Quantitation of daunorubicin and its metabolites by high-performance liquid chromatography with electrochemical detection

A selective and sensitive high-performance liquid chromatographic method was developed for the separation and quantitation of daunorubicin and its metabolites in serum, plasma, and other biological fluids. Daunorubicin and metabolites in human plasma were injected directly into the high-performance liquid chromatography system via a loop-column to pre-extract the drugs from the plasma, and quantitated against a multilevel calibration curve with adriamycin as the internal standard. The column effluent was monitored with an electrochemical detector at an applied oxidative potential of 0.65 V and by fluorescence. Daunorubicin and four metabolites were separted and characterized by this method. In a blinded evaluation of accuracy and precision, the mean coefficients of variation were 3.8, 3.6 and 9.8% at concentrations of 150, 75 and 15 ng/ml, respectively, and blank samples gave negligible readings. The amperometric sensitivity was greater than achieved by fluorescence detection, and offers an alternative method for quantitation of these compounds. The new method has a limit of detection of less than 2 ng on column, allowing quantitation of < 10 ng/ml in plasma samples without organic extraction prior to chromatographic analysis.     

Effects of high temperature on the germination of maize (Zea mays L.)

Poor emergence of maize seedlings, due to high soil temperatures, is a major limitation of crop potential in the lowland tropics. Ability to germinate at high temperature (>c. 37° C) is related to the temperature sensitivity of the embryo, and there is considerable genotypic variation for this character.Respiration and mitochondrial phosphorylation proceed normally in seeds imbibing at 41° C, and ATP levels are adequate for germination. However, the specific activities of several important enzymes are lower, and the rate of protein synthesis is severely reduced compared with seeds imbibing at 28° C. The depression of the rate of protein synthesis in the embryos of several tropical hybrids imbibing at high temperature correlated with their known temperature sensitivity. It is concluded that protein synthesis is an especially temperature sensitive process in germinating maize embryos, and that this is the principal reason for the sensitivity of germinating maize seeds to high temperature.Abbreviations ADP adenosine-5-diphosphate - ATP adenosine-5-triphosphate - BSA bovine serum albumin - EDTA ethylenediaminetetra-acetic acid - HEPES N-2-hydroxyethylpiperazinc-N-2-ethanesulphonic acid - NADH nicotinamide-adenine dinucleotide, reduced form - PPO 2, 5-diphenyloxazole - PVP polyvinylpyrrolidone - SEM standard error of the mean - tris tris (hydroxymethyl)-methylamine     

P nuclear magnetic resonance spectroscopy of lipopolysaccharides from pseudomonas aeruginosa

Intact lipopolysaccharide antigens isolated from seven different immunotypes of Pseudomonas aeruginosa have been examined by ³¹P-NMR spectroscopy. These macromolecular complexes contain phosphorus covalently attached to the carbohydrate residues present in the lipid A moiety and the ‘core’ oligosaccharide region. The spectral signals for various ortho- and pyro-phosphoric esters were observed. All phosphate groups appeared to be mono-esterified. Certain shifts characteristic for phosphate diester groups, observed in lipopolysaccharide complexes from other Gram-negative bacteria, were absent. Furthermore, no evidence was found to indicate that phosphate groups are involved in the covalent linkage of individual lipopolysaccharide complexes to form dimers or trimers.     

31P nuclear magnetic resonance spectroscopy of lipopolysaccharides from pseudomonas aeruginosa

Intact lipopolysaccharide antigens isolated from seven different immunotypes of Pseudomonas aeruginosa have been examined by ³¹P-NMR spectroscopy. These macromolecular complexes contain phosphorus covalently attached to the carbohydrate residues present in the lipid A moiety and the ‘core’ oligosaccharide region. The spectral signals for various ortho- and pyro-phosphoric esters were observed. All phosphate groups appeared to be mono-esterified. Certain shifts characteristic for phosphate diester groups, observed in lipopolysaccharide complexes from other Gram-negative bacteria, were absent. Furthermore, no evidence was found to indicate that phosphate groups are involved in the covalent linkage of individual lipopolysaccharide complexes to form dimers or trimers.     

The pattern of density dependent growth inhibition in murine fibroblasts

Observations on the pattern of nuclear incorporation of ³H-TdR in long term (8-day) and short term (3-day) 3T3 cultures with local cell densities between 0.2 × 10⁴ and 6.2 × 10⁴ cells/cm² are reported. Contrary to a number of previous studies our observations indicate that density dependent inhibition is exhibited in relatively sparse cultures, commencing at 0.5 × 10⁴ cells/cm². Various possible mechanisms which could have caused the observed pattern of density-dependent regression in labelling index are discussed.     

Hepatic estrogen receptor in the turtle, Chrysemys picta: partial characterization, seasonal changes and pituitary dependence

A hepatic estrogen receptor is described from female turtles, Chrysemys picta. The receptor adheres to DNA after incubation with [3H]estradiol and can be eluted with a linear salt gradient as a single component with an elution maximum of 0.21 M. It is steroid-specific, binding estrogens, but not androgens or progestins. Specific binding saturates between 3 and 7 nM [3H]estradiol-17 beta and Scatchard analysis gave a Kd of 2 X 10(-9) M and a maximal binding capacity of 3.02 fmol/mg protein. Hypophysectomy reduces hepatic estradiol receptor from 70 fmol/g tissue in control animals to non-detectable levels. Growth hormone replacement partially restored the receptor to 36% of control. Significant changes in receptor occur during the ovarian cycle.     

Distinct effects of IL-18 on the engraftment and function of human effector CD8 T cells and regulatory T cells

IL-18 has pleotropic effects on the activation of T cells during antigen presentation. We investigated the effects of human IL-18 on the engraftment and function of human T cell subsets in xenograft mouse models. IL-18 enhanced the engraftment of human CD8(+) effector T cells and promoted the development of xenogeneic graft versus host disease (GVHD). In marked contrast, IL-18 had reciprocal effects on the engraftment of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) in the xenografted mice. Adoptive transfer experiments indicated that IL-18 prevented the suppressive effects of Tregs on the development of xenogeneic GVHD. The IL-18 results were robust as they were observed in two different mouse strains. In addition, the effects of IL-18 were systemic as IL-18 promoted engraftment and persistence of human effector T cells and decreased Tregs in peripheral blood, peritoneal cavity, spleen and liver. In vitro experiments indicated that the expression of the IL-18Ralpha was induced on both CD4 and CD8 effector T cells and Tregs, and that the duration of expression was less sustained on Tregs. These preclinical data suggest that human IL-18 may have use as an adjuvant for immune reconstitution after cytotoxic therapies, and to augment adoptive immunotherapy, donor leukocyte infusions, and vaccine strategies.