Iwaniuk, Andrew

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https://opus.uleth.ca/handle/10133/4634

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Browsing Iwaniuk, Andrew by Subject "Cerebellum"

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    The cerebellar anatomy of red junglefowl and white leghorn chickens: insights into the effects of domestication on the cerebellum
    (Royal Society, 2021) Racicot, Kelsey J.; Popic, Christina; Cunha, Felipe; Wright, Dominic; Henriksen, Christina; Iwaniuk, Andrew N.
    Domestication is the process by which wild organisms become adapted for human use. Many phenotypic changes are associated with animal domestication, including decreases in brain and brain region sizes. In contrast with this general pattern, the chicken has a larger cerebellum compared with the wild red junglefowl, but what neuroanatomical changes are responsible for this difference have yet to be investigated. Here, we quantified cell layer volumes, neuron numbers and neuron sizes in the cerebella of chickens and junglefowl. Chickens have larger, more folded cerebella with more and larger granule cells than junglefowl, but neuron numbers and cerebellar folding were proportional to cerebellum size. However, chickens do have relatively larger granule cell layer volumes and relatively larger granule cells than junglefowl. Thus, the chicken cerebellum can be considered a scaled-up version of the junglefowl cerebellum, but with enlarged granule cells. The combination of scaling neuron number and disproportionate enlargement of cell bodies partially supports a recent theory that domestication does not affect neuronal density within brain regions. Whether the neuroanatomical changes we observed are typical of domestication or not requires similar quantitative analyses in other domesticated species and across multiple brain regions.
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    Zebrin II / Aldolase C expression in the cerebellum of the western diamondback rattlesnake (Crotalus atrox)
    (Public Library of Science, 2015) Aspden, Joel W.; Armstrong, Carol L.; Gutierrez-Ibanez, Cristian I.; Hawkes, Richard; Iwaniuk, Andrew N.; Kohl, Tobias; Graham, David J.; Wylie, Douglas R.
    Aldolase C, also known as Zebrin II (ZII), is a glycolytic enzyme that is expressed in cerebellar Purkinje cells of the vertebrate cerebellum. In both mammals and birds, ZII is expressed heterogeneously, such that there are sagittal stripes of Purkinje cells with high ZII expression (ZII+), alternating with stripes of Purkinje cells with little or no expression (ZII-). The patterns of ZII+ and ZII- stripes in the cerebellum of birds and mammals are strikingly similar, suggesting that it may have first evolved in the stem reptiles. In this study, we examined the expression of ZII in the cerebellum of the western diamondback rattlesnake (Crotalus atrox). In contrast to birds and mammals, the cerebellum of the rattlesnake is much smaller and simpler, consisting of a small, unfoliated dome of cells. A pattern of alternating ZII+ and ZII- sagittal stripes cells was not observed: rather all Purkinje cells were ZII+. This suggests that ZII stripes have either been lost in snakes or that they evolved convergently in birds and mammals.