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PubMed2005

Anticipating the effects of gravity when intercepting moving objects: differentiating up and down based on nonvisual cues.

Intercepting an object requires a precise estimate of its time of arrival at the interception point (time to contact or "TTC"). It has been proposed that knowledge about gravitational acceleration can be combined with first-order, visual-field information to provide a better estimate of TTC when catching falling objects. In this experiment, we investigated the relative role of visual and nonvisual information on motor-response timing in an interceptive task. Subjects were immersed in a stereoscopic virtual environment and asked to intercept with a virtual racket a ball falling from above or rising from below. The ball moved with different initial velocities and could accelerate, decelerate, or move at a constant speed. Depending on the direction of motion, the acceleration or deceleration of the ball could therefore be congruent or not with the acceleration that would be expected due to the force of gravity acting on the ball. Although the best success rate was observed for balls moving at a constant velocity, we systematically found a cross-effect of ball direction and acceleration on success rate and response timing. Racket motion was triggered on average 25 ms earlier when the ball fell from above than when it rose from below, whatever the ball's true acceleration. As visual-flow information was the same in both cases, this shift indicates an influence of the ball's direction relative to gravity on response timing, consistent with the anticipation of the effects of gravity on the flight of the ball.

Attention↗
PubMed2004

Deficits in saccades and fixation during muscimol inactivation of the caudal fastigial nucleus in the rhesus monkey.

The caudal fastigial nucleus (cFN) is a major nucleus by which the cerebellum influences the accuracy of saccades. In head-restrained monkeys generating saccades from a fixation light-emitting diode (LED) toward a flashed target LED, we analyzed the effects of unilateral pharmacological inactivation of cFN on horizontal, vertical, and oblique saccades. When animals were viewing the fixation LED, usually after one or more correction saccades, the positions of the eyes were slightly offset in comparison with the positions maintained before the injection (average offset = 1.1 degrees). The offset was ipsilateral to the injected side and did not depend on the target location. The horizontal component of all ipsilesional saccades was hypermetric and associated with a 32-42% increase in the amplitude of the deceleration displacement without significant change in the amplitude of the acceleration displacement. The horizontal component of all contralesional saccades was hypometric and associated with a decrease in the peak velocity and in the acceleration amplitude (30-35% decrease) without significant change in the deceleration amplitude. The amplitude of vertical saccades was not systematically affected, but their trajectory was always deviated toward the injected side. They missed the target with an error that depended on saccade duration or amplitude. If any, the effects of muscimol injections on the vertical component of oblique saccades were very small. The changes in fixation and the dysmetria are both viewed as consequences of an impairment in the cFN bilateral influence on the burst neurons located in the left and right brain stem.

Animals↗
PubMed1985

Intersegmental coordination of the leech swimming rhythm. II. Comparison of long and short chains of ganglia.

Preparations of the nearly isolated leech nerve cord containing as few as two ganglia are sufficient to generate intersegmentally coordinated swim oscillations, provided that they receive tonic excitation from other segments via the median connective (Faivre's nerve). Due to their greatly reduced complexity, these preparations should provide useful experimental models of neuronal coordination. As a step in the development of such models, we have characterized the intersegmental coordination of nerve-cord chains ranging from 2 to 18 ganglia in length. We found that increases in swim-cycle period give rise to increases in intersegmental delay between homologous motoneuron bursts. Thus the intersegmental phase relationships are nearly independent of period. The relationship between intersegmental delay and period is approximately linear and extrapolates to intersect the period axis at approximately 0.3 s. This value is in close agreement with the analogous measure derived from tension measurements in the intact swimming leech. Chain length (number of connected ganglia in a preparation) has a pronounced influence on the magnitude of intersegmental phase lag. The longest chains (18 ganglia) exhibited phase lags of approximately 8 degrees per segment, whereas for pairs of ganglia the phase lag was approximately 40 degrees per segment. This dependence of phase lags on chain length was apparent at both the motor and oscillator levels. The intersegmental phase lag is not the same in all parts of the nerve cord. Rather, it increases steadily toward the posterior end of the chain, providing a deceleration in the rearward progression of the metachronal activity. The rearward increase in intersegmental phase lag is paralleled by a propensity of chains taken from more posterior sections of the nerve cord to exhibit larger phase lags. That is, there appears to be a phase-lag gradient intrinsic to the nerve cord to account for the deceleration of activity. The anterior and posterior ends of an isolated nerve cord continue to exhibit phase-locked bursting when an intervening section of five ganglia is bathed in elevated Mg2+ saline. Thus, information sufficient to coordinate oscillations in separate ganglia travels at least six segments. The phase lag across the blocked section is reduced but within each unblocked section is increased so that the phase lag between extreme ends is nearly unchanged. This altered burst pattern is due to a combination of synaptic block in segmental ganglia and conduction block in through-fibers.

Animals↗
PubMed1989

Organizing principles for single-joint movements. I. A speed-insensitive strategy.

1. Normal human subjects made discrete elbow flexions and extensions in the horizontal plane from a stationary initial position to visually defined targets at different distances with a constant inertial load or made flexions to a visually defined target with different inertial loads. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects were instructed to move their limbs accurately but quickly to the targets. Movements of greater distances or lesser loads were performed at higher velocities. 3. Peak inertial torque, acceleration and velocity, movement time, and integrated, rectified EMG were all highly correlated with the task variables, distance and inertial load. We show that peak inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the tasks, the EMG, and movement kinematics. 4. The rate at which subjects initially developed torque to accelerate their movements was invariant over changes in the value of either task variable. The rising phase of the agonist EMG was also independent of the distance or load moved. 5. Two components were distinguished in the antagonist EMG. The first had a relatively constant latency and amplitude. It terminated on the onset of the second and larger component at a latency that was delayed as both distance and load increased. 6. The integrated, rectified antagonist EMG was proportional to inertial load and peak decelerating torque for changes in inertial load. When target distance varied, proportionality between peak decelerating torque and antagonist EMG could be found if correction was made for the effects of muscle length on the torque-EMG relationship. 7. We propose organizing principles for the control of single-joint human movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 8. A model is described in which movements made under a speed-insensitive strategy are executed by controlling the duration and the relative timing of amplitude invariant patterns of activation to the spinal motoneuron pools.

Elbow Joint↗
PubMed1990

Dynamic response of human muscle spindle afferents to stretch.

1. One hundred and twenty-four muscle afferents from the finger extensor muscles were recorded from the radial nerve in human subjects. 2. The afferents were provisionally classified as muscle spindle primary (78/124) and secondary afferents (25/124), and Golgi tendon organ afferents (21/124), on the basis of their response to 1) maximal twitch contractions, 2) 20- and 50-Hz sinusoids superimposed on ramp-and-hold stretches, 3) stretch sensitization, and 4) isometric contractions and sudden relaxations. 3. Ramp-and-hold stretches at two velocities, 10 and 50 degrees/s, were applied to the appropriate metacarpophalangeal (MCP) joint while the parent muscle remained relaxed. For each unit three discrete parameters were assessed: the presence or absence of 1) an initial burst at the commencement of the ramp stretch, 2) a deceleration response at the beginning of the hold phase, and 3) a prompt silencing at muscle shortening. In addition, two kinds of dynamic indexes were calculated for 79 of the muscle spindle afferents. 4. Most spindle afferents responded readily to stretch, whereas the Golgi tendon organ afferents produced very poor stretch responses. All of them lacked a static response, whereas the dynamic response, when present at all, consisted of only a few impulses. 5. The dynamic index was higher for spindle primaries than for secondaries, and this difference was statistically significant although the distribution was unimodal for spindle afferents as a group. Hence, this parameter was a poor discriminator. 6. Initial bursts, deceleration responses, and silences during imposed shortening were more common in spindle primaries than in secondaries. The differences were significant in all these respects. 7. The three discrete parameters were statistically pairwise independent for the spindle afferents, justifying the combination of the three into a useful battery for discrimination between primary and secondary spindle afferents and the use of this battery as a partial data base for a probability approach towards a solid classification of human muscle afferents.

Adolescent↗
PubMed1990

Dynamic analysis of sensory-inhibitory interactions in crayfish stretch receptor neurons.

1. The effects of regular and random inhibition at moderate rates on the sensory response evoked by sinusoidal stretches were investigated in slowly and rapidly adapting stretch receptors of crayfish (RM1 and RM2, respectively). 2. Although the RM1 has pacemaker properties and the RM2 is spontaneously silent, inhibitory postsynaptic potential (IPSP) effects were similar in both mechanosensory neurons. The most common consequence was the expected reduction of the sensory response and the increase of the elongation needed to reach firing threshold. With regular IPSPs there were regions where pre- and postsynaptic spikes alternated at fixed integer ratios, usually 1:1, more rarely 1:2 and 1:3. Increases or decreases of the sensory excitation caused sudden postsynaptic accelerations or decelerations when specific length bounds were crossed and where pre- and postsynaptic alternations changed to lower (e.g., from 1:1 to 1:2) or higher ratios (e.g., from 1:2 to 1:1), respectively. 3. Paradoxical effects were also observed because increasing or decreasing the inhibitory rate for a given alternation ratio (e.g., 1:1) accelerated or decelerated the output rate, respectively. Alternations and paradoxical behaviors disappeared with IPSP pattern irregularization. Random IPSPs strongly irregularized the receptor's output. Inhibition, especially if the pattern was irregular, could excite under special conditions. 4. With regular IPSPs, mechanical sensitivity became zero at the lengths at which receptors were silenced, low during alternations, and maximum at transitions between successive alternation ratios. Irregular IPSPs did not have this delinearizing consequence. 5. In conclusion, inhibition introduced important complex modifications in the coding of mechanosensory information. Effects were similar in both receptor types, indicating that self-sustained oscillations are not fundamental. The observed changes were critically dependent on pre- and postsynaptic rate and pattern. They cannot be explained by simple summation of converging sensory and inhibitory inputs and represent another observation of the complex dynamic behavior of periodically driven nonlinear systems.

Animals↗
PubMed1999

Turning strategies during human walking.

The mechanisms involved in rapidly turning during human walking were studied. Subjects were asked to walk at a comfortable speed and to turn toward the instructed direction as soon as they felt an electrical stimulus to the superficial peroneal nerve. Stimuli were presented repeatedly at random over 10- to 15-min periods of walking for turning in both directions. Electromyograms (EMGs), joint angular movements of the right leg, and forces under both feet were recorded. The step cycle was divided into 16 parts, and the responses to stimuli in each part were analyzed separately. Two turning strategies were used, depending on which leg was placed in front for braking. For example, to turn to the right when the right foot was placed in front, subjects generally altered direction by spinning the body around the right foot (spin turn). To turn left when the right foot was in front, subjects shifted weight to the right leg, externally rotated the left hip, stepped onto the left leg, and continued turning until the right leg stepped in the new direction (step turn). The step turn is easy and stable because the base of support during the turn is much wider than in the spin turn, so some subjects used it in all parts of the cycle. Initially, the deceleration of walking is similar to a rapid stopping task, which has been previously examined. The deceleration mechanism involves a sequence of distal-to-proximal activation of muscles on one side of the body (soleus, biceps femoris, and erector spinae). This pattern is similar to the "ankle strategy" used in postural control during forward sway. The control of foot placement in the swing leg and muscle activities for rotating the trunk in the stance leg occurred within a step after the cue. The action of ankle inverters and elevation of the pelvis by activity of gluteus medius may contribute to the control of trunk rotation. This activity was closely related to the timing of the opposite foot strike, independent of the part of the step cycle when the stimulus was applied. In most subjects, the turn was completed without resetting the underlying walking rhythm. This first EMG analysis of rapid turning shows how common strategies for postural sway and stopping can be combined with one of two turning strategies. This simplifies the complex task of turning at a random time in the step cycle.

Adult↗
PubMed1999

Comparison of external load compensation during rhythmic arm movements and rhythmic jaw movements in humans.

Experiments were performed on human elbow flexor and extensor muscles and jaw-opening and -closing muscles to observe the effect on rhythmic movements of sudden loading. The load was provided by an electromagnetic device, which simulated the appearance of a smoothly increasing spring-like load. The responses to this loading were compared in jaw and elbow movements and between expected and unexpected disturbances. All muscles showed electromyographic responses to unexpected perturbations, with latencies of approximately 65 ms in the arm muscles and 25 ms in the jaw. When loading was predictable, anticipatory responses started in arm muscles approximately 200 ms before and in jaw muscles 100 ms before the onset of loading. The reflex responses relative to the anticipatory responses were smaller for the arm muscles than for the jaw muscles. The reflex responses in the arm muscles were the same with unexpected and expected perturbations, whereas anticipation increased the reflex responses in the jaw muscles. Biceps brachii and triceps brachii showed similar sensory-induced responses and similar anticipatory responses. Jaw muscles differed, however, in that the reflex response was stronger in masseter than in digastric. It was concluded that reflex responses in the arm muscles cannot overcome the loading of the arm adequately, which is compensated by a large centrally programmed response when loading is predictable. The jaw muscles, particularly the jaw-closing muscles, tend to respond mainly through reflex loops, even when loading of the jaw is anticipated. The differences between the responses of the arm and the jaw muscles may be related to physical differences. For example, the jaw was decelerated more strongly by the load than the heavier arm. The jaw was decelerated strongly but briefly, <30 ms during jaw closing, indicating that muscle force increased before the onset of reflex activity. Apparently, the force-velocity properties of the jaw muscles have a stabilizing effect on the jaw and have this effect before sensory induced responses occur. The symmetrical responses in biceps and triceps indicate similar motor control of both arm muscles. The differences in reflex activity between masseter and digastric muscle indicate fundamental differences in sensory feedback to the jaw-closing muscle and jaw-opening muscle.

Adult↗
PubMed1999

Coordinated ground forces exerted by buttocks and feet are adequately programmed for weight transfer during sit-to-stand.

The purpose of this study was to test the hypothesis whether weight transfer during sit-to-stand (STS) is the result of coordinated ground forces exerted by buttocks and feet before seat-off. Whole-body kinematics and three-dimensional ground forces from left and right buttock as well as from left and right foot were recorded for seven adults during STS. We defined a preparatory phase from onset of the first detectable anterior/posterior (A/P) force to seat-off (buttock forces fell to 0) and a rising phase from seat-off to the decrease of center of mass (CoM) vertical velocity to zero. STS was induced by an increase of vertical and backward directed ground forces exerted by the buttocks that significantly preceded the onset of any trunk movement. All ground forces peaked before or around the moment of seat-off, whereas all kinematic variables, except trunk forward rotation and hip flexion, peaked after seat-off, during or after the rising phase. The present study suggests that the weight transfer from sit to stand is induced by ground forces exerted by buttocks and feet before seat-off, i.e., during the preparatory phase. The buttocks generate the isometric "rising forces," e.g., the propulsive impulse for the forward acceleration of the body, while the feet apply adequate damping control before seat-off. This indicates that the rising movement is a result of these coordinated forces, targeted to match the subject's weight and support base distance between buttocks and feet. The single peaked, bell-shaped profiles peaking before seat-off, were seen beneath buttocks for the "rising drive," i.e., between the time of peak backward directed force and seat-off, as well as beneath the feet for the "damping drive," i.e., from onset to the peak of forward-directed force and for CoM A/P velocity. This suggests that both beginning and end of the weight transfer process are programmed before seat-off. The peak deceleration of A/P CoM took place shortly ( approximately 100 ms) after CoM peak velocity, resulting in a well controlled CoM deceleration before seat-off. In contrast to the view of other authors, this suggests that body equilibrium is controlled during weight transfer.

Adult↗
PubMed2002

Effects of voluntary blinks on saccades, vergence eye movements, and saccade-vergence interactions in humans.

Blinks are known to change the kinematic properties of horizontal saccades, probably by influencing the saccadic premotor circuit. The neuronal basis of this effect could be explained by changes in the activity of omnipause neurons in the nucleus raphe interpositus or in the saccade-related burst neurons of the superior colliculus. Omnipause neurons cease discharge during both saccades and vergence movements. Because eyelid blinks can influence both sets of neurons, we hypothesized that blinks would influence the kinematic parameters of saccades in all directions, vergence, and saccade-vergence interactions. To test this hypothesis, we investigated binocular eye and lid movements in five normal healthy subjects with the magnetic search coil technique. The subjects performed conjugate horizontal and vertical saccades from gaze straight ahead to targets at 20 degrees up, down, right, or left while either attempting not to blink or voluntarily blinking. While following the same blink instruction, subjects made horizontal vergence eye movements of 7 degrees and combined saccade-vergence movements with a version amplitude of 20 degrees. The movements were performed back and forth from two targets simultaneously presented nearby (38 cm) and more distant (145 cm). Small vertical saccades accompanied most vergence movements. These results show that blinks change the kinematics (saccade duration, peak velocity, peak acceleration, peak deceleration) of not only horizontal but also of vertical saccades, of horizontal vergence eye movements, and of combined saccade-vergence eye movements. Peak velocity, acceleration, and deceleration of eye movements were decreased on the average by 30%, and their duration increased by 43% on the average when they were accompanied by blinks. The blink effect was time dependent with respect to saccade and vergence onset: the greatest effect occurred 100 ms prior to saccade onset, whereas there was no effect when the blink started after saccade onset. The effects of blinks on saccades and vergence, which are tightly coupled to latency, support the hypothesis that blinks cause profound spatiotemporal perturbations of the eye movements by interfering with the normal saccade/vergence premotor circuits. However, the measured effect may to a certain degree but not exclusively be explained by mechanical interference.

Adult↗
PubMed2000

Physiological parameters evaluation following apnea in healthy premature infants.

To assess responses to central and obstructive apnea, we performed 10-hour polygraphic recordings in healthy 33-34 wGA infants. Each apnea period was paired with a control period. The presence of body movements (BM) and augmented breaths (AB), the EEG, heart rate (HR), respiratory rate, phase relationships between thoracic and abdominal respiratory movements, and changes in SaO(2) were evaluated. No apnea caused awakening. Apnea were not usually followed by motor events (no significant differences with control periods), with the exception of most obstructive apnea longer than 10 s. The mean percentage of changes following apnea, normalized to baseline values, was significant for the EEG (frequency slightly increased, mainly after obstructive apnea), HR (deceleration), and respiratory rate (increased). However, the mean values masked heterogeneity across apnea in the direction of the change in each parameter. The only significant correlation was between changes in HR and SaO(2). The increases in EEG frequency and respiratory rate seen in our study can be considered markers of CNS activation, but were small and inconsistent. The heart rate decelerations and SaO(2) changes are not activation markers. Thus, mechanisms underlying restarting of breathing efforts following apnea remain unclear in premature babies. Our investigation establishes the importance of using control data to distinguish between spontaneous and apnea-related events.

Apnea↗
PubMedDate not supplied

Induction of labor in patients with term premature rupture of membranes. Effect on perinatal outcome.

OBJECTIVE: To determine whether delayed induction of labor in patients with premature rupture of membranes (PROM) at term has beneficial effects on the mother or the infant. STUDY DESIGN: Retrospective analysis of our database revealed 576 patients >37 weeks of gestation with PROM, who delivered live-born infants without major congenital anomalies. We analyzed the frequencies of primary cesarean, neonatal intensive care unit (NICU) admissions, and oxytocin use by time since hospital admission and interval until onset of labor. RESULTS: NICU admission increased from 1.9% in <3 h between admission to onset of labor to 13.3% after >18 h. Admission-onset of labor interval, birth weight of <2,500 or >4,000 g and meconium were all more important determinants of NICU admission than gestational age, duration of labor, PROM, and ROM. Prolonged admission-onset of labor interval was associated with an increased risk of variable decelerations (p < 0.001). Primary cesarean rates increased progressively with longer intervals between admission and onset of labor. Stepwise discriminant function analysis revealed that labor duration, admission-onset of labor interval, gestational age, and birth weight of <2,500 g were all more important determinants of primary cesarean delivery than the durations of PROM or ROM. CONCLUSIONS: The increased frequencies of NICU admission, variable decelerations, and primary cesarean suggest that delayed labor induction after hospital admission was linked to worsened perinatal outcomes. These results may have been influenced by usually performing a single digital examination as part of initial evaluation of term patients who present with PROM. Based on our data, we suggest immediate induction for PROM at term, especially if digital examination has been performed.

Adult↗
PubMed2001

Sensitivity to a neurosteroid is increased during addition of progestagen to postmenopausal hormone replacement therapy.

The aim of this study was to compare the pharmacodynamic response to a neuroactive steroid, pregnanolone, before and during different hormonal settings of postmenopausal hormone replacement therapy (HRT). Twenty-seven postmenopausal women with climacteric symptoms were administered HRT in a randomized, double-blinded, placebo-controlled crossover study. The women received 2 mg estradiol (E2) continuously during four 28-day cycles and 10 mg medroxyprogesterone acetate (MPA), 1 mg norethisterone acetate (NETA) or placebo sequentially for the last 14 days in each cycle. The pharmacodynamic response to pregnanolone was assessed before treatment and during the last week of each treatment, by comparing the effects of intravenous pregnanolone (3alpha-hydroxy-5beta-pregnan-20-one) on saccadic eye velocity (SEV), saccade deceleration, saccade latency and self-rated sedation. Throughout the study daily symptom rating scales were kept. During the progesta gen phase of the treatment cycles, negative mood symptoms and physical symptoms were increased, whereas positive mood symptoms were decreased. Compared to pretretreatment conditions, E2 alone did not change the responsiveness to pregnanolone. During progestagen addition to E2, the responsiveness to pregnanolone was increased. The sedation response increased compared to pretreatment conditions during both E2 + MPA and E2 + NETA treatment. Compared to E2 treatment alone, addition of MPA increased the postpregnanolone effect on saccade deceleration, whereas the SEV response to pregnanolone was increased during E2 + NETA treatment. It is concluded that pregnanolone sensitivity increases together with deterioration in mood symptoms during addition of progestagen to HRT.

Affect↗
PubMedDate not supplied

A retrospective evaluation of 1,25-dihydroxyvitamin D(3) and its potential effects on renal allograft function.

BACKGROUND/AIMS: 1,25-Dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) plays an important role in regulating immunologic responsiveness in addition to its effects on bone metabolism. This is potentially beneficial in the transplant setting. Animal studies have demonstrated the utility of 1,25-(OH)(2)D(3) in prolonging allograft survival. Therefore, we evaluated the effects of 1,25-(OH)(2)D(3) (oral calcitriol) in human renal transplant recipients. METHODS: A case-control study was undertaken assessing the effects of calcitriol on transplant function. The effect of calcitriol on renal function was analyzed using general linear mixed modeling of the change in slope of serum creatinine (Scr) prior to and following the start of calcitriol therapy. RESULTS: There was a significant increase in baseline Scr (p < 0.001) prior to starting calcitriol. Following initiation of calcitriol, there was a deceleration in the rate of loss of graft function (p = 0.031 at day 300 of therapy). Graft survival was also prolonged in calcitriol-treated patients compared to a control population with evidence of chronic allograft nephropathy but no calcitriol therapy (p < 0.03). Overall, there were no adverse or harmful effects related to calcitriol therapy. 1,25-(OH)(2)D(3) therapy was associated with (1) a deceleration in the rate of loss of renal function in transplant recipients with more than one year of allograft function, and (2) no significant change in allograft function early after transplantation. CONCLUSION: These data suggest that short- and long-term prospective trials evaluating 1,25-(OH)(2)D(3) or 1,25-(OH)(2)D(3) analogs in human kidney transplantation are warranted. Such trials may help us elucidate mechanism and duration of action, as well as safety issues related to these novel immunomodulatory agents.

Adult↗
PubMed2003

Conventional and computerized antepartum telecardiotocography. Experienced and inexperienced observers versus computerized analysis.

The study assessed the agreement in cardiotocogram interpretation between the 2CTG computerized system and experienced and inexperienced observers involved in a telecardiotocography project called 'TOCOMAT'. Both observers and computer analyzed FHR baseline, FHR variability, and number of large accelerations and of decelerations. The k coefficient was calculated for the statistical analysis. The interobserver agreement about the evaluation of the FHR baseline and of the large accelerations was good; it was poor about the assessment of the FHR variability and the decelerations. Similar results were obtained for the agreement among observers and computer. The use of a computerized system provides exact values for most CTG parameters; the experts, however, should rely both on clinical features and on the computerized interpretation, to make decisions about management.

Cardiotocography↗
PubMed2006

Doppler sonography of the fetal middle cerebral artery in the management of massive fetomaternal hemorrhage.

Massive fetomaternal hemorrhage (FMH) is a rare complication in pregnancy that may cause hydrops or can even be life-threatening for the fetus. We report on the case of a 19-year-old gravida I, para 0, who presented to our clinic at 32 weeks of gestation due to decreased fetal movements. The initial fetal heart rate tracing at admission showed a sinusoidal pattern without decelerations. The ultrasound examination performed immediately described a normally developed fetus with normal amounts of amniotic fluid and without abnormities of the placental structure. Doppler sonography of the fetal middle cerebral artery gave rise to the strong suspicion of fetal anemia, so that a cordocentesis was prepared for potential intrauterine blood transfusion. Meanwhile, the rate of fetal hemoglobin (HbF) cells in the maternal blood was found to be markedly increased with 66 per thousand. Correspondingly, cardiotocographic findings worsened with repeated decelerations, thus an immediate cesarean section was performed based on the suspected diagnosis of an acute FMH. A fetus weighing 1,860 g was delivered, who had severe anemia with hemoglobin level of 4.0 g/dl. After a direct blood transfusion, HbF levels normalized rapidly, the fetus stabilized, and a normal recovery has thus far been reported. The presented case demonstrates the successful and straightforward diagnosis, as well as the management of a case of severe FMH and illustrates the special value of Doppler sonography in this context.

Adult↗
PubMed1984

Quantitative analysis of salamander horizontal head nystagmus.

The horizontal optokinetic head nystagmus of salamanders (Salamandra salamandra) was investigated at various constant and sinusoidally modulated velocities. With constant velocities the best compensation (head velocity/stimulus velocity) measured was 0.6 at a stimulus velocity of 3 deg/s. With slow stimuli up to 5 deg/s, small oscillations in the slow phase of the nystagmus occurred. The nystagmus started with a delay of 1.1 s after onset of stimulus with an acceleration period of up to 6 s. After the stimulus terminated, the head was decelerated within (on average) 5 s, indicating a weak velocity storage element. The nystagmus frequency, the acceleration time, and the deceleration time were in correlation with the head velocity during the slow phase. With sinusoidal stimuli, nonlinearities were displayed: the gain was amplitude-dependent, and distortions of the sinusoidal head movements occurred with higher frequencies.

Animals↗
PubMed1993

Scaling of limb proportions and limb bone diameters in three species of Chinese snub-nosed langurs (genus Rhinopithecus).

In this study, aspects of the structural mechanics of the upper and lower limbs of the three Chinese species of Rhinopithecus were examined. Linear regression and reduced major axis (RMA) analyses of natural log-transformed data were used to examine the dimensions of limb bones and other relationships to body size and locomotion. The results of this study suggest that: (1) the allometry exponents of the lengths of long limbs deviate from isometry, being moderately negative, while the shaft diameters (both sagittal and transverse) show significantly positive allometry; (2) the sagittal diameters of the tibia and ulna show extremely significantly positive allometry--the relative enlargement of the sagittal, as opposed to transverse, diameters of these bones suggests that the distal segments of the fore- and hindlimbs of Rhinopithecus experience high bending stresses during locomotion; (3) observations of Rhinopithecus species in the field indicate that all species engage in energetic leaping during arboreal locomotion. The limbs experience rapid and dramatic decelerations upon completion of a leap. We suggest that these occasional decelerations produce high bending stresses in the distal limb segments and so account for the hypertrophy of the sagittal diameters of the ulna and tibia.

Animals↗