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  • 1.
    Dizdar (Dizdar Segrell), Nil
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Zsigmond, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Nezirevic, Dzeneta
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    Letter: Untitled2013In: Journal of Neuroscience Methods, ISSN 0165-0270, E-ISSN 1872-678X, Vol. 212, no 2, p. 363-363Article in journal (Refereed)
    Abstract [en]

    n/a

  • 2.
    Karlsson, Anna
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ejlertsson, Jörgen
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Nezirevic, Dzeneta
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Bo H.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Degradation of phenol under meso- and thermophilic, anaerobic conditions1998In: Anaerobe, ISSN 1075-9964, E-ISSN 1095-8274, Vol. 5, no 1, p. 25-35Article in journal (Refereed)
    Abstract [en]

    Based on the results of preliminary studies on phenol degradation under mesophilic conditions with a mixed methanogenic culture, we proposed a degradation pathway in which phenol is fermented to acetate: Part of the phenol is reductively transformed to benzoate while the rest is oxidised, forming acetate as end product. According to our calculations, this should result in three moles of phenol being converted to two moles of benzoate and three moles of acetate (3phenol+2CO2+3H2O→3acetate+2benzoate): To assess the validity of our hypothesis concerning the metabolic pathway, we studied the transformation of phenol under mesophilic and thermophilic conditions in relation to the availability of hydrogen. Hence, methanogenic meso- and thermophilic cultures amended with phenol were run with or without an added over-pressure of hydrogen under methanogenic and non-methanogenic conditions. Bromoethanesulfonic acid (BES) was used to inhibit methanogenic activity. In the mesophilic treatments amended with only BES, about 70% of the carbon in the products found was benzoate. During the course of phenol transformation in these BES-amended cultures, the formation pattern of the degradation products changed: Initially nearly 90% of the carbon from phenol degradation was recovered as benzoate, whereas later in the incubation, in addition to benzoate formation, the aromatic nucleus degraded completely to acetate. Thus, the initial reduction of phenol to benzoate resulted in a lowering of H2levels, giving rise to conditions allowing the degradation of phenol to acetate as the end product. Product formation in bottles amended with BES and phenol occurred in accordance with the hypothesised pathway; however, the overall results indicate that the degradation of phenol in this system is more complex.

    During phenol transformation under thermophilic conditions, no benzoate was observed and no phenol was transformed in the BES-amended cultures. This suggests that the sensitivity of phenol transformation to an elevated partial pressure of H2is higher under thermophilic conditions than under mesophilic ones. The lack of benzoate formation could have been due to a high turnover of benzoate or to a difference in the phenol degradation pathway between the thermophilic and mesophilic cultures.

  • 3.
    Karlsson, Anna
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Nezirevic, Dzeneta
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ejlertsson, Jörgen
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Bo H.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Degradation of aromatic compounds by micro-organisms in solid waste samples from landfills and landfill simulation reactorsManuscript (preprint) (Other academic)
    Abstract [en]

    The ability by micro-organisms developed in landfilled waste totransform phenol, dimethyl phthalate (DMP), aniline, tetrabromophthalic acid (TBPA), 3-chlorobenzoate (CB) and 2,4,6-trichlorophenol (TCP) was investigated using a method modified after ISO 17334. Forty-four solid waste samples from landfills and landfill simulation reactors (LSRs) were used. The LSRs were run over a five-year period and simulated acid and methanogenic landfill conditions. The biodegradability of each aromatic compound (0.5-0. 7 mM) was assayed over 100-200 days. The degradation capacity was monitored both by quantification of the aromatic compounds and by methane analysis

    The degradation capacity for the halogenated aromatics was poor or completely lacking by the landfill inocula investigated showing that this kind of compounds might persist in landfill. TCP inhibited both the methanogenic and fermentative micro-flora present in the waste samples, however, in early LSR assays no inhibition was observed. Phenol and DMP was transformed to non aromatic products in most assays. The biodegradation capacity towards these compounds increased over time in the LSR studies i.e. the acid and early methanogenic land fill phases had no or poor degradation capacity. These results indicates that the earlymethanogcnic tlora developing in landfills and landfill simulation reactors is different from the one later established by being less efficient in transformation of aromatic compounds but also less sensitive to aryl halides.

  • 4.
    Karlsson, Anna
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Nezirevic, Dzeneta
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ejlertsson, Jörgen
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Bo H.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Reduction of phenol to benzoate: an electron sink reaction used by a highly enriched anaerobic cultureManuscript (preprint) (Other academic)
    Abstract [en]

    A non-methanogenic pasteurised enrichment culture fermenting phenolto benzoate, butyrate and acetate was studied, focusing on the effects of adding yeast extract (0.1, 0.2 or I g!l) or glucose (1.5 mM) together with the phenol (5 mM). The results showed that the reductive formation of benzoate from phenol increased when either yeast extract (1 g 1-') or glucose was added to the medium. The culture also transformed phenol at a higher rate when glucose was added as a "co-substrate" than when it was grown on phenol alone. Furthermore, higher growth rates occurred in cultures grown on both substrates rather than on glucose or phenol alone.

  • 5.
    Nezirevic Dernroth, Dzeneta
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Pheomelanin markers in melanoma with reference to their excretion into urine2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Skin pigmentation is an important issue in most cultures. Until recently we have not understood the most important elements of pigmentation regarding detailed chemical structure. The synthesis of melanin is very complex, and although core enzymes, other important proteins, and parts of the melanin structure have been identified much information in this context awaits disclosure.

    The function of the melanocyte and the deposition of melanin pigments into the keratinocytes are very important in the protection against UV light. Melanin pigments consist of high-molecular structures often described as brown to black eumelanin and yellow to red pheomelanin. Eumelanin is photoprotective, whereas pheomelanin is believed to be carcinogenic after UV radiation. There is strong evidence that people of fair complexion with freckles who tan poorly are at higher risk of developing melanoma. These people have a higher pheomelanin to eumelanin ratio in their skin.

    Melanoma, one of the most widely spread cancers, is derived from melanocytes. There is accumulating evidence that pigment constitution is highly involved in the development of melanoma. We found that patients with advanced melanoma secrete substantial amounts of pigment structures into the urine, in particular those with diffuse melanosis. In subsequently performed experiments we purified these pigments and subjected the product to chemical degradation by either hydrogen peroxide oxidation or hydriodic hydrolysis. Several new chromatographic methods were developed for the structural analysis of these products. Structural analysis of new chromatographic peaks was performed. In conclusion, complex pheomelanin structures as well as low molecular weight pigments and free benzothiazoles have been identified in the urine of patients with melanoma and diffuse melanosis.

    The present thesis provides new insight into melanogenesis and melanoma progression. This opens the doorway to further approaches to the investigation of melanins and can help to understand fundamental problems about the structure and biosynthesis of natural melanins.

    List of papers
    1. HPLC analysis of pheomelanin degradation products in human urine
    Open this publication in new window or tab >>HPLC analysis of pheomelanin degradation products in human urine
    Show others...
    2003 (English)In: Pigment Cell Research, ISSN 1755-1471, E-ISSN 1755-148X, Vol. 16, no 5, p. 480-486Article in journal (Refereed) Published
    Abstract [en]

    A sensitive and specific high performance liquid chromatography (HPLC) method was developed to quantify 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP) in urine. In degradation studies of melanin pigment, 4-AHP and 3-AHP are derived from benzothiazine units of pheomelanin and pheomelanin-related metabolites such as trichochromes. 5-S-Cysteinyldopa-derived benzothiazine products give 4-AHP while 2-S-cysteinyldopa-derived benzothiazine products give 3-AHP. 3-AHP is also derived from nitrotyrosine formed by nitration of tyrosine with reactive nitrogen species. For this reason, the influence of this biological process on the amount of 3-AHP found in biological material have been investigated. The method is based on hydriodic acid hydrolysis of the melanin polymer and reversed-phase HPLC with electrochemical detection of the degradation products 4-AHP and 3-AHP. The mobile phase consists of 25 mM ammonium acetate and sodium octanesulfonate as an ion-pairing reagent. The 4-AHP and 3-AHP peaks were well separated and the detector response was linear within the range 0-2 ng injected for both compounds. With the developed chromatographic system, 4-AHP and 3-AHP showed good separation in the biological samples. There was a strong correlation between 4-AHP and 3-AHP in the urine of 50 malignant melanoma patients and two healthy subjects (R0.977). The two compounds were also strongly correlated with 5-S-cysteinyldopa in urine, the correlation coefficients being 0.862 and 0.907, respectively. The method described is sensitive enough for analysis of pheomelanin in urine and in several other biological samples. The results indicate that 3-AHP in urine is not influenced by excreted 3-nitrotyrosine and the data indicate that pheomelanins are excreted in the urine of melanoma patients.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-21494 (URN)10.1034/j.1600-0749.2003.00086.x (DOI)12950724 (PubMedID)
    Available from: 2009-10-02 Created: 2009-10-02 Last updated: 2017-12-13Bibliographically approved
    2. Hydrophilic interaction liquid chromatographic analysis of aminohydroxyphenylalanines from melanin pigments
    Open this publication in new window or tab >>Hydrophilic interaction liquid chromatographic analysis of aminohydroxyphenylalanines from melanin pigments
    2007 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1163, no 1-2, p. 70-79Article in journal (Refereed) Published
    Abstract [en]

    Malignant melanomas are more often seen in subjects with light colored skin who tan poorly than in persons who tan more rapidly. This has been attributed to the structure of their pigment, pheomelanin, which differs markedly from the eumelanin of persons with darker skin. To study the hydrolysis products of pheomelanin pigments a new method was developed for analysis of 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP). Pheomelanin samples were hydrolyzed and extracted with solid-phase extraction columns using strong cation-exchange (SCX) cartridges. Separation of 4-AHP and 3-AHP was achieved on a ZIC-HILIC column (150 mm × 2.1 mm I.D.) with a mobile phase consisting of acetonitrile:0.1 M ammonium acetate buffer, pH 4.5 (82:18, v/v). Detection was performed with an electrochemical detector at +400 mV. Run time was 30 min. The limits of detection were 73 pg and 51 pg for 4-AHP and 3-AHP respectively, using 2 μl injections. Good linearity was found within the range 0.05-5.0 μg/ml. Absolute recovery was 70% and relative recovery was 100%. The AHPs were stable for 1 year in the hydrolyzed samples, for 4 days in the eluates from solid-phase sorbents stored in the refrigerator, and for 2 days diluted with mobile phase and stored in the autosampler at 10 °C. The within-day imprecision was <5% and the between-day imprecision was <7% for the two analytes. The method, applied to the analysis of pheomelanin in urine from human melanoma patients, allows the analysis of 30 samples in one set and is suitable for routine work with human hair and melanoma cells. By using the ZIC-HILIC stationary phase, ion-pairing reagents could be avoided, which makes the method suitable to further analysis of degradation products from pheomelanins using mass spectrometric detection. © 2007 Elsevier B.V. All rights reserved.

    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-39471 (URN)10.1016/j.chroma.2007.06.007 (DOI)48765 (Local ID)48765 (Archive number)48765 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13Bibliographically approved
    3. Gas chromatography-mass spectrometry analysis of pheomelanin degradation products
    Open this publication in new window or tab >>Gas chromatography-mass spectrometry analysis of pheomelanin degradation products
    2009 (English)In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 30, p. 5730-5739Article in journal (Refereed) Published
    Abstract [en]

    Melanoma is most rapidly increasing in the white population and people with pheomelanin skin type are at high risk to develop melanoma. However, little is known about the pheomelanin structure and function, and further elucidation of this melanin is therefore an important task. A GC/MS method was developed based on hydriodic acid hydrolysis of pheomelanin in the urine. Derivatization was performed with ethyl chloroformate and ethanol:pyridine (4:1, v/v). N,O-Ethoxycarbonyl-ethyl esters were extracted with chloroform and analyzed by GC/MS. 4-Amino-3-hydroxyphenylaianine and 3-amino4-hydroxyphenylaianine together with one benzothiazinone and two benzothiazole compounds were detected and identified in hydrolyzed samples of synthetic pheomelanin and melanin from the urine of a patient with melanoma. These findings strongly suggest that heterocyclic pheomelanin-type units are incorporated in the pigment structures.

    Keywords
    Alkyl chloroformate; Aminohydroxyphenylalanine; Derivatization; Gas chromatography-mass spectrometry; Melanin; Melanoma; Pheomelanin; 7-(2-Amino-2-carboxyethyl)-5-hydroxy-3, 4-dihydro-2H-1, 4-benzothiazine-3-one 6-(2-Amino-2-carboxyethyl)-4-hydroxybenzothiazole 6-(2-Amino-2-carboxyethyl)-4-hydroxy-2-methyl-benzothiazole; Benzothiazine; Benzothiazole; Benzothiazinone
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-20135 (URN)10.1016/j.chroma.2009.05.063 (DOI)
    Available from: 2009-08-31 Created: 2009-08-31 Last updated: 2017-12-13Bibliographically approved
    4. Pheomelanin-related benzothiazole isomers in the urine of patients with diffuse melanosis of melanoma
    Open this publication in new window or tab >>Pheomelanin-related benzothiazole isomers in the urine of patients with diffuse melanosis of melanoma
    Show others...
    2010 (English)In: Clinica Chimica Acta, ISSN 0009-8981, E-ISSN 1873-3492, Vol. 411, no 17-18, p. 1195-1203Article in journal (Refereed) Published
    Abstract [en]

    Currently used as structural markers for pheomelanin identification and quantitation, benzothiazole compounds derived from isomeric cysteinyldopas have been indicated by recent in vitro studies as new potential pheomelanogenesis intermediates. Prompted by previous reports on the occurrence of large amounts of 5-S-cysteinyldopa (5-S-CD) and trichochromes in urine of patient with diffuse melanosis of melanoma we investigated the presence of benzothiazole compounds in the urine of these patients.

    Hydrophilic interaction liquid chromatography on zwitterionic stationary phase (ZIC-HILIC) and photo-diode array (PDA) detection was used for analysis of 6-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-5), and 7-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-2), derived from 5-S-CD and 2-S-cysteinyldopa (2-S-CD) isomers, respectively. Isocratic mobile phase with minimal sample preparation allowed efficient separation of the compounds, which were safely identified by their typical absorption features.

    Among 21 melanoma patients examined three showed diffuse melanosis. The levels of urinary BTCAs were found to be highly associated with melanosis but more loosely to excreted 5-S-CD. Analysis of the pigmented fraction of urine following alkaline hydrogen peroxide degradation and quantitation of BTCAs provided evidence for the presence of pheomelanins at higher levels in patients with melanosis.

    Place, publisher, year, edition, pages
    lsevier Science B.V., Amsterdam, 2010
    Keywords
    Benzothiazole, benzothiazole-2-carboxylic acids, diffuse melanosis, melanoma, HILIC, pheomelanin, BTCA
    National Category
    Other Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-21817 (URN)10.1016/j.cca.2010.04.019 (DOI)000280033400005 ()
    Available from: 2009-10-05 Created: 2009-10-05 Last updated: 2017-12-13Bibliographically approved
  • 6.
    Nezirevic Dernroth, Dzeneta
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Rundström, Annica
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Kågedal, Bertil
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Gas chromatography-mass spectrometry analysis of pheomelanin degradation products2009In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1216, no 30, p. 5730-5739Article in journal (Refereed)
    Abstract [en]

    Melanoma is most rapidly increasing in the white population and people with pheomelanin skin type are at high risk to develop melanoma. However, little is known about the pheomelanin structure and function, and further elucidation of this melanin is therefore an important task. A GC/MS method was developed based on hydriodic acid hydrolysis of pheomelanin in the urine. Derivatization was performed with ethyl chloroformate and ethanol:pyridine (4:1, v/v). N,O-Ethoxycarbonyl-ethyl esters were extracted with chloroform and analyzed by GC/MS. 4-Amino-3-hydroxyphenylaianine and 3-amino4-hydroxyphenylaianine together with one benzothiazinone and two benzothiazole compounds were detected and identified in hydrolyzed samples of synthetic pheomelanin and melanin from the urine of a patient with melanoma. These findings strongly suggest that heterocyclic pheomelanin-type units are incorporated in the pigment structures.

  • 7.
    Nezirevic Dernroth, Dzeneta
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Årstrand, Kerstin
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Greco, Giorgia
    Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Complesso Universitario Monte S. Angelo, Via Cyntia 4 I-80126, Naples Italy.
    Panzella, Lucia
    Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Complesso Universitario Monte S. Angelo, Via Cyntia 4 I-80126, Naples Italy.
    Napolitano, Alessandra
    Department of Organic Chemistry and Biochemistry, University of Naples Federico II, Complesso Universitario Monte S. Angelo, Via Cyntia 4 I-80126, Naples Italy.
    Kågedal, Bertil
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Pheomelanin-related benzothiazole isomers in the urine of patients with diffuse melanosis of melanoma2010In: Clinica Chimica Acta, ISSN 0009-8981, E-ISSN 1873-3492, Vol. 411, no 17-18, p. 1195-1203Article in journal (Refereed)
    Abstract [en]

    Currently used as structural markers for pheomelanin identification and quantitation, benzothiazole compounds derived from isomeric cysteinyldopas have been indicated by recent in vitro studies as new potential pheomelanogenesis intermediates. Prompted by previous reports on the occurrence of large amounts of 5-S-cysteinyldopa (5-S-CD) and trichochromes in urine of patient with diffuse melanosis of melanoma we investigated the presence of benzothiazole compounds in the urine of these patients.

    Hydrophilic interaction liquid chromatography on zwitterionic stationary phase (ZIC-HILIC) and photo-diode array (PDA) detection was used for analysis of 6-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-5), and 7-(2-amino-2-carboxyethyl)-4-hydroxybenzothiazole-2-carboxylic acid (BTCA-2), derived from 5-S-CD and 2-S-cysteinyldopa (2-S-CD) isomers, respectively. Isocratic mobile phase with minimal sample preparation allowed efficient separation of the compounds, which were safely identified by their typical absorption features.

    Among 21 melanoma patients examined three showed diffuse melanosis. The levels of urinary BTCAs were found to be highly associated with melanosis but more loosely to excreted 5-S-CD. Analysis of the pigmented fraction of urine following alkaline hydrogen peroxide degradation and quantitation of BTCAs provided evidence for the presence of pheomelanins at higher levels in patients with melanosis.

  • 8.
    Nezirevic Dernroth, Dzeneta
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of clinical chemistry.
    Årstrand, Kerstin
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of clinical chemistry.
    Kågedal, Bertil
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of clinical chemistry.
    Hydrophilic interaction liquid chromatographic analysis of aminohydroxyphenylalanines from melanin pigments2007In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1163, no 1-2, p. 70-79Article in journal (Refereed)
    Abstract [en]

    Malignant melanomas are more often seen in subjects with light colored skin who tan poorly than in persons who tan more rapidly. This has been attributed to the structure of their pigment, pheomelanin, which differs markedly from the eumelanin of persons with darker skin. To study the hydrolysis products of pheomelanin pigments a new method was developed for analysis of 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP). Pheomelanin samples were hydrolyzed and extracted with solid-phase extraction columns using strong cation-exchange (SCX) cartridges. Separation of 4-AHP and 3-AHP was achieved on a ZIC-HILIC column (150 mm × 2.1 mm I.D.) with a mobile phase consisting of acetonitrile:0.1 M ammonium acetate buffer, pH 4.5 (82:18, v/v). Detection was performed with an electrochemical detector at +400 mV. Run time was 30 min. The limits of detection were 73 pg and 51 pg for 4-AHP and 3-AHP respectively, using 2 μl injections. Good linearity was found within the range 0.05-5.0 μg/ml. Absolute recovery was 70% and relative recovery was 100%. The AHPs were stable for 1 year in the hydrolyzed samples, for 4 days in the eluates from solid-phase sorbents stored in the refrigerator, and for 2 days diluted with mobile phase and stored in the autosampler at 10 °C. The within-day imprecision was <5% and the between-day imprecision was <7% for the two analytes. The method, applied to the analysis of pheomelanin in urine from human melanoma patients, allows the analysis of 30 samples in one set and is suitable for routine work with human hair and melanoma cells. By using the ZIC-HILIC stationary phase, ion-pairing reagents could be avoided, which makes the method suitable to further analysis of degradation products from pheomelanins using mass spectrometric detection. © 2007 Elsevier B.V. All rights reserved.

  • 9.
    Takasaki, Akihiko
    et al.
    Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
    Nezirevic Dernroth, Dzeneta
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    Årstrand, Kerstin
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Wakamatsu, Kazumasa
    Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
    Ito, Shosuke
    Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
    Kågedal, Bertil
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Centre for Laboratory Medicine, Department of Clinical Chemistry.
    HPLC analysis of pheomelanin degradation products in human urine2003In: Pigment Cell Research, ISSN 1755-1471, E-ISSN 1755-148X, Vol. 16, no 5, p. 480-486Article in journal (Refereed)
    Abstract [en]

    A sensitive and specific high performance liquid chromatography (HPLC) method was developed to quantify 4-amino-3-hydroxyphenylalanine (4-AHP) and 3-amino-4-hydroxyphenylalanine (3-AHP) in urine. In degradation studies of melanin pigment, 4-AHP and 3-AHP are derived from benzothiazine units of pheomelanin and pheomelanin-related metabolites such as trichochromes. 5-S-Cysteinyldopa-derived benzothiazine products give 4-AHP while 2-S-cysteinyldopa-derived benzothiazine products give 3-AHP. 3-AHP is also derived from nitrotyrosine formed by nitration of tyrosine with reactive nitrogen species. For this reason, the influence of this biological process on the amount of 3-AHP found in biological material have been investigated. The method is based on hydriodic acid hydrolysis of the melanin polymer and reversed-phase HPLC with electrochemical detection of the degradation products 4-AHP and 3-AHP. The mobile phase consists of 25 mM ammonium acetate and sodium octanesulfonate as an ion-pairing reagent. The 4-AHP and 3-AHP peaks were well separated and the detector response was linear within the range 0-2 ng injected for both compounds. With the developed chromatographic system, 4-AHP and 3-AHP showed good separation in the biological samples. There was a strong correlation between 4-AHP and 3-AHP in the urine of 50 malignant melanoma patients and two healthy subjects (R0.977). The two compounds were also strongly correlated with 5-S-cysteinyldopa in urine, the correlation coefficients being 0.862 and 0.907, respectively. The method described is sensitive enough for analysis of pheomelanin in urine and in several other biological samples. The results indicate that 3-AHP in urine is not influenced by excreted 3-nitrotyrosine and the data indicate that pheomelanins are excreted in the urine of melanoma patients.

  • 10.
    Tesselaar, Erik
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Nezirevic Dernroth, Dzeneta
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Chemistry.
    Farnebo, Simon
    Linköping University, Department of Clinical and Experimental Medicine, Division of Surgery, Orthopedics and Oncology. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Anaesthetics, Operations and Specialty Surgery Center, Department of Hand and Plastic Surgery.
    Acute effects of coffee on skin blood flow and microvascular function2017In: Microvascular Research, ISSN 0026-2862, E-ISSN 1095-9319, Vol. 114, p. 58-64Article in journal (Refereed)
    Abstract [en]

    Objective

    Studies on the acute effects of coffee on the microcirculation have shown contradicting results. This study aimed to investigate if intake of caffeine-containing coffee changes blood flow and microvascular reactivity in the skin.

    Methods

    We measured acute changes in cutaneous vascular conductance (CVC) in the forearm and the tip of the finger, the microvascular response to transdermaliontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) and post-occlusive reactive hyperemia (PORH) in the skin, after intake of caffeinated or decaffeinated coffee.

    Results

    Vasodilatation during iontophoresis of ACh was significantly stronger after intake of caffeinated coffee compared to after intake of decaffeinated coffee (1.26 ± 0.20 PU/mm Hg vs. 1.13 ± 0.38 PU/mm Hg, P < 0.001). Forearm CVC before and after PORH were not affected by caffeinated and decaffeinated coffee. After intake of caffeinated coffee, a more pronounced decrease in CVC in the fingertip was observed compared to after intake of decaffeinated coffee (− 1.36 PU/mm Hg vs. − 0.52 PU/mm Hg, P = 0.002).

    Conclusions

    Caffeine, as ingested by drinking caffeinated coffee acutely improves endothelium-dependent microvascular responses in the forearm skin, while endothelium-independent responses to PORH and SNP iontophoresis are not affected. Blood flow in the fingertip decreases markedly during the first hour after drinking caffeinated coffee compared to decaffeinated coffee.

  • 11.
    Zsigmond, Peter
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Neurosurgery. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Nezirevic Dernroth, Dzeneta
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Clinical Chemistry.
    Kullman, Anita
    Linköping University, Department of Clinical and Experimental Medicine, Clinical Chemistry. Linköping University, Faculty of Health Sciences.
    Augustinsson, Lars-Erik
    Östergötlands Läns Landsting, Anaesthetics, Operations and Specialty Surgery Center, Department of Neurosurgery.
    Dizdar (Dizdar Segrell), Nil
    Linköping University, Department of Clinical and Experimental Medicine, Neurology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Local Health Care Services in Central Östergötland, Department of Neurology.
    Stereptactic microdialysis of the basal ganglia in Parkinson's disease2012In: Journal of Neuroscience Methods, ISSN 0165-0270, E-ISSN 1872-678X, Vol. 207, no 1, p. 17-22Article in journal (Refereed)
    Abstract [en]

    Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an efficacious treatment in patients with advanced Parkinson's disease, yet the mechanisms of STN DBS are poorly understood. The aims of this study were to develop a useful method for studying neurotransmitter alterations during DBS and for the pharmacokinetics of L-dopa in brain tissue. Ten patients with Parkinson's disease participated, whereof two had no previous L-dopa medication. The electrodes and catheters were placed using MRI-guided stereotaxic targeting. Two microdialysis probes were placed, one in the right internal globus pallidus, and one in a brachial vein. The quadripolar deep brain electrodes were placed in the right STN. Microdialysates from brain tissue and blood were collected in 15-min fractions at baseline and during DBS. After stimulation new baseline fractions were taken and finally three fractions during continuous intravenous infusion of L-dopa. Clinical evaluation showed that both DBS and L-dopa infusion gave good relief of rigidity and tremor in all ten patients. During DBS the L-dopa levels in the brain increased in some of the patients but did not persist during the whole stimulation period. The concentration in brain increased substantially during intravenous L-dopa infusion. A number of catecholamines and their metabolites were analysed with high pressure liquid chromatography (HPLC). With our study we could show that this model is suitable for the monitoring of neurotransmitters and for pharmacokinetic studies in human brain, although we found that the sampling time was too short to follow the possible alterations in brain activity caused by DBS.

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