The Morphological Services, a component of the Animal Reproduction and Biotechnology Laboratory, has been providing clinical and research support services to a broad-based clientele that includes veterinarians, physicians, and research scientists. We have been involved in studies evaluating male reproductive tissues from a variety of species including laboratory, domesticated and wild animals. One of the client services is evaluation of semen for sperm morphology and ultrastructural cytopathology.
Sperm Morphology: Beyond Shapes of Sperm Heads and Tails
The parameters most commonly measured for routine seminal evaluation are determination of total number of sperm in the ejaculate, percentage of progressively motile sperm, and normalcy of morphological features of sperm at a light microscopic level. Although important, none of these parameters, when used alone, serves as a reliable measure to assess reproductive health status or potential fertility. This is because not all motile sperm are morphologically normal and not all morphologically normal sperm are motile. Although these parameters usually are adequate to assess normalcy of a seminal sample in healthy animals, problems arise when any of the components that contribute to seminal secretions are affected. In disease conditions, a seminal ejaculate may contain, in addition to sperm, cells sloughed from testis, excurrent ducts, and accessory glands. Because routine methods of processing seminal samples for morphological evaluation do not permit characterization of subtle defects in sperm or definitive identification of denuded cells, light microscopic evaluation does not fully utilize the diagnostic and prognostic potential of a seminal sample in assessing health status of the reproductive organs.
We process seminal samples as biopsy material using methods that facilitate critical evaluation of sperm as well as any other cells from the reproductive tract that might be present in disease conditions. These methods utilize light and transmission electron microscopic techniques, which make it possible to identify and characterize subtle lesions that cannot be detected otherwise. Examples include sperm defects associated with plasma membrane and acrosome (Figure 1), chromatin condensation and nuclear integrity (Figure 2); autoimmune conditions resulting in agglutination or aggregation of sperm (Figure 3); degenerative conditions in testes resulting in shedding of immature germ cells and somatic cells or impaired spermiogenesis (Figure 4 and Figure 5); and inflammatory or infectious conditions in the reproductive tract -- excurrent ducts and accessory sex glands (Figure 6, Figures 7 and 8). The latter situations ultimately lead to manifestations such as premature acrosome reaction (Figure 1) rendering sperm non-functional.
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Veeramachaneni DNR. 2011. Spermatozoal Morphology. Chapter 126 In: Equine Reproduction, 2nd Edition (Ed McKinnon AO, Squires EL, Vaala WE, Varner DD), Oxford: Wiley-Blackwell, pp 1297-1307.
Veeramachaneni DNR, Moeller CL, Sawyer HR. 2006. Sperm morphology in stallions: Ultrastructure as a functional and diagnostic tool. Veterinary Clinics of North America: Equine Practice/Advances in Reproduction 22:683-692.
Veeramachaneni DNR, Sawyer HR. 1996. Use of semen as biopsy material for assessment of health status of the stallion reproductive tract. The Veterinary Clinics of North America: Equine Practice/Diagnostic Techniques and Assisted Reproductive Technology 12:101-110.
Seed J, Chapin RE, Clegg ED, Darney SP, Dostal L, Foote RH, Hurtt ME, Klinefelter GR, Makris S, Schrader S, Seyler D, Sprando R, Treinen KA, Veeramachaneni DNR, Wise LD. 1996. Methods for assessing sperm motility, morphology and counts in the rat, rabbit, and dog: A consensus report. Reprod Toxicol 10:237-244.
Veeramachaneni DNR, Moeller CL, Pickett BW, Shiner KA, Sawyer HR. 1993. On processing and evaluation of equine seminal samples for cytopathology and fertility assessment: the utility of electron microscopy. J Equine Vet Sci 13:207-215.