An electron microscope study of sectioned breast muscle of the domestic fowl

Self Cite

716

204

Previous papers in this series (1, 2) as well as numerous other reports on cell fine structure have provided evidence for the existence of a finely divided vacuolar system in the cytoplasm of all animal cells thus far examined except mature erythrocytes. The reticular character of the system and its exclusion from the thin cortical layer (ectoplasm) of the cytoplasm, as first observed in cultured cells (3,4), account for the name "endoplasmic reticulum." More recently, in electron microscope studies of thin sections, the term has been applied to small tubular or vesicular elements of the cytoplasm that are limited by a single continuous membrane and have a homogeneous, structurefree content. In the majority of cells, such elements make up a system that is continuous and reticular in form. By its presence the cytoplasm is divided into two phases: (a) a constantly continuous phase, the cytoplasmic matrix, containing such resolvable components as ribonucleoprotein (RNP) particles and fibrous elements of several kinds, and (b) the inner phase of the membranelimited reticulum, in general also continuous, but certainly discontinuous at times, and showing usually no resolvable elements. In some cells the system is abundantly represented; in others sparsely so. Its form, volume, and distribution tend to be characteristic for all cells of a particular type so that it becomes a feature of cellular differentiation. The system has also been observed to show local differentiations (2, 6) and to develop special associations with other components (e.g., the RNP particles (5) and the nucleus (6)). Since it is reasonable to look to them for clues to the functions of the system, these latter associations seem especially significant. Some attention is therefore being given, in this and subsequent studies, to their occurrence, form, and behavior.There are various indications to be found in published accounts of the structure of striated muscle that an equivalent of the endoplasmic reticulum is present in this as in Other types of cells, and that it may show a pattern of distribution relative to the myofibrils. For example, Bennett and Porter (7), in a report on the fine structure of striated muscle of the domestic fowl, directed attention to an interfibrillar component--in some instances vesicular--localized opposite the Z or N bands of the myofibrils. Similar elements were later depicted 269 J, BIOPHYSXC, ~tr~D Bloc~tz~, Cx-roL., 1957, Vol. 3, No. 2 on May 10, 2018 jcb.rupress.org Downloaded from http://doi.org/10. 1083/jcb.3.2.269 Published Online: 25 March, 1957 270 STUDIES ON T/-~ ENDOPLASMIC RETICULUM. HI in the sarcoplasm of insect muscle (8) and more clearly in muscle of Amblystoma larvae (9, 10) and the gracilis muscle of the mouse (11).These miscellaneous and preliminary observations have failed, however, to give more than a suggestion of the pattern the system adopts with respect to the myofibrils. In this regard, in fact, these recent observations are perhaps not so useful as older, somewhat neglected light microscop...

“…They seem not to differ in most fundamental respects from myofibrils of other vertebrate muscles for which there are now several descriptions in the literature (16,7,17,18).…”

Section: A the Myofibrilsmentioning

confidence: 82%

mentioning

confidence: 99%

Studies on the Endoplasmic Reticulum

Porter

Palade

1957

Self Cite

716

204

“…The smooth curves for the length of the A and I bands favor the latter interpretation. If this interpretation is accepted the densitometric tracings of Bennett and Porter (1) suggest that the A band changes very little in density during isotonic contraction, whereas the region of the H and M bands and the region around the Z line gain appreciably in density.…”

Section: Discussionmentioning

confidence: 99%

Electron Microscopical Study of Skeletal Muscle During Isotonic (Afterload) and Isometric Contraction

Knappeis

Carlsen

1956

Observations by light microscopy on contracted muscle have been made chiefly under isometric conditions: on striated muscle of frog (9,14,5,2,4,15), of Astracusfluviatilis and Carcinus maenas (17), and guinea pig (12); and on frog cardiac muscle (18).Studies dealing with isotonic contraction are those of Htirthle (13) (11) on the flight muscle of the blowfly.For both isometric and isotonic contraction the published results are contradictory. In part this may result from the fact that during isotonic contraction the shortening of the fibre may bring the length of the anisotropic and isotropic bands below the resolving power of the light microscope. The changes in length that occur in the anisotropic and isotropic bands of skeletal muscle during stretch were described in a previous study (6). The present electron microscopic study was undertaken to determine the length of the anisotropic and isotropic bands during isotonic (afterload) and isometric contraction. MethodBundles (75 to 100 fibres) from the curarized semitendinosus muscle of Rana temporaria and Rana esculenta were isolated and the equilibrium length determined. They were stretched to 30 to 40 per cent above the equilibrium length (L0 --100) for about 30 minutes in Ringer's solution at 0--4°C. The fibre bundle was then placed in a myograph (3), adjusted to the desired length (25 per cent stretch for aftefload and 0 to 50 per cent stretch for isometric contraction). The term "afterload contraction" denotes a contraction in a muscle initially stretched to a desired length by an external load. Upon stimulation the muscle first contracts isometrically until the developed tension equals the external force, and then it shortens against this "aftefload." The muscle was maintained at the desired length until the myograph gave constant readings for at least 30 minutes. The Ringer's solution was then removed, and the muscle stimulated directly before and for some time during fixation of the muscle in 10 per cent ice cooled neutral formalin solution. The stimulating square wave pulses had a duration of I0 201

“…5). For more details of normal muscle structure the reader is referred to the literature (19)(20)(21)(22)(23)(24)(25)(26)(27)32). …”

Section: Observationsmentioning

confidence: 99%

Electron Microscopic and Histochemical Observations of Muscle Degeneration After Tourniquet

Moore

Rüska

Copenhaver

1956

Muscle degeneration and a shock syndrome, which frequently results in death, follow the release of limb tourniquets. Albumin and other plasma components are transferred into the affected muscle tissue (1-4) while toxic products of autolysis and hemolytic substances appear in the circulating blood (5-7). It is possible that this abnormal transfer results in part from damage of capillaries and muscle fiber membranes. The application of cold delays autolysis and fluid exchange, modifies the shock symptoms, and reduces mortality (8). Chemical changes, such as the large decrease in phosphorus (9) and morphologic alterations, as revealed with the light microscope (9, 10), have been carefully studied. Wide interfibrillar spaces are observed in tissues taken immediately after release of the tourniquet, and some fibers show discoid decay of their fibrils. The primary alterations are followed several hours later by advancing granular and hyaline degeneration.The present communication extends the light microscopic observations of the succinic dehydrogenase distribution in normal fibers (11) to the degenerated fibers. With the electron microscope an attempt is made to visualize the finer details in the development of discoid, hyaline, and granular degeneration seen after release of the tourniquet. The alterations thus produced are common to an extremely wide variety of muscle lesions. Further experience will determine whether degenerations of different etiology, such as those caused by bacterial toxins, vitamin E deficiency, or Coxsackie virus infection will expose specific details characteristic of each lesion. MethodsAs in antecedent electrophoretic studies of blood and tissue extracts after shock-producing injuries (2-4), the technique of Rosenthal (12) was used for traumatizafion of hind legs of C57