Chemical mapping of co-existing RNA structures

In many cases RNA can assume co-existing or meta-stable structures preventing structure determination by chemical mapping. A novel method is described, by which RNA is modified with dimethyl sulphate without shifting the distribution of different structures. The different structures are then separated in native gel electrophoresis, and structure determination by primer extension can be carried out separately for each structure.     

Investigation of tissue preparation conditions for non-radioactive in situ hybridization: localization of transforming growth factor-alpha message in rat kidney

A non-radioactive method of in situ hybridization was used to localize transforming growth factor-alpha mRNA in epithelial cells of collecting ducts and tubules in rat kidney tissue sections. The intensity and specificity of staining were assessed under a variety of tissue preparation conditions, including a direct comparison of paraffin against frozen sections. Under optimal conditions, both the signal strength and the cellular localization of the growth factor message were superior in paraffin sections. The staining method could also be used to localize the message in lung tissue, indicating that the procedure is generally applicable to other tissues. Our results indicate that the use of paraffin sections for nonradioactive in situ hybridization affords a number of advantages for the localization of specific messages in tissue sections.     

Transformations of normal and inverted function tables

We develop a theory of function tables, similar to, and inspired by, that given in the work of D. Parnas. We consider, in particular, two classes of function tables: normal and inverted. We study effective transformations between tables of these two classes, as well as transformations which change the dimension of a table. We also consider the interrelationship between these three types of transformation.     

Performance of small diameter synthetic vascular prostheses with confluent autologous endothelial cell linings

Autologous grafts are superior to their synthetic counter-parts for grafting arteries smaller than 6-mm diameter both in terms of acute thrombogenicity and chronic intimal hyperplasia. Endothelial cell (EC) coating of the blood contacting surface may reduce thrombogenicity of synthetic small diameter vascular prostheses. In this study, the survival of EC monolayers on synthetic 4-mm diameter arterial prostheses over short-term implantations (< or = 6 weeks) was examined. Graft types examined were expanded polytetra-fluoroethylene (ePTFE) and microporous polyurethane (PU). Lumenal coverage with ECs was achieved by culturing ovine ECs on prostheses treated by either physical adsorption or covalent binding of ovine fibronectin (Fn). An ovine carotid interposition model was used to examine the performance of EC coated ePTFE and microporous PU over implantation periods of 1, 3, and 6 weeks. Outcomes assessed at the end of each experiment were graft patency, area covered by ECs, and thrombus free surface area (TFSA). Fn concentration, cell density at the time of coating and prostacyclin production in vitro were similar for both graft types. Occlusion occurred more frequently in unseeded grafts compared with EC coated grafts over 3 and 6 week implantation periods; however, the difference was not significant (p = 0.099). In prostheses precoated with ECs, approximately 40-60% of the surface area remained covered with endothelial-like cells following the first postoperative week. Recovery of EC layers occurred rapidly thereafter with 80-90% coverage at 3 weeks. TFSA remained low in comparison to EC cover in these prostheses until between 3 and 6 weeks postoperatively, suggesting a lag phase in recovery of EC function of seeded cells. In contrast, EC cover of unseeded prostheses only achieved 10-30% at 3 weeks, primarily by pannus EC ingrowth from the adjacent artery. TFSA of unseeded grafts increased in direct proportion to EC cover over time suggesting that there was no lag phase in function of these ingrowing cells.