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A H Mendis

Publications and source records attributed to A H Mendis.

27 records · Page 2Linked to original sources
PubMed1985

Evidence for the occurrence of respiratory electron transport in adult Brugia pahangi and Dipetalonema viteae.

Mixed-sex adult stages of Brugia pahangi and Dipetalonema viteae, in the absence of exogenous substrate, consumed oxygen at rates of 4.18 +/- 0.38 and 2.12 +/- 0.20 ngatoms O2 min-1 mg-1 dry wt. respectively. When calculated on a unit dry weight basis the endogenous O2 consumption rates (E-QO2) of mature adult male macrofilariae of B. pahangi and D. viteae were significantly greater than those of mature females, although the E-QO2 calculated per individual worm was essentially similar irrespective of sex. When assayed as separate unisexual groups, the oxygen uptake of male and female macrofilariae of both species was inhibited by classical inhibitors of respiratory electron transport (RET), and showed classical substrate bypass phenomena in response to succinate and ascorbate, N,N,N',N'-tetramethyl-p-phenylenediamine with respect to the RET inhibitors rotenone (inhibitor of complex I) and antimycin A (inhibitor of complex III). Since male worms elicited similar responses to the classical RET inhibitors as did mixed-sex and/or adult female populations, the possibility that developmental stages contained within the female filariids were contributing in any significant manner to the overall responses observed with the RET inhibitors can be discounted. Such responses as observed with live-intact macrofilariae are normally elicited only by mitochondrial preparations and suggest that the cuticles of both species are permeable to rotenone, succinate, antimycin A, N,N,N',N'-tetramethyl-p-phenylenediamine, azide and cyanide. The uncoupler 2,4-dinitrophenol stimulated the endogenous rate of oxygen consumption (E-QO2) of intact B. pahangi at 33-160 microM, indicating the probable occurrence of RET-coupled oxidative phosphorylation. Higher concentrations of 2,4-dinitrophenol proved inhibitory. Respiratory studies on subcellular fractions substantiated the responses elicited by the intact parasites, suggesting the presence of antimycin A-sensitive and -insensitive RET pathways capable of utilising alpha-glycerophosphate, succinate, and malate as substrates. Both B. pahangi and D. viteae macrofilariae therefore probably possess branched RET-pathways bifurcating on the substrate side of RET-complex III. The rates of substrate oxidation in terms of QO2 mg-1 mitochondrial protein compare well with those observed with other nematode parasites.

Animals↗
PubMed1984

The occurrence of ecdysteroids in the cestode, Moniezia expansa.

The occurrence of free ecdysteroids in the sheep cestode, Moniezia expansa, was demonstrated. Significant amounts of conjugated ecdysteroids were not detected. Characterization of the free hormones by high-performance liquid chromatography monitoring fractions by radioimmunoassay, and by gas chromatography/mass spectrometry (selected ion monitoring) indicated the presence of ecdysone, 20-hydroxyecdysone and 20,26-dihydroxyecdysone. Analysis of the ecdysteroids by radioimmunoassay in segments along part of the strobila indicated that the anterior parts contained the greatest amount of hormone. GC/MS (SIM) analysis of the hormones in a strobilar segment containing the most mature proglottids suggested the presence of several ecdysteroid metabolites.

Animals↗
PubMed1984

Substrates respired by mitochondrial fractions of two isolates of the nematode Aphelenchus avenae and the effects of electron transport inhibitors.

Electron transport has been assayed and compared in two isolates (M and F) of the free-living (model) nematode Aphelenchus avenae. Of the substrates tested only alpha-glycerophosphate and succinate were utilised to any significant extent by both isolates. Comparative data on respiratory rates, respiratory control ratios and ADP:O ratios for various substrates are given. Succinate oxidation by isolate-F mitochondria was ca 80-90% sensitive to antimycin A while that of isolate M was almost completely refractory to antimycin A. The response to other electron transport inhibitors suggests the operation of (a) azide/cyanide sensitive, (b) azide/salicylhydroxamic acid (SHAM) insensitive but carbon monoxide sensitive and (c) SHAM-sensitive terminal oxidases to varying degrees in the mitochondria of these two isolates of A. avenae.

Animals↗
PubMed1983

Ecdysteroids in adults of the nematode, Dirofilaria immitis.

Adult males and females of the dog heartworm, Dirofilaria immitis, were extracted separately and, following separation of the free and conjugated ecdysteroid fractions, the conjugates were hydrolysed enzymically. Both the ecdysteroids released by hydrolysis of the conjugates and the free hormones were further purified and analysed by a combination of radioimmunoassay, thin-layer chromatography and high-performance liquid chromatography monitoring fractions by radioimmunoassay, and by gas-liquid chromatography/mass spectrometry (selected ion monitoring). Both males and females contained free and conjugated ecdysteroids. Evidence was obtained for the presence of ecdysone, 20-hydroxyecdysone, 20,26-dihydroxyecdysone and possibly ponasterone A. The possible parallel between ecdysteroid endocrinology in nematodes and insects is discussed.

Animals↗
PubMedDate not supplied

Eosinophils and major basic protein damage but do not detach human amniotic epithelial cells.

Damage and detachment of epithelial cells is thought to contribute to the pathologenesis of asthma. Both eosinophils and neutrophils are found in asthmatic airways and several studies have suggested that eosinophils may be responsible for the epithelial cell detachment of asthma. To compare the capacity of purified human eosinophils and neutrophils to mediate epithelial cell detachment, we utilized a human amniotic epithelial cell-basement membrane model that we have recently described. Activated eosinophils induced little detachment at 4 h (less than 10% detachment), which contrasted with that seen with equivalent numbers of identically handled neutrophils (29 +/- 6% detachment, p less than .05). In contrast, eosinophils did induce damage to epithelial cells to an extent similar to neutrophils when assessed using a 51Cr release assay (17 +/- 6% and 18 +/- 9% release of 51Cr, respectively). When purified preparations of the major eosinophil-derived protein major basic protein (MBP) were studied, similar effects on epithelial cells were observed, i.e., damage (77 +/- 13% release of 51Cr) without detachment (less than 5% cell detachment). These data suggest that neutrophils are more effective in inducing detachment of human epithelial cells, whereas both eosinophils and neutrophils damage human epithelial cells.

Amnion↗