THE MYOFILAMENT ARRANGEMENT IN THE FEMORAL MUSCLE OF THE COCKROACH, LEUCOPHAEA MADERAE FABRICIUS

Abstract

The structure of the femoral muscle of the cockroach, Leucophaea maderae, was investigated by light and electron microscopy. The several hundred fibers of either the extensor or flexor muscle are 20 to 40 # in diameter in transverse sections and are subdivided into closely packed myofibrils. In glutaraldehyde-fixed and epoxy resin-embedded material of stretched fibers, the A band is about 4.5 # long, the thin filaments are about 2.3/z in length, the H zone and I band vary with the amount of stretch, and the M band is absent. The transverse sections of the filaments reveal in the area of a single overlap of thick and thin filaments an array of 10 to 12 thin filaments encircling each thick filament; whereas, in the area of double overlap in which the thin filaments interdigitate from opposite ends of the A band, the thin filaments show a twofold increase in number. The thick filament is approximately 205 to 185 A in diameter along most of its length, but at about 0.2 tz from the end it tapers to a point. Furthermore, some well oriented, very thin transverse sections show these filaments to have electron-transparent cores. The diameter of the thin filament is about 70 A. Transverse sections exhibit the sarcolemma invaginating clearly at regular intervals into the lateral regions of the A band. Three distinct types of mitochondria are associated with the muscle: an oval, an elongate, and a type with three processes. It is evident, in this muscle, that the sliding filament hypothesis is valid, and that perhaps the function of the extra thin filaments is to increase the tensile strength of the fiber and to create additional reactive rites between the thick and thin filaments. These sites are probably required for the functioning of the long sarcomeres.

The Filament Lattice of Cockroach Thoracic Muscle

“…Frequently nerve endings contact the muscle fiber at depressed areas on the sarcolemma. These neuromuscular junctions are similar to those found in the femoral muscle of this species (Hagopian, 1966). The cell membrane invaginates at regular intervals to form transverse tubules (T system) which make dyadic contacts with the unfenestrated areas of the sarcoplasmic reticulum (SR).…”

“…In previous studies of the femoral muscle of cockroach, Leucophaea maderae (Hagopian, 1966;Hagopian and Spiro, 1967), 10-12 actin filaments were found encircling each myosin filament. Other salient features such as long sarcomeres and a sarcoplasmic reticulum which is continuous longitudinally as well as laterally across the fibers are unusual.…”

IMMUNOHISTOCHEMICAL LOCALIZATION OF CONTRACTILE PROTEINS IN LIMULUS STRIATED MUSCLE

“…M band protein is immunologically distinct from other muscle proteins (25, 34), and was successfully localized in the central A bands of chicken skeletal muscle by the fluorescent antibody technique (25) . Long sarcomeres lacking M bands are found in several different invertebrate muscles, including cockroach femoral muscle (16), crab leg muscle (15), Tachypleus retractor muscle (21), and Limulus cardiac (28) and skeletal (26) muscle . All of these show some degree of thick filament misalignment in lengthened myofibrils, and thus an apparent increase in A band length is seen in such sarcomeres (26, 27) .…”

“…Such exposure of paramyosin antibodybinding sites may be explained by assuming that, except at the tapered ends of the thick filaments, all of the antigenic sites of the cortical myosin molecules are obscured by their interaction with actin in completely shortened sarcomeres . If the cortical layer is only one myosin molecule in thickness (10,16,38), heavy meromyosin-actin interaction and associated increase in lattice spacing between thick and thin filaments would reduce steric hindrance to antiparamyosin binding and allow staining of the thick filament core .…”

Muscles à striation oblique et à striation transversale chez les Annélides Polychètes

“…Ces caractiristiques structurales que l'on pourrai t considerer comme primitives correspondent 8: I'irrCgulariti et l'importante longueur des sarcom5res et des bandes A, l'absence de bande M, la decomposition de la strie 2 en 6lCments sipare's et au trajet en zig zag et parfois oblique, la disposition irriguliere des filaments Cpais dont les extrcmitis ne sont pas situ6es au m6me niveau, le diametre relativement important des filaments myosiniques et parfois la variation de leur calibre dans une mtme fibre, I'agencement non hexagonal des filaments fins et leur nombre souvent important par rapport aux filaments Cpais. Ces fibres peuvent 6tre rapprochies des fibres striies transversalement de Mollusques (Jensen et Tjonneland, 1977;Kamaguti, 1963;Nisbet et Plummer, 1968;Richardot et Wautier, 1971), de Pentastomides (Mill, et Riley, 1972, de Limules (De Villafranca et Philpott, 1961;Fourtner et Sherman, 1971, 1973Leyton et Sonnenblick, 1971), d'AraignCes (Sherman et Luft, 1972; Rathmayer, 1968), de Crustacis (Hoyle et MC Neill, 1968;Hoyle et coll., 1973;Jahromi et Atwood, 1967, 1969, de Myriapodes (Camatini et Saita, 1967;Camatini et Castellani, 1974), d'hsectes (Goldstein et Burdette, 1971Hagopian, 1966;Nagai et Graham, 1974;Smith et coll., 1966 (Bouligand, 1964;Fahrenbach, 1967); des muscles alaires des Insectes (Smith, 1961a(Smith, , b, 1966; des muscles de Chaetognathes (Duvert, 1969;Camatini et Lanzavecchia, 1966) (Chapman, 1968;Keough et Summers, 1976;Singla, 1978).…”