Showing papers on "Ultrastructure published in 2000"

Correlative Light-Electron Microscopy Reveals the Tubular-Saccular Ultrastructure of Carriers Operating between Golgi Apparatus and Plasma Membrane

Abstract: Transport intermediates (TIs) have a central role in intracellular traffic, and much effort has been directed towards defining their molecular organization. Unfortunately, major uncertainties remain regarding their true structure in living cells. To address this question, we have developed an approach based on the combination of the green fluorescent protein technology and correlative light-electron microscopy, by which it is possible to monitor an individual carrier in vivo and then take a picture of its ultrastructure at any moment of its lifecycle. We have applied this technique to define the structure of TIs operating from the Golgi apparatus to the plasma membrane, whose in vivo dynamics have been characterized recently by light microscopy. We find that these carriers are large (ranging from 0.3–1.7 μm in maximum diameter, nearly half the size of a Golgi cisterna), comprise almost exclusively tubular-saccular structures, and fuse directly with the plasma membrane, sometimes minutes after docking to the fusion site.

Mitochondrial morphology in human fetal and adult female germ cells.

Abstract: The aim of this study has been to observe, by electron microscopy, the morphological changes affecting mitochondria and associated organelles in the human female germ cell during oogenesis, maturation and fertilization. In the primordial germ cell (PGC), rounded mitochondria with a pale matrix and small vesicular cristae are disposed near the nucleus and significantly increase in number during PGC migration and settlement in the gonadal ridge, where they differentiate into oogonia. In these early stages of mammalian oogenesis, aggregates of mitochondria are typically clustered around or in close relationship with the nuage. In oocytes at early prophase stage, mitochondria proliferate while aligned along the outer surface of the nuclear membrane, contain a more dense matrix than before, and have lamellar cristae. Oocytes of primordial and primary follicles mostly contain round or irregular mitochondria whose matrix has become very light. These mitochondria show typical parallel, arched cristae, and are clustered near the nucleus with other organelles forming the Balbiani's vitelline body. When follicles grow, the mitochondria of the oocytes become even more numerous and are dispersed in the ooplasm. Both paranuclear accumulation and subsequent dispersion of mitochondria in the cytoplasm are likely to be regulated by microtubules. By ovulation, mitochondria are the most prominent organelles in the ooplasm. They form voluminous aggregates with smooth endoplasmic reticulum (SER) tubules and vesicles. These mitochondrial-SER aggregates (M-SER) and the mitochondrial-vesicle complexes (MV) could be involved in the production of a reservoir of substances or membranes anticipating subsequent fertilization and early embryogenesis. Just after fertilization, the mitochondria of the oocyte undergo a further substantial change in size, shape, and microtopography. In the pronuclear zygote, mitochondria concentrate around the pronuclei. During the first embryonic cleavage divisions, round or oval mitochondria with a dense matrix and few arched cristae are gradually replaced by elongated ones with a less dense matrix and numerous transverse cristae. A progressive reduction in size and number of M-SER aggregates and MV complexes also occurs. In summary, oocyte mitochondria show dynamic morphological changes as they increase in number and populate different cell domains within the oocyte. They form complex relationships with other cell organelles, according to the different energetic -metabolic needs of the cell during differentiation, maturation, and fertilization, and are ultimately inherited by the developing embryo, where they eventually assume a more typical somatic cell form.

Development of Peltate Glandular Trichomes of Peppermint

Abstract: Cryofixation and conventional chemical fixation methods were employed to examine the ultrastructure of developing peltate glandular trichomes of peppermint (Mentha x piperita). Our results are discussed in relation to monoterpene production and the mechanism of essential oil secretion. Peltate glands arise as epidermal protuberances (initials) that divide asymmetrically to produce a vacuolate basal cell, a stalk cell, and a cytoplasmically dense apical cell. Further divisions of the apical cell produce a peltate trichome with one basal cell, one stalk cell, and eight glandular (secretory) disc cells. Presecretory gland cells resemble meristematic cells because they contain proplastids, small vacuoles, and large nuclei. The secretory phase coincides with the separation and filling of the sub-cuticular oil storage space, the maturation of glandular disc cell leucoplasts in which monoterpene biosynthesis is known to be initiated, and the formation of extensive smooth endoplasmic reticulum at which hydroxylation steps of the monoterpene biosynthetic pathway occur. The smooth endoplasmic reticulum of the secretory cells appears to form associations with both the leucoplasts and the plasma membrane bordering the sub-cuticular oil storage cavity, often contains densely staining material, and may be involved with the transport of the monoterpene-rich secretion product. Associated changes in the ultrastructure of the secretory stage stalk cell are also described, as is the ultrastructure of the fragile post-secretory gland for which cryofixation methods are particularly well suited for the preservation of organizational integrity.

Effect of Salicylic Acid on Leaf Anatomy and Chloroplast Ultrastructure of Barley Plants

Abstract: Light and electron microscopy were used to relate histological and ultrastructural differences of barley leaves treated with different concentrations of salicylic acid (SA, 100 µM-1 mM). Light microscopy revealed that the thickness of all leaf tissue components decreased in SA-treated plants. The effect was most pronounced on the width of the adaxial epidermis and on the size of the bulliform cells. The chloroplast ultrastructure was also affected by SA treatment. Swelling of grana thylakoids in various degrees, coagulation of the stroma, and increase in chloroplast volume were observed. 1 mM SA caused a vast destruction of the whole plastid structure.

Macular hole retinal detachment in highly myopic eyes: ultrastructure of surgically removed epiretinal membrane and clinicopathologic correlation.

Abstract: Purpose:To elucidate the pathogenesis of macular hole retinal detachment (RD) in highly myopic eyes by investigating the ultrastructure of surgically removed epiretinal membranes (ERM).Methods:Five consecutive Japanese patients with macular hole RD in highly myopic eyes underwent vitrectomy with att

Isolation and Characterization of an Equine Foamy Virus

Abstract: Foamy viruses (FVs) are complex retroviruses which have been isolated from different animal species including nonhuman primates, cattle, and cats. Here, we report the isolation and characterization of a new FV isolated from blood samples of horses. Similar to other FVs, the equine foamy virus (EFV) exhibits a highly characteristic ultrastructure and induces syncytium formation and subsequent cell lysis on a large number of cell lines. Molecular cloning of EFV reveals that the general organization is that of other known FVs, whereas sequence similarity with its bovine FV counterpart is only 40%. Interestingly, EFV buds exclusively from the plasma membrane and not from the endoplasmic reticulum (ER), as previously shown for other FVs. The absence of the ER retrieval dilysine motif in EFV Env is likely responsible for this unexpected sorting pathway.

Long-term anoxia in encysted embryos of the crustacean, Artemia franciscana: viability, ultrastructure, and stress proteins.

Abstract: Cells of encysted embryos of Artemia franciscana, the brine shrimp, are among the most resistant of all animal cells to extremes of environmental stress. We focus here on their ability to survive continuous anoxia for periods of years, during which their metabolic rate is undetectable. We asked whether their impressive tolerance was reflected in changes at the ultrastructural level. The ultrastructure of encysted embryos previously experiencing 38 days and 3.3 years of anoxia was compared with those not undergoing anoxia (controls). Rough endoplasmic reticulum was abundant in anoxic embryos, in spite of the absence of protein biosynthesis in their cells. Other cytoplasmic changes had occurred in the anoxic cells, but overall their structure was remarkably intact, in view of their 3 years of continuous anoxia. A major difference was the presence of abundant electron-dense granules in the nuclei of anoxic embryos; these were present but rare in nuclei of controls. Biochemical fractionation and Western immunoblotting confirmed previous observations that substantial amounts of the small heat shock/α-crystallin protein (p26) translocated into nuclei of anoxic embryos. We have no evidence that the dense granules contain this protein, but that remains a possibility. In contrast, and contrary to expectation, proteins of the hsp70 and 90 families did not undergo anoxia-induced nuclear translocation, an unusual result since such translocations have been widely observed in cells from a variety of organisms.

Ultrastructure and function of mitochondria in gametocytic stage of Plasmodium falciparum.

Abstract: Morphological properties of the mitochondrial organelles in the asexual and sexual gametocytic stages of Plasmodium falciparum have been analyzed and found to be markedly different. From in vitro cultures of both stages in human erythrocytes, it has been demonstrated that the asexual stages contained a defined double-membrane organelle having a few tubular-like cristae. The numbers of mitochondria in the gametocytes were found to be approximately 6 organelles per parasite, and they showed a greater density of the cristae than that of the asexual stage parasite. The organelles of the gametocytes were successfully purified by differential centrifugation following Percoll density gradient separation with the results of approximately 7% yields and approximately 5 folds. The gametocytic organelles contained much more activities of mitochondrial electron transporting enzymes (i.e., cytochrome c reductase, cytochrome c oxidase) than the asexual stage organelles. Mitochondrial function as measured by oxygen consumption were found to be different between these two stages organelles. Their rates of oxygen consumption were relatively low, as compared to those of human leukocyte and mouse liver mitochondria. In contrast to the coupled mammalian mitochondria, the gametocytic organelles were in the uncoupling state between oxidation and phosphorylation reactions during their respiration. However, they were sensitive to inhibitors of the electron transport system, e.g., antimycin A, cyanide. Our results suggest that the mitochondria of the gametocytic stages are metabolically active and still underdeveloped, although their inner membranes are extensively folded. The biochemical significance of the unique structure of the mitochondria in these developing stages in host erythrocytes remains to be elucidated.

Mitochondrial free calcium levels (Rhod-2 fluorescence) and ultrastructural alterations in neuronally differentiated PC12 cells during ceramide-dependent cell death.

Abstract: Mitochondrial free calcium levels measured by Rhod-2 fluorescence and ultrastructure were examined during cell death in nerve growth factor (NGF)-differentiated PC12 cells that were 1) exposed to C2-ceramide, 2) deprived of serum to induce endogenous ceramide production, or 3) treated with calcium ionophore A23187. Rhod-2 fluorescence in mitochondria and also in the nucleolus increased to a maximum within 3 hours after C2-ceramide treatment or serum withdrawal. In A23187-treated cells, Rhod-2 fluorescence remained at baseline levels. In all three models, enlargement of the endoplasmic reticulum was the first ultrastructural alteration, followed by mitochondrial shrinkage in ionophore-treated cells, but by mitochondrial swelling in the ceramide-dependent models, in which rupture of the outer mitochondrial membrane and unfolding of the inner membrane were frequently seen. Dihydro-C2-ceramide, which did not cause cell death, had no effect on cellular ultrastructure. NGF, which inhibits ceramide-dependent cell death, prevented the effects of serum deprivation on mitochondrial ultrastructure but not on endoplasmic reticulum morphology or Rhod-2 fluorescence. Nuclear shrinkage with loss of nuclear membrane integrity, characterized by nuclear pores, free or surrounded by electron-dense filaments, was a late event in ceramide-dependent cell death. Chromatin condensation and other morphological features associated with apoptosis were seen in only a few atypical cells. Ceramide-mediated cell death, therefore, did not involve classical apoptosis but was mediated by a reproducible series of events beginning in the endoplasmic reticulum, followed by the mitochondria, and then the nucleus. NGF-dependent cell death inhibition intervenes at the mitochondrial level, not by blocking the increase in Rhod-2 fluorescence but by preventing the ultrastructural changes that follow. J. Comp. Neurol. 426:297–315, 2000. © 2000 Wiley-Liss, Inc.

Extracellular matrix assembly in diatoms (Bacillariophyceae). iv. ultrastructure of Achnanthes longipes and Cymbella cistula as revealed by high-pressure freezing/freeze substituton and cryo-field emission scanning electron microscopy

Abstract: Extracellular matrix (ECM) polymers secreted by the diatoms Achnanthes longipes Ag. and Cymbella cistula (Ehr.) Kirchn. completely encase the cell and are responsible for adhesion and other interactions with the external environment. To preserve details of the highly hydrophilic ECM in the native state and to preserve, with a high degree of fidelity, the intracellular structures involved in synthesis of extracellular polymers, we applied a suite of cryotechniques. The methods included high-resolution visualization of surfaces using cryo-field emission SEM (cryo-FESEM) and preservation for TEM observation of thin sections by high-pressure freezing (HPF) and freeze substitution (FS). The extracellular structures of diatoms plunge-frozen in liquid ethane, etched at low temperature, and observed on a cryostage in the FESEM showed overall dimensions and shapes closely comparable to those observed with light microscopy. Cryo-FESEM demonstrated the pervasive nature of the extracellular polymers and their importance in cell–substratum and cell–cell associations and revealed details of cell attachment processes not visible using other SEM techniques or light microscopy. The layer of ECM coating the frustule and entirely encapsulating cells of A. longipes and C. cistula was shown to have a significant role in initial cell adhesion and subsequent interaction with the environment. Trails of raphe-associated ECM, generated during cell motility, were shown at high resolution and consist of anastomoses of coiled and linear strands. Cryo-FESEM revealed a sheet-like mucilage covering stalks. HPF/FS of A. longipes resulted in excellent preservation of intra- and extracellular structures comparable to previous reports for animals and higher plants and revealed several organelles not described previously. Three distinct vesicle types were identified, including a class closely associated with Golgi bodies and postulated to participate in formation of the extracellular adhesive structures. HPF/FS showed a number of continuous diatotepic layers positioned between the plasma membrane and the silicon frustule and revealed that extracellular adhesive extrusion through frustule pores during stalk production was closely related to the diatotepum. The stalks of A. longipes consist of highly organized, multilayered, fine fibrillar materials with an electron-opaque layer organized as a sheath at the stalk periphery.

Ultrastructure of the midgut epithelium of Meliponinae larvae with different developmental stages and diets

Abstract: SUMMARYThe comparative study of the ultrastructure of the midgut epithelium of stingless bee larvae that eat plant protein (pollen) and animal protein (carrion) throughout the larval phase, shows variations in the digestive cells that are only relative to larval aging and not to the type of larval diet. The cells of older larvae present a cytoplasm with empty spaces that result from emptying of lipid and glycogen stocks, and the presence of autophagic vacuoles. These results are discussed in relation to the hypothesis that variations in the digestive tract of insects may be associated with different diets or phylogeny. We conclude that different diets do not determine cell morphology adaptations in the studied species. As the variations in the ultrastructure of the midgut epithelium are the same in all studied species, including the necrophagous species Trigona hypogea, throughout the larval stage, this sequence of changes seems to be due to different physiological state during larval development.

Immunolabeling for Electron Microscopy

Abstract: The protocols in this chapter concern postembedding immunolabeling for transmission electron microscopy; other schedules, such as pre-embedding methods, frozen tissue processes, and procedures for scanning electron microscopy, can be found elsewhere (1). In principle, immunolabeling at the electron microscope (EM) level follows the same precepts as immunolabeling at the light microscope level; in tissues or cells, the location of an antigen of interest is identified by a specific antibody, and must be visualized appropriately for investigation. Electron microscopy permits us to distinguish subcellu-lar organelles, and therefore ultrastructural localization of antigen position. At the EM level, however, the "visualizing step" needs to be provided by an electron-dense entity, most often a heavy metal, which reflects incident electrons; this is in contrast to the final step of light microscope level techniques, in which the final reaction product is sought to be colored (and where there is an element of choice of which color to use). Tissue processing for EM is considerably more severe than that for light microscopy, and thus maintenance of antigenicity in tissue is more taxing. Before immunolabeling for electron microscopy can be fruitful, the first step is to ensure that the antigen of interest is present (or is still present) in the tissue; this is done by performing a thorough procedure at the light microscope level on wax-embedded sections. Once a positive result has been obtained, studies can progress to the ultrastructural level. If the presence of an antigen cannot be demonstrated in a wax-embedded block, it will not be demonstrable in a resin-embedded EM block of the same tissue. In such a case, pre-embedding and frozen tissue techniques can be of use at both light and electron microscope levels.

Elastin Gene Deletions in Williams Syndrome Patients Result in Altered Deposition of Elastic Fibers in Skin and a Subclinical Dermal Phenotype

Abstract: Williams syndrome (WS) is a complex developmental disorder with multisystem involvement known to be the result of a microdeletion in the q11.23 region of chromosome 7. This deletion involves several genes, including the elastin gene. Although elastic fibers are important constituents of skin, little is known about the skin phenotype in WS patients. We have therefore studied the skin of four WS patients in which we've shown the deletion of one copy of the elastin gene. Physical examination and indirect immunofluorescent microscopy of elastin did not detect any major phenotypic or morphologic changes in the skin. We were able, however, to show subtle textural changes in skin and, by electron microscopy, that the amorphous component of elastic fibers in WS patients was consistently reduced when compared to normal controls. These findings indicate that deletion of one copy of the elastin gene results in reduced deposition of elastin in dermal elastic fibers, an altered elastic fiber ultrastructure, and a subclinical dermal phenotype in the children and young adult patients analyzed in this study.

Unusual ultrastructural features in three strains of Cyanothece (cyanobacteria)

Abstract: Three unicellular cyanobacterial strains (PCC 7425, PCC 8303, PCC 9308) assigned to the genus Cyanothece Komarek 1976, which showed an unusually high content of light refractile inclusions when viewed by phase-contrast microscopy, were characterized by confocal laser scanning microscopy and transmission electron microscopy. All strains had concentric cortical thylakoids and a compact central nucleoid. Frequently, the two innermost thylakoid membranes protruded to form circular enclosures containing cytoplasm or electron-transparent granules, or both. The largest granules were partially immersed in the nucleoid region, but they remained attached to the inner cortical thylakoids by a single narrow connection. The pattern of binary cell division in strain PCC 7425 was different than that in strains PCC 8303 and PCC 9308. In the former, all cell wall layers invaginated simultaneously, whereas in the latter the invagination of the outer membrane was delayed compared to that of the cytoplasmic membrane and the peptidoglycan layer. Thus, prior to completion of cell division, the new daughter cells of strains PCC 8303 and PCC 9308 were transiently connected by a thick septum, which was not observed in strain PCC 7425. Nucleoid partitioning coincided with initiation of cell division in all three strains and was unlike that reported in other bacteria and in archaea, in which separation of the nucleoids precedes cell division. Based on the common morphological and ultrastructural features, the three strains of Cyanothece examined constitute a distinct cluster, which might deserve independent generic status.

Ultrastructural and Biochemical Characterization of Promastigote and Cystic Forms of Leptomonas wallacei N. Sp. Isolated from the Intestine of its Natural Host Oncopeltus fasciatus (Hemiptera: Lygaeidae)

Abstract: Promastigote forms of a trypanosomatid were isolated from the third and fourth ventricles of the midgut and from the hindgut of the phytophagous hemipteran Oncopeltus fasciatus. Some individuals had adhered to its anterior region, close to the flagellar pocket, or to the flagellum up to four rounded aflagellated forms known as straphangers cysts. Scanning electron microscopy revealed that the flagellated forms presented a twisted cell body and a long flagellum, and the cysts, smaller than the parental promastigote, had a nascent flagellum. Transmission electron microscopy showed that promastigotes were typical, while cystic forms were ovoid dense cells devoid of a cyst wall, but presenting a cell coat, a special subpellicular region limited by a membrane unit, and a condensed cytoplasm. The kinetoplast-DNA fibrils appeared as dense spots and the condensed chromatin was arranged in a labyrinthic structure. Desmosome-like structures, observed in the region of adhesion of the precystic forms to the ...

Effects of Cadmium on Ultrastructure and Steroidogenesis in Cultured Porcine Ovarian Granulosa Cells

Abstract: Massányi P. , V. Uhrín, A. V. Sirotkin, K. Paksy, Zs. Forgács, R. Toman, J . Kováãik: Effects of Cadmium on Ultrastructure and Steroidogenesis in Cultured Porcine Ovarian Granulosa Cells. Acta Vet. Brno 2000, 69: 101–106. Cadmium is an environmental risk factor having various toxic effects both in animals and in humans. The aim of this study was to study its effects on the structure and function of porcine ovarian granulosa cells cultured in vitro. Ultrastructure of granulosa cells was studied after 48 h of culture with (0.2, 10 and 20 ng CdCl2/ml) of without cadmium using transmission electron microscopy (TEM). Quantification of progesterone and 17-β-oestradiol was performed directly from aliquots of the media from control and treated cells by radioimmunoassay (RIA). After cadmium administration cell membranes were disintegrated. It was manifested by occurrence of vacuoles in the cytoplasm.The vacuoles contained fibrillar or membranous material. The Golgi complex rarely remained intact. Increased number of lysosomes was detected. With increasing cadmium concentrations the number of lipid droplets increased. In some cells the changes were less evident and dense mitochondria with distinct membranes were found. In other cell types the amount of mitochondrial matrix increased and that of membranes decreased. Some mitochondria fused with lysosomes. The endoplasmic reticulum rarely remained intact, and its dilation was well visible on transverse sections. Nuclei with distinct heterochromatin at the nuclear membrane were often observed. In these nuclei perinuclear cistern was dilated. Less frequently nuclei with condensed chromatin reminiscent of pyknosis were observed. Some nuclei had dispersed fine granular chromatin. In other cells changes were less evident, and comprised condensed chromatin in the central part of nuclei. These structural changes of granulosa cells exposed to cadmium were related to premature luteinization of these cells. In the evaluation of steroidogenesis we found that cadmium induced an increase in progesterone production, and a decrease in 17-β-oestradiol production by ovarian granulosa cells; however, these differences were not significant. The results of our study elucidate some of the effects of cadmium on gonadal function, and should also serve to increase the level of awareness of its effects on human and animal

Ultrastructural changes associated with accumulation of inclusion bodies in rat retinal pigment epithelium.

Abstract: Purpose To determine the structural changes in the retinal pigment epithelium (RPE) and neighboring structures induced by intravitreal injection of a lysosomal protease inhibitor Methods Eleven-week-old Sprague-Dawley rats were injected with 5 microliter of a lysosomal protease inhibitor, E-64 (222 microM), intravitreally once and killed at 24 hours, 48 hours, or 7 days later Others received two or three injections at 48-hour intervals or three daily injections, and killed at 1, 4, and 7 days after the last injection Eyes were enucleated and retinal tissues were processed for light and electron microscopy Results A single injection of E-64 caused only a transient accumulation of phagosome-like and phagolysosome-like inclusion bodies in the RPE By contrast, repeated injection caused progressive accumulation of these inclusions followed by altered RPE cell conformation, and changes in organelles such as loss of smooth endoplasmic reticulum (SER) This was accompanied by shortening and loss of photoreceptor outer segments without prior dysmorphic changes, alteration of choroidal capillaries, and invasion of Bruch's membrane by fibroblasts and pericytes Intravitreal injection of vehicle as control induced no structural changes Conclusions E-64 treatment induced structural changes in the outer retina The causal relationship between accumulation of inclusions in RPE and changes in other subcellular organelles and neighboring cells systems is not clear However, there are possible explanations: physical disturbance of organelles, particularly SER by inclusions; cellular damage by consequent upon accumulation of A2-E; or, shortage of recycled material due to reduced degradation of phagosomes

'Sub-imbibed' storage is not an option for extending longevity of recalcitrant seeds of the tropical species, Trichilia dregeana Sond.

Abstract: Recalcitrant seeds of Trichilia dregeana were stored at 16 or 25°C, either at the water content at which they were shed or partially dried. Although having been exposed to a short period (approx. 6 h) at temperatures up to 30°C prior to storage, seeds at the original water content maintained viability for several weeks at 16°C. However, storage of undried seeds at 25°C was deleterious within 8 d, indicating a chemical basis for degeneration of hydrated recalcitrant seeds. Seeds that had been mildly dehydrated to the relatively high axis level of 1.68 g H 2 O g —1 dry mass, while maintaining full germinability immediately after drying, exhibited only 4% viability after 8 d in storage at 16°C and had completely lost viability after the same storage period at 25°C. Ultrastructural features characterizing hydrated seeds included indications of enhanced activity associated with initial exposure to the elevated temperature as well as some signs of stress. However, over an effective 15 d storage period at 16°C, ultrastructural features showed the cells to have retained little damage and to have been in an enhanced state of activity commensurate with ongoing development towards germination. After a longer storage period, however, signs of damage, including indirect evidence for disarray of the cytoskeleton in some axis cells, became apparent in line with the declining seed viability. Immediately following dehydration from an average axis water content of 1.97 to 1.68 H 2 O g g —1 (the sub-imbibed condition), some ultrastructural abnormalities were apparent, but the seeds remained 100% germinable. However, within the 8 d storage period in this sub-imbibed condition, a spectrum of severe ultrastructural degeneration, including indirect evidence of the collapse of the nucleoskeleton and extensive cell lysis, accompanied viability decline of the seeds to 4%.

Sperm ultrastructure of Taenia mustelae (Cestoda, Taeniidae), an intestinal parasite of the weasel, Mustela nivalis (Carnivora)

Abstract: Summary The present paper describes the ultrastructure of spermatozoa of Taenia mustelae as revealed by transmission electron microscopy. The mature spermatozoon of this tenid is filiform, tapered at both ends, and lacks mitochondrion. It is capped by an apical cone of electron-dense material and presents a single helical crest-like body 75-nm thick. The axoneme is of the 9+‘1’ pattern of trepaxonematan platyhelminthes and lacks a periaxonemal sheath. Transverse intracytoplasmic walls are observed in several regions of the spermatozoon. In cross-section, the spiralled nucleus shows a horse-shoe to annulus shape. The submembranous cortical microtubules are spiralled at an angle of about 45° to the hypothetical spermatozoon axis.

Ultrastructural features of the fat body and oenocytes of Rhinocricus padbergi Verhoeff (Diplopoda, Spirobolida).

Abstract: The fat body of the diplopod Rhinocricus padbergi is located in two preferential areas of its body: a) immediately below the tegument, denominated parietal, and b) filling the body cavity, close to the viscera, mainly the ovaries and alimentary canal, denominated perivisceral. Ultrastructurally, its cells, the adipocytes, presented varied morphology and contained organelles indicating that they are cells that mainly produce and store lipids and proteins. The presence of cells similar to the oenocytes found in insects was observed for the first time in diplopods, associated to the fat body of R. padbergi. Our observations suggest that this tissue probably maintains activity cycles, since the presence of cells undergoing apoptosis was detected.

Ultrastructural features of the gut in the white sturgeon, Acipenser transmontanus.

Abstract: Electron-microscopic examinations of the sturgeon gut were performed. Oesophageal goblet cells were abundant in the stratified epithelium. The ultrastructural features of the secretory granules of the oesophageal and intestinal goblet cells were quite similar to those of other vertebrates. Lobules of multilocular adipose tissue were observed in the deep tunica propriasubmucosa of the oesophagus, in close association with vasculature and large fibre bundles of myelinated and unmyelinated axons. Similarly composed nerve fibre bundles were observed in the cardiac stomach. too. The presence of myelinated axons is an unusual feature in the vertebrate enteric nervous system. Cardiac and fundic zones of the stomach showed an epithelium with columnar ciliated and non-ciliated cells, the latter equipped with fuzzy microvilli. Cells lining the tubular gastric proper glands were markedly granulated. Intestinal superficial epithelium was columnar and contained ciliated, as well as non-ciliated and goblet cells. In the tunica propria all over the intestine, the presence and ultrastructure of granulated cells was in addition described. Intraepithelial granulated leukocytes were seen throughout the alimentary canal. Various types of endocrine cells were seen both in the stomach and in the intestine, the size of their granules was measured and their ultrastructure described and compared to that of mammalian cell types.

Ultrastructure of the horse tongue: further observations on the lingual integumentary architecture.

Abstract: This investigation examined primarily epidermal specializations of the adult horse tongue by light, scanning and transmission electron microscopy. Samples were collected from seven regions of the normal tongue of various breeds of horse. The filiform papillae, present on the dorsal and lateral aspects but not the ventral aspect of the tongue, were short, slender and finger-like structures with variable-shaped terminae. The epidermal thickness and height of dermal ridges were reduced on fungiform and vallate papillae, but tissue architecture and keratinocyte ultrastructure of most of the lingual epidermis corresponded to the common mammalian epidermal paradigm. One unique finding was the highly localized clustering of epidermal cells with exceptionally high content of PAS-negative trichohyalin cytoplasmic granules at a location atop the dermal ridges and beneath the base of filiform papillae. These granular cells were immediately subjacent to clusters of clear, non-granulated epidermal cells. It is believed that this integumentary specialization may enhance the structural strength at this localized site of the tissue architecture, in relationship to the mechanical papillae.

Effects of glutathione on thiol redox systems, chromosomal aberrations, and the ultrastructure of meristematic root cells of Picea abies (L.) Karst.

Abstract: Young spruce seedlings (Picea abies [L.] Karst.) grown in hydroponic culture were exposed to three different concentrations (50,100, and 500 μM) of reduced glutathione for 24 h. These physiologically relevant concentrations of glutathione had a multiple effect on the investigated tissue. Feeding of glutathione to roots increased the concentrations of thiols (glutathione, cysteine, and γ-glutamyl-cysteine) in roots, decreased the rate of cell divisions, induced mitotic abnormalities, and affected the cell ultrastructure. Electron micrographs showed effects such as advanced vacuolation, dilated rough-endoplasmic-reticulum cisternae, and separations of the plasma membrane from the cell wall.

Mesangial cell necrosis in Thy 1 glomerulonephritis--an ultrastructural study.

Abstract: Cell death is central to many physiological and pathological processes. As tissue reactions to the two forms of cell death, necrosis and apoptosis, differ, it is critical to distinguish between them. Although ultrastructure is still the definitive means of assessing this, there are very few in vivo studies. Administration of anti-Thy 1 antibody in rats is a model of acute glomerular mesangial cell death due to their expression of the Thy 1.1 epitope. The nature of this process is unclear; apoptosis was suggested from early morphological studies and recent in vitro effects of anti-Thy 1.1 antibody. We have re-examined the changes by electron microscopy, and identified a process of cell necrosis starting within 30 min of anti-Thy1.1 antibody administration. Although there was chromatin condensation, the necrotic features distinctive from apoptosis were: loss of nuclear membranes, cell swelling and degeneration of cytoplasmic organelles, with liberation of chromatin and organelles into the interstitium causing acute inflammation without phagocytic uptake of apoptotic bodies. These findings accord with the known complement dependence of this model. Ultrastructure is a valuable means of differentiating between in vivo necrosis and apoptosis and this is important for understanding the pathogenesis of injury and subsequent tissue responses.