RPAP and UMN-Duluth provide significant, complementary educational programs that lead more graduates to choose rural and primary care practices. Efforts across the nation to address the crisis in rural primary care should build on these successful efforts.

As shown by scanning electron and phase contrast microscopy, Treponema pallidum attached in vitro to basement membranes purified from kidney cortex tissues or from retinal vessels. This organism also attached to the extracellular matrix remaining after cultured cells had been solubilised with Triton X. Fibronectin, laminin, collagen, IV, collagen I, and hyaluronic acid are structural components of basement membranes and extracellular matrices. Experiments were performed to investigate the in vitro attachment of T pallidum to each of these components. Viable or heat inactivated treponemes were added to glass coverslips precoated with different concentrations of each component. After various times of incubation, coverslips were washed and the attached organisms were counted. Large numbers of viable organisms attached to each of these five components. In contrast, heat inactivation sharply reduced numbers of attached organisms. The IgG fractions of immune and non-immune rabbit serum samples were affinity purified using protein A. T pallidum was preincubated with both fractions, then incubated with either intact cultured cells or with coverslips coated with the five tissue components. The IgG from immune serum blocked treponemal attachment to the cultured cells and to fibronectin, laminin, collagen IV, and collagen I, but not to hyaluronic acid. These results are discussed in terms of attachment mechanisms of T pallidum and potential applications to in vivo infection.

This study describes the distribution of fibronectin and its association with reticulin fibers (type III collagen) and hyaluronic acid in shallow rabbit wounds. Linear incisions were made dorsally with a surgical blade. Animals were sacrificed and 1 , 2, 3, 4, 5, and 8 day wounds were examined using peroxidase-antiperoxidase to localize affinity-punfied antibodies to fibronectin. Tissue samples were also stained with hematoxylin and eosin in addition to silver stains for reticulin, and Alcian blue for hyaluronic acid. After wounding, the incision filled with a fibnin clot that stained positively for fibronectin. The underlying dermis and adjacent, unwounded dermis also contained fibronectin. Epidermal cells that migrated from the wound margin between the clot and the dermis were in direct association with fibronectin in these wound components. By 72 hr, epidermal continuity was reestablished. Early granulation tissue formation was apparent just below the epidermis in 'Supported by grants from the Minnesota Medical Foundation #DMRF-53-80 and the University of Minnesota Graduate School #464-0325-4909 (to L.

The epidermal cells which migrate over the wound surface of the amputated limb of the adult newt were examined using the scanning electron microscope. Specimens were prepared routinely for scanning electron microscopy or were embedded in Epon 812 for light microscopic observations. A cuff of epidermal cells was seen at the edge of the wound, from which cells appeared to migrate over the wound surface. As early as five hours after transection of the limb, the basal layers of this cuff appeared to send out pseudopodial projections. These seemed to establish a physical contact with a fibrin-like substratum, which apparently served as a means of support for the migrating cells. Subsequently, the epidermal cells became elongate and had the appearance of streaming toward the center of the wound. Between 10 and 13 hours post-amputation, the cells in the central region of the stump were rounded up and some possessed microappendages resembling microplicae and microvilli. Throughout the entire period of wound coverage, the cells seemed to maintain contact with the fibrin network, which appeared to be the first structural element of wound architecture. As a result of these observations, the mechanism by which the epidermal cells migrate has been clarified.