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81.
Chantana Aromdee J. Paul Fawcett Robin Ledger 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,677(2):313
A sensitive assay for pilocarpine in biological fluids has been developed involving HPLC of a fluorescent derivative of 4-bromomethyl-7-methoxycoumarin. Pilosine as internal standard was added before the derivatisation step. The fluorescent derivatives were well resolved and separated from excess reagent and endogeneous compounds on a cyanopropyl silica column. The detection limit of pilocarpine in biological fluids was 1.0 ng/ml and the assay was linear up to a concentration of 150 ng/ml. The assay was applied to a preliminary study of pilocarpine disposition in man after a single oral dose. This is the first report of pilocarpine excretion into saliva. 相似文献
82.
Timothy Wachs Robin L. Sheppard Jack Henion 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,685(2):548
A simple self-aligning liquid junction-electrospray interface for coupling a capillary electrophoresis (CE) system to an atmospheric pressure ionization (API) mass spectrometer (CE-MS) was developed. In contrast to previous liquid junction interfaces, the self-aligning liquid junction interface simplifies the precise alignment of the CE capillary and the sprayer needle and uses a positive make-up flow. Several capillary CE-MS applications were run using both the self-aligning liquid junction interface and the widely used sheath flow interface for comparison purposes. The electrospray stability of the self-aligning liquid junction interface is consistently better even when non-volatile electrolyte solutions are used. At first, some band broadening was obtained with the self-aligning liquid junction interface. Experiments with different CE buffer systems suggested that this band broadening was caused by the materials used in constructing the interface. By using a more inert material for the sprayer needle, the self-aligning liquid junction exhibits excellent electrophoretic resolution, comparable sensitivity, and higher signal-to-noise ratios when run under the same conditions as the sheath flow interface. 相似文献
83.
Tiecheng Qiao Robert Witkowski Robin Henderson G. McLendon 《Journal of biological inorganic chemistry》1996,1(5):432-438
The kinetics of methemoglobin reduction by cytochrome b
5 has been studied by stopped-flow and saturation transfer NMR. A forward rate constant k
f = 2.44×104 M–1 s–1 and a reverse rate constant k
b = 540 M–1s–1 have been observed at 10 mm, pH 6.20, 25 °C. The ratio k
f/k
b = k
eq = 43.6 is in good agreement with the equilibrium constant calculated from the electrochemical potential between cyt b
5 and methemoglobin. A bimolecular collisional mechanism is proposed for the electron transfer from cyt b
5 to methemoglobin based on the kinetic data analysis. The dependence of the rate constants on ionic strengths supports such
collisional mechanism. It is also found that the reaction rate strongly depends on the conformations of methemoglobin.
Received: 20 February 1996 / Accepted: 4 June 1996 相似文献
84.
85.
Eggplants (Solanum melongena L. cv. Bonica) were grown in a glasshouse during summer under natural light with one unbranched shoot or one shoot with 3
to 4 branches and with or without fruit in quartz sand buffered and not buffered with 0.5% CaCO3 (w : v), respectively. Nutrient solutions supplied contained nitrate or ammonium as the sole nitrogen source.
Compared with nutrient solutions containing nitrate (10 mM), solutions containing ammonium (10 mM) caused a decrease in net photosynthesis of eggplants during early stages of vegetative growth when grown in quartz sand
not buffered with CaCO3. The decrease was not observed before leaves showed interveinal chlorosis. In contrast, net photosynthesis after bloom at
first increased more rapidly in eggplants supplied with ammonium than with nitrate nitrogen. However, even in this case, net
photosynthesis decreased four weeks later when ammonium nutrition was continued. The decrease was accompanied by epinasty
and interveinal chlorosis on the lower leaves and later by severe wilting, leaf drop, stem lesions, and hampered growth of
stems, roots, and fruits. These symptoms appeared later on plants not bearing fruits than on plants bearing fruits. If nutrient
solutions containing increasing concentrations of ammonium (0.5–30 mM) were supplied after the time of first fruit ripening, shoot growth and set of later flowers and fruits were promoted. In
contrast, vegetative growth and reproduction was only slightly affected by increasing the concentration of nitrate in the
nutrient solutions.
In quartz sand buffered with CaCO3 ammonium nutrition caused deleterious effects only under low light conditions (shade) and on young plants during rapid fruit
growth. If eggplants were supplied with ammonium nitrogen before bloom, vegetative growth was promoted, and set of flowers
and fruit occurred earlier than on plants supplied with nitrate. Furthermore, the number of flowers and fruit yield increased.
These effects of ammonium nutrition were more pronounced when plants were grown with branched shoots than with unbranched
shoots.
The results indicate that vegetative and reproductive growth of eggplants may be manipulated without causing injury to the
plants by supplying ammonium nitrogen as long as the age of the plants, carbohydrate reserves of the roots, quantity of ammonium
nitrogen supplied, and pH of the growth medium are favourable. T W Rufty Section editor 相似文献
86.
Reaction of LaCl3·7H2O containing small amounts of La(NO3)3·7H2O as an impurity with 12-crown-4 or 18-crown-6 in 3:1 CH3CN:CH3OH resulted in the isolation of the mixed anion complexes [LaCl2(NO3)(12-crown-4)]2, [La(NO3)(OH2)4(12-crown-4)]Cl2·CH3CN and [LaCl2(NO3)(18-crown-6)]. The nine-coordinate dimer, [LaCl2(NO3)(12-crown-4)]2, has all of the anions in the inner coordination sphere and La3+ has a capped square antiprismatic geometry. It crystallizes in the orthorhombic space group Pbca with (at −150 °C) a = 12.938(6), B = 15.704(3), C = 13.962(2) Å, and Dcalc = 2.08 g cm−3 for Z = 4. The second complex isolated from the same reaction, [La(NO3)(OH2)4(12-crown-4)]Cl2·CH3CN, has the bidentate nitrate anion in the inner coordination sphere but the two chloride anions are in a hydrogen bonded outer sphere. This complex is ten-coordinate 4A,6B-expanded dodecahedral and crystallizes in the monoclinic space group P21 with (at 20 °C) A = 7.651(2), B = 11.704(7), C = 11.608(4) Å, β = 95.11(2)°, and Dcalc = 1.80 g cm−3 for Z = 2. The 18-crown-6 complex, [LaCl2(NO3)(18-crown-6)], has all inner sphere anions and has ten-coordinate 4A,6B-expanded dodecahedral La3+ centers. It crystallizes in the orthorhombic space group Pbca with (at 20 °C) a = 14.122(7), B = 13.563(5), C = 19.311(9) Å, and Dcalc = 1.89 g cm−3 for Z = 8. 相似文献
87.
Graziella Bellone Massimo Geuna Anna Carbone Stefania Silvestri Robin Foa Giorgio Emanuelli Lina Matera 《Journal of cellular physiology》1995,163(2):221-231
The pituitary hormone prolactin (Prl) is known to act as a local regulator of immune cell function, and Prl-binding receptors (Prl-R) have been described to share distinctive features with the members of the newly described cytokine/hemopoietin receptor superfamily. Here we show that the hormone can functionally interact with lineage-specific hemopoietic factors. When highly purified progenitor cells (CD34+ve) were seeded in semisolid methylcellulose cultures in the presence of interleukin (IL)-3, granulocyte-macrophage colony stimulating factor (GM-CSF), and erythropoietin (Epo), a selective enhancing effect of Prl on the formation of colony forming unit-granulocyte (CFU-G) and burst forming unit-erythroid (BFU-E) colonies was observed. The effect of the hormone was plotted as a bell shaped curve, with the optimal response at the supraphysiological concentration of 50 ng/ml. Limiting dilution analysis showed that Prl acted directly on hemopoietic progenitors. This was confirmed by the observation on the CD34+ve cells of Prl-binding sites reacting with the specific monoclonal antibodies (mAbs), U5 and PrR-7A. Immunoprecipitation of the metabolically labeled CD34+ve cells with the PrR-7A mAb revealed a structure of 43 kD under reducing conditions. Analysis of the early events associated with the Prl/Prl-R interaction showed an increased number of cells engaged in DNA and hemoglobin synthesis. Enhanced erythroid differentiation of CD34+ve cells in the presence of Prl was secondary to upmodulation of receptors for the lineage-specific factor Epo. Together these data demonstrate the existence of a functional interplay between Prl. and hemopoietic factors. © 1995 Wiley-Liss, Inc. 相似文献
88.
Intratypic osteosarcoma hybrids were constructed by fusing the human osteoblast-like osteosarcoma SaOS-2 with the rat osteoblast-like osteosarcoma UMR-106. Both of these osteosarcomas express liver/bone/kidney alkaline phosphatase (ALPL), but only the UMR-106 cell line expresses osteopontin (OPN), a gene expressed during later stages of osteoblast differentiation. Analysis of osteoblast gene expression in these hybrids demonstrated that ALPL continued to be expressed; however, OPN steady-state mRNA levels were dramatically reduced in four hybrids. Quantitative measurements indicated theft OPN steady-state mRNA levels were extinguished by a factor of 20- to 1000-fold. Since SaOS-2 chromosomes are preferentially lost from these hybrids, subclones of extinguished hybrids were isolated that reexpressed OPN mRNA at levels similar to the UMR-106 parental line. These data indicate that trans-acting negative regulatory factors, expressed from the SaOS-2 genome, are responsible for OPN extinction. This report provides the first demonstration of the negative regulation of OPN gene expression and also provides additional evidence that extinction plays a role in the regulation of osteoblast gene expression. 相似文献
89.
Alexander A. Kortt Robin E. Guthrie Mark G. Hinds Barbara E. Power Neva Ivancic J. Bruce Caldwell L. Clem Gruen Raymond S. Norton Peter J. Hudson 《Journal of Protein Chemistry》1995,14(3):167-178
The VH domain of anti-influenza neuraminidase antibody NC41, with and without a C-terminal hydrophilic marker peptide (FLAGTM), has been expressed in high yield (15–27 mg/L) inEscherichia coli. Both forms were secreted into the periplasm where they formed insoluble aggregates which were solubilized quantitatively with 2 M guanidine hydrochloride and purified to homogeneity by ion-exchange chromatography. The VH-FLAG was composed of three isoforms (pI values of 4.6, 4.9, and 5.3) and the VH molecule was composed of two isoforms with pI values of 5.1 and 6.7; the difference between the VH isoforms was shown to be due to cyclization of the N-terminal glutamine residue in the pI 5.1 isoform. At 20°C and concentrations of 5–10mg/ml the VH domain dimerized in solution and then partly precipitated, resulting in the broadening of resonances in its1H NMR spectrum. Reagents such as CHAPS,n-octylglucoside, and ethylene glycol, which presumably mask the exposed hydrophobic interface of the VH molecule, prevented dimerization of the VH and permitted good-quality NMR spectra on isotope-labeled protein to be obtained. 相似文献
90.
Janet Katarina Nordqvist Christopher Tilmann Robin Lovell-Badge Blanche Capel 《Current biology : CB》1997,7(12)
Background: The gene Sry acts as a developmental switch, initiating a pathway of gene activity that leads to the differentiation of testis rather than ovary from the indifferent gonad (genital ridge) in mammalian embryos. The early events following Sry expression include rapid changes in the topographical organization of cells in the XY gonad. To investigate the contribution of mesonephric cells to this process, gonads from wild-type mice (CD1), and mesonephroi from a transgenic strain ubiquitously expressing β-galactosidase (ROSA26), were grafted together in vitro. After culture, organs were fixed and stained for β-galactosidase activity to identify cells contributed from the mesonephros to the male or female gonad.Results: Migration of mesonephric cells occurred into XY but not XX gonads from 11.5–16.5 days post coitum (dpc). Somatic cells contributed from the mesonephros were distinguished by their histological location and by available cell-specific markers. Some of the migrating cells were endothelial; a second population occupied positions circumscribing areas of condensing Sertoli cells; and a third population lay in close apposition to endothelial cells.Conclusions: Migration from the mesonephros to the gonad is male specific at this stage of development and depends on an active signal that requires the presence of a Y chromosome in the gonad. The signals that trigger migration operate over considerable distances and behave as chemoattractants. We suggest that migration of cells into the bipotential gonad may have a critical role in initiating the divergence of development towards the testis pathway. 相似文献