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P Agnew

Publications and source records attributed to P Agnew.

10 recordsLinked to original sources

Proteome of Aedes aegypti larvae in response to infection by the intracellular parasite Vavraia culicis.

We report on the modification of the Aedes aegypti larval proteome following infection by the microsporidian parasite Vavraia culicis. Mosquito larvae were sampled at 5 and 15 days of age to compare the effects of infection when the parasite was in two different developmental stages. Modifications of the host proteome due to the stress of infection were distinguished from those of a more general nature by treatments involving hypoxia. We found that the major reaction to stress was the suppression of particular protein spots. Older (15 days) larvae reacted more strongly to infection by V. culicis (46% of the total number of spots affected; 17% for 5 days larvae), while the strongest reaction of younger (5 days) larvae was to hypoxia for pH range 5-8 and to combined effects of infection and hypoxia for pH range 3-6. MALDI-TOF results indicate that proteins induced or suppressed by infection are involved directly or indirectly in defense against microorganisms. Finally, our MALDI-TOF results suggest that A. aegypti larvae try to control or clear V. culicis infection and also that V. culicis probably impairs the immune defense of this host via arginases-NOS competition.

Aedes↗

Sex-specific reaction norms to intraspecific larval competition in the mosquito Aedes aegypti.

As the relationship between a given life-history trait and fitness is not necessarily the same for the two sexes, an 'intersexual ontogenetic conflict' may arise. We analysed the phenotypic reaction to intraspecific larval competition of the mosquito, Aedes aegypti, asking: (i) Do both sexes pay the cost of competition with the same life-history traits and are they equal competitors? (ii) Is there a specific cost of competition beyond sharing food resources? We found that competition incurs a specific cost that was expressed differently by the two sexes. Indeed, each sex maintained the more important life-history trait(s) for their fitness (developmental time for males and body weight and size for females) at the expense of other traits, thus minimizing the effects of competition on their fitness. The competition exerted by females was estimated as being more intense, probably linked with the greater importance of body size for their fitness.

Aedes↗

Host life history responses to parasitism.

Parasites and their infections can adversely effect a host's growth, reproduction and survival. These effects are often not immediate, but increase with time since infection. A general prediction from evolutionary biology is that hosts suffering from this type of infection should preferentially allocate resources towards reproduction, even if this is at the expense of their growth and survival. This review illustrates this argument with several empirical studies showing hosts behaving in this manner. These studies indicate that one way for hosts to reduce the costs of parasitism is by altering their life history traits to bring forward their schedule of reproduction.

Animals↗

Effects of density and larval competition on selected life history traits of Culex pipiens quinquefasciatus (Diptera: Culicidae).

The effects of larval densities of one to four individuals in standard Drosophila-vials (diameter 25 by 95 mm) on the age at pupation, starved dry weight, and wing length of Culex pipiens quinquefasciatus Say were studied. This approach required relatively few larvae per replicate and included a control treatment, where individual larvae developed in the absence of competition. This design also tested for competitive interactions between male and female larvae. Mosquitoes pupated later, and emerged with lighter starved dry adult weight and shorter wings as larval density increased. The size of adult female mosquitoes, particularly their starved dry weight, was sensitive to larval density and also was influenced by the presence or absence of competition with another female larva. In contrast, the life history traits of males did not vary as a function of competition with female larva. Female larvae were also more likely to die in the highest density treatment. This design confirmed previous results and offered a potentially useful experimental approach to investigate the effects of density-dependent competition among mosquito larvae.

Animals↗

Coevolutionary interactions between host life histories and parasite life cycles.

Several recent studies have discussed the interaction of host life-history traits and parasite life cycles. It has been observed that the life-history of a host often changes after infection by a parasite. In some cases, changes of host life-history traits reduce the costs of parasitism and can be interpreted as a form of resistance against the parasite. In other cases, changes of host life-history traits increase the parasite's transmission and can be interpreted as manipulation by the parasite. Alternatively, changes of host's life-history traits can also induce responses in the parasite's life cycle traits. After a brief review of recent studies, we treat in more detail the interaction between the microsporidian parasite Edhazardia aedis and its host, the mosquito Aedes aegypti. We consider the interactions between the host's life-history and parasite's life cycle that help shape the evolutionary ecology of their relationship. In particular, these interactions determine whether the parasite is benign and transmits vertically or is virulent and transmits horizontally.

Aedes↗

Virulence, parasite mode of transmission, and host fluctuating asymmetry.

Horizontally transmitted parasites are broadly predicted to be more virulent, or costly to host fitness, than those with vertical transmission. This is mainly because vertical transmission, from host parent to offspring, explicitly links the reproductive interests of both parties. Underlying this prediction is a general assumption that parasite transmission success is positively correlated with its virulence. We report results where infection of larval yellow fever mosquitoes Aedes aegypti with the microsporidian Edhazardia aedis was experimentally manipulated. The parasite's complex life cycle allowed comparisons between estimates of horizontal and vertical transmission on host fitness. Our measure of virulence was the fluctuating asymmetry (FA) of adult female wings. Hosts harbouring spores showed higher FAs than controls. Horizontally transmitting spores were associated with higher FAs than vertically transmitting spores. Furthermore, within hosts FA correlated positively with the number of horizontally transmitting spores, while no relation was seen with the number of vertically transmitting spores. A developmental mechanism uncoupling the relationship between vertical transmission and virulence is proposed.

Aedes↗

Evaluation of the child with ligamentous laxity.

Many opportunities for participation in the care of children with ligamentous laxity have been described in this article. The podiatric physician must determine his or her contribution based on knowledge, experience, and interest. Each podiatric physician is not necessarily expected to be familiar with all of the diseases and treatments described here. Novice podiatrists should be mandated to recognize only the presence of ligamentous laxity and be familiar with an appropriate referral pattern. In addition to the previously listed podiatric concerns, Hobson has described some specific concerns in even the most basic podiatric treatment. He recommends the use of skin adherents to avoid wrinkling and tearing the skin of individuals with Ehlers-Danlos syndrome. He also reiterates research that has determined a resistance to local anesthetics in these individuals. He further provides some detail for the manufacture of appropriate orthoses. Continuing education may be obtained through a variety of sources. These may include not only traditional podiatric courses and conferences, but also similar venues offered by clinicians in other specialties. Also, courses and conferences held by organizations with a special interest in these unusual disorders can be educational and rewarding. The author has found interactions with this patient population rewarding. The patients and their families are often exceptionally knowledgeable regarding their illness because most have experienced many years with unsatisfactory medical help and delayed or incorrect diagnoses. Most of these families are also extraordinarily grateful for the concern and interest expressed by the clinician. They are particularly impressed when the health care professional has at least a cursory knowledge of their unusual disorder. As a member of the Ehlers-Danlos National Foundation Medical Advisors Panel, the author has contact with world-renowned geneticists, rheumatologists, and other specialists. The leader of the organization has pointed out that patients have found that podiatric clinics provided during the national meetings are often one of the most appreciated aspects of those meetings. He stated that although podiatrists may not cure the disease, small improvements in the everyday lives of these patients add up to a significant contribution. The author hopes that this article will stimulate further interests in the care and understanding of individuals with ligamentous laxity. It is further hoped that experience with these individuals will translate to the broader population who experience milder disorders of hypermobility.

Adolescent↗