Experimental Muscle Pain Impairs the Synergistic Modular Control of Neck Muscles.

A motor task can be performed via different patterns of muscle activation that show regularities that can be factorized in combinations of a reduced number of muscle groupings (also referred to as motor modules, or muscle synergies). In this study we evaluate whether an acute noxious stimulus induces a change in the way motor modules are combined to generate movement by neck muscles. The neck region was selected as it is a region with potentially high muscular redundancy. We used the motor modules framework to assess the redistribution of muscular activity of 12 muscles (6 per side) in the neck region of 8 healthy individuals engaged in a head and neck aiming task, in non-painful conditions (baseline, isotonic saline injection, post pain) and after the injection of hypertonic saline into the right splenius capitis muscle. The kinematics of the task was similar in the painful and control conditions. A general decrease of activity was noted for the injected muscle during the painful condition together with an increase or decrease of the activity of the other muscles. Subjects did not adopt shared control strategies (motor modules inter subject similarity at baseline 0.73±0.14); the motor modules recorded during the painful condition could not be used to reconstruct the activation patterns of the control conditions, and the painful stimulus triggered a subject-specific redistribution of muscular activation (i.e., in some subjects the activity of a given muscle increased, whereas in other subjects it decreased with pain). Alterations of afferent input (i.e., painful stimulus) influenced motor control at a multi muscular level, but not kinematic output. These findings provide new insights into the motor adaptation to pain.Open-Access Publikationsfonds 2015peerReviewe

Measurement of insulin and other glucose-regulating peptide hormones.

Insulin activity is an important laboratory parameter in the clinical evaluation of several diseases such as diabetes mellitus types I and II, states of impaired glucose tolerance, and insulin-producing tumors (insulinomas), where the insulin secretion released from pancreas β-cells is altered

Insulin analogs: Assessment of insulin mitogenicity and IGF-I activity.

The metabolic activity of insulin has been studied extensively in vitro and in vivo, based on the initial assessment of insulin receptor affinity, followed by methods to estimate the metabolic activity in vitro. These estimates provide some guidance about the biological activity which will be found in vivo; they need to be confirmed and supplemented by testing the glucose-lowering activity in animals (mice, rats, dogs, pigs). The biological effects (hypoglycemic activity) are related to the direct activation of the insulin receptor and subsequent signaling through intracellular mechanisms. The second group of biological effects is related to cell proliferation (mitogenic activity), which may be mediated by the insulin receptor, by the IGF-I receptor, and by hybrids of the two receptors. The evaluation of the relevance of mitogenicity estimates may be performed in in vitro and in vivo. One approach is cell proliferation in benign and malignant cell lines, for example, on mammary epithelial cell lines MCF-10 and MCF-7 (Milazzo et al. 1997)