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At least 1,621 records · Page 90Linked to original sources
PubMed1987

Affinity purified immunoglobulin G transfers immediate hypersensitivity to guinea pig colonic epithelium in vitro.

Our aim was to establish whether the epithelial type 1 hypersensitivity reaction in response to a dietary antigen, as we have previously described, had an immunologic basis. Using serum from guinea pigs fed with milk proteins we examined the passive transfer of sensitivity to beta-lactoglobulin. Biophysical methods were used to measure electrogenic chloride secretion across colonic epithelia. This response has been shown previously to be the cellular function that is altered after antigen challenge. Affinity column chromatography was used to separate immune serum into immunoglobulin G-(IgG)-rich and immunoglobulin G-depleted fractions and the purity of these fractions was established. Passive transfer of sensitivity was possible with the immunoglobulin G-rich, but not the immunoglobulin G-depleted, fraction. We have proven, therefore, that the reaction is mediated, at least in part, by immunoglobulins of the G class. This finding may have implications for the study of phenomena of food allergy.

Animals↗
PubMed1984

Circulating immune complexes, immunoglobulins, complement, antibodies to dietary antigens, cholesterol and lipoproteins levels in patients with occlusive coronary lesions.

The presence of circulating immune complexes, serum immunoglobulins, C3 (the third component of complement), antibodies to alpha-lactalbumin, beta-lactoglobulin and bovine serum albumin was studied in 39 patients subjected to coronary arteriography. Total serum cholesterol and triglycerides and cholesterol in VLDL, LDL and HDL were also estimated. The results obtained in the group of patients found with occlusive lesions were compared with those found in the group without lesions. With one of the five assays used for the detection of immune complexes, higher and significant levels were found in the group with lesions. A negative and significant correlation was found between the number of vessels with lesions and the levels of serum C3.

Adult↗
PubMed1986

Thermal behavior of proteins in high-performance hydrophobic-interaction chromatography. On-line spectroscopic and chromatographic characterization.

The thermal behavior of a series of standard proteins in hydrophobic interaction chromatography on a previously developed weakly hydrophobic ether-bonded phase column has been studied. Depending on the temperature and protein, conformational changes can occur in the chromatographic system. Methods for recognizing these conformational effects are presented, including retention and peak width variations with temperature, and Z values (the slope of the plot of log k' vs. log %B solvent. The Z value is shown to be a general index characterizing protein retention as a function of salt concentration. In addition, on-line UV spectroscopic analysis, (absorbance ratios and second derivative spectroscopy) with a photodiode array detector, is shown to corroborate chromatographic trends. Lysozyme maintains a stable conformation over the temperature range 10-40 degrees C, whereas beta-lactoglobulin A has a conformational transition between 25 degrees C and 40 degrees C. Calcium-depleted alpha-lactalbumin, a rather labile species, maintains a stable conformation up to ca. 20 degrees C, and then undergoes structural changes. Finally, cytochrome c appears to be relatively stable up to ca. 65 degrees C. Since conformational changes for this protein occur at ca. 35 degrees C on more hydrophobic phases, the extent of hydrophobicity of the stationary phase is important for maintenance of the native state. Based on this work, hydrophobic-interaction chromatography at sub-ambient temperatures appears promising.

Chromatography↗
PubMed1992

Adsorption behavior of milk proteins on polystyrene latex. A study based on sedimentation field-flow fractionation and dynamic light scattering.

Sedimentation field-flow fractionation (SdFFF) has been used to characterize the adsorption of the proteins beta-casein (BCN) or beta-lactoglobulin (BLG) on colloidal polystyrene latices; this system was used to model hydrophobic interactions between the proteins and the surfaces of fat droplets in protein-stabilized emulsions. It was found that the SdFFF technique could determine directly the surface concentrations of BCN and BLG irreversibly adsorbed to the latex surface, provided care was taken to maintain the ionic strength of the carrier at a level which suppressed particle-wall repulsion in the separation channel. The measured surface concentrations were similar for the two proteins (about 1 mg/m2), and this was verified by quantitative amino acid analysis. These concentrations were smaller than those found in depletion studies (3 and 4 mg/m2 respectively for BCN and BLG), in which loosely associated protein may have been included in the determinations. The thickness of the adsorbed layers was determined in situ by dynamic light scattering and was found to differ significantly for the two proteins (up to 15 nm for BCN vs. 2-3 nm for BLG). The implication of these findings in terms of different surface arrangements of the two proteins is discussed.

Calorimetry↗
PubMed1995

Comparison of capillary electrophoresis with traditional methods to analyse bovine whey proteins.

The separation of the four major whey proteins by sodium dodecyl sulphate (SDS)-capillary gel electrophoresis (CGE) is described. Whilst commercially purified whey proteins could be analysed using the recommended protocol, the more complex nature of an acid whey and a reconstituted whey protein concentrate (WPC) powder necessitated considerable refinement of the CGE sample buffer. Individual whey proteins in the acid whey and WPC samples were then also separated and quantitated using capillary zone electrophoresis, polyacrylamide gel electrophoresis (PAGE) and HPLC methods and the results were compared. The values obtained for alpha-lactalbumin (alpha-Lac) and beta-lactoglobulin (beta-Lg) were consistent throughout the various methods, although size-exclusion HPLC, SDS-PAGE and SDS-CGE could not separate the two beta-Lg variants or the glycosylated form of alpha-Lac from the beta-Lg. There was considerable variation in the values for the bovine serum albumin and immunoglobulin determined by the different methods and it was concluded that none of the methods could satisfactorily quantitate all four whey proteins.

Animals↗
PubMed1996

Characterization of ewe's milk by capillary zone electrophoresis.

The purpose of the present work was to develop a procedure able to separate and identify the major protein components of ewe's milk by capillary zone electrophoresis (CZE). Thirty-five individual milk samples of Massese breed were analyzed using a coated capillary. The analyses were performed at pH 3.0 at a temperature of 40 degrees C in the presence of 6 M urea. The purification of casein fractions was carried out by preparative fast protein liquid chromatography and the CZE results were confirmed by polyacrylamide agarose gel electrophoresis (PAAGE). The identification of whey proteins was also carried out by comparison with high-performance liquid chromatography data. The present study permitted the identification of the major components of ewe's milk by high-resolution electropherograms and characteristic migration times (tM). it was also possible to detect the presence of genetic variants of beta-lactoglobulin. The tM of k-casein was determined after enzymatic action of chymosin by verifying the simultaneous formation of p-k-casein. In most of the samples a fast moving alpha-s2-casein variant was identified by comparison with PAAGE results. Minor genetic differences were found in other casein fractions for this pool of samples.

Animals↗
PubMed1985

ELISA quantitation of IgG subclass antibodies to dietary antigens.

The IgG subclasses of human antibodies against 2 dietary antigens, ovalbumin (OA) and beta-lactoglobulin (BLG), were studied by ELISA using monoclonal anti-human IgG subclass antibodies. Under the assay conditions used, the anti-IgG subclass antibodies were subclass specific. Quantitative estimates of the subclass antibodies were obtained by reference to a 'capture' assay using F(ab')2 anti-light chain antibody as ligand and IgG myelomas as standards. The validity of these estimates was supported by antibody quantitation using the Farr assay. In healthy adults with serum anti-OA or anti-BLG antibodies, anti-OA antibodies were found mainly in the IgG1 (9/11) and IgG4 (6/11) subclasses, whereas 5 sera showed high levels of IgG2 antibodies. In contrast, the IgG subclass distribution of anti-BLG antibodies was predominantly IgG4 (10/10).

Adult↗
PubMed1993

Recombinant interleukin-1 receptor antagonist protein prevents sensitization and intestinal anaphylaxis in guinea pigs.

Recombinant interleukin-1 receptor antagonist protein (rlRAP, 0.5 mg/kg) administered intraperitoneally in guinea pigs one hour before primary and booster parenteral sensitization (1 ml) by cow milk, led to a reduced immunoglobulin E (IgE) production, as displayed by a passive cutaneous anaphylaxis test. rlRAP administered intraperitoneally in sensitized guinea pigs at 0.5 mg/kg 10 min before challenge administration (beta-lactoglobulin, 100 mg per os), also prevents the colonic motor and secretory changes induced by intestinal anaphylaxis. These results suggest the involvement of interleukin-1 in food allergy and evidence a double protective role for rlRAP in food hypersensitivity.

Anaphylaxis↗
PubMed1987

Peripheral and intestinal lymphocyte activation after in vitro exposure to cow's milk antigens in normal subjects and in patients with Crohn's disease.

We studied in Crohn's disease and controls the in vitro activation of either peripheral (PBMNC) or intestinal (LPMNC) mononuclear cells in response to the cow's milk antigen beta-lactoglobulin (Blg). The activation of mononuclear cells was investigated by analyzing the kinetics of the transferrin receptor (T9 antigen) and interleukin 2 receptor (Tac antigen) expression. In both controls and Crohn's disease patients Blg (1 microgram/ml) induced a significant (P less than 0.01) increase of T9 and Tac expression by both PBMNC and LPMNC cultured for 3 days. After Blg exposure the counts of T9- and Tac-bearing cells were significantly (P less than 0.05) higher in PBMNC cultures from healthy controls than in those from patients with Crohn's disease. In both groups peripheral T-enriched cell suspensions did not express T9 and Tac when stimulated with Blg but were restored to express either antigen by the addition of 10% autologous adherent cells. In LPMNC cultures from patients with Crohn's disease the Tac expression after 3 days of Blg stimulation was significantly (P less than 0.05) higher than in the autologous PBMNC. Data from this study indicate that in both controls and patients with Crohn's disease lymphocytes sensitized to Blg occur in the circulation as well as in the gut lamina propria. Our data also suggest that in Crohn's disease an increased proportion of lymphocytes sensitized to Blg are recruited from the circulation into the site of the intestinal lesion.

Adult↗
PubMed1990

Antibody response to milk proteins in patients with milk-protein intolerance documented by challenge.

To evaluate the role of specific antibody response to milk proteins in patients with milk-protein intolerance, allergen-specific IGE, IgG, and IgG4 to these proteins were measured by ELISA. Bovine casein, gamma globulin (GG), beta-lactoglobulin, and lactalbumin were the milk proteins used. Antibody production to these proteins were analyzed in 18 patients who underwent milk-protein challenges (eight positive and 10 negative) and in five normal children used in the analysis. ELISA results for specific IgE, IgG, and IgG4 to these specific proteins demonstrated no statistically different response to the four milk proteins among the three patient groups by multivariate analysis. When the specific antibody results from the positive challenge group, the negative challenge group, and the normal group were combined, the IgE and IgG4 to GG and the IgG to casein were significantly higher (p less than 0.01) than the corresponding specific antibody to the other proteins tested. The IgG or IgG4 to GG would differentiate the positive from the negative challenge group (p less than 0.05) but were not significantly different from the normal control group. Contrary to previously published studies, these results indicate IgG specific for the milk proteins are not increased in patients with milk-protein intolerance. The data also support the concept that IgE and IgG4 are not elevated in these patients. Therefore, there appears to be no pathogenic role for these specific immunoglobulins in milk-protein intolerance.

Antibody Formation↗
PubMed1990

Rectal gluten challenge and diagnosis of coeliac disease.

44 patients referred consecutively for jejunal biopsy underwent rectal gluten challenge with 2 g peptic-tryptic digest (Frazer's fraction III; FF3). Rectal biopsy was done before the challenge and 6 h afterwards. Total intraepithelial lymphocytes (IEL) overlying a 10(4) micron 2 test area of muscularis mucosae were quantified by computerised image analysis. The subjects comprised 21 controls with disorders other than coeliac disease and 23 patients (14 treated, 9 untreated) with coeliac disease diagnosed by strict jejunal biopsy gold standard criteria. There was no difference between the groups in IEL numbers before challenge. Coeliac disease patients but not controls responded to FF3 with a rise in mucosal IEL (median 60.5% rise for treated, 63.0% for untreated). There was no response to challenge with beta-lactoglobulin in coeliac disease or control subjects. When a predefined, post-challenge IEL "predictive index" of more than 10% above baseline was used to indicate a diagnosis of coeliac disease, it gave a sensitivity of 90% and specificity of 91% (95% confidence intervals 78-93%). Rectal gluten challenge is a simple, safe, and reliable test of gluten sensitivity, both as a screening test for untreated coeliac disease and as a confirmatory test in patients with treated coeliac disease.

Celiac Disease↗
PubMed1993

Preparation and characterization of whey protein hydrolysates: applications in industrial whey bioconversion processes.

A whey protein hydrolysate was prepared by incubation of reconstituted whey or a whey protein concentrate with Alcalase 0.6L. The proteolytic degradation of alpha-lactalbumin and beta-lactoglobulin initially resulted in 6-kDa and, later, 2.5-kDa degradation products, quickly followed by the appearance of multiple peptides of 1 kDa or smaller. The hydrolysate showed a steady increase in solubility and a biphasic change in foaming characteristics with decreasing peptide size. At the highest degree of hydrolysis achieved (22%), the majority of the peptides were smaller than 1 kDa and could be efficiently assimilated by the yeast Kluyveromyces marxianus growing in a defined medium.

Biotransformation↗
PubMed1996

Pressure-induced change in proteins studied through chemical modifications.

Pressure-induced change of two bovine proteins, alpha-lactalbumin (LA) and beta-lactoglobulin (LG), was investigated at neutral pH by means of fluorescence and CD spectroscopy. The rate and the extent of modification was considerably increased by applying high pressure during the dansylation reaction of LG, while those for LA were only moderately affected. This difference was accounted for by the structural deformation of these proteins under high pressure. The fluorescence spectrum of these proteins measured under elevated pressure, as well as their fluorescence and CD spectra after the pressure release, indicated different responses towards pressure. The structural change of LA was practically reversible up to 400 MPa, whereas that of LG lost reversibility at 150 MPa or lower. Fluorescent measurement of dansylated (prepared at atmospheric pressure) proteins, especially the energy transfer from the intrinsic Trp residue to the dansyl group, showed that the protein structure was deformed by pressure and that the energy transfer facility of the two proteins was differently affected by high pressure, probably reflecting the degree of compactness of their pressure-perturbed structures.

Animals↗
PubMed1991

Platelets process adsorbed protein: a morphological study.

The nature of the adsorbed protein on a non-biological biomaterial surface is known to influence cell adhesion. This work deals with the contribution of adherent platelets towards the redistribution of preadsorbed proteins. A redistribution was only observed with spread platelets on adsorbed fibrinogen and fibronectin, but not with adsorbed beta-lactoglobulin. The labelled protein images showed a dark outer ring with an inner region having fluorescent areas, with greater intensity than regions not covered by platelets. The fluorescent patterns observed may be a result of the binding of adsorbed fluorescent protein to the glycoprotein IIb/IIIa receptors of platelets, followed by their redistribution within the plasma membrane.

Adsorption↗
PubMed1979

Displacement chromatography of simple protein mixtures, using carboxymethyldextrans.

Simple mixtures of proteins have been used as models to demonstrate that the fractionation of proteins by carboxymethyldextrans on an anion exchanger (Peterson, E.A. (1978) Anal. Biochem. 90, 767--784) is fundamentally a displacement process. Examples include the separation of two closely similar proteins, the A and B forms of beta-lactoglobulin. The use of carboxymethyldextran spacers was essential for good separation, since resolution based on protein--protein displacement was generally inadequate. The origins and effects of heterogeneity in the preparations used as spacers are discussed.

Anion Exchange Resins↗
PubMed1981

Visualization of carrier ampholyte patterns in granular gel slabs. 2. Applications to preparative electrofocusing.

A topographic method for locating colorless proteins in focused Sephadex gel slabs is presented. The fluorescent isoelectric banding pattern of the carrier ampholyte (Servalyt) is utilized as a map to locate the proteins indirectly and non-destructively, and to guide their excision for preparative isolation. The method is illustrated with small-scale isolations of the major components of ovalbumin and human serum albumin, and with a scaled-up preparative isolation of the A and B components of beta-lactoglobulin. Fluorescence is used to localize accurately individual fractions of Servalyt in Sephadex slabs for preparative isolation. Isolated fractions were used to enrich selectively specific zones in the regular Servalyt mixture to increase the separation between close-lying proteins during focusing.

Electrolytes↗
PubMed1984

Solvent denaturation of proteins as observed by resolution-enhanced Fourier transform infrared spectroscopy.

Fourier self-deconvolution of Fourier transform infrared (FTIR) spectra and second derivative FTIR spectroscopy were applied to study solvent-induced conformational changes in globular proteins. For beta-lactoglobulin a total of three different denatured forms were identified in alkaline solution and in aqueous methanol-d1 and isopropanol-d1. In isopropanol-d1 solution a new conformation was identified which appears to resemble, but is not identical with, the beta-structure of native proteins. This conformation is characterized by absorption bands around 1615-1618 and 1684-1688 cm-1, and is also observed for concanavalin A and chymotrypsinogen A in aqueous isopropanol-d1 solution.

Animals↗