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PubMed2006

Charlson scores based on ICD-10 administrative data were valid in assessing comorbidity in patients undergoing urological cancer surgery.

BACKGROUND AND OBJECTIVES: Adjustment for comorbidity is an essential component of any observational study comparing outcomes. We evaluated the validity of the Charlson comorbidity score based on ICD-10 codes in patients undergoing urological cancer surgery within an English administrative database. STUDY DESIGN AND SETTING: Patients who underwent radical urological cancer surgery between 1998 and 2002 in the English National Health Service were identified from the Hospital Episode Statistics database (N = 20,138). ICD-9-CM codes defining comorbid diseases according to the Deyo and Dartmouth-Manitoba adaptations of the Charlson comorbidity score were translated into ICD-10 codes. RESULTS: Charlson scores derived by the ICD-10 translation of the Deyo and Dartmouth-Manitoba adaptations were identical in 16,623 patients (83%; kappa = .63). For both adaptations, ICD-10 scores increased with age, were higher in patients admitted on an emergency basis, and predicted short-term outcome. Addition of either the ICD-10 Charlson Deyo or Dartmouth-Manitoba score to risk models containing age and sex to predict in-hospital mortality resulted in a better model fit but only in small improvements of the predictive power. CONCLUSION: The ICD-10 translations of the Deyo and Dartmouth-Manitoba adaptations performed similarly in risk models predicting hospital mortality following urological cancer surgery. Adjustment for comorbidity over and above age and sex alone does not seem to provide a large improvement.

Aged↗
PubMed1993

Adaptive buffering of breath-by-breath variations of end-tidal CO2 of humans.

We have designed and implemented a computer-controlled system that uses an adaptive control algorithm (generalized minimum variance) to buffer the breath-by-breath variations of the end-tidal CO2 fraction (FETCO2) that occur spontaneously or are exaggerated in certain experimental protocols (e.g., induced hypoxia, any type of induced variations in the ventilatory pattern). Near the end of each breath, FETCO2 of the following breath is predicted and the inspired CO2 fraction (FICO2) of the upcoming breath is adjusted to minimize the difference between the predicted and desired FETCO2 of the next breath. The one-breath-ahead prediction of FETCO2 is based on an adaptive autoregressive with exogenous inputs (ARX) model: FETCO2 of a given breath is related to FICO2, FETCO2 of the previous breath, and inspiratory ventilation. Adequacy of the prediction is demonstrated using data from experiments in which FICO2 was varied pseudorandomly in wakefulness and sleep. The algorithm for optimally buffering changes in FETCO2 is based on the coefficients of the ARX model. We have determined experimentally the frequency of FETCO2 variations that can be buffered adequately by our controller, testing both spontaneous variations in FETCO2 and variations induced by hypoxia in young awake human subjects. The controller is most effective in buffering variations of FETCO2 in the frequency range of <0.1 cycle/breath. Some potential applications are discussed.

Adaptation, Physiological↗
PubMed1982

Adaptation in the long-wavelength pathways.

We describe and test predictions of a model of long-wavelength test sensitivity upon large, uniform backgrounds. The model explains changes in sensitivity in the red-green detection pathways strictly based upon losses of sensitivity in the receptors. We derive the prediction that field mixture data for field-mixtures of mu1 (fixed) and an addend, mu 2, must follow the same shape on different intensities of the fixed background, mu 1. This prediction is not in good agreement with the measurements.

Adaptation, Ocular↗
PubMed2000

Modifications of reward expectation-related neuronal activity during learning in primate orbitofrontal cortex.

This study investigated how neuronal activity in orbitofrontal cortex related to the expectation of reward changed while monkeys repeatedly learned to associate new instruction pictures with known behavioral reactions and reinforcers. In a delayed go-nogo task with several trial types, an initial picture instructed the animal to execute or withhold a reaching movement and to expect a liquid reward or a conditioned auditory reinforcer. When novel instruction pictures were presented, animals learned according to a trial-and-error strategy. After experience with a large number of novel pictures, learning occurred in a few trials, and correct performance usually exceeded 70% in the first 60-90 trials. About 150 task-related neurons in orbitofrontal cortex were studied in both familiar and learning conditions and showed two major forms of changes during learning. Quantitative changes of responses to the initial instruction were seen as appearance of new responses, increase of existing responses, or decrease or complete disappearance of responses. The changes usually outlasted initial learning trials and persisted during subsequent consolidation. They often modified the trial selectivities of activations. Increases might reflect the increased attention during learning and induce neuronal changes underlying the behavioral adaptations. Decreases might be related to the unreliable reward-predicting value of frequently changing learning instructions. The second form of changes reflected the adaptation of reward expectations during learning. In initial learning trials, animals reacted as if they expected liquid reward in every trial type, although only two of the three trial types were rewarded with liquid. In close correspondence, neuronal activations related to the expectation of reward occurred initially in every trial type. The behavioral indices for reward expectation and their neuronal correlates adapted in parallel during the course of learning and became restricted to rewarded trials. In conclusion, these data support the notion that neurons in orbitofrontal cortex code reward information in a flexible and adaptive manner during behavioral changes after novel stimuli.

Adaptation, Psychological↗
PubMed2006

Role of lysine versus arginine in enzyme cold-adaptation: modifying lysine to homo-arginine stabilizes the cold-adapted alpha-amylase from Pseudoalteramonas haloplanktis.

The cold-adapted alpha-amylase from Pseudoalteromonas haloplanktis (AHA) is a multidomain enzyme capable of reversible unfolding. Cold-adapted proteins, including AHA, have been predicted to be structurally flexible and conformationally unstable as a consequence of a high lysine-to-arginine ratio. In order to examine the role of low arginine content in structural flexibility of AHA, the amino groups of lysine were guanidinated to form homo-arginine (hR), and the structure-function-stability properties of the modified enzyme were analyzed by transverse urea gradient-gel electrophoresis. The extent of modification was monitored by MALDI-TOF-MS, and correlated to changes in activity and stability. Modifying lysine to hR produced a conformationally more stable and less active alpha-amylase. The k(cat) of the modified enzyme decreased with a concomitant increase in deltaH# and decrease in K(m). To interpret the structural basis of the kinetic and thermodynamic properties, the hR residues were modeled in the AHA X-ray structure and compared to the X-ray structure of a thermostable homolog. The experimental properties of the modified AHA were consistent with K106hR forming an intra-Domain B salt bridge to stabilize the active site and decrease the cooperativity of unfolding. Homo-Arg modification also appeared to alter Ca2+ and Cl- binding in the active site. Our results indicate that replacing lysine with hR generates mesophilic-like characteristics in AHA, and provides support for the importance of lysine residues in promoting enzyme cold adaptation. These data were consistent with computational analyses that show that AHA possesses a compositional bias that favors decreased conformational stability and increased flexibility.

Amino Acid Sequence↗
PubMed2000

Eukaryote-specific domains in translation initiation factors: implications for translation regulation and evolution of the translation system.

Computational analysis of sequences of proteins involved in translation initiation in eukaryotes reveals a number of specific domains that are not represented in bacteria or archaea. Most of these eukaryote-specific domains are known or predicted to possess an alpha-helical structure, which suggests that such domains are easier to invent in the course of evolution than are domains of other structural classes. A previously undetected, conserved region predicted to form an alpha-helical domain is delineated in the initiation factor eIF4G, in Nonsense-mediated mRNA decay 2 protein (NMD2/UPF2), in the nuclear cap-binding CBP80, and in other, poorly characterized proteins, which is named the NIC (NMD2, eIF4G, CBP80) domain. Biochemical and mutagenesis data on NIC-containing proteins indicate that this predicted domain is one of the central adapters in the regulation of mRNA processing, translation, and degradation. It is demonstrated that, in the course of eukaryotic evolution, initiation factor eIF4G, of which NIC is the core, conserved portion, has accreted several additional, distinct predicted domains such as MI (MA-3 and eIF4G ) and W2, which probably was accompanied by acquisition of new regulatory interactions.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Herbivore responses to plant secondary compounds: a test of phytochemical coevolution theory.

Literature data were collected on the floristic distribution and toxicity of phytochemicals to herbivores and on herbivore specialization in order to test phytochemical coevolution theory. The theory makes four predictions that can be tested with this information. Herbivores can adapt to novel, more toxic chemicals by becoming specialists, or they can become generalists but at the cost of lower feeding success on any particular host. Thus, the first two predictions are as follows: herbivores should do better on chemicals that are present in their normal host, and this pattern should be stronger for specialists than for generalists. The "escape and radiation" aspect of the theory holds that if a plant taxon with a novel defense chemical diversifies, the chemical will become widespread. Eventually, herbivores will adapt to and disarm it. So the third prediction is that more widespread chemicals are less toxic than more narrowly distributed ones. Because generalists should not do as well as specialists on chemicals disarmed by the latter, the fourth prediction is that the third prediction should be more true for generalists than specialists and should depend on presence/absence of the chemical in the normal host. Multiple regressions of toxicity (herbivore mortality and final weight) on three predictor variables (chemical presence/absence in the normal host, specialism, and chemical floristic distribution) and relevant interactions were used to test these predictions. Chemical presence/absence in the normal host, the interaction between this variable and specialism, and chemical floristic distribution had significant effects on both measures of toxicity, supporting the first three predictions of the model. Support for the fourth prediction (a three-way interaction among all predictor variables) was evident for final weight but not mortality, perhaps because growth is more responsive to toxicity differences than survival. In short, the phytochemistry literature provides broad support for the phytochemical coevolution model.

Adaptation, Physiological↗
PubMed2002

Acculturation and adaptation of Soviet Jewish refugee adolescents: predictors of adjustment across life domains.

This study explores how acculturation is related to adaptation across different life spheres for 162 Soviet Jewish refugee adolescents in a suburban community in Maryland. Because the different contexts of refugee adolescents' lives vary in acculturative demands, different patterns of acculturation should be related to adaptation in different life spheres. The study uses a multidimensional measure of acculturation and assesses acculturation to both American and Russian cultures as it relates to psychological adaptation, peer relations, and school and family outcomes. Findings support the general ecological thesis that acculturation to different cultures is differentially related to adaptation across life domains. Acculturation to American culture predicted better grades and perceived support from American peers. Acculturation to Russian culture predicted perceived support from Russian peers. Both American acculturation and Russian acculturation predicted reduced loneliness and perceived support from parents. Further, different dimensions of acculturation, such as language and identity, were differentially related to adaptation. Implications for acculturation theory and measurement are drawn, and cautions are offered about the interpretation of acculturation studies using single proxies such as language use or preference.

Acculturation↗
PubMed2003

Which REE prediction equation should we use in normal-weight, overweight and obese women?

BACKGROUND & AIMS: In our modern society, there is a growing and increasing prevalence of overweight, obesity and eating disorders and young female subjects frequently ask for nutritional counselling. Resting energy expenditure (REE) is essential to provide a sound diet to subjects seeking nutritional support. We perform a critical selection of accurate and reliable prediction equations employed on normal-weight, overweight and obese young women. METHODS: REE of 157 young women of Caucasian race (18-35 years)was measured with indirect calorimetry and was compared with the principal prediction equations (Harris and Benedict, Owen, Mifflin, WHO, Bernstein and Robertson and Reid). The statistical analysis used to compare measured and the predicted REE was paired t -test, +/-95% confidence interval and Bland and Altman method. The influence of weight loss on the prediction error was estimated in 31 subjects. An additional REE measurement was performed on patients who had lost >or=5% of the initial body weight due to a sound low-calorie diet. RESULTS: The equations more reliable in our study are Owen's equation in normal-weight subjects, Bernstein's equation in overweight subjects and Robertson and Reid's equation in obese subjects. Weight was a significant variable according to the stepwise regression analysis resulting in the following equation: 542.2 + 11.5 kg;R(2) : 0.59. Weight loss decisively increased the overestimation of the equations and only Owen's equation maintained the error of prediction within acceptable limits. CONCLUSIONS: The equation of Owen in normal weight, Bernstein in overweight and of Robertson and Reid in obese subjects should be chosen when we have to predict REE in young women. Due to metabolic adaptation occurring during therapeutic or spontaneous energy restriction, we suggest to use Owen' s equation.

Adaptation, Physiological↗
PubMed2000

Childhood depressive symptoms predict psychiatric problems in young adults.

OBJECTIVE: To evaluate the predictive value of childhood depressive symptoms for psychiatric symptoms, adaptive functioning, and self-performance in young adults. METHOD: The study sample consisted of 111 young adults born during 1975-1976 in the Helsinki region. The young adults were assessed in childhood (10 to 11 years of age) using the Children's Depression Inventory (CDI) and at the age of 20 to 21 years using Achenbach's Young Adult Self Report (YASR), the Beck Depression Inventory (BDI), and the Wallston Self-Performance Survey. RESULTS: Self-reported depressive symptoms in childhood predicted psychiatric symptoms (especially aggression), poor adaptive functioning, and low self-esteem in young adulthood. CONCLUSIONS: Depressive symptoms in children should be addressed to prevent later psychiatric problems. The CDI may be a measure of nonspecific psychopathology rather than of pure depression--thus, it may be a good screening tool for child populations.

Adaptation, Psychological↗
PubMed1997

Basal metabolism of weight-stable chronically undernourished men and women: lack of metabolic adaptation and ethnic differences.

The purpose of this study was to investigate whether weight-stable chronically energy-deficient subjects exhibit evidence of metabolic adaptation and to establish whether international predictive equations overestimate the basal metabolic rate (BMR) of tropical populations. BMR, body weight, height, and fat-free mass (FFM) by underwater weighing were measured in healthy, physically active urban dwellers of low socioeconomic status (178 men and women aged 22-38 y) in Bangalore, Southern India. Subjects were selected on the basis of body mass index (BMI; in kg/m2) and classified in three groups: severely undernourished (BMI < 17.0; n = 30 men, n = 25 women), marginally undernourished (BMI = 17.0-18.5; n = 31 men, n = 30 women), and well nourished (BMI > 18.5; n = 27 men, n = 35 women). The BMR of the well-nourished group, expressed in absolute terms (6.20 and 5.18 MJ/d for men and women, respectively), was significantly higher (P < 0.000) than that of the severely undernourished group (5.72 and 4.64 MJ/d for men and women, respectively). Normalizing BMR for either body weight or FFM by analysis of covariance abolished all differences. The mean BMR of the low-BMI study group was substantially higher (11-14%) than reported previously for undernourished Indian adults. The BMR of both men and women, regardless of their nutritional status, was accurately estimated by age- and sex-specific FAO/WHO/UNU equations. These findings suggest the absence of an enhanced metabolic response in weight-stable chronically undernourished adults. This is in contrast with earlier reports, and supports more recent views. The study also provides evidence of the absence of ethnic-specific energy turnover in Indians.

Adaptation, Physiological↗
PubMed2000

Quantification of plasma lipids and apolipoproteins by use of proton NMR spectroscopy, multivariate and neural network analysis.

New approaches for quantification of human blood plasma lipids and apolipoproteins are presented. One method is based on multivariate analysis of proton nuclear magnetic resonance spectra of human blood plasma. Although similar approaches have been developed previously, this is the first time principal component analysis (PCA) and partial least squares regression (PLS) have been applied to this particular task. Further, a large proportion of the subjects in this study were cancer patients undergoing treatment, which introduced a new dimension to the quantification of lipoprotein distributions. Calibration models for prediction of lipids and apolipoproteins were constructed by use of PLS, and blind samples were used to test the predictive ability. Comparison of the predicted vs observed data obtained by standard clinical chemical procedures gave good agreement; the correlation coefficient for total plasma triglyceride was 0.99, for total plasma cholesterol 0.98, for LDL cholesterol 0. 97, and for HDL cholesterol 0.88. These results are comparable with those obtained with other methods. The quantitative analysis of 14 components (including total cholesterol and total triglyceride) of human blood plasma was also undertaken using various neural network (NN) analyses of selected portions of the spectra. Conventional fully connected backpropagation neural network topologies were capable of providing excellent predictions for the majority of the variables, confirming and reinforcing literature related to this approach. However HDL triglycerides were poorly predicted, while intermediate-quality results were obtained for the LDL cholesterol, plasma apoA1 and LDL apoB variables. In these instances, applying significantly different neural network algorithms involving either general regression or polynomial neural networks in combination with genetic adaptive components for parameter optimisation made improved predictions.

Adult↗
PubMed1997

Adaptive mutation: a general phenomenon or special case?

A recent article by Galitski and Roth characterizes adaptive reversion of chromosomal lac- mutations in Salmonella typhimurium LT2. Using a classical genetic approach they show that adaptive reversion, as characterized by the appearance of late revertant colonies, is an exception rather than a general phenomenon for reversion of nonsense, missense, frameshift and insertion mutations. For certain mutations, however, the number of late revertants exceeds the predicted number. These excess revertants suggest that adaptive mutability is applicable to chromosomal genes as well as to genetic changes involving F plasmids and lysogenic phages.

Adaptation, Physiological↗
PubMed1994

Motion adaptation governs the shape of motion-evoked cortical potentials.

We recorded visually evoked potentials (VEPs) to motion onset/offset of square-wave gratings (dominant spatial frequency 0.69 c/deg, velocity 4.9 deg/sec, contrast 10%, luminance 15 cd/m2) with three electrode combinations (Oz vs Fz, Oz vs linked ears and parietal vs linked ears). In one experiment (seven subjects), we examined the effect of the duty-cycle of motion vs non-motion (5-80%) on the size of the various motion-evoked components. In another experiment (six subjects, duty-cycle 10%), we examined the effect of motion adaptation on the motion VEP. We observed both a positive VEP component around 110 msec (P1) and a negative component around 180 msec (N200). The amplitude of these components depended on duty-cycle and electrode position: N200 dominated at < or = 20% motion duty-cycle, P1 at > or = 50%; P1 dominated medially, N200 laterally. Motion adaptation enhanced the P1 and reduced the N200 by a factor of 3. Previous controversies regarding the major components of motion-evoked potential may be due to different duty-cycles. The effect of duty-cycle is probably caused by adaptation to the test stimulus; it can be predicted quantitatively by a simple one-parameter model based on the assumption that the VEP amplitude is proportional to the non-adapted proportion of motion-response generators.

Adaptation, Physiological↗
PubMed1999

Prediction games and arcing algorithms

The theory behind the success of adaptive reweighting and combining algorithms (arcing) such as Adaboost (Freund & Schapire, 1996a, 1997) and others in reducing generalization error has not been well understood. By formulating prediction as a game where one player makes a selection from instances in the training set and the other a convex linear combination of predictors from a finite set, existing arcing algorithms are shown to be algorithms for finding good game strategies. The minimax theorem is an essential ingredient of the convergence proofs. An arcing algorithm is described that converges to the optimal strategy. A bound on the generalization error for the combined predictors in terms of their maximum error is proven that is sharper than bounds to date. Schapire, Freund, Bartlett, and Lee (1997) offered an explanation of why Adaboost works in terms of its ability to produce generally high margins. The empirical comparison of Adaboost to the optimal arching algorithm shows that their explanation is not complete.

Journal Article↗
PubMed1999

Adaptive mechanisms in the elasmobranch hindbrain

The suppression of self-generated electrosensory noise (reafference) and other predictable signals in the elasmobranch medulla is accomplished in part by an adaptive filter mechanism, which now appears to represent a more universal form of the modifiable efference copy mechanism discovered by Bell. It also exists in the gymnotid electrosensory lateral lobe and mechanosensory lateral line nucleus in other teleosts. In the skate dorsal nucleus, motor corollary discharge, proprioceptive and descending electrosensory signals all contribute in an independent and additive fashion to a cancellation input to the projection neurons that suppresses their response to reafference. The form of the cancellation signal is quite stable and apparently well-preserved between bouts of a particular behavior, but it can also be modified within minutes to match changes in the form of the reafference associated with that behavior. Motor corollary discharge, proprioceptive and electrosensory inputs are each relayed to the dorsal nucleus from granule cells of the vestibulolateral cerebellum. Direct evidence from intracellular studies and direct electrical stimulation of the parallel fiber projection support an adaptive filter model that places a principal site of the filter's plasticity at the synapses between parallel fibers and projection neurons.

Journal Article↗
PubMed2000

Cerebrovascular reserve capacity in patients with hyperlipidemia.

PURPOSE: Because recent data are conflicting, it is not certain whether hyperlipidemia is an independent risk factor for cerebrovascular diseases. Decreased cerebrovascular reserve capacity refers to the decreased ability of the cerebral arterioles to adapt in critical conditions and probably predicts a higher risk of stroke. The aim of this study was to compare cerebrovascular reserve capacity in hyperlipidemic patients and healthy controls using transcranial Doppler sonography. METHODS: Thirty-four hyperlipidemic patients and 21 healthy controls were examined. With transcranial Doppler sonography, the mean blood flow velocity in the middle cerebral artery was registered at rest and at 5, 10, 15, and 20 minutes after intravenous administration of 1,000 mg acetazolamide. Cerebrovascular reactivity and reserve capacity were calculated from mean blood flow velocities. Various laboratory measurements were also made and assessed for correlation with resting cerebral blood flow velocity and cerebrovascular reserve capacity. RESULTS: No significant differences could be observed between controls and hyperlipidemic patients in cerebrovascular reactivity or cerebrovascular reserve capacity. No correlation was found between various laboratory measurements and resting cerebral blood flow velocity or cerebrovascular reserve capacity. CONCLUSIONS: We could not demonstrate any differences in cerebrovascular reserve capacity between hyperlipidemic patients and healthy controls. Thus, the vasodilatory ability of the cerebral arterioles seems to remain unchanged in this patient group and is not correlated with the severity of hyperlipidemia.

Acetazolamide↗
PubMed1987

Prediction of recovery for closed-head-injured adults: an evaluation of the MMPI, the Adaptive Behavior Scale, and a "Quality of Life" Rating Scale.

Twenty-five closed-head-injured adults (24 males, 1 female; M age = 28.8 years) were classified as "recovered" if they had returned to work, school, or a sheltered workshop for which pay was received and "non-recovered" if they did not meet these criteria. Current status was compared with MMPI, Adaptive Behavior Scale (ABS), and "Quality of Life" Rating Scale (QLRS) scores at time of entry into a rehabilitation program. The "non-recovered" group was significantly higher on the PD (Psychopathic deviate) scale. No differences were found between groups on the Sc (Schizophrenia) or K (Validity) scales. The "recovered" group was significantly higher on the ABS Economic Activity domain and significantly lower in the Violent & Destructive, Antisocial, Rebelliousness, Untrustworthiness, Stereotyped Behavior & Odd Mannerisms, and Psychological Disturbance behavior domains. The self-ratings (QLRS) of the "nonrecovered" subjects were significantly more distinct from the ratings made by their relatives or significant others than were those of the "recovered" subjects.

Adult↗