Daniel L. Feeback

Noninvasive analysis of human neck muscle function

Study Design Muscle use evoked by exercise was determined by quantifying shifts in signal relaxation times of T2-weighted magnetic resonance images. Images were collected at rest and after exercise at each of two intensities (moderate and intense) for head movements: 1) extension, 2) flexion, 3) rotation, and 4) lateral flexion. Objective This study examined the intensity and pattern of neck muscle use evoked by various movements of the head. The results will help elucidate the pathophysiology, and thus methods for treating disorders of the cervical musculoskeletal system. Summary of Background Data Exercise-induced contrast shifts in T2 has been shown to indicate muscle use during the activity. The noninvasive nature of magnetic resonance imaging appears to make it an ideal approach for studying the function of the complex neuromuscular system of the neck. Methods The extent of T2 increase was examined to gauge how intensely nine different neck muscles or muscle pairs were used in seven subjects. The absolute and relative cross-sectional area of muscle showing a shift in signal relaxation was assessed to infer the pattern of use among and within individual neck muscles or muscle pairs. Results Signal relaxation increased with exercise intensity for each head movement. The absoluta and relative cross-sectional area of muscle showing a shift in signal relaxation also increased with exercise load. Neck muscles or muscle pairs extensively used to perform each head movement were: extension-semispinalis capitls and cervicis and splenius capitis; flexion-sternocleidomastold and longus capitis and collirotation-splenious capitis, levator scapulae, scalenus, semispinalis capitis ipsilateral to the rotation, and sternocleidomastold contralateral; and lateral flexion-sternocleidomastoid. Conclusion The results of this study, in part, agree with the purported functions of neck muscles derived from anatomic location. This also was true for the few selected muscles that have been examined in human electromyographic studies. Neck muscle function and morphology can be studied at a detailed level using exercise-induced shifts in magnetic resonance images.

Enhanced protein electrophoresis technique for separating human skeletal muscle myosin heavy chain isoforms

Talmadge and Roy (J. Appl. Physiol. 1993, 75, 2337–2340) previously established a sodium dodecyl sulfate ‐ polyacrylamide gel electrophoresis (SDS‐PAGE) protocol for separating all four rat skeletal muscle myosin heavy chain (MHC) isoforms (MHC I, IIa, IIx, IIb); however, when applied to human muscle, the type II MHC isoforms (IIa, IIx) are not clearly distinguished. In this brief paper we describe a modification of the SDS‐PAGE protocol which yields distinct and consistent separation of all three adult human MHC isoforms (MHC I, IIa, IIx) in a minigel system. MHC specificity of each band was confirmed by Western blot using three monoclonal IgG antibodies (mAbs) immuno‐reactive against MHCI (mAb MHCs, Novacastra Laboratories), MHCI+IIa (mAb BF‐35), and MHCIIa+IIx (mAb SC‐71). Results provide a valuable SDS‐PAGE minigel technique for separating MHC isoforms in human muscle without the difficult task of casting gradient gels.

Syringe Loading: A Method for Assessing Plasma Membrane Function as a Reflection of Mechanically Induced Cell Loading

Publisher Summary This chapter describes syringe loading as a method for assessing plasma membrane function as a reflection of mechanically induced cell loading. During the syringe loading procedure, the mechanical force applied to the cells to produce plasma membrane wounding is fluid shear stress generated as a consequence of the cell suspension being forced through a narrow orifice in the form of a 30-gauge hypodermic needle. Although complex in nature, the membrane wound response in totality can be quantified using direct end point measures that describe the final outcome of the process. Wounded cells trap the wound marker in their cytoplasm by virtue of resealing the plasma membrane disruption. However, immediately after syringe loading there are cells in the loaded sample that are positive for the wound marker but will die within a matter of hours due to irreparable membrane damage. The apparent dose response in membrane wound susceptibility observed relative to radiation exposure in our model indicates that gamma irradiation induces alterations in the plasma membrane components of Jurkat cells, if not immediately, then most certainly within 2 h of exposure.