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PubMed1996

Similarity and complementarity of molecular shapes: applicability of a topological analysis approach.

Developments based on a topological analysis approach of electron density maps are presented and applied to two different fields: the interpretation of electron density maps of proteins and the description of shape complementarity between a cyclodextrin host and a guest molecule. A global representation of the electron density distribution, through the location, identification and linkage of its critical points (points where the gradient of the density vanishes, i.e., peaks and passes), is generated using the program ORCRIT. On one hand, the interpretation of protein electron density maps is based on similarity evaluations between graphs of critical points and known structures. So far, the method has been applied to 3 A resolution maps for the recognition of secondary structure motifs using a procedure relevant to expert systems in artificial intelligence. Satisfying matches between critical point graphs and their corresponding protein structure depict the ability of the topological analysis to catch the essential secondary structural features in electron density maps. On the other hand, mapping the accessible volume of a host molecule is achieved by representing the peaks as ellipsoids with axes related to local curvature of the electron density function. Related energies of the interacting species can also be estimated. A qualitative comparison is made between the results generated by the topological analysis and energy values obtained by conventional molecular mechanics calculations. A positive comparison and a close complementarity between cyclodextrin and ligands shows that the topological analysis method gives a good representation of the electron density function.

Computer Simulation↗

PubMed2005

Predicting in vivo clinical performance of anterior cruciate ligament fixation methods from in vitro analysis: industrial tests of fatigue life and tolerance limits are more useful than other cyclic loading parameters.

BACKGROUND: Anterior cruciate ligament graft fixations experience cyclic loads in vivo. Present cyclic loading studies testing fixation use "incremental cycling," "residual strength" protocols, or a combination. Industrial standards, however, rely on fatigue life testing and use tolerance limits to determine guaranteed minimum levels of cycles to failure. HYPOTHESIS: Industrial standards of fatigue life and lower tolerance limits provide a more conservative assessment of cycles to failure than do currently used cyclic loading models, and they facilitate interpretation of data toward clinical performance. STUDY DESIGN: Descriptive laboratory study. METHODS: Fatigue life curves and lower tolerance limits were calculated for porcine patellar tendon graft fixations that were tested to failure in single pulls or cycled to failure at 2 different load levels. A log curve was constructed so that the expected values at other load levels could be calculated. Comparison of a metal and a composite resorbable interference screw design was used as an example. RESULTS: Cycles to failure of both screw designs varied widely at each load level. The guaranteed minimum number of cycles calculated by tolerance limits was therefore much lower than the mean cycles to failure at any given load level. For example, at a load of 250 N, the predicted mean life for the composite screw and the metal screw was 2513 and 1490 cycles, respectively, whereas the 80/80 tolerance limits (the value that 80% could be expected to achieve with 80% confidence) were only 63 and 68 cycles, respectively. Small reductions in load level gave very large increases in minimally expected life. CONCLUSIONS: Fatigue testing of anterior cruciate ligament reconstructions better shows the wide variation between specimens and the large effect of load levels on expected life. Wide scatter makes mean levels over-optimistic and difficult to interpret. Tolerance limits give estimates that are more conservative and facilitate data interpretation. CLINICAL RELEVANCE: A method for testing and analyzing fatigue properties was presented, results of which are more readily interpreted to clinical practice.

Animals↗

PubMed2003

[The death of emperor Valentine I in the descriptions of Ammianus Marcellinus and other authors].

The history of neurology, especially before 1800, has been treated almost completely as "literary history". Most interest centred around the works of famous physicians and their writings. Especially in the classical era, non-medical testimonies have received little attention. This makes it a particularly pleasant surprise for a medical histroical in search of such material to come across a description of a "neurological illness" in a history book from ancient times. 'Rerum gestarum libri' by Ammianus Marcellinus, the last Roman historiographer of note, gives a fairly descriptive account of the fatal illness of Emperor Valentine I (30, 6, 1-6). Valentine was suddenly taken ill with apoplectiform symptoms during a campaign in Pannonia in 375 AD. He died few hours later, despite the attempts of a physician quickly brought to the scene. The account of Ammianus Marcellinus combines literary features with a clear interpretation of medical symptoms according to contemporary doctrines. This description was later to become a model for non medical references and commentaries dealing with this "famous case", written by Christian authors including Orosius, St. Jerome, Socrates and the pagan historian Zosimos.A retrospective diagnosis of Valentine's last disease is difficult. It is impossible to prove that he really died from a stroke. Death by infectious disease might also be supposed. Finally, similar symptoms can be found in the case of the Emperor Claudius, who was poisoned by his last spouse in Agrippina in 54 AD. Our study is an attempt to analyse this very important case report from a medical, historical and cultural perspective, thus contributing to the historiography of "neurology in the ancient world".

Cause of Death↗

PubMed1988

Cognitive organization of emotion: differences between labels and descriptors of emotion in jealousy situations.

The purpose of this study was to ascertain whether the cognitive organization of labels of emotion differs from descriptions of affective states. This was done in the context of determining whether the attributions of labels of emotion and descriptions of affective responses in jealousy situations differed according to the status of the interloper, presence of an audience to the untoward behavior, and sex of the respondent. The subjects, 300 male and female junior college students, read vignettes which placed them at a party where their mates passionately kissed interlopers of varying status, and whose transgressions were, or were not, observed by others. The subjects were required to indicate the likelihood that they would experience anger, disgust, fear, jealousy, sadness, and surprise, and 49 cognitive and physiological descriptions of the affective states referred to by the aforementioned labels of emotion. Different findings were obtained with the labels and descriptors of affective states. This was interpreted as support for the systems theory of G.E. Schwartz. The descriptions, but not the labels, indicated that men were most upset when the interloper was a best friend and least concerned when he was a stranger. In contrast, women were most upset when the interloper was someone of equal or lower status than themselves and least upset when the interloper was their best friend.

Adult↗

PubMed2005

Levels of description: a novel approach to dynamical hierarchies.

We present a novel formal interpretation of dynamical hierarchies based on information theory, in which each level is a near-state-determined system, and levels are related to one another in a partial ordering. This reformulation moves away from previous definitions, which have considered unique hierarchies of structures or objects arranged in aggregates. Instead, we consider hierarchies of dynamical systems: these are more suited to describing living systems, which are not mere aggregates, but organizations. Transformations from lower to higher levels in a hierarchy are redescriptions that lose information. There are two criteria for partial ordering. One is a state-dependence criterion enforcing predictability within a level. The second is a distinctness criterion enforcing the idea that the higher-level description must do more than just throw information away. We hope this will be a useful tool for empirical studies of both computational and physical dynamical hierarchies.

Information Theory↗

PubMed2005

Feasibility and potential clinical utility of goal-directed transthoracic echocardiography performed by noncardiologist intensivists using a small hand-carried device (SonoHeart) in critically ill patients.

OBJECTIVE: This study was designed to assess the clinical applicability of a small, handheld, portable transthoracic echocardiography device by noncardiologist intensivists. DESIGN: Prospective, observational study. After 10 one-hour tutorials, intensivists performed a limited transthoracic echocardiography (TTE) (2-4 views, without Doppler or M-mode) examination with the 5.6-lb SonoHeart Echo System (SonoSite, Bethell, WA) on critically ill patients admitted to the surgical intensive care unit. After initial cardiac clinical assessment in 90 patients, a limited TTE was performed by an intensivist to assess left ventricular (LV) function and LV volume status. Each study was immediately reviewed and repeated by an echocardiographer to determine the technical quality of the TTE and the accuracy of the intensivist's interpretation. Data were analyzed and presented in proportions using descriptive statistics. SETTING: Surgical intensive care unit of an academic medical center. PARTICIPANTS: Ninety critically ill adult patients. INTERVENTIONS: After initial cardiac clinical assessment, a limited TTE was performed by an intensivist to assess LV size and function, to rule out significant pericardial effusions, and to estimate circulatory volume. RESULTS: Intensivists successfully performed a diagnostic limited TTE in 94% of patients and interpreted their studies correctly in 84%. Limited TTE provided new cardiac information and changed management in 37% of patients. TTE added useful information in an additional 47% of patients but did not alter immediate management. The mean "goal-directed TTE" acquisition time was 10.5 +/- 4.2 minutes. CONCLUSION: After a brief formal training in using this handheld echocardiographic system in intensive care unit patients, surgical intensivists successfully performed and correctly interpreted a limited TTE in critically ill patients. Limited TTE provided new information and altered management in a significant number of patients. This study supports incorporating bedside goal-directed, limited TTE into intensivists' training programs.

Adult↗

PubMedDate not supplied

Reliability and validity of the Portage assessment scale for clinical studies of mentally handicapped populations.

The Finnish version of the Portage Assessment Scale was used with 114 aspartylglucosaminuria (AGU) persons aged between 1 and 56 years. Ninety-three persons with AGU were also given psychological tests, mainly SB (Finnish), WISC-R and WPPSI, but also Merrill-Palmer, Bayley, Leiter and WAIS tests. The data also include for the reliability assessment a sample of 30 normal pre-school children. The internal consistency reliability was calculated for the areas of socialization 0.80, language 0.81, self-help 0.73, cognitive 0.70, motor 0.75 and for the whole scale 0.80. The factor analysis produced one very strong factor. The results of the Portage assessment were compared to the developmental levels provided by the tests. Both methods gave almost identical cross-sectional descriptions of the skills of patients with AGU, which was interpreted as providing a cross-validation for Portage in clinical use and to mean that Portage can be used as a reasonable assessment method. The advantages of Portage include easy use by non-psychologists, concrete descriptions of the skills, the 5 areas, and the close relation to rehabilitation.

Acetylglucosamine↗

PubMed2001

Generation, description and storage of dendritic morphology data.

It is generally assumed that the variability of neuronal morphology has an important effect on both the connectivity and the activity of the nervous system, but this effect has not been thoroughly investigated. Neuroanatomical archives represent a crucial tool to explore structure-function relationships in the brain. We are developing computational tools to describe, generate, store and render large sets of three-dimensional neuronal structures in a format that is compact, quantitative, accurate and readily accessible to the neuroscientist. Single-cell neuroanatomy can be characterized quantitatively at several levels. In computer-aided neuronal tracing files, a dendritic tree is described as a series of cylinders, each represented by diameter, spatial coordinates and the connectivity to other cylinders in the tree. This 'Cartesian' description constitutes a completely accurate mapping of dendritic morphology but it bears little intuitive information for the neuroscientist. In contrast, a classical neuroanatomical analysis characterizes neuronal dendrites on the basis of the statistical distributions of morphological parameters, e.g. maximum branching order or bifurcation asymmetry. This description is intuitively more accessible, but it only yields information on the collective anatomy of a group of dendrites, i.e. it is not complete enough to provide a precise 'blueprint' of the original data. We are adopting a third, intermediate level of description, which consists of the algorithmic generation of neuronal structures within a certain morphological class based on a set of 'fundamental', measured parameters. This description is as intuitive as a classical neuroanatomical analysis (parameters have an intuitive interpretation), and as complete as a Cartesian file (the algorithms generate and display complete neurons). The advantages of the algorithmic description of neuronal structure are immense. If an algorithm can measure the values of a handful of parameters from an experimental database and generate virtual neurons whose anatomy is statistically indistinguishable from that of their real counterparts, a great deal of data compression and amplification can be achieved. Data compression results from the quantitative and complete description of thousands of neurons with a handful of statistical distributions of parameters. Data amplification is possible because, from a set of experimental neurons, many more virtual analogues can be generated. This approach could allow one, in principle, to create and store a neuroanatomical database containing data for an entire human brain in a personal computer. We are using two programs, L-NEURON and ARBORVITAE, to investigate systematically the potential of several different algorithms for the generation of virtual neurons. Using these programs, we have generated anatomically plausible virtual neurons for several morphological classes, including guinea pig cerebellar Purkinje cells and cat spinal cord motor neurons. These virtual neurons are stored in an online electronic archive of dendritic morphology. This process highlights the potential and the limitations of the 'computational neuroanatomy' strategy for neuroscience databases.

Algorithms↗

PubMed2004

Advances in surface electromyographic signal simulation with analytical and numerical descriptions of the volume conductor.

Surface electromyographic (EMG) signal modelling is important for signal interpretation, testing of processing algorithms, detection system design and didactic purposes. Various surface EMG signal models have been proposed in the literature. This study focuses on the proposal of a method for modelling surface EMG signals, using either analytical or numerical descriptions of the volume conductor for space-invariant systems, and on the development of advanced models of the volume conductor by numerical approaches, accurately describing the volume conductor geometry and the conductivity, as mainly done in the past, but also the conductivity tensor of the muscle tissue. For volume conductors that are space-invariant in the direction of source propagation, the surface potentials generated by any source can be computed by one-dimensional convolutions, once the volume conductor transfer function has been derived (analytically or numerically). Conversely, more complex volume conductors require a complete numerical approach. In a numerical approach, the conductivity tensor of the muscle tissue should be matched with the fibre orientation. In some cases (e.g. multi-pinnate muscles), accurate description of the conductivity tensor can be very complex. A method for relating the conductivity tensor of the muscle tissue, to be used in a numerical approach, to the curve describing the muscle fibres is presented and applied to investigate representatively a bi-pinnate muscle with rectilinear and curvilinear fibres. The study thus proposes an approach for surface EMG signal simulation in space invariant systems, as well as new models of the volume conductor using numerical methods.

Action Potentials↗

PubMedDate not supplied

Changes in quality-of-life scores in a population of patients treated for squamous cell carcinoma of the head and neck.

BACKGROUND: Quality of life levels fluctuate depending on treatment type and at various points throughout treatment. In patients with advanced head and neck cancer, quality of life is thought to be treatment dependent. The purpose of this study is to compare levels of patients self-reported quality of life across treatment. PATIENTS AND METHODS: Preliminary data presented here are based on 24 patients enrolled so far in an experimental organ-preservation protocol. The two treatment groups consist of one group treated with chemotherapy (paclitaxel and carboplatin) followed by radiation therapy and the second group which is treated with chemotherapy (paclitaxel and carboplatin) followed by surgery and postoperative radiation. Data is collected pretreatment and at uniform points throughout the course of treatment. RESULTS: Preliminary results suggest that quality of life is significantly higher in the nonsurgical group than in the surgical group at the last treatment point reported. Social distress/avoidance is also lower in the nonsurgical group. Because of the small number of patients represented in this study, results should be interpreted with caution and should be viewed as descriptive at this juncture. CONCLUSION: Quality of life seems to be preserved in patients who experience less invasive and disfiguring treatment, and who also have compromised eating and communication abilities. Data collection in this study is ongoing.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1989

Normal stages of cardiac organogenesis in the mouse: II. Development of the internal relief of the heart.

Normal stages of intracardiac development of the mouse heart are illustrated by a collection and analysis of two complementary SEM views, the septal and parietal halves of the right ventricle and conotruncus. These views are particularly suitable for understanding the septation of the outflow tract of the heart. They represent references for the studies of the pathogenesis of conotruncal malformations. The analysis is based on 90 hearts between 11ed and 15ed at intervals of 8 hours with an additional stage at 16ed. They were prepared by perfusion fixation, microdissection, and critical point drying and were examined in SEM. The following main features of the intracardiac morphogenesis were observed: 1) the presence of two spirally positioned conotruncal ridges, their disto-proximal fusion, and the formation of the semilunar valves at their distal part; 2) the trabecular transformation of the conotruncal wall; and 3) the presence of two different interventricular foramina (FIV II and FIV III), with the final closure of FIV III at 14ed16h-15ed. As a result of these observations, our description of the outflow tract septation and its interpretation are different from other conceptions based on mechanisms such as bulbar shift, bulbar absorption, torsions, or transfer of the aorta into the left ventricle.

Animals↗

PubMed2006

Azobenzene as conformational switch in model peptides.

The photoinduced isomerization of azobenzene between the extended (trans) and compact (cis) conformations is reversibly triggered by light of two differing wavelengths. The resulting changes in molecular geometry have been extensively utilized to photoswitch transformations in chemical species reversibly for applications in optoelectronic devises as well as to photocontrol conformational states in (bio)polymers. The high isomerization yield, remarkable photostability and ultrafast kinetics (few ps) of azobenzene are well suited for the design of small, defined model systems that allow detailed folding studies to be carried out both experimentally and theoretically on the same molecules. In our and other laboratories such systems were recently obtained with cyclic peptides of defined conformational preferences as well as with alpha-helical and beta-hairpin peptides. These should, by comparison of simulation and experiment, permit an assessment and improvement of the theoretical description on the one hand and a detailed interpretation of the ultrafast conformational dynamics on the other. The phototriggered changes in conformational states lead to concurrent changes in biophysical properties that can be exploited in the photocontrol of biochemical and biological events, as exemplarily discussed with redox-active cyclic bis-cysteinyl peptides and receptor ligands.

Azo Compounds↗

PubMedDate not supplied

Clinical judgement and information seeking by nurses and physicians working with cancer patients.

This study examined and compared the processes of information collection and clinical judgement by nurses (n=107) and physicians (n=27) working with cancer patients. The data was collected in two university hospitals by means of a computer-simulated case description and the thinking-aloud method. Data interpretation was based on SPSS statistical software and the method of content analysis. Statistical differences between the two groups were tested with non-parametric Kruskal-Wallis Anova or the Mann-Whitney U-test. The Wilcoxon test was applied in pairwise comparisons. Independent questions were analysed by cross-tabulation and Pearson's chi(2). According to the results nurses and physicians apply different approaches to clinical judgement and problem-solving. On the basis of the status statement they received in the program both groups pointed to similar problems and sought a great deal of additional information. However the type of information required was different in the two groups. There were also significant differences in the knowledge base applied for purposes of clinical judgement: nurses tended to rely on personal knowledge, physicians on theory. Physicians were able to identify their patient's major clinical problems, but nurses had more difficulty doing this. On the other hand, nurses took a broader view on the general well-being of patients than physicians did.

Decision Making↗

PubMed1996

A cellular automata model of the heart and its coupling with a qualitative model.

Cellular Automata (CA) models offer a good compromise between computational complexity and biological plausibility while qualitative models have expressive power for explicitly describing dynamic processes. In this paper we present a 2D CA model and its coupling with a qualitative model. The CA model includes elements characterizing muscle, nodal tissue, and bypass conduction. Each element exhibits adaptive properties to cycle length and to the prematurity of incoming impulses. A crude electrocardiogram is also simulated via an equivalent source formulation. Arrhythmias such as the Wenckebach phenomenon, atrial flutter, or extrasystole-triggered tachyarrhythmias can be simulated using relatively simple models when they incorporate the fast conduction system with muscle tissue and when the model elements exhibit adaptive properties. We then illustrate how a CA model can be coupled to a qualitative model to produce a system that combines the fine grained description of CA models with the high level interpretative role of qualitative models.

Adaptation, Physiological↗

PubMed1992

Ocular involvement in acute lymphoblastic leukemia: an echographic study.

We report a case of acute lymphoblastic leukemia (ALL) with ocular involvement in which bilateral swelling of the optic disk head was noticed. Massive direct infiltration of the optic nerve head by leukemic cells can give rise to a clinical picture identical to that of a true papilledema. Ocular echography allowed a better and more complete interpretation of the optic disk involvement. No echographic description of a leukemic infiltration of the optic nerve head has been reported previously.

Adult↗

PubMed1990

Cross-sectional anatomy of the knee.

Frozen knee joints from cadavers were cut into 7 mm slices. The anatomical structures of representative slices were described in detail in order to provide us with information of the topography of the anatomical structures as possible. The detailed description is thought to be helpful for the interpretation of MR images of the knee joint.

Humans↗

PubMed1992

Solvation of beta-lactoglobulin in alkylurea solutions.

Solvation of beta-lactoglobulin in aqueous solutions of urea, methyl-, N,N'-dimethyl- and ethylurea was studied by density measurements. From the densities at constant chemical potential and constant molality, the preferential solvation parameters and the partial specific volumes of beta-lactoglobulin in these solutions were determined. In urea and methylurea solutions urea is preferentially bound, whereas in N,N'-dimethyl- and ethylurea solutions at higher concentration water is preferentially bound. From preferential solvation data and partial specific volumes of protein Gibbs free energies of transfer from water to alkylurea solutions were calculated. Since the enthalpies of transfer were determined previously the entropies of transfer could also be obtained so that a complete thermodynamic description is available. An attempt is made to interpret the values of the thermodynamic quantities in terms of various interactions involved in solvation. In salvation of alkylureas the hydrophobic nature of alkyl groups is clearly reflected.

Journal Article↗

PubMed1996

Interactions of alpha-chymotrypsinogen A with alkylureas.

Solvation of alpha-chymotrypsinogen A (alpha-ctg A) in aqueous urea, methylurea, N,N'-dimethylurea and ethylurea was studied by density measurements. From the densities at constant molality and at constant chemical potential the preferential solvation parameters were determined. In urea and methylurea preferential solvation was observed, whereas in N,N'-dimethylurea and ethylurea at higher concentration water is preferentially bound. From preferential solvation data Gibbs free energy of transfer of alpha-ctg A from water to urea and alkylurea solutions were calculated. Since the enthalpies of transfer were determined previously, the entropies of transfer could also be obtained so that a complete thermodynamic description is available. An attempt is made to interpret the values of the thermodynamic quantities in terms of various interactions involved in solvation as well as to calculate the exchange constant by using the model of weak interactions. In solvation of alkylureas the hydrophobic nature of the alkyl groups is clearly reflected.

Chemical Phenomena↗