Cognitive testing.
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Endarterectomy, Carotid↗
Biomedical subjects
M Gaunt
Publications and source records attributed to M Gaunt.
Transcranial Doppler detected cerebral microembolism following carotid endarterectomy.
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Carotid Arteries↗
Transmission of louping ill virus between infected and uninfected ticks co-feeding on mountain hares.
Most of the data on oral infection of ticks by louping ill virus have been obtained from experiments in which animals were infected by syringe inoculation with infectious material. Using infected ticks to mimic the natural situation, we have demonstrated that louping ill (LI) virus transmission can occur from infected to uninfected Ixodes ricinus feeding in close proximity on mountain hares (Lepus timidus). Under these conditions the hares developed either low or undetectable viraemias. Highest prevalence of LI virus infection was observed in recipient nymphs which had fed to repletion between days 3 and 7 post-attachment of virus-infected adults; following engorgement, 56% of nymphs acquired virus. These results demonstrate the efficient transmission of LI virus between co-feeding ticks on naive mountain hares. However, when ticks were allowed to co-feed on virus-immune hares a significant reduction in the frequency of infection was observed. Neither red deer (Cervus elaphus) nor New Zealand White rabbits supported transmission of LI virus. The significance of virus transmission between cofeeding ticks on LI virus epidemiology is discussed.
Animals↗
The epidemiology of louping-ill, a tick borne infection of red grouse (Lagopus lagopus scoticus).
The epidemiology of louping-ill in red grouse was studied in northern Britain concentrating on the possible role of other species and mechanisms of disease persistence. This tick borne viral disease caused heavy mortality in red grouse, particularly chicks. Louping-ill induced mortality reduced the strength of the density dependence that generates the tendency of grouse populations to cycle and in some populations may cause population sinks. Four routes of transmission were examined and non-viraemic transmission of virus between ticks cofeeding on hares was considered significant. Field data supported the hypothesis that disease dynamics is influenced greatly by mountain hares, both as passive amplifiers and as hosts for the tick vector. Genetic variation in louping-ill within Britain was small.
Animals↗
Persistence and transmission of tick-borne viruses: Ixodes ricinus and louping-ill virus in red grouse populations.
The population dynamics of tick-borne disease agents and in particular the mechanisms which influence their persistence are examined with reference to the flavivirus that causes louping-ill in red grouse and sheep. Pockets of infection cause heavy mortality and the infection probably persists as a consequence of immigration of susceptible hosts. Seroprevalence is positively associated with temporal variations in vectors per host, although variation between areas is associated with the abundance of mountain hares. The presence of alternative tick hosts, particularly large mammals, provides additional hosts for increasing tick abundance. Grouse alone can not support the vectors and the pathogen but both can persist when a non-viraemic mammalian host supports the tick population and a sufficiently high number of nymphs bite grouse. These alternative hosts may also amplify virus through non-viraemic transmission by the process of co-feeding, although the relative significance of this has yet to be determined. Another possible route of infection is through the ingestion of vectors when feeding or preening. Trans-ovarial transmission is a potentially important mechanism for virus persistence but has not been recorded with louping-ill and Ixodes ricinus. The influence of non-viraemic hosts, both in the multiplication of vectors and the amplification of virus through non-viraemic transmission are considered significant for virus persistence.
Animals↗
Microinjection of human placenta. I: Techniques.
An apparatus is described which has been used successfully to microinject the syncytiotrophoblast of chorionic villi, the mesenchymal core of chorionic villi, and cultured cells grown from first-trimester human trophoblast. It will accurately and repeatedly pulse picolitre quantities of injectate from the micropipette.
Female↗
Microinjection of human placenta. II: Biological application.
Using microinjection of probes detectable by epifluorescence light microscopy and electron microscopy we have provided direct evidence that syncytiotrophoblast is a true syncytium. We have investigated the freedom of movement of probes injected into the syncytiotrophoblast. These probes appear to move relatively extensively within the cytosolic compartment which forms a 'maze' through the membrane-bounded organelles and reticula of the syncytium. Thus mathematical models of certain forms of transepithelial transport based on simple mean and harmonic mean histologically measured thickness of epithelia are unlikely to describe the transepithelial transport pathway of at least some larger molecules, particulates and organelles with great accuracy. Microinjection of probes directly into the mesenchymal core of chorionic villi has been used to demonstrate extensive freedom of movement in that compartment which is the region where exchange with elements contained in the fetal vascular tree takes place.
Chorion↗
The ecotopes and evolution of triatomine bugs (triatominae) and their associated trypanosomes.
Triatomine bug species such as Microtriatoma trinidadensis, Eratyrus mucronatus, Belminus herreri, Panstrongylus lignarius, and Triatoma tibiamaculata are exquisitely adapted to specialist niches. This suggests a long evolutionary history, as well as the recent dramatic spread a few eclectic, domiciliated triatomine species. Virtually all species of the genus Rhodnius are primarily associated with palms. The genus Panstrongylus is predominantly associated with burrows and tree cavities and the genus Triatoma with terrestrial rocky habitats or rodent burrows. Two major sub-divisions have been defined within the species Trypanosoma cruzi, as T. cruzi 1 (Z1) and T. cruzi 2 (Z2). The affinities of a third group (Z3) are uncertain. Host and habitat associations lead us to propose that T. cruzi 1 (Z1) has evolved in an arboreal, palm tree habitat with the triatomine tribe Rhodniini, in association with the opossum Didelphis. Similarly we propose that T. cruzi (Z2) and Z3 evolved in a terrestrial habitat in burrows and in rocky locations with the triatomine tribe Triatomini, in association with edentates, and/or possibly ground dwelling marsupials. Both sub-divisions of T. cruzi may have been contemporary in South America up to 65 million years ago. Alternatively, T. cruzi 2 (Z2) may have evolved more recently from T. cruzi 1 (Z1) by host transfers into rodents, edentates, and primates. We have constructed a molecular phylogeny of haematophagous vectors, including triatomine bugs, which suggests that faecal transmission of trypanosomes may be the ancestral route. A molecular clock phylogeny suggests that Rhodnius and Triatoma diverged before the arrival, about 40 million years ago, of bats and rodents into South America.
Animals↗