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Biomedical subjects

C M Davies

Publications and source records attributed to C M Davies.

31 records · Page 2Linked to original sources
PubMed1999

Host-parasite population genetics: a cross-sectional comparison of Bulinus globosus and Schistosoma haematobium.

The genetic population structures of the freshwater snail Bulinus globosus and its trematode parasite Schistosoma haematobium from 8 river sites in the Zimbabwean highveld were compared using randomly amplified DNA (RAPD) markers. There was significant variability between snail populations collected at different sites, but schistosome populations only showed differentiation at a wider geographical scale (between 2 non-connected river systems). For snails, genetic distance was better correlated with proximity along rivers than absolute geographical separation. In contrast, schistosome genetic distance was better correlated with absolute geographical separation than proximity along rivers. These results are consistent with different dispersal mechanisms for snails and schistosomes and the implications for host-parasite coevolution are discussed.

Animals↗
PubMed1998

Palatoplasty for snoring: a randomized controlled trial of three surgical methods.

In a randomized, controlled trial, 62 patients (47 men and 15 women) with severe antisocial snoring, but no sleep apnea, were allocated to one of three surgical treatments. These were uvulopalatopharyngoplasty, laser palatoplasty, and diathermy palatoplasty. Postoperative morbidity was measured on a visual analogue scale of severity of pain, dysphagia, and nasal regurgitation at 1, 2, and 7 days after the operation. Efficacy of each procedure was measured by asking the sleeping partner to record the severity of snoring before and after the operation, again on a visual analogue scale. Measurements were taken at 1, 3, and 6 months. There were no significant differences in early postoperative morbidity among the treatment groups. Diathermy palatoplasty is a new technique for the relief of snoring that is associated with low morbidity and requires little in the way of expensive equipment.

Adult↗
PubMed1998

The costs of early hearing screening in England and Wales.

A survey was carried out in 10 centres in England and Wales to determine the costs of hearing screening in the first year of life. The screens that were studied were targeted neonatal, universal neonatal, and the health visitor distraction test (HVDT) or alternative surveillance. Valid data were available from five centres for targeted neonatal screening (TNS), three for universal neonatal screening (UNS), and nine for the HVDT, although only five of the HVDT screens had valid data for follow up costs. The neonatal costs were consistent across the centres surveyed, whereas those for the HVDT screen varied considerably. The mean service costs for TNS, UNS, and the HVDT at 1994 prices were 5052 Pounds, 13,881 Pounds, and 24,519 Pounds for a standardised district of 1000 live births. Three conclusions seem justified. Firstly, UNS need not be prohibitively expensive as it costs considerably less than HVDT screening. Secondly, TNS appears to be a relatively inexpensive way of improving the age of identification of a proportion of the congenitally hearing impaired. Thirdly, given the published yields for UNS and the HVDT, the results indicate that UNS offers the most cost effective overall approach with alternative systems in place to identify late onset permanent hearing losses.

England↗
PubMed1998

Use of transient evoked otoacoustic emissions to detect and monitor cochlear damage caused by platinum-containing drugs.

Transient evoked otoacoustic emissions (TEOAE) have been evaluated as a means of monitoring cochlear function in patients receiving the chemotherapeutic agents cisplatin and carboplatin (-cis-diammine, 1,1-cyclobutane dicarboxylate (2) -0,0-platinum). Patients receiving these drugs were monitored prospectively with pure tone audiometry (PTA), tympanometry and TEOAE. Data was collected on 22 subjects receiving cisplatin and nine subjects receiving carboplatin. Significant deterioration in both PTA thresholds and TEOAE energy levels (with no change in tympanometry) were detected in the cisplatin group. No significant deterioration in audiological parameters occurred in the carboplatin group. It is indicated that cisplatin has a significant ototoxic effect in the majority of patients, whereas any ototoxic effect of carboplatin was undetectable. Our findings were different from previous studies in that the measurable changes in TEOAE occurred later than changes in the pure tone audiogram for the cisplatin group.

Acoustic Stimulation↗
PubMed1996

Remote in situ analytical spectroscopy and its applications in the nuclear industry.

An experimental system based on Laser Induced Breakdown Spectroscopy (LIBS) has been used to analyze various ferrous samples. A fibre optic system has been used to transmit the incident laser pulse which produces the plasma plume at the surface of the analyte and to transmit back to a spectrometer the optical radiation emitted by the plasma. The measuring system may therefore be placed remote from the analyte which may be situated in a hostile environment such as an operating nuclear reactor. Results show that the system is capable of detecting chromium, nickel, manganese, molybdenum, silicon and vanadium at concentrations smaller than 5x10(-4) g/g

Journal Article↗
PubMed1995

Possible interference of lactose-fermenting marine vibrios in coliform beta-D-galactosidase assays.

An investigation into possible interferences in beta-D-galactosidase-based assays for coliform bacteria in marine waters was carried out. A rapid instrumental fluorescence assay for beta-D-galactosidase activity, using 4-methylumbelliferyl-beta-D-galactoside as a substrate, was used to investigate activities of this enzyme in non-coliform bacterial isolates from coastal waters. Only 2% of isolates showed slight enzyme activity after a 1-h incubation period at 44.5 degrees C. At a lower incubation temperature of 20 degrees C, 51% and 94% of the isolates showed some enzyme activity within 6 h and 48 h, respectively. Fifty-nine out of 67 of these isolates were identified as Vibrio species. A lac+ strain of Vibrio vulnificus was found to produce beta-D-galactosidase which caused significant false-positive reactions in the Colilert-Marine Water assay when present at concentrations of 10 cfu ml-1 or greater. This interference could be overcome by addition of the vibriostatic agent O/129. The high fluorescence of this reagent, however, precluded the simultaneous determination of Escherichia coli in the Colilert test and also its use in instrumental fluorescence assays. It was concluded that in assays employing high temperatures and short incubation times, Vibrio species are unlikely to cause significant interferences.

Enterobacteriaceae↗
PubMed1995

Beta-D-galactosidase activity of viable, non-culturable coliform bacteria in marine waters.

The beta-D-galactosidase activity of viable but non-culturable (vnc) Escherichia coli cells in seawater was investigated using a rapid fluorimetric enzyme assay. Results from microcosm studies showed that loss of culturability did not necessarily result in loss of the ability to produce the galactosidase enzyme. Even when no culturable cells were detected, a positive enzyme assay response was observed and the activity of the inducible enzyme over time more closely reflected the number of vnc cells present.

Enzyme Induction↗
PubMed1995

Survival of fecal microorganisms in marine and freshwater sediments.

The survival of culturable fecal coliforms, fecal streptococci, and Clostridium perfringens spores in freshwater and marine sediments from sites near sewage outfalls was studied. In laboratory studies, the inhibition of protozoan predators with cycloheximide allowed the fecal coliforms to grow in the sediment whereas the presence of predators resulted in a net die-off. C. perfringens spores did not appear either to be affected by predators or to die off throughout the duration of the experiments (28 days). Studies using in situ membrane diffusion chambers showed that, with the exception of C. perfringens, die-off of the test organisms to 10% of their initial numbers occurred in both marine and freshwater sediments within 85 days. The usual exponential decay model could not be applied to the sediment survival data, with the exception of the data for fecal streptococci. It was concluded that application of the usual decay model to the fecal coliform data was confounded by the complex relationship between growth and predation. The survival of seeded Escherichia coli in marine sediment was studied by using an enumeration method which detected viable but nonculturable bacteria. Throughout the duration of the experiment (68 days), the same proportion of E. coli organisms remained culturable, suggesting that sediment provides a favorable, nonstarvation environment for the bacteria.

Animals↗
PubMed1994

Plant and algal interference in bacterial beta-D-galactosidase and beta-D-glucuronidase assays.

Several commonly occurring freshwater and marine plants and algae were screened for beta-D-galactosidase and beta-D-glucuronidase activities by using a 60-min enzyme assay based on the hydrolysis by these enzymes of 4-methylumbelliferyl-beta-D-galactoside and 4-methylumbelliferyl- beta-glucuronide, respectively. All freshwater plant extracts tested showed beta-D-galactosidase activity several at relatively high levels, and a number also showed beta-D-glucuronidase activity. A number of the macroalgae showed no activity of either enzyme, but those showing beta-D-galactosidase activity also showed beta-D-glucuronidase activity. The majority of microalgae showed some beta-D-galactosidase activity, but few showed beta-D-glucuronidase activity. Further studies, using the commercial Colilert test and the marine water formulation of Colilert, revealed that 2 of 11 of the microalgal species and several of the plant extracts tested caused positive reactions. It was concluded that several plant extracts and algae could significantly interfere with the detection of coliform bacteria and Escherichia coli with the use of rapid assays, on the basis of their production of beta-D-galactosidase and beta-D-glucuronidase, respectively. The significance of the plant and algal interferences in tests such as Colilert is dependent on the levels of enzymes released under natural conditions, the dilution which they may undergo, and the numbers of algal cells present. This also applies to interferences in rapid enzyme assays.(ABSTRACT TRUNCATED AT 250 WORDS)

Escherichia coli↗
PubMed1993

Mealtime interactions and family relationships of families with children who have cancer in long-term remission and controls.

This study investigated reports of parents (mothers and fathers) of 25 children with cancer in long-term remission and matched neighborhood control families on issues related to the quality of mealtime interactions, and the relationship between parental reports of overall family functioning and the quality of mealtime interactions. Results showed positive correspondence for both groups between fathers' and mothers' reports of favorable family environments (greater cohesion and expressiveness, less conflict) and positive mealtime interactions. No significant differences were found between parents of children with cancer and control parents with regard to mealtime conflicts, current concerns about their child's eating, or satisfaction with the child's food intake. The data demonstrate a moderate relationship between overall family functioning and the quality of mealtime interactions, but suggest a minimal relationship between children with cancer in long-term remission who are at low nutritional risk and the quality of mealtime interactions.

Adolescent↗
PubMed1991

Sunlight and the survival of enteric bacteria in natural waters.

Escherichia coli and some salmonellas were exposed in seawater and freshwater to natural sunlight, visible light of comparable intensity, and light containing a similar proportion of u.v. as natural sunlight but of a much lower intensity. Direct viable bacterial counts and culturable counts on selective and non-selective media were made at intervals. The rate of decrease in numbers of culturable bacteria was significantly faster in seawater than in freshwater when exposed to natural sunlight. No significant difference was found between the rates of decrease in numbers of culturable bacteria in seawater and those in freshwater when bacteria were exposed to light with a small u.v. component of similar intensity. The effect of salinity no loss of culturability is, therefore, more significant in the presence of u.v. radiation. Direct counts by the acridine orange direct viable count method decreased much more slowly than the culturable counts in seawater but comparably with culturable counts in freshwater in natural sunlight. Direct viable counts and culturable counts decreased at a similar rate in seawater and in freshwater in visible light. This may signify the evolution of enteric bacteria towards a viable but non-culturable form in seawater when exposed to natural sunlight. The presence of humic acids significantly reduced loss of culturability but only in low salinity conditions. Salinity appears to be an important factor influencing culturability in bacteria exposed to sunlight.

Escherichia coli↗