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PubMed1996

Orientation changes in myosin regulatory light chains following photorelease of ATP in skinned muscle fibers.

The orientation of the light-chain region of myosin heads in muscle fibers was followed by polarized fluorescence from an extrinsic probe during tension transients elicited by photolysis of caged ATP. Regulatory light chain from chicken gizzard myosin was covalently modified with iodoacetamidotetramethylrhodamine and exchanged into skinned fibers from rabbit psoas muscle without significant effect of the tension transients. Fluorescence polarization ratios Q parallel = (parallel I parallel-perpendicular I parallel)/ (parallel I parallel+perpendicular I parallel) and Q perpendicular = perpendicular I perpendicular - parallel I perpendicular)/ (perpendicular I perpendicular + parallel I perpendicular), where mIn denote fluorescence intensities for excitation (pre-subscript) and emission (post-subscript) parallel or perpendicular to the fiber axis, were simultaneously measured at 0.5 ms time resolution. Q perpendicular decreased and Q parallel increased promptly after ATP release in the presence or absence of CA2+, indicating changes in orientation of the light-chain region associated with ATP binding or cross-bridge detachment. Little further change in the Q signals accompanied either active tension development (+Ca2+) or the final relaxation (-Ca2+). The Q and tension transients slowed when liberated ATP concentration was reduced. Assuming that ATP is released at 118 s-1 (20 degrees C), the apparent second-order rate constants were 3-10 x 10(5) M-1 s-1 for Q parallel, 1-5 x 10(5) M-1 s-1 for Q perpendicular, and 0.5-2 x 10(5) M-1 s-1 for the convergence of tension traces starting from different rigor values. Fitting of model orientation distributions to the Q signals indicated that the angular disorder increases after ATP binding. This orientation change is specific to ATP because photo release of ADP caused much smaller changes in the Q signals.

Adenosine Diphosphate↗

PubMed1994

Unloaded shortening of skinned muscle fibers from rabbit activated with and without Ca2+.

Unloaded shortening velocity (VUS) was determined by the slack method and measured at both maximal and submaximal levels of activation in glycerinated fibers from rabbit psoas muscle. Graded activation was achieved by two methods. First, [Ca2+] was varied in fibers with endogenous skeletal troponin C (sTnC) and after replacement of endogenous TnC with either purified cardiac troponin C (cTnC) or sTnC. Alternatively, fibers were either partially or fully reconstituted with a modified form of cTnC (aTnC) that enables force generation and shortening in the absence of Ca2+. Uniformity of the distribution of reconstituted TnC across the fiber radius was evaluated using fluorescently labeled sTnC and laser scanning fluorescence confocal microscopy. Fiber shortening was nonlinear under all conditions tested and was characterized by an early rapid phase (VE) followed by a slower late phase (VL). In fibers with endogenous sTnC, both VE and VL varied with [Ca2+], but VE was less affected than VL. Similar results were obtained after extraction of TnC and reconstitution with either sTnC or cTnC, except for a small increase in the apparent activation dependence of VE. Partial activation with aTnC was obtained by fully extracting endogenous sTnC followed by reconstitution with a mixture of aTnC and cTnC (aTnC:cTnC molar ratio 1:8.5). At pCa 9.2, VE and VL were similar to those obtained in fibers reconstituted with sTnC or cTnC at equivalent force levels. In these fibers, which contained aTnC and cTnC, VE and VL increased with isometric force when [Ca2+] was increased from pCa 9.2 to 4.0. Fibers that contained a mixture of a TnC and cTnC were then extracted a second time to selectively remove cTnC. In fibers containing aTnC only, VE and VL were proportional to the resulting submaximal isometric force compared with maximum Ca(2+)-activated control. With aTnC alone, force, VE, and VL were not affected by changes in [Ca2+]. The similarity of activation dependence of VUS whether fibers were activated in a Ca(2+)-sensitive or -insensitive manners implies that VUS is determined by the average level of thin filament activation and that, with sTnC or cTnC, VUS is affected by Ca2+ binding to TnC only.

Animals↗

PubMed1996

Iliacus pyomyositis mimicking septic arthritis of the hip joint.

The iliacus muscle is closely associated with the psoas muscle, femoral nerve, hip joint, pelvic and intraabdominal structures; thus, its disorders may present as lower abdominal pain, hip pain, or femoral neuropathy. Iliacus pyomyositis, a primary bacterial infection of the skeletal muscle not secondary to a contiguous skin, bone, or soft-tissue infection, presenting as hip pain, femoral neuropathy, and sympathetic effusion of the hip joint in an 8-year-old boy mimicked septic arthritis of the hip joint. Computed tomography was helpful in delineating the accurate location of the lesion. Surgical drainage and appropriate antibiotic therapy led to complete resolution and full functional recovery.

Arthritis, Infectious↗

PubMed1994

Ultrastructure of skeletal muscle fibers studied by a plunge quick freezing method: myofilament lengths.

We have set up a system to rapidly freeze muscle fibers during contraction to investigate by electron microscopy the ultrastructure of active muscles. Glycerinated fiber bundles of rabbit psoas muscles were frozen in conditions of rigor, relaxation, isometric contraction, and active shortening. Freezing was carried out by plunging the bundles into liquid ethane. The frozen bundles were then freeze-substituted, plastic-embedded, and sectioned for electron microscopic observation. X-ray diffraction patterns of the embedded bundles and optical diffraction patterns of the micrographs resemble the x-ray diffraction patterns of unfixed muscles, showing the ability of the method to preserve the muscle ultrastructure. In the optical diffraction patterns layer lines up to 1/5.9 nm-1 were observed. Using this method we have investigated the myofilament lengths and concluded that there are no major changes in length in either the actin or the myosin filaments under any of the conditions explored.

Actin Cytoskeleton↗

PubMed1986

The fiber type of the rabbits' striated external urethral sphincter: electrophoretic analysis of myosin.

The fiber type of the rabbits' external urethral sphincter was investigated with O'Farrell's 2-dimensional electrophoresis of constituent proteins of glycerinated muscle, peptide mapping of myosin heavy chains and non-denaturing pyrophosphate gel electrophoresis of myosin. It was determined as fast type by all three methods. The relative proportions of muscle fibers which were estimated from myosin light chain contents were 88 per cent fast type and 12 per cent slow type. On the basis of the results presented, it was shown to be fast twitch muscle, but not identical to the psoas muscle.

Animals↗

PubMed1989

Modification of the contractile properties of rabbit skeletal muscle by ethylene glycol.

The effect of ethylene glycol on the contractile properties of skeletal muscles was studied using glycerinated rabbit psoas muscle fibers. Measurements were made at an ionic strength of 0.2 M, pH 7.0, and at 10 degrees C. Ethylene glycol reversibly reduced isometric tension, active stiffness, the tension-to-stiffness ratio, and the shortening velocity at zero load (Vo) in a dose-dependent fashion. Ethylene glycol also reduced the Ca sensitivity for contraction. The extent of the reduction in Vo by ethylene glycol was much larger than that in the actomyosin ATPase activity reported by Travers and Hillaire (Eur. J. Biochem. 98, 293-299 [1979]). Although ethylene glycol reduced tension and Vo, the MgATP concentration dependence of these two quantities was almost unaffected. These results suggest that in the presence of ethylene glycol, force produced by crossbridges in the principal force-producing state is reduced and/or the relative population of the attached crossbridges in the low-force state increases. The results also suggest that the reduction in Vo by ethylene glycol is caused not only by a reduction in the actomyosin ATPase activity but also by a reduction in the shortening distance per mole of ATP split.

Adenosine Triphosphate↗

PubMed1980

A method of locating the plane of CT scans of the abdomen.

Localization of the level of computed tomography (CT) sections and identification of the anatomical structures are prerequisites in the diagnostic process, A two-step method is described by which it is possible to determine quickly the plane of the CT scan of the abdomen using the spine as the reference landmark. The first step is to locate the level at which the vertebra under consideration is sectioned. The second, which consists of identifying the particular vertebra, is made by studying the topographical features of certain groups of paraspinal muscles, comprising mainly the diaphragmatic crura, psoas muscles, quadratus, lumborum, and the sacrospinalis.

Abdomen↗

PubMed1999

Fluorescence changes of a label attached near the myosin active site on nucleotide binding in rat skeletal muscle fibres.

1. Trinitrophenyl AMP (TNP-AMP) in the concentration range 10-300 microM induced an increase in fluorescence intensity at around 530 nm in skinned skeletal muscle fibres freshly obtained from rat psoas muscle. 2. The fluorescence intensity of the fibres depended on TNP-AMP concentration up to approximately 200 microM. The Kd of TNP-AMP binding to the muscle fibres was 38.0 +/- 8.4 microM (mean +/- s.d., n = 4 measurements) in three fibres. TNP-AMP fluorescence was readily washed out. 3. Various nucleotides affected the fluorescence of the fibres incubated in 20 microM TNP-AMP. MgATP (1 mM) and caged ATP (5 mM) reduced the fluorescence in 20 microM TNP-AMP by more than 40 % of the value measured in the absence of nucleotide. 4. When the fibres were stretched to almost no filament overlap, the extent of the quenching of the TNP-AMP (20 microM) fluorescence due to ATP binding was reduced by 14 %. This might be explained by assuming that the association of the thin filament affected the TNP-AMP fluorescence in muscle fibres. 5. The distance between the active site and the specific site for TNP was measured by the fluorescence resonance energy transfer between N-methylanthraniloyl-ATP (Mant-ATP) bound to the active site and the TNP-AMP bound to the TNP-specific site in muscle fibres. The results showed that the distance between the two may be less than 2 nm. 6. It may be concluded that the fluorescence intensity at 530 nm in skinned muscle fibres in low concentrations of TNP-AMP changes directly reflecting the conformational state of the nucleotide-binding region that is determined by the binding of nucleotides.

Adenosine Monophosphate↗

PubMed1982

Shortening induced deactivation of skinned fibres of frog and mouse striated muscle.

The depressant effect of active shortening, previously established in intact muscle fibres, was studied during calcium induced contractures of chemically skinned fibres from the semitendinosus muscle of Rana temporaria and the psoas muscle of the mouse. The decrease in contractile activity was determined by comparing the rate of force redevelopment (at a given tension level) after a large (test) and a small (control) release step. Under standard experimental conditions (ionic strength: frog 135 mM, mouse 190 mM; Ca2+ 3.0 microM; Mg2+: frog 25 microM, mouse 100 microM; MgATP2-: frog 1.0 mM, mouse 2.0 mM) active shortening of 0.15 microns per sarcomere (in excess of control release) reduced the contractile activity by approximately 50% of the control in both frog and mouse muscle fibres. Full contractile activity was regained within less than 4 s during isometric activity after the shortening phase. The depressant effect of shortening was steadily reduced, to almost complete disappearance of the effect, by increasing the free calcium concentration within the range 1.5-12.0 microM. Similarly, an increase in ionic strength from 105 to 235 mM reduced the depressant effect by approximately 40%. In contrast, there was a progressive enhancement of the shortening effect as the magnesium ion concentration was increased from 25 to 590 microM. It is proposed that interaction between the myosin cross-bridges and the thin filament during sarcomere shortening leads to a decrease in troponin-calcium binding resulting in a temporary deactivation of the contractile system.

Adenosine Triphosphate↗

PubMed1986

Acid and alkaline ceramidases of rat tissues.

Ceramidase (N-acylsphingosine deacylase) was measured in rat tissue homogenates with N-[1-14C]oleoyl- and N-[9,10-3H]palmitoyl-sphingosine. Two activities were observed with pH optima of approximately 5 and 8. The activity at pH 8 exceeded that at pH 5 in all tissues and tissue areas examined, and both activities decreased in the following order: kidney greater than brain stem greater than cerebrum greater than cerebellum greater than liver greater than spleen greater than cardiac muscle greater than lung greater than psoas muscle. The distribution of activity is not as tissue specific as that of neutral Mg2+-stimulated sphingomyelinase which is enriched in cells of neural origin and thus suggests a less specialized role for the alkaline ceramidase.

Amidohydrolases↗

PubMed1989

[Biochemical changes in skeletal muscles after chronic indirect stimulation].

The skeletal muscle has the capacity to respond adaptively to increased use. This observation could open up the feasibility of constructing pumping chambers to support or even replace cardiac work. We investigated the changes in enzyme activity due to chronic stimulation in an animal skeletal muscle. In 5 adult sheep the psoas muscle of one side was electrically stimulated through the muscle nerves, with an implantable stimulation unit for 5 weeks. The activity of the hexokinase (E.C.2.7.1.1.), lactate dehydrogenase (E.C.1.1.1.27), malate dehydrogenase (E.C.1.1.1.37), creatine kinase (E.C.2.7.3.2.) choline acetyltransferase and the contents of adenosine triphosphate and adenosine diphosphate were determined in bioptic specimen. The use of only 15 Hertz as a stimulation frequency led to a transformation of an originally fast-twitch muscle into a slow-twitch muscle with reduced susceptibility to fatigue. These results indicate a potential role of the skeletal muscle as an ideal myocardial substitute with the ability to perform hemodynamic work.

Adenosine Diphosphate↗

PubMed1977

Activity patterns of phosphofructokinase, glyceraldehydephosphate dehydrogenase, lactate dehydrogenase and malate dehydrogenase in microdissected fast and slow fibres from rabbit psoas and soleus muscle.

Methods for standardized determination of phosphofructokinase (PFK), glyceraldehydephosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) activities in nanogram samples of microdissected single fibres of rabbit psoas and soleus muscle are described. Fast and slow fibres in soleus muscle show lower absolute activities of these enzymes than the respective fibre types in psoas muscle. Slow fibres represent a more uniform population in the two muscles according to absolute and relative activities of the enzymes investigated. Slow fibres are characterized by high activities of MDH and relatively low activities of glycolytic enzymes. Fast fibres in the soleus muscle represent a population with high activities of MDH and glycolytic enzymes. Fast fibres in psoas muscle represent a heterogeneous population with high activities of glycolytic enzymes and extremely variable activity of MDH. More than 10-fold differences exist in the MDH activities of the extreme types of this fibre population. Differences in the activity levels of MDH in single fast type fibres but also in the activities of glycolytic enzymes between fast and slow fibres are greater than those reported between extreme white and red rabbit muscles.

Animals↗

PubMed2003

High mechanical efficiency of the cross-bridge powerstroke in skeletal muscle.

We were interested to estimate the maximum mechanical efficiency with which chemical energy derived from ATP hydrolysis is converted into mechanical work by individual cross-bridges when they perform their powerstroke synchronously. Glycerinated rabbit psoas muscle fibres, containing ATP molecules almost equal in number to the cross-bridges within the fibre, were activated to shorten under various afterloads by laser-flash photolysis of caged Ca(2+). In these conditions, almost all the cross-bridges are in the state where the ATP is hydrolyzed but the products have not yet been released from the cross-bridge (M-ADP-P(i)) immediately before activation, and can hydrolyze only one ATP molecule during the flash-induced mechanical response. Power output records of the fibres following activation indicated that the cross-bridges actually started their powerstroke almost synchronously. The amount of ATP utilized at 1 s after activation was estimated from the amount of isometric force developed after interruption of fibre shortening, while the amount of work done was calculated by multiplying the amount of afterload by the distance of fibre shortening. A conservative estimation of the maximum mechanical efficiency at a load of 0.5-0.6 P(o) was 0.7, suggesting that the actual maximum mechanical efficiency of cross-bridge powerstrokes may be close to unity.

Adenosine Triphosphate↗

PubMed1990

Hydrostatic pressure studies of native and synthetic thick filaments: II. Native thick filaments from rabbit skeletal muscle.

Native thick filaments isolated from freshly prepared rabbit psoas muscle were found to be resistant to pressure-induced dissociation. With increasing pressure application and release, a bimodal distribution of filament lengths was observed. The shorter filament length is associated with filament breakage at the center of the bare zone, while the longer length is associated with relatively intact filaments. Intact filaments and filament halves decrease in length by no more than 20% after exposure to and release of 14,000 psi. Bimodal distributions were not observed in equivalent experiments performed on filaments isolated from muscle glycerinated and stored at -20 degrees C for 6 months. Instead, filament dissociation proceeds linearly as a function of increasing pressure. Filaments prepared from muscle glycerinated and stored for 2 and 4 months exhibited pressure-induced behavior intermediate between the filaments prepared from fresh muscle and filaments prepared from muscle stored for 6 months. Since there appears to be no difference in the protein profiles of the various muscle samples, it is possible that stabilization of the native thick filament against hydrostatic pressure arises from trapped ions that are leached out over time.

Actin Cytoskeleton↗

PubMedDate not supplied

[Effect of vanadate on Ca++-activation in skeletal muscle].

Vanadate (0.1 mM) reduces tension of glycerinated rabbit psoas muscle fibers, shifts tension--pCa curve to lower pCa, increases the rate constant of delayed tension development and changes dependence of this rate constant on the level of Ca2+-activation. Vanadate influence stops the increase of the rate constant with the rise of Ca++-activated tension. Since actin-myosin-ADP complex is dissociated by vanadate, the muscle performance at low activation levels is supposed to be conditioned largely by the cross-bridges interacting with actin of the actin blocks switched on by myosin-ADP. Kinetics of such cross-bridges differs from that of the cross bridges interacting with actin activated by Ca++ binding to troponin C.

Actins↗

PubMed1996

The ileopsoas tunnel, a new antireflux technique for ureteroileal reimplantation: an experimental study in dogs.

A new antirefluxing ureteroileal anastomosis is described in which the implanted ureter is placed between the ileal segment and psoas muscle. The procedure was studied in eight experimental dogs, which were observed for 20 weeks. Radiologic and bacteriologic examinations, necropsy assessment and histopathologic results provided evidence that this ileo-psoas tunnel technique allows a unidirectional, non-obstructed flow of urine. The technique could be applied when ileal replacement of the ureter is necessary or in association with continent bladder replacement.

Anastomosis, Surgical↗

PubMed2002

The vaginal-psoas suspension repair of uterovaginal prolapse.

BACKGROUND: This article introduces a novel technique for the abdominal suspension of the prolapsed vagina. A Gore-Tex (WL Gore & Associates, Flagstaff, AZ) graft interposition between the vaginal apex and the right psoas muscle is performed under direct visualization to effect the repair. STUDY DESIGN: Between June 1998 and June 2001, seven consecutive cases of uterovaginal prolapse were repaired abdominally using the vaginal-psoas technique as outlined here. Patients were followed postoperatively for recurrent prolapse, urinary incontinence, and the development of new or progressive pelvic support defects. RESULTS: The mean operative time was 134 minutes, and the mean blood loss was 160mL for all procedures. One patient was lost to followup after 2 months. The remaining six patients have a median followup of 22 months (range 4 to 36 months), and in these patients, there have been no instances of recurrent prolapse or urinary dysfunction. One patient developed a progression of her rectocele. There were no peroperative or postoperative complications directly related to the procedure. Specifically, there were no instances of hemorrhage, transfusion, small bowel obstruction, graft erosion, or genitofemoral neuropathy. CONCLUSIONS: The vaginal-psoas colposuspension appears to be a simple, efficacious technique for the repair of uterovaginal prolapse. No significant morbidity directly related to the procedure has occurred to date. Further studies with longer followup will be required in the future before definitive conclusions can be reached.

Aged↗

PubMed1997

Length-dependence of actin-myosin interaction in skinned cardiac muscle fibers in rigor.

It has been suggested that the length dependence of myofilament Ca2+ sensitivity and of Ca2+ binding to troponin C, observed over the ascending limb of the cardiac force-length curve, is based on variation in the number of interacting cross-bridges. This interaction would be reduced at short sarcomere length as a consequence of double overlap of oppositely polarized actin filaments and increased lateral separation of actin and myosin filaments. Based on current evidence, it is not clear to what extent the actin-myosin interaction is hindered at sarcomere lengths where Ca2+ sensitivity is reduced. We have used two biochemical assays to assess cross-bridge attachment in rigor muscle at sarcomere lengths corresponding to the ascending limb of the cardiac force-length curve. These are based on (1) the inhibition of K+-activated myosin ATPase by the complexation of actin with myosin, and (2) the enhancement of Ca2+ binding to troponin C by rigor bridge attachment to actin. Measurements were made with skinned fibers from bovine ventricle. As a check on our method, measurements were also made with skinned rabbit psoas muscle fibers. With both muscle types, a reduction in sarcomere length along the ascending limb of the force-length curve was associated with an increase in K+-activated ATPase activity and a reduction in Ca2+ binding to the regulatory sites of troponin C. These results indicate that actin-myosin interaction is significantly reduced at short sarcomere length.

Actins↗