A Light and Scanning Electron Microscope Study of Stem Nodules in Vicia faba L

Stem nodules were observed on plants of Vicia faba L. cv. ThrowsMS grown in a variety of environmental conditions. Observationsby light and scanning electron microscopy indicated that theseorgans were morphologically similar to root nodules on the sameplants. Nodules arose following infection of stem hairs andsubsequent growth of infection threads into the stem cortex.They developed to a mature, nitrogen-fixing state.     

CEREBELLAR GRANULE CELLS IN VITRO : A Light and Electron Microscope Study

The behavior of granule cells in mature cerebellar cultures derived from newborn mice was studied by light and electron microscopy. Many granule cells remained in the explants as an external granular layer. These cells were differentiated, as evidenced by formation of bundles of parallel fibers and by development of synapses between granule cell axons and Purkinje cell branchlet spines, and between Golgi cell axons and granule cell dendrites. Although the over-all architecture of the cerebellar explants after 18–33 days in vitro was similar to that of the newborn mouse, the evident differentiation of the granule cells suggested that interneuronal relationships resemble those of the mature cerebellum in vivo.     

The structure and cytochemistry of the neurosecretory cells of Fasciola gigantica Cobbold and Fasciola hepatica L.

Histochemical studies of the nervous system of Fasciola gigantica and Fasciola hepatica were undertaken. Neurosecretory cells were detected by Gomori's aldehydefuchsin, Bargmann's chrome hematoxylin-phloxin, Mallory's triple stain, periodic acid-Schiff, Heidenhain's Azan and alcian blue after potassium permanganate oxidation. Two types of neurosecretory cells were recognized and designated as "A" and "B". Type "A" cells occurred in small numbers in the brain and subesophageal mass and type "B" cells ubiquitous in distribution. The reactions of these cells to the standard stains for neurosecretory substance generally, were less intense than the neurosecretory cells of other animals such as crustaceans and insects. The structure, organisation, distribution and cytochemistry of neurosecretory cells in Fasciola gigantica and Fasciola hepatica is discussed.     

Light and Electron Microscope Study of Dunaliella primolecta Butcher (Volvocida)*

SYNOPSIS. Light and electron microscope observations on Dunaliella primolecta Butcher from logarithmic and stationary phases of batch cultures are correlated. Except for the lack of a cell wall the fine structure has typical volvocid features. The transition from logarithmic to stationary phase is marked by changes in content and size of cytoplasmic vacuoles, accumulation of cytoplasmic lipid, accumulation of starch in the plastid matrix, and by the formation of autophagosome-like bodies. The organelles in stationary-phase flagellates are closely packed together because of the cytoplasmic lipid and starch-distended chloroplast. Organisms from logarithmic phase have an abundant ribosome-packed groundplasm supporting the organelles. In the cytochemical demonstration of acid phosphatase activity, Golgi cisternae and smooth and coated Golgi vesicles contain Gomori reaction product. The possible roles of the Golgi apparatus in this flagellate are discussed.     

Electron microscope studies of Fasciola hepatica. X. Egg formation

Evidence obtained would suggest that the processes involved in egg formation in Fasciola hepatica occur in the following sequence. The egg constituents, namely an ovum and some vitelline cells, pass through the proximal ootype and as they do so they are smeared by the secretions of Mehlis' gland which have accumulated there. A temporary interface is set up between the Mehlis' gland secretion and the fluid which surrounds the egg constituents. Shell globules are released by the vitelline cells and coalesce on the inner aspect of the interface. At the same time some of the Mehlis' secretion diffuses across the interface, thereby bringing about the dissociation of the interface. It is suggested that Mehlis' gland secretion brings about the fusion of the shell layer. During the initial stages of the process the developing egg is supported by the cells of the ootype epithelium. Later the egg passes into a wider, more distal part of the ootype where the process of shell deposition is continued. When complete, or almost complete, the egg passes into the uterus where changes indiciating the initial process of tanning are seen to take place. A thin, very uniform layer of Mehlis' gland secretion can still be identified on the surface of mature eggs.     

Specific and non-specific phosphatases in the miracidium of Fasciola hepatica L.

Localization and activities of alkaline phosphatase, ATPase, 5-nucleotidase, glucose-6-phosphatase, thiamine pyrophosphatase and nucleoside diphosphatase were studied in the miracidium of Fasciola hepatica L. Except for nucleoside diphosphatase whose activity in the miracidium was not observed, all the enzymes were most active in the archenteron, protonephridia and nerve ganglion. This localization of the reaction intensity allows the inference that the three organs mentioned are sites of both intense carbohydrate metabolism and lively active transport. The role of phosphatases in carbohydrate metabolism is discussed.     

Supravital Uptake of Methylene Blue by Dendritic Cells within Stratified Squamous Epithelia: a Light and Electron Microscope Study

Electron microscopic data on methylene blue staining of dendritic cells in the epithelia of the soft palate and skin of the moose after supravital dye injection are presented. The ultrastructural details were compared with corresponding light microscopic findings. Methylene blue stained tissue was fixed by immersion in a paraformaldehyde-glutaraldehyde solution containing phosphomolybdic acid. The ensuing dye precipitate was stabilized by ammonium heptamolybdate. The light microscopic investigation revealed that selective staining of dendritic cells depended on the presence of ambient oxygen. In addition, delicate morphological characteristics, like spinous structures of the dendrites, were visible. Some cells also showed terminal enlargements of the dendrites close to the surface of the epithelium. In general, visualization of morphological detail was superior to that obtained by conventional histological and immunohistochemlcal procedures. Nerve fibers were also stained within the epithelium as well as the subepithelial connective tissue. At the electron microscopic level, the dye was clearly identified as an electron dense precipitate that accumulated primarily within the cytoplasm near the plasma membrane. Furthermore, it was bound to the chromatin of the nuclei. No significant staining of mitochondria or other organelles was seen, within the cytoplasm, the oxygen-dependent binding sites may be associated with heme proteins that attract both the dye in its reduced lipophilic leuco form and oxygen, followed by generation of oxygen radicals and a reoxldation of the leuco form to the cationic blue dye. Because of its selectivity for intraepithelial dendritic cells, the method described here supplements immunocytochemical procedures at both the light and electron microscopic levels.     

Structure and Function in the Grass Ligule: the Newly-initiated Ligule of Lolium temulentum L., a Light and Electron Microscope Study

Initiation and early development of the membranous ligule ofLolium temulentum L. was studied by light and transmission electronmicroscopy. The ligule appeared to be derived solely from theleaf adaxial epidermis and at this stage had a structure andultrastructure typical of a meristematic tissue. Cells of thefuture collar region of the leaf appear to be initiated at thesame time as the ligule. The siting of the ligule upon the leafis briefly discussed. Darnel, ligule (initiation), Lolium temulentum L., Poaceae, ultrastructure     

Electron microscope studies of Fasciola hepatica. XI. Autophagy and parenchymal cell function

An electron microscope study of the function of parenchymal cells in Fasciola hepatica in relation to glycogen storage and metabolism was undertaken.Although no evidence of a relationship between morphological changes in parenchymal cells and glycogen was apparent, a correlation between glycogen depletion and autophagy was observed. The autophagic process started with the synthesis and “budding off” of membranes by mitochondria to form small vesicles (M bodies), either of a simple type (limited by a single membrane) or a complex type (limited by two or more membranes). These M bodies fused to form narrow, smooth cisternae (SCM), which wrapped around areas of cytoplasm containing glycogen; this process gave rise to β bodies. The β bodies (autophagosomes) were at first irregular in shape and limited by two or more membranes separated by a space of varied width. Older β bodies became more smooth and oval in outline and were limited by a single membrane due to membrane fusion. Primary lysosomes synthesized by the GER-GA system united with the late β bodies and formed secondary lysosomes (autolysosomes). Following the addition of these lysosomal hydrolases, the glycogen content of the autolysosomes was reduced and eventually disappeared. This resulted in the develpment of residual bodies containing unhydrolysed material in the form of dense granules, tubules, and myelin figures in a matrix of varied density.It was concluded that at least some glycogen in the parenchymal cells of F. hepatica is mobilized by autophagy. All the morphological structures observed in the experimental material were also present in controls, although in fewer numbers, and it is believed that autophagy is a normal process in this fluke.