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D J Morre

Publications and source records attributed to D J Morre.

18 recordsLinked to original sources
PubMed2001

Plasma membrane NADH oxidase of maize roots responds to gravity and imposed centrifugal forces.

NADH oxidase activities measured with excised roots of dark-grown maize (Zea mays) seedlings and with isolated plasma membrane vesicles from roots of dark-grown maize oscillated with a regular period length of 24 min and were inhibited by the synthetic auxin 2,4-dichlorophenoxyacetic [correction of dichorophenoxyacetic] acid. The activities also responded to orientation with respect to gravity and to imposed centrifugal forces. Turning the roots upside down resulted in stimulation of the activity with a lag of about 10 min. Returning the sections to the normal upright position resulted in a return to initial rates. The activity was stimulated reversibly to a maximum of about 2-fold with isolated plasma membrane vesicles, when subjected to centrifugal forces of 25 to 250 x g for 1 to 4 min duration. These findings are the first report of a gravity-responsive enzymatic activity of plant roots inhibited by auxin and potentially related to the gravity-induced growth response.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

Aqueous two-phase partition applied to the isolation of plasma membranes and Golgi apparatus from cultured mammalian cells.

Partitioning in dextran-poly(ethylene)glycol (PEG) aqueous-aqueous phase systems represents a mature technology with many applications to separations of cells and to the preparation of membranes from mammalian cells. Most applications to membrane isolation and purification have focused on plasma membranes, plasma membrane domains and separation of right side-out and inside-out plasma membrane vesicles. The method exploits a combination of membrane properties, including charge and hydrophobicity. Purification is based upon differential distributions of the constituents in a sample between the two principal compartments of the two phases (upper and lower) and at the interface. The order of affinity of animal cell membranes for the upper phase is: endoplasmic reticulum <mitochondria<Golgi apparatus<lysosomes and endosomes< plasma membranes. Salt concentrations and temperature affect partitioning behavior and must be precisely standardized. In some cases, it is more fortuitous to combine aqueous two-phase partition with other procedures to obtain a more highly purified preparation. A procedure is described for preparation of Golgi apparatus from transformed mammalian cells that combines aqueous two-phase partition and centrifugation. Also described is a periodic NADH oxidase, a new enzyme marker for right side-out plasma membrane vesicles not requiring detergent disruptions for measurement of activity.

Animals↗
PubMed1992

Temperature- and acceptor-specificity of cell-free vesicular transfer from transitional endoplasmic reticulum to the cis Golgi apparatus.

The temperature dependence and specificity of transfer of membrane constituents from donor transitional endoplasmic reticulum to the cis Golgi apparatus were investigated using a cell-free system from rat liver. The radiolabelled transitional endoplasmic reticulum donors were prepared from slices of rat liver prelabelled with [14C]leucine. The acceptor Golgi apparatus elements were unlabelled and immobilized on nitrocellulose. When Golgi apparatus stacks were separated by preparative free-flow electrophoresis into subfractions enriched in cisternae derived from the cis, medial and trans portions of the stack respectively, efficient specific transfer was observed only to cis elements. Trans elements were devoid of specific acceptor capacity. Similarly, when transfer was determined as a function of temperature, a transition was observed in transfer activity between 12 degrees C and 18 degrees C similar to that seen in vivo for formation of the so-called 16 degrees C cis Golgi-located membrane compartment. Transfer at temperatures below 16 degrees C and transfer to trans Golgi apparatus compartments at temperatures either above or below 16 degrees C was similar and unspecific. The unspecific transfer at low temperature was pH independent, whereas specific transfer was greatest at the physiological pH of 7, and was reduced to 10% and 18% of that occurring at pH 8 and pH 5.5 respectively. These findings show that the cell-free system derived from rat liver exhibits a high degree of fidelity to transfer in vivo, an efficiency approaching that observed in vivo, and a nearly absolute acceptor specificity for cis Golgi apparatus. The acceptor-, temperature- and pH-specificity of the cell-free transfer, as well as the saturation kinetics exhibited with respect to acceptor Golgi apparatus, support the concept of transition-vesicle-specific docking sites of finite number associated with cis Golgi apparatus cisternae.

Adenosine Triphosphate↗
PubMed1992

Stimulation of NADH oxidase activity from rat liver plasma membranes by growth factors and hormones is decreased or absent with hepatoma plasma membranes.

Plasma membranes of rat liver isolated by aqueous two-phase partition exhibited basal levels of NADH oxidase activity that were increased approx. 2-fold by addition of hormones and growth factors to which liver cells were known to respond. In contrast, hepatoma plasma membranes demonstrated an intrinsically increased level of NADH oxidase, which was not stimulated further by addition of growth factors. The results suggest that the NADH oxidase of the hepatoma plasma membrane is no longer correctly coupled to hormone and growth-factor receptors. This biochemical defect may parallel the loss of growth control that is characteristic of neoplastic transformation in hepatocarcinogenesis and other transformation systems.

Animals↗
PubMed1990

An ultrastructural evaluation of toluene toxicity using cultured mammalian cells.

Animal cells were cultured in media containing toluene and then examined by electron microscopy to determine changes in subcellular architecture. Cellular viability and cloning studies indicated toluene toxicity at concentrations of 50-500 ppm. At all dosage levels, toluene accelerated cell death compared to comparable control cells that had not been exposed to toluene. However, media composition and, particularly, the presence or absence of fetal bovine serum (FBS), markedly affected toluene toxicity. In media without FBS reversible changes in filopodia and cell shape were identified after 15 min of exposure to as little as 50 ppm toluene, and cell death occurred within 5 min at concentrations of 500 ppm toluene. In media with FBS, no filopodial changes were observed at 50 ppm toluene, and cell death, although accelerated, was clearly evident only after 24-48 h of exposure to 200-500 ppm toluene. Except for the cell-surface changes, chronic toluene exposures (50-100 ppm without FBS or 200-500 ppm with FBS in the growth medium) produced no unusual intracellular changes until 24-48 h of toluene exposure. With toluene exposures of 24 h or longer, cellular changes included condensation of heterochromatin in nuclei, formation of bulbous protuberances at the cell surface, loss of polyribosomes (but not ribosomes) and, ultimately, degeneration of organelles. These late changes were irreversible and the prelude to cell death.

Animals↗
PubMed1986

Transplasmalemma electron transport from cells is part of a diferric transferrin reductase system.

Intact cells are known to reduce external, impermeable electron acceptors. We now show that cells can reduce the iron in diferric transferrin at the cell surface and that this reduction reaction depends on the transferrin receptor as well as the transmembrane electron transport system. Reduction of external diferric transferrin is accompanied by oxidation of internal NADH which indicates that the transmembrane enzyme is an NADH diferric transferrin reductase. Highly purified liver plasma membranes have NADH diferric transferrin reductase activity which shows properties similar to the diferric transferrin reductases activity of intact cells. Cell growth stimulation by diferric transferrin and other impermeable oxidants which can react with the diferric transferrin reductase can be based on electron transport through he plasma membrane.

Cell Membrane↗
PubMed1977

Ganglioside biosynthesis. Characterization of CMP-N-acetylneuraminic acid : lactosylceramide sialyltransferase in Golgi apparatus from rat liver.

An enzyme that transfers sialic acid from GMP-sialic acid to lactosylceramide was concentrated 40-50 times in Golgi apparatus from rat liver relative to total homogenates. This enzyme required detergents as dispersing agents. Of the numerous detergents tested, the combination Tween 80-Triton CF-54 (1 : 2, w/w) was the most effective in stimulating the reaction. Two apparent pH optima, at 6.35 and 5.5, were observed. The enzyme showed no requirement for a divalent cation. The Km values calculated for CMP-N-acetylneuraminic acid and lactosylceramide were 2.7 - 10(-3) and 1.3 - 10(-4) M, respectively. The enzyme could not be dissociated from Golgi apparatus fractions by treatment with ultrasound, indicating that it is tightly associated with the membrane. The newly synthesized GM3, the product of the reaction, was incorporated into or became tightly associated with the membranes of the Golgi apparatus.

Animals↗
PubMed1977

Glycosyltransferases with endogenous acceptor activity in plasma membranes isolated from rat liver.

Plasma membrane fractions from rat liver exhibited glycosyltransferase activity with endogenous membrane-associated acceptors and either UDP-galactose, UDPglucose, UDP-N-acetylglucosamine, or GDPmannose donors. Of these, incorporation into non-lipid acceptors was most active with UDP-galactose and only with UDPgalactose and UDPmannose was there incorporation into endogenous lipid acceptors. CMP-N-acetylneuraminic acid was inactive as a donor with the isolated plasma membranes. In order to demonstrate transferase activity, low concentrations of substrate sugar nucleotides and short incubation times were used as well as sulfhydryl protectants and a phosphatase inhibitor (NaF) in the reaction mixtures. The findings support the concept of surface localization of at least a galactosyl transferase in cells of rat liver.

Animals↗
PubMed1968

Cell wall dissolution and enzyme secretion during leaf abscission.

Cell wall changes leading to the formation of the separation layer during abscission of unifoliate (Phaseolus vulgaris) leaves are reviewed. Based on evidence from explants and intact plants, dissolution of pectic substances between cells of adjacent tissue regions (petiole and pulvinus) is necessary and may be sufficient to form the separation layer. Initially, the abscission zone is not structurally weak. The decline in break strength accompanying formation of the separation layer correlates with the appearance of pectinase activity. Pectinase activity is not detectable in freshly harvested explants but increases to about 0.09 mug per abscission zone at the time of 50% separation. At the same time, water extractable pectin fractions increase with a corresponding decline in the pectin fraction extractable with dilute acid. Separation is aided by internal shear forces generated by differential growth and hydrostatic pressure or both.

Journal Article↗
PubMed1967

Inhibition of RNA synthesis and auxin-induced cell wall extensibility and growth by Actinomycin D.

A linear stress strain analyzer was used to determine the effects of inhibitors of RNA and protein synthesis on auxin-induced increases in cell wall extensibility. With etiolated soybean hypocotyl, maize mesocotyl and Avena coleoptile sections and light-grown pea internode sections, inhibition of RNA synthesis resulted in inhibition of auxin-induced extensibility changes and cell expansion. The results with both actinomycin D and cycloheximide support an earlier conclusion that unstable cell constituents, presumably enzymes, are essential for cell wall loosening induced by auxin as well as for cell elongation.

Cell Wall↗
PubMedDate not supplied

Soybean cell enlargement oscillates with a temperature-compensated period length of ca. 24 min.

Rate of enlargement of epidermal cells from soybean, when measured at intervals of 1 min using a light microscope equipped with a video measurement system, oscillated with a period length of about 24 min. This oscillation parallels the 24-min periodicity observed for the oxidation of NADH by the external plasma membrane NADH oxidase. The increase in length was not only non-linear, but intervals of rapid increase in area alternated with intervals of rapid decrease in area. The length of the period was temperature compensated, and was approximately the same when measured at 14, 24 and 34 degrees C even though the rate of cell enlargement varied over this same range of temperatures. These observations represent the first demonstration of an oscillatory growth behavior correlated with a biochemical activity where the period length of both is independent of temperature (temperature compensated) as is the hallmark of clock-related biological phenomena.

Cell Size↗
PubMedDate not supplied

Plasma membrane NADH oxidase is gravi-responsive.

NADH oxidase activities measured with intact tissue sections and with isolated plasma membrane vesicles from etiolated hypocotyls of soybean (Glycine max) respond to gravity and imposed centrifugal forces. The response is one of inhibition of activity with tissue sections lying flat for 20 min or less at 1 x g and one of stimulation with times of lying flat of 30 min or longer at 1 x g. Turning the tissue sections upside down resulted in stimulation of the activity with a lag of about 30 min. Returning the sections to the normal upright position resulted in a return to initial rates with a lag of less than 20 min. Both the stimulated and non-stimulated activities oscillate with a period of 24 min, precluding a more precise analyses of lag times. The activity was stimulated reversibly to a maximum of about 2-fold both in tissue sections and in isolated plasma membrane vesicles when subjected to centrifugal forces of 10 to 400 x g for 0.5 to 4 min duration. The findings are the first description of a gravi-responsive enzymatic activity related to the growth response in plants.

Cell Membrane↗