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  • Polymer and Materials Science  (17)
  • Cell & Developmental Biology  (5)
  • Electromyography  (5)
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  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Aging ; Electromyography ; Reaction time ; Motor control ; Muscle contraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00392041
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Key words Functional differentiation ; Electromyography ; Deltoid ; Motor control ; Muscle function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004210050410
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  • 3
    Digitale Medien
    Digitale Medien
    Effects of gamma radiation on two aromatic polysulfones. II. A comparison of irradiation at various temperatures in air-vacuum environmentsPresented in part at the First Chemical Congress of the North American Continent, Mexico City, December 1975. (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 23 (1979), S. 2763-2775 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The aromatic polysulfone poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyleneiso-propylidene-1,4-phenylene) (I) showed no change in flexural yield strength after doses of γ-radiation up to 600 Mrad in vacuum at 35,80, and 125°C (Tg = 190°C)). However, the flexural strength decreased markedly with doses above 100 Mrad on irradiation in air, to 40-60% of the initial value after 200-400 Mrad, depending on the sample and the irradiation conditions. Chain crosslinking was predominant over scission for irradiation in vacuum at all temperatures; (G(X), G(S), and G(S)/G(X) increased with the irradiation temperature, but G(S)/G(X) decreased to zero above Tg. Poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene) (II) behaved similarly, except that the flexural strength was found to be very dependent on the thermal treatment of the sample. This polymer showed a remarkable retention of its mechanical properties on irradiation up to 200°C (Tg = 230°C) in the absence of air, the flexural strength being retained up to 500 Mrad. Radiation annealing occurred at 35°C in vacuum and air and combined radiation and thermal annealing at 125 and 220°C. Progressive removal of surface layers from flexural test bars of I irradiated in air showed that the decrease in flexural strength with dose could be explained by a decrease in the molecular weight towards the surface resulting from radiation-oxidation reactions.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1979.070230921
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  • 4
    Digitale Medien
    Digitale Medien
    Observations on preadipocytes and their distribution patterns in rat adipose tissue (1981)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981), S. 281-288 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Microscopic examination of adipocytes isolated from adult rat epididymal adipose tissue revealed numerous small cells (〈 10 μm) morphologically similar to larger adipocytes. These small adipocytes appear identical to a new classification of adipose cells termed preadipocytes. Electron micrographs of these preadipocytes revealed examples of cells 〈 10 μm in diameter in various stages of maturation and lipid accumulation. The percent distribution pattern of these small adipocytes was not significantly altered by exercise although exercise shifted the distribution patterns of the larger cells (〉 30 μm) toward a smaller mean cell size. The quantitative significance of preadipocytes is not established but these preliminary observations indicate that adipocytes 〈 10 μm in diameter may account for a numerically greater proportion of the total adipocytes observed in collagenase isolated preparations than heretofore recognized, although their contribution to total adipose mass is probably negligible.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051680304
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  • 5
    Digitale Medien
    Digitale Medien
    Soluble polymeric carriers for drug delivery. Part I: Free radical copolymerization of N-(2-hydroxypropyl) methacrylamide with N-[2-(4-hydroxyphenyl) ethyl]acrylamide (1989)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 27 (1989), S. 515-525 
    Details
    ISSN: 0887-6258
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1989.140271302
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  • 6
    Digitale Medien
    Digitale Medien
    The electromyographical basis of inaccurate motor performance (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 132-140 
    Details
    ISSN: 1439-6327
    Schlagwort(e): Motor control ; Motor skill ; Electromyography ; Inaccuracy ; Isometric
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00636616
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  • 7
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Motor control ; Electromyography ; Muscle contraction ; Inaccurate movement ; Motor skill
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00643736
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  • 8
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Motor control ; Electromyography ; Motor skill ; Triphasic electromyogram ; Muscle contraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00364466
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  • 9
    Digitale Medien
    Digitale Medien
    Effects of gamma radiation on two aromatic polysulfones (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 405-417 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Two aromatic polysulfones, poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyleneisopropylidene-1,4-phenylene) (I) and poly (oxy-1,4-phenylenesulfonyl-1,4-phenylene) (II), undergo crosslinking and chain scission at 30°C during γ-irradiation, the former being predominant in vacuum and the latter in air. Both processes occurred more readily in I, which contains isopropylidene linkages. Gel measurements gave G(crosslink) = 0.051, G(scission) = 0.012 for this polymer at 30°C in vacuum. Increased irradiation temperatures resulted in higher crosslinking and gas yields, especially above the glass transition temperature. The tensile strength, flexural strength, and modulus of I were unaffected by γ-irradiation up to about 50 Mrad in air, but the strength decreased markedly at higher doses. The elongation at break decreased progressively with dose. For both polymers, G(gas) = 0.04 at 30°C with the main products being SO2, H2, CO2, CH4, and H2O.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1975.070190208
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  • 10
    Digitale Medien
    Digitale Medien
    Renal microvasculature of the rainbow trout, Salmo gairdneri: Scanning electron microscopy of corrosion casts of glomeruli (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 213 (1985), S. 505-513 
    Details
    ISSN: 0003-276X
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Scanning electron microscopy of corrosion casts of blood vessels permits detailed and accurate study of the microcirculation. The present study examined the renal microvasculature of the rainbow trout, Salmo gairdneri. The conventional picture of a glomerulus with one afferent arteriole was common, but glomeruli were often supplied by two afferent arterioles. In the majority of these, the intrarenal artery gave rise to a single afferent arteriole that branched to form two smaller vessels before reaching the glomerulus. Glomeruli with two afferent arterioles that arose independently from the intrarenal artery also occurred. The majority of glomeruli had a single efferent arteriole, but a proportion of glomeruli had two efferent arterioles. Efferent arterioles were smaller in diameter than the afferent arterioles. The glomerular capillaries were arranged in lobules, with few anastomoses between lobules, so that, for glomeruli with two afferent or two efferent arterioles, vascular perfusion and thus filtration within discrete lobules is probable.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ar.1092130405
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