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Ultrastructure of goat testes: intercellular bridge between germ cells
1Laboratory of Reproductive Physiology, Faculty of Agriculture, Shizuoka University, Japan.
Insights
Intercellular bridges (ICBs) in goat germ cells form during incomplete cell division, facilitating cytoplasmic organelle transfer. These structures change shape and size during spermatogenesis, aiding cell development.
Area of Science:
- Reproductive Biology
- Cell Biology
- Histology
Background:
- Intercellular bridges (ICBs) are crucial for germ cell development, connecting sister cells during meiosis.
- Understanding the structural dynamics of ICBs is essential for comprehending spermatogenesis.
Purpose of the Study:
- To investigate the fine structure and morphological changes of intercellular bridges in goat germ cells.
- To elucidate the developmental stages and functional significance of ICBs during spermatogenesis.
Main Methods:
- Transmission electron microscopy was used to examine testicular samples from goats.
- Perfusion fixation was employed to preserve the ultrastructure of germ cells and ICBs.
Main Results:
- ICBs were observed between spermatogonia, spermatocytes, and spermatids, originating from midbodies with microtubules.
- The ICB structure evolved, featuring a bridge-partitioning complex and electron-dense material, before opening to allow organelle passage.
- ICB morphology varied, appearing as double linear or drum shapes between early germ cells and horseshoe-like between spermatids, with changes in width and length during spermatogenesis.
Conclusions:
- Goat germ cell ICBs are dynamic structures essential for cytoplasmic exchange and development.
- The observed structural modifications of ICBs correlate with the progression of spermatogenesis, suggesting a key role in cell differentiation and maturation.
Abstract:
The fine structure of intercellular bridge (ICB) of goat germ cells was studied using testicular samples fixed by perfusion. In the seminiferous tubules, the ICBs were observed between sister cells of spermatogonia, spermatocytes and spermatids. As a result of incomplete division of germ cells, the ICB first appeared as a midbody containing a remnant of the bundle of microtubules (spindle fibers). These microtubules then disappeared and were replaced by a shutter apparatus which was composed of multiple lamellar cisternae (bridge-partitioning complex). The inner part of the ICB was reinforced with a layer of electron dense mass (bridge density) which persisted up to the residual cytoplasm of spermiation. After complete reconstruction of the sister cells, the cisternae of the bridge-partitioning complex disappeared and the channel of the ICB was opened. Evidently (see electron micrographs), almost all of the cytoplasmic organelles could pass through the channel of the ICB. In the longitudinal section, the appearance of the ICBs between sister spermatogonia and between sister spermatocytes was observed as a double linear or drum shape, and that between sister spermatids was noticed as a horseshoe-like or concave formation. With the process of spermatogenesis, the ICBs gradually became widened and shortened. The functional significance of the ICB in the goat was discussed.