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At least 1,423 records · Page 79Linked to original sources
PubMed1991

Protein adsorption at solid-liquid interfaces: Part I--Affinities of proteins for alumina surface.

Extent of adsorption (gamma pw) of bovine serum albumin, beta-lactoglobulin, gelatin and myosin at the alumina-water interface has been measured as function of protein concentration (Cp) at several temperatures, pH, and ionic strengths of the medium. gamma pw for proteins in most cases increases with increase of protein concentration but it attains maximum value gamma pw(m) when Cp is high. Values of maximum adsorption have been examined in terms of molecular orientation, molecular size and shape and unfolding of the packed proteins at the interface. In few cases, gamma pw increases with increase of Cp without reaching a real state of saturation as a result of aggregation of molecules or extensive unfolding of the protein at the interface. In the case of beta-lactoglobulin at pH 5.2 and ionic strength 0.05, gamma pw in high concentration region decreases to zero value when Cp increases. For myosin at 45 degrees C and pH 6.4, and also at 27 degrees and pH 7.8, the values of gamma pw are all negative and these negative values increase with increase of Cp. All these results have been explained in terms of significant competitions of water and protein for binding to the surface sites of the powdered alumina. Adsorption of myosin has also been found to be affected in the presence of NaCl, KCl, CaCl2, KI, Na2SO4, LiCl and urea. The relative affinities of the adsorption of various proteins for the surface of alumina at different physical conditions of the system have been compared in terms of maximum values of adsorption attained when gamma pw is varied with Cp. The affinities are shown to be compared more precisely in terms of the standard free energy decrease for the saturation of the surface by protein as a result of the change in its concentration from zero to unity in the mole fraction scale.

Adsorption↗
PubMed1990

Circulating and secretory antibodies to specific food proteins in adults.

Indirect enzyme-linked immunosorbent assays (ELISA) for the detection of antibodies to gliadin, beta-lactoglobulin and ovalbumin have been developed. Specific antibody immunoglobulin levels were quantified. Serum and saliva samples were collected from twenty normal subjects and measured for the presence of specific antibodies. For each subject food intake was calculated from a 7-d weighed food inventory record. The total IgG level was 14.2 +/- 4.3 mg/ml (mean +/- s.d.). Levels of beta-lactoglobulin IgG were significantly lower than ovalbumin IgG levels (130 +/- 130 micrograms/ml versus 637 +/- 703 micrograms/ml, P less than 0.01). Gliadin IgG levels were also significantly lower than ovalbumin IgG levels (262 +/- 398 micrograms/ml versus 637 +/- 703 micrograms/ml, P less than 0.05). However, no significant difference was observed between gliadin and ovalbumin IgA levels in the subjects (29 +/- 39 per cent versus 56 +/- 122 per cent). A significant correlation was observed between ovalbumin IgG levels in serum and dietary intake of egg protein (r = 0.46, P less than 0.05). No other significant correlations were observed.

Adult↗
PubMed1989

Diagnostic value of a lymphocyte stimulation test in cow milk protein intolerance.

In order to evaluate the diagnostic value of a lymphocyte stimulation test with casein and beta lactoglobulin in cow milk intolerance (CMI), we studied 26 patients with a diagnosis of CMI and 25 age-matched controls with intestinal diseases other than CMI. Lymphocyte stimulation test to casein (P less than .001) and beta lactoglobulin (P less than .001) was significantly higher among CMI patients. Seventeen patients were RAST positive and nine negative for whole milk proteins. No differences were found in the lymphocyte stimulation test response between RAST-positive and RAST-negative subjects. These results suggest that lymphocyte stimulation test with highly purified antigens in optimal concentrations is specific and could be useful in the diagnosis of CMI.

Animals↗
PubMed1989

[Experimental study of a new biological preparation for treating E. coli infection and Proteus dysbacteriosis in young infants].

The action of a new biological preparation intended for the treatment of E. coli infection and Proteus dysbacteriosis in children has been studied in experiments on mice and suckling rabbits. The protective activity of anti-E. coli and anti-Proteus lactoglobulin has been found to exceed that of normal lactoglobulin 6- to 13-fold. When subjected to the action of proteolytic enzymes of the gastrointestinal tract, the preparation retains its preventive properties on the level of the native preparation, which confirms the possibility of the oral administration of the preparation in clinical practice without protecting it from the proteolytic action of the enzymes of the gastrointestinal tract.

Animals↗
PubMed1988

Passage of food antigens into circulation of breast-fed infants with atopic dermatitis.

We have selected 13 babies presenting with atopic dermatitis during exclusive breast feeding. After evaluation of reaginic reaction, we detected beta-lactoglobulin (BLG) in breast milk and babies sera before and after maternal elimination diet and after maternal challenge. beta-Lactoglobulin was present only in the sera of infants ingesting breast milk containing BLG. We have seen reaginic reactions to cow's milk in seven babies. The maternal elimination diet improved eczema in 11/13 infants, maternal challenge worsened atopic dermatitis in 9/9 children. We demonstrated the transport of food antigen via breast milk into infants' circulation.

Breast Feeding↗
PubMed1988

Effect of cow's milk on jejunal mucosal macromolecular barrier in suckling guinea pigs.

The assumption that fresh cow's milk may have a direct effect on jejunal mucosal macromolecular permeability was tested in 14-day-old suckling guinea pigs, by in situ luminal perfusion of a proximal jejunal segment with horseradish peroxidase administered either in 0.9% NaCl or in cow's milk. For positive control, a group of guinea pigs previously sensitized to beta-lactoglobulin was similarly perfused with horseradish peroxidase in 0.9% NaCl or in cow's milk at 14 days of age. A segment of the wall of the perfused jejunal loop was processed for peroxidase staining and for examination of the extent and routes of macromolecular absorption by light and electron microscopy. Mucosal exposure to cow's milk was associated with penetration of tracer material across the jejunal epithelium only in the lactoglobulin-sensitized guinea pigs. In guinea pigs with a first-time exposure to cow's milk, no entry of tracer material beyond the brush border surface of the enterocytes was seen. Thus, whereas we could observe absorption of bystander antigens during antigenic challenge of the mucosa in sensitized animals, we found no evidence of a presumptive "permeability factor" in cow's milk that can disrupt the mucosal macromolecular barrier by an acute direct action.

Animals↗
PubMed1986

[Comparison of specific IgE levels versus various milk proteins in 76 eczematous children].

Among 76 eczematous children, we realized a RAST test for whole milk and milk specific proteins: lactalbumin, lactoglobulin and casein. One of these RAST tests, at least, was positive for 27 children. Whole milk RAST test is the most frequently positive (77%) but some non specific reactions seem to interfere: only three children are clinically milk sensitive. Among specific proteins, lactalbumin is more frequently positive (59%) than lactoglobulin (51%) and casein (18%). Eczematous children with positive milk RAST tests, if compared to other eczematous children, have currently more mite allergies and positive egg RAST tests. They have a tendency (non significative) to be more frequently breast fed. The positivity of milk RAST tests seems to belong to a polysensitization and infrequently concerns a clinical allergy.

Antibody Specificity↗
PubMed1979

Anaphylactic sensitivity of guinea-pigs drinking different preparations of cows' milk and infant formulae.

Guinea-pigs have been given various preparations of cows' milk or infant formulae to drink in an investigation of the capacity of these milk preparations to stimulate per os anaphylactic sensitivity. The treatment, presumably heat, used to concentrate the 'Evaporated' whole cows' milks (three brands were tested) almost abolished their sensitizing capacity to beta lactoglobulin. The brand presumed to be most heated as judged by the degree of caramelization had also lost most of its sensitizing capacity to casein. Injected parenterally, the 'Evaporated' milk adequately sensitized to anaphylaxis. An infant formula, which in its spray dried form was only moderately sensitizing to both beta lactoglobulin and casein, lost most of this sensitizing capacity when processed to a liquid concentrate state. The manufacturing process for the liquid concentrate involved greater and more prolonged heating than required for the spray-dried form. The relevance of these findings in the guinea-pig to cows' milk protein intolerance in the infant and possibly also to cot death is discussed.

Anaphylaxis↗
PubMedDate not supplied

The role of sensitizing proteins in milk allergy.

In clinical allergology and particularly during childhood, we quite frequently encounter patients who are allergic to milk. This has usually been confirmed by the clinical history and by skin testing. Statistics show a sensitization to cows' milk of between 0.3 and 7% of the world's population. In view of the diversity of opinions about an immunological problem of such clinical importance, we decided to carry out a clinical study to determine the sensitization to different fractions in patients allergic to milk. For this study, 82 patients were selected with a history of milk allergy together with strongly positive (++++) skin tests. Simultaneous intracutaneous tests were also performed with Alpha-lactalbumin, Beta-Lactoglobulin and Casein. The following points summarize our conclusions. 1. In milk allergy, lactoglobulin is the fraction with the greatest sensitizing potential (76.8% of our cases). 2. The alpha-lactalbumin fraction sensitized 59.7% of our cases, but gave weaker positive reactions. 3. Casein is the least sensitizing of the fractions studied, affecting 42% of the patients. 4. Taking into account that many patients with a positive history of milk allergy may show negative reactions when tested with whole milk and positive reactions to one of the three fractions discussed, it would be advisable to test routinely with these three fractions as well as with whole milk.

Albumins↗
PubMed1984

Immunochemistry of food antigens.

The complex mixture of molecules called food contains many types of molecules, some of which cause allergic or pseudo-allergic reactions in some humans. The identification of the antigenic molecules in the various foods and the type of allergic reaction they elicit is important for the satisfactory diagnosis in the individual patient and in the control of modified foods. The study of food antigens by crossed immunoelectrophoresis allows investigations of individual antigens without the interference of other antigens which are present simultaneously. We studied cow's milk electrophoresed into anti-bovine whey and anti-bovine casein. A number of precipitates are described, including albumin, alpha-lactalbumin, beta-lactoglobulin and immunoglobulin. The compositions of different infant milk formulae are compared with cow's milk heated under varying conditions. Albumin and immunoglobulins are the most labile components while beta-lactoglobulin is able to withstand even proteolysis by pepsin for some time. The antigenicity of these proteins in humans is shown by the presence of precipitating antibodies and specific IgE in human sera. Data from hen's egg white and wheat flour are reviewed in the same light. As an example of a reaction that is very difficult to differentiate from an immune reaction, the possible role of lectins is discussed.

Albumins↗
PubMed1984

Role of the microcirculation in ethanol-induced mucosal injury in the dog.

The aim of the present study was to assess the role of the intestinal microcirculation in the mucosal injury induced by intraenteric ethanol. Mucosal injury was assessed histologically in the ileum and jejunum and quantitated in the ileum by measuring clearance of albumin (37 A, radius) and beta-lactoglobulin A (27 A, radius). A steady-state analysis of the forces and flows governing transcapillary fluid movement was performed in autoperfused segments of jejunum and ileum. In the jejunum and ileum ethanol induced the formation of subepithelial blisters in 10%-40% of the villi. In the ileum, ethanol (5%, vol/vol) increased the clearance of both proteins but the ratio of lactoglobulin to albumin clearance decreased, indicating that the selectivity of the mucosal membrane was diminished. In both the jejunum and ileum ethanol produced similar alterations in the forces governing transcapillary fluid exchange. Ethanol increased the filtration coefficient (35%-40%), but did not alter the osmotic reflection coefficient of intestinal capillaries, indicating that surface area increased whereas vascular permeability was not affected. Capillary pressure increased (2-3 mmHg) whereas interstitial (lymph) protein concentration decreased resulting in an increase in the transcapillary oncotic pressure gradient (1-2 mmHg). The net result of the alterations in the forces governing transcapillary movement was only a doubling of the transcapillary filtration rate (lymph flow). It is concluded that the ethanol-induced increase in mucosal permeability to macromolecules cannot be explained solely on the basis of alterations in the forces and flows governing transcapillary fluid exchange in the small intestine.

Albumins↗
PubMed1980

In vitro cell-mediated immunologic assay for cow's milk allergy.

The production of a lymphokine, the leukocyte-migration-inhibition factor (LIF), by peripheral blood lymphocytes in response to an in vitro challenge with bovine beta-lactoglobulin was assayed in infants and children suspected of having allergy to cow's milk protein. Of the patients studied, 24 had cow's milk allergy, 24 were normal control subjects, 18 had recovered from milk allergy, 10 were newborns, and 10 were babies suffering from acute gastroenteritis. All patients with milk allergy demonstrated significant LIF production in response to beta-lactoglobulin (23.5% +/- 6.4%). In the normal control subjects, LIF was 3.1% +/- 4.3% (P < .0005). Only two of the 24 control subjects and two of the ten newborns had high-normal values bordering on the positive. None of the ten babies with acute gastroenteritis gave a positive response. Most of the children who had recovered from milk allergy and were ingesting cow's milk had negative assays. This cell-mediated immune assay is shown to be a reliable test for the diagnosis of sensitivity to milk protein in infants and children, and for determining dietary treatment and when this treatment can be safely terminated. In most cases, its use should eliminate the need for the potentially dangerous and ethically questionable provocation test, as well as the need for repeated intestinal biopsies.

Animals↗
PubMed1993

Enzyme-linked immunosorbent assays for gliadin and ovalbumin and their application in normal subjects.

Two quick, sensitive and direct sandwich enzyme-linked immunosorbent assays (ELISAs) for the measurement of gliadin and ovalbumin in serum have been developed. The ovalbumin assay has a sensitivity of 0.14 ng/ml (2 SD from zero). Cross-reactivities with ovomucoid and conalbumin were 58% and 0.2%, respectively. No cross-reactivity was observed with bovine serum albumin (BSA), human serum albumin (HSA), gliadin and beta-lactoglobulin. The gliadin assay did not cross-react with BSA, HSA, ovalbumin and beta-lactoglobulin and had a sensitivity of 7 pg/ml. In an acute feeding study, of 6 h duration, serum ovalbumin levels were measured in five non-food-allergic subjects who had been given raw eggs (5 g ovalbumin) after an overnight fast. Following a period of at least 1 week the same subjects were given 132 g wholemeal bread (5 g gliadin) after an overnight fast, and serum gliadin levels were measured. After the consumption of raw eggs ovalbumin levels peaked between 210 and 300 min with maximum serum concentration between 0.52 and 31.08 ng/ml. After the consumption of bread, gliadin levels reached a maximum between 180 and 300 min, reaching peak levels between 1.12 and 12.2 ng/ml. We conclude that levels of detected ovalbumin were higher than those for gliadin in this group of individuals.

Adult↗
PubMed1996

Gastroesophageal reflux associated with cow's milk allergy in infants: which diagnostic examinations are useful?

Gastroesophageal reflux (GER) in infants can be secondary to food allergy. We have evaluated the frequency with which GER is associated with cow's milk protein allergy (CMPA) in infants < 1 yr old and tried to indicate the laboratory and instrumental examinations useful in diagnosing GER + CMPA. We studied 140 infants (60 M, 80 F), mean age 6.0 +/- 2.8 months. After 24-h esophageal pH-metry, esophageal endoscopy, and elimination diet, followed by a double-blind challenge, the patients were divided into four groups: primary GER, GER secondary to CMPA, CMPA without GER, and a control group with subjects suffering from neither GER nor CMPA. Thirty of 72 patients with GER were also suffering from CMPA. No differences were observed as regards age, sex, symptoms, and clinical or family history between patients with GER only and those with GER + CMPA. The immunological test most useful for GER + CMPA diagnosis was the IgG anti-beta-lactoglobulin assay: positive in 27/30 subjects with GER + CMPA and in 4/42 patients with GER only. We also observed a characteristic pattern of the pH-monitoring tracing in 26/30 patients with GER + CMPA but in none of the 42 patients with GER only. This consisted of a progressive, constant reduction in esophageal pH at the end of a feed, which continued up to the following feed, when pH rose steeply. We conclude that the evidence of this characteristic tracing and of a high IgG anti-beta-lactoglobulin value are specific and sensitive tests for GER + CMPA diagnosis.

Chi-Square Distribution↗
PubMed1995

Performance of a Graesser contactor in the continuous extraction of whey proteins: mixing, mass transfer and efficiency.

The performance of a Graesser Raining Bucket Contactor in an extraction using aqueous two-phase systems was characterized by axial mixing coefficients and counter current mass transfer for whey protein purification. The influence of rotor speed, phase ratio and phase velocity on the salt phase axial mixing coefficients was determined applying a dispersion model to the residence time distribution experiments. When dissolving whey powder in the salt-rich phase of the system, alpha-lactalbumin was extracted to the polyethylene-glycol-rich phase, whereas beta-lactoglobulin predominantly remained in the bottom phase, making the process suitable for removal of the major allergen beta-lactoglobulin. The mass transfer in the phase system was determined from the steady state data of alpha-lactalbumin extraction. On the basis of a diffusion model, the efficiency of the counter current extraction under different process conditions was calculated from results of the mass transfer experiments.

Cheese↗
PubMed1976

[Changes in the total protein and protein fractions in cow's milk irradiated with ultraviolet rays].

Comparative experimental electrophoretic studies were carried out to establish the effect of ultraviolet treatment on cow's milk at various rates of irradiation (5, 10 and 15 min) with a view to raising and regulating the content of the total protein and the protein fractions in milk intended for the feeding of calves. Results showed that there were no substantial changes in the level of the total protein, the albumins having a rising trend that was manifested best at a 15-minute treatment. Most characteristic were the changes taking place in the immunoglobulin fraction which rose by 4.7 per cent. The beta-lactoglobulin fraction dropped by 4.5 per cent, on an average, at all rates of treatment, and the level of alfa-lactoglobulin at 5- and 10-minute irradiation underwent almost no changes, it rising by about 2.09 per cent, on an average, at 15-min treatment. Similar was the trend manifested by the proteoso-pepton fraction showing a rise as early as the first ten minutes of treatment.

Albumins↗
PubMed2001

Structural changes during heat-induced gelation of globular protein dispersions.

Macroscopic and molecular structural changes during heat-induced gelation of beta-lactoglobulin, bovine serum albumin, ovalbumin, and alpha-lactalbumin aqueous dispersions were probed by the mechanical and CD spectroscopy, respectively. Aqueous solutions of the native globular proteins, except for alpha-lactalbumin, exhibited solid-like mechanical spectra-namely, the predominant storage modulus G' over the loss modulus G" in the entire frequency range examined (0.1-100 rad/s), suggesting that these protein solutions were highly structured even before gelation, possibly due to strong repulsions among protein molecules. Such solid-like structures were susceptible to nonlinearly large shear but recovered almost immediately at rest. During gelation by isothermal heating, major changes in the secondary structure of the globular proteins completed within a few minutes, while values of the modulus continued to develop for hours with maintaining values of tandelta (= G"/G') less than unity. As a result, a conventional criterion for mechanically defining the gelation point, such as a crossover between G' and G", was inapplicable to these globular protein systems. beta-Lactoglobulin gels that had passed the gelation point satisfied power laws (G' approximately G" approximately omega(n)) believed to be valid only at the gelation point, suggesting that fractal gel networks, similar to those of critical gels (i.e., gels at the gelation point), were formed.

Circular Dichroism↗
PubMed2001

Model studies on reactions of plant phenols with whey proteins.

Whey proteins were modified by reaction with selected phenolic compounds (ferulic-, chlorogenic-, caffeic- and gallic acid) and related substances (quinic acid and p-quinone) as well as with extracts from coffee, tea, potato and pear at pH 9. The derivatives formed were characterized in terms of their physicochemical and digestion properties. The derivatization was accompanied by a reaction at the lysine and tryptophan side chains, whereby their content was decreased in comparison to that in the control whey proteins. Moreover, the solubility of the derivatives decreased over a broad pH range and the derivatization influenced the hydrophobe-hydrophile character of the whey proteins. The isoelectric points were shifted to lower pH values in the order of reactivity as follows: gallic acid > p-quinone > caffeic acid > chlorogenic acid. The other derivatives showed no or few changes compared to the control whey proteins. The formation of high molecular fractions was documented with SDS-PAGE. Especially the derivatives of chlorogenic-, caffeic-, gallic acid and p-quinone showed an increase in molecular weight of beta-lactoglobulin fraction from 18,300 to 20,000 Da. A dimer formation in molecular range 40,000 was also registered. MALDI-TOF-MS was applied to characterize the binding of the individual phenolic compounds or their oxidation products to the whey protein fractions, alpha-lactalbumin and beta-lactoglobulin. In vitro experiments showed that the digestion of the derivatized whey proteins with the enzymes of the gastrointestinal tract (trypsin, chymotrypsin, pepsin and pancreatin) was adversely effected. Similar results with regard to physicochemical characterization and digestion properties of the whey proteins treated with the applied extracts from plant beverages, fruit and vegetable were also documented. Coffee and tee were comparatively the most reactive extracts.

Electrophoresis, Polyacrylamide Gel↗