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Biomedical subjects

G Harding

Publications and source records attributed to G Harding.

34 records · Page 2Linked to original sources
PubMed1978

Prospective comparison of cefoxitin and cefazolin in infections caused by aerobic bacteria.

Intravenous cefazolin and cefoxitin were compared in a prospective randomized trial in infections where the suspected pathogen was expected to be susceptible to both antibiotics. In the cefazolin group (12 patients) the diagnosis was pneumonia in 4, including 2 with pneumococcal bacteremia, soft tissue infection in 5, Staphylococcus aureus bacteremia in 1, acute pyelonephritis in 1, and disseminated gonococcal infection in 1. In the cefoxitin group (10 patients) the diagnosis was pneumonia in 4, including 2 with pneumococcal bacteremia, soft tissue infection in 4, acute pyelonephritis in 1, and disseminated gonococcal infection in 1. In the cefazolin group receiving an evaluable course of therapy, a good clinical response was seen in 10 of 11 patients, and a bacteriological response was seen in 5 of 7. Cefazolin failed to eradicate S. aureus bacteremia in 1 patient and S. aureus in a skin ulcer of another patient. All 10 cefoxitin patients had good clinical and bacteriological responses, but in 1 patient S. aureus colonization of a postoperative wound recurred after discontinuation of the drug. Side effects in both groups included skin rash, phlebitis, and elevation of the serum alkaline phosphatase. Both cefoxitin and cefazolin appeared effective in infections caused by susceptible aerobic pathogens with the possible exception of S. aureus, although all 11 strains of S. aureus isolated in this study were susceptible in vitro to both antibiotics. Cefoxitin appeared to be equivalent to cefazolin in efficacy and occurrence of side effects.

Adult↗
PubMed1977

Optimum spread functions in linear tomography.

Recent attempts to reduce artefacts in tomographic blurring, using a transfer function approach, have so far taken little explicit account of the lessening in the degree of blurring which accompanies transfer function correction. A simple comparative measure R of the blurring effect of a linear tomographic movement is proposed. The parameter R is related to the ratio of the area of the point spread function (PSF) to its peak height. It is shown that the PSF having the greatest value of R (maximum blurring), whilst having an entirely positive transform, is of triangular form. Conversely, any PSF for which the value of R exceeds Rtriangle is inevitably associated with phase reversals. The problem of finding the PSF with R greater than Rtriangle, which leads to the minimum degree of phase reversal, has been tackled by determining the transfer function which, for the given value of R, has the minimum area under its subsidiary maxima. Transfer functions optimized in this way, and their corresponding PSFS, are calculated for four values of R using the method described by Jacquinot and Roizen-Dossier. The results of this procedure are discussed and its possible extensions noted.

Technology, Radiologic↗
PubMed1976

Blurring quality in spiral tomography.

In view of the close relationship which exists between image aberrations and the form of the transfer function, the transfer functions of some different types of spiral tomographic movements have been calculated numerically. The results allow prediction of a type of spiral movement which yields blurring of favourable quality. The validity of this approach has been demonstrated experimentally, by comparing the blurring characteristics of tomographs with single and multiple circular movements. When the radii of the circles in the latter case are chosen with reference to the form of the transfer function, a marked improvement in blurring quality is apparent.

Mathematics↗
PubMed1974

Microculture plaque neutralization test for California group arboviruses.

A microculture plaque neutralization test is described for California-group arboviruses that is as precise and quantitative as the standard test conducted in 60-mm petri dishes. It was shown that there was no significant between-panel or between-day variation in determinations and that a single pipette could be used for all serum-dilution levels within a titration without inoculum carry-over effect. The experimental protocol and statistical methods used produce 50% neutralization end points that meet the assumptions of parametric statistics. This permits the power and versatility of the analysis of variance to be exploited in testing for treatment effects in serological and immunological studies with viruses.

Analysis of Variance↗
PubMed1971

A co-operative evaluation of test systems used to assay tuberculosis vaccines.

The results of research on the immunogenicity of experimental mycobacterial vaccines are characterized by a remarkable lack of agreement about which substances are most immunogenic. The disagreement has usually been attributed to the differences in the methods of preparing the vaccines. An alternative hypothesis is that the conflicting results are a product of the different methods used to assess the potency of the vaccines.To determine if the method by which a vaccine is tested is a major factor contributing to the disagreement, an experiment was conducted in which a series of five different vaccines was distributed to each of nine participating laboratories. Each investigator evaluated the potency of the vaccines in one or more animal models of his own choosing. This in effect held the method of vaccine preparation constant while permitting all other variables to change.The ranking of the five vaccines was random, thus demonstrating that the method by which a vaccine is tested influences the apparent potency of a vaccine. These results cast doubt on the conclusions about the relative potency of tuberculosis vaccines evaluated by different methods.

Animals↗
PubMedDate not supplied

Dialysate contamination and back filtration may limit the use of high-flux dialysis membranes.

Endotoxins, or fragments thereof, can reach the blood stream of dialysis patients, transported by diffusion and connection across the intact high-flux membrane. This transfer depends upon the phenomenon of back filtration. Back filtration generally occurs under conventional high-flux dialysis conditions with membranes having an ultrafiltration coefficient in blood (UF-C) above 20 ml/hr/m2/mmHg. The clinical consequences of back filtration vary from center to center depending primarily on the quality of dialysate. We therefore surveyed the bacterial and endotoxin levels of purified water and effluent dialysate in a cross section of dialysis centers in the central United States. Using a high recovery medium, we found that 53% of the centers had bacterial counts above the Association for the Advancement of Medical Instruments standard in water (20% cfu/ml) and 35% above the standard in dialysate (2,100 cfu/ml). Endotoxin concentrations higher than 5.0 EU/ml in both water and dialysate were found in 4% and 11.8% of the centers, respectively. Since high-flux membranes are believed to be of benefit for long-term dialysis patients, manufacturers will have to offer dialysate preparation systems with additional safety features. The proper membrane design will be a key to the success of such systems.

Colony Count, Microbial↗
PubMedDate not supplied

Risk factors associated with echovirus 11' infection in a hospital nursery.

An outbreak of nosocomial echovirus 11' illness occurred between July 22 and August 12, 1983, infecting 14 infants in the nurseries at a hospital. Stool, throat or cerebrospinal fluid specimens for viral isolation were obtained from 142 and serum pairs from 98 of the 192 infants exposed to the nurseries during the outbreak. Infection was determined by isolation of virus from stool or cerebrospinal fluid and/or a 4-fold rise in neutralizing antibody to echovirus 11'. Eight infants were severely ill with seizures, pleocytosis or apnea; one infant died. Four infants were mildly ill; two were asymptomatic. Immune serum globulin, administered to all hospitalized infants on July 31, did not appear to attenuate echovirus 11' illness. Infants present in the Intermediate Care Unit greater than 48 hours were more likely to become infected than infants present less than or equal to 48 hours (attack rates, 25 and 3%, respectively). Among infants present in the Intermediate Care Unit, illness was associated with gavage feeding, mouth care and being a twin (P less than 0.05). These findings support the importance of good hygienic practices in preventing nosocomial viral infections.

Antibodies, Viral↗
PubMedDate not supplied

Towards optimum blurring in spiral tomography.

Attempts to increase the degree of blurring of nonfocused layers in tomography are inevitably associated with a worsening in the amount of artefactual detail introduced. A mathematical optimization technique has been employed to indicate how these conflicting characteristics may best be reconciled. The technique uses plausible definitions, based on the transfer function, of the effectiveness and the fidelity of the blurring, and generates a sequence of spread functions in which these two aspects are optimally combined.

Mathematics↗
PubMedDate not supplied

X-ray diffraction computed tomography.

Coherent scattering of x-ray photons leads to the phenomenon of x-ray diffraction, which is widely used for determining atomic structure in materials science. A technique [x-ray diffraction computed tomography (CT)] is described, analogous to conventional CT, in which the x-ray diffraction properties of a stack of two-dimensional object sections may be imaged. The technique has been investigated using a first generation (single pencil beam) CT scanner to measure small angle coherent scatter, in addition to the customary transmitted radiation. Diffraction data from a standard CT performance phantom obtained with this new technique and with an x-ray diffractometer are compared. The agreement is satisfactory bearing in mind the poor momentum resolution of our apparatus. The dose and sensitivity of x-ray diffraction CT are compared with those of conventional transmission CT. Diffraction patterns of some biological tissues and plastics presented in a companion paper indicate the potential of x-ray diffraction CT for tissue discrimination and material characterization. Finally, possibilities for refinement of the technique by improving the momentum resolution are discussed.

Computers↗
PubMedDate not supplied

X-ray diffraction measurements of some plastic materials and body tissues.

X-ray diffraction allows the investigation of the atomic or molecular structure of materials. The combination of diffractometry with computerized tomography enables spatially resolved imaging of the diffraction properties of extended objects as described in more detail in a companion article [Harding et al., Med. Phys. 14, 515 (1987)]. We present measured diffraction patterns of some plastics and several biological materials, which allow further optimization of our method and the selection of suitable application areas.

Humans↗