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PubMedDate not supplied

Biotransformation of dichloroaromatic compounds in nonadapted and adapted freshwater sediment slurries.

Nonadapted freshwater sediment slurries and sediment slurries adapted to dechlorinate 2,3-dichloropyridine (2,3-Cl2Pyd), 2,3-dichloroaniline (2,3-Cl2Anl), 2,3-dichlorophenol (2,3-Cl2PhOH), 3,5-dichloropyridine (3,5-Cl2Pyd), 3,5-dichloroaniline (3,5-Cl2Anl) and 3,5-dichlorophenol (3,5-Cl2PhOH) were studied to determine the rate, range and extent of biotransformation of structurally related compounds under anaerobic conditions. 2,3-dichloroanisole (2,3-Cl2Ans) and 3,5-dichloroanisole (3,5-Cl2Ans) were initially demethylated, producing 2,3-Cl2PhOH and 3,5-Cl2PhOH as intermediate transformation products. All other dichloroaromatic compounds examined were initially dechlorinated. The rates of dechlorination of 2,3-Cl2PhOH, 2,3-Cl2Anl, and 2,3-Cl2Pyd were significantly lower (5-15 times) in nonadapted sediment slurries compared to sediment slurries adapted to 2,3-Cl2Anl or 2,3-Cl2Pyd. In 2,3-Cl2PhOH adapted sediment, the rate of dechlorination of 2,3-Cl2PhOH was 15 times greater than in nonadapted sediment; however, the rates of dechlorination of 2,3-Cl2Anl and 2,3-Cl2Pyd were similar for 2,3-Cl2PhOH-adapted and nonadapted sediment slurries. In adapted and nonadapted sediment slurries, 2,3-Cl2PhOH, 2,3-Cl2Anl, and 2,3-Cl2Pyd were preferentially dechlorinated at the ortho, meta, and meta positions, respectively. Additionally, 2,3-Cl2Pyd adapted sediment slurries dechlorinated 2,3-Cl2PhOH and 2,3-Cl2Pyd at both ortho and meta positions. Rates of dechlorination of 3,5-Cl2PhOH, 3,5-Cl2Anl, and 3,5-Cl2Pyd were lower (2-4 times) in nonadapted sediment slurries compared to sediment slurries adapted to 3,5-Cl2Anl or 3,5-Cl2Pyd. In 3,5-Cl2PhOH adapted sediment, the rate of dechlorination of 3,5-Cl2PhOH was approximately 10 times greater than in nonadapted sediment.(ABSTRACT TRUNCATED AT 250 WORDS)

Aniline Compounds↗
PubMed1991

The squirrel monkey vestibulo-ocular reflex and adaptive plasticity in yaw, pitch, and roll.

The vestibulo-ocular reflex (VOR) was studied in adult squirrel monkeys before and after adaptation to magnifying and minifying viewing conditions. Monkeys were subjected to broadband (0.05-0.71 Hz) conditioning rotation for six hours in head yaw, pitch, and roll on separate occasions, and the VORs in these three planes were studied in darkness to assess adaptive plasticity in the reflexes. The gain of the horizontal VOR (H-VOR) averaged 0.8 across the frequency bandwidth studied (0.025-4 Hz). Phase was near 0 degrees from 4 to around 0.1 Hz, but developed a progressive lead as frequency declined further. Normal vertical VOR (V-VOR) gain climbed from 0.6 at 0.025 Hz to near 1 as frequency increased to 4 Hz. Phase lead was more pronounced at low frequencies than in the H-VOR. The normal torsional VOR (T-VOR) qualitatively resembled the V-VOR, showing similar phase but lower gains (0.3-0.7) across the frequency bandwidth. These findings suggest that the dynamics of the V-VOR and T-VOR resemble canal characteristics more closely than does the H-VOR. After adaptation to visual minification and conditioning rotation (0.5X for yaw and pitch, 0X for roll), gain decreased in each of the planes of conditioning. Similarly, gain increased in the plane of conditioning after adaptation to visual magnification (2X). The adaptive changes were greater at low (0.025-1 Hz) than at high (2.5-4 Hz) frequencies, and were more robust when gain was driven downward than upward. However, control (sham) adaptation experiments showed that VOR gain tended to drop slightly over 6 h in the absence of adaptive drive to do so, suggesting that the gain modifications may be more symmetric when referenced to the control. Adaptive VOR gain enhancement or decrement in the plane of conditioning did not result in systematic and parallel changes in orthogonal VOR planes.

Acclimatization↗
PubMed1986

Dynamics of chromatic adaptation in cones of freshwater turtle.

The closer the wavelength of a steady background of monochromatic light is to the peak sensitivity of a cone that is being illuminated, the stronger is the desensitization of that cone; this is chromatic adaptation. A model of the freshwater turtle retina with the neural components of chromatic adaptation via negative feedback circuits is used to simulate and study various aspects of chromatic adaptation. An internal negative feedback circuit resides solely within the cone pedicle and thereby, its adaptive effects are relatively specific, so that univariance is maintained. The cone-L-horizontal cell circuit is an external negative feedback circuit and its adaptive effects are less specific since all 3 chromatic cone types are involved, so that univariance is violated. Chromatic adaptation is the result of the decrease in the cone gain due to the dependency of the gains of the negative feedback circuits on the mean illuminance level. The results of the model are consistent with von Kries law, but the changes in gains of the cones due to chromatic adaptation are dependent on wavelength, intensity of the adapting light and size.

Acclimatization↗
PubMed1999

Fluctuating life-history parameters indicating temporal variability in metal adaptation in riverine chironomids

Adaptation to toxicants in animal populations is influenced primarily by two counteracting forces. First, the intensity and duration of peak concentrations of toxicants is responsible for the actual level of selection pressure on the population. Second, the process of adaptation can be disrupted by gene flow as a result of crossings with nontolerant individuals. These counteracting forces were analyzed in riverine insects in which we expected that the level of metal adaptation is subject of considerable fluctuations, due to variable dilution of metals and a variable transport of nontolerant individuals in river water. To this purpose, the stability of metal adaptation in different Chironomus riparius populations was analyzed during a 5-month period in a heavily polluted lowland river. This was examined by measuring mortality, larval dry weight, and accumulation of zinc under laboratory conditions. The results showed that in midge populations originating from metal-contaminated field sites several life-history parameters (like control mortality and growth response under cadmium exposure) of the laboratory reared F1 generations showed considerable temporal variation. In addition, the presence of metal-adapted midge populations was indicated on several occasions on the metal-exposed field sites. Reference populations on the other hand, showed stable life history patterns throughout the sampling period, and no signs of metal adaptation were found. These observations showed that the actual level of metal adaptation varies considerably, both in time and space. Adaptation to metals in riverine chironomids, therefore, should be looked on as a highly dynamic process.http://link. springer-ny.com/link/service/journals/00244/bibs/37n2p175.html

Journal Article↗
PubMed2004

Kinetics of the early adaptive response to gamma rays: induction of a cellular radioprotective mechanism in murine leukocytes in vivo.

The aims of the study were to establish the kinetics of the early adaptive response and to determine the minimum adaptive dose of gamma rays capable of inducing this response. The minimum adaptive dose was determined by exposing groups of five BALB/c male mice to an adaptive dose of 0.005 or of 0.02 Gy gamma rays from a 137Cs source and challenge with 1.0 Gy 60 min later. The kinetics of adaptive response induction was established by exposing mice to an adaptive dose of 0.01 Gy, and subsequently to a challenge dose of 1.0 Gy at different times. Blood samples were collected from the tail immediately after exposure to the challenge dose, and the percentage of DNA-damaged cells and the extent of damaged were determined by single cell gel electrophoresis in 300 leukocytes per animal in five mice. The results confirms the capability of an in vivo induction of an early radioprotective process against the DNA-damage produced by gamma rays in murine leukocytes, and allows us to conclude that the minimum adaptive dose lies between 0.005 and 0.01 Gy of gamma rays, and the early adaptive response is induced as early as 30 min after the exposure and persists for at least 18 hr.

Animals↗
PubMed1980

Light-dark adaptation of bacteriorhodopsin in triton-treated purple membrane.

Solubilization of purple membrane with Triton X-100 yields Triton micelles containing bacteriorhodopsin monomers. The absorption maximum of dark-adapted solubilized bacteriorhodopsin is blue-shifted to 549 nm. Light adaption increases the absorbance by 4% and shifts the absorption maximum to 553 nm, i.e., the extent of light adaptation is considerably less than in intact purple membrane. Extraction of dark-adapted bacteriorhodopsin in Triton yields a 13-cis- to all-trans-retinal ratio of 58 : 42 which changes after light adaptation to 38 : 62. It has been shown by Sperling et al. (Sperling, W., Carl, P., Rafferty, Ch.N. and Dencher, N.A. (1977) Biophys. Struct. Mech. 3, 79-94) that light adaptation in intact purple membrane occurs through a branching of the 13-cis photoreaction cycle, so that part of the pigment during each cycle crosses over into the all-trans photoreaction cycle. We explain the decreased extent of light adaptation in solubilized bacteriorhodopsin by assuming a significant back reaction from the all-trans to the 13-cis cycle. This assumption predicts a wavelength dependence of the extent of light adaptation, which is born out by experiment.

Bacteriorhodopsins↗
PubMed1993

Adaptive cancellation of the respiratory artifact in surface recording of small intestinal electrical activity.

In the human small intestine there is omnipresent electrical activity with a frequency of 0.15-0.2 Hz. The electrical activity of the small intestine can be measured by surface electrodes placed on the abdominal skin. The most annoying problem in the surface electrical recording is the respiratory artifact which is not discernible from the small intestinal signal. The frequency of the respiration is about 0.2-0.4 Hz, which is very close to that of small intestinal activity, making the use of the conventional bandpass filtering impractical. In this paper a selective frequency domain adaptive filter was proposed for the cancellation of the respiratory artifact. The basic principle of the selective frequency domain adaptive filter is that only selected filter weights are adapted based on the frequency characteristics of the respiratory artifact. Therefore, a substantial reduction of computation is achieved. A series of computer simulations was conducted for the optimization of the system parameters and for the investigation of the system performance. It was demonstrated in this paper that the selective frequency domain adaptive filter is as effective as, but more efficient than, the conventional frequency domain adaptive filter. The adaptive system for the cancellation of the respiratory artifact based on the selective frequency domain adaptive filter is very efficient in computation, has a fast convergence (about 100 adaptations), substantial reduction of the respiratory artifact and little effect (or distortion) on the small intestinal electrical signal.

Computer Simulation↗
PubMed1987

Chromosomal responses to ionizing radiation reminiscent of an adaptive response in cultured Chinese hamster cells.

When Chinese hamster V79 cells were internally exposed to low level chronic beta-rays from incorporated tritiated thymidine (3H-dThd), they showed an "adaptive" response to the induction of chromosomal damage by subsequent higher acute doses of gamma-rays. The yield of sister-chromatid exchanges (SCEs) in the 3H-dThd pretreated cells was less than the yield induced by gamma-rays alone (protective effects), and the micronucleus frequency was less than the sum of the induced frequencies by 3H-dThd and gamma-rays separately (below-additivity effects). No adaptation to the micronucleus induction by gamma-rays was observed after the 3H-adapted cells had divided once and when 3-aminobenzamide (3AB) was given before the challenge doses. The cross-resistance study revealed that the 3H-adapted cells were resistant to SCE induction but not to the micronucleus inductions by the challenge doses of reactor radiations. The results suggest that the SCE adaptation and the micronucleus adaptation or clastogenic adaptation are probably caused by different, inducible adaptive repair pathways.

Animals↗
PubMed1992

Protein selection by rats adapted to high or moderately low levels of dietary protein.

After preliminary studies on flavor acceptability, patterns and indices of subsequent feeding behavior were monitored by computer in young rats which were adapted to 15% or 70% casein diets before being offered, sequentially, choices between flavored diet pairs in which the proportions of percentage casein were 5/65, 5/55, 5/45, 5/35 and 5/25. Similarly adapted rats received these choices in the reverse sequence. Rats adapted to 15% casein usually ate randomly from the diet pairs and selected approximately 15-30% casein; individual behaviors were prominent. The 70% casein groups avoided the higher casein diet, often within minutes (except for the first-offered 5/25 choice), and seldom selected more than 10% casein; individual differences were infrequent. Such rats also distinguished between flavored 70% and 65% casein diets. Sizes and numbers of meals and rates of eating differed for the paired diets, especially for rats adapted to 70% casein. A flavor added to the 70% casein adaptation diet was not avoided when present only in the 5% casein diet of a 5/65 choice. Rats adapted to 70% soy protein before receiving flavored 5/65 to 5/25 choices selected 20-28% soy protein, a level far above those of casein selections by rats adapted to 70% casein. Dietary adaptation and type of protein thus affect subsequent diet selection and feeding patterns and indices.

Amino Acids↗
PubMed1982

Failure in the rate adaptation of the atrial refractory period: its relationship to vulnerability.

We evaluated the relationship of rate-dependent changes in atrial refractoriness to atrial vulnerability in 39 patients. Vulnerability was considered present when sustained atrial tachyarrhythmias, lasting longer than 1 minute, could be provoked with one to three extra stimuli. Adaptation of atrial refractory period duration to rate was defined as: normal: steep rate reduction with a linear correlation slope value of 0.08 or more; non-adaptation: absence of rate reduction, the slope value being 0 to 0.01; poor adaptation: slight reduction with rate, the slope having values of 0.02 to 0.07. Increased vulnerability was demonstrable in 16 of 17 patients with non-adaptation of the effective refractory period (ERP), and in 10 of 10 with a similar defect of the functional refractory period (FRP); in the intermediate category (poor adaptation) the results for ERP and FRP were 7/11 and 5/6. By way of contrast when both measurements showed normal adaptation, vulnerability was elicited in 2/9 patients. The significance between these groups showed P less than 0.005. Of 17 patients with atrial arrhythmia by Holter, 14 showed poor or non-adaptation of the ERP. It is suggested that poor or absent rate adaptation of the atrial refractory period, and a propensity to atrial fibrillation or flutter, constitute a clinical entity not previously described.

Adolescent↗
PubMed1985

Development and characterization of cold-adapted viruses for use as live virus vaccines.

Representative viruses from twelve RNA and two DNA virus genera have been successfully adapted to growth at sub-optimal temperature (cold-adapted). In almost every case, there was a correlation between acquisition of the cold-adaptation phenotype and loss of virulence in the normal host whether animal or man. Overall, the best method of cold adaptation to develop a live virus vaccine line appeared to be a stepwise lowering of the growth temperature allowing time for multiple lesions to occur and/or be selected. In addition, the starting virus should be a recent isolate not as yet adapted to a tissue culture host and the cold-adaptation process should then occur in a host heterologous to the virus' normal host. These viruses have been reviewed in the light of their cold-adaptation method and successful production of an attenuated line as virus vaccine candidate. Finally, detailed information is presented for the cold-adaptation process in influenza virus.

Acclimatization↗
PubMed2005

TICAM-1 and TICAM-2: toll-like receptor adapters that participate in induction of type 1 interferons.

Toll-like receptor (TLR) 3 and 4 mediate the expression of many genes, including NF-kappaB- and interferon-regulatory factor (IRF)-3/interferon (IFN)-inducible genes, in macrophages and dendritic cells (DCs) in response to their ligand stimuli, polyI:C and lipopolysaccharide (LPS). Toll-IL-1 receptor homology domain (TIR)-containing adapter molecule 1 (TICAM-1) facilitates expression of IFN-inducible genes via TLR3. Although MyD88 and Mal/TIRAP adapters function downstream of TLR4, they barely induce IFN-beta. In addition, DC maturation as well as IFN-beta induction are largely independent of MyD88 and Mal/TIRAP. TICAM-1 is the functional adapter for both TLR3 and TLR4 that induces type 1 IFN and MyD88-independent DC maturation. In LPS-mediated TLR4 activation, a complex of TICAM-1 and an additional TLR4-binding adapter serves as the adapter. We named this TLR4-TICAM-1-bridging adapter TICAM-2. Our results reveal the details of MyD88-independent pathways which separately recruit the distinct adapters downstream of TLR3 and TLR4 and variations of the TLR output are in part regulated by the two additional adapters in DCs.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Adapting electronic adherence monitors to standard packages of topical medications.

Adherence to topical medications is poorly characterized. Electronic monitors can provide objective adherence data, but these monitors are not designed to work with tubes of medications. We sought to adapt standard electronic monitors to commonly used medication tubes. An adapter was created to fit over standard medication tubes. Screw threads on the adapter were designed to fit standard electronic monitors. Adapters and monitors were tested with tubes of gel, ointment, and cream over an 8-week test period during which the adapters were opened and closed twice daily. The adapters were easily mated to both plastic and aluminum topical medication tubes. The bond between the adapter and the tube was maintained throughout the study. Electronic monitors were 100% accurate at identifying medication events over the study period. We conclude that adapting existing electronic monitors to medication tubes should facilitate a much better understanding of adherence to topical treatment.

Administration, Topical↗
PubMed2005

Multi-model direct adaptive decoupling control with application to the wind tunnel system.

In this paper, a new multi-model direct adaptive decoupling controller is presented for multivariable processes, which includes multiple fixed optimal controllers, one free-running adaptive controller, and one re-initialized adaptive controller. The fixed controllers provide initial control to the process if its model lies in the corresponding region. For each controller selected, the re-initialized adaptive controller uses the values of this particular controller to improve the adaptation speed. This controller may replace the fixed controller at a later stage according to the switching criterion which is to select the best one among all controllers. A free-running adaptive controller is also added to guarantee the overall system stability. Different from the multiple models adaptive control structure proposed in Narendra, Balakrishnan, and Ciliz [Adaptation and learning using multiple models, switching, and tuning. IEEE Control Syst. Mag. 15, 37-51 (1995)], the method not only is applicable to the multi-input multi-output processes but also identifies the decoupling controller parameters directly, which reduces both the computational burden and the chances of a singular matrix during the process of determining controller parameters. Several examples for a wind tunnel process are given to demonstrate the effectiveness and practicality of the proposed method.

Journal Article↗
PubMed2006

Intelligent adaptive nonlinear flight control for a high performance aircraft with neural networks.

This paper describes the development of a neural network (NN) based adaptive flight control system for a high performance aircraft. The main contribution of this work is that the proposed control system is able to compensate the system uncertainties, adapt to the changes in flight conditions, and accommodate the system failures. The underlying study can be considered in two phases. The objective of the first phase is to model the dynamic behavior of a nonlinear F-16 model using NNs. Therefore a NN-based adaptive identification model is developed for three angular rates of the aircraft. An on-line training procedure is developed to adapt the changes in the system dynamics and improve the identification accuracy. In this procedure, a first-in first-out stack is used to store a certain history of the input-output data. The training is performed over the whole data in the stack at every stage. To speed up the convergence rate and enhance the accuracy for achieving the on-line learning, the Levenberg-Marquardt optimization method with a trust region approach is adapted to train the NNs. The objective of the second phase is to develop intelligent flight controllers. A NN-based adaptive PID control scheme that is composed of an emulator NN, an estimator NN, and a discrete time PID controller is developed. The emulator NN is used to calculate the system Jacobian required to train the estimator NN. The estimator NN, which is trained on-line by propagating the output error through the emulator, is used to adjust the PID gains. The NN-based adaptive PID control system is applied to control three angular rates of the nonlinear F-16 model. The body-axis pitch, roll, and yaw rates are fed back via the PID controllers to the elevator, aileron, and rudder actuators, respectively. The resulting control system has learning, adaptation, and fault-tolerant abilities. It avoids the storage and interpolation requirements for the too many controller parameters of a typical flight control system. Performance of the control system is successfully tested by performing several six-degrees-of-freedom nonlinear simulations.

Aircraft↗
PubMed2000

Adaptive amplification: an inducible chromosomal instability mechanism.

Adaptive mutation is an induced response to environmental stress in which mutation rates rise, producing permanent genetic changes that can adapt cells to stress. This contrasts with neo-Darwinian views of genetic change rates blind to environmental conditions. DNA amplification is a flexible, reversible genomic change that has long been postulated to be adaptive. We report the discovery of adaptive amplification at the lac operon in Escherichia coli. Additionally, we find that adaptive amplification is separate from, and does not lead to, adaptive point mutation. This contradicts a prevailing alternative hypothesis whereby adaptive mutation is normal mutability in amplified DNA. Instead, adaptive mutation and amplification are parallel routes of inducible genetic instability allowing rapid evolution under stress, and escape from growth inhibition.

Base Pair Mismatch↗
PubMed2000

The adaptation of mussels Crenomytilus grayanus to cadmium accumulation result in alterations in organization of microsomal enzyme-membrane complex (non-specific phosphatase).

The kinetic parameters (V(m), K(m) and slope) of membrane-bound microsomal non-specific phosphatase (NPase, with G6P as the substrate) from the digestive gland of unexposed and cadmium adapted (45 days for 100 µg Cd(2+)/l) mussels were investigated. In vivo and in vitro approaches were used. Adaptation of mussels (Crenomytilus grayanus) to cadmium resulted in a 1.6-fold increase in NPase activity. V(m) was increased by 1.6-fold, but K(m) was the same in terms of enzyme kinetics. This indicates that the total concentration of the enzymes in the digestive gland increased. Cd(2+) (1 mM) did not significantly alter the activity of the membrane-bound enzyme in vitro both for unexposed and for cadmium adapted mussels, meaning that cadmium ions are not a direct inhibitor of the membrane-bound enzyme in this concentration. The microsomal NPase activity in both unexposed and cadmium adapted mussels was inhibited by in vitro solubilization of microsomes with non-ionic detergent (Triton X100, 0.01%). This inhibition was uncompetitive for microsomes of unexposed mussels (K(m) decreased 3.1-fold). The most drastic events were observed in cadmium adapted mussels, where inhibition was mixed (K(m) decreased 7.2-fold). The simultaneous actions of detergent and cadmium ions did not alter NPase activity significantly in comparison with action of the detergent alone. The differences in the types and the extents of inhibition of the enzymes activity by membrane disordering agent (Triton X100) indicated that the enzyme-membrane complex (NPase) has been altered as a result of adaptation of mussels to cadmium accumulation. We conclude that the mussels produced a new enzyme-membrane complex, with the same K(m) as the previous complex, but with other detergent sensitivity and greater amounts. Thus, the adaptation capacity of this enzyme is reduced as result of adaptation of mussels to cadmium accumulation.

Journal Article↗
PubMedDate not supplied

Effects of ketamine on the adaptive responses of second-order vestibular neurons of the cat.

The adaptive characteristics of 80 neurons in the vestibular nuclei of ketamine-anesthetized cats were investigated. All types I and II neurons responded to stimulation of the horizontal semicircular canals by an 8 degree/sec2 stepwise angular acceleration of 40 sec. For the purpose of this study, vestibular adaptation was defined as a decline in response at a rate of greater than -0.01 spikes/sec/sec. According to this criterion, 71 neurons (89 per cent) behaved as adapting neurons, and nine (11 per cent) showed either no adaptation or reverse adaptation. The rate of adaptation varied from neuron to neuron; the average rate was -0.312 spikes/sec/sec. The average resting discharge rate, the maximum response level, and the average adaptation rate were compared with similar neural responses in barbiturate-anesthetized cats. Although the average resting discharge rates of the two groups showed no significant difference, the average adaptation rate and the maximum response level of the ketamine-anesthetized group were significantly higher than those of the barbiturate-anesthetized group. These data suggest that the gain of the second-order neurons is higher and more actively modulated in more alert (ketamine-anesthetized) cats than in barbiturate-anesthetized cats.

Animals↗