scholarly journals Assimilation of α-glutamyl-peptides by human erythrocytes. A possible means of glutamate supply for glutathione synthesis

1985 ◽  
Vol 227 (3) ◽  
pp. 833-842 ◽  
Author(s):  
G F King ◽  
P W Kuchel
Keyword(s):  
Spin Echo ◽  
Linear Regression Analysis ◽  
Cell Suspensions ◽  
Human Erythrocytes ◽  
Peptide Hydrolysis ◽  
Whole Cell ◽  
Glutathione Synthesis ◽  
Whole Cells ◽  
Transmembrane Flux ◽  
Spin Echo Sequence

Human erythrocytes are essentially impermeable to glutamate and yet there is a continual requirement for the amino acid for glutathione synthesis. In addition, the intracellular glutamate concentration is approximately five times that of plasma. We present evidence that glutamate enters the red cell as small peptides which are rapidly hydrolysed by cytoplasmic peptidase(s) and that with the estimated physiological levels of plasma glutamyl-peptides the rate of inward flux would be adequate to maintain the glutamate pool at its observed level. Experimentally, we used 1H spin-echo n.m.r. spectroscopy to follow peptide hydrolysis, since peptide spectra are different from those of the free amino acids and the spin-echo sequence enables the monitoring of reactions in concentrated lysates and whole cell suspensions. Thus, the system was studied under near-physiological conditions. Weighted non-linear regression analysis of progress curves using the integrated Michaelis-Menten equation was used to obtain estimates of Km and Vmax. for the hydrolysis of alpha-L-glutamyl-L-alanine and L-alanyl-alpha-L-glutamate in lysates and whole cell suspensions; the values for lysates were Km = 3.60 +/- 0.29 and 5.4 +/- 0.4 mmol/l and Vmax. = 120 +/- 4 and 46.7 +/- 1.7 mmol/h per 1 of packed cells respectively. In whole cell suspensions the rate of peptide hydrolysis was much slower and dominated by the transmembrane flux-rate. The estimates of the steady-state kinetic parameters for the transport were Kt = 2.35 +/- 0.41 and 11.2 +/- 1.0 mmol/l and Vmax. = 3.26 +/- 0.13 and 19.7 +/- 0.7 mmol/h per 1 of packed cells respectively for the previously mentioned peptides. Using the n.m.r. procedure we failed to detect any glutaminase activity in whole cells or lysates; thus, we exclude the possibility that glutamate gains entry to the cell as glutamine which is subsequently hydrolysed by glutaminase.

scholarly journals A proton n.m.r. study of iminodipeptide transport and hydrolysis in the human erythrocyte. Possible physiological roles for the coupled system

1984 ◽  
Vol 220 (2) ◽  
pp. 553-560 ◽  
Author(s):  
G F King ◽  
P W Kuchel
Keyword(s):  
Concentration Dependence ◽  
Transport System ◽  
Human Erythrocytes ◽  
Whole Body ◽  
Differential Rate ◽  
Cell Water ◽  
Peptide Hydrolysis ◽  
Whole Cells ◽  
Progress Curve ◽  
Hydrolysis Of

The first description of a saturable iminodipeptide transport system present in human erythrocytes is given. The 1H-n.m.r. spectra of glycyl-L-proline and those of free glycine and L-proline are significantly different. This enabled the non-invasive monitoring by 1H-n.m.r. spectroscopy of the hydrolysis of the dipeptide in human erythrocytes and their lysates. The concentration-dependence of the rate of glycyl-L-proline hydrolysis by haemolysates was described by the Michaelis-Menten expression with Km = 14.1 +/- 2.4 mmol/litre and Vmax. = 130 +/- 10 mmol/h per litre of cell water. At concentrations of the dipeptide that saturated prolidase, hydrolysis of glycyl-L-proline by whole cells was approximately 130 times slower than by lysates. This rate difference indicated that transport is the rate-determining step in peptide hydrolysis by whole cells, and thus the concentration-dependence of the transport rate was determined. The membrane transport system was found to be saturable and could be described by the Michaelis-Menten expression with Kt = 4.7 +/- 0.4 mmol/litre and Vmax. = 0.997 +/- 0.026 mmol/h per litre of cell water. Numerical integration of a consistent set of differential rate equations that described a minimal model of the coupled transport-hydrolysis system successfully described prolonged time courses of peptide hydrolysis by whole cells. The simulations showed very low steady-state levels of dipeptide in the erythrocyte and very small lag periods (less than 5 min) in the progress curve describing the appearance of free amino acid inside the cells. The rates of transport of glycyl-L-proline into erythrocytes and kidney proximal-tubular epithelium were compared and the possible importance of erythrocyte prolidase in whole-body prolyl-peptide turnover is discussed.

scholarly journals THE ELECTROPHORETIC MOBILITY OF HUMAN ERYTHROCYTES—WHOLE CELLS, GHOSTS, AND FRAGMENTS

1938 ◽  
Vol 22 (1) ◽  
pp. 1-5 ◽  
Author(s):  
W. H. Byler ◽  
H. M. Rozendaal
Keyword(s):  
Cell Surface ◽  
Electrophoretic Mobility ◽  
Human Erythrocytes ◽  
Red Cell ◽  
Chicken Serum ◽  
Whole Cells ◽  
Slow Change ◽  
Foreign Substance ◽  
Pure Salt

The electrophoretic mobility of human red cell ghosts decreases in the presence of chicken serum. The decrease is not directly due to the presence of adsorbed material but to a change which is catalyzed by the foreign substance. It is suggested that abnormal serum materials resulting from disease may serve as catalysts. Fragments of broken cells have the same mobility as whole cells at first, then decrease even in pure salt suspension, while the whole cells remain essentially unchanged for hours. The results suggest that the slow change of whole cells, the change of ghosts in the presence of foreign serum, and the change of fragments are all manifestations of the same modification of structure or composition of the cell surface.

scholarly journals Sialolithiasis and Salivary Ductal Stenosis: Diagnostic Accuracy of MR Sialography with a Three-dimensional Extended-Phase Conjugate-Symmetry Rapid Spin-Echo Sequence

Radiology ◽  
2000 ◽  
Vol 217 (2) ◽  
pp. 347-358 ◽  
Author(s):  
Minerva Becker ◽  
Francis Marchal ◽  
Christoph D. Becker ◽  
Pavel Dulguerov ◽  
Georges Georgakopoulos ◽  
...  
Keyword(s):  
Diagnostic Accuracy ◽  
Spin Echo ◽  
Three Dimensional ◽  
Extended Phase ◽  
Phase Conjugate ◽  
Spin Echo Sequence ◽  
Conjugate Symmetry

scholarly journals Dynamic diffusion‐weighted hyperpolarized 13 C imaging based on a slice‐selective double spin echo sequence for measurements of cellular transport

2018 ◽  
Vol 81 (3) ◽  
pp. 2001-2010 ◽  
Author(s):  
Xucheng Zhu ◽  
Jeremy W. Gordon ◽  
Robert A. Bok ◽  
John Kurhanewicz ◽  
Peder E.Z. Larson
Keyword(s):  
Spin Echo ◽  
Cellular Transport ◽  
Double Spin ◽  
Diffusion Weighted ◽  
Spin Echo Sequence ◽  
Dynamic Diffusion

scholarly journals Magnetic resonance findings in amyotrophic lateral sclerosis using a spin echo magnetization transfer sequence: preliminary report

1999 ◽  
Vol 57 (4) ◽  
pp. 912-915 ◽  
Author(s):  
ANTÔNIO JOSÉ DA ROCHA ◽  
ANTONIO CARLOS MARTINS MAIA JUNIOR ◽  
ROBERTO GOMES NOGUEIRA ◽  
HENRIQUE MANOEL LEDERMAN
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Magnetic Resonance ◽  
Preliminary Report ◽  
Corticospinal Tract ◽  
Spin Echo ◽  
Magnetization Transfer ◽  
Control Group ◽  
Spin Echo Sequence ◽  
Lateral Sclerosis

We present the magnetic resonance (MR) findings of five patients with amyotrophic lateral sclerosis (ALS) using a spin-echo sequence with an additional magnetization transfer (MT) pulse on T1-weighted images (T1 SE/MT). These findings were absent in the control group and consisted of hyperintensity of the corticospinal tract. Moreover we discuss the principles and the use of this fast but simple MR technique in the diagnosis of ALS

Measurement of [Ca2+]i in Whole Cell Suspensions Using Fura-2

2003 ◽  
pp. 31-40 ◽  
Author(s):  
Robert A. Hirst ◽  
Charlotte Harrison ◽  
Kazuyoshi Hirota ◽  
David G. Lambert
Keyword(s):  
Cell Suspensions ◽  
Whole Cell ◽  
Fura 2
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