The acetylation and enzymatic degradation of starch films

The preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc.     

A fluorometric assay for the measurement of endothelial cell density in vitro

A fluorometric assay for determining endothelial cell numbers based on the endogenous enzyme acid phosphatase is described. In preliminary studies, three substrates--p-nitrophenyl phosphate, 4-methylumbelliferyl phosphate, and 2'-[2-benzthiazoyl]-6'-hydroxy-benthiazole phosphate (AttoPhos)--were compared with respect to their kinetic, optimum assay conditions, sensitivity, and detection limits. Only AttoPhos was found to have a high degree of sensitivity, reliability, and reproducibility for measuring both high and low cell numbers in the same plate. In subsequent experiments, assay conditions were validated for measuring endothelial cell density in response to basic fibroblast growth factor and fumagillin. Furthermore, the AttoPhos assay revealed a linear correlation between acid phosphatase activity and cell number in many cell types, including BALB/3T3, CHO-K1, A431, MCF7, 2008, SK-OV-3, T47-D, and OVCAR-3. This assay is potentially valuable for use in many in vitro systems in which the quantitation of cell density and proliferation is necessary. The practical advantages of AttoPhos assay for measuring endothelial cell numbers include (1) nonradioactivity, (2) simplicity, (3) economy, (4) speed of assessment of proliferation of large number of samples, and (5) amenability to high-throughput drug screening.     

Temperature regulator for irradiation systems designed for evaluation of microwave bioeffects

A temperature-regulating circuit, applicable to irradiation systems designed for investigation of microwave bioeffects (at cellular levels), is described. The temperature regulator provides a thermal balance between two biological suspensions in aqueous media, by heating one sample electrically when the second specimen is heated by means of microwaves.