Accumulation of pyrraline-modified albumin in phagocytes due to reduced degradation by lysosomal enzymes

Previous studies suggested that the interaction between proteins modified by advanced glycation end products (AGEs) and cells, such as macrophages, may be involved in diabetic angiopathy. Pyrraline is one of the AGEs and known to be elevated in plasma of diabetic rats and humans, and is present in vascular lesions of diabetic and elderly subjects. We examined whether modification of albumin by pyrraline influences its degradation by macrophage-like cell line, P388D1 cells. Degradation of pyrraline-modified albumin by these cells was diminished, causing accumulation of the albumin in these cells. The susceptibility of pyrraline-modified albumin to lysosomal proteolytic enzymes was reduced by approximately 40% in vitro, while lysosomal activity in the cells per se was not affected. This phenomenon was also observed when human monocytes were used instead of P388D1 cells. Our results suggest that accumulation of pyrraline-modified albumin in P388D1 cells is due to the reduced susceptibility of the protein to lysosomal enzymatic degradation. Such alterations in the interaction between AGEs-modified protein and phagocytes may contribute to angiopathy in elderly subjects and patients with diabetes.     

Glycated proteins modulate tissue-plasminogen activator-catalyzed plasminogen activation

Plasminogen activation by tissue-plasminogen activator (t-PA) is accelerated by the presence of a macromolecular surface, which acts as a template that brings enzyme and substrate in close proximity. Modification of lysine residues, which are important for this template function, occurs in diabetic patients as a consequence of glycation of proteins. In this study, we investigated the effects of glycation of fibrin and other proteins in t-PA-catalyzed plasmin formation. Plasminogen activation on glycated fibrin(ogen) was increased compared to non-glycated fibrin(ogen), which could fully be attributed to an increased affinity of t-PA for glycated fibrin(ogen). Binding of plasminogen to glycated fibrin was increased, but did not contribute to increased plasminogen activation. Both plasminogen activator inhibitor-1 (PAI-1) binding and activity were increased on glycated fibrin. Induction of template function in plasminogen activation was also observed on immobilized glycated bovine serum albumin (BSA) and human gamma-globulins (IgG). Increased plasmin generation at sites of deposition of glycated proteins may lead to increased extracellular matrix breakdown and thereby affect the integrity of the endothelial monolayer. Moreover, soluble glycated BSA and glycated IgG can inhibit t-PA binding to immobilized glycated fibrin and interfere with fibrinolysis in diabetic patients.     

Actinomycin D binding to single-stranded DNA: sequence specificity and hemi-intercalation model from fluorescence and 1H NMR spectroscopy

Various in vitro studies have shown that delta-9-tetrahydrocannabinol (THC), the major psychoactive component of marijuana, has a variety of inhibitory effects on immune functions including effects on macrophages. The present studies have examined the mechanism of THC's effects on tumor necrosis factor alpha (TNF-alpha), a major macrophage-produced cytokine and an important mediator involved in cytokine networks and in host defense mechanisms. Exposure of macrophages to medium containing THC has resulted in low levels of soluble TNF-alpha protein and reduced TNF-alpha bioactivity in the culture supernatant. However, THC did not inhibit the levels of LPS-induced TNF-alpha mRNA and intracellular TNF-alpha precursor protein, had only a weak effect on expression of membrane-bound TNF-alpha, but suppressed TNF-alpha maturation/secretion by macrophages. The higher the THC concentration in the medium during TNF-alpha induction, the greater the amount of intracellular TNF-alpha precursors that accumulated in the activated macrophages and the less mature TNF-alpha was released from the cells. Data suggest that TNF-alpha production by macrophages was altered greatly by exposure to THC at the levels of TNF-alpha precursor maturation and secretion.     

Effects of anandamide on gestation in pregnant rats

The present study was to test whether the recently described endogenous ligand for the cannabinoid receptor; arachidonyl-ethanolamide (anandamide, ANA), may produce similar effects on pregnancy as the main psychoactive component of marihuana: delta9-tetrahydrocannabinol (THC) in rats. ANA, THC (0.02 mg/kg i.p./day, respectively) or vehicle were injected daily over the third week of pregnancy. The pregnant rats were either killed on day 21 of pregnancy or followed up to delivery. Results show a significant increase in the duration of pregnancy after both THC and ANA treatment. Both drugs caused an increase in the frequency of stillbirths. The mothers' hormone contents in tissues and sera were measured. Decreased LH content was observed in the serum of treated animals. No changes in FSH content were observed either in the pituitary or in the sera. Pituitary prolactin (PRL) levels was lower in ANA treated animals as compared both to controls or THC treated subjects. The serum PRL content decreased in all experimental groups. Decrease in serum progesterone was more prominent in treated rats. Serum levels of prostaglandins (PGF 1alpha and PGF 2alpha) were significantly decreased after THC and ANA treatment. We conclude that ANA has the same tendency to change reproductory parameters in pregnant rats as THC, although in some cases the effects of ANA were slightly different from that of THC. Both endogenous and exogenous cannabinoids inhibit PG synthesis in pregnant rats and this maybe responsible for the delay constitute the mechanism in the onset of labour.     

Studies of human diploid fibroblast growth. I. Responses of normal and hypopituitary cells to fibroblast growth factor, insulin, and serum

We have assayed the growth stimulating activity of bovine insulin, fibroblast growth factor (FGF), and fetal bovine serum (FBS) in diploid human fibroblasts from normal and idiopathic hypopituitary donors. All three factors stimulated DNA synthesis in cells arrested by serum starvation. FGF was active at concentrations as low as 5 ng/ml with maximum effect at 100 ng/ml. FGF stimualted DNA synthesis at lower concentrations than did insulin and also produced a greater maximum response. Only serum was capable of supporting cell division and growth, but FGF accellerated this growth rate when it was added to serum-containing medium. Hydrocortisone, actinomycin D, and cycloheximide inhibit FGF stimulation. There was no significant difference between fibroblasts from normal and hypopituitary donors.     

Determination of cholesterol absorption in man by intestinal perfusion

Gel filtration was used to measure drug interaction with protein-bound bilirubin in 0.5 ml samples of Gunn rat serum, human serum and fraction V human serum albumin. Using sulfadimethoxine as a prototype differences in displacement were found in all 3 sera. The differences between human and rat serum were related to the binding characteristics of sulfadimethoxine whereas the differences between human serum and fraction V human serum albumin were attributed to displacement of bilirubin from albumin to other proteins in serum. Gel filtration permitted the use of small samples with bilirubin-albumin ratios less than 1.0 and provided data that were used for analysis of drug displacement of bilirubin using principles of drug-receptor theory. Ten of 14 drugs found to alter serum bilirubin concentrations in icteric Gunn rats had measurable effects on protein binding of bilirubin.     

Delta9-tetrahydrocannabinol suppresses macrophage costimulation by decreasing heat-stable antigen expression

Delta9-tetrahydrocannabinol (THC) suppresses several immunologic functions of macrophages. The costimulatory activity of a THC-exposed macrophage hybridoma was investigated by its ability to elicit interleukin-2 secretion by a helper T cell hybridoma activated with immobilized monoclonal anti-CD3 antibody. THC added at culture initiation inhibited the T cell response in a dose-dependent manner. When the macrophages were fixed with paraformaldehyde before culture, THC had no effect on T cell stimulation. However, macrophages, which were preincubated with THC and then fixed, were impaired in delivering costimulatory signals to T cells cultured without THC. The drug's inhibitory effect on macrophage costimulatory activity was reversible. THC exposure also decreased macrophage expression of heat-stable antigen (HSA). Antibody blocking experiments showed that HSA expressed on the macrophages provided an important costimulatory signal, whereas B7-1 and B7-2 molecules had a minor role. Treatment of the macrophages with phosphatidylinositol-specific phospholipase C cleaved HSA, but not the transmembrane B7 molecules, from the cell surface. Similar to THC, enzyme treatment significantly diminished macrophage costimulatory activity, which was also reversible. After drug or enzyme removal, HSA expression returned to the control level by 4 h. Therefore, THC suppresses macrophage costimulatory activity by diminishing cell surface expression of HSA.     

Salmonella typhi O:9,12 polysaccharide-protein conjugates: characterization and immunoreactivity with pooled and individual normal human sera, sera from patients with paratyphoid A and B and typhoid fever, and animal sera

Polysaccharide of O:9,12 specificity purified from Salmonella typhi was conjugated to tetanus toxoid or bovine serum albumin in order to obtain defined antigenic material that would contain O chain free of other S. typhi antigens and that would be suitable for characterizing host humoral response to only S. typhi O-chain antigens. These artificial conjugates were strongly reactive in immunodots with 18 pooled and 3 individual serum samples from patients with typhoid fever and with rabbit anti-Salmonella O antiserum (group D, factors 1, 9, and 12). They reacted weakly with one serum sample from one human with paratyphoid A. These results suggest that the periodate oxidation and the reductive amination used in the conjugation conserved the immunogenicity of the O chain and allowed its absorption to nitrocellulose. They also suggest that the bovine serum albumin conjugate could be used in the diagnosis of S. typhi infections as normal sera may react with the protein molecule of the tetanus toxoid conjugate.     

Transcription factor E2F and cyclin E-Cdk2 complex cooperate to induce chromosomal DNA replication in Xenopus oocytes

Although no chromosomal DNA replication actually occurs during Xenopus oocyte maturation, the capability develops during the late meiosis I (MI) phase in response to progesterone. This ability, however, is suppressed by Mos proteins and maturation/mitosis promoting factor during the second meiosis phase (meiosis II; MII) until fertilization. Inhibition of RNA synthesis by actinomycin D during early MI prevented induction of the replication ability, but did not interfere with initiation of the meiotic cell cycle progression characterized by oscillation of the maturation/mitosis promoting factor activity and germinal vesicle breakdown. Microinjection of recombinant proteins such as dominant-negative E2F or universal Cdk inhibitors, p21 and p27, but not wild type human E2F-1 or Cdk4-specific inhibitor, p19, into maturing oocytes during MI abolished induction of the DNA replication ability. Co-injection of human E2F-1 and cyclin E proteins into immature oocytes allowed them to initiate DNA replication even in the absence of progesterone treatment. Injection of cyclin E alone, which was sufficient to activate endogenous Cdk2 kinase, failed to induce DNA replication. Moreover, the activation of Cdk2 was not affected under the conditions where DNA replication was blocked by actinomycin D. Thus, like somatic cells, both activities of E2F and cyclin E-Cdk2 complex are required for induction of the DNA replication ability in maturing Xenopus oocytes, and enhancement of both activities enables oocytes to override DNA-replication inhibitory mechanisms that specifically lie in maturing oocytes.     

Iron-containing proteins augment responses of human lymphocytes to phytohemagglutinin and pokeweek mitogen in serum-free medium

The effects of various iron-containing compounds on the responses of human peripheral lymphocytes to phytohemagglutinin (PHA) and pokeweed mitogen (PWM) were studied in serum-free medium supplemented with bovine serum albumin. Hemoglobin, transferrin and ferritin enhanced the incorporation of 3H-thymidine into DNA after PHA-stimulation of lymphocytes, while hemin, iron metal powder, ferrous sulfate, chromium powder, and zinc sulfate have little effect. The response to PWM, measured by plaque formation, was enhanced only by transferrin. Desferrioxamine, a chelating agent specific for ferric iron, completely removed these augmentative effects. The results indicate that iron-containing proteins influenced the responses of lymphocytes to stimulation by PHA and PWM in serum-free medium.     

Genetic and clinical features of sensorineural hearing loss associated with the 1555 mitochondrial mutation

This article describes the modulation, by extracellular collagen, of DNA and proteoglycan synthesis in articular chondrocytes stimulated with transforming growth factor-beta 1. Type-I and type-II collagen, heat-denatured type-II collagen, and bovine serum albumin were each incorporated into alginate in increasing concentrations. Bovine articular chondrocytes were isolated and were resuspended in the alginate, yielding alginate beads with final extracellular protein concentrations of 0-1.5% (wt/vol) for the collagens and 0-2.5% (wt/vol) for bovine serum albumin. Cultures of beads were maintained for 7 days in basal Dulbecco's modified Eagle medium or in medium supplemented with 10 ng/ml transforming growth factor-beta 1. Subsequently, the synthesis of DNA and proteoglycan was measured by radiolabel-incorporation methods with [35S]sulfate and [3H]thymidine, and the values were normalized to the DNA content. Transforming growth factor-beta 1 stimulated the synthesis of both DNA and proteoglycan in a bimodal fashion. The presence of extracellular type-II collagen increased the rate of DNA and proteoglycan synthesis in a dose-dependent fashion in cultures stimulated by transforming growth factor-beta 1, whereas heat-inactivated type-II collagen abrogated the effects observed with type-II collagen for synthesis of both DNA and proteoglycan. In contrast, the presence of extracellular type-I collagen caused a dose-dependent inhibition of synthesis of both DNA and proteoglycan in cultures stimulated with transforming growth factor-beta 1. Extracellular bovine serum albumin brought about a limited increase in synthesis rates, presumably by blocking nonspecific cytokine binding. These results suggest that type-II collagen has a specific role in chondrocyte regulation and serves to mediate the response of chondrocytes to transforming growth factor-beta 1.     

Further studies on the endocytic activity of Tritrichomonas foetus

The endocytic activity of Tritrichomonas foetus was studied at the ultrastructural level using gold-labeled macromolecules (bovine lactoferrin, human and bovine transferrin, bovine albumin, human low-density lipoprotein, horseradish peroxidase, and protein A). All macromolecules were ingested by the protozoan. Binding experiments showed that only bovine lactoferrin bound to the parasite surface in a process that could be inhibited by the unlabeled protein, suggesting that it binds and is internalized via receptors. Label-fracture experiments showed that the receptors were distributed in clusters that did not colocalize with intramembranous particles. Kinetics analysis of the internalization of bovine lactoferrin and horseradish peroxidase, associated with the cytochemical detection of acid phosphatase, revealed that proteins were rapidly ingested through small uncoated vesicles and delivered to acid phosphatase-containing compartments. The colocalization of gold-labeled proteins and reaction product indicative of enzyme activity was confirmed by electron spectroscopic imaging. Simultaneous incubation of cells in the presence of two proteins labeled with gold particles of different diameters showed that they were ingested through the same pathway and were concentrated into cytoplasmic vacuoles corresponding to lysosome-like organelles. These data suggest that the endocytic process in T. foetus is very rapid and that the intracellular pathway for receptor-mediated and fluid-phase endocytosis seems to be the same.     

Bovine fetuin is an inhibitor of insulin receptor tyrosine kinase

Fetuin has been identified earlier as the bovine homolog of the human plasma protein, alpha2-Heremans Schmid glycoprotein (alpha2-HSG). Although bovine fetuin shares over 70% amino acid sequence similarity with alpha2-HSG and rat fetuin, no common function(s) have been identified. We report that immunoaffinity purified bovine fetuin acts as an inhibitor of insulin receptor tyrosine kinase activity (IR-TKA) with half-maximal inhibition at 1.5 microM. In vitro, bovine fetuin (1.5 microM) blocked insulin-induced autophosphorylation of the human IR completely and the half-maximal inhibitory effect was observed at 0.5 microM. Incubation of HIRcB cells (rat1 fibroblasts transfected with wild-type human insulin receptor cDNA) with bovine fetuin (1.5 microM) inhibited insulin-induced tyrosine phosphorylation of the IR beta-subunit by 40%. In addition, bovine fetuin (2 microM) completely blocked insulin-stimulated DNA synthesis in H-35 rat hepatoma cells. Our results, together with earlier reports on rat fetuin and human alpha2-HSG, indicate a common IR-TK inhibitory function for fetuin homologs.     

Rapid dissociation of human apurinic endonuclease (Ape1) from incised DNA induced by magnesium

We investigated the interaction dynamics of human abasic endonuclease, the Ape1 protein (also called Ref1, Hap1, or Apex), with its DNA substrate and incised product using electrophoretic assays and site-specific amino acid substitutions. Changing aspartate 283 to alanine (D283A) left 10% residual activity, contrary to a previous report, but complementation of repair-deficient bacteria by the D283A Ape1 protein was consistent with its activity in vitro. The D308A, D283/D308A double mutant, and histidine 309 to asparagine proteins had 22, 1, and approximately 0. 02% of wild-type Ape1 activity, respectively. Despite this range of enzymatic activities, all the mutant proteins had near-wild-type binding affinity specific for DNA containing a synthetic abasic site. Thus, substrate recognition and cleavage are genetically separable steps. Both the wild-type and mutant Ape1 proteins bound strongly to the enzyme incision product, an incised abasic site, which suggested that Ape1 might exhibit product inhibition. The use of human DNA polymerase beta to increase Ape1 activity by eliminating the incision product supports this conclusion. Notably, the complexes of the D283A, D308A, and D283A/D308A double mutant proteins with both intact and incised abasic DNA were significantly more stable than complexes containing wild-type Ape1, which may contribute to the lower turnover numbers of the mutant enzymes. Wild-type Ape1 protein bound tightly to DNA containing a one-nucleotide gap but not to DNA with a nick, consistent with the proposal that substrate recognition by Ape1 involves a space bracketed by duplex DNA, rather than mere flexibility of the DNA.     

Hydrational and intrinsic compressibilities of globular proteins

To evaluate further bacterial DNA immunization as a model to study antigen drive in the anti-DNA response, the specificity of induced monoclonal anti-DNA antibodies was characterized. A panel of IgM and IgG monoclonal anti-DNA antibodies was produced from spleen cells of BALB/c mice immunized with single-stranded DNA from E. coli complexed to methylated bovine serum albumin in complete Freund's adjuvant. The binding of these antibodies to DNA and non-DNA antigens was tested by ELISA to assess their range of polyspecificity. These monoclonal antibodies were found to bind to nucleic acid as well as non-nucleic acid antigens, such as beta-galactosidase, cardiolipin, Ro, La and Sm. These studies demonstrate that anti-DNA antibodies from normal mice, although induced by bacterial DNA, may display a broad range of antigen recognition and thus resemble lupus anti-DNA antibodies, many of which are polyspecific, in their pattern of cross-reactivity.     

Diffusion of albumins in rat cortical slices and relevance to volume transmission

The apparent diffusion coefficient, D*, was measured in rat cortical slices and compared to the free diffusion coefficient, D, for three negatively charged proteins, lactalbumin (mol. wt = 14,500), ovalbumin (45,000) and bovine serum albumin (66,000). The temporal evolution of the spatial distribution of albumin molecules labeled with the Texas Red fluorophore was determined using integrative optical imaging at intervals after a brief pressure injection from a micropipette in slices of adult rat cerebral cortex and dilute agarose gel. Diffusion coefficients were obtained by fitting appropriate equations to the data. In slices at 34 degrees C, the values of D* (10(-7) cm2/s, mean +/- S.E.M.) for lactalbumin, ovalbumin and bovine serum albumin were 2.37 +/- 0.10, 1.60 +/- 0.08 and 1.63 +/- 0.07, respectively. In agarose gel, values of D (10(-7) cm2/s) were 11.87 +/- 0.20, 10.02 +/- 0.25 and 8.29 +/- 0.17, respectively. From these data the tortuosity factors, (D/D*)0.5, were calculated, with 2.24 obtained for lactalbumin, 2.50 for ovalbumin and 2.26 for bovine serum albumin. Previous optical measurements using dextrans with mol. wts of 40,000 and 70,000 gave tortuosities of 2.16 and 2.25, but in contrast previous determinations with ion-selective microelectrodes using the small cation tetramethylammonium (mol. wt = 74.1) give tortuosities of about 1.6. The results show that proteins as large as bovine serum albumin diffuse through brain extracellular space but are more hindered than smaller molecules. A simple model compared the differences in diffusion properties of bovine serum albumin, dopamine and nitric oxide in brain tissue and discussed the implications for volume transmission of chemical information between cells. The results are also relevant to the behavior of diffusible factors in brain development and the delivery of therapeutic agents.     

Numerical inversion of the Perrin equations for rotational and translational diffusion constants by iterative techniques

An iterative numerical technique is presented which allows the semiaxes for prolate and oblate ellipsoids to be determined from the Perrin equations for rotational and translational diffusion constants. The use of this inversion technique is illustrated by application to the proteins: lysozyme, bovine serum albumin, human transferrin, and bovine rhodopsin solubilized in digitonin.     

Acoustic absorption due to proton transfer in solutions of proteins, peptides and amino acids at neutral pH

Measurements of ultrasonic absorption in the frequency range 2 to 60 MHz have been made on solutions of the amino acid histidine, dipeptides glycyl tyrosine and histidyl tyrosine, and proteins lysozyme and bovine serum albumin. Measurements were carried out at 37 degrees C and covered the pH range 6.8 to 7.7. Mechanisms for the observed excess acoustic absorption involving bimolecular and intramolecular proton transfer are considered.     

Partitioning of proteins in dextran/hydrophobically modified dextran aqueous two-phase systems

Partitioning of proteins was studied in aqueous two-phase systems composed of the polymers dextran and hydrophobically modified dextran. The modified dextrans were benzoyl dextran with a degree of substitution of 0.17 and valeryl dextran with a degree of substitution of 0.20. Phase diagrams for the systems of dextran/benzoyl dextran and dextran/valeryl dextran were determined at room temperature. The proteins studied were beta-galactosidase, bovine serum albumin, beta-lactoglobulin, lysozyme, myoglobin and cytochrome C. The partition coefficients of a series of salts were determined in dextran/benzoyl dextran two-phase systems. The addition of salts had strong effect on the partitioning of proteins. This effect was related to protein net charge and the position of the ions in the Hofmeister series. Cross partitioning of bovine serum albumin was studied in a dextran/benzoyl dextran aqueous two-phase system.     

Immunological and serological diversity of Neisseria gonorrhoeae: gonococcal serotypes and their relationship with immunotypes

Strains of gonococcus were shown to be immunologically heterologous. Serum bactericidal activity generally correlated with induced immunity to gonococcal challenge as detected by the guinea pig subcutaneous chamber model. Sera devoid of bactericidal activity reflected the lack of cross-protection in subcutaneous chambers. Factors affecting the bactericidal assay described in this report include (i) source of complement, (ii) concentration of test antigen and complement activity, and (iii) presence of calcium and magnesium ions and bovine serum albumin in diluent. Poor correlation was observed between agglutinating activity of the immune sera and protection.