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Parasite Defence (parasite + defence)

Distribution by Scientific Domains
Life Sciences100%

Selected Abstracts

Growth and Parasite Defence in Plants; the Balance between Resource Sequestration and Retention: In Lieu of a Guest Editorial

PLANT BIOLOGY, Issue 2 2002
R. Matyssek
Abstract: A hypothesis on regulation of the balance between growth and parasite defence in plants is formulated, namely that plants regulate their resource allocation in a way where stress tolerance and resistance inherently lead to constraints on growth and competitiveness. Seven reviews and the subsequent article in this issue of Plant Biology contributing to this problem are briefly introduced in context. [source]

Crowding and disease: effects of host density on response to infection in a butterfly,parasite interaction

ECOLOGICAL ENTOMOLOGY, Issue 5 2009
ELIZABETH LINDSEY
Abstract. 1. Hosts experiencing frequent variation in density are thought to benefit from allocating more resources to parasite defence when density is high (,density-dependent prophylaxis'). However, high density conditions can increase intra-specific competition and induce physiological stress, hence increasing host susceptibility to infection (,crowding-stress hypothesis'). 2. We studied monarch butterflies (Danaus plexippus) and quantified the effects of larval rearing density on susceptibility to the protozoan parasite Ophryocystis elektroscirrha. Larvae were inoculated with parasite spores and reared at three density treatments: low, moderate, and high. We examined the effects of larval density on parasite loads, host survival, development rates, body size, and wing melanism. 3. Results showed an increase in infection probability with greater larval density. Monarchs in the moderate and high density treatments also suffered the greatest negative effects of parasite infection on body size, development rate, and adult longevity. 4. We observed greater body sizes and shorter development times for monarchs reared at moderate densities, and this was true for both unparasitised and parasite-treated monarchs. We hypothesise that this effect could result from greater larval feeding rates at moderate densities, combined with greater physiological stress at the highest densities. 5. Although monarch larvae are assumed to occur at very low densities in the wild, an analysis of continent-wide monarch larval abundance data showed that larval densities can reach high levels in year-round resident populations and during the late phase of the breeding season. Treatment levels used in our experiment captured ecologically-relevant variation in larval density observed in the wild. [source]

Growth and Parasite Defence in Plants; the Balance between Resource Sequestration and Retention: In Lieu of a Guest Editorial

PLANT BIOLOGY, Issue 2 2002
R. Matyssek
Abstract: A hypothesis on regulation of the balance between growth and parasite defence in plants is formulated, namely that plants regulate their resource allocation in a way where stress tolerance and resistance inherently lead to constraints on growth and competitiveness. Seven reviews and the subsequent article in this issue of Plant Biology contributing to this problem are briefly introduced in context. [source]

Redox and antioxidant systems of the malaria parasite Plasmodium falciparum

MOLECULAR MICROBIOLOGY, Issue 5 2004
Sylke Müller
Summary The malaria parasite Plasmodium falciparum is highly adapted to cope with the oxidative stress to which it is exposed during the erythrocytic stages of its life cycle. This includes the defence against oxidative insults arising from the parasite's metabolism of haemoglobin which results in the formation of reactive oxygen species and the release of toxic ferriprotoporphyrin IX. Central to the parasite's defences are superoxide dismutases and thioredoxin-dependent peroxidases; however, they lack catalase and glutathione peroxidases. The vital importance of the thioredoxin redox cycle (comprising NADPH, thioredoxin reductase and thioredoxin) is emphasized by the confirmation that thioredoxin reductase is essential for the survival of intraerythrocytic P. falciparum. The parasites also contain a fully functional glutathione redox system and the low-molecular-weight thiol glutathione is not only an important intracellular thiol redox buffer but also a cofactor for several redox active enzymes such as glutathione S-transferase and glutaredoxin. Recent findings have shown that in addition to these cytosolic redox systems the parasite also has an important mitochondrial antioxidant defence system and it is suggested that lipoic acid plays a pivotal part in defending the organelle from oxidative damage. [source]