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At least 307 records · Page 17Linked to original sources
PubMed2003

AIRE-1 (autoimmune regulator type 1) as a regulator of the thymic induction of negative selection.

The monogenic autoimmune syndrome, APS-1 (autoimmune polyglandular syndrome type 1), is characterized by the loss of self-tolerance to multiple organs. Although mutations in the AIRE (autoimmune regulator) gene are responsible for the APS-1, the function of AIRE is not known. AIRE may determine thymic induction of tolerance to self-antigens in multiple organs. To study the function of AIRE in induction of self-tolerance, an in vitro negative selection system was made using 10(6) DO11.10 TCR transgenic thymocytes, 10(5) antigen-presenting cells (APC), and the different constructs of ovalbumin (OVA). In this system, the addition of the immunodominant epitopes of OVA peptide, the antigenic ligand for the DO11.10, made the thymocytes apoptotic and negatively selected. Overexpression of the AIRE gene in APC using retroviral transduction did not cause more thymocytes to become apoptotic. However, the suppression of the expression of AIRE in APC using the dominant-negative gene made the recovery rates of the thymocytes higher than those with the expression of LacZ as a control, and consequently inducing loss of self-tolerance. From these studies, it might be possible to suggest that the AIRE gene might regulate thymic induction of the negative selection process. The target genes for transcriptional regulation by AIRE have been investigated to study the influence of AIRE expression on other proteins in antigen presentation. The expression level of B7.1 was higher in APC expressing the dominant-negative form of AIRE. The target gene regulated by AIRE in transcription will be screened using cDNA microarray.

Animals↗
PubMed2004

Structural, topographical, and shear characteristics of milk protein and monoglyceride monolayers spread at the air-water interface.

In this contribution we are concerned with the study of structure, topography, and surface rheological characteristics under shear conditions of monoglyceride (monopalmitin and monoolein) and milk protein (beta-casein, kappa-casein, caseinate, and WPI) spread monolayers at the air-water interface. Combined surface chemistry (surface film balance and surface shear rheometry) and microscopy (Brewster angle microscopy: BAM) techniques have been applied in this study to pure emulsifiers (proteins and monoglycerides) spread at the air-water interface. To study the shear characteristics of spread films, a homemade canal viscometer was used. The experiments have demonstrated the sensitivity of the surface shear viscosity (eta(s)) of protein and monoglyceride films at the air-water interface, as a function of surface pressure (or surface density). The surface shear viscosity was higher for proteins than for monoglycerides. In addition, eta(s) was higher for the globular WPI than for disordered beta-casein and caseinate due to the strong forces acting on spread globular proteins. This technique makes it possible to distinguish between beta-casein and caseinate spread films, with the higher eta(s) values for the later due to the presence of kappa-casein. The eta(s) value varies greatly with the surface pressure (or surface density). In general, the greater the surface pressure, the greater the values of eta(s). Finally, the eta(s) value is also sensitive to the monolayer structure, as was observed for monoglycerides with a rich structural polymorphism (i.e., monopalmitin).

Air↗
PubMed2001

Serum Clara cell protein (CC16), a marker of the integrity of the air-blood barrier in sarcoidosis.

To test the hypothesis that sarcoidosis is associated with an intravascular leakage of lung epithelium secretory proteins, the occurrence and determinants in serum of sarcoid patients of CC16, a small size and readily diffusible lung-specific protein of 16 kDa secreted by bronchiolar Clara cells, was investigated. CC16 was measured by a sensitive latex immunoassay in the serum of 117 patients with established sarcoidosis and of 117 healthy subjects matched for age, sex and smoking status. Stepwise regression analysis was used to identify extrapulmonary variables of CC16 changes in serum. These changes were then compared with biochemical and cellular parameters in bronchoalveolar lavage fluid (BALF) as well as with the number of CC16 immunostaining cells on bronchial or pulmonary biopsy samples. CC16 concentration in serum of sarcoid patients was significantly increased, compared to their matched controls (25.9 +/- 16.2 versus 13.9 +/- 5.2 microg x L(-1)). In nonsmoking patients without significant renal impairment, CC16 in serum increased with the severity of the chest radiograph and computed tomography changes, and was on average 50-100% higher when parenchymal involvement was present. Sarcoid patients had, however, normal levels of CC16 in BALF and an unchanged number of CC16-immunopositive cells in lung biopsy samples, suggesting that an increased secretion of CC16 in the sarcoid lung is very unlikely, and that the elevation of CC16 in sarcoidosis results from an increased intravascular leakage of the protein across the air-blood barrier. The present study suggests that CC16 in serum might provide a useful tool to noninvasively evaluate the damage and increased permeability to proteins of the air-blood barrier associated with sarcoidosis.

Adult↗
PubMed1987

Interaction of proteins with lipid monolayers at the air-solution interface studied by reflection spectroscopy.

The interaction of a fluorescein-labelled insulin and of cytochrome C with the air-solution interface and with lipid monolayers at the air-solution interface has been studied by measuring the change in surface pressure at constant area and by reflection spectroscopy. Chromophores at the interface only give rise to enhanced light reflection without contribution to the signal from chromophores in the bulk. The accumulation of labelled insulin at the solution surface is very weak as concluded from the shape of the spectrum and reflection intensity. No interaction with a monolayer of dipalmitoyl-phosphatidylcholine at initial surface pressure of 5 mN/m was detected. In contrast, the interaction with monolayers of dioctadecyldimethyl-ammonium bromide at initial surface pressures between 5 and 40 mN/m is much stronger, leading to a remarkable increase of surface pressure at constant area and strong reflection signal. The technique was also used to detect cytochrome C at the air-solution interface.

Lipid Metabolism↗
PubMed1995

Pulmonary surfactant protein SP-A with phospholipids in spread monolayers at the air-water interface.

Spread monolayers of pulmonary surfactant protein SP-A, alone or mixed with phospholipid(s), were formed at the air-water interface. Binary monolayers of SP-A plus dipalmitoylphosphatidylcholine (DPPC) showed positive deviations from ideal behavior of the mean areas in the films consistent with partial miscibility and interaction between the protein and lipid. During compression of SP-A/DPPC films which contained > or = 5 wt % SP-A, properties were displayed which were consistent with the protein being partially squeezed out at surface pressures of about 30 mN/m. Some protein appeared to remain in the monolayers even when they were compressed to high surface pressures of about 65-70 mN/m, and it was possibly included in the collapse phase(s) that was (were) formed at 72 mN/m. During dynamic cyclic compression-expansion of SP-A/DPPC monolayers initially formed at low surface pressures, SP-A enhanced the respreading of the films compressed beyond collapse compared to the respreading after collapse of films containing DPPC alone. Spread monolayers of SP-A plus either dipalmitoylphosphatidylglycerol (DPPG) or a mixture of DPPC plus DPPG (7:3, mol/mol) displayed additivity of the mean areas in the films, consistent with complete immiscibility (or ideal miscibility, an unlikely effect) between the protein and lipid components. Electrostatic repulsion between SP-A and DPPG, both negatively charged at physiological pH, possibly governed the behavior of these lipid-protein films. Calcium ions in the subphase did not alter the properties of SP-A/DPPC films, whereas they improved the ability of SP-A to mix with DPPG and DPPC/DPPG. Binding of calcium to the negatively charged DPPG and SP-A may account for association of the protein with DPPG and DPPC/DPPG in the monolayers in the presence of the divalent ions.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Arterial air embolism: structural effects on the gerbil brain.

Air injection into the carotid artery of adult mongolian gerbils caused, within 10 minutes, multifocal brain lesions. The extracellular spaces were widened and neurons, oligodendrocytes and myelin sheaths remained unchanged. The "delayed" effects of air embolism (first seen after 3 h) were similar to those observed in gerbils after unilateral carotid ligation. The histologic alterations after 3 h consisted of astrocytic swelling and shrinkage/necrosis of neuronal soma. The observations reported here illustrate the temporal and spatial separations that exist between a) brain water retention, and b) intraparenchymal entry of horseradish peroxidase. Both alterations can be a consequence of either decreased blood flow or arterial air embolism. Edema and protein leakage in each situation may be initiated by different mechanisms.

Animals↗
PubMed2004

Increasing allergy potency of Zinnia pollen grains in polluted areas.

There is much evidence that allergic symptoms represent a major health problem in polluted cities. The aim of this research is to elucidate some microscopic effects of air pollutants on pollen structure, proteins, and allergenicity. A scanning electron microscopy study of pollen grains indicated that in polluted areas, airborne particles accumulate on the surface of pollen grains and change the shape and tectum of pollen. Also, many vesicles are released from polluted pollen grains and the pollen material agglomerates on the surface of pollen grains. SDS-PAGE revealed that different proteins exist in mature and immature pollen grains. There were no significant differences between protein bands of polluted and nonpolluted pollen grains, but in polluted pollen, protein content decreases in response to air pollution, causing the release of pollen proteins. The results indicate that mature pollen have more allergenicity than immature pollen. According to the experiments polluted pollen grains are more effective than nonpolluted pollen grains in inducing allergic symptoms. Air pollutants can cause allergic symptoms, but when associated with allergen pollen grains, their allergenicity power is increased.

Air Pollutants↗
PubMed1993

Biochemical characterization of air-filled albumin microspheres.

Heating and sonication of a solution of human serum albumin (HSA) yields air-filled microspheres that can be used as a contrast agent in ultrasound examinations. The microspheres are stabilized by a thin-layer of protein surrounding the air bubbles. As long as the microspheres were intact, the protein was insoluble in aqueous solutions. After disintegration of the microspheres, the protein could be solubilized in several solutions. The intermolecular interactions in the microsphere protein have been elucidated from its solubility properties. The microspheres were disintegrated by several detergents which also solubilized the protein. After pressure disintegration of the microspheres, the protein was solubilized immediately in urea and guanidinium chloride, and also in phosphate-buffered saline after incubation overnight. These results indicate that the protein was mainly stabilized by non-covalent forces. The solubilization in buffer was inhibited by a high salt concentration, suggesting that hydrophobic interactions were involved in stabilizing the microsphere structure. Analysis of the solubilized protein by gel filtration showed that the protein contained substantial amounts of soluble aggregates of HSA. Reduction of the disulphide bonds dissolved these aggregates into monomeric HSA, showing that intermolecular disulphide bonds were also involved in stabilization of the microspheres. The solubilized protein also contained less fatty acids than the soluble HSA used for the production of microspheres. These results show that the microsphere protein has the same characteristics as heat-denatured HSA.

Air↗
PubMed1994

Exposure of bus and taxi drivers to urban air pollutants as measured by DNA and protein adducts.

Urinary 1-hydroxypyrene, lymphocyte DNA adducts, serum protein-bound PAH and hemoglobin-bound alkene adducts were analysed from 4 groups of non-smoking men: urban and suburban bus drivers, taxi drivers and suburban controls. The only differences between the groups were in DNA adducts between suburban bus drivers and controls, and in DNA adduct and plasma protein PAH-adducts between taxi drivers and controls.

Air Pollutants↗
PubMed2006

A thermodynamic study of GPI-anchored and soluble form of alkaline phosphatase films at the air-water interface.

Glycosylphosphatidyl inositol (GPI) anchored proteins are localized and clustered on the outer layer of the plasma membranes forming microdomains. Among them, mammalian alkaline phosphatases (AP-GPI) are widely distributed enzymes. They can also exist as soluble proteins without anchor (APs). Using the Langmuir film technique, we study the thermodynamic properties of monolayers for both protein forms at the air-buffer interface. The enzymatic activity is maintained at the interface but the adsorption of the two forms of AP is very different. AP-GPI presents a higher surface activity and a larger molecular area than the soluble form. The molecular area deduced for high surface pressures suggests a different organization of the monolayers for these two forms. APs molecules seem to adsorb as a multilayer at the interface while AP-GPI appear to be orientated with the major axis parallel to the interface. This orientation allows the accessibility of AP-GPI enzymatic sites that are turned in direction of the subphase as in vivo where the active sites must be turned outside of the membrane.

Adsorption↗
PubMed1989

Hydrolytic Enzyme Activities and Protein Pattern of Avocado Fruit Ripened in Air and in Low Oxygen, with and without Ethylene.

The effect of 2.5% O(2) atmosphere with and without ethylene on the activities of hydrolytic enzymes associated with cell walls, and total protein profile during ripening of avocado fruits (Persea americana Mill., cv Hass) were investigated. The low 2.5% O(2) atmosphere prevented the rise in the activities of cellulase, polygalacturonase, and acid phosphatase in avocado fruits whose ripening was initiated with ethylene. Addition of 100 microliters per liter ethylene to low O(2) atmosphere did not alter these suppressive effects of 2.5% O(2). Furthermore, 2.5% O(2) atmosphere delayed the development of a number of polypeptides that appear during ripening of avocado fruits while at the same time new polypeptides accumulated. The composition of the extraction buffer and its pH greatly affected the recovery of cellulase activity and its total immunoreactive protein.

Journal Article↗
PubMed1970

An analysis of the interaction of protein with lipid monolayers at the air-water interface.

1. Measurements have been made of the interaction of cytochrome c, bovine serum albumin and synthetic oxytocin with low-pressure (2dyn/cm) monolayers of stearic acid, phosphatidylcholine and phosphatidylethanolamine. 2. [(14)C]Carboxymethylation of the cytochrome c and albumin followed by surface-radioactivity determinations have shown that only a proportion of the protein added to the subphase is bound to the monolayers and that initially the degree of binding is dependent on the protein concentration. The binding is irreversible in the sense that the adsorbed protein cannot be removed by transferring the film containing the interacted protein to a fresh subphase containing no protein. 3. Three successive types of interaction can usually be recognized. (a) Initially, whole molecules of protein penetrate the lipid film and occupy the same area as those of the protein spread at the air/water interface. (b) Above certain film pressures a part of each protein molecule, probably hydrophobic side chains, penetrates the film. The change in surface pressure per unit of bound protein is much smaller than in (a). (c) At higher film pressures, adsorption without penetration occurs. With cytochrome c this is initially dependent on a favourable electrostatic interaction.

Adsorption↗
PubMed1983

Dynamics of pulmonary water before and after birth.

In fetal life an electrochemical gradient across the pulmonary epithelium causes liquid to flow from the microcirculation of the lungs through the interstitium into potential air spaces. That liquid is rich in chloride (greater than 150 meq/l) and almost free of protein (less than 0.03 g/dl). At birth rapid reversal of the direction of liquid flow is essential for a smooth transition from placental to pulmonary gas exchange. Removal of liquid from the lungs begins even before birth. In fetal rabbits and lambs, a substantial decrease in extravascular lung water occurs late in gestation and during labor. When breathing begins, transpulmonary pressure inflates the lungs and displaces residual liquid from terminal respiratory units into the interstitium. Fluid accumulates in connective tissue spaces surrounding large pulmonary blood vessels, distant from sites of gas exchange. The concentration of protein in the interstitium decreases, thereby increasing the transvascular gradient of protein osmotic pressure. Air entry into the lungs also decreases hydraulic pressure in the pulmonary microcirculation and increases pulmonary blood flow, which expands microvascular surface area for fluid exchange in the lungs. These developments facilitate reabsorption of water into the pulmonary vascular bed. In lambs, the postnatal increase in lung lymph flow is small and transient, accounting for only 10-15% of the total amount of liquid drained from the lungs after birth. Normally, the pulmonary microcirculation directly absorbs most of the fetal lung liquid that is present at birth.

Animals↗
PubMed1981

Water radiolysis products and nucleotide damage in gamma-irradiated DNA.

The radiation chemistry of nucleotide damage introduction into DNA gamma-irradiated in dilute aqueous solution has been studied with a damage-specific DNA binding protein. Irradiation in air, N2 or N2O in the presence and absence of free radical scavengers revealed that protein-recognizable lesions were introduced both by the hydrated electron and by the combination of the hydroxyl radical and superoxide anion radical, but not by the hydroxyl radical alone. In addition, nucleotide damage was introduced into DNA by an enzymatic superoxide-generating system.

Carrier Proteins↗
PubMed2005

Quantitative structure-property relationships for interspecies extrapolation of the inhalation pharmacokinetics of organic chemicals.

The objectives of this study were to (i) develop quantitative structure-property relationships (QSPRs) for blood:air partition coefficients (Pb:a), tissue:air partition coefficients (Pt:a), and hepatic clearance (CLh) and (ii) conduct interspecies extrapolations of the pharmacokinetics of low molecular weight volatile organic chemicals (VOCs) by incorporating the above QSPRs within a physiologically based pharmacokinetic (PBPK) modeling framework. Pb:a and Pt:a were predicted using the following algorithm: FnlxPo:a+FwxPw:a+f(b)xFpxPp:a, where Fnl=content of neutral lipid equivalents in biological matrix, Fw=content of water equivalents in biological matrix, Fp=protein content of blood and tissues, Po:a=vegetable oil:air partition coefficient, Pw:a=water:air partition coefficient, f(b)=fraction of total protein involved in the partitioning process, and Pp:a=protein:air partition coefficient. CLh was estimated as follows: Qlx[(CLintxC(P4502E1)xVl)/(Ql+CLintxC(P4502E1)xVl)], where CLint=intrinsic clearance normalized for P450 2E1 content, Ql=blood flow to the liver, C(P4502E1)=hepatic concentration of P450 2E1 in the species of interest, and Vl=volume of liver. QSPRs relating molecular fragments of 46 VOCs and parameters required for estimating Pb:a, Pt:a, and CLh (namely, Po:a, Pw:a, Pp:a, and CLint) were established using a group contribution method (f(i)xCi, where f=frequency of occurrence of the group i in a given molecule and Ci=contribution of the group i to Po:a, Pw:a, Pp:a, or CLint). Values of group contributions were determined by multilinear regression of experimental data. The species specific parameters required for solving the above algorithms were obtained from the literature. These algorithms, once incorporated into a multispecies PBPK modeling framework, enabled extrapolation of the kinetics of chemicals across species. The inhalation pharmacokinetics of dichloromethane and toluene as well as two de novo compounds (1,2,4-trimethyl benzene and ethyl benzene) were extrapolated from rat to human, using the present modeling methodology. This study has demonstrated that it is possible to extrapolate the pharmacokinetic behavior of chemicals from rats to humans on the basis of QSPRs and species specific physiological information.

Administration, Inhalation↗
PubMed2006

Structural characteristics of dipalmitoylphosphatidylcholine and hydrolysates from sunflower protein isolate mixed monolayers spread at the air-water interface.

In this work, surface film balance and Brewster angle microscopy techniques have been used to analyze the structural characteristics (structure, topography, reflectivity, thickness, miscibility, and interactions) of hydrolysates from sunflower protein isolate (SPI) and dipalmitoylphosphatidylcholine (DPPC) mixed monolayers spread on the air-water interface. The degree of hydrolysis (DH) of SPI, low (5.62%), medium (23.5%), and high (46.3%), and the protein/DPPC mass fraction were analyzed as variables. The structural characteristics of the mixed monolayers deduced from the surface pressure (pi)-area (A) isotherms depend on the interfacial composition and degree of hydrolysis. At surface pressures lower than the equilibrium surface pressure of SPI hydrolysate (pi(e)(SPI hydrolysate)), both DPPC and protein are present in the mixed monolayer. At higher surface pressures (at pi > pi(e)(SPI hydrolysate)), collapsed protein residues may be displaced from the interface by DPPC molecules. The differences observed between pure SPI hydrolysates and DPPC in reflectivity (I) and monolayer thickness during monolayer compression have been used to analyze the topographical characteristics of SPI hydrolysates and DPPC mixed monolayers at the air-water interface. The topography, reflectivity, and thickness of mixed monolayers confirm at microscopic and nanoscopic levels the structural characteristics deduced from the pi-A isotherms.

1,2-Dipalmitoylphosphatidylcholine↗