Flavour profile of three novel acidic varieties of muskmelon (Cucumis melo L.)

Novel acidic varieties of muskmelon (Cucumis melo L.) are emerging onto the UK market. These melons contain almost twice the amount of citric acid compared to standard melons and are described as ‘zesty and fresh’. This study compared the flavour components of three acidic varieties with a standard Galia-type melon. The volatile and semivolatile compounds were extracted using dynamic headspace extraction (DHE) or solid-phase microextraction (SPME) and solid phase extraction (SPE) respectively, followed by gas chromatography – mass spectrometry (GC-MS) and gas chromatography – olfactometry (GC-O). More than 50 volatile and 50 semivolatile compounds were identified in the headspace and the SPE extracts respectively. GC-O revealed 15 odour-active components in the headspace, with esters being consistently higher in acidic variety. This study showed quantitative and qualitative differences between all four varieties and key differences between acidic varieties and standard melons.

Critical role for an acidic amino acid region in platelet signaling by the HemITAM (hemi-immunoreceptor tyrosine-based activation motif) containing receptor CLEC-2 (C-type lectin receptor-2)

CLEC-2 is a member of new family of C-type lectin receptors characterized by a cytosolic YXXL downstream of three acidic amino acids in a sequence known as a hemITAM (hemi-immunoreceptor tyrosine-based activation motif). Dimerization of two phosphorylated CLEC-2 molecules leads to recruitment of the tyrosine kinase Syk via its tandem SH2 domains and initiation of a downstream signaling cascade. Using Syk-deficient and Zap-70-deficient cell lines we show that hemITAM signaling is restricted to Syk and that the upstream triacidic amino acid sequence is required for signaling. Using surface plasmon resonance and phosphorylation studies, we demonstrate that the triacidic amino acids are required for phosphorylation of the YXXL. These results further emphasize the distinct nature of the proximal events in signaling by hemITAM relative to ITAM receptors.

Are sulfurous soil amendments (S0, Fe(II)SO4, Fe(III)SO4) an effective tool in the restoration of heathland and acidic grassland after four decades of rock phosphate Fertilization?

This paper deals with the complex issue of reversing long-term improvements of fertility in soils derived from heathlands and acidic grasslands using sulfur-based amendments. The experiment was conducted on a former heathland and acid grassland in the U.K. that was heavily fertilized and limed with rock phosphate, chalk, and marl. The experimental work had three aims. First, to determine whether sulfurous soil amendments are able to lower pH to a level suitable for heathland and acidic grassland re-creation (approximately 3 pH units). Second, to determine what effect the soil amendments have on the available pool of some basic cations and some potentially toxic acidic cations that may affect the plant community. Third, to determine whether the addition of Fe to the soil system would sequester PO4− ions that might be liberated from rock phosphate by the experimental treatments. The application of S0 and Fe(II)SO4− to the soil was able to reduce pH. However, only the highest S0 treatment (2,000 kg/ha S) lowered pH sufficiently for heathland restoration purposes but effectively so. Where pH was lowered, basic cations were lost from the exchangeable pool and replaced by acidic cations. Where Fe was added to the soil, there was no evidence of PO4− sequestration from soil test data (Olsen P), but sequestration was apparent because of lower foliar P in the grass sward. The ability of the forb Rumex acetosella to apparently detoxify Al3+, prevalent in acidified soils, appeared to give it a competitive advantage over other less tolerant species. We would anticipate further changes in plant community structure through time, driven by Al3+ toxicity, leading to the competitive exclusion of less tolerant species. This, we suggest, is a key abiotic driver in the restoration of biotic (acidic plant) communities.

Neurofilament heavy subunit in cerebrospinal fluid: A biomarker of amyotrophic lateral sclerosis?

The objectives of this study were to investigate the presence of the three neurofilament subunits, ubiquitin, proteasome and 3-nitrotyrosine, in CSF samples of ALS patients. CSF samples were obtained by lumbar puncture from 10 ALS patients and six controls. All samples were analysed by Western blotting. Results revealed that neurofilament heavy subunit was identified in 70% of ALS cases and we conclude that this subunit may be a promising biomarker for clinical diagnosis of ALS.

Upregulation of gp91(phox) Subunit of NAD(P)H Oxidase Contributes to Erectile Dysfunction Caused by Long-term Nitric Oxide Inhibition in Rats: Reversion by Regular Physical Training

OBJECTIVES To test the hypothesis that glyco protein 91phox (gp91(phox)) subunit of nicotinamide adenine dinucleotide phosphate [NAD(P) H] oxidase is a fundamental target for physical activity to ameliorate erectile dysfunction (ED). Vascular risk factors are reported to contribute to ED. Regular physical exercise prevents cardiovascular diseases by increasing nitric oxide (NO) production and/or decreasing NO inactivation. METHODS Male Wistar rats received the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) for 4 weeks, after which animals were submitted to a run training program for another 4 weeks. Erectile functions were evaluated by in vitro cavernosal relaxations and intracavernous pressure measurements. Expressions of gp91(phox) subunit and neuronal nitric oxidase synthase in erectile tissue, as well as superoxide dismutase activity and nitrite/nitrate (NO(x)) levels were determined. RESULTS The in vitro acetylcholine-and electrical field stimulation-induced cavernosal relaxations, as well as the increases in intracavernous pressure were markedly reduced in sedentary rats treated with L-NAME. Run training significantly restored the impaired cavernosal relaxations. No alterations in the neuronal nitric oxidase synthase protein expression (and its variant penile neuronal nitric oxidase synthase) were detected. A reduction of NO(x) levels and superoxide dismutase activity was observed in L-NAME-treated animals, which was significantly reversed by physical training. Gene expression of subunit gp91(phox) was enhanced by approximately 2-fold in erectile tissue of L-NAME-treated rats, and that was restored to basal levels by run training. CONCLUSIONS Our study shows that ED seen after long-term L-NAME treatment is associated with gp91(phox) subunit upregulation and decreased NO bioavailability. Exercise training reverses the increased oxidative stress in NO-deficient rats, ameliorating the ED. UROLOGY 75: 961-967, 2010. (C) 2009 Elsevier Inc.

Boosting systemic and secreted antibody responses in mice orally immunized with recombinant Bacillus subtilis strains following parenteral priming with a DNA vaccine encoding the enterotoxigenic Escherichia coli (ETEC) CFA/I fimbriae B subunit

Recombinant Bacillus subtilis strains, either spores or vegetative cells, may be employed as safe and low cost orally delivered live vaccine vehicles. In this study, we report the use of an orally delivered B. subtilis vaccine strain to boost systemic and secreted antibody responses in mice i.m. primed with a DNA vaccine encoding the structural subunit (CfaB) of the CFA/I fimbriae encoded by enterotoxigenic Escherichia coli (ETEC), an important etiological agent of diarrhea among travelers and children living in endemic regions. DBA/2 female mice submitted to the prime-boost immunization regimen developed synergic serum (IgG) and mucosal (IgA) antibody responses to the target CfaB antigen. Moreover, in contrast to mice immunized only with one vaccine formulation, sera harvested from prime-boosted vaccinated individuals inhibited adhesion of ETEC cells to human red blood cells. Additionally, vaccinated dams conferred full passive protection to suckling newborn mice challenged with a virulent ETEC strain. Taken together the present results further demonstrate the potential use of recombinant B. subtilis strains as an alternative live vaccine vehicle. (C) 2008 Elsevier Ltd. All rights reserved.

Characterization of Gtf1p, the Connector Subunit of Yeast Mitochondrial tRNA-dependent Amidotransferase

The bacterial GatCAB operon for tRNA-dependent amidotransferase (AdT) catalyzes the transamidation of mischarged glutamyl-tRNA(Gln) to glutaminyl-tRNA(Gln). Here we describe the phenotype of temperature-sensitive (ts) mutants of GTF1, a gene proposed to code for subunit F of mitochondrial AdT in Saccharomyces cerevisiae. The ts gtf1 mutants accumulate an electrophoretic variant of the mitochondrially encoded Cox2p subunit of cytochrome oxidase and an unstable form of the Atp8p subunit of the F(1)-F(0) ATP synthase that is degraded, thereby preventing assembly of the F(0) sector. Allotopic expression of recoded ATP8 and COX2 did not significantly improve growth of gtf1 mutants on respiratory substrates. However, ts gft1 mutants are partially rescued by overexpression of PET112 and HER2 that code for the yeast homologues of the catalytic subunits of bacterial AdT. Additionally, B66, a her2 point mutant has a phenotype similar to that of gtf1 mutants. These results provide genetic support for the essentiality, in vivo, of the GatF subunit of the heterotrimeric AdT that catalyzes formation of glutaminyl-tRNA(Gln) (Frechin, M., Senger, B., Braye, M., Kern, D., Martin, R. P., and Becker, H. D. (2009) Genes Dev. 23, 1119-1130).

Phylogenetic Analyses Based on Small Subunit rRNA and Glycosomal Glyceraldehyde-3-Phosphate Dehydrogenase Genes and Ultrastructural Characterization of Two Snake Trypanosomes: Trypanosoma serpentis n. sp from Pseudoboa nigra and Trypanosoma cascavelli from Crotalus durissus terrificus

We sequenced the small subunit (SSU) rRNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) genes of two trypanosomes isolated from the Brazilian snakes Pseudoboa nigra and Crotalus durissus terrificus. Trypanosomes were cultured and their morphometrical and ultrastructural features were characterized by light microscopy and scanning and transmission electron microscopy. Phylogenetic trees inferred using independent or combined SSU rRNA and gGAPDH data sets always clustered the snake trypanosomes together in a clade closest to lizard trypanosomes, forming a strongly supported monophyletic assemblage (i.e. lizard-snake clade). The positioning in the phylogenetic trees and the barcoding based on the variable V7-V8 region of the SSU rRNA, which showed high sequence divergences, allowed us to classify the isolates from distinct snake species as separate species. The isolate from P. nigra is described as a new species, Trypanosoma serpentis n. sp., whereas the isolate from C. d. terrificus is redescribed here as Trypanosoma cascavelli.

Mitochondrial bioenergetics and redox state are unaltered in Trypanosoma cruzi isolates with compromised mitochondrial complex I subunit genes

In trypanosomatids the involvement of mitochondrial complex I in NADH oxidation has long been debated. Here, we took advantage of natural Trypanosoma cruzi mutants which present conspicuous deletions in ND4, ND5 and ND7 genes coding for complex I subunits to further investigate its functionality. Mitochondrial bioenergetics of wild type and complex I mutants showed no significant differences in oxygen consumption or respiratory control ratios in the presence of NADH-linked substrates or FADH(2)-generating succinate. No correlation could be established between mitochondrial membrane potentials and ND deletions. Since release of reactive oxygen species occurs at complex I, we measured mitochondrial H(2)O(2) formation induced by different substrates. Significant differences not associated to ND deletions were observed among the parasite isolates, demonstrating that these mutations are not important for the control of oxidant production. Our data support the notion that complex I has a limited function in T. cruzi.

Stimulation of Acidic Reduction of Nitrite to Nitric Oxide by Soybean Phenolics: Possible Relevance to Gastrointestinal Host Defense

This study aimed to evaluate the potential of soybean-promoted acidic nitrite reduction and to correlate this activity with the content of phenolics and with the bactericidal activity against Escherichia coli O157:H7. Extracts of embrionary axes and cotyledons enriched in phenolics increased (center dot)NO formation at acidic pH at values that were 7.1 and 4.5 times higher, respectively, when compared to the reduction of the nonenriched extracts. Among the various phenolics accumulated in the soybean extracts, five stimulated nitrite reduction in the following decreasing order of potency: epicatechin gallate, chlorogenic acid, caffeic acid, galic acid and p-coumaric acid. Extracts of embrionary axes presented higher contents of epicatechin gallate and caffeic acid, compared to that of cotyledons, indicating a positive correlation between activity of the extracts and content of phenolics with regard to nitrite reducing activity. Soybean extracts enriched in phenolics interacted synergistically with acidified nitrite to prevent E. coli O157:H7 growth. The results suggest that soybean phenolics may interfere with the metabolism of (center dot)NO in an acidic environment by accelerating the reduction of nitrite, with a potential antimicrobial effect in the stomach.

Role of the triad N46, S106 and T107 and the surface charges in the determination of the acidic pH optimum of digestive lysozymes from Musca domestica

Structures of digestive lysozymes 1 and 2 from housefly (MdL1 and MdL2) show that S106-T107 delimit a polar pocket around E32 (catalytic acid/base) and N46 contributes to the positioning of 050 (catalytic nucleophile), whereas those residues are replaced by V109-A110 and D48 in the non-digestive lysozyme from hen egg-white (HEWL). Further analyses revealed that MdL1 and MdL2 surfaces are less positively charged than HEWL surface. To verify the relevance of these differences to the acidic pH optimum of digestive lysozymes it was determined that pKas of the catalytic residues of the triple mutant MdL2 (N46D-S106V-T107A) are similar to HEWL pKas and higher than those for MdL2. In agreement, triple mutant MdL2 and HEWL exhibits the same pH optimum upon methylumbelliferylchitotrioside. In addition to that, the introduction of six basic residues on MdL1 surface increased by 1 unit the pH optimum for the activity upon bacterial walls. Thus, the acidic pH optimum for MdL2 and MdL1 activities upon methylumbelliferylchitotrioside is determined by the presence of N46, S106 and T107 in the environment of their catalytic residues, which favors pKas reduction. Conversely, acidic pH optimum upon bacterial walls is determined by a low concentration of positive charges on the MdL2 and MdL1 surfaces. (C) 2010 Elsevier Inc. All rights reserved.

Kinetic and mechanistic investigation of the ozonolysis of 2,4-xylidine (2,4-dimethyl-aniline) in acidic aqueous solution

The ozonolysis of 2,4-xylidine (2,4-dimethyl-aniline) in acidic aqueous solution was investigated by determining the major reaction products and their evolution as a function of the reaction time and their dependence on the pH of the reaction system. 2,4-Dimethyl-nitrobenzene and 2,4-dimethyl-phenol were found to be primary reaction products; their formation might be explained by electron transfer and substitution reactions. 2,4-Dimethyl-phenol was further oxidized yielding 2,4-dimethyl- and/or 4,6-dimethyl-resorcinol by electrophilic addition of HO(center dot) radicals. The best fitting phenomenological kinetic model and the good convergence of calculated and experimentally determined rate constants imply two additional competitive pathways of substrate oxidation: (i) electrophilic addition of HO(center dot) radicals and fast subsequent substitution would also yield the resorcinol derivatives. (ii) Substrate and isolated products are thought to be oxidized by hydrogen abstraction at the benzylic sites, but the corresponding products (alcohols, aldehydes, and carboxylic acids) could not be identified. Fe(II) was added to probe for the presence of H(2)O(2), but had no or only a minor effect on the kinetics of the ozonolysis. (c) 2009 Elsevier B.V. All rights reserved.

On-line mass spectrometry of the electro-oxidation of methanol in acidic media on tungsten carbide

The electro-oxidation of methanol at supported tungsten carbide (WC) nanoparticles in sulfuric acid solution was studied using cyclic voltammetry, potentiostatic measurements, and differential electrochemical mass spectroscopy (DEMS). The catalyst was prepared by a sonochemical method and characterized by X-ray diffraction. Over the WC catalyst, the oxidation of methanol (1 M in a sulfuric acid electrolyte) begins at a potential below 0.5 V/RHE during the anodic sweep. During potentiostatic measurements, a maximum current of 0.8 mA mg(-1) was obtained at 0.4 V. Measurements of DEMS showed that the methanol oxidation reaction over tungsten carbide produces CO2 (m/z=44); no methylformate (m/z=60) was detected. These results are discussed in the context of the continued search for alternative materials for the anode catalyst of direct methanol fuel cells.

Isoelectric Point Determination for Glossoscolex paulistus Extracellular Hemoglobin: Oligomeric Stability in Acidic pH and Relevance to Protein-Surfactant Interactions

The extracellular hemoglobin from Glossoscolex paulistus (HbGp) has a molecular mass of 3.6 M Da, It has a high oligomeric stability at pH 7.0 and low autoxidation rates, as compared to vertebrate hemoglobins. In this work, fluorescence and light scattering experiments were performed with the three oxidation forms of HbGp exposed to acidic pH. Our focus is on the HbGp stability at acidic pH and also on the determination of the isoelectric point (pI) of the protein. Our results show that the protein in the cyanomet form is more stable than in the other two forms, in the whole range. Our zeta-potential data are consistent with light scattering results. Average values apt obtained by different techniques were 5.6 +/- 0.5, 5.4 +/- 0.2 and 5.2 +/- 0.5 for the oxy, met, and cyanomet forms. Dynamic light scattering (DLS) experiments have shown that, at pH 6.0, the aggregation (oligomeric) state of oxy-, met- and cyanomet-HbGp remains the same as that at 7.0. The interaction between the oxy-HbGp and ionic surfactants at pH 5.0 and 6.0 was also monitored in the present study. At pH 5,0, below the protein pI, the effects of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium chloride (CTAC) are inverted when compared to pH 7.0. For CTAC, in acid pH 5.0, no precipitation is observed, while for SDS an intense light scattering appears due to a precipitation process. HbGp interacts strongly with the cationic surfactant at pH 7.0 and with the anionic one at pH 5.0. This effect is due to the predominance, in the protein surface, of residues presenting opposite charges to the surfactant headgroups. This information can be relevant for the development of extracellular hemoglobin-based artificial blood substitutes.