Effects of alpha-tocopherol antioxidant on fracture strength and adhesion of endodontically treated teeth restored after dental bleaching.

This study evaluated the effect of different concentrations of alpha-tocopherol in gel form on fracture strength, hybrid layer formation, and microtensile bond strength of endodontically treated teeth bleached with 40% hydrogen peroxide (H2 O2 ). Sixty bovine incisors were randomized into one of six groups (n = 10 incisors per group) defined by the interventions carried out after endodontic treatment. In the control group, no additional intervention was carried out, while all teeth in the five intervention groups were bleached with 40% H2 O2 and subsequently treated with alpha-tocopherol at concentrations of 15% (15AT), 20% (20AT), or 25% (25AT), with 10% sodium ascorbate (10SA), or with nothing (40HP). Fracture strength was evaluated in a mechanical testing machine, hybrid layer formation was assessed using scanning electron microscopy, and bond strength was determined using microtensile bond-strength testing. Data were analyzed using Kruskal-Wallis and Dunn's tests. No statistically significant difference regarding fracture strength was observed among groups. Hybrid layer formation was greater in the 15AT group than in groups 40HP and 10SA. Teeth in groups 15AT, 20AT, and 25AT demonstrated higher bond strength than teeth in groups 40HP and 10SA. Alpha-tocopherol, preferably at 15%, effectively reverses the deleterious effects, of bleaching, on hybrid layer formation and bond strength to dentin.

Effect of antioxidant on tooth sensitivity after bleaching.

OBJECTIVES: This study aimed to investigate the effect of antioxidant (sodium ascorbate) on tooth sensitivity after two in-office bleaching techniques (light-activated and chemical bleaching). MATERIALS AND METHODS: Ten patients aged 18-25 were bleached in four groups according to bleaching materials and/or antioxidant used. Group A: Maxillary right quadrant received light-activated bleaching with antioxidant. Group B: Maxillary left quadrant received light-activated bleaching without antioxidant. Group C: Mandibular right quadrant received chemical bleaching without antioxidant. Group D: Mandibular left quadrant received chemical bleaching with antioxidant. The tooth sensitivity was recorded using Numerical Rating Scale (NRS) and Schiff Scale (SS) immediately after treatment, 1 day, 1 week, 2 weeks, and 1 month follow-up periods. RESULTS: Group B exhibited higher sensitivity values than Group A. This difference was statistically significant on the first day after treatment (p = 0.027* in NRS and p = 0.046* in SS). Furthermore, antioxidant incorporation in Group D led to a reduction in teeth sensitivity values compared to Group C. This disparity was highly significant on the first day after treatment (p = 0.001* in NRS and p < 0.001** in SS). CONCLUSIONS: The antioxidant (10% sodium ascorbate) reduces the intensity of tooth sensitivity at the different follow-up periods, especially after 1 day from bleaching. CLINICAL SIGNIFICANCE: Using 10% sodium ascorbate after bleaching is advisable to reduce post-operative tooth sensitivity.

Tumor Targeting of 211At-Labeled Antibody under Sodium Ascorbate Protection against Radiolysis.

Astatine-211 (211At) is an alpha emitter applicable to radioimmunotherapy (RIT), a cancer treatment that utilizes radioactive antibodies to target tumors. In the preparation of 211At-labeled monoclonal antibodies (211At-mAbs), the possibility of radionuclide-induced antibody denaturation (radiolysis) is of concern. Our previous study showed that this 211At-induced radiochemical reaction disrupts the cellular binding activity of an astatinated mAb, resulting in attenuation of in vivo antitumor effects, whereas sodium ascorbate (SA), a free radical scavenger, prevents antibody denaturation, contributing to the maintenance of binding and antitumor activity. However, the influence of antibody denaturation on the pharmacokinetics of 211At-mAbs relating to tumor accumulation, blood circulation time, and distribution to normal organs remains unclear. In this study, we use a radioactive anti-human epidermal growth factor receptor 2 (anti-HER2) mAb to demonstrate that an 211At-induced radiochemical reaction disrupts active targeting via an antigen-antibody interaction, whereas SA helps to maintain targeting. In contrast, there was no difference in blood circulation time as well as distribution to normal organs between the stabilized and denatured immunoconjugates, indicating that antibody denaturation may not affect tumor accumulation via passive targeting based on the enhanced permeability and retention effect. In a high-HER2-expressing xenograft model treated with 1 MBq of 211At-anti-HER2 mAbs, SA-dependent maintenance of active targeting contributed to a significantly better response. In treatment with 0.5 or 0.2 MBq, the stabilized radioactive mAb significantly reduced tumor growth compared to the denatured immunoconjugate. Additionally, through a comparison between a stabilized 211At-anti-HER2 mAb and radioactive nontargeted control mAb, we demonstrate that active targeting significantly enhances tumor accumulation of radioactivity and in vivo antitumor effect. In RIT with 211At, active targeting contributes to efficient tumor accumulation of radioactivity, resulting in a potent antitumor effect. SA-dependent protection that successfully maintains tumor targeting will facilitate the clinical application of alpha-RIT.

Mega-dose sodium ascorbate: a pilot, single-dose, physiological effect, double-blind, randomized, controlled trial.

BACKGROUND: Mega-dose sodium ascorbate (NaAscorbate) appears beneficial in experimental sepsis. However, its physiological effects in patients with septic shock are unknown. METHODS: We conducted a pilot, single-dose, double-blind, randomized controlled trial. We enrolled patients with septic shock within 24 h of diagnosis. We randomly assigned them to receive a single mega-dose of NaAscorbate (30 g over 1 h followed by 30 g over 5 h) or placebo (vehicle). The primary outcome was the total 24 h urine output (UO) from the beginning of the study treatment. Secondary outcomes included the time course of the progressive cumulative UO, vasopressor dose, and sequential organ failure assessment (SOFA) score. RESULTS: We enrolled 30 patients (15 patients in each arm). The mean (95% confidence interval) total 24-h UO was 2056 (1520-2593) ml with placebo and 2948 (2181-3715) ml with NaAscorbate (mean difference 891.5, 95% confidence interval [- 2.1 to 1785.2], P = 0.051). Moreover, the progressive cumulative UO was greater over time on linear mixed modelling with NaAscorbate (P < 0.001). Vasopressor dose and SOFA score changes over time showed faster reductions with NaAscorbate (P < 0.001 and P = 0.042). The sodium level, however, increased more over time with NaAscorbate (P < 0.001). There was no statistical difference in other clinical outcomes. CONCLUSION: In patients with septic shock, mega-dose NaAscorbate did not significantly increase cumulative 24-h UO. However, it induced a significantly greater increase in UO and a greater reduction in vasopressor dose and SOFA score over time. One episode of hypernatremia and one of hemolysis were observed in the NaAscorbate group. These findings support further cautious investigation of this novel intervention. Trial registration Australian New Zealand Clinical Trial Registry (ACTRN12620000651987), Date registered June/5/2020.

Effect of antioxidants after post-space irrigation on the adhesive interface of glass fiber post cementation.

OBJECTIVE: This study evaluated the effects of antioxidants, 10% sodium ascorbate (SA) or 20% alpha-tocopherol (AT), after post-space irrigation with 2.5% sodium hypochlorite +17% EDTA (SH) or 1% peracetic acid (PA) on the adhesive interface after glass fiber post cementation. MATERIALS AND METHODS: Sixty bovine roots were endodontically treated. After preparation, the post-space was irrigated with SH or PA followed or not by the use of antioxidants (SA or AT) (n = 10). Push-out bond strength test, failure mode, and dentin penetrability analysis using confocal laser microscope were performed in the cervical, middle, and apical thirds. Data from bond strength and dentinal penetrability were evaluated by one-way ANOVA and Tukey post hoc test (p < 0.05). RESULTS: SH showed the lowest bond strength regardless of the third (p < 0.05). In apical third, mixed failure was the most incident in all groups. Only in the cervical third of the post-space, SH-AT provided the greatest tag extension of the cementation system into dentin (p < 0.05). However, in the middle and apical thirds, SH-AT, SH-SA, and PA-SA provided the largest tag extensions (p < 0.05), but similar to each other (p > 0.05). CONCLUSIONS: The use of antioxidants only favored bond strength when SH was used and dentin penetrability of the adhesive and conventional resin cementation, regardless of the solution used to irrigate the post-space. CLINICAL SIGNIFICANCE: The use of antioxidants (10% sodium ascorbate and 20% alpha-tocopherol) after post-space irrigation with sodium hypochlorite appears to increase the bond strength favoring the glass fiber post-cementation.

Can antioxidant treatment replace delay in bracket bonding? An in vitro study.

BACKGROUND: Deterioration in shear bond strength has been reported after immediate bracket bonding following hydrogen peroxide bleaching. This study compared the effectiveness of three antioxidant agents, namely, alpha-tocopherol, green tea extract, and sodium ascorbate, in reversing the bleaching effect and as possible alternatives to delayed bonding. METHODS: A total of 105 extracted human premolars were arbitrarily assigned to 7 groups (n = 15 each), including group 1 as the unbleached control group and six experimental groups, which were bleached with 40% hydrogen peroxide in three sessions of 15 min each. In experimental group 2, bonding was performed immediately after bleaching, whereas in groups 3 and 4, bonding was delayed for 1 and 2 weeks, respectively; meanwhile, the specimens were immersed in artificial saliva at 37 °C. Groups 5, 6, and 7 were treated immediately after bleaching with 10% of alpha-tocopherol, green tea extract, and sodium ascorbate solutions, respectively, for 15 min. Specimens were processed using 500 thermal cycles between 5 and 55 °C, with a dwell time of 30 s after 24 h of bracket bonding, and then tested for shear bond strength. The adhesive remnant index was examined to evaluate fracture mode. One-way analysis of variance, Kruskal-Wallis H, and post hoc Tukey's honestly significant difference tests were used to compare the data. Significant results were subjected to pairwise comparisons with Bonferroni's correction-adjusted of p values ≤ 0.050. RESULTS: Shear bond strength was significantly lower (p < 0.001) in the immediate bonding and 1-week delay groups than in the control group. However, no significant difference was detected among the 2-week delay, antioxidant-treated, and control groups (p > 0.05). CONCLUSIONS: Application of 10% alpha-tocopherol, green tea extract, or sodium ascorbate for 15 min could restore shear bond strength after 40% hydrogen peroxide bleaching as an alternative to delay in bracket bonding.

Evaluation of the Effect of Different Antioxidants on Resin Bond Strength to Enamel after Bleaching: An In Vitro Study.

AIM: To compare and evaluate the efficacy of 10% sodium ascorbate (SA) solution, 10% alpha-lipoic acid (ALA) solution, 10% propolis solutions (PLS), and 10% pomegranate peel extract (PPE) solution on the shear bond strength (SBS) between composite resin and bleached enamel after 60 minutes. MATERIALS AND METHODS: Ninety extracted teeth were divided into 6 subgroups (n = 15) based on the antioxidant applied: Group I: Bleaching + application of 10% SA solution for 60 minutes. Group II: Bleaching + application of 10% ALA solution for 60 minutes. Group II: Bleaching + application of 10% PLS for 60 minutes. Group IV: Bleaching + application of 10% PPE solution for 60 min. Group V: Positive control (PC) bleaching without antioxidant application. Group VI: Negative control (NC) specimen neither subjected to bleaching nor application of an antioxidant solution. About 35% hydrogen peroxide (HP) was used for bleaching the labial surfaces in the groups considered. Labial surfaces were then bonded with composite using a customized cylindrical mold followed by storage in distilled water for 24 hours and shear bond strength was tested using universal testing machine. RESULTS: The mean shear bond strength values for groups I, II, III, IV, V, and VI are 5.04, 2.29, 5.02, 4.07, 1.42, and 9.08 respectively. The peak shear bond strength value is obtained for the negative control group; whereas the lowest mean SBS value is obtained for the positive control group. CONCLUSION: All herbal extracts used in the present study have demonstrated a reversal of reduced SBS between resin composite and bleached enamel surface. CLINICAL SIGNIFICANCE: The reduction in bond strength of adhesive restorations was conventionally overcome by delaying the bonding procedure for a specified period resulting in prolonged treatment duration and multiple appointments. Sodium ascorbate is most commonly used but it is postulated to form a porous scaffold capable of harboring bacteria. Herbal antioxidants are gaining popularity in this regard as they are naturally derived, effective and affordable phytochemicals in addition to being viable alternatives against drug-resistant strains of microorganisms.

Effect of UV-C Irradiation on the Shelf Life of Fresh-Cut Potato and Its Sensory Properties after Cooking.

Research background: Potato tissue is damaged during fresh-cut production, which makes fresh-cut potato susceptible to the quality loss and microbiological spoilage. At the same time, such products are desirable due to their convenience; however, they are extremely sensitive and have short shelf life. The main challenge of the fresh-cut potato industry is to find possibilities to overcome these drawbacks. UV-C treatment, known for its antibacterial activity, is a promising technique and it shows a potential to improve shelf life of fresh-cut potato products. Experimental approach: The influence of the UV-C treatment on the safety and quality, as well as sensory traits of fresh-cut potato (Solanum tuberosum L. cv. Birgit) during storage was examined. For this purpose, 0-, 3-, 5- and 10-min UV-C irradiation was applied on vacuum-packed potato slices pretreated with sodium ascorbate solution. During 23 days of storage at (6±1) °C, microbiological, physicochemical and sensory properties of raw samples were monitored, along with sensory properties of boiled and fried fresh-cut potatoes. Results and conclusions: The 5- and 10-min UV-C treatments significantly reduced microbial growth, increased total solids and lightness (L*), and positively affected odour and firmness of raw potatoes. Cooked UV-C-treated samples were described with more pronounced characteristic potato odour and taste. Overall, UV-C-treated fresh-cut potato retained its good quality and sensory traits up to 15 days at (6±1) °C. Novelty and scientific contribution: To the best of our knowledge, this is the first scientific article dealing with the effect of UV-C light on durability (safety, quality and sensory traits) of fresh-cut potato cv. Birgit and its suitability for boiling and frying. In general, UV-C treatment is a known antimicrobial technique, but its application on fresh-cut potato is poorly explored. Results confirmed that vacuum-packed fresh-cut potato treated only with UV-C and sodium ascorbate as anti-browning agent, without the addition of chemical preservatives, had twofold longer shelf-life at (6±1) °C than the fresh-cut potato not treated with UV-C. Fresh-cut potato treated with UV-C retained good overall quality and sensory properties either raw, boiled or fried. Results of this study could also be useful for producers in terms of potential UV-C application as a strategy for prolonging the shelf-life of fresh-cut potato.

Radioimmunotherapy with an 211 At-labeled anti-tissue factor antibody protected by sodium ascorbate.

Tissue factor (TF), the trigger protein of the extrinsic blood coagulation cascade, is abundantly expressed in various cancers including gastric cancer. Anti-TF monoclonal antibodies (mAbs) capable of targeting cancers have been successfully applied to armed antibodies such as antibody-drug conjugates (ADCs) and molecular imaging probes. We prepared an anti-TF mAb, clone 1084, labeled with astatine-211 (211 At), as a promising alpha emitter for cancer treatment. Alpha particles are characterized by high linear energy transfer and a range of 50-100 µm in tissue. Therefore, selective and efficient tumor accumulation of alpha emitters results in potent antitumor activities against cancer cells with minor effects on normal cells adjacent to the tumor. Although the 211 At-conjugated clone 1084 (211 At-anti-TF mAb) was disrupted by an 211 At-induced radiochemical reaction, we demonstrated that astatinated anti-TF mAbs eluted in 0.6% or 1.2% sodium ascorbate (SA) solution were protected from antibody denaturation, which contributed to the maintenance of cellular binding activities and cytocidal effects of this immunoconjugate. Although body weight loss was observed in mice administered a 1.2% SA solution, the loss was transient and the radioprotectant seemed to be tolerable in vivo. In a high TF-expressing gastric cancer xenograft model, 211 At-anti-TF mAb in 1.2% SA exerted a significantly greater antitumor effect than nonprotected 211 At-anti-TF mAb. Moreover, the antitumor activities of the protected immunoconjugate in gastric cancer xenograft models were dependent on the level of TF in cancer cells. These findings suggest the clinical availability of the radioprotectant and applicability of clone 1084 to 211 At-radioimmunotherapy.

Visual assay for determination of copper ions based on anti-etching of gold nanorods induced by cuprous ions.

The authors describe a colorimetric method for the determination of copper ions (Cu2+) based on anti-etching of gold nanorods (AuNRs) induced by cuprous ions (Cu+). The formation of Cu+ from the reaction between Cu2+ and sodium ascorbate causes the deactivation of the horseradish peroxidase (HRP), which is used as the catalyst for the reaction of 3,3',5,5'-Tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), resulting in a decrease in the amount of TMB2+ product that can etch AuNRs, which is accompanied by the color changes from yellow to light orange. Thus, determination of Cu2+ is achieved on the basis of AuNR absorbance at 450 nm. A determination limit as low as 0.28 nM at the 3Sblank level, and the detection of 0.4 nM Cu2+ in solution can be achieved with naked eyes, and a dynamic range of 0 to 1.6 nM toward Cu2+ was obtained. Graphical abstractSchematic representation of a colorimetric method for determination of Cu2+ based on the anti-etching of gold nanorods induced by Cu+, which is from the reaction of Cu2+ with sodium ascorbate.

Is α-Tocopherol or Sodium Ascorbate Effective as Antioxidant on Fracture Resistance of Bleached Teeth?

AIM: To evaluate the effect of two antioxidant formulations (sodium ascorbate and α-tocopherol) on fracture resistance of endodontically treated teeth. MATERIALS AND METHODS: Sixty human premolars were endodontically treated and divided into six groups (n = 10): G1 (negative control)-unbleached and restored with composite resin; G2 (positive control)-bleached in three sessions, using hydrogen peroxide (15 H2O2) plus titanium dioxide (TiO2) nanoparticles, photoactivated by LED laser system and restored with composite resin; G3-bleaching similar to G2, after the use of 10% sodium ascorbate gel for 24 hours and restored with composite resin; G4-similar to G3, but with the use of 10% sodium ascorbate solution and restored with composite resin; G5 and G6-similar to G3, but with the use of 10% α-tocopherol in alcohol or carbopol, respectively, and was also restored. A mechanical fracture resistance test was performed and the Kruskal-Wallis test was used to evaluate the results (α = 0.05). RESULTS: No statistical difference was observed in fracture resistance between groups (p > 0.05). Regarding the antioxidant and pharmaceutical formulation applied, no statistical difference was detected in any comparison (p > 0.05). The frequency of fractures considered favorable was higher in G1 and G3 compared to the other groups. CONCLUSION: The endodontically treated teeth bleached with 15 H2O2 plus TiO2 nanoparticles and photoactivated with the LED laser did not decrease the fracture resistance and the use of sodium ascorbate or α-tocopherol did not increase the crown fracture resistance. CLINICAL SIGNIFICANCE: The literature reports a significant reduction in the bond strength of restorations on the bleached dentin. Therefore, the use of antioxidant agents may have a promising effect on fracture resistance of endodontically treated teeth.

Comparative Evaluation of the Antioxidant Effects of Oregano on Bleached Enamel Using Energy-dispersive X-ray Spectroscopy Analysis: An In Vitro Study.

AIM AND OBJECTIVE: The aim of this study was to evaluate the efficacy of novel antioxidant oregano against conventional antioxidants sodium ascorbate and green tea through comparison of the baseline weight percentage (wt%) of minerals prior to bleaching with values after bleaching protocols and antioxidant application by employing energy-dispersive X-ray spectroscopy analysis (EDAX). MATERIALS AND METHODS: Thirty noncarious, freshly extracted human permanent maxillary incisors without any visible defects were selected as samples. They were divided into three groups (n = 10) based on the antioxidant treatment received as follows: group I-10% sodium ascorbate solution, group II-10% green tea solution, and group III-5% oregano solution. 35% hydrogen peroxide was employed for bleaching. The wt% of teeth was calculated at three time intervals. The initial wt% was calculated prior to the bleaching procedure. The second one was calculated after subjecting to bleaching protocols, and final one was calculated after antioxidant treatment using EDAX. RESULTS: There was a statistically significant decrease in the calcium/phosphorus ratio for the bleached samples in comparison with the sound enamel. There was a comparable and significant increase in the calcium/phosphorus ratio values after application of the antioxidant with insignificant difference among the antioxidants evaluated in the study. CONCLUSION: Treatment with antioxidants helped in the reversal of mineral loss, which occurred due to the bleaching procedure while the efficacy of 10% oregano on reversal of the calcium and phosphorus ratio was found to comparable to that of 10% sodium ascorbate and green tea. CLINICAL SIGNIFICANCE: Application of antioxidants after bleaching reduced the time delay in performing the adhesive procedures without compromising their clinical efficacy.

Effects of Antioxidants on the Shear Bond Strength of Orthodontic Brackets Bonded to Bleached Human Teeth: An In Vitro Study.

AIM: The aim of this study was to evaluate the effects of different concentrations of sodium ascorbate (SA), green tea (GT), and chamomile (CM) on the shear bond strength (SBS) of metal orthodontic brackets bonded to teeth bleached with 40% hydrogen peroxide (HP). MATERIALS AND METHODS: Ninety-four sound premolars were divided into eight groups: group I (control + no bleaching), group II (bleaching + immediate bonding), group III (bleaching + 10% SA), group IV (bleaching + 35% SA), group V (bleaching + 0.5% GT), group VI (bleaching + 1% GT), group VII (bleaching + 0.5% CM), and group VIII (bleaching + 1% CM). In groups III-VIII, teeth were treated with the antioxidants for 10 minutes after bleaching with 40% HP, but before bonding. All the specimens were bonded with the resilience adhesive, and the SBS was tested with a universal testing machine (Instron 5965). The cross-head speed to break the bond was 1 mm/minute. The adhesive remnant index (ARI) was tested under 50× magnification. One-way analysis of variance, Tukey's post hoc, and Chi-squared tests were used for analysis (p ≤ 0.05). RESULTS: The differences in SBS among the eight tested groups were highly significant (p < 0.001). Comparison of the eight groups using Tukey's post hoc test revealed significantly lower SBS (p < 0.001) in test groups II, III, IV, and VIII than in group I. Adhesive remnant index scores showed significant intergroup differences (p = 0.005). Most groups had a failure score of 1 (<50% of the bonding material adhering to the tooth), whereas groups II and VIII showed a failure score of 0 (no material adhering to the tooth). CONCLUSION: Bond strength can be enhanced by using 0.5% or 1% GT or 0.5% CM to allow bracket bonding immediately after bleaching. CLINICAL SIGNIFICANCE: The use of antioxidants would allow clinicians to bleach teeth before orthodontic treatment without delaying bonding.

Dentin pretreatment with Er:YAG laser and sodium ascorbate to improve the bond strength of glass fiber post.

Root-filled teeth that received fiber posts most frequently fail at the adhesive interface between resin cement and dentin. The objective of this study is to evaluate the effect of Er:YAG laser and/or sodium ascorbate (SA) on bond strength, microhardness of dentin, and penetration depth of cement into dentinal tubules. Forty-eight bovine incisor roots were endodontically treated, post spaces were prepared and equally divided into four groups (n = 12): G1-distilled water (control); G2-10% SA (10 min); G3-Er:YAG laser (150 mJ/4 Hz/40 s), and G4-Er:YAG laser + 10% SA. Glass fiber posts were cemented and roots sectioned into slices. In the first slice, the push-out bond strength (MPa) and failures were analyzed by confocal laser scanning microscope (CLSM). The second slice was subjected to microhardness test (KHN) and CLSM to assess the cement penetration. ANOVA and Tukey test were used for bond strength and microhardness data and Kruskal-Wallis and Dunn tests for the cement penetration (α = .05). The SA-treated samples had higher bond strength (10.02 ± 5.45a), similar to Er:YAG laser (9.91 ± 4.62a) and Er:YAG laser + SA (8.09 ± 4.07a). The least values (P < .05) were found on control (4.02 ± 2.39b). Significant differences were observed on root thirds (P < .05): cervical > middle > apical. There was a predominance of adhesive failures. The microhardness test revealed no differences between groups (P > .05). The experimental groups (G2, G3, and G4) had highest penetration into dentinal tubules when compared to the control (G1). Dentin pretreatments with Er:YAG laser or SA improved bond strength of cement-post-dentin interfaces; however, no synergistic effect of both treatments combined was observed.

Evaluation of Uracil, Sodium Ascorbate, and Rosiglitazone as Promoters of Urinary Bladder Transitional Cell Carcinomas in Male Sprague-Dawley Rats.

The purpose of this study was to establish a 2-stage model of urinary bladder carcinogenesis in male Sprague-Dawley rats to identify tumor promoters. In phase 1 of the study, rats ( n = 170) were administered 100 mg/kg of the tumor initiator, N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), twice weekly by oral gavage (po) for a period of 6 weeks. Phase 2 consisted of dividing rats into 4 groups ( n = 40 per group) and administering one of the following for 26 weeks to identify putative tumor promoters: (1) vehicle po, (2) 25 mg/kg/day rosiglitazone po, (3) 5% dietary sodium l-ascorbate, and (4) 3% dietary uracil. Rats were necropsied after 7.5 months, and urinary bladders were evaluated by histopathology. BBN/vehicle treatments induced the development of urothelial hyperplasia (83%) and papillomas (15%) but no transitional cell carcinomas (TCCs). Rosiglitazone increased the incidence and severity of papillomas (93%) and resulted in TCC in 10% of treated rats. Uracil was the most effective tumor promoter in our study and increased the incidence of papillomas (90%) and TCC (74%). Sodium ascorbate decreased the incidence of urothelial hyperplasia (63%) and did not increase the incidence of urothelial papillomas or TCC. These data confirm the capacity of our 2-stage model to identify urinary bladder tumor promoters.

Pattern of Hydroxyapatite Crystal Growth on Bleached Enamel Following the Application of Two Antioxidants: An Atomic Force Microscope Study.

OBJECTIVES: This study observed the topographical pattern of hydroxyapatite deposition and growth (D&G) on bleached enamel following application of two antioxidants (sodium ascorbate and catalase) using atomic force microscope. STUDY DESIGN: Twenty enamel specimens (4×3×2mm), prepared from extracted impacted third molars, were mounted in self-cure acrylic and randomly grouped as: Group I-untreated; Group II- 35%H2O2; Group III- 35%H2O2 + artificial saliva; Group IV- 35%H2O2 + catalase+ artificial saliva; Group V- 35%H2O2 + sodium ascorbate+ artificial saliva. Groups I and II were observed immediately after treatment. Groups III-V were observed after 72 hrs. Roughness average was also calculated and analyzed with non-parametric Kruskall-Wallis ANOVA and Mann-Whitney tests. RESULTS: H2O2 dissolved matrix, exposed hydroxyapatite crystals (HACs), causing dissolution on the sides of and within HACs and opening up of nano-spaces. Artificial saliva showed growth of dissoluted crystals. Antioxidants+saliva showed potentiated remineralization by D&G on dissoluted HACs of bleached enamel. Catalase potentiated blockshaped, while sodium ascorbate the needle-shaped crystals with stair-pattern of crystallization. Evidence of oxygen bubbles was a new finding with catalase. Maximum roughness average was in group V followed by group II > group IV > group III > group I. CONCLUSION: Post-bleaching application of catalase and sodium ascorbate potentiated remineralization by saliva, but in different patterns. None of the tested antioxidant could return the original topography of enamel.

Development of antioxidant active films containing sodium ascorbate (SA) and ethylene vinyl alcohol (EVOH) to extend the shelf life of peanut.

In this study, low-density polyethylene (LDPE) containing oxygen scavenger based on sodium ascorbate (SA) and ethylene vinyl alcohol (EVOH) at 5, 10 and 15 % concentrations were produced through extrusion method. In addition, the effect of size of SA, thickness LDPE (7.5, 15, 30 and 45 µm), and number of layers (monolayer, two-layers, three-layers and four-layers) were investigated. Oxygen and water vapor permeability, tensile stress, SA migration and antioxidant activity, thermal stability, scan electron microscopy (SEM), and FT-IR of the films were measured. Moreover, the performance of produced films to prevent of oxidation of packaged peanuts during storage at 40 °C was studied. The results revealed that the active films containing SA (especially at 10 % SA) present suitable performance and features to increase the shelf-life of peanuts.

Cytotoxic effects of high concentrations of sodium ascorbate on human myeloid cell lines.

The effect of high doses of intravenous (sodium) ascorbate (ASC) in the treatment of cancer has been controversial although there is growing evidence that ASC in high (pharmacologic) concentrations induces dose-dependent pro-apoptotic death of tumor cells, in vitro. Very few data are available on the role of ASC in the treatment of acute myeloid leukemia (AML). Ascorbate behaves as an antioxidant at low (physiologic), and as pro-oxidant at pharmacologic, concentrations, and this may account for the differences reported in different experimental settings, when human myeloid cell lines, such as HL60, were treated with ASC. Considering the myeloid origin of HL60 cells, and previous literature reports showing that some cell lines belonging to the myeloid lineage could be sensitive to the pro-apoptotic effects of high concentrations of ASC, we investigated in more details the effects of high doses (0.5 to 7 mM) of ASC in vitro, on a variety of human myeloid cell lines including the following: HL60, U937, NB4, NB4-R4 (retinoic acid [RA]-resistant), NB4/AsR (ATO-resistant) acute promyelocytic leukemia (APL)-derived cell lines, and K562 as well as on normal CD34+ progenitors derived from human cord blood. Our results indicate that all analyzed cell lines including all-trans retinoic acid (ATRA)- and arsenic trioxide (ATO)-resistant ones are highly sensitive to the cytotoxic, pro-oxidant effects of high doses of ASC, with an average 50 % lethal concentration (LC50) of 3 mM, depending on cell type, ASC concentration, and time of exposure. Conversely, high doses of ASC neither did exert significant cytotoxic effects nor impaired the differentiation potential in cord blood (CB) CD34+ normal cells. Since plasma ASC concentrations within the millimolar (mM) range can be easily and safely reached by intravenous administration, we conclude that phase I/II clinical trials using high doses of ASC should be designed for patients with advanced/refractory AML and APL.

A comparative study on the effect of rosemary extract and sodium ascorbate on lipid and pigment oxidative stability of liver pate.

A comparative study on the antioxidant effect of rosemary extract (RE) and sodium ascorbate (SA) on lipid and colour oxidation of liver pâté made of lard and pork liver was done. During the 48 hour experimental time all the pâtés were wrapped in a foil and stored in cold room of 3.5°C under light of 1000 lux. Colour stability was monitored by instrumental colour measurement (CIE L*a*b* colour space) whereas lipid stability was measured by the determination of the 2-thiobarbituric acid reactive substances (TBARS). In the present study RE doses range (0,125, 250, 375 and 500 ppm) showed no significant (p>0.05) and linear effect on colour stability. However thez RE revealed a significant effect (p<0.05) against lipid oxidation and linearly reduces the TBARS number. The added SA doses (0, 250, 500, 750 and 1000 ppm) revealed significant (p<0.05) and linear effect in reducing discoloration. However the studied SA dose ranges showed no significant (p>0.05) effect on TBARS number. In this study RE was showed better performance against lipid oxidation and SA was potent against discoloration. The effect of the added spices used in manufacturing of the studied product showed no significant (p>0.05) effect against lipid and color oxidation. However the added spices revealed possible antagonistic and synergetic relationship with the studied the antioxidant systems (RE & SA).

Sodium ascorbate as a quorum sensing inhibitor of Pseudomonas aeruginosa.

AIMS: Quorum sensing circuits regulate virulence factors in Pseudomonas aeruginosa and coordinate bacterial pathogenicity. We are interested in exploring available medications for their antiquorum sensing activity. METHODS AND RESULTS: First, we determined the MIC of ascorbate against Ps. aeruginosa strain PAO1, and all further experiments used concentrations below the MIC so that results could not be caused by reduced viability. Tests of subinhibitory concentrations of sodium ascorbate on cell signals were performed using a reporter strain assay. Sub-MICs of sodium ascorbate resulted in significant reduction of the signalling molecules C4-HSL and 3-oxo-C12-HSL (P < 0·01). The influence of sub-MIC of sodium ascorbate on virulence factors was also determined and ascorbate treatment led to significant depression of elastase, protease and haemolysin activities. In addition, inhibition of pyocyanin production, attenuation of biofilm formation and alteration of Pseudomonas motility was observed. Analysis by RT-PCR tested the effect of ascorbate on the expression of QS regulatory genes. Expression of QS regulatory genes, lasI, lasR, rhlI, rhlR, pqsR and pqsA, was repressed compared to untreated Ps. aeruginosa PAO1, confirming that ascorbate QS inhibition works on gene expression at the molecular level. CONCLUSION: Sodium ascorbate, even at low concentrations, inhibited QS and related virulence factors of Ps. aeruginosa PAO1. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated that sodium ascorbate could function as signal modulator and virulence inhibitor in Ps. aeruginosa.