Human recombinant apolipoprotein E-enriched liposomes can mimic low-density lipoproteins as carriers for the site-specific delivery of antitumor agents

This study investigated the effects of flooring on balance during quiet standing in healthy young and older participants. Seven flooring conditions were examined, including a hard tile floor and combinations of low-pile and high-pile carpet with urethane foam and rubber padding. The resulting floors provided a variety of compliant surfaces, ranging from very soft to hard. Participants stood during three separate visual conditions: eyes open, eyes closed, and looking at a moving visual surround. Three measures of postural sway were calculated using center of pressure recordings during the trails. The results showed that the amplitude of sway was higher in the older than in the younger participants, particularly in the moving visual surround condition. Flooring compliance was found to have an effect on sway during moving visual environments, with the largest effects found among the older participants. Softer floors increased the amount of sway in the older participants. These results suggest that floor compliance influences standing postural stability in older people, particularly in destabilizing visual environments.     

Sensory strategies in human postural control before and after unilateral vestibular neurotomy

Vestibular inputs tonically activate the anti-gravitative leg muscles during normal standing in humans, and visual information and proprioceptive inputs from the legs are very sensitive sensory loops for body sway control. This study investigated the postural control in a homogeneous population of 50 unilateral vestibular-deficient patients (Ménière's disease patients). It analyzed the postural deficits of the patients before and after surgical treatment (unilateral vestibular neurotomy) of their diseases and it focused on the visual contribution to the fine regulation of body sway. Static posturographic recordings on a stable force-plate were done with patients with eyes open (EO) and eyes closed (EC). Body sway and visual stabilization of posture were evaluated by computing sway area with and without vision and by calculating the percentage difference of sway between EC and EO conditions. Ménière's patients were examined when asymptomatic, 1 day before unilateral vestibular neurotomy, and during the time-course of recovery (1 week, 2 weeks, 1 month, 3 months, and 1 year). Data from the patients were compared with those recorded in 26 healthy, age- and sex-matched participants. Patients before neurotomy exhibited significantly greater sway area than controls with both EO (+52%) and EC (+93%). Healthy participants and Ménière's patients, however, displayed two different behaviors with EC. In both populations, 54% of the subjects significantly increased their body sway upon eye closure, whereas 46% exhibited no change or significantly swayed less without vision. This was statistically confirmed by the cluster analysis, which clearly split the controls and the patients into two well-identified subgroups, relying heavily on vision (visual strategy, V) or not (non-visual strategy, NV). The percentage difference of sway averaged +36.7%+/-10.9% and -6.2%+/-16.5% for the V and NV controls, respectively; +45.9%+/-16.8% and -4.2%+/-14.9% for the V and NV patients, respectively. These two distinct V and NV strategies seemed consistent over time in individual subjects. Body sway area was strongly increased in all patients with EO early after neurotomy (1 and 2 weeks) and regained preoperative values later on. In contrast, sway area as well as the percentage difference of sway were differently modified in the two subgroups of patients with EC during the early stage of recovery. The NV patients swayed more, whereas the V patients swayed less without vision. This surprising finding, indicating that patients switched strategies with respect to their preoperative behavior, was consistently observed in 45 out of the 50 Ménière's patients during the whole postoperative period, up to 1 year. We concluded that there is a differential weighting of visual inputs for the fine regulation of posture in both healthy participants and Ménière's patients before surgical treatment. This differential weighting was correlated neither with age or sex factors, nor with the clinical variables at our disposal in the patients. It can be accounted for by a different selection of sensory orientation references depending on the personal experience of the subjects, leading to a more or less heavy dependence on vision. The change of sensory strategy in the patients who had undergone neurotomy might reflect a reweighting of the visual and somatosensory cues controlling balance. Switching strategy by means of a new sensory selection of orientation references may be a fast adaptive response to the lesion-induced postural instability.     

Comparison of a functional obstacle course with an index of clinical gait and balance and postural sway

BACKGROUND: Older adults commonly experience falls because of balance and mobility problems. Better assessment methods are needed to understand and correct balance and mobility disorders. METHODS: We used a low technology, functional obstacle course (FOC) to measure balance and mobility in 352 community-dwelling elderly participants. To establish concurrent validity of the FOC, we compared performance on the FOC with two established measures of balance and mobility: performance on the Tinetti Index (TI) and postural sway area measured on a force platform. RESULTS: Bivariate correlation analyses revealed significant inverse correlations between FOC completion time, the TI balance and gait subscores, and the TI total score (r = -.73 to -.78). The FOC quality scores and TI balance and subscores gait and TI total scores (r = .76 to .82) were significantly positively correlated. FOC time had significant, but small, positive correlations with sway area with eyes open (r = .18) and closed (r = .17) and nonsignificant correlation with sway area with visual feedback. FOC quality also had significant, but smaller, inverse correlations with sway area with eyes open (r = -.024) and closed (r = -.015), and nonsignificant correlation with sway area with visual feedback. Regression analysis showed that TI gait and balance measures accounted for most of the variance found in FOC performance. CONCLUSIONS: Our findings support the position that the FOC and the TI measure dynamic balance, whereas postural sway measures a different aspect of balance. Advantages of the FOC include the evaluation of environmentally influenced falls and balance problems.     

Postural control--a comparison between patients with chronic anterior cruciate ligament insufficiency and healthy individuals

Postural control in the sagittal plane was evaluated in 22 patients with chronic anterior cruciate ligament (ACL) deficiency and the result was compared to that of a control group of 20 uninjured subjects. Measurement of the body sway was done on a fixed and sway-referenced force plate in both single-limb and two-limb stance, with the eyes open and closed, respectively. Further, an analysis of the postural reactions to perturbations backwards and forwards, respectively, was made in single-limb stance. The results demonstrated statistically significant deficits of the postural control in the patient group compared to the control group, but also within the patient group. There was a significantly higher body sway within the patient group when standing on a stable support surface on the injured limb than standing on the uninjured limb with the eyes open, but no difference with the eyes closed. When standing on a stable support surface, there was a significantly higher body sway in the patient group standing on the injured leg than in the control group, both with eyes open and closed. The patient group also showed a significantly impaired postural control compared to the control group when standing on the uninjured leg with the eyes closed. There was no difference between the groups in the two-limb stance. When standing on the sway-referenced support surface, the patient group had a significantly larger body sway than the control group when the eyes were open, but there was no significant difference between the groups with the eyes closed. The measurement of the postural corrective responses to perturbations backwards and forwards showed that the reaction time measured from the initiation of the force plate translation, and the amplitude of the body sway was significantly greater in the patient group than in the control group. We conclude that patients with a continuing chronic ACL insufficiency several years after injury have an impaired postural control in the antero-posterior direction in single-limb stance on their injured leg. They also show a greater body sway and a prolonged reaction time when subjected to antero-posterior perturbations when standing on their injured leg.     

Hemispheric asymmetry in the visual contribution to postural control in healthy adults

This study was carried out in order to test the hypothesis of a right hemisphere dominance in the visual control of body balance. Eight healthy adults were subjected to a self-regulated lateral balance task, performed while sitting on a rocking platform. Four visual conditions were tested: open eyes with normal vision, closed eyes in the dark, left visual field-right hemisphere and right visual field-left hemisphere. Head and support displacements in the roll plane were recorded by means of an optoelectronic system. Two main results emerged from this study: (1) head stabilization in space was much more efficient in the left visual field-right hemisphere condition than in the three other visual conditions, and (2) although vision played an important role in the body stability whatever the anatomical level, there was no right hemisphere dominance at the pelvic level. A clear right hemisphere dominance was thus demonstrated as regards the visual contribution to head stabilization in space.     

Postural stability in diabetic polyneuropathy

OBJECTIVE: To examine whether sensory changes in lower limbs associated with diabetic sensory polyneuropathy compromise postural stability in different visual sensory conditions. RESEARCH DESIGN AND METHODS: The presence and severity of sensory neuropathy was evaluated with a clinical scale and measures of nerve conduction velocity in the lower limbs. Balance control was evaluated by testing subjects' postural stability (with a force platform) with vision, without vision, and during a recovery period after being without vision. RESULTS: Neuropathic patients showed larger ranges of sway, a faster sway speed, and a greater dispersion of sway than control subjects in all conditions. They also exhibited similar or less stable postural performance with vision than that of control subjects without vision. There was a strong relationship between the severity of the neuropathy and the postural stability. CONCLUSIONS: This experiment highlights that even with vision, the postural stability of neuropathic patients is impaired and may put them at higher risk of falling when performing more challenging daily tasks.     

Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.     

Postural balance and its sensory-motor correlates in 75-year-old men and women: a cross-national comparative study

BACKGROUND: There are no earlier cross-national comparative studies analyzing the functions of the posture control mechanisms and its sensory-motor correlates in elderly subjects. We investigated whether there are differences in balance between elderly subjects living in different geographical areas, and analyzed the sensory-motor associates of balance in men and women separately. METHOD: Using a force platform method, the functioning of the posture control system under three standardized conditions (normal standing, eyes open; normal standing, eyes closed; and tandem standing, eyes open) was studied among samples of 75-year-old residents in three Nordic localities, namely Glostrup in Denmark, G?teborg in Sweden, and Jyv?skyl? in Finland. The associations of the variables describing performance in each test with other sensory and motor functions were studied using correlation analyses and multivariate regression models. RESULTS: Differences between the populations were observed in both tests with visual control, favoring the participants from Glostrup and Jyv?skyl? compared with those from G?teborg. However, only minor differences between the subjects from different localities were observed in the test performed with the eyes closed. In all localities there was a primary sex difference in favor of the women which, however, mainly disappeared when body height was taken into the analyses as a covariate. A good performance in the balance tests (body height-adjusted values) was associated with good visual acuity, low vibrotactile thresholds, and high psychomotor speed. Also, isometric muscle strength, especially hand grip and body extension, was positively associated with good performance in the balance tests. Among the women, a poorer balance was observed in women with a smaller body mass. The results of the multivariate analyses showed that among the men, the most important predictors of good performance in the balance tests were low vibrotactile threshold on the foot, high isometric hand grip strength, and low body stature. Among the women, the most important predictors were low body stature, high body mass, high isometric body extension strength, and high psychomotor speed. However, only a small proportion of the variance in balance (about 13% in the men and 11% in the women) could be explained by the help of these factors. CONCLUSIONS: As the same procedure was applied to the analysis of postural balance, some differences between the populations living in different localities could be detected in some of the tests. The better performance of the women in the balance tests may partly be explained by anthropometric factors, especially differences in body height. There may also be differences in sensory-motor associates of balance in elderly men and women. On the basis of the associations observed, it is difficult to explain the differences in balance between the sexes or subjects living in different localities. Within the sexes, only a small proportion (10-13%) of the variation in balance during normal standing with eyes open could be explained by the factors included in the study.     

Functional cortico-muscular coupling during upright standing in athletes and nonathletes: A coherence electroencephalographic-electromyographic study.

We tested the hypothesis that functional cortico-muscular coupling of brain rhythms is implied in the control of lower limb muscles for upright standing. Electroencephalographic (EEG; Be-plus Eb-Neuro) and electromyographic (EMG) data were recorded in 18 fencing and 19 karate elite athletes, 14 karate amateurs, and 9 non-athletes, during quiet upright standing with open and closed eyes conditions. Cortico-muscular coupling was evaluated by computing EEG-EMG spectral coherence and directed transfer function (DTF). Body sway area did not differ among the groups. In non-athletes, the EEG-EMG coherence (gastrocnemius lateralis) at centro-parietal and parasylvian alpha rhythms (about 8-12 Hz) was higher during the open than closed eyes condition. This was not true in the elite athletes. At the same alpha rhythms, the sport amateurs presented values halfway between the non-athletes and elite athletes. Finally, the DTF was higher for cortico-muscular than muscular-cortical direction. These results suggest that visual information affects cortico-muscular coherence at 8-12 Hz in non-athletes and amateur athletes but not in elite athletes. In elite athletes, this might be due to a long training for the control of equilibrium based on proprioceptive and tactile inputs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postural stability among manganese exposed workers

Postural stability was investigated by static posturography in 32 manganese exposed workers with exposure duration of 6.6 (range 1.1-15.7) years and 53 referent subjects. The mean current urine manganese concentration for the exposed was 6.0 micrograms/g creatinine (range 0.6 to 53.3). There was no significant differences between both groups for the postural sway parameters obtained during eyes open condition. However, significant differences were observed for L - length of sway path and Vel - mean velocity of the center of pressure along its path. The Romberg Ratios (the relationship between eyes closed/open conditions) for the exposed's Vel, L, and Ao were also significantly different from the referent. The study showed that manganese exposed workers had significantly poorer postural stability compared to a referent group. We postulate that this could be a subclinical effect of manganese on the basal ganglia (pallidus) resulting in the postural instability when the visual input is cut off. Based on the current urinary manganese levels, we were not able to obtain any significant association with the postural sway parameters.     

Auditory and visual interactions in postural stabilization

The interaction and subsequent interpretation of sensory feedback from different modalities are important determinants in the regulation of balance. The importance of sound in this respect is not, as yet, fully understood. The aim of the present study was to determine the interaction of specific auditory frequencies and vision on postural sway behaviour. The frequencies employed represent the geometrical mean of 23 of the 25 critical bandwidths of sound, each presented at two loudness levels (70 and 90 phones). Postural sway was recorded using a biomechanical measuring platform. As expected vision had a highly significant stabilizing effect on most sway parameters. The frequency of the sound, however, appeared to influence the regulation of anteroposterior sway, while increasing loudness tended to increase mediolateral sway. At some frequencies the sound appeared to compensate for the lack of visual feedback. The interaction of sound and vision, particularly in combinations that lead to increased sway behaviour, may have implications in the occurrence, and possible prevention, of industrial accidents.     

Voluntary head stabilization in space during oscillatory trunk movements in the frontal plane performed in weightlessness

The ability voluntarily to stabilize the head in space during lateral rhythmic oscillations (0.59+/-0.09 Hz) of the trunk has been investigated during microgravity (microG) and normal gravity (nG) conditions (parabolic flights). Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, during phases of either microG or nG. The main result was that head orientation with respect to vertical may be stabilized about the roll axis under microG with, as well as without vision, despite the reduction in vestibular afferent and muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as was previously reported. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may in fact be organized on the basis of either dynamic vestibular afferents or a short-term memorized postural body schema.     

Regulation and function of tinman during dorsal mesoderm induction and heart specification in Drosophila

Sensory-motor control of upright human posture may be organized in a top-down fashion such that certain head-trunk coordination strategies are employed to optimize visual and/or vestibular sensory inputs. Previous quantitative models of the biomechanics of human posture control have examined the simple case of ankle sway strategy, in which an inverted pendulum model is used, and the somewhat more complicated case of hip sway strategy, in which multisegment, articulated models are used. While these models can be used to quantify the gross dynamics of posture control, they are not sufficiently detailed to analyze head-trunk coordination strategies that may be crucial to understanding its underlying mechanisms. In this paper, we present a biomechanical model of upright human posture that extends an existing four mass, sagittal plane, link-segment model to a five mass model including an independent head link. The new model was developed to analyze segmental body movements during dynamic posturography experiments in order to study head-trunk coordination strategies and their influence on sensory inputs to balance control. It was designed specifically to analyze data collected on the EquiTest (NeuroCom International, Clackamas, OR) computerized dynamic posturography system, where the task of maintaining postural equilibrium may be challenged under conditions in which the visual surround, support surface, or both are in motion. The performance of the model was tested by comparing its estimated ground reaction forces to those measured directly by support surface force transducers. We conclude that this model will be a valuable analytical tool in the search for mechanisms of balance control.     

Vestibular and somatosensory contributions to responses to head and body displacements in stance

The relative contribution of vestibular and somatosensory information to triggering postural responses to external body displacements may depend on the task and on the availability of sensory information in each system. To separate the contribution of vestibular and neck mechanisms to the stabilization of upright stance from that of lower body somatosensory mechanisms, responses to displacements of the head alone were compared with responses to displacements of the head and body, in both healthy subjects and in patients with profound bilateral vestibular loss. Head displacements were induced by translating two 1-kg weights suspended on either side of the head at the level of the mastoid bone, and body displacements were induced translating the support surface. Head displacements resulted in maximum forward and backward head accelerations similar to those resulting from body displacements, but were not accompanied by significant center of body mass, ankle, knee, or hip motions. We tested the effect of disrupting somatosensory information from the legs on postural responses to head or body displacements by sway-referencing the support surface. The subjects' eyes were closed during all testing to eliminate the effects of vision. Results showed that head displacements alone can trigger medium latency (48-84 ms) responses in the same leg and trunk muscles as body displacements. Nevertheless, it is unlikely that vestibular signals alone normally trigger directionally specific postural responses to support surface translations in standing humans because: (1) initial head accelerations resulting from body and head displacements were in opposite directions, but were associated with activation of the same leg and trunk postural muscles; (2) muscle responses to displacements of the head alone were only one third of the amplitude of responses to body displacements with equivalent maximum head accelerations; and (3) patients with profound bilateral vestibular loss showed patterns and latencies of leg and trunk muscle responses to body displacements similar to those of healthy subjects. Altering somatosensory information, by sway-referencing the support surface, increased the amplitude of ankle muscle activation to head displacements and reduced the amplitude of ankle muscle activation to body displacements, suggesting context-specific reweighting of vestibular and somatosensory inputs for posture. In contrast to responses to body displacements, responses to direct head displacements appear to depend upon a vestibulospinal trigger, since trunk and leg muscle responses to head displacements were absent in patients who had lost vestibular function as adults.(ABSTRACT TRUNCATED AT 400 WORDS)     

Responsiveness and reliability of a pediatric strategy score for balance

Various motor patterns or 'strategies' can be used to maintain balance. The purpose of this study was to determine the responsiveness of a pediatric strategy score (PED-SS) compared to a standard strategy score (SS) as a measure of age-related changes in the force patterns used to maintain stance. Eighty-one healthy children between 3-6 years of age were tested during stance on a force platform while facing a visual surround. The platform, visual surround (or both) moved simultaneously with the child's body sway. Four sensory conditions that altered visual and somatosensory (support surface) inputs were presented. The PED-SS was found to be more responsive to age-related changes in balance behavior compared to the SS. The oldest children (aged 5 and 6 years) showed the greatest ability to utilize horizontal A/P shear force to maintain stance and this finding was reflected only in the PED-SS. The implications of evaluating force strategy as one component of balance in healthy children is discussed with respect to the early developmental assessment of vestibular and developmental coordination disorders.     

Influence of sensory manipulation on postural control in Parkinson's disease

Postural control was assessed on a tilting platform system in 20 patients with idiopathic Parkinson's disease and 20 age-matched controls. The amount of information provided by vision and lower limb proprioception was varied during the experiment to investigate the influence of changes in sensory cues on postural control. The patient group with clinical evidence of impaired postural control (Hoehn and Yahr III) had significantly higher sway scores over all sensory conditions than either the Hoehn and Yahr II group or controls. The pattern of sway scores indicated that no obvious deficit in the quality, or processing, of sensory information was responsible for the postural instability observed in this group. The patients in both Hoehn and Yahr groups were also able to respond appropriately to potentially destabilising sensory conflict situations and significantly improved their sway scores when provided with visual feedback of body sway. The results indicate that in Parkinson's disease, the main site of dysfunction in postural control is likely to be at a central motor level.     

Contribution of central and peripheral vision to the regulation of stance: developmental aspects

Postural oscillations in 6-, 8-, and 10-year-old children were analyzed in four conditions of vision of the environment (complete vision, peripheral vision, central vision and no-vision) and two conditions of ankle somatosensory information (normal and altered support surfaces with a 5-cm-thick foam). Children were more stable with than without vision. This was observed whether children had complete or partial vision (central or peripheral). They were also more stable with the normal than with the altered support surface. Overall, there was no effect of age. Beyond these well-established results, the present experiment showed the complementary role of peripheral and central vision in the regulation of children's posture. For the 6- and 10-year-olds, central and peripheral vision yielded similar postural stability, whereas for the 8-year-olds, central vision yielded greater postural stability than peripheral vision. The analysis of postural oscillations in the medio-lateral and antero-posterior planes showed that, for the three age groups, central vision was as efficient whatever the plane. On the other hand, after age 6, peripheral vision was more efficient for regulating antero-posterior than medio-lateral oscillations. The contribution of the different sensory systems and their interaction for stabilizing posture in children should be specifically interpreted with regard to the operating characteristics of each sensory system at each age.     

Eye-hand interactions during goal-directed pointing movements

Saccadic eye and hand movements made to step displacements in target position were measured under conditions designed to dissociate the output of the ocular and manual motor systems. This was accomplished by having subjects look and point, either with or without vision of the hand (closed or open loop, respectively) at peripheral targets starting from independent initial positions. The results showed that the amplitude of open loop pointing responses increased in size when accompanied by saccades that were larger than the required hand movement. Providing the subject with visual feedback of the hand during the response or asking them to visually fixate caused this effect to disappear. Taken together, this pattern of results suggests that when vision of the hand is unavailable the programming of saccade metrics influences the control of simultaneously produced pointing movements in an on-line manner.     

Neuromuscular responses to disturbance of balance in children with prenatal exposure to alcohol

Alcohol-exposed children display delayed motor development and impaired fine- and gross-motor skills, including deficits in the maintenance of balance. In a recent study, we assessed the contribution of visual, somatosensory, and vestibular information to the ability to maintain balance. Our findings suggested that alcohol-exposed children were overly reliant on somatosensory information and were unable to compensate by using the visual and/or vestibular systems. To understand the nature of these observed balance deficits, corrective postural reactions were examined by exposing standing subjects to rapid toe-up movements of the support surface. Subjects for this study were alcohol-exposed (ALC) and normal control (NC) children matched for age and sex. Postural reactions were quantified by measuring electromyographic activity of the triceps surae and anterior tibialis muscles. Analyses revealed no differences between the ALC and NC groups on short- and medium-latency electromyographic responses, which are thought to be involuntary mono- and polysynaptic spinal reflexes, respectively. However, when compared with the NC group, the ALC group displayed increased long-latency responses, which are thought to involve a transcortical pathway. Although we are not able to rule out the possibility of additional peripheral (e.g., vestibular) disturbance as a contributing factor to postural instability, our findings suggest that the balance deficits seen in alcohol-exposed children are, at least in part, central in nature.     

Using codon usage to predict genes origin: is the Escherichia coli outer membrane a patchwork of products from different genomes?

To assess changes in postural control among healthy elderly and to correlate with suspected age-related events, 33 women and 16 men were studied. Postural control was evaluated by vibration-induced body sway, measured on a force platform, and vibration sensation was tested with a tuning fork. Occurrence of spontaneous gaze and head-shake-induced nystagmus was observed with infrared charged couple device (CCD) cameras and the subjects' medical history was reviewed. Vibration perception was the major determinant for the magnitude of body sway. Although these senior citizens considered themselves healthy, they had a variety of ailments in their medical history, diminished vibration sensation and a high prevalence of vestibular asymmetry. Age per se was not a determinant factor in any of the findings. The study suggests that interest should also be directed to the status of sensation in the legs and vestibular asymmetry when assessing balance function in the elderly. Furthermore, the term "age concomitant" may be more appropriate than "age dependent" when describing decrements of functions such as postural control in elderly subjects.