Search PubMed⌕ Search

Biomedical subjects

C Roberts

Publications and source records attributed to C Roberts.

At least 181 records · Page 10Linked to original sources
PubMed1997

Comparison of out of hours care provided by patients' own general practitioners and commercial deputising services: a randomised controlled trial. II: The outcome of care.

OBJECTIVE: To compare the outcome of out of hours care given by general practitioners from patients' own practices and by commercial deputising services. DESIGN: Randomised controlled trial. SETTING: Four urban areas in Manchester, Salford, Stockport, and Leicester. SUBJECTS: 2152 patients who requested out of hours care, and 49 practice doctors and 183 deputising doctors (61% local principals in general practice) who responded to the requests. MAIN OUTCOME MEASURES: Health status outcome, patient satisfaction, and subsequent health service use. RESULTS: Patients seen by deputising doctors were less satisfied with the care they received. The mean overall satisfaction score for practice doctors was 70.7 (95% confidence interval 68.1 to 73.2) and for deputising doctors 61.8 (59.9 to 63.7). The greatest difference in satisfaction was with the delay in visiting. There were no differences in the change in health or overall health status measured 24 to 120 hours after the out of hours call or subsequent use of the health service in the two groups. CONCLUSIONS: Patients are more satisfied with the out of hours care provided by practice doctors than that provided by deputising doctors. Organisation of doctors into large groups may produce lower levels of patient satisfaction, especially when associated with increased delays in the time taken to visit. There seem to be no appreciable differences in health outcome between the two types of service.

Appointments and Schedules↗
PubMed1997

A community-wide hepatitis A outbreak in the Shoalhaven region, New South Wales.

We investigated a community-wide outbreak of hepatitis A virus infection in the Shoalhaven region of the New South Wales south coast. Epidemiological features of the outbreak suggested that transmission was predominantly person-to-person. These included: the prolonged course of the epidemic, the bimodal age-specific attack rate, the lower socioeconomic risk groups affected, and the large proportion of cases who reported prior contact with another case. Although widespread use of post-exposure immunoprophylaxis appeared to be effective in preventing symptomatic infection in individuals, it did not rapidly halt the outbreak. We review methods of mass intervention for community-wide outbreaks of hepatitis A virus infection, and define priorities for investigation of future outbreaks.

Disease Outbreaks↗
PubMed1997

Laser ablation of dyed acrylic bone cement.

Revision surgery of cemented implants is indicated when mechanical failure causes severe pain and/or loss of function for the patient. Successful revision arthroplasty of cemented implants requires complete removal of the existing cement. Removal of old cement is an arduous task often causing damage to the surrounding bone tissue. In this study, the authors investigate the use of an Argon laser and the addition of dyes to enhance the laser ablation of bone cement. Methylene blue and red dye #13 were each added separately to polymethylmethacrylate (PMMA) bone cement powder. A continuous wave Argon ion laser (lambda = 514 nm) was used for cement ablation. Cement samples were ablated at different power levels (1.5, 2.3, and 3.0 W) and exposure times (30, 60, 90, 120 sec). The results show that the Argon laser was unable to ablate undyed PMMA. However, the addition of either methylene blue or red dye #13 greatly improved cement ablation by altering the cements' absorption characteristics. Results of Student's t-tests show a statistical difference between red and blue dyed PMMA mean ablation areas at all energy levels tested (P < .0002). As expected, all red ablation areas were greater than blue ablation areas at each energy level tested since red dye absorbs more energy at 514 nm than methylene blue dye. The results of this study suggest that by selectively altering the absorption characteristics of PMMA, laser removal of bone cement can be achieved. In addition, this study also shows that bone tissue does not absorb visible light energy at 514 nm, suggesting that bone cement may be removed with minimal damage to the surrounding bone tissue.

Bone Cements↗
PubMed1997

In vitro frog sciatic nerve as a peripheral nerve model for studies of the mechanism of action of low energy lasers: Part one.

BACKGROUND AND OBJECTIVE: There have been numerous reports of modulation of peripheral nerve action potential characteristics through application of low energy laser irradiation (LELI), although no mechanism has yet been advanced to explain these observations. In order to investigate the mechanism of LELI effects in peripheral nerve tissue, a well-characterized, reliable, and robust peripheral nerve preparation is required. The objective of this study was to evaluate the in vitro frog sciatic nerve as a candidate model for future LELI mechanism studies. MATERIALS AND METHODS: Following 60-minute baseline recordings of compound action potential (CAP) amplitude, latency, depolarization rate, and repolarization rate, helium-neon (HeNe) laser irradiation (632 nm, 15 min, 1-7 J, 44-320 J/cm2) was delivered to one of two sites on the nerve. Laser-induced changes in CAP parameters were analyzed during irradiation and for 60 minutes post-irradiation using a repeated measures linear regression model. RESULTS: In the treatment group that received 7 J of HeNe energy over the recording electrode, CAP latency increased relative to nonirradiated controls during the postirradiation period. No other treatment group demonstrated laser-induced changes in CAP characteristics at any time during the experiment. CONCLUSION: HeNe irradiation demonstrated limited ability to alter the CAP under these conditions. As such, the in vitro frog sciatic nerve is an inappropriate model for mechanism of action studies.

Action Potentials↗
PubMed1997

Importance of using rigorous statistical methods to analyze low energy laser experimental data: Part two.

BACKGROUND AND OBJECTIVE: Numerous authors have reported successful alteration of peripheral nerve action potential characteristics through application of low energy laser irradiation (LELI). The statistical analysis that accompanies many of these reports frequently does not account for the special nature of the data generated in typical LELI experiments. The objective of this study was to evaluate the application of repeated measures linear regression techniques to the analysis of this type of data. Issues of analyzing raw versus normalized data, proper accounting for correlation between measurements, and discrete time point hypothesis testing were addressed. STUDY DESIGN/MATERIALS AND METHODS: The data analyzed in this work were generated from an experiment in which in vitro frog sciatic nerves were irradiated with a helium-neon laser using a variety of treatment protocols. Compound action potential (CAP) amplitude, latency, depolarization rate, and repolarization rate were recorded at 1-minute intervals for 135 minutes for each nerve. Laser-induced changes in CAP parameters were analyzed using various repeated measures linear regression models. RESULTS: The findings of statistical significance were highly dependent on the rigor of the regression model applied. Application of the same regression model to raw and normalized data produced different findings of significance. Determination of significant contrasts was highly dependent on how well the regression model accounted for the correlation between repeated measurements made on the same nerve. In general, models that failed to account adequately for this correlation produced more findings of significant contrasts than increasingly rigorous models. Finally, discrete time point hypothesis testing on normalized data can suggest improper statistical conclusions if the proper correlation structure is not applied to the data set. CONCLUSION: Linear regression analysis offers advantages over discrete time point hypothesis testing in the analysis of highly correlated serial data of this type. Trends in the behavior of the measured parameters are evident, rigorous accounting for correlation between measurements is facilitated, and hypothesis testing is highly flexible.

Action Potentials↗
PubMed1997

1H NMR measurements of wet/dry ratio and T1, T2 distributions in lung.

Proton-magnetic-resonance measurements have been carried out on juvenile porcine peripheral lung parenchyma. The free-induction-decay signal contained a motionally restricted component which decayed in a few tens of microseconds and a mobile component with a T2 time greater than 1 ms. The average second moment, M2, for the motionally restricted signal was found to be 3.42 +/- (0.25) x 10(9) s-2. The T2 distribution for the mobile signal consistently showed four resolvable components of T2 range: 2-6, 10-40, 80-110, and 190-400 ms. The 2-6 ms component was present in a fully dehydrated preparation and was therefore assigned to a nonaqueous lung constituent. The motionally restricted FID component had a T1 = 0.772 +/- 0.11 s and the mobile component had a T1 = 0.967 +/- 0.02 s. The hydrogen content per unit mass for lung parenchyma and water were estimated in two ways: (1) on the basis of chemical content and (2) on the basis of comparison of restricted and mobile signals to the gravimetric (G) water content for a lung sample studied at a wide range of water contents. Lung wet/dry weight ratios were estimated from the free-induction decays and compared with gravimetric measurement. The ratio of (wet/dry)NMR/(wet/dry)G was 1.00 +/- 0.08 and 1.00 +/- 0.05 for the two methods of estimation.

Animals↗
PubMed1997

SB-216641 and BRL-15572--compounds to pharmacologically discriminate h5-HT1B and h5-HT1D receptors.

Despite only modest homology between h5-HT1B and h5-HT1D receptor amino acid sequences, these receptors display a remarkably similar pharmacology. To date there are few compounds which discriminate between these receptor subtypes and those with some degree of selectivity, such as ketanserin, have greater affinity for other 5-HT receptor subtypes. We now report on two compounds, SB-216641 (N-[3-(2-dimethylamino) ethoxy-4-methoxyphenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)-(1,1'-biphenyl)-4-carboxamide) and BRL-15572 3-[4-(3-chlorophenyl) piperazin-1-yl]-1,1-diphenyl-2-propanol), which display high affinity and selectivity for h5-HT1B and h5-HT1D receptors, respectively. In receptor binding studies on human receptors expressed in CHO cells, SB-216641 has high affinity (pKi = 9.0) for h5-HT1B receptors and has 25-fold lower affinity at h5-HT1D receptors. In contrast, BRL-15572 has 60-fold higher affinity for h5-HT1D (pKi = 7.9) than 5-HT1B receptors. Similar affinities for these compounds were determined on native tissue 5-HT1B receptors in guinea-pig striatum. Functional activities of SB-216641 and BRL-15572 were measured in a [35S]GTPgammaS binding assay and in a cAMP accumulation assay on recombinant h5-HT1B and h5-HT1D receptors. Both compounds were partial agonists in these high receptor expression systems, with potencies and selectivities which correlated with their receptor binding affinities. In the cAMP accumulation assay, results from pK(B) measurements on the compounds again correlated with receptor binding affinities (SB-216641, pK(B) = 9.3 and 7.3; BRL-15572, pK(B) = <6 and 7.1, for h5-HT1B and h5-HT1D receptors respectively). These compounds will be useful pharmacological agents to characterise 5-HT1B and 5-HT1D receptor mediated responses.

Animals↗
PubMed1997

Diploma in Hospital Infection Control (Dip HIC)

The London School of Hygiene and Tropical Medicine (LSHTM) has established a Diploma in Hospital Infection Control (Dip-HIC). The course for this new Diploma is run under the auspices of the Hospital Infection Society (HIS) and the Public Health Laboratory Service (PHLS) and will commence in October 1997. The aim of this course is to provide infection control staff with systematic training in the sciences relevant to hospital infection control which will allow them to provide, and to take responsibility for, a broad-based infection control service. Topics will include the epidemiology of infectious diseases, clinical microbiology, health care economics, statistics, surveillance methods and patient management. The course will be multi-disciplinary and open to UK and overseas students, both medical and non-medical.

Certification↗
PubMed1997

Beyond guanine quartets: cation-induced formation of homogenous and chimeric DNA tetraplexes incorporating iso-guanine and guanine.

BACKGROUND: iso-Guanine (iso-G) is the purine component of an isomeric Watson-Crick base pair that may have existed prebiotically. By comparing the abiotic molecular recognition properties of iso-G and its complement, iso-cytosine (iso-C), with those of genomic nucleotide bases, it may be possible to explain the exclusion of the iso-G-iso-C base pair from modern genomes. Whether a nucleobase forms quartets may have a key role in determining its functionality. Biotically, nucleic acid tetraplexes have been implicated in cellular functions; prebiotically, tetraplexes would probably interfere with replication. Recently, in vitro selection has yielded receptors and catalysts that incorporate G quartets. The versatility of these structures could be enhanced by expanding the range of bases that can form the quartet motif. RESULTS: Native polyacrylamide gel electrophoresis of oligonucleotides bearing runs of iso-G provides strong support for tetraplex formation via cation-promoted DNA strand association. In particular, when strands of different lengths bearing the same iso-G tetrad recognition element were combined, five bands were observed after electrophoresis, corresponding to all possible heterotetraplexes with parallel strand alignment. An analogous experiment with a mixture of strands bearing iso-G or G tetrad recognition domains supports the existence of mixed iso-G/G tetraplexes with antiparallel strand alignment at chimeric junctions. iso-G tetraplex and quartet structure has also been probed by a photo-crosslinking experiment, ultra-violet spectroscopy and theoretical calculations. CONCLUSIONS: As iso-G and G both have a marked tendency to form tetraplexes, their tandem inclusion in genetic material may be problematic, leading to double-stranded DNA half composed of bases that have a tendency to auto-associate. The resulting density of 'selfish' bases could undermine Watson-Crick pair formation, especially in a prebiotic context devoid of enzymes. Nevertheless, the ability of iso-G to form mixed quartets with G may provide a basis for altering the properties of tetraplexes in the domain of artificial receptors or catalysts from in vitro selections.

Cations↗
PubMed1997

Cloning and developmental expression analysis of chick Hira (Chira), a candidate gene for DiGeorge syndrome.

Deletions within human chromosome 22q11 cause a wide variety of birth defects including the DiGeorge syndrome and velo-cardio-facial (Shprintzen) syndrome. Despite the positional cloning of several genes from the critical region, it is still not possible to state whether the phenotype is secondary to haploinsufficiency of one or more than one gene. In embryological studies phenocopies of these abnormalities are produced by a variety of actions which disrupt the contribution made by the cranial and cardiac neural crest to development. The TUPLE1/HIRA gene is related to WD40 domain transcriptional regulators and maps within the DiGeorge critical region. We have cloned the chick homologue of HIRA and conducted in situ expression analysis in early chick embryos. Hira is expressed in the developing neural plate, the neural tube, neural crest and the mesenchyme of the head and branchial arch structures. HIRA may therefore have a role in the haploinsufficiency syndromes caused by deletion of 22q11.

Amino Acid Sequence↗
PubMed1997

A genetically inactivated herpes simplex virus type 2 (HSV-2) vaccine provides effective protection against primary and recurrent HSV-2 disease.

A glycoprotein H (gH)-deleted herpes simplex virus type 2 (HSV-2) was evaluated as a vaccine for the prevention of HSV-induced disease. This virus, which we term a DISC (disabled infectious single cycle) virus, can only complete one replication cycle in normal cells and should thus be safe yet still able to stimulate broad humoral and cell-mediated antiviral immune responses. A gH-deleted HSV-2 virus that has been tested as a vaccine in the guinea pig model of recurrent HSV-2 infection was constructed. Animals vaccinated with DISC HSV-2 showed complete protection against primary HSV-2-induced disease, even when challenged 6 months after vaccination. In addition, the animals were almost completely protected against recurrent disease. Even at low vaccination doses, there was a high degree of protection against primary disease. A reduction in recurrent disease symptoms was also observed following therapeutic vaccination of animals already infected with wild type HSV-2.

Animals↗
PubMed1997

Industrial Genotoxicology Group collaborative trial to investigate cell cycle parameters in human lymphocyte cytogenetics studies.

Human lymphocyte cultures have been used for many years for assessing the in vitro clastogenic potential of test substances. In these assays the harvest time should be based on the cell cycle time in order to ensure that cells are sampled at an appropriate time for the detection of clastogenic effects. The sources of variation in the cell cycle time in routine cytogenetic assays have not been well studied. Consequently 13 laboratories, all members of the Industrial Genotoxicology Group, participated in a collaborative study to measure the variation in cell cycle time in cultured human peripheral blood lymphocytes under various conditions. The study was performed in two phases, spaced 6 months apart. The average generation time (AGT) was measured by the incorporation of bromodeoxyuridine. Very similar AGTs were found in the presence and absence of S9 mix. The mean AGT (mean of four donors) in each laboratory varied from 11.2 to 17.1 h, indicating there is significant variability in cell cycle times of human peripheral blood lymphocytes between laboratories. There was greater variation between laboratories than within laboratories. A comparison of AGT values at 72 h performed in experiments at least 6 months apart indicated good reproducibility in most laboratories. The study indicates that a 24 h post-treatment harvest may result in the analysis of very few first division cells unless very significant cell cycle delay is induced by the test substance. It was also found that a post-harvest time equivalent to 1.5 cell cycles will result in an approximately equal mixture of first and second division cells and therefore should by suitable for assessing both the induction of chromosome aberrations and polyploidy.

Animals↗
PubMed1997

Modified barium swallow does not affect how often PEGs are placed after stroke.

Dysphagia frequently follows stroke, but often resolves quickly. Percutaneous endoscopic gastrostomy (PEG) or other feeding tubes are placed to improve nutrition and hydration, and reduce the risk of aspiration pneumonitis. We evaluated the impact of modified barium swallow in determining PEG placements and the influence of specific swallowing abnormalities on PEG placement. The abnormalities assessed were presence of pharyngeal stasis and/or visualization of posterior pharyngeal transfer problems and aspiration of liquid or solids. A total of 302 patients with stroke were admitted to our hospital between 1989 and 1993, but only those with hemorrhagic or nonhemorrhagic stroke by computed tomographic (CT) scans or magnetic resonance imaging (MRI) or autopsy were included in our study. Patients with transient ischemic attacks (TIAs), central nervous system tumors, and traumas were excluded. Barium swallow studies were performed on 69 (23%) of patients; 49 (71%) were abnormal, based on aspiration of barium, pharyngeal stasis, or postpharyngeal transfer dysphagia. PEGs were placed in only 18% of those with abnormal studies. Of the patients with normal barium swallow studies, 25% had a PEG placed. Two hundred thirty-three patients underwent no barium swallow studies, but 11 (4.72%) of these had PEG placed. The rate of PEG placement was not related to any one of the abnormalities noted on the modified barium swallow. Rather, patients who received PEG had significant neurological deficits and increased prevalence of aspiration pneumonitis. The decision to insert PEG was made on clinical grounds and not on abnormal barium studies alone.

Aged↗
PubMed1997

Comparison of psychological symptoms of women requesting removal of breast implants with those of breast cancer patients and healthy controls.

Concern about the safety of silicone breast implants has led many women with numerous physical and psychological symptoms to seek breast implant removal. This retrospective group comparison study describes the psychological profile of women requesting breast implant removal compared with two control groups. The Brief Symptom Inventory was used to compare psychological symptoms of three groups of women: a preoperative breast implant group requesting removal of implants (n = 78), a postoperative breast cancer group without breast implants (n = 64), and a control group with no known breast disease and unknown breast implant status (n = 68). Scores were compared on the Global Severity Index of the Brief Symptom Inventory as well as on nine subscales: somatization, obsessive-compulsiveness, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychoticism. The breast implant group had significantly elevated Global Severity Index scores, as well as somatization, obsessive-compulsiveness, depression, hostility, and anxiety subscale scores, when compared with the other groups. Post hoc data analysis revealed that women who had implants after subcutaneous mastectomy as prophylaxis for breast cancer (n = 18) had a significantly different symptom profile and higher Global Severity Index scores than women who had cosmetic augmentation (n = 53). Additionally, women who had subcutaneous mastectomy and implants had significantly higher subscales of interpersonal sensitivity, phobic anxiety, paranoid ideation, and psychoticism than the cosmetic implant subjects. Women requesting removal of silicone breast implants had greater psychological distress than women who were recently diagnosed with breast cancer or controls with no known breast disease and unknown implant status. Within the implant group, however, women who had subcutaneous mastectomy showed greater psychological disturbance than those who had augmentation mammaplasty.

Adult↗
PubMed1997

Outcome study of the psychological changes after silicone breast implant removal.

INTRODUCTION: The purpose of this longitudinal study is to determine if there are changes in psychological well-being after breast implant removal. METHODS: Thirty-seven women underwent breast implant removal and completed a preoperative baseline, early postoperative (4 to 9 months), and late postoperative (> 10 months) Brief Symptom Inventory, a measure of psychological distress. RESULTS: After breast implant removal the mean Global Severity Scores on the Brief Symptom Inventory of women undergoing implant removal increased over the three time periods, indicating increasing psychological distress. When the group was divided into those who had breast reconstruction after implant removal (implant replacement with saline-filled implants or TRAM flaps) and those who did not have reconstruction, both groups had increasing psychological distress, but the women who had reconstruction had slightly higher scores. Women with a history of psychiatric treatment showed the greatest increase in psychological symptoms. CONCLUSION: Breast implant removal did not have psychological benefits in this group of women. Breast reconstruction after removal did not appear to be psychologically beneficial to this cohort.

Adult↗
PubMed1997

Increase in muscle IGF-I protein but not IGF-I mRNA after 5 days of endurance training in young rats.

Five days of treadmill training in rats leads to increased muscle size and running time. This was used to examine the effect of exercise on circulating insulin-like growth factor I [IGF-I; radioimmunoassay (RIA)], local muscle (hindlimb) IGF-I (by RIA), and muscle IGF-I mRNA (by ribonuclease protection assay). Eight-week-old female Sprague-Dawley rats were divided into three groups: control (n = 10); single-exercise test (n = 10), untrained but with one maximal exercise test at the end of the study; and training (n = 16), trained for 5 days and one maximal exercise test on day 6. There were no differences among the groups with respect to circulating IGF-I. Muscle IGF-I protein in trained rats (4.2 +/- 1.5 ng/g of muscle tissue) was significantly greater than both control (0.27 +/- 0.1 ng/g) and single-exercise test (0.62 +/- 0.19 ng/g, P < 0.05 by analysis of variance). There was no difference among the groups in IGF-I mRNA gene expression. These data suggest that there is an early, marked, local muscle increase in IGF-I protein in response to exercise. This increase, however, may not be related to increased muscle IGF-I gene expression. Moreover, the IGF-I response was probably local in nature since it was not matched by any increase in circulating IGF-I.

Animals↗