Biomedical subjects

Thomas E Gundersen

Publications and source records attributed to Thomas E Gundersen.

7 recordsLinked to original sources

PubMed2006

Simultaneous and trace determination of reduced and oxidized glutathione in minute plasma samples using dual mode fluorescence detection and column switching high performance liquid chromatography.

A robust method for the simultaneous quantification of endogenous reduced glutathione (GSH) and oxidized glutathione (GSSG) in as little as 5 microl human plasma employing two-dimensional chromatographic system with parallel Hypercarb columns coupled with dual fluorescence detectors (FLD) has been developed. After sample preparation, 10 microl of supernatant was injected into the chromatographic system. The limits of detection (LOD) of GSH and GSSG were 0.5 and 0.040 pmol on column, respectively. Derivatization of GSH and GSSG with monobromobimane (MBB) and ortho-phthalaldehyde (OPA) provides a sensitivity and specificity that allows analysis after fingertip sampling, blood sampling from infants or multiple blood sampling from mice or other small experimental animals without sacrificing the animal.

Chromatography, High Pressure Liquid↗

PubMed2006

Simultaneous quantification of reduced and oxidized glutathione in plasma using a two-dimensional chromatographic system with parallel porous graphitized carbon columns coupled with fluorescence and coulometric electrochemical detection.

A method for the simultaneous quantification of reduced and oxidized glutathione in human plasma employing a two-dimensional chromatographic system with parallel porous graphitized carbon (PGC) columns coupled with fluorescence (FLD) and coulometric electrochemical detection (ED) has been developed. Post-sampling oxidation of reduced glutathione (GSH) was prevented by derivatizing the -SH group with monobromobimane (MBB) and the glutathione-bimane adduct (GSMB) was detected by FLD. Oxidized glutathione (GSSG) was detected by ED optimized to give lowest possible limits of detection (LOD). The method is fully validated and is currently used for determination of GSH, GSSG and its redox potential in different clinical studies.

Anticoagulants↗

PubMed2006

Methods for detecting and identifying retinoids in tissue.

Methods for retinoid analysis in tissue include direct spectrophotometry or fluorometry and retinoid responsive reporter constructs in the form of cell reporter assays or transgenic reporter animals, but chromatographic methods dominate and posses several superior features in quantitative analysis. The multitude of extraction protocols used can coarsely be divided into manual liquid-liquid extraction protocols and semi- or fully automated solid phase extraction-based protocols. Liquid chromatographic separation in reversed phase dominates although normal phase is also used. Detection is mainly performed with UV detectors although electrochemical and fluorescence detection is also used. Mass spectrometry in combination with LC is more often used in retinoid analysis and is likely to dominate in the future.

Animals↗

PubMed2005

High-throughput analysis of vitamin C in human plasma with the use of HPLC with monolithic column and UV-detection.

Vitamin C plays a central role in the body. One of its important functions is its role as an antioxidant, and accurate measurements are important for interpretations of this role. However, its reactive nature and instability complicates the assessment, especially in biological samples. A high-throughput chromatographic method using monolithic column and UV-detection was developed for the assessment of plasma ascorbic acid and total ascorbic acid. The method showed excellent analytical sensitivity, specificity, precision, recovery and linearity during the validation study. The method was used for the assessment of ascorbic acid and total ascorbic acid during several clinical studies.

Adult↗

PubMed2004

[Biological effects of vitamin K and concentration of vitamin K in Norwegian food].

BACKGROUND: Vitamin K has several biological effects and dietary intake seems to be more important than previously believed because of low bioavailability of the vitamins from the colon. MATERIALS AND METHODS: Data from the literature were identified on PubMed, and data from NORKOST II (a dietary study from 1997 based on a nation-wide sample of respondents) were used to calculate dietary intake of vitamin K. RESULTS: The dietary intake of vitamin K in Norway seems to be < 50% of what is recommended. The stores of vitamin K are small and T/2 in the body is approximately 1-1.5 day. Vitamin K executes its effects by carboxylation of proteins and as ligand (vitamin K2) for a nuclear transcription factor. Biological effects beyond coagulation include bone formation, neural functioning and blood vessel calcification. Anticoagulation with warfarin inhibits vitamin K-dependent reactions and may have detrimental effects on bone formation. INTERPRETATION: It is possible that the high incidence of osteoporosis in Norway may be due to the low dietary intake of vitamin K, hence it is suggested that the intake of vitamin K should be increased and vitamin K antagonists be replaced with specific thrombin inhibitors. New technology allows measurements of plasma concentration of vitamin K in relation to malabsorption, insufficient diet, and osteoporosis.

Adult↗

PubMed2003

Capillary high-performance liquid chromatographic determination of lutein and zeaxanthin in aqueous humor from a single mouse eye.

To protect the eye from ultraviolet phototoxicity caused by free radicals, ocular components such as the aqueous humor accumulate antioxidants, such as the carotenoids. Lutein and zeaxanthin are the only carotenoids known to be present in the aqueous humor. Due to the small sample volume, pooling of samples from an undesirable large number of animals is often required for sufficient sensitivity and statistically significant differences to be achieved. In this paper we present a rapid, sensitive and robust packed capillary high-performance liquid chromatographic visible detection method for the quantification of lutein and zeaxanthin in the aqueous humor of single mouse eyes.

Animals↗

PubMed2003

Identification of novel roles of the cytochrome p450 system in early embryogenesis: effects on vasculogenesis and retinoic Acid homeostasis.

The cytochrome P450-dependent monooxygenase system catalyzes the metabolism of xenobiotics and endogenous compounds, including hormones and retinoic acid. In order to establish the role of these enzymes in embryogenesis, we have inactivated the system through the deletion of the gene for the electron donor to all microsomal P450 proteins, cytochrome P450 reductase (Cpr). Mouse embryos homozygous for this deletion died in early to middle gestation (approximately 9.5 days postcoitum [dpc]) and exhibited a number of novel phenotypes, including the severe inhibition of vasculogenesis and hematopoiesis. In addition, defects in the brain, limbs, and cell types where CPR was shown to be expressed were observed. Some of the observed abnormalities have been associated with perturbations in retinoic acid homeostasis in later embryogenesis. Consistent with this possibility, embryos at 9.5 dpc had significantly elevated levels of retinoic acid and reduced levels of retinol. Further, some of the observed phenotypes could be either reversed or exacerbated by decreasing or increasing maternal retinoic acid exposure, respectively. Detailed analysis demonstrated a close relationship between the observed phenotype and the expression of genes controlling vasculogenesis. These data demonstrate that the cytochrome P450 system plays a key role in early embryonic development; this process appears to be, at least in part, controlled by regional concentrations of retinoic acid and has profound effects on blood vessel formation.

Animals↗