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Results for “interaction frequencies”

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PubMed2005

Potential for drug interactions in hospitalized cancer patients.

OBJECTIVES: To quantify the frequency of potential drug interactions unrelated to chemotherapy in cancer patients admitted to our institution, and to define risk factors for such interactions. METHODS: Charts of 100 consecutive hospitalized cancer patients were reviewed. Patients receiving chemotherapy and/or hormone therapy were excluded, as were patients admitted for intensive care. Drug-drug interactions were screened with Drug Interaction Facts software, and manually by the authors. Potential interactions were graded by levels of severity (severe, moderate, minor) and significance (one to five, with one representing the highest level of evidence). RESULTS: The median age of the patients was 67 years, and the length of hospital stay and the number of drugs per patient were 6 days and eight drugs, respectively. In 63 patients 180 potential interactions were detected. Of the potential interactions, 18.3% were severe, 56.7% were moderate, and 25% were minor. Approximately 7%, 18% and 13% of potential interactions were graded as level 1, 2 and 3, respectively. In multivariate analysis, prescriptions with eight or more drugs (P=0.0004) and six or more days of hospital stay (P=0.014) were independent risk factors for potential interactions. CONCLUSION: Potential drug interactions are common among hospitalized cancer patients. Length of hospital stay and number of prescribed drugs are risk factors.

Adult↗

PubMed1996

Analysis of cellular interactions in limiting dilution cultures.

Limiting dilution (LD) cultures are often used to study cellular heterogeneity in responses of murine splenocytes to specific or polyclonal activation. LD titration curves often reveal a nonlinear dependence of response on input cell dose. Although 'zigzag' shaped curves of this kind are often interpreted and analyzed as resulting from interactions among three distinct cell types, we observe that a more parsimonious two cell model, including a cell type that can generate both positive and negative effects, provides better fit to a wide range of experimental data. We have developed mathematical models for the accurate estimation of the frequencies of both interacting cell types and of the parameters for their multi-hit interaction. We show examples of LD cultures in which specific experimental manipulations alter the frequency of only one of the two cell types, or alter the interaction parameters without a change in responder frequency. We also provide a simplified method for approximation of the model parameters using graphical approaches and simple algebra. Lastly, we present an improved method for calculation of the effect generated per responder cell in microclonal cultures.

Animals↗

PubMed1997

Clinically significant drug interactions with general anesthetics--incidence, mechanims and management.

The frequency of adverse drug interactions increases disproportionately with the increase in the number of drugs given to patients. It was shown that 40% of patients given 16 drugs experienced an adverse drug interaction, compared with 5% of patients given fewer than 6 drugs. The magnitude of the drug interaction problem increases substantially in anesthetised patients because of: (i) the increased use of multiple drugs in the preoperative and intraoperative periods; and (ii) the growing population of geriatric patients who, in addition to having diminished drug metabolising capacity, are often prescribed multiplied medications for concomitant medical illness. Drug interactions with volatile and intravenous anesthetics can be divided into those that are pharmacokinetic and pharmacodynamic in nature. Pharmacokinetic interactions occur when the absorption, distribution, metabolism or excretion of a drug is altered by the coadministration of a second drug. Pharmacodynamic interactions involve a change in the pharmacological effect of a drug as a result of the action of second drug at receptor sites.

Anesthetics, Inhalation↗

PubMed1986

The effects of a classroom manager role on the social interaction patterns and social status of withdrawn kindergarten students.

We examined the effects of assigning a classroom manager's role on the frequency of social interactions and the sociometric standing of three withdrawn kindergarten students. Results showed that when the three socially withdrawn students were placed in the manager's role they substantially increased the frequency of their positive social initiations during free-play time, were the recipients of many more positive and significantly fewer negative social bids from their peers, were rated more favorably by their classmates on a sociometric rating scale, and were selected more frequently as best friends by their peers. In addition, follow-up data suggested partial maintenance of treatment effects when students no longer occupied manager positions.

Child Behavior Disorders↗

PubMed1976

Hypoxia and carbon dioxide as separate and interactive depressants of ventilation.

The respiratory frequency, tidal volume and ventilization responses of 20 conscious cats to hypoxia, at controlled levels of alveolar CO2, revealed a characteristic steady state response in the majority of animals which indicated a negative interaction of stimuli on tidal volume and minute volume of ventilation, but a positive interaction on frequency. Another series of studies, conducted on seven conscious cats, sought to identify hypoxic response thresholds and depression thresholds, by determining responses over a wide range of hypoxic stimulus intensities, and at different controlled alveolar PCO2. Response threshold was at about 65 torr PAO2. Under eucapnic conditions, ventilation began to fail at PAO2 about 30 torr due to failure of tidal volume. The frequency continued to increase even in the lowest range of PAO2. With hypocapnia no failure of ventilation, frequency, or tidal volume was seen even at the lowest PAO2, but with hypercapnia, the tidal volume began to fail at PAO2 about 50 torr. The minute volume however, continued to increase into the lowest range of PAO2, because the frequency continued to respond at a rate greater than the tidal volume was failing. The results are discussed in terms of interactive depression manifest through the coupled responses of peripheral and central mechanisms.

Animals↗

PubMed1985

Potential drug interactions in surgical patients.

The incidence and frequency of potentially serious drug interactions were evaluated in hospitalized surgical patients. Drug profiles of patients on the general surgical service of a tertiary-care teaching hospital were retrospectively reviewed for two six-month periods to determine how often drugs that are known for major interactions were prescribed concurrently. Interactions were studied that were relatively well documented and potentially harmful to the patients. A total of 1825 patient profiles were reviewed (21,888 patient days). At least one potential drug interaction was found in 17% of the patients. Interactions were found to occur at the rate of 1 for every 59 patient days. Digoxin and cimetidine were the potential interacting drugs in almost 90% of the cases. Hospitalized surgical patients require close monitoring because they frequently receive potentially interacting drugs.

Cimetidine↗

PubMed1978

Dominance and effects of strange conspecifics on aggressive interactions in the hermit crab Pagurus longicarpus (say).

Dominance orders in the hermit crab Pagurus longicarpus were observed in the laboratory. Groups of four crabs formed loose dominance hierarchies as determined by repeated display and retreat behaviour. Stronger dominance orders were inversely correlated with the frequency of aggressive interactions. Recognition of individuals, as measured by frequency and intensity of aggressive encounters between familiar crabs and introduced strangers, was not important in maintaining dominance orders. Rather, P. longicarpus recognized the aggressive state of conspecifics, as shown by frequencies of aggressive encounters after individuals of different dominance rankings were exchanged between established hierarchies.

Aggression↗

PubMed1993

Cysteine conformation and sulfhydryl interactions in proteins and viruses. 3. Quantitative measurement of the Raman S-H band intensity and frequency.

The bond stretching vibration of the cysteine sulfhydryl (SH) group in a typical protein generates a Raman band in the spectral interval 2500-2600 cm-1, a region devoid of interference from any other fundamental mode of vibration of the protein. The relatively high Raman cross section associated with the S-H stretching vibration, the sensitivity of the vibrational frequency to hydrogen bonding interactions and side chain configurations, and the dependence of the Raman intensity on thiol-thiolate equilibria, combine to make the Raman SH band a potentially valuable marker of protein sulfhydryl interactions and a unique indicator of sulfhydryl participation in thiol-disulfide oxidoreductase activity. In order to exploit Raman spectroscopy for these purposes, accurate and precise measurements of Raman SH band profiles are required. We show here that the required precision and accuracy can be achieved by use of the Raman band corresponding to the stretching vibration of in situ nitrogen gas as a quantitative intensity and frequency standard. The Raman Q-branch center of the N2 band occurs at 2330.7 cm-1.

Bacteriophage P22↗

PubMed1999

Universal low-frequency vibrations of proteins from a simple interaction potential.

A pairwise Born potential connecting the heavy atom sites within a prescribed cutoff, and the equation of motion method (EOM), reproduce the existence of a universal singularity in the low-frequency vibrational density of states of typical globular proteins. This is due to quasilocalization of acoustic waves and an analogy with a similar feature found in glasses is stressed. We explain the dependence of this anomaly with the effective dimensionality of the protein. The EOM method allows for the study of even the largest proteins with a simple personal computer.

Animals↗

PubMed1995

Interaction of neuronal populations with delay: effect of frequency mismatch and feedback gain.

The effect of frequency mismatch, signal transduction delay and inter-population feedback gain on the interaction of neuronal populations, mediated by long-range excitation, is investigated using physiologically realistic system parameters. Self-consistent solutions for the frequency, amplitude, and relative phase of the component signals are derived for limit cycle oscillations. These solutions predict important qualitative features including discontinuous changes in frequency of oscillation and phase reversal between symmetric and antisymmetric limit cycles. A singularity in the solutions is used to predict parameter regions in which limit cycles do not exist. If limit cycles exist at zero delay, it is shown that limit cycles and quasi-periodic attractors alternate as a function of delay. The implications of these results for estimating physiologically meaningful delays from observed phase shifts in EEG time series are discussed. Spectral peaks for the quasi-periodic attractor occur at m nu 1 +/- n nu 2, where the difference nu 1 - nu 2 is approximately equal to the intrinsic population frequency mismatch delta nu. The cross-correlation function is amplitude modulated with a frequency equal to delta nu/2, indicating that the two populations slip in and out of phase with a mean correlation duration equal to 1/delta nu. These findings underpin the dynamical basis of delay induced "desynchronization" of oscillations reported in computer simulations. Bifurcation diagrams indicate that quasi-periodic attractors exist for a wide range of parameters in the presence of delay in long-range excitation and non-zero frequency mismatch. If the frequency mismatch is sufficiently large and the feedback gain is sufficiently small, quasi-periodic attractors exist for all delays. Delays of a few milliseconds, much smaller than the system time scale, can destabilize limit cycle oscillations. The role of synaptic change in inducing bifurcations of limit cycles to quasi-periodic attractors and vice versa is discussed. The implication of these findings for the generation of chaos in distributed neural systems is discussed.

Electroencephalography↗

PubMed1999

Differential parental communication with adolescents who are disabled and their healthy siblings.

PURPOSE: To examine the levels of parental communication and differential conversational styles with adolescents who are disabled and their healthy siblings, to better understand why the adolescent who is disabled has a higher risk of psychosocial problems during the transition into adulthood. METHODS: Families who had a disabled adolescent and at least one other adolescent who was not disabled were videorecorded during dinner at home. Twenty adolescents (12 girls and 8 boys) and their families participated. Analyses were conducted on the 392 interactions. RESULTS: Not only did the healthy adolescents participate in family interactions at higher frequencies than the adolescents who were disabled F(1, 383) = 14.00, p < .001, but the interactions were also more meaningful with healthy adolescents, F(2, 383) = 5.25, p < .01. Furthermore, healthy siblings had significantly greater conversational control than did their siblings with disabilities, chi2 (1) = 14.36, p < .001. Parents responded more negatively when adolescents who were disabled initiated a topic in comparison with their response to the healthy siblings, F(2, 69) = 5.44, p < .01. Finally, adolescents with disabilities were ignored more often than their healthy siblings, z = -3.75, p < .001, and they did not monopolize the conversation as often as did their healthy siblings, z = -3.91, p < .001. CONCLUSION: These results suggest that adolescents who are disabled may be at a disadvantage when engaged in family interactions in contrast with their healthy siblings.

Adolescent↗

PubMed1997

Effects of a behavioral intervention on treatment adherence and stress management in adolescents with IDDM.

OBJECTIVE: To evaluate the effects of a behavioral program to increase treatment adherence and to improve stress management in adolescents with IDDM. RESEARCH DESIGN AND METHODS: A quasi-experimental pretest-posttest design with a nonequivalent control group was used. Eighteen subjects were assigned to the experimental group, which received the program, while nineteen subjects made up the control group, which received routine medical care. During the 12 intervention sessions with diabetic adolescents, different procedures were applied: instruction, blood glucose discrimination training, role-playing, relaxation exercises, self-instructions, problem-solving strategies, and homework, among others. RESULTS: The results show significant changes in the experimental group in variables related to diabetes information (patients and their parents), adherence, daily hassles, uneasiness and likelihood of response in social interactions, skills and frequency of glycemic analyses, blood glucose estimate errors, and negative family support (parents). The program had no effect on either dietary and physical exercise or glycemic control. The improvements, which were maintained at a follow-up carried out 13 months after finishing the program, were: patients' information about physiopathology (P = 0.000), diet (P = 0.000), physical exercise (P = 0.048), glucose testing (P = 0.030), and insulin (P = 0.000), barriers to adherence frequency (P = 0.000), severity of daily hassles (P = 0.006), and degree of uneasiness in social interaction (P = 0.000). CONCLUSIONS: This research introduces the novelty of integrating several behavioral procedures within a wide-ranging package that affects aspects implied in diabetes control such as treatment adherence and stress management. The testing of similar programs on samples of subjects with glycemic control difficulties would be useful.

Adolescent↗

PubMed2005

Extent of potential drug interactions among patients receiving anti-hypertensive medications.

OBJECTIVE: To investigate the frequency of potential antihypertensive drug interactions among patients with cardiovascular diseases receiving antihypertensive medications. METHODS: The study took place in Nablus, Palestine starting April through October 2003. Patients with cardiovascular diseases (n=876) or who were receiving one or more antihypertensive medications were evaluated. All drugs prescribed for the patients were obtained from their medical files. A drug interaction database was developed based on updated Drug Interaction Facts to examine potential and level of drug interactions in each patient's regimen. Data were entered and analyzed using SPSS software. RESULTS: The number of "unique" pairs of potential drug interactions among the antihypertensive agents present in the data was 433. These included 16 cases (3.7%) level one; 34 cases (7.8%) level 2; 116 cases (26.8%) level 3; 136 cases (31.4%) level 4, and 131 (30.3%) level 5 interactions. Both increasing age and number of drugs were significantly associated with the potential for significant interactions at all levels with a p value less than 0.025. CONCLUSIONS: This study found a high frequency of potential drug interactions with agents typically used for hypertension. Similar investigations need to be carried out among patients with other types of chronic diseases. Drug interaction software might be necessary in governmental pharmacy departments.

Aged↗

PubMed2005

Central regulation of energy balance: inputs, outputs and leptin resistance.

The regulation of energy balance is complex and, in man, imprecise. Nevertheless, in many individuals intake and expenditure are balanced with <1% error with little or no conscious effect. Essential components of such a regulatory system are signals, leptin and insulin, that reflect the size of lipid stores. Leptin receptors signal via phosphatidylinositol 3-kinase (as do insulin receptors) and via the transcription factor signal transducer and activator of transcription-3 to activate various types of neurone. Obese rodents, and possibly man, are resistant to leptin; in some cases because of genetic or perinatal programming (primary resistance), but commonly in response to high leptin levels (secondary resistance). Secondary leptin resistance may be a result of reduced transport of leptin to the brain or down-regulation of leptin signalling. Signals that reflect lipid stores form the tonic homeostatic regulatory system. They interact with episodic homeostatic signals carried by neurones, hormones and metabolites to regulate meal size and frequency. They also interact with signals related to the palatability of food, biorhythms and learning. Many neurotransmitters and hormones mediate responses to more than one input (e.g. gastric and adipocyte leptin), but are nevertheless most involved with particular inputs (e.g. leptin with adipocyte fat stores). Feeding can be divided into appetitive (preparation for feeding) and consummatory phases, which can both be further subdivided. Different sets of neurotransmitters and hormones are involved at each stage. In the long term it may be possible to customise obesity therapies according to those inputs and outputs that are most disturbed and most amenable to intervention in individual subjects.

Adipose Tissue↗

PubMed2005

Nonlinear modeling of auditory-nerve rate responses to wideband stimuli.

The spectral selectivity of auditory nerve fibers was characterized by a method based on responses to random-spectrum-shape stimuli. The method models the average discharge rate of fibers for steady stimuli and is based on responses to approximately 100 noise-like stimuli with pseudorandom spectral levels in 1/8- or 1/16-octave frequency bins. The model assumes that rate is determined by a linear weighting of the spectrum plus a second-order weighting of all pairs of spectrum values within a certain frequency range of best frequency. The method allows prediction of rate responses to stimuli with arbitrary wideband spectral shapes, thus providing a direct test of the degree of linearity of spectral processing Auditory-nerve fibers are shown to rely mainly on linear weighting of the stimulus spectrum; however, significant second-order terms are present and are important in predicting responses to random-spectrum shape stimuli, although not for predicting responses to noise filtered with cat head-related transfer functions. The second-order terms weight the products of levels at identical frequencies positively and the products of different frequencies negatively. As such, they model both curvature in the rate versus level function and suppressive interactions between different frequency components. The first- and second-order characterizations derived in this method provide a measure of higher-order nonlinearities in neurons, albeit without providing information about temporal characteristics.

Acoustic Stimulation↗

PubMed2006

A systematic review on drug interactions in oncology.

OBJECTIVES: To systematically review drug interactions in oncology. METHODS: We searched PubMed for eligible articles and online databases abstracts of major oncology meetings from 2002 to 2005. RESULTS: One study reported on the frequency of drug interactions. Interactions between chemotherapy and nonchemotherapy agents have been reported mostly in small clinical trials and case series. Interactions between chemotherapic agents have been reported mostly in Phase I studies. Few studies described fatal outcomes of drug interactions in cancer patients. CONCLUSION: Drug interactions comprise an important issue in oncology, but very limited data exist on their frequency and clinical consequences.

Antineoplastic Agents↗

PubMed2002

Interdomain interactions within ryanodine receptors regulate Ca2+ spark frequency in skeletal muscle.

DP4 is a 36-residue synthetic peptide that corresponds to the Leu(2442)-Pro(2477) region of RyR1 that contains the reported malignant hyperthermia (MH) mutation site. It has been proposed that DP4 disrupts the normal interdomain interactions that stabilize the closed state of the Ca(2)+ release channel (Yamamoto, T., R. El-Hayek, and N. Ikemoto. 2000. J. Biol. Chem. 275:11618-11625). We have investigated the effects of DP4 on local SR Ca(2)+ release events (Ca(2)+ sparks) in saponin-permeabilized frog skeletal muscle fibers using laser scanning confocal microscopy (line-scan mode, 2 ms/line), as well as the effects of DP4 on frog SR vesicles and frog single RyR Ca(2)+ release channels reconstituted in planar lipid bilayers. DP4 caused a significant increase in Ca(2)+ spark frequency in muscle fibers. However, the mean values of the amplitude, rise time, spatial half width, and temporal half duration of the Ca(2)+ sparks, as well as the distribution of these parameters, remained essentially unchanged in the presence of DP4. Thus, DP4 increased the opening rate, but not the open time of the RyR Ca(2)+ release channel(s) generating the sparks. DP4 also increased [(3)H]ryanodine binding to SR vesicles isolated from frog and mammalian skeletal muscle, and increased the open probability of frog RyR Ca(2)+ release channels reconstituted in bilayers, without changing the amplitude of the current through those channels. However, unlike in Ca(2)+ spark experiments, DP4 produced a pronounced increase in the open time of channels in bilayers. The same peptide with an Arg(17) to Cys(17) replacement (DP4mut), which corresponds to the Arg(2458)-to-Cys(2458) mutation in MH, did not produce a significant effect on RyR activation in muscle fibers, bilayers, or SR vesicles. Mg(2)+ dependence experiments conducted with permeabilized muscle fibers indicate that DP4 preferentially binds to partially Mg(2)+-free RyR(s), thus promoting channel opening and production of Ca(2)+ sparks.

Amino Acid Sequence↗

PubMed1998

Adrenergic regulation of the force-frequency effect.

An important interaction between beta-adrenergic receptor (AR) stimulation and the myocardial contractile response to increased heart rate has only recently been identified. The effect of beta-AR stimulation to amplify the force-frequency effect is responsible for a large component of the positive inotropic effect of exercise in conscious dogs and also can be demonstrated at rest with dobutamine infusions over a range of paced heart rates. The interaction is apparent across species (dog, pig, mouse, rabbit, man). Amplification of the heart rate effect on myocardial contractility by dobutamine is lost in heart failure, which may play an important role in impaired exercise tolerance in that setting. In syndromes of chronotropic incompetence when adrenergic control is intact, it may be expected that a normal response of myocardial contractility to exercise will be achieved only when the interaction with heart rate is optimized by use of a rate-responsive cardiac pacemaker.

Adrenergic beta-Agonists↗