High cysteine diet reduces insulin resistance in SHR-CRP rats.

Increased plasma total cysteine (tCys) has been associated with obesity and metabolic syndrome in human and some animal studies but the underlying mechanisms remain unclear. In this study, we aimed at evaluating the effects of high cysteine diet administered to SHR-CRP transgenic rats, a model of metabolic syndrome and inflammation. SHR-CRP rats were fed either standard (3.2 g cystine/kg diet) or high cysteine diet (HCD, enriched with additional 4 g L-cysteine/kg diet). After 4 weeks, urine, plasma and tissue samples were collected and parameters of metabolic syndrome, sulfur metabolites and hepatic gene expression were evaluated. Rats on HCD exhibited similar body weights and weights of fat depots, reduced levels of serum insulin, and reduced oxidative stress in the liver. The HCD did not change concentrations of tCys in tissues and body fluids while taurine in tissues and body fluids, and urinary sulfate were significantly increased. In contrast, betaine levels were significantly reduced possibly compensating for taurine elevation. In summary, increased Cys intake did not induce obesity while it ameliorated insulin resistance in the SHR-CRP rats, possibly due to beneficial effects of accumulating taurine.

Control of the body vertical by vestibular and proprioceptive inputs.

The study examines the influence of vestibular and leg proprioceptive cues on the maintenance of the body vertical in human stance. Vestibular body orientation cues were changed by applying bipolar currents to both mastoid bones (cosine-bell wave form of 3.3 s duration, 1 mA current intensity). Proprioceptive input was modified by vibrating the tibialis anterior muscle (at f = 90 Hz, step of 5 s duration and 1 mm amplitude). Furthermore, the vestibular stimulus was paired with the muscle vibration using three different temporal relationships between the stimuli. Body lean responses were analyzed in terms of sway trajectories of the center of foot pressure on the body support surface (horizontal plane). With the anode on the right mastoid, vestibular body lean response was essentially straight towards the right side, and with the anode on left mastoid towards the left side. Vibration of right tibialis anterior muscle induced an almost straight body lean forward and to the right. Upon combined stimulation, responses with complex trajectory resulted, which depended on the stimulus interval. These responses reflected a superposition of the individual vestibular and proprioceptive effects. The results show that the body vertical is under the continuous control of leg proprioceptive and vestibular inputs, which sum linearly. We present a concept according to which these inputs are used for establishing a reference system for the control of the body vertical.

Modification of human postural response to leg muscle vibration by electrical vestibular stimulation.

In order to understand proprioceptive and vestibular contributions to human stance posture, the effect of electrical vestibular stimulation on body lean induced by leg muscle vibration was investigated. The magnitudes and directions of postural responses were registered as changes in the center of foot pressure (COP) with a force platform. Vestibular stimulation consisted of 1 mA, binaural, bipolar galvanic current and proprioceptive input from tibialis anterior or soleus muscles was altered vibratory stimulation. The body lean induced by combined vibratory and galvanic stimulation could be largely considered as a summation of responses evoked by the galvanic and vibratory stimulation alone. The results of the present study showed that both vestibular and proprioceptive signals play important roles in the estimation of internal representation of the body vertical.

Binaural monopolar galvanic vestibular stimulation reduces body sway during human stance.

The influence of monopolar binaural galvanic stimulation of the vestibular system was studied on body sway. Subjects, with eyes closed, were standing on a hard support or on foam rubber. Their body sway was registered on a force platform at intervals of 50 s. Both polarities of direct current with intensity 1 mA were used as a galvanic stimulus during the whole recording interval. Changes of body sway amplitude and velocity were analyzed in situations with and without galvanic stimulation on two different support surfaces. In stance on the hard support, the cathodal polarization of labyrinths (in most subjects) reduced body sway velocity and decreased body sway slightly in the anteroposterior direction. Anodal polarization of labyrinths during 50 s did not affect the body sway parameters. The results on the foam rubber platform exhibited a significant reduction of body sway velocity induced by both anodal and cathodal polarization of the labyrinths. The decrease of body sway in the anteroposterior direction was also observed during cathodal polarization. The stabilizing effect of vestibular binaural monopolar stimulation on the upright stance was mainly observed in the postural control situation where the leg proprioceptive input was changed (stance on soft surface) and the role of vestibular input was more important.

Visual control of human stance on a narrow and soft support surface.

The influence of additional visual feedback (VF) on stance control was studied under conditions of changed afferent information from the foot sole and ankle joint due to different support surfaces. The changes of body sway amplitudes were analyzed and their frequency spectrum was established. The effect of visual feedback on the amplitude and frequency characteristics of human stance was manifested as: a) a decrease of the mean amplitude of body sway during visual feedback, corresponding to the decrease of power spectrum density (PSD) of stabilograms in the frequency range below 0.05 Hz, b) an increase of mean velocity of body sway corresponding to the increase of PSD of stabilograms in the frequency range of 0.4-1.5 Hz. The results showed that the improvement of the upright stance by additional visual feedback is mainly mediated through activation of postural muscles at the ankle level, or ankle strategy. The stabilization effect of VF on stance control is slight or negligible if the performance part in ankle joint (narrow support) was reduced.

[The effect of head position and functional status of the cervical spine on body sway in the upright posture]. / Vplyv polohy hlavy a funkcného stavu krcnej chrbtice na výchylky tela vo vzpriamenom postoji.

In 30 subjects (16 men and 14 women) stabilometry was used to investigate the stability of posture with closed eyes and different positions of the head (backward, forward, right and left turn). Cervical spine mobility of the subjects studied was determined by vertebrogenic examination. The maximum backward extension of the head was found to reduce most markedly posture stability. Correlation analysis revealed a relationship between the functional state of the cervical spine and the degree of posture stability impairment induced by backward extension of the head, with the impairment being more pronounced in the forward-backward direction. The obtained results show that changes in the quality of proprioceptive information from the cervical spine region are also involved in determining the stability level of upright posture. The findings imply that posture with backward extension of the head can be used as a loading test for detecting ataxia of cervical origin.

Postural adjustments upon arm movement during sinusoidal induced body oscillations.

Postural adjustments due to the fast forward right arm elevation, performed during sinusoidal induced body oscillations in the phase of platform-induced dorsal, as well as plantar flexion of the foot were studied. Start times of the changes in the cyclic way of the center-of-gravity position (SG) and right ankle goniogram (GG) as well as the EMG onsets of the right soleus (S), anterior tibial (AT) and femoral biceps (FB) muscles relative to the ipsilateral anterior deltoid muscle (AD) EMG onset were measured. The EMG onset of FB muscle was found to occur significantly before the EMG onset of the AD muscle during plantar flexion series, wherever during dorsal flexion series the EMG onset of the AT muscle was significantly before the AD muscle EMG onset. Only the FB muscle changed significantly its EMG onset with the change of platform direction and started later in the dorsal flexion series. The results showed that two different strategies of postural adjustments might be distinguished depending on the direction of the platform movement.

[Physiologic range of stabilometry values obtained in the upright posture using a computer]. / Fyziologické rozsahy hodnôt parametrov stabilometrického vysetrenia vzpriameného postoja, vyhodnocovaného pocítacom.

The authors present physiological ranges of values of seven parameters of stabilometric examinations of the upright posture in man. In order to make the examination effective, the authors suggested and tested three situations which make it possible to characterize the activity of the visual, vestibular and proprioceptive feedback in the process of maintenance of the upright posture. For measuring the supporting forces during the upright posture the authors used a stabilometer with automatic compensation of the body weight. Amplitude analysis of the obtained stabilometric curves was made "on line" by means of a microcomputer PMD 85-2. The mentioned stabilometric parameters make it possible to evaluate objectively the ability of the subject to maintain an upright posture based on a) the median amplitude and velocity of deviations of the body in an anterioposterior and lateral direction, b) complex parameters of the length of the curve, the total area and root mean square deviation of the statokinezigram.

[Correlation of the evoked vestibulo-postural reaction and spontaneous body sway while standing]. / Korelácia evokovaných vestibulo-posturálnych reakcií a spontánnych výchyliek tela pri postoji.

The stability of upright posture was studied by the method of stabilometry in 16 healthy subjects. The efficacy of involving visual, vestibular and proprioceptive afferentation in maintaining posture was examined in four test situations. A direct correlation of stabilometric parameters was established at posture on soft surface and at galvanic stimulation of the vestibular analyzer. The recorded data indicate an indirect correlation between the sensitivity of the vestibular sensor and the sensitivity of that part of the central nervous system which processes vestibular information. The observed relationship results presumably from the action of central compensatory mechanisms in the function of the vestibulo-postural circuit.