Atomically Dispersed p-Block Aluminum-Based Catalysts for Oxygen Reduction Reaction

The main group metals are commonly perceived as catalytically inert in the context of oxygen reduction reactions (ORR) due to the delocalized valence orbitals. Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M-Nx) is a promising approach to accelerate catalytic dynamics. Herein, we, for the first time, report the atomically dispersed Al catalysts coordinated with N and C atoms for 4-electron ORR. The axial coordinated pyrrolyl N group (No) is constructed in the Al-N4-No moiety to regulate the p-band structure of Al center, effectively steering the local environment and structure of the square planar Al-N4 sites, which typically exhibit too strong interaction with ORR intermediates. The dynamic covalency competition of axial Al-No and Al-O bonding could endow the Al center with moderate hybridization between Al 3p orbital and O 2p orbital, alleviating the binding energy of ORR intermediates. The as-prepared Al-N4-No electrocatalyst exhibits excellent ORR activity, selectivity, and durability, along with the rapid kinetics as demonstrated by in situ Raman spectroscopy. This work offers a fundamental comprehension of the fine regulation on p-band and guides the rational design of main-group metal-based single atom catalysts.

Maternal Prenatal Factors and Child Adiposity in Associations with Cardiometabolic Risk Factors in Term-Born Chinese Children at the Age of 2 Years

Early growth has long-lasting associations with adult metabolic health. However, the association of adiposity with cardiometabolic risk factors in toddlers remains poorly understood. This study aimed to examine the association of maternal prenatal factors and child adiposity with child cardiometabolic risk factors among boys and girls aged 2 years. This was a birth cohort study of 549 term-born children in Shanghai, China, with follow-up data at the age of 2-years. Child anthropometric and adiposity measurements included weight, length, and skinfold thickness (triceps, subscapular, and abdominal). Child cardiometabolic risk factors included random morning plasma glucose, serum insulin, lipids, and systolic and diastolic blood pressure (SBP, DBP). At 2 years, overweight/obesity (weight-for-length z score, ZWFL > 2) was associated with 12.6 (95%CI 7.7, 17.4) mmHg higher SBP, and 7.9 (4.1, 11.8) mmHg higher DBP in boys, with similar results observed in girls. Maternal hypertensive disorders of pregnancy were associated with 3.0 (0.1, 5.8) higher SBP, 3.17 (0.90, 5.44) mmHg higher DBP, 0.24 (0.01,0.47) mmol/L higher plasma glucose, and 0.26 (0.01,0.51) mmol/L higher serum triglycerides after adjustment for child age, sex, and ZWFL. Maternal hypertensive disorders of pregnancy and child overweight/obesity were associated with higher SBP and DBP at the age of 2 years.

Low-Loading Sub-3 nm PtCo Nanoparticles Supported on Co-N-C with Dual Effect for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

Developing low-loading Pt-based catalysts possessing glorious catalytic performance can accelerate oxygen reduction reaction (ORR) and hence significantly advance the commercialization of proton exchange membrane fuel cells. In this report, we propose a hybrid catalyst that consists of low-loading sub-3 nm PtCo intermetallic nanoparticles carried on Co-N-C (PtCo/Co-N-C) via the microwave-assisted polyol procedure and subsequent heat treatment. Atomically dispersed Co atoms embedded in the Co-N-C carriers diffuse into the lattice of Pt, thus forming ultrasmall PtCo intermetallic nanoparticles. Owing to the dual effect of the enhanced metal-support interaction and alloy effect, as-fabricated PtCo/Co-N-C catalysts deliver an extraordinary performance, achieving a half-wave potential of 0.921 V, a mass activity of 0.700 A mg_Pt^-1@0.9 V, and brilliant durability in the acidic medium. The fuel cell employing PtCo/Co-N-C as the cathode catalyst with an ultralow Pt loading of 0.05 mg cm^-2 exhibits an impressive peak power density of 0.700 W cm^-2, higher than that of commercial Pt/C under the same condition. Furthermore, the enhanced intrinsic ORR activity and stability are imputed to the downshifted d-band center and the strengthened metal-support interaction, as revealed by density functional theory calculations. This report affords a facile tactic to fabricate Pt-based alloy composite catalysts, which is also applicable to other alloy catalysts.

Cord Blood Thyroid Hormones and Neurodevelopment in 2-Year-Old Boys and Girls

Objective: Thyroid hormones are essential for neurodevelopment in early life. However, the impact of mild alterations in neonatal thyroid hormones on infant neurodevelopment and its sex dimorphism is unclear. We aimed to assess whether mild variations in neonatal thyroid hormones of term-born newborns with maternal euthyroid are related to neurodevelopment in 2-year-old boys and girls.

Methods: This study used data from 452 singleton term-born infants of mothers with normal thyroid function in Shanghai, China, and their follow-up measure at the age of 2 years. Cord serum concentrations of free thyroxine (FT4), free triiodothyronine (FT3), thyroid-stimulating hormone (TSH), and thyroid peroxidase antibody (TPOAb) were measured by chemiluminescent microparticle immunoassays and classified into three groups: the low (1st, Q1), middle (2nd−4th, Q2–Q4), and high (5th, Q5) quintiles. Neurodevelopment indices were assessed using the Ages and Stages Questionnaire, third edition (ASQ-3), at 24 months of age.

Results: Compared to infants with thyroid hormones in the middle (Q2–Q4), boys with FT4 in the lowest quintile had 5.08 (95% CI: 1.37, 8.78) points lower scores in the communication domain, 3.25 (0.25,6.25) points lower scores in the fine motor domain, and 3.84 (0.04, 7.64) points lower scores in the personal-social domain, respectively. Boys with FT3 in the highest quintile had 4.46 (0.81, 8.11) points increase in the personal-social domain. These associations were not observed in girls. No associations were observed between cord blood serum TSH and ASQ-assessed neurodevelopment in the boys or the girls.

Conclusions: Mild alterations in thyroid hormones of newborns were associated adversely with neurodevelopment in boys, suggesting the importance of optimal thyroid hormone status for neurodevelopment in early life.

Effectiveness of Online-Delivered Project ImPACT for Children With ASD and Their Parents: A Pilot Study During the COVID-19 Pandemic

OBJECTIVE

During the COVID-19 pandemic, face-to-face intervention services for families of children with autism spectrum disorder (ASD) were limited. This study aimed to evaluate the effectiveness of an 8-week, online-delivered Project ImPACT program for children with ASD and their parents in China during the COVID-19 pandemic.

METHODS

A pilot non-randomized study with a waitlist control group was conducted in 68 children with ASD and their parents in the Department of Developmental and Behavioral Pediatrics between April 15, 2020 and March 19, 2021. Participants were allocated to either the intervention (IG) or the waitlist group (WLG) according to their order of recruitment. Parents in the IG immediately received 8 weeks of the online-delivered Project ImPACT program, and the WLG received the same program with a delay when the IG had completed all sessions. Participants in both groups received treatment as usual during the research period.

RESULTS

The online-delivered Project ImPACT program significantly improved the parent-reported social communication skills of children with ASD. Furthermore, parent's involvement in the training program produced a collateral reduction in parenting stress and an increase in perceived competence in the parental role. Parents rated the program acceptable in terms of curriculum schedule, session content, homework assignments, and therapist feedback.

CONCLUSIONS

The 8-week, online-delivered Project ImPACT program is a feasible and effective social skill training program for families of children with ASD in China during the COVID-19 pandemic. Due to the methodological limitations, randomized controlled studies with larger sample sizes are suggested to provide more solid evidence.

Can fecal calprotectin levels be used to monitor infant milk protein allergies?

Background

Milk protein allergy is one of the most common food allergies in infants. We aimed to test whether fecal calprotectin can be used to monitor food allergies in infants by comparing the fecal calprotectin levels in infants with a milk protein allergy before and after an intervention treatment.

Methods

The study was designed as a prospective case–control trial. Stool samples were collected at follow-up, and the concentration of fecal calprotectin was determined using an enzyme-linked immunosorbent assay. The infant’s weight and length were measured.

Results

The allergic group comprised 90 milk-allergic infants (41 boys, 49 girls), and the nonallergic group comprised 90 nonallergic infants (51 boys, 39 girls). Compared with the fecal calprotectin level in the nonallergic group (median: 141 μg/g), that in the allergic group (median: 410 μg/g) was significantly higher (z = − 9.335, p < 0.001). After two dietary interventions and treatments, the fecal calprotectin levels of the infants with a milk protein allergy at the first (median: 253 μg/g) and second follow-up visits (median: 160 μg/g) were significantly lower than those before the intervention (z = − 7.884, p < 0.001 and z = − 8.239, p < 0.001, respectively). The growth index values (LAZ and WAZ) of the infants with a milk protein allergy at the first and second follow-up visits were significantly higher than those before dietary intervention (p < 0.05). Fecal calprotectin was negatively and significantly correlated with the WLZ and WAZ at the second follow-up visit (Spearman’s rho = − 0.234, p = 0.01 and Spearman’s rho = − 0.193, p = 0.03, respectively).

Conclusion

The level of fecal calprotectin in infants with a milk protein allergy decreased after dietary intervention and seems to be a promising biological indicator for monitoring intestinal allergies.

Knowledge and attitudes among preschools staff in Shanghai, China, regarding epilepsy

Background

Epilepsy is one of the most common neurological problems among children. The aim of this survey was to assess the knowledge and attitude among preschool staff in Shanghai regarding epilepsy.

Methods

A cross-sectional survey was carried out among the staff at selected preschools. A stratified random sampling method was first used to identify suitable subjects. Data were obtained using a self-completed questionnaire. A standardized collection of demographic information was performed, and participants were given a questionnaire about their knowledge and attitudes regarding epilepsy.

Results

A total of 1069 subjects completed the questionnaire. In this survey, 387 (36.2%) staff members had previously participated in related training. 17.6% of teachers knew how to provide appropriate first aid for seizures. Correct responses regarding first aid for seizures, such as laying the person on his or her side (24.9%), moving harmful objects out of the way (20.7%), protecting the head (36.1%), waiting until the seizure ends (7.9%), and dialing the emergency number (40.1%), were low. The staff members had different attitudes towards children with epilepsy: some subjects had a positive attitude, some had a negative attitude.

Conclusions

The level of first-aid knowledge among preschool staff in Shanghai relevant to epilepsy was low. There is an urgent need to educate staff about epilepsy and appropriate first-aid practices for seizures.

Maternal prenatal urinary bisphenol A level and child cardio-metabolic risk factors: A prospective cohort study

Exposure to endocrine disrupting chemicals during the first 1000 days of life may have long-lasting adverse effects on cardio-metabolic risk in later life. This study aimed to examine the associations between maternal prenatal Bisphenol A (BPA) exposure and child cardio-metabolic risk factors at age 2 years in a prospective cohort. During 2012-2013, 218 pregnant women were enrolled at late pregnancy from Shanghai, China. Urinary BPA concentration was measured in prenatal and child 2-year spot urine samples, and classified into high, medium and low tertiles. Child adiposity anthropometric measurements, random morning plasma glucose, serum insulin, and lipids (high-density lipoprotein, low-density lipoprotein, cholesterol, triglyceride), systolic (SBP) and diastolic blood pressure (DBP) were measured. Linear regression was used to evaluate the associations between prenatal BPA and each of the cardio-metabolic risk factors in boys and girls, respectively, adjusting for pertinent prenatal, perinatal and postnatal factors. BPA was detectable (>0.1 μg/L) in 98.2% of mothers prenatally and 99.4% of children at age 2 years. Compared to those with low prenatal BPA, mean SBP was 7.0 (95%CI: 2.9-11.2) mmHg higher, and DBP was 4.4 (95%CI: 1.2-7.5) mmHg higher in girls with high prenatal BPA levels, but these associations were not found in boys. In boys, medium maternal prenatal BPA level was associated with 0.36 (95% CI: 0.04-0.68) mmol/L higher plasma glucose. No associations were found between prenatal BPA and child BMI, skinfold thicknesses, serum lipids, or insulin in either girls or boys. There were no associations between concurrent child urinary BPA and cardio-metabolic risk factors. These results support that BPA exposure during prenatal period, susceptible time for fetal development, may be associated with increase in child BP and plasma glucose in a sex-specific manner. Further independent cohort studies are needed to confirm the findings.

Effects of three different first-aid training methods on knowledge retention of caregivers and teachers: a randomized and longitudinal cohort study in China

OBJECTIVES

The purpose of this study was to assess the effects of pediatric first-aid training methods on caregivers' and teachers' knowledge retention.

STUDY DESIGN

This was a randomized longitudinal cohort study.

METHODS

A stratified random sampling method was used to select 1282 caregivers and teachers with the help of local education authorities in 18 districts and 1 county of Shanghai, China. The selected caregivers and teachers were randomly allocated into groups that were exposed to 3 models of training, including an interactive training model (group A), lecture-based training model (group B), and video instruction training model (group C), for pediatric first-aid training for caregivers and teachers (PedFACTs). Before and after the training, a descriptive questionnaire composed of demographic information and 37 simple-choice questions about first aid was administered. During the follow-up, 120 caregivers and teachers from each of the three methods were randomized and retested 9 months after their training and 120 caregivers and teachers were randomly reselected in each of the three methods and retested 4 years after their training.

RESULTS

Immediately after training, there was a significant difference in the postassessment results between groups A and B (P = 0.002) as well as between groups A and C (P < 0.001). The average interactive training model score was the highest, followed by the instruction training model and video instruction training model. There was no significant difference among the three groups in the reassessment scores at 9 months and 4 years after training (P = 0.744, P = 0.595). The difference in passing the assessment among the three groups at 9 months or 4 years after training was not maintained at a significant level.

CONCLUSION

The three training methods did not affect knowledge retention of the caregivers and teachers at nine months or four years after training completion. Video instruction may be an effective, convenient, and feasible method to train caregivers and teachers.

[Analysis of labor progression characteristics of 1 089 nulliparas managed by the new partogram]

Objective: To analyze labor progression characteristics among nulliparas and provide reference to labor progress management. Methods: A retrospective study was conducted on 1 089 women who went for vaginal delivery at the First Affiliated Hospital, Sun Yet-San University from January 1st, 2015 to May 31th, 2016. The duration of cervical dilation from 1.0 cm to the next and the process of initial cervical dilation (2.0 cm or 3.0 cm) to full cervical dilation of nulliparas were analyzed. Results: The cervical dilation speed was accelerating with the progress of labor. The rate of cervical dilation changed fastest between 5.0-6.0 cm dilation, which was more than 3.0 cm/hour. With regard to labor curves, at admission of 2.0 cm cervical dilation, it rose dramatically from 5.0 cm dilation. At admission of 3.0 cm dilation, it presented approximately linear rising before 5.5 cm dilation, then became steeper. Conclusions: The cervical dilation speed is fast. Both labor curves of initial cervical dilation (2.0 cm or 3.0 cm) to full cervical dilation show obvious acceleration stage with steep slope.

Genetic Diagnostic Evaluation of Trio-Based Whole Exome Sequencing Among Children With Diagnosed or Suspected Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a group of clinically and genetically heterogeneous neurodevelopmental disorders. Recent tremendous advances in the whole exome sequencing (WES) enable rapid identification of variants associated with ASD including single nucleotide variations (SNVs) and indels. To further explore genetic etiology of ASD in Chinese children with negative findings of copy number variants (CNVs), we applied WES in 80 simplex families with a single affected offspring with ASD or suspected ASD, and validated variations predicted to be damaging by Sanger sequencing. The results showed that an overall diagnostic yield of 8.8% (9.2% in the group of ASD and 6.7% in the group of suspected ASD) was observed in our cohort. Among patients with diagnosed ASD, developmental delay or intellectual disability (DD/ID) was the most common comorbidity with a diagnostic yield of 13.3%, followed by seizures (50.0%) and craniofacial anomalies (40.0%). All of identified de novo SNVs and indels among patients with ASD were loss of function (LOF) variations and were slightly more frequent among female (male vs. female: 7.3% vs. 8.5%). A total of seven presumed causative genes (CHD8, AFF2, ADNP, POGZ, SHANK3, IL1RAPL1, and PTEN) were identified in this study. In conclusion, WES is an efficient diagnostic tool for diagnosed ASD especially those with negative findings of CNVs and other neurological disorders in clinical practice, enabling early identification of disease related genes and contributing to precision and personalized medicine.

Association between bisphenol a exposure and idiopathic central precocious puberty (ICPP) among school-aged girls in Shanghai, China

BACKGROUND

Bisphenol A (BPA) is a well-known and widely used endocrine disrupter, but data on its association with childhood reproductive development are limited.

OBJECTIVES

We investigated the possible relationship between exposure to BPA and idiopathic central precocious puberty (ICPP) in school-aged girls.

METHODS

We conducted a 1:1 matched case-control study in Shanghai, China, between July 2011 and September 2012. This study included 136 school-aged (6 to 9 years old) girls diagnosed with ICPP and 136 controls matched for age and body mass index (BMI). We measured the urinary BPA concentrations of all the girls and examined the association with odds of having ICPP. Laboratory examinations including serum estradiol (E2) levels, basal and gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels, bone ages (BA), and uterine and ovarian sizes were conducted in the ICPP girls.

RESULTS

Median concentrations of urinary BPA in the ICPP and control groups were 6.35 and 1.17 μg/g creatinine (Cr), respectively (p < 0.001). After adjustment for confounders, compared to those with the lowest concentrations of BPA, the highest concentrations were associated with a 9.08-fold increased odds of having ICPP [odds ratio (OR) = 9.08, (95% confidence interval (CI): 2.83-29.15)]. In the ICPP group, modest negative correlation was present between urinary BPA concentrations (μg/g Cr) and peak FSH levels [β = -0.090 (95% CI: -0.178, -0.003), p = 0.044].

CONCLUSIONS

Our findings suggest that BPA exposure is associated with increased odds of having ICPP in school-aged girls, and the potential mechanism may be attributable to the relatively low FSH levels.

Marked yield of re-evaluating phenotype and exome/target sequencing data in 33 individuals with intellectual disabilities

The diagnosis of intellectual disability/developmental delay (ID/DD) benefits from the clinical application of target/exome sequencing. The yield in Mendelian diseases varies from 25% to 68%. The aim of the present study was to identify the genetic causes of 33 ID/DD patients using target/exome sequencing. Recent studies have demonstrated that reanalyzing undiagnosed exomes could yield additional diagnosis. Therefore, in addition to the normal data analysis, in this study, re-evaluation was performed prior to manuscript preparation after updating OMIM annotations, calling copy number variations (CNVs) and reviewing the current literature. Molecular diagnosis was obtained for 19/33 patients in the first round of analysis. Notably, five patients were diagnosed during the re-evaluation of the geno/phenotypic data. This study confirmed the utility of exome sequencing in the diagnosis of ID/DD. Furthermore, re-evaluation leads to a 15% improvement in diagnostic yield. Thus, to maximize the diagnostic yield of next-generation sequencing (NGS), periodical re-evaluation of the geno/phenotypic data of undiagnosed individuals is recommended by updating the OMIM annotation, applying new algorithms, reviewing the literature, sharing pheno/genotypic data, and re-contacting patients.

[Phenotypic and genetic analysis of four patients with 13q33-q34 microdeletion]

OBJECTIVE

To explore the correlation between 13q33-q34 microdeletion and clinical phenotype.

METHODS

Routine chromosomal banding was performed to analyze the karyotype, while array-based comparative genomic hybridization (aCGH array) and single nucleotide polymorphism array(SNP array) were employed to investigate the genome copy number variations.

RESULTS

The karyotype of patient 1 was 46, XY, 9qh+,13qs. Patient 2 showed 46, XX, der (13). Patient 3 showed 46, XX, r(13) (p11.2q32) [43]/45, XX, 13[4]/46, XX, r(13;13) [2]/47, XX, 2r(13;13) [1]. Patient 4 did not undergo chromosome karyotyping analysis. Array analysis showed that four patients have different microdeletions in 13q33-34 region and had common features of 13q33-q34deletion including intellectual disability, facial dysmorphism, microcephaly, hypotonia, low birth weight and genital abnormality.

CONCLUSION

The severity of phenotypes showed no correlation with the size of deletion in 13q33-q34. The lower percentage of patients with congenital heart disease suggested a complex pathogenesis of such disease. EFNB2, LIG4 and SOX1 in 13q33-34 region are promising candidates for mental retardation. LIG4 was also a likely candidate for microcephaly.

Perfluoroalkyl and polyfluoroalkyl substances in cord blood of newborns in Shanghai, China: Implications for risk assessment

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are commonly used in industrial applications and consumer products, and their potential health impacts are of concern, especially for vulnerable population like fetuses. However, in utero exposure to PFASs and health implications are far from fully characterized in China. To fill in the gap, we analyzed 10 PFASs in cord plasma samples (N=687) collected in Shanghai between 2011 and 2012, one of the regions widely polluted with PFASs in China. A questionnaire survey on maternal and diet-related factors was conducted. Except for perfluoroheptanoic acid (PFHpA) and perfluorooctane sulfonamide (PFOSA), all other PFASs were detected in ˃90% of the samples. Perfluorooctanoic acid (PFOA) was the most predominant PFAS (median value: 6.96ng/mL), followed by perfluorooctane sulfonate (PFOS) (2.48ng/mL). PFOA and PFOS combined contributed to 80% of the total PFASs. The final multiple regression models showed that maternal factors including maternal age, body mass index, gestational age, economic status and educational level as well as consumption of fish and wheat were significantly related with concentrations of PFASs in cord blood. The risk assessment using the hazard quotients (HQs) approach on the basis of plasma PFAS levels indicated no potential concern for developmental toxicity in the local newborns. The results demonstrate the unique profiles of local prenatal exposure to PFASs, suggesting that PFOA has been the primary human exposure due to its widespread use and pollution. Special attention to high PFOA exposure and confirmation of potential determinants should be taken as a priority in the future plan for risk management and actions in this area.

Fecal Calprotectin in Healthy Children Aged 1-4 Years

Objective

Calprotectin has been well emulated recently in adults as well as in children. The aim of this study was to assess fecal calprotectin concentrations in healthy children aged from 1 to 4 years.

Methods

Volunteers were enlisted from 3 nurseries. A brief questionnaire was used to ensure these children meet the inclusion criteria, and some clinical and sociodemographic factors were collected. Anthro software (version 3.1) was used to calculated Length-for-age Z-scores (LAZ), weight-for-age Z-scores (WAZ), and weight-for-length Z-scores (WLZ) respectively. Fecal calprotectin was detected by a commercially available ELISA.

Results

In total 274 children were recruited, with age ranging from 1 to 4 years old. The median FC concentration was 83.19 μg/g [range 4.58 to 702.50 μg/g, interquartile range (IQR) 14.69–419.45 μg/g] or 1.92 log10 μg/g (range 0.66 log10 to 2.85 log10 μg/g, IQR 1.17 log10-2.62 log10 μg/g). All of the children were divided into three groups, 1–2 years (12–24 months), 2–3 years (24–36 months), 3–4 years (36–48 months), with median FC concentrations 96.14 μg/g (1.98 log10 μg/g), 81.48 μg/g (1.91 log10 μg/g), 65.36 μg/g (1.82 log10 μg/g), respectively. There was similar FC level between boys and girls. FC concentrations showed a downward trend by the growing age groups. A statistic difference was found in FC concentrations among groups 1–2 years, 2–3 years and 3–4 years (P = 0.016). In inter-groups comparison, a significant difference was found between children aged 1–2 years and children aged 3–4 years (P = 0.007). A negative correlation trend was found between age and FC concentration (Spearman's rho = -0.167, P = 0.005) in all the participants. A simple correlation was performed among WLZ, WAZ, birth weight, or birth length with FC, and there was no correlation being observed.

Conclusion

Children aged from 1 to 4 years old have lower FC concentrations compared with healthy infants (<1years), and higher FC concentrations when comparing with children older than 4 years and adults.

Physical and mental development of children after levonorgestrel emergency contraception exposure: a follow-up prospective cohort study

Levonorgestrel (LNG), a dedicated emergency contraception (EC) product, has been available over-the-counter in China for more than 14 yr. Although LNG-EC is considered to have no effects on the developing fetus if the contraceptive fails and pregnancy occurs, there have been a few studies specifically examining this issue. The purpose of this study was to compare the physical and mental development of children born after LNG-EC failure with that of a cohort of children born to mothers with no history of exposure to LNG or any teratogenic substances. A group of 195 children who were exposed to LNG-EC during their mothers' conception cycle (study group) were matched to a group of 214 children without exposure to LNG (control group). The physical and mental development of the children were evaluated and compared over a 2-yr period. There were four congenital malformations in the study group and three in the control group (2.1% vs. 1.4%, respectively, P > 0.05). Over the 2-yr follow-up period, there were no statistically significant differences between the two groups with respect to children's weight, height, head circumference, and intelligence scores, and the values of all parameters of both groups were similar to those of the national standards. In summary, LNG-EC has no effect on the physical growth, mental development, or occurrence of birth defects in children born from pregnancies in which EC failed.

Parent-adolescent interaction and risk of adolescent internet addiction: a population-based study in Shanghai

BACKGROUND

Family-based intervention is essential for adolescents with behavioral problems. However, limited data are available on the relationship between family-based factors and adolescent internet addiction (AIA). We aimed to examine this relationship using a representative sample of Shanghai adolescents.

METHODS

In October 2007, a total of 5122 adolescents were investigated from 16 high schools via stratified-random sampling in Shanghai. Self-reported and anonymous questionnaires were used to assess parent-adolescent interaction and family environments. AIA was assessed by DRM-52 Scale, developed from Young's Internet-addiction Scale, using seven subscales to evaluate psychological symptoms of AIA.

RESULTS

Adjusting for adolescents' ages, genders, socio-economic status, school performances and levels of the consumption expenditure, strong parental disapproval of internet-use was associated with AIA (vs. parental approval, OR = 2.20, 95% CI: 1.24-3.91). Worse mother-adolescent relationships were more significantly associated with AIA (OR = 3.79, 95% CI: 2.22-6.48) than worse father-adolescent relationships (OR = 1.76, 95% CI: 1.10-2.80). Marital status of "married-but-separated" and family structure of "left-behind adolescents" were associated with symptoms of some subscales. When having high monthly allowance, resident students tended to develop AIA but commuter students did not. Family social-economic status was not associated with the development of AIA.

CONCLUSIONS

The quality of parent-adolescent relationship/communication was closely associated with the development of AIA, and maternal factors were more significantly associated with development of AIA than paternal factors. Family social-economic status moderated adolescent internet-use levels but not the development of AIA.

Predictors of consistent condom use based on the Information-Motivation-Behavior Skill (IMB) model among senior high school students in three coastal cities in China

BACKGROUND

High prevalence of risky sexual behaviors and lack of information, skills and preventive support mean that, adolescents face high risks of HIV/AIDS. This study applied the information-motivation-behavioral skills (IMB) model to examine the predictors of consistent condom use among senior high school students from three coastal cities in China and clarify the relationships between the model constructs.

METHODS

A cross-sectional study was conducted to assess HIV/AIDS related information, motivation, behavioral skills and preventive behaviors among senior high school students in three coastal cities in China. Structural equation modelling (SEM) was used to assess the IMB model.

RESULTS

Of the 12313 participants, 4.5% (95% CI: 4.2-5.0) reported having had premarital sex and among them 25.0% (95% CI: 21.2-29.1) reported having used a condom in their sexual debut. Only about one-ninth of participants reported consistent condom use. The final IMB model provided acceptable fit to the data (CFI = 0.981, RMSEA = 0.014). Consistent condom use was significantly predicted by motivation (β = 0.175, P < 0.01) and behavioral skills (β = 0.778, P < 0.01). Information indirectly predicted consistent condom use, and was mediated by behavioral skills (β = 0.269, P < 0.05).

CONCLUSIONS

The results highlight the importance of conducting HIV/AIDS preventive health promotion among senior high school students in China. The IMB model could predict consistent condom use and suggests that future interventions should focus on improving motivation and behavioral skills.

Personal characteristics related to the risk of adolescent internet addiction: a survey in Shanghai, China

Background

Paralleling the rapid growth in computers and internet connections, adolescent internet addiction (AIA) is becoming an increasingly serious problem, especially in developing countries. This study aims to explore the prevalence of AIA and associated symptoms in a large population-based sample in Shanghai and identify potential predictors related to personal characteristics.

Methods

In 2007, 5,122 adolescents were randomly chosen from 16 high schools of different school types (junior, senior key, senior ordinary and senior vocational) in Shanghai with stratified-random sampling. Each student completed a self-administered and anonymous questionnaire that included DRM 52 Scale of Internet-use. The DRM 52 Scale was adapted for use in Shanghai from Young’s Internet Addiction Scale and contained 7 subscales related to psychological symptoms of AIA. Multiple linear regression and logistic regression were both used to analyze the data.

Results

Of the 5,122 students, 449 (8.8%) were identified as internet addicts. Although adolescents who had bad (vs. good) academic achievement had lower levels of internet-use (p < 0.0001), they were more likely to develop AIA (odds ratio 4.79, 95% CI: 2.51-9.73, p < 0.0001) and have psychological symptoms in 6 of the 7 subscales (not in Time-consuming subscale). The likelihood of AIA was higher among those adolescents who were male, senior high school students, or had monthly spending >100 RMB (all p-values <0.05). Adolescents tended to develop AIA and show symptoms in all subscales when they spent more hours online weekly (however, more internet addicts overused internet on weekends than on weekdays, p < 0.0001) or when they used the internet mainly for playing games or real-time chatting.

Conclusions

This study provides evidence that adolescent personal factors play key roles in inducing AIA. Adolescents having aforementioned personal characteristics and online behaviors are at high-risk of developing AIA that may compound different psychological symptoms associated with AIA. Spending excessive time online is not in itself a defining symptom of AIA. More attention is needed on adolescent excessive weekend internet-use in prevention of potential internet addicts.

[Clinical and genetic study of a case with Smith-Magenis syndrome]

OBJECTIVE

To explore the clinical feature and genetic diagnosis for Smith-Magenis syndrome (SMS).

METHOD

The clinical data, including craniofacial anomalies, physical and mental status were analyzed. Routine and high resolution G-banding was performed to analyze the karyotype of the patient and her parents, and array comparative genomic hybridization (array CGH) was used to detect small chromosome anomaly.

RESULT

A-two-year old girl was sent to our clinic for mental retardation and cardiac malformation. Some sleep problems were reported by parents, including difficulties falling asleep, shortened sleep cycles. She also had some neurobehavioral symptoms including hyperactivity and self-injurious behaviors head-banging. She had distinctive craniofacial features including low hairline, frontal bossing, a broad face, broad nasal bridge, a tented upper lip, prognathism, low-set ears and high-vaulted arch. She had moderate mental retardation. Cardiac findings included ventricular septal defect, atrial septal defect, overriding aorta and pulmonary hypertension. Primary ventriculomegaly was seen in magnetic resonance imaging (MRI). Routine karyotype analysis showed a karyotype of 46, XX. However, high resolution karyotype analysis showed a suspected partial deletion of the short arm of chromosome 17. Array comparative genomic hybridization (array CGH) finely mapped the deletion to a 3.8 Mb region on 17p11.2. The molecular karyotype was then ascertained as 46, XX.arr17p11.2(16543655-20374751)×1dn. The parents had normal karyotypes.

CONCLUSION

Smith-Magenis syndrome is a multisystem disorder characterized by developmental delay and mental retardation, distinctive craniofacial features, sleep disturbance and behavioral problems. Array comparative genomic hybridization (array CGH) finely mapped the deletion on 17p11.2.

Association of the CD226 single nucleotide polymorphism with systemic lupus erythematosus in the Chinese Han population

A novel non-synonymous (Gly307Ser) variant, rs763361, of the CD226 gene on chromosome 18q22 was recently shown to be associated with multiple autoimmune diseases. Taking into consideration that different autoimmune diseases may share some common pathogenic pathways, in this study we performed case-control studies to assess any genetic linkage with systemic lupus erythemtosus (SLE). An association between the Gly307Ser single nucleotide polymorphism (SNP) and susceptibility to SLE was identified. The TT genotype [odds ratio (OR) = 1.79, 95% confidence interval (CI) = 1.07-3.01, P = 0.025] and the T allele (OR = 1.34, 95% CI = 1.05-1.74, P = 0.018) of the rs763361 SNP were associated with the risk of SLE. This finding indicates that polymorphism of Gly307Ser (rs763361) in exon 7 of the CD226 gene may be associated with the development of SLE.

Effectiveness of peer education in HIV/STD prevention at different types of senior high schools in Shanghai, People's Republic of China

The epidemic of HIV/AIDS greatly threatens Chinese youth. Our study was intended to examine the effectiveness of the peer education method in HIV/AIDS prevention in different types of senior high schools in Shanghai. A peer education intervention was conducted in 10 different types of senior high schools, including three key senior schools, four ordinary senior schools and three vocational schools in Shanghai for three months. A cohort of 1910 students was surveyed (n=976 intervention group, n=934 control group) through anonymous questionnaires, both pre- and postintervention. There were significant differences in the results among these different types of senior schools. Peer education is an efficient method of increasing the knowledge of AIDS/sexually transmitted diseases in senior school students. However, the contents and the schedule should be different between different types of schools, and students in vocational schools require more health education.

[Internet addiction among Shanghai adolescents: prevalence and epidemiological features]

OBJECTIVE

To study the prevalence of internet use and internet addiction in adolescents of Shanghai.

METHOD

From September to October 2007, a total of 5135 adolescents from 16 middle schools of 6 districts of Shanghai took part in the epidemiological study by a cross-sectional survey and 5123 adolescents finally enrolled in the study. A questionnaire of "DRM Adolescent Internet Use 52 Scale" was administrated to investigate the prevalence of internet use and internet addiction in adolescents of Shanghai. On this scale of 5-point rating, the scale includes seven parts of contents as tolerance, abstinence reaction, planning ability, self-control ability, whenness, sociability and hazard.

RESULTS

The rate of internet use among the surveyed adolescents was 94.32% (4673/5123), among which the incidence rate of internet addiction was 8.78% (450/5123). Boys, senior middle-school students were more susceptible to internet addiction than girls and junior middle-school students (male scores 122.42+/-43.46, female scores 116.92+/-38.10, F=23.22, P=0.00; senior middle-school students 125.24+/-39.02, junior middle-school students 110.30+/-42.35, F=164.68, P=0.00). Students from vocational senior middle-school were most susceptible (junior middle-school students 110.30+/-42.35, ordinary senior middle-school students 122.83+/-40.99, key senior middle-school students 120.05+/-37.87, vocational senior middle-school students 133.37+/-36.84, F=34.44, P=0.00). The 2nd grade students of senior middle-school have the highest risk for internet-addiction.

CONCLUSION

The prevalence of internet use and internet addiction in adolescents of Shanghai should be comparatively high in China, which indicates that great attention should be paid to the prevention and control.

Study on Peer-Led School-Based HIV/AIDS Prevention among Youths in a Medium-Sized City in China

HIV/AIDS epidemic is crucial in China; however, few studies were performed on youths. This study was performed to examine the effectiveness of peer-led HIV prevention intervention on HIV-related knowledge, attitudes and behaviour intention in senior high-school students in San-ming, a medium-sized city in Fujian province. Three thousand and sixty-eight students completed self-administered questionnaires before and after intervention, of which 981 students (the intervention group) accepted peer-led HIV/AIDS prevention intervention and others (the control groups) continued the usual teacher-led health education curriculum. Significant increases were observed in the intervention group in HIV-related knowledge, in attitudes and in behaviour intention after intervention. The results of this research also indicated an inconsistent level of HIV/AIDS knowledge and attitude among students, with a significant gender, health education history and style difference in session delivery. More concerted efforts in HIV prevention are needed to improve young people's sexual health.

Effects of yeast culture and fibrolytic enzyme supplementation on in vitro fermentation characteristics of low-quality cereal straws

The effects of yeast culture and fibrolytic enzyme preparation (containing cellulase and xylanase) on in vitro fermentation characteristics of rice straw, wheat straw, maize stover, and maize stover silage were examined using an in vitro gas production technique. Four levels of yeast culture and fibrolytic enzyme supplements (0, 2.5, 5.0, and 7.5 g/kg of straw DM, respectively) were tested in a 4 x 4 factorial arrangement. Supplementation of yeast culture increased the cumulative gas production, theoretical maximum of gas production, rate of gas production, IVDMD, and in vitro OM disappearance (IVOMD), and decreased the lag time for each type of straw. Fibrolytic enzyme supplementation tended to increase cumulative gas production, theoretical maximum of gas production, and rate of gas production; prolonged lag time of gas production; and enhanced IVDMD and IVOMD for 4 types of cereal straws, with the significance of this effect being dependent on the level of supplemented enzymes. There were significant interactions between fibrolytic enzymes and yeast on all in vitro gas production parameters, IVDMD, and IVOMD of each type of straw. The outcome of this research indicated that the application of fibrolytic enzyme preparation and yeast culture could improve in vitro gas production fermentation of cereal straws.

[Anxiety state and its related factors in Shanghai high school students]

OBJECTIVE

To investigate the anxiety state in high school students and related factors in order to get reasonable suggestions for prevention.

METHODS

The mental health test (MHT) for high school students, and the living environmental and parental style were used in this study.

RESULTS

MHT served as an assessment scale of anxiety. The efficiency sample was 3,050, aged 11 to 18 years old. The level of total anxiety and its each contents was low to moderate (0.24 to 0.54). The percentage of moderate to high of total anxiety was 16.7%, the percentage of moderate to high of each anxiety aspects were 8.8%-21.8%. The mostly high aspects were self-blame, schooling anxiety, social anxiety and over sensitiveness. In general, the girls' anxiety level was higher than boys', but the boys' lonely feeling was higher than the girls'. The total score of anxiety was decreased with age. Except of the over sensitiveness, the decrease tendency of each anxiety contents was significant in boys. For girls, the lonely feeling was deceased and the over sensitiveness increased with age. The age of fifteen seems as a significant changing age. The related disadvantage factors of students' anxiety were: the low education level, the parents' anxiety and depression characters, the authoritarian or neglecting parental style, the often contradiction parental styles between mother and father, parents often quarrel, the experience of often being scalded and physical punishment, lacking in care of others when in difficulties.

CONCLUSIONS

The schooling pressure should be decreased to an appropriate level. The students' self-confidence and social ability should be emphasized. Good family environments and the support outside the family should be quite important for adolescents' mental health, these factors might decrease the adolescents' anxiety.

[Studies on synthesis of glutathione by E. coli BL21 (pTrc-gsh) coupled with Saccharomyces cerevisiae]

During synthesis of GSH by the engineered strain E. coli BL21(pTrc-gsh) coupled with Saccharomyces cerevisiae producing ATP from adenosin, the inconsistency of two systems in the concentration of phosphate buffer was solved by decreasing concentration to 250 mmol/L. The conditions under 250 mmol/L phosphate buffer were optimized and the yield of GSH was 1.6 g/L, which was higher than that of summation by two systems under the same conditions respectively. Addition of glycine later after glutamate and cysteine weakened the inhibition of GSH to GSHI. It made the yield of GSH reach to 2.13 g/L which was 30.7% higher than the control.

[Cloning and expression of the genes of glutathione synthetases]

The genes(gsh-I,gsh-II) for gamma-glutamyl-cysteine synthetase(GSH-I) and glutathione synthetase(GSH-II) from Escherichia coli B were amplified by PCR and then subcloned into plasmid pUC19 respectively. The DNA fragments harboring gshII and gsh I were inserted into plasmid pTrc99A one by one to get a hybrid plasmid pTrc-gsh. E. coli BL21 was transformed by pTrc-gsh for expression of the related enzymes. Analysis of SDS-PAGE showed that the expected products were expressed. E. coli BL21(pTrc-gsh) were incubated at 37 degrees C and pH 7.2 to OD550 = 0.5. The conditions were then switched to 34 degrees C and pH6.7 after the addition of 0.1 mmol/L IPTG. The expressed products were up to 25% of the total protein of the bacteria. Acetone-treated cells of the engineered strain could synthesize GSH efficiently.

Pseudo-cyclic oligonucleotides: in vitro and in vivo properties

We have designed and studied antisense oligodeoxynucleotides (oligonucleotides; oligos) which we call 'pseudo-cyclic oligonucleotides' (PCOs). PCOs contain two oligonucleotide segments attached through their 3'-3'- or 5'-5'-ends. One of the segments of the PCO is an antisense oligo complementary to a target mRNA, and the other is a short protective oligo that is 5-8 nucleotides long and complementary to the 3'- or 5'-end of the antisense oligo. As a result of complementarity between the antisense and protective oligo segments, PCOs form intramolecular pseudo-cyclic structures in the absence of the target RNA. The antisense oligo segment of PCOs used for the studies described here is complementary to an 18-nucleotide-long site on the mRNA of the protein kinase A regulatory subunit RIalpha (PKA-RIalpha). Thermal melting studies of PCOs in the absence and presence of the complementary RNA suggest that the pseudo-cyclic structures formed in the absence of the target RNA dissociate, bind to the target RNA, and form heteroduplexes. The results of RNase H cleavage assays suggest that PCOs bind to complementary RNA and activate RNase H in a manner similar to that of an 18-mer conventional antisense PS-oligo. In snake venom (a 3'-exonuclease) or spleen (a 5'-exonuclease) phosphodiesterase digestion studies, PCOs are more stable than conventional antisense oligos because of the presence of 3'-3'- or 5'-5'-linkages and the formation of intramolecular pseudo-cyclic structures. PCOs with a phosphorothioate antisense oligo segment inhibited cell growth of MDA-MB-468 and GEO cancer cell lines similar to that of the conventional antisense PS-oligo, suggesting efficient cellular uptake and target binding. The nuclease stability studies in mice suggest that PCOs have higher in vivo stability than antisense PS-oligos. The studies in mice showed similar pharmacokinetic and tissue distribution profiles for PCOs to those of antisense PS-oligos in general, but rapid elimination from selected tissues.

Single-nucleotide polymorphisms can cause different structural folds of mRNA

Single-nucleotide polymorphisms (SNPs) are the most common type of genetic variation in man. Genes containing one or more SNPs can give rise to two or more allelic forms of mRNAs. These mRNA variants may possess different biological functions as a result of differences in primary or higher order structures that interact with other cellular components. Here we report the observation of marked differences in mRNA secondary structure associated with SNPs in the coding regions of two human mRNAs: alanyl tRNA synthetase and replication protein A, 70-kDa subunit (RPA70). Enzymatic probing of SNP-containing allelic fragments of the mRNAs revealed pronounced allelic differences in cleavage pattern at sites 14 or 18 nt away from the SNP, suggesting that a single-nucleotide variation can give rise to different mRNA folds. By using phosphorothioate oligodeoxyribonucleotides complementary to the region of different allelic structures in the RPA70 mRNA, but not extending to the SNP itself, we find that the SNP exerts an allele-specific effect on the accessibility of its flanking site in the endogenous human RPA70 mRNA. This further supports the allele-specific structural features identified by enzymatic probing. These results demonstrate the contribution of common genetic variation to structural diversity of mRNA and suggest a broader role than previously thought for the effects of SNPs on mRNA structure and, ultimately, biological function.

Impact of mixed-backbone oligonucleotides on target binding affinity and target cleaving specificity and selectivity by Escherichia coli RNase H

All phosphorothioate mixed-backbone oligonucleotides (MBOs) composed of deoxyribonucleotide and 2'-O-methylribonucleotide segments were studied for their target binding affinity, specificity, and RNase H activation properties. The 2'-O-methylribonucleotide segment, which does not activate RNase H, serves as a high affinity target-binding domain and the deoxyribonucleotide (DNA) segment, which binds to the target with a lower affinity than the former domain, serves as an RNase H-activation or target-cleaving domain. In order to understand the influence of the size and position of the DNA segment of MBOs on RNase H-mediated cleavage of the RNA target, we designed and synthesized a series of 18-mer MBOs with the DNA segment varying from a stretch of two to eight deoxyribonucleotides in the middle, at the 5'-end, or at the 3'-end, of the MBOs. UV absorbance melting experiments of the duplexes of the MBOs with the complementary and singly mismatched RNA targets suggest that the target binding affinity of the MBOs increases as the number of 2'-O-methylribonucleotides increases, and that the binding specificity is influenced by the size and position of the DNA segment. Analysis of RNase H assay results indicates that the minimum substrate cleavage site and cleavage efficiency of RNase H are influenced by the position of the DNA segment in the MBO sequence. RNA cleavage efficiency decreases as the position of the DNA segment of the MBO.RNA heteroduplex is changed from the 3'-end to the middle and to the 5'-end of the target strand. Studies with singly mismatched targets indicate that the RNase H-dependent point mutation selectivity of the MBOs is affected by both the position and size of the DNA segment in the MBO sequence.

A mild and efficient solid-support synthesis of novel oligonucleotide conjugates

Conjugates of oligodeoxyribonucleotide phosphorothioate (ODN-PS) with folic acid, retinoic acid, arachidonic acid, and methoxypoly(ethylene glycol)propionic acid have been synthesized. The procedure involved the initial solid-phase preparation of 5'-amino-functionalized ODN-PS using N-pent-4-enoyl-derived (PNT) nucleoside phosphoramidites followed by conjugation of the oligonucleotide either to the ligand acids, using 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide as a coupling reagent, or to their corresponding succinimidyl derivatives. Subsequent exposure of the support to aqueous ammonium hydroxide (28%, 2 h, 55 degrees C) resulted in the release of the fully deprotected ODN conjugates, which were purified by reversed-phase HPLC or by preparative polyacrylamide gel electrophoresis. The identity of the oligonucleotide conjugates was confirmed by MALDI-TOF mass spectral analysis.

A characteristic bent conformation of RNA pseudoknots promotes -1 frameshifting during translation of retroviral RNA

The structures of four different RNA pseudoknots that provide one of the signals required for ribosomal frameshifting in mouse mammary tumor virus have been determined by NMR. The RNA pseudoknots have similar sequences and assume similar secondary structures, but show significantly different frameshifting efficiencies. The three-dimensional structures of one frameshifting and one non-frameshifting RNA pseudoknot had been determined previously by our group. Here we determine the structures of two new RNA pseudoknots, and relate the structures of all four pseudoknots to their frameshifting abilities. The two efficient frameshifting pseudoknots adopt characteristic bent conformations with stem 1 bending towards the major groove of stem 2. In contrast, the two poor frameshifting pseudoknots have structures very different from each other and from the efficient frameshifters. One has linear, coaxially stacked stems, the other has stems twisted and bent, but in the opposite direction to the efficient frameshifters. Changes in loop size that favor bending (shorter loops) increase frameshifting efficiency; longer loops that allow linear arrangement of the stems decrease frameshifting. Frameshifting pseudoknots in feline immunodeficiency virus and simian retrovirus have different loop sequences, but the sequences at their stem junctions imply the same bent conformation as in the mouse mammary tumor viral RNA. The requirement for a precise pseudoknot conformation for efficient frameshifting strongly implies that a specific interaction occurs between the viral RNA pseudoknot and the host protein-synthesizing machinery.

Synthesis and NMR of RNA with selective isotopic enrichment in the bases

Efficient syntheses of pyrimidine and purine nucleosides and nucleotides with selective 13C enrichment in the base moieties are described. Uridine and cytidine are labeled at position C6 and adenosine and guanosine are labeled at position C8. The selectively labeled nucleosides were converted to nucleoside triphosphates and used with in vitro transcription to synthesize labeled RNA. Isotope-edited 12C and 13C sub-spectra of a omega 1-1/2-X-filtered NOESY experiment are demonstrated to be useful for making resonance assignments and for deriving structural information in large (> 20 nt) RNA molecules. The labeled RNAs also allow heteronuclear J-couplings and relaxation parameters to be measured without complications from 13C-13C J-couplings.

RNA structure at high resolution

Studies of RNA structural motifs at high resolution by NMR and X-ray crystallographic methods have provided many insights into the fundamental forces that give rise to the unique structural characteristics of RNA. Non-Watson-Crick purine-pyrimidine, purine-purine, and pyrimidine-pyrimidine base pairing, as well as base-phosphate and base-ribose hydrogen bonding, are important forces for folding and stabilizing RNA structures. Base stacking is as important in determining RNA conformations as hydrogen bonding interactions. With the noncanonical interactions, many single-stranded loop regions such as hairpin loops, bulge loops, and internal loops fold into well-defined secondary structures. Loop-loop and loop-helix interactions can produce tertiary structures such as pseudoknots. Also, single strands adjacent to helical regions can form tertiary contacts with base-paired nucleotides of the helices. As we learn more about the structures of the important motifs we can ask more specific questions about the mechanisms of RNA-mediated functions. Conformational flexibility rather than a specific shape of the RNA may be important for some biological reactions. However, knowledge of the structures and the ease of conformational change of the molecules involved in any process are essential for understanding and eventually controlling the process.

The structure of an RNA pseudoknot that causes efficient frameshifting in mouse mammary tumor virus

The structure of a 34-nucleotide RNA pseudoknot that causes efficient -1 frameshifting in the messenger RNA of mouse mammary tumor virus has been investigated by NMR. Spectral assignment of the pseudoknot was facilitated by comparative NMR studies on the pseudoknot and on two smaller hairpin RNAs, and by using selective 13C labeling and 13C-edited NMR techniques. The three-dimensional structure of the pseudoknot has been determined. The frameshifter pseudoknot possesses structural features not observed in previously reported model pseudoknots. It has a compact structure with a pronounced bend at the junction of its G.C-rich stems. A single adenylate residue is intercalated between the two stems so that direct coaxial staking of the stems is not possible. The lack of an opposing nucleotide for the stacked, intervening adenylate creates a hinge in the pseudoknot. Most of the loop nucleotides are restrained by base staking interactions which keep the loops from adopting extended conformations. The sterically constrained loops direct the bending of the pseudoknot at the stem-stem junction. The roles of the intercalated adenylate and loop lengths in causing bending can explain their requirement for efficient frameshifting. Our NMR data also indicate that there are internal dynamics associated with the pseudoknot. The unique, compact structure and conformational flexibility of the pseudoknot may be required for recognition and favourable interaction with the translating ribosome, or with translation factors associated with the ribosome.

Structural and functional studies of retroviral RNA pseudoknots involved in ribosomal frameshifting: nucleotides at the junction of the two stems are important for efficient ribosomal frameshifting

Ribosomal frameshifting, a translational mechanism used during retroviral replication, involves a directed change in reading frame at a specific site at a defined frequency. Such programmed frameshifting at the mouse mammary tumor virus (MMTV) gag-pro shift site requires two mRNA signals: a heptanucleotide shifty sequence and a pseudoknot structure positioned downstream. Using in vitro translation assays and enzymatic and chemical probes for RNA structure, we have defined features of the pseudoknot that promote efficient frameshifting. Heterologous RNA structures, e.g. a hairpin, a tRNA or a synthetic pseudoknot, substituted downstream of the shifty site fail to promote frameshifting, suggesting that specific features of the MMTV pseudoknot are important for function. Site-directed mutations of the MMTV pseudoknot indicate that the pseudoknot junction, including an unpaired adenine nucleotide between the two stems, provides a specific structural determinant for efficient frameshifting. Pseudoknots derived from other retroviruses (i.e. the feline immunodeficiency virus and the simian retrovirus type 1) also promote frameshifting at the MMTV gag-pro shift site, dependent on the same structure at the junction of the two stems.