Airway smooth muscle (ASM) shortening is the key event leading to broncho-constriction. The degree of airway narrowing which occurs with ASM shortening is a function both of the mechanical properties of the airway wall as well as the angle of orientation of ASM. If ASM is oriented very obliquely, ASM shortening would in part be transduced to a change in airway length rather than airway narrowing. Previous reports have suggested that the angle of ASM orientation may be as high as 30$ sp circ.$ To measure ASM orientation we have developed a technique based on en-face dissection. The lungs from 4 cats and one human were fixed with 10% buffered formalin at 25 cmH$ sb2$O for 48 hrs. The airway generations 4 to 17 were dissected out from the left lower lobes. Each airway generation was individually embedded in paraffin from which 5$ mu$m thick serial sections were cut parallel to the airway long axis ("en-face") and stained with haematoxylin-phloxine-saffron. Each block yielded 3-5 sections in which the orientation of ASM nuclei relative to the airway long axis ($ theta$) was measured as an index of ASM orientation. $ theta$ was measured clockwise and counterclockwise to the short axis by using a digitizing tablet and a light microscope (X250) equipped with a drawing tube attachment. Inspection of the sections revealed extensive ASM crisscrossing without a homogeneous orientation. Between 29 and 102 nuclei were measured per generation. Although there was considerable variation within airway generations, $ theta$ clustered between $-$20$ sp circ$ and 10$ sp circ$ in all generations and did not vary significantly between generations in any of the subjects. When $ theta$ was converted to an acute angle without regard to sign($ Theta$), the mean angle was 12-13$ sp circ$ both in cat and the human lung. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.22759 |
| Date | January 1995 |
| Creators | Lei, Min |
| Contributors | Eidelman, D. H. (advisor), Chen, M. F. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Pathology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001453826, proquestno: MM05582, Theses scanned by UMI/ProQuest. |
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