Etude ultrastructurale de la différenciation des hétérocystes chez la Cyanobactérie, Anabaena cylindrica Lemm

1983 ◽  
Vol 29 (11) ◽  
pp. 1564-1575 ◽  
Author(s):  
Monique Roussard-Jacquemin
Keyword(s):  
Lipid Droplets ◽  
Osmium Tetroxide ◽  
Thylakoid Membranes ◽  
Peripheral Region ◽  
Ultrastructural Changes ◽  
Anabaena Cylindrica ◽  
Vegetative Cells ◽  
Complex Envelope ◽  
Median Region ◽  
Thickened Ring

The differentiation of heterocystes from vegetative cells of Anabaena cylindrica, induced after transfer from a NH4+ medium to a medium without NH4+ under aerobic conditions, was studied by electron microscopy, the material being fixed with osmium tetroxide. The narrow septum separating the heterocyst and the vegetative cell originates from the median region of the normal septum which separates two adjacent vegetative cells. Its peripheral region is transformed into a thickened ring on which rests the complex envelope of the heterocyst. This structure presumably helps to create an anaerobic condition for nitrogenase. At the final stage of heterocyst maturation, the thylakoid membranes are significantly modified. They become flattened while at the previous stages they were expanded and vesiculated. In addition, some of them seem to be closely associated either with the remaining vesicular structures or with the plasmalemma. Polyphosphates bodies, cyanophycin granules, DNA fibres, and polyhedral bodies disappear. The presence of ribosomes, few polyglucosides, and numerous lipid droplets are observed at the end of the differentiation. A possible relationship between these ultrastructural changes and N2 fixation in the heterocysts of Anabaena cylindrica is discussed.

Effect of Acetone and Kerosene on Skin Ultrastructure

1972 ◽  
Vol 30 ◽  
pp. 92-93
Author(s):  
A. P. Lupulescu ◽  
H. Pinkus ◽  
D. J. Birmingham
Keyword(s):  
Electron Microscopy ◽  
Human Skin ◽  
Osmium Tetroxide ◽  
Human Epidermis ◽  
Ultrastructural Changes ◽  
Chemical Agents ◽  
Skin Ultrastructure ◽  
Volar Surface

Our laboratory is engaged in the study of the effect of different chemical agents on human skin, using electron microscopy. Previous investigations revealed that topical use of a strong alkali (NaOH 1N) or acid (HCl 1N), induces ultrastructural changes in the upper layers of human epidermis. In the current experiments, acetone and kerosene, which are primarily lipid solvents, were topically used on the volar surface of the forearm of Caucasian and Negro volunteers. Skin specimens were bioptically removed after 90 min. exposure and 72. hours later, fixed in 3% buffered glutaraldehyde, postfixed in 1% phosphate osmium tetroxide, then flat embedded in Epon.

scholarly journals Cell wall and organelle modifications during nitrogen starvation in Nannochloropsis oceanica F&M-M24

2021 ◽  
Author(s):  
Roncaglia Bianca ◽  
Papini Alessio ◽  
Chini Zittelli Graziella ◽  
Rodolfi Liliana ◽  
Mario R. Tredici
Keyword(s):  
Cell Wall ◽  
Wall Thickness ◽  
Lipid Droplets ◽  
Nitrogen Starvation ◽  
Photosynthetic Apparatus ◽  
Ultrastructural Changes ◽  
Total Biomass ◽  
Nannochloropsis Oceanica ◽  
Final Phase ◽  
Cell Functions

AbstractNannochloropsis oceanica F&M-M24 is able to increase its lipid content during nitrogen starvation to more than 50% of the total biomass. We investigated the ultrastructural changes and the variation in the content of main cell biomolecules that accompany the final phase of lipid accumulation. Nitrogen starvation induced a first phase of thylakoid disruption followed by chloroplast macroautophagy and formation of lipid droplets. During this phase, the total amount of proteins decreased by one-third, while carbohydrates decreased by 12–13%, suggesting that lipid droplets were formed by remodelling of chloroplast membranes and synthesis of fatty acids from carbohydrates and amino acids. The change in mitochondrial ultrastructure suggests also that these organelles were involved in the process. The cell wall increased its thickness and changed its structure during starvation, indicating that a disruption process could be partially affected by the increase in wall thickness for biomolecules recovery from starved cells. The wall thickness in strain F&M-M24 was much lower than that observed in other strains of N. oceanica, showing a possible advantage of this strain for the purpose of biomolecules extraction. The modifications following starvation were interpreted as a response to reduction of availability of a key nutrient (nitrogen). The result is a prolonged survival in quiescence until an improvement of the environmental conditions (nutrient availability) allows the rebuilding of the photosynthetic apparatus and the full recovery of cell functions.

scholarly journals Time-dependent growth of crystalline Au0-nanoparticles in cyanobacteria as self-reproducing bioreactors: 2.Anabaena cylindrica

2016 ◽  
Vol 7 ◽  
pp. 312-327 ◽  
Author(s):  
Liz M Rösken ◽  
Felix Cappel ◽  
Susanne Körsten ◽  
Christian B Fischer ◽  
Andreas Schönleber ◽  
...  
Keyword(s):  
Extracellular Polymeric Substances ◽  
Production Method ◽  
Wide Distribution ◽  
Time Dependent ◽  
Anabaena Cylindrica ◽  
Vegetative Cells ◽  
Breakdown Spectroscopy ◽  
Laser Induced Breakdown ◽  
Dependent Growth ◽  
Average Size

Microbial biosynthesis of metal nanoparticles as needed in catalysis has shown its theoretical ability as an extremely environmentally friendly production method in the last few years, even though the separation of the nanoparticles is challenging. Biosynthesis, summing up biosorption and bioreduction of diluted metal ions to zero valent metals, is especially ecofriendly, when the bioreactor itself is harmless and needs no further harmful reagents. The cyanobacteriumAnabaena cylindrica(SAG 1403.2) is able to form crystalline Au0-nanoparticles from Au3+ions and does not release toxic anatoxin-a. X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and laser-induced breakdown spectroscopy (LIBS) are applied to monitor the time-dependent development of gold nanoparticles for up to 40 hours. Some vegetative cells (VC) are filled with nanoparticles within minutes, while the extracellular polymeric substances (EPS) of vegetative cells and the heterocyst polysaccharide layer (HEP) are the regions, where the first nanoparticles are detected on most other cells. The uptake of gold starts immediately after incubation and within four hours the average size remains constant around 10 nm. Analyzing the TEM images with an image processing program reveals a wide distribution for the diameter of the nanoparticles at all times and in all regions of the cyanobacteria. Finally, the nanoparticle concentration in vegetative cells ofAnabaena cylindricais about 50% higher than in heterocysts (HC). These nanoparticles are found to be located along the thylakoid membranes.

Ultrastructure of the Intestinal Absorptive Cells of Fed and Fasted Tadpoles

1970 ◽  
Vol 28 ◽  
pp. 86-87
Author(s):  
Robert Giaquinta ◽  
M. A. Hayat
Keyword(s):  
Electron Microscopy ◽  
Small Intestine ◽  
Fine Structure ◽  
Osmium Tetroxide ◽  
Rana Pipiens ◽  
Ultrastructural Changes ◽  
Amphibian Metamorphosis ◽  
Absorptive Cells ◽  
Food Absorption ◽  
Tissue Specimens

The ultrastructural changes that occur in the intestinal absorptive cells during amphibian metamorphosis have been reported (Bonneville, 1963). These changes accompany a change in diet (from an herbivorous to a carnivorous state) during metamorphosis. Little information is available, however, on the ultrastructural changes in the absorptive cells of amphibians in relation to the state of feeding. This report describes the differences in the fine structure of these cells in the tadpole stage of Rana pipiens during periods of food absorption and fasting.Rana pipiens at tadpole stages were fed an herbivorous diet, and after a period of 48 hr, the animal was dissected and segments of the small intestine were collected for electron microscopy. A second group of tadpoles was fasted for 7 days, and segments of the small intestine were collected. The tissue specimens were immersed in phosphate-buffered glutaraldehyde (3%) for 1 hr at 4C and postfixed with phosphate-buffered osmium tetroxide (2%) for 1 hr at 4C.

Hepatic cytoprotection in treatment of canine heartworm

1989 ◽  
Vol 47 ◽  
pp. 918-919
Author(s):  
D.L. Friesen ◽  
A. Singh ◽  
M.E. Hitt
Keyword(s):  
Electron Microscopy ◽  
Phosphate Buffer ◽  
Osmium Tetroxide ◽  
Light And Electron Microscopy ◽  
Ultrastructural Changes ◽  
Sample Treatment ◽  
Host Animal ◽  
Thin Sections ◽  
Canine Heartworm ◽  
Toxic Metabolites

Thiacetarsamide is an arsenic-containing drug used in the treatment of heartworm in dogs. The effective antihelmintic dose is toxic to the host animal. Acetylcysteine decreases the hepatotoxicity of some compounds by forming a conjugate with toxic metabolites of the compound. The purpose of this study was to evaluate the effectiveness of a cytoprotectant for hepatocytes in dogs treated with therapeutic levels of thiacetarsamide.Eighteen dogs were divided randomly into two groups. All dogs were given four doses of thiacetarsamide over two days. Nine dogs were given 10% acetylcysteine 15 min prior to each dose of thiacetarsamide. Needle biopsies of the liver were taken from each dog prior to the treatment and again one week post-treatment. The biopsies were fixed in 2% gluraraldehyde in phosphate buffer, pH 7.3, post-fixed in 1% osmium tetroxide, and processed for electron microscopy. Semithin and thin sections of the liver were examined by light and electron microscopy, respectively, for histopathologic and ultrastructural changes. The specimens were coded and the sample treatment was not known to the researchers at the time of observation.

Electron Microscopic study of inner ear of guinea pig with special reference to morphological changes in vestibular macula in hypercholesterolemia

1993 ◽  
Vol 51 ◽  
pp. 430-431
Author(s):  
Yan Qiao ◽  
Goro Asano ◽  
Izumi Kashiwado ◽  
Yasuo Hattori
Keyword(s):  
Guinea Pig ◽  
Inner Ear ◽  
Vascular Function ◽  
Lipid Droplets ◽  
Morphological Changes ◽  
Ultrastructural Changes ◽  
Sensory Cells ◽  
Vascular Changes ◽  
Electron Microscopic ◽  
Microscopic Techniques

Vertigo may be induced by various factors such as vascular changes including arteriosclerosis and hypercholesterolemia in the inner ear. In orter to clarify the mechanism of vertigo, the inner ear of guinea pig in hypercholesterolemia condition was investigated by electron microscopic techniques.The guinea pigs have served as experimental materials. They were divided into two groups: one received non-administration of cholesterol and the other received the administration of cholesterol. The vestibular macula in inner ear were observed at 1, 2 and 3 months after the administration of cholesterol and also vascular function was investigated by using horseradish peroxidase as tracer.Ultrastructural changes such as the depletion of microvilli on the cell surface and increased microvesicles were detected in the cytoplasm of sensory cell after cholesterol administration. After two months, lipid droplets were demonstrated in the cytoplasm, associated with intercellular edema. The cytoplasmic projection with vacuolization was demonstrated in the surface of sensory cells in the vestibular macula after three months of cholesterol administration.

Ultrastructural effects of exogenous hydrogen peroxide on the myocardium

1989 ◽  
Vol 47 ◽  
pp. 1102-1103
Author(s):  
T. Oguro ◽  
K. Aida ◽  
T. Onodera ◽  
M. Ashraf
Keyword(s):  
Hydrogen Peroxide ◽  
Superoxide Anion ◽  
Osmium Tetroxide ◽  
Structure And Function ◽  
Ultrastructural Changes ◽  
Superoxide Anions ◽  
Isolated Hearts ◽  
Rat Hearts ◽  
And Function ◽  
Isolated Rat

It has been suggested that hydrogen peroxide (H2O2) is indirectly associated with postischemic-reperfusion injury of the heart. Previously, we reported that the heart was not damaged when perfused with exogenously generated superoxide anions. However, H2O2, a dismutation product of superoxide anion severely affected the heart structure and function. In this study, we evaluated the ultrastructural changes of the cel1 membranes in isolated rat hearts and cultured myocytes follow-ing treatment with exogenous H2O2.In the isolated hearts, 300 μM of H2O2, a concentration which was based on our earlier study was perfused for 5 minutes. For the last 2 minutes, 100 mg (2200 U/mg) of horseradish peroxidase was perfused to see the permeability of the cell membranes. In the isolated cultured myocytes, 300 μM of H2O2 was added to the medium for 30 minutes. Both the hearts and the isolated myocytes were fixed with 2.5% buffered glutaraldehyde, postfixed with 1% osmium tetroxide and were processed for electron microscopy.

Ultrastructural changes in chloroplasts resulting from fluctuations in NaCl concentration: freeze-fracture of thylakoid membranes in Dunaliella salina

1975 ◽  
Vol 18 (2) ◽  
pp. 287-299 ◽  
Author(s):  
A.O. Pfeifhofer ◽  
J.C. Belton
Keyword(s):  
Salt Concentration ◽  
Dunaliella Salina ◽  
Unit Area ◽  
Morphological Changes ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Thylakoid Membranes ◽  
Ultrastructural Changes ◽  
Thin Sections ◽  
Number Of Particles

The structure of chloroplasts isolated from Dunaliella salina has been studied with respect to changing concentrations of sodium chloride in the culture medium. Freeze-fracture replicas and thin sections of intact chloroplasts do not exhibit any noticeable changes in structure at concentrations ranging between 3.5 and 25% NaCl. Chloroplasts isolated from algal cells that have been acclimatized to the higher salt concentration show a change in the thylakoid membranes. The thylakoid membranes appear compressed over a major portion of the membrane surface, with only the end of the thylakoid membranes unappressed. The number of particles per unit area on the B face is also altered by the salt concentration. The chloroplasts acclimatized to 25% NaCl have about 3 times the number of particles per unit area on a B face of end-membranes as on a comparable face of thylakoid membranes acclimatized to low (3.5% NaCl) salt concentration. These morphological changes can be reversed if the chloroplasts acclimatized to high or low salt concentrations are returned to a medium of different salt concentration prior to freeze-fracturing.

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