Bakst Murray R, Bauchan Gary
Animal Biosciences and Biotechnology Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA.
Electron and Confocal Microscopy Unit, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA.
Theriogenology. 2015 Jun;83(9):1438-44. doi: 10.1016/j.theriogenology.2015.01.016. Epub 2015 Feb 4.
Located at the anterior end of the turkey hen's vagina are numerous discrete tubular invaginations of the surface epithelium, collectively referred to as the sperm storage tubules (SSTs). After mating or artificial insemination, sperm ascend the vagina, enter the SSTs, and over the ensuing days and weeks, gradually exit the SSTs and are transported to the anterior end of the oviduct to fertilize a daily succession of ova. Little is known regarding the cellular and molecular mechanisms responsible for sperm subsistence in the lumen of the SST. In this study, the origin of microvillus blebs (MvBs) on the apical tips of SST epithelial cells was examined, and their possible role in sperm survival was discussed. Regardless, if sperm are present or not, transmission electron microscopy revealed two types of microvilli differentiated by the presence or absence of pleomorphic unilaminar MvBs localized to their apical tips. Although some MvBs appeared to be discharging their contents into the SST lumen, others appeared to have pinched off the microvillus stem. When SSTs contained clusters of densely packed sperm, the sperm heads of those sperm adjacent to the SST epithelial cell surface were surrounded by the microvilli. Associated with the plasmalemma of sperm throughout the SST lumina were membrane fragments and small vesicles (30-130 nm in diameter), some of which appeared to have fused with sperm. It is concluded that the MvBs are a form of shedding vesicle released from the SST epithelial cell microvilli by apocrine secretion. On the basis of observations described herein and those of other authors, it is suggested that the MvBs contribute to sustained sperm storage in the SSTs by (1) supplying metabolic substrates used by resident sperm, (2) serving as fusogenic vehicles providing exogenous macromolecules that reversibly suppress sperm functions associated with fertilization (decapacitation?) and stabilize the sperm plasmalemma, and (3) acting as transport vesicles actively transporting fluid from the SST epithelial cells to the SST lumen.
在母火鸡阴道前端存在许多表面上皮的离散管状内陷，统称为精子储存小管（SSTs）。交配或人工授精后，精子沿阴道上行，进入SSTs，在随后的数天和数周内，逐渐从SSTs中排出并被运输到输卵管前端，使每日连续排出的卵子受精。关于精子在SST管腔内存活的细胞和分子机制知之甚少。在本研究中，检查了SST上皮细胞顶端微绒毛泡（MvBs）的起源，并讨论了它们在精子存活中的可能作用。无论是否存在精子，透射电子显微镜显示有两种类型的微绒毛，其区别在于顶端是否存在多形性单层MvBs。尽管一些MvBs似乎在将其内容物排入SST管腔，但其他一些似乎已从微绒毛茎上脱落。当SSTs含有密集排列的精子簇时，那些与SST上皮细胞表面相邻的精子头部被微绒毛包围。在整个SST管腔中，与精子质膜相关的是膜碎片和小泡（直径30 - 130nm），其中一些似乎已与精子融合。得出的结论是，MvBs是通过顶浆分泌从SST上皮细胞微绒毛释放的一种脱落小泡形式。基于本文所述的观察结果以及其他作者的观察结果，提示MvBs通过以下方式有助于精子在SSTs中的持续储存：（1）提供驻留精子使用的代谢底物；（2）作为融合载体，提供可逆地抑制与受精相关的精子功能（去能？）并稳定精子质膜的外源性大分子；（3）作为运输小泡，将液体从SST上皮细胞主动运输到SST管腔。
