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[Studies comparing the efficacy of root canal filling with gutta-percha lateral condensation and Thermafil obturators].

A comparative analysis of the efficacy of root canal filling with laterally condensed gutta-percha and Thermafil obturators with titanium carrier was performed on the basis of experimental and clinical findings. Experimental part. Twenty-four extracted human teeth with root canals filled with laterally condensed gutta-percha (12 teeth) or Thermafil obturators (12 teeth) were studied in order to evaluate the quality of root filling. The Apexit sealer was used in both groups. Radiographs were obtained and the linear dye penetration test was done. Placement, homogeneity and adaptation of root canal filling were evaluated on the radiographs. Twenty teeth with root canals filled with laterally condensed gutta-percha (10 teeth) or Thermafil obturators (10 teeth) were studied using SEM. Clinical part. Eighty-seven patients were enrolled. One hundred and sixty-two single canal teeth with irreversible pulp disease with vitale (70 cases) or necrotic (54 cases) pulp and chronic apical parodontitis (38 cases) comprised the study material. Group I consisted of 84 teeth with root canals filled with laterally condensed gutta-percha, while group II had 78 teeth with Thermafil obturators. The Apexit sealer was applied in both groups. In vitro radiological examination revealed a better quality of placement of root canal fillings in group I (11 correctly filled root canals, 1 underfilling) when compared to group II (1 correctly filled root canal, 11 overfillings). No differences were observed between groups as to homogeneity or adaptation of root canal filling. The seal evaluated using the linear dye penetration test revealed no differences between both types of root canal filling. SEM confirmed the presence of interfaces between the filling material and root canal wall in both groups. The width of interface in group I was 1-5 microns, seldom exceeding 10 microns, and uniform throughout the whole root canal. In group II the width varied from 1-5 microns in the apical part to 10-25 microns in the middle and coronal parts. SEM revealed no major differences regarding homogeneity between both groups. Radiographs performed in the clinical part showed a higher frequency of overfillings of root canal filling into the apical parodontium in group I (30.8%) than II (9.5%). Thermafil turned out to be less satisfactory with regard to adaptation of root canal filling to the canal walls. Evaluation of immediate results of treatment demonstrated no differences between both techniques. A positive result after one year was found in 94.2% of laterally condensed gutta-percha fillings and in 90.2% of Thermafil fillings. After two years, the respective figures were 93.7% and 90.0%. The use of Thermafil obturators seems to be less tedious and time-consuming when compared to laterally condensed gutta-percha.

Adolescent↗

NTP Toxicology and Carcinogenesis Studies of Oleic Acid Diethanolamine Condensate (CAS No. 93-83-4) in F344/N Rats and B6C3F1 Mice (Dermal Studies).

Oleic acid diethanolamine condensate is widely used as an emollient, thickener, and foam stabilizer present in cosmetic formulations of bath additives, shampoos, conditioners, lipsticks, and hair dyes. Male and female F344/N rats and B6C3F1 mice received dermal applications of diethanolamine in 95% ethanol for 13 weeks or 2 years. Genetic toxicology studies were performed in Salmonella typhimurium and L5178Y mouse lymphoma cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were admin istered 0, 25, 50, 100, 200, or 400 mg oleic acid diethanolamine condensate/kg body weight in ethanol dermally for 13 weeks. All male and female rats survived until the end of the study. The final mean body weights and body weight gains of 200 and 400 mg/kg males and the mean body weight gain of 400 mg/kg females were significantly less than those of the vehicle controls. The only chemical-related clinical finding was irritation of the skin at the site of application in most males administered 100 mg/kg or greater and in all females administered 50 mg/kg or greater. Segmented neutrophil counts were increased relative to the vehicle controls in the 400 mg/kg male group on days 5 and 19, in the 200 mg/kg female group on day 19 and at week 13, and in the 400 mg/kg female group on days 5 and 19 and at week 13. Alkaline phosphatase concentrations were significantly increased in the 200 mg/kg male group on day 19, the 200 mg/kg female group at week 13, and in the 400 mg/kg groups of males and females at week 13. Kidney weights of 200 and 400 mg/kg females were significantly greater than those of the vehicle controls. Lesions of the skin at the site of application included epidermal hyperplasia, parakeratosis, chronic active dermal inflammation, suppurative epidermal inflammation, and sebaceous gland hypertrophy in dosed rats. The severities of these lesions generally increased with increasing dose. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were admin istered 0, 50, 100, 200, 400, or 800 mg oleic acid diethanolamine condensate/kg body weight in ethanol dermally for 13 weeks. All male and female mice except one 800 mg/kg male survived until the end of the study. Final mean body weights and body weight gains of 800 mg/kg males and females and 400 mg/kg females were significantly less than those of the vehicle controls. Clinical findings in dosed mice included irritation of the skin at the site of application. Irritation occurred in all surviving dosed males and in most females administered 100 mg/kg or greater and progressed to ulcer in one 800 mg/kg male. The heart weights of 400 and 800 mg/kg males and females and 200 mg/kg females and the kidney weights of 50, 100, and 400 mg/kg males were significantly greater than those of the vehicle controls. Relative to the vehicle controls, the liver weights were increased in all dosed groups. Lesions of the skin at the site of application in dosed mice included epidermal hyperplasia, parakeratosis, suppurative epidermal inflammation, chronic active dermal inflammation, sebaceous gland hypertrophy, and ulcer. The severities of these lesions generally increased with increasing dose. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 50, or 100 mg oleic acid diethanolamine condensate/kg body weight in ethanol dermally for 2 years. Survival, Body Weights, and Clinical Findings: Survival of dosed male and female rats was similar to that of the vehicle control groups. Mean body weights of 100 mg/kg males were slightly less than those of the vehicle controls throughout most of the study. Mean body weights of 100 mg/kg females were less than those of the vehicle controls beginning at week 24. The only significant treatment-related clinical finding was mild to moderate irritation of the skin at the site of application in dosed males and females. Pathology Findings: The predominant effects of oleic acid diethanolamine condensate administration were minimal to moderate nonneoplastic lesions of the skin at the site of application in dosed rats. These lesioe lesions included epidermal hyperplasia, sebaceous gland hyperplasia, hyperkeratosis, parakeratosis, chronic active dermal inflammation, and ulcer. 2-YEAR STUDY IN MICE: Groups of 55 male and 55 female mice were administered 0, 15, or 30 mg oleic acid diethanolamine condensate/kg body weight in ethanol dermally for 2 years. Five animals from each group were evaluated at 3 months for gross lesions and skin histopathology. Survival, Body Weights, and Clinical Findings: Survival of dosed male and female mice was similar to that of the vehicle control groups. Mean body weights of dosed males and of 15 mg/kg females were similar to those of the vehicle controls throughout the study. Mean body weights of 30 mg/kg females were less than those of the vehicle controls from week 76 until the end of the study. The only significant treatment-related clinical finding was irritation of the skin at the site of application in 30 mg/kg males. Pathology Findings: The incidences of epidermal hyperplasia, sebaceous gland hyperplasia, and chronic active inflammation of the dermis in all dosed groups were significantly increased relative to the vehicle controls at 3 months and at 2 years. The increased incidences of hyperkeratosis in dosed males at 3 months and in dosed males and females at 2 years, of parakeratosis in 30 mg/kg males at 3 months and 2 years, and of ulcer in 30 mg/kg males and exudate in 30 mg/kg males and females at 2 years were also attributed to chem ical administration. GENETIC TOXICOLOGY: Oleic acid diethanolamine condensate was not mutagenic in S. typhimurium strain TA97, TA98, TA100, or TA1535, with or without S9 metabolic activation enzymes. In addition, it did not induce mutations in mouse L5178Y lymphoma cells treated with or without S9. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of oleic acid diethanolamine condensate in male or female F344/N rats administered 50 or 100 mg/kg or in male or female B6C3F1 mice administered 15 or 30 mg/kg. Dermal administration of oleic acid diethanolamine condensate to male and female rats was associated with epidermal hyperplasia, sebaceous gland hyper plasia, hyperkeratosis, parakeratosis, chronic active inflammation of the dermis, and ulceration of the skin at the site of application. Dermal administration of oleic acid diethanolamine condensate to mice was associated with epidermal hyperplasia, sebaceous gland hyperplasia, hyperkeratosis, chronic active inflammation of the dermis, and exudate of the skin at the site of application in males and females and parakeratosis and ulcer of the skin at the site of application in males. Synonyms: Diethanolamine oleate; diethanolammonium oleate; (Z)-9-octadecenoic acid, compound with 2,2.-imnobis(ethanol) (1:1); oleamide diethanolamine

Journal Article↗

[Examination of exhaled breath condensate in patients with asthma and chronic obstructive pulmonary diseases].

Considerable interest of specialists all over the world has focused on the measurement of the markers of inflammation and oxidative stress in the exhaled breath condensate in patients with asthma or chronic obstructive pulmonary diseases recently. Use of exhaled condensate is based on the hypothesis that aerosol particles exhaled in human breath reflect the composition of the bronchoalveolar extracellular lining fluid. The standard collection of the material requires condensation of exhaled air and the samples have to be kept in biologically inert containers. Measurement of the very low concentrations of selected substances requires very sensitive analytical methods. The examination of exhaled breath condensate is absolutely non-invasive method, which can be repeated as often as needed and it is extremely well tolerated both by children and seniors. Markers in the condensate enable detection and quantification of the inflammation process, the disease monitoring, and assessment of the response to the treatment. The breath condensate diagnostics is a new progressive method and in the patients with asthma and chronic obstructive pulmonary disease it can bring complementary information to the very sensitive method of determination of exhaled nitric oxide.

Asthma↗

ICSI outcome is not associated with the incidence of spermatozoa with abnormal chromatin condensation.

BACKGROUND: The condensation of sperm chromatin during spermiogenesis and epididymal transport is of essential importance for fertilization. The main purpose of this study was to examine whether abnormalities of sperm nuclear condensation can influence the outcome of intracytoplasmic sperm injection (ICSI) cycles. MATERIALS AND METHODS: Semen samples from 154 ICSI cycles were studied. Before semen preparation for ICSI, basic semen analysis was performed and a small portion from each sample was fixed. The condensation of sperm nuclear chromatin was evaluated with chromomycin A3 under a fluorescence microscope. RESULTS: The incidence of spermatozoa with abnormal chromatin condensation was positively correlated with sperm concentration (p = 0.020565), but was not correlated with other semen parameters such as morphology and motility. Abnormal chromatin condensation was also not correlated with fertilization rate, cumulative embryo score or pregnancy rate. CONCLUSION: The above results indicate that ICSI outcome is not influenced by the incidence of spermatozoa with abnormal chromatin condensation.

Chromatin↗

[Studies on the resolution of racemic gossypol. III. Study on the chemical and physical properties of the amino condensates of gossypol].

Fifteen condensates of chiral amines and racemic gossypol were prepared. Their 1HNMR spectra indicated that all the amine condensates tested had the same keto-enamine structures and shifts of protons on C11, C11 of various condensates were analyzed for their structural relationship. The Rf and delta Rf values (difference between (+) and (-)gossypol condensates) on TLC of these derivatives and stability of eight condensates of (-)gossypol were examined. All these properties were discussed in light of the configuration of gossypol. These studies not only provided rational basis of selecting resolving agent, but also gave indications of their relative absorbability and stereochemistry of the condensates which might be useful in postulating their in vivo behaviors and designing derivatives with better pharmacological actions.

Gossypol↗

[Secondary structure of condensed DNA. wide-angle, small-angle x-ray scattering and circular dichroism].

Ethanol precipitated DNA shows a CD spectrum of the +psi-type which is similar to that of DNA in the A-form. DNA condensed with cetyl-trimethylammonium-bromide shows, depending on the condensation velocity, a CD spectrum of the -psi-type, or a CD spectrum only slightly modified from that of DNA in solution. The first spectrum is similar to that of DNA in the C-form, and the second one, to that of DNA in the B-form. Using large-angle X-ray scattering of the three DNA condensates and comparing them with the scattering curves calculated from the atom coordinates for the A-, B-, and C-form of DNA it is shown that the secondary structure of the DNA belongs in all three cases to the B-family. It follows from this result that the secondary structure of DNA alone does not determine the type of CD spectrum. The CD spectrum of condensed DNA is essentially determined by the supramolecular structures of the partially crystalline DNA condensates. These supramolecular structures can be demonstrated by the small-angle X-ray diagrams. The condensation of DNA by ethanol and cetyl-trimethylammonium-bromide proceeds in the form of a partial crystallization of the DNA.

Animals↗

Prevention and reversal by a retinoid of 3,4-benzpyrene- and cigarette smoke condensate-induced hyperplasia and metaplasia of rodent respiratory epithelia in organ culture.

The influence of an aromatic analog of vitamin A, etretinate, on the effects of 3,4-benzpyrene and cigarette smoke condensate has been investigated in fetal mouse lung and neonatal rat tracheas grown in organ culture. In both tissues, 3,4-benzpyrene as well as cigarette smoke condensate induces a striking increase of epithelial mitosis within 12--14 days of treatment. The increase is associated with a loss of secretory activity and of ciliary function. These changes persist in the absence of benzpyrene or smoke condensate in explants transferred to control medium. Treatment with etretinate alone does not affect the normal epithelial growth rate or normal differentiation. If combined with either benzpyrene or smoke condensate, the aromatic compound inhibits the increase in cell division and prevents the loss of secretory activity or ciliary function. In explants pretreated with 3,4-benzpyrene or cigarette smoke condensate, etretinate reduces the carcinogen- or smoke condensate-induced increase in mitotic activity to normal levels and restores secretory differentiation and ciliary function. The mechanism of action involved in the anticarcinogenic activity of the retinoid is discussed.

Animals↗

Fibrillar centres and condensed nucleolar chromatin in resting and stimulated human lymphocytes.

To provide more information on the ultrastructural morphology of fibrillar centres and condensed nucleolar chromatin, both these nucleolar components were studied in ultrathin sections of resting and phytohemagglutinin stimulated human lymphocytes. In comparison with resting cells, in stimulated lymphocytes fibrillar centres increased in number but their total size was smaller. In stimulated cells the size of individual fibrillar centers remained about the same. The size of the intranucleolar condensed chromatin was larger in stimulated than in resting cells. The proportion of the intranucleolar areas with condensed chromatin to the whole nucleolar area was relatively constant since no difference was noted between resting and stimulated cells. On the other hand, the proportion of the condensed intranucleolar chromatin to the condensed perinucleolar chromatin increased in stimulated lymphocytes in comparison with resting cells. The close morphological relationship between fibrillar centres and condensed intranucleolar chromatin was noted in ring shaped nucleoli of resting lymphocytes, this relationship was frequently remaining in nucleoli with less or more distinct nucleolonemata of stimulated cells.

Cell Nucleolus↗

Mutagenicity of smoke condensates induced by CO2-laser irradiation and electrocauterization.

Smoke condensates generated from mucous membrane of the canine tongue irradiated with a CO2 laser showed mutagenicity on Salmonella typhimurium TA98 under metabolic activation with S9 mix. Strain TA100 was not so sensitive to the condensates with or without S9 mix. Smoke condensates from electrocauterization on the mucosa of the canine tongue also showed mutagenic activity on TA98 and TA100 with S9 mix. The revertant number per mg of the smoke condensates from laser irradiation was one-half that of the smoke condensates from electrocauterization (1623 and 3371) in TA98. The mutagenic potency observed was comparable to that of cigarette smoke. The amount of these smoke condensates from 1 g of tissue was equivalent to those from 3--6 cigarettes as to total mutagenicity.

Animals↗

Hygroscopic condenser humidifiers in chronically tracheostomized patients who breathe spontaneously.

The aim of this study was to test the usefulness of hygroscopic condenser humidifiers on secretion and on inspired gas temperature in tracheostomized patients. Forty spontaneously breathing chronically tracheostomized patients were divided into two groups: Group 1 received a hygroscopic condenser humidifier connected to the tracheostomy, 24 h daily for 10 days; Group 2, without any protection system, was chosen as the control group. The daily number of tracheal suctions, quantity of aspirate and thickness and colouring of secretions was evaluated. At baseline, and at days 5 and 10, patients were submitted to blood gas analysis, respiratory function tests and sputum analysis. The temperature of gases breathed was measured at rest and during a hyperventilation test, with and without the hygroscopic condenser humidifier. Statistically significant differences were found in thickness and colouring of secretions between the two groups during the period of 10 days. Group 2 showed a significantly greater trend in number of bacteria than Group 1. The group with the hygroscopic condenser humidifier showed respiratory function improvement over time for forced expiratory volume in one second (FEV1) and tidal volume (VT), maximal inspiratory pressure (MIP), and maximal voluntary ventilation (MVV) in comparison to the control group, who did not. Significant differences in the temperature between rest and hyperventilation, with and without a hygroscopic condenser humidifier were also found. In conclusion, a hygroscopic condenser humidifier may be useful in chronically tracheostomized patients who breathe spontaneously, improving viscosity and colouring of secretions, preventing further bacterial colonization, heating inspiratory flow, and helping to improve the functional outcome.

Aged↗

Douglas-fir: a third wood-drying condensate found to exhibit in vitro cytotoxicity and genotoxicity.

The present study applies the approach described in Mark et al. for the testing of toxic chemicals produced during the drying of Douglas-fir. The genotoxic potential of Douglas-fir condensate has been previously unexplored and is thus an area of appropriate concern to the forest products industry, regulatory, agencies, and the general public. Previous research conducted in this laboratory has identified two wood-drying condensates that yield positive cytotoxic and genotoxic effects. The results of testing Southern yellow pine and Eastern white pine condensates have been reported elsewhere. Douglas-fir condensate, a third wood-drying condensate, was added in vitro in concentrations ranging from 0.1 to 100 microliters/ml to cultures of Chinese Hamster Ovary (CHO-WBL) cells. A dose response curve was observed with this condensate for both cytotoxicity and genotoxicity. The number of viable cells as well as the mitotic index (MI) and proliferative rate index (PRI) varied inversely with dosage. The result of chromosome aberration (Abs) analysis and sister chromatid exchange (SCE) analysis, both cytogenetic measures of genotoxicity, also gave statistically significant results.

Animals↗

Mediator at the Helm: Coordinating transcription and biomolecular condensates in hematopoiesis.

Hematopoiesis relies on precisely coordinated transcriptional programs that balance stem cell self-renewal, lineage commitment, and terminal differentiation. Central to this regulation is the Mediator complex, a large multi-subunit transcriptional co-regulator that integrates signals from transcription factors and chromatin regulators to control RNA polymerase Ⅱ (Pol Ⅱ) activity. The dynamic and modular composition of Mediator enables context-dependent transcriptional outputs, while individual subunits can exert specialized regulatory functions during hematopoietic lineage specification, thereby contributing to cell-fate-specific transcriptional outputs. Recent advances further reveal that transcriptional regulation is shaped by the spatial organization of regulatory machinery with biomolecular condensates formed through liquid-liquid phase separation (LLPS), particularly at super-enhancers. In this emerging framework, Mediator functions not only as a transcriptional integrator but also as a key coordinator of transcriptional machinery within condensates at cell-fate-related gene loci. In this chapter, we summarize how distinct Mediator subunits confer specific modes of transcriptional regulation and discuss how the interplay between Mediator and phase-separated condensates shapes transcriptional control during hematopoiesis. We highlight how specific subunits, including MED1 and MED26, participate in distinct regulatory modes in erythropoiesis, spanning super-enhancer-driven transcriptional activation, progenitor expansion, and condensate-associated mechanisms that influence Pol Ⅱ pausing and global transcription repression during terminal differentiation. Together, these findings support a model in which Mediator integrates transcriptional regulation with nuclear organization through condensate-mediated mechanisms, providing a conceptual framework for understanding hematopoietic cell fate decisions and transcriptional dysregulation in hematological diseases.

Hematopoiesis↗

ATRX Condensates as Candidate Organizers of Enhancer-Centered Nuclear Microenvironments in Neural Progenitors: A Hypothesis for Enhancer-Associated ATRX Function in Neural Progenitors.

Neural progenitor cells (NPCs) must preserve lineage identity while remaining responsive to developmental cues. Here, we discuss the hypothesis that ATRX condensates help organize enhancer-centered nuclear microenvironments in NPCs. ATRX has long been studied in heterochromatin maintenance, histone variant deposition, and chromatin remodeling; earlier work has also shown that ATRX can occupy euchromatic and active regulatory regions and contribute to transcriptional regulation. Recent evidence in human NPCs indicates that ATRX forms nuclear puncta with condensate-like properties, associates with neurogenic enhancer-rich regions, and incorporates regulatory factors such as CHD7 and p300. Perturbation of ATRX condensate formation is associated with changes in enhancer-associated ATRX occupancy, neural gene-expression programs, and neuroepithelial organization, suggesting a regulatory mode that may complement canonical heterochromatin-associated functions. We propose a dual-mode model in which folded domains contribute to chromatin anchoring at repressive regions, whereas intrinsically disordered regions support condensate-associated organization at active developmental enhancers. We emphasize that whether ATRX condensates activate enhancers de novo, stabilize pre-existing enhancer states, buffer transcriptional variability, or primarily organize cofactor localization remains unresolved. We also discuss limitations of the current evidence and outline acute, locus-specific experiments needed to test the model.

X-linked Nuclear Protein↗

Molecular origins of pH gradients in charge-regulated biomolecular condensates.

Biomolecular condensates exhibit spontaneous electrochemical microenvironments characterized by asymmetric ion distributions and pH gradients that emerge from protein-sequence-dependent charge regulation. Despite their biological importance, mechanistic understanding of these microenvironments has been constrained by the absence of computationally tractable frameworks capable of treating proton exchange, counterion partitioning, and buffer equilibria on consistent thermodynamic footing. Here, we introduce the buffered Charge-Regulation Monte Carlo (b-CR-MC) framework, which couples grand-canonical exchange of ions and buffer species with explicit charge regulation of titratable residues. By extending the CR-MC ion-merging strategy to multicomponent reservoirs and employing the restricted primitive model, b-CR-MC achieves computational efficiency while maintaining thermodynamic rigor, achievingquantitative agreement with the more expensive generalized grand-reaction Monte Carlo approach. Applied to full-length FUS (net positive) and PGL-3 (net negative) under physiological conditions, the framework reveals sequence-dependent pH gradients: the dense phase of FUS exhibits an alkaline shift, while that of PGL-3 exhibits an acidic shift, in both cases driving the condensate interior toward the protein's isoelectric point. Slab-geometry simulations further resolve the Donnan potential and continuous ion profiles across the condensate interface, confirming the direction of these electrochemical shifts. Additionally, we identify spatially resolved buffer depletion within dense phases, establishing that dynamic charge regulation is a primary determinant rather than a secondary correction to condensate electrochemistry. By establishing a sequence-resolved, thermodynamically consistent computational platform, b-CR-MC enables quantitative prediction of how mutations and post-translational modifications reprogram condensate microenvironments across biological and pathophysiological contexts.

Hydrogen-Ion Concentration↗

Exhaled breath condensate: methodological recommendations and unresolved questions.

Collection of exhaled breath condensate (EBC) is a noninvasive method for obtaining samples from the lungs. EBC contains large number of mediators including adenosine, ammonia, hydrogen peroxide, isoprostanes, leukotrienes, nitrogen oxides, peptides and cytokines. Concentrations of these mediators are influenced by lung diseases and modulated by therapeutic interventions. Similarly EBC pH also changes in respiratory diseases. The aim of the American Thoracic Society/European Respiratory Society Task Force on EBC was to identify the important methodological issues surrounding EBC collection and assay, to provide recommendations for the measurements and to highlight areas where further research is required. Based on the currently available evidence and the consensus of the expert panel for EBC collection, the following general recommendations were put together for oral sample collection: collect during tidal breathing using a noseclip and a saliva trap; define cooling temperature and collection time (10 min is generally sufficient to obtain 1-2 mL of sample and well tolerated by patients); use inert material for condenser; do not use resistor and do not use filter between the subject and the condenser. These are only general recommendations and certain circumstances may dictate variation from them. Important areas for future research involve: ascertaining mechanisms and site of exhaled breath condensate particle formation; determination of dilution markers; improving reproducibility; employment of EBC in longitudinal studies; and determining the utility of exhaled breath condensate measures for the management of individual patients. These studies are required before recommending this technique for use in clinical practice.

Biomarkers↗

Biomolecular Condensates Integrate Transcriptional and Epigenetic Responses to Hypoxia.

Hypoxia is a defining feature of physiological stress and the core of solid tumors, where aberrant vascularization limits oxygen delivery; cells respond through mechanisms that extend beyond the canonical stabilization of hypoxia-inducible factors (HIFs). Recent studies suggest that hypoxia can promote the formation of specific biomolecular conden-sates, membraneless compartments generated through liquid-liquid phase separation in which regulatory proteins and RNAs become locally enriched at genomic regions, while chromatin mainly serves as an organizational scaffold. Transcription factors, the coacti-vators p300/CBP, Mediator, and BRD4, chromatin-modifying enzymes, and architectural RNAs such as NEAT1 and MALAT1 partition into these compartments, and their con-densation can help reorganize local chromatin structure and enhancer-promoter interac-tions. Because molecular oxygen is a shared co-substrate for the Jumonji-C histone demethylases and the ten-eleven translocation (TET) DNA dioxygenases, hypoxia reshapes histone methylation and DNA methylation in parallel, and readers that bridge these marks, including UHRF1, may participate in condensate-associated chromatin regulation. Hypoxia-driven condensation of ZHX2 rewires enhancer-promoter contacts and higher-order genome architecture, influencing cell identity, stemness, and metastatic potential, and Polycomb condensates represent another candidate epigenetic compartment that may be influenced by hypoxic signaling. These processes may be particularly important in cancer, where chronic hypoxia provides a sustained stimulus for condensate formation and epigenetic remodeling. Together, these findings support a model in which phase separation and epigenetic reprogramming are not separate layers but one integrated response to low oxygen, offering opportunities to target maladaptive condensates in disease.

Epigenesis, Genetic↗

Correlation of DNA fragmentation and chromatin condensation in apoptotic nuclei of the Ser 6 mouse retina.

The form of cell death known as apoptosis was first described in thymocytes. The hallmarks of apoptosis include chromatin condensation, membrane blebbing, formation of apoptotic bodies, and DNA fragmentation. DNA fragmentation can be visualized morphologically by the TdT-mediated dUTP-biotin nick end labeling (TUNEL) method that labels the cut DNA ends. However, at the light microscopic (LM) level, TUNEL-positive nuclei cannot readily be correlated with the other hallmarks of apoptosis. In the retina, chromatin condensation and DNA fragmentation are the major features of developmental cell death as well as photoreceptor degeneration. We performed TUNEL at the electron microscopic (EM) level, which permitted correlation of DNA fragmentation with chromatin condensation. We studied the retinas of transgenic mice (Ser 6) expressing the Pro347Ser mutant rhodopsin gene during developmental cell death (age 7 days) and photoreceptor degeneration (age 21 days). We found that 90% of the nuclei showing chromatin condensation were TUNEL positive as well. Our results demonstrated DNA fragmentation and chromatin condensation in the same cells as they underwent apoptosis in vivo, confirming the notion that these processes are concomitant events, and by implication, that activation of an endogenous endonuclease is an important step in the death process of retinal neurons.

Animals↗

Exchange of counterions in DNA condensation.

We measured the fluorescence intensity of DNA-bound fluorescent dyes YO-PRO-1 (oxazole yellow) and YOYO-1 (dimer of oxazole yellow) at various spermidine concentrations to determine how counterions on DNA are exchanged in the process of DNA condensation. A decrease of fluorescence intensity was observed with an increase of spermidine. Considering the chemical equilibrium under the competition between the dye and spermidine for counterion condensation on DNA, the theoretical curve well describes the decrease of the fluorescence intensity. These results indicate that dyes are exchanged for spermidine at the binding site on DNA; that is, the exchange of counterions occurs. The parameters associated with the decrease of the fluorescence intensity show that the relative affinity of the dye and spermidine for DNA depends on the state of DNA. Moreover, YOYO-1 prevents the DNA condensation, but the effect of YO-PRO-1 on the condensation is very slight, though both dyes intercalate for DNA; the high affinity of YOYO-1 compared to YO-PRO-1 enables prevention of the condensation.

Bacteriophage lambda↗