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Biomedical subjects

G Harding

Publications and source records attributed to G Harding.

At least 19 recordsLinked to original sources
PubMed1992

The topographic distribution of the magnetic P100M to full- and half-field stimulation.

Visual evoked magnetic responses were recorded to full-field and left and right half-field stimulation with three check sizes (70', 34' and 22') in five normal subjects. Recordings were made sequentially on a 20-position grid (4 x 5) based on the inion, by means of a single-channel direct current-Superconducting Quantum Interference Device second-order gradiometer. The topographic maps were consistent on the same subjects recorded 2 months apart. The half-field responses produced the strongest signals in the contralateral hemisphere and were consistent with the cruciform model of the calcarine fissure. Right half fields produced upper-left-quadrant outgoing fields and lower-left-quadrant ingoing fields, while the left half field produced the opposite response. The topographic maps also varied with check size, with the larger checks producing positive or negative maximum position more anteriorly than small checks. In addition, with large checks the full-field responses could be explained as the summation of the two half fields, whereas full-field responses to smaller checks were more unpredictable and may be due to sources located at the occipital pole or lateral surface. In addition, dipole sources were located as appropriate with the use of inverse problem solutions. Topographic data will be vital to the clinical use of the visual evoked field but, in addition, provides complementary information to visual evoked potentials, allowing detailed studies of the visual cortex.

Adult↗
PubMed1992

Single dose treatment failure in women with acute cystitis.

Single dose treatment regimens (SDT) are effective, inexpensive alternatives to longer courses of therapy for adult females with acute cystitis or asymptomatic bacteriuria. A number of SDT regimens consistently cure 85 to 100% of women with acute cystitis and 50 to 80% of women with asymptomatic bacteriuria. However, SDT is inherently less effective than longer regimens because many upper tract infections are not cured. Initial SDT studies suggested that most patients with significant renal invasive disease or underlying urological abnormalities fail therapy. As a result, SDT has been proposed as an efficient strategy to diagnose significant upper tract infections with accompanying pathology that merit additional investigation or treatment. Few studies have refuted or supported this hypothesis. Single-dose treatment studies show an association between the site of infection as determined by the antibody-coated bacteria (ACB) test and treatment outcome. Patients with ACB-negative tests have a cure rate of over 90% in almost all studies in which the organism is susceptible to the agent chosen. Patients with positive ACB tests tend to have treatment failure rates of 30 to 50%. However, imaging studies have not been carried out in parallel with these studies and the validity of using single-dose treatment failure to screen women for significant upper tract pathology has still not been established.

Acute Disease↗
PubMed1992

Bone composition measured by x-ray scattering.

Ten composite samples consisting of cortical bone and adipose tissue, in known proportions, were made. The intensity of monochromatic x-rays (energy 8 keV) scattered by these samples was determined as a function of the modulus of the scattering vector, K. The ratio of the heights of peaks at K values of around 134 and 22 nm-1 provided a measure of the ratio of adipose tissue to bone mineral in these samples. This method was then used to determine the ratio of adipose tissue to mineral in samples of trabecular bone from 16 vertebral bodies. The results were correlated with measurements of the bone composition determined by ashing (r = 0.66) and histomorphometry (r = 0.66). Furthermore, the ashing and histomorphometry results were correlated with each other (r = 0.68). The feasibility of using higher energy x-rays (35-80 keV) for obtaining the same information from bone within the body is briefly discussed.

Adipose Tissue↗
PubMed1992

Survey of Bacteroides fragilis group susceptibility patterns in Canada.

The in vitro activities of penicillin, clindamycin, chloramphenicol, metronidazole, piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillin-clavulanate, ampicillin-sulbactam, cefoxitin, ceftizoxime, cefotetan, moxalactam, and imipenem against 348 Bacteroides fragilis group isolates collected from six Canadian cities during 1990 were determined by the National Committee for Clinical Laboratory Standards (NCCLS) agar dilution technique. All isolates were susceptible to chloramphenicol, metronidazole, piperacillin-tazobactam, and imipenem. For the other antibiotics tested, the following resistance rates were observed: penicillin, 97%; clindamycin, 9%; piperacillin, 19%; ticarcillin, 31%; ticarcillin-clavulanate, 0.28%; ampicillin-sulbactam, 0.85%; cefoxitin, 26%; ceftizoxime, 15%; cefotetan, 53%; and moxalactam, 17%. Susceptibility profiles to beta-lactam antibiotics varied among the different species tested: B. fragilis and Bacteroides vulgatus demonstrated lower resistance rates than Bacteroides distasonis and indole-positive Bacteroides thetaiotaomicron and Bacteroides ovatus. Ceftizoxime results should be interpreted cautiously, because the MICs obtained with the recommended NCCLS control strain were lower than expected.

Anti-Bacterial Agents↗
PubMed1990

Somatosensory evoked potentials in schizophrenia. A lateralisation study.

The SSEPs obtained from 19 schizophrenics defined by RDC, DSM-III and PSE criteria were compared with those from a control group of healthy volunteers. Previous findings of an abnormal lack of lateralising response in schizophrenic patients were not replicated. No significant difference in either amplitude or morphology between the traces obtained from the two groups were recorded. Ipsilateral and contralateral latencies for stimulation of the left and right index finger showed no significant difference in peak latency for any component between patient and control group. When mean peak-to-peak amplitudes were plotted the contralateral component was always greater in amplitude than the ipsilateral one. An objective measure of the degree of lateralisation, the percentage lateralisation quotient, showed no lateralisation differences between the patient and control groups. A case of myogenic contamination of ipsilateral components was observed calling into doubt findings where no temporal region monitoring has been performed.

Adult↗
PubMed1990

Professional relationships between general practitioners and pharmacists in health centres.

The inclusion of pharmacies in health centres has created opportunities for general practitioners to become better acquainted with the potential contribution of pharmacists to health care. A qualitative study has been made to explore the extent to which this potential has been realized. Ten health centres with an integral pharmacy were selected, one from each of the regional health authorities in England which had at least one such health centre. Interviews were conducted with 13 general practitioners and 10 pharmacists working in the health centres. Nine general practitioners working in health centres without pharmacies and 10 community pharmacists were also interviewed. General practitioners' attitudes towards health centre pharmacists appeared to differ markedly from the attitudes of colleagues working in relative isolation from pharmacists. It appears that general practitioners working closely with the pharmacist develop a collaborative approach to health care.

Ambulatory Care Facilities↗
PubMed1989

A study of inter-reviewer reliability of attacks recorded on ambulatory EEG.

Eleven ambulatory EEG (A/EEG) cassette tapes were sent to 5 reviewers from different EEG laboratories in the U.K. Each tape included one attack recorded from a different patient. Attacks were chosen to include various possible EEG changes that can occur during attacks on A/EEG. Reviewers were asked to give details of EEG changes seen during attacks and to state whether they thought attacks were epileptic. Total agreement about the presence of abnormality was found on 2 tapes. Four out of 5 reviewers agreed on 4 tapes and on the remaining 5 tapes only 2 or 3 reviewers were in agreement. It was concluded that the amount of agreement amongst reviewers was poor but reasonable in view of the degree of difficulty of the tapes which were not a random sample. Compared to the final clinical opinion of referring consultants, these findings would have resulted in 16% false negatives, 7% false positives and 13% of cases in which no decision was made.

Ambulatory Care↗
PubMed1989

Once-daily therapy with ceftriaxone compared with daily multiple-dose therapy with cefotaxime for serious bacterial infections: a randomized, double-blind study.

A randomized, double-blind study was done to compare the efficacy and toxicity of daily single-dose therapy with intravenous ceftriaxone (2 g every 24 h) with daily multiple-dose therapy with cefotaxime (2 g every 6 h) for treatment of serious bacterial infections in nonneutropenic patients. Of the 325 patients who were evaluable for toxicity, 241 (74.2%) were evaluable for efficacy. Infection sites included lung (106), urinary tract (42), skin and soft tissue (43), bone and joint (23), bacteremia (21), and hepatobiliary (5). Definite infections were present in 173 cases (71.8%) and possible infections in 68 (28.2%). Analysis of clinical and bacteriologic responses and adverse drug reactions showed no significant differences between the regimens. Values for 95% confidence limits on the differences between regimens for positive clinical and bacteriological outcomes in definite infections were -0.8% to 3.0% and -1.9% to 9.1%, respectively. Thus, daily single-dose therapy with ceftriaxone was comparable to daily multiple-dose therapy with cefotaxime in treating these bacterial infections.

Adult↗
PubMed1989

The community pharmacist: over qualified dispenser or health professional?

This paper contributes to the debate introduced in a previous issue of this journal. The current and future roles of community pharmacists are outlined. It is suggested that although elements of their dispensing role are changing, pharmacists continue to have a vital function in the dispensing process. Proposed developments for the future role of community pharmacists in the treatment of minor illness are also discussed.

Community Pharmacy Services↗
PubMed1987

Status and outlook of coherent-x-ray scatter imaging.

X-ray scattering, including coherent, incoherent, and resonance (fluorescent) phenomena, is of fundamental importance in contemporary science as a tool to probe the structure of matter at an atomic level. This elevated status is in sharp contrast to the role of x-ray scatter in medical and industrial radiography, where it is generally regarded as an unmitigated nuisance to be corrected for or, preferably, eliminated. We introduce a novel x-radiographic technique [x-ray diffraction computed tomography (CT)] based on measurement of coherent scatter. The physical background to coherent scattering is described in a simple, classical way, and its importance in conventional radiography is demonstrated by using Monte Carlo analysis. Some diffraction patterns of plastics and animal tissues are presented to illustrate the relevance of coherent scattering to material characterization and diagnosis in industrial and medical radiology. An experimental first-generation (single-pencil-beam) CT system has been constructed to demonstrate the feasibility of x-ray diffraction CT. Some diffraction CT and coherent scatter projection images of simple objects are presented. Possibilities for improving the ratio of image contrast to noise and increasing the momentum resolution of the technique are illustrated.

Animals↗
PubMed1986

Dual-energy Compton scatter tomography.

A dual-energy Compton scatter imaging technique, analogous to that used in computed tomography and conventional radiography, has been explored. It is shown that this technique allows the photoelectric component of the attenuation factors for the primary and scattered radiations to be derived. Compton scatter images of the ear, corrected for photo-attenuation using dual energy, have been obtained with a novel Compton scatter scanner (Comscan) and are presented here. In addition, dual-energy Compton scatter imaging allows photo-effect slice images to be obtained which are a useful extension to the customary Compton images. The application of dual-energy Compton scatter to imaging bony structures and densitometry is illustrated.

Humans↗
PubMed1985

Coherent scatter in radiographic imaging: a Monte Carlo simulation study.

The significance of coherently scattered radiation in radiographic imaging is investigated using the Monte Carlo simulation technique. Recent data on the form factor of liquid water, which take into account intermolecular interference effects, have been used for the calculation of the coherent differential cross section. The spatial distribution of scattered radiation in the detection plane was calculated separately for coherent and incoherent single and multiple scattering. In the pencil beam geometry, it is found that coherent scattering leaving the object, is almost exclusively single scattering, is concentrated near but not exactly at the transmitted primary beam and dominates over multiple incoherent scattering in this region even for thick objects and polyenergetic radiation. Some consequences concerning the performance of grids, the choice of phantom materials and a new imaging method are given.

Humans↗