In vitro bacterial adherence onto pellicle-coated aesthetic restorative materials.

Adhesion of oral bacteria to teeth and restorative materials plays an important role in the pathogenesis of oral diseases. This study investigated the initial adhesion of Streptococcus mutans to enamel and restorative materials. Three types of composites and two types of glass ionomer cements were used. The specimens were coated with freshly collected human parotid saliva. The salivary coated samples were incubated with cell-free glucosyltransferase, and further incubated with sucrose solution. Finally, the specimens were incubated with 3H-thymidine labelled bacteria. Adhesion of the bacteria to the specimens was measured by scintillation counter. SEM observations were performed on each sample. The results showed no significant differences among the materials and the control. These findings can be explained by the pellicle which coated all the specimens. This biofilm, to which the bacteria were adhered and proved to probably masked existing surface properties of the specimens resulting in similar bacterial adhesion.

Effect of vitamin K on neonatal erythrocytes.

This study investigated the possible oxidative effect of vitamin K3 (menadione) and Vitamin K1 (Konakion) on neonatal erythrocytes by controlled in vitro exposure. Menadione caused only mild morphological changes and did not decrease ATP levels. However, it oxidized intracellular hemoglobin to methemoglobin in neonatal cells more than in adult cells. Reduced glutathione contents were higher in neonatal cells, but less available for antioxidant protection. Konakion did not increase methemoglobin levels in newborn infants after a prophylactic injection. In vitro exposure to Konakion did not affect reduced glutathione and ATP levels, nor did it oxidize hemoglobin. However, extensive morphological changes were observed, attributed to the effect of its solvent. Therefore, it seems that menadione, which is no longer administered to newborns, causes oxidative stress in neonatal cells whereas Konakion, the current vitamin K1, does not, either in in vitro studies or by therapeutic administration.

Oxidative stress in newborn erythrocytes.

Phenylhydrazine (PHZ) exposure is used to study in vitro red cell aging mechanisms dependent on Hb oxidation. The effect of PHZ on normal neonatal red blood cells was studied in unseparated blood and after separation into light and heavy cells. PHZ caused more extensive morphologic changes in neonatal than in adult red blood cells. PHZ exposure of neonatal cells caused less reduced glutathione depletion than in adult cells. Although we found the same total amount of oxidized Hb in both cells, a well-defined oxidation product of Hb was demonstrated by Mössbauer spectra only in neonatal cells. This oxidation product was not methemoglobin but a trivalent, high-spin iron compound. All neonatal cell populations were more sensitive to PHZ than were adult ones, as demonstrated by the presence of Heinz bodies at low PHZ concentration, which did not affect adult cells. These studies demonstrate greater sensitivity of neonatal cells to PHZ in all density-separated populations.