The qualities of a laser diffraction grain size analyser, the Coulter LS-100 (range claimed by the manufacturer: 0.4-900 mum in a single measurement), are evaluated on sediments of fluvial and lacustrine origin. Accuracy and resolution of measurement on standard latex spheres are excellent. Reproducibility of the results on natural sediments appears to be satisfactory, but the method underestimates the fraction of clay particles with an efficiency of detection (36-70%) proportional to the clay content determined from pipette analysis. This efficiency is somewhat higher than those reported from other instruments of the same generation. Comparison of the Coulter LS-100 with other sizing techniques shows good agreement with the sieving method but some differences appear with the electroresistance particle technique: median and mean size values measured by the Coulter Counter TA1 are systematically lower than those obtained by the Coulter LS-100. Analyses show good correlation with those of a Malvern Laser particle analyser but a discrepancy appears with very fine silt and clay sized sediments. The Coulter LS-100 detects a higher clay content than that measured with the Malvern Laser Sizer 2600. Except when precise measurements of clay content are needed, the Coulter LS-100 produces precise and accurate results in size ranges required for geological and environmental studies

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This study evaluated the influence of time after application of oxalate solutions in reducing dentin hydraulic conductance. Fifty dentin discs were obtained from extracted human third molars and assigned to 5 groups (n=10), according to the desensitizing agent used: Group I: OxaGel; Group II: experimental agent DD-1: Group III: experimental agent DD-2. In Groups IV and V, a placebo gel and deionized water were used as control, respectively. The agents were applied for 3 min, washed out and the hydraulic conductance was measured immediately and at 5-, 15-and 30-min intervals, and after acid etching. Data were analyzed statistically by two-way ANOVA and Duncan's test at 5% significance level. Groups I, II and III did not differ significantly from each other in any of the time intervals (p>0.05). Likewise, Groups IV and V were statistically similar to each other (p>0.05). The active agents reduced significantly dentin permeability in comparison to control groups (p<0.05). Dentin permeability measured in vitro decreased significantly with time regardless of the agent applied (either active or control agents). The results of Group V, in which no dentin desensitizing agent was employed, indicates that the assessment of dentin permeability by this method must be interpreted with caution.

This controlled clinical trial evaluated the 2-year clinical performance of a one-bottle etch-and-rinse adhesive and resin composite system (Excite/Tetric Ceram) compared to a resin-modified glass ionomer cement (RMGIC) (Vitremer/3M) in non-carious cervical lesions. Seventy cervical restorations (35 resin composite - RC- restorations and 35 RMGIC restorations) were placed by a single operator in 30 patients under rubber dam isolation without mechanical preparation. All restorations were evaluated blindly by 2 independent examiners using the modified USPHS criteria at baseline, and after 6, 12 and 24 months. Data were analyzed statistically by Fisher's exact and McNemar tests. After 2 years, 59 out of 70 restorations were evaluated. As much as 78.8% retention rate was recorded for RC restorations, while 100% retention was obtained for RMGIC restorations. Fisher's exact test showed significant differences (p=0.011) for retention. However, there were no significant differences for marginal integrity, marginal discoloration, anatomic form and secondary caries between the RC and RMGIC restorations. The McNemar test detected significant differences for Excite/TC between baseline and the 2-year recall for retention (p=0.02), marginal integrity (p=0.002) and anatomic form (p=0.04). Therefore, the one-bottle etch-and-rinse bonding system/resin composite showed an inferior clinical performance compared to the RMGIC.

The idea of G protein-coupled receptors (GPCRs) coupling to G protein solely in their active form was abolished when it was found that certain ligands induce a G protein-coupled but inactive receptor form. This receptor form interferes with signaling of other receptors by sequestering G protein. However, the spontaneous existence of this receptor species has never been established. The aim of the present work was to evaluate the existence of the spontaneous conformation of the receptor inactively coupled to G protein able to interfere with the response of other GPCRs. According to the law of mass action, receptor overexpression should lead to increased amounts of all spontaneously occurring species. Based on this, we generated Chinese hamster ovary (CHO-K1)-derived cell lines expressing various amounts of the human histamine H2 receptor. In these systems, the signaling of other endogenously and transiently expressed GPCRs was attenuated proportionally to human H2 receptor expression levels. G protein transfection specifically reverted this attenuation, strongly suggesting hijacking of the G protein from a common pool. Similar attenuation effects were observed when the ␤ 2 -adrenergic receptor was overexpressed, suggesting that this is a more general phenomenon. Moreover, in human mammary MDA-MB-231 cells, a consistent increase in the response of other GPCRs was observed when endogenous expression of ␤ 2 -adrenergic receptor was knocked down using specific small interfering RNAs. Our findings show that GPCRs may interact with the signaling of other receptors by modulating the availability of the G protein and suggest the existence of GPCR spontaneous coupling to G proteins in an inactive form. G protein-coupled receptors (GPCRs)2 form a large and functionally diverse superfamily of proteins that transduce signals across cell membranes. Although much is known about structural features of GPCRs involved in ligand recognition and G protein binding, the actual mechanism underlying GPCR signaling remains unclear.Traditionally, agonist occupancy of GPCRs is believed to result in a conformational change in the receptor, leading to activation of G proteins (1). However, in genetically engineered systems where receptors can be expressed at high densities, Costa and Herz (2) noted that high levels of receptor expression uncovered the existence of a population of spontaneously (unliganded) active receptors, resulting in an elevated basal response in the system.The histamine H2 receptor (H2R) is an extensively characterized member of the GPCR family, which in most systems couples to G s proteins to activate adenylyl cyclase (3-6). Compared with other GPCRs, the H2R is unique in that the wildtype receptor possesses a remarkably high degree of constitutive activity. With a receptor density of 300 fmol/mg protein, constitutive H2 receptor activity could be detected in Chinese hamster ovary (CHO-K1) cells (7).The notion that GPCRs also signal without an external chemical trigger, i.e. in a constitutive or spontaneous manner, res...

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Aim:The aim of this study was to evaluate the clinical performance of direct resin composite restorations (Tetric Ceram-TC) and indirect composite inlays (Targis-TG) after 12 months. Methods and Materials:Seventy-six Class I and II restorations (44 direct and 32 indirect) were inserted in premolars and molars with carious lesions or deficient restorations in 30 healthy patients according to the manufacturer's instructions. Each restoration was evaluated at baseline and after 12 months according to the modified USPHS criteria for color match (CM), marginal discoloration (MD), secondary caries (SC), anatomic form (AF), surface texture (ST), marginal integrity (MI), and pulp sensitivity (PS). Data were analyzed by Fisher and McNemar Chisquare tests. Results:No secondary caries and no pulpal sensitivity were observed after 12 months. However, significant changes in marginal discoloration (MD) criteria could be detected between baseline and one-year results for both materials (p<0.05). For marginal integrity (MI) criteria, the differences between baseline and oneyear recall were statistically significant (p<0.05). For marginal integrity (MI) criteria, Tetric Ceram (TC) showed results statistically superior to Targis (TG) in both observation periods (p<0.05). No statistically significant changes in color match (CM), anatomic form (AF), or surface texture (ST) appeared during the observation periods (p>0.05). Conclusions:Direct resin composite restorations performed better than indirect composite inlays for marginal integrity, but all restorations were judged to be clinically acceptable.Clinical Significance: Tetric Ceram direct restorations and Targis indirect inlays in posterior teeth provide satisfactory clinical performance and the comparison between them showed little difference after one year.

The toxicity associated with suspended sediments from the Rhone River (Switzerland-France) was determined with three acute bioassays. Large volume water samples were centrifuged for recovery of suspended solids in November 1989; one sample was taken as a control upstream from Lake Geneva and the 9 remainder downstream from Geneva to the Mediterranean Sea, with a single sample of the major tributary the Saone at Lyon. Heavy metals (Hg, Cd, Cr, Cu, Ni, Pb, Zn) and organic contaminants (OCs, PCBs, PAHs) bound to sediment were analysed and extracted by elutriation with filtered lake water and by organic solvent ( dichloromethane ). Sediment water elutriates were tested with algal fractionation bioassays (AFB) using Lake Geneva ambient phytoplankton, with Daphnia magna and Microtox® acute toxicity tests, whereas organic extracts were utilized in the latter two bioassays to evaluate the potential sediment toxicity. The bulk analyses of the sediment together with elutriate metal concentrations indicated the highest contamination of sediment downstream of Lyon. Medium contamination appeared for the stations downstream of Geneva, in the Saone River and at the Rhone River mouth. The station upstream of Lyon had low concentrations, comparable to the values in the Upper Rhone. Organic contaminants are mainly observed downstream of Lyon and their concentrations decline onwards to the sea. The bioassays Microtox ® on organic extracts and AFB on the elutriates show a similar toxicity trend, but differ in that Microtox was more sensitive to organics whereas the algal test responded predominantly to metals. This difference is believed to be due to the different extraction procedures used, rather than to the tests themselves. Daphnia magna was the least sensitive and appeared to give a broader band response to the observed contaminants in the sediment. The bioassay results when integrated confirm that the biotoxicity trends relate well to the composition of the sediment, a factor which emphasizes the need for battery testing in ecotoxicological assessment