7,744 research outputs found

    Evaluation of liposomes coated with a pH responsive polymer

    Get PDF
    Liposomes have been coated with the pH responsive polymer, Eudragit S100, and the formulation's potential for lower gastrointestinal (GI) targeting following oral administration assessed. Cationic liposomes were coated with the anionic polymer through simple mixing. The evolution of a polymer coat was studied using zeta potential measurements and laser diffraction size analysis. Further evidence of an association between polymer and liposome was obtained using light and cryo scanning electron microscopy. Drug release studies were carried out at pH 1.4, pH 6.3 and pH 7.8, representing the pH conditions of the stomach, small intestine and ileocaecal junction, respectively.\ud \ud The polymer significantly reduced liposomal drug release at pH 1.4 and pH 6.3 but drug release was equivalent to the uncoated control at pH 7.8, indicating that the formulation displayed appropriate pH responsive release characteristics. While the coating layer was not able to withstand the additional challenge of bile salts this reinforces the importance of evaluating these types of formulations in more complex media.\ud \u

    Utilization of C1 Compounds by Frankia and Effects of CO2 Enrichment of the Rooting Medium on Growth and N2-Fixation in Alnus glutinosa L. Gaertn

    Get PDF
    In the first part of this project, the effects of CO2 levels, that may be encountered in the soil atmosphere, on N2-fixation and growth of the alder plant Alnus glutinosa maintained in mineral N-free culture in perlite or water culture, pH 6.3, were examined

    Limnological study of Zealand Pond, White Mountains, New Hampshire

    Get PDF
    Zealand Pond, New Hampshire, was chosen as the site of a remote lake study. Data were collected between July 18 and August 29,1997. Zealand Pond had a relatively high pH (6.3-6.9) and alkalinity (2.3- 3.1 mg CaCO3 /liter), considering its small size and elevation (752 m). The lake was not thermally stratified, presumably due to its shallow depth and exposure to wind. Zealand Pond had a diverse zooplankton community, with two calanoid copepod species (Hesperodiaptomus wilsonae and Leptodiaptomus ashlandi), two cyclopoid copepods (Mesocyclops edax and Ectocyclops phaleratus), six cladoceran species (Daphnia ambigua, Daphnia pulex, Ceriodaphnia reticulata, Bosmina longirostris, Alona costata, and Polyphemus pediculus), and two rotifer species (Keratella taurocephala and Conochilus sp.). Densities of zooplankton ranged from 57.6 (Hesperodiaptomus) to 0.04 (Alona) animals per liter. Zooplankton species were documented with photographs and key identifying features. Low densities of fish were also present in the lake. Features of Zealand Pond are compared to other high altitude lakes

    PHOTOPHYSICAL AND PHYSICOCHEMICAL PROPERTIES OF Cu(II)CHLORIN e4 AND Cu(II)CHLORIN e6 AS A LEAD COMPOUND OF PHOTOSENSITIZER FOR PDT

    Get PDF
    Porphyrin derivatives are potential compounds for diagnostic agent and photosensitizer in photodynamic therapy. However, they have a weakness in molar absorptivity, especially in visible region of Q band which used to excite them. Due to incapabilities of porphyrin, other tetrapyrole derivatives, such as chlorophyllin can be alternative for a lead compound of photosensitizer. In the present research, two chlorin derivatives were isolated from commercial chlorophyllin product. Their photophysical and physicochemical properties, i.e. molar absorptivity, quantum yield of fluorescence and quantum yield of singlet oxygen were determined. Chlorophyllin carboxylic acid form, Cu(II)-chlorin e4 and Cu(II)-chlorin e6,were successfully isolated with recovery of 11.33% and 16.46%, respectively.         The absorption spectrum of Cu(II)-chlorin e4 showed an intense Soret band at 406 nm and two weaker Q bands at 628nm, 658nm. Fluorescence efficiency was 0.09 while efficiency for singlet oxygen at  pH 6.3 and 7.4 were 0.0052±0.0017 and 0.0066±0.0012. Cu(II)-chlorin e6 displayed soret band at 407nm and Q bands at 627nm, 663nm. Singlet oxygen at pH 6.3 was 0.0029±0.0007, while at pH 7.4 was 0.0034±0.0001. However,  Cu(II)-chlorin e6 did not show fluorescence.Key words: Chlorophyllin, Cu(II)-chlorin e4, Cu(II)-chlorin e6, singlet oxygen fluorescenc

    Effects of seawater pH on survival, growth, energy budget and oxidative stress parameters of juvenile turbot Scophthalmus maximus

    Get PDF
    This study aimed to elucidate the influence of environment pH on survival, growth, energy allocation and oxidative damage of juvenile Scophthalmus maximus (19.89±0.25 g). Six pH treatments (6.3±0.2, 6.8±0.2, 7.3±0.2, 7.8±0.2, 8.3±0.2, 8.8±0.2) lasting for eight weeks were included. Measurements of survival (SR), feed conversion ratio (FCR), specific growth rate (SGR), weight gain rate (WGR), energy allocation, liver superoxide dismutase activity (SOD), catalase activity (CAT), and malondialdehyde concentration (MDA) were done. Results show that SR did not vary from pH 6.3 to 7.8, but reduced then significantly (p0.05). CAT kept stable between pH 6.3 and 7.3, then sharply increased (p0.05). Subsequent decrease in MDA was found from pH 6.3 to 8.3 then the concentration smoothly increased. Overall, our results indicate that a pH in the range of 6.8 to 7.8 is recommended in the growth environment in cultivation of juvenile turbot

    Research Notes : United States : Evaluation of soybean germplasm for stress tolerance and biological efficiency towards : Micronutrients

    Get PDF
    A greenhouse study was conducted to evaluate the sensitivity and tolerance of various soybean genotypes to high levels of soil manganese, and to strongly acid soil conditions. Forty-four soybean genotypes in Maturity Groups V, VI, VII, and VIII were evaluated, the soil used for the study was very high in manganese (90 ppm) and strongly acidic (pH 4.8), and was col-lected from Buncombe County, North Carolina. The soil pH levels were pH 4.8 (original soil pH), and pH 6.3

    Solvent Extraction And Spectrophotomteric Determination Of Cu(Ii) With Dicyclohexyl - 18- Crown-6

    Get PDF
    Liquid-Liquid Extraction of Cu(II) ion in aqueous solution by dicyclohexyl-18-crown-6 as extractant in dichloroethane was studied .The extraction efficiency was investigated by a spectrophometric method. The reagent form a coloured complex which has been a quantitatively extracted at pH 6.3. The method obeys Beer`s law over range from (2.5-22.5) ppm with the correlation coefficient of 0.9989. The molar absorptivity the stoichiometry of extracted complex is found to be 1:2. the proposed method is very sensitive and selective

    Annual Production of Creek Chub and Southern Redbelly Dace in a Small Woodland Stream

    Get PDF
    Author Institution: Illinois Natural History Survey Laboratory and Department of Biology, Lakehead UniversityThe annual production of the creek chub, Semotilus atromaculatus, and southern redbelly dace, Phoxinus erytbrogaster, was measured in a small headwater stream in southeastern Ohio. Creek chub annual production was 13.60 g • m~2 per yr, and P/B was 1.16. Dace annual production was 2.77 g • m~2 and P/B was 1.82. Even though the stream was acidic (pH 6.3) and infertile, fish production compared favorably with that of small alkaline streams. Considerable production within allochthonous food chains probably overrides the effects of low in-stream fertility

    Coexpression of rat P2X2 and P2X6 subunits in Xenopus oocytes.

    Get PDF
    Transcripts for P2X(2) and P2X(6) subunits are present in rat CNS and frequently colocalize in the same brainstem nuclei. When rat P2X(2) (rP2X(2)) and rat P2X(6) (rP2X(6)) receptors were expressed individually in Xenopus oocytes and studied under voltage-clamp conditions, only homomeric rP2X(2) receptors were fully functional and gave rise to large inward currents (2-3 microA) to extracellular ATP. Coexpression of rP2X(2) and rP2X(6) subunits in Xenopus oocytes resulted in a heteromeric rP2X(2/6) receptor, which showed a significantly different phenotype from the wild-type rP2X(2) receptor. Differences included reduction in agonist potencies and, in some cases (e.g., Ap(4)A), significant loss of agonist activity. ATP-evoked inward currents were biphasic at the heteromeric rP2X(2/6) receptor, particularly when Zn(2+) ions were present or extracellular pH was lowered. The pH range was narrower for H(+) enhancement of ATP responses at the heteromeric rP2X(2/6) receptor. Also, H(+) ions inhibited ATP responses at low pH levels (<pH 6.3). The pH-dependent blocking activity of suramin was changed at this heteromeric receptor, although the potentiating effect of Zn(2+) on ATP responses was unchanged. Thus, the rP2X(2/6) receptor is a functionally modified P2X(2)-like receptor with a distinct pattern of pH modulation of ATP activation and suramin blockade. Although homomeric P2X(6) receptors function poorly, the P2X(6) subunit can contribute to functional heteromeric P2X channels and may influence the phenotype of native P2X receptors in those cells in which it is expressed

    Properties and stabilization of an extracellular α-glucosidase from the extremely thermophilic archaebacteria Thermococcus strain AN 1: enzyme activity at 130°C

    Get PDF
    An extracellular α-glucosidase from the thermophilic archaebacterium Thermococcus strain AN1 was purified 875-fold in five steps (Hiload Q-Sepharose, phenyl Sepharose, HPHT-hydroxyapatite, gel filtration and Mono Q chromatography) with a yield of 4%. It is a monomer with a molecular mass of about 60 kDa and a pI around 5. At 98°C, the purified enzyme in buffer has a half-life around 35 min, which is increased to around 215 min in presence of l% (w/v) dithiothreitol and 1% (w/v) BSA. Dithiothreitol (1%, w/v) and BSA (0.4%, w/v) also substantially increase the enzyme activity. The Km at 75°C is 0.41 mM with pNP-α- -glucopyranoside as substrate. The substrate preference of the enzyme is: pNP-α-D-glucoside > nigerose > panose > palatinose > isomaltose > maltose and turanose. No activity was found against starch, pullulan, amylose, maltotriose, maltotetraose, isomaltotriose, cellobiose and β-gentiobiose. A variety of techniques including immobilization (e.g., on epoxy and glass beads), chemical modification (cross- and cocross-linking) and the use of additives (including polyhydroxylic molecules, BSA, salts, etc.) were applied to enhance stability at temperatures above 100°C. The half-life could be increased from about 4 min at 110°C to 30–60 min at 130°C in presence of 90% (w/v) sorbitol, 1% (w/v) dithiothreitol and l% (w/v) BSA, and by cocross-linking with BSA in the presence of 90% (w/v) sorbitol. The stabilized enzyme showed good activity at 130°C
    corecore