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New observations on flagellar fine structure. The relationship between matrix structure and the microtubule component
Abstract:
The sperm flagella of the blowfly Sarcophaga bullata demonstrate the relationship of radial projections in the matrix region to the microtubule organization of the axoneme. The A microtubule of each peripheral doublet is connected to the central sheath by a series of paired radial links. The links lie along the tubule wall with a alternate spacing of about 320/560 A. The distal end of each link is enlarged into a globular head that connects via a transitional link to the helical sheath around the central microtubules. The radial link pairs are disposed in the form of a double helix with a pitch of about 1760 A. It is proposed that a similar organization is common to all cilia and flagella showing ninefold symmetry and must provide, in part, the morphological basis for motility.
Insights
Blowfly sperm flagella reveal radial projections linking A microtubules to the central sheath. This double-helical arrangement in cilia and flagella may explain motility.
Area of Science:
- Cell Biology
- Biophysics
- Structural Biology
Background:
- Sperm flagella are crucial for motility.
- Understanding the structural basis of flagellar movement is essential.
Purpose of the Study:
- To elucidate the relationship between radial projections and microtubule organization in blowfly sperm flagella.
- To propose a model for the structural basis of motility in cilia and flagella.
Main Methods:
- Detailed ultrastructural analysis of blowfly (Sarcophaga bullata) sperm flagella.
- Examination of the radial projections in the axonemal matrix region.
Main Results:
- Identified paired radial links connecting the A microtubule of peripheral doublets to the central sheath.
- Observed an alternate spacing of 320/560 A for these links.
- Described a double-helical arrangement of radial link pairs with a pitch of approximately 1760 A.
- Noted globular heads on distal link ends connecting to the central sheath via transitional links.
Conclusions:
- The radial projections form a double-helical structure within the axoneme.
- This organization likely contributes to the morphological basis of motility in cilia and flagella with ninefold symmetry.