Showing papers on "Ultrastructure published in 1992"

Estrogen receptors in dendrites and axon terminals in the guinea pig hypothalamus.

Abstract: The ultrastructural localization of steroid hormone receptors has been made possible by the development of immunocytochemical procedures using monoclonal antibodies. Estrogen receptor-immunoreactivity (ER-IR) in the brain is present most abundantly in neuronal nuclei when observed with light microscopy. However, we have also observed ER-IR in the perikarya and cytoplasmic processes of neurons. To determine the organelles with which the cytoplasmic ER-IR is associated, we developed a technique for ultrastructural visualization of ER-IR. Ovariectomized guinea pigs were perfused, brains vibratome-sectioned, and estrogen receptors immunostained by either an immunoperoxidase-diaminobenzidine technique or by an immunogold-streptavidin procedure, each followed by silver intensification. Electron microscopic analysis confirmed distribution of ER-IR throughout cell nuclei, but ER-IR was also observed in proximal and distal dendrites and rough endoplasmic reticulum. Most surprisingly, however, ER-IR was found in ma...

Epithelial-mesenchymal transformation during palatal fusion: carboxyfluorescein traces cells at light and electron microscopic levels

Abstract: During the fusion of rodent embryo palatal shelves, the cells of the outer epithelial layer slough off, allowing the cells of the medial edge basal layer to form a midline seam that undergoes epithelial-mesenchymal transformation, as judged by electron microscopy and immunohistochemistry. In this study, we analyze the fate of the transformed cells using a lipid soluble dye to label the medial edge epithelium in situ. Prefusion E14 mouse palates were exposed in vitro or in vivo to a fluoresceinated lipid soluble marker, carboxydichlorofluorescein diacetate succinimidyl ester (CCFSE), which localizes in epithelia as a lipid insoluble compound that does not pass into the connective tissue compartment. The midline seam that formed after 24 hours contained labelled epithelial cells that were replaced by individually labelled mesenchymal cells where the seam transformed. By light microscopy, the labelled cells were seen to contain intensely fluorescent bodies that do not react for acid phosphatase. We were able for the first time to identify these structures by electron microscopy as CCFSE isolation bodies. The cells with isolation bodies are clearly healthy and able to participate in subsequent development of the palate. At 4 days after labelling, individual CCFSE containing cells present in the palate mesenchyme occupy both midline and lateral areas and can clearly be classified as fibroblasts by electron microscopy. CCFSE is a far more useful marker than another lipid soluble marker, DiI, for following cells, because the cells can be fixed and identified both at the light and electron microscope levels. Interestingly, if labelled palatal shelves are not allowed to fuse in vitro, the basal epithelial cells do not form mesenchyme after sloughing, indicating that formation of the epithelial midline seam is necessary to trigger its epithelial-mesenchymal transformation.

Ultrastructural characterization and three-dimensional reconstruction of isolated maize (Zea mays L.) egg cell protoplasts

Abstract: Isolated egg cell protoplasts ofZea mays L., inbred line A 188, have been studied at the transmission electron microscope level. Their preparation for electron microscopy has been performed by embedding in ultra-low gelling agarose as a preliminary step. Five isolated egg cell protoplasts were serially ultrathin sectioned and studied in detail. One of these protoplasts was reconstructed in three dimensions to provide additional information on its structure. After enzymatic digestion and microdissection, isolated egg cells are true, highly vacuolized protoplasts. The structure of their organelles agrees with in situ observations, indicating an ultrastructural intactness after isolation: the mitochondria are polymorphic, form reticulate networks, and have well developed cristae; the plastids contain starch grains; and the spherical nucleus is euchromatic. As in situ, the organelles of the isolated egg cell protoplasts are aggregated near the nucleus. The complete picture provided by this work should serve as a comparative base for studies on in vitro fertilization products.

Ultrastructural study of M cells from colonic lymphoid nodules obtained by colonoscopic biopsy.

Abstract: The present study was undertaken to investigate ultrastructurally the epithelium covering lymphoid nodules obtained from colonoscopic biopsies of the human colon and rectum. Colonoscopy using the dye spraying contrast, method was performed in nine patients who showed x-ray evidence of lymphonodular hyperplasia. Fifty-two colonoscopical biopsy specimens, of lymphoid nodules were obtained from the ascending, transverse, and descending colon and rectosigmoid region. All specimens were observed by light and electron microscopy. Light microscopy disclosed large lymphoid follicles protruding into the lumen with a “dome-type” configuration. These extended to the lamina propria of the mucosa and were associated with a massive lymphoid aggregation extending as far as the muscularis mucosa from the submucosa. The epithelium covering these nodules contained a few goblet cells and many lymphocytes. Observation of the elevated surface at the apex by scanning electron microscopy revealed M cells with sparse microvilli in the dome epithelium surrounded by crypts. Transmission electron microscopy disclosed M cells enfolding many immature or mature lymphocytes and plasmocytes. The M cells had cytoplasmic microvilli (so-called “microfolds”) on their surfaces, well-developed tubulovesicular systems, and vacuoles in the cytoplasm. The basic structure of the M cells as observed by scanning and transmission electron microscopy was the same as that of M cells in the Peyer's patches of humans and mice. The apical surface of the colonic lymphoid follicles in Crohn's disease patients was associated with erosions observed by scanning electron microscopy. The erosions proved to be the naked surface of the dome after removal of the epithelium and many holes from 2.0 to 6.0 μm in diameter were observed on the naked surface. At high magnification, lymphocytes were seen projecting from holes (18%) on the naked surface of the dome. These ultrastructural findings indicate that human colonic lymphoid follicles are very similar to those seen in other species.

Functional Ultrastructure of the Proximal Tubule

Abstract: The sections in this article are: 1 Location of Proximal Tubule 2 Fixation of Proximal Tubule Cells for Electron Microscopy 3 Ultrastructure of the Mammalian Proximal Tubule Cell 3.1 General Cytology 3.2 Cell Shape 3.3 Segmentation of the Mammalian Proximal Tubule 3.4 Luminal Cell Surface 3.5 Basal and Lateral Cell Surface 3.6 Junctions 3.7 Nucleus 3.8 Mitochondria 3.9 Endoplasmic Reticulum 3.10 Golgi Apparatus 3.11 Vacuolar Apparatus (Lysosomes and Endocytic Vacuoles) 3.12 Peroxisomes 3.13 Cytoskeleton 3.14 Cytoplasmic Ground Substance and Inclusions 4 Structure of Proximal Tubule Cells in Submammalian Species 4.1 Birds 4.2 Reptiles 4.3 Amphibians 4.4 Fishes 5 Ultrastructure of Experimentally Perfused Tubules 6 Quantitative Ultrastructure of Proximal Tubules 7 Transepithelial Transport Routes 7.1 The Transcellular Route 7.2 The Paracellular Route 8 Functions of the Vacuolar Apparatus 8.1 Protein Absorption by the Proximal Tubule Cells 8.2 Transtubular Transport of Proteins 8.3 Basolateral Binding and Uptake of Proteins 8.4 Endocytosis of Nonproteins 8.5 Autophogocytosis 8.6 Lysosomal Accumulation of Metals and Other Substances

Myofibrosarcoma of subcutaneous soft tissue of the cheek.

Abstract: A low grade soft tissue sarcoma from the naso-labial fold and designated as myofibrosarcoma (sarcoma of myofibroblasts) is described using standard light microscopy techniques, immunohistochemistry and electron microscopy. Pink fibrillated cytoplasm, regarded as one of the typical histological features of leiomyosarcoma, was not obvious but immunostaining for alpha-smooth muscle actin was positive suggesting smooth muscle differentiation. By electron microscopy, tumour cells contained abundant rough endoplasmic reticulum cisternae and a large Golgi body; there were modest but numerous bundles of fine filaments with focal densities. A conventional lamina was lacking but the cell surface was characterised by fibronexus junctions in which there was a conspicuous extracellular, fibronectin-containing fibril, apparently mediating contact between cell and matrix. The tumour cells therefore showed myofibroblastic differentiation. The cell surfaces showed strong immunoreactivity with an anti-fibronectin antibody. Myofibrosarcoma is not a widely recognised entity and this case is only the 7th example to be documented in detail by means of both immunohistochemistry and ultrastructure. The combination of electron microscopy for detecting the fibronexus junction and immunostaining for fibronectin at the cell periphery is suggested as potentially useful for distinguishing myofibrosarcoma from leiomyosarcoma.

Internal reproductive system in adult males of the genus Camponotus (Hymenoptera: Formicidae: Formicinae)

Abstract: Descriptions are provided of the histology and ultrastructure of the male internal reproductive tracts from three species of Camponotus, representing three subgenera. This study is the first to provide ultrastructural information on the testes (including spermatogenesis and spermiogenesis), seminal vesicles, and accessory glands in ants. Testes contain about ten follicles each, and each follicle is capable of producing hundreds of cysts in which spermatozoa develop. Structural evidence of meiosis in late pupal testes includes cytoplasmic bridges between spermatocytes, centriole elimination, and fusion of mitochondria. Developing spermatids are in close contact with cyst cells in the region of the acrosome. Mature spermatozoa are similar in ultrastructure to those described previously for two other subfamilies of ants (Myrmicinae and Dolichoderinae). The ultrastructure of the seminal vesicle suggests that it is not merely a passive organ for sperm storage. Large numbers of both mitochondria and membranous whorls suggest a pH-regulating and/or hormonal function. The accessory gland is made up of secretory cells that contain a diversity of secretory granules. SDS-PAGE reveals several proteins found in the accessory glands but absent in the adjacent genitalia. Preliminary analyses indicate that carbohydrate is an important component of accessory gland secretions.

Human meibomian glands: the ultrastructure of acinar cells as viewed by thin section and freeze-fracture transmission electron microscopies.

Abstract: Heightened interest in meibomian glands dysfunction prompted the authors to examine the ultrastructure of the glandular epithelium in specimens of surgical origin, by thin section and freeze-fracture electron microscopies. In meibomian glands, the morphology and ultrastructure of acinar cells varies considerably according to their stage of holocrine differentiation. This study shows close interdependence between fat droplets and Golgi apparatus or endoplasmic reticulum. As the cells initiate their differentiation, the smooth endoplasmic reticulum and the Golgi apparatus become prominent and the first small lipid droplets appear in the cytoplasm. When fractured through a plane close to their surface, lipid droplets appear onion-like structured, ie made up of a variable number of irregular shaped concentric lamellae. This lamellar organization suggests that membranes are not only involved in synthesis, but also that some of their components are incorporated in the fat droplets. The authors conclude that human meibomian glands are a holocrine glandular complex that, despite great differences in type and location, present basic similarities with sebaceous glands.

Sperm cells in pollen tubes ofNicotians tabacum L.: three-dimensional reconstruction, cytoplasmic diminution, and quantitative cytology

Abstract: The organization of the sperm cells and vegetative nucleus (male germ unit) ofNicotiana tabacum was examined 18 h after semivivo pollination using transmission electron microscopy, computerassisted serial section reconstruction and quantitative cytology. Based on a measurement of 11 cellular parameters in nine reconstructed sperm cell pairs, there are no statistically significant differences between the two cells. The Svn is characterized by a strapshaped cytoplasmic extension that is physically associated with the surface of the vegetative nucleus. The nucleus is located adjacent to the sperm crosswall, with sperm organelles being distributed between the nucleus and the extension. The Sua is a tapered cell with cytoplasmic areas at both poles and deep axial invaginations near the crosswall. This cell has a centrally-located nucleus and a largely polar distribution of organelles. Three mechanisms for cytoplasmic diminution were observed that appear to contribute actively to the loss of cytoplasmic volume and organelles: (1) enucleated cytoplasmic body production in the Sua; (2) vesiculation at the tip of the cytoplasmic projection of the Svn; and (3) vesicle-containing body accumulation in the periplasm of both the Svn and Sua.

The fine structure of the follicular cells in growing and atretic ovarian follicles of the domestic goose.

Abstract: The structure of follicular layer of growing and atretic follicles in the ovary of the domestic goose, was studied by electron microscopy In small follicles, the wall is lined with a narrow layer of tightly packed small, cuboidal cells separated from the thecal tissue by the basal lamina During growth, they transform into tall, columnar cells arranged in a single row The cells display several peculiar ultrastructural features First, annulate lamellae are commonly observed Second, cytoplasmic dense-cored granules accumulate in close association with fenestrated cisternae and networks of tubuli derived from the RER They consist of spheres and strands of amorphous substance of unknown origin Third, the cells contain many transosomes, a unique organelle of the avian follicle cell consisting of a dense plaque associated with ribosome-like particles The mature forms of transosomes are located at the tips of lateral and apical cell projections, while bodies thought to be their precursors, are found in the apical cytoplasm In follicles larger than 8 mm in diameter, most of the transosomes and their precursors have disappeared Follicular atresia occurs in all of the size-classes of follicles investigated A loss of transosomes (in follicles up to 8 mm in diameter) and an accumulation of lipid droplets are the first atretic events detectable by electron microscopy Morphologic features, including deep nuclear indentations, accumulation of lipid droplets frequently encireled by membrane whorls, dilation and disintegration of RER cisterns, swelling of mitochondria and accumulation of dense irregular masses of unknown origin in the cytoplasm, are taken as evidence for advanced degradation We conclude that necrosis is the dominant type of cell death of the follicular cells during atresia However, a small fraction of cells, characterized by dark condensed cytoplasm, seems to die by apoptosis

Ultrastructure of root cortical cells parasitized by the ring nematodeCriconemella xenoplax

Abstract: Individuals of the plant-parasitic nematodeCriconemella xenoplax, monoxenically cultured on root expiants of clover, carnation, and tomato, fed continuously for up to 8 days from single cells in the outer root cortex. Individual cortical cells parasitized by nematodes were modified into discrete “food cells” in all hosts examined. The nematode's stylet penetrated between epidermal cells and frequently through a subepidermal cortical cell. Electron-transparent callose-like material continuous with the cell wall enveloped the portion of the stylet that traversed subepidermal cortical cells. Food cells were typically located in the first or second cell layers of the cortex. The stylet penetrated 5–6 μm through the wall of the food cell without penetrating the plasma membrane. Electron-transparent callose-like deposits formed between the invaginated plasma membrane and stylet, except at its aperture. The plasma membrane of the food cell was appressed tightly to the wall of the stylet aperture creating a 130–160 nm hole in the membrane. This opening provided continuity between the lumen of the stylet and the food cell cytosol for ingestion of nutrients by the nematode. Ribosomes were dissociated from the cisternae of the endoplasmic reticulum in food cells and accumulated with other cell organelles in a zone of modified cytoplasm around the stylet. A fibrillar material appeared to form a barrier in the cytosol around the stylet aperture that limited movement of cell organelles toward the aperture. Electron-dense secretory components were secreted into the food cell by the nematode. Clusters of putative nematode secretory components consisting of 20–40 nm diameter, electron-dense particles were dispersed in the densely particulate zone of cytoplasm around the stylet tip. The cytosol immediately around the stylet aperture in the center of the modified cytoplasm was finely granular.

Metamorphosis of calcareous sponges I. Ultrastructure of free-swimming larvae

Abstract: Summary Free-swimming larvae of two calcareous sponges were studied by electron microscopy. The larvae are composed of four kinds of cells, namely flagellated cells, granular cells, four cruciform cells, and several yolk-containing cells. In the anterior hemisphere of the larvae, the columnar flagellated cells are arranged in a single layer. Their nucleus and Golgi apparatus are located in close proximity to the flagellar rootlets. There are granular cells in the posterior hemisphere of the larvae. They have a nucleus with a nucleolus, large phagosomes, well-developed Golgi apparatus, and numerous RER cisternae. There is a cruciform cell in each quadrant of the larvae. From its characteristic arrangement of organelles, it is suggested but not concluded that the cruciform cells participate in photoreception. The yolk-containing cells are, most probably, nutritive cells derived from the mother sponge. The roles of these four kinds of cells in habitat selection and metamorphosis are discussed.

Fine structure of the dorsal epithelium of the tongue of the freshwater turtle, Geoclemys reevesii (Chelonia, Emydinae)

Abstract: Scanning electron microscopy shows that lingual papillae occur all over the dorsal surface of the tongue of the freshwater turtle, Geoclemys reevesii. The surface of each papilla is composed of compactly distributed hemispherical bulges, each composed of a single cell. Microvilli are widely distributed over the surface of cells. Histological examination reveals that the connective tissue penetrates deep into the center of papillae and that the epithelium is stratified columnar. Under the transmission electron microscope, the cells of the basal and the deep intermediate layers of the epithelium appear rounded. A large nucleus lies in the central area of each cell. The cytoplasm contains mitochondria, endoplasmic reticulum and free ribosomes. The cell membrane form numerous processes. The shallow intermediate layer contains two types of cell. The cytoplasm of the first has numerous fine granules, in addition to mitochondria, ribosomes, and endoplasmic reticulum. The other type of cell contains highly electron-dense granules. The surface layer shows two cell types. One type consists of typical mucous cells. The other type of cell contains fine, electron-lucent granules. The latter cells lie on the free-surface side, covering the mucous cells, and have microvilli on their free surfaces.

Nervous System of the Tornaria Larva (Hemichordata: Enteropneusta). A Histochemical and Ultrastructural Study

Abstract: Transmission electron microscopy (TEM) and histochemical approaches were used to investigate the topology and ultrastructure of the nervous system of the tornaria larva of an enteropneust, Balanoglossus proterogonius. Cholinesterase activity was detected in the epithelium of the pre- and postoral ciliary bands. Groups of catecholamine-containing cells (CA) were detected at the anterior tip of larva, in the ventral epidermis behind the mouth, and in the stomach wall near its junction with the intestine. Single CA neurons were detected in the telotroch epithelium. Axon tracts are described in ciliary band epithelia. At the base of the aboral plate, epithelial nerve cells form a ganglion-like cluster. Single neuron-like cells and single axons and axonal tracts were found in the epithelium of digestive tract. The data were compared with ones from the literature and with those obtained from other marine invertebrate larvae. The properties of the neural elements and their possible functions are discussed.

Membrane ultrastructure of alkaliphilic Bacillus species studied by rapid-freeze electron microscopy.

Abstract: Cells of Bacillus firmus OF4 and Bacillus alcalophilus were examined by rapid-freeze freeze-fracture and freeze-substitution electron microscopy. No special vesicular structures linked to growth at alkaline pH were found, either within or associated with the cytoplasmic membrane. The cytoplasmic membranes of the alkaliphilic bacilli and the neutrophilic Bacillus subtilis BD99 were indistinguishable. Distinctive intramembrane particle rings, presumed to be flagellar structures on the basis of distribution and morphological characteristics, were found in all of these species. These observations indicate that the adaptations required to effect oxidative phosphorylation and flagellar rotation at extreme alkaline pH occur without gross morphological rearrangement.

Replication of dengue viruses in mosquito cell cultures--a model from ultrastructural observations.

Abstract: Mosquito cell cultures infected with human sera from dengue-1 and dengue-2 outbreaks, started in Rio de Janeiro by 1986 and 1990 respectively, were examined by electron microscopy at different times post the infection of cell cultures. More information was obtained about cell penetration of virus particles in the presence or not of antibodies, their pathway inside the cells, replication mode and exit. Infectiveness of the virus at those different stages can only be attributed to the particles appearing inside the trans-Golgi vesicles; most of all newly formed virus particles remain inside the RER-derived cell vesicles or inside lysosomes, even during cell lysis. Groups of larges particles, 65-75 nm in diameter at dengue-2 infections, persist during cell passage. The large amounts of smooth membrane structures, as vesicles or tabules inside the RER are attributed to a cell response to viral infection.

Olfactory epithelium in young adult and aging rats as seen with high-resolution scanning electron microscopy.

Abstract: The present study uses mainly scanning electron microscopy to demonstrate the three-dimensional internal cell structures of rat olfactory epithelial cells. The aldehyde-prefixed osmium-DMSO-osmium (AODO) method devised by Tanaka and Mitsushima (1984) was applied to the present study to disclose intracellular structures such as endoplasmic reticulum, mitochondria, Golgi apparatus, and lysosomes. The spatial distribution pattern of these structures in olfactory and supporting cells is discussed, paying special attention to the formation of lipofuscin-like granules present in aged rats.

An electron microscope study of resin production and secretion by the glands of seedlings of Betula pendula Roth.

Abstract: summary Transmission and scanning electron microscopy were used to study the ultrastructure and secretory processes of resin glands on shoot stems of Betula pendula seedlings during seasonal growth. The multicellular peltate glands possess a cortex of columnar cells surrounding a parenchymal medulla differing from the stem parenchyma below. Myelin-like deposits comprising concentric layers of membranes and osmiophilic substances accumulate mainly in the cortical cells, while only the medullar cells have chloroplasts. Both of these deposits appear to be synthesized, initially, in the endoplasmic reticulum. The myelin-like material is believed to consist of steroidal triterpenoids in cytoplasmic membranes, and the osmiophilic deposits to represent phenolics. Studies of glands of different ages suggest that the electron-transparent resin ultimately exported is formed by combining the two initial products. In the cortical cells the secretion first accumulates in vesicles that fuse with larger ones and the periplasmatic space. From the latter the secretion diffuses through the cell wall and the resin is finally deposited in the subcuticular space. Secretion vesicles, but no periplasmatic deposits were seen in the medullar cells. At the end of seasonal growth the cortical cells are markedly vacuolate and appear to have lost their organelles. Some of the cells accumulate an electron-opaque material not seen earlier. The medullar cells of the glands are suberized before winter dormancy, but usually later than in the surrounding stem bark.

A new approach to the study of ovarian follicles by scanning electron microscopy and ODO maceration.

Abstract: The ultrastructure of the follicle-oocyte complex in rodents and humans was revealed by high resolution scanning electron microscopy (SEM) following the Osmium-DMSO-Osmium maceration method (TANAKA and NAGURO, 1981). In primary follicles, the majority of oocyte organelles such as mitochondria and Golgi complex components are concentrated in a juxtanuclear area. In particular, many spherical mitochondria are oriented all around the nucleus. After maceration of the ooplasm matrix, most of these mitochondria appear intermingled with numerous microtubules (MT) and associated with many Golgi vesicles. Such a nuclear polarization of organelles, essential to the oocyte metabolism, might depend upon a MT activity. MT might guide mitochondria to gather in the perinuclear region and further maintain their close associated to the nuclear envelope. A similar relationship among microtubules, vesicular Golgi complex and mitochondria has been also observed when, in maturing oocytes, these organelles migrate and gather in other areas of the ooplasm. A pattern common only to human developing follicles appears in the occurrence of long microvilli projected from follicle cells deep into the oocyte. These unusual microvilli running within the ooplasm are surrounded by several vesicles of the Golgi complex and endoplasmic reticulum, and often end close to the nucleus. In the antral follicle, the microvilli of corona cells, directed toward the oocyte (after their full exposure through the chemical dissolution of the zona pellucida matrix) are extremely numerous (up to 70/cell), long (up to 7/10 microns) and tortuous. They resemble epididymal stereocilia, may be ramified and possess bulbous tips. In contrast, oocyte microvilli are thin and short.(ABSTRACT TRUNCATED AT 250 WORDS)

High osmotic pressure enables fine ultrastructural and cytochemical studies on Pneumocystis carinii. I. Epon embedding.

Abstract: High osmotic pressure was used to preserve the ultrastructure of rabbit-, SCID mouse-, and rat-derivedPneumocystis carinii organisms from osmotic stress during fixation. Organelles and cytosol were well preserved within the tonicity range of 850–1,300 mosmol. Under these experimental conditions, we determined that the endoplasmic reticulum was well developed in all parasite stages and could observe the Golgi complex, autophagic vacuoles, dense bodies, type II endoplasmic saccules, and the recently described outer surface membrane, which was found in all parasite stages. The biological implications of these findings are discussed.

Ultrastructure of Heterodera glycines parasitized by Arkansas fungus 18

Abstract: Ultrastructure of Heterodera glycines cysts, eggs, and juveniles parasitised by Arkansas fungus 18 (ARF18) was studied with transmission and scanning electron microscopy. Transmission electron microscopy revealed that parasitised cysts, eggs, and first-stage juveniles in eggs were filled with ARF18 fungal hyphae. Numerous pores, apparently caused by fungal penetration, were found below the sclerotiumlike structures on the cyst cuticles. The cyst cuticles at the site of the sclerotiumlike structures appeared to have been dissolved. These results suggest that ARF18 penetrates the cyst cuticle enzymatically (...)

Light and electron microscopic abnormalities in diastrophic dysplasia growth cartilage

Abstract: Light and electron microscopic studies of diastrophic dysplasia iliac crest growth cartilage performed on five occasions in two patients from 1 to 10 years of age reveal extensive cell and matrix abnormalities at each time period. Light microscopy shows atypical chondrocytes with extreme variation in size and shape, and premature cytoplasmic degeneration, and formation of target ghost cells. Prominent, densely staining fibrotic foci are present throughout the cartilage. Ultrastructure reveals some structurally intact chondrocytes with a single large fat inclusion, slightly dilated rough endoplasmic reticulum, and abundant glycogen. As early as 1 year of age cystic degeneration of chondrocyte cytoplasm is evident with indistinct organelles seen. The cartilage matrix demonstrates a general increase in fibrous tissue as well as the fibrotic foci. The collagen in these foci is remarkably abnormal. It is composed of short, extremely broad fibrils ranging from 150 to 950 nm in width which are separated at their terminal ends but fused to each other centrally in random fashion. On cross-section there are very few round fibrils but rather a marked irregularity in shape giving the appearance of having fibrils randomly added to others to form enlarged nonuniform fibril aggregates. On longitudinal sectioning, regular cross-banding across the entire fibril width is seen but fibril splitting and aggregation are highly irregular.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural changes in suspension culture cells of Panicum maximum during cryopreservation.

Abstract: A Panicum maximum cell suspension was used to study ultrastructural changes during cryopreservation. Pregrowing the cells in mannitol caused reduction in the vacuolar volume by redistribution of the large central vacuole into a number of smaller vesicles. Invaginations were formed in the plasma membrane of the cells, to accommodate the reduced cell volume. Swelling of organelles occurred during different stages of cryopreservation. The cisternae of the endoplasmic reticulum dilated and formed vesicles. Although some damage was apparent, organelles were still recognizable in cells frozen slowly and freeze-fixed at −10°C. The cells were able to repair such damage within two days in culture, and regained their normal appearance. Cells frozen slowly without any cryoprotection, and cells frozen rapidly by direct immersion into liquid nitrogen after cryoprotection, were lethally damaged by destruction of membranous structures. Osmiophilic granules were found along the plasma membrane of lethally damaged cells, indicating that their formation is a consequence of freeze damage, rather than a mechanism to prevent injury.

Quick-freezing of cultured cardiac cells in situ with special attention to the mitochondrial ultrastructure.

Abstract: SUMMARY A new method has been developed which allows quick-freezing in situ of primary, cardiac cell cultures grown to confluence on gas-permeable membranes (Petriperm dishes). Small pieces of the growth substratum, with rhythmically beating myocardial cells, were slam-frozen, without cryoprotectants, against the surface of a helium-cooled copper block at approximately 16 K. The quality of the cellular cryopreservation, as judged by ultrastructural criteria, was studied in freeze-substituted specimens processed for transmission electron microscopy. The ultrastructure of cryofixed cardiac cells was compared with that of unfrozen, chemically fixed samples. The severity of cryodistortions increased progressively with increasing distance from the point of first impact. Of particular interest were the dramatic alterations of the mitochondrial ultrastructure. The concept that the reticular and the outer mitochondrial membranes are intimately and strongly associated was clearly demonstrated. Optimally frozen material revealed cryopreserved ultrastructure of high quality. The method described appears to offer an ideal model system for correlating the information gained by phase-contrast microscopy of living cell cultures with the ultrastructure of the same samples fixed in situ by chemical or physical techniques. Cryofixation would be particularly useful for studying dynamic cellular processes associated with physiological and pathophysiological conditions, e.g. metabolic inhibition, anoxia and substrate deprivation.

Ultrastructure of human osteoblasts and associated matrix in culture.

Abstract: The ultrastructure, as visualized by transmission electron microscopy, of cells obtained from human bone explants and subsequently cultured is described along with the electron microscopic appearance of the associated intercellular matrix. The cells were characterized as osteoblasts on the basis of immunohistochemical, enzymatic, and functional criteria. Although the osteoblasts could be cultured in standard culture media and always appeared singly, not forming syncytia, the cultures were eventually confluent and formed multilayers. The cells were fusiform or cuboidal with diameters ranging between 10-15 microns. The cytoplasm was characterized by numerous large mitochondria, and especially by a very prominent RER. The intercellular matrix was woven with collagen fibres surrounding large numbers of matrix vesicles. In areas with matrix vesicles, evidence for osteoblast activity, i.e. mineralization related to matrix vesicles, could be observed after incubation with beta-glycerophosphate. In conclusion, we provide evidence that human osteoblasts cultured in vitro synthesize collagen and produce a matrix with vesicles capable of initiating mineralization processes.

An ultrastructural study on the origin of glomerulocytes, a type of blood cell in a styelid ascidian, Polyandrocarpa misakiensis

Abstract: The glomerulocyte is a type of blood cell in the compound ascidian, Polyandrocarpa misakiensis. It is a discoidal cell, measuring 12-13 μm in diameter and about 3 μm in thickness. The outer half of the cell is occupied by concentrically-arranged fibers, usually 0.2-0.3 μm thick; the nucleus and organelles are confined to the central cytoplasm. The ordinary epidermal cells are columnar and are characterized by an apical homogeneous cytoplasmic bulge, vesicular bodies in the cytoplasm, and juctions between them. Growing or immature glomerulocytes are found only in the epidermis. They have intracellular fibers and vesicular bodies, and there are juctions between them and epidermal cells. These facts strongly suggest the origin of the glomerulocyte from an epidermal cell. However, no definite statement can be made as yet because earliest stages of differentiation have not been observed. The glomerulocyte fully differentiated in the epidermis is apparently released into the hemocoel.

Sample preparation for electron microscopy of internal cell structure

Abstract: Methods are reviewed for examination of internal cell structure by high-resolution scanning electron microscopy and compared with the rapid-freeze deep-etch replica technique used in transmission electron microscopy. Rapid freezing of fresh material, followed by freeze-fracture, provides a theoretically attractive approach in ultrastructure studies, but the high protein and solute content of most cells prevents a deep three-dimensional view for material frozen without some form of extraction. After discussion of other methods it is concluded that the most useful general approach, at least for cultured cells, is to first permeabilize or break open the cells in a medium which preserves the structure under study in a functional state as, for example, the movement of chromosomes along the division spindle, or transport of proteins within the Golgi region. After permeabilization, with attendant partial extraction, the preparation can be fixed, then viewed by either deep-etch replication, or by high-resolution scanning electron microscopy, with structure of interest revealed in deep view.