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Biomarkers of neuronal damage in saturation diving-a controlled observational study.
Rosén, A, Gennser, M, Oscarsson, N, Kvarnström, A, Sandström, G, Blennow, K, Seeman-Lodding, H, Zetterberg, H
European journal of applied physiology. 2020;(12):2773-2784
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PURPOSE A prospective and controlled observational study was performed to determine if the central nervous system injury markers glial fibrillary acidic protein (GFAp), neurofilament light (NfL) and tau concentrations changed in response to a saturation dive. METHODS The intervention group consisted of 14 submariners compressed to 401 kPa in a dry hyperbaric chamber. They remained pressurized for 36 h and were then decompressed over 70 h. A control group of 12 individuals was used. Blood samples were obtained from both groups before, during and after hyperbaric exposure, and from the intervention group after a further 25-26 h. RESULTS There were no statistically significant changes in the concentrations of GFAp, NfL and tau in the intervention group. During hyperbaric exposure, GFAp decreased in the control group (mean/median - 15.1/ - 8.9 pg·mL-1, p < 0.01) and there was a significant difference in absolute change of GFAp and NfL between the groups (17.7 pg·mL-1, p = 0.02 and 2.34 pg·mL-1, p = 0.02, respectively). Albumin decreased in the control group (mean/median - 2.74 g/L/ - 0.95 g/L, p = 0.02), but there was no statistically significant difference in albumin levels between the groups. In the intervention group, haematocrit and mean haemoglobin values were slightly increased after hyperbaric exposure (mean/median 2.3%/1.5%, p = 0.02 and 4.9 g/L, p = 0.06, respectively). CONCLUSION Hyperbaric exposure to 401 kPa for 36 h was not associated with significant increases in GFAp, NfL or tau concentrations. Albumin levels, changes in hydration or diurnal variation were unlikely to have confounded the results. Saturation exposure to 401 kPa seems to be a procedure not harmful to the central nervous system. TRIAL REGISTRATION ClinicalTrials.gov NCT03192930.
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Walnut consumption increases activation of the insula to highly desirable food cues: A randomized, double-blind, placebo-controlled, cross-over fMRI study.
Farr, OM, Tuccinardi, D, Upadhyay, J, Oussaada, SM, Mantzoros, CS
Diabetes, obesity & metabolism. 2018;(1):173-177
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AIMS: The use of walnuts is recommended for obesity and type 2 diabetes, although the mechanisms through which walnuts may improve appetite control and/or glycaemic control remain largely unknown. MATERIALS AND METHODS To determine whether short-term walnut consumption could alter the neural control of appetite using functional magnetic resonance imaging, we performed a randomized, placebo-controlled, double-blind, cross-over trial of 10 patients who received, while living in the controlled environment of a clinical research center, either walnuts or placebo (using a validated smoothie delivery system) for 5 days each, separated by a wash-out period of 1 month. RESULTS Walnut consumption decreased feelings of hunger and appetite, assessed using visual analog scales, and increased activation of the right insula to highly desirable food cues. CONCLUSIONS These findings suggest that walnut consumption may increase salience and cognitive control processing of highly desirable food cues, leading to the beneficial metabolic effects observed.
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Sleep restriction leads to increased activation of brain regions sensitive to food stimuli.
St-Onge, MP, McReynolds, A, Trivedi, ZB, Roberts, AL, Sy, M, Hirsch, J
The American journal of clinical nutrition. 2012;(4):818-24
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BACKGROUND Epidemiologic evidence shows an increase in obesity concurrent with a reduction in average sleep duration among Americans. Although clinical studies propose that restricted sleep affects hormones related to appetite, neuronal activity in response to food stimuli after restricted and habitual sleep has not been investigated. OBJECTIVE The objective of this study was to determine the effects of partial sleep restriction on neuronal activation in response to food stimuli. DESIGN Thirty healthy, normal-weight [BMI (in kg/m²): 22-26] men and women were recruited (26 completed) to participate in a 2-phase inpatient crossover study in which they spent either 4 h/night (restricted sleep) or 9 h/night (habitual sleep) in bed. Each phase lasted 6 d, and functional magnetic resonance imaging was performed in the fasted state on day 6. RESULTS Overall neuronal activity in response to food stimuli was greater after restricted sleep than after habitual sleep. In addition, a relative increase in brain activity in areas associated with reward, including the putamen, nucleus accumbens, thalamus, insula, and prefrontal cortex in response to food stimuli, was observed. CONCLUSION The findings of this study link restricted sleep and susceptibility to food stimuli and are consistent with the notion that reduced sleep may lead to greater propensity to overeat.
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Magnetic resonance study on fractional anisotropy and neuronal metabolite ratios in peritumoral area of cerebral gliomas.
Bieza, A, Krumina, G
Medicina (Kaunas, Lithuania). 2012;(10):497-506
Abstract
BACKGROUND AND OBJECTIVE Cerebral gliomas have a tendency to infiltrate the surrounding brain tissue for several centimeters from the core of tumor. The usefulness of structural magnetic resonance (MR) sequences is limited because of their insensitivity for the detection of tumor cells outside the visible tumor border. The aim of this study was to investigate the validity and the repeatability of 2 functional MR methods: fractional anisotropy (FA) and spectroscopy in the assessment of the peritumoral area of cerebral gliomas. MATERIAL AND METHODS Forty-five patients with histologically verified brain gliomas underwent diffusion tensor imaging (DTI) and MR spectroscopy (MRS). Metabolic ratios were calculated from choline (Cho), creatine (Cr), N-acetylaspartate (NAA), lactate/lipids (LL), myo-inositol (MI) spectroscopic values obtained within the tumor center, perifocal edema, and distant and contralateral normal-appearing white matter. DTI maps of FA were calculated at the same locations. RESULTS A significant gradual increase of FA and a decrease of LL/Cr ratios from the tumor center to the normal-appearing white matter were observed. The Cho/Cr ratio was significantly lower in the distant normal-appearing white matter than in the perifocal edema and the tumor center. The NAA/Cr ratio was significantly reduced in the tumor center, perifocal edema, and distant normal-appearing white matter compared with the contralateral hemisphere. MRS and DTI measurements of glioma and peritumoral area had a high degree of repeatability. CONCLUSIONS Our study shows that MRS and DTI measurements are reproducible. The combined use of Cho/Cr, LL/Cr, and FA measurements is a promising MR technique that provides valuable additional information about the location of glioma potential border.
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Anterior cingulate taste activation predicts ad libitum intake of sweet and savory drinks in healthy, normal-weight men.
Spetter, MS, de Graaf, C, Viergever, MA, Smeets, PA
The Journal of nutrition. 2012;(4):795-802
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After food consumption, the motivation to eat (wanting) decreases and associated brain reward responses change. Wanting-related brain responses and how these are affected by consumption of specific foods are ill documented. Moreover, the predictive value of food-induced brain responses for subsequent consumption has not been assessed. We aimed to determine the effects of consumption of sweet and savory foods on taste activation in the brain and to assess how far taste activation can predict subsequent ad libitum intake. Fifteen healthy men (age: 27 ± 2 y, BMI: 22.0 ± 1.5 kg/m2) participated in a randomized crossover trial. After a >3-h fast, participants were scanned with the use of functional MRI before and after consumption of a sweet or savory preload (0.35 L fruit or tomato juice) on two occasions. After the scans, the preload juice was consumed ad libitum. During scanning, participants tasted the juices and rated their pleasantness. Striatal taste activation decreased after juice consumption, independent of pleasantness. Sweet and savory taste activation were not differentially affected by consumption. Anterior cingulate taste activation predicted subsequent ad libitum intake of sweet (r = -0.78; P < 0.001(uncorrected)) as well as savory juice (r = -0.70; P < 0.001(uncorrected)). In conclusion, we showed how taste activation of brain reward areas changes following food consumption. These changes may be associated with the food's physiological relevance. Further, the results suggest that anterior cingulate taste activation reflects food-specific satiety. This extends our understanding of the representation of food specific-appetite in the brain and shows that neuroimaging may provide objective and more accurate measures of food motivation than self-report measures.
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Is there a change in water proton density associated with functional magnetic resonance imaging?
Jochimsen, TH, Norris, DG, Möller, HE
Magnetic resonance in medicine. 2005;(2):470-3
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In a recent series of studies (see, for example, Stroman et al. Magn Reson Imag 2001; 19:827-831), an increase of water proton density has been suggested to correlate with neuronal activity. Owing to the significant implications of such a mechanism for other functional experiments, the functional signal changes in humans at very short echo times were re-examined by spin-echo EPI at 3 T. The results do not confirm the previous hypothesis of a significant increase in extravascular proton density at TE = 0. Instead, an alternative explanation of the effect is offered: The use of a low threshold to identify activated voxels may generate an artificial offset in functional contrast due to the inclusion of false-positives in the analysis.
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MR spectroscopic evidence for glial increase but not for neuro-axonal damage in MS normal-appearing white matter.
Vrenken, H, Barkhof, F, Uitdehaag, BM, Castelijns, JA, Polman, CH, Pouwels, PJ
Magnetic resonance in medicine. 2005;(2):256-66
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Quantitative single-voxel, short echo-time (TE) MR spectroscopy (MRS) was used to determine metabolite concentrations in the cerebral normal-appearing white matter (NAWM) of 76 patients with multiple sclerosis (MS), and the WM of 25 controls. In NAWM of all MS disease types (primary progressive, relapsing-remitting, and secondary progressive), the concentration ratio of total N-acetyl-aspartate (tNAA)/total creatine (tCr) was decreased compared to controls. Remarkably, this was entirely due to an increase of tCr in MS patients, whereas there was no difference in tNAA. Separate quantification of the two tNAA components yielded no significant difference in NAA (N-acetyl-aspartate), while the concentration of NAAG (N-acetyl-aspartyl-glutamate) was slightly-but significantly-elevated in MS patients. Myo-inositol (Ins) was strongly increased in MS patients, and choline-containing compounds (Cho) were mildly increased. There were no metabolite differences between disease types, and no correlations with disability scores. The results are supported by measures of spectral quality, which were identical for patients and controls. In conclusion, MS NAWM containing very little perilesional tissue is characterized by increased glial cell numbers (increase of Ins and tCr) without evidence of axonal dysfunction (normal NAA). Further studies should elucidate the mechanism underlying increased NAAG in MS NAWM.
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Neuronal metabolic changes in the cortical region after subcortical infarction: a proton MR spectroscopy study.
Kang, DW, Roh, JK, Lee, YS, Song, IC, Yoon, BW, Chang, KH
Journal of neurology, neurosurgery, and psychiatry. 2000;(2):222-7
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OBJECTIVES To investigate whether proton magnetic resonance spectroscopy ((1)H MRS) can detect neuronal metabolic changes in the cortical region in patients with cortical dysfunction after subcortical infarction. METHODS Fifteen patients with subcortical large (diameter≥20 mm) infarcts were studied; nine patients with cortical dysfunction (group A), and six without (group B). Seven patients with lacunar infarction served as controls. Infarct volume was measured on T2 weighted images with an image analyser. (1)H MRS data were obtained in three regions; high signal intensity area on T2 weighted image, overlying cortex with a normal T2 MRI appearance, and contralateral homologous cortical region. RESULTS Infarct volume was not different between groups A and B. N-acetylaspartate (NAA)/creatine+phosphocreatine (Cr) ratios in the cortical region overlying subcortical infarcts in group A were significantly lower than those in group B and the control group (p=0.002). The NAA/Cr ratios in the overlying cortex were significantly lower than those in the contralateral normal cortex in group A on the initial (p=0. 015) and follow up (p=0.028) (1)H MRS, but these differences were not found in group B and the control group. CONCLUSIONS The results support the idea that the cerebral cortex is a responsible location for cortical dysfunction after subcortical infarctions. (1)H MRS can be used as a sensitive method for the detection of a neuronal metabolic damage, which is not demonstrated by conventional MRI.