Showing papers on "Serum albumin published in 1974"

Determination of Unbound Bilirubin in the Serum of Newborns

Abstract: An enzymatic assay is described for non-albuminbound bilirubin in the serum of newborn infants. Unbound bilirubin is oxidized to colorless compounds by ethyl hydroperoxide in the presence of horseradish peroxidase (EC 1.11.1.7), while albumin-bound bilirubin is protected from oxidation. Because the equilibrium between albumin and bilirubin occurs rapidly, the oxidation step is rate limiting, and the initial oxidation velocity of total bilirubin is proportional to the unbound bilirubin concentration. By titrating serum with bilirubin in vitro, the association constant and binding capacity of high-affinity sites for albumin binding can be determined. Normal human serum albumin tightly binds 1 mole of bilirubin per mole of albumin (binding constant, 2-4 x 108 liter/mol). Although weaker secondary binding occurs, the unbound bilirubin fraction increases rapidly after the high-affinity binding sites are saturated. Compromised newborns may have a decreased apparent binding capacity and (or) binding affinity. The method can be used to assess the risk of a jaundiced infant for bilirubin encephalopathy.

Studies of the human lymphocyte receptor for heat-aggregated or antigen-complexed immunoglobulin

Abstract: The lymphocyte receptor for complexed immunoglobulin was shown not to bind heat-aggregated human serum albumin, bovine serum albumin, transferrin, F(ab')2, reduced and alkylated Ig, and mildly oxidized Ig, which indicated that the receptor is specific for a site dependent on disulfide bond(s) on the Fc portion of complexed Ig. Inhibition experiments provided evidence that the same receptor binds both heat-aggregated Ig and antigen-antibody complexes. Lymphocytes treated with pronase were no longer able to bind Ig complexes, which suggested that the receptor is a protein or glycoprotein. Additional evidence was obtained that lymphocyte surface Ig and the receptor for complexed Ig are distinct since the former could be capped without affecting the distribution of the latter, and surface Ig was not detectable after trypsinization of lymphocytes, whereas the binding of Ig complexes was unaffected by such treatment. Incubation of lymphocytes which had bound Ig complexes in tissue culture medium at 37°C revealed that the complexes remained on the surface membrane for several hours, and that only a minority of lymphocytes binding complexes showed cap formation. Lymphocytes which had heat-aggregated IgG specifically bound to their receptors for complexed Ig were markedly inhibited in their ability to mediate antibody-dependent cytotoxicity, thus providing strong evidence for the necessity of the receptor in this immune activity. Titration of this inhibition with varying amounts of complexes revealed distinct plateaus in the dose-response curve. This suggested that there may be more than one kind of receptor and/or different populations of lymphocytes which bear the receptor.

Clearance of Antipyrine‐Dependence of Quantitative Liver Function

Abstract: . The purpose of the present study was to assess tile influence of liver disease on the hepatic drug-metabolizing enzyme systems. The clearance of antipyrine was found to be significantly decreased in 13 patients with liver disease compared with 9 control patients (18.5 and 58.6 ml/min. respectively). Among the patients with liver disease, those with a severely reduced capacity for work had significantly lower clearance of antipyrine than non incapacitated patients (12.5 and 25.4 ml/min. respectively). The clearance of anti pyrine was significantly correlated with the galactose elimination capacity, the serum albumin and the prothrombin values. The results indicate that the drug-metabolizing capacity of the liver changes in parallel with the other metabolic functions, and the use of the clearance of antipyrine as a quantitative test of liver function is suggested.

The induction of tolerance to a soluble protein antigen by oral administration.

Abstract: The repeated administration of bovine serum albumin by stomach tube to Charles River and Black Norwegian rats resulted in a state of partial tolerance to the antigen. A very small amount of antibody was detected in the serum at the end of the oral regime but anti-BSA-producing cells could not be demonstrated in the lamina propria, in the Peyer's patches of the small intestine, in the mesenteric nodes or in the spleen of these animals. Antibody was not demonstrated in the small intestinal contents or in the faeces of the same animals. The antigen was absorbed in the native form and not as constituent peptides bearing antigenic determinants in common with the native protein. Preliminary data, using a radioimmunoassay, indicate that the serum concentration of BSA after the administration of 25 mg of the protein by stomach tube, is in the range 1-10 ng/ml of serum. Preliminary experiments indicate that the state of partial tolerance could not be abrogated by syngeneic spleen cells or peritoneal exudate cells from normal rats. This form of tolerance therefore has some features in common with the state of tolerance induced by the parenteral administration of small amounts of bovine albumin (low zone tolerance).

The conformation of adsorbed blood proteins by infrared bound fraction measurements

Abstract: The likelihood that surface-induced blood coagulation results from specific protein-material interactions has led to a study of the conformation of adsorbed blood proteins. Infrared difference spectroscopy was used to determine the bound fraction, i.e., the fraction of carbonyl groups of an adsorbed molecule directly interacting with the surface, of serum albumin, prothrombin, and fibrinogen in situ. Measurements were carried out on individual proteins as a function of the amount adsorbed, time of absorption, pD, and ionic strength using a silica surface. The results obtained for serum albumin and prothrombin indicate that the internal bonding of these globular proteins is sufficient to prevent changes in the structure while adsorbed, even at low surface population. The bound fraction of fibrinogen increases with increasing adsorbance, suggesting possible interfacial aggregation. The conformation of all three proteins was found to be independent of the time of adsorption, although major differences in the rates of adsorption were observed. Studies of cross-linked and denatured serum albumin have provided information on the conformational changes concomitant with adsorption of the native protein. Qualitatively, such changes, if they occur, are small. This conclusion is supported by computer simulation studies of lysozyme adsorption. Studies of the effect of pD and ionic strength on the adsorbance and bound fraction of serum albumin show that caution must be exercised when identifying the plateau adsorbance of a protein isotherm with a close-packed monolayer.

Measurement of IgG and Albumin Content of Cerebrospinal Fluid, and its Interpretation

Abstract: A high correlation ( r = 0.85) normally exists between the concentration of albumin and of IgG in cerebrospinal fluid (CSF). The correlation is still better ( r = 0.96) if the concentrations of the two proteins are also measured in plasma and the CSF/ plasma ratios compared for albumin and IgG. The scatter diagram for these ratios in persons without disease of the nervous system is most useful as a reference when differentiating between local IgG production in the subarachnoid space and an increase in CSF protein for other reasons. The analysis can be performed on less than 0.1 ml of CSF, in contrast to agarose-gel electrophoresis, for which 5-10 ml is necessary.

Competitive Binding of Bilirubin and Drugs to Human Serum Albumin Studied by Enzymatic Oxidation

Abstract: The mechanism of drug-induced displacement of bilirubin from the blood into tissues was studied. A model of simple, competitive binding of bilirubin and drug to one site on serum albumin was established. Variations of the free bilirubin concentration after addition of drugs were studied in vitro by measuring velocities of oxidation with hydrogen peroxide and horseradish peroxidase. In all cases, the results were in agreement with the model. The competitive effects of 20 drugs were measured and expressed quantitatively as binding constants to the bilirubin site on human serum albumin. Several drugs caused changes of the bilirubin-albumin light absorption spectrum, indicating simultaneous binding of both ligands, without an effect on the free bilirubin concentration. Noncompetitive site-to-site effects on bilirubin binding could not be demonstrated. An equation is proposed for calculation of the maximal displacing effect of a drug from knowledge of its plasma concentration, the above-determined binding constant, and the degree of protein binding of the drug. Comparison of these results with previous observations of bilirubin displacement in newborn humans and in experimental animals indicates a general agreement with a simple competitive mechanism of binding of bilirubin and drug to one site on the albumin molecule. Binding of drugs to other, noncompetitive sites is common.

Disturbance of Serum Viscosity in Diabetes Mellitus

Abstract: The serum viscosity of diabetic patients has been found to be increased. The elevation averaged 8% above healthy subjects and 6% above nondiabetic patients. The serum viscosity elevation was greater when diabetic sequelae associated with microangiopathy were present. No relation of serum viscosity to age, sex, obesity, duration of disease, or type of treatment was demonstrated. Serum total protein and glucose levels were found to be correlated with serum viscosity, and increases in their serum concentrations were observed in diabetes. Analysis demonstrated that their elevation did not explain either the viscosity increase or the difference in viscosity between diabetics with and without sequelae.Intrinsic viscosity, abbreviated [eta], is a concentration-independent solute property related to molecular shape. [eta] was found to be 7% higher in diabetic than in normal serum. The [eta] difference accounted for at least half of the serum viscosity elevation. The rest of the increase was due to increased serum protein level and increased nonprotein solids, presumably glucose and lipid. Associated with increased [eta] was a decline in albumin: globulin ratio and elevation of the acute phase reactant proteins, alpha(1)-acid glycoprotein, alpha(1)-antitrypsin, haptoglobin, and ceruloplasmin. Studies comparing diabetic and normal serum fractionated by using 21.5% sodium sulfate showed that changes in [eta] were attributable to changes in serum protein composition rather than an inherent qualitative disturbance of protein present in one of the fractions. Since serum viscosity is elevated in early diabetes, it may be a part of the metabolic disturbance of diabetes and could play a role in the development of diabetic microangiopathy.

Slow evolution of transferrin and albumin in birds according to micro-complement fixation analysis

Abstract: Rabbit antisera were prepared to purified ovotransferrin from chicken (order Galliformes) and red-winged blackbird (order Passeriformes) and to purified serum albumin from chicken and rhea (order Rheiformes). Quantitative microcomplement fixation was used to compare these proteins immunologically with those of representatives of all 27 orders of birds. The average interordinal immunological distances were 123 units for transferrin and 53 units for albumin.

Human serum albumin phenotype activation in mouse hepatoma--human leukocyte cell hybrids.

Abstract: Murine hepatoma cells that secreted mouse serum albumin were fused with human leukocytes that did not produce albumin. The resulting hybrids secreted both mouse and human serum albumin, as demonstrated by immuno-electrophoretic techniques. The activation of the human genome suggests that mapping genes governing specialized functions in somatic cell hybrids may be accomplished by using adifferentiated human cells as a parental line.

Changes in blood coagulation and fibrinolysis in the nephrotic syndrome.

Abstract: In an attempt to elucidate the causes of the increased tendency to thrombosis in the nephrotic syndrome, changes in blood coagulation, fibrinolysis and biochemical function were measured in a group of patients with clinical and biochemical evidence of the nephrotic syndrome. These patients showed significant elevation of factor V, factor VIII, fibrinogen, plasminogen and α2-macroglobulin, while levels of antiplasmin activity and α1-antitrypsin were lowered. Fibrinogen, cholesterol, and antithrombin activity correlated significantly with each other as did levels of serum albumin, antiplasmin, and α1-antitrypsin. It appears that these changes take place passively as a result of increased protein synthesis and urinary loss of low molecular weight protein and not from primary changes in the coagulation or fibrinolytic mechanisms.

Electron Microscopic and Chemical Studies of the Vascular Changes and Edema of Lead Encephalopathy: A Comparative Study of the Human and Experimental Disease

Abstract: Lead encephalopathy was induced in suckling rats by administering lead to the mother. The brains were studied by light and electron microscopy, and the results were compared with observations in the human disease as well as in cases of cerebral ischemia in children. In their severe forms, both human and experimental lead encephalopathies are characterized by exudative extracellular edema and perivascular PAS-positive globules. The latter consist of osmiophilic non-membrane-limited cytoplasmic inclusions located, in the rat exclusively and in the human predominantly, in perivascular astrocytes. Intervascular strands are also found in both forms of the disease. In the rat these consist of basement membrane surrounding endothelial cytoplasm. Chemically, experimental lead encephalopathy with morphologically demonstrable edema is associated with an increase in brain water, sodium and serum albumin. Relative to the serum concentration, the increase in water is disproportionately greater than the sodium or albumin. There were no demonstrable changes in chloride or potassium.

Expression of Differentiated Functions in Hepatoma Cell Hybrids: High Frequency of Induction of Mouse Albumin Production in Rat Hepatoma-Mouse Lymphoblast Hybrids

Abstract: We have studied the production of serum albumin by somatic hybrids between well-differentiated 2s and 1s rat hepatoma cells (Faza), which produce serum albumin, and sub-diploid mouse leukemic lymphoblasts (Lc), which do not produce albumin. We determined the rat or mouse origin of the albumin by double immunodiffusion, using immuno-adsorbed noncrossreacting antisera. Each of 12 karyologically identified 2s hybrid clones (Lc2F) produces both rat and mouse albumin. Moreover, unlike 1s hybrids reported previously, eight of nine 1s hybrids (LcF) also produce mouse albumin; six of them produce rat albumin as well. One clone from the 1s cross produces only rat albumin.

Reduced Serum Somatomedin Activity in Patients with Chronic Liver Disease

Abstract: 1. Somatomedin (SM; sulphation factor) activity was estimated by a chick-cartilage assay in fasting sera from twenty-one patients with chronic liver disease. 2. Low SM values were found in nine out of the ten patients with cirrhosis and in two other patients, one with hepatofibrosis and one with hepatoma. 3. In general, the lowest serum SM activities were found in those patients with the most severe disease and significant correlations were found between serum SM and serum albumin, alkaline phosphatase and bilirubin. 4. Growth hormone was also measured in the samples and concentrations above 10 units/ml were found in seven patients, all of whom had reduced serum SM activities. 5. These findings indicate that low serum SM activity in liver disease is not related to growth hormone deficiency and suggest that the liver may be an important site for SM synthesis in man.

Protein handling by the renal tubule

Abstract: Indirect and direct studies indicate that a variety of proteins filtered at the glomerulus are absorbed by the proximal tubule by luminal endocytosis and are hydrolyzed by lysosomal enzymes. Studies on isolated, perfused tubular segments have not demonstrated contraluminal uptake of albumin or insulin. Evidence for transport of intact protein molecules across tubular cells is inconclusive, and additional studies are required to resolve this problem. Experimental findings suggest that the kidney plays an important role in albumin homeostasis. In health, greater than 90% of the small amount of albumin filtered by the glomerulus is absorbed by the proximal tubule and digested therein, which accounts for approximately 10% of total albumin catabolism. Only trace amounts of albumin appear in the urine. In disease, large loads of filtered albumin probably saturate the absorptive-digestive capacity of the proximal tubule and albuminuria ensues. In this circumstance, the kidneys may account for 30–40% of total albumin catabolism.

Selective release of content from microsomal vesicles without membrane disassembly. II. Electrophoretic and immunological characterization of microsomal subfractions.

Abstract: Rough and smooth microsomes were shown to have similar sets of polypeptide chains except for the proteins of ribosomes bound to the rough endoplasmic reticulum (ER). More than 50 species of polypeptides were detected by acrylamide gel electrophoresis, ranging in molecular weight from 10,000 to approximately 200,000 daltons. The content of rough and smooth microsomes was separated from the membrane vesicles using sublytic concentrations of detergents and differential centrifugation. A specific subset of proteins which consisted of approximately 25 polypeptides was characteristic of the microsomal content. Some of these proteins showed high rates of in vivo incorporation of radioactive leucine or glucosamine, but several others incorporated only low levels of radioactivity within short labeling intervals and appeared to be long-term residents of the lumen of the ER. Seven polypeptides in the content subfractions, including serum albumin, contained almost 50% of the leucine radioactivity incorporated during 5 min and cross-reacted with antiserum against rat serum. Almost all microsomal glycoproteins were at least partly released with the microsomal content. Smooth microsomes contained higher levels of albumin than rough microsomes, but after short times of labeling with [ 3 H]leucine the specific activity of albumin in the latter was higher, supporting the notion that newly synthesized serum proteins are transferred from rough to smooth portions of the ER. On the other hand, after labeling for 30 min with [ 3 H]glucosamine, smooth microsomes contained higher levels of radioactivity than rough microsomes. This would be expected if glycosidation of newly synthesized polypeptides proceeds during their transit through ER cisternae. The labeling pattern of membrane proteins in microsomes obtained from animals which received three daily injections of [ 3 H]leucine, the last administered 1 day before sacrifice, followed the intensity of bands stained with Coomassie blue, with a main radioactive peak corresponding to cytochrome P 450. After the long-term labeling procedure most content proteins had low levels of radioactivity; this was especially true of serum proteins which were highly labeled after 30 min.