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Biomedical subjects

R A Evans

Publications and source records attributed to R A Evans.

At least 19 recordsLinked to original sources
PubMed2005

Performance of a pilot-scale high rate algal pond system treating abattoir wastewater in rural South Australia: nitrification and denitrification.

As part of a study examining the efficacy of high-rate algal pond treatment of high-strength abattoir wastewater, the impact of pond configuration and loading rate on nitrification was determined. The extent of nitrification in all ponds was consistent with mass balance estimates of oxygen demand and availability. Deeper ponds were more stable nitrifying systems, with shallow ponds displaying greater variation in response to changes in nitrogen loading. In a separate experiment the pond system was modified by covering a part of an in-series HRAP to exclude light, providing conditions suitable for denitrification. Specific denitrification rates were often within the range typical for endogenous carbon sources, with mass balance calculations indicating removals of up to 95%.

Abattoirs↗
PubMed2004

Design-based estimation of surface area in thick tissue sections of arbitrary orientation using virtual cycloids.

Surface area is a first-order stereological parameter with important biological applications, particularly at the intersection of biological phases. To deal with the inherent anisotropy of biological surfaces, state-of-the-art design-based methods require tissue rotation around at least one axis prior to sectioning. This paper describes the use of virtual cycloids for surface area estimation of objects and regions in thick, transparent tissue sections cut at any arbitrary (convenient) orientation. Based on the vertical section approach of Baddeley et al., the present approach specifies the vertical axis as the direction of sectioning (i.e. the direction perpendicular to the tissue section), and applies computer-generated cycloids (virtual cycloids) with their minor axis parallel to the vertical axis. The number of surface-cycloid intersections counted on focal planes scanned through the z-axis is proportional to the surface area of interest in the tissue, with no further assumptions about size, shape or orientation. Optimal efficiency at each x-y location can be achieved by three virtual cycloids orientated with their major axes (which are parallel to the observation planes) mutually at an angle of 120 degrees. The major practical advantage of the present approach is that estimates of total surface area (S) and surface density (SV) can be obtained in tissue sections cut at any convenient orientation through the reference space.

Animals↗
PubMed2003

Characterisation of oxygen dynamics within a high-rate algal pond system used to treat abattoir wastewater.

As part of a study examining the efficacy of high-rate algal pond treatment of high-strength abattoir wastewater, the oxygen dynamics of a pilot scale system were characterised. The relationship between photosynthesis and irradiance was investigated using online data collected throughout a year of operation under varying conditions of climate and wastewater quality. Changes in climate were reflected in changes in the net rate of photosynthesis in deep ponds, consistent with adaptation of algal populations to changing light intensity, whilst the response of shallow ponds was more varied. The use of online monitoring and the calculation in real time of photosynthetic rates should allow for improved design and management of full scale treatment systems and further the understanding of factors driving biological reactions within these systems.

Abattoirs↗
PubMed2002

Hand exsanguination: prospective randomised blind study of an established versus a modified technique.

One hundred patients undergoing elective hand surgery were randomized to have their hands exsanguinated by either the Rhys-Davies exsanguinator alone or the Rhys-Davies exsanguinator supplemented by a 500 ml bag of intravenous fluid which was placed in the patient's palm as the exsanguinator was rolled up the limb. The quality of the exsanguination was assessed by the surgeon using a pre-defined subjective scoring system. There were no significant differences in the exsanguination scores of the two treatment groups.

Blood Loss, Surgical↗
PubMed2002

Efficacy of laser palatoplasty: four-year results.

There are few reports on the long-term results of laser-assisted uvulopalatoplasty (LAUP), with some casting doubt about its long-term efficacy. We report satisfactory results in patients with more than four years' follow-up. We conducted a retrospective study of patients who underwent LAUP at the Princess of Wales Hospital over a period of five years. Thirty-three patients underwent LAUP as a day case procedure. They had had a mean follow-up period of four years and five months. Twenty-eight of these were asked details of their pre- and postoperative levels of snoring regarding frequency, volume and disturbance to their partners. There was a 50% reduction in frequency of snoring, a 51.85% reduction in volume and a 53.7% reduction in disturbance to their partners. All these figures are statistically significant (p<0.001). Overall, 60.8% of the patients felt the surgery was successful and had reduced their snoring to acceptable levels. We conclude that LAUP is an effective treatment for snoring, even in the long term.

Adult↗
PubMed2001

Translational regulation of renal proximal tubular epithelial cell transforming growth factor-beta1 generation by insulin.

We have previously demonstrated that the proximal tubular cell may contribute to the pathogenesis of renal interstitial fibrosis in diabetes. Transforming growth factor (TGF)-beta1 is one of a group of pro-fibrotic cytokines and growth factors, which have been associated with the development of interstitial fibrosis. The aim of the current study was to examine the effect of insulin on the generation of TGF-beta1 by proximal tubular cells. HK-2 cells were grown to confluence in the absence of insulin, and serum deprived for 48 hours before all experimental manipulations. Addition of insulin (5 microg/ml) to the culture medium led to a time-dependent increase in TGF-beta1 concentration in the cell culture supernatant, and increased incorporation of radiolabeled amino acids into TGF-beta1 suggestive of de novo TGF-beta1 protein synthesis. Addition of insulin did not alter TGF-beta1 mRNA expression as assessed by reverse transcriptase-polymerase chain reaction or Northern analysis. Insulin-induced increase in TGF-beta1 concentration was not abrogated by actinomycin D, however, stimulation by insulin, in the presence of cycloheximide led to a dose-dependent decrease in TGF-beta1 production. Addition of insulin had no effect on TGF-beta1 mRNA stability as assessed by actinomycin D chase, but led to increased binding of a cytoplasmic protein to a putative stem loop structure in the 5'-UTR of TGF-beta1 mRNA, previously implicated in the posttranscriptional control of TGF-beta1 synthesis. To address the functional significance of insulin-induced alteration in TGF-beta1 synthesis, we examined its effect on matrix turnover. Insulin stimulated type IV collagen gene expression and an increase in the concentrations of the type IV collagen laid down in the extracellular matrix. This increase in type IV collagen was abrogated when cells were stimulated by insulin in the presence of an anti-TGF-beta1-blocking antibody. In conclusion the data demonstrate that insulin may directly alter the production of TGF-beta1 by renal proximal tubular cells by a posttranscriptional mechanism, and that this may have implications for the increase in extracellular matrix that accompanies diabetic nephropathy.

5' Untranslated Regions↗
PubMed2001

Pott's puffy tumour: an unusual presentation and management.

Pott's puffy tumour is a rare clinical entity in this era of antibiotics. It is usually seen as a complication of frontal sinusitis. This is the first report of Pott's puffy tumour presenting as a complication of maxillary sinusitis. This is also the first reported case of Pott's puffy tumour treated with debridement and gentamicin beads. We discuss the clinical presentation and successful treatment of this rare disease.

Abscess↗
PubMed2001

Early feeding strategies in preterm and critically ill neonates.

This two-part article presents feeding strategies for the NICU population over the first several weeks of life. It focuses primarily on the theory and approach to feeding extremely low birth weight (ELBW) infants, but also addresses some issues pertinent to larger, ill infants. The premise for these recommendations is that avoiding early malnutrition in ELBW and ill infants has both short- and long-term benefits. Many practitioners may consider our approach to be somewhat aggressive. In this strategy, total parenteral nutrition (TPN) is initiated in the first hours after birth and is given together with initially small, and then increasing, enteral feedings beginning on the first or second day of life. The role of the TPN is to provide rapid, maximal nutrition and that of the early enteral feedings is to "prime" the gut and stimulate normal gastrointestinal tract activity.

Age Factors↗
PubMed2001

Efficacy and safety of 'hot' tonsillectomy.

Recurrent acute tonsillitis, peritonsillar infections and quinsy (peritonsillar abscess) are common clinical conditions that present to a general practitioner. Management in general practice and in hospital is confounded by apparently conflicting treatment options in the medical literature. We have developed clear guidelines as part of an ongoing audit cycle which include performing quinsy or 'hot' tonsillectomy in selected cases, alongside conservative treatments to ensure the speedy recovery and minimal hospitalisation of all patients, with resultant cost benefits.

Acute Disease↗
PubMed2000

Rhys-Davies exsanguinator: pressure characteristics and technique for improving performance.

This paper reports the results of an investigation into the pressure exerted by the Rhys-Davies exsanguinator on the palm and dorsum of the hand. We hypothesised that, due to the shape of the hand, the palm is shielded from the full effect of the exsanguinator, but our study showed that it is compressed as well as the dorsum. However, placing a bag of fluid in the patient's palm significantly increased the pressure applied to the palm.

Adult↗
PubMed1999

Human Daxx regulates Fas-induced apoptosis from nuclear PML oncogenic domains (PODs).

Daxx was first identified as a protein that binds the cytosolic domain of Fas and links this receptor to an apoptosis pathway involving activation of Jun N-terminal kinase (JNK). We show here that cells overexpressing the human homolog of Daxx (hDaxx) display enhanced sensitivity to apoptosis induced by Fas but not by several other cell death stimuli. hDaxx-mediated enhancement of Fas-induced apoptosis was correlated with accelerated activation of caspases but not with JNK induction. Although specifically enhancing Fas function, hDaxx does not bind Fas and instead is found in the nucleus where it localizes to PML oncogenic domains (PODs). Moreover, the hDaxx protein also exhibits the ability to repress transcription. Mutagenesis studies demonstrated a correlation between the localization of hDaxx to PODs and its ability to enhance Fas-induced cell death. Arsenic trioxide (As(2)O(3)), an agent that accentuates POD formation, collaborated synergistically with overexpression of hDaxx to increase cellular sensitivity to Fas-induced apoptosis. Taken together, these findings argue that hDaxx promotes sensitivity to Fas from a nuclear location, probably by modulating the transcription of genes involved in Fas-induced caspase activation and apoptosis.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Cellular activation through the ligation of intercellular adhesion molecule-1.

In addition to its role in mediating leukocyte adherence to and migration across the endothelium, intercellular adhesion molecule (ICAM)-1 on the surface of interstitial cells has been implicated as a principal adhesion molecule controlling leukocyte infiltration at inflammatory sites. The present study demonstrates that leukocyte binding to fibroblasts isolated from both the human renal cortex and lung and to endothelial cells induced the de novo synthesis of ICAM-1 mRNA and protein through the ICAM-1-dependent activation of the cultured cells. This was mimicked by specifically cross-linking the ICAM-1 receptor with anti-ICAM-1 antibodies. Following cross-linking there was a two- to threefold increase in the steady state levels of ICAM-1 mRNA isolated from the cells. The expression of this mRNA peaked at 1-3 hours and was dose-dependent on the concentration of secondary cross-linking antibody. Peak protein expression was between 18 and 48 hours after cross-linking. Additional data demonstrated a similar increase in the expression of VCAM-1 following ICAM-1 cross-linking. In contrast, there was no reponse as a result of incubation with an isotype-matched control antibody. Both the binding of leukocytes and the cross-linking of ICAM-1 triggered a rise in cytosolic free calcium as the result, in part, of a calcium influx from the extracellular medium. Using BAPTA-AM to chelate intracellular calcium ions indicated that this increase in cytosolic free calcium was directly involved in the initiation of adhesion molecule upregulation. The present study demonstrates that both endothelial cells and fibroblasts can be stimulated by the direct cell surface interaction of ICAM-1 with its ligands on inflammatory cells. One phenotypic change resulting from this interaction is the upregulated synthesis and expression of more cellular adhesion molecules. This may have profound implications for the control and persistence of a leukocyte infiltrate and the progression of inflammatory disease.

Actins↗
PubMed1997

Retroperitoneal collections--aetiology and radiological implications.

PURPOSE: Retroperitoneal collections related to the psoas, in the absence of pancreatitis, are uncommon. This study reviews the imaging, pathogenesis and management of retroperitoneal collections with particular emphasis on distinguishing imaging features and the role of percutaneous drainage. MATERIALS AND METHODS: Twenty-three retroperitoneal collections in 22 patients were reviewed in a 2-year period. Twenty-one patients underwent computed tomography (CT), with ultrasound (US) conducted in 14 and magnetic resonance imaging (MRI) in four. The clinical history and associated aetiological factors were noted. Methods of drainage were compared, pathological/microbiological results were recorded and the clinical outcome noted. RESULTS: The mean age of presentation was 46.9 years (range 18-85 years). There was a male to female preponderance (17 to 6). Eighteen collections proved to be abscesses with five haematomas confirmed. Of the abscesses, three were primary and 15 were secondary to spinal, gastrointestinal or renal disease. Escherichia coli was the commonest isolated organism followed by Mycobacterium tuberculosis. No haematomas were drained. Twelve abscesses were drained successfully by percutaneous methods; three were managed with antibiotics alone; three were managed surgically. CONCLUSION: Secondary abscesses predominate and investigation should be directed at excluding a gastrointestinal or renal source. Tuberculous disease remains a significant problem. Percutaneous drainage allows effective management, even in the presence of a secondary abscess.

Adult↗
PubMed1997

Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: relevance for interpretation of biomarker records.

For the cyanobacterium Synechocystis UTEX 2470, grown photoautotrophically to a logarithmic stage of growth, the total lipid extract is depleted in 13C by 4.8% relative to average biomass. Depletions observed for acetogenic (straight-chain) lipids range from 7.6 (hexadecanoic acid) to 9.9% (a C16 n-alkyl chain bound in a polar-lipid fraction), with a mass-weighted average of 9.1%. Polyisoprenoid lipids fall into two isotopic groups, with phytol, diplopterol, and diploptene depleted by 6.4-6.9% and bishomohopanol (produced from the extracts by the preparative degradation of bacteriohopanepolyol) depleted by 8.4%. Analysis of the pattern of depletions indicates that two carbon positions in each C5 biomonomer leading to polyisoprenoid products are probably depleted in 13C relative to average biomass. The depletion of bacteriohopanepolyol relative to other polyisoprenoids can be ascribed to changes that occur over the life of each cell: (1) the 13C content of carbon flowing to lipid biosynthesis decreases as the cell size increases and (2) a greater proportion of the bacteriohopanepolyol which, unlike other polyisoprenoids, is present mainly in the cytoplasm rather than in membranes and is synthesized when cells are larger. Chlorophyll a is depleted relative to average biomass by O.7%. Given the observed depletion of 13C in phytol, the heteroaromatic, chlorophyllide portion of chlorophyll must be enriched in 13C by 2.7%. This enrichment is large relative to that in chlorophyllides produced by eukaryotes and may be related to a parallel enrichment of 13C in cyanobacterial glutamic acid. As in many previous investigations of cyanobacterial lipids, long-chain n-alkanes (C22-C29) are found in the extracts. They are, however, enriched in 13C relative to biomass and have isotopic compositions suggesting that they are contaminants of petrochemical origin. Available results indicate that cyanobacterial lipids will be depleted relative to dissolved CO2 that has served as a carbon source by 22-30% and that a wider range of depletions will be characteristic of eukaryotic products. The absence of long-chain n-alkanes in cyanobacteria reduces the possibility that petroleum ever formed from pre-eukaryotic sedimentary debris.

Acetic Acid↗