Comparison of the Efficacy and Safety of Rivaroxaban and Low Molecular Heparin in Preventing Venous Thromboembolism in Inpatient Cancer Patients

BACKGROUND

There are few studies on using rivaroxaban and low molecular heparin (LMWH) to prevent venous thromboembolism (VTE) in hospitalized cancer patients.

OBJECTIVE

We conducted a retrospective study to evaluate the efficacy and safety of rivaroxaban versus LMWH for the primary prevention of VTE in inpatient cancer patients.

METHODS

Information on patients was collected through 6-month follow-up and medical record inquiries. Clinical outcomes included VTE, total bleeding, thrombosis, major bleeding, minor bleeding, all-cause death, and a composite endpoint of bleeding, thrombosis, and death.

RESULTS

A total of 602 hospitalized cancer patients were included in this study. During 6 months of follow-up, there were 26 VTE events (8.6%), 42 total bleeding events (7.0%), 62 all-cause deaths (10.3%), and 140 composite endpoints (23.3%). After adjusting for various confounding factors, there were no significant differences between the rivaroxaban and LMWH for VTE events (OR = 0.851, 95% CI [0.387-1.872], P=0.688), total bleeding (OR = 1.690, 95% CI [0.768-3.719], P = 0.192], thrombosis events (OR = 0.919, 95% CI [0.520-1.624], P = 0.772], major bleeding (OR = 0.276, 95% CI [0.037-2.059], P = 0.209), all-cause death (OR = 0.994, 95% CI [0.492-2.009], P = 0.987), and composite endpoints (OR = 0.994, 95% CI [0.492-2.009], P = 0.987), while minor bleeding (OR = 3.661 95% CI [1.000-7.083], P = 0.050) was significantly higher in the rivaroxaban than in the LMWH.

CONCLUSIONS AND RELEVANCE

In thromboprophylaxis in inpatient cancer patients, rivaroxaban has a similar rate of VTE and bleeding events as LMWH. Our results may provide a reference for the clinical use of rivaroxaban to prevent VTE in hospitalized cancer patients.

Rheumatic heart disease burden, trends, and inequalities in Asia, 1990-2019

BACKGROUND

Rheumatic heart disease (RHD) is a serious global public health problem.

OBJECTIVES

This study aims to characterise the regional burden, trends, and inequalities of RHD in countries and territories in the Asian Region.

METHODS

The RHD disease burden was measured in terms of the numbers of cases and deaths, prevalence, disability-adjusted life years (DALYs), disability-loss healthy life years (YLDs), and years of life lost (YLLs) in 48 countries in the Asian Region. Data on RHD were extracted from the 2019 Global Burden of Disease. This study analysed changing trends in the burden between 1990 and 2019, quantified regional inequalities in mortality, and classified countries by 2019 YLLs.

RESULTS

There were an estimated 22 246 127 cases of RHD in the Asian Region in 2019 and 249 830 deaths. The prevalence of RHD in the Asian Region in 2019 was 9% lower than the global estimate, while mortality was 41% higher. The mortality rate for RHD in the Asian Region trended downwards from 1990 to 2019, with an average annual percentage change of -3.2% (95% UI -3.3 to -3.1). From 1990 to 2019, absolute inequality in RHD-related mortality decreased in the Asian Region while relative inequality increased. Of the 48 countries studied, twelve had the highest level of RHD YLLs in 2017 and the smallest reduction in YLLs from 1990 to 2019.

CONCLUSION

Although the burden of RHD in the Asian Region has steadily decreased since 1990, it remains a serious public health issue requiring greater attention. In the Asian Region, inequalities in the distribution of the RHD burden remain significant, with economically deprived countries typically bearing a greater share of the load.

Interpretable machine learning models for predicting venous thromboembolism in the intensive care unit: an analysis based on data from 207 centers

BACKGROUND

Venous thromboembolism (VTE) is a severe complication in critically ill patients, often resulting in death and long-term disability and is one of the major contributors to the global burden of disease. This study aimed to construct an interpretable machine learning (ML) model for predicting VTE in critically ill patients based on clinical features and laboratory indicators.

METHODS

Data for this study were extracted from the eICU Collaborative Research Database (version 2.0). A stepwise logistic regression model was used to select the predictors that were eventually included in the model. The random forest, extreme gradient boosting (XGBoost) and support vector machine algorithms were used to construct the model using fivefold cross-validation. The area under curve (AUC), accuracy, no information rate, balanced accuracy, kappa, sensitivity, specificity, precision, and F1 score were used to assess the model's performance. In addition, the DALEX package was used to improve the interpretability of the final model.

RESULTS

This study ultimately included 109,044 patients, of which 1647 (1.5%) had VTE during ICU hospitalization. Among the three models, the Random Forest model (AUC: 0.9378; Accuracy: 0.9958; Kappa: 0.8371; Precision: 0.9095; F1 score: 0.8393; Sensitivity: 0.7791; Specificity: 0.9989) performed the best.

CONCLUSION

ML models can be a reliable tool for predicting VTE in critically ill patients. Among all the models we had constructed, the random forest model was the most effective model that helps the user identify patients at high risk of VTE early so that early intervention can be implemented to reduce the burden of VTE on the patients.

Global, regional, and national burden of ischaemic heart disease and its trends, 1990-2019

OBJECTIVES

Ischemic heart disease (IHD) has high morbidity, disability, and mortality rates and is a major contributor to the global disease burden. This study aimed to obtain a more detailed description of the burden of IHD through secondary analysis of data from the Global Burden of Disease (GBD) 2019.

STUDY DESIGN

This is an epidemiological study.

METHODS

Data for this study were obtained from the GBD 2019 database. Annual average percentage change (AAPC) was calculated to assess trends in IHD prevalence, morbidity, mortality, and disability-adjusted life years (DALYs). Regional and national burden of IHD was assessed by stratifying by sex, age, and socio-demographic index (SDI).

RESULTS

From 1990 to 2019, the global prevalence of IHD, morbidity cases, deaths, and DALYs increased, but the age-standardized rates of IHD burden decreased. Morbidity, mortality, and DALY rates for IHD in both sexes increased with age. The prevalence, incidence, mortality, and DALY rates were higher in men than women in all age groups. In particular, the male-to-female ratios for mortality and DALY rates peaked among 35-39 year olds, while the male-to-female ratios for prevalence and morbidity peaked among 55-59 year olds. Age-standardized prevalence, incidence, and DALY rates were higher in low- and middle-income regions than in other SDI regions.

CONCLUSION

Although age-standardized prevalence, morbidity, mortality, and age-standardized DALY rates due to IHD decreased globally from 1990 to 2019, age-standardized prevalence and morbidity of IHD increased in Low SDI, Low-middle SDI, and Middle SDI regions.

Continuous Erroneous Feedback Processing during Deviation from the Road within a 2D Steering Task. Annu Int Conf IEEE Eng Med Biol Soc 2023;2023:1-4. [PMID: 38082976 DOI: 10.1109/embc40787.2023.10340764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Recent research of our group indicated that erroneous feedback processing can not only be detected via established correlates in the electroencephalogram (EEG) for discrete stimuli, but also arises as modulations of the brain signals when faced with a continuous and periodic error signal. However, limitations in our previous paradigm prevented a definitive statement on the error signal as the exclusive source of the modulations, as well as on the connection between the observed error-related negativity (ERN)-like and error positivity (Pe)-like continuous correlates. Within a new paradigm involving EEG recordings of 10 participants, we disentangled modulation sources, substantiating our hypothesis that the observed periodicity arises primarily due to feedback processing. Further, we provide evidence that the continuous ERN- and Pe-like potentials are locked to separate phases in the error signal, rather than time-locked to a shared event, indicating that both potentials arise independently of one another.

Global burden of cardiovascular disease attributable to metabolic risk factors, 1990-2019: an analysis of observational data from a 2019 Global Burden of Disease study

OBJECTIVES

An up-to-date, detailed global analysis of the current status of the metabolic-attributed cardiovascular disease (CVD) burden has not been reported. Therefore, we investigated the global burden of metabolic-attributed CVD and its association with socioeconomic development status over the past 30 years.

METHODS

Data on the burden of metabolic-attributed CVD were taken from the 2019 Global Burden of Disease (GBD) study. Metabolic risk factors of CVD included high fasting plasma glucose, high low-density lipoprotein cholesterol (LDL-c), high systolic blood pressure (SBP), high body mass index (BMI) and kidney dysfunction. Numbers and age-standardised rates (ASR) of disability-adjusted life-years (DALYs) and deaths were extracted and stratified by sex, age, Socio-demographic Index (SDI) level, country and region.

RESULTS

The ASR of metabolic-attributed CVD DALYs and deaths decreased by 28.0% (95% UI 23.8% to 32.5%) and 30.4% (95% UI 26.6% to 34.5%), respectively, from 1990 to 2019. The highest burden of metabolic-attributed total CVD and intracerebral haemorrhage was mainly in low SDI locations, while the highest burden of ischaemic heart disease and IS was mainly in high SDI locations. The burden of DALYs and deaths in CVD was higher in men than women. In addition, the number and ASR of DALYs and deaths were highest in those over 80 years old.

CONCLUSION

Metabolic-attributed CVD threatens public health, especially in low-SDI locations and among the elderly. Low SDI location should strengthen the control of metabolic factors such as high SBP, high BMI, and high LDL-c and increase the knowledge of metabolic risk factors for CVD. Countries and regions should enhance screening and prevention of metabolic risk factors of CVD in the elderly. Policy-makers should use 2019 GBD data to guide cost-effective interventions and resource allocation.

Efficacy and Safety of Direct Oral Anticoagulants in Patients With Atrial Fibrillation Combined With Hypertension: A Multi-Center, Retrospective Cohort Study

Whether there are differences in direct oral anticoagulants efficacy and safety in patients with atrial fibrillation combined with hypertension are unclear. We therefore conducted a multicenter retrospective cohort study to assess the differences in efficacy and safety of direct oral anticoagulants in patients with atrial fibrillation combined with hypertension. This multi-center retrospective cohort study was based on data from 15 centers in China and included 2086 patients with atrial fibrillation. We divided the patients into dabigatran and rivaroxaban groups according to their direct oral anticoagulants. Propensity score matching was used to balance the covariates between the groups. Due to our limited sample size, the number of cases of some clinical events with low incidence was small. During a mean follow-up period of 10 months, a total of 268 (12.9%) bleeding events occurred, including 27 (1.3%) major bleeding events and 241 (11.6%) minor bleeding events, and 45 (2.2%) thromboembolic events. In atrial fibrillation patients combined with hypertension, rivaroxaban was associated with a higher major bleeding incidence than dabigatran (OR: 2.89; 95%Cl: 1.22-6.87; P:0.012). In contrast, the risk of thromboembolism and minor bleeding was similar for rivaroxaban and dabigatran (OR: 0.55; 95%Cl: 0.29-1.01; P: 0.069) (OR: 0.82; 95%Cl: 0.63-1.08; P: 0.150). Based on the results of this study, in patients with atrial fibrillation and hypertension treated with direct oral anticoagulants, the incidence of thromboembolism and minor bleeding was not statistically different between dabigatran and rivaroxaban, but compared with rivaroxaban, dabigatran was associated with a lower risk of major bleeding. This article is protected by copyright. All rights reserved.

Safety and efficacy of direct oral anticoagulation in patients with and without radiofrequency ablation of non-valvular atrial fibrillation: a multicenter retrospective cohort study

BACKGROUND

Based on the few available studies on the prognostic benefit of using direct oral anticoagulants (DOACs) after atrial fibrillation (AF) ablation. Therefore, this study aimed to evaluate the prognostic differences between patients who underwent radiofrequency ablation (RFA) and those without RFA taking DOACs.

METHODS

This is a multicenter retrospective cohort study enrolling 6137 patients with non-valvular AF (NVAF) at 15 hospitals in China. Patient information was collected through a mean follow-up of 10 months and medical record queries. Clinical outcomes included major bleeding, total bleeding, thrombosis, all-cause death, and a composite endpoint of bleeding, thrombosis, and all-cause death.

RESULTS

After adjusting for confounders and propensity score matching (PSM), patients with RFA of NVAF had a significantly lower risk of major bleeding [OR 0.278 (95% CI, 0.150-0.515), P<0.001], thrombosis [OR 0.535 (95% CI, 0.316-0.908), P=0.020] and the composite endpoint [ OR 0.835 (95% CI, 0.710-0.982), P=0.029]. In the RFA PSM cohort, dabigatran was associated with reduced all-cause death in patients with RFA of NVAF [OR 0.420 (95% CI, 0.212-0.831), P=0.010]. In the no RFA PSM cohort, rivaroxaban was associated with a reduction in major bleeding [OR 0.521 (95% CI, 0.403-0.673), P<0.001], total bleeding [OR 0.114 (95% CI, 0.049-0.266), P<0.001], and the composite endpoint [OR 0.659 ( 95% CI, 0.535-0.811), P<0.001].

CONCLUSION

Among patients with NVAF treated with DOACs, RFA was a negative correlate of major bleeding, thrombosis, and composite endpoints but was not associated with total bleeding or all-cause mortality.

Direct oral anticoagulants for venous thromboembolism in cancer patients: a systematic review and network meta-analysis

BACKGROUND

The efficacy and safety of direct oral anticoagulants (DOACs), including dabigatran, apixaban, rivaroxaban, and edoxaban, for preventing and treating venous thromboembolism (VTE) in patients with cancer is unclear.

METHODS

We searched the PubMed, Embase, Web of Science, and Cochrane Library databases from the establishment to November 30, 2021. In the frequency-based network meta-analysis, the odds ratio with a 95% confidence interval was reported. The relative ranking probability of each group was generated based on the surface under the cumulative ranking curve (SUCRA).

RESULTS

We included 15 randomized controlled trials involving a total of 6162 patients. Apixaban reduced the risk of VTE compared with low-molecular heparin [OR = 0.53, 95% CI (0.32, 0.89)]. The efficacy of drugs was ranked from highest to lowest as follows: apixaban (SUCRA, 81.0), rivaroxaban (73.0), edoxaban (65.9), dabigatran (51.4), warfarin (30.8), and low-molecular-weight heparin (LMWH) (27.4). Edoxaban increased the risk of major bleeding compared with LMWH [OR = 1.83, 95% CI (1.04, 3.22)]. The safety of drugs was ranked from highest to lowest as follows: major bleeding-apixaban (SUCRA, 68.5), LMWH (55.1), rivaroxaban (53.0), warfarin (35.9), dabigatran (29.2), edoxaban (16.5) and clinically relevant non-major bleeding-LMWH (73.0), apixaban (57.8), edoxaban (45.8), rivaroxaban (35.3), and warfarin (10.8).

CONCLUSIONS

For preventing and treating VTE, in terms of VTE occurrence and major bleeding, apixaban had the lowest risk; in terms of clinically relevant non-major bleeding, LMWH had the lowest risk, followed by apixaban. Generally, apixaban is the most efficient and safest DOAC and presents better efficacy and relatively low bleeding risk among the VTE prevention and treatment drugs for patients with cancer.

Cross-genera amplification and identification of Colpodella sp. with Cryptosporidium primers in fecal samples of zoo felids from northeast China

The protozoans include many intracellular human pathogens. Accurate detection of these pathogens is necessary to treat the diseases. In clinical epidemiology, molecular identification of protozoan is considered a more reliable and rapid method for identification than microscopy. Among these protozoans, Cryptosporidium considered being one of the important water-borne zoonotic pathogens and a major cause of a diarrheal disease named cryptosporidiosis in humans, domestic animals, and wild animals. This study was aimed to identify Cryptosporidium in zoo felids (N= 56) belonging to different zoo of China, but accidentlly Colpodella was encountered in the zoo felids sample and phylogenetic data confirmed this unexpected amplification from fecal samples using two-step nested-PCR. Phylogenetic analysis revealed the fact about the specific primers used previously by many researchers and cross-genera amplification. We came to know that genetically sequenced amplicon gives more accurate identification of species. This study suggests more investigation on Colpodella which has been neglected previously but gains the attention of researchers after identified from humans and animals and has been known to correlate with neurological symptoms in patients.

[Correlation of baseline serum 25-hydroxyvitamin D level with the risk of type 2 diabetes mellitus: a prospective cohort study]

OBJECTIVE

To investigate the correlation of baseline serum 25(OH) D level with the risk of type 2 diabetes mellitus (T2DM) and blood glucose control in diabetic patients among the middle-aged and elderly individuals in Chengguan District of Lanzhou, Gansu Province.

OBJECTIVE

Residents aged 40 to 75 years in Lanzhou were selected from the "REACTION" study conducted in 2011 and had been followed up since 2014. A total of 5044 subjects with complete data from the two surveys were analyzed. Participants were divided into Q1, Q2, Q3, and Q4 subgroups based on quartiles of serum 25(OH)D level for comparison of the incidence of T2DM and blood glucose control.

OBJECTIVE

Baseline 25(OH)D level was not found to correlate with FPG, 2h-PG or HbA1c levels among the residents (P>0.05). The participants were followed up for a mean of 3.4±0.6 years, and compared with those in Q1 group, the participants in Q2, Q3 and Q4 groups did not show significantly lowered risk of prediabetes or diabetes regardless of glucose tolerance status. Among the patients with T2DM, the compliance rate of glycemic control after the follow-up was significantly higher than that before the follow-up (63.4% vs 60.6%), and the levels of HbA1c, FPG, and 2h-PG decreased obviously after the follow-up. But compared with Q1 group, Q2, Q3 and Q4 groups showed no significant changes in glycemic control compliance rate or levels of HbA1c, FPG and 2h-PG after the follow-up (P>0.05).

OBJECTIVE

There is no evidence that baseline 25(OH)D levels are associated with the risk of diabetes and blood glucose control in patients with T2DM.

Assessing alfalfa (Medicago sativa L.) tolerance to salinity at seedling stage and screening of the salinity tolerance traits

Salt is among the most harmful agents that negatively influences crop yield. Alfalfa is an important perennial forage crop that exhibits wide cultivar variations in salt tolerance. Developing salt-tolerant alfalfa plants is a promising way to utilize salinized land. A comprehensive method was developed to achieve reliable and effective evaluation of alfalfa salt resistance. This included principal components, membership functions and cluster and stepwise regression analyses. These were used to analyse the salt tolerance coefficients of 14 traits and to evaluate 20 diverse alfalfa cultivars at the seedling stage. The various morphological root parameters of six alfalfa cultivars with contrasting salt tolerance were also tested by a scanning apparatus. According to the comprehensive evaluation value (D value), one highly salt-tolerant, two salt-tolerant, four moderately salt-tolerant and 13 salt-sensitive alfalfa cultivars were screened. A mathematical equation for the evaluation of alfalfa salt tolerance was established: D' = -0.126 + 0.667SFW + 0.377SDW + 1.089K⁺ /Na⁺  + 0.172SFW/RFW (R²  = 0.988; average forecast accuracy of 96.95%), where four indices were closely related to the salt tolerance: shoot fresh weight, ratio of shoot fresh weight to root fresh weight, shoot dry weight and ratio of K⁺ to Na⁺ in the shoot. We also found that SSA correlated strongly with SFW, SDW, K⁺ /Na⁺ , D values, while SRV correlated obviously with SFW, SFW/RFW and D values after 150 mm NaCl treatment. In conclusion, the SFW, K⁺ /Na⁺ , SDW, SFW/RFW, SSA and SRV could be used as indicators of salt tolerance in alfalfa seedlings grown under 150 mm NaCl treatment.

[Association between lipoprotein (a) level and chronic cardio-renal syndrome in elderly patients]

Objective: To explore the relationship between lipoprotein(a) [Lp(a)] and chronic cardio-renal syndrome (CRS) in elderly patients. Methods: Chronic heart failure (CHF) patients age ≥ 65 years old, who hospitalized in the department of Cardiology of Hebei General Hospital from December 2017 to October 2019, were included in this study. According to the estimate glomerular filtration rate (eGFR) level, patients were divided into CRS group (eGFR<60 ml·min^-1·1.73 m^-2) and CHF group (eGFR ≥60 ml·min^-1·1.73 m^-2). The blood index and basic disease information were collected and compared. Left ventricular ejection fraction (LVEF) were measured by echocardiography. The correlation between clinical indicators and cardio-renal function (LVEF and eGFR) was assessed. The multivariate logistic regression analysis was used to evaluate the related risk factors of CRS in elderly patients; subgroup logistic regression analysis was performed according to the basic disease of patients to assess the relationship between Lp(a) and CRS. Results: A total of 172 elderly patients (85 males (49.4%), aged 79 (71, 84) years) were finally enrolled. Among them, 88 cases (51.2%) were in CRS group and 84 cases (48.8%) were in CHF group. Age (80 (74, 84) years old vs. 74 (70, 82) years old) and LP (a) levels (222.0 (112.0, 445.3) mg/L vs. 155.0 (97.0, 348.7) mg/L) were significantly higher in the CRS group than in the CHF group (P<0.05). Lp(a) levels were negatively correlated with LVEF (r=-0.155, P=0.043) and eGFR (r=-0.220, P=0.004) in total cohort. In the subgroup analysis of patients with 2 high-incidence basic diseases (coronary heart disease and hypertension), Lp(a) was negatively correlated with LVEF (r=-0.250, P=0.007) in the coronary heart disease group, and negatively correlated with eGFR (r=-0.233, P=0.013) in the hypertension group. Multivariate logistic regression analysis showed that age (OR = 1.069, 95%CI: 1.017-1.124, P= 0.009) and Lp(a) (OR = 3.719, 95%CI: 1.339-10.326, P = 0.012) were independent correlates of CRS. The results of logistic regression analysis showed that Lp(a) was an independent correlative factor of CRS in the subgroups of coronary heart disease (OR=3.207, 95%CI: 1.129-9.108, P=0.029) and hypertension (OR=3.054, 95%CI: 1.086-8.587, P=0.034). Conclusion: Serum Lp(a) level is independently related with CRS in elderly patients.

Psychology of cross cultural communication: an impact on the health care system

Cross culture communication has become an integral part of today's world, especially in developed countries with a large population of immigrants. The health care system is one of the important areas in which health care practitioners and patients may be of different cultures, therefore there is a need of effective communication between culturally different patients and health practitioners. However, cross-culture communication is affected by psychological factors related to cultures and mind-set. Acculturation orientation is one of the important factors, and people with different orientations interact differently with people of different cultures. Cultural orientation is another important factor is which different domains define the characteristic features of different cultures. Moreover, the inclination to use native or non-native language with culturally different patients is a key factor for establishing a good relationship between patients and health care practitioners.

Integrated carbon, sulfur, and nitrogen isotope chemostratigraphy of the Ediacaran Lantian Formation in South China: Spatial gradient, ocean redox oscillation, and fossil distribution

The Ediacaran Doushantuo Formation in South China is a prime target for geobiological investigation because it offers opportunities to integrate chemostratigraphic and paleobiological data. Previous studies were mostly focused on successions in shallow-water shelf facies, but data from deep-water successions are needed to fully understand basinal redox structures. Here, we report δ¹³ C_carb , δ¹³ C_org , δ³⁴ S_pyr , δ³⁴ S_CAS , and δ¹⁵ N_sed data from a drill core of the fossiliferous Lantian Formation, which is a deep-water equivalent of the Doushantuo Formation. Our data confirm a large (>10‰) spatial gradient in δ¹³ C_carb in the lower Doushantuo/Lantian formations, but this gradient is probably due to the greater sensitivity of carbonate-poor deep-water sediments to isotopic mixing with ¹³ C-depleted carbonate cements. A pronounced negative δ¹³ C_carb excursion (EN3) in the upper Doushantuo/Lantian formations, however, is spatially consistent and may be an equivalent of the Shuram excursion. δ³⁴ S_pyr is more negative in deeper-water facies than in shallow-water facies, particularly in the lower Doushantuo/Lantian formations, and this spatial pattern is interpreted as evidence for ocean redox stratification: Pyrite precipitated in euxinic deep waters has lower δ³⁴ S_pyr than that formed within shallow-water sediments. The Lantian Formation was probably deposited in oscillating oxic and euxinic conditions. Euxinic black shales have higher TOC and TN contents, but lower δ³⁴ S_pyr and δ¹⁵ N_sed values. In euxinic environments, pyrite was predominantly formed in the water column and organic nitrogen was predominantly derived from nitrogen fixation or NH₄⁺ assimilation because of quantitative denitrification, resulting in lower δ³⁴ S_pyr and δ¹⁵ N_sed values. Benthic macroalgae and putative animals occur exclusively in euxinic black shales. If preserved in situ, these organisms must have lived in brief oxic episodes punctuating largely euxinic intervals, only to be decimated and preserved when the local environment switched back to euxinia again. Thus, taphonomy and ecology were the primary factors controlling the stratigraphic distribution of macrofossils in the Lantian Formation.

Vertical migration of leachate pollutants in clayey soils beneath an uncontrolled landfill at Huainan, China: a field and theoretical investigation

To assess the extent of leachate migration, continuous samples of clayey soils (about 9m) were obtained beneath a 17-year old uncontrolled landfill in southeastern China. The soil samples were sub sectioned and analyzed to determine the concentrations of chloride, sodium and COD in the pore water. Total nitrogen and soil organic matter content of the soil samples were also determined. Leachate-derived chloride was detected in the clayey soil to a maximum depth of 9m. Sodium and COD were found to migrate into the soils to depths of 3-4m due to the attenuation of solutes by the soil organic matter and clay minerals at the shallow soils. The estimated migration depths for the chloride are 3m in the case of pure diffusion. Advection and mechanical dispersion were found to be more important than molecular diffusion for this site with an 8m high leachate mound. By comparing the results obtained by the mathematical modeling for layered advection-dispersion problem with the measured concentration profiles, the ranges of the effective diffusion coefficient, retardation factor and dispersivity of the soils were estimated. Better fits are obtained by employing an artificial effective interface about 1m above the observed interface. The clayey soils showed a relatively high attenuation capacity for COD with the estimated retardation factor of 5.

An analytical model for solute transport through a GCL-based two-layered liner considering biodegradation

An analytical model for solute advection and dispersion in a two-layered liner consisting of a geosynthetic clay liner (GCL) and a soil liner (SL) considering the effect of biodegradation was proposed. The analytical solution was derived by Laplace transformation and was validated over a range of parameters using the finite-layer method based software Pollute v7.0. Results show that if the half-life of the solute in GCL is larger than 1 year, the degradation in GCL can be neglected for solute transport in GCL/SL. When the half-life of GCL is less than 1 year, neglecting the effect of degradation in GCL on solute migration will result in a large difference of relative base concentration of GCL/SL (e.g., 32% for the case with half-life of 0.01 year). The 100-year solute base concentration can be reduced by a factor of 2.2 when the hydraulic conductivity of the SL was reduced by an order of magnitude. The 100-year base concentration was reduced by a factor of 155 when the half life of the contaminant in the SL was reduced by an order of magnitude. The effect of degradation is more important in approving the groundwater protection level than the hydraulic conductivity. The analytical solution can be used for experimental data fitting, verification of complicated numerical models and preliminary design of landfill liner systems.

A comparison of the clinical characteristics of women with recurrent major depression with and without suicidal symptomatology

BACKGROUND

The relationship between recurrent major depression (MD) in women and suicidality is complex. We investigated the extent to which patients who suffered with various forms of suicidal symptomatology can be distinguished from those subjects without such symptoms.

METHOD

We examined the clinical features of the worst episode in 1970 Han Chinese women with recurrent DSM-IV MD between the ages of 30 and 60 years from across China. Student's t tests, and logistic and multiple logistic regression models were used to determine the association between suicidality and other clinical features of MD.

RESULTS

Suicidal symptomatology is significantly associated with a more severe form of MD, as indexed by both the number of episodes and number of MD symptoms. Patients reporting suicidal thoughts, plans or attempts experienced a significantly greater number of stressful life events. The depressive symptom most strongly associated with lifetime suicide attempt was feelings of worthlessness (odds ratio 4.25, 95% confidence interval 2.9-6.3). Excessive guilt, diminished concentration and impaired decision-making were also significantly associated with a suicide attempt.

CONCLUSIONS

This study contributes to the existing literature on risk factors for suicidal symptomatology in depressed women. Identifying specific depressive symptoms and co-morbid psychiatric disorders may help improve the clinical assessment of suicide risk in depressed patients. These findings could be helpful in identifying those who need more intense treatment strategies in order to prevent suicide.

Expression and distribution of SIBLING proteins in the predentin/dentin and mandible of hyp mice

OBJECTIVES

Human X-linked hypophosphatemia (XLH) and its murine homologue, Hyp are caused by inactivating mutations in PHEX gene. The protein encoded by PHEX gene is an endopeptidase whose physiological substrate(s) has not been identified. Dentin matrix protein 1 (DMP1) and dentin sialophosphoprotein (DSPP), two members of the Small Integrin-Binding LIgand, N-linked Glycoprotein (SIBLING) family are proteolytically processed. It has been speculated that PHEX endopeptidase may be responsible for the proteolytic cleavage of DMP1 and DSPP. To test this hypothesis and to analyse the distribution of SIBLING proteins in the predentin/dentin complex and mandible of Hyp mice, we compared the expression of four SIBLING proteins, DMP1, DSPP, bone sialoprotein (BSP) and osteopontin (OPN) between Hyp and wild-type mice.

METHODS

These SIBLING proteins were analysed by protein chemistry and immunohistochemistry.

RESULTS

(1) Dentin matrix protein 1 and DSPP fragments are present in the extracts of Hyp predentin/dentin and bone; (2) the level of DMP1 proteoglycan form, BSP and OPN is elevated in the Hyp bone.

CONCLUSIONS

The PHEX protein is not the enzyme responsible for the proteolytic processing of DMP1 and DSPP. The altered distribution of SIBLING proteins may be involved in the pathogenesis of bone and dentin defects in Hyp and XLH.

Truncated hemoglobins in actinorhizal nodules of Datisca glomerata

Three types of hemoglobins exist in higher plants, symbiotic, non-symbiotic, and truncated hemoglobins. Symbiotic (class II) hemoglobins play a role in oxygen supply to intracellular nitrogen-fixing symbionts in legume root nodules, and in one case ( Parasponia Sp.), a non-symbiotic (class I) hemoglobin has been recruited for this function. Here we report the induction of a host gene, dgtrHB1, encoding a truncated hemoglobin in Frankia-induced nodules of the actinorhizal plant Datisca glomerata. Induction takes place specifically in cells infected by the microsymbiont, prior to the onset of bacterial nitrogen fixation. A bacterial gene (Frankia trHBO) encoding a truncated hemoglobin with O (2)-binding kinetics suitable for the facilitation of O (2) diffusion ( ) is also expressed in symbiosis. Nodule oximetry confirms the presence of a molecule that binds oxygen reversibly in D. glomerata nodules, but indicates a low overall hemoglobin concentration suggesting a local function. Frankia trHbO is likely to be responsible for this activity. The function of the D. glomerata truncated hemoglobin is unknown; a possible role in nitric oxide detoxification is suggested.

Effect of ocular artifact removal in brain computer interface accuracy

We report the effect of removing ocular artifacts on the performance of a word-processing application based on the event related potential P300. Various methods of removing artifacts have been reported. The efficiency of these algorithms are usually done by subjective visual comparisons. Noting that there is a direct correlation of artifact rectifying algorithms to the accuracy in a brain computer interface system's accuracy, we present this work as a means to compare different algorithms.

Composite structured light pattern for three-dimensional video

Based on recent discoveries, we introduce a method to project a single structured pattern onto an object and then reconstruct the three-dimensional range from the distortions in the reflected and captured image. Traditional structured light methods require several different patterns to recover the depth, without ambiguity or albedo sensitivity, and are corrupted by object movement during the projection/ capture process. Our method efficiently combines multiple patterns into a single composite pattern projection allowing for real-time implementations. Because structured light techniques require standard image capture and projection technology, unlike time of arrival techniques, they are relatively low cost.

[Affection of epidermal growth factor on VIP secretion and VIPR expression in airway epithelial cells]

In order to confirm the essential role of vasoactive intestinal peptide(VIP) on protection of local airway epithelium and investigate the modulation of the protective effect of VIP, secretion of VIP and expression of VIP receptor(VIPR) were studied in bronchial epithelial cells(BEC), and alveolar macrophages (AM). The radioimmunoassay was used for determining VIP secretion and the radio-ligand affinity analysis for VIPR expression. The effect of epidermal growth factor(EGF) was observed. The results showed that: 1. Both BEC and AM secreted VIP basically without remarkable stimulus, and some vesicles with electron-dense core which usually exist specifically in neuropeptide secreting cells were found in plasma of BEC; 2. In a dose-dependent manner, EGF promoted BEC to secrete VIP(r = 0.84, P < 0.05), and it was found that VIP secretion from AM was also elevated in EGF pretreated group(P < 0.05); 3. EGF exhibited a dose-dependent up-regulatory effect on the expression of VIPR in BEC(r = 0.95, P < 0.01). These results indicate that VIP may play an essential role in the protection at local airway by autocrine or paracrine, and the protective effect can be modulated by growth factors.

Root gravitropism: an experimental tool to investigate basic cellular and molecular processes underlying mechanosensing and signal transmission in plants

The ability of plant organs to use gravity as a guide for growth, named gravitropism, has been recognized for over two centuries. This growth response to the environment contributes significantly to the upward growth of shoots and the downward growth of roots commonly observed throughout the plant kingdom. Root gravitropism has received a great deal of attention because there is a physical separation between the primary site for gravity sensing, located in the root cap, and the site of differential growth response, located in the elongation zones (EZs). Hence, this system allows identification and characterization of different phases of gravitropism, including gravity perception, signal transduction, signal transmission, and curvature response. Recent studies support some aspects of an old model for gravity sensing, which postulates that root-cap columellar amyloplasts constitute the susceptors for gravity perception. Such studies have also allowed the identification of several molecules that appear to function as second messengers in gravity signal transduction and of potential signal transducers. Auxin has been implicated as a probable component of the signal that carries the gravitropic information between the gravity-sensing cap and the gravity-responding EZs. This has allowed the identification and characterization of important molecular processes underlying auxin transport and response in plants. New molecular models can be elaborated to explain how the gravity signal transduction pathway might regulate the polarity of auxin transport in roots. Further studies are required to test these models, as well as to study the molecular mechanisms underlying a poorly characterized phase of gravitropism that is independent of an auxin gradient.

[The preparation and study on hepatic targeting tendency of galactosyl-anti-CD3-McAb in mice]

OBJECTIVE

This study sought to reduce the recurrence rate of primary liver cacer (PLC) after hepatectomy by increasing the concentration of infiltrating lymphocytes(TILs) at the target organ.

METHODS

It has been reported that galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vitro. On the basis of that work, the present authors conducted a study in mice. Galactosyl-anti-CD3-McAb was prepared and its carbohydrate density was measured with the phenol-sulphyric acid method, and then anti-CD3-McAb (labeled with 125I) and galactosyl-anti-CD3-McAb (labeled with 131I) were infused respectively via the peripheral vein and the radioactivity in each organ was measured.

RESULTS

The carbohydrate density of galactosyl-anti-CD3-McAb in this experiment was 58.12, which effectively guaranteed the specific binding between galactosyl-anti-CD3-McAb and hepatic binding protein(HBP). It was also noticed that anti-CD3-McAb tended to aggregate in the lungs while being infused via the peripheral vein, and that galactosyl-anti-CD3-McAb had an obvious hepatic targeting tendency in vivo and it stayed in liver for quite a long period.

CONCLUSIONS

Galactosyl-anti-CD3-McAb has an obvious hepatic targeting tendency in vivo while being infused through peripheral vein; this may be due to the specific binding between galactose and HBP.

[The clinical and pathological research of supraglottic carcinoma with bilateral cervical nodal metastasis]

OBJECTIVE

To evaluate clinical and pathological characteristics in patients with supraglottic carcinoma and bilateral cervical nodal metastasis.

METHOD

60 patients with supraglottic carcinoma treated in this hospital from 1985 to 1994 were retrospectively reviewed, including 30 cases with bilateral metastasis (experiment group) and 30 cases with unilateral metastasis (control group). The two groups were contrasted according to site of tumor, tumor diameter, surface morphology, clinical staging, the degree of invading the contralateral semilarynx, Border's grading, growth mode of tumor edge, the degree of invading preepiglottic space.

RESULT

In stage T4 cases with low grading of cell differentiation made up 63.6% (7/11) in the bilateral metastasis group, while 10% in the ipsilateral metastasis group (P < 0.05). Significant differences lied between N0 group and N2 group (P < 0.05). Moderate and severe invasion of contralateral semilarynx in the bilateral group made up 87.5% (14/16), significantly higher than that in ipsilateral group 53.3% (16/30).

CONCLUSION

Bilateral neck dissection should be used in T4 cases with low grading of cell differentiation in which the contralateral semilarynx was invaded. Bilateral neck dissection should be taken for the treatment of supraglottic carcinoma with N2.3 diseases. Bilateral neck dissection is recommended for the patients with moderate and severe invasion of the contralateral semilarynx.

[Detection mucin gene in cervical lymph nodes in supraglottic cancer by reverse transcription polymerase chain reaction]

OBJECTIVE

To investigate the efficacy of discovery of cervical lymph nodes micrometastasis of supraglottic carcinomas by detection of mucin (MUC1) gene.

METHODS

Twenty-five supraglottic carcinoma patients with clinically negative lymph nodes were performed neck dissection. MUC1 gene mRNA in these resected lymph nodes was detected by reverse transcription polymerase chain reaction (RT-PCR) and histopathological examination to find the potential micrometastasis.

RESULTS

Of all 93 cervical lymph nodes, micrometastasis were found in 23 nodes of 6 case by histopathological examination and RT-PCR. Four of 19 cases with negative lymph nodes pathologically showed MUC1 gene expression and were identified to have metastasis by clinical recurrence and serial-sectioning. Therefore, the rate of detection of micrometastasis by this way was 16% (4/25), higher than that of regular pathologic methods.

CONCLUSION

Detection of lymph nodes micrometastasis with RT-PCR method was more sensitive than that of regular pathologic methods. It is a valuable method to detect early lymph nodes metastasis.

Pharmacokinetics of testosterone after percutaneous gel or buccal administration

OBJECTIVE

To determine the pharmacokinetics of testosterone following its administration using transdermal gel or buccal lozenges.

DESIGN

Pilot study.

SETTING

University-based hospital.

PATIENT(S)

Ten bilaterally oophorectomized women.

INTERVENTION(S)

Daily micronized testosterone gel (1 mg) and testosterone propionate lozenge (1 mg).

MAIN OUTCOME MEASURE(S)

Total testosterone, androstenedione, dihydrotestosterone, 3alpha-androstanediol glucuronide, and sex hormone-binding globulin were measured in serum by specific radioimmunoassays; free testosterone levels were also calculated.

RESULT(S)

Before treatment, serum testosterone levels in the groups using the lozenge and gel were 16 +/- 4.0 and 20 +/- 6.0 ng/dL, respectively. Mean maximum testosterone levels obtained with the lozenge occurred 1 hour after administration on days 1 (692 +/- 236 ng/dL) and 14 (836 +/- 309 ng/dL) of treatment and fell precipitously thereafter. In contrast, testosterone levels obtained with the gel showed a prolonged rise reaching maximal levels of 97 +/- 78 and 100 +/- 60 ng/dL after 18 hours. The serum level patterns of free testosterone, dihydrotestosterone, and 3alpha-androstanediol glucuronide were similar to the corresponding total testosterone levels.

CONCLUSION(S)

Administration of testosterone lozenge by buccal absorption produced a rapid and brief elevation of testosterone levels, with levels reaching upper limits of the male range. In contrast, transdermal testosterone gel absorption resulted in a prolonged elevation of testosterone levels, which were in the hyperandrogenic female range but resembled steady state pharmacokinetics.

DDT, PAH and PCB in sediments from the intertidal zone of the Bohai Sea and the Yellow Sea

Current contents of persistent organic contaminants, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and the congeners (naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo(a)anthracene, benzo(a)pyrene and benzo(e)pyrene), DDTs and metabolites in the intertidal sediments of the Bohai Sea and the Yellow Sea were studied. The mean levels of DDTs, PAHs and PCBs were 177.52, 877.2 and 3.4 ng g-1 dry weight, respectively. The spatial trends of the contaminant residue levels were analysed too.

Pathologic features of occult lymphatic metastasis in supraglottic carcinoma

OBJECTIVE

To study the pathologic features of occult lymphatic metastasis in supraglottic carcinoma.

METHODS

Serial sections of 153 neck dissection specimens in 100 patients with supraglottic carcinoma were evaluated under the microscope.

RESULTS

In 100 patients, 38 had occult metastatic lymph nodes. 51 metastatic lymph nodes were found in pathology, and their sizes ranged from 0.5 cm to 2.6 cm (average 1.1 cm). The distribution of 51 lymph nodes was 1 in level I (2%), 37 in level II (73%), 12 in level III (24%), and 1 in level IV (2%). Among the 51 nodes, 21 (41%) were early stage, 18 (35%) were growth stage, 7 (14%) were tull stage, and 5 (10%) were extracapsular stage. The differentiation degree and appearance of supraglottic carcinoma was not directly related with occult metastasis.

CONCLUSION

The occult metastatic rate of supraglottic carcinoma is high, and selective neck dissection may be necessary.

[Pharmacologic stress myocardial perfusion imaging]

This paper expounds the imaging methods, mechanism of action, hemodynamic responses, efficacy and side effects of three pharmacologic stressors (dipyridamole, adenosine and dobutamine) for clinical use in experiment of diagnosis, thus providing vital reference materials for clinical pharmacologic stress myocardial perfusion imaging.

[Coupling effect of water and fertilizers on spring wheat yield in semi-arid area of western Liaoning Province]

With optimum saturation design, a field experiment was conducted to study the coupling effect of water and fertilizers on spring wheat yield in semiarid area of western Liaoning Province. Regression model shows that water was the most important factor affecting spring wheat yield. Under natural raining and when the upper and the lower limit of irrigation was 360 mm and 45 mm, respectively, N was the most sensitive factor, water was the second, and P was the third. The effects of N, P and water on yield were statistically significant, and met the law of diminishing return. The most economic matching pattern of N, P and water was N 186 kg.hm-2, P 63 kg.hm-2, and water 300 mm. Properly increasing phosphorus fertilizer at the lack of water could strengthen the drought-resistance of spring wheat.

[Evaluation of side-effects after 131I-therapy for differentiated thyroid carcinoma]

The purpose of this study was to evaluate the side-effects of differentiated thyroid carcinoma after treatment with 3.7-7.4 GBq of 131I. A total of 342 patients were treated with 131I from May, 1989 to January, 1999. The acute side-effects, the short-term and long-term side-effects were analyzed. The follow-up lasted 1-10 years with an average of 5.4 years. The results showed that thyroiditis occurred predominantly in the patients with a rate of 131I uptake > 30%, whereas sialoadenitis occurred more prevalently in the patients with a rate of 131I uptake < 30% (P < 0.001). The rates of nausea, vomiting, diarrhea and gastralgia were 12.2%, 5.2%, 3.5% and 2.7% respectively. There were no significant changes in the hemogram after treatment, compared against that before treatment. The overall rates of transient platelet abnormalities and leukopenia were 10.4% and 4.0% respectively, but the rates of the abnormalities in the patients with cumulative doses of 131I > 18.5 GBq were significantly higher than those in patients with cumulative doses of 131 I < 18.5 GBq. The lower rate of acute and short-term side-effects and the absence of long-term side-effects in this study indicate that 131I can be safely used to treat differentiated thyroid carcinoma.

[Preparation of galactosyl-insulin with double saccharide density and a study of its hepatic targeting property]

This study was intended to improve the technical procedure so as to increase the saccharide density of galactosyl-recombinant insulin and elevate its liver targeting property. Using a branched compound 3,5-dihydroxy benzoic acid as the base of a conjugating bridge, the authors prepared a new double galactosyl-recombinant insulin, whose saccharide density being two times as high as that of galactosyl-recombinant insulin. The double gal-insulin conjugate, gal-insulin conjugate and original insulin were labeled with 131I, and then the three kinds of 131I labeled compounds were tested in rabbit whole body imaging to measure their properties of liver targeting. The peak values of rabbit liver concentration for double gal-insulin, gal-insulin and original insulin were 59.5%, 43.8% and 21.5%, respectively. These results demonstrate that for elevating the liver targeting property of galactosyl-recombinant compounds, a branched agent like 3,5-dihydroxyl benzoic acid can be adopted as an effective medium.

[Pharmacokinetic analysis of lactosaminated human growth hormone and human growth hormone]

This study was undertaken to explore and compare the pharmacokinetic features of lactosaminated human growth hormone(hGH-L) and human growth hormone (hGH). Radioimmunoassay (RIA) technique was used. After mice were intravenously injected with hGH-L, their blood and liver samples were collected and handled. The blood drug concentration and liver drug concentration were determined using RIA technique. Then the pharmacokinetic parameters were obtained by analysing the curves of blood drug concentration-time and liver drug concentration-time. hGH was determinated with the same methods. The results showed that the area under curve (AUC) of blood drug concentration-time curve of hGH-L was 32,686.90, the mean remain time (MRT) of hGH-L in blood was 21.37 minutes, but the AUC of blood drug concentration-time curve of hGH was 36,913.08 and the MRT of hGH in blood was 24.98 minutes. Therefore, in blood, the uptake of hGH-L was less than that of hGH, the removal of hGH-L was faster than the removal of hGH. In liver, for hGH-L, the half-time of distribution (t1/2 alpha) was 1.84 minutes, the half-time of removal(t1/2 beta) was 11.09 minutes, the AUC of liver drug concentration-time curve was 17,621.9; for hGH, the t1/2 alpha was 2.11 minutes, the t1/2 beta was 75.65 minutes, the AUC of liver drug concentration-time curve was 12,148.2. Therefore, in liver, the uptake of hGH-L was more than that of hGH, the distribution and removal of hGH-L were faster than those of hGH. Therefore, the pharmacokinetic features of hGH-L was better than the feature of hGH.

[Clinical value of 99mTc-MIBI imaging, 131I whole body scan and HTG determination for the follow-up of patients with differentiated thyroid carcinoma after 131I therapy]

The purpose of this study was to make a comparative evaluation of 99mTc-MIBI imaging, 131I whole body scan and HTG determination in use for the follow-up of patients with differentiated thyroid carcinoma (DTC) after 131I therapy. Fifty-three patients with DTC had undergone surgical treatment and 131I ablation. Clinical examinations showed that 22 of them had metastases or recurrences. In the follow-up of all the patients, the HTG determination, the 99mTc-MIBI imaging and the 131I-WBS were performed in sequence after the discontinuance of the administration of thyroxin for 4-6 weeks. The results showed that the sensitivity, specificity and accuracy of 99mTc-MIBI imaging were 86.36%, 87.10% and 86.79% respectively; those for HTG were 68.18%, 100% and 86.79% and those for 131I-WBS were 63.64%, 100% and 84.91% respectively. The total sensitivity of the three examinations was 100%; the total specificity and total accuracy were 87.10% and 92.45% respectively. The data of this study suggest that 99mTc-MIBI imaging is a highly sensitive method and the combined use of the three examinations can improve the sensitivity and accuracy of diagnosis for patients with DTC.

Purification and crystallization of precursors and autoprocessed enzymes of Flavobacterium glycosylasparaginase: an N-terminal nucleophile hydrolase

Glycosylasparaginase (GA) represents a novel group of proteins that are activated by self-catalyzed peptide-bond cleavage from a single-chain precursor to yield the two subunits required for hydrolase activity. The wild-type GA precursor autoproteolyzes spontaneously into alpha and beta subunits. Strategies are reported here for purification to homogeneity of GA from Flavobacterium meningosepticum in both single-chain precursor and mature (autoprocessed) forms. The recombinant proteins crystallize in different space groups: P1 and P2(1) for the precursor and mature enzymes, respectively. The precursor crystals diffract to 1.9 A resolution with laboratory X-ray radiation.

Mutations of endo-beta-N-acetylglucosaminidase H active site residueAs sp130 anG glu132: activities and conformations

Endo-beta-N-acetylglucosaminidase H hydrolyzes the beta-(1-4)-glycosidic link of the N,N'-diacetylchitobiose core of high-mannose and hybrid asparagine-linked oligosaccharides. Seven mutants of the active site residues, Asp130 and Glu132, have been prepared, assayed, and crystallized. They include single site mutants of each residue to the corresponding amide, to Ala and to the alternate acidic residue, and to the double amide mutant. The mutants of Asp130 are more active than the corresponding Glu132 mutants, consistent with the assignment of the latter residue as the primary catalytic residue. The amide mutants are more active than the alternate acidic residue mutants, which in turn are more active than the Ala mutants. The structures of the Asn mutant of Asp130 and the double mutant are very similar to that of the wild-type enzyme. Several residues surrounding the mutated residues, including some that form part of the core of the beta-barrel and especially Tyr168 and Tyr244, adopt a very different conformation in the structures of the other two mutants of Asp130 and in the Asp mutant of Glu132. The results show that the residues in the upper layers of the beta-barrel can organize into two very distinct packing arrangements that depend on subtle electrostatic and steric differences and that greatly affect the geometry of the substrate-binding cleft. Consequently, the relative activities of several of the mutants are defined by structural changes, leading to impaired substrate binding, in addition to changes in functionality.

Structural insights into the mechanism of intramolecular proteolysis

A variety of proteins, including glycosylasparaginase, have recently been found to activate functions by self-catalyzed peptide bond rearrangements from single-chain precursors. Here we present the 1.9 A crystal structures of glycosylasparaginase precursors that are able to autoproteolyze via an N --> O acyl shift. Several conserved residues are aligned around the scissile peptide bond that is in a highly strained trans peptide bond configuration. The structure illustrates how a nucleophilic side chain may attack the scissile peptide bond at the immediate upstream backbone carbonyl and provides an understanding of the structural basis for peptide bond cleavage via an N --> O or N --> S acyl shift that is used by various groups of intramolecular autoprocessing proteins.