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Biomedical subjects

D Marshall

Publications and source records attributed to D Marshall.

At least 91 records · Page 5Linked to original sources
PubMed1995

Monotherapy for fever and neutropenia in cancer patients: a randomized comparison of ceftazidime versus imipenem.

PURPOSE: To compare the efficacy of ceftazidime and imipenem monotherapy for fever and neutropenia, and to determine whether fewer antimicrobial modifications (additions or changes) are required by the broader-spectrum agent, imipenem. PATIENTS AND METHODS: Adult and pediatric patients undergoing chemotherapy for solid tumors, leukemias, or lymphomas were randomized to receive open-label ceftazidime or imipenem on presentation with fever and neutropenia. Success with or without modifications of the initial antibiotic was defined as survival through neutropenia; failure was death due to infection. Comparisons were based on numbers of modifications made to each monotherapy during the course of neutropenia, in patients stratified as having unexplained fever or a documented infection. RESULTS: Among 204 ceftazidime and 195 imipenem recipients, the overall success rate with or without modification was more than 98%, regardless of initial antibiotic regimen. Modifications occurred in half of all episodes, primarily in patients with documented infections on either monotherapy. Antianaerobic agents were more frequently added to ceftazidime (P < .001), but addition of other antibiotics, including vancomycin and aminoglycosides, was similar between the two monotherapy groups. Imipenem therapy was associated with significantly greater toxicity, manifested by Clostridium difficile-associated diarrhea and by nausea and vomiting, which required discontinuation of imipenem in 10% of recipients. CONCLUSION: Ceftazidime and imipenem are both effective in the management of fever and chemotherapy-related neutropenia, provided that modifications are made in response to clinical and microbiologic data that emerge during the course of neutropenia. Imipenem, despite its broader antimicrobial spectrum, does not significantly decrease the overall need for antibiotic modifications and is more often complicated by gastrointestinal toxicity.

Acyclovir↗
PubMed1994

The impact of laparoscopic cholecystectomy in Canada and Australia.

The introduction of laparoscopic cholecystectomy in Canada and Australia has been associated in each country with an increase in the rates of all cholecystectomies following a period where these had remained constant. Estimated costs of cholecystectomies to health programs declined by about 13% in Canada after the laparoscopic procedure became widely available, and about 2% in Australia. Days lost to patients because of surgery, and associated costs to them, decreased in each country. Neither country is realising the potential savings through use of laparoscopic cholecystectomy because of the increase in the number of procedures. The utility of these additional operations remains unclear. These trends associated with the advent of laparoscopic cholecystectomy suggest the need for caution in the introduction and application of other minimal-access surgery techniques.

Australia↗
PubMed1994

Diffusion of laparoscopic cholecystectomy in Canada.

Patterns of the diffusion of laparoscopic cholecystectomy in Canadian hospitals were determined by a telephone survey of 153 randomly selected hospitals over two years. Results were analyzed by region, hospital size, and type of hospital. Laparoscopic cholecystectomy has diffused very quickly compared with other technologies, before any comprehensive evaluation to consider its potential impact could take place.

Canada↗
PubMed1994

Clearance of circulating radio-antibodies using streptavidin or second antibodies in a xenograft model.

The improved tumour to non-tumour ratios needed for effective tumour targeting with antibodies requires that blood background radioactivity is reduced. We investigated the effect of streptavidin as a clearing agent for 125I-labelled biotinylated anti-CEA antibodies in a human colon carcinoma xenograft model. By comparing the biodistribution of the monoclonal antibody A5B7 with four, nine or 22 biotins per antibody molecule, we investigated how the degree of biotinylation of the primary radiolabelled antibody affects its clearance with streptavidin. Limiting the degree of biotinylation limited blood clearance, whereas nine or 22 biotins per antibody molecule resulted in a 13- to 14-fold reduction in blood radioactivity, the streptavidin-biotinylated antibody complexes clearing rapidly via the liver and spleen. Although a reduction in tumour activity was also seen, a 6.6-fold improvement in the tumour to blood ratio was achieved. A comparative study of streptavidin versus second antibody clearance was carried out using the polyclonal antibody PK4S biotinylated with 12 biotins per antibody molecule. This study indicated that second antibody was superior for clearance of the polyclonal antibody, resulting in a larger and faster reduction in blood radioactivity and improved tumour to blood ratios. In this case the primary antibody was polyclonal, and therefore non-uniformity of biotinylation may affect complexation with streptavidin. Therefore, the degree of biotinylation and type of antibody must be carefully considered before the use of streptavidin clearance.

Animals↗
PubMed1994

Investigation of touch-sensitive responses by hyphae of the human pathogenic fungus Candida albicans.

Candida albicans is a fungus that commonly infects the mucosal surface of humans. The hyphal growth form of this fungus may initiate the primary invasion of the host. Here we show that hyphae respond thigmotropically and morphologically to cues such as the presence of a surface, pores, grooves and ridges. Growth on some firm surfaces elicits a helical growth response. Hyphae follow grooves and ridges of inert substrates and penetrate pores of filtration membranes. Our in vitro experiments suggest that thigmotropism may enhance the ability of a hypha to invade epithelia of a host at sites of weakened integrity.

Candida albicans↗
PubMed1994

Magnetic field strength issues in magnetic resonance imaging.

The authors review the current status of magnetic resonance imaging (MRI) with respect to magnetic field strength. The discussion covers the practical aspects of MRI--safety, throughput and costs--as well as the clinical aspects as they are influenced by field strength. Data on the world distribution of MRI units of various field strengths are presented. Canada had the highest proportion of high-field units among the 11 countries or regions included in this comparison, probably because most Canadian MRI units are located in teaching hospitals, where they are used for both research and clinical work.

Costs and Cost Analysis↗
PubMed1993

Carbachol and naloxone synergistically elevate dopamine release in rat striatum: an in vivo microdialysis study.

Striatal dopamine (DA) release increased to 184% of baseline after 10-20 min of continuous intrastriatal perfusion with 10 mM carbachol, dropping to 124% after 30-40 min. The addition of 100 microM naloxone amplified (to 236% of baseline) and prolonged the increase in DA release, but naloxone alone (up to 1 mM) had no effect. These data suggest that activation of opiate-releasing striatal neurons suppresses cholinergic stimulation of DA release.

Animals↗
PubMed1993

Investigation of cell envelope damage to Pseudomonas aeruginosa and Enterobacter cloacae by dibromopropamidine isethionate.

Electron micrographs of log-phase Pseudomonas aeruginosa and Enterobacter cloacae cultured for 4 h in the presence of subinhibitory concentrations of dibromopropamidine isethionate indicate that this antibacterial agent can cause marked damage to the cell envelope structures of both species. This result provides an explanation of how dibromopropamidine can enhance the uptake and thus the activity of a second antibacterial agent used in combination with it.

Anti-Bacterial Agents↗
PubMed1993

Human immunodeficiency virus (HIV) type 1 strain MN neutralizing antibody in HIV-infected children: correlation with clinical status and prognostic value.

Protective immunity to human immunodeficiency virus (HIV) was examined in 228 serial sera from 58 HIV-infected children before and during antiretroviral therapy. Binding antibodies to putative protective V3 epitopes of HIV-1IIIB and HIV-1MN were investigated by a peptide ELISA, and neutralizing antibodies by inhibition of HIV-1MN cell-free viral infection. No difference in binding of total IgG or IgG subclasses was observed between patients with mild (group A) or advanced disease (group B). However, group A patients were more likely to possess neutralizing antibody titers > or = 225 (P = .040 after adjustment for CD4). This threshold titer also predicted clinical outcome in patients with age-adjusted CD4 count > 10% of normal median. Patients with titers < 225 more frequently encountered major clinical events during follow-up than did patients with titers > or = 225 (P = .0028). Epitopes other than the linear V3 loop contribute to this protective immune response. Identification of these epitopes should assist immune therapy of AIDS and HIV vaccine development.

Adolescent↗
PubMed1993

A noninvasive video-based method for measuring lens transmission properties of the human eye.

The Lens Absorption Monitor (LAM) is an automated video-based system for obtaining rapid objective noninvasive measurements of the spectral transmission properties of the human lens. The technique is based on intensity measurements of the 4th Purkinje image for different wavelengths, and incorporates several features that overcome some of the difficulties associated with previous studies using this approach. LAM transmission measures for the visible spectrum can be obtained in approximately 2 s, and in most instances can be obtained without having to dilate the subject's eye. This paper describes the technique and presents our initial findings for 40 normal observers between the ages of 24 and 77 years. Results of the LAM technique show that it is able to measure the wavelength-dependent properties of the lens accurately and to identify age-related changes in "yellowing" of the lens. Test-retest reliability of the LAM is better than for psychophysical estimates of ocular media transmission. LAM and psychophysical measures in the same subjects were found to be correlated, although LAM measures produced consistently lower values of lens density than the psychophysical determinations. There was only moderate agreement between LAM and psychophysical measures of lens density. Possible explanations for these differences are discussed. Future research will determine whether this technique is able to detect and quantify early cataract development.

Adult↗
PubMed1993

An electronmicroscope study of the effect of sulphadiazine and trimethoprim on Enterobacter cloacae.

Electronmicroscopy of thin sections of log phase cells of Enterobacter cloacae NCTC 10005 grown for 4 h in the presence of sulphadiazine 250 micrograms/ml, trimethoprim 12.5 microliters/ml or the combination of sulphadiazine 250 micrograms/ml plus trimethoprim 12.5 micrograms/ml indicated that both agents caused marked morphological damage even though the MIC of sulphadiazine for the E. cloacae strain was > 3000 micrograms/ml. The damage took the form of electron-transparent areas devoid of ribosomes in the cytoplasm and detachment of the outer membrane. The latter was most marked with trimethoprim, which also caused damage to the cytoplasmic membrane. It is postulated that the synthesis of the peptidoglycan layer was affected by the antimetabolites since the morphological effects were strikingly similar to those caused by treatment of E. cloacae with disodium edetate plus lysozyme. Viable counts of cultures undergoing the same treatments as those prepared for electronmicroscopy indicated that although sulphadiazine merely partially inhibited growth it nevertheless enhanced the bactericidal action of trimethoprim over a 5-h period.

Cell Membrane↗