Instrumentation for assessment of tremor, skin vibrations, and cardiovascular variables in MIR space missions.

A versatile and simple to use biomedical instrumentation for noninvasive examinations of cosmonauts at the Russian MIR space station was developed. It consists of a comfortable sensor jacket to assess signals from the body surface, a precision hand dynamometer to produce muscular and cardiovascular loads, and a small interactive microprocessor unit that controls the examination and stores measurement data. The sensor jacket includes highly sensitive piezo-resistive accelerometers, pulse sensors, an ECG system, and a skin-mountable mechanical vibrator. The functionality of this instrumentation was evaluated during long-term space flights and also proved very useful in laboratory and clinical studies.

Neurological status, sleep apnea frequency and blood oxygenation in six weeks old infants.

A study was carried out to investigate the correlation between sleep apnea frequency, blood oxygenation and neurological condition in 21 infants at six weeks of age with inconspicuous medical history. Polygraphic recordings of respiratory behaviour and transcutaneous blood gas monitoring lasted for at least five hours. To quantify the results of the neurological examination we established a neurological optimality score (NOS). We found statistically significant correlations between several indexes of apneas and indexes of blood oxygenation and NOS. Thus, a reduced NOS was strongly correlated with higher apnea frequencies and with pronounced drops of transcutaneous PO2-values. In addition all but one infant who were diagnosed as having a sleep apnea syndrome showed a greater than ten percent reduction of NOS. Some pathophysiological considerations to explain our findings are put forward and the possible role of the neuromodulator adenosine is emphasized.

Surface myomechanical responses recorded on a scanner galvanometer.

A moving magnet galvanometer equipped with lever and indentor was evaluated for mechanomyography (MMG). First, the precision of the galvanometer was tested on a piezo-electric disc actuator. Using a 50 mm lever, synthesised micromotions with an amplitude of 1 microm could be detected (noise level < 0.2 microm) at static indentation forces ranging from 0.1 to 2 N. Then the galvanometer was mounted on an isometric ankle dynamometer to sense calf-muscle responses (N = 6). In the first protocol, twitch contractions were elicited by electrical stimulation while the indentation force was increased. Twitch amplitudes, twitch contraction times and twitch half-relaxation times were analysed from the surface and contraction responses. With indentation force (0.1-0.5 N), the amplitude of the surface responses increased (+61%), contraction and half-relaxation times, however, were not influenced. The mean twitch contraction time from the surface responses (60 +/- 11 ms) was shorter than that from the contraction responses (115 +/- 7 ms), indicating more fast-contracting fibres under the indented area. In the second protocol, voluntary target contractions were produced, and the surface responses were simultaneously recorded on an accelerometer. After double differentiation of the galvanometer signal, both acceleration MMGs showed a high coincidence in the time and frequency domains. With an indentation force of 2 N applied on the accelerometer, the signal amplitude (-10%) and the mean frequency (-19%) decreased. A specific application of this galvanometer-dynamometer test system is the assessment of regeneration processes in paraplegics with long-term denervated muscles.

Influence of contact forces on wrist photoplethysmography--prestudy for a wearable patient monitor.

The practical setting shows that gentle manual pressure on a photosensor suffices to improve the detectability of arterial pulses, but changes in the pressure applied may also produce signal artefacts. To study these effects, stepwise increasing contact forces (0.5 to 4 N) were applied to a photosensor placed over the radial artery. Additionally, the influence of optical coupling between sensor and skin surface was examined by introducing an elastic distance ring. The AC and DC components from the recorded photoplethysmogram were analysed. The AC component (absorption due to arterial pulsation) increased with the pressure applied; at lower forces (0.5 to 3 N) an introduction of the ring enhanced this effect. The characteristic of the DC component (backscattering from non-pulsating tissues) depends on optical coupling: without the ring the DC component increased stepwise with force (slope 0.035 V/N), but with the ring in place this component decreased (slope -0.075 V/N). Since the sensitivity of the pulse signal to artifacts is related to the slope of the DC component, such artefacts can be minimized by making the slope small. The utilization of these results to improve pulse detection and reduce motion artefacts in a wearable wrist device is discussed.

Polygraphic belt with force-sensing expander for physiological tests on cosmonauts.

To study cardiorespiratory and neuromotor functions in cosmonauts a novel belt with embedded polygraphic sensors and a force sensing expander were developed. The sensors are: a three-electrode ECG/impedance plethysmographic system to capture cardiac and respiratory activity, two triaxial accelerometers to record limb micromotions and an IR reflex-sensor to detect peripheral pulse waves. The expander consists of an elastic cable in series with a load cell to measure the extension force and to adjust the extensions by visual feedback. The cable stiffness was chosen rather high (150-200 N/m) in order to induce involuntary limb oscillations at higher extension levels. The equipment was tested in MIR spaceflights and is projected for physiological tests on the ISS.

Body fixed ankle dynamometer for isometric tests in space flights.

To study neuromuscular variables in isometric contraction, a body-fixed ankle dynamometer with integrated electromyographic (EMG) system and software-controlled load tests was developed. It consists of a footplate acting against a load cell in plantar flexion. Counteraction is supported by a perpendicular telescopic stand which runs from the heel to the thigh with the knee flexed at an angle of 90 degrees C. Additional to contraction force, force tremor and surface EMG from the triceps surae and tibialis anterior muscles are recorded. The software consists of three load tests to assess variables of muscle fatigue, motor performance and motor memory. The dynamometer was optimised in relation to functionality and selection of construction materials for the use on the Russian MIR space station.

Passive viscoelastic properties of the rabbit aorta in vitro.

Tensile tests on longitudinal and circumferential strips of the rabbit aorta have been performed. Stress-strain and relaxation parameters have been estimated with respect to four stress levels and three positions on the aorta. Stress-strain data indicate that in longitudinal direction the aorta becomes more compliant with distance from the aortic arch. The opposite tendency is found for the circumferential direction. Stress-relaxation is found to be strongly dependent on the stress level. The results are discussed with regard to arterial dynamics.

Computer-based sleep monitoring in SIDS-risk infants--preliminary results.

A computerized, PC-based system is introduced for sleep monitoring in infants. The system is capable of digitizing and storing 22 physiological variables over a whole-night sleep period. The preprocessed data can be displayed on a single page; further processing can be done on the digitally stored data.

Vibrografic signs of autonomous muscle tone studied in long term space missions.

Signs of resting muscle tone, assessed by cardiac driven microvibrations (MV), were studied in two cosmonauts during long term space missions on the Russian MIR station. In the 1 g environment, MV showed the typical 7-13 Hz resonance oscillations triggered by the heart beat. In 0 g, these pulsations were damped and the waveform became similar to an acceleration ballistocardiogram. If resting tone was slightly increased by extending the arm in 0 g, the resonance oscillations reappeared in most cases. By means of a simple vibromechanic analog it is demonstrated that the elastic component of muscle has to be reduced during the fully relaxed state in 0g.

Arm tremor and precision of hand force control in a short and long term flight on the MIR-Space-Station.

To determine whether long and short time exposure of man in 0g alters normal physiological tremor patterns we recorded arm tremor using an accelerometer as well as hand forces and tremor during constant isometric contraction using a load cell. Arm tremor was decreased during both flights in amplitude and frequency. Shortly after the long term flight arm tremor amplitude was increased, indicating adaptive changes in the tonic reflex loop. Isometric hand tremor remained unchanged during the long and short time flight demonstrating that the contractile properties of hand muscles remained constant. Precision of hand force was decreased until the half duration of the long term flight.

Vibration stimulation during non-fatiguing tonic contraction induces outlasting neuroplastic effects.

The objective was to explore if vibration superposed to tonic contraction induces plastic changes in the contra- and ipsilateral motor cortex. Healthy subjects (n=12) abducted the right index finger with a force 5% of maximal voluntary contraction (MVC) against the lever of a torque motor while a 60 Hz vibration stimulus of 10 min was delivered. Motor evoked potentials (MEPs) after single and paired-pulse transcranial magnetic stimulation (TMS) were recorded from the first dorsal interosseous muscle of right and left hand pre, during, post and 30 min post-stimulation. The TMS assessments were employed with tonic contraction alone (TONIC) and with superposed vibrostimulation (VIBRO), each for the ipsi- and contralateral cortex separately. In the contralateral cortex: resting motor threshold (rMT) decreased, MEP amplitudes increased, short-interval intracortical inhibition (SICI) reduced and intracortical facilitation (ICF) increased post VIBRO, while no changes occurred post TONIC. In the ipsilateral cortex: rMT decreased, MEP amplitude increased and SICI reduced during TONIC, while no changes occurred post TONIC, during and post VIBRO. Vibration superposed to tonic contraction, induces lasting (30 min) plastic changes, whereas contraction alone caused no outlasting effects. Mainly intrinsic intracortical mechanisms are involved because spinal adaptation could be excluded (F-wave assessments). These findings have a therapeutic potential in the functional recovery of motor deficits with robot-aided devices.

Variability of BOLD response evoked by foot vibrotactile stimulation: influence of vibration amplitude and stimulus waveform.

The aim of the present was study to evaluate cortical and subcortical neural responses on vibrotactile stimulation of the food and to assess somatosensory evoked BOLD responses in dependence of vibration amplitude and stimulus waveform. Sixteen healthy male subjects received vibrotactile stimulation at the sole of the right foot. The vibration stimulus was delivered through a moving magnet actuator system (MMAS). In an event-related design, a series of vibration stimuli with a duration of 1 s and a variable interstimulus interval was presented. Four stimulation conditions were realized using a 2 (amplitudes 0.4 mm or 1.6 mm) x 2 (waveform sinusoidal or amplitude modulated) factorial design. Stimulating with 0.4 mm amplitude compared to 1.6 mm stimulus amplitude more strongly activated the pre- and postcentral gyrus bilaterally and the right inferior, medial and middle frontal gyrus. In the reverse comparison significant differences were observed within the left inferior parietal lobule, the left superior temporal gyrus, and the left temporal transverse gyrus. In the comparison of sinusoidal versus modulated waveform and vice versa no significant activation differences were obtained. The inter-subject variability was high but when all four stimulation conditions were jointly analyzed, a significant activation of S1 was obtained for every single subject. This study demonstrated that the BOLD response is modulated by the amplitude but not by the waveform of vibrotactile stimulation. Despite high inter-individual variability, the stimulation yielded reliable results for S1 on the single-subject level. Therefore, our results suggest that vibrotactile testing could evolve into a clinical tool in functional neuroimaging.

Characterisation of arm microvibration recorded on an accelerometer.

Microvibration (MV) of the freely hanging and firmly supported lower arm was studied (n = 8) using two accelerometers, one located over muscle tissue (brachioradialis muscle) and one over bony tissue (processus styloideus). Measurements were made in the completely relaxed arm (REST), during arterial occlusion (CUFF) and during mild handgrip (GRIP), first with the arm relaxed and hanging beside the chair and then repeated with the arm supported in a special rest. At REST. ballistocardiac forces were identified as the driving mechanism for the regular MV pattern, whereas actions of local pulse waves (CUFF) could be excluded. During GRIP irregular MV, related to the contraction process, became superimposed on both signals. The MV at REST was sensitive to arm position. In the freely hanging state, when the arm was family coupled to the trunk, ballistocardiac body motion was present over bony tissue, producing a low damped 7-13 Hz resonant response over muscle tissue. In the supported state, the arm became isolated from body motions. Nevertheless, ballistocardiac forces reached the arm, producing smaller oscillatory responses over bone and muscle tissue. Regionally produced MV (GRIP) was not sensitive to arm position, but the spectrum content in the 7-13 Hz region was very similar to REST. From these results it would appear, that a low damped 7-13 Hz resonance process exists in relaxed muscle tissue, which physiologically becomes stimulated by cardiac and muscle forces. From the close relationship of the simultaneous MV waveforms in the supported arm, evidence for mechanical coupling between bone and muscle tissue is given.

Stages of anti-N-like immunization: a further contribution to problems arising from anti-N-like antibodies in hemodialysis patients.

In the past years, the discussion around problems arising from anti-N-like antibodies has waned in spite of their continuing existence. Even highly sophisticated rinsing procedures of dialysers after sterilisation with Formalin are not capable of preventing an anti-N-like immunization. Therefore, formalin sterilisation should no longer be employed. Three stages of the formalin-dependent anti-N-like immunization are described. Hematological and immunohematological problems in this patient group are documented.

Hemispheric asymmetry and the processing of harmonies in music.

The purpose of the present study was to investigate to what extent the concept of hemispheric specialization is of importance for the perception and processing of harmonies in music. The method involves presenting mistuned intervals monaurally, which have to be tuned with a joy-stick. Subjects were divided according to their previous musical training and according to their ear and eye dominance. The accuracy of the tuning-performance yields data for an univariate analysis of variance. From the results the conclusion is drawn that the right hemisphere is more sensitive to the dimension of musical harmony. This superiority is discussed with respect to different theories of hearing and the question, if the observed differences are the expression of an innate or a learned ability.

Myo-electric signals from two extrinsic hand muscles and force tremor during isometric handgrip.

The objective of the present study was to investigate the myo-electric signs of muscle fatigue and the isometric force tremor of two extrinsic hand muscles, extensor digitorum communis and flexor digitorum superficialis, during isometric power grip. In addition, the synergy between flexor and extensor muscles and hand differences in a right-handed population have been studied. During isometric hand-dynamometry the myo-electric signal was recorded using surface electrodes and isometric force tremor was recorded using a special load cell. Eight subjects participated in this study and contractions were performed at 20%, 40%, 60% and 80% of maximal voluntary contraction (MVC) with left and right hands. The decrease of mean power frequency (MPF) with duration of contraction was greater in the left extensor as compared to the ipsilateral flexor muscle. No differences in the decrease in MPF with the duration of the contraction were found between the right extensor and flexor muscles. Isometric force tremor root mean square did not change during contractions at a given contraction level. Isometric tremor amplitude increased from 20% to 60% MVC and decreased at higher contraction levels. Tremor amplitude was higher in the left hand at all contraction levels but 60% MVC. These data would suggest differences in fatiguability and muscle fibre composition between the dominant and nondominant hand, which may be due to preferred use. The significance of force tremor for the evaluation of recruitment order and muscle fatigue is discussed.

Morphological and biomechanical studies of the ligamentum arteriosum.

Fifteen ligaments taken from individuals aged between 60 and 80 years were used for the study of the histological structure, the composition of the ground substance and the biomechanical behavior. Remnants of the original duct are recognizable in the ligament as artery of the muscular type. What had been the intima is thickened and consists mainly of cell-poor, fiber-rich connective tissue, which often shows chondrification along with calcification. The biomechanical behavior of the ligaments, evaluated with the force-length and force-relaxation test, was similar to that of peripheral arteries.

Characterization of formaldehyde-related antibodies encountered in hemodialysis patients at different stages of immunization.

In hemodialysis patients who reuse formaldehyde-sterilized dialysers we found that antibodies agglutinating native NN red cells belonged exclusively to the IgM fraction of immunoglobulins. In the same patients antibodies directed against formaldehyde-altered NN red cells proved to be mainly IgG in addition to IgM. Three stages of formaldehyde-dependent RBC immunization could be distinguished serologically. The production of these antibodies was dependent on the time of hemodialysis treatment. We found antibodies which could bind complement in the presence of soluble antigen. These antibodies are supposed to damage the patient's red cells immediately after contact to minute amounts of formaldehyde during hemodialysis.

[Amh, a Bombay variant with cryptantigen H]. / Amh, eine Bombay-Variante mit Kryptantigen H

Untreated red cells of the Bombay variant Amh have traces of A. They are Le(b)-positive but H-negative. Following RDE-(Receptor destroying enzyme) treatment H is demonstrable by anti-HLa, -BHEe, and -HUe but not by anti-HLt. This type of reaction resembles that in O-newborns: H is present only in the form of a glycolipoid but not in the form of a mucoid. The barrier of neuraminic acid prevents recognition of H as his own. Anti-H is present. It has been shown that H as a precursor is necessary only for A1 but not for Am, A3, and A2.