Interpreting HAVS Based on Rat Tail Vibration Injury Data

Details

• Personal Author:
  Bain JLW ; Riley, Danny A.
• Description:
  Introduction: Hand arm vibration syndrome (HAVS) is a vasospastic, neurodegenerative and musculoskeletal disease. The pathology of late stage disease persists after quitting vibration tool use. HAVS onset and severity is highest for percussive tools. One 12 min exposure to riveting hammer vibration damaged nerve endings in rat tails. Nerve fibers were assayed structurally by protein gene product 9.5 (PGP9.5) nerve immunostaining. PGP9.5 binds an ubiquitin pathway protein present in all types of nerve fibers, but PGP9.5 levels may change with injury and alter identification consistency. Markers specific for nerve subtypes are required to relate changes to functional alterations. The present study of hammer vibration was conducted to validate that complete cross sections of the tail could be cut and stained for nerve subtypes and mast cells. Methods: Adult male rats were distributed into riveting hammer and sham vibrated groups (n=6/group). Rats were restrained 12 min with their tails taped to a vibration platform that remained stationary for the sham controls. After treatment, rats were euthanized, and tail tissues were chemically fixed for histological analysis of nerves (PGP9.5, neuropeptide Y, calcitonin gene related protein) and mast cells (avidin, Alcian Blue/Safranin O).2 Single sections were doublestained for nerve fibers and mast cells to permit assessment of the degree of physical overlap. Microscope images were taken and analyzed by computer-assisted morphometry. Discussion: PGP9.5, NPY and CGRP staining of nerve fibers and avidin-positive mast cells is feasible in rat tail sections. PGP9.5 stains all nerve types which permits assessing the global effects. NPY and CGRP reveal subtype specific changes. NPY fibers richly innervate arteries, arterioles and veins. NPY potentiates sympathetic nerve vasoconstrictive effects. Vibration white finger is likely driven by somatosympathetic reflex activation, increased á2c adrenergic receptor expression and endothelin-1 release. CGRP stimulates relaxation of vascular smooth muscle. Mast cells moderate vasoconstriction by releasing proteases that degrade vasoactive neuropeptides and endothelin-1. The present study shows CGRP in some mast cells, but it is unknown whether this represents associated nerve fibers and/or uptake with re-release during vasoregulation. Mast cells secrete histamine that inhibits vasoconstriction via H2 receptors on smooth muscle cells. Mast cells are key players in vasoregulation. Chronic exposure to vibration is predicted to decrease mast cell number and result in untempered vasospastic activity. Previously, we demonstrated destruction of terminal nerve fibers by impact vibration.2 Nerve fibers can regenerate after damage. Regenerating axons sprout more terminal branches than normal, but eventually branches are lost. Repeated nerve injury can invoke death of the nerve cell body and failure to regenerate. We predict that multiple day exposure to vibration will decrease the total, PGP9.5 positive innervation. Loss of sensory fibers leads to loss of feeling. Nerve fibers of different types regenerate to different degrees. Vasoconstriction fiber (NPY) regeneration is expected to be higher than (CGRP) vasorelaxant fibers. This shifts in favor of vasoconstriction, a possible cause of white finger. It is hypothesized that the number of mast cells declines during weeks of vibration. Fewer mast cells means less histamine-induced vasodilation and protease inactivation of NPY and endothelin-1, favoring vasospasm. Repeated injury and smooth muscle remodeling in resistance arteries is expected to thicken the vessel wall and narrow the lumen and reduce blood flow. The neural and vascular changes from long term vibration are envisioned to generate the persistent vasospastic and neurodegenerative HAVS. [Description provided by NIOSH]
• Subjects:
  Animals Environmental Exposure Hot Temperature Hypersensitivity Laboratories Musculoskeletal Diseases Musculoskeletal System Occupational Health Pathology Risk Assessment Risk Factors Safety Skin Vibration

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• Keywords:
  Cell Damage Cellular Effects Exposure-levels Exposure Levels Hand-arm Vibration Syndrome HAVS Heat Histamines Injuries Laboratory Animals MSD Musculoskeletal System Disorders Risk-factors Risk Factors Skin Sensitivity Tissue Disorders Vibration-effects Vibration-exposure

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• Publisher:
  University of Guelph
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  OSHA Region 5 ; Wisconsin
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  11-12
• NIOSHTIC Number:
  nn:20052542
• Citation:
  Proceedings of the 5th American Conference on Human Vibration, June 10-13, 2014, Guelph, Ontario, Canada. Oliver M, ed. Guelph, Ontario, Canada: University of Guelph, 2014 Jun; :11-12
• Editor(s):
  Oliver M
• Federal Fiscal Year:
  2014
• NORA Priority Area:
  Construction
• Performing Organization:
  Medical College of Wisconsin, Milwaukee, Wisconsin
• Peer Reviewed:
  False
• Start Date:
  19990901
• Source Full Name:
  Proceedings of the 5th American Conference on Human Vibration, June 10-13, 2014, Guelph, Ontario, Canada
• End Date:
  20160831
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:fdd1efa95eb76907bf570c9db0e1756034e2518413de36443d805a9b8db14ee90b46f0f9f6fba3e1e60f0c35ad788310c8cbe031f6a5f3f7cc8fd499b62cfd0b
• Download URL:
  https://stacks.cdc.gov/view/cdc/212055/cdc_212055_DS1.pdf
• File Type:
  [PDF - 381.40 KB ]