An ultrastructural study of the stretch-induced hypertrophy of skeletal muscle

The teres minor muscle of the adult chicken was studied ultrastructurally following tonic stretch-induced hypertrophy. The contralateral control muscle fibres showed compact myofibrils and proliferation of normal Z-bands. Myofibrils of the hypertrophied muscle however, showed Z-band alterations as Z-band expansions and Z-band streaming. Thus Z-band is a highly responsive structure to tonic stretch. Since a number of neuromuscular conditions display Z-band anomalies, the latter occurring in response to a variety of metabolic and physiologic stimuli, including tonic stretch as shown here, represents a non-specific phenomenon.     

An ultrastructural study of mitotic division in differentiated gastric smooth muscle cells

Summary An ultrastructural examination of tissue from the gizzards of chicks just before and just after hatching showed numerous mitotic divisions in the well differentiated and functional smooth muscle. The nuclei in the very elongate, dividing cells were located centrally. The cytoplasm immediately adjacent to the nuclei contained the normal fully differentiated complement of myofilaments. During the active stages of division, after the breakdown of the nuclear membrane, myofilaments were shown to lie between the individual chromosomes. The process of division only occupied a small portion of the long muscle cells; the ultrastructural changes seen appeared similar to those described in other cell types.This work was supported by grants from the National Heart Foundation of Australia and the Australian Research Grants Committee. Part of this study was completed while J.L.S.C. was in receipt of a Queen Elizabeth II Research Fellowship. T. B. was supported by a Commonwealth Postgraduate Award.     

An ultrastructural study of isolated rat skeletal muscle mitochondria in various metabolic states

Summary An electron microscopic examination was made of isolated rat skeletal muscle mitochondria in various functional states. Shifts in the inner membrane ultrastructure of populations of mitochondria were observed under certain conditions. However, ultrastructural transformations reported by others during rapid changes in biochemical states were not observed in skeletal muscle mitochondria. There does not appear to be a strict correlation between metabolic states and ultrastructural states in isolated rat skeletal muscle mitochondria as has been observed in isolated mitochondria from several other tissue types.     

An ultrastructural study of the mantle of the barnacle, Elminius modestus Darwin in relation to shell formation

The fine structure of the mantle and shell of the barnacle, Elminius modestus Darwin has been examined by electron microscopy. The epithelial cells along the outer face of the mantle differ in size, shape, and organelle complexity according to the different components of the shell they secrete. The shell consists of a non-calcareous basis and calcareous mural and opercular plates which are connected by a flexible opercular hinge. Both the basis and opercular hinge are composed of two main units: an outer cuticulin layer and a lamellate component of well ordered arched fibrils. During the deposition of the latter structures morphological changes in the cells occur which may be correlated with the moulting cycle. Preliminary results show that the calcareous plates are covered by an outer epicuticle, which is bordered by a cuticulin layer; the inner calcareous component, consists of an orderly arrangement of organic matrix envelopes within which crystals may be initiated.

The cells lining the inner surface of the mantle are uniform in appearance with a thin cuticle at their free surface which lines the body cavity. The latter structure of the cuticle and manner of its deposition are similar to those of the basis and opercular hinge. Separating the outer and inner mantle epithelial cells is connective tissue which comprises several differing cell types. The possibilities are discussed of the rôle these cells may play in shell deposition. The modes by which underlying cells secrete the different shell components and the cuticle lining the inner face of the mantle, are also discussed.     

An ultrastructural study of regeneration of minced smooth muscle in the vas deferens of the guinea-pig

Summary Electron microscopic studies were made of the regeneration of minced smooth muscle of the vas deferens of the guinea-pig 3 days to 15 weeks after operation. At 3–5 days the mince contained degenerating smooth muscle cells and dedifferentiating cells showing characteristics of embryonic smooth muscle cells: numerous free ribosomes, well developed rough endoplasmic reticulum and Golgi apparatus with few peripherally placed myofilaments associated with dense bodies. During the first two weeks of regeneration, scattered cells surrounded by debris and collagen were separated by a large extra-cellular space. After three weeks, extracellular space was reduced to near normal values. Regenerating cells had a shorter length than normal cells, but during later stages of regeneration they showed an increase in diameter. Muscle effector bundles began to form after 2 to 3 weeks. Initially there were large gaps between the muscle cells, but at later stages of bundle formation, the extracellular space between the muscle cells was much reduced. From 3 weeks, arterioles appeared between the smooth muscle bundles in the regenerating areas. Regeneration of individual smooth muscle cells was complete by 15 weeks after the operation.This work was supported by grants from the Wellcome Trust and the Medical Research Council     

Rotator cuff muscle function and its relation to scapular morphology in apes

It is widely held that many differences among primate species in scapular morphology can be functionally related to differing demands on the shoulder associated with particular locomotor habits. This perspective is largely based on broad scale studies, while more narrow comparisons of scapular form often fail to follow predictions based on inferred differences in shoulder function. For example, the ratio of supraspinous fossa/infraspinous fossa size in apes is commonly viewed as an indicator of the importance of overhead use of the forelimb, yet paradoxically, the African apes, the most terrestrial of the great apes, have higher scapular fossa ratios than the more suspensory orangutan. The recent discovery of several nearly complete early hominin scapular specimens, and their apparent morphological affinities to scapulae of orangutans and gorillas rather than chimpanzees, has led to renewed interest in the comparative analysis of human and extant ape scapular form. To facilitate the functional interpretation of differences in ape scapulae, particularly in regard to relative scapular fossa size, we used electromyography (EMG) to document the activity patterns in all four rotator cuff muscles in orangutans and gibbons, comparing the results with previously published data for chimpanzees.     

An electron microscopical study of the salivary glands of the tettigoniid, Homorochoryphus nitidulus

The fine structure of the salivary glands of the tettigoniid, Homorocoryphus nitidulus vicinus, has been studied by electron microscopy. Three main types of cell are present; the parietal cells, the zymogenic cells and the extracellular duct cells. Of these, the zymogenic cells are almost certainly the major secretory cells of the gland whereas the other two cell types exhibit features indicative of transporting epithelia, suggesting that they may be responsible for controlling the ion and water content of the saliva. This rôle in ion and water transport is further supported by the light histochemical demonstration of a ouabain-sensitive sodium-dependent ATPase in both the parietal cells and the cells of the extracellular ducts.     

An ultrastructural study of pale eumycetoma grains

The electron microscopic appearances of grains from seven patients with pale grain eumycetoma infections have been studied. The infecting fungi were Pseudallescheria boydii (2), Fusarium sp. (1), Acremonium kiliense (1), a non-sporing mould (2) and Trichophyton violaceum (1). P. boydii grown in vitro and grains from a Madurella mycetomatis infection were used for comparison. The most important ultrastructural features of the pale eumycetoma grains were the gross thickening of the fungal cell walls maximal at the periphery of the grain, the predominance of grossly disorganised hyphae and the appearance of cytoplasmic membrane systems. In some areas adjacent cell walls appeared to fuse. These changes may account for some of the well recognised difficulties in isolating organisms from eumycetoma grains and treating the infections with antifungal drugs.     

An ultrastructural study of pyrenoids inLeptosiropsis torulosa

Summary The ultrastructure of the mature pyrenoid of the chaetophoracean algaLeptosiropsis torulosa is unlike any described for the green algae. The nucleus is surrounded by the pyrenoid, with only the endoplasmic reticulum interrupting the encircling pyrenoid. The pyrenoid possesses only the appressed plastid membranes that are in contact with the nucleus, with no traversing thylakoids present.     

Fusion between myogenic cells in Vivo: An ultrastructural study in regenerating murine skeletal muscle

Fusion of myogenic cells in adult murine skeletal muscle regenerating in vivo was examined at the ultrastructural level. Fusion of myoblast to myoblast, myoblast to myotube, and myotube to myotube was observed by 4 to 5 days after injury. Fusion between myogenic cells (myoblasts or myotubes) lacking a definitive glycocalyx or external lamina (basal lamina) occurred at multiple sites. It was defined by zones of cytoplasmic confluence between apposed cells at sites where contiguous segments of the cell membranes were interrupted while their edges had united resulting in linear continuity; vesicles of varying dimensions were frequent in these areas of fusion. Myoblasts were seen invaginating the surface of myofibres and again vesicles were seen in abundance in such regions. Cilia were often observed at this junctional zone suggesting that they might play a role in fusion. In the one example of probable fusion between a myotube and a myofibre, only a single area of cytoplasmic continuity was apparent.     

An ultrastructural and biochemical study of foot structure in "catch" smooth muscle cells of a clam

The foot structure of molluscan (clam) catch muscle cells was studied from the structural and biochemical standpoints. In vertebrate cross striated muscle cells, foot structures are situated in the interspaces between T-tubules and sarcoplasmic reticula (SRs). By contrast, T-tubules were not observed in clam catch muscle cells, but foot structures were ultrastructurally identified in the interspaces between the SRs and cell membranes. We isolated the SR fraction from muscle cells which contained vesicles with SRs and cell membranes. Foot structures were also observed in the SR fraction by thin sectioning. The size and shape of the foot structure in both intact muscle cells and the SR fractions appeared to be slightly smaller than those of vertebrates. However, the molecular weight of the foot structures (foot proteins) as determined by SDS-PAGE (450 kD) was similar to ryanodine receptors (RyRs) which were reported previously in cross striated muscle cells from pecten and vertebrates. The protein showing the 450 kD band reacted to an anti-ryanodine receptor by Western blotting. These findings are discussed in comparison with previous studies of foot structures and RyRs of vertebrates and invertebrates.     

An ultrastructural study of osmiophilia in the human rectum

Synopsis Rectal biopsies from subjects with a normal rectum and from patients with various forms of inflammatory bowel disease were studied by the prolonged osmication technique. No consistent ultrastructural differences were observed between these groups, but there were striking differences between individual epithelial cells in the same biopsy and between the epithelium and the cells of the lamina propria. The Golgi apparatus was demonstrated occasionally in the epithelium, often in endothelium. Endoplasmic reticulum, perinuclear cisterna and mitochondria were variably outlined. In plasma cells, there were striking differences in osmiophilia.The underlying mechanism of the different staining patterns is not clear. The findings do not appear to help in the differential diagnosis of inflammatory bowel disease nor to shed any new light on their underlying pathogenic mechanisms.     

An ultrastructural study of oogenesis in a marine triclad

The ultrastructural features of oocyte differentiation were studied in the marine triclad Cercyra hastata. Oocytes at several stages of maturation, each surrounded by follicle cell projections, are present within each of the two ovaries. A pre-vitellogenic and a vitellogenic stage have been detected in the oogenesis of C. hastata. The pre-vitellogenic stage is mainly characterized by an increase in the nuclear and nucleolar volume and activity, and the appearance and development of cortical granule precursors which are elaborated by the Golgi complex. In early phases of the vitellogenic stage, intense delamination and blebbing of the nuclear envelope occurs which probably contributes to an increase in number of cytoplasmic membranes and to transfer of nuclear material to the cytoplasm. The rough endoplasmic reticulum is extensively developed and often assumes a ‘whorl’ array. Several areas of yolk precursor formation appear in the whorls. Numerous 2–5 μm protein yolk globules are subsequently formed which appear surrounded by a double membrane (cisternae of the smooth endoplasmic reticulum) and become randomly distributed throughout the cytoplasm of mature oocytes. The peripheral ooplasm is occupied by a monolayer of electron-dense cortical granules. Finally, the evolutionary significance of the autosynthetic mechanism of yolk production is discussed.     

Features of the ultrastructural organization of the muscles of skaters in relation to their sport specialization and muscle fiber composition

An electron microscopical and histochemical investigation of bioptates obtained from the external broad femoral muscle of 74 sportsmen-skaters has been performed. Structural adaptation of the muscles to speed loadings and to endurance loadings has been analysed taking into consideration contents of muscle fibers (MF) of various type. Peculiarities in ultrastructural organization of the skeletal MF in the sprinter- and stayer-skaters, who undergo training according to a special program, are described; the character of the muscle changes is also followed in the sportsmen who undergo training according to the program that does not correspond to the contents of their MF. Lesions in the latter up to the necrotic ones are mostly found in the muscles of the stayer-skaters, as well as in the sprinters trained according to the stayer program. Presence of essential destructive alterations of the muscles in the skaters, especially in those whose contents of slow muscles do not correspond to their specialization, demonstrates, evidently, the fact that the given physical loading is not adequate to the functional or potential possibilities of the organism.