Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Antimicrobial peptides with therapeutic potential from skin secretions of polyploid frogs of the Pipidae family
Mechkarska, M.P.M. - \ 2013
University. Promotor(en): Jerry Wells. - [S.l.] : s.n. - ISBN 9789461735508 - 224
kikkers - pipidae - secreties - antimicrobiële peptiden - gastheer-pathogeen interacties - frogs - secretions - antimicrobial peptides - host pathogen interactions

The emergence of pathogenic bacteria and fungi resistant to commonly used antibiotics poses a serious threat to public health and necessitates novel treatment approaches in order to control infections. Antimicrobial peptides (AMPs) are one of the central components of the system of innate immunity and due to their non-specific and highly destructive mechanism of killing, pathogens will develop resistance at lower rates than conventional antibiotics.Skin secretions of frogs from the family Pipidae are a rich source of AMPs which show potential for development into therapeutic agents.

Until recently, the only representatives of the Pipidae family frogs from which dermal AMPs had been identified were the diploid frog Silurana tropicalis, the tetraploid frog Xenopus laevis and the octoploid frog Xenopus amieti. Therefore, this program of research was undertaken with the aim to isolate, purify and characterize AMPs with therapeutic potential from skin secretions of other polyploid species of African clawed frogs of the Pipidae family. Emphasis is given to the application of the AMPs as markers to elucidate the taxonomic relationships and evolutionary history of the frogs. The study also investigates the effects which polyploidization and interspecies hybridization have had on the multiplicity of AMPs in frog skin secretions.

Chapter 2 and Chapter 3 present data from the peptidomic analysis of norepinephrine-stimulated skin secretions of two well-characterized and closely related tetraploid Xenopus species – X. borealis and
X. clivii. Multiple peptides with varying degrees of antimicrobial activity were isolated. Structural characterization demonstrated that they were orthologous to magainins, peptide glycine-leucine-amide (PGLa), caerulein-precursor fragments (CPFs) and xenopsin-precursor fragments (XPFs), previously isolated from S. tropicalis, X. laevis and X. amieti. CPF-B1 and CPF-C1 were the most abundant AMPs in the skin secretions of X. borealis and X. clivii respectively. CPF-B1 (GLGSLLGKAFKIGLKTVGKMMGGAPREQ) was active against clinical isolates of the hospital-associated pathogens, methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Acinetobacter baumannii (MDRAB) with MIC = 5 µM and showed low hemolytic activity against human erythrocytes (HC50 >200 µM). CPF-C1 (GFGSLLGKALRLGANVL.NH2) also showed potent activity against a range of Gram-negative bacteria. CPF peptides, therefore, represent promising candidates for development into therapeutic agents for use against these emerging antibiotic-resistant pathogens.

The genera Silurana and Xenopus are united in the subfamily Xenopodinae and have a complex evolutionary history. Chapter 4 includes data from the peptidomic analysis of skin secretions from an incompletely characterized tetraploid species termed “S. new tetraploid 1”with chromosome number 2n=40 and the octoploid species X. andrei (2n=72). The species represent model systems in which to study of the fate of duplicated AMP genes following putative allopolyploidization events. Multiple peptides belonging to the PGLa, XPF, and CPF familes were identified. The primary structures of the AMPs from X. andrei indicate aclose phylogenetic relationship between this species and the previously studied X. amieti. Three CPF peptides from “S. new tetraploid 1” showed potent, broad-spectrum antimicrobial activity and are present in high abundance. In contrast, only a single CPF peptide was isolated in low yield from the X. andrei secretions. There is no increase in the multiplicity of the AMPs in skin secretions of “S. new tetraploid 1”and the octoploid X. andrei when compared to the diploid
S. tropicalis (2n=20) and the tetraploid X. laevis (2n=36). It is concluded that nonfunctionalization (gene silencing) has been the most common fate of duplicated AMP genes following polyploidization in the Silurana and Xenopus lineages.

AMPs constitute a characteristic ‘‘fingerprint’’ of a particular frog species that may be used for an unequivocal taxonomic classification. Two populations of the tetraploid X. muelleri, occupying separate non-contiguous ranges in east and west Africa, are studied in Chapter 5. Their taxonomic relationship is unclear and it has been proposed that the western population represents a separate species referred to as
X. muelleri West while the eastern population retains the original name X. muelleri. A comparison of the primary sequences of AMPs in skin secretions reveals that no orthologous peptide from the two populations of X. muelleri has the same amino acid sequence. Additionally, the X. muelleri secretions, like those from X. clivii, did not contain a PGLa peptide whereas the X. muelleri West secretions contained two members of this family. The data indicate that X. muelleri West is more closely related to X. borealis than to X. muelleri and so provide strong support for the proposal that X. muelleri and
X. muelleri West should be described as separate species.

In contrast to species in the subfamily Xenopodinae, frogs from the subfamily Pipinae have not been investigated as a source of AMPs. The AMP profile in skin secretions from Hymenochirus boettgeri as a representative of genus Hymenochirus (subfamily Pipinae) is described in Chapter 6. A novel family of five structurally-related peptides, designated as hymenochirins, was identified. Hymenochirin-1B (IKLSPETKDNLKKVLKGAIKGAIAV AKMV.NH2) is C-terminally α-amidated whereas hymenochirins-2B - 5B have the general structure XKIPX2VKDTLKKVAKG X2SX2 AGAX3.COOH. The most abundant peptide in the secretions was hymenochirin-3B (IKIPAVVKDTLKKVAKGVLSAVAGALTQ). Synthetic replicates of hymenochirin-1B - 4B possess broad-spectrum antimicrobial activity and relatively weak hemolytic activity and so represent potential candidates for development into therapeutically valuable agents against drug-resistant pathogens. The hymenochirins show very low structural similarity with the antimicrobial peptides isolated from skin secretions of S. tropicalis and X. laevis consistent with the proposed ancient divergence of the Pipinae and Xenopodinae.

The F1 hybrid frogs X. laevis x X. muelleri represent a model of interspecies hybridization in the Pipidae family that does not result in an increase in ploidy. They arestudied in Chapter 7 and the data obtained provide an insight into the mode of inheritance of AMPs. A total of 18 different AMPs were isolated from skin secretions of the female hybrids. In addition to the complement of AMPs from the parent species, three previously undescribed peptides (magainin-LM1, PGLa-LM1, and CPF-LM1) were purified from the secretions of the hybrid frogs that were not detected in secretions from either X. laevis or X. muelleri. Magainin-LM1 differs from magainin 2 from X. laevis by a single amino acid substitution (Gly13 ®Ala) but PGLa-LM1 and CPF-LM1 differ appreciably in structure from orthologs in the parent species. CPF-LM1 shows potent, broad-spectrum antimicrobial activity and is hemolytic. The data indicate that hybridization increases the multiplicity of host-defense peptides in skin secretions. As the female F1 hybrids are fertile, hybridization may represent an adaptive strategy among Xenopus species to increase protection against pathogenic microorganisms in the environment.

The thesis is completed by a general discussion in Chapter 8 of theresults and conclusions in Chapters 2-7. The potential of AMPs from skin secretions of frogs belonging to the Pipidae family is reviewed from three different aspects: promising candidates for development into therapeutic valuable anti-infective agents; reliable taxonomic and phylogenetic markers; and tools to study the fate of duplicated genes in Xenopus and Silurana. The interspecies Xenopus hybrids are proposed as a suitable model to perform future studies on the mode of inheritance of skin AMPs.

Gratis openluchtconcerten te beluisteren
Werkman, E. - \ 2010
Nature Today 2010 (2010)30-05.
anura - kikkers - soorten - voortplanting - frogs - species - reproduction
Wie nu op een zonnige dag langs sloten en poelen wandelt of fietst kan niet om de markante groene kikkerkoren heen. In grote groepen lokken de mannetjes al roepend de vrouwtjes naar zich toe. Groene kikkers zijn altijd wat later met paren dan de andere kikkersoorten. De piek van de paartijd valt rond eind mei, maar het paren gaat nog door tot ongeveer half juli.
De kleine groene kikker in Buitenvaart. Beoordeling van de effecten van de aanleg van bedrijventerrein Buitenvaart 2 in de gemeente Hoogeveen op het duurzaam voortbestaan van de Kleine groene kikker (Rana lessonae) en mogelijkheden voor compensatie
Blitterswijk, H. van; Stumpel, A.H.P. ; Vliet, C.J.M. van - \ 2003
Wageningen : Alterra (Alterra-rapport 765) - 25
rana - kikkers - industrieterreinen - milieueffect - milieuwetgeving - vergoeding - natuurbescherming - nederland - frogs - industrial sites - environmental impact - environmental legislation - compensation - nature conservation - netherlands
Mede in het licht van de Flora- en faunawet worden de effecten beoordeeld van de geplande aanleg van een bedrijventerrein in de gemeente Hoogeveen op de populaties Kleine groene kikker (Rana lessonae). Tevens worden maatregelen genoemd ter compensatie en mitigatie van deze effecten.
Zeven kikkers in een boerensloot : ontruiming van Buitenvaart 1 te Hoogeveen: kikkers moeten wijken voor bedrijventerrein
Stumpel, A.H.P. ; Blitterswijk, H. van - \ 2002
Wageningen : Alterra - 19
amphibia - kikkers - bedreigde soorten - wildbescherming - nederland - drenthe - amfibieën - aquatische ecologie - fauna - herpetologie - Hoogeveen - frogs - endangered species - wildlife conservation - netherlands
Genetic similarity as a measure for connectivity between fragmented populations of the moor frog (Rana arvalis)
Vos, C.C. ; Antonisse-de Jong, A.G. ; Goedhart, P.W. ; Smulders, M.J.M. - \ 2001
Heredity 86 (2001). - ISSN 0018-067X - p. 598 - 608.
fauna - amfibieën - genetica - herpetologie - kikkers - landschapsecologie - populatiebiologie - versnippering
Genetic differentiation among populations of the moor frog (Rana arvalis) was tested on a spatial scale where some dispersal between populations is expected to occur, in a landscape in The Netherlands that has become fragmented fairly recently, in the 1930s. Five microsatellite loci were used, with 2-8 alleles per locus. FIS was 0.049 across loci, and most populations were in HW equilibrium. The degree of population subdivision was low (FST=0.052). A significant positive correlation between genetic distance and geographical distance was found, indicating a limitation in dispersal among populations due to distance. To test the impact of the landscape mosaic on the connectivity between patches, distance measures were corrected for relative amounts of habitat types with known positive or negative influence on moor frog dispersal. Notably, the resistance variable for the fraction of negative linear elements (roads and railways) gave a higher explanatory value than geographical distance itself. Therefore, it is particularly the number of barriers (roads and railways) between populations that emerges as a factor that reduces exchange between populations. It is concluded that genetic techniques show promise in determining the influence of landscape connectivity on animal dispersal.
The effects of nonylphenol on Rana temporaria tadpole survival, development and longitudinal growth
Poorte, J. de; Naber, A.B. ; Stumpel, A.H.P. ; Bosveld, A.T.C. - \ 2000
In: Endocrine-disrupting compounds: wildlife and human health risks : proceedings of a symposium 27 October 1998, The Hague / Vethaak, A.D., Rijksinstituut voor Kust en Zee - ISBN 9789036934046 - p. 137 - 141.
amphibia - rana temporaria - oestrogenen - fenolen - overleving - amfibieën - ecotoxicologie - endocrinologie - fauna - herpetologie - kikkers - milieuverontreiniging - oestrogens - phenols - survival
Bezetting en kolonisatie van poelen door kamsalamander en bruine kikker in Twente
Sluis, T. van der; Bugter, R. - \ 2000
De Levende Natuur 101 (2000)4. - ISSN 0024-1520 - p. 107 - 111.
plassen - biotopen - habitats - aquatisch milieu - hydrobiologie - populatiedichtheid - populatiedynamica - populatie-ecologie - kolonisatie - dispersie - amphibia - kikkers - rana temporaria - inventarisaties - monitoring - natuurbescherming - salamanders - aquatische ecosystemen - populatiebiologie - overijssel - twente - ponds - biotopes - aquatic environment - hydrobiology - population density - population dynamics - population ecology - colonization - dispersion - frogs - inventories - nature conservation - aquatic ecosystems - population biology
Effects of road density; a case study of the moor frog.
Vos, C.C. - \ 1997
In: Habitat fragmentation & infrastructure : proceedings of the international conference "Habitat fragmentation, infrastructure and the role of ecological engineering", 17 - 21 September 1995, Maastricht - The Hague, The Netherlands. - - p. 93 - 97.
verkeer - verkeerspatronen - dichtheid - capaciteit - tellen - onderzoek - dieren - territorium - habitats - milieu - anura - kikkers - padden - multivariate analyse - correlatieanalyse - regressieanalyse - nadelige gevolgen - milieueffect - menselijke activiteit - traffic - traffic patterns - density - capacity - counting - research - animals - territory - environment - frogs - toads - multivariate analysis - correlation analysis - regression analysis - adverse effects - environmental impact - human activity
Versnippering
Effecten van wegen op het voorkomen van de heikikker in Zuidwest-Drenthe
Vos, C.C. ; Chardon, J.P. - \ 1996
Delft : Rijkswaterstaat, Dienst Weg- en Waterbouwkunde - 42
verspreiding - ranidae - kikkers - dieren - territorium - habitats - milieu - wegen - nadelige gevolgen - milieueffect - menselijke activiteit - nederland - diergemeenschappen - drenthe - habitatfragmentatie - dispersal - frogs - animals - territory - environment - roads - adverse effects - environmental impact - human activity - netherlands - animal communities - habitat fragmentation
Naar meetnetten voor reptielen en amfibieen
Stumpel, A.H.P. ; Siepel, H. - \ 1993
Wageningen : IBN (IBN - rapport 033)
amphibia - anura - caudata - kikkers - herpetologie - inventarisaties - nederland - reptielen - padden - veldwerk - observatie - frogs - herpetology - inventories - netherlands - reptiles - toads - field work - observation
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