Digital signal processing for step-scan phase and electrochemical potential double-modulation Fourier transform infrared spectrometry

Step-scan double-modulation (phase and electrochemical potential) Fourier transform infrared (FT-IR) spectrometry provides both spectroscopic and dynamic information about faradaic reactions. Recently introduced digital signal processing (DSP) can be used, instead of two lock-in amplifiers, for the optical signal demodulation at two modulation frequencies. In order to establish the merits of double-modulation FT-IR spectrometry with DSP, spectro-electrochemical experiments are performed in the attenuated total reflection configuration and with the commonly used ferri/ferrocyanide redox couple. Because of a large potential drop associated with the uncompensated resistance, a satisfactory signal-to-noise ratio for the alternating current (ac) optical measurements is obtained only with the employment of positive feedback compensation. In this arrangement, the amplitude of electrochemical modulation is sufficiently large to convert a significant fraction of the reduced form to the oxidized form and back to the reduced form. Large amplitude ac voltammetry demonstrates that the phase of faradaic admittance at the formal potential is approximately 45 degrees at 2.00 Hz. In addition, these experiments allow for calculation of the interfacial ac potential. This variable is needed for the normalization of the in-phase and the quadrature spectra in order to overcome the problem associated with the iR(u) drop. Because of the integral relationship between the faradaic current and the electromodulation reflectance coefficient, the phases of electromodulation reflectance coefficient with respect to the interfacial ac potential are expected to be -45 degrees and 135 degrees for the reduced and oxidized forms, respectively. However, dynamic information from double-modulation FT-IR spectrometry is available only if demodulation at the electrochemical potential modulation frequency is performed with respect to a defined phase. Because of an undefined demodulation phase implemented in the current version of DSP software, step-scan double-modulation FT-IR spectrometry with DSP is suitable only to provide spectroscopic information. In order to overcome this limitation, the demodulation of the ac optical signal at the electrochemical modulation frequency must be synchronized in phase with the ac potential modulation applied to the electrochemical cell.     

Comparison of cytotoxicity in vitro and irritation in vivo for aqueous and oily solutions of surfactants

The in vivo model on rabbit eyes and the in vitro cytotoxicity on fibroblasts were used to compare irritation effect of aqueous and oily (Miglyol 812) solutions of surfactants. Tween 20, Tween 80 and Cremophor EL were tested in different concentrations (0.1, 1 or 5%) and the in vitro test demonstrated that surfactants in oil are less cytotoxic than in aqueous solutions. In the in vivo study, the aqueous solutions of surfactants were characterized as non-irritant while small changes in conjunctiva were observed after application the oily solutions of surfactants and the preparations were classified as slightly irritant, however this effect was similar when Miglyol was applied alone. In conclusion, it is reported that the MTT assay does not correlate well with the Draize scores.     

Antiproliferative Activity and in Vivo Toxicity of Double-Point Modified Analogs of 1,25-Dihydroxyergocalciferol

Analogs of 1,25-dihydroxyergocalciferol, modified in the side-chain and in the A-ring, were tested for their antiproliferative activity against a series of human cancer cell lines in vitro and in vivo toxicity. The proliferation inhibition caused by the analogs was higher than that of the parent compounds, while the toxicity, measured as the serum calcium level, was lower. All analogs were able to induce, in HL-60 and MV4-11 leukemic cells, G₀/G₁ cell cycle arrest and differentiation expressed as morphological signs typical for monocytes. The analogs also induced the expression of CD11b and/or CD14 cell-differentiation markers. The most potent analogs, PRI-5105, PRI-5106, PRI-5201 and PRI-5202, were also able to induce vitamin D receptor (VDR) protein expression, mainly in the cytoplasmic fraction of HL-60 or MV4-11 cells. The most active analogs were the 19-nor ones with an extended and rigidified side-chain (PRI-5201 and PRI-5202), as in the former analogs PRI-1906 and PRI-1907. Epimerization at C-24 (PRI-5101) or introduction of an additional hydroxyl at C-23 (PRI-5104) reduced the toxicity of the analog with retained antiproliferative activity.     

Acid etching and silica coating effects on Y-TZP topography and ceramic/resin cement bond strength

Zirconia-based (Y-TZP) dental prostheses' retention loss remains one of the most frequently reported difficulties in dental practice. Selective Infiltration Etching (SIE) treatment has been proposed to alter the final Y-TZP topography improving its bond strength to resin cement. SIE consists of glass film deposition on the Y-TZP surface before glass removal with 10% hydrofluoric acid etching. This study's objective was to investigate the effects of SIE protocol steps on Y-TZP topography and its consequence on its bond strength to resin cement. The SIE protocol was divided into two main steps: silica coating (first step) and glass dissolution by hydrofluoric acid (second step), and the null hypothesis was that the SIE treatment has the same bond quality independently of the HF exposition time. Atomic Force Microscopy (AFM), Scanning Electron and Transmission Electron microscopy were used to characterize the zirconia surfaces. The bond strength was evaluated by the interfacial fracture toughness test, and data were analyzed by ANOVA and Tukey's Test (5%). As the main result, it was shown that, when exposed during sufficient time, the 10% HF can etch zirconia at room temperature, which is responsible for topographic changes, significantly improving the bond quality. Additionally, no glass components or dihedral angles modifications were observed at Y-TZP grain boundaries after silica coating. With the study limitations, it was possible to infer that the surface-modifying agent in SIE protocol is the HF etching, and the null hypothesis was rejected.     

Hospital food handlers in Niterói, RJ, Brazil: intestinal parasitism

A survey for intestinal parasites was carried out with food handlers from two private and three public hospitals in Niterói City, RJ, Brazil. The aim of this research was to verify the enteroparasites prevalence in this professional group. The investigation was divided in two phases. The first phase consisted of interviews with the participants; coproparasitological exams using Lutz, Faust et al. and Baermann techniques; under fingernail material analysis, using Mello et al. modified method; and educational lectures to food handlers. In the second phase, coproparasitological exams were repeated. Positive results were observed in 14.2% (17/120) and 17.1% (12/70) of the individuals in the first and second phases respectively. The most frequent parasite was Entamoeba coli, detected in 48.5% (16/33) of the samples with positive results. Under fingernail residues were observed in 19.2% (23/120) of the food handlers. E. coli cysts were found in one fingernail residue, likewise they were detected in the feces of the same food handler. Such data showed a potential transmission risk of intestinal parasites by food handling, indicating the need of adopting a diagnosis/orientation procedure as a bi-annual routine activity in hospitals, in order to improve the food service quality and population health condition.     

Mercury in Common Chanterelles mushrooms: Cantharellus spp. update

This paper reports the results of the determination of Hg contents of Common Chanterelles (Cantharellus cibarius) Fr. and surface soil layer (0–10 cm) underneath the fruiting bodies collected from 14 spatially distant areas across Poland between 1998 and 2008. Cantharellus mushrooms are important wild foods that are popular in Europe. The Hg contents of soils and Common Chanterelles showed different distributions, depending on the area studied. The range of Hg contents of the mushroom fruiting bodies was 18–66 ng/g dry weight with the highest mean contents of 46 ± 15 ng/g (range 23–66 ng/g) and 46 ± 13 ng/g (34–61 ng/g) observed for pristine areas of Podlasie land at the Bia?owie?a Forest and Wielkopolska land near the Pora?yn sites, respectively, and low concentration of 27 ± 8 ng/g (range 21–56 ng/g) observed for the Kujawy land at the Tuszynki site. The mean Hg levels in soil varied from 8 ± 6 ng/g (4–21 ng/g) for Kujawy land at the Tuszynki site to 200 ± 29 ng/g (145–240 ng/g) for Ma?opolska land at the high Tatra Mountains area of Zakopane. The mean soil Hg at the Zakopane site is approximately 25 times the concentration of Kujawy land, Tuszynki. Mercury bioaccumulations were in general low with the mean bioconcentration factor (BCF) ranging from 0.20 ± 0.05 to 3.8 ± 1.7 (overall range of 0.1–5.9). The Hg in soils and fruiting bodies of the present study are within acceptable ranges. The consumption of 300 g of popular Common Chanterelles from any of the investigated regions in Poland would not result in exposure to Hg that is in excess of the maximum weekly dose recommended by the WHO. The estimated dietary exposures to Hg for consumers of this mushroom were calculated and are shown to be below the guidelines for safe exposures. Also reviewed are published data on Hg and MeHg in C. cibarius and 11 other species of the Cantharellus genus collected worldwide.     

Determination of antioxidant activity and phenolic compounds of Muntingia calabura Linn. peel by HPLC‐DAD and UPLC‐ESI‐MS/MS

Antioxidant activity in Muntingia calabura Linn. peel was evaluated by DPPH radical, ORAC, ABTS cation radical, FRAP assays and total phenolic contents by different extraction conditions. In addition, a method for determination of phenolic compounds in calabura peel samples harvested in Brazil using methanol:water and magnetic stirring as the extraction method, HPLC‐DAD and UPLC‐ESI‐MS/MS analysis were developed. Calabura peel showed antioxidant activity for all extraction conditions and assays evaluated, the most polar solvents being more effective. The developed HPLC‐DAD method allowed the accurate determination of phenolic compounds, with recoveries in the range of 72–107% and precision values ≤4%, with exception for chlorogenic acid. Gallic acid was determined at the highest concentration levels, followed by myricetin, ferulic acid and vanillic acid. However, all the five proposed phenolic compounds were identified in calabura peel samples by UPLC‐ESI‐MS/MS. Thus, calabura peel, an uncommon edible fruit part, can be appointed as a rich source of phenolic compounds.     

Action of Pepsin on Emulsifying Properties of Globin

The emulsifying properties of bovine globin, extracted by the acidified acetone method, were studied at different pH values and after several times of peptic-hydrolysis. The emulsifying capacity, the emulsifying activity index, and the emulsion stability were determined. In general, the peptic hydrolysis was disadvantageous for the emulsifying properties of globin, since it only increased the emulsifying capacity (at pH = 3.0, after 30 and 60 minutes hydrolysis; at pH = 4.0, after 10 to 60 minutes hydrolysis), and the emulsifying activity index (at pH = 5.0 after 60 minutes hydrolysis; at pH = 6.0 after 15, 30, and 60 minutes hydrolysis). This treatment reduced the emulsion stability in almost all conditions studied.     

Design of DNA Intercalators Based on 4-Carboranyl-1,8-Naphthalimides: Investigation of Their DNA-Binding Ability and Anticancer Activity

In the present study, we continue our work related to the synthesis of 1,8-naphthalimide and carborane conjugates and the investigation of their anticancer activity and DNA-binding ability. For this purpose, a series of 4-carboranyl-1,8-naphthalimide derivatives, mitonafide, and pinafide analogs were synthesized using click chemistry, reductive amination, amidation, and Mitsunobu reactions. The calf thymus DNA (ct-DNA)-binding properties of the synthesized compounds were investigated by circular dichroism (CD), UV–vis spectroscopy, and thermal denaturation experiments. Conjugates 54–61 interacted very strongly with ct-DNA (∆T_m = 7.67–12.33 °C), suggesting their intercalation with DNA. They were also investigated for their in vitro effects on cytotoxicity, cell migration, cell death, cell cycle, and production of reactive oxygen species (ROS) in a HepG2 cancer cell line as well as inhibition of topoisomerase IIα activity (Topo II). The cytotoxicity of these eight conjugates was in the range of 3.12–30.87 µM, with the lowest IC₅₀ value determined for compound 57. The analyses showed that most of the conjugates could induce cell cycle arrest in the G0/G1 phase, inhibit cell migration, and promote apoptosis. Two conjugates, namely 60 and 61, induced ROS production, which was proven by the increased level of 2′-deoxy-8-oxoguanosine in DNA. They were specifically located in lysosomes, and because of their excellent fluorescent properties, they could be easily detected within the cells. They were also found to be weak Topo II inhibitors.