SEARCH · PubMed Health

Results for “Condensates”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources

PubMed2001

A noninvasive method to collect nasally exhaled air condensate in humans of all ages.

BACKGROUND: The analysis of exhaled breath condensate may provide valuable insights into inflammatory and other metabolic processes of the lungs. However, its collection by active exhalation with conventional methods is cumbersome, demands a substantial level of co-operation with high motivation and is very difficult or impossible in children younger than about 4-6 years or in the elderly. A comfortable, noninvasive and efficient method is desirable. DESIGN AND PATIENTS: For collection a high-performance pump connected to a cold trap and nasal prongs were used. The volume of the condensate collected was assessed in 141 children of all ages and five adults. As an example for a low molecular component, H2O2 a marker of oxidative stress, was determined fluorometrically. RESULTS: On average, in healthy children from 4 weeks to 18 years of age, 84.0 (79.4, 87.3) microL min(-1) of nasally exhaled air condensate were collected. The volume obtained was about 45% less in 1-6-year-old children, increased linearly with collection time, and averaged about 20-30% of the exhaled water vapour. The concentration of H2O2 in the healthy children was 0.49 (0.48, 0.61) microM and did not depend on age, the time of the day, family, or personal history of atopy and sex. CONCLUSIONS: The method described is generally applicable, comfortable, noninvasive, safe and efficient and allows the collection of nasally exhaled air condensate for the evaluation of metabolic processes of the lungs.

Adolescent↗

PubMed2003

In vitro evaluation of apical microleakage following canal filling with a coated carrier system compared with lateral and thermomechanical Gutta-Percha condensation techniques.

AIM: The apical sealing ability of a coated carrier system was evaluated in extracted human teeth and compared with lateral and thermomechanical condensation techniques using dye penetration. METHODOLOGY: Sixty-four extracted single-rooted teeth were instrumented to an apical size 30 using 4% taper Hero 642 trade mark instruments (Micromega, Besançon, France). The sample was divided into three experimental groups. Twenty teeth were randomly obturated with lateral condensation, 20 with thermomechanical compaction and 20 teeth with the Herofill trade mark Soft-Core system. Four teeth were used as positive and negative controls. The teeth were covered with nail varnish up to 2 mm from the apical foramen and immersed in a 2% aqueous methylene blue dye solution for 1 week and then washed, dehydrated and embedded in resin. The apical 1 mm of each tooth was removed to reveal the apical limit of the preparation. Transverse sections of the teeth were taken at 500, 1000 and 1500 micro m from this point and evaluated for apical leakage. Significant differences between the preparations were analysed with a semiautomatic analyser and the ratio of the dye-penetrated surface to the total dentinal surface was calculated. RESULTS: Statistical analysis of the results demonstrated significantly less leakage for the Herofill trade mark Soft-Core system compared to lateral condensation in terms of total mean dentinal surface and at the 500 micro m level. No other differences were noted between Herofill trade mark Soft-Core and thermomechanical or lateral condensation, either for the total mean value or at each level. CONCLUSIONS: The Herofill trade mark Soft-Core system was a reliable obturation system in the apical portion and compared favourably with other gutta-percha filling techniques.

Coloring Agents↗

PubMed2003

Functional analysis of fibronectin isoforms in chondrogenesis: Full-length recombinant mesenchymal fibronectin reduces spreading and promotes condensation and chondrogenesis of limb mesenchymal cells.

Fibronectin (FN), a large dimeric glycoprotein, functions primarily as a connecting molecule in the extracellular matrices of tissues by mediating both cell-matrix and matrix-matrix interactions. All members of the FN family are products of a single FN gene; heterogeneity arises from the alternative splicing of at least three regions (IIIB, IIIA, and V) during processing of a common primary transcript. During chick embryonic limb chondrogenesis, FN structure changes from B+A+ in precartilage mesenchyme to B+A- in differentiated cartilage, and exon IIIA has been shown to be necessary for the process of mesenchymal cellular condensation, a requisite event that precedes overt expression of chondrocyte phenotype. This study aims to investigate the mechanistic action of the FN isoforms in mesenchymal chondrogenesis and, in particular, to identify the specific cellular function in mesenchymal condensation mediated by the mesenchymal (B+A+) FN isoform. Full-length cDNAs corresponding to four splice variants (B+A+, B+A-, B-A+, B-A-) of FN were constructed, and expressed the corresponding proteins using a baculovirus expression vector system. Cell adhesion assays with purified proteins showed that, although the relative levels of cell attachment were approximately the same, chick limb-bud mesenchymal cells spread up to 40 % less on mesenchymal (B+A+) FN than on cartilage (B+A-) FN, (B-A+) FN, or plasma (B-A-) FN. Cellular condensation and chondrogenic differentiation were also promoted in high-density micromass cultures of limb mesenchymal cells plated onto B+A+ FN. These observations suggest that the process of mesenchymal condensation is mediated at least in part by the enhanced ability of chondrogenic mesenchymal cells to migrate and aggregate as a consequence of residing in and interacting with mesenchymal FN. Our findings are consistent with and provide a mechanistic basis for previous observations that rounding of limb mesenchymal cells precedes the onset of chondrogenesis.

Animals↗

PubMed2001

Total nitrite/nitrate in expired breath condensate of patients with asthma.

Production of nitric oxide (NO) is generally increased during inflammatory diseases including asthma. The eventual fate of NO is oxidation to nitrite (NO2) and nitrate (NO3), both of which are end-products of NO metabolism. Hydrogen Peroxide (H2O2) is increased in exhaled breath condensate of asthmatic subjects and may be used as a non-invasive marker of oxidative stress. NO has in some cases been shown to attenuate oxidant-induced lung injury. Total NO2/NO3 concentration and H2O2 levels were measured in expired breath condensate in 50 clinically stable asthmatics [all males, all atopics, mean age 22 (3) SD yrs, forced expiratory volume in 1 sec (FEV1) 91 (10)% predicted, PD20 to histamine 0.262 (0.16) mg 20 on inhaled steroids, 20 smokers, all steroid-naive] and in 10 normal, non-atopic subjects [all males, age 23 (4) yrs, FEV1 101 (14)% predicted, PD20 to histamine 1.3 (0.55) mg]. NO2/NO3 levels were significantly higher in patients with asthma than in normal subjects (1.08, 95% CI 0.86-1.3 microM vs. 0.6; 95% CI 0.46-0.8, P < 0.001). Patients who were on inhaled steroids had significantly ower values compared to steroid-naive (0.71, 95% CI 0.55-0.87 microM vs. 133, 95% CI 1-1.65 microM, P < 0.001). Similar results were observed between smokers and non-smokers (1.11, 95% CI 0.74-1.47 microM vs. 1.77, 95% CI 1.1-24 microM, P < 0.0001). There was a significant positive correlation between NO2/NO3 levels and H2O2 concentration in expired breath condensate (r = 0.48, P < 0.0001). No correlation was observed between NO2/NO3 levels, airway obstruction and bronchial hyper-reactivity as assessed by PD20 to histamine. Total NO2/NO3 levels in expired breath condensate are raised in patients with stable asthma and are significantly related to oxidative stress as assessed by H2O2 concentration. Measurement of expired breath NO2/NO3 and H2O2 levels may be clinically useful in the management of oxidation and inflammation mediated lung injury.

Administration, Topical↗

PubMed2005

Counterion condensation and release in micellar solutions.

Counterion condensation and release in micellar solutions are investigated by direct measurement of counterion concentration with ion-selective electrode. Monte Carlo simulations based on the cell model are also performed to analyze the experimental results. The degree of counterion condensation is indicated by the concentration ratio of counterions in the bulk to the total ionic surfactant added, alpha< or =1. The ionic surfactant is completely dissociated below the critical micelle concentration (cmc). However, as cmc is exceeded, the free counterion ratio alpha declines with increasing the surfactant concentration and approaches an asymptotic value owing to counterion condensation to the surface of the highly charged micelles. Micelle formation leads to much stronger electrostatic attraction between the counterion and the highly charged sphere in comparison to the attraction of single surfactant ion with its counterion. A simple model is developed to obtain the true degree of ionization, which agrees with our Monte Carlo results. Upon addition of neutral polymer or monovalent salts, some of the surfactant counterions are released to the bulk. The former is due to the decrease of the intrinsic charge (smaller aggregation number) and the degree of ionization is increased. The latter is attributed to competitive counterion condensation, which follows the Hefmeister series. This consequence indicates that the specific ion effect plays an important role next to the electrostatic attraction.

Journal Article↗

PubMed2006

Kinetics of droplet condensation through a double free-energy barrier.

Results are presented for the kinetics of nucleation of liquid droplets from a one-component vapor phase on a planar lyophobic substrate patterned with a large number of easily wettable (lyophilic) circular domains. If the wettability of these lyophilic domains is characterized by a contact angle smaller than pi2, for intermediate values of the supersaturation, the condensation of a droplet on a lyophilic domain occurs through a free-energy barrier with two maxima, that is, through a double barrier. A simple model is proposed for the kinetics of droplet condensation through a double barrier that combines Kramers's [Physica (Utrecht) 7, 284 (1940)] transition rate theory with known results of nucleation theory. In the framework of this model, the solution is derived for the steady-state limit of the nucleation process. The number of lyophilic domains available for droplet condensation reduces with time as domains are occupied by droplets. The problem of droplet condensation through a double barrier is solved taking into account the effect of the time-dependent depletion in the number of available lyophilic domains.

Journal Article↗

PubMed2007

Vapor phase nucleation on neutral and charged nanoparticles: condensation of supersaturated trifluoroethanol on Mg nanoparticles.

A new technique is described to study the condensation of supersaturated vapors on nanoparticles under well-defined conditions of vapor supersaturation, temperature, and carrier gas pressure. The method is applied to the condensation of supersaturated trifluoroethanol (TFE) vapor on Mg nanoparticles. The nanoparticles can be activated to act as condensation nuclei at supersaturations significantly lower than those required for homogeneous nucleation. The number of activated nanoparticles increases with increasing the vapor supersaturation. The small difference observed in the number of droplets formed on positively and negatively charged nanoparticles is attributed to the difference in the mobilities of these nanoparticles. Therefore, no significant charge preference is observed for the condensation of TFE vapor on the Mg nanoparticles.

Journal Article↗

PubMed1995

Chromosome condensation activity (CCA) in bisected C57BL/6JxCBA mouse oocytes.

Chromosome condensation activity (CCA) has been analysed in C57BL/6Jx CBA mouse oocytes bisected (i) shortly after germinal vesicle breakdown (GVBD), (ii) in metaphase I (MI) and (iii) in metaphase II (MII) into two equal halves (nucleated, enucleated) which were thereafter fused to S- or G2-phase 4-cell-stage mouse blastomeres. In nucleated halves, premature chromosome condensation (PCC) in transplanted nuclei was always induced irrespective of the cell cycle stage of the blastomere, whereas in enucleated halves only G2 nuclei underwent PCC after transplantation. Premature chromosome condensation in S-phase nuclei was induced only in enucleated halves produced shortly after GVBD. Although S-phase nuclei transplanted to MI or MII enucleated halves remained intact, their capacity to synthesize DNA was invariably suppressed. When spindles were destroyed by preincubation of the oocytes in colcemid before bisection, both nucleated and enucleated halves produced at MI or MII induced PCC of both G2- or S-phase nuclei. These results demonstrate that chromosome condensation activity in mammalian oocytes is compartmentalized rather than uniformly distributed across the cell, and that the enucleation of mammalian oocytes before nuclear transplantation may, under some conditions, influence the levels of CCA and subsequent response of introduced nuclei to cytoplasmic factors.

Animals↗

PubMed2006

Interference between independent fluctuating condensates.

We consider a problem of interference between two independent condensates that lack true long-range order. We show that their interference pattern contains information about correlation functions within each condensate. As an example, we analyze the interference between a pair of one-dimensional interacting Bose liquids. We find universal scaling of the average fringe contrast with system size and temperature that depends only on the Luttinger parameter. Moreover, the full distribution of the fringe contrast, which is also equivalent to the full counting statistics of the interfering atoms, changes with interaction strength and lends information on high-order correlation functions. We also demonstrate that the interference between two-dimensional condensates at finite temperature can be used as a direct probe of the Kosterlitz-Thouless transition. Finally, we discuss the generalization of our results to describe the interference of a periodic array of independent fluctuating condensates.

Journal Article↗

PubMed2006

Velocity of vortices in inhomogeneous Bose-Einstein condensates.

We derive, from the Gross-Pitaevskii equation, an exact expression for the velocity of any vortex in a Bose-Einstein condensate, in equilibrium or not, in terms of the condensate wave function at the center of the vortex. In general, the vortex velocity is a sum of the local superfluid velocity, plus a correction related to the density gradient near the vortex. A consequence is that in rapidly rotating, harmonically trapped Bose-Einstein condensates, unlike in the usual situation in slowly rotating condensates and in hydrodynamics, vortices do not move with the local fluid velocity. We indicate how Kelvin's conservation of circulation theorem is compatible with the velocity of the vortex center being different from the local fluid velocity. Finally, we derive an exact wave function for a single vortex near the rotation axis in a weakly interacting system, from which we derive the vortex precession rate.

Algorithms↗

PubMed1986

Relationship between the pharmacological activity of antitumor drugs Ametantrone and mitoxantrone (Novatrone) and their ability to condense nucleic acids.

Ametantrone (HAQ) and mitoxantrone (DHAQ) are structurally similar antitumor drugs of the anthracenedione class. The cytostatic, cytotoxic, and antitumor activities of these drugs are different, with DHAQ being 10-100 times more potent, per molar basis. Both drugs are strong intercalators and intercalative modes of binding are suspected as relevant to their pharmacological activity. No significant differences, however, that could explain the differences in pharmacological activity are observed in their intercalative properties with respect to base specificity and binding affinity. A correlation, however, is evident between their potency and ability to condense nucleic acids inasmuch as DHAQ condenses nucleic acids at concentrations that are lower by a factor of 5-40 than those of HAQ and these effects can be observed at their pharmacological concentrations. The condensation is base- and sugar-specific and the long purine sequences of single-stranded RNA are the most sensitive. Electron microscopy of L1210 cells exposed a short time (90 min) to 0.21-21 microM DHAQ reveals segregation of nucleoli; the segregated granular portion shows increased electron opacity. In some preparations patchy areas of nuclear chromatin characterized by increased electron opacity can be seen. The results are compatible with the possibility that pharmacological effects of these antitumor drugs could involve condensation of nucleic acids, primarily of RNA in nucleoli.

Animals↗

PubMed2000

DNA condensation in two dimensions.

We have found that divalent electrolyte counterions common in biological cells (Ca(2+), Mg(2+), and Mn(2+) ) can condense anionic DNA molecules confined to two-dimensional cationic surfaces. DNA-condensing agents in vivo include cationic histones and polyamines spermidine and spermine with sufficiently high valence (Z) 3 or larger. In vitro studies show that electrostatic forces between DNA chains in bulk aqueous solution containing divalent counterions remain purely repulsive, and DNA condensation requires counterion valence Z >/= 3. In striking contrast to bulk behavior, synchrotron x-ray diffraction and optical absorption experiments show that above a critical divalent counterion concentration the electrostatic forces between DNA chains adsorbed on surfaces of cationic membranes reverse from repulsive to attractive and lead to a chain collapse transition into a condensed phase of DNA tethered by divalent counterions. This demonstrates the importance of spatial dimensionality to intermolecular interactions where nonspecific counterion-induced electrostatic attractions between the like-charged polyelectrolytes overwhelm the electrostatic repulsions on a surface for Z = 2. This new phase, with a one-dimensional counterion liquid trapped between DNA chains at a density of 0.63 counterions per DNA bp, represents the most compact state of DNA on a surface in vitro and suggests applications in high-density storage of genetic information and organo-metallic materials processing.

Bacteriophage lambda↗

PubMed1996

Condensation of rat telomere-specific nucleosomal arrays containing unusually short DNA repeats and histone H1.

Vertebrate telomeres contain arrays of nucleosomes with unusually short and regular repeat lengths (Makarov, V. L., Lejnine, S., Bedoyan, J., and Langmore, J. P.(1993) Cell 73, 775-787; Lejnine, S., Makarov, V., and Langmore, J. P. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 2393-2397). In order to better define the specific structural features of telomere chromatin, we examined the condensation and H1 content of telomere nucleoproteins from rat liver. Velocity sedimentation analysis shows that telomeric nucleosome arrays condense with increasing ionic strength and molecular weight in a manner comparable with that of bulk chromatin despite the very short repeat length. However, these condensed structures do not exhibit the approximately 100-base pair deoxyribonuclease II repeat characteristic of condensed bulk chromatin. Frictional coefficient calculations suggest that telomere-specific higher order structure is more compact than bulk chromatin. Nucleoprotein gel electrophoresis shows that telomeric dinucleosomes from soluble chromatin contain H1. Finally, direct isolation and analysis of telomere nucleoproteins from formaldehyde-cross-linked nuclei indicate the presence of core histone proteins and H1. These results are consistent with the view that a major fraction of the long telomeres of rat are organized as specialized nucleosome arrays with features similar but not identical to those of bulk chromatin.

Animals↗

PubMed1997

The condensation of chromatin in apoptotic thymocytes shows a specific structural change.

Chromatin condensation and DNA cleavage at internucleosomal sites have been recognized early as hallmarks of apoptosis, and it has been suggested that extensive DNA chain scission could directly result in the formation of dense chromatin bodies. Here we have shown that no causal relationship exists between DNA degradation and chromatin condensation in glucocorticoid-induced thymocyte apoptosis. The chromatin rearrangement occurred independent of as well as prior to DNA cleavage and involved a specific conformational change at the nucleosome level. In the early stages of the process, the core particles appeared to be tightly packed face-to-face in smooth 11-nm filaments that progressively folded to generate a closely woven network. The network finally collapsed, producing dense apoptotic bodies. Since trypsin digestion relaxed condensed chromatin and histone H4 underwent appreciable deacetylation in the apoptotic cell, we suggest that changes in the DNA-histone interactions represented a major modulating factor of condensation.

Animals↗

PubMed1998

Peptide bond formation in nonribosomal peptide biosynthesis. Catalytic role of the condensation domain.

Recently, considerable insight has been gained into the modular organization and catalytic properties of nonribosomal peptide synthetases. However, molecular and biochemical aspects of the condensation of two aminoacyl substrates or a peptidyl and an aminoacyl substrate, leading to the formation of a peptide bond, have remained essentially impenetrable. To investigate this crucial part of nonribosomal peptide synthesis, an in vitro assay for a dipeptide formation was developed. Two recombinant holomodules, GrsA (PheATE), providing D-Phe, and a C-terminally truncated TycB, corresponding to the first, L-Pro-incorporating module (ProCAT), were investigated. Upon combination of the two aminoacylated modules, a fast reaction is observed, due to the formation of the linear dipeptide D-Phe-L-Pro-S-enzyme on ProCAT, followed by a noncatalyzed release of the dipeptide from the enzyme. The liberated product was identified by TLC, high pressure liquid chromatography-mass spectrometry, 1H and 13C NMR, and comparison with a chemically synthesized standard to be the expected D-Phe-L-Pro diketopiperazine. Further minimization of the two modules was not possible without a loss of transfer activity. Likewise, a mutation in a proposed active-site motif (HHXXXDG) of the condensation domain giving ProCAT(H147V), abolished the condensation reaction. These results strongly suggest the condensation domain to be involved in the catalysis of nonribosomal peptide bond formation with the histidine 147 playing a catalytic role.

Amino Acid Sequence↗

PubMed1998

Chromatin condensation is not associated with apoptosis.

Apoptosis plays an important role in the survival of an organism, and substantial work has been done to understand the signaling pathways that regulate this process. Characteristic changes in chromatin organization accompany apoptosis and are routinely used as markers for cell death. We have examined the organization of chromatin in apoptotic PC12 and HeLa cells by indirect immunofluorescence and electron spectroscopic imaging. Our results indicate that de novo chromatin condensation normally seen during mitosis does not occur when cells undergo apoptosis. Instead, the condensed chromatin typically observed results from aggregation of the heterochromatin. We present evidence that, early in apoptosis, there is a rapid degradation of the nuclease-hypersensitive euchromatin that contains hyperacetylated histones. This occurs coincident with the loss of nuclear integrity due to degradation of lamins and reorganization of intranuclear protein matrix. These events lead to collapse of the nucleus and aggregation of heterochromatin to produce the appearance of condensed apoptotic chromatin. This heterochromatin aggregate is then digested by nucleases to produce the oligonucleosomal DNA ladder that is a hallmark of late apoptosis. Unlike mitosis, we have not seen any evidence for the requirement of phosphorylated histones H1 and H3 to maintain the chromatin in the condensed state.

Animals↗

PubMed1999

Identification of a novel phosphorylation site on histone H3 coupled with mitotic chromosome condensation.

Histone H3 (H3) phosphorylation at Ser(10) occurs during mitosis in eukaryotes and was recently shown to play an important role in chromosome condensation in Tetrahymena. When producing monoclonal antibodies that recognize glial fibrillary acidic protein phosphorylation at Thr(7), we obtained some monoclonal antibodies that cross-reacted with early mitotic chromosomes. They reacted with 15-kDa phosphoprotein specifically in mitotic cell lysate. With microsequencing, this phosphoprotein was proved to be H3. Mutational analysis revealed that they recognized H3 Ser(28) phosphorylation. Then we produced a monoclonal antibody, HTA28, using a phosphopeptide corresponding to phosphorylated H3 Ser(28). This antibody specifically recognized the phosphorylation of H3 Ser(28) but not that of glial fibrillary acidic protein Thr(7). Immunocytochemical studies with HTA28 revealed that Ser(28) phosphorylation occurred in chromosomes predominantly during early mitosis and coincided with the initiation of mitotic chromosome condensation. Biochemical analyses using (32)P-labeled mitotic cells also confirmed that H3 is phosphorylated at Ser(28) during early mitosis. In addition, we found that H3 is phosphorylated at Ser(28) as well as Ser(10) when premature chromosome condensation was induced in tsBN2 cells. These observations suggest that H3 phosphorylation at Ser(28), together with Ser(10), is a conserved event and is likely to be involved in mitotic chromosome condensation.

Amino Acid Sequence↗

PubMed2006

Roles of the active site water, histidine 303, and phenylalanine 396 in the catalytic mechanism of the elongation condensing enzyme of Streptococcus pneumoniae.

beta-Ketoacyl-ACP synthases catalyze the condensation steps in fatty acid and polyketide synthesis and are targets for the development of novel antibiotics and anti-obesity and anti-cancer agents. The roles of the active site residues in Streptococcus pneumoniae FabF (beta-ketoacyl-ACP synthase II; SpFabF) were investigated to clarify the mechanism for this enzyme superfamily. The nucleophilic cysteine of the active site triad was required for acyl-enzyme formation and the overall condensation activity. The two active site histidines in the elongation condensing enzyme have different electronic states and functions. His337 is essential for condensation activity, and its protonated Nepsilon stabilizes the negative charge developed on the malonyl thioester carbonyl in the transition state. The Nepsilon of His303 accelerated catalysis by deprotonating a structured active site water for nucleophilic attack on the C3 of malonate, releasing bicarbonate. Lys332 controls the electronic state of His303 and also plays a critical role in the positioning of His337. Phe396 functions as a gatekeeper that controls the order of substrate addition. These data assign specific roles for each active site residue and lead to a revised general mechanism for this important class of enzymes.

Amino Acid Sequence↗