Spermatozoa

Spermatozoa, the haploid male gametes, are highly specialized cells capable to fertilize eggs in order to produce diploid zygote. The biogenesis of spermatozoa requires finely modulated occurrence of mitotic, meiotic, and differentiation events. Hence, the production of high-quality spermatozoa impacts fertilization with outcomes on the health of the offspring. This book provides a comprehensive overview on the biogenesis, maturation, functions and activities of spermatozoa in both physiological conditions and infertility. Particular attention has been addressed to the impact of environment on sperm quality and to the appropriate selection of high-quality spermatozoa for in vitro fertilization. Taken together, this book targets a wide audience of basic and clinical scientists, teachers and students, and offers a better understanding of spermatozoa health and disease.

Internal fertilization usually implies that a spermatozoon, with intact attributes for zygote formation, passes all hurdles during its transport through the female genitalia and reaches the oocyte. During this journey, millions to billions of other spermatozoa perish. Spermatozoa are highly differentiated motile cells without synthetic capabilities. They generate energy via glycolysis and oxidative phosphorylation to sustain motility and to maintain the stability and functionality of their plasma membrane. In vivo, they spend their short lifespan bathing in female genital tract fluids of different origins, or are in vitro exposed to defined media during diverse sperm handling i.e. extension, cryopreservation, in vitro fertilization, etc. Being excitable cells, spermatozoa respond in vivo to various stimuli during pre-fertilization (capacitation, hyperactivation, oocyte location) and fertilization (acrosome reaction, interaction with the oocyte) events, mediated via diverse membrane ion-conducting channels and ligand-gated receptors. The present Thesis has mapped the presence and reactivity (sperm intactness and kinematics) of selected receptors, water and ion channels in ejaculated boar spermatozoa. The final aim was to find a relevant alternative cell type for in vitro bioassays that could ease the early scrutiny of candidate drugs as well as decreasing our needs for experimental animals according to the 3R principles. Spermatozoa are often extended, cooled and thawed to warrant their availability as fertile gametes for breeding or in vitro testing. Such manipulations stress the cells via osmotic variations and hence spermatozoa need to maintain membrane intactness by controlling the exchange of water and the common cryoprotectant glycerol, via aquaporins (AQPs). Both AQPs-7 and -9 were studied for membrane domain changes in cauda- and ejaculated spermatozoa (un-processed, extended, chilled or frozen-thawed). While AQP-9 maintained location through source and handling, thawing of ejaculated spermatozoa clearly relocated the labelling of AQP-7, thus appearing as a relevant marker for non-empirical studies of sperm cryopreservation. Alongside water, spermatozoa interact with calcium (Ca2+) via the main Ca2+ sperm channel CatSper. Increments in intracellular Ca2+ initiate motility hyperactivation and the acrosome reaction. The four subunits of the CatSper channel were present in boar spermatozoa, mediating changes in sperm motility under in vitro capacitation-inducing conditions (increased extracellular Ca2+ availability and bicarbonate) or challenge by the CatSper antagonists mibefradil and NNC 55-0396. Uterine and oviduct fluids are richest in endogenous opioids as ?-endorphins during mating and ovulation. Both ?- and ?- opioid receptors were present in boar spermatozoa modulating sperm motility, as in vitro challenge with known agonists (?: morphine; ?: DPDPE and ?: U 50488) and antagonists (?: naloxone; ?: naltrindole and ?: nor-binaltrorphimine) showed that the ?-opioid receptor maintained or increased motility while the ?-opioid receptor mediated decreased motility over time. Finally, boar spermatozoa depicted dose-response effects on sperm kinematics and mitochondrial potential following in vitro challenge with 130 pharmacological drugs and toxic compounds as well as with eight known mito-toxic compounds. In conclusion, boar spermatozoa expressing functional water (AQPs-7 and -9) and ion (CatSper 1-4) channels as well as ?- and ?-opioid receptors are able to adapt to stressful environmental variations, capacitation and pharmacological compounds and drug components. Ejaculated sperm suspensions are easily and painlessly obtained from breeding boars, and are suitable biosensors for in vitro drug-induced testing, complying with the 3R principles of reduction and replacement of experimental animals, during early toxicology screening.

This 1987 book examines the structure, as seen by the scanning and transmission electron microscopes, of the spermatozoa of insects, centipedes, millipedes and onychophorans.

Physiology and biochemistry of male reproductive function and semen became the main area of my research in 1944, after my attention was finally diverted frorp. animal cells in general, to mammalian spermatozoa specifically~ Ever since, the interest has remained largely focussed on reproductive probletns in mammals, the work continuing mostly at the University of Cambridge, where I was privileged to hold also the Marshall Walton Professorship in Physiology of Reproduction. This work led to the publication of three books, The Biochemistry of Semen (Methuen 1954), The Biochemistry of Semen and of the Male Reproductive Tract (Methuen 1964) and lately, in co authorship with my wife, Dr. Cecilia Lutwak-Mann, Male Re productive Function and Semen - Themes and Trends in Phys iology, Biochemistry and Investigative Andrology (Springer Verlag 1981). In 1960, thanks to the Lalor Foundation, I was able to avail myself for the first time of a chance to visit the Marine Biological Laboratory at Woods Hole and there to take part in a study of reproduction in marine animals. Ever since, first as Visiting Professor of Biology at the State University of Florida, and later as the Walker Ames Professor and frequent visitor to the Department of Zoology at the University of Washington in Seattle, it has been my good fortune to sustain this pew interest and to pursue it further.

The Functional Anatomy of the Spermatozoon is the 23rd volume of the series Wenner-Gren Center International Symposium Series, documenting the proceedings of the Second International Symposium on Comparative Spermatology, held in August 1973. This volume mainly focuses on the understanding of the early events at fertilization and the preliminaries of this biological process. This text specifically tackles the sperm at fertilization of lower animals and mammals, sperm motility and diversity, and spermatogenesis. This book concludes with discussions on capacitation and maturation of mammalian spermatozoa. This compendium will be valuable to morphologists, physiologists, immunologists, and biochemists, as well as to academicians interested in the study of functional anatomy of the spermatozoon.