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At least 847 records · Page 47Linked to original sources

PubMed1987

Effect of tar condensate from smoking tobacco and water-extract of snuff on the oral mucosa of mice with latent herpes simplex virus.

Upper lips were inoculated with virus to establish a latent infection in the trigeminal ganglia. During the latent period, tobacco smoke tar condensate or water-extract of snuff were topically applied to the primary inoculation site for two or three consecutive months. Tar condensate induced re-activation of latent HSV in the ganglia of 10 to 20 per cent of animals but snuff extract did not. Infectious virus was also detected in lips after the chronic application of tar condensate in 10 per cent of animals. Three months' exposure to tobacco produced epithelial dysplasia and other changes in a significant number of latent HSV-infected mice, whereas tobacco alone did not induce dysplasia in the labial epithelium of uninfected mice.

Animals↗

PubMed1976

An x-ray study of the condensed and separated states of sciatic nerve myelin.

Low-angle X-ray diffraction patterns of peripheral nerve myelin after modification by either rehydration in various solutions or by chemical treatment have been recorded. These X-ray patterns and the previously reported modified nerve myelin patterns demonstrate that nerve myelin has at least five different states: the normal state, condensed state I and II and separated state I and II. There are two membranes per unit cell in the normal state and in states II whereas there is one membrane per unit cell in states I. Under certain conditions normal nerve can go reversibly into either of states II. With continued treatment the nerve myelin structure moves irreversibly from state II to state I and, once in state I, the nerve myelin layers cannot return to the normal state. Our results demonstrate that there is a reversible transformation between condensed state I and separated state I. Fourier profiles of nerve myelin in the normal state, condensed state I and separated state I are presented.

Animals↗

PubMed1994

The condensing effects of egg lecithin and cholesterol on triolein monolayers are inhibited by substitution of one saturated acyl chain in the triacylglycerol.

Previous work showed that the clearance from plasma of chylomicron-like emulsions injected intravenously was affected by the acyl chains of the constituent triacylglycerols. Compared with emulsions containing triolein (OOO) as the only triacylglycerol, clearances were decreased by a single saturated chain in emulsions containing 1,3-dioleoyl-2-stearoyl-sn-glycerol (OSO), 1,2-dioleoyl-3-stearoyl-sn-glycerol (OOS) or 1-stearoyl-2,3-dioleoyl-sn-glycerol (SOO). The differences in clearance may reflect physical differences at the oil-water interface related to chain interactions of the triacylglycerol structures with other lipid components. In the present work lipid monomolecular films at the air-water interface were used to establish the capacity of OOO to interact with the pure synthetic triacylglycerols OOS and SOO, and the capacity of OOS and SOO to co-exist in monolayers of lecithin and of cholesterol was compared with OOO. Substituting one oleoyl chain by a stearoyl chain induced a 20% condensation in monomolecular films of the pure triacylglycerols. Mixtures of OOO with either pure egg yolk phosphatidylcholine or cholesterol also showed substantial condensing effects. In contrast substituting one oleoyl chain by a stearoyl chain substantially lessened the condensing effects. At surface pressures above the collapse pressure of the pure triacylglycerols, substantially more OOO than OOS or SOO was retained in mixed monolayers with phosphatidylcholine. These differences could underlie the effects on metabolism of saturated chains in emulsion triacylglycerols.

Chemical Phenomena↗

PubMed1976

Ion binding and chromatin condensation.

1. The binding of 45Ca2+ to hen erythrocyte chromatin has been studied to help elucidate how cations induce a reversible condensation of this chromatin. 2. As the unbound Ca2+ of the medium rises from 0.5 to 4 mM, Ca2+ is bound to the chromatin with a stability constant of approx. 3.1 and a saturation value of 0.25 Ca2+ per DNA phosphate, or one-half the value for pure DNA. Condensation of the chromatin is half complete when this binding of calcium is roughly half complete. Hence the transition from the uncondensed to the condensed state occurs as repulsion between the free DNA phosphates of erythrocyte chromatin is neutralised by bound cations. Genetically active chromatin may be maintained in an uncondensed state in living cells by the presence of different negative groups that remain unneutralised at the unbound cation concentrations of the cell. 3. That only one-half of the calcium binding sites of DNA are masked in erythrocyte chromatin supports recent models of chromatin structure in which the DNA double helix is wound round a core of histones. 4. Competition for calcium binding sites in the chromatin by other cations was also studied.

Animals↗

PubMed1978

A spectroscopic and electron microscopic examination of the highly condensed DNA structures formed by denaturation in Mg(ClO4)2.

1. Thermal denaturation in 1.5 M Mg(ClO4)2 of the DNA from bacteriophage lambda results in four well-separated subtransitions, as monitored by the accompanying increase in absorbance. The midpoint of the hyperchromic spectrum is significantly lowered compared to either 1.5 M MgCl2 or 3.0 M NaClO4. 2. The first two subtransitions are associated with the melting of the A . T-richest regions of the lambda DNA, as revealed by electron micrographs following fixation with formaldehyde. 3. Commencing with the third subtransition, an unusual DNA structure is observed in electron micrographs. In this structure the A . T-rich half of the molecule appears completely condensed, whereas the G . C-rich half remains native. 4. During the fourth subtransition DNA molecules condense completely and eventually aggregate to form extremely high molecular weight particles containing centers of electron density. Tendrils of DNA, primarily duplex, radiate outward from these centers. 5. The aggregation may be reversed by the removal of magnesium. The intramolecular condensation may be at least partly reversed by increasing the Mg(ClO4)2 concentrations to saturating levels.

Coliphages↗

PubMed1980

Isolated hamster brown fat cells: a bioassay for toxicity tests at the cellular level. Effect of cigarette smoke condensates from high and low tar yield cigarettes.

A test system for the detection of substances with cell-irritating or cell-damaging effects using isolated brown fat cells is presented and the effects of cigarette smoke condensates (CSC) from high and low tar yield cigarettes on this system examined. The condensates inhibited noradrenaline stimulated respiration in a dose-dependent manner. Ethanol solutions of the condensates had a stronger inhibitory effect than DMSO solutions. The CSC strongly inhibited the mitochondrial function but other cellular functions were also impaired.

Adipose Tissue, Brown↗

PubMed1996

In vitro studies of the genotoxic effects of bitumen and coal-tar fume condensates: comparison of data obtained by mutagenicity testing and DNA adduct analysis by 32P-postlabelling.

Bitumens contain traces of polycyclic aromatic compounds (PACs), a part of which will end up in the fumes emitted during hot handling of bitumen-containing products, e.g. during roadpaving. Although exposure of workers to these fumes is low, it might lead to health problems. Studies on bitumen fume condensates (BFCs) showed weak to moderate mutagenic activities, but studies on DNA adduct formation have not been reported. Therefore, a study was initiated in which fumes were generated from two road grade bitumens, in such a way that they were representative of the fumes produced in the field. The combined vapour/particulates were tested in vitro for their ability to produce DNA adducts and in modified Ames mutation assays, using a number of different strains. An attempt was made to relate the results to chemical data, such as the content of a number of individual polycyclic aromatic hydrocarbons (PAHs) and with a measure for the total PAC content. As a reference material fume condensate from coal-tar (coal-tar pitch volatiles; CTPV) were subjected to the same tests. All fume condensates tested were mutagenic to all strains and induced the formation of DNA adducts. The patterns of DNA adducts, obtained by 32P-postlabelling, arising from the BFCs were qualitatively different from the patterns of adducts obtained from the CTPVs, implying qualitative differences in the nature of the compounds responsible for the formation of these adducts. This is corroborated by the observation that for BFCs quantitative adduct levels are higher than would be expected based on the PAH content. These data thus indicate that the PAHs analysed are not the sole components responsible for adduct formation from BFCs, but that an important contribution comes from other (hetero- and/or substituted-) PACs.

Animals↗

PubMed1986

Chromosome condensation activity in the cytoplasm of anucleate and nucleate fragments of mouse oocytes.

The activity of maturation promoting factor (MPF) which causes chromosome condensation and subsequent oocyte maturation was investigated in mouse oocytes using polyethylene-glycol-mediated cell fusion technique. Fully grown oocytes were bisected at germinal vesicle (GV) stage or shortly after germinal vesicle breakdown (GVBD) into anucleate and nucleate fragments. After 2-3 or 15-17 hr of culture these fragments were fused with interphase blastomeres from two-cell embryos. It was found that almost all the anucleate oocyte fragments cultured for a short term (2-3 hr), regardless of whether they were produced at GV stage or after GVBD, induced premature chromosome condensation in the blastomere nuclei, whereas only about 20% of those cultured for a long term (15-17 hr) could do so. On the other hand, the nucleate fragments always retain the cytoplasmic activity to induce chromosome condensation. Thus we suggested that the MPF initially could appear in mouse oocytes independently of the GV, that the mixing of GV material with the oocyte cytoplasm following GVBD had no effect on the activity of MPF in anucleate fragments, and that oocyte chromosomes or some components associated with them could play a significant role in maintaining the MPF activity.

Animals↗

PubMed1996

Macromolecular crowding and the mandatory condensation of DNA in bacteria.

Cellular DNA in bacteria is localized into nucleoids enclosed by cytoplasm. The forces which cause condensation of the DNA into nucleoids are poorly understood. We suggest that direct and indirect macromolecular crowding forces from the surrounding cytoplasm are critical factors for nucleoid condensation, and that within a bacterial cell these crowding forces are always present at such high levels that the DNA is maintained in a condensed state. The DNA affected includes not only the preexisting genomic DNA but also DNA that is newly introduced by viral infection, replication or other means.

Bacteria↗

PubMed1981

Time-dependent accuracy of elastomer impression materials. Part I: Condensation silicones.

1. Although condensation silicone elastomers can be used to produce multiple dies from a single impression, one can expect changes in dimensions of dies produced from successive pours. 2. Putty/wash systems exhibit variable behavior among different brands. Some products produce a series of dies of increasing diameter over a 4-day period, while other brands may produce a series of dies whose diameters decrease as they are successively poured. 3. Light-body wash silicone impressions made in adhesive-lined custom acrylic resin trays produce dies which increase in diameter with time. 4. Putty/wash system, in general, show a greater eccentricity of dies than is seen with custom-tray/adhesive/wash systems, but there were some significant exceptions among the brands tested. 5. There does not appear to be any difference in behavior between single-wash and double-mix techniques in the condensation-silicone systems. 6. For maximum accuracy, the condensation-silicone systems should be poured as soon as possible after making the impression.

Adhesives↗

PubMed1994

Induction of micronuclei and granular chromatin condensation in human skin fibroblasts influenced by cisplatin (cis-DDP) in vitro.

Chromosomal damage was evaluated by quantification of micronuclei (MN) in two cell lines of human skin fibroblasts treated with different concentrations of cisplatin (ranging from 2 to 80 mumol/l) over the following time intervals: 2, 24 and 48 h. The formation of micronuclei was dependent upon the concentration of cis-DDP as well as on the duration of exposure. The dose-response curve for micronuclei in treated cells revealed a bell shape with the maximum at 12.5 mumol/l cis-DDP. The results were compared with another toxicological phenomenon, granular condensation of nuclear chromatin. This change, which was closely related to apoptosis in the cells exposed to cis-DDP, occurred at 5 mumol/l. The degree of condensation of nuclear chromatin depended on the concentration of cis-DDP. In contrast to the observations for micronuclei, the dose-effect relationship was linear up to the highest tested concentration (80 mumol/l). This change was primarily due to the duration of cis-DDP treatment. Our results showed the comparison between micronucleus formation and granular condensation of nuclear chromatin, as two morphological manifestations of cisplatin-induced DNA damage.

Cell Line↗

PubMed1983

Efficacy of apical seal of Engine Plugger condensed root canal fillings--leakage to dyes.

A new rotatory instrument, the Engine Plugger, that is claimed to be less fragile than the McSpadden Compactor, has been introduced since the recognition of thermomechanical compaction as a valid technique for root canal filling. The purpose of this study was to test the efficacy of the apical seal afforded by the Engine Plugger in comparison with that of an established technique, lateral condensation. Eighty roots with round canals prepared to size 45 were randomly divided into two groups: one compacted with the Engine Plugger (Group 1) and the other with the lateral condensation technique (Group 2). AH-26 sealer was used in half the specimens. Four additional roots served as controls. The roots were cleared following immersion in Procion brilliant green, and the maximal depth of penetration of the dye was measured with a stereomicroscope. Severe leakage occurred in both groups when sealer was not used (mean depth: 3.17 mm in Group 1; 4.3 mm in Group 2). Addition of sealer reduced leakage significantly (p less than 0.001). There was no statistically significant difference in the depth of penetration of the dye between the two groups when AH-26 was used, although a trend in favor of the Engine Plugger method (0.15 mm versus 0.425 mm for lateral condensation) was noted.

Coloring Agents↗

PubMed1991

Periodontium response to a root canal condensing device (Endotec).

Two Macaca (fascicularis) monkeys were used to study the effect of two warm endodontic condensation techniques (Endotec and vertical condensation method) on periodontal tissues. The specimens were histologically evaluated at 3 and 32 days after the endodontic treatments were completed. In this study the periodontium was divided into coronal, middle, and apical thirds. Results indicated that there was no heat-related damage to periodontal tissues from either of the two methods employed. However, some Endotec specimens generated small, reactive inflammatory infiltrates that were restricted to the root canal opening or adjacent periodontal membrane. Similarly, some vertical condensation specimens developed periapical inflammatory processes as well, but they were more extensive and comprised the alveolar bone and marrow spaces.

Animals↗

PubMed1994

Microleakage comparison of thermafil versus vertical condensation using two different sealers.

The effect of two different sealers on the quality of the apical seal in roots obturated with Thermafil obturators (Tulsa Dental Products, Tulsa, Okla.) and vertical condensation was tested. Fifty extracted human maxillary anterior teeth were treated with the use of a step-back technique. Teeth were placed into five groups of 10 teeth each. One group served as the positive control. The root canals were obturated using either Thermaseal (Tulsa Dental Products) or Kerr (Kerr Manufacturing Co., Romulus, Mich.) sealer, and Thermafil or vertical condensation. All roots were placed in 1% methylene blue dye for 2 weeks. The roots were cleared, and the degree of linear dye penetration was measured using a Unitron light microscope with a Microcode II digital readout (Boeckeler Instruments, Tucson, Ariz.). The study showed that under in vitro conditions, the Thermafil technique was equivalent in linear leakage to vertical condensation. There were no statistical differences in the mean apical dye penetration between the two sealers or the two obturation techniques.

Analysis of Variance↗

PubMed1994

Apical seal using the GPII method in straight canals compared with lateral condensation, with or without sealer.

The purpose of this study was to test the apical seal provided by a recently introduced low-fusing gutta-percha, GPII, compared with lateral condensation, with or without a sealer. For this study, 84 roots with straight circular canals separated from extracted teeth were prepared to K-file size 45. A standardized gutta-percha master cone was fitted to 80 of these roots. The roots were then randomly separated into four groups of 20 each and filled with GPII or laterally condensed gutta-percha, with or without AH26 sealer. The roots were immersed in India ink, subjected to vaccuum for 2 hours and kept in the marker for 4 days for the study of apical leakage. Four unfilled roots served as an experimental control. The teeth were demineralized, cleared in methyl salicylate and examined with a stereomicroscope. When no sealer was used, 12 roots filled with GPII leaked from 0 to 2.5 mm and in the lateral condensation group ink penetrated from 0 to 6 mm in 14 roots (difference not significant at the 0.05 level). None of the specimens in which sealer was used showed any penetration of ink beyond the end of the preparation of the canal regardless of the filling technique.

Bismuth↗

PubMed1996

Differential inhibition of eukaryote protein kinases by condensed tannins.

Condensed tannins, isolated from a variety of plant sources, were characterized according to the constituent flavans, being based on procyanidin and/or prodelphinidin and having a cis or trans stereochemistry at positions 2 and 3. All the tannin preparations are potent inhibitors of rat liver cyclic AMP-dependent protein kinase catalytic subunit (cAK) with IC50 values (concentrations for 50% inhibition) ranging from 0.009 to 0.2 microM. The tannin preparations are very good inhibitors of rat brain Ca(2+)- and phospholipid-dependent protein kinase C (PKC) (IC50 values in the range 0.3-7 microM), wheat embryo Ca(2+)-dependent protein kinase (CDPK) (IC50 values in the range 0.8-7 microM) and of calmodulin (CaM)-dependent myosin light chain kinase (MLCK) (IC50 values in the range 7-24 microM). One of the most effective preparations, that from the leaves of Ribes nigrum, has IC50 values with respect to cAK, PKC, CDPK and MLCK of 0.009, 0.6, 2.0 and 16 microM, respectively. In general, the order with respect to sensitivity to inhibition by these condensed tannins is cAK > PKC > CDPK > MLCK. The Ribes nigrum preparation is a competitive inhibitor of cAK with respect to both ATP and synthetic peptide substrate. These condensed tannin preparations are the most potent plant-derived inhibitors of cAK yet found.

Animals↗

PubMed1991

Novel synthesis of cholesterol analogs: condensation of pregnenolone with dihydropyran or dihydrofuran.

Pregnenolone 3-(2'-tetrahydropyranyl) ether (1) was condensed with 3,4-[2H]dihydropyran to mainly give (20R)-[6'-(3',4'-[2'H]dihydropyranyl)]-pregn-5-ene-3 beta,20-diol 3-(2'-tetrahydropyranyl) ether (20R-3), according to nuclear magnetic resonance (NMR). Cold, dilute HCl in ethanol removed the tetrahydropyranyl group at C-3 and also opened the dihydropyranyl ring at the C-20 position of 20R-3 to give (20R)-27-norcholest-5-en-22-one-3 beta,20,26-triol (20R-5). Analogous results were obtained by condensing pregnenolone 3-acetate with 3,4-[2H]dihydropyran to provide (20R)-[6'-(3',4'-[2'H]dihydropyranyl)]-pregn-5-ene-3 beta,20-diol 3-acetate (20R-4). Acid-catalyzed opening of the dihydropyranyl ring at C-20 in 20R-4 yielded 20R-7, which, on acetylation followed by crystallization, provided (20R)-27-norcholest-5-en-22-one-3 beta,20,26-triol 3,26-diacetate (20R-8), identical to the diacetate made from 20R-5. Varying the reaction sequence beginning with 20(R,S)-4 gave an 84:16 ratio of 20R to 20S in a mixture of 20(R,S)-8, according to NMR analysis. Crystallization of the mixture from methanol provided pure 20R-8. Condensing 2,3-dihydrofuran and 1 for producing (20R)-[5'-(2',3'-dihydrofuranyl)]-pregn-5-ene-3 beta,20-diol 3-(2'-tetrahydropyranyl) ether (6) gave instead (20R)-26,27-bisnorcholest-5-en-22-one-3 beta,20,25-triol 3-(2'-tetrahydropyranyl) ether (20R-9) by partial hydrolysis during workup. Treating 20R-9 briefly with dilute HCl produced (20R)-26,27-bisnorcholest-5-en-22-one-3 beta,20,25-triol (20R-10).(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol↗

PubMed1991

A quantitative approach to assessing intercellular communication: studies on cigarette smoke condensates.

Analyses of intercellular communication is useful for assessing the effects of chemical treatment on the function of mammalian cell membranes in vitro. The objective of this study was to quantify and compare the activity of mainstream cigarette smoke condensate (CSC) from tobacco-heating and tobacco-burning cigarettes on both the rate and total amount of intercellular communication in vitro. Lucifer yellow uptake and lactate dehydrogenase release assays were used to evaluate plasma membrane toxicity. Gap junction intercellular communication (GJIC) was determined by quantifying fluorescence redistribution after photobleaching (FRAP) following a 1-hr exposure to concentrations of CSCs which were not toxic to the plasma membrane. GJIC was quantified in rat hepatic epithelial cells (WB cells) and human skin fibroblasts (MSU-2 cells) synchronized in the G1 phase of the cell cycle. In each of the cell types tested, CSC from tobacco-heating cigarettes did not inhibit GJIC at concentrations, where CSC from tobacco-burning cigarettes significantly inhibited both the total amount and the rate of GJIC. These results indicate that mainstream smoke condensate of cigarettes which heat tobacco is less biologically active than mainstream smoke condensate of cigarettes that burn tobacco as determined by in vitro gap junction intercellular communication.

Animals↗