Prussian blue technique is prone to yield false negative results in magnetoreception research

Scientific reports · 2022 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 825

Study snapshot

PublicationScientific reports · 2022

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Prussian blue technique is prone to yield false negative results in magnetoreception research Franziska Curdt, Katrin Haase, Laura Ziegenbalg, Helena Greb, Dominik Heyers, Michael Winklhofer. Prussian blue technique is prone to yield false negative results in magnetoreception research. Sci Rep. 2022 May 25;12(1):8803. doi: 10.1038/s41598-022-12398-9. Abstract Perls's Prussian blue staining technique has been used in magnetoreception research to screen tissues for iron- rich structures as proxies for putative magnetoreceptor structures based on magnetic particles. However, seemingly promising structural candidates in the upper beak of birds detected with Prussian blue turned out to be either irreproducible or located in non-neuronal cells, which has spurred a controversy that has not been settled yet. Here we identify possible pitfalls in the previous works and apply the Prussian blue technique to tissues implicated in magnetic-particle-based magnetoreception, in an effort to reassess its suitability for staining single-domain magnetite, i.e., the proposed magnetic substrate for the interaction with the external magnetic field. In the upper beak of night-migratory songbirds, we found staining products in great numbers, but not remotely associated with fiber terminals of the traced ophthalmic branch of the trigeminal nerve. Surprisingly, staining products were absent from the lamina propria in the olfactory rosette of rainbow trout where candidate magnetoreceptor structures were identified with different techniques earlier. Critically, magnetosome chains in whole cells of magnetotactic bacteria remained unstained. The failure to label single- domain magnetite in positive control samples is a serious limitation of the technique and suggests that two most influential but antipodal studies conducted previously stood little chances of obtaining correct positive results under the assumption that magnetosome-like particles were present in the tissues. Nonetheless, the staining technique appears suitable to identify tissue contamination with iron-rich fine dust trapped in epithelia already in vivo. pubmed.ncbi.nlm.nih.gov

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother

Effect directionunclear

PopulationNight-migratory songbirds; rainbow trout; magnetotactic bacteria (positive control samples)

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

In night-migratory songbirds, many staining products were observed in the upper beak but were not associated with fiber terminals of the traced ophthalmic branch of the trigeminal nerve. Staining products were absent from the lamina propria in the rainbow trout olfactory rosette, and magnetosome chains in magnetotactic bacteria remained unstained. The authors conclude that failure to label single-domain magnetite in positive controls is a serious limitation and that the technique may instead be useful for identifying contamination with iron-rich fine dust in epithelia.

Outcomes measured

Performance/validity of Perls's Prussian blue staining for detecting iron-rich structures/single-domain magnetite in tissues implicated in magnetic-particle-based magnetoreception
Presence/location of Prussian blue staining products in upper beak of night-migratory songbirds relative to trigeminal nerve fiber terminals
Presence/absence of staining products in lamina propria of olfactory rosette in rainbow trout
Staining of magnetosome chains in magnetotactic bacteria (positive control)
Ability of staining to identify tissue contamination with iron-rich fine dust

Limitations

No EMF exposure parameters (frequency, field strength, duration) described in abstract
Sample size not reported in abstract
Focus is on staining technique suitability/false negatives rather than direct measurement of magnetoreception outcomes

View raw extracted JSON

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  "exposure": {
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  },
  "population": "Night-migratory songbirds; rainbow trout; magnetotactic bacteria (positive control samples)",
  "sample_size": null,
  "outcomes": [
    "Performance/validity of Perls's Prussian blue staining for detecting iron-rich structures/single-domain magnetite in tissues implicated in magnetic-particle-based magnetoreception",
    "Presence/location of Prussian blue staining products in upper beak of night-migratory songbirds relative to trigeminal nerve fiber terminals",
    "Presence/absence of staining products in lamina propria of olfactory rosette in rainbow trout",
    "Staining of magnetosome chains in magnetotactic bacteria (positive control)",
    "Ability of staining to identify tissue contamination with iron-rich fine dust"
  ],
  "main_findings": "In night-migratory songbirds, many staining products were observed in the upper beak but were not associated with fiber terminals of the traced ophthalmic branch of the trigeminal nerve. Staining products were absent from the lamina propria in the rainbow trout olfactory rosette, and magnetosome chains in magnetotactic bacteria remained unstained. The authors conclude that failure to label single-domain magnetite in positive controls is a serious limitation and that the technique may instead be useful for identifying contamination with iron-rich fine dust in epithelia.",
  "effect_direction": "unclear",
  "limitations": [
    "No EMF exposure parameters (frequency, field strength, duration) described in abstract",
    "Sample size not reported in abstract",
    "Focus is on staining technique suitability/false negatives rather than direct measurement of magnetoreception outcomes"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "Prussian blue",
    "Perls's staining",
    "magnetoreception",
    "single-domain magnetite",
    "magnetosome",
    "trigeminal nerve",
    "upper beak",
    "songbirds",
    "rainbow trout",
    "magnetotactic bacteria",
    "false negative",
    "iron-rich dust contamination"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1038/s41598-022-12398-9
PubMed: 35614116

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