Freeze-Etched Surfaces of Membranes and Organelles in the Cells of Pea Root Tips

1968 ◽  
Vol 3 (2) ◽  
pp. 199-206
Author(s):  
D. H. NORTHCOTE ◽  
D. R. LEWIS
Keyword(s):  
Characteristic Surface ◽  
Clear Indication ◽  
Cell Wall Formation ◽  
Root Tips ◽  
Nuclear Pores ◽  
Surface Appearance ◽  
Golgi Bodies ◽  
Surface Areas ◽  
Cytoplasmic Surface ◽  
Microfibrillar Structure

The structure of the inner and outer surfaces of the plasmalemma, the tonoplast and the membranes of the nucleus and endoplasmic reticulum have been investigated. The structure of the plasmalemma probably varies with the metabolic state of the cell, in particular with the synthesis and transport of material for cell-wall formation. The organization of the plasmalemma during the deposition of material in the wall by reverse pinocytosis is shown, and evidence is presented for the possible synthesis of the microfibrillar structure of the wall by synthetic units arranged as particles on and near the plasmalemma surface. A clear indication of substructure along the length of microtubules has been shown, and since views of large surface areas are possible the distribution of the microtubules at the cytoplasmic surface inside the plasmalemma has been revealed; they bound the cell by running around the circumference in one direction only. A definite organization of nuclear pores has been observed and the structure and shape of the pores is described. By the freeze-etch technique it is possible to investigate crystal-containing bodies, amyloplasts with starch grains and bundles of fibres in addition to mitochondria and Golgi bodies. The method also distinguishes certain spherical organelles by their characteristic surface appearance.

Further Ultrastructural Observations on Polysaccharide Localization in Plant Cells

1968 ◽  
Vol 3 (1) ◽  
pp. 55-64
Author(s):  
J. D. PICKETT-HEAPS
Keyword(s):  
Cell Wall ◽  
Periodic Acid ◽  
Periodate Oxidation ◽  
Plant Cells ◽  
Primary Cell Wall ◽  
Root Tip ◽  
Root Tips ◽  
Golgi Bodies ◽  
Golgi Vesicles ◽  
Aldehyde Groups

Standard periodic acid/Schiff (PAS) techniques have not shown the existence of aldehyde groups in sections of glutaraldehyde-fixed, Araldite-embedded root-tip tissue; peroxidation of such sections resulted in a typical PAS staining pattern. Permanganate-fixed root tips also gave a weak PAS reaction which was intensified by prior peroxidation of the sections. At the ultrastructural level, silver hexamine was used to detect aldehyde groups produced in polysaccharide by permanganate and/or periodate oxidation. Golgi vesicles and slime material in root-cap cells always reacted strongly; the cell wall proper was less reactive. A marked increase in the stainability of the vesicles was evident, the further removed they were from Golgi bodies. This also occurred in root epidermal cells. In both these types of cells, smallersized vesicles and/or the contents of reticulate Golgi cisternae showed evidence of histochemical staining. In meristematic root tip cells, vesicles closely apposed to Golgi bodies did not stain convincingly, though cell walls stained readily. During cell-plate formation, however, both smaller (possibly Golgi) and larger vesicles (phragmoplasts) stained strongly. The walls of permanganate-fixed sieve-tube cells also stained quite strongly, but callose did not unless the tissue block had been treated with periodate before being embedded. In glutaraldehyde-fixed xylem cells, older wall thickenings reacted very strongly even when the sections had been blocked with iodoacetate and bisulphite (which rendered the rest of the section unreactive). If similar sections of younger xylem cells were peroxidized after such blocking reactions, the primary cell wall and the wall thickenings stained, as did many of the Golgi vesicles. The results are related to other experimental observations, both ultrastructural and histochemical, on plant cells.

The nuclear import factor p10 regulates the functional size of the nuclear pore complex during oogenesis

1998 ◽  
Vol 111 (13) ◽  
pp. 1889-1896 ◽  
Author(s):  
C. Feldherr ◽  
D. Akin ◽  
M.S. Moore
Keyword(s):  
Nuclear Import ◽  
Xenopus Oocytes ◽  
Nuclear Pore ◽  
28S Rrna ◽  
Nuclear Pores ◽  
Factors Analysis ◽  
Cytoplasmic Surface ◽  
Stage 1 ◽  
Translocation Factors ◽  
Functional Size

Previtellogenic, stage-1 Xenopus oocytes produce mainly 5S and tRNA, whereas vitellogenic oocytes, stages 2–6, synthesize predominantly 18S and 28S rRNA. Using nucleoplasmin-coated gold as a transport substrate, it was determined that the shift in synthesis from small to large RNAs during oogenesis is accompanied by an increase in both the rates of signal-mediated nuclear import and the functional size of nuclear pores. It was observed that, despite the reduction in transport capacity, gold still accumulated at the cytoplasmic surface of the pores in stage-1 oocytes. This suggested that transport in these cells is limited by translocation factors, rather than by cytoplasmic binding factors. Analysis of extracts prepared from stage-1 and vitellogenic oocytes revealed that the transport factor p10 is more abundant in stage-1 cells. Microinjection of purified p10 into stage-2 oocytes reduced the nuclear import of large gold particles to the level observed in stage-1 cells. It is concluded that p10 can modulate transport through the pores by regulating the functional size of the central transporter element.

UPTAKE OF 51Cr AS AN INDICATOR OF METABOLIC CHANGE IN WHEAT ROOT TIPS

1967 ◽  
Vol 45 (2) ◽  
pp. 235-239 ◽  
Author(s):  
Geneviève Bourque ◽  
P. Vittorio ◽  
Pearl Weinberger
Keyword(s):  
Wheat Root ◽  
Consistent Pattern ◽  
Metabolic Change ◽  
Sensitive Indicator ◽  
Clear Indication ◽  
Serial Sections ◽  
Root Tips ◽  
Metabolic State ◽  
Mode Of Entry ◽  
Cr Uptake

A consistent pattern of 51Cr incorporation was observed in serial sections of the roots of two varieties of wheat, both vernalized and unvernalized. The changed metabolic state attendant on vernalization was reflected by a higher level of 51Cr incorporation. A clear indication was given that 51Cr uptake can be used as a sensitive indicator of metabolic change in wheat root tips.The mode of entry and binding of the trivalent and hexavalent forms of chromium was also investigated.

Fine-structural studies of the gametes and embryo of Fucus vesiculosus L. (Phaeophyta). III. Cytokinesis and the multicellular embryo

1977 ◽  
Vol 24 (1) ◽  
pp. 275-294
Author(s):  
S.H. Brawley ◽  
R.S. Quatrano ◽  
R. Wetherbee
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Daughter Cell ◽  
Fucus Vesiculosus ◽  
Complete Disappearance ◽  
Annulate Lamellae ◽  
Nuclear Pores ◽  
Cell Stage ◽  
Golgi Bodies ◽  
Daughter Cells

Condensation of the chromosomes during the first cell division following fertilization of the brown alga Fucus vesiculosus L. is accompanied by the almost complete disappearance of the nuclear envelope. Golgi vesicles and other small vesicles appear within the spindle, which has paired centrioles at each end. A large amount of rough endoplasmic reticulum is in the surrounding cytoplasm during mitosis, and many vesicles at the spindle margin are encircled by stacks of endoplasmic reticulum. Annulate lamellae are observed during mitosis. The envelope which initially reforms around the chromatin in telophase has unevenly spaced nuclear pores. Cytokinesis results primarily by vesicle addition to a centripetal furrow. Mitochondria and chloroplasts concentrate around the partition site, possibly in association with microfilaments. Fibrillar material is added rapidly to the space between the daughter cells from vesicle discharge of both cells and seems to spread into the older cell wall surrounding the embryo. The rhizoid daughter cell contains numerous mitochondria and hypertrophied Golgi bodies whose vesicles increasingly pack the cell. The thallus daughter cell is packed with a variety of vesicles, and the nucleus is surrounded by many dilated cisternae of rough endoplasmic reticulum. By the four-cell stage, chloroplasts of the rhizoid cells have weakly staining lamellae, while chloroplasts of the thallus cells are actively dividing with deeply staining lamellae.

Cerebral Tissue Response in Chronic Electrode Implantation

1977 ◽  
Vol 35 ◽  
pp. 624-625
Author(s):  
R.F. Dodson ◽  
L.W-F Chu ◽  
N. Ishihara
Keyword(s):  
Tissue Response ◽  
Whole Body ◽  
Platinum Electrodes ◽  
Fixed Tissue ◽  
Electrode Implantation ◽  
Surface Areas ◽  
Tissue Changes ◽  
Micron Diameter ◽  
Extent Of Damage ◽  
Electrode Sheath

The extent of damage surrounding an implanted electrode in the cerebral cortex is a question of significant importance with regard to attaining consistency and validity of physiological recordings. In order to determine the extent of such tissue changes, 150 micron diameter platinum electrodes were implanted in the cortex of four adult baboons, and after eight days the animals were sacrificed by whole body perfusion with a 3% glutaraldehyde in 0.1M phosphate fixative.The calvarium was carefully removed and the electrode tracts were readily discernible in the firm, glutaraldehyde fixed tissue.Careful dissection of the zone of the electrode tract resulted in a small block which was further sectioned into tip, mid-tract and surface areas. Ultrastructurally, damage extended from the electrode sheath to the greatest extent of from 0.2 to 3.5 mm.

Tissue section lifting for electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 86-87
Author(s):  
Adrian F. van Dellen
Keyword(s):  
Infectious Disease ◽  
Electron Microscopy ◽  
Tissue Culture ◽  
Organ System ◽  
Surrounding Tissue ◽  
Paraffin Sections ◽  
Surface Areas ◽  
Specific Determination ◽  
High Degree ◽  
Accuracy And Repeatability

The morphologic pathologist may require information on the ultrastructure of a non-specific lesion seen under the light microscope before he can make a specific determination. Such lesions, when caused by infectious disease agents, may be sparsely distributed in any organ system. Tissue culture systems, too, may only have widely dispersed foci suitable for ultrastructural study. In these situations, when only a few, small foci in large tissue areas are useful for electron microscopy, it is advantageous to employ a methodology which rapidly selects a single tissue focus that is expected to yield beneficial ultrastructural data from amongst the surrounding tissue. This is in essence what "LIFTING" accomplishes. We have developed LIFTING to a high degree of accuracy and repeatability utilizing the Microlift (Fig 1), and have successfully applied it to tissue culture monolayers, histologic paraffin sections, and tissue blocks with large surface areas that had been initially fixed for either light or electron microscopy.

Scanning Electron Microscopic Study of the Cell Surface

1969 ◽  
Vol 27 ◽  
pp. 36-37 ◽  
Author(s):  
Toichiro Kuwabara
Keyword(s):  
Tissue Fluid ◽  
Biological Application ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Surface Appearance ◽  
Minute Amount ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
True Structure ◽  
Scanning Electron

Although scanning electron microscopy has a great potential in biological application, there are certain limitations in visualization of the biological structure. Satisfactory techniques to demonstrate natural surfaces of the tissue and the cell have been reported by several investigators. However, it is commonly found that the surface cell membrane is covered with a minute amount of mucin, secretory substance or tissue fluid as physiological, pathological or artefactual condition. These substances give a false surface appearance, especially when the tissue is fixed with strong fixatives. It seems important to remove these coating substances from the surface of the cell for demonstration of the true structure.

Effect of Niacin on Mitochondria of Allium Cepa Root Cells

1967 ◽  
Vol 25 ◽  
pp. 78-79
Author(s):  
M. Arif Hayat
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Hydrogen Transfer ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Root Tips ◽  
Root Cells ◽  
Transfer Processes ◽  
Standard Procedures ◽  
A Cell ◽  
Critical Interest

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.

The Formation, Structure, Distribution and Frequency of Nuclear Pores

1971 ◽  
Vol 29 ◽  
pp. 518-519
Author(s):  
G. G. Maul
Keyword(s):  
Nuclear Pore Complex ◽  
Nuclear Membrane ◽  
Dynamic Structure ◽  
Nuclear Pore ◽  
Nuclear Pores ◽  
Filter Function ◽  
Etching Technique ◽  
Selective Filter ◽  
Membranous Part

The chromatin of eukaryotic cells is separated from the cytoplasm by a double membrane. One obvious structural specialization of the nuclear membrane is the presence of pores which have been implicated to facilitate the selective nucleocytoplasmic exchange of a variety of large molecules. Thus, the function of nuclear pores has mainly been regarded to be a passive one. Non-membranous diaphragms, radiating fibers, central rings, and other pore-associated structures were thought to play a role in the selective filter function of the nuclear pore complex. Evidence will be presented that suggests that the nuclear pore is a dynamic structure which is non-randomly distributed and can be formed during interphase, and that a close relationship exists between chromatin and the membranous part of the nuclear pore complex.Octagonality of the nuclear pore complex has been confirmed by a variety of techniques. Using the freeze-etching technique, it was possible to show that the membranous part of the pore complex has an eight-sided outline in human melanoma cells in vitro. Fibers which traverse the pore proper at its corners are continuous and indistinguishable from chromatin at the nucleoplasmic side, as seen in conventionally fixed and sectioned material. Chromatin can be seen in octagonal outline if serial sections are analyzed which are parallel but do not include nuclear membranes (Fig. 1). It is concluded that the shape of the pore rim is due to fibrous material traversing the pore, and may not have any functional significance. In many pores one can recognize a central ring with eight fibers radiating to the corners of the pore rim. Such a structural arrangement is also found to connect eight ribosomes at the nuclear membrane.

Low temperature x-ray microanalysis of frozen-hydrated tobacco leaves

1984 ◽  
Vol 42 ◽  
pp. 284-285
Author(s):  
S. Edith Taylor ◽  
Patrick Echlin ◽  
May McKoon ◽  
Thomas L. Hayes
Keyword(s):  
Low Temperature ◽  
Lemna Minor ◽  
Root Tips ◽  
Tobacco Leaves ◽  
X Ray ◽  
Whole Cells ◽  
Carbon Coated ◽  
The Right ◽  
Beam Currents ◽  
The University

Low temperature x-ray microanalysis (LTXM) of solid biological materials has been documented for Lemna minor L. root tips. This discussion will be limited to a demonstration of LTXM for measuring relative elemental distributions of P,S,Cl and K species within whole cells of tobacco leaves.Mature Wisconsin-38 tobacco was grown in the greenhouse at the University of California, Berkeley and picked daily from the mid-stalk position (leaf #9). The tissue was excised from the right of the mid rib and rapidly frozen in liquid nitrogen slush. It was then placed into an Amray biochamber and maintained at 103K. Fracture faces of the tissue were prepared and carbon-coated in the biochamber. The prepared sample was transferred from the biochamber to the Amray 1000A SEM equipped with a cold stage to maintain low temperatures at 103K. Analyses were performed using a tungsten source with accelerating voltages of 17.5 to 20 KV and beam currents from 1-2nA.

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