Water transport in resin-modified glass-ionomer dental cement

Water uptake and water loss have been studied in a commercial resin-modified glass-ionomer cement, Fuji II LC, under a variety of conditions. Uptake was generally non-Fickian, but affected by temperature. At room temperature, the equilibrium water uptake values varied from 2.47 to 2.78% whereas at low temperature (12 degrees C), it varied from 0.85 to 1.18%. Cure time affected uptake values significantly. Water uptake was much lower than in conventional glass-ionomer restorative cements exposed to water vapor. Loss of water under desiccating conditions was found to be Fickian for the first 5 h loss at both 22 and 12 degrees C. Diffusion coefficients were between 0.45 and 0.76 x 10( -7) cm(2)/s, with low temperature diffusion coefficients slightly greater than those at room temperature. Plotting water loss as percentage versus s(-(1/2)) allowed activation energies to be determined from the Arrhenius equation and these were found to be 65.6, 79.8, and 7.7 kJ/mol respectively for 30, 20, and 10 s cure times. The overall conclusion is that the main advantage of incorporating HEMA into resin-modified-glass-ionomers is to alter water loss behavior. Rate of water loss and total amount lost are both reduced. Hence, resin-modified glass-ionomers are less sensitive to water loss than conventional glass-ionomers.

Fluoridation for dental public health

This article reviews the means by which fluoride is supplied to populations. Many public health authorities provide fluoridated drinking water, with typical concentrations of fluoride of between 0.5 and 1.0 ppm. This has been found to be safe and effective, though differences in caries incidence between fluoridated and non-fluoridated regions are less than they were 50 years ago, because of the wider availability of fluoridated products to the whole population. Concerns about the effect of fluoride on bone density and associated conditions are reviewed and the general conclusion from considering the literature on fluoride is that there is almost no cause for concern. Alternatives to water as a means of delivering fluoride to the general public that are being used in a number of countries are salt and milk. These alternatives are also reviewed and have been shown to give satisfactory levels of protection against caries, though milk is shown to be less satisfactory than water as a vehicle for fluoride delivery. Milk is also less effective in providing fluoride to individuals in the population, and is less likely to be consumed by people in lower socio-economic groups, precisely those who suffer most from dental caries. This study concludes that mass water fluoridation remains an important contribution to good oral health throughout the community.

The origin and evolution of synaptic proteins - choanoflagellates lead the way.

The origin of neurons was a key event in evolution, allowing metazoans to evolve rapid behavioral responses to environmental cues. Reconstructing the origin of synaptic proteins promises to reveal their ancestral functions and might shed light on the evolution of the first neuron-like cells in metazoans. By analyzing the genomes of diverse metazoans and their closest relatives, the evolutionary history of diverse presynaptic and postsynaptic proteins has been reconstructed. These analyses revealed that choanoflagellates, the closest relatives of metazoans, possess diverse synaptic protein homologs. Recent studies have now begun to investigate their ancestral functions. A primordial neurosecretory apparatus in choanoflagellates was identified and it was found that the mechanism, by which presynaptic proteins required for secretion of neurotransmitters interact, is conserved in choanoflagellates and metazoans. Moreover, studies on the postsynaptic protein homolog Homer revealed unexpected localization patterns in choanoflagellates and new binding partners, both which are conserved in metazoans. These findings demonstrate that the study of choanoflagellates can uncover ancient and previously undescribed functions of synaptic proteins.

Two-hybrid analysis of the interaction between the fission yeast proteins Sal3 and Cdc25

Cdc25 is a mitosis triggering phosphatase in Schizosaccharomyces pombe, and is transported in to the nucleus during G2 phase by the importin-β protein Sal3. Cdc25 triggers mitosis and cell division by dephosphorylating tyrosine 15 of Cdc2. In sal3 mutants, Cdc25 is not transported into the nucleus and the cells halt in G2. The purpose of this study is to use a two-hybrid system to determine the nature of the relationship between Sal3 and Cdc25. Previous research has failed to detect any interaction between the two proteins, but specific modifications were made to the two-hybrid system in this study including the separation of Sal3 into its two binding domains, the addition of fluorescent tags to the fusion protein, and the reversal of plasmids in the fusion proteins. Unique PCR primers were successfully designed, based on a multiple alignment of Sal3 and its homologues, to separate Sal3 into its two domains.

HAMSTER OVIDUCTIN ENHANCES TYROSINE PHOSPHORYLATION OF SPERM PROTEINS DURING CAPACITATION

Capacitation is essential for fertilization of ovulated oocytes. Capacitation is correlated with activation of a signal transduction pathway leading to protein tyrosine phosphorylation, an essential prerequisite for fertilization. Oviductin has been shown to bind to the acrosomal cap and the equatorial segment region of the sperm head. In light of findings reported in previous studies, we hypothesized that estrus stage-specific oviductin (EOV) enhances tyrosine phosphorylation. Immunofluorescent detection by light and confocal microscopy and immunogold labeling by electron microscopy and surface replica techniques were used to localize tyrosine phosphorylated proteins to the equatorial segment region and midpiece after incubation in medium in the presence or absence of EOV. In the presence of EOV, an increase in tyrosine phosphorylation in the equatorial segment region was observed as early as 5 minutes after incubation. On prolonging incubation in medium containing EOV immunostaining further increased, indicative of increased levels of tyrosine phosphorylation of sperm proteins as capacitation proceeds. Regardless of the presence or absence of EOV, phosphotyrosine expression was observed along the tail, specifically at the midpiece. However, this reactivity was enhanced in the presence of EOV. Western blot analysis of NP-40 extractable and non-extractable sperm proteins confirmed these observations. NP-40 extractable sperm proteins (25, 37, 44kDa) and non-extractable sperm proteins (70, 83, 90kDa) showed increased intensity when sperm were capacitated in the presence of EOV after 5-, 60-, 120- and 180-minutes of capacitation. Mass spectrophotometric analysis identified enolase, ATP-specific succinyl CoA, succinate CoA ligase, zona pellucida binding protein, heat shock protein 90, aconitase and hexokinase as proteins that undergo enhancement in tyrosine phosphorylation in the presence of EOV. The proteins identified are known to be involved in specific functions including cellular metabolism, molecular chaperoning and normal sperm development. In summary, the present investigation has provided new evidence showing that sperm capacitated in vitro in the presence of EOV display an enhanced expression of tyrosine phosphorylation compared to sperm incubated in capacitating medium alone. These results indicate that inclusion of oviductin in media used for in vitro fertilization (IVF) may improve success rates of IVF by enhancing the signaling pathways involved in sperm capacitation.

Extraction and radioimmunoassay quantitation of neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) from human dental pulp tissue

The measurement of neuropeptides in complex biological tissue samples requires efficient and appropriate extraction methods so that immunoreactivity is retained for subsequent radioimmunoassay detection. Since neuropeptides differ in their molecular mass, charge and hydrophobicity, no single method will suffice for the optimal extraction of various neuropeptides. In this study, dental pulp tissue was obtained from 30 human non-carious teeth. Of the three different neuropeptide extraction methods employed, boiling in acetic acid in the presence of protease inhibitors yielded the highest levels of neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP). High pressure liquid chromatography (HPLC) analysis of dental pulp tissue verified the authenticity of the neuropeptides extracted. © 2003 Elsevier Science Ltd. All rights reserved.