Post-embryonic cell lineages of the nematode, Caenorhabditis elegans

Research on framing is characterized by theoretical and empirical vagueness. This is due, in part, to the lack of a commonly shared theoretical model underlying framing research. Conceptual problems translate into operational problems, limiting the comparability of instruments and results. In this paper I systematize the fragmented approaches to framing in political communication and integrate them into a comprehensive model. I classify previous approaches to framing research along two dimensions: the type of frame examined (media frames vs. audience frames) and the way frames are operationalized (independent variable or dependent variable). I develop a process model of framing, identifying four key processes that should be addressed in future research: frame building, frame setting, individual-level processes of framing, and a feedback loop from audiences to journalists.

/pdf/framing-as-a-theory-of-media-effects-2r7ssng9hs.pdf

Framing as a theory of media effects

A comprehensive literature review identifies 1415 species of infectious organism known to be pathogenic to humans, including 217 viruses and prions, 538 bacteria and rickettsia, 307 fungi, 66 protozoa and 287 helminths. Out of these, 868 (61%) are zoonotic, that is, they can be transmitted between humans and animals, and 175 pathogenic species are associated with diseases considered to be 'emerging'. We test the hypothesis that zoonotic pathogens are more likely to be associated with emerging diseases than non-emerging ones. Out of the emerging pathogens, 132 (75%) are zoonotic, and overall, zoonotic pathogens are twice as likely to be associated with emerging diseases than non-zoonotic pathogens. However, the result varies among taxa, with protozoa and viruses particularly likely to emerge, and helminths particularly unlikely to do so, irrespective of their zoonotic status. No association between transmission route and emergence was found. This study represents the first quantitative analysis identifying risk factors for human disease emergence.

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Risk factors for human disease emergence.

Nematodes are important: parasitic nematodes threaten the health of plants, animals and humans on a global scale; interstitial nematodes pervade sediment and soil ecosystems in overwhelming numbers; and Caenorhabditis elegans is a favourite experimental model system. A lack of clearly homologous characters and the absence of an informative fossil record have prevented us from deriving a consistent evolutionary framework for the phylum. Here we present a phylogenetic analysis, using 53 small subunit ribosomal DNA sequences from a wide range of nematodes. With this analysis, we can compare animal-parasitic, plant-parasitic and free-living taxa using a common measurement. Our results indicate that convergent morphological evolution may be extensive and that present higher-level classification of the Nematoda will need revision. We identify five major clades within the phylum, all of which include parasitic species. We suggest that animal parasitism arose independently at least four times, and plant parasitism three times. We clarify the relationship of C. elegans to major parasitic groups; this will allow more effective exploitation of our genetic and biological knowledge of this model species.

A molecular evolutionary framework for the phylum Nematoda

The increasing popularity of the framing concept in media analysis goes hand in hand with significant inconsistency in its application. This paper outlines an integrated process model of framing that includes production, content, and media use perspectives. A typology of generic and issue-specific frames is proposed based on previous studies of media frames. An example is given of how generic news frames may be identified and used to understand cross-national differences in news coverage. The paper concludes with an identification of contentious issues in current framing research.

News framing: Theory and typology

Concepts in Nematode Systematics

The author reviews the relationship of meningeal worm (Parelapostrongylus tenuis) and its usual host, the white-tailed deer (Odocoileus virginianus). Important alterations in the environment in the past 100 years have greatly expanded the northern range of white-tailed deer and brought host and parasite into contact with other native cervids such as moose (Alces americana), mule deer (Odocoileus hemionus), and woodland caribou (Rangfier tarandus) in which meningeal worm is highly pathogenic. There is evidence the parasite is spreading westward with deer in the aspen-parklands of Canada. Meningeal worm can apparently have considerable impact on moose populations in endemic areas. Possibly the existence of clinical disease in moose in an area should be regarded as evidence of a much more widespread disease problem which may have eventually a serious impact on the population.

https://bioone.org/journals/journal-of-wildlife-diseases/volume-8/issue-4/0090-3558-8.4.304/THE-ECOLOGICAL-RELATIONSHIPS-OF-MENINGEAL-WORM-AND-NATIVE-CERVIDS-IN/10.7589/0090-3558-8.4.304.pdf

The ecological relationships of meningeal worm and native cervids in north america

Zooparasitic nematodes are derived from soil nematodes and parasitism apparently originated only after land animals appeared. A major line from soil dwelling rhabditids gave rise to the secernentea...

The origins of zooparasitic nematodes

Pneumostrongylus tenuis was found throughout the year in the cranium of 41% of 172 adult deer examined in Algonquin Park. Incidence was higher in summer (46%) than winter (24%). Two fawns were infected (October and March). Worms also occurred on the spinal dura mater and in veins of the dura. Thus, incidence of infection was higher than indicated by examinations of craniums. Larvae developed in species of Discus, Zonitoides, Deroceras, Triodopsis, Stenotrema, and Lymnea sp. Four fawns were infected experimentally. Fourth- and fifth-stage larvae were found in the brain and spinal cord of one fawn examined at 25 days. Fifth stages were found in the tissue and between the meninges of the spinal cord of a fawn examined at 40 days. Subadults were found on the spinal and cerebral dura mater of a fawn autopsied at 50 days. The final fawn passed larvae 91 days after exposure. At 115 days after exposure, mature worms were found on or in the cerebral dura; two were found in the intercavernous sinus. The inflamed du...

The incidence, development, and experimental transmission of pneumostrongylus tenuis dougherty (metastrongyloidea: protostrongylidae) of the meninges of the white-tailed deer (odocoileus virginianus borealis) in ontario

From May to October, 1966, gastropods from three different habitats on Navy Island, Ontario, were examined for larvae of Pneumostrongylus tenuis. Of 9940 examined individually, 4.2% contained larvae. A mean of 2.9 larvae was recovered from each infected gastropod. Deroceras laeve and Zonitoides nitidas were the most abundant and commonly infected species. The incidence of infective larvae in adult D. laeve from a wet forested area rose to 25% by late June but dropped to 1.5% during July, coinciding with the disappearance of adult slugs. The level of infection in Z. nitidus (4.3%) remained relatively constant. The wet forested habitat where gastropods were abundant, commonly infected, and active from May to October was probably most important for transmission. Experiments showed that snails already containing larvae can be reinfected and there is some evidence that they are repeatedly infected in nature. Larval development was retarded in aestivating snails. Numbers of larvae recovered and their rate of de...

Roy C. Anderson

Papers

Concepts in Nematode Systematics

The ecological relationships of meningeal worm and native cervids in north america

The origins of zooparasitic nematodes

The incidence, development, and experimental transmission of pneumostrongylus tenuis dougherty (metastrongyloidea: protostrongylidae) of the meninges of the white-tailed deer (odocoileus virginianus borealis) in ontario

Gastropods as intermediate hosts of Pneumostrongylus tenuis Dougherty of white-tailed deer