Cholinotrophic Molecular Substrates of Mild Cognitive Impairment in the Elderly
Bibliographic record
Abstract
Cholinergic nucleus basalis (NB) neurons provide the major cholinergic innervation to the cortical mantle, are selectively vulnerable in late stage Alzheimer's disease (AD) and require the neurotrophin, nerve growth factor (NGF) and its receptors (TrkA and p75(NTR)), for their survival. The molecular events underlying the demise of these neurons in AD were investigated using tissue harvested from participants in a longitudinal clinical pathological study of aging and AD who agreed to an annual clinical evaluation providing a categorization of no cognitive impairment (NCI), mild cognitive impairment (MCI) or AD and postmortem brain donation. Although the number of choline acetyltransferase (ChAT)-positive neurons was unchanged, TrkA and p75(NTR) receptor-containing neurons, which co-localize with ChAT, were significantly reduced in the NB of subjects with MCI and AD compared to those with NCI. These observations indicate a phenotypic down-regulation rather than frank NB neuronal degeneration in MCI. Expression profiling of single cholinergic NB neurons revealed TrkA but not p75(NTR) mRNA is reduced in MCI, suggesting that decreased neurotrophin responsiveness may be an early biomarker for AD. The NGF precursor molecule, proNGF, is increased in the cortex in MCI and AD. Since proNGF accumulates in the presence of reduced cortical TrkA and sustained levels of p75(NTR), a shift in the balance between cell survival and death molecules may occur in prodromal AD. Coincident with these phenomena, brain derived neurotrophic factor (BDNF) and its precursor molecule, proBDNF, are reduced in the MCI cortex, potentially depriving CBF neurons of additional trophic factor support. Moreover, there is a shift in the ratio of 3 repeat tau to 4 repeat tau gene expression, whereas total tau message is stable in NB neurons during the disease process. These data suggest there is a shift in cholinotrophic molecular events in MCI and early AD which may lead to cell dysfunction and eventual cell death over the course of the disease. These findings support the concept that from a neurotrophic pathobiologic perspective, MCI is already early AD.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".