Clinical efficiency of 2% chlorhexidine gel in reducing intracanal bacteria.

This study evaluated the clinical efficacy of 2% chlorhexidine (CHX) gel on intracanal bacteria reduction during root canal instrumentation. The additional antibacterial effect of an intracanal dressing (Ca[OH](2) mixed with 2% CHX gel) was also assessed. Forty-three patients with apical periodontitis were recruited. Four patients with irreversible pulpitis were included as negative controls. Teeth were instrumented using rotary instruments and 2% CHX gel as the disinfectant. Bacterial samples were taken upon access (S1), after instrumentation (S2), and after 2 weeks of intracanal dressing (S3). Anaerobic culture was performed. Four samples showed no bacteria growth at S1, which were excluded from further analysis. Of the samples cultured positively at S1, 10.3% (4/39) and 8.3% (4/36) sampled bacteria at S2 and S3, respectively. A significant difference in the percentage of positive culture between S1 and S2 (p < 0.001) but not between S2 and S3 (p = 0.692) was found. These results suggest that 2% CHX gel is an effective root canal disinfectant and additional intracanal dressing did not significantly improve the bacteria reduction on the sampled root canals.

Effect of intracanal medicament on the sealing ability of root canals filled with Resilon.

The purpose of this in vitro study was to investigate the effects of the use of calcium hydroxide as an intracanal dressing on the sealing ability of a thermoplastic synthetic polymer-based root filling (Resilon). Forty-seven single rooted teeth were decoronated and instrumented to ISO sizes 40. The teeth were randomly divided into three experimental groups of 15 roots each. Group 1 was immediately filled. Group 2 and group 3 had calcium hydroxide paste placed with lentulo-spiral filler. After 7 days, calcium hydroxide was removed from the canals with two different techniques: #15 K-file agitated irrigation with 17% Ethylenediaminetetracitic acid (EDTA) (group 2) or ultrasonically agitated irrigation with 17% EDTA (group 3) for 2 min. All teeth were filled with Resilon points and the resin sealer (Ephiphany root canal sealant) using lateral condensation technique. Two teeth were immediately filled with Resilon master point size 40/.04 without sealer to act as a positive control. A split chamber microbial leakage model using Streptococcus mutans was used and the leakage was evaluated daily for a period of 30 days. Overall, 6 of 44 (14%) of samples filled with Resilon points and the resin sealer had microbial leakage. Three samples in group 1 (21%), two samples in group 2 (13%), and one specimen in group 3 (7%) had bacterial leakage. Using the Fisher's Exact test, there was no statistically significant difference in leakage between the groups with calcium hydroxide dressing and the group without calcium hydroxide (p > 0.05). Under the condition of this study, calcium hydroxide did not adversely affect the seal of the root-canal system filled with Resilon.

The (alpha F(357)C)(3)(beta R(372)C)(3)gamma subcomplex of the F(1)-ATPase from the thermophilic Bacillus PS3 has altered ATPase activity after cross-linking alpha and beta subunits at noncatalytic site interfaces.

In crystal structures of bovine MF(1), the side chains of alpha F(357) and beta R(372) are near the adenines of nucleotides bound to noncatalytic sites. To determine if during catalysis these side chains must pass through the different arrangements in which they are present in crystal structures, the catalytic properties of the (alpha F(357)C)(3)(beta R(372)C)(3)gamma subcomplex of the TF(1)-ATPase were characterized before and after cross-linking the introduced cysteines with CuCl(2). The unmodified mutant enzyme hydrolyzes MgATP at 50% the rate exhibited by wild type. Detailed comparison of the catalytic properties of the double mutant enzyme before and after cross-linking with those of the wild-type subcomplex revealed the following. Before cross-linking, the (alpha F(357)C)(3)(beta R(372)C)(3)gamma subcomplex has less tendency than wild type to release inhibitory MgADP entrapped in a catalytic site during turnover when MgATP binds to noncatalytic sites. Following cross-linking, ATPase activity is reduced 5-fold, and inhibitory MgADP entrapped in a catalytic site during turnover does not release under conditions wherein binding of ATP to noncatalytic sites of the wild-type enzyme promotes release of MgADP from the affected catalytic site. When assayed in the presence of lauryldimethylamine oxide, which prevents turnover-dependent entrapment of inhibitory MgADP in a catalytic site, ATPase activity of the cross-linked form is 47% that of the unmodified mutant enzyme. These results suggest that, during catalysis, the side chains of alpha F(357) and beta R(372) do not pass through the extremely different relative positions in which they exist at the three noncatalytic site interfaces in crystal structures.

Interaction of fibroblast growth factor receptor 3 and the adapter protein SH2-B. A role in STAT5 activation.

Fibroblast growth factor receptor 3 (FGFR3) influences a diverse array of biological processes, including cell growth, differentiation, and migration. Activating mutations in FGFR3 are associated with multiple myeloma, cervical carcinoma, and bladder cancer. To identify proteins that interact with FGFR3 and which may mediate FGFR3-dependent signaling, a yeast two-hybrid screen was employed using the cytoplasmic kinase domain of FGFR3 as bait. We identified the adapter protein SH2-B as an FGFR3-interacting protein. Coimmunoprecipitation experiments demonstrate binding of the SH2-B beta isoform to FGFR3 in 293T cells. Tyrosine phosphorylation of SH2-B beta was observed when coexpressed with activated FGFR3 mutants such as the weakly activated mutant N540K or the strongly activated mutant K650E, both associated with human developmental syndromes. The extent of tyrosine phosphorylation of SH2-B beta correlates with receptor activation, suggesting that FGFR3 activation mediates tyrosine phosphorylation of SH2-B beta. Furthermore, two tyrosine phosphorylation sites of FGFR3, Tyr-724 and Tyr-760, are required for optimal binding of the Src homology-2 (SH2) domain of SH2-B beta. We also demonstrate the phosphorylation and nuclear translocation of Stat5 by activated FGFR3, which increases in response to overexpression of SH2-B beta. Taken together, our results identify SH2-B beta as a novel FGFR3 binding partner that mediates signal transduction.