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The posterior half of the channel catfish intestine has a similar histological organization to that of other teleost fishes. This region is organized into a muscosa, a submucosa, a double layered muscularis and a serosa. A "stratum compactum" of dense connective tissue was confirmed for the submucosa. In its histology and cytology, the midgut resembles the hindgut, except that in the hindgut the muscularis is thicker, the microvilli are shorter, there are fewer absorptive inclusions in the columnar cells and there are more goblet cells. With the exception of the serosa, the tissue layers of the intestine of the 6 cm juvenile catfish are fully developed. The most notable difference between the intestines of the juvenile and adult catfish occurs in the columnar epithelial cells. The mucosal cells of the juvenile catfish contain an abundance of large clear vacuoles while the mucosal cells of the mature catfish contain smaller dense granules. With few exceptions, the ultrastructural details of the cells in the catfish intestine are identical to those of the same cell types of the mammalian intestine. more...

The organization, morphological characteristics, and synaptic structure of photoreceptors in the adult zebrafish retina were studied using light and electron microscopy. Adult photoreceptors show a typical ordered tier arrangement with rods easily distinguished from cones based on outer segment (OS) morphology. Both rods and cones contain mitochondria within the inner segments (IS), including the large, electron-dense megamitochondria previously described (Kim et al.) Four major ultrastructural differences were observed between zebrafish rods and cones: (1) the membranes of cone lamellar disks showed a wider variety of relationships to the plasma membrane than those of rods, (2) cone pedicles typically had multiple synaptic ribbons, while rod spherules had 1–2 ribbons, (3) synaptic ribbons in rod spherules were ∼2 times longer than ribbons in cone pedicles, and (4) rod spherules had a more electron-dense cytoplasm than cone pedicles. Examination of photoreceptor terminals identified four synaptic relationships at cone pedicles: (1) invaginating contacts postsynaptic to cone ribbons forming dyad, triad, and quadrad synapses, (2) presumed gap junctions connecting adjacent postsynaptic processes invaginating into cone terminals, (3) basal junctions away from synaptic ribbons, and (4) gap junctions between adjacent photoreceptor terminals. More vitread and slightly farther removed from photoreceptor terminals, extracellular microtubule-like structures were identified in association with presumed horizontal cell processes in the OPL. These findings, the first to document the ultrastructure of the distal retina in adult zebrafish, indicate that zebrafish photoreceptors have many characteristics similar to other species, further supporting the use of zebrafish as a model for the vertebrate visual system. more...

The ultrastructure of the optic nerve, brain, and some associated structures of larval zebrafish, grown under three different light regimens were studied. Fish grown under cyclic light (control), constant dark (CD), and constant light (CL) were studied for 4 and 8 days postfertilization (dpf). We also studied the control and CD fish at 15 dpf. The brains of the control and CL fish were larger at 4 dpf than at 8 dpf. In all 4 dpf fish, the brain occupied the entire expanse between the two retinas and the optic nerve extended the shortest distance between the retina and the brain. The 15 dpf zebrafish had the smallest brain size. Groups of skeletal muscle cells associated with the optic nerves became visible in all older larvae. In the 15 dpf larvae, bulges and dilations in the optic nerve occurred as it reached the brain and optic chiasms occurred proximal to the brain. Electron microscopy yielded information about myelinated and unmyelinated axons in the optic nerve, the dimensions of neurotubules, neurofilaments, and myofilaments, including a unique variation in actin myofilaments, and a confirmation of reported myosin myofilament changes (but with dimensions). We also describe the ultrastructure of a sheath-like structure that is confluent over the optic nerve and the brain, which has not been described before in zebrafish. Also presented are images of associated fibroblasts, epithelial cells lining the mouth, cartilage plates, blood vessels, nerve bundles, and skeletal muscle cells, most of which have not been previously described in the literature. more...

Pt nanoparticles (NPs) of different shape (cubic and octahedral/tetrahedral) and size (5–10 nm) were synthesized by one-step polyol-based synthetic procedures that permit the concomitant control of the shape and size. The shape and size stability of these particles under repetitive methanol (MeOH) electro-oxidation cycles was investigated by transmission electron microscopy (TEM) as well as cyclic voltammetry (CV). The TEM images of the particles taken before and after being subject to 1000 MeOH electro-oxidation CV cycling and the corresponding hydrogen adsorption/desorption profile in the CVs indicated that, the octahedral/tetrahedral Pt NPs had the highest stability among the samples investigated. Infra-red measurements suggest that this observation may be a result of exceptionally strong interaction of the capping polymer with octa/tetrahedral Pt NPs. These findings indicate that the synthetic procedure employed in this study can be used to synthesize highly stable catalyst particles with tunable shape and size. more...

This study reports on morphological features of hepatic portal tracts in the liver of a rhesus monkey. The light microscope shows that the number of each type of principal component comprising a portal tract varies but that there are usually one to five lymphatics, one bile ductule, one bile duct, one arteriolar and one arterial branch of the hepatic artery, and one hepatic portal vein. Bile ductules, in cross section, have 6-10 cells (mostly low pyramidal, but with a few cuboidal) bordering the lumen, an outside diameter of from about 20 to 25 microm, and a luminal diameter of from 2 to 10 microm. Bile ducts, in cross section, have more than 10 cells (about equal numbers of low pyramidal and cuboidal) bordering the lumen, an outside diameter greater than 25 microm and a luminal diameter of greater than 10 microm. The term "pyramidal" has not previously been applied to the cells of the ductules and ducts. The monkey tracts show several cytological features previously undescribed, viz., abortive cilia and basal bodies in the duct cells, abortive cilia in the ductule cells, and an occasional aggregation of ribosomes in arterial endothelial cells. They also show a major histological feature previously mentioned but not illustrated, viz., bundles of nerve processes which exhibit a preferential location, i.e., proximity to the arterioles and arteries. more...

Based on a polyol process, one-step synthetic procedures were investigated for concomitant control of the shape and size of platinum nanoparticles (Pt NPs). Cubic and octahedral/tetrahedral particles of different sizes (5–10 nm) were synthesized using these procedures. Further attempts to control the shape of the NPs below 3–4 nm failed. It was found that 3–4 nm is the particle size limit for Pt NPs above which the particle size and shape can be concomitantly controlled. more...

Ketogenic diets are used in the treatment of epilepsy in children refractory to drug therapy. This study identifies changes in liver morphology in rats fed four different diets: a normal rodent chow diet, a calorie-restricted high-fat (ketogenic) diet and each diet supplemented with clofibric acid. Hepatocytes of rats fed the ketogenic diet show many lipid droplets and these are reduced to control levels when clofibrate is present in the diet. Mitochondria are enlarged in the livers of rats fed the ketogenic diet and further enlarged if clofibrate is present. Alterations in the appearance or numbers of other organelles are also found. more...

A light and transmission electron microscope study of sections of cells of—and of cells and tissues of—and of cells, associated with the previously undescribed tymbal muscle of a periodical cicada (Brood X of the 17-year cicada) was undertaken to (i) compare their features with similar features described for other cicada tymbal muscles, (ii) use that information to try to determine cytologically whether the muscle should be considered synchronous or asynchronous, and (iii) seek information about ultrastructural features not previously described for any cicada. In cross section the myofibrils are slightly angular and have an abundance of sarcoplasmic reticulum and T tubules. Longitudinal sections show a pair of T tubules, one of each pair located midway between the Z line and the center (H level) of each sarcomere. These cytological features are consistently found in the tymbal muscles of the majority of other cicada genera and species, which are designated synchronous muscles, and all of which are termed fast muscles. The amount of sarcoplasmic reticulum increases at the Z lines. The largest mitochondria occur in the largest axons, but the smallest axons have more neurotubules per cross-section area. Axon diameters range 0.14–20 μm. Multinucleate adipocytes, with vacuoles that appear either empty or content-containing, and tracheocytes, which could either be binucleate or have a lobate or U-shaped nucleus, are located at the periphery of the muscle. Large numbers of microtubules occur in the interface glia. The diameters of microtubules and neurotubules (∼27 nm) agree closely with the averages usually cited. This study indicates that the tymbal muscles of this cicada should be designated as synchronous, and it describes ultrastructural features that are typical and others that are unusual. more...

Four tunnels off the lumen of the proventriculus of the carpenter bee, Xylocopa virginica virginica, have been discovered. Light and electron micrographs revealed the presence in the tunnels of gram-positive, rod-shaped bacteria, some of which showed division stages. The occurrence of the bacteria exclusively in the tunnels—not in the lumen of the proventriculus—makes speculation as to their function difficult. The function of the tunnels is also obscure, as no glands were seen emptying into them. The bacteria may be symbionts that release enzymes into the tunnels, which are subsequently transported to the midgut to aid digestion. They could also be parasites. This is the first report of such bacterial-containing tunnels in insects. more...

Ultrastructural features of the pharynx, esophagus, and associated intrinsic visceral muscular and nervous structures of the booklouse, Liposcelis divinatorius, were studied to determine whether the anatomical arrangements of these structures differed from the general pattern found in insects. The results are compared with previous light microscope studies of this tiny insect. Variations from the usual arrangement reported for intrinsic visceral muscles associated with the pharynx in insects are described. Intrinsic visceral muscles include a narrow band of circularly disposed fibers and both extra-circular and intra-circular longitudinally disposed fibers. This represents a departure from the slightly developed inner longitudinal and more prominent outer circular fibers seen in most insects. The outer surface of some circular muscle cells has apparently unique pouches packed with mitochondria, which contain many cristae. Numerous bacteroids appear in the esophageal epithelial cells and in the sub-esophageal ganglion. Nerve processes associated with the foregut contain neurotubules, synaptic vesicles, and electron-dense granules. more...

The arrival of rose rosette disease (RRD) in the Washington D.C. area prompted a transmission electron microscope study of ultrathin sections of leaves from symptomatic Rosa wichuraiana x safrano plants. Virus-like particles (VLPs) or double membrane-bound particles (DMPs) resembling those associated with RRD in other types of roses, and found in several other plant diseases, were seen in the cytoplasm of parenchymal and vascular bundle cells and shown, for the first time, in guard cells and budding into the vacuoles. Contrary to previous reports, starch granules were found in chloroplasts of the infected cells. A presumably unique intramitochondrial crystal was also observed. Variations in vacuolar content were noted. more...

Ultrastructural examination of photoreceptor inner segment ellipsoids in larval (4, 8, and 15 days postfertilization; dpf) and adult zebrafish identified morphologically different types of mitochondria. All photoreceptors had mitochondria of different sizes (large and small). At 4 dpf, rods had small, moderately stained electron-dense mitochondria (E-DM), and two cone types could be distinguished: (1) those with electron-lucent mitochondria (E-LM) and (2) those with mitochondria of moderate electron density. These distinctions were also apparent at later ages (8 and 15 dpf). Rods from adult fish had fewer mitochondria than their corresponding cones. The ellipsoids of some fully differentiated single and double cones contained large E-DM with few cristae; these were surrounded by small E-LM with typical internal morphology. The mitochondria within the ellipsoids of other single cones showed similar electron density. Microspectrophotometry of cone ellipsoids from adult fish indicated that the large E-DM had a small absorbance peak (∼0.03 OD units) and did not contain cytochrome-c, but crocetin, a carotenoid found in old world monkeys. Crocetin functions to prevent oxidative damage to photoreceptors, suggesting that the ellipsoid mitochondria in adult zebrafish cones protect against apoptosis and function metabolically, rather than as a light filter. more...

The human tongue has been the subject of many cytological and histological studies. When a literature search disclosed no reports of the ultrastructure of the morphotypes of bacteria residing on the tongue's surface, a transmission electron microscope study of ultrathin sections of bacteria obtained by scraping eight human tongues was undertaken. The scrapings from the anterior dorsal tongue surfaces, processed conventionally for electron microscope study, revealed 33–35 different bacterial morphotypes. Several of the morphotypes were unique to a tongue. Morphotype differences were also related to donor characteristics such as smoking, tongue site, location in centrifuge pellet, diet, and medications. The predominant morphotypes were Gram-positive cocci. These preliminary findings suggest that the microbiota of the human tongue and variations in that microbiota, related to physical condition, lifestyle, medications, and dietary preferences, merit more attention from anatomists. Anat Rec 259:276–287, 2000. © 2000 Wiley-Liss, Inc. more...

The rat tongue has been the subject of many cytological studies, both purely descriptive and experimental. To assess the suitability of the organ for additional cytological and histological senior research thesis projects, light and transmission electron microscope studies of thin and ultrathin sections, respectively, were conducted. Several samples from the anterior dorsal surface of the tongue of a male rat (Sprague-Dawley) were processed conventionally for light and electron microscope study. About 170 sections, each approximately 1 × 1 mm in area and 1.0 μm thick, collected from 12 adjacent areas, all including the mucosa, of a tongue were studied in the light microscope. Numerous mast cells were observed scattered throughout the submucosal region, adjacent to nerve bundles, blood vessels, and skeletal muscle, and up to six bundles each consisting of many myelinated and unmyelinated nerve processes were seen per section. Single, double, and quadruple myelinated nerve processes were also seen. Several of the multiple, mixed nerve bundles contained a mast cell. Mast cells were not found within the endoneurium or perineurium of exclusively myelinated processes. Ultrathin sections adjacent to the thin sections containing mast cells within the nerve bundles were sought and studied in the transmission electron microscope to confirm the identification of these mast cells. Mast cells occur within bundles containing both myelinated and unmyelinated nerves in the rat tongue, and this is an apparently previously unreported event. Furthermore, no clear evidence has been found in the literature of such specific mast cell distribution in other parts of the animal body. Single, double, and quadruple myelinated nerve processes were noted, but none contained a mast cell. Anat Rec 256:347–353, 1999. © 1999 Wiley-Liss, Inc. more...

We have examined the UV/Visible spectra of nanoscopic gold particles adsorbed on antimony-doped tin oxide transparent electrodes in contact with aqueous electrolytes of varying type and concentration. For the four electrolytes KPF 6 , NaClO 4 , KCl, and KBr, we observe a positive shift in the Au-particle plasmon resonance absorption maximum λ max as the electrode potential is increased to more positive values. The degree of the potential-induced shift depends on the electrolyte type and concentration, and on the size of the Au particles. For all electrolytes, the shift in peak absorption is largest for smallest Au particles (Δλ max /ΔE ≈ 40 nm/V). At constant particle size, the potential-induced shift is largest in the presence of Cl − and Br − and smallest in the presence of PF 6 − and ClO 4 − . We discuss these results in the context of models which consider: 1) electrode potential effects on free electron concentration (Drude Theory); and 2) anion adsorption processes which affect the plasmon resonance condition via changes in the Au surface layer refractive index. more...

The distribution and ultrastructural features of peripheral nerve processes in the extra-retinal layers of the eyes of the zebrafish, Danio rerio (Hamilton), were investigated using light and transmission electron microscopy. A comparative study of the quality of preservation provided by three different fixation procedures revealed no consistently striking general differences. However, somewhat subjectively, the fixative containing Millonig's buffer did consistently provide better fixation of myelin. Overall, nerve processes, depending on the site studied, were distributed as either (1) bundles (in the choroid near the optic nerve head and in the choroid adjacent to the limbus), (2) linear arrays (in the junction between the sclera and cartilage and in the choroid adjacent to the retina) or (3) individual units (in the choroid under the cartilage or in the sclera). Both myelinated and unmyelinated processes were identified in these locations. Myelinated processes usually contained both neurofilaments and neurotubules, but a few apparently contained only neurofilaments. Unmyelinated processes usually contained mainly neurotubules, but a few apparently contained only neurofilaments. Taken together, these findings indicate innervation of extra-retinal structures, as seen in zebrafish, is highly conserved among vertebrates, further supporting the use of zebrafish as a model for the vertebrate visual system. more...

Ultrastructural features of the musculo-epidermal and epidermo-cuticular junctions in the abdomen of Pediobius foveolatus (Crawford) were studied with light and electron microscopes. The musculo-epidermal junction lacks interdigitations and a secondary myofilament association with its desmosomes. The epidermal cells lack a microtubular insertion into the desmosomes and hemidesmosomes, indentations from the epidermo-cuticular junction, and filamentous projections from the cell's surface into the cuticle. These configurations are compared with reports of other investigations of these insect junctions. more...

Samples from the liver of a male rat (Sprague-Dawley), a monkey (Macacus rhesus), and a longnose gar pike (Lepisosteus osseus) were studied in a transmission electron microscope to provide cytological and histological information about structures previously poorly documented in the literature. Glisson's capsule consisted of dense, irregular connective tissue of typical Type-I collagen fibrils. The capsule was formed by a single stratum of fibroblasts in the rat and in the pike, but by one or two strata of fibroblasts in the monkey. In the rat, but not in the monkey or pike, fibroblast processes interdigitated with processes from the hepatocytes. In the pike, fibroblast processes extended toward both mesothelium and hepatocytes. In some areas of the rat and pike, mesothelial cells had desmosomal connections and microvillous projections into the peritoneal cavity. Marginated heterochromatin was more abundant in the rat and monkey. The mesothelium was discontinuous in the rat and monkey but, in areas of discontinuity, the capsular surface was covered by a basal lamina, often barely perceptible beneath mesothelial cells of the rat and monkey, but prominent in the pike. In the pike, the mesothelium had numerous pinocytotic vesicles on both peritoneal and capsular surfaces. more...

To examine the functions of the Arf-like protein, Arl1p, in Saccharomyces cerevisiae, a null allele, arl1Δ::HIS3, was constructed in two strains. In one background only, loss of ARL1 resulted in temperature-sensitive (ts) growth (suppressed on high-osmolarity media). Allelic variation at the SSD1 locus accounted for differences between strains. Strains lacking ARL1 exhibited several defects in membrane traffic. First, arl1Δ strains secreted less protein as measured by TCA-precipitable radioactivity found in the media of [35S]-labelled cells. A portion of newly synthesized carboxypeptidase Y (CPY) was secreted rather than correctly targeted to the vacuole. Uptake of the fluid-phase marker, lucifer yellow, was reduced. All these phenotypes were exacerbated in an ssd1 background. The ts phenotype of the arl1Δssd1 strain was suppressed by YPT1, the yeast Rab1a homologue, suggesting that ARL1 and YPT1 have partially overlapping functions. These findings demonstrate that ARL1 encodes a regulator of membrane traffic. Copyright © 2002 John Wiley & Sons, Ltd. more...

Background and Methods: In an effort to review ultrastructural features of cells in the kidney of a male rat, transmission electron microscopy was used to study ultrathin sections. Results: One light cell in a collecting tubule contained a 2.3-μm long linear array of electron-dense asymmetric structures in a granular zone of greater electron density than the general cytoplasm. This inclusion body could be interpreted to consist of a parallel array of 100–150-nm × 24-nm electron-dense rodlets, or a parallel array of 100–150-nm×67-nm tubules. The inclusion showed no association with any cell organelle. The origin, chemical nature, frequency of occurrence, and functional significance of this inclusion are unknown. Conclusions: Although this inclusion body somewhat resembles previously described inclusions or granules, the differences in dimensions, frequency, and relation to other cell structures suggest it is a new observation. © 1995 Wiley-Liss, Inc. more...

Ultrathin sections of sporulating Bacillus thuringiensis were examined in a transmission electron microscope. Less than 1% of the about 2,000 approximately sagittal sections of the bacterial cells examined contained two endospores per cell. This finding clarifies the majority of textbook and research reports (which tend to be ambiguous), contradicts several of the most recent textbook reports, and confirms three unillustrated textbook reports, in relation to the occurrence of disporous bacilli. Electron microscopic evidence of the observation is presented, apparently for the first time. more...

General cytological and ultrastructural features of cells found in the peripheral blood of three captive beluga whales (Delphinapterus leucas) are described. We noted all major peripheral cell types common to the circulation of mammalian species, including polymorphonuclear neutrophils, eosinophils, basophils, lymphocytes, and monocytes, as well as myelocytes, erythroblasts, and plasma cells. Platelets and two populations (normal and hypochromic) of red blood corpuscles were observed. more...

Pt nanoparticles having the same size ( approximately 10 nm) but different shapes (cubic or octahedral/tetrahedral), as determined by transmission electron microscopy, were synthesized via a polyol-based synthetic procedure. Their respective electrocatalytic activities for methanol oxidation were characterized by cyclic voltammetry and chronoamperometry in both sulfuric and perchloric acid electrolytes, which showed clear shape (surface orientation) dependences. Furthermore, the octahedral/tetrahedral Pt nanoparticles displayed an unexpectedly large enhancement in methanol electro-oxidation activity; about 3-fold increase in transient intrinsic activity and 10-fold increase in CO tolerance steady-state activity when compared to commercial Pt black. Gaseous and methanolic CO adsorption on the synthesized nanoparticles were also investigated by surface-enhanced IR absorption spectroscopy in perchloric acid electrolyte, which suggested that the different trends observed might be related to the electronic effects specific to a given ensemble of the nanofacets. more...

The low molecular mass gelator, tetraoctadecylammonium bromide, can be removed from polymerized gels of methyl methacrylate or styrene to leave mesoscopic channels with submicrometre diameters.

Samples of Euhyperamoeba biospherica n. sp., a free-living, marine, multinucleate, limax ameba of Caribbean origin (via the Biosphere 2 Ocean and a Georgetown University marine aquarium) were examined by light and transmission electron microscopy. The amebas grossly resemble two previously described species of marine, multinucleate limax amebas, Euhyperamoeba fallax and Gruberellaflavescens. They differ, however, in their large size and thousands of nuclei. They also differ in containing structures that resemble bacteria more than mitochondria because of their ultrastructure and presumed division figures and because they produce rods composed of filaments or microtubules. We suggest that these amebas are more primitive than E. fallax or G. flavescens and may, therefore, contribute to our understanding of the evolution of organelles, such as mitochondria, in eukaryotic cells. Additional key words: Bacteria, mitochondria Limax amebas are free-living, multinucleate, naked amebas that move in slug-like fashion (Page 1984). The only marine limax amebas so far described are Gruberella flavescens (GRUBER 1889) PAGE 1984 and Euhyperamoeba fallax (SERAVIN & GOODKOV 1982) SERAVIN & GOODKOV 1985. These two species are not considered (Page 1984) to be related to the freshwater multinucleate genera Chaos LINNAEUS 1767, Pelomyxa GREEFF 1874, or Thecochaos PAGE 1981. Gruber (1889) was the first to describe a marine, multinucleate ameba, which he found in the Mediterranean Sea and named Amoeba flavescens. Page (1984) found the same ameba in a Cornish rock pool, and a light, and electron microscopical study led him to establish for it the new genus Gruberella. This ameba fed on bacteria, flagellates, other amebas, and cili more...

Transmission electron microscopy of ultrathin sections reveals multitubular pod inclusions in non-pathological cockroach granular hemocytes associated with skeletal muscle cells and tracheocytes. Each pod contains up to 39 simple (i.e., single-walled) or compound coaxial (i.e., doubleor triple-walled) tubules. Tubules are about 70-85 nm in diameter, depending on tubule complexity. The distribution of tubule types and tubule dimensions suggest that the outer tubule wall forms first, in the case of doubleor triplewalled tubules. Tubule lumens usually are empty. Insect hemocytes have been studied extensively (for recent reviews, see Gupta, 1979a, 1985). During a study of the ultrastructure of leg muscle in Periplaneta americana, we saw multitubular pod inclusions in a granular hemocyte closely associated with skeletal muscle cells and tracheocytes. A literature search revealed only three reports of the ultrastructure of these inclusions (Baerwald, 1979; Baerwald & Boush, 1970; Ennesser & Nappi, 1984). Because Baerwald (1979) and Baerwald & Boush (1970) described hemocytes collected by dripping hemolymph from a cut antenna end into fixative and because Ennesser & Nappi (1984) studied similarly collected hemocytes and hemocytes taken from an encapsulation response, we considered description of inclusions from an in situ and non-pathological granular hemocyte to be pertinent. MATERIALS AND METHODS A female of Periplaneta americana, about 6 cm in length, was captured in our greenhouse, chilled in a refrigerator for 15 min, and decapitated. The skeletal muscle from the femur was removed from the exoskeleton and immersed in a solution containing 2.5% glutaraldehyde buffered at a pH of 7.4 with 0.1 M phosphate buffer (Millonig, 1961). Primary fixation was carried out overnight (15 h) at 5?C. Four consecutive 15-min primary washes with buffer were followed by 2 h postfixation in 2% OsO4 in the same buffer. Four 15-min washes in the buffer followed. Dehydration was carried out by passage, at 10min intervals, through an ethanol series (1:1 50% ethanol: buffer, 50%, 75%, 85%, 95%, 100%, 100%, 100% ethanol), followed by three 10-min changes in propylene oxide. Overnight (12 h) infiltration was accomplished in a 1:1 mixture of propylene oxide and Epon LX-112 (Luft, 1961). A 1:3 mixture of propylene oxide and Epon was allowed to infiltrate the specimens for 8 h. Specimens were embedded in Epon in aluminum weighing dishes and subsequently placed in a polymerizing oven at 60?C for 48 h. Ultrathin (40-60 nm) sections were cut using a diamond knife (E.I. Dupont, Wilmington, Delaware) mounted on a Sorvall Porter-Blum MT2-B ultra-miTRANS. AM. MICROSC. Soc., 109(2): 168-173. 1990. ? Copyright, 1990, by the American Microscopical Society, Inc. This content downloaded from 207.46.13.162 on Thu, 30 Jun 2016 05:47:28 UTC All use subject to http://about.jstor.org/terms VOL. 109, NO. 2, APRIL 1990 crotome. Sections were stained with saturated uranyl acetate in 50% ethanol (Gibbons & Grimstone, 1960) followed with a 0.25% lead citrate solution (Venable & Coggeshall, 1965). Stained sections were examined with an RCA EMU2D transmission electron microscope operated at 50 kV. RESULTS AND DISCUSSION The terms "substructured inclusion" (Baerwald & Boush, 1970), "structured inclusion" (Baerwald, 1979; Ennesser & Nappi, 1984), "cylinder inclusion" (Baerwald & Boush, 1970; Ennesser & Nappi, 1984), and "structured granule" (Gupta, 1979b) have been applied to the objects of this report. We believe that "multitubular pod inclusions" is a more appropriate term inasmuch as "structured inclusions," "substructured inclusions," and "structured granules" include several different kinds of inclusions; e.g., those with "regular packed subunits" (fig. 7 of Baerwald & Boush, 1970) and those with "a series of band-like subunits" (fig. 5 of Baerwald & Boush, 1970). Furthermore, "cylinder" denotes either a solid or a hollow structure. These inclusions do resemble a pod composed of many tubular (i.e., hollow cylindrical) substructures. Incidentally, although considerable variation exists in hemocyte classification, we accept the term "granular hemocyte," used by Arnold (1972) in his comparative study of the hemocytes of cockroaches, for the host cell of the inclusions here described. The multitubular pod inclusions occurred in about 5% of the granular hemocytes studied by Baerwald & Boush (1970) and only in the experimental animals studied by Ennesser & Nappi (1984), who also found them extracellularly among cellular debris. We found them in three of about 50 different granular hemocytes examined. The earlier reports state that each inclusion is bounded by a unit membrane (Baerwald, 1979) surrounding 9-80 hollow cylinders, each with a diameter of about 800 A, a length of about 0.8-1.5 ,A, and a cylinder wall of the size of a unit membrane, but of a different structure (Baerwald & Boush, 1970). Baerwald & Boush (1970) reported single-, double-, and triple-walled cylinders, with the double-walled most numerous. Ennesser & Nappi (1984) reported only singleand double-walled cylinders. We believe the terminology requires some clarification. The tubules within a single pod are simple (single-walled) or a mixture of simple and compound (doubleor triple-walled). The compound tubules may be considered to be composed of two or three coaxial tubules, each with its own wall. This latter interpretation is necessary if one is to accept the statement of Baerwald & Boush (1970) that the cylinder wall is of the size of a unit membrane; i.e., each of the coaxial tubule walls has the size of a unit membrane. We refer, then, to tubules as single-, double-, or triple-walled. Our observations of the inclusions used to illustrate this report are derived from numerous serial and adjacent sections through a single elongated granular hemocyte which was closely applied to the surface of several skeletal muscle cells and tracheocytes (Fig. 1). Subsequent sections of about 50 different hemocytes revealed only two with pod inclusions. In each of these two hemocytes, 169 This content downloaded from 207.46.13.162 on Thu, 30 Jun 2016 05:47:28 UTC All use subject to http://about.jstor.org/terms TRANS. AM. MICROSC. SOC. more...

Helicodictyon planctonicum (Whitford) Whitford & Schumacher (Chlorophyta) is a rare freshwater alga usually assigned to the order Chaetophorales but also reported to show features resembling members of the order Chlorococcales. In order to help clarify its phylogenetic position, an ultra-structural study was performed. The filamentous branching pattern and absence of a perinuclear envelope of endoplasmic reticulum during mitosis in H. planctonicum resemble features found among members of the Chaetophorales. However, the first and second cell divisions are perpendicular to each other as is common among chlorococcalean algae (Biebel, 1968). Additional chlorococcalean features exhibited by H. planctonicum include pyrenoids traversed by thylakoids, centrioles at the division plane following mitosis, and cytokinesis by furrowing. Therefore, it appears that H. planctonicum may be more closely allied with the Chlorococcales. However, failure to observe a phycoplast suggests Helicodictyon should be exami... more...

The renal histopathology of bacterial kidney disease in both naturally and experimentally infected brook trout (Salvelinus fontinalis) was investigated here on the ultrastructural level. Abnormal changes in the glomerulus and renal tubule during the experimental infection are described chronologically and compared with the changes observed in the fully developed natural infection. These abnormalities are similar to those occurring in mammalian renal disease. Evidence of a host immune and inflammatory response is presented. The bacterial strains involved in the two infections are compared in cell size, internal morphology, and manner of division to help characterize the as yet unclassified causative agent. Key words: morphology, fine structure, pathology, Corynebacterium, renal, bacterium, trout, disease, Salmonidae more...

A sessile, tentacle-bearing protozoon, Heliophrya sp. (Suctoria, Ciliata), reproduces asexually by evaginative budding to form a ciliated swarmer, which begins metamorphosis to the adult form within 30 min of its release from the parent cell. Morphological features of embryogenesis were investigated using transmission and scanning electron microscopy and found to correspond, with certain exceptions, to the few previous reports concerning evaginative budding in suctorians. Following invagination of a portion of the pellicle to form an embryonic cavity within the parent cell, numerous kinetosomes, apparently formed de novo, organize into rows which surround the embryonic cavity and eventually develop cilia that project into the cavity. When the cavity is complete, its walls are extruded through an opening in the parent cell surface. Parent cell cytoplasm streams into the incipient swarmer, thus supplying it with at least the minimum requirement of all cytoplasmic organelles. The ciliated swarmer remains attached to its parent cell for several minutes before it detaches. A complete pellicle is formed in both parent and swarmer prior to detachment. The numerous mitochondria underlying the parent cell pellicle in the vicinity of the attachment area suggest that cross wall formation is an energy-dependent process. more...

The trophont stage in the life cycle of Ichthyophthirius multifiliis was studied in the electron microscope. Surface ridges contain up to 24 ridge microtubules, disposed as a ribbon. Kinetosomes show the classic morphology of 9 triplets of microtubules. Associated with each kinetosome is a kinetodesmal fibril, originating in proximity to triplets 5, 6, and 7, and having a 30 nm periodicity; 3 to 5 postciliary microtubules, originating between triplets 8 and 9; and up to 3 transverse microtubules, originating at triplet 4, as well as a parasomal sac. Each cell is partially enclosed by a system of 3 “unit” membranes: the outer limiting membrane, and the outer and inner alveolar membranes. The last two membranes define the alveolar sac. Mucocysts, each with a dense core, are present in large numbers. The contractile vacuole system includes the contractile vacuole, associated tubules and vesicles, injection canals, a discharge canal, and a pore. Microtubules abound in the walls of the contractile vacuole, injection and discharge canals, and in the region of the pores, where both ring and radial microtubular arrangements are noted. The ultrastructure suggests that I. multifiliis is more closely related to Tetrahymena pyriformis than to Paramecium aurelia. more...

The cells of Dufour's gland and of the associated visceral muscle and nerve of the carpenter bee, Xylocopa virginica virginica (L.), were studied with light and electron microscopes. The gland cells revealed short microvilli, interdigitations of plasma membrane-limited projections, associated glycocalyx and cuticle, a single nucleus with one to four nucleoli, many free ribonucleoprotein particles, septate junctions, and numerous mitochondria and microtubules. Many tracheoles accompanied the gland cells, the associated visceral muscle, and unmyelinated nerve. The muscle cells contained myofibrils, composed of thin and thick myofilaments. The myofilaments were somewhat greater in diameter than usually encountered, and their disposition patterns were irregular. Transverse tubules, A and I bands, and Z lines were present, but no H bands or dyads were seen. The nerve cell processes contained mitochondria, neurotubules, and, as they approached muscle cells, neurosecretory vesicles with electron-dense or electron-transparent contents. Carpenter bee Dufour's glands are compared with those of the megachilid Osmia cornifrons (Radoszkowski). more...

An electron-microscope study was made of thin sections of cells from several developmental stages involved in the transformation of the motile zoospore into the four-pronged adult cell type during asexual reproduction in Pediastrum biradiatum Meyen. The various stages were obtained by separating swarmers from adult colonies using fine nickel screening and allowing progressively longer periods of zoospore change before fixing in OsO4. Early adult stages were obtained by fixing cultures after approximately 6 hours of swarmer production. Chloroplasts are observed in cells from all developmental stages. No grana, typical of the chloroplasts of higher plants, are discernible, but a lamellar structure is present and the chloroplast is limited by a double membrane. The chloroplasts contain low density starch inclusions and small, dense inclusions, similar in texture and density to large, dense, spherical bodies which occupy a considerable proportion of the cell volume. The significance of the latter bodies is unknown, but reference is made to their possible role in cell-wall formation. Pyrenoid bodies are not present in any recognizable form until the adult cell type is achieved and appear to develop from the chloroplast. The pyrenoid appears homogeneous and is nearly surrounded by starch plates in the mature forms. The cell wall develops from a thin, membranous covering into a thickened structure containing a globular network. The latter is found in the early adult stages. A small amount of endoplasmic reticulum is present and a Golgi apparatus which in some instances resembles the Golgi forms of higher animals and in other cases is similar to the dictyosomes of protozoa and invertebrates. The nucleus, which is often nearly rectangular in profile, is enclosed by a double membrane which in some cases appears to have an intimate association with the Golgi apparatus. The mitochondria are very few in number and possess only a few randomly oriented cristae. Large vacuoles are described which contain secondary double-membrane limited vacuoles in addition to inclusions similar to those found in the cytoplasm. more...

Bacterial cells were fixed in OsO4, washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU-2D. The sections revealed that the cytoplasmic membrane undergoes a centripetal growth to form a membrane septum. This septum is formed as a double structure. Constriction of the daughter cells and deposition of cell wall material lead to the separation of the daughter cells. The bacterial cytoplasm appears to consist largely of 200 A granules and occasionally reveals arrays of parallel dense lines. more...

Introduction Although much literature has been published in the past concerning the trabecular meshwork, recent improvements in the technique of electron microscopy, particularly the use of Epon as an embedding medium, have indicated the desirability of additional work in this important area. In 1912, Salzmann's extensive histological study showed that the trabecular meshwork consisted of 2 zones: the uveal trabecular meshwork, which formed a small part of the entire structure, and the corneoscleral trabecular meshwork. Salzmann believed that each corneoscleral trabecula was made up of 4 elements. These included a thick, collagenous core; a thick elastic tissue surrounding the core; a glass membrane; and an endothelial layer which had no borders. He felt that the uveal meshwork differed from the corneoscleral meshwork in lacking elastic fibers and in showing less differentiation between the collagen bundle and the glass membrane. Flocks (1951) showed that each beam of uveal meshwork was circular more...

The fine structure of more than 20 marine pseudomonads and more than 15 achromobacters was examined. Under the conditions extant, clear differences between members of these two groups were seen. The pseudomonads displayed the characteristic gram-negative morphology: the cell wall was irregularly undulant and the cytoplasmic membrane more nearly planar, ribonucleoprotein (RNP) particles were loosely packed throughout the periphery of the cytoplasm, and the deoxyribonucleic acid (DNA) was axially disposed. Cell division appeared to be by constriction. Some strains characteristically produced evaginations or blebs of the cell wall. Occasionally, thick, densely stained ring structures were seen which are possibly analogous to mesosomes. In contrast, the achromobacters demonstrated a regularly undulant outer cell wall element and a planar inner wall. The cytoplasmic membrane was thin and not readily observed. RNP particles were densely stained and tightly packed in the cytoplasm; the DNA was most often lobate in disposition. Cellular division was mediated by the formation of a septum which consisted of the cytoplasmic membrane and the inner element of the cell wall. Mesosomes were observed in all of the strains examined. Dense inclusion bodies were also seen in many strains. more...

Microvilli, on the free border of endometrial cells lining the uterine cavity in the rat, vary in size and configuration as a result of different hormonal environments. Microvilli are a means by which the free surface area of the epithelial cell is increased. The functional potential of endometrial epithelial microvilli as instruments for attachment between ovum and endometrium and as devices which facilitate the first direct metabolic interchange between maternal and fetal tissue during ovoimplantation is stressed. The roles of estrogens, both in modifying the fine structure of the free border of endometrial epithelium and in bringing about attachment between fertilized ovum and endometrium, have been highlighted as keystones of rat reproductive biology. In this light some of the hormone-induced ultrastructure changes observed on the epithelial cell surface have been considered as adaptations for the active role of the epithelium in ovoimplantation. more...

The effect of ultraviolet light in delaying certain events in the cell division cycle has been examined. The time to fusion of the egg and sperm nucleus is not affected by doses of ultraviolet that cause considerable delay in other parts of the cycle. The principal delay occurs before anaphase. Between anaphase and cleavage there is only slight delay. The "refractory period" during which the radiation does not delay the immediate cycle of cell division, does not seem to represent complete refractoriness of the mitotic cycle to interference during this period. more...

The development of representative myeloid elements is traced by correlated light and electron microscopy. Cytoplasmic changes during maturation of granulocytes from the myeloblast include loss of basophilia, development of the endoplasmic reticulum complex, decrease in number of mitochondria, and granule formation. The endoplasmic reticulum vesicles increase in size and number during the promyelocyte and myelocyte stages, accompanied by the appearance of non-specific and specific granules, and decrease again during the cytosomal maturation of the metamyelocyte. A reduction in number of mitochondria is noted through the metamyelocyte stage. The apparent continuity of the limiting membranes of both the granules and mitochondria with those of the cisternae of endoplasmic reticulum suggests a direct connection among cytosomal organelles. The role of the endoplasmic reticulum in granulogenesis is discussed. Maturation of the nucleus involves a loss of nucleolar differentiation by a loosening of the compact fibrillar aggregates, and progressive chromatin condensation. more...