Role of three isoforms of phospholipase A2 in capacitative calcium influx in human T-cells.

The present study was conducted on human Jurkat T-cell lines in order to elucidate the role of phospholipase A2 in capacitative calcium entry. We have employed thapsigargin (TG) that induces increases in [Ca2+]i by emptying the calcium pool of endoplasmic reticulum, followed by capacitative calcium entry. We designed a Ca2+ free/Ca2+ reintroduction (CFCR) protocol for the experiments, conducted in Ca2+-free medium. By employing CFCR protocol, we observed that addition of exogenous arachidonic acid (AA) stimulated TG-induced capacitative calcium influx. The liberation of endogenous AA and its autocrine action seems to be implicated during TG-induced capacitative calcium influx: TG potentiates the induction of constitutively expressed mRNA of four PLA2 isoforms (type 1B, IV, V, VI), the inhibitors of the three PLA2 isotypes (type 1B, V, VI) inhibit TG-induced release of [3H]AA into the extracellular medium, and finally, these PLA2 inhibitors do curtail TG-stimulated capacitative calcium entry in these cells. These results suggest that stimulation of three isoforms of PLA2 by thapsigargin liberates free AA that, in turn, induces capacitative calcium influx in human T-cells.     

Peroxyl adduct radicals formed in the iron/oxygen reconstitution reaction of mutant ribonucleotide reductase R2 proteins from Escherichia coli

Catalytically important free radicals in enzymes are generally formed at highly specific sites, but the specificity is often lost in point mutants where crucial residues have been changed. Among the transient free radicals earlier found in the Y122F mutant of protein R2 in Escherichia coli ribonucleotide reductase after reconstitution with Fe2+ and O2, two were identified as tryptophan radicals. A third radical has an axially symmetric EPR spectrum, and is shown here using 17O exchange and simulations of EPR spectra to be a peroxyl adduct radical. Reconstitution of other mutants of protein R2 (i.e. Y122F/W48Y and Y122F/W107Y) implicates W48 as the origin of the peroxyl adduct. The results indicate that peroxyl radicals form on primary transient radicals on surface residues such as W48, which is accessible to oxygen. However, the specificity of the reaction is not absolute since the single mutant W48Y also gives rise to a peroxyl adduct radical. We used density functional calculations to investigate residue-specific effects on hyperfine coupling constants using models of tryptophan, tyrosine, glycine and cysteine. The results indicate that any peroxyl adduct radical attached to the first three amino acid alpha-carbons gives similar 17O hyperfine coupling constants. Structural arguments and experimental results favor W48 as the major site of peroxyl adducts in the mutant Y122F. Available molecular oxygen can be considered as a spin trap for surface-located protein free radicals.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> signal peptidase recognizes and cleaves archaeal signal sequence

Tk1884, an open reading frame encoding α-amylase in Thermococcus kodakarensis, was cloned with the native signal sequence and expressed in Escherichia coli. Heterologous gene expression resulted in secretion of the recombinant protein to the extracellular culture medium. Extracellular α-amylase activity gradually increased after induction. Tk1884 was purified from the extracellular medium, and its molecular mass determined by electrospray ionization mass spectrometry indicated the cleavage of a few amino acids. The N-terminal amino acid sequence of the purified Tk1884 was determined, which revealed that the signal peptide was cleaved between Ala26 and Ala27 by E. coli signal peptidase. To the best of our knowledge, this is the first report describing an archaeal signal sequence recognized and cleaved by E. coli signal peptidase.     

Structural and functional characteristics of plant proteinase inhibitor-II (PI-II) family

Plant proteinase inhibitor-II (PI-II) proteins are one of the promising defensive proteins that helped the plants to resist against different kinds of unfavorable conditions. Different roles for PI-II have been suggested such as regulation of endogenous proteases, modulation of plant growth and developmental processes and mediating stress responses. The basic knowledge on genetic and molecular diversity of these proteins has provided significant insight into their gene structure and evolutionary relationships in various members of this family. Phylogenetic comparisons of these family genes in different plants suggested that the high rate of retention of gene duplication and inhibitory domain multiplication may have resulted in the expansion and functional diversification of these proteins. Currently, a large number of transgenic plants expressing PI-II genes are being developed for enhancing the defensive capabilities against insects, bacteria and pathogenic fungi. Much emphasis is yet to be given to exploit this ever expanding repertoire of genes for improving abiotic stress resistance in transgenic crops. This review presents an overview about the current knowledge on PI-II family genes, their multifunctional role in plant defense and physiology with their potential applications in biotechnology.     

Chromium Exposure in the Adult Population,Consuming Different Types of Smokeless Tobacco Products in Pakistan

The pervasive smokeless tobacco (SLT) consumption and diseases related to its use is a hot topic for the public discussion. In this study, concentrations of chromium (Cr) were measured in different SLT products [snuff (dry and moist), mainpuri, and gutkha] offered and used in Pakistan. The current study was also designed to assess the Cr levels in the biological (scalp hair and blood) samples of male and female subjects, age ranged from 25 to 60 years, chewing different SLT products. For comparative purpose, the healthy persons of the same age group, who did not consume any SLT products, were selected as referents. The concentrations of Cr in SLT products and biological samples were measured by electrothermal atomic absorption spectrophotometer after microwave-assisted acid digestion. The validity and accuracy of the methodology were checked by certified reference materials (CRMs). The resulted data indicated that the adult persons, who consumed different SLT products, have 2–3 fold higher levels of Cr in biological samples as compared to referent subjects (p < 0.01). The persons, who chew/sniff different SLT products, have 50–80 and 42–82 % higher levels of Cr in their scalp hair and blood samples as related to referents. The daily intake of Cr is lower as compared to the recommended value of 50–200 μg/day. It was expected that 10 g consumption of various kinds of SLT products (snuff, mainpuri, and gutkha) may subsidize 21.2–220, 17.7–122, and 18.4–273 % of the recommended daily intake of Cr, respectively.     

Ethical frameworks for obtaining informed consent in tumour profiling: an evidence-based case for Singapore

Background

Genomic profiling of malignant tumours has assisted clinicians in providing targeted therapies for many serious cancer-related illnesses. Although the characterisation of somatic mutations is the primary aim of tumour profiling for treatment, germline mutations may also be detected given the heterogenous origin of mutations observed in tumours. Guidance documents address the return of germline findings that have health implications for patients and their genetic relations. However, the implications of discovering a potential but unconfirmed germline finding from tumour profiling are yet to be fully explored. Moreover, as tumour profiling is increasingly applied in oncology, robust ethical frameworks are required to encourage large-scale data sharing and data aggregation linking molecular data to clinical outcomes, to further understand the role of genetics in oncogenesis and to develop improved cancer therapies.

Results

This paper reports on the results of empirical research that is broadly aimed at developing an ethical framework for obtaining informed consent to return results from tumour profiling tests and to share the biomolecular data sourced from tumour tissues of cancer patients. Specifically, qualitative data were gathered from 36 semi-structured interviews with cancer patients and oncology clinicians at a cancer treatment centre in Singapore. The interview data indicated that patients had a limited comprehension of cancer genetics and implications of tumour testing. Furthermore, oncology clinicians stated that they lacked the time to provide in depth explanations of the tumour profile tests. However, it was accepted from both patients and oncologist that the return potential germline variants and the sharing of de-identified tumour profiling data nationally and internationally should be discussed and provided as an option during the consent process.

Conclusions

Findings provide support for the return of tumour profiling results provided that they are accompanied with an adequate explanation from qualified personnel. They also support the use of broad consent regiments within an ethical framework that promotes trust and benefit sharing with stakeholders and provides accountability and transparency in the storage and sharing of biomolecular data for research.

     

Formulation and <Emphasis Type="Italic">In Vitro</Emphasis> Characterization of Thiolated Buccoadhesive Film of Fluconazole

The present work is focused on the development of thiolated film for fluconazole buccal delivery. To this end, unmodified polymers chitosan and sodium carboxymethylcellulose (NaCMC) backbone was covalently modified by thioglycolic acid (TGA) and cysteine, respectively. The thiolated buccoadhesive film was evaluated in terms of thickness, weight uniformity, water-uptake capacity, drug content, and release patterns. Moreover, mucoadhesion profile was investigated on buccal mucosa. The resulting chitosan–TGA and NaCMC–cysteine conjugates displayed 171?±?13 and 380?±?19 μmol thiol groups per gram of polymer (mean?±?SD; n?=?3), respectively. The water binding capacity of the thiolated film was significantly ～2-fold higher (p?<?0.05) as compared to unmodified film. The obtained thiolated film displayed 5.8-fold higher mucoadhesive properties compared with corresponding film. Controlled release of drugs from film was observed over 8 h. The transport of fluconazole across excised buccal mucosa was enhanced up to 17-fold in comparison with fluconazole applied in buffer. Based on these findings, thiolated film seems to be promising for fluconazole buccal delivery.     

Pcal_1311, an alcohol dehydrogenase homologue from Pyrobaculum calidifontis,displays NADH-dependent high aldehyde reductase activity

Extremophiles - Genome sequence of Pyrobaculum calidifontis, a hyperthermophilic archaeon, harbors three open-reading frames annotated as alcohol dehydrogenases. One of them, Pcal_1311, does not...