Étude par electrophorèse et ultracentrifugation de la composition protéinique de la couche musculaire des carotides de bovidé

Efficiency of protein extraction and recovery from meat industry by-products

Data concerning the efficiency of protein extraction from meat waste tissues are presented. The tissues investigated were the lungs, stomach and small and large intestines of the ox, sheep and pig. Practically all of the protein, with the exception of connective tissue proteins, was solubilised under optimum extraction conditions both with alkali and anionic detergent. The disadvantages of isoelectric precipitation of alkaline extracted proteins have been investigated in detail using polyacrylamide gel electrophoresis incorporating sodium dodecyl sulphate (SDS). The compositions of the protein isolates from the various tissues studied differed from those of the soluble extracts and supernatants or wheys. However, a component of MW 75,000 daltons was characteristic of the wheys from each tissue. The compositions of both isolates and wheys are discussed in the light of structural and cytoplasmic proteins present in smooth muscle tissues. The usefulness of anionic polysaccharides as a means of whey protein recovery is discussed, together with similar benefits achieved using SDS.

Analysis of the birefringence of the smooth muscle anococcygeus of the rat, at rest and in contraction. I

The birefringence of the rat anococcygeus muscle was measured at rest and in contraction. A large increase (+30%) of the optical retardation was observed in muscles fully stimulated by Noradrenaline, in isometric conditions. This was associated with a reduction of the muscle thickness (-12%), so that the birefringence increased by 48%. These changes were reversed upon relaxation. The relationship between the birefringence increase and the mechanical response was investigated as a function of time and of Noradrenaline concentration. Possible origins for the birefringence increase are considered: an increased density of birefringent material, mainly filaments, seems the most likely explanation of the results.

Diffuse X-ray scatter from myosin heads in oriented synthetic filaments

X-ray results are presented concerning the structural state of myosin heads of synthetic filaments in threads. These were made from purified rabbit skeletal muscle myosin and studied by x-ray diffraction and electron microscopy by Cooke et al. (Cooke, P. H., E. M. Bartels, G. F. Elliott, and R. A. Hughes, 1987, Biophys. J., 51:947-957). X-ray patterns show a meridional peak at a spacing of 14.4 nm. We concentrate here on the only other feature of the axial pattern: this is a central region of diffuse scatter, which we find to be similar to that obtained from myosin heads in solution (Mendelson, R. A., K. M. Kretzschmar, 1980, Biochemistry, 19:4103-4108). This means that the myosin heads have very large random displacements in all directions from their average positions, and that they are practically randomly oriented. The myosin heads do not contribute to the 14.4-nm peak, which must come entirely from the backbone. Comparison with x-ray data from the unstriated Taenia coli muscle of the guinea pig indicates that in this muscle at least 75% of the diffuse scatter comes from disordered myosin heads. The results confirm that the diffuse scatter in x-ray patterns from specimens that contain myosin filaments can yield information about the structural behavior of the myosin heads.

Structural and biochemical analysis of skinned smooth muscle preparations

This paper describes a biochemical and immunocytochemical analysis of smooth muscle strips that were chemically skinned and subjected to contraction and relaxation cycles according to procedures commonly employed in current skinned smooth muscle work. The fate of four major proteins, myosin, filamin, caldesmon and actin, was followed with respect to the proportionate loss of these proteins to the bathing medium as well as to their structural redistribution within the cells in the muscle strips. Large losses (of the order of 50%) of both myosin and filamin occurred at the skinning step, using either Triton X-100 or Saponin as the detergent; losses of actin were up to 30% with Triton X-100 and around 15% with Saponin. Losses of caldesmon were difficult to assess due to the rapid degradation of this protein in the bathing medium. Subsequent cycles of contraction and relaxation resulted in accumulated loss, notably of myosin and filamin, so that after the third contraction as little as 20% and 40% respectively of the original complement of these proteins remained in the muscle strips. These changes in protein composition were accompanied by a drastic redistribution of the proteins in the muscle cells. Most marked were the changes seen with myosin, significant amounts of this protein being already found in the connective tissue space after the first relaxation. These findings point to the need for a careful reappraisal of the conditions currently used in skinned smooth muscle research.

Filament formation in smooth muscle homogenates

To provide more detailed information on the aggregation properties of smooth muscle myosin, we have extended earlier work on the formation of thick filaments when homogenates of guinea-pig taenia coli and chicken gizzard muscle are diluted. In both preparations there is a slow and a fast phase of filament formation. The slow phase, which generally develops over several hours, appears to depend primarily on the ATP concentration while the rapid phase, which develops over 5-15 min, is influenced by the extent of dilution, homogenization conditions, divalent cation concentration, ATP concentration and presence of chicken gizzard tropomyosin. Many of these effects on the rapid phase can be explained by postulating that filament formation only takes place when the ATP concentration is reduced. There are significant differences between the filament populations formed from each muscle, with those from taenia coli being shorter than those from gizzard. Two types of filament are present in preparations from each muscle, the first being characterized by the presence of a central bare zone and cross striations at both ends, whilst the second have cross striations along their entire length; the periodicity of the cross striations appears to be 14.5 nm. The bare zone filaments have an average length and width of 325 nm and 17.6 nm respectively, while the corresponding values for the cross striated filaments is 3 : 1 for taenia coli and 1 : 3 for chicken gizzard, which accounts for the difference in average filament length observed between these preparations. The gizzard filaments appear to form more readily than those of taenia coli.

Chicken-gizzard actin: polymerization and stability

Preparations of chicken gizzard actin obtained from acetone-dried muscle powders prepared with various methods developed for skeletal muscle contain variable amounts of a beta-actinin-like protein. This contamination is minimized if the procedure of muscle powder preparation includes washing with EDTA solution, and can be completely removed by gel filtration of G-actin on Sephadex G-100. The presence of beta-actinin activity manifests itself in an increased rate of actin polymerization, low filament lengths resulting in low reduced viscosity and enhanced ATP-splitting activity of actin polymer, and instability of the polymer in the absence of free ATP. Gizzard actin purified on a Sephadex G-100 column does not differ from rabbit skeletal muscle actin in its polymerization properties. The distinct property of gizzard actin is the instability of its G form in the absence of added Ca2+, indicating that the affinity of this cation for the single high-affinity site in gizzard actin is lower than in skeletal muscle actin.

Myosin from arterial smooth muscle: isolation following actin depolymerization

The contractile proteins from arterial smooth muscle are highly soluble, and can be extracted at I = 0.05. However, they can be precipitated by a prolonged dialysis at pH 6 to give an actomyosin with a high, although variable, actin:myosin ratio. The sedimentation behavior of this actomyosin at high ionic strength was examined as a function of pH, protein concentration and composition by preparative ultracentrifugation. Comparisons with synthetic skeletal muscle actomyosins of similar composition demonstrated significant differences in the behaviors of these two systems. It was found that much smooth muscle actomyosin is not dissociated by normally relaxing conditions, and that it sediments at a slower rate than F-actin. The solubility of the supernatant protein (a myosin-enriched actomyosin) in 0.2 M K Cl (pH 7) depended on the pH during centrifugation. A lower solubility was associated only with a higher actin concentration in the supernatant, suggesting a dependence on actin repolymerization. Pure myosin was selectively precipitated from the supernatant by polyethylene glycol-6000, but only when the protein was soluble at low ionic strength. The solubility of purified myosin was similar to that of myosin from striated muscles. A relationship between the presence of depolymerized actin and the high solubility of smooth muscle contractile proteins is suggested.

Immunohistochemical study of the ontogenetic development of smooth muscle in the mouse embryo

This work, performed by immunofluorescence on the mouse embryo, makes use of the remarkable specificity of human pathological anti-striated and anti-smooth muscle auto-antibodies. It makes it possible, on the one hand, to date the appearance of smooth muscle Actomyosin during embryogenesis, and, on the other hand, to witness the appearance of immunological distinctions between contractile proteins of smooth and striated muscle.

Preparation and properties of vertebrate smooth-muscle myofibrils and actomyosin

A new technique for obtaining a myofibril-like preparation from vertebrate smooth muscle has been developed. An actomyosin can be readily extracted from these myofibrils at low ionic strength and in yields 20 times as high as previously reported. The protein composition of all preparations has been monitored using dodecylsulfate-gel electrophoresis. By this method smooth muscle actomyosin showed primarily only the major proteins, myosin, actin and tropomyosin, while the myofibrils contained, additionally, three new proteins not previously described with polypeptide chain weights of 60000, 110000 and 130000. The ATPase activities of both the myofibrils and actomyosin preparations are considerably higher than previously described for vertebrate smooth muscle. They are sensitive to micromolar Ca2+ ion concentrations to the same degree as comparable skeletal and cardiac muscle preparations, even though troponin-like proteins could not be identified in these smooth muscle preparations. From the latter observation and the presence of Ca2+-sensitivity in tropomyosin-free actomyosin it is suggested that this calcium sensitivity is, as in some invertebrate muscles, a property of the myosin molecule.

Contribution of plastoelasticity to the tone of the cat portal vein

Isolated helical strips of cat portal vein were subjected to sudden stresses to produce immediate elastic extension followed by a slow plastoelastic extension or "creep". Recovery from this creep was evaluated by restretching with varying intervals between stretches. In appropriately stimulated vessels, significant creep recovery continues for periods in excess of 20 minutes. Both the rate and the ultimate magnitude of the creep recovery were substantially increased by contractile activity produced by norepinephrine or electrical stimulation. The rate and ultimate magnitude of creep recovery were decreased by dilator drugs, although some recovery persisted. The only factors found capable of blocking creep recovery were complete inactivation of the contractile machinery by removal of calcium from the system or maintainence of tension on the tissue during the recovery period. This behavior is explained by a model in which contracted elements are capable of slowly converting into a stable shortened configuration capable of passively maintaining venous tone until mechanical stress causes a plastoelastic extension to the longer configuration.

Isolement et proprietes de la creatine-kinase de muscle lisse de boeuf

A method of isolation of the isoenzyme BB of creatine kinase from ox stomach is described taking into account its high instability and the presence of notable amounts of tropomyosin in vertebrate smooth muscle extracts of low ionic strength. The molecular parameters of the enzyme isolated from ox stomach do not differ from those of the creatine kinases MM and BB of vertebrates. The amino acid composition and the peptide maps reveals significant differences from that of the ox brain isoenzyme BB.

An electron microscope study of the influence of divalent ions on myosin filament formation in chicken gizzard extracts and homogenates

Myosin as well as actin filaments could be seen in negatively stained preparations of fresh chicken gizzard homogenized in buffered KCI (I=0.12, pH 6.85), in a 1 : 1 ratio. Myosin filaments were also present when homogenates were diluted (1 : 9) with solutions containing additional Mg(++) and ATP provided naturally occurring traces of Ca(++) had not been chelated with EGTA. There were no myosin filaments when Mg(++), ATP, Ca(++) or Ca(++) +ATP were added respectively to the diluent. It is suggested that in vivo in relaxed muscles myosin is present in dimers, and only aggregates into filaments at the onset of contraction when Ca(++) are released.

The purification and amino acid composition of human uterus collagens, rheumatoid-arthritis-nodule collagen and ox tendon collagen

Collagens and gelatins were isolated from human post-menopausal uterus, puerperal (post-partum) uterus, rheumatoid-arthritis-nodule and ox tendon. Different means of purifying collagen were studied and a method was devised that enables highly purified collagen to be obtained, even from the uterus. This method involves the use of a number of aqueous and organic extractants as well as digestion with elastase to eliminate elastin. The purity of the collagen preparations was assessed and they were used to study the amino acid composition of collagen. The amino acid compositions of all the collagens studied were similar to those of human bone and tendon collagen, but certain small differences were noted and are discussed. The soluble collagen extracted from some of the tissues was also studied.