Biomedical subjects

Peter Walker

Publications and source records attributed to Peter Walker.

7 recordsLinked to original sources

PubMed2004

General condition biomarkers in relation to contaminant burden in European flounder (Platichthys flesus).

In respect to the differences found for vitellogenin (VTG) expression in male and immature flounder, general biological aspects and a set of chemical residues in the liver were compared between flounder from the Mersey and Dee estuaries (UK). Except for alpha-HCH, all pollutant chemicals analysed in flounder liver differed highly significantly between Mersey and Dee fish. Overall, the higher liver contaminant concentrations were found in VTG-induced Mersey flounder. The biomarkers studied were not found to indicate significant differences between Mersey and Dee fish. However, when all of the minor differences are taken into consideration, it appears that the slightly lower growth rates after age 2 in Mersey flounder, lower gonadosomatic index in both mature male and female animals, less precise seasonal patterns of condition factor (CF), hepatosomatic index and gonadosomatic index, and lower CF in immature Mersey fish may well be signs of a contaminant-affected Mersey population.

Age Factors↗

PubMed2004

Performance characteristics of ultrasound of the knee in a general radiological setting.

Ultrasound of the musculoskeletal system is an attractive imaging modality due to the lack of ionising radiation, cost and ease of availability. A role has been established in the shoulder and pediatric hip but not in the knee. Ultrasound studies of the knee performed at six general radiological practices without established musculoskeletal expertise were compared with clinical examination in 56 patients. Final diagnoses were established by arthroscopy and/or MRI. The sensitivity and specificity for detection of superficial lesions in the knee were 88 and 41% for clinical examination and 32 and 59% for ultrasound. For deep lesions sensitivity and specificity were 61 and 64% for clinical examination and 13 and 100% for ultrasound. Ultrasound studies of the knee in a general radiological practice do not offer significant information above clinical examination.

Adolescent↗

PubMed2004

Birthing Sphere.

This paper tells the story of the initiation and first year of Sphere. It traces the history of how the project was started and its relationship to other major events of that time, principally the multi-donor Rwanda evaluation. The paper describes how the basic structure of the Sphere standards was agreed upon and discusses why some sectors were eventually left out of the standards. Tensions and public disagreements between the agencies that created Sphere are discussed, along with the manner in which the chosen working processes contributed to the successful publication of the Sphere standards. We show how the process of policy formulation, which led up to the publication of the first edition of the Sphere standards, was as dependent upon the ability of the project team to work opportunistically as it was upon the application of agency principles. Finally the paper reflects upon the success of Sphere and lessons that can be learned from this early Sphere process.

Altruism↗

PubMed2004

The future of humanitarian action: mapping the implications of Iraq and other recent crises.

In late 2003 the Feinstein International Famine Center, in partnership with institutions in London, Geneva and Washington, organised a series of consultations on the future of humanitarian action post-Iraq. This article is based on those discussions. A number of recurring concerns are elaborated, ranging from the perception of humanitarianism as a Northern-driven and Northern-controlled enterprise, through the politicisation of security and the devaluation of the protective power of emblems, to the very nature of how the crisis in Iraq is perceived. The article explores the implications of such issues for humanitarian workers and their institutions. It concludes by framing an agenda for action by the humanitarian sector.

Afghanistan↗

PubMed2003

Autism and a deficit in broadening the spread of visual attention.

BACKGROUND: This study examines if visual attention in autism is spatially overfocused (Townsend & Courchesne, 1994) and if there is an associated deficit in broadening the spatial spread of attention. METHOD: Two crosshairs were presented on each trial separated by a brief (500 ms) interval. There was a modest difference in the lengths of the two hairs in each crosshair and participants had to decide which one was longest. Previous research (Mack & Rock, 1998) has revealed that in making this judgement people spread their visual attention to embrace the whole crosshair. Varying the overall size of each crosshair was intended to control participants' spread of attention. The impact of the size of the first crosshair gave an indication of participants' default setting for the spread of attention. The impact of the size transition between the first and second crosshair gave an indication of the fluency with which participants could change the spatial spread of visual attention. RESULTS: Based on the first proposal it was predicted that individuals with autism (N = 13), relative to ability-matched moderately learning disabled (N = 15) and typically developing individuals (N = 15), would be more accurate and quicker to respond when the first crosshair was small rather than large. However, the results revealed no effects of the size of the first crosshair and no group differences. Based on the second proposal it was predicted that individuals with autism, relative to both control groups, would be less accurate and slower to respond to the second crosshair when the size transition from the first crosshair involved a change from small to large (in comparison with large to large), but would not differ when the change was from large to small (in comparison with small to small). This prediction was confirmed. CONCLUSION: Autism is associated with a deficit in broadening the spatial spread of visual attention. The implications of this for other visual and attentional anomalies observed in autism are discussed.

Adolescent↗

PubMed2003

Perceptual completion and object-based representations in short-term visual memory.

Object-based representations in visual short-term memory (VSTM) were examined using a change detection memory task. A display comprising two rows of four differently colored elements was followed by a probe display in which only one of the rows reappeared. On same trials, the probed row was identical to the corresponding row in the memory display. On different trials, two of the elements in the probed row had their colors exchanged. In each memory display, a task-irrelevant visual element appeared between the two rows, with the potential to function as an occluder. Performance was enhanced when perceptual completion meant that four, rather than eight, objects were perceived in the memory display and when the probe display revealed that the occluded elements continued behind the occluder. It appears that several forms of representation can co-occur to support VSTM, one of which is object based.

Feedback↗

PubMedDate not supplied

Histopathological observations on liver, kidney and gonad of plaice (Pleuronectes platessa) taken from the Mersey estuary.

The Mersey estuary is the most contaminated estuary in British waters. Detailed studies are underway on the pathology of flounder (Platichthys flesus) from the Mersey and on flounder from the nearby, but less contaminated, Dee estuary. Flounder breed offshore but spend a lot of time in the estuaries, penetrating into freshwater. These flatfish are in close contact with sediments and will be exposed to exenobiotic stored in the sediments. Plaice (Pleuronectes platessa) are flatfish which enter the Mersey with the tidal flow but spend less time in the estuary than flounder and are less likely to show evidence of pollutant exposure. Over 20 plaice were collected from the Mersey. Samples of the liver, kidney and gonad were fixed in 10% formal saline, processed into paraffin wax and 5 microm sections cut and stained with haematoxylin and eosin. Liver changes consisted of variable amounts of glycogen/lipid storage product, minor perivenular and perivascular fibrosis, and helminth parasitisation. No tumours or foci of cellular alteration, necrosis and inflammation were seen. In the gonad only changes consistent with normal gonadal cycling was seen. These studies provide evidence that plaice show little or no evidence of toxic pathological damage resulting from their stay in the estuary.

Animals↗