Halvor Aarnes

• Aarnes, Halvor & Andersen, Tom (2014). Barnefødsler 1967 – 2012 analysert i R. Tidsskrift for Den norske legeforening. ISSN 0029-2001. 134(23-24), p. 2245–2246. doi: 10.4045/tidsskr.14.1316.
• Myhre, O; Mariussen, E; Reistad, T; Voie, OA; Fonnum, Frode & Aarnes, Halvor (2009). Effects of polychlorinated biphenyls on the neutrophil NADPH oxidase system. Toxicology Letters. ISSN 0378-4274. 187(3), p. 144–148. doi: 10.1016/j.toxlet.2009.02.014.
• Jørgensen, Per Magnus; Aarnes, Halvor & Lie, Thore (2007). Eksperimentell botanikk og laboratoriebotanikk. In Jørgensen, Per M. (Eds.), Botanikkens historie i Norge. Fagbokforlaget. ISSN 978-82-450-0499-1. p. 97–115.
• Aarnes, Halvor; Eriksen, Aud Else Berglen; Petersen, Dirk & Rise, Frode (2007). Accumulation of ammonium in Norway spruce (Picea abies) seedlings measured by in vivo 14N-NMR. Journal of Experimental Botany. ISSN 0022-0957. 58(5), p. 929–934. doi: 10.1093/jxb/erl247. Show summary

  http://jxb.oxfordjournals.org/cgi/content/abstract/erl247? ijkey=y8vx24OpXL2qpyu&keytype=ref 14N-NMR and 31P-NMR have been used to monitor the in vivo pH in roots, stems, and needles from seedlings of Norway spruce, a typical ammonium-tolerant plant. The vacuolar and cytoplasmic pH measured by 31P-NMR was found to be c. pH 4.8 and 7.0, respectively, with no significant difference between plants growing with ammonium or nitrate as the N-source. The 1H-coupled 14NH resonance is pH-sensitive: at alkaline pH it is a narrow singlet line and below pH 4 it is an increasing multiplet line with five signals. The pH values in ammonium-containing compartments measured by 14N-NMR ranged from 3.7 to 3.9, notably lower than the estimated pH values of the Pi pools. This suggests that, in seedlings of Norway spruce, ammonium is stored in vacuoles with low pH possibly to protect the seedlings against the toxic effects of ammonium (NH) or ammonia (NH3). It was also found that concentrations of malate were 3–6 times higher in stems than in roots and needles, with nitrate-grown plants containing more malate than plants grown with ammonium. Key words: Ammonium, cytoplasmic pH, in vivo 14N-NMR, in vivo 31P-NMR, malate, organic acids, Picea abies (L.) Karst, vacuolar pH

• Andersen, Jannike Mørch; Myhre, Oddvar; Aarnes, Halvor; Vestad, Tor Arne & Fonnum, Frode (2003). Identification of the Hydroxyl Radical and Other Reactive Oxygen Species in Human Neutrophil Granulocytes Exposed to a Fragment of the Amyloid Beta Peptide. Free radical research. ISSN 1071-5762. 37(3), p. 269–279.
• Myhre, Oddvar; Andersen, Jannike Mørch; Aarnes, Halvor & Fonnum, Frode (2003). Evaluation of the probes 2´,7´-dichlorofluorescin diacetate, luminol, and lucigenin as indicatos of reactive species formation. Biochemical Pharmacology. ISSN 0006-2952. 65, p. 1575–1582.
• Aarnes, Halvor (2002). Ozon, Sur nedbør - tilførsel og virkning. Landbruksforlaget. ISSN 82-529-2105-1. p. 108–113.
• Myhre, Oddvar; Vestad, Tor Arne; Sagstuen, Einar; Aarnes, Halvor & Fonnum, Frode (2000). The Effects of Aliphatic (n-nonane), Naphtenic (1,2,4-trimethylcyclohexane) and Aromatic (1,2,4-trimethylbenzene) Hydrocarbons on Respiratory Burst in Human Neutrophil Granulocytes. A Fluorescence and Electron Paramagnetic Resonance (EPR) Spectroscopy Study. Toxicology and Applied Pharmacology. ISSN 0041-008X. 167, p. 222–230. Show summary

  This study investigates the effects of aliphatic (n-heptane, n-nonane), naphtenic (methylcyclohexane, 1,2,4-trimethylcyclohexane (TMCH)) and aromatic (methylbenzene, 1,2,4-trimethylbenzene (TMB)) hydrocarbons on respiratory burst in human granulocytes, measured as 2,7-dichlorofluorescein diacetate-amplified fluorescence and by electron paramagnetic resonance (EPR) spectroscopy. The chemotactic peptide N-formyl-met-leu-phe (fMLP) and phorbol 12-myristate 13-acetate (PMA), a diacylglycerol analogue, were included for purposes of positive control. Fluorescence was elevated in a concentration dependent manner by C9 hydrocarbons. The C7 hydrocarbons did not stimulate respiratory burst in the concentration range examined. The naphtenic hydrocarbon TMCH showed strongest potential for elevation of respiratory burst, and was then selected for mechanistic studies of this free radical formation. In the absence of extracellular Ca2+, fluorescence in response to TMCH and fMLP was reduced by 77% and 90%, respectively. Preincubation of the granulocytes with the protein kinase C inhibitor bisindolylmaleimide reduced the fluorescence stimulated with TMCH, fMLP and PMA by 82%, 56% and 90%, respectively. The phospholipase C inhibitor U73122 lowered the TMCH- and fMLP activated fluorescence by 87% and 76%. In addition, the TMCH- and fMLP induced fluorescence, after the preincubation with the phospholipase D modulator n-butanol, was lowered by 83% and 52%, respectively. The importance of protein kinase C, phospholipase C and phospholipase D for elevation of respiratory burst were also demonstrated by the EPR experiments using the spin trap DEPMPO. Preincubation with the NADPH oxidase inhibitor diphenyleneiodonium, and diethyldithiocarbamate, which inhibits superoxide dismutase, led to an almost complete reduction of fluorescence in response to TMCH, fMLP and PMA. Preincubation with diethyldithiocarbamate led to the elevation of superoxide adducts of DEPMPO. In conclusion, our findings indicate that TMCH activated respiratory burst is dependent on the Ca2+ dependent phospholipase C, phospholipase D and protein kinase C prior to activation of the NADPH oxidase.

• Myhre, Oddvar; Vestad, Tor Arne; Sagstuen, Einar; Aarnes, Halvor & Fonnum, Frode (1999). Effects of the solvent 1,2,4-trimethylcyclohexane on respiratory burst in human neutrophil granulocytes: A chemiluminescence and electron paramagnetic resonance spectrometry study. Annals of the New York Academy of Sciences. ISSN 0077-8923. 893, p. 358–361. Show summary

  We investigated the effects of 1,2,4-trimethylcyclohexane (TMCH, 10-50 µM), n-nonane (10-50 µM) and 1,2,4-trimethylbenzene (TMB, 0.05-0.5 mM) on free radical production in vitro in human neutrophil granulocytes and rat brain synaptosomes. Human granulocytes and rat brain synaptosomes were incubated with 2',7'-dichlorofluorescein diacetate prior to exposure of the organic solvents. Reactive oxygen species (ROS) production was subsequently measured by chemoluminescence spectroscopy. The solvent-induced elevation of free radicals in human granulocytes were also measured by EPR spectroscopy after incubation with the spin trap DEPMPO. Mechanisms for ROS production was elucidated by use of enzymatic inhibitors. Low concentrations of TMCH, n-nonane and TMB stimulated respiratory burst (production of O2-) in human granulocytes and ROS production in rat brain synaptosomes. The respiratory burst in response to TMCH was dependent of extracellular calcium. U-73122, a phospholipase C (PLC) inhibitor, and 7,7-dimethyleicosadienoic acid, a phospholipase A2 (PLA2) inhibitor lowered the TMCH-stimulated O2- production in granulocytes. Furthermore, bisindolylmaleimide, a protein kinase C (PKC) inhibitor, and diphenyleneiodonium, a NADPH-oxidase inhibitor, reduced the TMCH-stimulated respiratory burst almost completely. In conclusion, these results indicates that TMCH-activated respiratory burst is dependent of Ca2+-dependent PLC, PLA2 and PKC prior to activation of the NADPH-oxidase.

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• Aarnes, Halvor (2007). Vårskrinneblom - liten og nyttig. Biolog. ISSN 0801-0722. p. 21–26.
• Aarnes, Halvor; Eriksen, Aud Else Berglen; Petersen, Dirk & Rise, Frode (2004). In Vivo 14N-NMR and 31P-NMR: intracellular pH in Norway spruce (Picea abies) seedlings grown on ammonium or nitrate.
• Vestad, Tor Arne; Myhre, Oddvar; Fonnum, Frode; Sagstuen, Einar & Aarnes, Halvor (2000). Effects of organic solvents on free-radical production in human neutrophil granulocytes. An EPR spin trapping study. Show summary

  As a consequence of interaction with a variety of stimuli, human neutrophil granulocytes (a group of leukocytes) undergo a marked increase in oxygen metabolism, termed the respiratory burst [1]. One oxygen-centered free radical (superoxide) has been unequivocally shown to result from this respiratory burst, and some experimental evidence for another (hydroxyl) has been published. Neutrophils kill microorganisms by ingesting them into phagocytic vacuoles and then bombarding them with reactive oxygen species and contents of cellular granules [2]. Whether organic solvents may lead to free-radical generation and the damages from organic solvents (particularly to the brain) are due to free radicals, have been subjects of discussion. Organic solvents such as toluene and "white spirit" have been shown to cause elevation of reactive oxygen species in mammal central nervous system [3]. Little is known about solvent-induced mechanisms for initiation of respiratory burst in human neutrophils. With background in inhalation experiments on rats, three organic solvents were chosen at relevant concentrations. Respiratory burst was assayed using EPR spin trapping, and by a fluorescence technique. Mechanisms for organic solvent-induced production of reactive oxygen species were elucidated by the use of enzymatic inhibitors. We evaluated the use of the spin trap DEPMPO for assessment of superoxide free radicals formed by human neutrophil granulocytes, and found it suitable. Effects of the organic solvents 1,2,4-trimethylcyclohexane, n-nonane and 1,2,4-trimethylbenzene on free-radical production in vitro in human neutrophil granulocytes were examined. Low concentrations of two of these organic solvents stimulated human neutrophil granulocytes to produce superoxide free radicals. Mechanisms for the free-radical production induced by 1,2,4-trimethylcyclohexane were elucidated by the use of enzymatic inhibitors [4]. Both an NADPH-oxidase inhibitor and a protein kinase C inhibitor blocked this production. Further, the free radical production depended on extracellular calcium, phospholipase C and phospholipase D. [1] Baldridge, C.W. and Gerard, R.W. American journal of physiology 1933, 103, 235-236. [2] Kettle, A.J. and Winterbourn, C.C. Redox Report 1997, 3, 3-15. [3] Lam, H.R.; Ostergaard, G.; Guo, S.X.; Ladefoged, O.; Bondy, S.C. Biochemical Pharmacology 1994, 47, 651-657. [4] Myhre, O.; Vestad, T.A.; Sagstuen, E.; Aarnes, H.; Fonnum, F. Toxicology and Applied Pharmacology, submitted.

• Andersen, Jannike Mørch; Myhre, Oddvar; Vestad, Tor Arne; Aarnes, Halvor & Fonnum, Frode (2000). bA(25-35) produces free radicals in human neutrophil granulocytes. A study including fluorescence, electron paramagnetic resonance (EPR) spectroscopy and aromatic acid hydroxylation.
• Myhre, Oddvar; Vestad, Tor Arne; Sagstuen, Einar; Aarnes, Halvor & Fonnum, Frode (1999). Effects of C-9 organic solvents on free radical production in human granulocytes and rat brain synaptosomes.
• Myhre, Oddvar; Vestad, Tor Arne; Fonnum, Frode; Sagstuen, Einar & Aarnes, Halvor (1999). Effects of Organic Solvents on Free Radical Production in Human Neutrophil Granulocytes and Rat Synaptosomes.
• Vestad, Tor Arne; Myhre, Oddvar; Fonnum, Frode; Aarnes, Halvor & Sagstuen, Einar (1998). Measurement of Superoxide Generation from Granulocytes using EPR Spin Trapping Techniques.
• Aarnes, Halvor (2000). Planteøkofysiologi: fra atom til økosystem. ISSN 82-90934-21-1.
• Aarnes, Halvor (2000). Planteanatomi. Plantenes indre bygning og morfologi. ISSN 82-90934-20-3.

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