Sliding controller design for a nonlinear fermentation system

The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.     

Heat maps for intramolecular communication in an RNP enzyme encoding glutamine

Allosteric signaling within large ribonucleoproteins modulates both catalytic function and biological specificity, but the spatial extent and quantitative magnitudes of long-distance free-energy couplings have yet to be well characterized. Here, we employ pre-steady-state kinetics to generate a comprehensive mapping of intramolecular communication in the glutaminyl-tRNA synthetase:tRNA(Gln) complex. Alanine substitution at 29 positions across the protein-RNA interface reveals distinct coupling amplitudes for glutamine binding and aminoacyl-tRNA formation on the enzyme, respectively, implying the existence of multiple signaling pathways. Structural models suggest that long-range signal propagation from the tRNA anticodon is dynamically driven, whereas shorter pathways are mediated by induced-fit rearrangements. Seven protein contacts with the distal tRNA vertical arm each weaken glutamine binding affinity across distances up to 40 ?, demonstrating that negative allosteric coupling plays a key role in enforcing the selective RNA-amino acid pairing at the heart of the genetic code.     

Hidden prenatal malnutrition in the rat: role of β₁-adrenoceptors on synaptic plasticity in the frontal cortex

Moderate reduction in the protein content of the mother's diet (hidden malnutrition) does not alter body and brain weights of rat pups at birth, but leads to dysfunction of neocortical noradrenaline systems together with impaired long-term potentiation and visuo-spatial memory performance. As β?-adrenoceptors and downstream protein kinase signaling are critically involved in synaptic long-term potentiation and memory formation, we evaluated the β?-adrenoceptor density and the expression of cyclic-AMP dependent protein kinase, calcium/calmodulin-dependent protein kinase and protein kinase Fyn, in the frontal cortex of prenatally malnourished adult rats. In addition, we also studied if β?-adrenoceptor activation with the selective β? agonist dobutamine could improve deficits of prefrontal cortex long-term potentiation presenting these animals. Prenatally malnourished rats exhibited half of β?-adrenoceptor binding, together with a 51% and 65% reduction of cyclic AMP-dependent protein kinase α and calcium/calmodulin-dependent protein kinase α expression, respectively, as compared with eutrophic animals. Administration of the selective β? agonist dobutamine prior to tetanization completely rescued the ability of the prefrontal cortex to develop and maintain long-term potentiation in the malnourished rats. Results suggest that under-expression of neocortical β?-adrenoceptors and protein kinase signaling in hidden malnourished rats functionally affects the synaptic networks subserving prefrontal cortex long-term potentiation. β?-adrenoceptor activation was sufficient to fully recover neocortical plasticity in the PKA- and calcium/calmodulin-dependent protein kinase II-deficient undernourished rats, possibly by producing extra amounts of cAMP and/or by recruiting alternative signaling cascades.     

Accumulation of β-catenin by lithium chloride in porcine myoblast cultures accelerates cell differentiation

The Wnt/β-catenin signaling pathway regulates cell proliferation and differentiation to determine cell fate during embryogenesis. Lithium chloride (LiCl) is known to activate canonical Wnt signaling by inhibiting glycogen synthetase kinase-3β and consequently stabilizing free cytosolic β-catenin. To understand the role of the Wnt/β-catenin pathway in the regulation of porcine myoblast differentiation, we studied the effects of LiCl on cultured porcine myoblasts and β-catenin expression. A supplementation of 25 mM LiCl induced myoblast differentiation into myotubes over 3 days of culture. By semi-quantitative RT-PCR analyses, levels of mRNA encoding MyoD, Myogenin, Myf5 and several Wnt-responsive genes in the cultured myoblast cells were significantly increased after LiCl treatment. Using Western blotting and immunofluorescence analysis, we found that the protein levels of β-catenin were consistently increased by LiCl. Meanwhile, phosphorylated GSK-3β at Ser9 levels were also increased as an indicator of GSK-3β inactivation. Additionally, the nuclear staining of endogenous β-catenin was also significantly increased in porcine myoblasts 48 h after LiCl treatment. These results provided additional evidence that Wnt/β-catenin is a significant pathway that regulates myogenic differentiation. An enhanced level of β-catenin plays a positive role in porcine myoblast differentiation.     

The moss genes <Emphasis Type="Italic">PpSKI1</Emphasis> and <Emphasis Type="Italic">PpSKI2</Emphasis> encode nuclear SnRK1 interacting proteins with homologues in vascular plants

The yeast Snf1, animal AMPK, and plant SnRK1 protein kinases constitute a family of related proteins that have been proposed to serve as metabolic sensors of the eukaryotic cell. We have previously reported the characterization of two redundant SnRK1 encoding genes (PpSNF1a and PpSNF1b) in the moss Physcomitrella patens. Phenotypic analysis of the snf1a snf1b double knockout mutant suggested that SnRK1 is important for the plant’s ability to recognize and adapt to conditions of limited energy supply, and also suggested a possible role of SnRK1 in the control of plant development. We have now used a yeast two-hybrid system to screen for PpSnf1a interacting proteins. Two new moss genes were found, PpSKI1 and PpSKI2, which encode highly similar proteins with homologues in vascular plants. Fusions of the two encoded proteins to the green fluorescent protein localize to the nucleus. Knockout mutants for either gene have an excess of gametophores under low light conditions, and exhibit reduced gametophore stem lengths. Possible functions of the new proteins and their connection to the SnRK1 kinase are discussed.     

Protein Bodies in the Pine Megagametophyte in vitro Culture: Ultrastructural, Histochemical and Electrophoretic Observations

The megagametophytes of the European black pine (Pinus nigra Arn.) were cultured on modified MS medium. After 10 d, protein bodies showed well-marked degradation on freeze-etched replicas and in preparations observed by scanning electron microscopy. After 20 d of cultivation, the megagametophyte cells were completely empty. Proteins secreted into the agar medium were determined by electrophoresis and 15 different proteins, in the range of 6.5 to 71 kDa, were identified.     

Isolation and Identification of a Novel Antioxidant with Antitumour Activity from <Emphasis Type="Italic">Serratia ureilytica</Emphasis> Using Squid Pen as Fermentation Substrate

The antioxidant activity of the culture supernatant of Serratia ureilytica TKU013 with squid pen as the sole carbon/nitrogen source was assessed by three methods, and the phenolic contents were assayed. The supernatant with the highest antioxidant activity was further purified by liquid–liquid partition, revealing the ethyl acetate extract exhibited the strongest antioxidant activity and the highest total phenolic content. Eight fractions were retrieved from silica gel column chromatography of this extract, designated F1–F8. F4 was found to possess the strong antioxidative activity and the highest total phenolic content and also exhibited strong cytotoxic activities against two different tumoural cell lines. A new compound (Serranticin) with antioxidant and antitumor activity was obtained from F4. The structure of Serranticin is analogous to that of siderophores (hexacoordinated catecholamine), which are iron chelators. As such, Serranticin has the potential for use as a deferration agent in various iron overload diseases.     

Identification of 11-amino acid peptides that disrupt Notch-mediated processes in <Emphasis Type="Italic">Drosophila</Emphasis>

Background  

The conserved Notch signaling pathway regulates cell fate decisions and maintains stem cells in multicellular organisms. Up-regulation of Notch signaling is observed in several types of cancer and is causally involved in proliferation and survival of cancer cells. Thus, it is of great interest to look for anti-Notch reagents for therapeutic purposes. In model animal Drosophila, Notch signaling restricts selection of sensory organ precursors (SOPs) during external sensory (ES) organ development. To look for novel genes that can suppress Notch signaling, we performed a gain-of-function modifier screen to look for genes that enhance the phenotype of ectopic ES organs induced by overexpression of phyllopod, a gene required for SOP specification.     

Neurotoxic Effect of the Complex of the Ovine Prion Protein (OvPrP<Superscript>C</Superscript>) and RNA on the Cultured Rat Cortical Neurons

Prion diseases are conformational diseases, many factors are involved in altering the conformation of prion, such as RNA, DNA, pH, and copper etc. However the neurotoxic mechanism of prion diseases is not clear yet. The aim of this study is to investigate the effect of the nucleoprotein complex of RNA and recombinant ovine prion protein (OvPrP^C) on the cultured rat cortical neurons in vitro. Our previous study revealed that the nucleoprotein complex (OvPrP^C-RNA) is characterized with high β sheet conformation and proteinase K resistance. Here we found that the OvPrP^C-RNA induced marked neuronal cell death by the MTT (3-(4,5-dimethyl-thiazole -2-yl)-2,5-diphenyl –tetrazolium bromide) and TUNEL (TdT mediated biotin-dUTP nicked-end labeling) assay, and the neurotoxic effects were confirmed by testing the content of Bcl-2 Associated X protein (Bax) in the immunoprecipitation assay and Western blot assay. Compared to the control group, there is no significant difference of active Bax or total Bax after RNA alone treatment or OvPrP^C alone treatment, but the OvPrP^C-RNA induced significant increases of active Bax level, while the contents of total Bax had no obvious changes after OvPrP^C-RNA treatment. The results suggested that OvPrP^C-RNA is neurotoxic in vitro, which added further evidence to the current understanding of mechanism of cellular injury by RNA molecules for transformation of the PrP^C to PrP^Sc.