Biomedical subjects

Mark Powell

Publications and source records attributed to Mark Powell.

9 recordsLinked to original sources

PubMed2006

Identification and expression of natriuretic peptide receptor type-A and -B mRNA in freshwater and seawater rainbow trout.

Natriuretic peptide receptors mediate the physiological response of natriuretic peptide hormones. One of the natriuretic peptide receptor types is the particulate guanylyl cyclase receptors, of which there are two identified: NPR-A and NPR-B. In fishes, these have been sequenced and characterized in eels, medaka, and dogfish shark (NPR-B only). The euryhaline rainbow trout provides an opportunity to further pursue examination of the system in teleosts. In this study, partial rainbow trout NPR-A-like and NPR-B-like mRNA sequences were identified via PCR and cloning. The sequence information was used in real-time PCR to examine mRNA expression in a variety of tissues of freshwater rainbow trout and rainbow trout acclimated to 35 parts per thousand seawater for a period of 10 days. In the excretory kidney and posterior intestine, real-time PCR analysis showed greater expression of NPR-B in freshwater fish than in those adapted to seawater; otherwise, there was no difference in the expression of the individual receptors in fresh water or seawater. In general, the expression of the NPR-A and NPR-B type receptors was quite low. These findings indicate that NPR-A and NPR-B mRNA expression is minimally altered under the experimental regime used in this study.

Adaptation, Physiological↗

PubMed2004

Experimental induction of gill disease in Atlantic salmon Salmo salar smolts with Tenacibaculum maritimum.

An experimentally induced bacterial infection of marine Atlantic salmon Salmo salar smolt gills was developed using strains of Tenacibaculum maritimum originally isolated from disease outbreaks in Tasmania. The gills of salmon were inoculated with a high concentration of bacteria (4 x 10(11) cells per fish) of either strain 00/3280 or 89/4747 T. maritimum. Gentle abrasion of the gills was used to enhance the progression of gill disease. One strain (00/3280) was highly pathogenic, causing morbidity and mortality within 24 h post-inoculation, and produced acute focal branchial necrosis associated with significant increases in plasma osmolality and lactate concentration compared with controls (non-inoculated) or strain 89/4747-inoculated fish. There were no differences in the whole body net ammonium flux between control (non-inoculated) and strain 00/3820-inoculated fish. Gill abrasion resulted in acute telangiectasis and focal lamellar hyperplasia in all fish regardless of bacterial inoculation. This work provides the basis of a challenge model suitable for investigating the pathophysiological processes associated with acute branchial necrosis in marine fish, suggesting that osmoregulatory and possibly respiratory dysfunction are the primary consequences of infection.

Animals↗

PubMed2004

Excretory calcinosis: a new fatal disease of wild American lobsters Homarus americanus.

A significant number of moribund and dead lobsters Homarus americanus were reported to New York state authorities by lobster fishers in Long Island Sound (LIS) during the summer of 2002. Morbid lobsters were characterised by an orange discolouration of the abdomen, lethargy, an excess of epibionts and poor post-capture survival. On necropsy, severe extensive multifocal or diffuse mineralised granulomatous inflammation of the gills and antennal glands was the most striking pathology. In the gills, granulomas often occluded the lumen of filaments, resulting in congestion, ischemia and coagulative necrosis of gill tissues. In the antennal glands, granulomas were concentrated along the border between the coelomosac and labyrinth. No significant pathogens were recovered from diseased individuals. In prechronic individuals, however, it was evident that granulomas were focused around calcium carbonate (aragonite) crystals. This disease may result from anomalously high sea-bottom temperatures in LIS (approximately 23 degrees C) during the summer of 2002 and associated disruptions of the calcium chemistry of lobsters in favour of deposition of minerals in soft tissues. The ultimate cause of death of affected lobsters is probably respiratory failure due to reduced effective surface area of the gills, exacerbated by hypermetabolic temperatures and an abundance of epibionts.

Animals↗

PubMed2004

Considering the complexity of microbial community dynamics in food safety risk assessment.

The potential for competitive inhibition to limit the growth of microbial pathogens in food raises questions about the external validity of typical predictive microbiology studies and suggests the need to consider microbial community dynamics in food safety risk assessment. Ecological theory indicates, however, that community dynamics are highly complex and may be very sensitive to initial conditions and random variation. Seemingly incongruous empirical results for Escherichia coli O157:H7 in ground beef are shown to be consistent with a simple theoretical model of interspecific competition. A potential means of incorporating community-level microbial dynamics into the food safety risk assessment process is explored.

Antibiosis↗

PubMed2004

Elimination of ephedrines in urine following multiple dosing: the consequences for athletes, in relation to doping control.

AIMS: To study the elimination of ephedrines with reference to the International Olympic Committee (IOC) doping control cut-off levels, following multiple dosing of over-the-counter decongestant preparations. METHODS: A double-blind study was performed in which 16 healthy male volunteers were administered either pseudoephedrine or phenylpropanolamine in maximal recommended therapeutic doses over a 36-h period. Urine was collected every two hours between 08:00 and 24:00 h and at 04:00 h throughout the testing period of three days. Urine drug levels were quantified using high performance liquid chromatography. Side-effects were assessed, including heart rate and blood pressure, every four hours between 08:00 and 20:00 h. RESULTS: Mean (95% CI) total phenylpropanolamine and pseudoephedrine eliminated unchanged was 75 (88, 61) and 81 (92, 71)%, respectively. Maximum urine concentrations of phenylpropanolamine and pseudoephedrine were 112.1 (164.2, 59.9) and 148.5 (215.0, 82.1) mg.l(-1), respectively. A peak in drug urine concentration occurred four hours following the final dose. There were no adverse cardiovascular effects and only mild CNS stimulation was evident. CONCLUSIONS: Following therapeutic, multiple dosing, drug levels remain above the IOC cut-off levels for a minimum of 6 h and 16 h following final doses of phenylpropanolamine and pseudoephedrine, respectively. Athletes require informed advice on this from their healthcare professionals.

Adult↗

PubMed2004

Automated performance evaluation of range image segmentation algorithms.

Previous performance evaluation of range image segmentation algorithms has depended on manual tuning of algorithm parameters, and has lacked a basis for a test of the significance of differences between algorithms. We present an automated framework for evaluating the performance of range image segmentation algorithms. Automated tuning of algorithm parameters in this framework results in performance as good as that previously obtained with careful manual tuning by the algorithm developers. Use of multiple training and test sets of images provides the basis for a test of the significance of performance differences between algorithms. The framework implementation includes range images, ground truth overlays, program source code, and shell scripts. This framework should a) make it possible to objectively and reliably compare the performance of range image segmentation algorithms; b) allow informed experimental feedback for the design of improved segmentation algorithms. The framework is demonstrated using range images, but in principle it could be used to evaluate region segmentation algorithms for any type of image.

Journal Article↗

PubMed2004

Risk assessment for invasive species.

Although estimates vary, there is a broad agreement that invasive species impose major costs on the U.S. economy, as well as posing risks to nonmarket environmental goods and services and to public health. The domestic effort to manage risks associated with invasive species is coordinated by the National Invasive Species Council (NISC), which is charged with developing a science-based process to evaluate risks associated with the introduction and spread of invasive species. Various international agreements have also elevated invasive species issues onto the international policy agenda. The World Trade Organization (WTO) Sanitary and Phytosanitary (SPS) Agreement establishes rights and obligations to adhere to the discipline of scientific risk assessment to ensure that SPS measures are applied only to the extent required to protect human, animal, and plant health, and do not constitute arbitrary or unjustifiable technical barriers to trade. Currently, however, the field of risk assessment for invasive species is in its infancy. Therefore, there is a pressing need to formulate scientifically sound methods and approaches in this emerging field, while acknowledging that the demand for situation-specific empirical evidence is likely to persistently outstrip supply. To begin addressing this need, the Society for Risk Analysis Ecological Risk Assessment Specialty Group and the Ecological Society of America Theoretical Ecology Section convened a joint workshop to provide independent scientific input into the formulation of methods and processes for risk assessment of invasive species to ensure that the analytic processes used domestically and internationally will be firmly rooted in sound scientific principles.

Animals↗

PubMed2004

Risk analysis for invasive species: general framework and research needs.

A joint workshop was convened by the Society for Risk Analysis Ecological Risk Assessment Specialty Group and the Ecological Society of America Theoretical Ecology Section to provide independent scientific input into the formulation of methods and processes for risk assessment of invasive species. In breakout sessions on (1) the effects of invasive species on human health, (2) effects on plants and animals, (3) risk analysis issues and research needs related to entry and establishment of invasive species, and (4) risk analysis issues and research needs related to the spread and impacts of invasive species, workshop participants discussed an overall approach to risk assessment for invasive species. Workshop participants agreed on the need for empirical research on areas in which data are lacking, including potential invasive species, native species and habitats that may be impacted by invasive species, important biological processes and phenomena such as dispersal, and pathways of entry and spread for invasive species. Participants agreed that theoretical ecology can inform the process of risk assessment for invasive species by providing guidelines and conceptual models, and can contribute to improved decision making by providing a firm biological basis for risk assessments.

Animals↗

PubMed2004

Species of the family Helicobacteraceae detected in an Australian sea lion (Neophoca cinerea) with chronic gastritis.

We describe the first case of gastritis in a male Australian sea lion (Neophoca cinerea) in which members of the family Helicobacteraceae, particularly the genus Wolinella, were detected. The sea lion exhibited clinical signs of gastrointestinal disease, including abdominal pain, lack of appetite, and lethargy. Examination of one ileal and five gastric biopsy specimens collected over a 10-year period revealed persistent fibrosis and/or superficial focal erosion and ulceration of the lamina propria. Spiral-shaped organisms 5 to 12 microm long were observed in two of the gut biopsy specimens. While Helicobacter species were detected by PCR in one of the gastric biopsy specimens, Wolinella species were detected in four of the five gastric specimens, including those in which spiral-shaped organisms were observed. Comparisons of biopsy specimen ribosomal DNA sequences with those obtained from the feces of this animal, the gastric tissue of a clinically healthy individual, and the feces of several other cohoused sea lions and fur seals revealed a separate and possibly novel gastric Helicobacter species. A possibly novel Wolinella species, along with Wolinella succinogenes, was also identified. These findings highlight the pathogenic potential of other members of this family in the etiopathogenesis of gastric disease in these animals.

Animals↗