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

Gametogenesis in Plasmodium gallinaceum involves bicarbonate-dependent processes and requires a continuous supply of glucose (presumably as an energy source). Emergence and exflagellation of gametocytes, in vitro, occur independently of the CO2 tension but are rigidly correlated with the pH of the external medium. In bicarbonate-saline gametogenesis is initiated only if the pH exceeds 7.7. Our results suggest that gamete development of malaria parasites is stimulated when infected blood is exposed to air because the decrease in the CO2 tension of the blood causes its pH to rise.
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PMID:Gamete development in malaria parasites: bicarbonate-dependent stimulation by pH in vitro. 2 12

The aim of this study was to find optimal conditions for the membrane feeding technique to obtain maximum infection rates of mosquitoes with Plasmodium yoelii nigeriensis. The results show that the malaria parasite Plasmodium yoelii nigeriensis is most infective to Anopheles stephensi mosquitoes on day 3 of the infection in the mice, 1 day before the peak of parasitaemia. The mortality rate of the mosquitoes fed on mice on day 3 after infection was the highest as compared to mosquitoes fed on other days after infection. Gametocytes from mice 3 days after infection were fed to mosquitoes by three different membrane feeding methods. The results indicate that feeding during the first 10 min after blood collection gave the highest infection rates. Keeping the blood meal at a pH of 7.2 yields higher infection rates than keeping it at pH of 8.5. Stirring of the blood and supplying it with CO2 is not necessary when feeding of the mosquitoes is completed within the first 10 min after collection of the blood.
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PMID:Trials to infect Anopheles stephensi with Plasmodium yoelii nigeriensis by the membrane feeding technique. 145 66

Plasmodium falciparum-infected human erythrocytes grown in vitro do not release 14CO2 when incubated in the presence of [1-14C]glutamate, despite the presence of glutamate dehydrogenase, implying the absence of alpha-ketoglutarate dehydrogenase activity and the lack of functional tricarboxylic acid cycle in the human malaria parasite. Cultures incubated with [14C]bicarbonate, however, fix CO2 into acid-stable metabolites; CO2 fixation proceeds linearly for up to two hours after an initial brief lag and may contribute appreciably to the metabolism of the parasite.
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PMID:Absence of alpha-ketoglutarate dehydrogenase activity and presence of CO2-fixing activity in Plasmodium falciparum grown in vitro in human erythrocytes. 614 96

Mosquitos were collected in three villages on the western coast of the island of Palawan, Republic of the Philippines, from June 1986 to April 1987, using 3 methods. Anopheles flavirostris, the primary malaria vector, was the most abundant of the Anopheles collected biting man, ranging from a low of 83.9% in June (16.1 collected/man/night) to 98.3% in April (29.1 collected/man/night). The number of species was greatest in the animal-baited traps with 54 species detected. The CO2-baited CDC light traps were neither effective nor economically feasible as a monitoring tool for malaria vectors at this site. People were at risk from An. flavirostris bites throughout the night except 1800-2000 which are low-risk hours. Anopheles flavirostris is slightly exophagic during most of the year, but moderately endophagic during the hot, dry season.
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PMID:A survey of the mosquitos (Diptera: Culicidae) of Napsan, Palawan, Republic of the Philippines. 790 82

The CO2-enriched atmosphere required for the short-term growth of human malaria parasites can be provided by a small, disposable environmental bag that is readily available in many laboratories. This provides an ideal alternative means for incubating malaria parasites when specially-prepared gas mixtures, air-tight incubation chambers or candle-jars are unavailable or they are too expensive or impractical to use. Such an environmental bag should encourage greater use of the WHO in vitro test for assessing the drug susceptibility of malaria parasites.
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PMID:Disposable environmental chamber for assessing the drug susceptibility of malaria parasites. 813 76

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


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