An efficient sampling scheme for estimating fibre number from nerve cross sections: the fractionator

Area of Science:

• Neuroscience
• Histology
• Quantitative Biology

Background:

• Accurate quantification of myelinated nerve fibers is crucial for understanding nerve structure and pathology.
• Exhaustive counting of all fibers in nerve trunks is time-consuming and labor-intensive.
• Efficient and unbiased sampling methods are needed for analyzing large nerve samples or numerous nerves.

Purpose of the Study:

• To compare the efficiency and accuracy of two unbiased sampling schemes: systematic random quadrat (SRQ) sampling and fractionator sampling.
• To estimate the number of myelinated fibers in rat tibial nerves using these sampling methods.
• To assess the time-saving benefits of sampling techniques over exhaustive counting.

Main Methods:

• Six rat tibial nerves were biopsied for fiber analysis.
• Exhaustive counting of all myelinated fibers was performed as a baseline.
• Systematic random quadrat (SRQ) sampling and fractionator sampling were applied to subsets of fibers.
• Estimates of total fiber numbers were derived using the ratio technique (SRQ) and the fractionator principle.

Main Results:

• Both SRQ and fractionator sampling captured approximately 200 out of 3000 myelinated fibers per nerve.
• Exhaustive counting took nearly 6 hours per nerve.
• SRQ sampling analysis took 77 minutes, while fractionator sampling took 65 minutes.
• Both sampling methods yielded efficient and unbiased estimates of myelinated fiber numbers.

Conclusions:

• Sampling techniques, specifically SRQ and fractionator methods, offer significant time savings for estimating myelinated nerve fiber numbers.
• These unbiased sampling approaches are practical for researchers analyzing nerves with high fiber density or a large number of samples.
• The fractionator method demonstrated slightly greater efficiency than SRQ sampling in this study.