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Biomedical subjects

D L Craig

Publications and source records attributed to D L Craig.

12 recordsLinked to original sources
PubMed2004

Use of microcosms to determine persistence of Escherichia coli in recreational coastal water and sediment and validation with in situ measurements.

AIMS: To determine the persistence of the faecal indicator organism Escherichia coli in recreational coastal water and sediment using laboratory-based microcosms and validation with in situ measurements. METHODS AND RESULTS: Intact sediment cores were taken from three distinct coastal sites. Overlying estuarine water was inoculated with known concentrations of E. coli and decay rates from both overlying water and sediment were determined following enumeration by the membrane filtration method at fixed time intervals over a 28-day period. It was demonstrated that E. coli may persist in coastal sediment for >28 days when incubated at 10 degrees C. Escherichia coli survival was found to have an inverse relationship with temperature in both water and sediment. In general the decay rate for E. coli was greater in water than in sediment. Small particle size and high organic carbon content were found to enhance E. coli survival in coastal sediments in the microcosms. CONCLUSIONS: Results of this microcosm study demonstrated the more prolonged survival of E. coli in coastal sediments compared with overlying water, which may imply an increased risk of exposure because of the possible resuspension of pathogenic micro-organisms during natural turbulence or human recreational activity. SIGNIFICANCE AND IMPACT OF THE STUDY: A more accurate estimate of exposure risk has been described which may subsequently be used in a quantitative microbial risk assessment for recreational coastal waters.

Bacteriological Techniques↗
PubMed2003

Effectiveness of guideline faecal indicator organism values in estimation of exposure risk at recreational coastal sites.

Decay rates in coastal water and sediment for the bacterial pathogens Salmonella typhimurium and S. derby were compared in laboratory-based microcosms with results previously obtained for a number of faecal indicators. In general, the decay rates of Salmonella spp. were greater than either enterococci or coliphage in overlying water and sediment. Decay rates of E. coli were similar to Salmonella spp. in overlying water, although greater in sediment. Raised temperature resulted in an increased decay rate for all organisms in the overlying water (and to a lesser extent in the surface sediment layer). It was demonstrated that decay rates for both S. typhimurium and S. derby were greater in overlying water compared with sediment. This suggested that sediments may be acting as a reservoir for pathogenic microorganisms released into the coastal environment during recreational activity and should be considered when estimating environmental exposure. Using measured decay rates and available dose-response data, a quantitative microbial risk assessment (QMRA) utilising Monte Carlo simulation was undertaken to estimate the risk of infection to Salmonella spp. following exposure to recreational coastal water subject to a range of faecal contamination levels. In waters of extremely poor quality, subject to contamination by faecal coliforms (10(6) CFU/100 mL), the maximum probability of infection on the day of an accidental release was above 2.0 x 10(-1) and remained above 1 x 10(-3) for three days following the initial high concentration.

Escherichia coli↗
PubMed2002

Enumeration of faecal coliforms from recreational coastal sites: evaluation of techniques for the separation of bacteria from sediments.

AIMS: To identify the most efficient techniques for the separation of micro-organisms from coastal sediments and, using these techniques, to determine the concentration of faecal indicator organisms in recreational coastal water and sediment. METHODS AND RESULTS: Sediment samples were taken from a range of recreational coastal sites and subjected to various physical techniques to separate micro-organisms from sediment particles. Techniques investigated included manual shaking, treatment by sonication bath for 6 and 10 min, respectively, and by sonication probe for 15 s and 1 min, respectively. The use of the sonication bath for 10 min was the most successful method for removing micro-organisms from sediment particles where sediments consisted mainly of sand. When sediments contained considerable proportions of silt and clay, however, manual shaking was most successful. Faecal coliforms were then enumerated by membrane filtration in both water and sediment from three recreational coastal sites, chosen to represent different physical sediment characteristics, over a 12-month period. Faecal coliform concentrations were generally greater in sediment compared with overlying water for all samples. This was most evident in sediment consisting of greater silt/clay and organic carbon content. CONCLUSIONS: This study demonstrated the importance of sediment characteristics in determining the most efficient method for the separation of micro-organisms from coastal sediments. Sediment characteristics were also found to influence the persistence of micro-organisms in coastal areas. SIGNIFICANCE AND IMPACT OF THE STUDY: Recreational coastal sediments can act as a reservoir for faecal coliforms; therefore, sampling only overlying water may greatly underestimate the risk of exposure to potentially pathogenic micro-organisms in recreational waters.

Bacteriological Techniques↗
PubMed2002

Inhibition of glycogen synthesis by fatty acid in C(2)C(12) muscle cells is independent of PKC-alpha, -epsilon, and -theta.

We have previously shown that glycogen synthesis is reduced in lipid-treated C(2)C(12) skeletal muscle myotubes and that this is independent of changes in glucose uptake. Here, we tested whether mitochondrial metabolism of these lipids is necessary for this inhibition and whether the activation of specific protein kinase C (PKC) isoforms is involved. C(2)C(12) myotubes were pretreated with fatty acids and subsequently stimulated with insulin for the determination of glycogen synthesis. The carnitine palmitoyltransferase-1 inhibitor etomoxir, an inhibitor of beta-oxidation of acyl-CoA, did not protect against the inhibition of glycogen synthesis caused by the unsaturated fatty acid oleate. In addition, although oleate caused translocation, indicating activation, of individual PKC isoforms, inhibition of PKC by pharmacological agents or adenovirus-mediated overexpression of dominant negative PKC-alpha, -epsilon, or -theta mutants was unable to prevent the inhibitory effects of oleate on glycogen synthesis. We conclude that neither mitochondrial lipid metabolism nor activation of PKC-alpha, -epsilon, or -theta plays a role in the direct inhibition of glycogen synthesis by unsaturated fatty acids.

Animals↗
PubMed1999

Ceramide generation is sufficient to account for the inhibition of the insulin-stimulated PKB pathway in C2C12 skeletal muscle cells pretreated with palmitate.

We have employed C2C12 myotubes to investigate lipid inhibition of insulin-stimulated signal transduction and glucose metabolism. Cells were preincubated for 18 h in the absence or presence of free fatty acids (FFAs) and stimulated with insulin, and the effects on glycogen synthesis and signaling intermediates were determined. While the unsaturated FFAs oleate and linoleate inhibited both basal and insulin-stimulated glycogen synthesis, the saturated FFA palmitate reduced only insulin-stimulated glycogen synthesis, and was found to inhibit insulin-stimulated phosphorylation of glycogen synthase kinase-3 and protein kinase B (PKB). However, no effect of palmitate was observed on tyrosine phosphorylation, p85 association, or phosphatidylinositol 3-kinase activity in IRS-1 immunoprecipitates. In contrast, palmitate promoted phosphorylation of mitogen-activated protein MAP) kinases. Ceramide, a derivative of palmitate, has recently been associated with similar inhibition of PKB, and here, ceramide levels were found to be elevated 2-fold in palmitate-treated C2C12 cells. Incubation of C2C12 cells with ceramide closely reproduced the effects of palmitate, leading to inhibition of glycogen synthesis and PKB and to stimulation of MAP kinase. We conclude that palmitate-induced insulin resistance occurs by a mechanism distinct from that of unsaturated FFAs, and involves elevation of ceramide by de novo synthesis, leading to PKB inhibition without affecting IRS-1 function.

Animals↗
PubMed1989

Commercialising biomedical technology.

Engineers and scientists working with biomedical technology are a highly inventive lot. However, it is disappointing to see how few of the products of that inventiveness ever see the light of day outside the hospitals or institutions in which they are developed. This is usually because the developers do not know how to go about commercialising their products. The two basic options in commercialising a new product are to license the product to an existing company, or to establish a new company to manufacture and market it. Whichever approach is taken, a "Business Plan" is an essential requirement. This is a selling document which is needed either to convince an existing company that it would be profitable for it to license the product, or to convince an investor/financier to fund the establishment of a new company to commercialise it.

Australia↗
PubMed1980

Nutritive value of green or yellow foxtail, wild oats, wild buckwheat or redroot pigweed seed as determined with the rat.

Pure green foxtail (Setaria viridis Beauv.), yellow foxtail (Setaria lutescens Hubb.), wild oats (Avena fatua L.), wild buckwehat (Polygonum convolvulus L.) and redroot pigweed (Amaranthus retroflexus L.) seeds were fed to growing male rats in two experiments. In the first experiment, green or yellow foxtail and wild oats seeds were found to be first-limiting in the amino acid lysine. Green or yellow foxtail seed supplemented with lysine produced satisfactory rat growth. Digestible energy (DE) values of lysine-supplemented diets were: 3.478, 3.068 and 2.696 kcal/g dry matter (DM) for green foxtail, yellow foxtail and wild oats, respectively. Protein digestibility values were 77.1, 68.6 and 54.2 for the respective diets. Wild oats were accepted poorly by the rats, even after lysine supplementation. In the second experiment, rats required approximately 7 days to adapt to voluntary consumption of an amino acid-supplemented wild buckwheat diet. Moderate weight gain of weanling male rats was obtained because of high consumption of the wild buckwheat diet, which had 2.206 kcal DE/g DM and 52.5% crude protein digestibility. In contrast, initial high acceptability of the redroot pigweed diet quickly declined. Digestibility values for the redroot pigweed diet were 2.884 kcal DE/g DM and 54.6% rude protein digestibility. The relationship between digestibility values obtained with rats and those obtained with swine is discussed.

Animal Nutritional Physiological Phenomena↗