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At least 829 records · Page 46Linked to original sources
PubMed1977

Trisialoganglioside synthesis by a chicken brain sialyltransferase. Comparative study with the similar reaction for the synthesis of disialoganglioside.

An enzyme preparation from embryonic chicken brain catalyzes the transfer of sialic acid from CMP-N-acetylneuraminic acid to ceramide-Glc-Gal(NeuAc-NeuAc)-GalNAc-Gal (GDlb) to form ceramide-Glc-Gal(NeuAc-NeuAc)-GalNAc-Gal-NeuAc (GTlb). The sialyltransferase activity was measured during the development of the embryo, the subcellular distribution of this activity was determined and several kinetic properties of the reaction were examined. A comparative study with the similar reaction involved in the transfer of sialic acid to the terminal galactose in ceramide-Glc-Gal(NeuAc)-GalNAc-Gal (GMl) was made. The results obtained in this comparative study suggest that the transfer of sialic acid in both reactions is catalyzed by the same enzyme.

Aging↗
PubMed1975

Chemotaxis of rabbit macrophages in vitro: inhibition by drugs.

Chemotaxis of rabbit macrophages was inhibited by phenylbutazone and sodium salicylate, but not by other antiinflammatory agents. Other inhibitory compounds were colchicine, vincristine, PHA, Con A, iodoacetic acid, cytochalasin B, and EDTA. Some of these in vitro results contrast apparently with in vivo effects.

Animals↗
PubMed1984

Vitamin E, catalase, manganous or cobaltous ions and dithiothreitol protect against Tween 20-induced hemolysis of vitamin E-deficient chick and kid erythrocytes.

The effective Tween 20 concentration at which 70% hemolysis was achieved in vitro correlated with the plasma vitamin E content of chicks (r = 0.85). Addition of catalase, MnCl2, CoCl2 or dithiothreitol in vitro showed significant protection against the hemolysis induced by Tween 20 in vitamin E-deficient chick and kid erythrocytes.

Animals↗
PubMed1977

Histamine release in dogs by Cremophor E1 and its derivatives: oxethylated oleic acid is the most effective constituent.

Several preparations of Cremophor E1, several of other non-ionic detergents and several components of Cremophor E1 were tested for their histamine-releasing capacity in dogs. Lutensol AP 10 and a derivative of 1,2-propylenglycol were ineffective, but showed excellent properties as detergents. Thus the histamine-releasing capacity was not necessarily combined with the tenside effect of the surfactants. Oleic acid found in Tween 80 as well as in Cremophor E1 seems to be the most effective constituent, but the alcohol seems also to be important for the histamine-releasing capacity. The development of a non-toxic solubilizer for lipophilic drugs seems of considerable clinical interest.

Animals↗
PubMed1986

Hydrophobic and adherence properties of Clostridium difficile.

Nine strains of Clostridium difficile isolated from symptomatic and asymptomatic patients and four other species of clostridia were tested for relative hydrophobicity by determining the degree of adherence to polystyrene. Under three different conditions of growth all strains of Clostridium difficile had high rates of adherence, whereas the other clostridial species showed no pronounced adherence. Isolates of Clostridium difficile were also tested for their ability to adhere to human embryonic intestinal cells and adult colon cells. All strains adhered to both cell lines, although the percentages of organisms adhering varied. Adherence was greatest at pH 5.5-6.0 but was not significantly altered at a pH of 7.0-7.8 (p = 0.15, p = 0.20); it decreased significantly upon washing with 1% Tween 80 but not with 0.1% Tween 80. This capacity for adherence may play a part in the organism's colonization of the human intestinal tract.

Bacterial Adhesion↗
PubMed1981

Use of the enzyme-linked immunosorbent assay (ELISA) for the estimation of serum antibodies in an influenza virus vaccine study.

The value of the enzyme-linked immunosorbent assay (ELISA) for determining the serum antibody responses of volunteers following immunisation with various inactivated influenza virus vaccines was assessed, and the incidence of seroconversions, as measured by both haemagglutination-inhibition (HI) and ELISA response of the volunteers determined. ELISA was found to be more sensitive than the HI test in detecting serum antibodies, but was also less specific under the conditions used. With regard to efficacy, the whole virus vaccine proved to be more effective in inducing serum antibody in an unprimed population than either tween-ether split or subunit adsorbed vaccines, but the reverse situation held when the population was primed with respect to the antigen concerned.

Adolescent↗
PubMed1995

Antioxidant and prooxidant roles of copper in Tween 20-induced hemolysis of hamster and pig erythrocytes containing marginal vitamin E.

The concentration-dependent effects of copper acting either as an antioxidant or as a prooxidant were examined in vitro using Tween 20-induced hemolysis. When cupric ion concentration was more than 10 microM, free copper(II) acted as a prooxidant; both extensive hemolysis and production of unknown thiobarbituric acid-reactive substance occurred in hamster and pig erythrocytes irrespective of vitamin E status. However, when cupric ion concentration was 2-4 microM in the incubation medium, copper showed a clear antioxidant activity, reducing both hemolysis and malondialdehyde production induced either by diluted peroxide-containing Tween 20 with ascorbic acid and sodium azide in vitamin E-deficient hamster erythrocytes, or by peroxide-containing Tween 20 in pig erythrocytes containing marginal amounts of vitamin E. Copper(II) is taken up by the erythrocytes, where copper(I)-complexes may contribute to the protection of cells with membrane vitamin E against oxidative radical attack.

Animals↗
PubMed1976

Phospholipid synthesis in mammary tissue. Choline and ethanolamine kinases: kinetic evidence for two discrete active sites.

Choline and ethanolamine kinases are located in the high speed supernatant of lactating bovine mammary gland. Maximum activities of choline and ethanolamine kinases were observed at pH 9.2 and 8.0, respectively, with the rate of ethanolamine phosphorylation being 1/15 that of choline phosphorylation. Activation energies of 29 joules (Q10--1.5) and 31 joules (Q10 = 1.5) were calculated between 3.4 and 31.3 C for choline kinase and ethanolamine kinase, respectively. Above 31.3 C, the Arrhenius plot deviated from linearity for both enzymes, suggesting that denaturation was occurring. An apparent Km of 0.25 mM for choline was obtained for choline kinase activity. The apparent Km of ethanolamine kinase for ethanolamine was unusually high (17 mM), the activity was not linear with increasing protein concentration. Activity was tripled and the Km decreased to 2.5 mM when the enzyme preparation was washed with butanol: benzene mixture, suggesting the presence of an endogenous competitive inhibitor(s), with respect to ethanolamine. Choline kinase was not affected by the solvent wash. Substrate competition studies revealed that choline kinase was slightly inhibited competitively by ethanolamine (apparent Ki = 19-21 mM), whereas choline was a potent competitive inhibitor of ethanolamine kinase (apparent Ki = 0.33-0.50 mM). The results indicated that these two kinase activities were mediated by two distinct active sites, possibly on a single protein. The significance of choline in the regulation of phosphatidylethanolamine synthesis is discussed.

Animals↗
PubMed1977

Kinetics of a micelle specific palmitoyltransferase isoenzyme of rabbit mammary gland.

Palmityl-CoA: monopalmityl-sn-glycerol 3-phosphate palmitoyltransferase [EC 2.3.1. -] in rabbit mammary gland microsomes is composed of two isoenzymic species. The alpha form (LPAT-alpha) is active with monomeric substrates and inhibited by micelles while the beta form (LPAT-beta) is active only with micelles. By combining the effects of time, temperature, and Tween 80 which selectively inhibited LPAT-alpha, the substrate saturation curve for the LPAT-beta isoenzyme has been successfully determined. Both theoretical and experimental curves are in good agreement.

Acyltransferases↗
PubMed1994

Effect of nonionic detergents on lipoxygenase catalysis.

In many studies on lipoxygenase catalysis, nonionic detergents are used to obtain an optically transparent solution of the fatty acid substrate. In order to resolve some controversies that exist with regard to the interpretation of kinetic data obtained with solutions containing nonionic detergents, a systematic investigation was undertaken into the effects of Lubrol, Tween-20 and Triton X-100 (0-0.8 g/L) on the kinetics of linoleate (2.5-110 microM) dioxygenation, catalyzed by lipoxygenase-1 or lipoxygenase-2 from soybean, at pH 9 or 10, at 25 degrees C. Under most conditions, it was found that the detergents slowed down the reaction. However, at high linoleate concentrations, where substrate inhibition of lipoxygenase is significant, small amounts of detergent increased the dioxygenation rate. In a quantitative analysis of the results, a kinetic model in which the incorporation of linoleate in the detergent micelles is formulated as a simple reversible equilibrium, and in which both lipoxygenase-1 and -2 interact with free linoleate, but not with linoleate incorporated in the micelles, appeared to be sufficient to predict experimental results over a wide range of experimental conditions. According to this model, the changes in the dioxygenation kinetics caused by the presence of nonionic detergents are similar (but not equal) to those caused by competitive inhibitors. The conclusions that monomeric, nonmicellar linoleate is the preferred substrate for lipoxygenase and that the observed inhibition and stimulation are solely due to changes in the effective linoleate concentration strongly corroborate the earlier observations by Galpin and Allen [Biochim. Biophys. Acta 488 (1977), 392-401].

Catalysis↗
PubMed1987

A study on the cell kinetics of the canine gastric mucosa by the cytofluorometric method: an evaluation of chemically induced gastric cancer.

The cell kinetic alteration in the background mucosa of canine gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) was evaluated by cytofluorometry in which the rate of S and G2 + M phase cell in gastric mucosal cells could be calculated, and a triphasic alteration was demonstrated; an initial reduction phase, an increase phase and a plateau phase with a high value. The initial reduction phase was caused by non-specific toxicity of ENNG as observed in drug induced gastric mucosal lesions, and subsequent increase and plateau phases originated from the action of ENNG itself to activate the mucosal turn-over and from histological changes in the background mucosa such as regenerative hyperplastic change after mucosal erosion and atrophic changes, sometimes including intestinal metaplastic change. Further, in comparison to carcinogenesis in chemically induced gastric cancer with and without a surfactant (Tween 60), it was suggested that one of the promotion effects of Tween 60 was closely related with activation of the mucosal turn-over.

Adenocarcinoma, Mucinous↗
PubMed1994

Activation and stabilization of enzymes entrapped into reversed micelles. Studies on hydrolyzing enzymes--protease and alpha-amylase.

Observations of the activity of two hydrolyzing enzymes-protease and alpha-amylase--entrapped inside the reversed micelles formed by surfactants in hexane, benzene, and cyclohexane are reported. The surfactants chosen for this study are: Tween 80, a nonionic surfactant, Cetyl pyridinium chloride, a cationic surfactant, and two anionic surfactants, sodium lauryl sulfate and Aerosol OT. Tween 80 enhances the activity of both protease and alpha-amylase. Sodium lauryl sulfate and Aerosol OT, which are ionic surfactants, enhance the activity of protease, but inhibit the activity of alpha-amylase. Cetyl pyridinium chloride, however, enhances the activity of alpha-amylase, but inhibits the activity of protease. Enhanced activity is generally severalfold greater in comparison to the activity observed in the usual aqueous system in the absence of reversed micelles. It has also been observed that the enhanced activity of the enzymes entrapped inside the reversed micelles remains preserved for a much longer period of time in comparison to the activity in the usual aqueous systems. These observations, which support the view that with proper choice of surfactant and the organic solvent, reversed micelles act like a microreactor that provides a favorable aqueous micro-environment for enzyme activity, have biotechnological overtones.

Benzene↗