The Filament Lattice of Cockroach Thoracic Muscle

Abstract

The fine structure of the tergo-coxal muscle of the cockroach, Leucophaea maderae, has been studied with the electron microscope. This muscle differs from some other types of insect flight muscles inasmuch as the ratio of thin to thick filaments is 4 instead of the characteristic 3. The cockroach flight muscle also differs from the cockroach femoral muscle in thin to thick filament ratios and diameters and in lengths of thick filaments. A comparison of these latter three parameters in a number of vertebrate and invertebrate muscles suggests in general that the diameters and lengths of the thick filaments and thin to thick filament ratios are related.

STRUCTURE OF LIMULUS STRIATED MUSCLE

“…The resemblance between Limulus telson muscle fibers and slow fibers of arthropodan (Fahrenbach, 1967 ;Hagopian and Spiro, 1968) and even vertebrate (Page, 1965) (Hoyle et al, 1965 ;Leyton and Ullrick, 1970) especially in long sarcomeres than they do the totally separate Z disks found in obliquely striated muscles (Rohlich, 1962 ;Reger, 1964) .…”

Skeletal Muscle

“…The lengths of the filaments and thereby the sarcomere lengths are often greater than in vertebrate muscles; the sarcomere length may be up to 10 llm (for references see HAGOPIAN 1966;REGER 1967a, b;REGER and COOPER 1967;HOYLE 1967HOYLE ,1969ZOBEL et al 1967;FAHRENBACH 1967;HAGOPIAN and SPIRO 1968;FRANZINI-ARMSTRONG 1970a;HAYES et al 1971;DEWEY et al 1973;PRINGLE 1974). The ratio of thick-to-thin filaments tends to be larger in muscles with fast contractions (1: 3 in insect flight muscles) than in muscles with slow contractions (1: 7 to 1: 10).…”

The Organization of Contractile Filaments in a Mammalian Smooth Muscle

“…A comparison of the shapes of thick filaments from smooth muscle reported here and from striated muscle (34)(35)(36) shows that various similar outlines are found in both muscles . In the region of the H zone, lacking M line bridges, striated muscle thick filament cross-sections exhibit circular and triangular outlines .…”

“…Limited penetration of stain might account for a hollow-appearing core, but sections which were not poststained with lead and uranium salts also show hollow thick filaments as do sections in which block staining was eliminated . Hollow thick filaments have been observed in several insect muscles (34,37), and recently a substructure of 12 globules forming a wall has been demonstrated in insect muscle examined by high-voltage RicE ET AL . Organization of Contractile Filaments 193 electron microscopy (38) .…”

“…In the latter observations, one could not clearly see tapered ends, and so its significance is not certain . Hagopian and Spiro have tabulated the diameters of glutaraldehyde-fixed thick filaments from a variety of striated muscles (34) . Thick-filament diameters vary from as small as 100 to as large as 230 A .…”