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Results for “ADAPTATION, PHYSIOLOGICAL”

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At least 55 records · Page 3Linked to original sources
PubMed1989

Histologic changes in the respiratory tract induced by inhalation of xenobiotics: physiologic adaptation or toxicity?

Toxicologists and pathologists are often faced with the dilemma of categorizing changes observed in the respiratory tract of laboratory animals as either "adaptive" or "toxic." However, it is often difficult to interpret the nature of a given change as either "adaptive" or "toxic." Certain lesions or changes in the respiratory tract are to be expected from the concentration of materials given or the experimental design of a study. Careful analysis suggests that some of these changes may be more properly described as adaptive rather than toxic within the context of a given study or situation. Tissue changes discussed in this paper include squamous metaplasia of laryngeal epithelium, goblet cell change in respiratory epithelium, macrophage accumulation within alveoli, and bronchiolization of alveolar epithelium. Examples provided show that some of these changes observed in inhalation studies are similar in severity but slightly increased in frequency over sham control animals. The introduction of exogenous material into the respiratory tract of laboratory animals in an experimental setting should be expected to result in certain changes. The challenge scientists must accept is to interpret these changes so that toxic events may be separated from adaptive changes. In order to meet this challenge, studies incorporating several species and novel technologies may have to be utilized.

Adaptation, Physiological↗
PubMed1979

Metabolic changes in Crithidia fasciculata accompanying physiological adaptation to growth in the presence of carbonyl cyanide m-chlorophenylhydrazone.

1. Crithidia fasciculata adapted to growth in the presence of 10(-5) M carbonyl cyanide m-chlorophenylhydrazone (CCCP), an uncoupler of oxidative phosphorylation, maintained adenosine phosphate pools and an adenylate energy charge comparable to those of control cells. 2. CCCP-adapted cells in the presence of the uncoupler respire endogenous substrate at a greater rate than control cells and this effect of CCCP appears readily reversible. 3. CCCP-treated, adapted cells, supporting high endogenous respiration rates, were not responsive to added substrates which significantly stimulated the oxygen utilization of normal C. fasciculata. 4. CCCP-adapted cells, provided with [U-14C]-labeled proline, utilize this substrate at 67% the rate of control cells, but divide the isotopic label between CO2 and protein in a ratio identical to that of normal cells. 5. The transport of alanine and proline by adapted C. fasciculata was severely impaired, while the transport of tyrosine and leucine was unaffected.

Adaptation, Physiological↗
PubMed2005

Interictal EEG as a physiological adaptation. Part I. Composition of brain oscillations in interictal EEG.

OBJECTIVE: In the present experimental study, we examined the compositions of brain oscillations and their temporal behavior in broad frequency band (0.5-30 Hz) in interictal EEG without epileptiform abnormalities during generalized epilepsy in resting conditions. METHODS: The exact compositions of brain oscillations and their percent ratio were assessed by a probability-classification analysis of short-term EEG spectral patterns (SPs), which reveals temporal dynamics of these SPs and results in the probability-classification profile. RESULTS: It has been demonstrated that the interictal EEG was characterized by (a) a shift towards higher frequencies in all observed brain oscillations, (b) an increased amount of polyrhythmic activity, (c) a decrease in SP types diversity, (d) a decreased relative incidence of the SP type change in the transition between neighboring EEG epochs of the same EEG, and (e) an increased temporal stabilization periods of polyrhythmic activity. All these were observed in distributed brain areas. CONCLUSIONS: It was suggested that these findings reflect a disorganization of neurodynamics in the epileptic brain. At the same time, the fact that all these indices were significantly different from surrogate EEG reflects a non-occasional and thus, most likely, an adaptive nature of the microstructural reorganization of interictal EEG. SIGNIFICANCE: Parameters of interictal EEG without the signs of epileptiform activity can be considered as additional information in premorbid diagnostics of epistatus.

Adaptation, Physiological↗
PubMed2006

Interictal EEG as a physiological adaptation. Part II. Topographic variability of composition of brain oscillations in interictal EEG.

OBJECTIVE: In the present experimental study, we examined topographic variability of composition of brain oscillations and their temporal behavior in frequencies from 0.5 to 30 Hz of interictal EEG without epileptiform abnormalities and healthy EEG. METHODS: Spatio-temporal variability of brain oscillations (indexed by short-term EEG spectral patterns (SPs)) was assessed by the probability-classification analysis of SPs. As a result, multi-dimensional SP-vector for each analysis EEG epoch was obtained. RESULTS: It was demonstrated that interictal EEG was characterized (a) by a significant decrease of spatio-temporal variability of brain oscillations, (b) by longer periods of temporal stabilization for operational modules which comprise larger number of cortical areas, and (c) by significantly more intermittent recurrence when compared with EEG of control subjects. Generally it was shown that EEG channels display different states of coordination independently on their correlation and coherence using brain oscillations at multiple frequencies. CONCLUSIONS: Results of this study suggested that EEG correlate of chronic epileptogenesis in the brain is a particular metastable state of biopotential field, which can be estimated by SP-vector. The fact that all results were significantly different from surrogate EEGs reflects a nonoccasional and thus, most likely, an adaptive nature of spatio-temporal reorganization in interictal EEG. SIGNIFICANCE: Parameters of spatio-temporal organization of interictal EEG without the signs of epileptiform activity can be considered as additional information in premorbid diagnostics of status epilepticus, and may also provide insights into basic laws that govern brain oscillations in general.

Action Potentials↗
PubMed2005

Physiological adaptation during short distance triathlon swimming and cycling sectors simulation.

The aim of this study was to typify cardiorespiratory and metabolic adaptation capacity at race pace of high-level triathletes during simulations of short distance triathlon swimming sector, first transition and cycling sector. Six national and international-level triathletes performed a 1500 m swimming trial followed by a transition and one hour on ergocycle at race pace, with sequenced measures of blood lactate concentration, gas exchange and heart rate recording. The mean speed obtained in the swimming sector was 1.29+/-0.07 m s(-1), matching 98+/-2% of MAS (Maximal Aerobic Speed), lactate concentration 6.8+/-2.1 mM and heart rate 162+/-15 beats min(-1). In the cycling sector, the mean power was 266+/-34 W, matching 77+/-10% of MAP (Maximal Aerobic Power), oxygen uptake 3788+/-327 mL min(-1) (82.8% of VO2max), heart rate 162+/-13 beats min(-1) (92% of maximal HR) and ventilation 112.8+/-20.8 L min(-1). MAS was correlated with performance in swimming sector (r = 0.944; P < 0.05). Despite intake 1.08+/-0.44 L of a solution with 8% of sugars, a significant loss of body weight (2.80%; P < 0.01) was observed. Changes in cycling power, speed and frequency, especially towards the end of the effort, were also found. By contrast, differences in lactate concentration and in cardiorespiratory or metabolic variables between the end of the swimming sector and the end of the first transition did not appear. In conclusion, this study remarks different relative intensities in cycling and swimming sectors. The observed loss of body weight does not modify pedalling economy in national and international-level athletes during the cycling sector, where effort intensity adapts itself to the one found in individual lactate threshold. However, changes in competition tactics and other effects, such as drafting in swimming and cycling, could alter the intensities established in this study for each sector.

Adaptation, Physiological↗
PubMed1997

Retinal physiology: adapting to the changing scene.

The retina needs to process visual information under a wide range of conditions, a feat facilitated by gain controls. Recent results have provided new insights into one such gain control, which enables the retina to adapt to wide variations in the level of contrast in the visual scene.

Adaptation, Physiological↗
PubMed1991

Physiological adaptations to concurrent endurance training and low velocity resistance training.

This study investigated the effects of concurrent endurances and low velocity resistance training (LVR) on measures of strength and aerobic endurance. One group (ES) performed concurrent endurance training 3 days a week and LVR training on alternate days, 3 days a week for 12 weeks. The other group (S) performed only LVR training 3 days a week for 12 weeks without any endurance training. Measurements and increases in training volume were made every three weeks in both groups. Group ES exhibited increases in submaximal exercise responses after 3, 9 and 12 weeks (p less than 0.05). Knee extension peak torque and total work as well as cross-sectional area of quadriceps femoris were significantly increased after 6 and 9 weeks of training in both groups. These findings indicate that no significant differences in strength gains were observed between subjects performing concurrent endurance and resistance training or resistance training only. However, the time-course of adaptations between groups was somewhat different.

Adaptation, Physiological↗