Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “predictability of adaptation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources
PubMed1992

Comparison of prognostic indices for burns and assessment of their accuracy.

Logistic regression was used to create four individual models of prognostic indices based on our patient population. The simplest index using only three factors, age, extent of full skin thickness burn and inhalation injury, proved to be best. These models were also compared with established indices, like Baux's, Bull's and Roi's. For a specificity below 80 per cent, Baux's rule fits as well as Roi's index does. Changes in treatment modalities and improvement in therapy will influence the accuracy of an index. Indices must be adapted to changing conditions to avoid increasing false prediction of death.

Adolescent↗
PubMed1987

Dynamic effects in the input/output relationship of auditory nerve.

Cyclic histograms of the responses of single auditory ganglion cells in the guinea pig were recorded during stimulation with amplitude modulated tones. Modulation frequencies ranged from 10 Hz to 800 Hz. The response histograms, phase-locked to the modulation signals, were analysed for mean action potential rate and for the amplitude of the fundamental component at the modulation frequency. Expected values for the amplitude of the modulation responses were calculated using the variation of mean firing rate with intensity. The observed responses differed from the expected responses in several ways. First, the amplitudes of the modulation responses were larger than expected. Second, the stimulus intensities at which the observed modulation responses peaked was greater by about 7-10 dB than the expected intensity for maximum response. Third, both the magnitude of the response at a given intensity and the intensity at which the response peaked increased with modulation frequency. Fourth, the responses extended to higher stimulus intensities than expected. The observed modulation responses were compared with predictions from the Schroeder and Hall model of adaptation and were found to agree with good quantitative precision. These results suggest that the observed modulation responses are another manifestation of the very rapid (less than 20 ms) adaptation seen in the onset responses of nerve fibres [(1985) Hear. Res. 17, 1-12]. It is concluded that the static input-output responses of auditory nerve are not a good predictor of the dynamic responses to fluctuating stimuli.

Adaptation, Physiological↗
PubMed2004

Solution structure and heparin interaction of human hepatoma-derived growth factor.

Hepatoma-derived growth factor (HDGF)-related proteins (HRPs) comprise a new protein family that has been implicated in nephrogenesis, tumorigenesis, vascular development, cell proliferation, and transcriptional activation. All HRPs share a conserved N-terminal homologous to the amino terminus of HDGF (HATH) domain, but vary significantly in the C-terminal region. Here, we show that in solution the N and C termini of human HDGF form two structurally independent domains. The 100 amino acid residue N-terminal HATH domain is well-structured while the 140 amino acid residue C-terminal domain is disordered. We determined the solution structure of the HATH domain by NMR. The core structure of the HATH domain is a five-stranded beta-barrel followed by two alpha-helices, similar to those of PWWP domains of known structures. Surface plasmon resonance results showed that the HATH domain is primarily responsible for heparin binding. On the basis of the chemical shift perturbation induced by binding of heparin-derived hexasaccharide, we identified a prominent, highly positively charged region as the putative heparin-binding site. Sequence comparison and structure prediction suggest that all HRPs are likely to adapt a similar modular structure.

Amino Acid Sequence↗
PubMed2002

Fuzzy control of multivariable process by modified error decoupling.

In this paper, a control concept for the squared (equal number of inputs and outputs) multivariable process systems is given. The proposed control system consists of two parts, single loop fuzzy controllers in each loop and a centralized decoupling unit. The fuzzy control system uses feedback control to minimize the error in the loop and the decoupler uses an adaptive technique to mitigate loop interactions. The decoupler predicts the interacting loop changes and modifies the input (error) of the loop controller. The controller was tested on the simulation model of "single component vaporizer" process. The results indicate that the decoupling controller shows better performance for set point and load changes.

Algorithms↗
PubMed2003

Proton affinity changes driving unidirectional proton transport in the bacteriorhodopsin photocycle.

Bacteriorhodopsin is the smallest autonomous light-driven proton pump. Proposals as to how it achieves the directionality of its trans-membrane proton transport fall into two categories: accessibility-switch models in which proton transfer pathways in different parts of the molecule are opened and closed during the photocycle, and affinity-switch models, which focus on changes in proton affinity of groups along the transport chain during the photocycle. Using newly available structural data, and adapting current methods of protein protonation-state prediction to the non-equilibrium case, we have calculated the relative free energies of protonation microstates of groups on the transport chain during key conformational states of the photocycle. Proton flow is modeled using accessibility limitations that do not change during the photocycle. The results show that changes in affinity (microstate energy) calculable from the structural models are sufficient to drive unidirectional proton transport without invoking an accessibility switch. Modeling studies for the N state relative to late M suggest that small structural re-arrangements in the cytoplasmic side may be enough to produce the crucial affinity change of Asp96 during N that allows it to participate in the reprotonation of the Schiff base from the cytoplasmic side. Methodologically, the work represents a conceptual advance compared to the usual calculations of pK(a) using macroscopic electrostatic models. We operate with collective states of protonation involving all key groups, rather than the individual-group pK(a) values traditionally used. When combined with state-to-state transition rules based on accessibility considerations, a model for non-equilibrium proton flow is obtained. Such methods should also be applicable to other active proton-transport systems.

Aspartic Acid↗
PubMed2004

[Comparison between optical and acoustical biometry].

INTRODUCTION: Our current standard biometric measurement was compared to IOL-Master measurement. MATERIALS AND METHODS: One hundred sixty-two consecutive cataractous eyes were examined using the IOL-Master as well as the acoustic biometry combined with the Javal-Keratometer. In all eyes, the intraocular lens power to be implanted was chosen by means of the SRK/T formula, based on the measurements conducted with our standard method. The postoperative refraction achieved, obtained at least 6 weeks after surgery from the treating ophthalmologists, was communicated to us. The results were compared and analysed statistically. RESULTS: Comparison of the eye lengths, as well as of the keratometric measurements showed good correlation between the measurements obtained by both methods, the acoustic biometry yielding significantly (p < 0.001) shorter axial-lengths than the IOL-Master (r = 0.985) and the Javal yielding significantly (p < 0.001) higher mean corneal refraction power than the IOL-Master. The accuracy of the refraction obtained postoperatively compared to the preoperative aim was better with our standard method compared to the IOL-Master. CONCLUSIONS: The presumed systemic differences in measurement results could be verified. The IOL-Master currently has two advantages: it provides a substantial gain in time and the measurements can be delegated. Analysis of the subgroups showed that the "A" constant should be adapted with the IOL-Master to improve predictability of the postoperative refraction.

Adult↗
PubMed1986

Prospective analysis of acute cervical spine injury: a methodology to predict injury.

We developed a prospective study to evaluate the clinician's ability to predict and diagnose cervical spine injury. Of 233 patients evaluated, 24 (10.4%) sustained cervical spine injury confirmed by radiography. The physician was able to predict injury with only 50% accuracy. The incidence of injury was 10.3% (24 of 233). Twenty percent (5 of 24) of cervical spine injuries would have been missed if physicians had used physical examination and mechanism of injury as criteria. Ten elements were identified as being associated statistically with cervical spine injury. Physicians cannot accurately predict the presence of cervical spine injury. Radiographs are ordered for many patients who have no evidence of injury. We used a logistic regression analysis to produce a system for predicting cervical spine injury. This methodology is easily adaptable for use in the emergency department.

Acute Disease↗
PubMedDate not supplied

Computer-assisted studies of molecular structure and carcinogenic activity.

Both quantitative and qualitative studies of the structure-activity relationships (SAR) of carcinogenic compounds are discussed. Using the ADAPT software system, examples are given of (1) predicting the gas and liquid chromatographic retention behavior of polycyclic aromatic compounds, (2) predicting the carcinogenicity of N-nitrosamines, and (3) predicting the mutagenic behavior of pesticides and other compounds in short-term test systems. It is concluded that the complexity and lack of understanding of the carcinogenic response should not prevent scientists from searching for useful empirical relationships between molecular structure and carcinogenicity. Computer generated molecular descriptors and statistical and pattern recognition techniques can be useful tools in this research.

Animals↗
PubMed2004

Heterologous production and characterization of bacterial nickel/cobalt permeases.

Nickel/cobalt permeases (NiCoTs, TC 2.A.52) are a rapidly growing family of structurally related membrane transporters whose members are found in Gram-negative and Gram-positive bacteria, in thermoacidophilic archaea, and in fungi. Previous studies have predicted two subclasses represented by HoxN of Ralstonia eutropha, a selective nickel transporter, and by NhlF of Rhodococcus rhodochrous, a nickel and cobalt transporter that displays a preference for the Co ion. In the present study, NiCoT genes of five Gram-negative bacteria and one Gram-positive bacterium were cloned and heterologously expressed in Escherichia coli. Based on substrate preference in metal-accumulation assays with the recombinant strains, two of the novel NiCoTs were assigned to the NhlF class. The remaining four NiCoTs belong to a yet unrecognized, third class. They transport both the nickel and the cobalt ion but have a significantly higher capacity for nickel. The observed substrate preferences correlate in many cases with the genomic localization of NiCoT genes adjacent to regions encoding nickel- or cobalt-dependent enzymes or enzymes involved in cobalamin biosynthesis. Alignment of 23 full-length NiCoT sequences and comparison with the available experimental data predict that substrate specificity of NiCoTs is an adaptation to specific transition metal requirements in various organisms from different taxa.

Biological Transport↗
PubMed2006

[Antibiotic strategy during septic shock].

Septic shock remains a true challenge to modern therapeutics. The quality and earliness of antibiotic administration are both fundamental elements. Treatment should be individually adapted to each patient. The pharmacokinetic indicators and predicted resistance of the bacteria targeted determine the choice of treatment, often empirical. Radical treatment of the source of infection, especially by surgery, should be combined with antibiotic treatment whenever possible.

Anti-Bacterial Agents↗
PubMed2003

Quality of life in patients with advanced colorectal cancer: what has been learnt?

Accurate assessment of health-related quality of life (HRQoL) in patients with advanced colorectal cancer is essential to improve our understanding of how cancer and chemotherapy influence patients' life and to adapt treatment strategies. Specific questionnaires have descriptive and predictive value and can be used to evaluate new therapies. Results from HRQoL assessments in randomised trials help patients and physicians to choose between treatment options. More than half of the patients treated with palliative chemotherapy have an improvement or at least a preservation of their HRQoL. However, several trials have found small differences in HRQoL between treatment groups. This may be due to the insufficient sensitivity of tools, low numbers of patients or missing data. An international consensus on the methods of measurement of HRQoL in oncology is warranted to enhance compliance, to better interpret results and to optimise the publication of precise HRQoL data.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

A discussion of potential exposure metrics for use in epidemiological studies on human exposure to radiowaves from mobile phone base stations.

There is currently a high level of concern in many countries that exposure to radiowaves from mobile phone base stations may be hazardous to health. When investigating such suggested risks, epidemiologists need to define an exposure metric that can reliably discriminate between exposed and unexposed groups of people. We conducted a feasibility study to investigate if either short-term measurements of electric field strength, calculations of electric field strength, or distance from nearby mobile phone base stations could be used to develop a metric reflecting an individual's exposure to radiowaves. With electric field strengths in the range of 0.012-0.343 V/m, radiowaves from mobile phone base stations were found to give a material contribution to total exposure; however, stronger signals were frequently measured from other sources such as broadcast radio and television transmitters. Theoretical considerations and the measurements made during this work demonstrated that studies at the population level on suggested adverse effects of radiowaves from mobile phone base stations are not feasible since no valid metric for estimating historical exposures is currently available. The pace of radio infrastructure development is also such that today's measurements are unlikely to be good proxies for either past or future exposures. The complex propagation characteristics affecting the beams from base station antennas include shielding effects and multiple reflections from house walls and other buildings. These factors, combined with the presence of other environmental sources of radiowaves, cause distance from a base station to be a poor proxy for exposure to radiowaves indoors. It may be possible to adapt computer models developed by network providers to predict network coverage for epidemiological purposes; however, this has yet to be investigated. Furthermore, there is little evidence that presently justifies epidemiological studies being restricted to adverse effects of radiowaves from mobile phone base stations while neglecting radiowaves at other frequencies produced by different transmitters.

Electromagnetic Fields↗
PubMed2004

Ground and excited states of NH4: Electron propagator and quantum defect analysis.

Vertical excitation energies of the Rydberg radical NH4 are inferred from ab initio electron propagator calculations on the electron affinities of NH4+. The adiabatic ionization energy of NH4 is evaluated with coupled-cluster calculations. These predictions provide optimal parameters for the molecular-adapted quantum defect orbital method, which is used to determine Einstein emission coefficients and radiative lifetimes. Comparisons with spectroscopic data and previous calculations are discussed.

Journal Article↗
PubMed2005

Ground and excited states of the Rydberg radical H3O: electron propagator and quantum defect analysis.

Vertical excitation energies of the Rydberg radical H(3)O are inferred from ab initio electron propagator calculations on the electron affinities of H(3)O(+). The adiabatic ionization energy of H(3)O is evaluated with coupled-cluster calculations. These predictions provide optimal parameters for the molecular-adapted quantum defect orbital method, which is used to determine oscillator strengths. Given that the experimental spectrum of H(3)O does not seem to be available, comparisons with previous calculations are discussed. A simple model Hamiltonian, suitable for the study of bound states with arbitrarily high energies is generated by these means.

Journal Article↗
PubMed2003

The Trojan exosome hypothesis.

We propose that retroviruses exploit a cell-encoded pathway of intercellular vesicle traffic, exosome exchange, for both the biogenesis of retroviral particles and a low-efficiency but mechanistically important mode of infection. This Trojan exosome hypothesis reconciles current paradigms of retrovirus-directed transmission with the unique lipid composition of retroviral particles, the host cell proteins present in retroviral particles, the complex cell biology of retroviral release, and the ability of retroviruses to infect cells independently of Envelope protein-receptor interactions. An exosomal origin also predicts that retroviruses pose an unsolvable paradox for adaptive immune responses, that retroviral antigen vaccines are unlikely to provide prophylactic protection, and that alloimmunity is a central component of antiretroviral immunity. Finally, the Trojan exosome hypothesis has important implications for the fight against HIV and AIDS, including how to develop new antiretroviral therapies, assess the risk of retroviral infection, and generate effective antiretroviral vaccines.

AIDS Vaccines↗
PubMed1993

Anthropometric profiles of elite male and female competitive sport rock climbers.

Over the past few years, competitive rock climbing--for a long time a popular sport in Europe--has increased in popularity in North America. An annual international World Cup competition circuit was started in 1988 which has shown growing success and a definite elite group of athletes has emerged. Descriptive anthropometric profiles of elite climbers have been unavailable. In order to fill this information void, 39 world-class climbers (21 males, 18 females) were assessed immediately prior to competition at an international World Cup sport climbing championship. All of the subjects tested were competition semi-finalists and, among these, seven males and six females advanced to the finals. The variables measured included age, years of climbing experience, height, body mass, height-weight ratio, sum of seven skinfolds, % body fat, fat-free mass, hand and arm volumes via plethysmography, average of right and left grip strengths, grip strength to body mass ratio (SMR), and climbing ability defined as the most difficult route climbed on lead. The results indicated that elite sport climbers are of small to moderate stature and exhibit very low % fat, moderate grip strength and high SMR when compared with other athletic groups. Values for the height-weight ratio and sum of seven skinfolds in the female finalists were very near those of the male finalists, which may indicate that reduction of body mass and % fat are primary adaptations in these female athletes. Climbing ability was predictable from SMR and % fat, though the R2 was low.

Adult↗
PubMed1989

Electro-olfactogram and multiunit olfactory receptor responses to binary and trinary mixtures of amino acids in the channel catfish, Ictalurus punctatus.

In vivo electrophysiological recordings from populations of olfactory receptor neurons in the channel catfish, Ictalurus punctatus, clearly showed that responses to binary and trinary mixtures of amino acids were predictable with knowledge obtained from previous cross-adaptation studies of the relative independence of the respective binding sites of the component stimuli. All component stimuli, from which equal aliquots were drawn to form the mixtures, were adjusted in concentration to provide for approximately equal response magnitudes. The magnitude of the response to a mixture whose component amino acids showed significant cross-reactivity was equivalent to the response to any single component used to form that mixture. A mixture whose component amino acids showed minimal cross-adaptation produced a significantly larger relative response than a mixture whose components exhibited considerable cross-reactivity. This larger response approached the sum of the responses to the individual component amino acids tested at the resulting concentrations in the mixture, even though olfactory receptor dose-response functions for amino acids in this species are characterized by extreme sensory compression (i.e., successive concentration increments produce progressively smaller physiological responses). Thus, the present study indicates that the response to sensory stimulation of olfactory receptor sites is more enhanced by the activation of different receptor site types than by stimulus interaction at a single site type.

Amino Acids↗
PubMed1999

Seed Dispersal as a Maternally Influenced Character: Mechanistic Basis of Maternal Effects and Selection on Maternal Characters in an Annual Plant.

Maternal influences on progeny characters affect phenotypic correlations between characters expressed in maternal and progeny generations and consequently influence evolutionary responses to selection. Net selection on maternally influenced characters depends on selection both on the progeny character and on the maternal characters that influence it. I used seed dispersal in Cakile edentula as a system in which to identify the mechanisms of environmentally mediated maternal effects and to determine how selection on maternal characters alters the adaptive value of dispersal. In C. edentula, maternal morphology responds to conspecific density experienced by the mother. Maternal morphology in turn affects offspring (seed) dispersal and density and thereby offspring morphology and fitness. I estimated the magnitude of density-mediated maternal effects on dispersal and identified their mechanism by characterizing the plasticity of maternal morphology to density. I also measured density-dependent selection on maternal characters that influence dispersal. Maternal plasticity to density was caused by both allometric and nonallometric variation in morphology, and this plasticity resulted in a negative correlation between maternal and progeny density. Such negative maternal effects are expected to retard responses to selection. Maternal morphology influenced maternal fitness, in part through the relationship of fitness to maternal plant size and in part through size-independent fitness effects. Maternal phenotypes that promote dispersal, and thereby increase progeny fitness, were associated with decreased maternal fitness. Selection on dispersal at the level of progeny favors increased dispersal; maternal influences on dispersal, however, not only cause a greatly reduced adaptive value of dispersal but lead to the prediction of a slower response to selection.

dispersal↗