sh.sePublications
Change search
Refine search result
2345678 201 - 250 of 771
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • harvard-anglia-ruskin-university
  • apa-old-doi-prefix.csl
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 201. Fox, Kate L.
    et al.
    Li, Jianjun
    Schweda, Elke K. H.
    Södertörn University, School of Life Sciences.
    Vitiazeva, Arvara
    Makepeace, Katherine
    Jennings, Michael P.
    Moxon, E. Richard
    Hood, Derek W.
    Duplicate copies of lic1 direct the addition of multiple phosphocholine residues in the lipopolysaccharide of Haemophilus influenzae2008In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, no 2, p. 588-600Article in journal (Refereed)
    Abstract [en]

    The genes of the lic1 operon (lic1A to lic1D) are responsible for incorporation of phosphocholine (PCho) into the lipopolysaccharide (LPS) of Haemophilus influenzae. PCho plays a multifaceted role in the commensal and pathogenic lifestyles of a range of mucosal pathogens, including H. influenzae. Structural studies of the LPS of nontypeable H. influenzae (NTHI) have revealed that PCho can be linked to a hexose on any one of the oligosaccharide chain extensions from the conserved inner core triheptosyl backbone. In a collection of NTHI strains we found several strains in which there were two distinct but variant lic1D DNA sequences, genes predicted to encode the transferase responsible for directing the addition of PCho to LPS. The same isolates were also found to express concomitantly two PCho residues at distinct positions in their LPS. In one such NTHI isolate, isolate 1158, structural analysis of LPS from lic1 mutants confirmed that each of the two copies of lic1D directs the addition of PCho to a distinct location on the LPS. One position for PCho addition is a novel heptose, which is part of the oligosaccharide extension from the proximal heptose of the LPS inner core. Modification of the LPS by addition of two PCho residues resulted in increased binding of C-reactive protein and had consequential effects on the resistance of the organism to the killing effects of normal human serum compared to the effects of glycoforms containing one or no PCho. When bound, C-reactive protein leads to complement-mediated killing, indicating the potential biological significance of multiple PCho residues.

  • 202. Funk, C
    et al.
    Wiklund, R
    Schröder, Wolfgang P
    Södertörn University, Avdelning Naturvetenskap.
    Jansson, C
    D1' centers are less efficient than normal photosystem II centers2001In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 505, no 1, p. 113-117Article in journal (Refereed)
    Abstract [en]

    One prominent difference between the photosystem II (PSII) reaction center protein D1 ' in Synechocystis 6803 and normal D1 is the replacement of Phe-186 in D1 with leucine in D1 '. Mutants of Synechocystis 6803 producing only D1 ', or containing engineered D1 proteins with Phe-186 substitutions, were analyzed by 77 K fluorescence emission spectra, chlorophyll a fluorescence induction yield and decay kinetics, and flash-induced oxygen evolution. Compared to D1-containing PSII centers, D1 ' centers exhibited a 50% reduction in variable chlorophyll a fluorescence yield, while the flash-induced O-2 evolution pattern was unaffected. In the F186 mutants, both the P680(+)/Q(A)(-) recombination and O-2 oscillation pattern were noticeably perturbed.

  • 203.
    Fürtenbach, Karin
    Södertörn University College, School of Life Sciences.
    Characterization of two Protein Disulfide Oxidoreductases from Thermophilic Organisms Pyrococcus furiosus and Aquifex aeolicus: Characterization of two Protein Disulfide Oxidoreductases2008Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    Members of the thioredoxin superfamily of proteins catalyze disulfide bond reduction and oxidation using the active site C-X-X-C sequence. In hyperthermophilic organisms, cysteine side chains were expected in low abundance since they were not believed to endure the high temperatures under which they grow. Recently it has been found that disulfide bonds in hyperthermophiles are more frequent, the higher the growth temperature of the organism. This is perhaps used as an adaptation to high temperature in order to stabilize proteins under harsh conditions. A protein with sequence and structural similarities to mesophilic members of the thioredoxin superfamily, called protein disulfide oxidoreductases (PDO), has been found in the genomes of recently sequenced hyperthermophilic genomes. In this study PDOs from the hyperthermophiles Aquifex aeolicus (AaPDO) and Pyrococcus furiosus (PfPDO) have been investigated. The molecular weight is about 26 kDa and their structures are comprised of two homologous thioredoxin folds, referred to as the N-unit and the C-unit, each containing a C-X-X-C motif. The sequence identity between the two units and the two proteins is low, but they are still structurally very similar. The function of these proteins in vivo is unknown. As a first step in characterizing the activity of these proteins, the redox characteristics of these domains will be investigated. During this project, the genes for AaPDO and PfPDO have been cloned into overexpression vectors, expressed in E. coli and purified to homogeneity. To allow for individual study of the activities of two units, mutated proteins were prepared in which the cysteine residues of the N-unit (AaPDOnm and PfPDOnm) and of the C-unit (AaPDOcm and PfPDOcm) and purified. Circular dichroism spectra recorded of the wild type and mutants indicate that all purified proteins are folded and that the N- and C-unit active site mutants are structurally similar to the corresponding wild type proteins.

    Download full text (pdf)
    FULLTEXT01
  • 204.
    Gallio, Marco
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institutet.
    The Rhomboid family of intramembrane proteases, conserved regulators of cell communication2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The development of multicellular organisms relies heavily on cell communication. Cells send and receive complex sets of signals, harmonising their growth and differentiation with that of other, often distant, cell populations. In animals, the Epidermal Growth Factor Receptor (EGFR) is an important mediator of cell communication. EGFR activation regulates various developmental events in nematodes, insects and vertebrates. In addition, mutations in human EGFRs have been associated with a number of cancers. In Drosophila, a key event triggering EGFR signalling is the regulated release of the extracellular portion of EGFR ligands. Rhomboid (Rho), an unusual polytopic protease, cleaves the transmembrane, inactive ligand precursor into an active, soluble form. Both the target sequence and Rho s catalytic site are embedded within the membrane bilayer and for this reason the reaction has been described as regulated intramembrane proteolysis. The work presented in this thesis begins with the characterisation of a classical fly mutation, roughoid (ru). Our results indicate that ru acts as a novel, positive regulator of EGFR signalling during eye development in Drosophila. ru was subsequently identified as rhomboid-3, one of seven rhomboid related genes encoded in the fly genome. Unexpectedly, we found that sequences related to Rhomboid are also common in unicellular organisms. A single microbial Rho has been previously studied, the aarA gene from the human pathogen Providencia stuartii. Strikingly, AarA appears to have a corresponding function to that of the Drosophila Rho: it is necessary for the release of a peptide-signal, which mediates cell communication in P. stuartii. AarA was indeed capable of substituting for the fly Rho in vivo. Vice versa, the fly Rho-1 restored the ability of aarA mutant bacteria to produce the extracellular signal mediating cell communication. These results suggest that Rho-mediated proteolysis might represent a very ancient mechanism for cell communication. The Drosophila genome contains seven Rhomboids. We began to investigate the possibility of additional substrates by analyzing the respiratory system phenotype observed in ru/rho-3 mutant embryos. During embryogenesis, specialised tracheal branches target and invade the ventral nerve cord, part of the central nervous system (CNS). In ru/rho-3 mutants, these branches are misrouted, and inappropriately cross the CNS midline. Also in this context Rho-3 functions to activate an EGFR ligand. Yet, the results reveal an unusual role for the pathway in the repulsion of migrating epithelial cells. EGFR ligands act as chemoattractants for a variety of cells in vivo and in vitro, including tumors. Our results provide a proof of principle that the EGFR can also mediate repulsion from the signal source.

  • 205.
    Gallio, Marco
    et al.
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Stockholm University / Karolinska Institute.
    Englund, C
    Stockholm University / Umeå University.
    Kylsten, Per
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science.
    Samakovlis, C
    Stockholm University.
    Rhomboid 3 orchestrates Slit-independent repulsion of tracheal branches at the CNS midline2004In: Development, ISSN 0950-1991, E-ISSN 1477-9129, Vol. 131, no 15, p. 3605-3614Article in journal (Refereed)
    Abstract [en]

    EGF-receptor ligands act as chemoattractants for migrating epithelial cells during organogenesis and wound healing. We present evidence that Rhomboid 3/EGF signalling, which originates from the midline of the Drosophila ventral nerve cord, repels tracheal ganglionic branches and prevents them from crossing it. rho3 acts independently from the main midline repellent Slit, and originates from a different sub-population of midline cells: the VUM neurons. Expression of dominant-negative Egfr or Ras induces midline crosses, whereas activation of the Egfr or Ras in the leading cell of the ganglionic branch can induce premature turns away from the midline. This suggests that the level of Egfr intracellular signalling, rather than the asymmetric activation of the receptor on the cell surface, is an important determinant in ganglionic branch repulsion. We propose that Egfr activation provides a necessary switch for the interpretation of a yet unknown repellent function of the midline.

  • 206.
    Gallio, Marco
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Kylsten, Per
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Providencia may help find a function for a novel, widespread protein family2000In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 10, no 19, p. R693-R694Article in journal (Refereed)
  • 207.
    Gallio, Marco
    et al.
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Karolinska Institutet.
    Kylsten, Per
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science.
    The roughoid locus identifies a novel function involved in epidermal growth factor receptor signalling in DrosophilaManuscript (preprint) (Other academic)
  • 208. Gao, L L
    et al.
    Knogge, W
    Delp, Gabriele
    Södertörn University, School of Chemistry, Biology, Geography and Environmental Science.
    Smith, F A
    Smith, S E
    Expression patterns of defense-related genes in different types of arbuscular mycorrhizal development in wild-type and mycorrhiza-defective mutant tomato2004In: Molecular Plant-Microbe Interactions, ISSN 0894-0282, E-ISSN 1943-7706, Vol. 17, no 10, p. 1103-1113Article in journal (Refereed)
    Abstract [en]

    The expression of defense-related genes was analyzed in the interactions of six arbuscular mycorrhizal (AM) fungi with the roots of wild-type tomato (Lycopersicon esculentum Mill.) cv. 76R and of the near-isogenic mycorrhiza-defective mutant rmc. Depending on the fungal species, wild-type tomato forms both major morphological AM types, Arum and Paris. The mutant rmc blocks the penetration of the root surface or invasion of the root cortex by most species of AM fungi, but one fungus has been shown to develop normal mycorrhizas. In the wild-type tomato, accumulation of mRNA representing a number of defense-related genes was low in Arum-type interactions, consistent with findings for this AM morphotype in other plant species. In contrast, Paris-type colonization, particularly by members of the family Gigasporaceae, was accompanied by a substantial transient increase in expression of some defense-related genes. However, the extent of root colonization did not differ significantly in the two wild-type AM morphotypes, suggesting that accumulation of defense gene products per se does not limit mycorrhiza development. In the mutant, interactions in which the fungus failed to penetrate the root lacked significant accumulation of defense gene mRNAs. However, phenotypes in which the fungus penetrated epidermal or hypodermal cells were associated with an enhanced and more prolonged gene expression. These results are discussed in relation to the mechanisms that may underlie the specificity of the interactions between AM fungi and the rmc mutant.

  • 209. Gardeström, Johanna
    et al.
    Dahl, Ulrika
    Kotsalainen, Ola
    Maxson, Anders
    Elfwing, Tina
    Grahn, Mats
    Södertörn University, School of Life Sciences.
    Bengtsson, Bengt-Erik
    Breitholtz, Magnus
    Evidence of population genetic effects of long-term exposure to contaminated sediments - A multi-endpoint study with copepods2008In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 86, no 3, p. 426-436Article in journal (Refereed)
    Abstract [en]

    In the environment, pollution generally acts over long time scales and exerts exposure of multiple toxicants on the organisms living there. Recent findings show that pollution can alter the genetics of populations. However, few of these studies have focused on long-term exposure of mixtures of substances. The relatively short generation time (ca. 4-5 weeks in sediments) of the harpacticoid copepod Attheyella crassa makes it suitable for multi generational exposure studies. Here, A. crassa copepods were exposed for 60 and 120 days to naturally contaminated sediments (i.e., Svindersviken and Trosa; each in a concentration series including 50% contaminated sediment mixed with 50% control sediment and 100% contaminated sediment), and for 120 days to control sediment spiked with copper. We assayed changes in FST (fixation index), which indicates if there is any population subdivision (i.e., structure) between the samples, expected heterozygosity, percent polymorphic loci, as well as abundance. There was a significant decrease in total abundance after 60 days in both of the 100% naturally contaminated sediments. This abundance bottleneck recovered in the Trosa treatment after 120 days but not in the Svindersviken treatment. After 120 days, there were fewer males in the 100% naturally contaminated sediments compared to the control, possibly caused by smaller size of males resulting in higher surface: body volume ratio in contact with toxic chemicals. In the copper treatment there was a significant decrease in genetic diversity after 120 days, although abundance remained unchanged. Neither of the naturally contaminated sediments (50 and 100%) affected genetic diversity after 120 days but they all had high within treatment FST values, with highest FST in both 100% treatments. This indicates differentiation between the replicates and seems to be a consequence of multi-toxicant exposure, which likely caused selective mortality against highly sensitive genotypes. We further assayed two growth-related measures, i.e., RNA content and cephalothorax length, but none of these endpoints differed between any of the treatments and the control. In conclusion, the results of the present study support the hypothesis that toxicant exposure can reduce genetic diversity and cause population differentiation. Loss of genetic diversity is of great concern since it implies reduced adaptive potential of populations in the face of future environmental change.

  • 210. Gardeström, Johanna
    et al.
    Gorokhova, Elena
    Gilek, Michael
    Södertörn University, School of Life Sciences.
    Grahn, Mats
    Södertörn University, School of Life Sciences.
    Bengtsson, Bengt-Erik
    Breitholtz, Magnus
    A multilevel approach to predict toxicity in copepod populations: Assessment of growth, genetics, and population structure2006In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 79, no 1, p. 41-48Article in journal (Refereed)
    Abstract [en]

    One of the goals of environmental risk assessment (ERA) is to understand effects of toxicant exposure on individual organisms and populations. We hypothesized that toxicant exposure can reduce genetic diversity and alter genotype composition, which may ultimately lead to a reduction in the average fitness of the exposed population. To test this hypothesis, we exposed a copepod, Nitocra psammophila, to a toxic reference compound and assayed resulting alterations in genetic structure, i.e. expected heterozygosity and percent polymorphic loci, as well as other population- and fitness-related measures, i.e. population abundance, demographic structure and juvenile growth. The copepods were exposed to 0.11-1.1 mu g of the pentabromo-substituted diphenyl ether (BDE-47) mg(-1) freeze-dried algae for 24 days (i.e. > 1 generation). There was no significant decline in total population abundance. However, there were significant alterations in population structure, manifested as diminished proportion of nauplii and increased proportion of copepodites. In addition, individual RNA content in copepodites decreased significantly in exposed individuals, indicating declined growth. Finally, in the exposed populations, heterozygosity was lower and genotype composition was altered compared to the controls. These results therefore confirm the hypothesized reduction in overall genetic variability resulting from toxicant exposure. Multilevel approaches, such as the one used in the present study, may help unravel subtle effects on the population level, thus increasing the predictive capacity of future ERA.

  • 211.
    Gatsinzi, Tom
    et al.
    Stockholm University.
    Ramberg, Veronica
    Stockholm University.
    Figueroa, Ricardo
    Södertörn University, School of Life Sciences, Molecular biology.
    Iverfeldt, Kerstin
    Stockholm University.
    Hallberg, Einar
    Södertörn University, School of Life Sciences, Molecular biology.
    Localized caspase sensors for live cell imaging of amyloid-β induced apoptosis2010In: Alzheimer's & Dementia, ISSN 1552-5260, E-ISSN 1552-5279, Vol. 6, no 4, Supplement, p. S259-S260Article in journal (Other academic)
    Abstract [en]

    Background: Apoptosis is an evolutionary conserved cellular process important for normal development, maintenance of tissue homeostasis and an effective immune system. Cysteine-aspartic proteases, or caspases, are the major mediators of apoptosis, triggering processes which lead to cellular disruption. Dysregulation of apoptotic signaling has been shown to be involved in several pathological conditions, like cancer and degenerative disorders. Alzheimer's disease (AD) is the most common form of dementia involving massive cell death of neurons. However, the cause of AD at the present time is still unknown, although, amyloid-β (Aβ) peptide has been suggested to be the triggering factor. 

    Methods:In order to detect localized caspase activation in live cells we designed sensors for caspase-3, -6 and -9 utilizing fluorescence resonance energy transfer (FRET). The FRET-ing sensor molecules, consisting of CFP and YFP separated by a linker containing a specific caspase cleavage motif, were designed to signal caspase cleavage by the loss of FRET. Differentiated SH-SY5Y cells were used as a model system for neurodegeneration. The cells were treated with oligomeric Aβ42 or staurosporine as a positive control of apoptosis. The cleavage of the sensors during induced apoptosis was verified by western blot analysis. Time-lapse FRET microscopy was used to monitor caspase activity in different parts of the cells. 

    Results: In our study, when the cells were exposed to staurosporine we were able to detect local activity of caspase-6 initially in the soma of the cells, whereas caspase-6 activity in the neurites was delayed. Furthermore, our study shows that oligomeric Aβ42 is able to activate caspase-3, -6 and -9. In contrast to staurosporine, in Aβ42 treated cells loss of FRET occurred globally indicating that caspase was activated simultaneously in soma and axons. 

    Conclusions: In conclusion, we show that our caspase-sensors are able to detect local caspase activity in vitro. We also show that exposure to oligomeric Aβ42 results in global activation of caspases in differentiated SH-SY5Y cells.

  • 212.
    Georgiev, Alexander
    et al.
    Södertörn University, School of Life Sciences, Biology. Stockholm University.
    Leipus, Arunas
    Umeå University.
    Olsson, Ida
    Södertörn University, School of Life Sciences, Biology.
    Berrez, Jean-Marc
    Södertörn University, School of Life Sciences, Biology.
    Mutvei, Ann
    Södertörn University, School of Life Sciences, Biology.
    Characterization of MYR1, a dosage suppressor of YPT6 and RIC1 deficient mutants2008In: Current Genetics, ISSN 0172-8083, E-ISSN 1432-0983, Vol. 53, no 4, p. 235-247Article in journal (Refereed)
    Abstract [en]

    Membrane traffic is tightly regulated and the Rab protein family of small GTPases plays a central role in this regulation. One member of this family is the Saccharomyces cerevisae protein Ypt6. To search for new genes interacting with Ypt6-related pathways, we performed a genetic screen for high copy suppressors of ypt6 Delta temperature sensitivity at 35 degrees C. Among the suppressors, MYR1 was also able to suppress the temperature sensitive mutant lacking Ric1, a subunit of the Ypt6 guanine exchanging factor complex Ric1/Rgp1. Myr1 is characterized by a coiled coil region and a GYF domain, a protein module binding proline-rich sequences. Myr1 is able to bind membranes but is also associated with larger structures insoluble in Triton X-100. By immunofluorescence, Myr1 shows a network-like pattern as well as small foci. Overexpression of Myr1 influences nuclear envelope morphology and high levels are lethal. This lethality is rescued when the N-terminal region, containing the GYF domain, is deleted. The transcription profile of a myr1 Delta strain shows effects on genes involved in nuclear migration, Ras signalling and transcription. Taken together, these results suggest that Myr1 is a novel factor linked to the secretory pathway and important cellular regulatory mechanisms.

  • 213. Gerremo, Inge
    et al.
    Wramner, Per
    Södertörn University College, School of Life Sciences, Coastal Management Research Center (COMREC).
    Diskussion och vägen framåt2006In: Jordbruk, handel och utveckling: mot ökad samstämmighet, Stockholm: Kungl. Skogs- och lantbruksakademien , 2006, p. 167-183Chapter in book (Other (popular science, discussion, etc.))
  • 214.
    Gilek, Michael
    et al.
    Stockholms universitet.
    Tedengren, Michael
    Kautsky, Nils
    Physiological performance and general histology of the blue mussle, Mytilus Edulis L, from the Baltic and North seas1992In: Netherlands Journal of Sea Research, ISSN 0077-7579, Vol. 30, p. 11-21Article in journal (Refereed)
    Abstract [en]

    A physiological approach has been proposed for studying the ecological consequences of diseases and parasitism in bivalve molluscs. We investigated effects of some naturally occurring non-lethal parasites and histological changes in the blue mussel, Mytilus edulis L., on some commonly used bivalve condition indices, viz the oxygen:nitrogen ratio, the scope for growth and the body condition index. We found no correlation between these physiological condition indices, which implies that an individual can be classified as in 'good condition' according to e.g. the O:N ratio and the body condition index, while at the same time this mussel may have a low scope for growth indicating a stressed status. This is probably because the O:N ratio, the scope for growth and the body condition index integrate metabolic processes over different periods of time. No general deleterious effects on these condition indices could be detected either due to parasitic infestation or general histological changes. Hence, it was not possible to translate detrimental effects of histological conditions directly into energy equivalents.

  • 215. Glaser, Elzbieta
    et al.
    Eriksson, AnnaCarin
    Sjöling, Sara
    Bifunctional role of the bc1 complex in plants Mitochondrial bc1 complex catalyses both electron transport and protein processing1994In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 346, no 1, p. 83-87Article in journal (Refereed)
    Abstract [en]

    Abstract Nuclear  encoded  mitochondrial  precursor  proteins  are  cleaved  to  mature  size products  by the  general  mitochondrial  processing  peptidase  (MPP). In  contrast  to  non-plant  sources  where  MPP  is  a matrix  enzyme,  the  plant  mitochondrial  MPP  is localised  in  the  inner  membrane  and  constitutes an  integral  part  of  the  bc,  complex  of  the  respiratory  chain.  Core  proteins  of  the  complex  are  immunologically  related  and  show  high  sequence similarity  to the MPP  subunits  from  non-plant  sources.  The bc,  complex  in plants  is thus  bifunctional,  being  involved  both  in respiration  and  in protein processing

  • 216. Glaser, Elzbieta
    et al.
    Sjöling, Sara
    Szigyarto, Cristina
    Eriksson, AnnaCarin
    Plant mitochondrial protein import: precursor processing is catalysed by the integrated mitochondrial processing peptidase (MPP)/bc1 complex and degradation by the ATP-dependent proteinase1996In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1275, no 1-2, p. 33-37Article in journal (Refereed)
    Abstract [en]

    Several hundreds of mitochondrial proteins are nuclear encoded and are synthesised on cytosolic polyribosomes as precursor proteins. Most of these precursors contain an N-terminal extension called presequence which functions as targeting signal and which is cleaved off after import. Despite the fact that there are no sequence similarities and no consensus for the cleavage site in mitochondrial presequences, cleavage of almost all presequences is catalysed by a single, highly specific metalloendopeptidase, called general mitochondrial processing peptidase (MPP). MPP in plants is integrated into the bc1, complex of the respiratory chain and both subunits, α-MPP and β-MPP, are identical to the core proteins of the complex. Despite the fact that the bc1 complex in plants is bifunctional, catalysing bothelectron transport and protein processing, these two functions are distinct. MPP belongs to the Pitrilysin family of peptidases, characterised by a zinc binding motif, HXXEH74–76E, involved in catalysis. Both the membrane-bound integrated MPP/bc1 complex of plants and the soluble mammalian MPP recognise similar higher-order structural elements upstream from the cleavage site that are important for processing. The secondary structure with flexibility and stabilising elements, hydrofobicity, charge and length seem to influence the interaction with MPP. The newly imported non-assembled precursor inside mitochondria is degraded by a proteinase that is distinct from MPP or any other previously characterised proteinases, a novel ATP-dependent, membrane-associated serine-type proteinase.

  • 217. Glaser, Elzbieta
    et al.
    Sjöling, Sara
    Södertörn University, Avdelning Naturvetenskap.
    Tanudji, Marcel
    Södertörn University, Avdelning Naturvetenskap.
    Whelan, James
    Mitochondrial protein import in plants: Signals, Sorting, Targeting, Processing and Regulation1998In: Plant Molecular Biology, ISSN 0167-4412, E-ISSN 1573-5028, Vol. 38, no 1-2, p. 311-338Article in journal (Refereed)
    Abstract [en]

    Mitochondrial biogenesis requires a coordinated expression of both the nuclear and the organellar genomes and specific intracellular protein trafficking, processing and assembly machinery. Mostmitochondrial proteins are synthesised as precursor proteins containing an N-terminal extension which functions as a targeting signal, which is proteolytically cleaved off after import into mitochondria. We review our present knowledge on components and mechanisms involved in the mitochondrial proteinimport process in plants. This encompasses properties of targeting peptides, sorting of precursor proteinsbetween mitochondria and chloroplasts, signal recognition, mechanism of translocation across the mitochondrial membranes and the role of cytosolic and organellar molecular chaperones in this process. The mitochondrial protein processing in plants is catalysed by the mitochondrial processing peptidase (MPP), which in contrast to other sources, is integrated into the bc1 complex of the respiratory chain. This is the most studied component of the plant import machinery characterised to date. What are the biochemical consequences of the integration of the MPP into an oligomeric protein complex and how are several hundred presequences of precursor proteins with no sequence similarities and no consensus for cleavage, specifically cleaved off by MPP? Finally we will address the emerging area of the control of protein import into mitochondria.

  • 218. Glinwood, R.
    et al.
    Gradin, Therese
    Karpinska, Barbara
    Södertörn University, School of Life Sciences.
    Ahmed, E.
    Jonsson, Lisbeth
    Södertörn University, School of Life Sciences.
    Ninkovic, V.
    Aphid acceptance of barley exposed to volatile phytochemicals differs between plants exposed in daylight and darkness2007In: Plant Signalling & Behavior, ISSN 1559-2316, E-ISSN 1559-2324, Vol. 2, no 5, p. 321-326Article in journal (Refereed)
    Abstract [en]

    It is well known that volatile cues from damaged plants may induce resistance in neighboring plants. Much less is known about the effects of volatile interaction between undamaged plants. In this study, barley plants, Hordeum vulgare cv. Kara, were exposed to volatiles from undamaged plants of barley cv. Alva or thistle Cirsium vulgare, and to the volatile phytochemicals, methyl salicylate or methyl jasmonate. Exposures were made either during natural daylight or darkness. Acceptance of exposed plants by the aphid Rhopalosiphum padi was assessed, as well as the expression of putative marker genes for the different treatments. Aphid acceptance of plants exposed to either barley or C. vulgare was significantly reduced, and an effect of the volatiles from undamaged plants was confirmed by the induction of pathogenesis-related protein, PR1a in exposed plants. However the effect on aphid acceptance was seen only when plants were exposed during darkness, whereas PR1a was induced only after treatment during daylight. Aphid acceptance of plants exposed to either methyl salicylate or methyl jasmonate was significantly reduced, but only when plants were exposed to the chemicals during daylight. AOS2 (allene oxide synthase) was induced by methyl jasmonate and BCI-4 (barley chemical inducible gene-4) by methyl salicylate in both daylight and darkness. It is concluded that (a) the effects on aphids of exposing barley to volatile phytochemicals was influenced by the presence or absence of light and (b) the response of barley to methyl salicylate/methyl jasmonate and to volatiles from undamaged plants differed at the gene and herbivore level.

  • 219. Gorokhova, Elena
    et al.
    Edlund, Anna
    Södertörn University, School of Life Sciences.
    Hajdu, Susanna
    Zhivotova, Elena N.
    Nucleic acid levels in copepods: dynamic response to phytoplankton blooms in the northern Baltic proper2007In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 349, p. 213-225Article in journal (Refereed)
    Abstract [en]

    We examined changes in nucleic acids and concomitant population development of the copepods Acartia bifilosa and Eurytemora affinis in relation to the progress of the phytoplankton spring bloom in the northern Baltic proper. Individual RNA and DNA concentrations and their ratios in female copepods as well as copepod abundance and population structure were analyzed in 2 coastal areas that differed in the degree of eutrophication and phytoplankton development. During the study period (February to June 2002), bloom conditions were evident, with chlorophyll (chl) a values being 42% higher in the eutrophic area than in the reference area. In both areas, diatoms dominated; in the reference area, they were replaced by dinoflagellates toward the end of the bloom. Copepod RNA-DNA concentrations increased rapidly at the onset of the bloom and gradually decreased thereafter. Moreover, in the eutrophic area, both copepods had higher RNA content and RNA:DNA ratios throughout the study period, suggesting higher productivity in this area. In both species, we found positive correlations between RNA-based indices and chl a. Thus, as suggested by RNA dynamics, growth rates of A. bifilosa and E. affinis appear to respond rapidly to both temporal variation in spring phytoplankton stock and spatial variation due to the magnitude of the bloom. In addition, we found that species-specific RNA dynamics and RNA-chl a relationships differed between species, indicating possible differences in feeding preferences and growth potential.

  • 220.
    Goulas, Estelle
    et al.
    Umeå universitet / Université des Sciences et Technologies de Lille 1, France.
    Schubert, Maria
    Södertörn University, School of Life Sciences. Karolinska Institutet.
    Kieselbach, Thomas
    Umeå universitet.
    Kleczkowski, Leszek A.
    Umeå universitet.
    Gardeström, Per
    Umeå universitet.
    Schröder, Wolfgang P
    Umeå universitet.
    Hurry, Vaughan
    Umeå universitet.
    The chloroplast lumen and stromal proteomes of Arabidopsis thaliana show differential sensitivity to short- and long-term exposure to low temperature2006In: The Plant Journal, ISSN 0960-7412, E-ISSN 1365-313X, Vol. 47, no 5, p. 720-734Article in journal (Refereed)
    Abstract [en]

    Cold acclimation and over-wintering by herbaceous plants are energetically expensive and are dependent on functional plastid metabolism. To understand how the stroma and the lumen proteomes adapt to low temperatures, we have taken a proteomic approach (difference gel electrophoresis) to identify proteins that changed in abundance in Arabidopsis chloroplasts during cold shock (1 day), and short- (10 days) and long-term (40 days) acclimation to 5 degrees C. We show that cold shock (1 day) results in minimal change in the plastid proteomes, while short-term (10 days) acclimation results in major changes in the stromal but few changes in the lumen proteome. Long-term acclimation (40 days) results in modulation of the proteomes of both compartments, with new proteins appearing in the lumen and further modulations in protein abundance occurring in the stroma. We identify 43 differentially displayed proteins that participate in photosynthesis, other plastid metabolic functions, hormone biosynthesis and stress sensing and signal transduction. These findings not only provide new insights into the cold response and acclimation of Arabidopsis, but also demonstrate the importance of studying changes in protein abundance within the relevant cellular compartment.

  • 221.
    Grahn, Mats
    Södertörn University College, Avdelning Naturvetenskap.
    MHC genotype and ornamentation2000In: Animal signals: signalling and signal design in animal communication / [ed] Yngve Espmark, Trond Amundsen, Gunilla Rosenqvist, Trondheim: Tapir , 2000, p. 421-436Chapter in book (Other academic)
  • 222.
    Grahn, Mats
    Södertörn University College, School of Chemistry, Biology, Geography and Environmental Science.
    Ny mat och gamla gener2004In: Forskare klargör myter om maten / [ed] Birgitta Johansson, Stockholm: Formas , 2004Chapter in book (Other (popular science, discussion, etc.))
  • 223.
    Grahn, Mats
    Södertörn University College, Avdelning Naturvetenskap.
    Varför evolutionär medicin: en förklaringsmodell för sjukdom2001In: Tidsrkiften Medikament, ISSN 1402-3881, Vol. 5, p. 28-32Article in journal (Other (popular science, discussion, etc.))
  • 224. Grahn, Mats
    et al.
    Langefors, Åsa
    von Schantz, Torbjörn
    The importance of mate choice in improving viability in captive populations1998In: Behavioural Ecology and Conservation Biology / [ed] Timothy M. Caro, New York: Oxford University Press , 1998, p. 341-363Chapter in book (Other academic)
  • 225. Granlund, Irene
    et al.
    Storm, Patrik
    Schubert, Maria
    Södertörn University, School of Life Sciences.
    Garcia-Cerdan, Jose G.
    Funk, Christiane
    Schröder, Wolfgang P.
    The TL29 Protein is Lumen Located, Associated with PSII and Not an Ascorbate Peroxidase2009In: Plant and Cell Physiology, ISSN 0032-0781, E-ISSN 1471-9053, Vol. 50, no 11, p. 1898-1910Article in journal (Refereed)
    Abstract [en]

    The TL29 protein is one of the more abundant proteins in the thylakoid lumen of plant chloroplasts. Based on its sequence homology to ascorbate peroxidases, but without any supporting biochemical evidence, TL29 was suggested to be involved in the plant defense system against reactive oxygen species and consequently renamed to APX4. Our in vivo and in vitro analyses failed to show any peroxidase activity associated with TL29; it bound neither heme nor ascorbate. Recombinant overexpressed TL29 had no ascorbate-dependent peroxidase activity, and various mutational analyses aiming to convert TL29 into an ascorbate peroxidase failed. Furthermore, in the thylakoid lumen no such activity could be associated with TL29 and, additionally, TL29 knock-out mutants did not show any decreased peroxidase activity or increased content of radical oxygen species when grown under light stress. Instead we could show that TL29 is a lumen-located component associated with PSII.

  • 226.
    Granquist, Anna
    et al.
    Södertörn University College, Lärarutbildningen.
    Mårdfjäll, Eva
    Södertörn University College, Lärarutbildningen.
    Jag trivs bäst när havet svallar, och måsarna ger skri: En textanalytisk studie av biologisk mångfald i läroböcker2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    Biological diversity is one out of four dimensions, characterizing the subject of Biology ac-cording to the school curriculum. As a concept, biological diversity had its break through at the UN environmental conference in Rio de Janeiro in 1992, where the convention about bio-logical diversity, named CBD, was signed. According to the convention, almost all the na-tions of the world have engaged themselves to preserve the national diversity of species, in-cluding the diversity of genetics and ecological systems.

    This thesis focuses the biological diversity from the perspective of school books. The aim is to find out how the biological diversity is presented in biology books for students aged 12-15 years.

    In 1994, the current Swedish secondary and high school curriculum called LPO-94 was pre-sented. The biology books used in this study were published between 1994 and 2007, all of them exist in many editions and are published by three different publishers.

    The conclusion of the study is that all the biology books that were examined have reached different levels of the development in the field of biological diversity.

    Download full text (pdf)
    FULLTEXT01
  • 227. Greenberg, L A
    et al.
    Hernnäs, B
    Brönmark, D
    Dahl, J
    Eklöv, A
    Olsén, K Håkan
    Södertörn University, Avdelning Naturvetenskap.
    Effects of kinship on growth and movements of brown trout in field enclosures2002In: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 11, no 4, p. 251-259Article in journal (Refereed)
    Abstract [en]

    The effect of kinship on growth and use of space by individually PIT-tagged 1+ brown trout was studied for 11 weeks in eight stream enclosures. Each enclosure consisted of two sections, separated by a region containing PIT-detecting antennae, which enabled us to measure use of sections by all individuals. Two types of sibling groups were tested, a single sibling group, F1, consisting of four individuals that were reared together in hatchery tank 'a' (F1(a)) plus four additional siblings of the same family but raised in hatchery tank 'b' (F1(b)), and a mixed sibling group, consisting of four F1(a) individuals plus four siblings from a second family, F2. Based on kin theory and earlier laboratory studies, we expected that growth of the F1(a) individuals in the single sibling group to be greater than that of F1(a) individuals in the mixed family sibling group, but instead we found just the opposite. The variance of growth did not differ between treatments. Nor was there a difference in time F1(a) individuals spent together when they were in mixed versus single sibling groups. We did find that F1(a) individuals changed habitat more frequently than F2 individuals in the mixed sibling group but less frequently than F1(b) in the single sibling groups. Thus, our predictions based on kin theory for growth and behavior of brown trout were not supported by our data, and we suggest that the role of kin recognition for the ecology of salmonids deserves further attention.

  • 228. Grimm, T
    et al.
    Teglund, Stephan
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Tackels, D
    Sangiorgi, E
    Gurrieri, F
    Schwartz, C
    Toftgard, R
    Genomic organization and embryonic expression of Suppressor of Fused, a candidate gene for the split-hand/split-foot malformation type 32001In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 505, no 1, p. 13-17Article in journal (Refereed)
    Abstract [en]

    The genes for human and mouse Suppressor of Fused (SU(FU)/Su(Fu)) in the Hedgehog signaling pathway were characterized and found to contain 12 exons. Human SU(FU) localized on chromosome 10q24-25 between the markers D10S192 and AFM183XB12. We detected three additional SU(FU) isoforms, two of which have lost their ability to interact with the transcription factor GLI1. Expression analysis using whole mount in situ hybridization revealed strong expression of Su(Fu) in various mouse embryonic tissues. SU(FU) was considered a candidate gene for the split-hand/split-foot malformation type 3 (SHFM3). However, no alterations in the SU(FU) gene were found in SHFM3 patients.

  • 229.
    Grivas, Spiros
    et al.
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institute / SLU.
    Schuisky, P
    SLU.
    Synthesis of imidazonaphthyridines and -quinolines1998In: Heterocycles, ISSN 0385-5414, E-ISSN 1881-0942, Vol. 48, no 8, p. 1575-1580Article in journal (Refereed)
    Abstract [en]

    Four 2-amino-3-methylimidazo[4,5-b][1,x]naphthyridines, x = 5-8 (6-9) have been obtained from aromatic aldehydes (11-14) and 2-amino-1-methyl-2-imidazolin-5-one (15) in one step. The N-1 - and N-3 -methyl isomers of 2-aminoimidazo-[4,5-b]quinoline (5 and 10) were prepared from 2-nitrobenzaldehyde via the isolated E-isomers of imidazolin-5-one (17) and imidazolin-4-one (20).

  • 230.
    Grube, Martin
    et al.
    Graz university, Austria.
    Gutmann, B.
    Graz university, Austria.
    Arup, Ulf
    Graz university, Austria.
    Rios, A. de los
    Graz university, Austria.
    Mattsson, Jan-Eric
    Uppsala university.
    Wedin, Mats
    Natural History Museum, London.
    An exceptional group I intron-like insertion in SSU rDNA of lichen mycobionts1999In: Current Genetics, ISSN 0172-8083, E-ISSN 1432-0983, Vol. 35, p. 536-541Article in journal (Refereed)
  • 231. Guduru, Shiva Krishna Reddy
    et al.
    Chamakuri, Srinivas
    Chandrasekar, Gayathri
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
    Kitambi, Satish Srinivas
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies. Karolinska Institutet.
    Arya, Prabhat
    Tetrahydroquinoline-Derived Macrocyclic Toolbox: The Discovery of Antiangiogenesis Agents in Zebrafish Assay2013In: ACS Medicinal Chemistry Letters, ISSN 1948-5875, E-ISSN 1948-5875, Vol. 4, no 7, p. 666-670Article in journal (Refereed)
    Abstract [en]

    A novel approach to incorporate the macrocyclic rings onto the privileged substructure, i.e. tetrahydroquinoline scaffold, is developed. The presence of an amino acid-derived moiety in the macrocyclic skeleton provides an opportunity to modulate the nature of the chiral side chain. Further, evaluation in a zebrafish screen identified three active small molecules (2.5b, 3.2d, and 4.2) as antiangiogenesis agents at 2.5 mu M.

  • 232.
    Gulin, Sofia
    et al.
    Södertörn University, Avdelning Naturvetenskap.
    Kussak, A
    Jansson, P E
    Widmalm, G
    Structural studies of S-7, another exocellular polysaccharide containing 2-deoxy-arabino-hexuronic acid2001In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 331, no 3, p. 285-290Article in journal (Refereed)
    Abstract [en]

    The exocellular polysaccharide S-7, a heteropolysaccharide from Azotobacter indicus var, myxogenes has been studied using methylation analysis, Smith degradation, partial acid hydrolysis, NMR spectroscopy and mass spectrometry as the principal methods. It is concluded that the repeating unit has the following structure: -->4)-beta -D-Glcp-(1 -->4)-alpha -L-Rhap-(1 -->3)-beta -D-2-deoxy-arabino-HexpA-(1 --> 6 up arrow 1 beta -D-Glcp-(1 -->6)-beta -D-Glcp The absolute configuration of the deoxyhexuronic acid was deduced from H-1 NMR chemical shifts and is most likely D. Approximately two O-acetyl groups per repeating unit are present, one of which is presumably on the Rha residue. The structure bears great resemblance to another polysaccharide, recently studied, produced by Sphingomonas paucimobilis I-886.

  • 233. Gupta, M P
    et al.
    Solis, P N
    Calderon, A I
    Guionneau-Sinclair, Francoise
    Södertörn University, School of Life Sciences.
    Correa, M
    Galdames, C
    Guerra, C
    Espinosa, A
    Alvenda, G I
    Robles, G
    Ocampo, R
    Medical ethnobotany of the Teribes of Bocas del Toro, Panama2005In: Journal of Ethnopharmacology, ISSN 0378-8741, E-ISSN 1872-7573, Vol. 96, no 3, p. 389-401Article in journal (Refereed)
    Abstract [en]

    Ethnomedical uses of 108 medicinal plant species, belonging to 52 families, 89 genera, used by the Teribe Amerindians of Bocas del Toro Province in Panama. along with their socio-cultural practices are reported here. The methods of administration of the herbal remedies, the plant parts used, their families and local names are also documented. The recorded medicinal plants were used mainly for fever, various type of pain and inflammation. The potential value of 26 plants and their traditional uses was elucidated through literature search.

  • 234. Güntert, P
    et al.
    Berndt, Kurt D
    Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
    Wüthrich, K
    The Program Asno for Computer-Supported Collection of Noe Upper Distance Constraints as Input for Protein-Structure Determination1993In: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 3, no 5, p. 601-606Article in journal (Refereed)
    Abstract [en]

    A new program, ASNO ('ASsign NOes'), for computer-supported NOE cross-peak assignments is described. ASNO is used for structure refinement in several rounds of NOESY cross-peak assignments and 3D structure calculations, where the preliminary structures are used as a reference to resolve ambiguities in NOE assignments which are otherwise based on the chemical shifts available from the sequence-specific resonance assignments. The practical use of ASNO for proteins is illustrated with the structure determination of Dendrotoxin K from Dendroaspis polylepis polylepis.

  • 235. Haas, S A
    et al.
    Hild, M
    Wright, Anthony P H
    Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
    Hain, T
    Talibi, D
    Vingron, M
    Genome-scale design of PCR primers and long oligomers for DNA microarrays2003In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 31, no 19, p. 5576-5581Article in journal (Refereed)
    Abstract [en]

    During the last years, the demand for custom-made cDNA chips/arrays as well as whole genome chips is increasing rapidly. The efficient selection of gene-specific primers/oligomers is of the utmost importance for the successful production of such chips. We developed GenomePRIDE, a highly flexible and scalable software for designing primers/oligomers for large-scale projects. The program is able to generate either long oligomers (40-70 bases), or PCR primers for the amplification of gene-specific DNA fragments of user-defined length. Additionally, primers can be designed in-frame in order to facilitate large-scale cloning into expression vectors. Furthermore, GenomePRIDE can be adapted to specific applications such as the generation of genomic amplicon arrays or the design of fragments specific for alternative splice isoforms. We tested the performance of GenomePRIDE on the entire genomes of Listeria monocytogenes (1584 gene-specific PCRs, 48 long oligomers) as well as of eukaryotes such as Schizosaccharomyces pombe (5006 gene-specific PCRs), and Drosophila melanogaster (21306 gene-specific PCRs). With its computing speed of 1000 primer pairs per hour and a PCR amplification success of 99%, GenomePRIDE represents an extremely cost- and time-effective program.

  • 236.
    Hallgren, Stefan
    Södertörn University, School of Life Sciences, Biology. Södertörn University, School of Life Sciences, Environmental science.
    Brain aromatase in the guppy, Poecilia reticulata: distribution, control and role in behaviour2009Doctoral thesis, comprehensive summary (Other academic)
  • 237.
    Hallgren, Stefan
    Södertörn University, School of Life Sciences.
    Neuroestrogen and male reproductive behaviour in the guppy2006Licentiate thesis, monograph (Other academic)
  • 238.
    Hallgren, Stefan
    et al.
    Södertörn University College, School of Life Sciences.
    Kitambi, Satish Srinivas
    Karolinska Institutet.
    Cloning, sequencing and In situ localisation of guppy brain aromatase, cyp19bManuscript (preprint) (Other academic)
    Abstract [en]

    Oestrogens are biosynthesised by cytochrome p450-aromatase (Cyp19). Brain oestrogens serve several important functions of which nerve protection, cell proliferation, nerve development and behaviour control are a few. Teleost brain aromatase activity is exceptionally high (between 100-1000 times) compared to mammals and birds. We have successfully cloned and sequenced a 950 bp long partial fragment of the guppy CYP19B gene (PrCyp19b) derived from adult brain mRNA. Sequence alignment of translated amino acid sequence shows PrCYP19b having high sequence similarity to teleost brain aromatase. Anatomical distribution of PrCYP19b expression in adult guppy brains was studied using in situ-hybridisation with an antisense riboprobe synthesised from the cloned PrCYP19b gene. Expression of brain aromatase appeared at ventricular surfaces of the ventral telencephalic zones and the pre-optic area, in the hypothalamus, the pituitary gland, optic tectum and the cerebellum. This pattern is similar to previously reported distribution of brain aromatase in other teleosts. Measurement of brain aromatase activity in telencephalon, mesencephalon/diencephalon and rhombencephalon revealed female guppies producing the most oestrogens in mesencephalon/diencephalon, whereas males produces the most oestrogens in both telencephalon and mesencephalon/diencephalon. This indicates that brain oestrogen production is sexually dimorphic in the guppy and may serve different functions in the two genders.

  • 239.
    Hallgren, Stefan
    et al.
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Biology.
    Olsén, K Håkan
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Biology.
    Effects on Guppy Brain Aromatase Activity Following Short-Term Steroid and 4-Nonylphenol Exposures2010In: Environmental Toxicology, ISSN 1520-4081, E-ISSN 1522-7278, Vol. 25, no 3, p. 261-271Article in journal (Refereed)
    Abstract [en]

    Brain estrogen production, performed by the enzyme aromatase, can be disrupted/affected in teleost fish exposed to endocrine disruptors found in polluted aquatic environments. The guppy (Poecilia reticulata) was previously studied and confirmed to suffer negative effects on reproductive behaviors following inhibition of the brain aromatase reaction. Here adult guppies (Poecilia reticulata) of both genders were subjected to known endocrine disruptors: the androgen androstenedione (A), the synthetic estrogen 17 alpha-ethinylestradiol (EE2), and the estrogenic surfactant 4-nonylphenol (NP), at high (50 mu g/L) and at environmentally relevant concentrations (10 ng/L EE2, 5 mu g/L NP, and 0.7 mu g/L A) for 2 weeks followed by measurements of brain aromatase activity (bAA). In the adult males, bAA was stimulated by A and EE2 at 50 mu g/L. Female activity was also stimulated by the higher estrogenic treatment. At environmentally relevant concentrations only the EE2 treatment affected bAA, and only in males. The alkylphenolic substance NP produced no effect in either of the experiments, not on males nor females. The results indicate that short-term steroid treatments have stimulatory effects on guppy brain aromatase even at concentrations that can be found in the environment. We thus suggest bAA of adult guppies to be a suitable bioindicator of endocrine disruptors.

  • 240.
    Hallgren, Stefan
    et al.
    Södertörn University College, School of Life Sciences.
    Olsén, K Håkan
    Södertörn University College, School of Life Sciences.
    Impacts of synthetic oestrogen and antioestrogen treatments on courtship and mating behaviours in male guppies (Poecilia reticulata)Manuscript (preprint) (Other academic)
    Abstract [en]

    Understanding the neuroendocrinological mechanisms behind reproductive behaviour is fundamental when studying endocrine disruption. Neuroestrogen production is a key step in the activation of reproductive behaviours among vertebrates. The actions of estrogens are transmitted through estrogen receptors (ERs) in distinct brain nuclei. Here we report alterations in reproductive behaviours in guppy males following 55-day food treatments with the antiestrogen fulvestrant (ICI) and the synthetic oestrogen 17α-ethinylestradiol (EE2). Male courtship and mating attempts were severely reduced in EE2 treated males after both 27-30 and 41-55 days of treatment when paired with females. ICI treatment gave a significant reduction in the frequency of sigmoid display behaviour after 27-30 days of treatment, and an almost 2.5-fold increase in gonopodium thrusting after 41-55 days of treatment. ICI treated males also decreased their frequency in successful mating attempts in comparison to the control males. The neurological effects of ICI were confirmed by Real Time-PCR analysis for brain aromatase and ERα gene expression. ICI treatment suppressed aromatase expression to 64% and stimulated ERα gene expression by over 300%. These results indicate that oestrogen action via ERs may play an important role for the complete display of male courtship and mating behaviour in the guppy. The results also suggest that local steroids are involved in regulating brain aromatase expression and that the negative effects of EE2 on sexual behaviour are linked via endocrine disruption of gonadal function.

  • 241.
    Hallgren, Stefan
    et al.
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Biology.
    Volkova, Kristina
    Södertörn University, School of Life Sciences, Environmental science.
    Reyhanian, Nasim
    Södertörn University, School of Life Sciences, Environmental science.
    Olsén, K Håkan
    Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Biology.
    Porsch Hällström, Inger
    Södertörn University, School of Life Sciences, Environmental science.
    Anxiogenic behaviour induced by 17α-ethynylestradiol in male guppies (Poecilia reticulata)2011In: Fish Physiology & Biochemistry, ISSN 0920-1742, E-ISSN 1573-5168, Vol. 37, no 4, p. 911-918Article in journal (Refereed)
    Abstract [en]

    Behaviour studies are used in toxicology research as they are excellent tools to measure physiological end-points caused by exogenous chemicals. In mammals both reproductive and non-reproductive behaviours have been used for a long period of time, whereas in teleost fishes non-reproductive behaviours have received little attention compared to reproductive behaviours. Recent advances in measuring stress related behaviours in zebrafish have provided additional tools to understand behaviour toxicology in fish. One species with well documented reproductive behaviour disturbed by different toxicants is the guppy, which is better suited than zebrafish for reproductive behaviour studies and therefore might be a better model organism for comparative behaviour studies in fish toxicology. Here we report new applications for non-reproductive behaviours in guppy and test these behaviours on males treated with the endocrine disruptor 17α-ethynylestradiol at environmentally relevant concentrations. 17α-ethynylestradiol increased freezing and bottom-dwelling when fish were placed in a non-familiar aquarium, but did not significantly affect shoaling behaviour. These results are similar to the anxiogenic behaviours seen in rats treated perinatally with 17α-ethynylestradiol and add more concern to the impacts of endocrine disruptors on aquatic wildlife.

  • 242. Hammarström, A
    et al.
    Berndt, Kurt D
    Karolinska Institutet.
    Sillard, R
    Adermann, K
    Otting, G
    Solution structure of a naturally-occurring zinc-peptide complex demonstrates that the N-terminal zinc-binding module of the Lasp-1 LIM domain is an independent folding unit1996In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 35, no 39, p. 12723-12732Article in journal (Refereed)
    Abstract [en]

    The three-dimensional solution structure of the 1:1 complex between the synthetic peptide ZF-1 and zinc was determined by H-1 NMR spectroscopy. The peptide, initially isolated from pig intestines, is identical in sequence to the 30 N-terminal amino acid residues of the human protein Lasp-1 belonging to the LIM domain protein family. The final set of 20 energy-refined NMR conformers has an average rmsd relative to the mean structure of 0.55 Angstrom for the backbone atoms of residues 3-30, Calculations without zinc atom constraints unambiguously identified Cys 5, Cys 8, His 26, and Cys 29 as the zinc-coordinating residues. LIM domains consist of two sequential zinc-binding modules and the NMR structure of the ZF-1(-)zinc complex is the first example of a structure of an isolated module. Comparison with the known structures of the N-terminal zinc-binding modules of both the second LIM domain of chicken CRP and rat GRIP with which ZF-1 shares 50% and 43% sequence identity, respectively, supports the notion that the zinc-binding modules of the LIM domain have a conserved structural motif and identifies local regions of structural diversity. The similarities include conserved zinc-coordinating residues, a rubredoxin knuckle involving Cys 5 and Cys 8, and the coordination of the zinc ion by histidine N-delta in contrast to the more usual coordination by N-epsilon observed for other zinc-finger domains, The present structure determination of the ZF-1(-)zinc complex establishes the N-terminal half of a LIM domain as an independent folding unit. The structural similarities of N- and C-terminal zinc-binding modules of the LIM domains, despite limited sequence identity, lead to the proposal of a single zinc-binding motif in LIM domains. The coordinates are available from the Brookhaven protein data bank, entry 1ZFO.

  • 243. Hamsten, C.
    et al.
    Starkhammar, M.
    Tran, T. A. T.
    Johansson, Magnus
    Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Biology. Örebro University.
    Bengtsson, U.
    Ahlen, G.
    Sallberg, M.
    Gronlund, H.
    van Hage, M.
    Identification of galactose-alpha-1,3-galactose in the gastrointestinal tract of the tick Ixode sricinus; possible relationship with red meat allergy2013In: Allergy. European Journal of Allergy and Clinical Immunology, ISSN 0105-4538, E-ISSN 1398-9995, Vol. 68, no 4, p. 549-552Article in journal (Refereed)
    Abstract [en]

    Patients with IgE antibodies against the carbohydrate epitope galactose--1,3-galactose (-Gal) have reported severe allergic reactions after consumption of red meat. Investigations have revealed associations between IgE to -Gal and tick bites. We provide the first direct evidence that -Gal is present within ticks thus potentially explaining the relationship between tick exposure and sensitization to -Gal, with development of red meat allergy as a secondary phenomena. Serum from Swedish patients with delayed severe reactions to red meat was included in the study. A dose-dependent inhibition of IgE responses to -Gal by the tick Ixodesricinus is demonstrated. Furthermore, using cryostat-cut sections of I.ricinus, we show that both a monoclonal and a polyclonal antibody against -Gal stains the gastrointestinal tract of the tick. The same pattern is seen when staining with patient sera IgE positive to -Gal. These results confirm that the -Gal epitope is present in I.ricinus and imply host exposure to -Gal during a tick bite. This provides further evidence that tick bites are associated with IgE responses to -Gal and red meat allergy.

  • 244. Hanson, K
    et al.
    Lönn, Mikael
    Effekter av hyggesbruk och habitat-egenskaper pa den demografiska strukturen hos populationer av glesgroe Glyceria lithuanica1999In: Svensk Botanisk Tidskrift, ISSN 0039-646X, Vol. 93, no 5/6, p. 249-256Article in journal (Other academic)
  • 245. Hao, Limin
    et al.
    Aspöck, Gudrun
    Bürglin, Thomas R
    Södertörn University, School of Life Sciences. Karolinska Institute.
    The hedgehog-related gene wrt-5 is essential for hypodermal development in Caenorhabditis elegans2006In: Developmental Biology, ISSN 0012-1606, E-ISSN 1095-564X, Vol. 290, no 2, p. 323-336Article in journal (Refereed)
    Abstract [en]

    The Caenorhabditis elegans genome encodes a series of hedgehog-related genes, which are thought to have evolved and diverged from an ancestral Hh gene. They are classified into several families based on their N-terminal domains. Here, we analyze the expression and function of a member of the warthog gene family, wrt-5, that lacks the Hint/Hog domain. wrt-5 is expressed in seam cells, the pharynx, pharyngeal-intestinal valve cells, neurons, neuronal support cells, the excretory cell, and the reproductive system. WRT-5 protein is secreted into the extracelluar space during embryogenesis. Furthermore, during larval development, WRT-5 protein is secreted into the pharyngeal lumen and the pharyngeal expression changes in a cyclical manner in phase with the molting cycle. Deletion mutations in wrt-5 cause embryonic lethality, which are temperature sensitive and more severe at 15 degrees C than at 25 degrees C. Animals that hatch exhibit variable abnormal morphology, for example, bagging worms, blistering, molting defects, or Roller phenotypes. We examined hypodermal cell junctions using the AJM-1: :GFP marker in the wrt-5 mutant background and observed cell boundary abnormalities in the arrested embryos. AJM-1: :GFP protein is also misplaced in pharyngeal muscle cells in the absence of WRT-5. In conclusion, we show that wrt-5 is an essential gene that - despite its lack of a Hint domain - has multiple functions in C. elegans and is implicated in cell shape integrity.

  • 246. Hao, Limin
    et al.
    Johnsen, Robert
    Lauter, Gilbert
    Södertörn University, School of Life Sciences. Karolinska Institute.
    Baillie, David
    Bürglin, Thomas R.
    Södertörn University, School of Life Sciences. Karolinska Institute.
    Comprehensive analysis of gene expression patterns of hedgehog-related genes2006In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 7, p. 280-Article in journal (Refereed)
    Abstract [en]

    Background: The Caenorhabditis elegans genome encodes ten proteins that share sequence similarity with the Hedgehog signaling molecule through their C-terminal autoprocessing Hint/Hog domain. These proteins contain novel N-terminal domains, and C. elegans encodes dozens of additional proteins containing only these N-terminal domains. These gene families are called warthog, groundhog, ground-like and quahog, collectively called hedgehog (hh)-related genes. Previously, the expression pattern of seventeen genes was examined, which showed that they are primarily expressed in the ectoderm. Results: With the completion of the C. elegans genome sequence in November 2002, we reexamined and identified 61 hh-related ORFs. Further, we identified 49 hh-related ORFs in C. briggsae. ORF analysis revealed that 30% of the genes still had errors in their predictions and we improved these predictions here. We performed a comprehensive expression analysis using GFP fusions of the putative intergenic regulatory sequence with one or two transgenic lines for most genes. The hh-related genes are expressed in one or a few of the following tissues: hypodermis, seam cells, excretory duct and pore cells, vulval epithelial cells, rectal epithelial cells, pharyngeal muscle or marginal cells, arcade cells, support cells of sensory organs, and neuronal cells. Using time-lapse recordings, we discovered that some hh-related genes are expressed in a cyclical fashion in phase with molting during larval development. We also generated several translational GFP fusions, but they did not show any subcellular localization. In addition, we also studied the expression patterns of two genes with similarity to Drosophila frizzled, T23D8.1 and F27E11.3A, and the ortholog of the Drosophila gene dally-like, gpn-1, which is a heparan sulfate proteoglycan. The two frizzled homologs are expressed in a few neurons in the head, and gpn-1 is expressed in the pharynx. Finally, we compare the efficacy of our GFP expression effort with EST, OST and SAGE data. Conclusion: No bona-fide Hh signaling pathway is present in C. elegans. Given that the hh-related gene products have a predicted signal peptide for secretion, it is possible that they constitute components of the extracellular matrix (ECM). They might be associated with the cuticle or be present in soluble form in the body cavity. They might interact with the Patched or the Patched-related proteins in a manner similar to the interaction of Hedgehog with its receptor Patched.

  • 247. Hao, Limin
    et al.
    Mukherjee, Krishanu
    Liegeois, Samuel
    Baillie, David
    Labouesse, Michel
    Bürglin, Thomas R.
    Södertörn University, School of Life Sciences. Karolinska institutet.
    The hedgehog-related gene qua-1 is required for molting in Caenorhabditis elegans2006In: Developmental Dynamics, ISSN 1058-8388, E-ISSN 1097-0177, Vol. 235, no 6, p. 1469-1481Article in journal (Refereed)
    Abstract [en]

    The Caenorhabditis elegans genome encodes ten proteins that share similarity with Hedgehog through the C-terminal Hint/Hog domain. While most genes are members of larger gene families, qua-1 is a single copy gene. Here we show that orthologs of qua-1 exist in many nematodes, including Brugia malayi, which shared a common ancestor with C. elegans about 300 million years ago. The QUA-1 proteins contain an N-terminal domain, the Qua domain, that is highly conserved, but whose molecular function is not known. We have studied the expression pattern of qua-1 in C. elegans using a qua-1::GFP transcriptional fusion. qua-1 is mainly expressed in hyp1 to hyp11 hypodermal cells, but not in seam cells. It is also expressed in intestinal and rectal cells, sensilla support cells, and the P cell lineage in L1. The expression of qua-1::GFP undergoes cyclical changes during development in phase with the molting cycle. It accumulates prior to molting and disappears between molts. Disruption of the qua-1 gene function through an internal deletion that causes a frame shift with premature stop in the middle of the gene results in strong lethality. The animals arrest in the early larval stages due to defects in molting. Electron microscopy reveals double cuticles due to defective ecdysis, but no obvious defects are seen in the hypodermis. Qua domain-only::GFP and full-length QUA-1::GFP fusion constructs are secreted and associated with the overlying cuticle, but only QUA-1::GFP rescues the mutant phenotype. Our results suggest that both the Hint/Hog domain and Qua domain are critically required for the function of QUA-1.

  • 248.
    Havervall, Carolina
    Södertörn University College, School of Life Sciences.
    CXCL13: A Prognostic Marker in Multiple Sclerosis2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In the demyelinating autoimmune disease multiple sclerosis (MS) there is a great need for validated prognostic biomarkers that can give information about both prognosis and disease course. So far only clinical parameters have been shown to predict future outcome. CXCL13 is a potent B cell chemoattractant that has been suggested to be a potential biomarker candidate. The aim of this study was to investigate the usefulness of CXCL13 as a prognostic biomarker for MS.

    Clinical, paraclinical, laboratory and MRI data about a large group of MS patients and controls were collected. CXCL13 levels in cerebrospinal fluid (CSF) samples from these patients were determined by standard enzymelinked immunosorbent assay (ELISA).

    In general CXCL13 were increased in CSF in MS, especially in relapsing-remitting MS during relapses, i.e. with ongoing inflammations in the central nervous system. CXCL13 is a good candidate prognostic marker for MS, since newly diagnosed MS with high CXCL13 levels showed worsened disease course within five years. Most importantly, MS conversion occurred in higher rate in possible MS patients with high concentrations of CXCL13 in CSF, and in a shorter time point. This observation may support an early treatment decision in these patients.

    In conclusion, this study provides support for an association between CXCL13 levels in the CSF and later development of disease severity in MS.

    Download full text (pdf)
    Carolina Havervall_CXCL13: A Prognostic Marker in Multiple Sclerosis
  • 249.
    Hedlund, Eva-Maria
    Södertörn University College, School of Life Sciences.
    Molecular mechanisms of angiogenic synergism between Fibroblast Growth Factor-2 and Platelet Derived Growth Factor-BB2006Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Download full text (pdf)
    FULLTEXT01
  • 250.
    Hedlund, Johanna S. U.
    Södertörn University College, School of Life Sciences.
    Living with males: benefits and costs to females of resident males in Colobus vellerosus2009Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Only in primates is permanent male-female association the most widespread social structure of all. The continuous presence of resident males in the social group can have significant impacts on female fitness, both in forms of costs and benefits. In this study I investigate particular short-term benefits and costs of resident males to females in a population of ursine colobus (Colobus vellerosus). I hypothesise that for females permanent association with males result in certain benefits and certain costs, exceeding those provided or imposed by other females. The results indicate that female derive greater benefits from males than from females during intergroup encounters and in the form of vigilance since males were the main participants in intergroup encounter and were more vigilant than females. I could not confirm any type of behaviour employed by resident males that is costly to females. However, the rarity and subtleness of some costly male behaviours imply that more data is needed before making a conclusion on their absence or occurrence in this population and I purpose that herding behaviour could occur at my study site. Moreover, multi-male groups (MM-groups) showed higher rates of vigilance than single-male groups (SM-groups) and had a tendency to experiencing fewer intergroup encounters than SM-groups. I interpret the former as a result of the demanding social conditions in the MM-groups. The latter indicate that females may benefit from MM-group living through a decrease in intergroup encounters.

    Download full text (pdf)
    FULLTEXT01
2345678 201 - 250 of 771
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • harvard-anglia-ruskin-university
  • apa-old-doi-prefix.csl
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf