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Force Development (force + development)
Selected AbstractsCardiac and coronary function in the Langendorff-perfused mouse heart modelEXPERIMENTAL PHYSIOLOGY, Issue 1 2009Melissa E. Reichelt The Langendorff mouse heart model is widely employed in studies of myocardial function and responses to injury (e.g. ischaemia). Nonetheless, marked variability exists in its preparation and functional properties. We examined the impact of early growth (8, 16, 20 and 24 weeks), sex, perfusion fluid [Ca2+] and pacing rate on contractile function and responses to 20 min ischaemia followed by 45 min reperfusion. We also assessed the impact of strain, and tested the utility of the model in studying coronary function. Under normoxic conditions, hearts from 8-week-old male C57BL/6 mice (2 mm free perfusate [Ca2+], 420 beats min,1) exhibited 145 ± 2 mmHg left ventricular developed pressure (LVDP). Force development declined by ,15% (126 ± 5 mmHg) with a reduction in free [Ca2+] to 1.35 mm, and by 25% (108 ± 3 mmHg) with increased pacing to 600 beats min,1. While elevated heart rate failed to modify ischaemic outcome, the lower [Ca2+] significantly improved contractile recovery (by >30%). We detected minimal sex-dependent differences in normoxic function between 8 and 24 weeks, although age modified contractile function in males (increased LVDP at 24 versus 8 weeks) but not females. Both male and female hearts exhibited age-related reductions in ischaemic tolerance, with a significant decline in recovery evident at 16 weeks in males and later, at 20,24 weeks, in females (versus recoveries in hearts at 8 weeks). Strain also modified tolerance to ischaemia, with similar responses in hearts from C57BL/6, 129/sv, Quackenbush Swiss and FVBN mice, but substantially greater tolerance in BALB/c hearts. In terms of vascular function, baseline coronary flow (20,25 ml min,1 g,1) was 50,60% of maximally dilated flows, and coronary reactive and functional hyperaemic responses were pronounced (up to 4-fold elevations in flow in hearts lacking ventricular balloons). These data indicate that attention to age (and sex) of mice will reduce variability in contractile function and ischaemic responses. Even small differences in perfusion fluid [Ca2+] also significantly modify tolerance to ischaemia (whereas modest shifts in heart rate do not impact). Ischaemic responses are additionally strain dependent, with BALB/c hearts displaying greatest intrinsic tolerance. Finally, the model is applicable to the study of vascular reactivity, providing large responses and excellent reproducibility. [source] Caffeine and theophylline block insulin-stimulated glucose uptake and PKB phosphorylation in rat skeletal musclesACTA PHYSIOLOGICA, Issue 1 2010A. J. Kolnes Abstract Aim:, Caffeine and theophylline inhibit phosphatidylinositol 3-kinase (PI3-kinase) activity and insulin-stimulated protein kinase B (PKB) phosphorylation. Insulin-stimulated glucose uptake involves PI3-kinase/PKB, and the aim of the present study was to test the hypothesis that caffeine and theophylline inhibit insulin-stimulated glucose uptake in skeletal muscles. Methods:, Rat epitrochlearis muscles and soleus strips were incubated with insulin and different concentrations of caffeine and theophylline for measurement of glucose uptake, force development and PKB phosphorylation. The effect of caffeine was also investigated in muscles stimulated electrically. Results:, Caffeine and theophylline completely blocked insulin-stimulated glucose uptake in both soleus and epitrochlearis muscles at 10 mm. Furthermore, insulin-stimulated PKB Ser473 and Thr308 and GSK-3, Ser9 phosphorylation were blocked by caffeine and theophylline. Caffeine reduced and theophylline blocked insulin-stimulated glycogen synthase activation. Caffeine stimulates Ca2+ release and force development increased rapidly to 10,20% of maximal tetanic contraction. Dantrolene (25 ,m), a well-known inhibitor of Ca2+ -release, prevented caffeine-induced force development, but caffeine inhibited insulin-stimulated glucose uptake in the presence of dantrolene. Contraction, like insulin, stimulates glucose uptake via translocation of glucose transporter-4 (GLUT4). Caffeine and theophylline reduced contraction-stimulated glucose uptake by about 50%, whereas contraction-stimulated glycogen breakdown was normal. Conclusion:, Caffeine and theophylline block insulin-stimulated glucose uptake independently of Ca2+ release, and the likely mechanism is via blockade of insulin-stimulated PI3-kinase/PKB activation. Caffeine and theophylline also reduced contraction-stimulated glucose uptake, which occurs independently of PI3-kinase/PKB, and we hypothesize that caffeine and theophylline also inhibit glucose uptake in skeletal muscles via an additional and hitherto unknown molecule involved in GLUT4 translocation. [source] Potassium-transporting proteins in skeletal muscle: cellular location and fibre-type differencesACTA PHYSIOLOGICA, Issue 2 2010M. Kristensen Abstract Potassium (K+) displacement in skeletal muscle may be an important factor in the development of muscle fatigue during intense exercise. It has been shown in vitro that an increase in the extracellular K+ concentration ([K+]e) to values higher than approx. 10 mm significantly reduce force development in unfatigued skeletal muscle. Several in vivo studies have shown that [K+]e increases progressively with increasing work intensity, reaching values higher than 10 mm. This increase in [K+]e is expected to be even higher in the transverse (T)-tubules than the concentration reached in the interstitium. Besides the voltage-sensitive K+ (Kv) channels that generate the action potential (AP) it is suggested that the big-conductance Ca2+ -dependent K+ (KCa1.1) channel contributes significantly to the K+ release into the T-tubules. Also the ATP-dependent K+ (KATP) channel participates, but is suggested primarily to participate in K+ release to the interstitium. Because there is restricted diffusion of K+ to the interstitium, K+ released to the T-tubules during AP propagation will be removed primarily by reuptake mediated by transport proteins located in the T-tubule membrane. The most important protein that mediates K+ reuptake in the T-tubules is the Na+,K+ -ATPase ,2 dimers, but a significant contribution of the strong inward rectifier K+ (Kir2.1) channel is also suggested. The Na+, K+, 2Cl, 1 (NKCC1) cotransporter also participates in K+ reuptake but probably mainly from the interstitium. The relative content of the different K+ -transporting proteins differs in oxidative and glycolytic muscles, and might explain the different [K+]e tolerance observed. [source] Lithium and KB-R7943 effects on mechanics and energetics of rat heart muscleACTA PHYSIOLOGICA, Issue 1 2002P. Bonazzola ABSTRACT The role of calcium influx on energy expenditure during cardiac contraction was studied. For this purpose, the described ability of lithium and KB-R 7943 (KBR) to diminish Ca entry through Na,Ca exchanger (Ponce-Hornos & Langer, J Mol Cell Cardiol 1980, 12, 1367, Satoh et al., Circulation 2000, 101, 1441) were used. In isolated contractions (contractions elicited after at least 5 min of rest) LiCl 45 mmol L,1 decreased pressure developed and pressure,time integral from 42.3 ± 2.7 and 14.5 ± 1.2 to 32.1 ± 3.4 mN mm,2 and 8.3 ± 0.9 mN mm,2 s, respectively. A similar effect was observed in regular contractions (at 0.16 Hz stimulation). The presence of KBR (5 ,mol L,1) in the perfusate induced a slight but not significant decrease in pressure developed and pressure,time integral in steady-state contractions. As it was previously described, the heat involved in a heart muscle contraction can be decomposed into several components (H1, H2, H3 and H4), but only one (H3) was associated with force generation. While H3 decreased with lithium in both types of contractions, H3/PtI ratio remained unaltered, indicating that the economy for pressure maintenance was unaffected. To further investigate the role of Ca entry on force development, a condition in which the contraction is mainly dependent on extracellular calcium was studied. An ,extra' stimulus applied 200 ms after the regular one in a muscle stimulated at 0.16 Hz induces a contraction with this characteristic (Marengo et al., Am J Physiol 1999, 276, H309). Lithium induced a strong decrease in pressure,time integral and H3 associated with this contraction (43 and 45%, respectively) with no change in H3/PtI ratio. Lithium also reduced (53%) an energy component (H2) associated with Ca cycling. The use of KBR showed qualitatively similar results [i.e. a 33% reduction in pressure,time integral associated with the extrasystole (ES) with no changes in H3/PtI ratio and a 30% reduction in the H2 component]. Li and KBR effects appear to be additive and in the presence of 45 mmol L,1 Li and 5 ,mol L,1 KBR the extrasystole was abolished in 77%. Lithium and KBR effects particularly for the extrasystole can be explained through the inhibition of Ca entry via Na,Ca exchange giving support to the participation of the Na,Ca exchanger in the Ca influx from the extracellular space. In addition, the results also suggest the possibility of an effect of Li on an additional Ca sensitive locus (different than the Na,Ca exchanger). In this connection, in isolated contractions lithium decreased the energy release fraction related to mitochondrial processes (H4) increasing the economy of the overall cardiac contraction. [source] Susceptibility of isolated myofibrils to in vitro glutathionylation: Potential relevance to muscle functions,CYTOSKELETON, Issue 2 2010Chiara Passarelli Abstract In this study we investigated the molecular mechanism of glutathionylation on isolated human cardiac myofibrils using several pro-glutathionylating agents. Total glutathionylated proteins appeared significantly enhanced with all the pro-oxidants used. The increase was completely reversed by the addition of a reducing agent, demonstrating that glutathione binding occurs by a disulfide and that the process is reversible. A sensitive target of glutathionylation was ,-actin, showing a different reactivity to the several pro-glutathionylating agents by ELISA. Noteworthy, myosin although highly sensitive to the in vitro glutathionylation does not represent the primary glutathionylation target in isolated myofibrils. Light scattering measurements of the glutathionylated ,-actin showed a slower polymerisation compared to the non-glutathionylated protein and force development was depressed after glutathionylation, when the myofibrils were mounted in a force recording apparatus. Interestingly, confocal laser scanning microscopy of cardiac cryosections indicated, for the first time, the constitutive glutathionylation of ,-cardiac actin in human heart. Due to the critical location of ,-actin in the contractile machinery and to its susceptibility to the oxidative modifications, glutathionylation may represent a mechanism for modulating sarcomere assembly and muscle functionality under patho-physiological conditions in vivo. © 2009 Wiley-Liss, Inc. [source] Sensorimotor memory and grip force control: does grip force anticipate a self-produced weight change when drinking with a straw from a cup?EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003Dennis A. Nowak Abstract We examined whether self-generated weight changes are anticipated by adequate grip force adjustments when repeatedly lifting an instrumented manipulandum. Subjects lifted a cup filled with 500 mL of water prior to and following drinking two portions of water with a straw without touching it. One half of the subjects drank from and lifted an uncovered cup receiving constant visual information about its filling level and the other half of the subjects drank from a covered cup without such visual feedback. During the lifts immediately following the drinking procedures, grip force scaling was erroneously programmed for the heavier weight of the preceding lift as was obvious from an inadequately high rate of grip force development. Vision had only a minor influence on the rate of grip force increase. The influence of vision on the scaling of peak grip force was more pronounced. More accurate force scaling was obtained with an increasing number of lifts performed under each weight condition, indicating an ongoing force adjustment process probably based on sensory feedback. We conclude that self-generation of a change in the weight of an object to be lifted is not, in itself, sufficient to elicit a predictive grip force output. Rather, accurate feedback information associated with the self-generated weight change is essential to update internal models related to the mechanical object properties. This assumption was confirmed in pilot experiments; when subjects lifted the cup after having poured water from it, they accurately scaled their fingertip force to the self-produced weight change. Here, direct sensory feedback from the grasping fingers could signal the weight change and update internal models while pouring water from the cup. Our data support the hypothesis that the sensorimotor system planning and processing predictive fingertip force can operate independently of higher-level cognitive and perceptual systems. [source] Nitric oxide synthase inhibition reduces O2 cost of force development and spares high-energy phosphates following contractions in pump-perfused rat hindlimb musclesEXPERIMENTAL PHYSIOLOGY, Issue 3 2006David J. Baker The purpose of the present experiments was to test the hypotheses that: (i) nitric oxide synthase (NOS) inhibition reduces the O2 cost of force development across a range of contractile demands; and (ii) this reduced O2 cost of force development would be reflected in a sparing of intramuscular higher energy phosphates. Rat distal hindlimb muscles were pump perfused in situ and electrically stimulated (200 ms trains with pulses at 100 Hz, each pulse 0.05 ms duration) for 1 min each at 15, 30 and 60 tetani min,1 and for 2 min at 90 tetani min,1 in three groups: 0.01 mm adenosine; 1 mm d -NAME and 0.01 mm adenosine (d -NAME); and 1 mm l -NAME and 0.01 mm adenosine (l -NAME). The gastrocnemius,plantaris,soleus muscle group was freeze clamped post-contractions for metabolite analyses. Force was 19% higher and oxygen uptake was 20% lower with l -NAME versus adenosine, and there was a 35% reduction in /time-integrated tension versus adenosine and 24% versusd -NAME that was independent of contraction frequency. l -NAME treatment produced a 33% sparing of muscle phosphocreatine (PCr), and intramuscular lactate was no different between groups. In contrast, d -NAME reduced force by 30%, by 29% and the O2 cost of force development by 15% compared with adenosine, but had no effect on the degree of intramuscular ATP and PCr depletion. These results show that NOS inhibition improved the metabolic efficiency of force development, either by improving the ATP yield for a given O2 consumption or by reducing the ATP cost of force development. In addition, these effects were independent of contraction frequency. [source] Grip force abnormalities in de novo Parkinson's diseaseMOVEMENT DISORDERS, Issue 5 2004Stuart J. Fellows PhD Abstract In recent years it has been shown that a variety of movement disorders are associated with abnormalities of the fine motor control of the hand. In Parkinson's disease (PD), these changes consist of a slowing of the rate of grip force development and the use of abnormally large grip forces both during lifting and static holding of an object. It has been suggested, however, that these changes are a direct effect of the patient's levodopa medication or associated with levodopa induced dyskinesias. Accordingly, we examined the performance of de novo Parkinson patients in a precision lifting task. All patients (n = 6) were newly diagnosed and showed rigidity, bradykinesia, or both, but were unaffected by tremor or dyskinesia. None of the patients had received antiparkinson medication. Grip force was abnormally high in both the lifting and hold phases. This exaggeration was equal in magnitude to that observed previously in medicated patients. Thus we conclude that the abnormalities in grip force observed here are intrinsic features of PD and not the result of dopamine medication or its side effects. © 2004 Movement Disorder Society [source] Contractile properties of the proximal urethra and bladder in female pig: Morphology and functionNEUROUROLOGY AND URODYNAMICS, Issue 1 2006J.J.M. Pel Abstract Aims To compare the contractile properties of proximal urethral and bladder muscle of the female pig. Materials and Methods In two proximal segments (I and II) of the urethra, small muscle bundles were excised to measure the force-length (maximum force) and the force-velocity (unloaded shortening velocity) relation using the stop-test. The rate of force development was calculated using phase plots. Contractile properties of urethral and bladder segments were statistically compared using the Mann,Whitney U -test. Immunohistochemical staining of whole circumference urethral cross sections was used to identify the location of smooth and striated muscle fibres. Results On isometric force development, the urethral muscle bundles revealed a fast (,0.5 sec) and a slow (,2.1 sec) time constant, whereas in bladder only a slow (,2.3 sec) component was measured. On average, isometric force was highest in bladder. The length range over which force was produced was smallest in urethral segment II, followed by urethral segment I and finally bladder. The unloaded shortening velocity was 0.15, 0.25 and 0.35 1/sec, respectively. Histological preparations showed that smooth as well as striated muscle was present in proximal urethra. In urethral muscle bundles, spontaneous contractions were measured with a frequency of 0.4 Hz. Conclusions Differences in contractility found between urethra and bladder may be ascribed to the presence of striated muscle in the proximal urethra. The regulation of tone and spontaneous contractions may be part of the continence mechanism in the female pig urinary tract. © 2005 Wiley-Liss, Inc. [source] Influence of ionic strength on the time course of force development and phosphate release by dogfish muscle fibresTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Timothy G. West We measured the effects of ionic strength (IS), 200 (standard) and 400 mmol l,1 (high), on force and ATP hydrolysis during isometric contractions of permeabilized white fibres from dogfish myotomal muscle at their physiological temperature, 12°C. One goal was to test the validity of our kinetic scheme that accounts for energy release, work production and ATP hydrolysis. Fibres were activated by flash photolysis of the P3 -1-(2 nitrophenyl) ethyl ester of ATP (NPE-caged ATP), and time-resolved phosphate (Pi) release was detected with the fluorescent protein MDCC-PBP, N -(2[1-maleimidyl]ethyl)-7-diethylamino-coumarin-3-carboxamide phosphate binding protein. High IS slowed the transition from rest to contraction, but as the fibres approached the isometric force plateau they showed little IS sensitivity. By 0.5 s of contraction, the force and the rate of Pi release at standard and high IS values were not significantly different. A five-step reaction mechanism was used to account for the observed time courses of force and Pi release in all conditions explored here. Only the rate constants for reactions of ATP, ADP and Pi with the contractile proteins varied with IS, thus suggesting that the actin,myosin interactions are largely non-ionic. Our reaction scheme also fits previous results for intact fibres. [source] Contraction kinetics of isolated human myometrium during menstrual cycle and pregnancyBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 1 2000Mikhail Tchirikov Objective To investigate the interaction between actin and myosin in the myometrium by studying the contraction kinetics of isolated samples of human myometrium. Design Experimental and observational cross-sectional study. Setting Eppendorf University Hospital, Hamburg. Samples Myometrium samples were taken from women in the follicular phase (n= 6) or luteal phase (n= 6) of the menstrual cycle and during pregnancy at term (n= 25). Methods The frequency, extent and rate of force development were determined in spontaneously active myometrial preparations. From a resting force of 2 mN, sustained tonic contractions were induced by K+ -depolarisation (124 mM), or by protein kinase C activation (19.9 ,M indolactam). The steady force was reversibly interrupted by rapid length changes (100 Hz sinus vibrations lasting 1 s, 5% of muscle length). Extent (steady plateau), as well as rate of force increase after cessation of vibrations, were derived from bi-exponential functions fitted to the time course of force recovery. Results Frequency of spontaneous contractions was higher in the follicular phase [mean (SD) 18.3 contractions/hour (1.0)] than in the luteal phase [13.4 contractions/hour (8.1)] or in pregnancy at term [8.8 contractions/hour (7.6)]. During indolactam treatment, steady force in pregnancy at term was significantly increased [8.8 mN (4.0)], compared with the follicular phase [3.7 mN (0.9)]. Force recovery was distinctly slower in pregnancy at term during indolactam treatment [time constant 99.2 s (57.9); P < 0.005] than during K+ -depolarisation [time constant 29.1 s (5.9)], whereas in the follicular phase the rate of force recovery was faster with indolactam [16.8 s (7.1)] than with K+ depolarisation [24.4 s (5.9); P < 0.005]. Conclusions The responses of human myometrium to contraction stimuli differ according to the reproductive state. Membrane depolarisation causes similar responses in all myometrial strips. In contrast, near term stimulation of protein kinase C generates a large tonic force and slow contraction kinetics, whereas early in the menstrual cycle contraction kinetics are fast. [source] Intra- and extrarenal arteries exhibit different profiles of contractile responses in high glucose conditionsBRITISH JOURNAL OF PHARMACOLOGY, Issue 8 2008K Nobe Background and purpose: The renal artery (RA) has been extensively investigated for the assessment of renal vascular function/dysfunction; however, few studies have focused on the intrarenal vasculature. Experimental approach: We devised a microvascular force measurement system, which allowed us to measure contractions of interlobar arteries (ILA), isolated from within the mouse kidney and prepared without endothelium. Key results: KCl (50 mM) induced similar force development in the aorta and RA but responses in the ILA were about 50% lower. Treatment of RA with 10 ,M phenylephrine (PE), 10 nM U46619 (thromboxane A2 analogue) or 10 ,M prostaglandin F2, elicited a response greater than 150% of that induced by KCl. In ILA, 10 nM U46619 elicited a response that was 130% of the KCl-induced response; however, other agonists induced levels similar to that induced by KCl. High glucose conditions (22.2 mM glucose) significantly enhanced responses in RA and ILA to PE or U46619 stimulation. This enhancement was suppressed by rottlerin, a calcium-independent PKC inhibitor, indicating that glucose-dependent, enhanced small vessel contractility in the kidney was linked to the activation of calcium-independent PKC. Conclusion and implications: Extra- and intrarenal arteries exhibit different profiles of agonist-induced contractions. In ILA, only U46619 enhanced small vessel contractility in the kidney, which might lead to renal dysfunction and nephropathy through reduced intrarenal blood flow rate. A model has been established, which will allow the assessment of contractile responses of intrarenal arteries from murine models of renal disease, including type 2 diabetes. British Journal of Pharmacology (2008) 155, 1204,1213; doi:10.1038/bjp.2008.365; published online 22 September 2008 [source] The mechanism for the contraction induced by leukotriene C4 in guinea-pig taenia coliBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2001Satoshi Ieiri The mechanism underlying the LTC4 -induced contraction of guinea-pig taenia coli was determined using the simultaneous measurements of [Ca2+]i and force in whole muscle preparations. Additional experiments were performed in receptor coupled permeabilized preparation. For comparison purposes, the contraction which was induced by a typical G-protein mediated agonist, carbachol was also characterized. LTC4 induced a contraction in the guinea-pig taenia coli in a concentration-dependent manner. The maximal response was obtained at 100 nM and the EC50 value was 5.4±1.9 nM. Both LTC4 and carbachol induced increases in [Ca2+]i and force. The maximum force induced by 100 nM LTC4 was significantly smaller than that induced by 10 ,M carbachol, although an increase in [Ca2+]i produced by both agonists was similar. In the permeabilized preparations, carbachol, but not LTC4, induced an additional force development at a fixed Ca2+ concentration. LTC4 induced no increase in [Ca2+]i and force in the Ca2+ -free solution, while carbachol induced transient increases in both [Ca2+]i and force in a Ca2+ -free solution. Both diltiazem and SK&F 96365 significantly inhibited the LTC4, and carbachol-induced increases in [Ca2+]i and force in normal PSS. The inhibitory pattern of [Ca2+]i by these drugs was also similar. We thus conclude that LTC4 induces the contraction of the guinea-pig taenia coli mainly through Ca2+ influx via both the diltiazem-sensitive and SK&F 96365-sensitive Ca2+ channels, without affecting either the Ca2+ -sensitivity or the intracellular Ca2+ release. These results indicated that the mechanism underlying the LTC4 -induced contraction differs greatly from that for conventional G-protein mediated agonists, such as carbachol. British Journal of Pharmacology (2001) 133, 529,538; doi:10.1038/sj.bjp.0704122 [source] Load force during manual transport in Parkinson's diseaseACTA NEUROLOGICA SCANDINAVICA, Issue 6 2004X. Guo Objectives , To search for a physiological method for the measurement of upper extremity dexterity during activities of daily life in Parkinson's disease (PD). Materials and methods , We examined load force output during manual transport in seven patients with PD and 10 healthy controls. PD patients were measured in both the non-medicated and medicated states. The test movement included two continuous sub-movements: an upward-forward transport of an object from the table to the stand, and a downward-backward transport of the object from the stand to the table. Hand movements were recorded using an optoelectronic camera, and load force was measured using a force sensor installed in the test object. Results , Compared with the controls, PD patients had a different pattern of load force output characterized by slower force development and release, lower peak force, and less dynamic force generation during movement. After medication, the speed of force development and the level of peak force increased in the patients. Conclusions , These findings suggest that PD impairs the production of preprogrammed movements. The movements observed in the PD patients may result from compensatory strategies relying more on feedback mechanisms. [source] Isometric force development in human horizontal eye muscles and pulleys during saccadic eye movementsACTA OPHTHALMOLOGICA, Issue 8 2009Gunnar Lennerstrand Abstract. Purpose:, The connective tissue elements forming the check ligaments and portals of the human eye muscles have recently been ascribed with a pulley function. Active positioning of the pulleys over orbital layer contraction during eye movements has been suggested. Other studies have instead demonstrated fibrous tissue connections between all parts of the muscle and the pulleys. We aimed to compare the isometric force developed at the muscle tendon and at the pulleys of the horizontal eye muscles, and to investigate which eye muscle structures might exert force on the pulleys. Methods:, Isometric force development was recorded from the lateral and medial rectus muscles in six patients operated for strabismus under topical anaesthesia. Two strain gauge probes were used, each attached with 5,0 silk sutures either to the muscle tendon or to the pulley. The eye muscles were activated by horizontal saccadic eye movements in steps from 30 degrees in the off-direction to 30 degrees in the on-direction of the muscles. Results:, The forces developed at the tendon and pulley were almost identical with respect to amplitude and other parameters. No differences were found in forces developed at the pulleys of the medial and lateral rectus muscles. Conclusions:, The results support the presence of fibrous tissue connections between all eye muscle fibres and pulley structures, rather than orbital fibre control of the pulley. [source] | |||||||||||||