scholarly journals In vitro release of physically separable factors from monocytes that exert opposing effects on erythropoiesis

Blood ◽  
1986 ◽  
Vol 67 (5) ◽  
pp. 1454-1459 ◽  
Author(s):  
L Feldman ◽  
CM Cohen ◽  
N Dainiak
Keyword(s):  
Plasma Membrane ◽  
Membrane Vesicle ◽  
In Vitro Release ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Wide Range ◽  
Dose Dependent Fashion ◽  
Membrane Bound ◽  
Opposing Effects

Abstract In order to investigate the capacity of monocytes to release erythroid burst-promoting activity (BPA), we added media conditioned by homologous monocytes to both serum-free human and serum-restricted murine marrow culture. We found that soluble, membrane vesicle-free culture medium is a potent source of the growth factor. On the other hand, monocyte membranes or exfoliated plasma membrane vesicles elaborate a factor that inhibits erythroid burst formation by up to 100%. Inhibitory activity is expressed in a dose-dependent fashion over a wide range of concentrations (0.001 to 10 micrograms/mL) tested. Experiments with antilymphocyte plasma membrane IgG, which has been shown to neutralize both soluble and membrane-bound lymphocyte-derived BPA in human marrow culture, indicate that the expression of soluble BPA by monocytes is unaffected by these antibodies. Furthermore, while antimembrane IgG is capable of absorbing BPA from LCM supernatants, these antibodies are ineffective in removing BPA from MCM supernatants, suggesting that these two soluble growth factors may be antigenically distinct. Our findings indicate that while monocytes release soluble BPA, they are also a source of membrane-associated factors that exert inhibitory effects on erythropoiesis in vitro.

scholarly journals In vitro release of physically separable factors from monocytes that exert opposing effects on erythropoiesis

Blood ◽  
1986 ◽  
Vol 67 (5) ◽  
pp. 1454-1459
Author(s):  
L Feldman ◽  
CM Cohen ◽  
N Dainiak
Keyword(s):  
Plasma Membrane ◽  
Membrane Vesicle ◽  
In Vitro Release ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Wide Range ◽  
Dose Dependent Fashion ◽  
Membrane Bound ◽  
Opposing Effects

In order to investigate the capacity of monocytes to release erythroid burst-promoting activity (BPA), we added media conditioned by homologous monocytes to both serum-free human and serum-restricted murine marrow culture. We found that soluble, membrane vesicle-free culture medium is a potent source of the growth factor. On the other hand, monocyte membranes or exfoliated plasma membrane vesicles elaborate a factor that inhibits erythroid burst formation by up to 100%. Inhibitory activity is expressed in a dose-dependent fashion over a wide range of concentrations (0.001 to 10 micrograms/mL) tested. Experiments with antilymphocyte plasma membrane IgG, which has been shown to neutralize both soluble and membrane-bound lymphocyte-derived BPA in human marrow culture, indicate that the expression of soluble BPA by monocytes is unaffected by these antibodies. Furthermore, while antimembrane IgG is capable of absorbing BPA from LCM supernatants, these antibodies are ineffective in removing BPA from MCM supernatants, suggesting that these two soluble growth factors may be antigenically distinct. Our findings indicate that while monocytes release soluble BPA, they are also a source of membrane-associated factors that exert inhibitory effects on erythropoiesis in vitro.

The iodide channel of the thyroid: a plasma membrane vesicle study

1992 ◽  
Vol 263 (3) ◽  
pp. C590-C597 ◽  
Author(s):  
P. Golstein ◽  
M. Abramow ◽  
J. E. Dumont ◽  
R. Beauwens
Keyword(s):  
Plasma Membrane ◽  
Chloride Transport ◽  
Membrane Vesicle ◽  
Membrane Vesicles ◽  
Anion Channel ◽  
Apical Plasma Membrane ◽  
Plasma Membrane Vesicle ◽  
Plasma Membrane Vesicles ◽  
Bovine Thyroid ◽  
Set Up

The uptake of radioactive iodide or chloride by plasma membrane vesicles of bovine thyroid was studied by a rapid filtration technique. A Na(+)-I- cotransport was demonstrated. When this Na(+)-I- cotransport is inactive (i.e., at 4 degrees C and in the absence of Na+), an uptake of iodide above chemical equilibrium could be induced, driven by the membrane potential. The latter was set up by allowing potassium to diffuse into the membrane vesicles in the presence of valinomycin and of an inward K+ gradient. This potential difference (positive inside) induced the uptake of iodide (or other anion present). The data support the existence of two anionic channels. The first one, observed at low near-physiological iodide concentration (micromolar range), which exhibits a high permeability and specificity for iodide (hence called the iodide channel), has a Km of 70 microM. The other one appears similar to the epithelial anion channel as described by Landry et al. (J. Gen. Physiol. 90: 779-798, 1987); it is still about fourfold more permeable to iodide than to chloride and presents a Km of 33 mM. Under physiological conditions the latter channel would mediate chloride transport, and the iodide channel, which is proposed to be restricted to the apical plasma membrane domain of the thyrocyte, transports iodide from the cytosol to the colloid space.

Alanine uptake by liver at midpregnancy in rats

1987 ◽  
Vol 252 (3) ◽  
pp. E408-E413 ◽  
Author(s):  
M. Pastor-Anglada ◽  
X. Remesar ◽  
G. Bourdel
Keyword(s):  
Plasma Membrane ◽  
Active Transport ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Pregnant Rats ◽  
Dependent Transport

The participation of the liver to the increase in alanine utilization seen at midpregnancy was studied in 9- and 12-day pregnant rats. Liver fractional extraction of alanine was assessed in vivo from the changes in concentration in afferent and efferent vessels. Hepatic active transport of alanine was determined in vitro using isolated plasma-membrane vesicles. Compared with nonpregnant controls, alanine fractional extraction was significantly increased on day 12 but not on day 9 of pregnancy. Vesicles isolated from 9- and 12-day pregnant animals had a greater capacity for Na+-dependent transport than those from controls. Eadie-Hofstee plotting showed that this increase was due to an increase in Vmax with no change in Km. Both A and ASC systems contributed to the Vmax increase. These results indicate that, although by day 9 the liver has developed an increased capacity for alanine uptake, the actual extraction is seen only by day 12 of pregnancy. At this stage the liver participates actively in the turnover of alanine and the development of hypoalaninemia.

scholarly journals Rat ovarian lutropin receptor is a transmembrane protein. Evidence for an Mr-20,000 cytoplasmic domain

1986 ◽  
Vol 239 (1) ◽  
pp. 83-87 ◽  
Author(s):  
K P Keinänen ◽  
H J Rajaniemi
Keyword(s):  
Plasma Membrane ◽  
Transmembrane Protein ◽  
Membrane Vesicles ◽  
Cytoplasmic Domain ◽  
Proteolytic Digestion ◽  
Plasma Membrane Vesicles ◽  
Human Choriogonadotropin ◽  
Lutropin Receptor ◽  
Membrane Bound ◽  
Inside Out

Membrane topography of the rat ovarian lutropin receptor was studied by two different approaches. Ovarian membrane preparation, labelled with 125I-labelled human choriogonadotropin in vivo, was subjected to extensive chymotryptic digestion. The soluble and membrane-bound radioactive complexes were cross-linked with glutaraldehyde, and analysed by SDS/polyacrylamide-gel electrophoresis and autoradiography. Chymotrypsin solubilized 70-75% of the radioactivity as Mr-96,000, Mr-74,000 and Mr-61,000 complexes, and decreased the size of the membrane-bound 125I-labelled human choriogonadotropin-receptor complex from Mr 130,000 to Mr 110,000. The Mr-110,000 complex was not observed when 0.1% Triton X-100 was present in the proteolytic digestion. Enrichment of inside-out-oriented plasma-membrane vesicles by concanavalin A affinity chromatography increased by 70% the fraction of radioactivity that remained in the membrane fraction after chymotrypsin treatment. Chymotrypsin also diminished the size of the membrane-bound unoccupied receptor from Mr 90,000 to Mr 70,000, as detected by ligand (125I-labelled human choriogonadotropin) blotting. These results suggest that the lutropin receptor is a transmembrane protein with a cytoplasmic domain of Mr 20,000 that is sensitive to proteolytic digestion in the inside-out-oriented plasma-membrane vesicles.

scholarly journals 131 PEROXIDATIVE CHALLENGE OF PLASMA MEMBRANE VESICLES FROM BELL PEPPER FRUIT LEADS TO DECREASED H+ATPase ACTIVITY

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 447c-447
Author(s):  
Darlene M. Cowart ◽  
Robert L. Shewfelt
Keyword(s):  
Plasma Membrane ◽  
Atpase Activity ◽  
Fruits And Vegetables ◽  
Chilling Injury ◽  
Membrane Vesicles ◽  
Thiobarbituric Acid ◽  
Plasma Membrane Vesicles ◽  
Water Control ◽  
Solubilized Enzyme

-Lipid peroxidation has been proposed as an important factor in chilling injury of susceptible fruits and vegetables. The effect of in vitro peroxidative challenge on H+ATPase activity in intact plasma membrane vesicles and solubilized enzyme was determined by incubation with (1) deionized water (control), (2) Fe3+-ascorbate, and (3) lipoxygenase (LOX) + phospholipase A2(PLA2) for 0, 30, and 60 min. Enzyme activity increased throughout the incubation period with no accumulation of thiobarbituric acid-reactive substances (TBA-RS) in the control, but vesicles challenged by the peroxidative systems showed significant increases in TBA-RS and decreases in membrane-bound H+ATPase activity. Greater losses in H+ATPase activity were observed in solubilized enzyme than in intact vesicles. The results indicate that loss of H+ATPase activity due to chemical modification of the protein rather than changes in membrane fluidity and suggest that modification is away from the active site.

Inhibition of Maize (Zea mays L.) Root Plasma Membrane-Bound Redox Activities by Coumarins

1994 ◽  
Vol 49 (7-8) ◽  
pp. 447-452 ◽  
Author(s):  
Sabine Lüthje ◽  
José A. Gonzaléz-Reyes ◽  
Placido Navas ◽  
Olaf Döring ◽  
Michael Böttger
Keyword(s):  
Zea Mays ◽  
Plasma Membrane ◽  
Zea Mays L ◽  
Membrane Vesicles ◽  
Dependent Manner ◽  
Plasma Membrane Vesicles ◽  
Two Phase ◽  
Concentration Dependent Manner ◽  
Oxidoreductase Activity ◽  
Membrane Bound

Modulation of plasma membrane-bound NADH:hexacyanoferrate III oxidoreductase activities by dicumarol and warfarin was investigated with plasma membrane vesicles of Zea mays L. (cv. Sil Anjou 18) roots, prepared by aqueous two phase partitioning. Vesicles were about 65% right-side out orientated as demonstrated by enzyme latency of vanadate sensitive ATPase activity. Dicumarol or warfarin, respectively, inhibited NADH:hexacyanoferrate III oxidoreductase activity in a concentration-dependent manner and inhibition could be reversed partially by addition of quinones

Differences in L-alanine uptake by livers of Wistar and lean Zucker rats

1991 ◽  
Vol 11 (2) ◽  
pp. 85-93
Author(s):  
B. Ruiz ◽  
J. Casado ◽  
M. Pastor-Anglada ◽  
A. Felipe
Keyword(s):  
Plasma Membrane ◽  
Wistar Rats ◽  
Membrane Vesicles ◽  
Hepatic Uptake ◽  
Zucker Rats ◽  
Plasma Membrane Vesicles ◽  
Blood Flows ◽  
Old Rats ◽  
Lower Capacity

The L-alanine uptake by livers of Wistar and lean Zucker rats has been studied. The hepatic uptake and fractional extraction rates of alanine were estimated in 50–55 day old rats. No significant differences in amino acid concentrations and blood flows in afferent and efferent liver vessels were seen in lean Zucker rats when compared with Wistar rats. However, the hepatic uptake (1.6±0.1 and 0.7±0.1 μmol/min/100 g bw, p<0.01) and the fractional extraction (26.8±2.1 and 15.2±3.1%, p<0.05) were much lower in Zucker than in Wistar rats. The hepatic active transport of L-alanine was determined in vitro using isolated plasma membrane vesicles. Vesicles isolated from livers of lean Zucker rats showed similar values of Km (2.5±0.7 vs 2.0±0.5 mM for Wistar and Zucker respectively, N.S.), but lower values of Vmax when compared with Wistar rats (1.1±0.1 vs 0.6±0.005 nmol/mg prot 5 s, p<0.01, for Wistar and lean Zucker rats respectively). These results indicate that, the liver of lean Zucker rats concentrates alanine less efficiently than the liver of Wistar rats. This fact correlates well with a lower capacity of the Na+-dependent L-alanine trasport in liver plasma membrane vesicles from lean Zucker rats.

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