PubMed Health⌕ Search

Biomedical subjects

M J Parnham

Publications and source records attributed to M J Parnham.

At least 37 records · Page 2Linked to original sources
PubMed1993

Antioxidant and anti-inflammatory activities of selenomethylene blue.

The selenium derivative of methylene blue, has been compared with the parent compound. Unlike some organic selenium compounds neither of the compounds affected macrophage chemiluminescence nor did they catalyse the glutathione-dependent breakdown of hydroperoxides in vitro. However, both inhibited iron-induced hepatic lipid peroxidation, in vitro and ex vivo, the selenium derivative being 3-fold more active in this respect. Both compounds inhibited inflammatory paw oedema in the rat, selenomethylene blue being the more active. Selenomethylene blue, thus, does not exhibit a different anti-oxidant/anti-inflammatory profile from that of the parent sulphur compound, but exhibits increased inhibitory activity.

Animals↗
PubMed1993

Toxicity screening of liposomes.

Phospholipids are the major components of most liposomes. Extensive testing of these naturally occurring compounds has revealed them to be remarkably safe for pharmaceutical use. Addition of other constituents to liposomes in order to alter stability or kinetics can result in an increase in toxic potential, particularly on parenteral administration of liposomes. This paper describes some simple in vitro cellular tests for direct toxicity of liposomes, particularly following intravenous (i.v.) or topical administration, including tests for haemolysis, thrombosis and cytotoxicity. In addition, an in vivo test for the effects on phagocytosis and for pyrogenicity are described, together with a brief outline of the requirements for the further toxicity testing of liposomal drugs at a later stage of development.

Animals↗
PubMed1993

Antioxidants as antirheumatics.

Reactive oxygen species (ROS) are generated by activated leukocytes and during ischaemia-reperfusion damage, such as that which occurs in the joint during exercise. Activities of endogenous scavengers in the synovial fluid are insufficient to deal with this excessive oxidative stress. Therapy with naturally occurring antioxidants, however, has been disappointing. This is due predominantly to poor pharmacokinetics. Studies on traditional anti-rheumatic drugs and the actions of novel compounds suggest that targeting to the joint coupled with defined mechanisms of action may lead to the development of effective antioxidant antirheumatics.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

Acute antiinflammatory and gastric effects of the seleno-organic compound ebselen.

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a seleno-organic compound with glutathione peroxidase-like activity in vitro, was compared with indomethacin, BW 755C, and levamisole as an inhibitor of carrageenan- and CVF (cobra venom factor)-induced paw oedema in the rat. The antiinflammatory potency of ebselen against CVF-induced oedema (ED50 = 56 mg/kg p.o.) was similar to that of BW 755C, while indomethacin was weakly active in this model, and levamisole exerted stronger activity. In the carrageenan model, ebselen exhibited weak inhibitory potency, like BW 755C, while indomethacin markedly inhibited this inflammatory response, and levamisole was inactive. Unlike cyclooxygenase inhibitors, ebselen produced almost no gastric irritation in rats up to 316 mg/kg p.o. Moreover, ebselen inhibited significantly diclofenac-induced gastric intolerance at 31.6 and 316 mg/kg p.o. Thus, ebselen represents a new tool for antiinflammatory therapy.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗
PubMed1989

Antimalarial properties of ebselen.

The seleno-organic compound ebselen showed anti-malarial activity in vitro against the murine Plasmodium berghei and the human P. falciparum. In P. berghei, the uptake and incorporation of [3H]-methionine and [3H]-adenosine was inhibited and the infectivity of plasmodia was reduced. Ebselen affects the development of asexual stages of chloroquine-resistant and -sensitive P. falciparum strains. Its IC50 for P. falciparum was about 14 mumol/l and that for P. berghei, about 10 mumol/l. The growth of P. falciparum was blocked by ebselen at all stages, including the invasion of erythrocytes by merozoites. In a human hepatoma cell line and in mouse peritoneal macrophages, no cytostatic or cytotoxic effects were found, indicating selective inhibition of plasmodia by ebselen. Its in vitro inhibitory effect is discussed in relation to its possible reactivity with thiol groups and its lack of an anti-malarial effect in infected mice.

Animals↗
PubMed1989

Antagonism of platelet activating factor-induced chemiluminescence in guinea-pig peritoneal macrophages in differing states of activation.

1. The effects of the platelet activating factor (Paf) antagonists alprazolam, BN 52021, kadsurenone, L 652,731 and SRI 63119 have been studied on Paf-induced chemiluminescence (CL) of guinea-pig, C. parvum-activated peritoneal macrophages in vitro. 2. All antagonists produced a shift to the right in the dose-response curve to Paf (0.001-10 mumol l-1). Schild plots for BN 52021, L 652,731, kadsurenone and SRI 63119 were linear, but only for BN 52021 and kadsurenone did the mean slope not differ significantly from unity. Mean pA2 values for BN 52021 and kadsurenone were 6.60 +/- 0.05 and 6.41 +/- 0.14 (mean + s.e.mean) respectively. Calculation of IC50 values for all antagonists (at 0.1 mumol l-1 Paf) gave an order of potency: L 652731 greater than kadsurenone greater than or equal to BN 52021 greater than alprazolam greater than SRI 63119. 3. When individual pA2 values for BN 52021 and kadsurenone were plotted against the maximal CL response to Paf of cell suspensions in the absence of antagonist (reflecting the degree of activation of the macrophages by the C. parvum), it was found that the affinity of both antagonists for macrophage Paf receptors remained relatively constant irrespective of the activation state of the cells. 4. We conclude that activation of guinea-pig peritoneal macrophages does not account for the increased affinity for macrophage Paf receptors previously observed for kadsurenone. Kadsurenone and BN 52021 presumably bind to a site on Paf receptors which is not affected by the activation process, while alprazolam and SRI 63119 are non-specific antagonists. The reason for the difference between the competitive nature of kadsurenone and its structural analogue L 652,731 is unclear.

Alprazolam↗
PubMed1988

Rosmarinic acid: a new inhibitor of complement C3-convertase with anti-inflammatory activity.

Rosmarinic acid (RA) is a naturally occurring compound, isolated from Rosmarinus officinalis or Melissa officinalis which inhibits the in vitro immunohaemolysis of antibody-coated sheep erythrocytes by guinea pig serum. In further experiments this reduced immunohaemolysis was found to be due to inhibition of the C3-convertase of the classical complement pathway. The threshold concentration for inhibition of C3-convertase was 10(-6) mol/l. RA with an optimal inhibitory concentration between 5 and 10 mumol/l., resulting in about 70% inhibition of haemolysis. However, higher concentrations of RA were less effective at inhibiting C3-convertase. The inhibition may not be specific for C3-convertase, since another serine protease, elastase, was also weakly inhibited by RA in vitro. RA also exhibited inhibitory activity in three in vivo models in which complement activation plays a role. Thus, RA (0.316-3.16 mg/kg i.m.) reduced paw oedema induced by cobra venom factor (CVF) in the rat, and at 1-100 mg/kg p.o. inhibited passive cutaneous anaphylaxis in the rat. In addition, at 10 mg/kg i.m. RA impaired in vivo activation by heat-killed Corynebacterium parvum (i.p.) of mouse macrophages, as measured by the decreased capacity of the activated macrophages to undergo the oxidative burst. RA (0.1-10 mg/kg i.m.) did not inhibit t-butyl hydroperoxide-induced paw oedema in the rat, indicating selectivity for complement-dependent processes.

Animals↗
PubMed1988

PAF receptors.

Explore the source record for details and available documents.

Animals↗
PubMed1987

Changes in glutathione peroxidase activities and the oxidative burst of leukocytes during inflammation in the mouse and rat.

The relationship between glutathione peroxidase (GSH-Px) activity and opsonized zymosan-induced chemiluminescence (CL) has been studied with exudate leukocytes obtained at different times after induction of inflammatory responses in the mouse peritoneal cavity with heat-killed Corynebacterium parvum and in the rat pleural cavity with lambda-carrageenin. GSH-Px activity in mouse peritoneal exudate cells fell markedly after 2-4 h, returning to normal within 1-2 days. The lowered enzyme activity was associated with an increased ability of the cells to generate CL. Rat pleural exudate cells exhibited a slight fall in GSH-Px activity after 6 h which increased to supranormal levels within 1-2 days. During this period the ability of the cells to generate CL continually increased. The data indicate that during the early phase of increased generation of reactive oxygen species (ROS) by inflammatory leukocytes, the intracellular protective mechanism, represented by GSH-Px, is compromised. Subsequently, GSH-Px activity increases to or above initial levels possibly due to the presence of mononuclear cells and/or as a response to the increased generation of ROS.

Animals↗
PubMed1987

Ebselen: a new approach to the inhibition of peroxide-dependent inflammation.

Ebselen is a novel organo-selenium compound which catalytically inactivates peroxides in vitro in a manner similar to that of glutathione peroxidase (GSH-Px). In addition, ebselen also inactivates leukotriene B4 (LTB4) generated by pig leukocytes in vitro by isomerizing this eicosanoid to its biologically inactive 6-trans isomer. In vivo, ebselen is a weak oral inhibitor of carrageenan paw oedema and adjuvant arthritis in the rat, differentiating it from classical NSAIDs such as indomethacin and diclofenac. In contrast, oral ebselen, like (intra-articular) catalase, is an effective inhibitor of monoarthritis induced in mice with amidated glucose oxidase (aGO) and dose-dependently inhibits cobra-venom-factor-induced paw oedema in rats. Indomethacin and piroxicam are weakly active or ineffective in these models. The data indicate that ebselen is likely to be useful in the therapy of inflammatory conditions in which reactive oxygen species, such as peroxides, play an aetiological role.

Animals↗