Different regions within the same muscle can have very different properties

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This research was part of the PhD thesis of CJ (Jo) de Ruiter. It shows how within a single muscle there may be marked regional differences in physiological characteristics implying task dependent differences in recruitment patterns of motor units. The work was carried out under the direction of Anthony J Sargeant and Arnold de Haan.

Physiological characteristics of two extreme muscle compartments in gastrocnemius medialis of the anaesthetized rat

De Ruiter CJArnold de HaanAnthony J Sargeant
Acta Physiologica Scandavica
Acta Physiol Scand. 1995 Apr;153(4):313-24
Rat medial gastrocnemius (GM) muscle is a compartmentalized muscle. The functional properties and fibre type composition of the most proximal and most distal compartment were studied in in situ preparations. The proximal compartment contained predominantly fast twitch oxidative fibres. The distal compartment was mainly composed of fast twitch glycolytic fibres. With the use of two small electrodes placed around the primary nerve branches, both compartments could be separately stimulated within the same muscle. The length-force relationship was less broad and maximal twitch and tetanic forces were obtained at lower muscle lengths for the proximal compartment. The differences (mm) were 0.9 +/- 0.2 and 1.2 +/- 0.2 for maximal twitch and tetanic force (120 Hz) production, respectively (P < 0.001). The shortening velocity for maximal power production was lower (P < 0.001) for the proximal compartment (proximal: 57.1 +/- 2.7 mm s-1, distal: 73.1 +/- 3.0 mm s-1). During a standard fatigue test the fatiguability was significantly lower for the proximal compared with the distal fibres. Our findings suggest that the proximal compartment is likely to be activated in vivo during activities requiring relatively low power outputs for longer time periods. In contrast the distal compartment is probably recruited only during high power demanding short lasting activities. The presented model makes it possible to study fatigue related changes in power production of the ‘red’ and ‘white’ areas of the GM separately in a way that is probably meaningful with respect to in vivo function.

Chronic Obstructive Lung Disease

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Rik Gosselink presented this research as part of his PhD in the Vrije University of Amsterdam. The work was directed by Professor Anthony J Sargeant and Professor Marc Decramer.

Diaphragmatic breathing reduces efficiency of breathing in patients with chronic obstructive pulmonary disease

R A Gosselink

R C Wagenaar

H Rijswijk

Anthony J Sargeant

and M L Decramer

American Journal of Respiratory and Critical Care Medicine
Am J Respir Crit Care Med. 1995 Apr;151(4):1136-42
The effects of diaphragmatic breathing learning on chest wall motion, mechanical efficiency of the respiratory muscles, breathing pattern, and dyspnea sensation were studied in seven patients with severe chronic obstructive pulmonary disease (COPD) (FEV1 34 +/- 7% of the predicted value) during loaded and unloaded breathing. Chest wall motion was studied focusing on amplitude and phase relation of rib cage and abdominal motion. Mechanical efficiency was defined as the ratio of added external power output and added oxygen consumption during inspiratory threshold loading (40% maximal inspiratory pressure [Plmax]). After 2 wk run-in, all subjects participated in a diaphragmatic breathing program for 3 wk. Variables obtained during diaphragmatic breathing were compared with those obtained during natural breathing. During diaphragmatic breathing the ratio of rib cage to abdominal motion decreased significantly during unloaded (0.86 versus 0.37; p < 0.01) as well as during loaded breathing (0.97 versus 0.50; p < 0.01). Chest wall motion became more asynchronous during diaphragmatic breathing in the unloaded conditions (mean phase difference for natural breathing 3.5 versus 10.4% for diaphragmatic breathing; p < 0.02) and loaded conditions (mean phase difference for natural breathing 6 versus 11.4% for diaphragmatic breathing; p < 0.02). Surprisingly, mechanical efficiency decreased significantly during diaphragmatic breathing (2.57 +/- 0.76%) in comparison with natural breathing (3.35 +/- 1.48%; p < 0.01). Tidal volume, respiratory frequency, and duty cycle did not change significantly during diaphragmatic breathing. Dyspnea sensation tended to increase during diaphragmatic breathing.

New research technique for studying human muscle fibre types – In memoriam Jose Sant’ana Pereira a highly talented but troubled scientist

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This paper describes the combination of a number of complementary techniques applied to the characterisation of human muscle fibre types using microdissection of fragments of fibres obtained by needle biopsy. The work was a collaboration between the Amsterdam Research Groups directed by Professors Anthony Sargeant and Anton Moorman and that of Professor Geoffrey Goldspink in London. The work was submitted by Jose Sant’ana Pereira as part of his PhD completed under the direction of Anthony Sargeant in the Vrije University of Amsterdam. Sadly Jose died some years later while working in Madison, Wisconsin.

New method for the accurate characterization of single human skeletal muscle fibres demonstrates a relation between mATPase and MyHC expression in pure and hybrid fibre type

Jose A A Sant’ana PereiraWessels ANijtmans LAnton F MoormanAnthony J Sargeant.

Journal of Muscle Research and Cell Motility

J Muscle Res Cell Motil. 1995 Feb;16(1):21-34

In the present study we have developed a method which, by combining histochemical, immunohistochemical, electrophoretic and immunoblotting analyses on a single fibre, enables a sensitive characterization of human skeletal muscle fibres dissected from freeze-dried biopsy samples.

For histochemical (and immunohistochemical) analysis fibre fragments (500 microns) of individual fibres were mounted in an embedding medium to allow cryostat sections of normalized thickness to be reproducibly obtained. The specificity of the myofibrillar Ca2+ ATPase (mATPase) staining profiles in gelatin-embedded single fibre sections was tested by immunohistochemical reactions with anti-myosin heavy chain (MyHC) monoclonal antibodies specific to human MyHC I, IIA, IIB and IIA + IIB and by gel electrophoresis. The combined methodologies demonstrated the specificity of the mATPase staining patterns which correlated to the expression of distinct MyHC isoforms. In addition the results provide evidence that many fibres co-expressed different MyHC isoforms in variable relative amounts, forming a continuum.  Staining intensities for mATPase, converted into optical density values by image analysis revealed that a relationship between mATPase and MyHC expression holds for hybrid fibres even when displaying one MyHC type with overwhelming dominance. The results also revealed that three MyHC isoforms I, IIA and IIB can be co-expressed on a single muscle fibre. In such a case mATPase alone, with the current protocols, does not allow an accurate characterization of the specific MyHC-based fibre type(s). Although some hybrid fibres may have displayed a non-uniform expression of myosins along their lengths, most fibres from the IIA/B group (type) remained very stable with respect to the relative amounts of the MyHCs expressed. Finally, a second slow MyHC isoform was recognized on immunoblots of a mixed muscle sample.

Human Muscle Fibre Types

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In this important series of studies a collaboration between the research group in Amsterdam led by Anthony Sargeant and that in London under the direction of Professor Geoffrey Goldspink used new techniques based on microdissection of fragments of human muscle fibre obtained by needle biopsy.
Characterization of human skeletal muscle fibres according to the myosin heavy chains they express

Steven EnnionJose A A Sant’ana PereiraAnthony J SargeantArchie YoungGeoffrey Goldspink.

Journal of Muscle Research and Cell Motility
J Muscle Res Cell Motil. 1995 Feb;16(1):35-43
Using a method of single muscle fibre analysis, we investigated the presence of RNA transcripts for various isoforms of the myosin heavy chain (MyoHC) gene in histochemically, immunohistochemically and electrophoretically characterized individual muscle fibres (n = 65) from adult human vastus lateralis muscle. A cDNA clone isolated in this study was shown to contain the 3′ end of a previously uncharacterized human MyoHC gene which is expressed specifically in human fast IIA muscle fibres and we conclude that this clone contains part of the human fast IIA MyoHC gene. In all the fibres histochemically, immunohistochemically and electrophoretically characterized as containing the previously classified IIB MyoHC (n = 23), it was shown that the human equivalent to the rat type IIX MyoHC gene is expressed. This observation was taken to suggest that the previously classified IIB muscles fibres in human muscle express a MyoHC isoform equivalent to the rat IIX, not the IIB, and would therefore be more accurately classified as IIX fibres.

Review of research into muscle power and fatigue

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Anthony Sargeant and David A Jones wrote this invited review for an important book on muscle fatigue edited by Simon Gandevia and others

The significance of motor unit variability in sustaining mechanical output of muscle

Anthony J Sargeant and David A Jones

Advances in Experimental Medicine and Biology
Adv Exp Med Biol. 1995;384:323-38
Neuromuscular function and fatigue have been studied using a wide variety of preparations. These range from sections of single fibers from which the cell membrane has been removed to whole muscles or groups of muscles acting about a joint in the intact animal. Each type of preparation has its merits and limitations. There is no ideal preparation; rather the question to be answered will determine the most appropriate model in each case and sometimes a combination of approaches will be needed. In particular, it is important to understand how the mechanical output of whole muscle can be sustained to meet the demands of a task and to take into account the organized variability of the constituent motor units.