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At least 505 records · Page 28Linked to original sources
PubMed1995

Crohn's disease: pathogenesis and persistent measles virus infection.

The Inflammatory Bowel Disease Study Group at the Royal Free Hospital School of Medicine has tested the hypothesis that the primary pathological abnormality in Crohn's disease is in the mesenteric blood supply. Early morphological studies involved arterial perfusion-fixation and either resin casting and scanning electron microscopy or vascular immunostaining of resected intestine affected by Crohn's disease. Granulomatous and lymphocytic damage to intramural blood vessels, even in macroscopically normal areas, was observed. We put forward possible mechanisms by which a chronic ischemic process might account for many of the idiosyncracies of Crohn's disease. It was proposed that persistent viral infection of the mesenteric microvascular endothelium might underly this vasculitic process; based on certain behavioral characteristics of measles virus, including its tropism for the submucosal endothelium of the intestine, this agent was investigated further. This report reviews the preliminary evidence from both epidemiological and basic scientific data for persistent measles virus in the intestine of patients with Crohn's disease. Possible mechanisms for virus persistence and subsequent reactivation are discussed. In conclusion, we believe that Crohn's disease may be a chronic granulomatous vasculitis in reaction to a persistent infection with measles virus within the vascular endothelium. This granulomatous inflammation, perhaps aggravated by either a hypercoagulable state or mechanical stress, results in the clinical features of Crohn's disease.

Colon↗
PubMed1995

Routine obstetric ultrasound.

A detailed review of the literature reveals that routine obstetric ultrasound has value in providing more accurate gestational dating and in the diagnosis of fetal anomalies. The recent RADIUS study, which has concluded that routine obstetric ultrasound is of no clinical benefit, is critically analyzed, focusing on four areas: the applicability of the results to the general population, the appropriateness of the outcome parameters, the quality of the ultrasound provided, and the issue of excessive cost. Finally, an ethical analysis of the role of routine obstetric ultrasonography is provided, focusing on the principles of beneficence and respect for autonomy. The offering obstetric ultrasound is necessary in both beneficence-based and autonomy-based ethical analyses, and the use of routine ultrasound is supported from an analysis of the scientific data.

Congenital Abnormalities↗
PubMed1988

The porcelain butt margin with hydrocolloid impression technique.

After preliminary scientific data, the dentist commonly evaluates the success of a recommended clinical technique. However, the accuracy of a restoration constructed in the laboratory depends directly upon the abilities of the laboratory technician. The communication between the dentist and the laboratory technician is crucial for success. This study examined the practicality of the porcelain/butt margin. When combined with the appropriate tissue management, sulcular placement, and impressions, this consistent procedure was easily evaluated, financially sound, and time-conserving.

Colloids↗
PubMed1994

Survival of fixed implant-supported prostheses related to cantilever lengths.

Various lengths of cantilevers for fixed implant-supported prostheses have been recommended in the literature. No scientific data are available for selecting specific lengths, and different views are reported. Authors contend that longer cantilevers lead to increased risk of failure. This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention.

Dental Implantation, Endosseous↗
PubMed1992

What do we really know about amyotrophic lateral sclerosis?

The cause of amyotrophic lateral sclerosis is unknown. In this review clinical and scientific data that are pertinent to understanding this disease are reviewed. There are currently several major controversies concerning the possible role of immunological factors, genetic factors, environmental toxins, and viral infection in pathogenesis. These concepts must be considered in relation to what is known about the disease in all its aspects, including epidemiological data, information on the classical and molecular pathology of the disease, and on associated involvement of other systems, e.g., the spinocerebellar pathways and frontal dementia. Only when all this information is assimilated can full understanding of the disease and, hopefully, a logical approach to treatment and prevention, be achieved.

Amyotrophic Lateral Sclerosis↗
PubMed1989

Effects of environmental conditions on the psychological well-being of primates: a review of the literature.

Amendments made to the Animal Welfare Act in 1985 require primate researchers to provide "a physical environment adequate to promote the psychological well-being of primates". Regulations have not yet been promulgated, in part because "the psychological well-being" of primates is extremely difficult to define. Ideally, those regulations would be based upon observable changes in behavior rather than assumed psychological changes. Regardless, new primate care regulations pertaining to social environment, cage size, exercise and other forms of environmental enrichment are anticipated. A review of the literature suggests that there is little scientific data to support changing existing regulations. For instance, although it is clear that total social isolation in very young primates can be behaviorally devastating in terms of normal social behaviors, there are few, if any, demonstrable adverse effects of individual housing in adult primates. On the other hand, group housing, particularly with groups changing frequently in composition, increases aggression, trauma and disease transmission. In addition, existing research suggests there are important species differences in terms of social preferences. It is impossible to justify an increase in cage size based upon the available literature. An additional practical consideration is that any change in cage size requirements will necessitate replacement of current primate housing on a national level, an enormously expensive proposition. Regarding environmental enrichment, research suggests that providing a naturalistic environment is not as critical as arranging dynamic events that are contingent upon behavior. However, new research is necessary to specify the types of environmental enrichment that are valuable and appropriate before useless, even damaging, and expensive changes are mandated.

Animal Welfare↗
PubMed1990

Efficiency of skin sterilization for a venipuncture with the use of commercially available alcohol or iodine pads.

Skin sterilization for a venipuncture is routinely done with commercially available alcohol or iodine pads. Selection of the antiseptics, alcohol or iodine, however, in most situations has been made on the basis of very little scientific data. With many patients with granulocytopenia who are undergoing venipunctures, the choice of antiseptic may be an important factor in preventing infections. We investigated two widely and commercially available disinfectant pads, alcohol and iodine, in the efficacy of skin sterilization. Seventy subjects (35 adults and 35 children) were randomly selected for this study. A designated area of the right and left forearm was sterilized either with alcohol or with an iodine pad in a predetermined uniform fashion. Specimens were obtained for cultures before and after sterilization. The bacterial cultures were performed with the use of blood agar plates and trypticase soy broth. For data analysis growth of any organisms on agar plates or trypticase soy broth after sterilization was interpreted as a sterilization failure. The iodine swab was significantly more efficient than the alcohol swab; the former yielded an 80% sterilization rate whereas the latter resulted in a rate of 61% (p less than 0.02). If, however, the growth only in agar plates was compared, the alcohol wipe yielded no growth in 83% and iodine in 84%, virtually identical success rates. Bacillus spp. predominated the residual organisms after either the alcohol or the iodine wipe. A variety of other organisms, however, including Staphylococcus and Corynebacterium spp., grew after alcohol but not after iodine sterilization.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗
PubMed1989

Impact of randomized clinical trials on medical practices.

The randomized clinical trial (RCT) is the most powerful tool available to assess the effectiveness of a medical procedure. It complies with the fundamentals of scientific human experimentation and it is accepted, as such, by the researchers as the yardstick of medical progress. Therefore RCTs should have had a major impact on current medical practices through health policy makers and prescribers. Though they are limited in number and they have investigated few medical fields, studies on the impact of RCTs on medical practice have shown large and frequent discrepancies between scientific data made available from RCTs and current prescription practices in France, the United States, Finland, Holland, and elsewhere. Hence the above expectation is frustrated because doctors are not trained to weigh the evidence on treatment benefit-risk ratios, to read clinical research reports, or to select the appropriate information. In addition, the number of pending problems addressed by RCTs are too few, too slow to give the answers, inadequately sized, and their outcome measures are more often than not inappropriate. Doctors are reluctant to participate in clinical trials despite such participation being one of their duties. Governmental agencies barely fund clinical trials. Researchers do not formulate the right questions.

Attitude of Health Personnel↗
PubMed1989

Variability of safe dose estimates when using complicated models of the carcinogenic process. A case study: methylene chloride.

Advances in understanding carcinogenesis have led to the development of mathematical models that have biologically interpretable parameters. These models utilize more of the available scientific data than the empirical models routinely employed for quantifying carcinogenic risk. They also require consideration of sources of uncertainty in risk estimates that were previously ignored, such as animal-to-animal variability of physiological and pharmacological constants. A numerical technique is proposed for studying the consequences of incorporating the intrapopulation variability of biologically interpretable parameters into the risk assessment process. To demonstrate the technique, the variability of safe dose estimates for exposure to methylene chloride is considered. The results suggest that intrapopulation variability of the model parameters can increase the variability of safe dose estimates an appreciable amount.

Animals↗
PubMed1987

Everything is a carcinogen?

The public has developed the impression that in an industrialized society environmental carcinogens are ubiquitous and that all chemical exposures, irrespective of the dose, influence carcinogenesis. Such impressions are influenced by many nonscientific considerations and often reflect insufficient knowledge of scientific data and methods. Such misconceptions are thus partly explained by the multistage nature of carcinogenesis, the absence of a clear understanding, and definition of the multiple factors which influence cancer induction. It is obvious that not all chemicals are carcinogenic and it is reasonable to accept that not all substances (including primary chemical carcinogens) that are found to enhance carcinogens in animals are necessarily carcinogenic to humans under conditions of usual human exposure.

Animals↗
PubMed1988

Drinking water standards and risk assessment.

The role and use of risk assessment methods in the establishment of drinking water standards are described with emphasis on recent applications. The process essentially includes an attempt to quantify human exposure from all routes including drinking water, animal toxicology, and human epidemiology, when available, to arrive at drinking water concentrations at which exposure would result in "no known or anticipated adverse effects on health, with a margin of safety." The process itself is straightforward; however, the application to decision making for substances that are considered to be potentially nonthreshold acting in their toxicity (e.g., carcinogenic) requires many policy choices beyond the scientific data and is subject to considerable controversy.

Carcinogens↗
PubMed1991

Screening radon risks: a methodology for policymakers.

This paper provides an easy-to-use screening methodology to estimate potential excess lifetime lung cancer risk resulting from indoor radon exposure. The methodology was developed under U.S. EPA Office of Policy, Planning, and Evaluation sponsorship of the agency's Integrated Environmental Management Projects (IEMP) and State/Regional Comparative Risk Projects. These projects help policymakers understand and use scientific data to develop environmental problem-solving strategies. This research presents the risk assessment methodology, discusses its basis, and identifies appropriate applications. The paper also identifies assumptions built into the methodology and qualitatively addresses methodological uncertainties, the direction in which these uncertainties could bias analyses, and their relative importance. The methodology draws from several sources, including risk assessment formulations developed by the U.S. EPA's Office of Radiation Programs, the EPA's Integrated Environmental Management Project (Denver), the International Commission on Radiological Protection, and the National Institute for Occupational Safety and Health. When constructed as a spreadsheet program, the methodology easily facilitates analyses and sensitivity studies (the paper includes several sensitivity study options). The methodology will be most helpful to those who need to make decisions concerning radon testing, public education, and exposure prevention and mitigation programs.

Female↗
PubMed1990

A comparison of attitudes and practices of episiotomy among obstetrical practitioners in New Mexico.

The routine use of episiotomy is a subject of considerable controversy. To delineate attitudes and practices, we surveyed various groups of obstetrical practitioners in New Mexico. Routine use was favored most by obstetricians, less by family practitioners, less yet by nurse midwives and least by lay midwives. Many of the reasons given both for and against routine use were the same, underscoring the lack of scientific data and prospective studies of episiotomy and its effects.

Adult↗
PubMed1994

Stability of reconstituted methohexital sodium.

The purpose of this study was to determine the stability of reconstituted solutions of methohexital sodium over a 6-week period. Stability of methohexital was examined using reversed-phase high-performance liquid chromatography. The results indicate that reconstituted methohexital is extremely stable for up to 6 weeks when stored at 4 degrees C. When stored at room temperature, reconstituted solutions of methohexital contained increasing levels of degradation products and showed a corresponding decrease in methohexital over a 6-week period. However, the rate of degradation of the drug was slow, with less than 10% of the methohexital undergoing breakdown. In addition, tests for microbial contamination of the solutions stored at room temperature and under refrigeration were negative for up to 6 weeks. This study demonstrates that methohexital, when stored under refrigeration for up to 6 weeks, is virtually chemically identical to a freshly reconstituted solution of the drug. When stored at room temperature, there is some degradation of the drug, but it is not known whether the small amount of degradation is clinically significant. This study emphasizes the importance of obtaining scientific data to support changes in guidelines related to handling and storage of drugs.

Analysis of Variance↗
PubMed1995

Through a glass darkly: predicting the future of radiation oncology.

To position ourselves professionally for the inevitable transition to managed care demands serious self-appraisal. Like most procedural medical specialties, radiation oncology is currently ill prepared for a capitated system of payment. To prosper under capitation, we need to increase the utility of radiation therapy per unit cost. This can be achieved by making the following adaptive responses: (a) we must ensure that the needs of medical practice drive the use of costly technology and not vice versa; (b) we must subordinate firmly held beliefs and prejudices to solid scientific data and be prepared to modify our practice when more cost-effective alternative exist; and (c) we must be increasingly conscious of outcome, not process, in deciding among treatment options; and (d) we must acknowledge the need to prioritize the use of finite resources so that the maximum effort is expended on those who have the most to gain from treatment. These changes will permit us to develop guidelines for appropriate use of radiation therapy, and to demonstrate the excellent value of the service we can provide, which is the ultimate key to success. Though the future may at times seem bleak, we can shape it with our actions: the best way to predict the future is to create it.

Costs and Cost Analysis↗
PubMed1993

Limiting the uncertainty in risk assessment by the development of physiologically based pharmacokinetic and pharmacodynamic models.

Analysis of the default cancer risk assessment methodology suggests that the confidence interval usually associated with the prediction of an upper bound on risk underestimates the uncertainty in the risk estimate. This underestimate of uncertainty is based on the use of a large number of policy decisions or professional judgements that are incorporated into the methodology as exact values with no estimate of error. An alternative approach is to develop a comprehensive biologically based risk assessment that provides scientific data to substitute for many of the policy decisions of the default methodology.

Acrylates↗
PubMed1995

Use of mechanistic information in risk assessment for toxic chemicals.

Risk assessment (RA) for toxic chemicals is assumed to be a scientific activity providing a framework of principles for the complication and evaluation of all available scientific information and the rational extrapolation to human health effects in as quantitative terms as possible and with a high degree of certainty. Sensible public health decisions are made more certain through the use of mechanistic information throughout the 4 steps in RA: hazard identification, dose-response assessment, exposure (dose) assessment and risk characterisation. Examples of the use of mechanistic information to assess risks of systemic, developmental/reproductive and neurotoxic effects show how to move away from the presently used threshold/no observable adverse effect/uncertainty factor default methodology towards an evaluation based on all available scientific data. The experience gained in cancer RA in the use of metabolic and tissue binding (receptor) models as well as physiologically based pharmacokinetic (PBPK) and pharmacodynamic (PBPD) models can be transferred to non-cancer RA. A good example is the use of a PBPK model for the hepatoxicity of chloroform. As in cancer RA, as default positions are replaced by biological data the risk assessments become less uncertain when extrapolating between species. Combining information on tissue dosimetry and response data can also provide an estimate of variability within populations, which is impossible with present default type methodology but essential for adequate risk characterisation. Unlike the cancer field there is no single hypothesis for the mechanism of action for the multitude of non-cancer end-points studied.

Animals↗
PubMed1993

Typology of drug abuse deaths in Hamburg.

Based on a multidisciplinary approach (social-scientific questionnaire and forensic-pathological investigations), a typology of the drug-related fatalities in Hamburg during the period from July 1991 to June 1992 was achieved. A distinction between 3 types of addicts is proposed. Each group represents a different consumption pattern: (1) the opioid type, (2) polyvalent-drug users, and (3) primary alcoholics. With respect to these 3 types of abuse, some medical (concentration of alcohol and opioids in the blood) and social-scientific data (age at the beginning of the drug career, consumption of different drugs, distribution of age and sex, the quality and frequency of contact to facilities of the drug aid in Hamburg) are discussed.

Adolescent↗