Structure and mechanism of human diacylglycerol O-acyltransferase 1.

Diacylglycerol O-acyltransferase 1 (DGAT1) synthesizes triacylglycerides and is required for dietary fat absorption and fat storage in humans1. DGAT1 belongs to the membrane-bound O-acyltransferase (MBOAT) superfamily, members of which are found in all kingdoms of life and are involved in the acylation of lipids and proteins2,3. How human DGAT1 and other mammalian members of the MBOAT family recognize their substrates and catalyse their reactions is unknown. The absence of three-dimensional structures also hampers rational targeting of DGAT1 for therapeutic purposes. Here we present the cryo-electron microscopy structure of human DGAT1 in complex with an oleoyl-CoA substrate. Each DGAT1 protomer has nine transmembrane helices, eight of which form a conserved structural fold that we name the MBOAT fold. The MBOAT fold in DGAT1 forms a hollow chamber in the membrane that encloses highly conserved catalytic residues. The chamber has separate entrances for each of the two substrates, fatty acyl-CoA and diacylglycerol. DGAT1 can exist as either a homodimer or a homotetramer and the two forms have similar enzymatic activity. The N terminus of DGAT1 interacts with the neighbouring protomer and these interactions are required for enzymatic activity.

Effects of physical activity on infertility in reproductive females.

OBJECTIVES: To explore the relationship between different types of physical activity and female infertility. METHODS: This study analyzed data from 2,796 female participants aged 18-44 years in the United States, obtained from the National Health and Nutrition Examination Survey (NHANES) database spanning the years 2013 to 2020. Multiple logistic regression analyses and generalized linear models were used to explore the relationship between different types of physical activity and infertility after adjusting for potential confounding factors. RESULTS: We found a non-linear relationship between recreational activities and infertility with an inflection point of 5.83 h/week (moderate intensity), while work activities and traffic-related activities did not. On the left side of the inflection point, there was no significant association between recreational activity time and infertility (OR = 0.93, 95% CI: 0.86 to 1.02, P = 0.1146), but on the right side of the inflection point, there was a positive association between recreational activity time and the risk of infertility (OR = 1.04, 95% CI: 1.02 to 1.06, P = 0.0008). CONCLUSIONS: The relationship between different types of physical activity and female infertility varies. We acknowledge the potential influence of confounding variables on this relationship. However, we have already adjusted for these potential variables in our analysis. Therefore, our findings suggest that appropriate recreational activity programs are essential for promoting reproductive health in women of reproductive age. Nevertheless, it is important to note that the observed association does not imply causality. Given the limitations of cross-sectional studies, further prospective cohort studies are needed to explore the causal relationship while accounting for additional confounding factors.

Current status and continuing medical education need for general practitioners in Tibet, China: a cross-sectional study.

BACKGROUND: The Tibetan area is one of China's minority regions with a shortage of general practice personnel, which requires further training and staffing. This research helps to understand the current condition and demand for general practitioner (GP) training in Tibetan areas and to provide a reference for promoting GP education and training. METHODS: We conducted a cross-sectional survey using stratified sampling targeting 854 GPs in seven cities within the Tibetan Autonomous Region, utilizing an online questionnaire. Achieving a high response rate of 95.1%, 812 GPs provided invaluable insights. Our meticulously developed self-designed questionnaire, available in both Chinese and Tibetan versions, aimed to capture a wide array of data encompassing basic demographics, clinical skills, and specific training needs of GPs in the Tibetan areas. Prior to deployment, the questionnaire underwent rigorous development and refinement processes, including expert consultation and pilot testing, to ensure its content validity and reliability. In our analysis, we employed descriptive statistics to present the characteristics and current training needs of GPs in the Tibetan areas. Additionally, chi-square tests were utilized to examine discrepancies in training needs across various demographic groups, such as age, job positions, and educational backgrounds of the participating GPs. RESULTS: The study was completed by 812 (812/854, 95.1%) GPs, of whom 62.4% (507/812) were female. The top three training needs were hypertension (81.4%, 661/812), pregnancy management (80.7%, 655/812), and treatment of related patient conditions and events (80.5%, 654/812). Further research shows that the training required by GPs of different ages in "puncturing, catheterization, and indwelling gastric tube use" (64.6% vs. 54.8%, p = 9.5 × 10- 6) varies statistically. GPs in various positions have different training needs in "community-based chronic disease prevention and management" (76.6% vs. 63.9%, p = 0.009). The training needs of GPs with different educational backgrounds in "debridement, suturing, and fracture fixation" (65.6% vs. 73.2%, p = 0.027) were also statistically significant. CONCLUSIONS: This study suggests the need for targeted continuing medical education activities and for updating training topics and content. Course developers must consider the needs of GPs, as well as the age, job positions, and educational backgrounds of GPs practicing in the Tibetan Plateau region. TRIAL REGISTRATION: Not applicable.

Alternative splicing of OsGS1;1 affects nitrogen-use efficiency, grain development, and amylose content in rice.

Excessive nitrogen fertilizer application is harmful to the environment and reduces the quality of cereal crops. Maintaining crop yields under low nitrogen (LN) conditions and improving quality are important goals for cereal crop breeding. Although the effects of nitrogen assimilation on crop nitrogen-use efficiency (NUE) have been intensively studied, natural variations of the key assimilation genes underlying grain development and quality are largely unclear. Here, we identified an NUE-associated gene, OsGS1;1, encoding glutamine synthase, through genome-wide association analysis, followed by validation experiments and functional analysis. Fifteen single-nucleotide polymorphisms in the OsGS1;1 region led to alternative splicing that generated two functional transcripts: OsGS1;1a and OsGS1;1b. The elite haplotype of OsGS1;1 showed high OsGS1;1b activity, which improved NUE, affected grain development, and reduced amylose content. The results show that OsGS1;1, which is induced under LN conditions, affects grain formation by regulating sugar metabolism and may provide a new avenue for the breeding of high-yield and high-quality rice (Oryza sativa).

Phylogenetic insight into the origin of tones.

The origin of tone, also known as tonogenesis, has long been a topic of great interest in language evolution and human cognition studies. Several linguistic studies of tonal languages have proposed various hypotheses that tonal origin may be related to different changes of phonological structures. However, such hypotheses have not been quantitatively tested in an evolutionary framework. Here, we conducted phylogenetic comparative analyses to assess the likelihood of different hypotheses of tonogenetic mechanisms across 106 Sino-Tibetan languages, of which approximately 70% are tonal. Our results showed that the presence of tones has a strong phylogenetic pattern and that Proto-Sino-Tibetan languages were most likely non-tonal. Our findings identified that tonal origin was strongly associated with the evolution of specific phonological structures, such as the loss of syllable-final consonants and voice quality on vowels. Furthermore, we found that tonal origin probably did not influence the diversification rates of Sino-Tibetan languages. These findings enabled us to better understand that tone arose as a compensatory mechanism for the structural organization and evolution of languages.

Enhanced CycleGAN Network with Adaptive Dark Channel Prior for Unpaired Single-Image Dehazing.

Unpaired single-image dehazing has become a challenging research hotspot due to its wide application in modern transportation, remote sensing, and intelligent surveillance, among other applications. Recently, CycleGAN-based approaches have been popularly adopted in single-image dehazing as the foundations of unpaired unsupervised training. However, there are still deficiencies with these approaches, such as obvious artificial recovery traces and the distortion of image processing results. This paper proposes a novel enhanced CycleGAN network with an adaptive dark channel prior for unpaired single-image dehazing. First, a Wave-Vit semantic segmentation model is utilized to achieve the adaption of the dark channel prior (DCP) to accurately recover the transmittance and atmospheric light. Then, the scattering coefficient derived from both physical calculations and random sampling means is utilized to optimize the rehazing process. Bridged by the atmospheric scattering model, the dehazing/rehazing cycle branches are successfully combined to form an enhanced CycleGAN framework. Finally, experiments are conducted on reference/no-reference datasets. The proposed model achieved an SSIM of 94.9% and a PSNR of 26.95 on the SOTS-outdoor dataset and obtained an SSIM of 84.71% and a PSNR of 22.72 on the O-HAZE dataset. The proposed model significantly outperforms typical existing algorithms in both objective quantitative evaluation and subjective visual effect.

Photoelectrochemical Performance Improving Mechanism: Hybridization Appearing at the Energy Band of BiVO4 Photoanode by Doped Quantum Layers Modification.

Surface passivation of the photoelectrode by wide bandgap semiconductor quantum layer is an important strategy to improve work stability and surface state inhibition. However, an inevitable energy barrier is generated during the quantum tunneling process of the photocarriers. To overcome this shortage, a tandem photo-generated hole transfer route is fabricated on BiVO4 photoanode by doped dual-quantum layers modification, Ni-ZnO (5 nm) and Rh-SrTiO3 (≈10 nm). Modulated photoelectrochemical (PEC), Scanning Kelvin Probe (SKP), and DFT calculation method results indicate that a tandem hole ohmic contact route is formed in the photoanode to reduce the quantum tunneling energy barrier, meanwhile, the photon absorption capacity of BiVO4 is improved after doped quantum layers modification. Both a phenomenal attribute to the energy band hybridization between Ni, Rh 3d orbits in quantum layers with BiVO4 photoanode. Then, the modified BiVO4 photoanode achieves the recoded photocurrent density of 6.47 and 5.18 mA cm-2 (Na2 SO3 electrolyte, VRHE  = 1.23 V) under simulated sun light (100 mW cm-2 AM 1.5 G) by xenon lamp illumination without and with UV composition cutting down to ≈5%, respectively. Generally, this work will highlight a potential application in the fields of PEC water splitting and photovoltaic conversion for various semiconductor nanomaterials.

Religious celibacy brings inclusive fitness benefits.

The influence of inclusive fitness interests on the evolution of human institutions remains unclear. Religious celibacy constitutes an especially puzzling institution, often deemed maladaptive. Here, we present sociodemographic data from an agropastoralist Buddhist population in western China, where parents sometimes sent a son to the monastery. We find that men with a monk brother father more children, and grandparents with a monk son have more grandchildren, suggesting that the practice is adaptive. We develop a model of celibacy to elucidate the inclusive fitness costs and benefits associated with this behaviour. We show that a minority of sons being celibate can be favoured if this increases their brothers' reproductive success, but only if the decision is under parental, rather than individual, control. These conditions apply to monks in our study site. Inclusive fitness considerations appear to play a key role in shaping parental preferences to adopt this cultural practice.

Magnetic Compression Technique for Esophageal Anastomosis in Rats.

INTRODUCTION: The magnetic compression technique (MCT) is used for the anastomosis of hollow organs by the means of suction between magnets. The MCT is useful for establishing digestive tract anastomoses in rats, for example, end-to-side small intestinal anastomosis and colonic anastomosis. We aim to determine the feasibility of MCT-based esophageal anastomosis in rats. METHODS: Twenty-four Sprague-Dawley albino rats (230-250 g) were randomly divided into an MCT group and a control group (hand-sewn esophageal anastomosis). The time required to construct the anastomosis, postoperative complications, and survival rate was compared between the two groups. At 2 wk postoperatively, the animals were sacrificed to assess the burst pressure and histological features of the anastomoses. RESULTS: The mean anastomosis time was significantly lower for MCT (11.17 ± 1.64 min) than for the hand-sewn technique (27.42 ± 2.23 min; P < 0.001). The survival rate was slightly higher in the MCT group (91.67%) than in the control group (66.67%, P = 0.317). The magnets were discharged from the body after 8.33 ± 0.89 d (range, 7-10 d). No anastomotic leakage or stenosis occurred in the MCT group. Three rats developed anastomotic stenosis and two rats developed anastomotic leakage in the control group. The burst pressures were similar in the two groups. An histological examination showed that compared with the control group, the MCT group had better alignment of the tissue layers and less inflammation. CONCLUSIONS: The MCT is a simple and feasible technique for esophageal anastomosis in rats and has the potential for clinical application.

Creation of gastroenteric anastomosis through natural orifice in rats by magnetic compression technique.

BACKGROUND: Being one of the core techniques of magnetic surgery, magnetic compression technique (MCT) has been used for digestive tract anastomosis reconstruction in experimental studies. This study verified the feasibility of gastroenteric anastomosis through natural orifice using MCT in rats. METHODS: The parent and daughter magnets were designed and manufactured for oral and anal insertion in 20 Sprague-Dawley rats. After anesthesia, the parent magnet was inserted into the colon spleen area through the anus, and the daughter magnet was inserted into the stomach through the mouth. Then the two magnets were positioned to attract each other and bind together. The position of the two magnets was monitored using X-ray. The time required for the formation of the anastomosis and expulsion of the magnets were recorded. 2 weeks later, the animal was sacrificed and the anastomotic specimen was obtained which was observed under naked eye and microscope. RESULTS: The gastroenteric anastomosis was successfully performed via natural orifices in 18 out of 20 rats. The mean time to construct the anastomosis was 3.78 ± 0.88 min. X-ray examination showed that the magnets were in the appropriate position in 17 rats. The magnets were excreted in 9.47 ± 1.62 days after surgery. The gross and microscopic examination of the specimen showed that the anastomoses were patent and the mucosa at the anastomotic was smooth. The mean bursting pressure of the anastomosis was 136.94 ± 6.79 mmHg. CONCLUSION: It is feasible to perform gastroenteric anastomosis through natural orifices by MCT.

Efficient side-chain deacylation of polymyxin B1 in recombinant Streptomyces strains.

OBJECTIVES: Polymyxins are antibacterial polypeptides used as "last resort" therapy option for multidrug-resistant Gram-negative bacteria. The expansion of polymyxin-resistant infections has inspired development of novel polymyxin derivatives, and deacylation is one of the critical steps in generating those antibiotics. Deacylase from Actinoplanes utahensis hydrolyze the acyl moieties of echinocandins, and also efficiently deacylates daptomycin, ramoplanin and other important antibiotics. Here, deacylase was studied considering its potential usefulness in deacylating polymyxin B1. RESULTS: All the six recombinant strains containing the deacylase gene catalyzed hydrolysis of polymyxin B1, yielding cyclic heptapeptides. The efficiency of recombinant S. albus (SAL701) was higher than that of the others, and deacylation was the most efficient at 40 °C in 0.2 M Tris buffer (pH 8.0) with 0.2 M Mg2+. The optimal substrate concentration of SAL701 was increased from 2.0 to 6.0 g/L. SAL701 was highly thermostable, showing no loss of activity at 50 °C for 12 h, and the mycelia could be recycled at least three times without loss of catalytic activity. SAL701 could not deacylate ß-lactam substrate such as penicillin G and cephalosporin C. Deacylase catalyzes the amide bond 1 closest to the nucleus of polymyxin B1 rather than the other bond, suggesting that it has high catalytic site specificity. Homology modeling and the docking results implied that Thr190 in deacylase could facilitate hydrolysis with high regioselectivity. CONCLUSIONS: These results show that SAL701 is effective in increasing the cyclic heptapeptide moiety of polymyxin B1. These properties of the biocatalyst may enable its development in the industrial production of polymyxins antibiotics.

[Design of Magnamosis System for Endoscopic Tissue Clamping].

Based on the principle of magnetic anastomosis technique, the design of magnetic anastomosis system for endoscopic tissue clamping is proposed. The system includes a semi-ring magnet, a special structure transparent cap and a detachable push rod. With the help of the existing digestive endoscopy and endoscopic tissue gripper, the endoscopic close clamping and anastomosis of the bleeding or perforated tissue can be completed. After the anastomosis, the magnet falls off and is discharged through the digestive tract. Animal experiments showed that the system was easy to use, the fistula was clamped firmly, the magnet was discharged for 7~21 days, and there was no magnet retention and digestive tract obstruction. Further safety verification, optimization of endoscopic operation, the system can be used in clinical trial.

The quality of primary care in community health centers: comparison among urban, suburban and rural users in Shanghai, China.

OBJECTIVE: Following World Health Organization's initiatives to advance primary care, China put forth forceful policies including the Personal Family Doctor Contract to ensure that every family sign up with a qualified doctor in a community health center (CHC) ever since its 2009 New Health Reform. We used the Johns Hopkins-designed Primary Care Assessment Tool (PCAT) to assess primary care quality experienced by the contracted residents and compare this across different socioeconomic regions. METHODS: Using a multistage sampling method, four CHCs each were randomly selected from urban, suburban and rural districts of Shanghai, a metropolitan with 24 million residents. ANOVA and Multivariate analyses were used to assess the association between location of CHC and the quality of primary care experience. FINDINGS: A total of 2404 CHC users completed our survey. Except for the domain of coordination (information systems), users from suburban CHCs reported best primary care experiences in all other domains, followed by users of rural CHCs. After controlling for covariates, suburban CHC users were more likely to report higher total PCAT scores (ß = 1.57, P <  0.001) compared with those from urban CHCs. CONCLUSION: That contracted residents from suburban CHCs reporting better primary care experience than those from urban CHCs demonstrates the unique value of CHCs in relatively medical-underserved areas. In particular, urban CHCs could further strengthen first contact (utilization), first contact (accessibility), coordination (referral system), comprehensiveness (available), and community orientation aspects of primary care performance. However, all CHCs could improve coordination (information system).

Effects of iron oxide nanoparticles on Fe and heavy metal accumulation in castor (Ricinus communis L.) plants and the soil aggregate.

In this study, the effects of iron (Fe) nanoparticles (NPs) on Fe and heavy metal accumulations by castor (Ricinus communis L.) plants were investigated. The castor cultivar was planted in the soil contaminated with Pb and Zn for 48 days with Fe2O3 NPs treatments. The Fe and heavy metal concentrations in the plant tissues, the plant tissues' ultrastructures, and the Fe and heavy metal distributions in the soil aggregate were analyzed. The results of this study indicate that there is a mutual promotion relationship between Fe and heavy metals (Pb and Zn). The scanning electron microscopy (SEM) revealed ultrastructural differences in the xylem and phloem with Fe2O3 NPs addition, and the presence of Fe2O3 NPs may influence the synthesis of starch granules in response to heavy metal stress. Based on the analysis of the soil aggregate, α-Fe2O3 NPs and γ-Fe2O3 NPs changed the size distribution of the soil aggregate, that is, the macro-aggregate and the clay fraction contents increased and the micro-aggregate content decreased. Moreover, in the different size fractions of the soil aggregate, Fe2O3 NPs can change the Zn and Fe enrichment and migration between the macro-aggregate and clay fractions, and there is a synergistic effect between the Fe and Zn migration. In addition, in the castor organs (roots and shoots), the Zn accumulation was mainly determined by the Zn concentration of the macro-aggregate fraction, while the Fe accumulation was mainly determined by the Fe concentration of the micro-aggregate fraction. Overall, these direct observations help improve our understanding of the migration and transport characteristics of Fe and heavy metals in soil-plant systems when Fe nanoparticles are added to metal-contaminated soils.

A Biocompatible Multilayer Film from an Asymmetric Picolinium-Containing Polycation with Fast Visible-Light/NIR-Degradability.

Finely tuning the photodegradation behavior of the layer-by-layer (LbL) film from the view of controlling the chemical structure of the film-building polymer is still a challenge in related fields. To meet this requirement, a photodegradable polymer (P1) is rationally designed for assembling a visible-light-degradable multilayer film with polystyrene sulfonate (PSS). Compared with similar photopolymers (P2 and P3), this asymmetric picolinium-containing polymer can significantly enhance the degradation rate of as-prepared LbL films; under the same degradation condition, the degradation rate of (P1/PSS)10 is 3 and 6.6 times that of (P2/PSS)10 and (P3/PSS)10, respectively. Moreover, near-infrared light (NIR) is available for triggering the degradation of this film with the assistance of upconversion nanoparticles of YbTm@Lu. The cell cytotoxicity and cell proliferation experiments reveal that P1 is nontoxic and favorable for cell proliferation at concentrations of up to 500 µg mL-1 . As for (PSS/P1)10 films, the ratio of cell number of these two samples ((PSS/P1)10 modified: photodegraded) increases dramatically and reaches about 1.67:1 after 72 h incubation. On the basis of these results, it is anticipated that P1 and this LbL film is an exceptional candidate for visible-light/NIR degradable materials in materials and biological science, medicine, and optics.

A Transparent, Highly Stretchable, Autonomous Self-Healing Poly(dimethyl siloxane) Elastomer.

An innovative self-healing polydimethylsiloxane (PDMS) elastomer, namely, PDMS-TFB, is reported by incorporating the reversibly dynamic imine bond as the self-healing points into the PDMS networks. The PDMS-TFB elastomer features good optical transmittance (80%) in full visible light region, high stretchability (≈700%), and excellent autonomous self-healing ability at room temperature. Surprisingly, the self-healing behavior can take place in water and even at a temperature as low as -20 °C in air, showing a promising outlook for broader applications. As a proof-of-concept, this study demonstrates the use of the PDMS-TFB elastomer for preparing anticorrosion coating and adhesive layer, and also the use of such an elastomer to be the platform for fabricating the flexible interconnector and chemical sensor. Remarkably, no significant difference is observed between the pristine and healed samples. Taking full advantage of these unique properties, it is anticipated that such a PDMS-TFB elastomer shows wide applications in the fields of materials science, electronics, biology, optics, etc.

Comparison of chelates for enhancing Ricinus communis L. phytoremediation of Cd and Pb contaminated soil.

We studied chelate effects on castor bean (Ricinus communis L.) growth. These effects included Cd and Pb accumulation in plant tissues and the chemical behavior of Cd and Pb in the plant rhizosphere and non-rhizosphere. Tests were conducted in a glasshouse using the rhizobag method. Two castor bean cultivars (Zibo-3 and Zibo-9) were grown in soil contaminated with 3.53mg/kg Cd and 274mg/kg Pb. The soil was treated with citric acid (CA), ethylenediamine disuccinic acid (EDDS) or ethylenediamine tetraacetic acid (EDTA) (5mmol/kg). EDDS-treated soil produced 28.8% and 59.4% greater biomass for Zibo-3 and Zibo-9 respectively. In contrast, CA and EDTA inhibited the growth of the two cultivars. Zibo-9 had greater tolerance than Zibo-3 to chelate toxicity. Based on Cd and Pb plant uptake, EDDS could substitute for EDTA for phytoremediation of Cd in soil. EDTA was the most effective of the three chelates for Pb phytoremediation but it is less suitable for field use due to toxicology environmental persistence. Acid extractable Cd and Pb in the rhizosphere or reducible Cd and Pb in the non-rhizosphere of soil were the main influences on Cd and Pb accumulation in castor bean.

Interaction between sulfur and lead in toxicity, iron plaque formation and lead accumulation in rice plant.

Human activities have resulted in lead and sulfur accumulation in paddy soils in parts of southern China. A combined soil-sand pot experiment was conducted to investigate the influence of S supply on iron plaque formation and Pb accumulation in rice (Oryza sativa L.) under two Pb levels (0 and 600 mg kg(-1)), combined with four S concentrations (0, 30, 60, and 120 mg kg(-1)). Results showed that S supply significantly decreased Pb accumulation in straw and grains of rice. This result may be attributed to the enhancement of Fe plaque formation, decrease of Pb availability in soil, and increase of reduced glutathione (GSH) in rice leaves. Moderate S supply (30 mg kg(-1)) significantly increased Fe plaque formation on the root surface and in the rhizosphere, whereas excessive S supply (60 and 120 mg kg(-1)) significantly decreased the amounts of iron plaque on the root surface. Sulfur supply significantly enhanced the GSH contents in leaves of rice plants under Pb treatment. With excessive S application, the rice root acted as a more effective barrier to Pb accumulation compared with iron plaque. Excessive S supply may result in a higher monosulfide toxicity and decreased iron plaque formation on the root surface during flooded conditions. However, excessive S supply could effectively decrease Pb availability in soils and reduce Pb accumulation in rice plants.

Subcellular cadmium distribution and antioxidant enzymatic activities in the leaves of two castor (Ricinus communis L.) cultivars exhibit differences in Cd accumulation.

The aims of this study were: (1) the study of cadmium (Cd) accumulation and toxicity in different castor cultivars (Ricinus communis L.); (2) to investigate changes in antioxidant enzymatic activities and the subcellular distribution of Cd in young and old leaves from two different castor cultivars, after exposure to two different Cd concentrations, and explore the underlying mechanism of Cd detoxification focusing on antioxidant enzymes and subcellular compartmentalization. The Cd concentration, toxicity, and subcellular distribution, as well as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were measured in Zibo-3 and Zibo-9 cultivars after exposure to two different concentrations of Cd (2mg/L and 5mg/L) for 10 days. This research revealed Cd accumulation characteristics in castor are root>stem>young leaf>old leaf. Castor tolerance was Cd dose exposure and the cultivars themselves dependent. Investigation of subcellular Cd partitioning showed that Cd accumulated mainly in the heat stable protein (HSP) and cellular debris fractions, followed by the Cd rich granule (MRG), heat denatured protein (HDP), and organelle fractions. With increasing Cd concentration in nutrient solution, the decreased detoxified fractions (BDM) and the increased Cd-sensitive fractions (MSF) in young leaves may indicate the increased Cd toxicity in castor cultivars. The BDM-Cd fractions or MSF-Cd in old leaves may be linked with Cd tolerance of different cultivars of castor. The antioxidant enzymes that govern Cd detoxification were not found to be active in leaves. Taken together, these results indicate Cd tolerance and toxicity in castor can be explained by subcellular partitioning.

Cadmium accumulation and tolerance of two castor cultivars in relation to antioxidant systems.

To investigate the effects of Cd on tolerance and antioxidant activities of castor, two different castor (Ricinus communis L.) cultivars (Zibo No. 5 and Zibo No. 8) were used for a hydroponic experiment (0, 1 and 2mg/L Cd) and a pot experiment using Cd-contaminated soil (34mg/kg) with the addition of ethylenedinitrilotetraacetic acid (EDTA). The results indicated that there were significant differences between the two cultivars with respect to Cd uptake in shoots (113-248mg/kg for Zibo No. 5 and 130-288mg/kg Zibo No. 8), biomass tolerance indexes (64.9%-74.6% for Zibo No. 5 and 80.1%-90.9% for Zibo No. 8) in the hydroponic experiment and survival rates (0% for Zibo No. 5 and 100% for Zibo No. 8) determined by the addition of EDTA in the pot experiment, suggesting that Zibo No. 8 has higher tolerance than Zibo No. 5. Moreover, the castor cultivars have low bioconcentration factors (4.80% for Zibo No. 5 and 5.43% for Zibo No. 8) and low translocation factors (<1%). Consequently, Zibo No. 8 can participate in Cd phytostabilization in highly Cd-polluted areas. The results indicated that glutathione (GSH) as a non-enzymatic antioxidant, and antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GPX), were cultivar- and dose-dependent. The higher tolerance of Zibo No. 8 compared with Zibo No. 5 can be attributed to the higher GSH levels in the root and higher GPX activity in the leaf.