Continuous recording of microvascular dimensions with a rotating mirror microscope

Area of Science:

• Physiology
• Biomedical Engineering
• Microscopy

Background:

• Accurate measurement of microscopic blood vessel dimensions is crucial for understanding vascular function and disease.
• Existing methods may lack the precision or continuous monitoring capabilities required for dynamic studies.
• The contractile responses of microvessels to vasoactive agents are fundamental to cardiovascular regulation.

Purpose of the Study:

• To describe a novel system for continuous, real-time recording of microscopic blood vessel dimensions.
• To validate the system's accuracy and linearity across a relevant size range.
• To investigate the differential contractile effects of adrenaline and noradrenaline on rat mesenteric arterioles.

Main Methods:

• A system combining a rotating mirror, pinhole aperture, and microscope to scan microvessel images at 1 Hz.
• Image signal processing involving conversion to digital, then analog signals via integration.
• Use of a B-12 optical filter to enhance contrast between vessels and surrounding tissue.
• In vivo observation of rat mesenteric arterioles following administration of adrenaline and noradrenaline.

Main Results:

• The system demonstrated a linear relationship between analog voltage output and vessel dimensions from 20-200 micrometers (SD +/- 3.0%).
• Enhanced contrast was achieved using a B-12 optical filter.
• Adrenaline induced a greater contractile response in mesenteric arterioles compared to noradrenaline.
• Maximum vessel outer diameter decrease was 20% with 5.5 x 10(-7) mmol adrenaline and 5.9 x 10(-6) mmol noradrenaline.

Conclusions:

• The developed system provides accurate and continuous measurement of microscopic blood vessel dimensions.
• The system is capable of resolving dynamic vascular responses to vasoactive substances.
• Adrenaline elicits a stronger contraction in rat mesenteric arterioles than noradrenaline at the tested concentrations.