Presence Of Plasma Proteins Research Articles

Radiolabelling of poly(butyl 2‐cyanoacrylate) nanoparticles with a technetium‐99m‐dextran complex

AbstractPoly(butyl 2‐cyanoacrylate) nanoparticles have been radiolabelled with a 99mTc‐dextran complex to allow their pattern of biodistribution to be followed by using the technique of gamma scintigraphy. The method involves the preforming of a 99mTc‐dextran complex and using this as a polymerie stabiliser during the formation of nanoparticles. Copolymerisation of this complex with the cyanoacrylate monomer results in the radiolabel being covalently linked to the nanoparticle matrix with a labelling efficiency of approximately 18%. The radiolabelled nanoparticles slowly degrade and release the activity into buffer solution. The release rate was relatively unaffected by the presence of plasma proteins indicating that the system should be suitable for use in vivo.

Enhanced hepatic extraction of estrogens used for replacement therapy.

Oral estrogen administration elicits greater effects on hepatic than on nonhepatic markers of estrogen action. This has important clinical implications, since the hepatic actions of estrogens are believed to account for several complications of this form of therapy. To date, the mechanism responsible has been attributed to the so-called first pass effect of the orally administered hormones. The present study was undertaken to examine the in vivo extraction from the circulation of all commercially available classes of estrogens used for replacement therapy. Influxes from the microcirculation into three important target organs of estrogen action, i.e. the brain, uterus, and liver, were assessed. This was accomplished by the use of previously described double isotope, single injection, timed tissue-sampling techniques. For the brain, two patterns of influx were found using different injection vehicles. The first was characterized by high extraction (80-100%) in the absence of plasma proteins. The only inhibitory effects on influx were exerted by plasma proteins. Estrogens displaying this pattern were estradiol, estrone, and ethinyl estradiol. The second pattern was characterized by very restricted influx in the absence of plasma proteins, and plasma protein binding had little or no additional effect. In the absence of plasma proteins, the percentages extracted of estrone sulfate (E1S) and diethylstilbestrol were 6.5% and 38.5%, respectively. For the uterus, the patterns of extraction of all five estrogens were similar to those found for the brain. In contrast, the hepatic microvasculature was freely permeable to all estrogens including E1S and diethylstilbestrol. Albumin binding had little or no effect on hepatic uptake. Significant reductions in the influx of estradiol and E1S were found only when the injection vehicle was human pregnancy serum (high sex hormone-binding globulin concentration). In the presence of plasma proteins, the hepatic extraction of all of the estrogens studied significantly exceeded that in the brain and uterus. We conclude that enhanced delivery of circulating estrogens to the liver compared to that to the brain and uterus provides a further explanation for the enhanced hepatic actions of these preparations when used for oral replacement therapy.

Phagocytosis of microcapsules by guinea-pig polymorphonuclear leucocytes.

Phagocytosis of microcapsules by guinea-pig polymorphonuclear leucocytes (PMNs) was examined particularly considering the method of measurement and the effects of surface negative charges of the microcapsules and plasma proteins. Estimation of phagocytosis by oxygen consumption was found to correlate fairly well with the measured amount of the microcapsules phagocytosed. In the absence of plasma proteins, microcapsules having the same surface negative charge as that of the PMNs underwent less phagocytosis than those having surface negative charges different from those of the PMNs. The presence of plasma proteins was found to suppress phagocytosis.

Human monocyte-endothelial cell interaction in vitro.

We have examined the interaction of freshly isolated human blood monocytes with cultured human umbilical vein endothelial cells in vitro. Purified monocytes incubated with confluent primary or passaged endothelial cells (EC) for 90 min at 37 degrees C bound at maximal densities of 6.5-7.0 X 10(3)/mm2 (8 or 9 per EC) without causing disruption of the monolayer. Monocyte-EC binding proceeded in the presence of plasma proteins or optimal phagocytic doses of opsonized zymosan particles. The avidity of attachment was not diminished by alternative monocyte isolation techniques. Monocyte attachment to EC was dependent upon the presence of divalent cations (magnesium greater than calcium) and was inhibited at 4 degrees C. Monocytes selectively bound to EC when incubated with monolayers composed of smooth muscle cells and EC. Neither EC monolayer confluence nor a variety of EC culture conditions affected the high levels of monocyte binding. In contrast, human neutrophils (less than 1 per EC) and lymphocytes (less than 2-3.5 per EC) bound at lower maximal densities under the same conditions, while platelet reactivity remained minimal. The distinctively higher affinity of human blood monocytes relative to other circulating white cells for binding to cultured human EC may have relevance to their function in vivo.

Role of Plasma Proteins in Corrosion of 316L Stainless Steel In Vitro

ABSTRACTPlasma proteins have been recognized as playing a role in the corrosion of metals used as medical implants. In this study, we examined the early events of anodic corrosion of 316L stainless steel in saline/plasma mixtures. Polished, annealed, cleaned and passivated 316L electrodes with a surface area/body fluid volume (SA/BFV) ratio of 23X were driven anodically in a 100 ml acid cleaned cell at 950 and 1150 mV (vs. SCE). Electrolyte solutions of isotonic saline (pH = 7.4) containing 0, 5, 10 and 25 volume percent human plasma were used. Aliquots of solution were taken at intervals and analyzed for Cr, Ni and Fe by atomic absorption spectrophotometry. Corrosion continued until a total charge of 1.0 to 1.5 C was passed. Plots of solution metal concentration versus electrolyte solution composition, calculated at an isocoulombic point (Q = 0.5 C) and adjusted for initial concentration, were prepared to test for effects of the presence of plasma proteins. Increases in elemental release rates of up to 3x (p 0.05) were found, with peak effects in 5 and 10 volume percent plasma solutions. The effects depend upon anodic potential, metal species, plasma protein concentration and possibly plasma composition.

Interference of heparin in carcinoembryonic antigen radioimmunoassays

A false Roche carcinoembryonic antigen (CEA) activity could be detected in all commercial and noncommercial heparin preparations we examined. The possibility of ‘due to contamination’ has been ruled out. Using the Roche procedure, heparin solutions, in the absence of CEA, gave positive CEA activity; on the other hand, no CEA activity was detected in solutions containing only heparin when the Abbott Kit was used. When heparin was present in specimens containing CEA, the Abbott Kit underestimated the CEA activity, whereas the Roche Kit gave false elevated values. However, the negative effect of heparin could be reduced by heat treatment in the presence of plasma proteins.

Fibrinogen and IgG in the hyaline zone in man after orthodontic movement.

Fibrinogen and IgG were demonstrated in the hyaline zone with direct immunofluorescent staining after orthodontic tooth movement in man. It was suggested that presence of plasma proteins in the hyaline zone contributed to its hyaline appearance. Fibrin and IgG may, furthermore, attract phagocytes and form a network for the reorganization of the necrotic tissue in the hyaline zone.

Plasma proteins in human cortical bone: enrichment of alpha 2 HS-glycoprotein, alpha 1 acid-glycoprotein, and IgE.

Human cortical bones were extracted with EDTA, and the residue after EDTA extraction was digested with bacterial collagenase. Ten plasma proteins were identified and quantitated in the EDTA extracts. Three of them--IgE, IgD, and alpha 1acid-glycoprotein--had not previously been described in bone or dentine. Five plasma proteins identified in collagenase digests are albumin, IgG, IgA, IgE, and alpha 1acid-glycoprotein. IgE, alpha 1acid-glycoprotein, and alpha 2HS-glycoprotein were found to be concentrated in the bone more than other plasma proteins by factors between 11 and 525. The identification of plasma proteins was facilitated by the addition of polyethylene glycol in agarose gel. The presence of plasma proteins both in EDTA extracts and in collagenase digests suggests their structural role in bone.

Functional impairments of human red cells, induced by dehydroepiandrosterone sulfate.

A study has been made on the incorporation of dehydroepiandrosterone sulfate (DHAS), one of the most abundant adrenal C-19 steroids, into human red cells, and of the resulting effects on red cell functions. 1. DHAS was incorporated into red cell membrane mainly by a partition mechanism: The apparent partition constant was small ([DHAS]cell/[DHAS]free = 1.34), indicating that DHAS in red cells would be easily removed by dilution. 2. At least part of the DHAS taken up was apparently bound to band 3 protein and thereby was able to inhibit the exchange of intracellular and extracellular SO4(2-) (Ki = 70 micro M). 3. Using a fatty acid spin label, it was established that the presence of DHAS in lipid bilayer of the membrane increased the acyl chain motion in the middle portion of the membrane. 4. DHAS induced echinocytosis of red cells. It is suggested that the increase in the viscosity of red cell suspension, the decreased deformability and the decrease in the deoxygenation rate of hemoglobin in the presence of DHAS probably reflect the presence of echinocytes. 5. In the presence of plasma proteins, the incorporation of DHAs into red cells was remarkably suppressed.

Low-density-lipoprotein apoprotein B in plasma as measured by radial immunodiffusion and rocket immunoelectrophoresis.

Radial immunodiffusion (RID) and rocket immunoelectrophoresis (RIE) are compared with respect to determination of LDL-bound apo B in plasma. Isolated VLDL could not enter a 15 g/L agarose gel when either technique was used. However, in the presence of plasma proteins, migration of VLDL into agarose was enhanced. Only when plasma samples were kept frozen before the assay was plasma VLDL unable to enter the agarose gel when RID was used. With RIE the contribution of plasma VLDL to the apo B determination under these conditions was not always negligible. Besides enhancing the entry of VLDL into the agarose, the presence of proteins also influences apo B immunoreactivity of LDL and VLDL. For measuring LDL-bound apo B directly in unfractionated plasma we recommend: (a) RID in 15 g/L agarose gel; (b) freezing the plasma samples before assay; (c) diluting the plasma samples in saline supplemented with protein in the same concentration as is present in plasma (70 g/L); and (d) using plasma as the assay standard.

Endoneurial vascular permeability in degenerating and regenerating peripheral nerves.

The endoneurial blood vessels of rodents are normally impermeable to proteins but they become permeable when the axons in the nerve have been severed. In this investigation, the increased permeability is examined in relation to the occurrence or absence of axonal regeneration. The sciatic and hypoglossal nerves of rats were either ligated and transected so that axons would not regenerate, or crushed and then allowed to regenerate. Changes in vascular permeability to fluorescently labelled albumin were examined in the endoneurium distal to the sites of both types of injury at postoperative intervals of 1–21 days. When axonal regeneration was prevented, the endoneurial vessels remained impermeable to the protein tracer until the 6th day. They then became permeable throughout the distal stump and remained so for the remainder of the experimental period. When axons regenerated, there was a considerably more intense exudation of the tracer in the distal segment of the nerve. The zone of greatly increased endoneurial vascular permeability advanced along the nerve at the same rate as that of the most rapidly regenerating axons, as observed in silver-stained sections. It is suggested that in the absence of regenerating axons, vascular permeability may be initiated by products of Wallerian degeneration. The greater permeability in regenerating nerves may be induced by vasoactive substances secreted by growth-cones. The results support a hypothesis in which it is maintained that the presence of plasma proteins around growth-cones is necessary for the occurrence of axonal regeneration. The further increase in permeability caused by the most rapidly elongating axons may assist the regenerative process by making larger quantities of plasma proteins available to other growing axons.

Regulation of platelet arachidonic acid oxygenation by cyclic AMP

Intracellular cyclic adenosine monophosate (AMP) levels regulate the generation of thromboxane by platelets by inhibiting the hydrolysis of arachidonic acid from membrane phospholipids. However, there is conflicting evidence regarding the role of cyclic AMP in the control of the subsequent oxygenation of arachidonic acid by cyclooxygenase. We studoed the regulation of cyclooxygenase activity by agents that elevate platelet cyclic AMP (dibutyryl cyclic AMP and prostaglandins), measuring arachidonate-induced aggregation, O2 consumption, and malonaldehyde formation. In platelet-rich cyclic AMP. This inhibitory effect of cyclic AMP was absent in gel-filtered platelets suspended in buffer containing 0.5% albumin, and was progressively restored as plasma was added in increasing concentrations. Increasing the albumin concentration in platelet buffer suspensions likewise increased the ability of cyclic AMP to block the arachidonate-induced O2 burst and MDA production. We conclude that (1) the presence of plasma proteins is important in investigating platelet plasma milieu or at least in the presence of physiologic albumin concentrations.

Regulation of Platelet Arachidonic Acid Oxygenation by Cyclic AMP

Intracellular cyclic adenosine monophosate (AMP) levels regulate the generation of thromboxane by platelets by inhibiting the hydrolysis of arachidonic acid from membrane phospholipids. However, there is conflicting evidence regarding the role of cyclic AMP in the control of the subsequent oxygenation of arachidonic acid by cyclooxygenase. We studoed the regulation of cyclooxygenase activity by agents that elevate platelet cyclic AMP (dibutyryl cyclic AMP and prostaglandins), measuring arachidonate-induced aggregation, O2 consumption, and malonaldehyde formation. In platelet-rich cyclic AMP. This inhibitory effect of cyclic AMP was absent in gel-filtered platelets suspended in buffer containing 0.5% albumin, and was progressively restored as plasma was added in increasing concentrations. Increasing the albumin concentration in platelet buffer suspensions likewise increased the ability of cyclic AMP to block the arachidonate-induced O2 burst and MDA production. We conclude that (1) the presence of plasma proteins is important in investigating platelet plasma milieu or at least in the presence of physiologic albumin concentrations.

Immunohistochemical evidence for an intracellular localization of plasma proteins in human foetal choroid plexus and brain

The intracellular distribution of plasma proteins in human foetal choroid plexus and brain was investigated by immunohistochemistry. Small groups of cells or single scattered cells in the epithelial layer of the choroid plexus exhibited positive staining for α-fetoprotein, albumin and transferrin, whereas prealbumin was found in the majority of the epithelial cells. Numerous nerve cells in the cerebral wall and in various brain stem nuclei were positively stained for α-fetoprotein, albumin and prealbumin. All appropriate controls were negative. The presence of plasma proteins within choroid plexus epithelial cells suggests that these proteins are transported from blood to CSF by a transcellular route across the choroid plexus epithelium. The intracellular distribution of plasma proteins in developing neurons may indicate that these proteins play some important role in neuronal differentiation or development.

The effect of metal ions on the activity of delta-aminolevulinic acid dehydratase.

The effects of lead, iron, copper, and zinc ions on delta-aminolevulinic acid dehydratase from red blood cell haemolysates in humans, both in the absence and presence of plasma proteins, have been investigated. delta-aminolevulinic acid dehydratase (ALAD) was not found to be a specific indicator of blood lead concentrations since it was also inhibited by copper and activated by zinc. Plasma protein protected the enzyme from both inhibition and activation. ALAD activity was found to be an indicator of the total metal ion concentration in the blood and was therefore considered to be of doubtful value in screening large populations for increased lead absorption.

17β-Estradiol Transport and Metabolism in Human Red Blood Cells

Attempts to measure the function of red blood cells as steroid metabolizing tissue showed that the membrane plays an important role. Of the 17beta-estradiol associated with red cells, 2/3 was bound to the membrane while 1/3 was in the soluble fraction. The binding appears to be nonspecific and linearly related to the amount incubated. Binding was more extensive at 2 C than at 26 C. Successive washes of red cells with isotonic sodium chloride solution increased their ability to bind 17beta-estradiol. Red cells incubated in isotonic salt media removed 85.1 plus or minus 3.2% (SD) of the total estrogens present and this value remained within narrow limits for incubation times as short as 15 s and as long as 19 h at 37 C. When incubated in homologous plasma, only 8-12% of estrogens in the media became associated with cells. The eight-fold difference in cell binding between salt solution and plasma can be attributed to competition with plasm aproteins. Presence of plasma proteins diminished but does not prevent activity of 17beta-hydroxysteroid dehydrogenase of red cells. Cells produce four times more estrone when incubated in saline media than when incubated in their own plasma. The enzyme is in the soluble portion of the cells and the steroids have to traverse the membrane in both directions. In the transfer of estrogens from plasma of cytoplasm, the membrane needs to be considered as a separate compartment.

Protein binding of bilirubin: Comparison of in vitro and in vivo measurements of bilirubin displacement by drugs

A comparison of methods for the in vitro and in vivo measurement of unbound bilirubin in the presence of plasma proteins, drugs and other chemicals was made to determine the best methods for preclinical investigation of new drugs that may be used during the perinatal period. The methods examined included: equilibrium dialysis, binding of 2-(4′-hydroxybenzeneazo)benzoic acid to serum, spectral shift of free and albumin-bound bilirubin, displacement of bilirubin from albumin to mitochondria in vitro, drug-mediated decrease in plasma bilirubin in hyperbilirubinemic Gunn rats, and Sephadex gel filtration for separation of protein bound and unbound bilirubin. Sephadex gel filtration appeared to be the most useful method for measurement of unbound bilirubin. There was good agreement between in vitro studies of sulfadimethoxine and salicylate displacement of bilirubin using Sephadex gel filtration and in vivo studies in the Gunn rat. Studies of bilirubin displacement in the icteric Gunn rat provide a basis for establishing realistic conditions of drug dosage, the time course of drug action and the possible role of metabolites where there is insufficient information to establish the appropriate conditions for in vitro investigations.

HEMOLYSIS FOLLOWING INFUSIONS OF FAT EMULSIONS.

The quantity of NEFA liberated in the bloodstream after fatty infusions is not sufficient to produce hemolysis. The NEFA concentrations in the spleen after fat infusions could produce hemolysis locally without elevation of circulating NEFA levels. Emulsifying agents may be implicated in the anemia. Phospholipids are hemolytic in saline, but are sufficiently bound by the proteins of plasma to become relatively inactive. Surface-active substances which bind to plasma proteins are the least hemolytic in vitro. Since the nonionic detergents are not bound by plasma proteins, they remain hemolytic in the presence of plasma even in low concentrations. The plasma-binding properties of lecithin, which mollify its hemolytic properties, cause the emulsion to cream in the presence of plasma proteins.

VASOACTIVE PROPERTIES OF PLASMA PROTEIN FRACTIONS.

The capacity of plasma to potentiate norepinephrine (NOR)-induced contractions of the rabbit aortic strip can be attributed to the plasma protein fractions, perhaps almost exclusively to their albumin content. Albumin, 0.2–2 mg/15 ml, potentiated a threshold test dose of NOR from minimal to maximal effect. In the presence of albumin 1–2 mg/15 ml, the threshold dose of NOR was decreased about five to ten times. Albumin, 500 mg/15 ml, did not have a greater potentiating effect. Albumin itself had no contracting ability. The blood of the anesthetized rabbit does not contain sufficient NOR to contract the aortic strip; such concentrations of NOR even in the presence of plasma proteins or albumin were ineffective. The data suggest that NOR does not contribute directly to the maintenance of normal vascular tone.

Observations on the presence of plasma proteins in skin and tendon.

Observations on the presence of plasma proteins in skin and tendon.