Lower risk of low bone mineral density in high vitamin E level in older people: A cross-sectional study.

INTRODUCTION: Osteoporosis and osteopenia, together known as low bone mineral density (LBMD), are common problems in the elderly. LBMD may cause fragility fractures in the elderly. The relationship between Vitamin E and LBMD in old Americans is still unclear. In this study, we investigated the relationship between serum Vitamin E levels and LBMD in the elderly. METHODS: We utilized data from the National Health and Nutrition Examination Survey (NHANES) 2017-2018 and ultimately included 378 participants aged 50 to 79. Multivariable logistic or linear regression models were applied to examine the associations between serum Vitamin E levels and LBMD, total femur or lumbar spine BMD after adjusting for covariates. RESULTS: After adjusting for all covariates, higher serum Vitamin E levels reduced the risk of LBMD (OR 0.76; 95% CI 0.58-1.00) and were positively associated with total femur BMD (ß: 0.02; 95% CI: 0.01-0.03)， after adjusting for all covariates. In the subgroup analysis, for the BMI normal group (BMI<25), the serum Vitamin E levels were positively associated with the total femur (ß: 0.03; 95% CI: 0.01-0.05) and lumbar spine BMD (ß: 0.04; 95% CI: 0.01-0.07). In the BMI normal group, people with high serum Vitamin E levels have a lower incidence of LBMD (OR:0.43; 95% CI: 0.21-0.88). Though the P for interaction was larger than 0.05. CONCLUSION: This study found serum Vitamin E levels were negatively associated with LBMD in older Americans. Serum Vitamin E levels were positively associated with femur BMD in older Americans.

Toward a Comprehensive Understanding of the Anomalously Small Contact Angle of Surface Nanobubbles.

Experimental studies have demonstrated that the gas phase contact angle (CA) of a surface nanobubble (SNB) is much smaller than that of a macroscopic gas bubble. This reduced CA plays a crucial role in prolonging the lifetime of SNBs by lowering the bubble pressure and preventing gas molecules from dissolving in the surrounding liquids. Despite extensive efforts to explain the anomalously small CA, a consensus about the underlying reasons is yet to be reached. In this study, we conducted experimental investigations to explore the influence of gas molecules adsorbed at the solid-liquid interface on the CA of SNBs created through the solvent exchange (SE) method and temperature difference (TD). Interestingly, no significant change is observed in the CA of SNBs on highly oriented pyrolytic graphite (HOPG) surfaces. Even for nanobubbles on micro/nano pancakes, the CA only exhibited a slight reduction compared to SNBs on bare HOPG surfaces. These findings suggest that gas adsorption at the immersed solid surface may not be the primary factor contributing to the small CA of the SNBs. Furthermore, the CA of SNBs formed on polystyrene (PS) and octadecyltrichlorosilane (OTS) substrates was also investigated, and a considerable increase in CA was observed. In addition, the effects of other factors including impurity, electric double layer (EDL) line tension, and pinning force upon the CA of SNBs were discussed, and a comprehensive model about multiple factors affecting the CA of SNBs was proposed, which is helpful for understanding the abnormally small CA and the stability of SNBs.

The biocontrol potentials of rhizospheric bacterium Bacillus velezensis K0T24 against mulberry bacterial wilt disease.

Mulberry bacterial wilt disease, caused by Ralstonia pseudosolanacearum, is a devastating soil-borne disease in the silk-mulberry-related industry. In this study, through high-throughput sequencing, we compared the rhizosphere bacterial composition of the mulberry-resistant cultivar (K10) and susceptible cultivar (G12), confirming Bacillus as a genus-level biomarker for K10. Next, twelve Bacillus spp. isolates, derived from the rhizosphere of K10, were screened for their antagonistic activity against R. pseudosolanacearum. The isolate showing strong antagonism was identified as B. velezensis K0T24 and selected for further analysis. The fermentation supernatant of B. velezensis K0T24 significantly inhibited the growth of R. pseudosolanacearum (82.47%) and the expression of its pathogenic genes. Using B. velezensis K0T24 in mulberry seedlings also increased defense enzyme activities and achieved a control efficacy of up to 55.17% against mulberry bacterial wilt disease. Collectively, our findings demonstrate the potential of B. velezensis K0T24 in suppressing mulberry bacterial wilt disease.

Encapsulated allyl isothiocyanate improves soil distribution, efficacy against soil-borne pathogens and tomato yield.

BACKGROUND: Crop quality, yield and farmer income are reduced by soil-borne diseases, nematodes and weeds, although these can be controlled by allyl isothiocyanate (AITC), a plant-derived soil fumigant. However, its efficacy against soil-borne pathogens varies, mainly because of its chemical instability and uneven distribution in the soil. Formulation modification is an effective way to optimize pesticide application. We encapsulated AITC in modified diatomite granules (GR) and measured the formulation's loading content and stability, environmental fate and efficacy against soil-borne pathogens, and its impact on the growth and yield of tomatoes. RESULTS: We observed that an AITC loading content in the granules of 27.6% resulted in a degradation half-life of GR that was 1.94 times longer than 20% AITC emulsifiable concentrate in water (EW) and shorter than AITC technical (TC) grade. The stable and more even distribution of GR in soil resulted in relatively consistent and acceptable control of soil-borne pathogens. Soil containing AITC residues that remained 10-24 days after GR fumigation were not phytotoxic to cucumber seeds. GR significantly reduced soil-borne pest populations, and tomato growth and yield increased as AITC dosage increased. GR containing an AITC dose of 20 g m-2 effectively controlled pathogens in soil for about 7 months and improved tomato yield by 108%. CONCLUSION: Our research demonstrates the benefits of soil fumigation with loaded AITC over other formulations for effective pest control, and improved tomato plant growth and fruit yield. Fumigant encapsulation appears to be a useful method to improve pest and disease control, environmental performance and fumigant commercial sustainability. © 2024 Society of Chemical Industry.

The potential for reducing aflatoxin B1 contamination of stored peanuts by soil disinfection.

Aflatoxins from the fungus Aspergillus flavus (A. flavus) that contaminate stored peanuts is a major hazard to human health worldwide. Reducing A. flavus in soil can decrease the risk of aflatoxins in stored peanuts. In this experiment, we determined whether peanuts grown on soil fumigated with dazomet (DZ), metham sodium (MS), allyl isothiocyanate (AITC), chloropicrin (PIC) or dimethyl disulfide (DMDS) would reduce of the quantity of A. flavus and its toxin's presence. The results of bioassays and field tests showed that PIC was the most effective fumigant for preventing and controlling A. flavus, followed by MS. PIC and MS applied to the soil for 14 d resulted in LD50 values against A. flavus of 3.558 and 4.893 mg kg-1, respectively, leading to almost 100% and 98.82% effectiveness of A. flavus, respectively. Peanuts harvested from fumigated soil and then stored for 60 d resulted in undetectable levels of aflatoxin B1 (AFB1) compared to unfumigated soil that contained 0.64 ug kg-1 of AFB1, which suggested that soil fumigation can reduce the probability of aflatoxin contamination during peanut storage and showed the potential to increase the safety of peanuts consumed by humans. Further research is planned to determine the practical value of our research in commercial practice.

Extracellular vesicle-encapsulated microRNA-296-3p from cancer-associated fibroblasts promotes ovarian cancer development through regulation of the PTEN/AKT and SOCS6/STAT3 pathways.

Cancer-associated fibroblasts (CAFs), as important components of the tumor microenvironment, can regulate intercellular communication and tumor development by secreting extracellular vesicles (EVs). However, the role of CAF-derived EVs in ovarian cancer has not been fully elucidated. Here, using an EV-microRNA sequencing analysis, we reveal specific overexpression of microRNA (miR)-296-3p in activated CAF-derived EVs, which can be transferred to tumor cells to regulate the malignant phenotypes of ovarian cancer cells. Moreover, overexpression of miR-296-3p significantly promotes the proliferation, migration, invasion, and drug resistance of ovarian cancer cells in vitro, as well as tumor growth in vivo, while its inhibition has the opposite effects. Further mechanistic studies reveal that miR-296-3p promotes ovarian cancer progression by directly targeting PTEN and SOCS6 and activating AKT and STAT3 signaling pathways. Importantly, increased expression of miR-296-3p encapsulated in plasma EVs is closely correlated with tumorigenesis and chemoresistance in patients with ovarian cancer. Our results highlight the cancer-promoting role of CAF-derived EVs carrying miR-296-3p in ovarian cancer progression for the first time, and suggest that miR-296-3p encapsulated in CAF-derived EVs could be a diagnostic biomarker and therapeutic target for ovarian cancer.

Comparison of drip-irrigated or injected allyl isothiocyanate against key soil-borne pathogens and weeds.

BACKGROUND: Allyl isothiocyanate (AITC) is a soil biofumigant used for controlling soil-borne pests that reduce the growth, quality, and yield of food crops. Its effectiveness against pathogens depends largely on its distribution in the soil, which is influenced mainly by the soil water content and application method. The distributions of AITC when injected with different moisture content or drip-irrigated into soils were compared. RESULTS: AITC injected at 50 g m-2 only diffused 10 cm deep in soil column with 5, 10 or 15% soil moisture content. The gas AITC peak concentration was 0.64 µg cm-3 at 5% moisture content. Diffusion was reduced when moisture content increased to more than 15%. The results of adsorption kinetics and release indicated that AITC's limited distribution was due to its low vapor pressure. AITC applied by drip irrigation at 7.5 g m-2 diffused 15 cm laterally and 30 cm deep where it reached concentrations of 0.022 µg cm-3 and 0.035 µg g-1 , respectively. Some soil-borne pathogens, nematodes and weed seeds closed to the point of AITC release were effectively controlled under drip irrigation, but efficacy decreased with increased distance. AITC applied by drip irrigation at 7.5 g m-2 and covered with PE film for 5 days provided a satisfactory efficacy against soil-borne pathogens and weeds without any phytotoxicity. CONCLUSION: Our results indicated that AITC applied by drip irrigation was more effective than injection, which will guide applicators on methods to optimize the application of AITC for efficient control of key pests and weeds. © 2023 Society of Chemical Industry.

Adaptive evolution characteristics of mitochondrial genomes in genus Aparapotamon (Brachyura, Potamidae) of freshwater crabs.

BACKGROUND: Aparapotamon, a freshwater crab genus endemic to China, includes 13 species. The distribution of Aparapotamon spans the first and second tiers of China's terrain ladder, showing great altitudinal differences. To study the molecular mechanisms of adaptive evolution in Aparapotamon, we performed evolutionary analyses, including morphological, geographical, and phylogenetic analyses and divergence time estimation. We sequenced the mitogenomes of Aparapotamon binchuanense and Aparapotamon huizeense for the first time and resequenced three other mitogenomes of Aparapotamon grahami and Aparapotamon gracilipedum. These sequences were combined with NCBI sequences to perform comparative mitogenome analysis of all 13 Aparapotamon species, revealing mitogenome arrangement and the characteristics of protein-coding and tRNA genes. RESULTS: A new species classification scheme of the genus Aparapotamon has been detected and verified by different aspects, including geographical, morphological, phylogenetics and comparative mitogenome analyses. Imprints from adaptive evolution were discovered in the mitochondrial genomes of group A, including the same codon loss at position 416 of the ND6 gene and the unique arrangement pattern of the tRNA-Ile gene. Multiple tRNA genes conserved or involved in adaptive evolution were detected. Two genes associated with altitudinal adaptation, ATP8 and ND6, which experienced positive selection, were identified for the first time in freshwater crabs. CONCLUSIONS: Geological movements of the Qinghai-Tibet Plateau and Hengduan Mountains likely strongly impacted the speciation and differentiation of the four Aparapotamon groups. After some group A species dispersed from the Hengduan Mountain Range, new evolutionary characteristics emerged in their mitochondrial genomes, facilitating adaptation to the low-altitude environment of China's second terrain tier. Ultimately, group A species spread to high latitudes along the upper reaches of the Yangtze River, showing faster evolutionary rates, higher species diversity and the widest distribution.

Manipulating Trapped Nanobubbles Moving and Coalescing with Surface Nanobubbles.

Trapped nanobubbles are observed nucleating at nanopits on a pitted substrate, while surface nanobubbles are usually formed on the smooth solid surface in water. In this work, trapped nanobubbles and surface nanobubbles were captured by a tapping-mode atomic force microscope (AFM) on a nanopitted substrate based on the temperature difference method. A single trapped nanobubble was manipulated to change into a surface nanobubble, then to change into the trapped nanobubble again. At the same time, surface nanobubbles can be moved to merge into a trapped nanobubble. Our results show that the scan load and the size of the scan area were the main factors that significantly affect the mobility of surface/trapped nanobubbles. The coalescence and mutual transformation of the two kinds of nanobubbles indicate that trapped nanobubbles and surface nanobubbles have the same chemical nature, which also provides vital experimental proof of the existence of nanobubbles in the course of contact line depinning. Our results are of great significance for understanding nanobubble stability and providing guidelines in some industrial applications.

Algal/bacterial uptake kinetics of dissolved organic nitrogen in municipal wastewater treatment facilities effluents.

The simulation and analysis of the degradation process of organic nitrogen contaminants in wastewater treatment facility effluent is important to the estimation of its actual contribution to eutrophication, and it is crucial to the developing of watershed protection plan. In this study, algal and algal/bacterial based bioassay was conducted to study the bioavailability of dissolved organic nitrogen contaminants in wastewater treatment plants effluents, and 4 kinetic models were used to describe the mineralization process. The traditional 1-pool model that was commonly used in water quality models showed poor correlation (r2 = 0.613 ± 0.261), while the other three models performed much better (r2 > 0.950). The model coefficient and simplicity were studied using Akaike information criterion and Bayesian information criterion, and Gamma model was indicated to be the best model since it presented the most parsimonious fit to the data with the fewest terms. This study exhibited that the bioavailability and degradation rate of organic nitrogen in wastewater effluent varied greatly, and this variation should be considered in water quality models. Besides, Gamma model could be used to modify the current Total Maximum Daily Load models to provide a scientific basis for making watershed protection plans and controlling eutrophication.

Relationship between water iodine and children's goiters.

Excessive iodine can lead to goiters. However, the relationship between the water iodine concentration (WIC) and goiter rate (GR) is unclear. This study aims to explore the factors that influence children's GR in areas with high WIC and analyse the threshold value of the GR increase associated with the WIC. According to the monitoring of the areas with high WIC in China in 2018-2020, a total of 54 050 children in eight high water iodine provinces were chosen. Drinking water, urine and edible salt samples of children were collected. The thyroid volume (Tvol) was measured. A generalised additive model (GAM) was used to analyse the relationship between the WIC and GR in children. Among the 54 050 children in areas with high WIC, the overall GR was 3·34 %, the median of water iodine concentration was 127·0 µg/l, the median of urinary iodine concentration was 318 µg/l and the non-iodised salt coverage rate (NISCR) was 63·51 %. According to the GAM analysis results, water iodine and urinary iodine are factors that influence the Tvol and GR, while the NISCR affects only the GR. When the WIC was more than 420 µg/l or the urinary iodine concentration was more than 800 µg/l, the GR increased rapidly. When the NISCR reached more than 85 %, the GR was the lowest. Thus, in areas with high WIC, WIC more than 420 µg/l may increase the risk of goiter, and the NISCR should be increased to over 85 % to avoid goiters in children.

Characterization of the complete mitochondrial genome of Pentatoma semiannulata (Hemiptera: Pentatomidae).

The Pentatoma semiannulata is an important fruit pest in Chinese agricultural system. In current study, the complete mitochondrial genome of P. semiannulata is determined. This mitogenome is 15,515 bp in size and comprises of 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. Gene order is identical to that of the putative ancestral arrangement of insects. All protein-coding genes initiate with ATN, except for ATP8, COX1 and NAD1 use GTG or TTG as the start codon, and terminate with TAA with the exception for COX2 which uses a single T residue as the stop codon. All tRNAs, ranging from 62 to 72 bp, have the clover-leaf structure except for tRNASer(AGN) . The monophyly of Pentatomidae is highly supported by the phylogenetic tree and P. semiannulata is very close to other herbivorous species of the remaining Pentatomidae species.

The mitochondrial genome of Xanthochlorus tibetensis (Diptera: Dolichopodidae).

The long-legged fly Xanthochlorus tibetensis belongs to the subfamily Xanthochlorinae of Dolichopodidae. The mitogenome of X. tibetensis was sequenced, it is the first representative complete mitogenome from this subfamily. This mitogenome is 15,580 bp in size, includes 13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs. All genes have the same location and coding strand as in other published species of Dolichopodidae. Nucleotide composition is biased toward A and T, which together made up 77.6% of the entire genome. Bayesian inference strongly supported the monophyly of Empidoidea, Empididae and Dolichopodidae, with the phylogenetic relationships within Empidoidea: ((Dolichopodinae + Xanthochlorinae) + Neurigoninae) + ((Trichopezinae + (Empidinae + Oreogetoninae)) + Ocydromiinae).

The complete mitochondrial genome of Neurigona zhejiangensis (Diptera: Dolichopodidae).

The long-legged fly Neurigona zhejiangensis belongs to the subfamily Neurigoninae of Dolichopodidae. The mitogenome (GenBank accession number: MT921956) of N. zhejiangensis was sequenced, the first representative complete mitogenome from this subfamily. The complete mitogenome is 17,141 bp, includes 13 protein-coding genes, 2 rRNAs, and 22 transfer RNAs. All genes have the same location and coding strand as in other published species of Dolichopodidae. Nucleotide composition is biased toward A and T, which together made up 77.3% of the entire genome. Bayesian inference strongly supported the monophyly of Empidoidea, Empididae and Dolichopodidae, with the phylogenetic relationships within Empidoidea: (Dolichopodinae + Neurigoninae) + ((Empidinae + (Trichopezinae + Oreogetoninae)) + Ocydromiinae).

TNNT2 Gene Polymorphisms are Associated with Susceptibility to Idiopathic Dilated Cardiomyopathy in Kazak and Han Chinese.

BACKGROUND: Dilated cardiomyopathy (DCM) is characterized by left ventricular enlargement, systolic dysfunction, and heart failure. Both genetic and non-genetic factors have been linked to DCM pathogenesis. Familial DCM (FDCM) accounts for 20%-50% of all DCM cases, highlighting the importance of genetics in pathogenesis. Indeed, more than 40 DCM-associated genes have been identified, including the gene encoding cardiac troponin T type-2 (TNNT2). We examined polymorphisms of the TNNT2 gene in idiopathic DCM (IDCM) patients of Kazak and Han ethnicity compared with healthy Kazak and Han controls. MATERIAL AND METHODS: Peripheral blood samples were collected from 180 patients with IDCM (90 Kazak and 90 Han), and 180 healthy controls (90 Kazak and 90 Han). PCR was used to amplify 15 exons and nearby introns of the TNNT2 gene. The amplified products were sequenced and compared to the standard sequence in PubMed by BLAST and CHROMAS software, to identify mutation sites. RESULTS: Results from Kazak and Han IDCM patients were complied for Hardy-Weinberg equilibrium analysis. There was a significant difference in the genotype distribution (χ2=6.67, P=0.015) and allele frequency (χ2=5.71, P=0.017) between Kazaks with IDCM and Kazak controls of SNP rs3729547. There was also a difference in the genotype distribution (χ2=6.62, P=0.036) and allele frequency (χ2=4.91, P=0.018) between Han with IDCM and Han controls. The TNNT2 gene polymorphism loci rs3729547 may be associated with the IDCM onset in Kazak and Han patients (OR=2.5, 95% CI: 1.233~5.068). CONCLUSIONS: The TNNT2 polymorphisms might play an important role in susceptibility to DCM in Xinjiang Kazak and Han patients.

[TPM1 gene mutation is associated with dilated cardiomyopathy in Kazaks in Xinjiang].

OBJECTIVE: Detect the relationship between TPM1 gene mutations and dilated cardiomyopathy (DCM) of Kazaks and Hans in Xinjiang. METHODS: TPM1 gene was screened from 31 family members in a Kazak family with familiar DCM (FDCM), 100 patients with idiopathic DCM (IDCM, 50 Kazaks and 50 Hans), and in 100 healthy controls (50 Kazaks and 50 Hans). All the samples were the inpatients or outpatients of First Affiliated Hospital of Xinjiang University from 2012 to 2014. PCR was used to amplify 9 exons and nearby introns of the TPM1 gene. The amplified products were sequenced and compared with the standard sequence with CHROMAS software and BLAST software in Pubmed to identify mutation sites. The relationship between TPM1 gene mutations in the Kazak IDCM and healthy volunteers, between Han and Kazak IDCM and healthy volunteers was analyzed. Tropomyosin was qualitatively and quantitatively detected by ELISA in all subjects. RESULTS: A novel variant (c.524 G > T) was identified in two FDCM patients at exon 3, this mutation caused an amino acid substitution, Gln111His. The FDCM, IDCM from Kazak and Han, healthy volunteers from Kazak and Han were founded a rs1071646 (c.644C > A, Ala151Ala). There was a significant difference in the genotype distribution (χ(2) = 13.36, P = 0.001) and allele frequency (χ(2) = 10.25, P = 0.001) between Kazaks with IDCM and Kazak controls of rs1071646, while these parameters were similar between Han IDCM patients and Han controls (all P > 0.05). The tropomyosin content of Kazak and Han IDCM patients were significantly lower than Kazak and Han controls ((1 764.2 ± 350.9) ng/L vs. (2 369.7 ± 345.9) ng/L, P = 0.001). CONCLUSION: TPM1 gene of rs1071646 polymorphism is a possible independent risk factor for IDCM in Kazaks but not Han Chinese.

Altered expression of hyperpolarization-activated cyclic nucleotide-gated channels and microRNA-1 and -133 in patients with age-associated atrial fibrillation.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels mediate pacemaker currents in the atrium. The microRNA (miR) families miR-1 and miR-133 regulate the expression of multiple genes involved in myocardial function, including HCN channels. It was hypothesized that age­dependent changes in HCN2, HCN4, miR­1 and miR­133 expression may contribute to age­associated atrial fibrillation, and therefore the correlation between expression levels, among adult (≤65 years) and aged patients (≥65 years), and sinus rhythm was determined. Right atrial appendage samples were collected from 60 patients undergoing coronary artery bypass grafting. Reverse transcription-quantitative polymerase chain reaction (PCR) and western blot analyses were performed in order to determine target RNA and protein expression levels. Compared with aged patients with sinus rhythm, aged patients with atrial fibrillation exhibited significantly higher HCN2 and HCN4 channel mRNA and protein expression levels (P<0.05), but significantly lower expression levels of miR­1 and miR­133 (P<0.05). In addition, aged patients with sinus rhythm exhibited significantly higher expression levels of HCN2 and HCN4 channel mRNA and protein (P<0.05), but significantly lower expression levels of miR­1 and ­133 (P<0.05), compared with those of adult patients with sinus rhythm. Expression levels of HCN2 and HCN4 increased with age, and a greater increase was identified in patients with age­associated atrial fibrillation compared with that in those with aged sinus rhythm. These electrophysiological changes may contribute to the induction of ectopic premature beats that trigger atrial fibrillation.

Effects of ivabradine on cardiac electrophysiology in dogs with age-related atrial fibrillation.

BACKGROUND: Ivabradine is an inhibitor of mixed Na+-K+ current that could combine with HCN channels to reduce the transmembrane velocity of funny current (If), heart rate, and cardiac efficiency, and thus be used for the treatment of cardiovascular diseases such as chronic heart failure. As an ion channel blocker, Ivabradine is also a potential antiarrhythmic agent. MATERIAL/METHODS: Twelve aging dogs (8-10 years old) underwent rapid atrial pacing for 2 months to induce age-related AF in this study. The dogs were randomly divided into the Ivabradine group and aging-AF group. The effects of Ivabradine on the electrophysiological parameters, including the effective refractory period (ERP) of the pulmonary veins and atrium, duration of AF, and inducing rate of AF, were investigated. RESULTS: As compared to the aging-AF group, the ERPs of the left superior pulmonary vein (139.00±4.18 ms vs. 129.00±4.08 ms, P=0.005) and left auricle (135.00±3.53 ms vs. 122.00±4.47 ms, P=0.001) were significantly increased, while the duration of AF (46.60±5.07 s vs. 205.40±1.14 s, P=0.001) and inducing rate of AF (25% vs. 60%, P=0.001) were significantly decreased. CONCLUSIONS: Ivabradine could effectively reduce the inducing rate of AF, and thus be used as an upstream drug for the prevention of age-related AF.

Association between reversal in the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel and age-related atrial fibrillation.

BACKGROUND: We compared cardiac electrophysiological indicators and regional expression levels of cardiac hyperpolarization-activated cyclic nucleotide-gated (HCN) channels between adult and aged dogs to identify possible mechanisms of age-related atrial fibrillation. MATERIAL/METHODS: Corrected sinus node recovery time (SNRTc) and effective refractory period (ERP) of the atrium and pulmonary veins were measured in 10 adult (3-6 years old) and 10 aged dogs (>9 years old). Expression levels of HCN2 and HCN4 channel mRNAs and proteins were measured in the sinoatrial node, atrium, and pulmonary veins by real-time PCR and Western blotting. RESULTS: Aged dogs exhibited a higher induction rate of atrial fibrillation (AF) in response to electrical stimulation, longer AF duration after induction, longer SNRTc, longer right atrial effective refractory period (AERP), shorter left AERP, and increased AERP dispersion compared to adults. Expression levels of HCN2 and HCN4 channel mRNAs and proteins were lower in the sinoatrial node but higher in the atrium and pulmonary veins of aged dogs. CONCLUSIONS: Changes in atrial electrophysiological indicators in aged dogs revealed sinoatrial node dysfunction. There was a reversal in the local tissue distribution of HCN2 and HCN4 channel mRNA and protein, a decrease in sinoatrial node expression, and increase in atrial and pulmonary vein expression with age. Changes in atrial electrophysiological characteristics and regional HCN channel expression patterns were associated with the onset and maintenance of age-related atrial fibrillation.