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 523 records · Page 29Linked to original sources

PubMed1988

The optimum condition for malonic dialdehyde liberation from smoked fish and curing smoke condensates.

The aim of this study was to establish the conditions for malonic dialdehyde liberation from smoked fish and curing smoke condensates, as well as to determine its content in smoked fish. The specific absorption peaks of coloured solutions of malonic dialdehyde, from curing smoke condensates, with 2-thiobarbituric acid were determined. The conditions for malonic dialdehyde liberation were established, i.e. time and degree of alkaline hydrolysis of condensate, degree of distillation of acidified condensate solution, the conditions of coloured solution development, determination of extinction and method of calculation of malonic dialdehyde content in smoked fish, in individual layers of smoked mackerel fillets. The mechanism of formation of polycyclic aromatic hydrocarbone and hydrogen peroxide or hydroxyl free radicals, formed during pyrolysis of organic compounds in the presence of liberated malonic dialdehyde, was proposed.

Animals↗

PubMed1981

The synthesis of protein(s) for chromosome condensation may be regulated by a post-transcriptional mechanism.

A temperature sensitive mutant of BHK21, tsBN2, showed a premature chromosome condensation (PCC) upon the temperature shift of 40.5 degrees, even in the absence of DNA replication. The induction of PCC requires new protein synthesis, but not necessarily new RNA synthesis. Our data suggested that the messenger RNA for chromosome condensation starts to be transcribed at the beginning of S phase. At the permissive temperature (33.5 degrees), the messenger RNA for chromosome condensation translated with a very slow rate during S phase and rapidly in G2-M phase. At the nonpermissive temperature (40.5 degrees), however, those messenger RNAs were translated anytime, so that various figures of PCC appeared depending on the cell cycle. On the way of PCC induction, ribosomal RNA synthesis was inhibited at first, as expected from mitosis. Our data suggested that the synthesis of protein(s) for chromosome condensation was regulated by the post-transcriptional mechanism, in which tsBN2 might be defective, especially at the translational level.

Animals↗

PubMed2006

Chromosome condensation outside of mitosis: mechanisms and new tools.

A basic principle of cell physiology is that chromosomes condense during mitosis. However, condensation can be uncoupled from mitotic events under certain circumstances. This phenomenon is known as "premature chromosome condensation (PCC)." PCC provides insights in the mechanisms of chromosome condensation, thus helping clarifying the key molecular events leading to the mitosis. Besides, PCC has proved to be an useful tool for analyzing chromosomes in interphase. For example, using PCC we can visualize genetic damage shortly after the exposure to clastogenic agents. More than 30 years ago, the first report of PCC in interphase cells fused to mitotic cells using Sendai virus was described (virus-mediated PCC). The method paved the way to a great number of fundamental discoveries in cytogenetics, radiation biology, and related fields, but it has been hampered by technical difficulties. The novel drug-induced PCC method was introduced about 10 years ago. While fusion-induced PCC exploits the action of external maturation/mitosis promoting factor (MPF), migrating from the inducer mitotic cell to the interphase recipient, drug-induced PCC exploits protein phosphatase inhibitors, which can activate endogenous intracellular MPF. This method is much simpler than fusion-induced PCC, and has already proven useful in different fields.

Animals↗

PubMed1993

Differences in chromatin condensation during spermiogenesis in two species of fish with distinct protamines.

The sperm cells of Mullus surmuletus (family Mullidae, order Perciformes) and Dicentrarchus labrax (family Percichthyidae, order Perciformes) belong respectively to "type I" and "type II" spermiogenesis categorized by Mattei ('70). The protein content in their sperm nuclei consists of two histone-like proteins (Mullus surmuletus) and one typical protamine (D. labrax). In order to correlate the molecular characteristics of these proteins with their function, we have analyzed the molecules in detail and studied at the ultrastructural level the condensation of chromatin during the spermiogenesis in both species. D. labrax has a true protamine of 34 amino acid residues and its sequence (PR4QASRPVR5TR2STAER5V2R4) contains four arginine clusters. The sperm proteins of M. surmuletus contain 110 and 115 amino acid residues and , by their composition (23-24% Lys, 21-22% Arg, 11-12% Ala), they are similar to protamine-like molecules from sperm of molluscs. During the spermiogenesis of D. Labrax, chromatin condensation progresses from small fibro-granular structures (25 +/- 5 nm in diameter), to larger granules (150 +/- 50 nm diameter). M. surmuletus accumulates 25 +/- 5 nm diameter structures in the basal pole of the nucleus; these structures grow till they reach a diameter of 50 +/- 10 nm and finally go through a process of fusion that changes the condensation of chromatin in sperm nuclei, acquiring a homogeneous aspect. These observations show that during spermiogenesis in the studied types, the last stages of chromatin condensation are dependent on the type of nuclear proteins.

Amino Acid Sequence↗

PubMed1995

Chromatin condensation activity and cortical activity during the first three cell cycles of a mouse embryo.

One-cell parthenogenetic haploid embryos and blastomeres of the 2- and 4-cell diploid mouse embryos were observed in vitro for the occurrence of two cytoplasmic activities: the cortical activity and the chromatin condensation activity. For this purpose anucleated halves (AHs) and nucleated halves (NHs) were produced by bisection of one-cell embryos and of blastomeres. The cortical activity (manifested by surface deformations) was observed only during the first cleavage cycle. In AHs the surface activity began at the same time as in NHs and disappeared before the time of the cleavage division of nucleated halves. Anucleate fragments of blastomeres from 2- and 4-cell embryos did not exhibit any cortical activity. In the absence of the native nucleus the chromatin condensation activity (assayed by premature chromatin condensation of interphase thymocyte nuclei introduced into cytoplasts by cell fusion) could also have been detected only in the first cleavage cycle. In AHs this activity appeared at the time when NHs started to cleave and disappeared after the NHs finished the first cleavage division. AHs obtained from 2-cell and 4-cell stage blastomeres did not reveal condensation activity.

Animals↗

PubMed1988

Human sperm nuclei can transform into condensed chromosomes in Xenopus egg extracts.

The conditions necessary for inducing pronucleus formation and chromosome condensation of human sperm nuclei were studied using Xenopus egg extracts. When lysolecithin (LC)-and dithiothreitol (DTT)-treated spermatozoa were incubated with egg extract prepared with an extraction medium containing 10 mM EGTA, sperm nuclei transformed into chromosomes, bypassing the pronuclear stage. On the contrary, LC-DTT-treated spermatozoa incubated in egg extract without EGTA mimicked LC-permeabilized Xenopus spermatozoa in that they underwent pronucleus formation accompanied by DNA synthesis and subsequent chromosome condensation in the correct chronological order. These observations suggest the importance of intracellular calcium for regulating the states of nuclear chromatin. LC-permeabilized human spermatozoa were not responsive to the egg extract without any additives, but formed pronuclei when incubated with the egg extract supplemented with 5-10 mM DTT. However, subsequent chromosome condensation of sperm nucleus did not occur in the DTT extract. This suggests that disulfide-reducing agent blocks transformation of sperm pronuclei into condensed chromosomes.

Animals↗

PubMed2006

Measuring exhaled breath condensates in infants.

There is growing interest in investigating compounds of exhaled breath condensates (EBC) as potential noninvasive markers of airways disease processes. Some of these markers have the potential to provide information on the early stages of disease. In this paper, we present a method for collecting EBC during both oral and nasal breathing in infants. Fifty-four infants (mean age, 13.3 months; range, 1-30 months) undergoing infant lung-function testing were recruited for this study. Breath condensates were collected during sedated sleep, using a custom-made collection device. Collections were made for 10 min during normal tidal breathing. Nasal measurements were attempted in all children by placing a face-mask over the nose and mouth and keeping the mouth closed. In 14 infants, oral measurements were made by placing a face-mask over the mouth only and occluding the nose. Condensates were collected successfully in all but one child. The collected volume ranged from 50-550 microl (mean +/- SD, 281.8 +/- 145.8 microl). The volume of EBC collected was correlated to age, length, weight, and minute ventilation. Significantly more EBC was collected during oral compared to nasal breathing (354.3 vs. 277.5 microl, P=0.03). There were no significant changes in heart rate, respiratory rate, or oxygen saturation during collection. The collection of EBC in young children and infants is feasible and safe, and the method used here allows the successful collection of reasonable amounts of exhaled condensate.

Breath Tests↗

PubMed1997

The region encoded by the alternatively spliced exon IIIA in mesenchymal fibronectin appears essential for chondrogenesis at the level of cellular condensation.

Fibronectin in the extracellular matrix of tissues acts as a substrate for cell adhesion and migration during development. Heterogeneity in the structure of fibronectin is largely due to the alternative splicing of at least three exons (IIIB, IIIA, and V) during processing of a single primary transcript. Fibronectin mRNA alternative splicing patterns change from B+A+V+ to B+A-V+ during chondrogenesis. In this report, immunohistochemical analysis demonstrates that while fibronectin protein containing the region encoded by exon IIIB is present throughout the limb at all stages of development, fibronectin protein containing the region encoded by exon IIIA disappears from cartilaginous regions just after condensation in vivo and in high-density mesenchymal micromass cultures in vitro. Treatment of mesenchymal micromass cultures prior to condensation with an antibody specific for the region encoded by exon IIIA disrupts the formation of cellular condensations and inhibits subsequent chondrogenesis in a dose- and time-dependent manner. Furthermore, microinjection of the exon IIIA antibody into embryonic chick limb primordia in vivo results in malformations characterized by smaller limbs and loss of limb skeletal elements. These results strongly suggest that the presence of the region encoded by exon IIIA in mesenchymal fibronectin is necessary for the condensation event that occurs during chondrogenesis.

Alternative Splicing↗

PubMed1999

Acquisition of competence to condense metaphase I chromosomes during spermatogenesis.

Little is known about the timing of meiotic prophase events during spermatogenesis in the mouse or how these events are related to cell-cycle progression. This work was designed to test hypotheses about the timing and biochemical correlates of developmental acquisition of competence to condense bivalent pairs of homologous chromosomes held together by chiasmata. The experimental approach takes advantage of the fact that okadaic acid (OA) treatment of pachytene spermatocytes causes precocious entry into metaphase I (MI) of meiosis. Leptotene and zygotene (L/Z) spermatocytes are not competent to respond to OA with condensation of chiasmate bivalent chromosomes. Competence for MI condensation of chiasmate bivalents is acquired by the middle of the pachytene stage of meiotic prophase, several days after homologous chromosomes become fully synapsed. The acquisition of MI competence is paralleled by the accumulation of histone H1t in the nuclei of mid-pachytene spermatocytes. Biochemical differences also exist between the incompetent L/Z spermatocytes and the competent pachytene spermatocytes. Both have the molecular components of metaphase promoting factor, CDC2 and CYCLIN B1; however, the histone H1 kinase activity of metaphase promoting factor of incompetent L/Z spermatocytes is not activated by OA, as it is in competent pachytene spermatocytes. Additionally, the CDC25C protein phosphatase is present in competent pachytene spermatocytes, but not in incompetent L/Z or early pachytene spermatocytes. Both incompetent and competent spermatocytes accumulate MPM-2 phosphoepitopes and phosphorylated histone H3 in response to OA treatment, indicating that presence of these antigens is not sufficient to promote condensation of meiotic chromosomes. These data demonstrate that meiotic competence of spermatocytes is acquired after homologous chromosome pairing is established and is coincident with first appearance of histone H1t and CDC25C protein phosphatase in spermatocytes.

Animals↗

PubMed1993

Stage-specific expression and localization of MENT, a nuclear protein associated with chromatin condensation in terminally differentiating avian erythroid cells.

Polyclonal antibodies have been raised against a non-histone protein (MENT) which has been previously shown to be associated with the repressed chromatin of mature chicken erythrocytes and to promote the in vitro condensation of chromatin of immature erythrocyte nuclei. Here we report that the expression pattern of MENT closely follows chromatin condensation in maturing avian erythrocytes of definitive and primary lineages. Accumulation of MENT correlates more strongly with chromatin condensation than does accumulation of histone H5. In addition to being present in erythrocytes, the protein was also found in neutrophil nuclei and an immunofluorescence reaction was observed with embryonic (nucleated) thrombocytes. MENT was not detected in other chicken tissues (brain, liver, testis). In intact erythrocytes, MENT immunofluorescence was found in foci close to the nuclear periphery, while in isolated, decondensed nuclei, the fluorescence signal was uniformly distributed. In neutrophil nuclei, containing approximately 10 times more MENT than adult erythrocytes, intense staining associated with the peripheral heterochromatin was observed. These findings are discussed in regard to a possible mechanism for chromatin condensation by MENT.

Animals↗

PubMed2000

Adsorption-Desorption Flow of Condensable Vapors through Mesoporous Media: Network Modeling and Percolation Theory.

Flow of condensable vapors in mesoporous media is investigated theoretically and experimentally during adsorption and desorption processes. A typical permeability curve of a condensable vapor is strongly enhanced in the capillary condensation region. This is because additional capillary pressure gradients are imposed on the capillary-condensed pores, which act as "good" conductors compared to the noncondensed pores, which are considered "poor" conductors. The percolation scaling properties that hold for a system of "good" and "poor" conductors are confirmed for the cases examined. As the ratio of gas flow/capillary-enhanced flow decreases, the rise of permeability with pressure becomes sharper. The network connectivity has a strong impact on the maximum permeability value and on the width of the scaling law regions. The contribution of surface flow does not affect the permeability in the peak region, but results in a shrinkage of the scaling law regions. During desorption, a marked hysteresis in the permeability curves is found and it is attributed only to thermodynamic hysteresis. The maximum permeability values in this case are higher and shifted to lower relative pressures. Copyright 2000 Academic Press.

Journal Article↗

PubMed2002

Immobilizing shortened single-walled carbon nanotubes (SWNTs) on gold using a surface condensation method.

We propose a surface condensation method for assembling single-walled carbon nanotubes (SWNTs) on gold. The as-prepared long and randomly tangled SWNTs were cut into short pipes by chemical oxidation, allowing the nanotubes to be terminated by carboxyl functionalities. A surface condensation reaction was then performed by immersing an amino self-assembled monolayer (SAM)-modified gold substrate into the dimethylformamide suspension of carboxylic nanotubes with the aid of dicyclohexylcarbodiimide condensation agent. Raman spectroscopy and atomic force microscopy (AFM) results show that a highly aligned assembly of SWNTs has been formed on gold, with the nanotubes standing on the surface stable enough for a long ultrasonication. In combination with the microcontact printing (muCP) technique, we have fabricated patterned nanotube assemblies using this surface condensation method. Moreover, we found that the "giant" carbon nanotubes tend to form bundles on an amino-terminating surface, likely following a nucleation-growth model.

Journal Article↗

PubMed1992

Condensed tannins in some forage legumes: their role in the prevention of ruminant pasture bloat.

For the past 20 years, the focus in our laboratory has been on finding the causes of ruminant pasture bloat and eventually breeding a bloat-safe alfalfa (Medicago sativa L.); i.e., with bloat potential reduced to the economic threshold. In the mid-seventies, the mechanisms of bloat were explored and found to be more physical than chemical. Characteristic of all bloating legumes after ingestion was a very rapid initial rate of ingestion by rumen microbes. Through the study of bloating and non-bloating legumes, factors were elucidated in the plant that would slow this process. One of these factors was the presence of condensed tannins in the herbage. Some of the non-bloating legumes contained these secondary metabolites, but no condensed tannins were found in any of the bloating legumes. Therefore, species containing an appreciable amount of condensed tannins in their leaves and stems are considered to be non-bloating. Conventional breeding methods have not been successful in producing an alfalfa with condensed tannins in its herbage. New approaches using tissue culture techniques are being attempted, but genetic engineering has the greatest potential for success.

Animals↗

PubMed1987

Induction by chemical clastogens of aberrations in prematurely condensed interphase chromatin of Chinese hamster ovary cells.

The clastogenic activities of diepoxybutane and bleomycin were comparatively studied on prematurely condensed interphase chromatin and metaphase chromosomes of Chinese hamster ovary cells. The yield of chromosomal aberrations was distinctly higher in G2-premature chromosome condensation as compared to metaphase. Most notably, the clastogenic activity of bleomycin was visible in premature chromosome condensation after application of much lower final concentrations than necessary for induction of chromosome aberrations in metaphase. In addition, the different mechanisms of action of both clastogens were reflected by the aberration yield in G1 and G2 immediately after exposure. While bleomycin induced aberrations throughout all stages of interphase, diepoxybutane did not induce aberrations in G1 or G2. Though certainly not a routine system for genotoxicity testing, premature chromosome condensation analyses provide a powerful opportunity to demonstrate relationships between DNA damage and repair, and the production of chromosomal changes at the site of their formation.

Animals↗

PubMed1981

High resolution analysis and differential condensation in RBA-banded human chromosomes.

Human prophase, premetaphase, and mid-metaphase chromosomes are prepared and analyzed using the thymidine cell synchronization technique and R-banding patterns (RBA). Haploid sets with 700-1000 bands can be demonstrated. Sequences of chromosomes of different degrees of condensation are helpful for a better understanding and classification of regions of extended chromosomes. A considerable variation in the condensation of parts of homologous chromosomes is reflected in the variability of the arm ratio. This differential condensation of chromosomes is entirely effected by variation of the degree of condensation in AT rich interbands and can be attributed to the degree of labeling by BrdU.

Acridine Orange↗

PubMed1986

The superstructure of chromatin and its condensation mechanism. I. Synchrotron radiation X-ray scattering results.

Synchroton radiation X-ray scattering experiments have been performed on chicken erythrocyte chromatin fibres over a wide range of ionic conditions and on various states of the fibres (i.e. "native" in solution, in gels and in whole nuclei; chromatin depleted of the H1 (H5) histones and chromatin with bound ethidium bromide). A correlation between the results obtained with the various chromatin preparations provides evidence for a model according to which at low ionic strength the chromatin fibre already possesses a helical superstructure, with a diameter comparable to that of condensed chromatin, held together by the H1(H5) histone. The most significant structural modification undergone upon an increase of the ionic strength is a reduction of the helix pitch, this leads to condensation in a manner similar to the folding of an accordion. The details of this process depend on whether monovalent or divalent cations are used to raise the ionic strength, the latter producing a much higher degree of condensation. Measurements of the relative increase of the mass per unit length indicate that the most condensed state is a helical structure with a pitch around 3.0-4.0 nm. In this paper we give a detailed presentation of the experimental evidence obtained from static and time-resolved scattering experiments, which led to this model.

Animals↗

PubMed1979

Self-condensation of activated dinucleotides on polynucleotide templates with alternating sequences.

We have prepared substantial quantities of the alternating polymers poly(U-G) and poly(C-A) and have used them as templates for the self-condensation of ImpApC, ImpCpA, ImpGpU and ImpG. We find that the condensation of ImpGpU and ImpUpG on poly(C-A) is efficient, the condensation of ImpCpA on poly(U-G) is moderately efficient, while the condensation of ImpApC on poly(U-C) proceeds poorly. In many cases, the product is predominantly 3'-5'-linked. These reactions demonstrate unequivocally, for the first time, that template-directed reactions occur in double-helical structures. Furthermore, they describe for the first time a pair of reactions in which each of two complementary polymers facilitates the synthesis of the other. The prebiotic significance of these findings is discussed.

Chemical Phenomena↗

PubMed1994

Selective capacity of glass-wool filtration for the separation of human spermatozoa with condensed chromatin: a possible therapeutic modality for male-factor cases?

PURPOSE: The aim of this study was to evaluate chromatin condensation of human spermatozoa following swim-up compared to glass-wool separation. Semen aliquots from men attending an andrological outpatient clinic were processed by means of a swim-up procedure and glass-wool filtration. Chromatin condensation was recorded using aniline blue staining and results were reported according to color intensity of stained sperm heads. Morphometric measurements of sperm heads were performed on stained sperm samples. RESULTS: Glass-wool filtration resulted (i) in a significantly higher total motile sperm count (P < 0.0005) compared to swim-up and (ii) in a significantly higher percentage of normal chromatin-condensed spermatozoa compared to the ejaculate (P < 0.01). CONCLUSION: In contrast, comparing swim-up to the ejaculate, the percentage of matured nuclei (unstained spermatozoa) retrieved following swim-up was significantly lower (P < 0.005). Glass-wool filtration separates human spermatozoa according to motility and size of the sperm head. The size of the sperm head closely correlated with the chromatin condensation quality.

Aniline Compounds↗