Psychophysics: how fielders arrive in time to catch the ball

Tracking an object moving in three dimensions, whether as an insect pursuing a mate on the wing or as a batsman aiming to hit an approaching ball, provides the spatial and temporal information needed to intercept it. Here we show how fielders use such tracking signals to arrive at the right place in time to catch a ball - they run so that their angle of gaze elevation to the ball increases at a decreasing rate while their horizontal gaze angle to the ball increases at a constant rate (unless the distance to be run is small). Allowing the horizontal angle to increase minimizes the acceleration that the fielder must achieve to reach the interception point at the same time as the ball.     

Aberrant protamine 1/protamine 2 ratios in sperm of infertile human males

Protamines were extracted from the sperm of fertile and infertile human males and the relative proportion of protamines 1, 2, and 3 were determined by scanning microdensitometry following electrophoresis of total protamine in polyacrylamide gels. The proportion of the three protamines was found to be similar in sperm obtained from different normal males. The distribution of protamines in sperm obtained from a select group of infertile males producing an elevated level of large sperm heads, in contrast, was different from that of the fertile males.     

Cloned and expressed nitric oxide synthase structurally resembles cytochrome P-450 reductase.

Nitric oxide is a messenger molecule, mediating the effect of endothelium-derived relaxing factor in blood vessels and the cytotoxic actions of macrophages, and playing a part in neuronal communication in the brain. Cloning of a complementary DNA for brain nitric oxide synthase reveals recognition sites for NADPH, FAD, flavin mononucleotide and calmodulin as well as phosphorylation sites, indicating that the synthase is regulated by many different factors. The only known mammalian enzyme with close homology is cytochrome P-450 reductase.