Molecular Reproduction & Development Volume 78, Issue 8 cover image

Transmission electron micrograph of a sea urchin (Strongylocentrotus purpuratus) spermatozoon (purple) bound to the tip of an egg microvillus (yellow) by the bindin protein (diffuse purple), which was released during exocytosis of the sperm acrosomal vesicle. Egg microvilli are approximately 0.25 µm in diameter. More on observing these events on the cellular level in a classroom laboratory setting is presented by VD Vacquier (this issue).     

Molecular Reproduction & Development Volume 78, Issue 12 cover image

Signal transduction across plasma membrane is prerequisite for activation of sperm motility and sperm chemotaxis at fertilization. An oscillatory increase in intracellular calcium occurs upon activation of tunicate sperm (shown in false color in the foreground, clockwise displaying later time points; starting at 11:00). Zhu and Inaba (this issue) report that lipid rafts are essential for these calcium dynamics and for subsequent activation of adenylyl cyclase. Background image is of a single tunicate, Ciona intestinalis.     

Molecular Reproduction & Development Volume 78, Issue 7 cover image

Ascidians are hermaphrodites, releasing sperm and eggs nearly simultaneously, but several species including the ascidian (prochodate) Ciona intestinalis are self‐sterile (self‐incompatible). In this species, the self‐incompatibility system is mediated by the vitelline coat ligand v‐Themis‐A/B and the sperm‐side receptor s‐Themis‐A/B. In this issue, it is described that a sperm GPIanchored protein CiUrabin in lipid rafts may play a key role in the primary binding of sperm to the vitelline coat. This image of a C. intestinalis egg was taken by Takako Saito.     

Molecular Reproduction & Development Volume 78, Issue 6 cover image

Artist's rendition of Xenopus sperm swimming in the jelly layers as they approach the egg surface. Burnett et al. (this issue) fi nd that water soluble components of this jelly layer directly interact with sperm, thereby initiating chemotactic motility towards the egg. Original art by Douglas Chandler.     

Molecular Reproduction & Development Volume 79, Issue 9, September 2012 cover image

Semen has a heterogeneous population of sperm with varying degrees of DNA damage. Increased sperm DNA fragmentation is a pathological trait observed in a large percentage of infertile men (Shamsi et al., this issue). Pictured here is the comet assay (background), which is used to assess DNA fragmentation in sperm populations from infertile men. It can distinguish individual sperm with intact DNA (circular halos) from those with DNA damage (smaller halo in the comet head, with most of the DNA migrating into the comet tail). A scanning electron micrograph of a human sperm (image courtesy of Judith Lyons, www.judithlyons.co.uk ) and DNA double helix and are shown in relief.