Role of fluid dynamics on the healing of an in vivo tissue engineered vascular graft.

A polyester (PET) reinforced fibrin-FN-VEGF-TGFbeta vascular graft, formed by a four-step preclotting technique of a porous PET arterial graft, shows the overlapping inflammation, proliferation, and remodeling steps of normal wound healing when implanted in the descending thoracic aorta (DTA) position in the dog, forming a surface layer of endothelial cells. While the DTA grafts readily healed (i.e., endothelialized), similar grafts implanted in the carotid-femoral artery position did not fully heal. Since the initial phases of healing were shown to be dependent upon the transport of blood-borne constituents to the graft surface, the extent of healing appears to be dependent on the fluid dynamics present in the artery-graft-artery construct. The length of the noncompliant graft, the construction of the anastomoses, bends in the construct, graft diameter, and graft compliance can affect the fluid dynamics in the implant, and thus the healing of the graft. This has clinical relevance for the testing and development of new vascular graft materials.

Fourier transform infrared attenuated total reflection analysis of human hair: comparison of hair from breast cancer patients with hair from healthy subjects.

A comparative study of Fourier transform infrared attenuated total reflection (FTIR-ATR) spectra of 32 scalp and pubic hair samples from individuals diagnosed with breast cancer and those who were negative for breast cancer showed increases in the beta-sheet/disorder structures (relative to alpha-helix structures) and C-H lipid content of hair from breast cancer patients. Thus, the presence of breast cancer appears to alter the hair growth process, resulting in changes in the composition and conformation of cell membrane and matrix materials of hair fiber. These appear to be consistent with the changes observed in X-ray diffraction patterns for hair from breast cancer patients. A blind study of 12 additional hair samples using these FTIR-ATR spectral differences as markers correctly identified all four hair samples from cancer patients (100%). Two of these samples were from breast cancer patients. Of the remaining two samples analyzing positive for cancer, one was from a prostate cancer patient and one from a lung cancer patient. Thus, it appears that the mechanism that alters hair fiber synthesis in the three types of cancer may be similar. The blind study incorrectly identified as positive for cancer three hair samples from two apparently healthy individuals and one patient considered cured from prostate cancer.

Vascular graft healing. III. FTIR analysis of ePTFE graft samples from implanted bigrafts.

A bigraft, composed of a 30-microm internodal distance expanded polytetrafluoroethylene (ePTFE) arterial graft segment and a preclotted polyethylene terephthalate arterial graft segment, was used to study the healing process of two different materials in the same dog. Healing was followed by FTIR-ATR spectroscopy and correlated with ELISA analyses of selected growth factors and matrix proteins. The FTIR analyses of the ePTFE explants from 1 and 3 h; 3, 5, 7, 10, and 14 days; and 4 and 8 weeks showed that the ePTFE grafts did not heal (endothelialize), but appeared to remain in overlapping inflammation and proliferation stages of wound healing. Although FN was found in the fibrin layer coating the luminal surface of the ePTFE, VEGF was not present. The inability of VEGF to complex with FN may be the result of FN binding sites being blocked or hidden by the conformation of the fibrin clot that forms on ePTFE. Also, TGF-beta was not present beyond the initial clot formation at 3 h postimplantation. The absence of these two growth factors may be an important factor in the lack of healing of 30-microm ePTFE grafts, because both were found to be present during the early stages of healing for the preclotted polyester grafts that did endothelialize.

FTIR-ATR analysis of brewed coffee: effect of roasting conditions.

FTIR-ATR was used to study the effect of roasting conditions on the flavor of brewed coffee using Guatemala Antigua coffee beans. The 1800-1680 cm(-1) carbonyl region for vinyl esters/lactones, esters, aldehydes, ketones, and acids was found to provide a flavor-print of the brewed coffee. A study of light, medium, and dark roasts indicated that when the rate of heating to the onset of the first and second cracks was kept constant, the types of carbonyl compounds formed were similar, varying only in their concentration. This difference in concentration is apparently due to the additional heating of the coffee bean beyond the second crack. When the heating rate to the onset of the first and second crack was varied, both the types and concentration of the carbonyl compounds formed during roasting were affected. Thus, heating rates of green coffee beans to the onset of the first and second cracks are important determinants of the basic taste and aroma of brewed coffee.