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1
Li, Dongmei. "Immune reactions involved in parasitoid-host interactions /". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phl6926.pdf.
Testo completo
2
DEBOLT, JACK WARNER. "PARASITIZATION OF LYGUS LINEOLARIS (HEMIPTERA: MIRIDAE) BY LEIOPHRON UNIFORMIS (HYMENOPTERA: BRACONIDAE): HOST DEFENSE AND HOST ACCEPTANCE". Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184000.
Testo completoAbstract (sommario):
The ability of Leiophron uniformis (Gahan) to parasitize 4 Lygus spp. was determined. While L. uniformis readily attacked Lygus hesperus (Knight), L. lineolaris (Palisot de Beauvois), L. elisus Van Duzee, and L. desertinus Knight, only 6.7% of the L. lineolaris attacked were parasitized compared to 84-87% parasitization of the other species. Two factors were found to cause the low rate of parasitism of L. lineolaris. L. uniformis oviposited in (accepted) few of the L. lineolaris nymphs attacked and most eggs found were encapsulated by the host. Nymphs less than 48-hr old were readily parasitized because they were accepted by the wasps and the hosts encapsulated few of the parasitoid eggs. As nymphal age increased, parasitism dropped rapidly as the acceptance of the host decreased and the host's encapsulation ability increased. Different strains of L. lineolaris were found to differ greatly in their susceptibility to parasitism, their ability to encapsulate, and their acceptance by the parasitoids. A host strain from Arizona was very resistant to parasitism, whereas a strain from Delaware (NJLBR) that had been in culture for 7 years was easily parasitized. The NJLBR strain had no encapsulating ability and it was readily accepted by L. uniformis. A recently established host strain from Delaware (DELBR) encapsulated 23-27% of the parasitoid eggs while an Arizona strain (FILBR) encapsulated 66-76% of the eggs. The DELBR nymphs were accepted in 42-43% of the attacks while the FILBR nymphs were accepted in only 5-14% of the attacks. Delaware and California parasitoid strains did not differ in their acceptance of L. lineolaris or in their ability to resist encapsulation. Rearing L. uniformis for only 1 generation on L. lineolaris did not precondition the wasps to accept that species as a host in preference to L. hesperus. L. uniformis, which had been reared on L. lineolaris for 5 or more generations, did accept that host 2.5 times as often as wasps reared on L. hesperus. The parasitoids did not known any increase in resistance to encapsulation even after they had been reared on L. lineolaris for 11 generations.
3
Gharbawi, W. Y. A. "Host-parasite relationships of the common goby, Pomatoschistus microps". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637049.
Testo completoAbstract (sommario):
Pomatoschistus microps at Salthouse Point, Burry Inlet, Wales return to the estuary and spawn during June, the 1-group adults then disappear and presumably die but the developing juveniles become heavily parasitized with overdispersed, innocuous, encysted digenean metacercariae namely Cryptocotyle jejuna and C.lingua in subcutaneous muscle, C.concava (Heterophydae), in the body cavity, Labratrema minimus (Bucephalidae), in the liver, Timoniella imbutiforme and T.praeterita (Acanthostoidae) in subcutaneous muscle. Host weight, condition and other growth parameters do not appear to be affected by these parasites. However, declining rates of heterophyid infections after August suggest that host defence responses or hyperparasitism may kill some parasites. Gobies leave the estuary after November and, as suggested by increasing C.lingua and L.minimus infections, may migrate to overwinter near West Cross, Swansea Bay. Sixteen allozyme loci were resolved in these fish, using gel electrophoresis based on a sample of 575 fish. Five of these loci are polymorphic namely LDH, IDH, PGM-1, PGM-2 and PGI. The mean heterozygosity per locus is 0.06 - 0.004 and individual heterozygosity is not usually correlated with host growth parameters but is usually negatively correlated with parasite burden. The relationship is statistically significant, however, only with C.jejuna in September, the sole parasite species which elicits an intense melanized host defence response namely 'black spot' disease. The possible reasons for this are discussed in detail. In Pomatoschistus minutus at Oldbury, Severn Estuary, very lightly parasitized with the larvae of Ligula intestinalis (Cestoda: Pseudophyllidea) and Hysterothylacium sp. (Nematoda: Anisakidae), five of seventeen loci are polymorphic. The mean heterozygosity per locus is 0.03 - 0.014. The results provide equivocal support for the parasite version of the Red Queen hypothesis which predicts that the most heavily parasitized populations will have the highest mean heterozygosity and, within populations, individuals with least parasites will have highest heterozygosity.
4
Barr, Kathryn J. "Aspects of the host-parasite relationships of Polymyxa betae". Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334265.
Testo completo
5
Arnold, Markus F. F. "Host-pathogen interactions in chronic infections". Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192267.
Testo completoAbstract (sommario):
The BacA protein plays a key role in the symbiosis of Sinorhizobium meliloti with the leguminous plant alfalfa (Medicago sativa) and is proposed to be the transmembrane subunit of an ATP‐binding cassette (ABC) transporter. BacA homologues are also present in Brucella species, enteric bacteria (known as SbmA) and Mycobacterium tuberculosis. The S. meliloti‐alfalfa symbiosis, although beneficial to both partners, can also be viewed as a chronic infection. The M. tuberculosis BacA protein is important for M. tuberculosis for the maintenance of a chronic infection. In order to study the M. tuberculosis BacA protein a codon optimised M. tuberculosis bacA gene was synthesised and cloned into vectors for expression in an S. meliloti ΔbacA mutant. Evidence is presented that M. tuberculosis BacA sensitises an S. meliloti ΔbacA mutant towards the glycopeptide bleomycin and the truncated proline rich peptide Bac71‐16, and further that a functional ATPase domain is essential to perform BacA mediated peptide transport. The M. tuberculosis BacA protein protected an S. meliloti ΔbacA mutant from being killed by host defensins. In addition, it was determined that M. tuberculosis BacA‐mediated protection of the legume symbiont S. meliloti against legume defensins as well as mouse alveolar lavages and human ‐defensin 2 is dependent on an ATPase domain which is present in the M. tuberculosis BacA protein. M. tuberculosis encounters ‐defensins during mammalian infections in the host’s lungs and my data show that BacA is likely to be important in conferring immunity to these peptides. The mechanism of persistent infection by M. tuberculosis is therefore very reminiscent of the Sinorhizobium ‐ legume interaction. Also Salmonella enterica is able to cause asymptomatic infections and about 5% of these develop a chronic carrier state and are able to spread the pathogen. In enteric bacterial species SbmA is in close proximity to the putative lipoprotein YaiW. In this study it was determined that YaiW is exposed on the cell surface and that it is involved in the protection of E. coli and potentially Salmonella spp. against a cysteine rich host peptide. YaiW is potentially involved in swarming motility. It was also determined that an alfalfa plant infection model can distinguish between Salmonella strains forming acute and chronic infections. Staphylococcus aureus is one of the major hospital acquired and opportunistic pathogens. Asymptomatic carriers, infected with multi‐drug resistant strains (MRSA) pose a threat to immunocompromised individuals. Here, novel compounds and ways from a variety of sources have been tested for their potential antimicrobial activity against a range of multi‐drug resistant clinical S. aureus isolates. This project significantly advanced the molecular understanding of asymptomatic bacteria‐host infections and helped to understand and establish novel ways to treat infections with multi‐drug resistant clinical pathogens.
6
Bhasin, Amit. "Host location cues of Culicoides spp. (Diptera: Ceratopogonidae)". Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=232286.
Testo completoAbstract (sommario):
This study has investigated the nature of host derived cues used by parous female C. impunctatus in the location of blood meal hosts. Olfaction has been shown to be a vital part of the process. The responses of antennal receptors of females to a variety of host-derived volatile compounds were assessed using the EAG technique. High antennal sensitivity to olfactory cues was indicated by low thresholds for response and, taking into account the volatility of the compounds, a clear hierarchy of response was obtained in which octenol was the most stimulatory, followed by phenolics, lactic acid and finally ketones. Of particular note with regard to phenolic compounds was the finding that 3-derivatives (3-n-propylphenol & 3-methylphenol) were more stimulatory than their 4-derivatives (eg 4-methylphenol). Behavioural assays conducted within a Y-tube olfactometer showed that attraction to olfactory cues was dose dependent. Supra optimal doses which caused receptor saturation (as demonstrated in the EAG assay), also induced marked changes in behaviour with responses being either no different to random expectation, or the compound appearing to be repellent. Wind tunnel assays corroborated these findings for octenol and acetone when used in conjunction with 0.01% CO2. Upwind flight was found to be maximal, and significantly different from responses to the CO2 standard, at concentrations within the tunnel of 1.33x10-8 g 1-1 and 1.5x10-6 g 1-1, respectively. These concentrations are approximately those released by a bovid host for octenol and 1/1000x for acetone. Females exhibited a linear dose dependent response to increases in the concentration of CO2 in the wind tunnel up to 0.09% whether gas was released as a plume or as a lightly turbulent cloud. However, at cloud concentrations above this, CNS mediated habituation is suggested to have arrested upwind flight.
7
Gray, Alexander Bruce. "Host-parasite relationships in tissue cultures of sunflower and downy mildew". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72834.
Testo completo
8
Price, Amanda Jane. "Host-pathogen interactions in lentiviral post-entry restriction and nuclear import". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609671.
Testo completo
9
Allen, Geoffrey Rowland. "Behaviour and ecology of the primary parasitoids Cotesia urabae and Dolichogenidia eucalypti (Hymenoptera: Braconidae) and their host Uraba lugens (Lepidoptera: Noctuidae)". Title page, contents and preface only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09pha425.pdf.
Testo completo
10
Radomiljac, Andrew M. "Santalum album L. plantations: a complex interaction between parasite and host". Thesis, Radomiljac, Andrew M. (1998) Santalum album L. plantations: a complex interaction between parasite and host. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/270/.
Testo completoAbstract (sommario):
This thesis examines a broad spectrum of physiological and silvicultural features of the highly valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to its culture in plantations in northern Western Australia. Topics covered include allometry of host and Santalum when grown as single plant pairings in both field and pot culture, nutritional interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences of parasitism on plantation productivity and heartwood induction in young trees.
In Western Australia sandalwood is grown in the nursery for 8 months before establishment in the field and during this time a pot host is introduced. Survival of Santalurn after field establishment and its subsequent growth were significantly affected by the time of introduction of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera association in the nursery to 109 days prior to field establishment markedly increased early growth of Salztalum plantations. Introduction at 134 days prior to field establishment was detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with Alternanthera in the nursery prior to field establishment compared with seedlings grown without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and Alternanthera DW.
In Western Australia Santalu~n is established in the field with an intermediate host which nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host and the intermediate host dies. The relationship between Santalum and several species tested as intermediate hosts was examined by pairing Santalum seedlings with intermediate host seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps), the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably between host treatments. Santalum growth was greater and root : shoot ratio lower for seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or with no host. The root : shoot ratio of unattached Santalum increased exponentially over time, whereas for all other treatments it remained relatively constant. An assessment of the value of the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW. The host use efficiency of A. trachycalpa was greater than that of the other hosts.
The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria of Santalzkm were analysed for amino acids, organic acids and sugars to determine which solutes were available in the host and which were extracted by the Santalum haustoria from different hosts. There were similarities between Santalum and legume hosts in concentration and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis and dissimilarities between its amino acid composition and that of Santalum. This indicated substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the predominant amino acid in the xylem sap of Santalum acurninatum growing in natural vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were particularly evident for the E. camaldulensis : Santalum partnership.
Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently more negative than that of corresponding hosts. Net photosynthesis and water use efficiency was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen concentrations of foliage of Santalum were higher than their hosts, and higher when on legume hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C values of shoot dry matter of Santalum were poorly correlated with instantaneous water use efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress tolerant species.
S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root nodules of legume hosts were parasitised by a small proportion of Santalum haustoria.
Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum was greatest when grown in association with hosts richest in the corresponding element. Net losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has limited ability for uptake of those minerals through its own root system.
To understand the effect of hosts on the productivity of a Santalum plantation a young plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and Acacia anuera was selected to study the relationship between host quality and distance of hosts from Santalunz on Santalum health. The selected plantation showed marked decline in health and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants were assessed to select the best predictor of Santalunz crown health. The height and diameter growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum crown health. Santaluin crown health and growth increased as host quality increased, and the distance of host fiom Santalum decreased. An index, which combined host quality and the distance of the host from that of Santalum, was a better predictor of Santalum crown health than host distance or quality alone.
The age at which heartwood is initiated in Santalum album under plantation conditions in Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a plantation. Trees injected with paraquat alone had a significantly greater extension of induced heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled water. Eight months after treatment with paraquat or ethrel or a combination of these chemicals induced heartwood was formed, which had high lipid, and low starch and polysaccharide concentrations compared to the sapwood. Induced heartwood from both chemical treatments and their combinations contained total volatile oil and santalol oil (alpha and beta santalol) concentrations that were equal to or greater than that of naturally formed heartwood and greater than that of sapwood. Moisture content, and concentrations of K and Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood. The thesis concludes with a synthesis of the findings and suggestions for future research, with special reference to mid-rotation aspects of Santaltrm plantation silviculture.
11
Radomiljac, Andrew M. "Santalum album L. plantations : a complex interaction between parasite and host". Murdoch University, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060818.134603.
Testo completoAbstract (sommario):
This thesis examines a broad spectrum of physiological and silvicultural features of the highly
valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to
its culture in plantations in northern Western Australia. Topics covered include allometry of
host and Santalum when grown as single plant pairings in both field and pot culture, nutritional
interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences
of parasitism on plantation productivity and heartwood induction in young trees.
In Western Australia sandalwood is grown in the nursery for 8 months before establishment in
the field and during this time a pot host is introduced. Survival of Santalurn after field
establishment and its subsequent growth were significantly affected by the time of introduction
of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera
association in the nursery to 109 days prior to field establishment markedly increased early
growth of Salztalum plantations. Introduction at 134 days prior to field establishment was
detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum
seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with
Alternanthera in the nursery prior to field establishment compared with seedlings grown
without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown
with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks
in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio
and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and
Alternanthera DW.
In Western Australia Santalu~n is established in the field with an intermediate host which
nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host
and the intermediate host dies. The relationship between Santalum and several species tested as
intermediate hosts was examined by pairing Santalum seedlings with intermediate host
seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three
N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps),
the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably
between host treatments. Santalum growth was greater and root : shoot ratio lower for
seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or
with no host. The root : shoot ratio of unattached Santalum increased exponentially over time,
whereas for all other treatments it remained relatively constant. An assessment of the value of
the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW.
The host use efficiency of A. trachycalpa was greater than that of the other hosts.
The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria
of Santalzkm were analysed for amino acids, organic acids and sugars to determine which
solutes were available in the host and which were extracted by the Santalum haustoria from
different hosts. There were similarities between Santalum and legume hosts in concentration
and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding
Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis
and dissimilarities between its amino acid composition and that of Santalum. This indicated
substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem
sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate
and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most
common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the
predominant amino acid in the xylem sap of Santalum acurninatum growing in natural
vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in
Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained
variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric
and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic
acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were
particularly evident for the E. camaldulensis : Santalum partnership.
Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those
for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently
more negative than that of corresponding hosts. Net photosynthesis and water use efficiency
was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen
concentrations of foliage of Santalum were higher than their hosts, and higher when on legume
hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage
was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C
values of shoot dry matter of Santalum were poorly correlated with instantaneous water use
efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress
tolerant species.
S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry
matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in
association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of
haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root
nodules of legume hosts were parasitised by a small proportion of Santalum haustoria.
Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that
of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum
was greatest when grown in association with hosts richest in the corresponding element. Net
losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when
Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has
limited ability for uptake of those minerals through its own root system.
To understand the effect of hosts on the productivity of a Santalum plantation a young
plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and
Acacia anuera was selected to study the relationship between host quality and distance of hosts
from Santalunz on Santalum health. The selected plantation showed marked decline in health
and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants
were assessed to select the best predictor of Santalunz crown health. The height and diameter
growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum
crown health. Santaluin crown health and growth increased as host quality increased, and the
distance of host fiom Santalum decreased. An index, which combined host quality and the
distance of the host from that of Santalum, was a better predictor of Santalum crown health
than host distance or quality alone.
The age at which heartwood is initiated in Santalum album under plantation conditions in
Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of
age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections
of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a
plantation. Trees injected with paraquat alone had a significantly greater extension of induced
heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled
water. Eight months after treatment with paraquat or ethrel or a combination of these
chemicals induced heartwood was formed, which had high lipid, and low starch and
polysaccharide concentrations compared to the sapwood. Induced heartwood from both
chemical treatments and their combinations contained total volatile oil and santalol oil (alpha
and beta santalol) concentrations that were equal to or greater than that of naturally formed
heartwood and greater than that of sapwood. Moisture content, and concentrations of K and
Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood.
The thesis concludes with a synthesis of the findings and suggestions for future research, with
special reference to mid-rotation aspects of Santaltrm plantation silviculture.
12
Hennecke, Berthold Rembertus. "Host-pathogen interactions between the fungal pathogen Phloeospora mimosae-pigrae and Mimosa pigra, giant sensitive plant /". [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17081.pdf.
Testo completo
13
Belmonte, da Silva Rodrigo Caetano. "Saprolegniosis : studies of the host-pathogen interaction in salmonids". Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=220447.
Testo completoAbstract (sommario):
Saprolegnia is a fresh water fish parasite responsible for significant economic losses in the aquaculture industry worldwide. The disease caused by this organism is termed saprolegniosis, being characterized by a mycosis-like infection of gills and fish skin. Without sustainable treatments available for controlling or preventing saprolegniosis, it has become a significant problem especially for salmon farming, frequently affecting the fish after vaccination. Little is known regarding how the fish immune system responds to infection and such information is vital for developing future treatments and preventive measures to saprolegniosis. To study the immune response of Atlantic salmon to Saprolegnia, a detailed immune profile of experimentally infected presmolts was performed by analyzing the expression levels of several immunity-related genes. Infected fish exhibit a very strong inflammatory response while the majority of genes associate with the adaptive immunity were found to be down regulated. The mechanisms behind this response were then investigated: It was discovered that the cell wall of Saprolegnia can be recognized by fish immune cells, triggering an inflammatory response. A protease secreted by the parasite that has the ability to degrade fish antibodies was identified and, for the first time in an oomycete, the production of prostaglandin E2 was characterized, a molecule that was later shown to potentiate inflammatory responses while suppressing host adaptive immunity genes. Lastly two metabolic pathways of the oomycete were explored as novel targets for control, prostaglandin and sterol metabolism by the use of cyclooxygenase and CYP51 inhibitors, respectively.
14
Kelly, Colleen Kay. "Host use and foraging in the parasitic plant Cuscuta subinclusa". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184543.
Testo completoAbstract (sommario):
Foraging theory predicts active responses by organisms upon encounter with a resource, as opposed to the passive responses of differential survivorship and growth. Stems of the parasitic plant Cuscuta subinclusa invest in resource acquisition (coil) relative to host quality in a way predicted by the marginal value theorem (MVT) in that: (1) stem coiling, the necessary antecedent and determinant of resource uptake, precedes exploitation of host materials; and (2) mean coiling on a host species is proportional to: (a) mean growth/haustorium, (b) mean biomass accumulation over the season, and (c) mean parasite growth/host individual. Coiling is correlated with growth/host individual for the 5 native host species examined, but not when a non-native species is added to the model, suggesting coiling response is a result of natural selection. Preliminary evidence indicates that coiling in C. subinclusa is induced by host bark chemicals. Resource-poor stems of C. subinclusa are more likely to coil, and coil more, than resource-rich stems, thus nutritional state of the parasite as well as host value affects foraging responses. Evidence from other experiments suggests that the costs of growth, or "search costs", may affect host acceptability. When water is readily available, transplanted C. subinclusa stems are less likely to coil on branches of Platanus racemosa. During the dry season, when cellular expansion is difficult, all p. racemosa branches were coiled upon. Large parasites are more likely to over-winter and set seed a second season, and parasites that start from over-wintered tissue are significantly larger at flowering than are those that have started from seed. Seed set is correlated with parasite size, thus linking foraging response and fitness of the plant. C. subinclusa's foraging response does not, however, predict population level patterns of host use. The principal determinant of host use by C. subinclusa is average proximity of a species to Malosma laurina. Parasite individuals infest many host species each season, but initially establish, set most seed, and over-winter only on M. laurina. Individual response of C. subinclusa contributes to the model of host use only after proximity to M. laurina is accounted for, suggesting that mechanisms maximizing exploitation of a host take effect after contact between host and parasite.
15
Lawrie, Charles Henderson. "The molecular basis of tick-host interactions". Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:0a920ddd-c623-49a6-b971-cb6049b419e3.
Testo completoAbstract (sommario):
Ticks are obligate haematophagous arthropods that represent a major economic drain upon the world's livestock as well being a significant medical and veterinary risk through the transmission of tick-borne pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. The tick-host relationship is a function of both ecological and physiological factors. Successful feeding requires the effective acquisition and digestion of a bloodmeal by the tick. Acquisition relies upon the ability of the tick to counteract host immune responses induced by the extended feeding periods of ixodid ticks (up to 2 weeks). The host response to tick infestation and the consequent countermeasures employed by the tick, constitute the tick-host interface. The immune response of hosts to Ixodes ricinus infestations was examined through antigenic profiling. The antigens exposed to the host were shown to vary throughout the feeding period and differed between the different development stages of I. ricinus. It was also shown that different host species infested with I. ricinus recognised different antigens. This was true of both natural and non-natural hosts, and even closely related species. Anti-complement activity was investigated in the salivary glands of Ixodes ticks. This activity was shown to inhibit some host species but not others. The pattern of inhibitory activity varied between the tick species tested in a way that was consistent with known tick host-preferences. The mechanisms of anti-complement activity in I. ricinus salivary glands were explored. The alternative but not the classical pathway of complement was inhibited. Activity was present in unfed ticks and throughout the feeding period. Three targets of the complement system were identified as being modulated by the tick. Digestion of the bloodmeal was explored and a haemolytic activity was associated with the salivary glands of I. ricinus ticks. The activity was demonstrated to be Mg2+- dependent. In addition, a subtractive cDNA library enriched for saliva-associated transcripts was successfully produced. Random sampling identified putative differentially expressed genes. The results of this thesis illustrate the complexity of tick-host interactions at the molecular level. It is apparent that the research described poses many more questions than answers.
16
Kneeland, Stephen C. "Identification of Fish Hosts for Wild Populations of Rare Freshwater Mussels (Lampsilis cariosa and Leptodea Ochracea) Using a Molecular DNA Key". Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/KneelandSC2006.pdf.
Testo completo
17
Soriano, Imelda Rizalina. "Novel inducible phytochemical defences against plant parasitic nematodes /". Title page, table of contents and summary only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phs7141.pdf.
Testo completo
18
Schreiber, Maria Fernanda. "Studying the host transcriptome and the role of flagella in infections mediated by Salmonella and other pathogens". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610270.
Testo completo
19
Wenzel, Marius. "Genomic, epigenomic and transcriptomic factors affecting host-parasite interactions in red grouse (Lagopus lagopus scotica)". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=227041.
Testo completoAbstract (sommario):
Host-parasite interactions are extremely important drivers of evolutionary change, characterised by co-evolutionary dynamics with strong reciprocal selective pressure on both host and parasite genomes. However, little is known about the genomic basis of host-parasite interactions, particularly which genes may affect parasite susceptibility, parasite burden and the ability to resolve energetic life-history trade-offs under chronic parasite insult. This thesis examines the genomic, epigenomic and transcriptomic basis of an avian host's physiological response to chronic parasite infection. The model system throughout is the red grouse (Lagopus lagopus scotica) and its main parasite, the gastrointestinal nematode Trichostrongylus tenuis. T. tenuis is highly prevalent and imposes substantial fitness costs that affect demography and population dynamics through an impact on territorial behaviour, energy balance, fecundity and mortality. Here, the genomic architecture of variation in individual T. tenuis burden is examined via de novo identified candidate genes, genome-wide SNPs and genome-wide cytosine methylation polymorphisms. Further, molecular signatures of natural selection in identified genomic regions are examined across a landscape in northeast Scotland with heterogeneous parasite pressure. Finally, the transcriptomic response of red grouse to experimental T. tenuis infection and manipulation of testosterone titre is harnessed to identify a transcriptomic component in testosterone-driven physiological trade-offs in a sexual selection context.
20
Watters, George Murray. "Models of parasitism and hyperparasitism on Paralomis spinosissima /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823698.
Testo completo
21
Williams, Emily Rose-Margaret. "Parasites and the ecological undead: marine snails and their suite of trematodes". Thesis, The University of Sydney, 2012. https://hdl.handle.net/2123/28920.
Testo completoAbstract (sommario):
The invisible interactions between parasites and their hosts are important elements of the ecology and biology of host populations. Parasites can shape the morphology, distribution, physiology and behaviour of individual hosts - some commonly studied host-parasite interactions often involve gastropods and trematodes. Trematodes can have detrimental effects on their snail hosts, yet many such relationships are relatively unknown. One such relationship is that of the mud whelks, Velacumantus australis, many of which are infected by several species of parasitic trematode. Australian estuaries and lagoons are commonly populated with these snails. Little work has been done, however, on how these snails are affected by their trematodes. My overall aim was to create a more comprehensive picture of the relationship between trematodes and their snail hosts, since it is unknown what is occurring within populations of these snails in Australia. Through dissections and experiments, I described all the species infecting the snails, including those previously unknown to science; quantified infection prevalence within different populations of snails in New South Wales; compared infection with host size, both in situ and through growth of host bodies over time; assayed proteins and lipids from host tissues to quantify energy reserves; and finally, tested whether snails displayed different behaviours depending on infection status. My results show that parasitism varies temporally and on small and large spatial scales, most likely because of recruitment and presence of other hosts. The effects of parasitism on the host body include differences in growth and energy reserves, and appear to be influenced depending on the species of trematode. The activity and locomotory behaviour of snails is also affected by trematode infection, whether the snail has a neighbour, and the infection status of the neighbouring snail. These results show that the relationship between V australis and its trematodes is more complex than predicted and is influenced by dynamic interactions between spatial variability and parasitism. Future experiments with these snails and other snail-trematode relationships in similar systems should include different spatial scales as well as different species of trematodes in order to disentangle the relationships between parasitism and environmental variation.
22
Wyatt, R. J. "Epidemiology, host-parasite relationships and strains of the fish tapeworm Ligula intestinalis". Thesis, University of Exeter, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374700.
Testo completo
23
Barker, Sarah E. "Host-parasite interactions between Lernaeocera branchialis (Copepoda: Pennellidae) and its host Gadus morhua (Teleosti: Gadidae)". Thesis, University of Stirling, 2009. http://hdl.handle.net/1893/1792.
Testo completoAbstract (sommario):
Lernaeocera branchialis (Linnaeus, 1767) is a parasitic copepod possessing a complex dual-host lifecycle. The “definitive” gadoid hosts, including Gadus morhua (Atlantic cod), Melanogrammus aeglefinus (haddock) and Merlangius merlangus (whiting), are infected by the fertilised female, which penetrates the host’s ventral aorta or bulbus arteriosus whilst undertaking extensive metamorphosis and a haematophagous lifestyle. The pathogenic effects of this activity upon the host have been well documented and mortality may occur, especially when multiple parasites are present. These negative impacts on cod, particularly juveniles, by L. branchialis have the potential to adversely affect cod aquaculture in the future, and already vulnerable wild cod stocks. This PhD project therefore, investigated the immune response of wild haddock and cultured-cod post-infection by L. branchialis, and the possible mechanisms by which the parasite modulates/evades the host’s immune response. The systemic immune response of both wild haddock and cultured-cod post-infection by L. branchialis depended on the maturation stage of the parasite, and in the former host species, upon the infection intensity. Wild haddock harbouring fully metamorphosed females showed an increase in circulating thrombocytes and a decrease in serum protein levels however; if multiple mature L. branchialis were present the haddock possessed reduced circulating monocytes, and increased circulating thrombocytes and serum anti-trypsin activity. Infection by L. branchialis was also associated with a suppressive effect on haddock serum spontaneous haemolytic activity. These responses were thought to be due to the host trying to counteract the increased damage caused by the massive increase in size and the feeding of the mature parasite, which is more pronounced when multiple parasites are present, resulting in the increase in some parameters and the ‘consumption’ of others. However, the effect of parasite-derived secretions and other pathogens due to observations on wild fish could not be discounted. The laboratory-infection of cultured-cod from two different sources was also performed in order to study the immune response over time. The two groups of cod showed differences in their immune response to L. branchialis. The first group showed suppressed respiratory burst activity of phagocytes, as the parasite reached the early penella sub-stage, whilst no suppression in phagocyte respiratory burst activity was found in the second group. The parasite was found to migrate along the afferent branchial artery of the cod where a thrombus formed and was present throughout its migration into the ventral aorta. At 14 d post-infection, leukocytes expressing Interleukin 8 mRNA were observed within the free-flowing blood at the periphery of the organising thrombus within the lumen of the ventral aorta. This was speculated to aid the recruitment and activation of leukocytes to the site, and the maturation and neovascularisation of granulation tissue. The infection of the second group subsided with the death of the parasite, and none of the parasites metamorphosed past the early penella sub-stage. The live parasites infecting the first group of cod did not possess IgM or complement component C3 binding on their cuticle, however, both IgM and C3 binding occurred on the dead parasites in the second infection trial. This may highlight the importance of these opsonins and the cytotoxic effect of phagocytes in the elimination of L. branchialis by some cod. However, the first infection was terminated as the parasite reached the early penella sub-stage due to a loss of stock cod prior to the study, so the long-term success of the infection can not be concluded. Therefore, the immune response to infection needs to be determined over the entire metamorphosis of L. branchialis to determine whether the infection was successful or not, and preferably in populations with varying susceptibility to L. branchialis. This will not be possible without further studies into the resistance of different stocks of cultured-cod. Many arthropod parasites, such as ticks and salmon lice, have been previously documented to produce pharmacologically active secretions, aiding host invasion and parasite feeding, preventing the host immune response from working effectively against the parasite, all aimed at improving survival of the parasite. Therefore, the effects of the secretory/excretory products (SEPs) produced during the initial infective stage and by the mature, fully metamorphosed female on the immune response of cultured-cod in vitro, and the location of exocrine glands associated with the oral region of the parasite were investigated. The SEPs from the infective stage of the parasite were found not to affect the intracellular hydrogen peroxide (H2O2) production of phagocytes. The practical difficulties in collecting large quantities of the SEPs from the infective stage meant that their effects could not be tested on the other host immune parameters studied. The SEPs from fully metamorphosed female L. branchialis, however, had a number of suppressive effects on the host immune response in vitro including: 1) suppression of the intracellular production of cytotoxic H2O2 during the respiratory burst of phagocytic leukocytes post-PMA stimulation, 2) suppression of the production of macrophage activating factor by leukocytes with a priming effect on naïve phagocyte function, and 3) suppression of the chemo-attraction ‘power’ of zymosan activated cod serum, i.e. anaphylatoxin activity, on head kidney-derived leukocytes. These effects were dose-dependent, and highlight the capacity of L. branchialis to suppress its host’s innate immune response at the local feeding area. Further work is required to establish the mechanisms by which the parasite-derived SEPs suppress these host immune parameters, and to identify which molecules produced by the parasite are responsible. The correlation between these in vitro results, and systemic immune parameters measured from laboratory-infected Atlantic cod and wild infected haddock are discussed. Host immuno-modulation by other arthropod parasites is mediated by pharmacologically active secretions produced by exocrine glands. Therefore, the exocrine glands of the infective and fully metamorphosed female L. branchialis were also investigated in order to identify those that might be responsible for the secretion of host-modifying products. Adult female exocrine glands were mapped using diaminobenzidine (DAB), most commonly known to stain peroxidases and catalases. These compounds are known to be involved in the neutralisation of harmful free radicals which are released during the respiratory burst and tissue damage. Such products may therefore be important protective secretory components at the site of feeding / infection. Exocrine glands were located in the infective stage associated with the oral region, one pair termed the anterior gland complex (AGC), and the other pair extending either side of the oral cone termed the circum-oral glands (CG). These were further investigated using light microscopy and transmission electron microcopy. The AGC and CGs possessed multi-component secretions and they possessed secretory vesicles, abundant and highly active rough endoplasmic reticulum and Golgi apparatus suggesting that protein is an important component of the secretory products. These glands were also observed in the fully metamorphosed females where they had increased in size within the cephalothorax post-metamorphosis. It is hoped that the identification of these glandular structures, which are thought to secrete within the local vicinity of the oral cone, will aid future studies regarding the identification and secretion kinetics of parasite-derived molecules during the infection and feeding process.
24
Beckmann, Max Johannes. "Saprolegnia infections after vaccination in Scottish salmon aquaculture : a host-pathogen interaction influenced by stress". Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230131.
Testo completo
25
Fredensborg, Brian Lund, e n/a. "Ecological interactions between the trematode parasite Maritrema novaezealandensis (Microphallidae) and its intermediate hosts in the New Zealand intertidal soft-sediment community". University of Otago. Department of Zoology, 2005. http://adt.otago.ac.nz./public/adt-NZDU20060810.154001.
Testo completoAbstract (sommario):
Most, if not all, animals will at some stage in their lives encounter parasites. Some of the most widespread and abundant parasites belong to the Class Trematoda. Trematodes often have a substantial negative impact on individual intermediate host ecology. In this thesis, I investigate ecological and evolutionary consequences of the interaction between the microphallid trematode, Maritrema novaezealandensis, and its intermediate snail and crustacean hosts.
Parasites often show a heterogeneous spatial distribution pattern in natural animal host populations. In this study, factors determining the spatial distribution of larval trematodes in Zeacumantus subcarinatus were investigated at two spatial scales (within and among bays). The distribution of shorebird definitive hosts explained a significant amount of the variation in the distribution of trematodes among bays. However, within a bay, other factors override the effect of bird distribution.
The influence of larval trematodes on reproduction, survival and population density of Z. subcarinatus was investigated using laboratory and field studies. In the laboratory, it was found that larval trematodes induce castration and mortality of Z. subcarinatus. The field study revealed that the local prevalence of trematodes had a significant negative effect on population density of Z. subcarinatus.
Through castration, trematodes act as strong selective agents on snail host life history. The effect of trematodes on life history characteristics (reproductive effort, juvenile growth, size at maturity and susceptibility to trematode infections) were investigated among natural populations of Z subcarinatus. Reproductive effort was not higher for uninfected females from populations where the risk of becoming infected was high. However, offspring from those populations were significantly larger, and laboratory-reared juveniles grew significantly faster than conspecifics from other populations. In addition, size at maturity was negatively correlated with trematode prevalence across snail populations. Z. subcarinatus thus adapts to a high local risk of trematode infection by reaching maturity early, thereby increasing the chance of reproducing.
The influence of M. novaezealandensis on the survial of the amphipod host, Paracalliope novizealandiae was examined using experimental infections and field observations. The experimental infections demonstrated that parasite-induced mortality was intensity-dependent. The number of M. novaezealandensis per amphipod was too low to significantly induce host mortality in the field. However, the transmission strategy of this parasite allows it to affect host populations during weather conditions ideal for trematode transmission.
Trematode strategies in the second intermediate host are important to the understanding of host-parasite co-evolution and the evolution of parasite life cycles. In this study, potential density-dependent effects at the metacercarial stage on size and fecundity of in vitro adult M. novaezealandensis was examined in both experimentally infected P. novizealandiae and naturally infected Macrophthalmus hirtipes. For this purpose, a method to excyst and cultivate M. novaezealandensis metacercariae to an egg producing stage, was developed. Naturally infected M. hirtipes also harboured larval stages of three other helminths. Crowding effects in the two crustacean hosts were expressed as a decreased volume and smaller egg production of in vitro adult M. novaezealandensis. In addition, interspecific interactions among parasite species were observed in crab hosts.
The work in this thesis provides evidence that M. novaezealandensis significantly and negatively affect intermediate host ecology. The heterogeneous distribution of trematodes causes differential effects among host populations with subsequent effects on the life history of snail hosts. In addition, this study demonstrates that parasites interact within their second intermediate host with possible implications for the way parasites exploit their hosts.
26
O'Callaghan, Michael George. "Studies on the systematics of the cestodes infecting the emu, Dromaius novaehollandiae (Latham, 1790) /". Title page, table of contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09pho151.pdf.
Testo completo
27
Heavyside, Rebecca. "Dietary modulation of the interaction between Salmonid fish and sea lice (Lepeophtheirus salmonis) : effects on host attractiveness, skin mucus and immune response". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235985.
Testo completo
28
Bonilla, Victoria. "The Succubus and the Suckers: the Soul-Siphoning Leeches in the Stories of Modernist Text". ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1851.
Testo completoAbstract (sommario):
This paper explores the various relationships found in John Steinbeck's "Of Mice and Men," Tennessee Williams's "A Streetcar Named Desire," Franz Kafka's "The Metamorphosis," and F. Scott Fitzgerald's "Tender is the Night." The exploration of each demonstrates the common theme of parasitic relations and the toll this dynamic takes on the persons involved.
29
Farmer, Kristy Lynn Roberts Sharon R. "Study of a novel host-parasite relationship Mycoplasma gallisepticum in house finches (Carpodacus Mexicanus) /". Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Dissertations/FARMER_KRISTY_6.pdf.
Testo completo
30
Dale, Denver Dudley Stanton. "Parasites and host nutrition". Thesis, University of Oxford, 1993. http://ora.ox.ac.uk/objects/uuid:5bc8aebc-fcfa-4301-8d04-4ebc89fb1c8a.
Testo completo
31
Gresty, Karen Ann. "The feeding biology of Mytilicola intestinalis Steuer in the mussel host Mytilus edulis L. and other host-parasite relationships". Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279748.
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32
Ortega, Nicole. "Flames and Frogs – The Impact of Environmental Disturbances on Host-Parasite Dynamics". Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7640.
Testo completoAbstract (sommario):
The successful completion of this work is dedicated first to my grandparents for having always shown their unwavering love and encouragement in my journeys (most of which they kindly and politely only pretended to understand) and for having also served as life-long role models who upheld an unparalleled work ethic. To many whom I consider to be my chosen family, especially Ann Williams and Brittany Sears, who kept me laughing, but more importantly, kept my crazy train from derailing during these tumultuous years. To Wayne Price and Tom Jackman, who fostered the success of my career and are the epitome of patience and kindness. To DeAngelis, for the many hours of laughter, conversations, and adventuresome treks that further kindled my knowledge, love, and respect for Florida’s ecology. To family in Alabama who have either helped shape my brazen character or made this education possible. To Taego, the one to whom I am bound through so many of the stories that begin with, “Remember when…?” and who is often so kind and thoughtful though he still holds tightly to the stereotype of the selfish youngest sibling. Finally, to Fen for being my smiling, bright blue-eyed, spunky kid who has been on this journey with me from the get-go; for keeping me from getting too big for my britches; for your intrinsic fire that burns for equality, fairness, and friendship; and for inspiring me to be the best example of a mother that I can possibly be.
33
Cotter, Sheena C. "Trade-offs in insect disease resistance". Thesis, University of Stirling, 2002. http://hdl.handle.net/1893/26688.
Testo completoAbstract (sommario):
The ability to mount an efficient immune response should be an important life-history trait as parasitism can impact upon an individual's fecundity and survival prospects, and hence its fitness. However, immune function is likely to be costly as resources must be divided between many important traits. Whilst many studies have examined host resistance to particular parasite types, fewer have considered general immune responses. Studies that have considered general immune responses tend to do so in vertebrate models. However, the complexity of the vertebrate immune system makes the examination of evolutionary aspects of immune function difficult. Using larvae of the genus Spodoptera (Lepidoptera: Noctuidae) as a model system, this study examines' genetic and phenotypic aspects of innate immunity. The aims were to assess the levels of additive genetic variation maintained in immune traits, to consider possible costs that could maintain this variation, and to assess the role of phenotypic plasticity in ameliorating those costs. A key finding of this study was that high levels of additive genetic variation were maintained in all of the measured Immune traits. Analysis of the genetic correlations between traits revealed potential trade-offs within the immune system and between immune components and body condition. In addition, it was shown that larvae living at high densities invest more in immune function than those living in solitary conditions, suggesting that larvae can minimise the costs of immune function by employing them only when the risk of pathogenesis is high.
34
French, Andrew Samuel. "Linking environmental variation across the Scottish Highlands with red deer (Cervus elaphus) trace element status, parasite burden, and skeletal morphometry". Thesis, University of the Highlands and Islands, 2016. https://pure.uhi.ac.uk/portal/en/studentthesis/linking-environmental-variation-across-the-scottish-highlands-with-red-deer-cervus-elaphus-trace-element-status-parasite-burden-and-skeletal-morphometry(b2c569ef-77f4-4fde-9c07-4c8290a9ae88).html.
Testo completo
35
Kinuthia, Wanja. "The molecular mechanism of immune evasion by the eggs and larvae of the Endoparasitoid Venturia canescens in its host, Ephestia kühniella /". Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phk56.pdf.
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36
Poole, Lindsey. "The role of intraflagellar transport in signaling in the African trypanosome Trypanosoma brucei /". Connect to online version, 2008. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2008/282.pdf.
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37
Berry, Katharine M. "The role of parasites in the invasion ecology of Harmonia axyridis". Thesis, University of Stirling, 2017. http://hdl.handle.net/1893/27336.
Testo completoAbstract (sommario):
The success of an invasive alien species is often attributed to the ecological advantage gained from natural enemy release. Numerous factors have been suggested as contributing to the success of Harmonia axyridis as an invasive alien species, including enemy release. This thesis studied the interactions of several parasites with H. axyridis, investigating parasite transmission, growth and virulence as well as host immune responses, thereby shedding light on the potential role of enemy release in the invasion biology of this ladybird. Benefits gained by invasive alien species from enemy release diminish if parasites of native species shift hosts to exploit the novel invader. The fungal ectoparasite Hesperomyces virescens began infecting H. axyridis shortly after it invaded the UK, probably as a result of a host shift from Adalia bipunctata. This study found a rapid increase in H. virescens prevalence over three years in London H. axyridis populations. Laboratory study showed H. virescens transmission and growth to be more efficient on A. bipunctata than the novel host. In addition, reciprocal interspecific transfers of H. virescens strains isolated from A. bipunctata and H. axyridis revealed that the infection characteristics of the fungi from these two hosts differed, suggesting strains may have diverged after the initial shift from A. bipunctata to better exploit the host from which they were derived. Laboulbenialian fungi were previously thought to have negligible impacts on host fitness. A detailed examination of H. virescens infecting H. axyridis found distinct virulence, with infections resulting in a 50% reduction in host lifespan. In addition, chronic H. virescens infection in males caused acceleration in the age-associated decline in body condition while for females, infection triggered fecundity senescence and a faster age-related decline in fertility. While their role in accelerating ageing is debated, the results presented here provide evidence that infectious diseases can drive the ageing process in this insect species. In nature, multiple parasites affecting a single host are common. The effect of co-infection on the virulence caused by two fungal infections was characterised using H. axyridis and A. bipunctata hosts. The ability of two ladybird species to defend against an acute fungal parasite, while infected with the relatively avirulent H. virescens was found to be sex-specific. While for females, the presence of co-infection did not alter the virulence seen in singly infected females, a higher mortality rate existed for co-infected males compared with those infected singly. Previously, H. virescens has been considered to be avirulent, however, this study provides evidence that this chronic fungal parasite may be important when considering the mortality associated with co-infections in the field. The invasive success of H. axyridis has, in part, been attributed to a more vigorous immune ability compared with other competitor species. Previously, field studies have shown that the prevalence of the parasitoid wasp Dinocampus coccinellae in H. axyridis is considerably lower than in the UK primary host of this wasp, Coccinella septempunctata. The extent to which the prevalence asymmetry in the field is driven by differences in host encapsulation response was tested by first comparing the encapsulation ability of C. septempunctata and H. axyridis directed against an artificial implant. Following this, the encapsulation response of D. coccinellae parasitized individuals was assessed and compared between the two host species. While encapsulation ability did not differ between the host species, and D. coccinellae did not affect the immune response of H. axyridis, wasp parasitism did alter the encapsulation ability of C. septempunctata, although it was inconsistent across sexes and populations. Overall, this thesis furthers our understanding of the fungal parasite H. virescens and its association with the notorious invader H. axyridis. The research presented here also demonstrates the use of H. axyridis as a model system in areas other than invasion ecology and furthermore, contributes to understanding the role of infectious disease in the rate of ageing. Finally, sex-specific effects were found across the chapters of this thesis, demonstrating the use of H. axyridis in the study of sex-specific effects of infections.
38
Gordon, David M. "Population dynamics of a host-parasitoid system with particular reference to age-structure effects". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75358.
Testo completoAbstract (sommario):
An experimental study of laboratory populations of the stored-products moth, Cadra cautella (Lepidoptera: Phycitidae) and its larval parasitoid, Venturia canescens (Hymenoptera: Ichneumonidae) identified and quantified density- and age-dependent demographic characteristics of the host-parasitoid system. Host imago longevity and fecundity depended on larval weight at pupation. Observed effects of C. cautella larval competition for food on larval mortality, stage duration, and weight at pupation were successfully captured in a mathematical model. Host larval age significantly influenced inter-stage cannibalism and susceptibility to mortality resulting from parasitoid oviposition wounds. Both larval parasitoid developmental rates and adult parasitoid attack rates depended on host larval age. Long-term population experiments of host and host-parasitoid populations revealed that host populations fluctuated with a period slightly in excess of host generation time and that parasitoid populations were in synchrony with host populations.
39
Dugger, Bruce D. "The impact of brood parasitism on host fitness in common pochards and tufted ducks /". free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9809678.
Testo completo
40
Ismaeel, Abdulrahman Yusuf. "Studies on host-parasite relationships of trypanosomatid flagellates in Drosophila, and Leishmania in phlebotomine sandflies". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240315.
Testo completo
41
Shariff, Mohamed. "Studies on the biology, host-parasite interactions and distribution of Lernaea spp. in West Malaysia". Thesis, University of Stirling, 1985. http://hdl.handle.net/1893/21892.
Testo completoAbstract (sommario):
Lernaea spp. was identified as a widespread problem in West Malaysia and various aspects of the parasite were studied. A survey of the distribution of Lernaea spp. in West Malaysia revealed its presence in all the 8 government owned fish breeding stations, 104 privately owned farms and 4 out of 5 consignments of imported fingerlings. The Lernaea spp. present in these ponds were identified as L. piscinae and L. cyprinacea "Asian" form (=b.elegans) and its morpha forms, L. ctenopharyngodonis and L.guadrinucifera. The life cycles of L. cyprinacea and L. piscinae were determined under laboratory conditions. Infection of ~. auratus with the offspring of L. cyprinacea "Asian" form produced adult females similar to the maternal form and another form identified as b. ctenopharyngodonis. A. nobilis, infected with L. cyprinacea "Asian" form and L. piscinae produced only species identical to the maternal form. A high degree of polymorphism was revealed and was further investigated. Morphometric studies on the larval stages and adult female parasites were investigated and reliable characteristics for the identification of Lernaea is discussed. The distribution frequency of b. cyprinacea on 3 host species and L. piscinae on A. nobilis in aquarium tanks was goodness of tested for/fit with the theoretical negative binomial distribution. The bases of fins were found to be the preferred site of infection for both species. studies on growth performance of A. nobilis infected with L. piscinae in ponds, revealed a significant reduction in Specific Growth Rates. Infected fish had a higher mortality than uninfected fish. A decrease in parasite infection on the body surface after 3 months was associated with its appearance in the eye. A challenge infection did not establish and the fish were suspected of being immune. Histopathological studies showed a typical inflammatory response with the formation of a granuloma. Eosinophilic granular cells, lymphocytes, and club cells which were identified in the hosts immune to the infection, were believed to play an important role in the rejection of parasites.
42
Prasad, Yugal Kishore. "On the searching efficiency of "Rodolia cardinalis" (Milsant) (Coleoptera, Coccinellidae) and its response to prey patches". Title page, table of contents and summary only, 1985. http://web4.library.adelaide.edu.au/theses/09PH/09php911.pdf.
Testo completo
43
Lagrue, Clement, e n/a. "Alternative life-history strategies in the trematode Coitocaecum parvum (Opecoelidae) : effects of environmental factors and within-host competition". University of Otago. Department of Zoology, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080905.111744.
Testo completoAbstract (sommario):
From simple beginnings, when only one host was required, numerous parasitic organisms have evolved complex life-cycles involving two or more host species. For example, trematode parasites reproduce in vertebrates, their definitive host, but their current life cycle also typically involves two intermediate hosts that were added during the course of evolution. Vertebrates are often considered to be the ancestral hosts of trematodes although other scenarios exist. While multi-host life cycles are observed in distantly related groups of parasites, their evolution remains largely unexplored.
In trematodes, while recent phylogenetic studies have shed light on the sequence along which the different hosts were incorporated in the cycle, conditions that favoured the evolution of such complex life cycles can only be hypothesized. However, one opportunity to understand the force shaping the evolution of complex life cycles is provided by the few trematode species in which the classical three-host cycle facultatively reverts to a shorter cycle (i.e. life cycle abbreviation). In this study, the effects of different environmental factors on the life history strategy of the trematode Coitocaecum parvum were investigated using laboratory and field studies. C. parvum is able to abbreviate its life cycle from three to two hosts by maturing early (i.e. progenesis) and producing eggs inside the second intermediate host; both life history strategies occur simultaneously in C. parvum populations.
Environmental factors such as predator densities should strongly influence parasite life history strategies. In fact, this study shows that laboratory reared Coitocaecum parvum adopt preferentially the normal three-host cycle when chemical cues from the definitive host are added to their environment, while the shorter cycle is favoured when these cues are absent. However, in nature, multiple environmental factors are likely to be perceived by parasites. Consequently, C. parvum�s ability to adapt its developmental strategy to definitive host densities may be confounded by the complex combination of various environmental parameters.
Within-host competition between parasites sharing a common host is also likely to influence individual life history strategies. Parasites could then use alternative life strategies to adaptively respond to intraspecific and interspecific competition. Indeed, this study found that C. parvum preferentially adopts the abbreviated cycle in the presence of competitors. However, in interspecific competition, C. parvum�s strategy also depends upon the competitor species, possibly influenced by the other species� transmission route. Furthermore, intensity of intraspecific competition proved to constrain C. parvum�s ability to use the abbreviated life cycle. Finally, genetic relatedness between co-infecting C. parvum individuals seems to affect parasite life strategy through kin selection: closely related individuals are more likely to adopt the same developmental strategy, when they share a host, than unrelated ones.
C. parvum individuals adopting the abbreviated cycle are enclosed within a cyst in their intermediate host and must produce eggs by self-fertilization, the most severe case of inbreeding. It was hypothesized that their offspring would have reduced fitness due to inbreeding depression, therefore selecting against the shorter cycle. However, this study found no difference in the survival and infection success of offspring produced through the abbreviated and normal cycles. Furthermore, no evidence for a genetic basis of life cycle abbreviation was detected: the same proportion of offspring from both reproductive strategies adopted the shorter life cycle.
The work in this thesis provides evidence that although life cycle abbreviation provides Coitocaecum parvum with a viable alternative life strategy, numerous factors promote or restrict the adoption of this strategy. While this life history strategy has no detectable effect on parasite fitness, both environmental parameters and within-host competition affect C. parvum life-history strategies, alternatively selecting for either the shorter or normal life cycle. Overall, the complexity of the parasite environment could maintain both developmental strategies in C. parvum populations and, on a broader scale, could have influenced the evolution of complex life cycles in parasites.
44
Heesch, Svenja, e n/a. "Endophytic phaeophyceae from New Zealand". University of Otago. Department of Botany, 2005. http://adt.otago.ac.nz./public/adt-NZDU20060901.141241.
Testo completoAbstract (sommario):
The aims of this study were to find endophytic brown algae in marine macroalgae from New Zealand, isolate them into culture and identify them using morphological as well as molecular markers, to study the prevalence of pigmented endophytes in a representative host-endophyte relationship, and to reveal the ultrastructure of the interface between the obligate parasite Herpodiscus durvillaeae (LINDAUER) SOUTH and its host Durvillaea antarctica (CHAMISSO) HARRIOT.
Three species of pigmented endophytic Phaeophyceae were isolated from New Zealand macrophytes. They were distinguished based on morphological characters in culture, in combination with their distribution among different host species and symptoms associated with the infection of hosts. ITS1 nrDNA sequences confirmed the identity of two of the species as Laminariocolax macrocystis (PETERS) PETERS in BURKHARDT & PETERS and Microspongium tenuissimum (HAUCK) PETERS. A new genus and species, Xiphophorocolax aotearoae gen. et sp. ined., is suggested for the third group of endophytic Phaeophyceae. Three genetic varieties of L. macrocystis as well as two varieties each of M. tenuissimum and X. aotearoae were present among the isolates. L. macrocystis and X. aotearoae constitute new records for the marine flora of the New Zealand archipelago, on genus and species level. The red algal endophyte Mikrosyphar pachymeniae LINDAUER previously described from New Zealand is possibly synonymous with Microspongium tenuissimum.
The prevalence of infection by Laminariocolax macrocystis was investigated in three populations of Macrocystis pyrifera along the Otago coast. Two of the populations situated inside and at the entrance of Otago Harbour showed high infection rates (average between 95 and 100%), while an offshore population was less infected (average of 35%).
The phylogenetic affinities of the parasitic brown alga Herpodiscus durvillaeae, an obligate endophyte of Durvillaea antarctica (Fucales, Phaeophyceae) in New Zealand, were investigated. Analyses combined nuclear encoded ribosomal and plastid encoded RuBisCO genes. Results from parsimony, distance and likelihood methods suggest a placement of this species within the order Sphacelariales. Even though H. durvillaeae shows a reduced morphology, molecular data were supported by two morphological features characteristic for the Sphacelariales: the putative presence of apical cells and the transistory blackening of the cell wall with 'Eau de Javelle'.
Ultrastructural sections showed evidence for a symplastic contact between the cells of the parasite H. durvillaeae and its host D. antarctica. Within the host cortex, parasite cells attack the fields of plasmodesmata connecting host cells. In these areas, parasite cells squeeze between the host cells and form secondary plasmodesmata connecting the primary plasmodesmata of the host cells with the cytoplasma of the parasite cell.
Moreover, despite being described as lacking pigments, H. durvillaeae possesses a rbcL gene, and its plastids show red autofluorescence in UV light, suggesting the presence of a possibly reduced, but functional photosynthetic apparatus. Vestigial walls between developing spores in the 'secondary unilocular sporangia' of H. durvillaeae confirm the identity of these sporangia as plurilocular gametangia, derived from reduced gametophytes which were entirely transformed into gametangia.
45
Matthews, Leslie Jeanne. "Synthetic vaccines from peptide libraries : lessons from a model pathogen /". free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924906.
Testo completo
46
Akbulut, Süleyman. "Effect of Bursaphelenchus xylophilus (Nematod:Aphelenchoididae) fourth stage dispersal of juveniles and log seasonality on life processes of Monochamus carolinensis (Coleoptera:Cerambycidae) /". free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901211.
Testo completo
47
Kunkel, Brian A. "Plant Fungal Endosymbionts Alter Host-Parasite Relationships Between Generalist Herbivores (Lepidoptera: Noctuidae) and An Entomopathogenic Nematode". The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1047328087.
Testo completo
48
Vanwalleghem, Gilles. "Adaptations of Trypanosoma brucei to the innate immunity proteins TNF-gas and ApoL-1". Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209725.
Testo completoAbstract (sommario):
This work allowed the first characterization of the three members of the chloride channel CLC family in T.brucei. The TbCLCs are expressed in the two proliferative stages of the parasite and two of their members appear non-essential. The three TbCLCs act as chloride transporters in X.laevis oocytes and some of their biophysical properties were determined. Furthermore, TbCLC-b appeared to be involved in lysis by the human innate immunity protein apoL-1A novel function of T.brucei adenylate cyclases was discovered in their ability to suppress expression of the innate immunity protein TNF-α. The suppression of the innate response occurs before the first peak of parasitemia and reduces the host ability to control the parasite.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
49
Davies, Claire Louise. "Parasite dynamics and community richness in a naturally fragmented water vole (Arvicola amphibious) metapopulation". Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=228192.
Testo completoAbstract (sommario):
Fragmentation can drive local populations to become smaller and more isolated, and consequently more susceptible to extinction. Movement between patches, however, can interconnect such populations so that they effectively behave as larger and more stable metapopulations. Over the past two decades metapopulations have been used to shed light on the complex interactions that occur between hosts and parasites. Effectively every host can be considered as a discrete habitat patch from the perspective of a parasite. As such, host-parasite interactions naturally lend themselves to being examined within the metapopulation paradigm. In this thesis I examine empirically how various aspects of metapopulation structure, such as local host population size and landscape isolation/connectivity, combine to determine the extinction and recolonization dynamics of parasites in the landscape. Using a naturally fragmented water vole (Arvicola amphibious) metapopulation, I describe the spatial and temporal variation in parasite infection prevalence or burden in a Scottish landscape. I specifically address the spatial and temporal dynamics of both ectoparasites, and vectortransmitted microparasites, since these are two groups of parasites commonly found in natural systems yet often overlooked in the host-parasite metapopulation literature. In addition, I attempt to understand how specific parasite characteristics, such as transmission mode and infectious period, can influence how parasites respond to host population structure. In the final chapter, I bring together a number of parasite groups to examine the impact of metapopulation dynamics on parasite communities as a whole by investigating its impact of parasite community richness. Overall the findings of my study indicate that host spatial structure and the level of connectivity between patches are important factors that affect parasite dynamics and community richness. However, the exact level of connectivity required to sustain a parasite population locally depended on specific parasite characteristics. In contrast, local effects host/vector population size and patch infection history) had no discernible impact on most parasite groups.
50
Pfarr, Kenneth M. "Studies of nitric oxide synthase in Brugia malayi and Acanthocheilonema viteae, and identification of gravid-specific transglutaminase substrates in Brugia malayi /". Thesis, Connect to Dissertations & Theses @ Tufts University, 2001.
Cerca il testo completoAbstract (sommario):
Thesis (Ph.D.)--Tufts University, 2001.Adviser: Juliet A. Fuhrman. Submitted to the Dept. of Biology. Includes bibliographical references (leaves 42-54). Access restricted to members of the Tufts University community. Also available via the World Wide Web;