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- Iriondo, A., et al.
(författare)
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Cerebrospinal Fluid 7-Ketocholesterol Level is Associated with Amyloid-beta(42) and White Matter Microstructure in Cognitively Healthy Adults
- 2020
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Ingår i: Journal of Alzheimers Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 76:2, s. 643-656
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Tidskriftsartikel (refereegranskat)abstract
- Background: Abnormal cholesterol metabolism changes the neuronal membrane and may promote amyloidogenesis. Oxysterols in cerebrospinal fluid (CSF) are related to Alzheimer's disease (AD) biomarkers in mild cognitive impairment and dementia. Cholesterol turnover is important for axonal and white matter (WM) microstructure maintenance. Objective: We aim to demonstrate that the association of oxysterols, AD biomarkers, and WM microstructure occurs early in asymptomatic individuals. Methods: We studied the association of inter-individual variability of CSF 24-hydroxycholesterol (24-OHC), 27-hydroxycholesterol (27-OHC), 7-ketocholesterol (7-KC), 7 beta-hydroxycholesterol (7 beta-OHC), amyloid-beta(42) (A beta(42)), total-tau (t-tau), phosphorylated-tau (p-tau), neurofilament (NfL), and WM microstructure using diffusion tensor imaging, generalized linear models and moderation/mediation analyses in 153 healthy adults. Results: Higher 7-KC levels were related to lower A beta(42), indicative of greater AD pathology (p = 0.041). Higher 7-KC levels were related to lower fractional anisotropy (FA) and higher mean (MD), axial (AxD), and radial (RD) diffusivity. 7-KC modulated the association between AxD and NfL in the corpus callosum splenium (B = 39.39, p = 0.017), genu (B = 68.64, p = 0.000), and fornix (B = 10.97, p = 0.000). Lower A beta(42) levels were associated to lower FA and higher MD, AxD, and RD in the fornix, corpus callosum, inferior longitudinal fasciculus, and hippocampus. The association between AxD and A beta(42) was moderated by 7K-C (p = 0.048). Conclusion: This study adds clinical evidence to support the role of 7K-C on axonal integrity and the involvement of cholesterol metabolism in the A beta(42) generation process.
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| 3. |
- Saldías, M., et al.
(författare)
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The Vocal Tract in Loud Twang-Like Singing While Producing High and Low Pitches
- 2021
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Ingår i: Journal of Voice. - : Elsevier BV. - 0892-1997 .- 1873-4588. ; 35:5, s. 807.e1-807.e23
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Tidskriftsartikel (refereegranskat)abstract
- Twang-like vocal qualities have been related to a megaphone-like shape of the vocal tract (epilaryngeal tube and pharyngeal narrowing, and a wider mouth opening), low-frequency spectral changes, and tighter and/or increased vocal fold adduction. Previous studies have focused mainly on loud and high-pitched singing, comfortable low-pitched spoken vowels, or are based on modeling and simulation. There is no data available related to twang-like voices in loud, low-pitched singing. Purpose: This study investigates the possible contribution of the lower and upper vocal tract configurations during loud twang-like singing on high and low pitches in a real subject. Methods: One male contemporary commercial music singer produced a sustained vowel [a:] in his habitual speaking pitch (B2) and loudness. The same vowel was also produced in a loud twang-like singing voice on high (G4) and low pitches (B2). Computerized tomography, acoustic analysis, inverse filtering, and audio-perceptual assessments were performed. Results: Both loud twang-like voices showed a megaphone-like shape of the vocal tract, being more notable on the low pitch. Also, low-frequency spectral changes, a peak of sound energy around 3 kHz and increased vocal fold adduction were found. Results agreed with audio-perceptual evaluation. Conclusions: Loud twang-like phonation seems to be mainly related to low-frequency spectral changes (under 2 kHz) and a more compact formant structure. Twang-like qualities seem to require different degrees of twang-related vocal tract adjustments while phonating in different pitches. A wider mouth opening, pharyngeal constriction, and epilaryngeal tube narrowing may be helpful strategies for maximum power transfer and improved vocal economy in loud contemporary commercial music singing and potentially in loud speech. Further studies should focus on vocal efficiency and vocal economy measurements using modeling and simulation, based on real-singers’ data.
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