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Appetite Control in C. elegans
Published in Ruth B.S. Harris, Appetite and Food Intake, 2017
Kristen Davis, Mi Cheong Cheong, Ji Su Park, Young-Jai You
In addition to conserved behavior and mechanisms, the simplicity of the nervous system of C. elegans makes it a great model to study neuronal mechanisms of appetite control. C. elegans has only 302 neurons (in a hermaphrodite), each of which is identifiable through differential interference contrast microscopy. The function of each neuron can be studied by selective ablation of that neuron by laser (Bargmann and Avery 1995). In addition, it is the only organism whose entire neural network is mapped by electron microscopy reconstruction, which allows researchers to decode the circuits for simple behaviors such as backward and forward movement as well as for complex learning behaviors such as chemotaxis and thermotaxis (Bargmann 2006, Mori et al. 2007, Zhen and Samuel 2015).
The Journey of the Porcine Spermatozoa from Its Origin to the Fertilization Site: The Road In Vivo vs. In Vitro
Published in Juan Carlos Gardón, Katy Satué, Biotechnologies Applied to Animal Reproduction, 2020
Cristina Soriano-Úbeda, Francisco Alberto García-Vázquez, Carmen Matás
The most used systems for IVF in porcine have been 4-well dishes and microdrops, but with the objective to mimic the strict spermatozoa selection process that takes place in the female genital tract and to allow the establishment of competition between spermatozoa, several methods and devices have been developed: IVF by climbing-over-a-wall (Funahashi and Nagai, 2000; Soriano-Úbeda et al., 2017), using biomimetic microfluidic technology (Clark et al., 2005), IVF in straws (Li et al., 2003), applying modified swim-up for spermatozoa selection (Park et al., 2009), using a microfluidic spermatozoa sorter (Sano et al., 2010) or 3-D OECs culture systems for IVF and embryo production (reviewed by Ferraz et al., 2017). Most of these methods reduce the number of spermatozoa that contact the oocytes, allowing a certain selection of spermatozoa population and expression of their heterogeneity in terms of motility, capacitation state and fertility. Many of them can include biofluids that can be replaced over time to mimic the dynamic oviductal environment in terms of composition of proteins, hormones and other molecules, and they even have different compartments for male and female gametes and/or OECs. Normally, there are methods or devices in which gametes, female and male, are physically distant from each other and spermatozoa must cross an artificial obstacle to reach the oocytes, more similar to the situation in vivo. However, none of them has managed to eliminate the problem of polyspermy under in vitro conditions in the pig. Many studies are currently underway to develop new devices in which spermatozoa are guided to the oocytes through the so-called ‘taxis’: chemo-, rheo- and thermotaxis. In each one of them, spermatozoa are attracted by a different stimulus gradient: chemical, fluid flow or temperature, respectively (revised by Pérez-Cerezales et al., 2015).
Temperature signaling underlying thermotaxis and cold tolerance in Caenorhabditis elegans
Published in Journal of Neurogenetics, 2020
Asuka Takeishi, Natsune Takagaki, Atsushi Kuhara
Among various environmental cues, temperature is an unavoidable stimulus which animals are constantly exposed to. Each animal has an acceptable environmental temperature range that matches their living conditions. For instance, parasitic worms prefer hosts’ body temperature, such as the human parasite A. ceylanicum which prefers around 38 °C (Bryant et al., 2018), and some species have a tolerance for extreme temperature, such as Diamesa kohshimai that lives at the North Pole and survives even at 16°C (Kohshima, 1984). The environmental temperature is particularly important for ectotherms as it largely regulates their body temperature as well as affects all internal biochemical reactions. Animals thus have evolved behavioral strategies to seek an appropriate environmental temperature. Thermotaxis is the initial behavior choice for most animals to relocate themselves to the appropriate temperature circumstances when they encounter an unpreferable temperature environment. Species-specific thermotaxis mechanisms have been described (Garrity, Goodman, Samuel, & Sengupta, 2010; Glauser & Goodman, 2016; Hoffstaetter, Bagriantsev, & Gracheva, 2018); however, the mechanism of thermosensation and signal transduction in the neural network is not fully understood.