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PubMed1989

Nutritional adaptation and variability.

In current nutrition literature man's requirement for energy for a given status and pattern of physical activity and body mass is fixed. Available experimental data on the other hand show that it is variable and self-regulated over a considerable range. This homoeostatic range is associated with covariance of man's genotype with local environmental effect under a sustained perturbation of common external environment. The implication is that man can have his intake anywhere in the range without being under nutritional stress. Below the lower limit of this range man is under energy stress, growth is retarded and man adapts to small body size. Unlike the homoeostatic range, this long-term adaptation is heritable, but there is no evidence that work output equals energy intake in adaptation to low intake. On the contrary, small subjects on a lower plane of nutrition are found to be metabolically more efficient. Evidence is cited to show that it is the decrease in BMR in subjects with low intake which plays a major role in facilitating a higher level of metabolic efficiency for subjects undergoing energy stress.

Adaptation, Physiological↗
PubMedDate not supplied

Comparison of the responses of AII amacrine cells in the dark- and light-adapted rabbit retina.

We studied the light-evoked responses of AII amacrine cells in the rabbit retina under dark- and light-adapted conditions. In contrast to the results of previous studies, we found that AII cells display robust responses to light over a 6-7 log unit intensity range, well beyond the operating range of rod photoreceptors. Under dark adaptation, AII cells showed an ON-center/OFF-surround receptive-field organization. The intensity-response profile of the center-mediated response component followed a dual-limbed sigmoidal function indicating a transition from rod to cone mediation as stimulus intensities were increased. Following light adaptation, the receptive-field organization of AII cells changed dramatically. Light-adapted AII cells showed both ON- and OFF-responses to stimulation of the center receptive field, but we found no evidence for an antagonistic surround. Interestingly, the OFF-center response appeared first following rapid light adaptation and was then replaced gradually over a 1-4 min period by the emerging ON-center response component. Application of the metabotropic glutamate receptor agonist APB, the ionotropic glutamate blocker CNQX, 8-bromo-cGMP, and the nitric oxide donor SNAP all showed differential effects on the various center-mediated responses displayed by dark- and light-adapted AII cells. Taken together, these pharmacological results indicated that different synaptic circuits are responsible for the generation of the different AII cell responses. Specifically, the rod-driven ON-center responses are apparently derived from rod bipolar cell synaptic inputs, whereas the cone-driven ON-center responses arise from signals crossing the gap junctions between AII cells and ON-center cone bipolar cells. Additionally, the OFF-center response of light-adapted AII cells reflects direct synaptic inputs from OFF-center cone bipolar cells to AII dendritic processes in the distal inner plexiform layer.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1990

Rod and cone contribution to adaptation processes in cat retinal ganglion cells.

Extracellular ganglion cell responses were recorded to investigate mechanisms of light adaptation. Monochromatic test spots (575 nm) were projected onto the receptive field center of off-center cells and superimposed on a steady blue-green Ganzfeld background (Schott Filter BG 28), the strength of which was increased in steps of 0.5 log units to adapt rods. Response vs. log intensity functions were determined over a range of 7 log units of test light irradiance at each background level. At higher adaptation levels response thresholds followed the typical Weber function. Surprisingly at lower adaptation levels the sensitivity of the cell increased by about 0.7 log units, most markedly in a range of 1 log unit of moderate light adaptation when the background was changed from dark to the dimmest detectable background (10(-5) lm/m2). In the dark-adapted state a small off-response of long latency (40-100 ms at 10(2) quanta.s-1.microns-2) is observed at low rod stimulating test light irradiances. A transition to a cone-dominated transient response of 2 to 5 ms duration occurred at high intensities (10(5) quanta.s-1.microns-2). At mesopic levels the two responses seem to cancel each other, rendering a delayed off-response that is probably the result of rod-cone interaction. As in psychophysics, saturation can be observed at very high background intensities (10(6) quanta.s-1 microns-2). These data suggest interactions between rods and cones that determine the sensitivity of cat retinal ganglion cells at low levels of adaptation for suprathreshold stimuli.

Action Potentials↗
PubMedDate not supplied

Adaptation of heterosexually infected HIV-positive women: a Swedish pilot study.

The experiences and adaptation of 8 women who were heterosexually infected with the HIV were examined. An interview schedule consisting of open-ended questions was used to elicit a full range of responses. Roy's (1984) adaptation model, focusing on physiological needs, self-concept, role-function, and interdependence provided the structure for analysis of each transcript. The interviews indicated that the women who had strong social and family support were coping better with their situation than were women who had little support. The interview responses also showed a lack of professional comportment among health care professionals in their contact with women who are HIV positive, indicating a need for further investigation of health care workers' knowledge and understanding of the needs of HIV-positive women. To plan effective programs, health care professionals need to identify the specific needs of each woman from a holistic perspective.

Adaptation, Psychological↗
PubMed1980

Correlation of dark adaptation test results with serum vitamin A levels in diseased adults.

Dark adaptation, is a reliable and highly reproducible indicator of vitamin A nutritional status in terms of function. Abnormal dark adaptation occurs over a fairly wide range of serum vitamin A values; however, the lower limit of serum vitamin A which is related to normal ocular function has not been determined. We studied dark adaptation in 67 patients with a variety of hepatic and gastrointestinal diseases or with chronic alcoholism. We found that a serum vitamin A level greater than or equal to 40 micrograms % predicted normal dark adaptation 95% of the time, a serum vitamin A level greater than or equal to 30 micrograms predicted normal retinal function 68% of the time and a level greater than or equal to 20 micrograms % predicted normal function 27% of the time. Thus, in individual patients with serum vitamin A levels less than 40 micrograms % one can be sure of vitamin A sufficiency only if a normal dark adaptation response is elicited.

Adult↗
PubMed2003

Adaptive significance of circadian clocks.

Circadian clocks are ubiquitous and are found in organisms ranging from bacteria to mammals. This ubiquity of occurrence implies adaptive significance, but to date there has been no rigorous empirical evidence to support this. It is believed that an organism possessing circadian clocks gains fitness advantage in two ways: (i) by synchronizing its behavioral and physiological processes to cyclic environmental factors (extrinsic adaptive value); (ii) by coordinating its internal metabolic processes (intrinsic adaptive value). There is preliminary circumstantial evidence to support both. Several studies using organisms living in constant environments have shown that these organisms possess functional circadian clocks, suggesting that circadian clocks may have some intrinsic adaptive value. Studies to assess the adaptive value of circadian clocks in periodic environments suggest that organisms may have a fitness advantage in those periodic environments, which closely match their own intrinsic periodicity. Furthermore, evidence from organisms living in the wild, selection studies, and studies on latitudinal clines suggest that circadian clocks may have an extrinsic adaptive value as well. In this paper, I have presented several hypotheses for the emergence of circadian clocks and have reviewed some major empirical studies suggesting adaptive significance of circadian clocks.

Adaptation, Physiological↗
PubMed1992

Subtractive processes in light adaptation.

We measured the time course of light adaptation in foveal vision following the onset of an adapting background. Several adaptational steps in the low to mid photopic range were examined. The time course of multiplicative and subtractive components of the adaptation were extracted from the data. Unlike previous findings there were no subtractive changes for several hundred milliseconds following light onset, and the process took 10-15 sec to reach steady state. It seems likely that the fast component previously observed results from effectively instantaneous center-surround antagonism, and that our measurements reflect a second subtractive process involving the slow loss of the d.c. signal over time.

Adaptation, Ocular↗
PubMed2000

Pharmacokinetic-pharmacodynamic modelling of tiagabine CNS effects upon chronic treatment in rats: lack of change in concentration-EEG effect relationship.

The pharmacodynamics of the gamma-aminobutyric acid (GABA) uptake inhibitor (R)-N-(4,4-di-(methylthien-2-yl)but-3-enyl) nipecotic acid (tiagabine) was quantified in rats following chronic (14 days) administration by an integrated pharmacokinetic-pharmacodynamic (PK/PD) modelling approach. The increase in beta activity (11.5-30 Hz) of the EEG as derived by fast Fourier transformation analysis was used as pharmacodynamic endpoint. Two groups of male Wistar rats were treated for 14 days with either tiagabine at a steady-state concentration of 198+/-10 ng ml(-1) or placebo. Chronic treatment with tiagabine resulted in an increase of the EEG effect parameter by 38+/-2 microV. In the PK/PD experiment the time course of the EEG effect was determined in conjunction with the decline of drug concentrations after an i.v. bolus administration of 10 mg kg(-1). The pharmacokinetics of tiagabine was most adequately described by a bi-exponential function. No influence of chronic treatment on the pharmacokinetics was observed. Hysteresis between plasma concentration and EEG effect was accounted for by incorporation of an 'effect-compartment' in the model. The observed relationship between tiagabine concentrations and EEG effect was non-linear and described on the basis of the Hill equation. Between the treatment groups no differences in the pharmacodynamic parameters were observed. The population means for the different pharmacodynamic parameters were: maximum EEG effect 82 microV, EC(50) 486 ng ml(-1), Hill factor 2.0 and k(e0) 0.060 min(-1). In the in vitro [(3)H]GABA uptake assay no changes in affinity or functionality for the GABA uptake transporter were observed, consistent with the absence of adaptation. It is concluded that chronic treatment with tiagabine in an effective dose range for 14 days does not produce functional adaptation to tiagabine-induced GABA-ergic inhibition in vivo.

Animals↗
PubMed2001

Efficiency and ambiguity in an adaptive neural code.

We examine the dynamics of a neural code in the context of stimuli whose statistical properties are themselves evolving dynamically. Adaptation to these statistics occurs over a wide range of timescales-from tens of milliseconds to minutes. Rapid components of adaptation serve to optimize the information that action potentials carry about rapid stimulus variations within the local statistical ensemble, while changes in the rate and statistics of action-potential firing encode information about the ensemble itself, thus resolving potential ambiguities. The speed with which information is optimized and ambiguities are resolved approaches the physical limit imposed by statistical sampling and noise.

Adaptation, Physiological↗
PubMed1976

Adaptation and dynamics in X-cells and Y-cells of the cat retina.

On the basis of the spatial summation properties of their receptive fields, cat retinal ganglion cells were classified as either X-cells (linear) or Y-cells (non-linear). Responses were then obtained to a small, centered spot, square-wave modulated in time and superimposed on various levels of diffuse, steady background illumination. When fully dark-adapted, both X-cells and Y-cells produced responses that were entirely sustained. When well light-adapted but still in the scotopic range, both cell types produced largely transient responses with only a very small sustained component. The sustained or transient nature of responses is, therefore, not an invariant characteristic of X-cells and Y-cells in the scotopic range. We also conclude that the mechanism which controls the center's sensitivity in the scotopic range is similar though not identical in the two types of cells.

Adaptation, Ocular↗
PubMed2000

Skeletal muscle adaptation to exercise: a century of progress.

Skeletal muscle physiology and biochemistry is an established field with Nobel Prize-winning scientists, dating back to the 1920s. Not until the mid to late 1960s did there appear a major focus on physiological and biochemical training adaptations in skeletal muscle. The study of adaptations to exercise training reveals a wide range of integrative approaches, from the systemic to the molecular level. Advances in our understanding of training adaptations have come in waves caused by the introduction of new experimental approaches. Research has revealed that exercise can be effective at preventing and/or treating some of the most common chronic diseases of the latter half of the 20th century. Endurance-trained muscle is more effective at clearing plasma triglyceride, glucose, and free fatty acids. However, at the present time, most of the mechanisms underlying the adaptation of human skeletal muscle to exercise still remain to be discovered. Little is known about the regulatory factors (e.g., trans-acting proteins or signaling pathways) directly modulating the expression of exercise-responsive genes. Because so many potential physiological and biochemical signals change during exercise, it will be an important challenge in the next century to move beyond "correlational studies" and to identify responsible mechanisms. Skeletal muscle metabolic adaptations may prove to be a critical component to preventing diseases such as coronary heart disease, type 2 diabetes, and obesity. Therefore, training studies have had an impact on setting the stage for a potential "preventive medicine reformation" in a society needing a return to a naturally active lifestyle of our ancestors.

Adaptation, Physiological↗
PubMedDate not supplied

[Pseudoarthrosis of the scaphoid bone associated with carpal collapse: factors in choice of surgical approach].

INTRODUCTION: The most common fracture involving the wrist is a fracture of the scaphoid bone [1], and only 5% to 10% of these fractures proceed to nonunion. Although not symptomatic initially, most (if not all) nonunions later produce a painful wrist with impaired function, clinically significant loss of motion, increased weakness and degenerative arthritis. Nonunion of the scaphoid bone should be treated by open reduction and internal fixation. Many surgical procedures have been advocated to achieve union. Most widely used technique for the treatment of scaphoid nonunion was described by Russe [2], but this method may overcome the flexion deformity of the scaphoid and carpal deformities. The ununited scaphoid usually undergoes resorption of the fractures surfaces, principally over the anterolateral aspect of the fracture, so that the scaphoid becomes misshapen. The restoration of the exact length and form is enabled by insertion of a tight-fitting trapezoidal corticocancellous graft, a technique described by Fernandez [11]. AIM: We analysed the results of treatment of scaphoid nonunion utilized by two bone-grafting techniques and pointed out the need of choice of the best operative method. METHODS: From 1977 to 1993, at the Institute of Orthopaedic Surgery and Traumatology in Belgrade, 40 patients were surgically treated for symptomatic nonunion of the scaphoid bone. The mean duration of follow-up was 10.2 years (range, from 6 to 22 years). Eighteen (45%) patients were operated by Fernandez technique and 22 (55%) patients were operated using Russe's technique. Volar approach and Kirschner's wire fixation were performed in both operative methods. We used two rating scales proposed by Cooney [13] to evaluate the results. Objective scale (Table 1a) included the radiographic appearance of the wrist, the range of motion and grip strength. Subjective scale (Table 1b) comprised function, pain perception of a decrease in performance because of limited motion or strength, and satisfaction. These scales were used to compare the objective and subjective results in patients who had postoperatively carpal collapse with the results in patients who had not such deformity. RESULTS: The union rate was 92.5% in both methods. Russe's technique resulted in union in 20 (91%) of 22 cases with two ununited. Fernandez technique achieved union in 17 (94%) of 18 cases. Fracture union was determined by both clinical and roentgenographic examinations. Correction of the lateral interscaphoid angle was obtained in 14 (82%) patients operated by Fernandez technique and 9 (45%) patients operated by Russe's technique. Correction of dorsal tilt of the lunate were achieved in 6 (30%) patients operated by Russe's technique, and 13 (76.6%) patients operated by Fernandez technique. There was a highly significant correlation (p < 0.01) between increased deformity of the scaphoid and extent of carpal collapse (Graph 1). Also, there was significant difference between two operative techniques regarding correction of lateral interscaphoid angle (p < 0.05). Arthrosis of the wrist was present in all patients. We could not demonstrate a significant difference (p > 0.05) between intensity of degenerative changes and increase of lateral interscaphoid angle, but obviously, the large flexion deformity of the scaphoid the worse intensity of degenerative changes (Graph 2). The grip strength significantly increased after Fernandez technique (p > 0.05) (Graph 3), but wrist motion changed a little. The average objective score was 71 points for the patients in whom the lateral interscaphoid angle was 45 degrees or less, and 63 points for those in whom the angle was more than 45 degrees. This difference was significant (p < 0.05), but we could not demonstrate a significant difference between the two groups in terms of the average subjective score. DISCUSSION: In our series, both procedures provided a high union rate [2]. In cases with severe scaphoid shortening and flexion deformity, Russe's procedure has proved to be insufficient to restore anatomic length and correction of carpal alignment [6, 11, 17]. Previous authors have reported that the progression in degenerative changes was slower in patients who had a lateral interscaphoid angle less than 45 degrees [13]. Also, grip strength and range of motion increased in patients in whom flexion deformity of the scaphoid had been corrected [2, 4, 6, 16, 17]. Our study supports these findings, except results regarding the movement. We believe that this was due to postoperative scarring. Discrepancy between the subjective and objective results may have been due to postoperative relief of pain obtained by increased carpal stability or decreased range of motion of the carpal joints due to postoperative scarring. If pain is relieved, patients readily adapt to the functional deficit of decreased range of motion. We concluded that angulatory collapse of the scaphoid resulted in nonunion as well as malunion with secondary functional loss. Recognition and avoidance in acute fractures were important. When recognised late, volar wedge grafting appeared to be a satisfactory method of treatment.

Adolescent↗
PubMed2005

Can greenhouses eliminate the development of cold resistance of the leafminers?

Latitudinal patterns for quantitative traits in insect are commonly used to investigate climatic adaptation. We compare the cold resistance of the leafminer (Liriomyza sativae) pupa among populations distributed from tropical to temperate regions, incorporating the thermal overwintering limit of the insect's range. The patterns of cold resistance for northern and southern populations differ. The southern populations significantly increased their cold resistance with latitude, showing a latitudinal pattern independent of seasons, acclimation regimes, and assay methods. In contrast, the northern populations showed no stable patterns; they were always intermediate in cold hardiness between the low-latitude and high-latitude populations within the overwintering limit. Integration of these data with those of the biologically similar congeneric leafminer, L. huidobrensis, suggests that a pattern shift in stress tolerance associated with the overwintering range limit is probably a general adaptive strategy adopted by freeze-intolerant species that have a high-latitude boundary of distribution, but can only overwinter and develop in protected greenhouses in harsh seasons. Considering the widespread availability of greenhouses for overwintering insects in northern China, we speculated that the large-scale existence of thermally-buffered microhabitats in greenhouses might eliminate the development of cold resistance of the leafminer populations. However, results suggest a strong selection for increased cold resistance for natural populations of Liriomyza species at higher latitudes that can overwinter in the field, but not for populations at latitudes above the thermal limit. Thus, habitat modification associated with greenhouses can limit gene flow and reduce cold tolerances even at latitudes above where the leafminers can overwinter in the field.

Adaptation, Biological↗
PubMed1986

A contribution to the geographical interpretation of biological change.

"Geography" has traditionally been assigned the role of handmaiden in evolutionary studies. In this work a different understanding of the relationship between biological change and locational setting is developed: evolution as a dynamic form of spatial interaction. In the causal model presented, adaptive change is portrayed as a negative feedback response contributing to a general spatial-temporal process of resource cycle tightening involving exchanges between the two fundamental structural sectors ("abiotic" and "biotic") of the earth's surface system. As such, it is rejected as "evolution" per se. This position makes it possible to circumvent the "adaptation yields adaptation" circularity, and to view locational circumstances as being evolutionarily causal, yet not deterministic with respect to population-level change. A parallel interpretation of the relation between range and range change and evolution is also implicit; the individualistic hypothesis is thereby superceded by a model of community evolution allowing for individualistic rates of population (adaptive and) range change, but operating on the principle that populations should tend to change range in common directions (as a response to spatially-varying degrees of efficiency of turnover of resources vital to biotic sector function). This in turn leads to the possibility of normative biogeographic modelling. Comment is also made on the relationship of the present understanding to disequilibrium and dynamic equilibrium interpretations of evolutionary change, and to human cultural evolution.

Animals↗
PubMed1993

Adaptation in short-bowel syndrome: reassessing old limits.

The improving survival of patients with severe short-bowel syndrome along with the advent of successful intestinal transplantation have accentuated the need to answer two questions. (1) Is there an intestinal length below which adaptation to full enteral nutrition can not be expected to occur? (2) How much time is necessary to complete intestinal adaptation? We reviewed the outcome of 21 infants with less than 50 cm of small intestine to answer these questions. Patients were divided into three groups based on intestinal length, regardless of ileocecal valve status: group I, < 10 cm (n = 3); group II, 10 to 30 cm (n = 11); and group III, 30 to 50 cm (n = 7). Data were collected to assess survival, incidence of adaptation, time to adaptation, and causes of mortality. Infants in group I did not achieve intestinal adaptation to full enteral nutrition. One survived and 2 died, one from varicella pneumonia and the other after intestinal transplantation. Eight of the 11 (73%) patients in group II survived and 5 of 8 (63%) survivors achieved full intestinal adaptation after a mean interval of 320 days (range, 148 to 506 days) on parenteral nutrition. Six of the seven patients (86%) in group III survived and all survivors (100%) achieved complete enteral adaptation after an average of 376 days (range, 58 to 727 days). The overall survival was 71% (15/21), but survival in patients with > 10 cm was 78%.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Central Venous↗
PubMed2026

Failure modes and effects analysis for clinical implementation of online adaptive radiotherapy: A systematic review.

BACKGROUND: The accuracy of radiotherapy is limited by anatomical variations occurring over time scales ranging from sub-seconds to days. Online Adaptive Radiotherapy (OART) addresses this by enabling daily plan adaptation based on real-time imaging. While OART offers improved dose conformity, its dynamic, time-constrained workflow introduces novel failure modes that challenge traditional quality assurance protocols. PURPOSE: This study aims to synthesize the existing literature on Failure Modes and Effects Analysis (FMEA) for OART to systematically catalog risks and identify mitigation strategies. METHODS: A systematic literature search was conducted to identify studies applying FMEA to OART workflows. Eleven studies were included, covering MR-guided (ViewRay MRIdian, Elekta Unity), CBCT-guided (Varian Ethos), and MR-enhanced C-arm linac systems. To address heterogeneity in risk scoring methodologies (e.g., TG-100 10-point scales vs. 5-point rankings), extracted failure modes were harmonized into a standardized three-tier risk classification system (Class I: Low, Class II: Intermediate, Class III: High). RESULTS: A total of 300 unique failure modes were identified, with 49.6 percent classified as high-risk (Class III). Analysis revealed that the majority of high-risk failures were concentrated in the online treatment delivery phase, specifically within human-computer interactions and anatomical contouring steps. CONCLUSIONS: This study supports the development of tailored, robust QA frameworks that prioritize human factors and process consistency to guide safe implementation in diverse clinical settings.

Humans↗
PubMed2000

Data model for the elimination of matrix effects in enzyme-based flow-injection systems.

This contribution presents a new conceptional enzyme-based flow injection analysis (FIA) system for the process and quality control of food processing and biotechnological systems. It provides the determination of different analytes in distinct process media on the base of a common experimental set-up. In contrast to known comparable systems, analysis is performed without the commonly used sample preparation and dilution steps. Instead, the adaptation to the necessary measurement range is realized by optimization of intrinsic system parameters. The central principle of the work presented is the elimination of occurring interferences by the heterogeneous matrix of the process sample. Based on a particular injection mode, the application of dehydrogenases as indicator enzymes and a specially developed data model using cognitive methods, cross sensitivities of the detector as well as disturbed reaction rates of the enzymes could be almost completely compensated. Two applications are presented, the analysis of ethanol in non-alcoholic beer and the online determination of D-/L-lactate during a lactic acid fermentation, which reveal the advantage of the developed system.

Alanine Transaminase↗
PubMed2026

Engineering the Vero Cell Lineage: Toward a Programmable Vaccine Manufacturing Platform.

Vero cells remain an indispensable continuous substrate for human viral vaccine manufacturing. Despite decades of empirical process optimization, intrinsic genomic instability, including segmental aneuploidy and dynamic chromatin rearrangements, continues to limit the durability of engineered phenotypes under sustained viral burden and bioreactor stress. Here, we review the expanding engineering toolkit for the Vero lineage across a three-layered functional framework: the membrane interface, cytoplasmic foundry, and nuclear blueprint, evaluating translational prospects at each level. Receptor transplantation and morphological reprogramming have broadened viral entry range and enabled suspension-adapted culture formats, while metabolic flux management and temporally controlled apoptosis modulation have addressed intracellular production bottlenecks, albeit often with trade-offs between productivity, biosafety, and long-term population stability. At the genomic level, targeted perturbations of transcriptional regulators and emerging epigenetic interventions offer more durable gains, yet expression drift, clonal heterogeneity, and karyotypic instability during extended passaging highlight the need for locus-level precision rather than constitutive trait installation. Looking forward, infection-responsive dynamic logic circuits and the systematic identification of Vero-specific genomic safe harbors could shift the paradigm toward a conditionally responsive manufacturing architecture. Collectively, these advances suggest a pathway for transitioning the Vero lineage from a passive, empirically optimized biological substrate into a conditionally responsive, genomically stable, and programmable platform for modern vaccine preparedness.

Vero cells↗