Biomedical subjects

Andrew R Thompson

Publications and source records attributed to Andrew R Thompson.

7 recordsLinked to original sources

PubMed2006

Screening and ultrasound surveillance of large abdominal aortic aneurysms do not improve suitability for endovascular repair.

OBJECTIVE: The effect of population screening for abdominal aortic aneurysm (AAA) disease on morbidity and mortality has been comprehensively studied and reported. However, the effect of early AAA detection on suitability for endovascular aneurysm repair (EVAR) remains unknown. Considering the importance of such an effect on future health economics, we sought to assess the possible effect of AAA ultrasound surveillance on suitability for EVAR. METHODS: This was a prospective cohort study. From January 2002 to August 2003, consecutive AAA patients selected for open elective repair were placed into one of two groups according to mode of presentation. The first group included patients referred from a local well-established AAA ultrasound screening and surveillance program (ultrasound surveillance [AAA-S] group). The second group included patients referred from neighboring unscreened regions with incidentally diagnosed AAA (incidental [AAA-I] group). All patients underwent preoperative computed tomographic angiography. By using three-dimensional reconstruction software, computed tomographic images were assessed by two blinded observers for suitability for EVAR by using the criteria for a modular endovascular device. RESULTS: Of 74 patients included in the study, 41 were in the AAA-S group, and 31 were in the AAA-I group. The median aneurysm diameter was 72.3 mm (range, 50.7-83.7 mm) for AAA-I and 65 mm (range, 50.7-79.2 mm) for AAA-S (P < .47). Suitability for EVAR was 41% in the AAA-S group and 45% in the AAA-I group (P < .47). CONCLUSIONS: Early detection and surveillance of AAA does not seem to increase suitability for EVAR. Suitability for EVAR seems to be determined early on in an aneurysm's life. On the basis of current device technology, referral for intervention from an AAA surveillance program may need to be initiated at a size well below 5.5 cm if an increase in EVAR suitability is to be expected.

Aged↗

PubMed2006

Dynamics of mutualist populations that are demographically open.

1. Few theoretical studies have examined the impact of immigration and emigration on mutualist population dynamics, but a recent empirical study (A.R. Thompson Oecologia, 143, 61-69) on mutualistic fish and shrimp showed that immigration can prevent population collapse, and that intraspecific competition for a mutualistic partner can curb population expansion. To understand in a theoretical context the implications of these results, and to assess their generality, we present a two-species model that accounts explicitly for immigration and emigration, as well as distinguishing the impacts of mutualism on birth rates, death rates and habitat acquisition. 2. The model confirms that immigration can stabilize mutualistic populations, and predicts that high immigration, along with enhanced reproduction and/or reduced mortality through mutualism, can cause population sizes to increase until habitat availability curbs further expansion. 3. We explore in detail the effects of different forms of habitat limitation on mutualistic populations. Habitat availability commonly limits the density of both populations if mutualists acquire shelter independently. If a mutualist depends on a partner for habitat, densities of that mutualist are capped by the amount of space provided by that partner. The density of the shelter-provider is limited by the environment. 4. If a mutualism solely augments reproduction, and most locally produced individuals leave the focal patch, then the mutualism will have a minimal effect on local dynamics. If the mutualism operates by reducing rates of death or enhancing habitat availability, and there is at least some immigration, then mutualism will affect local dynamics. This finding may be particularly relevant in marine systems, where there is high variability (among species and locations) in the extent to which progeny disperse from natal locations. 5. Overall, our results demonstrate that the consequences of immigration and emigration for the dynamics of mutualists depend strongly on which demographic rate is influenced by mutualism. 6. By relating our model to a variety of terrestrial and aquatic systems, we provide a general framework to guide future empirical studies of the dynamics of mutualistic populations.

Animal Migration↗

PubMed2005

Phylogeography of marine mutualists: parallel patterns of genetic structure between obligate goby and shrimp partners.

The survival of many organisms depends on interspecific, mutualistic interactions. Hence, it is important to assess the phylogeography of multiple mutualistic species simultaneously to gain insight into how their metapopulations persist, spread and recover from disturbance. Consequently, we sequenced mitochondrial DNA (cytochrome b) from a gobiid fish (Ctenogobiops feroculus) and its mutualistic partner, an alpheid snapping shrimp (Alpheus djeddensis). These obligate mutualists are common in shallow coral reef lagoons, and we collected individuals from 11 Indo-Pacific islands that were likely exposed to different disturbance histories due to sea level fluctuations associated with glaciation events [geological studies indicate that eastern oceanic islands (Cook Islands, French Polynesia) were more disturbed than western continental plate islands that have deeper, more extensive lagoons (Okinawa, Fiji)]. Both phylogenetic and population genetic analyses indicated that gobies from Okinawa and Fiji were genetically distinct both from each other and those in the Cook Islands and French Polynesia. Shrimp, by contrast, grouped into two distinct genetic groups that showed no geographic structure. Restricting the analysis to one clade of shrimp, which contained two-thirds of the individuals, showed that these shrimp had very similar phylogeographical structure to the gobies. Mismatch distributions demonstrated that both gobies and shrimp experienced a recent, rapid population expansion into French Polynesia. Finally, nucleotide and haplotype diversities per sample location were significantly correlated between mutualists and tended to be higher on western continental than eastern oceanic islands. Our results suggest that these mutualists recovered from a major disturbance by colonizing South Pacific islands in synchrony.

Animals↗

PubMed2005

The experience of stroke for men in retirement transition.

In this study, the authors aimed to explore how men manage when two significant life events, stroke and retirement, occur within a close time proximity. They selected 7 men purposively who were either in the process of planning to retire or had just retired when they had suffered a stroke, and used interpretive phenomenological analysis to guide data collection and to analyze the resulting transcripts. The authors derived three interrelated processes with eight subthemes. The three themes were associated with ambivalence about retirement, the impact of the stroke, and healing and adjustment. The themes suggested that significant interplay existed between the meanings made of the two life events. The emergent themes implied that stroke had a profound impact on the men's lives and affected them on a number of levels. The experience of suffering a stroke also led to some positive reframing of life.

Adaptation, Psychological↗

PubMed2005

An attitudinal study of responses to a range of dermatological conditions using the implicit association test.

The Implicit Association Test (IAT) was used to explore implicit attitudes to dermatological conditions. The stimuli employed were photographs representing skin conditions and clear skin. Explicit attitudes were measured using rating scales and questions concerning participants' experience of dermatitis. Participants (N=64) completed the IAT, explicit measures and demographics. The results showed a statistically significant implicit preference for people with clear skin and suggested that people who knew someone with a skin condition may exhibit stereotype inhibition. This concurs with earlier research into disfigurement, and in accord with previous IAT research, correlations between implicit and explicit measures were not significant.

Adolescent↗

PubMed2004

Dynamics of demographically open mutualists: immigration, intraspecific competition, and predation impact goby populations.

Although it is now recognized that mutualistic species are common and can have stable populations, the forces controlling their persistence are poorly understood. To better understand the mechanisms that impact the stability of obligate mutualists, I conducted several field experiments within a sandy coral reef lagoon in Moorea, French Polynesia that manipulated densities of fish (gobies) that interact mutualistically with shrimp. Obligate, mutualistic partnerships of gobies and shrimp are common on Indo-Pacific coral reefs and have been shown previously to interact as follows: shrimp construct burrows in which both species reside, and gobies warn shrimp of predators through tactile communication. Augmentation of gobies by up to 100% above ambient densities within 9 m2 plots produced no change in overall density of gobies or shrimp because gobies competed intraspecifically for a limited number of shrimp burrows and smaller gobies were outcompeted by larger individuals. I used predators to assess the impact of goby removal on the stability of goby and shrimp populations. First, although surveys taken throughout the lagoon revealed no relationship between goby and predator densities, predators correlated negatively with the proportion of adult gobies and positively with the proportion of small gobies paired with large shrimp. Second, experimental augmentation of predators resulted in a dramatic reduction of adult gobies within predator-addition plots, but had no impact on overall densities as immigrants rapidly replaced the missing adult gobies. Furthermore, goby turnover resulted in an increase in the proportion of small gobies paired with large shrimp because body sizes of gobies and shrimp in a burrow were similar prior to predator introduction, and predators apparently had a greater impact on gobies than shrimp. The mechanisms that prevent expansion (intraspecific competition) and collapse (immigration) of goby-shrimp populations likely contribute to local-scale stability of mutualistic populations in other terrestrial and aquatic environments.

Animals↗

PubMed2002

Living with vitiligo: dealing with difference.

OBJECTIVES: Individuals with a disfigurement are at risk of experiencing psychological distress, but the level of this distress is only marginally associated with clinical severity. This study examines the experience of living with the skin condition vitiligo with a view towards understanding its impact and the ways in which participants deal with this chronic and disfiguring disease. DESIGN: The qualitative method Interpretative Phenomenological Analysis was used. METHODS: In a semi-structured interview, seven white female vitiligo sufferers were asked to describe their experiences from the time the vitiligo first became apparent to the time of the interview. They were encouraged to elaborate on their own reactions and how they dealt with the reactions of others. RESULTS: Initially, participants felt overwhelmed by their illness but over time they developed several strategies in order to 'contain' their difference in appearance within manageable limits. The behavioural strategies of avoidance and concealment had several disadvantages, whereas cognitive strategies were less problematic but difficult to sustain consistently. Social support served to facilitate the development of coping methods associated with acceptance of difference. However, maintaining this acceptance was a struggle and the process fragile. CONCLUSIONS: Living with vitiligo was a continuous struggle. The results are consistent with Leventhal's (1970) notion that coping is a problem-solving process and with Moos and Schaefer's (1984) contention that dealing with a chronic disease involves the development of a variety of strategies in order to regain equilibrium. Further research is needed to examine whether the experiences described here are common to other disfiguring conditions.

Journal Article↗