In vitro effect of topical fluorides on sealant materials

The purpose of this study was to determine by visual inspection and by scanning electron microscopy (SEM) whether commercially available, topical, acidulated phosphate fluoride (APF) and neutral sodium fluoride (NaF) agents cause surface roughening of five sealant materials: two unfilled resins, two filled resins, and one glass-ionomer material. In addition, the effect of treatment with 1.23% APF and sonification on weight of an unfilled and a filled sealant was compared to treatment with controls. Unfilled sealants exhibited no surface changes visually or on micrographs following any treatment. Filled sealants and the glass-ionomer sealant exhibited visually apparent changes depending on the treatment. SEM inspection of filled sealants with visually apparent changes showed loss of filler particles whereas the glass-ionomer sealant exhibited apparent destruction both of the matrix and the filler particle. No significant differences in weight were found between sonicated and unsonicated specimens. However, significant loss of weight was found with filled sealant specimens, but not unfilled sealant specimens, treated with 1.23% APF gel as compared with the specimens treated with water. The results of this in vitro study indicate that preventive therapies that combine use of topical fluorides and sealants may cause deterioration of filled sealants and glass-ionomer sealant material, but not unfilled sealants.

Nanosecond study of fluorescently labeled troponin C

The time-resolved extrinsic fluorescence of rabbit skeletal troponin C was studied with the protein labeled at Cys-98 with N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine. Both the intensity and anisotropy decays followed a biexponential decay law, regardless of the ionic condition, pH, viscosity or temperature. The lifetimes and their fractional amplitudes were insensitive to Mg2+, and the lifetimes were also insensitive to Ca2+. In response to Ca2+ binding to all four sites, the fractional amplitude (alpha 1) associated with the short lifetime (tau 1) decreased by a factor of two, thus increasing the ratio of the two amplitudes alpha 2/alpha 1 from 1.6 to 4.3. These amplitude changes suggest the existence of two conformational states of TnC-IAEDANS, with the conformation associated with the long-decay component (tau 2) being promoted by saturation of the two Ca(2+)-specific sites. At pH 5.2 the ratio alpha 2/alpha 1 for the apo-protein was 3.5 indicating different relative populations of the two decay components when compared with pH 7.2. In the presence of Ca2+ at the lower pH, alpha 2/alpha 1 decreased to 2.1, suggesting a shift of the conformations in favor of the short-decay component. Thus Ca2+ elicited different conformational changes in TnC at the two pH values. The recovered anisotropies suggest that there were fast molecular motions that were not resolved in the present experiments, and some of these motions were sensitive to Ca2+ binding to the specific sites. These results support the notion of communication between the N-domain and the C-terminal end of the central helix of troponin C.

Preretinal membranectomy in idiopathic preretinal macular fibrosis

Idiopathic preretinal macular fibrosis (PMF) rarely causes progressive loss of vision. In 5 of 350 cases in which vision did markedly diminish, pars plana vitrectomy and membranectomy proved to be a useful surgical method of correcting the visual loss. There was an apparent recurrence of PMF in two of the five cases.