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Biomedical subjects

W A Taylor

Publications and source records attributed to W A Taylor.

At least 55 records · Page 3Linked to original sources
PubMed1986

Characterization and solubilization of membrane bound diacylglycerol lipases from bovine brain.

Bovine brain contains two diacylglycerol lipases. One is localized in purified microsomes and the other is found in the plasma membrane fraction. The microsomal enzyme is markedly stimulated by the non-ionic detergent, Triton X-100, and Ca2+, whereas the plasma membrane diacylglycerol lipase is strongly inhibited by Triton X-100 and Ca2+ has no effect on its enzymic activity. Both enzymes were solubilized using 0.25% Triton X-100. The solubilized enzymes followed Michaelis-Menten kinetics. The apparent Km values for microsomal and plasma membrane enzymes are 30.5 and 12.0 microM respectively. Both lipases are strongly inhibited by RHC 80267, with Ki values for microsomal and plasma membrane diacylglycerol lipases of 70 and 43 microM, respectively. The retention of microsomal diacylglycerol lipase on a concanavalin A-Sepharose column and its elution by methyl alpha-D-mannoside indicates the glycoprotein nature of this enzyme.

Animals↗
PubMed1985

Experimental allergic neuritis induced in SJL mice by bovine P2.

Bovine myelin or bovine myelin-derived P2 protein was injected into 4 inbred mouse strains. SJL mice developed neurological deficit, and histological lesions characteristic of experimental allergic neuritis. BALB/C, CBA and C57.B1/6 mice were relatively resistant to disease induction by this method.

Animals↗
PubMed1985

Role of calmodulin inhibition in the mode of action of ophiobolin a.

Calmodulin has been isolated from the root of Zea mays. It activates the bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase and has electrophoretic mobility very similar to that of bovine brain calmodulin. Ophiobolin A, a fungal toxin, interacts with the maize calmodulin. The interaction is not reversed by dilution or denaturation in SDS and results in the loss of ability of the calmodulin to activate the phosphodiesterase. The inhibition is much faster in the presence than in the absence of Ca(2+). The electrophoretic mobility of ophiobolin A-treated calmodulin is less than that of untreated calmodulin. Several similarities are found between the inhibition of maize calmodulin by ophiobolin A in vitro and the effects of ophiobolin A on excised roots. Both are irreversible and time-dependent. The concentration of ophiobolin A for half-maximal inhibition of calmodulin in the phosphodiesterase assay is similar to that for phytotoxicity. In both cases ophiobolin A derivatives behave similarly, i.e. 18-bromo-19-methoxyophiobolin A is as potent as ophiobolin A, while 3-anhydro-ophiobolin A and 6-epi-ophiobolin A are less potent. A smaller amount of active calmodulin was measured in the extract from ophiobolin A-treated roots than in those from untreated roots. The present study suggests that calmodulin is a target molecule in the root for the toxicity of ophiobolin A.

Journal Article↗
PubMed1984

Spectrophotometric determination of lipases, lysophospholipases, and phospholipases.

Spectrophotometric techniques for determining the activities of lipases, lysophospholipases, and phospholipases are reviewed. These methods involve the use of thioester substrate analogs as well as omega-nitrophenyl derivatives of the corresponding lipids. The most promising results are obtained with the thioester substrate analogs. Mono- and diacylglycerol lipases are assayed by using rac-1-S-decanoyl-1-mercapto-2,3-propanediol and rac-1,2-S,O-didecanoyl-1-mercapto-2,3-propanediol, respectively. Phospholipases A1 and A2 are determined by using rac-1,2-S,O-didecanoyl-3-phosphocholine-1-mercapto-2,3-propanediol and 2-hexadecanoylthio-1-ethyl-phosphocholine, respectively. Lysophospholipases are measured by using 2-hexadecanoylthio-1-ethyl-phosphocholine. Phospholipase C is assayed with rac-1-S-phosphocholine-2,3-O-didecanoyl-1-mercapto-2,3-propanediol. Thioester substrate analog assay procedures are more rapid, sensitive, convenient, continuous, and less expensive than the classical radiochemical techniques.

Lipase↗
PubMed1984

Separation of bovine brain mono- and diacylglycerol lipases by heparin sepharose affinity chromatography.

Mono- and diacylglycerol lipases are differentially inhibited by heparin. No other glycosaminoglycan resembles heparin in this respect. Mono- and diacylglycerol lipases can be separated by heparin Sepharose affinity chromatography. Diacylglycerol lipase was completely retained on a heparin--Sepharose column and was eluted with either 0.5 M NaCl or 2-5 mg/ml heparin, whereas monoacylglycerol lipase was recovered in the washings. Adenosine phosphates markedly affected the activity of diacylglycerol lipase in a concentration dependent manner. ATP was the most potent inhibitor followed by ADP. AMP had no effect and cAMP slightly stimulated the diacylglycerol lipase.

Adenine Nucleotides↗
PubMed1984

Ophiobolin A. A natural product inhibitor of calmodulin.

Ophiobolin A, a fungal metabolite and a phytotoxin which can stimulate the net leakage of electrolytes and glucose from maize seedling roots (Tipton, C. L., Paulsen, P. V., and Betts, R. E. (1977) Plant Physiol. 59, 907-910) was found to be a potent inhibitor of calmodulin-activated cyclic nucleotide phosphodiesterase. The physiologically less active analogue, 3-anhydro-ophiobolin A, was found to be less inhibitory than ophiobolin A in the phosphodiesterase assay. The direct interaction between ophiobolin A and calmodulin has been demonstrated by changes in fluorescence of the protein and by the effect of ophiobolin A on calmodulin activity upon preincubation. Addition of ophiobolin A to calmodulin solutions resulted in an instantaneous quenching of the intrinsic tyrosine fluorescence followed by a time-dependent quenching. The instantaneous quenching is probably due to the inner filtering effect of ophiobolin A. The time-dependent fluorescence quenching was correlated with a time-dependent inhibition of calmodulin upon preincubation with ophiobolin A. The inhibition of calmodulin by ophiobolin A could not be reversed by dialysis, dilution, nor denaturation by urea in the presence of methanol followed by renaturation, and was much more pronounced in solutions containing Ca2+ than in those containing EGTA. Ophiobolin A also was shown to inhibit spinach calmodulin. The results of the present study suggest that calmodulin may be one of the target proteins of the phytotoxic action of ophiobolin A and that the interaction of ophiobolin A with calmodulin may involve a covalent modification of the protein by the fungal metabolite.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1984

Grass Conjuvac. II. Pro-inflammatory activity and potential for inducing hypersensitivity.

Treatment of rats with Conjuvac induced no anti-pollen extract (PE) IgE and no sensitization, whereas alum-adsorbed pollen extract induced IgE antibody and marked sensitivity. Conjuvac induced anti-PE IgE in rats treated with Bordetella pertussis organisms but the antibody concentrations were less than those induced by PE with B. pertussis. There was no indication, either in rats injected with B. pertussis and Conjuvac or alginate (ALG), of sensitization to ALG. In guinea pigs, Conjuvac induced immediate hypersensitivity to PE but there was no delayed hypersensitivity. Furthermore, no immediate hypersensitivity and little or no delayed hypersensitivity to ALG was detected in guinea pigs injected with conjuvac or ALG. Histological studies at Conjuvac injection sites in rabbits revealed inflammatory reactions less intense than those produced by aluminium hydroxide.

Adjuvants, Immunologic↗
PubMed1983

Kinetic changes in rat renal 15-hydroxy-prostaglandin dehydrogenase induced by chronic ethanol exposure.

Several lines of investigation have suggested that exposure to ethanol may lead to alterations in both the synthesis and degradation of the E and F series of prostaglandins (PG). It has been suggested that these changes in PG metabolism underlie certain of the pathophysiological consequences of chronic alcoholism but few data are available as to the mechanism responsible for these changes. We now report that chronic exposure to ethanol in moderate doses (17% total dietary calories as ethanol) and high doses (35% total dietary calories as ethanol) results in a concentration dependent loss of renal 15-hydroxy-prostaglandin dehydrogenase for the NAD mediated reactions. Soluble fractions of kidney homogenates in the presence of greater than 10 Km concentrations of NAD exhibited dose dependent loss of specific and total organ PG dehydrogenase activity toward PGE2 and F2 alpha. A similar dose dependent decrease in the Vmax of the NAD mediated reaction was measured for the oxidation of PGE1, E2, and F2 alpha. Moderate doses of ethanol resulted in an increase in the Km for PGE2 and F2 alpha. Km values for the NADP mediated reactions were not significantly influenced by exposure to high doses of ethanol other than for PGE1. These data suggest that chronic ethanol consumption results in a dose dependent, selective inhibition of the metabolism of PGs of the "2" series by the renal PGDH enzyme which utilizes NAD.

Animals↗
PubMed1983

Grass conjuvac. I. Immunogenicity in rabbits, guinea pigs and rats.

Sera of rabbits injected with Conjuvac developed high titres of pollen-specific haemagglutinating antibody. Similarly, sera of guinea pigs treated with Conjuvac developed high titres of pollen-specific IgG1 antibody, as assessed using guinea pig passive cutaneous anaphylaxis (PCA). In both species, the immunogenicity of pollen extract was increased by conjugation to alginate to an extent greater than or equal to that resulting from adsorption to aluminium hydroxide. In contrast, in rats, Conjuvac alone failed to induce pollen-specific IgE antibody, and it suppressed the IgE response induced by pollen extract absorbed to aluminium hydroxide.

Adjuvants, Immunologic↗
PubMed1982

Selective inhibition by betamethasone of allergen-induced release of SRS-A from human lung.

Passively sensitized human lung, when incubated with the appropriate allergen, released histamine and slow-reacting substance (SRS-A). Betamethasone sodium phosphate (5-100 microgram/ml), preincubated with the lung overnight, suppressed, in a dose-related manner, the release of SRS-A without having an effect on the release of histamine. Preincubation for only 1 h produced little effect on the release of SRS-A or of histamine. These results may help to explain some of the beneficial effects of glucocorticoids in allergic asthma.

Allergens↗
PubMed1982

An adoptive cell transfer system for the evaluation of immunity to Herpes simplex virus in mice.

Lymphocytes adoptively transferred from syngeneic immune donors protect mice against challenge with Herpes simplex virus type 1. Normal mice require transfer 3 x 10(7) spleen cells for protection. Sublethal irradiation (450 rad) decreases the number required five-fold. Lymphocytes from non-immune donors do not protect, and hyperimmunization does not enhance the protection efficiency of donors. The viral LD50 varies through a range 10(5)-fold during the period of recovery from this amount of radiation, but over the same period there is little variation in the number of cells required for protection. Nor is there much variation in this number between strains of mice naturally susceptible (CBA) and resistant (C57) to the virus. We conclude that natural resistance operates at a level of virus handling prior to operation of the lymphocyte system, perhaps at the generation of interferon. As few as 1.3 x 10(6) immune T lymphocytes can protect against challenge provided that they are transferred together with normal spleen cells. We conclude that primed lymphocytes act in co-operation with non-immune cells.

Animals↗
PubMed1981

Adjuvant and suppressive effects of Grass Conjuvac and other alginate conjugates on IgG and IgE antibody responses in mice.

BALB/c mice were immunized with grass pollen extract (GPE), GPE conjugated to sodium alginate (Conjuvac) or GPE absorbed to aluminium hydroxide gel (alum). Conjuvac was a more potent immunogen than the other two preparations of GPE when anti-GPE IgG antibody levels were compared. In contrast, the highest IgE antibody titres in the Conjuvac treated mice, were some sixteen-fold lower than the highest titres in the mice immunized with GPE in alum. The suppressive effects of Conjuvac on IgE antibody titres were also studied. Mice were immunized with 1 microgram dinitrophenyl (DNP)-GPE in alum and the anti-DNP and anti-GPE IgE antibody titres determined. After 4 and 5 weeks, the mice were injected with GPE or Conjuvac. The Conjuvac and the GPE failed to reduce the ongoing primary anti-GPE IgE responses but both suppressed the secondary responses by up to eight-fold. The suppression was not dose-related however. The ongoing primary and secondary anti-DNP IgE titres were suppressed in a dose-related manner by up to sixty-four fold by Conjuvac but GPE treatment was much less suppressive. We went on to investigate the suppressive properties of DNR-alginate (DNP-alg) conjugates. In these experiments mice were immunized with 1 microgram DNP-ovalbumin (DNP-OA) mixed with alum. After 4 and 5 weeks, the mice were injected with a dose of 6--600 micrograms DNP-alg with an average hapten density of 2 or 10 per alginate molecule. After a further 8 weeks a second injection of 1 microgram DNP-OA was given. All dose levels of both DNP-alg conjugates suppressed the continuing primary as well as the secondary anti-DNP IgE responses. It is concluded that alginate has properties similar to those of known T-cell adjuvants and that Conjuvac may prove useful in the immunotherapy of atopic allergy.

Adjuvants, Immunologic↗