Kinetic characterization of the oxidation of chlorogenic acid by polyphenol oxidase and peroxidase. Characteristics of the o-quinone

Chlorogenic acid is the major diphenol of many fruits, where it is oxidized enzymatically by polyphenol oxidase (PPO) or peroxidase (POD) to its o-quinone. In spectrophotometric studies of chlorogenic acid oxidation with a periodate ratio of [CGA]0/[IO4-]0 < 1 and [CGA]0/[IO4-]0 > 1, the o-quinone was characterized as follows: lambda(max) at 400 nm and epsilon = 2000 and 2200 M-1 cm-1 at pH 4.5 and 7.0, respectively. In studies of o-quinone generated by the oxidation of chlorogenic acid using a periodate at ratio of [CGA]0/[IO4-]0 > 1, a reaction with the remaining substrate was detected, showing rate constants of k = 2.73 +/- 0.17 M-1 s-1 and k' = 0.05 +/- 0.01 M-1 s-1 at the above pH values. A chronometric spectrophotometric method is proposed to kinetically characterize the action of the PPO or POD on the basis of measuring the time it takes for a given amount of ascorbic acid to be consumed in the reaction with the o-quinone. The kinetic constants of mushroom PPO and horseradish POD are determined.     

Characterization of mammalian selenoproteomes

In the genetic code, UGA serves as a stop signal and a selenocysteine codon, but no computational methods for identifying its coding function are available. Consequently, most selenoprotein genes are misannotated. We identified selenoprotein genes in sequenced mammalian genomes by methods that rely on identification of selenocysteine insertion RNA structures, the coding potential of UGA codons, and the presence of cysteine-containing homologs. The human selenoproteome consists of 25 selenoproteins.     

The in vitro effects of proxymetacaine, fluorescein, and fusidic acid on real-time PCR assays used for the diagnosis of Feline herpesvirus 1 and Chlamydophila felis infections

Purpose To investigate the possible inhibition of qPCR assays used for the diagnosis of ocular infections in cats by proxymetacaine, fluorescein, and fusidic acid, which are commonly used in veterinary ophthalmology. Methods Fluorescein, proxymetacaine, and fusidic acid were tested for possible inhibition of a triplex qPCR assay designed to detect Chamydophila felis, Feline herpesvirus 1 (FHV‐1), and the feline 28S ribosomal DNA (28S rDNA) gene by comparing threshold cycle (C_t) values of samples with and without the three products. A second experiment was carried out to measure the effects of various dilutions of fusidic acid. Results No statistically significant differences were detected between the C. felis, FHV‐1, and 28S rDNA C_t values with and without proxymetacaine or fluorescein. However, there was a statistically significant increase in FHV‐1 (P < 0.01), C. felis (P < 0.01), and 28S rDNA (P < 0.05) C_t values when fusidic acid was used. When dilutions of fusidic acid were tested, the results revealed that only the 1:2 dilution caused a statistically significant increase (P < 0.01) in the FHV‐1 Ct values. Conclusion Proxymetacaine and fluorescein did not interfere with our qPCR assays for the detection of C. felis and FHV‐1. The presence of fusidic acid caused a small inhibitory effect of doubtful clinical significance. In vivo studies are required to establish the clinical relevance of this study and to confirm our findings.     

Bird assemblages in forest fragments within Mediterranean mosaics created by wild fires

The role of habitat heterogeneity as a key factor in determining species pools in habitat mosaics has been acknowledged, but we still know little on the relative importance of the different ecological processes acting within such complex landscapes. We compared species richness and distribution in forest fragments imbedded in shrub-lands to those in continuous forests or in continuous shrublands. We examined the consistency of our data with the predictions of two hypotheses: 1) the Habitat fragmentation hypothesis which states that fragmentation has negative effects on the species from the original continuous habitat; 2) the Habitat supplementation /complementation hypothesis which stipulates that the presence of a matrix habitat around the fragments will mitigate negative effects on the species from the original habitat (supplementation) or allow the presence of species that depend on the presence of both the fragment and matrix habitats (complementation). We show that: 1) species richness in forest fragments did not differ from species richness in segments of continuous forests of equal area; 2) the bird community of forest fragments got impoverished in some forest species but a higher proportion of species common in continuous forests were not affected by fragmentation; 3) fragment communities had a significant proportion of common species that were scarce in, or absent from both continuous forests and shrublands. While, a few forest species supported predictions from the fragmentation hypothesis, occurrence patterns observed in several other species were consistent with either the supplementation or the complementation hypotheses. Our results suggest that there is no single hypothesis that properly captures the consequences of a shift from continuous forests to a mosaic of forest fragments and shrublands and that different ecological mechanisms act in conjunction to determine species pools in habitat mosaics. Habitat heterogeneity at a local scale appears a key factor in maintaining bird diversity in fire driven Mediterranean landscapes.     

Phenolic Compounds and Vitamin Antioxidants of Caper (Capparis spinosa)

Capparis spinosa shows strong resistance to the adverse Mediterranean conditions and it has nutritional and medicinal value. The aim of this study was to evaluate the contents of total phenolic compounds, rutin, tocopherols, carotenoids and vitamin C in leaves and flower buds of C. spinosa from different locations in Tunisia. Results showed the richness of caper with these compounds, especially phenolic compounds. Interestingly, it was also found the presence of both α- and γ-tocopherol in buds. Moreover, C. spinosa contained an appreciable level of vitamin C. The significant amounts of these antioxidants confirm the nutritional and medicinal value of caper.     

Red‐light stimulation of boar semen prior to artificial insemination improves field fertility in farms: A worldwide survey

A survey of in vivo fertility data from 31 pig farms distributed worldwide was conducted to determine whether stimulating boar semen with LED‐based red light increases its reproductive performance following artificial insemination (AI). Red‐light stimulation with MaXipig^® was found to increase farrowing rates (mean ± SEM, control: 87.2% ± 0.4% vs. light stimulation 90.3% ± 0.5%) and the number of both total and live newborn piglets. Red‐light stimulation increased farrowing rates in 27 farms, with an increase ranging from 0.2% to 9.1%. Similar results were observed in litter sizes. Suboptimal management after AI was suggested in those farms with no response to red‐light stimulation. Our results indicate that a routine use of red‐light stimulation of boar semen can have a positive effect on the reproductive performance. However, the effectiveness of this system appears to highly rely upon proper management of pig farms.     

Low oxygen levels and light exposure affect quality of fresh-cut Romaine lettuce

Modified atmosphere packaging (MAP) has the potential to extend the shelf-life of fresh-cut lettuce mainly by limiting the oxidation processes. However, exposure to light conditions has been described as causing browning and quality loss. The influence of O₂ partial pressures (pO₂) and light exposure during storage on the shelf-life of fresh-cut Romaine lettuce was studied. Fresh-cut lettuce was exposed daily during storage to different light conditions: light (24 h), darkness (24 h) and photoperiod (12 h light + 12 h darkness). Changes in respiration rate, headspace gas composition, sensory quality, colour, electrolyte leakage, stomatal opening, water loss, texture and compositional constituents related to browning such as vitamin C and individual and total phenolic compounds were evaluated. Different weight samples (75–275 g), packaged with an initial pO₂ of 0.5–2.0 kPa balanced with N₂, reached pO₂ from 0.1 to 1.5 at the steady-state. Atmospheres with low pO₂ (0.2–0.5) at the steady-state preserved lettuce quality by the control of browning and the prevention of off-odours and off-flavours. Light exposure during storage positively influenced the number of open stomata (74% in light vs 24% in darkness) which contributed slightly to weight loss. Consumption of O₂ in samples exposed to light differed significantly from those stored in photoperiod or darkness (10.6 ± 7.0, 18.3 ± 3.5 and 25.8 ± 8.6 nmol O₂ kg^?1 s^?1, respectively). Packages exposed to light showed higher pO₂ compared with packages stored in darkness while those exposed to photoperiod had intermediate values. Moreover, location of the packages in the shelves affected package headspace gas composition and thus, packages near the front of the shelves showed higher pO₂ than those at the back. The different light conditions did not influence the content of vitamin C or the individual and total phenolic compounds. This study shows that under light conditions respiration activity was compensated by photosynthesis resulting in a higher pO₂. Thus, browning of fresh-cut Romaine lettuce can be promoted by light exposure during storage as it increases headspace pO₂.     

Enhanced photo- and antioxidative protection,and hydrogen peroxide accumulation in drought-stressed Cistus clusii and Cistus albidus plants

Mechanisms of drought stress resistance were studied in Cistus clusii Dunal and Cistus albidus L., two native Mediterranean shrubs that can withstand severe summer drought. While water deficit, solar radiation and temperature increased from winter to summer in the field, C. clusii and C. albidus reduced leaf area, increased root mass per leaf area, and showed diurnal changes in stomatal conductance to minimize water loss. In both species, the consequent reductions in CO2 assimilation were accompanied by reduced efficiency of photosystem II photochemistry, and protection against stress was afforded by enhanced de-epoxidation of violaxanthin in the xanthophyll cycle and increases in alpha-tocopherol and beta-carotene. In addition, hydrogen peroxide (H2O2) accumulation was observed in mesophyll cell walls of both species during the first stages of drought, although no accumulation of H2O2 was observed in chloroplasts or other organelles during the study. Despite these common responses, C. albidus and C. clusii differed in the extent of photo- and antioxidative protection. In response to drought, C. clusii showed a higher de-epoxidation state of the xanthophyll cycle and higher alpha-tocopherol and beta-carotene concentrations than C. albidus. We conclude that several structural and biochemical mechanisms underlie stress resistance in C. clusii and C. albidus, and are indicative of the different degrees of stress resistance of these shrubs.