A weighted rein refers to a rein that is heavier on one or both ends. Naturally weighted reins are cut from hides that are specifically chosen for their weights and thicknesses. No extra leather or additional materials are added to the them. Notice in the picture the difference in the thicknesses of the tail, center and bit ends of this pair of reins.
Mitomycin C is a potent DNA crosslinker. A single crosslink per genome has shown to be effective in killing bacteria. This is accomplished by reductive activation of mitomycin to form a mitosene, which reacts successively via N-alkylation of two DNA bases.
The milbemycins are a group of macrolides chemically related to the avermectins and were first isolated in 1972 from Streptomyces hygroscopicus. They are used in veterinary medicine as antiparasitic agents against worms, ticks and fleas.