally characterized by NMR spectroscopy and mass spectrometry. The concentrations of the library entities were determined in solution by NMR using an internal standard method. The library was successfully used in the validation work of a newly developed purity method for the drug product providing useful response factors and relative retention times (RRTs) of the degradation products.

Chromatography, High Pressure Liquid↗

PubMed2004

Supplementing pharmaceutical analysis techniques using radiotracers.

Radiolabeled compounds can be used for alleviating the degradation pathways and mass balance of drug products in the solid formulation, because it provides a very sensitive and specific method of locating and measuring particular compounds. The present study utilizes this methodology on levormeloxifene-a partial oestrogen receptor agonist-in the solid dosage form. It demonstrates how radiotracers can be used as a supplement to conventional analytical methods to investigate the degradation pathways and mass balance of drug substances as well as how they can be useful to cross validate the traditional analytical methods developed for the determination of uniformity of content, assay, and purity. To decrease the study time, pilot studies-in which the product was stored at high pressures of molecular oxygen and elevated temperatures-were performed. Conditions mimicking the degradation processes taking place under standard storage conditions of the drug substance were found, and these super-enhanced stress conditions were applied. The study time was thereby dramatically decreased. The produced degradation products were studied by liquid chromatography with mass spectrometric detection. The most important degradation pathway was ascribed to the oxidation of the pyrrolidine nitrogen atom in levormeloxifene to an N-oxide derivative of the drug substance.

Drug Contamination↗

PubMed2004

Production and purification of Bacillus anthracis protective antigen from Escherichia coli.

Anthrax is caused by the gram-positive, spore-forming bacterium, Bacillus anthracis. The anthrax toxin consists of three proteins, protective antigen (PA), lethal factor, and edema factor. Current vaccines against anthrax use PA as their primary component since it confers protective immunity. In this work, we expressed soluble, recombinant PA in relatively high amounts in the periplasm of E. coli from shake flasks and bioreactors. The PA protein was purified using Q-Sepharose-HP and hydroxyapatite chromatography, and routinely found to be 96-98% pure. Yields of purified PA varied depending on the method of production; however, medium cell density fermentations resulted in approximately 370 mg/L of highly pure biologically active PA protein. These results exhibit the ability to generate gram quantities of PA from E. coli.

Amino Acid Sequence↗