Prevalence of rabies in bats in Michigan, 1981-1993.

OBJECTIVES: To analyze the species distribution of animals submitted to the Michigan Department of Public Health (MDPH) for rabies testing during 1993. To determine whether any of the 9 species of bats residing in Michigan carries a disproportionate rabies burden, and to determine whether bats contributed the most cases of confirmed rabies during 1981 through 1992. DESIGN: Epidemiologic study. PROCEDURE: Records of animals submitted to the MDPH for rabies testing during 1993, and between 1981 and 1992, were reviewed. Information regarding type of animal submitted, specific species if the animal was a bat, county from which the animal was obtained, the identity of the submitting individual, species of the animal exposed, month of the submission, and results of rabies testing was extracted from these records. RESULTS: During 1993, the MDPH received 2,045 submissions for rabies testing. Seventeen rabid animals were identified: 1 cat, 1 skunk, and 15 bats. Two hundred forty-six bats were submitted for testing. Eptesicus fuscus, the big brown bat, accounted for 97.2% (239) of bat submissions and was the only species of bat that had positive results of testing for rabies. Annual percentages of submitted bats found to be rabid ranged from 2.0 to 11.0%, with a 13-year mean of 6.2%. CONCLUSIONS: 100% of the confirmed cases of rabies in bats reported in Michigan in 1993 were associated with in E fuscus. During 1981 through 1992, most of Michigan's confirmed cases of rabies in animals developed in bats.

Response of a human megakaryocytic cell line to thrombin: increase in intracellular free calcium and mitogen release.

The CHRF-288-11 cell line has been previously shown to exhibit properties consistent with a megakaryocytic origin. The response of these cells to thrombin has now been investigated. Thrombin treatment of CHRF-288-11 cells results in both an increase in intracellular free calcium levels and secretion of mitogenic activity and beta-thromboglobulin. Cell viability is not affected. The mitogenic activity released from the cells is due primarily to the presence of basic fibroblast growth factor. Immunohistochemical data indicate a packaging of basic fibroblast growth factor into granular structures. Trypsin and phorbol 12-myristate 13-acetate also initiate release of mitogenic activity from this cell line, whereas under non-stirred conditions collagen and ADP do not. Through measurements of intracellular calcium levels it was determined that thrombin pretreatment of cells ablates a further response to thrombin, but does not block an increase in intracellular calcium levels due to trypsin. This suggests that these two agonists may act through different mechanisms. The thrombin-induced release reaction is inhibited almost completely by the reagents hirudin and dipyridamole, and only partially by indomethacin. These data indicate that the CHRF-288-11 cell line should provide an excellent model system in which to study the packaging of factors into granules which undergo regulated release.

Structural basis for the low affinities of yeast cAMP-dependent and mammalian cGMP-dependent protein kinases for protein kinase inhibitor peptides.

Affinities of the catalytic subunit (C1) of Saccharomyces cerevisiae cAMP-dependent protein kinase and of mammalian cGMP-dependent protein kinase were determined for the protein kinase inhibitor (PKI) peptide PKI(6-22)amide and seven analogues. These analogues contained structural alterations in the N-terminal alpha-helix, the C-terminal pseudosubstrate portion, or the central connecting region of the PKI peptide. In all cases, the PKI peptides were appreciably less active as inhibitors of yeast C1 than of mammalian C alpha subunit. Ki values ranged from 5- to 290-fold higher for the yeast enzyme than for its mammalian counterpart. Consistent with these results, yeast C1 exhibited a higher Km for the peptide substrate Kemptide. All of the PKI peptides were even less active against the mammalian cGMP-dependent protein kinase than toward yeast cAMP-dependent protein kinase, and Kemptide was a poorer substrate for the former enzyme. Alignment of amino acid sequences of these homologous protein kinases around residues in the active site of mammalian C alpha subunit known to interact with determinants in the PKI peptide [Knighton, D. R., Zheng, J., Ten Eyck, L. F., Xuong, N-h, Taylor, S. S., & Sowadski, J. M. (1991) Science 253, 414-420] provides a structural basis for the inherently lower affinities of yeast C1 and cGMP-dependent protein kinase for binding peptide inhibitors and substrates. Both yeast cAMP-dependent and mammalian cGMP-dependent protein kinases are missing two of the three acidic residues that interact with arginine-18 in the pseudosubstrate portion of PKI. Further, the cGMP-dependent protein kinase appears to completely lack the hydrophobic/aromatic pocket that recognizes the important phenylalanine-10 residue in the N-terminus of the PKI peptide, and binding of the inhibitor by the yeast protein kinase at this site appears to be partially compromised.