Biomedical subjects

K Jørgensen

Publications and source records attributed to K Jørgensen.

At least 19 recordsLinked to original sources

PubMed2005

Diarrhetic shellfish poisoning toxin esters in Danish blue mussels and surf clams.

Until recently, little focus was given to the presence of diarrhetic shellfish poisoning (DSP) toxin esters in seafood products. However, during the last few years, the occurrence of a high percentage of esters of the total amount of DSP toxins present in some seafood products has been observed. Samples of Danish surf clams (Spisola spp.) and blue mussels (Mytilus edulis) from 1999-2004 were analysed by liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) for the presence of DSP toxin esters. The samples contained only okadaic acid and esters of okadaic acid. The level of total okadaic acid equivalents ranged from 224 to 2516 microg kg-1 in surf clams. The percentage of okadaic acid esters of the total okadaic acid equivalents ranged from 83 to 98%, mean 95%. The level of total okadaic acid equivalents ranged from 43 to 1631 microg kg-1 in blue mussels. The percentage of okadaic acid esters of the total okadaic acid equivalents ranged from 21 to 86%, mean 59%. The probability of a high percentage of okadaic acid esters seems to increase with higher amounts of total okadaic acid equivalents in the bivalves. The large prevalence of DSP toxin esters are of particular importance because of the increased use of chemical methods instead of mouse bioassay for the detection of DSP toxicity.

Animals↗

PubMed2004

Heavy resistance training increases muscle size, strength and physical function in elderly male COPD-patients--a pilot study.

This study investigated the effects of heavy resistance training in elderly males with chronic obstructive pulmonary disease (COPD). 18 Home-dwelling male patients (age range: 65-80 years), with a mean forced expiratory volume in the first second (FEV1) of 46 +/- 3.4% of predicted value, were recruited. Baseline and post-training assessments included: Cross-sectional area (CSA) of quadriceps assessed by MRI, isometric and isokinetic knee extension strength, isometric trunk strength, leg extension power, normal and maximal gait-speed on a 30 m track, stair climbing time, number of chair stands in 30 s, lung function (FEV1) and self-reported health. Subjects were randomized to a resistance training group (RE, n = 9) or a control group conducting breathing exercises (CON, n = 9). RE performed heavy progressive resistance training twice a week for 12 weeks. 6 RE and 7 CON completed the study. In RE the following improved (P < 0.05): Quadriceps CSA: 4%, isometric knee extension strength: 14%, isokinetic knee extension strength at 60 degrees /s.: 18%, leg extension power: 19%, maximal gait speed: 14%, stair climbing time: 17%, isometric trunk flexion: 5% and self-reported health. In CON no changes were found. In conclusion, 12 weeks of heavy resistance training twice a week resulted in significant improvements in muscle size, knee extension strength, leg extension power, functional performance and self-reported health in elderly male COPD patients.

Aged↗

PubMed2004

Chicken juice, a food-based model system suitable to study survival of Campylobacter jejuni.

AIMS: The purpose of this study was to develop a food-based model system that resembles the environment that Campylobacter jejuni experiences on raw poultry products and use this model system to investigate growth and survival of the bacterium. METHODS AND RESULTS: Chicken juice was collected from frozen chickens and subsequently cleared by centrifugation and subjected to sterile filtration. At low temperatures (5 and 10 degrees C) C. jejuni NCTC11168 remained viable in chicken juice for a remarkably longer period of time than in the reference medium BHI. When exposed to heat stress (48 degrees C) C. jejuni NCTC11168 also showed increased viability in chicken juice compared with the reference medium. Furthermore, agar plates made with chicken juice supported growth of four clinical isolates of C. jejuni and a C. jejuni strain obtained from chicken at both 37 and 42 degrees C. CONCLUSIONS: Our work shows that minimal processed and sterilized chicken juice is an ideal environment for survival of C. jejuni and that it is useful as a food-based model system. SIGNIFICANCE AND IMPACT OF THE STUDY: The developed model system may contribute to the understanding of C. jejuni viability on poultry products and can be instrumental in the development of alternative preservation strategies.

Animals↗

PubMed2004

Distribution of diarrhetic shellfish poisoning toxins in consignments of blue mussel.

Data describing the distribution of diarrhetic shellfish poisoning toxins in 13 consignments of Danish-produced blue mussels are reported. The content of diarrhetic shellfish poisoning toxins was measured by a liquid chromatography coupled with tandem mass spectrometry detection method, and mean levels in the 13 consignments varied from 58 to 243 microg kg(-1). The distributions of diarrhetic shellfish poisoning toxins in the consignments were relatively homogeneous as the relative standard deviation of the content varied from 7 to 19%. The results are discussed in relation to food safety, the uncertainty of sampling and analysis, and the newly introduced European Union maximum levels of marine biotoxins in seafood products.

Animals↗

PubMed2002

Anaerobic power and muscle strength characteristics of 11 years old elite and non-elite boys and girls from gymnastics, team handball, tennis and swimming.

The aim of the present investigation was to study the possible effects of specificity of training on muscle strength and anaerobic power in children from different sports and at different performance levels in relation to growth and maturation status. Hundred and eighty-four children of both gender participating either in swimming, tennis, team handball or gymnastics were recruited from the best clubs in Denmark. Within each sport, the coach had divided the children into an elite (E) and non-elite (NE) group according to performance level and talent. Tanner stage assessment and body weight and height measurements were performed by a physician. The anaerobic performances were assessed by Wingate tests and jumping performance in squat jump (SJ), countermovement jump (CMJ) and drop jump (DJ) from two heights. Most of the differences between groups in Wingate performance disappeared when the data were normalised to body mass. The gymnasts were the best jumpers and their superiority were increased in the more complex motor coordination tasks like DJ. The results may indicate some influence of training specificity, especially on the more complex motor tasks as DJ and there may be an effect of training before puberty. The performance in the less complex motor tasks like cycling and SJ and CMJ may also be influenced by specific training, but not to the same extent, and heritance may be an important factor for performance in these anaerobic tasks.

Anaerobic Threshold↗

PubMed2002

Content of ochratoxin A in paired kidney and meat samples from healthy Danish slaughter pigs.

In 1999, paired samples of kidney and meat were taken from 300 healthy Danish pigs and analysed for ochratoxin A. The concentrations of ochratoxin A in kidney ranged from 0 to 15 microg kg(-1) (mean 0.50 microg kg(-1), median 0.18 microg kg(-1)) and in meat from 0 to 2.9 microg kg(-1) (mean 0.12 microg kg(-1), median 0.03 microg kg(-1)). The data together with the Danish control data show that today the pig industry in Denmark has no problem keeping the content of ochratoxin A in pig at very low levels even in years with wet harvest conditions. The mean ratio 'content in meat/content in kidney' for paired samples was 39%. For kidney samples >1.0 microg kg(-1), the mean ratio was 22%. The Danish control system for ochratoxin A in pig kidney established in 1978 can be regarded as a success because the levels in pig have been reduced substantially, and hence for the consumer the contribution from pig products to the total intake of ochratoxin A is very small compared with other sources.

Animals↗

PubMed2002

Occurrence of ochratoxin A in Danish wheat and rye, 1992-99.

Ochratoxin A concentrations in rye and wheat in Denmark for 1992-99 are reported. The results show that the concentration of ochratoxin A is higher in rye than in wheat for both conventionally and organically grown rye and wheat. The levels in organically grown rye are higher than in conventionally grown based on multiyear mean contents. However, the difference between the two groups of cereals has decreased since the Danish food-monitoring system for ochratoxin A was started in 1986; 2.0% of all samples exceeded the Danish maximum limit of 5 micro g kg(-1) introduced in 1995. For rye samples, 3.2% exceeded the maximum limit, and for wheat samples, 0.5% exceeded the maximum limit.

Carcinogens↗

PubMed2002

Nondestructive measurement of light-induced oxidation in dairy products by fluorescence spectroscopy and imaging.

The purpose of this paper is to demonstrate the potential of solid-sample fluorescence spectroscopy in nondestructive assessment of light-induced oxidation in different dairy products such as Swiss cheese, cream cheese, and sour cream. Analytical and quantitative spectral properties of fluorescence were elucidated by use of principal component analysis with designed experiments involving different levels of air and light exposure. A significant reduction in fluorescence intensity at approximately 525 nm, and a corresponding increase in the region 415 to 490 nm as a result of illumination was observed on all the products. The effect was ascribed to photodegradation of riboflavin. Variation in two smaller peaks at approximately 620 nm and 630 nm was an interaction effect between exposure to light and air. A pronounced interaction effect between light and air produced intense blue fluorescence and off-flavors on Swiss-like Jarlsberg cheese. High correlations (0.83 to 0.93) between fluorescence spectra and sensory measured off-flavors were obtained for cream cheese. Results indicate that solid-sample fluorescence can be used as a nondestructive and rapid tool to measure the degree of light-induced degradation of riboflavin as well as sensory properties connected to storage of dairy products. Images of fluorescence can be used to visualize the intensity and propagation of this process. The simplicity and rapidity of the method offer rich opportunities for efficient evaluation of factors affecting light-induced oxidation in dairy products, such as packaging materials, light sources, exposure time, and temperature.

Air↗

PubMed2001

Phospholipase A(2) activity towards vesicles of DPPC and DMPC-DSPC containing small amounts of SMPC.

Phospholipase A(2) (PLA(2)) is an interfacially active enzyme whose hydrolytic activity is known to be enhanced in one-component phospholipid bilayer substrates exhibiting dynamic micro-heterogeneity. In this study the activity of PLA(2) towards large unilamellar vesicles composed of DPPC:SMPC and DMPC:DSPC:SMPC is investigated using fluorescence and HPLC techniques. Phase diagrams of the mixtures are established by differential scanning calorimetry and the PLA(2) activity, monitored by the lag time, is correlated with the phase behavior of the mixtures. In addition, the degree of lipid hydrolysis in the DMPC:DSPC:SMPC lipid mixtures is detected by HPLC. The PLA(2) activity is found to be significantly increased in the temperature range of the coexistence region where the lipid mixtures exhibit lateral gel-fluid phase separation. Furthermore, in the entire temperature range it is demonstrated that PLA(2) preferentially hydrolyzes the short chain DMPC lipid. This discriminative effect becomes less pronounced when the asymmetric lipid SMPC is present in the lipid substrate. Inclusion of SMPC into either DPPC or DMPC:DSPC vesicles prolongs the lag time. The results clearly show that the PLA(2) activity is significantly enhanced by lipid bilayer micro-heterogeneity in both one-component and multi-component lipid bilayer substrates. The PLA(2) activity measurements are discussed in terms of dynamic gel-fluid lipid domain formation due to density fluctuations and static lipid domain formation due to gel-fluid phase separation.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2001

Screening effect of PEG on avidin binding to liposome surface receptors.

This study investigates the screening effect of poly(ethylene glycol)-phospholipids (PE-PEG) on the interaction of avidin with PEGylated liposomes containing surface-bound biotin ligands. The influence of grafting density and lipopolymer chain length is examined. A simple fluorescence assay involving a receptor-mediated fluorescence increase of BODIPY-labeled avidin upon binding to biotinylated lipids is employed to study the screening effect of submicellar concentrations of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine-N-[poly(ethylene glycol)-2000] (PE-PEG(2000)) and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylethanolamine-N-[poly(ethylene glycol)-5000] (PE-PEG(5000)) incorporated into 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) liposomes. The results show that incorporation of lipopolymers into DPPC lipid bilayers reduces binding of avidin to the biotinylated liposomes, and it is found that the screening effect of PE-PEG(5000) is stronger than that for PE-PEG(2000). Thus, the results reveal that both the grafting density and the polymer length of the PE-PEG lipopolymers are of importance for the ability of water-soluble macromolecules to reach the surface of PEG liposomes. Furthermore, it is found that none of the lipopolymers completely prevents avidin from reaching the surface-bound biotin ligands.

Avidin↗

PubMed2001

Drug delivery by phospholipase A(2) degradable liposomes.

The effect of poly(ethylene glycol)-phospholipid (PE-PEG) lipopolymers on phospholipase A(2) (PLA(2)) hydrolysis of liposomes composed of stearoyl-oleoylphosphatidylcholine (SOPC) was investigated. The PLA(2) lag-time, which is inversely related to the enzymatic activity, was determined by fluorescence, and the zeta-potentials of the liposomes were measured as a function of PE-PEG lipopolymer concentration. A significant decrease in the lag-time, and hence an increase in enzymatic activity, was observed with increasing amounts of the negatively charged PE-PEG lipopolymers incorporated into the SOPC liposomes. The enhancement of the PLA(2) enzymatic activity might involve a stronger PLA(2) binding affinity towards the negatively charged and polymer covered PEG liposomes.

Drug Delivery Systems↗

PubMed2001

Association of an acylated model peptide with DPPC-DPPS lipid membranes.

The interaction between a small positively charged peptide with a N-terminally linked acyl chain and dipalmitoylphosphatidylcholine-dipalmitoylphosphatidylserine (DPPC-DPPS) lipid membranes has been studied by means of fluorescence resonance energy transfer. Two different lipid compositions were used: a neutral membrane (100 mol% DPPC), and a negatively charged membrane (30 mol% DPPS in DPPC). The fluorescence resonance energy transfer results reveal that the peptide associates with both types of membranes. Furthermore, it is found that the slope of the titration curve for the negatively charged membranes is much steeper than that for the neutral membranes. This indicates a higher binding affinity of the acylated peptide towards negatively charged lipid membranes as compared with neutral lipid membranes.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2001

Activity of mammalian secreted phospholipase A(2) from inflammatory peritoneal fluid towards PEG-liposomes. Early indications.

Due to an increase in the activity of phospholipase A(2) (PLA(2)) in various inflammatory diseases, this enzyme may play a key role in the degradation of liposomes and the subsequent release of drug when PEG-liposomes passively target inflammatory tissue. The activity of mammalian secreted phospholipase A(2) (sPLA(2)) in casein stimulated peritoneal fluid was tested toward liposomes of different compositions. Early results indicate only a slight degradation of conventional dipalmitoylphosphatidylcholine (DPPC) liposomes as well as DPPC liposomes incorporated with different concentrations of PEG(2000). However, the DPPC degradation increased to 7% when inclusion of 30 mol% phosphatidylethanolamine (PE) in the lipid bilayer. The increase in degradation may be due to an improvement of the substrate - as it is well known, that PE is a better substrate for the mammalian sPLA(2) than PC. Incorporation of PE into the bilayer may increase the binding properties of the bilayer resulting in improved conditions for the enzymatic attack by sPLA(2). In addition, inhibitory zones of Staphylococcus aureus in an agar diffusion test showed that PLA(2) from Crotalus atrox venom was able to catalyze the release of gentamicin from PEG-liposomes. In conclusion, this study suggest that degradation of the lipid bilayer of PEG-liposomes by PLA(2) result in release of incapsulated drug, e.g. gentamicin and inclusion of PE in the liposomal bilayer, may enhance the activity of the mammalian sPLA(2) toward liposomes composed of DPPC.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2001

Enzymatic degradation of polymer covered SOPC-liposomes in relation to drug delivery.

Polyethylenoxide (PEG) covered liposomes are used as lipid-based drug-delivery systems. In comparison to conventional liposomes the polymer-covered liposomes display a long circulation half-life in the blood stream. We investigate the influence of polyethyleneoxide-distearoylphosphatidylethanolamine (DSPE-PEG750) lipopolymer concentration on phospholipase A2 (PLA2) catalyzed hydrolysis of liposomes composed of stearoyloleoylphosphatidylcholine (SOPC). The characteristic PLA2 lag-time was determined by fluorescence and the degree of lipid hydrolysis was followed by HPLC analysis. Particle size and zeta-potential were measured as a function of DSPE-PEG750 lipopolymer concentration. A significant decrease in the lag-time, and hence an increase in enzyme activity, was observed with increasing concentrations of the anionic DSPE-PEG750 lipopolymer lipids. The observed decrease in lag-time might be related to changes in the surface potential and the PLA2 lipid membrane affinity.

Drug Delivery Systems↗

PubMed2001

Lateral organization and domain formation in a two-component lipid membrane system.

The thermodynamic phase behavior and lateral lipid membrane organization of unilamellar vesicles made from mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2 distearoyl-sn-glycero-3-phosphocholine (DSPC) were investigated by fluorescence resonance energy transfer (FRET) as a function of temperature and composition. This was done by incorporating a headgroup-labeled lipid donor (NBD-DPPE) and acceptor (N-Rh-DPPE) in low concentrations into the binary mixtures. Two instances of increased energy transfer efficiency were observed close to the phase lines in the DMPC/DSPC phase diagram. The increase in energy transfer efficiency was attributed to a differential preference of the probes for dynamic and fluctuating gel/fluid coexisting phases. This differential preference causes the probes to segregate (S. Pedersen, K. Jørgensen, T. R. Baekmark, and O. G. Mouritsen, 1996, Biophys. J. 71:554-560). The observed increases in energy transfer match with the boundaries of the DMPC/DSPC phase diagram, as measured by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). We propose that the two instances of probe segregation are due to the presence of DMPC-rich and DSPC-rich domains, which form a dynamic structure of gel/fluid coexisting phases at two different temperatures. Monitoring the melting profile of each lipid component independently by FTIR shows that the domain structure is formed by DMPC-rich and DSPC-rich domains rather than by pure DMPC and DSPC domains.

Calorimetry, Differential Scanning↗

PubMed2001

Association of acylated cationic decapeptides with dipalmitoylphosphatidylserine-dipalmitoylphosphatidylcholine lipid membranes.

The interaction of three acylated and cationic decapeptides with lipid membranes composed of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylserine (DPPS) has been studied by means of fluorescence spectroscopy and differential scanning calorimetry (DSC). The synthetic model decapeptides that are N-terminally linked with C(2), C(8), and C(14) acyl chains contain four basic histidine residues in their identical amino acid sequence. A binding model, based on changes in the intrinsic fluorescent properties of the peptides upon association with the DPPC-DPPS membranes, is used to estimate the peptide-membrane dissociation constants. The results clearly show that all three peptides have a higher affinity to liposomes containing DPPS lipids due to non-specific electrostatic interactions between the cationic peptides and the anionic DPPS lipids. Furthermore, it is found that the acyl chain length of the peptides plays a crucial role for the binding. A preference for fluid phase membranes as compared to gel phase membranes is generally observed for all three peptides. DSC is used to characterise the influence of the three peptides on the thermodynamic phase behaviour of the binary DPPC-DPPS lipid mixture. The extent of peptide association deduced from the heat capacity measurements suggests a strong binding and membrane insertion of the C(14) acylated peptide in accordance with the fluorescence measurements.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2001

Structural, physicochemical, and pasting properties of starches from potato plants with repressed r1-gene.

The aim of this work was to investigate the effect on starch molecular and physicochemical properties of down regulation of the R1 protein in potato (Solanum tuberosum L. cv. "Dianella") tubers. Most prominent is a 90% suppression of the phosphate content in the isolated potato tuber starch. The amylopectin chain length distribution profile as determined by HPAEC/PAD was not affected, but the amylose content was increased in the most down-regulated plants. The pasting properties of the transgenic starch revealed a pronounced decrease in peak viscosity and increased setback viscosity as measured using a rapid Visco analyzer. The starch gels displayed an increased hardness and stickiness with a maximum at 1.7 nmol of Glc-6P mg-1 of starch compared to the control lines. At very low phosphate levels (1.4 nmol of Glc-6P mg-1 of starch), the gel hardness was decreased as a result of increased gel brittleness. The increase in gel brittleness is believed to be an effect of an increased proportion of free amylopectin blocklets in the starch as determined by SEC/RI. The possible links between the structural and physicochemical parameters are discussed.

Amylopectin↗

PubMed2001

Dynamical and structural properties of lipid membranes in relation to liposomal drug delivery systems.

The structural and dynamical properties of DPPC liposomes containing lipopolymers (PEG-lipids) and charged DPPS lipids have been studied in relation to the lipid membrane interaction of enzymes and peptides. The results suggest that both the lipid membrane structure and dynamics and in particular the appearance of small-scale lipid structures might be of importance for the activity of membrane associated and liposome degrading enzymes as well as for the membrane interaction of acylated peptides. The combined experimental and simulation results are of relevance for a rational development of peptide loaded liposomal drug delivery systems that become destabilized by membrane degrading phospholipase A(2) enzymes, which are found at elevated concentrations at diseased sites.

Computer Simulation↗