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Biomedical subjects

D J Mason

Publications and source records attributed to D J Mason.

At least 73 records · Page 4Linked to original sources
PubMed1995

The ability of membrane potential dyes and calcafluor white to distinguish between viable and non-viable bacteria.

Various dyes were assessed for their ability to discriminate between viable and non-viable bacteria. Two methods of killing were employed: by heat treatment or by gramicidin treatment. Staining was carried out in two ways; by staining directly in the medium or by washing cells prior to staining in buffer. Carbocyanine and rhodamine 123 dyes only exhibited small changes in fluorescence between viable and non-viable populations of bacteria. Both oxonol dye (bis 1,3-dibutylbarbituric acid trimethine oxonol) and calcafluor white proved much more useful.

Bacterial Physiological Phenomena↗
PubMed1995

Antibacterial action of ciprofloxacin.

The mechanisms by which quinolones rapidly kill are ill defined. We have investigated the action of ciprofloxacin on Escherichia coli KL16 with a combination of traditional and flow cytometric methods and have analyzed cells for changes in membrane potential, membrane integrity, oxidative metabolism, morphology, and viability. Log-phase cultures were exposed to various concentrations (0.1, 1, 10, and 100 times the MIC) of ciprofloxacin and analyzed at regular intervals over 120 min. We also measured protein synthesis in the related strain PQ37 cultured under the same conditions over 300 min, using a colorimetric assay for beta-galactosidase release. Despite a 3-log order decrease in CFU after 60-min exposure to 10 and 100 times the MIC of ciprofloxacin, there was no equivalent decrease in bacterial numbers as determined by both light microscopy and flow cytometry. Furthermore, while these bacteria showed concentration-dependent morphological changes, most were capable not only of excluding the fluorescent nucleic acid-binding dye propidium iodide, but also of reducing the tetrazolium dye cyanoditodyl tetrazolium chloride. Over 90% of the bacteria maintained a membrane potential [as determined by exclusion of bis-[1,3-dibutylbarbituric acid) trimethine oxonol] when exposed to ciprofloxacin for 120 min, except at 100 times the MIC, when this figure fell to < 10%. Finally, protein synthesis was either maintained or induced at all concentrations of ciprofloxacin up to 5 h postexposure. Taken together, these results demonstrate the continuing physical and metabolic survival of ciprofloxacin-exposed bacteria; we suggest parallels with the concept of the viable nonculturable state.

Anti-Infective Agents↗
PubMed1995

Pilot studies in clinical nursing research.

As clinical nursing research gains prominence in the profession, the need for, and advantages of, pilot studies are increasing. This article describes the purposes of pilot studies, the potential positive and negative outcomes of these studies, and three examples of pilot studies with different outcomes. The emphasis is on issues related to clinical nursing research, particularly research done in acute care settings.

Clinical Nursing Research↗
PubMed1994

Rapid estimation of bacterial antibiotic susceptibility with flow cytometry.

Bacterial antibiotic susceptibility was rapidly estimated for Escherichia coli and Staphylococcus spp. by flow cytometry. This was achieved by measuring the uptake of a negatively charged membrane potential sensitive dye bis-(1,3-dibutyl-barbituric acid) trimethine oxonol and observing changes in low-angle light scatter (excitation light scattered by up to 15 degrees). Estimations of ampicillin, gentamicin and ciprofloxacin susceptibilities were possible within 2-5 h from a plate culture, depending on the species and antibiotic used. This includes the time necessary to establish steady-state growth in liquid culture.

Anti-Bacterial Agents↗
PubMed1994

Absorbed dose perturbation caused by diodes for small field photon dosimetry.

Uncertainties in dose measurements which may be considered acceptable for standard radiotherapy techniques may not be acceptable for radiosurgery or other precision radiotherapy techniques. One example of this type of uncertainty are the small perturbations to measured dose distributions which are caused by the use of diode detectors. In this article the effect of using diodes to measure small field penumbra is assessed and comments are made about diode orientation and diode construction.

Biophysical Phenomena↗
PubMed1994

Comminuted fractures of the posterior wall of the acetabulum. A biomechanical evaluation of fixation methods.

Reproducible simple fractures and osteotomies of the posterior wall of the acetabulum were created in twenty paired hemipelves from fresh human cadavera. Comminution was created with an additional fracture line that was either parallel (concentric comminution) or perpendicular (transverse comminution) to the posterior rim of the acetabulum. Under simulated weight-bearing, the stiffness of fixation of the transversely comminuted fractures that had been achieved with use of a reconstruction plate and screws was significantly higher than that achieved with fixation with screws alone (p < 0.05). The load to failure of the fixation of transversely comminuted fractures treated with a reconstruction plate and screws was also significantly higher than that of fixation of such fractures with screws alone (p = 0.05). The load to failure of the fixation of concentrically comminuted fractures was significantly higher when a reconstruction plate and accessory spring plates had been used than when a reconstruction plate alone had been employed (p < 0.05).

Acetabulum↗
PubMed1994

Perspectives on activity.

Activity is integral to human health, well-being, development, and functioning. Despite its importance to health, there have been few efforts to develop conceptual definitions of activity as a basis for nursing research in this area. The purposes of this paper are to review the major attributes of physical activity found in the nursing and health care literature, to formulate a comprehensive definition of activity based on the literature, and to suggest directions for future research.

Energy Metabolism↗
PubMed1993

An inexpensive infrared growth sensor array for detection of bacterial antibiotic susceptibility.

An inexpensive infrared sensor was constructed and used for the rapid testing of bacterial antibiotic susceptibility by detection of changes in absorbance at 950 nm. By comparing cultures of clinical isolates together with control strains (Escherichia coli NCTC 10418, Staphylococcus aureus NCTC 6571 or Pseudomonas aeruginosa NCTC 10662) after addition of an antibiotic, results on susceptibility were obtained within 3-5 h from the original plate culture. Representative strains of E. coli, P. aeruginosa, and S. aureus were tested successfully against ampicillin, penicillin, gentamicin or ciprofloxacin.

Ampicillin↗
PubMed1993

Health, income, and postretirement employment of older adults.

After a poor response to advertisements for employment for older adults, a community health nursing agency surveyed 216 individuals ranging in age from 60 to 96 years to examine their attitudes toward postretirement work, perceptions of barriers to and facilitators of employment, and the influence of perceived health status and income on these factors related to labor force participation. The findings are consistent with continuity theory of aging, and underscore the need for public policies aimed at supporting the decision of older persons to work or retire.

Aged↗
PubMed1992

Promoting the community health clinical nurse specialist.

The role of the community health nurse clinical specialist (CHNCS) has been clearly delineated by the profession as having a responsibility to the community as client. The need for this specialist has escalated as communities try to address health problems that are preventable and overwhelming their resources. Yet, a survey conducted in New Jersey and counsel from the Rutgers College of Nursing Community Health Nursing Advisory Committee suggest that nurses and agencies may not be aware of the role of the CHNCS and how to use this advanced practitioner most effectively. This article discusses the role of the CHNCS as described by the American Nurses' Association, the need for the CHNCS, a survey of the perceived need for Master's-prepared community health nurses, the role of a CHNCS in a New Jersey community health nursing agency (MCOSS, Inc.), and recommendations for promoting the role of the CHNCS.

Community Health Nursing↗
PubMed1992

Bovine platelets retain functional activity in the presence of penicillin G.

It has been reported that antibiotics of the penicillin family impair the functional response of human, canine and lapine platelets to a broad range of agonists. In contrast, we have shown that the bovine platelet retained full functional responses to stimulation by adenosine diphosphate (ADP) or platelet activating factor (PAF) following administration of penicillin G to clinically normal cattle at 20,000 IU/kg for three days. The aggregation response to collagen was transiently reduced to approximately 50% of pretreatment values, but only while the drug was detectable in the circulation. When penicillin was added to platelet rich plasma suspensions, ADP-induced aggregation was similar to that of the control untreated platelets, while the PAF-induced aggregation response was reduced by not more than 25%. Only collagen-induced aggregation exhibited a modest dose-dependent inhibitory response in the presence of penicillin. It is postulated that the relative insensitivity of the bovine platelet to penicillin may be related to differences in postreceptor biochemical events compared to the human platelet.

Animals↗