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Biomedical subjects

D G Brown

Publications and source records attributed to D G Brown.

141 records · Page 8Linked to original sources
PubMedDate not supplied

Criteria that optimize the potential of murine embryonic stem cells for in vitro and in vivo developmental studies.

Cultured mouse embryonic stem (ES) cells are used for both in vitro and in vivo studies. The uncommitted pluripotent cells provide a model system with which to study cellular differentiation and development; they can also be used as vectors to carry specific mutations into the mouse genome by homologous recombination. To ensure successful integration into the germ line, competent totipotent diploid ES cell lines are selected using a cell injection bioassay that is both time consuming and technically demanding. The prolonged in vitro culture of rapidly dividing ES cells can lead to accumulated changes and chromosomal abnormalities that will compromise the biological function and abrogate germ line transmission of chimeric mice carrying novel genetic mutations. Such in vitro conditions will vary between individual laboratories; for example, differences in the serums used for maintenance. Using a number of different criteria we attempt in this paper to define the parameters that we found to be key factors for optimization of the biological potential of established ES cell lines. The successful integration into the germ line is dependant on acquiring or deriving a competent totipotent mouse ES diploid cell line. In this paper parameters and criteria are defined which we found to be key factors for the optimization of the biological potential of established ES cell lines.

Animals↗
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Behavior modification.

Explore the source record for details and available documents.

Behavior Therapy↗
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Application of information theory to the assessment of computed tomography.

The imaging process has two fundamental stages: detection and display. The detection stage can be quantified rigourously using Shannon's information theory. This requires the contrast scale (CS), modulation transfer function (MTF), and noise power spectrum [N(f)] to be combined into a signal-to-noise ratio (SNR). This results in two fundamental summary figures of merit: the density of noise equivalent quanta (NEQ) in the image and the information bandwidth integral (IBWI). These algorithm-independent measures are used to quantify the recording stage. The display stage is less well understood since it couples to an external observer. Several types of decision makers are treated. Examples are drawn from first and second generation CT, demonstrating that thye are nearly quantum limited for large signals, indicating how their algorithms are matched or mismatched to the geometry, and calculating the contrast-detail diagrams for those decision makers.

Data Display↗
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Potential exposure to metal fumes, particulates, and organic vapors during radiotherapy shielding block fabrication.

The shielding-block fabrication areas of three hospitals were surveyed to assess inhalation exposure to lead (Pb), cadmium (Cd), bismuth (Bi), and tin (Sn) fumes, as well as styrene and methyl chloride vapors. Area and personal breathing zone samples were collected for various steps in the block fabrication process. Only 3 of 16 air samples for metals resulted in detectable levels of Pb and/or Cd. The levels were well below the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits, excluding a sample which contained a visible metal fragment. Bi and Sn were not detected in any samples. Methyl chloride and styrene vapors were not detected in any air samples during foam cutting procedures. Total particulates (TP) were measurable in 11 of 17 air samples (ranging from 0.01 to 2.1 mg/m3). TP values were below the OSHA federal standard for nuisance particulates, which is 15 mg/m3. The data suggest that the materials and procedures sampled do not present an inhalation hazard to employees who construct shielding blocks. Precautions should, however, be exercised to prevent exposure under extreme procedural conditions such as soldering or overheating of alloy, and by other means such as ingestion. Care should also be taken during cleanup or housekeeping to prevent re-entrainment into the work atmosphere of mechanically generated metal particles or materials condensed within melting pots (which may be high in metal content).

Air Pollutants, Occupational↗
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Exercise and arthritis.

Recreational exercise has achieved great popularity. Possible benefits to participants are increased longevity, decreased risk of cardiovascular disease, improved psychological well-being, and greater fitness. A very important but as yet unanswered concern is whether regular exercise will lead to degenerative joint disease or osteoarthritis. Many factors (e.g. physical characteristics of participants, biomechanical and physical features, nature of the playing surface and sport, manner of participation, preventive measures, and certain medical considerations) might influence the risk of developing osteoarthritis from sports participation. However, none of these have been evaluated. Although studies with animals have identified situations in which articular cartilage degeneration may be accelerated, experimental observations have not found normal joint motion in exercising animals to be harmful to joints. Anecdotal observations in man have suggested relationships between recreational activities and degenerative joint disease. However, those few controlled studies reported indicate that exercise need not be deleterious to joints. We interpret available data as suggesting that reasonable recreational exercise, carried out within limits of comfort, putting joints through normal motions, without underlying joint abnormality, even over many years, need not inevitably lead to joint injury.

Adult↗
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Health care rationing.

The following two-part article sets the scene for an ongoing dialogue in future Updates on rationing and its impact on our health care delivery system and on society at large. Part one establishes the framework for future discussions, while Part two zeros in on the efforts of one state to confront the issue head-on.

Catastrophic Illness↗
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The hospital vacuum cleaner: mechanism for redistributing microbial contaminants.

Carpeting patient care units in acute care hospitals is increasingly common. While the safety of carpeting has been heavily debated, there has been little epidemiological data to document risk to the hospitalized patient. With the report of a two-year study documenting human contamination and potential colonization by microorganisms spread from hospital carpeting, a need was established to document modes of transmission. The objective of this study was to define the potential of hospital vacuums for dispersing particles of a size comparable to the microbial cell. Both filter efficiency and vacuum exhaust turbulence are evaluated. Results document that of eight units claiming high efficiency filtration, none was capable of meeting advertising claims. In addition, exhaust air velocities for one unit reached 175 feet per minute at 30 inches above the floor.

Air Microbiology↗
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Environmental health and safety concerns in the health care setting.

Increasing attention to the physical, chemical, and biological aspects of the health care environment is evidenced by the actions of consumer groups, as well as state and federal regulatory bodies, and private accreditation and insurance agencies. This paper reviews the major areas of environmental concern within the health care industry and encourages active participation by environmental health professionals in evaluating environmental risk and impacting positive change.

Accident Prevention↗
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Environmental health and safety at the University of Michigan medical campus.

The Nation's acute care hospitals represent a significant source of employment. Like other communities, most traditional environmental concerns require attention, but because of the unique combination of an evolving and increasingly complex technology with an at-risk resident population, special environmental services are also required. Recognizing these facts, various agencies with the responsibility of overseeing the health and safety of the total population have developed rigorous standards to assure the safety of hospital employees, patients and visitors. There is need for improved organization of environmental services to reduce the inefficiencies so often present where responsibilities for environmental management are fragmented. The University of Michigan Hospital organizational system illustrates an attempt to comprehensively address environmental health issues, including the management of regulatory liaison functions.

Academic Medical Centers↗