scholarly journals Some enzymes present in the walls of mesophyll cells of tobacco leaves

1975 ◽  
Vol 151 (1) ◽  
pp. 141-144 ◽  
Author(s):  
K H Yung ◽  
D H Northcote
Keyword(s):  
Cell Wall ◽  
Acid Phosphatase ◽  
Horseradish Peroxidase ◽  
Malate Dehydrogenase ◽  
Enzyme Activities ◽  
Incubation Medium ◽  
Time Course ◽  
Mesophyll Cells ◽  
Cell Wall Enzymes ◽  
The Difference

Cell-wall enzymes were assayed by the difference between enzyme activities in the whole cell and the protoplast. Both peroxidase (85.2%) and acid phosphatase (21.9%) were located in the wall. However, malate dehydrogenase was found only in the protoplast. A study of the time-course of the release of peroxidase and malate dehydrogenase into the incubation medium from cells either treated with cellulase or untreated, also indicated that peroxidase and not malate dehydrogenase was located in the wall. Only two anodic isoenzymes of peroxidase were present in the cell wall. These were more negatively charged than those of horseradish peroxidase.

scholarly journals Enzyme activities and pectin breakdown of sapodilla submitted to 1-methylcyclopropene

2008 ◽  
Vol 43 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Patrícia Lígia Dantas de Morais ◽  
Luiz Carlos de Oliveira Lima ◽  
Maria Raquel Alcântara de Miranda ◽  
José Donizete Alves ◽  
Ricardo Elesbão Alves ◽  
...  
Keyword(s):  
Cell Wall ◽  
Enzyme Activities ◽  
Cellulose Microfibril ◽  
Modified Atmosphere ◽  
Cell Wall Degrading Enzymes ◽  
Manilkara Zapota ◽  
Postharvest Treatment ◽  
Cell Wall Enzymes ◽  
Ethylene Antagonist ◽  
Beta Galactosidase

The objective of this work was to investigate the influence of 1-methylcyclopropene (1-MCP) at 300 nL L-1 on activities of cell wall hidrolytic enzymes and pectin breakdown changes which Sapodilla (Manilkara zapota cv. Itapirema 31) cell wall undergoes during ripening. Sapodilla were treated with ethylene antagonist 1-MCP at 300 nL L-1 for 12 hours and then, stored under a modified atmosphere at 25º C for 23 days. Firmness, total and soluble pectin and cell wall enzymes were monitored during storage. 1-MCP at 300 nL L-1 for 12 hours delayed significantly softening of sapodilla for 11 days at 25º C. 1-MCP postharvest treatment affected the activities of cell wall degrading enzymes pectinmethylesterase and polygalacturonase and completely suppressed increases in beta-galactosidase for 8 days, resulting in less pectin solubilization. Beta-galactosidase seems relevant to softening of sapodilla and is probably responsible for modification of both pectin and xyloglucan-cellulose microfibril network.

The Influence of Short Ether Anesthesia on Some Liver Enzyme Activities in the Rat

1973 ◽  
Vol 51 (8) ◽  
pp. 604-607 ◽  
Author(s):  
E. Katona
Keyword(s):  
Alkaline Phosphatase ◽  
Acid Phosphatase ◽  
Malate Dehydrogenase ◽  
Enzyme Activities ◽  
Urate Oxidase ◽  
Arylsulfatase A ◽  
Ether Anesthesia ◽  
Arylsulfatase B ◽  
Thiamine Pyrophosphatase ◽  
Liver Homogenates

Rats were anesthetized by ether inhalation for 4–5 min and sacrificed 1–48 h after anesthesia. From their liver homogenates, the activities of nine enzymes were determined. Activities of urate oxidase and arylsulfatase-A did not change significantly but arylsulfatase-B was slightly decreased. Malate dehydrogenase, arylsulfatase-B, and thiamine pyrophosphatase reached their highest and "malic enzymes" their lowest activities at the same time, 5 h after anesthesia. Alkaline phosphatase first decreased, later increased. Acid phosphatase and glucose-6-phosphatase activities decreased following ether anesthesia. Thesechanges in the enzyme activities generally agree and partly explain previously reported effects of ether anesthesia observed in the serum.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

Destruction of Actin Filaments by Osmium Tetroxide

1977 ◽  
Vol 35 ◽  
pp. 466-467
Author(s):  
P. Maupin-Szamier ◽  
T. D. Pollard
Keyword(s):  
Actin Filaments ◽  
Time Course ◽  
Osmium Tetroxide ◽  
Rabbit Muscle ◽  
Muscle Actin ◽  
Sodium Phosphate Buffer ◽  
Transmission Electron ◽  
The Difference ◽  
Rates Of Decay ◽  
Short Time

We have studied the destruction of rabbit muscle actin filaments by osmium tetroxide (OSO4) to develop methods which will preserve the structure of actin filaments during preparation for transmission electron microscopy.Negatively stained F-actin, which appears as smooth, gently curved filaments in control samples (Fig. 1a), acquire an angular, distorted profile and break into progressively shorter pieces after exposure to OSO4 (Fig. 1b,c). We followed the time course of the reaction with viscometry since it is a simple, quantitative method to assess filament integrity. The difference in rates of decay in viscosity of polymerized actin solutions after the addition of four concentrations of OSO4 is illustrated in Fig. 2. Viscometry indicated that the rate of actin filament destruction is also dependent upon temperature, buffer type, buffer concentration, and pH, and requires the continued presence of OSO4. The conditions most favorable to filament preservation are fixation in a low concentration of OSO4 for a short time at 0°C in 100mM sodium phosphate buffer, pH 6.0.

Ultrastructure and Senescence in an Achloroplastic Mutant of Hordeum vulgare L. cv. Dyan

1992 ◽  
Vol 50 (1) ◽  
pp. 844-845
Author(s):  
R.H.M. Cross ◽  
C.E.J. Botha ◽  
A.K. Cowan ◽  
B.J. Hartley
Keyword(s):  
Cell Wall ◽  
Hordeum Vulgare ◽  
Leaf Tissue ◽  
Ultrastructural Changes ◽  
Hordeum Vulgare L ◽  
Mesophyll Cells ◽  
Lethal Mutant ◽  
Cytoplasmic Matrix ◽  
Close Proximity ◽  
Pinocytotic Vesicles

Senescence is an ordered degenerative process leading to death of individual cells, organs and organisms. The detection of a conditional lethal mutant (achloroplastic) of Hordeum vulgare has enabled us to investigate ultrastructural changes occurring in leaf tissue during foliar senescence.Examination of the tonoplast structure in six and 14 day-old mutant tissue revealed a progressive degeneration and disappearance of the membrane, apparently starting by day six in the vicinity of the mitochondria associated with the degenerating proplastid (Fig. 1.) where neither of the plastid membrane leaflets is evident (arrows, Fig. 1.). At this stage there was evidence that the mitochondrial membranes were undergoing retrogressive changes, coupled with disorganization of cristae (Fig. 2.). Proplastids (P) lack definitive prolamellar bodies. The cytoplasmic matrix is largely agranular, with few endoplasmic reticulum (ER) cisternae or polyribosomal aggregates. Interestingly, large numbers of actively-budding dictysomes, associated with pinocytotic vesicles, were observed in close proximity to the plasmalemma of mesophyll cells (Fig. 3.). By day 14 however, mesophyll cells showed almost complete breakdown of subcellular organelle structure (Fig. 4.), and further evidence for the breakdown of the tonoplast. The final stage of senescence is characterized by the solubilization of the cell wall due to expression and activity of polygalacturonase and/or cellulose. The presence of dictyosomes with associated pinocytotic vesicles formed from the mature face, in close proximity to both the plasmalemma and the cell wall, would appear to support the model proposed by Christopherson for the secretion of cellulase. This pathway of synthesis is typical for secretory glycoproteins.

scholarly journals METHODS FOR THE STUDY OF SMALL PHAGOSOMES AND THEIR RELATIONSHIP TO LYSOSOMES WITH HORSERADISH PEROXIDASE AS A "MARKER PROTEIN"

1967 ◽  
Vol 15 (7) ◽  
pp. 375-380 ◽  
Author(s):  
WERNER STRAUS
Keyword(s):  
Acid Phosphatase ◽  
Low Temperature ◽  
Horseradish Peroxidase ◽  
Acid Medium ◽  
Tissue Section ◽  
Double Staining ◽  
Marker Protein ◽  
Polar Media ◽  
The Stability ◽  
Blue Reaction

Small phagosomes (micropinocytic vesicles and vacuoles) which had taken up injected horseradish peroxidase were identified by staining for peroxidase with benzidine and H2O2. Because of the small size of the granules and the possibility of artifacts, previously described procedures had to be modified in several respects. Prefixation of the tissue by perfusion at 37°C prevented artifacts of diffusion and adsorption of peroxidase. The blue product of the reaction of peroxidase with benzidine in the small phagosomes was preserved and fading to brown was prevented by cooling the tissue section to –10° to –15°C during its processing through polar media. The blue reaction product was stable as soon as the section was transferred to an apolar medium. Small phagosomes were visualized together with lysosomes and phago-lysosomes in the same cells by double staining for acid phosphatase and peroxidase in contrasting colors. The incubation for acid phosphatase was performed at 4°C since low temperature increased the stability of peroxidase in the acid medium. Factors which form the basis for other improvements of the procedure are discussed.

Prefertilization ovule development in Capsella: the dyad, tetrad, developing megaspore, and two-nucleate gametophyte

1986 ◽  
Vol 64 (4) ◽  
pp. 875-884 ◽  
Author(s):  
Patricia Schulz ◽  
William A. Jensen
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Acid Phosphatase ◽  
De Novo ◽  
Periodic Acid ◽  
Aniline Blue ◽  
Ovule Development ◽  
Periodic Acid Schiff ◽  
Fluorescent Material ◽  
Autophagic Vacuoles

Ovules of Capsella bursa-pastoris at the dyad and tetrad stages of meiosis and at the megaspore and two-nucleate stages of the gametophyte were studied with the electron microscope. The cells of the dyad and tetrad are separated by aniline blue fluorescent cross walls and receive all types of organelles and autophagic vacuoles that were present in the meiocyte. Autophagic vacuoles enclose ribosomes and organelles and show reaction product for acid phosphatase. Autophagic vacuoles and some plastids are absorbed into the enlarging vacuoles of the growing megaspore. Other plastids appear to survive meiosis and there is no evidence for their de novo origin. Some mitochondria appear to degenerate in the enlarging megaspore but others look healthy and there is no evidence for the de novo origin of mitochondria. The nucleolus of the developing megaspore becomes very large and the cytoplasm is extremely dense with ribosomes. The cell wall is thickened by an electron-translucent, periodic acid – Schiff negative, aniline blue fluorescent material and contains plasmodesmata that link the megaspore with the nucellus. The plasmalemma of the growing megaspore produces microvilluslike extensions into this wall that disappear with the formation of the two-nucleate gametophyte. Plasmodesmata disappear from the cell wall at the four-nucleate stage.

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