The Structure and Origin of Mastigonemes in Ochromonas minute and Monas sp.*

Structure, function, and development of mastigonemes (flagellar hairs) of 2 chrysophycean flagellates were examined with light and electron microscopy in whole mount and sectioned preparations. Mastigonemes of both organisms are identical, consisting of a tapered base 0.25–0.3 μm long, maximum width of 0.03 μm; a hollow shaft 0.85 μm × 23 nm; and 2 types of laterally projecting filaments. Two rows of mastigonemes are attached to the long flagellum, one on each side in the same plane as the central pair of microtubules. One row is composed of single mastigonemes while the other bears them in “tufts.” The primary mastigonemal attachment is on the flagellar membrane. Developmental sequences as supported by electron micrographs and kinetic studies demonstrate the intracellular location of promastigonemes during reflagellation, colchicine-inhibited reflagellation, and release from inhibition. The promastigonemes first appear in the peri-nuclear space in association with the outer nuclear membrane and several dozen may accumulate there. These may pinch off as bundles and move into the cytoplasm, or if mastigonemes are being utilized rapidly by the cell, the promastigonemes are channeled a few at a time from the perinuclear space into the Golgi apparatus where some structural modifications are made. The mastigonemes are then transported in Golgi-derived secretory-type vesicles to the cell surface near the base of the growing flagellum where the vesicle membrane fuses with the plasma membrane and the mastigonemes become extracellular, although the membrane association is retained. The origin of the asymmetric arrangement of mastigonemes on the flagellum is discussed.     

The Structure and Morphogenesis of the Ventral Ciliature in Paraurostyla hymenophora*

SYNOPSIS. The structure and morphogenesis of the ventral ciliature of Paraurostyla hymenophora (Stokes) are described. The oral primordium apparently originates in association with transverse cirrus #6, from which it migrates anteriorly simultaneous with kinetosomal proliferation. The primordium eventually forms an elongate ciliary field from which the future opisthe's fronto-ventro-transverse (FVT) and undulating membrane primordial fields arise. Concomitantly, the future proter's FVT primordial field is initiated by the disaggregation of frontal cirri #4, #5, and #6. Primordia then develop simultaneously within marginal and ventral cirral rows by a disaggregation of cirri within the respective rows, and do not give rise to new cirri until the FVT fields complete segregation into discrete cirri. Near the completion of cirral production from the FVT primordia, each ventral cirral primordium (VCP) forms the 2 rightmost transverse cirri. Segregation of new cirri within the marginal cirral primordia and VCP then occurs, eventually replacing all old cirri within their respective marginal and ventral cirral rows. At the end of cortical morphogenesis, all old ciliary organelles, with the exception of the adoral zone of membranelles, are either reorganized or replaced. These results suggest an evolutionary affinity between the ventral and marginal cirral rows and raise questions about the control of the developmental competence of individual primordia.     

The Cell Surface of Trypanosoma musculi Bloodstream Forms. I. Fine Structure and Cytochemistry*†

SYNOPSIS. An extracellular surface coat was observed at the fine-structural level on the outer lamina of the pellicular and flagellar membranes of intact Trypanosoma musculi bloodstream forms. The surface coat had a mean width of 9.2 nm, and was composed of a somewhat electron dense, uneven, fibrillar-like matrix. Brief trypsin treatment of living blood forms completely removed the cell surface coat. Several cytochemical methods applicable to electron microscopy were used to detect the presence and distribution of carbohydrates in the trypanosome's surface coat and pellicular membrane. The polycationic dye compounds employed were: ruthenium red, ruthenium violet, Alcian blue chloride, and lanthanum nitrate. Electron-dense stain reaction products, indicative of polysaccharides, were evident in the surface coat of cells treated with these dyes, which also agglutinated both living and glutaraldehyde fixed cells. Like the surface coat, the pellicular membrane of trypsinized cells gave strong positive staining reactions with the several dyes, indicating the presence of membrane bounded carbohydrates, and living and glutaraldehyde-fixed trypsinized cells were agglutinated with the polycationic stains. Bloodstream forms were treated with the enzymes, α-amylase, dextranase, and neuraminidase. No obvious morphologic difference, however, was apparent between the surface coat of untreated cells and those subjected to treatment with any of the various glycoside hydrolase enzymes. Further, these enzymes had no apparent gross effect on the staining affinity of the surface coat for the several polycationic dyes. Cationized ferritin was used to visualize the negative cell surface charge of T. musculi bloodstream forms. Large quantities of cationized ferritin were bound in the surface coat matrix. Glycoside hydrolase enzyme treatments had no apparent effect on the amount of ferritin bound in the surface coat. Cationized ferritin was bound also to the outer lamina of the pellicular membrane in trypsinized cells, which had quantitatively less ferritin bound per surface unit area than bloodstream forms untreated by the enzyme. Living and glutaraldehyde-fixed cells were agglutinated with cationized ferritin. The results obtained in the various experiments indicated that polyanionic polysaccharides were constituent terminal ligands of the surface coat matrix and pellicular membrane in T. musculi bloodstream forms.     

Fine Structure of the Oocyst Wall of Eimeria nieschulzi

SYNOPSIS. Oocysts of Eimeria nieschulzi from the laboratory rat, Rattus, norvegicus , were studied by scanning and transmission electron microscopy. Oocysts had a rough outer wall with apparent random depressions. The oocyst wall is composed of 2 layers: an osmiophilic outer layer consisting of a rough external and smooth internal surface, and a relatively thick, electron-lucent inner layer. The outer layer is composed of a dense, coarsely granular matrix. The inner layer consists of homogeneous fine granular material interspersed with coarse osmiophilic granules and contains one closely applied membrane on the outermost surface. Several raised lenticular areas are seen on the coarse outer surface of the inner layer. These layers are 102 (75–128) and 176 (135–204) nm thick, respectively.
The sporocyst wall is thin, consisting of 3 to 4 unit membranes, and measures 27 (18–34) nm thick.     

Discotricha papillifera: Structure and Morphogenesis of a Marine Interstitial Ciliate*

SYNOPSIS. Discotricha papillifera Tuffrau, a marine interstitial ciliate, is redescribed with the aid of light, scanning, and transmission electron microscopy from cells collected at a New Hampshire beach. Presence of primitive membranelles as well an an advanced stomatogenesis is demonstrated. The ultrastructure, including a unique membrane-bounded septate structure, is described. The cell is tentatively placed in the nassulid suborder Microthoracina, but affinities with other groups are discussed.     

Selectivity of Ingestion and Digestion in the Chrysomonad Flagellate Ochromonas malhamensis

Ochromonas malhamensis cells were allowed to feed on autoclaved Aerobacter aerogenes, biochemically inert polystyrene latex particles of comparable size, shape and density, or a combination of these to determine if this protozoan is capable of phagotrophic selectivity under defined experimental conditions. Electron microscopic examination of Gomoristained food vacuoles indicated that the type of particle ingested was determined entirely by the type available. Apparently the biochemical or physical configuration of the particle surface is not decisive in particle selection. Gomori acid-phosphatase reaction product, which indicates digestive enzyme activity, was present in all particle-containing vacuoles, suggesting that digestive activity in O. malhamensis is due to the presence of particulate material in the vacuole, but not necessarily to the nature of the particle.     

The Fine Structure of the Centriolar Apparatus and Associated Structures in the Flagellates Deltotrichonympha and Koruga. I. Interphase

SYNOPSIS. An electronmicroscopic study was made of the centriolar apparatus in the rostrum of Deltotrichonympha operculata and Koruga bonita , 2 closely related hypermastigote flagellates from the Australian termite, Mastotermes darwiniensis. In interphase flagellates, the centriolar apparatus consists of 2 similar parts with a mutually perpendicular orientation. Each part contains a large, club-shaped centriolar body consisting of fibrillar and granular material, without recognizable internal symmetry or microtubules. The anterior centriolar body extends from the inner rostral wall, which is structurally related to the fibrous wall surrounding the posterior centriolar body. The 2 centriolar bodies are joined by connecting branches, which meet at 3 barren kinetosome-like structures located inside the rostrum. Thus, an interphase flagellate has 2 centriolar bodies oriented at a 90° angle to each other, like a pair of typical centrioles in an interphase metazoan cell.     

Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae)

LOURO, R. P., MIGUENS, F. C. & MACHADO, R. D., 1992. Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae). Trichomes occur on both faces of young leaves. They are peltate-stellate on the abaxial face, and comprise a stalk and radiating cells with a rudimentary central apex. On the adaxial face the trichomes arc stellate with a large apex comprising one to three cells. In both cases the stalk is formed by three to six cells of which the most distal may contain a tannoid substance. In the adult leaf only the abaxial surface exhibits stellate trichomes, with two to three celled stalks. The central region of radial cells is depressed. On the adaxial side the hairs are shed during maturation of the leaf.     

Structure and sensilla of the antennae and mouthparts of Loxocephala perpunctata Jacobi (Hemiptera: Fulgomorpha: Eurybrachidae)

The ultramorphology of the antennae and mouthparts of the adult Loxocephala perpunctata Jacobi was studied through a scanning electron microscope. Seven types of sensilla were found on antennomeres, including a Böhm bristle on the scape, sensillum trichoideum and plaque organ on the pedicel, two subtypes of sensilla chaetica and two subtypes of sensilla campaniformia on these two antennomeres; and Bourgoin's organ with sensory pegs and sensilla basiconicum on the basal bulb of the flagellum. The mouthparts of L. perpunctata are of the typical piercing-sucking type, similar to mouthparts found in other hemipteran insects. In general, six types of sensilla (i.e., four subtypes of sensilla chaetica, sensillum basiconicum, subapical labial sensillum, uniporous peg-like sensillum, multiporous peg-like sensillum and two subtypes of bristle-like sensilla) were detected on different locations of the labium, with the last three, and numerous cuticular processes, present on the labial tip. The potential functions of these sensilla are discussed.     

Ultrastructure of the pea cotyledon Golgi apparatus: Origin of dense vesicles and the action of brefeldin A

Summary We have followed the action of brefeldin A (BFA) on the Golgi apparatus of developing pea cotyledons, the cells of which are actively engaged in the synthesis and deposition of storage proteins. The Golgi apparatus of normal cells is characterized by the presence of three different types of vesicle: smooth-surfaced secretory vesicles, dense vesicles which carry the storage proteins, and clathrin-coated vesicles (CCV). The dense vesicles originate at the cis cisternae and undergo a maturation as they pass through the Golgi stack, presumably as a result of cisternal progression. CCV bud off from dense and smooth vesicles, which may be attached to one another, at the trans pole of the Golgi apparatus. BFA eliminates the CCV and leads, initially, to an increase in the number and length of the cisternae. Dense vesicles are still to be seen, and many show an increase in diameter. Longer BFA treatments result in a trans-driven vesiculation and an accumulation of vesicles within the vicinity of single cisternae. The vesicles were sometimes seen to be connected to one another via a network of tubules. As judged by immunocytochemistry with gold-coupled legumin and vicilin antisera, some of the dilated vesicles originate directly from dense vesicles by swelling whereas others probably arise by dilation of Golgi cisternae since they possess a layer of flocculent storage proteins at their periphery. By contrast the centre of the dilated vesicles labels positively with antibodies against complex glycans, indicating that the ability to segregate storage proteins from cell wall or lytic vacuole glycoproteins is lost during extended BFA treatment. The effects of BFA are reversible when cotyledons are further incubated on Gamborg's medium for 5 h without the inhibitor.Dedicated to Professor R. Kollmann on the occasion of his 65th birthday.     

On the Lamellar Structure of the Tracheid Cell Wall

Abstract: It is clear that cross sections of wood cells show a lamellar structure. This paper investigates the orientation of this lamellar structure of spruce (Picea abies) tracheids using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross sections of spruce wood were produced through fracturing in longitudinal bending and tensile testing. When investigated with SEM, the fracture surfaces show a structure of mostly larger radial lamellae, in the order of 30 - 100 nm, i.e., agglomerations of a few cellulose aggregates. Thin transverse sections of the fracture zones investigated with atomic force microscopy show concentric lamellae with a width in the order of a single cellulose aggregate, i.e., 15 - 25 nm. No structural connection to the splinters in the radial direction can be seen. It is suggested that the radial lamellar structure is a consequence of the energy released during fracturing of the wood samples and that the undistorted wood has a concentric lamellar structure on a smaller structural level.     

The overexpression of GMAP-210 blocks anterograde and retrograde transport between the ER and the Golgi apparatus

Golgi Microtubule-Associated Protein (GMAP)-210 is a peripheral coiled-coil protein associated with the cis -Golgi network that interacts with microtubule minus ends. GMAP-210 overexpression has previously been shown to perturb the microtubule network and to induce a dramatic enlargement and fragmentation of the Golgi apparatus (Infante C, Ramos-Morales F, Fedriani C, Bornens M, Rios RM. J Cell Biol 1999; 145: 83–98). We now report that overexpressing GMAP-210 blocks the anterograde transport of both a soluble form of alkaline phosphatase and the hemagglutinin protein of influenza virus, an integral membrane protein, between the endoplasmic reticulum and the cis /medial (mannosidase II-positive) Golgi compartment. Retrograde transport of the Shiga toxin B-subunit is also blocked between the Golgi apparatus and the endoplasmic reticulum. As a consequence, the B-subunit accumulates in compartments positive for GMAP-210. Ultrastructural analysis revealed that, under these conditions, the Golgi complex is totally disassembled and Golgi proteins as well as proteins of the intermediate compartment are found in vesicle clusters distributed throughout the cell. The role of GMAP-210 on membrane processes at the interface between the endoplasmic reticulum and the Golgi apparatus is discussed in the light of the property of this protein to bind CGN membranes and microtubules.     

The Fine Structure of the Colonial Colorless Flagellates Rhipidodendron splendidum Stein and Spongomonas uvella Stein with Special Reference to the Flagellar Apparatus

SYNOPSIS. The cell structure of the colorless colonial flagellates Rhipidodendron splendidum Stein and Spongomonas uvella Stein has been examined by electron microscopy to assertain their phylogenetic affinities. The cylindrical cells of R. splendidum have 2 smooth flagella of equal length, an asymmetrical flagellar pocket supported by microtubules, and a curved pit between the latter and an anterior prolongation of the cell. The matrix of the branched tubes comprising the fanshaped colony is composed largely of dense spherules which are produced in special cytoplasmic vesicles some of which contain symbiotic bacteria. The anterior nucleus has a flattened sac pressed closely against its posterior end. The sac has a long tail extending deep into the cytoplasm, a single bounding membrane and homogeneous contents. Several types of vesicle are described but food vacuoles and contractile vacuoles could not be positively identified. A kinetoplast mitochondrion is not present. The various cross-banded, microtubular and amorphous components of the complex and highly asymmetrical flagellar root system are described in detail and a 3-dimensional reconstruction is provided.
The ovoid cells of S. uvella are basically similar to those of R. splendidum ; though a nuclear sac is missing, there are some detailed differences in the structure of the flagellar root system, and bacteria are never present in the vesicles producing the matrix granules. Notwithstanding much similarity, Rhipidodendron is not combined with Spongomonas because of the basic difference in colony structure.
The possible relationships of R. splendidum and S. uvella with other groups are examined and it is concluded that they cannot be considered as colorless chrysomonads as previously thought or considered to be related to any of the other orders comprising the class Phytomastigophorea. They do not, however, appear to be related to any of the orders at present comprising the Zoomastigophorea.     

The steady-state distribution of glycosyltransferases between the Golgi apparatus and the endoplasmic reticulum is approximately 90:10

Several lines of evidence support a novel model for Golgi protein residency in which these proteins cycle between the Golgi apparatus and the endoplasmic reticulum (ER). However, to preserve the functional distinction between the two organelles, this pool of ER-resident Golgi enzymes must be small. We quantified the distribution for two Golgi glycosyltransferases in HeLa cells to test this prediction. We reasoned that best-practice, quantitative solutions would come from treating images as data arrays rather than pictures. Using deconvolution and computer calculated organellar boundaries, the Golgi fraction for both endogenous beta1,4-galactosyltransferase and UDP-N-acetylgalactosamine:polypeptide N-acetylgalactosaminyltransferase 2 fused with green fluorescent protein (GFP) was 91% by fluorescence microscopy. Immunogold labeling followed by electron microscopy and model analysis yielded a similar value. Values reflect steady-state conditions, as inclusion of a protein synthesis inhibitor had no effect. These data strongly suggest that the fluorescence of a GFP chimera with an organellar protein can be a valid indicator of protein distribution and more generally that fluorescent microscopy can provide a valid, rapid approach for protein quantification. In conclusion, we find the ER pool of cycling Golgi glycosyltransferases is small and approximately 1/100 the concentration found in the Golgi apparatus.     

Schistosoma mansoni: cytochemistry and morphology of the gastrodermal Golgi Apparatus

The gastrodermal Golgi apparatus of adult Schistosoma mansoni displays two distinct morphologies. In one type, there is an identifiable cis (forming) face where vesicles from the endoplasmic reticulum fuse to form the cisternae. A morphological change occurs in the cisternae as the trans (emitting) face is approached with the cisternae becoming progressively flattened. The cisternae at the emitting face produce a membrane-bound secretory granule with moderately electron-dense contents and a vacuolar structure that may be analogous to a condensing vacuole as reported in several vertebrate secretory cells. In a second type, vesicles possessing a thicker membrane than those of the transfer vesicles are observed at the emitting face. They are not observed when the secretory granules are present. Several cytochemical markers were used to aid in studying the polarity of the Golgi apparatus. Enzymes studied were thiamine pyrophosphatase (TPPase) (EC 3.6.1.1), nucleoside diphosphatase (NDPase) (EC 3.6.1.6) using uridine diphosphate as a substrate, and nicotinamide adenine dinucleotide phosphatase (NADPase) (EC 3.1.3.2). Reaction products from all enzyme markers were observed in the cisternae and, to some extent, in the transfer vesicles. At times, NADPase and TPPase reaction products were observed in all cisternae and in the transfer vesicles of the Golgi. When this distribution was evident, the latter vesicles were observed in clusters occasionally fusing with lipid-like globules dispersed throughout the gastrodermis. Heterogeneity in cisternae was observed when NDPase, TPPase, and osmium reduction techniques were used. NDPase activity was limited to the middle cisternae while reduced osmium was observed in the outer two cisternae and in some transfer vesicles. TPPase reaction product was also observed in the secretory granules and in the condensing vacuoles. It is hypothesized that a functional bipolarity may be demonstrated by the Golgi. Under certain stress conditions, the forming face of the Golgi may package lysosomal enzymes while the emitting region of the Golgi appears to be responsible for the packaging of the secretory granules. The fusion of transfer vesicles and, at times, secretory granules with lipid-like globules is postulated to represent a mechanism by which enzymes may be transported to the lumen of the cecum.     

The Structure and Development of the Dorsal Bristle Complex of Oxytricha fallax and Stylonychia pustulata*

SYNOPSIS. Oxytricha fallax and Stylonychia pustulata possess 6 rows of dorsal bristle units. Each dorsal bristle unit consists of a pair of kinetosomes; the anterior kinetosome has a cilium and the posterior kinetosome a ciliary stub. The kinetosome pair, located at the bottom of a cortical pit surrounding the cilium and ciliary stub, is surrounded by an asymmetrical fibrillar mass. Future rows 1-4 are formed from 2 sets of primordia originating within mature dorsal rows 1-3. Rows 5 and 6 originate from the anterior regions of both right marginal cirral primordia. Old dorsal bristle units utilized in formation of primordia are presumably maintained in the new rows of the proter and opisthe; those outside the primordia are resorbed. The morphogenetic pattern of the Oxytrichidae is similar to those of the Urostylidae and Holostichidae, but quite different from that of the Euplotidae.     

Segregation of the Qb‐SNAREs GS27 and GS28 into Golgi Vesicles Regulates Intra‐Golgi Transport

The Golgi apparatus is the main glycosylation and sorting station along the secretory pathway. Its structure includes the Golgi vesicles, which are depleted of anterograde cargo, and also of at least some Golgi‐resident proteins. The role of Golgi vesicles remains unclear. Here, we show that Golgi vesicles are enriched in the Qb‐SNAREs GS27 (membrin) and GS28 (GOS‐28), and depleted of nucleotide sugar transporters. A block of intra‐Golgi transport leads to accumulation of Golgi vesicles and partitioning of GS27 and GS28 into these vesicles. Conversely, active intra‐Golgi transport induces fusion of these vesicles with the Golgi cisternae, delivering GS27 and GS28 to these cisternae. In an in vitro assay based on a donor compartment that lacks UDP‐galactose translocase (a sugar transporter), the segregation of Golgi vesicles from isolated Golgi membranes inhibits intra‐Golgi transport; re‐addition of isolated Golgi vesicles devoid of UDP‐galactose translocase obtained from normal cells restores intra‐Golgi transport. We conclude that this activity is due to the presence of GS27 and GS28 in the Golgi vesicles, rather than the sugar transporter. Furthermore, there is an inverse correlation between the number of Golgi vesicles and the number of inter‐cisternal connections under different experimental conditions. Finally, a rapid block of the formation of vesicles via COPI through degradation of ϵCOP accelerates the cis‐to‐trans delivery of VSVG. These data suggest that Golgi vesicles, presumably with COPI, serve to inhibit intra‐Golgi transport by the extraction of GS27 and GS28 from the Golgi cisternae, which blocks the formation of inter‐cisternal connections .     

Taenia hydatigena—V. Surface structure of the adult worm and evaginated scolex

Scanning electron microscopy (SEM) of the surface of the adult tapeworm and the freshly evaginated scolex from the cysticercus indicated that in Taenia hydatigena there was a variety of microthrix form. This variety was found between different areas on the same specimen and between the adult and freshly evaginated scolex. In the latter there was a noticeable absence of pointed spikes from most areas. Artifacts attributable to techniques of preparation are also discussed.