Cation effects on sol-gel and gel-sol phase transitions of kappa-carrageenan-water system

Sol–gel and gel–sol phase transitions of κ-carrageenan in pure water and in KCl solution were studied using photon transmission technique. Photon transmission intensity, I_tr, was monitored against temperature to determine the sol–gel and gel–sol temperatures (T_sg and T_gs) and activation energies (ΔH_sg and ΔH_gs). It was observed that T_gs was notably higher than T_sg due to the hysteresis on the phase transition loops. T_gs and ΔH_gs values were also higher for gels containing KCl than for those without KCl. The increase in carrageenan content caused an increase in both critical temperatures and activation energies for the gels prepared in pure water and in KCl solution. Increases in the KCl/carrageenan ratio, raised both T_gs and T_sg. Similarly ΔH_sg was elevated by the increase in cation content of the gel. These results were interpreted as the formation of stronger gels in the presence of KCl in water.     

Photon transmission study on conformational ordering of iota-carrageenan in CaCl2 solution

Coil-to-double helix (c-h) and double helix-to-dimer (h-d) phase transitions of iota-carrageenan in CaCl(2) solution upon cooling were studied using photon transmission technique. Photon transmission intensity, I(tr) was monitored against temperature to determine the (c-h) and (h-d) transition temperatures (T(ch) and T(hd)) and activation energies (DeltaE(ch) and DeltaE(hd)). An extra dimer-to-dimer (d-d) transition was also observed during cooling at low temperature region. However, upon heating dimers disappear to double helices by making dimer-to-double helix (d-h) transition. Further heating resulted double helix-to-coil (h-c) transition at high temperature region. T(dh) and T(ch) temperatures and DeltaE(dh) and DeltaE(hc) activation energies were also determined. It was observed that T(hc) and T(ch) temperatures and DeltaE(dh) and DeltaE(hd) activation energies do not effected by carrageenan content. However, T(hd), T(dh) and T(dd) temperatures and DeltaE(ch) and DeltaE(hc) activation energies were found to be strongly correlated to the carrageenan content in the system.     

Microbial transformation of zearalenone to a zearalenone sulfate.

The conversion of zearalenone by various microorganisms was studied. A new polar metabolite was formed in addition to alpha- and beta-zearalenols. The structure of the new metabolite was determined as zearalenone-4-O-sulfate conjugate on the basis of enzymatic and acid hydrolysis, followed by mass spectrometry, nuclear magnetic resonance, and infrared spectroscopic analysis. The results obtained demonstrate that Rhizopus arrhizus catalyzes sulfation of zearalenone at the C-4 hydroxyl group.     

Mechanism and function of Drosophila capa GPCR: a desiccation stress-responsive receptor with functional homology to human neuromedinU receptor

The capa peptide receptor, capaR (CG14575), is a G-protein coupled receptor (GPCR) for the D. melanogaster capa neuropeptides, Drm-capa-1 and -2 (capa-1 and -2). To date, the capa peptide family constitutes the only known nitridergic peptides in insects, so the mechanisms and physiological function of ligand-receptor signalling of this peptide family are of interest. Capa peptide induces calcium signaling via capaR with EC₅₀ values for capa-1 = 3.06 nM and capa-2 = 4.32 nM. capaR undergoes rapid desensitization, with internalization via a b-arrestin-2 mediated mechanism but is rapidly re-sensitized in the absence of capa-1. Drosophila capa peptides have a C-terminal -FPRXamide motif and insect-PRXamide peptides are evolutionarily related to vertebrate peptide neuromedinU (NMU). Potential agonist effects of human NMU-25 and the insect -PRLamides [Drosophila pyrokinins Drm-PK-1 (capa-3), Drm-PK-2 and hugin-gamma [hugg]] against capaR were investigated. NMU-25, but not hugg nor Drm-PK-2, increases intracellular calcium ([Ca²⁺]i) levels via capaR. In vivo, NMU-25 increases [Ca²⁺]i and fluid transport by the Drosophila Malpighian (renal) tubule. Ectopic expression of human NMU receptor 2 in tubules of transgenic flies results in increased [Ca²⁺]i and fluid transport. Finally, anti-porcine NMU-8 staining of larval CNS shows that the most highly immunoreactive cells are capa-producing neurons. These structural and functional data suggest that vertebrate NMU is a putative functional homolog of Drm-capa-1 and -2. capaR is almost exclusively expressed in tubule principal cells; cell-specific targeted capaR RNAi significantly reduces capa-1 stimulated [Ca²⁺]i and fluid transport. Adult capaR RNAi transgenic flies also display resistance to desiccation. Thus, capaR acts in the key fluid-transporting tissue to regulate responses to desiccation stress in the fly.     

Effectiveness of honey bees in delivering the biocontrol agent Bacillus subtilis to blueberry flowers to suppress mummy berry disease

Honey bees are important pollinators of commercial blueberries in the southeastern United States, and blueberry producers often use supplemental bees to achieve adequate fruit set. However, honey bees also vector the plant pathogenic fungus Monilinia vaccinii-corymbosi which infects open blueberry flowers through the gynoecial pathway causing mummy berry disease. Here, we report the results of a 3-year field study to test the hypothesis that using bee hives equipped with dispensers containing the biocontrol product Serenade, a commercial formulation of the bacterium Bacillus subtilis which has shown activity against flower infection by M. vaccinii-corymbosi in laboratory experiments, can reduce mummy berry disease incidence when honey bees are used as pollinators in blueberries. Individual honey bees carried 5.1–6.4 × 10⁵ colony-forming units (CFU) of B. subtilis when exiting hive-mounted dispensers with Serenade. On caged rabbiteye blueberry bushes in the field, population densities of B. subtilis vectored by honey bees reached a carrying capacity of <10³ CFU per flower stigma within 2 days of exposure, and there was a highly significant non-linear relationship between B. subtilis populations per stigma and bee activity, expressed as number of legitimate flower visits per time interval per cage (R = 0.6928, P < 0.0001, n = 32). Honey bee density (1600 or 6400 individuals per 5.8-m³ cage) and Serenade treatment (presence or absence of the product in hive-mounted dispensers) significantly (P < 0.05) affected the incidence of fruit mummification on caged bushes, whereby increasing bee density increased disease incidence and application of Serenade reduced disease levels. Taken together, results of this study suggest that use of a hive-dispersed biocontrol product such as Serenade as a supplement during pollination can reduce the risk of mummy berry disease. This may be a prudent practice that optimizes the benefits to pollination of high bee densities while reducing the associated disease-vectoring risk.     

Biophysical Characterization of <Emphasis Type="Italic">β</Emphasis>-Thalassemic Red Blood Cells

Thalassemia is the world’s most common hereditary disease; therefore, more interest has been devoted for the development of the screening procedure of this disease. In β-thalassemia major, the subject of the current study, impaired biosynthesis of beta-globin leads to accumulation of unpaired alpha-globin chain. The objective of the present study, was to examine many of the biophysical properties of β-thalassemia major red blood cells (RBCs) and to study the possibility of use of any of them as a preliminary screening tool for β-thalassemia. The percentage of normal hemolysis, osmotic fragility test, turbidity test, rheological properties, and dielectric properties, were studied in 20 regularly blood transfused thalassemia major patients who were under chelation therapy and their status were compared with those of 10 healthy subjects. There was an increase in the percentage of hemolysis for β-thalassemia by 114.6% compared to the normal RBCs. The fragility curve for β-thalassemia RBCs showed a shift toward lower NaCl concentration compared to the normal curve. The average osmotic fragility (H ₅₀: the NaCl concentration producing 50% homolysis) for β-thalassemia was found to be 3.21 ± 0.67 g/l, whereas for normal RBCs it was 5.5 ± 0.31 g/l. The turbidity curve of the β-thalassemic RBCs showed a shift toward higher detergent concentration of the normal curve, with higher value for the average membrane solubilization (S ₅₀). The viscosity value of whole blood β-thalassemia was found to be 3.916 ± 0.56 cp whereas for normal blood was 2.516 ± 0.36 cp. The relative permittivity, dielectric loss, and AC conductivity of RBCs decreased significantly compared to normal samples. This could be attributed to the loss of the insulating properties of the membrane and loss of its surface charge of thalassemic RBCs. As can be noticed, several factors showed clear difference between thalassemic and normal blood samples. Some of these parameters could be measured immediately after sample withdrawal and require short time to perform the measurements. This offers the advantages of being effective, low cost, and fast techniques, therefore, we suggest that these techniques could be applied for β-thalassemia major screening purposes.