Assessment of potential application of binary mixtures of 2,4-d with novel aminophosphonates

A series of new aminoalkane- and aminofluorenephosphonates was synthesized for agrochemical application. The particular compounds had different alkyl substituents at the carbon, nitrogen and phosphorus atoms. Their pesticidal activity was checked by applying various experimental methods. These included the measurements of compounds' potency: to inhibit growth of cucumber and germination of white mustard seeds, to influence on the membrane potential of algae and to damage human erythrocyte membranes resulting in hemolysis. All the aminophosphonates were also used in equimolar binary mixtures with the well-known herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), to check, if using such mixtures, the biological efficiencies found for particular compounds could be enhanced due to interactions between aminophosphonates and 2,4-D. The results demonstrated, that depending on the structural features of the compounds, the final effects differed from antagonistic, through additive to the most promising synergistic ones. However, the type of interaction between 2,4-D and the compounds studied found in different experiments was somewhat different. In order to estimate those effects various statistical methods were used (toxic unit method, isobole method).     

Glutamatergic elements in an excitability and circumnutation mechanism

In plants, an electrical potential and circumnutation disturbances are a part of a response to environmental and internal stimuli. Precise relations between electrical potential changes and circumnutation mechanisms are unclear. We have found recently that glutamate (Glu) injection into Helianthus annuus stem induced a series of action potentials (APs) and a transient decrease in circumnutation activity. A theoretical explanation for this finding is discussed here taking into considerations data about the ion mechanism of AP and circumnutation as well as about the metabolic and signaling pathways of glutamate and their possible interactions.Key words: action potential, circumnutation, elongation, glutamate, Helianthus annuus, plant movement     

MHC class II derived recombinant T cell receptor ligands protect DBA/1LacJ mice from collagen-induced arthritis

We previously demonstrated the therapeutic effects of MHC class II derived recombinant T cell receptor ligands (RTL), single-chain two domain complexes of the alpha1 and beta1 domains of MHC class II molecules genetically linked with an immunodominant peptide, in experimental autoimmune encephalomyelitis. In the current study, we produced a monomeric murine I-Aq-derived RTL construct covalently linked with bovine collagen type II peptide (bCII257-270) suitable for use in DBA/1LacJ mice that develop collagen-induced arthritis (CIA), an animal model of human rheumatoid arthritis, after immunization with bCII protein in CFA. In this study, we demonstrate that the I-Aq-derived RTLs reduced the incidence of the disease, suppressed the clinical and histological signs of CIA and induced long-term modulation of T cells specific for arthritogenic Ags. Our results showed that the I-Aq/bCII257-270 molecule could systemically reduce proinflammatory IL-17 and IFN-gamma production and significantly increase anti-inflammatory IL-10, IL-13, and FoxP3 gene expression in splenocytes. Moreover, I-Aq/bCII257-270 molecule could also selectively inhibit IL-1beta, IL-6, and IL-23 expression in local joint tissue. This is the first report demonstrating effective prevention of joint inflammation and clinical signs of CIA with an I-Aq-derived RTL, thus supporting the possible clinical use of this approach for treating rheumatoid arthritis in humans.     

Monomeric recombinant TCR ligand reduces relapse rate and severity of experimental autoimmune encephalomyelitis in SJL/J mice through cytokine switch

Our previous studies demonstrated that oligomeric recombinant TCR ligands (RTL) can treat clinical signs of experimental autoimmune encephalomyelitis (EAE) and induce long-term T cell tolerance against encephalitogenic peptides. In the current study, we produced a monomeric I-A(s)/PLP 139-151 peptide construct (RTL401) suitable for use in SJL/J mice that develop relapsing disease after injection of PLP 139-151 peptide in CFA. RTL401 given i.v. or s.c. but not empty RTL400 or free PLP 139-151 peptide prevented relapses and significantly reduced clinical severity of EAE induced by PLP 139-151 peptide in SJL/J or (C57BL/6 x SJL)F(1) mice, but did not inhibit EAE induced by PLP 178-191 or MBP 84-104 peptides in SJL/J mice, or MOG 35-55 peptide in (C57BL/6 x SJL/J)F(1) mice. RTL treatment of EAE caused stable or enhanced T cell proliferation and secretion of IL-10 in the periphery, but reduced secretion of inflammatory cytokines and chemokines. In CNS, there was a modest reduction of inflammatory cells, reduced expression of very late activation Ag-4, lymphocyte function-associated Ag-1, and inflammatory cytokines, chemokines, and chemokine receptors, but enhanced expression of Th2-related factors, IL-10, TGF-beta3, and CCR3. These results suggest that monomeric RTL therapy induces a cytokine switch that curbs the encephalitogenic potential of PLP 139-151-specific T cells without fully preventing their entry into CNS, wherein they reduce the severity of inflammation. This mechanism differs from that observed using oligomeric RTL therapy in other EAE models. These results strongly support the clinical application of this novel class of peptide/MHC class II constructs in patients with multiple sclerosis who have focused T cell responses to known encephalitogenic myelin peptides.     

Acceptability of different species of Brassicaceae as hosts for the cabbage aphid

The probing and feeding behaviour of the cabbage aphid, Brevicoryne brassicae (L.), (Homoptera, Aphididae) was studied on several plant species that represented various levels of acceptability: Sinapis alba L. (a permanent host plant), Capsella bursa-pastoris (L.) Med., Thlaspi arvense L., Lunaria annua L., Erysimum cheiranthoides L. (accidental host plants), Vicia faba L. (a non-host plant), using the electrical penetration graph technique (EPG). B. brassicae on V. faba did not show any patterns related to penetration of phloem vessels. Stylet penetration was deterred on L. annua and E. cheiranthoides where non-penetration prevailed, the periods of sap ingestion were short or did not occur, the percentage of time spent in the phloem was consistently low (5–6%) and E1 salivation predominated. The pathway activities were not suppressed on C. bursa-pastoris and T. arvense and the aphids spent an average of 3 h in the phloem during the 8-h experiment. However, a considerable delay between finding and accepting the phloem and a substantial proportion of E1 salivation (20–30% of all phloem activities) indicated a deterrent factor in the sieve elements of these plants. Aphid probing and sap ingestion were rarely interrupted on S. alba. The results of this study suggest that the deterrent agents vary in activity and may hinder stylet penetration at different levels (epidermis, parenchymatous tissues and/or phloem elements), depending on the plant species.     

The cytochemical localization of nucleotide pyrophosphatase activity in plant tissues using naphthyl esters of thymidine-5''-phosphate.

Synopsis A cytochemical method for the localization of nucleotide pyrophosphatase activity in plants employing naphthol AS-BI thymidine 5-monophosphate and -naphthyl thymidine 5-monophosphate as specific substrates is reported. Biochemical evidence for the validity of this method is presented and the synthesis of the naphthol AS-BI ester is described.The application of this cytochemical technique to shoots ofTriticum sp. and roots ofVicia faba has shown nucleotide pyrophosphatase to be ubiquitous in its distribution in these organs and to occur in a structurally-bound form in the cytoplasm. The highest activity was detected in developing fibres adjacent to the leaf vascular bundles, in the coleoptile epidermal and hypodermal cells and in the coleoptile and leaf xylem.     

Structural basis for differential receptor binding of cholera and Escherichia coli heat-labile toxins: influence of heterologous amino acid substitutions in the cholera B-subunit

The closely related B-subunits of cholera toxin (CTB) and Escherichia coli heat-labile enterotoxin (LTB) both bind strongly to GM1 ganglioside receptors but LTB can also bind to additional glycolipids and glycoproteins. A number of mutant CT B-subunits were generated by substituting CTB amino acids with those at the corresponding positions in LTB. These were used to investigate the influence of specific residues on receptor-binding specificity. A mutated CTB protein containing the first 25 residues of LTB in combination with LTB residues at positions 94 and 95, bound to the same extent as native LTB to both delipidized rabbit intestinal cell membranes, complex glycosphingolipids (polyglycosylceramides) and neolactotetraosylceramide, but not to non-GM1 intestinal glycosphingolipids. In contrast, when LTB amino acid substitutions in the 1–25 region were combined with those in the 75–83 region, a binding as strong as that of LTB to intestinal glycosphingolipids was observed. In addition, a mutant LTB with a single Gly-33→Asp substitution that completely lacked affinity for both GM1 and non-GM1 glycosphingolipids could still bind to receptors in the intestinal cell membranes and to polyglycosylceramides. We conclude that the extra, non-GM1 receptors for LTB consist of both sialylated and non-sialylated glycoconjugates, and that the binding to either class of receptors is influenced by different amino acid residues within the protein.     

Sugar and Light Effects on the Condition of the Photosynthetic Apparatus of Arabidopsis thaliana Cultured in vitro

Light and sugars are fundamental elements of plant metabolism and play signaling roles in many processes. They are also critical factors determining the condition of plants cultured in vitro. The aim of this work was to investigate the simultaneous influence of irradiance and sugar content in the medium on the growth and photosynthetic apparatus condition of Arabidopsis thaliana in vitro. Plants were grown on media containing 1 or 3% of sucrose or glucose at three irradiances: 25, 100, and 250 μmol m⁻² s⁻¹ (weak, medium, and strong light). Media without sugar were used for control plants. Plant growth parameters were measured and the following physiological processes were investigated: photosynthesis, blue light-induced chloroplast relocations, and xanthophyll cycle activity. The expression of genes related to these processes was analyzed. The presence of sugar in the medium was found to be essential for the growth of Arabidopsis in vitro. Weak light significantly limited growth and the capacity to acclimate to changing light conditions. Strong light was a source of stress in some cases. Contrary to earlier reports, exogenous sugars showed a positive effect on photosynthesis. At higher concentration they acted as photoprotectants, overcoming the negative influence of strong light on photosynthesis and the xanthophyll cycle. The expression of all investigated genes was influenced by irradiance and sugar presence. In many cases differential effects of sugar type and concentration could be observed. The specific effects of some irradiance/sugar concentration combinations point to possible interactions between sugar- and light-induced signaling pathways.     

Mapping Organelle Motion Reveals a Vesicular Conveyor Belt Spatially Replenishing Secretory Vesicles in Stimulated Chromaffin Cells

How neurosecretory cells spatially adjust their secretory vesicle pools to replenish those that have fused and released their hormonal content is currently unknown. Here we designed a novel set of image analyses to map the probability of tracked organelles undergoing a specific type of movement (free, caged or directed). We then applied our analysis to time-lapse z-stack confocal imaging of secretory vesicles from bovine Chromaffin cells to map the global changes in vesicle motion and directionality occurring upon secretagogue stimulation. We report a defined region abutting the cortical actin network that actively transports secretory vesicles and is dissipated by actin and microtubule depolymerizing drugs. The directionality of this “conveyor belt” towards the cell surface is activated by stimulation. Actin and microtubule networks therefore cooperatively probe the microenvironment to transport secretory vesicles to the periphery, providing a mechanism whereby cells globally adjust their vesicle pools in response to secretagogue stimulation.