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The effectiveness of inorganic calcifying solutions to remineralize enamel with subsurface demineralization decreased with saliva pre-treatments conducive to the formation of enamel pellicles. Greater reductions in remineralization rates occurred with longer pellicle formation times. It is suggested that enamel pellicles may act to control surface deposition and favor subsurface precipitation.
OBJECTIVES: Despite its protective role, the dentine pellicle has rarely been studied, therefore we aimed to map out the proteomic profile of in vitro dentine pellicles before and after modification. MATERIALS AND METHODS: A total of 135 human dentine specimens were prepared. After initial pellicle formation with 150 µl pooled human saliva (37 °C, 30 min), the dentine specimens were immersed in one of 9 pellicle modification solutions (2 ml/specimen): deionized water (non-modified pellicle), SnCl2/NaF/AmF (commercial solution containing 800 ppm Sn2+ and 500 ppm F-), NaF solution (500 ppm F- ), and six polyphenol solutions (2 mg / ml) with or without 500 ppm F-: blueberry extract (BBE and BBE + F-), green tea extract (GTE and GTE + F-) and grape seed extract (GSE and GSE + F-). After another aliquot of saliva (150 µl, 37 °C, 60 min), the pellicles were harvested with sodium dodecyl sulphate by rubbing with cotton balls, and taken to proteomic analyses by Liquid Chromatography-Tandem Mass Spectrometry after tryptic digestion. RESULTS: A total of 382 proteins were identified in all the proteomic analyses for all groups. Pellicle modification with fluoride, either NaF or SnCl2/NaF/AmF, led to the presence of 12 or 14 exclusive proteins, respectively, whereas modification with the solutions containing polyphenols presented less exclusive proteins (4-6 proteins). The number of exclusive proteins was even lower for when polyphenols and fluoride (GTE + F- and GSE + F-) were used, with lower abundance of proteases. CONCLUSIONS: We conclude that NaF and SnCl2/NaF/AmF significantly modify the proteome of the dentine pellicle. The combination of fluoride with polyphenols further lowers the abundance of proteins and proteases, which explains the positive effect of these solutions on the dentine pellicles. CLINICAL RELEVANCE: Plant extract solutions with fluoride can significantly modify the proteomic structure of the dentine pellicle, which clarifies the mechanism of action of polyphenols on the protection of dentine demineralization.
Tetrahymena pyriformis NT-I cells in the early-logarithmic phase were incubated with phenethyl alcohol (2-phenylethanol) and effects on the lipid composition were examined in various membranes. 1. There was a marked modification in phospholipid head, as well as fatty acyl group composition in pellicles, mitochondria and microsomes of the phenethyl alcohol-treated cells. Compared with membranes of the control cells, the membranes from phenethyl alcohol-treated cells were found to contain a higher level of phosphatidylcholine content with the compensating decrease in phosphatidylethanolamine, while 2-aminoethylphosphonolipid showed only a slight decrease in these membranes. The acyl group profile of membrane phospholipids in the presence of phenethyl alcohol was also modified so that a profound elevation of the content of polyunsaturated fatty acids, linoleic and gamma-linolenic acids. The major monounsaturate, palmitoleate decreased. Such lipid alteration is a reversible process, and therefore upon removal of phenethyl alcohol the modified lipid composition returned to normal. 2. By freeze-fracture electron microscopy in combination with temperature quenching, the outer alveolar membrane of the phenethyl alcohol-treated cell was observed to reveal less aggregation of intercalated-membrane particles, as compared with the control membrane. The quantitative analysis of the thermotropic lateral movement of membrane particles provided evidence that the membrane in the phenethyl alcohol-treated cell became more fluid. Such fluidizing effects may result from an increase in the acyl group unsaturation and also in the phosphatidylcholine content. 3. With regard to the mechanism responsible for the marked decrease in palmitoleate in membrane phospholipids, there was found a depressed conversion of the palmitate to palmitoleate in the phenethyl alcohol-treated cells. It was further suggested that the drug may have an inhibitory effect on the synthesis of palmitoyl-CoA desaturase involving the (16 : 0 leads to 16 : 1) conversion. Also, it was demonstrated that the increase in a precursor-product fashion of phosphatidylcholine with the corresponding decrease in phosphatidylethanolamine was not due to transformation of phosphatidylethanolamine to phosphatidylcholine through stepwise methylation.
Fluorescence polarization of 1,6-diphenylhexatriene (DPH) was used to study the effects of temperature acclimation on Tetrahymena membranes. The physical properties of membrane lipids were found to be highly dependent on cellular growth temperature. DPH polarization in lipids from three different membrane fractions correlated well with earlier freeze-fracture and electron spin resonance observations showing that membrane fluidity progressively decreases in the order microsomes greater than pellicles greater than cilia throughout a wide range of growth temperatures. Changes in membrane lipid fluidity following a shift from high to low growth temperatures proceed rapidly in the microsomes, whereas there is a pronounced lag in the changes of peripheral cell membrane lipids. These data support previous observations that adaptive changes in membrane fluidity proceed via lipid modifications in the endoplasmic reticulum, followed by dissemination of lipid components to other cell membranes. The rapid changes in polarization observed in the microsomal lipids following a temperature shift correspond closely with the time-dependent alterations in both lipid fatty acid composition and freeze-fracture patterns of membrane particle distribution, suggesting that, in the endoplasmic reticulum, lipid phase separation is the primary cause of membrane particle rearrangements.
In an ultrastructural study the development of the sporozoite as well as the growth and development of the trophozoite of Gregarina blaberae were followed in the course of experimental infections of larvae of the cokroach Blaberus craniifer. The spectacular growth involved the transformation within 18 days of the sporozoite, measuring 15 X 1 micronm, to a cephaline--trophozoite affixed to the intestinal epithelium--of 250 micronm length and 65 micronm diameter. The sporozoite's ultrastructure is not different from that of sporozoites of other Sporozoa studies to date--the conoid and dense bodies are present. The pellicle consists of 3 membranes, but there are some interruptions in the internal membrane complex. The first dictyosomes are formed from the nuclear envelope. The migration of the nucleus and of the dense bodies, followed by the regression of all the structures characteristic of the sporozoites, and the establishment of a cortical zone that comes to cover the epimerite, take place within 48 h after infection and mark the transformation of the sporozoite into the trophozoite. Development of the cephaline involves the formation of the epicytic folds, which occurs at the base of the deutomerite, starting on the 3rd day of development. A regular system of longitudinal or epicytic folds is formed over the entire surface of the gregarine. On the 4th and 5th days of development, a vacuolar system and a chondriome become differentiated in the epimerite, while a fibrillar septum separates the protomerite from the deutomerite. The next stage, starting on the 6th day, is characterized by distribution of polysaccharide reserves between these 2 segments. The model studied allows us to determine the role of the epimerite in the parasite's nutrition, as well as the development of the chondriome and of the cortical membranes in the course of the vegetative growth phase of the cephaline gregarine.