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PubMed2003

[Structural and functional changes of the myocardium after coronary artery bypass surgery in patients with postinfarction left ventricular remodeling].

In patients with left ventricular end diastolic dimensions >5--< or =5.5 cm myocardial revascularization was associated with significant decreases of diastolic and systolic left ventricular dimensions in immediate postoperative period. This adaptational phenomenon was called passive reducing left ventricular remodeling. In patients with left ventricular end diastolic dimensions <5 and >5.5 cm revascularization was associated with dilation of the left ventricle. Restoration of myocardial blood supply produced overall positive effect on left ventricular functional capacity in patients with various severity of its postinfarction remodeling. Pathways of realization of this positive effect could be different.

Adult↗
PubMed1986

Growth, psychologic characteristics, and sleep-wakefulness cycle of children with sex chromosomal abnormalities.

This study of girls with Turner syndrome (16 cases) and boys with XXY (two cases) and XYY (eight cases) constitutions was designed to follow the longitudinal growth and to analyze the psychologic findings and the sleeping patterns in them. The growth curves of stature in Turner syndrome were below the 3rd percentile at all ages. The mean of SDS of height in cases less than 5 years old was -2.38, that in cases older than 6 years old -2.40. The shoulders in Turner syndrome have a tendency to broaden with time, in contrast to the development of the pelvis, which is not so good. The height of 47,XYY boys from infancy to 9 years of age was between the 10th and 90th percentiles, with one exception in which the height was above the 90th after 8 years of age. Relatively common psychologic findings in cases with Turner syndrome were as follows: low responsiveness to emotional stimuli, poor emotional expressions, passive and negative mental attitudes, low activity and low productivity, narrow and limited interests, passiveness and common sense adaptability, lower impulsiveness and aggressiveness, etc. The circadian oscillation was observed up to 3 years of age with shifting of the sleeping time to the night period. After that, day sleep gradually tends to decrease with age. Age variation in day and night sleep of an XXY boy was compared with that of a normal child. This showed the normal variation in circadian rhythms in early childhood, although the infant with this syndrome slept more, both day and night, than normal. In early childhood, no difference was noted. Similar studies were performed on a child with the chromosomal aberration XYY and revealed the sleep parameters to be quite normal in infancy and early childhood.

Adolescent↗
PubMed1993

Heart rate transient at the onset of active and passive dynamic exercise.

At the onset of dynamic exercise there is an almost instantaneous heart rate (HR) acceleration caused by neural activation of central motor areas (central command) and stimulation of mechanoreceptors located in the moving limbs. Aiming to identify the independent contribution of the peripheral mechanism to the initial HR response to exercise, 29 subjects performed two 4-s bouts of unloaded cycling (active (AEx) and passive (PEx)) on an adapted commercial tandem bicycle. PEx was accomplished by having a staff member pedal while sitting on the rear seat. The HR was continuously measured from electrocardiographic tracings. Records of electromyography (EMG) were obtained in a small sample of subjects during the exercise tasks. The number of pedal rotations was very similar (mean +/- SE) (AEx = 7.4 +/- 0.3, PEx = 7.5 +/- 0.2, P = 0.455), determining significant HR changes (P < 0.001) that were similar in the two types of exercise (AEx from 92 to 125 bpm: 35.9% increase; PEx from 87 to 111 bpm: 27.6% increase; P = 0.185). Contrasting to AEx, no muscle contraction was observed by EMG during PEx, suggesting that central command was absent. We concluded that independent activation of mechanoreceptors can promote HR acceleration at the onset of dynamic exercise.

Adult↗
PubMed2006

The effect of passive foot flexion on blood circulation in sports and clinical medicine.

UNLABELLED: The aim of the study was to analyze the effect of the passive foot flexion on peripheral and systemic blood circulations in the state of rest of persons adapted to endurance physical loads, and on patients during surgery. METHODS: In the first series of experiments which included 16 males in recumbent supine position adapted to endurance physical loads, the effect of the passive foot flexion by applying a leg muscle activator on the systemic and peripheral blood circulations was analyzed. In the second series of experiments conducted with 6 males and 12 females, the passive foot flexion was aimed at preventing thromboembologenesis during the intraoperative period. RESULTS: After a session of the passive foot flexion applied to persons adapted to endurance physical loads, the venous reserve volume in them increased to 1.68+/-0.3 mL/100 mL (p<0.05). The maximal venous emptying rate increased to 48.3+/-8.8 mL/100 mL/min (p<0.05). After 15 min of the passive foot flexion, the indices of the systemic blood circulation were analogous to the ones before passive foot flexion. The maximal venous emptying rate in the calves of the left and right legs at the end of the surgery decreased to 59.7+/-4.7 mL/100 mL/min (p>0.05) and to 62.9+/-4.0 mL/100 mL/min (p>0.05), respectively. CONCLUSIONS: The passive foot flexion applied to persons adapted to endurance physical loads increases venous reserve volume and maximal venous emptying rate. During the intraoperative period, the passive foot flexion increases maximal venous emptying rate from the triceps muscle of the calf thus decreasing the possible danger of thromboembologenesis.

Adult↗
PubMed1994

An examination of the validity of social subtypes in autism.

The validity of a social subtyping scheme forwarded by Wing and her colleagues is examined in a sample of 53 autistic individuals. Clinical ratings of subtype (aloof, passive, active-but-odd), IQ estimates, and measures of adaptive functioning and level of autism were obtained. Subjects were individually administered the Autism Diagnostic Observation Schedule (ADOS) by the principle examiner, who was blind to subtype assignment. The general findings supported the validity of aloof and active-but-odd subtypes as predictors of behavior across language/communication, reciprocal social interaction, and stereotyped behavior/restricted interest domains and suggested that individuals assigned to these respective groups differed in a number of important ways (e.g., level of autism, IQ, adaptive behavior). Partial support for an intermediate, passive subtype was garnered. The clinical utility of social subtypes is discussed as an important implication of this work.

Adolescent↗
PubMed2006

Health resources and health strategies among older Swedish-speaking Finns--a hermeneutic study.

Research has shown that the Swedish-speaking Finns have better health than the Finnish-speaking majority. The aim of this paper was to explore the health resources and health strategies among home-dwelling Swedish-speaking Finns aged 75 or older. The objective was to develop health-promotive nursing care for this group. Data was collected through recorded semistructured conversations with 22 older persons. The conversations were transcribed and interpreted through a hermeneutic approach. The material was read through several times and compiled into 22 narratives with relevant quotations. The narratives were subsequently summarised into one core narrative under each major category, to present the health resources and health strategies. Six categories were found: the Positive, the Social, the Active, the Adaptable, the Stubborn and the Passive. Within the Positive category, morale played an important role as a health resource and health strategy. Within the Social category, social activities were regarded as both health resources and health strategies, whereas their absence was a health obstacle. Within the Active category, a wide range of physical activities played an important role. Within the Adaptable category, contentment was a health resource. Within the Stubborn category, stubbornness itself was a health resource, whereas strong belief was a health strategy. Within the Passive category, although health obstacles permeated the life context, contentment and caution were seen as health resources. The vision of the future varied from the confidence found in the Positive category to the uncertainty prevalent in the Passive category. The main health resources and strategies used by the elderly Swedish-speaking Finns were related to social and other activities as well as to personality. Transforming health obstacles into resources could be an important health-promotive nursing strategy.

Adaptation, Psychological↗
PubMed2006

Passive sexual transmission of human immunodeficiency virus type 1 variants and adaptation in new hosts.

Human immunodeficiency virus type 1 (HIV-1) genetic diversity is a major obstacle for the design of a successful vaccine. Certain viral polymorphisms encode human leukocyte antigen (HLA)-associated immune escape, potentially overcoming limited vaccine protection. Although transmission of immune escape variants has been reported, the overall extent to which this phenomenon occurs in populations and the degree to which it contributes to HIV-1 viral evolution are unknown. Selection on the HIV-1 env gene at transmission favors neutralization-sensitive variants, but it is not known to what degree selection acts on the internal HIV-1 proteins to restrict or enhance the transmission of immune escape variants. Studies have suggested that HLA class I may determine susceptibility to HIV-1 infection, but a definitive role for HLA at transmission remains unproven. Comparing populations of acute seroconverters and chronically infected patients, we found no evidence of selection acting to restrict transmission of HIV-1 variants. We found that statistical associations previously reported in chronic infection between viral polymorphisms and HLA class I alleles are not present in acute infection, suggesting that the majority of viral polymorphisms in these patients are the result of transmission rather than de novo adaptation. Using four episodes of HIV-1 transmission in which the donors and recipients were both sampled very close to the time of infection we found that, despite a transmission bottleneck, genetic variants of HIV-1 infection are transmitted in a frequency-dependent manner. As HIV-1 infections are seeded by unique donor-adapted viral variants, each episode is a highly individual antigenic challenge. Host-specific, idiosyncratic HIV-1 antigenic diversity will seriously tax the efficacy of immunization based on consensus sequences.

AIDS Vaccines↗
PubMed2000

Aspects of body self-calibration.

The representation of body orientation and configuration is dependent on multiple sources of afferent and efferent information about ongoing and intended patterns of movement and posture. Under normal terrestrial conditions, we feel virtually weightless and we do not perceive the actual forces associated with movement and support of our body. It is during exposure to unusual forces and patterns of sensory feedback during locomotion that computations and mechanisms underlying the ongoing calibration of our body dimensions and movements are revealed. This review discusses the normal mechanisms of our position sense and calibration of our kinaesthetic, visual and auditory sensory systems, and then explores the adaptations that take place to transient Coriolis forces generated during passive body rotation. The latter are very rapid adaptations that allow body movements to become accurate again, even in the absence of visual feedback. Muscle spindle activity interpreted in relation to motor commands and internally modeled reafference is an important component in permitting this adaptation. During voluntary rotary movements of the body, the central nervous system automatically compensates for the Coriolis forces generated by limb movements. This allows accurate control to be maintained without our perceiving the forces generated.

Adaptation, Physiological↗
PubMed2006

Layer-specific touch-dependent facilitation and depression in the somatosensory cortex during active whisking.

Brains adapt to new situations by retuning their neurons. The most common form of neuronal adaptation, typically observed with repetitive stimulations of passive sensory organs, is depression (responses gradually decrease until stabilized). We studied cortical adaptation when stimuli are acquired by active movements of the sensory organ. In anesthetized rats, artificial whisking was induced at 5 Hz, and activity of individual neurons in layers 2-5 was recorded during whisking in air (Whisking condition) and whisking against an object (Touch condition). Response strengths were assessed by spike counts. Input-layer responses (layers 4 and 5a) usually facilitated during the whisking train, whereas superficial responses (layer 2/3) usually depressed. In layers 2/3 and 4, but not 5a, responses were usually stronger during touch trials than during whisking in air. Facilitations were specific to the protraction phase; during retraction, responses depressed in all layers and conditions. These dynamic processes were accompanied by a slow positive wave of activity progressing from superficial to deeper layers and lasting for approximately 1 s, during the transient phase of response. Our results indicate that, in the cortex, adaptation does not depend only on the level of activity or the frequency of its repetition but rather on the nature of the sensory information that is conveyed by that activity and on the processing layer. The input and laminar specificities observed here are consistent with the hypothesis that the paralemniscal layer 5a is involved in the processing of whisker motion, whereas the lemniscal barrels in layer 4 are involved in the processing of object identity.

Action Potentials↗
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↗
PubMed2006

Structural adaptation in adult rabbit ventricular myocytes: influence of dynamic physical interaction with fibroblasts.

The mechanism of induction of cardiomyocyte (CM) dedifferentiation, as seen in chronic hibernating myocardium, is largely unknown. Recently, a cellular model was proposed consisting of long-term cocultures of adult rabbit CMs and cardiac fibroblasts in which typical structural characteristics of hibernation-like dedifferentiation could be induced. Only CMs in close contact with fibroblasts underwent these changes. In this study, we further investigated the characteristics of the fibroblast-CM interaction to seek for triggers and phenomena involved in CM dedifferentiation. Adult rabbit CMs were cocultured with cardiac or 3T3 fibroblasts. Heterocellular interactions and the structural adaptation of the CMs were quantified and studied with vital microscopy and electron microscopy. Immunocytochemical analysis of several adhesion molecules, i.e., N-cadherin, vinculin, beta1-integrin, and desmoplakin, were examined. Upon contact with CMs, fibroblasts attached firmly and pulled the former cells, resulting in anisotropic stretch. Quantification of the attachment sites revealed a predominant binding of the fibroblast to the distal ends of the CM in d 1 cocultures and a shift towards the lateral sides of the CMs on d 2 of coculture, suggesting a redistribution of CM membrane proteins. Immunocytochemical analysis of cell adhesion proteins showed that these were upregulated at the heterocellular contact sites. Addition of autologous and nonautologous fibroblasts to the CM culture similarly induced a progressive and accelerated structural adaptation of the CM. Dynamic passive stretch invoked by the fibroblasts and/or intercellular communication involving cell adhesion molecule expression at the interaction sites may play an important role in the induction of hibernation-like dedifferentiation of the cocultured adult rabbit CMs.

Adaptation, Physiological↗
PubMed2000

Relationships between individual behavioural traits and post-weaning growth in segregated early-weaned piglets.

Piglets' individual behavioural traits have been studied in the last decade but no report has linked these traits with growth. This experiment was conducted to determine if behavioural traits of segregated early-weaned piglets could be good predictors of their post-weaning growth and, thus, help to predict their adaptation to early weaning. Following segregated early weaning at 17+/-1 days old, 252 piglets were submitted to three tests between 20 and 25 days of age: open-field, reaction to humans and rank order based on competition for a restricted-access feeder. The body weight of each piglet was measured the day before weaning and once a week for the next 4 weeks. A principal component analysis yielded five factors with an Eigenvalue higher than 0.90 that accounted for 81% of the total variation between individuals: reaction to humans (25%), active response to stress (21%), passive response to stress (14%), feeding behaviour (10%) and rank order (9%). Passive reaction to stress was associated with better weight gain during the first week post-weaning (r=0.18; P=0.01), and a positive correlation was found between social status and weight gain during the 4 weeks following weaning (-0.15</=r</=-0.10); P</=0.10). No relation was found between reaction to humans and growth. These results confirm the relationship between rank order and growth in pigs and may suggest that reacting passively to stress could facilitate adaptation to weaning.

Journal Article↗
PubMed1984

Early enhancement of passive potassium efflux from rat liver by thyroid hormone: relation to induction of Na,K-ATPase.

The effect of thyroid hormone treatment on the passive efflux of 42K+ from rat liver slices was studied to determine whether an increase in permeability might play a role in the known enhancement of active monovalent cation transport and Na,K-ATPase activity induced by thyroid hormone. Initial studies showed that the sc injection of 50 micrograms T3/100 g BW on 3 alternate days resulted in an 82% increase in the 42K+ passive efflux rate constant in liver slices and a 23% increase in the Na,K-ATPase activity of liver homogenates. Subsequent investigation of the relative time courses of these two hormonal effects showed that after a single injection of T3 the rate constant for 42K+ efflux increased within 6 h and reached a plateau between 24 and 48 h. In contrast, Na,K-ATPase activity was not augmented until 24 h and continued to rise between 24 and 48 h. These results suggest that an early increase in cation permeability (with resultant cation leak) may account for the known stimulatory effect of thyroid hormone on active monovalent cation transport in rat liver. The relatively late increase in Na,K-ATPase activity might then be regarded as an adaptive cellular response to increased passive cation fluxes rather than a direct effect of thyroid hormone. The magnitude and early onset of the effect of thyroid hormone treatment on cellular 42K+ efflux raise the possibility that an increase in passive cation permeability may be a proximal event in the mediation of thyroid hormone action.

Animals↗
PubMed2001

Passive extensibility of skeletal muscle: review of the literature with clinical implications.

The purpose of this article was to review the literature on passive extensibility of skeletal muscle with reference to its anatomic and physiologic properties, mechanisms of adaptations and clinical implications. Studies with animal muscles have shown that passive extensibility is influenced by the size (mass) and length of muscle fibers, and the amount and arrangement of the connective tissues of the muscle belly. The resistance to passive lengthening is influenced by the readily adaptable amount of muscle tissue, including the contractile proteins and the non-contractile proteins of the sarcomere cytoskeletons. The relationship of adaptable changes in the muscle tissue and in the extracellular connective tissues remains unclear. Muscle length adaptations result from changes in the number of sarcomeres in series, which depend on the imposed length of muscles, not on the level of muscle activation and tension. This mechanism of muscle length adaptations, termed 'myogenic', has not been demonstrated in human muscles, but it has been intimated by therapeutic lengthening studies showing that both healthy and neurologically impaired human muscles can undergo increased length adaptations in the presence of muscle activations. Studies have suggested that optimal muscle function is probably achieved by increasing muscle length, length extensibility, passive elastic stiffness, mass and strength, but additional studies are needed to investigate these relationships, particularly for aged muscles and for muscles affected by clinical disorders, disease and injury. Such studies could contribute to the development of new intervention strategies designed to promote the passive muscle extensibility that enhances total muscle function, and ultimately improves the ability to complete functional activities and excel in athletic performances.

Actins↗
PubMed2006

Adaptive force regulation of muscle strengthening rehabilitation device with magnetorheological fluids.

In rehabilitation from neuromuscular trauma or injury, strengthening exercises are often prescribed by physical therapists to recover as much function as possible. Strengthening equipment used in clinical settings range from low-cost devices, such as sandbag weights or elastic bands to large and expensive isotonic and isokinetic devices. The low-cost devices are incapable of measuring strength gains and apply resistance based on the lowest level of torque that is produced by a muscle group. Resistance that varies with joint angle can be achieved with isokinetic devices in which angular velocity is held constant and variable torque is generated when the patient attempts to move faster than the device but are ineffective if a patient cannot generate torque rapidly. In this paper, we report the development of a versatile rehabilitation device that can be used to strengthen different muscle groups based on the torque generating capability of the muscle that changes with joint angle. The device is low cost, is smaller than other commercially available machines, and can be programmed to apply resistance that is unique to a particular patient and that will optimize strengthening. The core of the device, a damper with smart magnetorheological fluids, provides passive exercise force. A digital adaptive control is capable of regulating exercise force precisely following the muscle strengthening profile prescribed by a physical therapist. The device could be programmed with artificial intelligence to dynamically adjust the target force profile to optimize rehabilitation effects. The device provides both isometric and isokinetic strength training and can be developed into a small, low-cost device that may be capable of providing optimal strengthening in the home.

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↗
PubMed1995

An experimental approach to the design of a scattering system for a proton therapy beam line dedicated to ophthalmological applications.

PURPOSE: The development of a scattering system for a proton therapy beam line dedicated to ophthalmological applications. METHODS AND MATERIALS: A protontherapy beam line has been developed for the treatment of uveal melanoma at the Orsay synchrocyclotron. The original 200 MeV proton beam is degraded to 76 MeV and the final beam characteristics (range, modulation, flatness, collimation) are obtained with beam modifiers in the treatment room. A passive scattering system is used to obtain a uniform dose distribution in the beam cross-section throughout 30 mm in diameter, with minimal losses in energy and dose rate. We have used an experimental approach for the scattering study. RESULTS: An elliptical ring shaped from 0.1-mm thick lead is the solution we have adopted for the scattering system. For a modulated beam, a flatness of 1% is obtained on transverse profiles. The energy loss introduced by this scatterer is only 0.5 MeV, with no appreciable change in the range over the treatment field. For an unmodulated beam, 21% of intensity is lost when the scatterer is used. The distal and the lateral dose fall-off (90-10%) for a modulated beam are 2.6 mm. These last values are independent of the range and the modulation currently used for the ophthalmic applications. CONCLUSION: A specific passive scattering system can be adapted to a particular beam emittance. A systematic experimental approach can easily be undertaken to obtain the scatterer adapted for small irradiation fields in proton therapy.

Equipment Design↗