Seglen P.O.,University of Oslo |
Brinchmann M.F.,Bodo University College
Autophagy | Year: 2010
To facilitate the purification of rat liver autophagosomes, isolated rat hepatocytes are first incubated for 2 h at 37° C with vinblastine, which induces autophagosome accumulation by blocking the fusion of these organelles with endosomes and lysosomes. The hepatocytes are then electrodisrupted and homogenized, and the various cellular organelles sequentially removed by subcellular fractionation. A brief incubation of the homogenate with the cathepsin C substrate, glycyl-phenylalanine-naphthylamide (GPN), causes rapid osmotic disruption of the lysosomes due to intralysosomal accumulation of GPN cleavage products. Nuclei are removed by differential centrifugation, and the postnuclear supernatant subsequently fractionated on a two-step Nycodenz density gradient. Autophagosomes are recovered in an intermediate density fraction, free from cytosol and mitochondria. The autophagosomes are finally separated from the membranes and vesicles of the endoplasmic reticulum, Golgi, endosomes, etc., by sieving through a density gradient of colloidal silica particles (Percoll). The final preparation contains about 95% autophagosomes and 5% amphisomes according to morphological and biochemical criteria. © 2010 Landes Bioscience.
Hagen T.,Bodo University College
Food Chemistry | Year: 2011
In the present study, fillet colour, pH and the activities of cathepsin B, B+L, D, H, collagenase and calpain were measured in 50 Atlantic halibut (Hippoglossus hippoglossus) farmed and harvested at Mørkvedbukta research station (Bodø University College) in May, 2009. May is a period of the year when a portion of the fish can temporarily lose its translucent colour, becoming milky instead, a phenomena referred to as chalky halibut. The aim of the present study was to discover whether enzymes, known to be involved in flesh quality degradation, are also involved in the post-mortem discoloration of halibut flesh. Colour assessment was performed using a Minolta instrument (L value) and a linear regression showed that pH had the most pronounced effect on chalkiness (r2=0.81, p<0.001). Of the investigated enzymes, cathepsins B and D explained 35 and 13% of the total variation, respectively (p<0.01). In addition, an unexpected inverse relationship between chalkiness and calpain was found (r2=0.48, p<0.001). The present results suggest that the activity of cathepsins contributes to the development of chalkiness in Atlantic halibut. © 2010 Elsevier Ltd.
Enoksen E.,Norwegian School of Sport Sciences |
Shalfawi S.A.I.,Bodo University College |
Journal of Strength and Conditioning Research | Year: 2011
The purpose of this study was to examine the effect of 2 different intervention training regimes on V̇o2max, V̇o2max velocity (vV̇o2max), running economy (RE), lactic threshold velocity (vLT), and running performance on a group of well-trained male middle-distance runners in the precompetition period. Twenty-six well-trained male middle-distance runners took part in the study. All participants were tested on V̇o2max, vV̇o2max, RE, lactate threshold (LT), vLT, and a performance test. The participants were matched according to their pretest results, then randomly assigned into 1 of 2 groups, a high-volume (70 km) low-intensity training group (HVLI-group); or a high-intensity low-volume (50 km) training group (HILV-group). No significant differences were found between the 2 groups on all measures both before and after the intervention period. Furthermore, the HILV-group had a marked increase in vV̇o2max and vLT after the training period when compared with pretest. Both groups had a marked improvement in RE. The performance test showed that the HILV-group made 301 ± 886 m (1.0 ± 2.8 minutes) and the HVLI-group 218 ± 546 m (0.9 ± 1.8 minutes) in progress. The production of lactic acid was notably higher in the HILV-group (0.9 mmol) when compared with the pretest. The findings show that male middle-distance runners tested in this study improved in vV̇o2max and vLT more when they train around LT, than training with low intensity for a short period of 10 weeks. © 2011 National Strength and Conditioning Association.
Hagen N.T.,Bodo University College
Scientometrics | Year: 2010
A collection of coauthored papers is the new norm for doctoral dissertations in the natural and biomedical sciences, yet there is no consensus on how to partition authorship credit between PhD candidates and their coauthors. Guidelines for PhD programs vary but tend to specify only a suggested range for the number of papers to be submitted for evaluation, sometimes supplemented with a requirement for the PhD candidate to be the principal author on the majority of submitted papers. Here I use harmonic counting to quantify the actual amount of authorship credit attributable to individual PhD graduates from two Scandinavian universities in 2008. Harmonic counting corrects for the inherent inflationary and equalizing biases of routine counting methods, thereby allowing the bibliometrically identifiable amount of authorship credit in approved dissertations to be analyzed with unprecedented accuracy. Unbiased partitioning of authorship credit between graduates and their coauthors provides a post hoc bibliometric measure of current PhD requirements, and sets a de facto baseline for the requisite scientific productivity of these contemporary PhD's at a median value of approximately 1.6 undivided papers per dissertation. Comparison with previous census data suggests that the baseline has shifted over the past two decades as a result of a decrease in the number of submitted papers per candidate and an increase in the number of coauthors per paper. A simple solution to this shifting baseline syndrome would be to benchmark the amount of unbiased authorship credit deemed necessary for successful completion of a specific PhD program, and then monitor for departures from this level over time. Harmonic partitioning of authorship credit also facilitates cross-disciplinary and inter-institutional analysis of the scientific output from different PhD programs. Juxtaposing bibliometric benchmarks with current baselines may thus assist the development of harmonized guidelines and transparent transnational quality assurance procedures for doctoral programs by providing a robust and meaningful standard for further exploration of the causes of intra- and inter-institutional variation in the amount of unbiased authorship credit per dissertation. © 2010 The Author(s).
Hagen N.T.,Bodo University College
Scientometrics | Year: 2010
Bibliometric counting methods need to be validated against perceived notions of authorship credit allocation, and standardized by rejecting methods with poor fit or questionable ethical implications. Harmonic counting meets these concerns by exhibiting a robust fit to previously published empirical data from medicine, psychology and chemistry, and by complying with three basic ethical criteria for the equitable sharing of authorship credit. Harmonic counting can also incorporate additional byline information about equal contribution, or the elevated status of a corresponding last author. By contrast, several previously proposed counting schemes from the bibliometric literature including arithmetic, geometric and fractional counting, do not fit the empirical data as well and do not consistently meet the ethical criteria. In conclusion, harmonic counting would seem to provide unrivalled accuracy, fairness and flexibility to the long overdue task of standardizing bibliometric allocation of publication and citation credit. © 2009 The Author(s).