The cardiovascular system at high altitude: A bibliometric and visualization analysis

BACKGROUND

When exposed to high-altitude environments, the cardiovascular system undergoes various changes, the performance and mechanisms of which remain controversial.

AIM

To summarize the latest research advancements and hot research points in the cardiovascular system at high altitude by conducting a bibliometric and visualization analysis.

METHODS

The literature was systematically retrieved and filtered using the Web of Science Core Collection of Science Citation Index Expanded. A visualization analysis of the identified publications was conducted employing CiteSpace and VOSviewer.

RESULTS

A total of 1674 publications were included in the study, with an observed annual increase in the number of publications spanning from 1990 to 2022. The United States of America emerged as the predominant contributor, while Universidad Peruana Cayetano Heredia stood out as the institution with the highest publication output. Notably, Jean-Paul Richalet demonstrated the highest productivity among researchers focusing on the cardiovascular system at high altitude. Furthermore, Peter Bärtsch emerged as the author with the highest number of cited articles. Keyword analysis identified hypoxia, exercise, acclimatization, acute and chronic mountain sickness, pulmonary hypertension, metabolism, and echocardiography as the primary research hot research points and emerging directions in the study of the cardiovascular system at high altitude.

CONCLUSION

Over the past 32 years, research on the cardiovascular system in high-altitude regions has been steadily increasing. Future research in this field may focus on areas such as hypoxia adaptation, metabolism, and cardiopulmonary exercise. Strengthening interdisciplinary and multi-team collaborations will facilitate further exploration of the pathophysiological mechanisms underlying cardiovascular changes in high-altitude environments and provide a theoretical basis for standardized disease diagnosis and treatment.

Electronic structures, transport properties, and optical absorption of bilayer blue phosphorene nanoribbons

Based on first-principles density functional theory and nonequilibrium Green's function, we study the electronic band structures, the electronic transport properties, and the optical absorption of bilayer blue phosphorene nanoribbons (BPNRs). Both bilayer armchair BPNRs (a-BPNRs) and zigzag BPNRs (z-BPNRs) behave as semiconductors in the narrow nanoribbon case and metals in the wide nanoribbon case, sharply different from their monolayer counterparts where the monolayer a-BPNRs (z-BPNRs) are always semiconducting (metallic). This indicates that interlayer couplings or the increasing layer number may induce the switching of the conductivity of the monolayer BPNRs, which is absent in graphene and phosphorene nanoribbons. Furthermore, we explore the edge states of the energy bands near Fermi energy, and find that there are almost no pure edge-state band branches in the bilayer BPNRs, which can be attributed to the interlayer couplings between the edge-states in one layer and the bulk-states in the other. Consequently, the resulting complex band structures cannot be directly analyzed any more in the framework of the two-body coupling picture just according to the simple band structures of the monolayer BPNRs. Finally, we present the current-voltage characteristics and the optical absorption of the bilayer a-BPNRs and z-BPNRs. The influences of the nanoribbon width and the interlayer couplings on the current and the anisotropic optical absorption can be understood based on the complex energy band structures. This research should be an important reference of extending the field of BPNRs from the monolayer to the bilayer case, and deepen the understanding of the difference between the monolayer and bilayer nanoribbons in different materials.

Early Enteral Nutrition and Sepsis-Associated Acute Kidney Injury: A Propensity Score Matched Cohort Study Based on the MIMIC-III Database

PURPOSE

We aimed to analyze the optimal timing of enteral nutrition (EN) in the treatment of sepsis and its effect on sepsis-associated acute kidney injury (SA-AKI.).

MATERIALS AND METHODS

The MIMIC-III database was employed to identify patients with sepsis who had received EN. With AKI as the primary outcome variable, receiver operating characteristic (ROC) curves were utilized to calculate the optimal cut-off time of early EN (EEN). Propensity score matching (PSM) was employed to control confounding effects. Logistic regressions and propensity score-based inverse probability of treatment weighting were utilized to assess the robustness of our findings. Comparisons within the EEN group were performed.

RESULTS

2364 patients were included in our study. With 53 hours after intensive care units (ICU) admission as the cut-off time of EEN according to the ROC curve, 1212 patients were assigned to the EEN group and the other 1152 to the delayed EN group. The risk of SA-AKI was reduced in the EEN group (odds ratio 0.319, 95% confidence interval 0.245-0.413, p<0.001). The EEN patients received fewer volumes (mL) of intravenous fluid (IVF) during their ICU stay (3750 mL vs. 5513.23 mL, p<0.001). The mediating effect of IVF was significant (p<0.001 for the average causal mediation effect). No significant differences were found within the EEN group (0-48 hours vs. 48-53 hours), except that patients initiating EN within 48 hours spent fewer days in ICU and hospital.

CONCLUSION

EEN is associated with decreased risk of SA-AKI, and this beneficial effect may be proportionally mediated by IVF volume.

Effects of High-Definition Transcranial Direct Current Stimulation Targeting the Anterior Cingulate Cortex on the Pain Thresholds: A Randomized Controlled Trial

BACKGROUND

The majority of existing clinical studies used active transcranial direct current stimulation (tDCS) over superficial areas of the pain neuromatrix to regulate pain, with conflicting results. Few studies have investigated the effect of tDCS on pain thresholds by focusing on targets in deep parts of the pain neuromatrix.

METHODS

This study applied a single session of high-definition tDCS (HD-tDCS) targeting the anterior cingulate cortex (ACC) and used a parallel and sham-controlled design to compare the antinociceptive effects in healthy individuals by assessing changes in pain thresholds. Sixty-six female individuals (mean age, 20.5 ± 2.4 years) were randomly allocated into the anodal, cathodal, or sham HD-tDCS groups. The primary outcome of the study was pain thresholds (pressure pain threshold, heat pain threshold, and cold pain threshold), which were evaluated before and after stimulation through the use of quantitative sensory tests.

RESULTS

Only cathodal HD-tDCS targeting the ACC significantly increased heat pain threshold (P < 0.05) and pressure pain threshold (P < 0.01) in healthy individuals compared with sham stimulation. Neither anodal nor cathodal HD-tDCS showed significant analgesic effects on cold pain threshold. Furthermore, no statistically significant difference was found in pain thresholds between anodal and sham HD-tDCS (P > 0.38). Independent of HD-tDCS protocols, the positive and negative affective schedule scores were decreased immediately after stimulation compared with baseline.

CONCLUSIONS

The present study has found that cathodal HD-tDCS targeting the ACC provided a strong antinociceptive effect (increase in pain threshold), demonstrating a positive biological effect of HD-tDCS.

[A multicenter, double-blind, randomized controlled clinical trial comparing ergometrine with oxytocin and oxytocin alone for prevention of postpartum hemorrhage at cesarean section]

Objective: To compare oxytocin combined with ergometrine with oxytocin alone in terms of primary prophylaxis for postpartum hemorrhage (PPH) at the time of cesarean section (CS). Methods: This was a multicenter double-blind randomized controlled interventional study comparing ergometrine combined with oxytocin and oxytocin alone administered at CS. From December 2018 to November 2019, a total of 298 parturients were enrolled in 16 hospitals nationwide. They were randomly divided into experimental group (ergometrine intra-myometrial injection following oxytocin intravenously; 148 cases) and control group (oxytocin intra-myometrial injection following oxytocin intravenously; 150 cases) according to 1∶1 random allocation. The following indexes were compared between the two groups: (1) main index: blood loss 2 hours (h) after delivery; (2) secondary indicators: postpartum blood loss at 6 h and 24 h, placental retention time, incidence of PPH, the proportion of additional use of uterine contraction drugs, hemostatic drugs or other hemostatic measures at 2 h and 24 h after delivery, the proportion requiring blood transfusion, and the proportion of prolonged hospital stay due to poor uterine involution; (3) safety indicators: nausea, vomiting, dizziness and other adverse reactions, and blood pressure at each time point of administration. Results: (1) The blood loss at 2 h after delivery in the experimental group [(402±18) ml] was less than that in the control group [(505±18) ml], and the difference was statistically significant (P<0.05). (2) The blood loss at 6 h and 24 h after delivery in the experimental group were less than those in the control group, and the differences were statistically significant (all P<0.05). There were no significant differences between the two groups in the incidence of PPH, the proportion of additional use of uterine contraction drugs, hemostatic drugs or other hemostatic measures at 2 h and 24 h after delivery, the proportion requiring blood transfusion, and the proportion of prolonged hospital stay due to poor uterine involution (all P>0.05). (3) Adverse reactions occurred in 2 cases (1.4%, 2/148) in the experimental group and 1 case (0.7%, 1/150) in the control group. There was no significant difference between the two groups (P>0.05). The systolic blood pressure within 2.0 h and diastolic blood pressure within 1.5 h of drug administration in the experimental group were higher than those in the control group, and the differences were statistically significant (P<0.05), but the blood pressure of the two groups were in the normal range. Conclusion: The use of ergometrine injection in CS could reduce the amount of PPH, which is safe and feasible.

[Regional disparities in trends of global gastric cancer incidence and mortality from 1990 to 2019]

Objective: To depict gastric cancer burden trends globally and analyze geographical and socioeconomic disparities among different countries and territories. Methods: We extracted the data from Global Burden of Disease 2019 Database. We conducted the Joinpoint regression and calculated the average annual percent change (AAPC) and corresponding 95% confidence interval (CI) for age-standardized gastric cancer incidence and mortality from 1990 to 2019. Linear regression was performed to measure the association of sociodemographic index (SDI) with each country's gastric cancer incidence and mortality AAPC. We applied the age-period-cohort analysis to assess the cohort effect on gastric cancer incidence and mortality. Results: The AAPCs for gastric cancer age-standardized incidence and mortality rates from 1990 to 2019 were -1.27% (95% CI: -1.43%, -1.11%) and -1.87% (95% CI: -2.01%, -1.72%), respectively. SDI levels were negatively associated with AAPCs, which means that countries with higher SDI had higher AAPC (P<0.001). The decrease of gastric cancer burden in countries with low or medium SDI levels was slower than that globally. The age-period-cohort analysis indicated that countries with higher SDI levels had more apparent decline in birth cohort effects from 1900 to 1999. Conclusions: Countries with different socioeconomic levels have various decreasing rates for gastric cancer incidence and deaths. Countries with higher SDI levels have higher declining rates for gastric cancer burden.

[A comparative analysis of the distribution of the high-risk population of upper gastrointestinal cancer and endoscopic screening compliance in two urban areas and two rural areas in China]

Objective: To analyze and compare the distribution of the high-risk population of upper gastrointestinal (UGI) cancer and the factors influencing the compliance rate of endoscopic screening in urban China and rural China. Methods: From 2015 to 2017, an epidemiological survey was conducted on residents aged 40-69 in two rural areas (Luoshan county of Henan province, Sheyang county of Jiangsu province) and two urban areas (Changsha city of Hunan province, Harbin city of Heilongjiang province). As a result, high-risk individuals were recommended for endoscopic screening. Chi-square χ(2) test was used to compare the high-risk rate of UGI cancer between urban and rural residents. In addition, the multivariate logistic regression model was used to analyze the factors influencing the compliance rate of endoscopic screening. Results: A total of 48, 310 residents aged 40-69 were enrolled in this study, including 22 870 (47.34%) residents from rural areas and 25 440 (52.66%) residents from urban areas. A total of 23 532 individuals were assessed with a high risk of UGI cancer, with an overall risk rate of 48.71%. A higher proportion of participants with high risk was observed in rural China (56.17%, 12 845/22 870) than in urban China (42.01%, 10 687/25 440). A total of 10 971 high-risk individuals with UGI cancer participated in endoscopic screening, with an overall compliance rate of 46.62% (10 971/23 532), 45.15% (5 799/12 845) in rural China, and 48.40% (5 172/10 687) in urban China. In rural population, the compliance rate of endoscopic screening was higher in those of females, aged 50-69 years, primary school education or above, high income, a family history of UGI cancer, history of gastric and duodenal ulcer, history of reflux esophagitis, and history of superficial gastritis, but lower in smokers (P<0.05). Among the urban population, the compliance rate of endoscopic screening was higher in those aged 40-49 years, uneducated, low income, family history of UGI cancer, history of reflux esophagitis, history of superficial gastritis, but lower in smokers (P<0.05). Conclusions: The proportion of participants with high risk of UGI cancer in rural areas is higher than that of urban areas. The compliance rates of endoscopic screening in urban and rural areas are low, and influencing factors of endoscopic screening exhibit some differences in rural China and urban China.

[The relationship between insulin resistance and risk of long-term mortality in people without diabetes: a 30-year follow-up of the Daqing Diabetes Study]

Objective: To determine whether insulin resistance is associated with all-cause mortality in subjects without diabetes. Methods: A total of 505 participants without diabetes, 198 with normal glucose tolerance (NGT) and 307 with impaired glucose tolerance (IGT), were recruited from the Daqing Diabetes Study. The participants were followed up for 30 years. They were stratified into three groups (tertiles) according to baseline homeostasis model assessment of insulin resistance(HOMA-IR) levels, as the HOMA-IR 0, the HOMA-IR 1 and the HOMA-IR 2 groups, to assess the predictive effect of insulin resistance on risk of all-cause mortality. Results: During the 30-year follow-up, 52, 56 and 78 participants died across the three HOMA-IR groups, respectively. The corresponding mortality per 1 000 person-years (95%CI) were 12.12 (9.56-15.01), 13.10 (10.46-16.03) and 19.91 (16.73-23.15), respectively. Participants in the HOMA-IR 2 group had a significantly higher risk of death than those in the HOMA-IR 0 group after adjustment of age, sex and smoking status (HR=1.97,95%CI 1.38-2.81, P<0.001). Cox analyses showed that a one standard deviation increase in HOMA-IR was associated with a 22% increase in the mortality after adjustment of potential confounders (HR=1.22, 95%CI 1.08-1.39, P=0.002). Conclusions: Insulin resistance is associated with increased risk of all-cause death in Chinese people without diabetes, suggesting that improving insulin resistance could be beneficial for people without diabetic in reducing risk of long-term all-cause mortality.

[Identification of New Psychoactive Tryptamines 4-OH-MET and 4-AcO-DMT Using High Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy]

Abstract

Objective To detect the uncontrolled new psychoactive tryptamines involved in drug-related cases with high resolution mass spectrometry and nuclear magnetic resonance spectroscopy. Methods White and brown powder obtained in actual cases were extracted and analyzed by gas chromatography-quadrupole time-of-flight mass spectrometry （GC-QTOF-MS）, ultra-high performance liquid chromatography-linear ion trap quadrupole-orbitrap mass spectrometry （UPLC-LTQ-Orbitrap MS） and ¹H-nuclear magnetic resonance spectroscopy （1H-NMR）. Results After detection by GC-QTOF-MS, the components of white powder showed main characteristic fragment ion peaks at m/z 218.141 0 （molecular ion peak）, 72.080 6 （base peak）, etc. After detection by UPLC-LTQ-Orbitrap MS, its protonated molecular ion was m/z 219.149 4. The main ions in the secondary mass spectrum under the collision-induced dissociation （CID） mode were m/z 160.076 3 and 72.080 8. After detection by GC-QTOF-MS, the components of brown powder showed main characteristic fragment ion peaks at m/z 246.135 7 （molecular ion peak）, 58.065 1 （base peak）, etc. After detection by UPLC-LTQ-Orbitrap MS, its protonated molecular ion was m/z 247.145 0. The main ions in the secondary mass spectrum under CID mode were m/z 202.087 1, 160.076 3 and 134.060 5. NIST 17 library retrieval and ¹H-NMR confirmed that the white powder and brown powder contained new psychoactive tryptamines 4-OH-MET and 4-AcO-DMT, respectively. Conclusion GC-QTOF-MS, UPLC-LTQ-Orbitrap MS and ¹H-NMR can be used together to identify unknown new psychoactive substances.

Spinal cord stimulation reduces cardiac pain through microglial deactivation in rats with chronic myocardial ischemia

Angina pectoris is cardiac pain that is a common clinical symptom often resulting from myocardial ischemia. Spinal cord stimulation (SCS) is effective in treating refractory angina pectoris, but its underlying mechanisms have not been fully elucidated. The spinal dorsal horn is the first region of the central nervous system that receives nociceptive information; it is also the target of SCS. In the spinal cord, glial (astrocytes and microglia) activation is involved in the initiation and persistence of chronic pain. Thus, the present study investigated the possible cardiac pain-relieving effects of SCS on spinal dorsal horn glia in chronic myocardial ischemia (CMI). CMI was established by left anterior descending artery ligation surgery, which induced significant spontaneous/ongoing cardiac pain behaviors, as measured using the open field test in rats. SCS effectively improved such behaviors as shown by open field and conditioned place preference tests in CMI model rats. SCS suppressed CMI-induced spinal dorsal horn microglial activation, with downregulation of ionized calcium-binding adaptor protein-1 expression. Moreover, SCS inhibited CMI-induced spinal expression of phosphorylated-p38 MAPK, which was specifically colocalized with the spinal dorsal horn microglia rather than astrocytes and neurons. Furthermore, SCS could depress spinal neuroinflammation by suppressing CMI-induced IL-1β and TNF-α release. Intrathecal administration of minocycline, a microglial inhibitor, alleviated the cardiac pain behaviors in CMI model rats. In addition, the injection of fractalkine (microglia-activating factor) partially reversed the SCS-produced analgesic effects on CMI-induced cardiac pain. These results indicated that the therapeutic mechanism of SCS on CMI may occur partially through the inhibition of spinal microglial p38 MAPK pathway activation. The present study identified a novel mechanism underlying the SCS-produced analgesic effects on chronic cardiac pain.

Determination of Azide Ions in Blood by Pentafluorobenzyl Derivation Followed by GC-MS

Abstract

Objective To establish a method for determination of the azide ions in blood by gas chromatography-mass spectrometry （GC-MS） following pentafluorobenzyl derivatization. Methods A blood sample of 0.2 mL was placed into a 10 mL glass test tube, and the internal standard sodium cyanide, derivatization reagent pentafluorobenzyl bromide and catalyst tetradecyl benzyl dimethyl ammonium chloride were added in turn. After vortex mixing, the mixture was heated with low-power microwave for 3 min. After centrifugation, the organic phase was taken for GC-MS analysis. Results The azide ions in blood had a good linear relationship in the mass concentration range of 0.5 to 20 μg/mL. The lowest detection limit was 0.25 μg/mL and the relative recovery was 91.36%-94.58%. The method was successfully applied to a case of death from sodium azide poisoning. The mass concentration of azide ions in the blood of the dead was 11.11 μg/mL. Conclusion The method developed in this paper has strong specificity and is easy to operate, which is suitable for the rapid detection of azide ions in blood.

[Analysis of Dimethyltryptamine in Captured Suspicious Substances：Three Case Reports]

Abstract.

[Quality assessment of guidelines on upper gastrointestinal cancer screening]

Objective: To systematically evaluate the methodological quality of screening guidelines for upper gastrointestinal cancer (including esophageal cancer and gastric cancer) both at home and abroad, and provide reference for the update of upper gastrointestinal cancer screening guidelines in China. Methods: Original articles and grey literature published as of 31^th Aug 2020 were retrieved using Chinese databases (CNKI, Wanfang, China Biomedical Literature Database and China Guideline Clearinghouse), PubMed, The Cochrane Library and Embase, as well as those from International Agency for Research on Cancer and the International Guide Collaboration Network. The inclusion criteria were being independent guidelines/recommendation documents for upper gastrointestinal cancer screening and meeting the definition of the institute of Medicine, USA. The exclusion criteria were being guideline abstracts, interpretation and evaluation literature, duplicate publications, updated original guidelines, and clinical treatment or practice guidelines for esophageal or gastric cancer. Appraisal of Guidelines for Research and Evaluation (AGREE Ⅱ) and Reporting Items for Practice Guidelines in Healthcare (RIGHT) were used to compare and evaluate the quality and reporting standard of esophageal or gastric cancer screening guidelines. Results: A total of 6 esophageal cancer screening guidelines and 5 gastric cancer screening guidelines were included. The results of the AGREE Ⅱ quality evaluation showed that the overall quality of eleven guidelines varied, including two guidelines recommended for "A", one for "B", five for "C" and three for "D". The guidelines had higher scores in the areas of scope and purpose, and clarity. The esophageal cancer screening guidelines had different scores in the areas of rigor and independence. The gastric cancer screening guidelines generally had low scores in the areas of participants and application. The RIGHT evaluation results showed that the quality of eleven guidelines should be improved. The six items with poor report quality were background, evidence, recommendations, review and quality assurance, funding and conflict of interest statement and management and others. Conclusion: The quality of the included upper gastrointestinal cancer screening guidelines is general, and the standardization needs to be strengthened.

[Research advances in the relationship of dietary factors and prostate cancer risk]

Prostate cancer is the second most common malignancy in men worldwide. An increasing trend for prostate cancer incidence was observed in China. Enormous studies have been conducted to investigate the association between dietary factors and prostate cancer, however conflicted results were obtained. Red meat, processed meat, and dairy products consumption were reported to be associated with the increased prostate cancer risk, while tomatoes, soybeans and green tea might reduce the risk of prostate cancer occurance. However, no consensus could be reached without strong evidence. Furthermore, further studies are needed to investigate the association between vitamin and mineral supplements and prostate cancer risk. Some studies reported that men with higher dietary inflammatory index scores increased prostate cancer risk. There may be a long susceptible period when dietary factors affect prostate cancer risk, which poses challenges for collecting exposure and the follow-up. Measure bias and detection bias are the main reasons which impair the authenticity of studies on the relationship of dietary factors and prostate cancer risk. Researchers should apply various methods to measure participants' dietary consumption levels and ascertain essential outcomes, such as prostate cancer death. This article reviews updated epidemiological evidences on the association of dietary factors and prostate cancer, aims to benefit future nutritional epidemiology studies focus on the prostate cancer prevention.

[Quality assessment of global prostate cancer screening guidelines]

Objective: To systematically review the quality of clinical practice guidelines for prostate cancer screening to serve as a reference for developing prostate cancer screening guidelines in China. Methods: We searched PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, Wanfang Data, and SinoMed with the term "prostate cancer" "prostate carcinoma" "prostate tumor" "screening" "early detection" "guideline" "recommendation" as keywords. The Appraisal of Guidelines for Research & Evaluation (AGREE) Ⅱ instrument and Reporting Items for Practice Guidelines in Healthcare (RIGHT) were used for critical appraisal. Results: A total of thirteen guidelines were included in this review. Evaluated by the AGREE Ⅱ instrument, ten were considered as A level. Two guidelines scored B level, and one was considered C level. Lowest mean domain scores were for stakeholder involvement (52.1%) and applicability (34.0%). Using the RIGHT checklist, we found that the low reporting quality of the thirteen guidelines could be attributable to incomplete disclosure of evidence (64.6%), funding, declaration and management of interest (44.2%), or other information (46.2%). Conclusions: No guidelines for prostate cancer screening was developed in China. The methodological quality of the guidelines in prostate cancer screening was good, which set a tone for the development of Chinese guidelines. However, all guidelines showed poor reporting quality.

[Course of Revision of the Diagnosis and Treatment Protocol for COVID-19 and the Forensic Contribution]

Abstract

From January 15 to March 3, 2020, seven editions of the guidelines for the diagnosis and treatment of COVID-19 have been issued successively by the National Health Commission of the People's Republic of China, and the guidelines' name was changed from Guidelines for Diagnosis and Treatment of Novel Coronavirus Pneumonia to Diagnosis and Treatment for COVID-19. It optimized and perfected the etiology, clinical manifestations and types, diagnostic procedures and specific treatment measures of the disease, so that the clinical management of the cases was more scientific. In the revision process of guidelines for diagnosis and treatment, forensic medicine experts have also made some positive suggestions on clinical diagnosis and treatment. Especially regarding the pathological changes of COVID-19, they have repeatedly called for rapid autopsy at different levels. With the support, understanding and cooperation of all parties, pathological examination of more than ten cases of the remains were carried out, which made an important contribution to the understanding of the clinical characteristics and pathological characteristics of the disease and the improvement of treatment plans.

Epitope Analysis and Efficacy Evaluation of Phosphatase 2C (PP2C) DNA Vaccine Against Toxoplasma gondii Infection

Toxoplasma gondii infects almost all warm-blooded animals and negatively affects the health of a wide range of these animals, including humans. Protein phosphatase 2C (PP2C) is a T. gondii protein secreted by rhoptry organelles during host cell invasion. However, very little is known about whether this protein can induce protective immunity against T. gondii. In this study, bioinformatics analysis of PP2C revealed some useful information in the context of anti-toxoplasmosis treatments and vaccine research. In addition, the PP2C gene was amplified, and a eukaryotic expression vector (pEGFP-PP2C) was successfully constructed to express PP2C. Finally, the constructed pEGFP-PP2C was injected into mice to evaluate whether it could induce immunoprotection. Compared with the control groups, we found that immunizations with the pEGFP-PP2C plasmid could elicit specific IgG antibodies and cytokines against T. gondii infection. The survival of mice immunized with the pEGFP-PP2C plasmid was significantly prolonged compared with that of the control group mice. Based on the ability of pEGFP-PP2C to induce specific immune responses against T. gondii, we propose that PP2C merits consideration as a potential vaccine candidate against toxoplasmosis.

Identification of Tiletamine, Zolazepam and Their Metabolites in Drug Facilitated Sexual Assault by GC-QTOF-MS

Objective To identify tiletamine, zolazepam and their metabolites in samples from drug facilitated sexual assault by gas chromatography-quadrupole time of flight mass spectrometry （GC-QTOF-MS）. Methods Urine samples of victims were collected, and detected by GC-QTOF-MS after liquid-liquid extraction and concentration. The molecular formula of fragments ions was identified by determination of accurate mass numbers, to detect related substances. Results Tiletamine, zolazepam, three metabolites of tiletamine and two metabolites of zolazepam were identified in urine samples from actual cases. Conclusion GC-QTOF-MS provides abundant and accurate information of fragment ions mass numbers, which can be used for qualitative identification of tiletamine, zolazepam and their metabolites in drug facilitated sexual assault.

[Data mining of esophageal squamous cell carcinoma from The Cancer Genome Atlas database]

Objective: To deeply investigate the gene expression profiles of esophageal squamous cell carcinoma (ESCC) and the relationship of gene expression levels with prognosis from The Cancer Genome Atlas (TCGA) database. Methods: RNA-seq V2 data of 11 normal samples and 81 esophageal squamous cell carcinoma patients, and their corresponding clinical data were downloaded from The Cancer Genome Atlas database. Differentially expressed genes between normal and tumor samples were identified by using edgeR package. Gene function enrichment analyses of differentially expressed genes were conducted. A protein-protein interaction network based on differentially expressed genes was constructed by using STRING database and the hub genes were identified based on the created gene co-expression network. In addition, survival analysis was performed. Results: Totally, 2 788 genes were identified as differential expression. Among these, 1 168 genes were up-regulated and 1 620 genes were down-regulated in tumor cases compared with normal samples. Up-regulated genes were enriched in cell cycle, DNA replication and mismatch repair pathways, while down-regulated genes were enriched in metabolic pathways. 707 genes and their 3 428 interactions were identified by protein-protein interaction analysis. Genes with copy number amplifications were considered to interact with other crucial genes. 10 co-expression modules were identified based on the gene co-expression network analysis and the ribosomal protein genes were illustrated to be correlated with tumor locations of ESCC patients (P=0.003). The 3-years survival rates of high and low expression of TNFRSF10B groups were 82.5% and 15.1%, respectively. Similarly, the 3-years survival rates of high and low expression of DDX18 groups were 82.4% and 15.2%, respectively. The survival differences stratified by these two genes were statistically significant (both P<0.1). Conclusions: The analysis results of TCGA database showed that ribosomal protein genes are correlated with tumor locations of ESCC patients. Low expressions of TNFRSF10B and DDX18 are associated with poor prognose of ESCC patients. Consequently, TNFRSF10B and DDX18 may serve as predictive markers for ESCC patients.

Research gaps in the management and prevention of cutaneous squamous cell carcinoma in organ transplant recipients

Although tremendous progress has been made in recent years in skin cancer care for organ transplant recipients, significant gaps remain in data-driven clinical guidelines, particularly for the treatment and prevention of cutaneous squamous cell carcinoma (cSCC), the most common malignancy among this population. In this review, we aim to summarize current knowledge around the management of cSCC and highlight the most significant gaps in knowledge that continue to pose challenges in the delivery of skin cancer care for organ transplant recipients. We suggest future directions for research that will bridge existing gaps and establish evidence-driven guidelines for primary prevention, screening and treatment of cSCC in this high-risk patient population.

Structural and antigenic analysis and cloning of surface antigen protein 5 in Toxoplasma gondii

Toxoplasma gondii is identified as an obligate intracellular apicomplexan parasite that infects warm blooded animals and humans worldwide. SAG5 protein includes SAG5A, -5B, -5C, -5D, and -5E five subtypes. SAG5A, -5B, -5C, and -5D are expressed on the surface of Toxoplasma gondii. In this study, we used online T-Coffee tool to analyze SAG5 proteins sequence alignment. SMART software was used to predict secondary structures of SAG5A, -5B, -5C, and -5D. The 3D models of SAG5 proteins were constructed and analyzed with SWISS-MODEL server and VMD software. Results indicated that SAG5A, -5B, -5C, and -5D are highly homologous proteins. Furthermore, liner-B cell epitopes and Th-cell epitopes of the four proteins were predicted using DNAMAN software and Epitope Database online service. The bioinformatics analysis of SAG5A, -5B, -5C, and -5D proteins could provide valuable information on prevention and treatment of toxoplasmosis. In addition, the four genes were obtained by PCR and inserted into an eukaryotic expression vector pEGFP-C1 respectively. Identified by restriction enzyme digestion, the four recombinant plasmids were transfected into HEK 293-T cells and tested by RT-PCR. Results showed that the constructed plasmids were all transfected to HEK 293-T cells successfully.

MicroRNA-146b inhibition augments hypoxia-induced cardiomyocyte apoptosis

MicroRNAs (miRs) regulate a number of physiological and pathological processes, including myocardial chronic hypoxia. Previous studies revealed that the expression of miR-146b is increased in vitro and in vivo following the induction of hypoxia. In the present study, the role of miR‑146b in hypoxic cardiomyocytes, and the mechanisms underlying its activity, were investigated. The expression of miR‑146b was measured in tissue samples from patients with congenital heart disease by reverse transcription‑quantitative polymerase chain reaction. The rat H9c2 cardiomyocyte cell line was transfected with an miR‑146b inhibitor or the experimental controls, and the cells were maintained under hypoxic conditions for 72 h. The expression of miR‑146b increased following the induction of hypoxia. Transfection with the miR‑146b inhibitor enhanced the release of lactate dehydrogenase and increased hypoxia‑induced apoptosis, as determined by terminal deoxynucleotidyl transferase dUTP nick‑end labeling, Hoechst 33258 staining, JC‑1 assay (measuring mitochondrial membrane permeability) and annexin V/propidium iodide analysis. A decreased expression of Bcl‑2 was observed, whereas the expression levels of cleaved‑caspase 3 and Bax were increased. Western blot analysis and a dual luciferase reporter assay confirmed that ribonuclease L is a direct target of miR‑146b. Furthermore, inhibition of miR-146b increased the activation of nuclear factor-κB and signal transducer and activator of transcription 3. In conclusion, the inhibition of miR‑146b may increase hypoxia-induced cardiomyocyte apoptosis.

Areas of potential suitability and survival of Dendroctonus valens in China under extreme climate warming scenario

The areas in China with climates suitable for the potential distribution of the pest species red turpentine beetle (RTB) Dendroctonus valens LeConte (Coleoptera: Scolytidae) were predicted by CLIMEX based on historical climate data and future climate data with warming estimated. The model used a historical climate data set (1971-2000) and a simulated climate data set (2010-2039) provided by the Tyndall Centre for Climate Change (TYN SC 2.0). Based on the historical climate data, a wide area was available in China with a suitable climate for the beetle in which every province might contain suitable habitats for this pest, particularly all of the southern provinces. The northern limit of the distribution of the beetle was predicted to reach Yakeshi and Elunchun in Inner Mongolia, and the western boundary would reach to Keerkezi in Xinjiang Province. Based on a global-warming scenario, the area with a potential climate suited to RTB in the next 30 years (2010-2039) may extend further to the northeast. The northern limit of the distribution could reach most parts of south Heilongjiang Province, whereas the western limit would remain unchanged. Combined with the tendency for RTB to spread, the variation in suitable habitats within the scenario of extreme climate warming and the multiple geographical elements of China led us to assume that, within the next 30 years, RTB would spread towards the northeast, northwest, and central regions of China and could be a potentially serious problem for the forests of China.

Association of gestational diabetes mellitus (GDM) with subclinical atherosclerosis: a systemic review and meta-analysis

BACKGROUND

Gestational diabetes mellitus (GDM) is associated with an elevated risk of adverse health outcomes such as type 2 diabetes and cardiovascular diseases. Carotid intima-media thickness (cIMT) is increasingly used as a noninvasive marker for subclinical atherosclerosis. Whether there is a direct correlation between GDM and elevated cIMT is still controversial.

METHODS

PubMed, Embase and reference lists of relevant papers were reviewed. Studies assessing the relationship between GDM and cIMT were included. Weighted Mean Difference (WMD) of cIMT was calculated using random-effect models.

RESULTS

Fifteen studies with a total of 2247 subjects were included in our analysis, giving a pooled WMD of 0.05 (95% confidence interval [CI] 0.03 -0.07). Furthermore, meta regression and subgroup analysis found that the association between GDM and larger cIMT already existed during pregnancy, and this relation was stronger in obese GDM patients.

CONCLUSIONS

GDM in and after pregnancy is associated with subclinical atherosclerosis. Weight control may be helpful to prevent cardiovascular diseases for GDM patients.

Roles of Fas/Fasl, Bcl-2/Bax, and Caspase-8 in rat nonalcoholic fatty liver disease pathogenesis

The aim of this study was to investigate the roles of Fas/FasL, Bcl-2/Bax, and Caspase-8 mRNA expressions in nonalcoholic fatty liver disease (NAFLD). The apoptosis percentage was measured by flow cytometry, the immunohistochemical assay was performed for the determination of Fas, FasL, Bcl-2, and Bax expressions, and a real-time polymerase chain reaction (PCR) assay was performed to detect Caspase-8 mRNA expression. Flow cytometry showed that the apoptosis percentage of the rat liver in the experimental group increased, which increased more obviously with the extension of modeling time. Immunohistochemistry showed that with increasing hepatic steatosis, Fas and FasL protein staining intensified and the number of positive cells increased; the number of positive cells for Bcl-2 and Bax gradually increased on the 4th, 8th, and 12th weeks in the experimental group, whereas the Bcl-2/Bax ratio decreased. The real-time PCR assay showed that Caspase-8 mRNA expression increased with increasing hepatic steatosis and inflammation, exhibiting a progressively rising trend. Hepatocyte apoptosis could promote NAFLD progression; Fas, FasL, and Caspase-8 mRNA activation were important contributing factors to NAFLD. The upregulation of Bax and Bcl-2 expression might be one important mechanism of the apoptosis in NAFLD.

Overexpression of the apple MpNPR1 gene confers increased disease resistance in Malus x domestica

The NPR1 gene plays a pivotal role in systemic acquired resistance in plants. Its overexpression in Arabidopsis and rice results in increased disease resistance and elevated expression of pathogenesis-related (PR) genes. An NPR1 homolog, MpNPR1-1, was cloned from apple (Malus x domestica) and overexpressed in two important apple cultivars, Galaxy and M26. Apple leaf pieces were transformed with the MpNPR1 cDNA under the control of the inducible Pin2 or constitutive Cauliflower mosaic virus (CaMV)35S promoter using Agrobacterium tumefaciens. Overexpression of MpNPR1 mRNA was shown by reverse transcriptase-polymerase chain reaction. Activation of some PR genes (PR2, PR5, and PR8) was observed. Resistance to fire blight was evaluated in a growth chamber by inoculation of the shoot tips of our own rooted 30-cm-tall plants with virulent strain Ea273 of Erwinia amylovora. Transformed Galaxy lines overexpressing MpNPR1 had 32 to 40% of shoot length infected, compared with 80% in control Galaxy plants. Transformed M26 lines overexpressing MpNPR1 under the control of the CaMV35S promoter also showed a significant reduction of disease compared with control M26 plants. Some MpNPR-overexpressing Galaxy lines also exhibited increased resistance to two important fungal pathogens of apple, Venturia inaequalis and Gymnosporangium juniperi-virginianae. Selected transformed lines have been propagated for field trials for disease resistance and fruit quality.

Crocetin improves endothelium-dependent relaxation of thoracic aorta in hypercholesterolemic rabbit by increasing eNOS activity

Our previous studies have proven that crocetin (CCT), extracted from Gardenia jasminoides Ellis, possesses the anti-atherosclerotic effect. Because endothelial dysfunction strongly contributes to the initiation and progression of atherosclerosis, the present study aims to investigate whether CCT is capable of improving this dysfunction and to explore the possible mechanisms. Endothelial dysfunction was induced by in vivo feeding high cholesterol diet (HCD) to rabbit and by in vitro treating bovine aortic endothelial cells (BAECs) with oxidized LDL (oxLDL). Endothelium-dependent relaxation (EDR) evoked by acetylcholine (Ach) and endothelium-independent relaxation (RIDR) mediated by sodium nitroprusside (SNP) of thoracic aorta isolated from rabbit were measured. The results indicated that the EDR in HCD alone treated rabbits was seriously impaired and the maximal relaxation induced by Ach (10(-5.5) M) was only 54% that in control rabbit fed with regular diet. Oral complementation with CCT (15, 30 mg/kg) dose-dependently improved this impairment and restored the maximal relaxation to 68% and 80% that in control group, respectively. However, the EIDR maintained comparable in all groups. Complementation with CCT (15, 30 mg/kg) simultaneously increased serum level of nitric oxide (NO), upregulated vessel activity and mRNA expression of endothelial NO synthase (eNOS) as well as vessel cyclic GMP (cGMP) content compared with those in rabbit treated with HCD alone. Inducible NOS (iNOS) activity remained unchangeable in all groups. In BAECs, oxLDL treatment decreased NO production, downregulated both activity and mRNA expression of eNOS. While those decrease or downregulation were inhibited by co-treatment with CCT (0.1, 1, 10 microM) in a dose-dependent manner. These findings suggested that CCT significantly restored the EDR of thoracic aorta in hypercholesterolemic rabbit, which might be explained by its action to increase the vessel eNOS activity, leading to elevation of NO production.

Oral immunization with a live recombinant attenuated Salmonella typhimurium protects mice against Toxoplasma gondii

The natural site of infection for T. gondii is the mucosal surface of the intestine, so the protective immunity obtained after natural infection with T. gondii points to the importance of developing a vaccine that stimulates mucosal defences. In this study, an aroA- and aroD- attenuated strain of Salmonella typhimurium (BRD509) has been used to deliver the recombinant eukaryotic plasmid pSAG(1-2)/CTA2/B expressing a multi-antigenic gene encoding SAG1 and SAG2 of T. gondii linked to A2/B subunits of cholera toxin as a candidate oral T. gondii vaccine. Immunoblot analysis showed compound gene expression in HeLa cells in vitro and intragastric immunization of mice with the recombinant salmonella resulted in the induction of humoral and Th1 type cellular immune responses and afforded protection against RH strain T. gondii challenge. Anti-T. gondii IgG values increased markedly in the BRD509/pSAG(1-2)-CTA2/B immunized group; these values were significantly higher than those in the negative controls (P = 0.008). With CTA2/B genetic adjuvant, the T. gondii-specific response was predominantly Th1, indicating that the CTA(2)/B genetic adjuvant was able to overcome the strong Th2-bias of the antigen (IgG2a >> IgG1). Antigen-specific T cell proliferative responses and CTL activity were significantly enhanced when cholera toxin CTA2/B genetic adjuvant was used (P = 0.009; P = 0.006). Culture supernatants from antigen-stimulated splenocytes from mice in these groups were also examined by ELISA for Th1- and Th2-type cytokines; mean IFN-gamma levels produced after oral immunization with BRD509/pSAG(1-2)-CTA2/B were about nine-fold higher than after immunization with BRD509/pSAG(1-2) (P = 0.007). On the other hand, the levels of IL-4 were low for all groups and no increase was seen in the presence of CTA2/B genetic adjuvant. When the immunized mice were intraperitoneally challenged with 10(3) tachyzoites of the highly virulent RH strain, the survival time of the mice immunized with BRD509/pSAG(1-2)-CTA2/B was markedly longer than other groups (P = 0.003) and a 40% survival rate was achieved. This is the first report that demonstrates that an oral attenuated salmonella DNA vaccine can induce protective immunity against the acute phase of T. gondii infection.

Role of the Hrp pilus in type III protein secretion in Pseudomonas syringae

Bacterial surface appendages called pili and needle-like filaments are associated with protein and/or DNA transfer to recipient plant, human, or bacterial cells during pathogenesis or conjugation. Although it has long been suspected that pili function as a conduit for protein or DNA transfer, direct evidence has been lacking. The Hrp pilus of Pseudomonas syringae is assembled by the type III secretion system. We used an in situ immunogold labeling procedure to visualize the extrusion of an effector protein, AvrPto, from the tip of the Hrp pilus, providing direct evidence that a bacterial pilus can function as a conduit for protein delivery.

[The development and application of oxypathor of standard atmosphere]

This paper introduces a newly-developed oxypathor under one absolute atmosphere. It provides both oxygen and mixed-oxygen therapies, featuring oxygen-supply and oxygen-inhalation of hyperbaric oxygen chamber, and broaden the clinical applications of oxygen-therapy, which gave shown satisfactory results.

Role of calcitonin gene-related peptide in nitric oxide-mediated myocardial delayed preconditioning induced by head stress

AIM

To study the role of calcitonin gene-related peptide (CGRP) in nitric oxide (NO)-mediated myocardial delayed preconditioning induced by heat stress.

METHODS

The isolated rat heart was perfused in a Langendorff model. Hearts for all groups were subjected to 4 h hypothermia (4 degrees C) and 40 min reperfusion (37 degrees C). In the hyperthermia-treated group, rats were subjected to whole-body hyperthermia (rectal 42 degrees C, 15 min) 24 h before the experiment. Heart rate, coronary flow, left ventricular pressure, and its derivative (+/- dp/dtmax) were recorded, and calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) in plasma and the activity of creatine kinase (CK) in the coronary effluent were measured.

RESULTS

Pretreatment with hyperthermia significantly improved the recovery of cardiac protection, reduced the release of CK, and increased plasma concentrations of CGRP. Pretreatment with L-NAME, an inhibitor of NOS, or capsaicin, which selectively depleted sensory neurotransmitter content, abolished the protective effects and the increased level of CGRP elicited by hyperthermia.

CONCLUSION

Endogenous NO is involved in the cardioprotection afforded by heat stress, and the beneficial effects of NO are mediated by CGRP in the rat.

Visualization of secreted Hrp and Avr proteins along the Hrp pilus during type III secretion in Erwinia amylovora and Pseudomonas syringae

Pili are required for protein and/or DNA transfer from bacteria to recipient plant or bacterial cells, based on genetic evidence. However, it has never been shown directly that the effector proteins or DNA are localized along or inside the pili in situ. Failure to visualize an association of effector proteins/DNA with pili is the central issue in the debate regarding the exact function of pili in protein and DNA transfer. In this study, a newly developed in situ immunogold labelling procedure enabled visualization of the specific localization of type III effector proteins of Erwinia amylovora and Pseudomonas syringae pv. tomato along the Hrp pilus, but not along the flagellum or randomly in the intercellular space. In contrast, PelE, a pectate lyase secreted via the type II protein secretion system, was not associated with the Hrp pilus. These results provide direct evidence that type III secretion occurs only at the site of Hrp pilus assembly and that the Hrp pilus guides the transfer of effector proteins outside the bacterial cell, favouring the 'conduit/guiding filament' model.

Monophosphoryl lipid A-induced delayed preconditioning is mediated by calcitonin gene-related peptide

The delayed preconditioning of the heart by monophosphoryl lipid A is mediated by endogenous nitric oxide (NO), and the cardioprotection afforded by nitroglycerin is related to stimulation of calcitonin gene-related peptide (CGRP) release. The objective of this study was to explore whether improvement of preservation with cardioplegia by monophosphoryl lipid A is mediated by CGRP. In addition, we examined the effect of monophosphoryl lipid A on the tumor necrosis factor-alpha (TNF-alpha) content of myocardial tissues. The isolated rat heart was perfused in the Langendorff mode. Heart rate, coronary flow, left-ventricular pressure, and its first derivatives (+/-dp/dt(max)) were recorded, and plasma levels of NO and CGRP, the release of creatine kinase in coronary effluent and the content of TNF-alpha in myocardial tissues were measured. Hypothermic ischemia for 4 h caused a decline in cardiac function, and an increase in the release of creatine kinase and in the content of TNF-alpha. Pretreatment with monophosphoryl lipid A (500 microg/kg, i.p.) for 24 h improved the recovery of cardiac function and reduced the release of creatine kinase concomitantly with a decrease in the content of cardiac TNF-alpha. Monophosphoryl lipid A markedly increased plasma concentrations of CGRP and NO. After pretreatment with L-nitroarginine methyl ester (L-NAME), the cardioprotection and the increased release of NO and CGRP induced by monophosphoryl lipid A were abolished. Capsaicin also abolished the cardioprotection and the increased release of CGRP induced by monophosphoryl lipid A, but did not affect the content of NO. The results suggest that monophosphoryl lipid A-induced preconditioning enhances preservation with cardioplegia and that the protective effects of monophosphoryl lipid A are related to stimulation of CGRP release.

Immunogold labeling of Hrp pili of Pseudomonas syringae pv. tomato assembled in minimal medium and in planta

Hypersensitive reaction and pathogenicity (hrp) genes are required for Pseudomonas syringae pv. tomato (Pst) DC3000 to cause disease in susceptible tomato and Arabidopsis thaliana plants and to elicit the hypersensitive response in resistant plants. The hrp genes encode a type III protein secretion system known as the Hrp system, which in Pst DC3000 secretes HrpA, HrpZ, HrpW, and AvrPto and assembles a surface appendage, named the Hrp pilus, in hrp-gene-inducing minimal medium. HrpA has been suggested to be the Hrp pilus structural protein on the basis of copurification and mutational analyses. In this study, we show that an antibody against HrpA efficiently labeled Hrp pili, whereas antibodies against HrpW and HrpZ did not. Immunogold labeling of bacteria-infected Arabidopsis thaliana leaf tissue with an Hrp pilus antibody revealed a characteristic lineup of gold particles around bacteria and/or at the bacterium-plant contact site. These results confirm that HrpA is the major structural protein of the Hrp pilus and provide evidence that Hrp pili are assembled in vitro and in planta.

Expression of a functional antizearalenone single-chain Fv antibody in transgenic Arabidopsis plants

The efficacy of cloning a recombinant mycotoxin antibody in plants was tested using Arabidopsis as a model. An antizearalenone single-chain Fv (scFv) DNA fragment was first cloned in the newly constructed phage display vector (pEY.5) and then recloned in the plant transformation vector pKYLX71::35S(2). After transformation, constructs of antizearalenone scFv were introduced into immature Arabidopsis seeds via Agrobacterium tumefaciens mediation by vacuum infiltration. Only plants transformed with the construct containing a PR-1b signal peptide sequence produced transgenic offspring. The antizearalenone scFv "plantibody" from these transgenic plants bound zearalenone with a high affinity (50% inhibitory concentration, 11.2 ng/ml) that was comparable to that of bacterially produced scFv antibody and the parent monoclonal antibody (MAb). By electron microscopic immunogold labeling, the presence of antizearalenone scFv was detected mainly in the cytoplasm and only occasionally outside the cell. Like bacterially produced scFv antibody, antizearalenone scFv plantibody exhibited greater sensitivity to methanol destabilization than did the parent MAb. The sensitivity of antizearalenone scFv plantibody to acidic disassociation was similar to the sensitivities of bacterially produced scFv antibody and MAb. Expression of specific plantibodies in crops might be useful for neutralizing mycotoxins in animal feeds and for reducing mycotoxin-associated plant diseases.

Conversion of compatible plant-pathogen interactions into incompatible interactions by expression of the Pseudomonas syringae pv. syringae 61 hrmA gene in transgenic tobacco plants

The hrmA gene from Pseudomonas syringae pv. syringae has previously been shown to confer avirulence on the virulent bacterium P. syringae pv. tabaci in all examined tobacco cultivars. We expressed this gene in tobacco plants under the control of the tobacco Delta0. 3 TobRB7 promoter, which is induced upon nematode infection in tobacco roots (Opperman et al. 1994, Science, 263, 221-223). A basal level of hrmA expression in leaves of transgenic plants activated the expression of pathogenesis-related genes, and the transgenic plants exhibited high levels of resistance to multiple pathogens: tobacco vein mottling virus, tobacco etch virus, black shank fungus Phytophthora parasitica, and wild fire bacterium Pseudomonas syringae pv. tabaci. However, the hrmA transgenic plants were not significantly more resistant to root-knot nematodes. Our results suggest a potential use of controlled low-level expression of bacterial avr genes, such as hrmA, in plants to generate broad-spectrum resistance to bacterial, fungal and viral pathogens.

The gene coding for the Hrp pilus structural protein is required for type III secretion of Hrp and Avr proteins in Pseudomonas syringae pv. tomato

Bacterial surface appendages called pili often are associated with DNA and/or protein transfer between cells. The exact function of pili in the transfer process is not understood and is a matter of considerable debate. The Hrp pilus is assembled by the Hrp type III protein secretion system of Pseudomonas syringae pv. tomato (Pst) strain DC3000. In this study, we show that the hrpA gene, which encodes the major subunit of the Hrp pilus, is required for secretion of putative virulence proteins, such as HrpW and AvrPto. In addition, the hrpA gene is required for full expression of genes that encode regulatory, secretion, and effector proteins of the type III secretion system. hrpA-mediated gene regulation apparently is through effect on the mRNA level of two previously characterized regulatory genes, hrpR and hrpS. Ectopic expression of the hrpRS gene operon restored gene expression, but not protein secretion, in the hrpA mutant. Three single amino acid mutations at the HrpA carboxyl terminus were identified that affect the secretion or regulatory function of the HrpA protein. These results define an essential role of the Hrp pilus structural gene in protein secretion and coordinate regulation of the type III secretion system in Pst DC3000.

The Pseudomonas syringae pv. tomato HrpW protein has domains similar to harpins and pectate lyases and can elicit the plant hypersensitive response and bind to pectate

The host-specific plant pathogen Pseudomonas syringae elicits the hypersensitive response (HR) in nonhost plants and secretes the HrpZ harpin in culture via the Hrp (type III) secretion system. Previous genetic evidence suggested the existence of another harpin gene in the P. syringae genome. hrpW was found in a region adjacent to the hrp cluster in P. syringae pv. tomato DC3000. hrpW encodes a 42. 9-kDa protein with domains resembling harpins and pectate lyases (Pels), respectively. HrpW has key properties of harpins. It is heat stable and glycine rich, lacks cysteine, is secreted by the Hrp system, and is able to elicit the HR when infiltrated into tobacco leaf tissue. The harpin domain (amino acids 1 to 186) has six glycine-rich repeats of a repeated sequence found in HrpZ, and a purified HrpW harpin domain fragment possessed HR elicitor activity. In contrast, the HrpW Pel domain (amino acids 187 to 425) is similar to Pels from Nectria haematococca, Erwinia carotovora, Erwinia chrysanthemi, and Bacillus subtilis, and a purified Pel domain fragment did not elicit the HR. Neither this fragment nor the full-length HrpW showed Pel activity in A230 assays under a variety of reaction conditions, but the Pel fragment bound to calcium pectate, a major constituent of the plant cell wall. The DNA sequence of the P. syringae pv. syringae B728a hrpW was also determined. The Pel domains of the two predicted HrpW proteins were 85% identical, whereas the harpin domains were only 53% identical. Sequences hybridizing at high stringency with the P. syringae pv. tomato hrpW were found in other P. syringae pathovars, Pseudomonas viridiflava, Ralstonia (Pseudomonas) solanacearum, and Xanthomonas campestris. DeltahrpZ::nptII or hrpW::OmegaSpr P. syringae pv. tomato mutants were little reduced in HR elicitation activity in tobacco, whereas this activity was significantly reduced in a hrpZ hrpW double mutant. These features of hrpW and its product suggest that P. syringae produces multiple harpins and that the target of these proteins is in the plant cell wall.

Type III protein secretion systems in plant and animal pathogenic bacteria

Among many interesting and sophisticated mechanisms used by bacterial pathogens to subvert eukaryotic hosts is a class of specialized protein secretion systems (known as type III protein secretion systems) that deliver bacterial virulence proteins directly into the host cell. Recent studies have revealed four important features of these secretion systems. First, they are widespread among plant and animal bacterial pathogens, and mutations affecting type III protein secretion often eliminate bacterial virulence completely. Second, at least eight type III secretion components share sequence similarities with those of the flagellar assembly machinery and flagellum-like structures are associated with type III secretion, raising the possibility that these secretion systems are derived from the presumably more ancient flagellar assembly apparatus. Third, type III secretion is activated in vivo upon contact with host cells. Fourth, the type III secretion mechanism is Sec-independent and the effector proteins may possess mRNA-based targeting signals. This review highlights the similarities and differences among type III secretion systems of selected model plant and animal pathogenic bacteria.

Hrp-controlled interkingdom protein transport: learning from flagellar assembly?

Plant pathogenic bacteria appear to deliver avirulence and virulence proteins through the cell wall and into the host cells via an Hrp (hypersensitive reaction and pathogenicity)-encoded type III secretion system. Recent results suggest that there is a similarity between this secretion system and the flagellum assembly apparatus.

Hrp pilus: an hrp-dependent bacterial surface appendage produced by Pseudomonas syringae pv. tomato DC3000

Hypersensitive response and pathogenicity (hrp) genes control the ability of major groups of plant pathogenic bacteria to elicit the hypersensitive response (HR) in resistant plants and to cause disease in susceptible plants. A number of Hrp proteins share significant similarities with components of the type III secretion apparatus and flagellar assembly apparatus in animal pathogenic bacteria. Here we report that Pseudomonas syringae pv. tomato strain DC3000 (race 0) produces a filamentous surface appendage (Hrp pilus) of 6-8 nm in diameter in a solid minimal medium that induces hrp genes. Formation of the Hrp pilus is dependent on at least two hrp genes, hrpS and hrpH (recently renamed hrcC), which are involved in gene regulation and protein secretion, respectively. Our finding of the Hrp pilus, together with recent reports of Salmonella typhimurium surface appendages that are involved in bacterial invasion into the animal cell and of the Agrobacterium tumefaciens virB-dependent pilus that is involved in the transfer of T-DNA into plant cells, suggests that surface appendage formation is a common feature of animal and plant pathogenic bacteria in the infection of eukaryotic cells. Furthermore, we have identified HrpA as a major structural protein of the Hrp pilus. Finally, we show that a nonpolar hrpA mutant of P. syringae pv. tomato DC3000 is unable to form the Hrp pilus or to cause either an HR or disease in plants.

The Pseudomonas syringae Hrp regulation and secretion system controls the production and secretion of multiple extracellular proteins

Pseudomonas syringae pv. tomato DC3000 produces seven to eight major extracellular proteins (EXPs) in a minimal medium inducing hrp genes. Using a polyclonal antibody against DC3000 EXPs, we have determined that the production and secretion of five EXPs (EXP-60, EXP-45, EXP-43, EXP-22, and EXP-10) are under the control of the Hrp regulation and secretion system.

hrp gene-dependent induction of hin1: a plant gene activated rapidly by both harpins and the avrPto gene-mediated signal

Two classes of bacterial genes are involved in the elicitation of the plant hypersensitive response (HR) in resistant plants: hrp genes and avr genes. hrp genes have been shown to be involved in the production and secretion of a new class of bacterial virulence/avirulence proteins, including harpin of Erwinia amylovora and harpinPss of Pseudomonas syringae. The ability of avr genes in the elicitation of the HR/resistance is dependent on functional hrp genes. The relationships between harpins and avr gene products are not known. This study investigates the plant genes induced by harpins and the effect of avr genes on the expression of such plant genes. A tobacco gene highly induced by harpins was isolated by a subtractive hybridization method. Induction of hin1 by P.s. pv. syringae 61 (Pss61) was found to be dependent on functional bacterial hrp genes. P. fluorescens (a saprophyte) or hrp mutants defective in the Hrp secretion pathway did not induce hin1 significantly. A hin 1-related gene in tomato cv. Rio Grande-PtoR was found to be rapidly induced by P. s. pv. tomato T1 (a virulent bacterium on Rio Grande-PtoR) containing the avrPto gene, which mediates the elictation of the HR/resistance in a Pto plant resistance gene-dependent manner. The induction of hin1 by bacteria correlates with production of harpins in planta. The putative open reading frame of hin1 encodes a novel protein of 221 amino acids. The data suggest that harpins and the avrPto-mediated signal induce a common plant gene in the elicitation of the HR.

Expression of the Pseudomonas syringae avirulence protein AvrB in plant cells alleviates its dependence on the hypersensitive response and pathogenicity (Hrp) secretion system in eliciting genotype-specific hypersensitive cell death

The nonpathogenic bacteria Pseudomonas fluorescens and Escherichia coli can elicit a genotype-specific hypersensitive response (HR) in plants if they express both the HR and pathogenesis (Hrp) protein secretion system and the HrpZ harpin from P. syringae pv syringae 61 and a P. syringae avirulence (avr) gene whose presence is recognized by a corresponding disease resistance gene in the plant. We have found that the recognition event appears to require transfer of the Avr protein into the plant cell. Elicitation of a genotype-specific HR was observed with avrB+ P. fluorescens in soybean and Arabidopsis plants carrying resistance genes RPG1 and RPM1, respectively, and with avrPto+ E. coll in tomato plants carrying resistance gene PTO, but only if the Hrp secretion system, HrpZ, and the appropriate Avr proteins were produced in the same bacterial cell. The failure of avrB hyperexpression and exogenous AvrB or HrpZ to alleviate these requirements in soybean and Arabidopsis suggests that the site of AvrB action is not in the bacterial cell or plant apoplast. An Arabidopsis rps3 (rpm1) glabrous1 mutant was transformed with constructs expressing avrB and was crossed with an Arabidopsis ecotype Columbia (RPM1 GLABROUS1) plant. F1 seedlings (identified by their kanamycin-resistant, pubescent phenotype) exhibited extensive necrosis on cotyledon leaves 10 days postgermination. Ecotype Columbia and rps3-1 leaves biolistically cobombarded with plasmids expressing the beta-glucuronidase (GUS) gene and avrB failed to produce GUS activity (indicative of cell death) only when RPM1 and avrB were present in the leaf. Thus, both stable and transient expression of avrB in Arabidopsis resulted in RPM1-dependent necrosis, and the only demonstrable site of action for AvrB was inside plant cells.

Expression of the Pseudomonas syringae avirulence protein AvrB in plant cells alleviates its dependence on the hypersensitive response and pathogenicity (Hrp) secretion system in eliciting genotype-specific hypersensitive cell death

The nonpathogenic bacteria Pseudomonas fluorescens and Escherichia coli can elicit a genotype-specific hypersensitive response (HR) in plants if they express both the HR and pathogenesis (Hrp) protein secretion system and the HrpZ harpin from P. syringae pv syringae 61 and a P. syringae avirulence (avr) gene whose presence is recognized by a corresponding disease resistance gene in the plant. We have found that the recognition event appears to require transfer of the Avr protein into the plant cell. Elicitation of a genotype-specific HR was observed with avrB+ P. fluorescens in soybean and Arabidopsis plants carrying resistance genes RPG1 and RPM1, respectively, and with avrPto+ E. coll in tomato plants carrying resistance gene PTO, but only if the Hrp secretion system, HrpZ, and the appropriate Avr proteins were produced in the same bacterial cell. The failure of avrB hyperexpression and exogenous AvrB or HrpZ to alleviate these requirements in soybean and Arabidopsis suggests that the site of AvrB action is not in the bacterial cell or plant apoplast. An Arabidopsis rps3 (rpm1) glabrous1 mutant was transformed with constructs expressing avrB and was crossed with an Arabidopsis ecotype Columbia (RPM1 GLABROUS1) plant. F1 seedlings (identified by their kanamycin-resistant, pubescent phenotype) exhibited extensive necrosis on cotyledon leaves 10 days postgermination. Ecotype Columbia and rps3-1 leaves biolistically cobombarded with plasmids expressing the beta-glucuronidase (GUS) gene and avrB failed to produce GUS activity (indicative of cell death) only when RPM1 and avrB were present in the leaf. Thus, both stable and transient expression of avrB in Arabidopsis resulted in RPM1-dependent necrosis, and the only demonstrable site of action for AvrB was inside plant cells.

Cardiac muscle lesions associated with chronic administration of methamphetamine in rats

Cardiovascular complications associated with methamphetamine abuse have increasingly been reported. However, chronic cardiotoxicity of methamphetamine is not experimentally well documented. In this study, methamphetamine (1 mg/kg/day) was subcutaneously injected into 5-week-old male Wistar Kyoto rats (n = 30). Age- and sex-matched Wistar Kyoto rats served as controls (n = 30). After 14 and 56 days, hearts were examined by light and electron microscopy. Foci of myocytic degeneration and necrosis appeared in the sub-endocardial areas on day 14 of methamphetamine exposure. Myocytic degeneration and necrosis became more extensive on day 56. At this stage, myocytolysis, contraction bands, atrophied myocytes, and spotty fibrosis were patchily distributed throughout the myocardium in most of rats treated with methamphetamine. The accompanying ultrastructural features included marked degeneration of cardiac mitochondria with fractured and disrupted cristae, hypercontraction of myofibrils, and loss of myofilament. In contrast, cardiac myocyte lesions were not observed in control rats. These myocardial lesions in rats treated with methamphetamine for 56 days resemble the cardiomyopathy associated with methamphetamine abuse in humans.

Morphological and morphometric investigation of cardiac lesions after chronic administration of methamphetamine in rats

The effects of chronic administration of methamphetamine on myocardium were morphologically and morphometrically studied in experimental models. Methamphetamine (1 mg/kg/day) was subcutaneously injected to five-week-old male Wistar Kyoto rats (WKY) for 8 weeks. Age- and sex-matched WKY served as controls. In light microscopy, scattered cytomyolysis, vacuolization, contraction bands and disarray of myofibers were prominent in methamphetamine-treated group; the electron microscopy showed degenerated mitochondria with disrupted cristae, myofibrillar hypercontraction and dissolution. Morphometric analysis was carried out using electron photographs and an image analyzer. The sizes of mitochondria and the number of mitochondria per unit area (100 microns2) in methamphetamine-treated group were significantly smaller than in the controls. No statistically significant difference was found regarding the percentage of myofibrillar area in cytoplasm between methamphetamine-treated and control groups. These findings show that chronic administration of methamphetamine can cause serious cardiac lesions and decrease in mitochondrial function.

The HrpZ proteins of Pseudomonas syringae pvs. syringae, glycinea, and tomato are encoded by an operon containing Yersinia ysc homologs and elicit the hypersensitive response in tomato but not soybean

The Pseudomonas syringae pathovars are composed of host-specific plant pathogens that characteristically elicit the defense-associated hypersensitive response (HR) in nonhost plants. P. s. pv. syringae 61 secretes an HR elicitor, harpinPss (HrpZPss), in a hrp-dependent manner. An internal fragment of the P. s. pv. syringae 61 hrpZ gene was used to clone the hrpZ locus from P. s. pv. glycinea race 4 (bacterial blight of soybean) and P. s. pv. tomato DC3000 (bacterial speck of tomato). DNA sequence analysis revealed that hrpZ is the second ORF in a polycistronic operon. The amino acid sequence identities of HrpZPss/HrpZPsg and HrpZPss/HrpZPst were 79 and 63%, respectively. Although none of the HrpZ proteins showed significant overall sequence similarity with other known proteins, HrpZPst contained a 24-amino acid sequence that is homologous with a region of the PopA1 elicitor protein of the tomato pathogen, Pseudomonas solanacearum GMI1000. hrpA, the upstream ORF, was highly divergent: The amino acid sequence identities of HrpAPss/HrpAPsg and HrpAPss/HrpAPst were 91 and 28%, respectively, and no HrpA sequence showed similarity to known proteins. In contrast, the predicted products of the downstream ORFs in P. s. pv. syringae and P. s. pv. tomato, hrpB, hrpC, hrpD, and hrpE showed varying levels of similarity to those of yscI, yscJ, yscK, and yscL. These are colinearly arranged genes in the virC locus of Yersinia spp., which are involved in the secretion of the Yop virulence proteins via the type III pathway. The similarity of the Ysc proteins was generally stronger in comparisons with the P. s. pv. tomato Hrp proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Methamphetamine-induced toxicity in cultured adult rat cardiomyocytes

In an attempt to differentiate the direct effects of methamphetamine from the indirect sympathomimetic effects on the myocardium, primary culture of adult rat myocytes were established under serum-free conditions, and they were exposed to methamphetamine (1 x 10(-5) and 1 x 10(-3) M) for 1 to 24 h in the presence and absence of 1 x 10(-6) M propranolol. Cardiotoxicity was evaluated by light and ultramicroscopy, release of cytoplasmic enzymes (Lactate dehydrogenase: LDH and Creatine phosphokinase: CPK) and change in membrane permeability (Trypan blue stain). After 24 h methamphetamine treatment, light microscopy exhibited cellular granulation and swelling, myocyte hypercontraction, broken cellular membrane and cellular destruction. After the same time, electron microscopy revealed swelling and irregular mitochondria with disrupted cristaes, clump of sarcomeres with nearly complete loss of organized contractile elements, injury of intracellular membrane system and dissolution of myofibrils. These injurious features were more severe with the 1 x 10(-3) M methamphetamine. Propranolol (1 x 10(-6) M), a beta-adrenergic antagonist, failed to protect the myocytes against methamphetamine-induced cell injury. Release of LDH from methamphetamine (1 x 10(-5) and 1 x 10(-3) M)-treated myocytes increased significantly only after 24 h, while significant CPK release was observed in 1 x 10(-3) M methamphetamine-treated myocytes at 4 h. These findings suggest that methamphetamine exerts direct toxic effects on adult rat myocytes rather than indirect ones via receptors, although further experiments on more concentrations of propranolol are required.