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Biomedical subjects

G Dickson

Publications and source records attributed to G Dickson.

106 records · Page 6Linked to original sources
PubMed1979

Fit of porcelain fused-to-metal crown and bridge castings.

The dimensional accuracy of porcelain fused to metal crown and bridge castings was determined on truncated cone-shaped steel dies. Ni-Cr castings produced in manufacturers' laboratories were consistently undersize, while precious metal castings were consistently oversize. Ni-Cr castings, produced in NBS laboratories using a modified investing technique, were routinely oversize.

Chromium↗
PubMed1977

Analysis of the ingredients and determination of the residual components of acrylic bone cements.

Rapid and reliable methods for the characterization and quantitative determination of ingredients usually present in self-curing methacrylate bone cements were developed using spectrophotometric, gas chromatographic (GC), and coventional gravimetric procedures. These procedures are applicable to non-crosslinked methacrylate resins. In the presence of some copolymers, polymer blends or crosslinking agents, or other ingredients which will result in the formation of insoluble methacrylate resins, some modification of the identification procedures and quantitative estimation of the resin components will be required. Molecular weight and molecular weight distribution of the powder and cured cement were obtained from viscosity and gel-permeation measurements. Residual low molecular weight materials in the cured cement were determined for various storage times. Residual and water-leachable monomer and residual dimethyl-p-toluidine (DMPT) were measured by GC. In air, The monomer content of the cured resin decreased from 3.3% after 1 hr to 2.4% after 215 days. When stored in water at 37 degrees C, over 65% of the extractable monomer is leached out within 10 min. After 6 hr, the rate of diffusion of monomer into the aqueous phase is low. The cured cement contains as much as 0.6% DMPT, which does not leach out. Residual peroxide, estimated spectrophotometrically, amounts to 0.8%, but decreases to 0.14% after 15 months in water at 37 degrees C. A semiquantitative colorimetric test indicated that the hydroquinone content of specimens analyzed within 24 hr after curing amounted to 9 ppm.

Benzoyl Peroxide↗
PubMed1975

A proposed specification for acrylic bone cement.

A proposed specification covering handling characteristics and physical and chemical properties of bone cement composed primarily of methyl methacrylate has been prepared on the basis of data from the authors' studies and from various other sources. Under handling characteristics, requirements included relate to dough, handling and setting time, proper plasticity for insertion and temperature rise on setting. Mechanical properties specified include compressive strength and indentation and recovery characteristics. Maximum limits are proposed for water sorption and solubility. Suggested packaging requirements are also included.

Bone Cements↗
PubMed1975

A characterization of polymethylmethacrylate bone cement.

Polymethylmethacrylate cement is characterized in terms of chemical composition, handling characteristics, and physical properties; the dough time, setting time, handling time, and temperature rise were found to be most affected by environmental temperature and kneading of the dough mass. As the set material ages, the residual monomer content gradually decreases and the strength increases. A volume shrinkage of up to 5 per cent was observed. The porosity, which is increased by rapid mixing, may reach 10 per cent. The mechanical properties of the cement approximate those of polymethylmethacrylate denture base material. Some variability encountered in the handling qualities of the cement could be attributed only to the variability of different batches.

Barium Sulfate↗
PubMedDate not supplied

Gene therapy in Duchenne muscular dystrophy.

Experiments in dystrophin gene transgenic mice have supported the concept of treating Duchenne muscular dystrophy (DMD) by demonstrating that regional expression of recombinant dystrophin in dystrophic muscle leads to regional restoration of normal muscle morphology and that dystrophin mini-genes driven by muscle specific regulatory elements are probably more effective than the full-length dystrophin gene. As a gene therapy trial for DMD, dystrophin cDNAs were introduced into skeletal muscle fibers of dystrophin-deficient mice (mdx) through direct DNA injection into plasmid expression vectors, and by replication-defective recombinant retrovirus or adenovirus vectors. With direct injection of dystrophin cDNA into a plasmid expression vector or retrovirus vectors, less than 10% of adult mdx fibers of the injected muscle expressed dystrophin. On the other hand, greater efficiency has been reported for recombinant adenovirus injection into young mdx muscle. However, it is necessary to develop vectors, viral or plasmid DNA, which can be injected intravenously and directed to muscle tissues. This will involve designing vectors possessing appropriate cell-type specific tropism and/or gene transcriptional activity for DMD treatment. This is anticipated to be a vital component in the second stage of experiments aimed at DMD treatment.

Animals↗
PubMedDate not supplied

Participatory action research: lessons learned with Aboriginal grandmothers.

Participatory action research is evolving as both a research methodology and an intervention for health promotion. Here we describe its use in conducting a health assessment as part of a larger project for older Aboriginal women (hereafter known as the grandmothers). The overall purpose of the project was to study the women's health needs and respond through health promotion programming. The experience of using participatory action research revealed a number of lessons, including challenges and points of tension, and determinants and indicators of success. The research team identified some implications for consideration by others interested in participatory action research.

Adult↗
PubMedDate not supplied

The establishment of good laboratory practices at the Naval Medical Research Institute Toxicology Detachment.

A quality-management program (QMP) has been launched at the Naval Medical Research Institute Toxicology Detachment to support the planning, assessment, interpreting, and reporting of toxicology study data. The QMP conforms to the intent of the Good Laboratory Practice established by the Food and Drug Administration and the Environmental Protection Agency for regulatory compliance. The biomedical data necessary to characterize the toxicity of materials of interest to the Navy are used to formulate occupational and environmental health-hazard evaluations and risk assessments, including appropriate exposure limits for personnel for Navy-specific circumstances of exposure. The goal of the QMP is to help management and investigators ensure the quality and integrity of the data collected in laboratory animal toxicology studies. These data are used to reduce or eliminate potential health risks from exposure to toxicants during Navy operations. The primary purpose of the risk-reduction program is to help ensure readiness to accomplish the military mission. This article briefly reviews the need for the QMP and the military relevance of the quality-assurance requirements. The pros and cons of establishing the QMP are discussed, and examples of specific research projects and programs that support the need for a quality management program are presented. Aspects of integrating the QMP program to ensure compliance with Good Laboratory Practice are reviewed, and the value of the improvements in the quality of data from the Naval Medical Research Institute/Toxicology Detachment is summarized.

Academies and Institutes↗