ROLE OF THE ERYTHROCYTES IN TRANSPORT AND METABOLISM OF 4-14C-CORTISOL

1961 ◽  
Vol 37 (3) ◽  
pp. 348-352 ◽  
Author(s):  
A. Vermeulen
Keyword(s):  
Half Life ◽  
Red Cells ◽  
Total Blood ◽  
Biological Half Life ◽  
Blood Radioactivity

ABSTRACT After infusion of 4-14C-cortisol, radioactivity associated with red cells amounts to 16 – 37 % of total blood radioactivity and its biological half life is similar to the half life of plasma radioactivity. Cortisol is not metabolized by erythrocytes in vitro. Our data suggest that the corticoids are adsorbed at the red cells surface.

Gastroretentive System of Fluvastatin Sodium by Using Natural Mucilage and Synthetic Polymer

2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Umamaheswara G. ◽  
Anudeep D.
Keyword(s):  
Half Life ◽  
Release Kinetics ◽  
Kinetic Studies ◽  
Diffusion Path ◽  
Synthetic Polymer ◽  
In Vitro Dissolution ◽  
Direct Compression ◽  
Drug Content ◽  
Biological Half Life

Fluvastatin sodium is a novel compound used as cholesterol lowering agent which acts through the inhibition of 3- hydroxyl-3- methyl glutaryl- coenzyme A (HMG-Co A) reductase. It has short biological half life (1-3h) in humans required a dosing frequency of 20 to 40mg twice a day. Due to its short variable biological half life it has been developed to a sustained gastroretentive system with a natural and synthetic polymer and to study how far the natural mucilage improves the sustained activity. Floating tablets were prepared by direct compression method using in combination of natural mucilage and synthetic polymer. Prior to the preparation of tablets the physical mixtures were subjected to FT IR studies and pre compression parameters. After preparation of tablets they were subjected to various tests like swollen index, drug content, In vitro dissolution and release kinetics with pcp disso software etc. The tablets prepared by direct compression shown good in thickness, hardness and uniformity in drug content, the prepared tablets floated more than 12h except FS1 and FS2 shows 9 and 11h. Swollen index studies shows with increase in concentration of polymer the swelling increases the diffusion path length by which the drug molecule may have to travel and cause lag time. In vitro results shows that on increasing the amount of hibiscus polymer the sustain activity is increased because of its integrity and forms a thick swollen mass and reduces the erosion property of the HypromelloseK100M, kinetic studies shows that FS 1, FS2, FS3 followed the Korsmeyer peppas model and the rest FS 4, FS 5, FS6 follows the zero order respectively. Based on n value indicating that the drug release followed super case II transport mechanism due to the erosion of the polymer.

Myocardial CO2 buffering: role of transmembrane transport of H+ or HCO3-ions

1976 ◽  
Vol 230 (4) ◽  
pp. 1037-1041 ◽  
Author(s):  
DR Strome ◽  
RL Clancy ◽  
NC Gonzalez
Keyword(s):  
Small Volume ◽  
Coronary Circulation ◽  
Myocardial Cell ◽  
Ringer Solution ◽  
Red Cells ◽  
Transmembrane Transport ◽  
High Degree

Isolated rabbit hearts were perfused with rabbit red cells suspended in Ringer solution. A small volume of perfusate was recirculated for 10 min at Pco2 of 33.4 +/- 0.9 or 150.8 +/- 7.5 mmHg. Hypercapnia resulted in an increase in perfusate HCO3- concentration that was smaller than that observed when isolated perfusate was equilibrated in vitro with the same CO2 tensions (delta HCO-3e = 1.6 mM, P less than 0.01). This difference is consistent with a net movement of HCO3- into or H+ out of the mycardial cell, and cannot be accounted for by dilution of HCO3- in the myocardial interstitium. Recirculation of perfusate through the coronary circulation at normal Pco2 for two consecutive 10-min periods was not followed by changes in perfusate HCO3- concentration. A high degree of correlation (r = 0.81) was observed between intracellular HCO-3e concentration and the corresponding delta HCO-3e in individual experiments. The results suggest that transmembrane exchange of H+ or HCO3- is a buffer mechanism for CO2 in the myocardial cell.

scholarly journals The Role of Red Cell Energy Metabolism in the Generation of Irreversibly Sickled Cells In Vitro

Blood ◽  
1973 ◽  
Vol 42 (6) ◽  
pp. 835-842 ◽  
Author(s):  
Michael Jensen ◽  
Stephen B. Shohet ◽  
David G. Nathan
Keyword(s):  
Energy Metabolism ◽  
Calcium Metabolism ◽  
Red Cells ◽  
Red Cell ◽  
Hemoglobin S ◽  
Cell Energy ◽  
Incubation Buffer ◽  
Membrane Defect

Abstract An acquired membrane defect is believed to be responsible for the maintenance of the sickled shape in oxygenated irreversibly sickled cells (ISC), because the hemoglobin S in these cells is not in the aggregated, "sickled" state. In the present study, it is demonstrated that the acquisition of the membrane defect in vitro depends on cellular metabolism. Only if cellular ATP is almost completely depleted while the cells are sickled, do they become unable to resume the biconcave disk shape upon reoxygenation. If calcium is omitted from the incubation buffer, ISCs are not generated despite metabolic depletion. This suggests an action of ATP mediated through calcium metabolism similar to that which prevents membrane stiffening in normal red cells. No ISCs were produced by repeated sickling and unsickling. Thus, a membrane alteration occurring as a consequence of metabolic depletion seems to be a more important factor in the generation of ISC than sickling-unsickling induced fragmentation.

EFFECT OF LITHIUM ON DEIODINATING ACTIVITY OF VARIOUS RAT TISSUES IN VITRO

1974 ◽  
Vol 76 (2) ◽  
pp. 260-272 ◽  
Author(s):  
P. T. Männistö
Keyword(s):  
Amino Acids ◽  
Lithium Chloride ◽  
Half Life ◽  
Rat Tissues ◽  
Biological Half Life ◽  
Liver And Kidney ◽  
Licl Treatment

ABSTRACT The effect of lithium chloride (LiCl) on the deiodination of iodotyrosines, on the degradation of 125I-L-thyroxine (125I-L-T4) in vitro and on the disappearance of exogenous 125I-L4 and 125I-rat-TSH in vivo was studied in rats. Iodotyrosine deiodination was studied in vitro with three techniques. The whole thyroid lobes were not satisfactory as substrate. When a diluted mixture of prelabelled iodo-amino acids was used as substrate, thyroid homogenates deiodinated iodotyrosines. The reaction was inhibited by boiling and by 3,5-dinitro-L-tyrosine (DNT), but LiCl (2 × 10−2 m) had no effect. When 125I-3-iodo-L-tyrosine (125I-L-MIT) served as substrate, increasing concentrations of thyroid homogenates showed an increasing deicdinating activity, which was stimulated by NADP (1.5 × 10−4 m). Inhibitors of dehalogenase DNT (10−4 and 10 −3 m) and menandione (10−4 m) inhibited deiodination, but LiCl (5×10−3 − 0.1 m) was again without effect. The degradation of 125I-L-T4 by liver and kidney homogenates was inhibited by LiCl (5 × 10−3 − 0.1 m). The disappearance of 125I-L-T4 was studied in rats treated with LiCl for 1 – 4 or 60 – 64 days in vivo. The half-lives were as follows: at 1 –4 days, the control rats 15.9 ± 1.3 h and the LiCl treated rats 19.1 ± 2.1 h (P < 0.05) and at 60 – 64 days 11.2 ± 2.0 h and 66.8 ± 12.3 h (P < respectively. The prolonged half-life in the LiCl treated rats was not due to the decreased excretion of radioactivity in the urine or faeces. The biological half-life of 125I-rat-TSH (11.4 ± 3.2 min) was not modified by LiCl treatment for 5 days. It can be concluded that the antithyroid effect of LiCl neither originates from the inhibition of iodotyrosine deiodination nor from the change in the half-life of TSH. The half-life of thyroxine is prolonged by LiCl, an effect which is perhaps due to the decreased degradation of thyroxine by tissues.

A Dictyostelium prespore-specific gene is transcriptionally repressed by DIF in vitro

Development ◽  
1988 ◽  
Vol 103 (3) ◽  
pp. 519-524 ◽  
Author(s):  
A.E. Early ◽  
J.G. Williams
Keyword(s):  
Half Life ◽  
Stalk Cell ◽  
Specific Gene ◽  
Transcriptional Level ◽  
Mrna Half Life ◽  
Spore Cell ◽  
Transcriptional Controls

One important role of DIF, the stalk cell-specific inducer of Dictyostelium, may be to divert cells from the spore cell pathway of differentiation. The D19 gene encodes an mRNA which is highly enriched in prespore over prestalk cells in the migratory slug. We show, using a mutant defective in DIF accumulation, that the concentration of D19, and several other prespore mRNA sequences, decreases in the presence of exogenous DIF. There is evidence that both transcriptional and post-transcriptional controls operate to regulate expression of these genes. We have performed in vitro nuclear transcription and mRNA half-life analyses, and find that DIF acts at the transcriptional level to repress the accumulation of the D19 mRNA.

scholarly journals cdk1- and cdk2-Mediated Phosphorylation of MyoD Ser200 in Growing C2 Myoblasts: Role in Modulating MyoD Half-Life and Myogenic Activity

1999 ◽  
Vol 19 (4) ◽  
pp. 3167-3176 ◽  
Author(s):  
Magali Kitzmann ◽  
Marie Vandromme ◽  
Valerie Schaeffer ◽  
Gilles Carnac ◽  
Jean-Claude Labbé ◽  
...  
Keyword(s):  
Half Life ◽  
Site Directed Mutagenesis ◽  
Cyclin B ◽  
Wild Type ◽  
E Box ◽  
Integral Role ◽  
Phosphopeptide Mapping

ABSTRACT We have examined the role of protein phosphorylation in the modulation of the key muscle-specific transcription factor MyoD. We show that MyoD is highly phosphorylated in growing myoblasts and undergoes substantial dephosphorylation during differentiation. MyoD can be efficiently phosphorylated in vitro by either purified cdk1-cyclin B or cdk1 and cdk2 immunoprecipitated from proliferative myoblasts. Comparative two-dimensional tryptic phosphopeptide mapping combined with site-directed mutagenesis revealed that cdk1 and cdk2 phosphorylate MyoD on serine 200 in proliferative myoblasts. In addition, when the seven proline-directed sites in MyoD were individually mutated, only substitution of serine 200 to a nonphosphorylatable alanine (MyoD-Ala200) abolished the slower-migrating hyperphosphorylated form of MyoD, seen either in vitro after phosphorylation by cdk1-cyclin B or in vivo following overexpression in 10T1/2 cells. The MyoD-Ala200 mutant displayed activity threefold higher than that of wild-type MyoD in transactivation of an E-box-dependent reporter gene and promoted markedly enhanced myogenic conversion and fusion of 10T1/2 fibroblasts into muscle cells. In addition, the half-life of MyoD-Ala200 protein was longer than that of wild-type MyoD, substantiating a role of Ser200 phosphorylation in regulating MyoD turnover in proliferative myoblasts. Taken together, our data show that direct phosphorylation of MyoD Ser200 by cdk1 and cdk2 plays an integral role in compromising MyoD activity during myoblast proliferation.

In vitro Production of ‘Glomerular Red Cells’: Role of pH and Osmolality

Nephron ◽  
1990 ◽  
Vol 56 (1) ◽  
pp. 13-18 ◽  
Author(s):  
V.A. Briner ◽  
W.H. Reinhart
Keyword(s):  
Red Cells ◽  
In Vitro Production ◽  
Vitro Production

Possible role of the erythrocyte in causing prolonged cerebral vasospasm

1979 ◽  
Vol 51 (6) ◽  
pp. 773-778 ◽  
Author(s):  
Nobuyuki Ozaki ◽  
Sean Mullan
Keyword(s):  
Cerebral Vasospasm ◽  
Contractile Activity ◽  
Platelet Rich Plasma ◽  
Red Cells ◽  
Significant Activity ◽  
Sephadex Column ◽  
Content Type ◽  
Canine Basilar Artery

✓ Contractile activity of the various fractions of fresh and incubated blood was studied in vitro using the isolated canine basilar artery. Of the various fractions of fresh blood, significant contraction was induced by serum, but moderate contraction was induced by platelet-rich plasma and lysed red cells, while intact red cells and platelet-poor plasma had no significant activity. The contractions induced by serum and platelet-rich plasma were blocked by phenoxybenzamine, while those induced by lysed red cells were not. Whereas serum and platelet-rich plasma lost their contractile activity after 24 hours of incubation, lysed red cells retained activity up to 7 days after incubation. Biochemical analysis of the hemolysate by means of Sephadex column chromatography revealed that the contractile substance(s) possessed a molecular weight above 5000. These results suggest the possibility that the above substance(s) may play a role in prolonged cerebral vasospasm.

scholarly journals Discrepancies in the in vitro and in vivo role of scavenger receptors in clearance of nanoparticles by Kupffer cells

2018 ◽  
Vol 1 (1) ◽  
pp. 76-84 ◽  
Author(s):  
Guankui Wang ◽  
Ernest Groman ◽  
Dmitri Simberg
Keyword(s):  
Kupffer Cells ◽  
Half Life ◽  
Scavenger Receptor ◽  
Superparamagnetic Iron Oxide ◽  
Macrophage Scavenger Receptor ◽  
Polyinosinic Acid ◽  
Efficient Uptake

Nanoparticles are recognized and cleared by Kupffer cells (KCs) in the liver. This process complicates the development of targeted nanoparticles because of significant reduction of number of nanoparticles that can reach target tissues. Macrophage scavenger receptor SR type AI/II is the central phagocytic receptor that has been shown to promote in vitro uptake of many nanoparticle types. In this paper, the authors set out to clarify the role of SR-AI/II in the in vivo liver clearance of 10kDa dextran superparamagnetic iron oxide (SPIO) Feridex-IV® and 20kDa dextran-coated SPIO nanoworms (SPIO NWs). Feridex showed efficient SR-AI/II-dependent uptake by isolated KCs in vitro, whereas SPIO NWs showed no uptake by KCs. Both Feridex and SPIO NWs showed a very short and nearly identical circulation half-life and efficient uptake by KCs in vivo. The SR-AI/II inhibitor, polyinosinic acid, prolonged the circulation half-life of both Feridex and SPIO NWs, but did not reduce the KC uptake. The circulation half-life and KC uptake of Feridex and SPIO NWs were identical in SR-AI/II-deficient mice and wild-type mice. These data suggest: (1) there is a limited correlation between in vitro and in vivo uptake mechanisms of nanoparticles in KCs; and (2) redundant, SR-AI/II independent mechanisms play a significant role in the nanoparticle recognition by KCs in vivo. Understanding the complexity of nanoparticle clearance assays and mechanisms is an important step to improving the design of “stealthy” nanoparticles.

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