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Biomedical subjects

P Buchanan

Publications and source records attributed to P Buchanan.

At least 19 recordsLinked to original sources

An anomalous x-ray diffraction study of the hydration structures of Cs+ and I- in concentrated solutions.

Anomalous x-ray diffraction experiments were carried out on concentrated aqueous solutions of sodium iodide (6 molal) and cesium iodide (3 molal). Data were gathered at two energies below the absorption edges of the Cs+ and I- ions in order to avoid contributions from fluorescence. The statistics and quality of the raw data were improved by the use of a focusing analyzer crystal. Differences were taken between the data sets and used to calculate the hydration structures of Cs+ and I-. The structures found are more complex than anticipated for such large ions with relatively low charge densities and show evidence of ion-pair formation in both solutions. A two-Gaussian fit to the Cs+ data gives information about the Cs+-O and Cs+-I- correlations. The central position of the Gaussian representing the Cs+-O was fixed at 3.00 A, that is, the maximum of this contribution. The other parameters were allowed to vary freely, giving a Cs+-I- distance of 3.84+/-0.05 A and coordination numbers of 7.9 and 2.7, respectively, for the Cs+-O and Cs+-I- correlations. The results on the structure of I- in the 6 molal NaI aqueous solution were also fitted to a model based on Gaussians; this gives correlations for I- -O and I- -Na+ at 3.17+/-0.06 and 3.76+/-0.06 A with respective coordination numbers of 8.8 and 1.6. The structure of I- in the 3 molal CsI solution shows overlapping contributions due to I- -H, I- -O, and I- -Cs+. The best Gaussian fit gives two peaks centered at 3.00+/-0.08 and 3.82+/-0.04 A and shows that the latter two correlations are unresolved. The hydration structures are compared with those of other alkali and halide ions. The results are also found to be in good agreement with those obtained from standard x-ray diffraction and computer simulation.

Cesium↗

Bacteriological efficacy of 5-day therapy with telithromycin in acute maxillary sinusitis.

Increasing resistance among the key pathogens responsible for community-acquired respiratory tract infections, namely Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis, has the potential to limit the effectiveness of the antibacterial agents available to treat these infections. Moreover, there are regional differences in the susceptibility patterns observed and, as treatment is usually empirical, choosing an effective treatment can be challenging. Telithromycin, the first ketolide to be approved for clinical use, offers an activity profile that covers the key respiratory pathogens including penicillin- and macrolide-resistant S. pneumoniae as well as beta-lactamase-producing H. influenzae and M. catarrhalis. In a pooled analysis of three large controlled clinical trials involving patients with acute maxillary sinusitis, the bacteriological efficacy of 5- or 10-day treatment with telithromycin and 10-day treatment with comparators was evaluated. Telithromycin administered as a once-daily 800 mg dose for 5 days achieved eradication rates of 91.8, 87.5 and 92.9% for S. pneumoniae, H. influenzae and M. catarrhalis, respectively. Bacteriological eradication of 8/10 and 12/14 isolates of S. pneumoniae resistant to penicillin and erythromycin, respectively, was also reported following 5-day treatment with telithromycin. The clinical efficacy of this regimen was equivalent to that of a 10-day regimen of telithromycin or standard 10-day courses of amoxicillin-clavulanic acid or cefuroxime axetil. Telithromycin 800mg given for 5 days was well tolerated, with the majority of adverse events being of mild or moderate intensity. These data suggest that telithromycin provides effective first-line therapy for use in patients with acute maxillary sinusitis in a short and convenient once-daily dosage regimen.

Adolescent↗

Involving consumers in research and development agenda setting for the NHS: developing an evidence-based approach.

OBJECTIVES: To look at the processes and outcomes of identification and prioritisation in both national and regional R&D programmes in health and elsewhere, drawing on experiences of success and failure. Also to identify the barriers to, and facilitators of, meaningful participation by consumers in research identification and prioritisation. DATA SOURCES: Electronic databases and interviews with UK consumers and research programme managers. REVIEW METHODS: A framework was devised for examining the diverse ways of involving consumers in research. It identified key distinguishing features as: the types of consumers involved; whether consumers or researchers initiated the involvement; the degree of consumer involvement (consultation, collaboration or consumer control); forums for communication (e.g. committees, surveys, focus groups); methods for decision-making; and the practicalities for implementation. Context (institutional, geographical and historical setting) and underpinning theories were considered as important variables for analysing examples of consumer involvement. This innovative framework was then applied to the review data from reports selected for inclusion and interviews. RESULTS: The study found 286 documents explicitly mentioning consumer involvement in identifying or prioritising research topics. Of these, 91 were general discussions, some of which included a theoretical analysis or a critique of research agendas from a consumer perspective, 160 reported specific efforts to include consumers in identifying or prioritising research topics and a further 51 reported consumers identifying or prioritising research topics in the course of other work. Detailed reports of 87 specific examples were identified. Most of this literature was descriptive reports by researchers who were key actors in involving consumers. A few reports were written by consumer participants. Fewer still were by independent researchers. Our conclusions are therefore not based on rigorous research, but implications for policy are drawn from individual reports and comparative analyses. CONCLUSIONS: Productive methods for involving consumers require appropriate skills, resources and time to develop and follow appropriate working practices. The more that consumers are involved in determining how this is to be done, the more research programmes will learn from consumers and about how to work with them. Further success might be expected if research programmes embarking on collaborations approach well-networked consumers and provide them with information, resources and support to empower them in key roles for consulting their peers and prioritising topics. To be worthwhile, consultations should engage consumer groups directly and repeatedly in facilitated debate; when discussing health services research, more resources and time are required if consumers are drawn from groups whose main focus of interest is not health. These barriers can largely be overcome with good leadership, purposeful outreach to consumers, investing time and effort in good communication, training and support and thereby building good working relationships and building on experience. Organised consumer groups capable of identifying research priorities also need to find ways of introducing their ideas into research programmes. Further research is suggested to develop and evaluate different training methods, information and education and other support for consumers and those wishing to involve them; to address the barriers to consumers' ideas influencing research agendas; and to carry out prospective comparative studies of different methods for involving consumers. Research about collective decision-making would also be further advanced by addressing the processes and outcomes of consensus development that involves consumers.

Community Participation↗

Involving consumers in a needs-led research programme: a pilot project.

OBJECTIVES: To describe the methods used for involving consumers in a needs-led health research programme, and to discuss facilitators, barriers and goals. DESIGN: In a short action research pilot study, we involved consumers in all stages of the Health Technology Assessment (HTA) Programme: identifying and prioritizing research topics; commissioning and reporting research; and communicating openly about the programme. We drew on the experience of campaigning, self-help and patients' representative groups, national charities, health information services, consumer researchers and journalists for various tasks. We explored consumer literature as a potential source for research questions, and as a route for disseminating research findings. These innovations were complemented by training, one-to-one support and discussion. A reflective approach included interviews with consumers, co-ordinating staff, external observers and other programme contributors, document analysis and multidisciplinary discussion (including consumers) amongst programme contributors. RESULTS: When seeking research topics, face-to-face discussion with a consumer group was more productive than scanning consumer research reports or contacting consumer health information services. Consumers were willing and able to play active roles as panel members in refining and prioritizing topics, and in commenting on research plans and reports. Training programmes for consumer involvement in service planning were readily adapted for a research programme. Challenges to be overcome were cultural divides, language barriers and a need for skill development amongst consumers and others. Involving consumers highlighted a need for support and training for all contributors to the programme. CONCLUSIONS: Consumers made unique contributions to the HTA Programme. Their involvement exposed processes which needed further thought and development. Consumer involvement benefited from the National Co-ordinating Centre for Health Technology Assessment (NCCHTA) staff being comfortable with innovation, participative development and team learning. Neither recruitment nor research capacity were insurmountable challenges, but ongoing effort is required if consumer involvement is to be sustained.

Biomedical Technology↗

First trimester biochemical screening for Down syndrome: free beta hCG versus intact hCG.

To compare free beta hCG versus intact hCG in first trimester Down syndrome screening we analysed 63 cases of Down syndrome and 400 unaffected control pregnancies between 10 and 13 weeks' gestation. The Down syndrome median multiple of the median (MoM) was significantly higher (p=0.001) for free beta hCG (1.89 MoM) than for intact hCG (1.37 MoM). Although distributions for free beta hCG (unaffected, 0.2157; DS, 0.2322) are wider than for intact hCG (unaffected, 0.1697; DS, 0.2158), overall 27% of Down syndrome cases were above the 95th percentile for free beta hCG compared to 19% for intact hCG. Combined with maternal age, free beta hCG detected 45% of Down syndrome pregnancies at a 5% false positive rate. Intact hCG combined with maternal age demonstrated a detection efficiency comparable to maternal age alone (35% versus 32%). In contrast, a recent study (Haddow et al., 1998-NEJM 338: 955-961) indicated that intact hCG yielded a higher first trimester Down syndrome detection efficiency than free beta hCG (29% versus 25% respectively). Re-analysis of distribution parameters in the Haddow et al. study, however, show that free beta hCG was actually the better marker (23% detection for intact hCG versus 29% for free beta hCG).

Adult↗

First-trimester Down syndrome screening using dried blood biochemistry and nuchal translucency.

OBJECTIVE: To assess the effectiveness of free beta-hCG, pregnancy-associated plasma protein A, and nuchal translucency in a prospective first-trimester prenatal screening study for Down syndrome and trisomy 18. METHODS: Risks were calculated for Down syndrome and trisomy 18 based on maternal age and biochemistry only (n = 10,251), nuchal translucency only (n = 5809), and the combination of nuchal translucency and biochemistry (n = 5809). RESULTS: The study population included 50 Down syndrome and 20 trisomy 18 cases. Nuchal translucency measurement was done on 33 Down syndrome and 13 trisomy 18 cases. Down syndrome screening using combined biochemistry and ultrasound resulted in a false-positive rate of 4.5% (95% confidence interval [CI] 3.9%, 5.2%) and detection rate of 87.5% (95% CI 47%, 100%) in patients under age 35 years. In older patients, the false-positive rate was 14.3% (95% CI 12.7%, 15. 8%) and detection rate was 92% (95% CI 74%, 99%). For trisomy 18 screening, the false-positive rate was 0.4% (95% CI 0.24%, 0.69%) and detection rate was 100% (95% CI 40%, 100%) in younger patients, whereas in older patients the false-positive rate was 1.4% (95% CI 0. 9%, 2.0%) and detection rate was 100% (95% CI 66%, 100%). Using modeling, at a fixed 5% false-positive rate, the Down syndrome detection rate was 91%. Conversely, at a fixed 70% Down syndrome detection rate, the false-positive rate was 1.4%. CONCLUSION: First-trimester screening for Down syndrome and trisomy 18 is effective and offers substantial benefits to clinicians and patients.

Adult↗

Prenatal diagnosis of a mosaic extra structurally abnormal chromosome by spectral karyotyping.

A de novo mosaic extra structurally abnormal chromosome (ESAC) was detected in 33 per cent of cultured amniotic fluid cells from a pregnant woman. Neither Q-banding nor fluorescence in situ hybridization (FISH) employing a DNA probe for nucleolar organizer region demonstrated the presence of satellites on the ESAC. Spectral karyotyping (SKY) was performed in this prenatal case and led to a quick and accurate determination of the ESAC as chromosome 14 in origin. The SKY finding was confirmed by conventional FISH analysis using a chromosome 14 specific painting probe. Subsequent hybridizations with a centromeric probe and a 14q subtelomeric probe were also performed to further characterize the ESAC. Absence of (TTAGGG)n sequence on the ESAC, determined postnatally, suggested it is a ring chromosome 14. Genetic counselling concerning these findings was provided to the parents who chose to continue the pregnancy. The male infant had no apparent abnormal phenotype at birth.

Adult↗

Anxiolytic activity of adenosine receptor activation in mice.

1. Purine analogues have been examined for anxiolytic- and anxiogenic-like activity in mice, by use of the elevated plus-maze. 2. The selective A1 receptor agonist, N6-cyclopentyladenosine (CPA) had marked anxiolytic-like activity at 10 and 50 microg kg(-1), with no effect on locomotor performance at these doses. 3. The A1 selective adenosine receptor antagonist, 1,3-dipropyl-8-cyclopentylxanthine (CPX) had no significant effect on anxiety-related measures or locomotor behaviour, but blocked the anxiolytic-like activity of CPA. The hydrophilic xanthine, 8-(p-sulphophenyl) theophylline did not prevent anxiolysis by CPA. 4. Caffeine had anxiogenic-like activity at 30 mg kg(-1) which was prevented by CPA at 50 micro kg(-1). 5. The A2 receptor agonist, N6-[2-(3,5-dimethoxyphenyl)-2(2-methylphenyl)-ethyl]adenosine (DPMA) had no effect on anxiety behaviour but depressed locomotor activity at the highest dose tested of 1 mg kg(-1). The A2 receptor antagonist, 1,3-dimethyl-l-propargylxanthine (DMPX) had no effect on anxiety-related measures or locomotion and did not modify the anxiolytic-like activity of CPA. 6. Administration of DPMA in combination with anxiolytic doses of CPA prevented the anxiolytic-like activity of the latter. 7. The results suggest that the selective activation of central A1 adenosine receptors induces anxiolytic-like behaviour, while the activation of A2 sites causes locomotor depression and reduces the effects of A1 receptor activation. The absence of any effect of CPX alone suggests that the receptors involved in modulating behaviour in the elevated plus-maze in mice are not activated tonically by endogenous adenosine.

Adenosine↗

Skeletal muscle responses to unloading with special reference to man.

The limited space flight data suggest that exposure to microgravity decreases muscle strength in humans and muscle mass in lower mammals. Several earth-based models have been used to address the effect of unloading on the human neuromuscular system due to the limited access of biological research to long-term space flight. Bedrest eliminates body weight bearing of both lower limbs. Unilateral lower limb suspension (ULLS), where all ambulatory activity is performed on crutches with an elevated sole on the shoe of one foot, has recently been used to unload one lower limb. The results from studies using these two models support their efficacy. The decrease in strength of m. quadriceps femoris, for example, after four to six weeks of bedrest, ULLS or space flight is 20 to 25%. The results from the earth-based studies show that this response can be attributed in part to a decrease in the cross-sectional area of the KE which reflects muscle fiber atrophy. The results from the ground based studies also support the limited flight data and show that reductions in strength are larger in lower than upper limbs and in extensor than flexor muscle groups. They also raise issue with the generally held concept that postural muscle is most affected by unweighting. Slow-twitch fibers in lower limb muscles of mixed fiber type composition and muscle composed mainly of slow-twitch fibers do not preferentially atrophy after bedrest or ULLS. Taken together, the data suggest that unloading causes remarkable adaptations in the neuromuscular system of humans. It should be appreciated, however, that this area of research is in its infancy.

Adaptation, Physiological↗

Adaptations to unilateral lower limb suspension in humans.

This study examined the effect of unilateral lower limb suspension (ULLS) on neuromuscular function in humans. Eight subjects (31 +/- 4 years old) performed all ambulatory activity on crutches for 6 weeks while wearing a shoe with a 10-cm sole on the right foot to unweight the left lower limb. Knee extensor (KE) torque during eccentric, concentric, and isometric actions, and electromyography (EMG) of m. vastus lateralis (m. VL), m. gastrocnemius medialis (m. GM) and m. soleus (m. SL) during isometric actions were assessed pre-ULLS, post-ULLS, and after 4 d of recovery. Average muscle cross-sectional area (CSA) of the KE was measured pre- and post-ULLS and that of the ankle extensors (AE) post-ULLS using magnetic resonance imaging. Strength of the KE of the suspended left limb was reduced (p less than 0.05) 21 and 15%, respectively, after ULLS and 4 d later. Average muscle CSA of the left KE decreased (p less than 0.05) 16%. The KE of the non-suspended right limb showed no changes in muscle CSA. Thus, average muscle CSA of the KE of the suspended limb was 17% less (p less than 0.05) than that of the non-suspended limb. Average muscle CSA of the AE, likewise, was smaller (18%, p less than 0.05) in the left than right leg after ULLS. Maximal integrated EMG of VL and overall mean power frequency of GM and SL for submaximal isometric actions were both decreased (p less than 0.05) post-ULLS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

Influence of eccentric actions on skeletal muscle adaptations to resistance training.

Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle-aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n = 8) performed coupled concentric and eccentric actions while group CON (n = 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n = 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P less than 0.05) Type IIA and decreased (P less than 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P less than 0.05). Type II area increased (P less than 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P less than 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P less than 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P less than 0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗