Kovalchuk, Olga

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https://opus.uleth.ca/handle/10133/4539

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Browsing Kovalchuk, Olga by Author "Ghose, Abhijit"

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    Liver irradiation causes distal bystander effects in the rat brain and affects animal behavior
    (Impact Journals, 2016) Kovalchuk, Anna; Mychasiuk, Richelle; Muhammad, Arif; Hossain, Shakhawat; Ilnytskyy, Slava; Ghose, Abhijit; Kirby, Charles; Ghasroddashti3, Esmaeel; Kovalchuk, Olga; Kolb, Bryan
    Radiation therapy can not only produce effects on targeted organs, but can also influence shielded bystander organs, such as the brain in targeted liver irradiation. The brain is sensitive to radiation exposure, and irradiation causes significant neurocognitive deficits, including deficits in attention, concentration, memory, and executive and visuospatial functions. The mechanisms of their occurrence are not understood, although they may be related to the bystander effects. We analyzed the induction, mechanisms, and behavioural repercussions of bystander effects in the brain upon liver irradiation in a well-established rat model. Here, we show for the first time that bystander effects occur in the prefrontal cortex and hippocampus regions upon liver irradiation, where they manifest as altered gene expression and somewhat increased levels of fH2AX. We also report that bystander effects in the brain are associated with neuroanatomical and behavioural changes, and are more pronounced in females than in males.
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    Profound and sexually dimorphic effects of clinically-relevant low dose scatter irradiation on the brain and behavior
    (Frontiers Media, 2016) Kovalchuk, Anna; Mychasiuk, Richelle; Muhammad, Arif; Hossain, Shakhawat; Ilnytskyy, Yaroslav; Ghose, Abhijit; Kirkby, Charles; Ghasroddashti, Esmaeel; Kolb, Bryan; Kovalchuk, Olga
    Irradiated cells can signal damage and distress to both close and distant neighbors that have not been directly exposed to the radiation (naïve bystanders). While studies have shown that such bystander effects occur in the shielded brain of animals upon body irradiation, their mechanism remains unexplored. Observed effects may be caused by some blood-borne factors; however they may also be explained, at least in part, by very small direct doses received by the brain that result from scatter or leakage. In order to establish the roles of low doses of scatter irradiation in the brain response, we developed a new model for scatter irradiation analysis whereby one rat was irradiated directly at the liver and the second rat was placed adjacent to the first and received a scatter dose to its body and brain. This work focuses specifically on the response of the latter rat brain to the low scatter irradiation dose. Here, we provide the first experimental evidence that very low, clinically relevant doses of scatter irradiation alter gene expression, induce changes in dendritic morphology, and lead to behavioral deficits in exposed animals. The results showed that exposure to radiation doses as low as 0.115 cGy caused changes in gene expression and reduced spine density, dendritic complexity, and dendritic length in the prefrontal cortex tissues of females, but not males. In the hippocampus, radiation altered neuroanatomical organization in males, but not in females. Moreover, low dose radiation caused behavioral deficits in the exposed animals. This is the first study to show that low dose scatter irradiation influences the brain and behavior in a sex-specific way.