Photothermal radiometric (FD-PTR or PTR) signals from human teeth have been used toward detecting an artificial surface demineralization. The aim of the study is to characterize PTR signals by using controlled mineral loss from human enamel to mimic surface and subsurface dental caries. At a fixed modulation frequency, an Ar + ion laser was used as a light source to scan across the tooth surface, and an MCT infrared detector was used for measuring the PTR signals. Several human molar teeth were etched using 37% phosphoric acid etching gel and scanned across the etched region at 30 Hz. PTR amplitude from the etched region shows that the signal decreases with increasing etching time. The PTR phase also shows the same behavior with the amplitude and better contrast between different etching times. The PTR technique could thus be used to detect early surface demineralization and may give the examiner quantitative information of the degree of demineralization in dental caries.

A calcium-sensitive, phospholipid-dependent protein kinase (protein kinase C) and its three isozymes were purified from rat heart cytosolic fractions utilizing a rapid purification method. The purified protein kinase C enzyme showed a single polypeptide band of 80 KDa on SDS-polyacrylamide gel electrophoresis, and was totally dependent on the presence of Ca2+ and phospholipid for activity. Diacylglycerol was also found to stimulate enzymatic activity. Autophosphorylation of the purified PKC showed an 80 KDa polypeptide. The identity of the purified protein was also verified with monoclonal antibodies specific for PKC. Further fractionation of the purified PKC on a hydroxylapatite column yielded three distinct peaks of enzyme activity, corresponding to type I, II and III based on similar chromatographic behaviour as the rat brain enzyme. All three forms were entirely Ca2+ and phosphatidylserine dependent. Type II was found to be the most abundant. Type I was found to be highly unstable. PKC activity studies demonstrate that types II and III isozymic forms are different with respect to their sensitivity to Ca2+.

The endogenous substrate proteins of rat cardiac protein kinase C type I, II, and III isozymic forms were studied in rat cardiac sarcolemma. The 19-, 21-, 29-, 35-, and 95-kDa proteins were phosphorylated by both types II and III, but not type I. The extent of phosphorylation by individual protein kinase C isozymic forms was additive and equal to the extent of phosphorylation observed when a mixture of isozymic forms was employed. The extent of phosphorylation of the 21-kDa protein by type III was much higher than that by type II. These results suggest that the protein kinase C isozymes have preferences for specific endogenous substrate proteins. The phosphorylation of these endogenous substrate proteins by protein kinase C isozymes probably plays a role in cardiac cell functions.