PubMed · 15412256
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C J RUDOLPH. 1950. Angiospasm; general application.. https://pubmed.ncbi.nlm.nih.gov/15412256/
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A method of encasing cardiovascular stents with an expandable polyurethane coating has been developed to provide a smooth homogeneous inner wall allowing for a confluent growth of endothelial cells. In this design, the metal wire stent structure is completely covered by the polyurethane film, minimizing biocorrosion of the metal (stainless steel or nitinol), and providing a homogeneous surface for surface treatment and incorporation of various eluting drugs to prevent platelet aggregation while supporting endothelialization. The polyurethane surface was treated with a helium plasma for sterilization and promotes growth of cells. The article details the performance of the coated film to expand with the metal stent up to 225% during deployment. Stress/strain behavior of polyurethane films, subsequent plasma treatment of the surface, and the adhesion of the coating to the stent structure upon expansion are presented. A film of less than 25 microm was found to be sufficient for corrosion resistance and flexibility without producing any excess stress on the stent structure. Straining the film to 225% and plasma modification did not affect the mechanical and surface properties, but allowed for improved biocompatibility as determined by the critical surface tension, surface chemistry, and roughness.
It has been demonstrated that gas-filled microbubble contrast agents, based on their volume changes, can serve as pressure probes in an MR field. It was recently reported that such an MR-based pressure measurement with microbubbles at 1.5 T must make use of microbubbles that have a volumetric magnetic susceptibility difference with the blood of at least 34 ppm in SI units. In this work, we show through analytical approximations and numerical simulations that such a microbubble formulation can be achieved by coating typical lipid-shelled microbubbles with particles of high dipole moment. Through finite-element simulations we demonstrate that the effective volumetric magnetic susceptibility of a coated microbubble is dependent on the radius, the shell volume fraction and the magnetic susceptibility of the particulates on the shell. Our calculations suggest that a suitable microbubble formulation which will be MR-sensitive to small pressure changes at 1.5 T must be 2-3 microm in radius and be uniformly coated with single-domain magnetic nanoparticles, such as magnetite, at shell volume fractions below 5%.
OBJECTIVE: To find whether plasma and follicular prorenin concentrations have any effect on the uterine arterial blood flow in women with polycystic ovarian syndrome (PCOS) compared to those with normal menstrual cycles (NMC). STUDY DESIGN: Controlled prospective clinical study involved 55 women undergoing in vitro fertilization: 24 with PCOS and 31 with NMC. In both groups transvaginal colour Doppler assessment of uterine arterial blood flow was analysed on day 22 of the cycle, on the day of human chorionic gonadotrophin (HCG) administration and 36 h after HCG. Plasma and follicular (in the dominant follicle containing mature oocyte, and in the pooled follicles) prorenin and active renin, and serum estradiol and androstenedione concentrations were measured at these time-points. The Student's t-test and Pearson correlation were used for the statistical analysis. RESULTS: The resistance index (RI) in the NMC group decreased from 0.84+/-0.05 on the day of HCG to 0.78+/-0.08 36 h after HCG (P < 0.05); in the PCOS group the RI did not decrease. Follicular prorenin concentrations in the dominant follicle and in the pooled follicles were lower in the PCOS than in the NMC group (20,210+/-10,831 microU/l, 16,753+/-8634 microU/l versus 42,637+/-35,400 microU/l, 33,067+/-26,200 microU/l; P < 0.05). CONCLUSIONS: Plasma prorenin concentrations do not affect vascular impedance to the uterine artery, but follicular prorenin do by newly formed low resistant vessels in the follicles.