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PubMed1990

Effect of ADP on the orientation of spin-labeled myosin heads in muscle fibers: a high-resolution study with deuterated spin labels.

We have used electron paramagnetic resonance (EPR) to determine the effects of ADP on the orientational distribution of nitroxide spin labels attached to myosin heads in skinned rabbit psoas muscle fibers. To maximize the specificity of labeling, we spin-labeled isolated myosin heads (subfragment 1) on a single reactive thiol (SH1) and diffused them into unlabeled muscle fibers. To maximize spectral and orientational resolution, we used perdeuterated spin labels, 2H-MSL and 2H-IASL, eliminating superhyperfine broadening and thus narrowing the line widths. Two different spin labels were used, with different orientation relative to the myosin head, to ensure that the results are not affected by unfavorable probe orientation. In rigor, a very narrow three-line spectrum was observed for both spin labels, indicating a narrow orientational distribution, as reported previously (Thomas & Cooke, 1980). ADP induced very slight changes in the spectrum, corresponding to very slight (but significant) changes in the orientational distribution. These changes were quantified by a digital analysis of the spectra, using a two-step simplex fitting procedure (Fajer et al., 1990). First, the magnetic tensor values and line widths were determined by fitting the spectrum of a randomly oriented sample. Then the spectrum of oriented fibers was fit to a model by assuming a Gaussian distribution of the tilt angle (theta) and twist angle (phi) of the nitroxide principal axes relative to the fiber axis. A single-Gaussian distribution resulted in inadequate fits, but a two-component model gave excellent results. ADP induces a small (less than 5 degrees) rotation of the major components for both spin labels, along with a similarly small increase of disorder about the average positions.

Actin Cytoskeleton↗

PubMed1996

Orientation of paramagnetic probes attached to gizzard regulatory light chain bound to myosin heads in rabbit skeletal muscle.

The orientation of the myosin neck was monitored using electron paramagnetic resonance (EPR) spectroscopy. Gizzard regulatory light chain was labeled with a nitroxide spin probe and exchanged for the native subunit, located in the myosin neck, in rabbit psoas muscle fibers. The EPR spectra of rigor fibers indicated a substantial degree of probe immobilization and showed a strong dependence on the orientation of the fiber axis relative to the magnetic field, indicating that the neck was ordered in this state. Spectra of relaxed fibers at 24 degrees C showed that the neck was disordered, but the spectra of relaxed fibers at 4 degrees C indicated that the neck was partially ordered. Active fibers at the two temperatures produced spectra identical to relaxed fibers, indicating that no novel angles could be seen in the neck during the powerstroke. Proteolytic fragments of myosin, S1 and HMM, were exchanged with labeled light chains and bound to thin filaments in unlabeled fibers. The distribution of probe orientations for HMM was identical to that of labeled rigor fibers, while S1 showed a slightly different distribution, suggesting that the neck is distorted (by a few degrees) by the interactions of the two heads of myosin when bound to actin.

Animals↗

PubMed2004

Xanthogranulamatous pyelonephritis with psoas abscess: 2 cases and review of the literature.

Xanthogranulomatous pyelonephritis (XGP) is a rare form of chronic pyelonephritis. With the review of the literature, we reported two cases of XPN with psoas muscle abscesses caused by Staphylococci aereus in one of the patient and Serratia mascerentes in the other. Both of the patients had renal calculus. We performed nephrectomy with psoas abscess drainage and started appropriate antibiotics, but one of the patients died of septic shock. Other patient is free of symptoms at the end of 5 years follow-up.

Adolescent↗

PubMed2003

Acute femoral neuropathy secondary to an iliacus muscle hematoma.

We present a patient with a spontaneous iliacus muscle hematoma, appearing immediately after a minor physical maneuver, presenting with pain and femoral neuropathy initially evidenced by massive quadriceps muscle fasciculations. A magnetic resonance imaging (MRI) study of the pelvic area confirmed the diagnosis, showing a hematoma secondary to a partial muscle tear. The patient was managed conservatively, and the continuous muscle activity ceased in 3 days, with progressive improvement of the pain and weakness. The recovery was complete. Femoral neuropathy is uncommon and usually due to compression from psoas muscle mass lesions of diverse nature, including hematomas. Usually subacute, femoral neuropathy may present acutely in cases of large or strategically placed compressive femoral nerve lesions, and may require surgical evacuation. The case presented herein is remarkable since the muscle hematoma appeared after a nonviolent maneuver, fasciculations were present at onset, and conservative management was sufficient for a full recovery.

Acute Disease↗

PubMed1965

Anomalous contraction of invertebrate striated muscle.

The phenomenon of A band shortening or contraction has been investigated in glycerinated myofibrils of Pecten irradians, Homarus americanus, Cambarus virilis, and Limulus polyphemus through the techniques of ultraviolet microbeam inactivation and polarization microscopy. With the former method, it has been shown that these muscles, even though exhibiting the shortening effect, contract in a manner consistent with only the sliding filament model. Intrinsic birefringence studies have indicated no significant changes in mass distribution or orientation within the shortened A bands. Except in the case of Limulus muscle, the shortening effect was seen only in contraction under tension. The magnitude of this anomalous phenomenon was dependent upon glycerination time and has been duplicated in rabbit psoas muscle through brief trypsin treatment. A band shortening could not be observed in glutaraldehyde-fixed muscle or in myofibrils glycerinated for only short periods. It has been concluded that the phenomenon of A band contraction is an artifact induced by the glycerination procedure, possibly through weakening of the sarcomere structure. However, the fact that the A band shortens under tension rather than lengthens poses an interesting paradox.

Adenosine Triphosphate↗

PubMed1993

Inhibitory action of 4-aminopyridine on Ca(2+)-ATPase of the mammalian sarcoplasmic reticulum.

In the isolated guinea pig diaphragm muscle, 4-aminopyridine (4-AP) elicited a marked potentiation of twitch contraction evoked by direct electrical stimuli. Although tetraethylammonium (TEA) and charybdotoxin only slightly potentiated twitch contraction, 4-AP, but not TEA, also augmented a contractile response to caffeine. These effects of 4-AP on muscle contraction could not be interpreted by a simple inhibition of potassium channels on the plasma membrane. In the fragmented sarcoplasmic reticulum (SR) prepared from the guinea pig psoas muscle, 4-AP inhibited the ATP-driven Ca2+ uptake from the extravesicular medium. Furthermore, 4-AP at concentrations less than 10 mM elicited a selective inhibition of Ca(2+)-activated SR ATPase in a competitive manner against the Ca2+ concentration of the medium and 10 mM 4-AP showed the unsurmountable inhibition. 4-AP at 30 mM apparently inhibited activities of other ATPases such as Na+,K+- and myosin ATPases. In contrast, other potassium channel blockers such as TEA, apamin, charybdotoxin, and glibenclamide did not inhibit the SR function. These results suggest that, although the specific concentration range is rather small, 4-AP elicits an inhibition of SR Ca(2+)-pumping activity, leading to the marked potentiation of muscle contractile responses to electrical stimuli and caffeine.

4-Aminopyridine↗

PubMed1988

Architecture of the sarcomere matrix of skeletal muscle: immunoelectron microscopic evidence that suggests a set of parallel inextensible nebulin filaments anchored at the Z line.

Nebulin, a giant myofibrillar protein (600-800 kD) that is abundant (3%) in the sarcomere of a wide range of skeletal muscles, has been proposed as a component of a cytoskeletal matrix that coexists with actin and myosin filaments within the sarcomere. Immunoblot analysis indicates that although polypeptides of similar size are present in cardiac and smooth muscles at low abundance, those proteins show no immunological cross-reactivity with skeletal muscle nebulin. Gel analysis reveals that nebulins in various skeletal muscles of rabbit belong to at least two classes of size variants. A monospecific antibody has been used to localize nebulin by immunoelectron microscopy in a mechanically split rabbit psoas muscle fiber preparation. Labeled split fibers exhibit six pairs of stripes of antibody-imparted transverse densities spaced at 0.1-1.0 micron from the Z line within each sarcomere. These epitopes maintain a fixed distance to the Z line irrespective of sarcomere length and do not exhibit the characteristic elastic stretch-response of titin epitopes within the I band domain. It is proposed that nebulin constitutes a set of inextensible filaments attached at one end to the Z line and that nebulin filaments are in parallel, and not in series, with titin filaments. Thus the skeletal muscle sarcomere may have two sets of nonactomyosin filaments: a set of I segment-linked nebulin filaments and a set of A segment-linked titin filaments. This four-filament sarcomere model raises the possibility that nebulin and titin might act as organizing templates and length-determining factors for actin and myosin respectively.

Actins↗

PubMed1995

Psoas abscess due to mucinous cystadenocarcinoma of the appendix: a case report.

Psoas muscle abscess is an uncommon and challenging entity. The present report describes a 64-year-old man presenting with right flank mass. Abdominal computerized tomography showed a right psoas abscess. Extraperitoneal drainage was performed, and pathology revealed metastatic mucinous adenocarcinoma. After further study, laparotomy and right hemicolectomy were performed under the impression of colon cancer. The final pathology showed mucinous cystadenocarcinoma of appendix. The literature about the etiology, diagnosis and treatment of psoas abscess are reviewed. Additionally, the treatment and prognosis for mucinous cystadenocarcinoma of the appendix are noted.

Appendiceal Neoplasms↗

PubMed1997

The lumbar cord location of the motoneurons innervating psoas and iliacus muscles: a single and double labeling study in the female Syrian golden hamster.

The spinal cord location of the motoneurons innervating the psoas and iliacus muscles was determined in the golden hamster. The results of single and double labeling studies, using the retrograde tracers horseradish peroxidase (HRP) and cholera toxin B-subunit (CTB), showed that both psoas and iliacus motoneurons were present ventrolaterally in the ventral horn in the caudal L1 to rostral L5 lumbar spinal segments with their motoneurons intermingled in one cell group. Further retrograde tracing studies demonstrated abdominal muscle motoneurons ventrolaterally in the ventral horn of the L1 and upper L2 segments. Double labeling experiments revealed that at these levels (caudal L1 and rostral L2), the abdominal muscle motoneurons were located dorsomedial to the psoas and iliacus motoneurons.

Abdominal Muscles↗

PubMed1993

Tension transients initiated by photogeneration of MgADP in skinned skeletal muscle fibers.

Addition of MgADP to skinned skeletal muscle fibers causes a rise in Ca(2+)-activated isometric tension. Mechanisms underlying this tension increase have been investigated by rapid photogeneration of ADP within skinned single fibers of rabbit psoas muscle. Photolysis of caged ADP (P2-1(2-nitrophenyl)ethyladenosine 5'-diphosphate) resulted in an exponential increase in isometric tension with an apparent rate constant, kADP, of 9.6 +/- 0.3 s-1 (mean +/- SE, n = 28) and an amplitude, PADP, of 4.9 +/- 0.3% Po under standard conditions (0.5 mM photoreleased MgADP, 4 mM MgATP, pH 7.0, pCa 4.5, 0.18 M ionic strength, 15 degrees C). PADP depended upon the concentration of photoreleased MgADP as well as the concentration of MgATP. A plot of 1/PADP vs. 1/[MgADP] at three MgATP concentrations was consistent with competition between MgADP and MgATP for the same site on the crossbridge. The rate of the transient, kADP, also depended upon the concentration of MgADP and MgATP. At both 4 and 1 mM MgATP, kADP was not significantly different after photorelease of 0.1-0.5 mM MgADP, but was reduced by 28-40% when 3.5 mM MgADP was added before photorelease of 0.5 mM MgADP. kADP was accelerated by about twofold when MgATP was varied from 0.5 to 8 mM MgATP. These effects of MgATP and MgADP were not readily accounted for by population of high force-producing states resulting from reversal of the ADP dissociation process. Rather, the results suggest that competition between MgADP and MgATP for crossbridges at the end of the cycle slows detachment leading to accumulation of force-generating crossbridges. Elevation of steady-state Pi concentration from 0.5 to 30 mM caused acceleration of kADP from 10.2 +/- 0.5 to 27.8 +/- 1.8 s-1, indicating that the tension rise involved crossbridge flux through the Pi dissociation step of the cycle.

Adenosine Diphosphate↗

PubMed1992

Latent psoas abscess after anterior spinal fusion.

This case is presented to emphasize that late infection should be considered in all postoperative patients as a cause of pain. A psoas abscess may remain dormant for many years after an anterior spinal procedure. It should be considered in the differential diagnosis of back pain and lumbar radiculopathy after anterior spinal fusion. The lumbar nerve plexus lies within the psoas muscle, and referred pain patterns may occur in the lumbar nerve distribution. In this case, dysesthesias occurred in the distribution of the genitofemoral nerve. The diagnosis and treatment of a psoas abscess has been greatly aided by use of CT and ultrasound. Either of these modalities may be used for directed percutaneous drainage of the abscess. The presence of metal fixation devices necessitates removal of the hardware in order to ensure eradication of the infection.

Adolescent↗

PubMed1996

Calmidazolium alters Ca2+ regulation of tension redevelopment rate in skinned skeletal muscle.

To examine if the Ca2(+)-binding kinetics of troponin C (TnC) can influence the rate of cross-bridge force production, we studied the effects of calmidazolium (CDZ) on steady-state force and the rate of force redevelopment (ktr) in skinned rabbit psoas muscle fibers. CDZ increased the Ca2(+)-sensitivity of steady-state force and ktr at submaximal levels of activation, but increased ktr to a greater extent than can be explained by increased force alone. This occurred in the absence of any significant effects of CDZ on solution ATPase or in vitro motility of fluorescently labeled F-actin, suggesting that CDZ did not directly influence cross-bridge cycling. CDZ was strongly bound to TnC in aqueous solutions, and its effects on force production could be reversed by extraction of CDZ-exposed native TnC and replacement with purified (unexposed) rabbit skeletal TnC. These experiments suggest that the method of CDZ action in fibers is to bind to TnC and increase its Ca2(+)-binding affinity, which results in an increased rate of force production at submaximal [Ca2+]. The results also demonstrate that the Ca2(+)-binding kinetics of TnC influence the kinetics of ktr.

Actomyosin↗

PubMed1994

Secondary psoas abscess twenty-seven years after nephrectomy.

Abscesses of the psoas muscle are due to a hematogenous dissemination, to the spread of infection from adjacent intestinal structures, to osteomyelitis of the spine or to tuberculous infection of a disc space. In contrast, psoas abscesses related to the urological tract have only been described on exception. The present report focuses on a right psoas abscess which developed 27 years after a nephrectomy. The infectious process resulted from the spread of an acute vesical infection through the residual ureter. Analysis of 4 other cases reported in the literature allows us to delineate the clinical features of psoas abscesses of urological origin.

Aged↗

PubMed1980

Effects of glucocorticoids on peptide chain initiation in heart and skeletal muscle.

Treatment of rats for 5 days with cortisone acetate reduced synthesis of skeletal muscle protein by 56% compared to untreated controls, but had no effect on protein synthesis in heart. The reduction in synthesis in skeletal muscle was accounted for by both a loss of tissue RNA and development of a block in peptide-chain initiation. Activity of an eIF-2-like initiation factor decreased in psoas muscle of hormone-treated rats in proportion to the loss of RNA. Peptide-chain initiation, RNA content, and initiation factor activity were unaffected in heart muscle. In skeletal muscle of rats treated for 4 hr with dexamethasone, peptide-chain initiation was inhibited, whereas tissue RNA content and initiation factor activity were unchanged. These experiments suggested that total activity of eIF-2 did not always correlate with the rate of initiation, but that there did appear to be a relationship between initiation factor activity and tissue RNA content. Purification of eIF-2 from bovine heart muscle was undertaken in order to directly investigate the mechanism by which glucocorticoids modify eIF-2-activity and control peptide-chain initiation.

Animals↗

PubMed1978

Internal ureteropexy: a simple technique to prevent reflux after ureteroneocystostomy.

An experimental study in dogs showed that the implantation of hydroureters onto a denuded area of the bladder muscle led to mucosal regeneration and formation of a submucosal tunnel. Reflux was prevented in all animals when the bladder wall was immobilized at the reimplantation site by fixation to the psoas muscle. Urinary stasis normalized after 10 to 12 reimplantations. Internal ureteropexy would seem to be a most simple and satisfactory technique for preventing reflux when dissection of a submucosal tunnel fails in ureteroneocystostomy. It has been used in three patients with good results.

Animals↗

PubMed1988

Demembranated muscle fibers catalyze a more rapid exchange between phosphate and adenosine triphosphate than actomyosin subfragment 1.

The rate of ATP in equilibrium with Pi exchange, that is, the incorporation of medium Pi into ATP during the net hydrolysis of ATP, has been measured for rabbit psoas muscle fibers, myofibrils, and actomyosin subfragment 1 (acto-S1). The maximum exchange rate in fibers at saturating [Pi] is 0.04 s-1 per myosin head at 8 degrees C, pH 7, and an ionic strength of 0.2 M. The dependence of the rate on Pi concentration can be approximated by a hyperbola with an apparent dissociation constant (Km) of 3 mM. Myofibrils catalyze ATP in equilibrium with Pi exchange with a similar Km but at a slightly lower rate. In contrast, the soluble acto-S1 system, in which ATP hydrolysis is not coupled to tension generation, catalyzes exchange at a rate 500 times lower than that of fibers at low Pi concentration, and the Km for Pi is greater than 50 mM. The difference between the ATP in equilibrium with Pi exchange of fibers and of acto-S1 is discussed in terms of a model in which Pi binds to a force-generating state AM'-ADP and, due to mechanical constraint, the average free energy of this state is higher in the fiber than in acto-S1.

Adenosine Triphosphate↗

PubMed1992

Tuberculous abscesses in patients with AIDS.

Five cases of large tuberculous abscesses in patients with AIDS were observed over a 2-year period at the New York Veterans Affairs Medical Center. These cases represent 11.6% of the 43 cases of tuberculosis diagnosed in patients with AIDS during that period. The abscesses were located in the liver, abdominal wall, psoas muscle, mediastinum, and peripancreatic area. All patients presented with localized pain or swelling, and four of five patients had fever. The diagnosis was made on the basis of detection of abscesses on computed tomography (CT) and the results of culture of abscess material obtained by CT-guided aspiration. CT-guided therapeutic drainage was performed in two cases. Despite administration of therapy, two of five patients died of tuberculous infection. Formation of tuberculous abscesses appears to be a common complication of tuberculosis in patients with AIDS. This diagnosis should be considered for patients with AIDS who have fever and localized pain or swelling.

Abdominal Muscles↗

PubMed2002

[[Primary psoas abscess. Presentation of 3 cases].

OBJECTIVE: To present 3 cases of primary abscess of the psoas muscle. The clinical features, diagnostic tests, treatment and outcome are discussed. METHODS/RESULTS: Three patients that presented with fever and pain referred to the renal and/or iliac fossa are described. Physical examination showed psoas involvement in only one patient. Among the complementary tests performed, ultrasound demonstrated the abscess in one of the cases; the definitive diagnosis was made by contrast-enhanced CT. One of the cases was treated only with antibiotics while the other two cases were treated with CT-guided percutaneous drainage and appropriate antibiotic therapy. CONCLUSIONS: Psoas abscess is an uncommon pathology whose presenting features are usually unspecific. CT with contrast enhancement is considered to be the technique of choice for the diagnosis and to corroborate the resolution of the condition. Recently, the use of CT or US-guided percutaneous drainage has replaced surgery as the initial therapeutic approach for this condition.

Adult↗