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.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Plastic ingestion by harbour porpoises Phocoena phocoena in the Netherlands: Establishing a standardised method
    Franeker, Jan A. van; Bravo Rebolledo, Elisa L. ; Hesse, Eileen ; IJsseldijk, Lonneke L. ; Kühn, Susanne ; Leopold, Mardik ; Mielke, Lara - \ 2018
    Ambio 47 (2018)4. - ISSN 0044-7447 - p. 387 - 397.
    harbour porpoise - marine litter monitoring - marine strategy framework directive - MSFD - North Sea - Phocoena phocoena - Plastic ingestion
    Stomach contents of harbour porpoises (Phocoena phocoena) collected in the Netherlands between 2003 and 2013 were inspected for the presence of plastic and other man-made litter. In 654 stomach samples the frequency of occurrence of plastic litter was 7% with less than 0.5% additional presence of nonsynthetic
    man-made litter. However, we show that when a dedicated standard protocol for the detection of litter is followed, a considerably higher percentage (15% of 81
    harbour porpoise stomachs from the period 2010–2013) contained plastic litter. Results thus strongly depended on methods used and time period considered. Occurrence of litter in the stomach was correlated to the presence of other
    non-food remains like stones, shells, bog-wood, etc., suggesting that litter was often ingested accidentally when the animals foraged close to the bottom. Most
    items were small and were not considered to have had a major health impact. No evident differences in ingestion were found between sexes or age groups, with the exception that neonates contained no litter. Polyethylene and polypropylene were the most common plastic types encountered. Compared to earlier literature on the harbour porpoise and related species, our results suggest higher
    levels of ingestion of litter. This is largely due to the lack of dedicated protocols to investigate marine litter ingestion in previous studies. Still, the low frequency of ingestion, and minor number and mass of litter items found in harbour
    porpoises in the relatively polluted southern North Sea indicates that the species is not a strong candidate for annual monitoring of marine litter trends under the EU marine strategy framework directive. However, for longerterm
    comparisons and regional differences, with proper dedicated protocols applied, the harbour porpoise has specific use in quantifying litter presence in the, for that specific objective, poorly studied benthic marine habitat.
    Remotely-sensed detection of effects of extreme droughts on gross primary production
    Vicca, Sara ; Balzarolo, Manuela ; Filella, Iolanda ; Granier, André ; Herbst, Mathias ; Knohl, Alexander ; Longdoz, Bernard ; Mund, Martina ; Nagy, Zoltan ; Pintér, Krisztina ; Rambal, Serge ; Verbesselt, Jan ; Verger, Aleixandre ; Zeileis, Achim ; Zhang, Chao ; Peñuelas, Josep - \ 2016
    Scientific Reports 6 (2016). - ISSN 2045-2322
    Severe droughts strongly impact photosynthesis (GPP), and satellite imagery has yet to demonstrate its ability to detect drought effects. Especially changes in vegetation functioning when vegetation state remains unaltered (no browning or defoliation) pose a challenge to satellite-derived indicators. We evaluated the performance of different satellite indicators to detect strong drought effects on GPP in a beech forest in France (Hesse), where vegetation state remained largely unaffected while GPP decreased substantially. We compared the results with three additional sites: a Mediterranean holm oak forest (Puéchabon), a temperate beech forest (Hainich), and a semi-arid grassland (Bugacpuszta). In Hesse, a three-year reduction in GPP following drought was detected only by the Enhanced Vegetation Index (EVI). The Photochemical Reflectance Index (PRI) also detected this drought effect, but only after normalization for absorbed light. In Puéchabon normalized PRI outperformed the other indicators, while the short-term drought effect in Hainich was not detected by any tested indicator. In contrast, most indicators, but not PRI, captured the drought effects in Bugacpuszta. Hence, PRI improved detection of drought effects on GPP in forests and we propose that PRI normalized for absorbed light is considered in future algorithms to estimate GPP from space.
    Er valt veel te leren van rotte kadavers : Raadselachtige ' mini-massastranding' bruinvissen
    Leopold, M.F. ; Hesse, E. ; Mielke, L. ; Begeman, L. ; Hiemstra, S. - \ 2015
    Zoogdier 26 (2015)2. - ISSN 0925-1006 - p. 4 - 6.
    marine mammals - fauna - mortality - marine areas - inventories - north sea
    In mei 2013 spoelden bij Camperduin vijf bruinvissen tegelijkertijd aan: vier grote dieren en een voldragen foetus. De vier grote bruinvissen waren allemaal erg rot, maar waren op het moment van hun dood in uitstekende voedingsconditie. Ze hadden zich volgegeten met zandspieringen en vlak voor de dood is voedsel uitgespuwd. Pathologisch en voedsel-ecologisch onderzoek komen tot dezelfde - voorzichtige - conclusie: deze dieren zijn als groep verdronken.
    Microplastic in a macro filter feeder: humpback whale Megaptera novaeangliae
    Besseling, E. ; Foekema, E.M. ; Franeker, J.A. van; Leopold, M.F. ; Kuhnel, S. ; Bravo Rebolledo, E. ; Mielke, L. ; Hesse, E. ; Ijzer, J. ; Kamminga, A. ; Koelmans, A.A. - \ 2015
    Porpoises: From predators to prey
    Leopold, M.F. ; Begeman, L. ; Hesse, E. ; Hiele, J. van der; Hiemstra, S. ; Keijl, G.O. ; Meesters, H.W.G. ; Mielke, L. ; Verheyen, D. ; Groene, A. - \ 2015
    Journal of Sea Research 97 (2015). - ISSN 1385-1101 - p. 14 - 23.
    seal halichoerus-grypus - bottle-nosed dolphins - harbor porpoises - phocoena-phocoena - violent interactions - wadden sea - digestion - abundance - fisheries - otoliths
    Along the Dutch shores hundreds of harbour porpoises Phocoena phocoena are stranded each year. A recurrent phenomenon in the Netherlands is a surge of strandings in late winter and early spring of severely mutilated porpoises, that are mostly in good nutritional body condition (thick blubber layer). These mutilated porpoises have parts of the skin and blubber, and sometimes of the muscle tissue missing. By reviewing photographs of stranded animals taken at the stranding sites as well as autopsy results we found 273 mutilated animals from 2005 to 2012. Mutilations could be classified into several categories, but wounds had been mostly inflicted to the sides of these animals, in a zigzag fashion, or to the throat/cheek region. The stomach contents of 31 zigzags, 12 throats/cheeks and 31 control animals that were not mutilated, from the same age and blubber thickness categories were compared; all these animals had stranded between December and April, 2006–2012. The diet of individuals with zigzag lesions to their sides consisted for a large part of gobies, while animals that had wounds at the throat/cheek had been feeding predominately on clupeids. In comparison, animals without mutilations had a more varied diet, including gobies and clupeids, but also a large proportion of sandeels and gadoids. The finding that the type of mutilation corresponds to a certain diet suggests that porpoises that were feeding on different prey, or in different micro-habitats, were hit in different ways. Animals feeding at the sea floor (on gobies) apparently run a risk of being hit from the side, while animals supposedly feeding higher in the water column (on schooling clupeids), were predominantly hit from below, in the throat region. The wider variation in the diets of non-mutilated porpoises is suggestive of them using a larger variety of micro-habitats.
    The recent occurrence of humpback whales in the southern North Sea: a range expansion
    Leopold, M.F. ; Bemmelen, R.S.A. van; Bravo Rebolledo, E. ; Franeker, J.A. van; Hesse, E. ; Kuhn, S. ; Mielke, L. ; Strietman, W.J. ; Camphuysen, K. - \ 2014
    Can the junk food hypothesis be applied to harbour porpoises (Phocoena phocoena) in Dutch waters?
    Hesse, E. ; Leopold, M.F. ; Mielke, L. ; Meesters, H.W.G. ; Keijl, G.O. ; Hiele, J. van der; Begeman, L. ; Hiemstra, S. ; Jauniaux, T. ; Grone, A. - \ 2014
    Diverse Lifestyles and Strategies of Plant Pathogenesis Encoded in the Genomes of Eighteen Dothideomycetes Fungi
    Ohm, R.A. ; Feau, N. ; Henrissat, B. ; Schoch, C.L. ; Horwitz, B.A. ; Barry, K.W. ; Condon, B.J. ; Copeland, A.C. ; Dhillon, B. ; Glaser, F. ; Hesse, C.N. ; Kosti, I. ; LaButti, K. ; Lindquist, E.A. ; Lucas, S. ; Salamov, A.A. ; Bradshaw, R.E. ; Ciuffetti, L. ; Hamelin, R.C. ; Kema, G.H.J. ; Lawrence, C. ; Scott, J.A. ; Spatafora, J.W. ; Turgeon, B.G. ; Wit, P.J.G.M. de; Zhong, S. ; Goodwin, S.B. ; Grigoriev, I.V. - \ 2012
    PLoS Pathogens 8 (2012)12. - ISSN 1553-7366
    ascomycete leptosphaeria-maculans - nonribosomal peptide synthetases - induced point mutations - polyketide synthase - cochliobolus-heterostrophus - colletotrichum-graminicola - fusarium-graminearum - stagonospora-nodorum - phylogenetic trees - neurospora-crassa
    The class Dothideomycetes is one of the largest groups of fungi with a high level of ecological diversity including many plant pathogens infecting a broad range of hosts. Here, we compare genome features of 18 members of this class, including 6 necrotrophs, 9 (hemi)biotrophs and 3 saprotrophs, to analyze genome structure, evolution, and the diverse strategies of pathogenesis. The Dothideomycetes most likely evolved from a common ancestor more than 280 million years ago. The 18 genome sequences differ dramatically in size due to variation in repetitive content, but show much less variation in number of (core) genes. Gene order appears to have been rearranged mostly within chromosomal boundaries by multiple inversions, in extant genomes frequently demarcated by adjacent simple repeats. Several Dothideomycetes contain one or more gene-poor, transposable element (TE)-rich putatively dispensable chromosomes of unknown function. The 18 Dothideomycetes offer an extensive catalogue of genes involved in cellulose degradation, proteolysis, secondary metabolism, and cysteine-rich small secreted proteins. Ancestors of the two major orders of plant pathogens in the Dothideomycetes, the Capnodiales and Pleosporales, may have had different modes of pathogenesis, with the former having fewer of these genes than the latter. Many of these genes are enriched in proximity to transposable elements, suggesting faster evolution because of the effects of repeat induced point (RIP) mutations. A syntenic block of genes, including oxidoreductases, is conserved in most Dothideomycetes and upregulated during infection in L. maculans, suggesting a possible function in response to oxidative stress.
    Optimising nutritional quality of crops
    Hawkesford, M. ; Höfgen, R. ; Galili, G. ; Amir, R. ; Angenon, G. ; Hesse, H. ; Rentsch, D. ; Schaller, J. ; Meer, I.M. van der; Rouster, J. ; Banfalvi, Z. ; Zsolt, P. ; Szabados, L. ; Szopa, J. ; Sirko, A. - \ 2006
    In: Metabolic engineering and molecular farming-I Huston, Texas 77272, USA : Studium Press, LLC (Plant Genetic Engineering 7) - ISBN 9781933699011 - p. 85 - 116.
    The weak acid preservative sorbic acid inhibits conidial germination and mycelial growth of Aspergillus niger through intracellular acidification
    Plumridge, A. ; Hesse, S.J.A. ; Watson, A.J. ; Lowe, K.C. ; Stratford, M. ; Archer, D.B. - \ 2004
    Applied and Environmental Microbiology 70 (2004)6. - ISSN 0099-2240 - p. 3506 - 3511.
    membrane h+-atpase - nuclear magnetic-resonance - a-producing fungi - saccharomyces-cerevisiae - plasma-membrane - aqueous-solutions - carboxylic-acids - abc transporter - sulfur-dioxide - ph
    The growth of the filamentous fungus Aspergillus niger, a common food spoilage organism, is inhibited by the weak acid preservative sorbic acid (trans-trans-2,4-hexadienoic acid). Conidia inoculated at 105/ml of medium showed a sorbic acid MIC of 4.5 mM at pH 4.0, whereas the MIC for the amount of mycelia at 24 h developed from the same spore inoculum was threefold lower. The MIC for conidia and, to a lesser extent, mycelia was shown to be dependent on the inoculum size. A. niger is capable of degrading sorbic acid, and this ability has consequences for food preservation strategies. The mechanism of action of sorbic acid was investigated using 31P nuclear magnetic resonance (NMR) spectroscopy. We show that a rapid decline in cytosolic pH (pHcyt) by more than 1 pH unit and a depression of vacuolar pH (pHvac) in A. niger occurs in the presence of sorbic acid. The pH gradient over the vacuole completely collapsed as a result of the decline in pHcyt. NMR spectra also revealed that sorbic acid (3.0 mM at pH 4.0) caused intracellular ATP pools and levels of sugar-phosphomonoesters and -phosphodiesters of A. niger mycelia to decrease dramatically, and they did not recover. The disruption of pH homeostasis by sorbic acid at concentrations below the MIC could account for the delay in spore germination and retardation of the onset of subsequent mycelial growth
    Intracellular pH homeostasis in the filamentous fungus Aspergillys niger
    Hesse, S.J.A. ; Ruijter, G.J.G. ; Dijkema, C. ; Visser, J. - \ 2002
    European Journal of Biochemistry 269 (2002)14. - ISSN 0014-2956 - p. 3485 - 3494.
    Intracellular pH homeostasis in the filamentous fungus Aspergillus niger was measured in real time by 31P NMR during perfusion in the NMR tube of fungal biomass immobilized in Ca2 -alginate beads. The fungus maintained constant cytoplasmic pH (pHcyt) and vacuolar pH (pHvac) values of 7.6 and 6.2, respectively, when the extracellular pH (pHex) was varied between 1.5 and 7.0 in the presence of citrate. Intracellular metabolism did not collapse until a pH over the cytoplasmic membrane of 6.6-6.7 was reached (pHex 0.7-0.8). Maintenance of these large pH differences was possible without increased respiration compared to pHex 5.8. Perfusion in the presence of various hexoses and pentoses (pHex 5.8) revealed that the magnitude of pH values over the cytoplasmic and vacuolar membrane could be linked to the carbon catabolite repressing properties of the carbon source. Also, larger pH values coincided with a higher degree of respiration and increased accumulation of polyphosphate. Addition of protonophore (carbonyl cyanide m-chlorophenylhydrazone, CCCP) to the perfusion buffer led to decreased ATP levels, increased respiration and a partial (1 ?m CCCP), transient (2 ?m CCCP) or permanent (10 ?m CCCP) collapse of the vacuolar membrane pH. Nonlethal levels of the metabolic inhibitor azide (N3, 0.1 mm) caused a transient decrease in pHcyt that was closely paralleled by a transient vacuolar acidification. Vacuolar H influx in response to cytoplasmic acidification, also observed during extreme medium acidification, indicates a role in pH homeostasis for this organelle. Finally, 31P NMR spectra of citric acid producing A. niger mycelium showed that despite a combination of low pHex (1.8) and a high acid-secreting capacity, pHcyt and pHvac values were still well maintained (pH 7.5 and 6.4, respectively).
    Measurement of Intracellular (compartmental) pH by 31P NMR in Aspergillus niger
    Hesse, S.J.A. ; Ruijter, G.J.G. ; Dijkema, C. ; Visser, J. - \ 2000
    Journal of Biotechnology 77 (2000). - ISSN 0168-1656 - p. 5 - 15.
    Exochorda: five species or one? : a biosystematic study of the Rosaceous genus Exochorda
    Gao Fangyou, - \ 1998
    Agricultural University. Promotor(en): L.J.G. van der Maesen. - S.l. : Gao Fangyou - ISBN 9789054858256 - 133
    rosaceae - plantkunde - taxonomie - classificatie - biologische naamgeving - azië - rosaceae - botany - taxonomy - classification - biological nomenclature - asia

    The Rosaceous genus Exochorda consisted sofar of five accepted species and is distributed in East Asia and Central Asia. Morphologically the taxa in the Exochorda complex have sirnilar characters, hence the classification in the complex was
    questionable. A further problem is the relationship between the genus Exochorda and other genera in Rosaceae. In this dissertation, based on wild material of 22 populations in China, cultivated accessions in the botanical gardens of Wageningen Agricultural University, the Netherlands, and herbarium material, a biosystematic study of this genus is reported. The results are summarized as follows:
    Leaf anatomy: The epidermis consists of one layer of cells and the shape of epidermis cells is irregular in outline as seen on both surface. Epidermal cell shape in surface view is quite uniform in Exochorda. Stomata are always confined to the lower leaf surface. An anornocytic pattern is found in all samples.
    Wood anatomy: growth rings are distinct, boundaries are marked by differences in vessel diameter between earlywood and latewood, and by rows of fiqtened late wood fibres. The wood is ring-porous to semi-porous. Quantitative anatomical characters express continuous variation- within the "species", wood of Exochorda shows a single wood structural type similar to that of the Prunoideae than to the Spiraeoideae.
    Pollen morphology and exine structure show little variation in this genus. Exochorda pollen grains are isopolar, three-colporate, small or medium-sized, grain shape is spheroidal. P = 20.9-30.5 (19.6-36.9) gm, E = 22.1-30.7 (17.9-35.7) μm, A = 5.2-9.5 (3.6-15.5) μm, P/E = 0.88-1.36 (0.81-1.73). Ornamentation is striate. All the samples are closely grouped due to similarities in these characters. These "species" have to be regarded as one species. Compared with pollen morphology of other genera in Rosaceae, Exochorda pollen is similar to that of Neillia, Sorbaria, Spiraea and Prunus.
    All the populations are diploid (2n = 16 or 2n = 18), both numbers are frequently in the same root tip preparation. The chromosomes are small, 1-2 μm; there is little difference between different pairs; the structure is basically rnetacentric; symmetry is high; no satellite chromosomes were observed.
    The results of embryological investigation in this genus showed that the rneiosis of the microspore mother cells is of the Simultaneous type. The tapetum belongs to the Glandular type. The mature embryo sac is of the Polygonurn type.
    Exochorda has a mixed mating system, inbreeding and outbreeding, and>7% of its progeny result from self-pollination. The most important vectors for pollination are honeybees, their relative abundance on the flowers and their intrafloral behaviour make them a major contributor to the reproductive success of Exochorda. Over 30% of the pistils degenerate during the flowering period, resulting in low fruit set. The fruit set varies from 11% to 70%.

    From the RAPD results in some Rosaceae, it is concluded that five previous taxa (five species) of Exochorda are not clearly separated. Instead, all Exochorda samples were defined in one group and are distinct from other genera in Rosaceae. These data indicate that the interspecific relationships in Exochorda are not very clear. The RAPD data also disturb the common opinion regarding the traditional subfamilies in Rosaceae. At least some of the four subfamilies as separate taxonomic units in Rosaceae are quite heterogeneous.
    The findings in multivariate analysis point to a continuous variation of morphological characters. This analysis supports the opinion that overall differences are small within the Exochorda complex. The multivariate analysis does not support five distinct taxa (species) in the Exochorda complex, but three loosely defined taxa can be recognized. E. korolkowii, E. tianshanica and E. racemosa appear conspecific. E. korolkowii and E. tianshanica are united with E. racemosa and treated as synonyms.
    The results obtained in the earlier chapters are used in the revision to delimit taxa. It is concluded that all the taxa. belong to one species. The original five different "species" are reduced to three subspecies, i.e. E. racemosa (Lindl.) Rehder subsp. racemosa, subsp. giraldii (Hesse) F.Y. Gao & Maesen and subsp. serratifolia (S. cont Moore) F.Y. Gao & Maesen.
    This genus does not fit in any of the four classical subfamilies in Rosaceae. A tribal status as Exochordeae is more suitable.
    Exochorda has a relatively narrow and disjunct distribution limited to East Asia and Central Asia. East Asia (mainly China) is the centre of geographical distribution and diversity. So far only one fossil was found in Fushun, Liaoning province of China, which is indicative, but is not decisive for the place of origin. It is inferred that Exochorda originated in the temperate mountain zone of East Asia, the time of origin dates back to the Early Tertiary. It can be logically deduced that Exochorda originated before the emergence of the Taklamakan Desert. The genus probably once occupied a large area in the northern hemisphere of Asia. A formerly continuously distributed taxon became separated into different areas and has been subjected to divergent evolution there. The disjunction may represent the relict of a former wide and continuous distribution pattern, the intervening areas having been depopulated by the rigours of the climate.

    Spirochaetes, serology, and salvarsan : Ludwik Fleck and the construction of medical knowledge about syphilis
    Belt, H. van den - \ 1997
    Agricultural University. Promotor(en): M.J.J.A.A. Korthals; H.A.M.J. ten Have. - S.l. : Van den Belt - ISBN 9789054857655 - 299
    ideologie - sociologie - kennis - geneeskunde - seksueel overdraagbare ziekten - kennistheorie - epistemologie - ideology - sociology - knowledge - medicine - sexually transmitted diseases - theory of knowledge - epistemology

    The theoretical and empirical scope of this study thus clarified, an outline of the chapters which follow can now be presented.

    In Chapter II 1 shall systematically compare Fleck's theories with the approaches adopted by contemporary constructivists. My strategy is partly to use modern forms of constructivism as a foil for extracting relevant and valuable insights from the richness of Fleck's elaborations, partly to identify theoretical and conceptual issues that can possibly be clarified through an empirical 'replication' of Fleck's work. In the following chapters I will therefore deliberately put on spectacles grinded according to different constructivist recipes in order to illuminate various aspects of the concrete episodes under study (always allowing for a comparison with Fleck's empirical analyses) and to elucidate, as far as possible, the theoretical issues involved. Starting out from moderate constructivist approaches (Chapters III and IV) I will move on to more radical forms of constructivism (Chapters V and VII). In the concluding chapter the spectacles themselves will be the object of examination.

    Chapter III reconsiders the historical genesis of the modem concept of syphilis, which is also the main subject of the first part of Fleck's monograph. Its purpose is to demonstrate the prima facie legitimacy and fruitfulness of a broadly constructivist approach towards the historical genesis of disease concepts. The aim of the chapter is therefore less to criticize than to consolidate and extend Fleck's insights. I do so by following the example of many modem constructivists in adopting Mary Hesse's finitist theory (or 'network theory') of meaning as my starting-point. The results of my explorations vindicate Fleck's view of the (socially) constructed and 'culture-laden' character of the modem concept of syphilis. I also follow up one of Fleck's more specific suggestive remarks, to the effect that moral considerations in particular entered into the construction of concepts of syphilis. To substantiate this suggestion, I pay special attention to the (formerly presumed) 'hereditary' and (still uncontested) venereal character of the disease. By performing a cross-cultural comparison with some non-venereal tropical and subtropical diseases closely related to syphilis, I hope to loosen the hold on our minds of the 'venereal fixation' characteristic of the modem concept of syphilis. Some of the findings discussed in this chapter are calculated to unsettle the tranquillity of mind of hard-headed anti-constructivists and thus, by the same token, to earn credibility for a broadly constructivist approach.

    Chapter IV describes and analyzes the discovery of the causative agent of syphilis, a subject to which Fleck devotes some brief but interesting passages in his monograph. In this chapter I shall put on the type of spectacles that belong to the special brand of (social) constructivism represented by Harry Collins. Characteristic of this approach, which preferably focuses on the study of scientific controversies, is that the analyst takes a strictly agnostic stance as to the reality or otherwise of the (purported) natural phenomenon under dispute and treats the arguments and actions of the conflicting parties in a symmetrical and impartial way. The empirical subject of this chapter provides a favourable occasion to follow these precepts. During the years 1905-1907 two different microorganisms, Spirochaeta pallida and Cytorrhyctes luis, were in fact proposed and defended as the looked-for aetiological agent of syphilis. Such a situation would seem to be a pre-eminent case calling for a symmetrical treatment in the modern constructivist sense. Indeed, Fleck himself already presented a symmetrical analysis of this episode in his monograph, but - as I will argue - the particular account he offered lacks plausibility. I will undertake a new effort, more sustained and hopefully more thorough-going than Fleck's failed attempt. In the debate on the aetiology of syphilis several issues were raised that are highly relevant for a constructivist analysis, e.g. about the reliability of (microscopic) observation and the possibility of creating 'artefacts' by staining tissue preparations. Fleck's general views on the role of perception and observation, expounded in his monograph and other writings, prove to be useful and pertinent. The case also illustrates the general constructivist insight that appeal to formal methodological rules and criteria is unable to resolve controversies. Finally, the chapter will present a conceptual analysis of the notion of 'discovery' in line with the findings of the historical case-study. A consistently sustained constructivist approach leads to a major rethinking of this notion, taking up but going beyond Thomas Kuhn's views on the matter. To put it briefly and somewhat paradoxically, using the familiar distinction of traditional philosophy of science, the constructivist proposal is to transfer the category of discovery from the 'context of discovery' to the 'context of justification', or rather, to the social context of validation and acceptance.

    Chapter V deals with the genesis and development of the Wassermann reaction as a clinically usable serological test for detecting syphilis. This is also the main subject of Fleck's monograph. The 'scientific fact' to which the title of his book refers is "the fact that the so-called Wassermann reaction is related to syphilis", which was, according to Fleck, "one of the best established medical facts". The establishment of this fact is seen as the result of a cooperative effort by the so-called 'serological thought collective' led by August Wassermann, which under the influence of the social urgency of the syphilis problem and ancient ideas about syphilitic blood worked unceasingly to improve and perfect the test until a practically usable diagnostic instrument was finally obtained.

    In this chapter I examine the empirical and theoretical adequacy of Fleck's analysis. I take issue with several elements of his account, but the main objection is that he simply ignores the 'clinical connection' and depicts the development of the Wassermann reaction as if it occurred exclusively within the four walls of the laboratory, with serologists busily 'tuning their sets'. In my alternative account of the whole episode, the interaction between serologists and clinicians figures much more prominently. This account is loosely inspired by Bruno Latour's ideas on 'enrollment' and 'translation of interests'. To convince clinicians of the value and reliability of the Wassermann reaction, serologists were initially caught in a 'dilemma of application' if the outcome of the test agreed with the clinicians' own judgement, it would tell them nothing new; if it disagreed with their judgement, they would doubt its validity and reliability. Through active involvement of clinicians ('enrollment'), the dilemma could be overcome by, on the one hand, changing the technical execution and clinical meaning of the Wassermann reaction, and, on the other, redefining the diagnostic and therapeutic interests of clinicians to which the test would attend. Ultimately, a practically usable serological test for syphilis was achieved by the joint efforts of serologists and clinicians. This analysis also elucidates some riddles that were left unresolved within Fleck's account. However, I intend to do more than rectifying the shortcomings of Fleck's account. I also want to venture, albeit rather cautiously, some radical- constructivist exercises. In addition to the Latourian notions of enrollment and translating interests already mentioned, I have taken into the account the views of Pickering and Rouse on the character of scientific activity as a practice, in particular with regard to the realization of experimental systems and the practical engagement with raw materials, test animals and 'patient material'. In contrast to these radical constructivists, however, I see no reason to reject the notion of interests as used by the moderate constructivists on grounds of principle. In my judgement, a modest role even accrues to the professional interests of serologists and clinicians to understand and explain the development of the Wassermann reaction. Interest explanations, in my view, are perfectly compatible with the phenomenon of interest translation highlighted by Latour.

    Chapter VI is devoted to an analysis of the dispute over the intellectual ownership of the Wassermann reaction, which erupted in the aftermath of the development of this serological test - as a bitter epilogue, so to speak. It was in 1921 that August Wassermann got embroiled in a lively polemics with, among others, his former collaborator Carl Bruck and his former critic Eduard Weil over the question of who could call himself the legitimate intellectual father of the Wassermann reaction. The reason for devoting a separate chapter to what was considered at the time a rather 'unsavoury' dispute, is that it offers us a unique possibility to critically examine on the basis of historical material the much-criticized 'collectivistic' or 'anti-individualistic' stance characteristic of Fleck's approach. The conclusion of my analysis is that this 'collectivistic' feature of Fleck's sociology of knowledge made him, indeed, illequipped to adequately deal with the struggle over the intellectual ownership of the Wassermann reaction. He uncritically takes the assertions made by the protagonists during the course of this struggle as simply reflecting their views on the development of the Wassermann reaction, without taking account of the fact that these utterances were made for strategic reasons to bolster up their respective claims to the intellectual property of the serological test or to defeat the claims of others. My own account of this 'unsavoury' episode is inspired by Robert Merton's sociology of science which takes a more balanced stance on the relationship between individual and collective. For the Mertonian sociology of science, the struggle over intellectual property between (former) team members is a still unexplored theme (it has mostly concentrated on priority disputes between independent scientists). I also relax Merton's restriction on analyzing the content of scientific knowledge: the question of who has had a creative part in the making of a discovery is indissolubly bound up with the question of what exactly has been discovered. In the struggle over the Wassermann reaction participants could argue their case only by taking a stand on both questions. In this way I attempt to integrate Mertonian insights within a broadly constructivist approach. In view of the fact that Merton's sociology of science has received a barrage of criticism from constructivist quarters, the attempt may be interpreted as a plea for rehabilitation.

    Chapter VII deals with the development of an effective chemotherapeutic medicine against syphilis by Paul Ehrlich and his co-workers. Fleck's monograph contains only a few passing remarks on this development. The reason for including a chapter on this subject, apart from the fact that it constitutes an important node in the expanding conceptual network of syphilology, is that Ehrlich's work appears to be an excellent case on which to perform the kind of analysis that has become customary in more recent forms of (radical) constructivism, viz. those connected with the movement away from 'science-as-knowledge' toward 'science-as-practice'. Andrew Pickering is the most outspoken exponent of this tendency, but it is also manifest in Joseph Rouse's work and in Karin Knorr-Cetina's earlier contributions. Some aspects of Latour's work too can be brought under this heading. The crucial question of how laboratory results can be applicable, or be made applicable, to the world outside the laboratory (in other words, how the 'science' gets out of the laboratory), which he has raised to such prominence, can be fruitfully taken up in an analysis of 'scienceas-practice'. Such an analysis had already been partially attempted in Chapter V, but is conducted in a more sustained and systematic way in this chapter. The object of analysis is Paul Ehrlich's practice of 'experimental therapeutics' (or 'chemotherapy'), which modem pharmacologists often consider to be the beginnings of rational drug design. To inaugurate this practice he built up a vast 'Construction machinery' (Knorr-Cetina) by acquiring the necessary funds and material and human resources through an intimate symbiosis with the German chemical (synthetic dye) industry. In order to put these resources to productive work, he borrowed from this same industry a model of research management and division of scientific labour, which he tailored to his own needs by combining chemical work with the large-scale testing of chemical preparations on experimental animals. The secret of Ehrlich's success was in fact the combination of 'chemical mass-labour' with 'biological mass- labour' and the creation of 'experimental systems' (Rouse) through the suitable selection of test animals. Of course, Ehrlich and his collaborators had to overcome many constraints and limitations of the raw materials and test animals. The entire venture was not oriented to finding a remedy against syphilis immediately from the start; it was only during the course of the programme and through 'opportunism in context' (Pickering) that the turn to this disease occurred. Initially, Ehrlich had boasted that through his approach, using animal experiments on an extensive scale, the most 'optimal' drugs could be developed and selected so as to make the final test on man no more, as it were, than proving the sum. Things would dramatically turn out otherwise. After an effective substance had been found against syphilitically infected rabbits, the gap separating laboratory and outside world had to be bridged and this proved to be an even more exacting task than developing the medicine in the first place. A constructivist analysis inspired by the science-as-practice approach highlights the difficulties that have to be confronted when laboratory products are to find their way into the 'wider' society. In this particular case, the insufficiency of Latour's own answer to the question he raised is clearly revealed: the clinical introduction of Salvarsan involved much more than simply transplanting laboratory conditions to the outside world, it also involved the 'normalization of the object' (Knoff-Cetina), legal, social and political intervention, and continued experimentation with the medicine after its commercial introduction (the thesis of 'society as laboratory').

    Chapter VIII does not deal with a particular episode in the history of syphilology, but offers a reconstruction of the so-called 'serological thought style' which according to Fleck determined the way of thinking and acting of the serologists' collective led by Wassermann. In contrast to Fleck, contemporary constructivists generally reject, on the basis of finitist arguments, such an explanatory use of the notion of thought style. This still leaves the possibility that the term refers to an interesting phenomenon worthy of investigation as an explanandum. Fleck's descriptive characterization of the serological thought style, however, also raises questions. Following Harwood I argue that this concept can be meaningfully employed only in a comparative way. It does not make sense to speak of the thought style of a serologists' collective, if this same style cannot be recognized in other sectors than serology and if it cannot be contrasted with different styles. To carry out this comparative investigation I will draw upon the various episodes in the history of syphilology as discussed in the preceding chapters, which together cover several sectors of medical science (nosology, aetiology, serology, and therapy). The unity of Fleck's 'serological' thought style will be found in the basic idea of specificity. Viewed in this way it represents the so-called 'pluralist' style, previously analyzed by Pauline Mazumdar, which can be contrasted with the so-called 'unitarian' style. Harwood's requirements for the meaningful employment of style concepts can thus be met. Finally I show that the 'power' of the pluralist style (and of the basic idea of specificity) can be partially explained from the unprecedented power structure which the Koch-Ehrlich group had built up in German medical science in the years around 1900.

    In Chapter IV, finally, I have attempted to develop, by building on the results of the preceding chapters, a reasoned and well-considered position vis-à-vis the two big fundamental problems which continue to haunt constructivist studies of science and technology, to wit, the problem of realism and the question of how to conceive of 'the social' and the relationship between the individual and the collective. The latter problem includes the question of how to adequately conceptualize the notion of 'social practices' in general and of 'scientific practices' in particular, Moderate and radical constructivism take very different positions with regard to both fundamental problems. Radical constructivists push the construction metaphor to such extent that in their view not just plastics or genetically modified organisms but also microbes, electrons and quarks are held to be constructed by science. Latour and Woolgar's 'splitting-and-inversion' model about the genesis of facts often lies hidden behind this view. It is because of such views that radical constructivism clashes with current realist conceptions, despite the fact that radical constructivists themselves believe to have transcended the entire debate between realism and anti-realism. Among the moderate constructivists, the term 'construction' refers exclusively to the formation of knowledge about natural reality, not to that reality itself or its constituent objects. The adherents of the Strong Programme even take a stance as common-sense realists vis-à-vis reality. I think such a position is excellently defensible. It is preferable, in my opinion, to so-called 'scientific realism', which is too strongly committed to the existence of those theoretical entities which are currently accepted in science. Moreover, this variety of realism also argues rather problematically from the practical success of applications of science to the truth of the underlying theories and fails to appreciate the open-ended character of concept application as emphasized in the finitist theory.

    As regards the second fundamental problem I should declare that I do not share the hypercritical skepticism which radical constructivists display vis-à-vis 'the social'. I have attempted to rebut each of several objections which they have adduced against 'social' explanations of the content of scientific knowledge. Latour's argument, for example, to the effect that society does not provide a solid basis for such explanations because technoscientists themselves act as 'society builders', is only a half- truth, for even when acting in that capacity technoscientists act under definite, not freely chosen or fully controllable societal relationships. I also confront Rouse's criticism that moderate constructivists tend to treat the validation of knowledge-claims within self-enclosed scientific communities and the position defended by Knorr-Cetina that the validation of such claims has no need for a social locus beyond the laboratory itself. I further reject the criticism expressed by Woolgar that any attempt to demonstrate the social determination of scientific knowledge invariably involves portraying competent and knowledgeable actors as mere puppets or 'cultural dopes'. I admit, however, that it is very difficult to strike a proper balance between the spontaneity and agency of individual actors, on the one hand, and the effects of social structures ('constraints'), on the other hand. It would therefore be very welcome to have a theory which is able to do justice to both aspects. That is why I finally examine Anthony Giddens's 'structuration theory' to see whether it fulfils these desiderata. In the end it appears that the modification of Giddens's theory proposed by William Sewell may be reasonably satisfactory. Whereas Giddens views social structure as a virtual order consisting of a set of rules and resources that is reproduced in concrete practices, Sewell reformulates the duality of structure as a duality of virtual elements, namely rules or cultural schemas, and actual elements, namely resources. The deployment of (material and human) resources is informed by cultural schemas; conversely, in order to be reproduced the latter must actually be used in the accumulation of resources. Within this framework the 'agency' of individuals is conceived as empowerment through access to resources and the competence to apply existing cultural schemas to new contexts. Sewell's emphasis on the transposability of cultural schemas to new situations exhibits similarity to the finitist view. He also conceives of 'agency' as thoroughly social. Finally I argue that his conceptualization of the notion of social practices is able to incorporate the valuable elements in Pickering's 'science-as-practice' approach and Rouse's 'practical hermeneutics' without taking the dubious 'posthumanist' and 'anti-social' tenor of the latter approaches also on board.

    The Tapetum: cytology, function, biochemistry and evolution
    Hesse, M. ; Pacini, E. ; Willemse, M.T.M. - \ 1993
    Berlin : Springer Verlag - ISBN 9783211824863 - 152
    biochemie - embryozak - metabolisme - stuifmeel - polymeren - sporen - celfysiologie - biochemistry - embryo sac - metabolism - pollen - polymers - spores - cell physiology
    The anther tapetum, present in all land plants, is a highly specialized, transient tissue surrounding the (micro-)spores and/or pollen grains during their development.Any tapetum malfunction causes male sterility. The exact knowledge of tapetum form and function therefore is indispensable not only for basic research, but also and especially in plant breeding and plant genetics.In fourteen contributions by reknown experts, a comprehensive account of the various characters and functions of the tapetum is provided, covering the areas of cytology, cytophysiology, biochemistry, tapetum development and function.
    Mutagenicity of food pellets from human diets in The Netherlands.
    Alink, G.M. ; Knize, M.G. ; Shen, N.H. ; Hesse, S.P. ; Felton, J.S. - \ 1988
    Mutation Research. Fundamental and Molecular Mechanisms of Mutagenesis 206 (1988). - ISSN 0027-5107 - p. 387 - 393.
    Isolatie en identificatie van een antimutagene component in sla.
    Lagerweij, W.J. ; Hesse, S.P. ; Jongen, W.M.F. ; Posthumus, M.A. ; Veldhuizen, A. van - \ 1986
    Voeding 47 (1986). - ISSN 0042-7926 - p. 233 - 233.
    A chemotaxonomic investigation of the plant families of Apocynaceae, Loganiaceae, and Rubiaceae by their indole alkaloid content
    Kisakurek, M.V. ; Leeuwenberg, A.J.M. ; Hesse, M. - \ 1983
    In: Alkaloids: chemical and biological perspectives - p. 211 - 376.
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