精蟲頭部呈現局部屈光現象與頂體反應有關，精蟲品質較佳

polescope下，精蟲頭部呈現局部屈光現象(Fig 1B)，與頂體反應，精蟲品質較佳有關
選擇這類精蟲可達較佳ICSI懷孕率

http://www.sciencedirect.com/science/article/pii/S1472648312000156

Head birefringence properties are associated with acrosome reaction, sperm motility and morphology

Abstract 

Birefringence in sperm heads reflects an organized and very compacted texture, indicating nuclear and acrosomal structural normality. This study performed a direct analysis of the acrosome integrity in single spermatozoa to verify whether a pattern of total or partial head birefringence reflected the acrosome status. The morphology in fresh samples was assessed according to World Health Organization criteria while the characteristics of birefringence were evaluated by polarized light. Acrosome integrity was evaluated by fluorescein isothiocyanate Pisum sativum agglutinin that binds selectively to the acrosome content. According to the results, a reacted acrosome was present in 96% of spermatozoa with partial birefringence and only in 35% of those with totally birefringent heads. A great proportion of sperm cells with normal morphology showed total birefringence both in the presence (59%) or in the absence of motility (45%; P<0.01), while in morphologically abnormal spermatozoa the frequency of total birefringence was comparable to that of partial birefringence irrespective of motility (26% and 27%, respectively, in motile spermatozoa; 22% and 19%, respectively, in immotile spermatozoa). These data support a strong association between partial birefringence and reacted acrosome and show that the patterns of birefringence vary depending on sperm motility and morphology.

Human sperm cells are naturally birefringent when observed in a polarizing light due to the presence of longitudinally oriented protein filaments. The detection of birefringence in sperm heads reflects an organized and very compacted texture that indicates nuclear and acrosomal structural normality. Basically, three types of head birefringence have been observed: total, partial (localized in the post acrosomal region) and abnormal (absent or irregular). Data from electron microscopy has suggested a correlation between acrosome integrity and birefringence patterns. The aim of this study was to verify this hypothesis by direct analysis of the acrosome status in single spermatozoa. The morphology in fresh samples was assessed according to World Health Organization criteria while the characteristics of birefringence were evaluated by polarized light. Acrosome integrity was evaluated by fluorescein isothiocyanate Pisum sativum agglutinin that binds selectively to the acrosome content. According to the results, 96% of spermatozoa with partial birefringence had a reacted acrosome, while 65% of totally birefringent heads had an intact acrosome. A large proportion of sperm cells with normal morphology showed total birefringence both in the presence (59%) or in the absence of motility (45%; P<0.01), while in morphologically abnormal spermatozoa the frequency of total birefringence was comparable to that of partial birefringence irrespective of motility (26% and 27%, respectively, in motile spermatozoa; 22% and 19%, respectively, in immotile spermatozoa). These data support a strong association between partial birefringence and reacted acrosome and show that the patterns of birefringence vary depending on sperm motility and morphology.

 In the sperm head, three types of birefringent patterns were basically distinguished: (i) spermatozoa with a totally birefringent head (Figure 1A); (ii) spermatozoa with a partially birefringent head localized in the post-acrosomal region, considering that the acrosome represents 40–70% of the sperm head (Figure 1B); and (iii) sperm heads with an abnormal pattern of birefringence due to absence of birefringence, the presence of vacuole-like structures or small areas of birefringence localized either in the nuclear or acrosomal area (Figure 1C,D).

Figure 1 Observation and measurement of sperm heads under polarized light (×63 objective; magnification ×630). (A) Spermatozoon with normal morphology having a total head birefringence. (B) Spermatozoon with normal morphology having partial birefringence localized in the post-acrosomal region. (C) Presence of a small vacuole-like structure in a partially birefringent spermatozoon with normal morphology; the vacuole occupies 15% of the sperm head volume. (D) A large vacuole-like structure covering 33% of a non-birefringent head. © 2012 Reproductive Healthcare Ltd.