Various mechanisms may alter corticomotor excitability to agonist and antagonist muscles during passive and active limb movement depending on parameters of movement and their functional role. A better understanding of these relationships is important for understanding basic motor control mechanisms, and may be relevant to motor rehabilitation programs after brain injury. The purpose of the present study was to compare changes in corticomotor excitability to wrist flexor and extensor muscles during different phases of movement (flexion/extension), and at rest and during actively or passively-mediated length changes. Motor evoked potentials (MEP) of the flexor carpi radialis (FCR) and extensor carpi radialis (ECR) were recorded from 17 participants during resting and four movement conditions (passive wrist flexion and extension, active wrist flexion and extension) with their palm inserted into a hand piece. Passive and active movements were carried out by moving the hand piece for 22.5° wrist flexion and 22.5° wrist extension from the neutral wrist position of oo at a cycle rate of 1 Hz. Transcranial magnetic stimulation (TMS) was delivered at the neutral position (0°) every ten cycles to obtain 12 MEPs. The mean MEP amplitude was compared across the resting, lengthening and shortening phases for passive and active movements for the FCR and ECR separately by a paired t-test. Comparison was also made between FCR and ECR, and between passive and active movements by a two-way repeated measures ANOVA. The MEP amplitude was significantly (P<0.05) reduced during passive lengthening for the FCR and ECR; but increased significantly during shortening only for the FCR compared with the resting state. In contrast, the MEP amplitude of the FCR and ECR increased in both active lengthening and shortening compared with the resting state, but the increase was significantly (P<0.05) greater for shortening than lengthening phase. These results suggest that changes in corticomotor excitability are similar between the FCR and ECR, and between passive and active movements, and suggest that common underlying mechanisms exist in the modulation of corticomotor excitability during passive and active wrist movements.

/pdf/modulation-of-corticomotor-excitability-during-passive-and-ggpkcscm3c.pdf

Human Anatomy and Physiology. 6th ed

Modulation of corticomotor excitability during passive and active wrist flexion and extension

An abnormality associated with all forms of cardiovascular diseases is cardiac hypertrophy, which is an overall increase in heart mass without improved contractile function. Prolonged cardiac hypertrophy eventually leads to heart failure, in which the heart can no longer supply adequate amounts of blood to meet the body’s hemodynamic demands, resulting in cardiac dilatation, thinning of the myocardial walls, decrease in contractile effectiveness, organ failure and death.

The Ca2+- dependent phosphatase, calcineurin (Cn) and its downstream target, nuclear factor of activated T-cells (NFAT), are major intracellular modulators of cardiac hypertrophy. In young 1-2 month old mice, the NFATc2 transcription factor has been identified as the major NFAT isoform responsible for Cn-mediated cardiac hypertrophy. We observed that adult 6-9 month old NFATc2-/- mice were more prone to sudden death, suggesting that the loss of NFATc2 was detrimental at later stages of life. Using histology, we showed that adult NFATc2-/- mice display left ventricular dilatation and thinning of the ventricular walls, characteristic of failure. Western blot and immunofluorescene results showed that NFATc2-/- mice displayed alterations in the signaling of growth pathways, which predisposed these mice to heart failure. Furthermore, angiotensin II-induced cardiac growth revealed that the hearts of NFATc2-/- mice displayed changes in contractile protein gene expression and an inactivation of both transcriptional and translational mechanisms. Our collective findings propose an uncharacterized role of NFATc2 for normal heart function and biochemical signaling in adult mice, providing further evidence that normal Cn-signaling is crucial in the heart.

/pdf/altered-growth-mediated-signaling-in-the-hearts-of-nfatc2-g943dao7uh.pdf

Altered growth-mediated signaling in the hearts of NFATc2 null mice

Evaluation of compression testing methods for the cortical ring in the distal femur metaphysis of adult male rats

Specialist monitoring technology and skills for the critically ill woman

Submitted in fulfilment of the Master's Degree in Clinical Technology, Durban University of Technology, 2010.

https://openscholar.dut.ac.za/bitstream/10321/621/1/Memela_2010.pdf

Human Anatomy and Physiology. 6th ed

Citations

Modulation of corticomotor excitability during passive and active wrist flexion and extension

Altered growth-mediated signaling in the hearts of NFATc2 null mice

Evaluation of compression testing methods for the cortical ring in the distal femur metaphysis of adult male rats

Specialist monitoring technology and skills for the critically ill woman

A prospective comparative study of continuous and intermittent endotracheal tube cuff pressure measurement in an adult intensive care unit

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