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      Strongyloides ratti and S. venezuelensis – rodent models of Strongyloides infection


      1 , * , 2


      Cambridge University Press

      Strongyloides, rats, rodent

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          Strongyloides spp. are common parasites of vertebrates and two species, S. ratti and S. venezuelensis, parasitize rats; there are no known species that naturally infect mice. Strongyloides ratti and S. venezuelensis overlap in their geographical range and in these regions co-infections appear to be common. These species have been widely used as tractable laboratory systems in rats as well as mice. The core biology of these two species is similar, but there are clear differences in aspects of their within-host biology as well as in their free-living generation. Phylogenetic evidence suggests that S. ratti and S. venezuelensis are the result of two independent evolutionary transitions to parasitism of rats, which therefore presents an ideal opportunity to begin to investigate the basis of host specificity in Strongyloides spp.

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          Most cited references 84

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          Control of C. elegans larval development by neuronal expression of a TGF-beta homolog.

          The Caenorhabditis elegans dauer larva is specialized for dispersal without growth and is formed under conditions of overcrowding and limited food. The daf-7 gene, required for transducing environmental cues that support continuous development with plentiful food, encodes a transforming growth factor-beta (TGF-beta) superfamily member. A daf-7 reporter construct is expressed in the ASI chemosensory neurons. Dauer-inducing pheromone inhibits daf-7 expression and promotes dauer formation, whereas food reactivates daf-7 expression and promotes recovery from the dauer state. When the food/pheromone ratio is high, the level of daf-7 mRNA peaks during the L1 larval stage, when commitment to non-dauer development is made.
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            An elegant mind: learning and memory in Caenorhabditis elegans.

            This article reviews the literature on learning and memory in the soil-dwelling nematode Caenorhabditis elegans. Paradigms include nonassociative learning, associative learning, and imprinting, as worms have been shown to habituate to mechanical and chemical stimuli, as well as learn the smells, tastes, temperatures, and oxygen levels that predict aversive chemicals or the presence or absence of food. In each case, the neural circuit underlying the behavior has been at least partially described, and forward and reverse genetics are being used to elucidate the underlying cellular and molecular mechanisms. Several genes have been identified with no known role other than mediating behavior plasticity.
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              Identification of tgh-2, a filarial nematode homolog of Caenorhabditis elegans daf-7 and human transforming growth factor beta, expressed in microfilarial and adult stages of Brugia malayi.

              A novel member of the transforming growth factor beta (TGF-beta) family has been identified in the filarial nematode parasite Brugia malayi by searching the recently developed Expressed Sequence Tag (EST) database produced by the Filarial Genome Project. Designated tgh-2, this new gene shows most similarity to a key product regulating dauer larva formation in Caenorhabditis elegans (DAF-7) and to the human down-modulatory cytokine TGF-beta. Homology to DAF-7 extends throughout the length of the 349-amino-acid (aa) protein, which is divided into an N-terminal 237 aa, including a putative signal sequence, a 4-aa basic cleavage site, and a 108-aa C-terminal active domain. Similarity to human TGF-beta is restricted to the C-terminal domain, over which there is a 32% identity between TGH-2 and TGF-beta1, including every cysteine residue. Expression of tgh-2 mRNA has been measured over the filarial life cycle. It is maximal in the microfilarial stage, with lower levels of activity around the time of molting within the mammal, but continues to be expressed by mature adult male and female parasites. Expression in both the microfilaria, which is in a state of arrested development, and the adult, which is terminally differentiated, indicates that tgh-2 may play a role other than purely developmental. This is consistent with our observation that TGH-2 is secreted by adult worms in vitro. Recombinant TGH-2 expressed in baculovirus shows a low level of binding to TGF-beta-receptor bearing mink lung epithelial cells (MELCs), which is partially inhibited (16 to 39%) with human TGF-beta, and activates plasminogen activator inhibitor-1 transcription in MELCs, a marker for TGF-beta-mediated transduction. Further tests will be required to establish whether the major role of B. malayi TGH-2 (Bm-TGH-2) is to modulate the host immune response via the TGF-beta pathway.

                Author and article information

                Cambridge University Press (Cambridge, UK )
                March 2017
                03 March 2016
                : 144
                : 3 , Strongyloides
                : 285-294
                [1 ]School of Biological Sciences, University of Bristol , Bristol BS8 1TQ, UK
                [2 ]Division of Parasitology, Faculty of Medicine, University of Miyazaki , Miyazaki, Japan
                Author notes
                [* ]Corresponding author: School of Biological Sciences, University of Bristol , Bristol BS8 1TQ, UK. E-mail: Mark.Viney@ 123456bristol.ac.uk
                S0031182016000020 00002
                © Cambridge University Press 2016

                This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                References: 84, Pages: 10
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                strongyloides, rats, rodent


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