Abstract. Previous studies of flagellar mutants have identified six axonemal polypeptides as components of a "dynein regulatory complex" (DRC). The DRC is thought to coordinate the activity of the multiple flagellar dyneins, but its location within the axoneme has been unknown Piperno et al., 1992). We have used improved chromatographic procedures (Kagami and Kamiya, 1992) and computer averaging of EM images (Mastronarde et al., 1992) three DRC mutants lack a crescent-shaped density above the second radial spoke, and pf3 axonemes lack additional structures adjacent to the crescent. We propose that the crescent corresponds in part to the location of the DRC, and that this structure is also directly associated with a subset of the inner dynein arms. This position is appropriate for a complex that is thought to mediate signals between the radial spokes and the dynein arms.

Abstract. We have characterized a group of regulatory mutations that alter the activity of the outer dynein arms. Three mutations were obtained as suppressors of the paralyzed central pair mutant pf6 (Luck, D. J. L., and G. Piperno. 1989 mutations are distinct, in-frame deletions. These deletions occur within a region that is predicted to encode a small oL-helical coiled-coil domain of the/~-DHC. This domain may play a role in protein-protein interactions within the outer dynein arm. Since both the size and location of this domain have been conserved in all axonemal and cytoplasmic DHCs sequenced to date, it presumably performs a common function in all dynein isoforms. T I-I~ dynein ATPases are a family of motor enzymes that provide the driving force for ciliary and flagellar motility and contribute to microtubule-based movements inside cells (reviewed in Porter and Johnson, 1989;Vallee, 1993). These enzymes convert the energy derived from nucleotide binding and hydrolysis into the directed movement of cellular cargoes toward the minus ends of microtubules (reviewed in Porter and Johnson, 1989). All dyneins characterized thus far are extremely large (>1-2 MD), multisubunit protein complexes. The large size and subunit complexity have hampered the identification of functional domains within the dyneins. However, the numerous flagellar mutations that affect dynein structure and function in Chlamydomonas, coupled with the recently published sequences of dynein heavy chains (DHCs) t, provide new op-

Abstract. The sup-p f-2 mutation is a member of a group of dynein regulatory mutations that are capable of restoring motility to paralyzed central pair or radial spoke defective strains. Previous work has shown that the flagellar beat frequency is reduced in sup-pf-2, but little else was known about the sup-pf-2 phenotype (Huang, B

Norway rats are an abundant synanthropic species in urban settings and serve as reservoirs for many pathogens. Attempts to control their populations have met with little success. Recent genetic studies suggest that local populations are structured and few individuals move significant distances, but there is substantial gene flow. To understand these observations and their implications on control strategies, we genotyped 722 rats from 20 alleys in Baltimore to establish paternity for 180 embryos. Up to 88 males may have contributed to the litters. All litters were sired by ≥2 males, with an average of 4.9 (range 2-7) males. For dams and sires with known locations, most matings (71.7%; n = 46) occurred among animals from different alleys. The average distance between sires and dams was 114 meters (range 8-352 meters). In 10/17 (58.8%) litters, the majority of the identified sires were captured in different alleys than the females. Sires were significantly less related to females than were the males captured in the females' alleys. Although rats may generally restrict their movements, either receptive females and/or breeding males engage in mate-seeking behaviors that extend beyond movement patterns at other times. This geographically extends the sizes of local populations and buffers them from the impacts of control strategies that focus on local infestations.

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