Octahedral Distortion and Displacement-Type Ferroelectricity with Switchable Photovoltaic Effect in a 3d^{3}-Electron Perovskite System

Because of the half-filled t_{2g}-electron configuration, the BO_{6} octahedral distortion in a 3d^{3} perovskite system is usually very limited. In this Letter, a perovskitelike oxide Hg_{0.75}Pb_{0.25}MnO_{3} (HPMO) with a 3d^{3} Mn^{4+} state was synthesized by using high pressure and high temperature methods. This compound exhibits an unusually large octahedral distortion enhanced by approximately 2 orders of magnitude compared with that observed in other 3d^{3} perovskite systems like RCr^{3+}O_{3} (R=rare earth). Essentially different from centrosymmetric HgMnO_{3} and PbMnO_{3}, the A-site doped HPMO presents a polar crystal structure with the space group Ama2 and a substantial spontaneous electric polarization (26.5  μC/cm^{2} in theory) arising from the off-center displacements of A- and B-site ions. More interestingly, a prominent net photocurrent and switchable photovoltaic effect with a sustainable photoresponse were observed in the current polycrystalline HPMO. This Letter provides an exceptional d^{3} material system which shows unusually large octahedral distortion and displacement-type ferroelectricity violating the "d^{0}-ness" rule.

Leaf trait association in relation to herbivore defense, drought resistance, and economics in a tropical invasive plant

PREMISE

Exploring how functional traits vary and covary is important to understand plant responses to environmental change. However, we have limited understanding of the ways multiple functional traits vary and covary within invasive species.

METHODS

We measured 12 leaf traits of an invasive plant Chromolaena odorata, associated with plant or leaf economics, herbivore defense, and drought resistance on 10 introduced populations from Asia and 12 native populations from South and Central America, selected across a broad range of climatic conditions, and grown in a common garden.

RESULTS

Species' range and climatic conditions influenced leaf traits, but trait variation across climate space differed between the introduced and native ranges. Traits that confer defense against herbivores and drought resistance were associated with economic strategy, but the patterns differed by range. Plants from introduced populations that were at the fast-return end of the spectrum (high photosynthetic capacity) had high physical defense traits (high trichome density), whereas plants from native populations that were at the fast-return end of the spectrum had high drought escape traits (early leaf senescence and high percentage of withered shoots).

CONCLUSIONS

Our results indicate that invasive plants can rapidly adapt to novel environmental conditions. Chromolaena odorata showed multiple different functional trait covariation patterns and clines in the native and introduced ranges. Our results emphasize that interaction between multiple traits or functions should be considered when investigating the adaptive evolution of invasive plants.

[Energy metabolism characteristic with risk of secondary bacterial infection in patients with hepatitis B virus-related chronic liver disease]

Objective: To investigate and analyze the energy metabolism characteristics and the correlation between energy metabolism and the risk of secondary bacterial infection in patients with hepatitis B virus-related chronic liver disease (HBV-CLD). Methods: Data of 183 cases admitted to the Mengchao Hepatobiliary Hospital of Fujian Medical University from November 2017 to November 2020 were retrospectively analyzed. 79 cases of chronic hepatitis B, 51 cases of hepatitis B-related liver cirrhosis, and 53 cases of hepatitis B-related liver failure were collected. Among them patients with liver failure and decompensated liver cirrhosis were defined as severe liver disease group. The Quark RMR indirect calorimetry (COSMED Corporation, Italy) was used to exam the patients' energy metabolism condition, and the incidences of secondary bacterial infection of the patients during hospitalization were recorded. Shapiro-Wilk test and normal QQ plot were used to analyze the normal distribution of continuous variable data, which was consistent with the normal distribution and was described by mean ± standard deviation. In addition, if it did not conform to the normal distribution, the median and interquartile distance were used to describe it. Levene's test was used to test the homogeneity of variance of the data, which was consistent with the normal distribution. The t-test was used to compare the means of the two groups of samples. One-way analysis of variance was used to compare the mean values of the three groups of samples, and then the Tukey's test was used to compare the two groups. If the variance was uneven or did not conform to the normal distribution, the Wilcoxon rank sum test was used to compare the differences between the two groups. Kruskal-Wallis test (H test) was used to compare the differences between the three groups of samples, and then the Dunnett's test (Z test) was used for comparison between the two groups. Categorical variable data were analyzed using chi-square test. Logistic regression analysis was used to screen independent risk factors, and the criteria for variable inclusion (P < 0.05). Results: The respiratory entropy (RQ) and non-protein respiratory entropy (npRQ) of the three groups had statistically significant difference (P < 0.05). Among them, the RQ and npRQ of the chronic hepatitis B group were higher than hepatitis B-related liver cirrhosis group and hepatitis B-related liver failure group. There were statistically significant differences in fat oxidation rate (FAT%) and carbohydrate oxidation rate (CHO%) between the three groups (P < 0.05). Compared with hepatitis B-related liver cirrhosis group and hepatitis B-related liver failure group, chronic hepatitis B group (P < 0.05) had lower FAT% and higher CHO%. There were no statistically significant differences in the measured and predicted resting energy expenditure and protein oxidation rate (PRO%) between the three groups. The incidence of secondary bacterial infection in patients with severe liver disease was 48.39% (45/93). Compared with the non-infected group, the RQ and npRQ values ​​of the infected group were significantly decreased (P < 0.05), while FAT% was significantly increased (P < 0.05). Logistic regression analysis showed that glutamyltransferase, cholesterol, and npRQ were independent risk factors for secondary bacterial infections in patients with severe liver disease. Glutamyltransferase elevation, and cholesterol and npRQ depletion had suggested an increased risk of secondary bacterial infection. Subgroup analysis of patients with hepatitis B-related liver failure also showed that compared with non-infected group, RQ value and npRQ value of secondary bacterial infection group were significantly decreased (P < 0.05), while FAT% was significantly increased (P < 0.05). Conclusion: Patients with hepatitis B virus-related chronic liver disease generally have abnormal energy metabolism. Low RQ, npRQ, CHO% and high FAT% are related to the severity of the disease; while npRQ reduction is related to the risk of secondary bacterial infection in patients with severe liver disease, and thus can be used as a clinical prognostic indicator.

Rapid genomic and phenotypic change in response to climate warming in a widespread plant invader

Predicting plant distributions under climate change is constrained by our limited understanding of potential rapid adaptive evolution. In an experimental evolution study with the invasive common ragweed (Ambrosia artemisiifolia L.) we subjected replicated populations of the same initial genetic composition to simulated climate warming. Pooled DNA sequencing of parental and offspring populations showed that warming populations experienced greater genetic divergence from their parents, than control populations. In a common environment, offspring from warming populations showed more convergent phenotypes in seven out of nine plant traits, with later flowering and larger biomass, than plants from control populations. For both traits, we also found a significantly higher ratio of phenotypic to genetic differentiation across generations for warming than for control populations, indicating stronger response to selection under warming conditions. As a measure for evolutionary rate, the phenotypic and sequence divergence between generations were assessed using the Haldane metric. Our approach combining comparisons between generations (allochronic) and between treatments (synchronic) in an experimental evolutionary field study, and linking population genomic data with phenotyping analyses provided a powerful test to detect rapid responses to selection. Our findings demonstrate that ragweed populations can rapidly evolve in response to climate change within a single generation. Short-term evolutionary responses to climate change may aggravate the impact of some plant invaders in the future and should be considered when making predictions about future distributions and impacts of plant invaders.

[Establishment of nutrition literacy core items for Chinese people]

Objective: To establish core items of nutrition literacy for general population in China. Methods: The framework system and preliminary items of nutrition literacy were established through literature review and experts' consultation. Content validity test was used to determine the nutrition literacy item. Thirteen experts in the field of human nutrition, health education and nutrition and diseases were invited to score the importance of each nutrition literacy item via Email. The judgment basis and familiarity of experts towards the items, active coefficient, and content validity were analyzed to generate the final list of nutrition literacy items. Results: 92.3% of questionnaires in two rounds were collected.The active coefficient of experts was satisfied and the authority coefficient was 0.96.In the content validity evaluation, the correlation I-CVI value of each item was above 0.83 and the κ value was above 0.74. The evaluation result was excellent.After the second round of expert consultation, all selected items met the inclusion criteria. We identified the final list of nutrition literacy items consisting of three scales (knowledge and concepts, lifestyles and dietary behaviors, and basic skills), ten subscales (basic nutrition philosophy, food classification and nutrition knowledge, healthy weight, eating behavior and culture, balanced diet, exercise health, food assessment, nutrition information acquisition and decision, nutrition safety, and weight management)with 25 items in total. Conclusions: The framework system and core items of nutrition literacy are established for Chinese people based on the content validity evaluation. The experts involved in the consultation process present a performance with good representativeness, enthusiasm and authority, and the content validity evaluation result is satisfied.

[Establishment of nutrition literacy core items for Chinese old people]

Objective: To establish the nutrition literacy core items for older people in China. Methods: The framework system and preliminary items of nutrition literacy were established through literature review and experts consultation. Content validity test was used to determine the nutrition literacy items. Seven experts in the field of human nutrition, health education and nutrition and diseases were invited to score the importance of each nutrition literacy item via Email. The judgment basis and familiarity of expertstowards the items, active coefficient, and content validitywere evaluated and analyzed to generate the final list of nutritionliteracy items. Results: A total of 85.7% (6/7) of questionnaires in two rounds were collected.The active coefficient of experts was satisfied and the authority coefficient was 0.96. In the content validity evaluation, the correlation I-CVI value of each item was above 0.90 and theκvalue was above 0.74. The evaluation result was excellent. After the second round of consultation, all selected items met the inclusion criteria. We identified the final list of nutrition literacy items consisting of three scales (knowledge and concepts, lifestyles and dietary behaviors, and basic skills), twelve subscales (reasonable nutrition, healthy weight, environment of dining, food classification, nutrition and disease, eat regularly, balanced diet, exercise health, information getting, household food measurement, reading nutrition label and calculating, and food safety)with 20 items in total. Conclusions: The framework system and core items of nutrition literacy are established for Chinese older people based on the content validity evaluation. The experts involved in the consultation process present a performance with good representativeness, enthusiasm and authority, and the content validity evaluation result is satisfied.

Spin-Canting-Induced Band Reconstruction in the Dirac Material Ca_{1-x}Na_{x}MnBi_{2}

The ternary AMnBi_{2} (A is alkaline as well as rare-earth atom) materials provide an arena for investigating the interplay between low-dimensional magnetism of the antiferromagnetic MnBi layers and the electronic states in the intercalated Bi layers, which harbor relativistic fermions. Here, we report on a comprehensive study of the optical properties and magnetic torque response of Ca_{1-x}Na_{x}MnBi_{2}. Our findings give evidence for a spin canting occurring at T_{s}∼50-100  K. With the support of first-principles calculations we establish a direct link between the spin canting and the reconstruction of the electronic band structure, having immediate implications for the spectral weight reshuffling in the optical response, signaling a partial gapping of the Fermi surface, and the dc transport properties below T_{s}.

Plasma D-dimer as a predictor of intraluminal thrombus burden and progression of abdominal aortic aneurysm

AIM

Intraluminal thrombus (ILT) is presented in most abdominal aortic aneurysms (AAAs) and is suggested to promote AAA expansion. D-dimer, a breakdown product in the thrombus remodeling, may have prognostic value for AAA. This study investigated the interrelation between plasma D-dimer level, ILT volume, AAA size and progression.

MAIN METHODS

This was a retrospective observational study that involved 181 patients with infra-renal AAA. They were divided into small and large AAA groups according to AAA diameter. 24 of them had repeated abdominal computed tomography angiography (CTA) scan and were divided into slow-growing and fast-growing AAA groups according to the median value of AAA growth rate. Baseline and follow-up plasma D-dimer level, maximum diameter of AAA, total infra-renal aortic volume and ILT volume were analyzed.

KEY FINDINGS

Plasma D-dimer level was positively correlated with ILT volume (R = 0.382, P < 0.001) and maximum diameter of AAA (R = 0.442, P < 0.001). Increasing value of plasma D-dimer was positively associated with the accelerated growth rate of AAA (R = 0.720, P < 0.01). ILT volume showed positive correlation with maximum diameter (R = 0.859, P < 0.001) and growth rate of AAA (R = 0.490, P < 0.05). After adjusting the baseline ILT volume, the positive correlations remained to be statistically significant between plasma D-dimer level and AAA size (R = 0.200, P < 0.05), as well as increasing value of plasma D-dimer and growth rate of AAA (R = 0.642, P < 0.05).

SIGNIFICANCE

Plasma D-dimer level reflected ILT burden in AAAs. Plasma D-dimer level and ILT volume were positively correlated with AAA size. Increasing value of plasma D-dimer and baseline ILT volume could be predictors of AAA progression.

Founder effects, post-introduction evolution and phenotypic plasticity contribute to invasion success of a genetically impoverished invader

Multiple mechanisms may act synergistically to promote success of invasive plants. Here, we tested the roles of three non-mutually exclusive mechanisms-founder effects, post-introduction evolution and phenotypic plasticity-in promoting invasion of Chromolaena odorata. We performed a common garden experiment to investigate phenotypic diversification and phenotypic plasticity of the genetically impoverished invader in response to two rainfall treatments (ambient and 50% rainfall). We used ancestor-descendant comparisons to determine post-introduction evolution and the Q_ST-F_ST approach to estimate past selection on phenotypic traits. We found that eight traits differed significantly between plants from the invasive versus native ranges, for two of which founder effects can be inferred and for six of which post-introduction evolution can be inferred. The invader experienced strong diversifying selection in the invasive range and showed clinal variations in six traits along water and/or temperature gradients. These clinal variations are likely attributed to post-introduction evolution rather than multiple introductions of pre-adapted genotypes, as most of the clinal variations were absent or in opposite directions from those for native populations. Compared with populations, rainfall treatments explained only small proportions of total variations in all studied traits for plants from both ranges, highlighting the importance of heritable phenotypic differentiation. In addition, phenotypic plasticity was similar for plants from both ranges although neutral genetic diversity was much lower for plants from the invasive range. Our results showed that founder effects, post-introduction evolution and phenotypic plasticity may function synergistically in promoting invasion success of C. odorata.

Species composition, functional and phylogenetic distances correlate with success of invasive Chromolaena odorata in an experimental test

Biotic resistance may influence invasion success; however, the relative roles of species richness, functional or phylogenetic distance in predicting invasion success are not fully understood. We used biomass fraction of Chromolaena odorata, an invasive species in tropical and subtropical areas, as a measure of 'invasion success' in a series of artificial communities varying in species richness. Communities were constructed using species from Mexico (native range) or China (non-native range). We found strong evidence of biotic resistance: species richness and community biomass were negatively related with invasion success; invader biomass was greater in plant communities from China than from Mexico. Harvesting time had a greater effect on invasion success in plant communities from China than on those from Mexico. Functional and phylogenetic distances both correlated with invasion success and more functionally distant communities were more easily invaded. The effects of plant-soil fungi and plant allelochemical interactions on invasion success were species-specific.

Integrating novel chemical weapons and evolutionarily increased competitive ability in success of a tropical invader

The evolution of increased competitive ability (EICA) hypothesis and the novel weapons hypothesis (NWH) are two non-mutually exclusive mechanisms for exotic plant invasions, but few studies have simultaneously tested these hypotheses. Here we aimed to integrate them in the context of Chromolaena odorata invasion. We conducted two common garden experiments in order to test the EICA hypothesis, and two laboratory experiments in order to test the NWH. In common conditions, C. odorata plants from the nonnative range were better competitors but not larger than plants from the native range, either with or without the experimental manipulation of consumers. Chromolaena odorata plants from the nonnative range were more poorly defended against aboveground herbivores but better defended against soil-borne enemies. Chromolaena odorata plants from the nonnative range produced more odoratin (Eupatorium) (a unique compound of C. odorata with both allelopathic and defensive activities) and elicited stronger allelopathic effects on species native to China, the nonnative range of the invader, than on natives of Mexico, the native range of the invader. Our results suggest that invasive plants may evolve increased competitive ability after being introduced by increasing the production of novel allelochemicals, potentially in response to naïve competitors and new enemy regimes.

Differences in competitive ability between plants from nonnative and native populations of a tropical invader relates to adaptive responses in abiotic and biotic environments

The evolution of competitive ability of invasive plant species is generally studied in the context of adaptive responses to novel biotic environments (enemy release) in introduced ranges. However, invasive plants may also respond to novel abiotic environments. Here we studied differences in competitive ability between Chromolaena odorata plants of populations from nonnative versus native ranges, considering biogeographical differences in both biotic and abiotic environments. An intraspecific competition experiment was conducted at two nutrient levels in a common garden. In both low and high nutrient treatments, C. odorata plants from nonnative ranges showed consistently lower root to shoot ratios than did plants from native ranges grown in both monoculture and competition. In the low nutrient treatment, C. odorata plants from nonnative ranges showed significantly lower competitive ability (competition-driven decreases in plant height and biomass were more), which was associated with their lower root to shoot ratios and higher total leaf phenolic content (defense trait). In the high nutrient treatment, C. odorata plants from nonnative ranges showed lower leaf toughness and cellulosic contents (defense traits) but similar competitive ability compared with plants from native ranges, which was also associated with their lower root to shoot ratios. Our results indicate that genetically based shifts in biomass allocation (responses to abiotic environments) also influence competitive abilities of invasive plants, and provide a first potential mechanism for the interaction between range and environment (environment-dependent difference between ranges).

Comparisons of plastic responses to irradiance and physiological traits by invasive Eupatorium adenophorum and its native congeners

To explore the traits contributing to invasiveness of Eupatorium adenophorum and to test the relationship between plasticity of these traits and invasiveness, we compared E. adenophorum with its two native congeners at four irradiances (10%, 23%, 40%, and 100%). The invader showed constantly higher performance (relative growth rate and total biomass) across irradiances than its native congeners. Higher light-saturated photosynthetic rate (P(max)), respiration efficiency (RE), and nitrogen (PNUE) and water (WUE, at 40% and 100% irradiances only) use efficiencies contributed directly to the higher performance of the invader. Higher nitrogen allocation to, stomatal conductance, and the higher contents of leaf nitrogen and pigments contributed to the higher performance of the invader indirectly through increasing P(max), RE, PNUE and WUE. The invader had consistently higher plasticity only in carotenoid content than its native congeners in ranges of low (10-40%), high (40-100%) and total (10-100%) irradiances, contributing to invasion success in high irradiance by photo protection. In the range of low irradiances, the invader had higher plasticity in some physiological traits (leaf nitrogen content, nitrogen contents in bioenergetics, carboxylation and in light-harvesting components, and contents of leaf chlorophylls and carotenoids) but not in performance, while in the ranges of high or total irradiances, the invader did not show higher plasticity in any variable (except Car). The results indicated that the relationship between invasiveness and plasticity of a specific trait was complex, and that a universal generalization about the relationship might be too simplistic.

Nonclassic functions of human topoisomerase I: genome-wide and pharmacologic analyses

The biological functions of nuclear topoisomerase I (Top1) have been difficult to study because knocking out TOP1 is lethal in metazoans. To reveal the functions of human Top1, we have generated stable Top1 small interfering RNA (siRNA) cell lines from colon and breast carcinomas (HCT116-siTop1 and MCF-7-siTop1, respectively). In those clones, Top1 is reduced approximately 5-fold and Top2alpha compensates for Top1 deficiency. A prominent feature of the siTop1 cells is genomic instability, with chromosomal aberrations and histone gamma-H2AX foci associated with replication defects. siTop1 cells also show rDNA and nucleolar alterations and increased nuclear volume. Genome-wide transcription profiling revealed 55 genes with consistent changes in siTop1 cells. Among them, asparagine synthetase (ASNS) expression was reduced in siTop1 cells and in cells with transient Top1 down-regulation. Conversely, Top1 complementation increased ASNS, indicating a causal link between Top1 and ASNS expression. Correspondingly, pharmacologic profiling showed L-asparaginase hypersensitivity in the siTop1 cells. Resistance to camptothecin, indenoisoquinoline, aphidicolin, hydroxyurea, and staurosporine and hypersensitivity to etoposide and actinomycin D show that Top1, in addition to being the target of camptothecins, also regulates DNA replication, rDNA stability, and apoptosis. Overall, our studies show the pleiotropic nature of human Top1 activities. In addition to its classic DNA nicking-closing functions, Top1 plays critical nonclassic roles in genomic stability, gene-specific transcription, and response to various anticancer agents. The reported cell lines and approaches described in this article provide new tools to perform detailed functional analyses related to Top1 function.

A novel polypyrimidine antitumor agent FdUMP[10] induces thymineless death with topoisomerase I-DNA complexes

FdUMP[10], a 10mer of 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP), the thymidylate synthase inhibitory metabolite of 5-fluorouracil (FU), is most closely correlated with the DNA topoisomerase I (Top1) inhibitor camptothecin in the National Cancer Institute COMPARE analysis, but not with FU. FdUMP[10] exhibits more potent antiproliferative activity than FdUMP or 5-fluoro-2'-deoxyuridine (FdU) and is markedly more active than FU. Camptothecin-resistant P388/CPT45 cells lacking Top1 are cross-resistant to FdUMP[10] as well as to FdUMP, FdU, and the thymidylate synthase inhibitor raltitrexed (Tomudex). FdUMP[10] induces DNA single-strand breaks and cellular Top1-DNA complexes. Such complexes are also observed in response to FdUMP, FdU, raltitrexed, and FU. The FdUMP[10]-induced Top1-DNA complexes are not inhibited by the caspase inhibitor z-VAD-fmk and form independently of apoptotic DNA fragmentation, indicating that they do not correspond to apoptotic Top1-DNA complexes. In biochemical assay, Top1 is directly trapped at uracil and FdU misincorporation sites. We propose that FdUMP[10] damages DNA by trapping Top1 at uracil and FdU misincorporation sites resulting from thymidylate synthase inhibition and thymine depletion.

Antigenic cross-reactivity between severe acute respiratory syndrome-associated coronavirus and human coronaviruses 229E and OC43

Cross-reactivity between antibodies to different human coronaviruses (HCoVs) has not been systematically studied. By use of Western blot analysis, indirect immunofluorescence assay (IFA), and enzyme-linked immunosorbent assay (ELISA), antigenic cross-reactivity between severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV) and 2 HCoVs (229E and OC43) was demonstrated in immunized animals and human serum. In 5 of 11 and 10 of 11 patients with SARS, paired serum samples showed a > or =4-fold increase in antibody titers against HCoV-229E and HCoV-OC43, respectively, by IFA. Overall, serum samples from convalescent patients who had SARS had a 1-way cross-reactivity with the 2 known HCoVs. Antigens of SARS-CoV and HCoV-OC43 were more cross-reactive than were those of SARS-CoV and HCoV-229E.

Identification and characterization of GH receptor and serum GH-binding protein in Chinese sturgeon (Acipenser sinensis)

Chinese sturgeon, a kind of cartilage ganoid, has a history of over one billion years and it is called the living fossil of aquatic biology since it keeps some evolutionary trace. Here, we characterized the growth hormone receptor (GHR) and serum growth hormone binding protein (GHBP) of Chinese sturgeon. It was shown that GHR was expressed in various tissues, mainly in hepatic, kidney and intestine tissues. GHR on the hepatic membrane has high and specific affinity for bream GH (brGH) and Scatchard analysis of the binding data showed a single class of high affinity binding site with an association constant Ka of 3.1x10(9) M(-1). A specific band around 94 kD was detected by SDS-PAGE in cross-linking studies of membrane receptors. After incubation of Chinese sturgeon serum with 125I-brGH, a 125I-brGH-GHBP complex was identified by Sephadex G-75, indicating that in the serum exists GHBP specially binding to brGH.

Sensitive and specific monoclonal antibody-based capture enzyme immunoassay for detection of nucleocapsid antigen in sera from patients with severe acute respiratory syndrome

A rapid antigen test for the diagnosis of severe acute respiratory syndrome (SARS) is essential for control of this disease at the point of management. The nucleocapsid (N) protein of SARS-associated coronavirus (SARS-CoV) is abundantly expressed in infected-cell culture filtrate as demonstrable by Western blotting using convalescent-phase sera from patients with SARS. We used monoclonal antibodies specifically directed against N protein to establish a sensitive antigen capture sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of SARS-CoV. The assay employed a mixture of three monoclonal antibodies for capture and rabbit polyclonal antibodies for detection of serum antigen in 32 cases of clinically probable SARS as defined by the World Health Organization during the epidemic in Guangzhou, China. Recombinant N protein was used as a standard to establish a detection sensitivity of approximated 50 pg/ml. The linear range of detection in clinical specimens was from 100 pg/ml to 3.2 ng/ml. Using a panel of sera collected at different points in time, the amount of circulating N antigen was found to peak 6 to 10 days after the onset of symptoms. The sensitivity of the assay was 84.6% in 13 serologically confirmed SARS patients with blood taken during the first 10 days after the onset of symptoms (11 of 13). The specificity of the assay was 98.5% in 1,272 healthy individuals (1,253 of 1,272). There was no cross-reaction with other human and animal coronaviruses in this assay. In conclusion, a sensitive and quantitative antigen capture ELISA was established for the early diagnosis and disease monitoring of SARS-CoV infection.

Topoisomerase I-DNA complexes contribute to arsenic trioxide-induced apoptosis

Topoisomerase I is an essential enzyme that relaxes DNA supercoiling by forming covalent DNA cleavage complexes, which are normally transient. Topoisomerase I-DNA complexes can be trapped by anticancer drugs (camptothecins) as well as by endogenous and exogenous DNA lesions. We show here that arsenic trioxide (a potent inducer of apoptosis that induces the intracellular accumulation of reactive oxygen species and targets mitochondria) induces cellular topoisomerase I cleavage complexes. Bcl-2 overexpression and quenching of reactive oxygen species, which prevent arsenic trioxide-induced apoptosis, also prevent the formation of topoisomerase I-DNA complexes, whereas enhancement of reactive oxygen species accumulation promotes these complexes. The caspase inhibitor, benzyloxycarbonyl-VAD partially prevents arsenic trioxide-induced topoisomerase I-DNA complexes and apoptosis, suggesting that activated caspases further maintain intracellular levels of reactive oxygen species that induce the formation of topoisomerase I-DNA complexes. Down-regulation of topoisomerase I expression decreases arsenic trioxide-induced apoptotic DNA fragmentation. Thus, we propose that arsenic trioxide induces topoisomerase I-DNA complexes that participate in chromatin fragmentation and programmed cell death during apoptosis.

Repair of and checkpoint response to topoisomerase I-mediated DNA damage

Topoisomerase I (Top1) catalyzes two transesterification reactions: single-strand DNA cleavage and religation that are normally coupled for the relaxation of DNA supercoiling in transcribing and replicating chromatin. A variety of endogenous DNA modifications, potent anticancer drugs and carcinogens uncouple these two reactions, resulting in the accumulation of Top1 cleavage complexes. Top1 cleavage complexes damage DNA and kill cells by generating replication-mediated DNA double-strand breaks (DSBs) and by stalling transcription complexes. The repair of Top1-mediated DNA lesions involves integrated pathways that are conserved from yeasts to humans. Top1-mediated DNA damage and cell cycle checkpoint responses can be studied biochemically and genetically in yeast and human cells with known genetic defects. Defects in these repair/checkpoint pathways, which promote tumor development, explain, at least in part, the selectivity of camptothecins and other Top1 inhibitors for cancer cells.

[Identification of interaction and interaction domains between neuroglobin and Na(+), K(+)-ATPase beta2 subunit]

The pre-transformed human fetal brain cDNA library was used to screen the protein interacting with neuroglobin by using yeast two hybrid system III from ClonTech Inc. The protein encoded by one of the clones interacting with neuroglobin (NGB) was confirmed to be the C terminus of the Na(+), K(+)-ATPase beta2 subunit (NKA1b2) based on amino acid sequences. Then the full-length coding region cDNA sequence of NKA1b2 was obtained from human fetal brain cDNA library by PCR. A set of experiments were designed to test the interaction between NGB and NKA1b2. Interaction between NGB and NKA1b2 was confirmed by binding assay in vitro. Furthermore, the interaction was also proved by co-immunoprecipitation test in vivo. Moreover, the structure integrity of neuroglobin was found to be essential for the interaction between NGB and NKA1b2 by yeast two hybrid method with a series of neuroglobin truncated mutants.

Non-camptothecin DNA topoisomerase I inhibitors in cancer therapy

Human DNA topoisomerase I is the target of camptothecins, which have been recently introduced in the clinic for cancer chemotherapy. The discovery of novel non-camptothecin inhibitors is facilitated by the availability of biochemical and cellular assays for testing topoisomerase I activity. Among the non-camptothecin inhibitors, the indolocarbazoles (NB-506 and J-107088) are the most advanced in their development, and are in clinical trials. A number of indenoisoquinolines and minor groove binders (benzimidazoles) have been reported recently. Their antitumor activity is promising for further development. The potential binding site(s) of topoisomerase I inhibitors in the enzyme I-DNA complex is discussed.

Phosphorylation of histone H2AX and activation of Mre11, Rad50, and Nbs1 in response to replication-dependent DNA double-strand breaks induced by mammalian DNA topoisomerase I cleavage complexes

DNA double-strand breaks originating from diverse causes in eukaryotic cells are accompanied by the formation of phosphorylated H2AX (gammaH2AX) foci. Here we show that gammaH2AX formation is also a cellular response to topoisomerase I cleavage complexes known to induce DNA double-strand breaks during replication. In HCT116 human carcinoma cells exposed to the topoisomerase I inhibitor camptothecin, the resulting gammaH2AX formation can be prevented with the phosphatidylinositol 3-OH kinase-related kinase inhibitor wortmannin; however, in contrast to ionizing radiation, only camptothecin-induced gammaH2AX formation can be prevented with the DNA replication inhibitor aphidicolin and enhanced with the checkpoint abrogator 7-hydroxystaurosporine. This gammaH2AX formation is suppressed in ATR (ataxia telangiectasia and Rad3-related) deficient cells and markedly decreased in DNA-dependent protein kinase-deficient cells but is not abrogated in ataxia telangiectasia cells, indicating that ATR and DNA-dependent protein kinase are the kinases primarily involved in gammaH2AX formation at the sites of replication-mediated DNA double-strand breaks. Mre11- and Nbs1-deficient cells are still able to form gammaH2AX. However, H2AX-/- mouse embryonic fibroblasts exposed to camptothecin fail to form Mre11, Rad50, and Nbs1 foci and are hypersensitive to camptothecin. These results demonstrate a conserved gammaH2AX response for double-strand breaks induced by replication fork collision. gammaH2AX foci are required for recruiting repair and checkpoint protein complexes to the replication break sites.

Functional expression of guinea pig growth hormone receptor and its mutants in mammalian cells

The cDNA of guinea pig (Cavia porcellus) growth hormone receptor (gpGHR) was cloned using RT-PCR in our laboratory. By sequence alignment, substitutions of amino acids conserved in other mammalian GHRs were found. For example, histidine-168 and tyrosine-332 equivalent to positions 170 and 333 in other mammalian GHRs, which were considered to be necessary for the dimerization of GHR and the specific GH-stimulated functions respectively, were replaced by tyrosine and serine in gpGHR. Here, we report the functional expression of gpGHR and its mutants, gpGHRY168H and gpGHRS332Y, in COS-7 cells and/or Chinese hamster ovary (CHO) cells. It was shown that the COS-7 cells transfected with pcDNA3-gpGHR possessed high affinity to bovine GH [K(a) = 1.3 x10(9) (mol/L)(-1)] and a protein band with molecular weight around 92 kD was detected by anti-mouse GHR monoclonal antibody (mAb263). When CHO cells were transfected with the expression vectors, pcDNA3-gpGHR, pcDNA3-gpGHRY168H and pcDNA3-gpGHRS332Y, the gpGHR and its mutants were expressed and the ligand binding, phosphorylation of JAK2, protein synthesis, and lipogenesis were studied. It was found that the mutation of serine to tyrosine at position 332 greatly increased the GH-stimulated protein synthesis and the phosphorylation of JAK2, while the mutation of tyrosine to histidine at position 168 increased the protein synthesis and decreased the phosphorylation of JAK2 only weakly. However, both mutations decreased the GH-stimulated lipogenesis. Thus, our study provides the experimental evidence that gpGHR may mediate the metabolic actions of GH and the substitutions of some conserved amino acids in gpGHR result in the changes of post-binding signaling.

B9-serine residue is crucial for insulin actions in glucose metabolism

AIM

To explore the importance of B9 and B10 amino acid residues in the insulin molecule.

METHODS

The [B9Glu, B10Asp] insulin (E,D-insulin) receptor binding activity, glucose upta ke activity, and lipogenesis activity were measured in isolated adipocytes. The translocation of glucose transporter 4 (Glut4) and the phosphorylation of insulin receptor (IR) stimulated by E, D-insulin were determined by Western blotting.

RESULTS

Compared with native insulin, the receptor binding activity of E,D-insulin was 31 %; the stimulating activity of E,D-insulin in glucose transport and lipogenesis were 45 % and 40 % respectively; the stimulations of Glut4 translocation and insulin receptor autophosphorylation of E,D-insulin were about 58 % and 46 % respectively.

CONCLUSION

B9-serine residue is crucial for insulin actions in glucose metabolism.

Synergistic effects of geldanamycin and antitumor drugs

AIM

To study the effect of geldanamycin (GDM) on cell-cycle of human hepatoma BEL-7402 cells and the antitumor activity of cisplatin and mitomycin C in combination with GDM in vitro and in vivo.

METHODS

MTT assay was used to determine the growth inhibition of hepatoma BEL-7402 cells. Cell cycle was analyzed by flow cytometry. Transplantable murine hepatoma 22 model was used to evaluate the antitumor activity of drugs in vivo.

RESULTS

The IC50 value of GDM for hepatoma BEL-7402 cells by MTT assay was found to be 0.28 mumol.L-1. At concentrations of 0.1, 1.0, and 10 mumol.L-1, GDM reduced the proportion of S phase and induced G2/M arrest in BEL-7402 cells. At relatively low cytotoxic concentration, 0.1 or 0.2 mumol.L-1, GDM markedly potentiated the cytotoxicity of a series of chemotherapeutic agents including cisplatin, mitomycin C, adriamycin and cytarabine against BEL-7402 cells. The inhibition of tumor growth by cisplatin and mitomycin C was also enhanced in transplantable hepatoma 22-bearing mice when these agents were administered in combination with GDM 0.38 mg.kg-1. The synergistic effects were very significant with CDI < 0.7.

CONCLUSION

These results suggest that GDM, as a biochemical modulator targeting Hsp90 function, may be potentially useful in cancer chemotherapy.

Tuberculosis versus lymphomas in the abdominal lymph nodes: evaluation with contrast-enhanced CT

OBJECTIVE

Tuberculosis in the abdominal lymph nodes may be difficult to distinguish from lymphomas. This study evaluated specific CT imaging criteria for differentiating these entities.

MATERIALS AND METHODS

We retrospectively reviewed the anatomic distribution and CT enhancement patterns of disease in 69 patients, 26 (38%) with tuberculosis and 43 (62%) with untreated lymphomas involving abdominal lymph nodes. Of the patients with tuberculosis, five (19%) had disseminated disease and 21 (81%) had nondisseminated disease. Of the patients with lymphomas, 16 (37%) had Hodgkin's disease and 27 (63%) had non-Hodgkin's lymphoma.

RESULTS

Disseminated and nondisseminated tuberculosis involved predominantly lesser omental, mesenteric, anterior pararenal, and upper paraaortic lymph nodes. Lower paraaortic lymph nodes were involved more often in Hodgkin's disease (15 patients [94%]), non-Hodgkin's lymphoma (24 patients [89%]), and disseminated tuberculosis (five patients [100%]) than in nondisseminated tuberculosis (one patient [5%]). Mesenteric lymph nodes were involved more often in disseminated tuberculosis (four patients [80%]) and nondisseminated tuberculosis (11 patients [52%]) than in Hodgkin's disease (one patient [6%]) (p < .01). Anatomic distribution was not different between disseminated tuberculosis and non-Hodgkin's lymphoma. Tuberculous lymphadenopathy commonly showed peripheral enhancement, frequently with a multilocular appearance, whereas lymphomatous adenopathy characteristically showed homogeneous attenuation (14 patients [87.5%] with Hodgkin's disease and 19 patients [70%] with non-Hodgkin's lymphoma [p < .01]).

CONCLUSION

Our findings indicate that the anatomic distribution and specific enhancement patterns of lymphadenopathy seen on contrast-enhanced CT can be useful in differentiating between tuberculosis and untreated lymphomas of the abdominal lymph nodes.