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Biomedical subjects

L F Hansen

Publications and source records attributed to L F Hansen.

15 recordsLinked to original sources
PubMed2001

Lipid oxidation in fish oil enriched mayonnaise: calcium disodium ethylenediaminetetraacetate, but not gallic acid, strongly inhibited oxidative deterioration.

The antioxidative effects of gallic acid, EDTA, and extra emulsifier Panodan DATEM TR in mayonnaise enriched with 16% fish oil were investigated. EDTA reduced the formation of free radicals, lipid hydroperoxides, volatiles, and fishy and rancid off-flavors. The antioxidative effect of EDTA was attributed to its ability to chelate free metal ions and iron from egg yolk located at the oil-water interface. Gallic acid reduced the levels of both free radicals and lipid hydroperoxides but promoted slightly the oxidative flavor deterioration in mayonnaise and influenced the profile of volatiles. Gallic acid may therefore promote the decomposition of lipid hydroperoxides to volatile oxidation products. Addition of extra emulsifier reduced the lipid hydroperoxide levels but did not influence the level of free radicals or the oxidative flavor deterioration in mayonnaisse; however, it appeared to alter the profile of volatiles. The effect of the emulsifier on the physical structure and rheological properties depended on the presence of antioxidants.

Antioxidants↗
PubMed2000

Determination of neutral lipid hydroperoxides by size exclusion HPLC with fluorometric detection. Application to fish oil enriched mayonnaises during storage.

A fast (12 min) high-performance size exclusion chromatography (HPSEC) method for the separation of neutral lipid class hydroperoxides in the oil phases from fish oil enriched mayonnaises was developed. Detection and quantification were performed using the postcolumn fluorometric (FL) diphenyl-1-pyrenylphosphine oxidation principle. The reproducibilities judged by intra- and inter-assay variations were 0.64 and 7.2%, respectively. The HPSEC-FL method was applied to assess the effect of supplementations with emulsifier, gallic acid, and EDTA on the oxidative processes in the mayonnaises during storage. Substantial amounts of hydroperoxy triacylglycerols (TAGOOH) and cholesterol esters (CEOOH), together with traces of TAGOOH-dimers, were detected. All supplementations significantly decreased the levels of TAGOOH and to a lesser degree CEOOH. Supplementations with EDTA and gallic acid resulted in constant and slightly increasing levels of TAGOOH, respectively, thus affecting the oxidation mechanisms seen in reference mayonnaise. The emulsifier Panodan TR DATEM reduced the levels of TAGOOH as compared to the appropriate controls.

Chromatography, High Pressure Liquid↗
PubMed2000

Dynamic headspace gas chromatography/mass spectrometry characterization of volatiles produced in fish oil enriched mayonnaise during storage.

Protection against lipid oxidation and formation of unpleasant fishy and rancid off-flavors in oil-in-water food emulsions, such as fish oil enriched mayonnaise, is difficult to achieve. Volatile profiles from stored mayonnaises with different oil phase compositions were collected using a developed dynamic headspace sampling technique, in which interfering acetic acid was removed in situ with potassium hydroxide, and subsequently 148 volatiles were characterized and monitored by gas chromatography/mass spectrometry. Multivariate statistics showed correlation between the concentration of 62 volatiles and the fish oil and storage parameters, indicating the formation of lipid oxidation products, which impose fishy off-flavors. Further verification was obtained by gas chromatography/olfactometry, by which, among 78 odors, cis-4-heptenal and trans,cis-2,4-heptadienal were detected as distinct fishy notes. In total, 27 volatiles, including 1-penten-3-one, cis-2-penten-1-ol, cis-3-hexenal, cis-4-heptenal, 1-octen-3-one, 1,cis-5-octadien-3-one, 1-octen-3-ol, trans,cis-2, 4-heptadienal, and trans,cis-2,6-nonadienal, were suggested to contribute to the developed unpleasant fishy and rancid off-flavors.

Fish Oils↗
PubMed1996

Bis-intercalation of a homodimeric thiazole orange dye in DNA in symmetrical pyrimidine-pyrimidine-purine-purine oligonucleotides.

One- and two-dimensional 1H NMR spectroscopy were used to characterize the binding of a homodimeric thiazole orange dye, 1,1'-(4,4,8,8-tetramethyl-4,8-diazaundecamethylene)-bis-4-(3 -methyl-2,3-dihydro-(benzo- 1,3-thiazole)-2-methylidene)-quinolinium tetraiodide (TOTO), to various double-stranded DNA oligonucleotides containing symmetric (5'-pyr-pyr-pu-pu-3')2 or (5'-pu-pu-pyr-pyr-3')2 sequences. It was found that TOTO binds preferentially to oligonucleotides containing a (5'-CTAG-3')2 or a (5'-CCGG-3')2 sequence. Binding to the (5'-CCGG-3')2 sequence is less favored than to the (5'-CTAG-3')2 sequence. The complexes of TOTO with d(CGCTAGCGCTAGCG)2 (10) and d(CGCTAGCCGGCG):d(CGCCGGCTAGCG) (11) oligonucleotides, each containing two preferential binding sites, was also examined. In both cases TOTO forms mixtures of 1:1 and 1:2 dsDNA-TOTO complexes in ratios dependent on the relative amount of TOTO and the oligonucleotides in the sample. Binding of TOTO to the two oligonucleotides is sequence selective at the (5'-CTAG-3')2 and (5'-CCGG-3')2 sites. The 1H NMR spectra of both the 1:2 complexes and the three different 1:1 complexes have been assigned. A slight negative cooperativity is observed in formation of the 1:2 complexes. The ratio between the two different 1:1 complexes formed with oligonucleotide 11 is 2.4 in favor of binding to the (5'-CTAG-3')2 site. This is very similar to results obtained when the two sites are in different oligonucleotides. Thus the distribution of TOTO among the (5'-CTAG-3')2 and (5'-CCGG-3')2 sites is independent of whether the two sites are in the same or two different oligonucleotides.

Base Sequence↗
PubMed1996

Sensory irritation mechanisms investigated from model compounds: trifluoroethanol, hexafluoroisopropanol and methyl hexafluoroisopropyl ether.

Quantitative structure-activity relationships (QSAR) have suggested the importance of hydrogen bonding in relation to activation of the sensory irritant receptor by nonreactive volatile organic chemicals. To investigate this possibility further, three model compounds with different hydrogen bond acidity, trifluoroethanol, hexafluoroisopropanol and methyl hexafluoroisopropyl ether, were selected for study. The potency of each chemical is obtained from the concentration necessary to reduce respiratory rate in mice by 50% (RD50). The RD50 values obtained were: methyl hexafluoroisopropyl ether (> or = 160,000 ppm), trifluoroethanol (11,400-23,300 ppm), and hexafluoroisopropanol (165 ppm). QSAR showed that trifluoroethanol and methyl hexafluoroisopropyl ether behaved as predicted as nonreactive sensory irritants, whereas hexafluoroisopropanol was much more potent than predicted. The higher than predicted potency of hexafluoroisopropanol could be due to a coupled reaction, involving both strong hydrogen bonding and weak Brönsted acidity. A concerted reaction could thus be more efficient in activation of the receptor. Hydrogen bonding properties and concerted reactions may be important in the activation of the sensory irritant receptor by nonreactive volatile organic chemicals.

1-Propanol↗
PubMed1995

Site selective bis-intercalation of a homodimeric thiazole orange dye in DNA oligonucleotides.

We have used one and two dimensional 1H NMR spectroscopy to characterize the binding of a homodimeric thiazole orange dye, 1,1'-(4,4,8,8-tetramethyl-4,8-diaza-undecamethylene)-bis-4- (3-methyl-2,3-dihydro-(benzo-1,3-thiazole)-2-methylidene)-quinolin ium tetraiodide (TOTO), to various double stranded DNA oligonucleotides. TOTO binds strongly to all the oligonucleotides used, but usually more than one complex is observed and exchange between different binding sites broadens the lines in the NMR spectra. Complete precipitation occurs when TOTO is bound to small oligonucleotides. Binding to larger oligonucleotides occurs by bis-intercalation. The 1:1 complex of TOTO with the oligonucleotide d(CCGACTGATGC):d (GCATCAGTCGG) gave only one complex that was shown to be a bis-intercalation in the CTGA:TCAG binding site. The binding to this site was also characterized by studying the TOTO complex with the d(CCGCTGAGC):d(GCTCAGCGG) oligonucleotide. NOE connectivities and molecular modelling were used to characterize the complex. The 1:1 complex of TOTO with the oligonucleotide d(CCGCTAGCG):d(CGCTAGCGG) containing a CTAG:CTAG binding site was similarly characterized by NMR. It was concluded that the binding of TOTO to larger oligonucleotides is site selective with CTAG:CTAG as the preferred binding site.

Base Sequence↗
PubMed1994

Sensory irritation, pulmonary irritation and structure-activity relationships of alcohols.

Sensory irritation due to inhalation of n-pentanol, n-heptanol, sec-butanol and tert-pentanol was determined from the reflexively induced decrease in respiratory rate in CF-1 mice. The concentration-effect relations followed Michaelis-Menten equations, complying with receptor mediated processes. The relations were transformed into nearly rectilinear relationships in log concentration-effect plots, and the extrapolated threshold concentrations (RD-0) from the lines were 120, 28, 640 and 1210 ppm, respectively, obtained from the first 2 min of the exposure period. These values were comparable to those found in Swiss-Webster mice and to those obtained by electrophysiological experiments in Sprague-Dawley rats. The hydrophobic properties of the receptor biophase were found to approach that of the internal part of the bilayer membrane. Estimates on threshold limit values (TLV) were obtained and were found in reasonable agreement with the established values. The nose has a scrubbing effect, which reduces the concentration in the lungs in normal mice. n-Pentanol, sec-butanol and tert-pentanol decreased tidal volume in normal mice, explained either by an activation of receptors in the upper airways or by a sensitization of the stretch receptors. Two types of pulmonary responses were seen in tracheal-cannulated mice, which could be explained by an effect on stretch receptors and another type of lung receptors.

Administration, Inhalation↗
PubMed1994

Sensory irritation and pulmonary irritation of n-methyl ketones: receptor activation mechanisms and relationships with threshold limit values.

Activation of the trigeminal nerve endings in eyes and nose, termed sensory irritation, was determined from the reflexively induced decrease in respiratory rate in mice for methyl propyl ketone, methyl butyl ketone, methyl amyl ketone and methyl hexyl ketone. The relationship between exposure concentration and the decrease in respiratory rate followed Michaelis-Menten equations. Two estimates of each agonist-receptor dissociation constant were obtained, one from the Michaelis-Menten equation and one from the threshold (RD-0) of the log concentration-effect curve. The values were equal and thus one receptor type could account for the activation process. The hydrophobic properties of the receptor biophase were found to approach that of the internal part of the bilayer membrane. It therefore follows that the receptor-air partition coefficients increase with the size of the ketones, thus accounting for the observed increase in potency. Estimates of Threshold Limit Values (TLV) were obtained and compared with established values. Close agreements were found for methyl propyl ketone and methyl amyl ketone, but not for methyl butyl ketone, where the neurotoxic effect constituted a more sensitive endpoint than sensory irritation.

Administration, Inhalation↗
PubMed1994

Effects of intranasal ZnSO4 irrigation on olfactory and trigeminal cues.

Intranasal irrigation with ZnSO4 solutions is used for experimental induction of anosmia. It is, however, unknown whether the trigeminal nerve is affected by the treatment. One day after irrigation (concentrations investigated were between 0.05-1%) the ability of food finding, an olfactory cue, was decreased in a concentration-dependent manner. The trigeminal effect was investigated from a reflexively induced decrease in respiratory rate due to n-propanol exposure. No impairment occurred at 1% ZnSO4. Anosmia was also seen 2-3 h after an irrigation with solutions of 0.05-1% ZnSO4. At the same time, 0.2 and 1% solutions in themselves decreased the respiratory rate due to reflexes from the upper and lower respiratory tract. A conspicuous systemic effect can be ruled out as the Zn++ antidote, CaNa2EDTA, had no effect on the decrease. A direct activation of the trigeminal nerve due to a reaction with a thiol group may explain the effect from the upper airways.

1-Propanol↗
PubMed1993

Ventilation, CO2 production, and CO2 exposure effects in conscious, restrained CF-1 mice.

Respiratory rate (f), tidal volume (VT) and carbon dioxide production (VECO2) were measured in restrained, conscious CF-1 mice. Mean f +/- S.D. and mean VT +/- S.D. were 270 +/- 8 breaths/min. and 0.123 +/- 0.024 ml (STPD) for male, and 274 +/- 15 breaths/min. and 0.115 +/- 0.023 ml (STPD) for female mice, respectively. VECO2 was obtained from a rebreathing (closed loop) system. The maximum VECO2 (STPD) amounted to 95.5 +/- 15.4 ml/(kg min.) in males and to 72.7 +/- 4.2 ml/(kg min.) in females. The CO2 concentration in the closed loop system increased slowly during a 30 min. rebreathing period and reached a concentration of about 2.7%. No effect was seen on f and on VT. Dynamic (abrupt) exposure up to 10.3% CO2 had no effect on f in male mice, whereas VT increased from 112% (2.3% CO2) to 181% (10.3% CO2). The estimated O2 concentrations decreased from 20.5% to 18.7% with increasing CO2 exposure. The equivalent CO2 experiments with O2 kept at 16% by N2 administration showed that the lower O2 concentration added an additional drive on the respiratory centre.

Animals↗
PubMed1992

Sensory irritation effects of methyl ethyl ketone and its receptor activation mechanism.

The burning and painful effect in nose and eyes, termed sensory irritation, of methyl ethyl ketone vapours was investigated in a mouse bioassay. Sensory irritation is mediated via the trigeminal nerves and results in a reflexively induced decrease in respiratory rate in mice. Methyl ethyl ketone was used as a model substance for ketones. At the lower exposure concentrations a partial fading (desensitization) of the response was seen. Little desensitization was seen at higher concentrations. n-Propanol, a model substance for alcohols, desensitized the receptor at all exposure levels. Preexposure to propanol did not influence the response at high methylethyl ketone concentrations. This suggests that the two substances bind to different receptive sites with different properties, if the ketone response is due to a high exposure concentration. A decrease in tidal volume was also mediated from the upper respiratory tract. The tidal volume effect is mediated by nerves different from those mediating the frequency response, as the time-response relationship, the desensitization pattern, the maximum response and the apparent dissociation constants were different for the two types of effect. Neither the location nor the perceived response related to the volume response is known.

1-Propanol↗
PubMedDate not supplied

Sensory irritation effects of n-propanol and ethylbenzene after pretreatment with capsaicin or indomethacin.

Irritation of upper respiratory tract (sensory irritation) due to two model solvents, ethylbenzene and propanol, were investigated from their reflex-induced decrease in respiratory rate in mice. Intranasal application of capsaicin decreased the sensory irritation response of both solvents, indicating that at least part of the sensory irritation effect must occur as a result of activation of capsaicin sensitive afferent nerves. The vehicle used for the application of capsaicin in itself decreased the respiratory rate strongly, either caused by effects on the upper respiratory tract or on the lungs. This demonstrates the need for a formulation of a pharmacologically inactive vehicle for nasal application of lipophilic substances. Pretreatment with indomethacin had no influence on sensory irritation of any of the solvents. This suggests that sensory irritation is caused by a direct interaction between receptors on the trigeminal nerves and the vapours rather than being an indirect effect of tissue damage giving rise to metabolites from the cyclooxygenase pathway.

1-Propanol↗