SEARCH · PubMed Health

Results for “passive adaptation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2004

Conditional osmotic stress in yeast: a system to study transport through aquaglyceroporins and osmostress signaling.

The accumulation and transport of solutes are hallmarks of osmoadaptation. In this study we have employed the inability of the Saccharomyces cerevisiae gpd1Delta gpd2Delta mutant both to produce glycerol and to adapt to high osmolarity to study solute transport through aquaglyceroporins and the control of osmostress-induced signaling. High levels of different polyols, including glycerol, inhibited growth of the gpd1Delta gpd2Delta mutant. This growth inhibition was suppressed by expression of the hyperactive allele Fps1-Delta1 of the osmogated yeast aquaglyceroporin, Fps1. The degree of suppression correlated with the relative rate of transport of the different polyols tested. Transport studies in secretory vesicles confirmed that Fps1-Delta1 transports polyols at increased rates compared with wild type Fps1. Importantly, wild type Fps1 and Fps1-Delta1 showed similarly low permeability for water. The growth defect on polyols in the gpd1Delta gpd2Delta mutant was also suppressed by expression of a heterologous aquaglyceroporin, rat AQP9. We surmised that this suppression was due to polyol influx, causing the cells to passively adapt to the stress. Indeed, when aquaglyceroporin-expressing gpd1Delta gpd2Delta mutants were treated with glycerol, xylitol, or sorbitol, the osmosensing HOG pathway was activated, and the period of activation correlated with the apparent rate of polyol uptake. This observation supports the notion that deactivation of the HOG pathway is closely coupled to osmotic adaptation. Taken together, our "conditional" osmotic stress system facilitates studies on aquaglyceroporin function and reveals features of the osmosensing and signaling system.

Biological Transport↗

PubMed1988

Interrelationship between organelles in kidney cells of adult and developing rat.

The morphologic interrelationships between mitochondria, the endoplasmic reticulum (ER) and other organelles were examined in rat kidney cells by stereomicroscopy of thick sections (0.3-1.0 micron) using either standard transmission (80-100 kV) or high voltage (1 mEV) electron microscopy. Mitochondria fit into three different categories: (1) elongated cylinders observed in S1 and S2 segments; (2) irregular lamina in the cortical ascending limb or plates in the distal straight and convoluted segments; (3) small spheres or short rods mostly in intercalated and principal cells of the collecting tubule. The chondrioma occupies a large volume in all cells except in the thin limb and in principal cells of the collecting tubule. This volume occupied by the chondrioma is likely to be related to metabolic functions, but its polymorphic configuration could also be explained by a passive adaptation of the mitochondria to the space left by the basilar membrane infoldings and the ER network, which was found to have an extensive three-dimensional organization which varies, as for the mitochondria, with the cell type. In fact, in the proximal nephron, mitochondria surrounded by the ER and the plasma membranes appear to form a functional unit. Organelle interrelationship is extensively modified during ontogeny or under hormonal influence. Disruption in organelle relationships or in their motility could probably have far reaching consequences which would be more deleterious than the pathological lesions observed at the level of a single organelle. The extent of the disassembly can be fully explored only with thick sections and stereomicroscopy.

Animals↗

PubMed1992

[An in-vitro study of the use of palatal arches in controlling the position of the upper molars].

An in-vitro study was performed analysing the forces and moments produced by the transpalatal arches of the Goshgarian type (0.036" x 0.032" stainless steel and and of the "Precision Lingual Arch System" advocated by Burstone (0.032" x 0.032" stainless steel and 0.032" x 0.032" TMA) using an electronic force-moment gauge recently developed by Planert. The palatal bars were adapted passively, and in addition, molar expansion, symmetrical molar rotation, and buccal root torque were applied. It was found that under clinical conditions it was impossible to fabricate an absolutely passive arch wire with any of the arch types under investigation. The highest precision in applying forces and moments together with the least side-effects was possible using the low stiffness TMA version of the Burstone system.

Biomechanical Phenomena↗

PubMed1986

Transfer of passive immunity from mother to young in a teleost fish: haemagglutinating activity in the serum and eggs of plaice, Pleuronectes platessa L.

Plaice were immunized against rabbit red blood cells (rbc) and the haemagglutinating activity in their sera and eggs was isolated by gel filtration in Sephacryl S300 SF. A "heavy" (greater than 6.69 X 10(5) Daltons) and a "light" (less than 2.32 X 10(5) Daltons) component of haemagglutinating activity were present in plaice immune serum and eggs. The "heavy" haemagglutinating component had the characteristics of immunoglobulin M (IgM) antibody. By contrast the "light" component was suppressed greatly by monosaccharides but not by 2-mercaptoethanol (2-ME) and it was not precipitable against heterologous rabbit anti-plaice Ig immune serum. Since this "light" component was also identified in the serum and eggs of non-immunized plaice the activity was attributed to non-specific lectin-like activity. The presence of an inducible, high molecular weight, haemagglutinating Ig-like protein in plaice serum and eggs suggests the possibility of transfer of passive adaptive immunity from mother to young in this fish.

Animals↗

PubMed1984

Tonic heart rate level, social class and antisocial behaviour in adolescents.

On the basis of previous empirical research it was hypothesised that (a) antisocial behaviour in adolescence would be characterised by lower tonic heart rate levels and (b) any such relationship would be particularly borne out in the higher social classes where the 'social push' towards antisociality may be relatively weaker. These predictions were tested by relating tonic heart rate levels in a sample of 15 year old male schoolchildren to self-report and teacher ratings of antisocial behaviour/undersocialization. An 'antisocial' group was found to have significantly lower heart rate levels than a 'prosocial' group. Several analyses on high and low class groups resulted in a significant low heart rate/antisociality relationship in the high classes only. It was speculated that the heart rate/antisociality relationship may be mediated by somatotype, or alternatively that low levels in high class antisocials may reflect a vagal passive adaptation to mildly aversive events.

Adolescent↗

PubMed1988

Pulmonary vasomotor responses to neural activation in man.

Passive adaptation to changes in flow is an established mechanism of regulation of pulmonary vasomotility. The role of the autonomic nervous system is not well defined in man. To separate the neural from the mechanical component (variation in flow) the venous return and the lung blood flow of six normal men (while undergoing haemodynamic diagnostic procedures) were impeded by a balloon tipped catheter placed in the inferior vena cava. Mental arithmetic and cold pressor tests were used as sympathetic activators. When the venous return was impeded cardiac output was reduced by a mean of 540 ml compared with baseline. During the arithmetic test the rise in cardiac output fell from 2140 ml when venous return was unimpeded to 890 ml when venous return was impeded. This stimulus changed from being a slight pulmonary vasodilator to being an unequivocal vasoconstrictor. Cold stimulation had little effect on cardiac output and caused an increase in pulmonary arteriolar resistance. This effect was more than doubled when flow through the lungs was impeded. These observations suggest that a neural regulation of the pulmonary circulation exists in man, which is disclosed (arithmetic test) or potentiated (cold pressor test) when the influence of mechanical factors is prevented or reduced.

Adult↗

PubMed1981

Distribution of ferrocyanide along the proximal tubular lumen of the rat kidney: its implications upon hydrodynamics.

1. Simultaneous determination of the single nephron glomerular filtration rate (s.n.g.f.r.) and the amount of [14C]ferrocyanide contained per unit length (Fe/mm) of the proximal tubule makes it possible to calculate the tubular radius and flow velocity along this structure. These measurements were made in normal rats, chronically salt-loaded rats, and rats rendered hypotensive by controlled haemorrhage or aortic constriction. 2. In normal rats, Fe/mm remains constant along the proximal tubule, indicating a gradual decrease in tubular radius and constant flow velocity. 3. In salt-loaded rats, with high s.n.g.f.r.s, Fe/mm also remains constant along the proximal tubule, but at a higher level than in normal rats. This indicates larger tubular radii, but the same evolutionary pattern for tubular radius and flow velocity along the proximal tubule, as in normal rats. 4. In rats with controlled haemorrhage, Fe/mm values are low but rise slightly along the proximal tubule. Tubular radius is reduced, and again, gradually decreases along the length. Considering the very low s.n.g.f.r.s, this implies that a large drop in reabsorption along the proximal tubule accompanies the reduction in s.n.g.f.r. 5. In rats with aortic construction, Fe/mm exhibits a large increase along the proximal tubule, suggesting a huge Fe concentration along the tubule, which in turn would indicate that water reabsorption may not diminish in proportion to the reduction in s.n.g.f.r. In some cases, this disruption of the glomerulo-tubular balance led to the cessation of tubular flow in the proximal tubule. 6. In all cases, Fe/mm and the calculated radius in the initial portion of the proximal tubule were correlated to the s.n.g.f.r., suggesting passive adaptation of tubular radius to fluid delivery.

Animals↗

PubMed2000

p50(Cdc37) can buffer the temperature-sensitive properties of a mutant of Hck.

Genetic studies have previously revealed that Cdc37p is required for the catalytic competence of v-Src in yeast. We have reasoned that temperature-sensitive mutants of Src family kinases might be more sensitive to the cellular level of p50(Cdc37), the mammalian homolog of Cdc37p, than their wild-type counterpart, thus potentially providing a unique opportunity to elucidate the involvement of p50(Cdc37) in the folding and stabilization of Src family kinases. A temperature-sensitive mutant of a constitutively active form of Hck (i.e., tsHck499F) was created by mutating two amino acids within the kinase domain of Hck499F. Significantly, overexpression of p50(Cdc37) rescues the catalytic activity of tsHck499F at 33 degrees C, while partially buffering it against inactivation at higher temperatures (e.g., 37 and 39 degrees C). Hsp90 function is required for tsHck499F activity and its stabilization by p50(Cdc37), but overexpression of Hsp90 is not sufficient to stabilize tsHck499F. Overexpression of p50(Cdc37) promotes the association of tsHck499F with Hsp90, suggesting that the cellular level of p50(Cdc37) might be the rate-limiting step in the association of tsHck499F with Hsp90. A truncation mutant of p50(Cdc37) that cannot bind Hsp90 still has a limited capacity to rescue the catalytic activity of tsHck499F and promote its association with Hsp90. This is a particularly important observation, since it argues that rather than solely acting as a passive adapter protein to tether tsHck499F to Hsp90, p50(Cdc37) may also act allosterically to enhance the association of tsHck499F with Hsp90. The findings presented here might also have implications for our understanding of the evolution of protein kinases and tumor development.

Amino Acid Sequence↗

PubMedDate not supplied

Men's experiences during the acute phase of their partners' myocardial infarction.

The men's narratives about the women reveal a disturbance in the balance of their daily life, showing how they, the men, perceive powerlessness, and also how they passively adapted themselves to what happened. The narratives reveal that the women are 'ignoring and withholding' their feelings and that they want to be as 'responsible and independent' as they used to be. The women are disclosed as 'not wanting to face reality': there is an enervating lack of communication.

Adaptation, Psychological↗

PubMed2003

[In the hospital setting, what is the patient's role?].

It is crucial for all medical institutions to maximize the selection of their actors in strict accordance to equality. As medical administrators, were are questioned on the problems linked with compartmentalization. Our investigation has allowed us to confirm that the ensemble of actors, including the patient, regulates compartmentalization, and that all in all it works rather well. However, this regulation has a price. It has an impact on organization, the energy used, not to mention the cumbersome side-effects that would be felt. We have chosen to focus our research on the patient's role on regulation by using his/her testimony. The patient is never passive. Adaptation requires real efforts on the patient's part in order to adapt to this new environment, while at the same time economizing his/her strength. The regulation carried out is often standardized. The patient conforms, but against his/her will. Does the patient's admittance to the hospital make him/her a second-class citizen? Our results lead us to believe that the prevailing views advocate that the patient be at the heart of the system remain an objective.

Adaptation, Psychological↗

PubMed1983

[Maintenance of the contraction time of the smooth muscle cell].

It has been analyzed the speed of contraction (measured as Vmax) of guinea-pig intestine in vitro, after stimulation with carbachol. High doses of carbachol induce an high Vmax; but repeating the dose at short interval (4 min) the speed of contraction is reduced until it reaches values of Vmax 4,3. Low doses of carbachol determine a low Vmax that with repeating doses increases until Vmax 4,2. On the base of this tendency at the same Vmax, and from the anomalous behaviour of the intestines to one dose in front to different doses in carbachol. The excludes that the process could be due to a passive adaptation and hypothesizes a model of behaviour inside the cell. A model to which the myocells balance the stimulus in the way to make constant their velocity of contraction.

Animals↗

PubMed2005

[Morpho-functional alterations of the adrenal cortex in rats with active and passive strategy of adaptive behavior].

In rats with the active (KHA strain) and passive (KLA strain) coping strategies, a post-stress depression develops respectfully on the 1st or 10th day after the inescapable stress. The present study revealed an increase of adrenal weight and blood corticosterone levels on a day following the inescapable stress, as well as marked fluctuations of blood glucose in one and five days post-stress in KHA rats. By the 10th day, these indices returned their basal levels. In contrast, the stress reactivity of KLA rats was lower in all terms and their corticosterone levels remained reduced on the 10th day after stress. In KLA rats, the fasciculate zone was reduced but reticulated zone grew in Ith day following the stress, while in KHA rats the inescapable stress resulted in growth fasciculate zone and concomitant reduction of reticulate zone, both evident on the 10th post-stress day. The data indicate that the development of post-stress depression in KLA rats is probably associated with exhaustion of adrenocortical function.

Adaptation, Psychological↗

PubMedDate not supplied

[Alteration of active and passive Wistar rats adaptive behavior in water-immersion model of depression].

Animals with active and passive behavioral strategy were selected among male Wistar rats by testing them in the T-maze. Using the results of rats testing in T-maze index of behavioral activity and index of behavioral passivity were calculated. The development of post-stress psychopathology and ils correlation with initial behavioral strategy were studied under water-immersion stress conditions consiclering individual alteration of adaptive behavior. Two paradigms were used--one time trial (stress) and two times trial (stress-restress). It was found that active and passive rats being subjected to inescapable aversive exposure develop different types of post-stress depression and only passive animals show the signs of posttraumatic stress disorder.

Adaptation, Psychological↗

PubMed1998

Thinning of the intervascular tissue layers of the human placenta is an adaptive response to passive diffusion in vivo and may help to predict the origins of fetal hypoxia.

OBJECTIVES: To test the hypothesis that thinning of the placental intervascular layers, and greater variability in thickness, are positive adaptations to facilitate passive diffusion and may help to resolve different categories of fetal hypoxia. STUDY DESIGN: Placentas from 12-41 weeks of normal gestation and from pregnancies associated with fetal hypoxic stress (high altitude, diabetes mellitus) were sampled systematically, fixed in formalin, wax-embedded and quantified using stereological methods. Arithmetic and harmonic mean distances across villous trophoblast, stroma and fetal plasma were estimated by measuring randomly sampled intercept lengths. In each case, an index of variability of layer thickness was calculated by dividing the arithmetic by harmonic mean distance. This index has the value I when a tissue layer is uniformly thick but increases in value as local layer thickness becomes more variable. Comparisons between groups were drawn using variance and regression analysis. RESULTS: During pregnancy, there were significant negative correlations between layer thickness (trophoblast, stroma) and gestational age and fetal weight, and significant positive correlations between thickness irregularity and age and weight. Compared with lowland controls, high-altitude placentas possessed thinner layers but only the trophoblast and stroma (and not fetal plasma) were more variably thick. In maternal diabetes, only fetal plasma distance was reduced but fetal and stromal layers appeared to be more irregular in thickness. CONCLUSIONS: Alterations in placental intervascular layer thicknesses occur in normal and abnormal pregnancies and represent real adaptations leading to improved diffusive conductances. Differences in the tissue location of the adaptive response may depend on the nature and origins of the fetal hypoxia.

Adaptation, Physiological↗

PubMed2006

Tracking control of cascade systems based on passivity: the nonadaptive and adaptive cases.

A new cascade passivity-based control scheme for tracking purposes is proposed in this paper. The proposed scheme is valid for a certain class of nonlinear systems even with unstable zero dynamic, and it is also useful for regulation and stabilization purposes. The cases where all system parameters are assumed to be known (nonadaptive case) and also the case when they are unknown (adaptive case) are considered. Some simulation examples are studied to analyze the behavior of the proposed scheme.

Algorithms↗

PubMed1986

Resection of rabbit ileum: effect on jejunal structure and carrier-mediated and passive uptake.

Adaptive changes occur in nutrient uptake following intestinal resection. A previously validated in vitro technique was used to measure the rate of uptake of solutes six weeks following surgical removal of the distal half of the small intestine in the rabbit. The rate of jejunal uptake of a homologous series of fatty alcohols, cholesterol, and six bile acids was unchanged in the resected animals. The uptake of short- and long-chain length fatty acids was also unchanged following resection, although there was a modest but significant increase in the uptake of decanoic and dodecanoic acid. The incremental change in free energy, integral of delta Fw----l, was increased in the jejunum of resected animals when assessed with the medium chain-length fatty acids, but was unchanged when estimated from the uptake of long chain-length fatty acids. The value of delta integral of Fw----l for bile acids was similar in the jejunum of control and resected animals. There was an increase in the maximal transport rate (Jdm) for D-glucose, galactose and L-leucine, an increase in the Michaelis constant (Km) for 3-O-methylglucose, and an increase in both the Jdm and Km for fructose. There was no change in the passive component of the uptake of these solutes following intestinal resection. In the resected animals there was no significant increase in the height, width, and surface area of the jejunal villi, the number of mucosal cells per villus, or in the mucosal surface area, although there was a significant increase in the weight of the scraped mucosa and in the height of the microvilli. The modifications in the active and passive kinetic constants were not related to the alterations in the microvillus surface area, and changes in the Km or delta integral of Fw----l were not due to any variation between control and resected animals in the effective resistance of the intestinal unstirred water layer. These results indicate that, ileal resection was not associated with changes in the effective resistance of the intestinal unstirred water layer; the variable changes in the uptake of passively adsorbed solutes following resection suggests a functional heterogeneity of the villus towards passive permeation; estimation of the incremental change in free energy of the intestine using a homologous series of saturated fatty acids may provide variable results depending upon the chain length of the probes.(ABSTRACT TRUNCATED AT 400 WORDS)

3-O-Methylglucose↗

PubMed1983

Compensatory eye movements during active and passive head movements: fast adaptation to changes in visual magnification.

Rotational eye and head movements were recorded with great precision with scleral and cranial search coils in a rotating magnetic field. Compensatory eye movements were recorded in light and darkness during active as well as passive head movements in the frequency range 0.33-1.33 Hz. From the recorded, nominal gaze movements the effective gaze was reconstructed taking into account magnification or reduction factors of corrective spectacles. Effective gain was calculated as the ratio between the velocities of the effective corrective eye movements and the head movements. In the light, effective gain of compensatory eye movements during active head motion was mostly between 0.97 and 1.03. It was never precisely unity and differed systematically between subjects and between the two eyes of each subject. During passive head motion in the light, gain was lower by about 3% than during active motion. During active head movement in the dark, gain was mostly between 0.92 and 1.00; values were about 5% lower than during active motion in the light. During passive head movement in the dark, gain was about 13% lower than during active motion, and the variability of the oculomotor response increased. Adaptation of these base-line conditions was induced by fitting the subjects with magnifying or reducing spectacles for periods of 40 min to 24 h. The largest required change in amplitude of eye movements was 36%. When active head movements were made, the amplitude of compensatory eye movements in the light as well as in the dark adjusted rapidly. Most of the adaptation of the vestibulo-ocular reflex in the dark was completed in about 30 min. This rate is much faster than that found in previous experiments requiring larger adaptive changes. Differential adaptation to unequal demands for the two eyes proved to be very hard or impossible. In a mild conflict situation the system adjusted to an intermediate level, distributing the error symmetrically between the eyes. When the discrepancy was large, the adaptive process of both eyes was controlled by the one eye which provided the most meaningful information. It is concluded that the system generating compensatory eye movements performs best during active rather than passive head movements, and that adaptation to moderate changes in optimal gain are made very rapidly.

Adaptation, Ocular↗

PubMed2002

[The effect of the duration of adaptation to laboratory conditions on the passive avoidance reflex in rats].

Influence of adaptation degree in new conditions on the passive avoidance was studied. The short period of habituation (3 days) positively influenced the rats' ability for memory trace retrieval. A negative correlation between the step through latency and anxiety in the elevated plus-maze, was shown. Prolongation of adaptation up to 9 days reduced levels of anxiety and retrieval of conditioned response. Modulating role of adaptation degree causing various anxiety levels in passive avoidance, is discussed.

Adaptation, Physiological↗