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Results for “interaction frequencies”

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PubMed1980

Effects of methionine supplementation on the incidence of dietary fat induced myocardial lesions in the rat.

Purified diets were prepared to evaluate the effect of methionine supplementation on the incidence and severity of vegetable oil-induced myocardial lesions in the rat. The unsupplemented basal diet fed was similar in nutrient composition to typical semipurified diets currently utilized for cardiopathogenic evaluation of dietary rapeseed oils and contained 1.276 mg of S-amino acid per kilocalorie. The methionine-supplemented diet contained an additional 0.25% (w/w) L-methionine or a total of 1.815 mg of S-amino acid per kilocalorie. Feeding trials were conducted in which weanling rats were fed either a diet containing 20% (w/w) soybean oil (SBO), low erucic acid rapeseed oil (LER) or high urucic acid rapeseed oil (HER) for 16 or 28 weeks. Dietary supplementation with methionine was found to reduce the incidence of focal myocardial lesions in SBO-fed animals to zero. These results suggest that marginal deficiencies in methionine may interact with the frequency and severity of myocardial changes reported for Sprague-Dawley rats fed various dietary oils. The results indicate that levels of essential nutrients should be adjusted when the energy level of the diet is increased.

Amino Acids, Sulfur↗

PubMed1990

Expression of cloned yeast NADPH-cytochrome P450 reductase gene in Saccharomyces cerevisiae.

The NADPH-cytochrome P450 reductase gene isolated from the yeast Saccharomyces cerevisiae [Yabusaki et al., J. Biochem. 103, 1004-1010 (1988)] was expressed on a multi-copy plasmid in the yeast. The transformed yeast cells with the recombinant plasmid carrying the reductase gene with a length of 3 kb produced the corresponding mRNA read from the original transcription initiation site under the control of its own promoter with a maximum length of 300 bp. The reductase content in the transformed cells was 25 times higher than that of the endogenous reductase. When the coding region for the reductase was placed between the alcohol dehydrogenase I gene promoter and the terminator of the expression vector pAAH5, the expression level was 32 times higher than at the endogenous level. These recombinant yeast strains showed enhanced cytochrome c reductase activity with increased cellular reductase levels. A simultaneous expression of yeast P450 reductase with rat P450c or bovine P450(17 alpha) resulted in 25 times or a 5 times increase in the corresponding P450-dependent monooxygenase activity of the recombinant yeast strains, respectively, as compared with that of the yeast cells expressing the corresponding P450 species. These results suggested that the overproduction of yeast P450 reductase with a simultaneous expression of the mammalian P450 species enhanced the P450c- and P450(17 alpha)-dependent monooxygenase activities in the recombinant yeast strains, probably due to the increased frequency of the interaction between yeast P450 reductase and P450c or P450(17 alpha) in the yeast microsomes.

Alcohol Dehydrogenase↗

PubMed1993

Neuroendocrine mechanisms that control seasonal changes of luteinizing hormone secretion in sheep are sexually differentiated.

The apparent earlier onset of seasonal breeding activity of adult male versus adult female sheep suggests that the neuroendocrine mechanisms that control onset of the breeding season may be sexually differentiated in this species. However, it is difficult to compare gradual onset of testicular growth to abrupt changes in ovarian activity. To determine the relative timing of seasonal transitions in neuroendocrine reproductive activity, we compared temporal changes of LH concentrations in adult, gonadectomized, estradiol (E)-treated (experiment 1), or testosterone (T)-treated (experiment 2) Suffolk male and female sheep held outdoors for 18 mo. In addition, we compared the rates at which E-treated males and females become photorefractory to a winter solstice hold (WSH) photoperiod. In all three experiments, blood samples were collected weekly. In addition, serial blood samples were collected every 12 min for 4 h at approximately 2-mo intervals for experiment 1 and at monthly intervals for experiment 2. Neither plasma E nor T concentrations differed (p > 0.05) between sexes. In E-treated animals, mean LH changed (p < 0.001) over time in both sexes, and there was a sex x time interaction (p < 0.001). LH pulse amplitude changed (p < 0.001) over time in both sexes, but there was no detectable (p > 0.05) sex x time interaction. LH pulse frequency varied significantly over time in E-treated females (p < 0.001) but not in males (p < 0.05). The amplitude of the annual oscillation of mean LH was greater (p < 0.01) in E-treated females than in males.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Functional topography during a visuoverbal judgment task studied with event-related desynchronization mapping.

Event-related desynchronization (ERD) of alpha components was studied in 10 subjects in a visuoverbal judgment task. EEG was recorded from 29 electrodes; ERD, measured by percentage of alpha power decrease, was calculated in 125-ms intervals and displayed in a time course over 7-s intervals and in the form of topographical ERD maps. ERD, interpreted as a measure of activated cortical areas, was studied in the upper and lower alpha bands. It was found that upper alpha band ERD was short-lasting (less than 1 s), localized to the posterior region and not found before stimulation; in contrast to this, lower alpha band ERD was longer-lasting (greater than 1 s), more widespread, with a left hemisphere dominance, and was already present before stimulation. ANOVA revealed significant interactions among alpha frequency bands, scalp location, and pre-/poststimulus intervals. The self-organizing topological Kohonen network was used to analyze the stability of consecutive ERD maps. There is evidence that topographical ERD patterns can be stable for about 300-400 ms.

Adult↗

PubMed2000

Incomplete recovery among endogenously depressed patients: an ethological analysis.

The paper reports on an ethological study comparing the behavior of hospitalized endogenously depressed (N = 11) and nonpsychiatrically ill control (N = 11) subjects hospitalized for somatic illnesses. All subjects participating in the study signed the Helsinki Declaration of 1964 for protection of human research subjects. Findings include: a) for the first hospital week behavioral differences between the two subject groups were highly significant with the most robust finding being the reduced frequency of social interaction among depressed subjects, b) an increase in communication among depressed subjects over the course of hospitalization but a decline of communication and an increase of self-activity among controls, and c) significant behavior profile differences between the two subject groups at the time of hospital discharge. The findings suggest that clinically remitted depressives are not fully recovered and socially capable when discharged from the hospital.

Adult↗

PubMedDate not supplied

Concern about aspects of body image and adjustment to early stage breast cancer.

OBJECTIVE: Several authors have suggested that patients adjust more poorly to breast cancer if they are heavily invested in body image as a source of their sense of self-worth. This prospective study examined this possibility, looking at two aspects of concern about body image as predictors of several indices of adjustment over the first postoperative year. METHODS: At diagnosis (and again a year later) 66 women with early stage breast cancer reported how much they valued a) a sense of body integrity (or intactness) and b) a good physical appearance. The day before surgery, a week afterward, and at 3-month, 6-month, and 12-month follow ups, they reported on their mood. At presurgery and at follow ups they also rated their attractiveness and sexual desirability and reported on frequency of sexual interaction. At follow-ups they also indicated how much their illness and treatment were interfering with social and recreational activities. RESULTS: Initial investment in appearance was related to distress across the postsurgical year. In contrast, investment in appearance made women more resilient against deterioration in their perceptions of attractiveness. Concern about body integrity did not strongly predict emotional distress, but it related to adverse impact on social and recreational activities in the follow-up period, to deterioration in feelings of sexual desirability, and to feelings of alienation from the self (feeling "not like yourself anymore"). CONCLUSIONS: Body image is often thought of in terms of physical appearance, but there is also a body image pertaining to integrity, wholeness, and normal functioning. People who are greatly concerned about either aspect of their body image are vulnerable to poorer psychosocial adjustment when confronting treatment for breast cancer. The poorer adjustment takes a different form, however, depending on the nature of the patient's body-image concern.

Adaptation, Psychological↗

PubMed1995

Physician religious beliefs and the physician-patient relationship: a study of devout physicians.

The purpose of this study was to determine the type and frequency of religious interactions that occur between devout physicians and their patients. Physicians identified by their peers as having religious or spiritual beliefs that were an important part of their lives were surveyed. Forty physicians responded (response rate 77%). In general, these physicians agreed that their religious beliefs have an important influence on their practice of medicine. Thirty-two percent reported having shared their beliefs with patients. Praying aloud with patients occurred with only 13% of patients, but 67% of respondents reported having done this on at least one occasion. Multivariate analysis showed the physician's religious group to be the most important determinant of sharing beliefs with patients, occurring most commonly with Protestant physicians. In this small sample of devout physicians, physician religious beliefs appear to influence the interactions between physicians and their patients.

Adult↗

PubMed1995

Glutathione S transferase-theta (GSTT1) genetic polymorphism among Chinese, Malays and Indians in Singapore.

Glutathione S-transferase-theta (GSTT1) is subject to a genetic polymorphism where approximately 50% of a Caucasian population are homozygous for the null allele. Because of the possible association of the polymorphism with increased cancer risk in individuals, we genotyped by polymerase chain reaction 187 normal Chinese, 167 normal Malays and 152 normal Indians from Singapore and Malaysia. The proportion of Chinese, Malays and Indians with the null genotype were 58%, 38% and 16% respectively and mirrored previously reported frequencies of the GSTM1 null genotype in these populations. The frequency of the combined GSTM1 and GSTT1 null genotypes among Chinese, Malays and Indians were 37%, 22% and 5% respectively. The similarity with predicted frequencies indicated no interaction between the two genetic polymorphisms.

Adolescent↗

PubMed2005

Hydroxyzine and metabolites as a source of interference in carbamazepine particle-enhanced turbidimetric inhibition immunoassay (PETINIA).

A 32-year-old epileptic patient with a lengthy history of multiple-drug abuse and psychotic disorders was found to have an elevated serum carbamazepine concentration of 40.5 mg/L (therapeutic range 4-12 mg/L) using particle-enhanced turbidimetric inhibition immunoassay (PETINIA). Serum reanalysis by LC-DAD revealed only high hydroxyzine (HDZ) concentration (HDZ = 0.55 mg/L; therapeutic range <0.1 mg/L), suggesting cross-reactivity between HDZ and PETINIA. To confirm this hypothesis, the authors tested 2 commercially available carbamazepine immunoassays, PETINIA and EMIT 2000, for in vitro cross-reactivity with HDZ and 2 HDZ metabolites (cetirizine and norchlorcyclizine). To determine the frequency of this interaction in a clinical setting, 40 sera of 39 patients taking HDZ without carbamazepine were tested by both immunoassays. For some samples, LC-ESI-MS analysis of HDZ metabolites was performed. Additionally, cross-reactivities produced by other benzhydrylpiperazine drugs were evaluated. in vitro, 5 mg of HDZ, cetirizine, and norchlorcyclizine cross-reacted with PETINIA at 85%, 125%, and 66%, respectively. Conversely, EMIT 2000 showed no cross-reactivity. For PETINIA, erroneous carbamazepine concentrations were detected in 35 out of 40 sera of patients taking HDZ. The magnitude of interference correlated moderately with serum HDZ concentrations (Spearman rho coefficient 0.58, P < 0.001), suggesting a major role for the multiple HDZ metabolites (4 serum metabolites were detected by LC-ESI-MS). Furthermore, other benzhydrylpiperazine drugs (eg, oxatomide) showed in vitro cross-reactivity with PETINIA. In conclusion, HDZ and its metabolites cross-react with carbamazepine PETINIA immunoassay, which could significantly affect the correct interpretation of serum carbamazepine concentrations in patients treated with HDZ.

Adult↗

PubMed2003

Radiation from high-intensity ultrashort-laser-pulse and gas-jet magnetized plasma interaction.

Using a gas-jet flow, via the interaction between an ultrashort high-intensity laser pulse and plasma in the presence of a perpendicular external dc magnetic field, the short pulse radiation from a magnetized plasma wakefield has been observed. Different nozzles are used in order to generate different densities and gas profiles. The neutral density of the gas-jet flow measured with a Mach-Zehnder interferometer is found to be proportional to back pressure of the gas jet in the range of 1 to 8 atm. Strength of the applied dc magnetic field varies from 0 to 8 kG at the interaction region. The frequency of the emitted radiation with the pulse width of 200 ps (detection limit) is in the millimeter wave range. Polarization and spatial distributions of the experimental data are measured to be in good agreement with the theory based on the V(p)xB radiation scheme, where V(p) is the phase velocity of the electron plasma wave and B is the steady magnetic field intensity. Characteristics of the radiation are extensively studied as a function of plasma density and magnetic field strength. These experiments should contribute to the development of a new kind of millimeter wavelength radiation source that is tunable in frequency, pulse duration, and intensity.

Journal Article↗

PubMed2005

Synchronization of spectral components and its regularities in chaotic dynamical systems.

The chaotic synchronization regime in coupled dynamical systems is considered. It has been shown that the onset of a synchronous regime is based on the appearance of a phase relation between the interacting chaotic oscillator frequency components of Fourier spectra. The criterion of synchronization of spectral components as well as the measure of synchronization has been discussed. The universal power law has been described. The main results are illustrated by coupled Rössler systems, Van der Pol and Van der Pol-Duffing oscillators.

Journal Article↗

PubMed2005

Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s(2)2s(2)2p2p0(3/2) level in boronlike argon.

The lifetime of the Ar13+ 1s(2)2s(2)2p2p0(3/2) metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately shorter than our experimental result.

Journal Article↗

PubMed2007

Costs of coexistence along a gradient of competitor densities: an experiment with arvicoline rodents.

1. Costs of coexistence for species with indirect resource competition usually increase monotonically with competitor numbers. Very little is known though about the shape of the cost function for species with direct interference competition. 2. Here we report the results of an experiment with two vole species in artificial coexistence in large enclosures, where density of the dominant competitor species (Microtus agrestis) was manipulated. Experimental populations of the subordinate vole species (Clethrionomys glareolus) were composed of same aged individuals to study distribution of costs of coexistence with a dominant species within an age-cohort. 3. Survival and space use decreased gradually with increasing field vole numbers. Thus, responses to interference competition in our system appeared to be similar as expected from resource competition. The total number of breeders was stable. Reproductive characteristics such as the timing of breeding, and the litter size were not affected. In the single species enclosures a proportion of surviving individuals were not able to establish a breeding territory against stronger conspecifics. Under competition with heterospecifics such nonbreeders suffered high mortality, whereas the breeders survived. 4. Combined interference of dominant conspecifics and heterospecifics probably increased the frequency of aggressive interactions, social stress and mortality for the weaker individuals within a homogeneous age cohort of the subordinate competitor population. 5. Our results suggest, that in open systems where bank voles are outcompeted over the breeding season by faster reproducing field voles, animals able to establish a territory may be able to withstand competitor pressure, while nonbreeding bank vole individuals are forced to emigrate to suboptimal forest habitats.

Animals↗

PubMed2005

Adaptive speciation when assortative mating is based on female preference for male marker traits.

Adaptive speciation occurs when frequency-dependent ecological interactions generate conditions of disruptive selection to which lineage splitting is an adaptive response. Under such selective conditions, evolution of assortative mating mechanisms enables the break-up of the ancestral lineage into diverging and reproductively isolated descendent species. Extending previous studies, I investigate models of adaptive speciation due to the evolution of indirect assortative mating that is based on three different mating traits: the degree of assortativity, a female preference trait and a male marker trait. For speciation to occur, linkage disequilibria between different mating traits, e.g. between female preference and male marker traits, as well as between mating traits and the ecological trait, must evolve. This can lead to novel speciation scenarios, e.g. when reproductive isolation is generated by a splitting in the degree of assortativeness, with one of the emerging lineages mating assortatively, and the other one disassortatively. I investigate the effects of variation in various model parameters on the likelihood of speciation, as well as robustness of speciation to introducing costs of assortative mating. Even though in the models presented speciation requires the genetic potential for strong assortment as well as rather restrictive ecological conditions, the results show that adaptive speciation due to the evolution of assortative mating when mate choice is based on separate female preference and male marker traits is a theoretically plausible evolutionary scenario.

Adaptation, Biological↗

PubMed1976

Ranks and relationships in Highland ponies and Highland Cows.

Recent studies of primates have questioned the importance of dominance hierarchies in groups living under natural conditions. In a herd of Highland ponies and one of Highland cattle grazing under free-range conditions on the Isle of Rhum (Inner Hebrides) well defined hierarchies were present. The provision of food produced a marked increase in the frequency of agonistic interactions but had no effect on the rank systems of the two herds. While rank was clearly important in affecting the distribution of agonistic interactions, it was poorly related to behaviour in non-agonistic situations.

Agonistic Behavior↗

PubMed2006

The effect of population structure on the adaptive radiation of microbial populations evolving in spatially structured environments.

Spatial structure is thought to be an important factor influencing the emergence and maintenance of genetic diversity. Previous studies have demonstrated that environmental heterogeneity, provided by spatial structure, leads to adaptive radiation of populations. In the present study, we investigate not only the impact of environmental heterogeneity on adaptive radiation, but also of population fragmentation and niche construction. Replicate populations founded by a single genotype of Escherichia coli were allowed to evolve for 900 generations by serial transfer in either a homogeneous environment, or a spatially structured environment that was either kept intact or destroyed with each daily transfer. Only populations evolving in the structured environment with intact population structure diversified: clones are significantly divergent in sugar catabolism, and show frequency-dependent fitness interactions indicative of stable coexistence. These findings demonstrate an important role for population fragmentation, a consequence of population structure in spatially structured environments, on the diversification of populations.

Adaptation, Physiological↗

PubMed1993

Data-dependent filter characteristics of peak-valley respiratory sinus arrhythmia estimation: a cautionary note.

Filter characteristics of the peak-valley respiratory sinus arrhythmia estimation method are described. To identify filter characteristics of this method, models were generated that combined signals of different frequencies with trends of varying slopes. These models simulate the influence of trend and changing respiratory frequency on the accuracy of peak-valley estimates. The transfer function of the peak-valley method, unlike that of other time domain filters, is not solely dependent upon signal frequency. Two factors interact to determine the relative accuracy of the peak-valley method: (a) slope of the signal component and (b) slope of the underlying trend. Combinations of these factors may result in significant distortion to the input signal. The direction of error is a function of the direction of the trend (i.e., overestimation with deceleration and underestimation with acceleration). In many situations when respiratory sinus arrhythmia amplitude is low in special populations (e.g., cardiovascular disorders, high-risk infants, or human fetuses) or under conditions that greatly reduce respiratory sinus arrhythmia amplitude (e.g., exercise, drugs, pharmacological manipulations), use of the peak-valley method may result in significant measurement error. The use of this method to evaluate respiratory sinus arrhythmia over short epochs (i.e., less than 2 min) or to quantify changes in respiratory sinus arrhythmia due to discrete stimulation (e.g., breath by breath) may result in inconsistent measurement error. Recommendations are made for detrending heart rate data prior to application of the peak-valley method.

Arrhythmia, Sinus↗

PubMed1999

Catheter obstruction effect on pulsatile flow rate--pressure drop during coronary angioplasty.

The coupling of computational hemodynamics to measured translesional mean pressure gradients with an angioplasty catheter in human coronary stenoses was evaluated. A narrowed flow cross section with the catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after balloon angioplasty; thus elevating the pressure gradient and reducing blood flow during the measurements. For resting conditions with the catheter present, flow was believed to be about 40 percent of normal basal flow in the absence of the catheter, and for hyperemia, about 20 percent of elevated flow in the patient group. The computations indicated that the velocity field was viscous dominated and quasi-steady with negligible phase lag in the delta p(t)-u(t) relation during the cardiac cycle at the lower hydraulic Reynolds numbers and frequency parameter. Hemodynamic interactions with smaller catheter-based pressure sensors evolving in clinical use require subsequent study since artifactually elevated translesional pressure gradients can occur during measurements with current angioplasty catheters.

Algorithms↗