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PubMedDate not supplied

Association of ventricular myosin heavy chains in functional states which lead to isoenzyme populations encompassing the whole range of possible distribution.

A statistical model is presented which describes quantitatively the distribution of ventricular myosin (VM) isoenzymes VM-1, VM-2 and VM-3. In order to account for the actual distribution of the isoenzymes, it was assumed that the probability for formation of the heterodimer VM-2 (alpha- and beta-heavy chain) is lower than that of the homodimers VM-1 (2 alpha-heavy chains) or VM-3 (2 beta-heavy chains). The relation VM-2 = 0.85 (VM-1 X VM-3)0.5 describes quantitatively the proportion of the 3 isoenzymes in a given population. The model was established for 252 sedentary normotensive Wistar rats and spontaneously hypertensive rats (SHR) fed ad libitum. It is demonstrated that the isoenzyme populations of rats subjected to 8 weeks experimental routines involving intermittent feeding (1 day feeding ad libitum, followed by 1 or 2 days fasting) or swimming also obey this theoretical distribution. Intermittent feeding led to an increased proportion of VM-3 in Wistar rats and SHR, whereby the latter approached the limits of the possible distribution. Intermittent swimming resulted in an increased proportion of VM-1 which was independent of the feeding schedule in SHR. In Wistar rats, however, the swimming rats fed intermittently exhibited a significantly smaller proportion of VM-1. By combining certain experimental routines, it is thus possible to induce within 8 weeks an isoenzyme population of a predefined composition, nearly within the whole range of possible distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Location of intracranial aneurysms associated with cerebral arteriovenous malformation: statistical analysis.

Distributions of cerebral aneurysms by site were compared statistically in 78 reported cases associated with arteriovenous malformation, including our five cases, and cases with solitary intracranial aneurysms without arteriovenous malformation. When the feeder of an arteriovenous malformation was one of the branches of anterior, middle, or posterior cerebral arteries, the aneurysms were located on these respective arteries much more frequently than expected in the general aneurysmal population. This was statistically significant. Our results strongly suggest that abnormal hemodynamic stresses on the arteries from which the feeders branch out to arteriovenous malformations play a significant role in the development of intracranial aneurysms on these arteries.

Adult↗
PubMed1999

Accidental iatrogenic intoxications by cytotoxic drugs: error analysis and practical preventive strategies.

OBJECTIVES: Drug errors are quite common. Many of them become harmful only if they remain undetected, ultimately resulting in injury to the patient. Errors with cytotoxic drugs are especially dangerous because of the highly toxic potential of the drugs involved. For medico-legal reasons, only 1 case of accidental iatrogenic intoxication by cytotoxic drugs tends to be investigated at a time, because the focus is placed on individual responsibility rather than on system errors. The aim of our study was to investigate whether accidental iatrogenic intoxications by cytotoxic drugs are faults of either the individual or the system. The statistical analysis of distribution and quality of such errors, and the in-depth analysis of contributing factors delivered a rational basis for the development of practical preventive strategies. METHODS: A total of 134 cases of accidental iatrogenic intoxication by a cytotoxic drug (from literature reports since 1966 identified by an electronic literature survey, as well as our own unpublished cases) underwent a systematic error analysis based on a 2-dimensional model of error generation. Incidents were classified by error characteristics and point in time of occurrence, and their distribution was statistically evaluated. The theories of error research, informatics, sensory physiology, cognitive psychology, occupational medicine and management have helped to classify and depict potential sources of error as well as reveal clues for error prevention. RESULTS: Monocausal errors were the exception. In the majority of cases, a confluence of unfavourable circumstances either brought about the error, or prevented its timely interception. Most cases with a fatal outcome involved erroneous drug administration. Object-inherent factors were the predominant causes. A lack of expert as well as general knowledge was a contributing element. In error detection and prevention of error sequelae, supervision and back-checking are essential. Improvement of both the individual training and work environment, enhanced object identification by manufacturers and hospitals, increased redundancy, proper usage of technical aids, and restructuring of systems are the hallmarks for error prevention. CONCLUSIONS: Errors follow general patterns even in oncology. Complex interdependencies of contributing factors are the rule. Thus, system changes of the working environment are most promising with regard to error prevention. Effective error control involves adapting a set of basic principles to the specific work environment. The work environment should allow for rectification of errors without penalty. Regular and ongoing intra-organisational error analysis needs to be an integral part of any error prevention strategy. However, it seems impossible to totally eliminate errors. Instead, if the environment guarantees timely error interception, most sequelae are avoided, and errors transform into a system-wide learning tool.

Antineoplastic Agents↗
PubMed2002

The statistical merits of various methods of calculating transfer coefficients between environmental media--development of the ideal formula for data-sets with a log-normal distribution.

The statistical treatment of data-sets from environmental pollutant studies in which different measurements are combined to produce averages or comparative factors (e.g., transfer coefficients (TCs), input-output balance values) are considered here, with particular reference to the analysis of data from input-output balance studies of pollutants such as PCBs in animals and humans. Many methods of statistical analysis ignore the fact that all measurements are subject to error, and generally assume that the normal distribution applies to all data-sets, which is commonly inappropriate for environmental (and particularly biological system) data. Considerably different estimations can be obtained by applying different, commonly used, statistical methods, as shown in a simulation study presented here and when applied to data from an input-output balance study of PCBs in humans. Alternative average and combined factor estimators for the treatment of data from these types of studies that give considerable advantages in terms of bias and the ease of assessment of accuracy are proposed.

Animals↗
PubMed2005

Adaptive sampling based on the cumulative distribution function of order statistics to delineate heavy-metal contaminated soils using kriging.

Correctly classifying "contaminated" areas in soils, based on the threshold for a contaminated site, is important for determining effective clean-up actions. Pollutant mapping by means of kriging is increasingly being used for the delineation of contaminated soils. However, those areas where the kriged pollutant concentrations are close to the threshold have a high possibility for being misclassified. In order to reduce the misclassification due to the over- or under-estimation from kriging, an adaptive sampling using the cumulative distribution function of order statistics (CDFOS) was developed to draw additional samples for delineating contaminated soils, while kriging. A heavy-metal contaminated site in Hsinchu, Taiwan was used to illustrate this approach. The results showed that compared with random sampling, adaptive sampling using CDFOS reduced the kriging estimation errors and misclassification rates, and thus would appear to be a better choice than random sampling, as additional sampling is required for delineating the "contaminated" areas.

Environmental Monitoring↗