Endocytosis of Polypeptides in Rabbit Nasal Respiratory Mucosa

Physiology ◽  
1997 ◽  
Vol 12 (5) ◽  
pp. 219-225 ◽  
Author(s):  
D Cremaschi ◽  
C Porta ◽  
R Ghirardelli
Keyword(s):  
Vesicle Fusion ◽  
Metabolic Inhibitors ◽  
Receptor Recycling ◽  
Respiratory Mucosa ◽  
Saturation Kinetics ◽  
Leaky Epithelium

The nasal respiratory mucosa of the rabbit has a leaky epithelium actively transporting polypeptides by a specific transcytosis probably involved in sampling antigens. The transfer displays saturation kinetics and is abolished by metabolic inhibitors, actin filamet and microtubule disassemblers, inhibitors of vesicle fusion, and receptor recycling;it accepts polypeptide-covered but not uncovered nanoparticles.

Copper transport kinetics by isolated rat hepatocytes

1983 ◽  
Vol 244 (2) ◽  
pp. G183-G191 ◽  
Author(s):  
R. C. Schmitt ◽  
H. M. Darwish ◽  
J. C. Cheney ◽  
M. J. Ettinger
Keyword(s):  
Trace Metals ◽  
Specific Inhibitor ◽  
Rat Hepatocytes ◽  
Competitive Inhibitor ◽  
Metabolic Inhibitors ◽  
Rapid Phase ◽  
Isolated Rat Hepatocytes ◽  
Simple Diffusion ◽  
Saturation Kinetics ◽  
Parenchymal Cells

Uptake and efflux of 64Cu were examined to determine whether hepatic parenchymal cells exhibit the kinetic criteria of a specific transport system for copper and related trace metals. Saturation kinetics were clearly indicated by both v versus [Cu] and 1/v versus 1/[Cu] plots (Km = 11 +/- 0.6 microM and Vmax = 2.7 nmol Cu X min-1 X mg prot-1). Identical results were obtained by cold-copper analyses, and contributions from simple diffusion or nonspecific binding were not detected. Virtually all of the accumulated 64Cu was intracellular by 0.5 min (the initial velocity period), with approximately 40% in the cytosolic fraction. Several related trace metals inhibited 64Cu uptake, but Ni(II) at a 10:1 molar excess did not. Zn(II) acted as a simple competitive inhibitor of 64Cu uptake (Ki = 16 microM). Efflux from preloaded cells was biphasic, with an initial rapid phase of approximately 5 min. Approximately 35% of preloaded 64Cu was transported out of the cells by 40 min, and little efflux occurred thereafter. Thus, hepatocytes exhibit saturation kinetics, competition by related substrates, and countertransport criteria of specific facilitated transport. A wide variety of metabolic inhibitors have no effect on 64Cu uptake under the same conditions that inhibit the active transport of bile acids. Specific inhibitor tests for electrogenic coupling were also negative. Because the identical kinetic parameters were obtained for free 64Cu and the 1:1 64Cu-histidine complex, it is inferred that copper is probably transported as the free ion. Cells incubated with greater than or equal to 10 microM 64Cu showed a net loss of copper after 40- to 60-min incubation, which may involve specific hepatic mechanisms in copper homeostasis.

scholarly journals Transporter-Mediated Uptake of 2-Chloro- and 2-Hydroxybenzoate by Pseudomonas huttiensis Strain D1

2003 ◽  
Vol 69 (12) ◽  
pp. 7401-7408 ◽  
Author(s):  
A. S. Yuroff ◽  
G. Sabat ◽  
W. J. Hickey
Keyword(s):  
Atp Hydrolysis ◽  
Maximum Velocity ◽  
Screening Tests ◽  
Metabolic Inhibitors ◽  
Atp Binding ◽  
Substrate Uptake ◽  
Intracellular Accumulation ◽  
Saturation Kinetics ◽  
Substrate Saturation ◽  
Catabolic Enzyme

ABSTRACT We investigated the mechanisms of uptake of 2-chlorobenzoate (2-CBa) and 2-hydroxybenzoate (2-HBa) by Pseudomonas huttiensis strain D1. Uptake was monitored by assaying intracellular accumulation of 2-[UL-ring-14C]CBa and 2-[UL-ring-14C]HBa. Uptake of 2-CBa showed substrate saturation kinetics with an apparent Km of 12.7 ± 2.6 μM and a maximum velocity (V max) of 9.76 ± 0.78 nmol min−1 mg of protein−1. Enhanced rates of uptake were induced by growth on 2-CBa and 2-HBa, but not by growth on benzoate or 2,5-di-CBa. Intracellular accumulations of 2-CBa and 2-HBa were 109- and 42-fold greater, respectively, than the extracellular concentrations of these substrates and were indicative of uptake mediated by a transporter rather than driven by substrate catabolism (“metabolic drag”). Results of competitor screening tests indicated that the substrate range of the transporter did not include other o-halobenzoates that serve as growth substrates for strain D1 and for which the metabolism was initiated by the same dioxygenase as 2-CBa and 2-HBa. This suggested that multiple mechanisms for substrate uptake were coupled to the same catabolic enzyme. The preponderance of evidence from tests with metabolic inhibitors and artificial electrochemical gradients suggested that 2-CBa uptake was driven by ATP hydrolysis. If so, the 2-CBa transporter would be the first of the ATP binding cassette type implicated in uptake of haloaromatic acids.

Copper efflux kinetics from rat hepatocytes

1984 ◽  
Vol 246 (1) ◽  
pp. G48-G55
Author(s):  
H. M. Darwish ◽  
R. C. Schmitt ◽  
J. C. Cheney ◽  
M. J. Ettinger
Keyword(s):  
Transport System ◽  
Rat Hepatocytes ◽  
Intracellular Concentration ◽  
Metabolic Inhibitors ◽  
Rate Data ◽  
Extracellular Medium ◽  
Saturation Kinetics ◽  
Intracellular Binding ◽  
Efflux Kinetics ◽  
Kinetics Of

The kinetics of copper efflux from rat hepatocytes were determined to further characterize the hepatic Cu(II) transport system. Efflux was biphasic. Net efflux was rapid for 1-5 min, and 35-45% of preloaded copper was lost by 40 min. Efflux was negligible after 40 min. The retained percentage was independent of the preloading concentration, but the total amount of intracellular copper that was available for efflux gradually decreased as the duration of the preloading period increased. Unlabeled extracellular Cu(II) displaced 64Cu from intracellular pools, but exchange with intracellular Cu was not required for uptake. Zinc also displaced copper but less effectively than copper. This implies some specificity in intracellular binding components. No transstimulation of uptake or efflux was detected. Copper efflux was strictly passive. Extracellular Cu(II) decreased the rate of efflux and preloading inhibited Cu(II) uptake. Metabolic inhibitors had no effect on the rate or total amount of 64Cu efflux, and significant efflux occurred at 4 degrees C. Moreover, when a steady state was attained at the end of a preloading period, the effective intracellular concentration of free copper approximated the Cu(II) concentration in the extracellular medium. By use of this estimate for the intracellular concentration of free copper, efflux kinetic parameters were obtained from initial (1-min) rate data (Km = 5.5 +/- 0.8 microM; Vmax = 1.1 +/- 0.1 nmol X min-1 X mg prot-1). These parameters are similar to those obtained for Cu(II) uptake, and the saturation kinetics observed are consistent with specific facilitated efflux by this copper transport system.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption of pantothenic acid in rat and chick intestine

1986 ◽  
Vol 250 (2) ◽  
pp. G155-G160
Author(s):  
D. K. Fenstermacher ◽  
R. C. Rose
Keyword(s):  
Pantothenic Acid ◽  
Potential Gradient ◽  
Metabolic Inhibitors ◽  
Transepithelial Transport ◽  
Simple Diffusion ◽  
Low Concentrations ◽  
Saturation Kinetics ◽  
Sodium Dependent

Pantothenic acid absorption was evaluated in the intestine of rat and chicken to reevaluate the concept that this nutrient crosses the mucosa by simple diffusion. Unidirectional influx of [3H]pantothenic acid (0.9 microM) across the brush-border membrane of rat jejunum in vitro demonstrates sodium dependence and saturation kinetics. Net transepithelial transport (absorption) of pantothenic acid takes place in everted sacs of jejunum against an electrochemical potential gradient. This accumulation does not occur in tissue exposed to metabolic inhibitors. Also, pantothenic acid accumulates in the transport cells of both rat and chicken intestine against a 9- to 10-fold concentration gradient. Recently absorbed pantothenic acid is freely diffusible from isolated chicken enterocytes. No metabolic conversion of pantothenic acid was detected during absorption in the intestine of either species under conditions in vitro or in vivo. The present results indicate that pantothenic acid present at low concentrations is absorbed in the intestine by a specific transport mechanism; the process is best described as sodium-dependent, secondary active transport.

The uptake of L-glutamate by the central nervous system of the cockroach, Periplaneta americana

1975 ◽  
Vol 62 (1) ◽  
pp. 55-67
Author(s):  
PD Evans
Keyword(s):  
Amino Acids ◽  
Nerve Cord ◽  
Periplaneta Americana ◽  
Metabolic Inhibitors ◽  
Uptake Mechanism ◽  
Glutamate Concentration ◽  
Saturation Kinetics ◽  
The Central Nervous System ◽  
Wet Weight ◽  
Kinetics Of

A concentrative uptake mechanism for L-glutamate with the following characteristics has been identified in the abdominal nerve cord: 1. The uptake can be divided into Na+-sensitive and Na-plus-insensitive components. 2. The Na-plus-sensitive component showed the typical saturation kinetics of a carrier mediate process. It had a V of 15.9 x 10(6) times 10(6) muM/mg wet weight/min and a Km of 0-33 mm. Its magnitude was proportional to the first power of the Na-plus concentration of the medium. The uptake was specific for L-dicarboxylic amino acids and was sensitive to the presence of metabolic inhibitors. 3. The Na-plus-insensitive component was linearly related to the glutamate concentration of the medium. An isosmotic saline is described for use with the isolated intact abdominal nerve cord of P. americana.

Absorption of homocitrulline from the gastrointestinal tract

1983 ◽  
Vol 49 (1) ◽  
pp. 35-42 ◽  
Author(s):  
D. F. Evered ◽  
J. V. Vadgama
Keyword(s):  
Small Intestine ◽  
Metabolic Inhibitors ◽  
Rat Small Intestine ◽  
Carrier System ◽  
Milk Products ◽  
Buccal Absorption ◽  
Saturation Kinetics ◽  
In Vivo Absorption

1. Transport ofL-homocitrulline, an amino acid which occurs in milk products, was studied with rat small intestine in vitro and from the human mouth in vivo. Absorption was partially dependent, in both systems, on the presence of sodium ions.2. Metabolic inhibitors decreasedL-homocitrulline uptake across the small intestine. Transport across the intestine did not occur against the concentration gradient but did show saturation kinetics.3. The barbiturate, amytal, did not inhibit buccal absorption. Saturation kinetics were demonstrated.4. Experiments were conducted withL-citrulline, or other amino acids, as possible inhibitors ofL-homocitrulline transport. Results were compatible with Na+-dependent carrier-mediated uptake across the buccal mucosa. Active transport could be involved with the small intestine assuming thatL-homocitrulline has a low affinity for the carrier system.

scholarly journals The uptake and efflux of l-phenylalanine and l-tyrosine from rat brain cerebral cortex slices

1973 ◽  
Vol 136 (1) ◽  
pp. 77-82 ◽  
Author(s):  
Pierre Joanny ◽  
Jean-Pierre Natali ◽  
Harold Hillman ◽  
Jacques Corriol
Keyword(s):  
Amino Acids ◽  
Cerebral Cortex ◽  
Rat Brain ◽  
Active Transport ◽  
Metabolic Inhibitors ◽  
Tissue Water ◽  
Carrier Mechanism ◽  
Saturation Kinetics ◽  
Cortex Slices

The uptake of radioactive l-phenylalanine and l-tyrosine into the tissue water of rat brain cerebral cortex slices was shown to have saturation kinetics. The apparent Km for the uptake of l-phenylalanine was 0.86mm and for l-tyrosine was 1.64mm; for phenylalanine the apparent Vmax. value was 0.64μmol/min per ml of tissue water, and for l-tyrosine it was 0.98μmol/min per ml of tissue water. The accumulation of the two amino acids by the tissue was depressed in the absence of O2, at 0°C, or in the presence of metabolic inhibitors. The influxes and effluxes of both l-isomers were more rapid than those of the d-isomers. Competition between these two amino acids and each with l-tryptophan in respect of uptake into tissue water was shown. Their rates of influx were faster, and rates of efflux were slower, in the presence than in the absence of Na+. It was concluded that these amino acids were taken up by active transport via a carrier mechanism.

Effect of Some Metabolic Inhibitors on Vinblastine-Induced Ribosomal-Granular Material Complexes

1971 ◽  
Vol 29 ◽  
pp. 548-549
Author(s):  
Awtar Krishan ◽  
Dora Hsu
Keyword(s):  
Granular Material ◽  
Rna Synthesis ◽  
Culture Medium ◽  
Actinomycin D ◽  
Metabolic Inhibitors ◽  
Protein And Rna Synthesis ◽  
Apparent Reduction ◽  
Plant Alkaloids ◽  
In Cells

Cells exposed to antitumor plant alkaloids, vinblastine and vincristine sulfate have large proteinacious crystals and complexes of ribosomes, helical polyribosomes and electron-dense granular material (ribosomal complexes) in their cytoplasm, Binding of H3-colchicine by the in vivo crystals shows that they contain microtubular proteins. Association of ribosomal complexes with the crystals suggests that these structures may be interrelated.In the present study cultured human leukemic lymphoblasts (CCRF-CEM), were incubated with protein and RNA-synthesis inhibitors, p. fluorophenylalanine, puromycin, cycloheximide or actinomycin-D before the addition of crystal-inducing doses of vinblastine to the culture medium. None of these compounds could completely prevent the formation of the ribosomal complexes or the crystals. However, in cells pre-incubated with puromycin, cycloheximide, or actinomycin-D, a reduction in the number and size of the ribosomal complexes was seen. Large helical polyribosomes were absent in the ribosomal complexes of cells treated with puromycin, while in cells exposed to cycloheximide, there was an apparent reduction in the number of ribosomes associated with the ribosomal complexes (Fig. 2).

Structural aspects of tracheary element differentiation in suspension cultures of Zinnia elegans

1989 ◽  
Vol 47 ◽  
pp. 768-769
Author(s):  
C. H. Haigler ◽  
A. W. Roberts
Keyword(s):  
Tracheary Element ◽  
Vesicle Fusion ◽  
Zinnia Elegans ◽  
Cellulose Synthesis ◽  
Tracheary Elements ◽  
Animal Cells ◽  
Mesophyll Cells ◽  
Fixation Techniques ◽  
Localized Patterns ◽  
Structural Aspects

Tracheary elements, the water-conducting cells in plants, are characterized by their reinforced walls that became thickened in localized patterns during differentiation (Fig. 1). The synthesis of this localized wall involves abundant secretion of Golgi vesicles that export preformed matrix polysaccharides and putative proteins involved in cellulose synthesis. Since the cells are not growing, some kind of endocytotic process must also occur. Many researchers have commented on where exocytosis occurs in relation to the thickenings (for example, see), but they based their interpretations on chemical fixation techniques that are not likely to provide reliable information about rapid processes such as vesicle fusion. We have used rapid freezing to more accurately assess patterns of vesicle fusion in tracheary elements. We have also determined the localization of calcium, which is known to regulate vesicle fusion in plant and animal cells.Mesophyll cells were obtained from immature first leaves of Zinnia elegans var. Envy (Park Seed Co., Greenwood, S.C.) and cultured as described previously with the following exceptions: (a) concentration of benzylaminopurine in the culture medium was reduced to 0.2 mg/l and myoinositol was eliminated; and (b) 1.75ml cultures were incubated in 22 x 90mm shell vials with 112rpm rotary shaking. Cells that were actively involved in differentiation were harvested and frozen in solidifying Freon as described previously. Fractures occurred preferentially at the cell/planchet interface, which allowed us to find some excellently-preserved cells in the replicas. Other differentiating cells were incubated for 20-30 min in 10(μM CTC (Sigma), an antibiotic that fluoresces in the presence of membrane-sequestered calcium. They were observed in an Olympus BH-2 microscope equipped for epi-fluorescence (violet filter package and additional Zeiss KP560 barrier filter to block chlorophyll autofluorescence).

Effect of in Vivo Oxidized Cellulose on in Vitro Growth of Human Respiratory Mucosa and Sub-mucosa During Endoscopic Skull Base Approaches

2016 ◽  
Vol 77 (S 01) ◽  
Author(s):  
Ezequiel Goldschmidt ◽  
Jorge Rasmussen ◽  
Joseph Chabot ◽  
Monica Loressi ◽  
Marcelo Ielpi ◽  
...  
Keyword(s):  
Skull Base ◽  
Oxidized Cellulose ◽  
In Vitro Growth ◽  
Respiratory Mucosa
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