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Assimilation of glucose carbon in subcellular rat brain particles in vivo and the problems of axoplasmic flow.

ABSTRACT: 1. Rats were injected with [U-(14)C]glucose and the content of (14)C in proteins and lipids of the cerebral P(1) (;nuclear'), P(2) (;mitochondrial'), P(3) (;microsomal') and high-speed supernatant fractions was measured 7, 22 and 93hr. after injection of labelled glucose. 2. The crude brain mitochondrial fractions (P(2)) were subfractionated on continuous sucrose gradients (0.32-1.8m-sucrose) and the (14)C content of the proteins and lipids of about 20 subfractions was measured. 3. About 40-50% of the (14)C assimilated by brain proteins was found in the P(2) (;mitochondrial') fraction. About 68-70% of the (14)C assimilated by brain lipids was also recovered from the lipids of the P(2) fraction. 4. Between 22 and 93hr. after injection of [U-(14)C]glucose both the amount of (14)C in the protein of the P(2) (;mitochondrial') fraction and the specific activity of this protein increased. The specific activity of the protein of all other particulate fractions (P(1), P(2) and P(3)) and subfractions (obtained from sucrose-density-gradient subfractionation of fraction P(2)) when related to the specific activity of the high-speed supernatant protein also increased during 93hr. after injection of [U-(14)C]glucose. The amount of (14)C in the protein of the high-speed supernatant and the specific activity of this protein decreased during the same period. 5. The distribution of (14)C in the lipids of all subcellular particulate fractions remained unchanged during the period 22-93hr. after injection of [U-(14)C]glucose. 6. It was concluded that a diffusion occurs of some supernatant proteins into subcellular particulate matter of the cerebrum and no significant preference for any subcellular particulate matter was observed. The lipids occur in the cerebrum mainly in a non-diffusible state, which is consistent with the view that they form almost entirely a part of the structure of the cerebrum. 7. The data obtained do not lend further support to the concept of axoplasmic flow within the cerebrum or the concept of a one-directional flow of mitochondria or other subcellular particles within the cerebrum.

SUBMITTER: Vrba R

PROVIDER: S-EPMC1198409 | biostudies-other | 1967 Dec

REPOSITORIES: biostudies-other

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Project description:ImportanceAmbient air pollution is a worldwide problem, not only related to respiratory and cardiovascular diseases but also to neurodegenerative disorders. Different pathways on how air pollutants could affect the brain are already known, but direct evidence of the presence of ambient particles (or nanoparticles) in the human adult brain is limited.ObjectiveTo examine whether ambient black carbon particles can translocate to the brain and observe their biodistribution within the different brain regions.Design, setting, and participantsIn this case series a label-free and biocompatible detection technique of nonincandescence-related white light generation was used to screen different regions of biobanked brains of 4 individuals from Belgium with neuropathologically confirmed Alzheimer disease for the presence of black carbon particles. The selected biological specimens were acquired and subsequently stored in a biorepository between April 2013 and April 2017. Black carbon measurements and data analysis were conducted between June 2020 and December 2022.Main outcomes and measuresThe black carbon load was measured in various human brain regions. A Kruskal-Wallis test was used to compare black carbon loads across these regions, followed by Dunn multiple comparison tests.ResultsBlack carbon particles were directly visualized in the human brain of 4 individuals (3 women [75%]; mean [SD] age, 86 [13] years). Screening of the postmortem brain regions showed a significantly higher median (IQR) number of black carbon particles present in the thalamus (433.6 [289.5-540.2] particles per mm3), the prefrontal cortex including the olfactory bulb (420.8 [306.6-486.8] particles per mm3), and the hippocampus (364.7 [342.0-448.7] particles per mm3) compared with the cingulate cortex (192.3 [164.2-277.5] particles per mm3), amygdala (217.5 [147.3-244.5] particles per mm3), and the superior temporal gyrus (204.9 [167.9-236.8] particles per mm3).Conclusions and relevanceThis case series provides evidence that ambient air pollution particles are able to translocate to the human brain and accumulate in multiple brain regions involved in cognitive functioning. This phenomenon may contribute to the onset and development of neurodegenerative disorders.

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Assimilation of glucose carbon in subcellular rat brain particles in vivo and the problems of axoplasmic flow.

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