Video game-based neuromuscular electrical stimulation system for calf muscle training: a case study.

A video game-based training system was designed to integrate neuromuscular electrical stimulation (NMES) and visual feedback as a means to improve strength and endurance of the lower leg muscles, and to increase the range of motion (ROM) of the ankle joints. The system allowed the participants to perform isotonic concentric and isometric contractions in both the plantarflexors and dorsiflexors using NMES. In the proposed system, the contractions were performed against exterior resistance, and the angle of the ankle joints was used as the control input to the video game. To test the practicality of the proposed system, an individual with chronic complete spinal cord injury (SCI) participated in the study. The system provided a progressive overload for the trained muscles, which is a prerequisite for successful muscle training. The participant indicated that he enjoyed the video game-based training and that he would like to continue the treatment. The results show that the training resulted in a significant improvement of the strength and endurance of the paralyzed lower leg muscles, and in an increased ROM of the ankle joints. Video game-based training programs might be effective in motivating participants to train more frequently and adhere to otherwise tedious training protocols. It is expected that such training will not only improve the properties of their muscles but also decrease the severity and frequency of secondary complications that result from SCI.

Design and development of a cost effective plantar pressure distribution analysis system for the dynamically moving feet.

This paper portrays the design and instrumentation of a low cost plantar pressure analysis system, suitable for clinical podiatry. The system measures plantar pressure between the foot and shoe during dynamic movement in real-time, which can be used in clinical gait analysis. It contains a pressure sensing insole which the patient can insert in his/her shoe, and user-friendly software to graph and analyze the data. Applications include occupational health and safety, research and private practice.

DNA cloning in Lactobacillus helveticus by the exconjugation of recombinant mob-containing plasmid constructs from strains of transformable lactic acid bacteria.

A system developed for the genetic transfer of plasmids between strains of nontransformable bacteria (P. Langella, Y. le Loir, S. D. Ehrlich and A. Gruss, 1993, J. Bacteriol., 175, 5806-5813) by the specific inclusion of a mobilization (mob) region into a nonconjugative shuttle vector was used successfully to deliver the genetic determinants for beta-glucanase, beta-glucuronidase, and green fluorescent protein to Lactobacillus helveticus. Expression of two of the genes could be detected in the new host. Data suggested that resolution of cointegrates into components could release the original recombinant plasmid or generate a cointegrate deletion. All the recombinant plasmids were segregationally unstable in Lb. helveticus and there was some evidence for structural instability. Intrinsic instability in the mob-containing vector was reduced by replacing the duplicated pBluescript polylinker with that from pUC19. Sites at which cointegrate formation could occur were localized at two distinct tracts close to the D-loop that forms at the primosome during plasmid replication.

Complete sequence of plasmid pLH1 from lactobacillus helveticus ATCC15009: analysis reveals the presence of regions homologous to other native plasmids from the host strain.

The complete sequence for plasmid pLH1 from Lactobacillus helveticus ATCC15009 has been determined. Analysis of the 19,360-bp primary sequence revealed a putative replication origin and initiation protein, information that could provide the basis for the construction of cloning vectors for L. helveticus. Evidence that pLH1 is theta-replicating could be deduced from the plasmid size, from the homology to the replication protein of the Bacillus natto theta-replicating plasmid pLS32, and from the identification of a putative resolvase gene (orf-195). Although 14 open reading frames capable of encoding polypeptides longer than 100 amino acids were identified, none, on the basis of homology with known sequences, appeared to encode a well-characterized trait relevant to milk fermentation. Plasmid pLH1 revealed regions of identity with the smaller cryptic plasmids (pLH2 and pLH3) from the same strain and with other tracts of DNA, including insertion sequence elements, from a variety of other lactic acid bacteria. The presence of such regions provides a basis for developing an explanation of the phenotypic variability observed in these bacteria. The plasmid also appears to possess a number of genetic elements present in other lactic acid bacterial plasmids, conservation of which would be consistent with an important functional or evolutionary role. It could be argued that the plasmid complement of L. helveticus ATCC15009 consists of parasitic entities concerned only with their own replication and survival.

Mutations to antibiotic resistance occur during the stationary phase in Lactobacillus plantarum ATCC 8014.

When Lactobacillus plantarum ATCC 8014 was maintained in LCM broth (which consists of buffered tryptone and is sufficient to support the growth of some species of Lactobacillus ) for long periods (120 d), viable bacteria persisted. Rifampicin-, streptomycin- and sodium-fusidate-resistant mutants were recovered from parallel LCM broth cultures following a stochastic pattern. Individual cultures appeared to yield mutants intermittently. One culture in particular yielded rifampicin-resistant colonies at a frequency of 1 in 100 viable bacteria after 20 d incubation and these persisted until the experiment was terminated at 115 d. In a separate experiment two parallel cultures yielded mutants resistant to low concentrations of streptomycin at a similar frequency. Using a chemostat it was shown that in continuous culture in LCM at slow growth rates the highest frequency of recovery of antibiotic-resistant mutants was achieved when the bacteria exhibited doubling times of 90 h or greater. The frequency of recovery of mutants was as high as 1 in 1000 viable bacteria. Thus, mutations to antibiotic resistance in L. plantarum ATCC 8014 can take place in the absence of measurable cell division. The data are consistent with the notion that populations of starved bacteria in stationary phase can be genetically dynamic.

Electrotransformation of Lactobacillus plantarum using linearized plasmid DNA.

Evidence is presented that linearized plasmid DNA is capable of electrotransforming Lactobacillus plantarum at a frequency 500-fold lower than with the covalently closed circular molecule. When the linearized plasmid was religated prior to transformation the transformation efficiency was < 10-fold higher, suggesting that open circular plasmid was only slightly more efficient in the transformation of Lact. plantarum than linear DNA. This observation has implications for direct cloning into this species since the high background transformation frequency produced by the linear DNA could potentially obscure the recovery of clones. Nevertheless, using positive selection for enhanced chloramphenicol resistance, cloned fragments of Lact. helveticus DNA were obtained using the shuttle vector pGKV110.

Behavior of eye-movement-related cells in the vestibular nuclei during combined rotational and translational stimuli.

1. Secondary position-vestibular-pause (PVP) neurons in the vestibuloocular reflex (VOR) pathway of adult rhesus monkeys were studied during combined semicircular canal and otolith stimulation. The head was rotated at 0.5 Hz with the axis of rotation centered between the otolith organs (on-axis, ON) and with the axis of rotation 23 cm in front of the otoliths (off-axis, OFF). Both conditions were tested with two different vergence angles by the use of 14-cm (near target, NT) and 100-cm (far target, FT) targets. 2. The tangential translational stimulus to the otoliths in the OFF trials should result in a compensatory eye movement that is opposite in direction to that resulting from the angular stimulus to the canals. The otolith stimulus should be great enough to reverse the eye movement response in the NT OFF trials according to geometric calculations. This reversal in eye movement direction occurred as expected although the latency of the reversal (70 ms) was somewhat greater than expected and the magnitude of the reversal was less than predicted solely on the basis of geometric considerations. 3. The responses of the PVP neurons were corrected for eye position sensitivity to investigate the head movement response components. The amplitude of the response in 22 of 24 PVP cells was reduced in the NT OFF condition compared with the FT OFF condition. This difference was not sufficient in itself to explain the observed reversal in eye movement response. 4. The average sensitivities of the neurons to rotation during the FT and NT ON trials were 1.38 and 1.41 spikes.s-1.deg-1.s-1, respectively. This is too small an increase to account for the increase in the angular VOR gain with near targets (approximately 25%); therefore cells other than PVP neurons must be responsible. 5. The average sensitivities of the PVP neurons to translational accelerations obtained from the FT and NT OFF trials were 305 and 484 spikes.s-1.g-1, respectively, which is higher than most otolith afferent sensitivities reported for 0.5-Hz stimuli in the literature. The otolith component is modified by ocular convergence (59% increase in sensitivity), but this increase is too small to account for the change in the translational VOR gain between the two conditions. 6. Although recordings were only obtained from seven eye-head-velocity cells, the results indicate that these neurons may provide the additional signals not present in the PVP cells. These neurons exhibited large differences between ON and OFF rotations and were found to substantially increase their modulation during the NT conditions compared with that observed during the FT conditions.

Behavior of cells without eye movement sensitivity in the vestibular nuclei during combined rotational and translational stimuli.

A total of 74 neurons that lacked eye movement sensitivity were recorded within the confines of the rostral medial and medial lateral vestibular nuclei. Of these, 36 had response characteristics that were consistent with combined canal and otolith inputs (CAOT neurons), 18 received canal inputs only (CA neurons), and 20 had otolith inputs only (OT neurons). Responses were measured during both rotational and combined rotational and translational stimuli at 0.5 and 3.0 Hz. The otolith signal was found to lag acceleration markedly at both frequencies. Indeed, one subset of CAOT neurons had otolith responses that led translational velocity by only 12 degrees at 0.5 Hz. All translation-responsive neurons decreased their phase lag with respect to acceleration when the stimulus frequency was increased and exhibited a large increase in sensitivity. As these cells have response dynamics that lie between those seen in otolith afferents and those required to drive the motoneurons during the translational VOR, they may represent an intermediate stage in the signal processing.

Eye position signals in the vestibular nuclei: consequences for models of integrator function.

Recordings from neurons in the vestibular nuclei indicate that the cells that carry eye position signals encode the position of a single eye (either ipsilateral or contralateral) during both conjugate and vergence eye movements. The fact that the vestibular nuclei are aware of the positions of each eye is not surprising as the otolith-based linear vestibulo-ocular reflex is known to change its behaviour as a function of uniocular eye position. This result suggests that the signal coming from the oculomotor velocity-to-position integrator specifies the position of each eye during vergence movements and thus must receive a vergence velocity input along with its conjugate velocity inputs. As there is no vergence system in laterally eyed animals, we have proposed two possible models of integrator arrangement that could have developed from conjugate directional (rather than uniocular) integrators in lower animals without frontally mounted eyes. Both of these models explain the existence of near-response cells and produce the required bidirectional gaze paretic nystagmus following unilateral lesions of one integrator. The models also make specific and different predictions concerning the effects of unilateral integrator lesions on the behaviour of the vergence system and thus make suggestions for further experiments.

Eye position signals in the abducens and oculomotor nuclei of monkeys during ocular convergence.

Many neurons in oculomotor pathways encode signals related to eye position. For example, motoneurons in the third, fourth, and sixth cranial nuclei discharge at highly regular rates during fixation intervals. During fixations of far targets, their tonic discharge is linearly related to conjugate eye position. Previous studies provided evidence that premotor cells in brainstem pathways also encoded conjugate eye position. McConville et al. (this volume), however, measured eye movements during binocular fixations when the eyes were converged and concluded that the position signal encoded by premotor position-vestibular-pause (PVP) cells in the vestibular nuclei is related to monocular (right or left) eye position rather than to conjugate eye position. This surprising relationship would not have been noticed in earlier studies that measured the movements of only one eye (using a single eye coil) or that measured only the conjugate movements of the two eyes (using bitemporal EOG electrodes). How general a feature of oculomotor signal processing is this finding? In this paper, we re-examine the eye position signal in abducens and oculomotor neurons when the movements of the two eyes are conjugate and when they are disjunctive and therefore disassociated. The data suggest that abducens neurons (AMNs and AINs) and oculomotor neurons (putative medial rectus motoneurons), unlike PVP cells, are not monocular but encode mixtures of right and left eye position signals.

An informational approach to sensory adaptation.

Concepts from information theory can enhance our understanding of perceptual processes by providing a unified picture of the process of perception. A single equation is shown to embrace adaptation phenomena, stimulus-response relations, and differential thresholds. Sensory adaptation is regarded as representing a gain in information by the receptor. It is calculated that for constant stimuli in the form of step inputs, insects and arachnids obtain approximately the same amount of information per stimulus from their respective environments as do human beings.