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At least 55 records · Page 3Linked to original sources
PubMed1998

Carbamylated hemoglobin and carbamylated plasma protein in hemodialyzed patients.

The carbamylation reaction in vivo involves the nonenzymatic, covalent attachment of isocyanic acid, the spontaneous dissociation product of urea, to proteins. Carbamylated proteins have been proposed as markers of uremia and indicators of uremic control. However, the utility of measuring carbamylated proteins has not been investigated adequately. Therefore, this study was done to determine the relationship between the carbamylation of long-lived protein (hemoglobin) with that of short-lived proteins (plasma proteins) in hemodialyzed patients. Significantly higher carbamylated hemoglobin (CHb; 157 +/- 40 microg valine hydantoin/g Hb) and carbamylated protein (CTP; 0.117 +/- 0.011 absorbance/mg protein) concentrations were found in hemodialyzed patients (N = 13) as compared to normal individuals (N = 9, 53 +/- 20 microg valine hydantoin/g Hb and 0.08 +/- 0.01 absorbance/mg protein, respectively). A high correlation was found between CHb and CTP concentrations (r = 0.87, P < 0.0001), demonstrating a strong relationship between these two different half-lived proteins. A six-month longitudinal study of seven hemodialyzed patients showed that the between subject correlations were significant for CHb versus CTP as well as CHb versus pre-dialysis urea. Correlations were not significant for CTP versus pre-dialysis urea or Kt/V, nor CHb versus Kt/V. Carbamylated hemoglobin fluctuated the most over this time period (30.1% +/- 20.2%), pre-dialysis urea and CTP varied less (18.3% +/- 13.4% and 14.9% +/- 7.5%, respectively), and Kt/V varied the least (6.3% +/- 3.3%). Within subject correlations were not significant between any two tests. It is unclear whether the lack of correlations found is real or a function of the small sample size. However, these data do show that CHb and CTP are positively associated and reflect the degree of urea exposure in the blood, but their usefulness for patients on maintenance hemodialysis is not clear.

Biomarkers↗
PubMed1979

Drug-protein interaction: plasma protein binding of furocoumarins.

The binding of six furocoumarins (angelicin, psoralen, 8-methoxypsoralen, 5-methoxypsoralen, 8-methylpsoralen, 4,5'8-trimethylpsoralen) to human serum and human serum albumin was studied by equilibrium dialysis using tritium labelled compounds. The results indicated that in serum all furocoumarins are bound mostly by albumin, the extent of binding being related to the structure of the furocoumarins; at any rate, high values of the bound drug, ranging from 84 to 97% were observed. The percentage of binding is strictly related to the water solubility of the compounds. A limited number of binding sites, n = 1-2.4, were detected in the albumin molecule, indicating a high specificity in the binding process. The association constants of the furocoumarins to albumin. Ka, ranged from 1.2 X 10(4) M-1 (8-methoxypsoralen) to 1.9 X 10(5) M-1 (4,5'8-trimethylpsoralen).

Biological Availability↗
PubMed1976

Plasma protein profiling: the diagnostic evaluation of disorders in plasma protein composition by a new immunoelectrophoretic method.

A new electroimmunoprecipitation technique is presented by means of which a great variety of antigens e.g. plasma proteins can be simultaneously and quantitatively determined with a single-step electrophoretic separation. The essential features of the new technique are: (a) subdivision of the antibody gel into gel strips containing monospecific antibodies to individual plasma proteins. (b) sample application as a "sample gel" filling a trough over the width of the immunoplate. Quantitation is based on the fact that the distance an antigen can migrate within a gel containing a defined amount of specific antibody directed against the antigen is determined by the concentration of the appropriate antigen within the sample. The area where the antigen is finally completely consumed by immunoprecipitation and antibody present in excess is sharply delineated. The applicability of the method in simultaneous quantitative determination of 15 plasma proteins is demonstrated with plasma from healthy blood donors and patients with various diseases. The advantage of the new technique as compared to commonly used clinical acetate folia electrophoresis is the high degree of specificity for the determination of a great number of individual, diagnostically meaningful plasma proteins. The advantage over common quantitative two-dimensional immunoelectrophoresis is its uncomplicated way of evaluation. The potential clinical application of the new quantitative immunoelectrophoretic technique in diagnostic screening and differential diagnosis is discussed.

Blood Proteins↗
PubMed1982

Some aspects of plasma protein metabolism as compared with intracellular protein breakdown.

Many plasma proteins are cleared according to first-order kinetics. Half-lives of individual plasma proteins are widely different, just like those of intracellular proteins. Plasma proteins with molecular weights up to about 50000 are often mainly cleared by glomerular filtration, especially if the protein has a high isoelectric point. An other important clearance mechanism is endocytosis. Fluid endocytosis might contribute significantly to the catabolism of plasma proteins with long-lives like serum albumin. Adsorptive endocytosis is responsible for the rapid clearance of complexes of some plasma proteins with other molecules, like antigen-antibody complexes. Other plasma proteins like certain glycoproteins and lipoproteins are bound to be specific receptors on the surface of endocytosing cells without previous complex formation. Experiments with sucrose-containing labels suggest that certain tissues are specifically involved in endocytosis of some plasma proteins. If endocytosis and renal filtration constitute the main mechanisms for the clearance of plasma proteins, one cannot expect extensive homologies between this process and catabolism of intracellular proteins.

Adsorption↗
PubMedDate not supplied

Quantitation of adsorption and conjugation of plasma proteins by residual glutaraldehyde in fixed collagenous tissue with radioiodinated plasma proteins.

Residual glutaraldehyde (GA) in collagenous cardiovascular tissue prostheses after multiple saline rinses remains in the prostheses and accounts for adsorption and conjugation of a variety of plasma proteins. This may account for later beneficial or adverse effects. Human serum albumin (SA), gamma globulin (GG), and fibrinogen (FB) were iodinated with 125I using the iodogen-transfer technique. Bovine pericardium (PC) was fixed with 0.5% GA for 24 hr and rinsed to remove excess GA. Fresh and GA-fixed PC (FRPC, GAPC: 1 x 1 cm2), in triplicate, were incubated with 0.5-1.0 microCi of tracers in human, porcine, or bovine blood (2 ml) for a period of 0.5, 1, 2, and 3 hr and washed (5x) with saline. Maximum adsorbed proteins per unit weight of collagen (pmol/mg of PC, mean +/- SD) at 3 hr on FRPC and GAPC were quantified with a gamma counter. Fixed PC absorbed significantly more plasma proteins from blood than fresh PC. These conjugated plasma proteins are tightly bound to fixed PC. The adsorbed and conjugated plasma proteins for GAPC and FRPC have the same sequence: SA > GG > FB vs SA > GG > FB. Protein conjugation may affect the remodeling of collagenous cardiovascular tissue prostheses post implantation.

Adsorption↗
PubMed1975

Effect of ionic strength and ionic composition of assay buffers on the interaction of thyroxine with plasma proteins.

When plasma proteins are diluted with buffer the ionic strength and ionic composition of that buffer affects the interactions between thyroxine (T4) and its plasma protein-binding sites. Increases in phosphate, chloride or barbiturate ion concentration from 50 to 200 mmol/l caused a significant decrease in the affinity of plasma proteins for T4, and a concurrent increase in the concentration of unbound T4. These results cannot be completely accounted for by changes in ionic strength since at the same ionic strength different anions caused quantitatively different effects on unbound T4 concentration. The degree of depression of T4 binding by the three anions studied was in the order barbiturate greater than chloride greater than phosphate. The results of a systematic study on the composition of diluent buffer systems indicated that when a 50 mM-sodium phosphate-100 mM-NaCl buffer (pH 7-4) was used as a plasma diluent, there were unlikely to be gross changes in the T4-binding properties of plasma proteins with dilution.

Barbiturates↗
PubMed1996

Comparison of ethanol plasma-protein precipitation with plasma ultrafiltration and trichloroacetic acid protein precipitation for the measurement of unbound platinum concentrations.

Sample preparation for the measurement of non-protein-bound platinum was evaluated by precipitation of plasma proteins with cold ethanol. The method was compared with the routinely used plasma ultrafiltration and with trichloroacetic acid (TCA) protein precipitation. After incubation of human plasma samples with cisplatin or carboplatin, unbound platinum concentrations were determined applying Amicon Diaflo ultrafiltration membranes and Millipore ultrafree-MC filters. For protein precipitation, 1 ml of cold (-20 degrees C) pure ethanol was added to 0.5 ml of human plasma and the supernatant was collected after 2 h, or 0.5 ml of cold 20% TCA was added to 0.5 ml of plasma. Platinum was analyzed by atomic absorption spectrophotometry (AAS). There was no significant difference between the ethanol and ultrafiltration methods in the unbound platinum concentration. The protein content in the supernatant (1.00 +/- 0.20%) was slightly higher than that in the Amicon (0.58 +/- 0.05%) and Millipore (0.55 +/- 0.04%) ultrafiltrates. On average, the TCA and ethanol method seemed to be equally appropriate. The ethanol precipitation method is concluded to be simple, convenient, and reproducible and has negligible costs.

Blood Proteins↗