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 325 records · Page 18Linked to original sources

PubMed1987

A new method to measure the condensation pressure of amalgam under in vivo conditions.

The purpose of this study was to investigate the condensation pressure of amalgam achieved under close to in vivo conditions by 42 general practitioners who were asked to fill a pre-cut standard class 2 cavity in a mannequin head. A measuring device was designed to allow the maximum and average condensation pressures and working and resting periods to be obtained. The results showed a maximum condensation pressure of 9.17 +/- 3.04 MPa and 4.09 +/- 1.41 MPa with a small (diameter, 1.15 mm) and a large (diameter, 1.8 mm) amalgam plugger, respectively. Only one of the 42 dentists reached the recommended condensation pressure of 15 MPa (Jørgensen, 1977). A significant (p less than or equal to 0.001) correlation between the duration of the working periods and the maximum condensation pressure was found (r = 0.61). Further investigations are required to determine the influence of these different condensation pressures on the physical properties of various amalgams.

Chemical Phenomena↗

PubMed1990

Interactions of nucleic acids with fluorescent dyes: spectral properties of condensed complexes.

Interaction of cations with nucleic acids (NA) often results in condensation of the product. The driving force of aromatic cation-induced condensation is the cooperative interaction between ligand and single-stranded (ss) NA. This type of reaction is highly specific with regard to the primary and secondary structure of NA, and results in destabilization of the latter. The spectral properties of fluorescent intercalating and non-intercalating ligands [acridine orange, pyronin Y(G), DAPI, Hoechst 33258, and Hoechst 33342]-NA complexes were studied in both the relaxed and condensed form. The changes in absorption, excitation, and fluorescence emission spectra and fluorescence yield that followed the condensation were examined. Although some of these effects can be explained by changes in solvation of the fluorophore and its interaction with NA bases and the solvent, the overall effect of condensation on spectral properties of the complex is unpredictable. In particular, no correlation was found between these effects and the ds DNA binding mode of these ligands. Nevertheless, the spectral data associated with polymer condensation can yield information about the composition and structure of NA and can explain some nonspecific interactions of these probes.

Acridine Orange↗

PubMed2006

Exhaled breath condensate pH standardised for CO2 partial pressure.

Exhaled breath condensate (EBC) pH is considered to reflect the acid-base balance of the airways. Current pH measurements do not take into account the effect of CO2. The aim of the present study was to determine the effect of condensate CO2 partial pressure on pH and to provide a more precise mode of EBC pH determination. Condensate pH and CO2 partial pressure were measured in parallel from 12 healthy volunteers and 12 asthmatics using a blood gas analyser in neat, argon de-aerated and CO2-loaded samples. The regression analysis was used to test the relationship between pH and CO2, and to calculate the pH at a CO2 level of 5.33 kPa (physiological alveolar CO2 partial pressure). Reproducibility of different pH readings was compared using the Bland-Altman test. Condensate CO2 concentration was variable both in neat and argon de-aerated samples. There was a close negative logarithmic relationship between CO2 and pH. Calculation of pH at a CO2 level of 5.33 kPa provided reproducibility approximately six times as good as that of the currently used measurements. Condensate CO2 partial pressure influences pH measurements. Determination of pH at a standard CO2 level provides the most reproducible condensate pH values to date.

Acid-Base Equilibrium↗

PubMed1999

Expired hydrogen peroxide in breath condensate of cystic fibrosis patients.

Stimulated inflammatory cells release large amounts of hydrogen peroxide (H2O2). Breath condensate H2O2 has been shown to be elevated in stable asthmatic children, chronic obstructive pulmonary disease and intubated adult respiratory distress syndrome. In cystic fibrosis airways, where neutrophilic inflammation dominates, it is postulated that H2O2 in breath condensate would be elevated and may be used as a marker of airways inflammation. Expired breath condensate was collected from 16 clinically stable cystic fibrosis (CF) patients (mean age 25.3 yrs, mean forced expiratory volume in one second (FEV1) 50.2%) and 14 normal subjects (mean age 29.9 yrs). Total plasma leukocyte, neutrophil, monocyte and eosinophil counts and lung function were also measured on the day of collection. A method of breath condensate collection excluding the confounding factors of nasal air and saliva contamination was validated and used and H2O2 measured fluorometrically using an optimized assay. The median level of H2O2 concentration in breath condensate of CF patients was lower than that in normal subjects (0.064 versus 0.089 microM), but this did not reach statistical significance (p = 0.20, Mann-Whitney rank sum test). Within the CF group, there was no correlation between H2O2 concentration and lung function. Expired breath condensate H2O2 is not elevated in patients with cystic fibrosis, and is thus not a suitable marker of airways inflammation in these patients. Possible explanations include physical barriers to its detection caused by viscous airways secretions, reaction with other reactive species or increased antioxidant activity caused by trapping of positively charged antioxidants in negatively charged airways secretions.

Adult↗

PubMed2006

Analysis of heat and mass transfer during condensation over a porous substrate.

Condensing heat exchangers are important in many space applications for thermal and humidity control systems. The International Space Station uses a cooled fin surface to condense moisture from humid air that is blown over it. The condensate and the air are "slurped" into a system that separates air and water by centrifugal forces. The use of a cooled porous substrate is an attractive alternative to the fin where condensation and liquid/gas separation can be achieved in a single step. We analyze the heat and mass transfer during condensation of moisture from flowing air over such a cooled, flat, porous substrate. A fully developed regime is investigated for coupled mass, momentum and energy transport in the gas phase, and momentum and energy transport in the condensate layer on the porous substrate and through the porous medium.

Journal Article↗

PubMed2002

The MAPK pathway triggers activation of Nek2 during chromosome condensation in mouse spermatocytes.

Chromosome condensation during the G2/M progression of mouse pachytene spermatocytes induced by the phosphatase inhibitor okadaic acid (OA) requires the activation of the MAPK Erk1. In many cell systems, p90Rsks are the main effectors of Erk1/2 function. We have identified p90Rsk2 as the isoform that is specifically expressed in mouse spermatocytes and have shown that it is activated during the OA-triggered meiotic G2/M progression. By using the MEK inhibitor U0126, we have demonstrated that activation of p90Rsk2 during meiotic progression requires activation of the MAPK pathway. Immunofluorescence analysis indicates that activated Erks and p90Rsk2 are tightly associated with condensed chromosomes during the G2/M transition in meiotic cells. We also found that active p90Rsk2 was able to phosphorylate histone H3 at Ser10 in vitro, but that the activation of the Erk1/p90Rsk2 pathway was not necessary for phosphorylation of H3 in vivo. Furthermore, phosphorylation of H3 was not sufficient to cause condensation of meiotic chromosomes in mouse spermatocytes. Other proteins known to associate with chromatin may represent effectors of Erk1 and p90Rsk2 during chromosome condensation. Nek2 (NIMA-related kinase 2), which associates with chromosomes, plays an active role in chromatin condensation and is stimulated by treatment of pachytene spermatocytes with okadaic acid. We show that inhibition of the MAPK pathway by preincubation of spermatocytes with U0126 suppresses Nek2 activation, and that incubation of spermatocyte cell extracts with activated p90Rsk2 causes stimulation of Nek2 kinase activity. Furthermore, we show that the Nek2 kinase domain is a substrate for p90Rsk2 phosphorylation in vitro. These data establish a connection between the Erk1/p90Rsk2 pathway, Nek2 activation and chromosome condensation during the G2/M transition of the first meiotic prophase.

Animals↗

PubMed1998

Histone H3 phosphorylation is required for the initiation, but not maintenance, of mammalian chromosome condensation.

The temporal and spatial patterns of histone H3 phosphorylation implicate a specific role for this modification in mammalian chromosome condensation. Cells arrest in late G2 when H3 phosphorylation is competitively inhibited by microinjecting excess substrate at mid-S-phase, suggesting a requirement for activity of the kinase that phosphorylates H3 during the initiation of chromosome condensation and entry into mitosis. Basal levels of phosphorylated H3 increase primarily in late-replicating/early-condensing heterochromatin both during G2 and when premature chromosome condensation is induced. The prematurely condensed state induced by okadaic acid treatment during S-phase culminates with H3 phosphorylation throughout the chromatin, but in an absence of mitotic chromosome morphology, indicating that the phosphorylation of H3 is not sufficient for complete condensation. Mild hypotonic treatment of cells arrested in mitosis results in the dephosphorylation of H3 without a cytological loss of chromosome compaction. Hypotonic-treated cells, however, complete mitosis only when H3 is phosphorylated. These observations suggest that H3 phosphorylation is required for cell cycle progression and specifically for the changes in chromatin structure incurred during chromosome condensation.

Amino Acid Sequence↗

PubMed1976

Fine structure of the heterochromatin of the kangaroo rat Dipidomys ordii, and examination of the possible role of actin and myosin in heterochromatin condensation.

Biochemical studies have suggested that some actin and myosin may be present in the nucleus. This raises the possibility that heterochromatin condensation might be the result of an actin-myosin rigour type complex. Since ATP dissociates actin and myosin, this possibility could be examined by determining the effect of ATP on heterochromatin condensation. Thin-section electron microscopy showed large amounts of condensed constitutive heterochromatin in the kidney nuclei and somewhat less in the liver nuclei of the kangaroo rat, Dipidomys ordii. Surprisingly, there were some nuclei in the brain which contained no condensed heterochromatin despite the fact that this genome is composed of 50% satellite DNA. Although washing kidney nuclei with solutions of 10 mM Tris-ATP caused marked decondensation of the heterochromatin, when they were washed with Mg-ATP the heterochromatin was more condensed than in the controls. This suggests the decondensation by Tris-ATP is due to its ability to chelate divalent cations and provides no support for condensation of heterochromatin being the result of myosin-actin interaction. Despite being decondensed, the chromatin fibres of heterochromatin were distinct from those of euchromatin. The heterochromatin formed rod-like 19-5 nm fibres, the euchromatin formed random coils of 11-0-nm fibres.

Actins↗

PubMed1993

Contribution of water condensation in endotracheal tubes to contamination of the lungs.

We postulated that water condensate in endotracheal tubes (ETTs) transports bacteria in the ETTs into the lungs during mechanical ventilation. Thirty-two ETTs obtained from freshly extubated patients were studied under wet and dry conditions using a physiologic lung model. All bacteria expelled from the ETTs were collected on culture plates positioned beneath the ETT. The lung model was ventilated with saturated air at 37 degrees C over two time periods (60 min each), one in which condensation formation was prevented and the second in which condensation formed within the ETT. A mean of 457.6 colony-forming units (CFU)/h were expelled with condensation compared to a mean of 2.4 CFU/h without condensation. We concluded that bacteria were continuously transported from the ETT into the lungs during mechanical ventilation in water droplets. Prevention of water condensation abolishes this constant bacterial inoculation in a lung model.

Air Microbiology↗

PubMed1998

A randomized clinical trial comparing an extended-use hygroscopic condenser humidifier with heated-water humidification in mechanically ventilated patients.

STUDY OBJECTIVE: To determine the safety and cost-effectiveness of mechanical ventilation with an extended-use hygroscopic condenser humidifier (Duration; Nellcor Puritan-Bennett; Eden Prairie, Minn) compared with mechanical ventilation with heated-water humidification. DESIGN: Prospective randomized clinical trial. SETTING: Medical and surgical ICUs of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital. PATIENTS: Three hundred ten consecutive qualified patients undergoing mechanical ventilation. INTERVENTIONS: Patients requiring mechanical ventilation were randomly assigned to receive humidification with either an extended-use hygroscopic condenser humidifier (for up to the first 7 days of mechanical ventilation) or heated-water humidification. MEASUREMENTS: Occurrence of ventilator-associated pneumonia, endotracheal tube occlusion, duration of mechanical ventilation, lengths of intensive care and hospitalization, acquired multiorgan dysfunction, and hospital mortality. RESULTS: One hundred sixty-three patients were randomly assigned to receive humidification with an extended-use hygroscopic condenser humidifier, and 147 patients were randomly assigned to receive heated-water humidification. The two groups were similar at the time of randomization with regard to demographic characteristics, ICU admission diagnoses, and severity of illness. Risk factors for the development of ventilator-associated pneumonia were also similar during the study period for both treatment groups. Ventilator-associated pneumonia was seen in 15 (9.2%) patients receiving humidification with an extended-use hygroscopic condenser humidifier and in 15 (10.2%) patients receiving heated-water humidification (relative risk, 0.90; 95% confidence interval=0.46 to 1.78; p=0.766). No statistically significant differences for hospital mortality, duration of mechanical ventilation, lengths of stay in the hospital ICU, or acquired organ system derangements were found between the two treatment groups. No episode of endotracheal tube occlusion occurred during the study period in either treatment group. The total cost of providing humidification was $2,605 for patients receiving a hygroscopic condenser humidifier compared with $5,625 for patients receiving heated-water humidification. CONCLUSION: Our findings suggest that the initial application of an extended-use hygroscopic condenser humidifier is a safe and more cost-effective method of providing humidification to patients requiring mechanical ventilation compared with heated-water humidification.

Adolescent↗

PubMed2005

Ligand-induced DNA condensation: choosing the model.

We test and compare different models for ligand-induced DNA condensation. Using 14C-labeled spermidine3+, we measure the binding to condensed DNA at micromolar to molar polyamine concentrations. DNA aggregates at a critical polyamine concentration. Spermidine3+ binding becomes highly cooperative at the onset of aggregation. At higher concentrations, spermidine3+ binding to condensed DNA reaches a plateau with the degree of binding equal to 0.7 (NH(4+)/PO3-). Condensed DNA exists in a wide range of spermidine concentrations with the roughly constant degree of ligand binding. At greater concentrations, the degree of binding increases again. Further spermidine penetration between the double helices causes DNA resolubilization. We show that a simple two-state model without ligand-ligand interactions qualitatively predicts the reentrant aggregation-resolubilization behavior and the dependence on the ligand, Na+, and DNA concentrations. However, such models are inconsistent with the cooperative ligand binding to condensed DNA. Including the contact or long-range ligand-ligand interactions improves the coincidence with the experiments, if binding to condensed DNA is slightly more cooperative than to the starting DNA. For example, in the contact interaction model it is equivalent to an additional McGhee-von Hippel cooperativity parameter of approximately 2. Possible physical mechanisms for the observed cooperativity of ligand binding are discussed.

Computer Simulation↗

PubMed2000

Polyethylene glycol as a means for reducing the impact of condensed tannins in carob pulp: effects on lamb growth performance and meat quality.

We conducted an experiment to evaluate the effects that a diet containing condensed tannins with and without polyethylene glycol (PEG) has on lamb growth and meat quality. Twenty-three male Comisana lambs were introduced to the three experimental diets between 45 and 50 d of age. Eight were given a diet containing 56% of Ceratonia siliqua (carob) pulp (tannin group), another eight received the same diet with a supplement of 40 g of PEG for each kilogram of diet (PEG group), and the remaining seven lambs were given a conventional maize-based diet (maize group). Voluntary feed intake and live weights were measured until slaughter at 105 d of age, and digestibility measurements were undertaken toward the end of the feeding trial. Carcass yield, meat quality characteristics, and a taste panel evaluation were conducted. The tannin-based diet contained 2.5% condensed tannins (DM basis), and lambs given this diet had lower growth rates and poorer feed efficiencies (P < .01) compared with the other treatment groups. Daily gain was similar between the maize and PEG lambs, although the efficiency of feed conversion was highest in the maize group. The digestibility of DM, N, and fiber was reduced (P < .05) by the condensed tannins. Lambs fed the tannin diet had a lower carcass yield (P < .05) and had less fat (P < .05), and the meat had a higher ultimate pH (P < .01) than those given the PEG or maize diets. Condensed tannins affected meat color, which was lighter (L*) than meat from lambs given the PEG-containing diet (P < .01). Sensory evaluation showed that panelists preferred meat from lambs receiving PEG and maize treatments compared with those receiving the tannin diet, and this could be related to differences in meat ultimate pH and carcass fatness. These results show that condensed tannins from carob pulp are very detrimental to feed digestibility and lamb performance. Inclusion of 40 g of PEG/kg diet eliminated the effects of condensed tannins so that lamb performance and meat quality were similar to lambs given a maize-based diet.

Animal Feed↗

PubMed1999

Expression of N-cadherin, N-CAM, fibronectin and tenascin is stimulated by TGF-beta1, beta2, beta3 and beta5 during the formation of precartilage condensations.

Cell surface adhesion and extracellular matrix proteins are known to play a key role in the formation of cell condensations during skeletal development, and their formation is crucial for the expression of cartilage-specific genes. However, little is known about the relationship between adhesion molecules (N-cadherin and N-CAM), extracellular matrix proteins (fibronectin and tenascin) and TGF-beta1, TGF-beta2 and TGF-beta3 during in vitro precartilage condensations in mouse chondrogenesis. On these bases, we determined the participation of mammalian TGF-beta1, TGF-beta2 and TFG-beta3 and Xenopus TGF-beta5 on the expression of cell surface adhesion and extracellular matrix proteins during the formation of precartilage condensations. Also, we characterized the effects of TGF-betas on proteoglycan metabolism at different cellular densities in mouse embryonic limb bud mesenchymal cells. In TGF-beta1 and TGF-beta5-treated cultures, proteoglycan biosynthesis was higher than in controls, while there were no differences in proteoglycan catabolism, which caused the accumulation of cartilage extracellular matrix. When mesenchymal cells were seeded at three different cellular densities in the presence of TGF-betas, only high density cultures presented increased stimulation of proteoglycan biosynthesis, compared to low and intermediate densities. To determine whether the effect of TGF-betas on precartilage condensations is mediated through the expression of N-cadherin, N-CAM, fibronectin and tenascin, we evaluated their expression. Results showed that TGF-beta1, TGF-beta2, TGF-beta3, and TGF-beta5 differentially enhanced the expression of N-cadherin, N-CAM, fibronectin and tenascin in precartilage condensations, suggesting that TGF-beta isoforms play an important role in the establishment of cell-cell and cell-extracellular matrix interactions during precartilage condensations.

Animals↗

PubMed1976

Circular dichroism studies on DNA condensed in NaCl cetyltrimethyl ammonium bromide solutions.

It is shown by means of circular dichroism studies of variously condensed forms of DNA that the specific supramolecular structure of DNA determines the type of CD spectra. DNA, condensed (crystallized) slowly in the presence of cetyltrimethyl ammonium bromide yields a spectrum very similar to that of DNA in solution in the B-form. The condensates appear in the phase-contrast microscope as spherulitic crystallites. Rapidly condensed DNA in the presence of cetyltrimethyl ammonium bromide shows a spectrum of the psi-type with large negative ellipticites. The influence of condensation velocity upon the supramolecular structure of DNA gives evidence that the various condensation forms of DNA are not thermodynamical equilibrium conformations.

Bromides↗

PubMed1999

Preliminary study of the forces developed by practitioners during amalgam condensation.

The aim of this preliminary study was to analyze, in vitro, the forces developed by practitioners during amalgam condensation. Standardized Class II cavities were drilled into 40 freshly extracted teeth. The forces exerted during condensation were then measured by means of a new device, the Endographe, and plotted online or offline as a function of time on Endogrammes. The work techniques of the different practitioners revealed similarities. The mean values of the vertical forces (+/- SEM) were: 15 +/- 2 N for manual compaction of capsule amalgam; 8 +/- 3 N for manual compaction of amalgam with a higher mercury-to-alloy ratio; 6 +/- 4 N for mechanical compaction of encapsulated amalgam; and 4 +/- 2 N for mechanical compaction of the modified amalgam. For the horizontal components, the forces were, respectively, 5 +/- 2 N, 0.1 +/- 0.05 N, 3 +/- 1 N, and 0.7 +/- 0.2 N. The mean values of condensation time were 20 +/- 15 s for each incremental application, with a great variation in durations between the beginning and end of condensation. By visually depicting forces as a function of time, the Endographe can be used to analyze the process of amalgam insertion and condensation. Future research will study the relationship between the forces developed during condensation and the adaptation of the amalgam to the walls of the cavity.

Analysis of Variance↗

PubMed1975

Metabolism of cigarette smoke condensates by human and rat homogenates to form mutagens detectable by Salmonella typhimurium TA1538.

Nineteen fractions of whole condensate of smoke from the University of Kentucky Reference Cigarette IRI were tested for mutagenicity in vitro using a bacterial indicator system. As little as 25 mug of the active fractions were mutagenic toward histidine-requiring Salmonella typhimurium TA1538, if the condensates were incubated in the presence of rat or human liver homogenates of lung were relatively inactive. Homogenates from livers of rats that had been treated with 3-methylcholanthrene converted condensates to mutagens more efficiently than did liver homogenates from man or from normal or phenobarbital-treated rats. Use of homogenates from animals treated with 3-methylcholanthrene gave much more reproducible results in smoke fraction assays because larger numbers of revertants were obtained, and dose-response curves were linear over the range 25 to 250 mug condensate. The linear dose-response curves permitted quantitative comparison of the various fractions. The mutagenicity per mg of basic fractions of whole smoke condensate is very high and that of neutral polycyclic hydrocarbons is very low. Because of the exquisite preferential sensitivity of the TA1538 test system to polycyclic amines and insensitively to alkyl polycyclics, there is a poor quantitative correlation between mutagenicity and carcinogenicity, as measured by skin painting or in vitro cell transformation. There is substantial evidence that many carcinogens are mutagens but that most of these compounds require metabolism before they are biologically active. If further development improves the sensitivity of the bacterial testing system to mutagenic derivatives of alkyl polycyclic and heteropolycyclic hydrocarbons, it may provide a convenient, rapid, quantitative, and inexpensive bioassay for the detection of potentially carcinogenic substances in tobacco smoke condensates.

Animals↗

PubMedDate not supplied

[Calculation of DNA condensation, caused by adsorption of ligands].

A method for calculating the curves of DNA transition from linear to condensed state upon binding of condensing ligands has been developed. The character of the transition and ligand concentration necessary for condensation have been shown to be governed by the length of DNA molecule, energy and stoichiometry parameters of DNA-ligand complex (equilibrium constant between linear and condensed form in the absence of ligands, constants for ligand binding to linear and condensed forms, the number of base pairs covered by one ligand, etc.). The results of the calculations indicate that only slight difference in the free energies of these states in free DNA (less than 6 cal/mole(bp) for DNA of 500 bp long) is sufficient for the existence of stable linear state in the absence of ligands (in free DNA) and the formation of stable condensed state upon complexation.

Adsorption↗

PubMed2000

Perfluorodecalin condensation on posterior surface of lens capsule and corneal endothelium during vitrectomy.

BACKGROUND: High-density vitreous substitutes, including perfluorodecalin, are widely used in current vitreoretinal surgery. We report 4 cases of perfluorodecalin condensation on the posterior capsule of the lens or corneal endothelium during vitrectomy. To the best of our knowledge, no such phenomenon has ever been reported. METHODS: This study consisted of 4 patients with retinal detachment and large retinal tears. All patients were men. All of the patients underwent pars plana vitrectomy, perfluorodecalin injection, endolaser retinopexy and air-fluid exchange. Two patients received additional surgery for scleral buckling. RESULTS: Perfluorodecalin condensation was observed on the posterior surface of the lens capsule in one phakic patient and on the endothelium in three aphakic patients during vitrectomy. The condensation obscured the image of the fundus and made air-fluid exchange difficult. The condensation could be dissipated by first removing the perfluorodecalin as completely as possible, and then by lowering the intraocular pressure below the vapor pressure of perfluorodecalin. CONCLUSIONS: Perfluorodecalin condensation may occur when perfluorodecalin is not properly used. To avoid forming condensation, high-density vitreous substitutes should never be injected into eyes that are completely air-filled, prolonged air-fluid exchanges should be avoided, and the intraocular pressure should always be kept at a higher level during air-fluid exchange.

Adult↗