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

This study was performed to investigate oxygen transport properties in whole blood (WB) of malaria-infected rats as well as in infected erythrocytes (IE) and noninfected erythrocytes (NIE) separated by density centrifugation. One week after inoculation with Plasmodium berghei, mean parasitemia was 26.5% and high correlations were found between parasitemia and hemoglobin concentration ([Hb]; r = -.902), mean cellular Hb concentration (MCHC; r = -.712), MetHb (r = .923), and base excess (r = -.922). Compared with control animals (C), the oxygen affinity was lower in WB under standard (pH 7.40) and simulated "in vivo" (pH 7.00) conditions (difference in P50, 5.7 and 5.1 mm Hg, respectively; 2P < .01, 2P < .05). In IE Hb and 2,3-biphosphoglycerate (2,3-BPG) concentrations were decreased (MCHC: IE 14.6 +/- 1.0, NIE 33.1 +/- 1.7 g/100 mL; [2,3-BPG]: IE 2.0 +/- 0.6, NIE 7.6 +/- 1.8 mmol/L), whereas [MetHb] and [ATP] were increased ([MetHb]: IE 19.0 +/- 3.7, NIE 0.7% +/- 0.8%; [ATP]: IE 33.5 +/- 2.4, NIE 6.2 +/- 1.0 mumol/g Hb). At pH 7.40, half-saturation oxygen tension (P50) was reduced in IE (29.6 +/- 2.6, NIE 39.2 +/- 5.4 mm Hg, 2P < .001), which correlates with lower [2,3-BPG], increased MetHb content, and higher intrinsic Hb-O2 affinity. However, at pH 7.00, the oxygen affinity was lower in IE when compared with NIE, which was most likely due to high [ATP] in IE. The resulting Bohr coefficients (BC) calculated for CO2 and lactic acid were extremely high in IE and low in NIE (at 50% O2-saturation BCCO2: IE -1.04 +/- 0.06, NIE -0.26 +/- 0.10, 2P < .001; BCLac: IE -0.82 +/- 0.16, NIE -0.47 +/- 0.07, 2P < .001), which was caused by different [2,3-BPG] and [ATP] as well as probably by structural changes of the Hb molecule. The O2 capacity was 14.1 mL per 100 mL erythrocytes in IE compared with 44.4 mL/100 mL in NIE. On the basis of the calculated arterio-venous O2 difference under "in vivo" conditions, the infected red blood cell fraction transports 30% of the O2 amount delivered to the tissues by the noninfected cells (IE 8.0, NIE 26.9 mL/100 mL red blood cells). We conclude that the O2 transport in malaria infected blood is not only affected by the degree of anemia but also by the percentage of infected erythrocytes.
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PMID:Oxygen transport properties in malaria-infected rodents--a comparison between infected and noninfected erythrocytes. 820 95

A 32-year-old woman in the 26th week of pregnancy became ill, 6 days after returning from a trip to Indonesia, with a fever up to 42 degrees C, haemolytic anaemia (haemoglobin 7.6 g/dl) and thrombocytopenia (7,000/microliters). She had not been on any malaria prophylaxis. Chloroquine, quinine and pyrimethamine, administered after macrogametocytes of Plasmodium falciparum had been found in the blood smear, eliminated the parasites from the peripheral blood, but respiratory failure and treatment-resistant pneumonia occurred, leading to the adult respiratory distress syndrome (Morel stage 4). Because of threatened intrauterine death (resulting from premature placental separation during artificial ventilation) the child was delivered by an emergency section. Despite extensive conventional therapeutic measures the mother's respiratory state progressively deteriorated so that extracorporeal membrane CO2 elimination was instituted on the 17th day. First signs of improvement in respiratory functions were noted after six days. The extracorporeal CO2 elimination was discontinued after twelve days, because artificial ventilation could now be adequately controlled. The woman was gradually weaned from the ventilator and discharged home without symptoms after a total of 11 weeks in hospital. Her child has not shown any neurological symptoms.
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PMID:[Acute respiratory failure in tropical malaria during pregnancy. Successful treatment using extracorporeal CO2 elimination]. 818 19

Mosquito responses to carbon dioxide were investigated in Noungou village, 30 km northeast of Ouagadougou in the Sudan savanna belt of Burkina Faso, West Africa. Species of primary interest were the main malaria vectors Anopheles gambiae s.s. and An.arabiensis, sibling species belonging to the An.gambiae complex. Data for An.funestus, An.pharoensis, Culex quinquefasciatus and Mansonia uniformis were also analysed. Carbon dioxide was used at concentrations of 0.04-0.6% (cf. 0.03% ambient concentration) for attracting mosquitoes to odour-baited entry traps (OBETs). The "attractiveness' of whole human odour was also compared with CO2 emitted at a rate equivalent to that released by the human bait. In a direct choice test with two OBETs placed side-by-side, the number of An.gambiae s.l. entering the trap with human odour was double the number trapped with CO2 alone (at the human equivalent rate), but there was no significant difference between OBETs for the other species of mosquitoes. When OBETs were positioned 20 m apart, again CO2 alone attracted half as many An.gambiae s.l. and only 40% An.funestus, 65% Ma.uniformis but twice as many An.pharoensis compared to the number trapped with human odour. The dose-response for all mosquito species was essentially similar: a linear increase in catch with increasing dose on a log-log scale. The slopes of the dose-response curves were not significantly different between species, although there were significant differences in the relative numbers caught. If the dose-response data are considered in relation to a standard human bait collection (HBC), however, the behaviour of each species was quite different. At one extreme, even the highest dose of CO2 did not catch more An.gambiae s.l. than one HBC. At the other extreme, the three highest doses of CO2 caught significantly more Ma.uniformis than did one HBC. An.pharoensis and Cx quinquefasciatus showed a threshold response to CO2, responding only at doses above that normally released by one man. An.funestus did not respond to CO2 alone at any dose in sufficient numbers to assess the dose response. Within the An.gambiae complex, An.arabiensis "chose' the CO2-baited trap with a higher probability than An.gambiae s.s. Also An.arabiensis, the less anthropophilic of the two species, was more abundant in CO2-baited OBETs than in human bait collections.
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PMID:Mosquito responses to carbon dioxide in a west African Sudan savanna village. 888 31

The efficiency with which mosquitoes transmit malaria is related to how closely associated they are with the human host. For example, the relative vectorial capacity of two species may be determined by differences in their degree of preference for human blood or in their degree of preference for blood-feeding indoors versus outdoors. Species complexes, such as Anopheles gambiae sensu lato, allow us to investigate how species differences in genetics, ecology and behaviour can lead to significant differences in vectorial capacity. The potential exists for identification of behaviour-regulating genes for exploitation by novel control measures. Close correlations have been demonstrated between certain behaviours and karyotypes in the An. gambiae s.l. complex, but the physiological basis for these correlations has yet to be determined. Recent evidence from behavioural studies suggests that differences in host preference may reflect differences in the relative responsiveness to CO2 and other, more specific, host odours.
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PMID:Genetics, ecology and behaviour of anophelines. 889 88

Carbon dioxide (CO2) is essential for the growth of intraerythrocytic malaria parasites to synthesize pyrimidine through CO2 fixation and to regulate intracellular pH. CO2 transport across the plasma membrane of erythrocytes is facilitated by carbonic anhydrase (CA). With the use of electron microscopy and CA-specific Hansson's stain, CA is found also in all the intraerythrocytic stages of Plasmodium falciparum. When CA inhibitors, including acetazolamide, potassium iodide, and sodium deoxycholate, were added to continuous culture of P. falciparum, they, particularly sodium deoxycholate, produced a marked reduction in parasitemia. These results explain the biochemical basis of some of the clinical conditions associated with malaria and strongly suggest that CA inhibitors have potential as a new class of antimalarials.
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PMID:The pivotal role of carbonic anhydrase in malaria infection. 948 77

In population-based studies it has been established that inherited deficiency of erythrocyte (E) glucose-6-phosphate dehydrogenase (G6PD) confers protection against severe Plasmodium falciparum (P falciparum) malaria. Impaired growth of parasites in G6PD-deficient E in vitro has been reported in some studies, but not in others. In a systematic analysis, we have found that with five different strains of P falciparum (FCR-3, KI, C10, HB3B, and T9/96), there was no significant difference in either invasion or maturation when the parasites were grown in either normal or G6PD-deficient (Mediterranean variant) E. With all of these strains and at different maturation stages, we were unable to detect any difference in the amount of P falciparum-specific G6PD mRNA in normal versus deficient parasitized E. The rate of 14C-CO2 production from D-[1-14C] glucose (which closely reflects intracellular activity of G6PD) contributed by the parasite was very similar in intact normal and deficient E. By contrast, in studies of phagocytosis of parasitized E by human adherent monocytes, we found that when the parasites were at the ring stage (ring-stage parasitized E [RPE]), deficient RPE were phagocytosed 2.3 times more intensely than normal RPE (P = .001), whereas there was no difference when the parasites were at the more mature trophozoite stage (trophozoite-stage parasitized E [TPE]). Phagocytic removal markers (autologous IgG and complement C3 fragments) were significantly higher in deficient RPE than in normal RPE, while they were very similar in normal and deficient TPE. The level of reduced glutathione was remarkably lower in deficient RPE compared with normal RPE. We conclude that impaired antioxidant defense in deficient RPE may be responsible for membrane damage followed by phagocytosis. Because RPE, unlike TPE, are nontoxic to phagocytes, the increased removal by phagocytosis of RPE would reduce maturation to TPE and to schizonts and may be a highly efficient mechanism of malaria resistance in deficient subjects.
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PMID:Early phagocytosis of glucose-6-phosphate dehydrogenase (G6PD)-deficient erythrocytes parasitized by Plasmodium falciparum may explain malaria protection in G6PD deficiency. 974 94

Intraerythrocytic malaria parasites meet part of their growth requirements by ingesting and digesting haemoglobin (Hb). To see whether this process is affected by Hb types, the growth and metabolism of Plasmodium falciparum in normal AA, heterozygous AS and homozygous SS erythrocytes were compared in this study. Parasites that have been adapted to continuous growth in AA and AS erythrocytes in vitro were used, and the cultures were incubated in an environment that contained 3% oxygen, 4% carbon dioxide and 93% nitrogen. It was found that exposure of the cultures to this gas mixture caused 5-10% of the AS and up to 90% of the SS erythrocytes to sickle. Parasite growth was essentially normal in the 3 cell types, although multiplication was significantly lower in SS than in AS and AA erythrocytes. Parasite metabolism was evaluated through measurement of haemozoin production. The mean quantity of haemozoin produced by the parasites in AA was comparable to that produced in AS, but significantly higher than that produced in SS erythrocytes. This finding suggests that P. falciparum metabolism is impaired in SS but not in AS erythrocytes. The impairment may be related to polymerization of Hb S.
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PMID:Malaria parasite metabolism in sickle cells. 1035 55

AnaeroPack Malaria Culture System (SUGIYAMA-GEN Co., Ltd.) using AnaeroPack.plas (5% O2, 5% CO2) and AnaeroPack.CO2 (15% O2, 6% CO2) was evaluated by comparing with the standard laboratory in vitro continuous culture technique. Two culture-adapted strains of Plasmodium falciparum, SGE-1 (chloroquine sensitive strain) and K1 (chloroquine resistant strain), were continuously cultured for 26 days in vitro under the 3 systems. The parasite proliferation curves under the different set systems were paralleled in both strains, which demonstrate that this AnaeroPack Malaria Culture System is useful for the culture-adapted strains of P. falciparum. Although further test using isolates from falciparum malaria patients should be carried out, the AnaeroPack Malaria Culture System seems promising for the culture in the field studies.
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PMID:[Continuous in vitro culture of Plasmodium falciparum using microaerophilic gas generators and portable incubator]. 1062 87

We have recently developed a method of in vitro cultivation of P. falciparum using a portable incubator and AnaeroPack.CO2 (Onda et al.), we applied semi-microtechnique drug susceptibility tests to the culture method to evaluate the system using several P. falciparum strains or isolates of different susceptibilities to chloroquine (SGE-1, FCR-3, K-1, Patient 1 and 2). The new method gave comparable results to those shown by the standard test employing a modular incubator chamber with standard gas composition of 5% O2, 5% CO2 and 90% N2. Many useful data on the epidemiology of drug resistant malaria such as the emergence of multi-drug resistant isolates could be collected by applying this new method to the field survey.
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PMID:[In vitro drug susceptibility test of Plasmodium falciparum using a portable thermostat and CO2 gas generator]. 1062 88

Present global temperatures are in a warming phase that began 200 to 300 years ago. Some climate models suggest that human activities may have exacerbated this phase by raising the atmospheric concentration of carbon dioxide and other greenhouse gases. Discussions of the potential effects of the weather include predictions that malaria will emerge from the tropics and become established in Europe and North America. The complex ecology and transmission dynamics of the disease, as well as accounts of its early history, refute such predictions. Until the second half of the 20th century, malaria was endemic and widespread in many temperate regions, with major epidemics as far north as the Arctic Circle. From 1564 to the 1730s the coldest period of the Little Ice Age malaria was an important cause of illness and death in several parts of England. Transmission began to decline only in the 19th century, when the present warming trend was well under way. The history of the disease in England underscores the role of factors other than temperature in malaria transmission.
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PMID:From Shakespeare to Defoe: malaria in England in the Little Ice Age. 1082 24


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