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V Segers

Publications and source records attributed to V Segers.

8 recordsLinked to original sources
PubMed2006

Kinematics of the transition between walking and running when gradually changing speed.

The purpose of this study was to examine kinematics of the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered with a constant acceleration of 0.1 m s(-2), respectively -0.1 m s(-2). Thirteen women (height: 168.9+/-3.36 cm) performed gait transitions on a motor-driven treadmill. WRT-speed was 2.16+/-0.12 m s(-1), RWT-speed 2.19+/-0.12 m s(-1). Kinematics were examined in the range from eight steps before to eight steps after transition in order to identify the possible occurrence of a transition process to facilitate the actual realization of transition. A transition step in which the main changes from one gait to another are realized is present in WRT and RWT. Despite this clear discontinuity, a transition process also appeared in both transitions. In the WRT, transition was prepared and kinematic adaptations were found in the last swing before transition leading to altered landing conditions. During RWT posttransition changes were observed and RWT was only completed after reorientation of the trunk in the first walking stride after transition. A noteworthy finding was that spatiotemporal (presence of a flight phase), kinematic (knee flexion) and energetic (kinetic and gravitational potential energy fluctuating in-phase versus out-of-phase) criteria to define transition stride correspond to each other. Furthermore, a functional interlimb asymmetry was recognized as a unique characteristic of the transition stride, offering a fourth way of identifying the transition stride.

Acceleration↗
PubMed2006

Influence of M. tibialis anterior fatigue on the walk-to-run and run-to-walk transition in non-steady state locomotion.

The purpose of this study was to examine the influence of muscular fatigue of tibialis anterior (TA) on the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered at different constant accelerations (a=0.01, 0.07 and 0.05 ms(-2)). Twenty women (height: 168.9+/-3.36 cm) performed WRTs and RWTs on a motor-driven treadmill, before and after a protocol inducing muscular fatigue of the TA. WRT-speed decreased after TA fatigue whereas RWT-speed did not change except during the intermediate deceleration. Integrated EMG (iEMG) of the activity burst of TA around heel contact was examined in the last steps before transition, the transition step and the first steps after transition. iEMG increased before WRT, then decreased after transition to running. In the RWT the opposite was observed: iEMG increased after RWT, then decreased with decreasing walking speed. After inducing fatigue in the TA, there was a decrease in iEMG in the WRT whereas no influence of fatigue was found on iEMG in the RWT. As a result of TA fatigue, WRT occurred at a lower speed, probably to avoid over-exertion of the TA. This indicates that the TA is a likely determinant of WRT as previously reported. The RWT, on the other hand, was not altered following TA fatigue, which would indicate that WRT and RWT are determined by different factors.

Acceleration↗
PubMed2005

Spatiotemporal characteristics of the walk-to-run and run-to-walk transition when gradually changing speed.

The purpose of this study was to examine spatiotemporal parameters of the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered with different constant accelerations. Twenty women (height: 168.9+/-3.36cm) performed three accelerations (0.05, 0.07 and 0.1ms(-2)) and three decelerations (-0.05, -0.07 and -0.1ms(-2)) on a motor-driven treadmill. The transition step in the WRT (first step with a flight phase) and RWT (first step with a double stance phase) occurred at the same speed for all accelerations but these did not occur in the same way. The most striking difference was the presence of a transition step with specific spatiotemporal characteristics in the WRT, whereas this was not observed in the RWT. The transition is not a sudden one-step-event. WRT occurred before transition and consisted of a "pre-transition period" and the transition step whereas RWT occurred after transition and consisted of the transition step and a "post-transition period". Both transition periods were characterized by an exponential evolution of step frequency and step length. Step frequency and step length showed a linear evolution before and after transition. The flight phase of the transition step in the WRT reached a minimum with comparable duration of the last flight phase in the RWT. The flight phase could be considered as an intrinsic dynamical factor of transition. Further research in kinematics, the trajectory of the body centre of mass and energy fluctuations will give more insight in these transitions.

Acceleration↗
PubMed1996

Does any correlation exist between the Gleason classification system and the computer-assisted microscope analysis of Feulgen-stained nuclei features in human prostate adenocarcinoma?

Grading prostatic adenocarcinomas remains an important problem. Various systems exist (including those proposed by Gleason) but none of these systems seems able to reliably predict either the lethal potential of a tumor in an individual patient or the responsiveness of an individual tumor to various forms of therapy. The most frequently used grading system, as proposed by Gleason, is essentially based on the description of tumor growth pattern. The aim of the present work is therefore to investigate whether the quantitative description of morphonuclear features (including cell anaplasia) and the DNA ploidy level can contribute significant information to the Gleason grading, thus partly at least reducing its subjective nature. This quantitative description was carried out by means of the Feulgen-stained nuclei image cytometry computation of 24 variables in 101 prostatic adenocarcinomas. The results show that both DNA ploidy- and morphonuclear-related variables were weak discriminators for the various grades of the Gleason classification system, and particularly between the high (Gleason 4 and 5) and the other Gleason-grades, i.e. the low (Gleason 1 and 2) and intermediate (Gleason 3) ones. The morphonuclear evidence of anaplasia is thus not redundant data on tumor growth pattern and may be expected to provide additional diagnostic information.

Adenocarcinoma↗
PubMed1993

Neuronal localization in the rat brain of the messenger RNA encoding calcyphosine, a new calcium-binding protein.

The cDNA encoding calcyphosine, a new calcium-binding protein of the calmodulin superfamily which is regulated by cAMP, has been cloned in the dog thyroid (EMBO J., 8 (1989) 111-116). By in situ hybridization with synthetic oligonucleotides, we here demonstrate for the first time its neuronal localization in the rat brain. Hybridization signal was detected in all the olfactory areas; in pyramidal and non pyramidal-shaped neurons in the different layers of the cerebral cortex, especially the superficial ones; in the pyramidal cells of the different sectors of the Ammon's horn and in the granule cells of the dentate gyrus of the hippocampus; in the subiculum; in the medium-sized and large neurons of the different quadrants of the caudate-putamen and accumbens and in the cerebellar Purkinje cells. Hybridization was also observed to a lesser extent in the majority of the neurons in the basal areas of the forebrain, including septum, nucleus of the diagonal band and amygdala; in the globus pallidus, entopeduncular nucleus, substantia nigra pars reticulata and compacta, ventral tegmental area; in the subthalamic nucleus; in the thalamus; in the hypothalamus; in the brainstem and in the upper cervical spinal cord. In addition to its neuronal localization, calcyphosine mRNA was also found in ependymal cells. The non-detection of positive cells in the white matter was not in favor of prominent glial localization, although it does not exclude it.

Animals↗
PubMedDate not supplied

Characterization of nuclear size, ploidy, DNA histogram type and proliferation index in 79 nerve sheath tumors.

The distribution values of ploidy, of the DNA histogram type, of the proliferation index and of the nuclear area are described in a series of 79 nerve sheath tumors including 7 traumatic neuromas, 55 primary and 9 recurrent benign schwannomas, 5 benign neurofibromas and 3 malignant tumors. The nuclear parameters were computed on Feulgen-stained nuclei (from archival formalin-fixed paraffin-embedded materials) by means of digital cell image analysis. The results show that 20-30% of benign nerve sheath tumors exhibit an abnormal nuclear DNA content (DNA index > 1.30). Such a feature was observed in the four groups of benign tumors, i.e. primary and recurrent schwannomas, neurofibromas and even traumatic neuromas. Aneuploid tumors exhibited triploid, hypertriploid or polymorphic DNA histogram types. The three malignant tumors under study were aneuploid. Lastly, the nuclear area and proliferation index measurements did not allow any clear distinction to be made between the four groups of benign tumors on the one hand, and between the benign and malignant tumors on the other.

Adult↗