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PubMed1972

Preparation of plasma membrane from isolated neurons.

A bulk fraction enriched with respect to neuronal cell bodies was used as starting material for the isolation of neuronal plasma membrane The cells were gently homogenized in isotonic sucrose and a crude membrane containing fraction sedimented at 3000 g. Subsequently, the membrane fraction was purified on a discontinuous sucrose density gradient between 35% and 25 5% sucrose (w/w). Enzymatic analyses showed a 4-5-fold enrichment in plasma membrane markers, and a 10-15% contamination of mitochondrial and microsomal material. Electron micrographs of the membrane fraction confirmed the enzymatic data Fragmented membranes were found, mainly in vesicular form No ribosomes, but a few mitochondria and some multilamellar membranes were seen

Adenosine Triphosphatases↗
PubMed1974

Resolution of three distinct populations of nerve endings from rat brain homogenates by zonal isopycnic centrifugation.

Conditions have been established for the fractionation of subcellular components of rat forebrain homogenates by zonal isopycnic equilibration in continuous sucrose density gradients using a B-XIV rotor. The fractions were analyzed biochemically and by ultra-structural morphometry. Starting from postnuclear supernates of forebrain homogenates, it has been possible to resolve three distinct populations of nerve endings from one another, as well as from free mitochondria and myelin fragments. The three types of nerve endings differ in their apparent specific gravity, their biochemical properties, and their ability selectively to accumulate exogenous transmitter substances in vitro. These three particle populations are likely to represent, in order of increasing modal equilibrium density, (a) cholinergic nerve endings, characterized by their high content of acetylcholine, (b) gamma-amino butyric acid (GABA)-containing nerve endings with high glutamate decarboxylase activity and the ability to accumulate exogenous GABA, (c) adrenergic nerve endings that accumulate exogenous dopamine and noradrenaline and exhibit high monoamine oxidase activity.

Acetylcholine↗
PubMedDate not supplied

Differences in isolated mitochondria are insufficient to account for respiratory depression during diapause in artemia franciscana embryos.

In response to cues signifying the approach of winter, adult Artemia franciscana produce encysted embryos that enter diapause. We show that respiration rates of diapause embryos collected from the field (Great Salt Lake, Utah) are reduced up to 92% compared with postdiapause embryos when measured under conditions of normoxia and full hydration. However, mitochondria isolated from diapause embryos exhibit rates of state 3 and state 4 respiration on pyruvate that are equivalent to those from postdiapause embryos with active metabolism; a reduction in these rates (15%-27%) is measured with succinate for two of three collection years. Respiratory control ratios for diapause mitochondria are comparable to or higher than those from postdiapause embryos. The P : O flux ratios are statistically identical. Our calculations suggest that respiration of intact, postdiapause embryos is operating close to the state 3 oxygen fluxes measured for isolated mitochondria. Cytochrome c oxidase (COX) activity is 53% lower in diapause mitochondria during one collection year; the minimal impact of this COX reduction on mitochondrial respiration appears to be due to the 31% excess COX capacity in A. franciscana mitochondria. Transmission electron micrographs of embryos reveal mitochondria that are well differentiated and structurally similar in both states. As inferred from the similar amounts of mitochondrial protein extractable, tissue contents of mitochondria in diapause and postdiapause embryos are equivalent. Thus, metabolic depression during diapause cannot be fully explained by altered properties of isolated mitochondria. Rather, mechanisms for active inhibition or substrate limitation of mitochondrial metabolism in vivo may be operative.

Animals↗
PubMed1970

The development of glyoxysomes in peanut cotyledons and maize scutella.

The development of glyoxysomes during germination has been studied in isolated peanut (Arachis hypogaea L.) cotyledons and in maize (Zea mays L.) scutella. In peanut cotyledons isocitratase, malate synthetase, and protein associated with the glyoxysomal fraction increase simultaneously from the 3rd to the 8th day of incubation. In scutella of germinating maize seeds the specific activities of isocitratase, malate synthetase, and catalase associated with the glyoxysomes rise until the 4th day of germination and then decline while the total amount of protein present in the fraction stays constant during the first 5 days. If the peanut cotyledons are cultured in 2% glucose, the development of isocitratase and malate synthetase is severely inhibited, but the level of the glyoxysomal protein is not measurably affected.

Arachis↗
PubMed1975

Microbody of methanol-grown yeasts. Localization of catalase and flavin-dependent alcohol oxidase in the isolated microbody.

Profuse appearance of microbodies was observed in the cells of methanol-utilizing yeasts in connection with the enhanced catalase activity. These microbodies were isolated successfully by means of sucrose gradient centrifugation from the methanol-grown cells of Kloeckera sp. no. 2201. Localization of a flavin-dependent alcohol oxidase as well as characteristic microbody enzymes (catalase and D-amino acid oxidase) were ascertained in the isolated microbodies, whereas formaldehyde and formate dehydrogenases were detected in the cytoplasmic region. Localization of catalase in the isolated microbody was also demonstrated by the cytochemical technique with 3,3'-diaminobenzidine.

Alcohol Oxidoreductases↗
PubMed1994

Generation of proton-motive force by an archaeal terminal quinol oxidase from Sulfolobus acidocaldarius.

The terminal quinol oxidase of the cytochrome aa3 type was isolated from the extreme thermoacidophilic archaeon Sulfolobus acidocaldarius. In micellar solution, the enzyme oxidized various quinols and exerted the highest activity with the physiological substrate caldariella quinol. The enzyme was functionally reconstituted into monolayer liposomes composed of archaeal tetraether lipids also derived from S. acidocaldarius. With the electron donor system ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine, the reconstituted enzyme was more active in the archaeal lipids as compared to lipids derived from Escherichia coli at temperatures above 50 degrees C. Due to the low proton permeability of the tetraether lipids, it was possible to generate a steady-state transmembrane electrical potential (delta psi, interior negative), and transmembrane pH gradient (delta pH, interior alkaline) at temperatures up to 70 degrees C. The successful functional reconstitution of the cytochrome aa3-type quinol oxidase from Sulfolobus identifies it as the key energy converter in the respiratory system of this hyperthermophilic archaeon.

Catalysis↗
PubMed2004

Plasmolysis induced by toluene in a cyoB mutant of Pseudomonas putida.

The cyoABCDE gene cluster of Pseudomonas putida DOT-T1E encodes a terminal cytochrome oxidase. A 500-bp 'cyoB' DNA fragment was cloned in pCHESI Omega Km and used to generate a cyoB knock-out mutant in vivo. The mutant strain was not limited in the generation of proton-motif force, although when grown on minimal medium with glucose or citrate, the CyoB mutant exhibited a slight increase in duplication time with respect to the wild-type strain. This effect was even more pronounced when toluene was supplied in the gas phase. In consonance with the negative effect of toluene on the growth was the finding that the CyoB mutant was hypersensitive to sudden 0.3% (v/v) toluene shocks, in contrast with the wild-type strain. This effect was particularly exacerbated in cells that reached the stationary phase. The increased sensitivity to solvents of the CyoB mutant did not appear to be related to the inability of the cells to strengthen the membrane package or to induce the efflux pumps in response to the solvent, but rather to solvent-induced plasmolysis that may be triggered by wrinkles in the cytoplasmic membrane at the poles of the mutant cells, and invagination of the outer membranes, which eventually lead to cell death.

Blotting, Southern↗
PubMed1969

The re-distribution of cytochrome oxidase, noradrenaline and adenosine triphosphate in adrenergic nerves constricted at two points.

1. The experiments correlate certain changes in the ultrastructure of cat hypogastric nerves constricted at two points with the distribution of a mitochondrial enzyme (cytochrome oxidase), noradrenaline (stored in some of the vesicles with an electron dense core, i.e. granular vesicles) and adenosine triphosphate (ATP) (present in noradrenaline storage granules, mitochondria and the soluble fraction of the axon).2. Noradrenaline (NA) and granular vesicles accumulated proximal but not distal to both constrictions. The total amount of NA and the concentration of granular vesicles above the first constriction was greater than that present in a similar piece of normal nerve, indicating that the cell body was continuing to produce the transmitter despite injury to its axon. The granular vesicles proximal to the first constriction were found in swollen or distorted axons and in new axonal outgrowths. It was concluded that the movement of NA in these constricted nerves was only centrifugal in direction.3. Mitochondria and cytochrome oxidase accumulated on both sides of the two constrictions, indicating a bi-directional movement of mitochondria in the damaged axons. The possibility that some of the increase in the cytochrome oxidase could be related to an increase in the number of mitochondria in cells other than neurones is considered.4. The adenosine triphosphate content increased on both sides of the two constrictions. This increase developed more slowly and was less marked than that of the other two substances.5. It was concluded that (a) there was a close correlation between the behaviour of noradrenaline and granular vesicles and between cytochrome oxidase and mitochondria, (b) the dense cored vesicles and the mitochondria moved independently of one another and at different rates after constriction of non-myelinated axons, (c) while some of the changes may be attributed to an obstruction to the free movement of axoplasm others may be due to an active reaction to axonal injury, and (d) localized intraaxonal synthesis of noradrenaline and cytochrome oxidase did not occur between the two constrictions.

Adenosine Triphosphate↗
PubMed1984

Cytochemistry of cytochrome oxidase in the cytoplasmic and intracytoplasmic membranes of Azotobacter vinelandii.

Vegetative cells of Azotobacter vinelandii contain a system of intracytoplasmic membranes in the form of numerous internal vesicles. The three-dimensional morphology of these internal vesicles was established by an examination of stereopair electron micrographs of negatively stained cells. The vesicles assumed a variety of forms ranging from nearly spherical units to short, curved tubules. These structures were found at the periphery of the cytoplasm, subjacent to the cytoplasmic membrane. Large flattened cisternae were also present in some cells. The amount of intracytoplasmic membrane varied widely even among individual cells from the same culture. The total surface area of the intracytoplasmic membranes was greater than that of the cytoplasmic membrane in many cells. To assess the possible association of cytochrome oxidase activity with the intracytoplasmic membranes, enzyme localization experiments were conducted with the cytochemical substrate 3,3'-diaminobenzidine. The results showed that a cyanide-sensitive cytochrome oxidase activity is located at the intracytoplasmic membrane. The quantity of cytochrome oxidase activity present in the internal membranes is probably less than that present in the cytoplasmic membrane.

Azotobacter↗
PubMed1987

Subcellular redistribution of lysosomal enzymes during caerulein-induced pancreatitis.

The subcellular distribution of the lysosomal enzymes cathepsin B and D in the pancreas was evaluated in rats infused with saline (control) or a maximal (0.25 microgram . kg-1 . h-1) or a supramaximally stimulating dose (5 micrograms . kg-1 . h-1) of the secretagogue caerulein. The latter results in acute edematous pancreatitis, inhibition of digestive enzyme secretion, and the localization of digestive zymogens in organelles whose fragility has been increased by caerulein infusion [A. Saluja et al. Am. J. Physiol. 249 (gastrointest. Liver Physiol. 12): G702-G710, 1985]. Samples from control animals were found to have 29.9 +/- 1.8% of the cathepsin B activity in the pellet centrifuged at 1,300 g for 15 min (containing primarily zymogen granules) and 54.7 +/- 2.5% in the pellet centrifuged at 12,000 g for 12 min (containing primarily lysosomes and mitochondria). After supramaximal stimulation with caerulein for 3.5 h the pellet centrifuged at 1,300 g for 15 min had 55.1 +/- 2.5%, and the pellet centrifuged at 12,000 g for 12 min had 30.6 +/- 2.0% of cathepsin B activity. This redistribution was time dependent, noted within 1 h of starting caerulein infusion, and maximal after 2.5 h of infusion. Electron microscopic immunolabeling studies revealed localization of cathepsin D in discrete organelles that, in the samples from animals infused with a supramaximally stimulating dose of caerulein, were larger, more abundant, and more concentrated in the pellet centrifuged at 1,300 g for 15 min than in the controls. During infusion with supramaximal doses of caerulein, the cathepsin B-containing organelles were found to become progressively more fragile.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1972

Mitochondrial lesions in reversible erythropoietic depression due to chloramphenicol.

The mechanism underlying the reversible depression of erythropoiesis by chloramphenicol has been investigated in rabbits in which hemolytic anemia had been induced by phenylhydrazine so that the compensatory erythroid hyperplasia would provide a situation where abnormalities in the bone marrow cells reflected predominantly those of erythroid precursors. Maintenance of chloramphenicol in the serum of these animals at concentrations in the order of 15 mug/ml resulted in erythropoietic depression after several days. The onset of this depression corresponded to the development of a cellular respiratory defect in the erythroid precursors which was associated with an abnormality in the composition of the mitochondrial respiratory pathway. The abnormality took the form of a selective depletion of cytochromes a + a(3) and b which can be explained by an inhibitory effect of the antibiotic on their formation by the mitochondrial protein-synthesizing system. The relationship between the mitochondrial lesion and the depression of proliferative activity was further indicated by the correlation between the restoration of the cytochrome deficit and the recovery of erythropoiesis after chloramphenicol administration was ceased. The features of the reversible depression of erythropoiesis corresponded closely to those in man, so that a specific action of chloramphenicol on mitochondrial formation provides a reasonable explanation for this important manifestation of chloramphenicol toxicity.

Anemia, Hemolytic↗
PubMed1995

Effect of light stimulation on the cytochemical localization of cytochrome C oxidase in photoreceptor cells of cichlid fish.

Cytochrome oxidase activity was evaluated cytochemically in rod photoreceptor cells in the retina of the cichlid fish Oreochromis mossambicus after different stimulation protocols. The enzyme activity was assessed semiquantitatively by estimating the volume ratio of mitochondria classified according to the intensity of enzyme reactivity. Dark adaptation for 5 hr induced an increase of cytochrome oxidase activity both in vivo and in vitro, i.e., in isolated retinas. Short-term illumination (1 hr) of isolated retinas adapted previously in vivo to darkness caused a significant decrease of enzyme activity, whereas short-term darkening after in vivo light adaptation had no effect. Chemical stimulation for 15 min with increased K+ concentration (20 mM) reduced the enzyme activity, i.e., chemical depolarization did not have the same effect as depolarization induced by darkening. Significant changes in cytochrome oxidase activity were apparent within 1 hr of stimulation, so that this method for analysis of neuronal activity can be applied even in short-term experiments.

Animals↗