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Biomedical subjects

B Davies

Publications and source records attributed to B Davies.

At least 73 records · Page 4Linked to original sources
PubMed1999

Decreased chronotropic drive as an adaptation to chronic exercise; possible mechanisms.

Cardiovascular function was determined at rest and during exercise in twenty-eight healthy, elite distance runners. Maximum heart rate was 184 +/- 6 b x min(-1), which was more than one SD lower than the age predicted value (p < 0.001), and an inverse correlation was observed between maximum heart rate and VO2max (r = - 0.82, p < 0.001). The most aerobically trained athlete, a 27 year old male, presented with a maximum heart rate of 139b x min(-1). Echo-cardiac ultrasound revealed unremarkable intra-cardiac dimensions and flow characteristics relative to other endurance-trained athletes. A decreased chronotropic drive may represent a favourable physiological adaptation to endurance exercise which increases cardiovascular efficiency.

Adaptation, Physiological↗
PubMed1999

Intensive training during a twin pregnancy. A case report.

This case study reports the clinical and physiological changes of a 33 year old elite marathoner undertaking intensive endurance training during and following a twin pregnancy. Prior to conception, the subject ran 155 km x week(-1) at an intensity equivalent to 140-180 b x min(-1) which following consultation decreased to 107 +/- 19 km x week(-1) at an intensity equivalent to 130-140 b x min(-1) during pregnancy. Physical exercise ceased 3 days prior to an elective Caesarean section following a 36 week gestation period and recommenced 8 days following the birth of healthy twins. Medical assessments conducted ante/post partum indicated that both the twins and mother were healthy. A field based test demonstrated that running velocity at a steady state HR of 140 b x min(-1), 150 b x min(-1) and 160 b x min(-1) decreased by 20%, 15% and 13% respectively between weeks 1 and 32 antepartum. Whole blood lactate ([La-]B), oxygen uptake (VO2), ventilatory equivalent for oxygen (V(E)/VO2), HR and Borg rating of perceived exertion (RPE) increased during a laboratory-based submaximal treadmill test at 29 weeks antepartum in comparison to a test conducted 10 weeks post partum. These data clearly demonstrate that it is possible for an elite endurance athlete to maintain a high level of cardiovascular fitness during pregnancy with no apparent adverse effects on maternal or foetal health. This will facilitate an earlier return to international competition.

Adult↗
PubMed1999

Mutational analysis of the Caenorhabditis elegans cell-death gene ced-3.

Mutations in the gene ced-3, which encodes a protease similar to interleukin-1beta converting enzyme and related proteins termed caspases, prevent programmed cell death in the nematode Caenorhabditis elegans. We used site-directed mutagenesis to demonstrate that both the presumptive active-site cysteine of the CED-3 protease and the aspartate residues at sites of processing of the CED-3 proprotein are required for programmed cell death in vivo. We characterized the phenotypes caused by and the molecular lesions of 52 ced-3 alleles. These alleles can be ordered in a graded phenotypic series. Of the 30 amino acid sites altered by ced-3 missense mutations, 29 are conserved with at least one other caspase, suggesting that these residues define sites important for the functions of all caspases. Animals homozygous for the ced-3(n2452) allele, which is deleted for the region of the ced-3 gene that encodes the protease domain, seemed to be incompletely blocked in programmed cell death, suggesting that some programmed cell death can occur independently of CED-3 protease activity.

Alleles↗
PubMed1999

The Royal Melbourne Hospital Lithium Clinic.

The Lithium Clinic at the Royal Melbourne Hospital was an innovative program for the management of mood disorders. The Clinic was a model for teaching and research, as well as a vehicle for expert treatment of patients. Many psychiatrists gained valuable experience and training during their period of involvement and many academics and psychiatric researchers were involved with the Clinic. Important research was performed in the Clinic, some aspects of which are highlighted in this paper.

Antimanic Agents↗
PubMed1999

Electron spin resonance spectroscopy, exercise, and oxidative stress: an ascorbic acid intervention study.

Oxygen free radicals are highly reactive species that are produced in increased quantities during strenuous exercise and can damage critical biological targets such as membrane phospholipids. The present study examined the effect of acute ascorbic acid supplementation on exercise-induced free radical production in healthy subjects. Results demonstrate increases in the intensity of the alpha-phenyl-tert-butylnitrone adduct (0.05 +/- 0.02 preexercise vs. 0.19 +/- 0.03 postexercise, P = 0.002, arbitrary units) together with increased lipid hydroperoxides (1.14 +/- 0.06 micromol/l preexercise vs. 1.62 +/- 0.19 micromol/l postexercise, P = 0.005) and malondialdehyde (0.70 +/- 0.04 micromol/l preexercise vs. 0.80 +/- 0.04 micromol/l postexercise, P = 0.0152) in the control phase. After supplementation with ascorbic acid, there was no significant increase in the electron spin resonance signal intensity (0.02 +/- 0. 01 preexercise vs. 0.04 +/- 0.02 postexercise, arbitrary units), lipid hydroperoxides (1.12 +/- 0.21 micromol/l preexercise vs. 1.12 +/- 0.08 micromol/l postexercise), or malondialdehyde (0.63 +/- 0.07 micromol/l preexercise vs. 0.68 +/- 0.05 micromol/l postexercise). The results indicate that acute ascorbic acid supplementation prevented exercise-induced oxidative stress in these subjects.

Adolescent↗
PubMed1999

First year of a fast track carotid duplex service.

BACKGROUND: The risk of major stroke is highest in the first three months after a transient ischaemic attack (TIA). Urgent carotid endarterectomy can reduce the risk in patients with a severe carotid stenosis. An express carotid duplex service has been established and this study analyses the effect in the first year. METHODS: Local GPs were offered a new service whereby a carotid duplex scan would be guaranteed within 14 days of referral of any patient who had a recent clearly documented TIA or amaurosis fugax. Referral letters were faxed directly to the Vascular Office where the duplex scan was authorised by a consultant vascular surgeon. Patients with significant carotid disease on duplex were assessed in the out-patient clinic in preparation for surgery. RESULTS: In the first 12 months of the service, 90 fast track duplex scans were performed. In the same interval 490 routine carotid duplex scans were carried out. Some 13 carotid endarterectomies were carried out on patients from the fast track group (13/90, 14%), with a median delay between referral and surgery of 30 days (range 20-45) and median duration between onset of symptoms and surgery of 51 days (range 27-406). In the non fast track group 14/490 (2.8%) scans resulted in carotid intervention, a median 127 days (range 64-184) after referral. CONCLUSION: The fast track service significantly reduced the delay between referral and surgery. Timing of carotid surgery is critical. Performing the surgery at the time of greatest risk increases the benefit of carotid endarterectomy. Urgent and appropriate referral from the GPs is vital for the service to run effectively.

Carotid Arteries↗
PubMed1999

A comparison of the shear bond strength of composite resin bonded by a fourth and a fifth generation dental adhesive to bovine teeth.

AIM: This study compared the shear bond strengths, to bovine enamel and dentine, of composite resin bonded using an established bonding agent (Syntac) and the more recent Syntac SC. METHOD: A total of 24 adult bovine incisors were divided into two equal groups and prepared by roughening the enamel surfaces with a medium-grit, high-speed diamond. The enamel was etched and 24 x 5 mm diameter composite discs were light-cured and bonded using Syntac and 24 using Syntac SC, following the manufacturer's instructions. The samples were shear tested 72 hours later at a crosshead speed of 50 mm/min using a Howden Universal Testing Machine. The labial enamel and 1 mm of dentine were removed and the experiment was repeated. RESULTS: The mean shear bond strengths (MPa) for the Syntac and Syntac SC bonded composite to enamel were 10.9 +/- 4.5 and 8.9 +/- 5.7, and to dentine 6.4 +/- 3.2 and 5.5 +/- 3.1, respectively. The differences between the values for each material on enamel and between each material on dentine were not significant (P > 0.01). However, nine (19%) Syntac SC bonded composite discs debonded during build-up and had to be remade, prior to testing. CONCLUSION: When a bond between composite and resin was achieved, no significant difference was found between the mean shear bond strengths of Syntac and Syntac SC bonded composite to either enamel or dentine. However, lack of composite adherence to the Syntac SC was noted during the preparation of specimens.

Animals↗
PubMed1998

DNA binding and dimerisation determinants of Antirrhinum majus MADS-box transcription factors.

Members of the MADS-box family of transcription factors are found in eukaryotes ranging from yeast to humans. In plants, MADS-box proteins regulate several developmental processes including flower, fruit and root development. We have investigated the DNA-binding mechanisms used by four such proteins in Antirrhinum majus, SQUA, PLE, DEF and GLO. SQUA differs from the characterised mammalian and yeast MADS-box proteins as it can efficiently bind two different classes of DNA-binding site. SQUA induces bending of these binding sites and the sequence of the site plays a role in determining the magnitude of these bends. Similarly, PLE and DEF/GLO induce DNA bending although the direction of the resulting bends differ. Finally, we demonstrate that the MADS-box and I-domains are sufficient for homodimer formation by SQUA. However, the K-box in SQUA can also act as an oligomerisation motif and in the full-length protein, the K-box plays a different role in mediating dimerisation in the context of SQUA homodimers or heterodimers with PLE. Together these results contribute significantly to our understanding of the function of SQUA and other plant MADS-box proteins at the molecular level.

Binding Sites↗
PubMed1998

Electron spin resonance spectroscopic detection of oxygen-centred radicals in human serum following exhaustive exercise.

Free radicals or oxidants are continuously produced in the body as a consequence of normal energy metabolism. The concentration of free radicals, together with lipid peroxidation, increases in some tissues as a physiological response to exercise - they have also been implicated in a variety of pathologies. The biochemical measurement of free radicals has relied in the main on the indirect assay of oxidative stress by-products. This study presents the first use of electron spin resonance (ESR) spectroscopy in conjunction with the spin-trapping technique, to measure directly the production of radical species in the venous blood of healthy human volunteers pre- and post-exhaustive aerobic exercise. Evidence is also presented of increased lipid peroxidation and total antioxidant capacity post-exercise.

Adolescent↗
PubMed1998

Implications of moderate altitude training for sea-level endurance in elite distance runners.

Elite distance runners participated in one of two studies designed to investigate the effects of moderate altitude training (inspiratory partial pressure of oxygen approximately 115-125 mmHg) on submaximal, maximal and supramaximal exercise performance following return to sea-level. Study 1 (New Mexico, USA) involved 14 subjects who were assigned to a 4-week altitude training camp (1500-2000 m) whilst 9 performance-matched subjects continued with an identical training programme at sea-level (CON). Ten EXP subjects who trained at 1640 m and 19 CON subjects also participated in study 2 (Krugersdorp, South Africa). Selected metabolic and cardiorespiratory parameters were determined with the subjects at rest and during exercise 21 days prior to (PRE) and 10 and 20 days following their return to sea-level (POST). Whole blood lactate decreased by 23% (P < 0.05 vs PRE) during submaximal exercise in the EXP group only after 20 days at sea-level (study 1). However, the lactate threshold and other measures of running economy remained unchanged. Similarly, supramaximal performance during a standardised track session did not change. Study 2 demonstrated that hypoxia per se did not alter performance. In contrast, in the EXP group supramaximal running velocity decreased by 2% (P < 0.05) after 20 days at sea-level. Both studies were characterised by a 50% increase in the frequency of upper respiratory and gastrointestinal tract infections during the altitude sojourns, and two male subjects were diagnosed with infectious mononucleosis following their return to sea-level (study 1). Group mean plasma glutamine concentrations at rest decreased by 19% or 143 (74) microM (P < 0.001) after 3 weeks at altitude, which may have been implicated in the increased incidence of infectious illness.

Adult↗
PubMed1998

The efficacy and safety of salmeterol compared to theophylline: meta-analysis of nine controlled studies.

The aim of this study was to compare the efficacy and safety of salmeterol vs theophylline in asthma management using meta-analysis of clinical trials. Nine clinical studies, containing a total of 1330 patients, met meta-analysis inclusion criteria: randomized, controlled study, minimum 2-week treatment duration with either salmeterol or theophylline. The main outcome measurements were morning and evening peak expiratory flow rate (PEFR), morning and evening symptom scores, use of salbutamol as rescue medication, and withdrawal from treatment for any cause. During the second week of treatment, salmeterol patients had a 10 l min-1 greater increase in mean morning PEFR from baseline than theophylline patients (P < 0.001). Similarly, in the second week, the increase in mean evening PEFR from baseline observed with salmeterol was significantly greater (P < 0.01) than that observed with theophylline. Salmeterol also produced a significantly greater increase in mean morning and evening PEFR than theophylline at weeks 3 and 4. Patients receiving salmeterol were free from daytime symptoms for a mean of 51% of days in the second week compared to 39% for theophylline patients (P < 0.001). Salmeterol patients experienced a mean of 63% symptom-free nights compared to 52% for theophylline patients (P < 0.001). Rescue medication with salbutamol was not required on 49% of days for salmeterol patients and 34% of days for theophylline patients. All results were maintained in the third and fourth weeks of treatment. Withdrawal and incidence of adverse events leading to withdrawal were significantly less frequent in patients receiving salmeterol (P < 0.001). Thus, this meta-analysis suggests that salmeterol has a superior safety and efficacy profile to theophylline in the management of symptoms of chronic asthma.

Adrenergic beta-Agonists↗
PubMed1998

Clinicopathological evidence that neovascularisation is a cause of recurrent varicose veins.

OBJECTIVES: Recurrent varicose veins may result from poor initial surgical technique or progression of varicosities in collateral veins. In some cases new veins may develop at the saphenofemoral junction (neovascularisation) and cause recurrent saphenofemoral incompetence. This was a histological study of recurrent varicose veins. DESIGN: This clinicopathological study included 20 patients (median age 55 years) who had surgery for recurrent saphenofemoral incompetence. MATERIALS AND METHODS: A total of 28 legs had groin re-exploration with repeat flush saphenofemoral ligation. The venous tissue block from the saphenofemoral region (including the proximal thigh varicosity) was excised and orientated for histological analysis. Evidence of neovascularisation was sought using routine histological sections and S100 immunohistochemistry. RESULTS: At operation, thin-walled, serpentine neovascular veins were detected clinically as the principal cause of recurrence in 19 groins. In five groins recurrence was due to a residual missed vein at the saphenofemoral junction, and in four recurrence was caused by cross groin collaterals. On histological sections, evidence of neovascularisation was present in 27 of 28 groins. In eight it co-existed with the veins missed at the original operation but it was the sole identified cause of recurrent saphenofemoral incompetence in 19 (68%) groins. CONCLUSIONS: Neovascularisation was the principal cause of recurrent saphenofemoral incompetence in this series.

Adult↗
PubMed1998

Evaluating the use of Snoezelen and chronic pain: the findings of an investigation into its use (Part II).

This is the second of two papers which describes a research project which was designed to evaluate the use of Snoezelen for the management of chronic pain. Part I explored the concepts underpinning both chronic pain and the Snoezelen itself which subsequently resulted in the development of an appropriate study design. The purpose of the study was to compare the use of Snoezelen for the management of chronic pain as a potential relaxation and distraction strategy, compared to the traditional relaxation approach used within the clinic. This paper will present the results that were obtained with the research project and in the light of these findings the author will discuss implications for future investigation and practice.

Adaptation, Psychological↗
PubMed1998

Guiding systems for computer-assisted surgery: introducing synergistic devices and discussing the different approaches.

Computer-assisted surgery (CAS) or computer-assisted therapy (CAT) attempt primarily to optimize the performance of medical tasks. CAS systems include a guiding system to connect the information world of data and plans to the physical world of surgeons, patients and instruments, and to supplement the surgeon's perception and dexterity. Passive, semi-active and active systems have been proposed and implemented in various clinical applications. In this paper we introduce synergistic devices which are an extension of semi-active systems. We also discuss the advantages of the different categories of guiding systems on the basis of a list of task-oriented and user-oriented qualitative factors.

Humans↗
PubMed1998

Management of acute leg ischaemia in the elderly.

BACKGROUND: Peripheral thrombolysis is advocated by some as the best initial treatment for acute leg ischaemia; but this may not be true for elderly patients. This study reviewed the management of acute leg ischaemia in patients aged over 75 years. METHODS: Over a 5-year interval, 91 events of acute leg ischaemia in 84 patients were managed in a single district general hospital according to a local protocol. There were 60 women and 24 men of median age 81 (range 75-100) years. Fifteen patients were too elderly and infirm for active treatment and received anticoagulation alone. Some 76 events (84 per cent) occurred in patients suitable for active therapy: 33 were managed by initial surgery and 43 by peripheral thrombolysis with tissue plasminogen activator. RESULTS: Overall outcome after 30 days was limb salvage in 48 (53 per cent), amputation in five (5 per cent) and death in 38 (42 per cent). In actively treated patients the corresponding values were 43 (57 per cent), four (5 per cent) and 29 (38 per cent). Initial successful revascularization was more likely following surgery (29 of 33 versus 25 of 43 events with thrombolysis, P < 0.01), but the 30-day outcome was similar in the actively treated groups owing to subsequent morbidity and mortality. CONCLUSION: A group of patients (mostly women) with emboli could be identified, using clinical criteria, who had a high chance of successful revascularization following embolectomy. Late outcome remained poor due to associated co-morbid conditions. Thrombolysis is associated with substantial risk in the elderly, and with high complication rates.

Aged↗
PubMed1998

Early results of a randomized trial of rifampicin-bonded Dacron grafts for extra-anatomic vascular reconstruction. Joint Vascular Research Group.

BACKGROUND: The aim of this study was to determine whether the routine use of an antibiotic-bonded gelatin-coated Dacron graft could reduce the incidence of prosthetic graft infection. Extra-anatomic grafts were chosen for study as they have the highest risk of graft infection. This paper reports early results up to 1 month after surgery. METHODS: This multicentre study involved 14 vascular units in the UK. A total of 257 patients underwent extra-anatomic bypass. Patients were randomized to rifampicin bonding (1 mg/ml rifampicin soak for 15 min before graft insertion) or a control group. Routine three-dose antibiotic prophylaxis was administered to patients in both groups. RESULTS: There were 178 men and 79 women of median age 69 (range 43-92) years. Rifampicin-bonded (n=123) and control (n=134) groups were well matched for clinical details, risk factors and operative techniques. No side-effects were noted from rifampicin bonding. Only one patient (in the control group) developed a graft infection and this proved fatal. There were no significant differences between bonded and unbonded grafts in terms of perioperative mortality rate (9 and 5 per cent respectively), median hospital stay (10 days for both groups), total infective complications (15 and 21 per cent respectively) or need for postoperative antibiotics (13 and 18 per cent respectively). CONCLUSION: Early results from this study have not identified any significant advantage in the routine use of rifampicin bonding, but the rate of graft infection was very low (0.4 per cent). Gelatin coating alone may provide protection against infection. Definitive recommendations about the role of antibiotic bonding cannot be made until longer follow-up becomes available.

Aged↗