Richard D. Lumsden

MACROMOLECULAR STRUCTURE OF GLYCOGEN IN SOME CYCLOPHYLLIDEAN AND TRYPANORHYNCH CESTODES.

Electron microscopy of Hymenolepis diminuta and Lacistorhynchus tenuis reveals polymorphism of glycogen deposits consistent with previous observations of molecular weight heterogeneity of the polysaccharide fraction isolated from H. diminuta and other helminths. Two types of glycogen particles are distinguishable morphologically: (1) single granules (beta particles) 200 to 400 A in diameter and (2) rosettes (alpha particles) comprised of varying numbers of 200 A particles, with an aggregate diameter of 600 to 2,000 A. Mixtures of these particles occur in certain parenchymal cells, though alpha particles tend to predominate in cells storing large quantities of polysaccharide while the beta particles are characteristic of the musculature and spermatozoa. Tissue-section autoradiography following in vitro administration of H3-glucose indicates a high rate of glycogen turnover in tissues containing this polysaccharide primarily in the beta form compared with those containing a preponderance of alpha glycogen. It is suggested from these and previous studies that the alpha configuration constitutes a reserve carbohydrate depot in cestode tissues, while the beta particle represents a source of more readily mobilizable hexose. A polydisperse glycogen fraction has been recently isolated by Orrell, Bueding, and Reissig (1964) from Hymenolepis diminuta. Two components, one with a sedimentation coefficient between 100 S and 500 S (average 200 S) and a second between 700 S and 1,500 S (average 1,100 S) were separated by differential zone centrifugation after mild cold water extraction of the homogenized tissues (Bueding and Orrell, 1961; 1964). Following short-term incubation of worms in C14-labeled glucose, the specific activity of the lower molecular weight fraction was found to be twice that of the heavier component, indicating more rapid synthesis of the lighter material (Colucci et al., 1964; Orrell et al., 1964). These authors have suggested that the heavier component might arise through polymerization of newly synthesized and performed lower molecular weight glycogen units. Similar heterogeneity has been obtained with glycogens from Ascaris lumbricoides and Fasciola hepatica (Bueding and Orrell, 1961; Orrell et al., 1964). Electron microscopy of the water-extracted Ascaris polysaccharide fraction revealed that the glycogen was organized as aggregates of smaller granules; the frequency in estimated number of subunits per aggregate corresponded roughly with the distribution of molecular weights calReceived for publication 27 February 1965. * This study was supported by grants (5 TI Al 106 and AI 01384) and a predoctoral fellowship from NIH. 501 culated from ultracentrifuge patterns (Orrell et al., 1964). Based on electron microscopic examination of negatively stained rat liver glycogen fractions, Drochmans (1962) suggested that glycogen particles as they occurred intracellularly possessed a two-stage structure. The macromolecular organization of filamentous gamma subunits, measuring 3 msu in diameter and 20 m/, long, was thought to constitute the basic cytological unit, the beta particle, which in the microscope usually appear as single granules 150 to 400 A in diameter. In such tissues as mammalian liver, the beta particles could then be reproduced and joined as components of a larger unit, the alpha particle, whose morphology is that of a complex of numerous granular subunits, apparently closely packed beta particles, with an aggregate diameter reaching several thousand mru. Within any given species, the appearance of the glycogen deposits (as alpha or beta particles) seems to be characteristic for a particular cell type, though as suggested by Revel (1964), the alpha and beta configurations may represent two extremes of a graded spectrum. Recent studies in this laboratory on the fine structure of Hymenolepis diminuta and several additional tapeworms support and extend the findings of Bueding and co-workers (op. cit.) concerning the properties of cestode glycogen. Further, the results presented in this paper suggest possible physiological implications of This content downloaded from 157.55.39.111 on Wed, 03 Aug 2016 05:04:39 UTC All use subject to http://about.jstor.org/terms 502 THE JOURNAL OF PARASITOLOGY, VOL. 51, NO. 4, AUGUST 1965

Microtubules in the peripheral cytoplasm of cestode spermatozoa.

Tubules measuring 280 A in diameter have been observed in the peripheral cytoplasm of mature spermatozoa of Hymenolepis diminuta. The tubules form a single row immediately adjacent to the plasma membrane and follow a helical course along the length of the spermatozoon. Morphologically, these structures resemble the ubiquitously occurring microtubules which have been implicated functionally in cytoplasmic movement and the maintenance of structural asymmetry. In an electron microscope study of spermatogenesis in cestodes, Rosario (1964) described the fine structure of Hymenolepis diminuta and H. nana spermatozoa. In tissues fixed with veronal-buffered osmium tetroxide (Palade, 1952), the surface of these cells was reported to be covered with oblique striations. Rosario (1964) indicated that these striations were components of the plasma membrane and were superficial to the spermatozoon cytoplasm. The present paper reports observations elucidating the nature of these surface striations and extends Rosarios description of the fine structure of hymenolepidid spermatozoa. MATERIALS AND METHODS Hymenolepis diminuta obtained from 10-day infections of Sprague-Dawley rats (Read et al., 1963) were fixed in ice-cold, phosphate-buffered acrolein or glutaraldehyde, postfixed in osmic acid, dehydrated in ethanol, and embedded in epoxy resins as described previously (Lumsden, 1965). Thin sections were stained with uranyl acetate (Watson, 1958) followed by lead citrate (Reynolds, 1963) and examined with an RCA EMU 3F electron microscope operated at 50 kv.