Structure,morphology, and composition of silicon biocomposites in the palm tree Syagrus coronata (Mart.) Becc

Syagrus coronata is an economically important palm tree grown as an ornament, for the oil extracted from its seeds, and the wax from its leaves which has several applications in industry. Silicon biocomposites were analyzed in leaves of S. coronata. Silica bodies were found as extracellular silica masses between the hypodermal-layer cell walls and in granules present in the vacuoles of palisade cells. Scanning electron microscopy of the hypodermal layer of cells showed a collection of spherical bodies embedded in enveloping cavities that outlined the general structure of the bodies. Globular subunits with sharp edges formed the spherical bodies that ranged from 6 to 10 microm in diameter (average, 7.8 microm). X-ray microanalysis detected only silicon and oxygen homogeneously distributed throughout the bodies. Vacuoles of palisade cells contained a large number of granules ranging from 20 nm to 1.2 microm in size (average, 300 nm). Transmission electron microscopy associated with electron spectroscopic imaging and electron energy loss spectroscopy were used to determine the elemental composition of the granules. Vacuolar granules were amorphous and composed of silicon and oxygen, suggesting they consist of amorphous silica biominerals. No nitrogen, indicative of organic matter, was detected in the granules.     

Riferimento del genereParacoccidioides agli Entomoftorali Imperfetti (Entomophthorales Coccidioidaceae)

Summary By comparison betweenParacoccidioides andDelacroixia, the former genus is adscribed to the Family Paracoccidioidaceae (Imperfect Entomophthorales).The relationship between the genera of Entomophthorales is discussed, together with the evolutive trend of the group.

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Quest' argomento è stato oggetto di una nota presentata al III Congresso Internazionale di Microbiologia di Rio de Janeiro, Agosto 1950.     

Photoreceptor ultrastructure in the Antarctic mussel shrimp Acetabulastoma (Crustacea; Ostracoda), a parasite of Glyptonotus antarcticus (Crustacea; Isopoda)

The ultrastructure of the nauplius eye of the tiny Antarctic ostracode Acetabulastoma sp. is described and conclusions about its possible function are drawn. Each of the three eye-cups measures approximately 20 μm in diameter and is optically isolated from its neighbour by screening pigments, which are contained in pigment cells behind a tapetum of concentrically arranged, ca. 1-μm-long and 0.1-μm-thick, crystals. Three and sometimes four separate rhabdoms with microvilli measuring 50–60 nm in diameter project from the concave side of the tapetum up to 5 μm deep into the eye-cup interior, which is filled by the retinula cell bodies with their spherical nuclei and various organelles. Desmosomes and microtubules are seen and light-induced cell or membrane damage was minimal. The observations suggest that the Acetabulastoma eye has photoreceptors that can tolerate an exposure to bright light and it may be used to inform its owner of the approach of danger, the depth of water, and/or the season. Accepted: 27 August 1998     

Leaf micromorphology of Antarctic pearlwort Colobanthus quitensis (Kunth) Bartl.

The leaf micromorphology of Antarctic pearlwort, Colobanthus quitensis (Kunth) Bartl. was analyzed. Plants were collected at King George Island (62°5′S, 58°23′W). Leaves were analyzed by optical and scanning electron microscopy, and quantitative analyses performed on leaf tissues and their internal geometry. C. quitensis leaves are ca. 588 μm thick, and composed of palisade and spongy parenchyma, respectively ca. 171 and 312 μm thick. Cuticles are thin and cover short epidermal cells. The central vein is surrounded by two bundles of achlorophyllous cells. Sclerenchymatic tissues are poorly developed. SEM analysis reveals faint striations over leaf surfaces. Stomata are present on both surfaces, but restricted to the leaf margins on the abaxial side. The ratio of mesophyll cell surface area per unit leaf area (Ames/A) is 34.2. The number of cells per cross-sectional area occupied was 24% higher for the palisade than for the spongy tissue, which determines a higher cell surface area per cross-sectional area for the former tissue. The authors correlate these results to plant ecological distribution in Antarctica and to water and carbon economy. Accepted: 14 January 2000     

Localization of sucrose synthase and callose in freeze-substituted secondary-wall-stage cotton fibers

Summary.  Methods for cryogenic fixation, freeze substitution, and embedding were developed to preserve the cellular structure and protein localization of secondary-wall-stage cotton (Gossypium hirsutum L.) fibers accurately for the first time. Perturbation by specimen handling was minimized by freezing fibers still attached to a seed fragment within 2 min after removal of seeds from a boll still attached to the plant. These methods revealed native ultrastructure, including numerous active Golgi bodies, multivesicular bodies, and proplastids. Immunolocalization in the context of accurate structure was accomplished after freeze substitution in acetone only. Quantitation of immunolabeling identified sucrose synthase both near the cortical microtubules and plasma membrane and in a proximal exoplasmic zone about 0.2 μm thick. Immunolabeling also showed that callose (β-1,3-glucan) was codistributed with sucrose synthase within this exoplasmic zone. Similar results were obtained from cultured cotton fibers. The distribution of sucrose synthase is consistent with its having a dual role in cellulose and callose synthesis in secondary-wall-stage cotton fibers. Received August 19, 2002; accepted November 12, 2002; published online June 13, 2003 RID="*" ID="*" Correspondence and reprints: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, U.S.A. E-mail: candace.haigler@ttu.edu     

<Emphasis Type="Italic">Candida middelhoveniana</Emphasis> sp. nov., a new yeast species found on the rhizoplane of organically cultivated sugarcane

A novel yeast species within the Metschnikowiaceae is described based on a strain from the sugarcane (Saccharum sp.) rhizoplane of an organically managed farm in Rio de Janeiro, Brazil. The D1/D2 domain of the large subunit ribosomal RNA gene sequence analysis showed that the closest related species were Candida tsuchiyae with 86.2% and Candida thailandica with 86.7% of sequence identity. All three are anamorphs in the Clavispora opuntiae clade. The name Candida middelhoveniana sp. nov. is proposed to accommodate this highly divergent organism with the type strain Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (IMUFRJ) 51965^T (=Centraalbureau voor Schimmelcultures (CBS) 12306^T, Universidade Federal de Minas Gerais (UFMG)-70^T, DBVPG 8031^T) and the GenBank/EMBL/DDBJ accession number for the D1/D2 domain LSU rDNA sequence is FN428871. The Mycobank deposit number is MB 519801.     

Localization of p210-related proteins in green flagellates and analysis of flagellar assembly in the green alga Dunaliella bioculata with monoclonal anti-p210

Summary.  Recently, p210 was identified as a component of the flagellar basal apparatus in the green flagellate Spermatozopsis similis. In a search for potential homologues to p210, isolated cytoskeletons of several green flagellates were probed with a monoclonal antibody, BAS4.13, against p210. In Western blots, cross-reacting bands in the molecular-mass range of 210 kDa were detected only in the quadriflagellate Spermatozopsis exsultans. As described earlier for S. similis, the flagellar transition region was decorated in Chlamydomonas reinhardtii and several other green flagellates, whereas in the marine alga Dunaliella bioculata the antigen was present in the proximal part of the axoneme. Double immunofluorescence of D. bioculata with an antitubulin antibody further revealed dotlike signals at sites where the probasal bodies are located. Since most of the antigen in D. bioculata was located in the axoneme, deflagellation offered a possibility to study the kinetics of its incorporation during flagellar regeneration. The antigen was only detected after a flagellum reached a length of 3–4 μm and its integration into the growing flagellar proceeded from proximal to distal. A similar delay in the incorporation of the antigen was also observed during flagellar assembly on new basal bodies during cell division. Thus, the antigen of BAS4.13 was incorporated late and from proximal to distal into the growing flagellum. We conclude that the pace and site by which individual proteins are integrated into the flagellum differ greatly. Received February 18, 2002; accepted May 17, 2002; published on line October 31, 2002 RID="*" ID="*" Correspondence and reprints: Botanisches Institut, Universit?t zu K?ln, Gyrhofstrasse 15, 50931 K?ln, Federal Republic of Germany     

Behavior of storage lipids during development and germination of olive ( Olea europaea L.) pollen

Summary.  The presence of abundant oil bodies in the mature olive pollen grain has led us to focus on the behavior of these lipid bodies during pollen development and in vitro pollen germination. The appearance, increase, and accumulation of lipid bodies have been determined by following the sequential development of the pollen grain. Semithin slices of anthers and pollen grains were stained with Sudan Black B in order to identify neutral lipids. Ultrastructural studies were also carried out. Our results show a notable increase in lipid bodies between the young-pollen-grain stage and the mature-pollen-grain stage. Substantial polarization of lipid bodies was observed after 1 or 2 h of pollen incubation in germination medium. During pollen tube growth, the lipid bodies are located near the germinative aperture after 3 h of incubation, as well as inside the pollen tube, thus suggesting that the lipid bodies move from the pollen grain to the pollen tube. After 7 h of germination the presence of lipid bodies inside the pollen tube is no longer substantial. Our results support the idea that lipid bodies are involved in pollen germination, stigma penetration, and pollen tube growth. These results are discussed in connection with their implications for the pollen germination process. Received June 4, 2002; accepted October 29, 2002; published online April 8, 2003 RID="*" ID="*" Correspondence and reprints: Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Profesor Albareda 1, 18008 Granada, Spain.     

New cell types of the pancreatic islets in the crucian carp,Carassius carassius

Summary The pancreatic islets ofCarassius carassius have been studied by electron microscopy. 1. Besides A-, B- and D-cells, two new cell types, the fourth and the fifth, have been identified. The fourth cell type is numerous; it occurs interposed among the other types of islet cells or in small clusters. The secretory granules (90–280 mg in diameter) are round or oval and usually with much lower electron density than α- and δ-granules. The secretory granules of the fifth type of cell (approximately 140–240 mμ in diameter) contain finely granular material and an electron dense core that is round or often tetra- or hexagonal. 2. The islet cells with clear cytoplasmic matrix generally contain large numbers of fine, agranular and cored vesicles 400–680 ? in diameter. They appear, in bead-like chains, or randomly scattered throughout the cytoplasm, or often clustered in aggregates close to the secretory granules and show evidence of incorporation into the secretory granules. The two types of vesicles may be formed by constriction or pinching-off of the tubular smooth endoplasmic reticulum.     

Electron microscopy of two types of reflecting chromatophores (iridophores and leucophores) in the guppy,Lebistes reticulatus Peters

Summary Reflecting chromatophores in the integument of the guppy, Lebistes reticulatus Peters, are of two distinct types, iridophores and leucophores. The iridophores are smaller and fixed, producing a metallic iridescent color. The cytoplasmic organelles involved in the coloration of iridophores are the reflecting platelets, as in the iridophores of other fish and amphibian species on which earlier reports have been made. Spherical granules of pleiomorphic internal structure, quite variable in size but generally 0.2 m to 1.0 m in diameter, are also numerous in the iridophores. The nature of these granules remains unknown.The leucophores are larger, and highly dendritic; their pigment granules are migratory and they exhibit a dull whitish color. Pigment granules of the leucophores are spherical in form, varying from 0.5–0.8 m in diameter, with a double membrane enclosing the internal fibrous materials. Melamine-treatment of the fish caused degenerative changes in the pigment granules and also the other cytoplasmic organelles of the leucophores, whereas the other kinds of chromatophores, including the iridiophores, remained intact. Some problems in general characterization and classification between these two types of chromatophores were discussed.The author wishes to thank Mr. Yoshiro Yamazaki for his assistance in operating the electron microscope, and Dr. Takao Kajishima (Biological Institute, Nagoya University) for his encouragements     

Multiple activities of a novel substance,dictyopyrone C isolated from Dictyostelium discoideum,in cellular growth and differentiation

Summary.  We report that a novel substance named dictyopyrone C (DPC) has remarkable effects on growth and differentiation of Dictyostelium discoideum Ax-2 cells, in a dose-dependent manner. In the presence of 3–15 μM DPC, differentiation of starving Ax-2 (clone MS) cells was greatly enhanced in submerged culture, when vegetative MS cells were harvested at the mid-late-exponential growth phase (>3 × 10⁶ cells per ml) and starved. In contrast, DPC above 30 μM markedly impaired the progression of differentiation including cell aggregation, most of starved cells being round after 3–4 h of DPC application and then lysed during further incubation. In the presence of 30 μM DPC however, MS cells that had been harvested at the early exponential growth phase (<5 × 10⁵ cells per ml) and starved became neither round nor lysed and exhibited rather enhanced differentiation. Essentially the same results were obtained in cultures of starved cells on nonnutrient agar. With respect to the DPC effect on MS cells growing in axenic medium, cell lysis and growth inhibition by DPC at concentrations higher than 15 μM were realized in the mid-late-exponential-growth-phase cells (>3 × 10⁶ cells per ml) but not in the early-exponential-growth-phase cells (<5 × 10⁵ cells per ml). Moreover, analysis using synchronized MS cells has demonstrated that the DPC effect changes in a cell-cycle-dependent manner. In contrast to such unique DPC actions, the pyrone ring of DPC had no effects on growth and differentiation within the range of 3–120 μM tested. These findings strongly suggested the importance of the combined structure of the pyrone ring and the linear carbon chain in revelation of the DPC activities. Received August 5, 2002; accepted November 11, 2002; published online April 8, 2003 RID="*" ID="*" Correspondence and reprints: Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan. E-mail: ymaeda@mail.cc.tohoku.ac.jp     

New species of Eimeria Schneider, 1875 and Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from the short-crested flycatcher Myiarchus ferox (Gmelin) (Passeriformes: Tyrannidae) in South America

In the current study, two new coccidian species (Protozoa: Apicomplexa: Eimeriidae) obtained from short-crested flycatcher Myiarchus ferox (Gmelin) are reported from Brazil. Isospora feroxis n. sp. has o?cysts which are spheroidal to sub-spheroidal, 18.7 × 18.0 μm, with a smooth and bi-layered wall, c. 1.2 μm. The micropyle and o?cyst residuum are absent, but two polar granules are present. Its sporocysts are broadly ellipsoidal and 11.7 × 8.5 μm. Stieda and substieda bodies are present. A sporocyst residuum is present and the sporozoites have a refractile body and nucleus. O?cysts of Eimeria sicki n. sp. are spheroidal to sub-spheroidal, 30.3 × 28.5 μm, with a smooth and bi-layered wall, c. 1.3 μm. The micropyle, o?cyst residuum and polar granule are absent. Its sporocysts are ellipsoidal, 18.4 × 10.0 μm. Stieda and substieda bodies are present. A sporocyst residuum is present and sporozoites have a refractile body and nucleus.     

Morphological differences among three species of newly settled pocilloporid coral recruits

 Investigation of the life history of corals is hampered by an inability to identify early recruits. In this study, the pattern of formation and morphology of the juvenile skeletons of three laboratory-reared pocilloporids, Seriatopora hystrix, Stylophora pistillata and Pocillopora damicornis, were compared to determine whether they could be reliably distinguished. The pattern of skeleton formation, including the origin and structure of the septa, columella and corallite wall was similar in all species. Following the completion of the primary corallite wall after 4–5 days, these species could be identified by differences in the diameter of the primary corallite. The mean diameter (±SE) of each species differed markedly: S. hystrix 400 ± 2.7 μm, range 325–450 μm; S. pistillata 505 ± 3.5 μm, range 400–550 μm; P. damicornis 697 ± 7.5 μm, range 492–885 μm. Values for the primary corallite diameter overlapped in only 3% of samples, demonstrating the potential utility of this feature as a tool for classifying recruits obtained from the field. Accepted: 4 January 2000     

Picophytoplankton biomass, community structure and productivity in the Great Astrolabe Lagoon, Fiji

 Phytoplankton biomass, community structure and productivity of the Great Astrolabe lagoon and surrounding ocean were studied using measurements of chlorophyll concentration and carbon uptake. The contribution of picophytoplankton to biomass, productivity and community structure was estimated by size fractionation, ¹⁴C-incubation and flow cytometry analysis. Picoplankton red fluorescence was demonstrated to be a proxy for chlorophyll <3 μm. Consequently, the percentage contribution to chl a<3 μm from each picoplankton group could be calculated using regression estimated values of ψ _i (fg chl a per unit of red fluorescence). In the lagoon, average chlorophyll concentration was 0.8 mg m^-3 with 45% of phytoplankton <3 μm. Primary production reached 1.3 g C m^-2 day^-1 with 53% due to phytoplankton <3 μm. Synechococcus was the most abundant group at all stations, followed by Prochlorococcus and picoeukaryotes. At all stations, Prochlorococcus represented less than 4% of the chl a <3 μm, Synechococcus between 85 and 95%, and Picoeukaryotes between 5 and 10%. In the upper 40 m of surrounding oceanic waters, phytoplankton biomass was dominated by the >3 μm size fraction. In deeper water, the <1 μm size fraction dominated. Prochlorococcus was the most abundant picoplankton group and their contributions to the chlorophyll a<3 μm were close to that of the picoeukaryotes (50% each). Accepted: 27 May 1999     

Superoxide synthase and dismutase activity of plasma membranes from maize roots

Summary.  Superoxide synthase and superoxide dismutase activity have been monitored in isolated maize (Zea mays) root plasma membranes spectrophotometrically by determination of nitro-blue tetrazolium and cytochrome c reduction, respectively. Superoxide production was induced by NADH and NADPH, with similar kinetics and approaching saturation at 0.06 mM in the case of NADPH and 0.1 mM in the case of NADH, with rates of 18.6 ± 5.0 and 21.8 ± 7.2 nmol/min · mg of protein, respectively. These activities exhibited a broad pH optimum between pH 6.5 and 7.5. Diphenylene iodonium inhibited about 25% (10 μM DPI) and 40% (100 μM DPI) of this activity, imidazole inhibited about 20%, while KCN, a peroxidase inhibitor, did not show any significant inhibition. Superoxide-dismutating activity was shown to occur in the same isolates and depended on the quantity of plasma membrane protein present. Growth of plants on salicylic acid prior to membrane isolation induced a rise in the activity of both of the enzymes by 20–35%, suggesting their coordinated action. Received May 15, 2002; accepted September 30, 2002; published online May 21, 2003 RID="*"     

The diversity of bacteria,eukaryotic cells and viruses in an oligotrophic lake

An in situ transmission electron microscopic study of biomass samples concentrated from oligotrophic lake water revealed a variety of virus-infected microbial cells and many free viruses and virus-like particles. The most abundant group of microorganisms in screened and filtered water-column samples were 2 μm or less in diameter, and included representatives of several oligotrophic genera, Prosthecomicrobium, Ancyclobacter, Caulobacter and Hyphomicrobium. Among the prokaryotic host cells, which included both heterotrophs and autotrophs, on the basis of electron microscope observations, approximately 17% were infected with bacteriophage or bore adherent phage particles on their surfaces. Several bacterial morphotypes were observed among the prokaryotic hosts. Water samples passed through a 20-μm Nitex screen allowed us to concentrate and examine the larger host cells as well, including several species of single-celled algae and two amoeba species. The infected algal cells included those Chlorella-like in appearance, photosynthetic flagellates and others that could not be positively identified. About one-third of the eukaryotic cells were infected by viruses that were larger (150–200 nm) and structurally more complex than bacteriophages (50–60 nm). None of the viruses have been isolated, but when 0.2 μm filtrate from a biomass sample was spotted onto lawns of four representative heterotrophs and a Chlorella, the clearing observed was taken as evidence of lysis. Cyanobacterial lawns showed no plaques. Thin sections of two amoeba showed food vacuoles containing what appeared to be virus particles of a type seen in certain prokaryotic and eukaryotic cells in the biomass. Received: 26 January 1996 / Received revision: 10 July 1996 / Accepted: 5 August 1996     

Morphological and Genetic Characterization of <Emphasis Type="Italic">Saimiri boliviensis</Emphasis>

The taxonomy of Saimiri is controversial because morphological characteristics, traditionally used for identification, are insufficient to distinguish species and subspecies. Genetic studies of specimens become relevant for captive management, especially considering their frequently unknown geographical origin. We analyzed phenotypic and genetic parameters in Saimiri spp. in Argentinean zoological gardens and biological stations to provide a more accurate taxonomic identification. We studied 27 males and 19 females of Saimiri spp. The cytogenetic analysis in mitotic metaphases corroborated a modal number of 2N = 44, XX/XY, and FN = 75 for males and FN = 76 for females. G- and C-bands, fluorescence in situ hybridization (FISH) and the pelage coloration pattern of all the specimens corresponded to Saimiri boliviensis boliviensis. We characterized for the first time the sperm cell morphology and morphometry (mean ± SE): total length: 71.39 ± 5.40 μm; head length: 5.71 ± 0.81 μm; head width: 3.76 ± 0.70 μm; acrosome length: 3.70 ± 0.82 μm; midpiece length: 12.20 ± 2.22 μm. Researchers can use the characterization of the sperm morphology as another parameter for taxonomic identification that, together with cytogenetic and molecular ones, would allow a more precise identification of individual Saimiri boliviensis boliviensis.     

Grazing by the Antarctic sea-ice ciliate Pseudocohnilembus

Potential uptake and clearance rates of fluorescent microspheres (FM) from 0.25 to 4.05 μm diameter were determined for the non-loricate ciliate Pseudocohnilembus sp. from Antarctic sea ice. The percentage of ciliate cells that ingested FM after 20 min incubation decreased with increasing particle diameter. Pseudocohnilembus sp. ingested FM between 0.25 and 4.05 μm in diameter. We offered FM at concentrations less than natural concentrations for plankton plus detrital material and obtained clearance rates less than those previously reported for bactivorous ciliates. Clearance rates were 3.6–5.4 nl cell⁻¹ h⁻¹ for FM 0.5 and 1 μm diameter, respectively, but decreased to 1.1 nl cell⁻¹ h⁻¹ for 1.97 μm diameter and 1.4 nl cell⁻¹ h⁻¹ for 4.05-μm-diameter FM. Clearance and uptake rates of FM 0.5 and 1 μm diameter indicate that Pseudocohnilembus sp. principally grazes on bacteria-sized particles. However, it can also ingest organisms as large as nanoplankton and may graze particles as small as femtoplankton and colloids. This suggests a feeding strategy that may suit the temporal and spatial changes in food availability in the sea-ice habitat. Accepted: 13 August 2000     

Poly(3-hydroxybutyrate) granules ofBacillus megaterium

Cells ofBacillus megaterium contain 35–45% of poly(3-hydroxybutyrate) (PHB) at the beginning of the stationary phase. This amount is only slightly affected by the medium composition. The PHB granules are spherical with the mean diameter of 1.15 μm.     

Reduction of potassium tellurite to elemental tellurium and its effect on the plasma membrane redox components of the facultative phototroph Rhodobacter capsulatus

Summary.  Anaerobically light-grown cells of Rhodobacter capsulatus B100 are highly resistant to the toxic oxyanion tellurite (TeO₃ ²⁻; minimal inhibitory concentration, 250 μg/ml). This study examines, for the first time, some structural and biochemical features of cells and plasma membrane fragments of this facultative phototroph grown in the presence of 50μg of K₂TeO₃ per ml. Through the use of transmission microscopy and X-ray microanalysis we show that several “needlelike” shaped granules of elemental tellurium are accumulated into the cytosol near the intracytoplasmic membrane system. Flash-spectroscopy, oxygen consumption measurements, and difference spectra analysis indicated that membrane vesicles (chromatophores) isolated from tellurite-grown cells are able to catalyze both photosynthetic and respiratory electron transport activities, although they are characterized by a low c-type cytochrome content (mostly soluble cytochrome c ₂). This feature is paralleled by a low cytochrome c oxidase activity and with an NADH-dependent respiration which is catalyzed by a pathway leading to a quinol oxidase (Qox) inhibited by high (millimolar) concentrations of cyanide (CN⁻). Conversely, membranes from R. capsulatus B100 cells grown in the absence of tellurite are characterized by a branched respiratory chain in which the cytochrome c oxidase pathway (blocked by CN⁻ in the micromolar range) accounts for 35–40% of the total NADH-dependent oxygen consumption, while the remaining activity is catalyzed by the quinol oxidase pathway. These data have been interpreted to show that tellurite resistance of R. capsulatus B100 is characterized by the presence of a modified plasma-membrane-associated electron transport system. Received May 2, 2002; accepted July 26, 2002; published online May 21, 2003 RID="*" ID="*" Correspondence and reprints: Department of Biology, University of Bologna, Via Irnerio 42, 40126 Bologna, Italy.