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Biomedical subjects

E C Nice

Publications and source records attributed to E C Nice.

81 records · Page 5Linked to original sources
PubMed1981

Progesterone synthesis, secretion and metabolism by human teratoma-derived cell-lines.

The synthesis, secretion and metabolism of progesterone have been examined in six human teratoma-derived cell lines with the objective of determining if they exhibit trophoblast-related or other specific steroidogenic functions. Progesterone was synthesised in nanogram amounts (per 10(6) cells/day) by the cell line SuSa, as measured by radioimmunoassay, and in lesser amounts by line LICR-LON HX-39. Lines Tera 1, Tera 2, T3B1 and PA-1 did not secrete detectable progesterone. All teratomas, however, metabolized added progesterone in microgram amounts (per 10(6) cells/day). In all cases the major metabolite was a polar compound, identified by reversed phase HPLC, TLC and GC-MS as 3 beta, 6 alpha-dihydroxy-5 alpha-pregnan-20-one. This pattern of metabolism was not confined to the teratomas as equivalent amounts of this polar metabolite were formed by cultures of adult differentiated human epithelial and fibroblast cells. When progesterone and its metabolites, separated by HPLC, were included in the estimation, the delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity of SuSa was equivalent to 47ng pregnenolone (3 beta-hydroxy-5-pregnen-20-one) metabolised/mg protein/day, that of HX-39 to 9ng/ml protein/day and those of other teratomas to less than 3.5ng/mg protein/day.

Cell Line↗
PubMed1980

Reversed- and normal-phase high-performance liquid chromatography of 18-hydroxylated steroids and their derivatives. Comparison of selectivity, efficiency and recovery from biological samples.

The chromatographic behaviour of adrenal 18-hydroxysteroids, and a series of derivatives thereof, has been studied in reversed-phase and normal-phase high-performance liquid chromatography (HPLC). Both 18-hydroxycorticosterone and 18-hydroxy-11-deoxycorticosterone exhibited a marked loss of chromatographic efficiency when separated on incompletely-covered C18 reversed-phase supports (as determined by methyl red adsorption) showed no such effect, nor was it seen when aprotic solvents, such as dioxane, were used. This phenomenon is unique among the wide range of adrenal and testicular steroids that we have studied and affords a useful test, applicable under aqueous conditions, of coverage by the alkylsilane reversed phase, a factor of considerable importance in the successful resolution of complex mixtures of adrenal steroids by reversed-phase HPLC. The retention times of the 20-methoxy, 20-ethoxy, 21-acetoxy, etiolactone, 11 beta, 18-ether and dimeric derivatives of the naturally-occurring 18-hydroxysteroids have been determined in relation to major adrenal steroids. Procedures for extraction and reversed-phase HPLC of 18-hydroxysteroids from tissues without the formation of these less polar forms, which can complicate their separation by other chromatographic techniques, are illustrated with respect to a human malignant adrenocortical tumour which caused hypermineralocorticism.

Chemical Phenomena↗
PubMed1979

Use of hydrophobic interaction methods in the isolation of proteins from endocrine and paraendocrine tissues and cells by high-performance liquid chromatography.

We have recently described the separation of a large number of polypeptide hormones, related peptides and some protein standards by hydrophobic interaction high-performance liquid chromatography (HPLC). This paper reports the practical application of these methods to the reproducible isolation and separation of components of a mixture of immunoreactive calcitonin-like proteins (less than 25 kD) synthesised and secreted by human tumour cells in vitro. Using hydrophobic interaction HPLC on ODS-silica for both preliminary bulk fractionation and subsequent analytical separation greater than 80% recoveries of small (ng) quantities of immunoreactive proteins were obtained from samples containing less than 100 mg total protein, and characteristic profiles of synthesised and secreted materials were established. Using a partially purified hypothalamic extract, containing a number of small proteins (12--25 kD), we have also examined the effects of varying chromatographic conditions in an attempt to modify the separations obtained with ODS-silica using an acid-saline-acetonitrile gradient elution system at ambient temperature, and achieve further resolution of its components. No useful selective effects were observed when temperature, organic modifier, gradient profile or hydrophobic stationary phase were altered. These techniques may not therefore be inherently capable of completely resolving all components of natural protein mixtures. They do, however, offer an adjunct to and in certain cases a substitute for conventional methods of protein separation.

Animals↗
PubMed1979

Hydrophobic high-performance liquid chromatography of hormonal polypeptides and proteins on alkylsilane-bonded silica.

Thirty-two hormonal polypeptides and nine proteins (8-65 kD) have been used to evaluate the potential of high-performance liquid chromatography on alkylsilane-bonded silica for separating and recovering biologically active compounds of this type. The basic method used was gradient elution with acetonitrile in an acid phosphate buffer. Variation of key chromatographic parameters demonstrated that low pH (less than 4.0) and high buffer molarity (greater than 0.1 M) are mandatory for reproducible high efficiency polypeptide chromatography. Simple NaCl-HCl mixtures of appropriate acidity and molarity could be substituted for the acid phosphate buffer, with the advantage of minimising non-physiological ion contributions to eluted materials. Minor selective effects were noted with different organic modifiers, but variation of other parameters, including choice of specific alkylsilane packings, did not materially influence separations. Under optimal conditions all of the polypeptides tested could be efficiently chromatographed, and many simultaneously resolved, as could most of the proteins tested. Three of the more hydrophobic proteins could not, however, be eluted from the alkylsilane packings. Retention orders of smaller compounds (less than 15 residues) generally correlated with the sum of the Rekker fragmental constants of their strongly hydrophobic residues. Larger polypeptides showed numerous anomalies when ranked by this means, however, limiting its predictive value. The separation of at least eighteen discrete components from a partially-purified posterior pituitary extract has demonstrated the capability of alkylsilane-type reversed-phase packings for the hydrophobic high-performance liquid chromatography of complex biological mixtures.

Animals↗
PubMed1976

High-pressure liquid chromatography of steroids secreted by human adrenal and testis cells in monolayer culture.

Reversed-phase high-pressure liquid chromatography with gradient elution on Zorbax-ODS columns has been used to separate, identify, and measure, spectrophotometrically, the steroids secreted by both human adrenal and testis cells in primary monolayer culture. Three related systems using exponential concave gradients have been developed with the specific objective of resolving the steroids produced by these two tissues. A methanol-water gradient has been used to separate most adrenal steroids, an acetonitrile-water gradient to separate testis steroids, and a dioxane-water gradient to separate polar steroids, including aldosterone. These three systems together permit the resolution of at least 43 naturally occurring steroids, plus four synthetic steroids with adrenocortical activity, with overall total elution times of 1 h or less for each system. Retention data for these steroids are given and the separation of steroids in the biological samples illustrated.

Adrenal Glands↗
PubMedDate not supplied

Micropreparative ion exchange high performance liquid chromatography: applications to microsequence analysis.

Data on the characterization of anion and cation micropreparative (50 x 1.6 mm i.d.) HPLC columns is presented. It is shown how subnanomole quantities of protein can be efficiently recovered from such columns, rendering them compatible for use in multidimensional chromatographic strategies for the purification of trace biological samples. By selection of appropriate solvent systems (e.g., buffer-free sodium chloride solutions), the small eluant peak volumes can be loaded directly onto the gas phase sequencer, and N-terminal sequence data obtained. The potential of the technique is illustrated for the purification of a GTPase activating protein (GAP-3).

Amino Acid Sequence↗
PubMedDate not supplied

Analysis of the interaction between a synthetic peptide of influenza virus hemagglutinin and monoclonal antibodies using an optical biosensor.

The interaction between two monoclonal antibodies and their corresponding Fab' fragments with a synthetic peptide, corresponding to the C-terminal 23 residues of the HA1 chain of influenza virus hemagglutinin against which they were generated, has been examined using an optical biosensor employing the detection principal of surface plasmon resonance (Pharmacia BIAcore). The data obtained has been analysed in detail by linear transformation of the primary data and nonlinear regression analysis, as well as by analysis of equilibrium binding data. The 2/1 antibodies and their Fab' fragments displayed higher affinity than the corresponding 1/1 proteins. The IgGs were found to have equilibrium association constants (KA) 10-20-fold higher than the corresponding Fab' fragments. This appears largely to be due to differences in the dissociation rate constant (kd) and probably reflects increased avidity due to bivalent binding.

Amino Acid Sequence↗