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Results for “Condensates”

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PubMed1998

Topological defects and the optimum size of DNA condensates.

Under a wide variety of conditions, the addition of condensing agents to dilute solutions of random-coil DNA gives rise to highly compact particles that are toroidal in shape. The size of these condensates is remarkably constant and is largely independent of DNA molecular weight and basepair sequence, and of the nature of condensing agent (e.g., multivalent cation, polymers, or added cosolvent). We show how this optimum size is determined by the interactions between topological defects, which unavoidably strain the circumferentially wound DNA strands in the torus.

Base Composition↗

PubMed1999

Brownian dynamics simulation of DNA condensation.

DNA condensation observed in vitro with the addition of polyvalent counterions is due to intermolecular attractive forces. We introduce a quantitative model of these forces in a Brownian dynamics simulation in addition to a standard mean-field Poisson-Boltzmann repulsion. The comparison of a theoretical value of the effective diameter calculated from the second virial coefficient in cylindrical geometry with some experimental results allows a quantitative evaluation of the one-parameter attractive potential. We show afterward that with a sufficient concentration of divalent salt (typically approximately 20 mM MgCl(2)), supercoiled DNA adopts a collapsed form where opposing segments of interwound regions present zones of lateral contact. However, under the same conditions the same plasmid without torsional stress does not collapse. The condensed molecules present coexisting open and collapsed plectonemic regions. Furthermore, simulations show that circular DNA in 50% methanol solutions with 20 mM MgCl(2) aggregates without the requirement of torsional energy. This confirms known experimental results. Finally, a simulated DNA molecule confined in a box of variable size also presents some local collapsed zones in 20 mM MgCl(2) above a critical concentration of the DNA. Conformational entropy reduction obtained either by supercoiling or by confinement seems thus to play a crucial role in all forms of condensation of DNA.

Biopolymers↗

PubMed1987

Enzyme induction in rat lung and liver by condensates and fractions from main-stream and side-stream cigarette smoke.

Aryl hydrocarbon hydroxylase (AHH) and dimethylnitrosamine demethylase (DMND) activities in pulmonary and hepatic tissues of male Sprague-Dawley rats were assayed following pretreatment with known inducers (benzo[a]pyrene, 3-methylcholanthrene, Aroclor 1254, phenobarbital) and with main-stream (MS) and side-stream (SS) cigarette smoke condensates and their related fractions. Biochemical assays by spectrophotofluorimetry (AHH activity) and spectrophotometry (DMND activity) and by a biological assay (Ames test) were performed to detect AHH and DMND induction. Ames test proved to be much less sensitive than the spectrophotofluorimetric analysis for AHH determination. Both main-stream and side-stream cigarette smoke condensates and some fractions, containing water-soluble bases, water-insoluble bases, and polycyclic aromatic hydrocarbons, were found to induce AHH activity in lung and liver, the lung being induced to the greatest extent. The highest levels of AHH inducibility were found for the SS-smoke condensate and related fractions. In particular, the insoluble bases fractions gave the highest induction. On the contrary, pulmonary DMND activity was not affected by pretreatment with the same materials, while hepatic DMND response was only minimally induced by Aroclor and phenobarbital treatment.

Animals↗

PubMed2000

Ultrasonic monitoring of film condensation for applications in reduced gravity

The film condensation of vapor on a cooled, downward-facing surface is a complex dynamic fluid phenomenon. This paper will describe the theoretical basis, instrumentation approach, and experimental results for a method for ultrasonic monitoring of film condensation. The ultrasound measurement system utilizes a 10 MHz broadband contact transducer, operating in pulse-echo mode. By appropriate signal processing, condensation layers over a wide thickness range, from much less than a wavelength to several wavelengths, can readily be measured.

Journal Article↗

PubMed2001

Treatment of a foul condensate from Kraft pulping with horseradish peroxidase and hydrogen peroxide.

Foul condensates originating from the Kraft recovery process contain phenolic compounds whose removal might render these process streams more useful for reuse in other plant operations or more amenable to biological degradation. Treatment of a foul condensate with horseradish peroxidase and H2O2 selectively targeted phenolic compounds resulting in a reduction of the total phenols concentration below 1 mg/L as well as a substantial toxicity drop as measured using the Microtox assay; however, only marginal COD removal was achieved. Comparisons of treatments between synthetic wastewaters and real wastewaters to which phenol were added revealed that the condensate contained species that protect the enzyme from inactivation by reaction products. Analytical data as well as experimental results suggest that these species are lignin derivatives.

Benzothiazoles↗

PubMed1997

Condensins, chromosome condensation protein complexes containing XCAP-C, XCAP-E and a Xenopus homolog of the Drosophila Barren protein.

We report here purification and characterization of chromosome condensation protein complexes (termed condensins) containing XCAP-C and XCAP-E, two Xenopus members of the SMC family. Sucrose density gradient centrifugation reveals two major forms of condensins. The 8S form is a heterodimer of XCAP-C and XCAP-E, whereas the 13S form contains three additional subunits. One of them is identified as a homolog of the Drosophila Barren protein whose mutation shows a defect in chromosome segregation. Chromosomal targeting of condensins is mitosis-specific and is independent of topoisomerase IIalpha. 13S condensin is required for condensation, as demonstrated by immunodepletion and rescue experiments. Our results suggest that the condensin complexes represent the most abundant structural components of mitotic chromosomes and play a central role in driving chromosome condensation.

Adenosine Triphosphatases↗

PubMed1999

Phosphorylation of histone H3 is required for proper chromosome condensation and segregation.

Phosphorylation of histone H3 at serine 10 occurs during mitosis in diverse eukaryotes and correlates closely with mitotic and meiotic chromosome condensation. To better understand the function of H3 phosphorylation in vivo, we created strains of Tetrahymena in which a mutant H3 gene (S10A) was the only gene encoding the major H3 protein. Although both micronuclei and macronuclei contain H3 in typical nucleosomal structures, defects in nuclear divisions were restricted to mitotically dividing micronuclei; macronuclei, which are amitotic, showed no defects. Strains lacking phosphorylated H3 showed abnormal chromosome segregation, resulting in extensive chromosome loss during mitosis. During meiosis, micronuclei underwent abnormal chromosome condensation and failed to faithfully transmit chromosomes. These results demonstrate that H3 serine 10 phosphorylation is causally linked to chromosome condensation and segregation in vivo and is required for proper chromosome dynamics.

Animals↗

PubMed2004

Cdc14 phosphatase induces rDNA condensation and resolves cohesin-independent cohesion during budding yeast anaphase.

At anaphase onset, the protease separase triggers chromosome segregation by cleaving the chromosomal cohesin complex. Here, we show that cohesin destruction in metaphase is sufficient for segregation of much of the budding yeast genome, but not of the long arm of chromosome XII that contains the rDNA repeats. rDNA in metaphase, unlike most other sequences, remains in an undercondensed and topologically entangled state. Separase, concomitantly with cleaving cohesin, activates the phosphatase Cdc14. We find that Cdc14 exerts two effects on rDNA, both mediated by the condensin complex. Lengthwise condensation of rDNA shortens the chromosome XII arm sufficiently for segregation. This condensation depends on the aurora B kinase complex. Independently of condensation, Cdc14 induces condensin-dependent resolution of cohesin-independent rDNA linkage. Cdc14-dependent sister chromatid resolution at the rDNA could introduce a temporal order to chromosome segregation.

Adenosine Triphosphatases↗

PubMed1994

Apical seal of teeth obturated by the laterally condensed gutta-percha, the Thermafil plastic and Thermafil metal obturator techniques after post space preparation.

This in vitro study was conducted to determine the effect of post space preparation on teeth obturated with the Thermafil technique, both plastic and metal carriers, and the lateral condensation method. Three groups of 30 teeth each were obturated using the lateral condensation technique and the Thermafil plastic and metal techniques. Post space preparations were accomplished on the obturated groups. All specimens were submerged in India ink under a vacuum for 15 min and then soaked for an additional hour at atmospheric pressure. The teeth were decalcified and cleared to permit visualization and measurement of the extent of dye penetration. There was approximately three times more dye penetration in group 2 (plastic carrier) when compared with group 1 (lateral condensation) and group 3 (metal carrier). This was statistically significant at the 99% confidence level.

Analysis of Variance↗

PubMed1993

Comparison of endodontic retreatment of laterally condensed gutta-percha and Thermafil with plastic carriers.

The purpose of this study was to evaluate canal wall cleanliness in cases of retreatment using laterally condensed gutta-percha and Thermafil with plastic carriers. Forty extracted mandibular canines were prepared using a step-back flared technique and divided into two groups: group A, obturated with lateral condensation and group B, obturated with Thermafil. AH26 was the sealer used in both groups. Retreatment of all teeth was done using Gates Glidden burs and a solvent. The teeth were then split longitudinally, photographed, and projected onto a screen at x10 magnification. The total area of the canal and the area of gutta-percha/sealer were then traced on white paper. Both areas were accurately quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Results showed that the average percentage of the remaining gutta-percha/sealer was 14.23 for the lateral condensation group and 15.70 for the Thermafil group with no statistically significant difference (Student's t test, p = 0.01). The plastic carrier was easily removed from the canals.

Humans↗

PubMed1994

A comparison between a new vacuum obturation technique and lateral condensation: an in vitro study.

A new machine that allows cleaning root canals without conventional instruments has been introduced. Because this noninstrumented technique does not enlarge the root canal system, a new device had to be developed to fill the root canal system. The new machine was able to produce a vacuum that allowed proper drying and filling of a root canal system. This study evaluated the new vacuum filling method and compared it with lateral condensation. Canals of 40 extracted human molars, instrumented using the step-back technique, were either filled with the new vacuum obturation technique using AH26 sealer and a gutta-percha single cone or by lateral condensation. Teeth were coated with wax and placed into India ink for 7 days. The wax was then removed and the teeth were cleared. All teeth were evaluated for linear dye penetration using a x20 viewer. Obturation with the new vacuum technique resulted in significantly less leakage than lateral condensation.

Analysis of Variance↗

PubMed1993

Improved density of gutta-percha after warm lateral condensation.

Simulated straight root canals in 30 transparent acrylic blocks were instrumented and obturated with gutta-percha without sealer using standard lateral condensation (group A). The "zap and tap" method of warm lateral condensation was then used on the same 30 canals (group B). A second treatment of warm lateral condensation was then applied to these same canals (group C). The acrylic blocks were weighed after initial canal preparation and after each subsequent obturation. A 14.63% increase in weight of the gutta-percha occurred in group B compared with group A, and a 2.43% increase in weight occurred in group C compared with group B. Both differences were statistically significant (p < 0.001).

Gutta-Percha↗

PubMed1995

Comparison of the sealing ability of laser-softened, laterally condensed and low-temperature thermoplasticized gutta-percha.

This study compared the effectiveness of four different techniques used for obturation of single rooted-teeth: lateral condensation, low-temperature gutta-percha (Ultrafil), vertical condensation of gutta-percha softened by means of three different laser devices (argon, CO2, and Nd:YAG), or composite resin photopolymerized by argon laser. Seventy single-rooted teeth were instrumented using a step-back technique and obturated using one of the methods listed previously. To evaluate apical sealing effectiveness techniques, samples were subjected to 1% methylene blue dye at 37 degrees C for 7 days. The most extensive dye penetration (4.3 mm) was observed in teeth obturated with composite resin, followed by gutta-perch laser with CO2 (2.15 mm), and the Nd:YAG laser (3.54 mm). Gutta-percha softened with argon laser created an apical seal almost identical to that obtained with the lateral condensation and Ultrafil techniques (1.50, 1.45, and 1.48 mm of leakage, respectively). These results indicate that the argon laser can be used for gutta-percha softening to produce good apical sealing results.

Analysis of Variance↗

PubMed1991

Leakage after lateral condensation with finger spreaders and D-11-T spreaders.

The purpose of the study was to determine the leakage after lateral condensation with the use of finger spreaders and D-11-T spreaders. Fifty root canals were instrumented, and laterally condensed with gutta-percha and Grossman's cement. In 20 canals finger spreaders were used for the condensation and in a further 20 canals D-11-T spreaders were used. After 24 h in 100% humidity, the roots were painted with nail polish except for their apical 2 mm, which remained exposed. Five canals were not obturated (negative control) and five canals were obturated and the apices sealed with sticky wax (positive control). The expressed root tips were suspended in 2% methylene blue dye for 48 h. The teeth were then split longitudinally and the apical leakage measured and compared for each group. The results obtained by the positive and negative control teeth confirmed the effectiveness of the methodology used. Average dye penetration for the finger spreaders was statistically significantly less than for the D-11-T spreaders. Dye penetration of more than 0.5 mm occurred in 6 roots for the finger spreaders and in 12 roots for the D-11-T spreaders.

Dental Leakage↗

PubMed2002

The dynamics of 57Fe nuclei in Fe(II)-DNA and [Fe(II)(1-methyl-2-mercaptoimidazole)2]-DNA condensates.

Alcoholic solutions of FeCl(2) and Fe(II)(Hmmi)(2)Cl(2) (Hmmi=1-methyl-2-mercaptoimidazole) induce calf thymus DNA condensation from aqueous solutions buffered at pH 7.4. A 1:1 Fe(II)-(DNA monomer) stoichiometry is assumed. The (57)Fe Mössbauer hyperfine parameters suggest an octahedral coordination environment, severely distorted, in both Fe(II)-(DNA monomer) and [Fe(II)(Hmmi)(2)]-(DNA monomer) condensates. The dynamic properties of iron nuclei in freeze-dried samples were investigated by means of variable temperature (57)Fe Mössbauer spectroscopy. Mean square displacements, (T), were calculated, such as the effective vibrating mass and the Mössbauer lattice temperature of the solids. increases linearly with the temperature in the whole temperature range explored; the absolute values are typical for lattice or solid-state vibrations. Very similar values for the effective vibrating masses were extracted, suggesting comparable covalency of the bonding interaction between the metal atom and its ligands, while the Mössbauer lattice temperatures show a softening of the lattice for [Fe(II)(Hmmi)(2)]-(DNA monomer) with respect to Fe(II)-(DNA monomer) condensate.

Animals↗

PubMed1997

A simple water-immersion condenser for imaging living brain slices on an inverted microscope.

Due to some physical limitations of conventional condensers, inverted compound microscopes are not optimally suited for imaging living brain slices with transmitted light. Herein is described a simple device that converts an inverted microscope into an effective tool for this application by utilizing an objective as a condenser. The device is mounted on a microscope in place of the condenser, is threaded to accept a water immersion objective, and has a slot for a differential interference contrast (DIC) slider. When combined with infrared video techniques, this device allows an inverted microscope to effectively image living cells within thick brain slices in an open perfusion chamber.

Animals↗

PubMed2003

Chromatin condensation during glutamate-induced excitotoxicity of cerebellar [correction of celebellar] granule neurons precedes disintegration of nuclear DNA into high molecular weight DNA fragments.

The disturbance of the intracellular ionic homeostasis after activation of channel-associated membrane receptors by the excitatory neurotransmitters represents a principle event that triggers excitotoxic cell death of neurons. Here we demonstrate that glutamate-induced excitotoxicity of cerebellar granule neurons was accompanied by apoptosis-like nuclear shrinkage, chromatin condensation, and disintegration of nuclear DNA into high molecular weight DNA fragments, but was neither associated with activation of caspase 1, -2, -3, -9, nor was protected by a pan-caspase inhibitor, zVAD-fmk. We further demonstrate that chromatin condensation took place at the early stages of excitotoxicity and preceded nuclear DNA fragmentation. The results suggest that fragmentation of nuclear DNA and condensation of chromatin are uncoupled events during neuronal cell death

Animals↗

PubMed1998

Use of tube condensation as an indicator of endotracheal tube placement.

STUDY OBJECTIVE: To determine whether condensation on the inner surface of the endotracheal tube (vapor trail) is a reliable indicator of intratracheal placement. METHODS: Twenty-seven separate experiments were conducted on 10 conditioned, mongrel dogs weighing 15 to 20 kg each. After induction of anesthesia, an endotracheal tube was placed in the trachea under direct visualization. A second, identical endotracheal tube was then placed in the esophagus. An attending emergency physician, blinded to tube placement, then used a bag-valve apparatus to manually ventilate each endotracheal tube in turn. Five ventilations were performed on each tube, and the presence or absence of condensation on the inner surface of the tube was recorded. A second physician, blinded both to tube placement and to the actions of the first assessor, then repeated the ventilation and assessment of both tubes. RESULTS: Vapor trail was observed in 27 (100%) of 27 endotracheal tubes correctly placed in the trachea (95% confidence interval [CI], 90% to 100%) and in 23 (83%) of 27 tubes placed in the esophagus (95% CI, 66% to 96%). Physicians concurred in all cases. Absence of vapor trail was 15% sensitive (95% CI, 4% to 34%) for indicating incorrect (esophageal) tube placement. CONCLUSION: In this model, condensation on the inner surface of the endotracheal tube was common after placement within the esophagus. If these results are confirmed in human studies, the presence of a vapor trial should not be used as a clinical indicator of correct endotracheal tube placement.

Animals↗