Showing papers on "Ultrastructure published in 1970"

Ultrastructural Features of Mycoplasma pneumoniae

Abstract: The ultrastructure of Mycoplasma pneumoniae cultivated in broth on glass and plastic surfaces was studied by scanning and transmission electron microscopy. The organisms grew as filaments, which by over-crossing eventually formed a dense network on the surface and in colonies composed mainly of rounded and elongated forms. The filaments were usually thinner at the ends and terminated with a knob-like structure. Some filaments possessed short ramifications which also ended with a knob, and others showed constrictions. Sectioned organisms were seen to contain ribosome-like structures. Many organisms had a specialized structure at their thinner end, which consisted of a dense rod surrounded by electron-lucent cytoplasm and ending with a platelike thickening.

Structure-function relationships in the adipose cell. I. Ultrastructure of the isolated adipose cell

Abstract: A method is described for preparing isolated rat adipose cells for electron microscopy. The ultrastructure of such cells and their production of 14CO2 from U-glucose-14C were studied simultaneously in the presence of insulin or epinephrine. Each adipose cell consists of a large lipid droplet surrounded by a thin rim of cytoplasm. In addition to typical subcellular organelles, a variety of small lipid droplets and an extensive system of membranes characterize the cell's cytoplasm. A fenestrated envelope surrounds the large, central lipid droplet. Similar envelopes surround cytoplasmic lipid droplets occurring individually or as aggregates of very small, amorphous droplets. Groups of individual droplets of smaller size also occur without envelopes. The system of membranes consists of invaginations of the cell membrane, vesicles possibly of pinocytic origin, simple and vesiculated vacuoles, vesicles deeper in the cytoplasm, flattened and vesicular smooth surfaced endoplasmic reticulum, and Golgi complexes. Neither insulin nor epinephrine produced detectable ultrastructural alterations even when cells were incubated under optimal conditions for the stimulation of 14CO2 evolution. Structural responses of the isolated adipose cell to hormones, if such occur, must, therefore, be dynamic rather than qualitative in nature; the extensive system of smooth surfaced membranes is suggestive of compartmentalized transport and metabolism.

The comparative ultrastructure of the algal chloroplast

Abstract: In preparing this paper, I had two big decisions to make. First, whose classification of the algae should I use, and second, which terminology should I use to describe chloroplast ultrastructure? I decided to use Christensen’s classification of the algae because overall it correlates fairly well with chloroplast ultrastructure. Since Christensen’s classification of the algae has not yet been mentioned in this conference, I will summarize it briefly. Christensen separates the algae into four divisions: the Cyanophyta, comprising one class, the Cyanophyceae; the Rhodophyta, comprising one class, the Rhodophyceae; the Chromophyta, comprising nine classes, the Cryptophyceae, Dinophyceae, Raphidophyceae (the Chloromonads) , Chrysophyceae, Haptophyceae, Craspedophyceae (the collared flagellates, which I will not mention again since none are known to have chloroplasts), the Bacillariophyceae, Xanthophyceae, and Phaeophyceae; and the Chlorophyta, into which he puts four classes. These are the Euglenophyceae, the Chlorophyceae, and two groups of algae that he removed from the green algae because of ‘differences in flagellation, the Prasinophyceae and Loxophyceae. The differences between these two classes are not clear-cut, and in this paper I will follow Peterfi and Manton * and lump the Loxophyceae with the Prasinophyceae. The question of which terminology of chloroplast ultrastructure to use is a more difficult one. For all other cell organelles, electron microscopists have now more or less agreed on a standard terminology. Who, for example, would still call the endoplasmic reticulum alpha cytomembranes? However, if you want to describe only the membranes of a chloroplast, you have a dozen odd terms to choose from-discs, thylakoids, frets, partitions, lamellae, lamellations, stacks, grana, bands-despite the fact that the membranes of all chloroplasts are built on a basic structural plan. The basic unit of the chloroplast is a flattened membrane-limited sac which Menke has named a thylakoid. Others, myself included, have called these sacs discs. In the interest of a uniform terminology, I propose that we abandon the word disc and use thylakoid henceforth. I propose to use the wbrd granum specifically to refer to a stack of appressed thylakoids, many of which are short and round and of approximately equal diameter, whereas others, which are interspersed with these, extend across the stroma to form part of a neighboring granum or even of the same granum. This leaves the problem of what to call the groups of two or three appressed or loosely associated thylakoids which extend across the chloroplasts of most algae. Stacks is probably the most descriptive word, but it is not a very euphonious one, and it implies a pile of some height rather than an extended flat layer.

Ultrastructure of sensory receptors in ascidian tadpoles

Abstract: An analysis of fine structure and function was conducted on three types of receptors in the cerebral vesicle of two species of ascidian tadpoles (Ciona intestinalis andDistaplia occidentalis). Theocellus is composed of one pigmented, cup-shaped supportive cell, an estimated 15–20 sensory cells, and three lens cells, each with a large body of granules (glycogen ?). The outer segments of the photoreceptoral processes are modified cilia, one per sensory cell, consisting of many lamellae, formed by infoldings of the ciliary membranes, and axonemes of 9 + 0 doublets of microtubules. The lamellae are homologous to retinal disks of vertebrates.Hydrostatic pressure (?)receptors are modified cilia containing tubules which open to the lumen of the cerebral vesicle. These receptors closely resemble the globular, ciliary processes of coronet cells in the saccus vasculosus of fishes. Thestatocyte is a onecell gravity receptor. The part extending into the lumen of the brain contains the nucleus and a large black body which is thought to function as a float. The foot-piece of the cell is firmly anchored in the brain wall; the neck is probably the site of generation of signals.

Ultrastructural study of characteristic organelles (paired organelles, micronemes, micropores) of sporozoa and related organisms.

Abstract: By means of electron microscopy a study has been made of different developmental stages of Eimeria callospermophili, E. falciformis, Toxoplasma gondii, Frenkelia spec. (= M-organism), Babesia bigemina, and B. ovis. Major emphasis was given to the analysis of some characteristic organelles of the motile stages of the sporozoans. These organelles were the paired organelle, the micronemes and the micropores.

SCALE FORMATION IN CHRYSOPHYCEAN ALGAE: I. Cellulosic and Noncellulosic Wall Components Made by the Golgi Apparatus

Abstract: The cell wall of the marine chrysophycean alga Pleurochrysis scherfellii is composed of distinct wall fragments embedded in a gelatinous mass. The latter is a polysaccharide of pectic character which is rich in galactose and ribose. These wall fragments are identified as scales. They have been isolated and purified from the vegetative mother cell walls after zoospore formation. Their ultrastructure is described in an electron microscope study combining sectioning, freeze-etch, and negative staining techniques. The scales consist of a layer of concentrically arranged microfibrils (ribbons with cross-sections of 12 to 25 x 25 to 40 A) and underlying radial fibrils of similar dimensions. Such a network-plate is densely coated with particles which are assumed to be identical to the pectic component. The microfibrils are resistant to strong alkaline treatment and have been identified as cellulose by different methods, including sugar analysis after total hydrolysis, proton resonance spectroscopical examination (NMR spectroscopy) of the benzoylated product, and diverse histochemical tests. The formation and secretion of the scales can be followed along the maturing Golgi cisternae starting from a pronounced dilated "polymerization center" as a completely intracisternal process which ends in the exocytotic extrusion of the scales. The scales reveal the very same ultrastructure within the Golgi cisternae as they do in the cell wall. The present finding represents the first evidence on cellulose formation by the Golgi apparatus and is discussed in relation to a basic scheme for cellulose synthesis in plant cells in general.

The morphology and fine structure of ceratium hirundinella (dinophyceae)1

Abstract: SUMMARY Some aspects of thecal morphology in Ceratium hirundinella are redescribed by means of scanning electron microscopy. The internal anatomy of the cell has been clearly revealed for the first time in serial sections examined by transmission electron microscopy. An unusual sulcus, termed the sulcul aperture, has been found to open into a large ventral chamber which extends toward the center of the cell. The 2 flagella are inserted at one side of the ventral chamber. The ultrastructure of the flagellar canals and root systems arc described in detail. A microtubular strand has been found to run from near the nucleus to near the flagellar bases but not to conned with either. The fine structure of the theca, trichocysts, nucleus, and chloroplasts is basically similar to that of other dinoflagellates. Food vacuoles are reported. These contain material thought to be undergoing digestion. It is suggested that the food particles enter the cell by way of the ventral chamber, which is lined only by membranes, unlike the rest of the cell, which is covered by thick plates. The new findings are discussed in relation to the earlier work on the species and to the fine structure of oilier dinoflagellates.

Ultrastructure of a Temperature-Sensitive Rod− Mutant of Bacillus subtilis

Abstract: Mutant 168ts-200B, resulting from nitrosoguanidine treatment of Bacillus subtilis 168 ( trp − C2), exhibits a rod-to-sphere morphogenetic interconversion when the incubation temperature is 30 or 45 C, respectively. Ultrathin sections of rods grown at 30 C, after glutaraldehyde-osmium uranium-lead fixation and staining, show trilaminar cell walls with a well-developed underlying periplasm as in wild-type cells. However, the outer wall layer is irregular, and abnormal protrusions of wall material occur at the cross-walls. In contrast, cells growing at 45 C become rounded and are intersected randomly by irregular cross-walls which fail to split normally, resulting in large spherical masses. In these, the outer and inner wall layers and periplasm are lost, and the wall consists only of irregularly thickened and loosely organized middle layer. Wall ultrastructure is reversible in either direction as cell shape changes during temperature shifts. Mesosomes are rare and atypical at either temperature. It thus appears that cell wall ultrastructure is altered by the conditional (temperature-sensitive) mutation, and that loss of normal wall and submural organization is correlated with changes in cell size and shape as well as with inability to complete cell division. Preliminary studies after transformation of the mutant locus to another strain and growth at 45 C showed an increase in mucopeptide, loss of wall teichoic acid, failure of phage adsorption, and identical ultrastructural changes. The site of expression of the basic defect—be it in wall, submural region, or membrane—is undetermined. Images

The Ultrastructure of the Human Stria Vascularis. PART I

Abstract: The human stria vascularis contains three types of cells (marginal, intermediate and basal) which are remarkably similar to those found in the smaller animals. The narginal cells are rich in a homo...

The effect of light intensity and temperature on plant growth and chloroplast ultrastructure in soybean

Abstract: A B S T R A C T Soybean plants grown in controlled environment cabinets under light intensities of 220 w/m2 or 90 w/m2 (400-700 nm) and day to night temperatures of 27.5-22.5 C or 20.0-12.5 C in all combinations, exhibited differences in growth rate, leaf anatomy, chloroplast ultrastructure, and leaf starch, chlorophyll, and chloroplast lipid contents. Leaves grown under the lower light intensity at both temperatures had palisade mesophyll chloroplasts containing well-formed grana. The corresponding leaves developed under the higher light intensity had very rudimentary grana. Chloroplasts from high temperature and high light had grana consisting of two or three appressed thylakoids, while grana from the low temperature were confined to occasional thylakoid overlap. Spongy mesophyll chloroplasts were less sensitive to growth conditions. Transfer experiments showed that the ultrastructure of chloroplasts from mature leaves could be modified by changing the conditions, though the effect was less marked than when the leaf was growing. LITTLE IS known concerning the influence of light intensities and temperatures characteristic of field conditions on the chloroplast ultrastructure of developing and mature leaves of normal plants. Bjorkman and Holmgren (1963) using the light microscope showed that their higher light intensity destroyed the chloroplasts of shade ecotypes of Solidago virgaurea, whereas chloroplasts from exposed ecotypes were unaffected. The effect of light intensity on the ultrastructure of chloroplasts from pigment-deficient mutants was investigated by Walles (1965), Schmid, Price, and Gaffron (1966), Clewell and Schmid (1969); the effect of temperature and light on the greening of detached, etiolated leaves by Klein (1960), Eilam and Klein (1962); and the eff ect of transference of dark-grown seedlings to light by \'IcWilliam and Naylor (1967). This study concerned differences in growth rate, leaf anatomy, chloroplast ultrastructure, and chemical composition in soybean plants grown in cabinets under combinations of temperature and light similar to those occurring naturally. Comparisons were made with plants grown outside and in the glasshouse. The plants used were well beyond the seedling stage.

The ultrastructure of the spiral ligament in the Rhesus monkey.

Abstract: Electron microscopy of the spiral ligament of the Rhesus monkey reveals two types of fibrocytes. Type I contains a relatively small number of cell organel-les and is found in the deeper part of the...

The ultrastructure of the fertilized embryo sac of petunia

Abstract: SUMMARY The ultrastructural changes of the embryo sac of Petunia during and after fertilization are described. The pollen tube enters the embryo sac by growing through the filiform apparatus and discharges its content into one of the synergids (penetrated synergid). The volume of the penetrated synergid increases and the cell bursts at its chalazal pole. The synergid and discharged pollen tube cytoplasm merge and subsequently degenerate. The degeneration is marked by the darkening of the cytoplasm and the disappearance of organelles. A complex rough endoplasmic reticulum and numerous small spheres remain discernible longest. Two degenerating nuclei are present in the penetrated synergid. The ultrastructure of the zygote changes slightly during its early development. 50 hrs after pollination (10–15 hrs after fertilization) the nucleus does not contain chromatin clumps any more and is surrounded by a shell of plastids. The primary endosperm cell shows a number of marked changes after the formation of its nucleus. The ribosomes become aggregated into large polysomes and the plasma matrix becomes homogeneously electron-dense. Both the mitochondria and dictyosomes change in ultrastructure and shape. Plastids, without starch, appear as the endoplasmic reticulum becomes very extensive. This ultrastructural differentiation indicates a changing metabolic activity.

The cytology, histochemistry, and ultrastructure of the cell types found in the digestive gland of the slug,Agriolimax reticulatus (Müller)

Abstract: Four cell types have been identified in the digestive glands from light and electron microscope studies. The possible functions of each cell type are discussed. Thin cells are undifferentiated. Calcium cells contain spherules of calcium salts which have a characteristic ultrastructure. Different protein granules are found apically. Digestive cells are present as two distinct forms. One form is believed to be absorbing food material and digesting it intracellularly, and the other form is a secreting cell. Both forms contain green and yellow granules and histochemistry shows these granules to be distinct. Protein granules also occur apically. Excretory cells are distinguished by having a large central vacuole containing excretory granules. Histochemistry shows these granules, like the yellow granules of digestive cells, to be composed mainly of lipofuscin. It is suggested that digestive cells form excretory cells.

Ultrastructural Development of Cork-Silica Cell Pairs in Avena Internodal Epidermis

Abstract: In this paper we report on the microscopic and ultrastructural changes that characterize the primary stages of differentiation of cork-silica cell pairs in Avena internodal epidermis. Cork-silica cell pairs arise from symmetrical division of short cell initials in the internodal intercalary meristem. The daughter cells appear essentially alike ultrastructurally following this division. They then embark on two remarkably different pathways of differentiation. The first changes involve differential wall thickening and cell expansion. Well after these changes have occurred, the nucleus in the upper cell of the pair (future silica cell) breaks down, whereas that in the lower cell (future cork cell) remains intact The upper cell then becomes filled with fibrillar material and osmiophilic droplets, presumably breakdown products of membranes and organelles. The membranes, organelles, and nucleus remain unaltered in the cork cell. Finally, silica is deposited as long chains of silica bodies in the lumen of the si...

Electron microscopy of the sporangium of Phytophthora capsici

Abstract: This paper reports results of a study on the ultrastructural cytology of sporangia of Phytophthora capsici Leonian with emphasis on flagellum formation, general sporangial structure during zoospore cleavage, and the presence, structure, and transition of cytoplasmic organelles and inclusions during these processes.Non-cleaving sporangial cytoplasm contains a high concentration of ribosomes, mitochondria, vacuoles, lipid inclusions, and endoplasmic reticular cisternae scattered throughout the cytoplasm. Nuclei in mature sporangia are located at the periphery of the cell, with their narrow poles aligned towards the plasma membrane. The apical papilla measures 4–5 × 10 μ, and is initiated as a fibrous third layer under the two-layered cell wall several microns from the apex. The outer wall layer surrounds the papilla while the inner wall narrows and disappears near the crown. The basal septal plug is a combination of the inner wall layer and slime substances.One of the first structural changes in the cytopla...

Ultrastructure and Cell Division of a Facultatively Parasitic Strain of Bdellovibrio bacteriovorus

Abstract: Some aspects of cell development and division of Bdellovibrio bacteriovorus strain UKi2 were examined by use of electron microscopic techniques. Under saprophytic and parasitic conditions of growth, the comma-shaped cells enlarge, elongate, and form helical filaments. The mechanism of division appears to consist of an asymmetrical constriction of the filamentous cell by the cytoplasmic membrane, accompanied by a breakdown of the outer layers of the cell wall in the division region. During regeneration of the cell wall, the flagellum and flagellar sheath are formed. The development of the flagellum of the daughter cell is initiated prior to separation of the newly formed cells from the filament. Observations of B. bacteriovorus UKi2 grown under saprophytic and parasitic conditions indicate that development and ultrastructure are similar in both modes of growth.

Ultrastructural characteristics of the mammalian and sauropsidan heart.

Abstract: The ultrastructure of the mature myocardium of reptiles, birds and mammals, as well as of the embryonic or in ovo hearts of the turtle and chick, is examined. The findings show that (1) the reptilian and avian myocardiums belong to one group of the sauropsida, with properties distinct from those of the mammalian heart; (2) a T system is present only in the myofibers of mammalian cardiac ventricular fibers, which contain densely packed rows of myofibrils; and (3) the occurrence of a specialized segment of sarcoplasmic reticulum in close association with the plasma membrane (subsarcolemmal cistern or coupling) is a common feature of all vertebrate myocardial cells including those of the embryo. A scheme is presented, showing the three types of vertebrate myocardium, based upon their ultrastructure. It is concluded that there is no definitive structural criterion pertinent to all species of vertebrates with which to identify the impulse generating or conducting tissue, or both, of the heart.

The ultrastructure of the egg and central cell of petunia

Abstract: SUMMARY The egg and central cell of Petunia hybrida undergo a number of changes and become mature during anthesis. The egg greatly enlarges and becomes highly vacuolated. The nucleus and the major part of the cytoplasm of the mature egg are located at the chalazal pole of the cell. The number of organelles decreases slightly during maturation. The ribosomes of the mature egg are clustered in polysomes. The chalazal part of the mature egg seems to be surrounded by the plasma membrane only, whereas the remainder of the cell has a normal cell wall. The number of mitochondria and plastids and the amount of endoplasmic reticulum (ER) in the central cell are almost constant during maturation. The number of ribosomes, however, increases greatly. Almost all ribosomes are free and the impression is that they are monosommes. A large amount of starch is formed in the plastids. Two types of dictyosomes are present in the mature central cell. The outer membranes of the polar nuclei are sometimes connected by ER membranes.

On the ultrastructure of the epidermis of the adult female of Kronborgia amphipodicola Christensen & Kanneworff, 1964 (turbellaria, neorhabdocoela)

Abstract: The epidermis of Kronborgia amphipodicola, an internal parasite of ampeliscid amphipods, has been examined by means of transmission and scanning electron microscopes. The animal has been studied before and after building of the cocoon and spawning of the egg capsules. Characteristic features of the epidermis are long cilia, numerous clavate microvilli, and cytoplasmic extrusions. These contain small vesicles of unknown function. In addition large vacuoles and small rhabdite-like structures have been found in the cells. Various subepidermal gland cells penetrate the fibrillar basal lamina and the epidermal cells. The mechanism of food uptake is discussed and compared with that of other plathyhelminthes.

Transmissible gastroenteritis of swine: virus-intestinal cell interactions. II. Electron microscopy of the epithelium in isolated jejunal loops.

Abstract: Electron microscopy studies on the morphology of the columnar cells covering the villi in small intestinal loops, which were surgically isolated in 7 day old pigs, showed that the fine structure of those cells is very similar to that in other mammalian species. Upon infection of the loops with TGE virus, virus particles with a diameter of 75 to 88 mμ became visible in the cytoplasm of these absorptive cells. The virus was taken up by pinocytosis, and newly produced particles maturated by budding at smooth cellular membranes particularly in the Golgi apparatus. Cellular morphological changes were first detectable at the microvillar border and appeared to develop concomitantly with virus release. Loss of cells occurred later through desquamation and cell disruption. Atrophied villi were, at 18 hours postinoculation, almost completely covered with newly produced cuboidal cells which ultrastructurally resembled the undifferentiated crypt cells. Gradual differentiation of these cells occured during the following days and at 72 hours postinoculation, they were morphologically similar to normal absorptive cells. A few of the differentiating and differentiated cells were seen to contain virus particles.

Electron microscopy and plant ultrastructure

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Ultrastructure of mouse egg-cylinder

Abstract: The mouse egg-cylinder prior to and after mesoderm formation was studied by means of electron microscopy. The ultrastructural appearance of the proximal entoderm of both embryonic and extraembryonic segments suggests an intensive absorptive and nutritional activity. Numerous pinocytotic vacuoles, microvilli, primary and secondary lysosomes and fair amounts of rough endoplasmic reticulum and free ribosomes were the most important characteristics of these cells. After mesoderm formation, the extraembryonic entoderm showed the aforementioned characteristics even more prominently, while the cells of embryonic entoderm became flattened and depleted of microvilli and of almost all organelles. The cells of the extraembryonic and embryonic ectoderm prior to and after mesoderm formation had the same ultrastructural appearance as mesodermal cells. The cytoplasm of these cells was replete with free ribosomes, but other organelles such as mitochondria and rough endoplasmic reticulum were few in number. The architecture of all cells of the egg-cylinder except those of the extraembryonic entoderm suggested a very low level of differentiation. The criteria and possibilities for the determination of the degree of differentiation on the ultrastructural level and possible differences in protein synthesis in extraembryonic entoderm as compared with other parts of the embryo are considered.