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At least 991 records · Page 55Linked to original sources
PubMed1977

Isolation of toxic metabolites of Phomopsis leptostromiformis responsible for lupinosis.

Two metabolites of P. leptostromiformis (phomopsins A and B) have been isolated as a crystalline mixture from a culture of the fungus on lupin seed. The mixture has been shown to be capable of inducing lupinosis in sheep and in young rats. Key steps in the isolation were the transfer of the phomopsins from crude aqueous solution to tetrahydrofuran and chromatography on macroreticular polystyrene resin. The bioassays used in monitoring fractions were based on inhibition of cell cultures and the mitosis-arresting effect of the metabolites on liver cells in vivo.

Animals↗
PubMed1974

Quantitative analysis of mass and energy balance in non-ideal models of the renal counterflow system.

A modified Newton-Raphson method for solving finite difference equations for the renal counterflow system is described. The method has proved generally stable and efficient, and has given significant computational results for a variety of models: calculations on single solute models of the coupled vasa recta nephron counterflow system have shown that for large water and solute permeabilities of the exchanging membranes, behavior of the non-ideal system approaches that of the previously described ideal central core model. Concentration by salt and urea mixing in two solute models has been analyzed and previous conclusions from central core models have been found to remain valid in non-ideal systems. The numerical solutions have set some order of magnitude bounds on permeability requirements for concentration in different types of non-ideal systems. Finally, from the detailed concentration profiles it has been possible to relate the rate of free energy creation and dissipation from transmembrane transport of solutes and water to the net rate of free energy efflux from the counterflow system, and so to compute in a given model the fraction of power used for solute concentration.

Biological Transport, Active↗
PubMed1979

Isolation and analysis of chemosensory behavior mutants in Drosophila melanogaster.

A behavioral countercurrent paradigm has been developed for assaying the chemotactic responses of wild-type and mutant Drosophila melanogaster adults. Oregon R males avoid both quinine sulfate and NaCl, whereas Oregon R females reject the quinine salt but are attracted to NaCl when tested in this paradigm. Wild-type behavior is sufficiently reproducible to allow identification of mutants affecting chemotaxis, and 12 such mutants, in six complementation groups, have now been isolated. Three of the mutants respond abnormally to NaCl, two in one complementation group with atactic behavior (no chemotaxis) and the other, in a separate group, with a mistactic response (attraction to the stimulus). Four mutants in another group respond mistactically to quinine sulfate. Of the remaining mutants, two in one group behave atactically and three, in two groups, respond mistactically to either chemical stimulus. Several of the mutants also show abnormal behavior in a proboscis extension assay when tested individually with sucrose solutions.

Animals↗
PubMed1979

Double strand-breaks and DNA-to-protein cross-links induced by fast neutrons in bacteriophage DNA.

Coliphage T7 was suspended in tryptone broth and exposed to a mixture of fast neutrons and gamma radiation. Plaque survival, double strand-breaks and DNA-to-protein cross-linkage were examined and the results compared with those found in phage exposed to gamma radiation alone. Neutral sucrose density sedimentation patterns indicate that neutron-induced double strand-breaks sometimes occur in clusters of more than 100 in the same phage and that the effeciency with which double strand-breaks form is about 50 times that of gamma-induced double strand-breaks. Neutron-induced protein-to-DNA cross-links probably also occur in clusters with enhanced efficiency relative to low LET radiation.

Coliphages↗
PubMed1998

Semi-preparative separation and purification of taxol analogs by high-speed countercurrent chromatography.

High-speed countercurrent chromatography (HSCCC) was applied to the semi-preparative separation of taxol and its analogs, such as cephalomannine and 7-epi-10-deacetyltaxol from the extract of the bark of Taxus yunnannesis. The experiments were performed with a quaternary two-phase solvent system composed of n-hexane-thyl acetate-ethanol-water through two steps. In the first step, the four components were separated into two groups at a volume ratio of 1:1:1:1 and, in the second step, two components in each group were separated at different volume ratios of 3:3:2:3 or 4:4:3:4. The present method also allows consecutive injections with reproducible results. HPLC analysis showed that the purity of the four components obtained from a partially purified sample, containing taxol at 10%, ranged from 85 to 99%. The results indicated that HSCCC can be effectively used for the semi-preparative separation and purification of taxol and its analogs.

Antineoplastic Agents, Phytogenic↗
PubMedDate not supplied

Preparative scale purification of shidasterone, 2-deoxy-polypodine b and 9a,20-dihydroxyecdysone from Silene italica ssp. nemoralis.

A suitable combination of preparative scale separation methods results in effective clean-up of the ecdysteroids of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman. The isolation of minor ecdysteroids from the partially purified extract is based on the use of both droplet counter-current chromatography and low-pressure reversed-phase liquid chromatography. The purification is completed by preparative thin-layer chromatography and preparative high-performance liquid chromatography to obtain the minor ecdysteroids, such as 2-deoxy-20-hydroxyecdysone, shidasterone, 2-deoxy-polypodine B, makisterone C, and 9alpha,20-dihydroxyecdysone.

Chromatography, High Pressure Liquid↗
PubMed2005

Isolation of flavanol-anthocyanin adducts by countercurrent chromatography.

Pigments of the flavanol-anthocyanin (F-A+) type detected earlier in wine are synthesized using a protocol adapted from the synthesis of procyanidin dimers. The F-A+ adduct thus obtained is purified by countercurrent liquid-liquid partition, currently referred to as countercurrent chromatography (CCC). The solvent system consists of tert-butyl methyl ether-n-butanol-acetonitrile-water (2:2:1:5, acidified with 0.1% trifluoroacetyl) with the light organic phase acting as a stationary phase and the aqueous phase as the mobile phase. Four fractions are recovered and analyzed by high-performance liquid chromatography coupled to a diode-array detector and electrospray ionization mass spectrometer. The multilayer CCC method allowed the separation of pigments in three different groups. The first group consists of hydrosoluble pigments present in fraction 1; the second group consists of the F-A+ adducts [catechin-malvidin 3 glucoside (Mv3glc), along with some (catechin)2-Mv3glc]; and the third group is their anthocyanin precursor, Mv3glc.

Anthocyanins↗
PubMed1975

Chemotaxis-defective mutants of the nematode Caenorhabditis elegans.

The technique of countercurrent separation has been used to isolate 17 independent chemotaxis-defective mutants of the nematode Caenorhabditis elegans. The mutants, selected to be relatively insensitive to the normally attractive salt NaCl, show varying degrees of residual sensitivity; some are actually weakly repelled by NaCl. The mutants are due to single gene defects, are autosomal and recessive, and identify at least five complementation groups.

Animals↗
PubMed1981

The application of droplet counter-current chromatography (DCC) for the separation of acidic glycolipids.

Droplet counter-current chromatography (DCC) a novel liquid-liquid partition technique, is a useful method for the separation of glycolipids. After a series of investigations on suitable experimental conditions for DDC, mouse brain chloroform-methanol-0.5% CaCl2-n-propanol (50:60:40:6) by the ascending method with 500 standard columns. GM1 and cerebroside sulfuric ester (CSE) from whale brain glycolipid fraction were separated by DCC into two peaks and three peaks, respectively, with chloroform-methanol-water-n-propanol (50:60:40:2) and 500 standard columns. The occurrence of two peaks of GM1 was due to the differences of sphingenine and fatty acid compositions. In the former peak of GM1, the majority of long chain base and fatty acid were 18:1 sphingenine and stearic acid, respectively, while the latter contained 18:1 (32%), 20:1 (68%) sphingenine and 16:0 (14.5%), 18:0 (61.4%), and 20:0 (21.0%) fatty acids. The three peaks of CSE were due to the difference of carbon chain length and to the presence or absence of a hydroxyl group in fatty acids. The first polar fraction (CSE-I) had hydroxy 23:0 (34%) and 24.1 (53.4%) fatty acids and the second fraction (CSE-II) contained hydroxy 24:0 (70.5%) and 25:1 (12.8%) fatty acids, while the third fraction (CSE-III) had normal 23:0 (11.9%), 24:1 (56.4%), hydroxy 25:0 (11.4%) and 26:1 (9.7%) fatty acids. Preparative DCC was also applied to the glycolipid fraction from Tay-Sachs' brain to give 242 mg of practically pure GM2 from 700 mg of crude brain extract without any preliminary purification.

Animals↗
PubMed1983

The separation of neutral glycosphingolipids from mammalian erythrocytes by droplet counter-current chromatography (DCC).

In a previous paper (Otsuka, H. & Yamakawa, T. (1981) J. Biochem. 90, 247-254), we reported the separation of acidic glycolipids by droplet counter-current chromatography using 500 columns with a commercially available DCC apparatus and described the precise conditions of the separation. In this paper, separation of neutral glycolipids from rabbit and human erythrocytes by DCC is described. For efficient separation of neutral glycolipids, addition of a definite amount of benzene was required. The solvent system of chloroform: benzene: methanol: water = 50: 50: 70: 20 gave clear separation of these glycolipids and further modification of this solvent system to chloroform: benzene: methanol: water = 50: 25: 65: 30 gave satisfactory results for the separation of Globoside I from human erythrocytes due to the difference between the amide linked fatty acids. Also under the same conditions, the clear separation of two peaks with blood group A activity was demonstrated by a hemagglutination inhibition test.

ABO Blood-Group System↗