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Results for “predictability of adaptation”

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PubMed2005

An empirical test of the kin selection hypothesis for male homosexuality.

The current investigation, following Bobrow and Bailey (2001), aimed to test the kin selection theory of homosexuality in human males using a survey design. A total of 60 heterosexual and 60 homosexual men from England completed items measuring psychological and behavioral indices of "special design" as predicted by adaptation due to kin selection. There were no significant differences between heterosexual and homosexual men in general familial affinity, generous feelings (willingness to provide financial and emotional resources), and benevolent tendencies (such as willingness to baby-sit). These remained non-significant after co-varying for level of personal income (higher among homosexual men), psychological gender, and interest in children. Overall, little support was found for the kin selection theory in a community sample.

Adult↗
PubMed1994

Antinatriuretic kidney response to weightlessness.

We have tested the effects of weightlessness on renal function in one subject who flew the recent week-long Russian-German MIR'92 space mission. Urine flow, renal sodium excretion, and the excretion of urodilatin were measured during the first and last days of the flight. Our results demonstrated, in contrast to expectations, that urine flow and sodium excretion during weightlessness were actually lower than the values obtained during preflight measurements. These results therefore are inconsistent with the commonly held hypothesis that weightlessness induces a diuresis and natriuresis in human subjects. It would seem that further studies are necessary to resolve this issue and to determine whether currently used ground-based models of weightlessness correctly predict physiological adaptations that occur during space flight.

Atrial Natriuretic Factor↗
PubMed1986

On the thermoregulatory consequences of NMR imaging.

A simple model of physiological thermoregulation has been adapted to predict the thermoregulatory consequences of exposure to the nuclear magnetic resonance (NMR) imaging environment. Based on our knowledge of thermoregulatory processes and how heat is exchanged between a person and the environment, the model can predict physiological heat loss responses in real time as a function of selected ambient temperature (Ta), air movement (v), and rate of whole-body radiofrequency (RF) energy deposition (SAR). Assuming a criterion elevation in deep body temperature (delta Tco) of 0.6 degree C, Ta = 20 degrees C and v = 0.8 m/sec, a 70 kg patient could undergo an NMR exposure of infinite duration at SAR less than or equal to 5 W/kg. Lowering Ta or increasing v permits a rise in permissible SAR for a given delta Tco. More restrictive delta Tco criteria result in lower permissible SARs and shorter exposure durations. The limiting response under all conditions tested was found to be the rate of peripheral blood flow, although sweating played a significant role in preventing excessive delta Tco. Some guidance for the clinical application of the predictions is offered.

Body Temperature Regulation↗
PubMed2005

Visual evoked potentials discrimination based on adaptive zero-tracking neural network.

A non-linear classifier is proposed to discriminate visual evoked potentials (VEP). It combines two techniques: the zero-tracking method and a multi-layer network. The first method consists of processing the VEP data through an adaptive linear prediction filter aiming at extracting the appropriate feature vector to be fed into the neural network. 105 VEPs collected from 48 healthy people and 57 patients are analysed to test the performances of the proposed classifier. The results obtained with a back-propagation network revealed a total success rate equal to 89%. It is also found more accurate than the latency method used in hospitals.

Algorithms↗
PubMed2026

Coarse-grained resource allocation modeling for decoding and rewiring microbial metabolism.

Microbial metabolism is a complex, emergent system driven by the coordinated interplay of intricate and dynamic molecular processes. To elucidate cellular behavior and enable biotechnological applications, quantitative models that address the inherent complexity of metabolism have been developed from a resource allocation perspective. Here, we synthesize recent advances in coarse-grained resource allocation frameworks and their applications in understanding microbial physiology and guiding gene circuit design. These frameworks reveal global regulatory constraints and predict cellular adaptation to nutrient and environmental changes. In addition, they enable the quantification of metabolic costs, the dissection of circuit-host interactions, and the development of strategies for burden mitigation. Collectively, these modeling frameworks provide a powerful platform for uncovering quantitative principles of microbial growth and engineering robust synthetic biological systems.

coarse-grained modeling↗
PubMed2002

A statistical model for the heterogeneous structure of porous catalyst pellets.

The complex structures of the void space of porous media are often characterised by parameters such as pore network connectivity and lattice size. This paper presents a comparison of the estimates of these parameters obtained from two previous methods based on nitrogen sorption and mercury porosimetry, and also from a new, completely independent approach based on pulsed-gradient spin-echo nuclear magnetic resonance (PGSE NMR). It was found that the new PGSE NMR technique obtains estimates of connectivity and lattice size in agreement with nitrogen sorption but different to mercury porosimetry. This difference was attributed to the various physical processes involved actually probing different aspects of the pore space geometry. It was further suggested that the representation of the pore structure derived from either nitrogen sorption or PGSE NMR is really a mapping of the real pore space onto an equivalent abstract, random pore bond network. However, it has been shown that this mapping does capture some of the characteristic properties of the pore space that control transport over mesoscopic ( < 10 microm) length scales. For materials which additionally possessed macroscopic (> 10 microm) structural heterogeneity, it was found that the model could also be adapted to predict the macroscopic transport properties of the porous medium.

Journal Article↗
PubMed2001

A mechanistic model for internal bone remodeling exhibits different dynamic responses in disuse and overload.

Bone is a dynamic tissue which, through the process of bone remodeling in the mature skeleton, renews itself during normal function and adapts to mechanical loads. It is, therefore, important to understand the effect of remodeling on the mechanical function of bone, as well as the effect of the inherent time lag in the remodeling process. In this study, we develop a constitutive model for bone remodeling which includes a number of relevant mechanical and biological processes and use this model to address differences in the remodeling behavior as a volume element of bone is placed in disuse or overload. The remodeling parameters exhibited damped oscillatory behavior as the element was placed in disuse, with the amplitude of the oscillations increasing as the severity of disuse increased. In overload situations, the remodeling parameters exhibited critically sensitive behavior for loads beyond a threshold value. These results bear some correspondence to experimental findings, suggesting that the model may be useful when examining the importance of transient responses for bone in disuse, and for investigating the role fatigue damage removal plays in preventing or causing stress fractures. In addition, the constitutive algorithm is currently being employed in finite element simulations of bone adaptation to predict important features of the internal structure of the normal femur, as well as to study bone diseases and their treatment.

Animals↗
PubMed2001

Hip-joint and abductor-muscle forces adequately represent in vivo loading of a cemented total hip reconstruction.

Using finite element analyses, we investigated which muscle groups acting around the hip-joint most prominently affected the load distributions in cemented total hip reconstructions with a bonded and debonded femoral stem. The purpose was to determine which muscle groups should be included in pre-clinical tests, predicting bone adaptation and mechanical failure of cemented reconstructions, ensuring an adequate representation of in vivo loading of the reconstruction. Loads were applied as occurring during heel-strike, mid-stance and push-off phases of gait. The stress/strain distributions within the reconstruction, produced by the hip-joint contact force, were compared to ones produced after sequentially including the abductors, the iliotibial tract and the adductors and vastii. Inclusion of the abductors had the most pronounced effect. They neutralized lateral bending of the reconstruction at heel-strike and increased medial bending at mid-stance and push-off. Bone strains and stem stresses were changed accordingly. Peak tensile cement stresses were reduced during all gait phases by amounts up to 50% around a bonded stem and 11% around a debonded one. Additional inclusion of the iliotibial tract, the adductors and the vastii produced relatively small effects during all gait phases. Their most prominent effect was a slight reduction of bone strains at the level of the stem tip during heel-strike. These results suggest that a loading configuration including the hip-joint contact force and the abductor forces can adequately reproduce in vivo loading of cemented total hip reconstructions in pre-clinical tests.

Biomechanical Phenomena↗
PubMed2003

Degraded EEG response of the human brain in function of gravity levels by the method of chaotic attractor.

The measurement of the influence of different gravity levels on the brain allows to explain how humans react to microgravity in space and to predict the adaptation capability of astronauts. Human electroencephalographic (EEG) signals were recorded during low and high gravity phases of three consecutive days of parabolic flights on the Caravelle aircraft in 1991. EEG signals were processed, using the method of correlation dimensions d of chaotic strange attractors. Results show clear differences between the three flights, with a general decrease over time in the attractor dimensions, a measure of the brain response to changing g levels. However, the dimension is not a one-to-one relation with g levels, as additional variations are observed. Two hypotheses are introduced, the "fatigue/stress" and the "g stress" hypotheses corresponding, respectively, to long-term fatigue accumulated over the three flights, and to short-term fatigue in response to change in g levels. The former explains the overall decrease of dimensions, the latter yields additional variations on shorter time scales. As the brain response degrades with time, at least six degraded modes were observed, explained by both short- and long-term fatigue.

Adaptation, Physiological↗
PubMed2000

Relationships between individual behavioural traits and post-weaning growth in segregated early-weaned piglets.

Piglets' individual behavioural traits have been studied in the last decade but no report has linked these traits with growth. This experiment was conducted to determine if behavioural traits of segregated early-weaned piglets could be good predictors of their post-weaning growth and, thus, help to predict their adaptation to early weaning. Following segregated early weaning at 17+/-1 days old, 252 piglets were submitted to three tests between 20 and 25 days of age: open-field, reaction to humans and rank order based on competition for a restricted-access feeder. The body weight of each piglet was measured the day before weaning and once a week for the next 4 weeks. A principal component analysis yielded five factors with an Eigenvalue higher than 0.90 that accounted for 81% of the total variation between individuals: reaction to humans (25%), active response to stress (21%), passive response to stress (14%), feeding behaviour (10%) and rank order (9%). Passive reaction to stress was associated with better weight gain during the first week post-weaning (r=0.18; P=0.01), and a positive correlation was found between social status and weight gain during the 4 weeks following weaning (-0.15</=r</=-0.10); P</=0.10). No relation was found between reaction to humans and growth. These results confirm the relationship between rank order and growth in pigs and may suggest that reacting passively to stress could facilitate adaptation to weaning.

Journal Article↗
PubMed1999

Somatic embryos of daylily in space.

Poor growth and nuclear abnormalities observable in some space-grown plants have been hypothesized as due to a combination of factors such as degree of development, the specific way the plants are grown and the way they experience multiple stresses, some of which are space-specific. Data from a 132-day experiment on 'Mir' using embryogenic cell cultures of daylily (Hemerocallis) allow seemingly contradictory evidence from earlier Shuttle missions to be harmonized: a) the more developed an embryo the less likely it is to suffer catastrophic cell stress during growth, whereas the less developed it is, the greater its vulnerability; (b) the extent to which the stress becomes manifest is also dependent on the extent of pre-existing stresses imposed by suboptimal growing conditions; (c) an appropriate, albeit undesirable, 'stress match' with other non-equilibrium determinants, much like a 'tug of war', can result in genomic variations in space. It is not understood what is/are the feature(s) of the space environment that cause the various cell division perturbations but they have not yet been mimicked on earth. The stress symptoms were found only in space materials and, as predicted, they were most frequently encountered in smaller, less-developed materials grown under non-optimized conditions. It is concluded that, while any substantial deviation from 'optimum' can be a 'stress', spaceflight subjects vulnerable materials to cell division or DNA-repair stress(es) that appear distinctive, but remain elusive so far. Fastidiously-controlled growing environments must be devised to resolve the matter of direct versus indirect effects of space. On a practical level, it is predicted that adapting plant biotechnologies to space conditions will not be a casual matter. Grant Numbers: NAG21026.

Cell Division↗
PubMed1977

Contextual influences on judgments of linear extent.

A series of experiments was performed to test the predictions of adaptation level, efferent readiness, and framing explanations of illusions of extent. The framing notion, that the ratio of total figure length to shaft length (i.e., the framing ratio) determines the magnitude of illusions, was supported for the Müller-Lyer, Baldwin, and divided line illusions. Peak overestimation of shaft length obtained when the framing ratio was 3:2. Variation of proximal figure size, achieved by altering either viewing distance or distal figure size, was found to be directly related to the magnitude of the illusions. A model was proposed to account for the effects of both the framing ratio and proximal shaft length on judgments of focal length.

Cues↗
PubMed1986

An information seeking disposition in child surgery patients.

Several studies in the last decade have demonstrated the importance of considering an information seeking versus information avoiding coping dimension in adult medical patients. However, there have been few empirical demonstrations of such a dimension in children. The present study utilized the Coping Strategies Interview to assign an information seeking score to child elective surgery patients. This information seeking score was related to several parent-rated variables, including the child's historical success in coping with medical procedures, the child's typical preference for information acquisition, and the child's typically emitted coping behaviors. In addition, the information seeking score was related to question asking and discussion of medical procedures as rated by an objective observer during the blood test, by the nurse during anesthesia induction, and by the parent during recovery from surgery. It was strongly related to the information acquired prior to hospitalization. Information seeking was also related to stress responses, such that high information seeking scores predicted more adaptive behaviors prior to the blood test. This cross-rater and cross-situation validation suggests the existence of an information seeking dimension in children and the utility of considering this dimension in future research.

Adaptation, Psychological↗
PubMed2000

Mechanisms of sudden infant death and the contamination of inspired air with exhaled air.

The physiological effects on an infant of repeatedly sleeping in an environment consisting of a mixture of exhaled air and fresh air is examined. It is found that adaptation can be predicted. A possible outcome of the adaptation is shown to be the development of hypoxia when the conditions change during sleep from a state with carbon dioxide contamination of inspired air to one without. This hypoxia can be associated with apnoea: this apnoea can provide an explanation for some instances of sudden infant death. This explanation is consistent with the known epidemiology and environmental associations of a proportion of sudden infant death syndrome. Safety precautions for the prevention of re-breathing are given.

Air↗
PubMed2006

Effect of ankle joint stiffness during eccentric phase in rebound jumps on ankle joint torque at midpoint.

The purposes of this study were to investigate firstly, the ankle joint stiffness during the eccentric phase in rebound jumps, and secondly, the effect of ankle joint stiffness during the eccentric phase on ankle joint torque at midpoint. Nine active males executed rebound drop jumps from a height of 30 cm (RDJ30) and 50 cm (RDJ50), and 5-repetition rebound jumps (5RJ). Force plate data, limb position and electromyogram (EMG) of the medial head of gastrocnemius (GAS), soleus (SOL), and tibialis anterior (TA) muscles were recorded simultaneously during all jumps. When compared with RDJ30 and RDJ50, 5RJ displayed significantly higher jumping height, ankle joint torque at midpoint, ankle joint stiffness during the eccentric phase, and integrated EMG (IEMG) of GAS and SOL. Furthermore, 5RJ displayed significantly lower contact time and IEMG of TA than RDJ30 and RDJ50 did. The ankle joint torque at midpoint showed a significant positive correlation with jumping height but a significant negative correlation with contact time in rebound jumps. There was a significant positive correlation between the ankle joint stiffness during the eccentric phase and ankle joint torque at midpoint in rebound jumps. These results suggested that for the rebound jumps to be effective, it may be important to enhance the ankle joint torque at midpoint by greater ankle joint stiffness during the eccentric phase. These results also suggested that compared to 5RJ, RDJ30 and RDJ50 may reduce ankle joint stiffness in order to protect the tendomuscular system from the stretch load. However, ankle joint stiffness is possibly increased in 5RJ because the restraint to defend the tendomuscular system is reduced by prediction or adaptation to the stretch load because it is a continuous jump.

Adult↗
PubMed2005

Acute physical stress elevates mouse period1 mRNA expression in mouse peripheral tissues via a glucocorticoid-responsive element.

In mammals, the circadian and stress systems (both centers of which are located in the hypothalamus) are involved in adaptation to predictable and unpredictable environmental stimuli, respectively. Although the interaction and relationship between these two systems are intriguing and have been studied in different ways since the "pre-clock gene" era, the molecular interaction between them remains largely unknown. Here, we show by systematic molecular biological analysis that acute physical stress elevated only Period1 (Per1) mRNA expression in mouse peripheral organs. Although behavioral rhythms in vivo and peripheral molecular clocks are rather stable against acute restraint stress, the results of a series of promoter analyses, including chromatin immunoprecipitation assays, indicate that a glucocorticoid-responsive element in the Per1 promoter is indispensable for induction of this mRNA both in vitro and in vivo. These results suggest that Per1 can be a potential stress marker and that a third pathway of Per1 transcriptional control may exist in addition to the clock-regulated CLOCK-BMAL1/E-box and light-responsive cAMP-responsive element-binding protein/cAMP-responsive element pathways.

Acute Disease↗