The present immunocytochemical study concerns the distribution of four neuropeptides, FMRF-amide, vasotocin, leu-enkephalin and neurotensin, and of the bioamine serotonin in the plerocercoid larva of Diphyllobothrium dendriticum. Anti-FMRF-amide and vasotocin-reactivity occurs in perikarya and nerve fibres in the CNS and PNS of this worm. The peptide-containing fibres surround and seem to innervate the musculature and to terminate beneath the basal lamina of the tegument at the inner surface of the bothridia, suggesting a neurotransmitter function. Anti-leu-enkephalin reaction occurs in perikarya and fibres in the main nerve cords and in the PNS. Anti-neurotensin reactive fibres were observed in the neuropile of the nerve cords. Serotonin immunoreactivity was found in neurons in the ganglionic commissure of the brain and along the main nerve cords. This study is the first immunocytochemical identification of neuropeptides and serotonin in a parasitic flatworm and the information gained may be of importance for the development of new antihelminthics.

PurposeThe philosophical position known as critical realism is briefly introduced, and some of its central features are used to connect the philosophy and the realist social theory to some current library and information science (LIS) models of information behaviour.Design/methodology/approachThe paper uses a literature‐based analysis of the critical realism concepts of a stratified social reality, the importance of contextualisation, and the relation between structure and agency. These features are discussed in relation to various models of information‐seeking behaviour, but also to the “interpretative” approach to information as meaning which can only be achieved through discourses in a human community.FindingsThe critical realism perspective could lay a fruitful foundation for an interdisciplinary research field like LIS, and its user studies in particular, concerned with many levels of information creation, seeking, use and processing. It is the task of the LIS researcher to explain the mechanisms that influence the information seeking, not only on an empirical level, by observing the user and his/her discourse community, but also by revealing possible underlying causes and relations.Originality/valueAn awareness of the fact that social and cultural structures exist independent of one's knowledge of them has implications on how many central problems in the LIS field are regarded and studied.

Internet health discussion groups form virtual communities, where people look for both health information and emotional support as a part of an everyday life information-seeking practice. This study reports the information-oriented behaviour of participants discussing general health issues like healthy food, diets and dietary supplements, in support groups for overweight persons, diabetics and vegetarians. The study analyses how the participants refer to health information sources, in order to acquire, disseminate and exchange information within the group, and how this information is assessed by other members of the virtual community. In this analysis of the content and the context of citations and references in 30 newsgroup discussion threads, focusing on health and nutrition, the sources referred to are categorized and discussed. The results show that over 80% of all citations refer to Web sources and that nearly 60% of all citations refer to sources with a scientific medical content. Other sources are diet books, alternative health sites and Web health portals. The citation behaviour and the use of information suggest normative information (citation) behaviour in these information-rich virtual cultures.

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The nervous systems of the turbellarians Microstomum lineare and Polycelis nigra and of the cestodes Diphyllobothrium dendriticum and Schistocephalus solidus were studied by means of the peroxidaseantiperoxidase (PAP) immunocytochemical method, with the use of antisera to the neuropeptides FMRFamide, vasotocin, leu-enkephalin, met-enkephalin, neurotensin, somatostatin, and VIP, and to the bioamine serotonin. Anti-FMRF-amide positive perikarya and fibers occurred in all species, while the occurrence of the vertebrate brain-gut peptides and serotonin varied between the species . Anti-somatostatin and anti-VIP gave a negative result . Anti-FMRF-amide and anti-vasotocin positive immunoreactivity was found in the brain and gut of M. lineare, and in the CNS and the peripheral nerve net of the cestodes . We suggest that the brain-gut peptides of free-living flatworms act on the subtegumental region in the cestodes, which lack a gut but absorb their nutrients directly through the tegument .