Avirulence and immunogenicity in mice of a bovine mastitis Staphylococcus aureus mutant.

An avirulent mutant, designated RC122, was derived from Staphylococcus aureus bovine mastitis strain RC108 after N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis. Mutant RC122, which was isolated on the basis of reduced colony size, showed diminished virulence in mice (LD50 of RC122: 3.1 x 10(10) cfu vs LD50 of RC108: 2.3 x 10(7) cfu). Mutant RC122 grew more slowly than its parental strain and showed decreased production of several exoproteins, such as alpha- and beta-hemolysin, DNAse and coagulase. The production of its capsule was induced only under in vivo growth conditions. Clearance studies performed in the mouse kidney revealed that the kinetics of disappearance of the mutant was similar to that of its parental strain. Protection experiments carried out by intraperitoneal administration in mice showed that mutant RC122 conferred a good degree of protection from challenge with homologous and heterologous strains.     

Formation of a Reservoir of Sperm in the Oviduct

A reservoir of sperm in the initial segment of the oviduct has been found in several species of domestic and laboratory mammals. Evidently, the reservoir serves to ensure successful fertilization by providing the appropriate number of sperm in the appropriate physiological state for fertilizing oocytes soon after they enter the oviduct. Recent evidence indicates that sperm are trapped in the reservoir by binding to specific carbohydrate moieties on the surface of the mucosal epithelium of the oviduct. A bovine seminal plasma protein has been identified that associates with sperm and confers on them the capacity to bind to the carbohydrate moiety.     

Rete mirabile of dolphin: its pressure-damping effect on cerebral circulation

In the bottlenose dolphin Tursiops truncatus, a massive retial complex is interposed between the systemic and cerebral circulations at the cervicothoracic level. Pressure measurements in the retial efferent arteries supplying the brain revealed relatively nonpulsatile pressure profiles. These measurements in the anesthetized dolphin demonstrate the pressure-damping effect of the retia mirabile.