Gαi protein subunit: A step toward understanding its non-canonical mechanisms.

The heterotrimeric G protein family plays essential roles during a varied array of cellular events; thus, its deregulation can seriously alter signaling events and the overall state of the cell. Heterotrimeric G-proteins have three subunits (α, ß, γ) and are subdivided into four families, Gαi, Gα12/13, Gαq, and Gαs. These proteins cycle between an inactive Gα-GDP state and active Gα-GTP state, triggered canonically by the G-protein coupled receptor (GPCR) and by other accessory proteins receptors independent also known as AGS (Activators of G-protein Signaling). In this review, we summarize research data specific for the Gαi family. This family has the largest number of individual members, including Gαi1, Gαi2, Gαi3, Gαo, Gαt, Gαg, and Gαz, and constitutes the majority of G proteins α subunits expressed in a tissue or cell. Gαi was initially described by its inhibitory function on adenylyl cyclase activity, decreasing cAMP levels. Interestingly, today Gi family G-protein have been reported to be importantly involved in the immune system function. Here, we discuss the impact of Gαi on non-canonical effector proteins, such as c-Src, ERK1/2, phospholipase-C (PLC), and proteins from the Rho GTPase family members, all of them essential signaling pathways regulating a wide range of physiological processes.

Novel non-resorbable polymeric-nanostructured scaffolds for guided bone regeneration.

OBJECTIVE: The aim of this study was to evaluate the bone-regeneration efficiency of novel polymeric nanostructured membranes and the effect of zinc, calcium, titanium, and bone morpho-protein loading on membranes, through an in vivo rabbit model. MATERIAL AND METHODS: Nanostructured membranes of methylmethacrylate were loaded with zinc, calcium, TiO2 nanoparticles, and bone-morphogenetic protein (BMP). These membranes covered the bone defects prepared on the skulls of six rabbits. Animals were sacrificed 6 weeks after surgery. Micro computed tomography was used to evaluate bone architecture through BoneJ pluging and ImageJ script. Three histological processing of samples, including von Kossa silver nitrate, toluidine blue, and fluorescence by the deposition of calcein were utilized. RESULTS: Zn-membranes (Zn-Ms) promoted the highest amount of new bone and higher bone perimeter than both unloaded and Ti-membranes (Ti-Ms). Ca-membranes (Ca-Ms) attained higher osteoid perimeter and bone perimeter than Zn-Ms. The skeleton analysis showed that Zn-Ms produced more branches and junctions at the trabecular bone than BMP-loaded membranes (BMP-Ms). Samples treated with Ti-Ms showed less bone formation and bony bridging processes. Both Zn-Ms and Ca-Ms achieved higher number of osteoblasts than the control group. BMP-Ms and Ca-Ms originated higher number of blood vessels than Ti-Ms and control group. CONCLUSIONS: Zn incorporation in novel nanostructured membranes provided the highest regenerative efficiency for bone healing at the rabbit calvarial defects. CLINICAL RELEVANCE: Zn-Ms promoted osteogenesis and enhanced biological activity, as mineralized and osteoid new bone with multiple interconnected ossified trabeculae appeared in close contact with the membrane.

Expression profiles of the Gα subunits during Xenopus tropicalis embryonic development.

Heterotrimeric G protein signaling plays major roles during different cellular events. However, there is a limited understanding of the molecular mechanisms underlying G protein control during embryogenesis. G proteins are highly conserved and can be grouped into four subfamilies according to sequence homology and function. To further studies on G protein function during embryogenesis, the present analysis identified four Gα subunits representative of the different subfamilies and determined their spatiotemporal expression patterns during Xenopus tropicalis embryogenesis. Each of the Gα subunit transcripts was maternally and zygotically expressed, and, as development progressed, dynamic expression patterns were observed. In the early developmental stages, the Gα subunits were expressed in the animal hemisphere and dorsal marginal zone. While expression was observed at the somite boundaries, in vascular structures, in the eye, and in the otic vesicle during the later stages, expression was mainly found in neural tissues, such as the neural tube and, especially, in the cephalic vesicles, neural crest region, and neural crest-derived structures. Together, these results support the pleiotropism and complexity of G protein subfamily functions in different cellular events. The present study constitutes the most comprehensive description to date of the spatiotemporal expression patterns of Gα subunits during vertebrate development.

Effect of hygroscopic expansion of resin filling on interfacial gap and sealing: a confocal microscopy study.

PURPOSE: To measure dimensional changes due to hygroscopic expansion and their effect on interface gaps and sealing in four light-cured restorative materials using an original confocal microscopic methodology. MATERIALS AND METHODS: The materials tested were an ormocer (Admira [Voco]), a compomer (Dyract AP [Dentsply]), a hybrid composite (Spectrum [Dentsply]), and a nanohybrid composite (Esthet·X [Dentsply]). Water sorption was evaluated by weighing material disks after immersion. Hygroscopic expansion was measured from volumetric variations of material fillings in cylindrical cavities in dentin slices; the interfacial gap size was obtained from the same cavities using a novel confocal microscopic method. Microleakage was evaluated in cavities prepared in extracted third molars. Measurements followed water immersion for 24 h, 1 week, 4 weeks, and 8 weeks. A factorial ANOVA, the Student Newman Keuls test for post-hoc comparisons, the Student's t-test, and the Pearson test were used for the statistical analysis (p < 0.05). RESULTS: Positive correlations were found among water sorption, hygroscopic expansion, and sealing. Hygroscopic expansion reduced post-polymerization interfacial gaps and improved cavity sealing. Dyract AP and Admira showed the highest water sorption, hygroscopic expansion, and gap size reduction. CONCLUSIONS: 1. The proposed methodology is valid to measure hygroscopic expansion and interfacial gap. 2. Water sorption and hygroscopic expansion are positively correlated, and hygroscopic expansion, gap size, and sealing are also positively correlated. 3. The adhesive influences the interfacial gap size and its variation after hygroscopic expansion. 4. Hygroscopic expansion reduces the interfacial gaps generated by polymerization shrinkage and improves cavity sealing.

Wettability and bonding of self-etching dental adhesives. Influence of the smear layer.

OBJECTIVES: To evaluate dentin wettability and bonding of self-etching and total-etch adhesives on smear layer-covered and smear layer-free dentin. METHODS: Three self-etching adhesives (Clearfil SE Bond, AdheSE and Xeno III) and one total-etch adhesive (SingleBond) were evaluated. The substrates were mid coronal smear layer-covered and smear layer-free dentin. Dentin wettability by resins was studied from contact angle measurement using sessile drop method and Axisymmetric Drop Shape Analysis (ADSA). Shear-bond strength was evaluated using a push-out technique (ad hoc design). Data were analysed with two-way ANOVA and Tukey's test. RESULTS: Similar values of dentin wettability were obtained for all adhesives tested regardless the presence of smear layer. Even though, Xeno III and AdheSE exhibited slightly lower wettability (higher contact angles values) on smear layer-free dentin. Likewise, the presence of smear layer did not affect the shear-bond strength. Total-etch adhesive obtained higher shear-bond strength than self-etching adhesives, which obtained similar values. SIGNIFICANCE: Wettability is similar between self-etching and total-etch adhesives. The smear layer affects slightly the wettability of self-etching adhesives. Shear-bond strength is not sensitive to the smear layer presence. Total-etch adhesion is stronger than self-etching adhesion. There is no clear relationship between wettability and bond strength.

Effect of acid etching on dentin wettability and roughness: self-etching primers versus phosphoric acid.

OBJECTIVE: To compare the effect of self-etching primers and phosphoric acid on the wettability and roughness of smear layer-covered and smear layer-free dentin. MATERIALS AND METHOD: Three self-etching primers (Clearfil SE Bond, AdheSE, and Xeno III) and 10% (w/w) phosphoric acid (H(3)PO(4)) solution were evaluated. The substrates were midcoronal dentin with and without smear layer. For each liquid, pH, density, and surface tension were determined. Water wettability of dentin and roughness were measured before and after each etching. Wettability of self-etching primers and phosphoric acid was measured on untreated dentin. RESULTS: Water wettability increased after acid conditioning similarly for all the liquids used. On smear layer-covered surfaces, self-etching primers achieved a comparable wetting but with greater contact angles than phosphoric acid. However, on smear layer-free surfaces, the increasing sequence of contact angle was Clearfil SE < AdheSE < Xeno III < Phosphoric acid. The treatment with phosphoric acid (lowest pH) produced the highest roughness increase on both dentin substrates. The roughening effect of the self-etching adhesives was more evident for AdheSE and Xeno III. CONCLUSIONS: Self-etching primers and phosphoric acid promote similar water wettability increase. However, self-etching primers provided lower dentin roughness increase than pretreatment with phosphoric acid. The presence of smear layer did not affect the results of self-etching and phosphoric acid treatments.

Influence of eugenol contamination on the wetting of ground and etched dentin.

Forty third molars were sectioned parallel to the occlusal surface in order to expose superficial and deep dentin. Exposed surfaces were ground flat with 500-grit sandpaper. Contact angle measurements were performed to assess wettability using the ADSA-CD technique. Specimens were divided into two groups. Group 1 was the control group (no contamination). Group 2 served as the test group. Dentin surfaces were covered with a provisional eugenol-containing material (IRM) and were placed into a humidor at 37 degrees C for one week. The provisional material was removed. Wettability measurements of the two groups were made with water on ground dentin, with water and resin on etched dentin. Data were statistically analyzed by ANOVA, Student-Newman-Keuls multiple comparison and Student t-tests. Eugenol contamination did not affect the dentin wetting. Acid etching significantly diminished contact angle values. Dentin wetting was greater on deep dentin than on superficial dentin.