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At least 757 records · Page 42Linked to original sources
PubMed1994

Alpha-thrombin and trypsin use different receptors to stimulate arachidonic acid metabolism.

Rat liver cells (the C-9 cell line) are stimulated to metabolize arachidonic acid by alpha-thrombin, its receptor polypeptide, gamma-thrombin, and trypsin. Prostaglandin (PG) I2 synthesis stimulated by alpha-thrombin is inhibited by dansylarginine N-(3-ethyl-1,5-pentanediyl) amide (DAPA), by hirudin, by the synthetic tyrosine-sulfated dodecapeptide corresponding to residues 53-64 of hirudin (hirugen), by the Tyr(SO3H)63-hirudin fragment 54-65 and by rabbit lung thrombomodulin. Stimulation of arachidonic acid metabolism by the receptor octapeptide, SFLLRNPN, is not affected by DAPA or hirudin. gamma-Thrombin stimulates arachidonic acid metabolism but at 300 to 400-fold higher concentrations. Trypsin stimulates arachidonic acid metabolism. Trypsin's proteolytic activity is required--its ability to stimulate is abolished if it is incubated with Na-p-tosyl-L-lysine chloromethyl ketone (TLCK) or bovine pancreatic trypsin inhibitor. Prior treatment of the rat liver cells with alpha-thrombin blocks subsequent stimulation by alpha-thrombin, but not by trypsin, whereas prior treatment with trypsin blocks subsequent stimulation by trypsin, but not the activity stimulated by alpha-thrombin. Prior treatment of the cells with the serine-proteases, chymotrypsin, pancreatic or neutrophil elastase and thrombocytin from Bothrups atrox venom, block alpha-thrombin's activation of PGI2 production, but not the activity stimulated by trypsin. These findings indicate that alpha-thrombin and trypsin stimulate PGI2 production via different receptors.

Amino Acid Sequence↗
PubMed1996

Pressure-induced change in proteins studied through chemical modifications.

Pressure-induced change of two bovine proteins, alpha-lactalbumin (LA) and beta-lactoglobulin (LG), was investigated at neutral pH by means of fluorescence and CD spectroscopy. The rate and the extent of modification was considerably increased by applying high pressure during the dansylation reaction of LG, while those for LA were only moderately affected. This difference was accounted for by the structural deformation of these proteins under high pressure. The fluorescence spectrum of these proteins measured under elevated pressure, as well as their fluorescence and CD spectra after the pressure release, indicated different responses towards pressure. The structural change of LA was practically reversible up to 400 MPa, whereas that of LG lost reversibility at 150 MPa or lower. Fluorescent measurement of dansylated (prepared at atmospheric pressure) proteins, especially the energy transfer from the intrinsic Trp residue to the dansyl group, showed that the protein structure was deformed by pressure and that the energy transfer facility of the two proteins was differently affected by high pressure, probably reflecting the degree of compactness of their pressure-perturbed structures.

Animals↗
PubMed1996

Characterization of hydrogels using luminescence spectroscopy.

In this contribution the literature relevant to characterization of polyelectrolytes, polyelectrolyte complexes and hydrogels using luminescence spectroscopy is reviewed. A brief introduction to the fundamentals of luminescence is followed by a description of the various types of spectroscopic studies which may be used to characterize hydrogels. In addition to experiments based upon the addition of a viscosity, temperature- or polarity-sensitive fluorescent probe to characterize the local environment, experiments and techniques based upon luminescence quenching, fluorescence polarization, phosphorescence depolarization and excimer fluorescence are discussed. This review succinctly describes the utility of luminescence spectroscopy in the characterization of hydrogel systems, with a focus on recent developments in the characterization of hydrogels and polyelectrolyte complexes.

Dansyl Compounds↗
PubMed1985

Kinetic investigations in single muscle fibres using luminescent and fluorescent Ca2+ probes.

The Ca2+-sensitive photoprotein aequorin and the Ca2+-dependent fluorescent indicators quin 2 and TnCDANZ have been used to investigate contractile processes in single crustacean muscle fibres. The investigations with quin 2 indicate that the free Ca2+ rises to a maximum value before peak force as with aequorin light (approximately 200 msec delay at 12 degrees C) and subsequently decays more slowly, unlike the majority of the aequorin signal, although an aequorin 'tail' signal remains. The resting quin 2 fluorescence from the cell suggests an upper limit of 348 nM for the resting calcium concentration. Experiments with TnCDANZ indicate that this fluorescence response rises rapidly but then the rate of rise slows to reach a maximum value at a time when peak force is achieved and then the fluorescence signal decays more slowly than force. The latter result implies that Ca2+ is attached to the Ca2+-specific sites of TnC when externally recorded force is small.

Aequorin↗
PubMed1983

Determination of prostaglandin E2 and the main prostaglandin E metabolite by micro high-performance liquid chromatography using fluorescence derivatization with dansyl hydrazine.

A micro high-performance liquid chromatographic method for the determination of prostaglandin E2(PGE2) and the main prostaglandin E metabolite (PGEMT) in rat organs and human urine has been developed. Prednisolone was added to the sample as the internal standard. The isolated PG's and the internal standard were subjected to reaction with dansyl hydrazine, separated by liquid chromatography on a mu Fine pack SIL C18 and determined fluorimetrically. The standard deviation of the method was +/- 6.5% for PGE2, and +/- 8.4% for PGEMT. The detection and simultaneous quantitation of less than 10 ng of PGE2 and PGEMT is possible. The proposed method is suitable for the pharmacological analysis of PGE2 and PGEMT in various rat tissues and human urine.

Animals↗
PubMed1983

Determination of catecholamines in rat tissue by precolumn dansylation using micro high-performance liquid chromatography with fluorescence detection.

A micro high-performance liquid chromatography (MHPLC)-precolumn dansylation procedure for determination of norepinephrine (NE), epinephrine (E), and dopamine (DO) in various kinds of rat tissue has been developed. After dansylation of the extracted catecholamines to get fluorescent derivatives, they were separated and determined using MHPLC equipment with a fluorimeter. The standard deviation of the method was +/- 8% for NE, +/- 4% for E, and +/- 8% for DO. This relatively simple and rapid procedure for determination of catecholamines provides an efficient and reproducible method. Furthermore, the procedure is readily adaptable to routine pharmacological study of catecholamine metabolism in various kinds of rat tissue.

Animals↗
PubMed1983

Histochemical labeling of drug receptors in schistosomes: quantitation using computer image analysis techniques.

Computer image analysis techniques were used to quantitate the histochemical labeling of schistosomes with dimethylaminonaphthalene-5-sulfonaminoethyl methylamine hydrochloride (DDNS), a fluorescent analog of acetylcholine (ACh). Dose-response curves, consistent with previous experiments, were obtained for DDNS, and for blockage of DDNS labeling, by trifluoperazine and mecamylamine.

Animals↗
PubMed1987

Determination of catecholamines in rat tissues by high-performance liquid chromatography using a precolumn fluorescence labeling method.

A high-performance liquid chromatographic method using solid-phase dansylation on alumina for precolumn fluorescence label has been developed for the determination of catecholamines (norepinephrine, epinephrine, and dopamine) in various rat tissues. After alumina treatment of the tissue homogenate, catecholamines adsorbed on the alumina were dansylated by solid-phase reaction. Both the excess reagent and fluorescent degradation products produced during dansylation were washed out from the alumina. Dansylated catecholamines were eluted from the alumina and separated by reversed-phase high-performance liquid chromatography. The four catecholamine derivatives, including the internal standard, were separated within 17 min, and no major interfering peak could be detected on any chromatograms. The calibration graph showed a good linearity in a range of 10 to 500 pmol for each catecholamine per sample. This method was applied to different rat tissues, and both the recovery and the reproducibility for all samples proved to be satisfactory. The present study provides a simple, sensitive, and selective method useful for routine pharmacological experiments of the determination of catecholamines.

Animals↗
PubMed1984

Restriction in IgM expression--VI. Affinity analysis of monoclonal anti-dansyl antibodies.

Affinity restriction in the IgM response to the 5-dimethylaminonaphthalene-1-sulfonyl (dansyl) group was studied with 56 monoclonal IgG and IgM affinity-purified antibodies. These were generated by immunization with dansyl-Ficoll or dansyl-B gamma G. Association constants for N epsilon-dansyl-lysine were determined by fluorescence titration based on resonance energy transfer. The antibodies were also characterized with respect to the emission maximum of the antibody-ligand complex. The distribution of binding constants covered a 100,000-fold range, demonstrating thereby a restriction in IgM affinity relative to IgG affinity. In the secondary response the IgG affinity exhibited a ceiling of about 1 X 10(10) M-1, a value in accord with the size and hydrophobic nature of the dansyl group. In the case of IgM, with one exception, the value of 1 X 10(7) M-1 was not exceeded with IgM antibodies isolated from 28 hybridomas. This system, therefore, provides further evidence for the restriction in expression of IgM as a general feature of the immune response.

Animals↗
PubMed1984

Restriction in IgM expression--V. Fine structure analysis in the anti-lactose system.

A methodology for the analysis of the fine specificity of monoclonal anti-lactose IgM and IgG antibodies is described using structural variants of the homologous lactoside epitope. These variants are used as inhibitors of the binding of a reference ligand N-(5-dimethylaminonaphthalene-1-sulfonyl)-p-aminophenyl-beta-lactoside. Excitation of the antibody with bound ligand at 295 nm leads to resonance energy transfer to and fluorescence emission by the ligand. Titration of the antibody-ligand mixture with the inhibitor and measurement of the emission at 550 nm provide the data for the calculation of the binding constants of the inhibitors. A comparison of two IgM and two IgG antibodies showed that the higher affinity of the IgG antibodies arises from their specific interaction with both hexosides of the lactoside in contrast to IgM antibodies which do not engage the non-terminal hexoside as effectively. The quantitative significance of this difference is a differential free energy contribution of about -3 kcal/mole to the binding of lactoside by IgG. A finer discrimination between homologous and several cross-reactive molecules is evident with IgG antibody compared to IgM. The former exhibits about 100-fold greater difference in their binding constants than does IgM. These differences applied to biologically relevant multivalent interactions, where functional affinity governs complex formation, suggest a possible explanation for the IgM to IgG conversion characteristic of the humoral immune response.

Antibodies, Monoclonal↗