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At least 73 records · Page 4Linked to original sources
PubMed2001

Effect of active shortening on the rate of ATP utilisation by rabbit psoas muscle fibres.

1. The rate of ATP utilisation during active shortening of single skinned fibres from rabbit psoas muscle at 10 degrees C was measured using an NADH-linked assay. Fibres were immersed in silicone oil and illuminated with 365 nm light. The amounts of NADH and carboxytetramethylrhodamine (CTMR) in the illuminated region of the fibre were measured simultaneously from fluorescence emission at 425-475 and 570-650 nm, respectively. The ratio of these two signals was used to determine the intracellular concentration of NADH, and thus the ATP utilisation, without interference from movements of the fibre with respect to the measuring light beam. 2. The total extra ATP utilisation due to shortening (ATP) was determined by extrapolation of the steady isometric rates before and after shortening to the mid-point of the shortening period. ATP had a roughly linear dependence on the extent of shortening in the range 1-15 % fibre length (L0) at a shortening velocity of 0.4 L0 s-1 from initial sarcomere length 2.7 microm. For shortening of 1 % L0, ATP was 21 +/- 1 M (mean +/- S.E.M., n = 3). 3. The mean rate of ATP utilisation during ramp shortening of 10 % L0 had a roughly linear dependence on shortening velocity in the range 0.05-1.2 L0 s-1. During unloaded shortening at 1.2 L0 s-1 the mean rate of ATP utilisation was 1.7 mM s-1, about 9 times the isometric rate. ATP was roughly independent of shortening velocity, and was 84 +/- 9 microM (mean +/- S.E.M., n = 6) for shortening of 10 % L0. 4. The implications of these results for mechanical-chemical coupling in muscle are discussed. The total ATP utilisation associated with shortening of 1 % L0 is only about 17 % of the concentration of the myosin heads in the fibre, suggesting that during isometric contraction either less than 17 % of the myosin heads are attached to actin, or that heads can detach without commitment to ATP splitting. The fraction of myosin heads attached to actin during unloaded shortening is estimated from the rate of ATP utilisation to be less than 7 %.

Adenosine Triphosphate↗
PubMed2002

Spontaneous haematoma of the iliac psoas muscle: a case report and review of the literature.

Spontaneous haematomas of the iliac psoas muscle are rare lesions seen in patients receiving anticoagulant agents or suffering from clotting disorders. We report the rare case of a spontaneous iliac psoas haematoma causing femoral neuropathy in a patient not undergoing anticoagulant treatment or suffering from a coagulopathy. After conservative treatment the patient was entirely asymptomatic, and magnetic resonance imaging demonstrated complete dissolution of the haematoma. Spontaneous iliac psoas haematomas should be considered in the differential diagnosis of leg pain in otherwise healthy patients.

Adult↗
PubMed1992

Effects of ethylene glycol and calcium on the kinetics of contraction induced by photo-release of low concentrations of ATP in rat psoas muscle fibres.

To induce isometric contraction in the absence of Ca2+ (10 mM EGTA), low concentrations (130 microM) of ATP were photoreleased from caged ATP in skinned fibres from rat psoas muscle at 15-16 degrees C. The magnitude of contraction was independent of the concentration of EGTA (1-30 mM). Each isometric transient (i) was paired with another (s) obtained under the same conditions but with 0.4% muscle stretch to elevate the rigor force before photolysis. The algebraic difference (d) between i and s was assumed to represent detachment of the crossbridges. The time course of force development (f) by the reattached crossbridges could be estimated by subtracting an appropriately scaled d from i (or s). Ethylene glycol (20% in solvent) reduced the magnitude and the rate of rise of f, although it scarcely affected d, suggesting that ethylene glycol inhibited reattachment of the crossbridges but not their detachment. The presence of Ca2+ (50 microM) increased the magnitude of f, but did not affect its time course (130 microM ATP). Detachment, d, was not influenced by Ca2+ in terms of both extent and rate. The effect of Ca2+ in the presence of ethylene glycol was indistinguishable from that in its absence. Ethylene glycol did not seem to substantially affect the extent of Ca-regulation on the contractile activity.

Adenosine Triphosphate↗
PubMed1986

The concentrations of glucose 1,6-bisphosphate and other regulatory metabolites, and the activities of enzymes of the glycogen metabolism in the perfused rabbit psoas muscle.

The following parameters were determined in the rabbit psoas muscle after perfusion in the presence of either insulin, propranolol, or isoproterenol: Concentrations of cyclic AMP, glucose 1,6-bisphosphate, fructose 2,6-bisphosphate, glucose-1-phosphate, glucose 6-phosphate, and fructose-1,6-bisphosphate. Maximum and "regulatory" activities of the enzymes glycogen phosphorylase, glycogen synthase, phosphofructokinase, and histone-phosphorylating protein kinase.

Animals↗
PubMed1981

Effect of ATP concentration and pH on rigor tension development and dissociation of rigor complex in glycerinated rabbit psoas muscle fiber.

Isometric rigor tension development of glycerinated rabbit psoas muscle fibers in a medium, due to the formation of rigor complexes, was estimated at varying ATP concentrations from 0 to 2.5 mM and pH values from 6.75 to 8.20. The dissociation of rigor complexes was also estimated under the same conditions. When muscle fibers developed rigor tension from the relaxed and rigor states, the magnitude of rigor tension increased with increasing concentration of ATP. Transition between rigor and relaxation in single fibers occurred discontinuously at constant levels (critical levels) of ATP which were determined by pH. The critical concentrations of ATP necessary for inducing the transitions between rigor and relaxed states were also increased exponentially with increased pH. Incomplete repetition of tension development by the same fiber was also observed. This incomplete reversibility was divided into two types: one which showed a decay in rigor tension and another which showed no decay. The reason for the incomplete reversibility was discussed

Adenosine Triphosphate↗
PubMed1993

State-dependent radial elasticity of attached cross-bridges in single skinned fibres of rabbit psoas muscle.

1. In a single skinned fibre of rabbit psoas muscle, upon attachment of cross-bridges to actin in the presence of ADP or pyrophosphate (PP(i)), the separation between the contractile filaments, as determined by equatorial X-ray diffraction, is found to decrease, suggesting that force is generated in the radial direction.2. The single muscle fibres were subjected to compression by 0-8% of dextran T(500). The changes in lattice spacings by dextran compression were compared with changes induced by cross-bridge attachment to actin. Based on this comparison, the magnitude and the direction of the radial force generated by the attached cross-bridges were estimated. The radial cross-bridge force varied with filament separation, and the magnitude of the radial cross-bridge force reached as high as the maximal axial force produced during isometric contraction.3. One key parameter of the radial elasticity, i.e. the equilibrium spacing where the radial force is zero, was found to depend on the ligand bound to the myosin head. In the presence of ADP, the equilibrium spacing was 36 nm. In the presence of MgPP(i) the equilibrium spacing shifted to 35 nm and Ca(2+) had little effect on the equilibrium spacing.4. The equilibrium spacing was independent of the fraction of cross-bridges attached to actin. The fraction of cross-bridges attached in rigor was modulated from 100% to close to 0% by adding up to 10 mM of ATPgammaS in the rigor solution. The lattice spacing remained at 38 nm, the equilibrium spacing for nucleotide-free cross-bridges at mu = 170 mM.5. Radial force generated by cross-bridges in rigor at large lattice spacings (38 nm </= d(10) </= 46 nm) appeared to vary linearly with lattice spacing.6. The titration of ATPgammaS to fibres in rigor provided a correlation between the radial stiffness of the nucleotide-free cross-bridges and the equatorial intensities. The relation between the equatorial intensity ratio I(11)/I(10) and radial stiffness appeared to be approximately linear.7. The fibres under different conditions showed a wide range of radial stiffness, which was not proportional to the apparent axial stiffness of the fibre. If the apparent axial stiffness is a measure of the fraction of cross-bridges bound to actin, it follows that the radial elastic constant is state dependent; or vice versa.8. Differences in equilibrium lattice spacing and in radial elastic constant, most probably reflect differences in the molecular structure of the acto-myosin complex and there is more than one single conformation of the various strongly bound cross-bridge states.9. Determining equilibrium spacings of the radial elasticity appears to be an effective new approach in detecting structural differences among the attached cross-bridges, since this approach is independent of the fraction of cross-bridges attached, a factor that frequently encumbers the interpretation of structural studies of attached cross-bridge states.

Journal Article↗
PubMed1987

Psoas muscle abscess due to Pasteurella multocida.

A 9-year-old girl with meningomyelocele, an ileal conduit and a living related kidney transplant presented with a progressive gait disturbance. Radiographic evaluation included a computerized tomography scan that disclosed a large right psoas muscle abscess. The abscess cavity was drained percutaneously and culture of its contents yielded Pasteurella multocida. This case illustrates an unusual presentation of a psoas muscle abscess caused by an uncommon organism that was diagnosed and treated by nonoperative methods.

Abscess↗
PubMed1992

Effects of ethylene glycol on the kinetics of contraction on flash photolysis of caged ATP in rat psoas muscle fibres.

ATP (1-1.2 mM) was photoreleased from caged ATP (5 mM) in skinned fibres from rat psoas muscle at 15-17 degrees C, to examine the effects of ethylene glycol (EG; 20% in solvent) on the kinetics of isometric contraction. Muscle fibres were stretched by 0.5-2% before photolysis, so that force just before photolysis was almost equal to the steady-state force after photolysis. At the phase of steady-state contraction, force and 500 Hz-stiffness in the presence of EG were 50% and 70% of the controls, respectively, resulting in a higher stiffness-to-force with EG, as reported previously. Following photolysis, force fell before rising to a steady-state plateau. The estimated rate constant of the force decay was approximately 90 s-1, and in the presence of EG was 80-85% of the control. This suggested a small effect of EG on the crossbridge detachment induced by ATP. The rate of force redevelopment was approximately 70 s-1, and EG decreased this rate to 50% of the control. This suggested that EG greatly slows the transition of the crossbridges from the detached state to the reattached force-producing state. The time course of the stiffness signals was consistent with this interpretation. The high stiffness-to-force ratio with EG indicated that EG not only reduces the rate constants which were directly examined in this study but also modifies other aspects of the crossbridge reaction.

Adenosine Triphosphate↗
PubMed2005

[Fistula between Wirsung and psoas muscle].

We describe a rare case of fistula between the Wirsung duct and the right psoas muscle. The initial clinical presentation was localised in the thigh and successful treatment was achieved by exclusive mini-invasive techniques.

Adult↗
PubMedDate not supplied

Thyroxine induced transformation in sarcoplasmic reticulum of rabbit soleus and psoas muscles.

The properties of the sarcoplasmic reticulum membranes isolated from slow-twitch type I soleus and fast-twitch type II psoas muscles of control and thyroxine treated rabbits were comparatively studied. Membrane yield, maximal calcium storing capacity, ATP-supported calcium uptake, calcium-dependent ATPase activity and calcium-dependent phosphoprotein formation were found to be 3-10 fold higher in psoas than in soleus preparations. Membrane yield, calcium-dependent ATPase activity, ATP-supported calcium transport and calcium-dependent phosphoprotein are at least twice enhanced in the membranes from soleus muscles of animals treated for 14-21 days with thyroxine. The corresponding capacities of the membranes from psoas muscles are not further augmented by the same thyroxine treatment. The maximal calcium storing capacity of the psoas membranes is their sole specific property which is significantly increased. The changes in the properties of the soleus muscles' sarcoplasmic reticulum membranes are engendered by an increase from 5 to 30-50% in the number of type II fibres. Since the calcium transporting properties of the sarcoplasmic reticulum membranes from type II fibres qualitatively differ from those of type I fibres, thyroxine does not only affect quantitative but also qualitative parameters of the muscles' sarcoplasmic reticulum membrane system.

Adenosine Triphosphatases↗
PubMed1994

Activation dependence and kinetics of force and stiffness inhibition by aluminiofluoride, a slowly dissociating analogue of inorganic phosphate, in chemically skinned fibres from rabbit psoas muscle.

To examine the mechanism by which aluminiofluoride, a tightly binding analogue of inorganic phosphate, inhibits force in single, chemically skinned fibres from rabbit psoas muscle, we measured the Ca(2+)-dependence of the kinetics of inhibitor dissociation and the kinetics of actomyosin interactions when aluminiofluoride was bound to the crossbridges. The relation between stiffness and the speed of stretch during small amplitude ramp stretches (< 5 nm per h.s.) was used to characterize the kinetic properties of crossbridges attached to actin; sarcomere length was assessed with HeNe laser diffraction. During maximum Ca(2+)-activation at physiological ionic strength (pCa 4.0, 0.2 M gamma/2), stiffness exhibited a steep dependence on the rate of stretch; aluminiofluoride inhibition at pCa 4.0 (0.2 M gamma/2) resulted in an overall decrease in stiffness, with stiffness at high rates of stretch (10(3)-10(4) nm per h.s. per s) being disproportionately reduced. Thus the slope of the stiffness-speed relation was reduced during aluminiofluoride inhibition of activated fibres. Relaxation of inhibited fibres (pCa 9.2, 0.2 M gamma/2) resulted in aluminiofluoride being 'trapped' and was accompanied by a further decrease in stiffness at all rates of stretch which was comparable to that found in control relaxed fibres. In relaxed, low ionic strength conditions (pCa 9.2, 0.02 M gamma/2) which promote weak crossbridge binding, stiffness at all rates of stretch was significantly inhibited by aluminiofluoride 'trapped' in the fibre. To determine the Ca(2+)-dependence of inhibitor dissociation, force was regulated independent of Ca2+ using an activating troponin C (aTnC). Results obtained with a TnC-activated fibres confirmed that there is no absolute requirement for Ca2+ for recovery from force inhibition by inorganic phosphate analogues in skinned fibres; the only requirement is thin filament activation which enables active crossbridge cycling. These results indicate that aluminiofluoride preferentially inhibits rapid equilibrium or weak crossbridge attachment to actin, that aluminiofluoride-bound crossbridges attach tightly to the activated thin filament, and that, at maximal (or near-maximal) activation, crossbridge attachment to actin prior to inorganic phosphate analogue dissociation is the primary event regulated by Ca2+.

Actomyosin↗
PubMed2005

Endothermic force generation, temperature-jump experiments and effects of increased [MgADP] in rabbit psoas muscle fibres.

We studied, by experiment and by kinetic modelling, the characteristics of the force increase on heating (endothermic force) in muscle. Experiments were done on maximally Ca2+-activated, permeabilized, single fibres (length approximately 2 mm; sarcomere length, 2.5 microm) from rabbit psoas muscle; [MgATP] was 4.6 mM, pH 7.1 and ionic strength was 200 mM. A small-amplitude (approximately 3 degrees C) rapid laser temperature-jump (0.2 ms T-jump) at 8-9 degrees C induced a tension rise to a new steady state and it consisted of two (fast and slow) exponential components. The T-jump-induced tension rise became slower as [MgADP] was increased, with half-maximal effect at 0.5 mM [MgADP]; the pre- and post-T-jump tension increased approximately 20% with 4 mM added [MgADP]. As determined by the tension change to small, rapid length steps (<1.4%L0 complete in <0.5 ms), the increase of force by [MgADP] was not associated with a concomitant increase of stiffness; the quick tension recovery after length steps (Huxley-Simmons phase 2) was slower with added MgADP. In steady-state experiments, the tension was larger at higher temperatures and the plot of tension versus reciprocal absolute temperature was sigmoidal, with a half-maximal tension at 10-12 degrees C; the relation with added 4 mM MgADP was shifted upwards on the tension axis and towards lower temperatures. The potentiation of tension with 4 mM added MgADP was 20-25% at low temperatures (approximately 5-10 degrees C), but approximately 10% at the physiological temperatures (approximately 30 degrees C). The shortening velocity was decreased with increased [MgADP] at low and high temperatures. The sigmoidal relation between tension and reciprocal temperature, and the basic effects of increased [MgADP] on endothermic force, can be qualitatively simulated using a five-step kinetic scheme for the crossbridge/A-MATPase cycle where the force generating conformational change occurs in a reversible step before the release of inorganic phosphate (P(i)), it is temperature sensitive (Q10 of approximately 4) and the release of MgADP occurs by a subsequent, slower, two-step mechanism. Modelling shows that the sigmoidal relation between force and reciprocal temperature arises from conversion of preforce-generating (A-M.ADP.P(i)) states to force-bearing (A-M.ADP) states as the temperature is raised. A tension response to a simulated T-jump consists of three (one fast and two slow) components, but, by combining the two slow components, they could be reduced to two; their relative amplitudes vary with temperature. The model can qualitatively simulate features of the tension responses induced by large-T-jumps from low starting temperatures, and those induced by small-T-jumps from different starting temperatures and, also, the interactive effects of P(i) and temperature on force in muscle fibres.

Adenosine Diphosphate↗
PubMed1985

Fluorescence properties and contraction characteristics of ANM (N-(1-anilinonaphthyl-4)maleimide)-labeled rabbit psoas muscle fibers.

Fluorescence spectra of ANM-labeled, glycerinated rabbit psoas muscle fibers were recorded in relaxed, contracted, and rigor states. SDS polyacrylamide gel electrophoresis of the ANM-labeled muscle fibers indicated that proteins labeled with ANM were myosin heavy chain, C protein, and actin. In a relaxed state in the presence of ATP, myosin heavy chain was mainly labeled. During the transition from rigor to the relaxed or contracted state, there was a blue shift (about 5 nm) of the ANM emission spectrum. Similar experiments with FAM (N-(3-fluoranthyl)-maleimide)-labeled muscle fibers showed that these fluorescence changes were not artifacts due to the movement of muscle fibers. The fibers labeled in the ATP relaxing solution showed a marked decrease in both isometric force and unloaded shortening velocity (Vo), while in the fibers labeled in the rigor solution isometric tension was not markedly suppressed, though Vo decreased to the same extent as in the fibers labeled in the ATP relaxing solution. Fluorescence spectra of ANM-labeled HMM in different states were also measured. A fluorescence enhancement and a blue shift (about 5 nm) of the emission maximum were observed in HMM + MgATP or HMM + MgATP + F-actin in comparison with HMM + F-actin. These results suggest that the fluorescence spectra of the ANM-labeled muscle fibers reflect their conformational changes between the rigor state (in the absence of MgATP) and the relaxed or contracted state (in the presence of MgATP).

Actomyosin↗
PubMed2005

Interexaminer reliability of the deltoid and psoas muscle test.

OBJECTIVE: To determine if 2 practitioners of differing skill levels could reliably agree on the presence of a weak or strong deltoid or psoas muscle. STUDY DESIGN: Interexaminer reliability study of 2 common muscle tests. MAIN OUTCOME MEASURES: Cohen kappa (unweighted) scores, observer agreement, and 95% confidence intervals (CIs). RESULTS: The results showed that an experienced and a novice practitioner have good agreement when using repeated muscle test procedures on the deltoid ( kappa 0.62) and the psoas ( kappa 0.67). CONCLUSIONS: The manual muscle test procedures using the anterior deltoid or psoas showed good interexaminer reliability when used by an experienced and a novice user. These techniques may be used between practitioners in multidoctor assessment/management programs.

Adult↗
PubMed2000

Psoas muscle and lumbar spine stability: a concept uniting existing controversies. Critical review and hypothesis.

Psoas muscle (PM) function with regard to the lumbar spine (LS) is disputed. Electromyographic studies attribute to the PM a possible role as stabilizer. Anatomical textbooks describe the PM as an LS flexor, but not a stabilizer. According to more recent anatomical studies, the PM does not act on the LS, because it tends to pull the LS into more lordosis by simultaneously flexing the lower and extending the upper region, but due to the short moment arms of its fascicles, this would require maximal muscular effort and would expose the LS motion segments to dangerous compression and shear. The findings of the present study indicate that the described opposite action of the PM on upper and lower LS regions, performed passively and requiring minimal muscular effort, may serve to stabilize the LS in an upright stance. It was demonstrated that a vertically placed elastic metal strip, modelled into a lordotic configuration to imitate the LS, will be brought into more lordosis, with maintenance of vertical position, if a string fastened at its upper end is pulled downward in a very specific direction. Conversely, any increase of lordosis of the strip brought about by vertical downward pushing of its top, will be stabilized by tightening the pulling string in the same specific direction. As this direction corresponded with the psoas orientation, the experiments show that the PM probably functions as a stabilizer of the lordotic LS in an upright stance by adapting the state of contraction of each of its fascicles to the momentary degree of lordosis imposed by factors outside the LS, such as general posture, general muscle activity and weight bearing. The presence of multiple PM fascicles, all of about equal length, and attaching to all LS levels, facilitates this function.

Biomechanical Phenomena↗