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Results for “passive adaptation”

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At least 19 recordsLinked to original sources
PubMed1975

[Study of the immunodepressive effect of passive immunization on a model of adaptive immunity].

The effect of various doses of specific serum administered in passive immunization on the formation of primary and secondary adaptive immunity in mice of the CBA strain was studied. Primary and secondary response was more sensitive to passive immunization on a model of adaptive immunity than in vivo. Most sensitive to the immunodepressive action of specific antibodies IgM and IgG were plaque-forming cells, and most resistant -- rosette-forming cells and cells. This led to a supposition that antibodies administered in passive immunization depressed the development of the immunological response acting at the level of T- and B cells.

Animals↗
PubMed1976

Sociopsychological factors influencing response to levodopa therapy for Parkinson's disease.

This article examines the effect of a series of physical and sociopsychological variables on the response shown by Parkinson patients to levodopa therapy. Of the ten major variables examined, six measure relatively enduring personality adaptations: suggestibility, passivity, self-expectations, stigma, attitudes toward illness, and the perception of the expectations of others. Four are illness-related characteristics: diagnosis (primary or secondary parkinsonism); the existence of health problems in addition to Parkinson's disease; whether or not the patient was hospitalized at the beginning of treatment; and symptom improvement as rated by the patient's physician. Age, sex, severity and duration of disease, and use of anti-Parkinson drugs in addition to levodopa were controlled in all of the analyses. The effect of levodopa therapy was assessed in four major areas: activity, social participation, depression, and enjoyment of life. Findings can be summarized as follows: Five of the six personality variables do, in fact, modify the amount of social or psychological change shown by Parkinson patients treated with levodopa. The only one which fails to have such an effect is passivity; this may reflect a measurement problem. However, only two of the four illness-related characteristics which were examined made a difference in treatment outcome: diagnosis and symptomatic improvement, as rated by the patient's physician.

Adaptation, Psychological↗
PubMed1978

Learning experiences of medical students by different instructional methods.

We made a prospective study to determine students' response and perception of the various instructional methods during their pediatric rotation. We found that even those students who were used to passive learning adapted to the more self active learning and became more interested in this method.

Curriculum↗
PubMed2025

Core passive and facultative mTOR-mediated mechanisms coordinate mammalian protein synthesis and decay.

The maintenance of cellular homeostasis requires tight regulation of proteome concentration and composition. To achieve this, protein production and elimination must be robustly coordinated. However, the mechanistic basis of this coordination remains unclear. Here, we address this question using quantitative live-cell imaging, computational modeling, transcriptomics, and proteomics approaches. We found that protein decay rates systematically adapt to global alterations of protein synthesis rates. This adaptation is driven by a core passive mechanism supplemented by facultative changes in mechanistic/mammalian target of rapamycin (mTOR) signaling. Passive adaptation hinges on changes in the production rate of the machinery governing protein decay and allows for partial maintenance of the cellular proteome. Sustained changes in mTOR signaling provide an additional layer of adaptation unique to naive pluripotent stem cells, allowing for near-perfect maintenance of proteome composition. Our work unravels the mechanisms protecting the integrity of mammalian proteomes upon variations in protein synthesis rates. A record of this paper's transparent peer review process is included in the supplemental information.

TOR Serine-Threonine Kinases↗
PubMed1977

[Hog cholera virus: influence of colostral passive antibody on immune response of pig following vaccination with the rabbit adapted Chinese strain (author's transl)].

Using the rabbit adapted chinese strain of Hog cholera, active immunization of piglets having passive colostral antibodies was studied. 65 piglets born from 11 sows were used. Concerning sows, vaccination was performed 5-6 months and 1 month before service (3 sows), 30 days (2 sows) and 60 days (3 sows) after service. Divided in 5 lots, piglets were vaccinated at 4 different periods after birth (15, 30, 60 and 90 days). Hog cholera immunity was determined for each animal by means of kinetic of serum neutralizing antibodies and resistance to virulent challenge performed 5 months after birth. High levels of neutralizing antibodies were observed in serum of each vaccinated sow at the time of farrowing. In piglets having ingested low quantities of colostrum, vaccination induces a good antigenic stimulation characterized by a normal humoral immune response and challenge resistance. But in piglets having ingested a normal quantities of colostrum, colostral passive antibodies have a partial or complete suppressive effect on primary immune response which is characterized by a delay in serum antibodies formation and by a low level at the time of challenge. According the conditions of sows vaccination, differences were observed in the properties of colostral passive antibodies (intensity of suppressive effect on active immune response, in vitro "avidity" for Hog cholera virus, mean value of half-life) present in piglets serum. On practical aspect, vaccination with the chinese strain becomes fully effective in piglets having passive immunity when they are 30-60 days old.

Animals↗
PubMed1992

Changes in monkey horizontal semicircular canal afferent responses after spaceflight.

Extracellular responses from single horizontal semicircular canal afferents in two rhesus monkeys were studied after recovery from a 14-day biosatellite (COSMOS 2044) orbital spaceflight. On the 1st postflight day, the mean gain for 9 different horizontal canal afferents, tested using one or several different passive yaw rotation waveforms, was nearly twice that for 20 horizontal canal afferents similarly tested during preflight and postflight control studies. Adaptation of the afferent response to passive yaw rotation on the 1st postflight day was also greater. These results suggest that at least one component of the vestibular end organ (the semicircular canals) is transiently modified after exposure to 14 days of microgravity. It is unclear whether the changes are secondary to other effects of microgravity, such as calcium loss, or an adaptive response. If the response is adaptive, then this report is the first evidence that the response of the vestibular end organ may be modified (presumably by the central nervous system via efferent connections) after prolonged unusual vestibular stimulation. If this is the case, the sites of plasticity of vestibular responses may not be exclusively within central nervous system vestibular structures, as previously believed.

Adaptation, Physiological↗
PubMed1978

Respiratory control and CO2 conductance: temperature effects in a turtle and a frog.

The respiratory control systems of the predominantly lung-breathing turtle. Pseudemys scripta, and the bimodal breathing frog, Rana catesbeiana, are compared. At constant temperature, control is effected in both species primarily by pulmonary ventilation, and appears to be similar in basic organization to the mammalian system. The skin CO2 exchange of the frog is largely passive and apparently under little adaptive control. CO2 exchange at different temperature is analyzed by means of the conductance equations: convective conductance [MCO2 = (VA/RT).pACO2] for lung exchange, and diffusive conductance (MCO2 = GCO2.transcutaneous deltaPCO2) for skin exchange. Predictions of conductance values, based on data for PaCO2 and MO2, agree well with measured values of both the turtle's ventilation and the frog's skin CO2 conductance at different temperatures. In each case the conductances increase only moderately, if at all, with temperature, a result that can be attributed to the similar Q10 values of PaCO2 and MO2. Because the conductances exhibit this blunted temperature dependence, both lung and skin breathers are provided with the respiratory effector mechanisms necessary to regulate PaCO2 and pHa at their characteristic values over the ectothermic temperature range.

Animals↗
PubMed1977

Sensory feedback does not cause selective adaptation of human "command neurons".

It has been proposed that body movements are partly controlled by a neural hierarchy, with cells at successively higher levels controlling increasing numbers of muscles engaged in functionally equivalent responses. In addition to physiological support for the hypothesis, obtained from infrahuman species, evidence from human subjects has been obtained in the form of negative transfer between successive similar responses. This negative transfer has been attributed to selective adaptation of "command neurons" in the human motor system. The present experiment found no evidence for negative (or positive) transfer between passive and active movements, suggesting that selective adaptation of human command neurons is caused by efference rather than afference.

Adolescent↗
PubMed1976

[General adaptation syndrome (Selye) in cattle. 6. Influence of stress conditions on antibody levels after active and passive immunization as well as on the topographic distribution of various groups of pathogens in the gastrointestinal canal].

The action of experimental and natural stressors on the humoral immune response of calf was studied. Particular attention was given to the H-antigen of S.dublin and equine erythrocytes,the degradation rate of passively acquired humoral antibody, as well as the quantity and topographic distribution of certain groups of germs in the gastrointestinal tract. The following results were obtained:1. Antibody formation was impededby repeated or lasting stressor effect (ACTH injections). 2. The immunological reactions of the calves involved to antigen injection immediately after transport into the rearing unit were stronger than those to antigen application three days from transfer. Immunisation of animals transferred to rearing or fattening units, therefore, should be applied immediately after arrival in the new accomodation, but no interval of three or four days should be allowed. 3. Antibody formation was no longer impaired in calves immunised two weeks from transfer, as compared to those immunised immediately after arrival in the rearing unit. This seemed to suggest that by that time adaptation of the animals to their new environment had been almost complete. 4. Lasting stress (slow drip infusion of ACTH, cortisol, colibacteria or coli-endotoxin) led to no detectable by paper electrophoresis. 5. Calves that had been given three weekly dosesof 1 IU ACTH per kilogram of live weight through four weeks,did not differ,withthe authors'method,from the controls regarding the decomposition rate of passively acquired humoral antibody. 6. ACTH slow drip infusions of calves over several days caused higher concentrations of colibacteria throughout the intestinal tract, including those proximal sections of the small intestine in which little or no colibacteria should occur under physiological conditions in calves of that age.

Adaptation, Physiological↗
PubMed2026

The proteomic origin of the genetic code.

INTRODUCTION: The origin and evolution of the genetic code is a central problem in molecular biology. Classical models have emphasized stereochemistry, frozen accidents, or adaptive optimization, often treating proteins as passive products of preexisting codes. More recent views instead portray the code as a dynamic, coevolving system shaped by reciprocal interactions among amino acids, RNA, and early catalysts. AREAS COVERED: Here, I review efforts of phylogeny reconstruction of the history of tRNA, protein structural domains, and dipeptide sequences in proteomes. These complementary approaches allow exploration of the entry of amino acids and codons into the code, and the transition from an operational RNA code in the tRNA acceptor arm to the canonical code in the anticodon loop. Evidence for ancestral synthetase enzymes with dual functions in aminoacylation and peptide-bond formation, as well as early bidirectional (sense-antisense) coding reflected in dipeptide-antidipeptide emergence is also discussed. EXPERT OPINION: The genetic code is best viewed as a proteome-driven, evolvable system in which early peptides actively shaped coding rules by stabilizing structure, expanding chemical diversity, and enhancing catalysis. This perspective connects origin-of-life studies with modern efforts of code expansion, translational engineering, and peptide-based therapeutics, highlighting the impact of the code's proteomic origin.

Genetic Code↗
PubMed1978

Voluntary movement control and adaptation to cross-coupled stimulation.

The rates at which protective adaptation was acquired to an incremental cross-coupled stimulus were compared under three conditions of movement control: 1) a passive condition in which the 45 degree lateral tilts of the subject's chair were controlled entirely by the experimenter (N = 12); 2) an active condition in which the same movements were achieved directly through the subject's own muscular effort (N = 12); and 3) an active-passive condition in which control was exercised indirectly through microswitches located on the chair arms (N = 12). Adaptation was measured by the rate of neutralization of the oculogyral illusion, as estimated from the apparent motion of a small, dimly illuminated target. The results supported the prediction that the passive condition would be the least effective mode for acquiring adaptation. An unexpected finding was that the active-passive condition proved to be the most efficient for the development of adaptation.

Adaptation, Physiological↗
PubMed1975

[Vessels of the heart and lung in some experimental defects].

Under study were changes of intraorganic blood vessels of the heart and lungs in some experimental defects (open arterial defect, coarctation of the aorta, simultaneous existence of these two defects, stenosis of the pulmonary trunk, defect of the interatrial septum, triad of Fallot, syndrom of Lutembachet). Morphological data correlated with blood pressure in the pulmonary circulation and cardiac chambers. The complex of compensatory-adaptational mechanisms consisting of comparatively active and passive zones is formed in the heart and lungs. In most cases the changes develop in the vessels already existing. In hypertrophy of the myocardium when there is hypertension and hypervolemia in coronary vessels, sinusoids perform the function of blood reservoir, to a certain degree balancing the blood pressure, and luminar ducts relieve the muscle from excessive blood. The changes in the vascular system of the lung are directly dependent upon the pressure in the pulmonary circulation and the duration of observation. The closing arteries are the most active link in the chain of compensatory-adaptational mechanisms.

Animals↗
PubMed1976

[Phasic character of the process of color sensitivity in the visual analyzer].

In subjects with normal three-chromatic vision, during long-term uninterrupted adaptation (6--8 min) to spectral stimuli of different spectral areas (lambda=650+585 nm; lambda=535+585 nm), it was found that the state of color sensitivity undergoes changes in the form of alternating active (correct) and passive (wrong) phases of color discrimination. First, the phase of active color discrimination prevails, then both phases become sort of balanced, and in the end of the adaptation the phase of passive color discrimination increases considerably. The time of duration of these phases depends on the wave--length of the adapting stimulus.

Adaptation, Physiological↗
PubMed1975

Response of primate cones to sinusoidally flickering homochromatic stimuli.

1. The response of the primate cone photoreceptors to sinusoidally flickering stimuli has been obtained by monitoring the late receptor potential (LRP). 2. By comparing the response characteristics of the foveal local electroretinogram (LERG) before and after the intraocular infusion of sodium aspartate, it was found that the b-wave in the foveal LERG does not affect the monitoring of the LRP to steady-state flicker. 3. Functions describing the supra-threshold frequency response characteristics of the photoreceptors were obtained. 4. Linearity was found to hold for low amplitude responses, and temporal modulation transfer functions (MTFs) were obtained for the photoreceptors at various adaptation levels. 5. The cone photoreceptors were found to act approximately as passive low pass filters compounded with some low frequency attenuation. 6. The high frequency response of the photoreceptors at various adaptation levels tends toward a common high frequency asymptote, much like human psychophysical findings, and can be described by a diffusion model. 7. Non-linearities (convexity-upwards) suggest modest positive feedback at the level of the photoreceptors. 8. Mechanisms limiting the magnitude of the receptor response at low frequencies have little effect on the phase lag of the response.

Adaptation, Ocular↗
PubMed1978

[Modulation of autonomic correlates of emotional stress and adaptive responses].

The character and dynamics of the cardio-vascular response to psychogenic stress (confrontation of cat and dog) depends on active or passive type of behavioral response. Tranquilizers inhibit long-lasting hypertension otherwise occurring after the stress stimulus. Adaptive cardio-vascular responses and baroreceptor reflexes did not alter after tranquilizers administration. Effects of psychotropic drugs correspond to the type of individual behavioral response.

Adaptation, Physiological↗
PubMed1977

Diffusion of 133Xe through frog skins, toad bladders, and water boundary layers.

We have measured the total permeability coefficients P as a function of stirring frequency omega for 133Xe through frog skins and toad bladders. The permeability coefficients for the frog skins and toad bladders proper are, respectively, Pm = (3.9 +/- 0.8) X 10(-4) cm/s and (7.4 +/- 4.2) X 10(-4) cm/s. "Unstirred" water layer thickness delta is determined concurrently, from the frequency dependence of P(omega); the result for frog skin is delta = (0.060 +/- 0.016) square root of omega(rad/s) cm. The stirring frequency range is from omega = 7.5 rad/s (72 rpm) to 55 rad/s (530 rpm). The results support the conclusions that the principal barrier to Xe diffusion in these epithelia is inter- and intracellular water, and that the diffusion is passive and rapid. The experimental method may be straightforwardly adapted to the measurement of diffusion or counterdiffusion of any gamma-radioactive soluble or partly soluble solute through any flat membrane or through a solvent. We estimate the amount of total body-absorbed radioactivity due to environmental 133Xe to be 50 fCi for an ambient concentration of 2.6 pCi/m3 of air.

Animals↗