LETTER TO THE EDITOR
Comment on the morphology of spermatozoa in air-dried seminal smears
Article first published online: 4 AUG 2011
© 2011 The Author. International Journal of Andrology © 2011 European Academy of Andrology
International Journal of Andrology
Volume 35, Issue 1, pages 105–106, February 2012
How to Cite
Cooper, T. G. (2012), Comment on the morphology of spermatozoa in air-dried seminal smears. International Journal of Andrology, 35: 105–106. doi: 10.1111/j.1365-2605.2011.01207.x
- Issue published online: 9 JAN 2012
- Article first published online: 4 AUG 2011
A recent letter by Lerchl (2012), commenting on the paper by Falzone et al. (2011), draws attention to the observation that apparently functional spermatozoa (as judged by head membrane permeability, time-dependent acrosome reactions and sperm-zona binding) have markedly abnormal morphology (reduced sperm head dimensions and calculated cell volumes). This discrepancy is an anomaly reflecting a common misconception about the interpretation of sperm morphology.
The rapid fixation of tissues and cells before subsequent processing (dehydration, embedding, rehydration, staining etc.) is demanded by anatomists, so that the images obtained reflect the reality of the living cell. For examining human ejaculated sperm morphology, however, the highly proteinaceous nature of seminal fluid has required a different approach: the air drying of seminal smears (made to prevent the overlap of free cells) before the cells are fixed and stained (WHO 2010). This method is also frequently used on sperm suspensions that have been washed, swum-up or purified by density gradient centrifugation (as in the Falzone et al. study), although such preparations easily could, and ideally should, be fixed before processing.
Caput epididymidal human and monkey spermatozoa that are air-dried before being fixed and stained display a common morphological artefact of head expansion, not shown by mature ejaculated spermatozoa (Yeung et al., 1997); this is an artefact of air drying, as it is prevented by fixation of the immature cells before drying and staining (Yeung et al., 1997). CASA can detect shrinkage of what appear to be non-swollen sperm heads upon epididymal maturation when the spermatozoa are air dried before fixation (Soler et al., 2000). Whatever the cause of the maturational increase in resistance of spermatozoa to the osmotic, dehydration and shear forces involved in smearing and air drying, the mobile phone radiation used in this study may have caused similar resistance in the mature cells, making them apparently smaller than the non-irradiated cells processed in the same manner. It is doubtful if any valid estimation of cell volume can be calculated from the dimensions of dried cells.
Such artefactual morphology, however, bears no relationship whatever to, and is totally irrelevant for, the interpretation of sperm function assessed in wet preparations (membrane integrity, acrosomal status, zona binding). In the study by Falzone et al., these data on the effects of the radiation on living cells are more meaningful. Measurement of the head dimensions of the spermatozoa bound to the zona pellucida (fixed in situ) would have been useful to determine if radiation had affected sperm head morphology. If there were no differences between treated and untreated samples, there may have been selection by the zona for the bound cells, in which case, measurement of sperm head size in the inseminate (fixed before processing) would indicate if the unbound sperm population had been changed by radiation.
Given that the ejaculate does not exist in men, and that any radiation reaching the scrotum of a man with an active mobile phone around his waist would affect spermatozoa within the cauda epididymidis, the experimental method in this study is far from physiological. Epididymal fluid composition differs from than that of semen and Ham’s F-10 (with higher osmolality and K+ concentration, and lower ionic strength and Na+ concentration: Cooper, 1999), and spermatozoa are stored at lower than body temperature. Subtle radiation effects on spermatozoa may well be modified by the nature of the fluid environment provided in the experiments.
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