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Biomedical subjects

D Lloyd

Publications and source records attributed to D Lloyd.

At least 37 records · Page 2Linked to original sources
PubMed2002

Garlic (Allium sativum) as an anti-Candida agent: a comparison of the efficacy of fresh garlic and freeze-dried extracts.

AIMS: To determine the effects of fresh and freeze-dried extracts of Allium sativum on the physiology and morphology of Candida albicans. METHODS AND RESULTS: Inhibition of growth in glucose-yeast extract-peptone was measured using a multiwell plate reader. Scanning and transmission electron microscopy investigations indicated loss of structural integrity. Gas chromatography-mass spectrometry of extracts was employed to separate and quantify putative inhibitory sulphur-containing components. CONCLUSIONS: Fresh garlic extract has a greater efficacy than garlic powder extract as indicated both by its effects on morphology and inhibition of growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The ubiquitous opportunistic pathogen C. albicans is sensitive to garlic; resistance to the broad spectrum of active principles present is unlikely so that its anticandidal effects may provide an important alternative route to chemotherapy.

Antifungal Agents↗
PubMed2002

Nitrite inhibits hydrogen production and kills the cattle parasite Tritrichomonas foetus.

AIMS: To investigate the effects of NaNO2 on the microaerophilic flagellated protozoan, Tritrichomonas foetus KV1, an economically important cattle parasite that inhabits the vagina and can spread rapidly through herds of animals by sexual transmission and leads to abortion of foetal calves. METHODS AND RESULTS: Growth of the parasite was inhibited by 50% in the presence of 4 mm NaNO2; immediate killing occurred at 10 mm. Mass spectrometric monitoring of gases showed that H2 and CO2 evolution were inhibited by NaNO2, and electron paramagnetic resonance spectrometry revealed a signal similar to that of a thiolate-iron-NO complex. Growth with sublethal concentrations of NaNO2 yielded organisms that produced ethanol rather than H2. CONCLUSIONS: NaNO2 probably inactivates FeS protein(s) of hydrogenosomes so as to inhibit the conversion of pyruvate (derived from maltose in the growth medium) to H2 and acetate. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of NaNO2 as a topical antitrichomonal agent in veterinary practice is a possibility. At present, slaughter of infected animals is the favoured method of control.

Animals↗
PubMed2002

The effects on GP prescribing of joining a commissioning group.

BACKGROUND: It is not known to what extent general practitioners (GP) can change their prescribing upon joining a commissioning group and what features of a commissioning group may promote prescribing change. The opportunity to study potential prescribing change arose with the formation of a limited number of Primary Care Commissioning Groups (PCCGs), a precursor of Primary Care Groups (PCGs) and Primary Care Trusts (PCTs). METHODS: This was a controlled study of general practice prescribing costs. All practices (n=24) within one inner city PCCG were compared with matched controls that were not part of a PCCG. Cross sectional survey data was collected from the PCCG practices to determine possible reasons for prescribing change. RESULTS: The total annual prescribing cost rose by 4.0% in the PCCG practices and by 6.9% in controls (P=0.01). Significant cost containment was found for gastrointestinal prescribing (P=0.03), attributable to differences in the cost of proton pump inhibitors (PPIs) which fell by 0.7% in the PCCG but rose by 7.3% in controls (P=0.03). Total relative savings in the PCCG practices amounted to around pound 220,000. General practitioners making the greater savings in PPI costs within the PCCG, were more likely to report being influenced by information from the prescribing adviser. CONCLUSION: General practice prescribing costs were contained to a greater degree in practices participating in the PCCG. The differences in gastrointestinal prescribing were most marked for PPIs which were specifically targeted by the prescribing adviser. The GPs themselves attributed their own prescribing change to information provided by the prescribing adviser. Other factors operating within the PCCG may also have influenced prescribing such as a more locally based management system, different financial incentives and a greater degree of co-operative working amongst GPs.

Contract Services↗
PubMed2002

The measurement of shoulder alignment in cricket fast bowling.

The aim of this study was to compare thoracic spine alignment with two- and three-dimensional calculations of shoulder alignment (defined as a line joining the acromion processes of the right and left scapula) when all measures were projected onto the transverse plane. A six-camera Vicon system was used to reconstruct three markers positioned on the plane of the thorax such that the orthogonal vector to the thoracic spine, projected onto the transverse plane, was used as a virtual shoulder alignment during cricket fast bowling. This same measurement system was used to calculate the three-dimensional line between the acromion processes projected onto the transverse plane. These acromion markers were also used to calculate the two-dimensional transverse plane alignment of the shoulders from images recorded by a video camera positioned above ball release. All cameras operated at 50 Hz. A significant association was recorded between thorax alignment and the three- (0.97) and two-dimensional (0.87) shoulder alignment estimations at back-foot impact. The strength of association remained at front-foot impact, when correlations of 0.89 (three-dimensional) and 0.84 (two-dimensional) were recorded. However, at ball release, non-significant associations of 0.58 (three-dimensional) and 0.41 (two-dimensional), representing shoulder alignment differences of approximately 10 degrees, were recorded. The 95% limits of agreement comparisons for shoulder alignment at back-foot impact, front-foot impact and ball release produced mean random errors for the two comparisons of 9.5 degrees, 11.7 degrees and 22.5 degrees respectively. Three- and two-dimensional transverse plane projections of shoulder alignment are reasonable estimates of thorax alignment at back-foot impact and front-foot impact but not at ball release.

Adolescent↗
PubMed2002

Choosing metaphases for biological dosimetry by fluorescence in situ hybridization (FISH).

Data are presented for a subset of lymphocytes characterized by FISH as missing painted chromosomal material. These lymphocytes occur in both control and irradiated subjects. These cells have a much greater frequency of one-way translocations than cells in which all of the painted chromosomal material is present. Their presence contributes to interindividual variability in control translocation yields. These cells do not appear to be more prevalent in persons exposed to high radiation doses. It is suggested that their exclusion when selecting cells for analysis may improve the sensitivity of FISH as a biological dosimeter at low doses. Mechanisms for the production of these one-way translocations in vivo are also discussed, with a proposal that their variable frequency in individuals may be consistent with exposure to chemical clastogens.

Adolescent↗
PubMed2002

Towards a standardization of biological dosimetry by cytogenetics.

When individuals are accidentally overexposed to ionising radiations, follow-up investigations may include dose assessment by cytogenetics. Scoring of unstable chromosome aberrations (dicentrics, centric rings and acentrics) in peripheral blood lymphocytes is regarded as the most specific method to estimate the exposure dose. It has acquired, in some countries, a medico-legal recognition. Paradoxically, there is no universally adopted technique and so important variations occur in methods and these may influence the quality of results. The only published documents supplying some standardization background are International Atomic Energy Agency (IAEA) Technical Reports No 260 (1986) and 405 (2001). Even they do not address crucial areas such as the organization of service laboratories and the need for quality assurance programmes. The significant role of biological dosimetry in many countries has proved the need for a standardized technique that is compatible with national radiological protection programmes. Thus, an International Standards Organization working group for the standardization of biological dosimetry by cytogenetics was created. This group comprises 13 scientists from 11 countries plus an IAEA representative. On the basis of a group consensus, a text defining minimal constraints on all the steps of the process was proposed. A working draft was submitted to ISO in 2001 and its structure is presented here.

Animals↗
PubMed2002

Information architecture for a federated health record server.

This paper describes the information models that have been used to implement a federated health record server and to deploy it in a live clinical setting. The authors, working at the Centre for Health Informatics and Multiprofessional Education (University College London), have built up over a decade of experience within Europe on the requirements and information models that are needed to underpin comprehensive multi-professional electronic health records. This work has involved collaboration with a wide range of health care and informatics organisations and partners in the healthcare computing industry across Europe though the EU Health Telematics projects GEHR, Synapses, EHCR-SupA, SynEx and Medicate. The resulting architecture models have fed into recent European standardisation work in this area, such as CEN TC/251 ENV 13606. UCL has implemented a federated health record server based on these models which is now running in the Department of Cardiovascular Medicine at the Whittington Hospital in North London. The information models described in this paper reflect a refinement based on this implementation experience.

Computer Communication Networks↗
PubMed2001

Counter-stimulatory effects on pain perception and processing are significantly altered by attention: an fMRI study.

Counter-stimulation reduces pain perception; however, the role of attention during this process is rarely discussed despite attention itself being a well known modulator of pain perception. This study investigated the effect of attentional modulation on pain perception during counter-stimulation using fMRI. Subjects received a noxious thermal stimulus together with an innocuous vibratory counter-stimulus. Subjects directed their attention towards either pain, vibration, or a neutral visual stimulus. During painful and counter-stimulation all subjects reported a reduction in pain perception when attending to counter-stimulation compared with attending to pain. Imaging data supported this behavioural finding showing reduced activity in pain processing areas (anterior cingulate, insula, thalamus). These results suggest attention plays an important part in the pain relief experienced from counter-stimulation.

Adult↗
PubMed2001

Membrane inlet mass spectrometric measurement of O2 and CO2 gradients in cultures of Lactobacillus paracasei and a developing Cheddar cheese ecosystem.

Membrane inlet mass spectrometry was used to measure O2 and CO2 as depth profiles in stab cultures of 0.1% agar Man Rogosa Sharpe medium inoculated with Lactobacillus paracasei CI3. Diffusion of CO2 from the central column of growth into the medium was observed to show lower concentrations where bacteria were absent. CO2 profiles developed in a manner similar to those in Cheddar cheese and O2 was undetectable at similar depths. Gases were analysed in Cheddar cheese over a maturation period of 200 d. O2 was detectable to depths of 13, 6 and 2.5 mm on days 2, 9 and 15, respectively, but then became undetectable at depths of 2.5-3 mm. CO2 concentrations measured within the cheese increased 10-fold from day 2 to day 200 to reach a value of around 15 mM. The progress of measured CO2 concentration over time at a given depth in cheese shows a hyperbolic type increase. Coefficient of regression values increase with depth to a maximum value of R2 = 0.93. In both systems, reductions and increases in CO2 were due to the absence or presence of bacterial growth, respectively. Confocal scanning laser and scanning electron microscopy was used to show spatial heterogeneity of microcolonies within the cheese ecosystem. This information can potentially be used as a non-sensory evaluation of cheese maturity status. Measurement of gases in a cheese ecosystem provides the first description of mass spectrometry being used to monitor the processes of microbial gaseous exchange with respect to O2 and CO2 in a cheese ecosystem.

Carbon Dioxide↗
PubMed2001

Why homeodynamics, not homeostasis?

Ideas of homeostasis derive from the concept of the organism as an open system. These ideas can be traced back to Heraclitus. Hopkins, Bernard, Hill, Cannon, Weiner and von Bertalanffy developed further the mechanistic basis of turnover of biological components, and Schoenheimer and Rittenberg were pioneers of experimental approaches to the problems of measuring pool sizes and dynamic fluxes. From the second half of the twentieth century, a biophysical theory mainly founded on self-organisation and Dynamic Systems Theory allowed us to approach the quantitative and qualitative analysis of the organised complexity that characterises living systems. This combination of theoretical framework and more refined experimental techniques revealed that feedback control of steady states is a mode of operation that, although providing stability, is only one of many modes and may be the exception rather than the rule. The concept of homeodynamics that we introduce here offers a radically new and all-embracing concept that departs from the classical homeostatic idea that emphasises the stability of the internal milieu toward perturbation. Indeed, biological systems are homeodynamic because of their ability to dynamically self-organise at bifurcation points of their behaviour where they lose stability. Consequently, they exhibit diverse behaviour; in addition to monotonic stationary states, living systems display complex behaviour with all its emergent characteristics, i.e., bistable switches, thresholds, waves, gradients, mutual entrainment, and periodic as well as chaotic behaviour, as evidenced in cellular phenomena such as dynamic (supra)molecular organisation and flux coordination. These processes may proceed on different spatial scales, as well as across time scales, from the very rapid processes within and between molecules in membranes to the slow time scales of evolutionary change. It is dynamic organisation under homeodynamic conditions that make possible the organised complexity of life.

Hemodynamics↗
PubMed2001

In situ kinetic characterization of methylthioadenosine transport by the adenosine transporter (P2) of the African Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense.

African trypanosomes are parasitic flagellates that live in the connective tissues of the host. Trypanosomes must obtain from their host adenine/adenosine and other nucleosides that can be salvaged through enzymatic cleavage. Methylthioadenosine (MTA) is a byproduct of polyamine metabolism, formed from the donation of an aminopropyl moiety by decarboxylated S-adenosylmethionine (dcAdoMet) to form spermidine. MTA is then cleaved phosphorolytically by MTA phosphorylase to methylthioribose-1-phosphate (MTR-1-P) and adenine. The uptake of MTA was compared with that of adenosine in two strains: Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense. The K(m) values for MTA and adenosine (with 5 mM inosine) transport by T. b. brucei were 1.4 and 0.175 mM, and the V(max) values were 70 and 7.8 micromol/L/min, respectively. The K(m) values for T. b. rhodesiense MTA and adenosine (with 5 mM inosine) transport were 1.2 and 0.11 mM, and the V(max) values were 52.6 and 2.9 micromol/L/min, respectively. Since MTA was not competitive with either AdoMet (100 microM), inosine (100 microM), or the methionine precursor ketomethylthiobutyrate (100 microM), it appears that MTA enters through the P(2) (adenosine/adenine) transport site. From this study and our previous work, we determined that these organisms transport adenylated intermediates of methionine metabolism found in sera for purine salvage and as an ancillary source of methionine. The significant ability of African trypanosomes to transport MTA and related intermediates is an important consideration in the design and development of selective chemotherapeutic agents.

Adenosine↗
PubMed2001

Rapid and sensitive quantitation of antibiotics in fermentations by electrospray mass spectrometry.

Electrospray ionisation mass spectrometry (ESI-MS) has been used for the determination and quantitation of a broad range of 24 antibiotics, from groups including aminoglycosides, beta-lactams, tetracyclines, antifungals and glycopeptides. Spectra have been acquired for all 24 antibiotics derived from pure samples dissolved in acetonitrile/water, along with samples extracted from complex fermentation liquor. Quantitation was carried out by the detection of the protonated molecules, using time-scheduled single-ion monitoring (SIM). ESI-MS was used to detect and quantify to 5-microM levels. A one-step extraction of antibiotics with an organic solvent (methanol) was used for this rapid and simple procedure. Specificity is not matched by other methods and antibiotic analogues (e.g. the five forms of erythromycin) can be determined within minutes.

Anti-Bacterial Agents↗
PubMed2001

Vision influences tactile perception at body sites that cannot be viewed directly.

Previous research has demonstrated that vision of a body site, without proprioceptive orienting of eye and head to that site, could affect tactile perception. The body site viewed was the hand, which can be seen directly under normal viewing conditions. The current research asked three further questions: First, can vision similarly affect tactile perception at a body site that cannot normally be viewed directly such as the face or neck? Second, does prior experience of seeing a body site, such as occurs when viewing the face in mirrors, produce larger effects of viewing than body sites rarely seen such as the back of the neck? And third, how quickly can visual information affect tactile target detection? We observe that: detection of tactile targets at these body sites was influenced by whether or not they were viewed, this effect was greater when viewing the more familiar site of the face than that of the neck, and significant effects were observed when the stimulus onset asynchrony between visual display and tactile target was as little as 200 ms.

Adult↗
PubMed2001

Antigiardial drugs.

Giardia intestinalis is a world-wide cause of intestinal infection. Treatment of this debilitating disease is usually accomplished using one of several drugs. Metronidazole is the treatment of choice, but benzimidazoles are now being used more frequently. Other treatments include quinacrine, paromomycin and furazolidone. Even though these drugs are all used to treat the same disease, their modes of action differ in all cases. However, resistance is increasing and new alternatives are being sought. New wave antigiardials all appear to have their roots in natural herbal remedies. This mini-review looks at the current treatments available, their efficacy, side effects and different modes of action and addresses a possible way forward using natural products.

Antiprotozoal Agents↗
PubMed2001

Antimicrobial properties of Allium sativum (garlic).

Although garlic has been used for its medicinal properties for thousands of years, investigations into its mode of action are relatively recent. Garlic has a wide spectrum of actions; not only is it antibacterial, antiviral, antifungal and antiprotozoal, but it also has beneficial effects on the cardiovascular and immune systems. Resurgence in the use of natural herbal alternatives has brought the use of medicinal plants to the forefront of pharmacological investigations, and many new drugs are being discovered. This review aims to address the historical use of garlic and its sulfur chemistry, and to provide a basis for further research into its antimicrobial properties.

Anti-Infective Agents↗