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Biomedical subjects

Y Yuthavong

Publications and source records attributed to Y Yuthavong.

At least 73 records · Page 4Linked to original sources
PubMed1983

Stimulation of Ca2+ uptake in the human liver fluke Opisthorchis viverrini by praziquantel.

45Ca2+ uptake by the human liver fluke Opisthorchis viverrini is enhanced by praziquantel. The drug-induced 45Ca2+ uptake was dependent on the presence of Ca2+ and was attenuated in the presence of 10 mM Mg2+. La3+ and vanadate at concentration of 1 mM partially reduced the amount of 45Ca2+ uptake into the liver fluke in response to praziquantel treatment. The stimulating effect of praziquantel was eliminated in the presence of 10 microM verapamil. These findings suggest that praziquantel increases the permeability of the liver fluke tegument to Ca2+ probably by interfering with the mechanism that regulates Ca2+ binding or transport across the tegumental membrane.

Animals↗
PubMed1983

Enhanced Ca2+ uptake by mouse erythrocytes in malarial (Plasmodium berghei) infection.

Erythrocytes from Plasmodium berghei-infected mice on incubation either in plasma or artificial isotonic media showed an increase in uptake of 45Ca2+ compared with erythrocytes from uninfected mice. Infected cells (55% parasitaemia) incubated in plasma from normal or infected mice gave uptake rates of 9.8 and 8.1 nmol h-1 per 10(10) cells, assuming equilibrium between added 45Ca2+ and plasma Ca2+. Uptake rates of erythrocytes from infected mice were increased in the presence of glucose, with a rate of 15.0 nmol h-1 per 10(10) cells (52-58% parasitaemia) at 5 mM glucose, compared with 1.5 nmol h-1 per 10(10) cells in the absence of glucose. The enhancement of 45Ca2+ uptake was more pronounced with increasing parasitaemia, and in the fraction relatively enriched with erythrocytes carrying mature parasites. It is likely, therefore, that the enhancement is due to changes in membrane permeability accompanying parasite development. Enhanced haemolysis accompanied 45Ca2+ uptake of erythrocytes carrying mature parasites, but not of those carrying young parasites or uninfected erythrocytes. The possible role of an altered Ca2+ status in erythrocyte pathophysiology during malarial infection is discussed.

Animals↗
PubMed1983

Analysis of DNA from various species and strains of malaria parasites by restriction endonuclease fingerprinting.

1. DNA from various rodent Plasmodium species and strains and from P. falciparum, the human parasite, were analysed by agarose gel electrophoresis following digestion with restriction endonucleases EcoRI, Hind III and Bam Hl. Complex patterns of ethidium-stained bands were obtained, which showed similarity but reproducible differences among the various parasite species (P. chabaudi, P. yoelii, P. berghei and P. falciparum). 2. No differences could be discerned among two cloned strains of P. yoelii (33X, and YM) and among pyrimethamine-resistant (pyrimethamine + chloroquine)-resistant and the drug-sensitive P. chabaudi clone from which the resistant clones were derived. 3. From the known complexity of Plasmodium DNA it could be concluded that the visible bands were derived from repetitive DNA fractions.

Animals↗
PubMed1983

Reduction of Ca2+ uptake induced by ionophore A23187 of red cells from malaria (Plasmodium berghei)-infected mice.

The Ca2+ ionophore A23187 has much less capacity to induce Ca2+ uptake of red cells from P. berghei-infected mice than of cells from normal mice. The reduction in Ca2+ uptake occurs in both uninfected and infected cells at all stages in the infected blood, as shown from experiments with cells separated on colloidal silica density gradient. Measurement of the ionophore concentration in the medium reveals that the ionophore is partitioned into red cells from infected blood to a greater extent than cells from normal blood. The reduction in A23187-induced Ca2+ uptake may be due to difference in the interaction of red cell membrane with the ionophore, and its already high Ca2+ permeability.

Animals↗
PubMed1983

Mechanism of enhanced fusion capacity of mouse red cells infected with Plasmodium berghei.

Plasmodium berghei-infected mouse red cells have enhanced fusion capacity as triggered by addition of poly(ethylene glycol) in the presence of Ca2+. The uptake of Ca2+ in P. berghei-infected cells is greater than in normal cells, and the difference in Ca2+ uptake was found to be enhanced in the presence of poly(ethylene glycol). Fusion of normal and P. berghei-infected red cells by poly(ethylene glycol) was significantly inhibited by N-tosyl-L-lysylchloromethyl ketone and phenylmethylsulphonyl fluoride. In addition, ethyleneglycolbis(aminoethylether)tetra-acetate, N-ethylmaleimide, iodoacetamide, cystamine and tetrathionate also prevented fusion in both systems. In contrast, N-tosyl-L-phenylalanylchloromethyl ketone and N-tosyl-L-arginine methyl ester did not inhibit cell fusion. The latter enhanced fusion of infected cells but was without effect on normal cells. These results indicate that a Ca2+-activated thiol proteinase may be involved in membrane fusion in malaria-infected as well as in normal red cells. However, differences in the effect of proteinase inhibitors and substrate on fusion and Ca2+ entry show that the processes leading to fusion may not be identical.

Animals↗
PubMed1982

Heterogeneity in filterability of erythrocytes from malaria (Plasmodium berghei)-infected blood.

Erythrocytes from Plasmodium berghei-infected blood show a decrease in deformability with increasing parasitaemia, as measured by filterability through polycarbonate sieves. A major fraction of cells carrying mature parasites and a smaller fraction carrying ring-stage parasites account for the obstruction of filtration, while the remaining infected cells do not contribute to the decrease in filterability. The relation of filterability to metabolic status in infected cells is discussed.

Animals↗
PubMed1980

Enhanced fusion capacity of malaria (Plasmodium berghei)-infected mouse red cells.

The capacity of normal and malaria-infected mouse red cells to undergo fusion was investigated by phase contrast microscopy. The fusion of mouse red cells induced by 50% w/w poly(ethylene glycol)-6000 in the presence of Ca+2 is enhanced by P. berghei infection. Cells carrying parasites in the ring form stage and early trophozoite stage show slightly higher fusion induced by dimethyl sulphoxide and Ca+2 than those carrying parasites in trophozoite and schizont stages.

Animals↗
PubMed1979

Alterations in membrane proteins of mouse erythrocytes infected with different species and strains of malaria parasites.

1. The membrane fraction, prepared by hypotonic lysis, of mouse red cells infected with Plasmodium berghei, P. yoelii YM, P. yoelii 17 X, P. yoelii 33 X, P. vinckei or P. chabaudi shows significant alterations from normal in protein composition as observed by dodecylsulphate-polyacrylamide gel electrophoresis. 2. There is a reduction in intensity of various protein bands, notably bands I and II (spectrin), of membranes prepared from infected red cells. 3. New bands are observed as a result of infection, the intensity and location of which depend on the parasite species and strain. A new band of apparent molecular weight 150,000 appears with a strong intensity in P. yoelii YM infection, with a moderate intensity in P. berghei infection, and with a weak intensity in P. vinckei and P. chabaudi infection. In P. yoelii 17X and 33X infection, multiple weak bands are seen in the molecular weight range 120,000-210,000.

Animals↗
PubMed1979

Relation between low erythrocyte acetylcholinesterase activity and membrane lipids in paroxysmal nocturnal haemoglobinuria.

Acetylcholinesterase of intact erythrocytes, their ghost and salt soluble extracts obtained from patients with paroxysmal nocturnal haemoglobinuria (PNH) does not differ from normal with respect to Km values for acetylthiocholine, and Ki values for phenyltrimethylammonium iodide. However, the enzyme from PNH sources has lower V max values than normal, has different thermal stability from normal, has less distinctive transition temperature in the Arrhenius plots, and is less subject to inhibition by stearic acid. These results and that from comparison of activation of deoxycholate-extracted enzyme by lipids from normal erythrocytes suggest that the low acetylcholinesterase activity in PNH erythrocytes is due, at least in part, to alteration in the lipid environment of the enzyme.

Acetylcholinesterase↗
PubMed1979

An examination of complement proteins on membranes of paroxysmal nocturnal haemoglobinuria (PNH) and PNH-like red cells.

Proteins obtained from membranes of PNH erythrocytes and of red cells treated with 2-aminoethylisothiouronium bromide (AET) following lysis in acidified serum (Ham's test) were compared by sodium dodecylsulphate-polyacrylamide gel electrophoresis. The peptide patterns were identical, providing support that AET-treated red cells afford a suitable experimental substitute for PNH red cells in studies involving complement fixation.

Blood Protein Electrophoresis↗
PubMed1978

Rate constants of individual steps in papain-catalysed reactions.

Rate constants for acylation of papain (EC 3.4.22.2) by specific substrates and its subsequent deacylation are derived from kinetic analysis of the reactions in the presence of aminoacetonitrile and methanol. Methyl and ethyl hippurate and methyl N-benzyloxycarbonylglycinate have marginally higher values of rate constants for acylation than for deacylation, while the reverse is true for ethyl N-benzoyl-L-arginate. Both acylation and deacylation are rate-determining for these substrates, while only deacylation irate-determining for methyl-N-acetyl-L-phenylalanylglycinate. Deacylation is the only rate-determining step for p-nitrophenyl esters of hippuric acid, N-benzyloxycarbonylglycine and N-acetyl-L-phenylalanylglycine. These results are discussed in relation to those from inactivation of the enzyme by alkylating agent in the presence of substrate.

Kinetics↗