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At least 127 records · Page 7Linked to original sources
PubMed1995

Rigor cross-bridges bind to two actin monomers in thin filaments of rabbit psoas muscle.

The mode of binding of myosin subfragment-1 (S1) to actin is known to depend on their molar ratio: when actin is in excess, S1 binds to two actin monomers within the actin filament, and when S1 is in excess or is equimolar with actin, each S1 binds to one actin monomer. Since in vertebrate striated muscle actin is in molar excess over myosin, we expect that in fibers each myosin head binds to two actin monomers. To test this idea, we compared the conformation of the heads in native muscle with the conformation of S1 in fibers that were loaded with either high (S1 equimolar with actin) or low (excess of actin over S1) concentration of extrinsic S1. Conformation was assessed by the accessibility of heads to trypsin (measured by the rate of trypsinolysis) and by their orientation with respect to the muscle axis (measured by a combination of polarization of fluorescence and linear dichroism). In muscle fibers loaded with a high concentration of S1, the region of the heavy chain of the myosin head at the junction of 20 and 50 kDa proteolytic fragments was readily digested by trypsin and its orientation was approximately perpendicular to an axis of a thin filament. In contrast, when muscle fibers were loaded with a low concentration of S1, the 20/50 kDa junction of S1 was protected from trypsinolysis and its orientation was more parallel with a filament axis. Native muscle in rigor behaved like muscle irrigated with a low concentration of S1, i.e. the 20/50 kDa junction of the myosin head was protected from trypsinolysis and the orientation of the heads was parallel to the filament axis. We conclude that in rigor rabbit psoas muscle each myosin head binds to two actin monomers in a thin filament, and that this binding is different from the binding of S1 to actin in equimolar solutions.

Actins↗
PubMed1998

Primary pyogenic abscess of the psoas muscle.

During a six-year period, eleven persons with primary pyogenic abscess of the psoas muscle were treated at the Mackay Memorial Hospital. Five were males and six were females and their average age was 47.2 years (range 6-83 years). The abscess was identified by CT in 7 patients, MRI in 2 and ultrasonography in 1. One abscess was found during laparotomy. Treatment included extraperitoneal drainage of the abscess in 7 patients and CT guided aspiration in 3. One patient improved after antibiotic therapy and they all recovered after treatment. The diagnosis of primary pyogenic abscess requires a high index of suspicion and the best treatment is early operative drainage and administration of systemic antibiotics.

Adolescent↗
PubMed2002

A model of cross-bridge attachment to actin in the A*M*ATP state based on x-ray diffraction from permeabilized rabbit psoas muscle.

A model of cross-bridges binding to actin in the weak binding A*M*ATP state is presented. The modeling was based on the x-ray diffraction patterns from the relaxed skinned rabbit psoas muscle fibers where ATP hydrolysis was inhibited by N-phenylmaleimide treatment (S. Xu, J. Gu, G. Melvin, L. C. Yu. 2002. Biophys. J. 82:2111-2122). Calculations included both the myosin filaments and the actin filaments of the muscle cells, and the binding to actin was assumed to be single headed. To achieve a good fit, considerable flexibility in the orientation of the myosin head and the position of the S1-S2 junction is necessary, such that the myosin head can bind to a nearby actin whereas the tail end was kept in the proximity of the helical track of the myosin filament. Hence, the best-fit model shows that the head binds to actin in a wide range of orientations, and the tail end deviates substantially from its lattice position in the radial direction (approximately 60 A). Surprisingly, the best fit model reveals that the detached head, whose location thus far has remained undetected, seems to be located close to the surface of the myosin filament. Another significant requirement of the best-fit model is that the binding site on actin is near the N terminus of the actin subunit, a position distinct from the putative rigor-binding site. The results support the idea that the essential role played by the weak binding states M*ATP <--> A*M*ATP for force generation lies in its flexibility, because the probability of attachment is greatly increased, compared with the weak binding M*ADP*P(i) <--> A*M*ADP*P(i) states.

Adenosine Monophosphate↗
PubMed1999

Anatomical differences in the psoas muscles in young black and white men.

The anatomy of the psoas major muscle (PMA) in young black and white men was studied during routine autopsies. The forensic autopsies included 44 fresh male cadavers (21 black, 23 white) with an age span of 14 to 25 y. The range for weight was 66-76 kg and for height 169-182 cm. The PMA was initially measured in its entire length before measuring the diameter and circumference at each segmental level (L1-S1). At each segmental level, the calculated anatomical cross-sectional area (ACSA) was more than 3 times greater in the black group compared with the white (P < 0.001). The psoas minor muscle (PMI) was absent in 91% of the black subjects, but only in 13% of the white subjects. These data show that the PMA is markedly larger in black than white subjects. The marked race specific difference in the size of the PMA may have implications for hip flexor strength, spine function and race specific incidence in low back pathology, and warrants further investigation.

Adolescent↗
PubMed2006

Structural characterization of the binding of Myosin*ADP*Pi to actin in permeabilized rabbit psoas muscle.

When myosin is attached to actin in a muscle cell, various structures in the filaments are formed. The two strongly bound states (A*M*ADP and A*M) and the weakly bound A*M*ATP states are reasonably well understood. The orientation of the strongly bound myosin heads is uniform ("stereospecific" attachment), and the attached heads exhibit little spatial fluctuation. In the prehydrolysis weakly bound A*M*ATP state, the orientations of the attached myosin heads assume a wide range of azimuthal and axial angles, indicating considerable flexibility in the myosin head. The structure of the other weakly bound state, A*M*ADP*P(i), however, is poorly understood. This state is thought to be the critical pre-power-stroke state, poised to make the transition to the strongly binding, force-generating states, and hence it is of particular interest for understanding the mechanism of contraction. However, because of the low affinity between myosin and actin in the A*M*ADP*P(i) state, the structure of this state has eluded determination both in isolated form and in muscle cells. With the knowledge recently gained in the structures of the weakly binding M*ATP, M*ADP*P(i) states and the weakly attached A*M*ATP state in muscle fibers, it is now feasible to delineate the in vivo structure of the attached state of A*M*ADP*P(i). The series of experiments presented in this article were carried out under relaxing conditions at 25 degrees C, where approximately 95% of the myosin heads in the skinned rabbit psoas muscle contain the hydrolysis products. The affinity for actin is enhanced by adding polyethylene glycol (PEG) or by lowering the ionic strength in the bathing solution. Solution kinetics and binding constants were determined in the presence and in the absence of PEG. When the binding between actin and myosin was increased, both the myosin layer lines and the actin layer lines increased in intensity, but the intensity profiles did not change. The configuration (mode) of attachment in the A*M*ADP*P(i) state is thus unique among the intermediate attached states of the cross-bridge ATP hydrolysis cycle. One of the simplest explanations is that both myosin filaments and actin filaments are stabilized (e.g., undergo reduced spatial fluctuations) by the attachment. The alignment of the myosin heads in the thick filaments and the alignment of the actin monomers in the thin filaments are improved as a result. The compact atomic structure of M*ADP*P(i) with strongly coupled domains may contribute to the unique attachment configuration: the "primed" myosin heads may function as "transient struts" when attached to the thin filaments.

Actins↗
PubMed1985

[Z-line structure of the rabbit psoas muscle studied by negative contrast staining].

The ultrastructure of the Z-disc of the rabbit psoas muscle was elucidated by electron microscopy using negative staining technique. Conclusions summarized from this work are as follow: (a) Z-disc involves two layers of Z-filaments, i.e. connecting filaments, which bind thin filaments of adjacent I-discs in the Z-line region. These layers are spaced about 380 A apart. (b) Z-filaments measure 380 A X 30 A. (c) The angle between the connecting filaments and the thin filaments depends on ionic conditions and varies from 20 degrees to 90 degrees. (d) We conclude that alpha-actinin is a structural component of Z-filaments, since dimensions of Z-filaments and their interaction with thin filaments are similar to those of alpha-actinin.

Actinin↗
PubMedDate not supplied

[Hydatid cyst of the psoas muscle (apropos of a case)].

A 39 year-old sardinian male patient was operated for psoas muscle hydatic cyst. Recovery was uneventful. Few of such cases have been published to date and are usually first diagnosed as tumors of the iliac fossae. Immunological tests are of little help.

Adult↗
PubMed2004

Myositis ossificans of psoas muscle: magnetic resonance imaging findings.

Myositis ossificans is a benign, localized, self-limiting ossifying soft tissue mass with unknown pathogenesis. It may be confused with a malignant tumor of bone or soft tissues, especially in the early stages of the disease. In this report, we present a case of myositis ossificans affecting unilateral psoas muscle, which to our knowledge is a very uncommon location. There was no history of trauma. We describe the imaging findings and clues to early diagnosis of myositis ossificans.

Adult↗
PubMed1992

Quantification of carbonic anhydrase III and myoglobin in different fiber types of human psoas muscle.

Carbonic anhydrase (CA III) and myoglobin contents from isolated human muscle fibers were quantified using a sensitive time-resolved fluoroimmunoassay. Human psoas muscle specimens were freeze-dried, and single fibers were dissected out and classified into type I, IIA and IIB by myosin ATPase staining. Fiber typing was further confirmed by SDS-PAGE. CA III and myoglobin were found in all fiber types. Type I fibers contained higher concentrations of CA III and myoglobin than type IIA and IIB fibers. The relative concentrations of CA III in type IIA and IIB fibers were respectively 24% and 10% of that in type I fibers. The relative concentrations of myoglobin in type IIA and IIB fibers were 60% and 28% of that in type I fibers. Anti-CA III immunoblotting results from fiber-specific pooled samples agreed well with quantitative measurements. The results indicate that CA III is a more specific marker than myoglobin for type I fibers.

Carbonic Anhydrases↗
PubMed2002

The length of cooperative units on the thin filament in rabbit psoas muscle fibres.

The length of cooperative units along the thin filament of rabbit psoas single muscle fibres was determined by reducing filament length by treatment with the thin filament severing protein, gelsolin, in the presence of Ca(2+) and 2,3-butanedione 2-monoxime (BDM). The average time for 50 % reduction in isometric tension was 6.7 min at 22 degrees C. The pCa-tension relationship was measured at 22 degrees C, pH 7.00 and ionic strength 200 mM, and the data were fitted to the Hill equation to determine the half-saturation point (K) and the cooperativity (n). Our results demonstrate that the cooperativity does not change much when the remaining isometric tension was in the range 20-100 %. The cooperativity quickly diminished when the remaining tension was reduced to less than 20 %. Our results further demonstrate that the change in the pK value was minimal and averaged 0.075 (less Ca(2+) sensitive) as the thin filament length was reduced. We infer from the first observation that the thin filament cooperativity extends up to 0.2 microm, which includes the maximum of about four basic cooperative units consisting of seven actin molecules, one tropomyosin dimer and one troponin complex. We infer from the second observation that the Ca(2+) sensitivity is slightly reduced by removal of the cooperative interaction between neighbouring cooperative units.

Animals↗
PubMed1992

Primary pyogenic abscess of the psoas muscle.

Nine children who were less than nine years old and had a primary pyogenic abscess of the psoas muscle were treated in a five-year period. This rare lesion often simulated septic arthritis of the hip. Ultrasonography was found to be the most reliable and easily performed diagnostic study. Because of the rarity of the lesion, the diagnosis requires a high index of suspicion. The best treatment is early operative drainage and administration of systemic antibiotics.

Child↗
PubMed1997

Ruptured abdominal aorta secondary to psoas muscle abscess due to Klebsiella pneumoniae in an alcoholic.

An alcoholic patient with low back pain and Klebsiella pneumoniae septicaemia is reported. Computed tomography revealed abdominal aortic rupture associated with a psoas abscess. Aortic ligation above and below the rupture site and an axillo-femoral bypass were performed, but the patient died on the first postoperative day. Alcoholism is a common underlying disease in K. pneumoniae septicaemia and its septic metastasis to the psoas muscle. The prognosis of aortic infection secondary to psoas abscess is very poor once aortic rupture occurs. Prompt abscess drainage following correct diagnosis and arterial reconstruction before aortic rupture are mandatory.

Adult↗
PubMed2002

Primary hydatid cysts of psoas muscle.

BACKGROUND: Hydatid cysts may occur in any area of the body, but they usually localize to the liver and the lungs. Primary localization in muscle is not common, accounting for 2-3% of all sites; even rarer is the development of multiple cysts. METHODS: The patient presented with a painless abdominal mass which gradually increased in size to a diameter of approximately 16 cm. Organ imaging scan revealed multiple hydatid cysts within the right psoas muscle. Because of the proximity of the lesions to the iliac vessels, ureter and nerves to the lower limb, percutaneous drainage and alcoholization under local anaesthesia were -performed with the aim of reducing the size of the cysts and sterilizing them prior to definitive surgery. This procedure was not effective. Two weeks after percutaneous treatment the patient underwent surgery. RESULTS: At operation the cysts were localized and successfully removed under ultrasound guidance. Postoperative stay was -uneventful. Two years after surgery the patient has no evidence of recurrent hydatid disease. CONCLUSIONS: Ultrasonography is the preferred method for detecting muscular hydatid cyst and for guiding the surgeon during resection.

Adult↗
PubMed1991

Cross-bridge kinetics in the presence of MgADP investigated by photolysis of caged ATP in rabbit psoas muscle fibres.

1. The interaction between MgADP and rigor cross-bridges in glycerol-extracted single fibres from rabbit psoas muscle has been investigated using laser pulse photolysis of caged ATP (P3-1(2-nitrophenyl)ethyladenosine 5'-triphosphate) in the presence of MgADP and following small length changes applied to the rigor fibre. 2. Addition of 465 microM-MgADP to a rigor fibre caused rigor tension to decrease by 15.3 +/- 0.7% (S.E.M., n = 24 trials in thirteen fibres). The half-saturation value for this tension reduction was 18 +/- 4 microM (n = 23, thirteen fibres). 3. Relaxation from rigor by photolysis of caged ATP in the absence of Ca2+ was markedly slowed by inclusion of 20 microM-2 mM-MgADP in the photolysis medium. 4. Four phases of tension relaxation occurred with MgADP in the medium: at, a quick partial relaxation (in pre-stretch fibres); bt, a slowing of relaxation or a rise in tension for 50-100 ms; ct, a sudden acceleration of relaxation; and dt, a final, nearly exponential relaxation. 5. Experiments at varied MgATP and MgADP concentrations suggested that phase at is due to MgATP binding to nucleotide-free cross-bridges. 6. Phase bt was abbreviated by including 1-20 mM-orthophosphate (Pi) in the photolysis medium, or by applying quick stretches before photolysis or during phase bt. These results suggest that phases bt and ct are complex processes involving ADP dissociation, cross-bridge reattachment and co-operative detachment involving filament sliding and the Ca(2+)-regulatory system. 7. Stretching relaxed muscle fibres to 3.2-3.4 microns striation spacing followed by ATP removal and release of the rigor fibre until tension fell below the relaxed level allowed investigation of the strain dependence of relaxation in the regions of negative cross-bridge strain. In the presence of 50 microM-2 mM-MgADP and either 10 mM-Pi or 20 mM-2,3-butanedione monoxime, relaxation following photolysis of caged ATP was 6- to 8-fold faster for negatively strained cross-bridges than for positively strained ones. This marked strain dependence of cross-bridge detachment is predicted from the model of A. F. Huxley (1957). 8. In the presence of Ca2+, activation of contraction following photolysis of caged ATP was slowed by inclusion of 20-500 microM-MgADP in the medium. An initial decrease in tension related to cross-bridge detachment by MgATP was markedly suppressed in the presence of MgADP. 9. Ten millimolar Pi partly suppressed active tension generation in the presence of MgADP.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate↗
PubMedDate not supplied

[X-ray diffraction study of the molecular nature of the dependence of rigor tension developed by skinned rabbit psoas muscle on the ionic strength of the solution].

Molecular origin of the dependence of rigor tension developed by skinned rabbit psoas muscle on the value of ionic strength in rigorizing solution was studied by means of X-ray diffraction technique. It is shown that a deviation of the ionic strength from "normal" value (= 0.125) either to high (= 0.34) or to low (= 0.04) values is accompanied by the changes in the relative intensities of some meridional reflections while their axial positions remained unchanged. This may be explained as the result of the detachment of myosin subfragments-2 from the surfaces of thick filaments. The data obtained indicate that there is a correlation between the structure and localization of myosin subfragments-2 and the value of force generated by the muscle.

Animals↗