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In atherosclerosis, miR-21 is increased in the aorta and associated with vitamin D deficiency. Vitamin D deficiency may influence aberrant miR-21 expression in vasculature and bone contributing to the concurrent development of atherosclerosis and osteoporosis.

A particularly important problem in plague epidemiology is concerned with the method of transfer of the disease from one rodent species to another. Since enzootic plague is known to be established in at least 15 of our western states, in western Canada, and in Mexico, the mechanism of plague transfer from wild rodents to domestic rats in the vicinity of human habitations is a particularly important question (1). Many investigators have suggested that the primary mechanism of plague spread is by transfer of infected fleas between hosts (2). Convincing circumstantial evidence that, in rural areas with a large rat population, the infection chain of "squirrel-squirrel flea-rat" may operate was obtained in studies of a plague epizootic in Ventura County, California (3). Although the evidence has been highly suggestive, the actual transfer of fleas from host to host has never been demonstrated.The means for evaluating ectoparasite transfer more precisely were obtained through the development of a method for tagging fleas and other arthropods with Ce144 (4). By use of the California vole (Microtus californicus), domestic rats (Rattus norvegicus) and radioactively tagged wild rodent fleas (Malaraeus telchinum), a preliminary study of flea transfer was conducted in experimental plots simulating field conditions. These plots were enclosed by steel screens and provided soil and native grasses for the establishment of the rodents. In one type of experiment, male and female Microtus were toe-clipped for identification and allowed to establish nests; then tagged fleas were placed on certain individuals. Traps were set each day, and the captured animals were lightly anesthetized. The fleas were removed, and checked for radioactivity, and then returned to the hosts. In another experiment, three rats were maintained in a closure adjacent to three Microtus harboring tagged fleas, or the rats were allowed to enter the vole enclosure after the wild rodents had been Observations on Flea Transfer between Hosts; a Mechanism in the Spread of Bubonic PlagueA particularly important problem in plague epidemiology is concerned with the method of transfer of the disease from one rodent species to another. Since enzootic plague is known to be established in at least 15 of our western states, in western Canada, and in Mexico, the mechanism of plague transfer from wild rodents to domestic rats in the vicinity of human habitations is a particularly important question (1). Many investigators have suggested that the primary mechanism of plague spread is by transfer of infected fleas between hosts (2). Convincing circumstantial evidence that, in rural areas with a large rat population, the infection chain of "squirrel-squirrel flea-rat" may operate was obtained in studies of a plague epizootic in Ventura County, California (3). Although the evidence has been highly suggestive, the actual transfer of fleas from host to host has never been demonstrated.The means for evaluating ectoparasite transfer more precisely were obtained through the development...