Malaria Obstacles and Opportunities (1991) / Chapter Skim
Currently Skimming:
Pages 90-117
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 90... ...
6Parasite Biology WHERE WANT TO BE IN THE YEAR 2010 For centuries, malaria parasites have successfully evaded the biological defenses of their human hosts. Researchers are perplexed by the complexity of these organisms, and many questions remain un-answered.
|
From page 91... ...
Depending on the developmental stage and species, malaria parasites can be spherical, ring shaped, elongated, or crescent shaped, and can range in size from 1 to 20 microns in diameter (1 micron equals 1 millionth of a meter or approximately 125,000 of an inch)
|
From page 92... ...
It is not clear how the parasite arrives at the surface of the hepatocytes, since liver cells are not in direct contact with the blood. Also, although many mechanisms have been postulated, details of how the parasites invade liver cells remain obscure (Miller, 1977)
|
From page 93... ...
provide some insight their roles (Coppel et al., 1987)
|
From page 94... ...
dioxide, pH, and a mosquito exflagellation factor, are thought to contribute to the maturation of gametocytes. Male microgametes are released during a process called exflagellation.
|
From page 95... ...
heme derived from hemoglobin. Although the chemistry of this complex is becoming better understood (Goldie et., al 1990; Slater et al.,1991)
|
From page 96... ...
the parasite are focused on supporting this enormous reproductive effort. The relatively recently acquired ability to cultivate P
|
From page 97... ...
that incorporation of labeled purines into DNA begins approximately 30 hours after merozoite invasion and increases logarithmically for another 14 to 18 hours, when schizogony is completed. Because erythrocytes contain considerable concentrations of amino acids and vitamins that may be important to parasite development, it is difficult to determine in experimental settings whether decreased parasite viability due to nutritional factors is a result of effects on the parasite itself or on the red blood cell.
|
From page 98... ...
other parasitic protozoans and all parasitic worms so far studied, has rather limited terminal respiration (Scheibel, 1988)
|
From page 99... ...
known to be microaerophilic and highly susceptible to oxidant stress, and prevents the cells from circulating through the spleen, where they would be destroyed. Infections with P
|
From page 100... ...
been determined. Table 6-1 outlines several important erythrocyte membrane alternations caused by parasite-derived antigens (Howard, 1988; Petersen et al., 1990)
|
From page 101... ...
Parasite Genetic Diversity There is considerable genetic diversity among malaria parasite populations (Fenton and Walliker, 1990; Kemp et al., 1990)
|
From page 102... ...
minor sequence differences (Coppel et al., 1985; Hope et al., 1985; Stahl et al., 1986; Simmons et al., 1987; Weber et al., 1988; Thomas et al., 1990)
|
From page 103... ...
suggestive of antigenic variation in P falciparum, it is not known how important this mechanism may be to malaria infections and disease.
|
From page 104... ...
metabolism, including lactate dehydrogenase (Simmons et al., 1985) and aldolase, which is of interest also as a potentially protective antigen (Certa et al., 1988; Dobeli et al., 1990)
|
From page 105... ...
bottlenecks that hinder efforts to control malaria result from a lack of basic information on the biology, physiology, and biochemistry of the parasite itself. If true progress is to be in understanding and controlling malaria, more scientists who appreciate and are interested in the biology of the malaria parasite need to be trained.
|
From page 106... ...
RESEARCH FOCUS: The genetic control of metabolic switches that allow the parasite to rapidly adapt from warm-blooded to cold-blooded hosts. The nutritional biochemistry and developmental events of sporogony are areas of study that could prove useful in new control strategies aimed at the mosquito host.
|
From page 107... ...
Physiology and Biochemistry The mitochondrion, an organelle essential to parasite survival, is the target of a number of antimalarial antibiotics. These antibiotics, while clinically useful, were formulated for used against bacterial infections but could be better focused to kill malaria parasites if more were known about the biochemistry of the parasite mitochondrion.
|
From page 108... ...
genes, and of chloroquine resistance genes in particular, do not explain the apparent lack of resistance seen with many other quinoline-containing antimalarial drugs. The danger is that newly developed antimalarial drugs may be clinically useless by the time their mechanism of action is discovered.
|
From page 109... ...
coli virtually impossible. Knowing the number and location of genes within the parasite DNA, and the proteins produced by each, would greatly aid efforts at understanding parasite function.
|
From page 110... ...
endopeptidase and its localization in merozoites. Molecular and Biochemical Parasitology 26:167–173.
|
From page 111... ...
recombination within subtelomeric repeat sequences generates chromosome size polymorphisms in P.falciparum.
|
From page 112... ...
F. Cowman.
|
From page 113... ...
parasite transferrin receptor of Plasmodium falcifarum-infected erythrocytes and its acylation via 1,2-diacyl-sn-glycerol. Proceedings of the National Academy of Science of the United States of America 83:8565–8569.
|
From page 114... ...
falciparum gene encoding a protein similar to the 78-kDa rat glucose-regulated stress protein. Proceedings of the National Academy of Sciences of the United States of America 85:6277–6281.
|
From page 115... ...
falciparum. Proceedings of the National Academy of Science of the United State of America 84:7139–7143.
|
From page 116... ...
1990. Heterologous expression of active thymidylate synthase-dihydrofolate reductase from Plasmodium falciparum.
|
From page 117... ...
Walliker, D
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.