Biomedical subjects

J M Mansour

Publications and source records attributed to J M Mansour.

At least 37 records · Page 2Linked to original sources

PubMed1988

Simulation of the double limb support phase of human gait.

Dynamic mechanical models of the double limb support phase of human gait were developed for both two-dimensional (sagittal plane) and three-dimensional motion. A "foot" model with a curved plantar surface was also developed such that the model foot motion was kinematically equivalent to that of a walking subject. This foot model was incorporated into the planar model for double limb support. The dynamic formulations were based on Kane's method and were implemented symbolically using MACSYMA. The development of the formulations for the constrained systems, application of these formulations to the study of normal gait, the sensitivity of the simulation to the frequency content of the input data, the sensitivity of limb displacements to changes in joint moments and the application of a nonlinear feedback controller to correct for perturbations in limb trajectories were investigated.

Ankle Joint↗

PubMed1987

Quantitative functional anatomy of the lower limb with application to human gait.

A scheme was developed to classify muscles according to their primary, secondary and tertiary functions, e.g. a muscle which produces primarily a flexion moment may also produce secondary abduction and tertiary internal rotation moments. The functions of muscles crossing the hip and knee joints were computed based upon the changing relative positions of joint centers and muscle origins and insertions during one gait cycle. The function of several of the major muscles crossing the hip and knee joints is reported for the different limb positions corresponding to normal gait. It was found that the amount of force necessary to produce a given moment about a joint was dependent upon the limb position. In addition, the muscle functions changed significantly with limb position. Electrical stimulation of muscles of a paralyzed subject gave qualitative support to the results.

Gait↗

PubMed1986

The passive elastic moment at the knee and its influence on human gait.

The elastic component of the passive moment at the knee was measured in situ. The force needed to manually range the knee from approximately 90 degrees of flexion to full extension was measured. Hip and ankle angle were held fixed. The passive knee moment, computed from the force and knee angle data, was compared to the total knee moment required for normal gait. This comparison suggested that the passive moment can contribute a significant portion of the total joint moment during some phases of the gait cycle.

Biomechanical Phenomena↗

PubMed1986

GTP-binding proteins associated with serotonin-activated adenylate cyclase in Fasciola hepatica.

The liver fluke Fasciola hepatica has serotonin (5-hydroxytryptamine) receptors that function through a transmembrane signalling system requiring GTP which activates adenylate cyclase (ATP pyrophosphate-lyase (cyclising), EC 4.6.1.1). Non-hydrolysable GTP analogs and NaF activate adenylate cyclase in membrane particles of these organisms. The nature of GTP-binding proteins in these membranes was studied using bacterial toxins and photoaffinity labelling. Treatment of membrane particles from flukes with cholera toxin increased basal adenylate cyclase activity, but markedly decreased activation by serotonin, non-hydrolysable GTP analogs, and NaF. [32P]ADP-ribosylation by cholera toxin or photoaffinity labelling with [32P]-8-N3GTP identified a 53 kDa protein and a 45 kDa protein which appeared to be similar to the forms of the alpha-subunit of the GTP-binding protein associated with adenylate cyclase in mammals. Treatment of membrane particles by pertussis toxin did not significantly change basal adenylate cyclase activity and did not change the stimulation of cyclase by activators. A 43 kDa protein which was [32P]ADP-ribosylated by either cholera or pertussis toxin, depending on the conditions used, and photoaffinity labelled by [32P]-8-N3GTP may be part of the transmembrane signalling system in the liver flukes.

Adenosine Diphosphate Ribose↗

PubMed1986

Swing phase simulation and design of above knee prostheses.

A detailed dynamic model of the stump-prosthesis system for an above knee amputee was developed. The model was used to examine the influence of controls and design parameters on the limb system performance during the swing phase of gait. The model duplicated the clinically known fact that hydraulic knee controllers allow the amputee to change walking speed while mechanical knee controllers limit the amputee to a single walking speed. Contrary to current practice, the simulations suggest that light weight prosthesis designs do not perform as well as heavier designs. A simple design based on a constant friction knee is shown to yield good overall performance.

Amputation, Surgical↗

PubMed1984

Linear approximations for swing leg motion during gait.

The applicability of a linear systems analysis of two-dimensional swing leg motion was investigated. Two different linear systems were developed. A linear time-varying system was developed by linearizing the nonlinear equations describing swing leg motion about a set of nominal system and control trajectories. Linear time invariant systems were developed by linearizing about three different fixed limb positions. Simulations of swing leg motion were performed with each of these linear systems. These simulations were compared to previously performed nonlinear simulations of two-dimensional swing leg motion and the actual subject motion. Additionally, a linear system analysis was used to gain some insight into the interdependency of the state variables and controls. It was shown that the linear time varying approximation yielded an accurate representation of limb motion for the thigh and shank but with diminished accuracy for the foot. In contrast, all the linear time invariant systems, if used to simulate more than a quarter of the swing phase, yielded generally inaccurate results for thigh shank and foot motion.

Gait↗

PubMed1983

The dual effects of aluminum as activator and inhibitor of adenylate cyclase in the liver fluke Fasciola hepatica.

The liver fluke, Fasciola hepatica, has a very active adenylate cyclase which can be stimulated by NaF or by serotonin and guanine nucleotides. Micromolar amounts of AlCl3 augment the activation by F-. In contrast, when the enzyme is activated with serotonin and guanine nucleotides, AlCl3 inhibits the activation. Aluminum also inhibits the activation by forskolin. Gallium mimics the effects of aluminum.

Adenylyl Cyclase Inhibitors↗

PubMed1982

The passive elastic moment at the hip.

The passive elastic moment at the hip was measured in normal male subjects in situ. The influence of two joint muscles crossing the hip was evaluated by performing hip moment measurements over a continuous range of hip angles and at prescribed knee angles. The experimentally acquired data was fitted by exponential functions which separately modeled the moment contribution of tissues deformed by hip flexion and extension. The results of the investigation are discussed with regard to the possible role of the passive joint moments as an energy storage and release mechanism during human walking.

Adult↗

PubMed1982

A three dimensional multi-segmental analysis of the energetics of normal and pathological human gait.

Segmental mechanical energy changes were studied in normal adults as a function of walking speed and in a group of subjects with pathologically impaired gait walking at their normal speed to determine the usefulness of this parameter in evaluating locomotor dysfunction. Of particular significance, the degree of exchange between potential and kinetic energy within and between limb segments was quantitatively evaluated. Due to the nature of most pathological gaits, no assumptions were made to impose symmetry between the right and left extremities and the translational as well as rotational kinetic energy of each of the limb segments was computed in three dimensions. Additionally, the torso was modeled as a group of segments with distributed mass in contrast to the commonly employed concentrated point mass model. In toto, a three dimensional twelve segment energetic analysis of the human body was developed and employed. In normal subjects, this analysis suggests a greater exchange between potential and kinetic energy near individually preferred walking speeds. Patterns of energy change noted in those subjects with locomotor dysfunction varied with the type of pathological disorder.

Adolescent↗

PubMed1982