Sarcopenic obesity is associated with cardiometabolic multimorbidity in Chinese middle-aged and older adults: a cross-sectional and longitudinal study.

OBJECTIVES: Sarcopenic obesity (SO) has been found to increase the risk of metabolic disorders, however, its relationship with cardiometabolic multimorbidity (CMM) remains unexplored. This study aims to investigate the potential association between SO and CMM in the middle-aged and older population. METHODS: Our study subjects were from CHARLS. SO was defined as the combination of impaired grip strength (grip strength <28 kg for men and <18 kg for women) and increased body mass index (BMI ≥25 kg/m2). CMM was defined as having two or more cardiometabolic diseases, including diabetes mellitus, stroke, and heart disease. The participants were divided into four groups according to their sarcopenia and obesity status, and logistic regression analysis was used to examine the association between SO and CMM. RESULTS: A total of 15,252 study subjects were included in the cross-sectional study, with an average age of 60.6 years and a male proportion of 47.4%. In the cross-sectional analysis conducted in 2015, the prevalence of CMM was highest in the SO group (9.1%), followed by the obesity (3.7%) and sarcopenia (3.5%) group. After adjustment for confounding factors, SO [OR (95%CI): 2.453 (1.742-3.455)], sarcopenia [OR (95% CI): 1.601 (1.157-2.217)], obesity [OR (95% CI): 1.446 (1.107-1.888)] were all observed to be associated with CMM, with the strongest association in the SO group. Furthermore, in the longitudinal analysis, only the SO group demonstrated a significant risk for developing CMM [OR (95% CI): 2.302 (1.239-4.228)]. CONCLUSIONS: SO was independently and positively associated with CMM in middle-aged and older population.

Smoking paradox in coronary function and structure of acute ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention.

BACKGROUND: The Smoking paradox has generated inconsistent findings concerning the clinical prognosis of acute ST-segment elevation myocardial infarction (STEMI) patients, while providing limited insights into coronary anatomy and function which are crucial prognostic factors. Therefore, this study aimed to further investigate the existence of smoking paradox in coronary anatomy and function. METHODS: This study divided STEMI patients into smokers and non-smokers. Quantitative coronary angiography, angiography­derived microcirculatory resistance (AMR) and quantitative flow ratio (QFR) were utilized to analyze coronary anatomy and function. These parameters were compared using multivariable analysis and propensity score matching. The clinical outcomes were evaluated using Kaplan-Meier curve and Cox regression. RESULTS: The study included 1258 patients, with 730 in non-smoker group and 528 in smoker group. Smokers were significantly younger, predominantly male, and had fewer comorbidities. Without adjusting for confounders, smokers exhibited larger lumen diameter [2.03(1.45-2.57) vs. 1.90(1.37-2.49), P = 0.033] and lower AMR [244(212-288) vs. 260(218-301), P = 0.006]. After matching and multivariate adjustment, smokers exhibited inversely smaller lumen diameter [1.97(1.38-2.50) vs. 2.15(1.63-2.60), P = 0.002] and higher incidence of coronary microvascular dysfunction [233(53.9%) vs. 190(43.6%), P = 0.002], but showed similar AMR and clinical outcomes compared to non-smokers. There was no difference in QFR between two groups. CONCLUSION: Smoking among STEMI patients undergoing pPCI was associated with smaller lumen diameter and higher occurrence of coronary microvascular dysfunction, although it had no further impact on clinical prognosis. The smoking paradox observed in coronary anatomy or function may be explained by younger age, gender, and lower prevalence of comorbidities.

Remnant cholesterol, preinflammatory state and chronic kidney disease: association and mediation analyses.

Blood lipid management is a key approach in the prevention of chronic kidney disease (CKD). Remnant cholesterol (RC) plays an important role in the development of multiple diseases via chronic inflammation. The aim of our study was to determine the relationship between RC and CKD and explore the role of inflammation in this relationship. The 7696 subjects from the Chinese Health and Nutrition Survey were divided into four subgroups according to the quartile of RC. The estimated glomerular filtration rate was calculated using the CKD Epidemiology Collaboration equation. Fasting RC was calculated as total cholesterol minus low-density lipoprotein cholesterol and high-density lipoprotein cholesterol. Logistic regression analysis was employed to evaluate the relationships between RC and CKD. Mediation analysis was undertaken to identify potential mediators of high-sensitivity C-reactive protein (hs-CRP) and white blood cells (WBCs). Of all participants, the mean age was 51 years, and the male accounted for 47.8%. The multivariable-adjusted odds ratios (95% CIs) for the highest versus lowest quartile of remnant cholesterol were 1.40 (1.10-1.78, p for trend = 0.006) for CKD. RC and preinflammatory markers have combined effect on CKD. The preinflammatory state, presented by increased hs-CRP or WBCs, partially mediated the association between RC and CKD with proportion of 10.14% (p = 0.002) and 11.65% (p = 0.012), respectively. In conclusion, this study suggested a positive relationship between RC and CKD, which was partially mediated by preinflammatory state. These findings highlight the importance of RC and inflammation in renal dysfunction.IMPACT STATEMENTWhat is already known on this subject?: Dyslipidemia plays an important role in the development of chronic kidney disease (CKD). Remnant cholesterol (RC), as a triglyceride-rich particle, can contribute to target organ damage, primarily through inflammatory pathways. However, the relationship between RC and CKD in the community-dwelling population, particularly the role of inflammation, is not yet fully understood.What do the results of this study add?: This study shows that RC was significantly associated with CKD. RC and preinflammatory status exhibit a combined effect on CKD. Preinflammatory state, presented by increased high-sensitivity C-reactive protein or white blood cells, partially mediated the association between RC and CKD.What are the implications of these findings for clinical practice and/or further research?: The study provides us with a better understanding of the role of RC and inflammation in kidney dysfunction and raises the awareness of RC in the management of CKD.

Determinants and Prognoses of Visual-Functional Mismatches After Mechanical Reperfusion in ST-Elevation Myocardial Infarction.

Background: Discordance between the anatomy and physiology of the coronary has important implications for managing patients with stable coronary disease, but its significance in ST-elevation myocardial infarction has not been fully elucidated. Methods: The retrospective study involved patients diagnosed with ST-elevation myocardial infarction (STEMI) who underwent percutaneous coronary intervention (PCI), along with quantitative coronary angiography (QCA) and quantitative flow ratio (QFR) assessments. Patients were stratified into four groups regarding the severity of the culprit vessel, both visually and functionally: concordantly negative (QCA-diameter stenosis [DS] ≤ 50% and QFR > 0.80), mismatch (QCA-DS > 50% and QFR > 0.80), reverse mismatch (QCA-DS ≤ 50% and QFR ≤ 0.80), and concordantly positive (QCA-DS > 50% and QFR ≤ 0.80). Multivariable logistic regression analyses were conducted to identify the clinical factors linked to visual-functional mismatches. Kaplan‒Meier analysis was conducted to estimate the 18-month adverse cardiovascular events (MACE)-free survival between the four groups. Results: The study involved 310 patients, with 68 presenting visual-functional mismatch, and 51 exhibiting reverse mismatch. The mismatch was associated with higher angiography-derived microcirculatory resistance (AMR) (adjusted odds ratio [aOR]=1.016, 95% CI: 1.010-1.022, P<0.001). Reverse mismatch was associated with larger area stenosis (aOR=1.044, 95% CI: 1.004-1.086, P=0.032), lower coronary flow velocity (aOR=0.690, 95% CI: 0.567-0.970, P<0.001) and lower AMR (aOR=0.947, 95% CI: 0.924-0.970, P<0.001). Additionally, the mismatch group showed the worst 18-month MACE-free survival among the four groups (Log rank test p = 0.013). Conclusion: AMR plays a significant role in the occurrence of visual-functional mismatches between QCA-DS and QFR, and the mismatch group showed the worst prognosis.

How to balance land demand conflicts to guarantee sustainable land development.

Severe arable land loss and ecological problems raise attention to protect/develop land for food and ecology demand. Spatial conflict appears in front of multidemand for urbanization, food, and ecology. Our study took China as an example and explicitly outlined spatial preference of urbanization, food, and ecology. From the aspect of land amount, there are enough lands to support multidemand with a surplus of agriculture land of 45.5 × 106 ha. However, spatial conflict widely appears among the multidemands. We tested the impacts of different priorities on urban pattern, crop yield, and ecology and found the priority of food > ecology > urbanization gave the best outcome. Our results verified the importance of including priority of land multidemand to avoid confusion and increase efficiency in the implementation of land policies.

Evaluation of river longitudinal connectivity based on landscape pattern and its application in the middle and lower reaches of the Yellow River, China.

River connectivity plays an essential role in maintaining the health and stability of river basin ecosystems. It is of great significance to protect river ecosystems to clarify the effect of water conservancy project construction and operation on river hydrological connectivity. The longitudinal connectivity is affected by the landscape patterns of river, such as the convergence and dispersion of the mid-channel bars and the river areas. This study aims to analyze the impacts of construction and regulation of Xiaolangdi Dam on the connectivity of the middle and lower reaches of the Yellow River from the perspective of landscape pattern. An improved longitudinal river connectivity evaluation method was proposed by accounting for the influence of the landscape pattern represented by mid-channel bars based on barrier coefficient method, and then was applied to analyze the connectivity pre- and post-dam construction. The results show that the amplitude and frequency of the oscillation of the river were greatly reduced and tended to be stable. The aggregation degree of mid-channel bars was reduced, and the distribution of mid-channel bars was more dispersed. The river longitudinal connectivity before and after the construction of the Xiaolangdi Dam were 1.35 and 1.50 respectively, indicating an increased river longitudinal connectivity. Overall, there are differences in connectivity before and after Xiaolangdi Dam construction, and connectivity fluctuates after dam construction. Because of the dam regulation of water and sediment, the river connectivity during the flood season increased significantly, and was greater than that before and after the flood season. The longitudinal connectivity evaluation method established in this study is accurate and efficient, and provides an intuitive and reliable new method for quantitatively analyzing the changing laws and characteristics of river connectivity.

Flow and turbulence in unevenly obstructed channels with rigid and flexible vegetation.

The pattern of vegetation along the cross-section of macrophyte-dominated shallow waters is generally uneven, which affects water velocity and turbulence. This study examined the velocity and turbulence in the open channel with an uneven transverse distribution of vegetation in laboratory flume experiments. Two vegetation patterns were tested: emergent vegetation which covered part of the channel, and a symmetrical combination of submerged and emergent vegetation canopies along the lateral direction of the flume. The flow was measured using a three-dimensional Acoustic Doppler Velocimeter. The velocity and turbulence characteristics were analyzed under three vegetation densities and five discharge scenarios. Results showed that the longitudinal mean velocity changed with vegetation density and flow discharge when vegetation was unevenly distributed in a lateral direction. The strong variation in shear stress at the emergent vegetation-open water intersections and submerged-emergent vegetation intersections resulted in large-scale vortices at the interfaces. The formation processes of stem-scale turbulence and shear-scale turbulence under different vegetation scenarios were discussed. A turbulent kinetic energy model within partly obstructed vegetation canopies was established, which helped to identify the development of horizontal and vertical coherent vertices.

Vegetation patterns governing the competitive relationship between runoff and evapotranspiration using a novel water balance model at a semi-arid watershed.

Vegetation patterns play an important role in precipitation partitioning into hydrological components, especially evapotranspiration and runoff. However, few studies focus on their competitive relationship and the influence of the vegetation on them. In this study, a vegetation threshold was postulated to prevent further decrease of runoff by determining a new hydrological component continuing evapotranspiration (partitioned from total and initial evapotranspiration) through a novel model coupled with the Budyko model (dimensional form) and two-stage partitioning model (nondimensional form) in the semi-arid watershed. The results showed significant correlations between model parameters ε (underlying surface index), λ (ratio of initial evapotranspiration) and vegetation coverage (M) (R2 = 0.95 and 0.97, p < 0.01) b Based on the modified Budyko model and λ. The nondimensional model showed high-precise estimations of KH (Horton index Fraction), KB (Baseflow Fraction), KV (evapotranspiration Fraction), KR (runoff Fraction), and KC (continuing evapotranspiration Fraction) (R2 > 0.98, p < 0.01) as a function of a new aridity index φ. KH, KB, KV, KR, showed symmetrical patterns correlated with φ both at between-subwatershed and between-year scale based on the dimensional model and λ. However, KC showed asymmetrical different correlation with M3 and φ (KC/M3 ∼ φ: in between-subwatershed: R2 = 0.92, p < 0.01; and between-year scale: R2 = 0.74, p < 0.01). Based on the solution of continuing evapotranspiration, the vegetation threshold has been solved with M = 0.73 (+0.09/-0.02) to prevent further decreasing runoff. The framework presented can be applied in other semi-arid watersheds worldwide to better protect the sustainability of the hydro-ecosystems.

A novel ecohydrological model by capturing variations in climate change and vegetation coverage in a semi-arid region of China.

Variations in vegetation are influenced by regional climate regimes and, in turn, control the water balance behavior in water-limited regions. Owing to its role in ecohydrological processes, vegetation is an essential link in modeling the relationships among climate conditions, vegetation patterns, and dynamic water balance behavior. However, previous ecohydrological models have been empirical and complex, without physically significant parameters. Here, we propose a novel ecohydrological model (a Budyko model-coupled vegetation model) that combines the impacts of climate change and vegetation variations, featuring simple and deterministic parameters. In addition to accounting for the fundamental water balance model and its factors, mean precipitation, potential evapotranspiration, runoff, and variations in water storage (δS), the model showed better performance when incorporating δS (RMSE = 2.72 mm yr-1) and its parameter ε -, which is mechanically and quantitively subject to the vegetation coverage (R2 = 0.95, p < 0.01). This was estimated as a function of vegetation potential canopy conductance, mean rainstorm depth, mean time between storms, and potential rate of evapotranspiration in a semi-arid watershed with impulsive precipitation in China (R2 = 0.80, p < 0.01). The model also found that vegetation growth was mainly controlled by soil water content and decoupled the impact of the total amount of precipitation on vegetation in the northeastern area of the watershed. Hence, our method presents a new tool for building an ecohydrological model that includes deterministic parameters of mechanical significance.

CaO-Assisted Alkaline Liquid Waste Drives Corn Stalk Chemical Looping Gasification for Hydrogen Production.

The chemical looping gasification (CLG) process is a promising pathway to produce hydrogen-enriched syngas with biomass. It is urgent to enhance the reactivity and thermal stability of oxygen carriers (OC) and capture the inherently separated CO2. This work presents the strategy of simultaneous modification of a Fe2O3/Al2O3 oxygen carrier and the supplement of an oxidant for corn stalk chemical looping gasification by introducing KNO3-containing ethanol liquid waste. CaO is employed to capture the generated CO2 and promote the reaction balance toward hydrogen production in a fuel reactor (FR). The highest carbon conversion reaction rate of 1.1 × 10-4 mol/g could be obtained at the ratio of CaO to fuel carbon and the reaction temperature of 1.5 and 600 °C, respectively. The kinetics and thermodynamics analyses under the optimized condition are further discussed to verify the possibility and high efficiency of using alkaline organic liquid waste to boost solid fuel gasification for hydrogen production. This CLG strategy shows multifunctional merits, including organic liquid waste treatment, biomass CLG promotion, and hydrogen production enhancement.

Impacts of climate and planting structure changes on watershed runoff and nitrogen and phosphorus loss.

It is important to explore the influence of climate and planting structure change on runoff and nitrogen and phosphorus loss in watersheds, as well as to clarify the quantitative relationship between each influencing factor with runoff, nitrogen and phosphorus to formulate reasonable soil and water conservation measures and reduce non-point source pollution in the watershed. In this study, the Lizixi watershed of the Jialing River was analyzed using a Global Climate Model to generate precipitation and temperature change sequences and the distributed hydrological model SWAT was used to simulate changes in runoff and nitrogen and phosphorus loss processes in the watershed under different climate change scenarios and planting structure changes. The results indicate that the increase in runoff caused by climate change in the next decade will be accompanied by an increase in the loss of total nitrogen and total phosphorus. Planting sweet potato under historical meteorological conditions had the best effect on controlling nitrogen and phosphorus loss in the Lizixi watershed, while large losses of nitrogen and phosphorus were produced when planting wheat and corn. At the same time, there is a positive correlation between the loss of nitrogen and phosphorus and the amount of fertilizer applied. For every 10% increase in fertilizer application, the loss of nitrogen and phosphorus increased by 1% and 4%, respectively. The results presented herein will serve as a reference for regional land use management planning.

Evaluation of the Persistence of Higher-Order Strand Symmetry in Genomic Sequences by Novel Word Symmetry Distance Analysis.

For the ubiquitous phenomenon of strand symmetry, it has been shown that it may persist for higher-order oligonucleotides. However, there is no consensus about to what extent (order of oligonucleotides or length of words) strand symmetry still persists. To determine the extent of strand symmetry in genomic sequences is critically important for the further understanding of the phenomenon. Based on previous studies, we have developed an algorithm for the novel word symmetry distance analysis. We applied it to evaluate the higher-order strand symmetry for 206 archaeal genomes and 2,659 bacterial genomes. Our results show that the new approach could provide a clear-cut criterion to determine the extent of strand symmetry for a group of genomes or individual genomes. According to the new measure, strand symmetry would tend to persist for up to 8-mers in archaeal genomes, and up to 9-mers in bacterial genomes. And the persistence may vary from 6- to 9-mers in individual genomes. Moreover, higher-order strand symmetry would tend to positively correlate with GC content and mononucleotide symmetry levels of genomic sequences. The variations of higher-order strand symmetry among genomes would indicate that strand symmetry itself may not be strictly relevant to biological functions, which would provide some insights into the origin and evolution of the phenomenon.

Health risk assessment of heavy metals in fish and accumulation patterns in food web in the upper Yangtze River, China.

This study aims to concern the distribution of As, Cr, Cd, Hg, Cu, Zn, Pb and Fe in surface sediment, zoobenthos and fishes, and quantify the accumulative ecological risk and human health risk of metals in river ecological system based on the field investigation in the upper Yangtze River. The results revealed high ecological risk of As, Cd, Cu, Hg, Zn and Pb in sediment. As and Cd in fish presented potential human health risk of metals by assessing integrated target hazard quotient results based on average and maximum concentrations, respectively. No detrimental health effects of heavy metals on humans were found by daily fish consumption. While, the total target hazard quotient (1.659) exceeding 1, it meant that the exposed population might experience noncarcinogenic health risks from the accumulative effect of metals. Ecological network analysis model was established to identify the transfer routes and quantify accumulative effects of metals on river ecosystem. Control analysis between compartments showed large predator fish firstly depended on the omnivorous fish. Accumulative ecological risk of metals indicated that zoobenthos had the largest metal propagation risk and compartments located at higher trophic levels were not easier affected by the external environment pollution. CAPSULE: A potential accumulative ecological risk of heavy metal in the food web was quantified, and the noncarcinogenic health risk of fish consumption was revealed for the upper reach of the Yangtze River.

The influence of changes in land use and landscape patterns on soil erosion in a watershed.

It is very important to have a good understanding of the relation between soil erosion and landscape patterns so that soil and water conservation in river basins can be optimized. In this study, this relationship was explored, using the Liusha River Watershed, China, as a case study. A distributed water and sediment model based on the Soil and Water Assessment Tool (SWAT) was developed to simulate soil erosion from different land use types in each sub-basin of the Liusha River Watershed. Observed runoff and sediment data from 1985 to 2005 and land use maps from 1986, 1995, and 2000 were used to calibrate and validate the model. The erosion modulus for each sub-basin was calculated from SWAT model results using the different land use maps and 12 landscape indices were chosen and calculated to describe the land use in each sub-basin for the different years. The variations in instead of the absolute amounts of the erosion modulus and the landscape indices for each sub-basin were used as the dependent and independent variables, respectively, for the regression equations derived from multiple linear regression. The results indicated that the variations in the erosion modulus were closely related to changes in the large patch index, patch cohesion index, modified Simpson's evenness index, and the aggregation index. From the regression equation and the corresponding landscape indices, it was found that watershed erosion can be reduced by decreasing the physical connectivity between patches, improving the evenness of the landscape patch types, enriching landscape types, and enhancing the degree of aggregation between the landscape patches. These findings will be useful for water and soil conservation and for optimizing the management of watershed landscapes.

Ecological risk assessment of heavy metals in sediment in the upper reach of the Yangtze River.

Heavy metal pollution in China's Yangtze River basin has been of high concern. The concentrations of heavy metals (Cr, Cd, Hg, Cu, Zn, Pb, and As) in the sediment were investigated in the upper reaches of the river, China. Sediment quality guidelines (SQGs), an enrichment factor (EF), an index of geo-accumulation (I geo), and potential ecological risk were used to evaluate the extent of contamination from the heavy metal concentrations in the sediment. Among the seven metals, a noticeable degree of pollution was seen only in the case of Cd and Cd posed a considerable ecological risk at some sample sites. The Pearson correlation analysis was implemented to determine the relationships among the heavy metals, and principal component analysis (PCA) was performed to determine the most common pollution sources. The elements As, Cd, Pb, and Zn were grouped together, and the anthropogenic sources of these heavy metals were closely related. The sites with higher Cd concentrations were mainly confined to the river's reach near industrial areas. Controlling the pollution sources will effectively reduce the pollutant concentrations in the sediment.

An integrated environmental decision support system for water pollution control based on TMDL--A case study in the Beiyun River watershed.

This paper details the development and application of an integrated environmental decision support system (EDSS) for water pollution control based on total maximum daily load (TMDL). The system includes an infrastructure, simulation, and application platforms. Using the water pollution control of Beiyun River in China as a case study, the key development processes and technologies of the EDSS are discussed including relations and links between various environmental simulation models, and model integration, visualization and real-time simulation methods. A loose coupling method is used to connect the environmental models, and an XML file is used to complete data exchange between different models. Project configuration and scheme configuration are used for simulation data organization. The integration approach is easy to implement and enables different development languages and reuse of existing models. The EDSS has been applied to water environment management of Beiyun River, and can be applied to other geographic regions.

Persistence and breakdown of strand symmetry in the human genome.

Afreixo, V., Bastos, C.A.C., Garcia, S.P., Rodrigues, J.M.O.S., Pinho, A.J., Ferreira, P.J.S.G., 2013. The breakdown of the word symmetry in the human genome. J. Theor. Biol. 335, 153-159 analyzed the word symmetry (strand symmetry or the second parity rule) in the human genome. They concluded that strand symmetry holds for oligonucleotides up to 6 nt and is no longer statistically significant for oligonucleotides of higher orders. However, although they provided some new results for the issue, their interpretation would not be fully justified. Also, their conclusion needs to be further evaluated. Further analysis of their results, especially those of equivalence tests and word symmetry distance, shows that strand symmetry would persist for higher-order oligonucleotides up to 9 nt in the human genome, at least for its overall frequency framework (oligonucleotide frequency pattern).

Conservation vs. variation of dinucleotide frequencies across bacterial and archaeal genomes: evolutionary implications.

During the long history of biological evolution, genome structures have undergone enormous changes. Nevertheless, some traits or vestiges of the primordial genome (defined as the most primitive nucleic acid genome for life on earth in this paper) may remain in modern genetic systems. It is of great importance to find these traits or vestiges for the study of the origin and evolution of genomes. As the shorter is a sequence, the less probable it would be modified during genome evolution. And if mutated, it would be easier to reappear at the same site or another site. Consequently, the genomic frequencies of very short nucleotide sequences, such as dinucleotides, would have considerable chances to be conserved during billions of years of evolution. Prokaryotic genomes are very diverse and with a wide range of GC content. Therefore, in order to find traits or vestiges of the primordial genome remained in modern genetic systems, we have studied the characteristics of dinucleotide frequencies across bacterial and archaeal genomes. We analyzed the dinucleotide frequency patterns of the whole-genome sequences from more than 1300 prokaryotic species (bacterial and archaeal genomes available as of December 2012). The results show that the frequencies of the dinucleotides AC, AG, CA, CT, GA, GT, TC, and TG are well-conserved across various genomes, while the frequencies of other dinucleotides vary considerably among species. The dinucleotide frequency conservation/variation pattern seems to correlate with the distributions of dinucleotides throughout a genome and across genomes. Further analysis indicates that the phenomenon would be determined by strand symmetry of genomic sequences (the second parity rule) and GC content variations among genomes. We discussed some possible origins of strand symmetry. And we propose that the phenomenon of frequency conservation of some dinucleotides may provide insights into the genomic composition of the primordial genetic system.

Two common profiles exist for genomic oligonucleotide frequencies.

BACKGROUND: It was reported that there is a majority profile for trinucleotide frequencies among genomes. And further study has revealed that two common profiles, rather than one majority profile, exist for genomic trinucleotide frequencies. However, the origins of the common/majority profile remain elusive. Moreover, it is not clear whether the features of common profile may be extended to oligonucleotides other than trinucleotides. FINDINGS: We analyzed 571 prokaryotic genomes (chromosomes) and some selected eukaryotic nuclear genomes as well as other genetic systems to study their compositional features. We found that there are also two common profiles for genomic oligonucleotide frequencies: one is from low-GC content genomes, and the other is from high-GC content genomes. Furthermore, each common profile is highly correlated to the average profile of random sequences with corresponding GC content and generated according to first-order symmetry. CONCLUSIONS: The causes for the existence of two common profiles would mainly be GC content variations and strand symmetry of genomic sequences. Therefore, both GC content and strand symmetry would play important roles in genome evolution.

Heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in seven fish species in relation to fish size and location along the Yangtze River.

PURPOSE: The objective of this paper is to assess the regulation of the accumulation of heavy metals in the aquatic environment and different fish species. METHODS: Water and fish samples were collected from upper to lower reaches of the Yangtze River. The heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in the muscle tissue of seven fishes were measured. Additionally, the relationships between heavy metal concentrations in fish tissue and fish size (length and weight), condition factor, water layer distribution, and trophic level were investigated. RESULTS: Metal concentrations (milligrams per kilogram wet weight) were found to be distributed differently among different fish species. The highest concentrations of Cu (1.22 mg/kg) and Zn (7.55 mg/kg) were measured in Pelteobagrus fulvidraco, the highest concentrations of Cd (0.115 mg/kg) and Hg (0.0304 mg/kg) were measured in Silurus asotus, and the highest concentrations of Pb (0.811 mg/kg) and Cr (0.239 mg/kg) were measured in Carassius auratus and Cyprinus carpio. A positive relationship was found between fish size and metal level in most cases. The variance of the relationships may be the result of differences in habitat, swimming behavior, and metabolic activity. In this study, fishes living in the lower water layer and river bottom had higher metals concentrations than in upper and middle layers. Benthic carnivorous and euryphagous fish had higher metals concentrations than phytoplankton and herbivorous fish. Generally, fish caught from the lower reach had higher metals concentrations than those from the upper reach. CONCLUSIONS: Cadmium and lead concentrations in several fishes exceeded the permissible food consumption limits, this should be considered to be an important warning signal.