Electroreduction of methyl viologen in the presence of nitrite. Its influence on enzymatic electrodes

The electroreduction of methyl viologen (MV) in the presence of nitrite was studied by cyclic voltammetry. A catalytic wave for the reduction of MV²⁺ was observed at ?0.740 V for which an EC catalytic mechanism is proposed. The rate constant for this chemical reaction under pseudo-first-order conditions, evaluated using working curves, was employed in the simulation of the voltammetric response. The second-order rate constant was also evaluated. Influences of the reaction at ?0.800 V on enzymatic electrodes employing nitrate reductase (NR) and MV⁺ as mediator were also analysed by chronoamperometry.     

Purification and characterization of a trypsin-like protease from the culture supernatant of Actinobacillus actinomycetemcomitans Y4

We purified and characterized a protease from Actinobacillus actinomycetemcomitans. The protease was isolated from the culture supernatant by sonication in phosphate-buffered 3-[(3 cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). The protease was purified by acetone precipitation, followed by column chromatography with Arginine Sepharose 4B, DEAE Sepharose CL-6B, Sephacryl S-200HR and HiTrap Q. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified protease showed a clear band at approximately 50 kDa. The protease showed trypsin-like activity with hydrolytic activity for the synthetic substrates N alpha-benzoyl-DL-arginine p-nitroanilide (BApNA) and N alpha benzoyl-DL-lysine p-nitroanilide (BLpNA). The activity of the protease was stable at pH 7.0 to approximately 8.0. The activity of the protease was inhibited by leupeptin, phenylmethylsulfonyl fluoride (PMSF), and EDTA, but was not affected by dithiothreitol (DTT), cysteine, 2-mercaptoethanol, pepstatin or soybean trypsin inhibitor. These data suggest that this protease is a serine protease or metallo protease. This enzyme extensively degraded collagen type I and fibronectin.     

Solubility and fluoride release in ionomers and compomers.

OBJECTIVE: The degree of solubility and the fluoride release of glass-ionomer cements and "compomers" were determined as a function of time. METHOD AND MATERIALS: Three conventional glass-ionomer cements, three hybrid ionomers, and two compomers were included in the study. Disk-shaped specimens were prepared and immersed in a lactic acid solution. Solubility was evaluated from determinations of loss of mass as a function of time. To evaluate fluoride release, similar specimens were immersed in 50 mL of deionized water to which 50 mL of buffer solution was added. A fluoride ion detector was used to read the concentration of fluoride ion in the overall solution at different times after immersion. RESULTS: Material and time factors had a significant influence on results. The compomers showed less corrosion and fluoride release than the ionomers. Some correlation was found between solubility and fluoride leakage values. CONCLUSION: Components of both the ionomers and compomers that were studied can dissolve in water. The materials leak fluoride ions in amounts that differ according to the characteristics of the individual products.     

Clinical and histologic evaluation of submerged and nonsubmerged hydroxyapatite-coated implants: a preliminary study in dogs

A clinical and histologic study was performed to evaluate the differences in the healing of submerged and nonsubmerged hydroxyapatite-coated 2-piece implants. Three foxhounds were used for this evaluation. Mandibular premolars 1, 2, 3, and 4 were extracted. Three months later, 2 submerged implants were placed on one side of the mandible, and 2 nonsubmerged implants were placed on the other side of the mandible. After 3 months of healing, the submerged implants were exposed, and a third implant was placed on each side of the mandible in a nonsubmerged procedure. Clinical parameters were recorded, the animals were sacrificed 6 months after placement of the first implants, and histologic and histometric analyses were performed. Results of the evaluation of the clinical parameters showed only minor differences among the different treatment groups. Regarding the percentage of bone-to-implant contact of the different treatment groups, the submerged implants showed a bone-to-implant contact of 63.4%, the nonsubmerged implants showed 70.3% contact, and the late nonsubmerged implants demonstrated a bone-to-implant contact of 58.7%. The average distance from the implant neck to the first bone-to-implant contact (fBIC) for submerged implants was 0.58 mm, for nonsubmerged implants it was 1.09 mm, and it was 1.13 mm for late nonsubmerged implants. The vertical distance between the gingival margin and the apical extent of the junctional epithelium (aJE) varied from 1.14 mm to 1.28 mm in the different groups. The distance from the aJE to fBIC was 1.00 mm for the submerged group, 1.08 mm for the nonsubmerged group, and 1.00 mm for the late nonsubmerged group. Generally, it can be concluded that the clinical and the histologic behavior of submerged or nonsubmerged 2-piece implants utilized in this experiment do not differ.     

Lipoxin A4 and aspirin-triggered 15-epi-LXA4 inhibit tumor necrosis factor-alpha-initiated neutrophil responses and trafficking: novel regulators of a cytokine-chemokine axis relevant to periodontal diseases

The impact of lipoxin A4 (LXA4) and aspirin-triggered-lipoxins (ATL) was investigated in tumor necrosis factor (TNF alpha)-initiated neutrophil (PMN) responses in vitro and in vivo using LX analogs that are metabolically more stable. At nanomolar levels, the LXA4 and ATL analog 15 R/S-methyl-LXA4 each blocked TNF alpha-stimulated IL-1 beta release by isolated human PMN in vitro. These LXA4-ATL actions were time- and concentration-dependent. The TNF alpha-induced IL-1 beta gene expression was also regulated by 15 R/S-methyl-LXA4. In addition, 15 R/S-methyl-LXA4 added to murine air pouches dramatically inhibited TNF alpha-stimulated leukocyte trafficking in vivo, as well as altered the appearance of both macrophage inflammatory peptide-2 and IL-1 beta and concomitantly stimulated IL-4 in pouch exudates. These findings from in vitro and in vivo experiments indicate that both LXA4 and ATL are regulators of TNF alpha-directed neutrophil actions and stimulate IL-4 in exudates and thus regulate mediators that are held to play an important role in the pathogenesis of periodontal disease.     

Use of biodegradable polylactic acid barrier materials in the treatment of grade II periodontal furcation defects in humans--Part I: A multicenter investigative clinical study.

This study evaluated two bioresorbable polylactic acid barriers (Epi-Guide and Guidor) to determine if design differences were of therapeutic significance in the treatment of Grade II furcation defects in humans. Forty patients with bilaterally matched, Grade II furcation defects in maxillary or mandibular first or second molars were treated in a multicenter study. Comprehensive initial periodontal therapy, followed by defect debridement and root preparation, preceded randomized membrane placement. Data collected from all three investigative centers were pooled and analyzed using an analysis of variance appropriate for a counterbalancing design. Both barrier types produced measurable improvements of clinical probing values. Barrier exposure scores taken through the eighth week postoperative revealed that Epi-Guide was less likely to become exposed than Guidor. The findings of this study, which was conducted over a 12-month period, demonstrated that Epi-Guide and Guidor were comparable as measured by clinical probing determinations.     

The distribution of nitric oxide synthetase in Vcx and its relation with the expression of FOS induced by teeth movement in rats]

It was studied the central role of nitric oxide(NO) during experimental teeth movement and the relation between nitric oxide synthetase (NOS) positive neurons and FOS like immunoreactivity (FLN) with the NADPH-diaphorase histochemistry and immunocytochemical reaction method. Results indicated that NOS positive neurons and FLN showed typical distribution in Vcx and there was some overlap between them. It suggests that NO is involved in the central modulation of the stimulating message of teeth movement, and which further explains the central modulation mechanism of experimental teeth movement in rats.