Browsing by Author "Adams, Michelle"
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Item Open Access The optomotor response of aging zebrafish reveals a complex relationship between visual motion characteristics and cholinergic system(Elsevier, 2020-10-23) Karaduman, Ayşenur; Karoğlu-Eravşar, Elif Tuğçe; Kaya, Utku; Aydın, Alaz; Adams, Michelle; Kafalıgönül, HulusiUnderstanding the principles underlying age-related changes in motion perception is paramount for improving the quality of life and health of older adults. However, the mechanisms underlying age-related alterations in this aspect of vision, which is essential for survival in a dynamic world, still remain unclear. Using optomotor responses to drifting gratings, we investigated age-related changes in motion detection of adult zebrafish (wild-type/AB-strain and achesb55/+ mutants with decreased levels of acetylcholinesterase). Our results pointed out negative optomotor responses that significantly depend on the spatial frequency and contrast level of stimulation, providing supporting evidence for the visual motion-driven aspect of this behavior mainly exhibited by adult zebrafish. Although there were no significant main effects of age and genotype, we found a significant three-way interaction between contrast level, age, and genotype. In the contrast domain, the changes in optomotor responses and thus in the detection of motion direction were age- and genotype-specific. Accordingly, these behavioral findings suggest a strong but complicated relationship between visual motion characteristics and the cholinergic system during neural aging.Item Open Access Short-term dietary restriction maintains synaptic plasticity whereas short-term overfeeding alters cellular dynamics in the aged brain: evidence from the zebrafish model organism(Elsevier, 2021-06-19) Karoğlu-Eravşar, Elif Tuğçe; Tüz Şaşik, Melek Umay; Adams, MichelleIncreased caloric intake (OF) impairs quality of life causing comorbidities with other diseases and cognitive deficits, whereas dietary restriction (DR) increases healthspan by preventing age-related deteriorations. To understand the effects of these opposing dietary regimens on the cellular and synaptic dynamics during brain aging, the zebrafish model, which shows gradual aging like mammals, was utilized. Global changes in cellular and synaptic markers with respect to age and a 12 week dietary regimen of OF and DR demonstrated that aging reduces the levels of the glutamate receptor subunits, GLUR2/3, inhibitory synaptic clustering protein, GEP, synaptic vesicle protein, SYP, and early-differentiated neuronal marker, HuC. DR significantly elevates levels of glutamate receptor subunits, GLUR2/3, and NMDA clustering protein, PSD95, levels, while OF subtly increases the level of the neuronal protein, DCAMKL1. These data suggest that decreased caloric intake within the context of aging has more robust effects on synapses than cellular proteins, whereas OF alters cellular dynamics. Thus, patterns like these should be taken into account for possible translation to human subjects.Item Open Access TERT distal promoter GC islands are critical for telomerase and together with DNMT3B silencing may serve as a senescence-inducing agent in gliomas(Taylor & Francis Inc., 2022-08-23) Şerifoğlu, Naz; Adams, Michelle; Erbaba, Begün; Arslan-Ergül, AyçaTelomerase is reactivated in the majority of cancers. For instance, in gliomas, it is common that the TERT promoter is mutated. Research on telomere promoter GC islands have been focused primarily on proximal TERT promoter but little is known about the distal promoter. Therefore, in this study, we investigated the proximal and distal TERT promoter, in terms of DNA methylation. We did bisulfite sequencing in zebrafish tissue samples for the distal tert promoter. In the zebrafish brain tissues, we identified a hypomethylation site in the tert promoter, and found that this hypomethylation was associated with aging and shortened telomeres. Through site directed mutagenesis in glioma cell lines, we changed 10 GC spots individually, cloned into a reporter vector, and measured promoter activity. Finally, we silenced DNMT3B and measured telomerase activity along with vidaza and adriamycin treatments. Site directed mutagenesis of glioma cell lines revealed that each of the 10 GC spots are critical for telomerase activity. Changing GC to AT abolished promoter activity in all spots when transfected into glioma cell lines. Then, through silencing of DNMT3B, we observed a reduction in hTERT expression levels, while hTR remained the same, and a major increase in senescence-associated beta-galactosidase activity. Finally, we propose a model regarding the efficacy of two chemotherapeutic drugs, adriamycin and azacytidine, on gliomas. Here, we show that distal TERT promoter is critical; changing even one GC to AT abolishes TERT promoter activity. DNMT3B, a de novo methyltransferase, together with GC islands in distal TERT promoter plays an important role in regulation of telomerase expression and senescence.Item Open Access Zebrafish aging models and possible interventions(InTechOpen Press, 2018) Birand, Dilan Ç.; Erbaba, Begün; Özdemir, Ahmet T.; Kafalıgönül, Hulusi; Adams, Michelle; Bozkurt, Y.Across the world, the aging population is expanding due to an increasing average life expectancy. The percentage of elderly over the age of 65 is expected to be more than 15% of the total world population by 2025. As the lifespan increases, there will be a need for maintaining a healthy state for these individuals. Our current knowledge on types and durations of potential anti-aging therapies is quite limited. Recently the zebrafish has emerged as a promising model for understanding the cognitive and neurobiological changes during aging, as well as its use with potential anti-aging interventions. Like humans this model organism ages gradually, displays similar behavioral properties and social characteristics, and in addition, there is a wealth of molecular and genetic tools to uncover the cellular mechanism that contribute to age-related cognitive declines. Drug effect and toxicity can be easily tested in the zebrafish. Therefore, this animal model can provide information about potential therapies that could be translated directly into human populations or provide a more focused treatment direction for testing in other mammalian animal models. The zebrafish will be a powerful tool for uncovering the mysteries of the aging brain.