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  • 1
    Electronic Resource
    Electronic Resource
    Muscles within muscles: the neuromotor control of intra-muscular segments (1998)
    Springer
    European journal of applied physiology 78 (1998), S. 219-225 
    Details
    ISSN: 1439-6327
    Keywords: Key words Functional differentiation ; Electromyography ; Deltoid ; Motor control ; Muscle function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this investigation was to anatomically identify, and then determine the function of, individual segments within the human deltoid muscle. The anatomical structure of the deltoid was determined through dissection and/or observation of the shoulder girdles of 11 male cadavers (aged 65–84 years). These results indicate that the deltoid consists of seven anatomical segments (D1–D7) based upon the distinctive arrangement of each segment's origin and insertion. Radiographic analysis of a cadaveric shoulder joint suggested that only the postero-medial segment D7 has a line of action directed below the shoulder joint's axis of rotation. The functional role of each individual segment was then determined utilising an electromyographic (EMG) technique. Seven miniature (1 mm active plate; 7 mm interelectrode distance) bipolar surface electrodes were positioned over the proximal portion of each segment's muscle belly in 18 male and female subjects (18–30 years). EMG waveforms were then recorded during the production of rapid isometric shoulder abduction and adduction force impulses with the shoulder joint in 40 degrees of abduction in the plane of the scapula. Each subject randomly performed 15 abduction and 15 adduction isometric force impulses following a short familiarisation period. All subjects received visual feed back on the duration and amplitude of each isometric force impulse produced via a visual force-time display which compared subject performance to a criterion force-time curve. Movement time was 400 ms (time-to-peak isometric force) at an intensity level of 50% maximal voluntary contraction. Temporal and intensity analyses of the EMG waveforms, as well as temporal analysis of the isometric force impulses, revealed the neuromotor control strategies utilised by the CNS to control the activity of each muscle segment. The results showed that segmental neuromotor control strategies differ across the breadth of the muscle and that individual segments of the deltoid can be identified as having either “prime mover”, “synergist”, “stabiliser” or “antagonist” functions; functional classifications normally associated with whole muscle function. Therefore, it was concluded that the CNS can “fine tune” the activity of at least six discrete segments within the human deltoid muscle to efficiently meet the demands of the imposed motor task.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050410
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  • 2
    Electronic Resource
    Electronic Resource
    Electromyographic basis of inaccurate movement; its dependence upon the mode of muscle contraction (1991)
    Springer
    European journal of applied physiology 62 (1991), S. 162-170 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Muscle contraction ; Inaccurate movement ; Motor skill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The electromyographic basis of inaccurate performance was investigated in two rapid precision-grip skills controlled by concentric and eccentric muscle contractions respectively. Surface electromyograms, recorded from the first dorsal interosseous (DI), adductor pollicis (AP) and abductor pollicis brevis, were utilised to identify changes in the timing and intensity of muscle activation which may be responsible for inaccurate performance. The results showed that when fast precision-grip skills were controlled by concentric DI and AP muscle contractions, variations in the intensity of muscle contraction were responsible for inaccurate performance. However, when these skills were controlled by eccentric DI and AP muscle contractions, inaccurate performance resulted from variations in the timing of muscle activation. It was concluded that the nature of the deficiency in the patterns of muscle activation resulting in inaccurate performance was dependent upon the type of muscle contraction used in the skill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643736
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of muscle activation dynamics on reaction time in the elderly (1994)
    Springer
    European journal of applied physiology 69 (1994), S. 344-349 
    Details
    ISSN: 1439-6327
    Keywords: Aging ; Electromyography ; Reaction time ; Motor control ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this investigation was to determine whether age-related changes in the dynamics of muscle activation were, in part, responsible for longer reaction times (RT) in the elderly. A group of 12 young (mean age, 20.6 years) and 12 elderly (mean age, 64.3 years) women performed a series of ballistic forearm supination movements in response to an auditory stimulus while using a simple reaction time test. Surface electromyographic waveforms from biceps brachii (agonist) and pronator teres (antagonist) muscles were recorded, together with the angle-time curves representing the motion of the forearm, on to an IBM compatible microcomputer. The results showed that an age-related increase (P〈0.05) in motor reaction time (MRT) contributed to longer RT in the elderly. In addition, the longer (P〈0.05) MRTs in the elderly were associated with a significantly slower rate (P〈0.05) of biceps brachii muscle activation and a significantly increased proportion (P〈0.05) of the initial biceps brachii muscle burst required to initiate the movement. This data suggested that an important part of the slowing of motor behaviour, commonly observed with increasing age, may be due to either decreases in the ability of aged skeletal muscle to rapidly generate tension or to a reduction in motor drive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392041
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  • 4
    Electronic Resource
    Electronic Resource
    The electromyographical basis of inaccurate motor performance (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 132-140 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Motor skill ; Electromyography ; Inaccuracy ; Isometric
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to investigate the electromyographical basis of inaccurate movement by identifying the variate and invariate characteristics of a ballistic, isometric precision-grip skill. Our results have shown that in most subjects investigated, IEMG, discharge rate and the paterns of muscle synergy were variate movement parameters while the sequence of muscle activation, the relative duration of muscle activity and the time to peak force (rise-time) remained essentially invariante. Based on these results, we can conclude that inaccurate performance of this skill, in most of the subjects investigated, was more dependant upon changes in muscle IEMG than in alterations in the temporal sequencing of muscle activity. It was apparent that from trial to trial, subjects had more difficulty in reproducing the appropriate levels of muscle contraction and synergy than in reproducing the required periods of action.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636616
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  • 5
    Electronic Resource
    Electronic Resource
    Transition from slow to ballistic movement: development of triphasic electromyogram patterns (1991)
    Springer
    European journal of applied physiology 63 (1991), S. 381-386 
    Details
    ISSN: 1439-6327
    Keywords: Motor control ; Electromyography ; Motor skill ; Triphasic electromyogram ; Muscle contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this investigation was to determine how the triphasic electromyogram (EMG) pattern of muscle activation developed from the agonist muscle only pattern as movement time (t mov) decreased. Six adult women produced a series of 30° elbow extension movements in the horizontal plane at speeds ranging from ballistic (〈 400-ms t mov) to very slow (〉 800-ms t mov). Surface EMG from triceps brachii (agonist) and biceps brachii (antagonist) muscles were recorded, together with elbow angle, on a microcomputer. The results showed that triphasic EMG patterns developed systematically as t mov decreased from 1000 ms to 〈 200 ms. In trials with very long t mov, many elbow extension movements were produced by a single continuous activation of the agonist triceps brachii muscle. As t mov decreased however, agonist activation became predominantly burst-like and other components of the triphasic EMG pattern [activation of the antagonist (Ant) and second agonist activation (Ag2)] began to appear. At the fastest movement speeds, triphasic EMG patterns (Ag1-Ant-Ag2, Ag1 being first activation of agonist muscle) were always present. This data indicated that the triphasic pattern of muscle activation was not switched on when a particular t mov was achieved. Rather, each component systematically developed until all were present, as distinctive bursts of activity, in most trials with t mov less than 400 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00364466
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  • 6
    Electronic Resource
    Electronic Resource
    Angiotensin II binding to tissues of the rainbow trout, Oncorhynchus mykiss, studied by autoradiography (1992)
    Springer
    Journal of comparative physiology 162 (1992), S. 197-202 
    Details
    ISSN: 1432-136X
    Keywords: Angiotensin II ; Autoradiography ; Seawater-adaptation ; trout, Oncorhynchus mykiss (= Salmogairdneri)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Tissue slices from seawater-adapted and freshwater-adapted rainbow trout, Oncorhynchus mykiss, were exposed to 125I-angiotensin II (1.01·10-9 M) and binding sites located by light-microscopic autoradiography. Binding/uptake was significantly inhibited by excess (10-5 M) unlabelled angiotensin II, suggesting specific binding/uptake of angiotensin II to the ventral and dorsal aorta (smooth muscle), urinary bladder (smooth muscle and epithelial lining), glomeruli and proximal tubules, the gill (lamellae and central filament), skin (epithelium), intestine and oesophagus (mucosal epithelium), liver, heart (ventricular myocytes), adrenocortical tissue and brain (cerebellum and medulla oblongata). The specific binding/uptake of angiotensin II to tissues of freshwater- and seawater-adapted animals were generally similar. However, binding/uptake by the proximal tubules was significantly higher in freshwater-adapted trout than seawater-adapted trout. Specific binding/uptake of angiotensin II by the smooth muscle of the bladder was significantly higher in trout adapted to seawater than trout adapted to freshwater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357523
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  • 7
    Electronic Resource
    Electronic Resource
    Direct effects of angiotensin II on glomerular ultrastructure in the rainbow trout, Salmo gairdneri (1990)
    Springer
    Cell & tissue research 260 (1990), S. 315-319 
    Details
    ISSN: 1432-0878
    Keywords: Glomerulus ; Angiotensin II ; Glomerular ultrastructure ; Seawater adaptation ; Salmo gairdneri (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Slices from the kidneys of the rainbow trout which were exposed to 10-6 or 10-5 M angiotensin II (AII) and isolated glomeruli exposed to 10-7 or 10-5 M AII showed ultrastructural changes compared to control tissues incubated without AII. The studies indicate that angiotensin II has a direct action on glomerular ultrastructure, flattening the epithelial podocytes and broadening the primary processes with fusion of pedicels in extreme cases. These changes suggest a probable effect of AII on water permeability of the trout glomerulus, an intrarenal action which is believed to form an essential part of the antidiuretic adaptation to increased environmental salinities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318634
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  • 8
    Electronic Resource
    Electronic Resource
    Glomerular ultrastructure of the trout, Salmo gairdneri: Effects of angiotensin II and adaptation to seawater (1987)
    Springer
    Cell & tissue research 249 (1987), S. 437-442 
    Details
    ISSN: 1432-0878
    Keywords: Angiotensin II ; Glomerulus ; Salmo gairdneri ; Seawater-adaptation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of angiotensin infusion on the glomerular ultrastructure of freshwater- and seawater-adapted rainbow trout, Salmo gairdneri, has been examined by scanning and transmission electron microscopy. Adaptation of trout to seawater resulted in epithelial podocyte flattening, primary process broadening and apparent loss of foot processes in almost all glomeruli, features which were uncommon in freshwater-adapted trout. Similar changes were induced by infusion of freshwater-adapted animals with angiotensin, suggesting that the renin-angiotensin system plays a role in the modification of glomerular epithelial ultrastructure. Adaptation of trout to seawater also reduced glomerular diameter, but infusion of freshwater-adapted animals with angiotensin did not mirror this effect. Infusion of angiotensin into seawater-adapted animals increased the overall thickness of glomerular basement membrane by increasing the lamina rara interna and lamina densa. This did not occur when freshwater-adapted fish were either infused with angiotensin or adapted to seawater. These findings suggest that other humoral systems are involved in the control of glomerular diameter and basement membrane thickness as part of an integrated response to increased environmental salinity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215528
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  • 9
    Electronic Resource
    Electronic Resource
    Glomerular binding of angiotensin II in the rainbow trout,Salmo gairdneri (1990)
    Springer
    Cell & tissue research 259 (1990), S. 479-482 
    Details
    ISSN: 1432-0878
    Keywords: Kidney ; Glomerulus ; Angiotensin II ; Salmo gairdneri (Teleostei)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Isolated glomeruli of the rainbow trout have been exposed in vitro to125I-angiotensin II (0.88 × 10−9 M) and binding sites located by light-microscopic autoradiography. These studies provide evidence of specific binding of angiotensin II by glomeruli. Binding was significantly inhibited by excess (10−5 M) unlabelled angiotensin II, but a high degree of non-specific binding also occurred. The mammalian competitive antagonist, saralasin (3 × 10−7 M) did not influence125I-angiotensin II binding to fish glomeruli. Intense binding of125I-angiotensin II was noted at the vascular pole of some glomeruli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01740774
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