José Bulas-Cruz

Methods for the experimental functional assessment of rat sciatic nerve regeneration

Abstract In experimental peripheral nerve studies, the rat sciatic nerve model is widely used to examine functional changes after different surgical repairs or pharmacological treatments, following nerve injury. The number and diversity of tests which have been used to assess functional recovery after experimental interventions often makes it difficult to recommend any particular indicator of nerve regeneration. Functional assessment after sciatic nerve lesion has long been focused on walking track analysis, therefore, this article describes in more detail the method to obtain and measure the walking tracks in order to calculate the sciatic functional index (SFI). However, it is important to note that the validity of the SFI has been questioned by several researchers. In addition, the present review includes other traditional tests described in the experimental peripheral nerve literature regarding the rate of return of motor function and sensation, such as the extensor postural thrust (EPT), nociceptive function, and the gastrocnemius-soleus weight parameters. In the last decade, several authors have designed a series of sensitive quantitative methods to assess the recovery of hind limb locomotor function using computerized rat gait analysis. This study aims to review kinematic measures that can be gathered with this technology, including calculation of sciatic functional index, gait-stance duration, ankle kinematics and toe out angle (TOA). A combination of tests, each examining particular components of recovered sensorimotor function is recommended for an overall assessment of rat sciatic nerve regeneration.

Motion of the foot and ankle during the stance phase in rats

Computerized analysis of rat gait is becoming an invaluable technique used by some peripheral nerve investigators for the evaluation of function. In this article we describe the use of a biomechanical model of the foot and ankle that allows a quantitative assessment and description of the ankle angle, reflecting plantarflexion and dorsiflexion during the stance phase of gait. Kinematic data of 144 trial walks from 36 normal rats were recorded with a high‐speed digital image camera at 225 images per second. The ankle angular changes associated with the specific temporal events of foot placement on the ground through the stance phase were assessed. The information obtained was used to propose a new subdivision of the stance phase in the rat into three major components. This approach will provide a helpful research tool to analyze gait data that rely on the accurate determination of spatiotemporal foot events.

Ankle kinematics to evaluate functional recovery in crushed rat sciatic nerve

Peripheral nerve researchers frequently use the rat sciatic nerve crush model in order to test different therapeutic approaches. The purpose of this study was to determine the sequence of changes after an axonotmetic injury by means of a biomechanical model of the foot and ankle, and compare them with walking track analysis, over a fixed period of time. A kinematic analysis program was used to acquire ankle motion data for further analysis. Although repeated measures analysis of variance showed significant cumulative changes induced by the crush lesion for both ankle kinematic parameters and sciatic functional index, post‐hoc multiple comparisons by the Student‐Neuman‐Keuls test revealed significant differences between week 0 and week 8 only for ankle kinematics. These results are of importance in showing the superiority of ankle kinematics in detecting small biomechanical deficits related to hyperexcitability of the plantarflexor muscles, in contrast with walking track analysis, which showed full motor functional recovery 8 weeks after the crush lesion. Muscle Nerve 27: 706–714, 2003

A comparison analysis of hindlimb kinematics during overground and treadmill locomotion in rats

The convenience of the motor-driven treadmill makes it an attractive instrument for investigating rat locomotion. However, no data are available to indicate whether hindlimb treadmill kinematic findings may be compared or generalized to overground locomotion. In this investigation, we compared overground and treadmill locomotion for differences in the two-dimensional angular kinematics and temporal and spatial measurements for the hindlimb. Ten female rats were evaluated at the same speed for natural overground and treadmill walking. The walking velocity, swing duration and stride length were statistically indistinguishable between the two testing conditions. Significant differences were found between overground and treadmill locomotion for step cycle duration and stance phase duration parameters. During the stance phase of walking, the angular movement of the hip, knee and ankle joints were significantly different in the two conditions, with greater flexion occurring on the overground. Despite this, the sagittal joint movements of the hindlimb were similar between the two walking conditions, with only three parameters being significantly different in the swing. Hip height and angle-angle cyclograms were also only found to display subtle differences. This study suggests that reliable kinematic measurements can be obtained from the treadmill gait analysis in rats.

Dynamic joint stiffness of the ankle during walking: Gender-related differences

OBJECTIVES To characterize and compare dynamic joint stiffness (DJS) of the ankle in the sagittal plane during natural cadence walking in both genders. DESIGN Observation, cross-sectional and matched pairs. PARTICIPANTS Twenty-one males (mean age=27+/-4.2 years) and 18 females (mean age=22.9+/-4.1 years). SETTING Laboratory at the University de Trás-os-Montes and Alto Douro. The DJS of the ankle was assessed while participants performed barefoot walking at a natural cadence, was measured using a force platform (1000 Hz), and synchronized with a high-speed camera (200 Hz). MAIN OUTCOME MEASURES DJS of the ankle in males and females was calculated in two sub-phases (the second and the fourth sub-phases) of the stance phase. The Wilcoxon non-parametric matched-pairs test and the Mann-Whitney U non-parametric test were used to analyse difference of DJS of the ankle within and between the groups with p0.05 regarded as significant. RESULTS Male and female participants demonstrated significantly (p<0.005) less DJS during the second sub-phase. DJS was not significantly (p>0.063) different between females (0.0511 N m/kg/ degrees ) and males (0.0596 N m/kg/ degrees ) during the second sub-phase. DJS was significantly (p<0.001) higher in males (0.0844 N m/kg/ degrees ) than females (0.0691 N m/kg/ degrees ) during the fourth sub-phase. CONCLUSIONS Gender-specific DJS characteristics demonstrated by females in this study may be used in preventative training programs designed to promote a greater ability to use contractile components to produce mechanical energy through the ankle.

A comparison of two-dimensional and three-dimensional techniques for the determination of hindlimb kinematics during treadmill locomotion in rats following spinal cord injury

Of all the detrimental effects of spinal cord injury (SCI), one of the most devastating effects is the disruption of the ability to walk. Therefore, much effort has been focused on developing several methods to document the recovery of locomotor function after experimental SCI. Computerized rat gait analysis is becoming increasingly popular in the SCI research community. The two-dimensional (2D) kinematic approach is by far the most popular technique in rat gait analysis. This is a simple inexpensive procedure, which requires only one camera to record the movement. Our study included an examination of locomotion on a treadmill using 2D and three-dimensional (3D) analysis, in neurologically intact animals and following moderate T9 contusion injury. Despite the overall time course patterns of the curves were identical, we found significant differences between values of the 2D and 3D joint angular motion. In conclusion, maximal precision and accuracy of the kinematic values are expected when the experimental protocol includes a 3D motion analysis methodology. Moreover, a 2D method cannot be used to determine the external or internal rotations of the foot because this movement occurs in the transverse plane.

Real-Time Number Plate Reading

Abstract Vehicle number plate recognition systems are expected to have numerous applications in traffic surveying and monitoring, e.g. finding stolen cars and controlling access to car parks. In this paper algorithmic improvements to a previous version of a number plate reading system are described. The work builds on the experience gained by the Computer Vision Group at the University of Bristol. This paper addresses the problem of locating the number plate area in the image and proposes a new line based method for number plate location, which is suitable for realtime number plate recognition.

The Effect of Gait Speed on Three-Dimensional Analysis of Hindlimb Kinematics during Treadmill Locomotion in Rats

The two-dimensional (2D) kinematic approach is by far the most popular technique in rat gait analysis. This is a simple inexpensive procedure, which requires only one camera to record the movement. However, maximal precision and accuracy of the kinematic values are expected when the experimental protocol includes a three-dimensional (3D) motion analysis methodology. Locomotor speed is a basic kinematic parameter that is often neglected in most studies of movement disorders and neurological diseases. Because locomotor speed can act as confounder for the interpretation of the obtained results we also focused our attention on the relation between speed and 3D hindlimb kinematics. Our experimental set-up consisted of a motion capture system with four CMOS cameras which allowed a non-invasive estimation of the instantaneous position of color markers in a 3D measurement volume. Data were recorded while rats walked at different treadmill speeds (30 vs 60 cm/s). For the first time we reported detailed kinematic data for the sagittal, coronal and transverse plane during treadmill locomotion in rats. Despite the overall time course patterns of the curves were identical, we found significant differences between values of joint angular motion at 30 and 60 cm/s at selected points of the step cycle. The adaptation to higher treadmill walking included greater joint angular excursions. The present report highlights the importance of walking speed when evaluating rat hindlimb kinematics during gait. Hopefully, this study will be useful in experimental data assessment when multiple gait abnormalities are expected to occur in all planes of motion.

Relevance as a new measure of relative importance of sets of rules

Process modelling is an important discipline both in science and engineering. The complexity of many real world systems has lead to sophisticated modelling approaches, where both the accuracy and readability of the models are of great importance. Fuzzy modelling is such an approach, which uses well-established machine learning techniques, producing models with the capacity of integrating expert knowledge with real world observations. The behaviour of these models is described as a series of linguistic rules. The readability of the models is related to the number of rules used to describe the system. In order to define methodologies for organising the information describing a system, it is important to define metrics for the relative importance of a set of rules in the description of a given region of the input/output space. This paper addresses this problem, and a new concept is proposed: the relevance of a set of rules.

Biggest Barriers to Effectiveness in CIO Role in Large Portuguese Companies

This study provides some empirical insight on the barriers that chief information officers face in their Job. The findings of the survey we conducted directed to the chief information officers of the 500 large Portuguese companies by gross revenue, suggest three main barriers: the lack of time to think and define strategies, the overwhelming backlog of requests and projects and inadequate budgets. The knowledge and understanding of the identified barriers contributes to the characterization of chief information officer role state of the art and should be useful for practitioners, who may use it as a basis for developing solutions in order to overcome these barriers.