Dynamics of annulate lamellae in Drosophila syncytial embryos

The mitotic events in eukaryotic cells are controlled by a family of evolutionary conserved cyclin-dependent kinases (cdk) that phosphorylate cell proteins, which results in the structural reorganization of the entire cell. Our recent studies of Drosophila syncytial embryos have demonstrated that changes in cdk1 activity controlling the assembly and disassembly of nuclear pore complexes also affect the structure of cytoplasmic pores in annulate lamellae. Here, we report a comparative electron microscopic analysis of the dynamics of these organelles during mitosis throughout the development of a Drosophila syncytial embryo. We presume that the distribution of annulate lamellae containing mature cytoplasmic pores across the cytoplasm reflects local reductions in the mitotic kinase cdk1 activity during the development of Drosophila syncytial embryos.     

Ultrastructure of leaves in C4 Cyperus iria and C3 Carex siderosticta

The ultrastructural aspects ofCyperus iria leaves showing the C₄ syndrome and the typical C₃ species,Carex siderosticta, in the Cyperaceae family were examined.C. iria exhibited the chlorocyperoid type, showing an unusual Kranz structure with vascular bundles completely surrounded by two bundle sheaths. The cellular components of the inner Kranz bundle sheath cells were similar to those found in the NADP-ME C₄ subtype, having centrifugally arranged chloroplasts with greatly reduced grana and numerous starch grains. Their chloroplasts contained convoluted thyla-koids and a weakly-developed peripheral reticulum, although it was extensive mostly in mesophyll cell chloroplasts. The outer mestome bundle sheath layer was sclerenchymatous and generally devoid of organelles, but had unevenly thickened walls. Suberized lamellae were present on its cell walls, and they became polylamellate when traversed by plasmodesmata. Mesophyll cell chloroplasts showed well-stacked grana with small starch grains. InC. siderosticta, vascular bundles were surrounded by the inner mestome sheath and the outer parenchymatous bundle sheath with intercellular spaces. The mestome sheath cells degraded in their early development and remained in a collapsed state, although the suberized lamellae retained polylamellate features. Plastids with a crystalline structure, sometimes membrane-bounded, were found in the epidermal cells. The close interveinal distance was 35–50 μm inC. iria, whereas it was 157–218 μm inC. siderosticta. These ultrastructural characteristics were discussed in relation to their photosynthetic functions.     

Genotoxic and Histopathological Effects of Water Pollution on Two Fish Species, <Emphasis Type="Italic">Barbus capito pectoralis</Emphasis> and <Emphasis Type="Italic">Chondrostoma nasus</Emphasis> in the Büyük Menderes River,Turkey

The genotoxic and histopathological effects of water pollution were investigated on two fish species caught from the Buyuk Menderes River and from its tributary, the Cine Stream. The Buyuk Menderes basin is an important agricultural area in Turkey. The levels of copper, zinc, cadmium, cobalt, and lead were measured at the surface of the water and in gills, liver, and muscle tissue of Chondrostoma nasus and Barbus capito pectoralis. In some tissues, the concentrations of some of these metals exceeded acceptable levels for human consumption. Zinc was found to be the most abundant metal in water and tissues. Maximal metal accumulation was observed in the liver. To detect the genotoxic potential of contaminants, the formation of micronucleus in erythrocytes was used as indicator of chromosomal damage. The frequency of micronucleus formation did not show significant differences between locations and controls in B. capito pectoralis caught from three locations and C. nasus from two locations. The histological changes included significant decreases of the mean lengths of primary and secondary lamellae. In gills epithelia, we observed cellular proliferation that developed Because of secondary lamellae fusion, ballooning degenerations, or club deformation of secondary lamellae and cystic structures in secondary lamellae. In the liver, the changes included swollen and ruptured parenchymal cells, loss of cord structure, vacuoles filled with cellular debris, focal necrosis, and a significant increase in Kupffer cells.     

The formation of “accessory nuclei” in the developing oöcytes of the parasitoid hymenopterans Ophion luteus (L.) and Apanteles glomeratus (L.)

Summary The appearance and subsequent distribution of accessory nuclei in the developing oöcytes of the Ichneumonoid Ophion luteus and Braconid Apanteles glomeratus is described. They are produced by a folding of annulate lamellae produced from the nuclear envelope. The nucleus and accessory nuclei give rise to other annulate lamellae by two distinct modes of budding. These organelles are involved in membrane formation.     

Ultrastructure changes of seedlings of <Emphasis Type="Italic">Kosteletzkya virginica</Emphasis> under waterlogging conditions

The changes in ultrastructure of leaf cell in waterlogged Kosteletzkya virginica seedlings were observed by transmission electron microscope. During waterlogging, the chloroplasts turned into a round shape and their volume was gradually reduced. Furthermore, the lamellae of thylakoids swelled, and the inclusions in chloroplast decreased. The shape of starch grains slightly changed, but their number and volume decreased, and they even disappeared in the end. On the other hand, plastoglobules enlarged and their amount enhanced gradually. The membrane and inner cristea of mitochondria gradually became unclear, while the mitochondria firstly enlarged but disappeared at the end. Similar to chloroplast, cell nucleus dwindled gradually, concentrated and tended to a round shape. Additionally, the annulate lamellae and multivesicular body occurred on the 20th day of experiment, and the cell wall distorted and twisted at the late stage of waterlogging. Consequently, these changes of organelles are the typical characteristics of the complete cell disintegration or death for Kosteletzkya virginica under long-term waterlogging.     

Ammonium sulphate induced stress related alterations in the respiratory epithelium of the airbreathing organ of the catfishHeteropneustes fossilis (Bloch)

In this paper, histopathological changes in the inner lining of the accessory respiratory organ ofHeteropneustes fossilis following exposure to sublethal concentration (0.2 g I^–1) of ammonium sulphate (3 mg I^–1 total ammonia-N) has been described. The goblet cells show periodic increased followed by decreased secretory activities. Necrosis and shedding of the epithelial cells over the secondary lamellae cause periodic haemorrhages which lead to degeneration and decreased number of secondary lamellae. Subsequently regeneration takes place each time as evidenced by the appearance of inflammatory tissue. Fusion of more than one secondary lamellae is also common. Regeneration also leads to uncontrolled hyperplasia of haphazardly arranged epithelial cells. This hyperplasia causes increased distance of respiratory blood-air barrier in the secondary lamellae, leading to impaired normal aerial respiration     

Ultrastructural changes in strawberry leaves infested by two-spotted spider mites

Ultrastructural changes in strawberry leaves after different periods of feeding by Tetranychus urticae were studied. Electron micrographs indicate that the first detectable changes in cells directly punctured by the mites usually occurred after 3 days of feeding and were confined to the chloroplasts. These organelles show instability of the lamellae and the thylakoid membrane system as well as the envelope. Longer times of mite feeding (6–9 days) caused severe alterations, not only within chloroplast. In heavily injured tissues, misshapen cells contain homogeneous protoplasts in which only remains of necrotic chloroplasts were visible. Mesophyll cells adjacent to directly punctured tissues also exhibited subcellular alterations. Possible mechanisms of plant-tissue responses to mite feeding are discussed.

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Zusammenfassung Ultrastrukturelle Veränderungen wurden in Erdbeerblättern nach verschiedenen Perioden Saugtätigkeit von Tetranychus urticae Koch gesucht. Elektronenmikroskopische Aufnahmen zeigen, dass die ersten sichtbaren Veränderungen in direkt von Milben angestochenen Zellen meist nach 3 Tagen Saugen auftraten und auf die Chloroplasten beschränkt waren. Diese Organellen zeigen eine Instabilität der Lamellen, des Thylakoidmem-bransystems sowie der Umhüllung. Ein längere Zeit dauerndes Saugen der Milben (6–9 Tage) verursachte schwere Veränderungen und zwar nicht bloss in den Chloroplasten. In schwer geschädigten Geweben enthalten deformierte Zellen homogene Protoplasten, in denen nur Reste nekrotischer Chloroplasten sichtbar waren.Mesophyllzellen in der Nachbarschaft von direkt angestochenem Gewebe zeigte ebenfalls subzelluläre Veränderungen. Mögliche Mechanismen der Reaktion des Pflanzengewebes auf Milbensaugen werden diskutiert.

     

Effect of freezing and thawing on cell membranes of Lentinus edodes,the shiitake mushroom

When cell membranes of Lentinus edodes mycelium were rapidly frozen at either 50 or 160°C/min, viability was lost and this correlated with rupture of the plasmalemma and residual membrane material and with alterations in the organelles. Although with slow cooling (1°C/min) 80% of the samples recovered viability, some cells still showed similar changes to those cooled rapidly, indicating that individual cells of the mycelium do not respond in the same way.     

High toxicity of the novel bloom-forming species Chattonella ovata (Raphidophyceae) to cultured fish

A toxicological study of an axenic cell line of novel species Chattonella ovata Y. Hara et Chihara (Raphidophyceae) revealed that cultured species of sea bream (Pagrus major), horse mackerel (Trachurus japonicus), and yellowtail (Seriola quinqueradiata) were killed by 4.1–6.8 × 10³, 5.4 × 10³, and 2.8 × 10³ cells/mL, respectively. The sensitivity of the gill lamellae to C. ovata differed among the fish species tested. This finding revealed that C. ovata was highly toxic to the cultured fish. Histological examination showed that edema and hyperplasia of the secondary gill lamellae of red sea bream and horse mackerel occurred when exposed to, or killed by C. ovata, whereas severe damage in the gill lamellae was not observed in yellowtail. Chattonella produced high amounts of superoxide anion radicals and hydrogen peroxide, possibly responsible for the fish death observed. Based on the results of this study and occurrence of a red tide by this organism in China in 2001, we consider this organism to be one of the harmful algae in coastal waters. This is the first report demonstrating that C. ovata is highly toxic to fish, and that it produces superoxide and hydrogen peroxide.     

Behavioral responses to fish kairomones and autotomy in a damselfly

The threat-sensitivity hypothesis predicts that prey species assess and adjust their behavior in accordance with the magnitude of the threat posed by a predator. A largely overlooked characteristic of a prey that will affect its sensitivity to predators is its history of autotomy. We studied threat-sensitive behavior to fish kairomones in larvae of Ischnura elegans damselflies, which had undergone autotomy, from a fishpond and from a fishless pond. In agreement with their higher perceived risk, larvae from the fishpond showed fewer rigid abdomen bends, foraged less and walked more slowly than larvae from the fishless pond. In line with their higher vulnerability to predators, larvae without lamellae spent less time foraging than larvae with lamellae. There was a decrease in swimming activity in the presence of fish kairomones except for larvae with lamellae from the fishless pond. This may reflect differences in vulnerability of larvae without lamellae between pond types. Such context-dependent responses in activity to kairomones should be kept in mind when evaluating the ability of a prey to recognize kairomones.     

Topochemical studies on the wall of beech bark sclereids by enzymatic and acidic degradation

Summary Sclereids isolated from the bark of beech (Fagus sylvatica L.) were delignified and treated with 1.3% sulfuric acid or with purified enzymes, viz., avicelase, carboxymethylcellulase, xylanase as well as combinations of xylanase and avicelase. Monitoring of the degradation was performed by quantitative liquid chromatography. Sulfuric acid dissolves about 30% sugars, especially hemicelluloses after 12 hours treatment. The avicelase (cellulase) and carboxymethylcellulase treatment degraded cellulose only to a very small extent. The xylanase degraded xylan selectively from the delignified sclereids amounting to about 60% after 51 hours incubation. The combined action of xylanase and avicelase brought about a xylan degradation of about 70%. Addition of avicelase to the initially xylanase-treated material resulted in the degradation of cellulase up to 25%.Electron microscopy of the variously treated samples showed the micromorphological changes effected and gave an indication of the topochemical distribution of xylan and cellulose. Sulfuric acid treatment removed wall components from all the lamellae of the sclereid wall, showing no definite pattern. Xylanase effects an intense decrustation of wall material both at the lumen boundary as well as near to the middle lamella, whereby the pattern of degradation is irregular; the cellulose fibrils also become well exposed. The addition of avicelase to xylanase-treated sclereid holocellulose creates an increase in the degradation, which is especially localized in the lamellated wall near to the middle lamella/primary wall region and at the lumen boundary. There appears to be a total hydrolysis of both matrix and fibrillar substances, characteristically more in the lamellae with longitudinal bow-shaped fibrils. Based on these results it is concluded that there appears to be no definite differential distribution pattern of xylan in the two lamellae. The higher contrast in the lamellae with transversely oriented fibrils is interpreted as resulting from the packing density of cellulose fibrils.     

Dynamics of polymorphism of acidocalcisomes in<Emphasis Type="Italic"> Leishmania</Emphasis> parasites

Growth of Leishmania mexicana amazonensis promastigotes in different culture media resulted in structurally and chemically different acidocalcisomes. When grown in SDM-79 medium, the promastigotes showed large spherical acidocalcisomes of up to 1.2 m diameter distributed throughout the cell. X-ray microanalysis and elemental mapping of the organelles showed large amounts of oxygen, phosphorus, sodium, potassium, magnesium, calcium, and zinc. Immunofluorescence microscopy using antisera raised against a peptide sequence of the vacuolar-type proton pyrophosphatase of Arabidopsis thaliana that is conserved in the Leishmania enzyme, indicated localization in acidocalcisomes. When cells were transferred to Warrens medium, the acidocalcisomes transformed from spherical into branched tubular organelles. The labeling pattern of the vacuolar proton-pyrophosphatase, considered as a marker for the organelle, changed accompanying the structural changes of the acidocalcisomes, and the enzyme showed an apparently lower proton-transporting activity when measured in digitonin-permeabilized promastigotes. X-ray microanalysis and elemental mapping of these structures revealed the additional presence of iron. Together, the results reveal that the morphology and composition of acidocalcisomes are greatly influenced by the culture conditions.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Studies on fish scale formation and resorption

Summary Electron microscopic investigation of scales of the goldfish Carassius auratus revealed that the lamellae of fibrillary plates contain sheet-like structures composed of vertically oriented collagen fibers embedded in an organic matrix. The fibers (TC fibers) are smaller in diameter (35–45 nm) than those of the lamellae and the matrix is stained intensely with lead citrate.The sheet-like structures as well as the lamellae are formed by fibroblasts located beneath the lamellae. The orientation of the collagen fibers of the sheets and the lamellae seems to be controlled by the orientation of the ridges and invaginations of the surface of the fibroblasts.The fibrillary plate of C. auratus was found to be partially calcified. Calcification was initiated by the deposition of needle-like or flaky crystals of hydroxyapatite in the organic matrix of the sheet-like structure and proceeded into the TC fibers and the matrix region of the lamellae. The potassium pyroantimonate-osmium tetroxide method showed a heavy concentration of calcium in the osteoblasts, fibroblasts, and in the matrix regions of the fibrillary plate. Calcium-containing precipitates were also present in the hole zone of the collagen fibers in the lamellae, but the significance of this location in calcification remains to be elucidated.Contribution No. 285, Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, Columbia, South Carolina, 29208, USA     

Ultrastructure of the mesophyll in scots pine and Norway spruce: Seasonal variation and molarity of the fixative buffer

Summary Resolution of the ultrastructure of the needles of both Scots pine (Pinus silvestris L.) and Norway spruce [Picea abies (L.) Karst.] is strongly influenced by the molarity of the buffer used in fixation. When 0.2 M or 0.1 M buffer is used in fixation during the summer, the constituents of the cytoplasm are precipitated, resulting in poor resolution of the membranes and lamellae and often in negative staining. The tannin in the central vacuole appears as a thick ribbon. By using correct molarities of buffer during each season (0.1 M for autumn and winter and ca. 0.05 M for the growing season), the best possible resolution will be achieved. With good resolution the tannin in the central vacuole appears in granular form throughout the year, and the cytoplasm and its organelles are clearly distinguishable during every season. During the growing season, the chloroplasts in the needles of Scots pine are spread to the cell walls and have large starch grains; the stroma and grana lamellae are well developed; the stroma and cytoplasm are rich in polysomes. Mitochondria and microbodies can be clearly resolved. During hardening and afterwords throughout the winter, the chloroplasts, which at this time contain no starch, and other cytoplasmic organelles aggregate in the corners of the cells. The chloroplast envelopes and the stroma and grana lamellae stay intact. The cytoplasm is netlike and rich in ribosomes, mitochondria and microbodies, all of which are intact and clearly distinguishable. During spring activation the structure returns to that described for the growing season.     

朱顶红花粉萌发过程中营养细胞质的超微结构变化

本文应用透射电镜对朱顶红成熟花粉水合、活化和萌发的动态过程中营养细胞质的结构和组成变化进行了观察。成熟花粉具质体、线粒体、内质网、高尔基体。微丝束以聚集体的形式存在。花粉活化后,细胞器的数目和结构发生显著变化：质体和线粒体的片层明显增加,内质网片层狭窄,高尔基体活跃产生小泡,脂体降解及微丝聚集体散开。花粉萌发后,细胞质中出现周质微管和被刺小泡,此期细胞器的变化不明显。微丝以纤丝状遍布整个花粉管中。     

Morphology and ultrastructure of Mammillaria gracillis (Cactaceae) in in vitro culture

Morphogenetic status of cactus Mammillaria gracillis Pfeiff. tissue culture was studied by light and electron microscopy. In vitro propagated shoots spontaneously developed callus. This callus regenerated normal and hyperhydric shoots without exogenous hormones. Tumour tissue induced by wild or rooty strains of Agrobacterium tumefaciens never expressed any morphogenetic potential. Light microscopy showed cellular characteristics of morphologically different tissues. Ultrastructural studies revealed changes in plastids: secondary dedifferentiation of mature chloroplasts, thylakoid swelling and disruption, phytoferritin accumulation, plastid elongation and increase in size. Changes in chlorophyll and carotenoid content were in accordance with degradation of the thylakoid system. Plastids were confirmed as very sensitive organelles to an artificial hyperhydric environment as well as to Agrobacteria-mediated cell transformation.     

Ultrastructural changes in the spermatogonia and spermatocytes of Poecilia reticulata during spermatogenesis

Summary The structure of guppy (Poecilia reticulata) spermatogonia and spermatocytes has been studied using electron microscopy. The spermatogonia, situated at the apex of the seminiferous tubule, are almost all surrounded by a network of Sertoli cells; they have very diffuse chromatin and one or two large nucleoli. The cytoplasm contains relatively few organelles, although annulate lamellae are found. The mitochondria have few cristae and are concentrated at one pole of the cell; they are sometimes found with intermitochondrial cement. These spermatogonia are separated from each other, having no intercellular bridges or inclusion in Sertoli cells, and are relatively undifferentiated; they correspond to stem cells. The spermatogonia beneath the apex are organized into cysts. First-generation spermatogonia are more dense and heterogeneous, their nuclei becoming smaller and their chromatin becoming denser during successive generations. In spermatocytes, the synaptinemal complex exists as a modified form until metaphase. The concentration of organelles in the cytoplasm increases and the organelles become more diversified as spermatogenesis progresses. Many cytoplasmic bridges are observed (several per cell), indicating that the cells remain in contact after several divisions. These changes in germ cell structure have been related to some of the characteristic features of spermatogenesis in guppy, e.g. the large number of spermatogonial generations and the complexity of spermiogenesis.     

Dedifferentiation of chloroplasts in interspecific and homospecific protoplast fusion products

Summary Interspecific and homospecific protoplast fusion products (Vicia narbonensis +V. hajastana,V. hajastana+V. hajastana) regenerated cell walls and divided when culturedin vitro for a period of 7 days. While most organelles appeared typical of actively growing plant cells, chloroplasts exhibited structural changes which were interpreted as dedifferentiation.     

A new type of photoreceptor in Anthopharynx sacculipenis (Plathelminthes,Solenopharyngidae)

The unpaired eye of A. sacculipenis consists of two sensory cells and one pigmented mantle cell. The light-sensing organelles are formed by flattened and rolled lamellae, which are not of ciliary origin but derive from the surface membrane of the sensory cells. The pigment of the mantle cell appears black in living animals, but electron-lucent in the EM picture. The significance of these special features is discussed.     

A new type of microtubular cytoskeleton in microsporogenesis of Lavatera thuringiaca L.

Summary. In Lavatera thuringiaca, kariokinesis and simultaneous cytokinesis during the meiotic division of microsporogenesis follow a procedure similar to that which takes place in the majority of members of the class Angiospermae. However, chondriokinesis occurs in a unique way found only in species from the family Malvaceae. Chondriokinesis in such species is well documented, but the relationship between the tubulin cytoskeleton and rearrangement of cell organelles during meiosis in L. thuringiaca has not been precisely defined so far. In this study, the microtubular cytoskeleton was investigated in dividing microsporocytes of L. thuringiaca by immunofluorescence. The meiotic stages and positions of cell organelles were identified by staining with 4′,6-diamidino-2-phenylindole. We observed that, during prophase I and II, changes in microtubular cytoskeleton configurations have unique features, which have not been described for other plant species. At the end of prophase I, organelles (mostly plastids and mitochondria) form a compact envelope around the nucleus, and the subsequent phases of kariokinesis take place within this arrangement. At this point of cell division, microtubules surround the organelle envelope and separate it from the peripheral cytoplasm, which is devoid of plastids and mitochondria. In telophase I, two newly formed nuclei are tightly surrounded by the cell organelle envelopes, and these are separated by the phragmoplast. Later, when the phragmoplast disappears, cell organelles still surround the nuclei but also move a little, starting to occupy the place of the disappearing phragmoplast. After the breakup of tetrads, the radial microtubule system is well developed, and cell organelles can still be observed as a dense envelope around the nuclei. At a very late stage of sporoderm development, the radial microtubule system disappears, and cell organelles become gradually scattered in the cytoplasm of the microspores. Using colchicines, specific inhibitors of microtubule formation, we investigated the relationship between the tubulin cytoskeleton and the distribution of cell organelles. Our analysis demonstrates that impairment of microtubule organization, which constitutes only a single component of the cytoskeleton, is enough to disturb typical chondriokinesis in L. thuringiaca. This indicates that microtubules (independent of microfilaments) are responsible for the reorganization of cell organelles during meiotic division. Correspondence: D. Tchórzewska, Department of Plant Anatomy and Cytology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland.