A new application of sequence Fourier analysis to specific ligand-protein interactions.
A frequency (or sequence)-dependent rule seems to be conserved in a simple and concerted interaction of various human proteins.
Fourier Analysis↗
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Additive and interactive effects of word frequency and masked repetition in the lexical decision task.
In previous studies, additive effects of masked repetition and word frequency on lexical decision latency have been reported. This additive pattern was replicated in Experiment 1 with the use of low-frequency words (range, 1-7 per million) selected at random. In contrast, in Experiment 2, in which low-frequency words known to be familiar to the subjects were used, the masked repetition priming effect was greater for low-frequency than for high-frequency words. It is suggested that the absence of an interaction between masked repetition and frequency observed in previous studies and in the present Experiment 1 was due to the fact that very-low-frequency words often have an unstable representation in the subjects' lexicon and, consequently, sometimes fail to produce repetition priming effects in full.
Decision Making↗
[Interaction of prescribed drugs in a population over 65 years of age].
OBJECTIVE: To assess the prevalence and the types of drug to drug interactions in a population 65 years and over and to identify the factors associated to the occurrence of interactions. DESIGN: Cross sectional study ("Aging in Leganés"), a community survey. SETTING: Community level. Leganés (Madrid). PATIENTS AND OTHER PARTICIPANTS: People 65 years and over (n = 1284, response rate 83%). MEASUREMENTS AND MAIN RESULTS: Information on use of health services and medication use was collected through home interviews. Drugs were classified by its active components and into therapeutic categories. Drug to drug interactions were identified using Hansten's classification. Bivariate and multivariate analysis were carried out to identify factors associated to the frequency of interactions. RESULTS: The prevalence of drug to drug interactions was estimated as 13.6%. Interactions of clinical significance occurred in 9.9% of the population 65 and over. Hypertension, diabetes, Parkinson and cardiovascular diseases are significatively associated to interactions. The number of visits to the specialists was a risk factor (OR = 2.1 for those with five or more visits), after controlling for specific chronic conditions. Contacts with primary care, age and sex of the elderly were not associated to the frequency of interactions. DISCUSSION: The frequency of interactions is associated to preventable factors. Improvements in the communication between specialists and primary care and cooperation with pharmacists could result in better monitoring of medication use in the elderly.
Aged↗
[The interaction of rabbit neocortical neurons during natural feeding motivation].
Interaction between neurons in the visual and sensorimotor, visual and frontal cortical areas of both brain hemispheres was studied by means of cross- and autocorrelation histogram analysis in fed up and hungry rabbits after daily food deprivation. In hungry rabbits as compared with fed up ones the total number of neurons with correlated activity was higher (43 +/- 3 and 32 +/- 3%, respectively), the number of neuronal pairs with the frequency of interaction in the theta-range was higher, and that with interaction frequency in the alpha-range was lower. Interhemispheric asymmetry in correlation between the visual and sensorimotor neurons was observed in hungry animals. Most expressed changes were observed in the left hemisphere, where increase in the number of neuronal pairs with correlated activity was the highest and certain order of neuronal activity dominated, i.e., discharges of the sensorimotor neurons were up to 120 msec ahead of those of the visual ones.
Action Potentials↗
A consistent set of statistical potentials for quantifying local side-chain and backbone interactions.
The frequencies of occurrence of atom arrangements in high-resolution protein structures provide some of the most accurate quantitative measures of interaction energies in proteins. In this report we extend our development of a consistent set of statistical potentials for quantifying local interactions between side-chains and the polypeptide backbone, as well as nearby side-chains. Starting with phi/psi/chi1 propensities that select for optimal interactions of the 20 amino acid side-chains with the 2 flanking peptide bonds, the following 3 new terms are added: (1) a distance-dependent interaction between the side-chain at i and the carbonyl oxygens and amide protons of the peptide units at i +/- 2, i +/- 3, and i +/- 4; (2) a distance-dependent interaction between the side-chain at position i and side-chains at positions i + 1 through i + 4; and (3) an orientation-dependent interaction between the side-chain at position i and side-chains at i + 1 through i + 4. The relative strengths of these 4 pseudo free energy terms are estimated by the average information content of each scoring matrix and by assessing their performance in a simple fragment threading test. They vary from -0.4 - -0.5 kcal/mole per residue for phi/psi/chi1 propensities to a range of -0.15 - -0.6 kcal/mole per residue for each of the other 3 terms. The combined energy function, containing no interactions between atoms more than 4 residues apart, identifies the correct structural fragment for randomly selected 15 mers over 40% of the time, after searching through 232,000 alternative conformations. For 14 out of 20 sets of all-atom Rosetta decoys analyzed, the native structure has a combined score lower than any of the 1700-1900 decoy conformations. The ability of this energy function to detect energetically important details of local structure is demonstrated by its power to distinguish high-resolution crystal structures from NMR solution structures.
Amino Acids↗
Spelling-sound regularity effects on eye fixations in reading.
An interaction of word frequency and word regularity has typically been observed in naming and lexical decision experiments in which, in addition to an overall effect of word frequency, responses to low-frequency exception words are slower than those to low-frequency regular words, while no such difference occurs with high-frequency words. The only eye movement study to examine this effect in reading (Inhoff & Topolski, 1994) reported only transient effects of regularity. In the present experiment, we examined the frequency x regularity interaction using different stimuli than those of Inhoff and Topolski and also varied the parafoveal preview of the target word prior to fixation. When the preview was valid, the frequency x regularity interaction appeared. However, with an invalid preview, the effect of regularity disappeared. The results suggest that the activation of phonological codes is a very early component of reading.
Adult↗
Frequency modulation of neuronal theta-bursts in rabbit's septum by low-frequency repetitive stimulation of the afferent pathways.
Activity of the neurons with stable theta-bursts was recorded extracellularly in intact and hippocampectomized septum of unanesthetized chronic rabbits during low-frequency (3-17 Hz) stimulation of horizontal limb of diagonal band or lateral septal nucleus. The stimulation rarely evoked standard oligosynaptic single-spike responses in stable theta-bursting units. Instead, gradual entrainment and phase-locking of the spontaneous theta-cycles occurred. Two types of entrainment were observed: "entrainment by the pause", where interburst interval was reset by the stimuli; and "entrainment by the burst", where bursts were time-locked to the stimuli. Such reorganization of the spontaneous bursts occurred in the narrow frequency range of stimulation (from 4 Hz up to 9-12 Hz), with the best resonance following in the range of "basic" theta frequencies of the awake rabbit (5-6 Hz). With stimulation beyond the theta-range three phenomena occurred: shift of the burst frequencies to higher or lower harmonics of stimulation frequencies; complex interactions of basic background frequency with rhythm of stimulation ("beating"); return to background theta-burst frequency in spite of continuing stimulation ("escape"). The properties of the septal theta-bursting cells as presumable intrinsic bursting pacemakers are discussed.
Afferent Pathways↗
Resident-directed communication patterns in community homes for persons with disabilities.
A descriptive assessment of environmental variables influencing patterns of staff communication with people living in three community-based residential facilities supporting persons with disabilities was presented. Each of the 16 participating staff persons was observed for 2 hours, and all resident-directed communication behaviors were coded according to staff person, activity context, and resident. Statistical analyses were performed examining frequencies of interaction across these variables. Frequencies of communication were found to differ across activities and residents (communicative partners), but not staff persons or homes. Directions for future research and clinical implications are given, including the development of a model of staff performance and the creation of self-reinforcing social communities in residential settings for persons with disabilities.
Activities of Daily Living↗
The effect of feature frequency on short-term recognition memory.
We report two experiments using Sternberg's (1969) multitrial recognition-memory paradigm. We used colored shapes as stimuli and manipulated the frequency of the shapes (but not of the colors) across trials. For lures containing an extralist shape (i.e., a shape not studied in the current study list), responses were faster if the shape had occurred infrequently than if it had occurred frequently in the preceding trials. For lures containing an extralist color and a studied shape, by contrast, the frequency of the shape in the preceding trials was irrelevant. We conclude that correct rejections depend solely on contradictory evidence. Furthermore, low-frequency target items were recognized more easily than high-frequency targets. Both the interaction of frequency with the features of the lures and the main effect of frequency for the targets are problematic for current accounts of recognition.
Form Perception↗
[Frequency modulation of theta volleys of septal neurons during rhythmic oligosynaptic stimulation in the rabbit].
Activity of the neurones with stable theta-bursts was recorded extracellularly in intact and hippocampectomized septum of unanaesthetized chronic rabbits during low-frequency (3-17 Hz) stimulation of horizontal limb of the diagonal band or the lateral septal nucleus. Gradual entrainment and phase-locking of the spontaneous theta-cycles occurred. Two types of entrainment were observed: "entrainment by pause", where interburst interval was reset by the stimuli; and "entrainment by burst", where bursts were time-locked to the stimuli. Such reorganization of the spontaneous bursts occurred in a narrow frequency range of stimulation (from 4 Hz up to 9-12 Hz), with the best resonance following in the range of "basic" theta frequencies of the awake rabbit (5-6 Hz). With stimulation beyond the theta-range three phenomena occurred: shift of the burst frequencies to higher or lower harmonics of stimulation frequencies; complex interactions of basic background frequency with the rhythm of stimulation ("beating"); escape from the influence of the stimuli with return to background theta-burst frequency.
Animals↗
Frequency dependence of the binaural interaction component of the auditory brainstem response.
The frequency dependence of the binaural interaction component of the auditory brainstem response was examined. Subjects included 24 with normal hearing and 5 with severe high-frequency losses. Tone pips of 100 and 80 dB pe SPL at 1 000 and 4 000 Hz were presented monaurally and binaurally. The binaural interaction component was derived by subtracting the binaural response from the addition of the left and right monaural responses. The binaural interaction component was produced by both 1 000 and 4 000 Hz, although it was larger and more reliable with 1 000 Hz. The absence of responses to 4 000 Hz in cochlear-impaired subjects did not alter appreciably the morphology of the binaural interaction component to 1 000 Hz. The correspondence between the binaural interaction component and the masking level difference was not good.
Adult↗
Frequency of potential azole drug-drug interactions and consequences of potential fluconazole drug interactions.
PURPOSE: To assess the frequency of potential azole-drug interactions and consequences of interactions between fluconazole and other drugs in routine inpatient care. METHODS: We performed a retrospective cohort study of hospitalized patients treated for systemic fungal infections with an oral or intravenous azole medication between July 1997 and June 2001 in a tertiary care hospital. We recorded the concomitant use of medications known to interact with azole antifungals and measured the frequency of potential azole drug interactions, which we considered to be present when both drugs were given together. We then performed a chart review on a random sample of admissions in which patients were exposed to a potential moderate or major drug interaction with fluconazole. The list of azole-interacting medications and the severity of interaction were derived from the DRUGDEX System and Drug Interaction Facts. RESULTS: Among the 4,185 admissions in which azole agents (fluconazole, itraconazole or ketoconazole) were given, 2,941 (70.3%) admissions experienced potential azole-drug interactions, which included 2,716 (92.3%) admissions experiencing potential fluconazole interactions. The most frequent interactions with potential moderate to major severity were co-administration of fluconazole with prednisone (25.3%), midazolam (17.5%), warfarin (14.7%), methylprednisolone (14.1%), cyclosporine (10.7%) and nifedipine (10.1%). Charts were reviewed for 199 admissions in which patients were exposed to potential fluconazole drug interactions. While four adverse drug events (ADEs) caused by fluconazole were found, none was felt to be caused by a drug-drug interaction (DDI), although in one instance fluconazole may have contributed. CONCLUSIONS: Potential fluconazole drug interactions were very frequent among hospitalized patients on systemic azole antifungal therapy, but they had few apparent clinical consequences.
Adverse Drug Reaction Reporting Systems↗
Dielectrical model of cellular structures in radio frequency and microwave spectrum. Electrically interacting versus noninteracting cells.
A model of dielectrical properties of cellular structures of a tissue has been proposed. Cellular structures were presented as a composition of membrane covered spheres and cylinders that do not interact with each other. No restrictions were applied to the thickness of cellular membranes. The model was further generalized into a case of electrically interacting cells. The difference in dielectrical properties calculated with the model of electrically noninteracting versus interacting cells is inversely dependent on frequency. At biological values of cellular volume fraction near 0.7 (packed configuration) the difference is about 10%-15% in resistance and in epsilon' for frequencies near 0.1 MHz. Experimental data for myocardial tissue and theoretical data, for both interacting and noninteracting models, reasonably agree at frequencies of 1-100 MHz.
Animals↗
Binaural interaction in the human frequency-following response: effects of interaural intensity difference.
The binaural interaction component (BIC) of the 500-Hz human frequency-following response (FFR) was evaluated as a function of interaural intensity difference (IID) using a lateralization paradigm. The robust FFR interaction component (FFR-BIC) was shown to decrease systematically with increasing IID with no discernible FFR-BIC for IID values larger than about 20 dB. These findings are similar to that observed for the high-frequency auditory brainstem response interaction component (ABR-BIC). Thus, like the ABR-BIC, the FFR-BIC may be correlated with binaural fusion and the perceived location of the fused image of the sound. These results taken together suggest that the binaural neurons in the brainstem are able to utilize IID cues presented in both low-frequency and high-frequency sounds.
Adolescent↗
Dissociations in memory for item identity and item frequency: evidence from hemispheric interactions.
Evidence for a dissociation between memory for the identity of an item and memory for its frequency of occurrence was provided by two tachistoscopic studies employing lateralized abstract designs as stimuli. In both experiments, subjects viewed a random series of presentation trials, in which certain designs appeared only once, others 5 times, and still others 9 times. Then in a series of probe trials, subjects decided, on each trial, if a design was familiar or novel, either by an old/new decision (Experiment 1) or a forced-choice decision (Experiment 2), after which they estimated the frequency of item occurrence. Presentation and probe trials were either displayed in the same visual field (within-hemisphere trials) or opposite visual fields (across-hemisphere trials). Both experiments revealed that the pattern of interhemispheric processing as well as lateralized processing differed for item identity as compared to item frequency, providing further evidence for a dissociation between these two memory processes.
Adult↗
Semantic context and word frequency effects in visual word recognition.
Semantic context and word frequency factors exert a strong influence on the time that it takes subjects to recognize words. Some of the explanations that have been offered for the effects of the two factors suggest that context and frequency should interact, and other explanations imply additivity. In a recent study, Schuberth and Eimas reported that context and frequency effects added to determine their subjects' reaction times in a lexical decision (word vs. nonword) task. The present experiment reexamines this question with improved procedures. The data show that context and frequency do interact, with a semantic context facilitating the processing of low-frequency words more than high-frequency words.
Discrimination Learning↗
Predicting performance in a child psychiatry program for pediatric residents.
As part of an evaluation of a program to train pediatric residents in child psychiatry, measures were made of the following variables predictive of the residents' performance in the program: personality traits, attitude toward psychiatry, willingness to treat psychological problems, preprogram interview performance, length of commitment to pediatrics, and frequency of interaction with teachers in the program. Outcome variables were pediatric residents' course evaluation, frequency of interaction with teachers in the program, and postprogram interview performance. In multiple regression equations the variables predictive of the residents' performance explained up to 72 percent of the variance of the residents' participation in the program, 88 percent of the variance of the postprogram interview, and 61 percent of the variance of the residents' course evaluations.
Attitude of Health Personnel↗
Suprathreshold spatial frequency detection and binocular interaction in strabismic and anisometropic amblyopia.
We have investigated suprathreshold contrast sensitivity and binocular interactions in strabismic and anisometropic amblyopes using a reaction time paradigm. For every spatial frequency, reaction time increased as the grating contrast decreased. At all spatial frequencies and contrast values the reaction times using the amblyopic eye were prolonged compared to the nonamblyopic eye, but most markedly at high spatial frequencies. In the middle range of spatial frequencies, the contrast vs. reaction time function for the nonamblyopic eyes was biphasic, suggesting that two separate mechanisms detect gratings at high and low contrast levels. These functions in deep amblyopia were monotonic, and in shallow amblyopia the break in the functions was present but shifted to lower contrast levels. Binocular interaction experiments showed that binocular summation was absent at all contrast levels, but binocular occlusion was evident at high contrast levels for amblyopic observers.
Adolescent↗