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Histological methods to determine blood flow distribution with fluorescent microspheres
D L Luchtel1, J C Boykin, S L Bernard
1Department of Environmental Health, School of Public Health, University of Washington, Seattle 98195-7234, USA. dluchtel@u.washington.edu
Summary
Histological methods for fluorescent microsphere studies vary in effectiveness. Paraffin embedding with specific mounting media best preserves microsphere fluorescence and tissue detail for accurate analysis.
Area of Science:
- Histology
- Biomedical Imaging
- Tissue Processing
Background:
- Accurate histological analysis of tissues perfused with fluorescent microspheres is crucial for research.
- Evaluating different histological techniques is necessary to optimize microsphere retention and tissue visualization.
Purpose of the Study:
- To compare the advantages and disadvantages of various histological methods for tissues containing fluorescent microspheres.
- To identify optimal embedding, sectioning, and mounting techniques for preserving both microsphere fluorescence and tissue morphology.
Main Methods:
- Evaluation of formalin-fixed, paraffin-embedded tissues with different anti-media (e.g., toluene, Histoclear II).
- Assessment of formalin-fixed, glycol methacrylate-embedded tissues.
- Analysis of air-dried lung tissue and formalin-fixed, unembedded tissue using Vibratome sectioning.
- Investigation of rapid freezing with cryo-microtome sectioning.
- Staining techniques (hematoxylin and eosin, methyl green, Lee's stain, Richardson's stain) and mounting media (toluene-based, aqueous-based) were examined.
Main Results:
- Paraffin sections (7-10 microm) retained fluorescence with specific anti-media; Histoclear II was a suitable toluene substitute.
- Glycol methacrylate embedding yielded thinner sections (3-5 microm) with better detail but fewer microspheres.
- Vibratome sectioning of unembedded tissue provided good detail for lung and other organs but was harder to handle.
- Air-dried lung sections (100 microm) allowed rapid survey but limited detail.
- Aqueous mounting media preserved fluorescence better than toluene-based ones but were less permanent.
Conclusions:
- Paraffin embedding with appropriate anti-media and aqueous mounting solutions offers a balance between microsphere fluorescence preservation and histological detail.
- The choice of histological method depends on the specific organ, desired level of detail, and whether rapid survey or detailed analysis is prioritized.
- Careful selection of mounting media is critical to prevent fluorescence quenching and ensure long-term sample stability.