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Biomedical subjects

J B Davies

Publications and source records attributed to J B Davies.

At least 19 recordsLinked to original sources
PubMed2005

Calibration of the Capintec CRC-712M dose calibrator for (18)F.

Primary standardisation was performed on a solution of (18)F using the 4pibeta-gamma coincidence counting efficiency-tracing extrapolation method with (60)Co used as a tracer nuclide. The result was used to calibrate the ANSTO secondary standard ionisation chamber which is used to disseminate Australian activity standards for gamma emitters. Using the secondary activity standard for (18)F, the Capintec CRC-712M dose calibrator at the Australian National Medical Cyclotron (NMC) Positron Emission Tomography (PET) Quality Control (QC) Section was calibrated. The dial setting number recommended by the manufacturer for the measurement of the activity of (18)F is 439. In this work, the dial setting numbers for the activity measurement of the solution of (18)F in Wheaton vials were experimentally determined to be 443+/-12, 446+/-12, 459+/-11, 473+/-15 for 0.1, 1, 4.5 and 9ml solution volumes, respectively. The uncertainties given above are expanded uncertainties (k=2) giving an estimated level of confidence of 95%. The activities determined using the manufacturer recommended setting number 439 are 0.8%, 1.4%, 4.0% and 6.5% higher than the standardised activities, respectively. It is recommended that a single dial setting number of 459 determined for 4.5ml is used for 0.1-9ml solution in Wheaton vials in order to simplify the operation procedure. With this setting the expended uncertainty (k=2) in the activity readout from the Capintec dose calibrator would be less than 6.2%.

Calibration↗
PubMed2005

Development of an Australian secondary standard for the reference air kerma rate measurement of 125I seeds.

Calibration of a High-Dose-Rate 1000 Plus ionisation chamber and associated electrometer for the determination of reference air kerma rate for 125I brachytherapy seeds has been developed. Traceability was established from ionisation chamber measurements of an Amersham model 6711 125I seed for which a primary standard measurement of reference air kerma rate has been made by the National Institute of Standards and Technology. The status of an Australian secondary standard is to be realised by establishing legal verifying authority from the National Measurement Institute. The calibrated chamber thus provides a measurement from which similar chambers in hospitals may be calibrated. For quality assurance this result was compared with the calibration certificate supplied by the Accredited Dosimetry Calibration Laboratory of the University of Wisconsin, USA.

Australia↗
PubMed2004

Blackflies (Diptera: Simuliidae) of Southern Guyana with keys for the identification of adults and pupae--a review.

A revision is made of the previously poorly studied blackfly fauna from the south-western border of Guyana with Brazil. Notes on the biosystematics of the species found are provided, together with keys and illustrations based on their morphology. Of the 14 species recorded, eight are anthropophilic and two of these (Simulium oyapockense s.l. and S. guianense s.l.) are proven vectors of human onchocerciasis in the nearby Amazonia focus of the disease in neighbouring Brazil.

Animals↗
PubMed2003

Cytotaxonomy, morphology and molecular systematics of the Bioko form of Simulium yahense (Diptera: Simuliidae).

Cytotaxonomic analysis of the polytene chromosomes from larvae of the Simulium damnosum Theobald complex from the island of Bioko in Equatorial Guinea is reported, and a new endemic cytoform is described. Chromosomally this cytoform is close to both S. squamosum (Enderlein) and S. yahense Vajime & Dunbar, but is not identical to either. However, it is morphologically and enzymatically identical to S. yahense. The Bioko form was also found to differ from other cytoforms of the S. damnosum complex in West Africa in the copy number or RFLP pattern of several different repetitive DNA sequences. It is clear that the Bioko form is genetically distinct from other populations of the S. damnosum complex, and whilst it is closest to S. yahense, it shows features that suggest a high degree of geographical and genetic isolation. Such isolation is an important consideration in the assessment of the potential for onchocerciasis vector eradication on Bioko.

Animals↗
PubMed2001

Levels of aggression among a group of anabolic-androgenic steroid users.

There have been numerous case studies and press reports of individuals committing acts of extreme violence while taking large doses of Anabolic-Androgenic Steroids (AAS). However, research using psychometric measures of aggression has tended to use small numbers of subjects which makes generalizing results difficult. In the current study the State Trait Anger Expression Inventory (STAXI) was administered to 50 AAS users and 40 non AAS-using control subjects. Subjects also underwent a semistructured interview focusing on AAS's effects on levels of aggression. Results showed that AAS users reported being significantly less in control of their aggression than controls. The semi-structured interview findings showed that elevations in aggression due to AAS use were reported by 60 per cent of AAS users. However, these elevations appeared more related to irritability and bad temper than acts of physical violence. The study also found that more AAS users than controls had worked as doormen/bouncers. This highlights the issue of whether AAS use causes aggression or whether aggressive individuals are attracted to AAS use. Future research should investigate this question.

Adolescent↗
PubMed2000

Phosphoglucomutase and trehalase isoenzymes of Venezuelan simulium vectors of Onchocerca volvulus.

Phosphoglucomutase (PGM) and trehalase (Tre) isoenzymes of five species of Simulium blackflies (Diptera: Simuliidae), vectors of onchocerciasis in Venezuela, were investigated by means of a portable electrophoresis field kit. Tre differed between S. incrustatum and S. oyapockense s.l. Electrophoretic variation of Tre in other members of the S. amazonicum and S. incrustatum groups merit further investigation. PGM appears to be more useful for separating populations within species complexes. Multiple populations and/or seasonal changes in population structure of S. guianense s.l., S. exiguum s.l. and S. metallicum s.l. were inferred from elecrophoretic variation of PGM.

Animals↗
PubMed2000

Risk behaviours for HIV and hepatitis infection among anabolic-androgenic steroid users.

This study examined HIV and hepatitis risk behaviours among anabolic-androgenic steroid (AAS) users and controls, providing a detailed assessment of both injection and sexual practices. Fifty AAS-using and 40 non-AAS-using weight trainers completed a semi-structured interview followed by a detailed questionnaire. The 'high risk' behaviour of sharing needles and syringes was not current practice among the AAS-using sample, with only one user reporting sharing injecting equipment in the past. However, for some users it was common practice to share multi-dose vials (19%) and to divide drugs using syringes (17%). Both these practices are potential routes for HIV and hepatitis infection. Significantly more AAS users (36%) reported increases in sex drive over the last three months than did the control subjects (5%). More AAS users than controls were engaging in sex with more than one partner while infrequently using condoms. These findings support the maintenance of needle exchange schemes which are essential to continued safe injecting practices among AAS users. The elevated sexual risk behaviour of AAS users could be due to AAS's effect of increasing sex drive or to a 'risk taking' personality trait among AAS users.

Adolescent↗
PubMed1998

Pharmacology versus social process: competing or complementary views on the nature of addiction?

Pharmacological/physiological models and social process/cognitive models of addiction are compared. These are discussed both in terms of the types of data produced and the philosophies of knowledge that underlie the two approaches. It is suggested that the notion of addiction confounds these two sets of issues, especially with respect to the notions of volition and compulsion. The problem is highlighted by data that reveal verbal reports to be variable and context dependent. It is concluded that a better understanding of the nature of addiction requires a clearer distinction between the pharmacological/physiological approach and the social process/cognitive approach. Both approaches contribute usefully to knowledge and have predictive value. Confusion arises, however, where workers fail to see not merely the benefits, but also the limitations, of these two approaches to the addiction problem.

Humans↗
PubMed1998

Diaphragmatic rupture resulting from gastrointestinal barotrauma in a scuba diver.

A fit young man sustained a ruptured diaphragm during a recreational scuba dive three months after undergoing an uncomplicated laparoscopic Nissen fundoplication for gastro-oesophageal reflux disease. It is proposed that this rare occurrence was attributable to gastrointestinal barotrauma. The injury was treated by laparotomy, mobilisation of herniated abdominal viscera back into the abdomen, repair of the crura and gastropexy. He made a full postoperative recovery. It is concluded that scuba diving should be avoided in patients who have undergone fundoplication.

Adult↗
PubMed1998

Detection of Onchocerca volvulus DNA in pools of wild-caught Simulium ochraceum by use of the polymerase chain reaction.

The presence of Onchocerca volvulus DNA in experimentally infected flies can now be detected by use of the PCR, so that, for example, one infected Simulium damnosum can be detected in a pool of 100 uninfected flies or one S. ochraceum can be detected in pools of 20-40. As this PCR technique is specific for O. volvulus, the results are not confounded by the presence of other, unimportant, Onchocerca species, and the technique could replace time-consuming, manual dissection of flies. In 1996 and 1997, pools of 16-21 Simulium ochraceum were tested by the PCR technique. These flies had been collected biting man, between 1992 and 1994, from two hyperendemic coffee estates (fincas) in Guatemala, and stored in commercial (95%) ethanol. Collections at finca Buena Vista (869 flies in 52 pools) were made 1-2 weeks and 46 weeks after 45% of eligible subjects had been treated with ivermectin for the first time. At finca El Brote, collections (360 flies in 18 pools) were made 13 weeks before and 7 weeks after 97% of eligible subjects had received their first treatment. DNA was easily recovered from simuliids that had been stored in ethanol for up to 4 years. Of the nine pools of flies with visible blood collected at Buena Vista, each of 20 flies, eight tested positive for O. volvulus DNA. In flies without blood, 13 of 22 pools collected at Buena Vista just after treatment tested positive, whereas there were 14 positives in 22 pools taken 46 weeks later (P > 0.05). At El Brote, nine of 10 pre-treatment pools were positive, compared with three of eight taken 7 weeks post-treatment (P = 0.04), indicating that the treatments in this finca had reduced infection in the vector, and possibly transmission, by about 60%. A sub-sample of Buena Vista flies was divided into 19 sets of three separate sub-pools containing heads, thoraces and abdomens. Three pools of heads alone were positive, and had corresponding pools of positive abdomens. Three positive pools of thoraces had negative corresponding pools of heads and abdomens. These results show that PCR can be used to determine the prevalence of O. volvulus DNA in wild-caught S. ochraceum. As the infection rates observed were higher than expected from dissections reported by other workers, PCR-determined rates may not be directly comparable with traditional parameters based on the dissection of flies to reveal O. volvulus larvae.

Animals↗
PubMed1997

Onchocerciasis control: Moving towards the millennium.

The recognition of onchocerciasis as a major public health problem in the savanna belts of West Africa resulted in the establishment of the Onchocerciasis Control Programme (OCP) in 1974. Control was initially based on vector control by weekly larviciding. The OCP is now in transition towards its final phase in which repeated treatment with ivermectin, a safe and effective microfilaricide, is incorporated with vector control, or in certain circumstances is used alone. Ivermectin distribution hingeing on sustainable community systems is the basis of a new programme in endemic African countries outside the OCP and in the Americas. David Molyneux and John Davies describe the latest trends and developments related to onchocerciasis control.

Journal Article↗
PubMed1997

Assessment of vector microfilarial uptake as a comparatively non-invasive technique for monitoring onchocerciasis treatment campaigns in the Americas.

Since 1992, efforts have been made to combat onchocerciasis in Guatemala through mass distribution of ivermectin. The impact of the campaign is assessed by taking skin-snips from sentinel groups within selected communities. This method gives an estimate of the prevalence and intensity of infection, and thus the efficacy of the treatment. In some communities people are becoming reluctant to volunteer for skin-snipping, and so there is a need for an alternative technique that will give quantitative results. In most hyperendemic communities in Guatemala, biting blackflies are so ubiquitous that few people object to allowing 10 to 20 flies to engorge upon them. We examined data on the quantitative uptake of microfilariae by Simulium ochraceum before and after ivermectin distribution to see whether results similar to skin-snip data could be obtained. Counts of microfilariae ingested by S. ochraceum are compared to the numbers found in skin-snips from the same volunteers. In a group of 31 untreated infected persons, a skin-snip survey detected 64.5% positive, while feeding flies (vector microfilarial uptake, VmfU) detected 96.8%. Post-treatment, in a sample of 58 of whom 52 (89.7%) had a history of infection, both skin-snips and VmfU detected 54.2%. Vector blood meals contained more microfilariae than a mg of skin before treatment, but both recorded about equal numbers after treatment. When the data set was subdivided to compare samples taken at 2-3, 6-8 and 14-17 months post-treatment, the effect of ivermectin was still apparent at 6-8 months, but had virtually disappeared by 14 months post-treatment. A surprising observation was that the flies ingested fewer microfilariae from treated persons than was expected from the skin densities as estimated by skin-snip. This effect lasted for over 8 months, and could indicate that ivermectin has a greater effect on transmission than previously suspected. We conclude that VmfU could be used as an alternative to skin-snipping, and discuss the ethical implications.

Adolescent↗
PubMed1996

Polymerase chain reaction for detecting Onchocerca volvulus in pools of blackflies.

The detection of Onchocerca volvulus infected simuliids or blackflies is routinely done by dissection and microscopic examination of individual flies, but this method is tedious and time consuming. Here we describe a method of detecting single O. volvulus infected blackflies in pools of uninfected blackflies. Using a PCR with Onchocerca specific primers it is possible to reproducibly detect one heavily infected blackfly in a pool of 80 flies, or to detect one blackfly inoculated with one microfilaria in a pool of 20 flies. With the method described large numbers of blackflies can be rapidly screened for the presence of O. volvulus infected flies.

Animals↗