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PubMedDate not supplied

Treatment variations on the Epley maneuver for benign paroxysmal positional vertigo.

PURPOSE: To determine if using more head rotation during the Epley maneuver or specific posttreatment instructions for sleeping position would affect treatment effectiveness, compared with the usual maneuver without extra instructions. MATERIALS AND METHODS: Patients with unilateral benign paroxysmal positional vertigo of the posterior semicircular canal were randomized to a standard Epley maneuver group, a group that received an additional 45 degrees head rotation during the maneuver (Augmented Epley), and a group that received instructions about sleeping position after treatment. RESULTS: Posttests from 1 week to 6 months showed no differences in vertigo intensity or frequency or responses to the Dix-Hallpike maneuver. All groups showed significant decreases in vertigo and Dix-Hallpike responses. Some subjects in each group had abnormal pretreatment scores on computerized dynamic posturography. Those subjects in the Augmented Epley group who had abnormal pretreatment posturography scores had significantly better posttreatment scores than those subjects in the Home Instruction group who had abnormal pretreatment scores. All subjects with abnormal responses, however, showed improvement. CONCLUSIONS: Although clinicians continue to give patients home instructions and to use additional head rotation during the maneuver, these variations are not essential for achieving improvement in symptoms.

Adult↗

PubMed2006

A new method for detecting interactions between the senses in event-related potentials.

Event-related potentials (ERPs) can be used in multisensory research to determine the point in time when different senses start to interact, for example, the auditory and the visual system. For this purpose, the ERP to bimodal stimuli (AV) is often compared to the sum of the ERPs to auditory (A) and visual (V) stimuli: AV - (A + V). If the result is non-zero, this is interpreted as an indicator for multisensory interactions. Using this method, several studies have demonstrated auditory-visual interactions as early as 50 ms after stimulus onset. The subtraction requires that A, V, and AV do not contain common activity: This activity would be subtracted twice from one ERP and would, therefore, contaminate the result. In the present study, ERPs to unimodal, bimodal, and trimodal auditory, visual, and tactile stimuli (T) were recorded. We demonstrate that (T + TAV) - (TA + TV) is equivalent to AV - (A + V), but common activity is eliminated because two ERPs are subtracted from two others. With this new comparison technique, the first auditory-visual interaction starts around 80 ms after stimulus onset for the present experimental setting. It is possible to apply the new comparison method to other brain imaging techniques, as well, e.g. functional magnetic resonance imaging.

Adult↗

PubMed2005

Critical thickness of microscopic thin liquid films.

This paper outlines the progress achieved during the four decades of research on the spontaneous destruction of the thinning microscopic liquid films through rupture or black spot formation at the so-called critical thickness. Although most of both experimental and theoretical results are primarily related to the foam films that form between gas bubbles, in many respects they can be principally generalized for emulsion films, as well as the wetting films confined between a bubble and a solid surface. The paper focuses on the validation, application and extension of the theory of the phenomenon. The experimental results are analysed with respect to the frequently observed deviations from the widely used model of a planar circular film with tangentially immobile surfaces. The applicability of the new theory of accelerated drainage due to spatial variation in thickness is expressed. The effects of surface tension, surface mobility, variation of the film size, and spatial thickness heterogeneity on the critical thickness are compared.

Adsorption↗

PubMed2005

Differences in kinematic parameters and plantarflexor reflex responses between manual (Ashworth) and isokinetic mobilisations in spasticity assessment.

OBJECTIVE: The purpose of this study was first to compare the kinematic parameters of imposed ankle mobilizations measured during Ashworth or isokinetic tests and, second, to better understand why the stretch reflex was more or less easily elicited by one method or the other. METHODS: Passive dorsiflexions were applied on eight adult patients with plantarflexor spasticity in two conditions: (i) manually, using the Ashworth test where passive dorsiflexions were performed freely by seven rehabilitation clinicians, and (ii) instrumentally, using an isokinetic device (Cybex Norm) and a dorsiflexion velocity at 300 degrees /s. Mean values of initial ankle position, maximal angular velocity (theta;'(max)), maximal angular acceleration (theta;''(max)) and plantarflexor reflex responses obtained with each method were compared. RESULTS: During the Ashworth test, all the patients presented reflex activities in the triceps surae while, during the isokinetic mobilization, only three out of the eight patients tested shown reflex responses. theta;'(max) values were significantly higher (P<0.05) in the manual test (308+/-80 degrees /s vs 216+/-5.5 degrees /s for the isokinetic test). The most marked difference concerned the theta;''(max) values (5046+/-2181 degrees /s(2) for the Ashworth test vs 819+/-18 degrees /s(2) for the isokinetic test, P<0.001). This parameter was significantly correlated with the mean rms-EMG values of the gastrocnemius lateralis (GL) and the soleus (SOL). CONCLUSIONS: This study indicates that passive dorsiflexions imposed during Ashworth and isokinetic tests largely differ in velocity and acceleration, and the higher dynamic parameters evaluated during the Ashworth test could mainly explain that the stretch reflex was more easily elicited during this manual testing. SIGNIFICANCE: If isokinetic devices offer numerous advantages in the assessment of passive resistance to spastic muscle stretch, they cannot be used to simulate the manual test.

Adult↗

PubMed2004

[Transvaginal ultrasound and voiding disorders after TVT procedure].

OBJECTIVE: This study was carried out to evaluate the ultrasonographic findings on patients with voiding disorders after the tension-free vaginal tape procedure (TVT). PATIENTS AND METHOD: Fifty-four women had ultrasonographic evaluation 3 months after TVT procedure. The prolene tape position was evaluated with a complete sagittal view and the width of the tape and the distance between the bladder neck and the tape were measured. In the same time, patients completely cured by TVT (group 1), postoperative dysuria (group 2), de novo urge incontinence (group 3) and ineffective treatment were evaluated with a self-questionnaire and physical examination. Statistical analysis was performed using ANOVA test. RESULTS: The distance between the tape and the bladder neck shows a significant difference between group 1 and 2 (13.2 mm compared to 7.6 mm) and between group 1 and 3 (13.2 mm compared to 17.7 mm). The width of the tape is significantly different between group 1 and 2 (8.8 mm compared to 6.6 mm) and between group 1 and 3 (8.8 mm compared to 6.5 mm). The distance between the tape and the bladder neck in group 2, compared with group 3, is significantly shorter (7.6 mm compared to 17.7 mm). There is no difference between the width of the tape between groups 2 and 3 (6.6 mm compared to 6.5 mm). DISCUSSION AND CONCLUSION: These results show a correlation between voiding disorders after TVT procedure and transvaginal ultrasonographic measurement of the distance between the prolene tape and the bladder neck.

Aged↗

PubMed2006

Variational free energy and the Laplace approximation.

This note derives the variational free energy under the Laplace approximation, with a focus on accounting for additional model complexity induced by increasing the number of model parameters. This is relevant when using the free energy as an approximation to the log-evidence in Bayesian model averaging and selection. By setting restricted maximum likelihood (ReML) in the larger context of variational learning and expectation maximisation (EM), we show how the ReML objective function can be adjusted to provide an approximation to the log-evidence for a particular model. This means ReML can be used for model selection, specifically to select or compare models with different covariance components. This is useful in the context of hierarchical models because it enables a principled selection of priors that, under simple hyperpriors, can be used for automatic model selection and relevance determination (ARD). Deriving the ReML objective function, from basic variational principles, discloses the simple relationships among Variational Bayes, EM and ReML. Furthermore, we show that EM is formally identical to a full variational treatment when the precisions are linear in the hyperparameters. Finally, we also consider, briefly, dynamic models and how these inform the regularisation of free energy ascent schemes, like EM and ReML.

Bayes Theorem↗

PubMed2006

The effect of elevated blood cortisol levels on the extinction of a conditioned stress response in rainbow trout.

Following previously published observations that a conditioned response (CR) was lost more quickly by rainbow trout (Oncorhynchus mykiss) exhibiting a high responsiveness to stressors than by low responding individuals this study was designed to investigate the effects of exogenous cortisol on the retention of a CR in unselected rainbow trout. Fish held in isolation were conditioned over a 10-day period by pairing an innocuous signal (conditioned stimulus, CS: a water jet played on the surface of the tank water) with a mild stressor (unconditioned stimulus, US: 30 min of confinement). This resulted in a brief elevation of plasma cortisol levels (the CR) when the fish was exposed to the CS only. The effect of exogenous cortisol on the retention of the CR was evaluated by comparing the performance of fish that received cortisol-containing slow-release intraperitoneal implants, with fish receiving vehicle-only implants. Retention of the CR was assessed at intervals up to 35 days after conditioning ceased. The CR was considered to be evident when 30 min following presentation of the CS, mean plasma cortisol levels were significantly higher in conditioned than untrained fish. On day 1 both cortisol-implanted and vehicle-implanted conditioned fish exhibited a CR. However, from day 5 onwards the CR was observed only in the vehicle-implanted and conditioned group. This finding indicates that administration of cortisol accelerated the extinction of the CR in the cortisol-implanted fish, suggesting that elevated plasma cortisol levels can impair memory processes in rainbow trout.

Analysis of Variance↗

PubMed2001

Computerized weight loss intervention optimizes staff time: the clinical and cost results of a controlled clinical trial conducted in a managed care setting.

OBJECTIVE: To evaluate the costs and effects of incremental components of a weight-loss program. DESIGN: A 3-arm, 12-month randomized controlled clinical trial to evaluate 3 incremental levels of intervention intensity. SUBJECTS/SETTING: The study included 588 individuals (BMI > 25 kg/m2) in a freestanding health maintenance organizalion and achieved an 81% completion rate. INTERVENTION: Using a cognitive behavioral approach for tailoring lifestyle modification goals, the incremental levels of intervention included a) a workbook alone, b) the addition of computerized tailoring using onsite computer kiosks with touch screen monitors, and c) the addition of both computers and staff consultation. MAIN OUTCOME MEASURES: Endpoints included weight parameters, lipid profile, plasma glucose, blood pressure, intervention costs, dietary intake, and physical activity. STATISTICAL ANALYSIS PERFORMED: Study endpoints were analyzed using analysis of variance for normally distributed variables and analysis of covariance to control for any baseline differences. Regression and correlation analysis assessed the relationship between weight loss and other variables. RESULTS: For the increasing levels of intervention intensity, the mean 12-month weight losses were 2.2, 4.7, and 7.4 pounds, with the respective cost per participant being $12.33, $41.99, and $133.74. The decreases in mean BMIs for these respective intervelation levels were 0.4, 0.9 and 1.2. All groups reported a decrease in energy and fat intake and an increase in blocks walked (P<.01). Intervention variables that correlated with weight loss included more computer log-ons, achieving computer-selected goals, more self-monitoring, increased walking, and decreased energy and fat intake, as well as higher attendance in staff consultation group sessions for that treatment condition. Weight loss correlated with decreases in fasting glucose and blood pressure. APPLICATIONS/CONCLUSIONS: In a weight-loss program, computers can facilitate selecting behavioral change goals. More frequent usage resulted in greater weight loss. Staff counseling to augment the computer intervention achieved the most weight loss.

Analysis of Variance↗

PubMed1998

Determinants of dietary intake in a sample of white and Mexican-American children.

OBJECTIVE: To assess the influence of several potential psychosocial determinants on children's eating behavior. PARTICIPANTS: Three hundred fifty-one Mexican-American and non-Hispanic white children (mean age = 4.4 years old at baseline) participated in the San Diego Study of Children's Activity and Nutrition for up to 2.5 years. METHODS: Child's eating behavior was described by 3 dependent variables: total energy, percentage energy from fat, and sodium intake per 1,000 kcal. Dietary information was collected 4 days a year using a 24-hour food intake record, which was a combination of direct observation and interviews with food preparers. The 35 predictor variables from child, parental, demographic, and environmental domains were collected by behavioral observation, interviewer-administered questionnaires, and physical measurements. STATISTICAL ANALYSES: Bivariate and regression analyses via mixed linear models were performed. RESULTS: Variables from the children's domain (such as skinfold thickness and weight) had the strongest associations with energy intake; parental variables (such as fat avoidance behavior and prompts to increase children's food intake) were associated with child's percentage energy from fat and sodium intake. In regression analyses, parsimonious subsets of variables accounted for 46% of variance in energy intake (3 variables), 40% of the variance in percentage of energy from fat (4 variables), and 44% of variance in sodium intake per 1,000 kcal energy (1 variable) in between-subject variance components. CONCLUSIONS: Fat and sodium intake of children may be improved by improving parents' nutrition habits and by having parents encourage children to eat a healthful diet. Few modifiable correlates of children's energy intake were identified.

California↗

PubMed2002

Numerical study of the entropy loss of dimerization and the folding thermodynamics of the GCN4 leucine zipper.

A lattice-based model of a protein and the Monte Carlo simulation method are used to calculate the entropy loss of dimerization of the GCN4 leucine zipper. In the representation used, a protein is a sequence of interaction centers arranged on a cubic lattice, with effective interaction potentials that are both of physical and statistical nature. The Monte Carlo simulation method is then used to sample the partition functions of both the monomer and dimer forms as a function of temperature. A method is described to estimate the entropy loss upon dimerization, a quantity that enters the free energy difference between monomer and dimer, and the corresponding dimerization reaction constant. As expected, but contrary to previous numerical studies, we find that the entropy loss of dimerization is a strong function of energy (or temperature), except in the limit of large energies in which the motion of the two dimer chains becomes largely uncorrelated. At the monomer-dimer transition temperature we find that the entropy loss of dimerization is approximately five times smaller than the value that would result from ideal gas statistics, a result that is qualitatively consistent with a recent experimental determination of the entropy loss of dimerization of a synthetic peptide that also forms a two-stranded alpha-helical coiled coil.

Biophysical Phenomena↗

PubMed2000

Kinetic modeling of lactose hydrolysis with an immobilized beta-galactosidase from Kluyveromyces fragilis.

The kinetic model of the hydrolysis of lactose with a beta-galactosidase from Kluyveromyces fragilis immobilized on a commercial silica-alumina (KA-3, from Südchemie) has been determined. A wide experimental range of the main variables has been employed: temperature, concentrations of substrate, and products and concentration of enzyme. The runs were performed in a complex buffer with the salt composition of milk. The effect of pH and temperature on the stability and the activity of the enzyme have been studied. The optimum pH for the enzyme activity was, approximately, seven. The immobilized enzyme was more stable than the free one at acidic pH, but more instable at basic pH. The maximum temperature used for the hydrolysis runs performed to select the kinetic model was 40 degrees C, so inactivation of the enzyme during the kinetic runs has been avoided. Agitation, concentration of enzyme in the solid and particle size were selected to ensure that the overall rate was that of the chemical reaction. Eleven kinetic models were proposed to fit experimental data, from first order to more complex ones, such as those taking into account inhibition by one of the compounds involved in the hydrolysis reaction. Applying statistical and physical criteria, a Michaelis-Menten model with a competitive inhibition by galactose has been selected. The model is able to fit the experimental data correctly in the wide experimental range studied. Finally, the model obtained is compared to the one selected in a previous work for the hydrolysis of lactose with the free enzyme.

Journal Article↗

PubMedDate not supplied

Source separation in astrophysical maps using independent factor analysis.

A microwave sky map results from a combination of signals from various astrophysical sources, such as cosmic microwave background radiation, synchrotron radiation and galactic dust radiation. To derive information about these sources, one needs to separate them from the measured maps on different frequency channels. Our insufficient knowledge of the weights to be given to the individual signals at different frequencies makes this a difficult task. Recent work on the problem led to only limited success due to ignoring the noise and to the lack of a suitable statistical model for the sources. In this paper, we derive the statistical distribution of some source realizations, and check the appropriateness of a Gaussian mixture model for them. A source separation technique, namely, independent factor analysis, has been suggested recently in the literature for Gaussian mixture sources in the presence of noise. This technique employs a three layered neural network architecture which allows a simple, hierarchical treatment of the problem. We modify the algorithm proposed in the literature to accommodate for space-varying noise and test its performance on simulated astrophysical maps. We also compare the performances of an expectation-maximization and a simulated annealing learning algorithm in estimating the mixture matrix and the source model parameters. The problem with expectation-maximization is that it does not ensure global optimization, and thus the choice of the starting point is a critical task. Indeed, we did not succeed to reach good solutions for random initializations of the algorithm. Conversely, our experiments with simulated annealing yielded initialization-independent results. The mixing matrix and the means and coefficients in the source model were estimated with a good accuracy while some of the variances of the components in the mixture model were not estimated satisfactorily.

Astronomy↗

PubMed2004

Decreases in glucocorticoid sensitivity as a factor of stress-producing changes in the activity of monoamine oxidase, lipid peroxidation, and behavior in rats.

Four episodes of immobilization stress induced a decrease in the sensitivity of rats to glucocorticoid hormones, which was accompanied by anxiogenic behavior, increased MAO-B activity, and a parallel increase in lipid peroxidation (LPO) in brain tissues. There was a simultaneous increase in MAO-B activity in the kidneys and accumulation of LPO products in the liver and kidneys. Administration of Kenalog (2 mg/kg), a pharmacological analog of glucocorticoid hormones, prevented the poststress activation of MAO-B and LPO and decreased the extent of anxiogenic behavioral abnormalities in rats.

Animals↗

PubMed2003

Probability analysis for diagnosis of endometrial hyperplasia and cancer in postmenopausal bleeding: an approach for a rational diagnostic workup.

OBJECTIVE: To develop an analytical approach to estimate the probability of endometrial hyperplasia and cancer in women with postmenopausal bleeding, using a combination of patient history and tests. METHODS: A prospectively collected database of 428 postmenopausal women investigated for abnormal uterine bleeding in an outpatient rapid access clinic was used. The probability of disease was estimated using multivariable logistic regression models considering a combination of age and the use of hormone replacement therapy (HRT) and tests (ultrasound and hysteroscopy) in keeping with the actual clinical process. RESULTS: The prevalence or prior probability of endometrial cancer in the sample studied was 4.4%. Hysteroscopy alone performed better than ultrasound alone. In all patients, a negative hysteroscopy reduced the probability of cancer to 1.3%. In women less than 60 years of age who use HRT, a negative hysteroscopy further reduced this probability to 0.1%. Overall, a positive hysteroscopy raised the probability of cancer to 38.9%. However, in women over 60 years of age not using HRT, a positive hysteroscopy increased this probability to 59.4%. Combining ultrasound results with hysteroscopy did not meaningfully alter the diagnostic probability. CONCLUSION: The combination of information obtained from patient history and tests allows generation of specific disease probabilities in postmenopausal bleeding. This type of multivariable analysis puts diagnostic information gained from history and other tests into a perspective that reflects actual clinical practice.

Databases, Factual↗

PubMed2003

Correlations between small aperture skin suction parameters: statistical analysis and mechanical model.

BACKGROUND/AIMS: Skin suction experiments are widely used in order to evaluate the effects of skin treatments, both for cosmetic and for dermatological purposes. Classically, the elevation of the skin is measured at different discrete time instances after the pressure has been changed. Relations between the classical parameters - Uv, Ur, Ue and Uf - have been investigated and used in order to develop a new model for interpreting the mechanical properties of the skin. METHODS: Within a group of 68 female subjects - aged between 37 and 68 - a Cutometer has been used in order to determine classical skin suction parameters on the female facial skin. Each skin suction measurement consists of three consecutive underpressure cycles. Within the resulting parameter set, a statistical analysis has been performed to investigate interparameter relations. RESULTS: Strong interparameter correlations have been found within a set of 12 classical skin suction parameters. The set contains three independent groups of interrelated parameters. Based on this observation, a one-dimensional mechanical model - consisting of springs and dampers - is constructed. When two extra independent parameters are included in the model, the elevation versus time curves as recorded during three consecutive underpressure cycles can be fully described. The model reveals that typical skin suction data can be described in terms of a quick and a slow deformation process. The two characteristic time scales are 0.1 and 7 s approximately. The 0.1 s-value matches the response time of the device used. In reality, the quick deformation process in the skin may have a shorter time scale. CONCLUSIONS: In skin suction data, each underpressure cycle is usually characterized by four classical parameters - Uv, Ur, Ue and Uf. Within the 12 parameters of a three-cycle measurement, three independent groups of interrelated parameters have been found. These groups can be represented by the parameters Uv1, Ur1 and Uf1 of the first underpressure cycle. A model that is based on these three independent groups and two other independent parameters is proposed. The model provides an accurate description of the skin deformation as recorded during a measurement involving three underpressure cycles. The model is an improvement over classical interpretations of skin suction data where interrelated parameters are used. Moreover, the five-parameter model accounts for well-known mechanical characteristics of the skin such as preconditioning and visco-elastic behavior.

Adaptation, Physiological↗

PubMed1981

Visual detection of multi-letter patterns.

This study addressed two basic questions about the detection of multi-letter patterns: (a) How is the detection of a multi-letter pattern related to the detection of its individual components? (b) How is the detection of a sequence of letters influenced by the observer's familiarity with that sequence? In three experiments observers searched for one-, two-, or three letter patterns embedded in a rapid series of multiple six-letter frames. In Experiment 1, unfamiliar two-letter patterns were detected more accurately than their one-letter components. This two-letter advantage reflects the fact that in an array of fixed size, larger target stimuli contain more information and are easier to discriminate from nontarget alternatives. Quantitative analyses indicated that observers combine information not decisions, about the component letters in a pattern. In Experiment 2, with statistical and physical properties equated, a familiar three-letter pattern (i.e., CAT) was detected more accurately than its unfamiliar anagram (i.e., TCA). This word advantage in word (not letter) detection persisted even after extensive practice and was uninfluenced by the lexical character of distractor items. In Experiment 3, words (e.g., FIB), pronounceable non words (e.g., FIF(, and familiar acronyms (e.g., FBI) were detected more readily than unfamiliar items (e.g., IBF). Thus both orthographic knowledge and familiarity with specific sequences can facilitate perceptual processing in "word" detection.

Cognition↗

PubMed2005

Increased vulnerability to stress following opiate exposures: behavioral and autonomic correlates.

The authors used rats to study the impact of a history of opiate exposures on behavioral and autonomic responses to restraint stress. Brief restraint (30 min) provoked tachycardia and a pressor response, anxiety (as indexed by social interaction), grooming, and reduced exploration. The pressor response was reduced at 1 day, but not 7 days, after last opiate exposure; tachycardia was unaffected (Experiment 1). Stress-induced anxiety was potentiated 1 and 7 days after last opiate exposure (Experiment 2), and this potentiation was a function of dose (Experiment 3) and duration (Experiment 4) of opiate exposure. The results show that a history of opiate exposures alters vulnerability to stress and has implications for understanding coping, anxiety, and emotionality in former opiate users.

Analgesics, Opioid↗

PubMed2000

Testosterone and leptin in older African-American men: relationship to age, strength, function, and season.

Testosterone (T) and bioavailable testosterone (BT) levels have been shown to decline with aging in Caucasian males. We are unaware of any studies that have examined this in African-American men. Previous studies have suggested a relationship of T to strength and leptin levels, but no such correlation with measured functional tests exists. This study explores these associations in a cross-sectional sample of older African-Americans from the Saint Louis University Inner City Aging Project. The participants were 65 African-American males aged 70 to 102 years. Measurements included T, BT, and leptin levels, isometric muscle strength, and relevant physical impairments. Statistical analysis included a t test and simple and multiple ordinary least-squares regression. Age was inversely related to T and BT. Of these older African-American males, 90.7% had a BT value less than the normal range for young males. T correlated with upper- and lower-limb strength and functional tests. Leptin was correlated with the body mass index (BMI) and inversely with T, but not with BT. Circannual rhythms for T, BT, and leptin were present. This study demonstrates for the first time an age-related decrease in T and BT in African-Americans and a circannual rhythm for leptin. T was correlated with upper- and lower-limb strength and functional status.

Aged↗