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Results for “interaction frequencies”

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PubMedDate not supplied

The effects of occupational therapy with sensory integration emphasis on preschool-age children with autism.

OBJECTIVE: Using single-subject research design, the effects of an occupational therapy intervention emphasizing sensory integration with five preschool children with autism were examined. METHOD: In the AB design, nonengagement, mastery play, and interaction were measured, using videotape clips of each child's free play in the preschool. Following a 3-week baseline, an occupational therapist provided one-on-one sessions and consultation to teachers for 10 weeks. RESULTS: When baseline and intervention phases were compared, four children demonstrated decreased frequency of nonengaged behavior, and three demonstrated increased frequency of mastery (goal-directed) play. Improvements in frequency of interaction were minimal. CONCLUSION: The results support descriptions in the literature regarding the behavioral changes that children with autism can make when participating in intervention using a sensory integration approach.

Attention↗

PubMed1972

Parametric effects of reinforcement frequency, amount of reinforcement, and required response force on sheltered workshop behavior.

Three experiments involving parametric manipulation of reinforcement contingencies were performed with retardates in an automated Sheltered Workshop token economy. Experiment I showed that with amount of reinforcement held constant, work rates were positively related to reinforcement rates on fixed-interval schedules and inversely related to reinforcement rates on fixed-ratio schedules. Experiment II demonstrated an interaction between frequency of ratio reinforcement and torque required to complete a work unit: work rates were positively related to reinforcement rates when required response force was high and negatively related to reinforcement rates when required response force was low. Experiment III revealed that, with reinforcement frequency held constant, there was in inverse relationship between amount of reinforcement and work rate.

Journal Article↗

PubMed1999

Neuronavigation in intraoperative MRI.

OBJECTIVE: We describe the development and implementation of an image-guided surgical system combining the best features of conventional frameless stereotactic systems and the recently developed superconductive vertically configured intraoperative magnetic resonance scanner. The incorporation of intraoperatively updated magnetic resonance imaging (MRI) data sets into the neuronavigation computer overcomes one of the main disadvantages of these systems, i.e., intraoperative brain shift. METHODS: The integrated system consists of a 0.5-T MRI scanner (Signa SP General Electric Medical Systems, Milwaukee, WI), a neuronavigation computer with associated software (OTS Radionics, Burlington, MA), and an emulation program linking the two. The scanner has a 60-cm-wide vertical gap where both imaging and surgery are conducted, in-bore infrared linear cameras and monitors for interactive surgical neuronavigation, and flexible surface coils specially designed for surgery. RESULTS: Phantom studies showed navigational accuracy to be better than that obtained using conventional preoperative images and surface markers for patient registration. Our initial 17 cases using this integrated system comprised 16 craniotomies and one biopsy, and demonstrated decreased operative duration, greater frequency of interactive image guidance utilization, and better assessment of the progress of surgery compared to the cases previously done in the intraoperative MRI. CONCLUSION: This initial study of the addition of frameless stereotactic systems to the basic intraoperative MRI concept has demonstrated its clinical usefulness. The use of the intraoperative MRI greatly reduces the basic weakness of neuronavigation inaccuracy due to target shift. The surgical procedure performed in the imaging volume of the MRI scanner eliminates the problems of patient or scanner transport during the procedure. Immobilization of the patient throughout the procedure eliminated the need for reregistration of the patient, by taking advantage of the fixed camera system in the bore of the MRI system.

Adult↗

PubMed1996

Wavelet formation in excitable cardiac tissue: the role of wavefront-obstacle interactions in initiating high-frequency fibrillatory-like arrhythmias.

High-frequency arrhythmias leading to fibrillation are often associated with the presence of inhomogeneities (obstacles) in cardiac tissue and reduced excitability of cardiac cells. Studies of antiarrhythmic drugs in patients surviving myocardial infarction revealed an increased rate of sudden cardiac death compared with untreated patients. These drugs block the cardiac sodium channel, thereby reducing excitability, which may alter wavefront-obstacle interactions. In diseased atrial tissue, excitability is reduced by diminished sodium channel availability secondary to depolarized rest potentials and cellular decoupling secondary to intercellular fibrosis. Excitability can also be reduced by incomplete recovery between successive excitations. In all of these cases, wavefront-obstacle interactions in a poorly excitable medium may reflect an arrhythmogenic process that permits formation of reentrant wavelets leading to flutter, fibrillation, and sudden cardiac death. To probe the relationship between excitability and arrhythmogenesis, we explored conditions for new wavelet formation after collision of a plane wave with an obstacle in an otherwise homogeneous excitable medium. Formulating our approach in terms of the balance between charge available in the wavefront and the excitation charge requirements of adjacent medium, we found analytically the critical medium parameters that defined conditions for wavefront-obstacle separation. Under these conditions, when a parent wavefront collided with a primitive obstacle, the resultant fragments separated from the obstacle boundaries, subsequently curled, and spawned new "daughter" wavelets. We identified spatial arrangements of obstacles such that wavefront-obstacle collisions leading to spawning of new wavelets could produce high-frequency wavelet trains similar to fibrillation-like arrhythmias.

Animals↗

PubMed1997

Circulating antibodies against nicotinic acetylcholine receptors in chagasic patients.

Human and experimental Chagas' disease causes peripheral nervous system damage involving neuromuscular transmission alterations at the neuromuscular junction. Additionally, autoantibodies directed to peripheral nerves and sarcolemmal proteins of skeletal muscle have been described. In this work, we analyse the ability of serum immunoglobulin factors associated with human chagasic infection to bind the affinity-purified nicotinic acetylcholine receptor (nAChR) from electric organs of Discopyge tschudii and to identify the receptor subunits involved in the interaction. The frequency of serum anti-nAChR reactivity assayed by dot-blot was higher in seropositive chagasic patients than in uninfected subjects. Purified IgG obtained from chagasic patients immunoprecipitated a significantly higher fraction of the solubilized nAChR than normal IgG. Furthermore, immunoblotting assays indicated that alpha and beta are the main subunits involved in the interaction. Chagasic IgG was able to inhibit the binding of alpha-bungarotoxin to the receptor in a concentration-dependent manner, confirming the contribution of the alpha-subunit in the autoantibody-receptor interaction. The presence of anti-nAChR antibodies was detected in 73% of chagasic patients with impairment of neuromuscular transmission in conventional electromyographical studies, indicating a strong association between seropositive reactivity against nAChR and electromyographical abnormalities in chagasic patients. The chronic binding of these autoantibodies to the nAChR could induce a decrease in the population of functional nAChRs at the neuromuscular junction and consequently contribute to the electrophysiological neuromuscular alterations described in the course of chronic Chagas' disease.

Autoantibodies↗

PubMed1990

Mathematical models of HIV infection. I. Threshold conditions for transmission and host survival.

This is the second in a series of papers modeling human immunodeficiency virus (HIV) infections at four levels: transmission, interaction with the immune system, gene regulation, and selection of mutants. In the previous paper (1) we described and presented a theory of the HIV cytopathic effect based upon the models (and a review of the literature). In this article we give mathematical equations of threshold conditions that connect infectivity, length of host survival, and frequency of acts conducive to transmission. The formula is derived not only for homogeneous populations but also for populations of an arbitrary number of subgroups with varying frequencies of risk behavior, varying rates of infection and latency periods, and varying frequencies of interaction with other groups.

Cytopathogenic Effect, Viral↗

PubMed2002

Interaction between excitation and inhibition affects frequency tuning curve, response size and latency of neurons in the auditory cortex of the big brown bat, Eptesicus fuscus.

Neurons in the auditory cortex (AC) receive convergent excitatory and inhibitory inputs from the lower auditory nuclei. Interaction between these two opposing inputs shapes different response properties of AC neurons. In this study, we examined how this interaction might affect the frequency tuning curves (FTCs), number of impulses and latency of AC neurons in the big brown bat, Eptesicus fuscus, using a probe (excitatory tone) and a masker (inhibitory tone) under different stimulation conditions. Excitatory FTCs of AC neurons were either V-shaped, closed (i.e. upper threshold) or double-peaked. Inhibitory FTCs were obtained either at both flanks or only at the low or high flank of excitatory FTCs. Application of bicuculline, an antagonist for gamma-aminobutyric acid A receptors, produced expansion of excitatory FTCs into predrug inhibitory FTCs. Inhibition of probe-elicited responses occurred when a masker was presented at certain intertone intervals. Maximal inhibition typically took place when a masker was presented within 4 ms prior to the probe. During maximal inhibition, a neuron had the minimal number of impulses and the longest response latency. Inhibition became stronger with increasing masker intensity but became weaker with increasing intertone interval. Biological significance of these data is discussed.

Acoustic Stimulation↗

PubMed1996

Dietary calcium, alcohol, and incidence of treated hypertension in the NHANES I epidemiologic follow-up study.

Evidence concerning the relation between dietary calcium intake and development of hypertension is inconsistent. Some of this inconsistency may be due to interaction of this relation with other factors. The current study was designed to test for an interaction between alcohol consumption and the relation of dietary calcium intake to 10-year incidence of hypertension in a sample of the US adult population: the Epidemiologic Follow-up Study (1982-1984) of the First National Health and Nutrition Examination Survey (NHANES I) (1971-1975). Interactive logistic regression models were estimated with incident hypertension defined as self-reported treatment with antihypertensive medication. After exclusion of participants with evidence of hypertension at baseline (resulting n = 6,634), odds ratios for hypertension were estimated for each 1-g/day increase in calcium intake. The relation between dietary calcium and incident hypertension showed significant interactions with frequency of alcohol use (odds ratio (OR) = 1.33 for daily drinkers, OR = 0.84 for others; p = 0.005 for difference), age (OR = 0.75 for < or = 40 years at baseline, OR = 1.00 for > 40 years; p = 0.004), and body mass index, defined as weight (kg) divided by height (m) squared (OR = 0.82 for < or = 26, OR = 1.01 for > 26; p = 0.018). Interactions with sex and race (black vs. white) were not significant (p > or = 0.4). These findings suggest that a protective effect of foods containing calcium on the risk of developing hypertension may vary across levels of alcohol consumption and other risk factors for hypertension.

Adult↗

PubMed1981

Staff performance: do attitudinal "effectiveness profiles" really assess it?

Performance differences were examined for mental hospital staff with divergent profiles on the Opinions About Mental Illness (OMI) that have been purported to reflect differential staff effectiveness. Two staff groups (N = 40 each) were selected, in pairs, from 19 treatment programs serving adult mental patients to provide extremes of "OMI-effective" vs. "OMI-ineffective" profiles while equating groups on demographic, experiential, and program characteristics that had previously been found to influence OMI scores or staff performance. Actual on-the-floor performance was assessed by direct hourly observations obtained on the Staff-Resident Interaction Chronograph over a full week in each program. The OMI effective group was found to perform greater amounts of overall activity and greater amounts of interaction with institutionalized residents than did the OMI-ineffective group. These differences in public job-relevant activity, likely, provide the basis for earlier reports of positive evaluations for staff who score in the OMI-effective direction. However, the groups did not differ in the specified nature and pattern of their staff-resident interactions when the overall rate of interactions was controlled. Such differences would be required for the OMI to be a measure of staff effectiveness in improving resident functioning. These results, in combination with previous studies, provide little support for the OMI as a measure of effectiveness or as an indirect measure of the goodness of staff performance. The OMI effective group did produce a higher frequency of interactions, and, thus, the OMI appears to serve as a useful descriptor of staff characteristics that might interact with other variables influencing effectiveness; but the absence of discrimination regarding the more crucial specific nature of interactions indicates that the OMI cannot substitute for direct assessment of actual staff performance.

Adult↗

PubMed1998

Optical recording of responses to frequency-modulated sounds in the auditory cortex.

Using an optical recording method with a voltage-sensitive dye, we recorded activities in the primary auditory cortex (AI) of anesthetized guinea pigs in response to frequency-modulated (FM) sounds and sounds with stepwise changes in frequency (SF). Responses to the FM sound showed a spatiotemporal pattern in which a localized active spot traversed the isofrequency bands in the AI, and they differed from the band-like responses to the SF sound. These results indicate that time-varying sounds are represented as spatiotemporal activation of tonotopic organization in the AI by spectral cues with interactions between frequency bands.

Acoustic Stimulation↗

PubMed2003

Alternative interpretation of the sign reversal of secondary Bjerknes force acting between two pulsating gas bubbles.

It is known that in a certain case, the secondary Bjerknes force (which is a radiation force acting between pulsating bubbles) changes, e.g., from attraction to repulsion, as the bubbles approach each other. In this paper, a theoretical discussion of this phenomenon for two spherical bubbles is described. The present theory based on analysis of the transition frequencies of interacting bubbles [M. Ida, Phys. Lett. A 297, 210 (2002)] provides an interpretation, different from previous ones (e.g., by Doinikov and Zavtrak [Phys. Fluids 7, 1923 (1995)]), of the phenomenon. It is shown, for example, that the reversal that occurs when one bubble is smaller and the other is larger than a resonance size is due to the second-highest transition frequency of the smaller bubble, which cannot be obtained using traditional natural-frequency analysis.

Journal Article↗

PubMed1999

Saccade selection in visual search: evidence for spatial frequency specific between-item interactions.

We present two experiments in which subjects were required to make a saccade to a target amongst distractors. Targets were oriented Gabor patches. Analysis of errors, when subjects fail to make a saccade to the target, showed two interesting features. First, most error saccades were directed towards a distractor and not to the blank space between distractors. This suggests that although the location of the target may not be encoded correctly, the locations of the items in the display are encoded. Second, when the display items were all of the same spatial frequency, a long-range effect occurred whereby the likelihood of an error saccade in a specific direction decreased systematically as the distance from the target increases. This systematic influence of the target location extended over practically the whole display. The long-range effect appeared whenever all display items had the same spatial frequency and showed little dependence on the spatial frequency of the display items. However, when the items had different spatial frequencies the long-range effects were absent.

Humans↗

PubMed1995

Voltage- and frequency-dependent pentobarbital suppression of brain and muscle sodium channels expressed in a mammalian cell line.

The voltage- and frequency-dependent interactions of pentobarbital with voltage-gated sodium channels were examined in whole-cell patch-clamp recordings. Using rat brain IIA and rat muscle rSkM1 sodium channels expressed in stably transfected Chinese hamster ovary cell lines, it was found that pentobarbital reduced peak inward sodium currents with IC50 values of 1.2 mM (brain) and 1.0 mM (muscle). Analysis of steady state channel availability curves revealed two distinct effects of pentobarbital on both channel isoforms, i.e., a voltage-independent current reduction and an additional hyperpolarizing shift in the voltage dependence of channel availability. The latter effect leads to a voltage dependence of pentobarbital potency. Pentobarbital was also found to slow channel recovery after depolarization, yielding an additional use-dependent component of current suppression. Use-dependent block was enhanced by higher stimulation frequencies, longer pulse durations, and more depolarized holding and pulse potentials. All effects were identical for both channels. These findings can be explained in terms of the modulated receptor hypothesis and are consistent with a preferential interaction of pentobarbital with the inactivated channel state. As a consequence, actual pentobarbital potency would depend largely on experimental conditions or, in vivo, on the physiological parameters of a particular cell.

Animals↗

PubMed1990

Temperature-dependent conformational changes in the bacteriopheophytins of Rhodobacter sphaeroides reaction centers.

Resonance Raman (RR) spectra are reported for the photosynthetic reaction center (RC) protein from Rhodobacter sphaeroides 2.4.1. The spectra were obtained with a variety of excitation wavelengths, spanning the UV, violet, and yellow-green regions of the absorption spectrum, and at a number of temperatures ranging from 30 to 270 K. The RR data indicate that the frequencies of certain vibrational modes of the bacteriochlorin pigments in the RC shift with temperature. These shifts are reversible and do not depend on external factors such as solvent or detergent. The acetyl carbonyl bands exhibit the largest shifts with temperature. These shifts are attributed to thermal effects involving the torsional vibrations of the acetyl groups of several (or all) of the bacteriochlorins rather than to specific pigment-protein interactions. The frequency of the structure-sensitive skeletal mode near 1610 cm-1 of one of the two bacteriopheophytins (BPhs) in the RC is also sensitive to temperature. In contrast, no temperature sensitivity is observed for the analogous modes of the bacteriochlorophylls or other BPhs. Over the range 160-100 K, the skeletal mode of the BPh upshifts by approximately 4 cm-1. This upshift is attributed to a flattening of the macrocycle at low temperatures. It is suggested that the BPh active in the electron-transfer process is the pigment whose structure is temperature dependent. It is further suggested that such structural changes could be responsible in part for the temperature dependence of the electron-transfer rates in photosynthetic RCs.

Bacterial Proteins↗

PubMed2004

A theoretical study of F0-F1 interaction with application to resonant speaking and singing voice.

An interactive source-filter system, consisting of a three-mass body-cover model of the vocal folds and a wave reflection model of the vocal tract, was used to test the dependence of vocal fold vibration on the vocal tract. The degree of interaction is governed by the epilarynx tube, which raises the vocal tract impedance to match the impedance of the glottis. The key component of the impedance is inertive reactance. Whenever there is inertive reactance, the vocal tract assists the vocal folds in vibration. The amplitude of vibration and the glottal flow can more than double, and the oral radiated power can increase up to 10 dB. As F0 approaches F1, the first formant frequency, the interactive source-filter system loses its advantage (because inertive reactance changes to compliant reactance) and the noninteractive system produces greater vocal output. Thus, from a voice training and control standpoint, there may be reasons to operate the system in either interactive and noninteractive modes. The harmonics 2F0 and 3F0 can also benefit from being positioned slightly below F1.

Humans↗

PubMed2005

The influence of social relations on mortality in later life: a study on elderly Danish twins.

PURPOSE: We examined whether the presence of a spouse and the frequency of interaction with children, relatives, and friends significantly influence the risk of dying in late life. We assessed these effects separately by gender, controlling for self-reported health. In addition, we examined whether interaction with the co-twin has a different impact on mortality for identical and fraternal twins. DESIGN AND METHODS: The data set consists of 2,147 Danish twins aged 75 years and older, who were followed prospectively from 1995 to 2001. We modeled the effect of social ties on mortality by using event history analysis. RESULTS: Survival is extended by having a spouse and close ties with friends and the co-twin. However, contact frequency with friends and the co-twin is significant, respectively, only for women and identical twins. IMPLICATIONS: Investigating social relations sheds light on the life span of individuals older than 75 years of age. We stress the importance of social relations beyond the presence of the spouse for survival even at very old ages.

Aged↗

PubMed2004

Solvent effects on infrared spectra of methyl 4-hydroxybenzoate in pure organic solvents and in ethanol/CCl4 binary solvents.

Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents.

Alcohols↗

PubMedDate not supplied

Selecting nonsteroidal anti-inflammatory drugs: pharmacologic and clinical considerations.

An increasing number of nonsteroidal anti-inflammatory drugs (NSAIDs) are available to treat a variety of conditions. There exist little comparative data examining efficacy for all NSAIDs for a particular illness. The major factors governing selection of these agents relate to the patient's condition and the drug's characteristics. Once efficacy has been established, selection of an NSAID is then determined by side-effect profile, potential for drug interactions, dosing frequency, and cost. This review presents a listing of commercially available NSAIDs, cost comparisons for average daily doses of NSAIDs, and the conditions and drug characteristics that might influence the choice of an NSAID.

Anti-Inflammatory Agents, Non-Steroidal↗