Search PubMed⌕ Search

Biomedical subjects

B L Johnson

Publications and source records attributed to B L Johnson.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Postural epigastric pain: a unique symptom of primary cytomegalovirus gastritis?

Cytomegalovirus (CMV) gastritis has been reported in transplant patients. Symptoms are considered nonspecific, and gastroscopy with biopsy is usually performed to establish the diagnosis. Three patients are described here 1 to 3 months after solid organ transplantation, with primary CMV gastritis, confirmed by gastroscopy, histopathologic examination and cultures. The clinical presentation in all three cases was sharp epigastric pain that decreased in a supine position, increased while sitting and further increased when standing or walking. The epigastric pain completely resolved after treatment with ganciclovir. To the best of our knowledge, such postural epigastric pain has not been described as a specific symptom in any other clinical entity and may be a unique sign of primary CMV gastritis.

Adolescent↗
PubMedDate not supplied

Neurobehavioral testing and hazardous chemical sites.

The Agency for Toxic Substances and Disease Registry (ATSDR) has focused its health assessment efforts on seven priority health conditions, including neurotoxic disorders, and has begun to select tests and associated measurement tools that can detect those health effects. The evaluation of community-level exposures has introduced new challenges beyond the earlier testing models based on occupational exposures. Community populations are far more diverse than those found in workplace settings, including children, elderly persons, and the infirm, and the neurotoxic agents present at most hazardous waste sites usually are incompletely characterized and commonly are found in complex mixtures. This article describes the background to the four following articles reporting on a 3-day national workshop convened to assist ATSDR in developing standardized neurobehavioral test batteries for studies of adverse health outcomes in communities.

Behavior↗
PubMedDate not supplied

Public health implications of hazardous waste sites: findings, assessment and research.

In this paper we present an overview of the chemicals released from hazardous waste sites (HWS) and some of the mixtures of substances that have been released into environmental media. We describe how this information can be used to assess the public health hazard of releases of chemical mixtures from waste sites. Wherever possible, research on chemical mixtures should use chemical mixtures actually identified in, or representative of, mixtures in environmental media. A narrative, weight-of-evidence approach to characterize the toxicity of mixtures that incorporates mechanistic insights on chemical interactions is described. The utility of this information in the context of risk analysis and public health practice is discussed.

Animals↗
PubMedDate not supplied

Feasibility of obtaining pulmonary venous flow velocity in cardiac patients using transthoracic pulsed wave Doppler technique.

The purpose of this study was to determine, in an adult population, the percentage of patients in whom high quality pulmonary venous flow velocity recordings can be obtained using current transthoracic pulsed wave Doppler techniques. Pulmonary venous and mitral flow velocity variables obtained with a pulsed wave Doppler method were used for the indirect assessment of left ventricular (LV) diastolic function and LV filling pressures. The general clinical use of these methods, however, remains uncertain because the transthoracic success rate of obtaining all components of pulmonary venous flow velocity has been variable, and sometimes reported to be as low as 30% to 60%. Mitral and pulmonary venous flow velocity variables were obtained using pulsed wave Doppler signals in 200 consecutive adult patients (mean age 68.2 +/- 11.4 years) in normal sinus rhythm who were referred for echocardiographic study. Six cardiac sonographers and five ultrasound systems were used. The success rate for obtaining pulmonary venous systolic and diastolic flow velocity was 95%, reverse flow velocity at atrial contraction was 90%, and the duration of reverse flow at atrial contraction was 89%. In the 5% to 11% of patients in whom pulmonary flow velocities could not be adequately recorded, the most common reasons were depth limitations of the pulsed wave Doppler machine, marked cardiac enlargement, or left atrial wall motion artifact. The success rate also was influenced by the ultrasound equipment used, individual variation among sonographers, and even the type (impaired, pseudonormal, restricted) of associated mitral filling pattern. Given current machine technology, sonographer education, and daily practice, high quality, complete recordings of pulmonary venous flow velocity can be obtained in approximately 90% of adult patients using the precordial transthoracic Doppler technique. These results suggest that using these variables as an aid for evaluating LV diastolic function and filling pressures may have broader clinical applicability than previously appreciated.

Adult↗
PubMedDate not supplied

Cancer policy framework for: public health assessment of carcinogens in the environment.

Cancer remains at the forefront of public health concerns in the United States and throughout the world. Over the past 20 years a wide range of federal agencies and other organizations have been involved in developing policy statements, classification strategies, and assessment methods to address carcinogenesis and health risks. Each of these documents was developed in response to issues confronted by those organizations in pursuing their mission, often as a direct function of legislative mandates. In pursuing its mandated responsibilities, the Agency for Toxic Substances and Disease Registry (ATSDR) must address public health concerns associated with exposure to carcinogens in the context of all available relevant information. This information includes both technical data as well as science policy positions adopted by the range of organizations with programs germane to the assessment and/or regulation of carcinogens. Because of distinct differences in perspective, practice, and policy dictated by the mandated activities of these organizations and the rapidly evolving understanding of carcinogenesis, apparently divergent positions may be reflected in their conclusions. The differences outlined above, coupled with requests from the public, other agencies, and the private sector for a statement reflecting the Agency's position on science and science policy issues related to cancer, prompted the development of this policy. This document is intended to serve as a framework to guide the Agency in its programs and actions regarding carcinogens and to harmonize such efforts with those of other federal agencies and relevant organizations. This framework reflects an assessment of current practice within the Agency and defines the appropriate roles of conclusions derived by other groups, professional judgment, and emerging scientific principles in ATSDR's public health assessments of exposures to carcinogens. This Cancer Policy Framework is not intended to encompass the development of operational guidelines per se, although the Agency recognizes the utility of such efforts. A central theme of this Cancer Policy Framework is the use of risk analysis as an organizing construct based on sound biomedical and other scientific judgment to define plausible exposure ranges of concern rather than single numerical conclusions that may convey an artificial sense of precision. The development and use of innovative tools for exposure and dose response assessment (with particular emphasis on molecular epidemiology) are also endorsed.

Carcinogens, Environmental↗
PubMedDate not supplied

"Environmental justice": the central role of research in establishing a credible scientific foundation for informed decision making.

Although much of the evidence is anecdotal and circumstantial, there are mounting concerns that environmental health risks are borne disproportionately by members of the population who are poor and nonwhite. We examine the central role of environmental health research in defining the dimensions of the problem, understanding its causes, and identifying solutions. Environmental health sciences, including epidemiology, exposure analysis. pharmacokinetics, toxicology, and surveillance monitoring, must be employed to determine the extent to which society has achieved "equity" and "justice" in safeguarding the health and safety of its citizens. By improving our ability to identify, evaluate, prevent, and/or reduce risks for all members of society, environmental health research can contribute directly to fair and equitable protection for everyone, regardless of age, ethnicity, gender, race, or socioeconomic status.

Decision Making↗
PubMedDate not supplied

Strategic elements of ATSDR's Great Lakes Human Health Effects Research Program.

The goal of the Agency for Toxic Substances and Disease Registry's (ATSDR) Great Lakes Human Health Effects Research Program is to identify at-risk populations and to prevent potential human health effects associated with exposure to chemical contaminants in the Great Lakes basin. While this research effort is mandated by the Great Lakes Critical Programs Act of 1990, it also represents a significant opportunity to define a broader model or strategy for other regional or systems-level studies of potential health effects in at-risk populations. This article describes the strategy developed by ATSDR for this purpose in the Great Lakes Basin, as well as the program's specific research objectives and current status. It also outlines the projected implications of this research effort for greater comprehension of the potential health effects of exposure to contaminants in the Great Lakes Basin.

Body Burden↗
PubMedDate not supplied

Neurophysiological and neuropathological evaluation of primates exposed to ethylene oxide and propylene oxide.

Over 500,000 workers in the United States are exposed to ethylene oxide and propylene oxide. These two solvents are used as chemical intermediates, as well as components in the manufacture of fumigants and food preparation. The neurophysiologic and neuropathologic effects of these two organic oxides were investigated in five groups of 12 primates after exposure to 50 or 100 ppm ethylene oxide, 100 or 300 ppm propylene oxide, or no chemical (sham-exposed). Animals were exposed for 7 h/day, 5 days/wk for 24 months. Body weights, electroencephalograms, and motor nerve conduction velocities of the sciatic and ulnar nerves were assessed six times throughout the exposure period. Although the monkeys exposed to 100 ppm ethylene oxide had significantly lower mean weights, nerve conduction velocities did not differ significantly among the groups. Following termination of exposures, ten animals (two from each exposure group) were sacrificed for neuropathological examinations. Multiple axonal bodies were found in the nucleus gracilis in seven of eight oxide-exposed animals, and demyelination was found in two monkeys exposed to ethylene oxide. In contrast, a single axonal body was found in one of the two sham-control monkeys. However, the lack of a dose-response relationship suggests that this effect may not be related to oxide exposure. In a follow-up study, nerve conduction velocity and neuropathology were assessed in the remaining monkeys seven years after exposure terminated, but again, treatment-related effects could not be detected.

Action Potentials↗