[Typing disability, not dyslexia].
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Computers↗
Biomedical subjects
A Patak
Publications and source records attributed to A Patak.
Evaluation of several common standards for the X-ray microanalysis of thin biological specimens.
The question of the best type of standard to use for X-ray microanalysis of thin biological specimens remains unanswered. Standards embedded in an organic matrix have the advantage that they resemble biological specimens, but their composition is generally not known exactly. We compared several standards and, surprisingly, inorganic binary salts sprayed onto a supporting film were the most suitable: they corresponded closely with several other methods using organic matrices; they were easily produced; and their composition is known. Glutaraldehyde-urea aminoplastic resin thin sections and thin films containing dissolved salts were problematic. The composition of the polymer appears to be variable, and the thin films did not correspond with any other standard tested. Chelex100 bio-standard beads and flakes loaded with accurately determined concentrations of ions, embedded in epoxy resin and thin sectioned, tended to correspond to the results obtained with the binary salts. However, the results from some bio-standards were inexplicably aberrant. An epoxy resin standard was used for bromine, and was found to agree closely with the binary standards.
Electron Probe Microanalysis↗
Introducing medical students to medical informatics.
Medical informatics (MI) has been introduced to medical students in several countries. Before outlining a course plan it was necessary to conduct a survey on students' computer literacy. A questionnaire was designed for students, focusing on knowledge and previous computer experience. The questions reproduced a similar questionnaire submitted to medical students from North Carolina University in Chapel Hill (NCU). From the results it is clear that although almost 80% of students used computers, less than 30% used general purpose applications, and utilization of computer-aided search of databases or use in the laboratory was exceptional. Men reported more computer experience than women in each area investigated by our questionnaire but this did not appear to be related to academic performance, age or course. Our main objectives when planning an MI course were to give students a general overview of the medical applications of computers and instruct them in the use of computers in future medical practice. As our medical school uses both Apple Macintosh and IBM compatibles, we decided to provide students with basic knowledge of both. The programme was structured with a mix of theoretico-practical lectures and personalized practical sessions in the computer laboratory. As well as providing a basic overview of medical informatics, the course and computer laboratory were intended to encourage other areas of medicine to incorporate the computer into their teaching programmes.
Computer Literacy↗
Use of ultra-thin window detectors for biological microanalysis.
Films and bulk samples of Nylon, gelatin, Makrofol, epoxy resin, aminoplastic resin and sodium acetate have been used as models of biological samples. It is shown that the use of ultrathin window (UTW) detectors in scanning transmission and scanning electron microsopes permits the quantitative analysis of light elements, yielding a total element analysis with hydrogen estimated by difference or "guesstimated". Comparison with known concentrations of concentrations obtained by chemical analysis shows that X-ray microanalysis of selections by the peak to continuum ratio model and bulk samples by the phi(pz) model gives sufficiently accurate results for biological purposes. It is also shown that sections may be analysed by the standardless ratio model. The application of UTW detectors to total element analysis by quantitative elemental imaging is demonstrated of bulk biological samples. which have been freeze-substituted, embedded in epoxy resin and surface polished. The possibility of imaging the oxygen content of frozen-hydrated bulk tissue samples which have been surface polished is also demonstrated. This may lead to the imaging of water distribution in frozen-hydrated bulk samples of biological tissues. UTW detectors are also useful for detecting mass loss in organic samples by monitoring the decrease in oxygen counts and for detecting contamination by monitoring the increase in carbon counts. It is also shown that changes in carbon counts are good indicators of folds in sections.
Animals↗
Validation of the medical expert system PNEUMON-IA.
The present study validates the expert system PNEUMON-IA. The aim of PNEUMON-IA is assessing the etiology of community-acquired pneumonias from clinical, radiological, and laboratory data obtained at the onset of the disease. Validation was performed using data from medical records of 76 patients with proven clinical diagnosis of pneumonia. The etiological diagnoses provided by PNEUMON-IA were compared to those established by five specialists unrelated to the development of the expert system. For each etiological possibility, both PNEUMON-IA and the experts provided a causal possibility, expressed as a linguistic label (i.e., "almost impossible"). Linguistic labels were then converted to numeric values. In the majority of cases, an etiological diagnosis was unavailable to be used as a gold standard. To overcome this limitation, distances between arrays of etiological possibilities given by specialists and by PNEUMON-IA were considered as an agreement measure between diagnoses. Cluster analysis based on those distances was used to classify PNEUMON-IA among experts. Results showed the same differences between specialists and PNEUMON-IA as among the specialists themselves. The method used to validate PNEUMON-IA could prove useful to assess the performance of expert systems in fields where no gold standard is available.
Adolescent↗
Development of the sensory innervation of muscle spindles in the kitten.
This is a report of the changes observed in the pattern of sensory innervation of muscle spindles in hindlimb muscles of kittens during the first four weeks of life. The structural analysis, made on teased, silver-stained preparations, was complemented by a series of recordings of afferent responses of kitten spindles during ramp-and-hold stretches of the muscle. The primary endings of spindles from newborn animals showed a large degree of variability in their branching pattern and branches formed a network across the intrafusal fibres. In older animals there was less variability and lateral branches of stem axons began to encircle the intrafusal fibres. The process of maturation was characterized by a more uniform shape of the endings and more complete, evenly spaced, annulospiral terminals. Recordings of the responses of primary endings of spindles during muscle stretch showed that several features of the adult response were already present in the newborn, although the overall rate of discharge was very much lower. It was concluded that the changes observed in the structure of the sensory endings of kitten spindles did not have clearly identifiable physiological correlates. It appears that an annulospiral shape of the sensory terminals is not a necessary prerequisite for the generation of stretch responses. The predominant factor which appears to determine the responses of spindles to stretch is the maturity of the intrafusal fibres, in particular, the bag2 fibre.
Aging↗
Effect of muscle length on phasic stretch reflexes in humans and cats.
1. This is a report of the effects at different muscle lengths of the muscle's immediate history on the tendon jerk and Hoffman (H)-reflex in triceps surae of human subjects and cats. 2. In adult human subjects the size of the tendon jerk was measured as electromyogram (EMG) and torque in response to a tendon tap. Before each test tap the muscle was conditioned by a maximum voluntary contraction carried out with the foot either plantarflexed or dorsiflexed by 30 degrees from the test position. After a contraction with the foot dorsiflexed, the subsequent reflex response was smaller than after a contraction with the foot plantarflexed. 3. The same conditioning procedure was carried out with the H-reflex. The reflex was elicited by transcutaneous electrical stimulation of the tibial nerve in the popliteal fossa. Here the reflex after a contraction with the foot dorsiflexed was larger than after plantarflexion. In other words, the effects of conditioning were the opposite for the tendon jerk and H-reflex. 4. The effects of muscle conditioning were tested over a range of muscle lengths. As the test length was made progressively longer, that is, the foot more dorsiflexed, the difference in size of the tendon jerk following the two forms of conditioning became less, whereas for the H-reflex it remained the same. 5. These findings were confirmed in cats anesthetized with alpha-chloralose. The tendon jerk was elicited by a quick stretch applied to the triceps surae muscle group, and the H-reflex represented by the monosynaptic reflex recorded from the central, cut end of the ventral root in response to electrical stimulation of the triceps nerve. Muscle conditioning consisted of a 1-s period of stimulation at 20 pulses/s, at fusimotor strength, of the peripheral end of the cut ventral root at a muscle length 5 mm longer or shorter than the test length. In the cat, as in human subjects, the effect of conditioning on the tendon jerk reversed at long muscle lengths, whereas the monosynaptic reflex showed no reversal. 6. It had been proposed previously that the effects of conditioning on stretch reflexes could be explained by development of slack in the intrafusal fibers of muscle spindles after a contraction at a longer-than-test length. The presence of slack lowers the resting discharge of spindles and reduces the afferent response to a tendon tap.(ABSTRACT TRUNCATED AT 400 WORDS)
Achilles Tendon↗
Effects of muscle history on the stretch reflex in cat and man.
1. This is a report of experiments on cat and man which demonstrate effects of a muscle's previous history of contraction and length changes on the size of the stretch reflex. 2. In adult human subjects the size of the tendon jerk was measured in ankle extensor muscles by tapping the Achilles tendon. Muscle conditioning consisted of a maximum voluntary contraction with the foot dorsiflexed or plantarflexed by 30 deg from the test position, after which the subject was asked to relax while the foot was held still for several seconds before being returned to the test position and a tendon tap given. After a contraction of the lengthened muscle the tendon jerk was smaller than after a contraction of the shortened muscle. 3. The experiment was then repeated, but instead of a tendon jerk an H (Hoffmann) reflex was elicited by transcutaneous electrical stimulation of the tibial nerve in the popliteal fossa. The reflex after a conditioning contraction of the lengthened muscle was larger than after a contraction of the shortened muscle. In other words muscle conditioning produced opposite effects on the tendon jerk and H reflex. 4. These findings were confirmed in cats anaesthetized with chloralose. After a conditioning contraction of triceps surae at a length 5 mm longer than the test length (hold-long) a quick tendon stretch produced a smaller reflex response than following a conditioning contraction with the muscle 5 mm shorter than the test length (hold-short). The reverse trend was seen with a reflex elicited by direct electrical stimulation of the muscle nerve, which stimulates the H reflex. 5. One consequence of a conditioning contraction is that it leads to an alteration of the level of resting discharge of muscle spindles. We propose that the larger tendon jerk after a contraction of the shortened muscle is the result of changes in stretch sensitivity of muscle spindles. The reverse effect on the H reflex we attribute to a rise in the level of resting discharge of muscle spindles, which, we propose, leads to reflex inhibition of motoneurones. 6. We support this conclusion with evidence from an experiment in which the size of the conditioning step was systematically altered. Even quite small hold-short conditioning steps led to depression of the H reflex in man and the monosynaptic reflex in cats. Recordings from single afferents showed that such small steps were also accompanied by a detectable rise in spindle resting discharge.(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
Newborn Touch: a CAI program in neonatal pathology.
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Clinical Competence↗