Towards practical cadmium phytoextraction with Noccaea caerulescens.

A series of field trials were conducted to investigate the potential of Noccaea caerulescens F.K. Mey [syn. Thlaspi caerulescens J &C Presl. (see Koch and Al-Shehbaz 2004)] populations (genotypes) derived from southern France to phytoextract localized Cd/Zn contamination in Thailand. Soil treatments included pH variation and fertilization level and application of fungicide. N. caerulescens populations were transplanted to the field plots three months after germination and harvested in May, prior to the onset of seasonal rains. During this period growth was rapid with shoot biomass ranging from 0.93-2.2 g plant(-1) (280-650 kg ha(-1)) DW. Shoot Cd and Zn concentrations for the four populations evaluated ranged from 460-600 and 2600-2900 mg kg(-1) DW respectively. Cadmium and Zn Translocation Factors (shoot/root) for the populations tested ranged from 0.91-1.0 and 1.7-2.1 and Bioaccumulation Factors ranged from 12-15 and 1.2-1.3. We conclude that optimizing the use of fungicidal sprays, acidic soil pH, planting density and increasing the effective cropping period will increase rates of Cd and Zn removal enough to facilitate practical Cd phytoextraction from rice paddy soils in Thailand.

Elevated levels of cadmium and zinc in paddy soils and elevated levels of cadmium in rice grain downstream of a zinc mineralized area in Thailand: implications for public health.

Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken. Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg(-1) and 100 to 8036 mg kg(-1), respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field's proximity to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60-100% of the Cd and Zn loading associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged from 0.05 to 7.7 mg kg(-1). Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg(-1). In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 mug Cd per kg Body. This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific 'high risk' areas.

Coincidence timing of finger, arm, and whole body movements.

Two experiments investigated the effects of different types of movement responses on coincidence timing skill. The view was taken that the sensory-motor integration of the movement responses would be reflected in the accuracy and consistency of anticipation timing. A Bassin anticipation timer provided a light stimulus velocity of 3 mph for both experiments and the movements studied included a simple key press using a finger, an arm movement to a key press, and whole body movements culminating with a kick or step to a target. The experiments were modelled closely on the seminal study by Grose (1967). The results of Exp. 1 supported our prediction by demonstrating superiority of the finger task over the two larger movements for all measures of coincidence timing ability. The purpose of Exp. 2 was to compare the slightly different versions of the whole body task-that used in the first experiment and that used by Grose (1967). The results confirmed the close similarity of the two movement tasks and re-affirmed the results of Exp. 1. Exp. 2 also investigated sex effects on coincidence timing ability and, in contrast to previous evidence indicating that females perform with less accuracy and consistency than do males, no significant differences were found. Analysis of practice effects showed that, although there were no significant improvements over trial blocks in Exp. 1, there were significant improvements in Exp. 2. Comparisons with other research suggests that repeated practice in solving a coincident timing problem using whole body movements can lead to improved performance. In general, the findings are consistent with the constructs of action theory and emphasize the roles perceptual and movement variables have in defining situational constraints. Also, findings indicate that proficiency in coincidence anticipation appears to be influenced by the planning and organisation required for movement execution.

The effects of muscle activation on postural stability in diabetes mellitus patients with cutaneous sensory deficit in the foot.

Activity of the lower leg muscles in response to an unexpected disturbance to upright standing was studied in diabetic patients and non-diabetic matched controls. The diabetic individuals were classified into two groups: diabetic patients with normal cutaneous sensitivity in the foot (n=27) and patients with cutaneous sensory deficit (n=23). All participants completed twenty trials standing on a force platform that rotated upward 8 deg at 50 deg/s. This movement produced short-latency and medium-latency responses in the gastrocnemius muscle and a single long-latency response in the anterior tibialis. All muscle activity was assessed using electromyography techniques. Results indicated that the average delay of the short-, medium- and long-latency responses produced by the diabetic groups was comparable to control group values. However, the within subject variability associated with activating the anterior tibialis was found to be statistically greater for the cutaneous deficit diabetic group. Additionally, fifty percent of the CD group failed to produce an observable stretch reflex response. The results suggest that the inability to generate a neuromuscular response with consistent temporal patterning is a contributing factor to greater postural sway observed in diabetic patients with cutaneous sensory deficit in the foot.

Balance retraining in a hemiparetic patient using center of gravity biofeedback: a single-case study.

A single-subject experimental design was used to evaluate the effects of center of gravity biofeedback on retraining balance control in a 72-yr.-old male hemiparetic patient. For both assessment and training the subject stood on dual force-plates enclosed on three sides by a visual surround. A 4-wk. training period consisted of subject-initiated shifts in body weight to control movement of a real-time computer display of the subject's center of gravity. A Sensory Organization Test and evaluation of weight distribution indicated that biofeedback retraining positively affected balance control during dynamic conditions and when the ground support moved forward.

Prenatal exposure to alcohol affects the ability to maintain postural balance.

Prenatal exposure to alcohol is known to affect gross motor functioning. Animal studies have shown that balance is particularly affected, and there is some evidence that similar deficits exist in alcohol-exposed children. In the current study, postural balance, or the ability to maintain equilibrium, was assessed in a group of alcohol-exposed children (ALC group; n = 11) and controls (NC group; n = 11) individually matched for age and sex. Balance was measured across six conditions designed to systematically manipulate or eliminate visual or somatosensory information. Equilibrium and strategy scores for each condition and a derived composite balance score were analyzed. Although the ALC group had a lower mean composite balance score, their performance was similar to that of the NC group on all conditions where somatosensory input was reliable. However, when somatosensory input was manipulated, and when both somatosensory and visual input were inaccurate, the ALC group performed more poorly than controls. Interestingly, there were no differences between the ALC group and NC group in the type of control strategy used to maintain balance. These results suggest that alcohol-exposed children are overly reliant on somatosensory input. When this input is atypical, alcohol-exposed children display significantly greater anterior-posterior body sway and are unable to compensate using available visual or vestibular information. These deficits may be related to cerebellar anomalies previously reported in fetal alcohol syndrome children.

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.

Limited joint mobility of the ankle in diabetic patients with cutaneous sensory deficit.

Limited joint mobility (LJM) of the ankle joint was measured in 48 diabetic patients classified into three groups: Insulin-dependent diabetes mellitus (IDDM = 15), non-insulin diabetes mellitus (NIDDM = 12) and patients with cutaneous sensory deficit in the foot (CD = 21). Specifically, plantar flexion, dorsiflexion and total range of motion was measured on both feet using goniometric techniques during active and passive movement conditions. No significant bilateral differences were established, therefore values for the right foot were used for statistical analyses. Diabetic patients were matched to 48 non-diabetic controls for age, weight and gender factors. A Semmes-Weinstein monofilament test was used on both feet to assess the integrity of cutaneous sensitivity in all patient and control subjects. Cutaneous sensory deficit patients (CD) had monofilament values greater than two standard deviations below control group mean values. There were no significant differences between the monofilament test values for the IDDM and NIDDM patients and control group data. LJM results indicated both plantar flexion and range of motion in CD patients under active and passive movement conditions were significantly reduced compared to control group data. No differences were observed for any pairwise comparisons between the IDDM and NIDDM groups compared to controls. The data is discussed in terms of the interaction between LJM in the foot and type of diabetic classification.

Postural stability of diabetic patients with and without cutaneous sensory deficit in the foot.

Postural stability was measured in 50 patients classified into two diabetic groups: insulin-dependent diabetes mellitus (IDDM: n = 27), and diabetic patients with bilateral cutaneous sensory deficit in the foot (CD: n = 23). All patients were matched to 50 non-diabetic controls on age, weight and gender variables. The integrity of cutaneous sensory information at the foot was assessed using a monofilament test. Static and dynamic balance was evaluated using an objective balance test involving computer-controlled dual force platforms enclosed by a visual surround. The apparatus provided six test conditions designed to systematically manipulate or eliminate visual, vestibular or somatosensory information. Scores for the six tests, and a derived composite balance score together with movement strategy scores were used for data analysis. For all six tests and composite score CD patients revealed significant postural instability compared to controls. Additionally, the CD group recorded reduced strategy scores indicating an atypical shift from ankle to hip strategy movement as postural control was stressed. IDDM patient test scores were not significantly different from control data on any pairwise comparison. Results indicated significant balance loss associated with CD putting the individual at increased risk for falling and compromising foot mechanics.

Response Timing Accuracy as a Function of Movement Velocity and Distance.

In two experiments, patterns of response error during a timing accuracy task were investigated. In Experiment 1, these patterns were examined across a full range of movement velocities, which provided a test of the hypothesis that as movement velocity increases, constant error (CE) shifts from a negative to a positive response bias, with the zero CE point occurring at approximately 50% of maximum movement velocity (Hancock & Newell, 1985). Additionally, by examining variable error (VE), timing error variability patterns over a full range of movement velocities were established. Subjects (N = 6) performed a series of forearm flexion movements requiring 19 different movement velocities. Results corroborated previous observations that variability of timing error primarily decreased as movement velocity increased from 6 to 42% of maximum velocity. Additionally, CE data across the velocity spectrum did not support the proposed timing error function. In Experiment 2, the effect(s) of responding at 3 movement distances with 6 movement velocities on response timing error were investigated. VE was significantly lower for the 3 high-velocity movements than for the 3 low-velocity movements. Additionally, when MT was mathematically factored out, VE was less at the long movement distance than at the short distance. As in Experiment 1, CE was unaffected by distance or velocity effects and the predicted CE timing error function was not evident.

Control of goal-oriented, rapid arm movements by individuals with diabetes mellitus.

Diabetic subjects completed a series of rapid, goal-directed arm movements under two conditions of unexpected external loading. Evaluation of electromyographic (EMG) patterns revealed that cocontraction and triphasic activity were predominantly associated with inertial and spring loading, respectively. During inertial load responses some EMG patterns indicated a modified cocontraction pattern. Response accuracy was unaffected by type of load but movement time was greater for the inertial load condition.

Effects of different types of mechanical load on the duration of the initial agonist pulse.

Ten right-hand-dominant subjects completed a series of unsighted, goal-directed, arm flexion movements under three different mechanical loading conditions: an inertial load, an elastic spring load, and a stretched-spring load. Subjects completed a series of inertial load training trials followed by random application of one of the three loads. Three time intervals of the first agonist pulse were considered for analysis: the time from initiation of agonist activity to the onset of movement, the interval from movement initiation to the end of the agonist pulse, and the duration of the entire agonist pulse. Analyses revealed that load type did not affect the duration of any of the time intervals studied. The results suggest the presence of a regulatory control process which temporally organizes an invariant agonist pulse even when the movement is perturbed by external loads possessing different mechanical characteristics.

Peripheral control of the antagonist muscle during unexpectedly loaded arm movements.

Ten subjects completed a series of goal-directed arm flexion movements unexpectedly perturbed by three different types of mechanical load. Examination of electromyograph (EMG) waveforms and kinematic information collected during randomly distributed test trials facilitated investigation into the interaction between loading conditions and the response-associated EMG innervation patterns. Results of the EMG waveform analysis revealed that inertial and spring loads produced cocontraction and triphasic activation patterns, respectively. Unexpected application of a stretched-spring load, which produced a change in initial torque values without changing the rate of loading, also resulted in the use of a triphasic activation pattern. These different EMG patterns were observed while movement displacement for all three loads fell within the limits of the target area.

Feedback control of limb stiffness and scaled phase invariance properties of skilled high-speed arm flexion movements of a loaded manipulator.

In this and a previous experiment it has been observed that subjects produce innervation patterns (EMG) that are load specific, i.e., they produce concentration patterns for movements made with inertial loads and triphasic patterns for movements made with elastic loads. The protocol of these experiments prevented any adaptive responses to the load changes, therefore, it was assumed that pattern matching to load type was a real time updating response of the peripheral feedback systems. This updating response was assumed to be a mechanism for fine tuning the muscle torque by regulation of the mechanical impedance (stiffness) of the limb. Using a standard equation of motion, it was shown that the velocity is equal to the ratio of the muscle torque to the mechanical impedance. Substitution of this ratio for the ordinate of the scaled phase diagrams was then suggested as a real time updating mechanism to account for the scaled phase invariance recorded in this experiment and in the experiment reported by Ruitenbeek, J.C., Biol. Cybernetics 51 (1984) 11-20.

Time series analysis of knowledge of results effects during motor skill acquisition.

Time series analysis was used to investigate the hypothesis that during acquisition of a motor skill, knowledge of results (KR) information is used to generate a stable internal referent about which response errors are randomly distributed. Sixteen subjects completed 50 acquisition trials of each of three movements whose spatial-temporal characteristics differed. Acquisition trials were either blocked, with each movement being presented in series, or randomized, with the presentation of movements occurring in random order. Analysis of movement time data indicated the contextual interference effect reported in previous studies was replicated in the present experiment. Time series analysis of the acquisition trial data revealed the majority of individual subject response patterns during blocked trials were best described by a model with a temporarily stationary, internal reference of the criterion and systematic, trial-to-trial variation of response errors. During random trial conditions, response patterns were usually best described by a "White-noise" model. This model predicts a permanently stationary, internal reference associated with randomly distributed response errors that are unaffected by KR information. These results are not consistent with previous work using time series analysis to describe motor behavior (Spray & Newell, 1986).

Peripheral regulation of stiffness during arm movements by coactivation of the antagonist muscles.

Two experiments investigated whether unexpected and differential loading of a rapid, unsighted arm movement resulted in the central nervous system (CNS) regulating limb stiffness by modifying the associated neuromuscular activity. In Experiment 1, subjects completed multiple, spring-loaded training trials until a prespecified criterion of learning was attained. On selected trials, the spring load was unexpectedly replaced by an inertial load. Results indicated that to maintain positional accuracy during this inertial load trial, limb stiffness was increased by coactivating the antagonist muscles, i.e. by changing the associated neuromuscular activity from a predominantly triphasic pattern to one of coactivation. In Experiment 2, the sequence of loading was reversed producing a change in the required limb stiffness from a relatively high to low level. This change was observed as a pattern of coactivation being replaced by a triphasic activity pattern. These results support the notion that limb stiffness is regulated primarily through modification of the neuromuscular activity pattern prior to movement termination. It was also demonstrated that the size of the unexpected load did not affect the basic activation pattern selected by the CNS. It is proposed that the signal which triggers the CNS to regulate limb stiffness is based on peripheral information generated as a result of agonist activity occurring during the first part of the movement.

Electromyographic and neuromuscular force patterns associated with unexpectedly loaded rapid limb movements.

A series of ballistic, unidirectional arm movements were studied to evaluate the electromyographic (EMG) and neuromuscular force patterns that occur when a limb is unexpectedly perturbed. Multiple training trials were continued with a control load spring attached to the apparatus until a pre-specified criterion for learning was attained. The limb was then unexpectedly loaded with one of four test load springs. Examination of the integrated EMG records revealed a coactivation pattern of neuromuscular activity during a major part of the movement. Analysis of applied force data supported the notion of sustained agonist activity. Reciprocal innervation and coactivation patterns were considered in terms of a common motor control system as proposed by the equilibrium point control hypothesis. Manifestation of coactivation rather than reciprocation in the present study was discussed in terms of the execution of unloaded/inertially loaded movements and variable loaded movements.

Maintenance of equilibrium point control during an unexpectedly loaded rapid limb movement.

Two experiments investigated whether the equilibrium point hypothesis or the mass-spring model of motor control subserves positioning accuracy during spring loaded, rapid, bi-articulated movement. For intact preparations, the equilibrium point hypothesis predicts response accuracy to be determined by a mixture of afferent and efferent information, whereas the mass-spring model predicts positioning to be under a direct control system. Subjects completed a series of load-resisted training trials to a spatial target. The magnitude of a sustained spring load was unexpectedly increased on selected trials. Results indicated positioning accuracy and applied force varied with increases in load, which suggests that the original efferent commands are modified by afferent information during the movement as predicted by the equilibrium point hypothesis.

Curled toes and perosis-like leg abnormalities in cage reared broilers.

A high incidence of perosis-curled toe type of leg disorder has consistently developed in both cage- and floor pen-reared male broiler chicks of two different genetic strains within 5 to 7 days when fed a nutritionally complete corn-soybean meal diet. Postmortem analysis of affected birds indicate classic perosis as seen in dietary manganese (Mn) deficiency. Ration modifications, such as inclusion of 50 ppm additional Mn or .5 mg/kg vitamin B-2 did not prevent or reduce the development of this leg problem. Birds reared in floor-pens had a reduced incidence (12 to 13%) of perosis-curled toe problem compared with incidence of leg disorders of battery-reared birds (20 to 60%). In most instances, a positive relationship between rate of weight gain and severity of leg abnormalities was apparent. Reduction in photoperiod from 24 hr/day to 12 hr/day substantially reduced incidence of leg disorders; however, growth rate was also reduced. The practical basal diet employed in all experiments promotes satisfactory rate of growth and feed efficiency and may be an excellent assay diet for experimentation into perosis-like broiler leg problems.

Response mechanisms underlying kinesthetic short-term memory.

The variables of reproduction cue, activity during retention interval, and orientation of the recall movement were manipulated to assess simultaneously the viability of two hypotheses of motor short-term memory. Data partially supported hypotheses as positive response biasing was evident in recall after a filled retention interval (Pepper & Herman, 1970) and that for a given range of movements some adaption to a central reference level occurred (Laabs, 1973).