Effect of dipicolinic acid on the haemolysis of human red blood cells.
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Aerobiosis↗
Biomedical subjects
M Malik
Publications and source records attributed to M Malik.
Toxicity profile of epichlorohydrin.
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Administration, Intranasal↗
Evaluation of receiver operator characteristics--optimum time of day for the assessment of heart rate variability after acute myocardial infarction.
The study reports a mathematical method for deciding which clinical data are of importance for treatment decisions in a given clinical setting. The method comprises the following steps: (A) the receiver operator characteristic (ROC) functions of the compared sets of data are computed; (B) the design and aim of the clinical study is expressed as an integral measure on the space of sensitivity values (this reflects the preference of low or high sensitivity values dependent on the clinical targets); (C) the sets of data being compared are characterised by the non-linear integrals of their ROC functions. The approach has been used to compare mean heart rate (HR) and heart rate variability (HRV) data calculated in 5113 different portions of 24-h ECG recordings and assessed in 365 patients surviving acute myocardial infarction, in order to evaluate the utility of Holter recording of varying lengths and starting times for the prediction of sudden cardiac death and/or serious arrhythmic events. The results of the study show that this approach is capable of evaluating and comparing the sets of medical data used for identification of patients who are at increased risk. The experimental part of the study showed that the optimum recording interval for the assessment of HR and HRV data in patients who survived acute myocardial infarction depends on the aim of the identification of increased risk patients. The optimum interval of recording is different for an identification which requires a low number of false negative cases and permits a higher number of false positive cases, than for the situation where a low number of false positive cases are required and a higher number of false negative cases are permissible.
Circadian Rhythm↗
Psychiatric disorders in primary care patients receiving complementary medical treatments.
This study investigated lifetime and current rates of axis I diagnoses and the personality traits of neuroticism and extraversion in patients receiving complementary medical care in the United Kingdom and United States. Eighty-three patients were interviewed by means of the Structured Clinical Interview for DSM-III-R, and 78 completed the Eysenck Personality Inventory (EPI). Subjects were drawn from the Royal London Homoeopathic Hospital (n = 50) and a holistic family practice in North Carolina (n = 33). High rates of lifetime (68.7%) and current (39.8%) axis I disorders were found, with no substantial differences between the groups, apart from lifetime posttraumatic stress disorder and current social phobia, which were higher in the US sample. The subjects were more introverted but not more neurotic as compared against normative population data with the EPI. The subjects were predominantly older women. We conclude that psychiatrists may need to be aware that patients with depressive or anxiety disorders are likely to seek out complementary treatments for a wide range of medical problems, and should inquire as to use of these in their patients. They may also need to cultivate greater awareness of the health beliefs of such patients.
Adult↗
Measurement and interpretation of QT dispersion.
QT dispersion was proposed as an index of the spatial inhomogeneity of ventricular recovery times. The results of studies that found significant correlation between dispersion of ventricular recovery times measured with monophasic action potentials and QT dispersion were interpreted as proof of the direct link between QT dispersion and the dispersion of ventricular recovery times. Later it was shown that QT dispersion is not a direct reflection of the spatial variation of the recovery times and cannot be used for quantification of this variation. The interlead variability of the QT intervals is a result of different projections of the spatial T-wave loop into the various electrocardiographic leads. The reliability of both manual and automatic measurement of QT dispersion is low and is often of the order of the differences of Qt dispersion between different patient groups. The measurement reliability is influenced by intrinsic factors (e.g., amplitude of the T wave) and extrinsic factors (e.g., noise, paper speed of recording, instruments for manual measurements, and type of algorithm and interalgorithmic settings for automatic measurement). There is very little to choose between the different indices of expression of QT dispersion, as well as between the different lead configurations used for its measurement. QT dispersion is not simply a result of measurement error, but a crude measure of abnormalities during the whole course of repolarization. Only grossly prolonged QT dispersion (e.g., > or =100 ms), must be interpreted simply as a sign of the abnormal course of the repolarization, and inferences about the actual dispersion of the ventricular recovery times should not be made. Newer concepts of assessment of the morphology of the T wave are already emerging and will probably be of higher clinical value.
Electrocardiography↗
Some aspects of computer modelling in cardiac electrophysiology.
A computer model simulating the electrical activity of the heart is described. The model is designed for use in clinical cardiological research. Its implementation is based on the methods of discrete process simulation. The simulation program is written in FORTRAN, has approximately 12,000 lines and requires 160 kilobytes of memory to run. The whole heart is modelled, including a realistic description of the conduction system and a 'hollow shell' structure with a central plane representing the atrial, ventricular and septal components of the cardiac musculature. The myocardium itself is represented by simple hexagonal elements, which are pieced together to form the 'hollow shell'. The ideas used to develop the model are briefly described, but emphasis is given to clinical applications. The model is first validated by examining its output under well-known pathological conditions. Clinical applications, including predictive value, testing of hypotheses, and evaluation of pacemaker function, are then described, results being presented in the form of orthogonal lead projections.
Computers↗
Autonomic function following myocardial infarction.
There is evidence that impaired autonomic function is a significant risk factor for ventricular arrhythmias and sudden death following myocardial infarction. Measurement of heart rate variability and assessment of baroreflex sensitivity can identify patients at high risk from arrhythmic complications postinfarction and may become useful in risk stratification and management.
Animals↗
Cold stress, reverse T3 and lymphocyte function.
Following a recently reported rise in serum reverse triiodothyronine levels in response to cold exposure, an initial in vitro study has been carried out on human lymphocyte function. The first part of the study demonstrated that the uptake of rT3 on lymphocyte nuclear receptors increased as the rT3 concentration was raised above the normal serum level. The binding is competitive with triiodothyronine. The lymphocytes were harvested from venous blood donated by young male U.S. naval personnel. The second part of the study involved lymphocyte proliferation assays carried out with the addition of increasing amounts of rT3. Both non-specific (three different mitogens) and specific (recall antigen) stimuli were used. There was an indication that lymphocyte function is depressed by increasing serum concentration of rT3. However, with a small number of test subjects and a resulting low statistical power, it was not possible to establish a statistically significant association. Lymphocytes from umbilical cord blood, which has a very high level of rT3 compared to that in normal adult sera, were also found to have a much reduced lymphocyte stimulation index. The requirements for a more definitive investigation are outlined.
Adult↗