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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Hypoglycaemia and lactic acidosis are important manifestations of severe falciparum malaria. To investigate hepatic gluconeogenesis in acute falciparum malaria, liver blood flow and galactose clearance were estimated in seven adult patients with moderately severe infection and seven patients with severe infection (three of whom died later). Nine patients were restudied in convalescence. 2. Liver blood flow, determined from the plasma clearance of Indocyanine Green, was lower in acute illness than in convalescence [16.1 (7.0) versus 23.9 (7.2) ml min-1 kg-1, mean (SD)], but this difference was not statistically significant (P = 0.15). There was a significant inverse correlation between admission venous plasma lactate concentrations and the liver blood flow estimated from the clearance of Indocyanine Green (rs = 0.71, P = 0.004). 3. The plasma clearance of galactose after intravenous injection was similar in the acute [15.4 (4.90) ml min-1 kg-1] and convalescent study [12.8 (2.1) ml min-1 kg-1]. The ratio of galactose clearance to Indocyanine Green clearance was significantly higher in acute disease [1.41 (0.51)] than in convalescence [0.70 (0.34)], largely because of the elevated ratios in severely ill patients [1.48 (0.50)]. 4. The rise in blood glucose concentration after galactose administration was significantly higher during acute illness [1.48 (0.72) mmol/l] than in convalescence [0.67 (0.41) mmol/l, P = 0.022], but the insulin response was similar, indicating reduced tissue insulin sensitivity. There was no significant change in the plasma concentrations of other metabolites (lactate, pyruvate, alanine and triacylglycerol) in either study. 5. These results suggest that the segment of the glycolytic pathway between galactose and glucose is unimpaired in patients with severe falciparum malaria.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hepatic blood flow and metabolism in severe falciparum malaria: clearance of intravenously administered galactose. 131 Sep 19

The multiplication of malaria parasites within red blood cells is energy dependent. Since these parasites lack a functional tricarboxylic acid cycle, the energy needs of the parasite are met by anaerobic glycolysis of exogenous glucose. High levels of glycolytic enzymes such as fructose-1,6-diphosphate aldolase, phosphoglycerate kinase and pyruvate kinase have been detected in infected erythrocytes. Here we report a 4-9 times increase in glucose phosphate isomerase (GPI) activity of infected erythrocytes over that of normal erythrocytes. This increase is of parasitic origin, as additional enzyme bands were observed in lysates of infected erythrocytes. The expression of GPI parallels parasite maturation and reaches a maximum at the trophozoite/schizont stage. Two distinct but closely related activity patterns consisting of 3-4 GPI isoenzymes (not shown in normal erythrocytes) with neutral to weakly acidic isoelectric points were observed in 6 P. falciparum isolates tested by isoelectric focusing. The purified P. falciparum GPI has an apparent size of 66 kDa. No size variation was observed in the 6 P. falciparum isolates studied. Furthermore, antiserum raised against this protein in BALB/c mice specifically inhibits parasite encoded GPI activity while no effect was observed on host enzyme activity.
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PMID:Identification and purification of glucose phosphate isomerase of Plasmodium falciparum. 143 56

Hexokinase, a key glycolytic enzyme, is involved in the initial phosphorylation reaction of imported glucose and specific blocking of this activity may therefore arrest the development of malaria parasites. We describe here the cloning of a single copy hexokinase gene of Plasmodium falciparum (PfHK) from cDNA or genomic DNA libraries. The deduced amino acid sequence of PfHK has 26% identity with human hexokinase I and its predicted molecular mass assigns it as an invertebrate type isoenzyme of hexokinase. A single 1.5-kb exon is translated from a 3-kb mRNA in asexual stages of the parasite. In contrast to aldolase and GPI, the gene for this glycolytic enzyme is located on chromosome 8. Poly- and monoclonal antibodies against recombinant PfHK support our cloning results at the protein level as they detect a protein of the predicted size and isoelectric point by Western blotting in parasite protein samples. Moreover, polyclonal rabbit IgG against recombinant PfHK partially inhibits the hexokinase activity of a P. falciparum lysate which provides direct proof that the gene cloned encodes hexokinase of the parasite.
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PMID:Molecular analysis of Plasmodium falciparum hexokinase. 147 5

Almost all of the important enzymes of glycolytic sequence were studied in isolated schizonts of Plasmodium knowlesi as well as in normal and P. knowlesi parasitized rhesus red blood cells. Significant activities of all the glycolytic enzymes assayed were observed in cell-free schizonts and the levels of all were found to be considerably elevated in infected host erythrocytes, confirming that the consumption of glucose is dramatically increased in host red cells, consequent to malaria infection.
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PMID:Studies on glycolytic enzymes of Plasmodium knowlesi, a simian malaria parasite, and infected host erythrocytes. 152 Sep 83

Chloroquine inhibits the growth of susceptible malaria parasites at low (nanomolar) concentrations because of an energy-requiring drug-concentrating mechanism in the parasite secondary lysosome (food vacuole) which is dependent on the acidification of that vesicle. Chloroquine resistance results from another energy-requiring process: efflux of chloroquine from the resistant parasite with a half-time of 2 min. Chloroquine efflux is inhibited reversibly by the removal of metabolizable substrate (glucose); it is also reduced by the ATPase inhibitor vanadate. These results suggest that chloroquine efflux is an energy-requiring process dependent on the generation and hydrolysis of ATP. Chloroquine efflux cannot be explained by differences in drug accumulation between chloroquine-susceptible and -resistant parasites because the 40-50-fold difference in initial efflux rates between -susceptible and -resistant parasites is unchanged when both parasites contain the same amount of chloroquine. Although chloroquine efflux is phenotypically similar to the efflux of anticancer drugs from multidrug-resistant (mdr) mammalian cells, it is not linked to either of the mdr-like genes of the parasite.
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PMID:Energy dependence of chloroquine accumulation and chloroquine efflux in Plasmodium falciparum. 153 Nov 76

To determine the incidence of hypoglycaemia in children suffering from severe falciparum malaria, 23 patients from Rourkela (Orissa), were investigated. Plasma glucose and immunoreactive insulin were estimated before and at hourly intervals during quinine infusion. No child had hypoglycaemia at the time of admission. Correlation between parasite count and prequinine plasma glucose was not significant. In the period of quinine infusion, 20 patients showed fall in plasma glucose during all the three hours (P less than 0.05, P less than 0.01, P less than 0.01 at the end of 1st, 2nd, and 3rd h respectively) but the decrease to hypoglycaemic level (plasma glucose less than or equal to 40 mg/dl) was observed in only one child. Concomitant increase in plasma insulin was noticed in 18 of these patients. Decrease in plasma glucose and increase in plasma insulin was found to correlate well (r-0.78, P less than 0.001). Hypoglycaemia was found to be an infrequent complication of severe falciparum malaria in children from the area studied. Though decrease in plasma glucose was observed after quinine infusion, it was less severe and did not reach the hypoglycaemic level.
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PMID:Incidence of hypoglycaemia in children with severe Plasmodium falciparum malaria around Rourkela, Orissa state. 160 75

Multiplication of the human malaria parasite Plasmodium falciparum within red blood cells is an energy-dependent process and glucose consumption increases dramatically in infected red blood cells (IRBC) versus normal red blood cells (NRBC). The major pathway for glucose metabolism in P. falciparum IRBC is anaerobic glycolysis. Phosphoglycerate kinase (PGK) is one of the key enzymes of this pathway as it generates ATP. We found that the PGK specific activity in P. falciparum IRBC is seven times higher than that in NRBC. The parasitic origin of the increase in PGK activity is confirmed by isoelectric focusing. Indeed, two P. falciparum isoenzymes with neutral isoelectric points were detected. P. falciparum PGK in purified form has a molecular mass of 48 kDa. Antiserum raised against purified P. falciparum PGK specifically recognizes the 48-kDa protein band in P. falciparum and also reacts with P. berghei and P. yoelii IRBC lysates but does not cross-react with PGK associated with NRBC.
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PMID:Plasmodium falciparum: identification and purification of the phosphoglycerate kinase of the malaria parasite. 163 56

The effects of antimalarial treatment on the blood oxygen-transporting properties and on the tissue hypoxia were investigated in severe murine malaria, using mice infected with Plasmodium berghei (NK65). Five week old male ddY mice were inoculated intraperitoneally with 1 X 10(7) of P. berghei-infected red blood cells and treated with Fansidar (20 mg/kg body weight sulfadoxine and 1 mg/kg body weight pyrimethamine orally) on day 5 after inoculation. Parasitemia in these mice decreased rapidly on day 1 after treatment. Blood hemoglobin concentration, however, decreased on days 1 and 2 of treatment, then began to increase. The actual oxygen equilibrium curve (OEC) in vivo (actual pH; actual Pco2; 36.5 degrees C) was calculated from the measured OEC and the results of blood gas analysis. Looking from arterial and venous Po2 of each group, blood oxygen-transporting properties decreased markedly on day 2 of treatment. This decrease resulted mainly from the decrease of hemoglobin concentration and also partly from the raised hemoglobin affinity for oxygen. Adenosine triphosphate concentration in liver tissues, however, began to increase on day 1 of treatment. Adenylate energy charge of liver tissues also recovered on day 1. Blood glucose concentration began to increase and blood lactate concentration began to decrease simultaneously on day 1 of treatment. Glucose concentration in liver tissues, in contrast, decreased on days 1 and 2 of inoculation. Lactate concentration in liver tissue decreased earlier on day 1. These data indicate that tissue hypoxia was removed on day 1 following antimalarial treatment although blood oxygen-transporting properties decreased on days 1 and 2 after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Trends of tissue hypoxia following chemotherapy of acute malaria in mice]. 178

Quinine is widely used for the treatment of severe and complicated malaria, although resistant strains of Plasmodium falciparum may occur. The drug has been incriminated as a cause of hypoglycaemia in some malaria patients. To determine if quinine has untoward metabolic effects during treatment of severe and complicated malaria we have studied the effects of quinine on blood glucose and intermediary metabolites, serum insulin, C-peptide, plasma glucagon and non-esterified fatty acids in 97 children with severe malaria in Dar es Salaam. All patients responded clinically. No patient developed hypoglycaemia while on quinine therapy given as 10 mg/kg in 10 ml/kg of 5% dextrose infused over 4 h every 8 h. Endogenous insulin secretion, as reflected by C-peptide levels, increased after 4 h but insulin levels did not change significantly. Blood lactate, 3-hydroxybutyrate, plasma non-esterified fatty acids and plasma glucagon all fell appropriately during treatment. We conclude that quinine, when administered at the recommended dose and rate, does not disrupt blood glucose homeostasis, and is still the drug of choice for severe and complicated malaria in children.
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PMID:The metabolic effects of quinine in children with severe and complicated Plasmodium falciparum malaria in Dar es Salaam. 129 76

Because hypoglycaemia is common in severe malaria, intravenous glucose is often given empirically to patients on admission to hospital. To investigate the metabolic response to rapid glucose injection in acute malaria, 50 ml of 50% w/v (25 g) dextrose was given over 5 min to 10 adult patients (7 males, 3 females; mean age 30 years) with acute falciparum malaria. Five patients with severe infections were studied between doses of intravenous quinine; 5 cases were uncomplicated and previously untreated. The patients with severe malaria had lower pre-injection plasma glucose concentrations than patients with uncomplicated infections (mean +/- standard deviation, 4.2 +/- 0.9 vs 5.8 +/- 1.1 mmol/litre, 2P less than 0.015). However, peak glucose concentrations (18.6 +/- 4.8 vs 17.0 +/- 2.4 mmol/litre) and integrated responses (AUC0-245 min) were similar in the groups (2P greater than 0.1 in each case), and pre- and post-injection plasma insulin concentrations and AUC0-245 min values were also not significantly different (2P greater than 0.05 in each case). No 'rebound' hypoglycaemia was observed. The patients with severe malaria had higher peak plasma lactate concentrations than the uncomplicated patients (2.5 +/- 0.7 vs 1.5 +/- 0.9 mmol/litre, 2P less than 0.05), but the highest plasma lactate achieved and the greatest maximum post-injection rise were only 3.8 and 0.8 mmol/litre respectively. The average maximum reduction in plasma potassium after injection was 0.2 mmol/litre at 35 min. These data suggest that injections of hypertonic dextrose given empirically in conventional doses to non-acidotic patients with acute, severe malaria are not harmful, but the metabolic response in patients with an established acidosis remains unknown.
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PMID:The metabolic response to rapid intravenous glucose injection in acute falciparum malaria. 188 67


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