N-Cyclo-N′-(4-Dimethylamino-α-Naphthyl)Carbodiimide Inhibits Membrane-Bound and Partially Purified Tonoplast ATPase from Maize Roots

After tissue homogenization, 43% of the total hexokinase activity found in maize radicles was recovered in the mitochondrial fraction and 35% was soluble, in the cytosol. The maize submitochondrial particles obtained after mitochondrial sonication retained a high hexokinase activity. The mitochondrial respiration (state 4 rate) was activated by glucose. This activation was blocked by carboxyatractyloside (0.5 mM) and by oligomycin (2 micrograms/ml). The affinities for ATP and glucose of both soluble and membrane-bound maize hexokinases are similar to those of yeast hexokinase. The Km for ATP of these different forms of hexokinase varied between 0.15 and 0.37 mM, and the Km for glucose between 0.05 and 0.13 mM. A major difference between the two maize hexokinase forms is that only the mitochondrial enzyme was strongly inhibited by ADP (Ki 0.04 mM). The soluble forms of hexokinase found both in the cytosol of maize radicles and in yeast are not inhibited by ADP. In a previous report [de Meis, Grieco and Galina (1992) FEBS Lett. 308, 197-201] it was shown that the mitochondrial F1-F0-ATPase can use glucose 6-phosphate and yeast hexokinase as an ATP regenerating system. We now show that the membrane-bound hexokinase and glucose 6-phosphate can also serve as an ATP regenerating system for the mitochondria of maize radicles provided that the ADP concentration is kept below 0.05 mM. Higher ADP concentrations inhibit the reverse reaction of the mitochondrial hexokinase.

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Modulation of maize roots H+-ATPase by sulfated polysaccharides

Bioscience Reports ◽

10.1007/bf01198459 ◽

1996 ◽

Vol 16 (6) ◽

pp. 439-451 ◽

Cited By ~ 3

Author(s):

Ana Maria Landeira-Fernandez ◽

Maricilia S. Costa ◽

Leopolde de Meis

Keyword(s):

Dextran Sulfate ◽

Atp Hydrolysis ◽

Inhibitory Effect ◽

Sulfated Polysaccharides ◽

Monovalent Cations ◽

Dual Effect ◽

Highly Sensitive ◽

Maize Roots ◽

Optimum Ph ◽

Membrane Bound

Vesicles derived from maize roots retain a membrane bound H+-ATPase that is able to pump H+ at the expense of ATP hydrolysis. In this work it is shown that heparin, fucose-branched chondroitin sulfate and dextran sulfate 8000 promote a shift of the H+-ATPase optimum pH from 6.0 to 7.0. This shift is a result of a dual effect of the sulfated polysaccharides, inhibition at pH 6.0 and activation at pH 7.O. At pH 6.0 dextran 8000 promotes an increase of the apparent Km for ATP from 0.28 to 0.95 mM and a decrease of the Vmax from 14.5 to 7.1 μmol Pi/mg · 30 min−1. At pH 7.0 dextran 8000 promotes an increase in Vmax from 6.7 to 11.7 μmol Pi/mg · 30 min−1. In the presence of lysophosphatidylcholine the inhibitory effect of the sulfated polysaccharides observed at pH 6.0 was not altered but the activation of pH 7.0 decreased. It was found that in the presence of sulfated polysaccharides the ATPase became highly sensitive to K+ and Na+. Both the inhibition at pH 6.0 and the activation promoted by the polysaccharide were antagonized by monovalent cations (K+>Na+≫Li+).

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Plasma-membrane-bound malate dehydrogenase activity in maize roots

PROTOPLASMA ◽

10.1007/bf01283001 ◽

1999 ◽

Vol 207 (3-4) ◽

pp. 203-212 ◽

Cited By ~ 13

Author(s):

V. Hadži-Taskovišković ◽

M. Vuletić ◽

D. Ignjatović-Micić ◽

Ž. Vučinić

Keyword(s):

Plasma Membrane ◽

Dehydrogenase Activity ◽

Malate Dehydrogenase ◽

Maize Roots ◽

Membrane Bound

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Molecular Analysis of the Nitrate-Reducing Community from Unplanted and Maize-Planted Soils

Applied and Environmental Microbiology ◽

10.1128/aem.68.12.6121-6128.2002 ◽

2002 ◽

Vol 68 (12) ◽

pp. 6121-6128 ◽

Cited By ~ 142

Author(s):

Laurent Philippot ◽

Séverine Piutti ◽

Fabrice Martin-Laurent ◽

Stéphanie Hallet ◽

Jean Claude Germon

Keyword(s):

Taxonomic Composition ◽

Gene Encoding ◽

Terminal Electron Acceptor ◽

Rflp Type ◽

Maize Roots ◽

Membrane Bound ◽

Environmental Sequences ◽

Reducing Bacteria ◽

First Time ◽

Nitrate Reducing Bacteria

ABSTRACT Microorganisms that use nitrate as an alternative terminal electron acceptor play an important role in the global nitrogen cycle. The diversity of the nitrate-reducing community in soil and the influence of the maize roots on the structure of this community were studied. The narG gene encoding the membrane bound nitrate reductase was selected as a functional marker for the nitrate-reducing community. The use of narG is of special interest because the phylogeny of the narG gene closely reflects the 16S ribosomal DNA phylogeny. Therefore, targeting the narG gene provided for the first time a unique insight into the taxonomic composition of the nitrate-reducing community in planted and unplanted soils. The PCR-amplified narG fragments were cloned and analyzed by restriction fragment length polymorphism (RFLP). In all, 60 RFLP types represented by two or more clones were identified in addition to the 58 RFLP types represented by only one clone. At least one clone belonging to each RFLP type was then sequenced. Several of the obtained sequences were not related to the narG genes from cultivated bacteria, suggesting the existence of unidentified nitrate-reducing bacteria in the studied soil. However, environmental sequences were also related to NarG from many bacterial divisions, i.e., Actinobacteria and α, β, and γ Proteobacteria. The presence of the plant roots resulted in a shift in the structure of the nitrate-reducing community between the unplanted and planted soils. Sequencing of RFLP types dominant in the rhizosphere or present only in the rhizosphere revealed that they are related to NarG from the Actinobacteria in an astonishingly high proportion.

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Presence of Two Different Membrane-bound, KCl-stimulated Adenosine Triphosphatase Activities in Maize Roots

PLANT PHYSIOLOGY ◽

10.1104/pp.55.4.678 ◽

1975 ◽

Vol 55 (4) ◽

pp. 678-685 ◽

Cited By ~ 14

Author(s):

Roger A. Leigh ◽

Francis A. Williamson ◽

R. Gareth Wyn Jones

Keyword(s):

Adenosine Triphosphatase ◽

Maize Roots ◽

Membrane Bound

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Two Distinct Types of Microfilaments in the Cytoplasm of Human Adenohypophysial Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100073787 ◽

1973 ◽

Vol 31 ◽

pp. 668-669

Author(s):

E. Horvath ◽

K. Kovacs ◽

I. E. Stratmann ◽

C. Ezrin

Keyword(s):

Pituitary Tumors ◽

Average Diameter ◽

Anterior Lobe ◽

Uranyl Acetate ◽

Type I ◽

Breast Cancer Patients ◽

Human Pituitary ◽

Severe Diabetes ◽

Pituitary Glands ◽

Membrane Bound

Surgically removed human pituitary glands as well as pituitary tumors fixed in glutaraldehyde, postfixed in osmium tetroxide, embedded in epon resin, stained with uranyl acetate and lead citrate have been investigated by electron microscopy in order to correlate ultrastructure with functional activity. In the course of this study two distinct types of microfilaments have been identified in the cytoplasm of adenohypophysiocytes.Type I microfilaments (Fig. 1) were found in the cytoplasm of anterior lobe cells of five female subjects with disseminated mammary cancer and two patients with severe diabetes mellitus. The breast cancer patients were treated pre-operatively for various periods of time with different doses of oxysteroids. The microfilaments had an average diameter of JO A, formed parallel bundles, were scattered irregularly in the cytoplasm and were frequently located in the perikaryon. They were not membrane-bound and failed to show any periodicity.

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Intranuclear Crystals in Regenerating Canine Kidneys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072502 ◽

1973 ◽

Vol 31 ◽

pp. 412-413

Author(s):

D.G. Osborne ◽

L.J. McCormack ◽

M.O. Magnusson ◽

W.S. Kiser

Keyword(s):

Epithelial Cell ◽

Epithelial Cells ◽

Tubular Epithelial Cell ◽

Tubular Epithelial Cells ◽

Cell Nuclei ◽

Crystalline Structures ◽

Small Crystals ◽

Membrane Bound

During a project in which regenerative changes were studied in autotransplanted canine kidneys, intranuclear crystals were seen in a small number of tubular epithelial cells. These crystalline structures were seen in the control specimens and also in regenerating specimens; the main differences being in size and number of them. The control specimens showed a few tubular epithelial cell nuclei almost completely occupied by large crystals that were not membrane bound. Subsequent follow-up biopsies of the same kidneys contained similar intranuclear crystals but of a much smaller size. Some of these nuclei contained several small crystals. The small crystals occurred at one week following transplantation and were seen even four weeks following transplantation. As time passed, the small crystals appeared to fuse to form larger crystals.

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Membrane-bound vesicles associated with the microvilli in the midgut of the freshwater microcrustacean, Daphnia magna

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076135 ◽

1983 ◽

Vol 41 ◽

pp. 480-481

Author(s):

Patricia L. Jansma

Keyword(s):

Daphnia Magna ◽

Intestinal Epithelial Cells ◽

Uranyl Acetate ◽

Intestinal Epithelial ◽

Chlamydomonas Reinhardii ◽

Thin Sections ◽

Saturated Water ◽

Cacodylate Buffer ◽

Membrane Bound ◽

Ethanol Series

The presence of the membrane bound vesicles or blebs on the intestinal epithelial cells has been demonstrated in a variety of vertebrates such as chicks, piglets, hamsters, and humans. The only invertebrates shown to have these microvillar blebs are two species of f1ies. While investigating the digestive processes of the freshwater microcrustacean, Daphnia magna, the presence of these microvillar blebs was noticed.Daphnia magna fed in a suspension of axenically grown green alga, Chlamydomonas reinhardii for one hour were narcotized with CO2 saturated water. The intestinal tracts were excised in 2% glutaraldehyde in 0.2 M cacodyl ate buffer and then placed in fresh 2% glutaraldehyde for one hour. After rinsing in 0.1 M cacodylate buffer, the sample was postfixed in 2% OsO4, dehydrated with a graded ethanol series, infiltrated and embedded with Epon-Araldite. Thin sections were stained with uranyl acetate and Reynolds lead citrate before viewing with the Philips EM 200.

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Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100099490 ◽

1981 ◽

Vol 39 ◽

pp. 614-615

Author(s):

Roy Skidmore

Keyword(s):

Endoplasmic Reticulum ◽

Secretory Granules ◽

Golgi Body ◽

The Body ◽

Secretory Cells ◽

Secretory Vesicles ◽

High Magnification ◽

Large Numbers ◽

Membrane Bound ◽

Sole Of The Foot

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).

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