Trafficking and homing of systemically administered stem cells: the need for appropriate analysis tools of radionuclide images.

AIM: Despite its enormous relevance, homing of hematopoietic stem cells (SCs) remains relatively uncertain due to the limitations of measuring small number of systemically administered cells in the different organs. Despite its high sensitivity, radionuclide detection has been relatively underutilized to this purpose since it cannot differentiate hematopietic SCs recruited by target tissues from those circulating in the blood pool. Our study aims to verify the potential of tracer kinetic approaches in estimating the recruitment of labeled SCs after their systemic administration. METHODS: Twenty-four Lewis rats underwent administration of 2 millions cells labeled with 37 MBq of 99mTc-exametazime. Animals were divided into 2 groups according to administered cells: hematopoietic SCs or cells obtained from a line of rat hepatoma. Cell injection was performed during a planar dynamic acquisition. Regions of interest were positioned to plot time activity curves on heart, lungs, liver and spleen. Blood cell clearance was evaluated according to common stochastic analysis approach. Either fraction of dose in each organ at the end of the experiment or computing the slope of regression line provided by Patlak or Logan graphical approach estimated cell recruitment. At the end of the study, animals were sacrificed and the number of cells retained in the same organs was estimated by in vitro counting. RESULTS: Cell number, documented by the dose fraction retained in each organ at imaging was consistently higher with respect to the "gold standard" in vitro counting in all experiments. An inverse correlation was observed between degree of overestimation and blood clearance of labeled cells (r=-0.56, P<0.05). Logan plot analysis consistently provided identifiable lines, whose slope values closely agreed with the "in vitro" estimation of hepatic and splenic cell recruitment. CONCLUSION: The simple evaluation of organ radioactivity concentration does not provide reliable estimates of local recruitment of systemically administered cells. Yet, the combined analysis of temporal trends of tracer (cell) tissue accumulation and blood clearance can provide quantitative estimations of cell homing in the different organs.

Alteration of Membrane Permeability of Bacteria and Yeast by High Frequency Alternating Current (HFAC).

AIMS: Endox((R)) Endodontic System (Endox) is used for endodontic treatment by a high frequency alternating current (HFAC). This device damaged the envelopes of spores and vegetative organisms. If the integrity of the envelope is compromised, the transit of compounds in the two directions is possible. This latter aspect was investigated here. METHODS: The instrument delivered a 60ms pulse at a frequency 300 kHz, and power 800 KV/m. DNA transfer was verified using Escherichia coli K-12 strain carrying a non conjugative plasmid pBP517 (gyrA(+)) as donor and a rifampicin and nalidixic acid resistant recipient. 0.2 ml of mixture of donor and recipient strains in saline was exposed to HFAC and plated on selective media. Uptake of antimicrobials and a delay in re-growth was assessed exposing the strains to HFAC. RESULTS: Plasmid transfer was detected under different experimental conditions. From 9 to 27 recombinants were found. Representative recombinants cured from plasmid showed the original phenotype. HFAC promoted the uptake of ineffective antibiotics, and induces a 1 h of delay in re-growth on the strains. CONCLUSIONS: Endox exhibited an effect on microrganisms which is reminiscent with that occuring in electroporation, but with a mode of action that saved materials and time.

Decontamination of root canals with the gallium-aluminum-arsenide laser: an in vitro study.

OBJECTIVES: In this in vitro study, we investigated the bactericidal effects on root canals of 810-nm diode laser irradiation, alone or combined with sodium hypochlorite and citric acid irrigation. MATERIALS AND METHODS: One hundred sixteen single-rooted human teeth extracted for periodontal reasons were randomly divided into four experimental groups. The canal of each tooth was prepared with a conventional step-back technique and a pure culture of vancomycin-resistant Enterococcus faecalis grown in brain heart infusion broth was used to contaminate the root canal. The specimens were incubated at 37 degrees C for 15 d in a test tube filled with agar, adding fresh bacterial suspension every 48 h, and sent them for microbiological analysis and bacterial count. Subsequently they were divided into four groups: in group A, 29 teeth were irrigated with 2 mL of 10% citric acid solution; in group B, 29 teeth were irrigated with 2 mL 5.25% sodium hypochlorite (NaOCl) solution; in group C, 29 teeth were irradiated with 810-nm laser energy via a 200-microm optic fiber at 2.5 W power in pulsed mode (10 msec on and 10 msec off) for 5 sec; and in group D, 29 teeth were irrigated with NaOCl, irradiated with the laser, then irrigated with citric acid, and irradiated with the laser, followed again by NaOCl irrigation and laser irradiation. All the samples were again sent for microbiological analysis and bacterial count. RESULTS: Group A had a bactericidal effect of 0.041 log mean CFU, that of group B was 3.381 log mean CFU, and that of group C was 1.459 log mean CFU, whereas group D showed the best results, with a bactericidal effect of 7.178 log mean CFU. CONCLUSIONS: The use of NaOCl, citric acid, and diode laser energy together have a synergistic effect, increasing treatment efficacy and leading to significantly better decontamination of the root canal.

In vitro activity of ceftibuten at sub-inhibitory concentrations in comparison with other antibiotics against respiratory and urinary tract pathogens.

Some new features of the in vitro activity of ceftibuten, an oral third generation cephalosporin, have been studied in reference to respiratory and urinary tract pathogens included in its antibacterial spectrum. At 0.25XMIC (minimum inhibitory concentration) and 0.5XMIC levels, ceftibuten was able to affect the biofilm production in 2/3 of both Escherichia coli and Proteus mirabilis strains, and reduced the number of strains capable of adhering to epithelial cells by about 35% in comparison to the control. Surface hydrophobicity was also influenced by ceftibuten and the other drugs at 0.25-0.5XMIC. In general, no marked variation in the virulence traits of the pathogens studied were found by exposing bacteria to sub-MICs of ceftibuten. Plasmid loss (from 1.8 to 37.2%), and Flac transfer inhibition (about 30-50% reduction in the number of recombinants) were detected under the experimental conditions used. This study confirms the excellent antibacterial properties of ceftibuten by adding new information about the effects of this antibiotic against pathogens often involved in respiratory and urinary tract infections that may be treated with this compound, supporting the appropriate use of this cephalosporin.