Preparation and properties of modified chitosan as potential matrix materials for drug sustained-release beads

Modified chitosan such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS) were successfully prepared. The modified chitosan were employed in the formation of drug-loaded, iron(III)-crosslinked polymeric beads. The produced polymers were characterized by IR, NMR, WXRD and DSC measurements. The resulting beads were evaluated in vitro as drug prolonging and potentially orally administered delivery system. Theophylline was used as the loaded model drug. The generated beads proved to be successful in prolonging drug release. The release kinetics was evaluated by fitting the experimental data to standard release equations (zero-, first- and Higuchi equation). The best fit was found with Higuchi model for the polymeric beads.     

Optimization of an ethanol production medium in very high gravity fermentation

Concentrations of Mg²⁺, glycine, yeast extract, biotin, acetaldehyde and peptone were optimized by a uniform design process for ethanol production by Saccharomyces cerevisiae. Using non-linear step-wise regression analysis, a predictive mathematical model was established. Concentrations of Mg²⁺ and peptone were identified as the critical factors: 50 mM Mg²⁺ and 1.5% (w/v) peptone in the medium increased the final ethanol titre from 14.2% (v/v) to 17% (v/v) in 48 h.     

<Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> as a novel biocatalyst for pyruvate production from<Emphasis Type="SmallCaps"> DL</Emphasis>-lactate

Pseudomonas stutzeri SDM oxidized dl-lactic acid (25.5 g l^-1) into pyruvic acid (22.6 g l^-1) over 24 h. Both NAD⁺-independent d-lactate dehydrogenase and NAD⁺-independent l-lactate dehydrogenase were found for the first time in the bioconversion of lactate to pyruvate based on the enzyme activity assay and proteomic analysis. Jianrong Hao and Cuiqing Ma contributed equally to this work     

The Improvement of Spinach Growth by Nano-anatase TiO<Subscript>2</Subscript> Treatment Is Related to Nitrogen Photoreduction

The improvement of spinach growth is proved to relate to N₂ fixation by nano-anatase TiO₂ in this study. The results show that all spinach leaves kept green by nano-anatase TiO₂ treatment and all old leaves of control turned yellow white under culture with N-deficient solution. And the fresh weight, dry weight, and contents of total nitrogen, , chlorophyll, and protein of spinach by nano-anatase TiO₂ treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good as nano-anatase TiO₂ treatment under N-deficient condition, confirming that nano-anatase TiO₂ on exposure to sunlight could chemisorb N₂ directly or reduce N₂ to NH₃ in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO₂ effect, however, was not as significant as nano-anatase TiO₂. A possible metabolism of the function of nano-anatase TiO₂ reducing N₂ to NH₃ was discussed.     

Efficient transient expression and transformation of PEG-mediated gene uptake into mesophyll protoplasts of pepper (<Emphasis Type="Italic">Capsicum annuum</Emphasis> L.)

PEG-mediated transformation was used for gene delivery and evaluation of various parameters affecting the transient expression of a gene for ß-glucuronidase (gus) in mesophyll protoplasts of Capsicum annuum. Transient expression was found to be dependent on PEG concentration and exposure time of plasmid DNA to protoplasts as well as the amount of plasmid DNA. Maximum GUS activity was obtained when protoplasts were applied to 40% concentration and molecular weight was 6,000 of PEG solution with 30 min of exposure time. Protoplasts of pepper were transformed with a vector, pCAMBIA::Ac, which contained a pCAMBIA1302 T-DNA vector carrying a maize transposable element, Ac (activator), a selection marker HPT (hygromycin phosphotransferase), and a GFP-coding region driven by the 35S promoter in the presence of PEG. Approximately 30% of the protoplasts expressed GFP. Visibly transformed colonies were obtained from protoplasts after 2 months of culture and GFP was expressed. Southern hybridization confirmed the presence of Ac in the pepper genome.     

Deproteinization of gellan gum produced by Sphingomonas paucimobilis ATCC 31461

Deproteinization is a technical bottleneck in the purification of viscous water-soluble polysaccharides. The aim of this work is to provide an appropriate approach to deproteinize crude gellan gum. Several methods of deproteinization were investigated, including Sevag method, alkaline protease, papain and neutral protease. The results revealed that Sevag method had high deproteinization efficiency (87.9%), but it showed dissatisfactory recovery efficiency of gellan gum (28.6%), which made it less advisable in industrial applications. The deproteinization by alkaline protease was demonstrated in this work for the first time, indicating alkaline protease was preferred in the deproteinization of crude gellan gum with high polysaccharide recovery (89.3%) and high deproteinization efficiency (86.4%).     

Overexpression of a NAC-domain protein promotes shoot branching in rice

For a better understanding of shoot branching in rice (Oryza sativa), a rice activation-tagging library was screened for mutations in tiller development. Here, an activation-tagging mutant Ostil1 (Oryza sativa tillering1) was characterized, which showed increased tillers, enlarged tiller angle and semidwarf phenotype. Flanking sequence was obtained by plasmid rescue. RNA-interfering and overexpression transgenic rice plants were produced using Agrobacterium-mediated transformation. The mutant phenotype was cosegregated with the reallocation of Ds element, and the flanking region of the reallocated Ds element was identified as part of the OsNAC2 gene. Northern analysis showed that expression of OsNAC2 was greatly induced in the mutant plants. Transgenic rice overexpressing the OsNAC2 resulted in recapture of the mutant phenotype, while downregulation of OsNAC2 in the Ostil1 mutant through RNA interfering (RNAi) complemented the mutant phenotype, confirming that the Ostil1 was caused by overexpression of OsNAC2. Overexpression of OsNAC2 regulates shoot branching in rice. Overexpression of OsNAC2 contributes tiller bud outgrowth, but does not affect tiller bud initiation. This suggests that OsNAC2 has potential utility for improving plant structure for higher light-use efficiency and higher yield potential in rice.     

A Ds-insertion mutant of OSH6 (Oryza sativa Homeobox 6) exhibits outgrowth of vestigial leaf-like structures, bracts, in rice

OSH6 (Oryza sativa Homeobox6) is an ortholog of lg3 (Liguleless3) in maize. We generated a novel allele, termed OSH6-Ds, by inserting a defective Ds element into the third exon of OSH6, which resulted in a truncated OSH6 mRNA. The truncated mRNA was expressed ectopically in leaf tissues and encoded the N-terminal region of OSH6, which includes the KNOX1 and partial KNOX2 subdomains. This recessive mutant showed outgrowth of bracts or produced leaves at the basal node of the panicle. These phenotypes distinguished it from the OSH6 transgene whose ectopic expression led to a “blade to sheath transformation” phenotype at the midrib region of leaves, similar to that seen in dominant Lg3 mutants. Expression of a similar truncated OSH6 cDNA from the 35S promoter (35S::ΔOSH6) confirmed that the ectopic expression of this product was responsible for the aberrant bract development. These data suggest that OSH6-Ds interferes with a developmental mechanism involved in bract differentiation, especially at the basal nodes of panicles. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Developmental steps in acquiring competence for shoot development in <Emphasis Type="Italic">Arabidopsis</Emphasis> tissue culture

Arabidopsis shoots regenerate from root explants in tissue culture through a two-step process requiring preincubation on an auxin-rich callus induction medium (CIM) followed by incubation on a cytokinin-rich shoot induction medium (SIM). During CIM preincubation, root explants acquire competence to respond to shoot induction signals. During CIM preincubation, pericycle cells in root explants undergo cell divisions and dedifferentiate, losing the expression of a pericycle cell-specific marker. These cells acquire competence to form green callus only after one day CIM preincubation and to form shoots after 2–3 days CIM preincubation. Reversible DNA synthesis inhibitors interfered with the acquisition of competence to form shoots. Genes requiring CIM preincubation for upregulation on SIM were identified by microarray analysis and included RESPONSE REGULATOR 15 (ARR15), POLYGALACTURONASE INHIBITING PROTEIN 2 (PGIP2) and WUSCHEL (WUS). These genes served as developmental markers for the acquisition of competence because the CIM preincubation requirements for ARR15 and PGIP2 upregulation correlated well with the acquisition of competence to form green callus, and the CIM preincubation requirements for WUS upregulation matched those for shoot formation. Unlike ARR15, another cytokinin inducible, A-type ARR gene, ARR5, was upregulated on SIM, but the induction did not require CIM preincubation. These findings indicate that competencies for various events associated with shoot regeneration are acquired progressively during CIM preincubation, and that a set of genes, normally upregulated on SIM, are repressed by a process that can be relieved by CIM preincubation.     

Effect of gap junctional intercellular communication on radiation responses in neoplastic human cells

Gap junctional intercellular communication (GJIC) is an important function of metazoan cells and is believed to have beneficial effects in anti-tumor therapy. In this study, we found that, when neoplastic human salivary gland (HSG) cells were irradiated with a 100 keV/microm carbon-ion beam, micronuclei, G(2)/M-phase arrest, and cell killing were induced and that their induction increased with dose. Treatment of confluent HSG cells with 8-Br-cAMP increased GJIC between cells. After release from this treatment, the cell cycle progress and the formation of binucleated cells were still similar to those of untreated cells. However, radiation-induced cellular damage, including micronucleus (MN) formation and G(2)/M-phase arrest of that cAMP-treated population, was less than that of the untreated population and that the surviving fraction was slightly enhanced by cAMP treatment, suggesting that increased GJIC protects HSG cells from lethal radiation damage. Moreover, when confluent HSG cells were treated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), a scavenger of nitric oxide (NO) free radical, MN induction and cell killing in the irradiated population were increased. Our results indicate that NO may be involved in GJIC-mediated radioprotection of HSG cells, which may have implications for radiotherapy.